Torrefaction of woody biomass (Acacia nilotica): Investigation of fuel and flow properties to study its suitability as a good quality solid fuel

Torrefaction of Acacia nilotica was carried out in a quartz fixed-bed reactor. Temperature and residence time varied from 220 to 280 degrees C and 20-60 min. The fuel (volatile ignitability (VI), combustibility index (CI), fuel ratio (FR)), and flow (Hausner ratio (HR), cohesion coefficient (C), Carr compressibility index (CCI), angle of repose) properties were investigated for raw and torrefled biomass. Torrefled biomass was also characterized through TGA, FTIR, SEM-EDX and ICP-MS analysis. For moisture sorption test, contact angle was measured. Finally, torrefled biomass was compared with coal using published literature. The HHV, fixed carbon content, FR of raw biomass at 280 degrees C for 40 min was increased from 19.31 to 24.76 MJ/kg, 11.35 to 60.40 wt %, and 0.13 to 1.63, respectively. While, VI, CI, C, CCI and bulk density of raw biomass at similar condition of torrefaction decreased from 15.76 to 15.37 (MJ/kg), 147.40 to 17.37 (MJ/kg), 0.40 to 0.33, 22.85 to 15.86 and 230.82 to 172.84 (kg/m(3)), respectively. ICP-MS analysis revealed that torrefled biomass was enriched in sodium, potassium, calcium, magnesium, etc. At similar torrefaction condition, the moisture absorbed by raw and torrefled biomass was 35.44% and 6.61%, respectively. Contact angle (79.1 degrees/77.5 degrees) for torrefled biomass suggested its hydrophobic nature. (C) 2020 Elsevier Ltd. All rights reserved.