新型导向筛板的研究

在φ600 mm的有机玻璃冷膜实验装置上,用水-空气体系对孔径为8 mm的新型导向筛板的流体力学性能进行了实验研究,测定了不同条件下的塔板压降、漏液量和雾沫夹带量等流体力学参数,对实验数据进行了关联,得出计算塔板压降、漏液、雾沫夹带的公式,可供导向筛板设计与研究使用.     

大孔径导向筛板流体力学性能研究

在长为500mm,宽为300mm冷模塔内,测定了φ9 mm大孔径导向筛板的流体力学性能参数.对实验数据进行了关联,得出计算塔板压降公式,可供大孔径导向筛板设计与研究使用.     

锥形筛孔塔板流体力学性能的研究

在一个φ500mm的有机玻璃塔中，以空气为物系，测试了普通筛孔塔板和锥形筛孔塔板的干板压降。根据Hughmark-O'Connell关联式计算出流量系数，并对上锥形筛孔塔板干板压降的Hughamrk-O'Connell公式进行修正，得到上锥形筛孔塔板的修正系数β'大于1，其干板压降比普通塔板低20％－30％。在此基础上对普通筛孔塔板和锥形筛孔塔板在气体穿孔时由于流体力不行为不同产生的压降差异进行了分析。     

板式塔中气液两相流乳化态的研究

在(φ)500 mm和(φ)334mm的冷模装置中观察和测定了气液两相流乳化态的流体力学性能.实验观察发现,按照Hofhuis和Zuiderweg提出的判据Ψ(气液动量参数)＞0.2时,确实出现了乳化态,塔板上的泡沫飞溅消失,降液管中的气泡明显细化.测定数据表明,在乳化态中,降液管中部平均气泡直径比泡沫态降低一倍,约为2～4mm,离开降液管的气含率也比泡沫态高得多,约有20%～40%.实验还发现,不同Ψ值,乳化程度不同,随着Ψ值的增大,乳化程度加深,表明乳化是一个伴随和渐进的过程.     

喷嘴孔VST的流体力学和传质性能研究

本文用空气-水系统,在φ1.2m的圆塔上研究了喷嘴孔垂直筛板塔盘(喷嘴孔VST)的流体力学性能,考察了各种几何因素和流体力学条件对塔板压降、漏液、气速下限、雾沫夹带和气速上限等参数的影响,获得了相应的关联式.在φ100mm的塔上,用乙醇-水系统测定了喷嘴孔VST的板效率,并与筛板搭进行了比较.     

板式塔降液管操作能力研究

在φ600mm的透明有机玻璃塔中,采用易发泡物系,在相同操作条件下,通过测量了CTST塔板和F1型浮阀塔板降液管中液体的RTD曲线和泡沫高度,对两种塔板的降液管操作能力进行了比较研究.实验结果显示CTST比较浮阀塔板,其降液管操作能力大许多.     

固定床有效导热系数及壁给热系数的实验测定及其关联式

在固定床反应器设计时,需要计算床层温度分布及热点位置,因此测定传热参数数值具有重要意义。本文作者在直径为φ76×4mm长1040mm,内部充填φ4.5mm刚玉球的固定床实验装置上测定了床层不同高度,不同径向位置上的温度分布值,并分别用理论解法、有限差分法及最优化法求得床层径向有效导热系数K_e及壁给热系数H_w值。作者认为最优化法求出的K_e、H_w值准确可靠,计算温度和实测温度较为吻合。     

非均匀开孔率穿流塔板板效率的研究

在φ150mm塔中,在较大范围的液量下进行了非均匀开孔率穿流塔板氧解析的传质试验,并与一般穿流塔板作了比较。结果表明:在相同的生产能力下,非均匀开孔率穿流塔板的板效率较一般穿流塔板高;相反,在相同的塔板效率下,非均匀开孔率穿流塔板的生产能力较一般穿流塔板大。另外,在操作弹性和稳定性方面也比一般穿流塔板优良。 通过对非均匀开孔率穿流塔板板效率数据的关联,得到了液相传质单元数的计算方程式。     

CTST-F1复合塔板的实验研究

结合CTST和F1浮阀各自的优点,在CTST塔板的基础上组合得到了新型的CTST-F1复合塔板.以空气-水为物系,在直径为570 mm的有机玻璃冷模实验塔内,对CTST-F1复合塔板的清液层高度、板压降、雾沫夹带、漏液量等流体力学性能进行了实验测定,并与CTST塔板和F1浮阀塔板的性能进行了比较.由实验数据关联得到了复...     

新型导向桥阀塔板的雾沫夹带和塔板压降

在φ1000mm的圆塔内,采用空气–水系统对新型导向桥阀塔板的流体力学性能进行了测试,考察了液流强度、出口堰高等因素对雾沫夹带和塔板压降的影响,并且与标准的F1型浮阀进行了对比实验。结果表明:新型导向桥阀塔板上气体分散均匀,泡沫层高度稳定,气液接触充分,在相同条件下压降比F1浮阀低10%～30%。具有较好的流体力学性能。     

蒸馏塔板上汽液传质系数的确定——非平衡池法(Ⅱ)实验数据处理

对文献报道的塔板操作数据用非平衡池法进行了分析处理.单相阻力控制系统(氨吸收)数据的处理结果与AIChE关联一致.对双相阻力控制系统(甲醇-水蒸馏)数据的处理表明,筛板汽相传质系数比AIChE关联的计算值高约20—70%.文中详细讨论了实验数据处理中各种问题的解决方法.结果表明,本文提出的传质系数确定方法比效率法和化学法更合理和方便.     

Effect of a variation in perforation size on performance of sieve tray absorbers

A six inch diameter sieve plate absorption column was used to assess the effect of perforation size on the performance of sieve trays under otherwise identical conditions. Four separate test trays with equal gas flow areas but perforations of 1/8-inch, 1/4-inch, 1/2-inch and 1-inch respectively, were used with the liquid phase absorption-controlled system of carbon dioxide — water at 77°F and approximately 830 mm. mercury. Comparisons of overall efficiencies indicated that the trays with 1-inch diameter perforations had efficiencies similar to, or slightly lower than those of 1/8-inch diameter. Concentration profiles within the froth were measured, with distinct profiles being observable in both the horizontal and vertical directions. This indicated that neither the plug flow nor the completely mixed models accurately described the actual transfer process. Accordingly, comparisons of volumetric mass transfer coefficients computed from both models were made. Comparison of volumetric mass transfer coefficients showed that for most gas and liquid flowrates the plates with 1-inch perforations performed as well as plates with smaller holes. For this system it was concluded that trays with large holes would be much better suited to fouling services and, indeed, they would be only marginally less attractive than trays with smaller holes for all services.     

The prediction of distillation plate efficiencies from froth properties

A compound optical probe is described which is used to determine the distribution of bubble sizes and velocities when liquids are distilled on sieve trays in the froth regime. It is shown how the plate efficiencies may be thereby evaluated by thus taking into proper account the derived distribution of vapour residence times and mass transfer coefficients. The results are seen to agree with published data. Froth properties for several boiling liquids on two sieve plates are reported.     

Predicting valve tray efficiency

Existing literature models for predicting the mass transfer efficiencies of binary hydrocarbon, distillation columns employing moving valve trays are evaluated. Only four models for predicting valve tray efficiencies exist in the open literature. All of these models use data from valve trays. The last theoretical model was published in 1972, 42 years ago. By comparison, sieve tray efficiency models are numerous and recent. Sieve tray models were developed from large databases. There are no valve tray equivalents to the fundamental mechanistic models available for sieve trays. Despite the differences between valve and sieve trays, many of the phenomena on sieve and valve trays are similar. Consequently, sieve tray models can be employed to provide estimates for valve trays. In this work, using public FRI data on round moving valves, the performance of the Chen and Chuang sieve tray mechanistic model is compared to the performance of four valve tray models. It appears that, in the absence of fundamental (and qualified) valve tray models, the sieve tray models present a potential alternative for valve tray efficiency predictions.     

Structured Packings in Liquid-Liquid Extraction

Abstract

Extractors equipped with structured packing are becoming more important in the chemical process industries. These devices provide high mass transfer efficiency and capacity relative to random packings and sieve trays. At the present time, many sieve tray extractors are being retrofitted with structured packings to enhance mass transfer efficiency and capacity. This paper will present a comparison of the performance of structured packing with sieve trays, some background on the commercial development of structured packings, and fundamental models required to design a liquid/liquid extractor equipped with structured packing.     

筛板精馏塔的板效率研究

在直径为0.75 m,塔高4m的不锈钢热模塔内,以正庚烷—环己烷为物系、在常压、全回流条件下,进行筛板塔传质效率的研究,选取孔径为13mm和6 mm,开孔率为3.9％和6.4％的塔板,测试了这些塔板的气液相默弗里板效率,通过排列组合,考察了孔径、不同塔板位置和出口堰高对传质效率的影响,并进行了传质效果对比.此外还运用A...     

The dynamics of extraction processes: Part III. The determination of steady state and transient concentration profiles

Techniques for determining concentration profiles during the transient and final steady state operation of a countercurrent extraction column are described and evaluated. The column is mechanically agitated and the stages are separated using Teflon sieve trays. The paper discusses numerical procedures for analyzing the behaviour of such columns, and the errors introduced by the measurement techniques studied. Mass transfer coefficients for the column under study are reported, and there is a discussion of the effect of concentration (or position along the column) on their value.     

Mass transfer and hydraulics of packed sieve trays

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.     

Hydraulic,mass transfer and heat transfer performance comparison between ordered bed packing and sieve trays

The Girdler–Sulfide (GS) heavy water production process has traditionally used tray columns because of their large size. In recent years, the chemical industry has extended the use of packing to larger columns because of economic and performance advantages. A pilot scale study was thus initiated to compare the hydraulic, mass transfer and heat transfer performance of an ordered bed packing (Mellapak) with sieve trays operating under GS process conditions. Mellapak offered lower pressure drops, higher throughputs and improved heat transfer over sieve trays. However, benefits to deuterium mass transfer were only marginal in large diameter columns.     

Performance and applications of flow-guided sieve trays for distillation of highly viscous mixtures

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.