Design And Control Of Reactive Dividing-wall Column For The Synthesis Of Diethyl Carbonate

In this paper,the design and control of reactive distillation process for the production of diethyl carbonate(DEC)is studied.Homogeneous catalyst sodium ethoxide is selected as the reaction catalyst.Due to the presence of azeotrope in the reaction system,feed location is discussed and an unusual feed location is used: the heavier DMC feed should be located in the middle of the reaction section,while the lighter EtOH feed should be located at the top part of the reaction section.A reactive distillation two tower process is developed and optimized by minimizing the total annual cost(TAC).A reactive dividing-wall column(R-DWC)is also designed with the same number trays,feed conditions and product specifications.The results show that the R-DWC can save 18.7% of the energy consumption and 13.9% of the TAC compared with the two tower process of reactive distillation.The dynamic control structure of reactive dividing-wall column is studied.Four control schemes are proposed,and the four control schemes are compared by introducing the flow and composition disturbances.The control structure CS1 can make the system reach the steady state,but the time is long and the instantaneous concentration deviation is large.On the basis of CS1,the control structure of CS2 is added with feedforward controller,which reduces the instantaneous concentration deviation of the product,but the system is still stable for a long time.On the basis of CS2,the control structure CS3 control the stripper column pressure,reduces the time to reach steady-state.Based on CS2,the control structure CS4,which maintain the liquid split ratio constant,can make the system reach the stable state quickly and maintain the product purities close to the set point,the instantaneous concentration deviations of products are small.