海水淡化纳滤膜渗透清洗技术研究
发布时间：2019-05-18 20:42
【摘要】：纳滤作为海水淡化中反渗透的预处理工艺,能够有效截留颗粒物、有机物、二价离子等,可缓解反渗透的污染,减少清洗频次,延长使用寿命等,但其污染问题不容忽视。目前,纳滤膜污染常用的清洗方式是酸洗(盐酸、柠檬酸等)和碱洗(氢氧化钠)。酸洗和碱洗虽然能够有效清除污染物,恢复水通量,但也存在着成本高、易造成二次污染、对膜结构产生不可恢复的损伤等缺点。因此,本文为海水淡化过程中纳滤膜污染提出一种新的清洗方式——渗透清洗。采用人工模拟海水为污染物,以NaCl溶液为汲取液,通过实验室小型实验,重点研究了海水淡化过程中纳滤膜污染过程及其影响因素、渗透清洗主要影响因素及其影响规律,以及渗透清洗与现有清洗技术的效果对比等。本研究得到了以下主要成果:(1)压力、浓度和温度是影响海水淡化纳滤膜污染的重要因素。压力越大,水通量越大,膜污染越严重;污染物浓度增大会提高料液的渗透压,使总跨膜压差降低,水通量降低,过高的浓度还会使浓差极化严重,加速膜污染;温度升高会使膜孔径扩张变大,提高水通量,但也会使海水中CaSO4、CaCO3等无机盐析出,加速污染。(2)渗透清洗效果受汲取液浓度和操作压力的影响较大。汲取液浓度增大,会加速水的逆向回流,加强对膜孔和膜表面的冲刷作用;操作压力增大,会降低总跨膜压差,水的逆向流速放缓,清洗效果下降。从微观角度看,17%的NaCl汲取液在25℃、操作压力为0的条件下运行5 min时,污染物基本被清除。(3)渗透清洗效果优于单独酸洗或碱洗,与酸碱交替清洗效果相当。与酸、碱清洗相比,渗透清洗技术不受污染物种类的限制,对有机物和无机物都有很高的去除率。且其清洗过程对纳滤膜无损伤,不会影响膜的截留性能。
[Abstract]:Nanofiltration, as a pretreatment process of reverse osmosis in seawater desalination, can effectively intercept particles, organic matter, bivalent ions and so on, which can alleviate reverse osmosis pollution, reduce cleaning frequency, prolong service life and so on, but its pollution problem can not be ignored. At present, pickling (hydrochloric acid, citric acid, etc.) and alkali washing (sodium hydroxide) are commonly used for nanofiltration membrane pollution. Although pickling and alkali washing can effectively remove pollutants and restore water flux, they also have some shortcomings, such as high cost, easy to cause secondary pollution, irreparable damage to membrane structure and so on. Therefore, a new cleaning method, osmotic cleaning, is proposed for nanofiltration membrane pollution in the process of seawater desalination. Using artificial simulated seawater as pollutant and NaCl solution as absorbent, the process of nanofiltration membrane pollution and its influencing factors, the main influencing factors of osmotic cleaning and its influencing law in seawater desalination process were studied by laboratory small-scale experiment. The effect of osmotic cleaning is compared with that of existing cleaning technology. The main results of this study are as follows: (1) pressure, concentration and temperature are important factors affecting nanofiltration membrane pollution in seawater desalination. The larger the pressure is, the greater the water flux is, the more serious the membrane fouling is. The increase of pollutant concentration will increase the osmotic pressure of the material liquid, reduce the total transmembrane pressure difference and decrease the water flux, and the excessive concentration will also make the concentration difference polarization serious and accelerate the membrane pollution. The increase of temperature will make the pore size of the membrane expand and increase the water flux, but it will also make the inorganic salt such as CaSO4,CaCO3 in seawater precipitate and accelerate the pollution. (2) the effect of osmotic cleaning is greatly affected by the concentration of absorbed liquid and operating pressure. The increase of the concentration of the absorbed liquid will accelerate the reverse reflux of water and strengthen the scouring effect on the membrane hole and membrane surface, and the increase of operating pressure will reduce the total transmembrane pressure difference, slow down the reverse flow rate of water and decrease the cleaning effect. From the microscopic point of view, when 17% of NaCl was operated at 25 鈩，
本文编号：2480321
[Abstract]:Nanofiltration, as a pretreatment process of reverse osmosis in seawater desalination, can effectively intercept particles, organic matter, bivalent ions and so on, which can alleviate reverse osmosis pollution, reduce cleaning frequency, prolong service life and so on, but its pollution problem can not be ignored. At present, pickling (hydrochloric acid, citric acid, etc.) and alkali washing (sodium hydroxide) are commonly used for nanofiltration membrane pollution. Although pickling and alkali washing can effectively remove pollutants and restore water flux, they also have some shortcomings, such as high cost, easy to cause secondary pollution, irreparable damage to membrane structure and so on. Therefore, a new cleaning method, osmotic cleaning, is proposed for nanofiltration membrane pollution in the process of seawater desalination. Using artificial simulated seawater as pollutant and NaCl solution as absorbent, the process of nanofiltration membrane pollution and its influencing factors, the main influencing factors of osmotic cleaning and its influencing law in seawater desalination process were studied by laboratory small-scale experiment. The effect of osmotic cleaning is compared with that of existing cleaning technology. The main results of this study are as follows: (1) pressure, concentration and temperature are important factors affecting nanofiltration membrane pollution in seawater desalination. The larger the pressure is, the greater the water flux is, the more serious the membrane fouling is. The increase of pollutant concentration will increase the osmotic pressure of the material liquid, reduce the total transmembrane pressure difference and decrease the water flux, and the excessive concentration will also make the concentration difference polarization serious and accelerate the membrane pollution. The increase of temperature will make the pore size of the membrane expand and increase the water flux, but it will also make the inorganic salt such as CaSO4,CaCO3 in seawater precipitate and accelerate the pollution. (2) the effect of osmotic cleaning is greatly affected by the concentration of absorbed liquid and operating pressure. The increase of the concentration of the absorbed liquid will accelerate the reverse reflux of water and strengthen the scouring effect on the membrane hole and membrane surface, and the increase of operating pressure will reduce the total transmembrane pressure difference, slow down the reverse flow rate of water and decrease the cleaning effect. From the microscopic point of view, when 17% of NaCl was operated at 25 鈩，
本文编号：2480321
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