某管壳式换热器在运行过程中发生了换热管泄漏现象,导致换热器失效。为防止此类事件再次发生,采用化学成分分析、微观形貌观察,腐蚀产物分析等手段对换热管失效的原因进行了全面研究。结果表明:换热管的C含量偏低,外壁出现了脱碳现象,脱碳层厚度约362 μm。换热管内壁和腐蚀坑内覆盖着大量絮状腐蚀产物,其Fe、O、S、C元素含量较高,腐蚀产物主要由铁的氧化物(Fe₃O₄和Fe₂O₃)、铁的硫化物(FeS和FeS₂)、铁的硫酸盐[Fe₂(SO₄)₃]和碳酸盐(FeCO₃)组成。认为是换热管在H₂S和CO₂的协同作用下引起了局部腐蚀破坏,H₂S破坏了换热管表面的FeCO₃产物膜,造成换热管局部区域形成了腐蚀电池,导致腐蚀破坏的发生。

Leakage happebed on the tube in a shell-tube type heat exchanger during operation, which led to the failure of the heat exchanger. In order to prevent such event, chemical composition analysis, microscopic morphology observation and corrosion product analysis were used to comprehensively study the causes of heat exchange tube failure. The results showed that the content of C in the heat exchange tube was low, decarburization occured on the outer wall, and the thickness of decarburization layer was about 362 μm. The inner wall of the heat exchange tube and the corrosion pit were covered with a large number of flocculent corrosion products, which contained high content of Fe, O, S and C elements. The corrosion products were mainly composed of iron oxides (Fe₃O₄ and Fe₂O₃), iron sulfides (FeS and FeS₂), iron sulfates [Fe₂(SO₄)₃] and carbonates (FeCO₃). It was consideered that, under the synergetic effect of H₂S and CO₂, localized corrosion damage happened on the heat exchange tube. H₂S had damaged the FeCO₃ product film on the surface of the heat exchange tube, resulting in the formation of corrosion cells in localized areas of the heat exchange tube, leading to corrosion damage.