In-depth study on the synergistic conversion mechanism of iron ore with waste biochar for co-producing directly reduced iron (DRI) and syngas

Waste biochar and waste iron ore sintering dust were synergistically resourced to produce directly reduced iron (DRI) and combustible syngas in this study. A solid product with 92.45 % metallization ratio and a combustible syngas (65.69 % CO, 8.03 % CH4) with a yield of 1170.9 ml/g were obtained at 1000 °C for 60 min with 1.2 mol(C/Fe). The CO production of biochar conversion was increased by adding iron ore sintering dust, about 769.3 mL/g at 1000 °C for 60 min, 7.17 times that of biochar pyrolysis alone (107.3 mL/g). The co-conversion was the generation, growth and aggregation of iron grains for the sintering dust. This synergistic conversion achieved the recycling of these two solid waste resources to produce high-value DRI and high-calorific-value syngas, as industrial raw materials and fuels, saving fossil resources and fuels. The biochar pyrolysis, gasification and the reconversion of pyrolysis products occurred during their co-conversion. The gas production of biochar pyrolysis and gasification were 280.7 ml/g and 933.8 ml/g, while the reduction degrees of iron ore by the gas and solid from biochar pyrolysis were 12.64 % and 79.98 %. Their well-mixed state during the co-conversion process facilitated the reconversions of pyrolysis products by improving diffusion efficiency.