Syngas Fire in in a Chemical Plant
The event occurred while re-starting the ammonia production unit after a technical stop, a synthesis gas (50% hydrogen, 17% ammonia, methane and nitrogen) leak ignited on a flange located just after the synthesis reactor. Emergency shutdown of the unit was executed and the fire was extinguished in a bit less than 1 hour. The leaking at the flange was caused by a tightening torques of the bolt which were not adapted to the exceptional conditions prevailing during the accident. The short technical breakdown had induced a very quick temperature evolution with significant temperature gradients between the bolts and the flange.
Event Date
April 24, 2006
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Cause Comments
The immediate cause was loss of tightness of the flange due to the temperature gradient occurred during the technical shutdown. flange were not adapted to the situation.The root cause (or at least an intermediate cause) is related to the fact that these temperature excursions had not been taken into account in the mechanical design of the reactor.
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
flange
Storage/Process Medium
Location Type
Location description
Industrial Area
Operational Condition
Pre-event Summary
The ammonia producing unit had to be shut down due to a technical issue. At the moment of the re-start, the reactor had been shut down for 1h30.
Consequences
Number of Injured Persons
1
Number of Fatalities
1
Currency
Property Loss (offsite)
115000
Lessons Learned
Lessons Learned
Improvements could be: i) modification of tightening torque; ii) improvement of leak collector on flange; iii) nitrogen injection system in leak collector; iv) installation of vapor injectors to protect the reactor.
Event Nature
Emergency Action
The units automatic alarms were triggered and the operator started the emergency shutdown, which isolated and depressurised the synthesis cycle. Steam was sprayed on to the leak using mobile fire nozzles to extinguish the fire that was brought under control 55 minutes following its start.
Release Type
Release Substance
Hydrogen Release Concentration (%)
50.00
Ignition Source
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Flame Type
Source Category
References
References
Event description in French database ARIA
https://www.aria.developpement-durable.gouv.fr/accident/32174/
(accessed September 2020)