压力延滞渗透技术在产能过程中的影响因素研究

发布时间：2018-01-21 10:53

本文关键词： 可再生能源压力延滞渗透能量密度膜结构参数反向盐通量　出处：《哈尔滨工业大学》2015年硕士论文　论文类型：学位论文

【摘要】：当前世界能源结构中化石燃料约占80%的比重,是极为重要的能源物质。但化石燃料的储量有限且不可再生,据美国地质局估计,全世界石油还能还能维持约200年,而天然气则可能在80年内枯竭。此外,化石燃料的过度使用会对环境造成巨大的破坏,温室效应、酸雨和雾霾等环境问题都与之相关。为了应对上述情况,必须研究并开发出可替代化石燃料的新型可再生绿色能源。盐差能是不同浓度的溶液混合时产生的能量,与太阳能和风能相比,受气象条件和地理条件影响小,能够持续发电,并且在海洋中储量巨大,近年来受到了广泛关注。压力延滞渗透(Pressure retarded osmosis,PRO)是一种利用盐差能进行产能的新型膜工艺,选择透过性膜是其核心部件。在本文研究的第一部分,首先利用多种技术对PRO中采用的三醋酸纤维素无纺布膜(CTA-NW膜)进行了一系列表征,得到其表面形貌、截面形貌、化学基团、亲水性和孔径等信息,论证其能应用于压力延滞渗透过程的可能性;之后再通过反渗透(RO)试验对CTA-NW膜的盐水分离性能和承压性能进行测试,得到其水的透过系数和盐的透过系数,以及膜性能在不同压力条件下的变化规律,为之后的理论研究和实验参数的确定提供条件;最后,根据PRO与正渗透(FO)的相关性,由FO水通量模型得到PRO的水通量模型,从理论上分析浓差极化现象对压力延滞渗透性能的影响。在本文研究内容的第二部分,以不同浓度的氯化钠溶液为原料液和汲取液,发现膜活性层朝向原料液(AL-DS)、增加汲取液浓度、降低原料液浓度、提高流速和温度等都有利于PRO过程中水通量和能量密度的提高。由于不同条件对PRO效果的影响实质是对渗透过程中内部浓差极化(ICP)强度的影响,而浓差极化的强度可以由膜的结构参数(S)体现,所以可以通过对S值的计算,直观看到各影响因素对浓差极化的影响程度:S值越大则浓差极化现象越严重,膜对水的传质阻力越大,水通量越小,产能密度越小。通过理论公式计算膜在不同条件下的扩散系数(D),再进一步推算出膜结构参数S,以S值对实验中膜对水的传质阻力进行评价。此外,在PRO过程中,传统的浓差极化模型假设膜的盐水分离性能不变,然而实验得到的能量密度低于预期值,这主要是由于盐的反向扩散引起内部浓差极化增强导致的。实验发现反向比盐通量随着外加压力的升高而增加,且实验结果比理论结果增长迅速,这可能是膜在高压下被损坏导致的。
[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.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P743;TQ028.8

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