Iron ore pellets are marble-sized balls of iron ore that are fused with clay for transportation and used in steel manufacture. The process of making pellets from iron ore is called pelletizing. The manufacture of steel from low-grade iron ore involves processes like mining, crushing, separating, concentrating, mixing, pelletizing, and shipping.
Iron ore pellets vary in size from 8 to 18 mm and are the principal raw material for blast furnaces. 67-72% of these pellets are composed of iron, and the rest is made up of binders (clay) and limestone, dolostone, and olivine. The reason why iron ore is preferred in the form of pellets, rather than as particles, is that pellets allow better airflow in the furnace, thereby ensuring better smelting of ore.
During the process of pelletizing, the non-agglomerated iron ores are mixed together with the additives. The ratio of mixing depends on the quality of the pellets and the quality of the sinter fines. The mixture is then molded in the form of round pellets. The pelletizing plant consists of a number of balling drums, which are aligned serially.
The iron ore concentrate is rolled in these drums to make pellets. Pellets are scrutinized and sorted according to their size specifications. The pellets that are over or undersized are crushed and returned to the balling drums. The pellets that are out of the balling drums are delivered to the roller feeder to remove the fines. The correctly sized pellets are hardened by preheating to temperatures of 1200-1300°C in a rotary kiln. After the heat treatment, iron ore transforms into hard pellets that are fit for transportation.
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