recovered from demolitions contain chem-icals from paints and other contaminants that can damage the burners so the staff is monitoring the boilers closely and increas-ing this kind of fuel gradually. At the time of the visit, 45 per cent of the fuel used was recovered wood. Igelsta is Sweden’s largest bio-fuelled CHP plant and is located in Södertälje, about 30 kilometres from Stockholm. Fired up in 2010, it produces 200MW of heat and 85 MW of electricity. The majority of the fuel burned at Ig-lesta is shipped to the plant by boat (about 500,000 tonnes) and arrives at the small port onsite. The port handles around 200 ships a year from Sweden and other parts of Europe. Fuel from nearby forest operations arrives by rail and is then trucked the short distance (15 kilometres) to the CHP plant. The company has placed strict require-ments on its fuel suppliers, taking samples from every load delivered. Quality checks are based on a fuel specification, which has been agreed upon by Söderenergi and the supplier. Random samples are taken me-chanically from various places in the load in order to obtain a representative result. Monthly samples are collected for each sup-plier and sent for analysis to an accredited laboratory. The company uses a data sys-tem, Safirs, to monitor the fuel quality and economy. It provides information on the fuel flow from supplier to combustion with data on fuel consumption and analysis results through a weighing system. Once on site, the fuel is stored in large silos at the back of the property. The wood chips or industrial waste pellets travel from the silos to the boiler on a system of con-veyor belts that feed the boiler. The boiler heats water to produce steam, which turns a turbine to power a generator that produc-es electricity. This electricity is fed into the power grid, while the surplus heat from the process is used in the district heating net-work for homes and industries (about 70 per cent). Heat, in the form of hot water at around 120 degrees Celsius, is pumped through underground pipes to a network of buildings where it supplies heat and hot water. Once these homes have been heated, the water is returned to the source where it is reheated to begin the process anew. The district heating network Igelsta supplies is 450 kilometres long. SUSTAINABLE FUTURE IN SIGHT District heating and co-generation facil-ities like the Igelsta CHP plant are part of the Swedish shift to a more sustainable and cleaner future. The shift began in the 1970s when residents became concerned with the levels of smog and acidification of the coun-try’s lakes and forests. District heating meant a shift from inefficient stoves in every home to a shared heat source run by professionals that would include sophisticated cleaning equipment to ensure the chimney plumes release steam rather than dirty smoke. The chimneys in both the Igelsta DH plant and the CHP plant contain fully equipped laboratories. Though the smoke may look hazardous as it flows from the chimneys, the exhaust is constantly moni-tored to ensure it is clean air and steam. The white smoke is the hot water in the flue gas, which forms droplets in the air. No matter which fuel is used to power the turbines, the proportion of contaminants in the steam is very small. 18 BiomassAdOutlines -02 07-2014.indd 1 Canadian BIOMASS JULY/AUGUST 2014 7/15/2014 10:06:27 AM
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