High-temperature pressure swing adsorption cycle design for sorption-enhanced water-gas shift

Sorption-enhanced water–gas shift (SEWGS) combines the water–gas shift reaction with in situ adsorption of CO2 on potassium-promoted hydrotalcite (K-HTC) and thereby allows production of hot, high pressure H2 from syngas in a single unit operation. SEWGS is a cyclic process, that comprises high pressure adsorption and rinse, pressure equalisation, and low pressure purge. Here, results are presented of a SEWGS cycle design study, based on recently developed expressions for the interaction of CO2 and H2O with K-HTC. It is shown that during the cycle, steam adsorbs in the rinse step and desorbs during the subsequent reduction in pressure, thereby improving the CO2 purity in the column and thus enhancing the efficiency of the rinse. A parameter study based on numerical simulations shows that the carbon capture ratio depends mainly on the purge steam to carbon feed ratio, whereas the CO2 product purity depends mainly on the rinse steam to carbon feed ratio. An optimisation yields a SEWGS cycle that consumes significantly less steam than cycle designs previously reported in the literature