engleski

Influence of pressing temperature and additive on mechanical properties of wood pellets

The use of wood pellets for energy purpose is widespread in developed European countries, but its use in Croatia is still not on desired level. Republic of Croatia has a wide raw material potential in pellet production, but there are certain problems. Since each species has a particular chemistry and structure, the approach of research of optimal production parameters should be individual for every raw material or mixture. The aim of this paper is to investigate quality of the pellets produced from mixture of three wood species and addition of starch additive according to the selected parameters. Wood types used in this research were fir (Abies alba Mill.), oak (Quercus robur L.) and white pine (Pinus sylvestris L.). The pellet production was carried out using a laboratory single pellet press (SPP) and their main properties were tested. The fixed input parameters were pressing time (20 s), feedstock mass (0.25 g), pressing force (4 kN) and particle size (2 mm) and changeable parameters were raw material composition (mixture of fir - oak in ratio 50 % : 50 % - (A1), fir - pine 50 % : 50 % (B1), fir – oak – starch 45% - 45% - 10 % (A2), fir – pine - starch 45% - 45% - 10% (B2)) and pressing temperature (120 °C and 200 °C). The results of the pellets analysis show greater initial density of the pellets pressed from the raw material without starch. Calorific value of raw material was greater for fir and pine in comparison to fir and oak raw material. Results show that fir-pine raw material with starch addition have decreased calorific value by 1, 1 % in comparison to fir-pine material without starch. In fir-oak raw material addition of starch increased calorific value by 3, 2 % in comparison to normal fir-oak raw material. Results also show that by adding starch, mechanical properties of fir-oak pellets decrease, but in fir-pine pellets mechanical properties increase by adding starch.

wood pellets, additives, pressing temperature, single pellet press, mechanical properties

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