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Valero (1238), Meraux

LDEQ Accident Report

Accident #142072
State Police #12-05457
Accident Date2012-08-14
Report Date 2012-08-22
Follow-up Date 2012-12-13
Follow-up: Yes

Pollutants Released

Pollutant Duration Point Source Greenhouse Gas Criteria Pollutant Ozone forming chemical Amount of Release
Sulfur Dioxide55h 24m#2 SRU Incineration and Boilers B-5, B-6, B-7, and TB-01NOYESNO1,040.0 pounds

Accident Classified As: Reportable Quantity

Cause of Problem: Corrosion

Excess emissions of sulfur dioxide at the #2 Sulfure Recovery Unity Incinerator Stack and Boilers due to the shutdown and subsequent startup of the #2 SRU and #2 Tall Gas Treater. They were shut down due to high pressure in the #2 SRU Furnace caused by plugging in the Sulfur Condenser Seal Legs. Valero has determined the root causes to be the operation of the #2 SRU with minimal acid gas feed to the unit and a steam leak into the process from a steam jacketed pipe between the Sulfur Condensor and the #4 Seal Leg. Past experience has shown that steam leaks into this system can form a mixture with sulfur and other contaminants present that can cause plugging. The reduced sulfur rate meant that there was less flow of sulfur to clear out any plugging that was forming. A corroded pipe cause the steam leak.

Discharge Preventable - No

This event was caused by the confluence of two independent factors: (1) the steam leak and (2) the low acid gas flow rates

Notes/Remedial Actions

After a fire in the Crude Unit, the #2 SRU and many of the units that send acid gas to the #2 SRU were shutdown. To manage a building sour water inventory, Valero started up the #2 SRU with very little acid gas feed. Normally, the feed to the #2 SRU is a combination of acid gas and sour water stripper off gas with the higher proportion being acid gas. After the fire in the Crude Unit, the feed composition changed to a much higher proportion of sour water off gas. Sour water off gas contains less sulfur and more contaminants (e.g hydrocarbons and ammonia) than acid gas. Valero replaced the section of corroded pipe that caused the steam leak prior to the start up on 8/16/12. Valero will also replace all the steam jacketed piping in the #2 SRU at the next turnaround. Valero has commissioned a new acid gas transfer line from the #3 SRU that allows greater flexibility in supplying acid gas to the SRUs which will help prevent running either SRU at low gas rates. Valero will also revise the SRU operating procedures to ensure that this transfer line is used to maintain adequate gas flow. Sulfur dioxide released exceeds the reportable quanitiy of 500 pounds.