JP6181953B2 - Sand substitute and manufacturing method thereof - Google Patents

Description

  The present invention relates to a sand substitute material and a manufacturing method thereof, and more particularly, to a sand substitute material using a steelmaking slag generated at the time of stainless steel making and a manufacturing method thereof.

In recent years, recycling of steelmaking slag generated in the manufacturing process of stainless steel that has been conventionally disposed of has been attempted. Since the steelmaking slag of stainless steel has high hardness, as shown in Patent Document 1, for example, the steelmaking slag can be used as an abrasive for blasting.
The abrasive for blasting described in Patent Document 1 has a main component composition of CaO (calcium oxide): 30 to 40% by mass, MgO (magnesium oxide): 6 to 15% by mass, Al ₂ O ₃ (alumina): 5 to 17 wt%, SiO ₂ (silicon dioxide): 20-36 steelmaking slag stainless steel by mass% were the material. This blasting abrasive is crushed after the steelmaking slag is slowly cooled, and further classified into sandy slag having a Mohs hardness of 7 to 9 and a particle size of 0.1 to 3.0 mm, Manufactured.

JP 2011-83869 A

  However, in Patent Document 1, steelmaking slag is reused as a grinding material for blasting treatment, but only by reusing it as a grinding material for blasting treatment, the amount of reused steelmaking slag is small and sufficient recycling is achieved. There is a problem that cannot be fulfilled. For this reason, it is necessary to be able to reuse steelmaking slag as a material with higher demand such as construction materials.

  The present invention has been made in order to solve such problems, and a sand substitute material and a method for producing the same that are intended to recycle stainless steel slag by making it usable as a sand material for construction materials. The purpose is to provide.

In order to solve the above problems, a method for producing a sand substitute according to the present invention is a method for producing a sand substitute consisting of coarse slag from a steelmaking slag produced in a steelmaking process of stainless steel, which comprises melting It is a cooling step for cooling the steelmaking slag in the slag pan discharged in a state over 24 hours to 30 hours after the steelmaking slag is put in the slag pan, and the temperature of the steelmaking slag is 700 ° C or higher. A cooling step for cooling the steelmaking slag to lower the temperature at 0.3 to 1 ° C. per minute, a crushing step for wet crushing the cooled steelmaking slag, and wet classification of the crushed steelmaking slag, and a classification step of separating particulate matter contained in the steelmaking slag, with the steelmaking slag is cooled, basicity (CaO / SiO ₂₎ is a 0.7 to 1.7, the composition quality %, The fluorine is less than 0.4%, CaO 35 to 65%, a SiO ₂ is 20 to 55%, _Al 2 _{O 3} from 1 to 15%, coarse slag from the steelmaking slag, hydraulic conductivity Is 4.96 × 10 ^{−4 to} 2 × 10 ⁻² cm / sec, unit volume mass is 1.9 to 2.1 kg / liter, and water absorption is 1.5 to 3.2%. And the elution amount of fluorine to water is less than 0.8 mg per liter of water, the elution amount of hexavalent chromium to water is less than 0.05 mg per liter of water, and the particle size is 5 mm or less .

In the classifying step, the crushed steelmaking slag is subjected to specific gravity separation, and then the steelmaking slag having a predetermined particle size or less is screened, and the steelmaking slag having a predetermined particle size or less is wet-classified and suspended in water. You may isolate | separate the powdery part and granular part which become cloudy.
Steelmaking slag exceeding 5 mm particle size may be wet-crushed again.
The classification step may include performing a magnetic separation process on the steelmaking slag to separate a metal component contained in the steelmaking slag.
In the steel making process, the hot metal of stainless steel may be subjected to a mechanical stirring type desulfurization treatment using a desulfurizing agent not containing calcium fluoride.

  According to the sand substitute material and the manufacturing method thereof according to the present invention, it is possible to recycle the steelmaking slag of stainless steel by making it usable as sand material for construction materials.

It is a figure which classify | categorizes and shows each process which manufactures a sand substitute material. It is a graph which shows the particle size distribution of the sand substitute material of Examples 1-8. It is a graph which shows the particle size distribution of the sand substitute material of Comparative Examples 1-6. It is a graph which shows the particle size distribution of the sand substitute material of Comparative Examples 7-12.

Hereinafter, the manufacturing method of the sand substitute material 100 in embodiment of this invention is demonstrated based on an accompanying drawing.
Referring to FIG. 1, the process of manufacturing the sand substitute 100 is roughly divided into a stainless steel making process 1 in which a steelmaking slag 10 as a raw material is generated, a cooling process 2 for cooling the steelmaking slag 10, and a cooling process. It is comprised by three processes of the slag mineral processing process 3 which classify | categorizes the granular sand substitute material 100 from the steelmaking slag 10 after.

  In the steelmaking process 1, steelmaking slag 10 is generated when melting stainless steel, and the generated steelmaking slag 10 is collected. The steelmaking slag 10 is produced in a desulfurization treatment process that removes sulfur contained in the molten slag produced by melting the raw material in an electric furnace to produce stainless steel hot metal and the produced hot metal. The desulfurization slag is formed and the refining slag generated in the refining process of removing the carbon contained in the hot metal with a converter and a vacuum degassing apparatus with respect to the hot metal after the desulfurization treatment. Then, before the desulfurization treatment and after the desulfurization treatment, the molten slag and the desulfurized slag are removed from the hot metal of the stainless steel, and the refined slag generated by the converter and the vacuum gas treatment apparatus is collected as the steelmaking slag 10. The steelmaking slag 10 is composed of impurities in the raw materials and products of the stainless steel in the steelmaking process, and includes a metal 13 that is a useful metal constituting the stainless steel.

  In the present embodiment, as a hot metal desulfurization method, a KR method is used in which hot metal is stirred with a mechanically driven stirring blade while a desulfurizing agent is added to slag and remove sulfur contained in the hot metal. . In the KR method, since the desulfurization reaction between the hot metal and the desulfurization agent is promoted by stirring, a desulfurization agent mainly containing CaO (quick lime, calcium oxide) is used. For this reason, the desulfurization agent used in the present embodiment does not include CaF2 (fluorite, calcium fluoride) used in the past to promote the desulfurization reaction.

The collected steelmaking slag 10 is placed in a slag pan, transferred to the cooling step 2, and cooled and solidified. At this time, the steelmaking slag 10 is cooled for 24 hours or more by cooling in combination with air cooling by natural cooling in the atmosphere and sprinkling cooling that sprinkles and cools the slag pot while being put in the slag pot. Is done. In this cooling process, the steelmaking slag 10 is charged into the slag pan and from about 1100 ° C. after starting solidification to about 700 ° C. at which the crystal structure change, that is, the phase transformation is almost finished, is reduced to a temperature. That is, while the temperature of the steelmaking slag 10 is about 700 ° C. or higher, the steelmaking slag 10 is gradually cooled so as to drop at a rate of 1.0 ° C./min or less. In addition, in order to fully solidify the steelmaking slag 10 so that sufficient crushing in the next crushing process is possible, the steelmaking slag 10 is applied for 28 to 30 hours or longer than that depending on the outside air temperature. Cooling is preferred.
On the other hand, when the temperature of the steelmaking slag 10 is about 700 ° C. or higher, the temperature of the steelmaking slag 10 is lowered at a rate exceeding 1.0 ° C./min by increasing the amount of cooling water or spraying the steelmaking slag 10 directly. As a result, a brittle slag having a low internal density is obtained after solidification.

Further, by gradually cooling the steelmaking slag 10 as described above, when the steelmaking slag 10 is solidified, a soft portion such as free CaO or MgO that is included in the steelmaking slag 10 and can cause a hydration reaction. And a hard mineral phase having high density (formed from silica [SiO ₂ ], alumina [Al ₂ O ₃ ], etc.) form different layers separated from each other. Actually, most of these mineral phases are dissolved in two or more of CaO, MgO, SiO ₂ , and Al ₂ O _{3 in} a complicated manner. Is formed. For this reason, when the steelmaking slag 10 after solidification is subjected to a crushing process described later, many of the hard mineral phases are separated from each other into a lump by fine crushing of the soft portions between the mineral phases, and this lump When the mineral phase is crushed, it becomes granular. Thereby, in the steelmaking slag 10, since it is mainly comprised by the soft part which is pulverized by crushing, there is little quantity pulverized.

The steelmaking slag 10 that has been solidified and its temperature has been sufficiently lowered is discharged from the slag pan and sequentially subjected to crushing by the jaw crusher crushing process 31 and the rod mill crushing process 32 constituting the slag beneficiation processing step 3.
In the jaw crusher crushing process 31, the steelmaking slag 10 is sandwiched and pressed between the fixed teeth in the jaw crusher and the movable teeth movable so as to approach and leave the fixed teeth in the air. Compression crushing. The steelmaking slag 10 is roughly dry crushed by this treatment. At this time, in the steelmaking slag 10, the mineral phase is separated into a large number of masses by the collapse of the soft portion layer such as CaO between the hard mineral phases.

In the rod mill crushing process 32 after the jaw crusher crushing process 31, the steelmaking slag 10 is put into a rod mill containing water inside and put in water, and the rod mill is rotated to further finely wet crush. Is done. In this wet crushing process, soft CaO or the like contained in the steelmaking slag 10 becomes fragile by a hydration reaction, and is crushed into a fine powder and suspended in water. Moreover, the massive hard mineral phase contained in the steelmaking slag 10 is crushed into grains having an angular shape in a rod mill. Note that sand formed by grains having an angular shape has better compactability than sand formed by grains having a smooth surface.
In the process of receiving the above two crushing treatments, the metal 13 contained in the steelmaking slag 10 is separated from the slag composed of components such as mineral phases and fine powders such as CaO. And since the steelmaking slag 10 is fully solidified by the cooling process 2, separation | separation with the metal 13 and slag at the time of a crushing process becomes easy.

  The steelmaking slag 10 that has completed the crushing process is subjected to the specific gravity beneficiation process 33 constituting the slag beneficiation process 3. In the specific gravity beneficiation process 33, the steelmaking slag 10 is thrown into the treated water, and sorting is performed using a specific gravity difference by a specific gravity sorter. In the steelmaking slag 10, those selected as having a high specific gravity are subsequently subjected to a magnetic separation process 34, and those selected as having a low specific gravity are subsequently subjected to a sieve classification process 35. Here, the magnetic separation process 34 and the sieve classification process 35 constitute a slag separation process 3.

In the magnetic separation process 34, the metal 13 is separated and collected by the magnetic separator with respect to the steelmaking slag 10 having a high specific gravity including the metal 13.
Further, in the sieve classification treatment 35, the low specific gravity steelmaking slag 10 taken out from the specific gravity sorter and contained in the treated water is supplied onto a vibrating screen (sieve) of the vibration sieve, Those having a mesh size (5 mm in this embodiment) or less are selected. The steelmaking slag 10 having a particle diameter of more than 5 mm that has not passed through the screen is returned to the rod mill crushing process 32 together with the treated water in which it is contained, and is subjected to a wet crushing process.

The steelmaking slag 10 having a particle diameter of 5 mm or less that has passed through the screen is in a sand slime state in which the particles, fine powdery particles, and treated water are mixed, and is subjected to the Akins classification process 36 to separate the granular components. That is, the steelmaking slag 10 contained in the treated water is sent to an Aikens classifier that is a spiral type classifier together with the treated water, and is subjected to classification, thereby obtaining particles having a specific particle size (about 0.15 mm) or more. The portion is separated from the powdery portion suspended in water and selected as coarse slag 11. Thereby, this coarse-grained slag 11 is comprised with a particle | grain with a particle size of 0.15 mm or more and 5 mm or less.
The steelmaking slag 10 after the coarse slag 11 is removed is in a slime state in which the fine powder particles and the treated water are mixed, and after receiving the thickener / dehydration treatment 37, the fine powder particles are separated from the treated water. The In this process, the steelmaking slag 10 contained in the treated water is sent to a thickener together with the treated water and subjected to classification, and the steelmaking slag 10 composed of fine powder particles is separated from the slime. Furthermore, the steelmaking slag 10 separated in a state containing moisture is subjected to a dehydration process and recovered as a powdery fine powder slag 12. Here, the Akins classification process 36 and the thickener / dehydration process 37 constitute a slag beneficiation process 3.

The coarse slag 11 having a particle size of 5 mm or less obtained by the above-described Akins classification process 36 is used as the sand substitute material 100.
The coarse-grained slag 11 has a water permeability of 4.96 × 10 ^{−4 to} 2.0 × when the steelmaking slag 10 before receiving the cooling treatment satisfies the following conditions and receives the cooling treatment described above in the cooling step 2. 10 ⁻² cm / sec (seconds), unit volume mass 1.9 to 2.1 kg / L (liter), and water absorption 1.5 to 3.2% are satisfied. Further, the coarse slag 11 has the characteristics that the elution amount of fluorine (F) with respect to water is less than 0.8 mg / L, and the elution amount of hexavalent chromium (Cr ⁶⁺ ) with respect to water is less than 0.05 mg / L. It becomes like this. Furthermore, since the coarse slag 11 satisfying the following conditions also appropriately includes fine particles of 0.7 mm or less, the corrected CBR which is an index indicating the quality standard of the roadbed material and the embankment material is within a range of 20 to 40%. Have good compaction. In the “Paving Construction Handbook” from the Japan Road Association, the corrected CBR required for the lower roadbed material is 20% or more.
Thus, the coarse grain slag 11 obtained by the component adjustment in the steelmaking process 1 according to the present invention, the cooling process 2, and the slag beneficiation treatment process 3 has a particle size distribution that conforms to JIS standards such as crushed sand for concrete. . Usually, in order to keep the particle size distribution within a certain range, materials obtained by sieving several stages according to particle size are mixed appropriately and mixed to obtain the target particle size distribution. However, in the present invention, this is not necessary, and a JIS standard-compliant particle size distribution can be obtained by a series of slag beneficiation treatments.
Moreover, the range which is less than 0.8 mg / L of elution amounts with respect to water of fluorine and less than 0.05 mg with respect to elution amounts of hexavalent chromium with respect to water satisfies the soil environment standard.

The conditions to be satisfied by the steel slag 10 is at the stage before steelmaking slag 10 is subjected to a cooling process are collected in the slag pot, basicity (CaO _/ SiO 2: mass ratio of CaO contents to the SiO ₂ content) 0.7-1.7, the composition is mass%, F (fluorine) is less than 0.4%, CaO is 35-65%, SiO ₂ is 20-55%, Al ₂ O ₃ Is 1 to 15%. And the reason for the said range limitation is demonstrated below.

The reason why the basicity (CaO / SiO ₂ ) is set to 0.7 to 1.7 is to suppress adverse effects on the desulfurization treatment of the hot metal of stainless steel. The basicity has a great influence on the hot metal desulfurization reaction. In the collected steelmaking slag 10, when the basicity is less than 0.7, sufficient desulfurization reaction between CaO contained in the steelmaking slag 10 and S (sulfur) contained in the hot metal during the desulfurization treatment. Is not obtained, the fluidity of the steelmaking slag 10 is low during the desulfurization treatment, the contact interface between the hot metal and the steelmaking slag 10 is reduced, and the desulfurization reaction is not promoted. The desulfurization reaction here refers to steelmaking slag produced in the melting process, desulfurization slag produced in the desulfurization treatment process, and all slag of refined slag produced in the converter and vacuum degassing treatment equipment. Function. In the present embodiment, the desulfurization treatment method is a mechanical stirring type KR method, and fluorite (CaF ₂ ) that has been used to improve the slag fluidity is not used. It is necessary to ensure the fluidity of the steelmaking slag 10.

  The reason why F (fluorine) is less than 0.4% by mass in the composition of the steelmaking slag 10 at the collected stage is that the sand substitute 100 satisfies the standard of the amount of fluorine eluted with respect to water stipulated in the soil environmental standards. It is to do. As described above, in this embodiment, since fluorite is not used for the desulfurization treatment, the F content in the composition of the steelmaking slag 10 is kept low, and the sand substitute 100 produced from the steelmaking slag 10 is a soil environment. The standard can be met.

The reason why the CaO content is 35 to 65% by mass in the composition of the steelmaking slag 10 at the collected stage is to perform an effective desulfurization treatment of the hot metal of stainless steel. CaO is a main component of the desulfurization material and an essential component for the desulfurization reaction. For this reason, in order to fully desulfurize the hot metal, the collected steelmaking slag 10 needs to contain CaO at 35% by mass or more. On the other hand, if the content of CaO is excessive with respect to the content of SiO ₂ in the steelmaking slag 10, the basicity becomes too high and the fluidity of the slag deteriorates, and the desulfurization reaction by the steelmaking slag 10 is not promoted. In the collected steelmaking slag 10, the CaO content needs to be 65% by mass or less.

The reason why SiO ₂ is ₂₀ to 55 mass% in the composition of the steelmaking slag 10 at the collected stage is to carry out effective desulfurization treatment of the hot metal of stainless steel. SiO ₂ is generated from a raw material of stainless steel and is generated as a deoxidation reaction product by a reducing agent. If the content of SiO _{2 in} the collected steelmaking slag 10 is less than 20% by mass, the basicity during the desulfurization process is too high, and the desulfurization reaction by the steelmaking slag 10 is not promoted. On the other hand, if the content of SiO _{2 in} the collected steelmaking slag 10 exceeds 55% by mass, the basicity during the desulfurization process is too low to obtain a sufficient desulfurization reaction. Therefore, the content of SiO ₂ in the steel slag 10 of the collected phase and 20 to 55 mass%.

The reason why Al ₂ O ₃ is 1 to 15 mass% in the composition of the steelmaking slag 10 at the collected stage is to ensure the fluidity of the steelmaking slag 10. Al ₂ O ₃ is mixed from refractory bricks and stainless steel raw materials for each pan used for steelmaking. If the content of Al ₂ O ₃ in the steelmaking slag 10 is too low or too high, the melting point of the slag increases and the fluidity of the slag decreases.
And in the steelmaking slag 10, based on the empirical rule about the mixing ratio of raw materials and the element distribution ratio between the slag and stainless steel, the type and mixing ratio of the raw materials of the slag generation source are adjusted for each steel type to be melted. By doing so, the basicity and composition can be adjusted as described above.

(Example)
Hereinafter, an example of the sand substitute 100 manufactured using the manufacturing method of the present embodiment and a comparative example of a sand substitute manufactured using a manufacturing method different from the manufacturing method of the present embodiment will be compared and verified. .
Table 1 shows the components of steelmaking slag constituting the sand substitutes of Examples and Comparative Examples, the desulfurization treatment method during steelmaking, the cooling treatment method of steelmaking slag, and the classification treatment method of steelmaking slag. Further, Table 2 shows the composition of the steelmaking slag at the stage that is a raw material of the sand substitute material of the example and collected in the steelmaking process.

The steelmaking slags of Examples 1 to 8 and Comparative Examples 1 to 9 are generated by the KR method using a desulfurization agent mainly composed of CaO during the desulfurization process in the steelmaking process. Further, these steelmaking slags are The basicity is between 0.7 and 1.7, the composition is mass%, F is less than 0.4%, CaO is between 35 and 65%, SiO ₂ is between 20 and 55%, The composition is produced by variously adjusting the components so that Al ₂ O ₃ is between 1 and 15%.
The steelmaking slags of Comparative Examples 10 to 12 are produced using a desulfurization agent containing fluorite that promotes the desulfurization reaction without using the KR method during the desulfurization process in the steelmaking process. Further, these steel slag basicity is between 1.9 to 2.5, in its composition by weight% CaO is between 55 to 65% while SiO ₂ is 25 to 35% Al _The components are produced with various adjustments such that ₂ O ₃ is between 1 and 15%.

Moreover, the cooling process of the steelmaking slag of Examples 1-8 and Comparative Examples 1-3 and 7-12 combines the air cooling by the natural cooling in air | atmosphere, and the sprinkling cooling which sprinkles and cools a slag pan, It took 25 hours. When the temperature of the steelmaking slag is about 700 ° C. or higher, the temperature drop rate of the steelmaking slag of Examples 1 to 8 is in the range of 0.3 to 0.7 ° C./min, and Comparative Examples 1 to 3 and 7 to 7 The cooling rate of 12 steelmaking slags was in the range of 0.3 to 0.8 ° C./min.
In the cooling treatment of the steelmaking slag of Comparative Examples 4 to 6, the steelmaking slag was rapidly cooled and granulated by injecting a large amount of pressure water into the high-temperature molten steelmaking slag using a water granulation facility. Thereby, the steelmaking slag was granulated.

  In the steelmaking slag classification treatment of Examples 1 to 8 and Comparative Examples 10 to 12, the steelmaking slag is subjected to a dry crushing treatment with a jaw crusher, a wet crushing treatment with a rod mill, a specific gravity beneficiation treatment, and a mesh size of 5 mm. The screen was sequentially subjected to a sieve classification process. Further, the Akens classification process was performed on the steelmaking slag that passed through the screen, and coarse slag having a particle size of 5 mm or less was separated and collected as a sand substitute.

In the classification process of the steelmaking slag of Comparative Examples 1 to 3, the steelmaking slag is subjected to a dry crushing process using a jaw crusher, a wet crushing process using a rod mill, a specific gravity separation process, and a sieve classification process using a screen having a mesh size of 5 mm. In addition, the steelmaking slag that passed through the screen was dehydrated using a dehydrator, and the solid content was collected as a sand substitute.
In the steelmaking slag classification process of Comparative Examples 7 to 9, a dry crushing process using a jaw crusher and a dry crushing process using a rod mill are sequentially performed on the steelmaking slag. Sieve classification was performed with a 5 mm screen, and the material that passed through the screen was collected as a sand substitute.
In addition, in the steelmaking slag of Comparative Examples 4-6, since the granular sand substitute material was formed in the cooling process, the classification process was not made.

  Table 3 shows the physical properties of the sand substitutes of Examples 1 to 8 and Comparative Examples 1 to 12 collected as described above.

  The in-house sand standards in Table 3 are the hydraulic conductivity, unit volume mass, modified CBR, water absorption, fluorine, and fluorine required when natural sand is used as a construction material such as concrete aggregate and backfill material. This is an in-house standard that includes the range of elution amount of hexavalent chromium in water and the JIS standard for particle size distribution.

  Moreover, the standard acceptance / rejection determination for the particle size distribution of the sand substitute material in Table 3 is determined to be acceptable when the condition of the particle size distribution of the fine aggregate for concrete is satisfied, and is determined to be unacceptable when not satisfied. That is, with reference to FIGS. 2 to 4, the particle size distribution lines E1 to E8 of the sand substitute materials of Examples 1 to 8 and the particle size distribution lines C1 to C12 of the sand substitute materials of Comparative Examples 1 to 12 are fine bones for concrete. When the particle size distribution falls between the upper limit line Lmax and the lower limit line Lmin of the material, the particle size distribution is determined to be acceptable, and when it protrudes from between the upper limit line Lmax and the lower limit line Lmin, it is determined to be unacceptable. 2 to 4, the horizontal axis represents the sieve mesh, that is, the sieve opening size, and the vertical axis represents the ratio of the sand substitute material that passes through the sieve having each mesh size.

The sand substitute materials of Examples 1 to 8 satisfy all the sand standards of water permeability, unit volume mass, modified CBR, water absorption rate, and elution amount of fluorine and hexavalent chromium, and the fine aggregate for concrete. The particle size distribution conditions are also satisfied.
Since the sand substitute materials of Comparative Examples 1 to 3 were produced without the Akins classification treatment compared with the sand substitute materials of Examples 1 to 8, the particle size was differentiated into a coarse particle portion and a powdery portion. Has a distribution and high compaction. The sand substitute materials of Comparative Examples 1 to 3 satisfy the sand volume of the unit volume mass and the elution amount of fluorine and hexavalent chromium, but do not satisfy the particle size distribution condition of the fine aggregate for concrete. Furthermore, the water permeability coefficient of the sand substitute materials of Comparative Examples 1 to 3 is smaller than the sand standard, and the corrected CBR and the water absorption rate are higher than the sand standard.
Since the sand substitutes of Comparative Examples 4 to 6 were produced by rapid water granulation, they were formed of grains having many pores and being brittle and lightweight. For this reason, as for the sand substitute material of Comparative Examples 4-6, a water permeability is so large that it cannot measure, and a water absorption is so low that it cannot measure. Furthermore, the unit volume mass and the corrected CBR are also smaller than the sand standard. Moreover, the sand substitute materials of Comparative Examples 4 to 6 satisfy the sand standard of the elution amount of fluorine and hexavalent chromium and the particle size distribution condition of the fine aggregate for concrete.

  Since the sand substitutes of Comparative Examples 7 to 9 were produced by the crushing process only by the dry method and without the specific gravity separation process and the Akins classification process as compared with the sand substitutes of Examples 1 to 8, The content rate of a granular part and a powdery part is increasing. For this reason, the sand substitute materials of Comparative Examples 7 to 9 have a partial water permeability smaller than the sand standard, a water absorption rate higher than the sand standard, and do not satisfy the particle size distribution condition of the fine aggregate for concrete. In addition, the sand substitute materials of Comparative Examples 7 to 9 have greatly improved compaction properties, so that the corrected CBR is significantly larger than the sand standard. In addition, the sand substitute material of Comparative Examples 7-9 satisfies the sand standard of the elution amount of fluorine and hexavalent chromium.

  The sand substitutes of Comparative Examples 10 to 12 were produced from steelmaking slag after receiving the same cooling treatment and classification treatment as the sand substitutes of Examples 1 to 8, but the desulfurization treatment method when producing steelmaking slag was an example. Different from 1-8. In the sand substitutes of Comparative Examples 10 to 12, the water permeability coefficient and unit volume mass are smaller than the sand standard, and the corrected CBR and the water absorption rate are larger than the sand standard. Furthermore, since the sand substitutes of Comparative Examples 10 to 12 are made of steelmaking slag in which fluorite is used during the desulfurization treatment, they do not satisfy the sand standard for the elution amount of fluorine, and the elution amount of hexavalent chromium Satisfies the sand standard. Therefore, the sand substitutes of Comparative Examples 10 to 12 are unsuitable for use as sand.

In addition, about the sand substitute material of Comparative Examples 10-12, since the lime (CaO) which is a desulfurization agent was used in large quantities at the time of steelmaking, and it operated by setting basicity high, fluorite in order to promote dissolution of slag It was used. However, as a result, many undissolved portions of CaO existed, so that coarse slag 11 obtained in the subsequent beneficiation treatment step 3 was mixed with a large amount of CaO, and water permeability was caused by the solidification reaction of CaO. On the other hand, it is considered that the compaction property is increased and the corrected CBR is increased. The reason why the water absorption rate is increased and the unit volume mass is decreased is also considered to be because the CaO content is increased compared to the examples.
From the above, it can be seen that the sand substitutes of Examples 1 to 8 have superior properties as sand substitutes than the sand substitutes of Comparative Examples 1 to 12.

As described above, the method for producing the sand substitute 100 according to the present invention is a method for producing the sand substitute 100 from the steelmaking slag 10 generated in the steel making process of stainless steel, and is a slag pan discharged in a molten state. A cooling step for cooling the steelmaking slag 10 inside for 24 hours or more, a crushing step for wet crushing the cooled steelmaking slag 10, and a granulation contained in the steelmaking slag 10 by wet classification of the crushed steelmaking slag 10 And a classification step for separating the minutes. Furthermore, in the steelmaking slag 10 to be cooled, the basicity (CaO / SiO ₂ ) is 0.7 to 1.7, the composition is mass%, the fluorine is less than 0.4%, and the calcium oxide is 35 to 65. %, Silicon dioxide is 20 to 55%, and alumina is 1 to 15%.

  At this time, by slowly cooling the steelmaking slag 10 whose crystal structure changes upon cooling over time as described above, the steelmaking slag 10 gradually hardens while causing a phase change, so that the inside does not become rough. It can be solidified in a high-density state with advanced crystallization. Thereby, the sand substitute material 100 consisting of high-density grains can be obtained from the steelmaking slag 10 after crushing and classification. And by crushing and classifying wet, the amount of powder generated from the steelmaking slag 10 at the time of crushing is reduced, and further, the granular content and the powdery content contained in the steelmaking slag 10 after crushing are effectively separated. Can do. Moreover, when the steelmaking slag 10 has the above-described characteristics, the sand substitute material 100 obtained from the steelmaking slag 10 can have characteristics that can be used as a construction material.

  Moreover, in the cooling step of the manufacturing method of the sand substitute material 100, when the temperature of the steelmaking slag 10 is 700 ° C. or higher, the temperature of the steelmaking slag 10 is cooled to 1 ° C. or less per minute. It is possible to prevent the density of the steelmaking slag 10 after cooling and solidification from being lowered by hardening the vicinity of the outer surface of the steelmaking slag 10 in the early stage of cooling. Furthermore, it can form in the different layer which isolate | separated soft parts, such as CaO in the steelmaking slag 10 after cooling solidification, and a hard mineral phase with a high density. Thereby, in the steelmaking slag 10 after crushing, a granular mineral phase with a small amount of powder can be obtained.

  Moreover, in the classification step of the manufacturing method of the sand substitute material 100, the steelmaking slag 10 that has been crushed is subjected to specific gravity separation, and then the steelmaking slag 10 having a predetermined particle size or less is screened to obtain a particle size that is equal to or less than the predetermined particle size. The steelmaking slag 10 is classified by a wet method to separate a powdery component suspended from water and a granular component. Furthermore, the steelmaking slag 10 exceeding the predetermined particle size is wet-crushed again. Thereby, the granular slag (sand substitute material 100) below the predetermined particle diameter formed from the mineral phase of the steelmaking slag 10 can be obtained.

In addition, the classification step of the method for manufacturing the sand substitute material 100 includes performing a magnetic separation process on the steelmaking slag 10 to separate the metal 13 that is a metal component contained in the steelmaking slag 10. Thereby, valuable metal components can be recovered. Furthermore, by the magnetic beneficiation treatment, in the sand substitute material 100, a chromium component whose amount of elution into water is limited can be removed, and a metal component that generates harmful impurities such as rust when removed can be removed.
Moreover, in the manufacturing method of the sand substitute material 100, in the steelmaking process, the hot metal of stainless steel is subjected to a mechanical stirring type desulfurization treatment using a desulfurizing agent not containing calcium fluoride. Thereby, the fluorine contained in the sand substitute material 100 can be reduced.

  1 Steelmaking process, 2 Cooling process, 3 Slag beneficiation treatment process, 10 Steelmaking slag, 11 Coarse grain slag, 13 Metal, 31 Jaw crusher crushing process, 32 Rod mill crushing process, 33 Density beneficiation process, 34 Magnetic beneficiation process, 35 Sieve Classification treatment, 36 Akins classification treatment, 100 Sand substitute.

Claims (5)

A method for producing a sand substitute consisting of coarse slag from steelmaking slag produced in a steelmaking process of stainless steel,
It is a cooling step for cooling the steelmaking slag in the slag pan discharged in a molten state over 24 hours to 30 hours after the steelmaking slag is put in the slag pan, and the temperature of the steelmaking slag is 700 ° C. At the time described above, a cooling step for cooling the steelmaking slag so as to decrease the temperature at 0.3 to 1 ° C. per minute ;
A crushing step for wet crushing the cooled steelmaking slag;
Separating the granular components contained in the steelmaking slag by wet classification of the crushed steelmaking slag, and
In the steelmaking slag to be cooled,
The basicity (CaO / SiO ₂ ) is 0.7 to 1.7,
The composition is mass%, fluorine is less than 0.4%, CaO is 35 to 65%, SiO ₂ is ₂₀ to 55%, Al ₂ O ₃ is 1 to 15%,
The coarse slag from the steelmaking slag has a water permeability of 4.96 × 10 ⁻⁴ to 2 × 10 ⁻² cm / sec, a unit volume mass of 1.9 to 2.1 kg / liter, and a water absorption rate. Is 1.5-3.2%, the elution amount of fluorine with respect to water is less than 0.8 mg per liter of water, and the elution amount of hexavalent chromium with respect to water is 0.05 mg per liter of water. A method for producing a sand substitute having a property of less than 5 mm and a particle size of 5 mm or less . In the classification step, against crushed the steel slags, after gravity beneficiation, the process of sieving the steel slag of the following particle size 5mm, classifying said the steel slag of the following particle size the 5mm wet The method for producing a sand substitute material according to claim 1, wherein a powdery part and a granular part suspended in water are separated. The method for producing a sand substitute material according to claim 2 , wherein the steelmaking slag exceeding the particle diameter of 5 mm is wet-crushed again. The said classification | category step performs the magnetic separation process with respect to the said steelmaking slag, and isolate | separates the metal component contained in the said steelmaking slag, The manufacture of the sand substitute material as described in any one of Claims 1-3. Method. In the steelmaking process, molten iron of the stainless steel, the production method of the sand alternative material according to any one of claims 1 to 4, subjected to desulfurization process of mechanical stirring type that uses a desulfurizing agent containing no calcium fluoride .

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