采用金相显微镜、扫描电镜(SEM)、能谱仪(EDS)和X射线衍射仪(XRD)等方法,分析了某焦化厂脱硫脱硝系统空冷管穿管的原因。结果表明:由于含有水汽的高温烟气在空冷管外壁产生冷凝水,烟气中SO₂、SO₃、O₂和Cl^-等腐蚀介质发生溶解,含有腐蚀性介质的冷凝水渗入,并在空冷管基体与搪瓷层界面处积存,空冷管基体发生腐蚀,生成较为单一的腐蚀产物α-FeOOH,α-FeOOH为多孔结构,附着在空冷管基体表面,使腐蚀介质在搪瓷层与基体界面富集,加速了腐蚀的扩展和空冷管壁减薄,最终导致穿管。

The causes of perforation of air-cooled tubes in desulfurization and denitrification system in a coking plant were analyzed by means of metallographic microscope, scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and X-ray diffractometer (XRD). The results showed that the high-temperature flue gas containing water vapor generated condensate water on the outer wall of the air-cooled tube, and the corrosive media such as SO₂, SO₃, O₂ and Cl^- in the flue gas was dissolved. The condensate water containing corrosive media infiltrated and accumulated at the interface between the air-cooled tube substrate and the enamel layer. The air-cooled tube substrate was corroded to form a relatively single corrosion product α-FeOOH. The α-FeOOH had a porous structure and was attached to the surface of the air-cooled tube substrate, so that the corrosive medium was enriched at the interface between the enamel layer and the substrate, which accelerated the expansion of corrosion and the thinning of the air-cooled tube wall, eventually leading to the penetration of the tube.