Calculation method of thermal conductivity of residual carbon bricks in blast furnace hearth

Abstract

The present invention discloses a method for calculating the thermal conductivity of residual carbon bricks in a blast furnace hearth. First, the composition and microstructure of the residual carbon bricks in the hearth are analyzed. The carbon bricks are divided into layers and regions based on the analysis results, and the thickness of each layer is measured. The heat transfer temperature distribution of the hearth is constructed by combining the temperature measuring thermocouple data with the heat flux of the region. The thermal conductivity of the carbon bricks in each region is constrained based on the microstructural characteristics. Multiple sequence data are constructed based on different regions. The least squares method with constraints is used to calculate the thermal conductivity of each residual carbon brick layer under service conditions in a regression manner, which makes up for the deficiency that the thermal conductivity of residual carbon bricks in service conditions is difficult to test with existing equipment. In addition, using the calculation method of the present invention, the thermal conductivity of each residual carbon brick layer can be calculated separately, which is conducive to calculating a more accurate erosion furnace type, thereby facilitating the monitoring of the working status of the blast furnace hearth and ensuring the safe production of the blast furnace.

Description

Technical Field

[0001] The invention relates to the technical field of blast furnaces, and in particular to a method for calculating the thermal conductivity of residual carbon bricks in a blast furnace hearth. Background Art

[0002] The hearth of a blast furnace is a storage area for high-temperature slag and iron. Its masonry structure from the outside to the inside generally includes a furnace shell, a cooling wall, a ramming layer, carbon bricks, and ceramic cups, of which the carbon bricks are laid in layers. In the middle and late stages of a furnace's service life, the ceramic cups of the blast furnace hearth are basically corroded and consumed. The carbon bricks are in direct contact with the high-temperature molten iron inside the hearth. The carbon bricks will be subject to different types of erosion along the radial direction of the hearth, and their thermal conductivity will also change accordingly, and the corresponding heat transfer performance will also change. As a limiting link in the life of a blast furnace, the monitoring of the working status of the hearth plays a very important role in the stable production of the blast furnace in the late stages of its service life. The calculation of the eroded furnace type is closely related to the thermal conductivity. The existing calculation method for judging the degree of erosion of carbon bricks mostly uses the thermal conductivity of the carbon bricks when they are not corroded for calculation. The resulting degree of erosion is quite different from the actual situation. At the same time, there are certain differences in the thermal conductivity of carbon bricks under different temperature conditions. Therefore, it is crucial to calculate the thermal conductivity of carbon bricks under actual service conditions.

[0003] In the prior art, a paper titled "Determination of Thermal Conductivity of Blast Furnace Carbon Bricks," published in 2008, disclosed a method for measuring the thermal conductivity of carbon bricks using a laser flash thermal diffusivity instrument. This method first measured the thermal diffusivity and specific heat of a small sample using a laser flash thermal diffusivity instrument. The thermal conductivity of the material was then calculated using a formula. Due to the relatively small sample size and the varying compositional distributions of the different samples, the resulting thermal conductivity values fluctuated significantly. Multiple samples were tested, and the average value was used as the thermal conductivity of the carbon brick. However, this method failed to determine the thermal conductivity of corroded carbon bricks at high temperatures, significantly differing from the thermal conductivity of actual service conditions.

[0004] In view of this, it is necessary to design a calculation method for the thermal conductivity of residual carbon bricks in the blast furnace hearth to solve the above problems. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for calculating the thermal conductivity of residual carbon bricks in a blast furnace hearth, which divides carbon bricks into regional layers according to the microscopic analysis results of carbon bricks, and proposes thermal conductivity constraint conditions for each regional layer in combination with the thermal conductivity of the original carbon bricks. At the same time, based on the constructed multiple sequence data, the least squares method with constraints is used to calculate the thermal conductivity of each residual carbon brick layer in the use environment in a regression manner.

[0006] To achieve the above-mentioned purpose of the invention, the present invention provides a method for calculating the thermal conductivity of residual carbon bricks in the blast furnace hearth, performs composition and microstructural analysis on sampled carbon bricks from the blast furnace hearth, divides the carbon bricks into regional layers according to the characteristics of the residual carbon bricks, and measures the thickness of each layer. At the same time, combined with the thermal conductivity of the original carbon bricks and the microstructure of the carbon bricks, thermal conductivity constraints of each residual carbon brick layer are proposed. Based on multiple sequence data constructed by analyzing relevant data of multiple different carbon bricks, the least squares method with constraints is used to calculate the thermal conductivity of different layers of the residual carbon bricks in the service state in a regression manner.

[0007] As a further improvement of the present invention, the method for calculating the thermal conductivity of residual carbon bricks in a blast furnace hearth comprises the following steps:

[0008] S1. Obtain the arrangement positions of different thermocouples installed in the furnace, and record the temperature T and insertion depth h of the thermocouples respectively;

[0009] S2. After the blast furnace stops operating, carbon bricks are sampled at different locations of the hearth. The sampled carbon bricks are analyzed for composition and microstructure along the radial direction of the hearth. Based on the analysis results, the carbon bricks are divided into regional layers, and the lengths of each regional layer of the residual carbon bricks are recorded. Based on the analysis results and the thermal conductivity of the original carbon bricks, thermal conductivity constraints for each residual carbon brick layer are proposed.

[0010] S3. respectively obtain the cooling parameters of the corresponding positions of the carbon bricks, and calculate the heat flux Q according to the calculation formula of the heat flux Q;

[0011] S4. The outer temperature of the protective layer is set at 1150° C. as the solidification temperature of the molten iron, and the thermal resistance R from the position of the thermocouple h to the hot surface of the furnace is calculated according to the calculation formula of the thermal resistance R;

[0012] S5. Construct the relationship function f(R) between the thermal resistance R and thermal conductivity of each residual carbon brick layer, and calculate the thermal conductivity of each residual carbon brick layer in the service state by regression using the least squares method with constraints on the thermal conductivity of carbon bricks sampled from different areas according to the multiple sequence data obtained in steps S1 to S4, combined with the constraints on the thermal conductivity of carbon bricks in S2.

[0013] As a further improvement of the present invention, in step S2, the composition and microstructure analysis is as follows: chemical element analysis is performed on some sampled carbon bricks, and the microstructure is analyzed using a light microscope and an electron microscope, including pores, carbon brick matrix, and other entering substances, and then the carbon brick layer is distinguished and analyzed based on the characteristics.

[0014] As a further improvement of the present invention, the carbon bricks are divided into an intact layer, a brittle layer, a harmful element enriched layer, an iron infiltrated layer and a protective layer according to the analysis results, and the length of each layer is recorded as L1, L2, L3, L4 and L5 respectively.

[0015] As a further improvement of the present invention, in step S3, the cooling parameters include cooling water temperature difference, cooling water flow rate, and cooling wall area.

[0016] As a further improvement of the present invention, in step S3, the calculation formula of the heat flux Q is as follows:

[0017]

[0018] Where: Q is heat flux, unit: Kw / m 2 , S is the cooling wall area, unit: m 2 ; c is the specific heat capacity of cooling water, unit: kJ / (kg·℃); ΔT is the cooling water temperature difference, unit: ℃; V is the cooling water flow rate, unit: m 3 / h.

[0019] As a further improvement of the present invention, in step S4, the calculation formula of the thermal resistance from the position h of the thermocouple to the hot surface of the carbon brick is as follows:

[0020]

[0021] As a further improvement of the present invention, in step S5, the relationship function f(R) between the thermal resistance R and thermal conductivity of each residual carbon brick layer is as follows:

[0022]

[0023] Wherein: λ5 is the thermal conductivity of the protective layer, unit: W / m℃; L5 is the length of the protective layer, unit: m; λ4 is the thermal conductivity of the iron-infiltrated layer, unit: W / m℃; L4 is the length of the iron-infiltrated layer, unit: m; λ3 is the thermal conductivity of the harmful element-enriched layer, unit: W / m℃; L3 is the length of the harmful element-enriched layer, unit: m; λ2 is the thermal conductivity of the brittle layer, unit: W / m℃; L2 is the length of the brittle layer, unit: m; λ1 is the thermal conductivity of the intact layer, unit: W / m℃; L1 is the length of the intact layer, unit: m; h is the insertion depth of the thermocouple, unit: m.

[0024] As a further improvement of the present invention, the thermal conductivity constraint conditions of each residual carbon brick layer proposed based on the microstructure of the carbon brick are based on the fact that the larger the porosity, the smaller the thermal conductivity, the looser the combination of iron infiltration and harmful elements with the carbon brick matrix, the smaller the thermal conductivity, and the size constraint judgment is made in combination with the porosity, material composition and bonding state of the carbon brick.

[0025] As a further improvement of the present invention, the thermal conductivity coefficient of each residual carbon brick layer in the service state calculated according to the calculation method can be used for the heat transfer calculation of each residual carbon brick layer, thereby obtaining an accurate erosion furnace profile to monitor the working status of the blast furnace hearth and ensure the safe production of the blast furnace.

[0026] The beneficial effects of the present invention are:

[0027] 1. The present invention first analyzes the composition and microstructure of the residual carbon bricks in the furnace hearth, divides the carbon bricks into layers and regions based on the analysis results, and measures the thickness of each layer. The furnace hearth heat transfer temperature distribution is constructed by combining the temperature measuring thermocouple data with the heat flux of the region, and the thermal conductivity of the carbon bricks in each region is constrained based on the microstructural characteristics. Then, using the constructed multiple sequence data, the least squares method with constraints is used to calculate the thermal conductivity of each residual carbon brick layer in the service state in a regression manner, which makes up for the deficiency that the thermal conductivity of each residual carbon brick layer in the service state cannot be detected by equipment.

[0028] 2. The present invention divides the carbon bricks into an intact layer, a brittle layer, a harmful element enriched layer, an iron-infiltrated layer and a protective layer along the radial direction of the hearth. The calculation method of the present invention can be used to calculate the thermal conductivity of each residual carbon brick layer, which is beneficial for the subsequent analysis of the heat transfer performance of each layer through the thermal conductivity coefficient to obtain a more accurate erosion furnace profile, thereby facilitating the monitoring of the working status of the blast furnace hearth and ensuring the safe production of the blast furnace.

[0029] 3. The calculation method of the present invention is simple, the data is easy to obtain, and the operability is strong. The thermal conductivity coefficient of the carbon bricks calculated by this method can be used as a basic data parameter for calculation to accurately calculate the degree of erosion of the carbon bricks, thereby guiding measures that are beneficial to the safety of the furnace hearth and reducing the risk of furnace hearth burn-through, providing a scientific theoretical basis for improving the service life of the blast furnace, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a design concept diagram of the method for calculating the thermal conductivity of residual carbon bricks in the blast furnace hearth of the present invention.

[0031] Figure 2 These are the optical microscopy (left) and electron microscopy (right) test results of the intact layer of residual carbon bricks in the example.

[0032] Figure 3 These are the light microscopy (left) and electron microscopy (right) test results of the embrittled layer residual carbon bricks in the example.

[0033] Figure 4 These are the optical microscopy (left) and electron microscopy (right) test results of the residual carbon bricks in the harmful element layer in the embodiment.

[0034] Figure 5 These are the light microscopy (left) and electron microscopy (right) test results of the residual carbon bricks in the iron-infiltrated layer in the example.

[0035] Figure 6 These are the optical microscopy (left) and electron microscopy (right) test results of the residual carbon bricks in the protective layer in the example. DETAILED DESCRIPTION

[0036] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] It should also be noted here that, in order to avoid obscuring the present invention due to unnecessary details, only structures and / or processing steps closely related to the solutions of the present invention are shown in the drawings, while other details that are not closely related to the present invention are omitted.

[0038] In addition, it should be noted that the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0039] The present invention provides a method for calculating the thermal conductivity of residual carbon bricks in a blast furnace hearth. First, the composition and microstructure of sampled carbon bricks from the blast furnace hearth are analyzed, the carbon bricks are divided into regional layers according to the characteristics of the residual carbon bricks, and the thickness of each layer is measured. At the same time, combined with the thermal conductivity of the original carbon bricks and the microstructure of the carbon bricks, thermal conductivity constraint conditions for each residual carbon brick layer are proposed. Based on multiple sequence data constructed by analyzing relevant data of multiple different carbon bricks, the least squares method with constraints is used to calculate the thermal conductivity of different layers of the residual carbon bricks in the service state in a regression manner.

[0040] Specifically, the thermal conductivity coefficient of each residual carbon brick layer in the service state calculated according to the calculation method can be used for the heat transfer calculation of each residual carbon brick layer, thereby obtaining an accurate erosion furnace profile to monitor the working status of the blast furnace hearth and ensure the safe production of the blast furnace.

[0041] Specifically, the method for calculating the thermal conductivity of residual carbon bricks in the blast furnace hearth includes the following steps:

[0042] S1. Obtain the layout positions of different thermocouples installed in the furnace, and record the temperature T and insertion depth h of each thermocouple respectively;

[0043] S2. After the blast furnace stops operating, carbon brick samples are obtained by core drilling at different locations of the hearth. The obtained carbon bricks are analyzed for composition and microstructure along the radial direction of the hearth. Based on the analysis results, the carbon bricks are divided into an intact layer, a brittle layer, a harmful element-enriched layer, an iron-infiltrated layer, and a protective layer. The lengths of each layer are denoted as L1, L2, L3, L4, and L5, respectively. Based on the analysis results and the thermal conductivity of the original carbon bricks, thermal conductivity constraints for each residual carbon brick layer are proposed.

[0044] S3. Obtain the cooling parameters of the corresponding positions of each carbon brick respectively, and calculate the heat flux Q according to the calculation formula of the heat flux Q;

[0045] S4. Set the outer temperature of the protective layer at 1150°C as the solidification temperature of the molten iron, and calculate the thermal resistance R from the position of the thermocouple h to the hot surface of the furnace according to the calculation formula of the thermal resistance R;

[0046] S5. Construct the relationship function f(R) between the thermal resistance R and thermal conductivity of each residual carbon brick layer, and calculate the thermal conductivity of each residual carbon brick layer in the service state by regression using the least squares method with constraints on the thermal conductivity of carbon bricks sampled from different areas according to the multiple sequence data obtained in steps S1 to S4, combined with the constraints on the thermal conductivity of carbon bricks in S2.

[0047] Specifically, in step S2, the composition and microstructure analysis is as follows: chemical element analysis is performed on some sampled carbon bricks, and the microstructure is analyzed using light microscopy and electron microscopy, including pores, carbon brick matrix, and other intruding substances, and then the carbon brick layers are distinguished and analyzed based on the characteristics.

[0048] Specifically, the thermal conductivity constraint conditions of each residual carbon brick layer proposed based on the microstructure of the carbon brick are based on the fact that the larger the porosity, the smaller the thermal conductivity, the looser the combination of iron infiltration and harmful elements with the carbon brick matrix, the smaller the thermal conductivity, and the size constraint judgment is made in combination with the porosity, material composition, and bonding state of the carbon brick.

[0049] Specifically, in step S3, the cooling parameters include cooling water temperature difference, cooling water flow rate, and cooling wall area.

[0050] Specifically, in step S3, the calculation formula of heat flux Q is as follows:

[0051]

[0052] Where: S is the cooling wall area, unit: m 2 ; c is the specific heat capacity of cooling water, unit: J / (kg·℃); ΔT is the cooling water temperature difference, unit: ℃; V is the cooling water flow rate, unit: m 3 / s.

[0053] Specifically, in step S4, the calculation formula of the thermal resistance from the thermocouple position h to the hot surface of the carbon brick is as follows:

[0054]

[0055] Specifically, in step S5, the relationship function f(R) between the thermal resistance R and thermal conductivity of each residual carbon brick layer is as follows:

[0056]

[0057] Where: λ5 is the thermal conductivity of the protective layer, unit: W / m℃, L5 is the length of the protective layer, unit: m, λ4 is the thermal conductivity of the iron-infiltrated layer, L4 is the length of the iron-infiltrated layer, λ3 is the thermal conductivity of the harmful element-enriched layer, L3 is the length of the harmful element-enriched layer, λ2 is the thermal conductivity of the brittle layer, L2 is the length of the brittle layer, λ1 is the thermal conductivity of the intact layer, L1 is the length of the intact layer, and h is the insertion depth of the thermocouple.

[0058] The calculation method of the thermal conductivity coefficient of the residual carbon bricks in the blast furnace hearth provided by the present invention is described below with reference to specific embodiments.

[0059] This embodiment provides a method for calculating the thermal conductivity of residual carbon bricks in a blast furnace hearth, which specifically includes the following steps:

[0060] S1. Obtain the arrangement positions of different thermocouples installed in the furnace, and record the temperature T and insertion depth h of each thermocouple respectively. The temperature recording results are shown in Table 2. The insertion depth h of the thermocouple is 240 mm.

[0061] S2. After the blast furnace stops working, carbon brick samples are obtained by drilling cores at different positions of the furnace. The obtained carbon bricks are microscopically analyzed along the radial direction of the furnace. The analysis results are as follows: Figures 2 to 6As shown in Table 1, the carbon bricks are divided into an intact layer, a brittle layer, a harmful element-enriched layer, an iron-infiltrated layer, and a protective layer based on the analysis results. As can be seen from the figure, the intact layer of residual carbon bricks has small pores and is primarily composed of a carbon matrix; the brittle layer of residual carbon bricks has larger pores and some cracks; the harmful element layer of residual carbon bricks contains a large amount of enriched zinc; the iron-infiltrated layer of residual carbon bricks contains a large amount of molten iron that has infiltrated the carbon bricks; and the protective layer of residual carbon bricks contains a large amount of slag and graphite carbon. Furthermore, the lengths of the corresponding residual carbon brick layers in each carbon brick are recorded as L1, L2, L3, L4, and L5, respectively, and the recording results are shown in Table 2. At the same time, based on the analysis results and the thermal conductivity of the original carbon bricks, the thermal conductivity constraints of each residual carbon brick layer are proposed. Since the residual carbon bricks in the brittle layer, the residual carbon bricks in the harmful element-enriched layer and the residual carbon bricks in the protective layer contain large pores, their thermal conductivity is smaller than that of the residual carbon bricks in the intact layer and the residual carbon bricks in the iron-infiltrated layer. At the same time, they are all smaller than the room temperature test values of the initial carbon bricks, and that is, λ2, λ3, λ5<λ4<21W / m℃. Among them, the thermal conductivity of the residual carbon bricks in the intact layer is greater than the design value, that is, λ1>18W / m℃.

[0062] Table 1 Chemical composition of residual carbon bricks

[0063]

[0064] S3. Obtain the cooling parameters of the corresponding position of the sampled carbon brick: cooling water temperature difference, cooling water flow rate, cooling wall area, and calculate the heat flux Q according to the calculation formula of heat flux Q. The specific calculation process is as follows:

[0065]

[0066] The heat flux Q corresponding to each carbon brick obtained by the above calculation is summarized and recorded in Table 2.

[0067] Table 2 Different layer lengths, thermocouple temperatures and heat fluxes of carbon bricks at different positions

[0068]

[0069]

[0070] S4. Set the outer temperature of the protective layer at 1150°C as the solidification temperature of the molten iron. Calculate the thermal resistance R from position h to the hot surface of the furnace according to the calculation formula of thermal resistance R. The specific calculation process is as follows:

[0071]

[0072] The corresponding thermal resistance is shown in Table 3.

[0073] Table 3 Thermal resistance from carbon brick thermocouple to carbon brick hot surface at different positions

[0074] Location 1 2 3 4 5 6 7 8 Thermal resistance 0.0929 0.0963 0.1134 0.1243 0.1034 0.1322 0.1099 0.1216

[0075] S5. Construct a relationship function f(R) between the thermal resistance R and thermal conductivity of each residual carbon brick layer. Based on the multiple sequence data obtained in steps S1 to S4, use the least squares method with constraints to calculate the thermal conductivity of each residual carbon brick layer in the use environment in a regression manner. The calculation process is as follows:

[0076]

[0077] The thermal conductivity coefficient is constrained. The design value of the thermal conductivity coefficient of the initial carbon brick at room temperature is not less than 18W / m℃. Therefore, λ1>18W / m℃, λ2, λ3, λ5<λ4<21W / m℃, and the constrained least squares method is used to fit the coefficients. The regression solution of , and then the thermal conductivity coefficient is solved as shown in Table 4.

[0078] Table 4 Thermal conductivity results of different layers

[0079]

[0080] Therefore, the thermal conductivity of the intact layer is 20.79W / m℃, the thermal conductivity of the brittle layer is 7.0922W / m℃, the thermal conductivity of the harmful element enriched layer is 6.8966W / m℃, the thermal conductivity of the iron-infiltrated layer is 9.0909W / m℃, and the thermal conductivity of the protective layer is 1.7301W / m℃.

[0081] In summary, the present invention discloses a method for calculating the thermal conductivity of residual carbon bricks in a blast furnace hearth. First, the composition and microstructure of the residual carbon bricks in the hearth are analyzed. According to the analysis results, the carbon bricks are divided into layers and regions, and the thickness of each layer is measured. The heat transfer temperature distribution of the hearth is constructed by combining the temperature measuring thermocouple data with the heat flux of the region. The thermal conductivity of the carbon bricks in each region is constrained based on the microstructural characteristics. Then, the thermal conductivity of each residual carbon brick layer in the service state is calculated by regression using the constructed multiple sequence data and the least squares method with constraints. This makes up for the deficiency of the existing equipment that cannot detect the thermal conductivity of each residual carbon brick layer in the service state. In addition, using the calculation method of the present invention, the thermal conductivity of the residual carbon bricks in each region can be calculated separately, which is conducive to the subsequent analysis of the heat transfer performance of each region through the thermal conductivity coefficient to obtain a more accurate erosion furnace type, thereby facilitating the monitoring of the working state of the blast furnace hearth, guiding the smooth progress of production work, and ensuring the safe production of the blast furnace. In addition, the calculation method of the present invention is simple, the data is easy to obtain, and the operability is strong. The thermal conductivity coefficient of the carbon brick calculated by this method can be used as a basic data parameter for calculation to accurately calculate the degree of erosion of the carbon brick, thereby guiding measures that are beneficial to the safety of the furnace hearth and reducing the risk of furnace hearth burn-through, providing a scientific theoretical basis for improving the service life of the blast furnace, and has broad application prospects.

[0082] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for calculating the thermal conductivity of residual carbon bricks in a blast furnace hearth, characterized by: The composition and microstructure of sampled carbon bricks from the blast furnace hearth were analyzed. The residual carbon bricks were divided into regional layers based on their characteristics, and the thickness of each layer was measured. Constraints for the thermal conductivity of each residual carbon brick layer were proposed based on the thermal conductivity of the original carbon bricks and their microstructure. Based on multiple sequence data constructed from relevant data of multiple different carbon bricks, the thermal conductivity of different layers of the residual carbon bricks in service was calculated using a least squares method with constraints by regression. The steps include: S1. Obtain the arrangement positions of different thermocouples installed in the furnace, and record the temperature T and insertion depth h of the thermocouples respectively; S2. After the blast furnace stops operating, carbon bricks are sampled at different locations of the hearth. The sampled carbon bricks are analyzed for composition and microstructure along the radial direction of the hearth. Based on the analysis results, the carbon bricks are divided into regional layers, and the lengths of each regional layer of the residual carbon bricks are recorded. Based on the analysis results and the thermal conductivity of the original carbon bricks, thermal conductivity constraints for each residual carbon brick layer are proposed. S3. respectively obtain the cooling parameters of the corresponding positions of the carbon bricks, and calculate the heat flux Q according to the calculation formula of the heat flux Q; S4. The outer temperature of the protective layer is set at 1150° C. as the solidification temperature of the molten iron, and the thermal resistance R from the position of the thermocouple h to the hot surface of the furnace is calculated according to the calculation formula of the thermal resistance R; S5. Construct a relationship function f(R) between the thermal resistance R and thermal conductivity of each residual carbon brick layer. For carbon bricks sampled from different regions, based on the multiple sequence data obtained in steps S1 to S4, combined with the constraints on the thermal conductivity of carbon bricks in S2, use the least squares method with constraints to calculate the thermal conductivity of each residual carbon brick layer in the service state in a regression manner; According to the analysis results, the carbon bricks are divided into intact layer, brittle layer, harmful element enriched layer, iron infiltration layer and protective layer, and the length of each layer is recorded as L1, L2, L3, L4 and L5 respectively; In step S5, the relationship function between the thermal resistance R and thermal conductivity of each residual carbon brick layer is f (R) as follows: ； in, is the thermal conductivity of the protective layer, L5 is the length of the protective layer, is the thermal conductivity of the iron-infiltrated layer, L4 is the length of the iron-infiltrated layer, is the thermal conductivity of the harmful element enriched layer, L3 is the length of the harmful element enrichment layer, is the thermal conductivity of the brittle layer, L2 is the length of the brittle layer, is the thermal conductivity of the intact layer, L1 is the length of the intact layer, Insertion depth of the thermocouple.

2. The method for calculating the thermal conductivity of residual carbon bricks in a blast furnace hearth according to claim 1, wherein: In step S2, the composition and microstructure analysis is as follows: chemical element analysis is performed on some sampled carbon bricks, and the microstructure is analyzed using light microscopy and electron microscopy, including pores, carbon brick matrix, and other intruding substances, and then the carbon brick layer is distinguished and analyzed based on the characteristics.

3. The method for calculating the thermal conductivity of residual carbon bricks in a blast furnace hearth according to claim 1, wherein: In step S3, the cooling parameters include cooling water temperature difference, cooling water flow rate, and cooling wall area.

4. The method for calculating the thermal conductivity of residual carbon bricks in a blast furnace hearth according to claim 1, wherein: In step S3, the calculation formula of the heat flux Q is as follows: ； Where Q is the heat flux, unit is: w / m 2 , is the cooling wall area, unit: m 2 ; is the specific heat capacity of cooling water, unit: kJ / (kg•℃); is the cooling water temperature difference, unit: ℃; is the cooling water flow rate, unit: m³ / h.

5. The method for calculating the thermal conductivity of residual carbon bricks in a blast furnace hearth according to claim 4, characterized in that: In step S4, the thermal resistance from the thermocouple h position to the hot surface of the carbon brick is The calculation formula is as follows: ； in, is the temperature of the thermocouple.

6. The method for calculating the thermal conductivity of residual carbon bricks in a blast furnace hearth according to claim 1, characterized in that: The thermal conductivity constraint conditions of each residual carbon brick layer proposed based on the microstructure of the carbon brick are based on the fact that the larger the porosity, the smaller the thermal conductivity, the looser the combination of iron infiltration and harmful elements with the carbon brick matrix, the smaller the thermal conductivity, and the size constraint judgment is made in combination with the porosity, material composition, and bonding state of the carbon brick.

7. The method for calculating the thermal conductivity of residual carbon bricks in a blast furnace hearth according to claim 1, characterized in that: The thermal conductivity coefficient of each residual carbon brick layer in the service state calculated according to the calculation method can be used for the heat transfer calculation of each residual carbon brick layer, thereby obtaining an accurate erosion furnace profile to monitor the working status of the blast furnace hearth and ensure the safe production of the blast furnace.

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