Method for producing refractory raw material and method for producing refractory for molten iron storage container

Abstract

To provide a technology for collecting high-quality refractory raw materials from used refractory material.SOLUTION: A method for producing a refractory raw material includes a recovery step of collecting used refractory material generated in a hot metal container; a removal step of removing a part of impurities in the collected used refractory material; and a crushing step of crushing the used refractory material before or after the removal step. In producing the refractory raw material, in the removal step, the impurities are removed so that the total content of the impurities in the refractory raw material is 7 mass% or less, and at lease one process selected from the following is conducted optionally: (1) the impurities are removed so that a total content of the impurities in the refractory raw material having a grain diameter of 1 mm or less is 3.5 mass% or less; (2) impurities are removed so that a total content of the impurities in the refractory raw material having a grain diameter of greater than 1 mm and 3 mm or less is 4.5 mass% or less; and (3) impurities are removed so that a total content of the impurities in the refractory raw material having a grain diameter of greater than 3 mm is 6 mass% or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a refractory raw material by recycling used refractories generated in a hot metal storage container and a refractory for a hot metal storage container.

Background Art

[0002] In steelworks, a large number of refractories are used in each facility in the hot metal production process, melting process in the steelmaking process, and transportation process of the molten material. As the equipment operates for a long time at high temperatures, the refractories are damaged. When it is determined that stable operation is impossible, the refractories used in the operating equipment are disassembled into refractory scraps. These refractory scraps have few uses and are treated as industrial waste. In recent years, it has been required to suppress the generation amount of refractory scraps, and it is necessary to effectively utilize the refractory scraps.

[0003] Here, for example, Patent Document 1 discloses a refractory containing a refractory raw material (hereinafter also referred to as a recycled raw material) manufactured by recycling used refractories generated in a hot metal pretreatment container. Further, Patent Document 2 discloses a method for recycling refractories by collecting and recycling used refractories.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the technology described in Patent Document 1, the durability of refractories containing recycled raw materials is improved by optimizing the particle size distribution of recycled raw materials and virgin raw materials and the amount of free carbon in all refractory raw materials. Further, in the technology described in Patent Document 2, the quality of the recycled refractory material is enhanced by classifying used refractories by type or by color sorting. However, in the technologies described in Patent Document 1 and Patent Document 2, no consideration is given to the allowable amount of impurities contained in the recycled raw materials, and there is room for improvement from the viewpoints of the raw materials of refractories and the quality of refractories.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for manufacturing a refractory raw material capable of improving the quality of a refractory formed by blending a recycled raw material by adjusting the amount of impurities contained in the recycled raw material, and a refractory for a molten iron receiving vessel.

Means for Solving the Problems

[0007] The method for manufacturing a refractory raw material according to the present invention that advantageously solves the above problems includes a recovery step of recovering used refractories generated in a molten iron receiving vessel, a removal step of removing at least a part of the impurities in the used refractories recovered in the recovery step, and a crushing step of crushing the used refractories before or after the removal step. When manufacturing a refractory raw material, in the removal step, the impurities are removed using a removal means so that the total content of the impurities in the refractory raw material becomes 7% by mass or less. Further, optionally, (1) removing the impurities so that the total content of the impurities in the refractory raw material having a particle size of 1 mm or less becomes 3.5% by mass or less; (2) removing the impurities so that the total content of the impurities in the refractory raw material having a particle size exceeding 1 mm and 3 mm or less becomes 4.5% by mass or less; (3) removing the impurities so that the total content of the impurities in the refractory raw material having a particle size exceeding 3 mm becomes 6% by mass or less. It is characterized in that at least one treatment selected from the above is selected.

[0008] Note that the method for manufacturing a refractory raw material according to the present invention (a) In the removal step, before the crushing step, the used refractory is passed through a sieve with an opening size of 8 mm or more as the removing means, and the impurities are removed by collecting the material on the sieve. (b) The hot metal storage container includes a refractory lining containing alumina, silicon carbide, and carbon, and a permanent refractory provided outside the refractory lining. In the recovery step, the refractory lining and the permanent refractory are recovered in a mixed state as the used refractory. (c) After the crushing step, there is further a drying step of drying the refractory raw material. (d) Simultaneously with the crushing step, there is further a sorting step of removing at least a part of the metallic iron in the refractory raw material. (e) In the sorting step, the metallic iron in the refractory raw material is removed by magnetic separation of the metallic iron with a magnetic force having a magnetic flux density of 0.3 T or less. etc. can be considered as more preferable solution means.

[0009] The refractory for a hot metal storage container according to the present invention that advantageously solves the above problems is a refractory for a hot metal storage container formed by blending refractory raw materials recovered from a hot metal storage container. The recovered refractory raw material is produced by reusing the used refractory generated in the hot metal storage container, and the total impurity content is 7% by mass or less. Further, optionally, (1) the total impurity content in the refractory raw material having a particle size of 1 mm or less is 3.5% by mass or less, (2) the total impurity content in the refractory raw material having a particle size exceeding 1 mm and 3 mm or less is 4.5% by mass or less, (3) the total impurity content in the refractory raw material having a particle size exceeding 3 mm is 6% by mass or less, and it is characterized by having at least one composition selected therefrom.

[0010] It is considered that it can be a more preferable solution means that the refractory raw material is blended in an amount exceeding 60% by mass in the refractory for a hot metal storage container according to the present invention.

Effects of the Invention

[0011] According to the present invention, by setting the total content of impurities in the refractory raw material recovered from the hot metal storage container to 7% by mass or less, the quality of the recovered refractory raw material can be improved, and the durability of the refractory formed by blending the refractory raw material can be made equivalent to that of virgin bricks. As a result, the blending ratio of recycled raw materials in the refractory can be increased more than before, the amount of used refractory generated can be significantly reduced, and thus the industrial waste treatment cost can be significantly suppressed. In particular, in a steelworks where a large amount of used refractory is generated, using a refractory made from used refractory has a great effect on reducing the refractory raw material cost.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention will be specifically described. Note that each drawing is schematic and may differ from the actual one. Also, the following embodiments illustrate devices and methods for embodying the technical idea of the present invention, and do not specify the configuration to be the following. That is, various changes can be made to the technical idea of the present invention within the technical scope described in the claims.

[0014] (Hot metal storage container) The refractory of this embodiment is a refractory for a molten iron container, particularly for a molten iron pretreatment container. Here, the molten iron pretreatment container is a container for holding and refining molten iron in the molten iron pretreatment process of the steel manufacturing process, and a representative example is a molten iron ladle. As shown in Fig. 1, the molten iron pretreatment container (molten iron ladle) 1 has an iron skin 2, a permanent refractory 3 is provided inside the iron skin 2, and a lining refractory 4 is provided inside the permanent refractory 3. And it contains and holds the molten iron 5. The refractory of this embodiment can also be applied to a mixed iron car or a charging ladle as a molten iron container.

[0015] For the lining refractory of the molten iron pretreatment container of this embodiment, an alumina-silicon carbide-carbon refractory containing alumina, silicon carbide, and carbon is used, and it may also contain flux stone. For the permanent refractory, flux stone bricks are used. The lining refractory is used under very harsh operating conditions such as abrasion caused by stirring of molten iron and rapid temperature changes accompanying repeated charging and discharging of molten iron. Therefore, in order to perform stable operation, it is preferable to use a refractory with high durability that can withstand harsh conditions.

[0016] (Refractory) The refractory of this embodiment is formed by blending a refractory raw material (hereinafter also referred to as a recycled raw material) manufactured by recycling the used refractory generated in the above molten iron pretreatment container. The recycled raw material of this embodiment has a total impurity content of 7% by mass or less, and further, optionally, (1) the total impurity content in the recycled raw material with a particle size of 1 mm or less is 3.5% by mass or less, (2) the total impurity content in the recycled raw material with a particle size exceeding 1 mm and 3 mm or less is 4.5% by mass or less, and (3) the total impurity content in the recycled raw material with a particle size exceeding 3 mm is 6% by mass or less. Here, "impurities" refers to "components other than refractory raw materials that affect the properties of the refractory", specifically MgO, CaO, etc.

[0017] As described above, in this embodiment, by setting the total content of impurities (MgO and CaO) in the entire recycled raw material, which is a combination of aggregate raw material and fine powder raw material, to 7% by mass or less, the purity of the entire recycled raw material is increased. Therefore, the corrosion resistance of the refractory formed by blending the recycled raw material (hereinafter also referred to as recycled brick) can be made equivalent to that of virgin brick. On the other hand, when the total content of impurities (MgO and CaO) in the recycled raw material exceeds 7% by mass, the purity of the entire recycled raw material decreases. In this case, the slag infiltrated into the matrix penetrates to the inside of the recycled raw material, and the corrosion resistance of the recycled brick is significantly inferior to that of the virgin brick. Preferably, the total content of impurities in the recycled raw material is 6% by mass or less, and more preferably 3% by mass or less.

[0018] Furthermore, in this embodiment, if the total content of impurities (MgO and CaO) in the recycled raw material with a particle size of 1 mm or less is 3.5% by mass or less, it is preferable because the purity of the recycled raw material that becomes the fine powder present in the matrix, which is the most easily corroded part in the brick structure, increases. By adopting the above configuration, the recycled brick can maintain the same corrosion resistance as the virgin brick.

[0019] Also, in this embodiment, if the total content of impurities (MgO and CaO) in the recycled raw material with a particle size exceeding 1 mm and 3 mm or less is 4.5% by mass or less, it is preferable because the purity of the recycled raw material that becomes the aggregate increases. By adopting the above configuration, even when the slag infiltrated into the matrix comes into contact with the recycled raw material, the slag does not penetrate to the inside of the recycled raw material, and the recycled brick can maintain the same corrosion resistance as the virgin brick.

[0020] In addition, in the present embodiment, if the total content of impurities (MgO and CaO) in the recycled raw material with a particle size exceeding 3 mm is 6% by mass or less, the purity of the recycled raw material as an aggregate becomes high, which is preferable, as in the case of the recycled raw material with a particle size exceeding 1 mm and 3 mm or less. By adopting the above configuration, even when the slag infiltrated into the matrix comes into contact with the recycled raw material, the slag does not penetrate into the interior of the recycled raw material, and the corrosion resistance of the recycled brick becomes equivalent to that of the virgin brick. Note that the particle size of the refractory raw material is preferably 5 mm or less. In this specification, "particle size N mm or less" means the material passing through a sieve with an aperture of N mm, and "particle size N mm or more" means the material remaining on a sieve with an aperture of N mm. As the sieve to be used, for example, a standard sieve defined in JIS Z8801-1:2019 can be used.

[0021] As described above, in the present embodiment, by adjusting the total content of impurities in the recycled raw material, the recycled raw material can be made highly pure and the quality can be improved. Therefore, the blending ratio of the recycled raw material in the recycled brick can be increased as compared with the conventional case. Specifically, even when the recycled raw material is blended at a high blending ratio exceeding 60% by mass, it is possible to achieve both spalling resistance and corrosion resistance equivalent to those of the virgin brick. In addition, by setting the blending ratio of the recycled raw material to exceed 60% by mass, the generation amount of refractory scraps to be treated as industrial waste can be reduced to zero. Preferably, the recycled raw material is blended at 70% by mass or more.

[0022] (Method for manufacturing refractory raw material) Fig. 2 shows a flow chart of the method for manufacturing a refractory raw material, that is, the steps from the dismantling to the classification of used refractories (hereinafter also referred to as recycling raw materialization). The steps of recycling raw materialization mainly include a recovery step S11, a removal step (screening step) S12, a crushing step S13, a sorting step S14, a drying step S15, and a classification step S16.

[0023] In the recovery step S11, the used refractories generated in the hot metal pretreatment vessel are disassembled and recovered. Here, in the present embodiment, the used refractories are recovered in a state where both the inner lining refractories and the permanent refractories of the hot metal pretreatment vessel are mixed. By disassembling and recovering the inner lining refractories and the permanent refractories together in the recovery step S11 in this way, it is possible to recover them in a shorter time compared to the case of separately recovering the inner lining refractories and the permanent refractories, and it is possible to reduce the number of workers and the man-hours. On the other hand, if the inner lining refractories and the permanent refractories are separately recovered, the quality of the recycled raw materials will be improved. In the recovery step S11, it is preferable to remove molten metal, slag, etc.

[0024] In the example of FIG. 2, as the removal step (screening step) S12, at least a part of the impurities (MgO and CaO) in the used refractories recovered in the recovery step S11 is removed. Specifically, the fine impurities (MgO and CaO) are removed by passing the used refractories through a screen, which is an example of a removal means, and recovering the material on the screen. At this time, the mesh size of the screen is preferably 8 mm or more. By removing the fine impurities (MgO and CaO) in the used refractories in this way, the total content of impurities in the recycled raw materials can be adjusted as described above, and the recycled raw materials can be made of high purity. On the other hand, if the mesh size exceeds 53 mm, useful used refractories may be included under the screen, and the overall recycling rate may decrease. Therefore, it is preferable to set the upper limit of the mesh size to about 53 mm. In the example of FIG. 2, the impurities in the used refractories are removed using a screen, but the removal means for removing the impurities is not limited to the screen, and other removal means such as a means for separating the impurities by running water may be used to remove the impurities.

[0025] In the example of FIG. 2, as the crushing step S13, the used refractory after removing impurities (MgO and CaO) is crushed to obtain a refractory raw material (recycled raw material). For crushing the used refractory, for example, in addition to a hammer crusher and a jaw crusher, a wet crusher can be used. At this time, the recycled raw material is crushed so that the particle size thereof is approximately 10 mm or less. Preferably, it is crushed to approximately 5 mm or less. In the above embodiment, after removing the impurities in the used refractory in the removing step S12, the used refractory is crushed in the crushing step S13. However, the crushing step S13 may be divided into a coarse crushing process and a fine pulverization process. After the used refractory is coarsely crushed, the impurities in the used refractory are removed in the removing step S12, and then, it may be configured to be finely pulverized to a predetermined particle size.

[0026] In the sorting step (magnetic separation step) S14, at least a part of the metallic iron (ingot) in the recycled raw material is removed. In the present embodiment, the sorting step S14 is performed simultaneously with the crushing step S13. That is, while crushing the used refractory, the metallic iron is removed by magnetic separation. In particular, it is preferably performed simultaneously with the coarse crushing process. Since metallic iron is not a component that affects the properties of the refractory, it does not correspond to "impurities". However, if the content of metallic iron in the used refractory is too large, the deterioration rate of the blade of the crusher will increase during crushing, and the frequency of blade replacement will increase. Therefore, it is preferable to remove the metallic iron in the refractory in the sorting step S14. Specifically, in the present embodiment, the metallic iron is magnetically separated by magnetic force. At this time, it is preferable that the magnetic flux density is 0.3 T (3000 G) or less. When the metallic iron is sorted using a magnetic force with a magnetic flux density of 0.3 T or less and when the metallic iron is sorted using a magnetic force with a magnetic flux density exceeding 0.3 T, the amount of metallic iron contained in the recycled raw material after the classification step is the same. However, by setting the magnetic flux density to 0.3 T or less, it is possible to suppress the removal of magnetic adherends other than metallic iron in the recycled raw material. Examples of magnetic adherends other than metallic iron include iron oxides such as magnetite and maghemite. These oxides may exist alone or mixed with other useful components, and if they are magnetically adhered and removed, the recycling rate of the useful components may be reduced.

[0027] In the drying process S15, the recycled raw material that has undergone crushing and magnetic separation is dried. This is particularly essential when a wet crusher is used in the crushing process. And in the classification process S16, the recycled raw material is classified by particle size in the same way as ordinary virgin raw materials. Specifically, the recycled raw material is classified into particle sizes of 1 mm or less, more than 1 mm and 3 mm or less, and more than 3 mm, respectively. Screens with respective mesh openings can be used for classification. The recycled raw material is manufactured through the above processes (S17).

[0028] (Method for manufacturing refractory) The refractory (recycled brick) of this embodiment is formed by the process shown in the flowchart in FIG. 3. That is, the recycled raw material manufactured by the above-described manufacturing method, refractory raw materials such as other virgin raw materials, a binder, and metal powder, etc. are blended, and these are kneaded in the kneading process S21 and molded in the molding process S22 to obtain a molded product. Here, as the metal powder, known metal powders such as metallic Si and metallic Al can be used, for example. Also, as the binder, known binders such as hexamine (hardening agent) in addition to phenol resin (main agent) can be used, for example. The addition amount of the binder can be, for example, about 3% by mass of phenol resin and about 0.3% by mass of hexamine on the outside of the refractory raw material in the case of phenol resin (main agent) and hexamine (hardening agent). Then, the molded product is dried in the drying process S23. And by processing into bricks of a desired size and shape in the processing process S24, recycled bricks can be formed from the recycled raw material (S25).

Example

[0029] (Example 1) Alumina - silicon carbide - carbon bricks were used for the inner lining refractory of the hot metal pretreatment vessel, and magnesite bricks were used for the permanent refractory. And the recycled raw material was manufactured in accordance with the recycled raw material production process (FIG. 2) described in the above embodiment.

[0030] Table 1 shows the chemical composition of recycled raw materials with a particle size of 1 mm or less, more than 1 mm and 3 mm or less, and more than 3 mm for the recycled raw materials of the inventive examples (Sample Nos. 1-1 to 1-5) and the recycled raw materials of the comparative examples (Sample No. 1-6), respectively. The composition is expressed as a mass percentage based on the total recycled raw material. As in Sample Nos. 1-1 to 1-5, the amount of MgO in the recycled raw material manufactured in accordance with the recycled raw material manufacturing process, that is, the recycled raw material recovered from the oversize in the removal process, was in the range of 0.5% to 3.1% by mass, and the amount of CaO was in the range of 0.9% to 3.9% by mass. The total content of MgO and CaO was within the range of 1.4% to 7.0% by mass. On the other hand, as in Sample No. 1-6, when the removal process (screening) shown in the recycled raw material manufacturing process was not carried out, the total content of MgO and CaO in the recycled raw material was more than 7.0% by mass. From these facts, it was found that if the recycled raw material was manufactured in accordance with the manufacturing process of Fig. 2, the total content of MgO and CaO in the entire recycled raw material could be suppressed to 7% by mass or less.

[0031]

Table 1

[0032] Table 2 shows the chemical composition of the undersize of the removal process. As shown in Sample Nos. 1-1 to 1-5 and 1-7, when the mesh size of the screen is increased, the amount of MgO and CaO in the undersize increases, but the amount of alumina (Al2O3), which is a useful component, also increases. Therefore, by using a screen with an opening size of 53 mm or less, the alumina content in the undersize can be made 50% or less, the waste rate of the useful component alumina can be reduced, and it can be seen that the recyclability is improved.

[0033]

Table 2

[0034] (Example 2) Next, screening was performed using sieves with different mesh sizes, and the effects of the mesh size of the sieve in the removal process on the amount of MgO and CaO in the recycled raw material were investigated. The impurity removal process was carried out using sieves with different mesh sizes. Then, the used refractories on the sieve were crushed, magnetically separated, dried, and classified into particle sizes of 1 mm or less, more than 1 mm and 3 mm or less, and more than 3 mm in the classification process. The results are shown in Table 3. The component compositions in Table 3 are expressed as mass percentages with respect to the classified refractory raw materials.

[0035]

Table 3

[0036] In the recycled raw material with a particle size of 1 mm or less after the classification process, as in Sample No. 2-1, when a sieve with a mesh size of 31.5 mm was used in the removal process before the crushing process, the total content of MgO and CaO was 3.5 mass% or less. Also, as in Sample Nos. 2-2 to 2-4, when a sieve with a mesh size less than 31.5 mm was used in the removal process before the crushing process, the total content of MgO and CaO exceeded 3.5 mass%.

[0037] In the recycled raw material with a particle size of more than 1 mm and 3 mm or less after the classification process, as in Sample Nos. 3-1 and 3-2, when a sieve with a mesh size of 26.5 mm or more was used in the removal process before the crushing process, the total content of MgO and CaO was 4.5 mass% or less. Also, as in Sample Nos. 3-3 to 3-4, when a sieve with a mesh size less than 26.5 mm was used in the removal process before the crushing process, the total content of MgO and CaO exceeded 4.5 mass%.

[0038] In the recycled raw material with a particle size of more than 3 mm after the classification process, as in Sample Nos. 4-1 to 4-3, when a sieve with a mesh size of 22.4 mm or more was used in the removal process before the crushing process, the total content of MgO and CaO was 6 mass% or less. Also, as in Sample No. 4-4, when a sieve with a mesh size less than 22.4 mm was used in the removal process before the crushing process, the total content of MgO and CaO exceeded 6 mass%.

[0039] From these facts, it can be seen that when using a sieve with an opening size of 31.5 mm or more in the removal process before the crushing process, the total content of MgO and CaO in the recycled raw material with a particle size of 1 mm or less can be suppressed to 3.5 mass% or less. Similarly, when using a sieve with an opening size of 26.5 mm or more, it can be seen that the total content of MgO and CaO in the recycled raw material with a particle size exceeding 1 mm and 3 mm or less can be suppressed to 4.5 mass% or less. Similarly, when using a sieve with an opening size of 22.4 mm or more, it can be seen that the total content of MgO and CaO in the recycled raw material with a particle size exceeding 3 mm can be suppressed to 6 mass% or less. It was found that increasing the opening size of the sieve in the removal process before the crushing process can reduce the total content of MgO and CaO in the recycled raw material with a particle size of 1 mm or less, the recycled raw material with a particle size exceeding 1 mm and 3 mm or less, and the recycled raw material with a particle size exceeding 3 mm, and further improve the purity of the recycled raw material.

[0040] (Example 3) Next, using the recycled raw materials shown in Sample Nos. 1-1 to 1-6, they were blended as shown in Table 4, and after producing recycled bricks according to the manufacturing flow shown in Fig. 3, the corrosion resistance was evaluated. The evaluation of the corrosion resistance was carried out by the internal lining separation method using the high-frequency induction furnace 10 shown in Fig. 4. As the internal lining refractory of the high-frequency induction furnace 10, Sample 41 was constructed on the bottom plate 13 so as to form a container with an octagonal cross-section (Fig. 4(b)), and the hot metal 5 and the slag 11 were accommodated and held. The induction coil 12 was energized, the test temperature of the hot metal was set to 1650 °C, the temperature holding time was 4 hours, and the synthetic slag shown in Table 5 was charged every 1 hour. After cooling, the amount of corrosion of Sample 41 was measured, and then the corrosion index was obtained with the amount of corrosion of virgin bricks (Sample No. 5-0) set to 100 and shown together in Table 4. As a result, the recycled bricks of Sample Nos. 5-1 to 5-5 had corrosion resistance that was acceptable even for actual use, but the recycled bricks of Sample No. 5-6 were significantly inferior in corrosion resistance compared to virgin bricks and were judged to be unsuitable for actual use.

[0041]

Table 4

[0042]

Table 5

[0043] From these results, it was found that the corrosion resistance of the recycled bricks blended with recycled raw materials with a total impurity (MgO and CaO) content of 7 mass% or less in the whole recycled raw materials can maintain the same corrosion resistance as virgin bricks.

[0044] (Example 4) Next, the influence of the blending amount of the recycled raw materials on the durability of the recycled bricks was examined. Using the recycled raw materials shown in Sample No. 1-1, the blending was carried out as shown in Table 6, and the corrosion resistance was evaluated in the same manner as described above. As shown in Sample Nos. 6-4 to 6-7, the recycled bricks with a blending amount of the recycled raw materials exceeding 60 mass% have the same corrosion resistance as the recycled bricks with a blending amount of the recycled raw materials of 60 mass% or less and virgin bricks, and it was possible to achieve zero industrial waste discharge by using up all the produced recycled raw materials. On the other hand, as shown in Sample Nos. 6-1 to 6-3, in the case of virgin bricks and recycled bricks with a blending amount of the recycled raw materials of 60 mass% or less, it was not possible to use up all the produced recycled raw materials, and zero industrial waste discharge could not be achieved.

[0045]

Table 6

[0046] From these results, it was found that when the blending amount of the recycled raw materials in the recycled bricks exceeds 60 mass%, it is possible to use up all the produced recycled raw materials and achieve zero industrial waste discharge.

[0047] As described above, the embodiments to which the invention made by the present inventors is applied have been described, but the present invention is not limited by the description that forms a part of the disclosure of the present invention according to this embodiment. All other embodiments, examples, and operation techniques made by those skilled in the art based on this embodiment are included in the scope of the present invention.

Industrial Applicability

[0048] According to the method for manufacturing a refractory raw material of the present invention, since the amount of waste used refractory can be significantly reduced, the industrial waste treatment cost can be significantly suppressed.

Explanation of symbols

[0049] 1 Molten iron container (molten iron pretreatment container, molten iron pot) 2 Iron skin 3 Permanent refractory 4 Inner lining refractory 41 Sample (inner lining refractory) 5 Molten iron 10 High-frequency induction furnace 11 Slag 12 Induction coil 13 Bottom plate

Claims

**Claim 1**: A recovery step of recovering used refractories generated in a hot metal storage container comprising a lined refractory containing alumina, silicon carbide, and carbon, and a permanent refractory provided outside the lined refractory; A removal step of removing at least a part of impurities in the used refractories recovered in the recovery step; A crushing step of crushing the used refractories before or after the removal step; which has, when manufacturing refractory raw materials, in the recovery step, the used refractories are recovered in a state where the lined refractory and the permanent refractory are mixed; in the removal step, before the crushing step, the used refractories are passed through a sieve having an opening size of 8 mm or more and 37.5 mm or less as a removing means, and the sieve top is recovered, so that the total content of the impurities in the refractory raw materials becomes 7% by mass or less to remove the impurities; (1) removing the impurities so that the total content of the impurities in the refractory raw materials having a particle size of 1 mm or less becomes 3.5% by mass or less; (2) removing the impurities so that the total content of the impurities in the refractory raw materials having a particle size exceeding 1 mm and 3 mm or less becomes 4.5% by mass or less, and (3) removing the impurities so that the total content of the impurities in the refractory raw materials having a particle size exceeding 3 mm becomes 6% by mass or less; A method for manufacturing refractory raw materials, wherein at least one treatment selected from the above is selected. **Claim 2** The method for manufacturing refractory raw materials according to claim 1, further having a drying step of drying the refractory raw materials after the crushing step. **Claim 3** The method for manufacturing refractory raw materials according to claim 1, further having a sorting step of removing at least a part of metallic iron in the refractory raw materials simultaneously with the crushing step. **Claim 4** In the sorting step, the metallic iron in the refractory raw materials is removed by magnetic separation of the metallic iron with a magnetic force having a magnetic flux density of 0.3 T or less. The method for manufacturing refractory raw materials according to claim 3. **Claim 5** A method for manufacturing a refractory for a hot metal storage container, in which refractory raw materials recovered from a hot metal storage container are blended based on the method for manufacturing refractory raw materials according to any one of claims 1 to 4. **Claim 6** The method for manufacturing a refractory for a hot metal storage container according to claim 5, wherein the refractory raw materials are blended in an amount exceeding 60% by mass.

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