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ExxonMobil Chemical Plant (286), Baton Rouge

Releases of Cyclohexane

LDEQ Accident Number
Accident Date
Point Source(s) Notes Amount of Release

control valve of HCE compressor
WILA tanks #8 and 9
Cause: The release was caused by the failure of a control valve downstream of the HCE compressor. The control valve downstream of the HCE compressor failed to close which caused the HCE compressor to trip off.


Notes: Since there was no outlet for the vapor in the HCE system, the pressure built in the tanks until the pressure vents lifted, released hydrocarbon to the atmosphere. The back up hydrocarbon emissions control system which uses vacuum jets to recover the excess vapors was comissioned. Proper operation of the vacuum jets was confirmed shortly thereafter. The control valve and instrumentation will be repaired and inspected before being returned to servvice.
0.5 pounds


WILA tanks #8 and 9
Cause: The release was caused by the pumping of low flash material into WILA Tanks 8 and 9. The material evolved a greater amount of vapor than the tank's vapor recovery system could manage. The evolution of the vapor caused the pressure in the tanks to exceed that of the pressure vent set point.

Followup: No

Notes: Introduction of low flash point material into these tanks was immediately halted. They could not expect the flash material to evolve too much vapors. Tanks could not handle the vapors and valve lifted. Operators will be trained to communicate better to prevent the overpressure happening again. RQs exceeded for benzene. Total release of hydrocarbons is 600 pounds.
9.0 pounds

Halobutyl Finishing Unit
Cause: A thermocouple failed, which resulted in the release. Halobutyl Finishing Unit Thermotreatment unit tripped.

Followup: No

Notes: The thermocouple was replaced allowing the unit to be restarted around 8:30am. no injuries, complaints, or offsite impact resulted from this event. Amount of chemicals released is unknown. After evaluation, it has been determined that all emissions were permitted and no reportable qualities were exceeded.

Tank 21 and Rain Basin 1
Cause: A failed bleeder plug was found at Tank 801 in the BRCP's Aromatics Tankfield. Approximately 411 barrels of steam cracked naptha reached the sewer system via this bleeder. All material was retained in waste water treatment facility. While the naphtha was being pumped to tanks #778, #26, #22 and #21, a rain event occurred, which overwhelmed the facility's ability to pump the liquid to the tanks. Therefore, the material was diverted to the Rain Basin I surface impoundment. Of the water pumped into the basin, there were 1,712 lbs of benzene and 419 lbs of toluene.

Followup: Yes

Notes: The water was to be pumped to the waste water treatment plant for treatment before being discharged to outfall 001. Firefighting foam was placed on top to reduce volatilized chemicals. Half the materials spilled were recovered. All values are based on the vaporized material and represents a very small amount of loss. The material is being pumped and moved to onsite storage to facilitate recovery and treatment of the material. All recovered liquid material is being placed in tanks 778, 21, 22, and 26, all of which are properly configured and permitted to store this material. On June 14, 2012, the site began the process of understanding the constituents of the steam cracked naptha that may have been released to the air by performing material balance calculations. During the first 24-48 hours of the incident response, the intial assumptions were that a majority of the material was being contained with minimal evaporative losses. Emissions reporting was based on the initial vaporization of material from the leak duration. Sample of the stored and liquid material were collected from multiple areas and storage facilities to help develop a more definitive material balance of the total steam cracked naptha released. As a precaution, at 1230pm on Jun 14, 2012, approximately 400 employees and contractors in the impacted areas of the complex were tested for potential exposure. ExxonMobil believes that none of these individuals will have any adverse impacts. The site conducted regular monitoring at the fence line every four hours and in three unit areas on an hourly basis during the incident response activites. All fence line readings remain below detection. ExxonMobil Industrial Hygiene personel continue to conduct air monitoring and are verifying safe conditions for areas were personnel are working. Fenceline monitoring will be conducted until the steam cracked naptha material in tank 21 and RB-1 have been treated through the Refinery Wastewater Treatment facilities. Firefighting foam was added to the sewer system every 1-2 hours to minimize the amount of evaporative losses. This foam did not impact wastewater treatment operations or capabilities in the quantities utilized during this incident.
1,431.0 pounds