Modernising to meet emissions standards


he 1980s vintage Rauhalahti power plant in Finland was recently modernised by Andritz so that it will be ready to meet more stringent emissions standards to be enacted in 2020. In addition, upgrades to certain boiler subsystems will extend the lifetime of the boiler.

Jyväskylä Energy Group (JEG) is the electricity, water and district heat provider for the city of Jyväskylä (about 270 km North and slightly East of Helsinki). The Group employs about 250 people. Electricity generation began in 1902 and district heating with wood chips was introduced in 1960. JEG has two power plants, the Rauhalahti plant being the older of the two.

In the Jyväskylä area, the building volume utilising district heating is about 27 million cu m. This represents about 4,600 customers. The network is about 435 km long and represents about 1,024 GWh of energy production. The Rauhalahti plant, which produces 85 MWe and 210 MWt, was commissioned in 1986. Keljonlahti, which is the larger of the two combined heat and power (CHP) plants at 495 MW, was inaugurated in 2010. “Our commitment to the environment is firm,” said Teemu Rönkkä, Vice-President of Energy Production. “We try to produce as much energy as possible with wood and peat sourced locally. In Finland, about 10% of electricity production is from renewable fuels. Here at JEG, the percentage is about 36%. Plus, 100% of the ash from our power plants is used as forest fertiliser or earthworks.”

Reducing particulates Markku Ylitalo, Production Manager, explained: “Our Rauhalahti plant uses peat,

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forest fuels (logging residue and stumps) and mill by-products such as sawdust and bark. A small amount of oil is needed for start-up and we have the capability to burn coal if there is a shortage of other fuels”. Rauhalahti’s boiler was originally designed to burn pulverised peat, but was converted to BFB technology in 1993. “In the late 1990s, we began adding forest fuels to the mix,” said Ylitalo. “Today, we burn a 50/50 mix of biomass and peat, all sourced domestically.” JEG’s volume of energy production increased significantly with the commissioning of the Keljonlahti plant in 2010, but emissions per megawatt hour (NOx, SO2, and dust/particulates) have fallen steadily. Still, there is a new Industrial Emissions Directive (IED) from the EU that will require Rauhalahti to lower its emissions by 2020.

“The new IED was the driver for our investment project,”

confirmed Ylitalo, “but we also wanted to take the opportunity to extend the life of the boiler”. In February, 2014, the Board approved an investment of 30 million Euros to upgrade the boiler at Rauhalahti. “With this investment, we will not only meet the new IED limits for SO2 and flue gas dust content, but also extend the boiler’s productive life to at least 2030,” added Ylitalo.

“This was a rather large investment for a small energy company,” Rönkkä said. “So we wanted to make sure we were getting the best, proven solution.”

JEG worked with experts from Fortum to do some test burns in order to analyse the chemical composition of the flue gas and the ash to be able to discuss in detail possible

Outside view of Rauhalahti showing the flue gas condenser building.

Water recirculation pump for flue gas condensing system.

technical solutions from potential suppliers.

Power plant services Kalle Aro, Product Manager for Andritz’s power plant services group, was part of the team that developed the technical solution for Rauhalahti and was then Commissioning Manager when the contract was awarded to Andritz in March, 2014. “To control dust emissions, we

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