Effects of temperature and particle size on biomass torrefaction in a slot-rectangular spouted bed reactor

Sawdust particles of different sizes (0.25-0.5, 0.5-1.0 and 1.0-2.0mm) were torrefied in a continuous slot-rectangular spouted bed reactor. The effects of particle size and temperature were investigated on the properties of the torrefied product, such as proximate analysis, ultimate analysis, HHV, skeletal density, and energy yield. Temperature was the most important variable in the torrefaction process. Increasing the particle size led to more weight loss of sawdust and increased mass of the torrefied product remaining in the reactor. The ash content evolution of the torrefied product showed that its properties approached a steady state within 20min. The reduction in Sauter mean particles size was up to 20.3% and 28.2% for 0.25-0.5mm and 0.5-1.0mm sawdust, respectively.