急冷油-稀释蒸汽发生器换热管泄漏原因分析

Leakage Analysis of Heat Exchange Tubes of Quench Oil-Dilution Steam Generator

某公司乙烯裂解装置急冷单元共有9台急冷油-稀释蒸汽发生器,投用8 a后换热管开始出现频繁泄漏。采用宏观检查、内外径测量、化学成分分析、金相组织分析、硬度测试、腐蚀形貌扫描电镜分析、EDS能谱分析及X射线衍射分析等方法对泄漏最为严重的换热管进行了针对性的理化分析。结合理化分析结果,认为工艺水的pH值频繁波动是导致换热管腐蚀的主要原因,汽化-冲刷腐蚀加剧了换热管腐蚀失效,氧浓差腐蚀对换热管腐蚀有一定的促进作用,最终导致换热管腐蚀穿孔。

After eight years of operation,nine quench oil-dilution steam generators in the quench unit of an ethylene cracking unit experienced frequent leakage of the heat exchange tubes.A series of analytical techniques were employed,including macroscopic examination,internal and external diameter measurement,chemical composition analysis,metallographic structure analysis,hardness testing,and scanning electron microscopy analysis of corrosion morphology.Energy-dispersive X-ray spectroscopy and X-ray diffraction analysis were employed to examine the physical and chemical characteristics of the heat exchange tube exhibiting the most severe leakage.The results of the physical and chemical analysis indicated that the primary corrosion mechanism was the frequent fluctuations in pH levels of the process water.The vaporization-erosion corrosion process accelerated the corrosion failure of the heat exchange tubes,while the oxygen concentration corrosion had a notable promoting effect on the corrosion of the heat exchange tubes.This ultimately led to a perforation in the heat exchange tubes.