Separation of Hydrogen Mixtures by a Two-Bed Pressure Swing Adsorption Process Using Zeolite 5A

A study on a two-bed six-step pressure swing adsorption (PSA) process using zeolite 5A was performed experimentally and theoretically for bulk separation of H₂/CO and H₂/CH₄ systems (70/30 vol %) as major components in coke oven gas. When the pressure is cycled between 1 and 11 atm at ambient temperatures, 70% H₂ in the feed could be concentrated to 99.99% in the product with a recovery of 75.87% in the H₂/CO mixture and 80.38% in the H₂/CH₄ mixture. The effects of adsorption pressure, P/F ratio, adsorption/purge step time, and pressure equalization step time were investigated experimentally. If the product end of an adsorption bed was not contaminated during the adsorption and depressurizing pressure equalization steps, elongation of both the adsorption and purge steps gave good adsorbent productivity and recovery without any decrease in purity. Certain elongations of step time in the pressure equalization step resulted in a better performance of a PSA process. When the H₂ mole fraction of effluent stream during the pressure equalization step was not high, the initial H₂ purity of the adsorption step was not good because of the contamination of the product end section. These results were analyzed by a mathematical model incorporating heat and momentum balances.