Research Of Evaporation And Movement Characteristics Of Droplets In A Certain Anodic Foil Plant And The Control Of The Internal Environment

There are many kinds of high-temperature heat reservoirs emitting droplets in the production process,such as electrolytic cells in the anodic foil plant,acid-soluble reaction tanks in the alumina production plant,and paper machines in the papermaking plant.As the high temperature of the heat reservoirs,coupled with some craft processes can't be sealed,a large amount of droplets disperse into the working environment in the production process.If a large number of droplets are gathered and not controlled effectively,the health of people would be harmed seriously,the quality of products and the equipment would also be influenced critically.This paper is based on an engineering project,through the investigation we found that plant interior layout of a large number of long high-temperature open tanks.Due process requirements the tank can not be completely sealed,it became the source for diffusing droplets.Additionally,due to the drawbacks of the ventilation system,the source term can not be effectively controlled,resulting in high temperature and high humidity and pollution in the workshop can not be ruled out in a timely manner,the environment is very harsh.In order to improve the internal environment of the workshop,it is necessary to control the source of droplets effectively.In this paper,CFD and user defined function are used to study the diffusion process of droplets in non-isothermal flow field and take it as the pointcut.The numerical simulation method of the evaporation and movement characteristics of the droplets in the non-isothermal flow field would be first explored.The influence of different modification methods of sensitivity parameters on the simulation results are compared,we found that during the simulation of diffusion process of droplets in non-isothermal flow field,the correction of the binary diffusion coefficient can be neglected,while the correction of the saturated vapor pressure is indispensable.The validity of the model is verified by comparing the theoretical data with the reference data.On this basis,the evaporation and movement of droplets in non-isothermal flow field are studied.The results show that the source term temperature,ambient water vapor concentration and droplet initial particle size and other parameters strongly influence the evaporation and movement of the droplets.The results laid a foundation for the study of the control methods of droplets in the non-isothermal flow field.Because the droplets' diameter and force are changing caused by evaporating during movement,the control methods of droplets are different from gaseous pollutants and solid particles.In order to control the droplets distributed by high temperature source more effectively,the results are evaluated by comparing the side suction hood and upper suction hood in this paper.It is found that upper suction hood is sufficient and could control better while the exhaust air volume is same.Control effect of upper suction hood is studied while exhaust momentum and mounting height varies.While the exhaust momentum is 30% of the designed value,the control efficiency could reach to 98%.Control efficiency decreases as mounting height raises.It is indicated that if the process permit,the upper suction hood should be used as much as possible,and the mounting height should not be more than 2 times of the hydraulic diameter of the source.In fact,control efficiency for source could not reach to 100% because of the disturb from environment.The polluting gases mix with polluting liquid would drift when local ventilation system could not control the source effectively.At this time,the general ventilation system seems to be essential.Through investigation,it is found that severe negative pressure exists because of unreasonable air flow organization,which causes the efficiency of local ventilation system decreases,also the pollution outside is sucked in,causes the deterioration of workshop environment.Because the energy density of air flow decreases slow,the parallel air flow supply device could be used to improve the air organization of internal plant.It is found that the parallel air flow supply device nearly reaches the effect of displacement ventilation from simulation.The temperature and water vapor in plant would stratification.The environment of breathing zone(1.5m height below)is better.The isolation between products and plant is achieved because of the characteristic of parallel air flow supply device.It is a way of protection for workers,products,and facilities.