The pellets (fuel granules) are standardised cylindrical products produced by pressing with high-pressure agricultural waste, dried and chopped wood or other biomass without the use of any binding elements. They have a high concentration of energy with low volume.
Granules differ from normal wood by their high dryness (8-12% moisture content compared to 30-50% in firewood) and more - about one and a half times the density.
These features provide a high calorific value compared to chips or wood - when burning granules, about 5000 kWh of heat is released, which is one and a half times more than in the case of conventional firewood.
Until now, pellets at the expense of heat are comparable to coal (however, the latter is difficult to automate and the main operations - loading / removing slag must be performed manually).
The pellets are delivered to the final consumer, packed in 15 kg plastic bags. Some customers prefer pellets packed in large bags - cubic polypropylene bags of about 1 meter size. The use of large bags can fully lower the bunker and the screw is placed directly in a bag that is recycled after devastation. The disadvantage of this method is that the large bag weighs about a ton and without special unloading and handling techniques it is not very convenient.
In the boiler, the pellets are fed directly from the hopper along the cochlea. The length of the screw feeder rarely exceeds 10 metres, because at a greater distance the granules will be ground into a powder which is agglomerated in the burner itself, which in turn may cause the boiler to shut down.
Compared to other types of fuel pellets, they leave no traces on surfaces and are easy to clean with a broom and bucket. Unlike, for example, liquid fuel whose leakage is dangerous to fire, dispersed pellets can be used as an absorbent, the pellets absorb their own weight several times. The pellets are not biologically active due to their high temperature of production.
When pellets are burned, the ash is formed by volume from 0.5% of the pellet weight (depending on the pellet category). For example, a 25 kW boiler ashtray must be cleaned every two weeks. The operation lasts no longer than half an hour and includes: cooling the burner, opening the combustion chamber, removing the ashtray chamber and then folding it again in reverse order.