【摘要】：納濾作為海水淡化中反滲透的預處理工藝,能夠有效截留顆粒物、有機物、二價離子等,可緩解反滲透的污染,減少清洗頻次,延長使用壽命等,但其污染問題不容忽視。目前,納濾膜污染常用的清洗方式是酸洗(鹽酸、檸檬酸等)和堿洗(氫氧化鈉)。酸洗和堿洗雖然能夠有效清除污染物,恢復水通量,但也存在著成本高、易造成二次污染、對膜結構產生不可恢復的損傷等缺點。因此,本文為海水淡化過程中納濾膜污染提出一種新的清洗方式——滲透清洗。采用人工模擬海水為污染物,以NaCl溶液為汲取液,通過實驗室小型實驗,重點研究了海水淡化過程中納濾膜污染過程及其影響因素、滲透清洗主要影響因素及其影響規(guī)律,以及滲透清洗與現(xiàn)有清洗技術的效果對比等。本研究得到了以下主要成果:(1)壓力、濃度和溫度是影響海水淡化納濾膜污染的重要因素。壓力越大,水通量越大,膜污染越嚴重;污染物濃度增大會提高料液的滲透壓,使總跨膜壓差降低,水通量降低,過高的濃度還會使?jié)獠顦O化嚴重,加速膜污染;溫度升高會使膜孔徑擴張變大,提高水通量,但也會使海水中CaSO4、CaCO3等無機鹽析出,加速污染。(2)滲透清洗效果受汲取液濃度和操作壓力的影響較大。汲取液濃度增大,會加速水的逆向回流,加強對膜孔和膜表面的沖刷作用;操作壓力增大,會降低總跨膜壓差,水的逆向流速放緩,清洗效果下降。從微觀角度看,17%的NaCl汲取液在25℃、操作壓力為0的條件下運行5 min時,污染物基本被清除。(3)滲透清洗效果優(yōu)于單獨酸洗或堿洗,與酸堿交替清洗效果相當。與酸、堿清洗相比,滲透清洗技術不受污染物種類的限制,對有機物和無機物都有很高的去除率。且其清洗過程對納濾膜無損傷,不會影響膜的截留性能。
[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，

本文編號：2480321