A blast furnace, or blast furnace as it is often called, is designed to smelt iron from iron ore. This happens as a result of chemical reactions occurring at high temperatures. At the final stage of the process, the smelted iron is saturated with carbon and converted into cast iron (see Iron, steel, cast iron).

Blast furnace.

In a blast furnace, as a rule, it is not iron ore that is melted, but agglomerate (fine ore sintered into pieces) or pellets (spherical lumps obtained from fine ore or finely ground concentrate). They are loaded into the furnace in layers, interspersed with coke. Fluxes - lime, sand and some other substances - are also added to the blast furnace layer by layer. What are they needed for?

Together with the agglomerate and pellets, rock that does not contain iron enters the blast furnace. Metallurgists call it waste rock. It must be removed so that it does not get into the cast iron as it hardens. Fluxes cause waste rock and some other unnecessary substances (all this is called slag) to float to the surface of the liquid metal, from where the slag can easily be poured into a special ladle. So, agglomerate (or pellets), coke, and fluxes are included in a mixture of materials that is loaded into a blast furnace and is called a charge.

The blast furnace resembles a large round tower and consists of three main parts: the upper part is the furnace, the middle part is the shaft and the lower part is the forge. The inside of the blast furnace is lined (lined) with refractory masonry. To prevent the masonry from deteriorating and protect the furnace casing from high temperatures, refrigerators are used in which water circulates.

The charge is loaded into the blast furnace through the furnace in portions of several tons each. The download is continuous. To do this, a bunker is installed near the blast furnace - a warehouse where agglomerate (or pellets), coke and fluxes are delivered. In the bunker, they are used to form a charge using automated scale cars. Raw materials are fed continuously into the bunkers of large modern domains using conveyors. Also, conveyors in modern blast furnaces move the charge from the hopper to the top. In old blast furnaces, skip trailers are used for this, which run on inclined rails.

Under the influence of its own weight, the charge descends, passing through the entire blast furnace. In the middle part of the furnace - the shaft - it is washed by gases coming from the bottom up - the products of coke combustion. They heat the charge and then leave the blast furnace through the top. But the most important thing happens in the lower part of the blast furnace - the forge.

Here, in the casing of the blast furnace there are tuyeres - special devices for supplying compressed hot air to the furnace. The tuyeres have windows protected by glass, through which blast furnace workers can look inside the furnace and see how the process is going on. To prevent the tuyeres from burning, they are cooled with water flowing through the channels inside the tuyeres.

Hot air is needed to further heat the charge before melting. This reduces the consumption of expensive coke and increases the productivity of the blast furnace. In addition, to further reduce coke consumption, natural gas or fuel oil is introduced into the blast furnace as a heat source. Before being fed into the tuyeres, the air is heated in high towers filled with bricks inside - air heaters.

In the furnace of a blast furnace, coke (as well as natural gas or fuel oil) is burned, developing a very high temperature - over 2000 °C, under the influence of which the ore is completely melted. When burned, coke combines with oxygen in the air to form carbon dioxide. Under the influence of high temperature, carbon dioxide turns into carbon monoxide, which removes oxygen from the iron ore, reducing iron. Flowing down through a layer of hot coke, the iron is saturated with carbon and turns into cast iron. Liquid iron accumulates at the bottom of the hearth, and a layer of lighter slag accumulates on its surface.

When a sufficient amount of cast iron has accumulated in the forge, it is released through the holes in the lower part of the forge - the tap hole. First, the slag is released through the upper tap hole, then the cast iron through the lower tap hole. Next, the cast iron falls into ditches, from where it is poured into large cast iron ladles standing on railway platforms and sent for further processing.

If cast iron is intended for the production of castings - foundry cast iron - it goes into a casting machine, where it solidifies in the form of bars - pigs. If the cast iron is intended for conversion into steel (pig iron), it is transported to the steelmaking shop. There it enters open-hearth furnaces, converters or electric furnaces (see Electrometallurgy). Of the total amount of cast iron produced, approximately 80% is pig iron.

The first blast furnace of the Magnitogorsk Iron and Steel Works, which went into operation in 1932, had a volume of 900 m 3 . In 1986, the Severyanka blast furnace with a volume of 5500 m 3, one of the largest in the world, began operating at the Cherepovets Metallurgical Plant.

Previously, blast furnaces produced cast iron every 3–4 hours. With an increase in their volume, the production of cast iron accelerated - every 2 hours. Large blast furnaces - with a volume of 3000 m 3 or more - produce cast iron almost continuously.

In modern giant blast furnaces, not only heated air is used to maintain combustion, but also natural gas along with pure oxygen. This increases the productivity of the unit, reduces coke consumption, but at the same time makes it difficult to control the technological process. Therefore, electronic computers are now increasingly appearing in blast furnace shops. They analyze the readings of numerous instruments, monitor the progress of the process, and select the best melting modes.

The blast furnace shop is a complex set of closely related technological and energy units, including the blast furnace itself, the foundry yard and the blast furnace, air heaters, dust collectors, a blast furnace lift, a skip pit and a coke breeze lift, a bunker rack, a casting machine, etc. (Fig. 5) .
A modern blast furnace is a massive structure over 35 m high and weighing several thousand tons. The furnace rests on a reinforced concrete foundation, usually multifaceted; the lower part (base) of the foundation is buried 6-7 m into the ground. For such foundations, order the production of anchor bolts http://metall-78.ru/katalog/ankernye-bolty/. The above-ground part of the foundation (stump), lined with refractory concrete, serves as the base of the flank (Fig. 6). The lower part of the furnace flank with a volume of 1719 m3 is made of carbon blocks, the upper part is made of high-alumina brick. The bottom of the flank is cooled by air coolers. In smaller-volume kilns, the bottom is lined with fireclay bricks or carbon blocks. The height of the masonry of the flank is 3450-5175 mm.

The progress of the blast furnace process largely depends on the profile of the furnace, i.e., on the internal outline of the furnace working space.
The modern profile of a blast furnace (Fig. 7) ensures a smooth and stable lowering of the loaded charge materials, a rational distribution of the gas flow moving towards the materials, the successful occurrence of reduction processes and the processes of formation of cast iron and slag, but is still not optimal. The most rational height of the furnace, the height of the shoulders, and the angles of inclination of the shaft and shoulders have not yet been worked out. Some blast furnace workers dispute the need for shoulders and the cylindrical part of the top. Individual profile elements play a certain role in the overall process of blast furnace smelting, and the completeness of the development of certain processes depends on their sizes.

The upper cylindrical part of the furnace - the top - is used to load charge materials and to remove gases. The dimensions of the top have a significant impact on the distribution of materials and gas flow. To protect it from destruction by loaded materials, the fire pit is lined with several rows of steel protective plates shaped like segments.
The conical part, the largest in height, is adjacent to the top - the shaft. The taper of the shaft facilitates the lowering of materials, their loosening and the creation of optimal gas flow. The height of the mine is important for the development of reduction processes and slag formation. The shaft mates with the lower conical part - the shoulders - through the cylindrical part - the steam, which creates a smoother transition, reducing the possibility of delay of charge materials and the formation of “dead space”.
The shoulders have a thin-walled (345-575 mm) fireclay lining and are cooled by plate-finned coolers. The thick-walled steam chamber and shaft are also made of fireclay bricks. For cooling, box-shaped refrigerators are placed in the masonry of the steam chamber and the shaft (at 2/3 of the height). There are designs of blast furnaces with a thin-walled shaft and steaming and cooling with peripheral plate refrigerators.
The conical shape of the shoulders is due to a sharp decrease in the volume of melted materials in this part of the furnace due to the formation of liquid cast iron and slag and the combustion of coke in the lower part of the furnace - in the forge. Along with the combustion of coke, a composition of cast iron and slag is formed in the forge, which accumulate during the process in its lower part.
The hearth consists of a metal receiver, in which pig iron and slag accumulate, and an upper hearth, where the tuyeres are located, and is lined with fireclay bricks or carbon blocks. The periphery of the hearth and blade is cooled by plate refrigerators and surrounded by a welded steel casing. In the lower part of the hearth, at a height of 600-1000 mm from the flange (see Fig. 6), there is a cast iron tap hole - a channel for periodic release of cast iron. In the intervals between cast iron releases, the tap hole is clogged with refractory mass. In large furnaces for releasing slag, two slag tapholes are installed. They are located at different levels above the cast iron tap hole (1.2-1.6 m) at a certain angle to it and to each other.
The slag tap hole consists of a hollow water-cooled copper lance that fits into a conical copper cooler, which is inserted into a cast iron cooler with a coil. The hole in the slag tap hole is closed with a special stopper with a steel plug (see Fig. 6).
In the upper part of the hearth there are tuyeres (up to 20 pieces) around the circumference, which serve to supply heated air to the furnace. The hot blast from the air heater enters the annular pipe surrounding the blast furnace through a lined air duct. From the annular pipe, air enters the lined sleeve and metal nozzle and is fed into the furnace through a copper water-cooled lance (175-300 mm in diameter). The lance is inserted into a conical cooler, which fits into an embrasure that fits tightly to the furnace casing (see Fig. 6). The shaft masonry is enclosed in an all-welded steel casing. Below, at the level of the transition of the shaft to the steam chamber, it ends with a support ring, which is supported by columns with special supports that transfer the load to the load-bearing foundation slab.
To remove gases in the furnace dome there are four lateral ascending gas outlets. The vertical sections of the gas outlets are connected in pairs into two gas outlets, which transform into one downward gas outlet, which enters from above along the axis into the primary dust collector. Gas outlets are lined with fireclay bricks.
In the upper part of the blast furnace there is a charging apparatus with a rotating distributor, a pile driver and a top platform.
The filling apparatus consists of a large cone with a funnel that covers the furnace top, and a small cone with a rotating receiving funnel. This design eliminates the loss of gases into the atmosphere and ensures a fairly uniform distribution of materials across the cross section of the furnace.
The cones are suspended from vertical rods attached to the short arms of the balancers. The small cone is attached to a hollow rod, inside which the rod of the large cone passes. The balancers are connected to the winch cable for maneuvering the cones and serve to raise and lower the cones.
The charge from the skip lifted onto the fire pit is loaded first into the receiving funnel of the small cone, and when lowering it, into the funnel of the large cone and then into the furnace. By turning the funnel with the charge at a successively increasing certain angle using a drive with a gear system, a fairly uniform distribution of materials is achieved.
The rotary distributor has 6, 8, 12 and 24 stations.
After turning at a certain angle (15-60°), the small cone automatically lowers and then rises. The large cone is lowered after the required number of skips (ore, limestone and coke) have been collected.
In Russia and the USA, stationless rotating distributors are used. Such a distributor begins to rotate when the skip approaches the funnel, and its rotation speed reaches 30 rpm by the time the skip is unloaded. This ensures very good uniformity of distribution of the charge materials.
Practice has developed certain relationships between the internal dimensions of individual parts of the furnace:

These relationships were scientifically substantiated by the outstanding Soviet metallurgist Academician M.A. Pavlov. In 1910, he developed a method for calculating the profile of a blast furnace.
In addition to the full height, there is also a distinction between the usable height of the blast furnace, i.e. distance from the axis of the cast iron tap hole to the fill level. The useful height is determined by the mechanical strength of the coke; for large furnaces it is 27-29 m. The usable volume, i.e., the volume of the furnace filled with charge materials and smelting products, is of great importance for the productivity of the furnace. Currently, the most powerful furnaces have a useful volume of up to 1500-2000 m3; furnaces with a volume of 2700 m3 are being designed.

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Charge materials are loaded into the blast furnace from above, and air is supplied from below to burn fuel. The products of blast furnace smelting - liquid pig iron and slag - are released from below. The profile of the internal melting space of the blast furnace is chosen in such a way that it allows uniform lowering of loaded materials and uniform distribution of released materials.

Rice. 16. Blast furnace profile:

1 - fire pit; 2 - mine; 3 - steam; 4 - shoulders; 5 - bugle

Rice. 17. General view of the blast furnace:

1 - tap hole for tapping iron; 2 - tuyere device for supplying combined blast; 3 - cylindrical part of the flue with protective plates; 4 - large cous of the throat; 5 - small cone of the fire pit; 6 - device for rotating the receiving funnel; 7 - receiving funnel; 8 - skip; 9 - inclined bridge; 10 - interconal space; 11 - taphole for slag release; 12 - platform

Gases across the cross section of the furnace. Gases rise from bottom to top. Furnace profile. In Fig. Figure 16 shows the profile of a modern blast furnace. The upper part of the furnace is called the flue (from the word kolosha: this is the name of the boxes in which coal was transported for loading into the furnace).

Through the furnace top, which has the shape of a cylinder, the charge is loaded and gases are removed. Below the top there is a UiaxTai, which is a truncated cone, widening downwards. This shape of the shaft allows materials to spread to the sides and freely fall down. In addition, expanding the shaft eliminates the compaction of the charge. The widest part of the furnace - the steam chamber - is a short cylinder necessary to create a smooth transition from the lower wide base of the shaft to the tapering shoulders - the part of the furnace that is a truncated cone with a wide part at the top and a narrow part at the bottom. If the shaft were directly connected to the shoulders, then at the point of their connection an obtuse angle would be formed, in which the descending raw materials would be retained. The presence of steam smoothes the transition and eliminates dead space. The shoulders acquired a tapering conical shape because there is a sharp reduction in the volume of loaded materials due to coke burnout and the formation of liquid smelting products.

The lower part of the furnace is a cylindrical furnace in which liquid smelting products - cast iron and slag - accumulate. In the lower part of the hearth there are holes - tap holes for releasing cast iron, in the upper part of the hearth there are tuyeres through which air is supplied to the furnace.

Let us consider in more detail the structure of the main parts of a blast furnace, the general view of which is shown in Fig. 17.

Furnace foundation. A modern furnace, together with all structures and metal structures, lining and the charge materials and smelting products contained in it, can have a mass of up to 30 thousand tons. This mass must be evenly transferred to the ground. The lower part of the foundation (base) is made in the form of an octagonal concrete slab up to 4 m thick. Columns supporting the metal structures of the furnace (casing) rest on the base.

The upper part of the foundation - the stump - is a monolithic cylinder made of refractory concrete, on which the furnace hearth is located.

The forge (Fig. 18) can be divided into three parts. The lower, flat part of the forge is the flange, on which there is liquid cast iron and slag. The blade can withstand high pressure from cast iron. It is laid out from carbon blocks on the outside, and on the inside from large-sized high-alumina bricks containing more than 45% AI2O3. The total thickness of the flange reaches 5.5 m. The flank is exposed to high temperatures and the hydrostatic effect of liquid cast iron. Liquid

Rice. 18. Diagram of a blast furnace hearth:

I - concrete base of the furnace; 2- furnace stump; 3- carbon blocks of the forge flank; 4- high alumina brick; 5 - cast iron stove refrigerators

Cast iron penetrates between the bricks at the seams and wedges the masonry. The destruction of the flange occurs, especially severe in the first time after the start of work. To preserve the flank, a “dead layer” of liquid cast iron up to 1000 mm thick is maintained in the furnace, which is not released from the furnace. On large furnaces, the bream is completely lined with carbon refractories.

The second lower part of the hearth - from the flange to the tap hole (metal receiver) - serves as a storage tank for molten cast iron and slag. The metal receiver is laid out from carbon blocks on carbon paste. Tuyere openings, cast iron and slag tapholes are lined with fireclay bricks. The masonry is up to 1500 mm thick at the bottom and 325 mm at the top. The masonry of the platform and the metal receiver is covered by slab refrigerators, which are metal plates with pipes through which water circulates.

In some ovens, metal plates with grooves for air cooling are placed between the flank and the stump. On the outside, the stove-top refrigerators and furnace are enclosed in a metal casing made of sheets 40-50 mm thick. To compensate for the thermal expansion of the masonry of the lower part of the hearth between the refrigerators and the masonry

A gap of ~100 mm is left, which is filled with a tightly compacted carbonaceous mass. In the lower part of the hearth, at a distance of 600-1700 mm from the flange, there are holes - tap holes for releasing cast iron and slag. In furnaces with a volume of up to 2000 m3, one hole is made, in larger furnaces - up to four. Through cast iron

Cast iron. The cast iron taphole is framed by a cast steel frame, attached

Flax to the furnace casing (Fig. 19). The frame opening is lined with high-alumina brick. Leave a through channel 300 mm wide and 400-500 mm high, which is clogged with fire-resistant mass. To release cast iron, a hole with a diameter of 50-80 mm is cut in it. After the cast iron is released, the tap hole channel is again clogged with refractory mass.

Above the level of the cast iron taphole, 1400-1800 mm, there are slag tapholes intended for the release of upper slag. The slag tapholes are located at an angle of 90° to each other and at an angle of 60° to the cast iron taphole. On medium-sized furnaces, two are made, and on large furnaces, one tap hole is made for releasing slag.

Rice. 19. Construction of a cast iron tap: Taps 18 20 times B CyT-

/ - case made of fire-resistant mass; 2-KI RELEASE LIQUID

Fireproof masonry; h- frame; 4 - refrigerator

A slag device is installed in the opening of the slag tap hole, the diagram of which is shown in Fig. 20. The main parts of the slag device: a copper water-cooled lance, a copper refrigerator, a cast-iron refrigerator with a flooded spiral coil for water, a cast-iron water-cooled embrasure with which the device

Attaches to the oven casing. The conical cavity of the slag device is filled with refractory mass, in which a hole is cut for the slag to exit the furnace. The slag tuyere is closed with a metal plug using a locking device. In large furnaces, slag is released together with cast iron from one tap hole.

Rice. 20. Diagram of a slag device:

1 - cast iron water-cooled embrasure; 2 - cast iron refrigerator; 3 - copper refrigerator; 4 - copper water-cooled lance

Tuyeres. In the upper part of the hearth, at a distance of 2700-3500 mm from the axis of the cast iron tap hole, lances are located around the circumference of the furnace for supplying hot air, natural gas, pulverized or liquid fuel to the furnace. The number of tuyeres depends on the size of the furnace and ranges from 18 to 42. Air to the furnace is supplied to a ring air duct with an internal diameter of up to 1650 mm surrounding the blast furnace. From the air duct, with the help of tuyere devices, the blast enters the furnace. The tuyere device (Fig. 21) consists of a water-cooled cast copper tuyere with an internal diameter of up to 200 mm, which protrudes into the furnace from the masonry by 300 mm. The lance is mounted in refrigerators. Refrigerators help cool the furnace masonry, located in close proximity to the combustion sources, allow you to install the tuyere in the nest and eliminate the blowing of gas from the furnace. The refrigerator is made composite. Air is supplied to the tuyere through a steel-lined nozzle, which is connected to a movable elbow. Using rods and springs, the nozzle is pressed against the tuyere. To change the nozzle or tuyere, the elbow must be pulled back using a swivel connection to the adapter pipe. The pipe is connected to a tuyere sleeve connected to an annular air duct. At the end of the tuyere device there is a peephole for monitoring the fuel combustion process. When gas or fuel oil is supplied to the furnace, tubes are passed through the tuyere through which fuel is supplied. Every

The tuyere device is equipped with a device for measuring and regulating air flow.

Shoulders. The shoulders are laid in one brick with a thickness of 345 mm. The masonry is cooled by plate-finned refrigerators. Experience shows that the fire-resistant masonry of the shoulders is subject to intense wear and quickly burns out. A protective layer is formed on bare areas on the surface of refrigerators

Rice. 21. Structure of the tuyere device:

1 - copper air lance; 2, 3 - refrigerators; 4 - nozzle; 5 - movable knee; 6 - adapter pipe to the air duct

Made from slag and charge materials (scavenge), which protects refrigerators from high temperatures and liquid smelting products.

Rasp. The walls of the steam chamber have a significant thickness - up to 690 mm; they are laid out from fireclay bricks and cooled by marator refrigerators, the ends of which are filled with fireproof bricks. The shaft casing rests on a massive metal marator ring and transfers the pressure of the masonry and structures of the upper part of the furnace to it. The ring rests on columns.

Mine. The shaft is lined with fireclay bricks. Its thickness depends on the method of cooling and can vary from 690 to 1020 mm, at the top the thickness of the masonry is 920 mm. Almost along the entire height of the shaft, at two-thirds of the steam, refrigerators are installed in a checkerboard pattern. Between the casing and the brickwork or between the bricks and refrigerators, a gap of 50-60 mm is left, filled with fireclay-asbestos filling to compensate for the thermal expansion of the shaft masonry. The shaft's masonry wears out greatly under the influence of a flow of hot gases carrying small solid particles of materials. In the lower part of the mine and in steam, fireclay bricks can be destroyed due to interaction with slag. In the upper and middle horizons of the mine, destruction of the masonry may occur due to the deposition of black carbon according to the reaction 2CO = CO2 + C.

The destruction of masonry is also facilitated by the deposition of zinc oxide in the seams of the masonry, which is formed as a result of the oxidation of zinc that evaporates during melting. The average duration of a mine campaign is 4-5 years. On the outside, the batch masonry is enclosed in a durable casing. Using a spray system, the casing is watered with water, which flows down into boxes welded at the bottom of the shaft.

Koloshnik. The furnace lining is made of steel plates that protect the furnace structure from impacts of raw materials sent into the furnace. Between the slabs and the furnace casing, a layer of fireclay brick is made. The top part of the furnace casing is called the dome. The filling apparatus ring is attached to it. The dome part is lined from the inside with cast iron slabs with bricks poured into them.

Furnace casing. The entire furnace is surrounded by a welded casing made of sheets with a thickness of 20 to 50 mm.

Pig iron is smelted in blast furnaces, which are a shaft furnace. The essence of the process of producing cast iron in blast furnaces is the reduction of iron oxides included in the ore with gaseous (CO, H2) and solid (C) reducing agents formed during the combustion of fuel in the furnace.

The blast furnace smelting process is continuous. Source materials (sinter, pellets, coke) are loaded into the furnace from above, and heated air and gaseous, liquid or pulverized fuel are supplied to the lower part. Gases obtained from fuel combustion pass through the charge column and give it their thermal energy. The descending charge is heated, reduced, and then melted. Most of the coke is burned in the lower half of the furnace, providing a source of heat, and part of the coke is spent on reducing and carburizing the iron.

A blast furnace is a powerful and highly productive unit that consumes a huge amount of materials. A modern blast furnace consumes about 20,000 tons of charge per day and produces about 12,000 tons of pig iron every day.

To ensure the continuous supply and release of such large quantities of materials, it is necessary that the furnace design be simple and reliable in operation over a long period of time. The outside of the blast furnace is enclosed in a metal casing welded from steel sheets 25–40 mm thick. On the inside of the casing there is a refractory lining, cooled in the lower part of the furnace using special refrigerators - metal boxes inside which water circulates. Due to the fact that a large amount of water is required to cool the furnace, some furnaces use evaporative cooling, the essence of which is that several times less water is supplied to the refrigerators than with the usual method. The water heats up to a boil and evaporates rapidly, absorbing a large amount of heat.

The internal outline of the vertical section of a blast furnace is called the furnace profile. The working space of the furnace includes:

• fire pit;
• mine;
• steam;
• shoulders;
• horn

Koloshnik

This is the upper part of the blast furnace, through which charge materials are loaded and blast furnace or top gas is removed. The main part of the blast furnace device is the filling apparatus. Most blast furnaces have double-cone charging devices. In the normal position, both cones are closed and reliably isolate the interior of the furnace from the atmosphere. After loading the charge into the receiving funnel, the small cone is lowered and the charge falls onto the large cone. The small cone closes. After the specified amount of charge has been collected on the large cone, the large cone is lowered with the small cone closed and the charge is poured into the furnace. After this, the large cone closes. Thus, the working space of the blast furnace is permanently sealed.

Charge materials are usually fed to the furnace throat from one side. As a result, a slope is formed in the funnel of a small cone. Long-term operation of a blast furnace with a skewed charge level is unacceptable. To eliminate this phenomenon, the receiving funnel and the small cone are made rotating. After loading the charge, the funnel together with the cone is rotated through an angle multiple of 60, due to which, after unloading several feeds, the unevenness is completely eliminated. 0

Modern furnaces can install charging devices that are more complex in design. Instead of a large cone, a rotating chute is installed, the angle of which can be adjusted. This design allows you to change the location of the material supply according to the diameter of the top.

During the blast furnace smelting process, a large amount of gas is formed, which is removed from the top part of the furnace. This type of gas is called top gas. The gas contains flammable components CO and H2 and, therefore, is used as a gaseous fuel in metallurgical production. In addition, passing through the charge column, the gas captures small particles of iron-containing materials, forming the so-called flue dust. Dust is collected in special gas purifiers and used as an additive to the charge during agglomeration or pellet production.

Mine

The shaft accounts for most of the total height and volume of the furnace. The profile of the shaft, which is a truncated cone expanding towards the bottom, ensures uniform lowering and loosening of the charge materials. The significant height of the shaft allows for thermal and chemical processing of materials by rising hot gases.

Raspar

This is the middle cylindrical part of the furnace working space, having the largest diameter. Steaming creates some additional increase in furnace volume and eliminates possible delays in charge materials.

Shoulders

This is part of the furnace profile located below the steam chamber and is a truncated cone with its wide base facing the steam chamber. The reverse taper of the shoulders corresponds to a decrease in the volume of melted materials during the formation of cast iron and slag.

Horn

This is the lower cylindrical part of the furnace where high-temperature blast furnace processes are carried out. In the furnace, coke is burned and blast furnace gas is formed, interaction between liquid phases, accumulation of liquid smelting products (pig iron and slag) and their periodic release from the furnace occur. The forge consists of an upper or tuyere part and a lower or metal receiver. The bottom of the metal receiver is called flaky.

At the bottom of the hearth there are cast iron and slag tapholes, which are holes for releasing cast iron and slag. After the cast iron is released, the tap hole is closed with a special refractory mass using a so-called gun, which is a cylinder with a piston. Before opening the cast iron tap hole, the gun is filled with tap hole refractory mass. After the end of cast iron production, the gun is brought to the tap hole, and with the help of a piston mechanism, the tap hole mass is squeezed out of the gun and fills the tap hole channel. To open a cast iron tap hole, a special drilling machine is used, which drills a hole in the tap hole mass through which the cast iron is released.

Slag tapholes are located at a height of 1500 - 2000 mm from the level of the cast iron taphole and are closed using a slag stopper, which is a steel rod with a tip. The cast iron and slag leaving the blast furnace are directed through chutes into cast iron and slag ladles. Currently, slag is mainly produced together with cast iron and is separated from the cast iron by a special device on the furnace chute.

The slag flowing from the blast furnace through the cast iron tap hole is separated from the cast iron on the furnace chute using a separating plate and pass, which act as a hydraulic seal. The high-density cast iron passes into the gap under the separating plate, while the lighter slag is discharged into a side chute.

If it is necessary to supply cast iron to other enterprises, it is poured into ingots (ingots) weighing 30–40 kg on a special casting machine.

In the upper part of the hearth, at a distance of 2700 - 3500 mm from the axis of the cast iron tap hole along the circumference of the hearth, air tuyeres are installed at equal intervals, through which blast heated to 1100 - 1300 °C is fed into the furnace, as well as natural gas and other fuel additives (fuel oil, pulverized coal fuel). Each blast furnace is provided with blast from its own blower. Blast heating is carried out in regenerative-type air heaters, when, under the influence of the heat of the burned gas, the nozzle of the air heater made of refractory bricks is first heated, and then air is passed through it, taking heat from the nozzle. During the heating period of the nozzle, gas and air are supplied to the combustion chamber for its combustion. The combustion products, passing through the nozzle, heat it and go into the chimney. During the blast heating period, cold air enters the heated nozzle, is heated, and then fed into the blast furnace. As soon as the nozzle has cooled down so much that the air cannot be heated to the set temperature, it is transferred to the next air heater, and the cooled one is put on heating. The air heater nozzle cools faster than it heats up. Therefore, the block of blast furnace air heaters consists of 3–4 devices, of which one heats the air, and the rest are heated. The profile of a blast furnace is characterized by the diameters, heights and angles of inclination of individual elements. The dimensions of some ovens are shown in Table 1.

Table 1 - Furnace dimensions

Dimensions, mm	Useful volume of the furnace, m3
	2000	3000	5000
Diameter:
forge	9750	11700	14900
raspara	10900	12900	16300
fire pit	7300	8200	11200
Height:
full	32350	34650	36900
useful	29200	32200	32200
forge	3600	3900	4500
mines	18200	20100	19500

The dimensions of each part of the furnace must be linked to each other and be in certain proportions with the sizes of other parts of the furnace. The furnace profile must be rational, which ensures the most important conditions for the blast furnace process:

• smooth and stable lowering of charge materials;
• favorable distribution of oncoming gas flow;
• favorable development of recovery processes and the formation of cast iron and slag.

The main quantities characterizing the dimensions of the working space are the usable volume of the oven and the usable height. They include the height and volume filled with materials and smelting products. When determining these parameters, the upper level is taken to be the mark of the lower edge of the large cone of the filling device in the lowered position, and the lower level is the level of the axis of the cast iron tap hole.

Test

in the discipline "Materials Science and Technology of Structural Materials"

Option No. 10

Is done by a student

URBAS, b-NFGDz-32

Code: 131720

Shcherbakov V. G.

Checked by: Melnikova I.P.

Saratov, 2017

Task No. 1. 3

1.1. Draw a diagram of a blast furnace. 3

1.2. Describe the essence of reduction smelting. 4

1.3. Indicate the products, blast furnace smelting and technical and economic indicators of the blast furnace. eleven

Task No. 2. 12

2.1. Describe the phenomena that occur in metal when heated. 12

2.2. Explain the concept of the temperature range of metal forming and the principle of its determination using a diagram. 14

2.3. Approximately determine from the diagram the temperature range of processing for steel with a carbon content of 0.5% ………………………………………………………………………………………………………………… …………15

Task No. 3. 22

Draw a diagram of an oxygen-acetylene flame and describe its structure. Indicate the features of welding copper. Develop a process for welding the shell (Fig. 38 a, b) from copper grade M3p. Production is piecemeal. Determine the nature of the gas welding flame, the type of torch and its power. Select the grade and diameter of filler wire. Specify the flux composition and welding method (left, right). Based on the dimensions of the weld, determine the mass of the deposited metal. Set the filler wire consumption taking into account losses, oxygen, acitylene, calcium carbide and welding time of the product. Specify the methods for quality control of the weld.. 22

Task No. 4. 23

Provide surface treatment schemes for parts 1, 2, 3, the drawing of which is given in Fig. 6. For each diagram, provide the name of the machine, tool, and fixtures. Provide sketches of a tool for surface treatment 3 and a device for securing the workpiece during surface treatment 1. 23

References.. 24

Test task No. 1

Draw a diagram of a blast furnace. Describe the essence of reduction smelting. Indicate the products, blast furnace smelting and technical and economic indicators of the blast furnace.

The blast furnace is designed for smelting cast iron.

Scheme of the domain process.

The essence of this process is that in the furnace there is a reduction of iron oxides, which are in the source material - ore, with fuel combustion products - hydrogen, carbon monoxide and solid carbon. The design of a shaft-type blast furnace is not very complicated. It consists of several parts.

Furnace design

The top part of a blast furnace is called the top. It is equipped with gas outlets used to remove blast furnace gas. Raw materials are loaded here using a special filling apparatus.

Under the top there is a shaft in the form of a truncated cone, expanding downward. This form makes it possible to simplify the process of receiving raw materials from the top. In the mine, the feedstock is prepared in a special way from ore oxides and iron is reduced.

The widest part of the blast furnace is called steam. This is where waste rock of flux and ore is melted, resulting in slag.

The next part of the furnace is a truncated cone, expanding upward. It's called shoulders. In this compartment of the structure, slag formation ends, leaving a certain amount of flux and solid fuel in it.

Combustion of the fuel supplied from above occurs in the forge. It also serves to accumulate cast iron and slag, which are in a liquid state.

For fuel combustion to occur, hot air is required. It enters the furnace from the air heaters through a ring air duct, passing through tuyeres. The bottom of the forge, called the bream, is located on a massive reinforced concrete foundation. This is where slag and cast iron accumulate. At the end of the smelting process, cast iron and slag are discharged through special chutes through tapholes designed for this purpose into ladles.

Operating principle of a blast furnace

Blast furnace diagram.

The design of the blast furnace is designed in such a way that the charge enters the bowl through a charging device made in the form of a small cone located at the top. Next, from the bowl, falling onto a large cone when it is lowered, the charge enters the furnace. This system prevents gas from the blast furnace from entering the environment. After loading, the small cone and funnel for receiving raw materials are rotated at an angle that is a multiple of 60 degrees. This is necessary to ensure that the mixture is distributed evenly.

The metallurgical furnace continues to operate, the charge melts and goes further down, making room for new portions of raw materials. The usable volume of the blast furnace must always be completely filled. A modern blast furnace can have a useful volume from 2,000 to 50,000 m³. Its height can reach 35 m, which is almost three times its diameter. This design was not invented by chance: the operating principle of a blast furnace is based on the movement of materials and gases towards each other, which allows increasing the use of heat by up to 85%.