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