The UK’s largest energy from waste facility is taking shape on the banks of the River Thames in north Kent. Martin Cooper reports.
The need to find alternative waste disposal methods is one of the main challenges facing local authorities throughout the UK. Coupled with the need for greener or renewable sources of fuel, a number of energy from waste plants are currently in the planning stage up and down the country.
One such facility in Belvedere, Kent has already secured planning permission and funding, and is rapidly taking shape on the southern bank of the River Thames. To be operated by Cory Environmental, it is expected to be the UK’s largest energy from waste plant when it goes online in 2011.
Located on the site of a former borax works, it will process more than 585,000t of municipal and commercial waste per year, and provide 66MW of electricity to the local grid.
To be operated by Cory Environmental, it is expected to be the UK’s largest energy from waste plant when it goes online in 2011.
A new jetty is being constructed as part of the scheme, and this will allow most of the waste to be delivered by barge, removing the need for 100,000 truck movements a year on local roads.
As the bulk of the waste will be sourced from four central London boroughs it is also envisaged that the facility will make a real contribution to the Capital’s ability to meet its landfill diversion targets.
The environment and sustainability have played key roles in the design of the project as well as the future plans for the facility. Riverside will be the first plant in Europe designed to reach at least a net electrical efficiency of 27%. The plant is expected to exceed this limit by reusing heat produced during the electricity generating process.
The site is located in an area earmarked for future development, and with this in mind the water-steam cycle of the plant has been designed for possible off-take of heat supply for approximately 60,000 local homes.
“The ground conditions are very poor as we are so close to the river.”
Nick Lowe, Costain
Main process contractor for the project is Swiss-based Von Roll Inova, a company with experience in similar projects around the globe. Design and build sub-contractor is Costain.
Work started on site in July 2008 with a major groundworks programme involving the installation of more than 2,400 continuous flight auger piles, the majority of which are more than 25m long.
“The ground conditions are very poor as we are so close to the river,” explains Costain steelwork and cladding agent Nick Lowe. “We had five piling rigs on site at one time to complete the foundation programme before Christmas 2008.”
Rough guide to what goes on inside the riverside facility
Waste from the jetty (and approximately 15% by road) will be deposited into the waste bunker before cranes then feed it into hoppers for processing via three process trains. Each train has a fourpass steam generator.
Electricity is generated from the produced steam and the waste is reduced in volume, by burnout, by up to 90%. A by-product - bottom ash - is collected for reuse in the construction industry.
The remainder of the process involves cooling and cleaning the resultant gases prior to discharge, via the plant’s flues.
Waste receiving and storage
- 1 Tipping hall
- 2 Waste bunker
- 3 Waste crane
Combustion and steam generator
- 4 Feed hopper
- 5 Incineration grate
- 6 Primary air intake
- 7 Auxiliary burner
- 8 Steam generator
- 9 Recirculation fan
Flue gas cleaning
- 10 Turbosorp reactor
- 11 Fabric filter
- 12 Induced draft fan
- 13 Silencer
- 14 Heat exchanger
- 15 Stack
Consumables and residues
- 16 Bottom ash bunker
- 17 Bottom ash crane
- 18 Bottom ash loading station
Construction of the main building began towards the end of last year. It is a massive structure and covers an area of over 13,000m², with a curved roof rising to a height of 55m. Most of the main frame of the building is structural steelwork.
This will eventually include more than 2,000t of steel, with a similar amount of steelwork being installed by another subcontractor, for internal supports and walkways.
The substructure and parts of the superstructure are constructed with more than 25,000m³ of concrete. One of the most critical parts of the project so far has been slip forming the waste bunker, which involved placing 4,000m³ of concrete during a three week 24 hour a day programme. Two of the largest concrete pumps in the UK carried out this operation.
One of the most critical parts of the project so far has been slip forming the waste bunker, which involved placing 4,000m³ of concrete during a three week 24 hour a day programme.
This large concrete box is approximately 60m long by 30m wide by 30m tall, and is partially sunk into the ground slab. It is where trucks will deposit waste for the initial process within the facility. An adjacent tipping hall will allow up to 12 trucks to tip waste into the bunker via chutes cast into the slip formed wall.
“The key to this project is integration,” explains Bourne Off-Site Solutions divisional director Nick Hayes. “We, as well as all the other subcontractors, are working around each other.
In some areas steelwork is being erected first, but in other sectors the equipment is installed first and we then have to come along and thread the steel columns, some 30m long, between large pieces of processing kit.”
Items such as water tanks and the turbines are too large to be installed once the building is complete, so they are being assembled on site and placed in their final locations before the main frame is finished. This will also ensure the facility can meet its important late 2010 commissioning period.
“We have some large crawler cranes on site which are shared by the subcontractors, and many trades working around each other, so collaboration is a key issue on site,” says Lowe.
Much of the steelwork will be erected on top of concrete walls, such as the waste bunker where 20m long steel columns will extend this part of the building upwards to connect to the steel roof. Two overhead grab cranes, which will pick up waste and deposit it into feed hoppers, will be suspended from the upper steelwork.
The main areas being built with a steel frame are the processing sectors, which also include the turbine hall, boiler house, flue gas treatment hall and a control room that will be suspended internally from the roof.
- Main client Cory Environmental
- Architect Race Cottam
- Main contractor Von Roll Inova
- Construction contractor Costain
- Structural engineer Jacobs Engineering
- Steelwork contractor for main frame Bourne Steel
- Overall steel tonnage 4,000t