Simulation Study On Intensification Of Distillation Separation Process Of Bioethanol Fuel

As a kind of renewable liquid fuel,bioethanol fuel have significant advantages in terms of improving the octane number of gasoline,increasing the oxygen content of gasoline and reducing the emission of harmful substances in automobile exhaust.It has now become the world’s largest consumer of biofuels,with huge market potential.Firstly,through the overview and analysis of distillation energy-saving technology and bioethanol separation process,azeotropic distillation（AD）and extractive distillation（ED）are used to study bioethanol dehydration.After solvent screening,entrainers used two process are cyclohexanethe and ethylene glycol respectively.For the two ternary systems of ethanol-water-glycol,ethanol-water-cyclohexane,the NRTL thermodynamic model was selected,and the correctness of the thermodynamic model was proved.The residual curves of the two ternary systems were also analyzed and demonstrated the feasibility of azeotropic distillation and extractive distillation.Secondly,the process simulation,optimization and comprehensive performance evaluation of the conventional bioethanol process,including concentration and dehydration by extractive distillation,concentration and dehydration by azeotropic distillation were carried out by simulation software Aspen plus.The result shows that concentration and dehydration by ED schemes has less total energy consumption,annual total cost（TAC）and CO₂ emissions.Again,based on the simulation results of the concentration distillation column,four heat integration schemes,namely,different pressure thermally coupled distillation（DPTCD）,vapor recompression heat pump（VRHP）,VRHP with intermediate reboiler（VRHPIR）and internally heat-integrated distillation column（HIDiC）,are used to concentration process,and then each process is optimized and evaluated economically.The results show that the VRHP scheme is economical,which could save up to 23.5%in TAC compared with the conventional distillation column.Finally,based on the simulation results of the VRHP,ED and AD schemes,,five novel configurations of heat integration are proposed,and then each process is optimized and evaluated comprehensively.The results show that the concentration and dehydration by extractive distillation configuration 2 is demonstrated the best choice,which could save up to23.6%in TAC,58.82%in energy consumption and 56.30%in CO₂ emissions with respect to its traditional process.Hence,it can be predicted that the design will bring good economic and environmental benefits when it applies to the industrial production.