Polytechnik

To ensure the heat supply for local industrial companies and reduce the use of fossil fuels, energy supplier EVN Wärme decided to build a biomass heating plant at its Ernsthofen site. The decommissioned combined heat and power plant was replaced by a 5 MW plant based on advanced combustion technology.

The new plant is a 5 MW biomass heating plant based on a hydraulic travelling grate combustion system with an integrated hot-water boiler. Installation of the plant began in November 2023, and full operation commenced in October 2024. The integration of the new heating plant was simplified by the existing infrastructure, as only the connection to the district heating network needed to be established.

The fuel storage facility, with a volume of 7,500 m³, is supplied weekly with wood chips by regional suppliers or from an energy supplier’s interim storage facility. The annual raw material input amounts to around 4,000 tonnes of wood chips.

Fuel is fed into the combustion chamber via five push rods and a trough chain conveyor. A mechanical airlock system and a sprinkler valve are integrated to prevent back-burning. The plant is refuelled every two days and is designed for seasonal operation of around 4,500 hours per year, from September to May.

The fuel is combusted on hydraulically movable grates, which distribute the fuel within the combustion chamber and convey it through the furnace. The fully automatic combustion plant features automatic ash removal and an integrated flue gas analyser. The controlled supply of primary and secondary air, combined with the flow-optimised combustion geometry, ensures a long residence time for the hot gases in the combustion chamber, resulting in efficient and low-emission combustion.

The flue gases are extracted from the combustion chamber by a speed-controlled flue gas fan and subsequently pass through a multi-cyclone and an electrostatic precipitator. The ash produced is transported to an ash hopper via ash push rods and ash screw conveyors. The fly ash generated during flue gas dedusting is also fed into the ash hopper.

EVN Wärme already operates several biomass CHP plants and heating stations and is a major provider of renewable heat from biomass. Biomass remains an important energy source for district heating. In future, other renewable heating concepts – such as power-to-heat plants, large-scale heat pumps and geothermal energy – are also set to play a greater role. The aim is to expand district heating and reduce the use of fossil fuels.