EP4722621A1

EP4722621A1 - System for injecting gas into an electric arc furnace

Info

Publication number: EP4722621A1
Application number: EP24020298.6A
Authority: EP
Inventors: Pascal Kwaschny
Original assignee: Linde GmbH
Current assignee: Linde GmbH
Priority date: 2024-10-02
Filing date: 2024-10-02
Publication date: 2026-04-08

Abstract

The present invention relates to a system for injecting gas into an electric arc furnace, comprising an electrode (111) with a bore (112), an electrode support beam (105) with an electrode holder, a gas supply (121), a supply hose (122) connected to the gas supply (121) and a gas coupler (204) for connecting the supply hose (122) to the bore (112) of the electrode (111). A telescope arm (201) is installed at the electrode support beam (105) and the supply hose (122) is mounted to the telescope arm (201).

Description

The present invention relates to a system for injecting gas into an electric arc furnace, comprising an electrode with a bore, an electrode support beam with an electrode holder, a gas supply, a supply hose connected to the gas supply and a gas coupler for connecting the supply hose to the bore of the electrode.

Background of the invention

Electric arc furnaces are used in metallurgy for processing, particularly melting of metallic material like metal scrap or direct reduced iron (DRI, also referred to as sponge iron). Power is passed through a transformer and high current cables to the electrode(s) of the electric arc furnace. The electrodes are usually made of graphite and are energised to produce an electric arc between the electrode and the metallic material or between the electrode and one or more other electrodes. The electric arc furnace can comprise e.g. one electrode of that kind if direct current is used or e.g. three electrodes if alternating current is used.
To make electrically non-conductive air inside the furnace conducting, the molecular nitrogen N₂ of the air is dissociated into atomic nitrogen N, which is then ionised. The conductive plasma generates an arc, which can be up to 8,600 K. This arc melts the metallic material.
A distinction can be made between a scrap melting phase in which the main part of the material in the furnace can be regarded as solid. Holes are drilled into the metal insert by means of the arc, in order to have a maximum energy yield and the lowest possible energy loss. This is because the arc itself melts scrap at the bottom of the holes and the arc radiation melts the sides of the holes.
Once all the material has melted in the furnace, the flat bath phase begins in which the arcs are surrounded by a foaming slag to have the lowest possible energy losses. In the case of stainless steel, a foam slag is not used due to the required chemical analysis.
Operation of an electric arc furnace of that kind typically involves high costs. With rising and varying energy prices, the costs for energizing the electrodes can be a significant factor of the economic efficiency of the furnace.
On the electricity side, many innovations have been implemented to reduce energy consumption. These include optimization of the transformers, the high-current side as well as the electrode control or foam slag control. Further, it has been suggested to use an argon-based gas to generate an argon-based arc instead of a nitrogen-based arc. In common electric arc furnaces, to generate an electric arc, molecular nitrogen N₂ is dissociated into atomic nitrogen N and then ionised. In contrast to nitrogen, argon is a one atomic gas, i.e. argon does not have to be dissociated. Thus, atomic argon only has to be ionised in order to create electrical conducting plasma.
WO 2020/249261 A1 discloses a method for operating an electric arc furnace (EAF) wherein an argon rich gas is injected into the furnace through a bore inside the at least one electrode. The argon expediently substitutes the air inside the furnace, especially in an area between the electrode and the metallic material in which the electric arc is to be created. Thus, a smaller amount of energy has to be provided in order to create a plasma. However, this method requires to supply argon into the bore inside the electrode, that is from the top of the electric arc furnace.
Another cost factor are the graphite electrodes. Wear of the graphite electrodes usually comprises sublimation at the tip of the electrode and burn-off at its sides due to oxidation. Their consumption is composed of 70% sublimation at the tip and 30% side burn by oxidation. Estimated costs vary greatly from current electrode prices, which range from 2,000 to 6,000 € per ton.
There have always been attempts to optimize the electrode consumption by innovative methods. However, the relevant processes cannot be changed for physical reasons. Thus, the hot electrodes oxidize on contact with oxygen from the furnace atmosphere. Increasing the current to generate a higher power in the furnace, the electrode consumption increases, since this is a function of the current. Since the electrodes consume themselves continuously, after a certain time the old electrode must be replaced, or a new electrode must be built up. Different methods are used:

Manual assembling on top of the EAF,
Manual or automatic assembly of a new electrode column outside the EAF and replacing a whole electrode column or
automatic assembling of a new electrode on the EAF with an electrode robot.

This electrode replacement costs a couple of minutes per column and results in a reduction of productivity.
It is an object of the invention to improve the replacement of gas supply for a hollow electrode which is supplied with gas from the top. In particular, the time for reconnecting the gas supply to the electrode shall be reduced.

Disclosure of the invention

This object is achieved by a system for injecting gas into an electric arc furnace, comprising an electrode with a bore, an electrode support beam with an electrode holder, a gas supply and a supply hose connected to the gas supply, a gas coupler for connecting the supply hose to the bore of the electrode, and which is characterized in that a telescope arm is installed at the electrode support beam and that the supply hose is mounted to the telescope arm.
The invention relates to an electric arc furnace wherein at least one hollow electrode is used to supply a gas, preferably argon or an argon-rich gas, into the furnace. The electrode's longitudinal extension, i.e. its length, is much greater than its maximum extension in a direction perpendicular to the longitudinal extension. For example, the electrode is of cylindrical shape wherein its length, or in this case the cylinder height, is a multiple of the electrode diameter. The term "hollow electrode" shall mean that the electrode is provided with a bore in its longitudinal direction. The bore is typically produced by drilling the electrode. In the following, the terms "hollow electrode", "electrode with a bore" and "drilled electrode" are used as synonyms.
The diameter of the longitudinal bore inside the electrode body is preferably less than 10%, more preferably less than 8%, more preferably less than 6%, more preferably less than 4% and even more preferably less than 2% of the diameter of the electrode. Such dimensioning helps achieve the required gas amounts and gas velocities. In typical applications, the diameter of the bore should be less than 50mm, preferably less than 40mm, preferably less than 30mm and more preferably less than 20mm. For non-circular cross sections of the electrode or of the bore, the term "diameter" shall be understood as the diameter of a circle having the same or essentially the same area as the non-circular cross-sectional area.
Such hollow electrodes are different from classical hollow electrodes. The borehole cannot be used for ducting solid particles since they would block the bore. The advantages of the small boreholes are, first, that the gas demand is reduced, and second, that higher pressures can be used. The higher pressure leads to a more exact supply of gas to the area of gas consumption, i.e. to the area of the electric arc.
The use of the hollow electrode allows to inject a gas through the inner of the electrode to its tip. The electric arc is then formed or assisted by the gas. The term "gas" shall include gas mixtures, too. A preferred gas is argon or an argon-rich gas mixture. Other gases which can be injected through the hollow electrode are CO2, CO2-argon-mixtures, helium, or hydrogen.
The term "argon-rich gas" is particularly to be understood as a gas or a mixture of gases, wherein the amount of argon is larger than the amount of any other gas. In particular, the amount of argon in the argon-rich gas is at least 50%, particularly at least 75%, particularly at least 90%, and particularly at least 95%. Pure argon can be used as "argon-rich gas", too. In particular, argon with a purity of at least 90% is injected as the argon-rich gas, particularly with a purity of at least 95%, more particularly with a purity of at least 99%. For example, argon 5.0 can be injected, i.e. argon with purity of 99.999%. Particularly, argon 6.0 can be injected with a purity of 99.9999%. Further, argon 7.0 can be injected, i.e. argon with a purity of 99.99999%.
The injection of an argon-rich gas through the electrode leads to a reduction of electricity consumption up to about 15%, to a reduction of electrode consumption up to around 6% and to a production increase by about 2% compared to electric arc furnaces where the arc is formed in air.
The electric arc furnace preferably comprises a furnace vessel or hearth designed as a bowl-type vessel with a substantially cylindrical shape which is open at the top. The furnace vessel may be closed by a cover or roof which can be opened.
A direct current electric arc furnace comprises one electrode which is provided with a longitudinal bore. An alternating current electric arc furnace has three electrodes. In this case all three electrodes are designed as hollow electrodes with a bore in their longitudinal extension. The electrodes extend from the top into the furnace vessel. If the furnace vessel is provided with a roof or a cover, the roof or cover has one or more apertures or through-holes for the electrode or for the electrodes.
Each electrode is held with its longitudinal extension in the vertical direction by a support beam and an electrode holder. The electrode holder is connected to the support beam and holds the electrode in its position. The electrode holder can be operated pneumatically and / or with clamps or spring clamps. The support beam extends above the furnace and above the roof or cover if present.
The inventive system further comprises a supply hose with one end connected to a gas supply. The other end of the supply hose is connected to a gas coupler. The gas coupler preferably comprises a male and a female part. Either the male part or the female part of the gas coupler is installed at the supply hose. The other part of the gas coupler (the female part if the male part is installed at the supply hose or the male part if the female part is installed at the supply hose) is temporarily installed in the electrode and ensures a continuous gas flow to the inside of the bore when the male part and the female part of the gas coupler are connected.
The hose is preferably a hose resistant against high temperatures and certificated for the use of up to 20bars. It is important that the hose is not electrically conductive.
In operation of the electric arc furnace the electrodes are subjected to wear and the electrodes are consumed and become continuously shorter. In order to maintain constant process conditions and to keep the electric arc stable the electrode is lowered relative to the support beam to compensate for the electrode wear and for the electrode consumption. The electrode holder is released, the electrode is lowered and then the electrode holder is fastened again.
The supply hose is fixed to the electrode via the gas coupler. Thus, when lowering the electrode, the supply hose has to follow the electrode. However, the thermal and operating conditions at the roof of the electric arc furnace or above the electric arc furnace are harsh with high temperatures of up to 600 °C Therefore, according to the invention a telescope arm is installed at the electrode support beam and the supply hose is fixed to the telescope arm. Preferably, the telescope arm can be tilted or rotated about a pivot point or fulcrum.
The telescope arm allows to vary its length. The necessity for variation of the length comes from the continuous consumption of the electrode. After assembling a new electrode, the electrode has a length "a" from the clamp and after some operation time it will have a shorter length "b".
The telescope arm can comprise two or more segments which can be moved relative to each other whereby the length of the telescope arm is changed. For example, the telescope arm is designed as a telescopic cylinder with two or more tubes of different diameters which are nested within each other. It is also possible to use tubes of other cross section instead of cylindrical tubes. In another example, the segments of the telescope arm are connected by a joint, which allow to tilt or fold the segments relative to each other and thereby change the length of the telescope arm.
The inventive system with the telescope arm holds the supply hose in a defined position and thereby protects it from the rough thermal conditions. When the electrode is lowered the supply hose does not come into contact with hot spots. Damages to the supply hose are prevented. The supply hose is fixed to the telescope arm such that it is guided and that it follows the telescope arm when the arm is extended or contracted.
In one embodiment the position of the telescope arm relative to the electrode support beam can be varied. Preferably, the angle between at least a portion of the telescope arm and the electrode support beam can be varied. The telescope arm can be tilted or rotated in a horizontal plane, in a vertical plane or in any other spatial direction. For example, the telescope arm is connected to the electrode support beam by means of a joint which allows to adjust the telescope arm within a specific range of angles.
In one embodiment, the telescope arm is attached to a support leg which is mounted on or at the support beam. The support leg may extend substantially vertically. The telescope arm is movably attached to the support leg. The telescope arm can be tilted in vertical and/or horizontal direction. The vertical movement direction allows to lower the tip of the telescope arm when the electrode is lowered. The horizontal movement allows to swing the telescope arm out of the area above the electrode and / or out of the area above the electric arc furnace.
In one embodiment the telescope arm is designed as a double-ended lever. The double-ended lever is connected to the electrode support beam or preferably to a support leg by a hinge or pivot which acts as the fulcrum of the telescope arm. The telescope is preferably designed as a straight lever. The fulcrum divides the telescope arm into a load arm and a force arm. The load arm extends from the fulcrum to the tip of the telescope arm which in practice comes close to the electrode and the force arm extends from the fulcrum into the opposite direction. The supply hose is fixed to the load arm. The length of the telescope arm is preferably adjusted to keep the distance between the end or tip of the load arm and the top of the electrode small. By applying a force to the force arm the telescope arm can be tilted or rotated about its fulcrum.
The force arm of the telescope arm extends in a direction away from the support leg or from the fulcrum of the telescope arm. The operator can operate the telescope arm from the end of the force arm and thereby does not come close to the electric arc furnace and its high temperatures.
In one embodiment, the electrode comprises a transportation pin at one of its ends (at its upper end). The transportation pin is used for transport or transfer of the electrode, for example to lift up the electrode by a crane or to assemble an electrode segment onto another electrode segment to form an electrode column or electrode assembly. The transportation pin can be fixed to the electrode by any appropriate means, for example it can be screwed into the electrode. In this case the transportation pin also serves as a dust protection for the thread of the electrode during operation of the furnace. The transportation pin and the gas coupler can be one connector unit which provides both features, namely a pin to lift the electrode and a gas flow connection between the supply hose and the bore in the electrode. The transportation pin and the gas coupler can also be two separate units, either completely separated or only temporarily connected to each other.
The electrode is preferably made of graphite or carbon, although other suitable materials may be used such as tungsten. The electrode size is chosen appropriately to accommodate the size and design of the electric arc furnace being used. Typically, a number of electrode segments are longitudinally connected to each other to form an electrode assembly or electrode column which serves as the ultimate "electrode". Thus, in this application, the terms "electrode", "electrode assembly" and "electrode column" are used interchangeably unless otherwise indicated. Further, the term "furnace" can also designate the "furnace vessel" in the narrower sense.
According to an embodiment the inner surface of the bore is sealed and/or coated and/or fitted with an inside tube in order to avoid the gas from diffusing through the electrode material, particularly when the electrode is made of graphite or carbon material.
According to one embodiment, the inner surface of the bore is sealed. Such a sealing can be achieved by a high-temperature resistant adhesive or resin, for example a furan resin on the basis of furfuryl alcohol. The inner surface of the bore can also be sealed by a silica based sealer or by a refractory concrete.
According to another embodiment, the inner surface of the bore is coated, for example by a soot layer, by pressurized graphite dust or particles generated from drilling the bore into the electrode body. This can be achieved by applying a pressure while and/or after drilling the longitudinal bore into the electrode body such that dust and small particles generated by the drilling are forced into the (porous) inner surface of the bore and/or are deposited onto the inner surface of the bore.
According to another embodiment, the inner surface of the bore is fitted with an inside tube, for example a steel or metal tube, a carbon fibre tube or a graphite tube.
Further advantages and embodiments of the invention will become apparent from the description and the appended figures.
It should be noted that the previously mentioned features and the features described below are usable not only in the indicated combinations but also in other combinations or even taken alone, without departing from the scope of the present invention as defined in the appended claims.

Short description of the figures

In the drawings

Fig. 1: schematically shows an electric arc furnace in a sectional side view,
Fig. 2: schematically shows the inventive system in detail,
Fig. 3: schematically shows the telescope arm in the contracted position and
Fig. 4: schematically shows the telescope arm in the extended position and
Fig. 5: schematically shows a transportation pin.

Detailed description of the figures

Fig. 1 schematically shows an electric arc furnace 100 in a sectional side view.
The furnace 100 comprises a furnace vessel 101 in which a metallic material 102 to be processed can be loaded, e.g. metal scrap. Further, the furnace 100 comprises an electrode unit 110 with at least one electrode 111. In the present example, the electrode unit 110 comprises three electrodes 111. Electrode support beams 105 are provided for holding the electrodes 111 in position.
Each electrode 111 comprises a bore 112. Each electrode 111 has a cylindrical shape with the bore 112 extending along the entire length of the electrode 111 in axial direction.
Each bore 112 is connected to a gas supply for supplying an argon-rich gas. This gas supply comprises a gas tank 121 and a supply hose 122. Although only one tank is exemplarily shown in Fig. 1 it is to be understood that an expedient number of gas tanks can be provided. For example, also a bundle of gas cylinders or on-site supply can be provided instead of the gas tank 121.
For the sake of clarity and better visibility figure 2 shows one electrode support beam and the gas supply system in more detail. For an AC system with three electrodes, the electric arc furnace can be provided with three electrode support beams and three telescope arms.
In figure 2, an electrode support beam 105 is provided on a pillar 104 and extends over the top of an electric arc furnace (not shown). The electrode support beam 105 holds an electrode 111 by electrode clamps (not shown) in a fixed position. A telescope arm 201 is attached to a vertical support leg 202 by means of a joint. The joint allows to tilt the telescope arm 201 around the vertical axis defined by the support leg 202. The joint further allows to tilt the telescope arm 201 in the vertical direction, i.e. to increase or decrease the angle between the telescope arm 201 and the support leg 202 so that the tip of the telescope arm 201 is raised or lowered.
The telescope arm 201 is a double-ended lever. The support leg 202 divides the telescope arm 201 in a load arm 201a and in a force arm 201b. The support leg 202 is fixed to the electrode support beam 105, for example to the upper side of the electrode support beam 105. The load arm 201a extends in a longitudinal direction from its connection to the support leg 202 to the top of the electrode 111. The load arm 201a comprises two or more segments which can be moved relative to each other in the longitudinal direction of the telescope arm 201, allowing to adjust the length of the telescope arm 201. In the embodiment, shown in figures 3 and 4 the load arm 201a comprises two segments 205, 206 wherein segment 206 is slidably inserted into segment 205 so that by moving segments 205 and 206 relative to each other the length of the load arm 201a is changed.
A spring 208 inside the segment 205 of load arm 201a holds segment 206 of the load arm 201a in a specific position. In this position the free end of the load arm 201a comes so close to the top of the electrode 111 that the male part and the female part of the gas coupler 204 can be connected. The gas coupler 204 will be described in more detail below. In this position the load arm 201a has a length L (figure 3). Over the time when the electrode 111 is consumed the spring 208 extends and with it the load arm 201a gets longer. The length of the load arm 201a increases to become L + Δx (figure 4).
A high temperature resistant supply hose 122 is fixed to the load arm 201a of the telescope arm 201. The supply hose 122 is not fixed at the middle part of the load arm 201a, so that a loop 203 of the supply hose 122 hangs down. When the load arm 201a is extended, the loop 203 of the supply hose 122 becomes smaller (figure 4).
A gas coupler 204 is used to connect the supply hose 122 to the bore 112 in the electrode 111. The gas coupler 204 comprises a female part and a male part. When the female part of the gas coupler 204 receives the male part of the gas coupler 204 a connection for the gas flow between the supply hose 122 and the bore 112 is provided. The female part of the gas coupler 204 may be provided with an internal funnel that matches an external counter-part on the male part. The gas coupler 204 may also be provided with a valve mechanism that controls the gas flow. The valve mechanism opens the gas flow through the gas coupler when the male part and the female part are correctly connected, and it stops the gas flow when the male part and the female part are separated.
In this embodiment, the female part of the gas coupler 204 is fixed to the load arm 201a at its end close to the top of the electrode 111. The male part of the gas coupler 204 is connected to the electrode such that gas supplied to the gas coupler can flow into the bore 112 of the electrode 111. The load arm 201a presses by its weight the female part of the gas coupler 204 down on the male part and the gas flows from the gas supply 121 through the supply hose 122 into the bore 112. The argon or the argon-rich gas flows through the bore 112 to the bottom part of the electrode 111 and into the furnace 100. It is to be understood that the female part and the male part of the gas coupler can be interchanged, too.

Detailed procedure

In operation of the furnace 100, the argon or the argon-rich gas flows via the supply hose 122 which is connected to the load arm 201a of the telescope arm 201. The gas flows to the female part of the gas coupler 204 installed at the end of the load arm 201a. During operation the electrode 111 is subjected to wear and it is consumed so that it becomes shorter and shorter. The distance between the tip of the electrode 111, i.e. its bottom part, and the metal material 102 in the furnace 100 increases.
Therefore, the electrode clamps at the electrode support beam 105 are opened, and the electrode 111 is moved down so that optimum melting conditions are achieved again. This procedure of moving down the electrode 111 is repeated until the electrode 111 is too short and the electrode 111 needs to be replaced by a new electrode 111.
Figure 3 shows the load arm 201a when the electrode 111 is new and figure 4 shows the load arm 201a when the electrode 111 has already been partly consumed and lowered as described above. Since the end or tip of the load arm 201a with the female part of the gas coupler 204 is connected to the top of the electrode 111, the load arm 201a needs to cover a larger distance when the electrode 111 has been lowered. Since the load arm 201a is at least indirectly connected to the electrode 111 via the gas coupler 204, the length of the load arm 201a will be automatically adjusted when the electrode is lowered.
When the length of the load arm 201a is adjusted, the supply hose 122 will be automatically adjusted, too. The supply hose 122 is fixed to the segment 205 and to the segment 206 of the load arm 201a. When the load arm 201a is in a contracted state and the length of the telescope arm 201 is at its minimum, the supply hose 122 forms a loop 203 (see figure 3). When the load arm 201a is extended the size of the loop 203 is reduced so that the extension of the load arm 201a is not restricted by the supply hose 122.
When the electrode 111 becomes too short it has to replaced. Typically, several electrode segments 111a, 111b, 111c are longitudinally connected to each other to form the electrode column 111. There are different methods of connecting or assembling the electrode segments 111a, 111b, 111c. Such assembling methods can be:

Assembling the electrode segments beside the electric arc furnace and change the whole electrode column.
Assembling a new electrode segment at the furnace on top of the electrode manually.
Assembling a new electrode segment at the furnace on top of the electrode with an automatic jointer.

In the first case, the used electrode 111 is lifted out of the electrode holder and replaced with a new electrode. In this procedure the telescope arm 201 will be lifted manually by an operator. The operator lifts the load arm 201a of the telescope arm 201 by pulling the force arm 201b down. The gas flow through the supply hose 122 is stopped and the male part and the female part of the gas coupler 204 are disconnected. The segments 205 and 206 of the telescope arm 201 move in their standard positions by relaxing the spring 208 automatically (see figure 3). The telescope arm 201 is tilted a few degrees to the side so that the tip of the telescope arm 201 (load arm 201a) is no more vertically above the electrode 111. A holding table may be provided besides the standard position of the telescope arm and the operator may place the telescope arm 201 there. The standard position of the telescope arm shall be the position when the supply hose is connected to the gas coupler.
After that, the operator continues with the standard electrode change. The electrode 111 is provided with a transportation pin 207 at its upper end. A crane lifts the electrode 111 at the transportation pin 207, removes it from the furnace and a new electrode is placed in the right position and fixed by the clamps of the electrode holder to the electrode support beam 105.
The operator lifts up the telescope arm 201 from the holding position and tilts it back so that the free end of the load arm 201a with the female part of the gas coupler 204 can be connected to the male part of the gas coupler 204. This procedure ensures that no person needs to go up on top of the furnace, which brings maximum safety for the steel workers.
In the second case, the assembling of an electrode 111 with a new electrode segment is done when the used electrode is in the electrode holder above the furnace. This procedure is mainly the same as the first case described above.
The transportation pin 207, installed at the top of the electrode 111 is removed and a new electrode segment with the male part of another gas coupler is placed on top of the electrode by means of a crane. The process of placing the load arm 201a of the telescope arm 201 with the female part of the gas coupler 204 onto the male part of the gas coupler 204 is the same as in the first case.
The third case (assembling a new electrode with an electrode robot) is mainly the same as the second case. However, instead of manual assembling the electrode is assembled by an electrode jointer (robot). Before or in parallel to taking a new electrode segment with the jointer/electrode robot, an operator needs to remove the load arm 201a with the female part of the gas coupler 204 and place it on the holding table. After the assembling procedure the female part of the gas coupler 204 is placed on the male part of the gas coupler 204 again to establish the gas flow connection to the bore 112 inside the electrode 111.
Figure 5 shows a more detailed view of a connector unit with transportation pin 207 and gas coupler 204. The transportation pin 207 comprises a thread 450 to be screwed into a corresponding thread in the upper part of an electrode 111. The crane mounting part of the transportation pin 207 is fixed to its lower part by screws 412.
In the embodiment of figure 5, a hole is drilled into the centre of the transportation pin 207 to provide access for a steel pipe 422. This steel pipe 422 is bent and leads to the periphery of the transportation pin 207. At the end of the pipe 422 the male part of the gas coupler 204 is installed.
The transportation pin 207 can remain in the electrode 111 during operation of the electric arc furnace. The male part of the gas coupler can already be installed outside the furnace such that, after having removed the crane hook from the transportation pin 207, the operator can easily connect the female part of the gas coupler 204 to the male part of the gas coupler 204. This takes only a few seconds in addition to the normal assembling time of the electrode assembly.

Claims

System for injecting gas into an electric arc furnace, comprising an electrode (111) with a bore (112), an electrode support beam (105) with an electrode holder, a gas supply (121), a supply hose (122) connected to the gas supply (121) and a gas coupler (204) for connecting the supply hose (122) to the bore (112) of the electrode (111),
characterized in that
a telescope arm (201) is installed at the electrode support beam (105) and that the supply hose (122) is mounted to the telescope arm (201).
System according to claim 1, characterized in that the telescope arm is designed as a telescopic cylinder with two or more tubes nested within each other.
System according to claim 1, characterized in that the telescope arm comprises two or more segments wherein two of the segments are connected by a joint so that the two segments can be tilted against each other.
System according to any one of the preceding claims, wherein the gas supply contains argon or an argon-rich gas.
System according to any one of the preceding claims, wherein a portion of the supply hose forms a loop when the telescope arm is in its collapsed position.
System according to any one of the preceding claims, wherein the telescope arm is attached to a support leg which is mounted on the support beam.
System according to any one of the preceding claims, wherein the telescope arm 201 is a double-ended lever with a load arm and a force arm.
System according to any one of the preceding claims, wherein the gas coupler comprises a male part and a female part.
System according to any one of the preceding claims, wherein the electrode (111) has a longitudinal bore.
System according to any of the preceding claims, characterized in that the inner surface of the bore is sealed and/or coated and/or fitted with an inside tube.
System according to any one of the preceding claims, wherein the diameter of the bore inside the electrode body is less than 10%, or less than 8%, or less than 6%, or less than 4%, or less than 2% of the diameter of the electrode.
System according to any one of the preceding claims, wherein the electric arc furnace is a direct current electric arc furnace with one electrode, one electrode support arm and one telescope arm.
System according to any one of the preceding claims, wherein the electric arc furnace is an alternating current electric arc furnace with three electrodes, three electrode support arms and three telescope arms.