膜分离技术在乳化态含油废水处理中的应用研究进展

总结了乳化态含油废水处理的难点,剖析了膜处理含油废水的基本原理、膜的分类以及膜的制备与改性,并讨论了油水分离膜的长效抗污问题和解决方法。从膜分离机理、膜的分类、制备与改性等多个方面介绍了膜分离技术应用于乳化态含油废水处理的研究进展,对膜处理乳化油的现状和未来发展方向进行了总结和展望。指出利用膜表面特殊润湿性协同破乳进而高效分离乳化态油水混合物是未来膜分离技术处理乳化态含油废水的研究重点。     

Gas separation in one- or two-step membrane processes

The purpose of these investigations was to find an answer to the question whether gas separation plants with membranes based on a new process engineering concept can be compared with conventional separation methods in terms of economic efficiency. In order to facilitate this task simplified equations were developed or adopted for five different arrangements, assuming an infinitely large pressure ratio between the high and the low pressure side of the membrane. These analytical equations enabled the major data of a plant, such as membrane area required or compressor stream, to be determined very quickly. In the present study the comparison of the separation process was based on oxygen enrichment from the air. For the concentration range investigated, namely, oxygen content of the product gas between 21% and 35%, the system of membrane rectification with dephlegmation was clearly shown to be the most economical solution.     

水处理中膜分离技术的应用

对水处理膜分离技术的发展历史和应用现状做了介绍,总结了国内外纳滤和反渗透技术在海水苦咸水淡化、废水处理等水处理领域的应用,指出了膜污染、浓差极化现象及成本较高等膜技术应用中普遍存在的问题。由于纳滤膜具有选择透过性,对纳滤技术应用于盐湖卤水资源开发中镁锂分离过程的可行性做了探讨,并从膜原件和配套工艺两方面对相关技术的应用做了展望。     

离子膜整流技术方案

介绍了整流变压器的应用,根据烧碱产量选用整流变压器的容量和电压等级,论述了整流变压器的工作原理,参数等特性。     

应用膜分离技术回收VCM精馏尾气

介绍了锦化化工(集团)有限责任公司树脂厂采用膜分离技术回收VCM精馏尾气的情况,阐述了气体膜分离技术的原理,并对该技术的各项工艺参数进行了优化、调试,总结出一套最佳控制方案,彻底解决了循环气在系统中的累积、膜组件传递动力等工艺参数影响膜分离效果的问题,可使精馏尾气中的VCM、C2H2回收率达到95%、85%以上,回收VCM 303 t/a、C2H289 t/a,获经济效益202万元/a。     

钯－银合金膜分离氢气的研究

采用厚为５０μｍ的Ｐｄ／Ａｇ（２３）合金膜进行了氢气渗透系数的测定和Ｈ＿２／Ｎ＿２混和气分离的研究，得出温度、压力、膜厚、进料气流量、膜的预处理和再活化及膜表面中毒等因素对氢气渗透的影响。分离Ｈ＿２／Ｎ＿２混和气可获得高纯氢气。     

钯－银合金膜分离氢气的研究

采用厚为５０μｍ的Ｐｄ／Ａｇ（２３）合金膜进行了氢气渗透系数的测定和Ｈ＿２／Ｎ＿２混和气分离的研究，得出温度、压力、膜厚、进料气流量、膜的预处理和再活化及膜表面中毒等因素对氢气渗透的影响。分离Ｈ＿２／Ｎ＿２混和气可获得高纯氢气。     

Industrial wastewater collection using a separation technique

Water is an essential element within normal functioning throughout the chemical industry. The reuse of water, or more precisely water condensate collection, is very important during real chemical processes because it can reduce raw materials, energy losses, and costs, and can improve the operations of energy and process systems.The effect of industrial activity on the environment has attracted considerable attention over the past few decades. Industry, therefore, has started looking at methods of reducing the volumes of produced wastewater. This paper presents the industrial separation of lower and higher temperature condensates’ collection using the heating utility of steam production, by separation techniques. The existing condensate collection regarding utilities’ preparation for steam-generation may no longer be optimal; the basic intention is that minimal changes in the system can produce an efficient improvement by using separate collections of low and high-temperature condensates, and the use of available heat with little heat flow rate loss. This separated water condensate collection preparation for the utility of steam production by using a separation technique and MINLP (mixed-integer nonlinear programming) was tested on an existing methanol process, which allowed for an efficient and additional 7% water condensate collection system for steam-generation.     

膜分离技术在镀镍废水处理中的应用

综述了电镀废水处理工艺的发展历史,介绍了膜分离技术处理镀镍废水的工艺特点,分析了二级膜分离技术的经济效益.     

离子膜整流系统的运行

介绍新疆石河子中发化工有限责任公司离子膜整流系统的运行情况，阐述了运行中出现的问题及采用的相应解决方法，并阐明了整流操作人员的责任和义务。     

Glycerol removal from biodiesel using membrane separation technology

Membrane separation technology was used to remove free glycerol from biodiesel in order to meet the ASTM D6751 and EN 14214 standards. Fatty acid methyl esters (FAME) produced from canola oil and methanol were purified using ultra-filtration. The effect of different materials present in the transesterification reaction, such as water, soap, and methanol, on the final free glycerol separation was studied. A modified polyacrylonitrile (PAN) membrane, with 100 kD molecular weight cut-off was used in all runs. Tests were performed at 25 °C and 552 kPa operating pressure. The free glycerol content in the feed, retentate and permeate of the membrane system was analyzed using gas chromatography according to ASTM D6584. Results showed low concentrations of water had a considerable effect in removing glycerol from the FAME even at approx. 0.08 mass%. This is four orders of magnitude less than the amount of water required in a conventional biodiesel purification process using water washing. It is suggested that the mechanism of separation of free glycerol from FAME was due to the removal of an ultrafine dispersed glycerol-rich phase present in the untreated FAME. This was confirmed by the presence of particulates in the untreated FAME. The size of the particles and the free glycerol separation both increased with increasing water content of the FAME. The trends of separation and particle size vs. water content in the FAME phase were very similar and exhibited a sudden increase at 0.08 mass% water in the untreated FAME. This supports the conclusion that water increased the size of the distributed glycerol phase in the untreated FAME leading to its separation by the ultra-filtration membrane. The technology for the removal of free glycerol from biodiesel was found to use 2.0 g of water per L of treated FAME (0.225 mass% water) vs. the current 10 L of water per L of treated FAME.     

Gas separation properties of polyvinylchloride (PVC)-silica nanocomposite membrane

Researchers have focused on improving the performance of polymeric membranes through various methods, such as adding inorganic nanoparticles into the matrix of the membranes. In the present study, the separation of oxygen, nitrogen, methane and carbon dioxide gases by PVC/silica nanocomposite membranes was investigated. Silica nanoparticles were prepared via sol-gel method. Membranes were prepared by thermal phase inversion method and characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermal gravimetry (TGA) analyses. The FTIR and SEM analyses demonstrated a nano-scale dispersion and good distribution of silica particles in the polymer matrix. According to TGA results, thermal properties of PVC membranes were improved and DSC analysis showed that glass transition temperature of nanocomposite membranes increased by adding silica particles. We concluded that the permeability of carbon dioxide and oxygen increased significantly (about two times) in the composite PVC/silica membrane (containing 30 wt% silica particles), while that of nitrogen and methane increased only 40 to 60 percent. Introducing 30 wt% silica nanoparticles into the PVC matrix, increased the selectivity of CO₂/CH₄ and CO₂/N₂ from 15.9 and 21 to 18.2 and 27.3, respectively. The diffusion and solubility coefficients were determined by the time lag method. Increasing the silica mass fraction in the membrane increased the diffusion coefficients of gases considered in the current study.     

A study using classical or membrane separation in the biodiesel process

Biodiesel is a clean burning biofuel produced from renewable resources (straight vegetable oil, animal oil/fats, tallow and waste cooking oil), which can be blended at any level with petroleum diesel to create a blend of biodiesel.The EU has adopted a series of directives to promote and to represent some of the most important renewable energy sources out of biofuels also covering biodiesel as well.The main processing stages currently applied for biodiesel technology are represented by transesterification, neutralization of mixture, phase separation, biodiesel and glycerine purifications. The reaction, generally occurring in a two-stage mixer-settler unit, arises some difficulties for clear cut separations.A new alternative technology, using hydrophobic porous membranes, can be used to prevent bulk mixing of the two phases and facilitate contact and mass transfer of species between the two phases.The glycerine side stream (roughly representing 10% of biodiesel) typically contains a mixture of many components, which are generally difficult to separate. Current methods for glycerine purification are complicated and conducted with higher costs.In this case, the new technology provides an economical solution for the purification of crude glycerine stream combining the high efficiency of electro-dialysis and nano-filtration processes.A comparative cost approach based on available information is sketched. Also, some examples sustain the aim of the study.     

Optimization of membrane gas separation systems using genetic algorithm

Genetic algorithm is applied for the optimization of the membrane gas separation systems. Air separation for enriched oxygen production is the selected system for investigation. Optimizations for single and triple objective functions are studied. The optimization problem involves the selection of the optimal system configurations from three alternatives, including continuous membrane column (CMC), single stripper permeator (SSP), and two stripper in series permeator (TSSP), as well as the optimal operating conditions. Models of the three configurations and the genetic algorithm procedure are computerized. The objective functions discussed are the Rony separation index, power consumption per unit equivalent pure oxygen, and the membrane area. Both high-pressure and low-pressure (vacuum) operation modes are optimized and the effects of different oxygen product purity and feed rate are analyzed. For single objective function optimization, the solutions obtained using genetic algorithm are slightly inferior in one case but superior in other cases compared to those by pure mathematical optimization methods. For triple objective function optimization, the Pareto plots presenting multiple trade-off solutions are generated. In general, compared to high-pressure operation mode, the product recovery and power consumption for low-pressure operation mode are lower. For almost all the cases studied, CMC configuration with its high flexibility appears in the optimal solutions.     

氯化苄精馏塔分离效率分析

介绍了填料塔的分离特点，分析了现有氯化苄精馏塔分离效率低的原因，并提出了改进设想。     

An experimental assessment of centrifugal membrane separation using spiral wound RO membrane elements

The influence of the rotating environment created in a centrifugal membrane separation (CMS) system on the performance of commercial spiral wound RO membrane elements has been examined. In CMS the membrane elements are located at the periphery of a centrifuge rotor. The spinning action develops the process pressure and alters the fluid flow pattern within the element due to Coriolis and centripetal acceleration. CMS has been shown to improve performance of a small-scale plate and frame element by reducing concentration polarization and fouling. The current study probes the benefits of spinning commercial spiral wound RO membrane elements in a radial orientation. Mechanical element stability at over 3000 `g' has been demonstrated as well as concentration polarization reduction and fouling alleviation. Results also indicate that rotation induced secondary flows are more effective in reducing concentration polarization than increasing cross-flow velocities for the non-rotating condition.     

Selectivity as a function of membrane thickness: Gas separation and pervaporation

In this article, the pervaporation selectivity as a function of the membrane thickness is studied for the dehydration of acetic acid. From this study, it appeared that the selectivity of polysulfone (PSF), poly(vinyl chloride) (PVC), and polyacrylonitrile (PAN) decreases with decreasing membrane thickness, below a limiting value of about 15 μm. However, in the case of gas separation, the selectivity of PSF membranes is independent of the membrane thickness. This phenomenon could not be explained by a difference in membrane morphology, sorption resistance, thermodynamic interaction, or coupling. It is believed that the decrease in selectivity for thin membranes has to be attributed to defects induced during pervaporation. These defects, crazes (and cracks), result from a reduced value of the critical strain, due to sorption of acetic acid/water and stresses between the polymer chains, due to a concentration gradient across the membrane. © 1994 John Wiley & Sons, Inc.     

膜分离技术在油田含油污水处理中的应用研究进展

介绍了膜分离技术及其优点,有机膜、无机膜和复合膜在油田含油污水处理中的应用研究进展;分析了膜处理含油污水过程中的破乳机理、影响含油污水处理效果的各种因素、产生膜污染的原因及其控制措施;探讨了膜分离技术的研究方向和发展前景.最后指出,深入研究分离膜的分离过程和机理,探索合适的清洗周期,研究合适的清洗剂和清洗工艺,明确分离膜的预处理指标要求,合理安排工艺流程,开发新型膜及膜组件是膜分离技术在油田含油污水处理中应重点解决的问题.     

渗透气化膜分离技术如何在燃料乙醇的生产中发挥作用

渗透气化作为一种新型的膜分离技术应用于发酵法制备燃料乙醇具有显著的优势.本文对渗透气化在发酵法制备燃料乙醇中的应用现状和存在问题进行了详细的综述,并对发展趋势作了展望.