Study On Limestone Activity In Flue Gas Desulfurization Process Of Coal-Fired Plant

The power generation in China is mostly generated by coal-fired plant. As the coal resources of high quantity of ash and sulfur, the pollution of sulfur dioxide, which produced by coal-fired power plant, becomes severe nowadays. The flue gas desulfurization (FGD) is an effective way to control the emitted sulfur dioxide. The wet FGD process is the most extensively used technology for desulfurization. As the absorbent in the FGD process, the limestone is of significance to the FGD process. In the limestone-gypsum wet FGD system, the absorption rate of sulfur dioxide is restricted by the melting rate of limestone. The melting rate is judged by the activity of limestone. The more active the limestone is, the easier the sulfur dioxide is absorbed. The basic physical properties such as the component, the particle size and the solubility have been studied. The influencing factors of limestone slurry viscosity also have been discussed. The experiment results indicated that the solubility of limestone influenced the slurry viscosity little when the mixture ratio of slurry was between 15% and 25%. Considering the impact extents on the viscosity, the mixture ratio of slurry affected the viscosity most, the reaction temperature took the second place, and the particle size ranked the third. The reaction mechanism of limestone absorbing sulfur dioxide has been analyzed. The mathematical model of the absorbing process has been built. It's been tested and verified by the experimental results. The activity of limestone has been defined. It reflected the changing tendency of reaction rate of limestone. The larger the value of the activity was, the more activate the limestone was. That meant the limestone reacted with sulfur dioxide faster. The experiments showed that the component and the particle size of limestone rarely impacted on the activity of limestone, when the percentage composition of calcium carbonate in the limestone varied from 84.81% to 97.14% and the particle size of limestone was between 45 and 75μm. The activity was influenced significantly by the pH, reaction temperature and the mixture ratio of slurry. By virtues of the results, the empirical model has been built.