PELLETISING

Pelletising is a process used to press material in to a more compact form.

Requirement

 Pellets can be made from different materials; yet the material must meet certain requirements:

Small particle size

Low moisture content (10-15%)

If the material does not have these properties, it can be treated with mechanical forces and thermal processes, e.g. with a disintegrator and a drying plant, in order to obtain the desired state.

The process

The pellet mill is a machine that is used to press the material into pellets by means of compacting.

The pellet mill consists of a round metal ring with drill holes, which is called matrix, and two small pressing rollers inside, which are called kollers. The substrate is directed into the internal space; when the small particles are in between the pressing rollers and the interior of the matrix, they can only exit through the holes of the matrix. After the compressed material has left the matrix, a knife cuts the pellet strand to pellet size.

The material is subjected to enormous pressure between the kollers and the matrix, which causes the temperature to rise to approx. 100°C. This heat leads to the leakage of the natural lignin, which coats the pellets with a thin crust.

Through this process, the volume is reduced 5-fold.

Raw material for pelletising

 Different kinds of pellets can be produced, e.g.:

Wood pellets, animal feed pellets, plastic pellets, fertiliser pellets, pellets as fuel for combustion, etc.

Because of the low moisture content (10-15%) and the high nutrient content, dried digest is the perfect raw material for pelletising.

After the pelletising, the dried digest is used as fuel or fertiliser.

Pellet properties

• low moisture content
• high density, between 600-700kg/m³
• high nutrient content
• high energy content
• very good storage properties
• good dosage properties