Study on calcium precursors for CaO preparation to capture CO<sub>2</sub> at high temperature

Abstract

As an abundant and cheap material,calcium oxide(CaO) is an efficient sorbent for CO2 capture at high temperature.The carbonation/calcination loop of CaO/CaCO3 is an effective process for CO2 capture and storage(CCS).However,both the gradual decline of the CO2 capture capacity and the poor stability,because of the pore filling and pore closure at the high calcination temperature,limit the industrial application of calcium-based sorbents.In this paper,study on calcium precursors was carried out in order to obtain CaO sorbents to capture CO2 with high efficiency.The candidate materials include seashell materials(oyster shells),natural minerals(calcite) and chemical reagents(calcium acetate hydrate).Oyster shell powder and calcite powder were analyzed by XRD,and CaO sorbents prepared from various precursors were characterized by nitrogen physisorption apparatus.The fresh CaO sorbents and CaO after multiple cycles to capture CO2 were characterized by scanning electron microscopy(SEM).The capture CO2 capability and the stability of CaO sorbents were investigated using a thermogravimetric analyzer(TGA),where multiple capture cycles were carried out alternatively in the simulation flue gas(10% CO2 in N2) and in decomposition purge gas(N2).Moreover,comparing the CO2 capture capability and the CaO stability with published works,and taking account of the market prices of precursors,calcium acetate hydrate is thought to be an economically appropriate calcium precursor,which has acceptable CO2 adsorption capacity and good stability at high temperature.