COWI and Babcock & Wilcox Vølund Upgrade Fynen Energy from Waste Plant : IN DEPTH: Danes Breath New Life into Old Waste to Energy Plant

Originally built as a utility owned coal-fired facility, the Fynen Power Station in Denmark’s third largest city, Odense, has also housed a waste to energy plant for two decades. Now a team including COWI and Babcock & Wilcox Vølund are about to bring it up to date with improved emissions and efficiency

In 2014 Fynen Power Station was sold by Swedish firm Vattenfall to municipally owned Fjernvarme Fyn for around €80 million. Shortly afterwards the new owners began investigating the potential to extend its lifespan and increase its efficiency of the incinerator.

As it began its evaluation the firm turned to Danish engineering and environmental consultants, COWI. “Around two years ago we started to conduct an analysis of what is needed in terms of refurb spend to have it operational until 2030. In late 2015 we decided to make a refurbishment and also to add a flue gas condensation plant,” explains Niels Kirkegaard, project manager at Fjernvarme Fyn.

The boilers of lines 11 and 12 at the plant were 20 years old and that of line 13 was 16 year old. All were in need of an overall refurbishment and Fjernvarme Fyn decided to take the opportunity to make the major upgrades that would allow it to not only manage locally sourced waste, but compete in the market.

In principle, the plant could manage with one line, (line 13), which is large enough to process the waste from the owner’s municipalities. Instead they decided to invest in attracting gate fees from outside waste with an upgrade project. The work will include new Inconel-welded panel walls in the boilers, district heating-cooled wear zones at the grates, flue gas condensation, enhanced waste water treatment and rebuilding existing electrostatic precipitators of Line 11&12 to bag house filters.

The plant currently processes approximately 290,000 tonnes of waste per year and generates 26 MW electricity and 70 MW of heat for district heating. After the plant has been upgraded the capacity will be 22 MW electricity and 108 MW heating from the processing of 290,000 tonnes of waste per year. The additional heat comes from a combination of flue gas condensation, electrical generation and heat production from the expansion of the waste processing capacity by 2 tonnes of waste per hour in furnace lines 11 and 12.

The total electricity production after upgrading will reduce slightly, as steam-operated absorption heat pumps will be installed for flue gas condensation. The Flue gas condensation system including absorption heat pumps are supplied by the Swedish company Radscan Intervex AB

Project Particulars

Jens Kenneth Larsen, chief project manager for bioenergy and thermal power at COWI explains that the work entails the installation of two plants for flue gas condensation. One plant for lines 11 and 12 and one plant for line 13. These will recover heat from the flue gas by condensing its moisture content. In lines 11 and 12 the electrostatic precipitator (ESP) filters will be rebuilt and baghouse filters added to the flue gas treatment to make it more effective. Line 13 is already equipped with a baghouse filter.

“Lines 11 and 12 were built the same year and operate as a parallel line going into the same turbine so we consider them as one line,” he says. “We are also going to build a new wastewater treatment plant for the entire three lines.”

Kirkegaard adds: “We have a lot of carry over from the ESP of fly ash and that will mean that all of that will come into the wastewater treatment plant, so if we increase the efficiency of the fly ash filtration we will not have it in the wastewater treatment.”

The wastewater treatment system will be altered so that it can also treat the water condensed by the new flue gas condensation systems before it is fed into the sewer system. However, some of the treated water will be used by the city’s district heating system.

One of the reasons for the need to upgrade the filters is that the changing nature of the materials being processed by waste to energy plants also changes the nature of the fly ash they produce.

“We see in the future a great variety of waste that the ESP will have more difficulty to catch the fly ash from,” explains Kirkegaard. “More of the household waste and biomass will be sorted and recycled and not come to the incineration facility. More of the biomass will be used at biogas plants and those type of facilities, but we will have more industrial waste. That’s one of the reasons we needed to upgrade – to be more competitive.”

Niels Jakobsen, project director for bioenergy and thermal power at COWI, adds that in Denmark such effects are likely to be multiplied in coming years with the liberalisation of the waste market.

The Build

In a tender process Danish waste to energy technology supplier, Babcock & Wilcox Vølund, was awarded a contract to supply Inconel-welded panel walls, water-cooled wear zones, baffle walls and a steam-supplied air preheater. "Technologically and financially it was the most advantageous bid. We are very familiar with B&W Vølund after years of excellent collaboration. But that is not why we chose B&W Vølund. It was because they submitted the best bid," comments Kirkegaard.

One of the big difficulties in upgrading any piece of vital infrastructure is losing it as an asset for the duration of the work. In Odense, Fjernvarme Fyn is able to mitigate that in two ways. Firstly, much of the work, such as construction of the bag house and wastewater treatment facilities, is being carried out while the plant continues to operate. Building work is able to progress on components outside of the facility, and those will then be covered before becoming operational.

The work is also being carried out in two phases, with lines 11 and 12 to close for one phase and line 13 for the other, allowing the remaining capacity to process locally generated wastes. The delivery will be implemented during an eight week maintenance shutdown in the spring (lines 11 and 12) and summer (line 13) so that the waste lines are ready for the next heating season from October 2017.

“It’s not a long time that we are going to be out of operation,” says Jens Kenneth Larsen. “We will do all the tie ins and all the refurbishment in eight weeks. The establishment of the flue gas condensing plant has already been started. Once the boilers are up and running and everything is going smoothly then the flue gas condenser will be ready for a trial run. We have not arranged it so that everything has to be started at once.”

More to Come

With a number of waste to energy plants, particularly in Western Europe, beginning to show their age, and with a changing waste stream, COWI sees a growing market for similar upgrade projects. With an investment of around 250 million Danish kroner (€33 million), Fjernvarme Fyn has not only extended the life span of its facility, but given it the option to compete on the open market for waste from elsewhere.

"A few years ago we were involved in a similar upgrade of the two units (28 and 35 ton/h) at waste to energy plant I/S Vestforbrænding in Copenhagen. We have also being involved in other plants adding flue gas condensation in order to improve the efficiency of the facilities and we are expecting others to follow", concludes Jakobsen.