JPH08253349A - Aging of slag - Google Patents

Abstract

PURPOSE: To prevent powdering and to promote aging in forcibly aging steel manufacturing slag and/or molten iron pretreating slag. CONSTITUTION: Steel manufacturing slag and/or molten iron pretreating slag or blast furnace slag and/or granulated slag-containing steel manufacturing slag and/or molten iron pretreating slag before aging or before completion of aging is blended with a silica-based substance or a substance containing both the silica-based substance and an alkali-based substance in an amount of more than 30% to 80%. Consequently, free CaO in the slag and a soluble silica in the silica-based substance are subjected to pozzolan reaction in the presence of water to promote hydration reaction of free CaO.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing pulverization and promoting aging when at least one of steelmaking slag and hot metal pretreatment slag is subjected to forced aging.

[0002]

2. Description of the Related Art Generally, steelmaking slag and hot metal pretreatment slag (hereinafter referred to as slag) remain in the form where lime is liberated in the slag (hereinafter referred to as free CaO). When used for free CaO
It is known that swelling occurs due to the hydroxylation and carbonation of.

Therefore, at present, the slag is generally cooled naturally,
After crushing, pile up outdoors and release CaO in slag
And Ca (O
H) ₂ or CaCO ₃ is stabilized. This process is called natural aging. In addition to natural water, there is also a method of artificially supplying at least one of hot water and steam to perform forced aging.

For example, as shown in Japanese Patent Application Laid-Open No. 4-202034, the first method of performing natural aging under atmospheric pressure
Aging method for steelmaking slag, which comprises a step and a second step of performing steam aging under atmospheric pressure,
As disclosed in Japanese Patent No. 254187, there is an aging method of steelmaking slag in which crushed steelmaking slag is immersed in a warm water bath and aged with warm water while being moved by a conveying / discharging means.

However, when the slag collapses during aging, the pulverization rate in the slag increases. When the pulverization rate increases, the strength of slag decreases, making it difficult to use as road material. Furthermore, the basicity of slag has recently increased due to the production of high-purity steel, and the amount of free CaO has increased. This is a cause of increased expansion and longer aging. The present inventor has carried out the method of the above-mentioned JP-A-4-202034 and JP-A-4-254187 for the latest slag.

However, it was found that the pulverization rate increased in all cases and the effective utilization rate of slag decreased. In addition, since the amount of free CaO is large, even with forced aging such as steam or hot water, the slag with a high basicity takes more time to stabilize and expand than the conventional slag, and the road material manufacturing cost is reduced by steam and hot water costs. There is an economic problem that it will significantly increase.

At least one of slag vapor and hot water
There is also a method aiming at shortening the expansion stabilization time in forced aging treatment with seeds and preventing the steam and hot water costs from significantly increasing road and civil engineering material manufacturing costs. For example, as proposed by the present applicant in Japanese Patent Application No. 5-316875, the slag before forced aging is blended with coal ash in an amount of 1 to 30% of the total weight after blending, Alternatively, at least one kind or two or more kinds of coal ash, silt, and blast furnace slag are mixed so as to be 1 to 30% by weight of the total weight after mixing, and treated with at least one kind of steam and warm water. There is a forced aging method for slag.

Further, as proposed by the present applicant in Japanese Patent Application No. 6-128892, the slag before aging, coal ash,
Silt, clay, concrete waste, volcanic ash, acid clay,
Aging promotion method for steelmaking slag that achieves aging in a short time and with a small amount of steam by aging by mixing 1 to 30% by weight with respect to the total weight of silica-based substances such as chaff ash and silica fume There is also.

However, in both cases, when the silica-based material is blended in an amount of 1 to 30% by weight based on the total weight of the slag, which has recently increased free CaO, the silica source is insufficient, and sufficient compulsion is required. There was a drawback that it did not lead to the effect of shortening the aging treatment time.

[0010]

SUMMARY OF THE INVENTION The present invention solves these problems, shortens the aging treatment time, can promote aging at low cost, and can improve the aging treatment equipment capacity. The purpose is to provide.

[0011]

DISCLOSURE OF THE INVENTION The present invention is to solve the above problems, and its gist includes at least one of blast furnace slag and granulated blast furnace before aging or before completion of aging, if necessary. , At least one of the steelmaking slag and the hot metal pretreatment slag is blended with a silica-based substance or a substance containing both a silica-based and an alkali-based slag in an amount of more than 30% and 80% or less based on the total weight after the addition. A slag aging method which is a feature.

Specifically, by utilizing cement concrete waste material as a silica-based material or a material containing both silica-based and alkaline-based materials, the aging processing time can be shortened, and aging can be promoted at low cost and the aging processing can be performed. It is possible to improve the equipment capacity, and also to improve the strength as road material and civil engineering material by stimulating alkali of slag of cement concrete waste material and re-hardening of unreacted cement.

[0013]

The present invention, when aging at least one kind of steelmaking slag and at least one kind of hot metal pretreatment slag containing at least one kind of blast furnace slag and granulated blast furnace, if necessary, is made of a silica-based material or a silica-based and alkali-based material. It is focused on that aging can be promoted by the pozzolan reaction by blending a substance containing both of them in an amount of more than 30 to 80% by weight based on the total weight after the aging or before the aging is completed.

That is, at least one of steel-making slag and hot-metal pretreatment slag generated in a converter, an electric furnace, a hot metal truck, or the like is cooled and solidified. Next, slag before aging completion such as before crushing slag, during crushing, before aging after crushing, during aging after slag crushing, between aging and other aging, etc. At least one of slag and granulated blast furnace is mixed, and a silica-based material or a material containing both silica-based and alkali-based is more than 30 to 8 with respect to the total weight after mixing.
Add 0% by weight. The timing of blending may be any time before aging is completed.

As the aging, any one of steam aging, hot water aging and atmospheric aging may be adopted, and the silica-based substance may be blended before the aging or before the completion of the aging including the aging,
Steam aging, hot water aging, atmospheric aging 2
It is also possible to employ a combination of two or more kinds and to mix the silica-based substance before the aging, during the aging, or before the completion of the aging such as a certain aging and another aging.

Here, the steam aging is a method of holding the slag in steam for a certain period of time to hydrate free CaO in the slag. The hot water aging is a method of holding the slag in a hot water bath for a certain period of time to hydrate free CaO in the slag. These methods can contact a large amount of water at a high temperature as compared with natural aging in which slag is piled up and free CaO is hydrated with rainwater or the like, so that the hydration reaction is accelerated.

The silica-based material or the material containing both silica-based and alkaline-based materials means cement concrete waste material, blast furnace slag, granulated blast furnace, coal ash, silt, clay, volcanic ash, acid clay, chaff ash, silica. 1 such as fume
They may be used alone or in combination of two or more.
In this case, the silica-based material alone is sufficient for the aging method, but if the material further contains both silica-based and alkali-based materials, the alkali stimulates the hydraulic properties of the slag, so it is used as a civil engineering material such as roadbed material. Better in some cases.

This silica-based substance or a substance containing both a silica-based substance and an alkali-based substance is, after drying the silica-based substance,
After adding an alkaline substance to distilled water and mixing and stirring in a solvent adjusted to have a pH range of 11 to 13, the amount of silica eluted into the solvent was 0.10 per 1 g of the dry weight of the silica-based substance.
A silica-based substance of 05 mg or more is desirable because it is an amount sufficient to promote aging of free CaO of steelmaking slag and / or hot metal pretreatment slag. Here, a solvent having a pH range of 11 to 13 is used because at least one of steel-making slag and hot metal pretreatment slag containing a silica-based material or a material containing both a silica-based material and an alkali-based material is p = H11. This is because it is a substance showing ~ 13.

Thus, when these agings are performed,
Free CaO in slag grains, silica concrete materials such as cement concrete waste materials, blast furnace slag, blast furnace granulation, coal ash, silt, clay, volcanic ash, acid clay, chaff ash, silica fume, or both silica-based and alkaline-based Of a substance containing C reacts with soluble silica in the presence of water to form insoluble C
aO-SiO ₂ -H ₂ O gel (hereinafter referred to as CSH gel)
Generate This reaction is called the pozzolan reaction.

As described above, the reason why the cement concrete waste material or the like is selected is that soluble silica is easily eluted and a pozzolanic reaction is likely to occur. Silts are among the soil materials in the particle size range of 5 to 74 microns. Blast furnace slag is generally classified into one that is gradually cooled from the molten state and one that is rapidly cooled with pressurized water. The former is called blast furnace slowly cooled slag, and the latter is called granulated blast furnace slag. In the present invention, either or both may be used.

By the formation of CSH gel by the pozzolan reaction, hardening proceeds, and free CaO reacts with water to react with Ca.
The crack generated by volume expansion when changing to (OH) ₂ is C
The SH gel blocks the particles and suppresses pulverization. In addition, since Ca ²⁺ in water is consumed by CSH gel formation,
Hydration of free CaO and dissolution of the formed Ca (OH) ₂ in water are promoted. This means that aging is accelerated.

That is, hydration of free CaO forms a solid layer of Ca (OH) ₂ on the surface thereof, and this solid layer prevents hydration of free CaO. Therefore, in order to promote hydration, the dissolution of Ca (OH) _{2 in} the solid layer must be promoted. However, since the solubility of Ca (OH) ₂ is small (0.185 at 0 ° C, 0.077 at 100 ° C), the water around the slag particles is immediately saturated with Ca ²⁺ and the solid layer of Ca
(OH) ₂ cannot be dissolved. However, if the insoluble CSH gel formation keeps the Ca ²⁺ concentration in water always low, the dissolution of Ca (OH) ₂ is promoted.

In general, the hydration reaction of free CaO has a higher reaction rate at higher temperatures. Therefore, forced aging such as steam or hot water requires less time for expansion stabilization than natural aging. However, when the amount of free CaO increases, the water around the slag particles is more likely to be saturated with Ca ²⁺ , and the Ca ²⁺ concentration in the water becomes the rate-determining hydration reaction. The present invention is characterized in that the Ca ²⁺ concentration in water is always maintained at a low state to promote the dissolution of Ca (OH) _{2 in} the solid layer.

More than 30 to 80% by weight of the silica-based material such as cement concrete waste material or the material containing both silica-based and alkali-based materials is blended in an amount of more than 30 to 80% by weight based on the total weight after blending. 30% by weight for slag with recently increased basicity and increased free CaO
In the following, the pozzolanic reaction is not sufficiently carried out and aging requires a long time, and when it exceeds 80% by weight, fine particles are increased, and it is easy to become mud and the characteristic as a civil engineering material is lost.

In addition, the timing of the blending is sufficient for the forced aging equipment capacity because the aging can be promoted by the pozzolan reaction either before aging, during aging, or before completion such as between some aging and another aging. In this case, it is advisable to mix the slag and the silica-based material or the material containing both the silica-based material and the alkali-based material before aging to improve the reaction efficiency of the forced aging by the pozzolan reaction.

When the capacity of the forced aging equipment is not sufficient, the silica-based substance or the substance containing both silica-based and alkaline-based substances is used after the forced aging with only slag to promote the hydration reaction to some extent. Mix it up again,
Efficient aging can be promoted to increase the capacity of forced aging equipment, such as continuing forced aging, waiting for shipment as road materials and civil engineering materials, or promoting aging by the pozzolan reaction in the shared period after use. .

[0027]

【Example】

Example 1 Table 1 shows the chemical compositions of steelmaking slag and hot metal pretreatment slag. After cooling and solidifying the steelmaking slag, cement concrete waste material is mixed as a substance containing both silica type and alkali type in a ratio shown in Table 2 before steam aging,
Steam aging was performed for 24 hours. The residual expansion rate due to free CaO after steam aging was measured by the 80 ° C. hot water expansion test of the iron continuous method.

Example 2 The same steelmaking slag as in Example 1 was steam-aged as a single material for 24 hours, and then at the ratios shown in Table 2, Example 1 was also used.
Atmospheric aging is performed by mixing cement concrete waste material as a substance containing both silica-based and alkaline-based materials similar to
I went for a month. The residual expansion coefficient was measured before the cement concrete waste was mixed after the steam aging was completed and after the atmospheric aging.

Example 3 The same steelmaking slag as in Example 1 was steam-aged as a single material for 24 hours, and then, in the proportions shown in Table 2, for the composite material containing blast furnace slag and granulated blast furnace, At the ratio shown in FIG. 2, cement concrete waste material was blended as a material containing both silica-based material and alkali-based material similar to that in Example 1, and air aging was performed for 3 months. The residual expansion coefficient was measured after atmospheric aging.

COMPARATIVE EXAMPLE 1 Steelmaking slag similar to that of Example 1 was mixed with 25% by weight of cement concrete waste as a substance containing both silica and alkali as shown in Table 2 before steam aging,
Steam aging was performed for 24 hours. The residual expansion coefficient was measured after steam aging.

Comparative Example 2 With respect to the same steelmaking slag as in Example 1, the residual expansion coefficient was measured when nothing was mixed and aging was not performed.

Comparative Example 3 The same steelmaking slag as in Example 1 was subjected to atmospheric aging for 2 months and then to steam aging for 48 hours.

[0033]

[Table 1]

[0034]

[Table 2]

As shown in Table 2, when 50% by weight of cement concrete waste material was blended into the steelmaking slag as a substance containing both silica and alkali, the blending timing was before steam aging and in Example 1 and steam. Comparative Example 1 in which 25% by weight was compounded in each of Example 2 compounded in the middle of performing both aging and atmospheric aging
It's getting better.

In the second embodiment in which the steam aging and the atmospheric aging are combined, the steam aging time is set in the first embodiment.
It can be seen that almost the same effect can be obtained even with half of the above, and efficient aging promotion can be achieved by increasing the capacity of the forced aging equipment. Further, Comparative Example 3 in which the silica-based substance is not mixed and the atmospheric aging and the vapor aging are used together has a considerably large expansion amount as compared with Example 1, and it is understood that the aging-promoting effect of the silica-based substance is large.

Example 4 After the hot metal pretreatment slag was cooled and solidified, cement concrete waste material was mixed as a substance containing both silica type and alkaline type in a ratio shown in Table 3 before steam aging,
Steam aging was carried out for 48 hours. The residual expansion coefficient was measured after steam aging.

Example 5 The same hot metal pretreatment slag as in Example 4 was steam-aged as a single material for 24 hours, and then, in the proportions shown in Table 3, with respect to the composite material containing blast furnace slag and granulated blast furnace. At the ratios shown in Table 3, cement concrete waste material was blended as a material containing both silica-based material and alkaline-based material similar to that in Example 4, and air aging was performed for 3 months. The residual expansion coefficient was measured after atmospheric aging.

Comparative Example 4 As shown in Table 3, a cement concrete waste material as a substance containing both a silica type and an alkaline type was mixed with 25% by weight of steam pre-aging before the steam aging as shown in Table 3, and steam was pre-treated. Aging was performed for 48 hours. The residual expansion coefficient was measured after steam aging.

Comparative Example 5 With respect to the same hot metal pretreatment slag as in Example 1, the residual expansion coefficient was measured when nothing was added and aging was not performed.

[0041]

[Table 3]

As shown in Comparative Example 5 in Table 3, the amount of expansion of the unaged material of the hot metal pretreatment slag is considerably larger than that of steelmaking slag. This is the free CaO contained in the slag.
It is thought to be due to the difference in quantity. With respect to the hot metal pretreatment slag having a large amount of free CaO, it is difficult to use as a civil engineering material with the expansion amount of Comparative Example 4 in which the silica-based material is blended at 25% by weight, and Example 1 in which the silica-based material is blended at 50% by weight is used. And in Example 2, it can be seen that it can be used as a composite material with a silica-based substance.

As in the case of steelmaking slag, the aging of the silica-based material is not limited to Example 1 in which the compounding timing is before the steam aging and Example 2 in which the silica-based material is compounded during the steam aging and the atmospheric aging. You can see that it is planned.

[0044]

According to the present invention, in the aging treatment of steelmaking slag and hot metal pretreatment slag, the aging treatment time is shortened, the aging can be promoted at low cost, and the aging treatment facility capacity can be improved. A method can be provided, and slag can be effectively used for road materials and civil engineering materials.

Claims (2)

[Claims] 1. A silica-based material or a material containing both a silica-based material and an alkali-based material is added to at least one of steelmaking slag and hot metal pretreatment slag before aging or before completion of aging, based on the total weight after mixing. Over 30% 8
A method for aging slag, characterized by containing 0% or less. 2. At least one of steelmaking slag and hot metal pretreatment slag containing at least one of blast furnace slag and blast furnace water granulation before aging or before completion of aging, silica-based material or both silica-based and alkali-based A slag aging method, characterized in that the substance containing the above is added in an amount of more than 30% and 80% or less with respect to the total weight after the addition.