Numerical Simulation Of Spray Drying Technology For Desulfurization Wastewater Bypass Flue

Coal-fired power plants account for more than 70%of the total annual power generation.Fossil fuels such as coal combustion produce a large amount of sulfur dioxide.Limestone-gypsum wet flue gas desulfurization is the most mature and widely used desulfurization technology in the world,and desulfurization wastewater,as its product,requires regular treatment.As the country’s wastewater discharge standards become increasingly stringent,it is extremely urgent to achieve zero discharge of desulfurization wastewater.Spray drying technology has experienced nearly a century of development and it has become the mainstream technology in the field of drying.Applying it to desulfurization wastewater treatment can achieve zero discharge of desulfurization wastewater.However,the temperature inside the spray drying tower is high,the flow field is complicated,so it is difficult to observe.It is not conducive to in-depth research and development.The traditional experimental research method requires a lot of manpower and financial resources.With the development of computer technology,numerical simulation technology has the advantages of low cost,quick effect and high accuracy.It has become an important means to research,analyze and optimize related equipment.It plays an increasingly important role in engineering practice,so numerical simulation method has become an effective way to study the treatment process of desulfurization wastewater.In order to study the problems of flow field,temperature field,droplet evaporation time and trajectory during the spray drying process of desulfurization wastewater,this paper has carried out research through computer simulation method,and the bypass flue of desulfurization wastewater for newly built 330MW unit.The results of the spray drying application demonstration project were analyzed.The main research contents and conclusions of this paper include the following aspects:（1）According to the related theory of fluid mechanics,heat transfer and other related theories,the mathematical model of droplet evaporation in hot flue gas was established for the evaporation characteristics of droplets during spray drying.The temperature of flue gas and the velocity of flue gas were investigated.The effect of droplet size,droplet initial velocity,desulfurization wastewater flow rate,etc.on the complete evaporation time of droplets and the variation of particle size with evaporation time.The study found that the complete evaporation time of the droplets is related to the temperature and velocity of the flue gas.As the temperature of the flue gas rises,the complete evaporation time of the droplets decreases significantly,and the decrease decreases.As the flue gas velocity increases,the complete evaporation time of the droplets decreases,and the decrease decreases.The complete evaporation time of the droplets is related to droplet size and wastewater flow.As the particle size of the droplet increases,the complete evaporation time of the droplet increases significantly,and the smooth endothermic time experienced by the droplet increases,and the rate of increase decreases.As the flow rate of the wastewater increases,the complete evaporation time of the droplet gradually increases.The increase in amplitude is increased,and the smooth endothermic time becomes longer.The complete evaporation time of the droplets is less related to the initial velocity of the droplets.（2）The structure of hot air distributor in key parts of spray drying technology was studied.The study found the baffle angle has a great influence on the flow field in the spray drying tower.As the angle of the baffle increases,the rotation of the hot flue gas into the spray drying tower is more pronounced and the high velocity flow area is reduced.The baffle angle has little effect on the complete evaporation time of the droplets,and has a great influence on the movement trajectory of the droplets.As the angle of the baffle increases,the farthest distance in the radial direction of the droplet increases,and the farthest distance in the axial direction decreases.The effect of the inner baffle angle on the spray drying tower is greater than the outer baffle angle.The number of deflectors has little effect on the flow field in the spray drying tower,the trajectory of the droplets,and the complete evaporation time of the droplets.When the number of baffles is zero,the flow field in the drying tower is disordered.With the increase of the number of baffles,the flow field,droplet trajectory and complete evaporation time in the drying tower tend to be stable,combined with the actual situation,the diversion The number of plates is 24 pieces.（3）Taking the desulphurization wastewater spray drying tower installed in the bypass flue of a 330MW coal-fired power plant as the research object,the numerical simulation method was used to study the heat and mass transfer process in the drying tower,and the application demonstration results were analyzed.The results show that under different working conditions,the flow field and temperature field in the spray drying tower are well distributed,and the gas-liquid heat and mass transfer process is mainly concentrated in the tower axis;after the desulfurization wastewater is dried,the total dust concentration at the outlet of the spray drying tower is reduced by 20%⁴0%,the water vapor content in the flue gas increases by 1%²%,and the solid product forms an irregular porous shape,which exists in the form of Al₂O₃,SiO₂,CaSO₄,KCl and the like.The Cl^-in the desulfurization wastewater is transferred to the solid product,solving the problem of Cl^-difficult treatment.The desulfurization waste water evaporates in the high-temperature flue gas to reduce the high specific resistance dust anti-corona and promote the accumulation of particulate matter,which is beneficial to be trapped by the electrostatic precipitator.