Carbonation−Calcination Cycle Using High Reactivity Calcium Oxide for Carbon Dioxide Separation from Flue Gas

Abstract

This study is focused on improving the reactivity of a CaO sorbent for its use in a reaction-based process for the separation of carbon dioxide (CO2) from flue gas. The separation process consists of cyclical carbonation (of a metal oxide) and calcination (of the metal carbonate formed) reactions to yield concentrated CO2 from flue gas. CaO sorbents synthesized from naturally occurring limestone and dolomite were microporous in nature. Pore filling and pore pluggage of these micropores limited the conversion of CaO in the carbonation reaction to about 45−50% of the stoichiometric limit. A wet precipitation process was tailored to synthesize high-surface-area precipitated calcium carbonate (PCC). The pores of PCC predominantly lie in the mesoporous range (5−20 nm). The CaO sorbent obtained from PCC (PCC-CaO) was less susceptible to pore pluggage and attained over 90% conversion. PCC-CaO was also capable of maintaining its high reactivity (>90%) over two carbonation−calcination cycles.