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|State Police #||13-23105|
|Pollutant||Duration||Point Source||Greenhouse Gas||Criteria Pollutant||Ozone forming chemical||Amount of Release|
|Sulfur Dioxide||2d 18h 30m||North Flare, South Flare, Area 1 Fuel Drum, Area 2 Fuel Drum, Area 4 Fuel Drum, HC Heaters Fuel Drum, HC Boilers Fuel Drum, #2 SRU, #3 SRU||NO||YES||NO||93,347.0 pounds|
|Hydrogen Sulfide||2d 18h 30m||North Flare, South Flare, Area 1 Fuel Drum, Area 2 Fuel Drum, Area 4 Fuel Drum, HC Heaters Fuel Drum, HC Boilers Fuel Drum, #2 SRU, #3 SRU||NO||NO||NO||304.0 pounds|
Accident Classified As: Reportable Quantity
On February 10, 2013, Valero Refining - Meraux LLC (Valero) experienced excess emissions of sulfur dioxide (SO2) and Hydrogen Sulfide (H2S) from all in service refinery heaters and boilers, the #2 and #3 Sulfur Recovery Unit (SRU) Incinerator Stacks, and the North and South Flares due to an unexpected shutdown of the #3 SRU. Shortly after the #3 SRU shut down the #2 SRU tripped offline as well. The #2 and #3 SRUs generated excess emissions due to these shutdowns and the subsequent start ups. Additionally, with both SRUs shutdown, the Amine units became saturated with H2S and were no longer capable of removing H2S from gaseous refinery process streams. As a result, the H2S concentrations in the refinery fuel gas and hydrotreater recycle gas systems began to increase. Elevated concentrations of H2S were then combusted in the refinery's heaters and boilers and in the North and South Flares. Root Causes: 1. Loss of 4160 Volt power to the #3 SRU Main Air Blower and #2 Lean Amine Pump. The investigation identified a 30 second power loss but was unable to identify the exact root cause because the plant power monitoring system was not running at the time. 2. The #2 SRU trip was caused by the failure to switch the acid gas interconnect line control scheme from flow control to pressure control. The episode occurred from approximately 06:42 on 2/10/13 to 01:13 on 2/13/13 for a duration of 66.5 hours.
The release was preventable. Despite not being able to identify the exact root cause of the loss of power that initiated this incident, Valero has determined that the magnitude of this incident was largely determined by the subsequent loss of the #2 SRU and the difficulties encountered in re-starting both the #2 and #3 SRUs. The loss of a single SRU should not have led to an incident of this magnitude and duration. The procedural error that resulted in the loss of the #2 SRU was preventable. The corrective actions identified above will address the procedural deficiencies and equipment malfunctions identified in the incident investigation.
Valero initiated the Sulfur Shedding Procedure and followed the MACT UUU SSM Plan to recover the #2 and #3 SRUs. Valero received reports of multiple citizen complaints called into the St. Bernard Fire Department. The wind direction of 2/10/13 placed the Valero Community Ambient Monitoring Site downwind of the refinery during the period of highest emissions and mobile ambient monitoring was performed by Valero and a third party. The highest single monitoring reading was 2.8ppm SO2; odors may be detected at this level.
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