Steelmaking slag separation method and steelmaking slag separation system

Abstract

To provide a steel making slag separation method which can correctly separate steel making slags even when smokeless coals, porous slags and dense slags are contained.SOLUTION: A steel making slag separation method for separating powdery steel making slags includes: a magnetic ore separation step for separating the steel making slags using magnetic ore separators; a sieving step for separating the steel making slags after the magnetic ore separation step into plural fractions with different grain sizes with a sieve; and a dry density separation step for separating the plural fractions with a dry density separator. The magnetic ore separation step includes first magnetic ore separation treatment for separating a magnetic object using a first magnetic ore separator and second magnetic ore separation treatment for separating a nonmagnetic object using a second magnetic ore separator having a magnetic force higher than that of the first magnetic ore separator.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a steelmaking slag separation method, and more particularly to a steelmaking slag separation method that can accurately separate steelmaking slag even when anthracite, porous slag, or dense slag is contained.The present invention also relates to a steelmaking slag separation system that can implement the steelmaking slag separation method. [Background technology]

[0002] In the steelmaking process at steelworks and other facilities, a large amount of slag (steelmaking slag), whose main components are oxides such as SiO2, CaO, and Al2O3, is produced as a by-product. Therefore, finding an effective way to utilize steelmaking slag has become an issue.

[0003] Steelmaking slag is mainly recycled as civil engineering materials such as roadbed materials and as a cement raw material, but typical steelmaking slag contains approximately 20-50 mass% Fe (mainly metallic iron) in addition to the slag content. Therefore, in order to improve the yield in the steelmaking process, it is necessary to separate the Fe contained in the steelmaking slag and reuse it as an iron source.

[0004] Therefore, the present inventors have proposed a method for separating steelmaking slag by magnetic separation (Patent Documents 1 and 2). That is, by separating steelmaking slag using a magnetic separator, it is possible to separate it into magnetized matter with a high Fe content and non-magnetized matter that is mainly composed of slag and has a low Fe content. The magnetized matter can then be recycled as an iron source, and the non-magnetized matter can be recycled as a cement raw material, etc. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-127647 [Patent Document 2] Japanese Patent Publication No. 2020-132458 Summary of the Invention [Problem to be solved by the invention]

[0006] However, since steelmaking slag may contain anthracite in addition to Fe, it is also necessary to separate the anthracite from the steelmaking slag in order to reuse the anthracite. However, the above-mentioned conventional techniques do not take into consideration the separation and recovery of anthracite.

[0007] Furthermore, the slag portion of steelmaking slag is not homogeneous, and may contain a mixture of porous slag with a relatively low density and dense slag with a relatively high density. For example, 3 If it is less than 1.8g / cm, it is considered porous slag. 3 If the density is higher, it can be considered dense slag. However, porous slag and dense slag not only differ in density, but also in composition. In particular, the chromium oxide (Cr2O3) content is low at about 3 mass% in porous slag, while it is high at about 20 mass% in dense slag. Due to this difference in composition, porous slag and dense slag are suitable for different recycling applications. Therefore, to increase their value in recycling, it is desirable to separate porous slag from dense slag. However, because there is almost no difference in the magnetic properties of porous slag and dense slag, separation using a magnetic separator has been difficult.

[0008] Another type of slag generated during the steelmaking process is furnace deposits, which spill from steelmaking vessels during refining and accumulate below the furnace. Because furnace deposits contain a variety of components, including metallic iron, carbon, porous slag, and dense slag, they are not only unsuitable for recycling as is, but are also difficult to dispose of. Therefore, separation of furnace deposits is required, but separation is particularly difficult because the majority of furnace deposits (approximately 80% or more) are fine particles with a particle size of 10 mm or less. Furthermore, slag generated in large quantities, such as furnace deposits, is generally stored outdoors at steelworks, resulting in a high moisture content due to rainwater and other factors, which further complicates separation.

[0009] For the reasons described above, steelmaking slag containing a large amount of fine particles, such as deposits under the furnace, is often stored without being recycled. Therefore, a method capable of separating even steelmaking slag containing a large amount of fine particles, such as deposits under the furnace, is desired.

[0010] The present invention has been made in consideration of the above circumstances, and aims to provide a steelmaking slag separation method that can accurately separate steelmaking slag even when anthracite, porous slag, or dense slag is present, and that can also be applied to steelmaking slag that contains a large amount of fine powder, such as furnace deposits. Another aim of the present invention is to provide a steelmaking slag separation system that can implement the steelmaking slag separation method. [Means for solving the problem]

[0011] The present invention has been made to solve the above problems, and its gist and configuration are as follows.

[0012] 1. A steelmaking slag separation method for separating powdered steelmaking slag, comprising: a magnetic separation step of separating the steelmaking slag using a magnetic separator; a sieving step in which the steelmaking slag after the magnetic separation step is separated into a plurality of fractions with different particle sizes using a sieve; a dry density separation step of separating each of the plurality of fractions using a dry density separation device; In the magnetic separation step, a first magnetic separation process for separating magnetic substances using a first magnetic separator; A steelmaking slag separation method, comprising: a second magnetic separation process using a second magnetic separator having a magnetic force higher than that of the first magnetic separator to separate non-magnetic materials.

[0013] 2. The method further includes a preliminary sieving step of separating the steelmaking slag using a sieve with a mesh size of 7 to 10 mm prior to the magnetic separation step, A steelmaking slag separation method as described in 1 above, wherein the steelmaking slag that has passed through the sieve in the preliminary sieving process is subjected to the magnetic separation process.

[0014] 3. A steelmaking slag separation method described in 1 or 2 above, wherein in the sieving step, a sieve with mesh sizes of 1 to 5 mm is used to separate the steelmaking slag after the magnetic separation step into two fractions: an over-sieve fraction and an under-sieve fraction.

[0015] 4. In the dry density separation step, both an air flow centrifugal separator and an air table are used as the dry density separation device; A steelmaking slag separation method described in 3 above, wherein the two fractions separated in the sieving process are separated by the air flow centrifugal separator, and the over-sieve fraction by the air table.

[0016] 5. A steelmaking slag separation system for separating powdered steelmaking slag, comprising: a magnetic separation unit that separates the steelmaking slag using a magnetic separator; a sieve unit that separates the steelmaking slag separated by the magnetic separation unit into a plurality of fractions having different particle sizes using a sieve; a dry density separation unit that separates each of the plurality of fractions using a dry density separation device; The magnetic separation unit is a first magnetic separation processing section that separates magnetic substances using a first magnetic separator; A steelmaking slag separation system having a second magnetic separation processing unit that separates non-magnetic materials using a second magnetic separator having a magnetic force higher than that of the first magnetic separator.

[0017] 6. The apparatus further includes a preliminary sieve unit that separates the steelmaking slag using a sieve with a mesh size of 7 to 15 mm prior to separation in the magnetic separation unit; 6. A steelmaking slag separation system as described in 5 above, wherein the steelmaking slag that has passed through the sieve in the preliminary sieve section is supplied to the magnetic separation section.

[0018] 7. A steelmaking slag separation system as described in 5 or 6 above, wherein the sieve section uses a sieve with a mesh size of 1 to 5 mm to separate the steelmaking slag after separation in the magnetic separation section into two fractions: over-sieve and under-sieve.

[0019] 8. The dry density separation unit includes both an air flow centrifugal separator and an air table as the dry density separation device; A steelmaking slag separation system as described in claim 7, wherein of the two fractions separated in the sieve section, the under-sieve fraction is separated in the air flow centrifugal separator and the over-sieve fraction is separated in the air table. [Effects of the Invention]

[0020] According to the present invention, Fe, anthracite, porous slag, dense slag, and the like contained in steelmaking slag can be accurately separated. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a schematic diagram showing an example of the structure of a pulley-type magnetic separator. [Figure 2] FIG. 2 is a flowchart showing a processing flow in one embodiment of the present invention. [Figure 3] FIG. 10 is a flowchart showing a process flow in another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0022] Next, a method for carrying out the present invention will be specifically described. Note that the following description shows a preferred embodiment of the present invention, and the present invention is not limited to the following description in any way.

[0023] A steelmaking slag separation method according to one embodiment of the present invention includes the following steps (1) to (3). (1)Magnetic selection process (2) Sieving process (3) Dry density separation process

[0024] Moreover, the steelmaking slag separation system according to one embodiment of the present invention includes the following components (A) to (C). (A) Magnetic separation department (B) Phloem (C) Dry density separation section

[0025] [Magnetic selection process] In the magnetic separation process, the steelmaking slag is separated using a magnetic separator (magnetic separation process). In the present invention, it is important to perform a first magnetic separation process in which a first magnetic separator is used to separate magnetized materials, and a second magnetic separation process in which a second magnetic separator having a magnetic force higher than that of the first magnetic separator is used to separate non-magnetized materials. In other words, the magnetic separation process is performed using a first magnetic separator with a relatively low magnetic force and a second magnetic separator with a relatively high magnetic force.

[0026] In the first magnetic separation process, particles with a high metallic iron content can be separated as magnetic particles from the steelmaking slag. This is because there is a large difference in magnetic properties between metallic iron and other components, so by performing magnetic separation with a relatively low magnetic force, particles with a high metallic iron content can be effectively separated from particles with a low metallic iron content.

[0027] In the second magnetic separation process, particles with a high carbon content in steelmaking slag can be separated as non-magnetic particles. This is because slag particles contain some metallic iron, and when magnetic separation is performed under high magnetic force, most particles are collected on the magnetic side, while particles with a high carbon content are collected on the non-magnetic side even under high magnetic force.

[0028] The first and second magnetic separation processes can be performed in any order. That is, in one embodiment of the present invention, the first magnetic separation process is performed using a first magnetic separator to separate magnetically attached materials, and then the second magnetic separation process is performed using a second magnetic separator having a magnetic force higher than that of the first magnetic separator to separate non-magnetically attached materials. In another embodiment of the present invention, the second magnetic separation process is performed using a second magnetic separator having a magnetic force higher than that of the first magnetic separator to separate non-magnetically attached materials, and then the first magnetic separation process is performed using the first magnetic separator to separate magnetically attached materials.

[0029] The first and second magnetic separators are not particularly limited and any magnetic separators can be used, but it is preferable to use a pulley-type magnetic separator 1. The pulley-type magnetic separator 1 is a magnetic separator in which one of the pulleys constituting the belt conveyor has a built-in magnetic field application means.

[0030] Figure 1 is a schematic diagram showing an example of the structure of a suitable pulley-type magnetic separator. The pulley-type magnetic separator 1 includes a main belt conveyor 2 for magnetic separation and a supply belt conveyor 3 for supplying steelmaking slag S to the main belt conveyor 2. One pulley 4 of the main belt conveyor 2 includes a pulley body 5 and a magnetic roll 6 that is built into the pulley body 5 and is driven to rotate independently of the pulley body 5. The magnetic roll 6 includes multiple magnetic poles 7 arranged at intervals along its outer circumferential surface, and the polarities of the multiple magnetic poles 7 are arranged alternately in the circumferential direction of the magnetic roll 6, with north and south poles.

[0031] In Figure 1, black squares represent ferromagnetic particles, and white triangles represent weakly magnetic particles. When steelmaking slag S is supplied to the magnetic roll 6 side of the main belt conveyor 2 by the supply belt conveyor 3, the ferromagnetic particles are attracted to the surface of the conveyor belt by magnetic force and are transported and collected in the magnetic material collection section 8. On the other hand, weakly magnetic particles are not attracted by magnetic force and so fall and are collected in the non-magnetic material collection section 9.

[0032] In the present invention, as described above, the magnetic force of the second magnetic separator used in the second magnetic separation process is set higher than the magnetic force of the first magnetic separator used in the first magnetic separation process. The magnetic forces of the first and second magnetic separators need only satisfy the above relationship, and the specific strength of the magnetic force may be adjusted to ensure appropriate magnetic separation. From the perspective of further improving separation accuracy, the magnetic force of the second magnetic separator is preferably 1.2 times or more, and more preferably 1.5 times or more, that of the first magnetic separator. On the other hand, since an excessively high magnetic force of the second magnetic separator will saturate the effect, the magnetic force of the second magnetic separator is preferably 5 times or less, and more preferably 3 times or less, that of the first magnetic separator. While not particularly limited, in one example, the magnetic force of the first magnetic separator can be approximately 500 to 1500 gauss, and the magnetic force of the second magnetic separator can be approximately 2500 to 3500 gauss.

[0033] The magnetic forces of the first and second magnetic separators can be adjusted by any method. For example, the magnetic force of the magnets used for magnetic separation can be adjusted. In the case of a pulley-type magnetic separator such as that shown in FIG. 1, the magnetic force applied to the steelmaking slag on the belt conveyor surface can be adjusted by changing the thickness of the pulley body 5 (also called the shell).

[0034] To confirm the effect of the magnetic force of the magnetic separator on the separation state of steelmaking slag, we actually separated steelmaking slag into magnetized and non-magnetized materials using pulley-type magnetic separators with different magnetic forces, and measured the composition of both. The magnetic force of the pulley-type magnetic separator was adjusted by changing the thickness of the pulley body (shell) within the range of 0 to 30 mm, while other conditions were kept the same. Note that a shell thickness of 0 mm means that there is no shell and the magnet is in direct contact with the conveyor belt.

[0035] The steelmaking slag used contained SiO2, CaO, Al2O3, MgO, P2O5, and Cr2O3 as slag components, as well as Fe and C. The compositions of the non-magnetized and magnetized materials before and after separation using a magnetic separator are shown in Tables 1 and 2, respectively. Note that the amounts of C, Cr2O3, and T.Fe (total amount of Fe) are shown here as representative components.

[0036] [Table 1]

[0037] [Table 2]

[0038] As can be seen from the results shown in Table 1, when the shell thickness is reduced to increase the magnetic force, the C content in the non-magnetized material becomes very high, at 30% or more. On the other hand, when the shell thickness is increased to decrease the magnetic force, the Fe content (T.Fe) in the magnetized material becomes very high. From the perspective of ease of recycling, the higher the Fe content (T.Fe) in the magnetized material, the better, and as a guideline, it is preferably 55% by mass or more.

[0039] [Sieving process] Next, the steelmaking slag after the magnetic separation step is separated into a plurality of fractions with different particle sizes using a sieve (sieving step). The reason for this will be explained below.

[0040] In the magnetic separation process, the first and second magnetic separation processes separate the particles that make up the powdered steelmaking slag into particles with a high metallic iron content and particles with a high carbon content, respectively. Therefore, particles with a high slag content remain in the steelmaking slag that has undergone the magnetic separation process. As mentioned above, slag contains a mixture of porous slag and dense slag, so it is desirable to separate the porous slag from the dense slag to facilitate recycling.

[0041] Since porous slag and dense slag have almost no difference in terms of magnetism, it is difficult to separate them using a magnetic separator. Therefore, dry density separation, which takes advantage of the difference in density, is considered. However, steelmaking slag contains a mixture of particles of different sizes, and dry density separation equipment is generally designed for each particle size, making it difficult to perform accurate dry density separation as is.

[0042] Therefore, in the present invention, prior to the dry density separation process, the steelmaking slag after the magnetic separation process is separated into multiple fractions with different particle sizes using a sieve, making it possible to perform dry density separation on each fraction using an apparatus appropriate for its particle size.

[0043] In the sieving step, any number of sieves can be used. In other words, the steelmaking slag after the magnetic separation step can be separated into any number of fractions with different particle sizes. The number of fractions may be two or more, and there is no upper limit. However, separating into too many fractions reduces work efficiency and increases equipment costs. Therefore, in the sieving step, separation into two to four fractions is preferable, and separation into two or three fractions is more preferable.

[0044] For example, when one sieve is used to separate into two fractions, the mesh size of the sieve is preferably 1 to 5 mm, more preferably 1 to 3 mm. When two sieves are used to separate into three fractions, the mesh size of one sieve is preferably 1 to 3 mm, and the other sieve is preferably 4 to 6 mm.

[0045] [Dry density separation process] Next, each of the multiple fractions is separated using a dry density separator (dry density separation process). The dry density separator is not particularly limited and any device can be used, but examples include an airflow centrifugal separator and an air table. An airflow centrifugal separator is a device that separates particles by utilizing the difference in the effect of airflow on particle density. An airflow centrifugal separator is suitable for separating relatively small particles, such as particles with a particle size of 3 mm or less. An air table is a device that has a table with small holes installed in an inclined position, and separates heavy particles from light particles by supplying air from below through the holes in the table and vibrating the table. An air table is suitable for separating particles with a particle size of approximately 1 to 10 mm. Therefore, it is preferable to separate the fractions separated in the sieving process using an airflow centrifugal separator for relatively small particle sizes and an air table for relatively large particle sizes.

[0046] For example, when the steelmaking slag after the magnetic separation process is separated into two fractions, an over-sieve fraction and an under-sieve fraction, in the sieving process, it is preferable that, of the two fractions separated in the sieving process, the under-sieve fraction is separated using an air flow centrifugal separator and the over-sieve fraction is separated using an air table in the dry density separation process.

[0047] [Preliminary screening process] The separation method of one embodiment of the present invention may further include a pre-sieving step of separating the steelmaking slag using a sieve with a mesh size of 7 to 10 mm prior to the magnetic separation step. Also, the separation system of one embodiment of the present invention may further include a pre-sieving unit that separates the steelmaking slag using a sieve with a mesh size of 7 to 10 mm prior to separation in the magnetic separation unit.

[0048] When the above-mentioned preliminary sieving step is performed, the steelmaking slag that has passed through the sieve in the preliminary sieving step can be subjected to the magnetic separation step. Since the separation method of the present invention is particularly suitable for separating fine slag, performing the preliminary sieving step in this manner allows for more effective separation. Furthermore, by removing coarse slag in advance through the preliminary sieving step, clogging of the magnetic separator can be prevented, further improving processing efficiency.

[0049] The steelmaking slag that does not pass through the sieve in the preliminary sieving step can be recycled by conventional processes, although there are no particular restrictions on this. That is, since the steelmaking slag that does not pass through the sieve has a relatively large particle size, it can be subjected to a process such as sintering as it is.

[0050] Next, a preferred embodiment of the present invention will be described with reference to a flow chart.

[0051] FIG. 2 is a flow diagram showing the process flow in one embodiment of the present invention. Powdered steelmaking slag, which serves as the starting material, is first separated in a preliminary sieving process. The slag that passes through the sieve is then subjected to the subsequent magnetic separation process. In the magnetic separation process, a first magnetic separation process is first performed using a first magnetic separator to separate magnetized materials, and then a second magnetic separation process is performed using a second magnetic separator with a stronger magnetic force than the first magnetic separator to separate non-magnetized materials. The magnetized materials from the first magnetic separation process are particles with a high iron content, and therefore can be reused as an iron source. Furthermore, the non-magnetized materials from the second magnetic separation process are particles with a high carbon content, and therefore can also be reused.

[0052] Next, the magnetically attached material from the second magnetic separation process is separated into two fractions, i.e., under-sieve and over-sieve, by a sieving process. The under-sieve and over-sieve fractions are then separated into low-density particles (porous slag) and high-density particles (dense slag) by a dry density separator. The under-sieve particles are preferably separated using a dry density separator (such as an airflow centrifugal separator) suitable for separating relatively small particles, while the over-sieve particles are preferably separated using a dry density separator (such as an air table separator) suitable for separating relatively large particles.

[0053] 3 is a flow chart showing the process flow in another embodiment of the present invention. This embodiment differs from the embodiment shown in FIG. 2 in that the first magnetic separation process is performed after the second magnetic separation process in the magnetic separation step, but the other points are the same.

[0054] In the magnetic separation process of this embodiment, first, a second magnetic separation process is performed using a second magnetic separator having a stronger magnetic force than the first magnetic separator to separate non-magnetic materials, and then a first magnetic separation process is performed using the first magnetic separator to separate magnetic materials. As shown in Figures 2 and 3, the first and second magnetic separation processes can be performed in any order. [Explanation of symbols]

[0055] 1 Pulley-type magnetic separator 2 Main belt conveyor 3 Supply belt conveyor 4 pulleys 5 Pulley body 6 Magnet Roll 7 magnetic poles 8 Magnetic object collection section 9. Non-magnetic object collection section

Claims

1. A steelmaking slag separation method for separating powdered steelmaking slag, comprising: a magnetic separation step of separating the steelmaking slag using a magnetic separator; a sieving step in which the steelmaking slag after the magnetic separation step is separated into a plurality of fractions with different particle sizes using a sieve; a dry density separation step of separating each of the plurality of fractions into porous slag and dense slag using a dry density separation device; In the magnetic separation step, a first magnetic separation process for separating metallic iron, which is a magnetic material, using a first magnetic separator; A steelmaking slag separation method, comprising: a second magnetic separation process using a second magnetic separator having a magnetic force higher than that of the first magnetic separator to separate anthracite, which is a non-magnetic material.

2. The method further includes a preliminary sieving step of separating the steelmaking slag using a sieve with a mesh size of 7 to 10 mm prior to the magnetic separation step, 2. The steelmaking slag separation method according to claim 1, wherein the steelmaking slag that has passed through the sieve in the preliminary sieving step is subjected to the magnetic separation step.

3. A steelmaking slag separation method according to claim 1 or 2, wherein in the sieving step, a sieve with a mesh size of 1 to 5 mm is used to separate the steelmaking slag after the magnetic separation step into two fractions, an over-sieve fraction and an under-sieve fraction.

4. In the dry density separation step, both an air flow centrifugal separator and an air table are used as the dry density separation device, 4. The steelmaking slag separation method according to claim 3, wherein the under-sieve fraction of the two fractions separated in the sieving step is separated using the air flow centrifugal separator, and the over-sieve fraction is separated using the air table.

5. A steelmaking slag separation system for separating powdered steelmaking slag, comprising: a magnetic separation unit that separates the steelmaking slag using a magnetic separator; a sieve unit that separates the steelmaking slag separated by the magnetic separation unit into a plurality of fractions having different particle sizes using a sieve; a dry density separation unit that separates each of the plurality of fractions into porous slag and dense slag using a dry density separation device; The magnetic separation unit is a first magnetic separation processing section that separates metallic iron, which is a magnetic material, from the steelmaking slag using a first magnetic separator; A steelmaking slag separation system having a second magnetic separation processing unit that separates anthracite, which is a non-magnetic material, from the steelmaking slag using a second magnetic separator having a magnetic force higher than that of the first magnetic separator.

6. The magnetic separation unit further includes a preliminary sieve unit that separates the steelmaking slag using a sieve with a mesh size of 7 to 10 mm prior to separation in the magnetic separation unit, The steelmaking slag separation system according to claim 5, wherein the steelmaking slag that has passed through the sieve in the preliminary sieve section is supplied to the magnetic separation section.

7. A steelmaking slag separation system as described in claim 5 or 6, wherein the sieve section uses a sieve with a mesh size of 1 to 5 mm to separate the steelmaking slag after separation in the magnetic separation section into two fractions: over-sieve and under-sieve.

8. The dry density separation unit includes both an air flow centrifugal separator and an air table as the dry density separation device, 8. The steelmaking slag separation system according to claim 7, wherein of the two fractions separated in the sieve section, the undersize fraction is separated in the air flow centrifugal separator and the oversize fraction is separated in the air table.

Images