JP2003105429A - Method for utilizing waste aluminium laminated film in electric furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for utilizing a waste aluminium laminated film in an electric furnace which reduces or dissolves troubles caused when aluminium ash is used as a combustion improving material in an electric furnace. SOLUTION: In the electric furnace where iron scrap 6 is fused by heat of arc generated among electrodes 3, the waste aluminium laminated film is used as the combustion improving material. The waste aluminium laminated film is stored into a flexible container bag 5 for example and the flexible container bag 5 is put into an iron scrap basket together with the iron scrap 6 and is charged into the furnace together with the iron scrap 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of using a waste aluminum laminate film in an electric furnace.

[0002]

2. Description of the Related Art In an electric furnace, arc heat between electrodes is used to melt iron scrap, but coal, coke, aluminum ash, and kerosene are used to reduce the power consumption and promote the melting of iron scrap. Also, auxiliary fuel such as heavy oil is used together.
When the burner material is a solid such as coal, coke, or aluminum ash, it is charged into an electric furnace together with iron scrap, or supplied from a work port through a lance pipe.

[0003]

Among the above-mentioned auxiliary combustion materials, aluminum ash is a waste and is inexpensive, but it has the following drawbacks. Oxidized slag increases significantly. Aluminum ash contains metallic aluminum as shown in Table 1, for example.
Oxides such as ₂ O ₃ and SiO ₂ account for the majority.

[Table 1] These oxides are directly converted into oxidized slag and discharged from the electric furnace. Furthermore, metallic aluminum is also oxidized and Al ₂ O ₃
Becomes For example, the aluminum ash of the above components is placed in an electric furnace at 100
When Kg is charged, the oxidized slag resulting from this aluminum ash becomes 119 Kg. The effect of reducing the power consumption rate of aluminum ash is small. Since about 60% of aluminum ash is an oxide, a part of the oxidation energy of metallic aluminum is spent on oxide dissolution. When aluminum ash of the above components is used, the calorific value per 1 kg of aluminum ash / ton of molten steel is 2.2 (Kwh / ton of molten steel), but 0.5 (Kwh / ton of molten steel) is oxide Is consumed for melting into the slag, and the electric power consumption rate reduction effect decreases to 1.7 (Kwh / molten steel ton). Oxide lumps in aluminum ash block the steel outlet of the electric furnace.
The oxides in aluminum ash may not be dissolved in the electric furnace and may float as lumps on the slag. This floating material blocks the tap hole during tapping in the electric furnace. Aluminum ash increases the nitrogen concentration in molten steel. Aluminum ash contains about 3% nitrogen, and the nitrogen concentration in molten steel increases with use. Nitrogen embrittles the steel, so its use is limited depending on the type of steel. Aluminum ash produces ammonia. It is not easy to store indoors because the nitrogen in aluminum ash reacts with the water in the air on humid days to generate ammonia, which is a pungent odor. Ammonia is also generated due to water leakage during transportation. Use of aluminum ash increases dust generation. Since aluminum ash is a powder, it dusts when it is charged into an electric furnace or when iron scrap is melted. As a result, it may cause deterioration of the work environment, increase in the amount of dust accumulated in the dust collector system, and troubles in the equipment attached to the electric furnace (for example, the electrode supporting arm).

[0004]

According to the present invention, a waste aluminum laminate film is used as a combustion improver in an electric furnace that melts iron scrap by the heat of an arc generated between electrodes. It is possible to reduce or eliminate the inconvenience caused by using, and to effectively use the waste aluminum laminate film.

Here, the aluminum laminated film will be described. The aluminum laminate film is widely used for packaging foods and medicines, and is a laminate of a plastic film or paper and an aluminum layer (including an aluminum foil, an aluminum vapor deposition film, etc.). There are aluminum laminate films having an aluminum content of 10 to 90%, which are properly used depending on the application. In the manufacturing process for packaging foods and medicines, when a long aluminum laminated film is punched out to obtain a package such as a lid, a surplus material is wound up. This surplus material becomes industrial waste as a waste aluminum laminate film in the form of a piece (roll). Further, in the process of printing a long aluminum laminate film, a waste aluminum laminate film in the form of a roll (roll) is generated due to a printing error or the like, and becomes an industrial waste. The waste aluminum laminate film as industrial waste includes not only cut pieces but also cut pieces. In addition, by unpacking foods and medicines from general households, a large amount of waste aluminum laminate film packaging is discharged as garbage and becomes general waste. Waste aluminum laminate film with high aluminum content is recovered as an aluminum raw material, but is not subject to recovery 50%
The following aluminum laminate films (including those with a content rate of more than 50% depending on the market conditions of aluminum) are considered unsuitable for incineration and disposed of in landfill because burning in an incinerator causes furnace clinker formation and furnace damage due to high temperature combustion. Was there. Therefore, effective use of this waste aluminum laminate film has been demanded.

There are the following measures for supplying the waste aluminum laminate film to the electric furnace. The waste aluminum laminated film is stored in a bag, and this bag is placed in an electric furnace together with iron scrap. Alternatively, a waste aluminum laminate film is compressed to be formed into a block shape, and this block is loaded into an electric furnace together with iron scrap. Or
The waste aluminum laminate film is cut into strips, the strips are formed into a grain shape, and the grains are supplied to an electric furnace through a lance pipe.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. The electric furnace used in the present embodiment is an alternating current bottom steel type electric furnace, and the total amount of iron scrap charging is 155 tons / heat. Structurally, it includes a furnace body 1, a furnace lid 2 that opens and closes an upper opening thereof, and an electrode 3 provided on the furnace lid 2. The furnace body 1 has a tap hole 1a and a working port 1b.
From the work port 1b, a lance pipe for supplying oxygen and a lance pipe 4 for introducing a combustion improver such as coal or coke can be inserted. 1 shows the three-phase AC electric furnace used in this embodiment, the same applies to a DC electric furnace.

As the waste aluminum laminate film, the above-mentioned waste aluminum laminate film (in this embodiment, a lamination of a plastic film and an aluminum layer) as an industrial waste is used. For example, this piece of cloth has a diameter of 100 mm to 200 mm and a width of 700 to 1000.
It has a bulk specific gravity of 500 kg / m ³ and is stored as it is in one or more flexible container bags (flexible bags made of resin, indicated by reference numeral 5 in FIG. 1). In this embodiment, the total volume of the waste aluminum laminate film for each flexible container bag is about 1 m ³ , and the weight is about 500 Kg.
Is.

Next, the operation of the electric furnace will be specifically described. After the tapping of the charge before the first step, the furnace lid 2 is rotated and the first charging (first
Perform the second iron scrap charge). As is known, iron scrap is stored in a raw material charging bucket, and is charged into the furnace from the raw material charging bucket through an upper opening. After returning the furnace lid 2, the electrodes are energized to start melting, and immediately supply of oxygen into the furnace via the lance pipe is started to promote melting. Also, if necessary, an auxiliary combustion material such as coke or coal is added. The injection of these combustion improvers is
It may be stored in a flexible container bag, placed in a raw material charging bucket, and put into the furnace together with iron scrap, or may be put in via a lance pipe 4 for supplying a combustion improver.
Further, if necessary, an auxiliary material such as lime is charged through the hole of the furnace lid 2.

Second step After the iron scrap is melted until the second charging (second iron scrap charging) becomes possible, the second charging is carried out in the same manner as the first charging. The state immediately after the second charging is shown in FIG. Prior to this charging, as described above, three flexible container bags 5 containing waste aluminum laminate film having the same metallic aluminum content (32%) as aluminum ash shown in Table 1
(1550 kg in total) is put in the raw material charging bucket together with the iron scrap 6 for the second charging as an auxiliary combustion material. Then, it is charged into the furnace together with the iron scrap 6. As a result, the supply amount of this waste aluminum laminate is 10 kg /
It becomes scrap ton. Further, auxiliary materials such as lime are supplied from the holes of the furnace lid 2 as needed. The supply of oxygen and the supply of co-burning agents such as coke and coal are the same as in the first step.

Third step Third charging (third time iron scrap charging) is carried out. This third charging is similar to the second charging. Further, the supply of the auxiliary combustion materials such as coal and coke, the supply of oxygen, and the supply of auxiliary materials in this step are the same as in the first step. Fourth step: After the iron scrap in the electric furnace is completely melted, the molten steel composition is adjusted to a predetermined molten steel component and molten steel temperature, and the molten steel is tapped from the tapping port 1a to a ladle.

Unlike the aluminum ash, the above-mentioned waste aluminum laminate film does not contain oxides, so that when it is used as a substitute for aluminum ash, oxidized slag can be greatly suppressed. That is, this waste aluminum laminated film is 1
There is only 60 kg of oxidized slag per 00 kg,
Compared with the case of aluminum ash in Table 1, the amount is reduced by 50% (in the case of aluminum ash, as described above, the amount of oxidized slag is 119 kg). Note that the plastic and paper in the waste aluminum laminate film become carbon dioxide gas and water vapor after combustion, and are discharged outside the furnace.

Since the waste aluminum laminate film does not contain an oxide, the oxidation energy of metallic aluminum is not lost due to the dissolution of the oxide. As a result, the power consumption reduction effect per 1 kg of waste aluminum laminate film / ton of molten steel is improved to 2.2 (Kwh / ton of molten steel),
1.3 times that of aluminum ash.

Since the waste aluminum laminated film does not contain an oxide, the oxide does not form a lump on the slag and does not cause the inconvenience of closing the tap hole 1a during tapping.

Since the plastic in the waste aluminum laminate film is an organic substance, it burns immediately when it is put into the electric furnace, and a large amount of carbon dioxide gas and water vapor are generated. These carbon dioxide gas and water vapor stir the steel bath to accelerate the dissolution of iron scrap and the dephosphorization reaction.

The waste aluminum laminate film usually does not use a nitrogen-containing polymer film. Therefore, the use of waste aluminum laminate film does not cause an increase in the nitrogen content of the steel and does not embrittle the steel. Even steel grades with an upper limit of nitrogen content are not subject to use restrictions. In the examples, the nitrogen content of the molten steel was reduced by 2 to 15 ppm as compared with the case where aluminum ash was used. Further, as described above, the waste aluminum laminate film does not usually contain nitrogen, and even if a nitrogen-containing polymer film is used, since it is a stable compound, it produces an irritating odor of ammonia even when it comes into contact with water. It is easy to store because it is not allowed. Furthermore, since the waste aluminum laminated film is not a powder, it does not generate dust and has no adverse effect on the working environment, the dust collector system, and the equipment attached to the electric furnace.

In the above-described embodiment, one piece or a plurality of pieces of waste aluminum laminate film, which is in the form of a piece of waste, are compression-molded (in some cases, heat-compressed) instead of being stored in a flexible container bag as it is, and this is used. It may be placed in the raw material charging bucket and charged into the furnace together with the iron scrap. By doing so, the bulk specific gravity increases,
Easy to handle. For example, the bulk specific gravity of this compression-molded block is about 700 to 1000 Kg / m ³ ,
The weight is 700 to 10 if one block is 1 m ^3.
It will be 00 kg.

Also, a piece of waste aluminum laminate film in the form of a piece of material is cut and compressed into a grain shape of, for example, 5 mm or less,
This may be continuously blown into the furnace from the lance pipe for supplying the combustion improver (the illustration is omitted because it is similar to the lance pipe 4 in FIG. 1). In this case, in the iron scrap melting step, it is possible to control the supply amount of the auxiliary combustion material using the waste aluminum laminate film as a raw material.

As the waste aluminum laminate film, only the lamination of the plastic film and the aluminum layer as in the above embodiment may be used, only the lamination of the paper and the aluminum layer may be used, or both may be used together. May be. Further, waste aluminum laminate films having different aluminum contents may be mixed and used.

As a raw material, it goes without saying that industrial waste consisting of waste aluminum laminate film of cut pieces and general waste can be used. Whatever shape the waste aluminum laminate film is put into, the charging time can be appropriately selected. For example, the first charging step or the third charging step may be performed, any two steps of the first, second, and third may be performed, or all steps may be performed.

All of the aluminum ash conventionally used may be replaced with the above-mentioned waste aluminum laminate film, or a part thereof may be replaced and used in combination with aluminum ash. When the entire amount of aluminum ash is replaced with the above-mentioned waste aluminum laminate film, the amount used is 20 kg / metal equivalent.
It is preferably within the molten steel ton.

[0022]

As described above, according to the present invention, by using a waste aluminum laminate film as an auxiliary combustion material, the amount of slag generated is reduced, the power consumption reduction effect is enhanced, and the tapping port at tapping It is possible to prevent clogging and prevent the rise of nitrogen in the molten steel. Moreover, it is possible to effectively use the waste aluminum laminate film that has been buried and disposed of. Further, the waste aluminum laminated film can be obtained at a lower cost than aluminum ash and does not generate an offensive odor, so that it can be easily stored and dust generated during operation can be prevented.

When the waste aluminum laminate film is stored in a bag and the bag is loaded into the electric furnace together with the iron scrap, pretreatment is not required, the cost can be reduced, and a large amount can be used at a time, so that the operation is also possible. It's easy.

When the waste aluminum laminate film is compressed into a block shape and the block is loaded into an electric furnace together with iron scrap, the pretreatment cost is relatively low, and the waste aluminum laminate film is used. The auxiliary material used as the raw material is easy to handle and can be used in large quantities at one time, so operation is easy.

When the waste aluminum laminate film is cut into strips, the strips are formed into a grain shape, and the grains are supplied to the electric furnace through the lance pipe, the amount of the auxiliary combustion material supplied in the melting step is controlled. It can be performed.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an electric furnace for carrying out an embodiment of the method of the present invention.

[Explanation of symbols]

1 Furnace body 2 Furnace lid 3 Electrode 5 Flexible container bag containing waste aluminum laminated film 6 Iron scrap

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takeshi Nakamura             9 Topy work, 5-4 Yonbancho, Chiyoda-ku, Tokyo             Business (72) Inventor Katsumasa Komatsuzaki             87-27 Elementary Kanbei Ina, Tsukuba-gun, Ibaraki             Matsuzaki Sangyo Co., Ltd. (72) Inventor Yuzo Sawa             87-27 Elementary Kanbei Ina, Tsukuba-gun, Ibaraki             Matsuzaki Sangyo Co., Ltd. F-term (reference) 4D004 AA07 AA12 AA16 AA50 BA03                       CA03 CA04 CA28                 4K001 AA10 BA22 FA10 GA16 GB01                 4K014 CB01 CB05 CB09 CC01 CC04                       CD13 CD18

Claims (4)

[Claims] 1. A method for utilizing a waste aluminum laminate film in an electric furnace, wherein the waste aluminum laminate film is used as an auxiliary combustion material in an electric furnace in which iron scrap is melted by heat of an arc generated between electrodes. 2. The method for using a waste aluminum laminate film in an electric furnace according to claim 1, wherein the waste aluminum laminate film is housed in a bag, and the bag is loaded into an electric furnace together with iron scrap. 3. The waste aluminum laminate in an electric furnace according to claim 1, wherein the waste aluminum laminate film is compressed and formed into a block shape, and the block is charged into an electric furnace together with iron scrap. How to use the film. 4. The waste aluminum laminate film is cut into strips, the strips are molded into a grain shape, and the grains are supplied to an electric furnace through a lance pipe. To use waste aluminum laminate film in electric furnaces in Japan.