JP2000143306A - Treatment of blast furnace slag - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating blast furnace slag at a low cost, in which a product has sufficient characteristics as a roadbed material sulfur- dissolved water is not formed. SOLUTION: This method for treating blast furnace slag comprises (A) retaining a mixture of blast furnace slag mixed with at least one kind selected from a group consisting of an oxide or and carbonate both including an alkali metal so as to be maintained at >=900 deg.C and (B) oxidizing the mixture. Or it is possible to prevent sulfur-dissolved water from being formed by adding an oxide including silicon to blast furnace slag.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating blast furnace slag for use in roadbed materials and the like, and more particularly to a method for preventing the generation of yellow water.

[0002]

2. Description of the Related Art In recent years, from the standpoint of environmental conservation, the use of natural high-quality crushed stones used for roadbed materials in civil engineering works has been restricted. Therefore, blast furnace slag and steelmaking slag generated in the iron making process are being actively studied for application to roadbed materials and the like.

One of the problems when using blast furnace slag as a roadbed material is the generation of yellow water. The cause of this is, for example, as described in Document 1 [“Blast furnace slag roadbed design and construction policy” published by the Iron and Steel Slag Association (1982)], CaS contained in blast furnace slag reacts with water, and the following equation ( 1) ~
It is considered that Sx ²⁻ dissolves in water by the reaction mechanism shown in (4) and turns water yellow. _{2CaS + 2H 2 O → Ca (} SH) 2 + Ca (OH) 2 ... (1) Ca (SH) 2 → Ca 2+ + 2SH - ... (2) SH - → S 2+ H + ... (3) S ^2- + S → Sx ^2- ... (4) Therefore, if CaS can be removed from the blast furnace slag, the generation of yellow water can be prevented.

The simplest method for removing CaS is to inject oxygen into the hot slag that has just been discharged to cause a reaction represented by the following formula (5). It is not preferable because SO ₂ is generated and causes air pollution. CaS + 3 / 2O ₂ → CaO + SO ₂ …… (5)

[0005] Therefore, usually, the reaction of the above (1) to (5) is allowed to proceed gradually by leaving it in the atmosphere for a long time of about 3 months, that is, by performing an aging treatment, and it is washed off as yellow water or converted into SO _2. A method of removing CaS by releasing it into the atmosphere has been adopted.

On the other hand, a method of eliminating such a long aging process is also being studied.
In Japanese Patent No. 54-1330, a Si compound such as ferrosilicon is added to blast furnace slag, and in Japanese Patent Application Laid-Open Nos. 54-138804 and 55-100247, high-temperature blast furnace slag discharged is used. A method of quenching to reduce CaS in slag is disclosed.

[0007]

SUMMARY OF THE INVENTION However, Japanese Patent Application Laid-Open
In the method described in JP-A-54-1330, an expensive raw material such as ferrosilicon is used, so that it becomes an expensive roadbed material and cannot be actually used. In the method described in JP-A-55-100247, the slag crystallization ratio is reduced. As a roadbed material, characteristics close to those of natural stone are required, and it is important that the material be crystalline.
Slags with a low crystallization rate are glassy and have a smooth surface, low frictional force, poor water absorption, and a sharp fracture surface, which poses safety problems. There is a problem that there is no.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a method for treating blast furnace slag which is inexpensive and which does not generate yellow water, and which can secure characteristics as a roadbed material. .

[0009]

[MEANS FOR SOLVING THE PROBLEMS]
The inventors used alkaline metals such as soda ash and waste glass.
Oxides or carbonates to blast furnace slag
In this way, CaS, which is the cause of yellow water generation,
For example, Na_TwoS_TwoS is oxidized to Na _TwoSO_Four
Invented blast furnace slag treatment method that reforms and renders harmless
did. As a result of further research on this,
Furnace slag has a structure in which CaS precipitates in gaps between crystal phases.
However, by adding waste glass, the gap between crystal phases
A structure in which CaS and a glass phase coexist in
Prevents the generation of yellow water by being wrapped in a phase
I found that. What is important in this case is the average of the blast furnace slag.
The composition is to make the glass phase easy to precipitate,
It was the silica in the waste glass that had this function. this
To prevent the generation of yellow water by the mechanism, react CaS
It is not necessary to perform oxidation treatment
It is a feature. Hereinafter, these will be described in detail.

[0010] The first invention comprises a step of maintaining a mixture obtained by adding one or more compounds selected from oxides or carbonates containing alkali metals to a blast furnace slag at a temperature of 900 ° C or more; Oxidizing the mixture. The second invention of the present invention is the method for treating blast furnace slag according to the first invention of the present invention, wherein the oxide or carbonate containing an alkali metal is waste glass or soda ash. The third invention of the present invention is to add an oxide containing silicon to blast furnace slag,
This is a method for treating blast furnace slag that prevents the generation of yellow water.
According to the fourth invention, an oxide containing silicon is added to the blast furnace slag, the temperature is maintained at a temperature of 900 ° C. or more, and then the temperature is slowly cooled in a temperature range of 900 to 1200 ° C. at a cooling rate of 15 ° C./min or less. A blast furnace slag treatment method according to the third aspect of the present invention. The fifth invention is the method for treating blast furnace slag according to the third invention or the fourth invention, wherein the oxide containing silicon is waste glass.

The problem to be solved by the above-mentioned invention is as follows. First, a mixture obtained by adding a predetermined amount of one or more compounds selected from oxides or carbonates containing alkali metals to blast furnace slag is used. The problem is solved by a method for treating blast furnace slag, comprising: a step of maintaining the temperature at a temperature of not less than ° C. for a predetermined time; and a step of oxidizing the mixture.

The blast furnace slag is one or two selected from oxides or carbonates containing alkali metals such as Li, Na and K.
When a predetermined amount of more than one compound is added, CaS in the slag
Is obtained by the reaction of the following formula (6): Li ₂ S, Na ₂ S, K ₂ S
These sulfides react with water to form yellow water. CaS + X ₂ O → X ₂ S + CaO (6) where X is Li, Na, K or the like.

However, the produced Li ₂ S, Na ₂ S, K ₂ S
When oxidizing such an alkali metal,
As an example, it is clear from the condensation diagram of Na-O ₂ -S ₂ at 1500 ° C. shown in FIG.
At the partial pressure of O ₂ and S ₂ (point A), Li ₂ SO ₄ , Na ₂ SO ₄ , K ₂ SO _4, etc. stabilized by the reaction of the following formula (7) (B
Point), the generation of yellow water can be completely prevented. In the case of an alkali metal, there is no generation of SO ₂ due to oxidation, so that no air pollution is caused. X ₂ S + 2O ₂ → X ₂ SO ₄ (7) where X is Li, Na, K, or the like.

In practice, it is necessary to carry out the reaction at a high temperature in order to promote the above-mentioned reactions (6) and (7). However, within the practical holding time (within 2 hours), the aging treatment time is reduced. Examination of the reaction temperature which can be reduced to 1/3 or less of the above revealed that the temperature should be increased to 900 ° C. or more. Note that the holding time at a high temperature needs to be appropriately determined depending on the temperature, the type of oxide or carbonate containing an alkali metal, and the like.

The reaction temperature is set to 1300 ° C. at which the slag becomes molten.
By doing so, the retention time can be significantly reduced,
Thereafter, it is possible to obtain a blast furnace slag which does not generate yellow water without performing aging treatment.

As the oxide or carbonate containing an alkali metal, soda ash (main component is Na ₂ CO ₃ ) and waste glass (containing about 15 wt% of Na ₂ O) are preferable because they are easily available at low cost. In particular, since waste glass has a remarkably low viscosity, it is effective when reacting at a low temperature.

The amount of the oxide or carbonate containing such an alkali metal is about 1% by weight in a normal blast furnace slag.
Since S is contained, an appropriate amount thereof, for example, about 3 wt% in the case of soda ash, may be added.

In order to maintain a mixture of blast furnace slag and an oxide or carbonate containing an alkali metal at a temperature of 900 ° C. or higher for a predetermined time, an oxide or carbonate containing an alkali metal is added to a blast furnace slag once cooled to a low temperature. Similar effects can be obtained by reheating afterwards or by adding an oxide or carbonate containing an alkali metal to the high-temperature slag discharged from the blast furnace. When an oxide or a carbonate containing an alkali metal is added to the high-temperature slag discharged from the blast furnace, the high-temperature slag may be added to the high-temperature slag discharged to the slag pit. It is more effective to introduce the molten slag into the molten slag that is passing through it because the reaction occurs while stirring at a higher temperature.

In order to oxidize a mixture of blast furnace slag and an oxide or carbonate containing an alkali metal, the mixture may be brought into contact with oxygen at a high temperature. When the mixture cooled after holding at a high temperature for a predetermined time is crushed and heat-treated in the air, or when an oxide or carbonate containing alkali metal is added to the high-temperature slag in the slag pit in the air, the slag If the thickness is reduced, oxidation is effectively performed. It is very effective to add an oxide or a carbonate containing an alkali metal to the molten slag passing through the first half of the gutter and oxidize the slag by blowing air into the second half of the gutter.

According to the method of the present invention, it is not necessary to rapidly cool the slag kept at a high temperature, so that the slag crystallization rate does not decrease and the characteristics as a roadbed material are not impaired.

Oxides or carbonates containing alkali metals
In addition to the above-mentioned soda ash and waste glass,
Tight (LiAlSiO_Four), Feldspar (LiSi_FourAlO_Ten), Lichi
Aphisite (LiAlSi_TwoO₆), Nepheline (NaAlSiO_Four),jadeite
(NaAlSi_TwoO₆), Soda mica (NaAl_Two(Si_ThreeAl) O_Ten(O
H)_Two), Potassium nepheline (KAlSiO_Four), Kalsilite (KAlSiO
_Four), Leopardite (KAlSi_TwoO₆), Microcline (KAlSi_ThreeO
₈), Muscovite (KAl_Two(Si_ThreeAl) O_Ten(OH)_Two) And it
These mixtures can be used. In addition, Na-based desulfurization
Rug can also be used.
If it is used, it is effective from the viewpoint of securing the temperature.

Next, the problem to be solved by the above invention is solved by a method for treating blast furnace slag which prevents generation of yellow water by adding an oxide containing silicon to the blast furnace slag.

Also, an oxide containing silicon is added to the blast furnace slag, and is maintained at a temperature of 900 ° C. or more.
This is solved by a method for treating blast furnace slag in which the temperature range is gradually cooled at a cooling rate of 15 ° C./min or less. Further, when the oxide containing silicon is waste glass, it can be particularly effectively treated.

It has already been mentioned that CaS in slag causes yellow water. However, when slag containing a large amount of silicon oxide is added to blast furnace slag, CaS and glass phase coexist in the gaps between crystal phases. We have found a method to reduce the elution of yellow water other than the reaction using an oxide or carbonate containing an alkali metal, which prevents the formation of yellow water by forming a structure and a structure in which CaS is enveloped in a glass phase. When a substance containing a large amount of silicon oxide is added to the blast furnace slag, the average composition of the blast furnace slag shifts, and when a crystal phase (mellite phase) precipitates from the molten slag, a glass phase remains at the grain boundary as a balance. Since CaS in the crystal phase gap is wrapped in the glass phase, Ca
It is thought that the outflow of S was suppressed.

When adding an oxide containing silicon to the blast furnace slag, it is important to ensure a temperature at which the blast furnace slag and the oxide containing silicon can be uniformly mixed. The blast furnace slag is discharged from the blast furnace at about 1450 ° C. and has a calorific value of about 1200 ° C. in a state where it falls into the dry pit. Therefore, if waste glass or the like is added thereto, the temperature also decreases. 900 sufficient temperature to mix slag and silicon-containing oxides
If the temperature is maintained at a temperature of at least 900 ° C. for a predetermined time, CaS existing in the gaps between the crystal phases can be covered with a glass phase. Practically, when adding oxides containing silicon to high-temperature blast furnace slag, heating is not particularly necessary to maintain the temperature if the blast furnace slag is added in a state where the blast furnace slag is 900 ° C or higher. When using blast furnace slag, it is necessary to heat it to 900 ° C or more and hold it.
The holding time at a high temperature needs to be appropriately determined depending on the temperature, the type of oxide containing silicon, and the like.

The cooling rate after adding the oxide containing silicon to the blast furnace slag may be a slow cooling. When the crystallization rate of the slag decreases due to rapid cooling with water or the like, the characteristics as a roadbed material are impaired. When cooling high-temperature molten slag, the initial cooling rate is fast, so when cooling molten slag at about 1400 ° C, the initial cooling rate may be about 50 ° C / min, Cooling rate of crystallization region up to 1200 ℃
What is necessary is just to cool slowly at about 10-15 degreeC / min. Of course, there is no problem if the cooling rate is low.

As the oxide containing silicon, waste glass (containing about 15 wt% of Na ₂ O in addition to silica), silica stone or silica sand (SiO ₂ ) is preferable because it is easily available at low cost. In particular, waste glass has a low viscosity in a crystallization region of 900 ° C. to 1200 ° C., and is therefore very effective for reacting in this temperature region. The addition amount of such silicon-containing oxide is 900
It is sufficient if the amount is sufficient to shift the composition of the slag so that a glass phase can be formed when the crystallization region of 12001200 ° C. is gradually cooled (about 10-15 ° C./min) and crystallized. When waste glass is used as an oxide containing silicon, the effective amount of waste glass is at least 8% by weight of the slag. However, as described above, when a large amount of waste glass is added, the temperature decreases, and thus there is a limit to the ability to melt the waste glass with the calorific value of the blast furnace slag that has been discharged. When a large amount of glass is added, heat may be applied from the outside, but the processing cost increases. It is preferable to add waste glass by crushing it.The finer the powder, the easier the reaction is.However, if the powder is too fine, it is difficult to handle at the time of addition. is there.

Blast furnace slag and oxides containing silicon are heated to 900 ° C.
In order to maintain the above for a predetermined time, even if the oxide containing silicon is added to the blast furnace slag once cooled to a low temperature and then reheated, the oxide containing silicon is added to the high-temperature slag discharged from the blast furnace. The same effect can be obtained by adding. In addition, when adding an oxide containing silicon to the high-temperature slag discharged from the blast furnace, the oxide may be added in a state of being discharged to the slag pit, but may be added while passing through a gutter before being discharged to the slag pit. Is more effective because the reaction occurs while stirring at a higher temperature.

After the oxide containing silicon is added to the blast furnace slag, no special oxidation is required. When silicon-containing oxides are added, even if oxides or carbonates containing alkali metals are added at the same time, these components will react with CaS by forming a solid solution in the crystal phase (melilite phase). No oxidation step is required.

[0030]

[Example] (Conventional example 1) Temperature 1450 discharged from taphole
High-temperature slag of 5501550 ° C. was discharged to a slag pit via a gutter so as to have a thickness of 40 to 80 cm.

After three days, the slag which had become room temperature was dug up and subjected to a slag color test according to JIS A 5015. As a result, a yellow water color reaction was observed. When this slag was subjected to aging treatment, no yellow water coloration reaction was observed after 3 months.

(Comparative Example 1)
Crushed to a maximum particle size of 25 mm, and 25 kg of the crushed Na _TwoCO_Three
Put into a carbon crucible with 1 kg
Heat treatment was performed at 0 ° C. for 2 hours.

Then, the particles were again crushed to a maximum particle size of 25 mm and subjected to a color test without oxidation, and a yellow water color reaction was observed. When this slag was aged, 70
After a day, no yellow water color reaction was observed, and the aging time was slightly reduced.

(Comparative Example 2) The slag at room temperature of the conventional example 1 was crushed to a maximum particle size of 25 mm, and only 25 kg thereof was placed in a carbon crucible and heat-treated at 900 ° C for 2 hours in a nitrogen atmosphere. Then, it was crushed again to a maximum particle size of 25 mm, transferred to an alumina crucible, and oxidized in the atmosphere at 1000 ° C. for 1 hour.

When a color test was performed after cooling,
A yellow water color reaction was observed. After 50 days of the aging treatment, the yellow water color reaction was not observed, and the aging time was slightly shortened, but a large amount of SO2 was generated during the oxidation.

[Example 1] A slur of the conventional example 1 at normal temperature
Crushed to a maximum particle size of 25 mm, and 25 kg of the crushed Na _TwoCO_Three
Put into a carbon crucible with 1 kg
Heat treatment was performed at 0 ° C. for 2 hours. After that, the maximum particle size again
Crush to 25mm and transfer to alumina crucible, 10 in air
Oxidized at 00 ° C. for 1 hour.

When a color test was performed after cooling,
A slight yellow water coloration reaction was observed, but the aging treatment
After 30 days, no yellow water coloration reaction was observed, and the aging time was greatly reduced to 1/3 of the conventional aging time.

[Example 2] Temperature 14 discharged from taphole
Blast furnace slag at 50 to 1550 ° C was discharged to a slag pit via a gutter so that the thickness became 20 to 40 cm. The temperature of the slag flowing from the gutter to the pit was 1350 to 1420 ° C. From the ash glass bucket installed above the slag pit, crushed waste glass with a maximum particle size of 1 mm was injected into the upper surface of the slag. At this time, the waste glass was melted on the upper surface of the slag and gradually penetrated into the slag. The ratio of the amount of waste glass charged to the slag was calculated from the total weight of the slag after cooling and the amount of waste glass charged from the bucket, and was found to be 14 parts by weight of waste glass with respect to 100 parts by weight of slag.

When a color reaction test was carried out after cooling, no yellow water color reaction was observed 20 days after the aging treatment, and the aging time was 1 / l of the conventional aging time.
It has been greatly reduced to 3 or less. Further, the slag after cooling was dense and crystallized, and had characteristics as a roadbed material.

Example 3 Temperature 14 discharged from taphole
Pour blast furnace slag at 50-1550 ° C into the gutter and pass through the first half of the gutter
Soda ash was charged into the slag at 1400-1470 ° C. this
The amount of slag flowing through the gutter is 3 to 4 tons / min.
The amount of soda ash entered was 55-62 kg / min. Late gutter
At about 10 cm, in slag of 1350-1430 ° C for oxidation
Blow compressed air from perforated refractory provided below gutter
I let it. Compressed air volume is 50Nm per meter ^Three/ Min
Set the total amount is 450 ~ 550Nm^Three/ Min. That
Later, the slag will be 40-80cm thick in the slag pit
Was released.

When a color reaction test was carried out after cooling, no yellow water color reaction was observed. Further, the slag after cooling was dense and crystallized, and had characteristics as a roadbed material.

Comparative Example 3 Granulated slag was crushed to a maximum particle size of 2 mm, and 25 kg of the slag was placed in a carbon crucible and heat-treated at 1400 ° C. for 1 hour in a nitrogen atmosphere. Cool the furnace at 15 ° C / min, then pulverize to a particle size of 1 mm or less, and add 100 cc of water to 10 g of sample.
And heated at about 60 ° C. for 45 minutes to remove S ^2-
Was determined by titration. The elution amount of S ^2- was about 4.5 mg / l.

Example 4 Granulated slag was crushed to a maximum particle size of 2 mm, 25 kg of the slag was placed in a carbon crucible together with waste glass (4 to 16 wt%), and heat-treated at 1400 ° C. for 1 hour in a nitrogen atmosphere. Was. Cool the furnace at 15 ° C / min, then crush to a particle size of 1mm or less, add 100cc of water to 10g of the sample, and add 45g at about 60 ° C.
After heating for 1 minute, S ^2- in the eluate was quantified by titration. S ^2-
The elution amount of waste glass was about 2.9 mg / l with 4 wt% of waste glass, but it was very low at 0.3 mg / l or less with 8 wt%, 12 wt% and 16 wt% of waste glass. Observation of the sample after cooling showed that when waste glass was added, CaS was precipitated at the grain boundary of the melilite crystal, and a glass phase was formed so as to cover the CaS.

[Example 5] Temperature 14 discharged from taphole
Blast furnace slag at 50 to 1550 ° C was discharged to a slag pit via a gutter so that the thickness became 20 to 40 cm. The temperature of the slag flowing from the gutter to the pit was 1350 to 1420 ° C. Ash glass previously crushed to a maximum particle size of 1 mm was sprayed on the slag pit. It was left as it was, and the slag cooled on the next day was collected. The average cooling rate is considered to be about 1 ° C / min.
The ratio of waste glass input to slag was determined by analyzing the total weight of slag after cooling and the amount of Na ₂ O contained,
Waste glass was 11 parts by weight with respect to 100 parts by weight of slag.
In addition, the slag of the part where the waste glass was not sprayed was collected.

After a color reaction test (JIS A 5015) was performed on these samples after cooling, the yellow index (0.5 or less) and the absorbance of the portion to which the waste glass was added were 0.5 and 0.04, respectively. However, in the slag where the waste glass was not sprayed, the yellow index and the absorbance were 4.0, respectively.
It was 2.52. The slag after cooling was dense and crystallized, and had characteristics as a roadbed material.

[0046]

Since the present invention is constructed as described above, it is possible to provide a method of treating blast furnace slag which is inexpensive and which does not generate yellow water, and which can secure characteristics as a roadbed material.

[Brief description of the drawings]

FIG. 1 is a condensation diagram at 1500 ° C. of the Na—O ₂ —S ₂ system.

Claims (5)

[Claims] 1. A step in which a mixture obtained by adding one or more compounds selected from oxides or carbonates containing alkali metals to a blast furnace slag is maintained at a temperature of 900 ° C. or more, and the mixture is oxidized. And a step of treating blast furnace slag. 2. The method for treating blast furnace slag according to claim 1, wherein the oxide or carbonate containing an alkali metal is waste glass or soda ash. 3. A method for treating blast furnace slag, wherein addition of an oxide containing silicon to blast furnace slag prevents generation of yellow water. 4. A method comprising adding an oxide containing silicon to a blast furnace slag, maintaining the temperature at a temperature of 900 ° C. or more, and gradually cooling the temperature in a temperature range of 900 to 1200 ° C. at a cooling rate of 15 ° C./min or less. Item 4. A method for treating blast furnace slag according to Item 3. 5. The method for treating blast furnace slag according to claim 3, wherein the oxide containing silicon is waste glass.