Investigation of novel naturally occurring manganocalcite for CO2 capture under oxy-fuel calcination

Abstract

The rapid capacity decay of CaO-based sorbents from limestone is one of the key issues for post-combustion CO2 removal using calcium looping process. Finding other naturally occurring Ca-containing minerals instead of limestone has been proved to be an effective way to acquire sorbents with highly improved cyclic CO2 capture performance. In the current work, a novel naturally occurring manganocalcite mineral was employed to produce CaO-based sorbent. EDS mapping has demonstrated that the inert solid support of Ca2MnO4 are homogeneously dispersed among the ultrafine active specie of CaO particles. As a result, calcined manganocalcite exhibits an obviously enhanced 20-cycle performance compared to calcined limestone when pure N2 calcination is used. Even under oxy-fuel calcination atmosphere, the sorbent still holds a surprisingly high conversion of ∼40% at the 20th cycle, 3.1 times as high as that of calcined limestone. Besides, the calcined manganocalcite is superior to calcined limestone for capturing CO2 under SO2-presence carbonation and oxy-fuel calcination. Coal combustion process during calcination stage was also investigated through employing synthetic char to simulate coal to burn with manganocalcite. It has been found that 0.5wt.% addition of synthetic char is the optimal ratio for manganocalcite in this study.