HYDROGEN PURIFICATION FROM REFINERY FUEL GAS BY PRESSURE SWING ADSORPTION

Hydrogen purification and recovery from various process streams consti tutes the largest commercial use of pressure swing adsorption (PSA) te chnology. This study investigates the performance of a sir-bed dual-so rbent PSA operation for hydrogen purification from the refinery fuel g as, Major impurities are methane, ethane, propane and butane, and comp rise 30-40% of the feed. The dual-sorbent PSA bed consists of an initi al layer of silica gel adsorbent for trapping heavier hydrocarbons and a subsequent layer of activated carbon for removing lighter hydrocarb ons. A numerical simulation model of the H-2-PSA process developed wit h all the essential features of the actual operation shows that butane is more strongly adsorbed on activated carbon than silica gel, and he nce, is less easily desorbed from the former using simple pressure red uction in the PSA cycle. Therefore, the initial layer serves to preven t butane from degrading the adsorptive capacity provided by activated carbon for other lighter hydrocarbons. The simulation model agrees wel l with the experimental results from a laboratory unit as well as with available H-2-PSA plant data from a refinery. The results also indica te the importance of heat effects in this process. Extensive parametri c studies, which show effects of feed velocity and cycle time on the v ariation of product recovery and purity obtainable from the industrial unit, provide a valuable guide for its proper operation.