Biomass pellet hammer mills and crushers

Before pellet or briquette compression can take place, the raw material must be reduced to a suitable particle size. Depending on the raw material size, a one or two stage size reduction process will be needed.

Depending on your chosen raw material, the equipment you require for size reduction may change. For example, if you wish to process logs or large pieces of wood into pellets or briquettes, a chipper/crusher is the first piece of equipment required for size reduction.

A chipper/crusher simply works on the principle of a rotating blade. As the wood comes into contact with the blade, small pieces (chips) are removed. The chips produced are generally still too large to be used in the briquette machine or pellet mill, therefore secondary particle size reduction of the chips is required in a hammer mill.

To reduce the size of wood chips and other suitably sized biomass raw materials to the correct particle size, a hammer mills is used. A hammer mill works on the principle of attrition. A rotating centre with a collection of flailing hammers impact at high speeds, shattering the material into particles. A screen with the desired particle size ensures the correct particle size is produced.

Once particle size reduction has taken place, a fan is used to extract the particles from the based of the hammer mill. However the particles are now mixed in the air stream, and need to be separated. To separate the particles from the air stream, a cyclone separator is used.

The cyclone has a vertical position, and the air stream and particles are injected into the top of the cyclone. The gas stream, due to the shape of the cyclone is sent into a spiral. During the spiral action, the particles are separated from the air stream and leave the based of the cyclone. The separated air then leaves the cyclone through a central pipe through the top. The particles are now a suitable size for briquette or pellet compression, depending they have a suitable moisture content of around 12% for briquette compression, and 15% for the pellet mill.

The SJ range of crushers and hammer mills can meet all your raw material particle reduction needs. The SJ range can process logs and other large wood pieces up to a 200mm diameter. Other units can process small branches straws, grasses etc up to 50mm in diameter. The particle size is reduced to 3-5mm, which is suitable for briquette and pellet production.