A method for determining the length of carbon bricks used in building the side walls of a blast furnace

Abstract

The present invention relates to a method for determining the length of carbon bricks for laying the side wall of a blast furnace hearth. The maximum length L of the carbon bricks for laying the side wall of a blast furnace hearth is: L=L 1 +L 2 +L 3 +....+L n Among them, L 1 , L 2 , L 3 ....L n The step length is 0.5-2℃, and the corresponding length of the carbon brick is calculated when the temperature of the hot surface of the carbon brick decreases by 0.5-2℃ every time the temperature of the cold surface decreases; #imgabs0# Among them, #imgabs1# and #imgabs2# are T 热 、T 热 ‑1. T 热 ‑2 and T 热 ‑n‑1 is the thermal conductivity of carbon bricks at temperature; q is the heat flux intensity of the blast furnace; where T 热 The temperature is the hot surface temperature of the carbon brick t 热 ; T 热 ‑n‑1 temperature is the cold surface temperature of the carbon brick t 冷 The advantages are: avoiding the use of overly long carbon bricks can reduce the cost of masonry and also reduce the difficulty of masonry.

Description

Technical Field

[0001] The invention belongs to the field of blast furnace hearth side wall masonry, and in particular relates to a method for determining the length of carbon bricks for masonry of blast furnace hearth side wall. Background Art

[0002] With the increase of blast furnace size and smelting intensity, the erosion problem of blast furnace hearth is becoming more and more prominent. It not only directly affects the life of the blast furnace, but also may cause a major accident of hearth burning. Therefore, many blast furnace design units often use long carbon bricks on the side wall of the blast furnace hearth in order to extend the life of the blast furnace by thickening the refractory material of the hearth. However, through the investigation of the damage of the blast furnace hearth after overhaul and the dissection of the blast furnace, it was found that the practice of thickening the side wall of the hearth not only did not extend the life of the hearth, but also caused the overall stress ring cracking due to the large temperature difference between the cold and hot surfaces of the carbon bricks caused by the use of too long carbon bricks. After the ring cracking, the carbon bricks will no longer remain intact, and their original heat transfer system will also be destroyed. The carbon bricks at the front end of the ring crack will be quickly eroded due to the lack of effective cooling protection, which accelerates the overall erosion of the blast furnace hearth. In addition, the use of too long carbon bricks will increase the manufacturing cost of carbon bricks and the difficulty of masonry during blast furnace overhaul. Therefore, it is necessary to determine the length of carbon bricks for masonry of the side wall of the blast furnace hearth.

[0003] In recent years, as steel mills pay more and more attention to the longevity of blast furnaces, new methods for the design of long-life blast furnace hearths have been proposed:

[0004] Patent application number CN201811190219.7 discloses a method for building a high-thermal-conductivity and long-life blast furnace hearth and brick lining, and provides methods for building brick linings for the lower, middle and lower, middle, middle and upper parts of the hearth. The brick lining includes small carbon bricks, carbon ramming material layers and large carbon bricks arranged in sequence; at the top of the hearth, the brick lining is built of several small carbon bricks. It can not only avoid cracking of the hearth brick lining caused by thermal stress and erosion and damage caused by harmful elements through cracks, but also effectively resist the circulation scouring of molten iron, thereby alleviating erosion and damage of the hearth and extending the service life of the blast furnace.

[0005] Patent application number CN202110800206.2 discloses a method for building a long-life blast furnace hearth with uniform erosion. From top to bottom, from the top of the hearth to the iron mouth, the furnace lining is built with high thermal conductivity graphite bricks; from top to bottom, from the iron mouth to the bottom of the furnace, the furnace lining is built with ultra-microporous carbon bricks with gradually increasing lengths; at least one layer of ceramic cups is built on the inner side of the hearth lining; 6 to 8 layers of carbon bricks are laid flat on the bottom of the furnace, and at least one layer of clay bricks is set on the carbon bricks at the bottom of the furnace. This method can not only avoid the situation where the maximum stress position of the hearth lining is fixed and the erosion speed of a single position in the hearth is too fast and the service life of a generation of furnaces is shortened, but also greatly reduce the cost of building blast furnaces.

[0006] Patent application number CN202020029567.2 discloses an erosion-guided long-life blast furnace hearth, in which several layers of hearth ring-laid microporous carbon bricks, several layers of hearth ring-laid ultra-microporous carbon bricks and several layers of hearth flat-laid carbon bricks are arranged from top to bottom on the inner side of the cooling wall, and vertical and flat ceramic cups are arranged on the inner side of the several layers of hearth ring-laid microporous carbon bricks and several layers of hearth ring-laid ultra-microporous carbon bricks; the top layer of several layers of hearth flat-laid carbon bricks is a combination of two types of carbon bricks, that is, the first hearth microporous carbon bricks are used in the central inner ring area, and the outer ring is used for the hearth ultra-microporous carbon bricks. By optimizing the design of the hearth and hearth structure and the arrangement of refractory materials, the erosion resistance of the elephant foot area is strengthened, and the hearth erosion is guided to form "pot bottom-shaped" erosion, thereby extending the overall life of the hearth.

[0007] Although the above-mentioned documents all propose design methods for a long-life blast furnace hearth, no specific requirements are put forward for the thickness of the hearth side walls. When overly long carbon bricks are used to thicken the hearth side walls, the hearth side wall carbon bricks may produce circumferential cracks, which will have a negative impact on the longevity of the blast furnace. Summary of the invention

[0008] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a method for determining the length of carbon bricks for building the side walls of a blast furnace hearth, which can avoid the overall circumferential cracks of the hearth caused by the increase in the temperature difference between the cold and hot surfaces of the carbon bricks due to the excessive thickness of the refractory material on the side walls of the blast furnace hearth, thereby extending the overall life of the blast furnace hearth.

[0009] To achieve the above object, the present invention is implemented through the following technical solutions:

[0010] A method for determining the length of carbon bricks for blast furnace hearth side walls, wherein the maximum length L of the carbon bricks for blast furnace hearth side walls is: L = L 1 +L 2 +L 3 +....+L n ;

[0011] Among them, L 1 , L 2 , L 3 ....L n The step length is 0.5-2℃, and the corresponding length of the carbon brick is calculated when the temperature of the hot surface of the carbon brick starts to the cold surface temperature, and the temperature of the carbon brick decreases by 0.5-2℃;

[0012]

[0013]

[0014]

[0015] …

[0016]

[0017] In formula (1), and T 热 , T 热 -1, T 热 -2 and T 热 -n-1 is the thermal conductivity of carbon bricks at temperature, W / (m·k); q is the heat flux intensity of the blast furnace, J / (m 2 ·s); where T 热 Temperature is the hot surface temperature of the carbon brick t 热 ; T 热 -n-1 temperature is the cold surface temperature of the carbon brick t 冷 .

[0018] The thermal conductivity of the carbon bricks is divided into three ranges according to the temperature, room temperature to 600°C, 600°C to 800°C and greater than 800°C. The Lagrange interpolation method is used to fit the functional relationship between various carbon bricks and temperature, and the following is obtained:

[0019]

[0020] In formula (2), T 0 , T 1 , T 2 , T 3 They are room temperature, 300℃, 600℃, 800℃ respectively; K 0 , K 1 , K 2 and K 3 It is divided into thermal conductivity coefficients of various types of carbon bricks at room temperature, 300℃, 600℃ and 800℃.

[0021] The carbon brick cold surface temperature t 冷 and the hot surface temperature of the carbon bricks t 热 Calculation of the maximum temperature difference:

[0022] Thermal stress on carbon bricks in the furnace:

[0023] б=0.5×E n (t 热 -t 冷 )×α (3)

[0024] In formula (3), б is thermal stress, MPa; E n is the elastic modulus of carbon brick, MPa / m; t 热 ,t 冷 are the hot and cold surface temperatures of the carbon brick, respectively, ℃; α is the linear expansion coefficient of the carbon brick, m / ℃;

[0025]

[0026] In formula (4), γ 铁 , γ 渣 are the density of molten iron and the density of liquid slag, t / (m 3 ·d); H 铁 , H 渣 are the heights of molten iron level and slag level, m; P 风 is the tuyere cross-sectional pressure, kPa; μ is the molten iron viscosity, Pa·s; F is the flexural strength of the carbon brick, kPa; v is the gradient of the molten iron circulation velocity, s -1 ;

[0027] When the blast furnace is started, the hot surface of the carbon bricks is in direct contact with the molten iron. At this time:

[0028] t 热 =t 铁 -q / (h 铁 ) (5)

[0029]

[0030] In formula (5) and (6), h 铁 is the heat transfer coefficient between molten iron and carbon bricks, w / (m 2 ·℃); q is the heat flux intensity of the blast furnace, J / (m 2 ·s); t 铁 is the molten iron temperature, ℃.

[0031] When the flexural strength F of the carbon brick is greater than the sum of thermal stress, molten iron static pressure and shear force, the carbon brick will not produce ring cracks:

[0032] F>P+τ+б (7)

[0033] In formula (7): P is the static pressure of molten iron, kPa; τ is the shear force borne by the carbon brick, kPa; б is the thermal stress borne by the carbon brick, kPa;

[0034] The thermal stress that the first layer of carbon bricks of the blast furnace hearth side wall refractory can withstand is:

[0035] б=FP-τ (8)

[0036] Thermal stress on carbon bricks in the furnace:

[0037] б=0.5×E n (t 热 -t 冷 )×α (9)

[0038] In formula (9): б is the thermal stress of the carbon brick in the furnace, MPa; E n is the elastic modulus of carbon brick, MPa / m; t 热 ,t 冷are the hot and cold surface temperatures of the carbon brick, respectively, ℃; α is the linear expansion coefficient of the carbon brick, m / ℃.

[0039] Calculation of molten iron static pressure:

[0040] P = γ 铁 *(H 铁 +H 死 )+γ 渣 *H 渣 +P 风 (10)

[0041] In formula (10), P is the static pressure of molten iron, kPa; γ 铁 , γ 渣 , respectively represent the density of molten iron and liquid slag, t / (m 3 ·d); H 铁 , H 渣 are the heights of molten iron level and slag level, m; P 风 is the tuyere cross-sectional pressure, kPa; H 死 is the height of the dead iron layer, m.

[0042] The friction force generated by the flow of molten iron on the furnace wall, that is, the shear force τ borne by the carbon bricks:

[0043] τ=μ×v (11)

[0044] In formula (11), τ is the shear force, Pa; μ is the viscosity of the molten iron, Pa·s; v is the gradient of the molten iron circulation velocity, s -1 .

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] The method of the present invention can determine the appropriate length of the carbon bricks for the side wall of the blast furnace hearth, avoid using too long carbon bricks, reduce the masonry cost, and also reduce the masonry difficulty. The method of the present invention can determine the appropriate thickness of the refractory material for the newly built blast furnace hearth side wall, avoid the overall stress ring crack caused by the excessive temperature difference between the cold and hot surfaces of the carbon bricks due to the use of too long carbon bricks for the hearth side wall, maintain the integrity of the hearth, protect the heat transfer system of the blast furnace hearth from being damaged, and thus achieve the purpose of longevity of the blast furnace hearth. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a flowchart of the program iterative calculation of the maximum length of the carbon brick. DETAILED DESCRIPTION

[0048] The present invention is described in detail below, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0049] A method for determining the length of carbon bricks for blast furnace hearth side walls, wherein the maximum length L of the carbon bricks for blast furnace hearth side walls is: L = L 1 +L 2 +L 3 +....+L n ;

[0050] Among them, since the thermal conductivity of carbon brick is a function that changes with temperature, L 1 , L 2 , L 3 ....L n It is 0.5~

[0051] The step length is 2℃, and the corresponding length of the carbon brick is calculated when the temperature of the hot surface of the carbon brick decreases by 0.5-2℃ from the hot surface temperature to the cold surface temperature.

[0052]

[0053]

[0054]

[0055] …

[0056]

[0057] In formula (1), and T 热 , T 热 -1, T 热 -2 and T 热 -n-1 is the thermal conductivity of carbon bricks at temperature, W / (m·k); q is the heat flux intensity of the blast furnace, J / (m 2 ·s); where T 热 Temperature is the hot surface temperature of the carbon brick t 热 ; T 热 -n-1 temperature is the cold surface temperature of the carbon brick t 冷 .

[0058] After the carbon brick is used, its thermal conductivity changes with the temperature, and the change range is also closely related to the type of carbon brick. If the thermal conductivity is considered a constant, it will cause a large error in the accuracy of the judgment. Therefore, according to the physical and chemical indicators of the carbon bricks after use during the damage investigation, it was found that in the range of room temperature to 300℃, the thermal conductivity showed a rapid upward trend, and in the range of 300℃ to 600℃ (excluding 600℃), the thermal conductivity showed an upward trend and the increase rate slowed down slightly; in the range of 600℃ to 800℃, the thermal conductivity showed a gentle upward trend, and it showed a downward trend after exceeding 800℃. Therefore, the temperature is divided into three regions, namely: the range of room temperature to 600℃, the range of 600℃ to 800℃, and the range of greater than 800℃, and the Lagrange interpolation method is used to fit the functional relationship and mathematical expression of various carbon bricks and temperature:

[0059]

[0060] In formula (2), T 0 , T 1 , T 2 , T 3 They are room temperature, 300℃, 600℃, 800℃ respectively; K 0 , K 1 , K 2 and K 3 It is divided into thermal conductivity coefficients of various types of carbon bricks at room temperature, 300℃, 600℃ and 800℃.

[0061] Since the calculation is cumbersome, a computer program is designed to use an iterative method to calculate the final maximum design length of the carbon brick, see Figure 1 .

[0062] Calculation of the maximum temperature difference between the cold surface temperature tcold and the hot surface temperature thot of the carbon brick:

[0063] Thermal stress on carbon bricks in the furnace:

[0064] б=0.5×E n (t 热 -t 冷 )×α (3)

[0065] In formula (3), б is thermal stress, MPa; E n is the elastic modulus of carbon brick, MPa / m; t 热 ,t 冷 are the hot and cold surface temperatures of the carbon brick, respectively, ℃; α is the linear expansion coefficient of the carbon brick, m / ℃;

[0066]

[0067] In formula (4), γ 铁 , γ 渣are the density of molten iron and the density of liquid slag, t / (m 3 ·d); H 铁 , H 渣 are the heights of molten iron level and slag level, m; P 风 is the tuyere cross-sectional pressure, kPa; μ is the molten iron viscosity, Pa·s; F is the flexural strength of the carbon brick, kPa; v is the gradient of the molten iron circulation velocity, s -1 ;

[0068] When the blast furnace is started, the hot surface of the carbon bricks is in direct contact with the molten iron. At this time:

[0069] t 热 =t 铁 -q / (h 铁 ) (5)

[0070]

[0071] In formula (5) and (6), h 铁 is the heat transfer coefficient between molten iron and carbon bricks, w / (m 2 ·℃); q is the heat flux intensity of the blast furnace, J / (m 2 ·s); t 铁 is the molten iron temperature, ℃.

[0072] The carbon bricks used for blast furnace hearth masonry are a brittle material with compressive strength far greater than its flexural strength. The appearance of annular cracks along the circumference of the carbon bricks is a comprehensive manifestation that the flexural strength of the carbon bricks is less than the forces they are subjected to: the forces on the carbon bricks include shear force, static pressure, and thermal stress.

[0073] When the flexural strength F of the carbon brick is greater than the sum of thermal stress, molten iron static pressure and shear force, the carbon brick will not produce ring cracks:

[0074] F>P+τ+б (7)

[0075] In formula (7): P is the static pressure of molten iron, kPa; τ is the shear force borne by the carbon brick, kPa; б is the thermal stress borne by the carbon brick, kPa;

[0076] The thermal stress that the first layer of carbon bricks of the blast furnace hearth side wall refractory can withstand is:

[0077] б=FP-τ (8)

[0078] Thermal stress on carbon bricks in the furnace:

[0079] б=0.5×E n (t 热 -t 冷 )×α (9)

[0080] In formula (9): б is the thermal stress of the carbon brick in the furnace, MPa; E n is the elastic modulus of carbon brick, MPa / m; t 热 ,t 冷 are the hot and cold surface temperatures of the carbon brick, respectively, ℃; α is the linear expansion coefficient of the carbon brick, m / ℃.

[0081] When designing blast furnaces, a certain depth of dead iron layer is retained. Since a certain amount of molten iron and slag are stored in the dead iron layer, the hot surface of the carbon bricks below the iron mouth of the furnace will be subjected to the static pressure of the liquid molten iron and slag. The static pressure of the molten iron and slag will penetrate into the micropores of the hot surface of the carbon bricks. As the depth of the molten iron increases, the pressure increases and increases. Correspondingly, the damage to the carbon bricks becomes more and more serious.

[0082] Calculation of molten iron static pressure:

[0083] P = γ 铁 *(H 铁 +H 死 )+γ 渣 *H 渣 +P 风 (10)

[0084] In formula (10), P is the static pressure of molten iron, kPa; γ 铁 , γ 渣 , respectively represent the density of molten iron and liquid slag, t / (m 3 ·d); H 铁 , H 渣 are the heights of molten iron level and slag level, m; P 风 is the tuyere cross-sectional pressure, kPa; H 死 is the height of the dead iron layer, m.

[0085] The friction force generated by the flow of molten iron on the furnace wall, that is, the shear force τ borne by the carbon bricks:

[0086] τ=μ×v (11)

[0087] In formula (11), τ is the shear force, Pa; μ is the viscosity of the molten iron, Pa·s; v is the gradient of the molten iron circulation velocity, s -1 .

[0088] Embodiment 1

[0089] Design 2580m 3 The thickness of the first layer of carbon bricks on the side wall of the blast furnace hearth and the flexural strength F were measured to be 13.56 MPa.

[0090] 1) Calculate the static pressure of molten iron

[0091]

[0092] When the furnace is filled with molten iron, the static pressure P of the first layer of carbon bricks on the side wall of the furnace is calculated to be 0.71 MPa according to formula (10);

[0093] 2) Calculate the shear force of molten iron

[0094] The viscosity of blast furnace molten iron is 0.05 Pa·s, and the molten iron circulation velocity gradient is 1850s -1 According to formula (11), the shear force τ of the molten iron flow on the circumferential carbon brick is 9.25×10 -5 MPa;

[0095] 3) Calculate the maximum thermal stress that the carbon brick can withstand

[0096] To ensure that the first layer of carbon bricks on the carbon side wall of the blast furnace hearth does not have circumferential cracks, the maximum thermal stress that the carbon bricks bear should be less than 12.85 MPa according to formula (8);

[0097] 4) Calculate the maximum temperature difference between the cold and hot surfaces of the carbon brick

[0098] The maximum temperature difference between the cold and hot surfaces of the carbon brick can be calculated according to formula (4), where the elastic modulus coefficient E n It is 7453.42MPa / m, the linear expansion coefficient of carbon brick is 0.0000045m / ℃, and the maximum temperature difference that the material can withstand is 383.7℃;

[0099] 5) Calculate the cold surface temperature of the carbon brick t 冷 and hot surface temperature t 热

[0100] The temperature of molten iron in the blast furnace is t 铁 The heat transfer coefficient between the molten iron and the side wall of the furnace is h 铁 45w / (m 2 ·℃), the heat flux intensity of the furnace is generally controlled at 5kw / m 2 The following is the temperature t of the hot surface of the carbon brick calculated according to formula (5): 热 =1389℃. Calculate the cold surface temperature of the carbon brick according to formula (6): 冷 =1005.7℃.

[0101] 6) Calculate the length of the carbon brick

[0102] The thermal conductivity of carbon bricks at room temperature, 300℃, 600℃, and 800℃ were measured to be 12.43, 16.58, 17.82, and 18.36w / (m·k), respectively. Figure 1 The program shown iteratively calculates the maximum length of the carbon brick to be 1.38m.

[0103] Embodiment 2

[0104] Design 4080m 3 The thickness of the first layer of carbon bricks on the side wall of the blast furnace hearth is domestically produced, and the flexural strength F is measured to be 12.06MPa.

[0105] 1) Calculate the static pressure of molten iron

[0106]

[0107]

[0108] When the furnace is filled with molten iron, the static pressure P of the first layer of carbon bricks on the side wall of the furnace is calculated to be 0.95 MPa according to formula (10);

[0109] 2) Calculate the shear force of molten iron

[0110] The viscosity of molten iron in blast furnace is 0.05 Pa·s, and the velocity gradient of molten iron circulation is 2850s -1 According to formula (11), the shear force τ of the molten iron flow on the circumferential carbon brick is 1.42×10 -4 MPa;

[0111] 3) Calculate the maximum thermal stress that the carbon brick can withstand

[0112] To ensure that the first layer of carbon bricks on the carbon side wall of the blast furnace hearth does not have circumferential cracks, the maximum thermal stress that the carbon bricks bear should be less than 11.11 MPa according to formula (8);

[0113] 4) Calculate the maximum temperature difference between the cold and hot surfaces of the carbon brick

[0114] The maximum temperature difference between the cold and hot surfaces of the carbon brick can be calculated according to formula (4), where the elastic modulus coefficient E n The linear expansion coefficient of carbon brick is 7000.36MPa / m, 0.0000056m / ℃, and the maximum temperature difference that the material can withstand is 566.8℃;

[0115] 5) Calculate the cold surface temperature of the carbon brick t 冷 and hot surface temperature t 热

[0116] The temperature of molten iron in the blast furnace is t 铁 The heat transfer coefficient between the molten iron and the side wall of the furnace is h 铁 45w / (m 2 ·℃), the heat flux intensity of the furnace is generally controlled at 5kw / m 2 The following is the temperature t of the hot surface of the carbon brick calculated according to formula (5): 热 =1389℃. Calculate the cold surface temperature of the carbon brick according to formula (6): 冷 =822.2℃.

[0117] 6) Calculate the length of the carbon brick

[0118] The thermal conductivity of carbon bricks at room temperature, 300℃, 600℃, and 800℃ were measured to be 10.33, 12.58, 13.82, and 13.96w / (m·k), respectively. Figure 1 The program shown iteratively calculates the maximum length of the carbon brick to be 1.57m.

Claims

1. A method for determining the length of carbon bricks for building the side wall of a blast furnace, characterized in that: The maximum length L of the carbon bricks on the side wall of the blast furnace is: L = L1 + L2 + L3 + .... + L n ; Among them, L1, L2, L3....L n The step length is 0.5-2℃, and the corresponding length of the carbon brick is calculated when the temperature of the hot surface of the carbon brick starts to the cold surface temperature, and the temperature of the carbon brick decreases by 0.5-2℃; …… In formula (1), and T 热 ,(T 热 -1)S, (T 热 -2)S and (T 热 -n-1)S temperature, W / (m·k), S is the step size; q is the heat flux intensity of the blast furnace, J / (m 2 ·s); where T 热 Temperature is the hot surface temperature of the carbon brick t 热 ;(T 热 -n-1)S temperature is the cold surface temperature of the carbon brick t 冷 .

2. A method for determining the length of carbon bricks for laying the side wall of a blast furnace according to claim 1, characterized in that: The thermal conductivity of the carbon brick is divided into three intervals according to the temperature, namely, the thermal conductivity intervals of the carbon bricks from room temperature to 600°C, 600°C to 800°C and above 800°C. The Lagrange interpolation method is used to fit the functional relationship between various carbon bricks and temperature, and the following is obtained: In formula (2), T0, T1, T2, and T3 are room temperature, 300°C, 600°C, and 800°C, respectively; K0, K1, K2, and K3 are the thermal conductivity coefficients of various types of carbon bricks at room temperature, 300°C, 600°C, and 800°C, respectively.

3. A method for determining the length of carbon bricks for laying the side wall of a blast furnace according to claim 1, characterized in that: The carbon brick cold surface temperature t 冷 and the hot surface temperature of the carbon bricks t 热 Calculation of the maximum temperature difference: Thermal stress on carbon bricks in the furnace: б=0.5×E n (t 热 -t 冷 )×α (3) In formula (3), б is the thermal stress of the carbon brick in the furnace, MPa; E n is the elastic modulus of carbon brick, MPa / m; t 热 ,t 冷 are the hot and cold surface temperatures of the carbon brick, respectively, ℃; α is the linear expansion coefficient of the carbon brick, m / ℃; In formula (4), γ 铁 , γ 渣 are the density of molten iron and the density of liquid slag, t / (m 3 ·d); H 铁 , H 渣 are the heights of molten iron level and slag level, m; P 风 is the tuyere cross-sectional pressure, kPa; μ is the molten iron viscosity, Pa·s; F is the flexural strength of the carbon brick, kPa; v is the gradient of the molten iron circulation velocity, s -1 ; When the blast furnace is started, the hot surface of the carbon bricks is in direct contact with the molten iron. At this time: t 热 =t 铁 -q / (h 铁 ) (5) In formula (5) and (6), h 铁 is the heat transfer coefficient between molten iron and carbon bricks, w / (m 2 ·℃); q is the heat flux intensity of the blast furnace, J / (m 2 ·s); t 铁 is the molten iron temperature, ℃.

4. A method for determining the length of carbon bricks for laying the side wall of a blast furnace according to claim 3, characterized in that: When the flexural strength F of the carbon brick is greater than the sum of thermal stress, molten iron static pressure and shear force, the carbon brick will not produce ring cracks: F>P+τ+б (7) The thermal stress of the carbon bricks in the furnace is: б<FP-τ (8) In formulas (7) and (8), P is the static pressure of molten iron, kPa; τ is the shear force on the carbon brick, kPa; б is the thermal stress on the carbon brick in the furnace, kPa.

5. A method for determining the length of carbon bricks for laying the side wall of a blast furnace according to claim 4, characterized in that: Calculation of molten iron static pressure: P=γ 铁 *(H 铁 +H 死 ) +γ 渣 *H 渣 +P 风 (10) In formula (10), P is the static pressure of molten iron, kPa; γ 铁 , γ 渣 , respectively represent the density of molten iron and liquid slag, t / (m 3 ·d); H 铁 , H 渣 are the heights of molten iron level and slag level, m; P 风 is the tuyere cross-sectional pressure, kPa; H 死 is the height of the dead iron layer, m.

6. A method for determining the length of carbon bricks for building the side wall of a blast furnace according to claim 4, characterized in that: The friction force generated by the flow of molten iron on the furnace wall, that is, the shear force τ borne by the carbon bricks: τ=μ×v (11) In formula (11), τ is the shear force, Pa; μ is the viscosity of the molten iron, Pa·s; v is the gradient of the molten iron circulation velocity, s -1 .

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