Heat Pump Distillation Process And Dynamics For Close-boiling And Special Wide-boiling Mixture

In this paper,the mechanical vapor recompression heat pump(MVRHP)distillation process and the separate heat pump distillation(SHPD)process were studied by using close-boiling system n-butanol-isobutanol and special wide-boiling system isopropanol-chlorobenzene as examples.The optimal operation parameters of these processes were determined by the optimization method with the total annual cost(TAC)as the objective function.The effective control structures of different distillation processes were also obtained according to the performances of various control schemes.For the close-boiling binary system n-butanol-isobutanol,the dynamic controllability of MVRHP distillation process and pressure-swing distillation with heat integration was investigated.For the MVRHP distillation process,temperature control was used,it was found that there were two temperature slope peaks in the distillation column,and the selection of different temperature control stages has important influence on the dynamic performance of the control system;for the pressure-swing distillation with heat integration,two composition controllers were used.It was found that the composition-reflux ratio cascade control structure can realize robust control.Comparisons between the robust dynamic scheme of the two separation processes show that the MVRHP process has better controllability with simple control structure.For the special wide-boiling binary system isopropanol-chlorobenzene,the influence of split point concentration of the upper and lower columns on the economy of the SHPD process was investigated,and the dynamic control strategy of the process was put forward for the first time.The optimal processes of the traditional single column distillation process,the traditional heat pump distillation process,and the SHPD process were investigated.The results show that,compared with the traditional single column distillation process and the traditional heat pump distillation process,the TAC of the SHPD process decreased by 34.06% and 32.04%,respectively.Different dynamic strategies of isopropanol-chlorobenzene separation process by SHPD were put forward,and the results show that the improved QRe/F and Wm/F control structure have advantage on the control of SHPD which has less freedom degree.In this paper,the separation method and dynamic control strategy of n-butanol-isobutanol and isopropanol-chlorobenzene binary system by heat pump distillation were studied,which have a certain reference value on the study of steady-state process optimization and dynamic performance of similar close-boiling and special wide-boiling point systems.