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%.

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 a 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.

Topic 1. General scheme of blast furnace process 1

1.1. Goals and objectives of domain process 1

1.2. Blast furnace 2 design

1.3. General operating diagram of a blast furnace 5

1.3.1. Charge materials 5

1.3.1.1. Iron ore materials 6

1.3.1.2. Fluxes 6

1.3.1.3. Solid fuel 8

1.3.2. Combined blast 9

1.3.3. Blast furnace products 10

1.3.3.1. Cast iron 10

1.3.3.2. Slag 10

1.3.3.3. Top gas 11

1.3.4. Conclusions 12

1.4. Blast furnace performance indicators 13

1.5. Blast furnace cast iron 14

1.5.1. Classification of cast iron by purpose. 14

1.5.2. Chemical composition of pig iron, foundry and special cast iron. 15

1.5.2.1. Pig iron 15

1.5.2.2. Cast irons 17

1.5.2.3. Special cast irons. 19

1. General diagram of the blast furnace process

   1. Goals and objectives of the domain process

In order to have a complete understanding of the blast furnace process and blast furnace production in general, it is necessary to first become familiar with the general scheme. This will then allow us to consider individual elements, having an idea of ​​their place in the overall complex of various processes occurring in a blast furnace, and the general technological scheme for the production of cast iron.

The goal of blast furnace production is to produce high-quality cast iron (of a given composition with a low content of impurities) with the lowest fuel and energy costs and maximum (specified) productivity. The requirement for minimum fuel and energy reserves will become more obvious when considering the general scheme of blast furnace production, production volumes, raw material costs for the production of 1 ton of products and prices for raw materials.

The main product of blast furnace smelting is pig iron. It should be noted that there are also blast furnace smelting technologies, the main product of which is slag. For example, the product of bauxite smelting, slag, is used to produce high-quality concrete.

1. Blast furnace design

The main unit for extracting iron from iron ores is the blast furnace.

According to the principle of operation, a blast furnace belongs to shaft-type smelting furnaces, furnaces whose working space is elongated vertically, and the horizontal section is a circle. The flow of processes in shaft furnaces is based on the counterflow of materials and hot gases.

The outline of the furnace working space in a vertical axial section is called a profile. The profile of the furnace, depending on their geometric shape and technological purpose, is divided into five parts (Fig. 1.1 -1).

The upper part of the furnace, which has a cylindrical shape, is called the top (K). The blast furnace top is equipped with a top device. The flue device is a complex of metal structures for various purposes and includes devices for feeding and loading materials into the furnace, gas outlets for uniform removal of gases from the furnace (at least 4), devices for carrying out repair and installation work. The charging apparatus of the blast furnace loading device is used to load and distribute materials in the blast furnace. At the same time, it hermetically closes the oven and isolates its internal space from the atmosphere.

ABOUT

Rice. 1.1‑1. Blast furnace

The main part of the furnace in terms of volume is the shaft (Ш), which is a truncated cone. The widest part of the furnace, shaped like a cylinder, the steam (P) goes into the shoulders (Z) in the shape of an inverse truncated cone.

The lower part of the furnace, which is shaped like a cylinder, is called the forge (G). The hearth, in turn, is divided into an upper and lower hearth or a tuyere zone and a metal receiver, respectively. In the upper part of the hearth there is a large number (30...40) of tuyere holes (F) evenly distributed around the circumference, through which blast is supplied from the ring air duct 5 to the furnace through special devices - tuyeres. The bottom of the metal receiver is called the flange . The part of the metal receiver below the cast iron tap hole is called the sump or “dead” layer. This zone, filled with liquid metal, protects the bream from high-temperature processes occurring in the forge. The lower hearth is equipped with cast iron and slag tapholes - devices for releasing cast iron and slag. Tapholes for tapping iron are made in the hearth wall above the sump in the form of rectangular channels of dimensions 250...300 x 450...500 mm, in which holes are drilled in the carbon lining of the metal receiver with a diameter of 50...60 mm. A hole for processing the upper slag - a slag tap hole - is made in the furnace at a mark determined when calculating the furnace profile. The diameter of the slag taphole is usually 50...65 mm, depending on the diameter of the furnace hearth.

This configuration of the working space has developed in the process of improving the technological unit, and creates the most favorable conditions for the occurrence of aerodynamic and physical-chemical processes.

The outside of the blast furnace is enclosed in a metal casing consisting of a number of cylindrical and conical belts. The metal structures of the furnace rest on a foundation, which serves to uniformly transfer the pressure of the furnace with raw materials loaded into it to the ground.

The interior of the furnace is lined with refractory bricks, the safety of which is ensured by a cooling system for several years of operation. Refractory masonry serves to reduce heat losses and protect the furnace casing from various influences: temperature stress, gas pressure, charge and liquid smelting products, chemical exposure, abrasive effects of descending charge materials and rising gas flow carrying a large amount of dust, etc.

The dimensions of the components of a blast furnace determine its working space, its so-called useful volume. The useful volume is equal to the volume of the furnace from the axis of the cast iron tap hole to the filling device in its extreme lowered position. The distance from this level to the axis of the cast iron tap hole is called the usable height of the furnace. These parameters of the furnace profile: the useful volume of the furnace and the useful height of the furnace, as well as the ratio of the diameters of the flue, steam and hearth determine the configuration of the furnace profile and are its characteristics.

Dimensions of an average blast furnace with a volume of 2002 m 3.

The blast furnace is installed on a foundation (reinforced concrete mass, designed for enormous loads, heat-resistant concrete) up to 10 m high. Taking into account the dimensions of the top device - up to 15...18 m, one can imagine that the blast furnace is a very serious structure with a height of about 60 m.

The largest blast furnace is blast furnace No. 5 of CherMK. Its volume is 5580 m 3 , useful height is 33.5 m, steam diameter is 16 m.

A modern blast furnace is a complex technological complex that includes the blast furnace itself, as well as main and auxiliary equipment, the purpose of which is determined by the technological tasks of blast furnace production.

Blast furnace design

The internal outline of the vertical section of a blast furnace is called its profile (Figure 6), which distinguishes between the top 1, shaft 2, steam 3, shoulders 4 and hearth 5. For modern large furnaces, the useful height is 29-32 m. The average volume of furnaces is 1000-3000 m3, the largest furnace with a volume of 5000 m3.

Figure 6 - Blast furnace: 1 - charge; 2 - drops of cast iron; 3 - slag; 4 - tuyeres for supplying air to the furnace; 5 - slag cell; 6 - chute for releasing slag; 7 - liquid cast iron; 8 - chute for releasing cast iron; 9 - cast iron tap hole; 10 - liquid slag

The blast furnace is enclosed in a metal casing with a thickness of 20-25 mm in the upper part and 35-40 in the lower part, consisting of a number of cylindrical and conical belts. The casing is made entirely welded. On the inside of the casing there is a refractory lining, cooled by refrigerators. The material is fed to the fire pit using a conveyor. The main part of the blast furnace device is a filling apparatus consisting of a large and small cone with a receiving funnel. To distribute the charge evenly, the small cone rotates around its axis, which is lowered into the intercone space. A large cone is lowered into the blast furnace. The presence of two alternately lowering cones ensures sealing of the furnace when loading the charge. At the bottom of the furnace there are tuyere devices through which heated blast and additives of gaseous, liquid or pulverized fuel are supplied. The liquid products of smelting continuously flow down into the hearth of the furnace, in which tapholes are located for the release of pig iron and for the release of slag. The smelting products are periodically released through these tapholes. Thus, the processes in the furnace and the supply of charge occur continuously, and the release of cast iron and slag occurs periodically.

Charging apparatus - a device for loading bulk materials into shaft furnaces - blast furnaces, roasting furnaces and others (Figure 7).

Charging devices are used mainly in blast furnace production. The charge is fed into it by skips or conveyors. From the receiving funnel, the charge flows first to the small and then to the large cones. The large cone lowers when the small one is closed, which prevents gases from escaping from the furnace into the atmosphere. To ensure uniform loading of the charge around the circumference of the furnace, rotating charge distributors are used.

In modern blast furnaces, per 1 ton of cast iron produced, 1250-1800 m 3 of gas is formed, removed from the furnace through the top. Blast furnace or top gas is used as fuel for air heaters in blast furnaces, coke ovens, heating wells and furnaces of rolling mills, and boiler plants. At the outlet of the furnace, the blast furnace gas contains from 10 to 40 g/m 3 of dust, and before being supplied to the burner devices to prevent their failure (clogging, etc.), the dust content in it should be no more than 5 mg/m 3, in connection, which requires mandatory cleaning.

Figure 7 - Blast furnace charging apparatus: 1 - guide funnel; 2 - hollow rod of a small cone; 3 - charge distributor; 4 - gas seal; 5 - large cone; 6 - ore; 7 - coke; 8 - bowl of a large cone; 9 - main ring (top flange); 10 - large cone rod; 11 - small cone; 12 - receiving funnel; 13 - inclined bridge; 14 - skip

The foundation of a blast furnace (Figure 8) serves to uniformly transfer the pressure of the furnace with raw materials loaded into it to the ground. The foundation is divided into two: the upper ground - part 1, called the stump, and the lower underground - part 2, called the sole. The depth of the foundation base depends on the properties of the soil and the depth of its freezing. The dimensions of the sole are determined by the permissible ground pressure. In case of weak soil, the foundation must be supported on artificial foundations (slab, sinkhole, etc.) in order to avoid excessive settlement of the foundation, which disrupts the connection of the furnace with neighboring structures and causes dangerous deformations in them. Uneven precipitation is especially harmful, disrupting the operation of the filling apparatus.

Figure 8 - Blast furnace foundation diagram

The foundation of a blast furnace is exposed to intense thermal influences and therefore must have sufficient thermal strength without collapsing or cracking when heated. Therefore, the upper part of the foundation is made of refractory concrete, and the lower part is made of ordinary concrete. Heat resistance is imparted to concrete by using a fireproof filler - fireclay. Portland cement with finely ground additives (ground fireclay or fireclay) is used as a binder. The shape of the foundation should contribute to better resistance to temperature stress and uniform distribution of pressure on the foundation.

The lower part of the columns is attached to the furnace foundation individually or on one powerful metal support ring laid in the foundation. This support ring ensures the rigidity of the system in the event of cracks in the foundation. In both cases, to reduce pressure on the foundation, shoes are installed under the ring, which expand the supporting area of ​​​​each column. Modern furnaces have four support columns. To give greater stability and better access to the hearth, the columns are installed with a slight inclination. To avoid damage during breakthroughs from the furnace of liquid cast iron, the bottom of the columns at a height located in the threatened zone is lined with refractory bricks.

The metal casing of a blast furnace creates a tightness, which is necessary when the furnace operates at high gas pressure in the working space. In the lower part (under the flange) the furnace casing sometimes has a bottom designed to seal the furnace. The upper part of the casing is tightened with a cast steel flange, which serves as a support for the filling apparatus.

Refractory masonry is designed to reduce heat losses and protect the furnace casing from thermal and other harmful influences. The furnace masonry undergoes a variety of influences: temperature stress, pressure of gases, charge and liquid smelting products, chemical effects, abrasive effects of descending charge materials and rising gas flow carrying a large amount of dust, etc.

In different parts of the furnace, the effects on the refractory masonry are different, therefore the lining material and the design of individual parts of the furnace must be selected taking into account these effects. The lining is used to create a working space during the construction and repair of blast furnaces, to preserve it during operation, to absorb the pressure of materials and gases, to reduce heat loss and thermal loads on refrigerators and casings. The lining operates under difficult conditions: high temperatures, gas and material pressure, exposure to molten cast iron and slag, various elements and compounds.

The main requirements for the lining are as follows: sufficient fire resistance (the ability to withstand high temperatures without melting); high mechanical strength in a heated state; slight shrinkage during prolonged exposure to high temperatures; low porosity and gas permeability; accuracy of shape and geometric dimensions; high slag resistance.

The flange, which is the bottom of the blast furnace working space, consists of a fairly capacious array of lining and cooling system, enclosed in a solid metal casing.

Shoulders are an element of the furnace profile that ensures the desired nature of the flow of materials into the hearth, mainly into the tuyere hearths, and a certain state of stress in the charge column, especially in its lower part.

In the shoulders, located above the forge and expanding towards the top, the final stages of the melting and reduction processes take place. For successful flow, the volume of their shoulders must ensure sufficient residence time for materials in this zone with appropriate organization of counterflow.

To ensure uninterrupted supply of raw materials to blast furnaces, it is necessary to create an ore yard. In addition to storing the reserve, the ore yard is used for averaging materials.

Each blast furnace is supplied with hot blast by 3-4 air heaters. Blast furnace air heaters are heated regenerative devices, the purpose of which is to ensure heating of the blast to a given temperature and maintain it at a given level.

The introduction of blast heating was an important stage in the development of blast furnace production, which ensured a significant reduction in fuel consumption and an increase in furnace productivity. Blast heated to 150 °C was first used in 1829, which led to a significant reduction in coke consumption, and most importantly, to a significant improvement in the processes in the furnace (higher heating of smelting products, better separation of slag from cast iron, increased degree of silicon recovery and manganese). In 1860, E. A. Cowper first used a regenerative apparatus for heating. The design of an air heater with an internal side combustion chamber (Figure 9) developed by him has remained virtually unchanged to this day and has become widespread.

Figure 9 - Air heater with an internal combustion chamber: 1 - gas pipeline; 2 - gas throttle; 3 - fan; 4 - burner; 5 - cut-off throttle; 6 - burner fitting; 7 - hatch; 8 - combustion chamber; 9 - hot blast pipeline; 10 - hot blast separation valve; 11 - hot blast fitting; 12 - internal wall of the combustion chamber; 13 - dividing wall of the combustion chamber; 14 - dome; 15 - under-dome space; 16 - hatch; 17 - thermocouple; 18 - casing; 19 - radial wall; 20 - nozzle with zones made of different refractories; 21 - sub-nozzle grid and columns; 22 - sub-nozzle space; 23 - smoke pipe; 24- smoke valve; 25 - thermocouple; 26 - hog; 27 - cold blast pipeline; 28 - cold blast gate

The high efficiency of blast heating ensured its rapid and widespread distribution. Soon the blast began to be heated to 350-400, and then to 500-700 °C. Back in the 40s of the 20th century, many factories were unable to raise the blast temperature above the specified limits, not because the technical means for such heating did not allow, but due to the fact that this caused a disruption in the blast furnace smelting process. Analysis of this phenomenon made it possible to determine the most important factors that provide conditions for increasing the heating of the blast, which include:

Replacement of unprepared and especially silty ores with agglomerated ores, i.e. agglomerate and pellets;

The use of increased gas pressure in the furnace;

Injection of gaseous and liquid hydrocarbons into the hearth;

Moisture blast conditioning.

The lining of blast furnace air heaters is tested:

Thermal loads, varying in magnitude and nature depending on the location in the air heater. They are greatest in the masonry of walls and, especially in the combustion chamber, where the observed temperature differences are maximum;

Mechanical loads under the influence of the self-weight of refractories. When they are heated, various compressive stresses are also formed in the masonry, for example, in the combustion chamber up to 7.8 MPa, in the nozzle 83-117 kPa;

The impact of dust, which is insignificant during the heating process, but increases sharply when the device is taken “for traction”. Dust and alkaline vapors diffusing inside the bricks contribute to phase transformations, namely the formation of anorthite and ganite, and in the reaction zone - a glassy phase containing corundum.

Instruments used for continuous monitoring of the composition of blast furnace gas are essential. Various schemes for automatic control of the blast furnace process have been developed and are being tested, including mathematical processing of instrument readings by computers and automation of individual control control units: distribution of gas flow along the radius of the furnace, discharge of charge materials, thermal state of individual zones of the furnace, distribution of gas flow along the circumference of the furnace .

An individual gas cleaning system is built for each blast furnace; gas is supplied to gas cleaning devices located at the zero level from the top through an inclined gas pipeline (there are two of them on a furnace with a volume of 5000 m 3). A gas cleaning system usually includes several gas cleaning devices installed in series. On modern domestic furnaces operating with increased gas pressure, two different gas purification schemes are used - with a throttle device designed to reduce gas pressure, and with a gas recovery non-compressor turbine.

Most of the furnaces are equipped with a gas purification system with a throttle device, shown in Figure 10. From the top part of the furnace, gases flow through an inclined gas pipeline, and a dry radial dust collector with a diameter of up to 16 m, which has a narrowing at the top and bottom.

Figure 10 - Diagram of the blast furnace gas removal and purification system: 1 - top part of the furnace; 2 - radial dust collector; 3 - nozzle scrubber; 4 - Venturi pipes; 5 - gas pipeline; 6 - throttle device; 7 - water separator; 8 - leaf gate valve; 9 - collector

Gas enters it from above and changes the direction of movement by 180°, and large dust particles are deposited in the lower cone of the dust collector, from where the dust is periodically released into railway cars.

Next, the gas enters the nozzle-less scrubber, where dust particles are captured by the water supplied through the nozzles and deposited in the lower part of the scrubber in the form of sludge; The gas here is cooled to 35-40 °C. The gas then passes through unregulated venturis, where dust particles are absorbed by water droplets, which are captured in a downstream mist eliminator.

Final gas purification occurs in the throttle device. The latter is designed to reduce gas pressure and at the same time ensure its purification, working as a gas cleaning apparatus on the same principle as Venturi pipes. Next, the gas passes through the water separator and through a leaf valve enters the collector (shop network). The gas is discharged through a gas pipeline to the top to balance the pressure in the intercone space.

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 raised 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 through 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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