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|State Police #||13-03177|
|Pollutant||Duration||Point Source||Greenhouse Gas||Criteria Pollutant||Ozone forming chemical||Amount of Release|
|NOx||31h 24m||Flare 1,2||NO||NO||YES||139.0 pounds|
|Carbon Monoxide||31h 24m||Flare 1,2||NO||YES||NO||756.0 pounds|
|Sulfur Dioxide||31h 24m||Flare 1,2||NO||YES||NO||3,769.0 pounds|
|Hydrogen Sulfide||31h 24m||Flare 1,2||NO||NO||NO||20.0 pounds|
|Volatile Organic Compounds (VOCs)||31h 24m||Flare 1,2||NO||NO||YES||286.0 pounds|
|Particulate Matter||31h 24m||Flare 1,2||NO||YES||NO||5.0 pounds|
Accident Classified As: Reportable Quantity
Valero experienced intermittent flaring from Flares 1 and 2 when the slop oil degassing drum exceeded the capacity of our flare gas recovery system. On July 17, 2013 intermittent flaring from flares #1 and #2 started. The source was initially unknown and being investigated. The flaring was discovered to be associated with the startup of the hydrocracker unit, which began on July 12, 2013. Per startup procedure, off-spec product (naptha)was rerouted to the rerun tank, which allows the recovery and reprocessing of this material. On the way to the rerun tank, the naptha was degassed to the flare header so that the light hydrocarbons are kept out of the tank. Normally, these light hydrocarbons are then collected by flare gas recovery and returned to our fuel gas system. However, after about four days after the startup procedure was initiated, these vapors exceeded the capacity of the flare gas recovery system, causing intermittent flaring from flares #1 and #2. The flaring ceased when the off-spec product was routed to the gasoline blending tanks instead of the rerun tank.
The incident was not considered reasonably preventable. It occurred as a result of an unanticipated design flaw that resulted in the production of significantly more off-spec product than expected. Additionally, Valero had reviewed incidents associated with the priior startup of a similar unit at a different facility. The review did not lead us to anticipate this event.
Emissions were minimized by localizing and redirecting the source of the flare gas to another unit. In addition, the flare gas recovery unit remained in operation to reduce the amount of flared gas. The following corrective actions have been identified to prevent recurrence: 1) Review this incident with affected personnel and attach a sign-off sheet. 2) Revise the startup procedures to address this situation.