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Louisiana Refinery Accident Database

Valero (1238), Meraux

LDEQ Accident Report

Pollutants Released

Accident Classified As: Reportable Quantity

Cause of Problem: Equipment Design

On March 15, 2013 at approximately 08:40, Valero experienced excess emissions of Sulfur Dioxide at the North Flare during a planned shutdown of the Hydrocracker/Hydrotreater Unit. Valero was conducting a normal shutdown for a planned maintenance turnaround. During start ups and shut downs, H2S containing gases can pass through the Pre-fractionator stripper and accumulate in the Fractionator Overhead Receiver. The Fractionator Overhead Recveiver has no means of removing this gas, so Valero must vent it to the flare to prevent the pressure safety valve from lifting. The root cause of excess sulfur dioxide emissions from the Hydrocracker/hydrotreater during start ups and shutdowns has been identified from previous incidents to be inherent to the original design of the unit.

Discharge Preventable - No

The release was not preventable. Valero followed written shutdown procedures, which were based on unit design and sound engineering judgement. Valero has concluded that the Hydrocracker/Hydrotreater unit cannot be shutdown up as currently designed without venting a quantity of H2S containing gas to the flare.

Notes/Remedial Actions

As a corrective action for previous incidents, Valero designed a vent line that will direct the gases vented from the Fractionator Overhead Receiver to the refinery's HiJet so that these gases will no longer need to be flared during startups and shutdowns. Valero will install this vent line during this maintenance turnaround. SO2 emissions from the North Flare occurred on 3/15/13 from 08:40 to 3/16/13 00:00 for a duration of 15.34 hours (15 hours and 20 minutes). Valero completed the shutdown of the Hydrocracker/Hydrotreater Unit according to procedure. Valero will install the vent line designed to prevent the Fractionator Overhead Receiver from being flared.