Clean iron production through direct reduction of mineral iron carbonate with low-grade hydrogen sources; the effect of reduction feed gas composition on product and exit gas composition

Direct reduction of mineral iron carbonate with hydrogen is a high-potential candidate for carbon dioxide emission reduction in the iron and steel industry. This novel technology provides a new route for ‘clean’ iron production. For economic implementation, a sufficient supply of hydrogen is crucial. Up to now only highly pure hydrogen sources were used for the direct reduction. On the way to a sustainable, completely hydrogen-based iron production, low-grade hydrogen sources need to be considered. The effect of the hydrogen concentration and the impact of matrix constituents such as methane and carbon dioxide in the hydrogen source on the direct reduction of mineral iron carbonate with hydrogen at 873 K were investigated in this project. It was shown that complete iron carbonate conversion is possible at a metallization degree of 78 wt% with hydrogen concentrations as low as 55 vol%. Carbon dioxide in the feed gas (27–63 vol%) favors magnetite formation instead. Hydrogen is also consumed by the reverse water gas shift reaction in the formation of carbon monoxide. Methane in the feed gas (15–80 vol%) does not have a negative impact on the composition of the solid product. These results suggest that methane-rich hydrogen sources (e.g., coke oven gas) are viable options for direct iron carbonate reduction opening up a novel pathway for clean iron production from mineral iron carbonate with low-grade hydrogen sources.