Power Engineering International

Building the next generation of energy-from-waste facilities

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An increase in municipal solid waste and advancements in sustainable recycling have led to a growing need for energy-from-waste plants. Paul Gouland explores the challenges of delivering the next generation of large-scale projects

Backed by increased investment under the Public Private Partnership/Public Finance Initiative regime, the UK’s energy-from-waste (EfW) capacity has grown considerably over the past decade, consuming around
12 mtpa of waste annually and generating some 5.57 TWh of electricity per annum, according to a report from Tolvik Consulting.

And with 27 million tonnes of municipal solid waste and 47 million tonnes of waste from businesses produced every year, there is huge potential for growth and further investment in the UK waste-to-energy sector in years to come.

Despite such significant growth, the UK still falls behind the rest of Europe when it comes to EfW. Across the European continent, there are currently 430 operational plants providing sufficient energy to power seven million homes.

Although questions have been raised about future capacity requirements – with Suez recently predicting a 14 million tonne shortfall in processing capability (contrary to a Eunomia report suggesting oversupply in EfW) – a predicted annual residual waste output of
6.8 million tonnes between 2017 and 2025 suggests there remains a strong case for waste-to-energy facilities.

Conventional EfW technology is now well established across the UK and Europe. However, as the processes involved with converting waste to energy continue to evolve, so do the facilities in which they are housed. In recent years, EfW plants have undergone a fundamental shift towards smarter, automated and more efficient working environments.

Constructing the new breed of EfW projects in the UK and Europe brings its own unique set of challenges. Today’s modern facilities not only house a surplus of pioneering technology, from advanced turbines to automated material processing equipment and combustion apparatus, but also present several trials when it comes to their design.

Increasingly EfW plants are moving away from the traditional ‘square box’ designs and implementing modern architecture to build eye-catching facilities, which better depict the modern hi-tech facilities they house. This is especially the case when facilities are located within close proximity of residential areas, such as the UK and Europe’s highly-populated cities.

Whilst the advent of such modern facilities presents considerable benefits for the UK’s energy infrastructure, it also brings a number of challenges when it comes to building the next generation of plants. Modern construction companies, therefore, are adapting their building practices and techniques to meet the demands of the smart EfW plant.

One of the companies heavily involved in supporting the sector and delivering the next generation of plants is Clugston Construction. The company has established a strong track record of providing building and civil engineering services to the waste recovery and energy sector – stretching back to the company being established in 1937 when it set up an operation to recycle waste slag from the North Lincolnshire steel industries.

In more recent years the company has focused efforts on the mass burn market, working closely with French process specialists CNIM. Together, the firms have delivered a large number of major EfW plants across the UK.

The award-winning Leeds Recycling and Energy Recovery Facility (RERF) is a prime example of one such project. Awarded the Project of the Year at the National Structural Timber Awards, the innovative facility features a striking 42-metre-high arched timber frame which houses the process hall and is visible from many points of the city.

A mix of innovative and sustainable materials and techniques are incorporated throughout the construction and design, reflecting the environmental role the facility plays. The
123 metre-long and 35 metre-wide timber arch, for instance, is manufactured using Glulam laminated timber, one of the most sustainable construction materials available, whilst the building structure, in keeping with the environmental aspects, also includes a living green wall which is also believed to be the longest on any building in the UK.

Sustainability remains at the very core of the building’s structure; in fact, the construction of the site also used recycled products in its foundations. The old concrete slabs which had been covering the brownfield site were broken up and crushed for reuse, which saved importing new aggregate and disposing of the old concrete to landfill, thereby cutting out hundreds of wagon movements.

Leeds RERF is more than just a remarkable architectural feat, however, with the facility having the capacity to divert and process approximately 214,000 tonnes of waste annually. Of this waste, around 20 per cent is recycled and the remainder incinerated to generate up to 15 MW of electricity, exported to the National Grid. The facility also has the potential to capture steam from the processes and provide it to local businesses in the district.

Wheelabrator Parc Adfer EfW plant in Flintshire, North Wales, is another example of a move towards a smarter waste-to-energy facility. Once constructed, it is expected to process up to 200,000 tonnes of non-recyclable waste per year that would have otherwise be sent to landfill, and to generate up to 19 MW (gross) of electricity annually for the National Grid. It will also be capable of providing valuable steam or heat to local industry and housing when plant operations commence in 2019.

Situated next to the Shotton Paper Mill, Clugston’s building and civil works include construction of a 3300 m2 central process building, including a waste storage bunker which had to be cast in situ and a tipping hall which incorporates high speed roller shutter doors, as well as a 3722 m2 main boiler hall which incorporates bottom ash storage, flue gas treatment, turbine hall, and associated industrial waste water pit and electrical
rooms.

Waste transported to the facility will go through an initial periodic inspection to ensure only acceptable waste is treated. Any recyclable materials such as cardboard, plastic or ferrous and non-ferrous metals will be removed. Following the initial inspection, suitable waste is loaded into the energy recovery facility by overhead cranes and stored within large waste hoppers, from where it is fed into the integrated fast boiler units for combustion.

Integration of the building and process equipment has been fundamental to the construction of the facility. In order to house such advanced processing equipment, careful consideration has to be given throughout the design and build process, not only to ensure optimum performance, but also to safeguard employee safety. Clugston and CNIM utilized a range of collaborative software packages and BIM design protocols to ensure the facility not only met the requirements of Wheelabrator, but also the 30,000-plus homes to which it will supply energy.

Following the example of many plants across Europe, the objective of the UK government is to see EfW facilities connected to urban district heating networks. Although it presents countless challenges for developers in terms of planning, coordination and costs, locating EfW plants near existing or proposed heat networks, such as industrial and commercial sites, also presents countless opportunities – as demonstrated at Wheelabrator’s Kemsley plant in Kent.

The new advanced plant is designed to process up to 550,000 tonnes of residential and business waste fuel annually – which would otherwise have been sent to landfill or pre-treated and then exported to European EfW plants – generating up to 50 MW (gross) of clean, renewable energy to power UK homes and businesses. The electricity generated is then exported to the National Grid transmission network with renewable steam supplied directly to the adjacent Kemsley Paper Mill, owned and operated by DS Smith. This will help to reduce the mill’s reliance on fossil fuels, as DS Smith looks to decarbonize the production of recyclable packaging for the retail industry.

At Kemsley, Wheelabrator sought to utilize the latest advances in technology within the facility. As such, the plant will incorporate a two-line moving grate with a combined thermal combustion capacity of 100 MW.

Whilst the core elements of EfW plants are relatively consistent, the required process capacity, site constraints and local planning all impact the layout and building design. As a result, no two facilities are the same, with several eye-catching architectural and structural solutions recently being constructed.

Paul Gouland is marketing director at Clugston Construction. www.clugston.co.uk

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