Reactivity of the limestone in wet flue gas desulfurization

On the basis of the analysis of chemical components of the natural limestones from different deposits in China, the pore structures of the typical limestones, with the different CaCO₃ content, were examined. The reactivity of the limestones was investigated by sulfuric acid titration and gas-liquid absorption methods. The research results showed that the specific surface area of the natural limestones studied in this work was about 1.8 m²/g. It was seen that the pH of the limestone slurry rapidly decreased and then back up when the sulfuric acid was added. The higher the CaCO₃ content was, or the smaller the particle size was, the larger the pH back-up rate was, and similarly the faster the SO₂ concentration of the reactor outlet increased. The Reactivity of the limestone obtained by the sulfuric acid titration had the same features as that obtained by the gas liquid absorption. Compared with the specific surface area, the CaCO₃ content had more effect on the reactivity of the limestones. The particle size of the limestones had a significant effect on the reactivity when the particle size was relatively large, that is less than 300-360 mesh, vice versa.