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Louisiana Refinery Accident Database

Valero (26003), Norco

LDEQ Accident Report

Pollutants Released

Accident Classified As: Reportable Quantity

Cause of Problem: Process Upset

The refinery experienced an upset in the 3700 sulfur recovery unity (SRU) which resulted in excess SO2 emissions. The 1600 SRU Tail Gas Treater Unit (TGTU) amine regenerator column overflowed sending rich amine to the thermal oxidizer (TOX), which cause it to trip offline. A similar incident occurred in the 3700 SRU. Rich amine from the 3700 SRU regenerator clump overflowed, shutting down both the 3700 SRU inline mixer and TOX. Both the inline mixer and TOX for the 3700 SRU were restarted but tripped offline again. As a result of the malfunctions in the 1600 and 3700 SRUs both were shut down. The remaining sulfur plan feed was routed to the still operating 30 SRU while the feed was cut to all upstream operating process units in order to reduce sulfur loading. The malfunction in the 1600 SRU led to excess SO2 and H2S emissions from the unit's TOX before shutting down. The TOX trip at the 3700 SRU led to excess H2S emissions from the 3700 SRU. Excess feed to the 30 SRY resulting from the shutdown of the 1600 and 3700 SRU led to excess emissions SO2 emissions from the 30 SRU TOX. During the shutdown the TOX tripped offline for short duration periods on multiple occasions which led to excess H2S emissions from the 3700 and 1600 SRUs.

Discharge Preventable - No Information Given

Notes/Remedial Actions

Emissions were minimized by shutting down the 3700 and 1600 SRUs and reducing feed to upstream operating units. Subsequently, repairing and restarting the 1600 SRU reduced sulfur loading on the 30 SRU, which caused it to resume operation. The limits were exceeded and final calculations are pending and will be reported in a follow- up letter.