反渗透海水淡化后浓海水的理化性质及镁元素的可利用性研究

发布时间：2018-08-19 15:44

【摘要】：海水淡化是一项特别适合海岛环境的造水、节水新技术。因其能有效缓解淡水资源稀缺问题,在世界和中国沿海地区得到广泛的推广、应用,同时也产生大量的浓海水。如果浓海水处置利用不当,将对环境产生极大危害。本文针对目前市场占有率最高的反渗透海水淡化技术,以其副产品浓海水中的第三大资源镁元素为主要研究对象,以水质分析为主要研究手段,结合化学反应热力学的相关原理,通过数值模拟,研究淡化后浓海水中镁资源的提取机理。本文共分六部分研究内容。第一部分是文献综述,第二部分是反渗透海水淡化后浓海水的水质特点,第三部分是结晶法从反渗透海水淡化浓海水中提取镁,第四部分是沉淀法从反渗透海水淡化浓海水中提取镁,第五部分是热力学计算,第六部分是结论。本文首先采集5个生产厂家反渗透海水淡化浓海水和进料海水,较全面的分析反渗透海水淡化浓海水的理化性质,其中以舟山六横反渗透海水淡化浓海水为主要研究对象,研究反渗透海水淡化浓海水中镁元素的提取及热力学过程。所取得的主要结论如下:1、与进料海水相比,由于反渗透海水淡化过程中的预处理、反渗透膜的拦截等影响,使反渗透海水淡化后浓海水的溶解氧、化学需氧量、电导率、盐度、溶解性总固体量、常量离子浓度等理化性质发生较大变化,而且反渗透海水淡化浓海水的常量元素的浓度更高,浓海水中镁资源的含量是进料海水中镁元素含量的1.924倍,更加利于镁元素的提取。2、蒸发浓缩结晶过程中Ca SO4和KCl先析出,镁盐的析出在Ca SO4和KCl之后,且需更多的能量用于镁盐的蒸发浓缩结晶析出,所以结晶法提镁的经济性较差;沉淀法更适合提镁,反渗透海水淡化后浓海水固定CO2脱钙后,Na OH加入脱钙母液,生成Mg(OH)2的产率较高且纯度较高。本论文为反渗透海水淡化后浓海水的利用提供理论参考,且能够为我国海水淡化与综合利用产业提供新的思路。
[Abstract]:Seawater desalination is a new water-making and water-saving technology especially suitable for island environment. Because it can effectively alleviate the scarcity of fresh water, it has been widely used in the world and coastal areas of China, but also produced a large amount of concentrated seawater. If the concentrated seawater is used improperly, it will do great harm to the environment. Aiming at the reverse osmosis desalination technology which has the highest market share at present, this paper takes the third largest resource magnesium element in its by-product concentrated seawater as the main research object and the water quality analysis as the main research means. The extraction mechanism of magnesium resources in desalination concentrated seawater was studied by numerical simulation based on the related principles of chemical reaction thermodynamics. This paper is divided into six parts. The first part is the literature review, the second part is the characteristics of the concentrated seawater after reverse osmosis desalination, the third part is the crystallization method to extract magnesium from the concentrated seawater of reverse osmosis desalination. The fourth part is the precipitation method to extract magnesium from the concentrated seawater of reverse osmosis desalination, the fifth part is the thermodynamic calculation, the sixth part is the conclusion. In this paper, the physical and chemical properties of the concentrated seawater of reverse osmosis desalination were analyzed comprehensively, and the main research object of this paper was the concentrated seawater of reverse osmosis desalination in Zhoushan. The extraction and thermodynamic process of magnesium in the concentrated seawater of reverse osmosis desalination were studied. The main conclusions obtained are as follows: compared with feed seawater, due to the influence of pretreatment in reverse osmosis desalination process and interception of reverse osmosis membrane, the dissolved oxygen, chemical oxygen demand, electrical conductivity, salinity of concentrated seawater after reverse osmosis desalination, The physical and chemical properties such as the total solid content of solubility and the concentration of constant ions have changed greatly, and the concentration of major elements in the concentrated seawater is higher than that in the seawater of reverse osmosis desalination. The content of magnesium in the concentrated seawater is 1.924 times as high as the content of magnesium in the feed seawater. It is more favorable for extracting mg element. 2. Ca SO4 and KCl precipitate first in the process of evaporating and concentrating crystallization, and magnesium salt precipitates after Ca SO4 and KCl, and needs more energy for evaporating and condensing crystallization of magnesium salt, so the economy of magnesium extraction by crystallization method is poor. The precipitation method is more suitable for the extraction of magnesium. After desalination of seawater by reverse osmosis, CO2 is fixed by desalcification in concentrated seawater, then NaOH is added to the decalcification mother liquor, the yield of Mg (OH) _ 2 is higher and the purity of Mg (OH) _ 2 is higher. This paper provides a theoretical reference for the use of concentrated seawater after reverse osmosis desalination, and provides a new idea for the industry of desalination and comprehensive utilization of seawater in China.
【学位授予单位】：浙江海洋学院
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P746;P747

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