Inside a plant manufacturing biofuel by reusing by-products from animal feed processes, fire broke out at 11:20 pm on a pellet cooler located downstream of a press. The technicians activated the unit’s emergency shutdown procedure and placed the rest of the plant in secure mode. The smoke, intensified by combustion of paint on the cooler, limited accessibility to the site; the watchman and a technician wore self-breathing apparatuses and flooded the cooler using fire hoses. Fire-fighters arrived on the scene at 11:50 pm even though the fire had already been extinguished since they needed to verify the phone number that had been concealed. One of the workers was slightly hurt; the cables running between the coolers and many of the instrumentation devices were destroyed. The 4 tonnes of wheat slop present in the burned cooler were clogged, and the installations could only be placed back online after lengthy drainage and cleaning steps. No other equipment sustained damage.

During the few hours preceding the accident, the press feeding the cooler got jammed three times, causing a temperature rise to 100°C, as opposed to 90°C under normal conditions. The operational press bypass valve, which sent flour to the cooler while the jams were being repaired, would have blocked. The sensor positioned on the dryer’s air extraction outlet did not relay any warning. Moreover, the steam injection valve for the cooler was inaccessible due to its proximity to the fire. The operator forwarded 3 hypotheses to explain this fire: sending flour onto very hot pellets, hence causing the flour to self-ignite; flicking embers into the cooler during one of the jam repair operations carried out on the press; or projecting very hot pellets leading to self-ignition.

These installations, except for the damaged cooler (which would remain inoperable for several months), were placed back into service following a number of steps, including: replacing the cable path; blocking the door to the press if the cooler’s feeder hopper was still open; plating the press bypass; and shutting down the press feeder should the feed temperature exceed 100°C (sign of a system jam). The operator performed a risk analysis according to the HAZOP method, which indicated that the only eventual source of embers was found at the level of the pellet press. The operator then laid out a series of organisational and technical prevention / protection measures, e.g. more extensive controls and monitoring, press lubrication, alarms, a design to remove the flour feed bypass, temperature measurements inside the cooler, a remote steam injection controller, and automated steam suffocation.

The Classified Facilities Inspectorate also observed that the workshops were extremely dusty and moreover that the installations’ washing water was not flowing smoothly to the sewer network; as a result, the operator ordered completion of the asphalted zone.