Key Process of Pellet Machinery
GrindingPrior being fed into the pellet machinery, the raw material must be given a homogeneous consistency. This can be achieved by various types of granulation machinery such as a hammer mill. Particles should be no larger than the diameter of the die-holes; any larger and the quality of the pellet is damaged. However, it is also possible to grind too finely, resulting in the loss of the fibrous quality of the material, which prevents the pellets from binding properly. The optimum consistency is something similar to breadcrumbs.
Pelletizing (or pressing)
Pellets are manufactured from the granulated material using the pellet machinery. (Sometimes referred to as an extruder), which is usually a mill that presses the raw material into pellet form through ready-made metal dies. Large-scale purpose-built mills are the best at maintaining pellet quality, but there are plenty of examples in Europe and North America of mills intended for animal feed production that have been converted to manufacture wood pellets by pellet machinery. The size and efficiency of mills vary but, roughly speaking, 100 horsepower provides the production capacity for 1 ton of pellets per hour.
Pressure is used to force the granulated wood through the holes in the pellet die, the size of the holes determining the diameter of the pellets produced by this pellet machinery. As the pressure and friction increases so does the temperature of the wood. The high temperature softens the lignin, allowing the fibers of the granulated wood to be compressed into cylindrical pellets. The size of the die is very important in creating the appropriate level of resistance and controlling the pressure and temperature conditions in the process of pellet machinery. If the holes are too large, the material simply slips through, whereas if the holes are too small the temperature becomes too high and the material is scorched .
Cooling and screening
The pellets leave the pellet machinery soft and hot and must be air-cooled using a cooler machine to allow the natural resins (or other blinding agents) to set without caking. Once cooled, the pellets are passed over a vibrating screen to sieve out any fine particles and ensure the end product is clean and dust-free.
These fine particles can then be reintroduced into the production system of the pellet machinery processing, so no raw material is wasted.
Distribution
Your pellets are then ready for packaging and distribution.