Torrefaction is a thermo-chemical conversion which conducted in the absence of oxygen, at temperature of 200 to 300°C, and heating rate less than 50°C/min. Torrefaction of six biomass materials (poplar branch, willow branch, rice husk, corn stalk, saw dust briquette, rice husk briquette) was carried out in a fixed-bed reactor in nitrogen atmosphere. Two main torrefaction parameters of temperature and residence time were varied in the range of 200-300°C and 20-40 min, respectively. The results obtained indicate that the volatile matters, O/C and H/C ratios of biochar decrease with increasing temperature and residence time. The fixed carbon and heating value of biochars increase with temperature and residence time. It is noticed that relative energy density of pelletized biomass is only 1.10 and raw biomass is 1.20-1.40 at the same torrefied conditions. This indicates pelletized one is hard to torrefy, and woody biomass could be a potential high-quality fuel after torrefaction.
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