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

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 N-2 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 0.5 wt.% addition of synthetic char is the optimal ratio for manganocalcite in this study. (C) 2016 Elsevier B.V. All rights reserved.