| The desulfurization wastewater bypass tower evaporation technology use the flue gas heat in the flue to evaporate the desulfurized wastewater after being atomized in the tower,and the evaporation product is collected by the cyclone and the electric dust in the flue to achieve zero discharge of the wastewater.This method has greatly reduced the cost of wastewater treatment and has been welcomed by thermal power plants.In this paper,a spray evaporation test bench is designed.Through the PIV experiment and theoretical calculation,the applicable nozzle、evaporation tower size and auxiliary equipment selection are determined.The effects of air volume,water volume,wastewater concentration change on evaporation efficiency and the physical characteristics of evaporation products are studied.The experimental results show that the change of atomized water volume and inlet air volume has the greatest influence on evaporation efficiency.The outlet temperature of the evaporation tower reaches 95°C.It can be considered that the wastewater is completely evaporated.From the solid product after evaporation,the product collection rate is low,about 32.50%,there is a certain viscosity wall phenomenon,the product moisture content is less than 2%.Based on the evaporation test bench,the temperature distribution,velocity distribution and flow characteristics of the tower were studied by numerical simulation and compared with the experimental results.The validity of the model was verified.It can be seen from the gas-liquid two-phase flow field that the temperature and velocity in the tower are basically triangular changes with low middle and high sides,and the flow velocity of the flue gas has a great influence on the temperature field and velocity field in the tower.Through this mathematical model,the application research of the 330MW thermal power unit was carried out.The evaporation tower added the“whistle type”inlet,which alleviated the phenomenon of fogging and adhering to the wall.Subsequently,a multi-jet combination jet was carried out,which more fully utilized the space inside the tower to reduce the accumulation of mist droplets in the tower.The proportion of flue gas extracted from the 2.16t/h wastewater is 2.27%of the total flue gas volume,and the flue gas field can fill the entire evaporating tower.The atomization evaporation effect of the three nozzles can make the evaporating tower outlet temperature reach the design of120°C;the droplet diameter is below 80μm,the droplet particles are not attached,and the evaporation effect is good when the droplet diameter is 60μm;in order to prolong the residence time of the particles,the particles are not adherent and less agglomerated,the flue gas swirling method should be adopted,three nozzle,atomized particle size of 60μm and inlet flue gas temperature of 600 k or more.The influence of heat from the extraction unit of the evaporation tower and the disposal and utilization of the product are the key factors that restrict the application of the atomization evaporation technology of the bypass tower of the desulfurization wastewater.Through theoretical calculations,the amount of flue gas required for a specific amount of evaporation is determined,and the amount of flue gas extracted is converted to the exhaust gas loss,thereby determining the decrease in boiler efficiency and the increase in coal consumption of the power supply.The calculation results show that under the rated load,the treatment of waste liquid below 6t/h will reduce the furnace efficiency by less than 0.2%,and the coal consumption will be less than0.5g/kwh.When the load is reduced to 40%ECR,the boiler efficiency will be significantly reduced.About 1.8%,coal consumption increased by about5.5g/kwh,and the smaller the treatment volume,the smaller the impact on the economics of the unit.The on-site evaporation product was analyzed by ion chromatography,and the Cl~-content in the product far exceeded the utilization limit of fly ash,which needs to be blended and utilized. |
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