Assessment of Biochar for Utilization in Electric Smelting Furnace-Based Ironmaking: Study on Physicochemical Properties and Intrinsic Reactivity

Carbon sources are fundamental to ironmaking, primarily functioning as reducing and carburizing agents, thermal and chemical energy sources. In electric smelting furnace (ESF)–based ironmaking, selecting an appropriate carbon source remains important to sustain reducing conditions and supply carbon. This study investigates the physicochemical properties and intrinsic reactivity of wood chips biochar and woodcoal pellets compared to reference anthracite and coke for application in ESF. Wood chips biochar and woodcoal pellets show sufficiently high fixed carbon content with low sulfur, while woodcoal pellets possess higher volatile matter and phosphorus levels. X-ray diffraction analysis confirms a more ordered microstructure in anthracite and coke, whereas the two biochars show greater disorder, which correlates with their reactivity. Thermogravimetric analysis under synthetic air or carbon dioxide (CO2) conditions reveals higher reactivity for biochar samples compared to anthracite and coke. Kinetic analysis allows for the determination of average activation energies, with the following rank order: coke ≥ anthracite > wood chips biochar > woodcoal pellets. Eventually, to align biochar with ESF, a strategic approach is assumed: pyrolysis temperatures of ≥600 °C should be applied to decrease volatiles and increase fixed carbon. Mechanical densification of loose biochar is advised to enhance handling and transportation, increase density, and decrease reactivity.