Refractory lining structure of blast furnace gutter

Abstract

To provide a refractory lining structure which can improve the durability of a blast furnace gutter.SOLUTION: In a refractory lining structure of a blast furnace gutter of the present disclosure, a first part of an inner wall face in the blast furnace gutter is made of a first refractory, a second part of the inner wall face in the blast furnace gutter is made of a secondary refractory, and a third part of the inner wall face in the blast furnace gutter is made of a third refractory. An upper end of the first par is located above a boundary between molten slag and a vapor phase, and a lower end of the first part is located below a boundary between molten iron and the molten slag. The second part is the part below the low end of the first part, and the third part is the part above the upper end of the first part. The first refractory is an unfired brick comprising magnesia of 3 mass% or more to 10 mass% or less, alumina of 65 mass% or more to 90 mass% or less, SiC of 1 mass% or more to 20 mass% or less and carbon of 1 mass% or more to 20 mass% or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] This application discloses a refractory lining structure for a blast furnace trough. [Background technology]

[0002] Various refractories are used as lining materials for blast furnace runners. For example, in the inner wall surface of the blast furnace runner, a spinel-SiC-alumina-carbon type monolithic refractory is used in the boundary between molten iron and molten slag, which is the part that determines durability, and a SiC-alumina-carbon type monolithic refractory is used in the boundary between molten slag and the gas phase. Different monolithic refractories (castables) can be used depending on the part of the blast furnace runner. However, when the inner wall surface of the blast furnace runner is made of a monolithic refractory (castable), there is a limit to the improvement of durability, such as an increase in the apparent porosity of the refractory.

[0003] On the other hand, as disclosed in Patent Document 1, the inner wall surface of the gutter may be made of a shaped refractory material, and unshaped refractory material may be poured behind the shaped refractory material. However, when the inner wall surface of the gutter is made of a shaped refractory material, it is necessary to install a plurality of shaped refractories side by side, and gaps are generated between one shaped refractory material and another shaped refractory material, and molten iron may enter the gaps, which may easily cause wear of the refractory material. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2005-336588 A Summary of the Invention [Problem to be solved by the invention]

[0005] According to the findings of the present inventors, wear of the refractory material is likely to occur on the inner wall surface of the blast furnace runner, particularly at the boundary between the molten iron and the molten slag and at the boundary between the molten slag and the gas phase. In other words, the durability of the blast furnace runner is governed by the durability of the refractory material on the inner wall surface of the blast furnace runner, including the boundary between the molten iron and the molten slag and the boundary between the molten slag and the gas phase. In the prior art, the durability of the refractory material lining this portion has not been fully considered, and there is still room for improvement in the durability of the blast furnace runner. [Means for solving the problem]

[0006] The present application discloses the following aspects as means for solving the above problems. <Aspect 1> A refractory lining structure for a blast furnace trough, comprising: a first portion of an inner wall surface of the blast furnace runner is made of a first refractory material, The second portion of the inner wall surface of the blast furnace runner is made of a second refractory material, a third portion of an inner wall surface of the blast furnace runner is made of a third refractory material, The upper end of the first portion is located above the boundary between the molten slag and the gas phase, The lower end of the first portion is located below the boundary between the molten iron and the molten slag, the second portion is a portion below the lower end of the first portion, the third portion is a portion above the upper end of the first portion, The first refractory material is 3% by mass or more and 10% by mass or less of magnesia, 65% by mass or more and 90% by mass or less of alumina; 1% by mass or more and 20% by mass or less of SiC, and Carbon: 1% to 20% by mass An unfired brick comprising: Refractory lining structure of blast furnace trough. <Aspect 2> The refractory lining structure of the blast furnace trough according to embodiment 1, The second refractory material is 40% to 80% by mass of spinel, 1% by mass or more and 25% by mass or less of SiC, 5% by mass or more and 30% by mass or less of alumina, and Carbon: 1% to 15% by mass A castable comprising: Refractory lining structure of blast furnace trough. <Aspect 3> The refractory lining structure of the blast furnace trough according to embodiment 1 or 2, The second refractory material has the following properties: Properties: Linear change rate is 1.0% or more after sintering at 1500℃ for 3 hours in an inert atmosphere having Refractory lining structure of blast furnace trough. <Aspect 4> The refractory lining structure of a blast furnace trough according to any one of aspects 1 to 3, The third refractory material is 50% to 90% by mass of alumina, and 5% to 30% by mass of spinel A castable comprising: Refractory lining structure of blast furnace trough. <Aspect 5> The refractory lining structure of a blast furnace trough according to any one of aspects 1 to 4, A fourth refractory material is present on the back side of the first refractory material, The fourth refractory material is 50% to 90% by mass of alumina, and 5% to 30% by mass of spinel A castable comprising: Refractory lining structure of blast furnace trough. <Aspect 6> The refractory lining structure of a blast furnace trough according to any one of aspects 1 to 5, The distance from the upper end of the first portion to the boundary between the molten slag and the gas phase is 200 mm or less; The distance from the lower end of the first portion to the boundary between the molten iron and the molten slag is 200 mm or less. Refractory lining structure of blast furnace trough. Effect of the Invention

[0007] According to the technique of the present disclosure, the durability of the blast furnace trough is likely to be improved. [Brief description of the drawings]

[0008] [Figure 1] 1 is a schematic diagram showing a refractory lining structure of a blast furnace runner according to one embodiment, the structure being taken along a cross section perpendicular to the longitudinal direction of the blast furnace runner. [Diagram 2] 1 is a schematic diagram showing a flow of a refractory lining method for a blast furnace trough according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, one embodiment of the refractory lining structure of a blast furnace trough according to the present disclosure will be described. However, the structure of the present disclosure is not limited to the following embodiment.

[0010] 1. Basic structure of refractory lining for blast furnace trough As shown in FIG. 1, in the refractory lining structure 100 of the blast furnace runner according to one embodiment, the first portion 11 of the inner wall surface 10 of the blast furnace runner is made of the first refractory 21, the second portion 12 of the inner wall surface 10 of the blast furnace runner is made of the second refractory 22, and the third portion 13 of the inner wall surface 10 of the blast furnace runner is made of the third refractory 23. The upper end of the first portion 11 is located above the boundary between the molten slag 30 and the gas phase 40. The lower end of the first portion 11 is located below the boundary between the molten iron 50 and the molten slag 30. The second portion 12 is a portion below the lower end of the first portion 11. The third portion 13 is a portion above the upper end of the first portion 11. The first refractory 21 is an unfired brick containing 3% by mass to 10% by mass of magnesia, 65% by mass to 90% by mass of alumina, 1% by mass to 20% by mass of SiC, and 1% by mass to 20% by mass of carbon.

[0011] 1.1 Part 1 The first portion 11 constitutes at least a part of the inner wall surface 10 of the blast furnace runner (the surface that serves as a flow path for the molten iron 50 and the molten slag 30). The upper end of the first portion 11 is located above the boundary between the molten slag 30 and the gas phase 40, and the lower end of the first portion 11 is located below the boundary between the molten iron 50 and the molten slag 30. That is, the first portion 11 is a portion including the boundary between the molten iron 50 and the molten slag 30 and the boundary between the molten slag 30 and the gas phase 40. According to the findings of the present inventor, wear of the refractory material is likely to occur at the boundary between the molten iron 50 and the molten slag 30 and the boundary between the molten slag 30 and the gas phase 40 on the inner wall surface 10 of the blast furnace runner. That is, by improving the durability of the refractory material constituting the first portion 11, the durability of the blast furnace runner as a whole is likely to be improved. In this embodiment, by employing a first refractory 21 described below as the refractory constituting the first portion 11, it becomes possible to improve the durability of the blast furnace runner as a whole.

[0012] The upper end of the first portion 11 is located above the boundary between the molten slag 30 and the gas phase 40. In particular, when the distance from the upper end of the first portion 11 to the boundary between the molten slag 30 and the gas phase 40 (distance X1 in FIG. 1) is 200 mm or less, buckling of the refractory material is less likely to occur when the blast furnace trough is used, and the stability of the refractory material is more likely to be improved. The distance from the upper end of the first portion 11 to the boundary between the molten slag 30 and the gas phase 40 may be 150 mm or less, or 100 mm or less.

[0013] The lower end of the first portion 11 is located below the boundary between the molten iron 50 and the molten slag 30. In particular, when the distance from the lower end of the first portion 11 to the boundary between the molten iron 50 and the molten slag 30 (distance X2 in FIG. 1) is 200 mm or less, buckling of the refractory material is less likely to occur when the blast furnace trough is used, and the stability of the refractory material is more likely to be improved. The distance from the lower end of the first portion 11 to the boundary between the molten iron 50 and the molten slag 30 may be 150 mm or less, or 100 mm or less.

[0014] 1.2 First refractory The first portion 11 is made of a first refractory material 21. The first refractory material 21 is an unfired brick containing 3% by mass or more and 10% by mass or less of magnesia, 65% by mass or more and 90% by mass or less of alumina, 1% by mass or more and 20% by mass or less of SiC, and 1% by mass or more and 20% by mass or less of carbon.

[0015] 1.2.1 Magnesia The first refractory 21 contains 3 mass % to 10 mass % of magnesia. When the first refractory 21 contains magnesia, the magnesia reacts with alumina, which will be described later, to generate spinel when the blast furnace runner is used.

[0016] According to the findings of the present inventors, the erosion of the refractory at the boundary between the molten iron 50 and the molten slag 30 is likely to be accelerated by FeO present near the interface between the molten iron 50 and the molten slag 30. The spinel has a function of enhancing the corrosion resistance against this FeO. According to the findings of the present inventors, the erosion of the refractory at the boundary between the molten slag 30 and the gas phase 40 is likely to be accelerated by CaO-SiO2-Al2O3-based complex oxides contained in the slag. The spinel also has a function of enhancing the corrosion resistance against these complex oxides. That is, since the first refractory 21 contains magnesia and alumina, a spinel is generated in the first refractory 21 during use of the blast furnace runner, and the first refractory 21 is less likely to be eroded by the spinel, and its durability is significantly improved.

[0017] The first refractory 21 is an unfired brick. Therefore, compared with castables, the porosity is small and the durability is excellent. On the other hand, when an unfired brick is used as the first refractory 21, gaps (joints) are easily generated around the first refractory 21. If gaps exist between the refractories when the blast furnace runner is used, molten iron may enter the gaps, which may cause deterioration. In contrast, when the first refractory 21 contains magnesia and alumina, the magnesia and alumina react to form spinel with a relatively small specific gravity when the blast furnace runner is used, and the volume of the first refractory 21 expands, making it difficult for gaps to be generated around the first refractory 21. As a result, it is possible to eliminate the disadvantages of unfired bricks (gaps are easily generated and molten iron or the like is easily allowed to enter the gaps) while securing the advantages of unfired bricks (low porosity and excellent durability).

[0018] If the content of magnesia in the first refractory 21 is too low, the effect of spinel generation as described above may be insufficient. On the other hand, if the content of magnesia in the first refractory 21 is too high, the components other than magnesia may become relatively too small, and the performance of the refractory may be reduced. If the content of magnesia in the first refractory 21 is 3% by mass or more and 10% by mass or less, the effect of spinel generation is sufficient and the performance balance of the refractory is excellent. The content of magnesia in the first refractory 21 may be 4% by mass or more, 5% by mass or more, 6% by mass or more, 7% by mass or more, or 8% by mass or more, or 9% by mass or less, 8% by mass or less, 7% by mass or less, 6% by mass or less, or 5% by mass or less. These lower and upper limits may be any combination.

[0019] 1.2.2 Alumina The first refractory 21 contains 65 mass % or more and 90 mass % or less of alumina. When the first refractory 21 contains alumina, as described above, spinel can be generated when the blast furnace runner is used. In addition, when the main component of the first refractory 21 is alumina, the durability of the refractory is further improved.

[0020] If the content of alumina in the first refractory 21 is too low, the effect of spinel generation as described above may be insufficient. In addition, the performance balance as a refractory may be poor. On the other hand, if the content of alumina in the first refractory 21 is too high, the components other than alumina may be relatively too small, and the performance as a refractory may be deteriorated. When the content of alumina in the first refractory 21 is 65 mass% or more and 90 mass% or less, it is possible to achieve both the effect of spinel generation and the performance balance as a refractory. The content of alumina in the first refractory 21 may be 70 mass% or more, 75 mass% or more, 80 mass% or more, or 85 mass% or more, or 85 mass% or less, 80 mass% or less, 75 mass% or less, or 70 mass% or less. These lower and upper limits may be any combination.

[0021] 1.2.3 SiC The first refractory 21 contains 1 mass % or more and 20 mass % or less of SiC. When the first refractory 21 contains SiC, the durability of the refractory is further improved.

[0022] If the content of SiC in the first refractory 21 is too low, the effect of improving the durability of the refractory may not be sufficient, whereas if the content of SiC in the first refractory 21 is too high, the components other than SiC may become relatively too small, and the performance of the refractory may be deteriorated. When the content of SiC in the first refractory 21 is 1 mass% or more and 20 mass% or less, the performance of the refractory is good. The content of SiC in the first refractory 21 may be 3 mass% or more, 5 mass% or more, 7 mass% or more, 9 mass% or more, or 11 mass% or more, or 18 mass% or less, 16 mass% or less, 14 mass% or less, 12 mass% or less, or 10 mass% or less. These lower and upper limits may be any combination.

[0023] 1.2.4 Carbon The first refractory 21 contains carbon in an amount of 1 mass % to 20 mass %. When the first refractory 21 contains carbon, the durability of the refractory is further improved.

[0024] If the carbon content in the first refractory 21 is too low, the effect of improving the durability of the refractory may not be sufficient, while if the carbon content in the first refractory 21 is too high, the components other than carbon may be relatively too low, and the performance of the refractory may be reduced. When the carbon content in the first refractory 21 is 1 mass% or more and 20 mass% or less, the performance of the refractory is good. The carbon content in the first refractory 21 may be 3 mass% or more, 5 mass% or more, 7 mass% or more, 9 mass% or more, or 11 mass% or more, or 18 mass% or less, 16 mass% or less, 14 mass% or less, 12 mass% or less, or 10 mass% or less. These lower and upper limits may be any combination.

[0025] 1.2.5 Other ingredients The first refractory 21 may contain other components in addition to the above-mentioned magnesia, alumina, SiC, and carbon. For example, the first refractory 21 may contain SiO2 or CaO as other components. The first refractory 21 may also contain various impurities as other components. The type and content of the other components are not particularly limited because they do not substantially affect the problem-solving mechanism of the technology disclosed herein. For example, the content of SiO2 in the first refractory 21 may be 0% by mass or more and 0.3% by mass or less, and the content of CaO may be 0% by mass or more and 0.5% by mass or less.

[0026] 1.2.6 Unfired bricks As described above, the first refractory 21 is an unburned brick. The shape and size of the first refractory 21 as an unburned brick may be any shape and size that can form the first portion 11 of the inner wall surface 10 of the blast furnace trough, and an appropriate shape and size may be selected according to the lining structure. Also, as described above, the unburned brick has a smaller apparent porosity than the castable brick and is less likely to be worn. The apparent porosity of the unburned brick may be, for example, more than 0% and 5% or less. The apparent porosity of the unburned brick can be measured in accordance with JIS R2205:1992.

[0027] 2.Other configurations of refractory lining structure of blast furnace trough As described above, in the refractory lining structure 100 for a blast furnace runner according to one embodiment, the first portion 11 of the inner wall surface 10 of the blast furnace runner is made of a specific first refractory 21, thereby making the blast furnace runner highly durable. In the lining structure 100, the configuration other than the first portion 11 is not particularly limited. An example of the configuration other than the first portion 11 will be described below.

[0028] 2.1 Part below the bottom edge of the first part 1, in the refractory lining structure 100 of the blast furnace runner, the second portion 12 of the inner wall surface 10 of the blast furnace runner is made of a second refractory 22. The second portion 12 is a portion below the lower end of the first portion 11. The second refractory 22 may be a castable containing, for example, 40% by mass or more and 80% by mass or less of spinel, 1% by mass or more and 25% by mass or less of SiC, 5% by mass or more and 30% by mass or less of alumina, and 1% by mass or more and 15% by mass or less of carbon.

[0029] 2.1.1 Second part The second portion 12 is a portion below the lower end of the first portion 11, and is a portion that comes into contact with molten iron 50 flowing through the blast furnace runner. For example, as shown in Fig. 1, the second portion 12 may be the entire portion below the lower end of the first portion 11, including the bottom surface of the inner wall surface 10 of the blast furnace runner.

[0030] 2.1.2 Second refractory As described above, the durability of the blast furnace runner is governed by the durability of the first refractory 21 lining the first portion 11 including the boundary between the molten iron 50 and the molten slag 30 to the boundary between the molten slag 30 and the gas phase 40 on the inner wall surface 10 of the blast furnace runner. The second refractory 22 constituting the second portion 12 does not need to be an unfired brick and may be a castable material. In addition, the second refractory 22 constituting the second portion 12 does not need to cause the above-mentioned spinel generation reaction, that is, the second refractory 22 does not need to contain magnesia. From the above viewpoint, the second refractory 22 may be a castable material containing, for example, 40% by mass to 80% by mass of spinel, 1% by mass to 25% by mass of SiC, 5% by mass to 30% by mass of alumina, and 1% by mass to 15% by mass of carbon.

[0031] The spinel content in the second refractory material 22 may be 45 mass% or more, 50 mass% or more, 55 mass% or more, or 60 mass% or more, or 75 mass% or less, 70 mass% or less, 65 mass% or less, or 60 mass% or less, and these lower and upper limits may be any combination.

[0032] The SiC content in the second refractory material 22 may be 3 mass% or more, 5 mass% or more, 7 mass% or more, 9 mass% or more, or 11 mass% or more, or 23 mass% or less, 21 mass% or less, 19 mass% or less, 17 mass% or less, 15 mass% or less, or 13 mass% or less, and these lower and upper limits may be any combination.

[0033] The alumina content in the second refractory 22 may be 7 mass% or more, 9 mass% or more, 11 mass% or more, 13 mass% or more, or 15 mass% or more, and may be 28 mass% or less, 26 mass% or less, 24 mass% or less, 22 mass% or less, or 20 mass% or less, and these lower and upper limits may be any combination.

[0034] The carbon content in the second refractory material 22 may be 3 mass% or more, 5 mass% or more, or 7 mass% or more, and may be 13 mass% or less, 11 mass% or less, or 9 mass% or less, and these lower and upper limits may be any combination.

[0035] The second refractory 22 may contain other components in addition to spinel, SiC, alumina, and carbon. For example, the second refractory 22 may contain silica or alumina cement as other components. The second refractory 22 may also contain various impurities as other components. The type and content of the other components are not particularly limited since they do not substantially affect the problem-solving mechanism of the technology disclosed herein. For example, the content of silica in the second refractory 22 may be 0% by mass or more and 5% by mass or less, and the content of alumina cement may be 1% by mass or more and 3% by mass or less.

[0036] 2.1.3 Linear change rate of second refractory As described above, in the refractory lining structure 100 for the blast furnace runner, the specific first refractory 21 is adopted for the first portion 11, so that the volume of the first refractory 21 expands when the blast furnace runner is in use, and gaps are unlikely to occur around the first refractory 21. For example, even if castables as the second refractory 22 exist under unburned bricks as the first refractory 21, gaps are unlikely to occur between the unburned bricks and the castables. However, the effect of suppressing such gaps is likely to be more significant when the volume of the second refractory 22 expands when the blast furnace runner is in use. According to the knowledge of the present inventor, when the second refractory 22 has the following properties, the gaps are more unlikely to occur, and the durability of the blast furnace runner is further improved.

[0037] Properties: Linear change rate is 1.0% or more after sintering at 1500℃ for 3 hours in an inert atmosphere

[0038] The linear change rate of the second refractory 22 may be 1.1% or more, 1.2% or more, 1.3% or more, 1.4% or more, or 1.5% or more. The upper limit of the linear change rate is not particularly limited, and may be, for example, 2.0% or less, 1.9% or less, or 1.8% or less. The linear change rate of the second refractory 22 can be determined based on the average length of the test piece before and after the firing in accordance with JIS R2554:2005 (Test method for linear change rate of castable refractories).

[0039] 2.2 Part above the top of the first part 1, in the refractory lining structure 100 of the blast furnace runner, the third portion 13 of the inner wall surface 10 of the blast furnace runner is made of a third refractory 23. The third portion 13 is a portion above the upper end of the first portion 11. The third refractory 23 may be, for example, a castable containing 50% by mass or more and 90% by mass or less of alumina and 5% by mass or more and 30% by mass or less of spinel.

[0040] 2.2.1 Third part The third portion 13 is a portion above the upper end of the first portion 11, and is a portion that does not come into contact with either the molten iron 50 or the molten slag 30 flowing in the blast furnace launder.

[0041] 2.2.2 Third refractory As described above, the durability of the blast furnace runner is governed by the durability of the first refractory 21 lining the first portion 11 including the boundary between the molten iron 50 and the molten slag 30 to the boundary between the molten slag 30 and the gas phase 40 on the inner wall surface 10 of the blast furnace runner. The third portion 13 does not come into contact with the molten iron 50 or the molten slag 30, and is relatively less susceptible to wear compared to other portions. Therefore, the durability of the refractory is not so required in the third portion 13, and the third refractory 23 constituting the third portion 13 does not need to be an unfired brick, and may be a castable material. The third refractory 23 may be a castable material containing, for example, 50% by mass to 90% by mass of alumina and 5% by mass to 30% by mass of spinel.

[0042] The alumina content in the third refractory material 23 may be 55 mass% or more, 60 mass% or more, 65 mass% or more, or 70 mass% or more, or 85 mass% or less, 80 mass% or less, or 75 mass% or less, and these lower and upper limits may be any combination.

[0043] The spinel content in the third refractory material 23 may be 7 mass% or more, 9 mass% or more, 11 mass% or more, 13 mass% or more, or 15 mass% or more, and may be 28 mass% or less, 26 mass% or less, 24 mass% or less, or 22 mass% or less, and these lower and upper limits may be any combination.

[0044] The third refractory 23 may contain other components in addition to alumina and spinel. For example, the third refractory 23 may contain alumina cement as other components. The third refractory 23 may also contain various impurities as other components. The type and content of the other components are not particularly limited since they do not substantially affect the problem-solving mechanism of the technology of the present disclosure. For example, the content of alumina cement in the third refractory 23 may be, for example, 5 mass% or more and 12 mass% or less.

[0045] 2.3 Back side of first refractory As described above, the unburned brick is used as the first refractory 21 in the first portion 11 of the inner wall surface 10 of the blast furnace runner. In this case, as described later, when the refractory is applied, a gap is likely to be formed between the unburned brick and the lining refractory 70 on the back side of the unburned brick. In this case, the durability of the blast furnace runner is further improved by pouring castable into the gap to eliminate the gap. For example, as shown in FIG. 1, in the refractory lining structure 100 of the blast furnace runner, a fourth refractory 24 may be present on the back side of the first refractory 21. The fourth refractory 24 may be a castable containing 50% by mass to 90% by mass of alumina and 5% by mass to 30% by mass of spinel.

[0046] The alumina content in the fourth refractory material 24 may be 55 mass% or more, 60 mass% or more, 65 mass% or more, or 70 mass% or more, or 85 mass% or less, 80 mass% or less, or 75 mass% or less, and these lower and upper limits may be any combination.

[0047] The spinel content in the fourth refractory material 24 may be 7 mass% or more, 9 mass% or more, 11 mass% or more, or 13 mass% or more, and may be 28 mass% or less, 26 mass% or less, 24 mass% or less, or 22 mass% or less, and these lower and upper limits may be any combination.

[0048] The fourth refractory 24 may contain other components in addition to alumina and spinel. For example, the fourth refractory 24 may contain alumina cement as the other components. The fourth refractory 24 may also contain various impurities as the other components. The type and content of the other components are not particularly limited since they do not substantially affect the problem-solving mechanism of the technology of the present disclosure. For example, the content of alumina cement in the fourth refractory 24 may be, for example, 5 mass% or more and 12 mass% or less.

[0049] As shown in Fig. 1, there may be substantially no discontinuity between the third refractory 23 constituting the third portion 13 of the inner wall surface 10 of the blast furnace runner and the fourth refractory 24 present on the back surface of the first refractory 21. That is, the third refractory 23 and the fourth refractory 24 may have the same composition. Alternatively, the third refractory 23 and the fourth refractory 24 may have different compositions.

[0050] 2.4 Composition other than the above refractories In the refractory lining structure 100 of the blast furnace runner, in addition to the various refractories described above, a general configuration for a blast furnace runner may be provided. For example, as shown in FIG. 1, an outer skin 60 (e.g., iron shell), a lining refractory 70, a retaining metal fitting 80, etc. may be provided. These configurations are obvious to those skilled in the art, and do not affect the problem-solving mechanism of the technology disclosed herein, so detailed explanations are omitted here. In addition, in the refractory lining structure 100 of the blast furnace runner, the cross-sectional shape of the flow path formed by the various refractories described above (the shape of the inner wall surface 10 of the blast furnace runner) is not particularly limited, and it is sufficient to adjust the above-mentioned first portion 11 to be lined at an appropriate position, taking into account the positional relationship of the molten iron 50 and molten slag 30 flowing through the blast furnace runner, etc.

[0051] 3. Refractory lining method for blast furnace trough The method for obtaining the refractory lining structure 100 of a blast furnace runner is not particularly limited. Fig. 2 shows the flow of a refractory lining method for a blast furnace runner according to one embodiment (a manufacturing method of a refractory lining structure for a blast furnace runner). For ease of understanding, the retaining metal fittings 80 are omitted from Fig. 2. As shown in Fig. 2, the refractory lining method for a blast furnace runner according to one embodiment includes the following steps: S1: Lining the inner wall surface of the outer shell 60 with the refractory material 70; S2: Lining the inner wall surface of the lining refractory 70 with a second refractory 22 to form a second portion 12; S3: Lining the first refractory 21 on the second refractory 22 to form a first portion 11; S4: pouring a fourth refractory 24 onto the back surface of the first refractory 21; and S5: Lining the first refractory 21 and the fourth refractory 24 with the third refractory 23 to form the third portion 13. Details of the first portion 11, the second portion 12, the third portion 13, the first refractory 21, the second refractory 22, the third refractory 23, and the fourth refractory 24 are as described above. As described above, the third refractory 23 and the fourth refractory 24 may be made of a common material.

[0052] 4. Molten iron discharging system The technology of the present disclosure also has an aspect of a system for discharging molten iron 50 (molten pig iron) produced in a blast furnace to a next process through a blast furnace runner. That is, the discharging system of the present disclosure includes a blast furnace, the above-mentioned refractory lining structure 100 of the blast furnace runner, and molten iron 50 and molten slag 30 discharged from the blast furnace through the blast furnace runner. In the discharging system, for example, the molten iron 50 and molten slag 30 are discharged through the blast furnace runner so that the upper and lower ends of the slag line are included between the upper and lower ends of the first portion 11 of the inner wall surface 10 of the blast furnace runner. The upper end of the slag line coincides with the interface between the molten slag 30 and the gas phase 40, and the lower end of the slag line coincides with the interface between the molten slag 30 and the molten iron 50. A general blast furnace may be used as the blast furnace. There is no particular limitation on the type and temperature of the molten iron 50 and the type and temperature of the molten slag 30. The refractory lining structure 100 in the blast furnace trough is as described above. EXAMPLES

[0053] The present invention will be further described below with reference to examples, but the present invention is not limited to the following examples. The present invention can adopt various conditions as long as it does not deviate from the gist of the invention and achieves its object.

[0054] 1. Evaluation conditions The following evaluation was carried out on the refractory lining structure of a blast furnace trough as shown in Fig. 1, while changing the position of the first portion 11, the type and composition of the first refractory 21, the composition of the second refractory 22, and the compositions of the third refractory 23 and the fourth refractory 24. In this example, refractories of the same composition were used for the third refractory 23 and the fourth refractory 24. The construction of the lining structure was carried out according to the flow shown in Fig. 2. The position of the first portion 11 was as follows: Position (1): When the distance from the upper end of the first portion 11 to the boundary between the molten slag 30 and the gas phase 40 is 200 mm or less, and the distance from the lower end of the first portion 11 to the boundary between the molten iron 50 and the molten slag 30 is 200 mm or less, Position (2): When the distance from the upper end of the first portion 11 to the boundary between the molten slag 30 and the gas phase 40 is 150 mm or less, and the distance from the lower end of the first portion 11 to the boundary between the molten iron 50 and the molten slag 30 is 150 mm or less, Position (3): When the distance from the upper end of the first portion 11 to the boundary between the molten slag 30 and the gas phase 40 is 100 mm or less, and the distance from the lower end of the first portion 11 to the boundary between the molten iron 50 and the molten slag 30 is 100 mm or less. The test was conducted using one of the following methods.

[0055] 2. Measurement of refractory wear rate The wear rate of the refractory of the blast furnace runner was measured by measuring the width of the runner after 10,000 tons of molten pig iron had passed through it and the width of the runner before the molten pig iron passed through it. In this embodiment, the wear rate (mm / kt) when 1,000 tons of molten pig iron passed through the blast furnace runner was used as an index of evaluation. According to the knowledge of the inventors, wear of the refractory is likely to occur in the boundary between the molten pig iron and the molten slag and the boundary between the molten slag and the gas phase in the first portion, and the wear rate is high. In this embodiment, the higher of the wear rates at these boundaries was used as an index of evaluation for the wear rate of the first portion.

[0056] 3. Measurement of apparent porosity of unfired bricks and castable refractories The apparent porosity was measured for the unburned bricks or monolithic refractory (castable) lining the first portion 11 of the inner wall surface of the blast furnace trough. The measuring method was as described above.

[0057] 4. Measurement of linear change rate of refractory The linear change rate after firing was measured for the castable refractory lining the second portion 12 below the first portion 11 of the inner wall surface of the blast furnace trough. The method for measuring the linear change rate is as described above. The linear change rate also differs depending on the particle size of the refractory, the type of carbon, etc. In other words, the linear change rate may differ significantly even for the same composition.

[0058] 5. Evaluation Results Table 1 below summarizes the position of the first portion (any of the above positions (1) to (3)), the type and composition of the refractory in the first portion, the wear rate of the refractory in the first portion, the composition of the castable in the second portion, the linear change rate of the castable in the second portion, the wear rate of the castable in the second portion, the composition of the castable in the third portion, and the wear rate of the castable in the third portion. In this example, the durability of the back castable (fourth refractory) was not evaluated. This is because the durability of the back castable has little effect on the durability of the blast furnace runner as a whole.

[0059] [Table 1]

[0060] According to the findings of the present inventors, wear of the refractory tends to be relatively large on the inner wall surface of the blast furnace runner, particularly at the boundary between the molten iron and the molten slag and the boundary between the molten slag and the gas phase (i.e., the first portion). In this regard, in this embodiment, a method for suppressing wear of the refractory in the first portion was mainly studied.

[0061] Regarding the wear of the refractory in the first portion, the results shown in Table 1 reveal the following.

[0062] When castable refractory was used in the first portion as in Comparative Examples 1 and 4, the wear rate was high and durability was poor. It is understood that castable refractory has a high apparent porosity and there is a limit to how much durability can be improved.

[0063] As in Comparative Examples 2 and 3, by using unburned bricks in the first portion, the wear rate is lower than that of Comparative Example 1. However, the wear rate is still high, and it is difficult to say that the durability of the blast furnace trough has been sufficiently improved.

[0064] In contrast, by using unfired bricks containing a predetermined amount of magnesia in the first portion as in Examples 1 to 7, the wear rate of the first portion can be significantly reduced, and the durability of the blast furnace trough can be significantly improved. This is believed to be because the magnesia and alumina contained in the unfired bricks react with each other to produce spinel, which improves the corrosion resistance against complex oxides derived from FeO and slag.

[0065] Regarding the wear of the refractory material in the areas other than the first portion, the following can be said from the results shown in Table 1.

[0066] The wear of the second portion is considered to be due to the composition of the refractory material constituting the second portion, as well as the gap between the first portion and the second portion. In Comparative Examples 1 and 4, the refractory material in the first portion is castable, so that a gap is unlikely to occur between the first portion and the second portion. Therefore, the wear rate of the second portion was low.

[0067] In Comparative Example 2, the refractory in the first portion was unfired brick, and a gap was easily generated between the first portion and the second portion. In Comparative Example 2, the content of magnesia in the unfired brick was insufficient, so that the spinel generation reaction in the unfired brick hardly occurred, and the volume expansion of the unfired brick was small, and it is considered that the gap between the first portion and the second portion was not eliminated when the blast furnace trough was used. In addition, the linear change rate of the refractory in the second portion was also small, so that the refractory in the second portion did not easily contribute to the elimination of the gap, and it is considered that this also caused the gap to not be sufficiently eliminated. As a result, it is considered that the wear rate of the second portion increased due to the intrusion of molten iron into the gap, etc.

[0068] In Comparative Example 3, the refractory in the first portion was unfired bricks, and gaps were likely to occur between the first portion and the second portion, as in Comparative Example 2. In Comparative Example 3, the content of magnesia in the unfired bricks was excessive, and when the blast furnace trough was used, the magnesia and alumina contained in the unfired bricks reacted excessively to generate a large amount of spinel, which caused the volume of the unfired bricks to expand excessively, causing buckling, cracking, etc. in the refractory in the second portion. As a result, it is believed that the wear rate of the refractory in the second portion increased.

[0069] In Examples 1 to 7, the refractory in the first portion is unburned brick, as in Comparative Examples 2 and 3, and the gap between the first portion and the second portion is problematic. However, in Examples 1 to 7, the unburned brick contains a moderate amount of magnesia, and when the blast furnace trough is used, the magnesia contained in the unburned brick reacts with alumina to generate a moderate amount of spinel, and the volume of the unburned brick expands moderately, eliminating the gap between the first portion and the second portion. As a result, the wear rate of the refractory in the second portion is considered to be low. In particular, when a refractory with a linear change rate of 1.0% or more is used in the second portion as in Examples 1 to 6, the wear rate in the second portion is likely to be low.

[0070] The wear of the third part is believed to be due to splashing and abrasion by molten pig iron and molten slag, and thermal spalling when the launder is cooled during use and inspected. The high wear rate of this part in Comparative Examples 2 and 3 is believed to be due to the difference in materials from the other examples. Specifically, it is believed that Comparative Example 2 had a slightly low spinel content, so wear was greater due to splashing and abrasion by molten pig iron and molten slag, while Comparative Example 3 had a high alumina cement content, so wear was greater due to thermal spalling.

[0071] From the above results, it can be said that if the following requirements (I) to (III) are satisfied in the refractory lining structure of a blast furnace runner, the wear rate of the refractory during use of the blast furnace runner can be reduced and the durability of the blast furnace runner can be improved. (I) A first portion of an inner wall surface of the blast furnace trough is made of a first refractory material. (II) The upper end of the first portion is located above the boundary between the molten slag and the gas phase, and the lower end of the first portion is located below the boundary between the molten iron and the molten slag. (III) The first refractory material is an unfired brick containing 3% by mass or more and 10% by mass or less of magnesia, 65% by mass or more and 90% by mass or less of alumina, 1% by mass or more and 20% by mass or less of SiC, and 1% by mass or more and 20% by mass or less of carbon. [Explanation of symbols]

[0072] 10. Inner wall surface of blast furnace trough 11 Part 1 12 Part 2 13 Part 3 21 No. 1 refractory 22 Second refractory 23 Third refractory 24 No. 4 Refractories 30 Molten Slag 40 Gas Phase 50 Molten Iron 60 Hull 70 Refractory lining 80 Retaining hardware 100 Refractory lining structure of blast furnace trough

Claims

1. A refractory lining structure for a blast furnace trough, comprising: a first portion of an inner wall surface of the blast furnace trough is made of a first refractory material, a second portion of the inner wall surface of the blast furnace trough is made of a second refractory material, a third portion of an inner wall surface of the blast furnace runner is made of a third refractory material, The upper end of the first portion is located above the boundary between the molten slag and the gas phase, The lower end of the first portion is located below the boundary between the molten iron and the molten slag, the second portion is a portion below the lower end of the first portion, the third portion is a portion above the upper end of the first portion, The first refractory material is 3% by mass or more and 10% by mass or less of magnesia, 65% by mass or more and 90% by mass or less of alumina; 1% by mass or more and 20% by mass or less of SiC, and Carbon: 1% by mass or more and 20% by mass or less An unfired brick comprising: Refractory lining structure of blast furnace trough.

2. The refractory lining structure of a blast furnace trough according to claim 1, The second refractory material is 40% by mass or more and 80% by mass or less of spinel, 1% by mass or more and 25% by mass or less of SiC, 5% by mass or more and 30% by mass or less of alumina, and Carbon: 1% by mass or more and 15% by mass or less A castable comprising: Refractory lining structure of blast furnace trough.

3. The refractory lining structure of a blast furnace trough according to claim 2, The second refractory material has the following properties: Properties: Linear change rate is 1.0% or more after sintering at 1500°C for 3 hours in an inert atmosphere having Refractory lining structure of blast furnace trough.

4. The refractory lining structure of a blast furnace trough according to claim 1, The third refractory material is 50% by mass or more and 90% by mass or less of alumina, and 5% by mass or more and 30% by mass or less of spinel A castable comprising: Refractory lining structure of blast furnace trough.

5. The refractory lining structure of a blast furnace trough according to claim 1, A fourth refractory material is present on the back surface of the first refractory material, The fourth refractory material is 50% by mass or more and 90% by mass or less of alumina, and 5% by mass or more and 30% by mass or less of spinel A castable comprising: Refractory lining structure of blast furnace trough.

6. The refractory lining structure of a blast furnace trough according to any one of claims 1 to 5, The distance from the upper end of the first portion to the boundary between the molten slag and the gas phase is 200 mm or less; The distance from the lower end of the first portion to the boundary between the molten iron and the molten slag is 200 mm or less. Refractory lining structure of blast furnace trough.

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