Type of CHP system: BFB boiler

Plant owner: Jyväskylän Energiantuotanto Oy is owned by Fortum (60%) and Jyväskylän Energia Oy (40 %)

Commissioned: (reconstructed):1986 (1993)

Status of plant: Commercial

Contractor details:

The main boiler of Rauhalahti plant was commissioned by Tampella Power (today Kvaerner Power) in 1986. Bubbling fluidised bed boiler conversion was delivered by Tampella/Steam Service (today Kvaerner Power, Finland).

Power generation: Steam turbine

The boiler is a fluidised bed boiler with a maximum fuel input capacity of 295 MWth and maximum thermal output of 267 MW.

Main fuel: Multifuel (more biofuels and/or peat)

Rauhalahti power plant was designed for peat fuels and for coal when pulverised fuels were used. Fluidised bed boiler was installed in 1993. That is when the power plant also started to use wood fuels. The main fuels are peat, by-products from sawmills and wood chips. Also small amounts of RDF is used. The share of wood fuels was about one third in 2002. Due to the new wood fuel feeding system, the share of forest fuels, forest chips and stumps, has been increasing.

Nominal capacities & efficiencies:

Thermal input, biomass & waste: 295 MW

Total thermal input, incl. fossil fuels: 295 MW

Gross electrical output: 87 MWe

Heat output: 180 MJ/s

Electrical efficiency, gross: 29 %

Overall efficiency, gross: 88 %

Power to heat ratio: 0,48

Maximum district heat capacity is 140 MW, maximum process heat capacity is 65 MW and maximum electric output is 87 MW (generator capacity). The maximum total heat production capacity is 180 MW.

How is plant controlled: Plant is controlled by the heat demand.

Heat backup:

Jyväskylän Energiantuotanto Oy owns many oil fired boilers and one sod peat fired boiler which are connected to the district heating network. Total heat production capacity of the boilers is almost 400 MWth. Also the 65 MWth boiler (heavy fuel oil) at Rauhalahti power plant is used for peak and back-up production. Process steam for a local paper mill is produced with this boiler when the main biomass fired boiler is being shut-down for the annual revision.

Heat usage: Heating and process steam

Energy usage:

Heat is used for district heating in the city of Jyväskylä. In 2002 district heat production was 750 GWh and process steam generation was about 315 GWh. Net electricity generation was about 402 GWh. A local paper mill buys all steam needed in their processes from the Rauhalahti power plant. The mill uses around 350 GWh of steam annually. Condensing water of the paper mill and the DH return water is used for heat production through a separate heat exchanger to supply heat for a horticultural cultivation centre located next to the power plant.

District heat coverage (% of total demand in DH network): 78 %

DH inlet temperature: 75-120 °C

DH return temperature: 45-60°C

Heat storage size:A new heat storage of 10000 m3 commissioned November 2003, is located in another power plant in Jyväskylä city but it is controlled by Rauhalahti plant. Heat storage can be charged with heat produced in any of the production sites connected to the city’s district heating network, but mostly it is used by Rauhalahti plant. m3

Hours of full load that the heat storage can meet: 10 hours (30 MW/hour)

Fuel storage: The biofuels are transported  into the plant by  lorries owned by private contractors.

The wood/peat storage is cylindrical and it is discharged with a screw unloader. Its volume is 2500 m3. The capacity of the new wood fuel storage is 1100 m3. At full load the storage is sufficient for 9 hours.

Waste water: Annually 168000 m3 of waste water is produced.

Ash discharge:

The amount of ashes generated is around 20 000 tonnes per year. It is all used for landscaping the near-by field, which in future will be a park and garden area. Also some ash is used for foundation of roads.

Plant description:

The Rauhalahti plant commissioned in 1986 was originally equipped with pulverised fuel boiler. In 1993 new fluidised bed boiler retrofit was installed. The boiler conversion was carried out to enable the plant to meet the 1995 Finnish emission limits. It also has allowed multi-fuel use and eliminated flue gas odours. The boiler conversion was carried out by removing the peat drying and pulverising equipment, the peat burners and the lower part of the old boiler. A new peat feeding system, fluidised bed grate and lower part of the furnace were installed.

In addition, the superheaters were modified, because combustion place closer to the bottom of the furnace in a BFB system. To absorb the heat from the flue gas which had been used for peat drying, two existing economisers were linked in parallel to form a single unit, and an extra economiser was fitted. The wood fuel feeding system was modified in 2001.

The operation-time energy availability factor is very high, about 99 %.

In 1994, Rauhalahti power plant became the first power plant in the Nordic countries to be awarded an ISO 9002 quality certificate, which was followed by an ISO 14 001 environmental certificate in 1996, and BS 8 800 occupational health and safety certificate in 2000.

Fuel feeding system:

There are two 60 m3 a-frame boiler bins or feeding bins for peat. Fuel feed is controlled in such way that the boiler load regulates the rotation speed of the discharge screws in the bins. For wood fuels there is only a compensating bin of 5 m3, no separate feeding bin.

Boiler: BFB boiler by Kvaerner Power.

Turbine: Asea Stahl back pressure turbine.

Steam data: 110 kg/s, 533°C, 135 bar

Flue gas cleaning: Electric precipitator.

Cooling system: There is no condenser but an auxiliary heat exchanger.

Staff: The company employes a staff of approx.50 persons. About 10 man-years is used for maintenance annually.

Electricity sale info: Electricity is sold by the plant owners Fortum and Jyväskylän Energia Oy to their clients.

Total capital cost: € 84,000,000

Total costs were about € 84 million (1986).

The costs of the power plant conversion were about € 8.4 million (1993). The investment costs of the new wood fuel feeding system were € 3 million (in 2001).

Data collected and quality assured by: VTT Processes.

Contact person: Kati Veijonen