Separation of carbon dioxide from gas mixtures by calcium based reaction separation

Abstract

A reaction-based process has been developed for the selective removal of carbon dioxide (CO) from a multicomponent gas mixture to provide a gaseous stream depleted in CO2 compared to the inlet COconcentration in the stream. The proposed process effects the separation of COfrom a mixture of gases (such as flue gas/fuel gas) by its reaction with metal oxides (such as calcium oxide). The Calcium based Reaction Separation for CO(CaRS—CO) process consists of contacting a COladen gas with calcium oxide (CaO) in a reactor such that CaO captures the COby the formation of calcium carbonate (CaCOa). Once 'spent', CaCOis regenerated by its calcination leading to the formation of fresh CaO sorbent and the evolution of a concentrated stream of CO. The 'regenerated' CaO is then recycled for the further capture of more CO. This carbonation-calcination cycle forms the basis of the CaRS—COprocess. This process also identifies the application of a mesoporous CaCOstructure, developed by a process detailed elsewhere, that attains >90% conversion over multiple carbonation and calcination cycles. Lastly, thermal regeneration (calcination) under vacuum provided a better sorbent structure that maintained reproducible reactivity levels over multiple cycles.