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

Abstract

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.