Numerical Simulation And Optimization Analysis Of Process In Square Desulfurization Tower With Swirling Atomization Method

Under the current situation that the domestic atmospheric environment pollution is severe,traditional soot-type pollution has not been effectively controlled.Among them,the amount of sulfur dioxide（SO₂）emitted by coal-fired power plants is large,which is the main source of soot-type pollution.Therefore,our country has intensified the prevention and control of SO₂ emitted in coal-fired power plants,proposing ultra-low emission requirements which sulfur dioxide emission concentrations must be below 35 mg/m³ in some areas.However,traditional process technology has difficulties to meet the increasingly stringent SO₂ emission requirements.Therefore,on the basis of safe and stable operation of the desulfurization system,carrying out ultra-low emission reform,improving the desulfurization efficiency and reducing the sulfur dioxide emission concentration further is a hot issue in the field of environmental protection in power plants.Based on the ultra-low emission technologies of sulfur dioxide,this paper briefly summarizes several ultra-low emission technologies applied in engineering frequently（such as:increasing the spray layer,increasing the number of tray,two towers in series connection,the double dual cycle,swirl atomizing method）.Combined with the actual operating conditions of the power plant,with the goal of ultra-low emission requirements,the swirl atomization method was finally selected to carry out the ultra-low emission reform of sulfur dioxide in the square desulfurization tower of a power plant in Shandong.The flow process in the square desulfurization tower based on swirl atomization was studied by CFD software.This paper uses FLUENT software to give a modeling calculation based on the wet flue gas square desulfurization tower of 330MW unit in a power plant in Shandong.The standard k-εturbulence model is used to describe the turbulent motion of the flue gas in the tower,the discrete phase model is used to track the droplet motion,and the random tracking model is used to calculate the turbulent diffusion of the particles with the use of structured grid technology of ICEM.According to the double membrane theory,the corresponding SO₂source term is introduced by user-defined function（UDF）,and the SIMPLE algorithm is used to simulate and analyze the smoke flow field,temperature field and SO₂ concentration field inside the square desulfurization tower before and after ultra-low emission reform.After that,this paper optimizes the position and quantity of the swirling atomization layer,the spacing between the swirling atomization layer and the conventional spray layer,and the slurry ejection speed of the swirling atomization layer of the modified square desulfurization tower.The results prove that:（1）After the reform of the original square desulfurization tower by the swirl atomization method,the flue gas spirals up along the tower height,extending the motion track and increasing the gas-liquid contacting time;The smoke velocity in the tower increases and the temperature distribution is more uniform;the desulfurization efficiency is improved,and the sulfur dioxide concentration at the outlet is lowered;（2）The optimal process conditions are determined after analyzing the parameters of the swirling atomization layer:when operation mode are ABCDF,the DF layer spacing is 2.4m,and the swirling atomization layer slurry ejection speed is 6m/s,the combined effect of energy consumption and desulfurization efficiency of the square desulfurization tower is the best.