JP2927150B2 - Method of manufacturing slag roadbed material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a roadbed material from steelmaking slag, and more particularly to a method for producing a stable roadbed material in which expansion and collapse do not occur in a short period of time and at low cost.

[0002]

2. Description of the Related Art Steelmaking slag contains so-called unslagized lime (free lime) in which a portion of quicklime added during refining remains in an unreacted state. Unslagified lime has the property of swelling and swelling when it reacts with water, so that steelmaking slag cannot be directly used as a roadbed material. Further, since it is inevitable that CaO crystallizes during the cooling process of the slag, the crystallized CaO also exists and causes the same expansion collapse. Unslagged lime and crystallized CaO are collectively referred to as free lime.

Conventionally, natural aging treatment is most commonly used as a method for eliminating the expansive collapse property of steelmaking slag. In this method, crushed steelmaking slag is piled up in the atmosphere, and the free lime waits for natural immersion expansion and stabilization. However, this method requires a long period of 6 to 12 months to stabilize and lacks certainty.
In addition, it requires a fairly large processing space.

[0004] In order to solve such a problem, several methods for shortening the aging processing period have been proposed.

JP-A-57-57815 discloses a method of accelerating aging in which converter slag after crushing is wetted, subjected to natural aging treatment in a pile for 15 days, and further maintained in a saturated state for 30 days. . Although this method can shorten the period, it still has a problem in stability, and particularly lacks in stabilization of crystallized CaO generated in the cooling process of steelmaking slag.

Japanese Patent Application Laid-Open No. 61-101441 discloses a method of accelerating aging in which a high-temperature steam containing water is blown in a piled state after crushing and exposed to air for 48 hours or more while heating. I have. However, only a method such as steam aging can stabilize slag-free lime, but it is still difficult to stabilize crystallized CaO.

[0007] The present applicant has disclosed in Japanese Patent Application Laid-Open No. Hei 4-202034 a method of treating steelmaking slag combining natural aging treatment and steam aging treatment. However, this method also has the same problem as described above, and furthermore, it is necessary to clarify the properties of the slag before treatment and the treatment conditions.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to further improve the aging treatment method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 4-202034. The present invention provides a method for efficiently manufacturing a stable roadbed material from the same.

[0009]

The gist of the present invention is as follows (1).
(4) The method of manufacturing the roadbed material and (5) the roadbed material.

(1) Slag basicity (CaO / SiO ₂ ) during steelmaking process
Is controlled to a weight ratio of 2.0 to 5.0, the slag to which fluorite and / or calcium chloride is added is cooled, naturally aged under atmospheric pressure, crushed after this end, and the particle size is adjusted. A method for manufacturing a steelmaking slag roadbed material, comprising performing forced aging treatment in which steam is blown under atmospheric pressure.

(2) Slag basicity (CaO / SiO ₂ ) during steelmaking process
Is controlled to a weight ratio of 2.0 to 5.0, the slag to which fluorite and / or calcium chloride is added is cooled, naturally aged under atmospheric pressure, crushed after this end, and the particle size is adjusted. A method for producing a mixed slag base material, further comprising mixing blast furnace slag and / or waste concrete material with a steel slag base material subjected to forced aging treatment in which steam is blown under atmospheric pressure.

(3) Slag basicity (CaO / SiO ₂ ) during steelmaking
After controlling the slag to which fluorite and / or calcium chloride was added by controlling the weight ratio to 2.0 to 5.0, the slag was crushed to adjust the particle size, and then subjected to natural aging treatment under atmospheric pressure, and then again to atmospheric pressure. A method for producing a steelmaking slag roadbed material, wherein a forced aging treatment of blowing steam underneath is performed.

(4) Slag basicity (CaO / SiO ₂ ) during steelmaking
After controlling the slag to which fluorite and / or calcium chloride was added by controlling the weight ratio to 2.0 to 5.0, the slag was crushed to adjust the particle size, and then subjected to natural aging treatment under atmospheric pressure, and then again to atmospheric pressure. A method for producing a mixed slag base material, further comprising mixing blast furnace slag and / or waste concrete material with a steel slag base material subjected to forced aging treatment in which steam is blown below.

(5) A roadbed material manufactured by any one of the above methods (1) to (4).

[0015]

The expansion and collapse of steelmaking slag is a phenomenon that occurs when free lime present therein causes the following reaction and expands in volume.

[0016] _{CaO + H 2 O = Ca (} OH) 2 ( _{hydration) ··· CaO + CO 2 = CaCO} 3 Not slag lime of (carbonation reaction) .. free lime (hereinafter, non-slag formation CaO Is CaO 2 contained in quicklime, fresh dolomite, lightly burned dolomite, etc. added for adjusting the basicity in the steelmaking process, and did not react and remained as it was. In order to eliminate unslagged CaO, it is necessary to sufficiently melt and fluidize slag in the steelmaking process. For this purpose, fluorite or calcium chloride, which is a slag-making accelerator, is added alone or in combination to remove the CaO surface film that inhibits melting.

However, if this amount is large, the refractory erosion of the steelmaking furnace is promoted and the furnace life is remarkably deteriorated. Therefore, it is desirable to add a small amount. For example, before and / or during the refining of the steelmaking process, either fluorite or calcium chloride or a total amount of 0.1 to 3.
0 kg, preferably 0.3-1.0 kg, are added.

In order to suppress the generation of crystallized CaO in the free lime, the slag basicity (CaO / SiO ₂ ) in the steel making process needs to be 2.0 to 5.0, preferably 2.0 to 4.5 by weight ratio. This is because when CaO / SiO ₂ exceeds 5.0, the amount of 3CaO · SiO ₂ generated in the primary crystal increases, and the transformation according to the following formula occurs in the cooling process, and the amount crystallized as CaO increases. . Further, in such a situation, since the concentration of CaO is high in the cooling process, it does not become 3CaO.SiO ₂ or 2CaO.SiO _2, and crystallization of CaO is promoted. On the other hand, if it is less than 2.0, desulfurization and dephosphorization, which are the original purposes of the steel refining treatment, become insufficient.

3CaO · SiO ₂ → 2CaO · SiO ₂ + CaO ··· However, since it is difficult to eliminate unslagged CaO and crystallized CaO only by the above method, after cooling the steelmaking slag, Further, it is necessary to stabilize these free limes. As a reliable stabilization method, natural aging and subsequent forced aging for further blowing steam are used in combination. The reason for the combined use is that the natural aging treatment alone requires a long time because the hydration reaction or the carbonation reaction according to the above formula is slow. In addition, the hydration reaction near the slag surface is fast only by forced aging treatment in which steam is blown, but the steam has a specific volume (m ³ / kg)
Is much larger than water, so that even if it is hydrated, it hardly penetrates to the center of the slag granules and cannot be a reliable stabilization method.

There are basically the following two methods (a) and (b) in the slag treatment process after cooling.

(A) After cooling, piled under atmospheric pressure, subjected to natural aging treatment, crushed and subjected to particle size adjustment,
In addition, forced aging treatment is performed by blowing steam under atmospheric pressure. FIG. 1A shows this step.

(B) After cooling, this is first crushed, subjected to particle size adjustment, piled up under atmospheric pressure, subjected to natural aging treatment, and further subjected to forced aging treatment by blowing steam under atmospheric pressure. FIG. 1B shows this step.

In the method shown in FIG. 1 (a), the natural aging treatment is carried out at atmospheric pressure for 1 to 4 months, preferably for 2 to 3 months. This causes a hydration reaction and cracks in the slag. On this occasion,
If the water content in the slag is low, it is desirable to sprinkle water to supply sufficient water.

FIG. 2 is a diagram showing an example of the shape of a single mountain during the natural aging process.

FIG. 2A is a plan view, and FIG. 2B is a longitudinal sectional view taken along line SS of FIG. 2A. As shown in the figure, the shape of the peak of the steelmaking slag 1 is desirably a square truncated pyramid having a bottom side and an upper side length of about 20 m, about 10 m, and a height of about 3.5 m, respectively. This is for increasing the surface area as much as possible and for convenience in lot management.

As shown in FIG. 4, which will be described later, when the basicity is controlled within the range defined by the present invention and an appropriate amount of a slagging accelerator is added, free lime may be used for such a short period of time. The amount of water immersion is small even in an unaged state, and the amount of water immersion expanded as an average almost reaches the JIS standard value in the natural aging treatment for at least about two months. is there.

Thereafter, in order to increase the reaction surface area at the time of the forced aging treatment and to reduce the distance from the surface of the slag to the center thereof, the slag is crushed as small as possible to a particle size of 30 mm or less and then adjusted to a predetermined particle size. . However, since the particle size of the roadbed material is specified in JIS-A5015, it is desirable to crush the roadbed material so as to satisfy the specified range. Therefore, the maximum particle size at the time of crushing is preferably set to be 10 to 20% larger than the maximum particle size specified in JIS in consideration of a change in particle size due to forced aging treatment.

The temperature at which the hydration of free lime is maximized is
It was found that the temperature was 200 ° C.
Further, if steam is blown under atmospheric pressure and forced aging treatment is performed, even if free lime that has not yet been sufficiently stabilized remains, the steam flows through the slag cracks through the above-mentioned slag cracks. And the free lime is completely hydrated, so that a reliable stabilization treatment can be achieved. Such an effect cannot be obtained by the forced aging treatment using warm water. That is, since the enthalpy of the hot water is much lower than that of the steam, the effect is remarkably reduced especially in the stabilization of crystallized CaO.

The period of the forced aging process is 2 to 4
It is desirable to be in the range of days. If it is less than 2 days, the aging effect is partially poor, and the variation in the amount of expansion is large. On the other hand, when the period exceeds 4 days, the aging effect is saturated, and the steam intensity increases, which is economically disadvantageous.

The specific number of days for treatment is determined by performing sampling during the natural aging process, grasping the amount of water immersion expansion before the forced aging process, and estimating the remaining amount of water immersion expansion. be able to. Therefore,
It is also easy to reduce the cost by setting the appropriate treatment days and minimizing the amount of steam used.

FIG. 3 is a diagram showing an example of an apparatus used for a forced aging process using steam. 3A is a plan view, and FIG. 3B is a longitudinal sectional view taken along line TT in FIG. 3A.
In the illustrated apparatus, a steam retaining pipe 2 is provided at the bottom of a rectangular processing tank having three sides as concrete retaining walls 2 and one side (lower in FIG. 3A) as a gate for carrying in and out of the steelmaking slag 1. In the figure, reference numeral 3 denotes a steam supply main pipe, 4 denotes a steam supply valve, 6
Is a crushed stone layer for securing stable air permeability, and 7 is a heat retaining sheet. From the viewpoint of reaction efficiency, the height of the steelmaking slag is preferably about 2 m.

In the method of FIG. 1 (b), the crushing and particle size adjustment in the method of FIG. 1 (a) are performed prior to the natural aging treatment. Other methods are the same as those in FIG. 1 (a). However, in this step, since the natural aging treatment is performed after the reaction surface area is increased by crushing, the hydration reaction is easily accelerated, and the treatment period is further reduced to about one month.

If the same natural aging treatment period is used for the method shown in FIG. 1A and the method shown in FIG. 1B, the remaining free lime will eventually decrease in the latter method.

The steelmaking slag base material manufactured by the above method can be used as it is, but from the viewpoint of effective use of resources, it is used as a mixed slag base material further mixed with blast furnace slag and / or concrete waste material. Is also good. In particular, hydraulic graded slag (HM
When used as S), the granulated blast furnace slag is preferably mixed with the steelmaking slag base material by several weight%, preferably 5 to 10 weight%.

[0035]

[Example] Using slag generated from a 300t converter, Table 1
And the steelmaking slag roadbed material was manufactured on the conditions shown in Table 2.

In the steel making process, slag basicity (CaO / SiO ₂ )
From the difference between the Si during hot metal Si and tapping the SiO _2, the medium in the solvent
CaO was calculated from the CaO content. Fluorite was used as the slag formation accelerator and was added in the range of 0 to 5.0 kg per ton of molten steel before the start of refining.

After cooling the slag generated in the converter, the slag was immediately sampled, the slag surface was polished, and the mineral composition was determined by SEM and EPMA quantitative analysis. Further, the polished slag was immersed in ethylene glycol to investigate the form of free lime. Table 1 shows the results.

[0038]

[Table 1]

As shown in Table 1, when CaO / SiO ₂ is 5.2 (test E), the amount of unslagged CaO is small but
Were observed. 3.0 CaO / SiO ₂ without fluorite addition
In the case of 3.5 (Test G) as in (Test F), no residue
Both CaO and crystallized CaO were found in large quantities. On the other hand, in the range of CaO / SiO ₂ specified in the present invention, fluorite is
In Tests A to D in which 0.5 to 2.8 kg was added, almost no unslagged CaO was recognized, and the amount of crystallized CaO was also small.

After the cooling slag was aged under the conditions shown in Table 2, at each aging stage, 12 places were sampled from one mountain, and the amount of water immersion expansion was compared by the method specified in JIS-A5015. The effect of aging was evaluated. For comparison, in each test, the same water immersion expansion was measured for each slag in the unaged state, two months after natural aging, and four days after forced aging with steam without natural aging. These results are also shown in Table 2.

[0041]

[Table 2]

As is clear from Table 2, the present invention defines
The difference between the maximum value and the minimum value when the steel slag filled with CaO / SiO ₂ is subjected to natural aging and forced aging with steam has a very small difference between the maximum value and the minimum value.
All satisfied the JIS standard. In the case of only forced aging with steam, the water immersion expansion amount satisfies the JIS standard on average, but the difference between the maximum value and the minimum value is large.
Some were out of the range of the S standard. In addition, CaO / SiO ₂
In cases where the aging was too high (test E) and where fluorite was not added even though CaO / SiO ₂ was appropriate (tests F and G), natural aging and forced aging with steam were used together.
The water immersion expansion was large and did not satisfy the JIS standard.

FIG. 4 shows the steelmaking slags shown in Table 1 (tests A to
It is a figure which shows the relationship between the processing period by only natural aging processing, and the amount of water immersion expansion in case of G). As shown in the figure, in the CaO / SiO ₂ range defined in the present invention and in the tests A to D in which fluorite is added, the amount of water immersion expansion (average value) satisfying the JIS standard only by natural aging treatment. It is understood that a long-term aging treatment for at least 8 months is necessary to obtain the above.

FIG. 5 is a diagram showing the effect of forced aging on the amount of water immersion expansion of the steelmaking slag after the natural aging treatment for two months and the steam intensity. As shown
According to the method of the present invention, JI is obtained by forced aging for 2 days.
The water immersion expansion amount that almost satisfies the S standard can be achieved, and the steam intensity can be reduced.

Next, a steelmaking slag base material manufactured by the method of the present invention shown in FIG. 1 and a mixed slag base material (HM) mixed with blast furnace slag and / or waste concrete material.
A physical property comparison with S-25) was performed. Table 3 shows the mixing conditions and the measurement results of the physical properties. For comparison, the physical property values of the blast furnace slowly cooled slag are also shown. Blast furnace slow cooling slag is MS-
25 (The name specified in JIS-A5015.
mm), granulated blast furnace slag was used as it was in the granulated state, and concrete waste was crushed to a size of 25 to 0 mm.

[0046]

[Table 3]

As shown in Table 3, the mixed slag roadbed materials according to the method of the present invention all had good physical properties satisfying JIS standards.

[0048]

According to the method of the present invention, a roadbed material having excellent physical properties can be efficiently produced from steelmaking slag in a short period of time.

[Brief description of the drawings]

FIG. 1 is a diagram showing basic manufacturing steps of the method of the present invention.

FIG. 2 is a diagram illustrating an example of a pile shape during natural aging processing used in the method of the present invention.

FIG. 3 is a diagram showing an example of a forced aging processing device used in the method of the present invention.

FIG. 4 is a diagram illustrating a relationship between a processing period of only natural aging processing and a water immersion expansion amount.

FIG. 5 is a diagram showing the effect of forced aging on the amount of water immersion expansion after natural aging treatment for two months and the steam intensity.

[Explanation of symbols]

1: steelmaking slag, 2: concrete retaining wall, 3: steam supply main pipe, 4: steam supply valve, 5: steam injection pipe, 6: crushed stone layer, 7: heat insulation sheet

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-61-48446 (JP, A) JP-A-49-26112 (JP, A) JP-A-4-202034 (JP, A) (58) Investigation Field (Int.Cl. ⁶ , DB name) C04B 5/00-5/06

Claims (5)

(57) [Claims] In the steel making process, the slag basicity (CaO / SiO ₂ ) is controlled at a weight ratio of 2.0 to 5.0, and the slag to which fluorite and / or calcium chloride is added is cooled and then naturally aged under atmospheric pressure. A method for producing a steelmaking slag roadbed material, which comprises subjecting the steel to crushing after the completion of the treatment, adjusting the particle size, and then performing forced aging treatment in which steam is blown again under atmospheric pressure. 2. The slag basicity (CaO / SiO ₂ ) is controlled at a weight ratio of 2.0 to 5.0 in the steel making process, and the slag to which fluorite and / or calcium chloride is added is cooled, and then naturally aged under atmospheric pressure. After crushing and grain size adjustment after the completion of this process, blast furnace slag and / or concrete waste are further mixed with steelmaking slag base material subjected to forced aging treatment in which steam is blown again under atmospheric pressure. Production method of mixed slag roadbed material. 3. The slag basicity (CaO / SiO ₂ ) is controlled at a weight ratio of 2.0 to 5.0 in the steel making process, and the slag to which fluorite and / or calcium chloride is added is cooled and then crushed to adjust the particle size. A method for producing a steelmaking slag roadbed material, which comprises performing a natural aging treatment at a subsequent atmospheric pressure and then performing a forced aging treatment of blowing steam again at the atmospheric pressure. 4. The slag basicity (CaO / SiO ₂ ) is controlled at a weight ratio of 2.0 to 5.0 in the steelmaking process, and the slag to which fluorite and / or calcium chloride is added is cooled and then crushed to adjust the particle size. Then, after natural aging treatment is performed under atmospheric pressure, blast furnace slag and / or concrete waste are further mixed with steelmaking slag base material subjected to forced aging treatment in which steam is blown again under atmospheric pressure. Manufacturing method of mixed slag roadbed material. 5. A roadbed material manufactured by the method according to any one of claims 1 to 4.