Productivity and Particle Size Distribution In Chipping (over)seasoned Poplar Biomass

The research aimed to investigate the influence of knife sharpness on chipping productivity and wood chips quality regarding particle size distribution. The research was conducted in Croatian lowland forests where wood chips were produced from tree residues using the Albach Diamant 2000 drum chipper. The time study was used to determine time consumption, and sampling of wood chips was done according to EN ISO 18135:2017. Particle size distribution was determined according to the EN ISO 17827-1:2016. The highest share in wood chips produced had 34 months of air-dried poplar biomass (80%); the rest was narrowed-leaf ash, American ash, and other hardwood biomass. During the nine working days, wood chips were produced with 60 truckloads or 1 670.1 t (average moisture content was 27.57±2.47%). In total, 33 samples were taken for laboratory analysis for particle size distribution determination. The production rate, on average, was 1.35 min/t of effective time or 2.20 min/t, including all delays. Productivity (min/t) showed no statistically significant dependence on cumulative chipped wood chip mass (denoting knife wear). The highest share in particle size distribution was in the diameter class 16-31,5 mm. The share of fines fraction (< 3.15 mm) was negatively correlated with cumulative produced mass. Despite the unexpected absence of a significant relation between cumulative produced wood chip mass and chipper productivity as well as between particle size distribution and knife worn, the research opened new questions regarding the differences in cut surfaces between wood chips produced with sharp and worn knives. During particle size distribution determination, evident differences in cut surfaces of coarse wood chip particles were noticed. Wood chips produced with sharp knives had clean surfaces in contrast to wood chips produced with worn knives with a hog fuel-like shape with distinctive torn surfaces.