(131b) Structure Packing Fire Risk and Mitigation Plan at Distillation Column – Eneos Corporation Oita Refinery

On May 26, 2020, a fire occurred inside a crude distillation column, 6.2-meter diameter – 50 meters tall. During refinery turnaround, liquid distributor at a top of structure packing had been removed a day before the incident. Next day, part of structure packing was removed as a part of structured packing replacement work. Console operator observed temperature rise and whitish plume was observed from outside operator about six hours after internal work finished. Water spray was started by utilizing remaining liquid distributor but column collapse about 70 minutes after temperature rise. No one was hurt by the incident. As a part of incident investigation, it was found that pyrophoric material (iron sulfide) and residual coke contributed high temperature (900-1000 degree Celsius) by laboratory experiment and computational fluid dynamics (CFD) modeling. Lesson learnt includes identification of high-risk service, developing routine water washing practice, emergency preparedness and maintenance practice to mitigate similar incidents.