Investigation into the Behavior of Reductive Decomposition of Calcium Sulfate by Carbon Monoxide in Chemical-Looping Combustion

Abstract

Chemical-looping combustion is a promising technology with no contact between fuel and combustion air, featuring the inherent separation of CO2 and avoidance of nitrogen oxide formation. To some metal oxide oxygen carriers, the high costs and positive hazard to living environment inhibit the application of chemical-looping combustion systems in large scale. In this work, we investigate the possibility of using calcium sulfate as oxygen carrier. The release amount of SO2 was not only due to the reacting temperature but also affected by the partial pressure of CO in the reaction. If the partial pressure of CO in the atmosphere is big enough, the release amount of SO2 or the occurrence of side reactions can be eliminated fully even if the temperature is as high as 1000 °C. The reactivity behavior of the reduction of CaSO4 by CO in the heating process is also studied. The values of activation energy, frequency factor, and linear factor corresponding to five different heating rates are calculated using an accurate kinetics integral expression and a temperature integral approximation with high precision. The most probable mechanism function in the decomposition process is characterized by G(α) = [−ln(1 − α)]1/2.