What is a blast furnace and how does it work?

After examining the necessity of bag filter in cement factory, in this article we will talk about iron smelting blast furnace.

 Iron is the most abundant element on earth, sometimes even its ores are used as a concentrate because of its high grade, and there is no need to extract them. For iron smelting, a special technology is needed, for this purpose two methods of iron smelting blast furnace and induction furnace are used, both of which are types of smelting furnaces.

In the smelting and pyrometallurgy industry, we deal with different furnaces for different elements. Each furnace works in a special way. But among them, the most important and widely used types are the rotary furnace and the induction furnace, the first of which is very favorable for copper and lead. Stay with us in the next article.

What is a blast furnace?

As the name suggests, the blast furnace is a very tall furnace that is placed vertically. Unlike the Welsh furnace, which is placed horizontally. The capacity of these furnaces is different and can be made in the range of 70 to 6000 square meters, which can be changed depending on the needs of each factory.

The capacity of the blast furnace depends on what factors?

Many factors affect the capacity of these types of furnaces. In addition to height and diameter, which determine the capacity of these furnaces, other factors are also involved in the capacity. Among them, by reducing or increasing the fuel volume of the furnace, its capacity can be increased or decreased. For example, if the furnace fuel volume is reduced, the furnace capacity will increase. That is, by reducing the volume of fuel, there will be more space for raw materials.

If you decide to equip your workshop, you may also need a bag filter.

Types of blast furnaces for iron smelting

South Korea and Russia are the best manufacturers of blast furnaces. The blast furnace is produced in two forms, with and without rust. Its bell type, which is older, was made by the Russians, and the Russians had this technology for years. But with the progress of the smelting industry, non-rust types were made by South Korea, which have advantages over the rust type.

In rust-free types, raw materials including iron ore, coke and lime are mixed together before they are charged to the furnace. When they are charged into the furnace, they are poured into the furnace by a device that is rotating, which causes homogeneous raw materials to enter the furnace, and the energy needed to mix and mix these materials is saved. 

The advantage of other stainless steel ovens compared to its old model is the preheat part. In order to save energy, in this type of furnaces, a part is considered where raw materials are heated before entering the blast furnace. By the time they enter the furnace, both less time and less energy will be required to melt the raw materials. The energy of this heating comes from the exhaust gases of the furnace, and with this work, the waste of energy is avoided.

This condition does not exist in the case of the bell blast furnace. It is good to know that the Isfahan iron smelting furnace was built by the Russians and it is a bell type with a capacity of 2000 square meters.

Effective factors in blast furnace performance

Several factors can affect the efficiency or performance of the furnace, including the preheated part of the furnace that was explained in the previous title.

The amount of oxygen in the iron smelting furnace

which is referred to as air, and in fact, along with fuel, it can be a very important factor in the melting of raw materials.

Air pressure in iron smelting blast furnace

It is also important with what pressure the same air is thrown into the furnace, because if it is less than the air pressure, melting may not be done well in some parts of the furnace.

Reducing the volume of fuel in the iron smelting furnace

By reducing the volume of fuel, there will be more space for raw materials, which increases the capacity of the furnace.

Blast furnace for other metals

The blast furnace is mainly used for melting iron, but sometimes it is used for melting lead and other elements. However, it does not work well for other elements. The lead blast furnace has a height of about 5 to 6 meters, which is much shorter than the iron blast furnace. Also, this furnace is rectangular in the shape of a cube in lead, while it is cylindrical in iron. The product of these furnaces can never be equal to the lead smelting rotary furnace.

Iron smelting in blast furnace

To melt iron in a blast furnace, raw materials including iron ore, coke, and limestone are mixed together and poured into the furnace using a rotating device. The furnace includes two lines that work in opposite directions. Line 1, where raw materials are placed, will move downwards, and Line 2, where gases and dusts are often spent, will be upward.

Counting the charging of raw materials in line 1, the materials are prepared in the preheated part and enter the main furnace. When the raw material reaches the middle of the furnace, almost the majority of the material has melted. From this point onwards, mixing and separation of the mixture begins. Pure molten iron is separated from its slag. Separation is based on their weight difference. From the main outlet, which is located at the lowest point, molten iron, which is also called raw iron, comes out, and iron slag or slag is separated from a little higher.

Now by pouring this molten material in different molds, cast iron, steel or malleable cast iron can be produced.

Cast iron is produced by pouring molten iron into sand moulds. If they want to produce malleable cast iron, they add some magnesium iron and iron silicate. Also, in the case of steel, which is one of the most consumed and important materials in the whole world, carbon is added to raw iron.

Aso Sanat Company is a producer of the best melting furnaces for various industries, which is with you with 18 years of useful work experience and by carrying out several successful projects in the field of equipping factories with melting furnaces and other equipment such as bag filters and all kinds of industrial tanks.