Pollution
Humain
Environnement
Economique

At 8:15 pm, a shutdown of the main boiler caused flaring of the current gaseous phase of a portion of the refining units (especially fluid catalytic cracking), causing an unusually high flame and thick black smoke emissions.

Fire-fighters, local gendarmes and the Classified Facilities Inspectorate all visited the site.

Many nearby residents showed their concern by phoning the site operator. The internal emergency plan was not activated, but instead a crisis response cell was assembled and disseminated information to neighbouring municipalities.

The refinery was equipped with 2 main boilers and 2 backup boilers; 1 of the main boilers, fed by refinery gas from the fluid catalytic cracking unit, was running at the time of the accident. The second one was shut down during the afternoon to prepare for scheduled maintenance the next day. The backup boilers were thus started to generate sufficient vapour pressure on the circuits and safety action sequences; due to their lesser power however, a gas surplus on the plant’s network had to be channelled towards the flare. Plant production was reduced to the greatest extent possible. Since the available vapour pressure was inadequate for a flare tip injection, the incineration of gas containing sulphur components was accompanied by the emission of black smoke.

Some 50 t of refinery gas were burned by a flare for 2 hrs before restarting the main boiler and returning to normal conditions by 10:30 pm.

Activating an automated safety mechanism, for unspecified reasons, caused the boiler to be triggered.

The air quality monitoring network sensors did not detect a sulphur dioxide (SO2) pollution peak in air both during and after the incident.

The Inspectorate requested a detailed incident report.