Stege Fjernvarme A.m.b.a.

In 2020, Stege District Heating decided to replace their older straw-fired boiler with a new Linka boiler. In addition to the new boiler, the project also included an upgrade of the straw crane.

Stege District Heating supplies heat to approximately 1,300 consumers in Stege and the surrounding areas. Following the installation of the new boiler, the heating plant expects to expand its service area.

After the installation of the new Linka boiler, the operating staff can remotely control the system from home via PC. The entire system of Stege District Heating, including the solar panel system, is connected to remote control, allowing for technical support on short notice as well.

The boiler system is an 8.0 MW Linka GVB hot water boiler, ensuring maximum utilization of straw while maintaining flue gas temperatures at 115-120°C at full load.

The entire combustion process begins at the straw storage, where the straw crane deposits a bale into the safety box, then onto an 11.6-meter-long Linka tipping table (including straw table and inlet) and further to a Linka cutting machine that slices a portion off the bale. The straw slice is then fed into the combustion chamber using a hydraulic firing piston. The firing process is modulating, meaning variable piston speed/firing speed is controlled based on load and oxygen percentage.

The boiler is constructed with a combustion chamber followed by a reversal chamber. The flue gas then passes through a 3-pass economizer section with vertical flue pipes and shot valves at the top for cleaning the flue pipes. Shot valves are also installed in the reversal chamber at the bottom of the economizer for cleaning the reversal chamber.

The flue gas from the boiler passes through a multicyclone, LIN-KA type, and the new bag filter, Green Line 466-55-960 type. From here, the cleaned flue gas is directed to the new flue gas fan before being discharged through the existing chimney. The ash is transported to the existing wet ash storage.

The control of the system is managed through a PLC control system that monitors the plant and sends alarms via the internet and SMS. Additionally, it is possible to monitor the system via smartphones, tablets, and/or PCs. The new control system and electrical installations are integrated into the existing plant.

To comply with tightened emission requirements for new medium-sized combustion plants according to the Council of Europe Directive 2015/2193, implemented in Danish legislation through BEK 751 of 28/05/2018, an SNCR (Selective Non-Catalytic Reduction) system was also supplied for necessary compliance with NOx emission limits. The SNCR system is a “stand alone” system consisting of a tank for the reducing agent, a standardized pump module for softened water and the reducing agent, a process cabinet, injector(s), and control.

As part of the contract, the new boiler system was also to be delivered with complete additional firing for Stege District Heating’s existing wood pellet boiler system, and where possible, existing components were to be reused.