Explosion of a Potassium Storage Tank at an Ammonia Plant
The accident happened in an anhydrous ammonia plant, commissioned in March 1977. Hydrogen accumulated inside a Benfield solution (hot potassium) storage tank and was ignited by a static charge, which caused the explosion.Mechanism by which hydrogen may have entered the storage tank are described in the paper (block valve leakage, H2 solubility in Benfield solution, etc.).The explosion sent the tank roof and sidewalls some 37m into the air, expelling an estimated amount of 114 m3 of solution into the process area. Major damage was produced on synthesis gas piping in some heat exchangers, instrumentation, air and N2 lines, steam header, electrical equipment, etc. Inspection after the accident revealed greater weld strength at the tank roof to side wall than the floor to side wall welds. This was the cause of sidewalls adhering to the roof and not to the floor during explosion. Neither environmental pollution nor personnel injuries were produced. Many design modifications (different roof type, continuous air purging, better block valve, etc.) and new operation procedures were implemented.
Event Date
December 3, 2006
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Cause Comments
Immediate cause was the injection of hydrogen into the Benfield Solution Storage Tank, with consequent static charge ignition.
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
Benfield Solution Storage Tank
Storage/Process Medium
Location Type
Location description
Industrial Area
Pre-event Summary
The Benfield Process is a technique used to remove the acid-gases, CO2 and H2S from petroleum and industrial gases. The process contains a gas absorption step and an carbonate regeneration step.
Lessons Learned
Lessons Learned
The investigation has been performed in association with the University of Erlangen. The formation and the ignition of hydrogen has found the immediate cause of the explosion.CO2-containing solutions could produce significant amount of hydrogen in alkaline conditions. large capacity tanks for holding solutions could be dangerous even though combustible substances seems to he absent. Many design modifications (different roof type, continuous air purging, better block valve, etc.) and new operation procedures were implemented after the incident.
Event Nature
Emergency Action
Unknown
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Source Category
References
References
Summary of the 54th Annual AIChE Ammonia Safety Symposium (Oct 22, 2009)
available at https://issuu.com/fitiri/docs/54th_aiche_ammonia_safety_symposium
(accessed July 2020)
J.T. McDaniel, Explosion of a benfield solution storage tank, Plant/Operation Progress, 1986, https://doi.org/10.1002/prsb.720050111