Steam aging method for slag

Abstract

To provide a method for aging slag with steam for supplying steam into a treatment tank by stacking slag layers therein, capable of improving a basic unit without treatment unevenness even if the stacking height is raised to a certain degree.SOLUTION: In a method for aging slag with steam in which the slag is piled up in a treatment tank 1 to form a slag layer A and the steam is supplied to the slag layer A, an easily ventilated point is determined based on a temperature distribution at several points in the slag layer A, and an additional layer B is placed on an upper surface of the easily ventilated point.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for steam aging of iron and steel slag to suppress expansion of the slag and stabilize it. [Background technology]

[0002] One of the important issues is how to recycle the large amounts of steelmaking slag (hereinafter simply referred to as slag) generated in the steelmaking process, such as from converters. Because slag has a hard, stony quality, it is used as roadbed material and aggregate for roads. However, steelmaking slag, in particular, contains free lime, which causes problems due to its tendency to expand upon reaction with moisture, such as rainwater. When steelmaking slag is used for roads, it is required to meet certain expansion characteristics (a water-immersion expansion ratio of 1.0% or less) (see Non-Patent Document 1). Therefore, steelmaking slag requires a process of reacting the free lime with moisture, i.e., an aging process, before use. The water-immersion expansion ratio is measured in accordance with Appendix B of Non-Patent Document 1.

[0003] A widely known method for efficiently aging steelmaking slag is the steam aging method, which uses steam to promote the reaction with water at high temperatures.

[0004] Regarding steam aging, for example, Patent Document 1 discloses a method in which steelmaking slag is stored in a container enclosed by sides and a bottom, and steam is supplied from a nozzle embedded in the steelmaking slag to rapidly react with the water at high temperature. Patent Document 2 also discloses a method in which the surface of steelmaking slag stored in a container is divided into multiple compartments, the temperature change on the steelmaking slag surface is measured in each compartment, the distribution of steam flow rates is estimated based on the temperature change, and the steam flow rate for each compartment is controlled based on the estimated steam flow rate. Patent Document 3 also discloses a method in which steelmaking slag crushed to a predetermined particle size is placed in a pressure vessel and subjected to pressurized steam aging in the pressure vessel under predetermined conditions. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 63-260842 [Patent Document 2] WO2020-209174 publication [Patent Document 3] Japanese Patent Application Publication No. 8-165151 [Non-patent literature]

[0006] [Non-Patent Document 1] JIS A5015:2018 "Iron and steel slag for roads" [Non-patent document 2] Ergun, S.: Chem. Eng. Frog., 48, 89 (1952) Summary of the Invention [Problem to be solved by the invention]

[0007] In the method disclosed in Patent Document 1, steam flow variations within the slag layer are likely to occur, which causes variations in the aging process (uneven processing). In recent years, large amounts of steelmaking slag (several thousand tons per pit) are aged in a limited area, so the slag pile height during steam aging has tended to increase to a certain level (for example, up to about 3 m). The higher the slag pile height, the more likely it is that steam flow variations within the slag layer and the resulting uneven processing during aging will occur.

[0008] This problem is also due to the uneven stacking of steelmaking slag, but due to the properties of the slag itself and the constraints of stacking work, it is practically difficult to achieve a uniform stacking state of steelmaking slag. Patent Document 1 does not consider eliminating the occurrence of the above-mentioned uneven processing.

[0009] On the other hand, Patent Document 2 proposes dividing the surface of the slag piled up in a treatment tank, which is a container for storing slag and injecting steam, into multiple compartments, and controlling the amount of steam injected based on the temperature measured for each compartment. The areas where the temperature increase is delayed are areas where the pressure loss is high due to the state of the pile, etc., and steam is difficult to pass through in the first place. Therefore, even if the amount of steam is increased, it remains a difficult area to pass through, and the steam will flow to surrounding areas with low pressure loss, so it cannot be said that the steam is being used sufficiently efficiently.

[0010] The method disclosed in Patent Document 3 can suppress the occurrence of the above-mentioned processing unevenness. However, this method requires a large-scale device because it is a processing using a pressurized container (pressurized steam aging processing), and also requires complicated processes such as pressure management, transport handling, and equipment maintenance.

[0011] Therefore, the present invention aims to provide a steam aging method for slag, in which a slag layer is piled up in a treatment tank and steam is supplied, which can prevent treatment unevenness and improve the unit consumption even if the piled up height is increased to a certain extent. [Means for solving the problem]

[0012] The present inventors have conducted extensive research to solve the above problems and have come to the following findings. (a) As mentioned above, in steam aging, which involves supplying steam into a piled slag layer, it is practically difficult to make the slag piled up uniformly, and temperature variations occur depending on the location. (a) The temperature variations that occur randomly with each treatment are closely related to the variations in the air resistance within the slag layer, and it is thought that areas with low air resistance allow water vapor to pass through more easily, causing the temperature to rise first. (c) To prevent this, it is effective to determine the locations of easily permeable areas based on the temperature distribution and / or vapor distribution at multiple locations in the slag layer and place an additional layer on top of the easily permeable areas. Here, the easily permeable areas refer to the locations in the slag layer through which steam easily passes before the additional layer is placed. Furthermore, locations in the slag layer other than the easily permeable areas are called non-easy-to-permeable areas. The additional layer is a layer for increasing the airflow resistance of the easily permeable areas. (d) This reduces the amount of ventilation in the easily ventilated areas, while increasing the amount of ventilation in the less ventilated areas. As a result, the progress of steam aging is equalized between different areas, reducing unevenness in the treatment.

[0013] The present invention has been made based on the above findings and further studies, and has the following gist and configuration. [1] In a steam aging method in which slag is piled up in a treatment tank to form a slag layer A and steam is supplied into this slag layer A, A method for steam aging of slag, characterized in that easily permeable areas are determined based on the temperature distribution at multiple points in the slag layer A, and an additional layer B is placed on top of the easily permeable areas. [2] The method for steam aging slag described in [1], wherein the additional layer B is a layer having a higher air resistance than the slag layer A. [3] The method for steam aging slag described in [2], characterized in that the additional layer B consists of fine-grained slag having an average particle size smaller than that of the slag constituting the slag layer A. [4] The method for steam aging slag according to [3], characterized in that the fine slag is undersized sieved through a sieve with mesh sizes of 1.18 to 5.6 mm. [5] The method for steam aging slag according to [3] or [4], characterized in that the thickness of the additional layer B is 0.1 to 0.3 m. [6] The method for steam aging slag according to any one of [1] to [5], wherein the slag constituting the slag layer A has an average particle size of 15 to 40 mm. [7] The method for steam aging slag according to any one of [1] to [6], wherein the slag layer A is made of steelmaking slag. [8] The method for steam aging of slag according to any one of [1] to [7], characterized in that a steam distribution is used instead of or in addition to the temperature distribution. [Effects of the Invention]

[0014] According to the present invention, in a steam aging method in which a slag layer is piled up in a treatment tank and steam is supplied, stable steam aging treatment without uneven treatment is possible even when the pile height is increased. Since the progress of the steam aging treatment is equalized between different locations, it is not necessary to extend the treatment time or increase the amount of steam injected into the non-ventilated areas, which improves the unit consumption. [Brief explanation of the drawings]

[0015] [Figure 1] In a longitudinal cross-sectional view of a treatment tank after the placement of additional layer B, which schematically shows an example of an embodiment of the present invention, (a) is an explanatory diagram showing slag layer A and additional layer B, and (b) is an explanatory diagram showing the flow of water vapor within slag layer A due to the placement of additional layer B. [Figure 2] FIG. 2 is a plan view showing an example of an installation form of thermocouples for acquiring the temperature distribution at multiple locations in the slag layer A. [Figure 3] 3 is a diagram showing an example of temperature history measured by thermocouples at the locations a-x1 to a-x5 in FIG. 2 during steam aging treatment without placing the additional layer B. FIG. [Figure 4] This is a conceptual diagram showing the temperature distribution of the top surface temperature of slag layer A measured over time with a thermal camera during steam aging treatment without placing additional layer B, using shades of color. [Figure 5] This is a graph showing an example of the relationship between the sieve size (particle size of the slag) and the pressure loss per unit aeration length of the slag for the slag that falls below the sieve when steelmaking slag is sieved, in a dry state. [Figure 6]In a longitudinal cross-sectional view of a treatment tank before the placement of additional layer B, which schematically shows an example of an embodiment of the present invention, (a) is an explanatory diagram showing slag layer A, and (b) is an explanatory diagram showing the flow of water vapor within slag layer A. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0017] As shown in FIG. 6(a), the present invention is premised on a steam aging method in which slag is piled up in a treatment vessel 1 to form a slag layer A, and steam is supplied into this slag layer A.

[0018] Under the above premise, the present invention is characterized in that the easily ventilated areas are determined based on the temperature distribution at multiple locations in the slag layer A, and an additional layer B is placed on top of the easily ventilated areas, as illustrated in Figure 1(a).

[0019] [Treatment tank] The treatment tank 1 (sometimes called a treatment pit) is composed of a curing bed, which is the bottom of the treatment tank where the slag layer A is piled up, and at least two side walls (slag holding walls) surrounding it. The curing bed is equipped with a steam pipe (not shown) that supplies steam from below into the slag layer A, forming a steam injection section 2. The size of the treatment tank 1 is determined by the curing bed area being 250 to 1000 m. 2 The height of the side walls is set to 1 to 3 m. The stacking height of slag layer A is set to 1 to 3 m. The amount of steam used per slag treatment amount is 0.04 to 0.4 (t steam / t slag treatment).

[0020] [Slag layer A] The slag to be piled in the treatment tank 1 can be steel slag for road construction. Steel slag is roughly divided into blast furnace slag and steelmaking slag. Steelmaking slag, in particular, contains free lime, and therefore has a significant effect in reducing the water immersion expansion ratio due to steam aging. Therefore, in the present invention, it is preferable that the slag layer A is a layer of steelmaking slag in order to effectively obtain this effect ([7] of the present invention). There are no limitations on the type of steelmaking slag, and it may be one or more of, for example, dephosphorization slag, desulfurization slag, converter decarburization slag, desiliconization slag, and electric furnace slag.

[0021] [Easy-to-ventilate area of slag layer A] Generally, when steelmaking slag with a particle size distribution is piled up in the treatment tank 1, particle size segregation occurs in the slag layer A, resulting in areas with a high proportion of fine particles and high pressure drop, and areas with a high proportion of coarse particles and low pressure drop. Steam injected from the steam injection section 2 preferentially flows through areas with low pressure drop, forming a "pathway" for the steam. Once formed, this "pathway" is difficult to change without particle rearrangement. As a result, as shown in Figure 6(b), in the slag layer A before the placement of the additional layer B, permeable areas (thick arrows indicating the flow of steam) and non-permeable areas (thin arrows indicating the flow of steam) are formed, resulting in uneven steam aging. In the example in Figure 6, permeable areas with a high proportion of coarse particles are unevenly distributed in the horizontal center, while non-permeable areas with a high proportion of fine particles are unevenly distributed at both ends.

[0022] [Temperature distribution] The time required for the easily permeable areas to reach the maximum temperature (approximately 100°C) is shorter than that required for the non-easy-permeable areas. Therefore, based on the information on the temperature distribution at multiple locations within the slag layer A, it is possible to determine the easily permeable areas as those locations where the temperature rise is leading, i.e., excluding the locations where the temperature rise is delayed.

[0023] The temperature distribution can be detected by using thermocouples or a thermal camera to monitor the temperature (measure the temperature over time) at multiple locations in slag layer A during the steam aging treatment before laying additional layer B. Thermocouples or a thermal camera can be used for this temperature monitoring.

[0024] (a) Use of thermocouples The method for detecting the temperature distribution inside a slag layer using thermocouples is described below. For example, as shown in Figure 6, thermocouples 3 are installed at multiple locations inside slag layer A and used to monitor the temperature. The installation heights of the multiple thermocouples 3 (the heights of the thermocouple temperature measurement points from the curing bed) are preferably the same so that the temperature distribution within the same plane can be obtained at the same time. The installation height of the thermocouples 3, which is the ratio of the height to the piled height of slag layer A, is preferably 0.6 or greater. If the height ratio is less than 0.6, it is difficult to determine the speed of the temperature rise between locations. In Figure 6(b), the height ratio is approximately 0.7.

[0025] Furthermore, it is preferable that the spacing between adjacent thermocouples at multiple locations for acquiring the temperature distribution be such that the "relative spacing," which is the ratio of the spacing to the stacked height of the slag layer A, is in the range of 0.2 to 2.0. If the relative spacing is less than 0.2, the spacing between adjacent thermocouples will be too narrow, and the number of thermocouples per easily permeable location may be excessive. If the relative spacing is more than 2.0, the spacing between adjacent thermocouples will be too wide, and the reliability of the determination of easily permeable locations may be impaired.

[0026] Figure 2 shows an example of the thermocouple installation configuration, where the processing area (area of the upper surface) of slag layer A is x (m) × y (m), and the thermocouple installation locations are the intersections (referred to as a-x1, etc.; a total of 30 points) of vertical lines on x coordinates x1 to x5 and horizontal lines on y coordinates a to f. For example, if the piled height of slag layer A is 3 m, the preferred range for the adjacent thermocouple spacing is 0.6 m to 6 m, which is 0.2 to 2.0 times 3 m.

[0027] Figure 3 shows an example of the temperature history measured by thermocouples at locations a-x1 to a-x5 (a total of five locations) in Figure 2 during steam aging treatment without the placement of additional layer B. As shown in Figure 3, the time it takes for the temperature to reach 100°C can vary by half a day to a day depending on the location in slag layer A. In the example in Figure 3, locations a-x1, a-x2, and a-x5 can be determined to be easily permeable locations based on the temperature history approximately 12 to 24 hours after the start of treatment.

[0028] (b) Use of thermal cameras This section explains how to detect the temperature distribution on the top surface of a slag layer using a thermal camera. Measurement data is obtained for a number of points corresponding to the pixels of the thermal camera. The measurement data for each pixel can be acquired directly, or as a continuous value with the pixels interpolated, or the interpolated data can be appropriately subdivided into multiple sections.

[0029] Figure 4 shows an example of a temperature distribution obtained by monitoring the temperature of the top surface of slag layer A with a thermal camera during steam aging without the placement of additional layer B. The stacking state of slag layer A is the same as in the example shown in Figure 2. The top surface of slag layer A is divided into 30 rectangular sections, divided into 5 sections in the x direction and 6 sections in the y direction, and the maximum temperature within each rectangle is the temperature associated with the temperature distribution. In the example shown in Figure 4, after approximately 12 to 24 hours of treatment, the different sections can be distinguished by their different shading, and the dark sections can be identified as easily ventilated areas. Thus, using a thermal camera, as with the use of thermocouples, allows for the identification of easily ventilated areas based on the temperature distribution at multiple locations. Therefore, the progress of the steam aging process can be ascertained depending on the location of slag layer A.

[0030] [Fume distribution in slag layer] In the present invention, the easily permeable areas may be determined by acquiring information on the steam distribution instead of or in addition to acquiring information on the temperature distribution ([8] of the present invention). Here, the steam distribution refers to the distribution of steam points, which are steam emission points on the top surface of the slag layer A. The steam points can be identified visually, and unevenly distributed steam points are considered to correspond to easily permeable areas and can be determined to be easily permeable areas. The uneven distribution of steam points can be confirmed by visually observing the top surface of the slag layer A at predetermined intervals (for example, every 1 to 8 hours) during the steam aging treatment before the placement of the additional layer B. This method of acquiring steam distribution information can be used in combination with the above-mentioned method based on temperature distribution, or can be used alone.

[0031] [Additional layer B] As shown in Figure 1(a), additional layer B is placed on top of the easily permeable areas determined based on the temperature distribution or the steam distribution. This increases the pressure loss at the easily permeable areas, balancing it with the pressure loss at the non-easy permeable areas, thereby suppressing uneven processing. Figure 1(a) illustrates an example of an additional layer B placed on top of the easily permeable areas (shown by the thick arrows) determined in Figure 6(a). Figure 1(b) illustrates an example of an additional layer B placed on top of the easily permeable areas (shown by the thick arrows), increasing the airflow resistance at the easily permeable areas and increasing the pressure loss. As a result, the steam in the easily permeable areas is deflected toward the non-easy permeable areas, promoting steam aging in the non-easy permeable areas (shown by the thick arrows). This equalizes the progress of steam aging between the easily permeable and non-easy permeable areas.

[0032] In the present invention, it is not necessary to increase the amount of steam used in areas where steam aging progresses slowly or to unnecessarily extend the retention time in areas where steam aging progresses quickly, as is the case in conventional steam aging treatment operations, and it is possible to improve the unit consumption.

[0033] In order to increase the pressure loss at the easily permeable portions of the slag layer A, the additional layer B is preferably a layer with a higher airflow resistance than the slag layer A (refer to [2] of the present invention). An example of the additional layer B with a higher airflow resistance than the slag layer A is a layer made of fine slag with a smaller average particle size than the slag constituting the slag layer A, i.e., a fine slag layer (refer to [3] of the present invention). In the example of Figure 1(a), the additional layer B is a fine slag layer. Here, the average particle size is defined as the particle size at which the cumulative undersize distribution value is 50%, i.e., D50 (median diameter).

[0034] [Preferred particle size of fine slag] The fine slag is preferably sieved through a sieve size of 1.18 to 5.6 mm (refer to [4] of the present invention). If the sieve size is less than 1.18 mm, the pressure loss is too large and the aging of the additional layer B is insufficient. If the sieve size is more than 5.6 mm, the difference in pressure loss between the slag layer A and the additional layer B may be insufficient.

[0035] The thickness of the fine slag layer (additional layer B) is preferably 0.1 to 0.3 m ([5] of the present invention). If the thickness is less than 0.1 m, the effect of increasing the air resistance (increasing pressure loss) of the easily permeable areas may be insufficient. On the other hand, if the thickness exceeds 0.3 m, the pressure loss will be too large, resulting in insufficient aging of the additional layer B.

[0036] In the following explanation (including examples), when the particle size (not the average particle size) of the slag is simply stated as "less than ... mm," it means that the particle size is under the sieve mesh of the numerical value. Also, as will be described later, when the particle size is stated as "more than ... mm," it means that the particle size is over the sieve mesh of the numerical value.

[0037] The Ergun equation (see Non-Patent Document 2) is well known for explaining the pressure loss when gas passes through powder and granular materials. According to this equation, if the powder and granular materials have a uniform particle size (a uniform state with no particle size distribution), the smaller the particle size, the greater the pressure loss. Generally, powder and granular materials handled have a particle size distribution, and when the particle size distribution changes, both the specific surface area and void ratio according to the Ergun equation change, resulting in a change in airflow resistance. If there is a range of particle sizes among the particles making up the powder and granular materials, the proportion of fine particles increases, increasing the specific surface area and allowing the fine particles to infiltrate between the coarse particles, reducing the void ratio and increasing the pressure loss.

[0038] Steelmaking slag samples of each particle size standard specified in Non-Patent Document 1 were sieved, and the pressure loss of the sample that fell under the sieve was measured. Air was introduced into a particle layer packed in a cylindrical container, and the flow rate was measured with a flow meter while adjusting it to a predetermined value, and the pressure loss was measured with a pressure gauge. An example of the pressure loss measurement results for the sample that fell under the sieve is shown in Figure 5. As shown in Figure 5, the pressure loss in the particle layer increases as the particle size of the sample becomes finer, but the increasing trend becomes stronger around a sieve opening of 5 mm, and it was found that the pressure loss increases sharply around a sieve opening of 1 mm.

[0039] If there is a fine slag layer with a particle size of 5 mm or less as additional layer B, steam cannot flow freely there and a large pressure loss occurs, so it can be used as additional layer B with a high pressure loss.

[0040] The fine slag may be obtained by classifying the slag to be aged, but is not limited thereto and may be prepared separately. In other words, if the slag to be aged is classified each time and the use of the fine slag increases processing costs, slag layer A may be formed without classifying the slag to be aged, and additional layer B may be formed using fine slag that has been prepared separately.

[0041] Furthermore, when using fine slag obtained by classifying the slag to be aged in additional layer B, all of the fine slag of a specified particle size contained in the target slag (for example, undersize slag with a sieve opening of 5.6 mm or less) may be used, or a portion may be used and the remainder may be retained in the target slag.

[0042] The additional layer B is not limited to the fine slag layer mentioned above; any material that increases pressure loss, such as a fine-mesh filter sheet or porous material, can be used. Since such materials are placed on top of the slag layer A, a flexible material with good conformability is preferable. For materials to be recovered after the steam aging process, it is desirable for them to be heat-resistant to approximately 120°C, as they will be exposed to steam. For example, a vinyl sheet with low water vapor permeability can be used. Alternatively, materials that do not need to be recovered after the steam aging process can also be used. Materials other than the fine slag layer that are used as additional layer B are removed after a certain period of time has passed after the process is completed.

[0043] [Layout method for additional layer B] The timing for determining the easy-to-ventilate areas and laying out the additional layer B can be selected appropriately depending on the specifications of the treatment tank 1, the stacking height of the slag layer A, etc., and is not particularly limited. In the example of Figure 3, the easy-to-ventilate areas can be determined 12 hours after the start of treatment, and the layout can be carried out as soon as this is determined. In addition, the airflow resistance can be varied depending on the degree of temperature rise in the easy-to-ventilate areas. For example, the average particle size and thickness of the fine slag layer as the additional layer B can be changed.

[0044] The work of laying additional layer B can be carried out using a shovel, a mobile belt conveyor, a gantry type, a chain block type, an arm type crane, or a robot.

[0045] [Slag in slag layer A] The slag constituting the slag layer A is not particularly limited, but it is preferable to use slag that is in high demand for roads and has a larger average particle size than the additional layer B. Examples of such slag include slag with an average particle size of 15 to 40 mm ([6] of the present invention).

[0046] The piled height of the slag layer is preferably 1 to 3 m. If the piled height is less than 1 m, the number of piles increases unnecessarily, which may reduce the treatment efficiency. If the piled height exceeds 3 m, it may be difficult to suppress uneven treatment. [Example]

[0047] Steelmaking decarburization slag crushed to pieces under 37.5 mm and conforming to the CS-40 particle size standard (see Non-Patent Document 1) was used as the test material for aging. The particle size distribution is shown in Table 1. The average particle size (median) of this test material (slag layer A) was 19 mm. Steelmaking slag (converter furnace decarburization slag) was piled to a layer thickness (piling height) of approximately 3 m in a steam aging treatment vessel 1 (treatment capacity: approximately 2,800 t) with multiple steam pipes installed at the bottom (curing bed). This piled bed (slag layer A, top surface area: 24 m × 20 m) was subjected to steam aging treatment for 5 days.

[0048] In the present invention, the determination of easily ventilated areas was made based on the temperature distribution obtained by monitoring the temperature with thermocouples 3 installed at multiple locations in the slag layer A. The thermocouples 3 were arranged at intervals of approximately 4 m, with x = 20 m and y = 24 m in Figure 2.

[0049] As a comparative example, an operation was performed without placing additional layer B during the treatment. The temperature history shown in Figure 3 was obtained for the thermocouple temperatures at a-x1 to a-x5. It is expected that the pressure loss in slag layer A was high at a-x3 and a-x4, which prevented steam from passing through well. Parts of the other areas b to f also showed delayed temperature rise.

[0050] In this example, the temperature history of all 30 points a to f was monitored, and based on the acquired temperature distribution, points exceeding 60°C 12 hours after the start of steam aging were determined to be easily permeable points. On top of these easily permeable points, fine-grained steelmaking slag of 5 mm or less was placed 0.1 m thick as additional layer B. The average particle size of this additional layer B was 2.36 mm. This placement was performed using a moving belt conveyor.

[0051] Table 2 shows the results of comparing the time it took for the sample to reach 98°C for all 30 samples a to f. Looking at the average values, the inventive example was better than the comparative example, but the difference between the two was only about 1 hour. However, when comparing the maximum time it took to reach 98°C, the comparative example took 31.5 hours and the inventive example took 26 hours, a difference of 5 hours.

[0052] In the comparative example, as in the conventional example, the processing time and steam amount are set according to the location where the progress of the aging process is delayed in order to prevent untreated steam aging. Therefore, the processing efficiency and steam consumption rate are worse than those of the present invention example by the difference in the maximum time required for temperature rise. In other words, it can be seen that the processing efficiency and steam consumption rate are improved according to the present invention compared to the conventional example.

[0053] [Table 1]

[0054] [Table 2]

[0055] After treatment, the water immersion expansion ratio of both the inventive example and the comparative example was measured in accordance with Appendix B of Non-Patent Document 1, and it was confirmed that the ratio passed the test (1.0% or less). [Explanation of symbols]

[0056] 1 Treatment tank 2 Steam blowing section 3 Thermocouples A Slag layer B Additional layer

Claims

1. In a steam aging method, slag is piled up in a treatment tank to form a slag layer A, and steam is supplied into the slag layer A, A method for steam aging of slag, characterized in that easily permeable areas are determined based on the temperature distribution at multiple points in the slag layer A, and an additional layer B, which has a higher air resistance than the slag layer A, is placed on top of the easily permeable areas.

2. 2. The method for steam aging slag according to claim 1, wherein the additional layer B comprises fine-grained slag having an average grain size smaller than that of the slag constituting the slag layer A.

3. The method for steam aging slag according to claim 2, characterized in that the fine slag is undersized after sieving with a mesh size of 1.18 to 5.6 mm, and / or the thickness of the additional layer B is 0.1 to 0.3 m.

4. 4. The method for steam aging slag according to claim 1, wherein the slag constituting the slag layer A has an average particle size of 15 to 40 mm.

5. The method for steam aging slag according to any one of claims 1 to 3, characterized in that the slag layer A is made of steelmaking slag.

6. 5. The method for steam aging slag according to claim 4, wherein the slag layer A is made of steelmaking slag.

7. 4. The method for steam aging of slag according to claim 1, wherein a steam distribution is used instead of or in addition to the temperature distribution.

8. 5. The method for steam aging of slag according to claim 4, wherein a steam distribution is used instead of or in addition to the temperature distribution.

9. 6. The method for steam aging of slag according to claim 5, wherein a steam distribution is used instead of or in addition to the temperature distribution.

10. 7. The method for steam aging of slag according to claim 6, wherein a steam distribution is used instead of or in addition to the temperature distribution.

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