Abstract:

The leakage of furnace tubes in the convection section of cracking furnace of ethylene plant is common in the industry. The locations and causes of leakage vary from plant to plant. All the plants have carried out in-depth study on this problem and developed relevant preventive measures. In view of the leakage in the convection section of cracking furnace in a plant, the appearance inspection of corroded furnace tubes, the chemical composition determination of corroded pipelines, the metallographic inspection, the electron microscope and energy spectrum analysis of pipelines and corrosives, and the XRD analysis of corrosion products were carried out. Through inspection, it was determined that the leakage of furnace tubes in convection section was due to the scaling of phosphorus-containing salts, which resulted in under-deposit corrosion and then the perforation of furnace tubes. Based on the analysis, some measures were put forward such as strengthening the monitoring of phosphorus elements in the materials in furnace tubes and prohibiting the use of phosphorus-containing chemicals, so as to ensure the stable production.

Key words: cracking furnace, convection section, corrosion failure, coking inhibitor