Structure And Anslysis Of Double Dividing-wall Reactive Distillation Columns

Reactive distillation is an effective process intensification technology and has an important position in the field of chemical engineering.However,the currently proposed reactive distillation structure cannot be applied to all separation systems,especially for quaternary reversible reaction with the most unfavorable ranking of relative volatilities(MURRV),it is often necessary to connect multiple conventional rectification towers(CDC)to achieve effective reaction separation,and different structures are required for the separation of exothermic and endothermic reactions,there also have a low degree of energy coupling between the reaction zone and the separation zone.Defects,which bring about greater operating energy consumption,so it is necessary to develop a new structure to solve the above problems.The dividing-wall technology has been extensively studied because of its advantages such as simplifying the structure,increasing design selectivity,and strengthening thermal coupling to achieve a significant cost reduction effect.Based on the above content,this paper introduces the dividing-wall technology in ER-RDC,and designs 8 double dividing-walls reactive distillation structures(R-DDWDC),which are used to separate exothermic and endothermic reactions.Based on the Trial-and-Error Testing and the Gradient Method,the optimal steady-state structure is searched out,and the feasibility and effectiveness of the proposed R-DDWDC are evaluated based on the ideal quaternary reversible reaction case.(1)The structures of R-DDWDC1 and R-DDWDC5 were designed using the material transfer strategy.The new structures introduce gas-phase reflux on the basis of the original liquid phase side stream,which realizes the material coupling between the left and right sides of the tray at the connecting stream;the upper and lower tower shells at the connecting stream are respectively equivalent to two horizontal partitions to form a single tower.The structures reduce the cost of a tower shell and its land occupation.(2)Proposed the concentration restriction strategy of the reactant in the side stream,and designed the structures of R-DDWDC2 and R-DDWDC6.The new structures restrict the mole fraction of unconverted reactants entering the separation tower by displacing the two dividing-walls and extending them in the reverse direction,enhancing the pre-separation effect,and at the same time improving the energy coupling degree of the substances in the reaction and separation zones.(3)Proposed the coordinated dividing-wall partition configuration strategy and designed R-DDWDC3 and R-DDWDC7 structures.The new structures achieve the purpose of reducing the energy consumption required for the separation operation by further coordinating the position of the right side dividing-wall and the position of a certain product.(4)The R-DDWDC4 and R-DDWDC8 structures are designed using the heat exchanger coupling strategy.The new structures combine the tower shell and the heat exchanger,and places the two dividing-walls at one side of the reaction section,which reduce the cost of one heat exchanger,two tower shells and their land occupation.The fact that the R-DDWDC structures reduce operating energy consumption proves that the introduction of dividing-wall technology can overcome the multi-tower problem and achieve the effect of reducing operating energy consumption.Among them,R-DDWDC7 has become the best choice because of its lowest heat exchanger heat load and good steady-state performance.