At a refinery early in the evening (8:22 pm), a leak ignited on a stripping column of the gasoline hydrotreatment unit. This step was intended to eliminate a number of impurities (sulfurized, nitrogenated and oxygenated compounds, metals) before being routed into the reforming unit. A mix of gasoline, petroleum gases (fuel gas, butane, propane) and hydrogen was circulating in the reboiler exchanger; its temperature had risen to 440°C for 25 bar of pressure. The leak occurred at the level of this exchanger’s joint plane, on the hot fluid side, and immediately self-ignited in causing a flame cone to extend some 10 metres. The alarm was sounded and the internal emergency plan activated. The unit was disabled within 5 min, in accordance with the emergency shutdown protocol, and then decompressed towards the fuel gas unit as well as the flare. To protect nearby units and avoid spreading of the blaze, water curtains were installed using 9 water cannons until complete fire extinction. Moreover, external fire-fighters set up a foam blanket as a preventive measure. After 1 hour, the intensity of the fire had significantly eased; at 11:30 pm, the incident was under control. The various units were placed in safe operating mode by means of nitrogen and water vapour inerting. An employee was slightly injured while attempting to isolate the exchanger. Property damage was appraised at €4.3 million. Both the hydrotreatment unit and reformer were shut down for several weeks : operating losses amounted to €1.7 million. Facility restart was contingent upon following a standardised protocol. Once the initial findings had been recorded, a first hypothesis was forwarded subject to subsequent investigation. The leak may have resulted from a defect originating in the exchanger : a circularity problem around the joint housing tube could have complicated positioning of this housing. During the most recent joint replacement, poor docking would thus have compromised the seal on part of the circumference. The refinery operator inspected all exchangers of the same type in order to check the connections. A judicial appraisal was undertaken.

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