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NIVELLES - 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 world-wide efforts against gas emissions.
Picture: Two Pneumatic Continuous Ship Unloaders Type NIV 600 for wood pellets unloading at RWE co-firing power plant in Tilbury / U.K.
New power plants, as well as some existing energy producers, are upgrading their existing technologies with the 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 at 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 installa-tions.
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) with 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 tons/hour to 75 tons/hour) the incorporation of wood pellets up to a rate of 20 % of the total energy produced by this upgraded plant.
Since its operational start in 2010, this ELECTRABEL power plant has become one of the world largest co-firing plant with wood pellets.
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 a key sector requesting 24 hours per day reliability requires the highest quality and the most efficient operational performances.
Pneumatic Unloading Of Wood Pallets
The transport of any wood residue is usually facing the challenge of the low density of those materials. Therefore the most common process is pelletizing 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 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: -
the use of 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 recognized as a more convenient solution for unloading barges, compared to grabs or mechanical unloaders:
Picture: Pneumatic unloading of wood pellets prevents dust emission
First pneumatic unloaders were manufactured already at the end of the 19th century but continuous technological improvements were introduced for a higher reliability, a better safety and optimum running costs.
Three turbo blowers groups (each four stages) with direct drive and controlled by latest speed variators ( frequency inverters) by Schneider Electric.
The direct drive is a major improvement because it reduces not only the numbers of bearings which are existing on traditional drive with belts but also the mechanical efforts on the turbine shaft.
The multi-stage turbo blowers are maximizing the suction capabilities for a larger range of product characteristics to be handled with no need of any special feeding device and in combination with the speed control system, it make feasible to precisely optimize the energy consumption.
Some VIGAN customers reported figures as low as 0.6 to 0.7 kWh/ton thanks to those technology developments and also chosen by ELECTRABEL.
As also observed in this project, those 3 turbo blower groups are giving to the customer a convenient extra capacity of suction power reserve to face any unexpected event and to guarantee his daily unloading target.
Air jet pulse system for automatic cleaning of the filter.
Widely recognized among the food and feed industry sectors for the global best performances and reliability, this system offers also a major advantage about safety: no running mechanical parts are in contact with the air flow which could be eventually contaminated with dust and there-fore could be the origin of explosion.
Major reliability and safety of this equipment are also due to special alloys against wear used for instance in the elbow between the vertical and horizontal suction pipes, in the airlock components and generally speaking by integrating most compulsive rules concerning latest European norms about engineering design, equipment manufacture and human resource protection.
The use of alternative sources of energy such as biomass will certainly increase during the coming years and all the logistic aspects of these inputs require very careful approach.
Electrabel receives full credit for this landmark project in green electricity production.
It also receives the credit for having understood the benefits of the pneumatic technology for a reliable and efficient unloader.
Pneumatic unloading of wood pellets prevents dust emission
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