Micromixing Efficiency Of A Novel Helical Tube Reactor And Its Application

Micromixing (i.e. mixing at the molecular scale) is the last stage of turbulent mixing and consists of the viscous-convective deformation of fluid elements, followed by molecular diffusion. It is recognized to play a very important role in the chemical industry when the time scale of the chemical reaction involved is at the same magnitude or smaller than the time scale of the mixing process. Industrial processes, such as crystallization, precipitation and polymerization and so on are greatly influenced by micromixing.In this study, three kinds of charging components (including Vertical type, Parallel type and Impinging type) were designed. Charging components were jointed with helical tube to form a novel helical tube reactor. Micromixing efficiency of this novel helical tube reactor was characterized by iodide-iodate test system. Then toluene sulfonation reaction was employed as working system. Effects of operational conditions on conversion and selectivity were investigated. Some major findings obtained in this work as follows:1. Three kinds of charging components, including parallel type, vertical type and impinging type were designed, and the macromixing of these components were simulated using CFD. Segregation intensity Is was used to measure the macromixing efficiency. The simulated results showed that IS,verticai<IS,impinging<IS.parallel, i.e. the macromixing performance of the vertical type was best among these three components.2. Micromixing efficiency of this novel helical tube reactor was characterized by iodide-iodate test system and measured by segregation index Xs. The main results are as follows:(1) The micromixing efficiency were Xs decreased with Re increased. And the Xs increased with increase of volumetric flow ratio of regeant A to B.(2) For different components, the experimental results indicated that XS,verticai<XS,impinging<XS.parallel.This result had the same trend with the simulated results of macromixing. The micromixing efficiency of the vertical type was increasing much more in vertical type than the others.(3) Effects of charging position on Xs were investigated, which has remarkable effect on vertical type of charging component. The optimum charging position was X=3mm from charging point and the minimum value of Xs is 0.005.(4) The helical tube reactor with a small bending diameter can improve micromixing efficiency much more than that with a large diameter or the straight tube in same length.3. Toluene sulfonation reaction was conducted in helical tube reactor, the proportion of p-TsOH reached 90% (at 80℃, in 2h). The increase of circulating flowrate of toluene and the decrease of feed rate of sulfuric acid and can increase proportion of p-TsOH.