Helping power stations switch to biomass

Written by: RWW | Published:

Changes in environmental policy are bringing about a transformation in the UK’s energy industry and forcing the hand of the ‘Big Six’ to review the operating philosophy of their ageing generation facilities. Lynn Campbell reports on how a contractor helped Ironbridge Power Station convert to biomass.

Power generators, namely coal-powered power stations, and traditionally the most polluting and carbon intensive, are beginning to switch from fossil fuels to abiomass.

There can be no doubt that the energy industry is serious about pursuing this change. Last year Drax, the UK’s biggest coal-burning power station and the country’s single biggest emitter of carbon dioxide, announced that it was to make the switch from coal to biomass. 

Current legislation states that any fossil fuel power station in the UK without flue gas desulphurisation (FGD) technology will be forced to close by the end of 2015, hence, in 2010 E.ON UK took the decision to carry out a 100% conversion of Ironbridge Power Station from coal to wood pellet fuel (biomass). 

This 1000mW power station, which produces enough electricity to power around 750,000 homes, is located in the Ironbridge Gorge on the River Severn, just half a mile upstream from Ironbridge; the birthplace of the industrial revolution and a World Heritage site.


Ironbridge, a conventional 1000mW power station, is made up of two 500mW units, both of which have been converted to give a de-rated power output of approximately 800mW; significant for any biomass power generation facility. 

The challenge as always was budgetary constraint. Also due to the short term nature of the conversion, a low cost solution was required, however, the design had to meet all legislative and permitting requirements and comply with all relevant standards. 

The task of delivering the new 20,000t capacity fuel store and modifying the existing handling systems was the responsibility of principle contractor, AJS Contracts. 

Central to the biomass handling system was the fuel store feed system. AJS Contracts drew on the knowledge and experience of Staffordshire-based Roltech Engineering to undertake the design, construction and installation of the bespoke designed tripper conveyor.

Manufactured at Roltech’s workshop in Newcastle-under-Lyme, the new 150m long tripper conveyor had to meet strict performance guarantees, achieving a throughput rate into the fuel store of 1000mtph. 

The fuel store operational procedures adopted by E.ON meant that the 200 tonne conveyor had to be suspended from the roof structure and had to be capable of depositing biomass fuel at any point along its length.

Roltech’s project manager Richard Austin explains: “Being under-slung, all of the conveyor support is overhead, this made installation extremely challenging as the huge sections had to be winched into place. Due to the potential risk of fire and explosion within the store, every moving component of the conveyor had to be intrinsically safe, meeting the strict ATEX zoning that had been applied to the fuel store. All electrical and mechanical installations, such as our gearboxes, are ATEX rated and there are sprinklers and fire detectors installed throughout.”

ATEX is the name commonly given to the two European Directives for controlling explosive atmospheres: Directive 99/92/EC and Directive 94/9/EC

Design and manufacturing process

AJS Contracts first engaged with Roltech in June 2012 and the design and manufacturing process took just 12 weeks with installation starting in September - completing 10 weeks later in November. 

Martin Wylie, AJS Contracts’ renewable energy divisional manager, explains: “Working on a renewable energy project in the UK brings its own challenges, however, combine this with constructing within a world heritage site of which Ironbridge is, really increases the need and focus to operate efficiently and to achieve a build that is aesthetically pleasing.”

Ironbridge Power Station is now entirely wood-fuelled. However, Roltech’s involvement in the project is far from over.

“On the back of this contract we have been awarded the contract to supply handling equipment to the same client at Liverpool bulk terminal,”continues Austin. This is where the wood chip fuel for the Ironbridge power station is shipped in by bulk carrier from Canada and the United States.

“This will be a major project involving the supply of a ship unloading hopper, a tripper conveyor and a number of other troughed conveyors to get the fuel out of the vessels and on to freight wagons for delivery to the power station by rail,” adds Roltech’s project manager. 

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