The effect of $H_2O$ 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 ppmv $SO_2$, 2% $O_2$, and the $H_O$ content waschanged 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 andreacted 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.