Removal of sulphur dioxide by calcium-based materials from different sources in South Africa.

Abstract

The sulphation reactions of two limestone and two dolomite materials from quarries in South Africa were investigated in an isothermal fixed bed reactor under conditions similar to those encountered in fabric bag filters of the dry flue gas desulphurization system. The raw materials used in this study were calcined at 900 ºC and the produced quicklime slaked. The fixed bed reactor was operated batchwise with a single charge (0.1g of the sorbent material dispersed in 3g of inert silica sand) of particles for obtaining the SO2 breakthrough curves. Experiments were carried out at different temperatures (60≤T≤100oC), varying SO2 feedstock concentration (1000≤C≤3000 ppm), and relative humidity (0%≤RH≤40%). Both the limestone and dolomite samples showed appreciable desulphurization activity at the conditions tested. The SO2 concentration was found not to have any significant effect on the final sorbent conversion although the initial conversion rate was seen to increase with an increase in the SO2 concentration in the flue gas. There was no temperature dependence of the sorbent activity in the temperature range investigated. The sorbent activity increased with an increase in the relative humidity and this was concluded to be the most influential factor in the sorbent conversion.