Methods for Analyzing the Composition of Steelmaking Dust and Methods for Recycling Steelmaking Dust

Abstract

This invention provides a method for determining the composition of steelmaking dust rapidly and with good accuracy. The method comprises: a dust preparation step of preparing steelmaking dust with a moisture content of less than 10 wt%; a particle size adjustment step of adjusting the particle size of the steelmaking dust to form an analytical sample; and an analytical step of analyzing the composition of the steelmaking dust using the intensity of fluorescent X-rays from the analytical sample; wherein the maximum particle size of the analytical sample is less than 2 mm, and the powder satisfies the following formulas (1) and (2): (W1+W2) / W≦0.70･･･(1) 0.50≦W1 / W2≦0.75･･･(2)

Description

Technical Field

[0001] This invention relates to a method for analyzing the composition of steelmaking dust and a method for recycling steelmaking dust. Prior Technology

[0002] Generally speaking, steelmaking dust is generated during the high-temperature steelmaking process, when molten steel is cooled after being vaporized. While iron is the main component of steelmaking dust, elements that are easily vaporized, such as Cr, Zn, and Pb, are also present in higher concentrations.

[0003] From the perspective of reducing waste, conserving resources, and saving energy, steelmaking dust is reused in the steelmaking process as a cheap source of iron. Since the entire process from the generation of steelmaking dust to its reuse in the steelmaking process is completed within the ironworks, this method is sometimes referred to as in-plant recycling.

[0004] However, steelmaking dust also contains elements other than Fe from raw materials. Therefore, when steelmaking dust is reused as an iron source, some of these elements other than Fe may remain as impurities in the manufactured steel, potentially causing unintended effects on quality. Therefore, it is required to perform compositional analysis on steelmaking dust used as a recycling feedstock to determine the amount of impurities it contains beforehand.

[0005] Fluorescence X-ray diffraction (FXRD) is widely used as a method for analyzing the composition of steelmaking dust. When analyzing steelmaking dust using FXRD, either the briquette method or the fused bead method can be used. In the briquette method, steelmaking dust that has been pulverized into fine powder is compressed into briquettes (molded bodies) for analysis. In the fused bead method, glass beads are obtained by melting steelmaking dust with a solvent such as borate at high temperature for analysis (Patent Documents 1 and 2).

[0006] Furthermore, the composition of steelmaking dust can also be analyzed using chemical analysis methods. Examples of such chemical analysis methods include atomic absorption spectrometry and ICP (inductively coupled plasma) luminescence analysis. When using chemical analysis methods, steelmaking dust can be finely pulverized and then analyzed after decomposition with acid or alkali. [Previous Technical Documents] [Patent Literature]

[0007] Patent Document 1: Japanese Patent Application Publication No. 11-064186 Patent Document 2: Japanese Patent Application Publication No. 53-069096 Summary of the Invention

[0008] (The problem the invention aims to solve) However, conventional chemical analysis and X-ray fluorescence analysis involve complex sample preparation and require a long time to obtain analytical results. Therefore, determining the recycling volume of steelmaking dust is time-consuming, delaying the treatment of steelmaking dust, leading to increased inventory and insufficient storage space for steelmaking dust within the plant. Therefore, in order to smoothly utilize the in-plant recycling of steelmaking dust, a component analysis method that can quickly and accurately determine the composition of steelmaking dust is required.

[0009] In view of the above-mentioned problems, the present invention aims to provide a component analysis method that can quickly and accurately determine the component content of steelmaking dust. (Technical means to solve the problem)

[0010] The essence of the present invention for solving the above-mentioned problems is as follows.

[0011] 1. A method for analyzing the composition of steelmaking dust, comprising: The dust preparation steps involve preparing steelmaking dust with a moisture content of less than 10 wt%. The particle size adjustment step involves adjusting the particle size of the steelmaking dust to prepare an analytical sample; and The analytical procedure uses the intensity of fluorescent X-rays from the above-mentioned analytical sample to analyze the composition and content of the steelmaking dust. The maximum particle size of the above-analyzed sample is less than 2 mm, and it is a powder that satisfies the following formulas (1) and (2). (W1+W2) / W≦0.70･･･(1) 0.50≦W1 / W2≦0.75･･･(2) in, W1: Weight of the above-mentioned analytical samples with a particle size range of 125 μm or less. W2: Weight of the above-mentioned analytical samples with a particle size range exceeding 500 μm but less than 2 mm. W: The weight of the above-mentioned analytical samples with a particle size of less than 2 mm.

[0012] 2. The method for analyzing the composition of steelmaking dust as described in 1 above, wherein, in the dust preparation step, steelmaking dust with a moisture content of less than 10 wt% is selected from a plurality of steelmaking dust samples.

[0013] 3. The method for analyzing the composition of steelmaking dust as described in 1 above, wherein in the dust preparation step, the moisture content of the steelmaking dust is reduced to less than 10 wt% by heating the steelmaking dust.

[0014] 4. The method for analyzing the composition of steelmaking dust as described in any of 1 to 3 above, wherein in the particle size adjustment step above, a sieve with a sieve aperture size of 2 mm is used to screen the steelmaking dust and the undersize material is recovered.

[0015] 5. A method for recycling steelmaking dust, wherein the type and amount of steelmaking dust to be recycled to the steelmaking step are determined based on the component content of the steelmaking dust analyzed by any one of the steelmaking dust component analysis methods described in 1 to 4 above.

[0016] Furthermore, another aspect of the present invention is as follows.

[0017] 1. A method for analyzing the composition of steelmaking dust, comprising: The selection step involves choosing steelmaking dust with a moisture content of less than 10 wt% from the aforementioned steelmaking dust. The particle size adjustment step involves adjusting the particle size of the steelmaking dust selected in the above-mentioned selected steps to prepare an analytical sample; and The analytical procedure involves using the intensity of fluorescent X-rays from the aforementioned analytical sample to analyze the composition and content of the steelmaking dust. The maximum particle size of the above-analyzed sample is less than 2 mm, and it is a powder that satisfies the following formulas (1) and (2). (W1+W2) / W≦0.70･･･(1) 0.50≦W1 / W2≦0.75･･･(2) in, W1: Weight of the above-mentioned analytical samples with a particle size range of 125 μm or less. W2: Weight of the above-mentioned analytical samples with a particle size range exceeding 500 μm but less than 2 mm. W: The weight of the above-mentioned analytical samples with a particle size of less than 2 mm.

[0018] 2. The method for analyzing the composition of steelmaking dust as described in 1 above, wherein in the particle size adjustment step, the steelmaking dust is screened using a sieve with a sieve aperture of 2 mm, and the undersize material is recovered.

[0019] 3. A method for recycling steelmaking dust, wherein the type and amount of steelmaking dust to be recycled to the steelmaking step are determined based on the component content of the steelmaking dust analyzed by the component analysis method of steelmaking dust described in 1 or 2 above. (Compared to the effectiveness of previous technologies)

[0020] According to the present invention, a component analysis method can be provided to quickly and accurately determine the component content of steelmaking dust. Simple Explanation of the Diagram

[0021] Figure 1 is a graph showing the contents of Cr, Zn, and Pb, with the vertical axis representing the fluorescence X-ray analysis values ​​and the horizontal axis representing the chemical analysis values. Implementation

[0022] The present invention will now be described in detail. However, the present invention is not limited to the following embodiments.

[0023] (Steelmaking dust) This invention relates to a method for analyzing the composition of steelmaking dust. Here, steelmaking dust refers to the dust generated during the steelmaking process as described above, typically referring to the microparticles generated by iron evaporation and dispersion during blowing. Steelmaking dust is mainly separated and recovered from the exhaust gas using wet dust collection devices installed in the exhaust gas treatment systems of refining furnaces such as electric arc furnaces, decarburization furnaces, and smelting reduction furnaces.

[0024] In this invention, no particular type of steelmaking dust is limited and any type of steelmaking dust can be used as the analytical object. The aforementioned steelmaking dust may be, for example, selected from at least one of the group consisting of electric furnace dust, decarburization furnace dust, and molten reduction furnace dust.

[0025] The main component of steelmaking dust is usually iron oxide, thus it can be reused as a cheap source of iron in the steelmaking process. However, besides iron oxide, steelmaking dust also contains various components resulting from the use of raw materials. For example, in most cases, steelmaking dust contains silicon dioxide (SiO2) due to the silicon (Si) contained in iron ore. Furthermore, when iron scrap is used as a raw material, such as for galvanized steel sheets, the recovered steelmaking dust contains a significant amount of zinc oxide (ZnO). In converters, when lime is used as a slagging agent to remove impurities such as phosphorus or sulfur, the recovered steelmaking dust contains a significant amount of calcium oxide (CaO).

[0026] Since this invention relates to a method for analyzing the composition of steelmaking dust, it is not particularly limited and can be used to analyze steelmaking dust with any composition. Typically, the steelmaking dust contains iron oxide. Furthermore, in addition to iron oxide, the steelmaking dust may contain at least one component selected from the group consisting of SiO2, Zn, and CaO. The content of these components is not particularly limited; for example, the SiO2 content in the steelmaking dust may be 1-10% by mass. The Zn content may be 0.5-30% by mass, and the CaO content may be 1-20% by mass. Furthermore, the steelmaking dust may also contain one or both of Cr and Pb.

[0027] Furthermore, steelmaking dust can also be stainless steel dust. Stainless steel dust is the dust generated during the steelmaking process in the manufacture of stainless steel. Generally, stainless steel dust can contain 0.5% to 20% by mass of Cr and, for example, 0.03% to 0.5% by mass of Zn. Like other steelmaking dust, stainless steel dust can be recycled as an iron source.

[0028] However, stainless steel dust contains a relatively high amount of chromium (Cr), so the amount of stainless steel dust used as a recycling material must be carefully managed. That is, since the amount of Cr introduced from the pig iron manufacturing process is reflected in the Cr content of the molten iron, stainless steel dust exceeding the Cr removal capacity of the steelmaking process cannot be reused as an iron source. Therefore, this invention is particularly suitable for use with stainless steel dust.

[0029] [Methods for Compositional Analysis of Steelmaking Dust] The method for analyzing the composition of steelmaking dust in this embodiment includes: a preparation step, a particle size adjustment step, and an analysis step.

[0030] (Preparation steps) The preparation step involves using steelmaking dust with a moisture content of less than 10 wt%. If the moisture content of the steelmaking dust exceeds 10 wt%, the measured value of the component content will be lower than the actual value because X-rays are absorbed by the moisture. Therefore, from the point of view of measurement accuracy, steelmaking dust with a moisture content of less than 10 wt% must be used. There is no particular limitation on the lower limit of moisture content; it can also be 0%.

[0031] In one embodiment of the present invention, in the above-mentioned preparation step, steelmaking dust with a moisture content of 10 wt% or less is selected from a plurality of steelmaking dust. In this case, the above-mentioned dust preparation step can be referred to as the selection step. Furthermore, in another embodiment of the present invention, in the above-mentioned dust preparation step, the moisture content of the steelmaking dust is reduced to 10 wt% or less by heating the steelmaking dust. In this case, the above-mentioned dust preparation step can also be referred to as the heating step or the drying step.

[0032] In the above preparation steps, the moisture content of the steelmaking dust can be measured, or it can be omitted.

[0033] In the above preparation steps, if the moisture content of the steelmaking dust is measured to be 10 wt% or less, it is considered that steelmaking dust with a moisture content of 10 wt% or less has been prepared. In other words, in one embodiment of the present invention, in the above preparation steps, measuring the moisture content of the steelmaking dust is to provide the steelmaking dust with a moisture content of 10 wt% or less for the subsequent particle size adjustment step.

[0034] For example, in the above preparation steps, when selecting steelmaking dust with a moisture content of less than 10 wt% from a plurality of steelmaking dust, the moisture content of the plurality of steelmaking dust is measured, and steelmaking dust with a moisture content of less than 10 wt% is selected based on the measurement results.

[0035] Furthermore, in the above-mentioned dust preparation steps, when the moisture content of the steelmaking dust is reduced to below 10 wt% by heating the steelmaking dust, the moisture content of the steelmaking dust is measured after drying by heating, and it is confirmed to be below 10 wt%.

[0036] There are no particular limitations on the method used to determine moisture content; any method can be used. For example, the loss on drying, time domain reflectometry, and capacitance methods can be used. From the viewpoint of being able to perform the measurement more quickly, it is preferable to use a moisture meter using time domain reflectometry or capacitance methods.

[0037] However, the above dust preparation steps do not necessarily require actual measurement of moisture content. For example, if heating conditions that can reduce the moisture content to below 10 wt% are predetermined, and heating is carried out under these conditions, then moisture content measurement is not necessary. In this case, when determining the heating conditions in advance, the moisture content can be measured by any method, as long as it is confirmed to be below 10 wt%.

[0038] In cases other than those described above, even if no actual measurement is performed, a moisture content of 10 wt% or less is acceptable. In this case, if the moisture content measured by time-domain reflectometry is 10 wt% or less, it is considered that the moisture content of the steelmaking dust is 10 wt% or less.

[0039] (Particle size adjustment steps) In the particle size adjustment step, the particle size of the steelmaking dust is adjusted to prepare the analytical sample. The maximum particle size of the analytical sample is less than 2 mm, and the powder satisfies the above formulas (1) and (2).

[0040] • Maximum particle size: less than 2mm If the maximum particle size of the analyzed sample exceeds 2 mm, not only will the measured value be lower than the actual value, but the repeatability accuracy will also deteriorate. Therefore, from the viewpoint of measurement accuracy, the maximum particle size is set to be 2 mm or less. Furthermore, the maximum particle size can be obtained through sieve analysis. On the other hand, from the viewpoint of measurement accuracy, finer particle size is better; therefore, the lower limit of the aforementioned maximum particle size is not particularly limited and can be greater than 0 mm. That is, in one embodiment of the present invention, particle size adjustment is performed with a maximum particle size greater than 0 mm and less than 2 mm.

[0041] • Formula (1) If the combined amount of coarse and fine powders in the analytical sample is large, the measurement accuracy will decrease. Furthermore, if (W1+W2) / W exceeds 0.70, sufficient measurement accuracy cannot be obtained. Therefore, (W1+W2) / W is set to 0.70 or lower. On the other hand, there is no particular limitation on the lower limit of (W1+W2) / W. However, from the viewpoint of further improving measurement accuracy, it is preferable to be 0.40 or higher.

[0042] • Formula (2) If the content of fine powder is too high relative to the coarse powder content in the analytical sample, the measured value will be lower than the actual value. Furthermore, if W1 / W2 exceeds 0.75, sufficient measurement accuracy cannot be obtained. Therefore, W1 / W2 is set to 0.75 or lower. On the other hand, if the content of fine powder is too low relative to the coarse powder content in the analytical sample, the measurement accuracy will decrease. Furthermore, if W1 / W2 is less than 0.50, sufficient measurement accuracy cannot be obtained. Therefore, W1 / W2 is set to 0.50 or higher.

[0043] Here, W1 in equations (1) and (2) above refers to the weight of the analytical sample with a particle size of 125 μm or less. In other words, W1 refers to the mass of particles with a particle size of 125 μm or less contained in the analytical sample.

[0044] Furthermore, the weight of the W2 series analytical samples containing particles with a diameter exceeding 500 μm but less than 2 mm. In other words, the mass of particles with a diameter exceeding 500 μm but less than 2 mm contained in the W2 series analytical samples.

[0045] W represents the weight of the analytical sample with a particle size of 2 mm or less. In this invention, since the maximum particle size of the analytical sample is 2 mm or less, W can also be replaced by the weight of the analytical sample.

[0046] The units of W, W1, and W2 are set to be the same (e.g., g). Therefore, (W1+W2) / W and W1 / W2 are both dimensionless.

[0047] Furthermore, W, W1, and W2 can be obtained by sieving the analytical sample using a sieve with a corresponding mesh size and measuring the weight after sieving. Specifically, they can be obtained by the method described in the examples.

[0048] There are no restrictions on the methods used to adjust particle size during the particle size adjustment process. For example, the particle size of steelmaking dust can be adjusted by sieving.

[0049] The steelmaking dust being screened can be a portion of the steelmaking dust being analyzed. That is, it can be the steelmaking dust sampled from the steelmaking dust being analyzed and then screened.

[0050] The sieve used for sieving is not limited; any sieve can be used. When sieving, it is sufficient to recover either the material passing through the sieve or the material passing through the sieve. To set the maximum particle size of the analytical sample to below 2 mm, it is preferable to use a sieve with an aperture size of 2 mm for sieving steelmaking dust and to recover the material passing through the sieve. This allows for more rapid particle size adjustment. Preferably, a test sieve with an aperture size of 2 mm as specified in JIS Z 8801 is used.

[0051] Furthermore, the moisture content of the analytical sample is usually the same as that of the steelmaking dust before particle size adjustment. That is, the moisture content of the analytical sample is usually below 10 wt%.

[0052] (Analysis Steps) The analytical procedure involves using the intensity of fluorescent X-rays from the analytical sample to analyze the composition of steelmaking dust. More specifically, fluorescent X-ray analysis is performed on the analytical sample, and the content of at least one element contained in the analytical sample (i.e., steelmaking dust) is calculated from the measured intensity of the fluorescent X-rays.

[0053] As explained above, conventional methods for analyzing steelmaking dust using fluorescence X-ray analysis employ powder briquetting or fused bead methods. However, the briquetting process is time-consuming and requires equipment for powder crushing and compression molding. Similarly, the production of glass beads is also time-consuming and requires equipment for melting the sample. In contrast, the present invention allows the analytical sample to be directly supplied for fluorescence X-ray analysis in its powder state, eliminating the need for compression molding, melting, or other processing. Therefore, according to the present invention, the compositional analysis of steelmaking dust can be performed rapidly without the need for specialized equipment.

[0054] The fluorescence X-ray intensity from the analytical sample can be obtained using a fluorescence X-ray analysis device. From the viewpoint of rapid analysis, a fluorescence X-ray analysis device that allows for on-site analysis is preferred. Examples include, for instance, handheld, battery-powered fluorescence X-ray analysis devices. This allows for compositional analysis even in locations where steelmaking dust is generated during the steelmaking process.

[0055] During analysis, the analytical window of the fluorescence X-ray analyzer is simply placed against the sample for analysis. If the analytical window and sample are not in sufficient contact, the analytical accuracy may be reduced. Therefore, it is preferable to flatten the sample so that its smooth surface is in close contact with the analytical window without any gaps. Furthermore, it is even more preferable to expand the smooth surface to be wider than the size of the analytical window, so that the entire analytical window is covered by the sample.

[0056] During analysis, the analytical sample can also be filled into a container. When filled into a container, the analytical sample can be leveled using a scraper operation. The container shape can be, for example, cylindrical. The diameter of the portion of the analytical sample filled can be determined in accordance with the size of the analytical window of the X-ray fluorescence spectrometer. For example, it can be 15 mmφ or more. For example, when the analytical window of the X-ray fluorescence spectrometer is an 8 mmφ circle, the aforementioned steelmaking dust can be filled into a cylindrical container with an approximate 20 mmφ.

[0057] There are no particular limitations on the material of the aforementioned containers, but it is preferable to use rigid rubber such as polysiloxane. Rigid rubber, due to its appropriate hardness and elasticity, allows for a tight seal between the filled analytical sample and the analytical window. For example, a container made of rigid rubber approximately 30 mm thick with a cylindrical hole of approximately 20 mm φ can be used.

[0058] There is no particular limitation on the thickness of the analytical sample in the direction of X-ray irradiation by the X-ray fluorescence analyzer. However, if the thickness of the analytical sample is less than 10 mm, the X-ray intensity dependent on the thickness will change, leading to a deterioration in measurement accuracy. Therefore, the thickness of the analytical sample is preferably 10 mm or more. When filling the container with the analytical sample, it is preferable to set the depth of the filled portion of the analytical sample to 10 mm or more.

[0059] The elements analyzed in the above analytical steps are not particularly limited, and the content of at least one arbitrary element can be determined. Furthermore, when determining the recycling rate of steelmaking dust, the focus is often on Cr, Zn, and Pb. Therefore, it is preferable to analyze at least the contents of Cr, Zn, and Pb.

[0060] To analyze the content of a certain element, the intensity of the fluorescent X-rays emitted by that element can also be measured. For example, when analyzing the Cr content using an energy-dispersive X-ray fluorescence analyzer, the content can be calculated based on the intensity of Cr-Kα rays (5.4 keV) or Cr-Kβ rays (5.9 keV). Similarly, when analyzing the Zn content, the content can be calculated based on the intensity of Zn-Kα rays (8.6 keV) or Zn-Kβ rays (9.5 keV). When analyzing the Pb content, the content can be calculated based on the intensity of Pb-Lα rays (10.5 keV) or Pb-Lβ rays (12.6 keV).

[0061] As a method for determining the content of a component from the measured intensity of X-ray fluorescence, any method can be used, typically the standard curve method or the basic parameter method. When using the standard curve method, a standard curve (equation) showing the relationship between X-ray fluorescence intensity and the content of a specific component is prepared beforehand. Then, the content of the component is determined from the measured X-ray fluorescence intensity using the standard curve. On the other hand, the basic parameter method is a method that theoretically obtains analytical results from the measurement results. Using the basic parameter method, the content can be calculated without using a standard curve.

[0062] Alternatively, the component content can be determined using the built-in functions of the fluorescence X-ray analysis device. For example, if the fluorescence X-ray analysis device has a built-in function to determine the component content using the basic parameter method, that function can also be used.

[0063] The specific embodiments have been described above, but in other embodiments of the present invention, the method for analyzing the composition of steelmaking dust may also have, for example, the following configuration. A method for analyzing the composition of steelmaking dust, comprising: The sample preparation step involves preparing the analysis sample from the aforementioned steelmaking dust; and The analytical procedure involves using the intensity of fluorescent X-rays from the aforementioned analytical sample to analyze the composition and content of the steelmaking dust. The above-analyzed sample is a powder with a moisture content of less than 10 wt% and a maximum particle size of less than 2 mm, and satisfies the above formulas (1) and (2).

[0064] Furthermore, in other embodiments of the present invention, the method for analyzing the composition of steelmaking dust may also have, for example, the following configuration. A method for analyzing the composition of steelmaking dust, comprising: The selection step involves choosing steelmaking dust with a moisture content of less than 10 wt% from the aforementioned steelmaking dust. The particle size adjustment step involves using a sieve with an aperture size of 2 mm or less to screen the steelmaking dust, and recovering the undersize material as analytical sample; and The analytical procedure involves using the intensity of fluorescent X-rays from the aforementioned analytical sample to analyze the composition and content of the steelmaking dust. The above-analyzed sample is a powder that satisfies formulas (1) and (2).

[0065] [Methods for Recycling Steelmaking Dust] As described above, steelmaking dust can be recycled as an iron source in the steelmaking process. The steelmaking dust recycling method of this embodiment determines the type and quantity of steelmaking dust to be recycled to the steelmaking process based on the component content of the steelmaking dust analyzed using the aforementioned component analysis method. For example, the type and quantity of recycled steelmaking dust can be determined by ensuring that the total amount of a predetermined component contained in the recycled steelmaking dust falls within a predetermined range. This range can be determined based on the target value of the component content of the steel obtained in the steelmaking process. According to this method, the type and quantity of steelmaking dust designated for recycling to the steelmaking process can be precisely controlled. Therefore, by managing the inventory of steelmaking dust according to this method, inventory reduction of steelmaking dust can be promoted. Furthermore, by promoting in-plant recycling through this method, the consumption rate of the steelmaking process can be reduced.

[0066] Furthermore, steelmaking typically involves multiple steps. In this invention, steelmaking dust can be used in any of these multiple steps. For example, in one embodiment of the invention, steelmaking dust analyzed by the aforementioned compositional analysis method can be used in the sintering step. That is, steelmaking dust can be recycled as an iron source in the sintering step used to manufacture sintered ore. [Example]

[0067] The present invention will now be described in further detail with reference to embodiments. However, the present invention is not limited to the following embodiments.

[0068] (Example 1) Two types of steelmaking dust, A and B, were collected from a steelmaking plant as the subjects of analysis. For comparison, before performing the analysis using the method of this invention, the contents of Cr, Zn, and Pb in each steelmaking dust were determined by known chemical analysis methods. The obtained chemical analysis values ​​are shown in Table 1.

[0069] Next, using the steelmaking dusts A and B mentioned above, complex analysis samples with different moisture contents and particle sizes were prepared, and the contents of Cr, Zn, and Pb were determined by fluorescence X-ray analysis. The specific procedure is as follows.

[0070] First, the collected steelmaking dust was dried. Then, approximately 200g of the steelmaking dust was sieved using sieves with aperture sizes of 2mm, 1mm, 500μm, and 125μm, and the oversize or undersize material was recovered. All sieves used were test sieves as specified in JIS Z 8801. Specific sieving conditions are shown in Table 1.

[0071] In the table, examples where the "Undersize" column records the sieve aperture size and the "Oversize" column is marked with "-" indicate that a sieve with the aperture size recorded in the "Undersize" column was used for screening steelmaking dust, and the undersize was recovered. Examples where both the "Oversize" and "Undersize" columns record the sieve aperture size indicate that the sieve with the aperture size recorded in the "Undersize" column was placed on top and the sieve with the aperture size recorded in the "Oversize" column was placed on the bottom for screening steelmaking dust, and the steelmaking dust between the two sieves was recovered. Examples where both the "Oversize" and "Undersize" columns are marked with "-" indicate that no screening was performed.

[0072] Furthermore, in Nos. 9 and 19, samples were first sieved using 2 mm, 500 μm, and 125 μm sieves to obtain samples with the four particle size ranges described below. These samples were then mixed in predetermined ratios to prepare analytical samples. The particle sizes of each analytical sample are shown in Table 1. Below 1:125μm 2: 125μm or more but less than 500μm 3: Exceeding 500μm and below 2mm 4: More than 2mm

[0073] Furthermore, W1, W2, and W are obtained from the weight after sieving. Here, W1: Weight of the above-mentioned analytical samples with a particle size range of 125 μm or less. W2: Weight of the above-mentioned analytical samples with a particle size range exceeding 500 μm but less than 2 mm. W: The weight of the above-mentioned analytical samples with a particle size of less than 2 mm.

[0074] Next, the obtained steelmaking dust is filled into the container, and the top is leveled by a scraping operation. The container is a block of polysiloxane rubber with a thickness of about 30 mm and a cylindrical hole with a diameter of about 20 mm.

[0075] Next, to evaluate the effect of moisture content, moisture was added to a portion of the analytical samples to facilitate the preparation of analytical samples with different moisture contents. The moisture contents are shown in Table 1.

[0076] Next, the portion of the container filled with the analytical sample was placed against the analysis window of a fluorescence X-ray analyzer (Thermo Scientific Niton XL3t) to measure the intensity of the fluorescence X-rays emanating from the sample. The analytical conditions were set as follows: X-ray source: Rh, tube voltage: 50 kV, analysis mode: mineral analysis mode, and accumulation time: 60 seconds. The obtained fluorescence X-ray intensities were substituted into a pre-determined standard curve to calculate the content of each component. Five samples were analyzed for each condition, and the measured values ​​(average) and standard deviations were calculated. The results are shown in Table 1.

[0077] [Table 1] No. steelmaking dust Particle size adjustment Maximum particle size (mm) (W1+W2) / W W1 / W2 Moisture content (wt%) Chemical analysis value (mass%) Measured value (mass%) Standard deviation Remark sieve material Screening material Cr Zn Pb Cr Zn Pb Cr Zn Pb 1 A 500μm 1mm 1 [1.00] [0.00] 0 8.60 0.07 0.013 8.89 0.059 0.011 0.11 0.009 0.0011 Comparative example 2 - 1mm 1 0.56 [1.91] 0 8.33 0.066 0.013 0.12 0.012 0.0010 Comparative example 3 1mm 2mm 2 [1.00] [0.00] 0 8.32 0.061 0.013 0.15 0.010 0.0010 Comparative example 4 - 2mm 2 0.65 0.62 0 8.61 0.069 0.013 0.06 0.007 0.0006 Invention Examples 5 - 2mm 2 0.65 0.62 5 8.64 0.069 0.013 0.07 0.007 0.0006 Invention Examples 6 - 2mm 2 0.65 0.62 10 8.56 0.068 0.013 0.08 0.006 0.0005 Invention Examples 7 - 2mm 2 0.65 0.62

[20] 8.21 0.052 0.012 0.09 0.011 0.0011 Comparative Example 8 - 2mm 2 0.65 0.62

[30] 6.84 0.047 0.010 0.09 0.010 0.0010 Comparative Example 9 * 2 0.63 [0.27] 0 6.11 0.067 0.013 0.10 0.009 0.0014 Comparative Example 10 - - [>2] 0.65 0.62 0 7.71 0.057 0.011 0.12 0.013 0.0011 Comparative Example 11 B 500μm 1mm 1 [1.00] [0.00] 0 5.80 0.12 0.017 6.35 0.101 0.017 0.08 0.012 0.0010 Comparative example 12 - 1mm 1 0.43 [0.90] 0 5.61 0.114 0.017 0.11 0.018 0.0012 Comparative example 13 1mm 2mm 2 [1.00] [0.00] 0 5.49 0.111 0.016 0.11 0.013 0.0010 Comparative example 14 - 2mm 2 0.61 0.58 0 5.81 0.122 0.017 0.05 0.007 0.0007 Invention Examples 15 - 2mm 2 0.61 0.58 5 5.79 0.121 0.017 0.03 0.008 0.0007 Invention Examples 16 - 2mm 2 0.61 0.58 10 5.78 0.116 0.017 0.06 0.006 0.0008 Invention Examples 17 - 2mm 2 0.61 0.58

[20] 4.89 0.081 0.015 0.10 0.012 0.0011 Comparative example 18 - 2mm 2 0.61 0.58

[30] 3.33 0.071 0.015 0.14 0.012 0.0010 Comparative example 19 * 2 0.59 [0.33] 0 4.12 0.095 0.016 0.11 0.015 0.0011 Comparative example 20 - - [>2] 0.61 0.58 0 4.58 0.091 0.014 0.13 0.019 0.0016 Comparative example *After sieving using 2mm, 500μm, and 125μm sieves, mix according to a predetermined ratio.

[0078] When powder with a moisture content of less than 10 wt%, a maximum particle size of less than 2 mm, and satisfying the above formulas (1) and (2) is used as the analytical sample, it is confirmed that the deviation between the fluorescence X-ray analysis value and the chemical analysis value is small, and the standard deviation is also small.

[0079] (Example 2) On-site analysis was conducted at the dust field where steelmaking dust was stored within the ironmaking plant. First, the moisture content of the steelmaking dust was confirmed to be below 10 wt% using a moisture meter (Fujiwara Manufacturing Co., Ltd. TDR-341F). Next, samples of the steelmaking dust were collected and sieved using a test sieve with a sieve aperture size of 2 mm as specified in JIS Z 8801, and the undersize material was recovered. It was confirmed that the obtained analytical sample satisfied the above formulas (1) and (2). Then, the contents of Cr, Zn, and Pb in the obtained analytical sample were determined using a fluorescence X-ray analysis device (Thermo Scientific Niton XL3t). The above operations were performed at 15 dust fields, and the chemical analysis values ​​of the same sample were subsequently obtained. The results are shown in Figure 1.

[0080] Figure 1 shows the values ​​of Cr, Zn, and Pb, with the vertical axis representing X-ray fluorescence analysis and the horizontal axis representing chemical analysis. In each figure, the dashed lines represent the approximation of the relationship between chemical analysis and X-ray fluorescence analysis using the least squares method. Furthermore, R² in the figure is the coefficient of determination for this approximation; a value closer to 1 indicates a higher correlation.

[0081] As shown in Figure 1, the R² values ​​of Cr, Zn, and Pb are all very close to 1, and the deviation between the fluorescence X-ray analysis values ​​and the chemical analysis values ​​is small. These results indicate that the compositional analysis method of the present invention can quickly and accurately determine the compositional content of steelmaking dust.

Claims

1. A method for analyzing the composition of steelmaking dust, comprising: a dust preparation step, wherein steelmaking dust with a moisture content of less than 10 wt% is prepared; a particle size adjustment step, wherein the particle size of the steelmaking dust is adjusted to prepare an analytical sample; and an analysis step, wherein the intensity of fluorescent X-rays from the analytical sample is used to analyze the composition of the steelmaking dust; wherein the maximum particle size of the analytical sample is less than 2 mm and is a powder satisfying the following formulas (1) and (2); (W1+W2) / W≦0.70･･･(1) 0.50≦W1 / W2≦0.75･･･(2) Wherein, W1: Weight of the above-mentioned analytical sample with a particle size of 125 μm or less. W2: Weight of the above-mentioned analytical sample with a particle size of more than 500 μm but less than 2 mm. W: Weight of the above-mentioned analytical sample with a particle size of 2 mm or less.

2. As in Request 1, the method for analyzing the composition of steelmaking dust, wherein, In the above dust preparation step, steelmaking dust with a moisture content of less than 10 wt% is selected from a plurality of steelmaking dusts.

3. As in Request 1, the method for analyzing the composition of steelmaking dust, wherein, In the above-mentioned dust preparation step, the moisture content of the steelmaking dust is reduced to less than 10 wt% by heating the steelmaking dust.

4. The method for analyzing the composition of steelmaking dust as requested in any of items 1 to 3, wherein, In the above particle size adjustment step, a sieve with a sieve aperture of 2 mm is used to screen the steelmaking dust and recover the undersize material.

5. A method for recycling steelmaking dust, wherein the type and amount of steelmaking dust to be recycled to the steelmaking step are determined based on the component content of the steelmaking dust as analyzed by any one of the steelmaking dust component analysis methods in claims 1 to 4.

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