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Screen trays are proprietary devices similar to sieve trays which are used in distillation and absorption applications. The pressure drop, liquid holdup and entrainment are measured for screen trays in an air/water column and compared to results obtained with sieve trays. The effciencies of both types of trays were compared in a distillation column using systems of various physical properties (methanol/water, acetic acid/water and cyclohexane/n-heptane mixtures). It was found that the screen tray has a lower dry pressure drop, higher liquid holdup, lower entrainment and weeping, and higher jet flooding capacity than the sieve tray. However, the effciencies of both trays are similar for the systems studied. A model was developed for predicting total pressure drop for screen trays using an air/water column. The model was tested using results for methanol/water, cyclohexane/n-heptane and acetic acid/water systems at total reflux. The deviations are within +/- 20% for 90% of the data points. The effect of a bed of mesh packing on the screen tray was also studied. It was found that the packing led to a higher tray effciency, but resulted in a higher tray pressure drop. 相似文献
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《Gas Separation & Purification》1992,6(4):207-213
The hydraulics and mass transfer performance of wire-mesh-packed sieve trays have been studied for their use in the distillation of acetic-acid-water mixtures, a surface-tension negative system, in a 150 mm diameter column. It was found that packing led to a larger capacity, higher mass transfer efficiency, lower entrainment and slightly greater pressure drop. These results are similar to those obtained for the distillation of methanol-water mixtures, a surface-tension positive system. Surface tension effects on efficiency and transition point are also discussed. Hydraulic tests in a 600 mm diameter air-water column showed a similar effect of packing on tray pressure drop, capacity and entrainment for sieve trays with hole diameters in the range from 7 to 12.5 mm. 相似文献
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Sieve tray efficiencies for the distillation of methanol/water, acetic acid/water and cyclohexane/n-heptane mixtures were measured as a function of composition under fixed vapour and liquid rates in a 0.15 m diameter distillation column. Experimental results show that surface tension has a significant effect on tray efficiency and the number of transfer units. Further tests in a simulator column with air/water, air/methanol and air/(water + surfactant) systems having different surface tensions revealed that bubble sizes in froths are mainly determined by surface tension. The results also show that bubble break-up and coalescence occurs in the froths. 相似文献
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Qun Shen Li Chun Ying Song Hai Long Wu Hui Liu Yi Qiu Qian 《Korean Journal of Chemical Engineering》2008,25(6):1509-1513
With a particular focus on the distillation of highly viscous or self-polymerized mixtures, this study reports the hydrodynamic
and mass transfer performance of two flow-guided sieve trays, including their pressure drop, entrainment, weeping and tray
efficiency, obtained experimentally with an air-water/oxygen system in a Φ600 mm plexiglass column. The results show that the 8 mm hole flow-guided sieve tray tested shows better characteristics than
the 7 mm flow-guided hole tray in terms of pressure drop and mass transfer. Then we present practical industrial examples
of applications of the flow guided trays for distillation of viscous mixtures, i.e., the separation of vinyl acetate (VAC)
from a polyvinyl acetate (PVAC) polymer solution with dynamic viscosity μ=50,000 mPas, the separation of highly unsaturated
C5 mixtures by extractive distillation, and the distillation of thick, condensed and highly viscous fermentation mixtures
made from fermented mash. It is demonstrated that flow-guided sieve trays with relatively large holes are an excellent candidate
for distillation of mixtures with suspended solids, or concentrated/self-polymerized polymer solutions. 相似文献
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基于欧拉-欧拉模型,采用CFX软件对筛板式填料的气液两相并流流动进行了模拟。将模拟所得的压降与填料的出厂特性值进行了对比,发现在液气动能参数较小的情况下,两者吻合较好。分析了该流场内的速度分布和压力分布的特点,射流卷吸作用使流场内两相流体混合,但涡旋使筛板下方压强减小,射流撞击使筛板上方压强增加。对不同结构的矩形筛板式填料的压降进行研究,结果表明:筛板孔径和液相流量是影响筛板压降的重要因素,开孔直径越小,液相流量对单板压降的影响越大;上层筛孔投影与下层筛孔相交的结构更能有效降低单板压降。液相流量较大时,两个不同板间距的单板压降曲线将相交于一点,气相流量低于此交点时,板间距越小,单板压降越大;气相流量高于此交点时,则相反。 相似文献
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The hydraulic and mass transfer performance of a combined knitted mesh packing and sieve tray has been measured for the distillation of methanol-water mixtures. It was found that by adding a shallow bed of packing, the Murphree tray efficiency increased by 40–50% over a wide range of concentrations and flow rates. This increase in tray efficiency can be attributed to a much smaller and more uniform bubble formation on the packed tray. Hydraulic measurements have shown that the packed trays have lower weeping and entrainment, as well as slightly higher froth heights and pressure drops. 相似文献
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Shuo Yang Jilong Zhang Jiaxing Xue Qingpeng Wu Qunsheng Li Hongkang Zhao Liqun Zhang 《中国化学工程学报》2021,39(11):59-67
Distillation is the most common separation technology utilized in the petroleum and chemistry industries. Due to the wide usage of the distillation column, even a small improvement in performance may result in significant energy cost savings. Aiming to improve the hydrodynamics and mass transfer performance, the flow-guided trapezoid spray-packing tray (FTS-PT) was designed by combining flow-guided holes and trapezoidal caps with structured packing. And the experimental measurements of the FTS-PT, including pressure drop, clear liquid height, weeping, entrainment, and tray efficiency, were conducted in a 500 mm diameter plexiglass column with the air-water-oxygen system. Moreover, the performance of the FTS-PT was compared with that of new vertical sieve tray (New VST) and F1 valve tray. The results show that FTS-PT has a significant advantage in pressure drop, entrainment, and capacity. Furthermore, the calculation model of the pressure drop was derived and used for the FTS-PT with a relative deviation of less than 5%. 相似文献
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以筛板塔为塔板基础构型,以原料转化率最大为目标,以塔径和出口堰高为主要调节参数,以塔板水力学可行性为约束条件,建立了一种可优化塔板液相持液量的塔板结构设计方法. 塔模拟计算在Aspen Plus平台上进行,化学反应采用动力学方程表达,塔板水力学计算采用Cup-Tower软件. 结果表明,本设计方法应用于DPC反应精馏过程,在满足流体力学可行性条件下,塔板上液相持液量比基础设计提高了1.39倍,苯酚转化率提高了33.6%. 相似文献
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Column setup has been widely utilized in the petroleum and chemistry industries. However, with the fast progress of industries and the increasingly serious energy shortage, designing a new column setup with better performance and higher capacity becomes more urgent. In order to improve column's capacity and expand operating condition, a new type of column tray named novel vertical spray packing (NVSP) tray was designed and experimented. The performances of the novel tray, including pressure drop, weeping, entrainment and tray efficiency, were tested in a plexiglass column. In addition, performances of the novel tray were compared with that of the sieve tray and the Glitsch V1 valve tray. Based on the experiment data, the mathematical correlations of pressure drop, weeping and entrainment for the novel tray were established by regression analysis method. A fundamental model of dry pressure drop of the novel tray was promoted at the form of sum mode. The results indicate that the novel tray has wider operating condition and better performance. 相似文献
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Fouling due to the deposition of solids on sieve trays was studied in a 153 mm diameter column and a 90 mm diameter simulator. Tests were carried out with various gas-liquid-solid systems to determine the effect of the fouling mechanism on tray performance. For an air-water system containing saturated NaHCO3, fouling from crystallisation occurs due to water evaporation by dry air at the tray holes. For a CO2-water system containing K2C03 and saturated KHC03 the reaction between C02 and K2CO3 causes the precipitation of KHCO3 at the gas-liquid interface. For the air-water system containing insoluble solids, flour and Ca(OH)2, no fouling was observed for a 48 hour test period. Interesting results on tray performance were also obtained. Test results indicate that (1) trays with larger holes have higher resistance to fouling, (2) fouling does not occur when trays are operated under weeping conditions, (3) fouling rate increases with increasing gas loading, (4) a bed of mesh packing on the sieve tray accelerates the fouling rate. A mathematical model has been developed for predicting the effect of crystallisation fouling on tray pressure drop as a function of time. 相似文献
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Sieve trays are widely used in fractionating devices like tray distillation towers existing in separation and purification industries. The weeping phenomenon that has a critical effect on the efficiency of tray towers was studied by a numerical model and some experiments. The experiments were carried out in a pilot scale column with the diameter of 1.22 m that includes two test trays and two chimney trays. Weeping rates and some hydraulic parameters were measured in sieve trays with the hole area of 7.04%. Furthermore, the total weeping rate and weeping rate in inlet and outlet halves of the test tray were determined. It was also used an Eulerian–Eulerian computational fluid dynamics (CFD) method for the present study. The model was able to predict the dry tray pressure drop, total pressure drop, clear liquid height, froth height, and weeping rate simultaneously. Furthermore, the obtained CFD results were in a good agreement with the experimental data in terms of pressure drop and the model properly predicted several hydraulic parameters like the liquid weeping behavior along the tray. 相似文献
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精馏是化学工业中应用最广泛的关键共性技术,广泛应用于石油、化工、化肥、制药、环境保护等行业。精馏具有应用广泛、技术成熟等优点,但存在设备投资大、分离能耗高等问题,因此研究开发新型高效传质元件、开发新型节能精馏技术,具有重要的社会意义和经济价值。本文从精馏塔类型、流体力学性能、传质性能、塔器大型化、过程节能、过程强化等方面,介绍了精馏技术的研究进展与工业应用。对于板式塔,从气液两相流动状态、压降、漏液和雾沫夹带方面研究了塔板的流体力学性能;对于填料塔,从压降、液泛和持液量方面研究了填料塔的流体力学性能,但目前的研究仍以经验关联式为主,缺乏严谨的的理论模型。对于气液两相的传质性能研究,简述了气液两相传质理论,但科学、精准的传质模型尚未提出。对于塔器大型化的应用研究,介绍了塔板、气液分布器和支撑装置等大型化关键技术的工业应用。从精馏过程典型节能技术、耦合节能技术、流程节能技术、低温余热回收和特殊精馏等方面,介绍了精馏过程节能与强化的应用进展。文章最后对精馏过程的传质、强化和集成进行了展望。 相似文献
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网填筛板流体力学性能研究 总被引:2,自引:0,他引:2
在直径为600mm有机玻璃塔内,以水-空气系统对放置网孔填料层的筛板(称网填筛板)和普通筛板进行了流体力学性能对比实验。研究发现,在普通筛板上加一层厚度为15mm的网孔填料,可以使雾沫夹带明显减少,负荷上限提高50%~80%。同时,塔板压降和漏液有所增加。 相似文献
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《Gas Separation & Purification》1992,6(4):215-219
Parallel-flow trays incorporating slotted sieve tray decks were originally developed for air separation applications. They are still used for that purpose and also in a wide range of chemical and petrochemical separations. The present paper outlines the main features of the trays, including the liquid flow-path arrangement and the slotting pattern that is typically used. The results of an experimental study are presented in which the tray efficiency was measured by using a 6.1 m diameter air-water tray simulator. The system used was acetone stripped from water by air. This is a convenient system because the slope of the equilibrium line is close to unity and so the results are relevant to distillation systems. For purposes of comparison, trays were tested both with and without a slotted tray deck. In the latter case, severe liquid maldistribution was evident. The measured tray efficiencies of the slotted and unslotted trays were found to be similar when no outlet weirs were used, but the slotted tray had a lower froth height and pressure drop. Theory was used to predict the point efficiencies for the two trays and to show that the slotted tray had a larger enhancement of tray efficiency over point efficiency than the unslotted tray. The measured tray efficiencies divided by the calculated point efficiencies were compared with theoretical predictions and reasonable agreement was demonstrated. 相似文献