海水蒸发蒸汽发电机理研究

发布时间：2018-03-24 07:04

本文选题：海水淡化　切入点：蒸发发电　出处：《天津工业大学》2017年硕士论文

【摘要】：水资源危机,水质污染,淡水短缺是全球面临的严峻问题。在工业生产中,淡水用量巨大,火力发电尤其是用水大户,其用水量约占工业总用水量的40%,主要用于锅炉产生蒸汽和乏汽冷却用水等。沿海城市电厂有丰富的海水资源,如能利用海水蒸发产生蒸汽,蒸汽推动汽轮机发电,用海水对乏汽进行冷凝,将极大地降低用水投资和成本,对节约水资源,缓解淡水紧缺压力和实现社会经济效益最大化以及可持续发展具有重大的意义。海水水质成分复杂,含盐量高,腐蚀性强,不能像淡水一样直接蒸发产生蒸汽,蒸汽推动汽轮机发电。本文探讨对海水进行脱硬预处理,将硬度离子——钙、镁离子处理至含量为零,再采用蒸发方式产生蒸汽,由于蒸汽中会夹带盐,需要对蒸汽进行洗涤,洗至电导率低于1μs/cm,满足汽轮机进汽要求,探索出海水直接蒸发发电的新工艺。本论文以海水为原料,采用化学沉淀法除钙,即向海水中加入碳酸钠将钙离子以碳酸钙的形式去除,考察钙离子的去除率及最佳去除工艺条件,对除钙后的海水用纳滤装置对钙、镁、硫酸根及二价以上离子进行去除处理,对比考察了脱钙海水和原料海水纳滤膜通量和离子截留率的差异,并通过接触角、SEM、EDX等表征方法研究了膜面污染物的主要成份及其对膜性能的影响,结果表明,钙离子是造成纳滤膜无机污染的主要离子,脱钙处理能有效减缓海水淡化过程中纳滤预处理阶段的无机结垢问题,延长纳滤膜的使用寿命。对纳滤膜产水用碳酸钠和氢氧化钠将钙、镁离子完全沉淀去除,处理后海水蒸发产生蒸汽,通过收集蒸汽冷凝水研究蒸汽的品质,分析测定了蒸汽冷凝水的TDS和电导率,确定其是否满足汽轮机进汽要求及其用于发电的可行性。实验结果表明,采用化学脱钙预处理+纳滤+二次化学除钙镁的工艺,能有效去除海水中的硬度离子,首次化学脱钙处理能去除海水中90%以上的钙离子,剩余钙离子含量低于40mg/L,采用纳滤膜进一步去除钙、镁离子及硫酸根,再采用二次化学法除钙镁后,钙、镁离子基本可完全除去,解决了蒸发产生蒸汽过程中的结垢问题,所得蒸汽经洗气塔洗汽后,蒸汽冷凝水的TDS低于1mg/L,电导率低于1μs/cm,蒸汽品质可满足汽轮机进汽要求,蒸发海水发电具有可实现性。
[Abstract]:Water crisis, pollution of water quality and shortage of fresh water are serious problems facing the whole world. In industrial production, the consumption of fresh water is huge, and thermal power generation, especially large water users, Its water consumption accounts for about 40 percent of the total industrial water consumption and is mainly used for boiler steam production and spent steam cooling water etc. Coastal city power plants have abundant sea water resources, such as steam evaporation to produce steam, steam to promote steam turbine power generation, etc. Using seawater to condensate the spent steam will greatly reduce the investment and cost of water, save water resources, relieve the pressure of fresh water shortage, maximize social and economic benefits, and achieve sustainable development. The composition of seawater water quality is complex. Because of its high salt content and strong corrosion, steam can not be evaporated directly as fresh water to produce steam, and steam can drive steam turbine to generate electricity. In this paper, the desalting pretreatment of seawater is discussed, and the hardness ions-calcium and magnesium ions are treated to zero content. The steam is produced by evaporation. Because of the salt in the steam, it is necessary to wash the steam until the conductivity is less than 1 渭 s / cm, which meets the requirement of steam turbine entry, and explores a new process of direct evaporation power generation by seawater. In this paper, the seawater is used as raw material. Calcium removal was carried out by chemical precipitation, in which calcium ion was removed in the form of calcium carbonate by adding sodium carbonate into seawater. The removal rate of calcium ion and the optimum technological conditions were investigated. After removing calcium, calcium and magnesium were treated by nanofiltration device. The difference of nanofiltration membrane flux and ion retention between decalcified seawater and raw seawater was compared. The main components of membrane surface pollutants and their effects on membrane properties were studied by means of contact angle SEMN edX. The results showed that calcium ion was the main ion that caused inorganic pollution of nanofiltration membrane. Decalcification treatment can effectively reduce the inorganic scaling problem in the pretreatment stage of nanofiltration and prolong the service life of nanofiltration membrane. Calcium and magnesium ions are completely precipitated by sodium carbonate and sodium hydroxide for water production of nanofiltration membrane. Steam was produced by evaporation of seawater after treatment. The quality of steam was studied by collecting steam condensate, and the TDS and conductivity of steam condensate were analyzed and measured. The experimental results show that the pretreatment process of chemical decalcification with nanofiltration secondary chemical removal of calcium and magnesium can effectively remove the hardness ions in seawater. The first chemical decalcification treatment could remove more than 90% of calcium ions in seawater. The residual calcium ion content was less than 40 mg / L. The nanofiltration membrane was used to further remove calcium, magnesium ion and sulfate radical. Mg ~ (2 +) can be removed completely, which solves the problem of scaling in the process of vaporization. After the steam is washed by the washing tower, the TDS of steam condensate water is less than 1 mg / L, the conductivity is less than 1 渭 s / cm, and the steam quality can meet the steam intake requirement of steam turbine. Evaporative seawater power generation is realizable.
【学位授予单位】：天津工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM61

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