Kinetic model for calcium sulfate decomposition at high temperature

A modified shrinking unreacted-core model, based on thermogravimetric analysis, was developed to investigate CaSO4 decomposition in oxy-fuel combustion, especially under isothermal condition which is difficult to achieve in actual experiments due to high-temperature corrosion. A method was proposed to calculate the reaction rate constant for CaSO4 decomposition. Meanwhile, the diffusion of SO2 and O2, and the sintering of CaO were fully considered during the development of model. The results indicate that the model can precisely predict the decomposition of CaSO4 under high SO2 concentration (>1100×10−6). Concentrations of SO2 and O2 on the unreacted-core surface were found to increase first and then decrease with increasing temperature, and the average specific surface area and porosity of each CaO sintering layer decreased with increasing time. The increase of SO2 and/or O2 concentration inhibited CaSO4 decomposition. Moreover, the kinetics of CaSO4 decomposition had obvious dependence on temperature and the decomposition rate can be dramatically accelerated with increasing temperature.