Kiln feed refers to the processed and prepared material — whether ore concentrate, filter cake, calcined intermediate product, or a blended mixture of chemical compounds — that is introduced into a rotary kiln or other thermal processing furnace as feedstock for high-temperature treatment. In the mining and minerals processing industry, the concept of kiln feed is directly relevant across several commodity sectors: in bauxite and alumina production, in gold processing via roasting circuits, and in iron ore pelletising operations.
In the Bayer process alumina refinery — the primary downstream processing route for bauxite — kiln feed refers to the aluminium hydroxide (gibbsite) filter cake or hydrate precipitated from supersaturated sodium aluminate liquor, which is fed into a calcination kiln to drive off chemically bound water and produce anhydrous aluminium oxide (Al2O3), also known as smelter-grade alumina (SGA). The quality of kiln feed is carefully controlled in terms of moisture content, particle size distribution, chemical purity, and flow characteristics to ensure stable kiln operation and consistent product quality. In gold mining, refractory sulphide concentrates are roasted in kilns or multiple hearth furnaces to oxidise sulphide minerals and liberate encapsulated gold particles before cyanide leaching. In iron ore pellet plants, a carefully prepared mixture of iron ore fines, binder (bentonite), and additives constitutes the kiln feed to be indurated (hardened) in a travelling grate-rotary kiln or straight grate system.