Top Plant: Kaukaan Voima Oy Biomass-Fired Power Plant, Lappeenranta, Finland

Owner/operator: Pohjolan Voima Oy, Lappeenrannan Energia, and UPM Kymmene Corp.

Located in the heavily forested country of Finland, the Kaukaan Voima biomass-fueled power plant produces process steam and electricity for UPM’s Kaukas pulp and paper mill as well as electricity and district heating for Lappeenrannan Energia, a city-owned power company. Launched in 2009, the plant can provide 125 MW of electricity, 110 MWth of district heat, and 150 MWth of process steam thanks to one of the world’s largest wood-fired fluidized bed boilers.

Finland is a diverse country whose sophisticated capital of Helsinki is counterbalanced by large areas of forested wilderness. The country has a population of approximately 5,250,275 (July 2010 estimate) and has been a member of the European Union since 1995. During the past 50 years, the Finns have made a remarkable transformation from a farm/forest economy to a diversified modern industrial economy, with a per capita income that is now among the highest in Western Europe.

According to estimates by the U.S. Central Intelligence Agency (CIA) for 2008, Finnish electricity production was approximately 77.44 billion kWh, consumption was about 87.25 billion kWh, electricity exported totaled 3.335 billion kWh, and imports were about 16.11 billion kWh. To maintain its strong economy, Finland needs reliable, affordable electricity that preferably is generated using local fuel sources.

To help meet the country’s energy needs, Pohjolan Voima Oy (PVO, an energy and heat distribution company), Lappeenrannan Energia (a city-owned power company), and UPM Kymmene Corp. (a forest products company) formed a joint venture and recently built the Kaukaan Voima Oy Power Plant, which uses wood products as a fuel source. It is located near the city of Lappeenranta in southeastern Finland, on the border between the European Union and Russia. The new plant replaces the old Mertaniemi natural gas power plant.

The Kaukaan Voima power plant produces process steam and electricity for the UPM Kaukas paper and pulp mill, and electricity and district heating for Lappeenrannan Energia. The plant is connected to UPM’s steam pipeline network and helps ensure a sufficient supply of steam at the mill site. The power plant supplies about 85% of the total district heating consumed by residents and businesses in the city of Lappeenranta.

The Plant’s Financial Background

Jukka Kiuru, managing director and plant manager of the Kaukaan Voima Oy Power Plant, told POWER that the final cost to build the plant was €232 million (US$323 million), which was less than the €244 million that was originally budgeted for the project.

Similar to PVO, the Kaukaan Voima power plant operates on an “at-cost” basis, where the shareholders bear the operating costs, according to Kiuru. This operating model is also known as the “Mankala principle.” PVO owns 54% of the bioenergy plant and consequently has a controlling interest in it.

Plant Operations Details

In August 2009, trial production began at the biomass-fired power plant and commercial operations commenced in November 2009. The electrical capacity is 125 MW, and the plant produces around 500 GWh/year with fuel from wood bark, stumps, logging waste, and other wood-based fuels, as well as peat. Natural gas and light fuel oil are used for backup and start-up.

“The facility has been built to use quite conservative technology, according to a Finnish point of view,” Kiuru said. “All of the machines are best available technology.”

The turbine, manufactured by Siemens AG, can deliver a maximum of 110 MWth of district heat to the city of Lappeenranta (around 600 GWh/year) and 152 MWth of process steam to UPM’s mills (around 650 GWh/year).

Kaukaan Voima Oy has a contract with UPM’s Kaukas mill for the power plant’s maintenance. Under the agreement, the same workers who take care of the Kaukas mill also handle maintenance work at the bioenergy power plant. The Kaukaan Voima plant results in approximately 30 staffers from the Kaukas mill being directly employed. In addition, the power plant provides approximately 200 to 400 indirect jobs in the Lappeenranta area, including but not limited to truck drivers, loggers, and maintenance service workers.

The facility did not face any challenges as far as grid interconnectivity because the new plant was able to connect to the Kaukas mill’s grid, Kiuru said. He explained that the Kaukaan Voima power plant purchased its own transformers, which were later connected to the Kaukas electrical grid. In order to supply the roughly 85% of all district heating consumed by the city of Lappeenranta, the power plant had to construct a 1-kilometer-long connection pipeline to the city.

Controlling Air Emissions

“The Kaukaan Voima plant is an extension of PVO’s bioenergy program aimed at the reduction of CO2 emissions in energy production, as well as increasing the use of renewable fuels through utilization of locally available bioenergy sources,” said Kiuru.

Environmental technologies used at the power plant include:

  • Two separate electrostatic precipitators
  • Ammonia spraying technology
  • A lime-feeding facility
  • Continuous emission monitoring equipment

“We don’t have any plans to make additional investments in our air emission handling system,” Kiuru said. “But, of course, the improvement of plant operations (combustion, fuel quality, and the like) will continue into the future.”

Using Biomass in the Plant’s CFB Boilers

“The Kaukas pulp and paper mill is the biggest wood user in Finland,” said Kiuru. “The mill uses about 5 million cubic meters (m3) of wood a year. This means about 500,000 m3 of by-products (bark and wood pieces) stream to the Kaukaan Voima plant by conveyers (Figure 1). This decreases wood-based fuel transportation by truck and creates a competitive advantage for Kaukaan Voima. The Kaukas mill is also a big steam consumer, and our boiler can run at a good efficiency level.”

1. From forest to fuel. The wood-handling system was supplied by Raumaster Oy (a Finnish company). A new 2-km-long fuel-handling conveyor starts at the Kaukas pulp and paper mill site and goes to the Kaukaan Voima Power Plant. The new power plant will be soon be the biggest biofuel user in Finland. Courtesy: PVO

The plant’s fuel supplier is Raumaster Oy. Fuel sources used by the Kaukaan Voima plant are as follows:

  • 40% biomass from the Kaukas mill (mainly bark and wood pieces from wood handling)
  • 20% bark and wood pieces from other forest industry plants (within a 100-km radius)
  • 20% stumps, branches, and logging refuse from the forest (within a 100-km radius)
  • 20% peat from within a 50-km radius
  • ~1% natural gas for start-up and support

In addition, the power plant uses fuel ash as a fuel source.

The facility has been set up with the following locations to handle and process the wood products:

  • Separate stations for receiving peat and biofuel
  • Approximately 10,000 m3 of covered storage space for biofuel
  • A storage silo (5,000 m3) for peat
  • A wood stump and twig crushing plant

Typically, biomass fuels such as wood products are more difficult to use than conventional fuels like coal and peat. Fuel quality varies, moisture can be high, and fuel handling and feeding are more demanding. As a result of such fuel-handling challenges, the most common technologies for industrial combustion of solid biomass fuels are bubbling fluidized bed boilers, circulating fluidized bed (CFB) boilers, and grate-fired boilers. Unfortunately, biomass-fired CFB boilers often suffer from ash-related problems and bed agglomeration.

The Kaukaan Voima plant uses a large-scale, 125-MWe (385 MWth) CFB boiler island manufactured by Foster Wheeler; it is one of the largest biomass-fired CFB boilers in the world. The boiler runs at 149 kg/s, 115 bar, and 550C. In addition, the boiler uses an INTREX superheater that has been specifically designed to deal effectively with erosion and corrosion problems. The use of this superheater allows the boiler to better handle the firing of more challenging fuels with high corrosion potential, such as wood fuels.

Promoting Biodiversity

UPM, one of the joint owners of the power plant, has developed a global biodiversity program—involving Finland, the UK, Canada, and the U.S.—that aims to maintain and increase natural biodiversity on UPM forest land and to promote best practices in forestry and wood sourcing. UPM’s biodiversity program focuses on six key elements for biodiversity: native tree species, deadwood, valuable habitats, forest structure, water, and natural forests. The program is implemented through country-level targets and action plans.

UPM’s biodiversity program is regarded as very innovative and was showcased at the United Nations’ 10th meeting of the Conference of the Parties to the Convention on Biological Diversity, known as COP 10, in Nagoya, Japan, in October.

“Our operations are based on the sustainable utilization of woody biomass. This means that biodiversity is our business.” said Robert Taylor, environmental director, engineered materials and functions at UPM.

Angela Neville, JD, is senior editor of POWER.

More Stories You Might Like