Evaluation and mitigation of fire and explosion risks due to aerosol cans in metal waste recycling

Aerosols consumed at home are supported in France in the recycling of aluminum or steel household waste stream. This process requires storage and crushing in a press, the latter operation leading as indirect consequence in random perforation of aerosols. As aerosols include flammable gaseous, liquid or liquefied chemical compounds, this process can induce fire and explosion hazards. Indeed, even after full use by the consumer, an aerosol still contains a residual gas or liquid product. The estimated residual weight filling rate is about 2% of the original overall content in most commercially available products. Moreover, it is not uncommon to find in the waste not completely emptied aerosols. It is why the press operation, and more generally the storage and the treatment of waste containing aerosol cans, generates fire and explosion risks. Numerous incidents and accidents have been reported by many waste sorting plants in France. Non-desirable events identified are fires in the press machine, at the output of waste balls, and explosions in press compression chamber. The impact of these events is sometimes significant: pressure effects, fires spreading and other domino effects have been observed. This work analyses potential of hazard associated to full or empty aerosols recycling. Three types of hazardous scenarios have been identified: 1) an ignition of an explosive atmosphere, 2) a BLEVE occurrence and 3) a liquid pool fire. In each case, the potential effects have been quantified. Finally, one aim of this study is to identify technical and organizational solutions to prevent these fires and explosions and to protect waste sorting plants, regarding hazards associated to the treatment of aerosols. This is particularly important insofar as the amount of waste to be recycled is still increasing. In addition, labor regulation requires from employers that the explosion and fire hazards be assessed and that appropriate measures be taken to ensure workers safety