Hydrogen Explosion in a Refinery
The explosion occurred when a spark from welding equipment ignited flammable vapours from a 415,000-gallon (ca. 1.5 million of litres) sulfuric acid storage tank at the refinery.The investigation showed that the explosion was caused by the ignition of hydrogen leaking from the tank as result from years of neglect. Hydrogen is produced when sulfuric acid comes into contact with the steel tanks.One worker was killed and eight other workers were injured. The surrounding sulfuric acid tank farm was heavily damaged in the blast, and an estimated 1.1 million gallons of the acid were released into the environment, including nearly 100,000 gallons (400000 l) that flowed into the river.
Event Date
July 17, 2001
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Cause Comments
The immediate cause was the ignition of hydrogen leaked from H2SO4 tanks.The root cause was failure to maintain and inspect the tanks, due to the lack of a safety and risk management plan.Contributing cause was the loss of containment of the tanks due to corrosion and formation of gaseous hydrogen .
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
sulfuric acid storage
Storage/Process Medium
Location Type
Location description
Industrial Area
Pre-event Summary
On the day of the accident, the maintenance contractor was repairing (grinding, welding, open flame) a corroded catwalk at the acid tank farm. The corrosion had been caused by SO2 vapors from the storage tanks combined with moisture in the air to form (H2SO3). H2SO4 is used as the catalyst in the refinerys alkylation process. In this process, smaller molecules (such as isobutane and butylene) are combined in the presence of H2SO4 to form compounds called alkylates, which are high-octane components of gasoline.After being used in the alkylation process, the spent acid (typically 88 to 95% H2SO4 , 5% H2O and the rest (light) hydrocarbons) is sent through a regeneration process.
Number of Fatalities
3
Lessons Learned
Lessons Learned
Unknown
Event Nature
Emergency Action
The first fire brigade truck arrived on scene within 5 minutes of the explosion and sprayed a large amount of water into the tank farm area. The tank was equipped with spill collection boxes inside the dike that ran to a common header. The header ran to a valve box south of the tank farm, where it entered an internal sump system that directed flow to an acid neutralization system. However, the large amounts of acid and firewater overwhelmed the system, and acid flowed up through the sewer gratings onto the streets outside the diked area.Immediately following the incident, there was concern that the remaining acid tanks could catastrophically fail due to damage from the fire and the spill of acid. Because of acid contamination and the amount of acid remaining in the undamaged tanks, workers wereunable to enter the diked area for one month, when the tanks were emptied32 days after the incident.Because of the presence of large quantities of H2SO4 and an ongoing search and rescueoperation, the area was an active emergency response site for many weeks.
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Source Category
References
References
U.S. CHEMICAL SAFETY AND HAZARD INVESTIGATION BOARD (CBS) report
NO. 2001-05-I-DE ISSUE DATE: OCTOBER 2002