At 18:58, after the restart of production, an explosion followed by a fire occurs in a drying tower of a food processing plant located in the enclosure of a chemical platform. The POI of the platform is triggered. A security perimeter of 50 m is established. Firefighters are alerted. The sprinkler system went off and the internal firefighters extinguished the fire before the emergency services arrived. These check the absence of hot spots. The product concerned is a fungicide (with 80% sulfur). Firefighters make SO2, SO3 and SOx measurements that are below detection limits. The POI is raised around 22h40. A press release is issued by the operator.

The production of the unit is stopped for 2 months, causing the technical unemployment of 20 employees. The opening of the explosion vents limited the damage. Some pieces of corrugated tiles and corrugated sheets have been projected. The atomizing chamber, the static bed, the vibrofluidizer and the air extraction duct were impacted. Property damage amounted to € 0.35 million and operating losses to € 0.75 million.

The analysis of the process parameters shows that the explosion occurred in the atomization chamber (sudden overpressure in the chamber, then rapid increase in temperature at the outlet). This explosion would be due to a spraying problem resulting in an increase in temperature and promoting the formation of incandescent embers that would have ignited in contact with particularly sensitive fines. This study shows a discrepancy between the explosivity data of the powder transmitted by the customer and those measured by the operator on the fine powder manufactured on the incriminated drying tower. The granulometry, the EMI (Minimum Inflammation Energy) and the explosion characteristics reveal a ST3 class Powder against ST1 announced by the customer. The operator takes the following measures :

• stop the production of the product considering its explosive class not compatible with the protection means of the drying tower provided for powders class ST1
• Installation of an air extraction duct offering better resistance to mechanical stresses (round shape against square shape previously)
• Installation of rupture disc on this sheath
• The fines continue to be recycled at the atomizer head even in case of stopping liquid supply tower, stopping the recycling of fines is enslaved to stop the liquid supply of the tower
• Internal trainings for staff recalling the risks associated with the company’s activity, the instructions for the management of the installations and the safety procedures. A refresher course on fire risk training is also planned.