Process Optimization And Control Strategy Of Reactive Distillation For Amyl Acetate Synthesis

Amyl acetate is an important chemical raw material,and it occupies an important position in the industrial applications of chemical industry,medicine and spices.With the continuous research and development of the synthesis method and new catalyst of amyl acetate,the synthesis of amyl acetate has transformed from the traditional multi-stage continuous production into the advanced production process of reactive distillation,and the method has been widely studied and applied.In recent years,the price of energy has been on the rise and the problem of energy shortage has become more and more serious.The optimization of energy saving in the production process has become a pressing issue for green development.In this paper,the different pressure thermally coupled reactive distillation(DPT-RD)and the reactive dividing-wall column(RDWC)technology are applied to further energy saving transformation of conventional reactive distillation(CRD)process,and its energy-saving optimization and control strategy are carried out in-depth research.Firstly,the optimization and control of the CRD process under the two operating ways of equal reactant feed(single-column process)and excess reactant feed(two-column process)are studied.The total annual cost(TAC)is used as the objective function,and the minimum TAC of single-column process and two-column process is584.66×10~3$/y and 790.77×10~3$/y,respectively.And the control performance of two dynamic processes is investigated.The dynamic results indicate that both processes can achieve stable control under a suitable control structure when the system introduces a step change of±20%in feed flow and 5%in feed composition.Based on the optimal operating parameters of the CRD process under the two operating modes,their improvement processes,DPT-RD process and RDWC process are proposed.As well the design and control of the improved process are studied.Steady-state optimization results show that the DPT-RD process saves energy consumption by 33.74%and TAC decreases 7.96%compared with the single-column process,and the RDWC process saves energy consumption by 8.35%and TAC reduces12.15%compared with the two-column process.Through the research on the control performance of DPT-RD and RDWC processes under various control schemes,the optimal control strategy suitable for each process is obtained.The DPT-RD process can effectively deal with the disturbances of feed flow and feed composition under the composition-temperature cascade control structure CS3.And the RDWC process can also achieve robust control under the control structure CS2(composition-temperature cascade control)and CS3(vapor split ratio control).However,the control structure CS2 needs to use the composition controller and has a long settling time,so the control structure CS3 is a superior control scheme.Finally,the steady-state economics and dynamic controllability of the four different processes are analyzed and compared in a comprehensive way.The improved process and the CRD process may be different in steady-state and dynamic characteristics due to the increase of integration degree.By the comparison results,we can see that the“neat”operation has better steady-state economics.For example,the single-column process decreases TAC by 26.06%compared with the two-column process,and the DPT-RD process reduces TAC by 22.53%compared with the RDWC process.However,there is a large value of integral absolute error(IAE)in the dynamic response of the equal reactant feed process,which shows that the controllability is not as good as the process with excess reactant.In summary,according to the trade-off between the economics and controllability of different processes,the RDWC process is a better choice to meet the current status of industrial production.