Jerry Wilks - CITGO Lemont
Severe corrosion has been observed under hexmesh refractory in FCC units located in the United States and overseas. In regenerators the corrosion was seen in plenums, crossover ducts, and cyclones where the steel was heated to the process temperature. Damage has also been found in FCC reactors with hot wall design. The Lemont regenerator provided an opportunity to observe this unexpected corrosion as it was occurring early in the regenerator life. This regenerator was in service for only 5 years, and the results of tests conducted on samples from this regenerator will be discussed. Damage occurring under hexmesh refractory in the FCC reactors will also be reviewed. The following degradation mechanisms pertaining to the support systems that hold hexmesh refractory in FCC systems will be discussed:
- Carburization of weld metal and hexmesh leading to embrittlement and corrosion
- Oxidation and sulfidation of stainless steel
- Embrittlement of stainless steel leading to brittle fracture during shut-downs
photo courtesy of Jerry Wilks, CITGO Lemont