As described above, in {TAIL ~ the procedures} of switching to a reductive operation, after the flow rate of the product gas is reduced by {HEAD ~ the flow control valve} 33 corresponding to the degree of reductive operation, the operational mode of the PSA apparatus 11 is changed corresponding to the reduced flow rate 
As described above , in { TAIL ~ the procedures } of switching to a reductive operation , after the flow rate of the product gas is reduced by { HEAD ~ the flow control valve } 33 corresponding to the degree of reductive operation , the operational mode of the PSA apparatus 11 is changed corresponding to the reduced flow rate
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