Effects of carbon‐to‐zeolite ratio on layered bed H₂ PSA for coke oven gas

Abstract

Abstract Effects of carbon‐to‐zeolite ratio on a layered bed H 2 PSA using activated carbon and zeolite 5A were studied experimentally and theoretically. Coke oven gas (56.4 vol. % H 2 , 26.6 vol. % CH 4 , 8.4 vol. % CO, 5.5 vol. % N 2 , and 3.1 vol. % CO 2 ) was used as a feed gas for the seven‐step two‐bed PSA process incorporating a backfill step. In these experiments, the effects of three operating variables such as adsorption pressure, feed rate and purge rate on the performance of a layered bed PSA were investigated. The layered bed gave better purity than the single‐adsorbent bed at the same operating condition, except at low purge rate. Since every component had its own front velocity at each layer, a carbon‐to‐zeolite ratio affected product purity at a given recovery or throughput. Moreover, for a high‐purity H 2 product from coke oven gas, an optimum carbon‐to‐zeolite ratio had to be determined to control a leading wavefront of N 2 . In layered bed PSA processes, the temperature variations inside the bed reflected a kind of inflection or plateau at which a roll‐up phenomenon occurred and showed the dynamics of adsorption well at each step during a cycle. Simulated results of the dynamic model incorporating mass, energy and momentum balances agreed well with the PSA experimental results.