Adsorption dynamics of a layered bed PSA for H₂ recovery from coke oven gas

The adsorption dynamics of a layered bed packed with activated carbon and zeolite 5A were studied experimentally and theoretically through breakthrough experiments and two-bed pressure swing adsorption (PSA) processes by using coke oven gas (56.4 vol % H₂; 26.6 vol % CH₄; 8.4 vol % CO; 5.5 vol. % N₂; and 3.1 vol % CO₂). The results of breakthrough curves of a layered bed showed an intermediate behavior of those of zeolite-5A bed and activated carbon bed, because each concentration front propagates with its own wavefront velocity in each layer by a different adsorption equilibrium. Since a fast and dispersed mass-transfer zone of CO in the zeolite layer of a layered bed leads to a long leading front of the N₂ wavefront, controlling the leading wavefront of the N₂ plays a very important role in obtaining a high-purity product and in determining the optimum carbon ratio of a PSA process for H₂ recovery from coke-oven gas. The layered bed PSA process was simulated in a simplified form of two single-adsorbent beds linked in series. The dynamic model incorporating mass, energy, and momentum balances agreed well with the experimental data. Concentration profiles inside the adsorption bed were also investigated.