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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

On August 16, 2014 at approximately 22:00, 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. Sour water generated in the Ultra Low Sulfur Diesel Hydrotreater (ULSDHT) is accumulated in the High Pressure Stripper Receiver before flowing to one of the two Sour Water Strippers. At approximately 20:00 on August 16th, Valero personnel began redirecting sour water from the #2 Sour Water Stripper to the #1 Sour Water Stripper. During this process, the liquid level increased in the Stripper Receiver and sour water entered the ULSDHT Fractionator, where it flashed into steam. This caused a sudden pressure increase in the overhead line which, in turn, caused a Pressure Safety Valve (PSV) to open to the South Flare. The root cause of this incident was an improper valve line-up. Operators lacked a clear and adequate procedure for switching between the two Sour Water Strippers, and the high-high alarms did not allow sufficient time to respond to the rising liquid level in the Receiver.

Discharge Preventable - Yes

Notes/Remedial Actions

The feed to the ULSDHT was reduced and sour water was drained from the Stripper Receiver. The sulfur concentration in the South Flare returned to normal. Level alarms in the Stripper Receiver were set to a lower level, allowing additional response time during an upset. Operations procedures were revised to more clearly describe the process of rerouting sour water from one stripper to another.