Improved removal of selenium by calcite-derived CaO with porosity and anti-sintering in presence of acid gas

Ca-based sorbent injected into furnace is a promising technology for control emission of selenium. As commercially available CaO was easy to sintering under actual furnace temperature or in presence of CO2/SO2, calcite-derived CaO on removal of Se were tested by a gas-solid reaction system, which was designed to simulate process of gaseous trace elements in flue gas fast contacting with injected minerals, showing a simple, economical and practical method to improve anti-sintering. Results showed conspicuous superiority of calcite-derived CaO for its porosity and anti-sintering. Capture efficiency at 700–800 °C could reach to 80% basically, even to 90% as maximum, and chemisorption was dominance for capture by analysis of thermal desorption. Both CO2 and SO2 could affect capture, while their effects mechanisms on Se capture were quite different. The impact of CO2 depended on the adsorption temperature. Below 700 °C, existence of CO2 could inhibit Se capture due to formed CaCO3, so Se capture was suggested at above 700 °C after considering both capture efficiency and leachability. Effects of SO2 was relevant to content of CaSO4 formed. Se retention was promoted as low content of CaSO4 formed, but capture was inhibited by thickened product layer as high content formed.