【作者】 刘宁；

【导师】 张旭斌； 靳登超；

【作者基本信息】 天津大学 ， 工程硕士（专业学位）， 2021， 硕士

【摘要】 冷氢化过程是多晶硅生产中用来回收四氯化硅的重要一环,流化床反应器是其中的核心设备。挡板结构对流化床中的气固接触效果和反应性能具有重要影响。目前槽钢型挡板已被用于工业级冷氢化流化床中,但流化效果还有待提高。对于挡板结构的优化设计,若单纯采取实验手段需付出巨大的经济代价,因此通过计算流体力学（Computational Fluid Dynamics,CFD）方法建立数学模型来研究挡板结构对流化床反应器的影响具有重要意义。本文首先建立了工业级的槽钢型挡板流化床模型,采用欧拉-欧拉多相流模型,研究挡板结构对于流化床中流场的影响。通过流化床内压力分布的模拟结果与工业装置的压力数据间的对比验证,表明了所建立的CFD模型是有效的。然后在槽钢型挡板流化床中进行了冷氢化反应的模拟,对文献中报道的冷氢化反应动力学模型进行修正,化学反应的模拟结果与工业装置的转化率数据吻合良好。模拟结果表明,槽钢型挡板导致固体颗粒在流化床内壁面和挡板表面发生团聚,气固接触效果较差,气体在床层内流动不均匀,不利于冷氢化反应的进行,Si Cl₄的转化率仅为22.69%。针对上述问题,使用百叶窗型挡板替代槽钢型挡板,进行了流化床内流体流动的模拟。与槽钢型挡板相比,百叶窗型挡板有效减少了固体颗粒的团聚现象,同时气体速度的径向分布更加均匀。气体停留时间分布测定的结果表明,百叶窗型挡板流化床中气体的返混程度更低,气体流动更接近于活塞流。随后在百叶窗型挡板流化床中进行了冷氢化反应的模拟。模拟结果表明,气体产物形成了较好的轴向浓度梯度,Si Cl₄的转化率提高至27.44%。最后考察了百叶窗型挡板的叶片倾角对流化床反应器性能的影响。模拟结果表明,适当减小叶片倾角,流化床中固体颗粒的分布更均匀,气固接触效果更好;气体速度的径向分布更均匀,返混程度减小,有助于气体反应物转化率的提高。更多还原

【Abstract】 The fluidized bed reactor is the core apparatus in the cold hydrogenation process,and the structure of baffles has an important influence on the gas-solids contact and reaction performance.At present,the channel baffles have been used in the industrial fluidized bed for cold hydrogenation,but the fluidization conditions need to be improved.For the optimization and design of the structure of baffles,it will pay a huge economic cost if only experimental methods are adopted.Therefore,it is with much significance to establish a mathematical model through Computational Fluid Dynamics(CFD)methods to study the influence of the structure of baffles on the fluidized bed reactor.In this paper,an industrial fluidized bed model with channel baffles was first established,and the Eulerian-Eulerian multiphase flow model was used to study the influence of the structure of baffles on the flow field in the fluidized bed.The comparison between the simulation results of the pressure distribution in the fluidized bed and the pressure data of the industrial device showed that the established CFD model was effective.Then,the cold hydrogenation reaction was simulated in the fluidized bed with channel baffles,and the cold hydrogenation reaction kinetic model reported in the literatures was revised.The simulation results of the chemical reaction were in good agreement with the conversion data in the industrial device.The simulation results showed that the channel baffles could lead to the aggregation of solid particles on the inner wall of the fluidized bed and the surface of baffles,the poor contact between gas and solids,and the nonuniform gas flows in the bed,which was not conducive to the cold hydrogenation reaction.In view of the above problems,the louver baffles were used to replace the channel baffles,and the hydrodynamics in the fluidized bed was simulated.Compared with the channel baffles,the louver baffles effectively reduced the aggregation of solid particles,and the radial distribution of the gas velocity was more uniform.The results of gas residence time distribution measurement showed that the degree of gas back-mixing was lower in the fluidized bed with louver baffles,and the gas flow was closer to the plug flow.Subsequently,the cold hydrogenation reaction was simulated in the fluidized bed with louver baffles.The simulation results showed that a good axial concentration gradient of gas product was formed,and the conversion of reactants improved.Finally,the influence of the vane inclination angle of louver baffles on the performance of the fluidized bed reactor was investigated.The simulation results showed that when the vane inclination angle was reduced appropriately,solid particles became more uniformly dispersed in the fluidized bed,the contact between gas and solids would was better,the gas velocity distributed more uniformly in radial direction,and the degree of back-mixing was weaker,which is helpful for the improvement of the conversion of gas reactants.更多还原