给水加氧处理引发蒸汽通道氧化皮剥落的机理  

Mechanism of OT-Induced Exfoliation of Duplex Scale in Steam Path

作　　者：徐洪[1] 

机构地区：[1]江苏方天电力技术有限公司,南京211102

出　　处：《动力工程学报》2011年第9期672-677,699,共7页Journal of Chinese Society of Power Engineering

摘　　要：提出用"环境破坏说"来阐释锅炉给水加氧处理(OT)引发蒸汽通道氧化皮剥落的机理,即高温蒸汽通道双层金属氧化皮中的次层尖晶石化合物可与高温含氧蒸汽反应生成气态羟基氧化铬,导致蒸汽中氢电导率显著升高.双层氧化皮界面由于铬蒸发散逸形成空穴,随着空穴逐步增多,双层氧化皮界面结合强度逐步降低,最终发生灾难性的氧化皮剥落事故."环境破坏说"还可以预测运行锅炉采用OT工艺可能带来的风险:采用给水加氧处理的起始时间距锅炉投运时间越长,风险越大;蒸汽含氧量越高,风险越大;蒸汽参数越高,风险越大.新建锅炉投运后越早采用OT工艺,风险就越小.The mechanism of Oxygenated Treatment （OT）-induced exfoliation of duplex scale in steam path can be interpreted with Ecocide Hypothesis, of which the core ideas are： the inner iron/chromium-mixed oxide layer in the duplex scale reacts with high-temperature steam to form gaseous Cr oxyhydroxides, which subsequently lead to obvious rise of cation conductivity. Cavities form at the interface of duplex scale due to reactive evaporation of Cr from the scale, and with the growth of cavity, the bond strength at interface drops gradually, thus the catastrophic exfoliation of duplex scale will inevitably happen. Ecocide Hypothesis may not only explain the mechanism of OT-induced exfoliation of duplex scale in steam path, but also help to predict the risk of OT. Greater risk will be created with the elongation of time duration from boiler commissioning to OT, with the rise of oxygen content in steam and with the improvement of steam parameters. To avoid the risk of exfoliation, OT should be synchronously scheduled in commissioning.

关 键 词：材料失效与保护 环境破坏说 氢电导率 给水加氧 氧化皮 剥落 

分 类 号：TG174.43[金属学及工艺—金属表面处理]