Method for calculating residual thickness of carbon brick in blast furnace hearth

Abstract

This invention discloses a method for calculating the residual thickness of carbon bricks in a blast furnace hearth. Based on the erosion characteristics of carbon bricks, the carbon bricks are divided into an intact layer, an embrittled layer, and a ferroplated layer along the radial direction of the hearth. The residual thickness of the carbon bricks is calculated using the thermal conductivity of each layer. First, based on the principle that the radial heat flux of the hearth sidewall is equal, the boundary line between the intact layer and the embrittled layer is calculated to obtain the length of the intact layer. Then, based on the temperature boundary line between the embrittled layer and the ferroplated layer, the lengths of the embrittled layer and the ferroplated layer are calculated to obtain a more accurate residual thickness of the carbon bricks. The calculation method of this invention is simple, the data is easy to obtain, and it is highly operable. By using the corresponding thermal conductivity to calculate the residual carbon bricks in different regions, it more realistically and accurately reflects the degree of erosion of the carbon bricks. This allows blast furnace operators to obtain the internal working status of the hearth in a timely and accurate manner, effectively avoiding production accidents and showing broad application prospects.

Description

Technical Field

[0001] This invention relates to the field of blast furnace smelting technology, and in particular to a method for calculating the residual thickness of carbon bricks in the hearth of a blast furnace. Background Technology

[0002] The blast furnace hearth is a high-temperature slag and iron storage area. Its structure, from the outside in, generally includes the furnace shell, cooling wall, ramming layer, carbon bricks, and ceramic cups, with the carbon bricks being laid in layers. In the later stages of furnace operation, after the ceramic cups are consumed, the carbon bricks come into direct contact with the high-temperature slag and iron inside the hearth. With fluctuations in hearth operating conditions, the carbon bricks are damaged by thermal stress and harmful elements, leading to internal cracks and iron seepage. This results in a significant decrease in their thermal conductivity and corresponding changes in heat transfer performance. As the limiting factor in the blast furnace's lifespan, the degree of carbon brick erosion directly affects the blast furnace's service life. Current technology uses heat transfer theory to calculate the remaining thickness of the carbon bricks to determine the degree of erosion. However, this calculation does not fully consider the structural changes in the carbon bricks caused by erosion and the changes in the thermal conductivity of each structural layer, resulting in significant discrepancies between the calculated and actual results.

[0003] In the prior art, patent CN 114896546 A discloses a high-precision calculation method for the residual thickness of carbon bricks in a blast furnace hearth. First, boundary conditions are selected, and then the thermal conductivity of the carbon bricks is substituted into the heat transfer formula as a function of temperature to calculate the location and degree of erosion at the end of the blast furnace's service life. However, this calculation method does not take into account the significant changes in the microstructure of the carbon bricks after erosion, such as the appearance of a large number of pores and the enrichment and infiltration of other substances, which will cause a great change in its thermal conductivity. In the calculation process, it is still assumed that its thermal conductivity is only affected by temperature, which will lead to a certain deviation between the actual result and the calculated result.

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

[0005] The purpose of this invention is to provide a method for calculating the residual thickness of carbon bricks in the hearth of a blast furnace by calculating the residual thickness of carbon bricks based on the thermal conductivity of different regions after the residual carbon bricks have been eroded, so as to accurately reflect the degree of erosion of the carbon bricks.

[0006] To achieve the above-mentioned objective, this invention provides a method for calculating the residual thickness of carbon bricks in the hearth of a blast furnace, comprising the following steps:

[0007] S1. Collect the arrangement position and temperature data of thermocouples in the blast furnace hearth, record the insertion depth of the thermocouples near the center of the blast furnace as H3, and preprocess the temperature data of the thermocouples.

[0008] S2. Divide the residual carbon bricks in the hearth along the radial direction of the hearth into a sound layer, a embrittled layer, and an iron-penetrated layer, respectively obtain the thermal conductivities λ1, λ2, and λ3 of each regional layer, and record the residual thicknesses of the respective regional layers as L1, L2, and L3;

[0009] S3. Based on the principle of equal radial heat flux in the blast furnace hearth and in combination with the different insertion depths of the thermocouples, judge the size relationship between the thickness L1 of the sound layer of the carbon bricks and the insertion depth H3 of the thermocouple close to the center of the blast furnace through coupled calculation, and calculate the thickness L1 of the sound layer in different cases according to the judgment result;

[0010] S4. Take 1150 °C as the critical temperature point of the hearth hot surface and 907 °C as the demarcation temperature point between the embrittled layer and the iron-penetrated layer, and calculate the thickness L2 of the embrittled layer and the thickness L3 of the iron-penetrated layer respectively to obtain the residual thickness L of the carbon bricks.

[0011] As a further improvement of the present invention, in step S1, at least three thermocouples 1, 2, and 3 with different insertion depths are respectively arranged in the hearth. The calculation starting point of the insertion depth is calculated starting from the starting point of the carbon bricks close to the furnace shell direction. The insertion depths are H1, H2, and H3 respectively, and H1 < H2 < H3. The temperature data of the thermocouples 1, 2, and 3 are T1, T2, and T3 respectively; the temperature data of the thermocouples are preprocessed by removing the data where the temperature does not conform to T 3> and the data with T2 > T1.

[0012] As a further improvement of the present invention, in step S3, the coupled calculation refers to the method of combining T1 and T2, T2 and T3, and using λ1 as the thermal conductivity to calculate the heat flux difference value s to judge the relationship between the thickness L1 of the sound layer and H3.

[0013] As a further improvement of the present invention, if s is greater than the preset difference value a, it is considered that L1 < H3; if s is less than the preset difference value a, it is considered that L1 > H3; the calculation formula of the heat flux difference value s is as follows:

[0014]

[0015] where, q 21 is the heat flux from L2 to L1, and q 32 is the heat flux from L3 to L2.

[0016] As a further improvement of the present invention, the calculation formulas of q 21 and q 32 are as follows:

[0017] [[ID=4|0]]

[0018]

[0019] As a further improvement of the present invention, when L1 < H3, the calculation formulas of L1 and L2 are as follows:

[0020]

[0021]

[0022] As a further improvement of the present invention, when L1 > H3, it indicates that the residual state of the carbon brick is good. Take L1 = H3 for calculation to obtain the minimum length of the embrittlement layer L2 of the residual carbon brick. The calculation formula for the minimum length of L2 is as follows:

[0023]

[0024] As a further improvement of the present invention, when the molten iron in the hearth contacts the carbon brick, due to the cooling effect, slag-iron condensation will occur, thereby forming a protective layer on the hot surface of the carbon brick. The thermal conductivity of the protective layer is λ4, and the temperature range of the iron penetration layer and the protective layer is 907 - 1150 °C.

[0025] As a further improvement of the present invention, in step S4, the calculation formula for the thickness L3 of the iron penetration layer is as follows:

[0026]

[0027] where b is the thickness of the protective layer, with the unit of m; λ4 is the thermal conductivity of the protective layer, with the unit of W / m·°C.

[0028] As a further improvement of the present invention, in step S4, when L1 < H3, the residual thickness L of the carbon brick = L1 + L2 + L3; when L1 > H3, the minimum residual thickness L of the carbon brick min = L1 + L2 + L3.

[0029] The beneficial effects of the present invention are as follows:

[0030] 1. According to the erosion change of the carbon brick, the present invention divides the carbon brick along the radial direction of the hearth into a sound layer, an embrittlement layer, and an iron penetration layer, and calculates the residual thickness of the carbon brick by using the thermal conductivity of each regional layer respectively, avoiding a large deviation between the calculation result of the residual thickness of the carbon brick and the actual result due to the large change in the thermal conductivity of different regional layers of the carbon brick not being fully considered, so as to more accurately calculate the residual thickness of the carbon brick.

[0031] 2. The calculation method of this invention is simple, the data is easy to obtain, and it is highly operable. Based on the thermal conductivity of the residual carbon bricks after actual erosion, the thickness of the carbon bricks is calculated in different regions. The calculation results can more accurately reflect the degree of erosion of the carbon bricks, thereby guiding the implementation of measures that are beneficial to the safety of the hearth and reducing the risk of hearth burn-through. It provides a scientific theoretical basis for improving the service life of blast furnaces and has broad application prospects. Attached Figure Description

[0032] Figure 1 This is a schematic diagram illustrating the design concept of the method for calculating the residual thickness of carbon bricks in the blast furnace hearth according to the present invention.

[0033] Figure 2 This is a schematic diagram of the thermocouple arrangement in Example 1. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to specific embodiments.

[0035] It should also be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0036] This invention provides a method for calculating the residual thickness of carbon bricks in the hearth of a blast furnace, comprising the following steps:

[0037] S1. Collect the arrangement position and temperature data of thermocouples in the blast furnace hearth, record the insertion depth of the thermocouples near the center of the blast furnace as H3, and preprocess the temperature data of the thermocouples.

[0038] S2. The residual carbon bricks in the hearth are divided into three layers according to their structure along the radial direction of the hearth: intact layer, embrittled layer, and iron-infiltrated layer. The thermal conductivity λ1, λ2, and λ3 of each layer are obtained, and the residual thickness of each layer is recorded as L1, L2, and L3, respectively.

[0039] S3. Based on the principle of equal radial heat flux in the blast furnace hearth and combined with different thermocouple insertion depths, the relationship between the thickness L1 of the intact carbon brick layer and the thermocouple insertion depth H3 near the center of the blast furnace is determined by coupling calculation. The thickness L1 of the intact layer under different conditions is calculated according to the judgment result.

[0040] S4. Take 1150 °C as the critical point of the hearth hot surface temperature; harmful element zinc is deposited at one end of the embrittlement layer close to the iron penetration layer, and take the boiling point of zinc, 907 °C, as the demarcation point between the embrittlement layer and the iron penetration layer, and calculate the thickness L2 of the embrittlement layer and the thickness L3 of the iron penetration layer respectively to obtain the residual thickness L of the carbon brick.

[0041] Specifically, in step S1, at least three thermocouples 1, 2, and 3 with different insertion depths are respectively set in the hearth. The calculation starting point of the insertion depth starts from the starting point of the carbon brick close to the furnace shell direction, and the insertion depths are H1, H2, and H3 respectively, and H1 < H2 < H3. The temperature data of the thermocouples 1, 2, and 3 are T1, T2, and T3 respectively. According to the distribution of the insertion depths of the thermocouples, the temperatures from thermocouple 1 to thermocouple 3 should increase in sequence.剔除 the temperature data that does not conform to T3 > T2 > T1 through preprocessing of the temperature data.

[0042] Specifically, in step S3, the coupled calculation refers to the method of combining T1 and T2, and T2 and T3, and take λ1 as the thermal conductivity to calculate the heat flux difference value s to judge the relationship between the intact layer thickness L1 and H3. If s is greater than the preset difference value a, it is considered that L1 < H3; if s is less than the preset difference value a, it is considered that L1 > H3. The calculation formula of the heat flux difference value s is as follows:

[0043]

[0044] where, q 21 is the heat flux from L2 to L1, and q 32 is the heat flux from L3 to L2.

[0045] Specifically, the calculation formulas of q 21 and q 32 are as follows:

[0046]

[0047]

[0048] Specifically, when L1 < H3, calculate the intact layer thickness L1 based on the principle that the heat fluxes of different thermocouple couplings are consistent. The calculation formula of L1 is as follows:

[0049]

[0050] In addition, combine T3 and 907 °C to calculate the embrittlement layer thickness L2. The calculation formula of L2 is as follows:

[0051]

[0052] Specifically, when L1 > H3, it indicates that the residual state of the carbon brick is good. Calculate by taking L1 = H3 to obtain the minimum length of the embrittlement layer L2 of the residual carbon brick. The calculation formula for the minimum length of L2 is as follows:

[0053]

[0054] Specifically, when the hot metal in the hearth contacts the carbon brick, due to the cooling effect, slag and iron condensation will occur, thereby forming a protective layer on the hot surface of the carbon brick. Its thermal conductivity is λ4, and the temperature range of the iron penetration layer and the protective layer is 907 - 1150 °C. Therefore, the calculation formula for the thickness L3 of the iron penetration layer is as follows:

[0055]

[0056] Where, b is the thickness of the protective layer, with the unit of m; λ4 is the thermal conductivity of the protective layer, with the unit of W / m°C.

[0057] Specifically, in step S4, when L1 < H3, the residual thickness L of the carbon brick = L1 + L2 + L3; when L1 > H3, the minimum residual thickness L of the carbon brick min = L1 + L2 + L3.

[0058] The following will illustrate the calculation method for the residual thickness of the blast furnace hearth carbon brick provided by the present invention with specific embodiments.

[0059] Embodiment 1

[0060] This embodiment provides a calculation method for the residual thickness of the blast furnace hearth carbon brick, which specifically includes the following steps:

[0061] S1. Collect the arrangement positions and temperature data of the thermocouples in the blast furnace hearth. The insertion depths of thermocouples 1, 2, and 3 are 200 mm, 330 mm, and 730 mm respectively. Among them, the 280 mm position is the boundary between the molded small carbon brick and the large microporous carbon brick. The range of 0 - 280 mm is the molded small carbon brick, and after 280 mm is the large microporous carbon brick. Denote the temperatures of thermocouples 1, 2, and 3 as T1, T2, and T3 respectively. Since thermocouple 3 is closest to the center of the hearth, the data with temperatures not satisfying T3 > T2 > T1 are excluded to obtain the temperature data of the temperature measurement area, as shown in Table 1.

[0062] Table 1 Temperature data of each thermocouple

[0063] Temperature point temperature <![CDATA[T1]]> 124 <![CDATA[T2]]> 203.67 <![CDATA[T3]]> 438.75

[0064] S2. The residual carbon bricks in the hearth are divided into three layers according to their structure along the radial direction of the hearth: an intact layer, an embrittled layer, and an iron-infiltrating layer. The thermal conductivity λ0 of the small molded carbon bricks at the front end of the intact layer is 15 W / m℃, the thermal conductivity λ1 of the large microporous carbon bricks in the intact layer is 20.2 W / m℃, and the length of the intact layer is denoted as L1; the thermal conductivity λ2 of the carbon bricks in the embrittled layer is 6.5 W / m℃, and the length is denoted as L2; ​​the thermal conductivity λ3 of the carbon bricks in the iron-infiltrating layer is 8.7 W / m℃, and the length is denoted as L3.

[0065] S3. Based on the principle of equal radial heat flux in the blast furnace hearth and combined with different thermocouple insertion depths, the heat flux difference value s is calculated using a combination of T1 and T2, and T2 and T3, with λ1 as the thermal conductivity. The difference value a is set to 0.03, and the relationship between the intact layer thickness L1 and H3 is determined. In this embodiment, the calculation result of the heat flux difference value s is as follows:

[0066]

[0067]

[0068]

[0069] Therefore, L1 <H3。

[0070]

[0071] In other embodiments of the present invention, only one type of carbon brick may be used, corresponding to q 21 The formulas for calculating L1 are as follows:

[0072]

[0073]

[0074] S4. A harmful element, zinc, is deposited near the iron-seeping layer in the embrittlement layer. The boiling point of zinc, 907℃, is used as the boundary between the embrittlement layer and the iron-seeping layer to facilitate more accurate calculation of their thicknesses. After the ceramic cups are consumed in the later stages of furnace operation, a 10mm protective layer remains at the front end of the carbon brick. The thermal conductivity of this protective layer is 2.5W / m℃. From 907℃ to 1150℃, it consists of the iron-seeping layer and the protective layer. Based on heat flux calculations using thermocouples 1 and 2, the length L3 of the iron-seeping layer is obtained as follows:

[0075]

[0076] The length of the embrittlement layer was calculated by combining T3 and the 907℃ iron infiltration layer initiation temperature point, and L2 was obtained as follows:

[0077]

[0078] Therefore, the total length of the carbon bricks is: L = 0.6921 + 0.3165 + 0.1587 = 1.1673 m

[0079] Example 2

[0080] Example 2 provides a method for calculating the residual thickness of carbon bricks in the hearth of a blast furnace, specifically including the following steps:

[0081] S1. Collect the placement and temperature data of thermocouples in the blast furnace hearth. The insertion depths of thermocouples 1, 2, and 3 are 200mm, 330mm, and 730mm, respectively. The 280mm mark is the boundary between the molded small carbon bricks and the large microporous carbon bricks; 0-280mm represents the molded small carbon bricks, and beyond 280mm represents the large microporous carbon bricks. The temperatures of thermocouples 1, 2, and 3 are denoted as T1, T2, and T3, respectively. Since thermocouple 3 is closest to the hearth center, data where the temperature does not satisfy T3>T2>T1 are discarded. The resulting temperature data for the measurement area is shown in Table 2.

[0082] Table 2 Temperature data for each thermocouple

[0083]

[0084]

[0085] S2. The remaining carbon bricks in the hearth are structurally divided into three layers along the radial direction: an intact layer, an embrittled layer, and an iron-infiltrating layer. The thermal conductivity λ0 of the small molded carbon bricks at the front end of the intact layer is 15 W / m℃; the thermal conductivity λ1 of the large microporous carbon bricks in the intact layer is 20.2 W / m℃; and the length of the intact layer is denoted as L1. The thermal conductivity λ2 of the carbon bricks in the embrittled layer is 6.5 W / m℃, and its length is denoted as L2. The thermal conductivity λ3 of the carbon bricks in the iron-infiltrating layer is 8.7 W / m℃, and its length is denoted as L3.

[0086] S3. Based on the principle of equal heat flux and combined with different thermocouple insertion depths, the heat flux difference value s is calculated using a combination of T1 and T2, and T2 and T3, with λ1 as the thermal conductivity. The difference value a is set to 0.03, and the relationship between the intact layer thickness L1 and H3 is determined. The calculation results of the heat flux difference value s are as follows:

[0087]

[0088]

[0089]

[0090] Therefore, L1 > H3, and H3 = L1. The minimum length of L2 is calculated as follows:

[0091]

[0092] L3 is:

[0093]

[0094] The minimum total length of the remaining carbon brick is: L min =0.73+0.3422+0.1747=1.2469m

[0095] In summary, this invention discloses a method for calculating the residual thickness of carbon bricks in a blast furnace hearth. Based on the erosion characteristics of carbon bricks, the carbon bricks are structurally divided into an intact layer, an embrittled layer, and an iron-infiltrating layer along the radial direction of the hearth. The residual thickness of the carbon bricks is calculated using the thermal conductivity of each layer, avoiding significant deviations between the calculated and actual results due to insufficient consideration of the large changes in thermal conductivity after erosion. Furthermore, the location of thermocouples near the blast furnace center is determined by the principle of equal radial heat flux in the blast furnace hearth. Different calculation methods are proposed for each layer where the thermocouples are located, resulting in a more accurate calculation of the residual thickness. This invention's calculation method is simple, the data is readily available, and it is highly operable. Calculating the residual thickness by using the thermal conductivity of the residual carbon bricks in different regions more accurately reflects the degree of erosion, thereby guiding measures beneficial to hearth safety and reducing the risk of hearth burn-through. This provides a scientific theoretical basis for improving the service life of blast furnaces and has broad application prospects.

[0096] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for calculating residual thickness of carbon bricks of a blast furnace hearth, characterized by, It includes the following steps: S1. Collect the arrangement positions and temperature data of the thermocouples in the blast furnace hearth, record the insertion depth of the thermocouple close to the center of the blast furnace as H3, and preprocess the temperature data of the thermocouples; S2. Divide the residual carbon bricks in the hearth along the radial direction of the hearth into a sound layer, a embrittled layer and an iron-permeated layer, respectively obtain the thermal conductivities λ1, λ2, λ3 of each regional layer, and record the residual thicknesses of each regional layer as L1, L2, L3 respectively; S3. Based on the principle of equal radial heat flux in the blast furnace hearth and combined with the different insertion depths of the thermocouples, judge the size relationship between the thickness L1 of the sound layer of the carbon bricks and the insertion depth H3 of the thermocouple close to the center of the blast furnace through coupled calculation, and calculate the thickness L1 of the sound layer in different cases according to the judgment results; S4. Taking 1150 °C as the critical temperature point of the hearth hot surface and 907 °C as the demarcation temperature point between the embrittled layer and the iron-permeated layer, calculate the thickness L2 of the embrittled layer and the thickness L3 of the iron-permeated layer respectively to obtain the residual thickness L of the carbon bricks; In step S4, when L1 < H3, the remaining thickness L of the carbon brick is L = L1 + L2 + L3; when L1 > H3, the minimum remaining thickness L of the carbon brick min = L1 + L2 + L3.

2. The method of claim 1, wherein: In step S1, at least three thermocouples 1, 2, 3 with different insertion depths are respectively arranged in the hearth. The calculation starting point of the insertion depth starts from the starting point of the carbon bricks close to the furnace shell direction. The insertion depths are H1, H2, H3 respectively, and H1 < H2 < H3. The temperature data of the thermocouples 1, 2, 3 are T1, T2, T3 respectively. The preprocessing of the temperature data of the thermocouples is to剔除 the data whose temperature does not meet T3 > T2 > T1.

3. The method for calculating the residual thickness of carbon bricks in the blast furnace hearth according to claim 2, characterized in that: In step S3, the coupled calculation refers to the method of combining T1 and T2, T2 and T3, and using λ1 as the thermal conductivity to calculate the heat flux difference value s to judge the relationship between the thickness L1 of the sound layer and H3.

4. The method for calculating the residual thickness of carbon bricks in the blast furnace hearth according to claim 3, characterized in that: If s is greater than the preset difference value a, it is considered that L1 < H3; if s is less than the preset difference value a, it is considered that L1 > H3. The calculation formula of the heat flux difference value s is as follows: where q 21 is the heat flux from L2 to L1, q 32 is the heat flux from L3 to L2.

5. The method of claim 4, wherein: q 21 With q 32 The calculation formula is as follows: ; . ​ 6. The method for calculating the residual thickness of carbon bricks in the blast furnace hearth according to claim 4, characterized in that: When L1 < H3, the calculation formula of L1 and L2 is as follows: ; 。 7. The method of claim 4, wherein: When L1 > H3, it indicates that the residual state of the carbon bricks is good. Take L1 = H3 for calculation to obtain the minimum length of the residual carbon brick embrittled layer L2. The calculation formula of the minimum length of L2 is as follows: ​ 。 8. The method of claim 1, wherein: When the molten iron in the hearth is in contact with the carbon brick, slag and iron condense due to the cooling effect, thereby forming a protective layer on the hot face of the carbon brick, the thermal conductivity coefficient of the protective layer is , and the temperature range of the iron permeated layer and the protective layer is 907-1150℃. ​ 9. The method of claim 8, wherein: In step S4, the calculation formula of the thickness L3 of the iron-permeated layer is as follows: ​ Where, q 21 denoted as heat flux from L2 to L1, and b as the thickness of the protective layer in meters. The value represents the thermal conductivity of the protective layer, expressed in W / m℃.

Images