Study On The Separation Process Design And Control Of The TFP-water Azeotrope System

2,2,3,3-Tetrafluoro-l-propanol(TFP)and water form a minimum temperature azeotrope under atmospheric pressure,which is difficult to separate TFP by ordinary distillation.In this paper,the azeotropic distillation and the dividing-wall column(DWC)of the lowest total annual cost(TAC)as the objective function were designed and optimized via the Aspen Plus and Aspen Dynamics of chemical process simulation software,and the optimal process were dynamically controlled.Firstly,the isobaric vapor-liquid equilibrium(VLE)data for the systems TFP + water,TFP+chloroform,and TFP+ p-xylene at atmospheric pressure were measured by a recirculating type equilibrium still.The saturated vapor pressure,activity coefficient,and excess Gibbs free energy were calculated by the extended Wagner 25 liquid vapor pressure equation.And the thermodynamic consistency of the VLE data were checked by the method of Herington test,van Ness test,infinite dilution test,pure component consistency test and QVLE.Secondly,the VLE data for the systems TFP+water,TFP+chloroform,and TFP+p-xylene were correlated by the NRTL,UNIQUAC and Wilson activity coefficient models,and the binary interaction parameters of the three models were regressed.The root mean square deviations of the vapor-phase fraction and temperature between the correlated and the measured values are less than 0.0098 and 0.30 K,respectively,by the regression binary interaction parameters of the three models.Finally,the thermodynamic model UNIQUAC was selected,chloroform and p-xylene were adopted as azeotropic agents,and separated azeotrope via the residue curve maps design in azeotropic distillation.In Aspen Plus simulation,the TACs for the separation of the mixture(TFP+water)by adding chloroform and p-xylene as the azeotropic agents are 2.42 × 106 $ and 4.93 × 106 $,respectively.Therefore,chloroform is considered as an azeotropic agent for the separation of the mixture(TFP+water).When chloroform is adopted as the azeotropic agent,the total condenser duty reduction of 44.57%,total reboiler duty reduction of 42.66%and TAC reduction of 37.79%are obtained in the DWC design,compared with those in the conventional design.The control strategy performance for the conventional and DWC designs are satisfactory,since TFP is separated with high purity,despite the fresh feed flow rate,fresh feed composition and liquid split ratio disturbances.