發(fā)布時間：2018-01-21 10:53

  本文關(guān)鍵詞： 可再生能源 壓力延滯滲透 能量密度 膜結(jié)構(gòu)參數(shù) 反向鹽通量　出處：《哈爾濱工業(yè)大學》2015年碩士論文　論文類型：學位論文

【摘要】：當前世界能源結(jié)構(gòu)中化石燃料約占80%的比重,是極為重要的能源物質(zhì)。但化石燃料的儲量有限且不可再生,據(jù)美國地質(zhì)局估計,全世界石油還能還能維持約200年,而天然氣則可能在80年內(nèi)枯竭。此外,化石燃料的過度使用會對環(huán)境造成巨大的破壞,溫室效應、酸雨和霧霾等環(huán)境問題都與之相關(guān)。為了應對上述情況,必須研究并開發(fā)出可替代化石燃料的新型可再生綠色能源。鹽差能是不同濃度的溶液混合時產(chǎn)生的能量,與太陽能和風能相比,受氣象條件和地理條件影響小,能夠持續(xù)發(fā)電,并且在海洋中儲量巨大,近年來受到了廣泛關(guān)注。壓力延滯滲透(Pressure retarded osmosis,PRO)是一種利用鹽差能進行產(chǎn)能的新型膜工藝,選擇透過性膜是其核心部件。在本文研究的第一部分,首先利用多種技術(shù)對PRO中采用的三醋酸纖維素無紡布膜(CTA-NW膜)進行了一系列表征,得到其表面形貌、截面形貌、化學基團、親水性和孔徑等信息,論證其能應用于壓力延滯滲透過程的可能性;之后再通過反滲透(RO)試驗對CTA-NW膜的鹽水分離性能和承壓性能進行測試,得到其水的透過系數(shù)和鹽的透過系數(shù),以及膜性能在不同壓力條件下的變化規(guī)律,為之后的理論研究和實驗參數(shù)的確定提供條件;最后,根據(jù)PRO與正滲透(FO)的相關(guān)性,由FO水通量模型得到PRO的水通量模型,從理論上分析濃差極化現(xiàn)象對壓力延滯滲透性能的影響。在本文研究內(nèi)容的第二部分,以不同濃度的氯化鈉溶液為原料液和汲取液,發(fā)現(xiàn)膜活性層朝向原料液(AL-DS)、增加汲取液濃度、降低原料液濃度、提高流速和溫度等都有利于PRO過程中水通量和能量密度的提高。由于不同條件對PRO效果的影響實質(zhì)是對滲透過程中內(nèi)部濃差極化(ICP)強度的影響,而濃差極化的強度可以由膜的結(jié)構(gòu)參數(shù)(S)體現(xiàn),所以可以通過對S值的計算,直觀看到各影響因素對濃差極化的影響程度:S值越大則濃差極化現(xiàn)象越嚴重,膜對水的傳質(zhì)阻力越大,水通量越小,產(chǎn)能密度越小。通過理論公式計算膜在不同條件下的擴散系數(shù)(D),再進一步推算出膜結(jié)構(gòu)參數(shù)S,以S值對實驗中膜對水的傳質(zhì)阻力進行評價。此外,在PRO過程中,傳統(tǒng)的濃差極化模型假設(shè)膜的鹽水分離性能不變,然而實驗得到的能量密度低于預期值,這主要是由于鹽的反向擴散引起內(nèi)部濃差極化增強導致的。實驗發(fā)現(xiàn)反向比鹽通量隨著外加壓力的升高而增加,且實驗結(jié)果比理論結(jié)果增長迅速,這可能是膜在高壓下被損壞導致的。
[Abstract]:At present, fossil fuels account for about 80% of the world's energy structure, which is an extremely important energy material. However, the reserves of fossil fuels are limited and non-renewable, according to the estimate of the Geological Administration of the United States. Oil could last for another 200 years around the world, and natural gas could run out within 80 years. Moreover, excessive use of fossil fuels can cause enormous damage to the environment, Greenhouse Effect. Environmental problems such as acid rain and haze are relevant. It is necessary to study and develop new renewable green energy sources that can replace fossil fuels. Salt difference energy is the energy produced by mixing solutions of different concentrations and is less affected by meteorological and geographical conditions than solar and wind energy. Continuous power generation and huge reserves in the ocean have attracted extensive attention in recent years. Pressure delay permeates pressure retarded osmosis. Pros is a new kind of membrane process which uses salt difference energy to carry out the production capacity. The selection of permeable membrane is the core part of it. In the first part of this paper. Firstly, CTA-NW (cellulose triacetate nonwoven fabric film) used in PRO was characterized by a series of techniques, and its surface morphology, cross-section morphology and chemical group were obtained. The information of hydrophilicity and pore size proves the possibility that it can be applied to the permeation process of pressure delay. Then through reverse osmosis (RO) test, the brine separation performance and pressure bearing performance of CTA-NW membrane were measured, and the water and salt transmittance coefficients were obtained. The changes of membrane properties under different pressure conditions provide conditions for the later theoretical research and determination of experimental parameters. Finally, according to the correlation between PRO and normal osmotic FOO, the water flux model of PRO is obtained from FO water flux model. The effect of concentration polarization on the permeability of pressure delay was analyzed theoretically. In the second part of this paper, different concentrations of sodium chloride solution were used as raw material solution and extraction solution. It was found that the membrane active layer was oriented towards the raw material solution, which increased the concentration of the absorbent solution and decreased the concentration of the raw material solution. The increase of flow rate and temperature is beneficial to the increase of water flux and energy density in the process of PRO, because the effect of different conditions on the effect of PRO is essentially to the internal concentration polarization during the permeation process. The impact of strength. The intensity of concentration polarization can be reflected by the structure parameter of the film, so the S value can be calculated. It can be seen directly that the greater the concentration polarization is, the more the concentration polarization is, the greater the mass transfer resistance of the membrane to water is, and the smaller the water flux is. The smaller the productivity density is, the more the diffusion coefficient of the membrane under different conditions is calculated by the theoretical formula, and the membrane structure parameter S is further calculated, and the mass transfer resistance of the membrane to water is evaluated by S value. In the PRO process, the traditional concentration polarization model assumes that the membrane's brine separation performance is constant, but the experimental energy density is lower than the expected value. It is found that the reverse specific salt flux increases with the increase of the applied pressure, and the experimental results are faster than the theoretical results. This may be due to damage to the membrane at high pressure.
【學位授予單位】：哈爾濱工業(yè)大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：P743;TQ028.8

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本文編號：1451289