Performance analysis of four‐bed H2 PSA process using layered beds

Abstract

AbstractHydrogen purification from a typical cracked gas mixture (H2/CO2/CH4/CO) by the four‐bed PSA process was studied experimentally and theoretically using layered bed of activated carbon and zeolite 5A. The mathematical model accounts for the mass and heat transfer resistance using the linear driving force approximation for the particle uptake, and the ideal adsorbed solution model represents the multicomponent adsorption equilibrium. Effects of the superficial velocity, heat transfer resistance and the bed layering on the process performance were investigated. Since the recovery sharply decreases above a certain productivity at the given purity, the relation between the productivity and recovery was studied before the process design. Its performance decreased with the increase in heat transfer resistance, but increased with heat transfer resistance in some range. Both the experiment and theory showed optimum carbon‐to‐zeolite ratios. Those optimum ratios depend on such operating variables as the superficial velocity, heat transfer resistance and product purity. For higher product purity more zeolite was used. As the superficial velocity increased, the process performance has its maximum at higher carbon‐to‐zeolite ratio. Except for the adiabatic conditions, the optimum carbon‐to‐zeolite ratio increased with the increase in the heat transfer resistance. At the adiabatic conditions, however, the optimum carbon‐to‐zeolite ratio was lower than that at the nonisothermal conditions.