(408d) Sustainable Pig Iron Production Via Reduction of Mineral Iron Carbonate with Hydrogen

Innovative technologies are necessary to limit CO₂-emissions from energy-intensive iron and steel production from carbonate based ores. Iron carbonate reserves are found worldwide including reservoirs in the United States (e.g. Bisbee and Antler Mine in Arizona) and China. Pig iron is produced from iron ores in a multi-step process. This process includes roasting and sintering (Eq. 1) of iron carbonate minerals. Instead of roasting in air to produce hematite suitable for iron production via the blast furnace process, we suggest direct reduction of iron carbonate [1] with sustainably produced hydrogen (Eq. 2) as a ‘green’ alternative.

FeCO₃ + 0.25 O₂ = 0.5 Fe₂O₃ + CO₂ (1)

FeCO₃ + H₂ = Fe + H₂O + CO₂ (2)

Carbon dioxide emission (due to the thermal decomposition of iron carbonate according to Eq. 2) could even be diminished in a two-step process. In the first step, iron carbonate is directly reduced to iron and carbon dioxide. In the second step, the process gas is fed to a reactor for catalytic carbon dioxide hydrogenation to yield value-added carbonaceous products. In order to develop an environmentally benign synthesis route, an insight into reaction mechanism and kinetics is important. Therefore, thermogravimetric linear heating rate data was recorded and analyzed according to the ICTAC recommendations [2]. Iron formation according to Eq. 2 follows a nucleation and growth mechanism, verified by the prediction of the measured data with an Avrami-Erofeev A2 reaction model. Thermodynamic analysis revealed that the energy demand for iron production can partially be provided by the outlined process gas treatment by means of catalytic carbon dioxide hydrogenation to produce hydrocarbons.

1. Baldauf-Sommerbauer, G., Lux, S., and Siebenhofer, M. (2016) Sustainable iron production from mineral iron carbonate and hydrogen. Green Chem., 18 (23), 6255–6265.

2. Vyazovkin, S., Burnham, A.K., Criado, J.M., et al. (2011) ICTAC Kinetics Committee recommendations for performing kinetic computations on thermal analysis data. Thermochim. Acta, 520 (1–2), 1–19.