| There are crystallization and corrosion problems in dehumidification system and lithium bromide absorption refrigeration system.Ionic liquid[Emim]OAc is proposed to be added into lithium bromide?LiBr?solution,in order to increase solubility,decrease saturated vapor pressure,reduce generation temperature and alleviate corrosiveness.Solid-liquid equilibrium and vapor-liquid equilibrium data of LiBr+[Emim]OAc+H2O ternary system are measured in this paper and are correlated and predicted with different models.Dehumidification effect and absorption characteristics of the ternary solution are also analyzed.It's of great necessity for this paper to study on solid-liquid equilibrium and vapor-liquid equilibrium of ternary system containing ionic liquids,since solubility and saturated vapor pressure are important physical parameters in liquid desiccant and absorption refrigeration systems and there are few research on it at present.The main research contents and results are as follows:Firstly,the solid-liquid equilibrium data of LiBr+[Emim]OAc+H2O ternary solution at288.15 K,303.15 K,323.15 K and 343.15 K are measured,and the isothermal dissolution diagram is obtained.The experimental data are correlated by four-parameter semi-empirical formula,Apelblat model and the solubility equation proposed in this paper.It is found that[Emim]OAc increases the solubility of LiBr in water.The mass fraction of[Emim]OAc?2 in ternary saturated solution is negatively correlated with the mass fraction of LiBr?1.The solubility of ternary solution is positively correlated with temperature and negatively correlated with the mass ratio of LiBr to[Emim]OAc.The mass ratio mentioned in this paper refers to the mass ratio of lithium bromide to ionic liquid.Secondly,a window reactor which has great sealing effect and can be disassembled conveniently is designed and customized.A saturated vapor pressure measurement system with high precision is also established.Several tests are carried out on the system.The vacuum tast shows that the absolute pressure in the system can be pumped to 13.8 Pa,which is close to the absolute vacuum state.Sealing performance test finds that the pressure rises from 13.8 Pa to 176.6 Pa within 4.5 hours.The system is proved to be reliable by measuring the saturated vapoe pressure of deionized water and lithium bromide solution.The uncertainty of temperature measurement and pressure measurement are analyzed in this paper.Next,the vapor-liquid equilibrium data of LiBr+[Emim]OAc+H2O ternary saturated and unsaturated solution in the temperature range of 303.15 K?388.15 K are measured and are correlated by Antonie equation.The ternary saturated solution has the following conclusions.The vapor pressure of LiBr+[Emim]OAc+H2O ternary saturated solution reaches the lowest value,when the mass ratio of lithium bromide to ionic liquid is within 3?4.The lowest vapor pressure of ternary saturated solution is lower than that of lithium bromide saturated solution,which decreases by 10.4%and 13.7% respectively at 30? and 70?.The ternary unsaturated solution has the following conclusions.At the same concentration,the saturated vapor pressure of ternary solution is higher than that of lithium bromide solution and increases with the decrease of mass ratio.At the same mass fraction of lithium bromide,the saturated vapor pressure of ternary solution is lower than that of lithium bromide solution and decreases with the decrease of mass ratio.At the same mass ratio,the saturated vapor pressure of ternary solution decreases with the increase of concentration.The saturated vapor pressure of ternary solution is close to that of lithium bromide solution with 10%lower mass fraction when the mass ratio is 3.Under the same absorption capacity,the crystallization temperature of ternary solution?mass ratio is 3,concentration is less than 73%?is about 10?lower than that of lithium bromide solution.Under the same absorption capacity,the saturated vapor pressure of ternary solution rises slower than lithium bromide solution when the temperature rises.Then,the saturated vapor pressure of LiBr+[Emim]OAc+H2O ternary system is predicted by statistical thermodynamic model with high accuracy.The average absolute relative deviation between the predicted and experimental values was 3.95%.It is checked that the saturated vapor pressure of ternary solution is between LiBr+H2O solution and[Emim]OAc+H2O solution.The theoretical analysis is carried out by using statistical thermodynamic model.The simple mixing rule was modified and average absolute relative deviation?AARD?is 4.86%Finally,the dehumidification effect and absorption characteristics of LiBr+[Emim]OAc+H2O ternary solution are discussed.Compared with saturated lithium bromide solution,ternary saturated solution can theoretically reduce the humidity of outlet aie by 0.2 g/kg and 1.5g/kg,respectively by 10.9%?14.3%at 30?and 70?.The generation temperature of ternary solution in absorption refrigeration system with separation device is 72.6?,which is 7.6?lower than that of conventional lithium bromide absorption refrigeration system?80.2??.Therefore,LiBr+[Emim]OAc+H2O ternary solution has the potential to become an alternative desiccant for higher drying requirements,as well as an alternative working pair for absorption refrigeration system. |
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