The impact of using different wood qualities and wood species on chips produced using a novel type of pilot drum chipper

Resource-efficient wood chipping for forest-industrial processes demands large fractions of accept chips and small fractions of small-sized material, such as pin chips and fines. In Kraft pulping, a narrow distribution of wood chip thickness is important for even impregnation and for making high-quality pulp. Using newly developed forest-industrial drum-chipping technology, the investigation covered wood of varying moisture content, frozen versus unfrozen wood, and the use of different wood species. Using conventional techniques for analyzing wood chip dimensions, fast-grown spruce wood with high moisture content gave 4.2 % pin chips and fines, which was less than half of the fractions obtained with spruce wood with lower moisture content. A comparison between frozen and unfrozen pine resulted in slightly thinner and shorter chips for the frozen wood, but in both cases accept yields of up to ∼85 % were achieved. A comparison of different tree species (aspen, birch, pine, and spruce) resulted in larger accept fractions (∼90 %) for the hardwood species, even though the average length of these wood chips was as low as 17 mm. The results provide a first indication of how basic wood log properties affect the yields of accept chips and small-sized material when using modern industrial drum-chipping technology