Wood chipper, biomass dryer and pellet mill, the necessary machinery for wood pellets production!



Wood pellets usage is friendly for the environment because of the fact that natural raw materials like logging residues, sawdust and special crops are used for their production. Wood pellets absorb about equal amounts of carbon dioxide for their growth related with the amount  they emit when burning, and according to this the total carbon dioxide transfer in the atmosphere is roughly zero.



Woody residues can be used for wood pellets production which by their combustion in special boilers contribute to the production of bioenergy, as well as to the production of electricity, but primarily to meet heating needs.

The stages of wood pellets production are as follows:
• Raw material storage
• Raw material cleaning of foreign bodies (stones, nails etc)
• Raw material initial shredding and production of biomass
• Biomass sifting
• Biomass drying
• Biomass storage
• Biomass grinding (thin cutting)
• Biomass pelletizing
• Pellets cooling
• Pellets sifting
• Pellets weighing, packing and storage

The machinery used in wood pellets production are as follows:
• Wood chipper (drum chipper, disk chipper)
• Biomass dryer (rotary dryer, superheated steam dryer, belt dryer)
• Pellet mill or pellet press (flat die pellet mill, ring die pellet mill, screw press, hydraulic press)

Wood chippers usually consist of the raw material intake container, the shredder, and an optional collecting container for wood after shredding. A piece of tree or branches are introduced into the raw material container where its walls serve as a shield from the fragments that are cut. Most wood chippers work with the energy accumulated in a flywheel, although some use drum shredders (drum chippers). In a newer wood chipper design a steel disc with knives is used for shredding the raw material such as a peeling mechanism (disk chippers).

Rotary dryers are the most widespread dryers of biomass but also have the greatest risk of fire. Superheated steam dryers use steam to provide heat and dry the biomass. Belt dryers on the other hand, use a moving strap usually in a horizontal position that carries the biomass through a drying area which is divided into several sections. In these sections air flows into or over the biomass to be dried.

The pellet mill or pellet press is a type of mill or mechanical press used in the production of wood pellets. There are many types of pellet machines and a generalized grouping of them is to divide them on a large and a small scale. On a large scale there are two types, flat die pellet mills and ring die pellet mills. Small scale pellet machines are usually variations of screw presses and hydraulic presses.
 

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