At around 1:15 p.m., an explosion, followed by a fire, occurred a dryer while in emptying mode. The unit contained 20 t of corn at the time, whereas in normal operation it contains 100 t. The accident occurred on the last day of the annual drying season. Only the lower burner was in operation. The blast from the explosion threw an employee backwards and blew the dryer’s external sheeting into the middle of the yard. The employee was only slightly injured. The adjacent concrete storage silos were not affected by the explosion or the subsequent fire. The dryer was in fact completely separate from the two silo assemblies. The adjacent roadway was closed off to traffic.

Two fire trucks were mobilised for this incident. The operator emptied the container using a worm screw, but the burning grain remained trapped in the conduits. The firefighters were faced with difficulties due to the instability of many metal elements, deformed during the explosion. The fire was put out at 4:30 a.m. The next day, a fire was observed as a result of the influx of air caused by operations to cut away scrap metal that risked falling off the structure. The firefighters intervened again and were able to extinguish the fire by spraying water directly into the heart of the fire.

Probable cause of the explosion:

• pre-storage of a batch of several tonnes of unusually wet (> 45% humidity) product over an extended period (> 48 h);
• excessive emptying of the drying column and maintenance of the ventilation system creating a large quantity of suspended dust;
• absence of a well-defined procedure or instructions for non-compliant batches: high moisture content, long pre-storage time.

The operator replaced the dryer and installed an automatic gas detection system on all the site’s dryers.