Sulzer BX gauze: Fluid dynamics and absorption of acid gases

The aim of this work is a fluid dynamics study of the structured packing Sulzer BX gauze. A new model is proposed which, on the basis of a knowledge of the dynamic component of the liquid holdup, permits calculation of the fraction of the geometric area of the packing that effectively participates in the mass transfer. Both the metal and plastic versions of the packing are studied. Experimental data are supplied on the absorption of pollutants such as HCl and SO₂ by aqueous solutions of NaOH in columns in cocurrent operation. The results obtained by the proposed model are in good agreement with experimental data obtained by the present authors as well as with experimental data published in the literature.     

Hydrodynamic analogy approach for modelling of reactive stripping with structured catalyst supports

Modelling of gas/vapour–liquid separation processes usually requires experimentally determined parameters, e.g., mass transfer coefficients. This results in expensive experimental work, especially for new types of column internals. A novel modelling approach based on hydrodynamic analogies (HA) has recently been developed for distillation units equipped with structured corrugated sheet packings. The HA model takes the packing geometry directly into account whereas the experimental determination of mass transfer coefficients is not required.In this work, the HA approach is extended to cover heterogeneously catalysed reactive stripping processes. Experimental investigations are performed with a test system, esterification of hexanoic acid and 1-octanol, using different types of catalytically coated supports as column internals (one corrugated sheet packing and three film-flow monoliths with different channel geometries). Simulation results obtained with the extended HA model are in a good agreement with experimental values.     

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.     

Simulation of random packing of polydisperse particles

An optimization based model that simulates random packings of polydisperse particles to mimic porous media systems is presented in this paper. The model simulates systems with properties that map back to physically measured quantities. The model is composed of three main procedures: detachment of an existing sphere from a target sphere by moving its center to a new position, movement of an existing sphere to touch the target sphere, and addition of a new sphere to touch the target sphere. Each procedure is performed to satisfy a constrained nonlinear optimization formulation. Input parameters include radius and coordination numbers density functions. A monodisperse and polydisperse packings were simulated by incorporating physically based properties of glass bead packings obtained from 3D computed tomography images. In each simulated system, the packing density obtained was very close to the packing density of the physical system. The packings were tested for isotropy, homogeneity and randomness and then compared to experimental microtomography images. Findings indicate that the packings generated were isotropic, homogenous, random, and in a good agreement with the experimental data.     

Modelling spatial distributions of moisture and quality during drying of granular baker's yeast

A distributed parameter model was developed to predict the drying behaviour of granular baker's yeast by setting up material and heat balances at the particle level. Temperature and moisture gradients were calculated for cylindrical and spherical granules. The performance of the model with two granule sizes was compared with experimental measurements. The model was initially used for non‐shrinking granules but later modified to take shrinkage into account. The reduction in granule size during the course of drying was estimated and good correspondence with experimental measurements was obtained. In addition to temperature and moisture gradients, the product quality was predicted during drying and compared to experimental results. The accuracy of the model was better than the lumped parameter model.     

新型规整填料的性能及其在硫酸工业中的应用

针对硫酸干吸塔研制出了TJ160X型陶瓷规整填料，通过试验研究和分析证明该填料比传统的散堆填料具有更大的比表面积、更大的通量，其效率高、压降低。该填料在相同的条件下，压降是散堆填料的1／3，通量提高2倍以上。结合先进的液体分布器，模拟设计了一套硫酸干吸塔。探讨了将先进的陶瓷规整填料塔技术用于硫酸干吸系统的途径和方法。     

Performance characteristics of a packing with boundary layer turbulizers Part 1. Pressure drop and loading point

A novel design of a honeycomb packing with turbulizers in the region of the boundary layer (Turbo-Pack) has been designed and investigated. The presence of turbulizers is shown to decrease the pressure drop per mass transfer unit in cases of both gas-film and liquid-film controlled mass transfer. A comparison of the best packings known so far from the literature shows that, regarding such an important parameter as pressure drop per mass transfer unit, the novel packing has significant advantages. On the basis of experimental data obtained by studying 11 different packing designs in liquids of various viscosity, equations for determining the performance characteristics of the novel packing are obtained. In the first part of this work, the data on packing design, pressure drop and loading point are presented.     

Modelling the Effective Thermal Conductivity in Polydispersed Bed Systems: A Unified Approach using the Linear Packing Theory and Unit Cell Model

A comprehensive, unified approach, using the Linear Packing Theory and Unit Cell Model, is proposed for calculating of the effective thermal conductivity of polydispersed packed beds. In this new approach, the effect of packing density is incorporated by the use of (i) an initial porosity to take into account the packing of mono‐sized particles, and (ii) the packing size ratio as a measure of the particle‐particle interaction. The proposed approach was validated with the experimental measurements of binary and ternary beds. This new approach demonstrates that the effective thermal conductivity of beds composed of polydispersed particles can be simulated for any composition without the need to measure the in situ porosity.     

规整填料内单相流的LDV实验研究

To date, many models have been developed to calculate the flow field in the structured packing by the computational fluid dynamics （CFD） technique, but little experimental work has been carried out to serve the vali-dation of flow simulation. In this work, the velocity profiles of single-phase flow in structured packing are measured at the Reynolds numbers of 20.0, 55.7 and 520.1, using the laser Doppler velocimetry （LDV）. The time-averaged and instantaneous velocities of three components are obtained simultaneously. The CFD simulation is also carried out to numerically predict the velocity distribution within the structured packing. Comparison shows that the flow pattern, velocity distribution and turbulent kinetic energy （for turbulent flow） on the horizontal plane predicted by CFD simulation are in good agreement with the LDV measured data. The values of the x-and z-velocity components are quantitatively well predicted over the plane in the center of the packing, but the predicted y-component is sig-nificantly smaller than the experimental data. It can be concluded that experimental measurement is important for further improvement of CFD model.     

Counter-current absorption of oxygen by a frequency response technique: Die Untersuchung der Gegenstromabsorption von Sauerstoff mit der Frequenzgangtechnik

A theoretical and experimental study has been carried out on the dynamics of two-phase counter-current flow with interfacial transfer in a packed bed absorption column. An eight-parameter model has been formulated consisting of axially dispersed plug flow for the gas phase and a piston-diffusion exchange model for the liquid phase. In addition, three limiting cases of this model have been analysed. Solutions of the models have been obtained in the Laplace domain with four possible transfer functions for each model as a result. Only two of these transfer functions have been found useful for an experimental study of the absorption of a poorly soluble gas. Experimental measurements of these two transfer functions, in the form of frequency characteristics, have been carried out in a 0.105 m diameter column packed to a height of 2.1 m by glass spheres 0.01 m in diameter. The absorption system studied was water—air—oxygen. Evaluation of the parameters of the formulated models was carried out in the frequency domain. The results showed that models with a stagnant liquid zone are considerably better than axially dispersed models. For a more reliable assessment of the various models, however, combination of several independent measurements is recommended.     

A transport model for the absorption of mixed solvents in glassy polymer membrane

Transport model for mixed solvents in glassy polymer membrane is rare in literature. In our previous work, a new experimental method has been developed and absorption kinetic curves for two mixed solvent systems (ethanol/1,2-dichloroethane and ethanol/ethyl acetate) in polyurethane (PU) membrane at have been measured. In this work, based on Liu et al.'s transport model for single solvent/polymer membrane system, a transport model for the absorption of mixed solvents in glassy polymer membrane is established. Three model parameters in this model can be obtained by correlating the experimental data of the corresponding single solvent/polymer membrane systems; the other three should be determined by correlating the experimental data of mixed solvents/polymer membrane system. The effect of model parameters on diffusion is studied by numerical simulation. The correlated results agree well with the experimental absorption curves. The model has the ability to predict the transport phenomena of mixed solvents in polymer membrane.     

Modeling and rheology of HTPB based composite solid propellants

The propellant with the minimum viscosity required for a defect-free casting can be obtained by proper selection of the size and fractions of solid components leading to maximum packing density. Furnas' model was used to predict the particulate composition for the maximum packing density. Components with certain size dispersions were combined to yield a size distribution that is closest to the optimum one given by Furnas for maximum packing. The closeness of the calculated size distribution to the optimum one was tested by using the least square technique. The results obtained were experimentally confirmed by viscosity measurement of uncured propellants having HTPB binder and trimodal solid part accordingly prepared by using aluminum (volumetric mean particle diameter of 10.4 μm) and ammonium perchlorate with four different sizes (volumetric mean particle diameters: 9.22, 31.4, 171, and 323 μm). The experimental measurements showed that the compositions for the minimum viscosity are in good agreement with those predicted by using the model for maximum packing. The propellant consisting of particles with mean diameters of 10.4, 31.4, and 323 μm was found to yield the minimum viscosity. This minimum viscosity was observed when the fraction of the sizes with respect to total solids was 0.141, 0.300, and 0.559, respectively.     

内弯弧形筋片扁环填料的特点和应用前景

内弯弧形筋片扁环填料是一种结构新疆，性能优异的高效填料，获国家发明专利系统的实验研究和工业应用表明，这种填料的性能优于多种国外引进的新型填料，可望在石油炼制，化工，湿法冶金和医药等领域的萃取，精馏和吸收等过程中获得更广泛的应用。     

A tool for mass transfer evaluation in packed-bed columns for chemical engineering students

This paper presents a Microsoft Excel tool to calculate liquid-gas mass transfer coefficients in packed towers to support numerical design activities in the courses of Unit Operations for Industrial Process and Sustainable Process Design for the Master’s degree in Chemical Engineering of the University of Naples Federico II (Italy).The Mass Transfer Solver Tool (MT Solver Tool) uses several available models to estimate, separately, the values of liquid and gas mass-transfer coefficients and the wet surface area for 144 random and structured packings of interest for absorption/stripping and distillation processes. In addition, a separate spreadsheet can be used in a user-defined mode, to evaluate the mass transfer coefficients with new packing types or to interpret experimental data when the geometrical and physical characteristics of the packing are known. Eventually, the tool is supplied with a data library, where packing geometry and model fitting parameters can be retrieved.The software is aimed to support students and educators in the Unit Operations for Industrial Process and Sustainable Process Design courses. In particular, this is meant to be an example on how the accuracy of design algorithms adopted in unit operation processes is affected by the use of the underpinning correlations for mass transfer rate or pressure drops. Besides, this is aimed to encourage comparison of different correlations when exact field data are not available. Besides, chemical engineers and researchers interested in packed columns design and modelling data may also benefit from the utilization of the software. The MT Solver Tool was introduced to students in a dedicated tutorial lesson after lecturers on packed column design algorithms for distillation, absorption and stripping. Most of the students of the course participated to a group training aimed to simulate the design of an absorption column supported by the MT Solver Tool providing feedback on its application.After the training, an anonymous survey was proposed to the students to monitor the approval rating of the proposed activity and the use of the MT Solver Tool software to support numerical calculations.     

填料塔气体分布器二相流场计算流体力学数值模拟

填料塔内气体分布器对进料气流的分布作用和填料塔的分离效率,特别是对低压降、高效填料有重大影响。文中运用计算流体力学(简称CFD),采用欧拉-拉格朗日二相流模型建立了填料塔内双切向气体分布器内三维瞬态气液二相流模型,气体的湍流运动采用k-ε湍流模型计算。模型中考虑了二相之间的作用力,包括液滴所受的曳力和虚拟质量力。求解时时间项采用隐式格式,时间步长取1×10-4s,对流项采用二阶迎风格式,压力-速度耦合方程的求解采用了S imp lec方法。在不同操作条件下,模型计算得到的压降、夹带、气体分布不均匀度和文献报道的实验值吻合较好。从而可以看出,CFD模型可以较为准确地描述双切向环流式气体分布器内瞬时气液二相流场。     

新型多管塔流体力学特性

1 INTRODUCTION The column packed with Dixon gauze ring or heli-pak has been widely used for separating isotopes and isomerides for its remarkably low HETP when operated under optimum conditions. However a fatal weakness of such columns is that it works well only for small diameter columns. No matter whatever type of packing is used in the column, normally the HETP increases with the increase of the diameter of the column, and it appears that the more efficient the packing is, the more …     

On Densification of Porous Materials Using Precursor Solutions

A quantitative model describing the densification of porous compacts using liquid solutions that takes into account the gradual sealing-off of the porosity has been proposed. The model was applied to experimental data on densification of alumina compacts and alumina fiber-reinforced ceramic composites infiltrated by an aqueous CrO₃ solution. The results obtained with the present model were in good agreement with those expected based on the statistical models and computer simulations of the packing of spheres. Recommendations to improve the efficiency of the densification of porous materials using precursor solutions are suggested based on the results of the present work.     

倒锥型真空填料精馏塔的性能

在倒锥型塔中,采用两种小型散装高效填料和三种回流比,在5～50 mmHg的塔压范围内,就塔压、空塔汽速、回流比、填料类型和塔的结构等诸要素对真空填料精馏塔的传质性能和流体力学性能的影响进行了研究,并与文献报导的直塔和四段塔进行了比较。实验结果表明,锥型塔在传质和流体力学性能两方面,都较为优越。作者还推导了一个能较好地描述锥型塔传质特性的数学模型。     

Mathematical Model of the Phase Diagrams of Ionic Liquids-Based Aqueous Two-Phase Systems Using the Group Method of Data Handling and Artificial Neural Networks

Development of ionic liquid-based aqueous two-phase systems as a new viewpoint in the expansion of research in the field of biological materials separation depends on accurate determination of phase diagram. In this work, the efficiency of artificial neural network was studied aiming to forecast the formation possibility of phase diagrams of aqueous two-phases systems for the ability of range of ionic liquids composed of different anions with a selected salt. In order to investigate effects of the anion of ionic liquids on phase diagram, this study was performed on 472 of experimental data. On the basis of the accurate set of statistical measurements obtained, a good agreement between the experimental data points and the predicted values was gained. Furthermore, the group method of data handling was applied to model the molality of ionic liquids and a reasonable agreement was obtained between experimental data and the predicted values of this model.     

超重力旋转床中水脱氧过程的模型化研究

超重力旋转床是一种高效的强化传质和混合的新型设备。今提出了超重力旋转床中的水脱氧过程的传质模型,分别采用欧拉方法和拉格朗日方法对超重力旋转床中的气相和液滴的运动行为进行了数值模拟;在此基础上计算了液滴的传质系数,计算结果和实验结果符合较好,平均误差为7．9％。当超重力旋转床中液体存在的主体形式更接近于液滴时,模型计算结果误差减小。进一步讨论分析了液体和气体流量、转速以及填料内径的变化对于超重力旋转床体积传质系数的影响,分析表明旋转填料对液体剧烈地剪切破碎分散作用是强化传质过程的主要原因。