Slag aging method

Abstract

To provide a slag aging method capable of inhibiting expansion of a product using slag by reducing variation in aging with respect to the slag with a simple method.SOLUTION: A slag aging method is intended to carry out aging of slag by supplying water vapor to a sediment 3 formed by stacking the slag. The method includes an inhibition processing step of increasing a ventilation resistance of water vapor in an excessively small ventilation resistance part 8 in the sediment 3 which is present at least on a side of an outer peripheral part 5 of the sediment 3, and which has a smaller water vapor ventilation resistance than other parts.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for aging slag by hydrating the slag to suppress expansion of products using the slag, and more particularly to a method for aging the slag by steam. [Background technology]

[0002] In the steel industry, slag is produced as a by-product from processes such as blast furnaces, pretreatment processes (e.g., torpedo cars), converters, and electric furnaces. Among these, the slag produced from pretreatment processes, converters, and electric furnaces is specifically referred to as steelmaking slag. In the steelmaking process, a large amount of lime is added as an auxiliary material to remove phosphorus and silicon from molten pig iron. As a result, undissolved lime and lime crystallized during cooling remain in the steelmaking slag as free calcium oxide (f-CaO). This f-CaO undergoes hydration to form calcium hydroxide (Ca(OH)2), which expands in volume approximately twice that of f-CaO. Therefore, if the f-CaO in steelmaking slag hydrates and expands in volume, the steelmaking slag may pulverize. This pulverization may result in the steelmaking slag's particle size deviating from the specified size. There is also concern that the steelmaking slag may expand after shipping.

[0003] Applications of steelmaking slag include roadbed material and fine aggregate for concrete. In these applications, if the volume of f-CaO in the steelmaking slag expands due to hydration, it may cause the roadbed to bulge or cracks to form in the concrete. Therefore, steelmaking slag used for the above applications is required to satisfy the expansion characteristics specified in JIS A 5015. Currently, steelmaking slag is aged in air or steam before shipping to stabilize its volume. This reduces the risk of expansion or powdering of the steelmaking slag after shipping (see, for example, Patent Documents 1, 2, and 3).

[0004] Specifically, Patent Document 1 describes a slag treatment method in which slag is charged into a rotating drum and sprayed with water to generate steam, which is then used to age the slag. Patent Document 2 describes a method for manufacturing roadbed material in which steelmaking slag stored in a container is aged by supplying steam to the slag. Patent Document 3 describes a method for aging steelmaking slag by supplying steelmaking slag and pressurized steam to a pressure vessel. Note that air aging refers to a method for aging steelmaking slag in which the slag is stored for a long period of time in a slag yard or the like to cause a hydration reaction between moisture in the air and the f-CaO in the steelmaking slag. Steam aging refers to a method for aging steelmaking slag in which steam is supplied to the steelmaking slag to cause the above-mentioned hydration reaction.

[0005] Patent Documents 4 and 5 describe a method for aging steelmaking slag in which a slag layer formed by piling up steelmaking slag is provided with an air-permeability-resistant layer on top of the slag layer, thereby generating a circulating flow of steam within the slag layer and suppressing aging variations (uneven processing). Patent Document 6 discloses a method for performing stable steam aging by changing the deposition state of the slag while supplying steam to the slag. Furthermore, Non-Patent Document 1, as a related technology, describes the wall effect, in which, when particles are packed into a specified container, the porosity of particles near the container wall is greater than the porosity of particles near the container center. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-227490 [Patent Document 2] Patent No. 2814481 [Patent Document 3] Patent No. 2873178 [Patent Document 4] Japanese Patent Application Publication No. 2020-117420 [Patent Document 5] Japanese Patent Application Publication No. 2020-121899 [Patent Document 6] Japanese Patent Publication No. 2020-152601 [Non-patent literature]

[0007] [Non-Patent Document 1] M.Suzuki, T.Shinmura, K.Iimura and M.Hirota: Advanced Powder Technology, Vol. 19, Issue 2, 2008, p.183-195. Summary of the Invention [Problem to be solved by the invention]

[0008] The aging method described in Patent Document 1 may require a long aging process time.

[0009] In the aging method described in Patent Document 2, the flow of steam in the slag layer may become uneven, which may result in variations in aging.

[0010] The aging method described in Patent Document 3 may result in a reduction in the amount of steelmaking slag to be aged, i.e., the processing volume, and may require time and costs for equipment maintenance and handling.

[0011] The aging methods described in Patent Documents 4 and 5 require the provision of a layer with high airflow resistance, which takes time and costs.

[0012] The aging method described in Patent Document 6 takes time and costs money to change the deposition state of the steelmaking slag.

[0013] The present invention has been made to solve the above-mentioned problems, and aims to provide a method for aging slag that can reduce variation in aging of slag in a simple manner and suppress expansion of products using slag. [Means for solving the problem]

[0014] In order to achieve the above object, the present invention provides: [1] A slag aging method for ageing a deposit formed by piling up slag by supplying steam to the deposit, the method comprising an inhibition treatment step of increasing the resistance to the passage of steam in a low-resistance portion of the deposit that is present at least on the outer periphery of the deposit and has a lower resistance to the passage of steam compared to other portions. [2] The slag aging method described in [1] above, wherein in the inhibition treatment step, air is blown to the low air resistance portion to resist the water vapor flow in the deposit, or water is sprayed on the low air resistance portion. [3] The slag aging method described in [1] above, wherein in the inhibition treatment process, additional slag having a smaller particle size than the slag forming the deposit is piled on top of the low air resistance portion. [4] The slag aging method according to [1] above, wherein the low air resistance portion is in a range that satisfies the following formula: X≧10×D "X" is at least one of the distance (mm) from the edge of the top surface of the deposit and the distance (mm) from a wall when a wall is installed around at least a portion of the periphery of the deposit and the deposit is in contact with the wall, and "D" is the maximum particle size (mm) of the slag. [5] The slag aging method described in [2] above, wherein the low air resistance portion is in a range that satisfies the following formula: X≧10×D "X" is at least one of the distance (mm) from the edge of the top surface of the deposit and the distance (mm) from a wall when a wall is installed around at least a portion of the periphery of the deposit and the deposit is in contact with the wall, and "D" is the maximum particle size (mm) of the slag. [6] The slag aging method according to [3] above, wherein the low air flow resistance portion is in a range that satisfies the following formula: X≧10×D "X" is at least one of the distance (mm) from the edge of the top surface of the deposit and the distance (mm) from a wall when a wall is installed around at least a portion of the periphery of the deposit and the deposit is in contact with the wall, and "D" is the maximum particle size (mm) of the slag. [7] A method for aging slag described in any of [1] to [6] above, further comprising a temperature measurement process for measuring the surface temperature of the deposit, and in the inhibition treatment process, the areas where the surface temperature is measured and the surface temperature is higher than the other areas are designated as the areas with low air resistance. [Effects of the Invention]

[0015] According to the present invention, in the inhibition treatment process, the airflow resistance is increased in the low-airflow resistance portion, which has a lower airflow resistance than other portions. The inhibition treatment process is a relatively simple method, since it is sufficient to increase the airflow resistance. As a result, water vapor is less likely to escape from the deposit as a whole, which means that the variation in airflow resistance is reduced. This reduces the variation in slag aging. This allows the expansion of products using slag after shipping to be suppressed. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a diagram illustrating an example of an aging treatment facility. [Figure 2] FIG. 1 is a diagram illustrating an example of an inhibition processing device. [Figure 3]This figure shows an example of the relationship between the depth from the top surface of a deposit other than the portion of the deposit with excessively low air resistance and the estimated pressure loss at that depth when the deposit is formed from slag of product particle size. [Figure 4] FIG. 10 is a perspective view showing another example of an aging treatment facility. [Figure 5] FIG. 5 is a cross-sectional view showing a part of the aging treatment facility shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0017] (First embodiment) Hereinafter, embodiments of the present invention will be described. The slag according to the present invention is a by-product of the steelmaking process and contains f-CaO. Examples of steelmaking processes that produce the slag include pretreatment and refining. Therefore, the slag is sometimes referred to as steelmaking slag. Because the slag contains f-CaO, it is piled in an aging treatment facility and aged to convert the f-CaO into Ca(OH)2 by reacting the f-CaO with water. In the aging method according to the present invention, steam is supplied from the bottom of the pile formed by piling the slag in the aging treatment facility to react the f-CaO with water.

[0018] FIG. 1 is a diagram showing an example of an aging treatment facility. The aging treatment facility 1 shown in FIG. 1 has a permeation layer 2 that supplies steam to the slag, and slag is piled on top of the permeation layer 2 to form a slag pile, or deposit 3. The shape of the deposit 3 is not limited, but may be frustum-shaped, as shown in FIG. 1. The permeation layer 2 supplies steam almost evenly to the bottom surface of the slag deposit 3 shown in FIG. 1. Multiple steam pipes 4 are buried in the permeation layer 2, and these steam pipes 4 are connected to a steam supply source (not shown). The steam supply source may be a conventionally known source, such as a boiler.

[0019] The deposit 3 shown in Figure 1 has a truncated cone shape, and therefore the outer peripheral surface of the deposit 3 is inclined downward. The angle between this inclined surface and the permeation layer 2 is approximately the same as the angle of repose of the slag. The amount of slag deposited in the vertical direction is smaller in the outer peripheral portion 5 of the deposit 3, where the inclined surface is formed, than in the central portion 6 of the deposit 3 (the central portion of the deposit 3 in the horizontal direction in Figure 1). Furthermore, the particle size of the slag varies, and small-particle slag has lower fluidity than large-particle slag. Therefore, small-particle slag tends to remain where it is piled. In contrast, large-particle slag tends to flow from the piled area to the surrounding area. As a result, large-particle slag tends to collect near the outer peripheral portion 5, and the gaps between the slag are larger than in the central portion 6, reducing the airflow resistance and allowing water vapor to escape more easily.

[0020] A predetermined range from the edge of the top surface of the deposit 3 toward the central portion 6 is a portion 7 (hereinafter referred to as the intermediate portion) where the airflow resistance of water vapor is lower than that of the central portion 6 due to the influence of the outer peripheral portion 5. In the following explanation, the outer peripheral portion 5 and the intermediate portion 7 will be collectively referred to as the extremely low airflow resistance portion 8. The above range can be determined by experiments or calculations, and an example of a formula for calculating the range is described below. In the example shown in Figure 1, "X" in the following formula (1) is the distance (mm) from the edge of the top surface of the deposit 3 toward the central portion 6, and "D" is the maximum particle size (mm) of the slag to be stacked in the aging treatment facility 1. In this embodiment, the above-mentioned extremely low airflow resistance portion 8 is the range that satisfies at least the following formula (1). X≧10×D (1)

[0021] That is, in this embodiment, for example, the extremely low airflow resistance portion 8 is a distance obtained by multiplying at least the maximum particle size (mm) of the slag by 10. Note that the upper limit of the extremely low airflow resistance portion 8 is, for example, a distance obtained by multiplying the maximum particle size (mm) of the slag by 50 (X≦50×D).

[0022] In this embodiment, an inhibition process is performed to make it difficult for water vapor to escape by increasing the airflow resistance in the extremely low airflow resistance portion 8. Specifically, water is sprayed or air is blown onto the extremely low airflow resistance portion 8 to resist the water vapor flow in the extremely low airflow resistance portion 8.

[0023] FIG. 2 is a diagram showing an example of an inhibition treatment device that sprays water or blows air onto the extremely low airflow resistance portion 8. The inhibition treatment device 9 shown in FIG. 2 has a spray pipe 10 that sprays water or blows air while in contact with the deposit 3 above the extremely low airflow resistance portion 8, while not in contact with it, or while inserted into the deposit 3. In the example shown in FIG. 2, the spray pipe 10 is arranged at a distance from the deposit 3 above the extremely low airflow resistance portion 8. One end of the spray pipe 10 is airtightly closed, and the other end of the spray pipe 10 is connected via a supply pipe 11 to an air source (not shown) such as a blower or compressor, or a water source (not shown).

[0024] The spray pipe 10 has a plurality of openings (not shown) that penetrate the pipe thickness direction and are spaced apart along its length. These openings (not shown) allow continuous or intermittent airflow or water spraying to the low-airflow resistance portion 8. The water may be industrial water. In the above embodiment, an air source or a water supply source is connected to the spray pipe 10 to either spray air or spray water onto the deposits 3. However, an air-powered inhibition treatment device 9 connected to the air source and a water-powered inhibition treatment device 9 connected to the water source may be provided, allowing selection of either airflow or water spraying depending on the conditions. The choice of whether to perform airflow or water spraying as the inhibition treatment is determined by comprehensively considering factors such as the installation space (surrounding environment) for the air source and the water supply source, installation costs, and equipment constraints of the aging treatment facility 1.

[0025] FIG. 3 shows an example of the relationship between the depth from the top surface of the deposit (excluding the extremely low airflow resistance portion) and the estimated pressure loss at that depth (hereinafter simply referred to as "pressure loss") when the deposit is formed from slag of product particle size. The "product particle size" refers to the particle size of slag that can be shipped as a product. In this embodiment, the particle size satisfies the CS40 standard specified in JIS A 5015, for example. The "depth" refers to the vertical distance from the top surface of the deposit 3. As shown in FIG. 3, the pressure loss per unit depth is approximately 0.1 kPa / m. Therefore, the airflow rate and water spray rate of the inhibition treatment device 9 are preferably set to an amount that can increase the pressure loss near the surface of the extremely low airflow resistance portion 8 by approximately 0.1 kPa / m. The airflow rate and water spray rate that can increase the pressure loss by approximately 0.1 kPa / m can be determined in advance through experimentation.

[0026] Furthermore, it is preferable that the temperature difference between the steam supplied to the slag pile 3 and the water used for watering or the air used for ventilation is small. This is because if the temperature difference is large, the steam will be cooled by the water or air and condense, turning into liquid water. This liquid water may then fill the gaps between the slag particles, preventing the steam from flowing through the gaps. This is to avoid this situation. In other words, this is to maintain the flow of steam through the gaps while increasing the pressure loss in that state. Therefore, it is preferable to provide a temperature adjustment device that adjusts the temperature of the water used for watering or the air used for ventilation.

[0027] (Operation of the first embodiment) The operation of the aging treatment facility shown in Figure 1 will be described. Slag is piled in the permeation layer 2 of the aging treatment facility 1 shown in Figure 1 to form a frustum-shaped deposit 3. Steam is supplied from the permeation layer 2 to the bottom of the deposit 3. The steam flows through the gaps between the slag particles. The outer periphery 5 and middle 7 of the deposit 3 may be areas of low airflow resistance 8, through which steam can easily escape, due to the above-mentioned principle. Therefore, an inhibition treatment device 9 is used to blow air or spray water onto the areas of low airflow resistance 8. Specifically, a spray pipe 10 of the inhibition treatment device 9 is placed on the inclined surface of the outer periphery 5 or on the top surface of the middle 7. Alternatively, the spray pipe 10 is inserted under the surface of the outer periphery 5 or the middle 7. In this state, air or water is continuously or intermittently sprayed onto the areas of low airflow resistance 8. The process of blowing air or spraying water using the inhibition treatment device 9 corresponds to the inhibition treatment process of this invention.

[0028] This allows air or water to flow against the steam flow in the gaps between the slag particles in the extremely low airflow resistance portion 8. This increases the steam resistance, i.e., the pressure loss, in the extremely low airflow resistance portion 8. As a result, steam leakage from the extremely low airflow resistance portion 8 can be suppressed compared to before the air supply or water spraying. This allows the steam to be distributed throughout the deposit 3 and increases the contact time between the steam and the slag. This also promotes the hydration reaction of f-CaO in the slag, reducing variations in aging and insufficient aging throughout the deposit 3.

[0029] Instead of blowing air or spraying water onto the extremely low airflow resistance portion 8, the airflow resistance of water vapor in the extremely low airflow resistance portion 8 may be increased by piling up slag (hereinafter referred to as additional slag). The additional slag is preferably slag having an overall smaller particle size than the slag having the product particle size. Specifically, it is preferable that the average particle size of the additional slag is equal to or smaller than the average particle size of the slag having the product particle size, and that the maximum particle size is equal to or smaller than one-third of the maximum particle size of the slag having the product particle size. This is because the additional slag functions as a lid for the extremely low airflow resistance portion 8. The above-mentioned additional slag corresponds to the other slag in this invention.

[0030] The amount of additional slag piled up in the low-air-permeability resistance section 8, i.e., the thickness of the additional slag in the vertical direction of the pile 3, is preferably 60 cm or less, and more preferably about 20 cm. This is to avoid the gaps between the additional slag particles being smaller than the gaps between the slag particles in the low-air-permeability resistance section 8, which makes it difficult for water vapor to flow and may result in insufficient aging of the additional slag itself. Furthermore, the means for piling up the additional slag is not limited, and any conventional means used to pile slag on the low-air-permeability resistance section 8 may be used, such as a wheel loader or bulldozer, to pile slag into the aging treatment facility 1.

[0031] Additional slag is piled on the extremely low airflow resistance portion 8 of the deposit 3 by a predetermined means so that the thickness of the additional slag layer is approximately 20 cm to 60 cm. This increases the steam resistance, i.e., pressure loss, in the extremely low airflow resistance portion 8. The additional slag functions as a lid for the extremely low airflow resistance portion 8, suppressing steam leakage from the extremely low airflow resistance portion 8. This promotes the hydration reaction of f-CaO in the slag in the extremely low airflow resistance portion 8, thereby reducing variations in aging and insufficient aging throughout the deposit 3. Furthermore, since the additional slag is not piled up excessively, the additional slag can also be aged approximately uniformly. The process of piling additional slag on the extremely low airflow resistance portion 8 corresponds to the inhibition treatment process in this invention.

[0032] (Second embodiment) FIG. 4 is a perspective view showing another example of an aging treatment facility. FIG. 5 is a cross-sectional view showing a portion of the aging treatment facility shown in FIG. 4. The aging treatment facility 12 shown in FIGS. 4 and 5 has three walls 13a, 13b, and 13c. Of the three walls 13a, 13b, and 13c, two walls 13a and 13b are arranged at a predetermined interval and substantially parallel to each other. The remaining wall 13c is arranged between the two walls 13a and 13b in the width direction of each of the two walls 13a and 13b so as to connect one end to the other. In this way, a permeation layer 2 is formed in the space partitioned by the three walls 13a, 13b, and 13c.

[0033] As shown in Figure 4, the portion between the other ends of the two walls 13a, 13b in the width direction forms an opening 14, which is used to transport and stack slag into the space. When a slag deposit 3 is formed in the space in this manner, a portion of the deposit 3 comes into contact with each of the three walls 13a, 13b, and 13c, as shown in Figure 4. The outer surface of the deposit 3 facing the opening 14 is an inclined surface that slopes downward. The angle between this inclined surface and the permeation layer 2 is approximately the same as the angle of repose of the slag.

[0034] As mentioned above, small-grained slag has lower fluidity than large-grained slag, and therefore tends to remain in the area where it is piled. In contrast, large-grained slag has higher fluidity and tends to flow around the area where it is piled. Therefore, in the aging treatment facility 12 shown in Figures 4 and 5, the gaps between the slag particles are larger near the walls 13a, 13b, and 13c and in the area near the opening 14, including the slope of the deposit 3, compared to the central area 6, and steam tends to escape more easily.

[0035] Here, the vicinity of walls 13a, 13b, and 13c refers to a predetermined range from walls 13a, 13b, and 13c. Furthermore, the portion on the opening 14 side refers to a predetermined range from the edge of the upper surface of the deposit 3 toward the central portion 6. These ranges can be calculated using the above formula (1). In other words, in the above formula (1), the distance (mm) from the edge of the upper surface of the deposit 3 and the distance (mm) from walls 13a, 13b, and 13c are defined as X. The vicinity of walls 13a, 13b, and 13c and the portion on the opening 14 side, including the slope of the deposit 3, that satisfy the above formula (1) are the extremely low airflow resistance portions 8 of the aging treatment facility 12 shown in Figures 4 and 5. Figure 5 illustrates the extremely low airflow resistance portions 8 near the two walls 13a and 13b.

[0036] In the second embodiment, an inhibition treatment device 9 shown in FIG. 2 is configured to blow air or spray water onto the extremely small airflow resistance portion 8.

[0037] (Operation of the second embodiment) The spray pipe 10 of the inhibition treatment device 9 is brought into contact with the surface of the extremely low airflow resistance portion 8 of the deposit 3, or the spray pipe 10 is inserted into the surface of the extremely low airflow resistance portion 8. In this state, air or water is continuously or intermittently supplied to the extremely low airflow resistance portion 8. This allows air or water to flow through the gaps between the slags in the extremely low airflow resistance portion 8 against the flow of water vapor, thereby increasing the pressure loss in the extremely low airflow resistance portion 8. This also promotes the hydration reaction of f-CaO in the slag in the extremely low airflow resistance portion 8, thereby reducing aging variations and insufficient aging throughout the deposit 3. Therefore, the second embodiment can achieve the same effects as the first embodiment.

[0038] Furthermore, in the aging treatment facility 12 shown in FIGS. 4 and 5 , instead of blowing air or spraying water onto the extremely low airflow resistance portion 8, the airflow resistance of the steam in the extremely low airflow resistance portion 8 may be increased by piling up the above-described additional slag. The amount of additional slag piled up may be the same as in the first embodiment. The additional slag piled up in the extremely low airflow resistance portion 8 functions as a lid for the extremely low airflow resistance portion 8, thereby increasing the airflow resistance of the steam, i.e., the pressure loss, in the extremely low airflow resistance portion 8. This promotes the hydration reaction of f-CaO in the slag in the extremely low airflow resistance portion 8, thereby reducing variations in aging and insufficient aging of the deposit 3 as a whole. Furthermore, because the additional slag is not piled up excessively, the additional slag can also be aged almost uniformly.

[0039] The present invention is not limited to the above-described embodiments. In the first embodiment, the outer peripheral portion 5 and the middle portion 7 of the deposit 3 were considered to be the low-airflow resistance portion 8, and the inhibition treatment was performed. In the second embodiment, the portions near the walls 13a, 13b, and 13c and the portion on the opening 14 side, including the inclined surfaces, were considered to be the low-airflow resistance portion 8, and the inhibition treatment was performed. In addition, portions other than those described above may be determined to be the low-airflow resistance portion 8 and the inhibition treatment may be performed. Because water vapor easily escapes from the low-airflow resistance portion 8, the surface temperature of the deposit 3 and the flow rate of water vapor blowing from the surface of the deposit 3 tend to be higher than those of the surrounding area. Therefore, a method for determining a low-airflow resistance portion may include, for example, measuring the surface temperature of the deposit 3 with a thermometer and determining the low-airflow resistance portion 8 based on the measurement results. Alternatively, a method may be used to measure the flow rate of water vapor blowing from the surface of the deposit 3 with a flow meter and determining the low-airflow resistance portion 8 based on the measurement results. Another method is to visually check the location where steam is coming out and determine that the location is the portion 8 with extremely low ventilation resistance.

[0040] Furthermore, instead of the above formula (1), the following formula (2) may be used to calculate the range considered to be the extremely low airflow resistance portion 8. In the following formula (2), "X" is the distance (mm) from the edge of the top surface of the pile 3 or the distance (mm) from the walls 13a, 13b, and 13c. X≧500 (2) When formula (2) is used to calculate the range considered to be the under-airflow resistance portion 8, X can be set to a fixed value regardless of the particle size of the slag being stacked, as compared to when formula (1) is used. Therefore, the range considered to be the under-airflow resistance portion 8 can be easily calculated. When formula (2) is used, it is preferable that the upper limit of the under-airflow resistance portion 8 be 2000 mm, for example. The process of measuring the surface temperature of the deposit 3 described above corresponds to the temperature measurement process in this invention.

[0041] (First Example) Next, an example conducted to verify the effects of the present invention will be described. Slag aging was performed in the aging treatment facility 12 described in the second embodiment. The slag used was slag of product particle size, with a maximum particle size of 40 mm. When the slag was piled, the depth from the top surface of the pile was 4 m. When aging the slag, inhibition treatment was performed using an inhibition treatment device 9 shown in FIG. 2 on the sloped surface of the pile 3 facing the opening 14 and near the walls 13a, 13b, and 13c, i.e., on the low airflow resistance portion 8. Examples 1 to 5 and Comparative Examples 1 to 3 each used a different slag production lot. Furthermore, in Comparative Examples 1 to 3, the slag was aged without the inhibition treatment described below.

[0042] The ranges determined to be the extremely low airflow resistance portions 8 and subjected to the inhibition treatment were specifically the range calculated from the edge of the upper surface of the deposit 3 seen from the opening 14 using the above formula (1), the range calculated from the walls 13a, 13b, and 13c using the above formula (1), and the inclined surfaces of the deposit 3. In addition, any areas that rose in temperature faster than the inclined surfaces or the vicinity of the walls 13a, 13b, and 13c after the supply of water vapor to the deposit 3 was started were also determined to be the extremely low airflow resistance portions 8, and the inhibition treatment was performed thereon.

[0043] After the supply of steam to the deposit 3 began, the surface temperature of the deposit 3 was measured with a thermometer to determine the temperature history of the deposit 3. Twelve hours after the temperature of the sloped surface and the vicinity of the walls 13a, 13b, and 13c of the deposit 3 reached 100°C, the low-airflow resistance portion 8 was subjected to an inhibition treatment. Air was blown into the low-airflow resistance portion 8 under conditions such that the wind pressure on the surface of the low-airflow resistance portion 8 was 0.4 kPa, i.e., conditions such that the airflow resistance increased by approximately 0.1 kPa / m. Aging was completed 48 hours after the start of air blowing. Table 1 summarizes the lot average expansion coefficients (%) and standard deviations of the lot average expansion coefficients (%) for each of the slags of Examples 1 to 5 and Comparative Examples 1 to 3 after such aging treatment.

[0044] [Table 1]

[0045] As shown in Table 1, it was found that in Examples 1 to 5, both the lot average expansion rate (%) and the standard deviation of the lot average expansion rate (%) were smaller overall compared to Comparative Examples 1 to 3. This is presumably because the inhibition treatment was able to suppress the leakage of water vapor from the extremely low airflow resistance portion 8, allowing for nearly uniform aging. On the other hand, in Comparative Examples 1 to 3, it was not possible to suppress the leakage of water vapor from the extremely low airflow resistance portion 8. Therefore, there were areas where aging was insufficient compared to Examples 1 to 5, and it is presumed that this was the cause of the larger standard deviation of the lot average expansion rate (%).

[0046] (Second Example) Instead of blowing air into the areas determined to be the extremely low airflow resistance areas 8 as an obstruction treatment, additional slag (hereinafter referred to as "additional slag") having a particle size smaller than that of the slag used in Example 1 was piled up. Specifically, the extremely low airflow resistance areas 8 were within a 1-m range from the edge of the top surface of the slag pile 3 visible through the opening 14, within a 1-m range from the walls 13a, 13b, and 13c, and on the slope of the pile 3. Furthermore, Examples 6 to 11 each used different production lots of additional slag. Furthermore, Comparative Examples 4 to 5 were aged without adding additional slag. Aging was performed under the same conditions as Example 1. Table 2 summarizes the lot average expansion rates (%) and standard deviations of the lot average expansion rates (%) for the slag in Examples 6 to 11 and Comparative Examples 4 to 5 after the aging treatment. Table 2 also lists the packing particle size, i.e., the particle size of the additional slag.

[0047] [Table 2]

[0048] As shown in Table 2, it was observed that the standard deviation of the lot average expansion rate (%) was smaller in Examples 6 to 11 compared to Comparative Examples 4 and 5. This is presumably because the addition of additional slag suppressed steam leakage, increased pressure loss in the low airflow resistance area 8, and homogenized aging by steam throughout the entire pile 3.

[0049] On the other hand, in Comparative Examples 4 and 5, areas of low airflow resistance, through which steam leaked, were found near walls 13a, 13b, and 13c and near the inclined surfaces. Furthermore, no additional slag was piled in these areas of low airflow resistance to prevent steam leakage. Therefore, it is estimated that there were areas where aging was insufficient, resulting in a large standard deviation in the lot average expansion rate (%).

[0050] Furthermore, the maximum particle size of the added slag used in Example 11 does not satisfy the condition of being one-third or less of the maximum particle size of the slag forming deposit 3. Therefore, it is estimated that the lot average expansion rate (%) is larger in Example 11 than in Examples 6 to 10, which satisfy the condition of being one-third or less of the maximum particle size of the slag forming deposit 3. [Explanation of symbols]

[0051] 1,12 Aging processing facility 2 Penetration layer 3 Sediment 4 Steam Pipes 5 Outer periphery of the deposit 6. Central part of the deposit 7 Middle part of the deposit 8. Area with low ventilation resistance 9. Inhibition treatment device 10 Spray tube 11 Supply pipe 13a, 13b, 13c Wall

Claims

1. A method for aging slag, comprising supplying steam to a deposit formed by piling slag to age the slag, the deposit is frustum-shaped; The method includes an inhibition treatment step of blowing air against the steam flow to an intermediate portion of the upper surface of the pile, which is a range from the edge of the pile to the center by a distance X (mm), and to an outer peripheral portion outside the intermediate portion, spraying water against the steam flow, or stacking additional slag having a particle size smaller than that of the slag on the intermediate portion and the outer peripheral portion, The method for aging slags, wherein the distance X (mm) from the edge of the intermediate portion is in a range that satisfies the following formula: X≦50×D "D" is the maximum particle size (mm) of the slag.

2. A method for aging slag, comprising supplying steam to a deposit formed by piling slag to age the slag, A wall is installed around at least a portion of the periphery of the deposit, the deposit is in contact with the wall; A method for aging slag, comprising an inhibition treatment step of blowing air against the steam flow to the area of ​​the deposit up to 2000 mm from the wall, spraying water against the steam flow, or stacking additional slag having a smaller particle size than the slag on top of the area up to 2000 mm from the wall.

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