【作者】 陈宁；

【导师】 刘明言；

【作者基本信息】 天津大学 ， 化学工程， 2010， 硕士

【摘要】 地热作为一种新能源,具有分布广、成本低、可直接利用、对环境污染小等优点。但是地热水的结垢与腐蚀是地热利用中存在的两个突出问题,结垢与腐蚀的出现导致传热效率及出水量下降、能耗和物耗增加,同时带来严重的安全隐患。目前,针对地热水换热器设备的防垢与防腐问题,研究者主要采用添加化学抑制剂、涂覆有机涂层等方法以减缓或防止设备的结垢与腐蚀,但是,这些方法存在各种问题,有必要探索用于地热水换热设备防垢防腐的新方法。文献分析表明,传热表面的表面能对污垢的附着有较大影响,降低表面能可以减少地热流体中污垢在传热表面的附着,从而达到防垢的目的。所以本文拟采用液相沉积法在经过打磨、抛光、清洗等处理的紫铜基底样片上制备厚度不同SiO₂薄膜,通过对紫铜表面进行修饰,以降低表面能,由于薄膜为微纳米级厚度,对传热效率几乎没有影响;同时SiO₂薄膜具有良好的耐腐蚀、耐磨损等特点,防垢的同时也达到了防腐的效果。本文研究了氟硅酸浓度、硼酸浓度、沉积温度、沉积时间对薄膜的沉积速率的影响,并对各样片的粗糙度、表面形貌、组成成分、接触角、表面能、薄膜厚度等进行了测量与表征,获得了优化的沉积条件,而经SiO₂薄膜修饰样片的表面能降低。在污垢实验中,以碳酸氢钠与无水氯化钙配制碳酸钙饱和溶液为工质,研究了未处理样片、抛光样片及沉积SiO₂薄膜样片在不同温度及时间下的表面结垢状况及结垢速率,结果表明,经薄膜修饰样片的防垢效果明显优于未处理样片及抛光样片;同时,本实验采用全浸试验方法,以地热井水为工质进行腐蚀实验,研究了未处理样片、抛光样片及沉积SiO₂薄膜样片在不同温度及时间下的腐蚀状况,对腐蚀产物的形貌及成分进行分析,结果表明,沉积SiO₂薄膜的样片在地热水中的防腐蚀效果较差,经长时间浸泡后发生起皮、剥落,不能发挥防腐作用,各样片在地热水中主要发生电化学腐蚀,且属于均匀腐蚀类型,腐蚀产物为铜的含氧化合物。更多还原

【Abstract】 Geothermal water is a new source of energy, owning lots of advantages, like widespread, low cost, direct utilization and little environment pollution. Fouling and corrosion emerged during the use process was detrimental, resulting in the decrease of heat t ransfer e fficiency an d w ater yield, t he i ncrease o f en ergy a nd m aterial consumption, a nd pot ential s afety d anger. A t present, t he m ethods us ed b y t he researchers to mitigate fouling and corrosion focused on a dding chemical inhibitors into w ater or c oated t he s urfaces w ith or ganic c oatings. B ut t he e nvironmental pollution was caused and the thermal resistance was increased, furthermore, coatings were e asy t o d eteriorate w ith ag eing. T herefore, f urther s tudy w as n ecessary f or finding new methods of anti-fouling and anti-corrosion.Research showed that the adhesion of fouling could be greatly affected by the surface energy of heat transfer surface, and the attachment of fouling could be largely reduced with the decrease of surface energy. So, in this paper, SiO₂ thin film with the micro nanometer thickness was prepared on copper substrate samples by Liquid Phase Deposition method to reduce the surface energy for anti-fouling and anti-corrosion of geothermal w ater i n h eat ex changers. T he effect o f t hin f ilm o n t he h eat t ransfer efficiency could b e n eglected. In addition, w ith t he pr operties of good c orrosion resistance and abrasive performance of SiO₂ thin film, the effect of anti-corrosion could be reached besides anti-fouling.In this paper, liquid phase deposition rate of SiO₂ thin film as a function of the concentrations of f luosilicate, bor ic a cid, t emperature a nd t ime were i nvestigated. Surface r oughness, m orphology, c omposition, t hickness a nd s urface e nergy were measured and characterized, and optimal deposition conditions were obtained. The static s imulation f ouling e xperiment w as c arried out us ing s upersaturated C aCO3 solution prepared by NaHCO3 and anhydrous CaCl2. Fouling deposition rate and its morphology under different temperatures and time were studied, and it showed that the anti-fouling property of the samples modified with SiO₂ thin film was better than the unt reated and pol ished s amples. T he anti-corrosion t est w as conducted b y immersing samples in real geothermal water, and the dependence of etching rate on different t emperature and t ime w ere s tudied, a s w ell a s t he m orphology a nd composition of t he c orrosive pr oducts. T he r esults s howed t hat e lectrochemical corrosion occurred and general corrosion was detected, and oxygenated compounds of copper were the main corrosive products. It was also found that passive film formed on the surface of blank samples could protect the copper from further corrosion, and its anti-corrosion performance was better than the samples modified by SiO₂ thin film.更多还原