EFFECTS OF SALTS ON LIMESTONE DISSOLUTION RATE IN WET LIMESTONE FLUE-GAS DESULFURIZATION

To understand how the dissolution rate of limestone used for absorbent in a wet flue gas desulfurization plant is affected by the soluble salts formed from hydrogen chloride gas in flue gas as well as from the impurities contained in the used raw material limestone itself, various limestone slurries each added with a single salt of CaCl2, MgCl2, NaCl, Na2SO4 and MgSO4 were titrated with sulfuric acid. From the titration results the dissolution rate was found to vary greatly with the kind and the concentration of the salts with a general tendency to decrease in chloride solution but to increase in sulfate solutions. Based on this finding, the authors proposed a semi-empirical simplified model. The evaluated results using this model closely agreed with the measured values of the limestone dissolution rate both in single-salt solutions and mixed salt solutions.