Juniperus waste wood as a source for obtaining pellets by single-screw extrusion method

Abstract

Waste wood (biomass) is one of the most valuable and multifunctional environmental, long term resources of Earth. The aim of this paper was to study the possibilities for obtaining pellets from Juniperus. excelsa M. Bieb. biomass by a single-screw extrusion pre-treatment method. Biomass obtained after aqueous distillation of J. excelsa was used. The sample was grounded and sieved into dp ⩽ 500 μm and dp ⩽ 500 μm particle in size. The experiments were carried out on a single-screw laboratory extruder “Brabender 20 DN”. According to our results, the pellets with dp < 500 μm particle size were characterized with the following indicators: the mass flow rate (1.92 kg/h), sectional expansion index (1.03), specific mechanical energy (215.65 kJ/kg), density of the extrudates (0.44 g/cm3) and volumetric flow rate (4337.58 cm3/h). The samples obtained with dp > 500 μm particle size showed the following characteristics: the mass flow rate (1.30 kg/h), sectional expansion index (1.09), specific mechanical energy (535.23 kJ/kg), density of extrudates (0.48 g/cm3) and volumetric flow rate (2719.78 cm3/h). The biomass was a potential source for biofuel production. Pellets produced from biomass with a particle size dp > 500 μm had a higher density and sectional expansion index than those with a particle size dp ⩽ 500 μm. However, their production was more economically impractical, which is due to their lower mass and volumetric flow rate, as well as higher specific mechanical energy.