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EP-4154681-B1 - PLANT FOR MELTING AND/OR HEATING METAL MATERIAL, AND METHOD TO SUPPLY ELECTRICAL ENERGY TO SAID PLANT

EP4154681B1EP 4154681 B1EP4154681 B1EP 4154681B1EP-4154681-B1

Inventors

  • MOLTENI, ROBERTO
  • MORDEGLIA, Antonello

Dates

Publication Date
20260506
Application Date
20210520

Claims (8)

  1. Plant (10) for melting and/or heating metal material comprising at least one induction furnace (11) and electric power supply means (12), wherein said electric power supply means (12) comprise at least one transformer (13) connected to an alternating current mains power network (14), at least one rectifier (15) located downstream of said transformer (13), at least one converter (16) located downstream of said rectifier device (15) and at least one coil (17) for melting and/or heating metal material, said plant (10) being characterized in that said electric power supply means (12) comprise at least one alternative energy source (18) provided upstream of said converter (16) and able to supply power energy to said induction furnace (11) in addition, or as an alternative, to the electrical energy supplied by said mains power network (14) and said plant comprises a management unit (31) configured to select one, or the other, or both between said mains power network (14) and said alternative energy source (18) as a function of one or more parameters, wherein said alternative energy source (18) is connected to said induction furnace (11) by means of at least one direct current connection system (24) located upstream of said converter (16) and wherein said direct current connection system (24) is a DC-Link, configured to accumulate and filter electrical energy and suitable to guarantee better reliability and quality of the power supply to the converter (16), wherein said induction furnace (11) comprises at least one regulation circuit (21), located downstream of said converter (16) and upstream of said coil (17) and configured to reduce the reactive power and transfer the maximum active power to said coil (17), said at least one regulation circuit (21) comprising at least one inductor (22) and at least one capacitor (23), or a bank of capacitors (23).
  2. Plant as in claim 1, characterized in that said induction furnace (11) comprises a plurality of coils (17) and a plurality of corresponding converters (16) located upstream of each of said coils (17).
  3. Plant as in any claim hereinbefore, characterized in that said alternative energy source (18) comprises a renewable energy source selected from a hydroelectric power plant (25), a wind power plant (26) or a photovoltaic solar plant (27).
  4. Plant as in any claim hereinbefore, characterized in that it comprises at least one accumulation device (29) positioned between said at least one alternative energy source (18) and said induction furnace (11) to allow the accumulation of the electrical energy produced by the alternative energy source (18) when it is not used to power said induction furnace (11).
  5. Plant as in any claim hereinbefore, characterized in that said at least one alternative energy source (18) comprises a non-renewable energy source (30), configured to obtain electrical energy by burning fossil fuels, wherein said non-renewable energy source (30) is selected from a group comprising gas turbines, or auxiliary current generators.
  6. Plant as in any claim hereinbefore, characterized in that said management unit (31) is configured to monitor one or more parameters between the functioning status, the quality, the quantity and/or the cost of the electrical energy available from said mains power network (14) and from said at least one alternative energy source (18), and the quantity of energy required by said induction furnace (11) and select one, the other, or both in order to supply electrical energy to said induction furnace (11) at least as a function of the respective functioning status and overall energy costs.
  7. Method to supply electrical energy in a plant (10) for melting and/or heating metal materials, comprising at least one induction furnace (11) and means (12) for supplying electrical energy to said induction furnace (11), wherein said electric power supply means (12) comprise at least one transformer (13) connected to an alternating current mains power network (14), at least one rectifier (15) located downstream of said transformer (13) to transform the alternating current at exit from the transformer (13) into direct current, at least one converter (16) located downstream of said rectifier device (15) to transform the direct current at exit from said rectifier (15) into alternating current, and at least one coil (17) for melting and/or heating metal material, characterized in that said method is providing to supply electrical energy to the induction furnace (11) in addition, or as an alternative, to the electrical energy supplied by the mains power network (14), by means of at least one alternative energy source (18), different and independent from the mains power network (14) and associated with said induction furnace (11) and to select one, the other, or both between said mains power network (14) and said alternative energy source (18) as a function of one or more parameters, wherein said alternative energy source (18) is connected to said induction furnace (11) by means of at least one direct current connection system (24) located upstream of said converter (16), wherein said direct current connection system (24) is a DC-Link, configured to accumulate and filter electrical energy and suitable to guarantee better reliability and quality of the power supply to the converter (16), and wherein the induction furnace (11) comprises at least one regulation circuit (21), located downstream of said converter (16) and upstream of said coil (17) and configured to reduce the reactive power and transfer the maximum active power to said coil (17), said at least one regulation circuit (21) comprising at least one inductor (22) and at least one capacitor (23), or a bank of capacitors (23).
  8. Method as in claim 7, characterized in that it provides to detect and/or monitor one or more parameters between functioning status, energy availability, and cost of the energy supplied by said mains power network (14) and said alternative energy source (18) and the quantity of electrical energy required by said induction furnace (11) and determine whether to use one, the other, or both, between said mains power network (14) and said alternative energy source (18) in order to power said induction furnace (11), at least as a function of the status detected and/or the quantity of energy required by said induction furnace (11).

Description

FIELD OF THE INVENTION The present invention concerns a plant for melting and/or heating metal material. In particular, the present plant comprises at least one induction furnace which carries out the melting and/or heating of metal material. The present invention also concerns a method to supply electrical energy in a plant for melting and/or heating metal material comprising an induction furnace. BACKGROUND OF THE INVENTION Plants for heating and/or melting metal materials are known, comprising induction furnaces into which metal products to be melted or heated are introduced. Induction furnaces are associated with power supply means that take energy from a mains power network and transmit it to the electrical components of the furnace. As is known, induction furnaces are used in metallurgy to melt or heat metal materials according to the principle of electromagnetic induction. Induction heating is widely used in the metal industry, and offers several advantages, for example high production speeds, high energy efficiency, heat localized only where needed. Induction furnaces are characterized by low energy consumption or unwanted overheating, high process control and repeatability, excellent quality of the finished product, little maintenance required, easy integration into production lines, great safety as there are no open flames and toxic fumes, reduced sizes and more free spaces. An induction furnace can comprise, for example, a transformer connected to the alternating current mains power network, a rectifier downstream of said transformer in order to rectify the alternating current at exit from the transformer into direct current, a converter located downstream of the rectifier to transform the direct current at exit from the rectifier into alternating current, and at least one coil to melt and/or heat the metal material that passes through the coil. The coil, or spiral, generally surrounds a chamber through which the metal material to be heated is made to pass, so that the magnetic field generated uniformly hits the metal product to be heated. It is also known that melting and/or heating plants, for example used for the production of steel in the steel industry, require a high power supply, usually a few dozen megawatts (MW), depending on the size of the plant and/or the induction furnace used. To have a sufficient energy supply it is therefore necessary that the melting and/or heating plants are continuously connected to the mains power network. Furthermore, the absorption of three-phase alternating electric current is a function of the production, so the greater the melted material produced by the furnace, the greater the amount of electrical energy that has to be purchased. One disadvantage of traditional solutions is the need to be constantly connected to the public mains power network. Another disadvantage is that taking electrical energy from the mains power network can be expensive, particularly in some geographical areas, or it can become expensive following significant socio-economic events, also considerably increasing the estimated supply costs. Several steel plants are therefore forced, for example, to concentrate production during periods in which the electrical energy supplied by the mains power network has a lower cost. Furthermore, in the event of a possible black-out of the mains power network, it is necessary to stop the plant and production, with consequent loss of productivity and therefore delay in the delivery of production batches. Document CN208675572U describes a known heating inductor for a melting furnace, in which the alternating line current is first rectified into direct current and subsequently transformed into alternating current to be fed to the coils of the inductor. Electrical energy is supplied by a traditional mains power network. Document EP3361595A1 describes an apparatus and a method to accumulate and supply electrical energy to a user, in which the apparatus comprises a mains power network and a renewable energy supply unit connected to an accumulation unit. The primary purpose of the solution is in fact to accumulate the electrical energy supplied by the renewable energy supply unit in order to use it as an alternative to the mains power network. DE202008012031 describes a control unit for an apparatus to supply electrical energy to a domestic user device, connected to a mains power network, and to energy accumulation devices supplied by a renewable energy source, in which the control unit monitors the condition of the accumulation devices in order to alternatively connect the user device to accumulation devices or to the mains power network. These last solutions refer in particular to domestic user devices and are not suitable for application in industrial plants, in particular in plants for heating and/or melting metal materials, which require very high supply power, that is, in the order of dozens of megawatts. There is therefore a need to perfect a plant