CFD‐assisted Characterization and Optimization of the Structured Mass Transfer Packing QVF DURAPACK®

The glass packing QVF DURAPACK® was developed to use the advantages of structured mass transfer packings, especially when handling corrosive media. To match up with the latest developments for sheet metal packings, further optimization for liquid‐liquid separation processes was performed for the QVF DURAPACK®. The complex geometry of structured packings and the wall thickness of glass sheets complicate the numerical investigations. The modeling strategy is presented, and the limitations of CFD tools are given. The experimental and numerical results show similar trends as known for perforated metal structures. The extraction efficiency of the packing prototype could also be reproduced with the column design tool LLECMOD.     

Holdup and Pressure Drop of Packed Beds Containing a Modular Catalytic Structured Packing

A comparative experimental study has been carried out to establish the hydraulic behavior of a new modular catalytic packing (Sulzer's Katapak^®‐SP 12) and the hybrid packed bed consisting of a catalytic packing section placed in between two sections comprising elements of a high capacity structured packing (MellapakPlus 752.Y). Air‐water experiments were carried out at ambient conditions using a Perspex column with an internal diameter of 0.45 m. As expected, the liquid holdup and the pressure drop of the combined bed were between those measured for beds consisting purely of the catalytic and structured packings. However, unlike the two reference beds, the combined bed exhibited a clear upper gas load limit due to a pronounced liquid buildup at the transition from the structured packing to the top element of the catalytic packing section. Also it appeared that the Delft model, with appropriate packing geometry modifications is capable of reliably predicting the preloading region holdup and pressure drop of a hybrid packed bed containing Katapak‐SP.     

Liquid load point determination in a reactive distillation packing by X‐ray tomography

In this paper, we report on the use of X‐ray tomography to determine the liquid load point in 0.1 m diameter modular catalytic distillation packings Katapak‐SP11 and Katapak‐SP12. The liquid load point corresponds to the overall packed bed liquid load above which there is an increment in the liquid flowing outside the catalytic baskets and the catalytic baskets themselves are saturated with liquid. From tomographic images, we show that several factors affect the wetting and filling of catalytic baskets. The complex hybrid structure of catalytic packings influences the liquid distribution inside the elements. The liquid preferentially fills the external catalytic baskets because they receive the liquid not only from the packing element situated above but also from the wall wipers. Moreover, liquid hold‐up inside a catalytic basket section depends significantly on the vertical position in the packing element and on the position of the packing in the column packed bed. The counter–current gas flow speeds up the process of liquid filling of the baskets, also for low liquid loads. The non‐uniform distribution of liquid in catalytic basket which is observed experimentally makes the identification of a unique liquid load point not straightforward.     

Investigation of dynamic liquid distribution and hold-up in structured packings using ultrafast electron beam X-ray tomography

Dynamic cross-sectional liquid distribution and hold-up in a DN80 separation column filled with structured packings was studied using an ultrafast electron-beam X-ray tomograph with high temporal resolution of 2000 images per second. The modality allows visualisation and characterisation of the counter-current flow before and at the flooding point representing the upper operation limit. Two packings of the same type (Montz B1-MN) with different specific surface area were used to investigate the influence of the packing geometry on the spatial liquid distribution. The system studied was water/air at different gas and liquid loads. The results of the tomographic imaging and corresponding post-processing routines were validated by comparison with conventional draining measurements.     

金属板波填料液流分布的研究

根据金属板波填料的结构,建立其液流分布模型.在φ500mm和φ200mm塔内,实测了6.3型和4.5型不锈钢板波填料的液流分布.结果表明:模型值与实测值基本相符.对不同填料在相同条件下的实测证明:金属板波填料的液流分布性能,优于拉西环、鲍尔环和阶梯环.文中就气液负荷和喷淋装置等因素的影响作了讨论,并提出了分布器喷淋点密度的推荐范围.     

A multi-scale approach for CFD calculations of gas-liquid flow within large size column equipped with structured packing

This work has been carried out in the framework of post-combustion CO₂ capture process development. Considering the huge amount of gases to be treated and the constraints in terms of pressure drop, it appears that the absorption column will be equipped with high efficiency high capacity packings such as structured packings. The present paper focuses on the CFD modellisation of the two-phase flow within this complex geometry. For limited computational resources reasons, it is presently impossible to run computations at large scales taking into account the gas-liquid interaction and the real geometry of the packing and original approaches must be developed. In the present work, a multi-scale approach is proposed. It first considers liquid-wall and liquid-gas interaction at small scale via two-phase flow calculations using the VOF method. Second, the latter results are used in three-dimensional calculations run at a meso-scale corresponding to a periodic element representative of the real packing geometry. Last, those results are further used at large scale in three-dimensional calculations with a geometry corresponding to a complete column. Results are compared with experimental data and with other CFD simulations in terms of liquid hold-up, pressure drop and unit operation. Some suggestions are made for further development.     

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。     

液相流动方式对波纹规整填料性能的影响

根据液相在波纹规整填料片上呈现渗流、膜状流等不同的流动方式,选择5种不同的波纹规整填料对其流体力学和传质性能进行研究,以探究液相在波纹片上的流动方式对波纹规整填料性能的影响.研究结果表明,液相呈渗流流动的泡沫碳化硅波纹规整填料(SCFP型)有利于液体横向扩散和液膜均匀分布,当液相喷淋密度和气相F因子均较小时,其压降最低,传质效率最高;液相主要呈渗流流动、兼有膜状流动的双层错孔丝网填料(DMⅢ型)有利于波纹片两侧液体交换,强化液体在流动过程中的扰动,其压降及传质性能略逊于SCFP型填料;液相主要呈膜状流动的BX型、DMⅠ型及DMⅡ型填料波纹片表面液膜较厚,横向扩散能力差,其传质效率低于SCFP型和DMⅢ型填料.研究揭示了依靠渗流作用的波纹规整填料具有较好的应用性能,为波纹规整填料的进一步发展开拓了新思路.     

Cover Chem. Eng. Technol. 4/2013

CFD‐assisted Packing Optimization The glass packing QVF DURAPACK® was developed to use the advantages of structured mass transfer packings, especially when handling corrosive media. To match up with the latest developments for sheet metal packings, further optimization for liquid‐liquid separation processes was performed for the QVF DURAPACK®. The complex geometry of structured packings and the wall thickness of glass sheets complicate the numerical investigations. The modeling strategy is presented, and the limitations of CFD tools are given. The experimental and numerical results show similar trends as known for perforated metal structures. The extraction efficiency of the packing prototype could also be reproduced with the column design tool LLECMOD. DOI: 10.1002/ceat.201200531 CFD‐assisted Characterization and Optimization of the Structured Mass Transfer Packing QVF DURAPACK® C. Dreiser, G. Gneist, H.‐J. Bart* Chem. Eng. Technol. 2013 , 36 (4), 545–551     

Mass transfer performance of structured packings in a CO2 absorption tower

This paper studies the mass transfer performance of structured packings in the absorption of CO2 from air with aqueous NaOH solution. The Eight structured packings tested are sheet metal ones with corrugations of different geometry parameters. Effective mass transfer area and overall gas phase mass transfer coefficient have been measured in an absorption column of 200 mm diameter under the conditions of gas F-factor in 0.38–1.52 Pa0.5 and aqueous NaOH solution concentration of 0.10–0.15 kmol·m?3. The effects of gas/liquid phase flow rates and packing geometry parameters are also investigated. The results show that the effective mass transfer area changes not only with packing geometry parameters and liquid load, but also with gas F-factor. A new effective mass transfer area correlation on the gas F-factor and the liquid load was proposed, which is found to fit experiment data very well.     

规整丝网填料旋转填充床的气相压降特性及脱硫性能

采用空气-水体系,对装有4种不同规格规整丝网填料的旋转填充床的压降特性进行了实验研究,考察了转速、气体流量、液体流量等操作参数及填料特性对气相压降的影响规律,并与传统不锈钢波纹丝网填料旋转填充床压降进行了比较. 结果表明,装有规整丝网填料的旋转填充床压降可降低35%~70%. 进一步采用压降较低的规整丝网填料以(NH4)2SO3为吸收剂进行氨法脱硫性能研究,结果表明,随转子转速和(NH4)2SO3浓度增大,SO2脱除率升高;随进气口SO2浓度升高及气液比增大,SO2脱除率降低;SO2脱除率最高可达97%,可满足国家排放标准.     

Gel Permeation Chromatography Column Packings—Types and Uses

Abstract

Proper selection of the column packing material is an essential part of a successful gel permeation analysis. Generally the desirable properties of a packing are good chemical, thermal, and mechanical stabilities combined with good resolution and low resistance to liquid flow. Pore size distribution, particle size distribution, polar characteristics, as well as other physical parameters play a role in how well a packing will perform. This paper describes the different types of column packings which are commercially available, as well as briefly mentioning several packings used on an experimental scale. Physical characteristics of the various packings are compared. Suggested uses along with some limitations are given.     

Determination of Liquid Radial Spreading Coefficients of Some Highly Effective Packings

The liquid radial spreading coefficient of packings for absorption and rectification columns is necessary to determine the packing height which ensures uniform liquid distribution over the column cross section. The existing calculation methods can be used theoretically only when this coefficient is independent of the liquid superficial velocity, which is often not the case. A tracer method free from this limitation is developed and tested. The spreading coefficients for different sizes of modern, highly effective packings (Raschig Super‐Ring, Ralu‐Flow, and impulse metal tower packing) are determined. Practically, in the range of the experimental error, the spreading coefficients of these packings are independent of the liquid superficial velocity. For such packings the tracer method is expected to give the same results as the existing single jet method. Some differences between the results of these two methods are discussed and an explanation is proposed.     

Hydrodynamique et transfert gaz-liquide dans un réacteur verlifix rempli de différents garnissages

This study concerns several Verlifix three phase reactors formed by the association of a jet venturi upper on a column filled with different solid packings. The gas and liquid flows are downstream cocurrent. Four packings are studied: glass Raschig rings, Coming's monolithic ceramics, microporous alumina pellets and glass beads. For these packings and gas and liquid flow rates fixed, we measure the hydrodynamic characteristics (flow regime, liquid dynamic retention, pressure drop) of the fixed bed and gas-liquid mass transfer conductance of the whole reactor, then we specify the influence of the operative conditions and the type of packing.     

复合板网填料性能研究

对一种新型的金属复合板网填料进行了研究,它是由三层板网贴合为复合基材后加工成波纹填料。在500冷模实验塔内对250Y型填料的测试结果表明复合板网填料具有显著的性能优势。三层复合板网填料的压降比常用的金属板波纹填料低60%以上,通量大20%～40%。氧解吸实验结果表明三层复合板网填料的分离效率明显高于单层板网填料,尤其在液气比低的工况下,效率可以倍增,和广泛应用的金属Mellapac填料相比,复合板网填料的分离效率能高30%左右。     

Hydraulic Calculations for Cross‐channeled Packings in Distillation Unit Based on a Physical Model

A physically based calculation model has been developed in order to describe the liquid and the gas flow in column packings with any arbitrary cross‐channel structure. An equation system is presented which characterizes the film flow on the surface as influenced by the countercurrent flowing gas stream and the respective geometric parameters of the packing. The considered hydraulic operating parameters are the pressure drop, the film thickness, and the radial liquid distribution as a function of the column load up to the flooding point. Care was taken to introduce only constants that can be interpreted physically. Their number was reduced to a minimum of three in order to provide the possibility of easy extrapolation to other packing dimensions. Numerical simulations have been carried out for different liquids assuming a fully wetted packing surface. A distribution width is introduced as the parameter characterizing the radial liquid distribution. Its value together with the respective gas split factors are important variables for the inclusion of maldistribution in the calculation of a distillation column. The numerical simulations up to the flooding point correspond well to the experimental data obtained from a test column.     

A Study on Modern High Effective Random Packings for Ethanol‐Water Rectification

Raschig Super‐Ring is a modern and high‐efficient packing used for intensification of absorption and distillation processes. The aim of this work is to characterize the efficiency of this packing applied to rectification of an important industrial system, ethanol‐water, and to compare its efficiency to that of some random packings of the third generation as well as to the structured packing, HOLPACK, which is used in the ethanol production industry. The experiments were carried out in a column installation, 0.213 m in diameter with a packing height of 2.8 m. The column is heated by a number of electrical heaters (total power 45 kW), which can be switched gradually. Operation at total and partial reflux is possible. Eight types of random packings were studied: five types of Raschig Super‐Ring, four metallic (with characteristic dimensions 0.5, 0.6, 0.7, and 1”) and one of plastic material 0.6”; two types of packing IMTP and one plastic Ralu Flow. Some experiments were conducted at total reflux operation at vapor velocity, 0.253–0.936 m/s, and liquid superficial velocity, 4.44 · 10^–4–1.63 · 10^–3 m³/(m²s). Experiments at partial reflux were carried out at constant liquid superficial velocity and changeable vapor velocity as well as at constant vapor velocity and changeable liquid velocity. The results are presented as height of transfer unit, HTU, and height equivalent to a theoretical plate, HETP, as a function of the velocity of phases.     

Models describing the behavior of new carbon fiber packings inn rectification processes

Many rectification processes are used to separate corrosive substances with high boiling points. This reports deals with a new type of structured column pacing mode of corrosion-resistant carbon fiber material. These column internals allows for low pressure drop at high throughput rated with reasonable column efficiency. Experiments in columns of 50 and 100 mm diameter have been carried out to investigated separation efficiency, pressure drop and liquid holdup of the packing even at low operation pressures. In the respective columns twp geometrical different types of packing have been tested using binary mixtures of chlorobenzene/ethylbenzene with a packing geometry similar to the Sulzer EX packing, the 100 mm diameter column was filled with elements of rougher structure and smaller specific surface. Basing on the experimental results, model equations are presented, which allow the calculation of the investigated performance characteristics.     

Packungskolonnen

Packed columns . Packed towers with dumped or regular packings are widely used in industry for accomplishing chemical engineering processes. Packed columns are able to work economically even under extreme process conditions (e. g. vacuum, high temperature, aggressive flow mediums), because of the available variety of packing types and the straight-forward manufacture of the individual packing elements from almost any material. The present contribution shows the different kinds of packings arranged according to their geometry and physical properties. A packed tower for gas/liquid countercurrent operation is shown as a basic construction with the necessary internals. Since packed columns are mostly used in gas/liquid countercurrent operation, the fundamentals of fluid dynamics and mass transfer are presented for this operating condition.     

Reactive distillation with KATAPAK

KATAPAK-SP and -S are structured catalytic packings for reactive distillation or gas–liquid reactors available from laboratory to industrial scale. Applying the KATAPAK-SP concept, the ratio of catalyst volume fraction to separation efficiency can be varied over a wide range, therefore the design of a reactive distillation column can be further optimized to fit each reaction system best.

Pressure drop, separation efficiency, dynamic liquid hold-up and residence time distribution have been investigated for KATAPAK-SP in a diameter of 250 mm. Results for different gas and liquid loads are presented. The findings are compared with results for the structured laboratory scale packing KATAPAK-S and the industrial scale packing KATAPAK-S 170.Y.

The dehydration of tert-butyl alcohol was selected as a sample reaction to illustrate the influence of different catalytic structures on the performance of the reactive distillation column. The setups are compared with respect to dimensions and economics.