Kinetic model of CaO/fly ash sorbent for flue gas desulphurization at moderate temperatures

Characteristics of the sulphation reaction between SO2 and CaO/fly ash sorbent were analyzed based on TGA results to develop a kinetic model for a dry moderate temperature (400–800 °C) FGD process. It was found that SO2 diffusion within sorbent particles involved three sub-processes: inter-particle diffusion, inter-grain diffusion and diffusion through product layers and the diffusion dominated the whole sulphation reaction process. The activation energy for product layer diffusion Ediff of 49.3 kJ mol−1 being greater than the chemical reaction activation energy Ea of 13.9 kJ mol−1 verified the importance of the diffusion. Predictions using the kinetic model in which k0 varies with temperature agree well with the experimental data.