丙烯膜法脱水工艺技术的研究分析

传统的丙烯脱水工艺存在能耗高、丙烯浪费大、再生氦器气用量大等缺点。蒸汽渗透技术具有能耗低、过程简单、分离因子高、操作灵活等优点，而且它的渗透通量较低，这使得它特别适用于微量可凝组分的分离。本研究以脱除丙烯中微量水分为目的，以聚乙烯醇、壳聚糖为复合膜活性层，聚砜中空纤维膜为支撑层，制备出多种中空纤维复合膜。考察制膜条件及实验操作条件对膜性能的影响。     

The assessment of microorganism growth in the membrane distillation system

Growth of microorganism in the membrane distillation (MD) system has been evaluated, and their presence on the membrane surface was studied using scanning electron microscopy (SEM) coupled with energy dispersion spectrometry (EDS). The membrane samples were collected from MD modules used for the following applications: concentration of salts and acids, production of demineralized water from tap water, separation of ethanol from fermentation broth in a membrane bioreactor and treatment of saline wastewater containing Pseudomonas and Streptococcus faecalis bacteria and Penicillium and Aspergillus fungi. The MD experiments were performed with polypropylene capillary membranes. SEM examinations of the membranes used for the treatment of saline wastewater indicated a significant amount of S. faecalis bacteria and Aspergillus fungi. The polypropylene membranes used did not reject S. faecalis bacteria, which were detected on the membrane surface on the distillate side. The presence of fungi in the membrane pores was observed only on the feed side. The contamination of the membrane surface by yeast cells was not observed in the case of the membrane bioreactor operated over one year. The running conditions of the MD process (such as elevated temperature, significant salt concentrations and low pH values) inhibited the growth of microorganism in the MD system.     

Mechanical analysis of hollow fiber membrane integrity in water reuse applications

In order to gain insight into membrane fiber failure (i.e., loss of integrity), properties of five hollow fiber membranes and four hollow fiber modules were evaluated. Specifically, membrane material, membrane symmetry, fiber modulus of elasticity, fiber diameter and thickness, module potting technique, module flow pattern (inside-out or outside-in), and coliform breakthrough were investigated. The approach combined evaluation of the above properties with mathematical modeling of structure-fluid interactions to comprehensively evaluate the properties most important for maintaining hollow fiber membrane integrity. Tensile strength testing revealed that the strongest fiber was an asymmetric polyacrylonitrile membrane fiber. The weakest fiber was a symmetric polyethylene membrane fiber. Pilot plant testing on the four membrane modules revealed that membrane symmetry may be a more important factor than potting technique for hollow fiber integrity. Results from the SEM and tensile testing were used as input to a finite element analysis model used to evaluate time-dependent structure-fluid interactions. It was found that additional stresses at the juncture of the potting material and the hollow fiber membranes exist. These stresses likely lead to the formation of fractures.     

Modeling and economic analysis of CO<Subscript>2</Subscript> separation process with hollow fiber membrane modules

The main purpose of the study was to develop a model using ASPEN and Excel simulation method to establish optimum CO₂ separation process utilizing hollow fiber membrane modules to treat exhaust gas from LNG combustion. During the simulation, optimum conditions of each CO₂ separation scenario were determined while operating parameters of CO₂ separation process were varied. The characteristics of hollow fibers membrane were assigned as 60 GPU of permeability and 25 of selectivity for the simulation. The simulation results illustrated that 4 stage connection of membrane module is required in order to achieve over 99% of CO₂ purity and 90% of recovery rate. The resulted optimum design and operation parameters throughout the simulation were also correlated with the experimental data from the actual CO₂ separation facility which has a capacity of 1,000 Nm³/day located in the Korea Research Institute of Chemical Technology. Throughout the simulation, the operating parameters of minimum energy consumption were evaluated. Economic analysis of pilot scale of CO₂ separation plant was done with the comparison of energy cost of CO₂ recovery and equipment cost of the plant based on the simulation model. This work was presented at the 6 ^th Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006.     

Characterization of catalysts and membrane in DMFC lifetime testing

The lifetime and performance of a direct methanol fuel cell (DMFC) were investigated to understand the correlation between the structure of catalysts/membrane and cell performance versus time. The cell polarization and performance curves were obtained during the DMFC operation with the time. The catalysts and Nafion^® membrane of the membrane electrode assembly (MEA) from the lifetime test were comprehensively examined by XRD, HRTEM, FTIR and Raman spectroscopy techniques. The results revealed that there was significant performance degradation during the first 200 h operation; while the degradation was slowing down between 200 and 704 h operation. The degradation became worse after 1002 h operation. The increases of the catalyst particle size from both anode and cathode catalysts were observed after the DMFC lifetime test. The changes of microstructure, surface composition, the interfacial structure of the MEA, and the aging of Nafion^® under the DMFC lifetime tests were also observed.     

膜生物反应器在废水处理中的应用

膜生物反应器 (MembraneBio -Reactor ,MBR)是一种传统活性污泥法的改进技术 ,它应用于给水和废水处理的研究发展过程。介绍了膜生物反应器的发展状况、结构形式、优点和应用领域。     

MBR法处理污水的研究

本文介绍了目前MBR的主要类型、膜污染情况、膜清洗方式以及MBR在不同领域的应用情况和工程实例,并对MBR技术未来的发展趋势进行了预测。     

Studying Fluid Characteristics Atop Surface Patterned Membranes via Particle Image Velocimetry

Surface patterning is a recent promising approach to promote performance of pressure-driven membranes in water treatment and desalination. Nevertheless, knowledge about foulant deposition mechanisms, especially at early stage of filtration, is still lacking. The applicability of particle imaging velocimetry to study fluid characteristics atop surface patterned thin-film composite membranes was investigated at different operating conditions. This work is an important first step toward reliable understanding of the impacts of topographical membrane surface modification on hydrodynamic conditions and foulant deposition mechanisms.     

Surface Modification of Ready-to-Use Hollow Fiber Ultrafiltration Modules for Oil/Water Separation

Reusing wastewater from oil-related industries is becoming increasingly important, especially in water-stressed oil-producing countries. Before oily wastewater can be discharged or reused, it must be properly treated, e.g., by membrane-based processes like ultrafiltration. A major issue of the applied membranes is their high fouling propensity. This paper reports on mitigating fouling inside ready-to-use ultrafiltration hollow-fiber modules used in a polishing step in oil/water separation. For this purpose, in-situ polyzwitterionic hydrogel coating was applied. The membrane performance was tested with oil nano-emulsions using a mini-plant system. The main factors influencing fouling were systematically investigated using statistical design of experiments.     

浸没式超滤膜工艺应用中几个问题及调整

北京地区3座采用浸没式超滤膜工艺的净水厂在实际运行过程中出现了一些影响工艺运行的现象和问题,其中膜丝材料老化、膜孔变形甚至断丝等现象加剧了初滤水现象,并对出水水质产生了不利影响;膜池污染物富集则一定程度上加剧了膜污染和膜丝间积泥,导致膜组件断丝现象加剧及清洗困难。对于运行而言,低温造成的反冲洗压差增加比产水过程的通量下降和跨膜压差增加的影响更为直接和难以克服。此外,实际运行过程的膜出水中有相当数量的微生物检出,表明仍存在着生物泄漏的风险。