JPH1036148A - Treatment of molten iron dephosphorized slag and slag - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a treatment for readily modifying a large amount of dephosphorized molten iron slag to a raw material of high added value by adding a specific modifying agent to molten slag prepared by dephosphorizing molten iron and blowing oxygen into the slag and provide modified slag. SOLUTION: This slag-modification installation is a revolving furnace or a slag port equipped with a vessel for molten slag, a feeder for the modification materials and a blower for blowing or injecting oxygen. In the first method, metallic aluminum, metallic silicon and one or more kinds of substances containing the same are added to the dephosphorized molten slag as modifiers and oxygen in blown in. From the view point of costs, the modifier is preferably FeSi, aluminum ash and aluminum can wastes. The amount of the modifier is adjusted so that the ratios of SiO2 and Al2 O3 are 1 and 0.3 to 1 of CaO, respectively. These modifier is injected in a granular or powder form using a carrier gas in order to secure the uniformity of the system. In the second method, aluminum oxide and silicon oxide are additionally added as modifiers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for modifying hot metal dephosphorized slag into a raw material that can be effectively used, and a slag treated by the method.

[0002]

2. Description of the Related Art At present, tens of millions of tons of smelting slag are generated annually in steel production in Japan. The generated slag is classified into blast furnace slag, hot metal dephosphorization slag, converter slag, ingot slag, and the like according to the generation process.
Some of these, like blast furnace slag, have been successfully reused as roadbed materials and cement raw materials.
Most others are disposed by landfill. Reducing the amount of waste slag in this way not only leads to a reduction in steelmaking costs, but is also an important issue in terms of protecting resources and the global environment.

[0003] As a new use of these slags, recycling in the steelmaking process and use of roadbed materials have been conventionally studied (for example, Japanese Patent Publication No. 59-37322,
See JP-A-6-100919).

[0004]

Among the above-mentioned uses, in the recycling in the iron making process, in order to prevent impurities such as phosphorus removed from the molten iron into slag from being picked up again by the molten iron, a recycling method is required. And various restrictions are attached to the amount and the like.

[0005] Even if it is made into a roadbed material, it is included in the material.
The roadbed material is a low value-added product such as "better than landfill" because extra cost is required while aging is required to prevent swelling caused by free-CaO, but the selling price is low.

The present invention has been made in view of the above circumstances. An object of the present invention is to provide a processing method capable of easily reforming a large amount of hot metal dephosphorized slag into a raw material having a high added value and a slag having a blast furnace slag composition by this method.

[0007]

The gist of the present invention is as follows.
The method for treating hot metal dephosphorization slag of (1) and (2) and the slag of blast furnace slag composition of (3) by these methods.

(1) A hot metal characterized by adding at least one of metal Al, metal Si and a substance containing these as a modifier to molten slag after the hot metal has been dephosphorized, and blowing oxygen therein. A method for treating dephosphorized slag. Hereinafter, this is referred to as a first method of the present invention.

(2) A method according to the above (1), wherein at least one of Al oxide, Si oxide and a substance containing them is added as a modifier. Hereinafter, this is referred to as a second method of the present invention.

(3) A slag having a blast furnace slag composition, which has been modified by the method (1) or (2).

At present, if hot metal dephosphorized slag, which has to be landfilled, is reformed to a composition equivalent to that of blast furnace slag, this modified slag can be used for high value-added applications such as cement raw materials, like blast furnace slag. Available to

The main differences in the composition of blast furnace slag and other slag are the following three points.

The basicity (CaO / SiO ₂ ratio) value is as low as about 1 for blast furnace slag (that is, the SiO ₂ concentration is relatively high), while 1.5 to 6 for other slag.
And high.

The concentration of Al ₂ O ₃ is 10 in blast furnace slag.
%, Whereas other slags are as low as 5% at the maximum.

In blast furnace slag, FeO, MnO and P
_Although the concentration of components such as ₂ O ₅ is low, other slags contain many of these components removed from the molten iron.

The present inventors studied a method of reforming slag other than blast furnace slag into a composition of blast furnace slag, and obtained the following findings.

That is, FeO, MnO and P ₂ O ₅ contained in slag other than blast furnace slag are all A
1, Fe-Mn-P
It becomes an alloy, while Al and Si change to Al ₂ O ₃ , SiO _2, etc., which are contained in blast furnace slag, respectively.

Carbon is another example of an additive element for reducing slag. In the case of carbon, FeO, MnO and P ₂
After O ₅ is reduced, it is released outside the system in the form of CO gas.
There is no effect of increasing the concentration of Al ₂ O ₃ and SiO _{2 in the} slag, and it is difficult to approach the blast furnace slag composition.

The use of Si and Al has the following advantages in addition to the fact that the slag composition after reduction is close to that of blast furnace slag.

FeO and P ₂ O ₅ are components that lower the melting point of slag, and when these are reduced to a certain extent, usually,
The slag solidifies, and further reduction reaction is inhibited. However, the reduction of slag by Si and Al is a strong exothermic reaction, and the heat of the reaction causes the temperature of the entire slag to rise, causing an increase in melting point due to a decrease in the concentration of FeO and P ₂ O _{5 and} a decrease in temperature during processing. Can compensate.

Further, when carbon is used as a reducing agent, CO gas is generated by a reduction reaction, slag is formed, and the volume increases. Therefore, the reduction must be performed in a container having a sufficient volume so that the formed slag does not overflow. In contrast, when Si or Al is used as the reducing agent, there is no CO gas generated, so there is little slag forming, and there is an advantage that processing can be performed in a small vessel.

Among the slags not currently recycled, the hot metal dephosphorization slag has a relatively low basicity of about 1.5 to 2.5 and is closest to the composition of the blast furnace slag. Therefore,
In the method of the present invention, this hot metal dephosphorization slag was subjected to reuse.

However, even with this hot metal dephosphorization slag,
FeO, MnO and P ₂ O ₅ contained therein are converted to S
i, only reduction with Al results in SiO ₂ and Al ₂ O
The concentrations of ₃ are not as high as those in blast furnace slag. Therefore, the SiO _{2 in the} slag after the reforming treatment
In addition, Si and Al are added to the hot metal dephosphorization slag in an appropriate excess so that the concentration of Al ₂ O ₃ becomes substantially equal to that of the blast furnace slag, or at the same time, Si oxide (SiO ₂ ) and Al oxide (Al ₂ O ₃ ) is added or oxygen is blown in to generate SiO ₂ and Al ₂ O ₃ , or their concentrations are adjusted.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The reforming apparatus to which the method of the present invention is applied is not limited as long as it has a container for molten slag, a means for adding a modifier, and a means for blowing oxygen by upward blowing or injection. For example, a converter or a slag pot equipped with the above-described addition and oxygen blowing means (hereinafter referred to as a noro pot) can be used.

However, since the reforming slag and the blast furnace slag may be mixed, considering the ease of mixing, a slag reforming treatment place is provided near the blast furnace, and the slag is transported in a noro pot. It is preferable that the hot metal dephosphorized slag in the molten state is reformed in a noro pot as it is.

Although the noro pot may be made of cast iron, it is easy to prevent a decrease in temperature and damage to the noro pot body by using a refractory lining.

In the first method of the present invention, the molten slag after the hot metal has been dephosphorized is added with a metal Al or a metal Si as a modifier.
And one or more substances containing these are added, and oxygen is blown in to perform the reforming treatment.

The modifier is not limited to metal Si and metal Al, and may be any substance containing them. But,
Considering the cost, FeSi (Fe-75% Si etc.), aluminum ash (powder Al containing 40-60% metal Al)
₂ O ₃ ) and waste aluminum cans are preferred.

The amount of the modifier added depends on the composition of the hot metal dephosphorization slag, but in the slag composition after the reforming treatment, the CaO content is 1, the SiO ₂ content is 1, and the Al ₂ O ₃
It is desirable to adjust the minute to 0.3.

Therefore, selection from the modifiers and combinations thereof are not particularly limited. The selection may be determined based on the slag composition before the reforming treatment and the target slag composition after the treatment.

The method of adding the modifier is simply a method of placing on top or placing it in place. However, except for the modifier which is difficult to make into powder like the above-mentioned waste aluminum cans, it is scattered. From the viewpoint of preventing loss and ensuring uniformity of the obtained modified slag, it is desirable to inject a granular or powdery modifier with a carrier gas such as Ar or N ₂ .

After these modifiers are added to the molten metal dephosphorization slag in the molten state, oxygen is blown from above or injected into the slag. At this time, the added S
i, part of Al is FeO, MnO and P in the slag
It reacts with ₂ O ₅ and the like as shown in the following formula (1),
O ₂ and Al ₂ O ₃ are obtained.

[0033] At this time, S which did not contribute to the reduction reaction as described above
The i and Al components react with oxygen gas, for example, as shown in the following formula (2) to become SiO ₂ and Al ₂ O ₃ .

4Al + 3O ₂ → 2 (Al ₂ O ₃ ) (2) Since the reactions represented by the formulas (1) and (2) are exothermic reactions, the slag temperature during the reforming treatment is lowered. Slag temperature can be increased. For example, when Al ash (40% Al) is used,
The slag temperature is increased by about 20 ° C. by the reaction shown in the equation (1) at an addition amount of 10 kg per slag ton.

Since the slag temperature increases during the reforming process, the slag does not solidify even if the melting point of the slag increases due to the reduction of FeO and P ₂ O ₅ . Therefore, it is not necessary to heat the slag specially.

In the second method of the present invention, metal Al, metal S
In addition to i, a substance containing at least one of Al oxide and Si oxide as a modifier is added.

Depending on the composition of the hot metal dephosphorization slag, the temperature of the slag may be too high, which may accelerate the erosion of the container and its lining brick. In this case, the addition amount of the modifier of metal Al, metal Si and a substance or / and an alloy containing them is limited to a level that maintains the slag temperature required for the reforming treatment, and further as other modifiers , Oxidation S
It is effective to add at least one selected from i, Al oxide, and substances containing these (for example, silica sand, brick debris, etc.).

The selection from the above other modifiers and their combinations are not particularly limited. The selection may be determined according to the slag composition and temperature before the reforming treatment, the amount of addition of metal Al and Si, the target slag composition after the treatment, and the like.

As for the method of adding the oxide-based additive, a simple top-up method or a bottom-up method is sufficient.
As described above, a mixture of particles or powders
This is an injection method using a carrier gas such as r or N ₂ .

The slag modified by the method of the present invention can have the same composition as the blast furnace slag. Therefore, the modified slag having the same composition can be used as a cement raw material, and particularly when rapidly cooled by granulation, can be used as a blast furnace cement raw material. Cooling may be performed on the reformed slag alone, but it is advantageous from the viewpoint of equipment costs etc. to cool the slag after transporting it in a molten state in a processing vessel such as a noro pot or a gutter and mixing it with the blast furnace slag. It is.

On the other hand, the Fe—Mn—P alloy produced by the reduction of FeO, MnO and P ₂ O ₅ is effective as ferromagnetic iron, and can be separated from the slag after the reforming treatment, recovered and used. I can do it.

[0042]

EXAMPLE A 250-ton top-bottom blowing converter was used as a dephosphorization furnace.
Hot metal (C: 4.5%, Si: 0.15%, Mn: 0.3
3%, P: 0.110%, S: 0.025%, temperature: 1
After adding dephosphorizing material (converter slag generated at the time of decarburization blowing of dephosphorized pig: 25 kg / t, iron ore: 10 kg / t: quicklime: 5 kg / t), oxygen was blown from the top blowing lance. 7Nm3 / t was blown upward to perform a dephosphorization treatment for about 10 minutes. The amount of slag generated at this time is 40k per ton of hot metal.
g.

The obtained hot metal (C: 4.0%, Si: trace, Mn: 0.20%, P: 0.020%, S: 0.
015%, temperature 1350 ° C.) After tapping into a ladle, dephosphorized slag was washed with 80 kg of FeSi alloy (Fe-75% Si).
Was placed in the noro vase in which was placed.

Into this dephosphorized slag, using an iron pipe coated with alumina, while using Ar as a carrier gas and blowing 125 kg of aluminum ash and 100 kg of silica sand per slag tongue, oxygen gas was blown into the slag tongue by another top blowing lance. It sprayed over 50 Nm3. Table 1 shows the slag composition and temperature before and after the reforming.

[0045]

[Table 1]

The modified slag thus obtained was quenched in a water granulator, and a cement was produced using the modified slag as a raw material. This cement was equivalent in quality to blast furnace slag cement.

In addition, about 90 kg of metal lump was recovered from 1 g of slag from the bottom of the pot. When this lump was analyzed, it was an Fe-Mn-P alloy having the chemical composition shown in Table 2.

[0048]

[Table 2]

[0049]

According to the method of the present invention, hot metal dephosphorization slag which has been used only for landfill treatment, recycling in a steelmaking process having a large constraint, or low value-added roadbed material, etc., can be replaced with blast furnace slag. It can be modified to have an equivalent composition. The obtained modified slag is a high value-added material particularly suitable as a cement raw material.

Claims (3)

[Claims] 1. A hot metal degassing method comprising adding at least one of metal Al, metal Si and a substance containing these as a modifier to molten slag after dephosphorizing hot metal, and blowing oxygen therein. How to treat phosphorus slag. 2. A molten slag obtained by dephosphorizing hot metal, as a modifier, at least one of metal Al, metal Si and a substance containing them, and Al oxide, Si oxide and a substance containing these A method for treating hot metal dephosphorization slag, characterized by adding one or more of the above and blowing oxygen. 3. A slag having a blast furnace slag composition, wherein the slag has been reformed by the method according to claim 1.