Tail gas pressure

The adsorber is purged at tail gas pressure with hydrogen recovered from other adsorbers. The gas desorbs impurities from the adsorbent and flows out the tail gas line. The impurity front is returned to the feed end of the adsorbent bed. The tail gas can be used as fuel or for subsequent processing. 

The optimum feed pressure range for PSA units in refinery applications is 15-30 bar. The optimum tail gas pressure is as low as possible. Since vacuum is normally avoided, tail gas pressure between 1.1 and 1.4 bar are typically used when high recovery is needed. 

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