Ports, Terminals & Transport
Moving pellets A co-firing power plant produces more ecological energy with wood
pellet
Alternative and renewable sources of energy are a major concern not only due to limited resources of fossil origin but also within the context of the worldwide efforts against gas emissions. New power plants, as well as some existing energy producers, are upgrading their existing technologies with latest innovations in order to fulfill their legal obligations of protecting the environment while containing costs.
The French group Suez is a major player in Europe and on worldwide level with about 200,000 workers and an annual turnover of more than 110 billions USD. Suez has integrated this approach for many years with very significant investment in engineering developments and state-of-the art industrial installations.
Electrabel, the electricity division of the group developed a special project during the last few years for its power plant in Gelderland (city of Nijmegen in The Netherlands) of a capacity of about 600 MW. Tractebel, its Belgian engineering affiliate, was in charge of developing this co-firing project (biomass + coal) by increasing about 10 times (from 8 tonnes/hour to 75 tonnes/hour) the incorporation of wood pellets up to a rate of 20% of the total energy produced by this up-graded plant. Since its operational start in 2010, this Electrabel power plant has become one of the world largest co-firing plant with wood pellets This co-firing process allows Electrabel to benefit from a large number of “green certificates”. This system of “green certificates” is a European mechanism balancing on one side the promotion of investment in green renewable energy such as wind mills or biomass powerplants, with on the other side, the obligation for fossil fuel plants to buy those “green certificates”. Geldof, a leading supplier of industrial components and turnkey-projects based in Western Belgium, was selected by Electrabel as turnkey contractor for this process transformation,
Vigan pneumatic barge unloader in operation at an Electrabel plant
including new installations for the reception and the storage of the estimated 550.000 tonnes per year of wood pellets required by the power plant. Wood pellets are transported to Electrabel plant by barges from various origins, thanks to the excellent hinterland river and canal system in the Netherlands for bulk transport. Nevertheless the discharge of such volume for such a key sector requesting 24 hours per day reliability requires the highest quality and the most efficient operational performances. Vigan Engineering, also a Belgium company specialised in pneumatic and mechanical ship-unloaders mainly for agri-bulk cargoes, with 40 years of experience and more than 1150 equipment around the world, was selected to manufacture and to install the pneumatic unloader for the barges of wood pellets.
Pneumatic unloading of wood pellets
The transport of any wood residue is usually facing the challenge of the low density of those materials. Therefore the most common process is pelletising in order to condense them into granules (usually about 10 – 15 mm length and a diameter around 5 – 6 mm).
Thanks to this process and with a reasonable content of humidity, the wood pellets are quite free flowing and therefore allows for an easy conveying from the production facility up to its use as an input in the power co-firing with coal. During the transport up to the plant, those pellets can easily break with dust emission: to use grabs is not convenient due to several factors such as important mechanical efforts of quay structure, dust escaping into the environment, eventual spillage that can be difficult and costly to clean, and of course a low “through the ship” efficiency when unloading small barges. Pneumatic unloaders however are recognised as a more convenient solution for unloading barges, compared to grabs or mechanical unloaders:
• Higher unloading rate mainly during the cleaning of the hold with the intake nozzle being able to suck down to the latest product particle on the hold floor but also to reach the hidden corners.
• Safety: one operator is able to manage the whole unloading not only thanks to a remote control for all major displacements of the suction nozzle into the hold but also as the driver of an auxiliary skid steer loader for speeding up even more the final cleaning. • Environment: no dust as the whole unloading system is under negative pressure and/or totally enclosed. • No spillage and need to clean the quay around. • Minimum breakage by optimizing the air and product speed in the pipes. • Low weight equipment with far less mechanical efforts on the quay structure.
14 Solids & Bulk Handling • November 2010
www.solidsandbulk.co.uk
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