A Comparison of Gas Separation Performance by Different Pressure Swing Adsorption Cycles

By simulations using an equilibrium model, a quantative comparison is made for different pressure swing adsorption (PSA) processes for gas separation. The comparison is based on the performance curve, which is defined as the relationship between product purity and product recovery at a fixed feed throughput. For bed repressurization in the PSA cycle, the use of the light product yields superior separations compared to that using the feed mixture. For the pressure reduction step, it is found that the separation results are better when the heavy-product purge step is used, as compared to that using cocurrent depressurization. For an ultrahigh-purity light product, however, the PSA process using cocurrent depressurization is superior. A new PSA process is suggested in which the heavy-product purge step is accomplished by using (or pressure-equalizing with) the effluent from another bed which undergoes the countercurrent blowdown step.