Process Simulation For The Separation Of Ethanol-Water Azeotropic Mixture Through Ionic Liquids

Ethanol is considered as a clean fuel for burning and reduces total CO2 emissions which is a serious problem associated with fossil fuels.Besides,ethanol has importance in various types of industries.The main problem for the use of ethanol is associated with its water impurity.Ethanol can be separated out from water up to 89.4 mol%,but more purity is not possible through conventional methods due to formation of azeotropes.Therefore,special methods like extractive distillation are adopted for obtaining further purity.In extractive distillation method,conventional solvents are facing some problems like solvent loss,hard to regenerate toxic and require more energy.New Ionic Liquids(ILs)are getting more attentions for breaking ethanol water azeotropes due to good properties like negligible vapor pressure and higher boiling point leads less solvent loss,easy regeneration and less energy requirements.Hence,there is a need to simulate an ILs based extractive distillation process to check feasibility.Aspen plus simulation is used in present work for designing ILs based extractive distillation process.New establishment of COSMO-SAC thermodynamic model is used for dehydration of ethanol in extractive distillation by ILs.Common thermodynamic model relay on binary interaction or group contribution parameters which is difficult to obtain due to limited experiments.While,COSMO-SAC model is based on sigma profile values which can be defined in Aspen plus software through recent ionic liquid databank(ILUAM).The COSMO-SAC model was inherently validated with large number of ILs and it accuracy is similar with other thermodynamic models.In present study,two ILs[Bmim]BF4 and[Emim]BF4 were used as a solvent to design Aspen plus extractive distillation process for ethanol dehydration.The designed process was mainly consisted of extractive distillation column and flash tank for ILs regeneration.Through sensitivity analysis,governing parameters of extractive distillation were optimized as feed position for ethanol mixture 34 and for solvent 8,total number of theoretical plates 45,Solvent to feed(S/F)ratio 0.32,reflux ratio 1 and flash tank temperature and pressure for ILs regeneration was 200? and 0.01 atm.The current simulation results were verified and agreed well with previously reported results on same capacity of ethanol dehydration plant.While comparing both ILs,present results shows that ethanol purity was achieved 99.43 mol.%and water removal was 96.78 mol.%with[Bmim]BF4.However,purity was increased in case of[Emim]BF4 as 99.96 mol.%and more water was removed up to 99.73 mol.%.The total energy consumption(TEC)was almost similar for both ILs but[Emim]BF4 performed well based on ethanol purity and water removal.The energy,ethanol purity and solvent regeneration comparisons in between current ILs and conventional solvent were made,which indicate that use of ILs in extractive distillation for the separation of ethanol and water require less energy than conventionally used solvent.The solvent loss was reduced and ethanol purity was also improved.Therefore,ILs can make ethanol dehydration process more feasible.Hence,there are several advantages of using non-volatile ILs-solvents.Because ILs-solvents have negligible vapor pressure,easy to regenerate and tuneable cation+anion options for more optimize the process design.In the future study,COSMO-SAC model can father apply on other families(Pyridine,Triazole)of ILs more practical solution.