Waste to energy: How wood pellets are made

Bangor Daily News
Posted July 24, 2008, at 12 a.m.

The creation of wood pellets at the Corinth Wood Pellets LLC begins when pulverized waste wood and sawdust are dumped into hoppers and fed into two dryers. The dryers are 10? feet in diameter and 32 feet long and contain three chambers that tumble the wood and sawdust until they are dry.

A cyclone then separates the hot air from the sawdust and an auger feeds the sawdust into a chute that brings it into the processing building.

The hot, dried sawdust is then pushed under great pressure — using a 400-horsepower motor — through a series of dies, and the resulting pellets fall onto conveyor belts. The pellets, now at about 170 to 200 degrees, are funneled through a cooler. Once cooled, they are shaken on a screen to remove all the dust. The dust is retained and put back into the pellet process.

The pellets then proceed through an automated bagging machine, which weighs each bag (40 pounds), seals it and stacks it on a pallet for delivery.

Pellet quality is not legislated but is industry-driven. There are two grades of pellets, standard and premium. The grade is based on the ash content of the pellet, which comes from the level of bark in the product. The higher the bark content, the more ash and the less Btus. Premium grade means the ash content is 1 percent or less.

The moisture content in pellets is 5 percent to 7 percent, compared to 18 percent to 20 percent for seasoned firewood, but pellets will degrade if kept in moist or damp areas.

http://bangordailynews.com/2008/07/24/sports/waste-to-energy-how-wood-pellets-are-made/ printed on July 10, 2014