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– its new bioplant generates heat for almost 100,000 people

Together with the City of Espoo, Espoo-based energy company Fortum is committed to making district heating production carbon-neutral in Espoo, Kauniainen and Kirkkonummi by 2025. The new bio-heating facility built in Kivenlahti, Espoo,Finland, is a big step towards the goal: it replaced one of the two coal-fired units in the Suomenoja power plant. The replaced coal unit was permanently decommissioned in spring 2020.

“The new bioplant in Kivenlahti is a significant part of our Espoo Clean Heat program, where we replace fossil energy sources with smart and flexible solutions, including bioenergy, utilization of waste heat, and geothermal energy,” states Olli Heinonen, Fortum’s project manager.

The Kivenlahti bioplant is the largest plant supplied by KPA Unicon Oy to date. The Unicon Renefluid fluidized bed boiler has a fuel output of about 49 megawatts, but due to a flue gas condenser and heat pump technology, the plant can produce up to 58 megawatts of heat for the grid at best. On an annual basis, that means about 350 gigawatt hours, which is enough heat for nearly 100,000 people.

“According to our calculations, the new plant will increase the share of energy produced from biomass in the Espoo district heating network by about 60 percent. The carbon dioxide emissions will decrease by about 90,000 tons per year. For us, this project proved our ability to supply plants of this size, and it opened up a whole new market,” says Ilkka Linnas, project manager of KPA Unicon.

Citizens as neighbors

The Kivenlahti bioplant is located very close to a residential area, which is why special attention was paid to curbing plant noise, environmental impacts and local emissions.

“We have had an active dialogue with the City. In addition, we carried out noise modeling, and the noise has also been minimized with technical solutions and equipment placement. KPA Unicon has designed the layout of the plant and, for example, the air intakes, in such a way that the noise and sounds are directed away from the neighborhood,” says Heinonen.

The plant produces district heat from wood-based biomass, which consists mainly of fractions unsuitable for industry: forest residue chips and clean recycled wood. Energy sources come from the capital area and its surroundings. This will significantly reduce the supply of imported fossil fuels.

On average, 32 trucks—about half of which are fuel transports to the new plant—visit the plant site every day. In addition to the new biomass boiler plant, there are also two pellet-fired boilers at the plant site. According to Heinonen, transports are not made during the weekend.

“The new plant has two silos, and when the plant operates at full capacity, the two full silos can fuel the plant for about 2.5–3 days, depending on the quality of the fuel. Fuel transports are generally carried out on weekdays from 6 am to 10 pm.”

The best technologies in use

The plant is run all year round, which adds up to about 8,000 hours a year. The plant has all the best technologies in place, and its efficiency is very good.

“For example, a flue gas condenser has a heat pump connection that covers heat from the condensate that goes into the sewer. We get almost one megawatt more of district heating power from it. The plant itself is heated with condenser heat, so there´s no need to use district heat for that,” says Linnas.

The boiler plant is also equipped with a combustion air humidifier, which helps to increase the efficiency of the flue gas condenser.

The return water is heated with bottom ash, which provides another 0.5 megawatts of energy to be utilized.

“We have also paid special attention to the consumption of clean water. The condensate generated from the boiler is used as additional water for district heating, which decreases the use of raw water.”

Similarly, the plant’s dust, nitrogen oxide and sulphur dioxide emissions have been managed using the most advanced technologies in the industry, which ensure local emissions that are significantly lower than the regulations and recommendations of the authorities.

“The customer wanted to prepare for the tightening emission limits, so the plant was equipped with a special SNCR system that can minimize the nitrogen oxides in the flue gases. The system has not been implemented yet, as the emissions remain well under current limit values with the contemporary energy sources,” says Linnas.

In the future, the plant operation, maintenance and annual maintenance break will be carried out by a partner that Fortum has selected through publicly requested bids.

“Typically, plants are maintained in mid-summer, but since this plant’s maintenance is adapted to our whole production structure, the annual maintenance is scheduled for early summer or fall. In summer, this plant will improve the base load of district heating,” says Heinonen.

A shared story

The customer’s role in the project was significant: the plant was built on a relatively small plot in a challenging location, and the construction required close cooperation with the City of Espoo, for example regarding the building permit. Other partners were also involved in the large project.

“The customer took care of the foundations and the fuel handling; we took care of the overall delivery of the plant together with our partners, such as Ehox Tuote, Laitex and Kyrön Sähkö,” says Linnas.

He goes on to say, “Ehox Tuote Oy has been involved in dimensioning the plant’s efficiency and also has played a significant role in the plant’s commissioning. Laitex Oy manufactured the fuel supply equipment and bottom ash transfer systems, and Kyrön Sähkö performed electrical and instrumentation installations. Yes, this is our shared story.”

Fact box:

Kivenlahti bioplant, Espoo, Finland

Customer: Fortum PLC
Plant: Unicon Renefluid
Commissioning: 06/2020
Fuel output: 49 MW
Total output: 58 MW
Flue gas processing: flue gas condenser
Fuels: forest residue chips and clean recycled wood