An analytical solution to equilibrium PSA cycles

A general pressure swing adsorption (PSA) cycle, involving pressure equalization, forward depressurization, incomplete purge, product backfill and feed pressurization steps, has been analyzed with an isothermal local equilibrium model assuming linear isotherms. The operation conditions of such a process could be characterized by the extents of feed, backfill and purge. Analytical expressions have been derived for the recovery ratio and the cycle throughput as a function of these extents. Critical conditions that ensure the formation of a simple shock and best utilization of column have also been identified. Product backfill plus pressure equalization steps were found the best policy when both recovery and throughput are important.