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新型二甲基二氯硅烷反应器的优化及工程应用
王强
学位类型博士
导师高林
2018-05-24
学位授予单位中国科学院大学
学位授予地点北京
学位专业材料物理与化学
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
摘要

有机硅单体合成常用的大型流化床反应器的内部换热装置多是采用U型管或指形换热套管结构,在其中导入换热介质,来进行换热,以达到控制反应区温度的目的。但对于大型流化床反应器,这种换热结构易导致床层内的温度场分布不均匀,从而影响反应效率。针对此问题,结合不同反应温度、不同初始反应压力的动力学计算和硅粉流化气速的计算,本论文提出一种多列管分段换热式流化床反应器。该反应器型制与以往的流化床反应器完全不同。该反应器由反应器扩大段、反应区和气体进料锥体三部分组成。在反应区采用多段和多列管换热器的形式,气体物料和固体物料在反应器纵向多列管的管程内进行反应,换热介质在各段纵向多列管的壳程间流动换热。多列管内物料反应温度的调控可分别通过调节各段壳程内换热介质的流动状态和换热介质进出口温度的方法来实现。对于整个流化床反应器来说,在反应器纵向分段后,反应在纵向多列管的管程内是上下全贯通的;换热介质在各段的纵向多列管的壳程间流动换热,即反应器的换热是采用分段多列管换热器的形式换热,以实现根据管程内纵向反应进程的差异,分段调控反应区温度,使反应区效能最大化。建立了多列管分段换热式流化床反应器的中试装置,并在该装置上对二甲基二氯硅烷合成反应的温度、压力、一氯甲烷流量等工艺条件进行了研究。在其他操作条件一定的情况下,考察了一氯甲烷流量和反应压力对一氯甲烷转化率和甲基氯硅烷产率的影响,获得了该反应体系的较佳工艺操作条件。本论文采用计算流体动力学模拟软件FLUENT中的欧拉-欧拉多相流模型和PC-SIMPLE算法,建立了多列管分段换热式流化床内单管的气固多相流数学模型,考察了单管内径分别为20mm和30mm,高为8000mm,网格尺寸为0.5mm×0.5mm时,不同气体流速条件下流化床内硅粉颗粒的流态化特性。模拟计算的结果表明,随着气体流速的增加,固体硅粉颗粒完全流化的时间越短。新型多列管分段换热式流化床反应器单管内径为20mm时,在所考察的气体流速范围内,在不同床层高度处总会出现不同程度的沟流现象,尤其气体流速大于0.30m/s后,沟流现象更为严重,这将影响硅粉颗粒与气相间的传热、传质以及化学反应。内径为30mm、气体流速为0.15m/s~0.30m/s时,在不同床层高度处硅粉颗粒与气相的混合相对较为充分。本论文的研究工作将对该新型多列管分段换热式流化床反应器尺寸结构、工艺操作条件的优化和示范性工业装置的设计提供一定的依据。

其他摘要

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.

页数101
文献类型学位论文
条目标识符http://ir.xjipc.cas.cn/handle/365002/5436
专题资源化学研究室
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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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