| China's environmental protection requirements are increasingly strict,and more and more power plants consider the rational recycling and utilization of desulphurization wastewater.However,the current zero-emission treatment process for desulphurization wastewater is very expensive.After desulfurization of flue gas,the temperature drops rapidly.A lot of heat is absorbed by the desulfurization system instead of be used.It would be economical to use this waste heat to treat desulfurization wastewater.The falling film evaporator has the advantages of small temperature difference,compact structure and short retention time.It is widely used in chemical industry,food,sewage treatment,seawater desalination and medicine industry.This paper simulates the application of falling film evaporation in seawater desalination.The CaCl2 solution was used to simulate desulphurization wastewater.Low temperature flue gas was used to evaporate liquid film.In order to better utilize the low grade heat source,the flue gas is in contact with the solution.Using the vertical drop film,the gas liquid countercurrent evaporates the solution.This paper studies the characteristics of the evaporative desulfurization waste water from the low temperature flue gas.Low temperature of flue gas temperature range is 80?120 ?.The control equation for the evaporation process of the adiabatic reverse flow film is established.A numerical simulation method is used to study the transfer process of the evaporative heat transfer.By establishing the control equation of the evaporation process of adiabatic reflux film,the heat transfer process is studied by numerical simulation.The effect of gas liquid Reynolds number,solution salt concentration,flue gas temperature and smoke humidity on evaporative properties was studied.The simulation results show that the temperature distribution of the flue gas is the opposite of the moisture content in the evaporation tube.Near the liquid film,the gas has the highest moisture content and the lowest temperature.The heat in the flue gas is first used to evaporate the solution,followed by the heating solution.Increasing the temperature of the air-liquid Reynolds number and the inlet flue gas can increase the evaporative capacity of the low-temperature flue gas.In the other hand,Increasing the inlet flue gas humidity will reduce the evaporation capacity of the flue gas.The quality fraction of CaCl2 dilute solution increased from 0 to 4%,and the evaporation capacity of flue gas was basically unchanged.In this paper,we design and build a reverse vertical falling film evaporation test stand.The experimental results are compared with the simulation results.The influence of smoke Reynolds number,inlet flue gas temperature and humidity on the evaporation capacity of low temperature flue gas is consistent with the simulation results.To increase the inlet flue gas temperature and flow rate,reduce the inlet flue gas humidity can promote evaporation.Although the increase of solution Reynolds number can promote the evaporation of solution.However,when the solution Reynolds number is greater than 1600,the flue gas begins to take liquid,and the evaporative capacity of the flue gas begins to decrease.Therefore,the increase of solution flow in the appropriate range can promote evaporation.The results of CaCl2 dilute solution were similar between 1%and 3%of flue gas evaporation.But more than 3%evaporates rapidly;In the case of gas-liquid high Reynolds number,the salt in the solution is carried away by the flue gas.The infiltration surface of the descending film tube is uniform.The gas inlet position is prone to scaling.According to the experimental data analysis,the evaporation capacity of the experimental unit was 0.54 kg/(m2.h)?2.16kg/(m2.h),and the mass transfer coefficient was between 0.012m/s?0.036m/s in each working condition,and the coefficient of mass transfer coefficient is hm=X0.753Resol0.021Rea0.568Tain0.25.. |
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