本文選題：聚四氟乙烯 + 平板膜　； 參考：《浙江理工大學(xué)》2015年碩士論文

【摘要】：膜蒸餾（MD）是膜技術(shù)與蒸餾過程有機(jī)結(jié)合的一種新型膜分離技術(shù)，其以膜兩側(cè)的蒸汽壓差為傳質(zhì)驅(qū)動力，氣體分子擴(kuò)散透過膜孔，液體和難揮發(fā)性物質(zhì)被阻隔在料液測從而實(shí)現(xiàn)分離目的。MD具備分離純度高、運(yùn)行條件溫和等優(yōu)點(diǎn)。然而，其產(chǎn)水通量低、MD膜材料抗污性差等缺點(diǎn)限制其應(yīng)用。聚四氟乙烯（PTFE）平板膜具有強(qiáng)疏水、物化性能穩(wěn)定、抗污性強(qiáng)、孔徑小、孔隙豐富等優(yōu)點(diǎn)，是MD膜的理想材料。 鑒于此，本文采用“擠出-拉伸-熱定型”方法制備PTFE平板膜，并將其用于氣掃式膜蒸餾（SGMD）進(jìn)行脫鹽實(shí)驗(yàn)，研究平板膜制備參數(shù)對膜結(jié)構(gòu)、膜性能及SGMD脫鹽性能的影響，設(shè)計正交試驗(yàn)，優(yōu)化SGMD過程中的操作參數(shù)。通過連續(xù)性實(shí)驗(yàn)研究膜污染及通量恢復(fù)性能。結(jié)果表明： （1）“擠出-拉伸-熱定型”方法可制備PTFE平板膜，其具有獨(dú)特的“原纖-結(jié)點(diǎn)”網(wǎng)狀微孔結(jié)構(gòu)。在制備過程中，縱向拉伸倍數(shù)增加，PTFE原纖伸長，平均孔徑、孔隙率增大；橫向拉伸倍數(shù)增加，節(jié)點(diǎn)發(fā)生劈裂，原纖傾斜，平均孔徑降低，，孔隙率增大；熱定型溫度升高，熱定型時間延長，原纖、節(jié)點(diǎn)收縮熔融，孔徑先增大后減小，孔隙率減小。此外，PTFE平板膜熱定型后結(jié)晶減小，導(dǎo)致其表面能降低，疏水性增強(qiáng)。 （2）SGMD脫鹽過程中，PTFE平板膜平均孔徑增加，傳質(zhì)效率增加，產(chǎn)生通量提高；料液溫度升高，膜兩側(cè)蒸汽壓差增大，傳質(zhì)驅(qū)動力增強(qiáng)，產(chǎn)水通量增大；料液流速加快，溫差極化、濃度極化現(xiàn)象削弱，產(chǎn)水通量提高；料液濃度增加，水的活性下降和濃差極化引起產(chǎn)水通量降低。脫鹽率均保持在99.9%以上。 （3）SGMD連續(xù)運(yùn)行200小時實(shí)驗(yàn)過程中，膜表面會發(fā)生污染，導(dǎo)致產(chǎn)水通量有所下降。周期性清洗恢復(fù)實(shí)驗(yàn)表明，試劑清洗可以緩解膜污染，恢復(fù)產(chǎn)水通量，實(shí)驗(yàn)用1M酸性清洗膜的產(chǎn)水通量恢復(fù)率達(dá)到95%以上。
[Abstract]:Membrane distillation (MD) is a new membrane separation technology which combines membrane technology with distillation process. The vapor pressure difference on both sides of the membrane is the driving force of mass transfer, and the gas molecules diffuse through the membrane pore. Liquid and difficult volatile substances are separated in the material liquid to achieve the purpose of separation. MD has the advantages of high purity, mild operating conditions and so on. However, its low water flux and poor fouling resistance of MD membrane materials restrict its application. Polytetrafluoroethylene (PTFE) flat membrane has the advantages of strong hydrophobicity, stable physical and chemical properties, strong anti-fouling property, small pore size and abundant porosity, etc. It is an ideal material for MD membrane. In this paper, PTFE flat membrane was prepared by extrusion, tensile and heat setting method, and was used in desalination experiment of air-swept membrane distillation (SGMD). The effects of plate preparation parameters on membrane structure, membrane properties and SGMD desalination performance were studied. Design orthogonal test to optimize the operation parameters of SGMD process. The membrane fouling and flux recovery performance were studied by continuous experiments. The results show that: (1) PTFE flat films can be prepared by "extrusion-extension-heat setting" method, which has a unique "fibrillary-node" reticular micropore structure. During the preparation process, the longitudinal tensile ratio increased, the average pore size and porosity increased, the transverse tensile ratio increased, the node split, the original fiber tilted, the average pore size decreased, the porosity increased, and the heat setting temperature increased. The heat setting time is prolonged, the original fiber, the node shrinks and melts, the pore diameter increases first and then decreases, and the porosity decreases. In addition, the crystallization of PTFE plate membrane decreases after heat setting, which leads to the decrease of surface energy and the enhancement of hydrophobicity. (2) during the desalting process of SGMD, the average pore size, mass transfer efficiency and production flux of PTFE plate membrane increase, and the temperature of feed solution increases. The vapor pressure difference on both sides of the membrane increases, the mass transfer driving force increases, the water flux increases, the flow rate of the feed increases, the temperature polarization, the concentration polarization weakens, the water flux increases, the concentration of the feed increases. The decrease of water activity and concentration polarization resulted in the decrease of water flux. The desalinization rate is above 99.9%. (3) during 200 hours of continuous operation of SGMD, the membrane surface will be polluted and the water flux will decrease. The experiment of periodic cleaning and recovery showed that reagent cleaning could reduce the membrane fouling and restore the water flux. The recovery rate of water production flux reached more than 95% when the membrane was cleaned with 1m acid.
【學(xué)位授予單位】：浙江理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TQ028.8

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