On the Intrinsic High Temperature Calcium Oxide-Sulfur Dioxide Reaction Using the Vacuum Thermogravimetric Analysis Technique.

The high temperature CaO/SO2 reaction was studied using four Swedish limestones and one dolomite as sorbents. The measurements were carried out in a vacuum thermogravimetric analysis (TGA) apparatus in order to investigate the intrinsic reaction mechanism. The reaction was found to be fast at the beginning due to the surface reaction, while the subsequent stage was controlled by the product layer diffusion, showing a lower reaction rate. The reaction rate increased as temperature increased up to 1000 °C in the range tested. SO2 partial pressure weakly affected the reaction. The fine sorbent particles used in the study resulted in the high CaO conversion. Further grinding of the sorbents gave a small increase in CaO conversion. Sintering generally decreased the initial reactivity but might not affect the ultimate CaO capacity. The larger pores in nascent CaO particles were valuable for the initial reaction conversion.