| This paper has a deep research to static mixer and falling film reaction and release tower which are used in the concentrated acid hydrolysis process of dimethyl dichloro-silane.The flow field of kenics static mixer under high Reynolds number is simulated with application of computational fluid dynamics (CFD) software Fluen. The velocity distribution, eddy current phenomenon, turbulent kinetic energy distribution and pressure distribution inside the mixer were studied deeply. Fluid mechanics characteristic and the mixing mechanism in the mixer were also described in detail. The influence of Reynolds number, aspect ratio and twist angle of helical blade on pressure drop and mixing efficiency is also studied, and obtained pressure drop correlations under certain conditions. The research shows that mixing efficiency does not improve as the flow rate, on the contrary, improve flow rate greatly increases the pressure drop. Therefore, low flow operation is suggested. It is better to choose a mixer with bigger diameter, so as to reduce the speed of the fluid and reduce the pressure drop, lower power consumption. A mixer with1.0aspect ratio and120°twist angle is recommended in order to reduce energy consumption on the premise of meet the mixing effect.The reactants are mixed and reaction in static mixer firstly, but due to short residence time the reaction can’t complete absolutely. Fluid that comes from static mixer then entered falling film reaction and release tower to reaction and release of gas. Falling film reaction and release tower is a new kind of reaction and release device which was put forward according to falling film theory. Falling film can increase the contact area of two reactants and has high heat and mass transfer efficiency. A deep research to various factors that can influence the flow of falling film was conducted through theoretical analysis, experiment research and CFD simulation. The following conclusions can be drawn:(1) Hole and disk type of liquid distributor is recommended, aperture is6-8mm and holes spacing between40mm to60mm, square arrangement.(2) The liquid film is thinner and more uniform when the film board is40°to50°to horizontal direction. The minimum wetting flow rate of fluid is different on different board, but after complete wetting, the average thicknesses of liquid film on different boards have little difference under same flow rate. Liquid with a bigger viscosity is thicker under the same flow rate. The films are thicker and have a stronger volatility with the increase of Reynolds number, but the volatility of high viscosity fluid has no obvious change.(3) The microstructure on the surface of the board as well as the nature of the liquid, especially the viscosity and surface tension of liquid play an important role on the formation of a continuous liquid film. Changing the microstructure on the surface of the board and lower the surface tension of the liquid can promote the formation of the continuous liquid film.(4) The residence time of liquid film on the corrugated plate is longer than that on the flat plate is longer in a same time, and this contributes to a fully reaction.(5) Volatility of gas-liquid-liquid three phase falling film is stronger than gas-liquid two phase falling film, it is benefit to liquid micelles in the bottom of the film rise to the surface, thus improve the heat and mass transfer efficiency between gas and liquid.(6) Open diversion channels in the lower edge of the boards are conducive to the distribution of the film on the next boards.Therefore, the film board is adviced change from60°to45°to horizontal direction and corrugated board is suggested. Nylon boards which have better wettability for materials can be used at the stages of alkali washing and water washing for hydrolysate. Open rectangle grooves in the lower edge of the boards are conducive to the distribution of the film on the next boards. |
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