Effects of pelletization conditions on breaking strength and dimensional stability of Douglas fir pellet

The compression behavior of Douglas fir ground particles using a heated piston-cylinder unit was investigated. A complete randomized design (CRD) of experiment with three factors (die temperature, applied pressure and relaxation time), three levels and five replicates were studied. From the analysis of variance (ANOVA) with α = 0.05, all of the three pelletization factors were significant parameters to the maximum breaking strength and the relaxed pellet density. The significant factors to the initial pellet density of pellets were the die temperature and the applied pressure. Three out of five compaction models of Walker, Jones, Kawakita and Ludde were well described to the compression behavior of Douglas fir ground particles with R2 values between 0.90 and 0.99. The optimum processing condition to produce the best quality of Douglas fir pellets was 100 °C die temperature, 126 MPa applied pressure and 30 s relaxation time.