The iron ore used in blast furnace ironmaking is mainly divided into natural rich ore and artificial rich ore. Natural rich ores with iron content of more than 50% can be directly used for blast furnace smelting after proper crushing and screening. Natural massive ores are collectively referred to as raw materials. Generally, the lean iron ore cannot be directly fed into the furnace. It needs to be crushed, enriched and re collected to produce industrial rich ore (sinter or pellet), and then fed into the furnace. The iron content of artificial rich ore is generally between 55% and 65%. Because the artificial rich ore is roasted or sintered at high temperature in advance, it is also called clinker. Its smelting performance is much better than that of natural rich ore, and it is the main raw material for modern blast furnace smelting.
Natural iron ore is divided into magnetite, hematite, limonite and siderite according to its main minerals.
Composition and characteristics of common iron ores
Magnetite: its reducibility is worse than other iron ores, and its melting temperature is 1500-1580 ℃.
Hematite: due to the low content of sulfur and phosphorus, its reducibility is better than that of magnetite. It is an excellent raw material. The melting temperature of hematite is 1580-1640 ℃.
Limonite: usually refers to the general term of hydrous iron oxide. Generally, this kind of ore has low iron content, but after roasting to remove crystal water, the iron content increases significantly, and there are more harmful impurities such as sulfur, phosphorus, arsenic and so on.
Siderite: also known as carbonated iron ore, generally has low iron content, but if it is decomposed by heat and releases CO2, its grade will increase significantly, and its structure will become more loose and easy to reduce, so it is generally roasted before using this kind of ore.