Sawdust pellets use eucalyptus, birch, poplar, fruit wood, bamboo chips, and crop straw as raw materials. Different types of raw materials have significant differences in compression forming characteristics. The type of raw material not only affects the quality of formation, such as pellet density, strength, and calorific value, but also affects biomass pellet machine output and power consumption.

If glue blocks, coking, and other phenomena occur after burning pellets, it is mostly due to excessive and varied ash content from the pellets themselves and processing. These impurities change the ash melting point of biomass pellet fuel, intensifying coking on heat transfer surfaces.

When raw material size is too large, biomass pellet machine cannot work effectively, consuming more energy and producing less output. When raw material size is uneven, especially when morphological differences are large, sawdust pellet surfaces will produce cracks, and their density and strength will decrease.

It will also cause increased wear on pellet machine rollers and molds, increasing loss costs.

Raw materials contain appropriate amounts of bound water and free water, which act as lubricants. Raw material moisture content being too high or too low does not allow good forming.

When moisture content is too low (such as less than 8%), particles do not extend sufficiently, and bonding with surrounding particles is insufficient, so they are difficult to form; when moisture content is too high (such as greater than 18%), particles can extend fully in directions perpendicular to maximum principal stress and mesh with each other, but because excess moisture from raw materials is squeezed out and distributed between particle layers, the layers cannot bond tightly, so they are also difficult to form. For sawdust pellets, optimal raw material moisture content is around 15%.

During pellet production, friction between raw materials and machine parts heats the material to 100°C, softening the lignin content and acting as a binder.

Too high temperatures cause carbonization of materials and pellet surfaces, and excessively high working temperatures also affect roller bearing service life, so biomass heating temperature during formation should be adjusted to a reasonable range.

Formation pressure (compression ratio) is the most basic condition for material compression forming. The greater the pressure applied, the finer the material particles, the more significant the particle extension, the tighter the bond of the formed product, and the greater the density.

Formation pressure has a close relationship with mold shape and dimensions. Friction magnitude directly relates to mold shape and dimensions, and the key mold dimensions are the cone angle and length of forming holes. Therefore, for different materials to achieve better pellet forming effects, different pressures (different compression ratios) are needed, and appropriate mold compression ratios should be selected based on raw materials.

After pellet formation, formed pellets pass through screens and conveyors to cooling towers. However, some pellet plants actually don't use cooling towers, and many people ignore this process.

Formed pellets coming out of biomass pellet machine have temperatures of approximately 75-85°C, with moisture content around 15-17%. Such high-temperature and high-moisture pellets have relatively flat structures and are easy to break. If not cooled directly into bags, the heat cannot dissipate, generating moisture vapor. When sawdust pellets encounter moisture vapor, they disintegrate, ensuring quality cannot be guaranteed by the time they reach customers. Direct entry into feed tubes, conveyor belts, and other supporting equipment also causes corrosion, creating unnecessary losses.