Plant for melting and / or heating metallic material and method for supplying electrical energy to the same

Abstract

To provide a plant for melting and / or heating a metallic material and a corresponding method for supplying electrical energy.SOLUTION: A plant includes at least one induction furnace (11) and means (12) for supplying the induction furnace (11) with electrical energy. The power supply means (12) includes: at least one transformer (13) connected to an AC power network (14); at least one rectifier (15) arranged downstream of the transformer (13); at least one converter (16) arranged downstream of the rectifier device (15); and at least one coil (17) for melting and / or heating a metallic material.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a plant for melting and / or heating metallic materials. In particular, the plant comprises at least one induction furnace for melting and / or heating metallic materials.

[0002] The present invention also relates to a method for supplying electrical energy in a plant for melting and / or heating metallic materials, comprising an induction furnace.

Background Art

[0003] Plants for heating and / or melting metallic materials are known, which comprise an induction furnace into which a metallic product to be melted or heated is introduced. The induction furnace is associated with power supply means for extracting energy from the power grid and sending it to the electrical components of the furnace.

[0004] As is known, induction furnaces are used in metallurgy for melting or heating metallic materials according to the principle of electromagnetic induction. Induction heating is widely used in the metal industry and offers several advantages, such as high production speeds, high energy efficiency, localized heat only where needed. Induction furnaces provide low energy consumption or unwanted overheating, high process control and reproducibility, excellent quality of the finished product, little need for maintenance, ease of integration into production lines, high safety due to the absence of open flames and toxic fumes, miniaturization and increased free space.

[0005] An induction furnace can comprise, for example, a transformer connected to an alternating current power grid, a rectifier downstream of the transformer for rectifying the alternating current at the outlet of the transformer into a direct current, a converter arranged downstream of the rectifier for converting the direct current at the outlet of the rectifier into an alternating current, and at least one coil for melting and / or heating the metallic material passing through the coil.

[0006] A coil or spiral generally surrounds a chamber through which the metal material to be heated is passed so that the generated magnetic field impinges uniformly on the metal product to be heated. For example, melting plants and / or heating plants used in the production of steel in the steel industry are known to require a high power supply (usually several tens of megawatts (MW)), depending on both or either the size of the plant and the induction furnace used.

[0007] Therefore, in order to obtain a sufficient energy supply, it is necessary for either or both of the melting plant and the heating plant to be continuously connected to the power grid. Furthermore, since the absorption of three-phase alternating current depends on the production volume, the greater the amount of molten material produced by the furnace, the greater the amount of electrical energy that must be purchased.

[0008] One drawback of conventional solutions is the need to be constantly connected to the public power grid. Another drawback is that obtaining electrical energy from the power grid can be expensive, particularly in certain geographical regions or after major socio-economic events, and the estimated supply costs can also increase significantly.

[0009] Therefore, some steelworks are forced to concentrate production, for example, during periods when the cost of electrical energy supplied by the power grid is relatively low. Furthermore, in the event of a possible power grid outage, it is necessary to stop the plant and production, resulting in a loss of productivity and, consequently, a delay in the delivery of production batches.

[0010] The document of Patent Document 1 describes a known heating inductor for a melting furnace that first rectifies an alternating line current into a direct current and then converts it into an alternating current to be sent to the coil of the inductor. The electrical energy is supplied by a conventional power grid.

[0011] The document of Patent Document 2 describes an apparatus and method for storing electrical energy and supplying it to users. The apparatus includes a power grid and a renewable energy supply unit connected to a storage unit. The main purpose of this solution is actually to store the electrical energy supplied by the renewable energy supply unit for use as an alternative to the power grid.

[0012] Patent Document 3 describes a household user device connected to a power grid and a control unit for an apparatus that supplies electrical energy to an energy storage device supplied by a renewable energy source. The control unit monitors the state of the storage device in order to alternately connect the user device to the storage device or the power grid.

[0013] These recent solutions particularly describe household user devices and are not suitable for applications in industrial plants, especially plants for heating and / or melting metallic materials that require a very high supply power, i.e., on the order of dozens of megawatts.

[0014] Therefore, there is a need to complete a plant for heating and / or melting metallic materials equipped with an induction furnace that can overcome at least one of the drawbacks of the current state of the art.

[0015] Specifically, one object of the present invention is to provide a plant for melting and / or heating metallic materials that can operate at least partially independently of the power grid in order to reduce the energy supply cost and thus the overall production cost.

[0016] One object is also to reduce the risk of interruption of the operation of a processing plant or treatment plant due to a power outage in the power grid, which can last for several days in the most serious cases. Another object is to reduce the use of energy from the public power grid and thus reduce the consumption brought about by this power grid.

[0017] Another object is to perfect a method for supplying power to a plant comprising an induction furnace for heating and / or melting metallic materials, which makes it possible to limit the supply of electrical energy from the power grid.

[0018] It is also an object to operate a plant for heating and / or melting metallic materials both during the day and at night or during one of them. Another benefit and advantage provided by the present invention is also the possibility of reducing CO2 emissions when the production of energy by the public power grid is not entirely generated by renewable energy sources.

[0019] The applicant has devised, tested and embodied the present invention in order to overcome the drawbacks of the state of the art and to obtain these and other objects and advantages.

Prior Art Documents

Patent Documents

[0020]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

[0021] The present invention is set forth and characterized in the independent claims. The dependent claims explain other features of the present invention or variants of the main inventive idea. In accordance with the above object, a plant for melting and / or heating a metallic material according to the present invention comprises at least one induction furnace and power supply means. The power supply means includes at least one transformer connected to an alternating current power grid, at least one rectifier arranged downstream of the transformer for converting the alternating current at the outlet of the transformer into direct current, at least one converter arranged downstream of the rectifier for converting the direct current at the outlet of the rectifier device into alternating current, and at least one coil for melting and / or heating the metallic material.

[0022] According to one aspect of the present invention, the power supply means further comprises at least one alternative energy source that is different from and independent of the power grid, is connected to the induction furnace upstream of the converter, and is selectively available for supplying electrical energy to the induction furnace in addition to or as an alternative to the electrical energy supplied by the power grid.

[0023] Thanks to the alternative energy source, it is possible to at least partially supply power to the induction furnace independently of the power grid, and optionally to disconnect the melting plant and / or heating plant from the power grid at least temporarily, or in any case to reduce the supply of energy from the power grid over time, and optionally to limit the supply of energy to a time period when it is not relatively expensive.

[0024] Furthermore, the presence of the alternative energy source makes it possible to utilize the melting plant and / or heating plant even in the event of a malfunction or power outage of the power grid. Since the alternative energy source can supply electrical energy to the induction furnace even simultaneously with the power grid, the power supply means is able to obtain a high flexibility in adjusting the electrical energy supplied to the induction furnace each time, to optimize the supply of electrical energy according to both the demand or fluctuations of the load to be powered, and furthermore, it also serves to minimize the draw from the power grid and thus minimize costs.

[0025] The alternative energy source can be connected to the induction furnace by means of at least one DC current connection system, for example a so-called "DC link", which is suitable for storing and filtering electrical energy and for ensuring an improved reliability and quality of the power supply to the converter device and is connected upstream of the converter.

[0026] The induction furnace can also be provided with at least one regulating circuit which is arranged downstream of the converter and upstream of the coil and is configured to reduce the reactive power and transmit the maximum active power to the coil.

[0027] Also, in some embodiments, the induction furnace can comprise a plurality of coils and a plurality of corresponding converters arranged upstream of each of the coils. The alternative energy source can comprise a renewable energy source selected from a hydroelectric power plant, a wind power plant or a solar power plant.

[0028] The plant can also be provided with at least one storage device which is positioned between at least one alternative energy source and the induction furnace and is configured to enable the storage of the electrical energy generated by the alternative energy source when it is not used to supply the induction furnace.

[0029] Thus, the stored energy can be used at a later point in time, for example when the alternative energy source is not available or when sufficient energy is not supplied. The alternative energy source can comprise a non-renewable energy source configured to obtain electrical energy by burning fossil fuels, and the non-renewable energy source is selected from the group comprising a gas turbine or an auxiliary current generator.

[0030] In some embodiments, the plant can also be provided with a management unit configured to select one, the other or both between the power grid and the alternative energy source depending on one or more operating parameters.

[0031] In particular, the management unit monitors one or more parameters among the operating state, quality, quantity, and / or cost of the electrical energy available from the power grid and at least one alternative energy source, and the amount of energy required by the induction furnace, and is configured to select one, the other, or both of the power grid and at least one alternative energy source to supply electrical energy to the induction furnace, at least according to each operating state and the overall energy cost.

[0032] One advantage is that, for example, the operation with a high power load can be maintained even when the availability of energy from at least one alternative energy source is low, or when a power outage occurs in the public power grid.

[0033] Advantageously, the management unit can detect one or more parameters among the availability of the energy supplied by the power grid, the energy cost, and the degree of integration with the energy available from at least one alternative energy source to supplement the energy demand of the load.

[0034] Thus, in each case, it is possible to choose the most appropriate supply energy source, that is, the energy supplied by the power grid or the energy supplied by at least one alternative energy source, also based on the energy cost. Therefore, this prevents the need to reduce production or stop the operation of the processing plant in case of energy shortage or its excessive cost.

[0035] Furthermore, the present invention includes a method of supplying electrical energy in a plant for melting and / or heating a metallic material, the plant comprising at least one induction furnace and means for supplying electrical energy to the induction furnace. The method serves to supply electrical energy to the induction furnace by at least one alternative energy source that is different from and independent of the power grid and is associated with the induction furnace, in addition to or as an alternative to the electrical energy supplied by the power grid.

[0036] The method can also serve to detect and / or monitor one or more parameters of the operating state, energy availability, and cost of the energy supplied by the power grid and the alternative energy source, and the amount of electrical energy required by the induction furnace, and to determine whether to use one, the other, or both of the power grid and the alternative energy source to supply power to the induction furnace, at least according to both or one of the detected state and the amount of energy required by the induction furnace.

[0037] These and other aspects, features, and advantages of the present invention will become apparent from the following description of several embodiments given as non-limiting examples with reference to the accompanying drawings.

Brief Description of the Drawings

[0038]

Figure 1

Embodiments for Carrying Out the Invention

[0039] Here, a possible embodiment of the present invention will be described in detail, and one example thereof is shown in the accompanying drawings. This example is provided as an illustration of the present invention and should not be construed as a limitation of the present invention.

[0040] Referring to FIG. 1, a plant 10 according to the present invention for melting and / or heating a metallic material comprises at least one induction furnace 11 and means 12 for supplying electrical energy to the induction furnace 11.

[0041] The power supply means 12 comprises at least one transformer 13 connected to an alternating current power grid 14, at least one rectifier 15 arranged downstream of the transformer 13 for converting the alternating current at the outlet from the transformer 13 into a direct current, at least one converter 16 arranged downstream of the rectifier 15 for converting the direct current at the outlet from the rectifier device 15 into an alternating current, and at least one coil 17 for melting and / or heating a metallic material, for example a metallic article passing through the coil 17.

[0042] Between the rectifier device 15 and the converter 16, there can also be a direct current connection system 24, also called a DC link, which is suitable for accumulating and filtering electrical energy and for ensuring an improved reliability and quality of the power supply to the converter 16.

[0043] The power supply means 12 also comprises at least one alternative energy source 18, which is different from and independent of the power grid 14 and is connected to the induction furnace 11 upstream of the converter device 16 and is configured to supply electrical energy to the induction furnace 11 in addition to, or as an alternative to, the electrical energy supplied by the power grid 14.

[0044] The power grid 14 can supply electrical energy having, for example, a high voltage, in particular an alternating current, a predetermined voltage value, a current value and a power grid frequency value. Downstream of the power grid 14, there is provided a high voltage / medium voltage (HV / MV) transformer 32 configured to convert the high voltage energy into medium voltage energy.

[0045] Downstream of the transformer 32, a transformer 13 is provided which can be a medium-voltage / medium-voltage (MV / MV) transformer configured to convert the medium-voltage energy to a medium-voltage value suitable for powering the induction furnace 11.

[0046] The transformer 13 can be provided with a secondary side of the transformer arranged in a star or delta configuration and having an offset phase to obtain an alternating current wave that gives better results with respect to rectification by the rectifier device 15.

[0047] The rectifier device 15 can include, for example, a pair of thyristor bridges 19 or a diode bridge. According to a possible solution, the rectifier device 15 comprises a device selected from the group including diodes, SCRs (Silicon Controlled Rectifiers), GTOs (Gate Turn-Off thyristors), IGCTs (Integrated Gate-Commutated Thyristors), MCTs (Metal-Oxide Semiconductor Controlled Thyristors), BJTs (Bipolar Junction Transistors), MOSFETs (Metal-Oxide Semiconductor Field-Effect Transistors) and IGBTs (Insulated-Gate Bipolar Transistors).

[0048] Converter device 16 can be, for example, an inverter comprising a transistor 20, for example an IGBT bridge, or an insulated gate bipolar transistor, as illustrated. According to a possible solution, converter device 16 comprises a device selected from the group comprising, for example, an SCR (silicon controlled rectifier), a GTO (gate turn-off thyristor), an IGCT (integrated gate-commutated thyristor), an MCT (metal-oxide semiconductor controlled thyristor), a BJT (bipolar transistor), a MOSFET (metal-oxide semiconductor field effect transistor) and an IGBT (insulated gate bipolar transistor).

[0049] Downstream of converter 16 and upstream of coil 17, an adjustment circuit 21 can be provided which is configured to reduce the reactive power and transmit the maximum available active power to coil 17. Adjustment circuit 21 can comprise at least one inductor 22 and at least one capacitor 23, or a bank of capacitors 23, which are capable of reducing the reactive power.

[0050] As can be seen in FIG. 1, the induction furnace 11 can comprise a plurality of induction coils 17, each of which can be passed through by an electric current in order to generate the magnetic field necessary to heat the metal product to be melted or heated.

[0051] Each of coils 17 can be associated with a corresponding converter device 16 arranged upstream of coil 17. Each of converter devices 16 can be connected to the same direct current connection system 24.

[0052] Alternative energy source 18 is preferably connected to induction furnace 11 by means of at least one direct current connection system 24 arranged between the output of rectifier device 15 and the input of converter device 16.

[0053] As described, the DC current connection system 24 can be a so-called "DC link" circuit or connection suitable for accumulating and filtering electrical energy and ensuring improved reliability and quality of power supply to the converter device 16, which requires a stable and clean DC voltage at the input.

[0054] The DC current connection system 24 can also be configured to create a separation between the converter 16 and the rectifier 15, and thus between the power grid 14 connected upstream thereof, or an alternative energy source 18. In this way, possible power fluctuations are partially filtered by the DC current connection system 24 to reduce its impact on the side of the power grid 14 and / or the alternative energy source 18.

[0055] The alternative energy source 18 can comprise one or more renewable energy sources selected from a hydroelectric power plant 25, a wind power plant 26, or a solar power plant 27 provided with, for example, a plurality of solar panels 28.

[0056] The alternative energy source 18 can supply DC current or AC current. In the latter case, the energy source 18 can be provided with its own converter device or other means to enable connection to the DC current connection system 24 associated with the induction furnace 11.

[0057] The plant 10 can also comprise a storage device 29 positioned between the alternative energy source 18 and the induction furnace 11 and configured to enable storage of the electrical energy generated by the alternative energy source 18 when it is not used to supply power to the induction furnace 11.

[0058] In this case, the induction furnace 11 can be powered directly by the electrical energy generated by the alternative energy source 18, and also indirectly, for example, by the storage device 29 when the alternative energy source 18 is not available.

[0059] The storage device 29 can be used in addition to, or as an alternative to, the power grid 14. The alternative energy source 18 can comprise one or more non-renewable energy sources 30 configured to obtain electrical energy by burning fossil fuels, and the non-renewable energy source 30 is selected from the group including gas turbines or auxiliary current generators.

[0060] The plant 10 can advantageously be provided with a management unit 31, which can comprise, for example, one or more processors. The management unit 31 is configured to select one, the other, or both between the power grid 14 and the alternative energy source 18 in order to supply electrical energy to the induction furnace 11 according to one or more parameters. Thus, it is possible to increase or decrease the electrical energy supplied by one, the other, or both of the power grid 14 and the alternative energy source 18, both in relation to the operating needs and in relation to the cost of the electrical energy.

[0061] The management unit 31 can be configured to monitor at least one parameter among the operating state, quality, quantity, and / or cost of the electrical energy available from the power grid 14 and at least one alternative energy source 18.

[0062] The management unit 31 can also be configured to monitor the amount of energy required by the induction furnace 11 and to select one, the other, or both between the power grid 14 and the alternative energy source 18 in order to supply electrical energy to the induction furnace 11, at least according to each operating state and the overall energy cost.

[0063] Substantially, the method for supplying electrical energy to the induction furnace 11 of the plant 10 for melting and / or heating a metallic material serves to supply electrical energy to the induction furnace 11 in addition to, or as an alternative to, the electrical energy supplied by the power grid 14, by means of at least one alternative energy source 18 that is different from and independent of the power grid 14 and is associated with the induction furnace 11.

[0064] The method serves to detect and / or monitor one or more parameters of the operating state, energy availability, and cost of the energy supplied by the power grid 14 and the alternative energy source 18, and the amount of electrical energy required by the induction furnace 11, and to determine whether to use the power grid 14, the alternative energy source 18, or both to supply power to the induction furnace 11, depending at least on the detected state and / or the amount of energy required by the induction furnace.

[0065] If an energy storage device 29 is also present, the power supply method also serves to monitor the operating state, i.e., the charge amount present therein, and to determine whether to use the energy supplied by the energy storage device 29 in addition to, and / or as an alternative to, the energy supplied by both or one of the power grid 14 and the alternative energy source 18, and how to use such energy.

[0066] It is obvious that, without departing from the field and scope of the invention defined by the claims, changes and / or additions to the components can be made to the plant 10 for melting and / or heating a metallic material and the method for supplying electrical energy, which have been described so far.

Claims

1. A plant for melting and / or heating metallic materials, comprising at least one induction furnace (11) and power supply means (12), The power supply means (12) of the plant (10) comprises at least one transformer (13) connected to an alternating current power grid (14), at least one rectifier (15) arranged downstream of the transformer (13), at least one converter (16) arranged downstream of the rectifier (15), and at least one coil (17) for melting and / or heating metallic material, the power supply means (12) comprises at least one alternative energy source (18) arranged upstream of the converter (16) and capable of supplying the induction furnace (11) with electrical energy in addition to or as an alternative to the electrical energy supplied by the power grid (14), 13. The plant, characterized in that it comprises a management unit (31) configured to select one, the other or both between the power grid (14) and the alternative energy source (18) depending on one or more parameters.

2. 2. The plant according to claim 1, characterized in that the alternative energy source (18) is connected to the induction furnace (11) by means of at least one direct current connection system (24) arranged upstream of the converter (16).

3. 3. The plant according to claim 1 or 2, characterized in that the induction furnace (11) comprises at least one regulating circuit (21) arranged downstream of the converter (16) and upstream of the coil (17) and configured to reduce reactive power and transfer maximum active power to the coil (17).

4. 4. A plant according to claim 1, characterized in that the induction furnace (11) comprises a number of coils (17) and a number of corresponding converters (16) arranged upstream of each of the coils (17).

5. 5. The plant according to any one of claims 1 to 4, characterized in that the alternative energy source (18) comprises a renewable energy source selected from a hydroelectric plant (25), a wind power plant (26) or a solar power plant (27).

6. 6. The plant according to claim 1, further comprising at least one storage device (29) positioned between the at least one alternative energy source (18) and the induction furnace (11) and configured to allow storage of electrical energy generated by the alternative energy source (18) when it is not used to power the induction furnace (11).

7. 7. The plant according to any one of claims 1 to 6, characterized in that the at least one alternative energy source (18) comprises a non-renewable energy source (30) configured to obtain electrical energy by burning a fossil fuel, the non-renewable energy source (30) being selected from the group comprising a gas turbine or an auxiliary current generator.

8. 8. The plant according to claim 1, characterized in that the management unit (31) is configured to monitor one or more parameters of the operating conditions, quality, quantity and / or cost of the electric energy available from the power grid (14) and from the at least one alternative energy source (18) and the amount of energy required by the induction furnace (11) and to select one, the other or both of the power grid (14) and the at least one alternative energy source (18) for supplying the electric energy to the induction furnace (11) depending at least on the respective operating conditions and on the overall energy cost.

9. A method for supplying electrical energy to a plant (10) for melting and / or heating metallic materials, comprising at least one induction furnace (11) and means (12) for supplying electrical energy to said induction furnace (11), comprising the steps of: said power supply means (12) comprising at least one transformer (13) connected to an alternating current power network (14), at least one rectifier (15) arranged downstream of said transformer (13) for converting an alternating current at the outlet from said transformer (13) into a direct current, at least one converter (16) arranged downstream of said rectifier device (15) for converting a direct current at the outlet from said rectifier (15) into an alternating current, and at least one coil (17) for melting and / or heating metallic material, The method provides for supplying electrical energy to the induction furnace (11) by the at least one alternative energy source (18) associated with the induction furnace (11) different from and independent of the power grid (14) in addition to or as an alternative to electrical energy supplied by the power grid (14), and for selecting one, the other or both between the power grid (14) and the alternative energy source (18) depending on one or more parameters.

10. 10. The method according to claim 9, characterized in that it provides for detecting and / or monitoring one or more parameters of the operating conditions, energy availability and cost of energy supplied by the power grid (14) and the alternative energy source (18) and the amount of electric energy required by the induction furnace (11), and determining whether to use one, the other or both between the power grid (14) and the alternative energy source (18) to power the induction furnace (11) depending at least on the detected conditions and / or on the amount of energy required by the induction furnace (11).

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