煤气化装置“三水”系统的腐蚀研究

Study on Corrosion of“Three Water”Systems in Coal Gasification Unit

煤在气化过程中产生的硫、氯、氮的水溶性化合物,其具有很强的腐蚀性,会对煤气化设备及后续系统产生严重危害,已成为影响装置安全稳定运行的“瓶颈”。采用质量损失法、扫描电镜(SEM)和金相显微分析,分别研究了煤气化黑水、渣水和灰水(“三水”)系统的腐蚀机理及腐蚀规律。研究结果表明:煤气化黑水随温度的升高其腐蚀性增强,氯离子对腐蚀具有明显的促进作用;腐蚀产物主要由FeSX和小部分FeCO3组成,为均匀腐蚀,其腐蚀速率由硫化氢腐蚀控制;煤气化渣水和灰水中甲酸与铁反应生成甲酸亚铁,在150℃以上发生分解生成铁的氧化物覆盖在金属表面,一定程度上减缓了腐蚀的发生。

Water-soluble compounds of sulfur,chlorine,nitrogen and other elements produced in the process of coal gasification have a strong corrosive effect on metals,which cause serious harm to the coal gasification equipment and subsequent systems,and become the“bottleneck”affecting the safe and long-term operation of the unit.In this paper,corrosion mechanisms and behaviors of black water,slag water and grey water systems in coal gasification unit were studied by mass loss method,scanning electron microscopy and metallographic analysis.The results showed that corrosion of the black water aggravated with the increase of temperature.Meanwhile,the chloride ion promoted the corrosion obviously.The corrosion products were mainly composed of FeS x with small amounts of FeCO 3,which were uniform corrosion,and the corrosion rate was controlled by hydrogen sulfide corrosion.In addition,ferrous formate was formed by the reaction of formic acid and iron in the slag water and grey water of coal gasification,and decomposed above 150℃to form iron oxide which coated on the metal surface to slow down the rate of corrosion.