Stevens Croft
Summary
A Biomass Waste EFW CHP 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 MWe and 6.5 MWth, 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]
The facility also provides electricity to its fuel provider AW Jenkinsons and suplies heat to the neighbouring saw mil, James Jones and Sons[3].
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].