Reactive Double Dividing-wall Distillation Column For Inhibiting Side Reaction Of Quaternary Cascade Reaction

As an important technology in the field of chemical process intensification,reactive distillation technology fully coupling the reaction process with the separation process,which can save energy and improve the dynamic characteristics of the reaction,has great economic advantages.However,this advantage is difficult to be realized when the reaction system with low selectivity is applied to the less favorable relative volatility sequence(the sequence of reactants and products’ volatilities).Specifically,the unreacted reactants because of higher volatility than the products are mixed in the discharge and the products of side reaction products are interfering with the product composition.The increased energy consumption and investment in equipment associated with the secondary separation of reactants and side reaction products using an external circulation back to the reactive distillation column using a conventional distillation column sequence(CRDCS)followed by several conventional distillation columns severely reduces the benefits of reactive distillation technology.In this paper,the isolation wall distillation technology was used to improve the defect,making full use of the material and energy coupling between the columns in the CRDCS structure,and according to the different coupling degree,three kinds of reaction isolation wall distillation columns with different structures were successively deduced.They are reactive dividing-wall distillation column connect Distillation Colum(R-DWDC+DC),reactive distillation column connect dividing-wall distillation column(RDC+DWDC)and reactive double dividing-wall distillation column(R-DDWDC).And taking the ideal quaternary reversible reaction(the main reaction is A+B(?)2C,the side reaction is A+C(?)2D)as an example,the steady-state models of four structures are built in the simulation software Aspen.To economic indicators of total investment(TAC)as the optimization goal,the structure of the model was optimized,the optimal TAC of each structure is obtained Compared with CRDCS,the energy saving efficiency,equipment cost saving rate and total TAC saving of three kinds of reaction wall distillation column were observed.On the basis of steady-state design,the basic control loop and temperature control loop are designed for the structure with the smallest TAC,and the control structure is built and adjusted in Aspen Dynamics to obtain the dynamic control structure with the optimal steady-state structure.The dynamic characteristics of the control system were studied by applying a flow disturbance of±20%to the feed.The results show that the R-DDWDC structure with the highest coupling degree can achieve a TAC saving of 26.31%,including 28.97%energy saving and 23.77%equipment cost saving.And the dynamic control structure based on the design can quickly return to the set stable state in the face of flow disturbance,which indicates that it has strong stability and anti-interference ability.The study of ideal system provides some reference value for the separation and operation of similar systems.