Investigating effects of temperature on fuel properties of torrefied biomass for bio-energy systems

Abstract

Torrefaction of selected agro-residues (rice straw and cotton stalk) was successfully carried out on indirectly heated, batch-type fixed-bed reactor under different reactor temperatures (200–300°C) at a fixed heating rate of 10°C/min. Our preliminary results demonstrated that the rice straw, torrefied at 275°C, exhibited higher mass yield (64%) and energy yield (84%) with better fuel properties, i.e. lower moisture content (1.2%), volatile matters (54.7%), higher fixed carbon (24.8%), and higher heating value (HHV) 18.7 MJ/kg. On the other hand, cotton stalk showed a slightly lower mass yield (56.3%) and energy yield (74.4%) compared to rice star with very high HHV 22.5 MJ/kg torrefied at a relatively lower temperature of 250°C. Interestingly, the lignocellulosic composition showed a drastic increase in the lignin content of rice straw and cotton stalk, torrefied at 275°C and 250°C, respectively, which indicates good binding ability of bio-fuel leading to improved energy density. Our present work gives an insight that the torrefied rice straw and cotton stalk could be a promising biomass feedstock for bio-energy based systems such as biomass pyrolsyis and gasification.