Design Of Dividing-wall Reactive Distillation Columns

In the new era of energy development,China’s energy industry should construct a sustainable modern energy institutional system.Especially in the petrochemical industry,traditional extensive low-efficiency and high-consumption equipment should be transformed into accurate high-efficiency and low-consumption equipment.As an effective separation process strengthening technology in the petrochemical industry,reactive distillation can simultaneously promote the reaction operation and separation operation,overcome the ambiguity of the equilibrium reaction,and thus greatly reduce the equipment investment cost and operation energy consumption.However,these advantages exist only in the case of using a reactive distillation column to separate a reaction mixture having more favorable kinetic characteristics,and the advantages brought by conventional reactive distillation are often difficult when faced with the separation of a reaction mixture having relatively unfavorable kinetic characteristics.In this paper,in order to solve the problem of the conventional reactive distillation column(RDC)reactant accumulation from the theoretical level,firstly,the reactants which are easily accumulated on the rectifying section or stripping section of the column are mixed with the product,and then the separated mixture is separated by a conventional distillation column.The separated reactants are introduced into the reaction section through an external circulation,so that a certain reactant is fed in excess,which not only solves the problem that the reactants accumulate in the column affects the separation effect,but also improves the reaction efficiency of the reaction section.In order to further strengthen the internal energy coupling of the distillation column,a dividing-wall device is introduced on the basis of the double column external loop reactive distillation column(ER-RDC),and then coupled into an excess feed reactive dividing-wall distillation column(ER-DWDC).Firstly,the ideal system with a relatively unfavorable relative volatility ranking is used to optimize the design of the conventional reactive distillation column,the double-column external circulation reactive distillation column,and the ER-DWDC with the total annual distillation cost(TAC)as the objective function,then comprehensive comparison and analysis;secondly,based on the ideal system research,the actual methanol methyl acetate hydrolysis reaction was used to verify the advantages of the ER-DWDC compared with the conventional reaction distillation column,and the practical application effect of excess feed reactive dividing-wall distillation was evaluated.By analyzing and comparing the optimal steady-state design of the conventional reactive distillation column,the double-column external circulation reactive distillation column,and the excess feed reactive dividing-wall distillation column,the results show that DWDC with the lightest reactant feed excess has a minimum total annual cost and superior steady-state performance for the separation of less favorable relative volatility sorting system.The structural advantage is mainly reflected in the energy relationship between the reaction section and the separation section of the dividing-wall,which greatly enhances the energy coupling in the column;the external circulation promotes the excess feed of a certain reactant,thereby shifting the equilibrium of the chemical reaction to the right and improving the average reaction rate,the efficiency of the reaction section is improved,and the coupling of the whole column material is greatly enhanced.Therefore,the reactive dividing-wall distillation column with excessive reaction of the light reactant has superior steady-state performance,which can significantly reduce the equipment investment cost and operation energy consumption during industrial separation process.