Follo Fjernvarme AS Boiler 5 and 6 –Drømtorp 4

Due to the increasing number of customers wishing to connect to Follo Fjernvarmes district heating network, the heat production needed to be significantly expanded, and the new capacity helps to manage peak loads, providing a more even heat production.

In 2024, Linka Energy A/S delivered a new fully automated 2 x 5.0 MW pellet boiler plant, which ensures a stable, competitively priced, and CO2-neutral energy supply for Follo Fjernvarmes many new district heating customers.

The boiler plant consists of two 5,000 kW Linka® H hot water boilers, which are cylindrical, high-efficiency fire tube boilers with a three-pass design, smooth fire tubes, and water-cooled reversal chambers, designed to ensure complete combustion and efficient utilisation of radiant heat in the fire tube. The convection heat is extracted in the two fire tube sections, and the economisers further cool the flue gas, thereby increasing the overall efficiency of the plant.

The moving step grate minimises slag formation, and together with Linka’s globally patented system, which employs a counter-current principle for combustion air, it ensures maximum fuel utilisation.

The boiler is also equipped with pressure tanks and blow valves, which blast compressed air through the boiler’s flue tubes at each pass, thus cleaning them of ash and reducing the need for manual cleaning of the boiler tubes.

When there is a demand for heat from the boiler, the firing procedure is activated: The stoker screw conveyor starts and retrieves the required amount of fuel, depending on the heat demand, from one of the new pellet silos via the silo screw conveyor and forwards it to the fuel sluice, from where it is fed via the stoker to the moving step grate in the boiler.

Additionally, two multi-cyclones and two bag filters of the Teldust (Greenline) type are installed, which clean the flue gas and thereby reduce dust emissions before it is discharged through the new 20-metre-high steel chimney.

Bottom and fly ash are transported via ash screws and the parallel ash handling system to four ash containers, which are automatically configured so that when one ash container is full, the system automatically switches to another.

The plant is controlled by a PLC control system, which monitors the facility and sends alarms via the internet and SMS. It is also possible to monitor the plant via smartphones, tablets, and/or PCs. This fully automated system can therefore operate with minimal manual intervention.