Role and Enhancement Mechanism of Carbon Deposition in the Low‐Temperature CO Reduction of Bayan Obo Iron Concentrate Pellets

The production of direct reduced iron (DRI) by reducing pellets in a shaft furnace is an important pathway to lower carbon emissions, replacing the conventional blast furnace–converter process with a shorter shaft furnace–electric furnace route. Low‐temperature CO reduction of Bayan Obo iron ore concentrate pellets was investigated using a thermogravimetric analyzer (TGA) to understand the role of carbon deposition. Thermodynamic results indicate that the decomposition reaction of CO (2CO → C+CO 2 ) predominates below 644°C. At 703°C, Fe 3 C forms via the reaction between CO and FeO, while at 814°C, it is generated by the direct reduction reaction (3Fe+C → Fe 3 C). Experimental findings show that after 6 h of reduction, a carbon deposition layer about 2 mm thick with evident stratification forms on the pellet surface at 600°C. At 700°C, the free carbon layer decreases to around 1 mm with an indistinct stratified structure, and the reduction degree reaches 90.53%, meeting shaft furnace smelting requirements. At 800°C, both free carbon and the stratified structure disappear, and a small amount of Fe 3 C is formed. The amount of Fe 3 C increases at 900°C, but it disappears at 1000°C, where the reduction degree reaches 97.01%.