Pig iron production

O pig iron is a league composed of iron (about 0.1%), carbon (from 3% to 6%), manganese (about 0.5%), silicon (from 1% to 4%) and sulfur (about 0.1%). Your production it is routinely carried out in blast furnaces in the shape of a vat, about 30 meters high.

THE production ofpig iron is an activity of the steel industry of extreme economic importance because it corresponds to a large part of the cost of production of the steel. The production of this alloy occurs through the process of reducing the iron present in ores that contain this element.

So, the pig iron production depends on the use of iron ores, that is, ores formed by iron oxides, which do not have any use for the production of steel, but are essential for the extraction of iron.

There are several ways to extract iron from ores, which have been improved throughout history, since the use of alloys formed from iron dates back to before Christ. However, the most used technique for pig iron production is the reduction in blast furnaces, which will be addressed in this text.

Ores for the production of pig iron

The main iron ores used in the production of pig iron are:

• Hematite (Fe₂O₃);

• Magnetite (Fe₃O₄);

• Limonite (Fe₂O₃.nH₂O);

• Siderite carbonate (FeCO₃).

Raw material

For the production of pig iron in a blast furnace, the following raw materials are required for each ton of material produced:

• Iron ore: about 1700 kg;

• Coke (a type of charcoal): about 500 kg;

• Calcium oxide (CaO) or magnesium oxide (MgO): about 140 kg;

• Hot air: about 1800 kg.

Stages of pig iron production

1^O Step: Iron ore extraction;

2^O Step: Mixture of iron ore with coke and calcium oxide (or magnesium oxide);

3^O Step: Preheated air injection (at a temperature of approximately 1200 ^OÇ). The oxygen gas in the air reacts with the coal and produces carbon monoxide (CO), which is the reducing agent in the pig iron production process;

C + O₂ → CO_(g)

4^O Step: The heat from hot air and coal combustion smelt iron ore;

5^O Step: Concomitantly, there is a chemical reaction between carbon monoxide and iron oxide (such as hematite), forming molten metallic iron (Fe), that is, pig iron, in addition to elements such as carbon, sulfur, manganese, etc.

Faith₂O₃ + 3 CO → 2 Fe + 3CO₂

Cast iron collection

Note: There are steel companies that produce pig iron that, when producing it, then produce steel from it. Likewise, there are still those industries that only produce pig iron to serve as a source of supply for others that work with the production and manufacture of steel.

Damage to the environment

THE pig iron production it is extremely important economically and industrially, however, its realization, mainly in blast furnaces, leads to the following environmental damage:

• Intense deforestation for charcoal production;

• Increased emission of carbon dioxide in atmospheric air;

• Emission of sulfur oxides into the atmosphere;

• Emission of organic pollutants with carcinogenic potential.

However, contrary to the environmental damage caused, several companies that carry out the production of pig iron carry out the planting of trees that will be used in the production of charcoal. These trees use in photosynthesis part of the carbon dioxide formed in the production of pig iron.

By Me. Diogo Lopes Dias

Source: Brazil School - https://brasilescola.uol.com.br/quimica/producao-ferro-gusa.htm