气氛条件对超临界锅炉水冷壁高温腐蚀的影响

Influence of Atmospheric Conditions on High Temperature Corrosion of Waterwall of Supercritical Boiler

研究了湖南某厂660 MW超临界锅炉水冷壁在管式炉中炉温450℃、不同O_2,N_2,H_2S,CO混合气氛条件下的腐蚀情况,建立了腐蚀速率与时间的函数,用扫描电镜及能谱研究了气氛条件和腐蚀时间对水冷壁高温腐蚀的影响.结果表明,烟气中H_2S含量每提高0.01%(Φ),腐蚀速率增加约15%,H2S含量为0.02%~0.05%(Φ)时,腐蚀速率随时间增加不断减慢;复合膜中FeS不断累积会加速Fe向表面迁移,强化金属氧化;当H_2S含量上升至0.07%(Φ)时,复合膜表面形成晶体间裂隙结构,将进一步加快高温硫化及氧化.

The corrosion of the water wall of a 660 MW supercritical boiler in certain plant in Hunan province was researched in a tube furnace under different kinds of gas mixtures of 02, N2, H2S, CO at 450℃. The function that reveals the relationship of corrosion rate and time was established by measuring the change of the mass of the specimen over time. Meanwhile the effects of atmosphere condition and corrosion time on the high temperature corrosion to water wall were studied by using scanning electron microscopy （SEM） and energy dispersive spectrometry （EDS）. The results showed that the corrosion rate increases by 15% when the hydrogen sulfide content in the flue gas grow by 0.01%（φ）. The corrosion rate continuously decreases with time when the hydrogen sulfide content stays around 0.02%-0.05%（（0）. The Fe transfers to the surface when FeS accumulated in the composite film with accelerating metal oxidation. The fissure structure on the surface of the composite film forms when the hydrogen sulfide content increases to 0.07%（φ） with further accelerating the high-temperature vulcanization and oxidation.