海水中硬度离子对海水深度淡化浓缩的影响

发布时间：2018-01-02 08:16

本文关键词：海水中硬度离子对海水深度淡化浓缩的影响　出处：《天津工业大学》2016年博士论文　论文类型：学位论文

【摘要】：本文以海水资源综合利用为目的对海水浓缩进行了系统研究。根据海水淡化工程现状和机理分析确定影响海水深度浓缩的主要因素是结垢问题,起主要影响的硬度离子为钙离子。因此,本文深入研究了海水脱钙及脱硬预处理工艺;以腐殖酸为例,考察了钙离子存在下,海水中有机物对反渗透膜污染的影响;依据六效蒸发器实验数据建立高温多效蒸发器的数学优化模型,合理的分配各效的有效传热温差,使整个系统的总传热(?)损失最小,最终求出系统的最佳运行参数与设备参数;模拟电厂机力冷却塔对脱硬处理后海水进行浓缩,考察冷却塔替代蒸发器的可行性。用化学沉淀法去除钙、镁离子,Na2CO3用量为理论量的1.3倍,NaOH为理论量的1.1倍,分别通过中空纤维微滤膜和陶瓷膜进行固液分离,最终脱硬海水的钙、镁离子含量均能达到低于15 mg/L。比较了不同预处理产水对反渗透膜通量和污染的影响,发现脱钙和脱硬预处理能延缓膜通量衰减,并通过表征分析确定海水中钙离子形成的难溶盐导致了反渗透膜的污染,钙离子与腐殖酸的协同作用会加速反渗透膜的污染。通过水平管降膜蒸发对比实验,发现在料液沸点温度高于70℃时,脱硬后海水的传热系数明显大于海水。考察了脱硬后海水的沸点升高与海水的不同,依据实验数据对一台塔式六效高温多效蒸发系统进行了优化计算,分析了效数、造水比、生蒸汽加热温度对蒸发器系统运行性能的影响。通过中试实验,研究了以低温多效海水淡化后的浓盐水为原料,经纳滤、反渗透浓缩分离,用反渗透浓水作为冷却塔冷却循环水的工艺,结果表明:脱硬浓盐水散热效率高于浓海水,并能节省用水量,提高海水浓缩倍率,有利于浓盐水的工厂化制盐。
[Abstract]:Based on the comprehensive utilization of seawater resources for the purpose of a systematic study of seawater concentration. According to the analysis of the main affecting factors of concentrated seawater depth is the scaling problem of project status and mechanism of seawater desalination, hardness ions play a major role in the calcium ion. Therefore, this article studies the decalcification and removal of Seawater Pretreatment process to hard; humic acid as an example, investigates the presence of calcium ions, organic matter in seawater on the reverse osmosis membrane pollution; mathematical model based on the experimental data of six evaporator high temperature multi effect evaporator, effective heat transfer temperature difference reasonable distribution of each effect, so that the total heat transfer of the whole system (?) loss for the final the optimum operation parameters and equipment parameters of the system; power plant simulation machine cooling tower on the removal of hard after treatment of seawater concentration, feasibility study of cooling tower instead of evaporator. Calcium removal by chemical precipitation method, Magnesium ion, the content of Na2CO3 was 1.3 times of the theoretical amount, NaOH is 1.1 times of the theoretical amount, respectively by hollow fiber microfiltration membrane and ceramic membrane for solid-liquid separation, the final removal of hard water calcium, magnesium ion content can reach below 15 mg/L. compared with the different pretreatment water on the reverse osmosis membrane flux and pollution the discovery of decalcification and pretreatment can delay the removal of hard membrane flux attenuation, and determine the calcium ion in seawater to form insoluble salts leads to the fouling of reverse osmosis membrane was characterized by analysis, synergistic effect will accelerate the fouling of reverse osmosis membrane calcium ion and humic acid. Falling film evaporation experiments by horizontal pipes, found in the the liquid temperature is higher than the boiling point of 70 DEG C, and hard after the heat transfer coefficient of seawater was significantly greater than that of seawater. Were studied using hard water boiling and water, according to the experimental data of a tower six effect high temperature multi effect evaporation system. The optimization calculation of effective number, water ratio, effect of steam heating temperature on the performance of the evaporator system. By experiment, the brine LT-MED as raw material after by nanofiltration, reverse osmosis separation, as the cooling tower circulating water cooling process, with strong the results show that the reverse osmosis water and brine cooling efficiency is higher than that of hard concentrated seawater, and can save water, improve water concentration rate, is conducive to the factory production of salt brine.

【学位授予单位】：天津工业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P746

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