计算流体力学在反渗透膜分离中的应用

综述了计算流体力学(CFD)在反渗透膜分离中的应用情况及研究成果.阐述了CFD技术由于精确、效率高、成本低、不受实验条件限制等优势而得到的广泛应用,为研究流体流动提供了新的手段.指出浓差极化和膜污染限制了反渗透技术的进一步广泛应用,而CFD技术则为研究该问题提供了一种强有力的工具.     

渗透蒸发法膜分离技术及其应用

随着生产的不断发展，对分离技术的要求越来越高，分离的难度越来越大。为了适应这些要求，新的分离方法不断地涌现，膜分离技术即是其中之一。膜分离是指分子混合状态的气体或液体，经过特定的膜的渗透作用，改变其分子混合物的组成，直至能使某一种分子从其他混合物中分离出来，实现混合物分离的目的。一般膜分离没有相的变化，它是利用物质透过膜的速度差而实现的，是一种理想的、节能的分离方法。高分离效率的膜分离技术，由于分离所需能量少，工艺可连续化，装置比较紧凑，并且又能以低浓度存在的物质，分子结构类似的物质，分子间作用…     

膜分离技术的发展

<正> 膜分离现象的揭示可以追溯到200多年以前。膜分离技术在工业上获得重要应用并取得高速发展却是近二、三十年的事。估计膜技术将成为本世纪末至下世纪中叶推动产业革命的重大技术之一。     

渗透蒸发膜分离技术的研究与进展

渗透蒸发膜分离技术的研究与进展许振良，倪秀元，施亚钓（华东理工大学化学工程研究所）一、前言渗透蒸发（Ｐｅｒｖａｐｏｒａｔｉｏｎ，简称ＰＶ）是具有相变化的膜分离过程，它是通过蒸馏法与膜法相结合而推动运行的、，与微滤、超滤、反渗透、电渗析等膜法相比，它是...     

渗透汽化膜分离技术在工业中的应用

渗透汽化膜做为近年发展起来的现代液体膜分离技术，显示了技术可靠，工艺灵活，操作方便及费用经济的特点。本文主要介绍了渗透汽化膜分离原理，以及国外在工业应用中的进展     

膜分离技术的新进展

膜分离现象的揭示,可追朔到二百多年以前,而膜分离技术在工业上得到应用是近二十多年来的事.它是一项有着十分广阔前景的分离技术.二十年来美国的膜分离技术称雄世界,但近年来欧洲和日本已成为世界上膜分离技术的主流.膜系统(装置)1990年产值为16亿美元,现正以年增长率12-15%的速度递     

膜分离技术在石化工业中的应用与研究

概述了膜分离技术在石油化学工业中的应用及其所进行的研究。     

乳化液膜分离技术及其在烃类分离中的应用

乳化液膜技术是一种新型的分离技术，在许多领域中有着广阔的应用前景，综述了乳化液膜分离技术的过程，原理，数学模型，影响乳化液膜分离的各种因素及其在液体烃类分离中的应用，总结了这种分离技术的优缺点，分析了其在煤焦油产品的分离和精制中应用的可行性。     

Transient computational fluid dynamics modeling of pervaporation separation of aromatic/aliphatic hydrocarbon mixtures using polymer composite membrane

Pervaporation (PV) separation of toluene/n‐heptane mixtures was studied experimentally and theoretically by means of a molecular surface engineering (MSE) polymer composite membrane. A comprehensive mathematical model was developed to predict unsteady state transport of toluene and n‐heptane (nC₇) through the membrane. Conservation equations including continuity, and heat transfer equations were solved using finite element method (FEM). Computational fluid dynamics (CFD) technique was applied to solve the model equations. The model was then verified with PV experimental data. The simulation results were in good agreement with the experimental data. The simulation results revealed that the proposed model could provide a general simulation of transport in the PV process. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Nanofiltration membranes broaden the use of membrane separation technology

Most reverse osmosis (RO) research has concentrated on the development of single-pass seawater membranes. The success of these high rejection membranes has created interest in other applications requiring less demanding salt rejection, or desiring the elimination of salt from a feed stream (diafiltration), or having severe chemical resistance requirements. All would prefer to operate at lower net driving pressures than demanded by the high rejection membranes. This paper reports on the characteristics of three such tailored membranes. These membranes have been designated as “quo;nanofiltration”quo; membranes to distinguish them from the “quo;hyperfiltration”quo; seawater membranes. The first is XP45, a polyamide membrane with a low sodium chloride rejection that makes it an excellent candidate for applications such as the processing of salty cheese wheys and pharmaceutical preparations. The second is NF70, another polyamide, a low pressure membrane with rejections suited for converting mildly brackish water and organic-laden raw water to potable water that meets WHO standards. The third is XP20, a new developmental membrane for the maintenance of electroless copper plating baths.     

On the implementation of membrane models in computational fluid dynamics calculations of polymer electrolyte membrane fuel cells

The implementation of phenomenological membrane models within computational fluid dynamics (CFD) codes requires coupling of the conservation equation for water content within the membrane to the conservation equations for species mass outside the membrane. It is common practice to treat water and current transport within the membrane as one-dimensional (1D), i.e., normal to the membrane surface only. The purpose of this study is to investigate the accuracy and efficiency of various strategies of implementing a phenomenological membrane model within the framework of a two-dimensional (2D) CFD code. Springer's membrane model was compared against two other models available from the literature, and the accuracy of each model was assessed by comparing predicted results against experimental data. Results appear to indicate that the Springer model and the Nguyen and White model over-predict the drying of the membrane, while the Fuller and Newman model provides the best match with experimental data. Following these studies, three strategies for implementation of the membrane model were investigated: (1) 2D transport in membrane, (2) 1D transport in membrane and (3) 1D transport with approximate transport properties. Fuller and Newman's membrane model was used for these studies. The results obtained using the three approaches were found to be within 4% of each other, while there was no significant difference in the computational time required by the three models, indicating that an analytical 1D transport model for the membrane that uses approximate properties is adequate for describing transport through it.     

Applications of computational fluid dynamics in the chemical industry

In order to illustrate the use of CFD in providing an understanding of mixing processes, three examples, mixing in a pipe, homogenization with a static mixer and flow in a mixing vessel with a Rushton turbine, are discussed and compared with experimental results. Special attention is focussed on the resultant concentration distribution, which is closely linked to turbulent properties. A semi-empirical model is presented for a quantitative prediction of the initial turbulent conditions. Using special numerical techniques a mixing vessel with wall-separated baffles, which represents a problem generally regarded as beyond the capabilities of numerical analysis, can be simulated.     

Using computational fluid dynamics in combating erosion-corrosion

Computational fluid dynamics was used to search for the links between the observed pattern of attack seen in a bauxite refinery's heat exchanger headers and the hydrodynamics inside the header. Validation of the computational fluid dynamics results was done by comparing then with flow parameters measured in a 1:5 scale model of the first pass header in the laboratory. Computational fluid dynamics simulations were used to establish hydrodynamic similarity between the 1:5 scale and full scale models of the first pass header. It was found that the erosion-corrosion damage seen at the tubesheet of the first pass header was a consequence of increased levels of turbulence at the tubesheet caused by a rapidly turning flow. A prismatic flow corrections device introduced in the past helped in rectifying the problem at the tubesheet but exaggerated the erosion-corrosion problem at the first pass header shell. A number of alternative flow correction devices were tested using computational fluid dynamics. Axial ribbing in the first pass header and an inlet flow diffuser have shown the best performance and were recommended for implementation. Computational fluid dynamics simulations have revealed a smooth orderly low turbulence flow pattern in the second, third and fourth pass as well as the exit headers where no erosion-corrosion was seen in practice. This study has confirmed that near-wall turbulence intensity, which can be successfully predicted by using computational fluid dynamics, is a good hydrodynamic predictor of erosion-corrosion damage in complex geometries.     

计算流体力学在化学工程中的应用

计算流体力学(CFD)用于求解固定几何形状设备内的流体的动量、热量和质量方程以及相关的其他方程,已成为研究化工领域中流体流动和传质的重要工具。本文概述了CFD的基本原理以及CFD在化学工程领域方面的应用,重点介绍了CFD在搅拌槽、换热器、蒸馏塔、薄膜蒸发器、燃烧等方面的应用。     

Numerical methodology for proton exchange membrane fuel cell simulation using computational fluid dynamics technique

To analyze the physical phenomena occurring in the Proton Exchange Membrane Fuel Cell (PEMFC) using Computational Fluid Dynamics (CFD) technique under an isothermal operating condition, four major governing equations such as continuity equation, momentum conservation equation, species transport equation and charge conservation equation should be solved. Among these governing equations, using the interfacial boundary condition is necessary for solving the water transport equation properly since the concept of water concentration in membrane/electrode assembly (MEA) and other regions is totally different. It was first attempted to solve the water transport equation directly in the MEA region by using interfacial boundary condition; and physically-meaningful data such as water content, proton conductivity, etc. were successfully obtained. A detailed problem-solving methodology for PEMFC is presented and result comparison with experimental data is also implemented in this paper.     

计算流体力学在填料塔中的应用

本文综述了计算流体力学在填料塔中的应用和进展情况,并根据研究方法的不同,将其分为两类,即整体平均的研究方法和单元综合的研究方法。并对各研究方法的优势和不足及其应用前景进行了评述,认为用计算流体力学来研究填料塔内流体的流动状况是今后的发展趋势。     

化工过程膜分离技术的发展

近年,膜分离技术在化工领域广泛应用,使传统的分离方法发生了质的变化。预计未来,膜分离技术将有取代传统分离技术之势。文中介绍了膜分离技术开发过程与特点,当前的应用水平和技术经济分析,指出今后研究方向,并对我国的开发工作提出了建议。