|关键词||流化床反应器 二甲基二氯硅烷 分段换热 分段控温 数值模拟|
The internal heat exchanging devices of large-scale fluidized bed reactor for organic silicon monomer synthesis are U-tube or finger-type heat exchange tube structure. The heat transfer medium is introduced therein to perform heat exchange so as to achieve the purpose of controlling the temperature. However, this kind of heat exchange structure can easily lead to non-uniform temperature field distribution in the bed, which affects the reaction efficiency for large-scale fluidized bed reactors. In this paper, combined with the dynamic calculation of different reaction temperature and different initial reaction pressure and the calculation of gas velocity of silicon powder fluidization, we proposed a fluidized bed reactor of multiple tubular and segmented heat transfer to solve this problems. This type of reactor is completely different from the conventional fluidized bed reactor, which combined with reactor expansion zone, reaction zone, and gas feed cone. The multi-stage and multi-tube heat exchangers are used in the reaction zone. The gas and solid materials are reacted within the tube length of the reactor in multiple longitudinal tubes, and the heat transfer medium flows and exchanges heat between the shells of the longitudinal tubes in each section. The purpose of controlling the reaction temperature of the material in the multiple tubes of the reactor is achieved through the regulation of the flow state of the heat exchange medium and the temperature of the heat exchange medium inlet and outlet. After the reactor is longitudinally segmented, the reaction is fully up and down within the tube length of the vertical tube for the entire fluidized bed reactor. The heat transfer medium flows and exchanges heat between the shells of the longitudinal tubes in each section, in another word, the heat exchange of the reactor is heat exchange in the form of a segmented multi-tube heat exchanger. In order to realize the difference in the vertical reaction process within the pipeline, and stepwise control of the reaction zone temperature, and maximizes the effectiveness of the reaction zone. The pilot plant of fluidized bed reactor of multiple tubular and segmented heat transfer was established. The process conditions such as reaction temperature、reaction pressure and methyl chloride mass flow rate of synthesis of dimethyldichlorosilane were studied in this device. The effects of mthtyl chloride mass flow rate and reaction pressure on the conversion rate of methyl chloride and yield of methylchlorosilane were investigated under the reaction condition. The preferred process operating conditions of the reaction system were obtained.In this paper, the model of gas-solid multiphase flow was established in a single tube of the fluidized bed reactor of multiple tubular and segmented heat transfer by using Eulerian-Eulerian multiphase models and PC-SIMPLE algorithm in Computational Fluid Dynamics simulation software FLUENT. The fluidization characteristics of silicon powder particles in the single tube under different gas velocity conditions were investigated when the inner diameter of the single tube was 20mm and 30mm respectively, the height was 8000mm, and the grid size was 0.5mm×0.5mm. The results of simulation calculation show that the time of the complete fluidization of silicon powder particles is shorter with the increase of gas velocity. when the inner diameter of the single tube of the fluidized bed reactor of multiple tubular and segmented heat transfer is 20mm, there is always different degree of channel flow at the different bed heights, especially after the gas velocity is greater than 0.30m/s, the channel flow is more serious. This will affect the heat transfer, mass transfer and chemical reaction between silicon powder particles and gas phase. When the inner diameter of the single tube is 30mm and the gas velocity is from 0.15m/s to 0.30m/s, the mixing of silicon powder particles and the gas phase is relatively sufficient at the different bed heights.The reaearch work will provide a certain basis for the optimization of the size structure of the fluidized bed reactor of multiple tubular and segmented heat transfer and the process operation conditions and the design of the demonstration plant.
|王强. 新型二甲基二氯硅烷反应器的优化及工程应用[D]. 北京. 中国科学院大学,2018.|
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