Enhancement of the Direct Sulfation of Limestone by Alkali Metal Salts, Calcium Chloride, and Hydrogen Chloride

The enhancement of the direct sulfation of limestone by various Li + -, Na + -, and K + -containing inorganic salts, calcium chloride, and hydrogen chloride has been studied in a bench-scale quartz reactor. Experimental results indicate that Li + - and Na + -containing salts enhance the sulfation process by increasing ionic mobility in both the solid reactant (calcite) and the solid product (anhydrite), whereas K + -containing salts and CaCl 2 promote the direct sulfation of limestone only by increasing ionic mobility in the solid reactant. The significant increase in ionic mobility in limestone causes serious sintering of the limestone particles and formation of significantly fewer but larger product nuclei/grains. The significant increase in ionic mobility in the product phase causes serious deformation and easy coalescence of the product grains. The enhancement by HCl is related to a eutectic which is formed by simultaneous formation of calcium chloride by the chlorination of limestone and calcium sulfate by the sulfation of limestone.