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Gasification of sorted waste reduces the consumption of fossil fuels

The Kymijärvi II plant is one of the most modern waste-to-energy CHP plants in Europe.

The gasification-based plant developed by Valmet, which operates at Lahti Energia's Kymijärvi II power plant and uses waste as the source of energy, has been in commercial use for more than 25 000 hours, producing electricity and district heat for Lahti Energia's network. This solution utilizes the gasification of sorted waste in energy production, which proves that Valmet is capable of delivering commercially working technology for the gasification of sorted waste and gas purification in an industrial scale.

Valmet's solution supports the utilization of energy produced by waste in compliance with the principles of circular economy. Accordingly, fuel is sorted and all materials applicable for recycling are separated before the utilization of fuel in energy production. The gasification technology developed by Valmet provides for a considerably high efficiency in electricity production.

The delivery of the Kymijärvi II plant was received in accordance with the delivery contract and the demonstration project was completed. Furthermore, Lahti Energia and Valmet have agreed on a long-term cooperation for further development, marketing and commercialization of gasification technology.

Environmental intelligent efficiency for energy production

The Kymijärvi II plant is one of the most modern waste-to-energy CHP plants in Europe. The harmful components contained in waste can be safely removed before the gas is utilized in a conventional power plant process. This method helps cut down on the use of fossil fuels. 140 000 tonnes of coal can be replaced by renewable fuel at the Kymijärvi II plant each year. Otherwise, this amount of coal would be used for the production of electricity and district heat in a traditional coal-fired power plant.

The electricity production capacity of the Kymijärvi II plant for the city of Lahti is 50 MW and the district heat production capacity is 90 MW. For energy production, the plant utilizes sorted waste from industry, commerce, construction and households, which amounts to 250 000 tonnes per year. This waste is converted into product gas, which is combusted in a conventional gas boiler. Before the combustion process, the gas is cleaned, which enables the high values of steam supplied to the turbine without the risk of boiler corrosion. In Lahti Energia's case, the electricity efficiency is over 30%, whereas it remains between 20% and 25% in a conventional mass burning plant. This allows for excellent steam parameters for an incinerator: 540 °C and 120 bar. Based on the development work, full electrical output can also be achieved with fuels with a clearly higher moisture content compared to those originally developed for the plant.

Positive operating experiences encourage continuing the development

The first years of operation have provided an excellent framework for improving the operation of the plant and strengthening the expertise in different parts of the process. For example, the operation of the plant was improved by introducing the regeneration of hot filters. The separation of recycling materials from ash has been enhanced, the number of plant consumables has been minimized and the operational economy has been optimized.

"The development of waste gasification technology at the Kymijärvi II plant has been one of our largest energy projects in recent years. This development work has required a great deal of effort from us and Lahti Energia. This project presented many challenges typical of new technology. However, a long and demanding development project has now reached its ending happily. The Kymijärvi II plant is an extremely important technological step forward and a reference for Valmet and the Finnish exports of technology. We would like to thank Lahti Energia for this opportunity and excellent partnership in this project," says Kai Mäenpää, Vice President, Energy Sales and Services Operations, EMEA, Valmet.

"After the completed development work, the Kymijärvi II plant operates as the base load power plant for the district heat network in Lahti. With the gasification plant, Lahti Energia is capable of utilizing different waste lots from local producers in the joint generation of district heat and electricity. As a result of the use of recycled fuel, Lahti is no longer as strongly dependent on fossil fuels and greenhouse gas emissions have decreased significantly," says Eero Seesvaara, CEO of Lahti Energia.

Gasification technology provides significant benefits

Gasification technology gives significant economic and social benefits. The portion of renewable fuel can also be increased in the existing power plants with technical service life still remaining. The combination of new and existing technology can help ensure the delivery reliability of energy in all circumstances and support the circular economy, while significantly reducing the consumption of coal and CO2 emissions.