When it came to delivering one of the largest biomass stores in Western Europe, the project team of specialist contractor (De Boer Structures UK Ltd) and structural engineer (PEP Civil & Structures Ltd) felt that quality of finish and timely delivery would be key contributors to the success of the project, turning to Total Steelwork and Fabrications Ltd to undertake fabrication, outsourcing the galvanizing and subsequent erection of the steel structure.
Located 150 metres from the Irish Sea, the new storage facility is a 34 metre high structure using over 1,200 tonnes of galvanized steel to accommodate 65,000 tonnes of wood pellet which will be used for co-firing at UK power stations. Consisting of universal columns and box and circular section lattice truss frames, the 39° pitch to the roof mimics the angle of repose for stored materials, creating an efficient storage area.
The biomass fuel is taken from vessels at Liverpool Port and relayed via a series of conveyors into the facility at high level and is discharged as required from a moving tripper. Internally, six inclined chain conveyors carry stored material to a further longitudinal conveyor which takes outbound material to a nearby rail-head. The entire stock is intended to be rotated on a ‘first in, first out’ basis over a four week cycle.
One of the main concerns when storing biomass pellets ‘on the flat’ relates to the amount of dust that can be created during the handling process. The basic design was enhanced by using CHS in the bottom chord and connecting members with a view to eliminating dust traps wherever possible.
Unusually for a project of this size, the whole frame was clad in PVC, creating a refined structure. One of the requests from the client related to the use of both grey and white PVC within the roof – it was anticipated that the use of grey material at the apex would help the structure blend into the skyline, thereby reducing the perceived mass of the completed building. The white PVC was introduced in order to bring diffused natural light into the structure, helping to provide a safe working environment and reducing whole-life operating costs.
Images © Paddy Yates