Arc furnace and carbon dioxide treatment method using arc furnace

Abstract

To reduce carbon dioxide by treating the carbon dioxide in an arc furnace itself, and to provide a carbon dioxide treatment method using a carbon dioxide treatment technique in the arc furnace itself.SOLUTION: An arc furnace for melting metal is used, carbon dioxide-containing gas is introduced into the arc furnace, and the carbon dioxide-containing gas is brought into contact with an arc in the arc furnace to decompose carbon dioxide into oxygen and carbon monoxide. Carbon monoxide and oxygen after decomposition are recovered and reused by a recovery system, and undecomposed carbon dioxide is also recovered by the recovery system and introduced into the arc furnace again to be treated.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an arc furnace and a method for treating carbon dioxide using an arc furnace. [Background technology]

[0002] Recently, global warming has become a global issue, and there is an international demand for measures to combat it. In particular, reducing emissions of carbon dioxide, a greenhouse gas that is a major cause of global warming, is an urgent issue.

[0003] For example, carbon capture storage (CCS) is a technology that captures carbon dioxide and stores it underground by injecting it into the ground, and carbon capture usage (CCU) is a technology that captures and reuses carbon dioxide. Typical CCU technologies include immobilization in concrete, conversion to carbon materials using molten salt electrolysis (used as a raw material for LIB anode materials), methanation to synthesize methane from carbon dioxide, and conversion to hydrocarbon fuels (methane, kerosene, etc.) using chemical reactions (such as the Fischer-Tropsch process). Other methods that have been proposed include direct use of carbon dioxide after capture (using it as dry ice or carbon dioxide bubbles in carbonated drinks).

[0004] The manufacturing industry accounts for 35% of carbon dioxide emissions in Japan, of which 35% comes from the steel industry (Non-Patent Document 1). In other words, the steel industry is an important industrial sector for achieving carbon neutrality for the entire country of Japan, and as part of the carbon neutralization effort, attempts are being made to switch the production of molten iron from the blast furnace method, which emits a lot of carbon dioxide, to arc furnaces (also called electric furnaces or electric arc furnaces), which emit less carbon dioxide.

[0005] On the other hand, as a proposal for using an arc furnace to treat carbon dioxide itself, a reforming method has been proposed in which the carbon dioxide in the exhaust gas of an arc furnace is reformed with a reducing agent to reduce the amount of carbon dioxide generated (Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-31470 [Non-patent literature]

[0007] [Non-Patent Document 1] Ministry of Economy, Trade and Industry, Agency for Natural Resources and Energy website, "Global efforts to decarbonize the steel industry: What is green steel?", dated August 10, 2023 Summary of the Invention [Problem to be solved by the invention]

[0008] The proposal described in Patent Document 1 focuses on reforming the exhaust gas from an arc furnace, and as part of that, it reforms the carbon dioxide in the exhaust gas using a reducing agent. To begin with, the exhaust gas from an arc furnace does not contain much carbon dioxide, and the concentration is basically about the same as that of atmospheric carbon dioxide. Furthermore, since this does not treat carbon dioxide in the arc furnace itself, but merely treats carbon dioxide in the exhaust gas, there are limitations to the carbon dioxide reduction effect.

[0009] Therefore, the present invention aims to reduce carbon dioxide by treating carbon dioxide in the arc furnace itself, and to propose a carbon dioxide treatment method that utilizes carbon dioxide treatment technology in the arc furnace itself. [Means for solving the problem]

[0010] The present inventors have conducted extensive research and development to achieve the above object, and as a result have obtained the following findings.

[0011] [a] An arc furnace is a furnace that melts metals and other materials by utilizing the phenomenon of high-density current flowing through a gas due to arc discharge and the thermal energy dissipated during the arc discharge. It is known that the temperature around the arc during arc discharge can reach approximately 5000°C. On the other hand, it is known that carbon dioxide (CO2) begins to decompose at high temperatures of 2000°C or higher, decomposing into CO (carbon monoxide) and O2 (oxygen), and that theoretically 100% of CO2 is decomposed at temperatures above 5000°C. Therefore, the inventors conceived of applying arc discharge to the decomposition of carbon dioxide and conducted research and development. As a result, they discovered that by actively exposing carbon dioxide to an arc, 5 to 30% of the carbon dioxide in the atmosphere is decomposed.

[0012] [b] Arc furnaces for producing metals such as steel and aluminum are usually operated in the atmosphere, and no active treatment of carbon dioxide is considered. Therefore, we discovered that by introducing excess carbon dioxide from outside, introducing that carbon dioxide into the arc furnace, and actively bringing it into contact with the discharging arc, the introduced carbon dioxide can be efficiently decomposed.

[0013] [c] Even if carbon dioxide is decomposed by contacting it with an arc, as mentioned above, only 5 to 30% is decomposed, leaving the remaining 70 to 95% as carbon dioxide, which is emitted as carbon dioxide. Furthermore, the exhaust gas after decomposition contains harmful carbon monoxide (CO), so it cannot be emitted as is. Therefore, the inventors discovered that carbon dioxide can be decomposed efficiently by separating the carbon monoxide from the exhaust gas and also separating the carbon dioxide from the exhaust gas and returning it to the arc furnace.

[0014] The present invention was made based on the above findings, and the gist of the present invention is as follows.

[0015] [1] 1. An electric arc furnace for melting metals, comprising: An arc furnace comprising a CO2 supply cylinder (e.g., a lance) that supplies a carbon dioxide-containing gas into the arc furnace, and the CO2 supply cylinder is positioned so that the carbon dioxide-containing gas discharged from the outlet of the CO2 supply cylinder comes into contact with the arc in the arc furnace. [2] The arc furnace has an exhaust gas treatment device that treats exhaust gas discharged from the arc furnace, The exhaust gas treatment device comprises: It has an oxygen recovery system, a carbon monoxide recovery system, and a carbon dioxide recovery system, 10. The arc furnace of claim 1, wherein the carbon dioxide captured by the carbon dioxide capture system is returned to the CO2 supply tube. [3] Using an arc furnace to melt metal, A method for treating carbon dioxide using an arc furnace, comprising introducing a carbon dioxide-containing gas into the arc furnace and bringing the carbon dioxide-containing gas into contact with an arc in the arc furnace. [4] Separating carbon dioxide and carbon monoxide from the exhaust gas discharged from the arc furnace; The carbon dioxide treatment method according to [3], wherein the separated carbon dioxide is mixed with the carbon dioxide-containing gas introduced into the arc furnace. [5] The carbon dioxide treatment method according to [3] or [4], further comprising separating oxygen from the exhaust gas. [6] The arc furnace according to [1] or [2], wherein the metal is an iron alloy. [7] The method for treating carbon dioxide using an arc furnace according to any one of [3] to [5], wherein the metal is an iron alloy. [Effects of the Invention]

[0016] The present invention enables carbon dioxide to be treated using the arc furnace itself, contributing to the reduction of the amount of carbon dioxide in the environment. Furthermore, by recovering undecomposed carbon dioxide from the exhaust gas of the arc furnace and treating it again in the arc furnace, not only can carbon dioxide in the environment be efficiently reduced, but also CO (carbon monoxide) can be separated to remove its harmful properties and be effectively used as a fuel or reducing agent. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a conceptual diagram for explaining an arc furnace and a carbon dioxide treatment method according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] An embodiment of the present invention (hereinafter referred to as the present invention) will be described below, although it goes without saying that the present invention is not limited to this embodiment.

[0019] [Decomposition of carbon dioxide by arc] It is known that carbon dioxide (CO2) decomposes into carbon monoxide (CO) and oxygen (O) at high temperatures. The decomposition of carbon dioxide begins at approximately 1500°C and progresses as the temperature rises, with 20% of carbon dioxide decomposing at approximately 2500°C, 50% at approximately 3000°C, 90% at approximately 4000°C, and nearly 100% at approximately 5000°C. Carbon dioxide (CO2) → CO+1 / 2O2

[0020] Although on a different scale from an arc furnace, carbon dioxide arc welding also involves welding while shielding the arc with carbon dioxide (CO2), and it is known that 2-5% of the carbon dioxide supplied during this process decomposes into CO and oxygen. The principle is similar to that of the present invention, and it is thought that the carbon dioxide is heated to a high temperature by the thermal energy of the arc and decomposed. It can be assumed that, rather than the entire supplied carbon dioxide gas being heated uniformly, only a portion of the carbon dioxide is locally heated and decomposed.

[0021] It is known that the temperature of the arc generated in an electric arc furnace reaches approximately 5,000°C to 20,000°C. For example, arc heating, which is commonly used in electric furnaces for steel production, involves passing current between electrodes (graphite electrodes) installed at the top of the furnace and the steel scrap that is charged into the furnace, generating an arc between the electrodes and the material to be heated, and using the thermal energy generated to heat the material. This heating method, in which current flows directly into the material to be heated, is called direct arc heating. A method in which no current flows through the material to be heated, in which an arc is generated between electrodes placed outside the material to be heated and the material is heated using the thermal energy of the arc, is called indirect arc heating. The arc furnace used in the present invention may be either a direct arc heating method or an indirect arc heating method, and the heating method is not limited. Other direct heating methods include three-phase and single-phase methods, and indirect heating methods include vibration and Lennerfeld methods, but these types are not particularly limited. The arc furnace constituting the present invention is an arc furnace for melting metals. The metals to be melted are metals targeted in the steel industry and metal industry (aluminum, copper, etc.). More preferably, they are iron alloys (Fe-containing alloys), and even more preferably, they are steel materials (scrap materials).

[0022] The present invention utilizes the thermal energy of an arc generated in an arc heating system, and promotes the decomposition of carbon dioxide by increasing the temperature of the carbon dioxide using the thermal energy of the arc. The use of the following CO2 supply tubular object makes it possible to efficiently contact a carbon dioxide-containing gas with the arc generated in an arc furnace. Details will be described later. In an experiment using a test furnace, the inventors generated an arc equivalent to that used in a steel arc furnace, contacted a carbon dioxide-containing gas containing 90% carbon dioxide, and measured the decomposition rate. They confirmed that 5 to 30% of the carbon dioxide was decomposed. It is speculated that this variation in decomposition rate is due to the contact quality between the carbon dioxide-containing gas and the arc. Furthermore, the carbon dioxide content of the carbon dioxide-containing gas is not particularly limited, but since the higher the content, the better the reactivity. Therefore, it is preferably 70% or more, more preferably 75% or more, 80% or more, 85% or more, 90% or more, or 95% or more. 100% CO2 (carbon dioxide) is also acceptable.

[0023] [CO2 supply cylinder] It is important to efficiently transfer the thermal energy of the arc to carbon dioxide. Therefore, when supplying carbon dioxide-containing gas into an arc furnace, it is preferable to supply the carbon dioxide gas near the arc using a CO2 supply cylinder. By using a CO2 supply cylinder, it is possible to bring the CO2 supply cylinder's nozzle (e.g., a lance nozzle) closer to the arc. In addition, by adjusting the shape of the CO2 supply cylinder's nozzle, it is possible to change the contact of the carbon dioxide-containing gas with the arc. For example, it is preferable to inject the carbon dioxide-containing gas along the arc flow direction (the direction from the electrode toward the heated material, usually a vertical direction from above to below) and so as to contact the center of the arc. By flowing in this way, it is possible to ensure the contact time between the carbon dioxide-containing gas and the arc, and to increase the temperature rise of the carbon dioxide-containing gas.

[0024] The material and shape of the CO2 supply cylinder are not particularly limited. The temperature inside an arc furnace reaches approximately 1,500°C due to the radiant heat from the arc and the molten iron, so it is preferable to use a structure that can withstand such high temperatures. For example, the CO2 supply cylinder may have a cooling structure inside and a refractory material on its outer surface. A lance structure, such as that used in steel converters, may be used. The cooling structure is also not particularly limited. A double-tube structure with a water-cooled structure may be used. Furthermore, the shape may be, for example, any shape that allows carbon dioxide gas to be supplied to the vicinity of the arc, such as a shape in which the inner diameter of the portion near the arc is smaller than the inner diameter of the remaining portion, a shape in which the inner diameter of the portion near the arc is the same as the inner diameter of the remaining portion, or a shape in which the inner diameter of the portion near the arc is larger than the inner diameter of the remaining portion. The cross-sectional shape may be circular, triangular, rectangular, or polygonal. A lance-type cylinder is more preferable because it can efficiently supply carbon dioxide to the arc.

[0025] The number of CO2 supply cylinders is not particularly limited. For example, in the case of a three-phase direct arc heating system, a CO2 supply cylinder (three cylinders) may be provided for each electrode. Alternatively, for example, one CO2 supply cylinder may be provided, and carbon dioxide-containing gas may be sprayed from one electrode to the other electrode so that it contacts the three arcs.

[0026] When the temperature of the carbon dioxide-containing gas in contact with the arc rises above about 1500°C, the decomposition of carbon dioxide occurs. The higher the temperature of the carbon dioxide-containing gas, the more rapidly the decomposition of carbon dioxide is promoted.

[0027] [Exhaust gas treatment device] Carbon dioxide-containing gas is discharged from the arc furnace (this discharged carbon dioxide-containing gas is called exhaust gas). The exhaust gas contains CO (carbon monoxide), which is produced by the decomposition of some of the carbon dioxide. Because CO (carbon monoxide) is a substance harmful to living organisms, it cannot be released into the atmosphere as is, so at the very least, it must be treated to remove and separate the CO. Although CO is a harmful substance, it can be reused as a reducing agent or fuel. When CO is reused as fuel, carbon dioxide is produced when it is burned, but the produced carbon dioxide can be injected back into the arc furnace and decomposed by the arc. For this reason, it is recommended to have a carbon monoxide recovery system as an exhaust gas treatment device.

[0028] Exhaust gas also contains oxygen (O), which is also produced by the decomposition of carbon dioxide. Oxygen can also be effectively reused by separating it. For this reason, it is a good idea to install an oxygen recovery system as part of the exhaust gas treatment equipment.

[0029] Furthermore, the exhaust gas also contains undecomposed carbon dioxide. In order to reduce and eliminate the atmospheric release of carbon dioxide, it is advisable to separate and capture the carbon dioxide as well. The captured carbon dioxide can be mixed with the carbon dioxide-containing gas supplied to the arc furnace and decomposed again by the arc. In this way, circulating the undecomposed carbon dioxide can ultimately contribute to reducing carbon dioxide. Therefore, it is advisable to also install a carbon dioxide capture system as an exhaust gas treatment device.

[0030] [Carbon monoxide recovery system] The mechanism for separating carbon monoxide in the carbon monoxide recovery system is not particularly limited, and any known mechanism (hereinafter referred to as "separation mechanism") can be used. Examples include cryogenic separation, pressure swing adsorption (PSA), and membrane separation.

[0031] The separated carbon monoxide can be supplied to an arc furnace and used to stir the molten metal to improve its heat transfer. It is known that in arc furnaces, carbon is added to the molten metal to generate carbon monoxide for stirring, but the CO gas recovered by the carbon monoxide recovery system can be used as a substitute for carbon monoxide gas for stirring. This makes it possible to reduce the amount of carbon added to the molten metal in the arc furnace, which is desirable.

[0032] As an example of a specific mechanism, carbon monoxide separated and recovered by a carbon monoxide recovery system is supplied into an arc furnace from a carbon monoxide supply nozzle through piping. The carbon monoxide supply nozzle can be shaped like a CO supply cylinder (lance type). Carbon monoxide is supplied from the lower or bottom of the arc furnace and is fed into the molten metal placed at the lower or bottom of the arc furnace.

[0033] The separated and recovered carbon monoxide can be used as a chemical feedstock or for conversion to hydrocarbon combustion. Examples of chemical feedstocks include formic acid and methanol. Examples of conversion to hydrocarbon combustion include the Fischer-Tropsch process. These utilization methods may be carried out individually or in combination.

[0034] [Oxygen recovery system] The mechanism for separating oxygen in the oxygen recovery system is not particularly limited, and any known mechanism (hereinafter referred to as "separation mechanism") can be used. Examples include cryogenic separation, pressure swing adsorption (PSA), and membrane separation.

[0035] The separated and recovered oxygen can be supplied to, for example, an arc furnace to oxidize impurities in the molten metal, which increases its vapor pressure, allowing the oxidized impurity components to be discharged as gas. In addition, it can be used to stir the molten metal to improve its heat transfer.

[0036] As a specific example of the mechanism, the separated oxygen is supplied into the arc furnace from an oxygen supply nozzle. The shape of the oxygen supply nozzle can be exemplified by an O2 supply cylinder (lance type). It is preferable to supply oxygen from the lower or bottom part of the arc furnace and blow it into the molten metal placed at the lower or bottom part of the arc furnace so that it comes into contact with the molten metal.

[0037] [Carbon dioxide capture system] The mechanism for separating carbon dioxide in the carbon dioxide capture system is not particularly limited, and any known mechanism can be used, such as chemical absorption using amines or the like, cryogenic separation, pressure swing adsorption (PSA), and membrane separation.

[0038] The separated and recovered carbon dioxide can be supplied to the arc furnace again and decomposed into carbon monoxide and oxygen by contacting the arc. In other words, the decomposition rate of carbon dioxide in the arc furnace can be improved by contacting the unreacted carbon dioxide with the arc again.

[0039] In a specific example of the mechanism, the separated and recovered carbon dioxide is returned to the CO2 supply cylinder and supplied to the arc furnace. The CO2 supply cylinder for supplying the separated and recovered carbon dioxide may be the same as the CO2 supply cylinder that initially supplied the carbon dioxide-containing gas, or may be a different CO2 supply cylinder.

[0040] [Carbon dioxide treatment using an arc furnace] It is recommended to construct a carbon dioxide treatment system (method) using an arc furnace by arranging an arc furnace, a carbon monoxide recovery system, an oxygen recovery system, and a carbon dioxide recovery system in series. Figure 1 shows an example of an arc furnace, including an exhaust gas treatment device. The arc furnace shown in Figure 1 has an arc furnace body 6 and graphite electrodes 4. A metal to be melted (not shown) is placed inside. An arc 5 is generated between the graphite electrodes 4 and the metal to be melted. The heat of the arc 5 melts the metal, producing molten metal 7. At this time, carbon dioxide gas (CO2 gas) 2 is supplied through a CO2 supply cylinder 3 so that it comes into contact with the arc 5. The heat of the arc 5 causes the carbon dioxide gas 2 to decompose into oxygen and carbon monoxide, which are then discharged as arc furnace exhaust gas 10. The exhaust gas 10 passes through a separation mechanism for exhaust gas treatment, where the oxygen, carbon monoxide, and carbon dioxide contained in the exhaust gas are separated and recovered. First, an oxygen recovery system 21 is installed as a first separation mechanism, which recovers oxygen 11 from the exhaust gas of the arc furnace and reuses the recovered oxygen gas 11 as oxygen gas to be blown into the molten metal 7 from an oxygen supply nozzle 9 located at the bottom of the arc furnace.

[0041] Next, a carbon monoxide recovery system 22 is installed as a second separation mechanism to separate carbon monoxide 12 from the remaining gas. One of the recovered carbon monoxide 12 is blown in from a carbon monoxide supply nozzle 8 installed at the bottom of the arc furnace as a gas for stirring the molten metal. The other is used for producing chemical products, such as chemical raw materials.

[0042] Furthermore, a carbon dioxide capture system 23 is provided as a third separation mechanism to separate carbon dioxide 13 from the remaining gas. The captured carbon dioxide 13 is returned to the CO2 supply cylinder 3 and fed back into the arc furnace 1, where it is decomposed by the arc 5.

[0043] As mentioned above, the order in which the carbon monoxide, oxygen, and carbon dioxide recovery systems are arranged is not limited. [Example]

[0044] The effects of the present invention were confirmed through tests using a small arc furnace, and examples thereof are described below. The arc furnace used was a 2L arc test furnace with a mirror-finished lower part made of SUS316L, lined with internal refractory material, and equipped with a cooling jacket. The metal to be melted was steel (scrap material), which was charged into the arc furnace up to one-third of its total height from the bottom. The electrodes used were graphite electrodes with a diameter of 5 cm, which were inserted from the top of the arc furnace and positioned 1 cm above the top of the steel material.

[0045] The CO2 supply cylinder was made of SUS316L and had a diameter of 1 / 4 inch. It was placed from the side of the arc furnace, directly below the graphite electrode, between the electrode and the steel material. The oxygen supply nozzle was made of SUS316L and had a diameter of 1 / 4 inch, and was inserted 5 cm from the bottom of the arc furnace. The carbon monoxide supply nozzle was made of SUS316L and had a diameter of 1 / 4 inch. A supply port was provided at the bottom of the arc furnace, and the nozzle tip was connected to the supply port.

[0046] The gas outlet was installed at the top of the arc furnace, and a pipe made of SUS316L with a diameter of 1 / 4 inch was installed from the gas outlet, and an oxygen recovery system, a carbon monoxide recovery system, and a carbon dioxide recovery system were installed in this order.

[0047] A 1L SUS316L container with a built-in separation membrane was installed as an oxygen recovery system. The oxygen recovered by the oxygen recovery system was connected to an oxygen supply nozzle installed in the arc furnace via a pipe.

[0048] A 1L SUS316L container with a built-in separation membrane was installed as a carbon monoxide recovery system. The carbon monoxide recovered by the carbon monoxide recovery system was connected to a carbon monoxide supply nozzle installed in the arc furnace via a further pipe.

[0049] A 1L SUS316L container with a built-in separation membrane was installed as a carbon dioxide capture system. The carbon dioxide capture system was equipped with an exhaust gas outlet. Further piping was installed so that the carbon dioxide captured by the carbon dioxide capture system could be connected to the CO2 supply cylinder.

[0050] In the test equipment configured in this way, a voltage of 100 V was applied to the graphite electrode as the anode and the steel as the cathode to generate an arc. This voltage was continued for 2 minutes after the entire steel had melted. During this time, air containing 90% carbon dioxide was supplied from the CO2 supply tube at a rate of 0.1 L / min. The temperature inside the arc furnace at this time was approximately 1500°C, and the pressure inside the furnace was atmospheric.

[0051] The carbon dioxide passing through the outlet of the CO2 supply tube, the exhaust gas at the outlet of the arc furnace, and the exhaust gas after the carbon dioxide recovery system were collected and analyzed by gas chromatography to measure the carbon dioxide decomposition rate. It was confirmed that when the stable region was reached, 5-30% of the supplied carbon dioxide (CO2) was decomposed into CO (carbon monoxide) and O (oxygen). It was also confirmed that more than 90% of the exhaust gas at the outlet of the exhaust gas treatment device was nitrogen. [Industrial Applicability]

[0052] The present invention can be used in arc furnaces, that is, in industries that use arc furnaces, such as the steel industry and the metal industry (aluminum, copper, etc.). [Explanation of symbols]

[0053] 1. Arc furnace 2 Carbon dioxide gas (CO2 gas) 3 CO2 supply tubes 4. Graphite electrodes 5. Arc 6. Arc furnace body 7 Molten Metal 8 Carbon monoxide supply nozzle 9 Oxygen supply nozzle 10. Arc furnace exhaust gas 11 Oxygen gas 12 Carbon monoxide gas 13 Carbon dioxide gas 21 Oxygen Recovery System 22 Carbon Monoxide Recovery System 23 Carbon dioxide capture system

Claims

1. 1. An electric arc furnace for melting metals, comprising: CO containing gas is supplied into the arc furnace ２ a supply tube; The CO ２ The carbon dioxide-containing gas is discharged from the outlet of the supply cylinder so as to contact the arc in the arc furnace. ２ An electric arc furnace, characterized in that it is provided with a feed tube.

2. The arc furnace has an exhaust gas treatment device that treats exhaust gas discharged from the arc furnace, The exhaust gas treatment device comprises: It has an oxygen recovery system, a carbon monoxide recovery system, and a carbon dioxide recovery system, The carbon dioxide captured by the carbon dioxide capture system is ２ 10. The electric arc furnace of claim 1 configured to return to a feed tube.

3. Using an arc furnace to melt metal, A method for treating carbon dioxide using an arc furnace, comprising introducing a carbon dioxide-containing gas into the arc furnace and bringing the carbon dioxide-containing gas into contact with an arc in the arc furnace.

4. Separating carbon dioxide and carbon monoxide from the exhaust gas discharged from the arc furnace; 4. The method for treating carbon dioxide according to claim 3, wherein the separated carbon dioxide is mixed with the carbon dioxide-containing gas to be introduced into the arc furnace.

5. 5. The carbon dioxide treatment method according to claim 3, further comprising separating oxygen from the exhaust gas.

6. 3. An electric arc furnace according to claim 1 or 2, wherein the metal is an iron alloy.

7. 5. The method for treating carbon dioxide using an arc furnace according to claim 3 or 4, wherein the metal is an iron alloy.

8. 6. The method for treating carbon dioxide using an arc furnace according to claim 5, wherein the metal is an iron alloy.

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