Abstract:Torrefaction experiments of six biomass including polar branch,willow branch,rice husk,corn stalk,pelletized rice husk and pelletized sawdust are investigated in a fixed-bed reactor at the temperature of 200~300℃ and the residence time of 20~40 min.The variation of H/C ratio,O/C ratio,energy yield,energy density of biochars are analyzed based on the results of proximate analysis,ultimate analysis and low heating value.The obtained results indicate that volatile matter,mass yield,H/C ratio,O/C ratio and energy yield decease,but the fixed carbon,low heating value and energy density increase with the increase of torrefaction temperature and residence time.The influence of torrefaction temperatureon biochar is significantly better than that of residence time,and torrefaction has a significant effect on woody and agricultural biomass compared with pelletized biomass.The energy density of pelletized biomass is only 1.10,but the energy density of woody biomass is 1.40 at the temperature of 300℃ and the residence time of 40 min.