Pressure swing adsorption process for recovering H₂ from the effluent gas of a melting incinerator

A two-bed pressure swing adsorption (PSA) process using activated carbon was studied to recover hydrogen from the effluent gas (H₂/CO/CO₂, 39.3:35.4:25.3 vol.%) of a melting incineration process. The adsorption dynamics of the activated carbon bed were investigated by breakthrough experiments. Since the product purity needs depend on demands of the incinerator site, various PSA operating conditions, such as purge to feed (P/F) ratio, adsorption (AD) step time, adsorption pressure, and feed flow rate, were investigated to recover H₂ with a wide range of purities. The purity varied with P/F ratio, and the recovery varied with AD step time asymptotically because bed purification by H₂ product purge approached a limitation. On the other hand, the variations in purity and recovery with P/F ratio, AD step time, and adsorption pressure were almost linear or only slightly curved. The variation in purity with feed flow rate was similar to the variation with P/F ratio while the recovery trend was more similar to the variation with the AD step time. Because the propagation velocity was significantly different for CO and CO₂, the PSA performance was mainly affected by CO propagation, but the contribution of the CO₂ heat of adsorption to the bed should be considered. The PSA process in this study produced hydrogen with a purity of 75.43-99.99% and a recovery of 90.99-49.29%. When a syngas (H₂ and CO) is needed, the PSA process can result in high recovery and productivity because the major impurity in the product is CO.