Method for manufacturing slag products and road base materials

Abstract

To provide a method for manufacturing slag products that removes foreign matter mixed in the slag without using materials other than steelmaking slag, such as solidifying agents or water-reducing agents, and simultaneously adjusts the particle size of the slag. [Solution] A method for manufacturing a slag product containing steelmaking slag as a raw material, comprising: a first step of mixing steelmaking slag and ejected slag that does not meet the standards for road steel slag specified in JIS A5015:2018; a second step of burning off foreign matter contained in the ejected slag; a third step of forming a mixed slag consisting of the steelmaking slag and ejected slag that does not contain foreign matter; and a fourth step of adjusting the particle size of the particles constituting the mixed slag.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing slag products and a roadbed material for roads. More specifically, the present invention relates to a method for manufacturing slag products that can manufacture slag products such as roadbed materials for roads using ejected slag that does not meet the standards of road steel slag, and a roadbed material for roads.

Background Art

[0002] Steel slag generated as a by-product in a so-called steelmaking process is reused and consumed as a raw material for slag products such as roadbed materials for roads. On the other hand, slag ejected outside the furnace during refining in a converter (referred to as "ejected slag") accumulates on the ground. However, when trying to recover and reuse the ejected slag deposited on the ground in this way, unnecessary foreign matter may be mixed in the ejected slag. Therefore, it has not been possible to reuse the ejected slag as a raw material for slag products. Examples of the foreign matter mixed in the ejected slag mainly include a part of a disposable paper temperature measuring device used during converter refining.

[0003] Thus, due to the fact that the ejected slag cannot be reused as a raw material for slag products, a large amount of ejected slag remains as industrial waste in the steelworks. Ultimately, there is a problem that a large amount of ejected slag that has become industrial waste remaining in the steelworks must be disposed of.

[0004] By the way, a roadbed material for roads is one of the slag products using steel slag as a raw material. The product standard of road steel slag, which is the raw material for roadbed materials for roads, is defined in "JIS A5015". According to this product standard, as a general matter, it is stipulated that "road steel slag shall not contain a harmful amount for use in foreign matter such as long or thin ones, dust, mud, and organic substances."

[0005] This product standard specifies the following regarding the physical and chemical properties and particle size of road steel slag: Specifically, it stipulates that the coloration judgment result must be "no coloration", the moisture immersion expansion ratio (%) must be 1.0 or less, the unit volume mass (kg / L) must be 1.50 or more, the unconfined compressive strength (MPa) must be 1.2 or more, and the modified CBR must be a specified value.

[0006] Furthermore, this product standard specifies the particle size of road steel slag as follows: For example, for road steel slag (CS-40) with a particle size range of 40 to 0 mm, the mass fraction of material passing through a sieve is specified as follows: 5 to 25% at a nominal mesh size of 12.36 mm for metal steel sieves specified in JIS Z8801-1, 15 to 40% at 14.75 mm, 50 to 80% at 19.0 mm, 95 to 100% at 37.5 mm, and 100% at 53 mm.

[0007] A method for removing foreign matter from slag, such as unburned material and unmelted dust, which is mixed into slag obtained by melting waste materials and ash, has been proposed (for example, Patent Document 1). Specifically, Patent Document 1 describes a method for removing foreign matter from slag, characterized by the fact that water-cooled molten slag discharged from a melting furnace is used to obtain water-granulated slag, which is then dried, and the dried water-granulated slag is subjected to a dry specific gravity separation process to separate and remove foreign matter such as unburned material and unmelted dust, which have a specific gravity lower than that of the slag.

[0008] Furthermore, in order to utilize the steel slag generated in the steelmaking process as a raw material for steelmaking or cement production, a processing method has been proposed to treat the steel slag in a state suitable for utilization (for example, Patent Document 2). Specifically, Patent Document 2 describes a method for processing steel slag, characterized by comprising a classification step (A) in which steel slag generated in the steelmaking process is recovered and classified into multiple particle size ranges, and a magnetic separation step (B) in which the steel slag of each particle size range classified in the classification step (A) is magnetically separated into magnetically attached material (x) and non-magnetically attached material (y).

[0009] Furthermore, a method for manufacturing steel slag roadbed material has been proposed that allows for the inexpensive and effective use of steel slag containing fine particles that do not meet JIS standards as a roadbed material (for example, Patent Document 3). Specifically, Patent Document 3 describes a method for manufacturing steel slag roadbed material, characterized by mixing steel slag, a solidifying agent, water, and a water-reducing agent, forming a hydrated solidified body, curing it, and then crushing it to adjust it to the required particle size.

[0010] Furthermore, a method has been proposed for the converter steelmaking process that controls the amount of slag recycled after decarburization, ensuring that the amount is neither excessive nor insufficient, or that it is accurately determined, without worsening the controllability of phosphorus removal refining (for example, Patent Document 4). Specifically, Patent Document 4 describes a converter steelmaking process characterized by including a first step of charging the main raw materials into the converter, a second step of removing Si and P, a third step of tilting the converter to discharge the slag generated in the second step, a fourth step of raising the furnace upright and supplying oxygen from an upper blowing lance to remove carbon, and a fifth step of tapping the molten steel produced. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] Japanese Patent Publication No. 2006-142136 [Patent Document 2] Japanese Patent Publication No. 2020-132458 [Patent Document 3] Japanese Patent Publication No. 2014-189446 [Patent Document 4] Japanese Patent Publication No. 2007-308773 [Overview of the Initiative] [Problems that the invention aims to solve]

[0012] However, the aforementioned conventional technology still had the following problems that needed to be solved. Specifically, the method for removing foreign matter from slag described in Patent Document 1 had the problem that it could not remove foreign matter of the same size that was not magnetically attached. As a result, it was inconvenient that slag containing foreign matter that could not be removed could not be sold to the public.

[0013] On the other hand, the processing methods for treating steel slag to a state suitable for commercialization described in Patent Documents 2 to 4 do not allow for an increase in the particle size of the slag after cooling and crushing. In other words, no technology for coarsening the slag particles has been established in the processing methods for treating steel slag to a state suitable for commercialization. As a result, the slag obtained by the processing methods for treating steel slag to a state suitable for commercialization does not meet the particle size standard, and there is an inconvenience in that this slag that does not meet the particle size standard cannot be sold externally.

[0014] Thus, the slag ejected from the converter during smelting, known as ejected slag, has not been used as a raw material for slag products because it may contain dirt and organic matter, and its particle size is fine. Furthermore, as a method for adjusting the particle size of steelmaking slag, a method of mixing steelmaking slag with a solidifying agent, water, and a water-reducing agent and then molding it has been proposed, as described in Patent Document 3. However, no method has been proposed to remove the dirt and organic matter mixed in the slag.

[0015] In other words, when foreign matter that cannot be separated from the slag using conventional methods is mixed in, the slag particle size is too fine and does not meet the standards for slag products such as roadbed material, making it unusable as a raw material for slag products. This resulted in the problem of unusable slag accumulating within the steel mill. Therefore, the present invention provides a method for manufacturing a slag product and a road base material that can remove foreign matter mixed in the ejected slag without using materials other than steelmaking slag, such as solidifying agents or water-reducing agents, and can simultaneously adjust the particle size of the slag.

[0016] The present invention has been made in view of the above circumstances, and provides a method for removing foreign matter mixed in ejected slag without using materials other than steelmaking slag, such as solidifying agents or water-reducing agents, and simultaneously adjusting the slag particle size. In other words, the present invention aims to provide a method for manufacturing slag products such as road base materials, land-based civil timber, marine civil timber, and embankment materials that use steelmaking slag as a material, in which even if foreign matter is mixed in the ejected slag, the foreign matter is burned by mixing it with the molten steelmaking slag, thereby enabling the removal of foreign matter from the slag and the adjustment of the slag particle size. [Means for solving the problem]

[0017] Therefore, in order to solve the above problems, the inventors conducted various experiments and found that even when foreign matter is mixed in the ejected slag, the foreign matter can be burned off and removed by mixing the ejected slag containing the foreign matter with molten steelmaking slag. The present invention is based on the above finding, and its gist is as follows.

[0018] In other words, the method for manufacturing a slag product according to the present invention is a method for manufacturing a slag product that includes steelmaking slag as a raw material, and is characterized by comprising: a first step of mixing steelmaking slag and ejected slag that does not meet the standards for road steel slag specified in JIS A5015:2018; a second step of burning off foreign matter contained in the ejected slag; a third step of forming a mixed slag consisting of the steelmaking slag and ejected slag that does not contain foreign matter; and a fourth step of adjusting the particle size of the particles constituting the mixed slag.

[0019] Furthermore, the method for manufacturing slag products according to the present invention is as follows: (a) The steelmaking slag is in a molten state. (b) The ejected slag is the slag ejected from inside the converter to the outside in the refining process of hot metal using a converter. (c) In the first step, the mass ratio of the steelmaking slag and the ejected slag is 10:90 to 90:10. (d) In the first step, after spraying the ejected slag on the slag discharge site for the ejected slag, the steelmaking slag is discharged onto the surface of the ejected slag, thereby mixing the steelmaking slag and the ejected slag. (e) In the first step, after spraying the steelmaking slag on the slag discharge site for the steelmaking slag, the ejected slag is discharged onto the surface of the steelmaking slag, thereby mixing the steelmaking slag and the ejected slag. (f) It is considered that the slag product being a roadbed material for roads and the like can be a preferable solution. (g) The roadbed material for roads according to the present invention is characterized by being manufactured by a method for manufacturing a slag product.

Effect of the Invention

[0020] According to the present invention, it becomes possible to reuse the ejected slag as a raw material for a slag product by this technology. That is, by applying the present invention, foreign substances in the ejected slag are removed by combustion. Further, by mixing with molten steelmaking slag, an effect is obtained in which the slag with a fine particle size is fused and sintered, etc., and the particle size of the slag becomes larger. Thereby, there is an advantage that slag that did not satisfy the product specifications of slag products conventionally can be used as a raw material for slag products.

Brief Description of the Drawings

[0021] [Figure 1] It is a flow showing each step of the method for manufacturing a slag product according to the present invention. [Figure 2] In Invention Example 1, it is a confirmation photograph of the slag temperature by a thermo camera. [Figure 3] In Invention Example 1, it is a graph showing the result of measuring the slag particle size of the slag product. [Figure 4] This graph shows the results of measuring the slag particle size of the slag product in Comparative Example 1. [Figure 5] This graph shows the particle size distribution of slag products manufactured using the slag product manufacturing method according to this embodiment and slag products manufactured using a conventional slag product manufacturing method. [Modes for carrying out the invention]

[0022] The embodiments of the present invention will be described in detail below. Note that the drawings are schematic and may differ from actual ones. Furthermore, the following embodiments are illustrative examples of devices and methods for realizing the technical concept of the present invention, and do not limit the configuration to those described below. In other words, the technical concept of the present invention can be modified in various ways within the technical scope described in the claims.

[0023] [First Embodiment] A method for manufacturing a slag product according to the first embodiment will now be described. Figure 1 is a flowchart showing each step of the method for manufacturing a slag product according to this embodiment. As shown in Figure 1, the method for manufacturing a slag product according to this embodiment is a method for manufacturing a slag product that includes steelmaking slag as a raw material, and is characterized by including: a first step of mixing steelmaking slag and ejected slag that does not meet the standards for road steel slag specified in JIS A5015:2018; a second step of burning off foreign matter contained in the ejected slag; a third step of forming a mixed slag consisting of the steelmaking slag and ejected slag that does not contain foreign matter; and a fourth step of adjusting the particle size of the particles constituting the mixed slag. The following describes each step included in the manufacturing method of the slag product according to this embodiment.

[0024] <Step 1: Mixing steelmaking slag and ejected slag> The method for manufacturing the slag product according to this embodiment includes a first step of mixing steelmaking slag with ejected slag that does not meet the standards for road steel slag specified in JIS A5015:2018. That is, the first step is to prepare the steelmaking slag and ejected slag that will be the raw materials for the slag product, and to mix these slags.

[0025] The steelmaking slag used in the manufacturing method of the slag product according to this embodiment may be converter-type steelmaking slag produced from a converter, or electric furnace-type steelmaking slag produced in an electric furnace steelmaking process using scrap as raw material. The steelmaking slag must be capable of burning off foreign matter contained in ejected slag that does not meet the standards for road steel slag specified in JIS A5015:2018. The steelmaking slag may be in a solid state or in a molten state.

[0026] Converter steelmaking slag is produced in the steelmaking process that transforms pig iron produced in a blast furnace into "steel" with high toughness and workability. Specifically, when auxiliary materials such as lime are added to pig iron produced in a blast furnace and oxygen is blown in to remove carbon, phosphorus, sulfur, etc. contained in the pig iron, the oxides produced when refining it into tough steel are the converter steelmaking slag. Like blast furnace slow-cooled slag, converter steelmaking slag is processed after being slowly cooled in a cooling yard by air cooling or water spraying, and then used as converter steelmaking slag. Approximately 110 kg of converter steelmaking slag is produced for every 1.0 ton of converter steel.

[0027] Converter steelmaking slag mainly consists of CaO, SiO2, and FeO. Compared to so-called blast furnace slag, converter steelmaking slag contains more CaO. Therefore, when converter steelmaking slag reacts with water, it becomes alkaline (pH = 11.0 to 12.0). Converter steelmaking slag contains free lime, etc. Therefore, steelmaking slag expands when calcium hydroxide (slaked lime) is produced through a water absorption reaction. From this technical standpoint, in the first step of the manufacturing method of the slag product according to this embodiment, the steelmaking slag may be subjected to expansion stabilization treatment (steam aging).

[0028] Electric furnace steelmaking slag is produced when iron scrap is melted and refined. Electric furnace steelmaking slag may be oxide slag produced by oxidation refining, or it may be reduction slag produced by reduction refining. Approximately 70 kg of oxide slag is produced per 1.0 ton of electric furnace steel. Approximately 40 kg of reduction slag is produced per 1.0 ton of electric furnace steel.

[0029] Electric furnace steelmaking slag is mainly composed of iron oxide (FeO), manganese oxide (MnO), silicon dioxide (SiO2), aluminum oxide (Al2O3), which are generated by the melting and oxidative refining of iron scrap, and calcium oxide (CaO), which is added for refining. Furthermore, electric furnace steelmaking slag may contain small amounts of magnesium oxide (MgO) originating from the refractory material of the electric furnace. The basicity of electric furnace steelmaking slag ranges from 1.0 to 4.0. By reducing the magnesium oxide (MgO) content in the electric furnace steelmaking slag to 10% by mass or less, the precipitation of free magnesia can be prevented, and the expansion of the electric furnace steelmaking slag can be suppressed.

[0030] The ejected slag used in the manufacturing method of the slag product according to this embodiment is slag that does not meet the standards for road steel slag specified in JIS A5015:2018. Ejected slag is, for example, slag ejected outside the furnace during refining in a converter, and is also called furnace slag. Since ejected slag is slag ejected outside the furnace during the refining of molten iron in a converter, it contains foreign matter such as garbage and organic matter. Examples of foreign matter include disposable paper thermometers used mainly during converter refining, waste probes, moisture, garbage, mud, organic matter, etc. In other words, ejected slag has foreign matter contained in the slag itself during the molten iron refining process, and foreign matter that adheres to the slag when the slag is ejected onto the ground outside the converter, such as a slag field. Foreign matter that adheres to the slag includes cloth pieces such as gloves and flexible container bags.

[0031] The ejected slag has a small particle size. That is, the slag ejected outside the furnace during molten iron refining has a small particle size and low viscosity. After being ejected outside the furnace during molten iron refining, the slag is cooled as soon as it comes into contact with the ground, such as a slag field. As a result, the particle size of the ejected slag is small.

[0032] Furthermore, the ejected slag does not meet the standards for road steel slag specified in JIS A5015:2018. In other words, the ejected slag does not meet the standards required for slag products in terms of various physical properties such as moisture immersion expansion ratio (%), unit volume mass (kg / L), unconfined compressive strength (MPa), and modified CBR.

[0033] In the first step of the manufacturing method for slag products according to this embodiment, mixing steelmaking slag and ejected slag is only necessary if the slags are mixed so that they have a uniform composition. The ejected slag may be mixed with the steelmaking slag, or the steelmaking slag may be mixed with the ejected slag. In the first step, it is preferable that the mass ratio of steelmaking slag to ejected slag is 10:90 to 90:10. In the first step of the manufacturing method for slag products according to this embodiment, it is preferable to use more ejected slag than steelmaking slag because this allows for the processing of the ejected slag, which is industrial waste, by using a larger amount as a raw material for the slag product.

[0034] <Second step: A process to burn off foreign matter contained in the ejected slag> Next, the method for manufacturing the slag product according to this embodiment includes a second step of burning off foreign matter contained in the ejected slag. That is, the second step is a step to eliminate foreign matter contained in the ejected slag by burning it off, so that the ejected slag can be used as a raw material for the slag product and is free of foreign matter. Steelmaking slag is usually in a molten state at 1300 to 1700°C.

[0035] Therefore, considering that the combustion temperature of foreign matter, including paper and cloth, is around 500°C, the foreign matter contained in the ejected slag is almost completely burned upon contact with the steelmaking slag. In the second step, for example, even if the mass ratio of steelmaking slag to ejected slag is 10:90, the foreign matter contained in the ejected slag is completely eliminated by thoroughly mixing the high-temperature steelmaking slag with the ejected slag and bringing the foreign matter into contact with the steelmaking slag. Furthermore, in the second step, the moisture generated by the combustion of foreign matter contained in the ejected slag is removed by contact with the steelmaking slag. When no more moisture is generated from the ejected slag, the foreign matter contained in the ejected slag is completely removed. As a result, the ejected slag that contained foreign matter becomes processed slag that does not contain foreign matter. In contrast, conventional ejected slag is often unsuitable as a slag product due to the significant influence of foreign matter. The manufacturing method for the slag product according to this embodiment includes a second step of burning off foreign matter contained in the ejected slag, thereby eliminating the influence of foreign matter and obtaining processed slag that is suitable as a slag product.

[0036] <Third step: Process to form a mixed slag that does not contain steelmaking slag or foreign matter> Furthermore, the method for manufacturing the slag product according to this embodiment includes a third step of forming a mixed slag consisting of the steelmaking slag and the ejected slag that does not contain foreign matter. In other words, the third step is the process of forming mixed slag, which is the raw material for slag products, consisting of steelmaking slag and ejected slag that does not contain foreign matter, and in which the particle size of the slag has not been adjusted. Mixed slag consists of steelmaking slag and ejected slag that does not contain foreign matter, and therefore does not contain foreign matter. Thus, mixed slag consists of steelmaking slag and ejected slag that does not contain foreign matter. However, the average particle size of the particles that make up the ejected slag contained in the mixed slag is extremely small, at 50 to 100 μm. For this reason, mixed slag, which is simply a mixture of steelmaking slag and ejected slag that does not contain foreign matter, cannot meet the standards for road steel slag specified in JIS A5015:2018.

[0037] <Step 4: Process to adjust the particle size of the particles that make up the mixed slag> Furthermore, the method for manufacturing the slag product according to this embodiment includes a fourth step of adjusting the particle size of the particles constituting the mixed slag. That is, the fourth step is a step of adjusting the slag particle size of the mixed slag necessary for use as a slag product. In other words, the fourth step included in the method for manufacturing the slag product according to this embodiment solves the problem that the particle size of the particles constituting the slag product cannot be controlled due to the unstable particle size distribution of the slag.

[0038] In the method for manufacturing slag products according to this embodiment, in order to obtain a slag product from a mixed slag consisting of steelmaking slag and ejected slag that does not contain foreign matter, it is necessary to process and adjust the slag to a particle size that corresponds to the desired specifications of the slag product. Therefore, in the method for manufacturing slag products according to this embodiment, the mixed slag, which is the raw material for the slag product, may be crushed after cooling, and the particles constituting the mixed slag may be classified and adjusted according to the particle size of the slag by using a sieve or the like. In other words, the method for manufacturing the slag product according to this embodiment may employ an efficient process in which crushers, magnetic separators, sieves, etc., are appropriately arranged to crush, magnetically separate, and sieve the mixed slag that will be used as the raw material for the slag product.

[0039] Furthermore, in the steelmaking slag used in the manufacturing method of the slag product according to this embodiment, some of the calcium oxide (CaO) and magnesium oxide (MgO) added as refining flux remain unreacted in the steelmaking slag or crystallize during the cooling of the mixed slag. The calcium oxide (CaO) and magnesium oxide (MgO) present in the steelmaking slag react with water to undergo a hydration reaction, and their volume approximately doubles as a result of this hydration reaction.

[0040] Therefore, in the fourth step of the method for manufacturing the slag product according to this embodiment, an aging treatment may be performed in advance to complete the hydration reaction of calcium oxide (CaO) and magnesium oxide (MgO) in order to prevent the expansion of calcium oxide (CaO) and magnesium oxide (MgO) that remain in the steelmaking slag or crystallize during the cooling of the mixed slag. The aging process may be carried out using an atmospheric aging method that utilizes natural rainwater in the yard to initiate the hydration reaction, or it may be carried out using an accelerated aging method that completes the hydration reaction in a short period of time.

[0041] On the other hand, in the method for manufacturing slag products according to this embodiment, by mixing steelmaking slag and ejected slag, the fine particles constituting the ejected slag are melted by the heat contained in the molten steelmaking slag. As a result, the fine particles constituting the ejected slag become coarser by fusing with each other upon melting. Consequently, in the method for manufacturing slag products according to this embodiment, the mixed slag obtained by mixing steelmaking slag and ejected slag can have a larger particle size without processing or adjusting it to the desired particle size of the slag product. Generally speaking, the particle size of each particle constituting the slag that has become coarser by fusing with each other upon melting hardly changes.

[0042] Thus, in the manufacturing method of the slag product according to this embodiment, by mixing ejected slag with molten steelmaking slag, foreign matter in the ejected slag is burned off, and the particles constituting the fine-grained ejected slag are fused and sintered, thereby increasing the particle size of the slag. As a result, it has been revealed that the slag product manufactured by the manufacturing method of the slag product according to this embodiment meets the CS40 standard of JIS A5015:2018.

[0043] As explained above, the manufacturing method for slag products according to the first embodiment makes it possible to reuse ejected slag as a raw material for slag products. Specifically, according to the manufacturing method for slag products according to the first embodiment, foreign matter contained in steel slag that does not meet the standards for road steel slag specified in JIS A5015:2018 is burned off, and by mixing the steel slag with molten steelmaking slag, the finer particles of the slag fuse and sinter, resulting in an increase in particle size. In other words, the invention according to the first embodiment has the advantage that slag that did not meet the product standards for slag products in the past can be used as a raw material for slag products.

[0044] [Second Embodiment] A method for manufacturing a slag product according to the second embodiment will now be described. The method for manufacturing a slag product according to this embodiment is characterized in that, in the first step included in the above embodiment, the steel slag is scattered in a slag discharge area for ejected slag, and then the steelmaking slag is discharged onto the surface of the steel slag, thereby mixing the steelmaking slag and the steel slag. The following describes the characteristic features of the manufacturing method for the slag product according to this embodiment.

[0045] The method for manufacturing the slag product according to this embodiment involves preparing a container for spreading ejected slag that does not meet the standards for road steel slag specified in JIS A5015:2018. The container for spreading ejected slag is a so-called molten slag storage container. That is, the container for spreading ejected slag should be able to store ejected slag and spread the ejected slag stored in the molten slag storage container onto the ground.

[0046] Therefore, the container for distributing ejected slag has an inlet for introducing ejected slag into the container. The container for distributing ejected slag also has an outlet for distributing the ejected slag stored inside the container to the outside, thereby distributing the ejected slag onto the ground. The container for distributing ejected slag may have one or more outlets. It is preferable to have multiple outlets in the container for distributing ejected slag so that a large amount of ejected slag can be distributed widely and uniformly onto the ground. The capacity of the container for distributing ejected slag is preferably in a range that allows for the distribution of ejected slag to be, for example, 1 to 100 tons, preferably 5 to 80 tons.

[0047] Next, in the method for manufacturing the slag product according to this embodiment, a container for distributing ejected slag containing a predetermined amount of ejected slag is lifted by an overhead crane, and the ejected slag is distributed to the ground by tilting the container onto the ground, which is the ejected slag discharge area. At this time, it is desirable to tilt the container for distributing ejected slag while moving the overhead crane horizontally and horizontally to prevent the ejected slag from being distributed unevenly to a particular location.

[0048] Subsequently, molten steelmaking slag is discharged from above the ejected slag, which has been scattered on the ground in the designated slag discharge area. As the molten steelmaking slag is discharged from above the scattered ejected slag, it permeates the ejected slag. This permeation of the molten steelmaking slag into the ejected slag causes any foreign matter contained in the ejected slag to burn.

[0049] Here, the molten steelmaking slag permeates the ejected slag, and after at least 5 minutes have passed, it is confirmed that no steam is being emitted from the ejected slag. If steam is being emitted from the ejected slag, it is considered that moisture remains in the ejected slag or that foreign matter is burning, so the slag is not moved until the steam generation stops. In this way, the foreign matter contained in the ejected slag is burned and disappears. As a result, the ejected slag that contained foreign matter becomes ejected slag that does not contain that foreign matter.

[0050] Ultimately, a mixed slag is formed consisting of ejected slag free of foreign matter and steelmaking slag, which serves as a waste disposal area for ejected slag. In other words, in the method for manufacturing the slag product according to this embodiment, after confirming that the generation of steam has stopped, the mixed slag is collected, and the steps of the process included in the method for manufacturing the slag product according to this embodiment are completed.

[0051] Herein, taking these technical points into consideration, in order to enhance the foreign matter removal effect, it is desirable that the moisture content of the ejected slag (ejected residue) before mixing with the molten steelmaking slag is 4.5% by mass or less in the manufacturing method of the slag product according to this embodiment. If the moisture content of the ejected residue before mixing with the molten steelmaking slag exceeds 4.5% by mass, the combustion of foreign matter will not proceed, which is undesirable because the foreign matter removal effect will decrease.

[0052] Furthermore, after carrying out the manufacturing method of the slag product according to this embodiment, the temperature of the waste disposal area after the ejected slag has been collected can be measured, for example, by using an infrared thermal camera. For example, in the manufacturing method of the slag product according to this embodiment, if the temperature of the waste disposal area after the ejected slag has been collected is 250°C or higher (for example, 262°C), it can be considered that the water contained in the slag, which is a mixture of ejected slag and molten steelmaking slag, has completely evaporated.

[0053] On the other hand, in the method for manufacturing a slag product according to this embodiment, a container for distributing steelmaking slag containing a predetermined amount of steelmaking slag is lifted by an overhead crane, and the steelmaking slag is distributed to the ground by tilting the container onto the ground, which is the steelmaking slag discharge area. After that, ejected slag may be discharged from above the steelmaking slag distributed on the ground, which is the steelmaking slag discharge area. As the slag ejected from above the scattered steelmaking slag is discharged from above, the ejected slag permeates the steelmaking slag. As the ejected slag permeates the steelmaking slag, the foreign matter contained in the ejected slag is burned.

[0054] Thus, the method for manufacturing a slag product according to this embodiment involves preparing a container for distributing ejected slag, storing the ejected slag inside the container, and then distributing the ejected slag stored in the container onto the ground. For this reason, the method for manufacturing a slag product according to this embodiment allows for the widespread and uniform distribution of a large amount of ejected slag onto the ground, which is the ejected slag discharge area, and enables the distribution of a large amount of steelmaking slag onto the surface of the ejected slag formed by the large amount of ejected slag.

[0055] As described above, according to the method for manufacturing slag products of the second embodiment, after scattering ejected slag in the slag discharge area for ejected slag, steelmaking slag is discharged onto the surface of the ejected slag, thereby enabling the widespread and uniform distribution of a large amount of ejected slag onto the ground in the slag discharge area. Furthermore, by widely and uniformly distributing a large amount of ejected slag onto the ground in the slag discharge area for ejected slag, these slags are mixed, and the finer-grained slag is fused and sintered, resulting in an effect where the particle size of the particles constituting the slag product becomes larger.

[0056] [Third Embodiment] A road base material according to the third embodiment will now be described. The road base material according to this embodiment is characterized by being manufactured by the method for manufacturing slag products according to the above embodiment. That is, the road base material according to this embodiment is characterized in that the slag product manufactured by the method for manufacturing slag products according to the above embodiment is the road base material.

[0057] The roadbed material according to this embodiment uses ejected slag containing foreign matter as a raw material. However, in the process included in the manufacturing method of the slag product according to the above embodiment, the foreign matter contained in the ejected slag used as a raw material for the slag product is burned away by the steelmaking slag. Therefore, the ejected slag containing foreign matter becomes ejected slag that does not contain said foreign matter. When ejected slag and steelmaking slag do not contain foreign matter, they become a mixed slag. This mixed slag constitutes road base material, which is a slag product. The particle size of the particles that make up the ejected slag containing foreign matter before it is mixed with the steelmaking slag is extremely small.

[0058] On the other hand, the particle size of the ejected slag containing foreign matter before mixing with steelmaking slag increases as the particles constituting the ejected slag fuse and sinter due to heat. As a result, the particle size of the particles constituting the mixed slag has a particle size range that allows it to be used as roadbed material.

[0059] Thus, the roadbed material for roads according to this embodiment uses ejected slag, which conventionally did not meet the product standards for slag products, as a raw material for slag products. This allows for the effective utilization of ejected slag that conventionally did not meet the product standards for slag products. Ejected slag is industrial waste. Therefore, by effectively utilizing ejected slag as a raw material for slag products, the ejected slag is consumed. As a result, the inventory of industrial waste remaining in the steelworks can be reduced.

[0060] As described above, according to the invention of the third embodiment, it is possible to provide a road base material that includes ejected slag, which conventionally did not meet the product standards for slag products, as a raw material for slag products.

[0061] [Other embodiments] Although the present invention has been described above with reference to embodiments, the present invention is not limited to the above embodiments. Various modifications to the structure and details of the present invention can be made, as can be understood by those skilled in the art within the technical scope of the present invention. Furthermore, any system or apparatus that combines the different features included in each embodiment is also within the technical scope of the present invention. [Examples]

[0062] The effects of the present invention will be described in detail below based on examples, but the present invention is not limited to these examples.

[0063] (Example of Invention 1) A container for spreading ejected slag (furnace residue) that did not meet the standards for road steel slag specified in JIS A5015:2018 was prepared. Approximately 40 tons of ejected slag (furnace residue) were loaded into this container. It was confirmed that the ejected slag (furnace residue) used in Invention Example 1 contained approximately 0.5 to 2.0 tons of foreign matter, specifically a portion of a disposable paper temperature measuring device used during converter refining. The container for distributing ejected slag evenly spread the slag contained inside it onto the slag field, which served as the slag disposal area, by discharging it from its outlet. Furthermore, the ejected slag (furnace residue) was evenly spread in the slag field, which is the designated area for the ejected slag, and then the ejected slag (furnace residue) was spread and leveled.

[0064] Next, the container for spreading the steelmaking slag, which contains the steelmaking slag, is lifted by an overhead crane and spread onto the slag (furnace slag) that has been scattered in the slag field, which is the slag discharge area for the ejected slag that will be used as the spreading site. By tilting the container used for spreading steelmaking slag, the steelmaking slag is scattered onto the ground. At this time, the overhead crane was moved horizontally and horizontally while tilting the container for spreading the steelmaking slag, so that the steelmaking slag would not be scattered unevenly in any particular location.

[0065] Subsequently, molten steelmaking slag was discharged from above the ejected slag that had been scattered on the ground, which served as a slag disposal area for the ejected slag. As the molten steelmaking slag was discharged from above the scattered ejected slag, it permeated into the ejected slag. This permeation of the molten steelmaking slag into the ejected slag caused any foreign matter contained in the ejected slag to burn.

[0066] It was confirmed that the molten steelmaking slag had permeated the ejected slag and that no steam was being generated from the ejected slag after at least 5 minutes had elapsed. In Invention Example 1, it was visually inspected whether any foreign matter remained in the slag mixture of ejected slag and molten steelmaking slag. As a result, no foreign matter was found under the conditions of Invention Example 1. Table 1 shows the manufacturing conditions of the slag product in Invention Example 1.

[0067] [Table 1]

[0068] Figure 2 shows a photograph of the slag temperature confirmed by a thermal camera. As is clear from Figure 2, in Invention Example 1, after carrying out the manufacturing method of the slag product according to the present invention, the temperature of the waste disposal area after the ejected slag was collected was measured with an infrared thermal camera and confirmed to be 262°C or higher. From this result, it is considered that the water contained in the slag, which is a mixture of ejected slag and molten steelmaking slag, has evaporated. Furthermore, in Invention Example 1, after carrying out the method for manufacturing slag products according to the present invention, a visual inspection was performed to check whether any foreign matter remained in the slag obtained by mixing the ejected slag and the molten steelmaking slag. As a result, no foreign matter was found to remain under the conditions of the present invention.

[0069] Next, after confirming that the molten steelmaking slag had permeated the ejected slag and that no steam was being generated from the ejected slag, the formed slag was cooled to a predetermined temperature. The obtained slag was recovered as a slag product. Then, the slag particle size of the slag product obtained in Invention Example 1 was measured. The slag particle size was measured by measuring the particles that passed through the finest mesh, a 2.36 mm square mesh, and calculating the ratio of these particles as frequency (%).

[0070] Figure 3 shows a slag particle size histogram as a result of measuring the slag particle size of the slag product. As is clear from Figure 3, the slag permeability after implementing the present invention was found to be 17.0%. In other words, considering the results with Comparative Example 1 described later, the slag permeability decreased, confirming the effect of making the slag particle size of the particles constituting the slag product coarser.

[0071] (Examples 2-5 of the invention) Except for changing the amount of ejected slag (furnace slag) spread and first uniformly spreading steelmaking slag in the steelmaking slag discharge area before spreading the ejected slag, the slag product was manufactured in the same manner as in Invention Example 1. Table 1 shows the manufacturing conditions for the slag products in Invention Examples 2 to 6. The results of Invention Examples 2 to 6 are shown in Table 1.

[0072] (Comparative Example 1) The slag product was manufactured in the same manner as in Invention Example 1, except that the ejected slag containing foreign matter was not mixed with the molten steelmaking slag. Table 1 shows the manufacturing conditions for the slag product in Comparative Example 1. The results of Comparative Example 1 are shown in Table 1. Figure 4 shows a slag particle size histogram as a result of measuring the slag particle size of the slag product. As is clear from Figure 4, the slag permeability after carrying out the manufacturing method of the slag product in Comparative Example 1 was found to be 17.2%. In other words, considering the results with Invention Examples 1 to 5, the slag permeability of the particles constituting the slag product manufactured in Comparative Example 1 increased, confirming the effect of making the slag particle size of the particles constituting the slag product finer. Furthermore, Figure 5 shows the calculated average particle size distribution of slag products manufactured using the slag product manufacturing method according to this embodiment (indicated as "After Application" in the graph in Figure 5) and slag products manufactured using a conventional slag product manufacturing method (indicated as "Before Application" in the graph in Figure 5). Furthermore, the slag products manufactured using the manufacturing method of the slag products according to this embodiment were based on two months' worth of steelmaking slag and ejected slag discharged from the converter used in Invention Example 1. As is clear from Figure 5, it was found that the particle size of the slag product obtained by applying the manufacturing method of the slag product according to this embodiment was larger. In other words, the particle size of the slag product obtained by applying the manufacturing method of the slag product according to this embodiment became the optimal size for road base material.

[0073] These experimental data revealed that by scattering steelmaking slag on the ground over ejected slag (furnace slag), foreign matter contained in the ejected slag (furnace slag) was eliminated by combustion. Furthermore, these experimental data revealed that the particle size of the slag constituting the mixed slag, which consists of ejected slag (furnace slag) and steelmaking slag, is suitable for road base material. Furthermore, based on these experimental data, the inventory of ejected slag was calculated when the slag product manufacturing method according to the present invention was applied.

[0074] Traditionally, slag that did not meet product specifications could not be sold externally. In addition, since slag that did not meet product specifications is generated regularly as industrial waste, it could not be disposed of as industrial waste. As a result, such slag accumulated within steel mills and became inventory. The manufacturing method of slag products according to the present invention makes it possible to effectively utilize ejected slag by using it as roadbed material.

[0075] Therefore, the slag product manufacturing method according to the present invention is expected to successfully reduce the inventory accumulated in steel mills by approximately 10 to 1 million tons. Furthermore, to balance the reduction, it is estimated that in the future, the inventory of slag that does not meet product specifications, such as ejected slag, will be reduced to almost zero.

[0076] Thus, it has become clear that the method for manufacturing slag products according to the present invention is a method for manufacturing road base material that can burn off foreign matter in the ejected slag and reuse the ejected slag as a raw material for slag products. Furthermore, it has become clear that the method for manufacturing slag products according to the present invention is a method for manufacturing road base material that can increase the particle size of the slag by mixing the ejected slag with molten steelmaking slag and fusing and sintering the fine-grained slag. [Industrial applicability]

[0077] According to the invention of the present invention, it becomes possible to reuse ejected slag as a raw material for slag products, and since steel slag that previously did not meet the product standards for slag products can now be used as a raw material for slag products, it contributes to the development of related industries such as steelmaking and construction, and is extremely useful from an industrial perspective.

Claims

1. A method for manufacturing slag products containing steelmaking slag as a raw material, The first step involves mixing steelmaking slag with ejected slag that does not meet the standards for road steel slag specified in JIS A5015:2018, A second step involves burning off foreign matter contained in the ejected slag, A third step of forming a mixed slag consisting of the steelmaking slag and the ejected slag that does not contain foreign matter, A method for producing a slag product, comprising a fourth step of adjusting the particle size of the particles constituting the mixed slag.

2. The method for producing a slag product according to claim 1, characterized in that the steelmaking slag is in a molten state.

3. The method for manufacturing a slag product according to claim 1, characterized in that the ejected slag is ejected from inside the furnace to outside the furnace in a molten iron refining process using a converter.

4. The method for producing a slag product according to claim 1, characterized in that in the first step, the steelmaking slag and the ejected slag are in a mass ratio of 10:90 to 90:

10.

5. A method for manufacturing a slag product according to any one of claims 1 to 4, characterized in that, in the first step, the ejected slag is scattered in a slag discharge area for ejected slag, and then the steelmaking slag is discharged onto the surface of the ejected slag to mix the ejected slag and the steelmaking slag.

6. A method for manufacturing a slag product according to any one of claims 1 to 4, characterized in that, in the first step, the steelmaking slag is scattered in a slag discharge area for steelmaking slag, and then the ejected slag is discharged onto the surface of the steelmaking slag to mix the steelmaking slag and the ejected slag.

7. A method for manufacturing a slag product according to any one of claims 1 to 4, characterized in that the slag product is a road base material.

8. A road base material characterized by being manufactured by the method for manufacturing slag products described in claim 7.

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