Numerical Simulation Study On The Spray Drying System For Treatment Of Salt-containing Wastewater With High Organic Concentrations

Salt-containing wastewater with high organic concentrations is mainly produced in industry of fine chemicals.With the improvement of the level of the national economy and the development of chemical industry technology,the proportion of fine chemical output value to total output value of chemical industry is increasing.Industry of fine chemicals involved in a wide range of industries,and it has many kinds of products,the product can be involved in all areas of the national economy.However,at the same time as the rapid development of the industry,the production of salt-containing wastewater with high organic concentrations has also greatly increased,which has brought a great threat to the ecological environment.The harm caused by Salt-containing wastewater with high organic concentrations produced in industry of fine chemicals is very serious.The dye industry was analyzed as an example to analyze this kind of wastewater,it was found that such wastewater is generally characterized by a high concentration of organic substances and contains a large number of substances that are toxic and harmful to microorganisms and difficult to biodegrade.In addition,its salt content is high and it is usually a large amount of inorganic salts and some heavy metal salts.Besides,high levels of waste that can cause carcinogenicity,teratogenicity,and mutations.Moreover,it has strong acid or alkalinity,high chromaticity,and large variations in water quality and water volume,etc.It is difficult to obtain good treatment effect by traditional methods,and the new spray drying method is more suitable for the treatment of such waste liquids.To explore the influence of the temperature,velocity of the gaseous drying medium and initial temperature on the drying rate in the spray drying process,the influencing factors involved in the spray drying process were analyzed in this paper.The mathematical model of droplet movement and mass transfer and heat transfer in the drying tower was established.Combined with FLUENT software,numerical simulation calculation is carried out.Through the analysis of the calculation results,the following conclusions have been drawn:(1)The higher the temperature of the gaseous drying medium,the faster the drying rate,when the initial temperature of the waste liquid and the speed of the gaseous drying medium remain the same and the temperature of the gaseous drying medium changes from 573 K to 773 K.However,as the temperature of the gaseous drying medium continues to increase,the drying rate of the evaporation efficiency is no longer significantly increased.Considering all aspects,the temperature of the gaseous drying medium is 723 K.(2)The faster the initial speed of the gaseous drying medium is,the faster the drying rate is,when the initial temperature of the waste liquid and the temperature of the gaseous drying medium are kept constant and the speed of the gaseous drying medium is changed from 10 m/s to 25 m/s.However,when the initial velocity of the gaseous drying medium exceeds 20m/s,the initial velocity of the gaseous drying medium becomes limited to the increase of the droplet drying rate in the spray drying tower.In order to improve the evaporation efficiency and reduce energy consumption,and at the same time to avoid the droplet residence time is too short,the best choice for the velocity of the gaseous drying medium is 20m/s.(3)When the speed and temperature of the gaseous drying medium are kept constant,different droplet initial temperatures are simulated by changing the temperature of the waste liquid,the four curves representing the variation of the mass of the droplets with temperature at four different temperatures are merged or intersected with each other,it shows that the initial temperature drop does not affect the spray drying process.The application of numerical simulation results of spray drying process in engineering practice is discussed.The analysis shows that the conclusion obtained by numerical simulation is reliable,and the numerical simulation work has guiding significance for engineering practice.