低氮燃烧改造后煤粉炉内最上层燃烧器同燃尽风喷口之间区域水冷壁附近的还原性气氛变强，管壁发生硫化型高温腐蚀的风险骤增。以一台330 MW四角切圆煤粉锅炉为对象，取样收集炉内多处水冷壁区域进行了灰渣与腐蚀层元素与矿物相表征，分析炉内水冷壁结焦的原因以及管壁高温腐蚀机制。结果表明，不同位置水冷壁所黏附熔渣中Si和Al元素均主要以莫来石（Al₆Si₂O₁₃）和硅线石（Al₂SiO₅）形式存在，提高了灰颗粒的熔融温度；而Fe元素主要以Fe₂O₃存在，其富集度显著高于碱金属或碱土金属。B层和F层燃烧器水冷壁所在高度区域黏附层状沉积物中高度富集S、Zn元素及少量Pb元素，Zn元素质量分数高达20%，主要以PbS、ZnS和ZnAl1.04S2.13的形式存在。F层燃烧器高度收集灰渣表面所附着的浮灰中仍含有约7%未燃尽碳，说明该区域旋转气流存在刷墙行为；灰样由Si、Al、Fe、C、S和Zn元素构成，主要以莫来石、赤铁矿、硫化物形式存在。管壁硫化氢腐蚀层以Fe₁-xS、Fe₇S₈、Fe₉S₁₀和Fe₃O₄为主，还含有少量PbS和PbO1.57。腐蚀层中Fe1-xS存在多种晶型结构，可能源于当地不同的H2S分压和温度。黏附灰渣中的含Zn和Pb组分主要通过气化-冷凝和所黏附未燃尽碳颗粒释放析出2种方式富集，而富硅铝酸盐和富铁颗粒则主要是通过惯性撞击和热泳沉积的方式发生黏附。

The reducing atmosphere at these regions between the top burner and the SOFA nozzle becomes stronger after the low-NO_x combustion retrofit for a coal-fired boiler. Under this condition，the risk in high-temperature corrosion on water-walls increases sharply. Taking a 330 MW Tangentially Pulverized coal boiler as the object，samples were collected from water-walls surface at different position. The ash and corrosion layer were characterized by elements and minerals，and the causes of slagging on the water-cooled wall in the furnace and the high-temperature corrosion mechanism of pipe wall were analyzed. The results show that Si and Al elements in slags adhered to the water wall at different positions mainly exist as Al₆Si₂O₁₃ and Al₂SiO₅，which increase the fusion temperature of ash particles. Fe element mainly exists in Fe₂O₃ and its enrichment is significantly higher than alkali or alkali earth metals. S and Zn elements and a small amount of Pb element are highly enriched in the layered deposits on water-walls which are located at the central height of B and F layer of burner. The content of Zn element is as high as 20%，mainly in the form of PbS，ZnS and ZnAl1.04S2.13. The fly ashes deposited on the surface of slags collected at the central height of F layer burner still contains about 7% unburnt carbon，which indicates that swirling flue gas may scour the water-walls. These fly ashes are mainly composed of Si，Al，Fe，C，S and Zn elements，mainly in the form of mullite，hematite and sulfides. The corrosive layer on the water-wall is mainly Fe₁-xS，Fe₇S₈，Fe₉S₁₀ and Fe₃O₄，and contains a small amount of PbS and PbO1.57. The formation of Fe1-xS with varied crystal structure may be attributed to the difference in the local H2S partial pressure and temperature. Zn and Pb containing species are enriched in layered deposits via vaporization-condensation and the release from unburnt carbon particles adhered on depositing surfaces. While silicoaluminate-rich and iron-rich ash particles stick to the surfaces of water-walls via inertial impaction and thermophoresis deposition.

0 引言

1 机组概况

2 燃用煤种分析方法

3 沉积物分析

   3.1 元素成分

   3.2 矿物相成分

4 水冷壁表面颗粒沉积与高温腐蚀原因分析

5 结论