TECHNICAL FIELD  
       [0001]     The present invention involves a two-stage complete recycle pressure-swing adsorption process for gas separation using two-stage pressure swing adsorption gas separation technology. It belongs to the field of pressure swing adsorption gas separation.  
       BACKGROUND OF THE INVENTION  
       [0002]     It is well known that the former pressure swing gas separation technology usually has the following disadvantage whether obtaining the product from the strongly adsorbed phase (e.g. this technology has been employed to produce pure carbon dioxide from the strongly adsorbed phase.) or obtaining the product from the weakly adsorbed phase (e.g. this technology has been employed to produce pure hydrogen from the weakly adsorbed phase) or obtaining the product from both of the weakly adsorbed and the strongly adsorbed phase (e.g. this technology has been also applied in the production of carbamide from synthetic ammonia shift gas by removing carbon). These kinds of the patents include CN 1235862A, CN1248482A, CN1357404A CN1347747A, CN1342509A, CN1334135A and CN1334136A, etc. However it has been seen that the conventional pressure-swing gas adsorption technology possesses significant disadvantages in terms of the lost of the effective gases and the high operation cost, etc. The present invention involves improvements based on the pressure-swing adsorption gas separation technology mentioned above, namely, in this invention there is almost no lost of the effective gas, and in addition, this invention does not need the complicated vacuum facilities under suitable adsorption pressure. Therefore, the cost of the equipment and the power consumption will be remarkably reduced.  
       SUMMARY OF THE INVENTION  
       [0003]     The present invention adopts the two-stage pressure swing adsorption process to separate the strongly adsorbed and the weakly adsorbed component from the gas mixture, and the product may be the strongly adsorbed component or the weakly adsorbed component or both of them at the same time. In the present invention, the strongly adsorbed and the weakly adsorbed is relative and isn&#39;t absolute, that means that the same component is the strongly adsorbed component in one gas mixture, but it is the weakly adsorbed component in another gas mixture. In order to achieve different goals, the same component even if in the same gas mixture may be the strongly adsorbed component or may be the weakly adsorbed component; moreover, the strongly adsorbed component and the weakly adsorbed component in the invention may be a single component or may be sum of several components. For example, in the synthetic ammonia shift gas, it contains hydrogen sulfide, organic sulphur, gaseous water, carbon dioxide, methane, carbon monoxide, nitrogen, oxygen, argon and hydrogen, etc. When this mixture is utilized to produce carbamide, the hydrogen sulfide, the organic sulphur, the gaseous water, and the carbon dioxide are called strongly adsorbed components; the methane, the carbon monoxide, the nitrogen, the oxygen, the argon and the hydrogen are called the weakly adsorbed components. When this mixture is utilized to produce the high pure hydrogen (99.99 v %), the hydrogen sulfide, the organic sulphur, the gaseous water, the carbon dioxide, the methane, the carbon monoxide, the nitrogen, the oxygen and the argon are called strongly adsorbed components, but the hydrogen is called the weakly adsorbed component. Here in the above statement, the nitrogen in the synthetic ammonia shift gas is called weakly adsorbed component when it is utilized to produce carbamide, but it is called strongly adsorbed component when it is utilized to produce high pure hydrogen (99.99 v %). The methane, the carbon monoxide, the nitrogen, the oxygen are the same too.  
         [0004]     The aim of the present invention is to provide a kind of gas Separation process which has low investment and lower operation cost using two-stage complete recycle pressure swing adsorption. The process can overcome the disadvantages of the prior art by adopting the combination of different equipments and adsorbents, and can save the operation cost largely and reduce the effective gas loss at maximum extent comparing with the prior art.  
         [0005]     The present invention adopts the two-stage complete recycle pressure swing adsorption process for gas separation. The process is used to separate the strongly adsorbed component and the weakly adsorbed component from the gas mixture; the product can be the strongly adsorbed component or the weakly adsorbed component or both of them at the same time; the process adopts two-stage pressure-swing adsorption device operating in series; the gas mixture is fed into the first stage pressure-swing adsorption device, and the strongly adsorbed component of the gas mixture is adsorbed and is concentrated as product; the interim gas mixture from the outlet of the adsorption tower of the first stage pressure-swing adsorption device is fed into the second stage pressure-swing adsorption device; the strongly adsorbed component in the interim gas mixture is adsorbed further, and the nonadsorbed weakly adsorbed component acts as product and is fed into next step; all of the gas excepting for the weakly adsorbed component entering into next step in the second stage is returned into the first stage to increase the pressure of the adsorption tower; the adsorption tower of the first stage sequentially undergoes the following steps in one circulation period: adsorption step A, two-end equalization depressurization  2 ED′, backward depressurization BD, second stage gas repressurization  2 ER, two-end equalization repressurization  2 ER′ and final repressurization FR; the adsorption tower of the second stage sequentially undergoes the following steps in one circulation period: adsorption A, cocurrent equalization depressurization ED, backward depressurization BD, backward equalization repressurization ER and final repressurization FR.  
         [0006]     The adsorption tower of the first stage adds the cocurrent equalization depressurization ED step after the adsorption A step; at the same time, the adsorption tower of the first stage adds the backward equalization repressurization ER step after the two-end equalization repressurization  2 ER′.  
         [0007]     The adsorption tower of the first stage adds the evacuation step VC after the backward depressurization step BD or/and the adsorption tower of the second stage adds the evacuation step VC after the backward depressurization step BD.  
         [0008]     The adsorption tower of the second stage adds the cocurrent depressurization step PP after the cocurrent equalization depressurization ED; at the same time, the adsorption tower of the second stage adds the purge step P after the backward depressurization step BD; the gas of the purge step P comes from the adsorption tower which is in the cocurrent depressurization step PP directly or comes from the buffer vessel V that is used to store the gas of the cocurrent depressurization step PP.  
         [0009]     The adsorption tower of the second stage adds the first cocurrent depressurization step PP 1  and the second cocurrent depressurization step PP 2  after the cocurrent equalization depressurization step ED; at the same time, the adsorption tower of the second stage adds the first purge step P 1  and the second purge step P 2  after the backward depressurization step BD; the gas of the first purge step P 1  comes from the adsorption tower which is in the second cocurrent depressurization step PP 2  directly or comes from the buffer vessel V 1  that is used to store the gas of the second cocurrent depressurization step PP 2 ; the gas of the second purge step P 2  comes from the adsorption tower which is in the first cocurrent depressurization step PP 1  directly or comes from the buffer vessel V 2  that is used to store the gas of the first cocurrent depressurization step PP 1 .  
         [0010]     The adsorption tower of the second stage adds the first cocurrent depressurization step PP 1  and the second cocurrent depressurization step PP 2  and the third cocurrent depressurization step PP 3  after the cocurrent equalization depressurization step ED; at the same time, the adsorption tower of the second stage adds the first purge step P 1  and the second purge step P 2  and the third purge step P 3  after the backward depressurization step BD; the gas of the first purge step P 1  comes from the adsorption tower which is in the third cocurrent depressurization step PP 3  directly or comes from the buffer vessel V 3  that is used to store the gas of the third cocurrent depressurization step PP 3 ; the gas of the second purge step P 2  comes from the adsorption tower which is in the second cocurrent depressurization step PP 2  directly or comes from the buffer vessel V 4  that is used to store the gas of the second cocurrent depressurization step PP 2 ; the gas of the third purge step P 3  comes from the adsorption tower which is in the first cocurrent depressurization step PP 1  directly or comes from the buffer vessel V 5  that is used to store the gas of the first cocurrent depressurization step PP 1 .  
         [0011]     In the first stage, the average concentration of the strongly adsorbed components in the gas mixture finally discharged from the top of the adsorption tower after the two-end equalization depressurization step  2 ER′ is over 30%.  
         [0012]     In the first stage, the average concentration of the strongly adsorbed components in the gas mixture finally discharged from the top of the adsorption tower after the two-end equalization depressurization step  2 ER′ is over 75%.  
         [0013]     In the first stage, the average concentration of the strongly adsorbed components in the outlet gas of the adsorption step is over or equal to 2 v %.  
         [0014]     The gas discharged from the adsorption tower is discharged into the buffer vessel V 6  at first and then the buffer vessel V 7  when the adsorption tower is performing the backward depressurization step BD in the second stage.  
         [0015]     When the adsorption tower of the first stage is performing the two-end equalization depressurization step, less than 50% of the gas discharged from the equalization depressurization step is introduced from the bottom of the adsorption tower into the other adsorption tower which is performing the equalization repressurization step.  
         [0016]     When the adsorption tower of the first stage is performing the two-end equalization depressurization step, 17-25% of the gas discharged from the equalization depressurization step is introduced from the bottom of the adsorption tower into the other adsorption tower which is performing the equalization repressurization step.  
         [0017]     The present invention is used to separate the strongly adsorbed component and the weakly adsorbed component from the gas mixture; the product can be the strongly adsorbed component or the weakly adsorbed component or both of them at the same time; the process adopts two-stage pressure-swing adsorption device operating in series; the gas mixture is fed into the first stage pressure-swing adsorption device, and the strongly adsorbed component of the gas mixture is adsorbed and is concentrated as product; the interim gas mixture from the outlet of the adsorption tower of the first stage pressure-swing adsorption device is fed into the second stage pressure-swing adsorption device; the strongly adsorbed component in the interim gas mixture is adsorbed further, and the nonadsorbed weakly adsorbed component acts as product and is fed into next step; the gas discharged from the adsorption tower which is in the first backward depressurization step BD 1  in the first stage is returned into the adsorption tower of the first stage at the bottom to increase the pressure; all of the gas excepting for the weakly adsorbed component entering into next step in the second stage is returned into the first stage to increase the pressure of the adsorption tower; the adsorption tower of the first stage sequentially undergoes the following steps in one circulation period: adsorption step A, cocurrent equalization depressurization ED, first backward depressurization BD 1 , second backward depressurization BD 2 , first stage gas repressurization  2 ER 1 , second stage gas repressurization  2 ER, backward equalization repressurization ER and final repressurization FR; the adsorption tower of the second stage sequentially undergoes the following steps in one circulation period: adsorption A, cocurrent equalization depressurization ED, backward depressurization BD, backward equalization repressurization ER and final repressurization FR.  
         [0018]     The adsorption tower of the first stage adds the evacuation step VC after the second backward depressurization step BD 2  and/or the adsorption tower of the second stage adds the evacuation step VC after the backward depressurization step BD. The adsorption tower of the second stage adds the first cocurrent depressurization step PP 1  and the second cocurrent depressurization step PP 2  and the third cocurrent depressurization step PP 3  after the cocurrent equalization depressurization step ED; at the same time, the adsorption tower of the second stage adds the first purge step P 1  and the second purge step P 2  and the third purge step P 3  after the backward depressurization step BD; the gas of the first purge step P 1  comes from the adsorption tower which is in the third cocurrent depressurization step PP 3  directly or comes from the buffer vessel V 3  that is used to store the gas of the third cocurrent depressurization step PP 3 ; the gas of the second purge step P 2  comes from the adsorption tower which is in the second cocurrent depressurization step PP 2  directly or comes from the buffer vessel V 4  that is used to store the gas of the second cocurrent depressurization step PP 2 ; the gas of the third purge step P 3  comes from the adsorption tower which is in the first cocurrent depressurization step PP 1  directly or comes from the buffer vessel V 5  that is used to store the gas of the first cocurrent depressurization step PP 1 .  
         [0019]     In the first stage, the average concentration of the strongly adsorbed components in the gas mixture finally discharged from the top of the adsorption tower after the two-end equalization depressurization step  2 ER′ is over 40%.  
         [0020]     In the first stage, the average concentration of the strongly adsorbed components in the gas mixture finally discharged from the top of the adsorption tower after the two-end equalization depressurization step  2 ER′ is over 75%.  
         [0021]     In the first stage, the average concentration of the strongly adsorbed components in the outlet gas of the adsorption step is over or equal to 2 v %.  
         [0022]     The pressure of the raw material gas mixture is over or equal to 1.8 MPa(G).  
         [0023]     In the first stage, the average concentration of the strongly adsorbed components in the gas mixture finally discharged from the adsorption tower after the first backward depressurization step BD 1  is over 30%.  
         [0024]     In the first stage, the average concentration of the strongly adsorbed components in the gas mixture finally discharged from the adsorption tower after the first backward depressurization step BD 1  is over 80%.  
         [0025]     The adsorbents in the adsorption tower of the first stage are activated alumina and fine-porous-silicagel; the activated alumina is packed at the bottom of the adsorption tower; the fine-porous-silicagel is packed at the top of the adsorption tower; the adsorbent in the adsorption tower of the second stage is fine-porous-silicagel only.  
         [0026]     The adsorbents in the adsorption tower of the first stage are activated alumina and fine-porous-silicagel, or activated alumina and activated carbon, or activated alumina and activated carbon and molecular sieve in sequence from the bottom up; the adsorbents in the adsorption tower of the second stage are activated carbon and molecular sieve, or molecular sieve. The adsorbents in the adsorption tower of the first stage are activated alumina and molecular sieve in sequence from the bottom up; the adsorbent in the adsorption tower of the second stage is molecular sieve. The adsorbents in the adsorption tower of the first stage are activated alumina and molecular sieve in sequence from the bottom up; the adsorbent in the adsorption tower of the second stage is molecular sieve. The present invention may increase the recovery of the effective gas up to 99.9%, decrease the Electricity consumption by 50-90% (increase with increase of the adsorption pressure). It is observed that the present invention makes an innovation of the gas separation methods in art (including wet way gas separation technology and pressure swing adsorption gas separation technology), solves the problem of the effective gas loss and the high Electricity consumption drastically. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0027]      FIG. 1  is the working procedure scheme of technology steps for the first stage pressure-swing adsorption device of example 1.  
         [0028]      FIG. 2  is the working procedure scheme of technology steps for the second stage pressure-swing adsorption device of example 1.  
         [0029]      FIG. 3  is the technology flow sheet of example 1.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0030]     The gas mixture in the present invention may be synthetic ammonia shift gas, synthetic ammonia deflating gas, synthesis gas, water gas, natural gas, semi water gas, high temperature furnace gas, gas, cracking dry gas, oilfield associated gas and oil making gas and so on, also may be any other gas mixture.  
         [0031]     The present invention adopts two-stage complete recycle pressure swing adsorption process for gas separation. The process is used to separate the strongly adsorbed component and the weakly adsorbed component from the gas mixture; the product can be the strongly adsorbed component or the weakly adsorbed component or both of them at the same time; the process adopts two-stage pressure-swing adsorption device operating in series; the gas mixture is fed into the first stage pressure-swing adsorption device, and the strongly adsorbed component of the gas mixture is adsorbed and is concentrated as product; the interim gas mixture from the outlet of the adsorption tower of the first stage pressure-swing adsorption device is fed into the second stage pressure-swing adsorption device; the strongly adsorbed component in the interim gas mixture is adsorbed further, and the nonadsorbed weakly adsorbed component acts as product and is fed into next step; all of the gas excepting for the weakly adsorbed component entering into next step in the second stage is returned into the first stage to increase the pressure of the adsorption tower; the average concentration of the strongly adsorbed components in outlet gas of the adsorption tower of the first stage is over or equal to 2 v % generally. The adsorption towers of the second stage are used to adsorb the strongly adsorbed components in outlet gas of the adsorption tower of the first stage to the desired level of the next step. Each adsorption tower of the two-stage pressure swing adsorption device goes through the steps in turn in one cycle as follows:  
         [0032]     The first stage:  
         [0000]     (1) Adsorption A  
         [0033]     Part of strongly adsorbed component is adsorbed by the adsorbent in the adsorption tower after the gas mixture is introduced to the inlet of the adsorption tower which is in the adsorption step; nonadsorbed weakly adsorbed component and part of strongly adsorbed component discharged from the outlet go into the adsorption tower of the second stage which is in the adsorption step. The total amount of adsorbed strongly adsorbed components will increase continuously with the increase of time the feed of gas is stopped when the adsorbed component mentioned above reach to the saturation on adsorbent, it means that the adsorption step is finished.  
         [0000]     (2) Cocurrent Equalization Depressurization ED  
         [0034]     The weakly adsorbed component concentration of the dead-space gas inside adsorption tower is rather high after finishing the adsorption step, this stream of the weakly adsorbed component need to be recovered and reused. The dead-space gas discharged at different times from the outlet of the adsorption tower enters into the adsorption tower which has completed the evacuation step VC to increase the pressure. The gas is discharged every time and pressure equalization is performed once. The strongly adsorbed component concentration at outlet of the adsorption tower increases continuously with the increase of the pressure equalization times. The pressure equalization times is determined by the adsorption pressure and the strongly adsorbed component concentration at the outlet of the adsorption tower after the adsorption step. In general, the strongly adsorbed component concentration at the top of the adsorption tower ought to be over 30 v %, better over 75 v % after the last cocurrent equalization depressurization step ED.  
         [0000]     (3) Two-End Equalization Depressurization  2 ED  
         [0035]     The weakly adsorbed component concentration of the dead-space gas inside adsorption tower is rather high and the strongly adsorbed component concentration is relative lower after finishing the adsorption step; on the one hand this part weakly adsorbed component need to be recovered and reused, on the other hand the strongly adsorbed component concentration need to be increased, therefore, the gas inside the absorption tower must be discharged to perform the depressurization desorption. The dead-space gas discharged at different times from the outlet of the adsorption tower enters into the adsorption tower which has completed the first stage regeneration step to pressurize. The gas is discharged every time and the pressure equalization is performed once. The strongly adsorbed component concentration at the inlet and the outlet of the adsorption tower increases continuously with the increase of the equalization repressurization times, at the same time, the weakly adsorbed component is recovered and reused. Every time the equalization depressurization operation mentioned above is performed, it may be operated at the two ends of the adsorption tower at the same time, or it may begin with the cocurrent equalization depressurization from the top of the adsorption tower at first, and then do with the backward equalization depressurization to another adsorption tower at the latter time prior to achieving the cocurrent equalization depressurization balance, the goal is to increase the concentration of the strongly adsorbed component and to recover the weakly adsorbed component inside the adsorption tower; the third way is to perform the cocurrent equalization depressurization at first, and then to stop it before the balance of the pressure between two adsorption tower, and then to perform the backward equalization depressurization. The first way can increase the adsorbent&#39;s efficiency. The amount of gas discharged from the bottom of the adsorption tower ought to be less than the amount discharged from the top of the adsorption tower while performing the two-end equalization depressurization. The two-end equalization depressurization step  2 ED′ in the present invention is different from the usual equalization depressurization step ED the gas is discharged from the outlet of the adsorption tower at the usual equalization depressurization step ED, as to the said the cocurrent equalization depressurization, however, the gas is discharged from both the inlet and the outlet of the adsorption tower in the two-end pressure equalization depressurization  2 ED′ step in the present invention.  
         [0036]     After the adsorption step A of the adsorption tower, the first several pressure equalization operation may use cocurrent equalization depressurization ED, but latter several times pressure equalization or the last pressure equalization adopts the two-end equalization depressurization  2 ED′. The concentration of the strongly adsorbed component in product still meet the production requirement after the equalization depressurization.  
         [0037]     The pressure equalization times is determined by the adsorption pressure and the concentration of the strongly adsorbed component at the outlet of the adsorption tower after the adsorption step. In ordinary circumstances, after the last two-end equalization depressurization step  2 ED′. The concentration of the strongly adsorbed component at top of the adsorption tower ought to be over 30 v %, better over 75 v %. The concentration of the strongly adsorbed component at bottom of the adsorption tower ought to be over 30 v %, better over 80 v %.  
         [0000]     (4) Backward Depressurization BD  
         [0038]     After the two-end equalization depressurization step  2 ED′, the strongly adsorbed component inside the adsorption tower is introduced into the next stage till to balance with the pressure of the next stage; the strongly adsorbed component can be as product or as fuel or venting.  
         [0000]     (5) First Backward Depressurization Step BD 1   
         [0039]     After the cocurrent equalization depressurization step ED, the weakly adsorbed component at the bottom inside the adsorption tower is discharged into the buffer vessel at first, and then the gas is introduced inside the buffer vessel into the adsorption tower to pressurize; in ordinary circumstances, after the first backward depressurization step BD 1 , the concentration of the strongly adsorbed component at bottom of the adsorption tower ought to be over 30 v %, better over 80 v %.  
         [0000]     (6) Second Backward Depressurization Step BD 2   
         [0040]     After the second backward depressurization step BD 1 , the strongly adsorbed component inside the adsorption tower is introduced into the next stage till to balance with the pressure of the next stage; the strongly adsorbed component can be as product or as fuel or venting.  
         [0000]     (7) Evacuation VC  
         [0041]     After the backward depressurization step BD, the strongly adsorbed component adsorbed on adsorbent pulled by vacuum pump from the bottom of the adsorption tower is introduced into the next stage. After the backward depressurization step BD, the purge step P is performed if the evacuation step VC is not performed; the dried strongly adsorbed component or another dry gas inside the system can be as purge gas. This step is adopted when the adsorbent amount need to be decreased.  
         [0000]     (8) First Stage Gas Repressurization  2 ER′ 
         [0042]     After the backward depressurization step BD or evacuation step VC, the gas discharged from the adsorption tower of the first stage in the first backward depressurization step BD 1  is returned to the outlet of the adsorption tower of the first stage to pressurize the adsorption tower which has finished the backward depressurization step BD or the evacuation step VC. The added step can increase the recovery of the effective gas.  
         [0000]     (9) Second Stage Gas Repressurization  2 ER  
         [0043]     After the backward depressurization step BD or evacuation step VC or the first stage gas repressurization step  2 ER 1 , in second stage, other gas excepting the weakly adsorbed component entering into the next stage is returned into the outlet of the adsorption tower of the first stage to pressurize the adsorption tower which has finished the backward depressurization step BD or the evacuation step VC. The added step can increase the recovery of the effective gas.  
         [0000]     (10) Two-End Equalization Repressurization  2 ER′ 
         [0044]     After the second stage gas repressurization step  2 ER, the gas discharged from the two-end equalization depressurization step  2 ED′ in first stage is introduced into the adsorption tower from the inlet and the outlet to pressurize the adsorption tower gradually. The times of the two-end equalization repressurization step  2 ER′ and the times of the two-end equalization depressurization step  2 ED′ are the same. Every time the gas used for the two-end equalization repressurization step  2 ER′ comes from the gas of the two-end depressurization step  2 ED′ of the different adsorption tower. The two-end equalization repressurization step  2 ER′ in first stage is different from the usual equalization repressurization step ER, the gas discharged from the usual equalization repressurization step ER is introduced at the outlet, however, the gas discharged from the two-end equalization repressurization step  2 ER′ in first stage is entered at both the inlet and the outlet.  
         [0045]     After the adsorption step A, while performing the cocurrent equalization depressurization step ED for the first several times, the gas discharged from the equalization repressurization step ER of the adsorption tower enter into the adsorption tower at its outlet, not at its inlet.  
         [0000]     (11) Backward Equalization Repressurization ER  
         [0046]     After the second stage gas repressurization step  2 ER or the two-end equalization pressurization step  2 ER′, the gas discharged from the cocurrent equalization depressurization step is introduced into the adsorption tower at outlet to pressurize the adsorption tower which has finished the backward depressurization step BD or the evacuation step VC or purge step P gradually, the times of the equalization repressurization step and the equalization depressurization step are the same. Every time the gas used for the equalization repressurization step comes from the gas of the equalization depressurization step of the different adsorption tower.  
         [0000]     (12) Final Repressurization FR  
         [0047]     After the two-end equalization repressurization step  2 ER′, the gas discharged from the outlet of the adsorption tower at the adsorption step is utilized to pressure the adsorption tower from the top till the adsorb pressure is reached.  
         [0048]     The second stage:  
         [0000]     (1) Adsorption A  
         [0049]     The outlet gas discharged from the adsorption tower of the first stage which is in the adsorption step is introduced to the adsorption tower of the second stage device which is in the adsorption step. The strongly adsorbed component is adsorbed selectively by the adsorbent in the adsorption towers and is discharged from the outlet into the next stage. The strongly adsorbed component that adsorbed will increase continuously with the increase of time. The gas feed is stopped when the adsorbed component mentioned above reaches to the saturation on adsorbent, it means that the adsorption step finishes. The concentration of the strongly adsorbed component of the outlet gas is controlled according to the production requirement, it can be decreased lower to several ppm.  
         [0000]     (2) Cocurrent Equalization Repressurization ED  
         [0050]     After the adsorption step, the weakly adsorbed component concentration in the dead-space gas is rather high and this stream gas need to be recovered and reused. The dead-space gas discharged at different times from the outlet of the adsorption tower enters into the adsorption tower which has completed the evacuation step VC to increase the pressure. The gas is discharged every time and the pressure equalization is performed once. The concentration of the strongly adsorbed component at outlet of the adsorption tower increase continuously with the increase of the pressure equalization times. The pressure equalization times is determined by the adsorption pressure and the strongly adsorbed component concentration at the outlet of the adsorption tower after the adsorption step.  
         [0000]     (3) Cocurrent Depressurization PP  
         [0051]     After the cocurrent equalization depressurization step ED, the gas inside the adsorption tower is discharged cocurrent directly into the another adsorption tower to purge the strongly adsorbed component adsorbed on the adsorbent, another way, the gas is discharged into the buffer vessel at first, and then is discharged from the vessel into the another adsorption tower to purge the strongly adsorbed component adsorbed on the adsorbent to achieve the adsorbent regeneration. Cocurrent depressurization step PP can be performed once, and also two times, third times, even if many times. The more times of the cocurrent depressurization step PP are adopted, the better purge effect is obtained and the less adsorbent dosage is used, but the higher investment in non-standard equipment, special sequence valve, oil pressure system, control system and apparatus, moreover the dosage decreasing of the adsorbent is limited less and less along with the times of the cocurrent depressurization step PP increasing, the investment in non-standard equipment, special program control valve, oil pressure system, control system and apparatus will be more and more, so times of the cocurrent depressurization PP are not suitable for repeating many times.  
         [0000]     (4) Backward Depressurization BD  
         [0052]     After the cocurrent equalization depressurization step ED or cocurrent depressurization step PP, the gas is discharged at backward direction into the adsorption tower of the first stage.  
         [0000]     (5) Evacuation VC or Purge P  
         [0053]     After the backward depressurization step BD, the strongly adsorbed component and other component adsorbed on adsorbent pulled by vacuum pump from the bottom of the adsorption tower is introduced into the first stage device to achieve the adsorbent regeneration; another way, the gas mixture discharged from the cocurrent depressurization step PP is used to purge the strongly adsorbed component adsorbed on the adsorbent to achieve the adsorbent regeneration. The gas mixture after the adsorbent purge step is discharged into the adsorption tower of the first stage device.  
         [0000]     (6) Backward Equalization Repressurization ER  
         [0054]     After the backward depressurization step BD or the evacuation step VC or the purge step P, the gas discharged from the cocurrent equalization depressurization step is introduced into the adsorption tower at outlet to pressurize the adsorption tower which has completed the backward depressurization step BD or the evacuation step VC or purge step P gradually, the times of the equalization repressurization step and the equalization depressurization are the same. Every time the gas used for the equalization repressurization step comes from the gas after the equalization depressurization step of the different adsorption tower.  
         [0000]     (7) Final Repressurization FR  
         [0055]     After the equalization repressurization step, the gas discharged from the outlet of the adsorption tower at adsorption step is utilized to pressurize the adsorption tower from the top till the adsorb pressure is reached.  
       EXAMPLE 1  
       [0056]     The feed gas in the present example is the synthetic ammonia shift gas, including those from coal, natural gas, oil and so on.  
         [0057]     The components of synthetic ammonia shift gas are shown in the following table:  
                                                                                                                         Component   H2   N2   CO2   CO   CH4   O2 + Ar   Total sulfur   Water (steam)                                Conc.(%) V   46   53   12   17   18   30   ≦1   9   1   2   ≦0.8   150 mg/Nm3   saturation                 Temperature ≦40            Pressure 3.0 MPa G             
 
         [0058]     As shown in  FIG. 3 , the first stage device comprises of eleven adsorption towers (A-K). The adsorbents in the adsorption tower from the bottom up in sequence are activated alumina and fine-porous-silicagel. Single tower is simultaneously in an adsorption step and the pressure equalization step performs nine times in the working procedure. The second stage device comprises of eight adsorption towers (a-h). The adsorbent in the adsorption tower is fine-porous-silicagel. Single tower is simultaneously in an adsorption step and the pressure equalization step performs six times in the working procedure. In the first stage, carbon dioxide is purified to over 98 v % for synthesizing carbamide. In the second stage, the outlet gas of the first stage is further purified to meet the requirement of the next procedure in synthetic ammonia production; carbon dioxide concentration in hydrogen, nitrogen at the top outlet of the adsorption tower of the second stage is controlled less than 0.2 v %.  
         [0059]     The shift gas enters into the first stage in adsorption step. The adsorbents adsorb selectively water, organic sulfur, inorganic sulfur and carbon dioxide and so on in turn from the shift gas. The nonadsorbed partial carbon dioxide and the weakly adsorbed components such as carbon monoxide, methane, nitrogen, hydrogen and other components are discharged from the outlet and enter into the absorption tower of the second stage in adsorption step. The adsorbents adsorb selectively carbon dioxide, the weakly adsorbed components such as carbon monoxide, methane, nitrogen, hydrogen and other components are discharged from the outlet and enter into the compressing procedure. In the first stage, the adsorption tower sequentially undergoes pressure swing adsorption step in one circulation period as adsorption A, first two-end equalization depressurization  2 E 1 D′, second two-end equalization depressurization  2 E 2 D′, third two-end equalization depressurization  2 E 3 D′, fourth two-end equalization depressurization  2 E 4 D′, fifth two-end equalization depressurization  2 E 5 D′, sixth two-end equalization depressurization  2 E 6 D′, seventh two-end equalization depressurization  2 E 7 D′, eighth two-end equalization depressurization  2 E 8 D′, ninth two-end equalization depressurization  2 E 9 D′, carbon dioxide product backward depressurization BD, second stage gas repressurization  2 ER, ninth two-end equalization repressurization  2 E 9 R′ eighth two-end equalization repressurization  2 E 8 R′ seventh two-end equalization repressurization  2 E 7 R′, sixth two-end equalization repressurization  2 E 6 R′, fifth two-end equalization repressurization  2 E 5 R′, fourth two-end equalization repressurization  2 E 4 R′, third two-end equalization repressurization  2 E 3 R′, second two-end equalization repressurization  2 E 2 R first two-end equalization repressurization  2 E 1 R, final repressurization FR. The gas obtained from the first stage in carbon dioxide product depressurization BD step is carbon dioxide product. In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, fourth equalization depressurization E 4 D, fifth equalization depressurization E 5 D, sixth equalization depressurization E 6 D, backward depressurization BD 1 , backward depressurization BD 2 , sixth equalization repressurization E 6 R, fifth equalization repressurization E 5 R, fourth equalization repressurization E 4 R, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The gas mixture discharged from the outlet of the absorption tower of the second stage in adsorption step is mainly nitrogen and hydrogen product, wherein containing little carbon monoxide and methane. The gas discharged from the second stage in backward depressurization BD step is returned into the adsorption tower of the first stage which has completed carbon dioxide product backward depressurization BD step totally to pressurize, abbr.  2 ER. Taking the adsorption tower A as an example and crossing reference to  FIG. 1  and  FIG. 2 , we demonstrate the steps of the adsorption tower of the first stage in one circulation period in this example:  
         [0000]     (1) Adsorption A  
         [0060]     By now, adsorption tower A has completed FR step, open the sequence valve  1 A,  2 A. The shift gas goes through pipeline G 11  and enters into the adsorption tower A. In adsorption tower A, the adsorbents adsorb selectively water, organic sulfur, inorganic sulfur and carbon dioxide in turn from the shift gas. The nonadsorbed partial carbon dioxide and the weakly adsorbed component such as carbon monoxide, methane, nitrogen, hydrogen and other components flow from the outlet through the sequence valve  2 A and enter into the adsorption tower in adsorption step of the second stage. The total amount of adsorbed water, organic sulfur, inorganic sulfur and carbon dioxide increases gradually with the increase of time. Stop feeding gas when the adsorbents are saturated by the components mentioned above, and the adsorption ends. Close  1 A,  2 A. The concentration of carbon dioxide in the outlet gas should be controlled at 6 to 15% (V).  
         [0000]     (2) The First Two-End Equalization Depressurization, abbr.  2 E 1 D′ 
         [0061]     After the adsorption step, open the sequence valve  3 A,  3 C,  11 A and  11 C. The gas inside the adsorption tower A goes through pipeline G 13  and G 111  and enters into the adsorption tower C to perform the first two-end equalization repressurization (abbr.  2 E 1 R′). When the pressure in the adsorption tower A balances with the pressure in the adsorption tower C, close  3 A, 11 C.  
         [0000]     (3) The Second Two-End Equalization Depressurization, abbr.  2 E 2 D′ 
         [0062]     After  2 E 1 D′ step, open the sequence valve  4 A, 4 D, 11 D. The gas inside the adsorption tower A goes through pipeline G 14  and G 111  and enters into the adsorption tower D to perform the second two-end equalization repressurization (abbr.  2 E 2 R′). When the pressure in adsorption tower A balances with the pressure in adsorption tower D, close  4 D, 11 A and  11 D.  
         [0000]     (4) The Third Two-End Equalization Depressurization, abbr.  2 E 3 D′ 
         [0063]     After  2 E 2 D′ step, open the sequence valve  4 E, 12 A, 12 E. The gas inside the adsorption tower A goes through pipeline G 14  and G 112  and enters into the adsorption tower E to perform the third two-end equalization repressurization (abbr.  2 E 3 R′). When the pressure in the adsorption tower A balances with the pressure in the adsorption tower E, close  4 A, 4 E, and  12 E.  
         [0000]     (5) The Fourth Two-End Equalization Depressurization, abbr.  2 E 4 D′ 
         [0064]     After  2 E 3 D′ step, open the sequence valve  5 A, 5 F, 12 F. The gas inside the adsorption tower A goes through pipeline G 15  and G 112  and enters into the adsorption tower F to perform the fourth two-end equalization repressurization (abbr.  2 E 4 R′). When the pressure in the adsorption tower A balances with the pressure in the adsorption tower F, close  5 F, 12 A and  12 F.  
         [0000]     (6) The Fifth Two-end Equalization Depressurization, abbr.  2 E 5 D′ 
         [0065]     After  2 E 4 D′ step, open the sequence valve  5 G, 13 A, 13 G. The gas inside the adsorption tower A goes through pipeline G 15  and G 113  and enters into the adsorption tower G to perform the fifth two-end equalization repressurization (abbr.  2 E 5 R′). When the pressure in the adsorption tower A balances with the pressure in the adsorption tower G, close  5 A, 5 G and  13 G.  
         [0000]     (7) The Sixth Two-End Equalization Depressurization, abbr.  2 E 6 D′ 
         [0066]     After  2 E 5 D′ step, open the sequence valve  6 A, 6 H, 13 H. The gas inside the adsorption tower A goes through pipeline G 16  and G 113  and enters into the adsorption tower H to perform the sixth two-end equalization repressurization (abbr.  2 E 6 R′). When the pressure in the adsorption tower A balances with the pressure in the adsorption tower H, close  6 H, 13 A and  13 H.  
         [0000]     (8) The Seventh Two-End Equalization Depressurization, abbr.  2 E 7 D′ 
         [0067]     After  2 E 6 D′ step, open the sequence valve  6 I, 8 A, 8 I. The gas inside the adsorption tower A goes through pipeline G 16  and G 18  and enters into the adsorption tower I to perform the seventh two-end equalization repressurization (abbr.  2 E 7 R′). When the pressure in the adsorption tower A balances with the pressure in the adsorption tower I, close  6 A, 6 I and  8 I.  
         [0000]     (9) The Eighth Two-End Equalization Depressurization, abbr.  2 E 7 D′ 
         [0068]     After  2 E 7 D′ step, open the sequence valve  7 A, 7 J, 8 J. The gas inside the adsorption tower A goes through pipeline G 17  and G 18  and enters into the adsorption tower J to perform the eighth two-end equalization repressurization (abbr.  2 E 8 R′). When the pressure in the adsorption tower A balances with the pressure in the adsorption tower J, close  7 J, 8 A and  8 J.  
         [0000]     (10) The Ninth Two-End Equalization Depressurization, abbr.  2 E 9 D′ 
         [0069]     After  2 E 8 D′ step, open the sequence valve  7 K, 9 A, 9 K. The gas inside the adsorption tower A goes through pipeline G 17  and G 19  and enters into the adsorption tower K to perform the ninth two-end equalization repressurization (abbr.  2 E 9 R′). When the pressure in the adsorption tower A balances with the pressure in the adsorption tower K, close  7 A, 7 K and  9 K.  
         [0070]     After  2 E 9 D′ step, the concentration of the strongly adsorbed components at the top is over 70% (V); the concentration of the strongly adsorbed components at the bottom is over 75% (V).  
         [0000]     (11) Carbon Dioxide Product Backward Depressurization BD  
         [0071]     After  2 E 9 D′ step, first open the sequence valve KV- 14   a . The carbon dioxide product in the adsorption tower A is introduced into the interim buffer vessel V 9  of carbon dioxide product. When the pressure in the adsorption tower A reaches the pressure in vessel V 9  closely, close KV- 14   a , and then open the sequence valve KV 14 , introduce the carbon dioxide product in the adsorption tower A into the interim buffer vessel V 8  of carbon dioxide. When the pressure in the adsorption tower A reaches the pressure in vessel V 8  closely, close KV- 14 .  
         [0000]     (12) Second Stage Gas Repressurization  2 ER  
         [0072]     After BD step, open the sequence valve  10 A. The gas in V 6  and V 7  enters into the adsorption tower A to pressurize it, when the pressure in V 6  and V 7  balances with the pressure in the adsorption tower A, close  10 A.  
         [0000]     (13) The Ninth Two-End Equalization Repressurization, abbr.  2 E 9 R′ 
         [0073]     After  2 ER step, open the sequence valve  7 A, 7 B, 9 A and  9 B. The gas inside the adsorption tower B goes through pipeline G 19  and G 17  and enters into the adsorption tower A to perform the ninth two-end equalization repressurization (abbr.  2 E 9 R′). When the pressure in the adsorption tower A balances with the pressure in the adsorption tower B, close  7 B, 9 A and  9 B.  
         [0000]     (14) The Eighth Two-End Equalization Repressurization, abbr.  2 E 8 R′ 
         [0074]     After  2 E 9 R′ step, open the sequence valve  7 A, 7 C, 8 A and  8 C. The gas inside the adsorption tower C goes through pipeline G 17  and G 18  and enters into the adsorption tower A to perform the eighth two-end equalization repressurization (abbr.  2 E 8 R′). When the pressure in the adsorption tower A balances with the pressure in the adsorption tower C, close  7 A, 7 C and  8 C.  
         [0000]     (15) The Seventh Two-End Equalization Repressurization, abbr.  2 E 7 R′ 
         [0075]     After  2 E 8 R′ step, open the sequence valve  6 A, 6 D, 8 D. The gas inside the adsorption tower D goes through pipeline G 16  and G 18  and enters into the adsorption tower A to perform the eighth two-end equalization repressurization (abbr.  2 E 7 R′). When the pressure in the adsorption tower A balances with the pressure in the adsorption tower D, close  6 D, 8 A and  8 D.  
         [0000]     (16) The Sixth Two-End Equalization Repressurization, abbr.  2 E 6 R′ 
         [0076]     After  2 E 7 R′ step, open the sequence valve  6 E, 13 A, 13 E. The gas inside the adsorption tower E goes through pipeline G 16  and G 113  and enters into the adsorption tower A to perform the sixth two-end equalization repressurization (abbr.  2 E 6 R′). When the pressure in the adsorption tower A balances with the pressure in the adsorption tower E, close  6 A, 6 E and  13 E.  
         [0000]     (17) The Fifth Two-End Equalization Repressurization, abbr.  2 E 5 R′ 
         [0077]     After  2 E 6 R′ step, open the sequence valve  5 A, 5 F, 13 F. The gas inside the adsorption tower F goes through pipeline G 15  and G 113  and enters into the adsorption tower A to perform the fifth two-end equalization repressurization (abbr.  2 E 5 R′). When the pressure in the adsorption tower A balances with the pressure in the adsorption tower F, close  5 F, 13 A and  13 F.  
         [0000]     (18) The Fourth Two-End Equalization Repressurization, abbr.  2 E 4 R′ 
         [0078]     After  2 E 5 R′ step, open the sequence valve  5 G, 12 A, 12 G. The gas inside the adsorption tower G goes through pipeline G 15  and G 112  and enters into the adsorption tower A to perform the fourth two-end equalization repressurization (abbr.  2 E 4 R′). When the pressure in the adsorption tower A balances with the pressure in the adsorption tower F, close  5 A, 5 G and  12 G.  
         [0000]     (19) The Third Two-End Equalization Repressurization, abbr.  2 E 3 R′ 
         [0079]     After  2 E 4 R′ step, open the sequence valve  4 A, 4 H, 12 H. The gas inside the adsorption tower H goes through pipeline G 14  and G 112  and enters into the adsorption tower A to perform the fourth two-end equalization repressurization (abbr.  2 E 3 R′). When the pressure in the adsorption tower A balances with the pressure in the adsorption tower H, close  4 H, 12 A, 12 H.  
         [0000]     (20) The Second Two-end Equalization Repressurization, abbr.  2 E 2 R′ 
         [0080]     After  2 E 3 R′ step, open the sequence valve  4 I, 11 A, 11 I. The gas inside the adsorption tower I goes through pipeline G 14  and G 111  and enters into the adsorption tower A to perform the fourth two-end equalization repressurization (abbr.  2 E 2 R′). When the pressure in the adsorption tower A balances with the pressure in the adsorption tower I, close  4 A, 4 I, 11 I.  
         [0000]     (21) The First Two-End Equalization Repressurization, abbr.  2 E 1 R′ 
         [0081]     After  2 E 2 R′ step, open the sequence valve  3 A, 3 J, 11 J. The gas inside the adsorption tower J goes through pipeline G 13  and G 111  and enters into the adsorption tower A to perform the first two-end equalization repressurization (abbr.  2 E 1 R′). When the pressure in the adsorption tower A balances with the pressure in the adsorption tower J, close  3 J, 11 A, 11 J.  
         [0000]     (22) Final Repressurization FR  
         [0082]     After  2 E 1 R′ step, open the sequence valve KV- 12 . The outlet gas discharged from the adsorption tower in adsorption step is used to increase the pressure at the top of the adsorption tower A, when the pressure in A balances with the adsorption pressure, close KV- 12  and  3 A.  
         [0083]     By far, the adsorption tower A has completed a circulation period and can enter into the next circulation. The steps of B to D adsorption towers are the same, but the operating time are staggered, see  FIG. 1  and  FIG. 3 .  
         [0084]     Now taking the adsorption tower a as an example and crossing reference to  FIG. 2  and  FIG. 3 , we demonstrate the steps of the adsorption tower of the second stage in one circulation period in this example:  
         [0000]     (1) Adsorption A  
         [0085]     By now, the adsorption tower a has completed FR step, open the sequence valve  1   a ,  2   a . The interim gas mixture goes through pipeline G 21  and enters into the adsorption tower a. In the adsorption tower a, the adsorbents adsorb selectively carbon dioxide and other components in outlet gas of the first stage. The little nonadsorbed carbon dioxide and the weakly adsorbed component such as carbon monoxide, methane, nitrogen, hydrogen and other components flow out the outlet through the sequence valve  2   a  and enter into the synthetic ammonia compressing procedure. The total amount of adsorbed carbon dioxide increases gradually with the increase of time. Stop feeding gas when the adsorbents are saturated by carbon dioxide, and the adsorption ends. Close  1   a ,  2   a . The carbon dioxide concentration in the outlet gas should be controlled at lower 2% (V).  
         [0000]     (2) The First Cocurrent Equalization Depressurization, abbr. E 1 D  
         [0086]     After the adsorption step, open the sequence valve  3   a , 3   c . The gas inside the adsorption tower a goes through pipeline G 23  and enters into the adsorption tower C to perform E 1 R step. When the pressure in the adsorption tower a balances with the pressure in the adsorption tower c, close  3   a.    
         [0000]     (3) The Second Cocurrent Equalization Depressurization, abbr. E 2 D  
         [0087]     After E 1 D step, open the sequence valve  4   a , 4   d . The gas inside the adsorption tower a goes through pipeline G 24  and enters into the adsorption tower d to perform E 2 R step. When the pressure in the adsorption tower a balances with the pressure in the adsorption tower d, close  4   d.    
         [0000]     (4) The Third Cocurrent Equalization Depressurization, abbr. E 3 D  
         [0088]     After E 2 D step, open the sequence valve  4   e . The gas inside the adsorption tower a goes through pipeline G 24  and enters into the adsorption tower e to perform E 3 R step. When the pressure in the adsorption tower a balances with the pressure in the adsorption tower e, close  4   a , 4   e.    
         [0000]     (5) The Fourth Cocurrent Equalization Depressurization, abbr. E 4 D  
         [0089]     After E 3 D step, open the sequence valve  5   a , 5   f . The gas inside the adsorption tower a goes through pipeline G 25  and enters into the adsorption tower f to perform E 4 R step. When the pressure in the adsorption tower a balances with the pressure in the adsorption tower f, close  5   f.    
         [0000]     (6) The Fifth Cocurrent Equalization Depressurization, abbr. E 5 D  
         [0090]     After E 4 D step, open the sequence valve  5   g . The gas inside the adsorption tower a goes through pipeline G 25  and enters into the adsorption tower g to perform E 5 R step. When the pressure in the adsorption tower a balances with the pressure in the adsorption tower g, close  5   f , 5   a.    
         [0000]     (7) The Sixth Cocurrent Equalization Depressurization, abbr. E 6 D  
         [0091]     After E 5 D step, open the sequence valve  6   a , 6   h . The gas inside the adsorption tower a goes through pipeline G 26  and enters into the adsorption tower h to perform E 6 R step. When the pressure in the adsorption tower a balances with the pressure in the adsorption tower h, close  6   h.    
         [0000]     (8) Backward Depressurization BD  
         [0092]     After E 6 D step, open the sequence valve  8   a ,KV- 15   a . The gas inside adsorption tower a is backward (BD 1 ) discharged into the buffer vessel V 6  at first, close KV- 15   a  after the pressure balance, then to open the sequence valve KV- 17   a . The gas is backward (BD 2 ) discharged into the buffer vessel V 7 , close  8   a ,KV- 17   a  after pressure balance. The backward depressurization BD step ends.  
         [0000]     (9) The Sixth Backward Equalization Repressurization, abbr. E 6 R  
         [0093]     After BD step, open the sequence valve  6   a , 6   b . The gas inside the adsorption tower b goes through pipeline G 26  and enters into the adsorption tower a to perform E 6 R step. When the pressure in the adsorption tower b balances with the pressure in the adsorption tower a, close  6   a , 6   b.    
         [0000]     (10) The Fifth Backward Equalization Repressurization, abbr. E 5 R  
         [0094]     After E 6 R step, open the sequence valve  5   a , 5   c . The gas inside the adsorption tower c goes through pipeline G 25  and enters into the adsorption tower a to perform E 5 R step. When the pressure in the adsorption tower c balances with the pressure in the adsorption tower a, close  5   c.    
         [0000]     (11) The Fourth Backward Equalization Repressurization, abbr. E 4 R  
         [0095]     After E 5 R step, open the sequence valve  5   d . The gas inside the adsorption tower d goes through pipeline G 25  and enters into the adsorption tower a to perform E 4 R step. When the pressure in the adsorption tower d balances with the pressure in the adsorption tower a, close  5   a , 5   d.    
         [0000]     (12) The Third Backward Equalization Repressurization, abbr. E 3 R  
         [0096]     After E 4 R step, open the sequence valve  4   a , 4   e . The gas inside the adsorption tower e goes through pipeline G 24  and enters into the adsorption tower a to perform E 3 R step. When the pressure in the adsorption tower e balances with the pressure in the adsorption tower a, close  4   e.    
         [0000]     (13) The Second Backward Equalization Repressurization, abbr. E 2 R  
         [0097]     After E 3 R step, open the sequence valve  4   f . The gas inside the adsorption tower f goes through pipeline G 24  and enters into the adsorption tower a to perform E 2 R step. When the pressure in the adsorption tower f balances with the pressure in the adsorption tower a, close  4   f , 4   a.    
         [0000]     (14) The First Backward Equalization Repressurization, abbr. E 1 R  
         [0098]     After E 2 R step, open the sequence valve  3   a , 3   g . The gas inside the adsorption tower g goes through pipeline G 23  and enters into the adsorption tower a to perform E 1 R step. When the pressure in the adsorption tower g balances with the pressure in the adsorption tower a, close  3   g.    
         [0000]     (15) Final Repressurization FR  
         [0099]     After E 1 R step, open the sequence valve KV- 16 . The outlet gas discharged from the adsorption tower in adsorption step is used to increase pressure at the top of the adsorption tower a. When the pressure in the adsorption tower a reaches the adsorption pressure, close KV- 16  and  3   a.    
         [0100]     By far, the adsorption tower a has completed a circulation and can enter into the next circulation. The steps of b to h adsorption towers are the same, but the operating time are staggered, see  FIG. 2  and  FIG. 3 .  
         [0101]     The result of this example is that the purity of carbon dioxide product is 98.5 v %. The recovery of carbon dioxide, hydrogen, nitrogen and carbon monoxide is above 99.9 v %. The concentration of carbon dioxide in hydrogen and nitrogen product is lower 0.2 v %. Electricity consumption 2 kwh per ton ammonia used for instrument and light  
         [0102]     For this example, using the given adsorbents combination of the present invention and performing the steps at the same other condition (e.g. adsorption pressure at 3.0 MPa(g), shift gas composition and temperature, adsorption cycle time, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system), the preliminary equipment invest used for removing carbon can save 8%.  
       EXAMPLE 2  
       [0103]     The conditions of this example, such as shift gas composition and temperature, adsorbent style, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system and so on other conditions are all the same with those in example 1. The adsorption pressure in this example is 1.8 MPa(g), the transporting pressure of carbon dioxide product is 0.005 MPa.  
         [0104]     The first stage device comprises of twelve adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs ten times in the working procedure. The second stage device comprises of eight adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs six times in the working procedure. In the first stage, carbon dioxide is purified to over 98 v % for synthesizing carbamide. In the second stage, the outlet gas of the first stage is further purified to meet the requirement of the next program in synthetic ammonia production. The concentration of carbon dioxide in hydrogen, nitrogen at the top outlet of the adsorption tower of the second stage is controlled lower 0.8 v %.  
         [0105]     In the first stage, the adsorption tower sequentially undergoes such pressure swing adsorption steps in one circulation period as adsorption A, first two-end equalization depressurization  2 E 1 D′, second two-end equalization depressurization  2 E 2 D′, third two-end equalization depressurization  2 E 3 D′, fourth two-end equalization depressurization  2 E 4 D′, fifth two-end equalization depressurization  2 E 5 D′, sixth two-end equalization depressurization  2 E 6 D′, seventh two-end equalization depressurization  2 E 7 D′, eighth two-end equalization depressurization  2 E 8 D′, ninth two-end equalization depressurization  2 E 9 D′, tenth two-end equalization depressurization  2 E 10 D′, carbon dioxide product backward depressurization BD, second stage gas repressurization  2 ER, tenth two-end equalization repressurization  2 E 10 R′ ninth two-end equalization repressurization  2 E 9 R′ eighth two-end equalization repressurization  2 E 8 R′ seventh two-end equalization repressurization  2 E 7 R′, sixth two-end equalization repressurization  2 E 6 R′, fifth two-end equalization repressurization  2 E 5 R′, fourth two-end equalization repressurization  2 E 4 R′, third two-end equalization repressurization  2 E 3 R′, second two-end equalization repressurization  2 E 2 R first two-end equalization repressurization  2 E 1 R, final repressurization FR. The gas obtained from the first stage in carbon dioxide product depressurization BD step is carbon dioxide product. In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, fourth equalization depressurization E 4 D, fifth equalization depressurization E 5 D, sixth equalization depressurization E 6 D, backward depressurization BD, sixth equalization repressurization E 6 R, fifth equalization repressurization E 5 R, fourth equalization repressurization E 4 R, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The gas mixture discharged from the outlet of the absorption tower of the second stage in adsorption step is mainly nitrogen and hydrogen product, wherein containing little carbon monoxide and methane in it. The gas discharged from the second stage in backward depressurization BD step is returned into the adsorption tower of the first stage which has completed carbon dioxide product backward depressurization BD step totally to pressurize, abbr. 2 ER.  
         [0106]     The result of this example is that the purity of carbon dioxide product is 98 v %, the recovery of carbon dioxide, hydrogen, nitrogen and carbon monoxide is above 99.8 v %. The concentration of carbon dioxide in hydrogen and nitrogen product is lower 0.8 v %, Electricity consumption 2 kwh per ton ammonia used for instrument and light.  
         [0107]     For this example, using the given adsorbents combination of the present invention and performing the steps at the same other conditions (e.g. adsorption pressure at 1.8 MPa(g), shift gas composition and temperature, adsorption cycle time, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system), the preliminary equipment invest used for removing carbon can save 9%.  
       EXAMPLE 3  
       [0108]     The conditions of this example, such as shift gas composition and temperature, adsorbent style, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system and so on other conditions are all the same with those in example 1. The adsorption pressure in this example is 3.0 MPa(g), the transporting pressure of carbon dioxide product is 0.005 MPa.  
         [0109]     The first stage device comprises of twelve adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs ten times in the working procedure. The second stage device comprises of eight adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs six times in the working procedure. In the first stage, carbon dioxide is purified to over 98 v % for synthesizing carbamide; in the second stage, the outlet gas of the first stage is further purified to meet the requirement of the next program in synthetic ammonia production. The concentration of carbon dioxide in hydrogen, nitrogen at the top outlet of the adsorption tower of the second stage is controlled lower 0.2 v %.  
         [0110]     In the first stage, the adsorption tower sequentially undergoes such pressure swing adsorption steps in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, fourth equalization depressurization E 4 D, fifth equalization depressurization E 5 D, sixth equalization depressurization E 6 D, seventh equalization depressurization E 7 D, eighth two-end equalization depressurization  2 E 8 D′, ninth two-end equalization depressurization  2 E 9 D′, two-end tenth equalization depressurization  2 E 10 D′, carbon dioxide product backward depressurization BD, second stage gas repressurization  2 ER, tenth two-end equalization repressurization  2 E 10 R′ ninth two-end equalization repressurization  2 E 9 R′ eighth two-end equalization repressurization  2 E 8 R′ seventh equalization repressurization E 7 R, sixth equalization repressurization E 6 R, fifth equalization repressurization E 5 R, fourth equalization repressurization E 4 R, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The gas obtained from the first stage in carbon dioxide product depressurization BD step is carbon dioxide product. In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, fourth equalization depressurization E 4 D, fifth equalization depressurization E 5 D, sixth equalization depressurization E 6 D, backward depressurization BD, sixth equalization repressurization E 6 R, fifth equalization repressurization E 5 R, fourth equalization repressurization E 4 R, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The gas mixture discharged from the outlet of the absorption tower of the second stage in adsorption step is mainly nitrogen and hydrogen product, wherein containing little carbon monoxide and methane in it. The gas discharged from the second stage in backward depressurization BD step is returned into the adsorption tower of the first stage which has completed carbon dioxide product backward depressurization BD step totally to pressurize, abbr. 2 ER.  
         [0111]     The result of this example is that the purity of carbon dioxide product is 98 v %, the recovery of carbon dioxide, hydrogen, nitrogen and carbon monoxide is above 99.9 v %. The concentration of carbon dioxide in hydrogen and nitrogen product is lower 0.2 v %. Electricity consumption 2 kwh per ton ammonia used for instrument and light.  
         [0112]     For this example, using the given adsorbents combination of the present invention and performing the steps at the same other conditions (e.g. adsorption pressure at 3.0 MPa(g), shift gas composition and temperature, adsorption cycle time, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system), the preliminary equipment invest used for removing carbon can save 7%.  
       EXAMPLE 4  
       [0113]     The conditions of this example, such as shift gas composition and temperature, adsorbent style, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system and so on other conditions are all the same with those in example 1. The adsorption pressure in this example is 1.8 MPa(g), the transporting pressure of carbon dioxide product is 0.005 MPa.  
         [0114]     The first stage device comprises of thirteen adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs eleven times in the working procedure. The second stage device comprises of six adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs four times in the working procedure. In the first stage, carbon dioxide is purified to over 98 v % for synthesizing carbamide; in the second stage, the outlet gas of the first stage is further purified to meet the requirement of the next program in synthetic ammonia production. The concentration of carbon dioxide in hydrogen, nitrogen at the top outlet of the adsorption tower of the second stage is controlled lower 0.8 v %.  
         [0115]     In the first stage, the adsorption tower sequentially undergoes such pressure swing adsorption steps in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, fourth equalization depressurization E 4 D, fifth equalization depressurization E 5 D, sixth equalization depressurization E 6 D, seventh equalization depressurization E 7 D, eighth two-end equalization depressurization  2 E 8 D′, ninth two-end equalization depressurization  2 E 9 D′, tenth two-end equalization depressurization  2 E 10 D′, eleventh two-end equalization depressurization  2 E 11 D′, carbon dioxide product backward depressurization BD, second stage gas repressurization  2 ER, eleventh two-end equalization repressurization  2 E 11 R′ tenth two-end equalization repressurization  2 E 10 R′ ninth two-end equalization repressurization  2 E 9 R′ eighth two-end equalization repressurization  2 E 8 R′, seventh equalization repressurization E 7 R, sixth equalization repressurization E 6 R, fifth equalization repressurization E 5 R, fourth equalization repressurization E 4 R, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The gas obtained from the first stage in carbon dioxide product depressurization BD step is carbon dioxide product. In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 11 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, fourth equalization depressurization E 4 D, backward depressurization BD, fourth equalization repressurization E 4 R, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 11 R, final repressurization FR. The gas mixture discharged from the outlet of the absorption tower of the second stage in adsorption step is mainly nitrogen and hydrogen product, wherein containing little carbon monoxide and methane in it. The gas discharged from the second stage in backward depressurization BD step is returned into the adsorption tower of the first stage which has completed carbon dioxide product backward depressurization BD step totally to pressurize, abbr. 2 ER.  
         [0116]     The result of this example is that the purity of carbon dioxide product is 98 v %. The recovery of carbon dioxide, hydrogen, nitrogen and carbon monoxide is above 99.5 v %. The concentration of carbon dioxide in hydrogen and nitrogen product is lower 0.8 v %. Electricity consumption 2 kwh per ton ammonia used for instrument and light.  
         [0117]     For this example, using the given adsorbents combination of the present invention and performing the steps at the same other conditions (e.g. adsorption pressure at 1.80 MPa(g), shift gas composition and temperature, adsorption cycle time, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system), the preliminary equipment invest used for removing carbon can save 7%.  
       EXAMPLE 5  
       [0118]     The conditions of this example, such as shift gas composition and temperature, adsorbent style, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system and so on other conditions are all the same with those in example 1. The adsorption pressure in this example is 0.6 MPa(g), the transporting pressure of carbon dioxide product is 0.005 MPa.  
         [0119]     The first stage device comprises of twelve adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs ten times in the working procedure. The second stage device comprises of six adsorption towers Single tower is simultaneously in an adsorption step and the pressure equalization step performs three times in the working procedure. In the first stage, carbon dioxide is purified to over 98 v % for synthesizing carbamide; in the second stage, the outlet gas of the first stage is further purified to meet the requirement of the next program in synthetic ammonia production. The concentration of carbon dioxide in hydrogen, nitrogen at the top outlet of the adsorption tower of the second stage is controlled lower 0.2 v %.  
         [0120]     In the first stage, the adsorption tower sequentially undergoes such pressure swing adsorption steps in one circulation period as adsorption A, first two-end equalization depressurization  2 E 1 D′, second two-end equalization depressurization  2 E 2 D′, third two-end equalization depressurization  2 E 3 D′, fourth two-end equalization depressurization  2 E 4 D′, fifth two-end equalization depressurization  2 E 5 D′, sixth two-end equalization depressurization  2 E 6 D′, seventh two-end equalization depressurization  2 E 7 D′, eighth two-end equalization depressurization  2 E 8 D′, ninth two-end equalization depressurization  2 E 9 D′, tenth two-end equalization depressurization  2 E 10 D′, carbon dioxide product backward depressurization BD, evacuation VC, second stage gas repressurization  2 ER, tenth two-end equalization repressurization  2 E 10 R′ ninth two-end equalization repressurization  2 E 9 R′ eighth two-end equalization repressurization  2 E 8 R′ seventh two-end equalization repressurization  2 E 7 R′, sixth two-end equalization repressurization  2 E 6 R′, fifth two-end equalization repressurization  2 E 5 R′, fourth two-end equalization repressurization  2 E 4 R′, third two-end equalization repressurization  2 E 3 R′, second two-end equalization repressurization  2 E 2 R first two-end equalization repressurization  2 E 1 R, final repressurization FR. The gas obtained from the first stage in carbon dioxide product depressurization BD step and evacuation VC step is carbon dioxide product. In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, backward depressurization BD, evacuation VC, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 11 R, final repressurization FR. The gas mixture discharged from the outlet of the absorption tower of the second stage in adsorption step is mainly nitrogen and hydrogen product, wherein containing little carbon monoxide and methane in it. The gas discharged from the second stage in backward depressurization BD step and evacuation VC step is returned into the adsorption tower of the first stage which has completed evacuation VC step totally to pressurize, abbr. 2 ER.  
         [0121]     The result of this example is that the purity of carbon dioxide product is 98 v %. The recovery of carbon dioxide is above 99 v %. The recovery of hydrogen, nitrogen and carbon monoxide is above 99.9 v %. The concentration of carbon dioxide in hydrogen and nitrogen product is lower 0.2 v %. Electricity consumption 95 kwh per ton ammonia used for instrument and light.  
         [0122]     For this example, using the given adsorbents combination of the present invention and performing the steps at the same other conditions (e.g. adsorption pressure at 0.6 MPa(g), shift gas composition and temperature, adsorption cycle time, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system), the preliminary equipment invest used for removing carbon can save 12%.  
       EXAMPLE 6  
       [0123]     The conditions of this example, such as shift gas composition and temperature, adsorbent style, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system and so on other conditions are all the same with those in example 1. The adsorption pressure in this example is 0.6 MPa(g), the transporting pressure of carbon dioxide product is 0.005 MPa.  
         [0124]     The first stage device comprises of thirteen adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs eleven times in the working procedure. The second stage device comprises of six adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs three times in the working procedure. In the first stage, carbon dioxide is purified to over 98 v % for synthesizing carbamide; in the second stage, the outlet gas of the first stage is further purified to meet the requirement of the next program in synthetic ammonia production. The concentration of carbon dioxide in hydrogen, nitrogen at the top outlet of the adsorption tower of the second stage is controlled lower 0.2 v %.  
         [0125]     In the first stage, the adsorption tower sequentially undergoes such pressure swing adsorption steps in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, fourth equalization depressurization E 4 D, fifth equalization depressurization E 5 D, sixth equalization depressurization E 6 D, seventh equalization depressurization E 7 D, eighth two-end equalization depressurization  2 E 8 D′, ninth two-end equalization depressurization  2 E 9 D′, tenth two-end equalization depressurization  2 E 10 D′, eleventh two-end equalization depressurization  2 E 11 D′, carbon dioxide product backward depressurization BD, evacuation VC, second stage gas repressurization  2 ER, eleventh two-end equalization repressurization  2 E 11 R′ tenth two-end equalization repressurization  2 E 10 R′ ninth two-end equalization repressurization  2 E 9 R′ eighth two-end equalization repressurization  2 E 8 R′ seventh equalization repressurization E 7 R, sixth equalization repressurization E 6 R, fifth equalization repressurization E 5 R, equalization repressurization E 4 R, third equalization repressurization E 3 R, second equalization repressurization E 2 R first equalization repressurization E 1 R, final repressurization FR. The gas obtained from the first stage in carbon dioxide product depressurization BD step and evacuation VC step is carbon dioxide product. In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, backward depressurization BD, evacuation VC, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The gas mixture discharged from the outlet of the absorption tower of the second stage in adsorption step is mainly nitrogen and hydrogen product, wherein containing little carbon monoxide and methane in it. The gas discharged from the second stage in backward depressurization BD step and evacuation VC step is returned into the adsorption tower of the first stage which has completed evacuation VC step totally to pressurize, abbr. 2 ER.  
         [0126]     The result of this example is that the purity of carbon dioxide product is 98 v %. The recovery of carbon dioxide, hydrogen, nitrogen and carbon monoxide is above 99.9 v %. The concentration of carbon dioxide in hydrogen and nitrogen product is lower 0.2 v %. Electricity consumption 95 kwh per ton ammonia used for instrument and light.  
         [0127]     For this example, using the given adsorbents combination of the present invention and performing the steps at the same other conditions (e.g. adsorption pressure at 0.6 MPa(g), shift gas composition and temperature, adsorption cycle time, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system), the preliminary equipment invest used for removing carbon can save 7%.  
       EXAMPLE 7  
       [0128]     The conditions of this example, such as shift gas composition and temperature, adsorbent style, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system and so on other conditions are all the same with those in example 1. The adsorption pressure in this example is 0.8 MPa(g), the transporting pressure of carbon dioxide product is 0.005 MPa.  
         [0129]     The first stage device comprises of thirteen adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs eleven times in the working procedure. The second stage device comprises of seven adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs four times in the working procedure. In the first stage, carbon dioxide is purified to over 98 v % for synthesizing carbamide; in the second stage, the outlet gas of the first stage is further purified to meet the requirement of the next program in synthetic ammonia production. The concentration of carbon dioxide in hydrogen, nitrogen at the top outlet of the adsorption tower of the second stage is controlled lower 0.2 v %.  
         [0130]     In the first stage, the adsorption tower sequentially undergoes such pressure swing adsorption steps in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, fourth equalization depressurization E 4 D, fifth equalization depressurization E 5 D, sixth equalization depressurization E 6 D, seventh equalization depressurization E 7 D, eighth two-end equalization depressurization  2 E 8 D′, ninth two-end equalization depressurization  2 E 9 D′, tenth two-end equalization depressurization  2 E 10 D′, eleventh two-end equalization depressurization  2 E 11 D′, carbon dioxide product backward depressurization BD, second stage gas repressurization  2 ER, eleventh two-end equalization repressurization  2 E 11 R′ tenth two-end equalization repressurization  2 E 10 R′ ninth two-end equalization repressurization  2 E 9 R′ eighth two-end equalization repressurization  2 E 8 R′ seventh equalization repressurization E 7 R, sixth equalization repressurization E 6 R, fifth equalization repressurization E 5 R, equalization repressurization E 4 R, third equalization repressurization E 3 R, second equalization repressurization E 2 R first equalization repressurization E 1 R, final repressurization FR. The gas obtained from the first stage in carbon dioxide product depressurization BD step is carbon dioxide product. In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, fourth equalization depressurization E 4 D, backward depressurization BD, evacuation VC, fourth equalization repressurization E 4 R, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The gas mixture discharged from the outlet of the absorption tower of the second stage in adsorption step is mainly nitrogen and hydrogen product, wherein containing little carbon monoxide and methane in it. The gas discharged from the second stage in backward depressurization BD step and evacuation VC step is returned into the adsorption tower of the first stage which has completed carbon dioxide product backward depressurization BD step totally to pressurize, abbr. 2 ER.  
         [0131]     The result of this example is that the purity of carbon dioxide product is 98 v %. The recovery of carbon dioxide, hydrogen, nitrogen and carbon monoxide is above 99.9 v %. The concentration of carbon dioxide in hydrogen and nitrogen product is lower 0.2 v %. Electricity consumption 65 kwh per ton ammonia used for instrument and light.  
         [0132]     For this example, using the given adsorbents combination of the present invention and performing the steps at the same other conditions (e.g. adsorption pressure at 0.8 MPa(g), shift gas composition and temperature, adsorption cycle time, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system), the preliminary equipment invest used for removing carbon can save 7%.  
       EXAMPLE 8  
       [0133]     The conditions of this example, such as shift gas composition and temperature, adsorbent style, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system and so on other conditions are all the same with those in example 1. The adsorption pressure in this example is 0.6 MPa(g), the transporting pressure of carbon dioxide product is 0.005 MPa.  
         [0134]     The first stage device comprises of thirteen adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs eleven times in the working procedure. The second stage device comprises of four adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs two times in the working procedure. In the first stage, carbon dioxide is purified to over 98 v % for synthesizing carbamide; in the second stage, the outlet gas of the first stage is further purified to meet the requirement of the next program in synthetic ammonia production. The concentration of carbon dioxide in hydrogen, nitrogen at the top outlet of the adsorption tower of the second stage is controlled lower 0.2 v %.  
         [0135]     In the first stage, the adsorption tower sequentially undergoes such pressure swing adsorption steps in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, fourth equalization depressurization E 4 D, fifth equalization depressurization E 5 D, sixth equalization depressurization E 6 D, seventh equalization depressurization E 7 D, eighth two-end equalization depressurization  2 E 8 D′, ninth two-end equalization depressurization  2 E 9 D′, tenth two-end equalization depressurization  2 E 10 D′, eleventh two-end equalization depressurization  2 E 11 D′, carbon dioxide product backward depressurization BD, evacuation VC, second stage gas repressurization  2 ER, eleventh two-end equalization repressurization  2 E 11 R′ tenth two-end equalization repressurization  2 E 10 R′ ninth two-end equalization repressurization  2 E 9 R′ eighth two-end equalization repressurization  2 E 8 R′ seventh equalization repressurization E 7 R, sixth equalization repressurization E 6 R, fifth equalization repressurization E 5 R, fourth equalization repressurization E 4 R, third equalization repressurization E 3 R, second equalization repressurization E 2 R first equalization repressurization E 1 R, final repressurization FR. The gas obtained from the first stage in carbon dioxide product depressurization BD step and evacuation VC step is carbon dioxide product. In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, backward depressurization BD, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The gas mixture discharged from the outlet of the absorption tower of the second stage in adsorption step is mainly nitrogen and hydrogen product, wherein containing little carbon monoxide and methane in it. The gas discharged from the second stage in backward depressurization BD step is returned into the adsorption tower of the first stage which has completed evacuation VC step totally to pressurize, abbr. 2 ER.  
         [0136]     The result of this example is that the purity of carbon dioxide product is 98 v %. The recovery of carbon dioxide, hydrogen, nitrogen and carbon monoxide is above 99.9 v %. The concentration of carbon dioxide in hydrogen and nitrogen product is lower 0.2 v %. Electricity consumption 52 kwh per ton ammonia.  
         [0137]     For this example, using the given adsorbents combination of the present invention and performing the steps at the same other conditions (e.g. adsorption pressure at 0.6 MPa(g), shift gas composition and temperature, adsorption cycle time, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system), the preliminary equipment invest used for removing carbon can save 7%.  
       EXAMPLE 9  
       [0138]     The conditions of this example, such as shift gas composition and temperature, adsorbent style, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system and so on other conditions are all the same with those in example 1. The adsorption pressure in this example is 0.8 MPa(g), the transporting pressure of carbon dioxide product is 0.005 MPa.  
         [0139]     The first stage device comprises of thirteen adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs eleven times in the working procedure. The second stage device comprises of five adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs two times in the working procedure. In the first stage, carbon dioxide is purified to over 98 v % for synthesizing carbamide; in the second stage, the outlet gas of the first stage is further purified to meet the requirement of the next program in synthetic ammonia production. The concentration of carbon dioxide in hydrogen, nitrogen at the top outlet of the adsorption tower of the second stage is controlled lower 0.2 v %.  
         [0140]     In the first stage, the adsorption tower sequentially undergoes such pressure swing adsorption steps in one circulation period as adsorption A, first two-end equalization depressurization  2 E 1 D′, second two-end equalization depressurization  2 E 2 D′, third two-end equalization depressurization  2 E 3 D′, fourth two-end equalization depressurization  2 E 4 D′, fifth two-end equalization depressurization  2 E 5 D′, sixth two-end equalization depressurization  2 E 6 D′, seventh two-end equalization depressurization  2 E 7 D′, eighth two-end equalization depressurization  2 E 8 D′, ninth two-end equalization depressurization  2 E 9 D′, tenth two-end equalization depressurization  2 E 10 D′, eleventh two-end equalization depressurization  2 E 11 D′, carbon dioxide product backward depressurization BD, second stage gas repressurization  2 ER, eleventh two-end equalization repressurization  2 E 11 R′ tenth two-end equalization repressurization  2 E 10 R′ ninth two-end equalization repressurization  2 E 9 R′ eighth two-end equalization repressurization  2 E 8 R′ seventh two-end equalization repressurization  2 E 7 R′, sixth two-end equalization repressurization  2 E 6 R′, fifth two-end equalization repressurization  2 E 5 R′, fourth two-end equalization repressurization  2 E 4 R′, third two-end equalization repressurization  2 E 3 R′, second two-end equalization repressurization  2 E 2 R′ first two-end equalization repressurization  2 E 1 R′, final repressurization FR. The gas obtained from the first stage in carbon dioxide product depressurization BD step is carbon dioxide product. In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, cocurrent depressurization PP, backward depressurization BD, purge P, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The gas mixture discharged from the adsorption tower in cocurrent depressurization PP step is used directly to purge the adsorption tower that has completed backward depressurization BD step by regulating its flow. The impurity adsorbed on the adsorbent is desorbed. The gas mixture discharged from the outlet of the adsorption tower of the second stage in adsorption step is mainly nitrogen and hydrogen product, wherein containing little carbon monoxide and methane in it. The gas discharged from the second stage in backward depressurization BD step and purge P step is returned into the adsorption tower of the first stage which has completed carbon dioxide product backward depressurization BD step totally to pressurize, abbr. 2 ER.  
         [0141]     The result of this example is that the purity of carbon dioxide product is 98 v %. The recovery of carbon dioxide, hydrogen, nitrogen and carbon monoxide is above 99.9 v %. The concentration of carbon dioxide in hydrogen and nitrogen product is lower 0.8 v %. Electricity consumption is 3 kwh per ton ammonia.  
         [0142]     For this example, using the given adsorbents combination of the present invention and performing the steps at the same other conditions (e.g. adsorption pressure at 0.8 MPa(g), shift gas composition and temperature, adsorption cycle time, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system). Electricity consumption per ton ammonia decrease 30%, the preliminary equipment invest used for removing carbon can save 7%.  
       EXAMPLE 10  
       [0143]     The conditions of this example, such as shift gas composition and temperature, adsorbent style, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system and so on other conditions are all the same with those in example 1. The adsorption pressure in this example is 0.8 MPa(g), the transporting pressure of carbon dioxide product is 0.005 MPa.  
         [0144]     The first stage device comprises of thirteen adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs eleven times in the working procedure. The second stage device comprises of seven adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs two times in the working procedure. In the first stage, carbon dioxide is purified to over 98 v % for synthesizing carbamide; in the second stage, the outlet gas of the first stage is further purified to meet the requirement of the next program in synthetic ammonia production. The concentration of carbon dioxide in hydrogen, nitrogen at the top outlet of the adsorption tower of the second stage is controlled lower 0.2 v %.  
         [0145]     In the first stage, the adsorption tower sequentially undergoes such pressure swing adsorption steps in one circulation period as adsorption A, first two-end equalization depressurization  2 E 1 D′, second two-end equalization depressurization  2 E 2 D′, third two-end equalization depressurization  2 E 3 D′, fourth two-end equalization depressurization  2 E 4 D′, fifth two-end equalization depressurization  2 E 5 D′, sixth two-end equalization depressurization  2 E 6 D′, seventh two-end equalization depressurization  2 E 7 D′, eighth two-end equalization depressurization  2 E 8 D′, ninth two-end equalization depressurization  2 E 9 D′, tenth two-end equalization depressurization  2 E 10 D′, eleventh two-end equalization depressurization  2 E 11 D′, carbon dioxide product backward depressurization BD, second stage gas repressurization  2 ER, eleventh two-end equalization repressurization  2 E 9 R′ tenth two-end equalization repressurization  2 E 10 R′ ninth two-end equalization repressurization  2 E 9 R′ eighth two-end equalization repressurization  2 E 8 R′ seventh two-end equalization repressurization  2 E 7 R′, sixth two-end equalization repressurization  2 E 6 R′, fifth two-end equalization repressurization  2 E 5 R′, fourth two-end equalization repressurization  2 E 4 R′, third two-end equalization repressurization  2 E 3 R′, second two-end equalization repressurization  2 E 2 R′ first two-end equalization repressurization  2 E 1 R′, final repressurization FR. The gas obtained from the first stage in carbon dioxide product depressurization BD step is carbon dioxide product. In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, cocurrent depressurization PP 1 , cocurrent depressurization PP 2 , cocurrent depressurization PP 3 , backward depressurization BD, purge P 1 , purge P 2 , purge P 3 , second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The gas mixture discharged from the adsorption tower in cocurrent depressurization PP 1  step is used directly to purge the adsorption tower that has completed purge P 2  step by regulating its flow. The impurity adsorbed on the adsorbent is desorbed. The gas mixture discharged from the adsorption tower in cocurrent depressurization PP 2  step is used directly to purge the adsorption tower that has completed purge P 1  step by regulating its flow. The gas mixture discharged from the adsorption tower in cocurrent depressurization PP 3  step is used directly to purge the adsorption tower that has completed backward depressurization BD step by regulating its flow. The impurity adsorbed on the adsorbent is desorbed. The gas mixture discharged from the outlet of the adsorption tower of the second stage in adsorption step is mainly nitrogen and hydrogen product, wherein containing little carbon monoxide and methane in it. The gas discharged from the second stage in backward depressurization BD step and purge P 1  step and purge P 2  step and purge P 3  step is returned into the adsorption tower of the first stage which has completed carbon dioxide product backward depressurization BD step totally to pressurize, abbr. 2 ER.  
         [0146]     The result of this example is that the purity of carbon dioxide product is 98 v %. The recovery of carbon dioxide, hydrogen, nitrogen and carbon monoxide is above 99.9 v %. The concentration of carbon dioxide in hydrogen and nitrogen product is lower 0.2 v %, Electricity consumption is 2 kwh per ton ammonia. For this example, using the given adsorbents combination of the present invention and performing the steps at the same other conditions (e.g. adsorption pressure at 0.8 MPa(g), shift gas composition and temperature, adsorption cycle time, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system). Electricity consumption per ton ammonia decrease 30%, the preliminary equipment invest used for removing carbon can save 7%.  
       EXAMPLE 11  
       [0147]     The conditions of this example, such as shift gas composition and temperature, adsorbent style, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system and so on other conditions are all the same with those in example 1. The adsorption pressure in this example is 0.9 MPa(g), the transporting pressure of carbon dioxide product is 0.005 MPa.  
         [0148]     The first stage device comprises of thirteen adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs eleven times in the working procedure. The second stage device comprises of seven adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs two times in the working procedure. In the first stage, carbon dioxide is purified to over 98 v % for synthesizing carbamide; in the second stage, the outlet gas of the first stage is further purified to meet the requirement of the next program in synthetic ammonia production. The concentration of carbon dioxide in hydrogen, nitrogen at the top outlet of the adsorption tower of the second stage is controlled lower 0.2 v %.  
         [0149]     In the first stage, the adsorption tower sequentially undergoes such pressure swing adsorption steps in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, fourth equalization depressurization E 4 D, fifth equalization depressurization E 5 D, sixth equalization depressurization E 6 D, seventh equalization depressurization E 7 D, eighth two-end equalization depressurization  2 E 8 D′, ninth two-end equalization depressurization  2 E 9 D′, tenth two-end equalization depressurization  2 E 10 D′, eleventh two-end equalization depressurization  2 E 11 D′, carbon dioxide product backward depressurization BD, second stage gas repressurization  2 ER, eleventh two-end equalization repressurization  2 E 11 R′ tenth two-end equalization repressurization  2 E 10 R′ ninth two-end equalization repressurization  2 E 9 R′ eighth two-end equalization repressurization  2 E 8 R′ seventh equalization repressurization  2 E 7 R′, sixth equalization repressurization  2 E 6 R′, fifth equalization repressurization  2 E 5 R′, fourth equalization repressurization  2 E 4 R′, third equalization repressurization  2 E 3 R′, second equalization repressurization  2 E 2 R′ first equalization repressurization  2 E 1 R′, final repressurization FR. The gas obtained from the first stage in carbon dioxide product depressurization BD step is carbon dioxide product. In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, cocurrent depressurization PP 1 , cocurrent depressurization PP 2 , cocurrent depressurization PP 3 , backward depressurization BD, purge P 1 , purge P 2 , purge P 3 , second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The gas mixture discharged from the adsorption tower in cocurrent depressurization PP 1  step is used directly to purge the adsorption tower that has completed purge P 2  step by regulating its flow. The impurity adsorbed on the adsorbent is desorbed. The gas mixture discharged from the adsorption tower in cocurrent depressurization PP 2  step is used directly to purge the adsorption tower that has completed purge P 1  step by regulating its flow. The gas mixture discharged from the adsorption tower in cocurrent depressurization PP 3  step is used directly to purge the adsorption tower that has completed backward depressurization BD step by regulating its flow. The impurity adsorbed on the adsorbent is desorbed. The gas mixture discharged from the outlet of the adsorption tower of the second stage in adsorption step is mainly nitrogen and hydrogen product, wherein containing little carbon monoxide and methane in it. The gas discharged from the second stage in backward depressurization BD step and purge P 1  step and purge P 2  step and purge P 3  step is returned into the adsorption tower of the first stage which has completed carbon dioxide product backward depressurization BD step totally to pressurize, abbr.  2 ER. The result of this example is that the purity of carbon dioxide product is 98 v %. The recovery of carbon dioxide, hydrogen, nitrogen and carbon monoxide is above 99.9 v %. The concentration of carbon dioxide in hydrogen and nitrogen product is lower 0.2 v %, Electricity consumption is 2 kwh per ton ammonia.  
         [0150]     For this example, using the given adsorbents combination of the present invention and performing the steps at the same other conditions (e.g. adsorption pressure at 0.9 MPa(g), shift gas composition and temperature, adsorption cycle time, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system). Electricity consumption per ton ammonia decrease 30%, the preliminary equipment invest used for removing carbon can save 7%.  
       EXAMPLE 12  
       [0151]     The material gas in the present example is gas mixture containing hydrogen, such as light oil making gas, synthetic ammonia shift gas, syngas, synthetic ammonia deflating gas, methanol synthesis deflating gas, semi water gas, water gas and cracking dry gas and so on. The components of light oil making gas are shown in the following table:  
                                                                                                             Component   H2   CO2   CO   CH4   O2 + Ar   Total sulfur   Water (steam)                                Conc. % V   69   72   15   20   ≦2   6   3   7   ≦0.8   150 mg/Nm3   saturation                 Temperature ≦40            Pressure 3.0 MPa G             
 
         [0152]     In the first stage, the adsorbents in the adsorption tower from the bottom up in sequence are activated alumina and fine-porous-silicagel or activated alumina and activated carbon or activated alumina, activated carbon and molecular sieve. In the second stage, the adsorbents in the adsorption tower are activated carbon and molecular sieve or molecular sieve. This example is a pressure swing adsorption device for making hydrogen. In the gas mixture containing hydrogen, hydrogen is weakly adsorbed component, other components are strongly adsorbed component. In the first stage, the outlet hydrogen of the adsorption tower is controlled at over 80 v %, and strongly adsorbed components are concentrated to over 97 v %, but hydrogen in it is lower 0.6 v %; in the second stage, strongly adsorbed components in the outlet gas of the first stage is further purified to meet the requirement of the next procedure; hydrogen concentration at the top outlet of the adsorption tower of the second stage is controlled over 99.9 v %.  
         [0153]     The first stage device comprises of thirteen adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs eleven times in the working procedure. The second stage device comprises of six adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs four times in the working procedure.  
         [0154]     In the first stage, the adsorption tower sequentially undergoes such pressure swing adsorption steps in one circulation period as adsorption A, first two-end equalization depressurization  2 E 1 D′, second two-end equalization depressurization  2 E 2 D′, third two-end equalization depressurization  2 E 3 D′, fourth two-end equalization depressurization  2 E 4 D′, fifth two-end equalization depressurization  2 E 5 D′, sixth two-end equalization depressurization  2 E 6 D′, seventh two-end equalization depressurization  2 E 7 D′, eighth two-end equalization depressurization  2 E 8 D′, ninth two-end equalization depressurization  2 E 9 D′, tenth two-end equalization depressurization  2 E 10 D′, eleventh two-end equalization depressurization  2 E 11 D′, backward depressurization BD, second stage gas repressurization  2 ER, eleventh two-end equalization repressurization  2 E 11 R′ tenth two-end equalization repressurization  2 E 10 R′ ninth two-end equalization repressurization  2 E 9 R′ eighth two-end equalization repressurization  2 E 8 R′ seventh two-end equalization repressurization  2 E 7 R′, sixth two-end equalization repressurization  2 E 6 R′, fifth two-end equalization repressurization  2 E 5 R′, fourth two-end equalization repressurization  2 E 4 R′, third two-end equalization repressurization  2 E 3 R′, second two-end equalization repressurization  2 E 2 R′, first two-end equalization repressurization  2 E 1 R′, final repressurization FR. The gas obtained from the first stage in backward depressurization BD step is vented or for other use. In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, fourth equalization depressurization E 4 D, backward depressurization BD, fourth equalization repressurization E 4 R, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The product gas discharged from the outlet of the absorption tower of the second stage in adsorption step is mainly hydrogen. The gas discharged from the second stage in backward depressurization BD step is returned into the adsorption tower of the first stage which has completed backward depressurization BD step totally to pressurize, abbr.  2 ER.  
         [0155]     The result of this example is that the concentration of hydrogen is over 99.9 v %, the recovery of hydrogen is over 99 v %.  
       EXAMPLE 13  
       [0156]     The conditions of this example, such as material gas composition and temperature, adsorbent style, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system and so on other conditions are all the same with those in example 12. The adsorption pressure in this example is 1.8 MPa(g).  
         [0157]     The first stage device comprises of thirteen adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs eleven times in the working procedure. The second stage device comprises of five adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs three times in the working procedure.  
         [0158]     In the first stage, the adsorption tower sequentially undergoes such pressure swing adsorption steps in one circulation period as adsorption A, first two-end equalization depressurization  2 E 1 D′, second two-end equalization depressurization  2 E 2 D′, third two-end equalization depressurization  2 E 3 D′, fourth two-end equalization depressurization  2 E 4 D′, fifth two-end equalization depressurization  2 E 5 D′, sixth two-end equalization depressurization  2 E 6 D′, seventh two-end equalization depressurization  2 E 7 D′, eighth two-end equalization depressurization  2 E 8 D′, ninth two-end equalization depressurization  2 E 9 D′, tenth two-end equalization depressurization  2 E 10 D′, eleventh two-end equalization depressurization  2 E 11 D′, backward depressurization BD, second stage gas repressurization  2 ER, eleventh two-end equalization repressurization  2 E 11 R′ tenth two-end equalization repressurization  2 E 10 R′ ninth two-end equalization repressurization  2 E 9 R′ eighth two-end equalization repressurization  2 E 8 R′ seventh two-end equalization repressurization  2 E 7 R′, sixth two-end equalization repressurization  2 E 6 R′, fifth two-end equalization repressurization  2 E 5 R′, fourth two-end equalization repressurization  2 E 4 R′, third two-end equalization repressurization  2 E 3 R′, second two-end equalization repressurization E 2 R′, first two-end equalization repressurization  2 E 1 R′, final repressurization FR. The gas obtained from the first stage in backward depressurization BD step is vented or for other use. In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, backward depressurization BD, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The product gas discharged from the outlet of the absorption tower of the second stage in adsorption step is mainly hydrogen. The gas discharged from the second stage in backward depressurization BD step is returned into the adsorption tower of the first stage which has completed backward depressurization BD step totally to pressurize, abbr.  2 ER.  
         [0159]     The result of this example is that the concentration of hydrogen is over 99 v %, the recovery of hydrogen is over 98 v %.  
       EXAMPLE 14  
       [0160]     The conditions of this example, such as material gas composition and temperature, adsorbent style, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system and so on other conditions are all the same with those in example 12. The adsorption pressure in this example is 3.0 MPa(g).  
         [0161]     The first stage device comprises of thirteen adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs eleven times in the working procedure. The second stage device comprises of six adsorption towers, Single tower is simultaneously in an adsorption step and the pressure equalization step performs four times in the working procedure.  
         [0162]     In the first stage, the adsorption tower sequentially undergoes such pressure swing adsorption steps in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, fourth equalization depressurization E 4 D, fifth equalization depressurization E 5 D, sixth equalization depressurization E 6 D, seventh equalization depressurization E 7 D, eighth two-end equalization depressurization  2 E 8 D′, ninth two-end equalization depressurization  2 E 9 D′, tenth two-end equalization depressurization  2 E 10 D′, eleventh two-end equalization depressurization  2 E 11 D′, backward depressurization BD, second stage gas repressurization  2 ER, eleventh two-end equalization repressurization  2 E 11 R′ tenth two-end equalization repressurization  2 E 10 R′ ninth two-end equalization repressurization  2 E 9 R′ eighth two-end equalization repressurization  2 E 8 R′ seventh equalization repressurization E 7 R, sixth equalization repressurization E 6 R, fifth equalization repressurization E 5 R, fourth equalization repressurization E 4 R, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The gas obtained from the first stage in backward depressurization BD step is vented or for other use. In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, fourth equalization depressurization E 4 D, backward depressurization BD, fourth equalization repressurization E 4 R, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The product gas discharged from the outlet of the absorption tower of the second stage in adsorption step is mainly hydrogen. The gas discharged from the second stage in backward depressurization BD step is returned into the adsorption tower of the first stage which has completed backward depressurization BD step totally to pressurize, abbr.  2 ER.  
         [0163]     The result of this example is that the concentration of hydrogen is over 99.9 v %, the recovery of hydrogen is over 99 v %.  
       EXAMPLE 15  
       [0164]     The conditions of this example, such as material gas composition and temperature, adsorbent style, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system and so on other conditions are all the same with those in example 12. The adsorption pressure in this example is 1.8 MPa(g).  
         [0165]     The first stage device comprises of thirteen adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs eleven times in the working procedure. The second stage device comprises of five adsorption towers Single tower is simultaneously in an adsorption step and the pressure equalization step performs three times in the working procedure.  
         [0166]     In the first stage, the adsorption tower sequentially undergoes such pressure swing adsorption steps in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, fourth equalization depressurization E 4 D, fifth equalization depressurization E 5 D, sixth equalization depressurization E 6 D, seventh equalization depressurization E 7 D, eighth two-end equalization depressurization  2 E 8 D′, ninth two-end equalization depressurization  2 E 9 D′, tenth two-end equalization depressurization  2 E 10 D′, eleventh two-end equalization depressurization  2 E 11 D′, backward depressurization BD, second stage gas repressurization  2 ER, eleventh two-end equalization repressurization  2 E 11 R′ tenth two-end equalization repressurization  2 E 10 R′ ninth two-end equalization repressurization  2 E 9 R′ eighth two-end equalization repressurization  2 E 8 R′ seventh equalization repressurization E 7 R, sixth equalization repressurization E 6 R, fifth equalization repressurization E 5 R, fourth equalization repressurization E 4 R, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The gas obtained from the first stage in backward depressurization BD step is vented or for other use. In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, backward depressurization BD, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The product gas discharged from the outlet of the absorption tower of the second stage in adsorption step is mainly hydrogen. The gas discharged from the second stage in backward depressurization BD step is returned into the adsorption tower of the first stage which has completed backward depressurization BD step totally to pressurize, abbr.  2 ER.  
         [0167]     The result of this example is that the concentration of hydrogen is over 99 v %, the recovery of hydrogen is over 98 v %.  
       EXAMPLE 16  
       [0168]     The conditions of this example, such as material gas composition and temperature, adsorbent style, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system and so on other conditions are all the same with those in example 12. The adsorption pressure in this example is 0.5 MPa(g).  
         [0169]     The first stage device comprises of twelve adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs ten times in the working procedure. The second stage device comprises of five adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs two times in the working procedure.  
         [0170]     In the first stage, the adsorption tower sequentially undergoes such pressure swing adsorption steps in one circulation period as adsorption A, first two-end equalization depressurization  2 E 1 D′, second two-end equalization depressurization  2 E 2 D′, third two-end equalization depressurization  2 E 3 D′, fourth two-end equalization depressurization  2 E 4 D′, fifth two-end equalization depressurization  2 E 5 D′, sixth two-end equalization depressurization  2 E 6 D′, seventh two-end equalization depressurization  2 E 7 D′, eighth two-end equalization depressurization  2 E 8 D′, ninth two-end equalization depressurization  2 E 9 D′, tenth two-end equalization depressurization  2 E 10 D′, backward depressurization BD, evacuation VC, second stage gas repressurization  2 ER, tenth two-end equalization repressurization  2 E 10 R′ ninth two-end equalization repressurization  2 E 9 R′ eighth two-end equalization repressurization  2 E 8 R′ seventh two-end equalization repressurization  2 E 7 R′, sixth two-end equalization repressurization  2 E 6 R′, fifth two-end equalization repressurization  2 E 5 R′, fourth two-end equalization repressurization E 4 R, third two-end equalization repressurization  2 E 3 R′, second two-end equalization repressurization  2 E 2 R′, first two-end equalization repressurization  2 E 1 R′, final repressurization FR. The gas obtained from the first stage in backward depressurization BD step is vented or for other use. In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, backward depressurization BD, evacuation VC, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The product gas discharged from the outlet of the absorption tower of the second stage in adsorption step is mainly hydrogen. The gas discharged from the second stage in backward depressurization BD step and evacuation VC step is returned into the adsorption tower of the first stage which has completed backward depressurization BD step totally to pressurize, abbr.  2 ER.  
         [0171]     The result of this example is that the concentration of hydrogen is over 99 v %, the recovery of hydrogen is over 99.5 v %.  
       EXAMPLE 17  
       [0172]     The conditions of this example, such as material gas composition and temperature, adsorbent style, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system and so on other conditions are all the same with those in example 12. The adsorption pressure in this example is 0.5 MPa(g).  
         [0173]     The first stage device comprises of thirteen adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs eleven times in the working procedure. The second stage device comprises of five adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs two times in the working procedure.  
         [0174]     In the first stage, the adsorption tower sequentially undergoes such pressure swing adsorption steps in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, fourth equalization depressurization E 4 D, fifth equalization depressurization E 5 D, sixth equalization depressurization E 6 D, seventh equalization depressurization E 7 D, eighth two-end equalization depressurization  2 E 8 D′, ninth two-end equalization depressurization  2 E 9 D′, tenth two-end equalization depressurization  2 E 10 D′, eleventh two-end equalization depressurization  2 E 11 D′, backward depressurization BD, evacuation VC, second stage gas repressurization  2 ER, eleventh two-end equalization repressurization  2 E 11 R′ tenth two-end equalization repressurization  2 E 10 R′ ninth two-end equalization repressurization  2 E 9 R′ eighth two-end equalization repressurization  2 E 8 R′ seventh equalization repressurization E 7 R, sixth equalization repressurization E 6 R, fifth equalization repressurization E 5 R, fourth equalization repressurization E 4 R, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The gas obtained from the first stage in backward depressurization BD step is vented or for other use. In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, backward depressurization BD, evacuation VC, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The product gas discharged from the outlet of the absorption tower of the second stage in adsorption step is mainly hydrogen. The gas discharged from the second stage in backward depressurization BD step is returned into the adsorption tower of the first stage which has completed backward depressurization BD step and evacuation VC step totally to pressurize, abbr.  2 ER.  
         [0175]     The result of this example is that the concentration of hydrogen is over 99 v %, the recovery of hydrogen is over 99.5 v %.  
       EXAMPLE 18  
       [0176]     The conditions of this example, such as material gas composition and temperature, adsorbent style, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system and so on other conditions are all the same with those in example 12. The adsorption pressure in this example is 0.5 MPa(g).  
         [0177]     The first stage device comprises of thirteen adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs eleven times in the working procedure. The second stage device comprises of seven adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs four times in the working procedure.  
         [0178]     In the first stage, the adsorption tower sequentially undergoes such pressure swing adsorption steps in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, fourth equalization depressurization E 4 D, fifth equalization depressurization E 5 D, sixth equalization depressurization E 6 D, seventh equalization depressurization E 7 D, two-end eighth equalization depressurization  2 E 8 D′, two-end ninth equalization depressurization  2 E 9 D′, two-end tenth equalization depressurization  2 E 10 D′, two-end eleventh equalization depressurization  2 E 11 D′, backward depressurization BD, evacuation VC, second stage gas repressurization  2 ER, eleventh two-end equalization repressurization  2 E 11 R′ tenth two-end equalization repressurization  2 E 10 R′ ninth two-end equalization repressurization  2 E 9 R′ eighth two-end equalization repressurization  2 E 8 R′ seventh equalization repressurization E 7 R, sixth equalization repressurization E 6 R, fifth equalization repressurization E 5 R, fourth equalization repressurization E 4 R, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The gas obtained from the first stage in backward depressurization BD step is vented or for other use. In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, fourth equalization depressurization E 4 D, backward depressurization BD, evacuation VC, fourth equalization repressurization E 4 R, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The product gas discharged from the outlet of the absorption tower of the second stage in adsorption step is mainly hydrogen. The gas discharged from the second stage in backward depressurization BD step is returned into the adsorption tower of the first stage which has completed backward depressurization BD step and evacuation VC step totally to pressurize, abbr.  2 ER.  
         [0179]     The result of this example is that the concentration of hydrogen is over 99 v %, the recovery of hydrogen is over 99.5 v %.  
       EXAMPLE 19  
       [0180]     The conditions of this example, such as material gas composition and temperature, adsorbent style, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system and so on other conditions are all the same with those in example 12. The adsorption pressure in this example is 0.5 MPa(g).  
         [0181]     The first stage device comprises of thirteen adsorption towers. Single tower simultaneously is in an adsorption step and the pressure equalization step performs eleven times in the working procedure. The second stage device comprises of four adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs two times in the working procedure.  
         [0182]     In the first stage, the adsorption tower sequentially undergoes such pressure swing adsorption steps in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, fourth equalization depressurization E 4 D, fifth equalization depressurization E 5 D, sixth equalization depressurization E 6 D, seventh equalization depressurization E 7 D, eighth two-end equalization depressurization  2 E 8 D′, ninth two-end equalization depressurization  2 E 9 D′, tenth two-end equalization depressurization  2 E 10 D′, eleventh two-end equalization depressurization  2 E 11 D′, backward depressurization BD, evacuation VC, second stage gas repressurization  2 ER, eleventh two-end equalization repressurization  2 E 11 R′ tenth two-end equalization repressurization  2 E 10 R′ ninth two-end equalization repressurization  2 E 9 R′ eighth two-end equalization repressurization  2 E 8 R′ seventh equalization repressurization E 7 R, sixth equalization repressurization E 6 R, fifth equalization repressurization E 5 R, fourth equalization repressurization E 4 R, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The gas obtained from the first stage in backward depressurization BD step is vented or for other use. In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, backward depressurization BD, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The product gas discharged from the outlet of the absorption tower of the second stage in adsorption step is mainly hydrogen. The gas discharged from the second stage in backward depressurization BD step is returned into the adsorption tower of the first stage which has completed backward depressurization BD step totally to pressurize, abbr. second gas repressurization  2 ER.  
         [0183]     The result of this example is that the concentration of hydrogen is over 99 v %, the recovery of hydrogen is over 99.5 v %.  
       EXAMPLE 20  
       [0184]     The conditions of this example, such as material gas composition and temperature, adsorbent style, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system and so on other conditions are all the same with those in example 12. The adsorption pressure in this example is 0.8 MPa(g).  
         [0185]     The first stage device comprises of thirteen adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs eleven times in the working procedure. The second stage device comprises of five adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs two times in the working procedure.  
         [0186]     In the first stage, the adsorption tower sequentially undergoes such pressure swing adsorption steps in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, fourth equalization depressurization E 4 D, fifth equalization depressurization E 5 D, sixth equalization depressurization E 6 D, seventh equalization depressurization E 7 D, eighth two-end equalization depressurization  2 E 8 D′, ninth two-end equalization depressurization  2 E 9 D′, tenth two-end equalization depressurization  2 E 10 D′, eleventh two-end equalization depressurization  2 E 11 D′, backward depressurization BD, evacuation VC, second stage gas repressurization  2 ER, eleventh two-end equalization repressurization  2 E 11 R′ tenth two-end equalization repressurization  2 E 10 R′ ninth two-end equalization repressurization  2 E 9 R′ eighth two-end equalization repressurization  2 E 8 R′ seventh equalization repressurization E 7 R, sixth equalization repressurization E 6 R, fifth equalization repressurization E 5 R, fourth equalization repressurization E 4 R, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The gas obtained from the first stage in backward depressurization BD step is vented or for other use; In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, cocurrent depressurization PP, backward depressurization BD, purge P second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The gas mixture discharged from the adsorption tower in cocurrent depressurization PP step is used directly to purge the adsorption tower that has completed backward depressurization BD step by regulating its flow. The impurity adsorbed on the adsorbent is desorbed. The product gas discharged from the outlet of the absorption tower of the second stage in adsorption step is mainly hydrogen. The gas discharged from the second stage in backward depressurization BD step is returned into the adsorption tower of the first stage which has completed backward depressurization BD step and evacuation VC step totally to pressurize, abbr.  2 ER.  
         [0187]     The result of this example is that the concentration of hydrogen is over 99.9 v %, the recovery of hydrogen is over 99.8 v %.  
       EXAMPLE 21  
       [0188]     The conditions of this example, such as material gas composition and temperature, adsorbent style, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system and so on other conditions are all the same with those in example 12. The adsorption pressure in this example is 0.8 MPa(g).  
         [0189]     The first stage device comprises of thirteen adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs eleven times in the working procedure. The second stage device comprises of seven adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs two times in the working procedure.  
         [0190]     In the first stage, the adsorption tower sequentially undergoes such pressure swing adsorption steps in one circulation period as adsorption A, first two-end equalization depressurization  2 E 1 D′, second two-end equalization depressurization  2 E 2 D′, third two-end equalization depressurization  2 E 3 D′, fourth two-end equalization depressurization  2 E 4 D′, fifth two-end equalization depressurization  2 E 5 D′, sixth two-end equalization depressurization  2 E 6 D′, seventh two-end equalization depressurization  2 E 7 D′, eighth two-end equalization depressurization  2 E 8 D′, ninth two-end equalization depressurization  2 E 9 D′, tenth two-end equalization depressurization  2 E 10 D′, eleventh two-end equalization depressurization  2 E 11 D′, product backward depressurization BD, second stage gas repressurization  2 ER, eleventh two-end equalization repressurization  2 E 9 R′ tenth two-end equalization repressurization  2 E 10 R′ ninth two-end equalization repressurization  2 E 9 R′ eighth two-end equalization repressurization  2 E 8 R′ seventh two-end equalization repressurization  2 E 7 R′, sixth two-end equalization repressurization  2 E 6 R′, fifth two-end equalization repressurization  2 E 5 R′, fourth two-end equalization repressurization  2 E 4 R′, third two-end equalization repressurization  2 E 3 R′, second two-end equalization repressurization  2 E 2 R′, first two-end equalization repressurization  2 E 1 R′, final repressurization FR. The gas obtained from the first stage in backward depressurization BD step is vented or for other use; In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, cocurrent depressurization PP 1 , cocurrent depressurization PP 2 , cocurrent depressurization PP 3 , backward depressurization BD, purge P 1 , purge P 2 , purge P 3 , second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The gas mixture discharged from the adsorption tower in cocurrent depressurization PP 1  step is used directly to purge the adsorption tower that has completed purge P 2  step by regulating its flow. The impurity adsorbed on the adsorbent is desorbed. The gas mixture discharged from the adsorption tower in cocurrent depressurization PP 2  step is used directly to purge the adsorption tower that has completed purge P 1  step by regulating its flow. The gas mixture discharged from the adsorption tower in cocurrent depressurization PP 3  step is used directly to purge the adsorption tower that has completed backward depressurization BD step by regulating its flow. The impurity adsorbed on the adsorbent is desorbed. The product gas discharged from the outlet of the absorption tower of the second stage in adsorption step is mainly hydrogen. The gas discharged from the second stage in backward depressurization BD step is returned into the adsorption tower of the first stage which has completed backward depressurization BD step and evacuation VC step totally to pressurize, abbr.  2 ER.  
         [0191]     The result of this example is that the concentration of hydrogen is over 99.9 v %, the recovery of hydrogen is over 99.8 v %.  
       EXAMPLE 22  
       [0192]     The conditions of this example, such as material gas composition and temperature, adsorbent style, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system and so on other conditions are all the same with those in example 12. The adsorption pressure in this example is 0.9 MPa(g).  
         [0193]     The first stage device comprises of thirteen adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs eleven times in the working procedure. The second stage device comprises of seven adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs two times in the working procedure.  
         [0194]     In the first stage, the adsorption tower sequentially undergoes such pressure swing adsorption steps in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, fourth equalization depressurization E 4 D, fifth equalization depressurization E 5 D, sixth equalization depressurization E 6 D, seventh equalization depressurization E 7 D, eighth two-end equalization depressurization  2 E 8 D′, ninth two-end equalization depressurization  2 E 9 D′, tenth two-end equalization depressurization  2 E 10 D′, eleventh two-end equalization depressurization  2 E 11 D′, backward depressurization BD, second stage gas repressurization  2 ER, eleventh two-end equalization repressurization  2 E 11 R′ tenth two-end equalization repressurization  2 E 10 R′ ninth two-end equalization repressurization  2 E 9 R′ eighth two-end equalization repressurization  2 E 8 R′ seventh equalization repressurization E 7 R, sixth equalization repressurization E 6 R, fifth equalization repressurization E 5 R, fourth equalization repressurization E 4 R, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The gas obtained from the first stage in backward depressurization BD step is vented or for other use; In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, cocurrent depressurization PP 1 , cocurrent depressurization PP 2 , cocurrent depressurization PP 3 , backward depressurization BD, purge P 1 , purge P 2 , purge P 3 , second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The gas mixture discharged from the adsorption tower in cocurrent depressurization PP 1  step is used directly to purge the adsorption tower that has completed purge P 2  step by regulating its flow. The impurity adsorbed on the adsorbent is desorbed. The gas mixture discharged from the adsorption tower in cocurrent depressurization PP 2  step is used directly to purge the adsorption tower that has completed purge P 1  step by regulating its flow. The gas mixture discharged from the adsorption tower in cocurrent depressurization PP 3  step is used directly to purge the adsorption tower that has completed backward depressurization BD step by regulating its flow. The impurity adsorbed on the adsorbent is desorbed. The product gas discharged from the outlet of the absorption tower of the second stage in adsorption step is mainly hydrogen. The gas discharged from the second stage in backward depressurization BD step is returned into the adsorption tower of the first stage which has completed backward depressurization BD step and evacuation VC step totally to pressurize, abbr.  2 ER.  
         [0195]     The result of this example is that the concentration of hydrogen is over 99.9 v %, the recovery of hydrogen is over 99.8 v %.  
       EXAMPLE 23  
       [0196]     The conditions of this example, such as shift gas composition and temperature, adsorbent style, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system and so on other conditions are all the same with those in example 1. The adsorption pressure in this example is 3.0 MPa(g), the transporting pressure of carbon dioxide product is 0.005 MPa.  
         [0197]     The first stage device comprises of twelve adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs ten times in the working procedure. The second stage device comprises of eight adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs six times in the working procedure. In the first stage, carbon dioxide is purified to over 98.5 v % for synthesizing carbamide. In the second stage, the outlet gas of the first stage is further purified to meet the requirement of the next program in synthetic ammonia production. The concentration of carbon dioxide in hydrogen, nitrogen at the top outlet of the adsorption tower of the second stage is controlled lower 0.2 v %.  
         [0198]     In the first stage, the adsorption tower sequentially undergoes such pressure swing adsorption steps in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, fourth equalization depressurization E 4 D, fifth equalization depressurization E 5 D, sixth equalization depressurization E 6 D, seventh equalization depressurization E 7 D, eighth equalization depressurization E 8 D, ninth equalization depressurization E 9 D, tenth equalization depressurization E 10 D, first backward depressurization BD 1 , second carbon dioxide product backward depressurization BD 2 , first stage gas repressurization  2 ER 1 , second stage gas repressurization  2 ER, tenth equalization repressurization E 10 R, ninth equalization repressurization E 9 R eighth equalization repressurization E 8 R seventh equalization repressurization E 7 R, sixth equalization repressurization E 6 R, fifth equalization repressurization E 5 R, fourth equalization repressurization E 4 R, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. After E 10 D step, the concentration of carbon dioxide at the top of the adsorption tower is over 70 v %; after BD 1  step, the concentration of carbon dioxide at the bottom of the adsorption tower is over 75 v %. The gas discharged from BD 1  step is returned into the adsorption tower of the first stage to pressurize at its bottom. The gas obtained from the first stage in second carbon dioxide product backward depressurization BD 2  step is carbon dioxide product. In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, fourth equalization depressurization E 4 D, fifth equalization depressurization E 5 D, sixth equalization depressurization E 6 D, backward depressurization BD, sixth equalization repressurization E 6 R, fifth equalization repressurization E 5 R, fourth equalization repressurization E 4 R, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The gas mixture discharged from the outlet of the absorption tower of the second stage in adsorption step is mainly nitrogen and hydrogen product, wherein containing little carbon monoxide and methane in it. The gas discharged from the second stage in backward depressurization BD step is returned into the adsorption tower of the first stage which has completed second carbon dioxide product backward depressurization BD 2  step totally to pressurize, abbr.  2 ER.  
         [0199]     The result of this example is that the purity of carbon dioxide product is 98.5 v %, the recovery of carbon dioxide, hydrogen, nitrogen and carbon monoxide is above 99.9 v %. The concentration of carbon dioxide in hydrogen and nitrogen product is lower 0.2 v %, Electricity consumption is 2 kwh per ton ammonia used for instrument and light.  
         [0200]     For this example, using the given adsorbents combination of the present invention and performing the steps at the same other conditions (e.g. adsorption pressure at 3.0 MPa(g), shift gas composition and temperature, adsorption cycle time, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system), the preliminary equipment invest used for removing carbon can save 7%.  
       EXAMPLE 24  
       [0201]     The conditions of this example, such as shift gas composition and temperature, adsorbent style, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system and so on other conditions are all the same with those in example 1. The adsorption pressure in this example is 0.7 MPa(g), the transporting pressure of carbon dioxide product is 0.005 MPa.  
         [0202]     The first stage device comprises of twelve adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs ten times in the working procedure. The second stage device comprises of six adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs three times in the working procedure. In the first stage, carbon dioxide is purified to over 98 v % for synthesizing carbamide; in the second stage, the outlet gas of the first stage is further purified to meet the requirement of the next program in synthetic ammonia production. The concentration of carbon dioxide in hydrogen, nitrogen at the top outlet of the adsorption tower of the second stage is controlled lower 0.2 v %.  
         [0203]     In the first stage, the adsorption tower sequentially undergoes such pressure swing adsorption steps in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, fourth equalization depressurization E 4 D, fifth equalization depressurization E 5 D, sixth equalization depressurization E 6 D, seventh equalization depressurization E 7 D, eighth equalization depressurization E 8 D, ninth equalization depressurization E 9 D, tenth equalization depressurization E 10 D, first backward depressurization BD 1 , second carbon dioxide product backward depressurization BD 2 , evacuation VC, first stage gas repressurization  2 ER 1 , second stage gas repressurization  2 ER, tenth equalization repressurization E 10 R, ninth equalization repressurization E 9 R eighth equalization repressurization E 8 R seventh equalization repressurization E 7 R, sixth equalization repressurization E 6 R, fifth equalization repressurization E 5 R, fourth equalization repressurization E 4 R, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 11 R, final repressurization FR. After E 10 D step, the concentration of carbon dioxide at the top of the adsorption tower is over 70 v %; after BD 1  step, the concentration of carbon dioxide at the bottom of the adsorption tower is over 75 v %. The gas discharged from BD 1  step is returned into the adsorption tower of the first stage to pressurize at its bottom. The gas obtained from the first stage in second carbon dioxide product backward depressurization BD 2  step and evacuation VC step is carbon dioxide product. In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, backward depressurization BD, evacuation VC, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The gas mixture discharged from the outlet of the absorption tower of the second stage in adsorption step is mainly nitrogen and hydrogen product, wherein containing little carbon monoxide and methane in it. The gas discharged from the second stage in backward depressurization BD step and evacuation VC step is returned into the adsorption tower of the first stage which has completed evacuation VC step totally to pressurize, abbr.  2 ER.  
         [0204]     The result of this example is that the purity of carbon dioxide product is 98% (v), the recovery of carbon dioxide is above 99 v %, the recovery of hydrogen, nitrogen and carbon monoxide is above 99.9 v %. The concentration of carbon dioxide in hydrogen and nitrogen product is lower 0.2 v %, Electricity consumption 95 kwh per ton ammonia used for instrument and light.  
         [0205]     For this example, using the given adsorbents combination of the present invention and performing the steps at the same other conditions (e.g. adsorption pressure at 0.6 MPa(g), shift gas composition and temperature, adsorption cycle time, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system), the preliminary equipment invest used for removing carbon can save 12%.  
       EXAMPLE 25 OF INVENTION  
       [0206]     The conditions of this example, such as shift gas composition and temperature, adsorbent style, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system and so on other conditions are all the same with those in example 1. The adsorption pressure in this example is 0.8 MPa(g), the transporting pressure of carbon dioxide product is 0.005 MPa.  
         [0207]     The first stage device comprises of thirteen adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs eleven times in the working procedure. The second stage device comprises of seven adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs four times in the working procedure. In the first stage, carbon dioxide is purified to over 98 v % for synthesizing carbamide; in the second stage, the outlet gas of the first stage is further purified to meet the requirement of the next program in synthetic ammonia production. The concentration of carbon dioxide in hydrogen, nitrogen at the top outlet of the adsorption tower of the second stage is controlled lower 0.2 v %.  
         [0208]     In the first stage, the adsorption tower sequentially undergoes such pressure swing adsorption steps in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, fourth equalization depressurization E 4 D, fifth equalization depressurization E 5 D, sixth equalization depressurization E 6 D, seventh equalization depressurization E 7 D, eighth equalization depressurization E 8 D, ninth equalization depressurization E 9 D, tenth equalization depressurization E 10 D, eleventh equalization depressurization E 11 D, first backward depressurization BD 1 , second carbon dioxide product backward depressurization BD 2 , first stage gas repressurization  2 ER 1 , second stage gas repressurization  2 ER, eleventh equalization repressurization E 11 R, tenth equalization repressurization E 10 R, ninth equalization repressurization E 9 R eighth equalization repressurization E 8 R seventh equalization repressurization E 7 R, sixth equalization repressurization E 6 R, fifth equalization repressurization E 5 R, fourth equalization repressurization E 4 R, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. After E 11 D step, the concentration of carbon dioxide at the top of the adsorption tower is over 70 v %; after BD 1  step, the concentration of carbon dioxide at the bottom of the adsorption tower is over 75 v %. The gas discharged from BD 1  step is returned into the adsorption tower of the first stage to pressurize at its bottom. The gas obtained from the first stage in second carbon dioxide product backward depressurization BD 2  step is carbon dioxide product. In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, fourth equalization depressurization E 4 D, backward depressurization BD, evacuation VC, fourth equalization repressurization E 4 R, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The gas mixture discharged from the outlet of the absorption tower of the second stage in adsorption step is mainly nitrogen and hydrogen product, wherein containing little carbon monoxide and methane in it. The gas discharged from the second stage in backward depressurization BD step and evacuation VC step is returned into the adsorption tower of the first stage which has completed carbon dioxide product backward depressurization BD step totally to pressurize, abbr.  2 ER.  
         [0209]     The result of this example is that the purity of carbon dioxide product is 98 v %, the recovery of carbon dioxide, hydrogen, nitrogen and carbon monoxide is above 99.9 v %. The concentration of carbon dioxide in hydrogen and nitrogen product is lower 0.2 v %, Electricity consumption 65 kwh per ton ammonia used for instrument and light.  
         [0210]     For this example, using the given adsorbents combination of the present invention and performing the steps at the same other conditions (e.g. adsorption pressure at 0.8 MPa(g), shift gas composition and temperature, adsorption cycle time, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system), the preliminary equipment invest used for removing carbon can save 7%.  
       EXAMPLE 26  
       [0211]     The conditions of this example, such as shift gas composition and temperature, adsorbent style, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system and so on other conditions are all the same with those in example 1. The adsorption pressure in this example is 0.6 MPa(g), the transporting pressure of carbon dioxide product is 0.005 MPa.  
         [0212]     The first stage device comprises of thirteen adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs eleven times in the working procedure. The second stage device comprises of four adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs two times in the working procedure. In the first stage, carbon dioxide is purified to over 98 v % for synthesizing carbamide; in the second stage, the outlet gas of the first stage is further purified to meet the requirement of the next program in synthetic ammonia production. The concentration of carbon dioxide in hydrogen, nitrogen at the top outlet of the adsorption tower of the second stage is controlled lower 0.2 v %.  
         [0213]     In the first stage, the adsorption tower sequentially undergoes such pressure swing adsorption steps in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, fourth equalization depressurization E 4 D, fifth equalization depressurization E 5 D, sixth equalization depressurization E 6 D, seventh equalization depressurization E 7 D, eighth equalization depressurization E 8 D, ninth equalization depressurization E 9 D, tenth equalization depressurization E 10 D, eleventh equalization depressurization E 11 D, first backward depressurization BD 1 , second carbon dioxide product backward depressurization BD 2 , evacuation VC, first stage gas repressurization  2 ER 1 , second stage gas repressurization  2 ER, eleventh equalization repressurization E 11 R, tenth equalization repressurization E 10 R, ninth equalization repressurization E 9 R eighth equalization repressurization E 8 R seventh equalization repressurization E 7 R, sixth equalization repressurization E 6 R, fifth equalization repressurization E 5 R, fourth equalization repressurization E 4 R, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. After E 10 D step, the concentration of carbon dioxide at the top of the adsorption tower is over 70 v %; after BD 1  step, the concentration of carbon dioxide at the bottom of the adsorption tower is over 75 v %. The gas discharged from BD 1  step is returned into the adsorption tower of the first stage to pressurize at its bottom. The gas obtained from the first stage in second carbon dioxide product backward depressurization BD 2  step and evacuation VC step is carbon dioxide product. In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, backward depressurization BD, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The gas mixture discharged from the outlet of the absorption tower of the second stage in adsorption step is mainly nitrogen and hydrogen product, wherein containing little carbon monoxide and methane in it. The gas discharged from the second stage in backward depressurization BD step is returned into the adsorption tower of the first stage which has completed evacuation VC step totally to pressurize, abbr.  2 ER.  
         [0214]     The result of this example is that the purity of carbon dioxide product is −98 v %, the recovery of carbon dioxide, hydrogen, nitrogen and carbon monoxide is above 99.9 v %. The concentration of carbon dioxide in hydrogen and nitrogen product is lower 0.8 v %, Electricity consumption 52 kwh per ton ammonia used for instrument and light.  
         [0215]     For this example, using the given adsorbents combination of the present invention and performing the steps at the same other conditions (e.g. adsorption pressure at 0.6 MPa(g), shift gas composition and temperature, adsorption cycle time, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system), the preliminary equipment invest used for removing carbon can save 7%.  
       EXAMPLE 27  
       [0216]     The conditions of this example, such as shift gas composition and temperature, adsorbent style, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system and so on other conditions are all the same with those in example 1. The adsorption pressure in this example is 0.9 MPa(g), the transporting pressure of carbon dioxide product is 0.005 MPa.  
         [0217]     The first stage device comprises of thirteen adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs eleven times in the working procedure. The second stage device comprises of seven adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs two times in the working procedure. In the first stage, carbon dioxide is purified to over 98 v % for synthesizing carbamide; in the second stage, the outlet gas of the first stage is further purified to meet the requirement of the next procedure in synthetic ammonia production. The concentration of carbon dioxide in hydrogen, nitrogen at the top outlet of the adsorption tower of the second stage is controlled lower 0.2 v %.  
         [0218]     In the first stage, the adsorption tower sequentially undergoes such pressure swing adsorption steps in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, fourth equalization depressurization E 4 D, fifth equalization depressurization E 5 D, sixth equalization depressurization E 6 D, seventh equalization depressurization E 7 D, eighth equalization depressurization E 8 D, ninth equalization depressurization E 9 D, tenth equalization depressurization E 10 D, eleventh equalization depressurization E 11 D, first backward depressurization BD 1 , second carbon dioxide product backward depressurization BD 2 , first stage gas repressurization  2 ER 1 , second stage gas repressurization  2 ER, eleventh equalization repressurization E 11 R, tenth equalization repressurization E 10 R, ninth equalization repressurization E 9 R eighth equalization repressurization E 8 R seventh equalization repressurization E 7 R, sixth equalization repressurization E 6 R, fifth equalization repressurization E 5 R, fourth equalization repressurization E 4 R, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. After E 11 D step, the concentration of carbon dioxide at the top of the adsorption tower is over 70 v %; after BD 1  step, the concentration of carbon dioxide at the bottom of the adsorption tower is over 75 v %. The gas discharged from BD 1  step is returned into the adsorption tower of the first stage to pressure at its bottom. The gas obtained from the first stage in second carbon dioxide product backward depressurization BD 2  step is carbon dioxide product. In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, cocurrent depressurization PP 1 , cocurrent depressurization PP 2 , cocurrent depressurization PP 3 , backward depressurization BD, purge P 1 , purge P 2 , purge P 3 , second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The gas mixture discharged from the adsorption tower in cocurrent depressurization PP 1  step is used directly to purge the adsorption tower that has completed purge P 2  step by regulating its flow. The impurity adsorbed on the adsorbent is desorbed. The gas mixture discharged from the adsorption tower in cocurrent depressurization PP 2  step is used directly to purge the adsorption tower that has completed purge P 1  step by regulating its flow. The gas mixture discharged from the adsorption tower in cocurrent depressurization PP 3  step is used directly to purge the adsorption tower that has completed backward depressurization BD step by regulating its flow. The impurity adsorbed on the adsorbent is desorbed. The gas mixture discharged from the outlet of the absorption tower of the second stage in adsorption step is mainly nitrogen and hydrogen product, wherein containing little carbon monoxide and methane in it. The gas discharged from the second stage in backward depressurization BD step and purge P 1  step and purge P 2  step and purge P 3  step is returned into the adsorption tower of the first stage which has completed second carbon dioxide product backward depressurization BD 2  step totally to pressurize, abbr.  2 ER.  
         [0219]     The result of this example is that the purity of carbon dioxide product is 98 v %, the recovery of carbon dioxide, hydrogen, nitrogen and carbon monoxide is above 99.9 v %. The concentration of carbon dioxide in hydrogen and nitrogen product is lower 0.2 v %, Electricity consumption is 2 kwh per ton ammonia used for instrument and light.  
         [0220]     For this example, using the given adsorbents combination of the present invention and performing the steps at the same other conditions (e.g. adsorption pressure at 0.9 MPa(g), shift gas composition and temperature, adsorption cycle time, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system). Electricity consumption per ton ammonia decrease 30%, the preliminary equipment invest used for removing carbon can save 7%.  
       EXAMPLE 28  
       [0221]     The conditions of this example, such as material gas composition and temperature, adsorbent style, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system and so on other conditions are all the same with those in example 12. The adsorption pressure in this example is 3.0 MPa(g).  
         [0222]     The first stage device comprises of twelve adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs ten times in the working procedure. The second stage device comprises of eight adsorption towers Single tower is simultaneously in an adsorption step and the pressure equalization step performs six times in the working procedure.  
         [0223]     In the first stage, the adsorption tower sequentially undergoes such pressure swing adsorption steps in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, fourth equalization depressurization E 4 D, fifth equalization depressurization E 5 D, sixth equalization depressurization E 6 D, seventh equalization depressurization E 7 D, eighth equalization depressurization E 8 D, ninth equalization depressurization E 9 D, tenth equalization depressurization E 10 D, first backward depressurization BD 1 , second backward depressurization BD 2 , first stage gas repressurization  2 ER 1 , second stage gas repressurization  2 ER, tenth equalization repressurization E 10 R ninth equalization repressurization E 9 R eighth equalization repressurization E 8 R seventh equalization repressurization E 7 R, sixth equalization repressurization E 6 R, fifth equalization repressurization E 5 R, fourth equalization repressurization E 4 R, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. After E 10 D step, the concentration of the strongly adsorbed component at the top of the adsorption tower is over 70 v %; after BD 1  step, the concentration of the strongly adsorbed component at the bottom of the adsorption tower is over 75 v %. The gas discharged from BD 1  step is returned into the adsorption tower of the first stage to pressurize at its bottom. The gas obtained from the first stage in first backward depressurization BD 1  step is vented or for other use. In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, fourth equalization depressurization E 4 D, fifth equalization depressurization E 5 D, sixth equalization depressurization E 6 D, backward depressurization BD, sixth equalization repressurization E 6 R, fifth equalization repressurization E 5 R, fourth equalization repressurization E 4 R, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 11 R, final repressurization FR. The product gas discharged from the outlet of the absorption tower of the second stage in adsorption step is mainly hydrogen. The gas discharged from the second stage in backward depressurization BD step is returned into the adsorption tower of the first stage which has completed second backward depressurization BD step totally to pressurize, abbr.  2 ER.  
         [0224]     The result of this example is that the concentration of hydrogen is over 99.9 v %, the recovery of hydrogen is over 99.8 v %.  
       EXAMPLE 29  
       [0225]     The conditions of this example, such as material gas composition and temperature, adsorbent style, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system and so on other conditions are all the same with those in example 12. The adsorption pressure in this example is 0.7 MPa(g).  
         [0226]     The first stage device comprises of twelve adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs ten times in the working procedure. The second stage device comprises of six adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs three times in the working procedure.  
         [0227]     In the first stage, the adsorption tower sequentially undergoes such pressure swing adsorption steps in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, fourth equalization depressurization E 4 D, fifth equalization depressurization E 5 D, sixth equalization depressurization E 6 D, seventh equalization depressurization E 7 D, eighth equalization depressurization E 8 D, ninth equalization depressurization E 9 D, tenth equalization depressurization E 10 D, first backward depressurization BD 1 , second backward depressurization BD 2 , evacuation VC, first stage gas repressurization  2 ER 1 , second stage gas repressurization  2 ER, tenth equalization repressurization E 10 R ninth equalization repressurization E 9 R eighth equalization repressurization E 8 R seventh equalization repressurization E 7 R, sixth equalization repressurization E 6 R, fifth equalization repressurization E 5 R, fourth equalization repressurization E 4 R, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. After E 10 D step, the concentration of the strongly adsorbed component at the top of the adsorption tower is over 70 v %; after BD 1  step, the concentration of the strongly adsorbed component at the bottom of the adsorption tower is over 75 v %. The gas discharged from BD 1  step is returned into the adsorption tower of the first stage to pressure at its bottom. The gas obtained from the first stage in second backward depressurization BD 2  step is vented or for other use. In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, backward depressurization BD, evacuation VC, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 11 R, final repressurization FR. The product gas discharged from the outlet of the absorption tower of the second stage in adsorption step is mainly hydrogen. The gas discharged from the second stage in backward depressurization BD step is returned into the adsorption tower of the first stage which has completed evacuation VC step totally to pressurize, abbr.  2 ER.  
         [0228]     The result of this example is that the concentration of hydrogen is over 99.9 v %, the recovery of hydrogen is over 99.9 v %.  
       EXAMPLE 30  
       [0229]     The conditions of this example, such as material gas composition and temperature, adsorbent style, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system and so on other conditions are all the same with those in example 12. The adsorption pressure in this example is 0.8 MPa(g).  
         [0230]     The first stage device comprises of thirteen adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs eleven times in the working procedure. The second stage device comprises of seven adsorption towers Single tower is simultaneously in an adsorption step and the pressure equalization step performs four times in the working procedure.  
         [0231]     In the first stage, the adsorption tower sequentially undergoes such pressure swing adsorption steps in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, fourth equalization depressurization E 4 D, fifth equalization depressurization E 5 D, sixth equalization depressurization E 6 D, seventh equalization depressurization E 7 D, eighth equalization depressurization E 8 D, ninth equalization depressurization E 9 D, tenth equalization depressurization E 10 D, eleventh equalization depressurization E 11 D, first backward depressurization BD 1 , second backward depressurization BD 2 , first stage gas repressurization  2 ER 1 , second stage gas repressurization  2 ER, eleventh equalization repressurization E 11 R tenth equalization repressurization E 10 R ninth equalization repressurization E 9 R eighth equalization repressurization E 8 R seventh equalization repressurization E 7 R, sixth equalization repressurization E 6 R, fifth equalization repressurization E 5 R, fourth equalization repressurization E 4 R, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. After E 11 D step, the concentration of the strongly adsorbed component at the top of the adsorption tower is over 70 v %; after BD 1  step, the concentration of the strongly adsorbed component at the bottom of the adsorption tower is over 75 v %. The gas discharged from BD 1  step is returned into the adsorption tower of the first stage to pressure at its bottom. The gas obtained from the first stage in second backward depressurization BD 2  step is vented or for other use. In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, fourth equalization depressurization E 4 D, backward depressurization BD, evacuation VC, fourth equalization repressurization E 4 R, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The product gas discharged from the outlet of the absorption tower of the second stage in adsorption step is mainly hydrogen. The gas discharged from the second stage in backward depressurization BD step is returned into the adsorption tower of the first stage which has completed second backward depressuriation BD 2  step totally to pressurize, abbr.  2 ER.  
         [0232]     The result of this example is that the concentration of hydrogen is over 99.9 v %, the recovery of hydrogen is over 99.9 v %.  
       EXAMPLE 31  
       [0233]     The conditions of this example, such as material gas composition and temperature, adsorbent style, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system and so on other conditions are all the same with those in example 12. The adsorption pressure in this example is 0.6 MPa(g).  
         [0234]     The first stage device comprises of thirteen adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs eleven times in the working procedure. The second stage device comprises of four adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs two times in the working procedure.  
         [0235]     In the first stage, the adsorption tower sequentially undergoes such pressure swing adsorption steps in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, fourth equalization depressurization E 4 D, fifth equalization depressurization E 5 D, sixth equalization depressurization E 6 D, seventh equalization depressurization E 7 D, eighth equalization depressurization E 8 D, ninth equalization depressurization E 9 D, tenth equalization depressurization E 10 D, eleventh equalization depressurization E 11 D, first backward depressurization BD 1 , second carbon dioxide product backward depressurization BD 2 , evacuation VC, first stage gas repressurization  2 ER 1 , second stage gas repressurization  2 ER, eleventh equalization repressurization E 11 R tenth equalization repressurization E 10 R ninth equalization repressurization E 9 R eighth equalization repressurization E 8 R seventh equalization repressurization E 7 R, sixth equalization repressurization E 6 R, fifth equalization repressurization E 5 R, fourth equalization repressurization E 4 R, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. After E 11 D step, the concentration of the strongly adsorbed component at the top of the adsorption tower is over 70 v %; after BD 1  step, the concentration of the strongly adsorbed component at the bottom of the adsorption tower is over 75 v %. The gas discharged from BD 1  step is returned into the adsorption tower of the first stage to pressure at its bottom. The gas obtained from the first stage in second backward depressurization BD 2  step is vented or for other use. In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, backward depressurization BD, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The product gas discharged from the outlet of the absorption tower of the second stage in adsorption step is mainly hydrogen. The gas discharged from the second stage in backward depressurization BD step is returned into the adsorption tower of the first stage which has completed evacuation VC step totally to pressurize, abbr.  2 ER.  
         [0236]     he result of this example is that the concentration of hydrogen is over 99.9 v %, the recovery of hydrogen is over 99.9 v %.  
       EXAMPLE 32  
       [0237]     The conditions of this example, such as material gas composition and temperature, adsorbent style, power equipment performance, apparatus and instrument and its control function, construction and life of special sequence valve and liquid pressure system and so on other conditions are all the same with those in example 12. The adsorption pressure in this example is 0.6 MPa(g).  
         [0238]     The first stage device comprises of thirteen adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs eleven times in the working procedure. The second stage device comprises of seven adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs two times in the working procedure.  
         [0239]     In the first stage, the adsorption tower sequentially undergoes such pressure swing adsorption steps in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, third equalization depressurization E 3 D, fourth equalization depressurization E 4 D, fifth equalization depressurization E 5 D, sixth equalization depressurization E 6 D, seventh equalization depressurization E 7 D, eighth equalization depressurization E 8 D, ninth equalization depressurization E 9 D, tenth equalization depressurization E 10 D, eleventh equalization depressurization E 11 D, first backward depressurization BD 1 , second backward depressurization BD 2 , first stage gas repressurization  2 ER 1 , second stage gas repressurization  2 ER, eleventh equalization repressurization E 11 R tenth equalization repressurization E 10 R ninth equalization repressurization E 9 R eighth equalization repressurization E 8 R seventh equalization repressurization E 7 R, sixth equalization repressurization E 6 R, fifth equalization repressurization E 5 R, fourth equalization repressurization E 4 R, third equalization repressurization E 3 R, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. After E 11 D step, the concentration of the strongly adsorbed component at the top of the adsorption tower is over 70 v %; after BD 1  step, the concentration of the strongly adsorbed component at the bottom of the adsorption tower is over 75 v %. The gas discharged from BD 1  step is returned into the adsorption tower of the first stage to pressurize at its bottom. The gas obtained from the first stage in second backward depressurization BD 2  step is vented or for other use. In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, cocurrent depressurization PP 1  cocurrent depressurization PP 2  cocurrent depressurization PP 3 , backward depressurization BD, purge P 1 , purge P 2 , purge P 3 , second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The gas mixture discharged from the adsorption tower in cocurrent depressurization PP 1  step is used directly to purge the adsorption tower that has completed purge P 2  step by regulating its flow. The impurity adsorbed on the adsorbent is desorbed. The gas mixture discharged from the adsorption tower in cocurrent depressurization PP 2  step is used directly to purge the adsorption tower that has completed purge P 1  step by regulating its flow. The gas mixture discharged from the adsorption tower in cocurrent depressurization PP 3  step is used directly to purge the adsorption tower that has completed backward depressurization BD step by regulating its flow. The impurity adsorbed on the adsorbent is desorbed. The product gas discharged from the outlet of the absorption tower of the second stage in adsorption step is mainly hydrogen. The gas discharged from the second stage in backward depressurization BD step is returned into the adsorption tower of the first stage which has completed second backward depressurization BD 2  step totally to pressurize, abbr.  2 ER.  
         [0240]     The result of this example is that the concentration of hydrogen is over 99.9 v %, the recovery of hydrogen is over 99.8 v %.  
       EXAMPLE 33  
       [0241]     The material gas in the present example is air.  
         [0242]     The components of air are shown in the following table:  
                                                                                               Component                N2   O2   Ar   Water (steam)                            Conc. % V   78   21   1   saturation                         Temperature ≦40                Pressure 0.15 MPa G             
 
         [0243]     In the first stage, the adsorbents in the adsorption tower from the bottom up in sequence are activated alumina and molecular sieve in the second stage, the adsorbent in the adsorption tower is molecular sieve. This example is a pressure swing adsorption device for making oxygen. In air, oxygen and argon is weakly adsorbed component, nitrogen and water(steam) is strongly adsorbed component. In the first stage, outlet nitrogen concentration is controlled at 78 v % (adjusting between 30-78 v % during actual operation); in the second stage, nitrogen in the outlet gas of the first stage is further purified to meet the requirement of the next procedure Oxygen concentration at the top outlet of the adsorption tower of the second stage is controlled at over 93 v %, maximum to 95 v %.  
         [0244]     The first stage device comprises of seven adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs four times in the working procedure. The second stage device comprises of four adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs once in the working procedure.  
         [0245]     In the first stage, the adsorption tower sequentially undergoes such pressure swing adsorption steps in one circulation period as adsorption A, first two-end equalization depressurization  2 E 1 D′, second two-end equalization depressurization  2 E 2 D′, third two-end equalization depressurization  2 E 3 D′, fourth two-end equalization depressurization  2 E 4 D′, evacuation VC, second stage gas repressurization  2 ER, fourth two-end equalization repressurization  2 E 4 R′, third two-end equalization repressurization  2 E 3 R′, second two-end equalization repressurization  2 E 2 R′ first two-end equalization repressurization  2 E 1 R′, final repressurization FR. In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 1 D, backward depressurization BD, first equalization repressurization E 1 R, final repressurization FR. The gas discharged from backward depressurization BD step is returned into the adsorption tower of the first stage which has completed evacuation VC step totally to pressurize. The product gas discharged from the outlet of the absorption tower of the second stage in adsorption step is mainly oxygen and a little argon.  
         [0246]     The result of this example is that the concentration of oxygen is above 93 v %, the concentration of nitrogen is above 99 v %, the recovery of oxygen is above 96.2 v %.  
       EXAMPLE 34  
       [0247]     The material gas in the present example is air.  
         [0248]     The components of air are shown in the following table:  
                                                                                               Component                N2   O2   Ar   Water (steam)                            Conc. % V   78   21   1   saturation                         Temperature ≦40                Pressure 0.15 MPa G             
 
         [0249]     In the first stage, the adsorbents in the adsorption tower from the bottom up in sequence are activated alumina and molecular sieve. In the second stage, the adsorbent in the adsorption tower is molecular sieve. This example is a pressure swing adsorption device for making oxygen. In air, oxygen and argon is weakly adsorbed component, nitrogen and water(steam) is strongly adsorbed component. In the first stage, outlet nitrogen concentration is controlled at 78 v % (adjusting between 30-78 v % during actual operation); in the second stage, nitrogen in the outlet gas of the first stage is further purified to meet the requirement of the next procedure. Oxygen concentration at the top outlet of the adsorption tower of the second stage is controlled at over 93 v %, maximum to 95 v %.  
         [0250]     The first stage device comprises of six adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs three times in the working procedure. The second stage device comprises of four adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs once in the working procedure.  
         [0251]     In the first stage, the adsorption tower sequentially undergoes such pressure swing adsorption steps in one circulation period as adsorption A, first two-end equalization depressurization  2 E 1 D′, second two-end equalization depressurization  2 E 2 D′, third two-end equalization depressurization  2 E 3 D′, backward depressurization BD, evacuation VC, second stage gas repressurization  2 ER, third two-end equalization repressurization  2 E 3 R′, second two-end equalization repressurization  2 E 2 R first two-end equalization repressurization  2 E 1 R′, final repressurization FR. In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 1 D, backward depressurization BD, first equalization repressurization E 1 R, final repressurization FR. The gas discharged from backward depressurization BD step is returned into the adsorption tower of the first stage which has completed evacuation VC step totally to pressurize. The product gas discharged from the outlet of the absorption tower of the second stage in adsorption step is mainly oxygen and a little argon.  
         [0252]     The result of this example is that the concentration of oxygen is above 93 v %, the concentration of nitrogen is above 99 v %, the recovery of oxygen is above 96 v %.  
       EXAMPLE 35 OF INVENTION  
       [0253]     The material gas in the present example is air.  
         [0254]     The components of air are shown in the following table:  
                                                                                               Component                N2   O2   Ar   Water (steam)                            Conc. % V   78   21   1   saturation                         Temperature ≦40                Pressure 0.3 MPa G             
 
         [0255]     In the first stage, the adsorbents in the adsorption tower from the bottom up in sequence are activated alumina and molecular sieve. In the second stage, the adsorbent in the adsorption tower is molecular sieve. This example is a pressure swing adsorption device for making oxygen. In air, oxygen and argon is weakly adsorbed component, nitrogen and water(steam) is strongly adsorbed component. In the first stage, outlet nitrogen concentration is controlled at over 78 v %; in the second stage, nitrogen in the outlet gas of the first stage is further purified to meet the requirement of the next procedure. Oxygen concentration at the top outlet of the adsorption tower of the second stage is controlled at over 93 v %, maximum to 95 v %.  
         [0256]     The first stage device comprises of seven adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs four times in the working procedure. The second stage device comprises of five adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs two times in the working procedure.  
         [0257]     In the first stage, the adsorption tower sequentially undergoes such pressure swing adsorption steps in one circulation period as adsorption A, first two-end equalization depressurization  2 E 1 D′, second two-end equalization depressurization  2 E 2 D′, third two-end equalization depressurization  2 E 3 D′, fourth two-end equalization depressurization  2 E 4 D′, backward depressurization BD, evacuation VC, second stage gas repressurization  2 ER, fourth two-end equalization repressurization  2 E 4 R′, third two-end equalization repressurization  2 E 3 R′, second two-end equalization repressurization  2 E 2 R′ first two-end equalization repressurization  2 E 1 R′, final repressurization FR. In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, backward depressurization BD, second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The gas discharged from backward depressurization BD step is returned into the adsorption tower of the first stage which has completed evacuation VC step totally to pressurize. The product gas discharged from the outlet of the absorption tower of the second stage in adsorption step is mainly oxygen and a little argon.  
         [0258]     The result of this example is that the concentration of oxygen is above 93 v %, the concentration of nitrogen is above 99.7 v %, the recovery of oxygen is above 99 v %.  
       EXAMPLE 36 OF INVENTION  
       [0259]     The material gas in the present example is air.  
         [0260]     The components of air are shown in the following table:  
                                                                                               Component                N2   O2   Ar   Water (steam)                            Conc. % V   78   21   1   saturation                         Temperature ≦40                Pressure 0.3 MPa G             
 
         [0261]     In the first stage, the adsorbents in the adsorption tower from the bottom up in sequence are activated alumina and molecular sieve in the second stage, the adsorbent in the adsorption tower is molecular sieve. This example is a pressure swing adsorption device for making oxygen. In air, oxygen and argon is weakly adsorbed component, nitrogen and water(steam) is strongly adsorbed component. In the first stage, outlet nitrogen concentration is controlled at 78 v % (adjusting between 20-78 v % during actual operation); in the second stage, nitrogen in the outlet gas of the first stage is further purified to meet the requirement of the next procedure. Oxygen concentration at the top outlet of the adsorption tower of the second stage is controlled at over 93 v %, maximum to 95 v %.  
         [0262]     The first stage device comprises of seven adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs four times in the working procedure. The second stage device comprises of seven adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs two times in the working procedure.  
         [0263]     In the first stage, the adsorption tower sequentially undergoes such pressure swing adsorption steps in one circulation period as adsorption A, first two-end equalization depressurization  2 E 1 D′, second two-end equalization depressurization  2 E 2 D′, third two-end equalization depressurization  2 E 3 D′, fourth two-end equalization depressurization  2 E 4 D′, backward depressurization BD, evacuation VC, second stage gas repressurization  2 ER, fourth two-end equalization repressurization  2 E 4 R′, third two-end equalization repressurization  2 E 3 R′, second two-end equalization repressurization  2 E 2 R′ first two-end equalization repressurization  2 E 1 R′, final repressurization FR. In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, cocurrent depressurization PP 1 , cocurrent depressurization PP 2 , cocurrent depressurization PP 3 , backward depressurization BD, purge P 1 , purge P 2 , purge P 3 , second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The gas mixture discharged from the adsorption tower in cocurrent depressurization PP 1  step is used directly to purge the adsorption tower that has completed purge P 2  step by regulating its flow. The impurity adsorbed on the adsorbent is desorbed. The gas mixture discharged from the adsorption tower in cocurrent depressurization PP 2  step is used directly to purge the adsorption tower that has completed purge P 1  step by regulating its flow. The gas mixture discharged from the adsorption tower in cocurrent depressurization PP 3  step is used directly to purge the adsorption tower that has completed backward depressurization BD step by regulating its flow. The impurity adsorbed on the adsorbent is desorbed. The gas discharged from backward depressurization BD step and purge P step is returned into the adsorption tower of the first stage which has completed evacuation VC step totally to pressurize. The product gas discharged from the outlet of the absorption tower of the second stage in adsorption step is mainly oxygen and a little argon.  
         [0264]     The result of this example is that the concentration of oxygen is above 93 v %, the concentration of nitrogen is above 99.7 v %, the recovery of oxygen is above 99 v %.  
       EXAMPLE 37 OF INVENTION  
       [0265]     The material gas in the present example is air.  
         [0266]     The components of air are shown in the following table:  
                                                                                               Component                N2   O2   Ar   Water (steam)                            Conc. % V   78   21   1   saturation                         Temperature ≦40                Pressure 0.3 MPa G             
 
         [0267]     In the first stage, the adsorbents in the adsorption tower from the bottom up in sequence are activated alumina and molecular sieve in the second stage, the adsorbent in the adsorption tower is molecular sieve. This example is a pressure swing adsorption device for making oxygen. In air, oxygen and argon is weakly adsorbed component, nitrogen and water(steam) is strongly adsorbed component. In the first stage, outlet nitrogen concentration is controlled at 78 v % (adjusting between 20-78 v % during actual operation); in the second stage, nitrogen in the outlet gas of the first stage is further purified to meet the requirement of the next procedure. Oxygen concentration at the top outlet of the adsorption tower of the second stage is controlled at over 93 v %, maximum to 95 v %.  
         [0268]     The first stage device comprises of seven adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs four times in the working procedure. The second stage device comprises of seven adsorption towers. Single tower is simultaneously in an adsorption step and the pressure equalization step performs two times in the working procedure. In the first stage, the adsorption tower sequentially undergoes such pressure swing adsorption steps in one circulation period as adsorption A, first two-end equalization depressurization  2 E 1 D′, second two-end equalization depressurization  2 E 2 D′, third two-end equalization depressurization  2 E 3 D′, fourth two-end equalization depressurization  2 E 4 D′, backward depressurization BD, second stage gas repressurization  2 ER, fourth two-end equalization repressurization  2 E 4 R′, third two-end equalization repressurization  2 E 3 R′, second two-end equalization repressurization  2 E 2 R′ first two-end equalization repressurization  2 E 1 R′, final repressurization FR. In the second stage, the adsorption tower sequentially undergoes such pressure swing adsorption step in one circulation period as adsorption A, first equalization depressurization E 1 D, second equalization depressurization E 2 D, cocurrent depressurization PP 1 , cocurrent depressurization PP 2 , cocurrent depressurization PP 3 , backward depressurization BD, purge P 1 , purge P 2 , purge P 3 , second equalization repressurization E 2 R, first equalization repressurization E 1 R, final repressurization FR. The gas mixture discharged from the adsorption tower in cocurrent depressurization PP 1  step is used directly to purge the adsorption tower that has completed purge P 2  step by regulating its flow. The impurity adsorbed on the adsorbent is desorbed. The gas mixture discharged from the adsorption tower in cocurrent depressurization PP 2  step is used directly to purge the adsorption tower that has completed purge P 1  step by regulating its flow. The gas mixture discharged from the adsorption tower in cocurrent depressurization PP 3  step is used directly to purge the adsorption tower that has completed backward depressurization BD step by regulating its flow. The impurity adsorbed on the adsorbent is desorbed. The gas discharged from backward depressurization BD step and purge P step is returned into the adsorption tower of the first stage which has completed evacuation VC step totally to pressurize. The product gas discharged from the outlet of the absorption tower of the second stage in adsorption step is mainly oxygen and a little argon.  
         [0269]     The result of this example is that the concentration of oxygen is above 93 v %, the concentration of nitrogen is above 99.7 v %, the recovery of oxygen is above 99 v %.  
         [0270]     The present invention is not limited to the application scope mentioned above. It can be used to obtain the strongly adsorbed or the weakly adsorbed component from the gas mixture, and to obtain the strongly adsorbed component and the weakly adsorbed component from the gas mixture at the same time. The strongly adsorbed component and the weakly adsorbed component in the present invention can be one component, also can be more than one component.  
       INDUSTRIAL APPLICATION  
       [0271]     The present invention can be applied to the industrial field of chemical engineering, petrochemical processing, pharmacy, building materials, environmental protection and so on.
A two-stage complete recycle pressure-swing adsorption process for gas separation features that separating more adsorptable component and less adsorptable component from gas mixture, and the product is more adsorptable component or less adsorptable component or both of them. Serially-connected operation of two-stage pressure-swing adsorber is employed. The gas mixture is fed into the first stage pressure-swing adsorption gas separation system, and the more adsorptable component of the gas mixture is absorbed, then is abstracted into product. The semifinished gas mixture from the outlet of the first stage pressure-swing adsorption tower is fed into the second stage pressure-swing adsorption gas separation system. The more adsorptable component of the semifinished gas mixture is absorbed further, and the less adsorptable component is fed into next stage. The gas in the second stage pressure-swing adsorption gas separation system except for the less adsorptable component fed into next stage is reintroduced into the first stage pressure-swing adsorption gas separation system to increase pressure. The first stage pressure-swing adsorption tower in one cyclic period comprises the steps in turn: the adsorption step A, tow-end pressure-equalizing and reduction  2 ED′, converse pressure-reduction BD, two-stage gas pressure-boosting  2 ER, two-end pressure-equalizing and boosting  2 ER′ and final boosting FR. The second stage pressure-swing adsorption tower in one cyclic period comprises the steps in turn: the adsorption step A, sequence pressure-equalizing and reduction ED, converse pressure-reduction BD, converse pressure-equalizing and boosting ER and final boosting FR.