A Technical Review on Direct Reduction of Iron Ore Using Nh3

Traditional ironmaking technologies are notably energy intensive and significantly contribute to carbon emissions. Several pathways exist for reducing or eliminating CO₂ emissions from iron production, including carbon capture and storage and the use of carbon-free or carbon-neutral renewable reductants. This review critically examines the thermodynamics and kinetics involved in the direct reduction of iron oxides using various reductants, such as carbon monoxide, hydrogen, and ammonia, with a particular emphasis on the potential of direct ammonia reduction with iron ore as a means of decarbonising the ironmaking industry. Subsequently, the review explores current ironmaking technologies, including the coke-based blast furnace process, the pulverized coal-based HIsmelt process, gas-based direct reduced iron (DRI) processes (including fluidized bed reactors and shaft furnaces), and coal-based DRI processes (such as rotary kilns and rotary hearth furnaces). The analysis encompasses process flowsheets, reduction mechanisms, feedstock types, operating conditions, and the prospective adaptation of ammonia as a carbon-free reductant. The review identifies the challenges associated with using ammonia as a reducing agent in ironmaking, highlighting unresolved scientific questions, technical obstacles, and economic and environmental problems. Finally, it concludes by proposing directions for future research efforts aimed at addressing these challenges.