【作者】 高国华；

【导师】 姜斌；

【作者基本信息】 天津大学 ， 化学工程， 2008， 硕士

【摘要】 化工两相流包括气体-液滴、气体-固体、液体-固体与液体-气泡等多种不同体系。各体系由于受两相物性、操作条件和过程环境等的影响,其流型又是多种多样,其流体力学行为非常复杂。本文主要研究了多孔介质碳化硅塔盘的流体力学行为及催化裂化装置中流化床反应器中的气固两相流问题,研究的主要内容如下:对于多孔介质碳化硅塔盘,使用CFX提供的多孔介质模型对多孔介质塔盘进行了二维单相模拟,得到与实验结果类似的干板压降随气相动能因子变化曲线。然后,使用软件中的双欧拉两相流模型并结合多孔介质模型,模拟得到的湿板压降与实验结果基本吻合。从液体体积分率分布和气相速度分布等方面,将多孔介质塔盘的模拟结果与筛孔塔板的模拟结果进行对比,说明多孔介质塔盘具有更好的气液分布性能,气液接触面更大,气体速度扰动更剧烈,这都更有利于气液传质的进行。对于流化床反应器,改造前,混合碳四和原料油气进入反应器后没有任何扰动和混合,直接离开反应器。这不利于反应物与催化剂的反应,原料的利用率很低。而且催化剂颗粒在反应器内分布不均。径向上,催化剂颗粒主要集中在反应器中央,壁面处的原料无法与催化剂接触并反应;轴向上,反应器中上部颗粒体积分率很低,进入的混合原料油气几乎不能反应。根据对改造前结构模拟的结果分析,对反应器两种进料管及反应器相关尺寸做出了改进与优化。改进后,催化剂颗粒在反应器内分布状况明显得到改善,颗粒分布更均匀,而且壁面附近也有一定量的催化剂颗粒存在,促进了壁面处反应的进行,提高了原料的利用率。更多还原

【Abstract】 There are many kinds of different systems included in chemical industrial two phase flow, such as gas-droplet, gas-solid, liquid-solid, liquid-bubble, and so on. Their flow patterns are of great difference because of their difference in the physical properties of their two phases, the operating conditions and the process environment. It’s known that flow characters of the two phase flow is very complex. Both the fluid mechanics of the porous SiC tray and the gas-solid two phase flow of the fluidised bed reactor in catalytic cracking unit were studied in this paper. The main contents are as follows:Firstly, as for the porous SiC tray, the Porous Model provided by CFX was known to have reference value and predictive value for modelling of the flow problems in the porous/pure fluid area through the study on the the Porous Model in CFX. And then, the flow of two-dimensional single-phase on the porous tray was modelled using the Porous Model to acquire the dry pressure drop. It came to that the change curve of the dry pressure drop following the F was the same to the experimental results. The wet pressure drop from the gas-droplet two phase simulation corresponded to the experimental results. It was proved that air and water had better distribution, larger contact area and more drastic velocity disturbance on the porous tray compared to that on the sieve tray from both the water volme faction and the air velocity vector.Secondly, as for the fluidised reactor, the mixed C4 and the raw petrol gas in the reactor before transformation depart directly without any disturbance and mixture after they enter the reactor. Therefore, not only did the structure of the previous reactor go against the reaction of the reactant and the catalyst particle, but also made low utilization ratio of the reactants. The catalyst particle had uneven distribution in the whole reactor. In the radial direction, the particles mainly concentrated on the center of the reactor so that the raw materials near the wall couldn’t contact and react with the catalyst particles. In the axial direction,the raw petrol gas nearly wasn’t able to react because of the low volume fraction of the particle in the upper part of the reactor. The two kinds of feed pipes and the relative dimension of the reactor were improved and optimized accroding to the analysis of the simulation results from modelling the structure of the previous reactor. The distribution situation of the catalyst particles in the reactor had achieved significant improvements.Not only was the distribution of the particles more even, but also involved the wall of the reactor. Such distribution could promote the react near the wall and increased the utilization rate of the raw materials.更多还原