Economics And Dynamics Of Pressure-swing Distillation And Extractive Distillation With Varied-diameter Column For Separating Binary Azeotropic Mixtures

Varied-diameter column was adopted in pressure-swing distillation and extractive distillation for separating five common azeotropic systems,including acetone-chloroform,acetone-methanol,methanol-chloroform,benzene-cyclohexane,and isopropyl alcohol-diisopropyl ether.The distillation processes of the five azeotropic systems were investigated.The cost model was established.On the basis of minimum total annual cost(TAC),sequential iterative optimization procedure was adopted for optimizing the five azeotropic systems,getting the optimal flowsheets of pressure-swing distillation and extractive distillation,respectively.The saving costs for each system were calculated.Compared with extractive distillation,pressure-swing distillation was more suitable for adopting varied-diameter column in the view of economics.The saving percentage of pressure-swing distillation was larger than that of extractive distillation for every system.Pressure-swing distillation processes with varied-diameter column for no heat integration,partial heat integration,and full heat integration were studied and the TAC values were calculated,respectively.The TAC of fully heat-integrated process was minimum among the three heat-integrated types.The saving percentages of no,partially,and fully heat-integrated pressure-swing distillation were 10.36%,10.36%,and 15.73%,respectively.Pressure-swing distillation without heat integration was studied from the point of controllability,the process with full heat integration was also explored because of its superiority in economics.The control difficulty was the same between the pressure-swing distillation without heat integration and with full heat integration in adopting varied-diameter column,the combination of common control structure could achieve effective control.The dynamics of separating acetone-methanol by pressure-swing distillation and extractive distillation with varied-diameter column was explored.The process of pressure-swing distillation could get robust control for ±20% feed flow rate and feed composition disturbances after improving the control structure,the design of control structure for extractive distillation with varied-diameter column was relatively complicated,±10% feed flow rate and feed composition disturbances could be handled using the final control structure.The pressure-swing distillation with varied-diameter was better in dynamics,which was more suitable for adopting varied-diameter column.The distillation process with varied-diameter column for separating azeotropic mixtures was explored from economics and dynamics for the first time.The general rule of pressure-swing distillation and extractive distillation with varied-diameter column was summarized,which could provide guidance to the process design and evaluation of production investment for the special distillation column separating process.