| Coal-fired power plants in view of the desulfurization wastewater processing mainly by chemical treatment system,using the triple box of desulfurization wastewater by neutralization,precipitation and enrichment and clarification.This method,although technology is mature,the chloride ions in waste water and trace metal removal efficiency is low,and there is the problem of high cost.If the flue gas desulfurization wastewater is treated by the residual heat of boiler flue gas through spray evaporation,the micron solid particles in the wastewater and suspended dust in the flue pipe will be captured when entering the electrical precipitator and discharging ashes.This treatment method can achieve zero discharge of wastewater.If the boiler tail flue evaporation wastewater technology is utilized,the atomized wastewater is sprayed into the flue between the air preheater and the electrostatic precipitator.The desulfurized wastewater is converted into water vapor after being heated and evaporated the fine solid particles in the waste water and dust enters the electrostatic precipitator under the push of flue-gas,which is captured by the electrode in the dust collector.This treatment method successfully achieved zero discharge of desulfurization wastewater.However,the wastewater must be completely evaporated before entering the electrostatic precipitator,and the temperature of the flue gas entering the electrostatic precipitator after the heat exchange between the flue gas and the wastewater must be above the acid dew point,otherwise the tiny droplets that have not evaporated will cause the flue and subsequent equipment.corrosion.In this dissertation,a domestic 300 MW coal-fired boiler as the prototype.The flue from air preheater to the tail of ESP is the calculation area.The atomized droplets injected into the tail flue of boiler are numerically simulated by commercial software Fluent.Firstly,based on the analysis of the composition of desulfurization wastewater,three kinds of two-component acid,alkali and salt solutions with different physical properties of wastewater and one-component pure water were selected as the research objects.The effects of temperature,vapor pressure and particle size of different physical properties of droplets on droplet evaporation were discussed.Then,the factors affecting the evaporation of desulfurization wastewater were analyzed,mainly from the three directions of flue gas,nozzle and droplet.The key factors affecting the life of wastewater droplets were found.The temperature of flue gas,flue gas velocity and atomization particle size were found.Finally,each of the key factors by numerical simulation to determine the optimum velocity liquid;And the optimal injection quantity of nozzle injection is determined,and the curve of the optimal injection flow rate of the same nozzle under different flue gas temperature conditions is fitted,which ensures that the wastewater completely evaporates before entering the electrostatic precipitator,and the flue gas temperature is at the acid dew point.The results show that the vapor pressure of the solution has a great influence on the evaporation time of the droplets.The temperature of the single-component and two-component solutions changes with time in the pre-heating stage.After the critical temperature,the temperature of the single-component pure water reaches a stable state.The component acid,alkali and salt solution are continuously reduced due to the continuous decrease of vapor pressure,and the droplet temperature is continuously decreased;In the case of the same initial diameter of droplets,the particle size of different physical droplets changes substantially with time,and the droplet diameter changes exponentially with time;When the tail flue gas flow rate is 10m/s and the initial velocity of the atomized droplet is 5m/s,the evaporation time is the shortest;The jet flow rate and evaporation time of the nozzle are linearly increasing,and the temperature of the flue gas before entering the electrostatic precipitator after heat transfer to the droplet is approximately linearly decreasing. |
