Device and method for heating rod-shaped metal workpieces
Patent Information
- Application Number
- EP2023757893
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-08-19
- Filing Date
- 2023-08-16
- Publication Date
- 2025-06-25
- Estimated Expiration
- 2043-08-16
AI Technical Summary
Inductive bolt heating systems face inefficiencies in heating non-ferritic materials like aluminum and copper due to magnetic coupling issues, leading to significant energy losses and requiring gas-heated preheating methods that contribute to CO2 emissions.
The system employs a liquid medium in a closed loop for cooling and preheating, utilizing waste heat from the induction process for initial warming, and includes a heat exchanger for indirect warming, potentially using a secondary loop for additional warming and incorporating a preheating chamber with mixing and cleaning features to optimize energy use.
This approach enhances energy efficiency by minimizing energy losses and eliminating the need for gas-heated preheating, reducing CO2 emissions and achieving a higher overall energy utilization rate.
Smart Images
Figure 1.1
Abstract
Description
[0001]August 7, 2023: Device and method for heating rod-shaped metallic workpieces. The present invention relates to a device and a method for heating rod-shaped metallic workpieces, in particular billets made of aluminum or copper and their alloys, comprising an induction furnace for inductive heating, wherein the induction coils of the induction furnace are cooled by means of a cooling device, and a preheating device for preheating the workpieces, as well as a corresponding method for heating such rod-shaped metallic workpieces. Such devices are also referred to as "inductive billet heating systems (IBE)." These are used to heat metallic extrusion billets and have proven themselves for decades for numerous reasons. A generic device is known, for example, from WO 2010 / 031503 A1. The very high heat output enables high throughput with a small space requirement.With such high heat output, a targeted temperature profile can be set in the billet, which offers advantages in subsequent processing. The fact that inductive heating is based on electricity makes the system even more interesting these days, as CO2-free energy can be used when using renewably generated electricity. Compared to extrusion billets made of ferritic materials, heating non-ferritic materials, such as aluminum and copper, as well as their alloys, results in lower efficiency. This is due to the different magnetic coupling of the induction field. However, due to the advantages mentioned above, its use is quite common for aluminum and copper, for example. Magnetic coupling and thus inductive heat transfer therefore result in efficiency losses, particularly with non-ferritic feedstocks.This requires cooling of the induction furnace's induction coils, which is usually implemented as a water cooling system. This cooling also simultaneously dissipates the heat radiation from the preheated billets to the induction coil(s). To a lesser extent, waste heat is also generated in the electrical control system, which is also dissipated via the cooling water. The overall efficiency is in the order of approximately 60%, so that approximately 40% of the supplied electrical energy must be dissipated predominantly via the cooling water. To save primary energy, gas-fired preheating furnaces are often installed upstream of inductive billet heating systems. These preheat to a base temperature level. Above this level, the very rapid residual heating required by the process takes place with the inductive billet heating system.In current developments, it should be noted that gas-fired preheating leads to CO2 emissions that can only be avoided by using renewably produced hydrogen as the fuel gas. Based on this, the present invention is based on the object of designing and developing the device and corresponding method mentioned at the outset and described in more detail above, in such a way that a gas-fired preheating furnace for preheating the rod-shaped workpieces can be dispensed with. In particular, the energy efficiency of inductive billet heating should be increased in order to minimize energy losses as much as possible or avoid them entirely. This object is achieved in a device having the features of the preamble of patent claim 1 in that the cooling device uses a liquid tempering medium guided in a cooling circuit, and that the workpieces are heated in the T.H / lh 220723WOAugust 7, 2023 preheating device. In this way, the unused residual heat from the induction furnace can be fully utilized for preheating the workpieces. Direct heating of the workpieces (billets) with the cooling device's temperature control medium is possible. The problem is also solved in terms of the method in that the cooling device uses a liquid temperature control medium conducted in a cooling circuit, and the workpieces are heated by the heated temperature control medium in the preheating device before entering the induction furnace. A further teaching of the invention provides that the cooling circuit has a heat exchanger. A treatment medium conducted in a second circuit can be heated indirectly via the heat exchanger with the temperature control medium of the cooling device of the induction furnace and used for the direct heating of the billets fed to the preheating device.Another preferred embodiment of the invention provides for an intermediate heating device between the preheating device and the induction furnace. This is always useful when a sufficient temperature level of the workpieces / bolts cannot be achieved by preheating. The preheating device can preferably have a basin for preheating the bolts with the tempering medium. Devices for mixing the tempering medium and / or for increasing heat transfer can be arranged in the basin. Such mixing devices can include nozzles or circulation units. Alternatively, or additionally, a spray / shower chamber can also be provided as a preheating device for preheating the bolts, which ensures intensive contact between the treatment medium and the bolt surface. H / lh 220723WOAugust 7, 2023. In any case, according to a further preferred embodiment of the invention, it is advantageous if the preheating device has devices for cleaning and / or descaling the billets. The cleaning of the billets can be carried out mechanically, and for this purpose, driven brushes, for example, can be provided within the preheating device. A further teaching of the invention provides that devices for drying or blowing off the tempering medium from the billets are provided between the preheating device and the induction furnace so that they can be fed to the induction furnace as dry as possible. Water is preferably used as the tempering medium and / or treatment medium; the water can be mixed with chemical additives. It is also possible to use a thermal oil as the tempering medium and / or treatment medium instead of water, whereby an increase in the temperature level can be achieved.According to a further teaching of the invention, it is provided that the cooling circuit of the cooling device is separated into different circuits and only one circuit, or several individual circuits, are used for preheating the bolts. According to a preferred embodiment of the invention, a fuel-heated heating system can be connected upstream and / or downstream of the inductive heating of the bolts. Such a fuel-heated heating system can be gas-heated, wherein the heating can be carried out in particular using hydrogen or natural gas. However, it is also possible for the fuel-heated heating to be carried out with liquid fuel. The inductive heating of the bolts can also be preceded and / or downstream of an electrical (resistance-heated) heating system, wherein the T. H / lh 220723WOAugust 7, 2023 Heat can be transferred to the billets by convection or radiation. In another alternative, exhaust-heated heating can also be installed upstream and / or downstream of the inductive heating of the billets. In any case, it is advisable to control the preheating of the billets using a mathematical model. Such a mathematical model records the preheating temperature and optimally adjusts the inductive heating in the inductive billet heating system to the desired target temperature based on a model of the entire heating process. This is also referred to as a "digital twin." Optimization for maximum performance or maximum energy savings is possible. Environmental influences (e.g., air temperature or cooling water temperature) or process influences (e.g., shutdown of the downstream press line) can also be taken into account. möglich.The invention is explained in more detail below with reference to a drawing illustrating only preferred embodiments of the invention. The drawing shows, all schematically, Fig. 1 shows an inductive billet heating system according to the prior art, Fig. 2 shows a first embodiment of a device according to the invention using a heat exchanger, Fig. 3 shows a second embodiment of the device according to the invention. und Fig. 4 shows another embodiment of the invention.T H / lh 220723WOAugust 7, 2023. Fig. 1 schematically shows the structure of an inductive billet heating system (IBE) in which a metallic, non-ferritic extrusion billet (for example, made of aluminum or copper) is inductively heated in an induction furnace 2 (only indicated). The schematically shown induction coil of the induction furnace 2 and a necessary electrical control unit 4 can be seen. A cooling device 5 (only indicated) uses a liquid temperature control medium guided in a cooling circuit, which removes the unused heat (approximately 40% of the supplied electrical energy) of the induction coil 3 from the induction furnace 2. To a lesser extent, waste heat is also generated in the electrical control unit 4, which is also dissipated via the temperature medium and fed to a heat exchanger 7.It is not shown that the further circuit extracts the heat supplied to the heat exchanger and can be used, for example, for heating buildings for domestic water heating. A pump 6 ensures that the temperature control medium, after leaving the heat exchanger 7, is fed back to the induction furnace 2 or the electrical control 4 for cooling purposes. Fig. 2 schematically shows a first embodiment of the device according to the invention, wherein the further circuit behind the heat exchanger 7 has a line 8, which is fed to a preheating device 9. This can have a basin 10 for receiving the treatment medium carried in the second circuit, wherein the supplied bolts 1 come into full contact with the treatment medium in order to heat the bolts 1.Alternatively or additionally, it is also possible to provide a spray / shower chamber 11 or a sprinkler system (shown only schematically) in the area of the preheating device 9. A pump 12 ensures that the treatment medium cooled during preheating is fed back to the heat exchanger 7 to complete the second circuit. H / lh 220723WOAugust 7, 2023. Fig. 3 shows only a schematic representation of a second embodiment of the invention, in which no heat exchanger is present. The heat of the tempering medium extracted from the induction furnace 2 and also from the electrical control system 4 is fed directly to the preheating device 9 by means of a heat pump 6' via a line 8. The preheating device 9 has the same structure as the device according to Fig. 2. The tempering medium is then fed from the basin 10 by means of the pump 6 in the cooled state to the cooling device 5, as already described above. Finally, Fig. 4 shows a modification of the device according to Fig. 2, in which an intermediate heating device (only indicated) can be provided between the preheating device 9 and the induction furnace 2. This intermediate heating device can be heated with different forms of energy, as described in the subclaims. werden. T H / lh 220723WO August 7, 2023
Claims
7 August 2023 Patent claims 1. Device for heating rod-shaped metallic workpieces (1), in particular bolts made of aluminum or copper and their alloys, with an induction furnace (2) for inductive heating, wherein the induction coils (3) of the induction furnace (2) are cooled by means of a cooling device (5), and with a preheating device (9) for preheating the erkstücke (1),characterized in that the cooling device (5) uses a liquid tempering medium guided in a cooling circuit, and in that the workpieces (1) are heated by the heated tempering medium in the preheating device (9) before entering the induction furnace (2).
2. Device according to claim 1, characterized in that the cooling circuit has a heat exchanger (7), and in that a treatment medium guided in a second circuit is heated indirectly via the heat exchanger (7) with the tempering medium of the cooling device (5) of the induction furnace (2) and is used for the direct heating of the workpieces (1) fed to the preheating device (9).
3. Device according to claim 1 or 2, characterized in that an intermediate heating device (13) is provided between the preheating device (9) and the induction furnace (2).
4. Device according to one of claims 1 to 3, - 2 - characterized in that the preheating device (9) has a basin (10) for preheating the bolts (1) by the tempering medium.
5. Device according to claim 4, characterized in that devices for mixing the tempering medium and / or for increasing the heat transfer are arranged in the basin (10).
6. Device according to claim 5, characterized in that the mixing devices comprise nozzles or units for circulation aufweist.
7. Device according to one of claims 1 to 3, characterized in that a spray / shower chamber (11) is provided for preheating the bolts.
8. Device according to one of claims 1 to 7, characterized in that the preheating device has devices for cleaning and / or descaling the bolts.
9. Device according to claim 8, characterized in that the cleaning of the bolts is carried out mechanically and that driven brushes are provided for this purpose within the preheating device.
10. Device according to one of claims 1 to 9, characterized in that H / lh 220723WO August 7, 2023 - 3 - between the preheating device and the induction furnace, devices for drying or blowing off the tempering medium from the bolts are provided sind.
11. Device according to one of claims 2 to 10, characterized in that the tempering medium and / or the treatment medium is water.
12. Device according to claim 11, characterized in that the water is mixed with chemical additives.
13. Device according to one of claims 1 to 10, characterized in that the tempering medium and / or the treatment medium is thermal oil.
14. Method for heating rod-shaped metallic workpieces, in particular bolts made of aluminum or copper and their alloys, using a device according to one of claims 1 to 13, characterized in that the cooling device uses a liquid tempering medium guided in a cooling circuit and that the workpieces are heated by the heated tempering medium in the preheating device before entering the induction furnace.Method according to claim 14d, characterized in that the cooling circuit of the cooling device is separated into different circuits and only one circuit or several individual circuits are used for preheating the bolts.T. H / lh 220723WO August 7, 2023 - 4 -16. Method according to claim 14 or 15, characterized in that the inductive heating of the bolts is preceded and / or followed by a fuel-heated heating means.
17. Method according to claim 16, characterized in that the fuel-heated heating means is gas-heated, in particular heated by means of hydrogen or natural gas.
18. Method according to claim 16d, characterized in that the fuel-heated heating means is liquid fuel-heated.
19. Method according to claim 14 or 15, characterized in that the inductive heating of the bolts is preceded and / or followed by an electrical resistance-heated heating means.
20. Method according to claim 18, characterized in that the heat is transferred to the bolts by means of convection.21.Method according to claim 18, characterized in that the heat is transferred to the bolts by means of radiation.
22. Method according to claim 14 or 15, characterized in that the inductive heating of the bolts is preceded and / or followed by exhaust gas-heated heating.T. H / lh 220723WO August 7, 2023 - 5 -23. Method according to one of claims 14 to 22, characterized by regulating the preheating of the bolts with the aid of a mathematical Modells. T H / lh 220723WO August 7, 2023