Fuel properties evaluation and inherent correlation analysis of oxidatively torrefied corn stalk

Fuel properties evaluation and inherent correlation analysis of the biochar are important in assessing the variation of fuel performance. This study investigates fuel performance changes under different oxidative torrefaction conditions of corn stalks. The obtained results imply that such a method is conducive to enhancing fuel properties, with the values of energy-mass co-benefit index (EMCI), upgrading energy index (UEI), Hardgrove grindability index (HGI), and equilibrium moisture content (EMC) range at 4–9, 500–3500, 60–120, and 9.5–12. This indicates that oxidative torrefaction is efficient for fuel performance improvement. For elemental transformation and carbonization degree, the oxidatively torrefied biochar possesses a higher proportion of elemental carbon content and better graphitization degree (GD), thus contributing to a more stable structure. Good linear relationships are exhibited from the analysis of comprehensive pyrolysis index (CPI) versus elemental carbon proportion (ECP), comprehensive combustion index (CCI) versus ECP, CPI versus GD, and CCI versus GD, with correlation coefficients of 0.9741, 0.9524, 0.9689, and 0.9166, respectively. This suggests that the carbonization extent is highly related to biochar pyrolysis and combustion characteristics. Overall, the obtained results are conducive to enhancing inherent correlation cognition of fuel property indicators. In doing so, the fuel property can be better adjusted for performance enhancement, thus facilitating efficient biochar production with better industrial application potential.