Energy-mass co-benefit torrefaction performances of corn stalk biomass as affected by temperature and time

Torrefaction is a key pretreatment technology for biomass fuel upgrading. In this study, torrefaction experiments were carried out in a horizontal tubular furnace. Six temperature gradients (200, 220, 240, 260, 280, 300 °C) and three residence time gradients (10, 20, 30 min) were established. Multiple key indicators of torrefied corn stalk were systematically tested. These indicators include color, transient mass, proximate analysis, ultimate analysis, higher heating value (HHV), energy yield, energy density, and energy-mass co-benefit index (EMCI). The results show that torrefaction effectively improves the physicochemical properties of corn stalk. Torrefaction temperature has a more significant effect than residence time. When torrefaction is carried out at 240 °C or 260 °C for 20 min, the product has excellent comprehensive performance. Its mass yield, fixed carbon content, energy density and EMCI value are above 85%, 14.5%, 1.05 and 5.0, respectively. This mild and efficient optimal torrefaction window achieves a notable process intensification effect. It provides a solid theoretical basis and technical support for the low-cost, large-scale industrial application of corn stalk torrefaction.