Plasma torch and corresponding use

Abstract

The invention relates to a plasma torch (1) and a use of a plasma torch (1).

Description

[0001] The invention relates to a plasma torch and a corresponding use.

[0002] Plasma torches are used to efficiently heat gaseous media, particularly in metallurgical processes. These torches generate an extremely hot plasma jet, primarily through the ionization of a gas. An electric arc is passed through a gas such as argon or nitrogen, causing the gas to transition into a plasma state. The plasma can reach temperatures of up to 30,000 °C, which is extremely hot and energetic. An electrode (cathode) located inside the plasma torch is subject to intensive wear and tear and must be replaced at regular intervals, usually every few hundred to a thousand hours.

[0003] There are two different designs of plasma torches: Plasma torches with an integrated anode, wherein an electric arc is generated within a nozzle tip located at the plasma outlet, allowing plasma to exit freely from the nozzle tip; plasma torches with a metallic counterpart as the anode, wherein an electric arc forms between the cathode, acting as the electrode in the nozzle, and the metallic counterpart. An example of an application is the plasma cutter.

[0004] A nozzle positioned at the outlet of the plasma torch focuses the plasma jet to concentrate energy onto a small area or section. This high energy can be used to melt and / or vaporize materials, or to cut them. Plasma torches are also used in processes such as plasma spraying, where material is applied to surfaces, and in plasma chemistry, where reactions are initiated by a plasma.

[0005] Plasma torches can be controlled via precise control systems to regulate temperature and gas flow. Therefore, a plasma torch is a versatile tool used in many industrial and scientific applications.

[0006] A plasma torch works by generating an extremely hot plasma jet through the ionization of a gas. An electric arc is created within a nozzle of the plasma torch, ionizing the gas flowing through the torch and thus through the nozzle. The gas, often argon, nitrogen, or air, is heated so intensely by the arc that it transitions into a plasma state. This process ionizes the gas atoms, creating an electrically conductive plasma. The nozzle and other components of the plasma torch are often cooled, particularly with water, to manage the high temperatures and prevent overheating.

[0007] Conventional plasma torches generate an electric arc by applying a high voltage between a cathode and an anode, which heats the gas and produces plasma. This technology has the disadvantage that the extremely high temperatures severely limit the lifespan of the cathode and anode.

[0008] Furthermore, a method and a device for automatically replacing electrodes (cathodes) in plasma torches is known from US 2022 / 0256683 A1 in order to maintain almost continuous operation, but the plasma torch is not in operation during the cathode change.

[0009] Also known as "hot-wire," this technique in plasma cutting technology involves using an auxiliary anode in the form of an external wire, which is fed in front of the nozzle and thus directly into the plasma jet. Furthermore, a plasma cutting system with water injection is also known, in which the water is directed so that it hits and touches the plasma arc between the constricting nozzle bore and the front part of the nozzle. The force of the water promotes a (further) constriction of the plasma arc, enabling higher cutting speeds and improved cut quality.

[0010] Furthermore, it is known from DE 695 29 459 T2 to use plasma torches for the heat treatment of metallic workpieces.

[0011] The object of the present invention is to provide a maintenance-friendly plasma torch and a corresponding application.

[0012] This problem is solved with respect to a plasma torch having the features of claim 1 and with respect to a use having the features of claim 12, 14 or 15. Further embodiments are set out in the dependent claims.

[0013] The first teaching of the invention relates to a plasma torch with a nozzle arranged at the outlet of the plasma torch for directing a plasma jet, which can be generated with a plasma gas flowing through the nozzle in conjunction with an arc generated inside the nozzle, wherein the arc can be generated by applying a voltage between a cathode arranged inside the plasma torch and an anode arranged inside the nozzle, wherein the anode is arranged as a wire electrode that can be tracked inside the nozzle.

[0014] The inventors have discovered that a plasma torch requiring minimal maintenance can be provided if an anode, functioning as a wire electrode, is positioned within the nozzle in a trackable manner. This allows the anode to be successively advanced to ensure a stable and uninterrupted process.

[0015] For example, the anode is located in the area of ​​the plasma torch exit inside the nozzle, preferably in the area of ​​the narrowest cross-section inside the nozzle.

[0016] According to one embodiment, the anode can be arranged in a helical shape within the nozzle. "Helix shape" within the meaning of the invention means that the anode, which consists of a wire electrode, corresponds to a ring in a top view. According to a preferred embodiment, the helical shape can thus have a number of turns between at least 1 and n, where n can, for example, be a maximum of 10. The turns do not necessarily have to be complete to result in a natural number as the number of turns, but can also be non-integers (positive numbers), such as 1.4, 2.3, or 3.7. Therefore, any number, including any non-integer, where only one decimal place is considered, between 1.0, 1.1, 1.2, ... 9.8, 9.9, 10.0 is conceivable as a number of turns and is hereby explicitly disclosed.

[0017] According to one embodiment, the cathode can be arranged to be tracked within the plasma torch. This allows both a trackable anode and a trackable cathode to result in a stable and uninterrupted process.

[0018] According to one embodiment, the nozzle can include a contoured section on its inner wall in which the anode can be received and / or tracked. This can facilitate and / or support the tracking of the anode, and in particular ensure that, preferably during targeted tracking of the cathode, especially into a defined operating position, a constant distance between the anode and cathode is maintained, thus guaranteeing a stable process. According to a preferred embodiment, the contour is a helical shape. This preferably ensures precise and / or defined positioning of the tracked anode. The helical shape can be cylindrical or conical.

[0019] According to a preferred embodiment, the anode, which functions as a wire electrode, can be withdrawn from a coil. This allows for the provision of a virtually endless long product.

[0020] According to one embodiment, the anode can be arranged in a channel so that it can be tracked. This allows, for example, for the trouble-free feeding of the anode into or to the nozzle. Thus, according to a preferred embodiment, the channel can be arranged outside the plasma torch, and the anode can be inserted and / or tracked into the interior of the nozzle via a feed opening in the nozzle.

[0021] The anode can be a highly electrically conductive metal, such as copper or a copper alloy, and / or a wear-resistant metal, such as hafnium or a hafnium alloy. In particular, the anode can be made of a composite material that is both highly electrically conductive and wear-resistant, preferably comprising or consisting of a composite of copper or a copper alloy and hafnium or a hafnium alloy. The anode can, for example, have a diameter between 0.5 and 10 mm, in particular at least 1, 2, or 5 mm, and in particular at most 9, 8, or 7 mm.

[0022] According to one embodiment, additional cathodes can be inserted laterally from the plasma torch or from the rear on the opposite side of the outlet into the plasma torch and thus be advanced within the plasma torch. Preferably, these additional cathodes can be advanced from the rear on the opposite side of the outlet into the plasma torch and connected to the remaining cathode within the plasma torch, preferably by a material bond, so that a quasi-extension of the cathode can be achieved and thus the cathode can be extended virtually indefinitely.

[0023] The cathode can be a highly electrically conductive metal, such as copper or a copper alloy, and / or a wear-resistant metal, such as hafnium or a hafnium alloy. In particular, the anode can be made of a composite material that is both highly electrically conductive and wear-resistant, preferably comprising or consisting of a composite of copper or a copper alloy and hafnium or a hafnium alloy. The cathode can, for example, have a diameter between 5 and 100 mm, in particular at least 8, 10, or 15 mm, and in particular at most 90, 70, or 60 mm, depending in particular on the dimensions of the plasma torch.

[0024] A second aspect of the invention relates to the use of at least one plasma torch according to the invention in at least one blast furnace. The construction of blast furnaces and the process for producing crude steel are well known to those skilled in the art. Thus, at least one essentially maintenance-friendly plasma torch can be used in the harsh environment of a blast furnace, in particular to introduce heat and / or energy into the blast furnace process, which is currently (still) achieved by means of so-called hot blast, which is introduced via several blast flues distributed around the circumference of the blast furnace. The use of a corresponding plasma torch can also serve as a replacement for at least one blast flue. Preferably, a plurality of corresponding plasma torches can completely replace the blast flues and thus the standard hot blast operation.At least one or preferably several plasma torches can be arranged in the shaft of the blast furnace, in a second plane, particularly above the tuyere plane. By selecting a suitable plasma gas, such as carbon monoxide, carbon dioxide, air, argon, nitrogen, blast furnace gas, coke oven gas, hydrogen, steam, natural gas, or a mixture of these gases, at least part of the reduction of the iron ore introduced into the blast furnace process can be achieved via the ionized gas. This reduces the input of coke or, more generally, fossil carbon carriers, which in turn can have a positive effect on the CO₂ balance.

[0025] A further teaching of the invention relates to the use of at least one plasma torch according to the invention in at least one heat treatment furnace for metal products. Plasma torches can be used in indirectly or, preferably, in directly fired heat treatment furnaces. The temperature, in particular the furnace atmosphere temperature, in a heat treatment furnace for the heat treatment of metal products can be at least 500 °C, 600 °C, 700 °C, 800 °C, in particular at least 900 °C, 1000 °C, 1100 °C and up to, for example, 1500 °C, 1450 °C, 1400 °C. According to a preferred application, steel slabs can be heat treated in a walking beam furnace or a pusher beam furnace, which are directly fired heat treatment furnaces. By a suitable selection of the plasma gas, such as nitrogen or argon, a substantially hydrogen- and / or water vapor-free orAt least a reduced furnace atmosphere can be created, which has a positive influence on the steel slab, resulting in low scaling on the surface and / or reduced hydrogen input.

[0026] A further aspect of the invention relates to the use of at least one plasma burner according to the invention in a (different) metallurgical unit heated by a natural gas burner and / or hydrogen burner, such as ladle furnaces, rotary drum furnaces, or tilting refining furnaces (TRFs). Preferably, the metallurgical unit is used in the non-ferrous (NF) industry.

[0027] To avoid repetition, reference is made to the design of the first teaching. Corresponding features of the first teaching are therefore also applicable and / or implementable in the second or subsequent teaching and are thus comprehensible to the person skilled in the art. Consequently, all combinations of individual features of the first teaching with the second or subsequent teaching are also disclosed.

[0028] The invention is explained in more detail with reference to the following exemplary embodiments in conjunction with the drawing. Identical parts are provided with the same reference numerals. They show Figure 1 a schematic longitudinal section of a first embodiment of a plasma torch according to the invention and Figure 2 a schematic longitudinal section of a second embodiment of a plasma torch according to the invention.

[0029] In Figure 1Figure 1 shows a schematic longitudinal section of a plasma torch (1) according to a first embodiment. The plasma torch (1) comprises a nozzle (3) arranged at its outlet for directing a plasma jet (12), which can be generated by a plasma gas (10) flowing through the nozzle (3) in conjunction with an electric arc (13) generated within the nozzle (3). The electric arc (13) can be generated by applying a voltage, for example, by means of a voltage source (5), between a cathode (4) arranged inside the plasma torch (1) and an anode (6) arranged inside the nozzle (3). The cathode (4) can be arranged within the plasma torch (1) in a tracking manner, and the anode (6) is arranged as a wire electrode within the nozzle (3) in a tracking manner. The tracking of the cathode (4) is indicated by the arrow in conjunction with the reference numeral (4.1).The tracking of the anode (6) is indicated by the arrow in conjunction with the reference numeral (6.1). The anode (6) is arranged in a helical shape (6.2) within the nozzle (3). In this embodiment, the helical shape (6.2) has a number of turns of at least 1.0, in particular 1.5. The nozzle (3) comprises a section with a contour (3.2) on its inner wall (3.1) in which the anode (6) can be received and / or tracked. The contour (3.2) preferably corresponds to a helical contour. The anode (6) can be withdrawn from a coil (6.4). The anode (6) can be arranged to be tracked in a channel (2), wherein the channel (2) is located outside the plasma torch (1) and the anode (6) can be inserted and / or tracked into the interior of the nozzle (3) via a feed opening (not shown) in the nozzle (3).Further cathodes (4), not shown, can be inserted laterally to the plasma torch (1) or from the rear on the opposite side of the outlet into the plasma torch (1), preferably connected to the (residual) cathode (4) still present in the plasma torch (1), and thus be adjustable within the plasma torch (1). If the anode (6) is damaged in the area of ​​arc generation (13), the anode (6) is advanced, for example, by at least one turn. This creates a temporary protrusion (6.3) at the outlet of the nozzle (3), which gradually melts, burns off, or vaporizes over time. If the cathode (4) is damaged in the area of ​​arc generation (13), particularly in the front area, the anode (6) is advanced, for example, by at least one turn.At the tip of the cathode (4), the cathode (4) is pushed forward, for example by a few millimeters to centimeters, towards the outlet of the nozzle (3) or anode (6), so that the tip is brought closer to the anode (6) or the outlet of the nozzle (3) and gradually melts, burns off or evaporates over time.

[0030] Figure 2Figure 1 shows a schematic longitudinal section of a plasma torch (1) according to a second embodiment. The construction is almost identical to the first embodiment, with the difference that in this embodiment the helical shape (6.2) has a number of turns of at least 4.0, in particular 4.5. Although not shown, the nozzle in the second embodiment can nevertheless include a section on its inner wall with a contour in which the anode can be received and / or guided, the contour corresponding to a helical contour. The helical contour, and thus also the helical shape (6.2), can be cylindrical or conical (not shown here) in both embodiments.

[0031] In both illustrations, the use of the respective plasma torch (1) is indicated by a reference line (B), which symbolizes a wall of an exemplary blast furnace, a heat treatment furnace for the heat treatment of metal products not shown, or a metallurgical unit for the non-ferrous metals industry. Thus, the plasma (12) radiates into the interior (A) of a blast furnace, a heat treatment furnace, or metallurgical unit. The insertion of additional cathodes (4) and the provision of coils (6.4) therefore take place outside the reference line (B). The arrangement of the plasma torch (1) on / in a wall is only exemplary, as, of course, depending on the application, the plasma torch (1) may extend further into the furnace chamber than shown, or it may be recessed in / on the wall.The nozzle (3) and optionally other parts of a plasma torch (1) connected to the nozzle (3) are usually cooled by means of a cooling system (7) due to the high heat generation by the plasma (12).

Claims

1. Plasma torch (1) with a nozzle (3) arranged at the outlet of the plasma torch (1) for directing a plasma jet (12), which can be generated with a plasma gas (10) flowing through the nozzle (3) in conjunction with an electric arc (13) generated inside the nozzle (3), wherein the electric arc (13) can be generated by applying a voltage between a cathode (4) arranged inside the plasma torch (1) and an anode (6) arranged inside the nozzle (3), characterized by the fact that the anode (6) is arranged as a wire electrode within the nozzle (3) in a way that allows it to be tracked.

2. Plasma torch according to claim 1, wherein the anode (6) is arranged in a helical form (6.2) inside the nozzle (3).

3. Plasma torch according to claim 2, wherein the helical shape (6.2) has a number of turns between at least 1 and n.

4. Plasma torch according to claim 2 or 3, wherein the nozzle (3) comprises on its inner wall (3.1) a section with a contour (3.2) in which the anode (6) can be received and / or tracked.

5. Plasma torch according to claim 4, wherein the contour (3.2) corresponds to a helical contour.

6. Plasma torch according to one of the preceding claims, wherein the cathode (4) is arranged to be tracked within the plasma torch (1).

7. Plasma torch according to one of the preceding claims, wherein the anode (6) is removable from a coil (6.4).

8. Plasma torch according to one of the preceding claims, wherein the anode (6) is arranged to be tracked in a channel (2).

9. Plasma torch according to claim 8, wherein the channel (2) is arranged outside the plasma torch (1) and the anode (6) can be inserted and / or moved into the interior of the nozzle (3) via a feed opening in the nozzle (3).

10. Plasma torch according to claim 6, wherein further cathodes (4) can be inserted laterally of the plasma torch (1) or from the rear on the opposite side of the outlet into the plasma torch (1) and can thus be advanced within the plasma torch (1).

11. Plasma torch according to claim 10, wherein further cathodes (4) are arranged to be guided from the rear on the opposite side of the exit into the plasma torch (1) and are connectable to the (residual) cathode (4) still present in the plasma torch (1).

12. Use of at least one plasma torch (1) according to one of the preceding claims in at least one blast furnace.

13. Use according to claim 12 as a replacement for at least one wind form.

14. Use of at least one plasma torch (1) according to any one of claims 1 to 11 in at least one heat treatment furnace for metal products.

15. Use of at least one plasma torch (1) according to any one of claims 1 to 11 in at least one metallurgical furnace for the non-ferrous metals industry.

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