JP2022045088A - EXPANSION SUPPRESSION TREATMENT METHOD OF STEELMAKING SLAG, UTILIZATION METHOD OF STEELMAKING SLAG, AND PRODUCTION METHOD OF LOW f-CAO-CONTAINING SLAG - Google Patents

Abstract

To provide an expansion suppression treatment method of steelmaking slag in which the treatment can be performed at low cost and in a short time.SOLUTION: The expansion suppression treatment method of the steelmaking slag includes a step of immersing the steelmaking slag containing f-CaO in a polyol compound or a mixture of the polyol compound with water. Preferably, the polio compound comprises one or more selected from a diol compound and a triol compound. Furthermore, the triol compound preferably contains glycerin.SELECTED DRAWING: None

Description

The present invention relates to a method for suppressing expansion of steelmaking slag containing f-CaO, a method for utilizing the steelmaking slag subjected to the expansion suppression treatment by the method, and a method for producing low f-CaO-containing slag.

Steelmaking slag is divided into blast furnace slag produced as a by-product from the blast furnace and steelmaking slag such as converter slag and electric furnace slag produced as a by-product in the steelmaking process. From the viewpoint of effective utilization of by-products and preservation / maintenance of natural resources, attention is being paid to the use of such steel slag as a raw material for cement, fine aggregate for concrete, roadbed material, earthwork material and the like. In particular, steelmaking slag is used for roadbed materials and earthwork materials.

Steelmaking slag may contain unreacted lime (hereinafter, also simply referred to as “f-CaO”), unreacted magnesium oxide (hereinafter, also simply referred to as “f-MgO”), etc., which react with water. It has the property of causing volume expansion. Therefore, for example, if steelmaking slag is applied to the roadbed material as it is, the asphalt laid on the roadbed material may rise or crack. Therefore, when steelmaking slag is used for roadbed materials and the like, it is necessary to use steelmaking slag that has been subjected to expansion suppression treatment.

Many methods for suppressing expansion of steelmaking slag have been developed. Typically, as an aging treatment method for accelerating the hydration reaction of steelmaking slag in advance, a method of long-term exposure to the atmosphere (atmospheric aging), a method of exposure to steam (steam aging), and exposure to pressurized steam. There is a method (pressurized steam aging). Specifically, for example, in Patent Document 1, a pile of steelmaking slag crushed to a predetermined particle size is exposed to the atmosphere for 48 hours or more while being heated by blowing a high-temperature gas containing water. A method for aging steelmaking slag is described. Further, in Patent Document 2, a steel slag at room temperature crushed so that a particle size of 25 mm or less is 80% or more is charged into a pressure vessel, the pressure vessel is sealed, and pressurized steam is supplied into the vessel. By heating the vessel and slag, the pressure inside the pressure vessel is raised and increased while discharging the condensed hot water, and then the inside of the vessel is placed in a saturated steam atmosphere with a pressure of 2 to 10 kg / cm ² G for 1 to 5 hours. A method for aging steelmaking slag is described, which comprises reducing the pressure inside the pressure vessel to atmospheric pressure and discharging the steelmaking slag after holding the pressure vessel.

Japanese Unexamined Patent Publication No. 61-101441 Japanese Unexamined Patent Publication No. 8-165151

However, according to the method of Patent Document 1, since a high temperature gas containing a large amount of water vapor is used, the cost is high and the aging treatment requires a long time. Further, it is clear that the method of Patent Document 2 also uses a device for pressurization and a large amount of pressurized steam, resulting in higher cost. Furthermore, it cannot be said that the processing time is sufficiently shortened by adding the temperature rise and pressurization time and the pressure holding time during the aging treatment of the steelmaking slag.

As described above, a new more efficient method for suppressing expansion of steelmaking slag is required, especially from the viewpoint of cost and processing time.

Therefore, an object of the present invention is to provide a method for suppressing expansion of steelmaking slag, which can be processed at low cost and in a short time.

The present inventors have reached the present invention as a result of diligent studies to solve the above problems. That is, the present invention includes the following preferred embodiments.

The method for suppressing expansion of steelmaking slag according to the first aspect of the present invention includes a step of immersing the steelmaking slag containing f-CaO in a polyol compound or a mixture of a polyol compound and water.

In the above-mentioned method for suppressing expansion of steelmaking slag, the polyol compound preferably contains one or more selected from a diol compound and a triol compound.

In the above-mentioned method for suppressing expansion of steelmaking slag, the triol compound preferably contains glycerin.

In the above-mentioned method for suppressing expansion of steelmaking slag, the diol compound preferably contains one or more selected from ethylene glycol, propylene glycol and diethylene glycol.

In the above-mentioned method for suppressing expansion of steelmaking slag, the mass ratio of the polyol compound to the water in the mixture of the polyol compound and water is more preferably 0.2 or more.

In the method of using the steelmaking slag according to the second aspect of the present invention, the steelmaking slag subjected to the expansion suppression treatment by the method according to the first aspect described above is used as the roadbed material.

The method for producing low f-CaO-containing slag according to the third aspect of the present invention is a step of immersing a steelmaking slag containing f-CaO in a polyol compound or a mixture of a polyol compound and water, and a step of immersing the slag after the immersing step. Includes a step of obtaining f-CaO-containing slag.

According to the present invention, it is possible to provide a method for suppressing expansion of steelmaking slag, which can be processed at low cost and in a short time.

The present inventors have conducted various studies on a more efficient method for suppressing expansion of steelmaking slag without using steam or pressurized steam, and have developed a method for efficiently and selectively extracting only f-CaO in steelmaking slag. Focusing on it, the present invention was completed. Specifically, for example, by using a solvent containing glycerin or ethylene glycol and water, f-CaO in the steelmaking slag can be maximized in a short time of about 1 hour as compared with the case where a solvent containing only water is used. It was found that about 7 to 8 times can be extracted. In addition, at that time, it was found that almost all of f-CaO contained in general steelmaking slag could be extracted. Furthermore, steelmaking slag contains many other minerals that are expansion sources such as f-MgO in addition to f-CaO, but by selectively extracting only f-CaO, the expansion rate of slag can be efficiently increased. It turned out that it could be lowered sufficiently.

Hereinafter, embodiments of the present invention will be described in detail. The scope of the present invention is not limited to the embodiments described here, and various modifications can be made without impairing the gist of the present invention.

<Method of suppressing expansion of steelmaking slag>
The method for suppressing the expansion of steelmaking slag in the present embodiment is a step of immersing the steelmaking slag containing f-CaO in a polyol compound or a mixture of a polyol compound and water (hereinafter, also referred to as “immersion step” or “immersion treatment”). )including.

According to the expansion suppression treatment method in the present embodiment, f-CaO in the steelmaking slag is efficiently selected because the immersion treatment uses a solvent containing a polyol compound instead of using the conventional steam or pressurized steam. Can be extracted as a target. Therefore, the expansion rate of the steelmaking slag can be efficiently and stably reduced in an extremely short time.

In addition, the solvent containing the polyol compound can be recovered as calcium carbonate by immobilizing carbon dioxide in the calcium extracted from the solvent after use by adding water as needed and exposing it to carbon dioxide. The solvent from which calcium has been removed can be reused as a solvent repeatedly. Therefore, for example, even when the mass ratio of f-CaO in steelmaking slag is high, it is preferably 3% or less by repeatedly reusing the solvent while recovering calcium without adding a large amount of solvent. The mass content of f-CaO can be reduced to 1% or less, more preferably 0.5% or less, and most preferably to the detection limit or less, and cost reduction can be realized.

First, the material used in the expansion suppressing treatment method for steelmaking slag in the present embodiment will be described.

As used herein, the term "f-CaO" generally means unreacted CaO and unreacted Ca (OH) ₂ contained in steelmaking slag.

As used herein, the term "steelmaking slag" means steelmaking slag such as converter slag and electric furnace slag produced as a by-product from the pretreatment process, converter, secondary refining process and the like. The composition of the steelmaking slag is not particularly limited as long as it contains f-CaO. For example, compounds such as FeO, Fe ₂ O ₃ , Fe ₃ O ₄ , CaO, SiO ₂ , MgO, Al ₂ O ₃ , MnO, P ₂ O ₅ , and TiO ₂ are β-Ca ₂ (SiO ₄ ), Ca. ₂ Fe ₂ O ₅ , γ-Ca ₂ (SiO ₄ ), 2CaO / MgO / 2SiO ₂ , 2CaO / Al _{2O 3} , SiO ₂ and the like can be solidified and contained in the form of minerals. Further, f-MgO may also be included.

The mass ratio of f-CaO in the steelmaking slag used as the treatment target of the expansion suppression treatment method in the present embodiment is also not particularly limited. The steelmaking slag used for the treatment target contains f-CaO in an amount of, for example, 20% by mass, preferably 15% by mass, more preferably 10% by mass as an upper limit value, and as a lower limit value, based on the total mass thereof. It contains 1.0% by mass, preferably 0.5% by mass, and more preferably 0.2% by mass.

The components of the steelmaking slag before the expansion suppression treatment and after the expansion suppression treatment (or before and after the immersion treatment) in the present embodiment, and the components of the low f-CaO-containing slag described later are the same as those in the method of the example described later. It can be measured by the method of. That is, a value can be obtained by identifying each component from the spectrum analyzed using the X-ray diffractometer and performing a quantitative analysis of each component.

As used herein, the term "polypoly compound" refers to a plurality of alcoholic hydroxyl groups (groups in which a hydrogen atom of an aliphatic hydrocarbon is substituted with a hydroxy group (-OH)) capable of reacting with f-CaO in steelmaking slag. An organic compound that has. The purity (% by mass) of the polyol compound used in the treatment method in the present embodiment is not particularly limited, but is preferably 95% by mass or more, preferably 98% by mass or more, from the viewpoint of the extraction efficiency of f-CaO in the dipping step. Is even more preferable, and 99.5% by mass or more is even more preferable. Alternatively, when cost reduction and waste reduction are emphasized, a polyol compound derived from a by-product having low purity may be used as long as f-CaO in the steelmaking slag can be extracted.

The polyol compound preferably comprises one or more selected from diol compounds and triol compounds. This is because the diol compound and the triol compound are usually liquids at normal temperature and pressure, so that the steelmaking slag can be easily immersed and a mixture with water can be easily produced.

The "diol compound" refers to an organic compound having two of the above-mentioned alcoholic hydroxyl groups, and the "triol compound" refers to an organic compound having three of the above-mentioned alcoholic hydroxyl groups.

Examples of the diol compound include ethylene glycol, propylene glycol, diethylene glycol, butanediol, and diethanolamine. Of these, the diol compound preferably comprises one or more selected from ethylene glycol, propylene glycol and diethylene glycol.

More preferably, the diol compound contains ethylene glycol (for example, in a commercially available reagent manufactured by Fuji Film Wako Pure Chemical Industries, Ltd., density: 1.11 g / cm ³ ). By using ethylene glycol, the expansion rate of the steelmaking slag after the expansion suppression treatment can be more significantly reduced. This is not only because the solubility of calcium in ethylene glycol is more than 10 times that of water, but also because of the high selective dissolution action of ethylene glycol on f-CaO in the steelmaking slag, the expansion rate of the steelmaking slag is extremely high. This is because it can be reduced efficiently.

The triol compound preferably contains glycerin (for example, in a reagent manufactured by Fuji Film Wako Pure Chemical Industries, Ltd., density: 1.26 g / cm ³ ). By using glycerin, the expansion rate of the steelmaking slag after the expansion suppression treatment can be significantly reduced. This is not only because the solubility of calcium in glycerin is more than 10 times that of water, but also because of the high selective dissolution action of glycerin on f-CaO in the steelmaking slag, the expansion rate of the steelmaking slag is extremely efficient. This is because it can be reduced to. Further, glycerin is more preferable than ethylene glycol from the viewpoint of effective utilization and availability of industrial by-products because it is produced as a by-product in the biofuel production process and the like.

The water used in the mixture of the polyol compound and water may be, for example, pure water.

Next, a method for suppressing expansion of the steelmaking slag in the present embodiment will be described. The expansion suppressing treatment method in the present embodiment may further include any steps known to those skilled in the art such as filtration, phase separation, pulverization, and drying, if necessary, after the dipping step.

The specific method of the dipping step may be any method known to those skilled in the art, and is not particularly limited. For example, a steelmaking slag containing f-CaO crushed to an appropriate size may be placed in a container, and then a polyol compound or a mixture of a polyol compound and water may be added for immersion. When the steelmaking slag after the dipping treatment is used as a roadbed material as described later, the crushed particle size is preferably 40 mm or less, more preferably 20 mm or less, still more preferably, when crushing before the dipping. It is preferably 10 mm or less, more preferably 2 mm or less. As a result, it can be used as a roadbed material without re-crushing the steelmaking slag after immersion. The steelmaking slag after the immersion treatment may be subjected to treatments such as filtration, phase separation, further pulverization, washing, and drying, if necessary. As described above, since the solvent can be reused by recovering calcium, the number of dipping steps may be two or more.

The immersion time is not particularly limited, and the mass ratio of f-CaO in the steelmaking slag before the immersion treatment, the shape of the steelmaking slag before the immersion treatment, the mass ratio of the polyol compound in the solvent, the amount of the solvent added, and the immersion step can be determined. It may be appropriately adjusted so that a steelmaking slag having a desired expansion ratio can be obtained while considering factors such as the number of times the slag is performed. For example, when f-CaO in a general steelmaking slag is extracted to 1% or less in one dipping step, the dipping time can be set as an upper limit of 10 hours, preferably 5 hours, and also. The lower limit can be shortened to 0.5 hours, preferably 0.1 hours.

The temperature at the time of immersion is not particularly limited, and it is preferable to set the temperature to be suitable for the polyol compound of the solvent used or a mixture of the polyol compound and water.

The mass ratio (volume ratio) of the polyol compound or the mixture of the polyol compound and water as a solvent to the total mass of the steelmaking slag at the time of immersion, that is, the addition amount is not particularly limited. Specifically, the addition amount is the mass ratio of f-CaO in the steelmaking slag before the dipping treatment, the shape of the steelmaking slag before the dipping treatment, the mass ratio of the polyol compound in the solvent, the dipping time, and the number of times the dipping step is performed. It may be appropriately adjusted so as to obtain a steelmaking slag having a desired expansion ratio while considering factors such as the above. Alternatively, for example, the amount may be set so that the entire amount of the steelmaking slag to be treated is sufficiently immersed.

When a mixture of a polyol compound and water is used as the solvent, the mass ratio of the polyol compound to the mixture is the mass ratio of f-CaO in the steelmaking slag before the dipping treatment, the shape of the steelmaking slag before the dipping treatment, and the amount of the solvent added. It may be appropriately adjusted so that a steelmaking slag having a desired expansion ratio can be obtained, taking into consideration factors such as the dipping time and the number of dipping steps. Specifically, for example, the mass ratio of the polyol compound to the mixture is preferably 0.2 or more. By setting the mass ratio to 0.2 or more, f-CaO in a general steelmaking slag can be extracted in a sufficient amount or below the detection limit in one or a plurality of dipping steps. The upper limit of the mass ratio of the polyol compound is not particularly limited, but is preferably less than 1.0 from the viewpoint of cost reduction.

The mass ratio of the polyol compound is more preferably 0.4 or more, further preferably 0.5 or more, still more preferably 0.7 or more. By further increasing the mass ratio of the polyol compound, a more sufficient amount of f-CaO in the steelmaking slag can be extracted in one dipping step. The mass ratio of the polyol compound is more preferably 0.9 or less, still more preferably 0.8 or less. Lowering the mass ratio of the polyol compound leads to cost reduction. In other words, when the mass ratio of the polyol compound is low, the mass ratio of f-CaO may be lowered by reusing the solvent and performing dipping and extraction a plurality of times.

Further, from the viewpoint of reducing the expansion rate in a shorter time in the dipping step, it is preferable to perform the shaking dipping treatment using a shaker or the like as described in a later example. Alternatively, the stirring and dipping treatment may be performed using a stirrer or the like. Alternatively, a liquid flow immersion treatment in the slag packed bed or a liquid immersion treatment in the slag packed bed may be performed so that a flow occurs at the solid-liquid interface.

According to the method for suppressing expansion of steelmaking slag in the present embodiment, the steelmaking slag after the expansion suppression treatment preferably has a water immersion expansion rate measured according to, for example, JIS A 5015: 2018 (steel slag for roads). It is 1.0% or less, more preferably 0.8% or less, still more preferably 0.7% or less, still more preferably 0.5% or less. The lower limit of the water immersion expansion rate is not particularly limited, but is, for example, 0.01% or more.

According to the method for suppressing expansion of steelmaking slag in the present embodiment, the mass ratio of f-CaO of the steelmaking slag after the expansion suppression treatment is preferably 3 mass with respect to the total mass of the steelmaking slag after the expansion suppression treatment, for example. % Or less, more preferably 1% by mass or less, still more preferably 0.5% by mass or less, and most preferably the detection limit or less. The other components contained in the steelmaking slag after the expansion suppression treatment are not particularly limited, and may be substantially unchanged from the components of the steelmaking slag before the expansion suppression treatment.

<How to use steelmaking slag>
The method of using the steelmaking slag in the present embodiment includes using the steelmaking slag that has been subjected to the expansion suppression treatment by the method in the above-described embodiment as a roadbed material.

In the present embodiment, the steelmaking slag subjected to the expansion suppression treatment by the method in the above-described embodiment is adjusted to a desired particle size or the like by using an arbitrary method known to those skilled in the art such as pulverization and sieving, and the roadbed material (road). Used as a material). Since it is used for roadbed materials, the expansion-suppressed steelmaking slag satisfies the condition of water immersion expansion rate of 1.0% or less specified in JIS A 5015: 2018 (road steel slag). .. As described above, the water immersion expansion rate of the steelmaking slag is the mass ratio of f-CaO in the steelmaking slag before the dipping treatment, the shape of the steelmaking slag before the dipping treatment, the mass ratio of the polyol compound in the solvent, and the addition of the solvent. It can be controlled to 1.0% or less by appropriately adjusting the amount, the soaking time, the number of times the soaking step is performed, and the like.

<Manufacturing method of low f-CaO-containing slag>
The method for producing low f-CaO-containing slag in the present embodiment includes a step of immersing a steelmaking slag containing f-CaO in a polyol compound or a mixture of a polyol compound and water, and a step of immersing the low f-CaO-containing slag after the immersion step. Including the step of obtaining.

The present embodiment includes a step of obtaining a low f-CaO-containing slag after performing the same step as the dipping step of the expansion suppressing treatment method for steelmaking slag in the above-described embodiment. After the dipping step, if necessary, any method known to those skilled in the art such as filtration, phase separation, pulverization, and drying may be further applied to obtain low f-CaO-containing slag.

As described above, the mass ratio of f-CaO in the steelmaking slag before the dipping treatment, the shape of the steelmaking slag before the dipping treatment, the mass ratio of the polyol compound in the solvent, the amount of the solvent added, the dipping time, and the dipping step are performed. A slag having a desired low f-CaO content can be produced by appropriately adjusting the slag while considering factors such as the number of times.

The f-CaO mass ratio of the low f-CaO-containing slag obtained by the production method in the present embodiment is, for example, preferably 3% by mass or less, more preferably 1% by mass or less, still more preferably, with respect to the total mass of the slag. Is 0.5% by mass or less, most preferably not more than the detection limit. The other components contained in the low f-CaO-containing slag are not particularly limited, but are, for example, FeO, Fe ₂ O ₃ , Fe ₃ O ₄ , CaO, SiO ₂ , MgO, Al ₂ O ₃ , MnO, P. Compounds such as _{2O 5} and TiO ₂ are β-Ca ₂ (SiO ₄ ), Ca ₂ Fe ₂ O ₅ , γ-Ca ₂ (SiO ₄ ), 2CaO · MgO · 2SiO ₂ , 2CaO · Al ₂ O ₃ ·. As a component such as SiO ₂ , it may be solidified and contained in the state of a mineral. Further, f-MgO may be contained.

Since the low f-CaO-containing slag produced by the method in the present embodiment has a remarkably low expansion rate, it can be used as it is, or after being crushed or sieved as necessary, the roadbed material, cement raw material, concrete. It is suitably used for fine aggregates, earthwork materials, etc. Specifically, the produced low f-CaO-containing slag has a water immersion expansion rate of preferably 1.0% or less, more preferably 1.0% or less, as measured according to JIS A 5015: 2018 (road steel slag). It is 0.8% or less, more preferably 0.7% or less, still more preferably 0.5% or less. The lower limit of the water immersion expansion rate is not particularly limited, but is, for example, 0.01% or more.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the examples.

In this example, the steelmaking slag A1 shown in Table 1 below was used as the treated sample. Here, the f-CaO in this example was (unreacted) CaO and (unreacted) Ca (OH) ₂ . As shown in Table 1 below, the steelmaking slag A1 contains CaO and Ca (OH) ₂ . In addition, the value after the decimal point of the mass% of each component is rounded down.

Each component of the steelmaking slag A1 in Table 1 was analyzed using an X-ray diffractometer. The details of the analysis conditions are shown below. Each component was identified from the obtained spectrum, and each component was quantitatively analyzed by the Rietveld analysis method. As the software used for the Rietveld analysis method, "JADE PRO" manufactured by MDI Corporation was used.
<Analysis conditions>
Analytical device: Horizontal X-ray diffractometer "SmartLab" (manufactured by Rigaku Co., Ltd.)
Target: Cu
Monochromator: Use a monochromator (Kα)
Target output: 45kV-200mA
Scanning method: θ / 2θ (concentration method)
Slit: divergence 2/3 °, scattering 2/3 °, light reception 0.6mm
Monochromator light receiving slit: 0.8 mm
Scanning speed: 2.0 ° / min
Sampling width: 0.02 °
Measurement angle (2θ): 5 ° to 90 °

In this example, the solvent B1, the solvent B2, and the solvent C1 shown in Table 2 below were mixed and used as the solvent for immersing the steelmaking slag A1 as a sample. Specifically, the solvent B1 is glycerin (reagent manufactured by Fuji Film Wako Pure Chemical Industries, Ltd. (purity: min99.5% by mass, density: 1.26 g / cm ³ )), and the solvent B2 is ethylene glycol (Fuji Film Wako Pure Chemical Industries, Ltd.). It is a medicinal reagent (purity: min99.5% by mass, density: 1.11 g / cm ³ ), and the solvent C1 is an ultrapure water production device (EliX® Essential 10 (UV) manufactured by Merck Millipore) and Pure water produced using Milli-Q (registered trademark) Reference).

(Example 1)
In Example 1, 40 g of steelmaking slag A1 crushed to a particle size of less than about 2 mm and a total of 400 mL of a mixed solution of solvent B1 and solvent C1 were added to seal the container. The solvent ratio (volume ratio) of the mixed solution of the solvent B1 and the solvent C1 is shown in Table 3 below together with the conditions of the immersion treatment and the measurement results of the expansion rate. Then, the closed container was shaken and immersed for 1 hour using a shaker (a shaker in which the number of shakes was adjusted to about 200 times per minute and the shake width was adjusted to 4 cm or more and 5 cm or less in advance). .. After the shaking dipping treatment, the filtrate was removed by filtering with a filter to obtain steelmaking slag A2 (after the solvent B1 + solvent C1 dipping treatment).

Next, the expansion rate of the steelmaking slag A2 in Example 1 was measured. The steelmaking slag A2 was obtained from under the sieve using a sieve having an opening of 250 μm to obtain a steelmaking slag A1 having a particle size of less than 250 μm. About 8 g of the obtained steelmaking slag A2 having a particle size of less than 250 μm was placed in a container having an inner diameter of Φ20.5 mm and a height of 100 mm, pressure-molded at 3 KN, and then immersed in a water tank at 80 ° C. for 96 hours. The expansion rate was calculated from the displacement difference of the disk installed on the upper surface of the pressure-molded sample by measuring it with a laser displacement meter. The measurement results of the expansion rate in Example 1 are shown in Table 3 below.

Further, each component of the steelmaking slag A2 obtained in Example 1 was analyzed using an X-ray diffractometer in the same manner as before the immersion treatment. The detailed methods such as analysis conditions, component identification, and component quantitative analysis are the same as the method using the steelmaking slag A1 before the dipping treatment as a sample. The measurement results of each component of the steelmaking slag A2 are shown in Table 4 below.

(Example 2)
In Example 2, the treatment was carried out in the same manner as in Example 1 except that the mixed solution of the solvent B2 and the solvent C1 was added as the solvent to obtain steelmaking slag A3 (after the solvent B2 + solvent C1 immersion treatment). Only the expansion rate was measured. The measurement results of the solvent ratio (volume ratio) of the mixed solution of the solvent B2 and the solvent C1 in Example 2, the treatment conditions of the dipping treatment, and the expansion rate are summarized in Table 3 below.

(Comparative Example 1)
In Comparative Example 1, the expansion rate was measured by the same method as in Example 1 except that no solvent was added and the shaking immersion treatment was not performed. The treatment conditions and the measurement results of the expansion rate in Comparative Example 1 are summarized in Table 3 below. Since the dipping treatment is not performed in Comparative Example 1, the component thereof is the same as that of the steelmaking slag A1 before the dipping treatment. For comparison, it is shown in Table 4 below together with the components of the steelmaking slag A2 of Example 1.

<Discussion>
As can be seen from the results of Examples 1 and 2 in Table 3 above, the expansion rate of the steelmaking slag can be reduced by performing the dipping treatment with the solvent B1 or the mixed solution of the solvent B2 and the solvent C1, and the steelmaking slag A2 ( Solvent B1 + after soaking in solvent C1) and steelmaking slag A3 (after soaking in solvent B2 + solvent C1) achieved low expansion rates well below 1.0%. Further, as shown in Table 4, the amount of f-CaO of the steelmaking slag subjected to the dipping treatment was reduced to 1% or less of the amount before the dipping treatment, and the treatment time was as short as 1 hour, but the steelmaking slag was reduced. It can be seen that the f-CaO inside is efficiently and selectively extracted, and the expansion of the steelmaking slag can be suppressed in a significantly shorter time than the conventional method. Further, the mixed solution of the solvent B1 or the solvent B2, that is, the mixed solution of glycerin or ethylene glycol can be reused by recovering calcium after use, so that the cost can be significantly reduced. In addition, from the results of Examples 1 and 2, not only glycerin and ethylene glycol but also other polyol compounds as a solvent are used to enhance the selective dissolution action on f-CaO in the steelmaking slag. It is considered that the expansion rate of the steelmaking slag can be significantly reduced.

Further, according to the conventional methods such as steam aging or pressurized steam aging, a large amount of steelmaking slag is often processed at the same time, so that the speed of the hydration reaction of f-CaO may differ and uneven processing may occur. be. According to the methods of Examples 1 and 2, since the method of extracting f-CaO itself from the target steelmaking slag is used, the expansion rate of the steelmaking slag can be stably reduced to a desired value.

It should be understood that the embodiments and examples disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is shown by the scope of claims rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

Claims (7)

A method for suppressing expansion of steelmaking slag, which comprises a step of immersing a steelmaking slag containing f-CaO in a polyol compound or a mixture of a polyol compound and water. The method for suppressing expansion of steelmaking slag according to claim 1, wherein the polyol compound contains one or more selected from a diol compound and a triol compound. The method for suppressing expansion of steelmaking slag according to claim 2, wherein the triol compound contains glycerin. The method for suppressing expansion of steelmaking slag according to claim 2, wherein the diol compound contains one or more selected from ethylene glycol, propylene glycol and diethylene glycol. The method for suppressing expansion of steelmaking slag according to any one of claims 1 to 4, wherein in the mixture of the polyol compound and water, the mass ratio of the polyol compound to the mixture is 0.2 or more. A method for using steelmaking slag, which uses the steelmaking slag subjected to the expansion suppression treatment by the method according to any one of claims 1 to 5 as a roadbed material. A step of immersing a steelmaking slag containing f-CaO in a polyol compound or a mixture of a polyol compound and water, and
A method for producing low f-CaO-containing slag, which comprises a step of obtaining low f-CaO-containing slag after the dipping step.