Stevens Croft
Summary
A Biomass Waste EFW facility based on 480,000 tonnes per annum of Wood Waste generating 44MWe to the grid [1]. The plant was developed and is owned by E.ON UK and cost an estimated €132m[2].
Steven's Croft in Lockerbie Scotland, is the UK's largest wood fired biomass facility, with an output of 44 MW, the facility supplies c. 70,000 homes, displacing 140,000 tonnes of greenhouse gases[1].
The feedstock for the plant includes forest wood and agricultural residues, urban wastes and energy crops, all of which are readily available in the local area, the feedstock comprises[1]:
- 60% sawmill co-products and small roundwood
- 20% short rotation coppice (willow)
- 20% recycled fibre from wood product manufacture.
Construction of the facility at Steven's Croft not only included the biomass plant but a fuel processing facility and 26km of underground electrical cable connecting the plant to Chapel Cross electriclal sub-station[1]. The fuel processing facility was designed to blend all the various sources of fuel mentioned above into one homogeneous material. It includes up to 14 days of round wood storage, a facility for reception of pre-chipped fuel, up to 6000m3 of covered chipped fuel storage, a round wood chipping facility, fuel reclamation and forwarding equipment with systems for final preparation of the fuel before delivery to the power plant.[1]
Plant
Construction of the plant began in October 2005 with the plant entering commissioning in Autumn 2007 [2]. Construction was carried out by a Siemens/Kvaerner consortium with the boiler being a Kvaerner Power Bubbling Fluidised Bed power boiler, fuel handling and flue gas cleaning equipment[2]. The boiler conditions were designed to allow the best efficiency at 537°C, 137Bar with a capacity to raise 16 MWth of energy. The high steam conditions dictate the need for specialist corrosion resistant materials in the high temperature components and to control fuel quality.[1]
Siemens provided overall coordination, engineering and project management as well as the civil works and electrical and I&C equipment[2].
The power plant can reach full output even with high moisture fuels. It is able to burn a maximum of 20% recycled wood (limited by Planning and IPPC) and a maximum of 20% short rotation coppice. Moisture content for the plant is between 46% and 58%, with a design blend of 53%[2].