Iron ore

Iron ores are mixture of chemical compounds of iron with non-ferrous rocks ( the so-called gangue or " numb " rock). The chemical compounds of iron in the iron ore are substantially iron oxides, that is, chemical compounds of iron with oxygen or iron carbonates. Add small amounts of iron ores are smelted, in which the iron with sulfur ( pyrite ) or some other elements is connected.

The main ore minerals are magnetite (up to 72 % iron content), hematite (up to 70 % iron content) and siderite (up to 48% iron content).

Development of iron ore deposits

Magmatic origin

Ore deposits are common magmatic origin. In geologically active areas magma penetrates with a high content of precious metals in the Earth's crust. During the cooling of the magma it comes to the crystallization of the minerals and the formation of ore deposits.

Secondary deposition

Iron-rich melt rocks are either relocated or disbanded and elsewhere excreted, for example at black smokers. The latter iron ore formations are called sedimentary exhalative - formations. These include, inter alia, the iron ores of the Lahn -Dill type.

Biogenic table

Certain bacteria produce elemental oxygen as a metabolic product and thus lead to the oxidation of Fe (2 ) ( bivalent) to Fe ( 3 ) ( trivalent). Fe (3 ) compounds are much less soluble in water as Fe (2 ) Compounds. The corresponding iron oxides / hydrated oxides ( red to diagenesis / metamorphism ) fall out of it, as long as there is dissolved in seawater nor sufficient Fe (2 ). For bands ores may occur if the metabolism of the bacteria under unfavorable conditions ( lower temperature, less food supply etc. ) is lower. Then store primarily silicates (clay ) or silica gel ( solidified: Chert, chalcedony, corresponds to about Jasper ), which appear in light gray. This alternation leads to the harness red to dark gray-light gray. It is believed that this oxidation of Fe ( 2 ) has formed by the bacteria oxygen prevents a long time in the world's oceans, the oxygen content of the atmosphere could rise. Only when the dissolved iron was oxidized and precipitated in the oceans, this oxygen bacteria-produced reached the atmosphere.

Harness:

• When much oxygen was formed, falls ⇒ red iron oxide from layers
• In low oxygen ( ie little bacteria) can not think of iron oxide from ⇒ gray layers

This results in layers of different colors, hence the name.

Lawn iron ores are the oldest iron sources of man, apart from the very rare iron meteorites, they are to be reduced most easily degradable and easily ( limonite ), but mostly exhausted on a small scale and fast.

Iron can be used as easily soluble Fe (2 ) are transported (e.g., released from weathered silicate rocks ) and precipitate in the soil after the oxidation from these iron-containing solutions and accumulate. Verkarsten / weather, for example, slightly ferruginous limestone, the iron-containing solutions often fall in karst columns of cavities after oxidation to Fe (3 ) and form concretions of hydrated iron oxides ( limonite ). These are mainly in argillaceous basis (bolus ), which forms an insoluble residue of limestones weathering. The Limonitkonkretionen were called Bohnerz and formed for example as so-called Doggererze in Southwest Germany ( Markgraeflerland, plateau of the Swabian Alb, in the Swiss Jura ) the basis of a small iron industry.

The States with the largest funding

In the Amazon jungle of Brazil, in the Serra dos Carajás, the largest iron ore deposit in the world, there is an estimated 17 billion tonnes of iron ore bands, obtained in a huge open pit.

The four major iron ore producing countries, home to 83 % of the global production ( 2009), China, Brazil, Australia and India.

Processing of iron ores

Following extraction, iron ores are processed at the place of decomposition and thereby separated from the bulk of gangue. Thereby, the costs for transportation and further processing are substantially reduced.

In the preparation of the iron ore raw material is first comminuted in several steps. As Crushing machines are cone crusher or jaw crusher and mills such as ball mills are used. If a sufficiently large shed is constructed, it is the further sorting. Possible steps are flotation and magnetic separation. Subsequently, the iron ore concentrate is further processed to iron ore pellets.

Reduction of iron ore in the blast furnace

In the blast furnace process, iron oxide is removed by chemical reaction with carbon monoxide and oxygen. We call this type of reaction redox reaction.

Here are other oxides, such as manganese dioxide and silicon dioxide is reduced. Further, the iron shall on carbon. Therefore, in the blast furnace process there is no pure, but pig iron containing carbon, silicon, manganese, phosphorus and sulfur. Then steel from the pig iron produced (see: steel production ).