Air Dehydration Using Ionic Liquid

Air is a mixture comprised of nitrogen,oxygen and other gases.The water content in air is an important indicator when it is applied industrial production.For example,air can be used to prepare nitrogen and oxygen,the water content in air must be controlled in a very low level to prevent the air separation plant from damaging due to the freezing of water.Thus,it is necessary to remove the water in air effectively.In this work,to avoid the problems in the process with traditional methods,the suitable ionic liquid is selected according to the simulation calculation to apply in air dehydration process,the process parameters is optimized to reduce the energy consumption.Firstly,the activity coefficient of components in 240 ionic liquids is calculated by COSMO-RS model.The ionic liquid[EMIM][BF4]is selected as suitable solvent for air dehydration process considering the selectivity and the relative properties of IL.The excess enthalpies and σ-profiles were calculated by the COSMO-RS model to achieve further understanding on the dehydration mechanism at molecular scale.Secondly,as the ionic liquid[EMIM][BF4]is selected to use in dehydration process,the solubility of nitrogen and oxygen in pure[EMIM][BF4]and H20 +[EMIM][BF4]solution is measured with static method.The group interaction parameters between groups of components were obtained by correlating the experimental solubility data and other relative VLE data in literatures using Mod.UNIFAC model,these parameters can be used in the simulation calculation by Aspen Plus.Thirdly,the air dehydration experiment is conducted in laboratory to investigate the effect of air dehydration using[EMIM][BF4],the influence of flow rate,water content,and species of ionic liquid on the effect of air dehydration is considered.On the other hand,after the group interaction parameters are imported to Aspen Plus,the process is simulated under the same operating condition with the dehydration experiment.The reliability of Mod.UNIFAC model applied in air dehydration using IL is verified according to the comparison of experimental and simulation results.Finally,the air dehydration process using ionic liquid/TEG as solvent are designed and simulated after the operation parameter are optimized.With the comparison of simulation results between two processes,the advantages of air dehydration with ionic liquid are discussed.The results show that comparing with TEG,[EMIM][BF4]have obvious advantages,such as high efficiency of removing water(98%),and recovery of N2 and 02(the recovery efficiency is 99.99%and 99.81%for N2 and 02),less loss of solvent.The heating and cooling duties can be reduced by 77.89%and 78.69%.Thus,the air dehydration process using ionic liquid has obvious advantages in energy saving and consumption.