Iron ore

All ores containing economically available iron are called iron ores. There are many kinds of iron ores, mainly used for iron making are magnetite (Fe3O4), hematite (Fe2O3) and siderite (FeCO3).

Iron ore is an international commodity, strategic material, which belongs to the economic lifeline. The world's iron ore resources are concentrated in Australia, Brazil, Russia, Ukraine, Kazakhstan, India, the United States, Canada, South Africa and other countries.

China, as the world's largest iron ore demander, has not a small reserve of iron ore, but its grade is unfortunately low. From the perspective of industrial economy, it is better to import from Australia, Brazil and other countries rich in iron ore. Iron ore which can be directly invested in steelmaking in steel-making furnace is called "flat furnace rich ore", and iron ore which can be directly used for iron making is called "rich ore in blast furnace", all of which have the word "rich". These rich minerals are preferably magnetite and hematite, which contain more than 70 percent of iron. Poor ore, or iron ore with more harmful impurities, needs to be beneficiation first, and the cost will go up at once. The classification of iron ore is very complex, and can be divided according to the main components, harmful impurities, structure and gangue types. Each angle can be divided into many kinds. Which one is selected in industry and what kind of process is corresponding to, and there are many stresses. It is a great knowledge. Our country's Beijing University of science and technology, formerly known as Beijing Iron and Steel Institute, is the whole university to study how to make iron and steel.

Classification of iron minerals

Iron is in the state of compounds in nature, especially in the state of iron oxide. Several important iron ores are presented to explain:

magnetite

（MagnetITe）

It is a kind of iron oxide ore, mainly composed of Fe3O4, a complex of Fe2O3 and FeO, which is black gray with a specific gravity of about 5.15 magnetite

The results show that the magnetic properties of the two groups are about 72.4% and 27.6% respectively. Magnetic separation can be used in beneficiation, which is very convenient to deal with; But because of its fine structure, it is not reducible. After long-term weathering, it becomes hematite.

Hematite

（Hematite）

It is also an iron oxide ore, mainly composed of Fe2O3, which is dark red, with a specific gravity of about 5.26, containing Fe70% and O 30%, which is the most important iron ore. It can be divided into many categories according to its own structure, such as red hematite, specialhematite, micaceous hematite, red ocher, etc[ 5] Limonite

（Limonite）

This is the ore containing iron hydroxide. It is a general term for goethite hfeo2 and lepidocrocite FeO (OH), and it is also regarded as the main limonite

The chemical formula of the composition is mfe2o3.nh2o, which is yellowish or brown, containing about 62%, O 27%, H2O 11%, and the specific gravity of about 3.6-4.0, and most of them are attached to other iron ores.

Siderite

（Siderite）

It is a mineral containing ferrous carbonate, mainly composed of FeCO3, which is green gray with a specific gravity of about 3.8. Most of the ore contains a considerable amount of calcium and magnesium salt. Because carbonate will absorb a lot of heat and release carbon dioxide at high temperature of 800-900 ℃, most of them will be roasted before adding blast furnace. Grade 4 requires the grade of iron ore refers to the mass fraction of iron elements in iron ore, and it is popular for iron ore

That is, the iron content. For example, the grade of iron ore is 62, which means that the mass fraction of iron element is 62%

For hematite (Fe2O3), the theoretical highest grade is 70%

For magnetite (Fe3O4), the theoretical highest grade is 72.4%

For siderite (the main component is FeCO3), the theoretical highest grade is 48.3%

For limonite (fe2o3.h2o), the theoretical highest grade is 62.9%