Sägewerk Schösswendter

Overall planning

Saalfelden, Austria

Operational since 2006


The plant

The family Schößwendter operates a sawmill at its site in Saalfelden. Due to the increased heat demand, a comprehensive concept for future heat supply has been developed. The project was designed as a biomass combined heat and power plant based on a steam process. The required thermal energy for the sawmill is provided by a biomass combustion system with a steam boiler rated at 23 t/h (21.5 MW of combustion heat output).

The technology

The combustion is fueled with sawmill residues such as bark, offcuts, sawdust, and wood chips, as well as selective thinning wood as needed. The fuel is either unloaded in the storage area near the push floors and transported to the push floors by a wheel loader or directly fed to the push floors. The push floors convey the fuel material with a closed-type mechanical conveyor to the combustion’s feeding device. The high-pressure steam boiler, with a fuel heat output of approximately 21,5 MW, is a radiant boiler with a steam generation capacity of 23 t/h at an operating pressure of 65 bar. It is designed as a multi-pass natural circulation boiler, including superheaters, economizers, and air preheaters, in a vertical arrangement. The flue gas temperature after the steam boiler is around 150 °C. A pre-separator and an electrostatic precipitator are used for flue gas dedusting. In the pre-separator (multicyclone type), the flue gas is pre-cleaned through centrifugal force separation. Additional dust particles are separated when the flue gas passes through the electric fields of the electrostatic precipitator, where the effect of high-voltage current causes them to deposit on the collecting electrodes. The induced draft fan provides the necessary negative pressure and directs the clean gases to the flue gas condensation system and further through the chimney into the atmosphere. To generate electricity, a steam turbine with a rated power of up to 5.000 kW is installed. The electrical power is fed into the public grid.

Technical data

Steam boiler

Combustion heat capacity

21,5 MW

Steam capacity

23 t/h

Permissible steam pressure

74 bar

Operating steam pressure

66 bar

Steam temperature

485 °C

Feedwater temperature

105 °C


Untreated sawmill residues or forest residual wood

Push floors

4 units (1.500 m³)


Extraction-condensing turbine


2 bara

Exhaust steam

0,1 bara

Heat exchanger

14 MW

Flue gas dedusting

Pre-separator with electrostatic precipitator

Flue gas volume

60.000 Nm³/h