Study On Evaporation Characteristics Of High Salty Wastewater By Rotating Spray

The existing high-salt wastewater treatment technology has high energy consumption,high cost and unsatisfactory effect of salt water separation.In order to improve the evaporation rate of high-salt wastewater,a new type of rotary spray evaporation Dryer which has low energy consumption was developed,and the related experimental research was conducted.The effects of different factors on the outlet temperature of the Dryer and the evaporation rate of the droplets were explored by numerical simulation.The major findings of the study are as follows:(1)Research and development of rotary spray dryer:spray evaporator was designed for the high salt wastewater with a treatment amount of 5 kg/h and a salt concentration of 10%.The material balance of the amount of water vapor and the amount of air used was calculated,and the diameter and height of the dryer were calculated.This paper provides a design reference for the application of the spray evaporation technology in the engineering application of high salt wastewater.(2)numerical simulation study on evaporation characteristics of Rotary Spray:A geometric model of the dryer consistent with the designed size was established,based on the DPM model.The influence of different operation parameters on the droplet evaporation rate was explored.The results show that:(1)In the surrounding area of the atomizing disk,the hot air produces a pronounced gyration.The formation of the recirculation zone makes the droplet particles move in a couple with the hot air,the trajectory of the individual particles is parabola-like,and the particles have a longer residence time in the drying chamber,this causes more heat transfer between the droplet and the air.(2)In the dryer,the most intense heat transfer area is the surrounding area of the atomizing disk.This is mainly due to the droplet has a large kinetic energy when it is just separated from the atomizing disk,which results in a large initial velocity of the droplet.Contact with dry hot air,the droplets heat up rapidly,while the hot air cools down rapidly.(3)The temperature and the flow rate of the hot air have obvious change tendency on the evaporation rate,while the flow rate of liquid and rotating speed of atomization disk have little influence on the evaporation performance.(3)experimental study on the evaporation characteristics of Rotary Spray:An experimental platform for Rotary spray drying of high-salt wastewater was designed and set up to study the effects of hot air temperature,hot air flow rate,rotating speed of atomizing disk and concentration of feed liquid on the evaporation effect,The results show that:(1)with the increase of hot air temperature,the outlet temperature of the dryer increases gradually,and the droplet evaporation rate also increases gradually,but the increase rate slows down.(2)when the hot air volume is less than 80m3/h,the evaporation rate increases rapidly,but the increasing range gradually slows down.Until the air volume is 90m3/h the droplet evaporates completely,after which the evaporation rate begins to decrease.The larger the hot air volume is,the higher the hot air outlet temperature is.It shows that the thermal energy of hot air is not well utilized and the thermal efficiency of the system is reduced.(3)The higher the feed flow rate is,the lower the evaporation rate is and the larger the evaporation rate is.When the hot air temperature and flow rate are constant,the evaporation capacity of the system is limited.With the continuous increase of feeding flow,the evaporation rate of the system will decrease.(4)As atomizing disc speed increases,air temperature at the dryer outlet will continue to drop and change rate will become slower,while evaporation rate of fluid will increase and the growth rate will be slower.When atomizing disc speed is 24000r/min,the evaporation rate reaches 100%,after which the evaporation rate no longer changes.It shows that the optimum speed of atomizing disk is 24000r/min.(5)The higher the concentration of the solution,the higher the evaporation rate of the solution,but the increasing range will gradually slow down.Compared with other factors,the concentration of solution has little effect on evaporation.(6)It can be find that the experimental curve and the simulation curve have the same trend,but the experimental value is slightly larger than the simulation value,and the maximum error is less than 20%.The results show that the best evaporation effect can be obtained when the temperature of hot air is 498K,the volume of air is 80m~3/h and the rotating speed of atomizing disk is 24000r/min.The results of numerical simulation are reliable and can be used as a reference for engineering design and research of Rotary spray evaporation technology for high-salt wastewater treatment.