Biomass–Coal Hybrid Fuel: A Route to Net-Zero Iron Ore Sintering

Abstract

The global steel industry uses fossil fuels to produce millions of tonnes of iron ore sinter each year. Sintering is an energy-intensive process that fuses iron ore and flux to produce material that balances a high mechanical strength at a sufficient particle size to ensure a macroporous burden in the blast furnace to enable rapid gas flow. As significant CO2 greenhouse emissions are emitted, the defossilisation of these CO2 emissions is vital to net-zero carbon targets. Two iterations of a new biomass–coal hybrid fuel (ecoke®(A) and ecoke®(B)) were compared with coke breeze and an anthracite coal using oxygen bomb calorimetry, simultaneous thermal analysis (STA) combining thermogravimetry and differential scanning calorimetry, and isoconversional kinetic modelling and pyrolysis–GCMS to study the volatile matter. The calorific values of both ecoke®(A) and (B) were marginally higher than that of the coke breeze: 27.9 MJ/kg and 27.8 MJ/kg, respectively, compared with 26.5 MJ/kg for the coke breeze. A proximate analysis revealed both ecoke® samples to have higher volatile matter contents (ca. 12–13%) than the coke breeze (7.4%), but less than the anthracite coal (ca. 14%). The thermogravimetric analysis of the burnout kinetics of the fuels heated up to 1000 °C, at heating rates from 5 to 25 °C/min, showed that that the coke breeze and anthracite coal had higher ignition and burnout temperatures than the ecoke® samples. Kinetic analysis using the Freidman and Ozawa methods found that the ecoke® samples showed comparable maximum mass loss rates to the coke breeze but lower activation energies. From these results, both ecoke® samples have the potential to replace some of the coke breeze in the sintering process or EAF processes to help achieve net zero by offsetting up to 30% of the CO2 emissions.