At 11.25 a.m., the bag filters in an animal feed dehydration plant caught fire. Before the fire, the line had been shut down at around 2 a.m., following a violent increase in alfalfa dry matter (from 51 to 75%), causing an increase in the flow rate of both lines and filling of the mixers. When the line was started back up at 3.10 a.m., the chimney spat out burning fragments of soot and small fires were detected on the ground but were quickly extinguished. However, at 8 a.m., smoke was observed in the other line’s filter in the explosion vent elbow. The filter was opened, cleaned, and restarted. At 9.30 a.m., burning particles were again observed under the filters and extinguished. At 11.25, a large amount of smoke was discharged from the filters, triggering the filter outlet spark detection system. Both lines were shut down. As staff were unable to extinguish the fire and fresh outbreaks of fire were observed in other areas of the building, the fire department was called. When they arrived, they shut off power supplies, extinguished burning spots, checked other facilities, and drained affected facilities to prevent any fires breaking out again. The water used on the fire was collected and contained in the retention basin. The emergency services left the site the next day at 12 p.m.

The fire was due to discharge of incandescent matter from the chimney. The hot restart phase facilitated this phenomenon. In fact, following a modification made several years earlier, there was an obstacle in the chimney duct, facilitating build-up of soot and dust. Upon startup, this soot heated up and eventually broke loose, forming incandescent particles. In addition, there was a shift change at 5 a.m., between the appearance of the initial hot embers and the outbreak of the fire, delaying the response.

Following the fire, the operator put in place the following actions:

• creation of a hot startup procedure;
• modification in the chimney duct to eliminate obstacles;
• introduction of formal detection system checks even if these systems were not suspected of involvement;
• addition of water injection to the main fan suction system to cool the flow of hot gas when the facility is started up.