Method for manufacturing recycled refractory raw materials and method for manufacturing refractory materials

Abstract

To provide a method for producing a recycled refractory raw material in which a carbon content of the recycled refractory raw material can be sufficiently reduced by heat treatment at a lower temperature than that of conventional technologies, and to provide a method for producing a refractory product using the recycled refractory raw material as a raw material.SOLUTION: A method for producing a recycled refractory raw material includes: a granulation step of granulating a carbon-containing refractory brick to obtain a granulated brick; and a heating step of heating the granulated brick in an externally heating rotary kiln in the presence of an oxidizing gas to produce the recycled refractory raw material, wherein a heating temperature in the heating step is 850°C or more and 1,000°C or less, and a heating time in the heating step is 4 hours or more.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing a recycled refractory raw material and a method for producing a refractory product.

Background Art

[0002] For the purpose of effective use of resources, the recycling of carbon-containing refractories has been promoted. For example, Japanese Patent Application Laid-Open No. 3-75255 (Patent Document 1) discloses a method of heating a graphite-containing refractory in an internally heated rotary kiln to extract the refractory composition in the black lead-containing refractory.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the method according to Patent Document 1, since the combustion gas of the internal heating burner is used as a heat source, the oxygen partial pressure inside the processing vessel cannot be increased. Therefore, the carbon content of the recycled refractory raw material could not be sufficiently reduced unless the processing temperature was increased.

[0005] The problem to be solved by the present invention is to provide a method for producing a recycled refractory raw material capable of sufficiently reducing the carbon content of the recycled refractory raw material by heat treatment at a lower temperature compared with the prior art, and a method for producing a refractory product using such a recycled refractory raw material as a raw material.

Means for Solving the Problems

[0006] The present invention relates to a method for producing recycled refractory raw materials, comprising: a granulation step of granulating carbon-containing refractory bricks to obtain granulated bricks; and a heat treatment step of heating the granulated bricks in an externally heated rotary kiln in the presence of an oxidizing gas to obtain recycled refractory raw materials, wherein the heating temperature in the heat treatment step is 850°C or higher and 1000°C or lower, and the heating time in the heat treatment step is 4 hours or longer.

[0007] Furthermore, the method for producing refractories according to the present invention includes a granulation step of granulating carbon-containing refractory bricks to obtain granulated bricks, a heat treatment step of heating the granulated bricks in an externally heated rotary kiln in the presence of an oxidizing gas to obtain recycled refractory raw materials, and a refractory manufacturing step of producing refractories using the recycled refractory raw materials as raw materials, characterized in that the heating temperature in the heat treatment step is 850°C or more and 1000°C or less, and the heating time in the heat treatment step is 4 hours or more.

[0008] With these configurations, it is possible to obtain recycled refractory raw materials with a sufficiently reduced carbon content while keeping the heating temperature in the heat treatment process lower than in conventional technologies using an internally heated rotary kiln.

[0009] Preferred embodiments of the present invention will be described below. However, the scope of the present invention is not limited by the examples of preferred embodiments described below.

[0010] In one embodiment of the method for producing recycled refractory raw materials according to the present invention, it is preferable that the carbon content of the recycled refractory raw materials is 1% by mass or less.

[0011] This configuration yields recycled refractory materials that can be used as raw materials for a wide range of refractory applications.

[0012] In one embodiment of the method for producing recycled refractory raw materials according to the present invention, it is preferable that the carbon content of the carbon-containing refractory brick is 50% by mass or less.

[0013] This configuration makes it easier to reduce the carbon content of the resulting recycled refractory material.

[0014] In one embodiment, the method for producing recycled refractory raw materials according to the present invention preferably includes at least one of the following steps in the granulation step: crushing the carbon-containing refractory bricks and bringing the carbon-containing refractory bricks into contact with water.

[0015] This configuration allows for easy granulation using a general-purpose method.

[0016] In one embodiment, the method for manufacturing refractories according to the present invention further includes a classification step of classifying the recycled refractory raw material into a first component that does not pass through a sieve with a nominal mesh size of 300 μm as specified in JIS Z8801-1 and a second component that passes through the sieve, and it is preferable that a shaped refractory is manufactured using the first component as the raw material in the refractory manufacturing step.

[0017] This configuration allows for the production of refractories using relatively high-purity components from recycled refractory raw materials, thus enabling the suitability of manufacturing standardized refractories, which generally require high purity.

[0018] In one embodiment, the method for manufacturing refractories according to the present invention further includes a classification step of classifying the recycled refractory raw material into a first component that does not pass through a sieve with a nominal mesh size of 300 μm as specified in JIS Z8801-1 and a second component that passes through the sieve, and it is preferable to manufacture an amorphous refractory material using the second component as the raw material in the refractory manufacturing step.

[0019] With this configuration, the second component, which has a relatively low purity among the recycled refractory materials obtained through the heat treatment process, can be used for applications with low purity requirements, thereby enabling the effective utilization of all of the recycled refractory materials obtained.

[0020] Further features and advantages of the present invention will become clearer through the following description of exemplary and non-limiting embodiments. [Modes for carrying out the invention]

[0021] An embodiment of a method for manufacturing a recycled refractory raw material and a method for manufacturing a refractory according to the present invention will be described. The method for manufacturing a recycled refractory raw material according to this embodiment includes a granulation step, a heat treatment step, and a classification step, and is a method for manufacturing a recycled refractory raw material using a carbon-containing refractory brick as a starting material. Further, the method for manufacturing a refractory according to this embodiment includes a granulation step, a heat treatment step, and a classification step, and a refractory manufacturing step for manufacturing a refractory using the recycled refractory raw material obtained through these steps as a raw material, and is a method for manufacturing a refractory using a carbon-containing refractory brick as a starting material.

[0022] 〔Carbon-containing refractory brick〕 The definition of the term "refractory brick" follows JIS R2001-1985. That is, "refractory brick" is "a refractory having various forms suitable for the construction of kilns and other structures used at high temperatures". Further, the term "carbon-containing refractory brick" refers to a refractory brick as defined above that contains carbon.

[0023] The carbon-containing refractory brick contains a metal oxide and carbon. The carbon-containing refractory brick is classified according to the type of metal oxide it contains. For example, types such as magnesia-carbon, spinel-carbon, magnesia-spinel-carbon, alumina-carbon, and alumina-silicon carbide-carbon are exemplified. As the carbon-containing refractory brick used as the starting material in the method for manufacturing a recycled refractory raw material according to this embodiment, any carbon-containing refractory brick including those exemplified above can be used.

[0024] When the carbon content of the carbon-containing refractory brick is 50% by mass or less, it is preferable because it is easy to obtain a recycled refractory raw material with a carbon content of 1% by mass or less. The carbon content of the carbon-containing refractory brick is more preferably 50% by mass or less, and even more preferably 25% by mass or less. The lower limit of the carbon content of the carbon-containing refractory brick is not particularly limited. For example, the carbon content of the carbon-containing refractory brick can be 15% by mass or more.

[0025] Carbon-containing refractory bricks are typically obtained by kneading a mixture of a refractory raw material, which is a raw material containing a metal oxide, a carbon raw material, which is a raw material containing carbon, and any other optional additives (such as binders and additives), shaping the resulting formulation, and then heat-treating it. The type of carbon-containing refractory brick obtained here will correspond to the selected refractory raw material (metal oxide). The refractory raw material and the carbon raw material are generally provided in powder form, but are not limited to this. The obtained carbon-containing refractory bricks are widely used, for example, in locations in the steel manufacturing process where they come into contact with molten metal, and an appropriate type of carbon-containing refractory brick is selected according to the location where it is used.

[0026] In the method for manufacturing a recycled refractory raw material according to the present embodiment, used carbon-containing refractory bricks can be used as the carbon-containing refractory bricks serving as the starting material. Here, the used carbon-containing refractory bricks refer to carbon-containing refractory bricks that have a history of being used in a steel manufacturing process or the like after being manufactured by the method exemplified above. The used carbon-containing refractory bricks may have metals, slag, etc. adhering thereto that are derived from the process and location where the carbon-containing refractory bricks were used. Therefore, the method for manufacturing a recycled refractory raw material according to the present embodiment may include a removal step of removing at least one of the metal and slag adhering to the carbon-containing refractory bricks. Obtaining a recycled refractory raw material using used carbon-containing refractory bricks as the starting material has significance as a method for recycling used carbon-containing refractory bricks.

[0027] As described above, in the method for manufacturing a recycled refractory raw material according to the present embodiment, the type of carbon-containing refractory bricks serving as the starting material is arbitrary, but it is preferable to use a single type of carbon-containing refractory brick. This is because in this case, the recycled refractory raw material can be obtained as a single type of refractory raw material, making it easier to use the recycled refractory raw material as a raw material for bricks. Therefore, the method for manufacturing a recycled refractory raw material according to the present embodiment may include a classification step of classifying the carbon-containing refractory bricks by type.

[0028] For example, it is preferable to use carbon-containing refractory bricks containing magnesia (carbon-containing refractory bricks with magnesia carbon) as the starting material. This is because using carbon-containing refractory bricks containing magnesia as the starting material allows for the production of recycled refractory materials containing magnesia, thereby reducing the amount of naturally derived magnesia raw materials used. In particular, Japan relies heavily on imports for much of its magnesia raw materials, so it is desirable to reduce the amount of naturally derived magnesia raw materials used. Furthermore, when carbon-containing refractory bricks with magnesia carbon are recycled using conventional techniques, the proportion of magnesia in the resulting recycled refractory material may be lower than that of the starting material (low magnesia yield). However, according to the method for producing recycled refractory materials of this embodiment, magnesia can be recycled with a relatively high yield.

[0029] Furthermore, it is also preferable to use carbon-containing refractory bricks made of alumina silicon carbide carbon as the starting material. In this case, a recycled refractory material containing a mixture of alumina raw material and silicon carbide raw material is obtained.

[0030] [Refining process] The granulation process is a process of granulating carbon-containing refractory bricks to obtain granulated bricks.

[0031] Any method can be used to carry out the granulation process, as long as it is a method that can granulate the carbon-containing refractory bricks. The granulation process may include, for example, crushing the carbon-containing refractory bricks. In this case, the carbon-containing refractory bricks are crushed using a known crushing device such as a jaw crusher.

[0032] When carbon-containing refractory bricks subjected to a granulation process contain aluminum carbide, the granulation process may include contacting the carbon-containing refractory bricks with water. When carbon-containing refractory bricks containing aluminum carbide are brought into contact with water, the aluminum carbide expands due to hydration, causing the structure of the carbon-containing refractory bricks to break down from the inside. In this case, if the carbon-containing refractory bricks are left exposed to the elements after contact with water, they will naturally disintegrate. Thus, carbon-containing refractory bricks can be granulated by bringing them into contact with water. In this case, the energy consumed in the granulation process can be reduced compared to when machinery such as a crushing device is used.

[0033] Furthermore, carbon-containing refractory bricks containing aluminum carbide can occur, for example, when carbon-containing refractory bricks containing metallic aluminum as an additive are used in the steel manufacturing process. This is because heating during use causes a reaction between metallic aluminum and carbon, producing aluminum carbide.

[0034] In the granulation process, it is preferable to set the conditions so that the maximum particle size of the resulting granulated brick is 35 mm or less, as this facilitates carbon oxidation. The adjustment of the maximum particle size may be achieved by setting the conditions of the granulation method as exemplified above, or by removing components with a particle size exceeding 35 mm from the granulated brick as exemplified above. The latter method can be carried out, for example, using a sieve with a nominal mesh size of 31.5 mm as specified in JIS Z8801-1. The maximum particle size of the granulated brick obtained in the granulation process is more preferably 35 mm or less, and even more preferably 10 mm or less. There is no particular lower limit to the maximum particle size of the granulated brick obtained in the granulation process, but it may be, for example, 5 mm or more.

[0035] [Heat treatment process] The heat treatment process involves heating the granulated bricks in the presence of an oxidizing gas to obtain recycled refractory material. The carbon content of the recycled refractory material obtained is 1% by mass or less.

[0036] In this embodiment, the heat treatment process is carried out using an externally heated rotary kiln. A rotary kiln is a device that heats a retort (container) containing the material to be heat-treated by rotating it while heating, thereby applying heat to the material. Rotary kilns are classified into externally heated and internally heated types depending on the type of heating device. The externally heated type indirectly applies heat to the material by heating the retort, while the internally heated type applies heat directly to the material inside the retort by applying a burner flame or the like. In this embodiment, by using the former externally heated rotary kiln, the temperature distribution inside the retort becomes uniform, so the carbon content of the recycled refractory material can be sufficiently reduced even if the set temperature is low.

[0037] Rotary kilns are further classified into batch and continuous types depending on how the material to be heat-treated is supplied. The batch type does not involve loading or unloading the material between heat treatment cycles, processing a predetermined amount of material in each cycle. The continuous type allows for the supply of new material and the discharge of heat-treated material while the retort is in operation, performing heat treatment continuously. In this embodiment, either a batch or continuous externally heated rotary kiln can be used, but a continuous type is preferred because it allows for the continuous heat treatment process, potentially improving the overall efficiency of the manufacturing method for recycled refractory materials.

[0038] In this embodiment, the heating temperature in the heat treatment process is 850°C or higher and 1000°C or lower. An externally heated rotary kiln generally includes a temperature measuring device for measuring the internal temperature of the retort, and a control device for controlling the heating device so that the internal temperature measured by the temperature measuring device reaches a predetermined set temperature. The heating temperature refers to the set temperature input to the control device.

[0039] By heating the granulated bricks at a temperature of 850°C or higher, the carbon contained in the granulated bricks can be suitably converted to carbon dioxide, thus removing the carbon from the system. This allows the carbon content of the resulting recycled refractory material to be reduced to 1% by mass or less. Furthermore, by keeping the heating temperature below 1000°C, the retort can be operated under conditions that make deformation less likely, thus reducing the likelihood of equipment failure. The heating temperature is preferably below 900°C. In conventional methods using an internally heated rotary kiln, it was necessary to set the heating temperature (the set temperature of the heating device) above 1400°C, but in this embodiment, sufficient heat treatment can be achieved even if the heating temperature is kept below 1000°C.

[0040] In this embodiment, the heating time in the heat treatment process is 4 hours or more. Heating for 4 hours or more can reduce the carbon content of the recycled refractory material to 1% by mass or less. The upper limit of the heating time is not particularly limited, but it may be, for example, 16 hours or less. This is because shortening the heating time contributes to reducing the energy required for the heat treatment process. The heating time is preferably 10 hours or less, and more preferably 8 hours or less. However, the heating time sufficient to reduce the carbon content of the obtained recycled refractory material to 1% by mass or less varies depending on various conditions such as the particle size of the granulated brick, the temperature and atmosphere of the heat treatment process, and the specifications (shape, material, etc.) of the externally heated rotary kiln used in the heat treatment process. Therefore, the heating time should be set appropriately according to the actual implementation conditions.

[0041] The carbon content of the recycled refractory material obtained in the heat treatment process is preferably 1% by mass or less, and more preferably 0.7% by mass or less. Furthermore, there is no particular lower limit to the carbon content of the obtained recycled refractory material, but it may be, for example, 0.1% by mass or more.

[0042] The oxidizing gas used in the heat treatment process is preferably an oxygen-containing gas, such as air. Therefore, the heat treatment process can be carried out as a process of heating the granulated bricks in air. Alternatively, the granulated bricks may be heated in an oxygen-enriched atmosphere instead of air. In this case, the oxidation reaction proceeds more easily than when the granulated bricks are heated in air, thus shortening the time required for the heat treatment process. Furthermore, by using an externally heated rotary kiln, it is easier to maintain an oxygen-enriched atmosphere when heating the granulated bricks, so the benefit of using an oxygen-enriched atmosphere is particularly great in this embodiment.

[0043] [Classification process] The classification process involves sieving recycled refractory materials to separate them into a first component that does not pass through the sieve and a second component that does pass through the sieve. The classification process can be carried out, for example, using a known sieving apparatus equipped with a sieve with a nominal mesh size of 300 μm as specified in JIS Z8801-1.

[0044] The first component obtained in the classification process is relatively high in purity and suitable for use as aggregate. Therefore, the first component can be used as a raw material for refractories requiring high purity, such as shaped refractories.

[0045] On the other hand, the second component obtained through the classification process has relatively low purity because it contains ash and other components. Therefore, the second component can be used as a raw material for general-purpose refractories that require a relatively low level of purity, such as monolithic refractories.

[0046] Furthermore, in the classification process, the recycled refractory material may be classified into multiple grades. In this case, recycled refractory material classified into predetermined particle size categories can be obtained, making it easier to select the appropriate recycled refractory material for use as a refractory raw material depending on the purpose.

[0047] In the method for producing recycled refractory raw materials according to the present invention, it is optional whether or not a classification step is included.

[0048] [Refractory manufacturing process] The refractory manufacturing process is a process for manufacturing refractories using recycled refractory raw materials. The method used here may employ known methods for manufacturing refractories, other than using recycled refractory raw materials obtained by the above-mentioned method for manufacturing recycled refractory raw materials (a granulation process, a heat treatment process, and an optional classification process).

[0049] However, if the refractory material to be manufactured is a shaped refractory material, it is preferable to implement the classification process described above and carry out the refractory material manufacturing process using the first component as the raw material. As stated above, the first component has a relatively high purity and is therefore suitable for use as a raw material for shaped refractory materials, which generally require high purity.

[0050] Furthermore, if the refractory material to be manufactured is an amorphous refractory material, it is preferable to include the classification process described above and carry out the refractory material manufacturing process using the second component as the raw material. In this embodiment, the carbon content in the recycled refractory raw material is sufficiently reduced in the heat treatment process, so even the second component, which has a relatively low purity, is still suitable for use as a raw material for amorphous refractory materials. By using the second component, which has a relatively low purity among the recycled refractory raw materials obtained by the heat treatment process, for applications with low purity requirements, the entire recycled refractory raw material obtained can be effectively utilized.

[0051] [Other Embodiments] With regard to other configurations, the embodiments disclosed herein are illustrative in all respects, and it should be understood that the scope of the present invention is not limited thereto. Those skilled in the art will readily understand that modifications can be made as appropriate without departing from the spirit of the invention. Therefore, other embodiments modified without departing from the spirit of the invention are naturally included within the scope of the present invention. [Examples]

[0052] The present invention will be further described below with reference to examples. However, the following examples are not limiting to the present invention.

[0053] [Test conditions] (Carbon-containing refractory bricks) In each of the examples and comparative examples, one type of carbon-containing refractory brick selected from magnesia carbon (MgO-C), spinel carbon (SP-C), magnesia spinel carbon (MgO-SP-C), alumina carbon (Al2O3-C), and alumina silicon carbide carbon (Al2O3-SiC-C) was used as the starting material. In the table below, the type of carbon-containing refractory brick is indicated by the symbol in parentheses above. The carbon content of the carbon-containing refractory brick used in each example is also listed in the table below. In all examples, carbon-containing refractory bricks that had been used in the steel manufacturing process were used.

[0054] (Refining process) In all examples except Example 17, the granulation process was carried out using a pulverizing device. This is indicated as "pulverization" in the table below. In Example 17, the granulation process was carried out using a method that utilizes a hydration reaction, that is, by bringing carbon-containing refractory bricks into contact with water and then leaving them exposed to the elements. The exposure period was one month. This is indicated as "hydration reaction" in the table below.

[0055] (Heat treatment process) In the examples, the heat treatment process was carried out using an externally heated rotary kiln. In Comparative Examples 1 and 2, the heat treatment process was carried out using an internally heated rotary kiln. The heating temperature and heating time in the heat treatment process for each example are shown in the table below.

[0056] (Composition of recycled refractory materials) The composition of the recycled refractory materials obtained in each example is shown in the table below. The carbon (C) content was determined according to JIS R2011:2007. The content of each metal oxide (MgO, CaO, Al2O3) was determined according to JIS R2212-4:2006 or JIS R2216:2005. The silicon carbide (SiC) content was determined according to JIS R2011:2007. In each example and comparative example, the sum of the content of each component listed in the table below may be less than 100% by mass because trace amounts of other components are present. Examples of such other components include Fe2O3, Cr2O3, and TiO2.

[0057] [Test Results] (Comparison of heating methods and heating temperatures) Table 1 shows the effects of heating method, heating temperature, and heating time on the carbon content of the recycled refractory material. Example 1 is an example using a batch-type externally heated rotary kiln, where the carbon content of the recycled refractory material was reduced to 1% by mass or less under treatment conditions of 850°C for 8 hours. Comparative Example 1 is an example using a batch-type internally heated rotary kiln, where a higher heating temperature and longer heating time than in Examples 1-3 were required to reduce the carbon content to 1% by mass or less. Comparative Example 2 is an example using a batch-type internally heated rotary kiln with the same heating time as in Examples 1-3 (8 hours), but in this case, the carbon content of the obtained recycled refractory material was high.

[0058] Examples 1-3 and Comparative Example 3 were conducted using a batch-type externally heated rotary kiln, with the heating time fixed at 8 hours and the heating temperature varied between 600 and 1000°C. In Examples 1-3, where the heating temperature was between 850°C and 1000°C, the carbon content of the resulting recycled refractory material was 1% by mass or less, indicating that recycled refractory material with sufficiently reduced carbon content was obtained. On the other hand, in Comparative Example 3, where the heating temperature was 600°C, the carbon content of the recycled refractory material could not be sufficiently reduced.

[0059] In Table 1 and all subsequent tables, the composition (in mass percent) of recycled refractory materials is listed with two significant figures.

[0060] Table 1: Comparison of external heating type and internal heating type [Table 1]

[0061] (Comparison of heating times) Table 2 shows examples where the heating time was varied between 0.3 and 20 hours. Note that Example 1 is reproduced here. In all examples, the carbon content of the obtained recycled refractory material could be reduced to 1% by mass or less. On the other hand, in Comparative Example 4, where the heating time was 0.3 hours, the carbon content of the recycled refractory material could not be sufficiently reduced.

[0062] Table 2: Comparison of heating times [Table 2]

[0063] (Comparison of types of carbon-containing refractory bricks) Table 3 shows examples using different types of carbon-containing refractory bricks as starting materials. Note that Example 1 is identical to the previously published Example 1, but Table 3 also includes the content of components other than carbon. In all cases, the carbon content of the resulting recycled refractory material could be kept below 1% by mass. The recycled refractory material obtained in each example contained components corresponding to the type of carbon-containing refractory brick used as the starting material. For example, in Example 10, which used spinel-carbonized carbon-containing refractory bricks as the starting material, a recycled refractory material was obtained whose main components were spinel-derived components (magnesia (MgO) and alumina (Al2O3)).

[0064] Table 3: Comparison of types of carbon-containing refractory bricks [Table 3]

[0065] (Comparison of carbon content in carbon-containing refractory bricks) Table 4 shows examples of carbon-containing refractory bricks used as starting materials with different carbon content. Note that Example 1 is the same as the previously published Example 1, but Table 4 also includes information on the carbon content of the starting material. In all examples, it was possible to obtain recycled refractory materials with a reduced carbon content compared to the starting material. However, from the viewpoint of obtaining recycled refractory materials with a particularly low carbon content (1% by mass or less) within an economically advantageous heat treatment time, it is preferable to use starting materials with a carbon content of 50% by mass or less (Examples 1 and 13-15).

[0066] Table 4: Comparison of carbon content in carbon-containing refractory bricks [Table 4]

[0067] (Comparison of methods for implementing the granulation process) Table 5 shows examples of different methods for carrying out the granulation process. Note that Example 1 is the same as the previously described Example 1, but Table 5 also describes the method for carrying out the granulation process. In both Example 1, which was granulated using a pulverizing device, and Example 17, which was granulated using a hydration reaction, recycled refractory raw materials with sufficiently reduced carbon content were obtained.

[0068] Table 5: Comparison of methods for the granulation process [Table 5]

[0069] (Comparison of maximum particle sizes of finely granulated bricks) Table 6 shows examples of finely granulated bricks with different maximum particle sizes obtained in the granulation process. Note that Example 1 is identical to the previously described Example 1, but Table 6 also includes information on the maximum particle size of the finely granulated bricks. Examples 18 and 19 use the same starting materials as Example 1, and therefore the carbon content of the starting materials is 15% by mass in all three examples (1, 18, and 19). In all examples, recycled refractory materials with a reduced carbon content compared to the starting materials were obtained.

[0070] Table 6: Comparison of maximum particle sizes of finely granulated bricks [Table 6] [Industrial applicability]

[0071] This invention can be used, for example, in a method for producing recycled refractory materials by reusing carbon-containing refractory bricks after use.

Claims

1. A granulation process is performed to obtain granulated bricks having a maximum particle size in the range of 5 to 35 mm by granulating carbon-containing refractory bricks. The process includes a heat treatment step of heating the aforementioned granulated brick in an externally heated rotary kiln in the presence of an oxidizing gas to obtain recycled refractory material, The heating temperature in the heat treatment step is 850°C or higher and 1000°C or lower. The heating time in the aforementioned heat treatment step is 4 hours or more. A method for producing a recycled refractory raw material, wherein the carbon content of the recycled refractory raw material obtained by the heat treatment step is 1% by mass or less.

2. The method for producing recycled refractory raw materials according to claim 1, wherein the carbon content of the carbon-containing refractory brick is 50% by mass or less.

3. A method for producing recycled refractory raw materials according to claim 1 or 2, wherein the granulation step includes at least one of crushing the carbon-containing refractory brick and bringing the carbon-containing refractory brick into contact with water.

4. A granulation process is performed to obtain granulated bricks having a maximum particle size in the range of 5 to 35 mm by granulating carbon-containing refractory bricks. A heat treatment step is performed to obtain recycled refractory material by heating the aforementioned granulated brick in an externally heated rotary kiln in the presence of an oxidizing gas, A refractory manufacturing process that produces a refractory material using the aforementioned recycled refractory raw material as a raw material, The heating temperature in the heat treatment step is 850°C or higher and 1000°C or lower. The heating time in the aforementioned heat treatment step is 4 hours or more. A method for producing a refractory material, wherein the carbon content of the recycled refractory raw material obtained by the heat treatment step is 1% by mass or less.

5. The aforementioned recycled refractory material further includes a classification process that separates it into a first component that does not pass through a sieve with a nominal mesh size of 300 μm as specified in JIS Z8801-1, and a second component that passes through the sieve. The method for manufacturing a refractory material according to claim 4, wherein a shaped refractory material is manufactured using the first component as a raw material in the refractory material manufacturing process.

6. The aforementioned recycled refractory material further includes a classification process that separates it into a first component that does not pass through a sieve with a nominal mesh size of 300 μm as specified in JIS Z8801-1, and a second component that passes through the sieve. The method for manufacturing a refractory material according to claim 4, wherein an amorphous refractory material is manufactured using the second component as a raw material in the refractory material manufacturing process.

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