Syngas Fire at an Ammonia Production Plant
The leak occurred at the ammonia reactor after a technical shutdown of 4 days. When the production was resumed and the syngas compressor restarted 14 hours later, a jet-fire occurred. The Internal Operation Plan was launched and the fire immediately extinguished.The cause of the gas release was a thermal dilatation difference between the joint and the reactor body. While the latter was still hot, the joint was cooled by the gas upon starting up the synthesis process. The high hydrogen concentration of the synthesis gas explains probably its spontaneous ignition. An additional cause was the procedure of quickly and completely exposing synthesis loop components to air by systematically opening all sectional valves, even in the event of short-term shutdowns, increased the units vulnerability to this type of incident.
Event Date
October 20, 2003
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Cause Comments
The immediate cause was the loss of containment of the syngas due to thermal gradients between joint and reactor, and the spontaneous ignition of the gas. Contributing cause was the shutdown procedure which opens all the valves, which exposes to air the whole ammonia synthesis loop. In conclusion, root cause would be probably a deficiency in the design of the operation procedures
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
Joint, inlet pipe, ammonia reactor
Storage/Process Medium
Actual Pressure
80
Location Type
Location description
Industrial Area
Operational Condition
Pre-event Summary
The ammonia production unit was stopped 4 days due to a technical incident. A syngas jet fire occurs when restarting the unit. The shutdown prior to the accident stemmed from an incident on the turbo air compressor lubrication circuit of the NH3 unit that stopped the machine and nearly the entire unit.
Currency
Lessons Learned
Lessons Learned
A rapid and total opening to the atmosphere of the reactor and of all the valves even for a short stop of the unit increase the likeliness of an incident. The corrective actions undertaken entailed: keeping the reactor pressurized by injecting nitrogen (80-100 bar) during short down periods; and automatically closing the synthesis compressor connection in order to reduce the pressure decrease rate.
Event Nature
Emergency Action
The Internal Operation Plan was launched and the fire is immediately extinguished.
Release Type
Release Substance
Ignition Source
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Flame Type
Source Category
References
References
Description of the event in French database ARIA
https://www.aria.developpement-durable.gouv.fr/accident/30720/
(accessed September 2020)