Zeolite Psa Cycles for Producing a High-Purity Hydrogen from a Hydrogen-Lean Mixture

Two pressure swing adsorption (PSA) cycles are used to produce a high-purity H₂ from an H₂-lean mixture containing strongly adsorbable gases. Zeolite 5A is used as the sorbent. The use of an evacuation step in the cycle is found necessary for this difficult separation. In addition, a new vacuum purge step is found efficient and a promising step for commercial application, A bidisperse pore diffusion model along with a simple algorithm is developed for the cycle performance. The model is simpler than all previous bidisperse pore models due to two justified simplifying assumptions: parabolic concentration profiles in crystal and pellet, and a double volume-average technique. The effects of both micropore and macropore diffusion resistances on the cyclic separation are found to be small but significant. A basic understanding of the transient adsorber dynamics is obtained through the bidisperse pore diffusion model.