A fire broke out in a refinery at 10.15 am in the ETX2 oil aromatic extraction unit, using N-Methyl Pyrrolidone (NMP).After having been shut down for regulator inspection and work, the unit resumed operations on April 19th, then when into production phase on April 20th. A fire developed on April 21st, with flames shooting 15 m high followed by periods of the fire decreasing then starting up again.
The operator used the establishment’s fixed and mobile firefighting means, including two emulsifier nozzles (450 l/min.) to cool and protect the structures, then initiated the internal contingency plan at 10.40 am. At 10.46 am, an 8,000-litre foam truck resupplied a pump-and-wagon truck already in action on the scene. The fire was put out at 11 am, and operations to cool down the structure continued.The operator discovered the cause of the accident at 12.20 pm: a leak on the seal of a temperature sensor mounted on the lower circuit of tower T103 of the solvent (NMP) and raffinate recover section. The break was approximately 10 mm in diameter. The internal contingency plan was lifted at 1.25 pm. The operators continued spraying down the site with a water nozzle to prevent any subsequent re-ignition of the fire.The flames deformed the scaffolding still present in the zone and numerous electrical cables had melted. The concrete base protecting the two columns of the solvent and raffinate recovery section was damaged superficially. 3 to 4 tonnes of hydrocarbons were released or burned during the fire. Emergency operations were terminated at 3.00 pm.
The unit was shut down, decompressed, emptied and injected with nitrogen. The fire had no significant environmental consequences although its economic impact on the site was evaluated at 1 million euros.
Accident causal analysis highlighted the organisational and human factor during the maintenance operations on the unit. A reducer fitting, not requested by the operator, had been installed on a section of the tower which should have been replaced with an identical piece of equipment during work performed by a sub-contracting company. When the work was finished, the reducer fitting was equipped with a screw-type plug to allow the new circuit to be tested, then removed after the test leaving the pipe open and its contents in direct contact with the temperature sensor, as the operator had not provided a thermowell.The operator had modified the procedures regarding cooperation with external companies for the various operations on the piping, and particularly for the removal and installation of thermowells and the interface with the site’s internal instrumentation department.
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