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PELLET SILOS WITH AN EFFICIENT PELLET HANDLING SYSTEM

Phone: (403) 948-7810   Fax: (403) 948-3189   Toll Free: 1 800-561-5625   contact@skywaygrainsystems.com

Burns Lake, British Columbia

Pinnacle Renewable Energy Groups Pellet SilosPinnacle Renewable Energy Groups Pellet Silos

Since 2004 years Skyway has built six pellet storage systems to support the Pinnacle Renewable Energy Groups pellet mills. Pinnacle Renewable Energy Group produces wood pellets as an alternative energy source for use as fuel for commercial and municipal central heating systems in Europe and far northern Canada communities. The Mountain Pine Beetle epidemic in Western Canada has resulted in thousands of acres of softwood lumber that is useful as fuel. Pinnacle produces wood pellets for local and overseas markets in six pellet plants located throughout British Columbia.

Over the course of the construction of the six pellet storage systems the design evolved so that each successive facility was more effective than the previous one. This learning process enabled Skyway to develop an efficient pellet handling system that can store and handle wood pellets with minimum pellet deterioration during the handling process.

The last facility, at Burns Lake, British Columbia, has the most efficient wood pellet handing system.

If we followed a wood pellet as it enters the finished pellet storage system, it arrives from the pellet mill via a galvanized curved incline conveyor, 20 X 20 on a 35° incline. This incline conveyor allows the pellets to arrive at the top of the pellet silo and drop 4’ into the belt conveyor, an improvement over the Bucket Elevator designed into the first wood pellet system, where the pellets dropped from a height of 140’. In the first design it was found that the 100’ spout length fractured too many wood pellets and the result was an excess of fines. In marketing wood pellets the goal is to have minimum fines in the finished product, where the bucket elevator produced fines in as much as 7 or 8%.

From the incline pellet conveyor, the pellets drop on to a reversing belt conveyor that services the two bulk storage pellet silos. The pellets travel to either the right or left and drop into the pellet silo. To prevent further pellet fracturing from an extreme drop, each pellet silo is equipped with a modified bean ladder. This prevents the pellets from dropping an excessive distance to the bottom of the 75’ silo and allows the pellets to drop a short distance and slide down the bean ladder and drop a further short distance and slide further down the heights of the silos and so on until, at the level of the pile, the pellets drop out the side of the bean ladder.

The wood pellets are removed from the storage silo through slide gates at the bottom of a concrete wedge built into the bottom of each pellet silo. In the original installation the pellets were removed from the silo with the aid of a bin sweep. This proved to be a problem because unlike grain, wood pellets do not have the same flow characteristics as grain. Hard smooth hulls on grain allow grain to flow freely into a bin sweep. Wood pellets, not being as hard, and with a surface that has a higher friction characteristic than grain, tended to “cliff” as the bin sweep moved forward and then collapse as the bin sweep advanced, which buried the bin sweep and caused it to plug and stall.

A solution to this problem was designed first around a wedge of pellets left in the bin to act as a funnel guiding pellets into the chain conveyor. The drawback to this method proved to be the surface friction caused by the rolling pellets creating excessive fines in the finished product. This problem was solved by the addition of a wedge of sand across the bottom of each bin, overlaid with a layer of concrete. This allowed the pellets to roll smoothly down the wedge through the sliding gates into the transfer conveyor and then on out to a long belt conveyor that moved the pellets to a rail car loader when they were loaded for shipping.

The Burns Lake pellet storage facility is the most efficient pellet handling system Skyway has built, with an optimum speed and minimum fines in the finished product.