On a Sunday, in a non-hazardous waste incinerator, the furnace combustion chamber became over-pressurized. This led to the installation’s automatic reset, the projection of waste at the outlet of the clinker extractor, the opening of the safety rupture discs located under the incineration furnace grate and the opening of the boiler’s pressure relief hatch. Untreated fumes were then released for several minutes via the rupture discs and pressure relief hatch, which were spotted by local residents.

The on-call teams intervened, and the furnace was emptied of its waste. After a general inspection of the equipment, the furnace was restarted, and the burners were restarted in the evening. The temperature rose to 850 °C, and the waste was reintroduced. Samples were taken from the gauges located around the site. No environmental impact was noted.

The facility operator analysed the event in conjunction with the manufacturer. The overpressure was reportedly caused by a large quantity of material falling onto the furnace’s grate and in the clinker pit. The falling material created a “piston effect” compression on the gases contained in the clinker pit.

The facility operator undertook complete maintenance of the boiler pressure relief hatch. During the next technical shutdown, the boiler was opened up to inspect the areas where the clinker was hanging up. No apparent anomalies were found, but it was determined that the boiler was very dirty and a cleaning operation was performed. Certain combustion control parameters were modified (waste layer height on the first rollers, primary air control, secondary air mapping, furnace vacuum).

In addition, to better ensure technician safety, the operator checked that the guillotines located in the clinker pits were closed for all operations in front of the extractors (to prevent injury to persons in the event of waste ejection). Chains were installed to maintain the skips and prevent tipping, and a protected corridor was created for pedestrians. An on-site inspection was conducted the following month to check that all these measures had been undertaken.

An explosion, followed by a fire, had already occurred in this incineration furnace a few months prior (ARIA 45433).