共查询到18条相似文献,搜索用时 187 毫秒
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多降液管塔板目前在精馏、吸收和解吸等领域应用日益广泛.多降液管塔板由于降液管悬挂,且上、下塔板的降液管垂直布置,故它的液相流场分布较为复杂.提出了测试塔板上液相流场分布的一项新技术:与塔板上液体同质的高温示踪剂液体在塔板上阶跃注入,用红外热像系统拍摄高温示踪剂液体的流动,从而作出塔板上等停留时间分布图.实验在直径1200 mm的有机玻璃塔中进行,测试塔板为单根悬挂降液管塔板和两根悬挂降液管塔板,物系为空气-水.实验得到不同液量下单根和两根悬挂降液管塔板上等停留时间分布图.结果表明:该测试技术方便、精确、且示踪剂对塔内液体无干扰污染.多降液管塔板存在滞流区,且滞流区随液量增大而增大. 相似文献
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采用计算流体力学方法对直径为2 600 mm的工业规模双溢流立体传质塔板板上气液二相流动进行了模拟研究。计算了不同工况下收缩流和扩张流2种流型的液相流场分布,得到了双溢流塔板收缩流和扩张流2种流型的板上气液二相流场分布规律。通过将清液层高度的CFD结果和经验公式的计算结果进行对比,验证了所建模型的正确性。模拟计算结果表明:边降液管收缩流板面液相流动较均匀,近似于均匀的收缩流,不存在回流区;中降液管扩张流板面液相流动不均匀,靠近塔板中心流速较快,塔板弓形区存在着回流现象;板孔处的帽罩区液层较其他地方小,液相体积分数较其他地方低,扩张流受气相的影响较收缩流大。 相似文献
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开发了一种流场均匀且液相处理能力大的新型多降液管塔板。本文以水和空气为介质,在内径1219mm的有机玻璃塔内,研究了新型多降液管塔板的流体力学性能。结果表明,在相同气液负荷下,相较于弓形降液管塔板,新型多降液管塔板具有湿板压降低、雾沫夹带量小和漏液少等优点。同时新型多降液管塔板继承了多降液管(MD)塔板液相负荷高的特点,在空塔动能因子2.4(m/s)·(kg/m3)0.5的条件下,全塔喷淋密度仍可高达80m3/(m2·h)。对塔板上液相流场的流体流动特性进行了计算流体力学(CFD)分析,并将模拟结果与MD塔板进行对比。结果表明,新型多降液管塔板降液管的结构和排布方式使得塔板上液体流动更加均匀,预期可以获得更高的塔板效率。 相似文献
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<正>引言 塔径较大的塔板上液体流动的不均匀性对板效率的影响早已引起了人们的注意,在大型塔板上,由于气液两相的剧烈湍动,致使不同区域液体的流动各不相同,如果只采用单一形式描述塔板上液体的运动特点,未免有失普遍性。因而,本文将在分析塔板上液体运动特点的基础上,提出一种新的计算模型,力求更好地符合实际情况。1 实验现象 塔板上流体力学的测定是在前已述及的装置上进行的,用热膜风速仪直接测定了塔板上气液两相流场的分布,发现不仅塔板弓形区存在返混,而且塔板入口堰附近一段距离内,液体也存在返混,其具体长度随液流强度、气相负荷以及出口堰高度等因素而异。采用逐步回归分析方法对实验数据进行回归,得到入口堰返混段长度关联式 相似文献
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利用计算传质学方法研究了直径12.6 m的四溢流大型塔板上液相流动结构对塔板效率的影响,建立了描述多溢流塔板上液相流动和传质状况的理论化计算模型。应用该模型,研究了传统等鼓泡面积设计方法条件下单块塔板的速度场和浓度场。结果表明,所模拟四溢流塔板的左侧翼塔板出现返流区,而右侧翼塔板流动结构相对均匀未出现返流区。为进一步优化塔板结构,提高传质效率,对左侧翼塔板提出了加设导流板的改进结构。计算结果表明,改进的塔板结构在一定程度上改善了塔板上液相的流动结构,使得塔板效率较传统设计方法提升了4.53%~9.22%(当Q1/Q2=[0.5,1.5]时)。 相似文献
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引 言传统的板式塔塔板开孔率有限 ,当处理量较大时 ,压降较高 ,板效率降低 .因此开发新型大通量高效率塔板具有重要的现实意义 .本研究通过改进降液管结构和板面设计 ,提高塔板的有效传质区面积 ,开发了一种新型大通量塔板——— 95型塔板 ,因该板的有效传质区面积约占全部塔板面积的95%而得名 .本文以水和空气体系对 95型塔板进行了流体力学和流动性能试验 ,同时与传统筛板进行了比较 ,对试验测定的数据进行了关联 .1 试验装置及筛板结构参数试验塔为一直径Φ1 0 0 0mm的不锈钢塔 .塔内设置两块塔板 ,上板为测试板 ,下板为气体分布板 … 相似文献
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Two important structural factors that affect distillation efficiencies, the outlet weir heigh and the liquid flowpath length, are investigated. Performance and efficiency data of an industrial scale i-butane/n-butane distillation column equipped with two-pass trays are used as a basis for the calculations. A mathematical development for a new method for predicting the numbers of vapor and liquid phase transfer units is given. This method together with some other NTU calculation methods is used to assess the effect of the outlet weir height on efficiencies. The effect of outlet weir height on the Murphree tray efficiencies is investigated using the observed point efficiencies and different point efficiency to the Murphree tray efficiency relation methods. The effect of varying liquid flowpath lengths on efficiencies is studied by calculating the Murphree tray efficiencies for one-pass and two-pass trays. The results obtained using the NTU calculation method presented in this study show that a certain outlet weir height point efficiency reaches its maximum. Most of the other methods give opposite results giving a minimum for point efficiency at a certain outlet weir length. The results also show that the Murphree tray efficiencies for one-pass trays are higher than for two-pass trays. Obviously, this is caused by the longer liquid flowpath length of one-pass trays. The Murphree tray efficiencies are also calculated for an industrial-scale MTBE purification column. The column is equipped with two-pass trays in the stripping section and with one-pass trays in the rectifying section. The Murphree tray efficiencies of one-pass trays are considerably higher than the two-pass tray Murphree tray efficiencies. 相似文献
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介绍一种新型穿流塔板--正交波纹板。以欧拉-欧拉两相流模型为基础,建立了正交波纹板上气液两相流场的三维数学模型。CFD模型中主要考虑了气液两相间的曳力作用,相间动量传递源相采用Krishna计算方法。以清液层高度为指标,对CFD模型的可靠性进行了验证。在不同气液负荷下,对正交波纹板的压降、板上液相速度分布及塔内气液分布状况等流体力学性能进行了研究,并与淋降筛板进行对比,结果表明正交波纹板具有更高的操作弹性和更好的操作稳定性。 相似文献
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《分离科学与技术》2012,47(4):445-455
Abstract The operation of a distillation column plate was simulated by using air for the vapor phase and water for the liquid phase; the turbulent mixing effect in the liquid on the tray and in the downcomers was analyzed by following composition changes of salt (sodium chloride). Composition changes entering the plate and in the downcomer leaving the plate were monitored. The composition–time data was numerically Laplace transformed, and the frequency response form was fit to each of five models: (1) perfect mixing; (2) plug flow; (3) perfect mixing with time delay in the downcomer; (4) dispersion; and (5) dispersion with dead zones on the tray. The composition–time data was reconstructed from each of the best fitting parameters of each of the models, and this data is given for comparison with the experimental data. The model utilizing dispersion was the best statistical model. The model of perfect mixing on the tray and delay in the downcomer gives a satisfactory fit and is much simpler. 相似文献
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Experimental study of flow pattern and liquid velocity distribution by the tracer technique in a twometers diameter single pass sieve half-tray using air-water system reveals that there exists a highlynonideal flowing behavior.Typical residence time distribution curves covering the whole tray are presented,from which four flow regions can be observed: a main channelling region of nonuniform flow,a slowly forward flow region in the segmental area,a small region of backward flow and a complete-mixing region next to the inlet weir.The tray models available in literature seem incapable to simulateall these complicated hydrodynamic phenomena in a large tray.An eddy diffusion model with consideration of nonuniform liquid velocity field has been developedfrom the basic partial differential equation of mass transfer by introducing a velocity distributionfunction j.The nonlinear partial differential equation is solved by the method of finite element.Acomputer program is compiled according to this method to compute numerically the concentration pro-files in the whole tray as well as the Murphree tray efficiency enhancement under various operatingconditions.Typical computed results are presented and discussed. 相似文献
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Erich A. Mü ller Antonio Cavero L. Antonio Est vez 《Chemical Engineering Communications》1988,74(1):195-208
A simple modification of the downcomer apron shape has been proposed and experimentally studied. Experiments were carried out in a 40 [cm] diameter tray with water and with no vapor flow. Weir length to diameter ratios were varied from 0.6 to 0.775 and water flow rates between 150 and 600 [cm3/s]. Curved, triangular, trapezoidal and toothed apron shapes were tested. Velocity distributions on the plate were measured using the hydrogen bubble technique up to a flow rate of 200 [cm3/s]. Stagnation point loci were determined for all operating conditions, and the fractional forward-flow area (FFA) was then calculated. The FFA's were considered a measure of the efficiency of the tray, and hence used to compare the performance of the various apron shapes.
Three flow patterns were experimentally observed: regular, inverted and transition. Flow pattern maps were obtained, which permit the selection of an optimum shape when an appropriate scale up criterion is used. To this end, it was found that the best criterion was to use the same liquid residence time in the prototype and model. The results proved that the FFA values for a modified apron were always higher than for the standard or conventional apron. This is important in tray design, since it provides an easy way of improving distillation plate efficiencies. 相似文献
Three flow patterns were experimentally observed: regular, inverted and transition. Flow pattern maps were obtained, which permit the selection of an optimum shape when an appropriate scale up criterion is used. To this end, it was found that the best criterion was to use the same liquid residence time in the prototype and model. The results proved that the FFA values for a modified apron were always higher than for the standard or conventional apron. This is important in tray design, since it provides an easy way of improving distillation plate efficiencies. 相似文献