Biomass handling system to reduce emissions

27 August 2008

Ferrybridge Power Station, part of Scottish and Southern Energy’s UK operation, has chosen Portasilo Bulk Handling Systems to help power its vast boilers with organic, carbon neutral “biomass” fuel. The biomass wood pellets are delivered into tipping booths, from where six Portasilo Augerflo variable-speed feeders transfer the product into a pipe conveyor.

Biomass handling system to reduce emissions

This fully enclosed conveyor protects the volatile pellets from moisture and is ideal for transporting material over long distances. The pellets are then deposited into a 5,000m³ intermediate storage silo.

Portasilo fitted more than 120m² of explosion relief vents to the existing silo roof due to the material’s potentially explosive nature. The silo is fitted with a hydraulically driven rotating screw extractor, which sweeps the 14-metre base to collect material from the full silo cross-section. From the silo pit a chain conveyor, feeds the pellets into another pipe conveyor, which transports the material to the boiler house.

Two Portasilo 900mm diameter screw conveyors feed the pellets into two five-metre diameter day-silos. Screw conveyors are used to achieve a controlled transfer of accurate volumes of material into the silos. The day-silos were constructed at the purpose-built Portasilo facility, which is capable of fabricating very large silos up to 15m in diameter in a single piece, significantly reducing site costs and build time.
The installation of these silos demanded a precision operation, since they had to be lowered into a steel framework by crane with only inches of clearance on all sides. This operation was carefully planned by Portasilo to minimise disruption to the plant.

From the day-silos, biomass is transferred into six disc mills that feed the fuel into new state-of-the-art burners that are required to ignite the fuel. To enable the feed rate from the day-silos to be independently variable, Portasilo Osciflo bin dischargers were used, giving a variable discharge rate of between 0.4 and four tonnes per hour into the mills.

These modifications ensure the silo meets the requirements of ATEX legislation.

Andrew Mills, Project Manager at Ferrybridge Power Station said: “The advanced system devised by Portasilo fulfils all of our requirements and is successfully delivering increased volumes of biomass into our new burners.

“The installation and commissioning of the Portasilo equipment was completed with no disruption to the normal operation of the plant.”