Ørsted’s Asnæs 6 CHP plant completed

Ørsted reported that its new wood-chip-fired CHP plant, unit 6 at the Asnæs site, Kalundborg, Denmark, was connected to the grid and started producing electricity on 20 November 2019, a further step towards the 50% state owned Danish energy company’s goal of becoming coal free by 2023.

The Asnæs 6 plant (rated at 25 MWe, 129 MWt) began supplying district heating and process steam in August. Among its process steam users are Novozymes’ enzyme production facility in Kalundborg and Novo Nordisk’s insulin factory, the largest in the world.

The CHP unit also provides heat to the municipality of Kalundborg, district heating network, which is in addition connected to
a 10 MW heat pump installation (owned/ operated by municipal utility Kalundborg Forsyning) and an electric boiler on the Asnæs power station site (allowing power from wind and solar PV to be “utilised when it’s available at competitive prices”, along with “wood chips from sustainably managed forests”). This ensures that “Kalundborg’s need for process steam for industry, district heating for homes”, as well as power generation for the national grid, is “fully covered without using coal, while delivering a high reliability of supply and a high degree of flexibility”.

Ørsted says it initiated the Asnæs biomass project in 2017. Funding for construction of Asnaes 6 was made possible thanks to a 20-year agreement between Novo Nordisk, Novozymes, Kalundborg Forsyning and Ørsted.

The wood chips will be certified and sourced from wood residues from forestry producing wood for furniture and flooring. “These forests are growing forests in which new vegetation is constantly replacing the trees that are felled.”

The boiler, supplied by Valmet, is a 140 MWt HYBEX unit, employing bubbling fluidised bed (BFB) technology. Steam conditions are 50 kg/s, 100 bar and 540°C.

Valmet’s 80 million euro scope also included flue gas treatment, consisting of a baghouse filter, combustion air humidification, flue gas condensing, condensate treatment and stack.

The flue gas condensing system increases efficiency by recovering heat from water vapour in the flue gas, while combustion air humidification boosts efficiency further.

Valmet has also supplied ancillary equipment, and been responsible for all power plant buildings above ground as well as electrification and instrumentation. The facility is equipped with a plant-wide Valmet DNA automation system, which includes information management and safety related functions.

Doosan Skoda Power provided the steam turbine and was responsible for the supply of a complete machine hall.

The scope of Doosan’s 14 million euro contract included an innovative double-casing extraction turbine, plus generator, auxiliaries, and all equipment for the machine hall.

The innovative design “makes it possible to disconnect one of the two turbine casings, thereby providing a broad range of uses for the installation, which will generate electricity, supply process steam to the neighbouring pharmaceuticals plant, and also supply heat to households in the vicinity,” said Toma´s Winkler, Doosan project manager.

The conversion from coal to wood chips at Asnæs means that the remaining operable coal fired units at the site, Asnæs 2 (147 MWe) and Asnæs 5 (640 MWe), will be decommissioned. Recently, it has primarily been unit 2 in operation, with unit 5 in reserve.

Subject to approval from the Danish energy regulator (Energistyrelsen), the plan  was to shut down Asnæs 2 and Asnæs 5 on 1 February 2020, which would mean the only power generation capacity on the site will be biomass fuelled unit 6.

“Only a decade ago, oil, gas, and coal were our core business”, says Ørsted (formerly DONG (Danish Oil and Natural Gas)). “We were one of the most coal-intensive utilities in Europe with an expanding oil and gas production business. The emissions from our coal-fired combined heat and power plants accounted for one third of all Danish carbon emissions. But we decided to phase out fossil fuels and significantly expand our production of green energy. Since then, we have reduced carbon emissions by phasing out our use of fossil fuels. We have divested our oil and gas production. And since 2006, we have reduced our consumption of coal by more than 80%. We have reduced our greenhouse gas emissions by 83% since 2006, and by 2025 our power and heat production will have become essentially carbon neutral.

It means that we are 27 years ahead of schedule if we were to adhere to the requirements for emission reductions in a 2°C scenario” (see graph).

Main Image: Asnæs 6