Development of empirical drying correlations for ground wood chip and ground wood pellet particles

In this research, the drying rates of ground chip and ground pellet particles of pine were investigated. Pulp wood chips and whole pellets were ground in a hammer mill. Grinder screens with perforations 3.2, 6.3, 12.7, and 25.4 mm were installed in the hammer mill to produce a range of ground particle sizes. Particle size of ground chips had a broad range of 0.25–6 mm, while pellet particles had a smaller range of 0.5–2 mm. Initial moisture contents of ground particles were conditioned to 0.1, 0.3, and 0.5 (dry mass basis) using sprayed water. The moistened particles were dried isothermally in a thin-layer dryer set at the temperatures of 50, 100, 150, and 200°C. Chip particles dried faster than pellet particles of the same particle sizes. In addition to water loss, the particles exposed to a temperature of 200°C lost 3–7% of their dry mass. Smaller particles lost more dry mass than larger particles. The modeling revealed that the drying constants of pellet particles are less than those of chip particles with the same particle size.