Study On Quality Control Technology Of Desulphurized Gypsum In Coal - Fired Power Plant

China is a country with coal as the main energy, and coal occupies an important position in China’s energy structure. Coal-fired power plants inevitably produce large amounts of SO2, which influences the environment badly. At present and in the future for a long period of time, to reduce SO2emissions, control air pollution by SO2and protect the quality of atmospheric environment is an important issue of China’s environmental protection.At present, the flue gas desulfurization of coal-fired power plants mostly adopts wet-desulphurization craftwork, in that during combustion, the sulphur in the coal reacts with the limestone to create the final product, gypsum, with about90%calcium sulfate crystal. The desulfurization gypsum quality directly affects the economic benefits of FGD in power plants.In allusion to the departure from control targets, the paper analyzed the running process of flue gas desulfurization in coal-fired power plant. By mathematical statistics, it analyzed control targets such as the limestone quality, the flue gas dust content at the entrance of absorber, the pH of the slurry, the slurry density, the liquid-gas ratio and the amount of forced oxidation air. It also analysed the operation control situation of gypsum dewatering system. Through data analysis, we obtained the running control range of influencing factors, which meeting the requirements of the commercialization of desulfurization gypsum. The main conclusions are as follows:(1) By analyzing the solubility of limestone and the absorption of SO2, determined the relationship between the limestone activity with the percentage of CaO, and required that the CaO percentage of limestone into the plant should be controlled greater than or equal to53%.(2) Found by mathematical statistics that it exist a linear relationship between the efficiency of desulfurization and flue gas dust content. When the flue gas dust content was larger, the efficiency of desulfurization was lower, and the quality of gypsum was worse, and vice-versa. According to the view of the actual running situation of ESP and the overhaul inspection, the original ESP system had not meet the requirements of FGD operating. Adopted bag dust extractor instead of the original ESP system, ensured the imported flue gas dust content Absorber be less than or equal to30mg/m3.(3) Analyzed the effects on FGD gypsum quality by control targets such as the limestone quality, the flue gas dust content at the entrance of absorber, the pH of the slurry, the slurry density, the liquid-gas ratio and the amount of forced oxidation air. And analyzed the effect on the moisture of gypsum by the operation control situation of gypsum dewatering system. The liquid-gas ratio of absorber should be controlled at about15L/m3. The pH of the slurry should be controlled from5.49to5.93. The residence time of slurry which circled once in the oxidation zone should not be less than5min. Generally, the slurry density should be controlled between1.111to1.1500kg/m. The mass concentration of chloride ions in slurry should be below10000mg/L. The thickness of gypsum cake should be controlled at about20mm. We defined the range of control targets above, and detailed operating procedures, ensured the quality of FGD gypsum.