Research On Evaporation And Transpotation Of Sulfuric Acid And Hydrochloric Acid Droplet Emitted From The Tank Surface

In the production process of industrial pickling,electroplating and smelting of metals,a large amount of droplets of pollutants are emitted from the open surface tank to the environment.Sulfuric acid and hydrochloric acid droplets are two typical solution droplets that are emitted from the surface tank.If these pollutants accumulate in the room and stay for a long time,it will have an impact on the building personnel,equipment and building envelopes.Studying the evaporation and motion characteristics of sulfuric acid and hydrochloric acid droplets in the building can help guide the efficient control of pollutants and assess their damage to the indoor environment of industrial buildings.A phase transition and motion coupling model of droplets considering both solvent evaporation and solute volatilization was established.The surface water vapor partial pressure of the droplet is one of the main factors affecting the evaporation of the droplets of the solution.Therefore,the partial pressure of the water vapor of sulfuric acid and hydrochloric acid droplets can be accurately described to accurately predict the evaporation and motion characteristics of the droplet.In this paper,the surface water vapor partial pressures of sulfuric acid and hydrochloric acid droplets predicted by the Osmotic coefficient method and the Van't Hoff factor method are obtained by theoretical calculation,and the calculated results are compared with the experimental measurements.It is found that under the condition of solute mass fraction??35%,the sulfuric acid and hydrochloric acid droplets are predicted by Osmotic coefficient method is more accurate.However,as the mass fraction of solute increases,the error of the Osmotic coefficient method also increases.In order to accurately predict the evaporation characteristics of the two droplets,this paper proposes a fitting prediction method based on the droplet mass fraction and temperature of the droplet surface water vapor partial pressure.Based on the experimental data verification of evaporation and motion during the free fall of pure water droplets,the water vapor partial pressures of three droplets were compared and analyzed by MATLAB programming.The accuracy of evaporation and movement of sulfate and hydrochloric acid droplets during free fall is predicted.The study found that the Fanthof Huff factor method has lower accuracy for the prediction of both types of droplets.The Osmotic coefficient method has higher accuracy for predicting hydrochloric acid droplets and lower accuracy for sulfuric acid droplets.The applicable conditions for the evaporation and movement of droplets predicted by the sulfate droplet Osmotic coefficient method were analyzed.The critical humidity of the droplet mutation was RH=62%,the corresponding mass fraction was?=40%,and the critical humidity and mass fraction were mutated.It does not vary with ambient temperature,initial mass fraction of droplets,or initial droplet size.In general,the fitted prediction method can more accurately predict the evaporation and sedimentation characteristics of the two droplets.Based on the fitting prediction method,the effects of four factors including initial droplet size and initial mass fraction of solute,ambient relative humidity and temperature on the free sedimentation characteristics of sulfuric acid and hydrochloric acid droplets were analyzed by MATLAB.It has been found that the volatilization of HCl molecules makes the particle size change trend of single hydrochloric acid droplets completely different from the particle size change trend of sulfuric acid droplets.The hydrochloric acid droplets can be completely evaporated,while the sulfuric acid droplets can reach the"equilibrium particle size".The"equilibrium particle size"of the sulfuric acid droplets at different RH and initial particle sizes is given.When the initial particle diameter D_di?40?m,the sedimentation of sulfuric acid and hydrochloric acid droplets is not obvious due to evaporation.Based on the fitting equation of the fitting prediction method,the UDF of the partial pressure of water vapor on the surface of the sulfuric acid droplet was prepared.Fluent calculation and analysis software was used to study the evaporation and motion characteristics of sulfate droplets emitted from the large aspect ratio open channel surface in the building.The migration and dynamic distribution characteristics of sulfate droplets in the building room under different initial particle sizes and relative humidity were analyzed.It is found that,under the condition of RH=50%,for the sulfate droplets with the initial particle size D_di?70?m,the droplets follow the airflow with the evaporation of the droplets,and the droplets will follow the gas flow when they are easily affected by the lateral interference gas flow.In a larger building environment,droplets of D_di?80?m will fall back or deposit on both sides of the groove surface,and are not susceptible to lateral interference airflow.At the same time,the relative humidity has a significant effect on the evaporation of sulfuric acid droplets,but it has little effect on the diffusion in the building.