锅炉补给水中典型有机物分解规律及其对低压缸叶片腐蚀特性研究

doi:10.11902/1005.4537.2016.125

中国腐蚀与防护学报

2017, Vol. 37

Issue (6): 597-604 DOI: 10.11902/1005.4537.2016.125

研究报告

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锅炉补给水中典型有机物分解规律及其对低压缸叶片腐蚀特性研究

王娜娜¹, 王锋涛², 常亮², 朱志平¹(

)

1 长沙理工大学化学与生物工程学院电力与交通材料保护湖南省重点实验室长沙 410014
2 国网河南省电力公司电力科学研究院郑州 450052

Decomposition of Typical Organic Substance in Water Supply of Boiler and Corrosivity of Its Decomposition Products

Nana WANG¹, Fengtao WANG², Liang CHANG², Zhiping ZHU¹(

)

1 Hunan Provincial Key Laboratory of Materials Protection for Electric Power and Transportation, School of Chemistry and Biological Engineering, Changsha University of Science and Technology, Changsha 410014, China
2 Henan Electric Power Research Institute, Zhengzhou 450052, China

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摘要:

针对补给水中典型有机物—腐植酸,进行了350 ℃、10个浓度 (0~20 mg/L) 下的高压釜分解实验,并进行了350 ℃、典型浓度7.5 mg/L下间隔时间取样的分解实验,采用离子色谱仪、TOC分析仪测定高温分解后的汽、液相分解样,根据分解产物组分含量,利用电化学及微观表征 (SEM,EDS,XRD等) 研究了低分子有机酸+杂质离子对汽轮机材质腐蚀行为的影响。结果表明：腐植酸高温分解产物中低分子有机酸主要为乙酸、甲酸,杂质阴离子主要为SO₄^2-,Cl^-,NO₃^-,F^- 4种;其中SO₄^2-,NO₃^-,Cl^-的存在对汽轮机叶片钢的腐蚀有明显的促进作用,但随着F^-浓度的增大出现抑制作用。

关键词 ：补给水, 杂质阴离子, 腐植酸, 分解产物, TOC

Abstract：

Since the retrofitting of a thermal power unit for heat delivery, correspondingly, the supplied water of boiler significantly increased from ordinary 3%~5% to above 50%, thereby the conductivity of the water generally exceeded, resulting in serious acid corrosion troubles in low pressure cylinder of the steam turbine. It is known that humic acid is a typical organic substance related with corrosion troubles in the water system, thus the decomposition behavior of humic acid at 350 ℃ was studied in concentration range 0~20 mg/L, while decomposition products specially from the test by 7.5 mg/L of humic acid at different time intervals were extracted for composition determination with ion chromatography and TOC analyzer. Thereafter the effect of low molecular organic acids with impurities on the corrosion behavior of steel 1Cr13 was characterized by means of electrochemical methods as well as SEM, EDS and XRD. The results showed that high temperature decomposition products of humic acid contained low molecular organic acids mainly of acetic acid and formic acid,and impurity ions of SO₄^2-, Cl^-, NO₃^- and F^-. Obviously, the ions of SO₄^2-, NO₃^- and Cl^- were aggressive to the steel 1Cr13, in the contrary, F^- exhibited inhibition effect with the increasing concentration.

Key words： make-up water anion humic acid decomposition product TOC

收稿日期: 2016-08-25

ZTFLH:

TG172.42

基金资助:湖南省科技计划重点项目 (2013GK2016) 和河南省电力公司电力科学研究院自筹科研项目 (19151209)

作者简介:

作者简介王娜娜,女,1991年生,硕士生

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引用本文:

王娜娜, 王锋涛, 常亮, 朱志平. 锅炉补给水中典型有机物分解规律及其对低压缸叶片腐蚀特性研究[J]. 中国腐蚀与防护学报, 2017, 37(6): 597-604.
Nana WANG, Fengtao WANG, Liang CHANG, Zhiping ZHU. Decomposition of Typical Organic Substance in Water Supply of Boiler and Corrosivity of Its Decomposition Products. Journal of Chinese Society for Corrosion and protection, 2017, 37(6): 597-604.

链接本文:

https://www.jcscp.org/CN/10.11902/1005.4537.2016.125 或 https://www.jcscp.org/CN/Y2017/V37/I6/597

图1 腐植酸的基本单元结构

图2 350 ℃下12 h分解后汽、液相样pH值随腐殖酸浓度的变化

图3 350 ℃下12 h分解样液相离子含量随腐殖酸浓度的变化

图4 350 ℃下12 h分解样汽相离子含量随腐植酸浓度的变化

图5 350 ℃下7.5 mg/L腐植酸分解间隔取液相样离子含量随时间的变化

图6 350 ℃下12 h分解样汽、液相TOC含量随腐植酸浓度的变化

图7 350 ℃下7.5 mg/L腐植酸分解间隔取汽、液相样TOC含量随时间的变化

图8 80 ℃下1Cr13钢在不同浓度NaCl溶液中的电化学极化曲线

图9 80 ℃下1Cr13钢在不同浓度NaCl溶液中的电化学阻抗Nyquist图

图10 阻抗谱的等效模拟电路图

表1 80 ℃下1Cr13钢在不同浓度NaCl溶液中的电化学极化曲线参数

表2 80 ℃下1Cr13钢在不同浓度NaCl溶液中的电化学阻抗参数

图11 80 ℃下,Cl-模拟溶液中腐蚀试片表面SEM像及EDS结果

图12 80 ℃下,Cl-模拟溶液中腐蚀前后试片表面金相图谱

图13 80 ℃下,F-模拟溶液中腐蚀试片表面SEM像及EDS结果

图14 80 ℃下,含F-模拟溶液中腐蚀试片表面XRD谱

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