JP2000185322A - Metal melting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to reduce an energy cost in melting metals and to suppress the environmental disruption or the like due to waste tires or the like. SOLUTION: This melting method comprises melting metal scraps S by utilizing waste tires T and/or waste plastics as fuel or some part of the fuel by charging the metal scraps S, the waste tires T and/or the waste plastics in a melting furnace 1 for melting the metal scraps S by blasting oxygen through pipes 12 or the like in the furnace under the state that tires T or the like are charged in the melting furnace 1 as scrapped and respective tires T or the like are mixed with the scraps S under nearly uniformly distributed state or charged in alternately laminated layers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for dissolving and recycling metal scraps such as scrap iron.

[0002]

2. Description of the Related Art Generally, a metal is melted by adding a metal scrap containing scrap iron as a main raw material, necessary alloying elements and a new steel ingot as appropriate, and charging the molten metal into a melting furnace, and using a burner using heavy oil as a main fuel. The metal scrap and the like are melted by the flame from the heater and the heat of the arc generated between the electrode and the scrap. In addition, in order to meet the needs for cost reduction, various technical improvements have been made to improve the melting efficiency of metal scrap by the flame of the burner or the arc of the electrode.
However, the cost reduction due to the improvement of the dissolution efficiency is approaching the limit. For this reason, it has been attempted to convert a part of the fuel into pulverized coal, wood chips, and the like, but it has been insufficient.

On the other hand, with the recent rise in environmental awareness, disposal of various wastes has become a problem. In particular, waste tires and waste plastic require enormous costs to detoxify and dispose of. For example, burning discarded tires and discarded plastics can damage the incinerators and spread odors around the incinerator while releasing them. For this reason, in order to increase the combustion efficiency of the waste tire or the like, it is conceivable that the waste tire or the like may be burned into fine chips in advance by a cutting device and burned, but the cutting leads to an increase in cost. Therefore, they are often piled up in a state of being discarded at an industrial waste disposal site or the like. In some cases, it is illegally discarded in a wilderness or the like and piled up in a pile, resulting in a problem that the environment falls into a vicious cycle.

[0004]

However, waste tires and waste plastics contain a large amount of carbon (C) in their components. Therefore, when waste tires and the like are incinerated, a large amount of carbon dioxide (CO ₂ ) is released together with combustion energy. Therefore, there is also a problem that global warming is promoted by incinerating waste tires and the like. It is an object of the present invention to provide a metal melting method that can further reduce the cost of metal melting described above and contribute to suppressing environmental degradation and environmental destruction due to waste tires and the like.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention has been made by focusing on utilizing carbon contained in waste tires and waste plastics as fuel when melting metal scrap and the like. is there. That is, in the metal melting method of the present invention, a metal scrap or the like and a waste tire and / or a waste plastic are charged into a melting furnace in which oxygen or air is blown into the furnace to melt the metal. Alternatively, metal scrap or the like is dissolved using waste plastic as a fuel or a part thereof.
According to this method, the scrap can be melted by using the energy generated when carbon contained in the waste tire or the like is oxidized, so that the cost of the fuel and electric power used for melting can be reduced. Moreover, waste tires and waste plastics can be used as fuel, which can contribute to solving environmental problems. The oxygen blown into the furnace includes pure oxygen as well as oxygen-enriched air.

In addition, the waste tire and / or waste plastic is charged into a melting furnace in a state of being discarded without being formed into fine chips or crushed forms.
Metal melting methods are also included. According to this, the waste tire is finely cut, and without cutting or crushing the waste plastic having a three-dimensional shape, the waste tire is charged into the melting furnace in the form as it is, and is used as fuel. The processing cost is unnecessary, and the fuel cost required for melting the metal can be further reduced. In addition, it can contribute to enhancing the recycling efficiency of discarded tires and the like, which is preferable in terms of environmental measures. Note that the present invention includes a case where the waste tire or the like is charged into the melting furnace together with a discarded tire or the like as well as a fine chip or a crushed form.

Further, there is also included a metal melting method in which when the waste tire and / or waste plastic is charged into the melting furnace, the waste tire and / or the waste plastic is charged in a mixed state having a substantially uniform distribution with metal scrap or the like. According to this, since the scrap of the raw material and the waste tires and the like serving as fuel are inserted in the melting furnace in a state of being mixed with each other, the combustion heat of the waste tires and the like can be effectively used for melting the adjacent scrap. , Can increase the combustion efficiency. In addition, when loading the waste tire and / or waste plastic into a melting furnace, the waste tire and / or waste plastic and the metal scrap or the like are layered and alternately stacked, and then loaded. Is also included. This facilitates the work of loading the scrap with the waste tire and the like, and the combustion heat of the waste tire can be effectively used for melting the scrap, so that the combustion efficiency can be reliably increased.

[0008] The present invention further includes a metal melting method in which the waste tire and / or waste plastic is charged into the melting furnace at a charging height of 80% or less of the upper limit of the charged material in the melting furnace. . According to this, the combustion heat of the waste tires and the like used as fuel can be reliably and effectively used as the melting energy of the scrap without being immediately discharged to the outside of the furnace. In addition, when the charging height exceeds 80%, the combustion heat of the discarded tires and the like can be discharged to the outside of the furnace without being used for melting. The lower limit of the loading height of discarded tires and the like is theoretically the hearth surface (0%) in the melting furnace.
However, in actual operation, the upper limit of the charge is about 5
About 10%.

In addition, a metal melting method in which the amount of the waste tire and / or waste plastic charged into the melting furnace is 3 kg / metal scrap ton or more is also included. According to this, it is possible to secure the combustion heat and reduce the fuel cost by loading the waste tire or the like.
In addition, if the amount of waste tires and the like is less than the amount, the combustion heat is not sufficiently secured, and therefore, it is excluded. Such a charging amount is desirably 10 kg to several 100 kg / metal scrap ton or more. However, from the viewpoint of actual operation, the upper limit of the amount of waste tires charged is about 1 ton / metal scrap ton.
It is about. It should be noted that, in addition to ordinary scrap iron, scraps may include metal products used for specific applications and a part of the waste depending on the metal or alloy to be melted. At the same time as the scrap, an alloying element component or a new steel ingot or metal ingot is charged.

[0010]

Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1A shows a longitudinal section of a melting furnace 1 used in the present invention. The melting furnace 1 is a so-called Elle-type three-phase arc furnace, and includes a hearth 2 made of a refractory and a furnace wall 1 provided with a water-cooled jacket or a refractory inside a steel shell.
3, 14, 15, and 17, and a furnace lid 20. The hearth 2 has a floor surface 4 that is loosely spherically recessed, a tapping gutter 6 projecting outward from an opening 5 on the left side in the figure, and a rear end 8 having an opening 7 on the opposite side. Consists of Such a hearth 2 is placed on a base 9 via a round surface 10 of a support structure 11 provided on the bottom surface thereof, and the whole furnace 1 can be tilted gently so that the tip of a tapping gutter 6 can be lowered. It has been.

In the opening 7 and in the furnace walls 15 and 17, pipes 12 and 16 for oxygen injection penetrating therethrough are provided.
18 are arranged. Furthermore, three electrodes 24 penetrate vertically and equidistantly into an opening 22 formed at the top of the furnace lid 20. These electrodes 24 generate an arc with the metal scrap S to be charged into the furnace 1 later. An exhaust pipe 26 for discharging gas and the like in the furnace 1 is provided on the upper surface of the furnace lid 20. The furnace lid 20 is used for the furnace wall 1.
The moving means (not shown) can move in the horizontal direction so as to be able to freely contact and separate from the upper ends of 5, 17. Therefore, after moving the furnace lid 20 to another position and loading the metal scrap S and the waste tire T into the furnace 1, as shown in FIG. Return on walls 15,17.

In the state shown in FIG.
Oxygen is blown into the furnace 1 from the furnace
The three-phase alternating current is supplied to each electrode 24 lowered from the opening 22 of the zero. In order to increase the voltage as the current stabilizes and shorten the melting time of the metal scrap S,
Apply the highest voltage as quickly as possible. When the charged metal scrap S and the waste tire T are bulky in the melting furnace 1 and all the raw materials cannot be charged at one time, the initially charged scrap S is melted to some extent, and When the level of the charge (S, T) drops, the remaining scrap S
And waste tires T are loaded. In addition, in the initial charging, together with the discarded tire T that has been discarded as it is, the discarded tire T in the form of fine chips is simultaneously charged into the melting furnace 1 to facilitate the combustion of the tire T. It is also possible.

An arc is generated between each of the electrodes 24 and each of the scraps S, and each of the scraps S
Is melted, and the waste tire T is also burned by the injected oxygen by the heat of melting or the arc heat. That is, the carbon contained in the tire T is oxidized to carbon dioxide (CO ₂ ).
Or, it becomes carbon monoxide (CO), and the latter carbon monoxide is further oxidized (secondary combustion) to carbon dioxide. Energy (combustion heat) is generated during each oxidation reaction. The heat of combustion of the tire T is also used for melting the scrap S.

The electric power supplied to the electrode 24 is set at or near the maximum voltage before the time when the combustion heat of the waste tire T can be used. However, the combustion heat of the tire T can be used together with the arc heat of the electrode 24. After the period, the voltage can be gradually reduced. Therefore, the amount of electric power required for melting the scrap S can be saved, and the waste tire T can be effectively used, so that both energy saving and environmental improvement can be achieved at once. The power supply during the melting period is performed by changing the temperature in the melting furnace 1 and / or the charge.
Automatic control is performed so that the shift can be performed sequentially according to the degree of melting and combustion of (S, T). The gas and dust generated by the melting and burning are discharged from the exhaust pipe 26 of the furnace cover 20 and sent to a dust collector (not shown).

By the way, the waste tire T is charged into the melting furnace 1 in such a manner that the metal scrap S and the waste tire T are mixed in advance so as to be uniformly distributed, and then transported by a bucket (not shown). It is charged into the melting furnace 1 from a bucket. Then, as schematically shown in FIG. 2 (A), the scrap S and the waste tire T are charged in the melting furnace 1 in a mixed state having a substantially uniform distribution. Thereby, each pipe 12,
Oxygen blown from the tires 16 and 18 is supplied to each waste tire T in a substantially uniform manner, and the combustion of each tire T is performed in parallel, and the combustion heat is efficiently transmitted to the adjacent scrap S so that the waste heat is efficiently transmitted to the scrap S. It can be used effectively as heat of dissolution.

Further, the metal scrap S and the waste tire T are put in individual dedicated buckets, and the tire T and the scrap S are charged into the melting furnace 1 in the order of the tire T and the scrap S. Then, as shown in FIG. 2 (B), the layers of the waste tires T, T,... And the layers of the scraps S, S,. . Also in this case, the oxygen blown from the pipe 12 or the like is supplied to the tires T substantially uniformly, and the combustion of the tires T is performed in parallel, and the combustion heat is efficiently transmitted to the vertically adjacent scraps S. It can be transmitted and used effectively for the heat of dissolution. If the scraps S are formed in a flat shape in advance as shown in the figure, the above-mentioned layered loading becomes easy.

Here, the waste tire T in the melting furnace 1
3A will be described with reference to FIG. As described above, each tire T supplies heat of dissolution of the surrounding scrap S by oxidation and combustion. However, if the position where the tire T is charged in the melting furnace 1 is too high, the combustion heat is not transmitted to the tire T, but is directly discharged from the exhaust pipe 26 to the outside of the furnace 1, and the power supply to the electrode 24 is reduced. It does not contribute effectively. Then, the charging height h of the waste tire T was changed variously with respect to the upper limit height H of the charging material in the melting furnace 1, and the change of the power consumption unit of the melting furnace 1 at that time was measured. The results are shown in the graph of FIG.

From the above graph, the charging height h of the tire T is:
The ratio of the charge to the upper limit height H in the melting furnace 1 is 80.
%, The unit power consumption increases sharply. Therefore, the charged height h of the discarded tire T loaded together with the scrap S is 80% in terms of the ratio to the charged upper limit height H.
% Is understood to be effective. Furthermore, from the graph of FIG. 3B, the charging height h of the tire T is
It is also understood that a range of about 50-80% of the upper charge height H is desirable. The normal level of 100% in the basic unit of power in the graph of FIG. 3 (B) is the power required when the scrap S is melted only by the power supplied to the electrode 24 without loading the waste tire T. Indicates the basic unit.

The waste tire T charged into the melting furnace 1
The effective charging amount was also examined. That is, with respect to all the scraps S (ton) charged into the melting furnace 1, the total charging amount (kg) of the tire T was variously changed, and the change in the power consumption unit of the melting furnace 1 was measured. The results are shown in the graph of FIG. From this graph, the normal level (100%) at which the scrap S is melted only by the power supplied to the electrode 24 without loading the waste tire T
On the other hand, it can be understood that the power consumption unit tends to gradually decrease with an increase in the loading amount of the tire T. However, tire T
If the charging amount is too small, the reduction of the power consumption unit does not appear remarkably, and only the charging operation becomes complicated, which is not effective.

Therefore, as shown by the broken line in the graph of FIG. 4, when the amount of the waste tire T charged is at least 3 kg per 1 ton of scrap S, the unit power consumption is reduced by about 3%. be able to. Desirably, the loading amount of the waste tire T is 60 to 70 kg / scrap Stone.
Or if it is more than this, as shown in the graph of FIG. 4, the power consumption can be reduced by about 40%. The upper limit of the loading amount of the tire T is theoretically considered to be substantially equal to the upper limit of the loading amount of the scrap S, but is estimated to be about several hundred kg / scrap Stone from the viewpoint of actual operation.

As described above, according to the metal melting method of the present invention using the melting furnace 1 which is an embodiment of the electric furnace, the waste tire T is charged into the furnace 1 together with the metal scrap S such as scrap iron. In addition, by blowing oxygen, the arc heat generated by the electrode 24 and the combustion heat of the tire T can be used together, and the power consumption during the melting and oxidation phases of the scrap S can be reduced. In addition, the tire T can be used as it is without being chipped, and the processing cost of the tire T can be significantly reduced. Furthermore, by charging the scrap S in the melting furnace 1 in a substantially uniform mixed state or a stacked state, the scrap S can be used as a reliable melting energy source, and contributes to effective use of waste tires and resolution of environmental problems. It is also possible to do.

Incidentally, for example, polyethylene, polypropylene,
By loading various waste plastics made of polyamide or the like into the melting furnace 1 in the same manner as the tire T, it is possible to save energy in melting the metal. In this case, the furnace 1 remains in the form of discarded plastic.
Although it is charged inside, since it has various shapes and sizes, a large object such as an automobile bumper is cut or crushed as necessary. Further, the waste tire T and the waste plastic may be loaded into the melting furnace 1 at the same time as the scrap S, or the waste tire T and the plastic which has been finely cut like chips may be loaded at the same time. And waste plastic can be loaded at the same time. However, it is necessary to take care that the type of waste plastic is limited to a material that does not generate harmful gas during its combustion, or that a combustion temperature that does not generate harmful gas is selected.

The present invention is not limited to the embodiment described above. FIG. 5 shows a DC arc furnace (melting furnace) 30 to which the present invention is applied. The arc furnace 30 has a hearth 32 made of refractory material, a cylindrical furnace wall 40 provided with a water-cooled jacket or a refractory material inside a steel shell, and a furnace lid 44 covering an upper part thereof. The hearth 32 is located at the center of the hearth 32, with a tapping portion 34 projecting having an opening 33 at a part thereof, a refractory plug 36 closing a through hole 35 formed in the bottom surface thereof. And a furnace bottom electrode 38. The furnace wall 40 has a furnace 3
A plurality of pipes 42 for blowing oxygen into 0 pass through.
Further, the furnace lid 44 has a single electrode 48 vertically penetrating through an opening 46 provided at the top thereof so as to be vertically movable.
An exhaust pipe 47 for discharging gas and the like inside is provided at an upper portion. In addition, any of air cooling, water cooling, or a water spray electrode is used for the furnace bottom electrode 38.

Then, as shown in FIG.
A metal scrap S, a waste tire T, and a waste plastic (not shown) are charged into the inside. The charging mode of the scrap S and the tire T is the mixed state or the stacked state described above.
Oxygen is blown into the furnace 30 from each pipe 42, and a DC current is applied from the electrode 48 to the furnace bottom electrode 38. Then, an arc is generated between the electrode 48 and each scrap S, and the scrap heat is melted by the arc heat. At the same time, the tire T and the like are also burned by the arc heat, and the scrap S in the vicinity is melted by the burn heat. Accordingly, power consumption during the melting and oxidizing phases of the scrap S can be saved as described above,
The power consumption can be reduced.

FIG. 6 relates to a further different type of melting furnace to which the present invention is applied. The melting furnace 50 shown in FIG. 6 (A) is a so-called pure oxygen bottom blower, which has a substantially barrel shape as a whole and
A refractory 54 is adhered to the inside 2, a charging port 51 and a tap hole 53 are provided at an upper portion, and a pipe 57 for blowing oxygen and a pipe 58 for blowing propane are provided at a bottom portion 56. As shown in FIG. 6 (A), after the molten metal M previously melted in the melting furnace 1 or the like is poured into the melting furnace 50 in advance, the metal scrap S, the waste tire T, and the waste plastic (not shown) are additionally charged. I do. The charging state of the scrap S and the tire T is the mixed state or the stacked state described above, and oxygen or propane is blown into the furnace 50 from each of the pipes 57 and 58. Thereby, since the tire T and the like burn by the oxygen and the heat of the molten metal M and contribute to the dissolution of the scrap S, the energy required for refining the molten steel can be saved. It is to be noted that the present invention can be applied to a pure oxygen top-blowing converter having no pipes 57 and 58.

A melting furnace 60 shown in FIG. 6 (B) is a side-blowing converter used in a so-called argon-oxygen injection method (AOD method), and has a substantially barrel shape as a whole, and a refractory 64 is provided in a steel shell 62. In the drawing, a charging port 61 is provided at an upper end, and a pipe 66 for blowing oxygen and argon and a pipe 68 for blowing only argon are provided on a lower side surface. As shown in the drawing, a molten metal M separately melted in advance in the melting furnace 60 is poured, and then a metal scrap S, a waste tire T and the like are additionally charged. The charging state of the scrap S and the tire T is the mixed state or the stacked state described above, and oxygen and / or argon is blown into the furnace 50 from each of the pipes 66 and 68. As a result, the tire T and the like burn with the oxygen and the heat of the molten metal M, thereby contributing to the dissolution of the scrap S, and can save energy for secondary scouring of various metals.

It should be noted that the present invention is not limited to the melting furnaces of the above-described embodiments, but it is possible to use metal scrap for at least a part of the raw material and to blow oxygen or air containing the same into the furnace. If it is a melting furnace, it can be applied to either primary scouring or secondary scouring of ordinary steel, special steel, stainless steel and the like. Further, the melting energy source used together with the waste tire or the like in melting the metal in the present invention also includes oils such as heavy oil or a propane gas which inserts a burner into a melting furnace and blows a flame from the tip to a scrap or the like. . Further, the waste tire used in the present invention includes not only tires of automobiles, special vehicles, aircrafts, and bicycles, but also endless track rubber (plastic) crawlers used for small construction machines and agricultural machines, or various conveyors. Belts etc. are also included.

[0028]

According to the metal melting method of the present invention described above, not only energy such as electric power required for melting scrap and the like can be reduced, but also effective use of discarded tires and the like and contribution to solving environmental problems can be achieved. be able to. Further, according to the second aspect of the present invention, the tire and the like can be utilized as they are without being chipped, and the processing cost of the tire can be significantly reduced. Further, according to the third or fourth aspect of the present invention, the tires and the like can be reliably and efficiently utilized as an energy source for melting by charging the tires and the like in a melting furnace in a mixed or laminated state with scrap. In addition, according to the invention of claim 5 or claim 6, it becomes more certain that the combustion heat of a tire or the like is efficiently and effectively utilized in the melting furnace.

[Brief description of the drawings]

FIG. 1A is a vertical sectional view of one embodiment of a melting furnace to which the present invention is applied, and FIG. 1B is a schematic diagram showing a method of the present invention using the melting furnace.

FIGS. 2A and 2B are schematic diagrams showing different charging modes in the method of the present invention using the melting furnace of FIG. 1A.

3 (A) is a schematic diagram illustrating a charging mode of the present invention using the melting furnace of FIG. 1 (A), and FIG. 3 (B) is a graph illustrating a relationship between a charging height of a tire and a basic unit of electric power. .

FIG. 4 is a graph showing the relationship between the amount of tire charged and the basic unit of electric power.

FIG. 5 is a schematic diagram showing the method of the present invention using different types of melting furnaces.

6 (A) and 6 (B) are schematic views showing the method of the present invention using a melting furnace having a further different form.

[Explanation of symbols]

 1,30,50,60 Melting furnace S Metal scrap T Waste tire H Upper limit height of charge h …………………… Charge height

Continued on the front page F-term (reference) 4D004 AA07 AA11 AA21 AC05 BA03 BA05 CA04 CA28 CA29 CB02 CB34 DA03 DA20 4F301 AA03 AA11 AC11 AD05 BA09 BA15 BA21 BA29 BD05 BE08 BE31 4K045 AA04 BA02 BA10 RB02 RB11 RB16

Claims (6)

[Claims] 1. In a melting furnace for blowing oxygen or air into a furnace to melt metal, metal scraps and the like and waste tires and / or
Or a method of dissolving metal scrap or the like by charging waste plastic and waste tire and / or waste plastic as a fuel or a part thereof. 2. The method according to claim 1, wherein the waste tire and / or waste plastic is charged into a melting furnace in a form of being discarded without being formed into fine chips or crushed forms. 2. The metal melting method according to 1. 3. The method according to claim 1, wherein said waste tire and / or waste plastic is charged into said melting furnace in such a manner that said waste tire and / or waste plastic is mixed with a substantially uniform distribution of metal scrap and the like. The metal dissolving method according to 1. 4. When the waste tire and / or waste plastic is charged into a melting furnace, the waste tire and / or waste plastic is charged.
The metal melting method according to claim 1 or 2, wherein the waste plastic and the metal scrap or the like are layered and alternately stacked and charged. 5. The charging height for charging the waste tire and / or waste plastic into the melting furnace is 80% or less of the upper limit of the charged material in the melting furnace. Item 5. The metal melting method according to any one of Items 1 to 4. 6. The amount of waste tire and / or waste plastic charged into the melting furnace is 3 kg / metal scrap t.
The metal melting method according to any one of claims 1 to 5, wherein the value is on or more.