embedded in the UHMW (ultra-high mo- lecular weight polyethylene material) and will wear out chain quickly, so take care where you use them. Chain conveyors are costly, so resist the urge to undersize com- ponents to save on cost. Avoid chute valley angles less than 45°. With some materials and in some condi- tions, even this is not steep enough. Dilute phase pneumatic conveyors have long been used for transporting hog fuel. They are less costly than belt or chain conveyor systems, but have high power requirements and can generate a lot of fugitive dust. Screening/metal removal system – in extreme cold climates. Biomass delivery by rail requires a railcar scale, a railcar moving system, an unloading system, receiving hoppers, and conveyors to storage. Unloading systems can be as simple as mobile equipment or can be an end-dumper or, for high capacity, a roll-over dumper. Biomass delivery by barge is popular on the west coast, and the unloading equipment varies. The best and most simple system uses mobile equipment that drives onto the barge via a ramp. The ramp is equipped with a receiving hopper that the mobile equipment fills. The hop- per discharges into the conveyor system to storage. Other systems use dockside knuckleboom loaders or overhead cranes with clamshell buckets. Delivery by barge requires a docking or mooring facility, and possibly a warping system, that will ac- commodate water level changes. Conveying systems – Belt and chain conveyors are most common because of their reliability. Generally, belt conveyors are less costly, but require more real estate because of their lower operating slope; however, belt conveyor slope is greatly reduced in cold climates to prevent ma- terial slippage. Conveyor speed should be kept quite low, less than 400 feet/minute. Belt loading should also be kept low to allow for oversized material. A belt weigh scale is often included. Chain conveyors can operate at steeper slopes and are suitable for shorter or complicated runs. Avoid concave vertical curves. Use abrasion-resistant wear plates; however, rocks and grit tend to become A scalping screen is recommended for removing gross over-sized material, which you can expect to get in your system re- gardless of the assurances of your biomass supplier. The disc type of screen is best suited to this tough application and is also quite good at removing stones larger than the screen opening. Use abrasion-resistant steels and don’t undersize the screen. Depending on the quantity of gross over-sized material rejected by the screen, there may or may not be a grinder/hog. If one is required, use a solid rotor, high inertia hog. Additionally, a metal detector belt should be installed before the hog to stop the feed if large pieces of tramp metal are detected. Ferrous metal removal is essential and can be accomplished with a magnet. There are several magnet types and arrangements available, but the primary magnet should be self-cleaning. Avoid locating magnets in the cross-belt configuration, as the magnet will have difficulty removing metal that is underneath the load. Locate the magnet over a pulley transition, where the mate- rial is falling and is suspended. If possible, locate the magnet after the scalping screen to ensure that gross over-sized material will not jam between magnet and conveyor. Storage and reclaiming system – The amount of storage required depends on: (1) the minimum amount of material required to maintain reliable operation; (2) the longest period of time that the flow of incoming material may be interrupted; and (3) the longest amount of time that the plant must continue to receive bio- mass when it is not consuming fuel. Covered storage is costly and only Wood Grinding (Wet and Dry) Optimum crushing of wood chips! AMANDUS KAHL GmbH & Co. KG SARJ Equipment Corp., Mr. Rick B. MacArthur 29 Golfview Blvd., Bradford, Ontario L3Z 2A6 Phone: 001-905-778-0073 Fax: 001-905-778-9613 [email protected] www.akahl.de CanadianBIOMASS 15 Photos: Paul Janzé
Canadian Biomass May/June 2010: Page 15
