Forssa, 100km west of Helsinki, was the first medium-sized CHP plant in Finland to be fired solely on wood-derived fuels. Today, the plant also burns municipal waste and peat with peak and stand-by steam supplies catered for by two heavy-fuel oil boilers. With an output of 17.2MWe of electricity and 48MWth heat, the Forssan plant, operating in CHP mode, is 90% efficient.
Ari Simola, plant manager, told Electrical Review that it takes 4,000 trucks a year to supply the sawdust, bark and small branches from the local logging industry that Forssa uses. “The price we pay for the fuel is dependent on its moisture content,” he said. “Wood is burnt during summer and peat in winter for this reason.” He also said that the household waste it currently burns will no longer be available when the EU’s 2005 waste directive on emissions comes into force in Finland
Built in 1996 at a cost of 1000euros per megawatt, Forssa has been a model for subsequent bio-fuelled plant although with the opening up of Nordic electricity markets the electrical output is no longer competitive. The bubbling fluidised-bed boiler, built by Foster Wheeler, is capable of burning a variety of fuels, generating steam at 22.8 kg/s, 61 bar and at 510 degreesC.
Hot corrosion, possibly due to chlorine from green chips, has been a problem and superheater tubes need to be replaced occasionally.
30% of Finland’s energy needs are met through renewable sources such as hydropower, forestry products and residues from the pulp and paper industries. The world’s largest bio-power plant is on the west coast next to the Wisaforest saw mill. Its circulating fluid bed boiler generates 240Mwe, 100MWth of process steam and 60MWth for district heating.
Today, Finland has adequate plant to meet its district heating needs but electricity demand is out stripping the country’s ability to generate or import sufficient supplies. A new 1,600MW nuclear power plant, the country’s fifth, is planned for 2010.
