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How does carbon monoxide remove oxygen from iron ore inside a blast furnace?

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How iron is turned into steel — iron processing Iron ore is one of the most abundant elements on Earth, and one of its primary uses is in the production of steel. When combined with carbon, iron changes character completely and becomes the alloy steel.

Inside a blast furnace, carbon monoxide (CO) acts as a reducing agent to extract oxygen from iron ore. This process occurs as the furnace charge—a mixture of iron-bearing materials, coke, and flux—descends through the vertical shaft, or stack.12

As coke burns in the presence of a preheated air blast near the bottom of the furnace, it generates heat and produces carbon monoxide gas. This gas rises through the furnace and reacts with the iron oxide present in the descending ore. During this chemical reduction, the carbon monoxide strips oxygen atoms from the iron oxide, resulting in the production of metallic iron and carbon dioxide (CO $_{2}$ ).123

While this gas-based reduction removes a significant portion of the oxygen, any remaining iron oxide is further reduced by direct contact with carbon from the coke at the higher temperatures found in the furnace's intermediate zone, known as the bosh. This process ultimately yields molten iron that collects in the hearth.12