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PELLETIZING Pelletizing: It is a process to transform material by compression to produce a sheep of pellet. Requirement: Pellets can be done from several raw materials; nevertheless the material should fulfill some properties: - Small particle size - Low moisture content (about 10-15%) If the material does not have these characteristics, it can be treated by mechanical forces and thermal process by means of Milling machines and Dryer Systems, to achieve the desired properties. Pellet process: Pellet Mill is the device used to transform the material into pellets, by means of compacting. The Pellet Mill consists in a rotational metal matrix and small metal press rollers in the interior of it. The substrate is feed into the matrix; then when the particles are between the press roller and the matrix, the only path to exit is the holes of the matrix. After the compressed material has exits the matrix, a device (as a knife) will cut it, producing the pellet.
The enormous high pressure suffered by the material, between the matrix and the rollers, produce a increase of temperature around 100°C, this heat will produce the extraction of the natural lignin, which will act as resin bonding the surface of the pellet. The process will reduce the volume up to 5 times.
Raw materials for pelletizing: Pellets can be done by several raw materials to produce: wood pellets, animal food pellets, plastic pellets, fertilizer pellets, pellets used as fuel for combustion, etc. Dried digestate is an ideal raw material for pelletizing, due to the low moisture content (around 15%), and high nutrients content. Therefore, after pelletizing the dried digestate can be used as fuel or as fertilizer.
Pellet characteristics: - Low moisture content (around 10-15%) - High volume reduction - Better storage capacity - High density, between 600-700 kg/m3 - High nutrient content - High heating value - Excellent durability - Better dose capacity
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