裂解炉对流段原料炉管失效分析与预防

Analysis of Failure of Feed Tubes in Convection Section of Ethylene Cracking Furnace and Prevention

乙烯裂解炉对流段原料炉管穿孔问题在国内各乙烯装置均有发生,各厂对此均有较多的研究,原因也各有不同。针对某厂乙烯裂解炉对流段原料炉管发生的穿孔,通过宏观观察、测厚检测、硬度检测、金相观察、扫描电镜及能谱分析等方法对失效原因进行了系统分析。分析确认该厂对流段原料炉管的穿孔主要原因是由于炉管内结垢导致的垢下腐蚀引起,而垢的主要成分是由管内介质中的磷元素在炉管局部形成的盐。基于以上分析,提出了加强对系统磷元素来源的控制管理以及维持生产平稳操作等预防措施,为今后裂解炉的操作提出指导。

Fractures of feed tubes of ethylene cracking furnace have occurred in almost all the ethylene cracking units in China. Each plant has made studies of the fractures and different root causes are found. The causes of fracture of feed tubes in the convection section of ethylene cracking furnace of a plant are studied by macro-observation, pachometer testing, hardness testing, metallographic analysis, scanning electron microscope analysis and energy dispersive spectrometer analysis. It is concluded that the fracture of the feed tubes in the convection section of the ethylene cracking furnace is caused by the under-deposit fouling corrosion of furnace tubes. The main component of the fouling is phosphorus salts formed from phosphorus in the media of tubes. On the basis of analysis, effective preventive measures have been proposed such as strengthening the control of phosphorus sources and maintaining a stable operation of the process unit, which provide good guidelines for the smooth operation of ethylene cracking fumance.