Simulation And Analysis Of Droplet Trajectory In The Chimney

With the development of modern science and technology, the demand for electricity is growing. In the thermal power, coal is regarded as the main raw material. Sulfur will generate sulfur dioxide through chemical reaction by burning coal and this will pollute the environment without purification. Therefore, in the process of production, sulphur dioxide emission must be strictly controlled. Limestone-gypsum wet desulfurization is one of the most commonly used methods of flue gas desulfurization. Owning to the limestone- gypsum wet desulphurization canceling gas-gas heat exchanger(GGH) device, the chimney flue gas temperature decreases, the pressure of the flue gas which contains the saturated water vapor at the exit drops along the flow direction and the heat dissipates to the surrounding. Plaster droplets carrying by flue gas at the outlet of chimney lands around the chimney under the influence of gravity, which is forming "plaster rain." The "plaster rain" will cause serious environmental pollution and erode equipments. Therefore, preventing and controlling "gypsum rain" is very important.In this paper, the models of straight chimney and chimneys with different diameters are built by numerical simulation method. Flue gas flow fields and droplets tracks under different boundary conditions are analyzed. The results show that, in the wet stack emission scheme, changing the straight chimney to straight chimney with gradually shrinking spout has little influence on adsorption rate of gypsum droplets but it can increase the flue gas average velocity at the exit and promote the lifting capacity of flue gas. This has a certain positive role in enhancing the capacity of the spread of the flue gas into the surrounding and slowing down the "gypsum rain" around the chimney. Under the same conditions, flue gas flow resistance in the horizontal direction is lower than the resistance in the vertical direction while the impact is not significant for the adsorption rate of the inner wall to the flue condensation or gypsum droplets. Through the analysis of the heat transfer process inside the chimney flue gas with the surrounding environment, we theoretically analyzed the relationship of the temperature drop between dry and wet stack emission chimney emissions scheme plan. The analysis results show that: under the same conditions, the temperature drops by wet stack emission of flue gas through the chimney system scheme is far lower than that of the dry stack scheme, and the temperature drop by wet flue gas chimney emissions scheme will not be higher than the dry flue gas chimney emissions scheme of 1/3. Through the analysis of flue gas flow field on the system model in different conditions of different flue gas temperature and different flue lining material, we know that: in the same condition, while the flue gas flow in the duct system, the flow resistance increases with the flue lining from the composite titanium plate, the foam glass tile, the shoulder supporting bricks gradually increased. The flow resistance of the flue gas flow is increases gradually with the increase of the temperature of the exhaust too. Through the analysis and calculation of static pressure inside the chimney flue gas system, we discuss the different climatic conditions and different exhaust temperature effects of static pressure distribution on the system., The analysis results show that: under the same conditions, as the air density in the coastal area is greater than the northern area, the suction of chimney system in the coastal area is higher than the northern area and the inland area, it renders the static pressure in chimney micro vacuum state in the coastal area while the static pressure in chimney is micro positive state in the northern area and the inland area. The static pressure within the system gradually moves to the pressure direction with the gradual increase in exhaust gas temperature. The results of this study provide a reliable data for realizing the purpose of reducing the absolute value of the droplet. while in the same entrance conditions, it plays a role in helping to optimize the chimney structure.