本文選題：凝汽器　切入點(diǎn)：不銹鋼管　出處：《華北電力大學(xué)(北京)》2017年博士論文

【摘要】：凝汽器是電廠熱力循環(huán)的冷端,凝汽器換熱管腐蝕泄漏以及由此引發(fā)的鍋爐爆管、爐前系統(tǒng)腐蝕、汽輪機(jī)結(jié)垢等是電廠運(yùn)行中常見的事故,對(duì)整個(gè)電廠的安全經(jīng)濟(jì)運(yùn)行有著重大影響,對(duì)投資和運(yùn)行維修費(fèi)用的影響也不容忽視。本課題的目的就是通過調(diào)查、統(tǒng)計(jì)分析和試驗(yàn)研究,分析不銹鋼管凝汽器的主要腐蝕失效形態(tài)、原因和機(jī)理,掌握凝汽器冷卻水的主要腐蝕影響因子及其變化規(guī)律,探索不銹鋼管鈍化和點(diǎn)蝕的特征及其監(jiān)測(cè)方法,改進(jìn)現(xiàn)有的選材方法,合理選擇凝汽器換熱管材料,改進(jìn)現(xiàn)有的質(zhì)量標(biāo)準(zhǔn)和條款,避免或者減少凝汽器腐蝕泄漏,提高凝汽器和電廠的安全經(jīng)濟(jì)性能。通過對(duì)電廠、凝汽器及換熱管制造商的大量調(diào)查,搜集了各種不銹鋼管凝汽器、換熱器的失效案例。對(duì)一些典型的失效案例通過腐蝕形貌觀察、化學(xué)成分分析、金相分析、能譜分析、電化學(xué)檢測(cè)等方法對(duì)腐蝕形態(tài)、原因、機(jī)理和防控措施進(jìn)行了研究。結(jié)果表明,凝汽器不銹鋼焊接管有點(diǎn)蝕、垢下腐蝕、全面腐蝕等形態(tài),無應(yīng)力腐蝕,未發(fā)現(xiàn)晶間腐蝕,最主要的腐蝕失效形態(tài)是點(diǎn)蝕,焊縫及其熱影響區(qū)是薄弱環(huán)節(jié),提高制造質(zhì)量特別是焊縫質(zhì)量,正確選材,安裝儲(chǔ)存得當(dāng),運(yùn)行時(shí)保持清潔是防止點(diǎn)蝕的重要措施。冷卻水成分是合理選材的依據(jù),它隨空域、時(shí)域而變化,特別是河口水含鹽量、Cl-和SO42-等成分變化巨大。通過對(duì)大量不同空域、時(shí)域的電廠冷卻水成分的調(diào)查,運(yùn)用數(shù)理統(tǒng)計(jì)分析方法,揭示了凝汽器冷卻水主要成分特別是珠江河口水Cl-濃度的變化規(guī)律。結(jié)果表明,珠江河口水1、2、3和12月Cl-濃度月均值服從或近似服從正態(tài)分布,概率為0.999時(shí),其最大月均Cl-濃度為4876mg/L,而最大Cl-濃度約為9000 mg/L。通過點(diǎn)蝕電位試驗(yàn),提出了“基準(zhǔn)水樣”的概念,即將作為比較基準(zhǔn)的不銹鋼在試驗(yàn)水樣中的點(diǎn)蝕電位調(diào)節(jié)到300~800 mV,此時(shí)的試驗(yàn)水樣即稱為“基準(zhǔn)水樣”。當(dāng)冷卻水中腐蝕或緩蝕成分濃度在常規(guī)范圍變化時(shí),不銹鋼在“基準(zhǔn)水樣”中的點(diǎn)蝕電位才會(huì)顯著變化。用“基準(zhǔn)水樣”和方差分析方法較全面的鑒別了對(duì)選材有影響的冷卻水成分,結(jié)果表明,HCO3-的緩蝕作用非常顯著,與SO42-相當(dāng);當(dāng)NO3-濃度小于37mg/L時(shí),緩蝕作用不顯著,當(dāng)NO3-濃度大于37mg/L時(shí),NO3-的緩蝕作用大幅度陡升到析氧電位附近;鹵素離子F-的作用不顯著。用極化曲線、EIS、Rp、SEM和EDS等方法研究了冷卻水中不銹鋼鈍化和點(diǎn)蝕的特征及不銹鋼管腐蝕狀態(tài)的監(jiān)測(cè)方法。發(fā)現(xiàn):可用Rp數(shù)值大小監(jiān)測(cè)不銹鋼管的腐蝕狀態(tài),以10kΩ·cm2為界,判別不銹鋼管是否發(fā)生了點(diǎn)蝕,該方法簡單、方便、可靠;2個(gè)容抗弧不是點(diǎn)蝕的唯一特征,也可能是1個(gè)較扁的容抗弧;用EIS監(jiān)測(cè)不銹鋼的點(diǎn)蝕狀態(tài),很難滿足穩(wěn)定性要求;Cl-的作用有時(shí)間效應(yīng),超高Cl-濃度的短期(1-2個(gè)月)作用一般不會(huì)引起不銹鋼管點(diǎn)蝕,但是隨著時(shí)間延長,耐蝕性能會(huì)下降,點(diǎn)蝕和活化的概率不斷增大。在上述研究的基礎(chǔ)上,改進(jìn)了現(xiàn)有的選材方法:1)河口水選材點(diǎn)蝕試驗(yàn)應(yīng)用Cl-最大月均濃度而不是最大濃度,兩者可相差數(shù)千毫克/升,溫度用對(duì)應(yīng)時(shí)期的冷卻水最高溫度而不是最高溫度,按正態(tài)分布用樣本容量n≥8的小樣本統(tǒng)計(jì)推斷方法求取Cl-最大月均濃度;2)緩蝕性離子不僅要考慮SO42-,還要考慮HCO3-和NO3-,可將HCO3-濃度換算成SO42-濃度。通過點(diǎn)蝕電位法及技術(shù)經(jīng)濟(jì)性能的比較研究,篩選出了選材導(dǎo)則中沒有的高性價(jià)比的新型鐵素體不銹鋼管SSF-53和SSF-4。SSF-53的耐點(diǎn)蝕性能介于超級(jí)不銹鋼和317L之間,可用于Cl-濃度≥5000mg/L的冷卻水;SSF-4的耐點(diǎn)蝕性能介于317L和316L之間,可用于Cl-濃度≥1000mg/L的冷卻水。擴(kuò)大了選擇范圍,填補(bǔ)了技術(shù)空白。關(guān)于凝汽器不銹鋼焊接管質(zhì)量標(biāo)準(zhǔn),基于本文的研究成果,通過分析評(píng)價(jià),提出了多項(xiàng)重要修改建議,如焊縫腐蝕比試驗(yàn)列為必檢項(xiàng)目,檢測(cè)頻率“2/500根批”為宜;晶間腐蝕試驗(yàn)可少做,檢測(cè)頻率“2/批”較合適;焊縫必須軋平,并有一定的變形量,熱處理要有足夠的停留時(shí)間等等。
[Abstract]:The condenser is cold end cycle thermal power plant, the condenser tube corrosion leakage caused by the boiler and furnace tube explosion, corrosion, fouling in turbine is a common accident in power plant operation, has great influence on safety and economic operation of the power plant, the impact on investment and operation cost of maintenance can not be ignored. The purpose of this paper is through investigation, statistical analysis and experimental research, analysis of the main corrosion of stainless steel tube condenser failure forms, causes and mechanism, grasp the main corrosion of condenser cooling water effect and the changes of factors, explore the characteristics of stainless steel passivation and pitting corrosion and monitoring methods, improved material the existing methods, a reasonable choice of condenser heat transfer tube material, improve the quality of the existing standards and conditions, to avoid or reduce the corrosion leakage of the condenser, improving safety and economic performance of condenser and the power plant. Power plant condenser and heat exchanger tube manufacturers a lot of investigation, collection of all kinds of stainless steel tube condenser, heat exchanger failure cases. Some typical failure cases by corrosion morphology, chemical composition analysis, metallographic analysis, energy spectrum analysis, the reasons for the corrosion morphology, electrochemical detection method and mechanism the prevention and control measures were studied. The results show that the condenser of stainless steel welded pipe with pitting corrosion under the scale, comprehensive corrosion morphology, stress corrosion, intergranular corrosion is not found, the main failure form is pitting corrosion, weld and heat affected zone is the weak link, to improve manufacturing quality especially the welding quality. Correct selection, installation and proper storage of clean operation is an important measure to prevent corrosion. The cooling water composition is reasonable material basis, with its airspace, time changes, especially the Salt River slobber, changes of Cl- and SO42- components Great. Based on a large number of different space, time of cooling water of power plant components of the investigation, with the method of statistical analysis, reveals the main components of condenser cooling water especially the change law of water Cl- concentration in the Pearl River Estuary. The results show that the Pearl River Estuary 1,2,3 and December Cl- monthly mean concentration obey or approximate obeys normal distribution. The probability is 0.999, the maximum monthly average concentration of Cl- was 4876mg/L, and the maximum concentration of Cl- is about 9000 mg/L. by pitting potential test, put forward the concept of "standard samples", will be the benchmark of the pitting potential of stainless steel in the test samples were adjusted to 300~800 mV, the test sample is called "reference samples" when the cooling water corrosion or corrosion inhibitor concentration in the conventional range, significant changes will be in the "benchmark pitting potential of stainless steel water". With the analysis of "reference samples" and variance A comprehensive method for the identification of the cooling water has an effect on the material composition, the results showed that the inhibition effect of HCO3- is very significant, and quite SO42-; when the NO3- concentration is less than 37mg/L, the inhibition effect was not significant when the concentration of NO3- is higher than 37mg/L, the inhibition effect of NO3- greatly steep rise to near the oxygen evolution potential F-; halogen ions had no significant effect. Using polarization curve, EIS, Rp, SEM and EDS monitoring method were used to study the corrosion characteristics of stainless steel pipe cooling water and the pitting corrosion of stainless steel passivation. The results showed that the corrosion state in order to monitor available Rp stainless steel pipe, with 10K. Cm2 is bounded, discrimination of stainless steel the tube is pitting, the method is simple, convenient and reliable; the only feature 2 capacitive arcs not pitting, may also be 1 relatively flat capacitive arc with pitting state monitoring; EIS stainless steel, it is difficult to meet the requirements of stability; the effect of Cl- time effect, Ultra high Cl- concentration of short-term (1-2 months) effects do not cause pitting stainless steel tube, but with time, the corrosion resistance will decline, increasing the probability of pitting and activation. On the basis of the above research, the improvement of the existing methods of material: 1) estuary water material pitting test by Cl- maximum monthly average concentration instead of the maximum concentration, both can be a difference of thousands of mg / L, rather than the highest temperature cooling water temperature maximum temperature of the corresponding period, according to the small sample statistical inference method of normal distribution with sample size n = 8 for Cl- maximum monthly average concentration; 2) inhibition of ion should consider not only the SO42-, but also considering HCO3- and NO3-, can be converted into HCO3- concentration SO42- concentration. Through the comparison of the pitting potential method and technical and economic performance, selected the new iron and high cost of no material selection guideline for ferritic stainless steel tube SSF-53 and SSF-4.SSF-53 The pitting corrosion resistance between super stainless steel and 317L, can be used for cooling water Cl- concentration is between 5000mg/L; the corrosion resistance of SSF-4 between 317L and 316L, can be used for cooling water Cl- concentration is 1000mg/L. Broaden the scope of selection, fill the technology gaps. About the quality standard of condenser tube welding of stainless steel. Based on this research, through analysis and evaluation, put forward a number of important modifications, such as weld corrosion as test experiment, detection frequency "2/500 root group"; intergranular corrosion test can do less, "2/ group" detection frequency is appropriate; the weld shall be flat rolling, and deformation the heat treatment must have sufficient residence time and so on.

【學(xué)位授予單位】：華北電力大學(xué)(北京)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類號(hào)】：TM62

【參考文獻(xiàn)】

相關(guān)期刊論文 前10條

1 王叢;徐鳴悅;劉志新;李運(yùn)剛;;超純鐵素體不銹鋼的研究進(jìn)展[J];鑄造技術(shù);2015年11期

2 劉世宏;梁磊;張建良;趙陽;;316L不銹鋼在吸收式熱泵中耐蝕性能的研究[J];熱加工工藝;2015年20期

3 王學(xué)娟;葛紅花;張敏;周國定;廖強(qiáng)強(qiáng);;黃銅在含硫酸鹽還原菌的模擬冷卻水中的腐蝕行為[J];腐蝕與防護(hù);2015年10期

4 梁磊;劉世宏;呂楠楠;張建良;趙陽;;凝汽器材料磨蝕性能及影響因素試驗(yàn)研究[J];熱加工工藝;2015年14期

5 張雅君;王燾;許萍;張麗;;工業(yè)循環(huán)冷卻水系統(tǒng)中再生水與河湖水水質(zhì)指標(biāo)對(duì)比分析[J];給水排水;2015年01期

6 李美明;徐群杰;韓杰;張志國;;綠色銅緩蝕劑的研究進(jìn)展[J];腐蝕與防護(hù);2014年12期

7 王怡;范麗煈;張超;柯莉;袁園;彭黨聰;夏四清;;再生水的生物穩(wěn)定性研究[J];中國給水排水;2014年21期

8 潘逸瓊;梁磊;劉世宏;張建良;;管材種類和污垢對(duì)凝汽器傳熱性能的影響[J];汽輪機(jī)技術(shù);2014年04期

9 何德孚;王晶瀅;;C+N共控時(shí)代普通奧氏體不銹鋼管性能控制——中外不銹鋼管標(biāo)準(zhǔn)細(xì)節(jié)比較研究之五[J];焊管;2014年03期

10 呂楠楠;梁磊;林建珍;李明利;潘逸瓊;;凝汽器不銹鋼管錳致腐蝕初探[J];腐蝕與防護(hù);2013年01期

相關(guān)博士學(xué)位論文 前1條

1 毛飛雄;基于PDM對(duì)純銅鈍性和點(diǎn)蝕的研究[D];東北大學(xué);2015年

相關(guān)碩士學(xué)位論文 前3條

1 程春茂;超純鐵素體不銹鋼酸洗工藝的研究[D];太原理工大學(xué);2013年

2 田文明;304不銹鋼在3.5%NaCl溶液中的點(diǎn)蝕動(dòng)力學(xué)研究[D];南昌航空大學(xué);2013年

3 趙翠仙;回用中水對(duì)不銹鋼凝汽器管腐蝕的研究[D];華北電力大學(xué)（河北）;2005年

，

本文編號(hào)：1683273