泡沫碳化硅波纹规整填料内的液体流动特性

通过采用配备微距镜头的高速摄像仪记录单波纹片上的液体流动行为,发现了泡沫碳化硅波纹规整填料内同时存在液膜流动和准壁流两种液体流动模式。同时测定了组合波纹片之间的液体传递量,并将泡沫碳化硅波纹规整填料与金属丝网波纹填料和金属板波纹规整填料的测试结果进行比较,结果表明泡沫碳化硅波纹规整填料的单波纹片上的液体扩散程度较大,组合波纹片之间的液体传递量高于金属丝网波纹填料和金属板波纹规整填料。研究结果揭示了泡沫碳化硅波纹规整填料具有高效传质特性的根本原因在于其独特的三维空间网孔结构增强了液体在单波纹片上的横向扩散能力和在组合波纹片之间的径向传递能力,为新型高效规整填料的机理研究和进一步开发开拓了思路。     

泡沫碳化硅波纹规整填料内的液体流动特性

通过采用配备微距镜头的高速摄像仪记录单波纹片上的液体流动行为,发现了泡沫碳化硅波纹规整填料内同时存在液膜流动和准壁流两种液体流动模式。同时测定了组合波纹片之间的液体传递量,并将泡沫碳化硅波纹规整填料与金属丝网波纹填料和金属板波纹规整填料的测试结果进行比较,结果表明泡沫碳化硅波纹规整填料的单波纹片上的液体扩散程度较大,组合波纹片之间的液体传递量高于金属丝网波纹填料和金属板波纹规整填料。研究结果揭示了泡沫碳化硅波纹规整填料具有高效传质特性的根本原因在于其独特的三维空间网孔结构增强了液体在单波纹片上的横向扩散能力和在组合波纹片之间的径向传递能力,为新型高效规整填料的机理研究和进一步开发开拓了思路。     

泡沫碳化硅波纹规整填料骨架结构对其传质性能的影响机理

在?100mm×2000mm的常压精馏塔中使用乙醇-正丙醇作为标准物系，对6种不同骨架结构及表面性质的泡沫碳化硅波纹规整填料（SCFP）的传质性能及操作压降进行了实验测试，探究了结构对填料传质性能的影响。结果表明，6种填料都有着较优秀的传质性能表现，理论板最低可达每米5块。其中，纯质碳化硅型填料的整体传质性能要优于富硅型填料；随着孔隙率的增大，富硅型填料的传质性能有所下降，纯质碳化硅型填料的性能则有所提高；压缩比的增大有利于纯质碳化硅填料的传质性能。在压降表现方面，6种填料的操作压降均随着气相负荷的增大而有所增加，但彼此之间差异不大。同时采用紫外荧光示踪剂方法对单波纹片上液体的流动行为进行了观察，对不同填料表面液体的润湿面积、横向润湿长度进行了对比，结果表明，传质效率表现较高的填料其表面的液体润湿效果更好，有着更大的润湿面积、更长的横向润湿长度。     

金属斜孔板波纹填料流体力学与传质性能研究

介绍了自行开发的新型规整填料———金属斜孔板波纹填料,在内径500mm有机玻璃塔中,对金属斜孔板波纹填料的流体力学和传质性能进行了研究,推出了其压降、液泛气速和液相总传质单元高度的关联式,并与传统Mellpak孔板波纹填料相比,新填料保持Mellpak250Y相当的流体力学性能,同时具有更高的传质性能,该研究结果对金属斜孔板波纹填料的应用有指导意义。     

新型垂直板规整填料流体力学及传质性能

采用氧解吸实验,在直径190 mm的有机玻璃塔内,液相喷淋密度10～38 m³·m^-2·h^-1,F因子0.2～3.2 m·s^-1·（kg·m^-3）^0.5的实验条件下测定了一种新型垂直板规整填料的流体力学及传质性能。实验结果表明：垂直板填料的操作压降及传质性能均显著优于商业波纹填料。通过与几种经改进的250型波纹填料相比发现,两者泛点F因子整体上相当;在较高液体喷淋密度下,垂直板填料传质性能及压降均高于改进250型波纹填料;在低喷淋密度下,垂直板填料可实现压降低于改进250型波纹填料,而两者传质性能相当。此外,对填料结构改进对其性能的影响进行了单因素考察。     

规整填料塔中离子液体吸收CO2的传质与流体力学性能

在规整填料塔中采用离子液体吸收二氧化碳气体,利用计算流体力学(CFD)软件建立可靠的数学模型,系统考察了离子液体结构及规整填料几何参数对吸收过程的传质特性和流体力学性能的影响规律。结果表明,床层压降随气体流速增大而增大,液相传质系数随液体流速的增大而增大。相同阴离子时,随着阳离子碳链长度的增长,吸收过程压降增大,同时液相传质系数减小。相同阳离子时,不同阴离子的离子液体压降大的同时传质系数也大。但离子液体的结构对压降影响不明显。离子液体筛选主要考虑传质系数和溶解度因素,但二者与离子液体结构表现出相反的规律。两种折线结构的规整填料传质性能优于传统的X型和Y型结构。     

泡沫碳化硅波纹规整填料的流体力学及传质性能

将碳化硅陶瓷材料用于精馏过程,将该材料与波纹板类填料形状相结合开发出泡沫碳化硅波纹规整填料和光滑碳化硅波纹规整填料.对2种填料进行了流体力学性能与传质性能的测试,研究了泡沫结构对规整填料性能的影响.在直径100mm的有机玻璃塔中使用空气-水体系对填料进行干填料压降、湿填料压降、泛点气速、持液量等流体力学性能测试；在直径100mm的常压玻璃塔中,使用环己烷-正庚烷标准物系进行全回流操作,对填料进行传质性能测试.实验结果表明,在填料外形相同的情况下,与光滑填料相比,泡沫填料的干、湿填料压降较高,泛点气速相当,持液量增大,传质效率显著提高.     

规整波纹填料内气体流动和传质的CFD模拟

为了研究规整填料局部特征单元内流体的流动状况和传质效果,采用计算流体力学的方法对JKB-250Y交叉波纹填料以及增加隔板后的JKB-250Y交叉波纹填料进行了模拟计算比较。结果表明,加入隔板后有效改善了传质的局部均匀性,并且消除了两股气体交叉流动带来的阻力,降低了通道的单位压降。增加隔板后的交叉波纹填料压降比传统交叉波纹填料压降降低20%~50%,增加隔板后的交叉波纹填料传质系数比传统交叉波纹填料传质系数提高约20%,可见提高传质分布的局部均匀性是提高传质效率并且降低阻力的较为有效途径之一。     

填料塔基础理论研究新进展

规整填料塔具有效率高、压降低、放大效应不明显等优点,其成功应用有赖于对二相流动与传质的深入认识。文中综述了规整填料塔内的气液二相流动与分布、返混、气液二相在常压和高压下的传质特性、M arangon i效应以及计算流体力学(CFD)在规整填料塔中的应用等方面的国内外研究进展。填料塔内液体的分布与返混的研究较多,气相的流动分布与返混特性的研究较少,高压传质、M arangon i效应,特别是利用计算流体力学(CFD)模拟填料塔内的液体流动与传质等已逐渐成为研究的热点。     

激光诱导荧光技术观测填料表面非等温降膜流动形态变化

非等温降膜流动在精馏过程中较为常见,其流动特性较为特殊,对填料表面的质量和热量传递有重要影响。本文搭建了可视化的实验装置,在保证液相室温进料的前提下升高填料温度,在规整填料表面构造液相被加热的非等温降膜流动,运用激光诱导荧光技术对液膜形态变化进行观测分析,对液体润湿面积、液膜厚度等参数进行比较。结果表明,随着填料温度的升高,液体润湿面积显著减小,波谷处液膜厚度显著增加,液膜逐渐收缩为沟流,填料表面的不规则液滴数目增多,干板现象越发严重。液体的聚并和分散轨迹消失,液相再分布及表面更新能力降低。因此,填料表面的非等温降膜流动液膜收缩现象十分明显,降低传热传质能力,需在工业生产中引起足够重视。     

Mass transfer characteristics of liquid films flowing down a vertical wire in a counter current gas flow

The wetted-wire packing, mainly consisting of a bundle of vertical parallel wires, is a promising concept for the use in separation columns. To investigate the multiphase flow inside the packing in detail and to estimate the performance of the packing, experiments on liquid films on a single vertical wire in a counter current gas flow were carried out. To get information about the interfacial area, an optical measurement of the film thickness was carried out with a digital high speed camera and image recognition tools. By measuring the evaporation of water and aqueous polyvinylpyrrolidone solutions into air, the gas-side mass transfer was determined. The liquid-side mass transfer was examined by measuring the desorption of CO₂ from water into air. The results show that the mass transfer coefficients are comparable to those appearing in common structured packings. When assuming a sufficiently high wire packing density, a specific interfacial area similar to corrugated sheet structured packings can be reached. Previous studies predicted a low pressure drop per packing height and extended capacity limits compared to common packings. In consideration of these results, the wetted wire packing therefore is shown to be suitable especially for absorption processes where a low pressure drop is favourable.     

波纹填料技术的进展与多孔基材的开发

简述波纹填料的发展历程，强调复网借助毛细力提高分离效率的重要意义，提出“液体多向扩散”的理论观点，介绍金属复合板网波纹填料的研究进展。     

规整填料表面液膜流动特性的数值模拟

精馏过程气液两相流运动分布特征对分离效率具有重要影响。为研究规整填料表面液膜流体动力学特性建立了基于VOF方法的CFD分析模型,并基于文献试验结果进行了验证。对液膜随时间和空间的演化分布特征、速度场分布和液相流量影响进行了模拟分析。液膜在波纹顶部下沿聚集形成凸起状波峰,在波纹底部波峰消失,而到达下节波纹上沿时,波峰重新形成;瞬态液膜厚度随时间波动,且沿填料表面液膜平均厚度先减小后保持稳定;发现液相聚集及形成液滴坠落容易导致出现干板区。不同位置液膜速度分布存在明显差异,沿填料表面液膜平均速度先增后减或保持稳定;液膜绕过波纹顶部时会加速,在波纹底部和上沿处会减速。液相流量增大,液膜平均厚度和速度均有所增大。     

Liquid‐bridge flow in the channel of helical string and its application to gas–liquid contacting process

To solve the problems of the traditional packings, such as high pressure drop, mal‐distribution and short liquid residence time, a helical flow structured packings was proposed. Two different flow patterns, liquid‐bridge flow and liquid‐drop flow were identified when the width of the channel of the helical string was adjusted. Moreover, the characteristics of the helical liquid‐bridge flow including maximum liquid loading, mean thickness of liquid film, mean residence time and effective specific surface area, were examined. And the separation efficiency was studied by the lab‐scale distillation column. In comparison, the effective specific surface area of the helical flow type packings is almost as large as the traditional B1‐350Y structured packings, but with thinner liquid film, longer liquid residence time and finally higher separation efficiency. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3360–3368, 2018     

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.     

Liquid film flow on structured wires: Fluid dynamics and gas‐side mass transfer

The liquid film flow on different structured wires and chains is observed experimentally to assess the suitability of a structured packing consisting of vertical wires. The results show that liquid beads as they appear on cylindrical wires are inhibited by certain chain geometries. This increases the flooding gas load up to F = 12 Pa^0.5. As the stabilized film shows no liquid bead motion, the liquid velocity at the interface is less which results in lower gas‐side mass‐transfer coefficients. An estimation of the packing characteristics for different chain geometries with an assumed wire packing density of 40,000 wires/m² is made. The interfacial area, mass‐transfer coefficients, and consequently the separation efficiency strongly depend on the liquid load. However, the proposed gas‐side separation efficiencies are slightly lower compared to common structured packings but the advantages are higher load limits, a better liquid distribution, and lower pressure drop. © 2012 American Institute of Chemical Engineers AIChE J, 59: 295–302, 2013     

Performance characteristics of a packing with boundary layer turbulizers. III. Liquid film controlled mass transfer

Liquid film controlled mass transfer in a novel design of a honeycomb packing (Turbo-Pack) with turbulizers in the region of the boundary layer has been studied. For comparison, packings without turbulizers have also been investigated. Dimensionless equations for evaluation of mass transfer are proposed and their constants have been analyzed statistically. It is shown that the presence of turbulizers leads to an increase of the mass-transfer coefficient by up to 55% and to a decrease of up to 4.5-times in the packing pressure drop per mass transfer unit. A comparison over the most effective packings known from the literature shows that, as far as its low pressure drop per mass transfer unit is concerned, the novel packing is superior to all other packings.     

波纹板填料表面液体降膜流动的特性分析

基于降膜流动实验台,结合计算流体力学方法(Computational Fluid Dynamics, CFD)研究了波纹板表面液体的平均液膜厚度和有效润湿面积等定量信息,并通过三维模拟进一步分析了喷淋密度和波纹倾斜角度β对降膜流动特性的影响。结果表明,液体在波纹板表面的流动并非均匀,分为沟流和溪流两种形式;当喷淋密度较小时,液体在波谷内形成沟流,当喷淋密度达到400 m3/(m2?h),液体跨越相邻波纹进行溪流流动;两种形式波纹板整体的润湿性能均较差,且液膜厚度分布不均;波纹倾斜角度对降膜流动特性影响较大,90°时更有利于提高有效润湿面积。