水冷壁高温腐蚀原因分析

Causes Analysis of High-temperature Corrosion of Station Boiler Water Walls

通过宏观分析、显微组织观察、扫描电镜与能谱成分分析和X射线衍射分析,对某电厂水冷壁向火侧进行高温腐蚀原因分析。结果表明:由于该锅炉采用四角切圆燃烧方式导致水冷壁局部高温;复合空气分级低NO_(x)燃烧系统导致部分燃烧器区域处于贫氧还原性气氛,使烟气中CO+H_(2)S浓度过高;锅炉入炉煤硫份超过设计值较多,形成高浓度的H_(2)S和SO_(2);水冷壁向火侧腐蚀以硫腐蚀为主。针对该锅炉水冷壁高温腐蚀问题,给出以下建议:控制入炉煤硫份,降低煤中的硫元素含量,减少H_(2)S和SO_(2)浓度;燃烧优化调整,采用侧边风技术,向炉膛内通入空气,降低水冷壁高温腐蚀区域的还原性气氛浓度,增加局部含氧量;在高温腐蚀严重的区域,对其水冷壁管进行防高温腐蚀喷涂处理,以增强其抗高温腐蚀性能。

The causes of high temperature corrosion of water wall was investigated by means of macro analysis,microstructure observation,scanning electron microscopy,energy spectrum composition analysis,and X-ray.Results showed that due to the use of tangential firing at four corners in the boiler,local high temperatures in the water-cooled wall were observed;the composite air classification low NO_(x) combustion system causes some burner areas to be in a reducing atmosphere with low oxygen concentration,resulting in excessively high CO+H_(2)S concentration in the flue gas;the sulfur content of the coal fed into the boiler exceeds the design value significantly,resulting in the formation of high concentrations of H_(2)S and SO_(2);the corrosion of the water-cooled wall towards the fire side is mainly caused by sulfur corrosion.In summary,the fllowing suggestions are given:the sulfur content of the incoming coal is controlled to reduce the sulfur element content in the coal,in order to reduce the concentration of H_(2)S and SOz;Optimize and adjust combustion by using side air technology to introduce air into the furnace,reduce the reducing atmosphere concentration in the high-temperature corrosion area of the water wall,and increase local oxygen content;In areas with severe high-temperature corrosion,spray coating treatment is applied to the water-cooled wall pipes to enhance their high-temperature corrosion resistance.