The furnace is designed for smelting cast iron. First appeared in the XV century. in Europe. In Russia, the first blast furnace was built in 1620 near Tula. Then the fuel for such stoves was charcoal. Only a century later (1709) did the English inventor Abraham Derby manage to carry out blast-furnace smelting, replacing charcoal with coke.
Centuries-old experience has changed the design of the blast furnace, its appearance and the very scheme of cast iron production. But the basics remained the same. Today, a blast furnace is a structure of about 30 meters (height varies ± 5 m). The height of the entire structure can exceed 80 m.
How is a blast furnace arranged?
Blends (sinter, pellets, iron ore, manganese ore , fuel and fluxes) are loaded through the upper part (top). Below is the mine, the largest part of the blast furnace, which is a cone expanding downward. Thanks to this expansion, solid materials that increase in volume when heated are easier to drop. To the bottom of the mine adjoins a steam (wide, cylindrical). The mixture is melted in it. Behind the pair, below, are shoulders made in the shape of a truncated cone with a reduced base below. Such a cross section is most suitable for a decreasing volume of materials due to melting.
In a cylindrical furnace, the lower part of the profile, coke is burned and the liquid melting product is collected.
The forge is divided into parts: the upper zone (tuyere) and the lower (metal receiver, in which the melting products are collected). The bottom of the furnace is called the hearth.
In the tuyere zone there are tuyere devices that supply blast into the blast furnace (heated air). It is this area that is responsible for the burning of coke, the temperatures here rise to their maximum values - 2000 degrees. At the top of the top, the temperature is lower (up to 350 degrees).
A cast-iron notch is built into the lower part of the hearth, allowing the products of melting to pass - slag and cast iron itself.
Slag tap holes were previously used, but the practice of recent decades has shown that it is more practical to pass slag and pig iron through a pig iron tap hole, with their further separation in the main channel adjacent to the furnace.
The so-called foundry adjoins the furnace, where there are devices that open the cast iron notch and close it after the release of slag and cast iron. There are also gutters with ditches guiding the product of melting into ladles.
The product released from the furnace is sent to the main trough, where the iron is separated from the slag (density difference). Two ditches leave the gutter. Slag is sent along one, and pig iron along the other. Cast iron is poured into continuously moving molds (type of conveyor), after cooling, the molds overturn and then the cast iron is sent already to the cars. Slag is poured into pools, cooled by water and granulated.
Each furnace height has its own specific temperature, and it is precisely because of this that the process of transition to metal from ore proceeds.
A sufficient amount of oxygen is supplied to the bottom of the furnace for coke burning. Coke burns, being converted to carbon dioxide, which reacts with coke, being converted to carbon monoxide. Next is the reaction between carbon monoxide and iron oxides. Recovery to metal occurs. Iron is saturated with carbon and cast iron is obtained. In addition to three to four percent of carbon, manganese and silicon, sulfur, and phosphorus are present in small proportions in the alloy.
Actually, a blast furnace, the principle of operation of which was described here, may well be considered waste-free production. By-products that appear during the production process are well used outside the walls of iron plants. Slag is added to cement suitable for construction (the cinder block is so widespread now), and blast furnace gas is a good fuel that heats the air supplied to the blast furnace.