Copenhill - A Danish Waste to Energy Icon is Born

A new generation of waste to energy facilities is being established in Europe. One of these facilities, Copenhill, is now rising from the ground in Copenhagen - complete with ski slope and climbing wall.

Recycling Waste to Energy Markets & Policy
Copenhill WtE facility with recreational areas on the roof top Credit: ARC A new generation of waste to energy facilities is being established in Europe. One of these facilities - Copenhill - is now rising from the ground in Copenhagen. With a ski slope and climbing wall facilities, can the project change perceptions about public buildings?

By Tore Hulgaard, Lasse Tobiasen and Inger Anette Søndergaard

The Copenhill Waste to Energy (WtE) facility is being established by Amager Ressourcecenter (ARC) in the centre of Copenhagen, adjacent to ARC's existing facility and a new housing area and close to the Opera and the Queen's Palace.

ARC is an inter-municipal resource company owned by five municipalities in the Greater Copenhagen area. The company receives and processes waste from approximately 550,000 residents and 45,000 businesses and provides recycled materials, electricity and district heating to the city. The Copenhill WtE facility will be replace ARC's existing waste treatment facility, which is now over 40 years old, has high maintenance costs, moderate energy efficiency and does not meet contemporary standards for occupational health and safety.

Copenhill is a bar-raising project in several respects. For example, it will have a total net energy efficiency of more than 107%, a high potential for recycling and recovery and outstanding environmental performance. It also raises the bar by offering unique architecture with recreational facilities open to the public. Ski slopes on the roof and the highest climbing wall in the world are among the facilities planned.

Technical concept

The concept for the new facility was based on a comprehensive financial and technology review process. The final solution, both economically and with respect to the lifecycle analysis of the environmental impact.

The financial framework represents a key driver in reaching the high energy recovery and environmental performance. Investments in improved efficiency prove their value when allowed to work over a long financial planning period and with moderate demands for return on investment. The Copenhill WtE facility is financed by a loan guaranteed by the five municipalities. Also the prospect of being able to sell district heating instead of power only greatly increases the overall energy recovery and the overall economy. The investment for Copenhill is about €500 million excluding the ski slope, climbing wall, cafeteria etc.

The facility features two grate-fired 35 tonne per hour boilers supplied by Babcock and Wilcox Vølund (112 MW fired per boiler), a wet flue gas cleaning system supplied by LAB - a subsidiary of CNIM - including a flue gas condensation system with heat pumps, and finally a high efficiency 67 MWe steam turbine SST-800 from SIEMENS.

Over 100% energy efficiency

Energy recovery/optimisation is an integrated part of the Copenhill WtE facility. The main features include:

High steam parameters: 440°C/70 bar, prepared for 480°C/70 bar The boiler operates at low excess air ratio (only 6% dry O2 in the flue gas) thus yielding high boiler efficiency A front-end (hot) SCR means high deNOx rates without energy consuming steam-fed flue gas re-heaters that are necessary in systems with a tail-end SCR Low turbine back pressure through large turbine condensers Steam turbine with high isentropic efficiency and many bleeds allow for a complex and efficient water-steam cycle Cooling of flue gas to 160°C at the boiler exit Two-step flue gas condensation: first step cools the flue gas by heat exchange with the district heating return line, yielding 10 MW of extra district heating per boiler, and second step cools the flue gas down to as low as 20-30°C by using an absorption heat pump, adding another 15 MW of extra district heating per boiler. In total the flue gas condensation adds around 20 percentage points to the energy recovery Recovering heat from component cooling system, which removes heat from a large number of components.

In addition, the facility is designed to have a very high availability, which is important in relation to continuously harvesting the benefit of having high energy efficiency.

Copenhill construction site, June 2014

The turbine has a controlled extraction supplying steam to a heat pump system – which drives the flue gas condensation. And finally, a full turbine bypass system is implemented, thus allowing for very high heat sales in periods with low power prices, or with high heating demands.

The resulting main modes of possible operation are:Normal operation with combined heat and power, including direct flue gas condensation; Flue gas condensation boosting using approximately 30 MW from heat pumps; Complete turbine bypass operation with heat pumps in operation.

In addition to multiple ski slopes, the facility will feature the world's tallest climbing wall  Credit: BIG Environmental performance

The flue gas cleaning concept includes an SCR system for NOx abatement, a wet scrubbing system and flue gas condensation. This was deemed attractive because of its high flexibility with respect to the very tough environmental requirements, its robustness towards relatively high raw gas pollutant loads, the environmentally friendly nature of consumables (limestone instead of burnt lime, in particular), its relatively low raw materials consumption, the limited amount of solid residues, high energy recovery, the possibility of recycling water generated from condensation, and low net present value over the planning period compared with other options despite the relatively high initial investment.

The deNOx concept is a front end low dust SCR system with a three layer catalyst located downstream a high-temperature electrostatic precipitator operating at around 270°C, which in turn requires the boiler economiser to be located downstream the SCR system.

In this system there is no need for flue gas reheating and associated systems, which are draw-backs of conventional tail-end solutions. The catalyst also destroys dioxins and furans. The tax on NOx emissions facilitated the choice of the highly efficient SCR system over the conventional SNCR system.

In the first stage of the four-stage wet scrubbing system HCl, HF are removed, as well as most of the heavy metals which have not been completely captured by the ESP. Sulfur dioxide is removed in the second-stage limestone scrubber - two-stage flue gas condensation not only ensures heat recovery, but also provides two-stage polishing of the flue gas including an additional dioxin and mercury removal stage through injection of activated carbon. The outstanding efficiency of the flue gas treatment system hardly leaves any trace of pollutants in the flue gas when emitted to the air.

The flue gas condensation also removes water vapour and turns it into a valuable source of water for the entire facility, as well as for potential purposes outside the plant such as make-up water to cover the water loss of Copenhagen's district heating network.

Thanks to the highly effective emissions scrubbing technology, almost no trace of pollutants will be emitted to the air Credit:Big

Because treated wastewater and excess condensate is discharged to the adjacent sea (Øresund), its treatment must comply with very strict requirements for discharge. These requirements surpass the EU directive requirements for most heavy metals by a factor of 10 or more and even surpass drinking water requirements on several parameters.

The wastewater discharge therefore represents a mass flow of pollutants that is insignificant to the environment. Process wastewater is treated in a conventional precipitation system, supplemented by a fine treatment with sand filters, carbon filters and ion exchangers and an ammonia stripper that recycles liberated ammonia to the furnace. Condensate is treated in its own system including reverse osmosis (RO) to produce very clean water that is virtually free of salt and pollutants.

'True recycling' is more than 50%

Optimal resource management is a key topic in waste management. At the Copenhill WtE facility the incineration process provides the opportunity for material recycling through recovery of resources that would not otherwise be recycled.

Metal segregation from bottom ash is expected to reach more than 90% of the potential for most ferrous and non-ferrous metals when modern techniques are deployed.

Few other metal segregation systems for municipal solid waste management reach a similar efficiency. The recovered metals are sold at high prices to replace virgin materials.

Bottom ash will be used for road construction and similar construction purposes under strict requirements for heavy metal content and leaching behaviour. Thereby the bottom ash in Denmark can replace natural resources of similar nature, i.e. sand and gravel.

The water contained in the waste is recovered in the flue gas condensation stage and is foreseen to replace other water resources, e.g. for covering the losses of the district heating network.

Conclusion

According to current EU definitions of 'recycling' none of these activities are considered recycling as the WtE facility as such is defined as a 'recovery' operation from which no official 'recycling' is possible (as far as Ramboll understands common interpretations of these matters).

This illustrates that EU and government recycling targets based on calculated recycling rates according to the present definitions give little information on the true resource recycling amounts, let alone the true resource value in the local context.

Tore Hulgaard is the technical manager, Lasse Tobiasen the chief consultant and Anette Søndergaard is head of the WtE department at Ramboll.

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Meet the architect

Back in 2010 Danish architecture firm BIG-Bjarke Ingels Group (BIG) won an international architectural competition for ARC's new waste to energy facility. The design it proposed was an ambitious idea with the goal of creating a facility which, in addition to electricity and district heating, will provide recreational facilities to the citizens of Copenhagen.

Since then ARC and BIG have worked intensively on realising this idea together with among other some of the best ski facility designers in the world. The design of the building has been optimised to meet both the requirements from the process equipment and the recreational project.

As of July 2014 the status is that the idea has come very close to realisation. The project will include four ski slopes - two for beginners, one for intermediates and on the main roof a black slope with practically the same characteristics as an Olympic super half-pipe in terms of length and steepness.

The renowned ski-slope designers International Alpine Design and Scandinavian Shaper (the latter responsible for the ski-cross slopes during the last four Olympic games) will ensure the best possible experience for the coming users.

On the facade the highest climbing in the world is planed to be established, inspired by some of the best climbing passes from the most challenging mountains in the world.

On the rooftop boulders (climbing sculptures) will be integrated into the green landscape and on the top - 85 metres above the ground - a cafeteria will cater visitors, who can also enjoy the marvelous view of the city skyline. The budget for the recreational project is around €10 million.

In a recent interview the Architect himself, Bjarke Ingels, said that he hoped the ski slope on the roof would provide a breeding ground for future Danish Winter Olympians. He also said that the plant would “transform people's perceptions” about public utility buildings.

“We don't just answer one question. We try to actively find more questions to answer – more problems to solve,” said Ingels.