In Denmark, at the Studstrup power plant, a large wood pellet silo has been burning for three weeks straight. The fire started for an unknown reason on Thursday, September 22.
According to the Danish newspaper Ingeniøren, which published a summary of the accident on Wednesday, since then the fire brigades have been trying to put out the fire around the clock, but without success.
Located on the northern edge of the city of Aarhus on the east coast of Denmark, the Studstrup power plant is a very large combined heat and power power plant. Its two units currently in use produce a total of 700 megawatts of electricity and 900 MW of district heating. Two older units have already been decommissioned.
No information was found on how the silo fire affected the operation of the power plant. Presumably, however, energy production has not ended.
The fire has progressed by smoldering inside the silo, Ingeniøren writes. Since smoldering fires are known to create a lot of smoke, it is no wonder that the smell of smoke has spread up to 50 kilometers away on the worst days.
The spread of the smell is written by Danish TV2’s local news. According to the channel, the silo initially contained 56,000 tons of wood pellets. According to Ingeniøren, about a fifth of this amount was saved in the early stages of the fire by transporting it away from the fire site with a conveyor belt, which was still working at first.
The Studstrup power plant is owned by Denmark’s largest energy company Ørsted . The company has apologized for the disturbance caused by the smoke to the residents of the surrounding area.
Water extinguishing difficult or impossible
According to Ingeniøren, during the first two weeks, no attempt was made to extinguish the pellet fire with water. Then the risk would have been taken that the water vapor generated by the heat would tear the silo apart and the fire would spread. Therefore, attempts have been made to extinguish the fire by feeding in nitrogen gas.
The silo’s structures have still been cooled from the outside by pumping water up to 8,000 liters per minute, or about 130 liters per second – that is, just under 500,000 liters per hour, or 11–12 kilotons per day.
Two weeks after the fire, i.e. on October 4, a remote-controlled clearing tractor of the Norwegian army arrived at the fire site. With that, the fire brigades finally got inside the silo to continue transporting the pellets away.
On October 7, the fire brigade began pumping water into the silo as well, but this attempt to extinguish it was unsuccessful. The water didn’t soak into the coils, it just drained away.
At the moment, the fire continues, but it will probably start to weaken in the next few days at the latest. A week ago, it was estimated that there would be 15,000 tons of unburned pellets in the silo.
On the other hand, the fading of the fire within “a few days” or even “a few hours” has been predicted for at least a week, without this optimism having actually come true yet.