The Design Method Of Reactive Distillation Process Based On Quasi-binary Approach

The process of reactive distillation (RD) is an operation process coupling chemical reaction and rectification in one column. It is characterized by low energy consumption, high conversion rate and low capital investments comparing with traditional technics like reaction followed by separation process, so RD process has become the hot spot problem in chemical engineering domain at present. Because of the strong coupling effect of reaction and separation, the RD design problem is very complicated and is not solved successfully at present. Based on the influence characteristics of the reflux ratio and the theoretical stages to the effect of reaction and separation, this paper presents a new design method of reactive distillation based on quasi-binary approach.1,The research on the influence characteristics of reflux ratio and theoretical stages to the product purity in reactive distillation system. In the base of chemical reaction and vapor-liquid phase reaching equilibrium state, Aspen software is applied to simulation of three representative examples in according with the theory of minimum Gibbs free energy in this paper. It is found that there exists optimal theory stages (or reflux ratio) corresponding to high product purity according to fixed reflux ratio over changed theory stages (or fixed theory stages over changed reflux ratio).This characteristics is some different from ordinary distillation.2,Considering the disadvantage of graphical design method can not be used in polycomponent RD system, a quasi-binary based reactive distillation graphical design method is put forward. The components of the system being studied are divided into two groups according to degree of volatility, named quasi-heavy component and quasi-light component, then through solving the vapor-liquid equilibrium data of the system, quasi-binary method can be applied to carry out RD graphical design calculation. This method can be used to design RD system of over four components, consequently RD graphical design method is developed.3,Based on quasi-binary method built agone, a new RD column design method is put forward. Considering the influence characteristics of the reflux ratio and the theoretical stages to the product composition, an RD optimal design model is built with the maximum of product composition being as objective function, the reflux ratio and the quasi-light component composition in feed stage(corresponding with theory stages) being as decision variables. Compared with methods of other literatures, this design method only has two decision variables, it is characterized by simple model, using convenient.4,In order to realize automatic operation of the design method , the interface integration technique is used in the software integration of RD column optimal design method . Through analysing the run mechanism of Windows and characteristics of the software in this paper, the interface integration technique based on message manage mechanism of Windows is applied. The Shell function and SendKeys sentence are used and Visual Basic and Aspen software integration are realized.This design method is used to study the reactive distillation design examples of synthesizing MTBE, DEC and olefin disproportionating reaction systems and the design results are compared with results from other literatures. It can be concluded that the design results of this paper fit close with results of other literatures, and can maintain low energy consummation at the same time, furthermore the method have advantage of using simply , so it can be used to design RD process.