Rich Premixed Combustion Characteristic of H₂-O₂ for Hydrogen Metallurgy and Cement Calcination

To achieve low-emission and high-efficiency in the metallurgy and cement industries, the high-temperature reducing gases generated by hydrogen-oxygen rich premixed combustion can be used for low-carbon and efficient reduction of metallic ores and calcium carbonate. Hydrogen-oxygen rich premixed combustion technology is one of the core methods for this process and provides theoretical support for the development of related burners. In this study, the combustion characteristics of hydrogen-oxygen rich premixed combustion in a combustor with a bluff-body are numerically simulated. The results show that the flammability limits of the hydrogen-oxygen mixture are wide at different Reynolds numbers, and stable operating equivalence ratios range from 1.75, 2.05 and 2.10 at Reynolds numbers of 300, 400 and 500, respectively. The flame remains symmetrically stable before flashback or blow-off occurs, and is C-shaped. The reverse flow of the flow field carries the hydrogen gas to the vicinity of the recirculation zone immediately adjacent to the bluff-body, where it subsequently mixes with the high temperature combustion products and flows out of the burner. However, oxygen is completely consumed near the upstream boundary of the flame front. Further analysis indicates that as the Reynolds number increases, the hydrogen content in the exhaust gas decreases slightly, while the hydrogen content increases almost linearly with the equivalence ratio. By adjusting the flow rate and equivalence ratio, the hydrogen percentage in the reductive gas can be precisely controlled over a wide range. This study offers a new approach to achieving ultra-low CO₂ emissions while efficiently reducing limestone or metallic minerals using green hydrogen.