JP2001089135A - Calcium aluminate excellent in homogeneity - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high-quality calcium aluminate having a main composition of 12CaO.7Al2O3 as a fluorite substitute at a low cost. SOLUTION: This low-melting calcium aluminate comprises a principal component of 12CaO.7Al2O3 and has excellent homogeneity. The calcium aluminate is produced by completely melting an aluminum dross produced when melting and refining aluminum or an aluminum alloy and a calcium-containing compound in an electric furnace. The calcium aluminate has <0.5 half-width of the main peak (211) according to the X-ray diffractometry and at least >=300 counts/s (cps) X-ray diffraction intensity and is excellent in homogeneity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a calcium aluminate excellent in homogeneity, and more particularly to a composition mainly composed of 12CaO.7Al2 O3, which has a small amount of impurities and a uniform structure. For this reason, the present invention relates to a calcium aluminate which can be easily used as a slag-making agent or a raw material for adjusting components in cement in a steelmaking process and is inexpensive.

[0002]

2. Description of the Related Art A slag-making agent is used for desulfurizing, dephosphorizing, deoxidizing, and controlling the form of inclusions during smelting of steel in order to reduce impurity elements in the steel material in a steelmaking process. Raw material to be added to the steel being melted. As this auxiliary material, fluorite has been used as having excellent slagging properties, but recently its use has been compromised because fluorite contains fluorine.

[0003] This is because fluorine has become an environmental standard item due to the revision of the Notification of the Environment Agency, and fluorine may affect the human environment through environmental pollution, and measures for water pollution should be comprehensively and effectively implemented. This is because it has been recognized that it is necessary to take appropriate measures, and as a result, the regulation of fluorine elution has become strict. Due to the regulation of fluorine, there is a strong possibility that practical use will not be possible in the steelmaking process in the future. Therefore, an alternative to fluorite is urgently required.

As an alternative to this fluorite, calcium aluminate-based ones, particularly those having 12CaO.7Al2O3, hardly contain fluorine, and the waste after melting of steel clears environmental problems. It is recognized as being optimal. In addition, this 12CaO.7
Al2O3 has excellent desulfurization ability, and is particularly suitable for producing high-quality steel by reducing nonmetallic inclusions in the steel or controlling the form of inclusions.

[0005] Therefore, various 12CaO · 7Al2
Methods for producing O3 have been studied. Generally, a so-called pre-melt type 12CaO.7Al2O3 includes a melting method in which a mixture of high-purity CaO, Al2O3, and CaF2 is melted at a high temperature of 1300 ° C. or more.

[0006] A calcined calcium aluminate, 12CaO · 7A, which is baked at a temperature of 1200 ° C. or less
A method of mixing and granulating Ca (OH) 2 and Al2O3 in l2O3 and calcining the mixture in a rotary kiln, cupola furnace, or the like, or adding CaO to sodium aluminate obtained as an intermediate in the process of producing alumina from bauxite. And calcining the obtained calcium aluminate to obtain 12Ca
Wet baking method for obtaining O.7Al2O3, CaO and Al2
There is a method in which O3 is obtained by wet grinding and kneading with a ball mill, followed by firing. For example, Japanese Patent Application Laid-Open No. Hei 10-53411 discloses that aluminum slag, which is industrial waste, is used in order to reduce the production cost, and calcium aluminum is produced by causing an exothermic oxidation reaction of metallic aluminum in a rotatable kiln. This is for producing nate.

[0007]

SUMMARY OF THE INVENTION The calcium aluminate 12CaO.multidot.
7Al2O3 has the following problems. The premelt type has problems such as high cost, inferior products in fired products, and reduced workability in injection mixing use in the smelting process. Specifically, in the case of a pre-melt type manufactured product, the use of high-purity alumina as a raw material increases costs, but when aluminum slag, which is a waste, is used as Al2O3 as a raw material, Unlike a baked product that cannot decompose and remove nitrogen N contained in 3 to 8% of slag, it can not only achieve 1% or less of nitrogen N, but also obtains 12CaO.7Al2O3, which is a calcium aluminate. Does not generate ammonia smell due to humidity.

In the case of calcium aluminate obtained by firing, it takes time and energy to decompose and remove nitrogen in aluminum slag, and the resulting calcium aluminate is a mixture of powder and granules,
There were portions where O.7Al2O3 was generated and portions where O.7Al2O3 was not generated, and variation in quality was large. When the calcium aluminate obtained by this calcination is used as a slag-making agent in an electric furnace during the steel making process, the calcium aluminate is a mixture of powder and granules. Not only does the workability during use deteriorate significantly, but the nitrogen that cannot be completely removed makes it impossible to use it during the reduction phase and in the out-of-furnace smelting process. This is because the metallic aluminum contained in the aluminum slag, which is the raw material, has not completely reacted in the firing method, so it remains in the obtained calcium aluminate, reacts with nitrogen in the atmosphere, and adsorbs. Furthermore, ammonia is synthesized by reacting with moisture in the atmosphere, and as a result, the working environment is deteriorated due to the smell of ammonia. Further, when the calcium aluminate obtained by the calcination comes into contact with the molten steel, nitrogen is transferred to the molten steel, which also causes a deterioration in the quality of the molten steel.

Due to these problems, in the production of calcium aluminate 12CaO.7Al2O3, a universal material having characteristics that can be used in all processes of iron making and steel making is required, as is the case with conventional fluorite. The present invention has been made in order to solve the above-mentioned problems, and realizes the production of a low-cost calcium aluminate which is a high-grade pre-melt type which is easily introduced in a steelmaking process and does not have a bad odor. Aim.

[0010]

SUMMARY OF THE INVENTION The present invention relates to a method for producing an aluminum or aluminum alloy by melting and solidifying aluminum slag and a calcium-containing compound which are produced by melting and refining aluminum or aluminum alloy in an electric furnace. 12Ca
The present invention proposes calcium aluminate which is O.7Al2O3, has a half width of the main peak (211) determined by X-ray diffraction of less than 0.5-, and has an X-ray intensity of at least 300 cps or more and is excellent in homogeneity. is there.

According to the present invention, the calcium aluminate of the present invention has a main peak (21
Since the half width of 1) is 0.5- or less, the degree of crystallization of the obtained calcium aluminate is high and the homogeneity is high. When this half width becomes larger than 0.5-
The degree of crystallization of 12CaO.7Al2O3 is low, and the homogeneity is low. Further, since the calcium aluminate of the present invention has an X-ray intensity of 300 cps or more, it contains few impurities and has a main component of 12CaO.7Al2O.
3 can have 70% or more. If the X-ray intensity is lower than 300 cps, the content of impurities is large and 12
The strength relatively decreases with the content of CaO.7Al2O3.

As described above, since the calcium aluminate of the present invention is completely melted, the original forms of the aluminum slag and the calcium-containing compound as the raw materials are not kept, and the degree of crystallization is high, and the crystal is not crystallized. It is coarse. Furthermore, since 12CaO.7Al2O3 is synthesized homogeneously, the mineral composition becomes hard and brittle,
The product can be made into a lump product that is easy to classify and handle, and as a result, can be easily introduced as a slag-making agent in a steelmaking process or the like.

Further, since the aluminum slag as a raw material and the calcium-containing compound are completely reacted by melting, the metal aluminum contained in the aluminum slag does not exist in the calcium aluminate. As a result, since there is no reaction with nitrogen in the air accompanying the remaining metallic aluminum, a high-quality pre-melt-type calcium aluminate which does not generate an odor caused by ammonia is obtained.

[0014] The aluminum slag referred to here is waste in aluminum refining, and is 45 to 60%
Al2O3 as the main component, and 5 to 4 metallic aluminum
0%, AlN which is aluminum reacted with nitrogen is 2 to 2%
15%. The calcium-containing compound is preferably CaO, but is preferably Ca (OH) 2 or C
aCO3 may be used. These compounds contain at least 40% or more as a main component, and the content of sulfur (S) is 2%.
% Is preferable.

[0015] Further, the calcium-containing compound can be reduced slag which is a by-product generated in the reduction smelting process. This is because the calcium-containing compound of the reducing slag is CaO, which can be used as a raw material of the present invention, and in particular, the reducing slag is mainly landfilled as industrial waste. Needless to say, resources are saved by effective use of industrial waste and the cost is low.

Alternatively, the calcium-containing compound can be incinerated fly ash or incinerated molten fly ash, which is industrial waste. This is because the calcium-containing compound of the incinerated fly ash or the incinerated molten fly ash is CaO, so that, like the above-described reduction slag, resource saving by effective use of industrial waste, and needless to say, it is inexpensive. Absent.

As described above, the main component of the calcium aluminate of the present invention is 12CaO.7Al2O.
In the production, the aluminum slag and the calcium-containing compound as raw materials are put into an electric furnace and completely melted and solidified in the electric furnace, so that the degree of crystallization is high and the homogeneity is excellent. The resulting 12CaO.7Al2O3 is synthesized and can be easily introduced in a refining process or the like. In addition, since it is completely reacted, there is no metallic aluminum component in the calcium aluminate and no reaction with nitrogen in the atmosphere occurs, so that a high-quality calcium aluminate that does not generate an ammonia odor is obtained.

The above-mentioned calcium aluminate can be used as a slag-making agent or a cement raw material for a steelmaking process. In particular, as a slag-making agent, it can be used as an inexpensive calcium aluminate having excellent desulfurization and dephosphorization action, while suppressing generation of fluorine gas restricted by regulations in the future.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention relates to a homogeneity produced by completely melting and solidifying aluminum slag and a calcium-containing compound produced when aluminum or an aluminum alloy is melted and refined in an electric furnace. Excellent calcium aluminate. The aluminum slag is a main component of the residual ash of aluminum including aluminum oxide, aluminum nitride, metallic aluminum, etc. from each step when refining aluminum or an aluminum alloy. As an example, Table 1 shows the chemical composition of the aluminum slag.

[0020]

[Table 1]

The calcium-containing compound includes C
Preferred are aO, Ca (OH) 2, CaCO3, reduction slag which is a by-product generated in the reduction and smelting process containing these as main components, and incinerated fly ash or incinerated molten fly ash which is industrial waste. In particular, since the slag and fly ash in the reduction period are industrial wastes, their utilization is preferable from the viewpoint of resource saving and reuse. As an example, Table 2 shows the chemical composition of the calcium-containing compound.

[0022]

[Table 2]

Hereinafter, Examples 1 to 3 of the present invention will be described in detail. (Example 1) Powder having a particle size of 100 mesh under as aluminum slag and powder having 3 mm under under (CaO: 92%) generated from a quicklime manufacturing process as a calcium-containing compound were previously mixed at a weight ratio of 1: 1. Tables 3 and 4 show the main components of the aluminum slag and the calcium-containing compound.

[0024]

[Table 3]

[0025]

[Table 4]

As the melting condition of the mixture, 1000 kg of the initial mixture was charged into a 10-ton electric furnace of 2500 KVA, heated by electricity, and melted while alternately adding 500 kg of quicklime and 500 kg of aluminum slag.

After it was visually confirmed that the mixture and the charge charged in the middle were completely melted, the melt was received in a slag pot and gradually cooled to solidify. It takes about 3 hours from current heating to complete melting. Final charge (initial 100
0 kg, intermediary lime 500 kg, aluminum slag 5
00 kg), the weight of the obtained calcium aluminate was 1810 kg, and the yield was 90.5%.
Met. The power per ton of the obtained calcium aluminate was 998 KWH.

Table 5 shows the composition of the obtained calcium aluminate.

[0029]

[Table 5]

According to Table 3, the composition of the obtained calcium aluminate was about 45% Al2O3 and about 40% CaO.
%, Others were SiO, MgO, etc. It should be noted that the amount of nitrogen contained in the obtained calcium aluminate was only 0.2%. Thereby, even when the calcium aluminate is wet with water, no ammonia gas is generated, so that the obtained calcium aluminate is stored or white smoke or ammonia is generated when the obtained calcium aluminate is used. The risk of gas generation can be avoided.

X of the obtained calcium aluminate
Analysis by a line diffraction method confirmed that 12CaO.7Al2O3 was present as a main component as shown in FIG. Moreover, the half width of the main peak (211) is 0.235 and the diffraction intensity is about 1200 cp.
s, indicating that the melting reaction of the present example was uniform with respect to the aluminum slag and the calcium-containing compound, and was completely completed. In addition, there are few impurities,
Excellent homogeneity. Table 6 shows the results of quantitative analysis by the X-ray diffraction method.

[0032]

[Table 6]

From Table 6, the obtained calcium aluminates according to the present invention are Sample A and Sample B, and Sample C and Sample D are shown as comparative examples. Sample A had a mineral composition particle size ratio of 30
Since 85% or more is contained at 85% or more, the charging operation in the refining process can be easily performed. Sample B is inferior to Sample A in half-width and X-ray intensity, but is 30% or less in the mineral composition having 75% of the particle size. It becomes possible. On the other hand, for samples C and D as comparative examples, 30 m
Since the ratio of the particle size finer than m is high, the powder tends to be formed into a powdery form instead of a lump, so that the handling property including the charging in the refining process is poor.

(Example 2) Next, in the same electric furnace as in Example 1, 50% by weight of the same aluminum slag as in Example 1, 30% by weight of 3 mm under powder generated from the quicklime manufacturing process, and refuse incineration 20% by weight of high alkali fly ash
Was premixed. The main component of the high alkali fly ash was almost the same as the fly ash of Table 2 except that CaO was 45.2% and S was 1.0%.

The above mixture was mixed with one of 1000 kg and 5
Two pieces of 00 kg were produced. First 1000kg
Is charged in an electric furnace in advance, electric heating is started, 500 kg is charged about 1 hour later as the first intermediate period, and the remaining one is charged 1 hour after the first intermediate period as the second intermediate period. Melted. The resulting calcium aluminate is 1820
kg. The obtained calcium aluminate was analyzed by the X-ray diffraction method in the same manner as in Example 1. As a result, the calcium aluminate 12CaO.7Al2
It was confirmed that O3 was the main component.

Example 3 In the same electric furnace as in Example 1, 40% by weight of aluminum slag and 40% by weight of 3 mm under powder generated from the quicklime manufacturing process as a calcium-containing compound were added.
2% by weight of magnesia clinker (91% MgO)
0% by weight was mixed in advance, and the mixture was charged into an electric furnace in the same manner as in Example 2 to perform melting. This magnesia clinker is used to reduce Al2O3
When the content increases, erosion of the refractory of the furnace wall of the smelting furnace becomes severe. Therefore, by providing MgO in the slag component at 8% or more, the effect of greatly reducing erosion is utilized. The obtained calcium aluminate weighed 1860 kg. The obtained calcium aluminate was analyzed by the X-ray diffraction method as in Example 1. As a result, as in Example 1, it was confirmed that 12CaO.7Al2O3 of calcium aluminate was the main component.

[0037]

As described above, according to the present invention, a predetermined amount of the raw material aluminum slag and the calcium-containing compound are charged into the electric furnace and completely melted, so that the obtained calcium aluminate has few impurities. The tissue is homogeneous. In addition, even after it has become a complete lump, it can be easily pulverized and classified, so it is easy to put it in the smelting process, and since it does not generate ammonia odor even when wet with water, Calcium aluminate can be easily controlled.

In addition, since the obtained calcium aluminate is a high-quality pre-melt type of 12CaO.7Al2O3, industrial wastes such as slag and fly ash can be used as a raw material for the production, so that it is inexpensive. It can be used as a slag-making agent and cement raw material as a natural calcium aluminate.

[Brief description of the drawings]

FIG. 1 shows the result of X-ray diffraction of the calcium aluminate obtained in Example 1 of the present invention.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Tetsuo Toyoda 79 Zenta Nitta Nishita, Saya-machi, Kaifu-gun, Aichi Prefecture F-term (reference) 4G076 AA02 AA18 AB02 AB06 AB09 AB16 AB28 AC04 BA17 BC08 BC09 BG10 CA01 CA33 CA36 DA30

Claims (3)

[Claims] 1. The main component produced by completely melting and solidifying aluminum slag and a calcium-containing compound produced by melting and refining aluminum or an aluminum alloy in an electric furnace is 12CaO.7Al2O3, and X A calcium aluminate excellent in homogeneity, characterized in that the half width of the main peak (211) in X-ray diffraction is smaller than 0.5- and the X-ray diffraction intensity is at least 300 cps or more. 2. The calcium aluminate having excellent homogeneity according to claim 1, wherein the calcium-containing compound is a reduction phase slag which is a by-product generated in a reduction smelting process. 3. The calcium aluminate according to claim 1, wherein the calcium-containing compound is incinerated fly ash or incinerated molten fly ash, which is an industrial waste.