The effect of H2O on the sulfation of Havelock limestone under oxy-fuel conditions in a thermogravimetric analyser

Abstract

A gas mixture representing oxy-fuel combustion conditions was employed in a thermogravimetric analyser to determine the effect of water vapor and SO 2 concentration on limestone sulfation kinetics over the temperature range of 800 to 920 °C . Here, experiments used small samples of particles (4 mg), with small particle sizes (d p < 38 µm) and large gas flow rates (120 mL/min@ NTP) in order to minimize mass transfer interferences. The gas mixture contained 5000 ppm v SO 2 , 2% O 2 , and the H 2 O content was changed from 0% to 25% with the balance CO 2 . When water vapor was added to the gas mixture at lower temperatures (800-870 °C ), the limestone SO 2 capture efficiency increased. However, as the temperature became higher, the enhancement in total conversion values decreased. As expected, Havelock limestone at higher temperatures (890 °C , 920 °C , and 950 °C ) experienced indirect sulfation and reacted at a faster rate than for lower temperatures (800-870 °C ) for direct sulfation over the first five minutes of reaction time. However, the total conversion of Havelock limestone for direct sulfation was generally greater than for indirect sulfation.