Comparison of the efficiency of carbon dioxide capture by sorption-enhanced water-gas shift and palladium-based membranes for power and hydrogen production

Pre-combustion capture of carbon dioxide requires the industrial separation of carbon dioxide from hydrogen-rich streams. The present study analyses the thermodynamic efficiency penalty of this separation step and the achievable carbon capture ratio, with particular focus on high-temperature separation technologies: sorption-enhanced water–gas shift (SEWGS) and palladium membranes. Twelve different cases have been simulated, starting from coal-derived syngas or from natural gas derived reformate, using carbon dioxide capture by conventional absorption, SEWGS, and palladium membranes, and producing hydrogen-rich fuel for power production or pure hydrogen. For the production of decarbonised fuel from coal syngas, SEWGS always yields the lowest efficiency penalty per unit of carbon dioxide captured. For the production of pure hydrogen from coal syngas, SEWGS has a significantly higher carbon capture ratio than the alternatives while palladium membranes yield the lowest efficiency penalty per unit of carbon dioxide captured. For the production of decarbonised fuel from natural gas reformate, SEWGS is the most efficient technology in terms of efficiency penalty. For the production of pure hydrogen from natural gas syngas, palladium membranes yield the lowest efficiency penalty.