Comprehensive Design And Optimization Of Heat Pump Assisted Distillation Dividing Wall Column For The Separation Of Azeotropic Systems

The chemical sector accounts for almost 30%of energy use in all industrial sectors.In the chemical and related industries,distillation is one of the oldest processes in the chemical industry and,being an energy-intensive process,accounts for about 40%of the total energy consumption in the process industry.While simple distillation processes cannot separate azeotropic mixtures,they need to be separated with high purity by special distillation methods.In this paper,the chemical process simulation software Aspen Plus is used for modeling to establish the design flow of the dividing wall column in the azeotrope separation process,and the heat coupling with the dividing wall column is realized by heat pump distillation technology.Taking the minimum annual total cost as the optimization objective,the sequential iterative optimization design was completed.Verification of the potential of heat pump assisted distillation dividing wall columns in azeotropic separation processes by comparing total annual costs,CO₂ emissions and thermodynamic efficiency indicators.In the separation process of acetone-n-heptane azeotrope system,butyl propionate was used as the entrainer to establish extractive distillation and extractive dividing wall column.The optimal design is determined by the sequential iterative optimization process,and the heat pump is added to the optimal design of the extractive distillation tower to save energy.By comparing with the extractive distillation process,the TAC of the heat pump assisted extractive dividing wall column process is 808.87×10³$/year in 3 period years,with a 5.74%saving in comparison;CO₂ emission is 366 kg/h,with a 34.80%reduction year-on-year;and the thermodynamic efficiency is 9.61%,with a 48.53%improvement year-on-year.In the separation process of azeotropic system of acetonitrile and water,the steady-state model of extractive dividing wall column is established with ethylene glycol as the entrainer,and the optimal parameters are determined by sequential iterative optimization with the minimum total annual cost as the objective function.The optimal process is combined with a heat pump to form two heat pump assisted extractive dividing wall column structures.In comparison with the extractive dividing wall column process,the TAC of the two heat pump assisted extractive dividing wall column processes were1312.76×10³$/year and 1314.99×10³$/year,respectively,with a year-on-year saving of 25.76%and 25.64%;the CO₂ emissions were 1016.90 kg/h and 899.62 kg/h,respectively,with a year-on-year reduction of 19.67%and 28.93%respectively;thermodynamic efficiency is 9.16%and 10.35%respectively,39.85%and 58.02%higher year-on-year.Aiming at the azeotrope system of acetonitrile and water,an azeotropic distillation process using benzene as azeotrope was established.Aiming at the azeotropic dividing wall column process to preheat the flow into the rectification column,the azeotropic dividing wall column process with feed preheating was built.The optimal process obtained by sequential iterative optimization method is combined with a heat pump to form a heat pump assisted azeotropic dividing wall column process.Compared with the azeotropic dividing wall column process,the TAC of the heat pump assisted azeotropic dividing wall column process is 623.09×10³$/year in 10 period years,saving 19.42%;CO₂ emission is 278.60 kg/h,which is 60.23%lower year-on-year;thermodynamic efficiency is 10.56%,which is 135.71%higher year-on-year.