Smelting iron in an industrial scale is impossible without dimensional, complex and powerful furnaces. Blast Furnace - vertical shaft type structure in which iron ore is melted into a useful metal. The apparatus includes a continuous blast furnace construction work for 3-12 years, up to overhaul.
The device blast furnace
Modern oven - it is a huge structure weighing 35,000 tons and a height of 40 m to many years of smelting have been possible without downtime, the oven must be robust and reliable.. Outside the device is covered with a steel cover - base lined with thick sheets (up to 4 cm).
The inside is fire-resistant lining. It requires constant cooling, so the bottom of the assembled metal content, in which the water circulates. Since the fluid must be very much, sometimes use evaporative cooling. The essence of the method - in the evaporation of boiling water strongly absorbs thermal energy at the same time.
The oven is a structure consisting of a plurality of elements. Key presented:
- furnace throat (grate);
- to steam;
- mine;
- mountain;
- shoulders.
throat
This upper element, which serves for loading raw material (burden), and exhaust. The main part of the furnace top - the filling unit. In most cases, machines for filling charge dvukonusnye. Backfilling between the two cone covered. After smaller feed element is lowered and iron ore falls to the larger. Once typed the necessary portion, the small cone is closed, from the large ore falls into the oven. After that, the device is sealed, and large.
More advanced blast furnaces have improved design of the furnace top. The role played by the large cone rotary chute with adjustable angle. Due to the possible filling of the raw material from either side.
Throat and serves as venting. In the smelting process a huge amount of gas is formed. With him is removed and iron-containing dust which Scrubber.
Mine
Mine occupies a large part of the furnace space. Structure, expanding downwardly, is a truncated cone. Due to this charge flow is uniform. Blast Furnace - building vertical and sufficiently high. This is to ensure him- and heat treatment of the raw material heated gases.
steamed
An element in a cylindrical shape located in the middle of the working area domain. For bosh characterized by the largest diameter. Purpose design - the increase in the furnace space and the elimination of unnecessary materials. There is formed gangue.
shoulders
The truncated cone-shaped embodiment bosh - truncated component converted wider part upwards. With shoulders reduce the volume of the batch smelted pig iron production.
horn
The main part, and in which there is metal smelting. Here burns coke and gas is produced, and accumulates iron and slag occurs regular release molten metal from the structure. Horn consists of tuyere area and metallopriomnika. Through the lance by an annular duct and a heater, the hot air enters the furnace. It is required for fuel combustion. The bottom metallopriomnika called hearth.
At the bottom of the hearth and slag are iron taphole - openings through which the molten metal passes. After the release of cast hole is closed by the piston mechanism fireproof mass.
Slag holes are 1.5-2 m above the iron tapholes. Their closed using steel tipped corkscrews. Iron is separated from slag by the machine, located on the furnace trough. Both components are supplied in special buckets.
All of this gigantic structure has an enormous mass. This weight must be transmitted uniformly ground. Therefore, the blast furnace is mounted on the massive concrete foundation, the thickness of which may reach 4 m sole. The sole supports the columns, which in turn are based metal. The upper part of the foundation is made of heat-resistant concrete in a monolithic cylinder format.
Pressure huge mass ground offset device powerful foundation
The table shows the relationship of the size of some modern furnaces.
| Dimensions in mm | Useful volume of blast furnace, m3 | ||
| 2000 | 3000 | 5000 | |
| Diameter: | |||
| furnace top | 7300 | 8200 | 11200 |
| bosh | 10900 | 12900 | 16300 |
| hearth | 9750 | 11700 | 14900 |
| Height: | |||
| mine | 18200 | 20100 | 19500 |
| hearth | 3600 | 3900 | 4500 |
| helpful | 29200 | 32200 | 32200 |
| total | 32350 | 34650 | 36900 |
Additional elements of the furnace
Operation of the furnace operation requires auxiliary devices. Among them:
- heaters; major elements of a tower-type beside the oven; they receive the blast furnace gas, which then burns; This produces even more hot gas through a complex system of heating the air; last - heated to a temperature of at least 1000 degrees - comes into play for the production of pig iron;
- blowers; compressed air needed for combustion of the fuel; air enters into the furnace through devices forming pressure of about 25 MPa;
- Device for lifting and filling of the charge;
- scrubbers for flue gas purification;
- Other accessories - such as overhead cranes, which are equipped with casting yards.
Modern furnaces are equipped with automatic systems. Computerization makes it possible to control and regulate the basic parameters associated with the operation of the blast furnace. Under the control of the level of filling materials, gas pressure, temperature and blowing m. P.
Modern blast furnaces are at the mercy of automation. The computer controls the main production processes
On what principle works the blast furnace?
The principle of operation of a blast furnace based on complex physical and chemical processes. Allocate these operations:
- combustion of the fuel;
- reduction of iron;
- decomposition of limestone to calcium oxide and carbon dioxide;
- carbon saturation iron;
- metal smelting;
- melting slag, etc..
In the most general sense of the blast-furnace smelting - is the production of pig iron from iron ore. Root materials are available via pig iron:
- Fuel - coke;
- iron ore - the raw material from which iron is smelted;
- Flux - spetsdobavki of sand, limestone and other materials.
Furnace charge is flagged as melkoporodnyh fused lumps - pellets or agglomerates. As an ore material may act manganese ore or iron ore variations. The raw material is poured into throat layers alternating with layers of flux and coke.
Purpose flux - separation from the impurities iron and gangue (slag)
The slag floats on the surface of red-hot iron. Impurities emptied before the molten metal solidifies.
Feed of raw material as the operation of the furnace, must be continuous. The constancy of the process is provided by special conveyors. Entering through the elements described in the furnace, the charge is passed through a series of processes.
Burning coke provides the required temperature, which should not fall below 2000 degrees. Combustion compound promotes oxygen and coal. In parallel, it produces carbon dioxide. Under the influence of heat the latter becomes carbon monoxide. Due to this reduced iron.
reduction of iron - one of the most important stages of production. Without this process, the metal can not be finding the necessary strength.
Cast iron becomes so after a pass through the molten iron coke. That result was possible, the iron should be filled with carbon. To cast iron alloys include, as part of which carbon accounts for 2-5%.
Once finished metal accumulated in the furnace, it is discharged through the tap hole. Through the upper opening initially discharged slag, and then - through the bottom - iron. Last merges the channels in buckets and sent for further processing.
conclusion
Blast furnace - one of the most important components of the steel industry. In the current situation the blast furnace usually "embedded" in the steel mills. Average daily furnace can give about 12,000 tons of pig iron, while consuming about 20,000 tons of feedstock.
