Design And Control Of Reactive Distillation Column With A Top-bottom External Recycle:Effect Of Thermodynamic And Kinetic Parameter

For the separation of reacting mixtures with the most unfavorable relative volatilities,introducing an external recycle between the top and the bottom in reactive distillation column can enhance the contact of the reactants,hence can effectively boost the reaction rate;therefore,it can enhance significantly process thermodynamics efficiency.As compared with conventional reactive distillation columns,this kind of reactive distillation columns with a top-bottom external recycle(RDC_TBER)can save capital investment and reduce the utility consumption.For the seperations of chemical reacting mixtures with different thermodynamic characteristics and kinetic characteristics,rational arrangement of external recycle is the key factor for exploiting the internal mass integration and energy integration of RDC_TBER.Meanwhile,the introducing of external recycle change the mode of interaction between reaction operation and separation operation,thus influencing largely the dynamics and controllability of RDC TBER.Therefore,studying the steady-state design and controllability of RDC TBER based on the thermodynamic characteristics and kinetic characteristics of the chemical reacting mixtures is crucial.For the seperation of quaternary ideal exothermic reactions,this thesis study in detail the effect of thermodynamic characteristics(constant relative volatility and temperature-dependent relative volatility)and kinetic characteristics(Equilibrium constant and reaction heat)of chemical reacting mixures on the steady-state design of RDC_TBER.Based on the objective function of minimum total annual cost(TAC),this thesis used heuristic search algorithm to search the optimal synthesis and design stuctures of RDC_TBER.The method not only can fully exploit the potential of process internal mass integration and energy integration,but also can reduce capital investment and save operating utility consumptio.For the seperation of quaternary ideal exothermic reactions,this thesis study in detail the effect of thermodynamic characteristics(constant relative volatility and temperature-dependent relative volatility)and kinetic characteristics(Equilibrium constant and reaction heat)of chemical reacting mixures on the dynamics and controllability of RDC_TBER.Four kinds of decentralized control schemes(CSI,CSII,CSIII,and CSIV)were derived.The simulation results showed that these decentralized control schemes can attenuation disturbance while the feed flow rate and the feed composition change.They can servo control while the product specifications are adjusted.In summary,for the seperation of reacting mixtures with the most unfavorable relative volatilities,RDC_TBER can significantly enhance the system steady-state performance and controllability.