Optimizing Of Wet Limestone-gypsum Flue Gas Desulphurization System In Power Plant

With the rapid economy development of China, in order to construct harmonious society and assure economic sustainable development, it becomes an urgent requirement to control the environmental pollution caused by energy consumption, especially to control SO₂ and the acid rain pollution caused by coal combustion. But the investment, operation and maintenance cost of the limestone-gypsum wet flue gas desulfurization system are very high, while the available rate of this system is low. Therefore, to some extent, it hinders the application of flue gas desulfurization project in our thermal power plants. With the improvement of the state's environmental protection requirement and the further stipulation of SO₂ discharge standards, optimizing and adjusting SO₂ flue gas control technique becomes a key problem which should be solved urgently. Thus, it is necessary to optimize and adjust flue gas desulfurization system, to master the designation and operating technical parameters of this system, which is of great significance to the improvement of the thermal power plants'flue gas desulfurization in our country.This paper thoroughly introduces flue gas desulfurization technique's characters, technological process and its application both at home and abroad. Based on that, this paper lays emphasis on systematically adjusting and analyzing the limestone-gypsum wet flue gas desulfurization system. Aiming at the problems of raising the FGD's efficiency and reducing operating cost, this paper takes the case of a certain thermal power plant in Shandong to carry out a research on FGD's process technology then gains the research results as follows:(1) Through the experiment, it is further proved that desulphurization efficiency rises with the decrease of the absorption tower inlet's flue gas's temperature; with the flue gas's oxygen content rises, desulphurization rate presents an upward trend. It can assure desulphurization efficiency effectively by controlling the density of absorption tower inlet's flue gas (less than 100 mg/m3), limestone purity (CaCO₃ more than 90%) and slurry's pH value (5.4～5.5).(2) In the practical project, liquid-gas ratio should be as small as possible on the basis of satisfying some conditions. Generally, liquid-gas ratio should be controlled at 18L/m3 or so. Supersaturation of a normally-operating desulphurization system should be controlled between 120%～130%, and Ca/S should be controlled between 1.02～1.05. It is proper to control the absorption tower's gas velocity between 3.5～4.5m/s.(3)GGH is not the necessary component for FGD equipment. According to the concrete situations, a power plant could decide whether or not to set GGH. After cancelling GGH and taking anticorrosion measures on chimney and flue, the investment rate and operating cost can be reduced.(4) The operating cost of limestone wet milling pulping system is relatively low, so the ratio of performance to price is high. From the economic viewpoint, it's good for the large power plant to apply limestone wet milling pulping scheme in order to maintain long-term operation.(5) During the operation of desulphurization, circulating pump can be changed according to flue gas volume of FGD, SO₂'s concentration and etc. The density of limestone slurry should be controlled within (1075～1085 kg/m3). Limestone's crystallization temperature should be controlled between 40℃～60℃. All these above can make FGD operate effectively and economically.