关键词: 裂解装置, 稀释蒸汽, 发生器, 腐蚀机理

Abstract: This paper briefly introduces the corrosion morphology and corrosion mechanism of tube bundle corrosion leakage in the dilution steam generator ABSTRACTS PETROCHEMICAL SAFETY AND ENVIRONMENTAL PROTECTION TECHNOLOGY Bimonthly. 20 Oct. 2019 Vol. 35 No. 5 ·Ⅱ· of a cracking unit of a petrochemical company and preventive measures for such leakage. From analysis on process flow, process parameters, corrosion morphology and corrosion medium, it is pointed out that the corrosion leakage of dilution steam generator is mainly caused by local alkali condensate corrosion. Although the working environment of the heat exchanger is vapor-liquid twophase, the temperature of the exchanger is above 170 °C. Meanwhile, the pH value is faintly alkaline, which indicates that there is no corrosion environment of wet hydrogen sulfide acid. The corrosion morphology is partially chiseled, which conforms to the description of API 571 on alkali corrosion morphology. Energy spectrum analysis also shows that there are Na and other alkali metal ions in the failure part. The corrosion environment and corrosion morphology show that there is alkali corrosion in the failure part of the heat exchanger. In addition, the process conditions require that liquid phase should be much larger than gas phase, and the vapor-liquid ratio should be 1:7 so that the liquid vapor can take away the sediments generated during heat transfer in time. However, since the heat exchanger has been operating at high load, the vapor-liquid ratio cannot meet the requirements at all, resulting in alkali condensate corrosion cracking. This analysis method can provide reference for the judgment of similar corrosion cases.

Key words: cracker, dilution steam, generator, corrosion mechanism