| 摘要 |
PROBLEM TO BE SOLVED: To accurately detect a decrease in performance of a gas separation membrane. SOLUTION: A gaseous nitrogen generator 11 is constituted so that membrane modules 12, 13 consisting of gas separation membranes are used to separate gaseous nitrogen. A control circuit 42 determines whether the membrane modules 12, 13 are at a time for replacement or not, based on pressure change detected by a pressure gauge 28 on device stoppage. That is, pressure change on stoppage in certain operating conditions (for example, inlet and outlet pressure of the membrane modules 12, 13 temperature of a hollow fiber membrane, the flow rate of nitrogen-rich gas discharged as product gas, and the like) is measured by the pressure gauge 28, and time t1' or t2' until the pressure lowers to a prescribed reference pressure is measured, and by comparing it with time t1 or t2 measured in advance when the membrane modules 12, 13 are at an initial state, whether the membrane modules 12, 13 reach the time for replacement is determined.
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