Complete Biomass Pellet Plant

The basic pellet plant process:

• Initial size reduction
• Drying
• Initial sieving
• Grinding
• The mill: pelletization
• Cooling
• Final sieving
• Storage

Initial Size Reduction: Wood

When using wood-based materials, size reduction technology is an important consideration in pelletization because it can be the limiting factor in production as well as one of the most costly steps in the entire process. Not only does size reduction equipment consumes large quantities of power, it determines, to a great extent, the operating, maintenance, and lifecycle costs of other equipment in the line. For instance, if material is sized properly when it reaches the mill, the die need only act as a forming device, not as a sizing device, which greatly enhances the die life and decreases energy consumption. Analogously, if material is less than 10 centimeters in diameter when it reaches the dryer, the resultant energy costs for the drying process than if it were greater than 10 centimeters as the smaller particles allow for the evaporation of moisture much more quickly.

As a result, the typical wood pellet line that utilizes branches, logs, or other large-sized materials must engage in primary reduction before proceeding to other stages. Primary reduction is usually done with a disk chipper or a crusher. Chippers use replacement knives to split or shear whole logs or clean residue so that the geometry of the particles is relatively uniform and the structure of the wood remains intact. They are highly sensitive to contaminants, such as sand, rocks, and metal, which dull the blades. However, in the process of blowing the chips from the chipper to the next operational stage, most of the leaves and dirt are removed by the difference in particle density. The rotary speed may be as high as 3,600 rpm, which is two to three times faster than the rotary speed for the secondary piece of reduction equipment—the hammermill. In a pellet line, the primary reduction should reduce the material to less than 10 centimeters.