District heating plant will be connected to hydrogen production in Tampere

The Tarastenjärvi power plant already produces heat and electricity from the mixed waste of Pirkanmaa residents. The aim is that from 2026, the plant's flue gases will be directed to a Ren-Gas plant on a neighbouring site, where carbon dioxide will be recovered from the flue gases. In the same Ren-Gas plant, hydrogen will be produced electrolytically from water using wind power. Hydrogen is combined with carbon dioxide in the plant to produce methane, the fuel of which natural gas is almost entirely composed, in an environmentally friendly way. The methane can be further processed and liquefied to fuel heavy transport.

Half of the electrical energy used is converted into heat in electrolysers. Here, the waste heat can be recovered and returned to Tammervoima, which uses it to produce district heat.

"This substantially improves profitability," says Jukka Joronen, Director of Tampereen Energia.

The district heating company benefits

Tampereen Energia is a company owned by the City of Tampere. The company’s main task is to heat the city.

"We are interested in all heat energy that can be obtained cost-effectively and environmentally friendly."

Tampereen Energia has strict environmental targets, which have come from both the owner and its customers. Heating must be fully carbon neutral by 2030.

The partnership with Ren-Gas is part of the effort to achieve these targets. The Tarastenjärvi project is currently progressing on schedule. Preliminary studies have been carried out, and contracts will be signed this year. The environmental impact assessment process for the plant has been completed, and the environmental permit process has started. A final investment decision should be taken early next year if everything progresses as smoothly as it has so far.

"It now looks as if Tampereen Energia's carbon neutrality target will be achieved perhaps even a little ahead of schedule. In 2027, only about 3% of our heating would be provided by fossil fuels, which would only be used during winter peak periods," says Joronen.

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Jukka Joronen, Director of Tampereen Energia. Credit: Tampereen Energia

Carbon capture technology is ready to go

Before the flue gas from the thermal power plant is delivered to Ren-Gas, Tammervoima has already done a lot of processing on the gas side.

"At the Tarastenjärvi plant, the combustion boiler takes up only a small part of the power plant's space, and a large part is used to clean the flue gas to meet environmental requirements. It is a large-scale and multi-stage process," says Joronen.

To transfer the treated flue gas from Tammervoima to Ren-Gas, a suitable point in the flue gas pipeline is identified where the flue gas is of the right quality and where the flue gas can be injected before the chimney without disturbing the plant's operation.

The flue gas is then transported by pipeline a few tens of metres to a neighbouring property, where Ren-Gas separates the carbon dioxide from the flue gas using equipment purchased by Ren-Gas. Carbon dioxide capture has never been carried out on this scale in Finland. However, according to Mr Joronen, the technology has been used elsewhere for a long time, so the principle of operation can be trusted.

Several different carbon dioxide capture methods are available, and more are being developed. Still, the most common at present is the chemical absorption of flue gas carbon dioxide into a liquid: the chosen chemical captures, or absorbs, the carbon dioxide from the flue gases after combustion. This is done by bringing the upward flow of flue gas into contact with the downward flow of liquid solvent.

In the process, the carbon dioxide and the chemical used are subsequently separated, resulting in pure carbon dioxide and allowing the absorption barrier to be used repeatedly. After treatment, the flue gas is almost entirely devoid of carbon dioxide and is discharged through a chimney to the sky.

Careful planning for district heat recovery

Ren-Gas will have its own pumps and heat exchangers to recover waste heat, after which the water heated by the electrolysis will be combined with the water flow from Tammervoima. A suitable connection will be built for this connection, which could, for example, be an expansion tank. This avoids pressure surges or other sudden changes. This ensures a steady flow of district heat, even if the hydrogen production fluctuates.

"We do careful engineering to ensure reliability in all up and down situations," says Joronen.

Similar projects elsewhere

Ren-Gas has similar projects underway elsewhere. In addition to Tampere, it has announced four other plant plans - Lahti, Kotka, Mikkeli, and Pori - with a total methane capacity of 300 MW. Tampere accounts for 60 MW of this.

Ren-Gas aims to build a production network in Finland capable of producing around 20% of the fuel used by heavy transport and 8% of Finland's district heating needs by 2030. Ren-Gas projects will reduce Finland's greenhouse gas emissions by more than 1.5 million tonnes per year.

Join us on the BotH2nia goes Pirkanmaa Field Tour on 19 September 2023 to learn more about the Tammervoima power plant and the cooperation plans between Tampereen Energia and Nordic Ren-Gas. Programme, further information and registration at https://www.both2nia.com/en/events/future-events/both2nia-goes-pirkanmaa