Hydrogen Fire in a sulfur Recovery Unit of a Refinery
Three workers were working in the sulfur recovery unit (SRU), trying to restore the hydrogen flow. The workers were trying to isolate the cause of a flow problem: hydrogen was entering the regulators at 200 psi (14 bar), but the pressure was dropping to 18 to 20 psi (approximately 1.3 bar) after the passed through the various components of the unit. They closed a valve preceding the regulators and vented the bleed manifold before removing a flange located beyond the valve. One of the worker then re-opened the closed valve to check the flow. A hiss was heard, followed by a pop, and the area became engulfed in flames. The three workers suffered burns .
Event Date
April 23, 1987
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Cause Comments
Immediate cause was the wrong operation during the search for a flow problem. Nothing is known on the main problem which triggered the action.
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
sulfur recovery unit, pressure regulator, valve, flange
Storage/Process Medium
Actual Pressure
14
Location Type
Location description
Industrial Area
Pre-event Summary
Because of a problem on the hydrogen flow of the sulfur recovery unit (SRU), workers were looking for the cause of the problem. The OHSA report does not specify if the unit was shut down or operating. A sulfur recovery unit (SRU) is used to recover sulfur-containing, poisonous acidic gas in oil refinery process.The event occurred apparently on the so-called SCOT-component of the SRU. The SCOT process, integrated with the other component of the SRU, the Claus process) converts COS, CS2 and remaining SO2 by reacting with H2 in the catalytic reactor back to H2S. The hydrogenating catalysts used in SCOT contain nickel or tungsten on alumina support and the reaction takes place at 250-300C.
Consequences
Number of Injured Persons
6
Lessons Learned
Lessons Learned
Unknown
Event Nature
Emergency Action
Unknown
Release Type
Release Substance
Release Pressure (bar)
14.00
Ignition Source
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Flame Type
Source Category
References
References
Occupational Safety and Health Administration (OHSA) Accident Report Detail #14402283,
https://www.osha.gov/pls/imis/accidentsearch.accident_detail?id=14402283,
(accessed October 2020)