CHP plant with bark combustion

In 2004, Urbas built a 10 MW double boiler system, including a boiler building and an electrostatic precipitator, at the production site which was still part of the Klausner Group at the time. In 2015, HS Timber Group (formerly known as Holzindustrie Schweighofer) took over the sawmill and renamed it HS Timber Productions. “We have Urbas plants in operation in Romania and we have had very good experiences with the Carinthian boiler experts,” factory manager Thomas Kienz explains. At the end of 2018, the decision was made to not repair the old plant. Instead, €24 million were invested in an additional combined heat and power (CHP) plant with electricity generation in order to upgrade the site.

State-of-the-art energy technology

Construction of the plant started in the summer of 2019. The concrete structure was built by HS Timber Productions and, based on it, Urbas built the turnkey CHP plant. The steam boiler, which was put into operation in June 2020, has an output power of 21.3 MW, the combustion heat output is 24.8 MW and the turbine power output is 5.5 MWel. “In order to ensure the turbine’s service life, the water is treated and permanently monitored through online measurement,” Kienz explains. The safety temperature of the steam boiler is 535°C at a maximum operating pressure of 81 bar. The biomass boiler has been running at full capacity since it was started up last summer. The last regulatory and company-related requirements were met in December 2020. “The CHP plant is in line with the latest emission standards,” Kienz explains.

Bark as fuel

Only bark with a water content of up to 60% is used as fuel for the boiler plant in Kodersdorf. The consumption is 600 to 800 steres of bark a day. “Due to the big volumes of damaged wood, 95% of the wood we use at the moment is spruce. Of course, it is also possible to burn a mix of half spruce and half pine bark. Pine bark burns very well but from a financial point of view, it is better to sell the pine wood,” Kienz says. Located in the tri-country border region, one third of the raw material comes from the Czech Republic, Poland and Germany.

Heat for the drying chambers

Two people in a four-shift operation are responsible for the handling of the fuel and the infeed management and processes. The water-tube boiler with the vertical flue gas pipes has been the standard design at Urbas for decades. All boiler components are prefabricated as modules in the biggest possible size at Urbas’s production site, which significantly reduces assembly times. The turnkey plant with its step grate conveyor and generously dimensioned combustion chamber is equipped with a vertically positioned secondary combustion chamber. In the new power plant, 15.5 MWth are decoupled for heating the 28 Mahild drying chambers with an annual drying capacity of 600,000 m³. The existing Urbas double boiler system can be used at any time to cover peaks, for example, when the drying chambers need more heat output. The generated electricity, which equals the consumption of around 20,000 households, is fed into the local grid.

Optimized ash removal

The ash is removed with a robust wet trough chain conveyor and a container filling station, which considerably reduces the amount of dust which workers are exposed to. “All of the power plant’s functions are controlled and monitored centrally. The unmanned operation of the plant is permitted according to the BOSB standard,” power plant manager Siegfried Lehfeld explains.