锅炉SNCR脱硝水冷壁管泄漏失效分析

采用宏微观分析、力学性能试验、化学成分分析、金相检验以及能谱、X射线衍射分析等方法,对某锅炉SNCR脱硝水冷壁管泄漏原因进行了分析。结果表明:该水冷壁管泄漏系在尿素腐蚀介质作用下产生的局部腐蚀穿孔所致;从脱硝喷枪泄漏的尿素液滴滴落在高温水冷壁管上和水冷壁管鳍片焊趾处的拉应力分别为水冷壁管的腐蚀泄漏提供了介质条件、温度条件和应力条件。     

锅炉水冷壁管防腐耐磨技术应用

锅炉水冷壁管高温腐蚀和磨损是目前火力发电厂普遍存在的难题它形成机理复杂,解决难度大,针对乌海热电厂#1、#2炉火嘴区域采用表面防护式即超音速电弧喷涂方法解决水冷壁管高温腐蚀和磨损。     

炉内CO测量在防高温腐蚀中的应用

一直以来,高温腐蚀是很多火力发电电站锅炉的痼疾,在锅炉运行过程中,无法监测和判断正在运行的锅炉水冷壁是否正在发生高温腐蚀,因此运行人员也就无从调整。等到停炉甚至因腐蚀爆管后,才能在炉膛内观察到高温腐蚀已发生,这种被动和无法预知给锅炉安全运行带来很大的安全隐患。该文针对高温腐蚀发生的原因,采用炉内水冷壁区域烟气中CO的在线测量技术,通过被测量区域CO的浓度值与高温腐蚀的对应关系,确认炉内燃烧是否出现还原性气氛过浓或火焰刷墙,并进行相应的运行调整,以防止或减轻锅炉水冷壁发生高温腐蚀的现象。     

600MW烟气超低排放锅炉水冷壁的失效分析

为满足当前对大气环境质量越来越高的要求,现有燃煤锅炉必须实现超低排放改造才能达到大气排放标准,其中锅炉的低氮燃烧改造是必由之路。锅炉改造后燃烧工况发生了变化,易造成水冷壁的高温化学腐蚀产生裂纹失效。以某600 MW锅炉为例,通过金相和能谱等手段分析了化学腐蚀的特性,结果表明:水冷壁的高温腐蚀主要是由煤燃烧产生的硫化物对水冷壁高温硫化的作用,加之热交变应力形成腐蚀裂纹。提出了预防发生高温化学腐蚀的措施,即减小外二次风旋流强度,增强炉膛中心氧浓度,使主燃区中心燃尽率提高,减少腐蚀气体生成;在锅炉侧墙易腐蚀部位增加贴壁风,减小腐蚀气体浓度;在腐蚀区域喷涂防腐蚀层,使金属外壁与燃烧气氛隔离开;通过上述措施可阻止进而抑制腐蚀裂纹的产生。     

660 MW锅炉水冷壁高温腐蚀原因分析及应对措施

某厂锅炉水冷壁发生高温腐蚀现象,通过煤质分析、腐蚀形貌观察和腐蚀产物分析等方法研究了导致腐蚀的原因。结果表明:产生高温腐蚀的主要原因为机组实际燃煤硫分含量较设计偏高,燃烧器设计缺陷导致炉内强还原性气氛和定期的大出力试验使大量煤粉聚集粘结在水冷壁鳍片附近造成的。为此,提出了调整煤粉细度,燃烧器局部改造,燃烧优化调整等建议。     

一台电站锅炉水冷壁管壁厚异常减薄的原因分析

电站锅炉定期检验是保障锅炉安全运行的重要手段,对于定期检验过程中发现的问题,分析其成因,对于预防锅炉事故具有重要意义。该文作者通过对某台电站锅炉定期检验时,发现的水冷壁管减薄的问题,通过对减薄部位割管金属进行宏观检查、金相检验、扫描电镜检验和化学实验分析等,结果表明,造成该锅炉壁厚减薄的原因为硫化物和S原子高温烟气腐蚀。通过该次分析论证,对于后期锅炉的安全运行提出了指导意见。     

火电厂水冷壁管腐蚀失效常见形式简介

在火电厂锅炉的4种受热管中以水冷壁管的腐蚀风险最高,水冷壁管的腐蚀失效严重威胁电厂锅炉的安全性与经济性。从水冷壁的水侧和烟气侧两方面介绍了火电厂水冷壁管常见的几种腐蚀形式,重点分析了引起这几种腐蚀的常见原因,并提出了相应的防护措施。电厂实际运行中应综合分析水冷壁的运行工况、腐蚀特征等来判定水冷壁的腐蚀失效形式。     

电厂水冷壁管爆裂失效分析

某垃圾发电厂锅炉水冷壁管在运行过程中发生爆管事故,采用宏观分析、化学成分分析、金相检验、力学性能测试等方法对水冷壁管爆裂失效的原因进行了分析。结果表明:高温烟气和烟气中所含的有害物质造成水冷壁管外壁的腐蚀减薄,导致水冷壁管抗内压强度严重降低而发生爆裂。     

锅炉水冷壁爆管分析

锅炉水冷壁发生了钝边和无明显塑性变形爆管。通过对失效的锅炉水冷壁管进行宏观检查、化学分析和金相试验以及X射线衍射分析，发现该管向火侧外壁(烟气侧)发生了导致管壁严重减薄的高温硫腐蚀和内壁(水侧)垢下酸性腐蚀，而垢下腐蚀产物为氢原子渗入基体与Fe3C反应生成的CH4，由它引发沿晶微裂纹，最终由氢致裂纹引起管材失效。     

350MW对冲燃烧锅炉侧墙高温腐蚀研究与优化措施分析

以350 MW对冲燃煤锅炉为研究对象,针对侧墙高温腐蚀进行数值模拟分析研究,研究发现对冲燃烧锅炉炉膛内煤粉气流存在向两侧墙扩散流动的漩涡气流现象,该漩涡气流流动会冲刷侧墙水冷壁壁面,并在侧墙区域形成高还原性气氛和高煤粉浓度的炉膛侧墙环境,导致高温腐蚀和结焦发生,根据该现象,该文提出了一种改进的前后墙贴壁风结合侧墙贴壁风综合技术,数值模拟分析表明,在侧墙布置有贴壁风喷口周围O_2浓度大于3%、煤粉颗粒浓度接近0,可以有效地控制高温腐蚀的发生。     

超临界“W”火焰炉水冷壁防腐优化及过程监督探讨

综合国内超临界锅炉燃用劣质煤易发生水冷壁高温腐蚀的现状,分析了珙县发电公司煤质特性及高温腐蚀机理,对几种常见的表面防护方法进行了对比分析,得出采用超音速电弧喷涂技术进行防腐优化是可行有效的,并提出确保涂层质量的监督方法.     

Experimental studies on fly-ash erosion behavior of Ni-Cr based nanostructured thermal spray coating in boiler tubes

Erosion study was performed on the uncoated and coated SA210Gr-C boiler tube substrates. This study was performed in a view to reducing the scaling on boiler water-wall and super-heater tubes. In the present work, the High Velocity Oxygen Fuel (HVOF) coating process was used to deposit nanostructured and conventional coatings on the boiler tube substrates. Fly-ash produced after the combustion of coal in an Indian thermal power station was used as erodent. The erosion loss of coated and uncoated substrates was recorded at a regular interval of 30?minutes. The study was conducted at 30°, 60°, and 90° impingement angles and at two different operating temperatures (300°C, 550°C). Surface morphology of eroded samples was analyzed using macro and micro imaging techniques, and surface roughness was also recorded for the eroded samples. The phases present in the eroded substrates were indexed using the X-Ray diffraction (XRD) analysis. HRTEM images of nanostructured coated samples at 550°C with varying impingement angles were analyzed. The result reveals that the nanostructure in the coating was retained even after high-temperature erosion test. Comparative study was made with nanostructured and conventional coatings against the uncoated materials.     

锅炉水冷壁管爆管分析

通过化学成分分析、力学性能测试、宏观和微观检验等方法,对锅炉水冷壁管爆管事故的原因进行了分析。结果表明:该水冷壁管是由于过热造成珠光体球化而导致材料性能下降,因此发生了爆管。     

新型不锈钢材料的耐高温氧化及耐高温KCl蒸汽腐蚀性能

为缓解生物质电厂锅炉烟气侧的高温碱性环境腐蚀,对我国自主研发的4种新型不锈钢材料采用高温挂片试验(包括高温氧化试验和高温KCl蒸汽腐蚀试验)检测并绘制腐蚀动力学曲线;采用扫描电镜(SEM)、能谱仪(EDS)对试验后试片的形貌、结构、元素含量进行了分析,比较了4种新型不锈钢材料、传统TP316材料和高铬材料的耐高温氧化及耐高温KCl蒸汽腐蚀性能。结果表明:4种新型材料均表现出较好的耐腐蚀性能,明显优于传统的TP316材料和以往试验的高铬材料,当前更适用于生物质电厂锅炉烟气侧的高温碱性环境。     

Feed Water Chemistry-Related Corrosion Failures in Subcritical 250 MW Coal-Fired Boiler

This paper emphasis on the study of typical premature failure of water wall tubes of two thermal power plant boiler of same capacity (250 MW) and same operational parameter but with different boiler water chemistry. The investigation concludes on the water-side corrosion in both of the cases. One boiler is running with coordinated phosphate treatment (CPT) and another with all volatile treatment (AVT). The causes of corrosion were discovered and proposed measures for their elimination were given. Visual examination, chemical analysis of deposits, oxide scale thickness measurement, and microstructural examination were carried to ascertain the probable cause/causes of failure. From the investigation, it was finally concluded that the combination of localized high tube metal temperature and wall thinning due to under deposit corrosion led to the premature tube failure in boiler running with CPT and localized pitting corrosion in boiler running with AVT. Based on the results and discussions, a possible way to combat the corrosion was proposed.     

Field test corrosion experiences when co-firing straw and coal: 10 year status within Elsam

Abstract

In Denmark, straw is utilised for the generation of energy and district heating in power plants. Combustion of straw gives rise to high contents of potassium chloride and some sulphur dioxide in the flue gas. These compounds can lead to deposits with high content of potassium chloride and potassium sulphate on superheater tubes resulting in increased corrosion rates. From field experimental results this paper show, that by co-firing straw with coal, corrosion rates can be brought down to an acceptable level.

This paper firstly deals with the results from a demonstration program co-firing coal and straw at the 150MW pulverized coal fired boiler Studstrup unit 1. Two exposure series lasting 3000 hours each were performed for co-firing 10 and 20% of straw (% energy basis) with coal. Using built in test tubes in the hot end of the actual superheaters and air/water cooled corrosion probes, the corrosion during these experiments was monitored. Various ferritic and austenitic materials were investigated at steam temperatures ranging from 520 to 580°C and flue gas temperatures ranging from 925 to 1100°C.

The results obtained in the demonstration program led to the rebuilding of the 350MW pulverized coal fired boiler, Studstrup unit 4, into a co-firing boiler with straw in 2002. During the rebuilding, test tube sections of X20CrMoV12 1 and TP347H FG were built into the superheater and the reheater loops. The temperature ranges during these exposures was for the steam from 470 to 575°C and for the flue gas from 1025 to 1300°C. All these test tubes have been removed during the last three years at one year intervals for corrosion studies.

The corrosion studies performed on all investigated tubes included measurements of the corrosion attack, light optical microscopy and scanning electron microscopy of the corrosion products.     

高压汽包锅炉水冷壁管爆管分析

某电厂高压汽包锅炉水冷壁管频繁发生爆管事故，水冷壁管爆破口呈凿槽型。光学显微镜下观察，爆管的显微组织为铁素体＋珠光体，珠光体球化三级；管子内壁腐蚀抗凹凸不平，坑上覆盖着叠片状腐蚀产物；坑下金属的金相组织无脱碳现象。经刮垢法测定，水冷壁管爆破口周围结垢量达630g/m^2左右。用扫描电镜和X射线衍射仪分别对结垢进行了检测，结果表明其含有氧化铁、硅酸盐和氧化铜、氧化铁成分主要以Fe3O4形式存在。锅炉运行记录显示，炉水长期处于高pH值状态，而磷酸根含量通常维持在3．5－7．0范围内，Na/PO4摩尔比R值经常高达4．0以上，具有明显的碱腐蚀倾向。综合理化检验结果，判定由于锅水中存在过量游离碱以及水冷壁管存在局部过热，致使该管产生严重的碱腐蚀而导致爆管。     

火电机组锅炉受热面合金烟气腐蚀与应力协同作用失效行为研究进展

为响应国家提出的2030年碳达峰及2060年碳中和的目标, 火电发电机组蒸汽参数(如蒸汽温度与压力)尚需进一步提高, 这无疑为火电机组的安全运行带来严峻挑战。作为影响火电机组锅炉安全服役的两个重要因素, "高温烟气腐蚀"与"应力"协同作用导致锅炉受热面材料失效常被简化或独立研究。本文首先从烟气腐蚀和应力失效着手, 简述锅炉受热面合金烟气腐蚀机理, 分析影响烟气腐蚀性能的材料因素(金属种类、合金元素、金属表面状态)及环境因素(温度、腐蚀气氛及煤灰成分), 并从腐蚀与应力相互影响的角度, 讨论火电机组受热面合金在高温烟气腐蚀与应力协同作用下的失效行为。此类合金虽然在高温烟气腐蚀环境中不存在应力腐蚀开裂倾向, 但腐蚀产物会显著影响材料的高温蠕变及持久寿命。同时, 应力造成的缺陷会改变材料的腐蚀过程。因而, 本文重点介绍了火电机组锅炉环境下, 高温烟气腐蚀与应力协同作用对不同材料性能的影响, 并以18-8型奥氏体钢Super304H为例, 完整分析从烟气腐蚀行为到腐蚀与应力耦合作用行为。最后, 对未来烟气腐蚀与应力之间的相互作用及协同作用下材料的失效机理进行展望。