A fire broke out in the biomass boiler room of a perfume factory at around 7:00 a.m. The factory’s first responders saw flames coming out of the side protection plates on the boiler’s firebox. These plates buckled and paint spatter was visible on the floor. The safety procedure was implemented for the facility and the power supply was shut down by the electricity company. Swift intervention allowed to reduce the pressure inside the boiler and put out the flames. The firefighters did not need to intervene. A thermal imaging camera was used to check for hot spots throughout the premises.

Backup gas-fired boilers were started up to maintain the factory’s production. After the biomass boiler was allowed to cool down completely, its flues were cleaned, and it was opened up for inspection by its manufacturer and the insurer. Deliveries of wood to the site were halted.

Analyses revealed particularly high ash content from the fuel (measured at 4.8% whereas the rate contractually agreed with the supplier is 3%). In November 2017, the supply plan for the biomass boiler plant was changed from ‘woodchips, then shredded pallet wood’ to a mixed supply of ‘combined woodchips and shredded pallet wood’. The higher ash content of the woodchip/pallet mixture had led to an accumulation of clinker during combustion, which led to the blockage of exhaust gas flue. In addition, the setting of the combustion air damper was incorrect for a “mixed” fuel. Visual inspections inside the boiler had been too infrequent to identify any anomalies.

Since the accident, the operator has implemented the following measures:

• the flue is cleaned twice a year;
• the combustion settings have been changed to reduce the build-up of deposits;
• the supply plans have been changed to reduce soot build-up;
• the type of incoming biomass is inspected more frequently;
• two pressure sensors have been fitted in the boiler’s firebox to detect the accumulation of clinker and flue-gas exhaust faults;
• daily visual inspections of the boiler’s firebox have been improved;
• a safety bulletin with the action plan was distributed.