Process Optimization And Control Strategy Of Ethyl Acetate-amylacetate Reactive Distillation Co-production

Ethyl acetate and amyl acetate are very important raw materials for organic chemical industry.The increasing market demand for these two compounds requires strengthening production management and adopting more efficient processes.The traditional method of producing ethyl acetate and amyl acetate decreases the conversion efficiency due to the large amount of azeotrope in the reaction system.The main reason are that ethyl acetate has insufficient capacity to carry water while amyl acetate has too much water,which requires a multi-stage continuous production processes.Although there is a great demand for high purity amyl acetate（≥99.5mol%）,little has been reported on its production process.China is a big consumer of ethyl acetate and amyl acetate.If a technological process can be proposed to reduce production cost,improve conversion and purity,it will be more widely used in these two solvents.In this paper,an energy-efficient new process is proposed which utilizes reactive distillation for the combined production of ethyl acetate and amyl acetate,and the feasibility is determined by thermodynamic analysis.The conventional reactive distillation process is further energy-efficient by using intermediate heated exchanger reactive distillation（RD-IC-IR）and reactive dividing wall column（RDWC）technologies through a process intensification approach,and its energy-saving optimization and control strategies are thoroughly investigated.Firstly,the ethyl acetate-amyl acetate conventional reactive distillation co-production process of different alcohol（amyl alcohol/ethanol）feeds ratio,the intermediate heat exchanger reactive distillation process with different alcohol feed ratio and the reactive distillation column process with different alcohol feed ratio were established.The annual total cost（TAC）was used as the objective function to optimize.When the feed rate was Am OH:Et OH=1:2,The minimum TAC of the three processes were 508.26×10⁴$/year,502.95×10⁴$/year and 530.22×10⁴$/year,respectively.When the feed amount was Am OH:Et OH=1:1,the minimum TAC of the three processes were488.38×10⁴$/year,426.39×10⁴$/year and 427.23×10⁴$/year,respectively.When the feed amount was Am OH:Et OH=2:1,the minimum TAC of the three processes were414.19×10⁴$/year,314.12×10⁴$/year and 264.61×10⁴$/year,respectively.Secondly,the economy,environmental friendliness and thermodynamic efficiency of the three reactive distillation processes are comprehensively analyzed and compared.From the comparison results,it can be seen that the three processes established have good effects when the feed ratio of amyl alcohol to ethanol is 2:1.Compared with the RD process,the TAC and CO₂emissions of the RD-IC-IR process were reduced by21.92%and 28.27%,respectively,and the thermodynamic efficiency was increased by38.86%.The TAC and CO₂emissions of the RDWC process were reduced by 36.11%and 42.49%,respectively,and the thermodynamic efficiency was increased by 74.45%.Finally,based on the complex network analysis,the key variables that have a greater impact on the process are analyzed:the key variables of the conventional co-production of ethyl acetate-amyl acetate process are the organic phase flow rate and the raw material feed rate;the key variables of the reactive distillation process for co-production of ethyl acetate and amyl acetate by intermediate heat exchanger are organic phase flow rate and side-stream liquid phase recovery.The key variables of reactive distillation dividing wall column co-production process of ethyl acetate-amyl acetate are organic phase flow rate and side-stream vapor phase recovery.Through the research on the performance of various control schemes established by the three processes,the optimal control strategy of each process is obtained.The RD process can effectively deal with the disturbance of organic phase flow and feed flow under the CC-TC control structure CS2 with Q_R/F ratio,and achieve robust control.The RD-IC-IR process can achieve stable control under the pressure-composition cascade control structure CS3 and the RDWC process under the temperature-composition cascade control structure CS4.The IAE index is used to evaluate the dynamic control structure,and the results show that the improved RDWC process has better dynamic controllability.Therefore,the the reactive distillation dividing wall column combined with ethyl acetate-amyl acetate process has great advantages in both steady-state evaluation and dynamic control evaluation.