纳滤膜系统优化设计模式探讨

纳滤膜技术在水处理领域中的规模化应用正在受到广泛关注.而纳滤膜的筛选与膜系统的优化设计是应用过程中首要解决的关键问题之一.由于纳滤膜种类繁多、对溶质截留范围宽、分离机理复杂等多变因素决定了纳滤膜系统应该采用多元化的设计模式,而不是简单模拟反渗透膜系统.选择NF270芳香族聚酰胺材料纳滤膜为例,论述了不同类型的无机盐溶液在不同压力、流量、盐度、温度、pH值等条件下,浓差极化因子对商品化纳滤膜性能的影响;并与反渗透膜性能变化规律和系统设计进行对比,给出了此类纳滤膜在一定盐度进水条件下的合理化设计建议:1)设计压力与进水盐度无关;2)系统回收率与流程长度无关;3)盐的截留率只取决于系统收率.试图为纳滤膜选择及纳滤膜系统设计新模式提供理论依据,并为提出完整的纳滤膜系统设计新模式做出初步的探索.

Discussion on the optimum design of nanofiltration system

In recent years,the large scale application of nanofiltration membrane technology has been concerned widely in water treatment.The model of nanofiltration system design should be various rather than a simple simulation of reverse osmosis system design due to the characteristics of nanofiltration with the variety membrane material,wide range of solutes rejection and complex separation mechanism.In this paper,NF270 polyamide nanofiltration membrane module was employed to investigate the impacts of concentration polarization on commercialized nanofiltration membrane performance in different types of inorganic salt solution as well as different operating conditions including pressure,flow,salinity concentration,temperature and pH value.By comparison with reverse osmosis membrane separation performance and system design,some reasonable suggestions on NF system design are given for such type nanofiltration membrane under a certain salinity range of feed water: 1) operating pressure is independent with the salinity of feed water;2) system recovery is irrelevant to the process length;3) the salt retention rate only depends on the recovery.Attempt to provide a theoretic basis for a new model of nanofiltration system design and do some preliminary exploration for creating a complete nanofiltration design model.