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This data is from the European Hydrogen Incidents and Accidents database HIAD 2.1, European Commission, Joint Research Centre.

Fire on the Hydrodesulfurization Unit of a Refinery
Around 4 a.m., a major leak occurred at the outlet of the diesel hydrodesulfurization furnace in a refinery. The goal of this unit is to lower the sulfur content of diesel fuels produced in other units, by a catalytic reaction in the presence of hydrogen. At the moment of the leak the furnace was restarting. The alarms of the temperature sensors at the oven outlet were triggered. At 4:08 a.m., the operator shut down the hydrogen compressors and diesel charging pumps, closed the supply valves and called the emergency status. The first emergency operation was to decompress the unit. Preventive foam mats were then placed under the oven, as well as under the heat exchangers. It was decided to not blown out the flame, to avoid introduction of air into the circuit. The drop in pressure in the unit caused eventually the decrease of the flame and smoke intensity. At 9 a.m., the emergency plan was terminated and the fire was gradually extinguished around 10 a.m. The leak occurred at the joint of a flange of the piping at the furnace outlet. This connection was not provided by evidence of controlled tightening or formal verification. Moreover, many successive shutdowns had already occurred, the last 4 the day before the event. The day before at a small leak had already been observed, but no LEL measurement had been taken, and it was decided to continue the start-up procedure.
Event Date
May 28, 2022
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Cause Comments
The immediate cause was a leaking flange of the piping at the furnace outlet.Poor inspection processes and wrong assumption of the severity of the initial leak are contributing or root causes.
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
furnace, outlet flange
Storage/Process Medium
Location Type
Location description
Industrial Area
Operational Condition
Pre-event Summary
Several successive shutdowns had already occurred, the last 4 the day before the event. The day before at a small leak had already been observed, but no LEL measurement had been taken, and it was decided to continue the start-up procedure.
Consequences
Number of Injured Persons
3
Lessons Learned
Lessons Learned
Unknown
Event Nature
Emergency Action
The first emergency operation was to decompress the unit. Preventive foam mats were then placed under the oven, as well as under the heat exchangers. It was decided to not blown out the flame, to avoid introduction of air into the circuit. The drop in pressure in the unit caused eventually the decrease of the flame and smoke intensity. The operator set up an environmental detection system by means of portable sensors and detectors). On-site measurements of H2, volatile oxide compound and SO2 did not show any anomalous signal. The measurements of air quality by the fixed measurement stations in the area and on the mobile stations did not show any effect from the fire. The water used to extinguish the flame were safely stored.
Release Substance
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Source Category
References
References
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