The Research On Optimization And Control Of Reactive And Extractive Distillation Process For The Synthesis Of Isopropyl Acetate

The esterifications which forms an azeotrope between the products were defined as type-? systerm,such as ethyl acetate systerm,isopropyl acetate systerm.A conventional reactive distillation column could not be able to produce high purity water and acetate due to the complex azeotropic behaviors in the system.In this paper,took the case of isopropyl acetate,analyzed the characteristics of type-?systerm,then a novel reactive and extractive distillation(RED)process was proposed.The extractive distillation and reactive distillation were integrated into one column,and the reaction and separation could promote each other in this progress.Since the RED progress had features of great nonlinearity and complexity,different control schemes were designed based on the optimal process to ensure good operability under the disturbances.In this paper,the feasibility of reactive extractive distillation was analyzed in terms of thermodynamics,and NRTL-HOC was validated that it has a precise prediction to isopropyl acetate system.Then the RED process was designed and optimized by Aspen plus,and the TAC of optimized flowsheet was estimated to be256($1000/year).After that,a basic control structure and an improved control structure were designed for the RED process.A step change of ±20% in feed flow and 5% in feed composition was introduced,and the integral of squared error(ISE)was used to evaluate the performance of control systems,it revealed that the improved control structure had better controllability.In order to improve the efficiency of energy utilization,and reduce the energy consumption and TAC of RED process,two kinds of process intensification schemeswas proposed by matching the cold and hot flow: intermediate reboiling reactive and extractive distillation(IR-RED)process and feed preheating reactive and extractive distillation(PF-RED)process.Steady-state optimization results show that IR-RED process saves energy consumption by 24.8% and TAC decreases 12.5%,and the PF-RED process saves energy consumption by 35.7% and TAC reduces 16.4%compared with the conventional RED process.The temperature difference control structure and Q/F-temperature cascade control structure were designed for PF-RED process.Two control schemes(temperature difference control structure and Q/F-temperature cascade control structure)were established for RED process.The dynamic simulation results showed that neither the feed composition disturbance nor the feed flowrate disturbance,both the control schemes could perform a good control effect.Finally the dividing wall column reactive extractive distillation(DWC-RED)was suggested,the reactive extractive distillation and recovery column were integrated into one column.In addtion,the optimal operating conditions are obtained by simulation and optimization.Then the vapour distribution ratio control structure was design for the DWC-RED process,The dynamic simulation results showed that the control scheme performed well when the ±20% feed flowrate disturbances and 5% IPOH composition disturbance were introduced,but the control effect was slightly worse when 5% HAc disturbance were introduced.