Numerical Simulation Of Low Temperature Flue Evaporation Synergistic Dechlorination Of Desulfurization Wastewater

The SO₂ gas produced by coal-fired power plants has brought great loss to the earth’s environment and human economy.Limestone gypsum wet desulfurization technology is widely used in thermal power plants to remove SO₂ from flue gas,but the desulfurization wastewater produced by this method is one of the most complex and difficult industrial wastewater in power plants.With the increasingly strict environmental protection policy,zero discharge technology of desulphurization wastewater has become the main means to solve desulphurization wastewater at present,among which low temperature flue evaporation technology of desulphurization wastewater has been developed rapidly.In this paper,a physical model of the evaporation movement of desulfurization wastewater in the tail flue between the air preheater and the electrostatic precipitator of a 300MW unit is established.The effects of flue gas temperature,flow rate,water content,average particle size of droplets,mass flow rate,initial velocity and initial temperature on the evaporation time and distance of wastewater droplets in the tail flue are analyzed by numerical simulation.The results show that flue gas temperature,flow rate and average droplet size have great influence on the droplet evaporation effect of desulfurization wastewater.The initial droplet velocity and temperature have little effect on the droplet evaporation.With the increase of nozzle atomization angle,the evaporation distance of droplet decreases gradually,but the decrease decreases gradually.The vapor content of flue gas has a certain effect on the evaporation of wastewater,and the evaporation distance increases with the increase of vapor content,but the increase is small.The evaporation distance increases with the increase of droplet mass flow rate,but the evaporation rate increases with the increase of droplet mass flow rate,and the maximum evaporation rate occurs at the initial moment of droplet evaporation.The actual amount of desulfurization waste water in the coal-fired unit is large,and the amount of wastewater water in the abbreviated water of the single atomized nozzle is limited,and the atomization evaporation of the desulfurization waste water content of the actual unit is not possible,and therefore,there is a variety of forms in the flue under safe distance conditions.Atomized nozzle group atomized evaporation of desulfurized wastewater,realizing the practical application of the evaporation technology of desulfurization waste treasury with coal-fired power plant.The numerical simulation of the process of flexion of the desulfurization wastewater in a multi-nozzle group arrangement,and the results show that when the number of nozzles is the same,the evaporation time and evaporation distance of droplet decrease with the increase of flue gas temperature,flow rate and droplet average particle size.As the number of nozzles increases,the evaporation time and evaporation distance of droplet decrease,and the amount of desulfurization wastewater that can be treated increases,but the actual installation difficulty increases.Aiming at the root problem of desulfurization wastewater,the desulfurization wastewater produced by the unit is pretreated and used as the solvent for preparing Ca（OH）₂ slurry.The computational particle fluid dynamics（CPFD）method is used to simulate the chemical reaction process of removing HCl gas from Ca（OH）₂ slurry droplets.The effects of stoichiometric ratio（SR）,flue gas temperature and flow rate,average particle size of Ca（OH）₂ slurry droplet,initial temperature and concentration on dechlorination reaction were analyzed.The results show that with the increase of SR,the dechlorination efficiency increases gradually,but the increase gradually slows down.Flue gas velocity and Ca（OH）₂ slurry droplet temperature have little effect on dechlorination efficiency,and the dechlorination efficiency has little change.The dechlorination efficiency decreases with the increase of flue gas temperature and Ca（OH）₂ slurry concentration in the same SR.The dechlorination efficiency increased firstly and then decreased with the increase of the average particle size of Ca（OH）₂slurry droplets.The maximum dechlorination efficiency was obtained when the average particle size of Ca（OH）₂ slurry droplets is 110μm.When the unit load and chloride control concentration constant,the desulfurization waste water produced by the unit is negatively correlated with the removal efficiency of HCl.