Economic Optimization And Dynamic Control Of Reactive Distillation To Produce Isobutyl Acetate

In recent years,with the increasingly prominent of the problems of environment and energy shortage,energy saving and green production have become the obvious trend in the chemical industry process.Isobutyl acetate is widely used in chemical industry and pharmaceutical industry.With the continuous study of the synthesis methods of isobutyl acetate by many researchers,the continuous production of isobutyl acetate in industry has been realized.At present,the process of synthesizing isobutyl acetate in industry is mostly a process of reaction first and then multi-step separation.The process has many shortcomings,such as high energy consumption and complicated process.In this paper,the process optimization and control of synthesis of isobutyl acetate by reactive distillation are studied by Aspen simulation software.Firstly,the economic optimization and dynamic control of conventional reactive distillation(CRD)process with neat operation mode were studied.Taking the annual total cost(TAC)as the target,the optimized TAC of CRD process is 5.26×10~5$/year.The control performance of CRD process is studied when the disturbance of±20%feed flow rate and 5%feed composition is introduced,and a nice control scheme CS2is obtained.In order to further reduce TAC,the bottom reboiling heat pump reactive distillation(BR-HPRD),and the intermediate reboiling heat pump reactive distillation(IR-HPRD-1)and the intermediate reboiling heat pump reactive distillation with preheater(IR-HPRD-2)processes are studied.The optimization results show that the TAC of BR-HPRD,IR-HPRD-1 and IR-HPRD-2 processes are reduced by 10.00%,16.92%and 19.13%compared with CRD process,respectively.By studying the controllability of the IR-HPRD-2 process under the disturbance of±20%feed flow rate and 5%feed composition,a effective control structure is obtained and a robust control can be achieved.Then,we studied the economics and dynamic controllability of the reactive dividing-wall column(RDWC),the vapor recompression heat pump and reactive dividing-wall column partially integrated(VRHP-RDWC-1)and the vapor recompression heat pump and reactive dividing-wall column fully integrated(VRHP-RDWC-2)processes with excess reactant operation mode.The results of economic optimization show that the TAC of RDWC,VRHP-RDWC-1 and VRHP-RDWC-2 processes are 7.45×10~5$/year,6.68×10~5$/year and 5.79×10~5$/year,respectively.Compared with RDWC process,TAC of VRHP-RDWC-1 and VRHP-RDWC-2 process decreased by 10.23%and 22.30%,respectively.Two control schemes are designed for RDWC process.The results show that control structure CS2(vapor split ratio control)can control product quality more effectively.The controllability of VRHP-RDWC-1 and VRHP-RDWC-2 processes are investigated by introducing(±20%)feed flow rate and 5%feed component disturbance.The results show that both processes can effectively control product purity under the control scheme with vapor split ratio controller.Finally,the economics and dynamic controllability of different processes are compared comprehensively.The results show that the neat operation mode has a greater advantage in terms of economics and the excess reactant operation mode has a greater advantage in terms of dynamic controllability.Although the IR-HPRD-2process of the neat operation mode has obvious advantage in economics,the VRHP-RDWC-1 process of the excess reactant mode is a better choice bacause it is difficult to control of the neat operation mode in industrial production.