旋转填料床中MDEA脱硫的多相流特性研究

发布时间：2018-06-19 10:32

本文选题：旋转填料床 + MDEA溶液　；参考：《西南石油大学》2015年硕士论文

【摘要】：旋转填料床是一种以离心力来模拟超重力环境,强化气液传质和反应等过程的新型高效的化工设备,在化工行业有着广阔的应用前景。目前,关于旋转填料床强化吸收过程的研究较少,且多数集中在试验和应用性研究,对旋转填料床内气液接触、运动以及变化规律方面的基础理论研究还存在不足。本文以旋转填料床内天然气醇胺法脱硫过程为研究对象,根据现场中试装置结构,建立其二维和三维物理模型,借助CFD数值模拟技术,对旋转填料床内MDEA脱硫过程进行分析和研究。首先,采用非结构化网格剖分流体区域,选用"Realizable "k-ε模型,对气、液相单相的三维流场进行模拟,分析了气相、液相速度场的分布,得到气相、液相速度场分布和气相压降分布特点；其次,采用VOF模型和滑移网格模型,在建立的二维模型下对MDEA溶液的流动分布形态做了模拟,分析了转速、入口速度、填料层厚度等对流动分布的影响；最后,借助DPM模型,对MDEA溶液在旋转填料床内的运动轨迹做了模拟,研究了转速和入口速度对液滴运动轨迹、液滴平均停留时间和液滴平均粒径分布的影响。研究表明：在旋转填料床内,气液相存在径向和切向速度分布,液相径向速度主要受入口速度控制,转速对其影响较小,而切向速度则相反。和传统吸收塔相比,旋转填料床的干床压降较小,一般在几百帕到几千帕之间。干床压降主要来自丝网填料区,空腔区域压降较小,且随着入口速度和转速的增加而增加。和传统填料塔内液膜形态不同,MDEA溶液在旋转填料床内以孔流、液滴流和液膜流的形态流动。且随着转速的升高,液滴流的尺寸减小,气液接触表面积增大,有利于脱硫过程。通过研究发现,提高MDEA溶液与丝网填料间的周向相对碰撞速度,可以改善MDEA溶液在旋转填料床内分布的不均匀性,加强旋转填料床对MDEA溶液的微粒化作用。在旋转填料床中MDEA溶液的平均停留时间较短,一般数量级在1×10-2秒左右,可提高对H2S和CO2的选择性,降低C02的共吸收率。同时,在靠近旋转填料床内壁部分,液滴粒径下降较快,当达到一定值后,液滴粒径下降减慢,粒径总体呈减小趋势。因此,旋转填料床是一个能强化传质过程的脱硫装置,通过研究旋转填料床内MDEA脱硫过程,为旋转填料床强化常规天然气醇胺法脱硫过程的应用以及旋转填料床的工业设计提供一定理论基础。
[Abstract]:Rotating packed bed is a new type of high efficient chemical equipment which simulates the hypergravity environment by centrifugal force and strengthens the gas-liquid mass transfer and reaction processes. It has a broad application prospect in the chemical industry. At present, there are few researches on the enhanced absorption process of rotating packed bed, and most of them are focused on experiments and application studies. The basic theoretical studies on gas-liquid contact, motion and variation in rotating packed bed are still insufficient. In this paper, the natural gas alcohol-amine desulfurization process in rotating packed bed is studied. According to the structure of the pilot plant in the field, the two-dimensional and three-dimensional physical models are established, and the CFD numerical simulation technique is used. The MDEA desulfurization process in rotating packed bed was analyzed and studied. Firstly, the unstructured grid is used to divide the fluid region, and the "realizable" k- 蔚 model is used to simulate the three-dimensional flow field of single phase of gas and liquid phase. The distribution of velocity field of gas phase and liquid phase is analyzed, and the gas phase is obtained. Secondly, using VOF model and slip grid model, the flow pattern of MDEA solution is simulated under the established two-dimensional model, and the rotational speed and inlet velocity are analyzed. Finally, with the help of DPM model, the motion trajectory of MDEA solution in rotating packed bed is simulated, and the effects of rotational speed and inlet velocity on droplet trajectory are studied. Effects of droplet mean residence time and droplet average particle size distribution. The results show that there are radial and tangential velocity distributions in the gas-liquid phase in the rotating packed bed. The radial velocity of the liquid phase is mainly controlled by the inlet velocity, and the rotational speed has little effect on it, but the tangential velocity is opposite. Compared with the traditional absorption column, the dry bed pressure drop of the rotating packed bed is smaller, ranging from several hundred Pa to several thousand Pa. The dry bed pressure drop mainly comes from the mesh packing area and the pressure drop in the cavity region is small and increases with the increase of inlet speed and rotational speed. Different from the traditional packing column, the liquid membrane shape of MDEA solution in rotating packed bed flows in the form of pore flow, droplet flow and liquid film flow. With the increase of rotational speed, the size of droplet flow decreases and the gas-liquid contact surface area increases, which is beneficial to the desulfurization process. It is found that the distribution of MDEA solution in rotating packed bed can be improved by increasing the circumferential relative collision velocity between MDEA solution and wire mesh filler, and the particle effect of rotating packed bed on MDEA solution can be enhanced. The average residence time of MDEA solution in rotating packed bed is shorter, and the order of magnitude is about 1 脳 10 ~ (-2) second, which can improve the selectivity of H _ 2S and CO _ 2 and decrease the common absorption rate of CO2. At the same time, near the inner wall of the rotating packed bed, the droplet size decreased rapidly, and when the value reached a certain value, the droplet size decreased, and the overall particle size showed a decreasing trend. Therefore, rotating packed bed is a desulphurization device which can enhance mass transfer process. The MDEA desulfurization process in rotating packed bed is studied. It provides a theoretical basis for the application of conventional natural gas alcohol-amine desulfurization process and the industrial design of rotating packed bed.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE644

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