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ŠUMARSKI LIST 3-4/2018 str. 45     <-- 45 -->        PDF

(3.0 and 6.0 kN) and 2 temperatures (150 and 200 °C). After pressing, pellets were left for 15 days to stabilise in dimension and their dimension and density were determined. Then, pellets were checked for pressure strength in a radial direction by a testing machine. Pellets from all the mixtures, pressed by a force of 6.0 kN at 200 °C showed a high density in the range from 1 207 – 1 234 kg/m3. Pellets of basic ash mixture at force of 3.0 kN and at 200 °C gave high density≈ 1200 kg/m3, while the smallest density was generally given by pellets of basic hornbeam mixture in all pressing regimes. The results of pressure strength in radial direction give best results in pellets pressed at 6.0 kN and 200 °C which is 13.59 MPa with the basic ash mixture, 11.1 MPa with the basic oak mixture and 9.06 MPa of basic hornbeam mixture.
If the pressure strength of a pellet is considered collectively according to the mixture, pellets made from the mixture of ash, poplar and alder give significantly better results in comparison to other two mixtures.
Key words: wood pellets, ash content, calorific value, pellet density, pressure strength