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.

In 2017 Linka delivered a new straw system for the heating plant in Ørnhøj-Grønbjerg. This will replace the use of gas with CO2 neutral biomass.

Ørnhøj-Grønbjerg District Heating is located in Ørnhøj and supplies around 500 households in both Ornhoj and Gronbjerg.

The biomass plant was installed as a supplement to the existing solar panels, which cannot supply enough heat during winter seasons. Biomass will fuel 70% of the heat production while solar heating will supply around 20%. The remaining 10% will be produced using gas.

Linka delivered and commissioned a full boiler sy-stem with a 1,500 kW Linka H boiler designed for straw combustion. The two extra passes, in the 5-pass boiler, ensures higher efficiencies and savings on fuel.

A Linka double shredder is installed in the straw storage. The 30 meter double conveyor can hold 30 bales, and only needs refilling every other day.

This ensures little operating maintenance as the plant is fully automatic, controlled and monitored by a PLC control system. By installing a bag filter the flue gas is cleaned, thus reducing dust from the plant and ensuring better valu-es on emission.

Viborg Varme supplies heat to up to 10,000 households and businesses in the city of Viborg and Hald Ege using district heating.

Their goal is to achieve CO2 neutrality by 2030, and they have initiated five concrete, green, and ambitious initiatives in and around Viborg, one of which includes the transition from natural gas to district heating.

In Hald Ege, groundwater heat pumps and a pellet boiler will be used for heating in the future.

This case from 2023 describes Linka Energy A/S’s complete delivery to the new heating plant in Hald Ege, which is based on wood pellet combustion and thus provides Viborg Varme A.m.b.a’s customers with a stable, competitive, CO2-neutral energy supply.

The boiler system, an 830 kW Linka® H hot water boiler, is a cylindrical and efficient flue pipe boiler in a 3-pass design with a smooth fire tube and water-cooled reversing chambers. Together with Linka’s patented combustion technology and the use of flue gas recirculation, it ensures maximum fuel utilization.

When the boiler is called upon for heat, the firing procedure is activated: the stoker auger starts and retrieves the amount of fuel, depending on the heat demand, from the new “walking floor” fuel storage, which is located underground in a basement. The fuel is transported via the silo auger to the cell sluice, from where it is fed through the stoker to the moving step grate in the boiler.

The new economizer can extract an additional 85 kW from the boiler by cooling the flue gas.

Additionally, a multicyclone is installed, which cleans the flue gas, thereby reducing dust emissions before it is sent through the new flue pipes to the newly established chimney.

The ash is transported via the new ash handling system to the new ash container.

The plant is controlled via a PLC control system, which monitors the plant and sends out alarms via the internet and SMS. It is also possible to monitor the plant via smartphones, tablets, and/or PCs.

The existing heat production – initially a coal boiler, which was converted to wood pellets and subsequently replaced with a Linka H boiler for wood pellets – on Parkvej, built in 1966, faced the challenge of technical wear and tear, technological and energy obsolescence, and had been supplying heat to consumers in Mørke for over 50 years.

Therefore, 2017 became a milestone for Mørke Fjernvarmeselskab A.m.b.a. and its consumers when the new, state-of-the-art straw-fired heating plant on Fabriksvej was constructed.

The investment in a greener future with the new heating plant allows for the complete coverage of heat production using straw – a renewable and local energy source – considering necessary service periods where the new oil boiler, as a backup, ensures a stable and reliable heat supply even during maintenance periods.

The project was tendered on functional requirements and in a turnkey contract covering both buildings and the technical installation, which was won by Linka Energy A/S.

The boiler plant is a 4.5 MW Linka GVB with an economizer, featuring Linka’s patented combustion technology ensuring maximum utilization of the straw.

The plant comes with a built-in concrete bridge scale (3×24 meters), which registers the weight of the straw before it is transported to the straw storage. Here, the straw bales are arranged so that the traversing straw crane can effectively sort the rows according to the quality of the straw before delivering them to the LINKA Safety Box. From the safety box, the straw is led through a hydraulic fire door in the firewall into the chopping room. The straw chopper in the chopping room lifts the straw bale into a vertical position, after which a slice of approximately 50 cm is cut from the bale. The slice is slowly pushed into the boiler. The speed at which the straw is pushed onto the combustion grate of the boiler is determined by the oxygen control.

The straw boiler itself is specially designed for biomass, making it more efficient with higher efficiency, and it is designed with a combustion chamber where, in the first smoke passage, connections at different levels can be placed for DeNOx injectors.

The combustion grate is an integral part beneath the boiler construction and is carried on water-cooled bearings with 3 zones, under which grate fall-through, and ash are automatically removed with longitudinal ash augers.

Subsequently, this is led to a water-cooled ash chute, which with a ‘crusher’ destroys any stones and slag formations, allowing it to be further handled in the ash system to the 2 new ash containers.

The flue gas is cleaned in a LINKA Multicyclone and a Teldust bag filter, which reduces dust emissions before being discharged through the 30-meter-high steel chimney. A silencer is installed between the flue gas fan and chimney to future-proof the plant against noise pollution.

The accumulator tank, with a capacity of 1400 m³, is pressure less and equipped with a nitrogen system that delivers nitrogen with purity better than 99.5%, capable of maintaining an overpressure of min. 50 mmWS at the tank top during a discharge of 4.5 MW.

The oil boiler plant serves as a backup for the straw boiler and consists of a 5.0 MW oil boiler, type Danstoker Global 9 LUX.

The oil burner, a Low NOx gas oil burner, type Weishaupt RGL70/2-A, is adapted and installed on the hot water boiler, designed to handle, and maintain an efficient combustion process. For the oil boiler, a double-walled, horizontal 30 m³ oil tank has been provided, equipped with leak monitoring among other features.

At full boiler load, the requirements for NOx and CO are met due to the boiler’s combustion efficiency.

The control of the complete system is managed through a comprehensive PLC control system, which monitors the entire installation and sends alarms via internet and SMS. Additionally, it will be possible to monitor the system via smartphones, tablets, and/or PC.

Nimtofte Varmeværk (Nimtofte District Heating), owned by Brdr. Thorsen I/S supplies heat to 405 households.

The heating plant was built during 2007 and was put into operation in the fall of the same year. It is designed to burn biofuels, primarily consisting of straw. Therefore, it is a 100% sustainable heating plant.

Nimtofte Varmeværk (Nimtofte District Heating) provides heat to a network owned by NOFF (Nimtofte og Omegns Fjernvarme Forsyning/District Heating Supply), and the network currently covers Nimtofte town, Lübker Golf Resort, and Ramten town.

The operation of the district heating plant is managed daily by Steffen Thorsen, and Brdr. Thorsen is responsible for supplying straw and labour for the maintenance of the plant.

The boiler plant is a 5 MW Linka GVB with an economizer, featuring Linka’s patented combustion technology, en- suring maximum utilization of straw.

The plant is equipped with a 2-rail straw crane for transporting straw bales before they are delivered to a LINKA Safety Box. From the safety box, the straw is conveyed to the straw chopping room.

When the straw bale is fully sliced, a hydraulic straw feed system will transport the straw slice to the boiler door and move onto a set pressure so that the straw is always steady. When the pressure is correct, the boiler door will open, and the firing cylinder will start again. The speed at which the straw is pushed onto the boiler’s combustion grate is determined by the oxygen control.

The boiler will be designed with a square combustion chamber, where nozzles are placed at 3 different levels on the sides. Similarly, nozzles are also placed in the front of the boiler. At the rear of the boiler, a transverse water-cooled tube with nozzles for counter-current combustion is located.

The boiler is configured so that the flue gas temperature at full load is kept at 120°C. To avoid too low flue gas temperature during decreasing load, the boiler is equipped with a damper for bypassing flue gas around the 3rd and 4th flue gas passes.

The flue gas is cleaned in a square LINKA Multicyclone with a cone-shaped bottom, where the smoke is drawn to the top of the cyclone and then forwarded to the bag filter. The ash removal from the boiler consists of an auger, which is placed in a recess under the floor in the boiler room, transversely under the boiler, and is then conveyed from there to the large ash room.

The cleaned flue gas is further released through the 30-meter-high steel chimney.

The 1000 m³ accumulator tank and the nitrogen plant, which supplies nitrogen with a purity of 99.5%, can together maintain a nitrogen pressure of at least 50 mmWS in the tank top under all operating conditions.

The oil boiler system serves as a backup for the straw boiler and is a 5 MW oil boiler, Danstoker Global 9 ”Standard” model.

The oil burner, a gas oil burner type Weishaupt RGL70/1-B, is adapted and mounted on the hot water boiler, designed to handle, and maintain an efficient combustion process. For the oil boiler, a double-walled, horizontal 30 m³ oil tank has been supplied, equipped with leakage monitoring, among other features.

The control of the entire system is carried out through a comprehensive PLC control system that monitors the entire plant, providing a quick overview of the system’s operation during daily inspections. Additionally, the operator panel will be helpful during service or any necessary repair work.

Gjerlev Varmeværk A.m.b.a. was established in 1989 and shortly thereafter set up the first straw-fired boiler system – at that time, a preferable alternative to natural gas, which the area was already designated for. In 1990, the new straw plant was inaugurated.

In 2014, the heat plant added a 3,500 m² solar heating system as a supplement to the existing straw-fired boiler system, concurrently with the modernization of the original heat plant.

After careful consideration, in early 2018, Gjerlev Varmeværk A.m.b.a. applied to Randers Municipality for a loan guarantee to establish a new straw and wood chip plant to replace the existing straw plant, which was becoming obsolete.

The combined straw and wood chip boiler system provides the plant with more flexibility to switch between fuels, straw, and wood chips, offering complete freedom in fuel selection – and, not least, carbon-neutral energy and potentially lower heating bills for consumers in the long run.

Linka Energy A/S’ new 2000 kW multifuel biomass system was handed over to Gjerlev Varmeværk A.m.b.a. at the end of 2018.

The boiler system consists of a 2000 kW Linka® H 2000 hot water boiler, capable of handling either straw or wood chips. This allows the boiler line with two feeding systems to operate independently of each other, ensuring a high level of security in the heat supply to the process, regardless of whether one of the feeding lines is taken out for service or similar reasons.

The straw handling system is equipped with a Linka TWIN straw table and a Linka TWIN shredder with rotating drums, controlled based on the boiler’s heat consumption. If the straw production is insufficient, the drum speed is increased. The shredded straw is transported to the straw auger, further to the cell lock and stoker auger (including fire extinguishing system), after which the straw is conveyed to the movable step grate located at the front of the boiler.

The wood chip handling system is delivered with 3 inclined augers and 6 cross augers.

The hot water boiler, type Linka® H 2000, is designed for complete combustion and efficient utilization of radiant heat in the fire channel, while convective heat is maximized in the two subsequent flue gas tube sections. The step grate is constructed to prevent slag formation. Through Linka’s globally patented system, air from the firing end is drawn into the boiler in a counter current principle, efficiently burning the flue gas and yielding improved results in terms of efficiency and emission levels.

For automatic flue gas cleaning, several pressure tanks with shot valves are mounted on the front of the boiler. These valves release air through the boiler’s flue tubes, cleaning them of ash. This results in minimal manual cleaning time for the boiler’s flue tubes.

Additionally, a multicyclone is installed to clean the flue gas, thereby reducing dust emissions through the chimney. The ash is finally transported to a 20m³ ash container.

Control of the plant is done with a PLC control system that monitors the plant and sends out alarms via internet and SMS.