Pollution
Humain
Environnement
Economique

The site processes medical and industrial waste using three rotating drum ovens. These furnaces are fed directly from the liquid waste tankers parked in a tank farm.

At around 3:45 p.m., in a hazardous waste processing facility, the wall of a tank containing waste from an acrolein cyanohydrin acetate production plant suddenly ripped open. A white cloud formed and immediately ignited. The flames extended to the other tanker lorries in the area, and contributed to the fire. Packaged chemical waste, located in an adjacent warehouse, also caught on fire, releasing a significant plume of black smoke. The municipal emergency plan was put into action. The site’s 117 employees were evacuated. Firefighters took air samples: no dangerous levels of harmful substances were detected. The fire was brought under control at around 7 p.m., and the municipal emergency plan was lifted. The fire brigade left the site in the evening the following day.

Consequences

The extinguishing water was confined to a retention basin and then treated through appropriate channels. The rotary furnace connected to the tank that had initiated the event was severely damaged. The electrical wiring on the other two furnaces was also damaged and had to be repaired.

Follow-up after an accident

All of the site’s facilities were shut down, and all the buildings containing waste were inspected and secured. The three rotary furnaces and the direct supply lines between tanks and furnaces underwent extensive inspections. Tank residues were dismantled by specialised companies. After a few days, the competent authorities lifted the operating restriction on the site’s installations not involved in combustion activities (physicochemical treatment and storage of waste). The work to remove the waste generated by the accident and redevelop the impacted area continued until mid-March. The operator searched for alternative solutions to manage its customers’ waste (shipment to the Group’s other facilities in Germany or shipment to other specialised treatment centres in Europe).

Causal analysis

The lorry had been present in the tank farm since the previous day. Acrolein cyanohydrin acetate waste was in the process of being transferred to the furnace at the time of the incident. To allow this transfer to take place, the waste had been preheated. This process takes place in an inerting nitrogen atmosphere and with the tanker lorry earthed. During the transfer phase, due to the temperature reached (why was an excessive temperature reached?), a spontaneous exothermic decomposition reaction of the waste began. This uncontrolled decomposition led to an untimely increase in pressure and ripping of the tank. The safety devices on the supply line and the tanker lorry were unable to contain the overpressure (which devices were involved: rupture discs, pressure relief valves?)

Measures taken

The accident revealed that the knowledge of the properties of the most dangerous substance contained in a waste stream (here ACA) was not sufficient to know the behavior of the waste itself. Following the accident, the operator, in collaboration with its supplier customers, reinforces the analysis of the choice of the appropriate treatment method according to the characterization of the waste. Customers will provide more information on the waste delivered. The operator is equipped with devices to make tests for determining the temperature of spontaneous decomposition (“Self Accelerating Decomposition Temperature” or SADT).

A new fatal accident occurred on this site in September 2018 (ARIA 52226).