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Louisiana Refinery Accident Database

Valero (1238), Meraux

LDEQ Accident Report

Pollutants Released

Accident Classified As: Reportable Quantity

Cause of Problem: Maintenance/Procedures

Leaking PSV on compressor in Diesel Hydrotreater Unit to blame for the release. On June 8, 2014 at approximately 12:00 hours, Valero exceeded the reporting threshold for Sulfur Dioxide (SO2) emissions at the South Flare. Valero calculates flare SO2 emissions based on continuous monitoring of flow and total sulfur concentration in the flare header. The reporting threshold is exceeded when the 24-hour aggregate exceeds the baseline average SO2 emissions by 500 pounds. Sulfur concentration in the south flare began to increase at 2100 on 6/7/14. At 0830 on 6/8/14, Valero began to flare sweet (low sulfur) propane while starting up the depropanizer section of the alkylation unit, which had been shut down for a week for repairs. At the same time as this startup, SO2 mass emissions increased to 100-120 lbs/hr. Valero executed its procedure for checking high sulfur sources (Process Safety Valves) and identified a leaking PSV in the diesel hydrotreater unit. Compressor was shut down, and the sulfur concentration returned to normal.

Discharge Preventable - Under Investigation

Notes/Remedial Actions

There remains some uncertainty about the accuracy of the monitoring at the south flare, as sulfur-free flaring from the alky depropanizer should not have increased SO2 emission rate. Valero provided verbal notification before reaching the emissions threshold. Valero implemented its procedure for checking high sulfur sources (process safety valves (PSV), process vents, etc) and identified a leaking PSV on a compressor in the Diesel Hydrotreater Unit. The compressor was shut down and the sulfur concentration in the South Flare returned to normal.