微细泡塔盘流体力学的测定与传质性能的研究

发布时间：2018-02-14 02:33

本文关键词： 痕量分离整微板塔板效率气含率功率谱密度解吸效率　出处：《青岛科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：塔设备是广泛应用于炼油、化工等行业物质分离的一种重要的气液和液液传质设备。在痕量分离中,无论是对填料塔还是板式塔的开发,都存在结构复杂和生产成本高的缺点,所以研究者们开始寻找不使塔板效率降低同时又能使筛板结构简单的方法。因在痕量分离过程中,气泡直径大小对塔板效率的高低起着决定性的作用,所以提高分离效率的有效方法是破除较大气泡,强化表面更新和增大两相接触面积。其中破除大气泡最简单直接的方法是在筛板上铺设一层筛网,即建立重整化微尺度筛板结构。基于这种结构,本文通过CFD模拟和实验验证的方法对整微板的结构和流体力学性能进行了系统的研究。本文采用欧拉-欧拉双流体模型构建了非稳态三维塔板气液流场,通过对气含率和开孔率等分析得出其最佳结构：方形筛网的安装高度为25mm,开孔率为55.7%为最佳；且单层筛网更适用于工业推广应用；采用CFD-PBM耦合模型对整微板进行模拟分析,得出大、小气泡群在塔内的分布规律,且整微板中气泡平均直径仅为筛板的12%；通过对比两种塔板的模拟结果,可以发现筛网能够使气相分布变得更为均匀,还消除了所在位置上的大旋涡,规整了气相流动方向,这些改变都是有利于传质的。为了定量分析影响塔板效率的各参数,本文选用空气-水系统进行筛板和整微板的流体力学实验测定,并对气泡特性进行了一系列的研究,实验结果表明整微板的最优结构是：筛网的安装高度为25mm,孔径为5目。并与筛板做了对比,结果表明：整微板的平均湿板压降达到0.243kPa,比筛板高出44个百分点,导致能耗较大；整微板的平均气泡直径为5.16mm,仅为筛板的15%,与模拟值基本吻合；整微板的气含率较筛板平均高出3.28%；整微板中的压力波动较为平稳,且功率谱密度图也反映了小气泡能更好的保持其形态,破碎频率远远低于筛板,对塔的操作状态有较大程度的改善。本文选取SO2的解吸实验来分析筛板和整微板的传质效率。实验结果表明：普通解吸时,同等条件下,整微板的解吸效率为86.85%,是筛板的1.87倍；痕量解吸时,整微板的解吸效率仍能保持在50%以上,远远大于筛板的解吸效率,且解吸效果良好,能将SO2浓度降至20mg·L-1以下,远低于筛板的解吸极限。故在痕量分离过程中,整微板具有很好的应用前景。
[Abstract]:Column equipment is an important gas-liquid and liquid-liquid mass transfer equipment widely used in oil refining, chemical industry and other industries. In trace separation, both the development of packed column and plate column have the disadvantages of complex structure and high production cost. So researchers started looking for ways not to reduce the efficiency of trays and to make the structure of sieve plates simple, because in trace separation, bubble diameters play a decisive role in the efficiency of trays. So the effective way to improve the separation efficiency is to break down the larger bubble, to strengthen the surface renewal and to increase the contact area of two phases. The simplest and most direct way to break the big bubble is to lay a screen net on the sieve plate. That is, to establish a renormalization microscale sieve plate structure, based on this structure, In this paper, the structure and hydrodynamic properties of microplates are systematically studied by means of CFD simulation and experimental verification. In this paper, the gas-liquid flow field of unsteady three-dimensional trays is constructed by using Euler-Euler two-fluid model. Through the analysis of gas holdup and opening rate, the optimum structure is obtained: the installation height of square screen is 25mm, the opening ratio is 55.7%, the single-layer screen is more suitable for industrial application, and the CFD-PBM coupling model is used to simulate the microplate. The distribution of large and small bubble groups in the tower is obtained, and the average diameter of the bubbles in the whole plate is only 12 of that of the sieve plate. By comparing the simulation results of the two trays, it is found that the gas phase distribution can be more uniform by the sieve mesh. In order to quantitatively analyze the parameters affecting the efficiency of the tray, the large vortex in the position is eliminated and the flow direction of the gas phase is regularized, and these changes are beneficial to mass transfer. In this paper, the air-water system is used to measure the hydrodynamics of sieve plate and microplate, and a series of studies on the bubble characteristics are carried out. The experimental results show that the optimum structure of the microplate is that the installation height of the screen is 25mm and the aperture is 5 meshes. The results show that the average wet plate pressure drop of the microplate is 0.243 KPA, which is 44 percentage points higher than that of the sieve plate, which results in higher energy consumption. The average bubble diameter of the microplate was 5.16 mm, which was only 15 mm of the sieve plate, which basically coincided with the simulated value. The gas holdup of the whole microplate was 3.28 mm higher than that of the sieve plate, and the pressure fluctuation in the whole plate was more stable. And the power spectral density diagram also shows that the small bubble can better maintain its shape, the breaking frequency is much lower than that of the sieve plate. In this paper, the mass transfer efficiency of sieve plate and microplate is analyzed by SO2 desorption experiment. The results show that under the same conditions, the desorption efficiency of the whole plate is 86.85, which is 1.87 times of that of the sieve plate. For trace desorption, the desorption efficiency of microplate is still above 50%, which is much higher than that of sieve plate, and the desorption efficiency is good, and the concentration of SO2 can be reduced to less than 20mg 路L ~ (-1), which is far lower than the desorption limit of sieve plate, so in the process of trace separation, The microplate has a good application prospect.
【学位授予单位】：青岛科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ053.5

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