Evaporation Performance And Process Optimization Of Mechanical Spray Evaporation Of FGD Wastewater

With the announcement of"Water pollution control plan",the zero discharge of industrial wastewater has become a trend,and nearly zero discharge of FGD wastewater in power plants has drawn much attention.Compared with evaporation crystallization technology and flue gas evaporation technology,mechanical spray evaporation could also be used to evaporation FGD wastewater,due to its low cost and the simple system.However,few studies had been carried out to FGD wastewater treatment by mechanical spray evaporation,this paper concentrated on the evaporation performance and process optimization.Characteristics and influencing factors of the natrual evaporation and spray evaporation of simulated desulfurization wastewater and FDG wastewater were studied by lab experiments.The results showed that solar radiation,atmospheric pressure and concentration,pH,salt type,density,kinematic viscosity,temperature of FGD wastewater had little effect on the evaporation rate of natrual evaporation and spray evaporation.Wind velocity was the major influlencing factor of the evaporation rate.The order of effect on environmental factors were wind velocity>temperature>humidity.It was worth paying attention to droplet float with wind,and the maximum ratio was 98%.The results by site tests showed that the actual capacity to evaporation rate of FGD wastewater was low of spray evaporation system.The evaporation rate of spray evaporation system was largest in autumn and slowest in spring.During the site tests,the average evaporation rate of the single sprayer was 2.24t/h（in autumn）,1.14t/h（in summer）,0.80t/h（in spring）and and treatment cost was 3.0¹8.8 yuan/t.Spray evpaporation polluted the environment,such as vegetation,air and so on.The corrosion behavior of different metal materials in FGD wastewater was investigated by immersion test,which provided theoretical guidance for selecting suitable material of the system.In order to reduce the amount of waste water,calcined Mg-Al hydrotalcite was used to adsorb Cl^-of FGD wastewater during lab experiments.Characterization of XRD,BET,SEM,EDS,XPS,FT-IR and so on were carried out to find reaction mechanism.The immersion experimental results showed that the product film included scaling products and corrosion products,which were CaSO₄,MgSO₄ and FeOCl.The corrosion rate of 20#carbon steel was the biggest,although scaling could slow its corrosion rate while have little effect on 304,316 stainless steel.316 stainless steel was the best choice for metal materials on near zero emissions technology equipment of FGD wastewater,due to its best corrosion resistance.The adsorption experimental results showed that the calcined Mg-Al layered double hydroxide（CLHD）adsorped Cl^-was due to its"structural memory"function.The Cl^-adsorption conformed to the first-order kinetic model and the adsorption isotherm was fitted the Freundlich equation.The adsorption capacity enhangced with the increase of initial concentration of Cl^-.At 4h,65℃,pH=8,adsorption of Cl^-was the best in simulated solution.CLDH had good reproducible reusability on dechlorination in FGD wastewater.When temperature at 65℃,pH at 8,the removal rate of Cl^-by CLDH for FGD wastewater was 50.90%,and CLDH was reproducible for FGD wastewater.This paper provided a theoretical basis for to FGD wastewater treatment of mechanical spray evaporation,theoretical direction for the actual operation and basic research for the suitable metal materials to system.To process optimization,basis research was carried out to FGD wastewater reduction.This paper had great significance to industrialization of mechanical spray evaporation for FGD wastewater.