Relative fuel property variation of gas-pressurized and conventional torrefaction for biochar performance assessment

Exploring biochar from gas-pressurized torrefaction for solid biofuel production is of great concern for the process performance assessment. This study conducts several relative indexes of biochars produced from gaspressurized and conventional torrefaction, identifying the merits of the former. The results suggest that a higher pressure is more feasible for reducing biochar volume and enhancing energy efficiency. The results of the relative higher heating value (1.01-1.07) and relative enhancement factor (1.00-1.06) indicate that gaspressurized torrefaction is more efficient for energy density improvement. Furthermore, gas-pressurized torrefaction dramatically facilitates biochar grindability, with the relative Hardgrove grindability index value ranging from 1.20 to 2.40. The proximate and elemental analysis results suggest that a higher pressure facilitates biochar carbonization and deoxygenation with a higher carbonized component. The energy consumption, efficiency, and expense calculation results imply that gas-pressurized torrefaction is more energy-efficient and cost-saving, with the relative upgrading energy index range of 1.00-1.12.