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ExxonMobil Chemical Plant (286), Baton Rouge

LDEQ Accident Report

Accident #121122
PDF AvailablePDF
State Police #10-00581
Accident Date2010-01-29
Report Date 2010-02-04
Follow-up Date 0000-00-00
Follow-up: No

Pollutants Released

Pollutant Duration Point Source Greenhouse Gas Criteria Pollutant Ozone forming chemical Amount of Release
Benzene48 mBlowdown drum D-106NONOYES31.0 pounds

Accident Classified As: Reportable Quantity

Cause of Problem: Instrument Failure

Earlier that morning, a TCD box, which contains computer hardware for controlling unit operations, had gone into "reset: mode and could not be restarted.

Discharge Preventable - No

Notes/Remedial Actions

The box was shut down and the processor card replaced. An output card failed upon attempted restart of the box, which resulted in a steam drum safety valve lifting. Steam was sent to the Aromatic unit's blowndown drum, D-106, which has an atmospheric seal. The resultant pressure increase in D-106 caused brief venting of steam through the atmospheric seal leg. A small quantity of benzene was entrained with the steam as it vented to the atmosphere, resulting in an excess of the 10 lb reportable quantity threshold. The output card was replaced and the TCD box returned to full control. An investigation is underway to determine the root cause and prevent recurrence. This incident was not preventable because it was caused by unforseen computer hardware failure.