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Louisiana Refinery Accident Database

Valero (1238), Meraux

LDEQ Accident Report

Pollutants Released

Accident Classified As: Reportable Quantity

Cause of Problem: Under Investigation

On May 3, 2013 starting at approximately 02;00, Valero experienced excess emissions of Sulfur Dioxide and Hydrogen Sulfide at the North Flare during startup of the Gas Oil Hydrocracker/Hydrotreater Unit (HCU) following a planned maintenance outage and catalyst replacement. Because the catalyst was new, this particular startup include a procedure for sulfiding the catalyst prior to resuming normal operations. Sulfiding consists of circulating the feed in the reactors with an additive chemical to produce H2S, which is then maintained at a high concentration in the Recycle Gas for a period of time to allow the sulfides to deposit on the catalyst. Based on an initial assessment of the available data, excess emissions during the HCU startup are associated with the following: 1. The pressure safety valve (PSV) on the fractionator tower opened to flare. 2. The PSV on the Cold Separator was found to be leaking by the flare. 3. The Recycle Gas Compressor tripped and activated an automatic unit depressurization to flare. 4. The PSV on the Cold Separator opened to the flare. 5. The PSV on the Fractionator Tower opened to flare a second time. This incident is currently under investigation and Valero will submit additional information upon completion.

Discharge Preventable - Under Investigation

Notes/Remedial Actions

While the PDF of the attached document bears the LDEQ # 147895, this number is also linked to an incident of a different date (April 5, 2013). Valero reduced pressure to reseat PSV's that had lifted and attempted to stop the leakage on the Cold Separator PSV. Sulfur dioxide estimated at 3131 pounds and hydrogen sulfide estimated at 34 pounds were released during the "start up period" 5/3 02:00 to 5/4/13 22:00. Sulfur dioxide emissions associated with the leaking Cold Separator PSV have continued at approximately 20-30 pounds/hour. As of 08:00 on 5/10/13, an additional 3932 pounds of sulfur dioxide and 43 pounds of hydrogen sulfide are estimated to have been released.