Canada has become a major producer and exporter of wood pellets in the world. But the low water resistivity and the high transportation cost impede the market development. Torrefaction may provide a solution. The present study developed the torrefaction kinetics, studied the torrefaction reaction conditions in two bench-scale reactors, and identified the suitable conditions for making durable torrefied pellets in a press machine. The weight loss of softwood significantly depended on the torrefaction temperature, the residence time, the particle size, and the oxygen concentration in the carrier gas. A two-component and one-step first order reaction kinetic model gave a good agreement with the weight loss range of 0 to 40% at the temperature of 260-300 oC. Considering the quality of torrefied pellets, the optimal torrefaction conditions appeared to correspond to a weight loss of about 30%, which gave a 20% increase in pellet heating value. The suitable densification conditions corresponded to a die temperature of 230 oC, or over 110 oC for torrefied samples conditioned to 10% moisture content.

Dr Peng investigated the BC softwood torrfaction, identified the suitable conditions for making torrefied pellets, and evaluated the torrefied pellet economics. His research significantly advanced the fundamental understanding on biomass torrefaction and densification and its potentials for commercialization.