Type of CHP system: Grate fired boiler

Plant owner: The Admont CHP plant is owned by STIA -Holzindustrie GmbH, a wood manufacture company.

Commissioned: 1999

Status of plant: Demonstration

Contractor details:

Thermooil boiler and hot water boiler: Kohlbach; Oil boiler (back up): Viessmann, Type: PD150; Turbine – ORC: Turboden; Generator – ORC: Turboden,  Flue gas cleaning: Kohlbach

Power generation: ORC

The main innovative component of the process is the ORC process. The ORC process is connected with the biomass-fuelled furnance via a thermal oil cycle and the thermal oil boiler (nominal capacity 3.2 MW; 0.95 MW of the thermal oil power are directely utilised via hot proces). The ORC unit itself operates as a completely closed process utilising a silicon oil as organic working medium. This pressurised organic working medium is vaporised by the thermal oil in the evaporator and then expanded in a two-stage axial turbine which is directly connected to an asynchronous generator. Subsequently, the expanded silicon oil passes through a regenerator (where cycle-internal heat recuperation takes place) before it enters the condenser. There condensation of the working medium takes place at a temperature level which allows the heat recovered to be utilised (hot water feed temperature about 80 to 90°C). The liquid working medium then passes the feed pumps to achieve the appropriate pressure level of the hot end of the cyle again.

The choice of a new, environmentally friendly and suitable organic working medium necessitated by the higher temperature levels on the hot and cold side of the ORC process as compared to electricity-only applications (e.g. geothermal applications) is another innovative aspect of the biomass CHP plant in Admont. Furthermore it is the first demonstration of docking an ORC plant to a biomass-fired furnace via a thermal oil cycle.

Main fuel: Wood chips

In total 40.704 m3/a mainly shavings and sawdust, as well as wood chips and briquets

Nominal capacities & efficiencies:

Thermal input, biomass & waste: 4,4 MW

Gross electrical output: 0,43 MWe

Net electrical output: 0,4 MWe

Heat output: 1,97 MJ/s

Electrical efficiency, gross: 19,1 %

Electrical efficiency, net: 17,8 %

Overall efficiency, gross: 97,8 %

Several efficiency factors refer to a thermo oil capacity of 2250 kW

How is plant controlled: The plant operation is controlled by the heat demand.

Heat backup: Two oil boilers

Heat usage: Heating and process steam

Energy usage:

The plant supplies STIA-Holzindustrie GmbH with process and space heat and the Benedictine monastery of Admont with space heat from biomass. Furthermore, the ORC process covers almost half of the electricity demand (approx. 45%) of STIA-Holzindustrie GmbH are on a renewable basis.

DH inlet temperature: 90 °C

DH return temperature: 55°C

Hours of full load that the heat storage can meet: 297

Fuel storage: The fuel storage has a size of 2,010 m3

Waste water: Approx. 0.097 m3/hour of waste water are generated amounting to a total of 800 m3/a.

Plant description:

In the wood manufacturing company STIA in Admont a new and especially for biomass CHP developed ORC technology was realised within an European demonstration project for the first time. An ecological and cost-effective operation of the process is only possible, if not only the electricity but also the heat produced by the ORC process can be utilised. The proper integration of the ORC process into the heat supply system and the installation of a flue gas condensation unit result in a maximum increase in the total efficiency of the whole process. The plant supplies STIA-Holzindustrie with process and space heat and the Benedictine monastery of Admont with space heat from biomass. Furthermore, the ORC process covers almost half of the electricity demand ( approx. 45%) of STIA-Holzindustrie on a renewable basis. Only sawdust and chemically untreated wood residuals arising in-house are fired at the plant.

The overall plant consists of two combustion units, one with a thermal oil boiler (nominal capacity 3.2 MWth) and the other with a hot-water boiler (nominal capacity 4.0 MWth). Each furnance is followed by a dust precipitator combined with a common flue gas condensation unit. The ORC plant is connected with the thermal oil boiler via a thermal oil cycle and has an electric nominal capacity of 400 kWel.

Fuel feeding system: The fuel feeding occurs mechanically.

Flue gas cleaning:

An innovative SNCR process based on glue water injection has been tested to reduce Nox emissions. For the efficient reduction of dust emissions with the flue gas a rotational particle separator, which represents a new and innovative technology, has been tested for the first time in large-scale biomass combustion plants. The rotational particle separator has a significantly lower cut-diameter than conventional multi-cyclones and therefore aims at higher dust precipitation efficiencies.

Electricity sale info: The feed in rate in Austria is regulated by law and depends on the type of biomass used and on the size of the plant.

Total capital cost: € 3,200,000

The investment costs amounted to about € 3,200,000 including monitoring and dissemination costs. The project was supported by national grants (“Austrian Kommunalkredit AG”) with € 890,000 and by the European Community with € 576,991. The rest of the project costs was financed by own capital and bank loans.

Data collected and quality assured by: Austrian Energy Agency.

Contact person: Elvira Lutter