Modification method for blast furnace slag, modification device for blast furnace slag and manufacturing method for modified blast furnace slag

Abstract

To provide a modification method capable of efficiently and uniformly modifying blast furnace slag.SOLUTION: A modification method for blast furnace slag includes adjusting the basicity of molten blast furnace slag by spraying heated basicity-adjusting agent onto the molten blast furnace slag.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for reforming blast furnace slag, an apparatus for reforming blast furnace slag, and a method for producing reformed blast furnace slag. [Background technology]

[0002] One known method of utilizing molten blast furnace slag discharged from a blast furnace is to spray high-pressure water onto the molten slag to rapidly cool and refine it into fine particles, which can be used as a cement raw material or fine aggregate. However, when using granulated blast furnace slag as a cement raw material, the basicity b (CaO + MgO + Al2O3 / SiO2) value has a significant effect on the strength development of concrete, so JIS A6206:2013 granulated blast furnace slag for concrete stipulates that b ≥ 1.60.

[0003] As a method for adjusting the basicity of granulated blast furnace slag, for example, Patent Document 1 proposes a method in which molten blast furnace slag is stored in a ladle-shaped container, a lance with an ejection hole at its tip is immersed in the molten blast furnace slag, the temperature of the molten blast furnace slag is raised to 1400°C or higher, fly ash is injected as a mixed powder together with iron oxide-containing dust using an oxygen-containing gas, and the molten blast furnace slag is then granulated under specified conditions. Patent Document 2 also proposes a blast furnace slag modifier, which is a mixed powder and granular material made of coal ash (fly ash) mixed with a specified amount of CaO-containing material. The modifier is introduced in powder form from above the molten blast furnace slag, and the powder form is injected into the slag. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-315906 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-231918 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the method proposed in Patent Document 1, a lance is immersed in molten blast furnace slag to inject fly ash and other materials, which causes significant wear on the lance and requires frequent replacement, making it inefficient. Furthermore, the lance contains bricks and metal, and there is a concern that if defective parts are introduced into the slag, the quality of the slag product will deteriorate.

[0006] Furthermore, in the method proposed in Patent Document 2, the results of the production of blast furnace slag in the examples show that the undissolved modifier (coal ash) ratio is 13% or more. This undissolved modifier leads to variations in cement quality, which is undesirable as it also leads to variations in compressive strength when made into concrete. Furthermore, Patent Document 2 is understood to involve the addition of a room-temperature modifier, but in this case, the temperature of the molten blast furnace slag decreases and its viscosity increases, making it difficult to homogenize the composition of the molten blast furnace slag.

[0007] In order to solve the above problems, the present invention aims to provide a method for reforming blast furnace slag efficiently and uniformly, together with a reforming apparatus that can be used in the method. Here, "reforming" means adjusting the basicity. [Means for solving the problem]

[0008] The gist and configuration of the present invention are as follows. [1] A method for modifying blast furnace slag, comprising adjusting the basicity of the molten blast furnace slag by spraying a heated basicity adjuster onto the molten blast furnace slag. [2] The method for modifying blast furnace slag according to [1], wherein the basicity adjuster is sprayed onto the molten blast furnace slag in a tapping runner connected to a blast furnace. [3] The method for modifying blast furnace slag according to [1] or [2], wherein the basicity adjuster is sprayed from above the molten blast furnace slag. [4] The method for modifying blast furnace slag according to any one of [1] to [3], wherein the basicity adjuster is heated by a flame and sprayed together with an inert gas. [5] The flame is generated by a fuel gas and a combustion-supporting gas, and the supply amount of the fuel gas (unit: Nm 3 / min) of the basicity adjuster is 70 kg / Nm 3 The following is a method for modifying blast furnace slag according to [4]. [6] The method for modifying blast furnace slag according to any one of [1] to [5], wherein the basicity adjuster is heated by a burner lance and sprayed onto the molten blast furnace slag. [7] The method for modifying blast furnace slag according to any one of [1] to [6], wherein the heated basicity adjuster is sprayed at a location where the temperature of the molten blast furnace slag is 1500°C or higher. [8] A blast furnace slag reforming apparatus for adjusting the basicity of molten blast furnace slag, comprising a heating means for heating a basicity adjuster and a spraying means for spraying the heated basicity adjuster. [9] The blast furnace slag reforming apparatus according to [8], comprising a burner lance as the heating means and the blowing means.

[10] The burner lance, an inner pipe for supplying the basicity adjuster and an inert gas; a fuel gas supply pipe for supplying a fuel gas and a combustion-supporting gas supply pipe for supplying a combustion-supporting gas, both of which are provided radially outside the inner pipe; a cooling pipe containing the fuel gas supply pipe and the combustion-supporting gas supply pipe; [9] The blast furnace slag reformer has a multi-tube structure.

[11] A blast furnace slag reforming device according to [9] or

[10] , having an adjustment means for varying the distance between the burner lance and the surface to be sprayed according to the flow rate of the molten blast furnace slag.

[12] A method for producing modified blast furnace slag, comprising a step of modifying blast furnace slag by any one of the modification methods described in [1] to [7]. [Effects of the Invention]

[0009] The blast furnace slag reforming method and reforming apparatus of the present invention enable efficient and uniform reforming of blast furnace slag. The reformed blast furnace slag obtained by the blast furnace slag reforming method of the present invention stabilizes the quality of cement made from the blast furnace slag, making it possible to precisely control the quality of the cement. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of a blast furnace and a portion of a granulated blast furnace slag manufacturing facility. [Figure 2] FIG. 2 is a longitudinal cross-sectional view of a burner lance as seen from the side, illustrating an example of a blast furnace slag reforming device. [Figure 3] FIG. 2 is a longitudinal sectional view of a burner lance as seen from the front, illustrating an example of a blast furnace slag reforming device. DETAILED DESCRIPTION OF THE INVENTION

[0011] The embodiments of the present invention will be specifically described with reference to the accompanying drawings, but the present invention is not limited to these examples.

[0012] <Blast furnace granulated slag facility> First, we will explain Figure 1. Figure 1 is a schematic diagram of a blast furnace and part of a blast furnace granulated slag manufacturing facility. Molten pig iron and molten blast furnace slag are discharged from a tap hole 2 of a blast furnace 1 into a tap runner 3. The molten pig iron and molten blast furnace slag that flow through the tap runner 3 reach a skimmer device (not shown) and are separated due to their difference in specific gravity, with the molten pig iron flowing into a molten pig iron runner 4 and the molten blast furnace slag flowing into a granulation runner 5. The molten blast furnace slag that flows through the granulation runner 5 is sprayed with water in a blowing box 6, turning it into granulated blast furnace slag, which is then discharged into a cooling runner 7.

[0013] <Method for improving blast furnace slag> The method for modifying blast furnace slag of the present invention is a method for modifying blast furnace slag that includes spraying a heated basicity adjuster onto molten blast furnace slag.

[0014] Molten blast furnace slag (hereinafter sometimes referred to as "slag") is blast furnace slag in a molten state, and as shown in FIG. 1, molten blast furnace slag may be molten slag tapped from the tap hole 2 of the blast furnace 1 into the tap runner 3, or may be molten slag recovered in a container and reheated to a molten state. From the viewpoint of energy efficiency, molten slag tapped from the tap hole 2 of the blast furnace 1 into the tap runner 3 is preferable.

[0015] In the present invention, the temperature of the molten blast furnace slag onto which the basicity adjuster is sprayed is preferably 1500° C. or higher. If the temperature is lower than 1500° C., solidified slag is formed on the surface of the molten slag, and the thickness of the solidified slag tends to increase. Therefore, even if the basicity adjuster is sprayed, it may not be possible to sufficiently mix it with the slag, and the composition of the slag may not be homogenized.

[0016] The basicity adjuster is preferably added to the slag in the tap runner 3 connected to the blast furnace 1. The basicity adjuster can be sprayed at any position in the longitudinal direction of the tap runner 3 (the direction in which the slag flows) as long as the slag is at 1500°C. This can be done at any of the tap runner 3, the granulation runner 5, and the blown box 6. The tap runner 3 is preferred, and the position immediately after the slag is discharged from the tap hole 2 or the upstream side of the tap runner 3 (near the tap hole 2) is more preferred. The slag temperature is higher upstream of the tap runner 3. Near the tap hole 2 of the blast furnace 1, the slag temperature is approximately 1550°C. The temperature of the slag to which the basicity adjuster is sprayed can be set to 1500 to 1550°C. The basicity adjuster is preferably sprayed from above the slag. Spraying may be performed at one location or multiple locations.

[0017] The basicity adjuster is not particularly limited as long as it can change the basicity of the slag. However, it is preferable to use one that contains a large amount of CaO, MgO, Al2O3, or SiO2, which are the main components of blast furnace slag. Examples include steelmaking slag, calcium aluminate, dust, fly ash, and electric furnace slag. It is preferable to use one or more of these. The basicity adjuster is preferably granular in order to dissolve the basicity adjuster in the slag in a short time, and a basicity adjuster with an average particle diameter of 5 mm or less is more preferable. The lower limit of the average particle diameter is not particularly limited, but can be, for example, 1 μm or more. Such a basicity adjuster is also preferable in order to prevent clogging when the basicity adjuster is sprayed using a blast furnace slag reforming device equipped with a burner lance.

[0018] The amount of basicity adjuster can be adjusted appropriately depending on the amount of slag. Specifically, when the amount of slag flowing through the tapping runner 3 is small, it is preferable to reduce the amount of sprayed basicity adjuster, and when the amount of slag flowing through the tapping runner 3 is large, it is preferable to increase the amount of sprayed basicity adjuster.

[0019] The basicity adjuster is heated and sprayed onto the slag. It is preferable to heat the basicity adjuster to about 800 to 1000°C before spraying. At the time of spraying onto the slag, the basicity adjuster is preferably at a temperature of 800 to 1000°C, more preferably 900 to 1000°C.

[0020] The heating means for heating the basicity adjuster and the means for spraying the heated basicity adjuster onto the slag are not particularly limited. For example, the basicity adjuster may be heated by a flame and sprayed onto the slag together with an inert gas (e.g., nitrogen gas, argon gas, etc.).

[0021] <Blast furnace slag reforming equipment> The blast furnace slag reforming apparatus of the present invention is an apparatus for reforming blast furnace slag that adjusts the basicity of molten blast furnace slag, and is equipped with a heating means for heating a basicity adjuster and a spraying means for spraying the heated basicity adjuster.

[0022] A burner lance can be used as such a blast furnace slag reformer. An example of a blast furnace slag reformer equipped with a burner lance is shown in a longitudinal cross section in Fig. 2 and a longitudinal cross section from the front in Fig. 3.

[0023] The burner lance of the present invention is a device that serves both as a heating means (heating function) for heating the basicity adjuster and as a spraying means (spraying function) for spraying the heated basicity adjuster onto the slag, and can spray the basicity adjuster onto the slag together with an inert gas while heating it with a flame.

[0024] 2 and 3, the burner lance 10 can have a multi-pipe structure, for example, having an inner pipe 11 for supplying a basicity adjuster and an inert gas, a fuel gas supply pipe 12 for supplying a fuel gas, and a combustion-supporting gas supply pipe 13 for supplying a combustion-supporting gas, which are provided radially outside the inner pipe 11. A cooling pipe 14 containing the fuel gas supply pipe 12 and the combustion-supporting gas supply pipe 13 is provided outside the fuel gas supply pipe 12 and the combustion-supporting gas supply pipe 13, and cooling water for cooling the burner lance 10 can be flowed through the cooling pipe 14.

[0025] It is preferable that the fuel gas supply pipe 12 is enclosed within the combustion-supporting gas supply pipe 13. In FIG. 2, the inner pipe 11, the fuel gas supply pipe 12, the combustion-supporting gas supply pipe 13, and the cooling pipe 14 are arranged coaxially, but this structure is not limiting.

[0026] The burner lance 10 generates a flame using a fuel gas and a combustion-supporting gas, and while the basicity adjuster is heated by the flame, the basicity adjuster can be sprayed onto the slag by the pressure of the inert gas.

[0027] Examples of fuel gases include LPG (liquefied petroleum gas), LNG (liquefied natural gas), hydrogen, and steel mill by-product gases (C gas, B gas, etc.), with LPG being preferred. These can be used alone or in combination.

[0028] Examples of the combustion-supporting gas include pure oxygen (industrial oxygen), oxygen-enriched air, and air, with pure oxygen (industrial oxygen) being preferred.

[0029] If the amount of basicity adjuster injected relative to the fuel gas supplied is too large, the heat of the generated flame will not be sufficient to heat the basicity adjuster, and the basicity adjuster will not be heated sufficiently. As a result, the temperature of the slag will drop when the basicity adjuster is sprayed onto the slag, and the basicity adjuster will not be able to dissolve uniformly in the slag. Therefore, the ratio of the basicity adjuster to the fuel gas (the amount of basicity adjuster supplied (unit: kg / min) / the amount of fuel gas supplied (unit: Nm 3 / min) is 70kg / Nm 3 By setting the ratio of basicity adjuster to fuel gas under the above conditions, the temperature of the basicity adjuster sprayed onto the slag can be easily raised to about 800 to 1000°C. The ratio of basicity adjuster to fuel gas is set to 40 kg / Nm or less, because if this value is too small, unburned fuel gas is generated, which is uneconomical, and the accumulation of unburned fuel gas can be a safety problem. 3 It can be more than that.

[0030] It is preferable to adjust the flow rate of the combustion-supporting gas so that the amount of oxygen contained in the combustion-supporting gas is 1.0 to 1.4 times the amount of oxygen theoretically required for complete combustion of the fuel gas, as this allows the flame of the burner lance to reach a sufficiently high temperature.

[0031] The description of the modification method applies to the type and form of the basicity adjuster.

[0032] When the basicity adjuster is sprayed using the burner lance 10, the amount of the basicity adjuster can be set to 0.2 to 0.5 t / min.

[0033] The installation position of the burner lance 10 is not particularly limited as long as it is a position where the basicity adjuster can be sprayed onto the molten blast furnace slag, but it is preferable to install it above the tapping runner 3. The burner lance 10 is preferably installed so that the distance from the tip of the inner tube 11 of the burner lance 10 to the tapping runner 3 is 0.5 to 1.5 times the flame length of the flame generated by the burner lance.

[0034] For example, the reformer may include a burner lance and a means for adjusting the distance between the burner lance and the surface to be sprayed. The distance may be varied depending on the amount of fuel gas used. The distance may also be varied depending on the flow rate of the molten blast furnace slag.

[0035] For example, a basicity adjuster and an inert gas can be supplied to the inner tube 11 of a burner lance installed above the tapping runner 3, a fuel gas to the fuel gas supply pipe 12, and a combustion-supporting gas to the combustion-supporting gas supply pipe 13, and the fuel gas can be burned to generate a flame, which can heat the basicity adjuster. The heated basicity adjuster can then be sprayed onto the slag flowing through the tapping runner 3 under the pressure of the inert gas. This allows the basicity adjuster to be mixed with the slag, and the basicity of the slag can be adjusted by the basicity adjuster.

[0036] The reforming method of the present invention can be carried out using the blast furnace slag reforming apparatus of the present invention. However, the reforming method may also be carried out by separately applying a heating means for heating the basicity adjuster and a spraying means for spraying the basicity adjuster onto the slag. Specifically, for example, the basicity adjuster may be heated to a predetermined temperature by a heating means such as a heater, and then the heated basicity adjuster may be sprayed onto the slag together with an inert gas by a spraying means such as a lance.

[0037] According to the present invention, the basicity of the slag can be increased. For example, the slag basicity b (CaO + MgO + Al2O3 / SiO2) can be adjusted to a value of 1.60 or higher. In the present invention, the basicity adjuster is heated before being sprayed onto the slag, which reduces the temperature of the slag upon spraying and prevents the viscosity of the slag from increasing. By spraying the slag at a temperature of 1500°C or higher, these two factors combine to ensure that the sprayed basicity adjuster dissolves sufficiently in the slag, thereby enabling the slag to be uniformly modified. Furthermore, the uniform modification of the slag allows the slag composition to be homogenized. Specifically, the coefficient of variation of the basicity b of the modified slag can be reduced. The coefficient of variation is calculated by dividing the standard deviation by the mean value and multiplying the result by 100. Specifically, the coefficient of variation can be reduced to 10% or less, preferably 2% or less. The basicity b and coefficient of variation can be measured by the method described in the Examples.

[0038] The modified blast furnace slag obtained by rapidly cooling and granulating molten blast furnace slag modified using the modification method and the blast furnace slag modification apparatus of the present invention can be used as a cement raw material, fine aggregate, roadbed material, or fertilizer, and when used in these applications, can stabilize the strength of the target object, such as cement strength. [Example]

[0039] Next, the present invention will be described in more detail based on examples. The following examples are intended to illustrate preferred examples of the present invention, and the present invention is not limited to these examples in any way.

[0040] The materials and equipment used in the examples are as follows: Basicity adjuster: Steelmaking slag sand. Average particle size: 0.7 mm Melting furnace: 3 ton scale. The blast furnace slag melted in the melting furnace was discharged into a trough. The discharge amount was adjusted to match the amount of blast furnace slag shown in the table. Burner lance: Has the structure shown in Figure 2. A basicity adjuster and inert gas (argon) are supplied to the inner pipe 11, fuel gas (LPG) is supplied through the fuel gas supply pipe 12, and pure oxygen (industrial oxygen) is supplied through the combustion-supporting gas supply pipe 13. Cooling water is passed through the cooling pipe 14.

[0041] Measurement of basicity: Ten samples were taken from the slag before and after spraying the basicity adjuster, and after cooling with water, their composition was analyzed to determine the average value and coefficient of variation of basicity before and after modification. Composition analysis was performed based on JIS R 5202:2015 and JIS R 5204:2019, and basicity was determined from CaO + MgO + Al2O3 / SiO2.

[0042] Blast furnace slag was melted using a melting furnace under the conditions shown in Table 1. A flame was generated from the top of the melting furnace using a burner lance, and the basicity adjuster was heated to 970°C by the flame and sprayed onto the molten blast furnace slag together with inert gas. The flame length of the burner lance was 4 m, and the distance from the surface of the molten blast furnace slag to the tip of the burner lance was 3.5 m. In the comparative example, spraying was carried out using a burner lance without generating a flame or heating the basicity modifier. Table 1 shows the measurement results and coefficient of variation of basicity.

[0043] [Table 1]

[0044] In Examples 1 to 6, the basicity increased after reforming, and the coefficient of variation was 10% or less. 3 The coefficient of variation was 2% or less for Examples 1 to 6 in which spraying was performed as described below. On the other hand, for Comparative Examples 1 to 3 in which the basicity adjuster was sprayed without heating, although the basicity increased after modification, the coefficient of variation was large at 20% or more, and the composition fluctuated significantly. [Industrial Applicability]

[0045] The blast furnace slag reforming method and reforming apparatus of the present invention enable efficient and uniform reforming of blast furnace slag. The reformed blast furnace slag obtained by the blast furnace slag reforming method of the present invention stabilizes the quality of cement made from the blast furnace slag, enabling precise control of cement quality and is highly useful industrially. [Explanation of symbols]

[0046] 1 blast furnace 2 Taphole 3 Tapping sluice 4 Molten metal trough 5 Breaking water gutter 6 Blown boxes 7 Cooling trough 10 Burner Lance 11 Inner tube 12 Fuel gas supply pipe 13 Combustion-supporting gas supply pipe 14 Cooling pipe

Claims

1. A method for modifying blast furnace slag, comprising adjusting the basicity of the molten blast furnace slag by spraying a heated basicity adjuster onto the molten blast furnace slag.

2. 2. The method for modifying blast furnace slag according to claim 1, wherein the basicity adjuster is sprayed onto the molten blast furnace slag in a tapping runner connected to a blast furnace.

3. 2. The method according to claim 1, wherein the basicity adjuster is sprayed from above the molten blast furnace slag.

4. 2. The method for modifying blast furnace slag according to claim 1, wherein the basicity adjuster is sprayed together with an inert gas while being heated by a flame.

5. The flame is generated by a fuel gas and a combustion-supporting gas, and the supply amount of the fuel gas (unit: Nm ３ / min) is 70 kg / Nm 3 The method for modifying blast furnace slag according to claim 4, wherein:

6. 2. The method for modifying blast furnace slag according to claim 1, wherein the basicity adjuster is heated by a burner lance and sprayed onto the molten blast furnace slag.

7. 2. The method for modifying blast furnace slag according to claim 1, wherein the heated basicity adjuster is sprayed at a location where the temperature of the molten blast furnace slag is 1500°C or higher.

8. A blast furnace slag reforming apparatus for adjusting the basicity of molten blast furnace slag, comprising a heating means for heating a basicity adjuster and a spraying means for spraying the heated basicity adjuster.

9. 9. The apparatus for reforming blast furnace slag according to claim 8, further comprising a burner lance as said heating means and said blowing means.

10. The burner lance, an inner pipe for supplying the basicity adjuster and an inert gas; a fuel gas supply pipe for supplying a fuel gas and a combustion-supporting gas supply pipe for supplying a combustion-supporting gas, both of which are provided radially outside the inner pipe; a cooling pipe containing the fuel gas supply pipe and the combustion-supporting gas supply pipe; 10. The apparatus for reforming blast furnace slag according to claim 9, having a multi-tube structure comprising:

11. 10. The apparatus for reforming blast furnace slag according to claim 9, further comprising an adjusting means for varying the distance between the burner lance and the surface to be sprayed in accordance with the flow rate of the molten blast furnace slag.

12. A method for producing modified blast furnace slag, comprising a step of modifying blast furnace slag by the modification method according to any one of claims 1 to 7.

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