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Why must fine iron ore be agglomerated before blast-furnace use?

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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.

Fine iron ore, or "fines" (particles smaller than 7 millimetres), must be agglomerated before being used in a blast furnace primarily to ensure the efficient and regular descent of the furnace charge.12

The blast furnace requires ore particles to be within a specific size range—typically between 7 and 25 millimetres—to maintain consistent gas flow. If the ore is too fine, it can cause the charge to stick or impede the upward movement of combustion gases, which prevents the necessary heat and oxygen exchange required to convert iron oxides into metallic iron.123

Agglomeration processes, such as sintering, fuse these small particles into larger, evenly sized lumps. By narrowing the range of particle sizes, the charge descends more regularly, enhancing the contact between the rising gases and the descending solids, which significantly improves furnace productivity and process control.2451