Flue gas heat recovery is saving energy

Valuable energy is no longer breaking free into thin air at the Suosiola CHP plant located in Rovaniemi, known as the capital of Finnish Lapland and the official hometown of Santa Claus. The plant owned by Rovaniemen Energia Oy recently started up a flue gas cleaning system with heat recovery supplied by Valmet.

“Over the first few months, we have gained positive experiences with flue gas heat recovery: up to 22 MW more district heat production capacity in trial runs, 95% reduction in SO2 emissions and 75% reduction in dust emissions,” says Jukka Partanen, Production Director, Rovaniemen Energia. “The scrubber capacity naturally depends on the boiler’s flue gas flow and moisture, as well as the moisture contents of the fuel. In our total district heat production, the contribution of the scrubber has been 20% at best.”

According to him, the company chose Valmet based on its reputation as a well-known and reliable technology supplier. “Valmet’s solution offered the best alternative, both technically and economically. We have calculated that we will save about EUR 1.5 million per year in fuel costs with the scrubber, depending on weather conditions and boiler load.”

During a two-year development program, the plant increased its district heat production capacity from 62 megawatts (MW) to 110 MW. Of this amount, 22 MW originates in heat energy recovered from the 140˚C water vapor in flue gas using Valmet’s flue gas condensing technology.

The plant produces district heat for the city of Rovaniemi and electricity for the national grid. Wood chips and peat fuel the boiler, along with light fuel oil during startups. Heavy fuel oil is used in separate peak load boilers during peak load demand. One of the development program targets was to reduce the need for using HFO. The total investment in the flue gas scrubber and heat recovery equipment amounted to about EUR 5.9 million.

Well prepared for the Industrial Emissions Directive

In addition to improving the plant’s energy economics, the new equipment has a major impact on emissions. Earlier, an electrostatic precipitator captured the emissions.

“With the new system, we are well prepared for the Industrial Emissions Directive and will stay within the permit limits set for us with regard to SO2 and dust emissions,” points out Matti Virta, Production Engineer, Rovaniemen Energia. “Now was a good time to carry out the project, since I expect there will be a big rush when other plants start to invest in this equipment.”

Turnkey delivery on time and on budget

Valmet’s comprehensive delivery covered the flue gas scrubber, the condensate treatment system, a condensate cooler (patent pending), plant automation and a building to house them all.

“A turnkey delivery was a safe and good alternative for us. The project was on budget and on time, and quality matched our expectations,” Partanen points out. “We are especially excited about Valmet’s innovative condensate cooler with which we can utilize the heat of the cleaned condensate coming from the scrubber to warm and moisten secondary air in the power boiler and eventually use the heat to increase district heat production.”

Matti Virta wants to thank all Valmet people involved in the project: “Although there were challenges, we trusted that we had a strong supplier by our side. The project left us with a good feeling – and the hopes to see the same people in connection with another project in the future.”

Laura Kuukkanen, Product Manager, Environmental Systems, Valmet, is satisfied with the outcome, too. ”We are happy to see power plants investing in better energy efficiency and emissions control. In fact, we would like to see a flue gas condensing system after every boiler that runs on moist fuel to utilize the fuel as efficiently as possible. Today, almost all new plants in the Nordic countries are equipped with flue gas condensing.”

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