The oxygen blast furnace (OBF) process has been extensively studied theoretically because of the potentials of promising energy conservation and CO2 emission reduction. Herein, investigations of the OBF process are reviewed and some suggestions for its future development are presented. The main findings can be condensed into the following: static and dynamic models of the OBF should be revised to considering the newest theoretical findings in the thermodynamics and kinetics involved as well as the particular limitations of the technology. Models focusing on energy demand and emissions should be further developed and applied to enhance the design for increased efficiency and sustainability of the complicated OBF system. It will be challenging to operate the full OBF process with top gas recycling (TGR). The development of mathematical models focusing on the practical operation is therefore warranted and would provide useful tools for tackling control problems and difficulties that will arise in forthcoming industrial trials. Considering these potential challenges, a medium oxygen‐enriched blast furnace with TGR as a forerunner is suggested because its operation conditions show greater resemblance with those of the traditional blast furnace. This furthermore provides a path of transition to the use of the full OBF in industrial scale.

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The thermodynamic data of iron oxides reduction reactions from the most recognized thermodynamic database (NIST‐JANAF) show remarkable difference between stoichiometric and nonstoichiometric iron oxides. Iron oxides reduction equilibria in both CO‐CO2 and H2‐H2O atmospheres are calculated with Dieckmann's and Weiss’ defect models. Relevant literatures are investigated and reduction experiments are carried out to complement and interpret the newly calculated equilibrium diagram. The results suggest a conjecture of two routes for hematite reduction reactions. With the ideal and widely accepted mechanism, hematite is reduced to magnetite and then to iron below 576 °C, while the reduction route follows the sequence of Fe2O3 → Fe3−δO4 → FexO → Fe above 576 °C. With the regular but always unrecognized mechanism, the reduction process of hematite experiences Fe3O4, FeO, and Fe step by step in all possible temperature above 156 °C. In the regular mechanism, sufficient scattered impurities occupy crystal interstices of magnetite and prevent the newly produced FeO unit cell from dissolving into the solid solution of magnetite, and then the FeO will accumulate above 156 °C. Actually the regular mechanism is hard to realize and usually confused with the ideal mechanism. The presence of the regular mechanism is proved by experimental phenomena of the drop of eutectoid temperature.

The carburization of molten iron is close to saturation in the blast furnace process, while that in the flash ironmaking process is uncertain because there is no pressure from solid charge and no carburization reactions occurring between the deadman and hot metal. Some experiments were conducted to reveal the kinetic mechanism of coke dissolving in carbon-iron melts. Reduced iron powder, electrolytic iron as well as chemical pure graphite were used as experiment materials. With high-purity argon injected as the protective gas, the specimens were heated up to 1873 K in a tubular resistance furnace to study the isothermal mechanism. The results show that the composition of the ferrous sample affects the dissolution rate. When the FeO content of the iron-bearing material rises from 0% to 4.76%, the apparent dissolution rate constant, kt, falls from 7.98 × 10−6 m/s to 5.48 × 10−6 m/s. There are some differences amongst the dissolution rate coefficients of different cokes despite interacting with similar carbon-iron melts, with coke 1 of 7.98 × 10−6 m/s, coke 2 of 5.17 × 10−6 m/s, and coke 3 of 3.77 × 10−6 m/s. Besides, this index decreases with the increase of the dissolution time and solely depends on the procedure of the mass transfer. A negative correlation is demonstrated between kt and the sulfur content in the iron bath as well. The content of silicon dioxide in the coke has a significant influence on kt. Additionally, the dissolution rate coefficient increases with the increase of the graphitization degree of coke.