Smoke and flames were seen coming from the feed hopper and swivel joint of a roasting furnace at a steel plant. The furnace is used to process spent petroleum catalysts. The technicians sounded the alarm. Heating and loading were stopped. The operator implemented the plant’s internal emergency plan. The flames went out before the firefighters arrived. The event generated 150 kg of sulphur dioxide that was released to the atmosphere and the roasting shop was shut down for 17 hours.

Poor positioning by maintenance technicians of the sodium bicarbonate feed line at the reactor filters of the flue-gas cleaning system is what caused the incident. This poor positioning prevented the flue gases from being treated properly, allowing flue gases to build up inside the flue and reducing the rate at which the fumes were exhausted to the outdoors. The vacuum inside the furnace was insufficient. As a result, the smoke produced by the furnace flowed out of its inlet and outlet. The smoke was caused by the combustion of carbon monoxide, a gas that is produced during the roasting of the catalysts and which is normally burnt by the furnace’s afterburner. The analysis of the event also revealed that the production technicians were unable to interpret the drift in the flue-gas exhaust flow rate, a parameter that is supposed to be checked. Their training was not yet finished. In addition, it is not easy for the production technicians to visually check the position of the feed line because this requires the use of an aerial work platform.

The operator heightened the awareness of his technicians and maintenance personnel. He is considering adding a means to directly access the feed line in order to visually check its position.

Nevertheless, the inspection authorities for classified facilities required the operator to also revise his organisational methods for technician training, fitting of alarms on the flue exhaust and control system to be added, management of sodium bicarbonate consumption and management of maintenance.