Ca- and Ba-Decorated CuO Oxygen Carriers for In Situ Dechlorination in Chemical Looping Combustion

In the chemical looping combustion of chlorine-rich biomass or coal, a trace element, chlorine, will cause serious corrosion of oxygen carriers and heat exchange equipment in boilers. To address this issue, we design Ca- and Ba-decorated oxygen carriers to achieve two goals: on one hand, reducing the concentration of chlorine-containing gases by in situ dechlorination; on the other hand, employing protective materials to preferentially bind with gaseous chlorine to safeguard the active components of the oxygen carriers. Carefully designed experiments are conducted under simplified experimental conditions using 50 ppmv HCl-containing CH4 to evaluate the intrinsic characteristics of oxygen carriers in terms of dechlorination efficiency and reactivity. The results demonstrate that both the reaction performance and the chlorine-resistance performance of Ca–Cu and Ba–Cu composite oxygen carriers are significantly improved. This is because (a) Ca and Ba preferentially form chlorides with HCl, effectively shielding the active Cu component of the oxygen carrier from chlorine poisoning and (b) the specific surface area and pores of Ca/Ba-decorated oxygen carriers are increased, which not only strengthens the heterogeneous reaction between oxygen carrier and combustible gas but also improves the chemical looping combustion performance. The Cl-resistant oxygen carriers, Ca–Cu and Ba–Cu, emerge as promising candidates for the chemical looping combustion of fuels with high chlorine content.