【摘要】：儲(chǔ)熱介質(zhì)是太陽(yáng)能熱發(fā)電轉(zhuǎn)化效率的核心,硝酸熔鹽體系是太陽(yáng)能熱發(fā)電系統(tǒng)中一種較為成熟的傳儲(chǔ)熱介質(zhì),其中Solar Salt(60%KNO3-40%NaN03)和HITECT(53%KN03-7%NaNO3-40%NaNO2)已經(jīng)被廣泛地應(yīng)用于太陽(yáng)能熱發(fā)電站中。但由于硝酸熔鹽在高溫下仍具有腐蝕性且極易分解,因此儲(chǔ)鹽管道材料在熔融硝酸鹽中的腐蝕成為太陽(yáng)能熱發(fā)電技術(shù)發(fā)展歷程上的一個(gè)重要問(wèn)題。材料在熔鹽中的腐蝕主要表現(xiàn)為金屬的活性溶解,而熔鹽體系中的微量雜質(zhì)和溫度是腐蝕的主要推動(dòng)力。材料在熔鹽中的腐蝕本質(zhì)上是一個(gè)電化學(xué)過(guò)程,故利用電化學(xué)技術(shù)監(jiān)測(cè)材料的腐蝕過(guò)程,可獲得腐蝕過(guò)程的動(dòng)力學(xué)參數(shù)等信息。本文采用電化學(xué)監(jiān)測(cè)技術(shù)研究316不銹鋼在HITECT(53%KNO3-7%NaNO3-40%NaNO2)熔鹽中的腐蝕行為,采用SEM/EDS觀察了腐蝕產(chǎn)物的微觀形貌和元素分布,利用XRD確定了腐蝕產(chǎn)物以及熔鹽的相結(jié)構(gòu),分析了添加微量稀土元素、Cl-以及溫度對(duì)腐蝕行為的影響。論文取得的主要結(jié)果如下:1.添加氧化釔可以降低316不銹鋼的腐蝕速率,其腐蝕電流密度由9.47mA·cm-2分別降至7.13mA·cm-2和3.73mA·cm-2。電化學(xué)阻抗測(cè)試結(jié)果表明,316不銹鋼在含稀土氧化物的三元硝酸鹽中電荷轉(zhuǎn)移電阻值升高,因此耐蝕性得以提高。2.Cl-會(huì)減緩三元硝酸鹽的分解,顯著提高不銹鋼在三元硝酸鹽中的腐蝕速率。極化曲線表明,其腐蝕電流密度由3.02mA·cm-2升至8.76mA·cm-2。電化學(xué)阻抗測(cè)試結(jié)果表明,316不銹鋼在添加Cl-的三元硝酸鹽中電荷轉(zhuǎn)移電阻值降低,因而耐蝕性降低。3.溫度升高使得316不銹鋼的自腐蝕電流由2.02mA·cm-2升至8.09mA·cm-2和34.4 mA·cm-2。電化學(xué)阻抗譜測(cè)試結(jié)果表明,溫度升高使得316不銹鋼在三元硝酸鹽中的轉(zhuǎn)移電阻減小,說(shuō)明溫度升高會(huì)降低不銹鋼在三元硝酸鹽中的耐蝕性。從不銹鋼腐蝕后的形貌和成分可以看出,不銹鋼在三元硝酸熔鹽中會(huì)發(fā)生選擇性腐蝕,腐蝕層出現(xiàn)明顯的元素富集區(qū)。溫度升高會(huì)促進(jìn)三元硝酸鹽的分解,所以在保證太陽(yáng)能儲(chǔ)熱蓄熱正常的情況下,合理控制熔鹽工作的溫度,有助于降低材料在熔鹽中的腐蝕及熔鹽自身的分解。
[Abstract]:Heat storage medium is the core of conversion efficiency of solar thermal power generation. Nitric acid molten salt system is a more mature heat transfer medium in solar thermal power generation system. Solar Salt (60%KNO3-40%NaN03) and HITECT (53%KN03-7%NaNO3-40%NaNO2) have been widely used in solar thermal power plants. However, the corrosion of salt storage pipeline materials in molten nitrate has become an important problem in the development of solar thermal power generation technology because the nitric acid molten salt is still corrosive and easy to decompose at high temperature. The corrosion of materials in molten salt is mainly due to the active dissolution of metal, and the trace impurities and temperature in molten salt system are the main driving force of corrosion. The corrosion of materials in molten salt is essentially an electrochemical process, so the kinetic parameters of corrosion process can be obtained by using electrochemical technology to monitor the corrosion process of materials. The corrosion behavior of 316 stainless steel in HITECT (53%KNO3-7%NaNO3-40%NaNO2) molten salt was studied by electrochemical monitoring technique. The microstructure and elemental distribution of corrosion products were observed by SEM/EDS. The phase structure of corrosion product and molten salt was determined by XRD. The effect of adding trace rare earth elements, Cl- and temperature on corrosion behavior was analyzed. The main results are as follows: 1. The corrosion rate of 316 stainless steel can be reduced by adding yttrium oxide, and the corrosion current density of 316 stainless steel decreases from 9.47mA cm-2 to 7.13mA cm-2 and 3.73mA cm-2., respectively. The electrochemical impedance test showed that the charge transfer resistance of 316 stainless steel in the ternary nitrate containing rare earth oxides was increased, and the corrosion resistance of 316 stainless steel was improved. 2. The decomposition of nitrate was slowed down by Cl-. The corrosion rate of stainless steel in ternary nitrate was significantly increased. The polarization curve shows that the corrosion current density increases from 3.02mA cm-2 to 8.76mA cm-2.. The results of electrochemical impedance measurement show that the charge transfer resistance of 316 stainless steel decreases with the addition of Cl- in the ternary nitrate, thus the corrosion resistance of 316 stainless steel decreases. The temperature increases the corrosion current of 316 stainless steel from 2.02mA cm-2 to 8.09mA cm-2 and 34.4 mA cm-2.. The results of electrochemical impedance spectroscopy show that the transfer resistance of 316 stainless steel in the ternary nitrate decreases with the increase of temperature, which indicates that the corrosion resistance of 316 stainless steel in the ternary nitrate is decreased with the increase of temperature. It can be seen from the morphology and composition of stainless steel after corrosion that stainless steel can be selectively corroded in ternary nitric acid molten salt. The increase of temperature will promote the decomposition of ternary nitrate, so the reasonable control of the temperature of molten salt can reduce the corrosion of the material in molten salt and the decomposition of molten salt itself under the condition that the solar energy storage and heat storage is normal.
【學(xué)位授予單位】：西安科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TG178

【參考文獻(xiàn)】

相關(guān)期刊論文 前10條

1 王志華;朱明;王明靜;何騰;;Inconel 625合金在熔融碳酸鹽中的腐蝕行為[J];稀有金屬材料與工程;2016年03期

2 劉義林;陳素清;黃國(guó)波;張誠(chéng);項(xiàng)軍偉;;硝酸熔鹽對(duì)不銹鋼材料腐蝕行為的研究[J];廣州化工;2016年02期

3 賈培英;趙豐宇;王宏生;;塔式太陽(yáng)能熱發(fā)電技術(shù)現(xiàn)狀及發(fā)展淺析[J];鍋爐制造;2015年05期

4 邱杰;鄒楊;李志軍;徐洪杰;;不同Cr含量的鎳基高溫合金在LiF-NaF-KF熔鹽中的腐蝕行為[J];核技術(shù);2015年07期

5 劉可;徐良;劉哲;龍時(shí)磊;曹玲玲;包良滿;李曉林;張桂林;李燕;;不同溫度FLiNaK熔鹽對(duì)Hastelloy-N合金腐蝕的影響[J];核技術(shù);2015年02期

6 張宏韜;趙有t，

本文編號(hào)：2419675