Experimental and Modeling Study on Reduction of Iron Oxide–Carbon Composite Briquette Under N2-H2-H2O Atmosphere

In this paper, the reaction behavior of an iron oxide–carbon composite briquette (ICCB) under an H2-H2O-N2 atmosphere was experimentally and numerically studied. The employed ICCB had a composition of 21.07 wt.% Fe3O4, 49.89 wt.% FeO,16.46 wt.% carbon, and 18.73 wt.% gangue. A mathematical model was developed to describe the reaction process. Isothermal and non-isothermal experiments were conducted using a thermal-gravimetric device. The reliability of the model was confirmed by comparing its predictions with isothermal experimental data. Simulation and experimental results under non-isothermal conditions revealed that, in the reduction process of ICCB, the main reactions were the stepwise reduction of iron oxide by hydrogen and the carbon gasification by H2O, and reactions involving the reduction of iron oxide by CO and gasification by CO2 were found to be negligible. The compressive strength of ICCB presented a V-type change as temperature increased, and its minimum was 1274 N/briquette at 1273 K, The ICCB presented a successive contraction, achieving a final volume shrinkage degree of 15%. Phase changes in ICCB included the conversion of iron oxides to metallic iron and the decomposition of fayalite. The development of morphology in ICCB consisted of disintegration of the sintered matrix, formation of irregular iron grains, and the emergence of a metallic iron network.