Electrical equipment for glass manufacturing furnace

Abstract

The invention relates to an at least partially electrical glass manufacturing furnace (1) comprising a melting tank (2) made of a refractory material adapted to contain a bath (3) of molten vitrifiable material and a plurality of electrodes (An, Bn, Cn, Dn) for heating said bath (3), said electrodes being supplied with alternating current by an electrical device (4) comprising at least one transformer (6), the transformer (6) is adapted to generate groups of outputs in one phase, with a phase difference between each output group, each output being connected to at least one of the electrodes (An, Bn, Cn, Dn) by a conductor (7) in one phase generating a first magnetic field (B1). The device comprises means capable of generating a magnetic reversal field mounted in a first electromagnetic field.

Description

[0001] The present invention belongs to the general field of glass production. The present invention more particularly relates to at least partially electric glass furnaces suitable for melting vitrifiable materials. The present invention also relates to a method for melting vitrifiable materials in order to be able to manufacture glass. The present invention has particularly advantageous but by no means limiting applications in the production of glass wool, rock wool, textile glass yarn, and / or flat or hollow glass.

[0002] In the present specification, the "vitrifiable material" or "raw material" is understood to mean all materials, natural ores or synthetic products that can enter the composition fed to the glass furnace, materials derived from recycling such as cullet, etc. This includes silica sand, but also all additives (sodium carbonate, limestone, dolomite, alumina, etc.), waste materials (including mineral fibers) that can be generated from the production of said fibers or from construction sites or demolition sites, all possible liquid or solid fuels (compounded or uncompounded plastics, organic materials, coal), and any type of cullet. Also included are recyclable materials containing combustible (organic) elements, such as sized mineral fibers with adhesives (of the type used for thermal insulation or sound insulation or for reinforcing plastic materials), laminated assembly glass (such as windshield glass) with sheets of polyvinyl butyral polymer, glass bottles (household cullet), or any type of "composite" material combining glass and plastic materials, such as certain bottles. Also recyclable are "glass-metal composites or metal compounds", such as functionalized assembly glass with a metal-containing coating. In the specification, the "bath of vitrifiable materials" or "glass bath" refers to the molten product of these raw materials.

[0003] Similarly, "glass" is understood to mean glass in a broad sense, i.e., covering any material having a vitreous, glass-ceramic or ceramic matrix.

[0004] Furthermore, the term "manufacture" includes the indispensable step of melting the vitrifiable materials, and all subsequent steps of refining / conditioning the molten glass for its final shaping, particularly in the form of flat glass (assembly glass), hollow glass (bottles, jars), glass in the form of mineral wool (particularly rock wool or glass wool) used for its thermal insulation or sound insulation properties, or even optionally glass in the form of textile yarns used for reinforcing materials.

[0005] Various examples of electric furnace designs are known from the prior art, in which an electric current is conducted through heating electrodes in a bath of vitrifiable material. Such electrodes can be of the "submerged" type - arranged vertically in the bath from the furnace floor, or horizontally, through the side wall of the furnace - and / or of the "top entry" type, by immersion from the free surface of the bath.

[0006] These electrodes are supplied with alternating current by an electrical installation that includes at least one transformer adapted to generate a plurality of single-phase output groups with a phase difference between each output group, and each output is connected to at least one of said electrodes by a single-phase conductor.

[0007] Surprisingly, the inventor, being a designer of glass furnaces, has observed the heating phenomenon of certain metal structures located near these single-phase conductors. This phenomenon is a priori harmless in the case of small electric furnaces, but turns out to be problematic in the case of large furnaces, where the bath of molten vitrifiable material has a surface area greater than 25 m 2 and preferably greater than 49 m 2 and preferably a distance between two opposite walls of said tank greater than 5 m and preferably greater than 7 m. Given the electrical power required to supply these large furnaces, the single-phase conductors carry a current, the intensity of which is greater than 1000 A, preferably greater than 4000 A, preferably greater than 6000 A. At these electrical intensity levels, the heating of the said metal structures located near these single-phase conductors is much more significant, to the extent that it can lead to the deterioration of the said metal structures.

[0008] The object of the present invention is to overcome some or all of the drawbacks of the prior art, in particular those set out above.

[0009] To this end, and according to a first aspect, the present invention relates to a glass furnace that is at least partially electrical and includes a melting tank made of refractory material adapted to contain a bath of molten vitrifiable material and a plurality of electrodes for heating said bath. The electrodes are supplied with alternating current by an electrical installation that includes at least one transformer, the transformer being adapted to generate a plurality of single-phase output groups with a phase difference between each output group, and each output is connected to at least one of said electrodes by a single-phase conductor that generates a first magnetic field. The glass furnace is characterized in that it includes at least one, preferably a plurality of counter-reaction devices arranged in the first magnetic field and adapted to generate a magnetic counter-field.

[0010] For the purposes of the present invention, an opposing field is a magnetic field in a relative direction, which thus cancels the first magnetic field.

[0011] The present invention is first based on the inventors', the designers of the glass furnace, surprising observations of the heating phenomenon of certain metal structures in the vicinity of the single-phase conductors supplying current to the electrodes, then on the understanding of this phenomenon, and finally on the implementation of a counter-reaction device that makes it possible to mitigate this undesirable heating of these metal structures.

[0012] More precisely, in the inventors' view, this heating phenomenon is related to the generation of currents induced in these metal structures by a first magnetic field (i.e., the magnetic field generated by the current flow in the single-phase conductors). Such induced currents not only indeed increase the risk of electric shock, but they also heat the metal structures by the Joule effect.

[0013] In response, the present invention is based on a novel and creative concept that includes implementing a counter-reaction device arranged in the first magnetic field and adapted to generate a magnetic opposing field, thereby reducing the risk of generating induced currents and thus reducing the associated risks of overheating and electric shock.

[0014] According to a particular embodiment, such a glass furnace includes a single counter-reaction device arranged in the first magnetic field of each single-phase conductor and adapted to generate a magnetic opposing field.

[0015] According to a particular embodiment, such a counter-reaction device includes a closed loop, at least a part of which is made of a conductive metal material selected from the group comprising copper, aluminum, and iron, said part being arranged in the first magnetic field and adapted to generate the magnetic opposing field.

[0016] Specifically, and according to the principles of Faraday's law and Lenz's law, when a conductive material is placed in a variable magnetic field, an electric field is generated therein, which in turn generates a circular induced current called an "eddy current". The induced current in turn generates a magnetic opposing field that opposes the change in magnetic flux that triggered them, thereby weakening the latter.

[0017] According to a particular embodiment, the part of the closed loop is in the form of a cable, a metal bar, or a box.

[0018] According to a particular embodiment, the closed loop is connected to ground at a single point.

[0019] According to a particular embodiment, the voltage difference between the closed loop and the transformer is monitored to detect a voltage increase associated with a possible ground fault.

[0020] According to a particular embodiment, the closed loop includes a current control system having a cut-off threshold of the closed loop.

[0021] Such a safety device prevents the risk of overheating of the closed loop and thus the risk of fire.

[0022] According to a particular embodiment, the portion of the closed loop is arranged at a distance of less than 1.0 m, preferably less than 0.5 m, preferably less than 0.3 m from the single-phase conductor (7).

[0023] Positioning the portion of the closed loop in close proximity to the single-phase conductor enables it to capture a greater proportion of the magnetic field emitted by the single-phase conductor and thus better attenuate the magnetic field.

[0024] According to a particular embodiment, the portion of the closed loop is arranged at a distance of more than 0.1 m, preferably more than 0.2 m, from the single-phase conductor and / or in that the single-phase conductor is coated with an electrical insulator, preferably plastic.

[0025] Maintaining a minimum distance between the closed loop and the single-phase conductor and / or electrically insulating the single-phase conductor to prevent the risk of direct contact, especially after an electric arc is formed. This risk is particularly high during the switching-on phase of the electrical equipment when a current with a very high voltage (referred to as the magnetization voltage) flows through the system.

[0026] According to a particular embodiment, the melting bath is dimensioned such that the bath of the molten vitrifiable material has a surface area of greater than 25 m 2 、preferably greater than 40 m 2 、preferably greater than 60 m 2 、preferably greater than 100 m 2 and preferably has a distance between two opposite walls of the bath of greater than 5 m, preferably greater than 6.5 m.

[0027] Such dimensions relate to so-called large electric furnaces for which the use of a two-phase system is particularly advantageous.

[0028] According to a particular embodiment, the electrical equipment is adapted to generate two-phase or three-phase alternating current.

[0029] Three-phase current offers many advantages, especially the fact that said three-phase current is the so-called "industrial" current that is usually distributed by energy suppliers to factories, thus leading to the adjustment of machines. In addition, for example, unlike single-phase current, three-phase current also delivers instantaneous power without a pulsating component. However, it should be noted that the principle of phase balance tends to a triangular or hexagonal arrangement of the electrodes on the surface of the glass bath. While such a geometric constraint does not seem a priori to pose a problem in the case of small electric furnaces, it does pose a problem in the case of large electric furnaces (where the area of the glass bath extends greater than 25 m 2 , preferably greater than 40 m 2 , preferably greater than 60 m 2 , preferably greater than 100 m 2 , and preferably having a distance between two opposite walls of said trough (2) greater than 5 m, preferably greater than 6.5 m). In such a configuration and taking into account the above geometric constraints, the current tends to concentrate between the electrodes at the same trough edge and / or adjacent trough edges, thereby reducing the distance covered by the current within the glass bath and thus reducing the resistance of the glass bath to the passage of this current. For a predetermined electric power corresponding to the energy required to melt the vitrifiable material, and in the case of a glass bath that only offers a reduced resistance, it is therefore necessary to increase the intensity of the current delivered. However, the wear of the electrodes and the refractory material constituting said trough increases with the intensity of the current delivered through the electrodes. To overcome this wear problem, the natural solution is to distribute the delivered current between a greater number of electrodes, but this has the disadvantage of increasing the operating cost of these electrodes - because there are more electrodes - without solving certain problems of non-uniform current distribution within the glass bath.

[0030] According to a particular embodiment, at least one heating electrode, preferably all heating electrodes, is immersed from the surface of the bath of the molten vitrifiable material.

[0031] Top-entry electrodes offer many advantages compared to so-called "immersion" type electrodes. Firstly, they avoid the difficulties associated with the immersion of electrodes through the refractory material, as well as the problem of replacing these electrodes when worn, problems related to the sealing of the melting trough or refractory material wear, especially due to the high temperatures that favor refractory material erosion and the strong convection currents generated near the electrodes during operation.

[0032] According to a particular embodiment, the transformer is two-phase and supplies a plurality of electrodes less than or equal to 16, preferably less than or equal to 12, preferably less than or equal to 8.

[0033] Depending on whether each output group supplies power to two sets of four electrodes, two sets of three electrodes, or two sets of two electrodes, the total number of electrodes powered by a single two-phase transformer varies between 16, 12, and 8 electrodes respectively.

[0034] Compared to a three-phase system, and for a glass bath module with an equivalent surface area - and thus an equivalent electric power - the two-phase system offers the possibility of reducing the number of electrodes used in the furnace.

[0035] According to a specific embodiment, the transformer is adapted to generate single-phase alternating current with a current value greater than 1000 A, preferably greater than 4000 A, and preferably greater than 6000 A at each output group.

[0036] According to a specific embodiment, the present invention relates to a method for melting vitrifiable materials implemented by means of such a glass furnace, characterized in that the method comprises at least one step of electrically heating the bath of the molten vitrifiable materials by means of the plurality of electrodes supplied with alternating current by the electrical device.

[0037] According to a specific embodiment, the current value of the alternating electric current is greater than 1000 A, preferably greater than 4000 A, and preferably greater than 6000 A.

[0038] According to a specific embodiment, all electrode pairs connected to the same output group of the two-phase transformer are supplied with current at the same voltage.

[0039] According to a specific embodiment, the present invention relates to a method for manufacturing glass wool, rock wool, textile glass filaments, and / or flat or hollow glass, characterized in that it implements such a melting method.

[0040] Other features and advantages of the present invention will become apparent from the non-limiting description given below with reference to the accompanying drawings, which show exemplary embodiments of the present invention. In the drawings:

[0041] Figure 1 Figure 1 shows a schematic cross-sectional view of an electric glass furnace;

[0042] Figure 2 Figure 2 shows a schematic top view of the glass bath and electrodes of an electric furnace according to a specific embodiment of the present invention;

[0043] Figure 3 Figure 3 schematically shows the electrical equipment and the back reaction device of a glass furnace according to a specific embodiment of the present invention; ​​​​​​

[0044] Figure 4 Figure 4 schematically shows details of a reverse reaction device of a glass melting furnace according to a specific embodiment of the present invention;

[0045] Figure 5 Figure 5 is a flowchart showing consecutive steps of a manufacturing method according to a specific embodiment of the present invention.

[0046] Figure 1 shows a schematic cross-sectional view of an electric glass melting furnace 1. Such a glass melting furnace 1 includes a melting trough 2 made of refractory material adapted to accommodate a bath 3 of molten vitrifiable material and a plurality of heating electrodes (An, Bn), said heating electrodes including top-entry electrodes An and so-called "immersion" electrodes Bn, both of which are supplied with current by an electrical device 4 and are connected to the electrical device 4 via single-phase conductors 7.

[0047] According to an alternative embodiment of the present invention, all electrodes are immersed, or all electrodes are top-entry.

[0048] According to Figure 1 shown in the specific embodiment, the melting furnace 1 is completely electric and is equipped with a cold crown 5. According to an alternative embodiment, such a glass melting furnace is hybrid and, in addition to electrodes, includes combustion heating means, preferably immersion and / or exposed burners, and a hot crown.

[0049] According to a specific embodiment and as shown in Figure 2 , the electrical device includes a two-phase transformer 6 adapted to generate two single-phase output groups (A-B, C-D) with a phase difference of 90° between each output group (A-B, C-D). According to this specific embodiment, the output group includes only a single output (A-B, C-D), said single output (A-B, C-D) being connected to a bundle of three pairs of electrodes ((An; Bn); (Cn; Dn), where n = 1, 2, 3), and the single output is supplied with single-phase alternating current. The bundle of electrodes is arranged in the bath 3 in a square shape and in a manner that follows central symmetry along the theoretical horizontal plane with respect to a point O located at the center of the bath 3.

[0050] ​​​​​In practice, the first single-phase current is generated by the transformer 6 at the terminals of the first output group A - B and passes, on the one hand, through the glass bath between the electrodes A1, A2, A3 and, on the other hand, through the glass bath between the electrodes B1, B2, B3, thereby heating the bath 3 of vitrifiable material by the Joule effect. In parallel, a second single-phase current is generated by the transformer 6 at the terminals of the second output group C - D, the second single-phase current having the same frequency and amplitude as the first current but being phase-shifted by 90° or π / 2 radians relative to the first current, and passing, on the one hand, through the glass bath between the electrodes C1, C2, C3 and, on the other hand, through the glass bath between the electrodes D1, D2, D3, thereby heating the bath 3 of vitrifiable material by the Joule effect. Overall, the electrical device 6 is thus adapted to generate a two-phase alternating current within the glass bath 3.

[0051] Figure 3 schematically shows the electrical device 4 and the inverse reaction device 8, the details of which are shown in Figure 4 . Such an inverse reaction device 8 is arranged in a first magnetic field B1 generated by the conductor 7 and is adapted to generate a magnetic inverse field B2.

[0052] More precisely, the inverse reaction device 8 includes a closed loop 9, at least a part of which is in the form of a copper bar 10, the copper bar 10 being located in the first field B1 and then performing the function of generating the magnetic inverse field B2, thereby reducing the risk of generating an induced current and thus reducing the associated risks of overheating and electric shock. According to an alternative embodiment, the part 10 may take the form of a cable or a box and is made of a conductive material such as aluminum or iron.

[0053] According to the Figure 3 shown embodiment, the closed loop 9 is grounded at a single point to significantly limit the risk of electric shock. It also includes a system (not shown) for controlling the current flowing through the closed loop to prevent the risk of overheating of the closed loop and thus prevent the risk of fire.

[0054] It should be noted that, even if not obvious in the figure, due to the absence of scale, the electric furnace under consideration is considered large because it has a bath of molten vitrifiable material with a surface area greater than 40 m 2 and a distance between two opposite walls of the bath greater than 6.5 m. Considering the electric power required to supply the furnace, the single-phase conductor load has a current with an intensity of 7000 to 8000 A.

[0055] Figure 5 ​​is a flowchart showing successive steps of a manufacturing method according to a particular embodiment of the present invention, which includes a first step S1 of melting a vitrifiable material by electroheating the bath 3 of the vitrifiable material by means of a two-phase alternating current, and a second step S2 of manufacturing glass wool, rock wool, textile glass filaments, and / or flat or hollow glass.

Claims

1. An at least partially electrical glass melting furnace (1), comprising a melting trough (2) made of refractory material adapted to contain a bath (3) of molten vitrifiable material and a plurality of electrodes (An, Bn, Cn, Dn) for heating said bath (3), said electrodes (An, Bn, Cn, Dn) being supplied with alternating current by an electrical device (4), said electrical device (4) comprising at least one transformer (6), said transformer (6) being adapted to generate a plurality of single-phase output groups with a phase difference between each output group, each output being connected to at least one of said electrodes (An, Bn, Cn, Dn) by a single-phase conductor (7) generating a first magnetic field (B1), characterized in that it comprises at least one, preferably a plurality of, reverse reaction devices (8), said reverse reaction devices (8) being arranged in said first magnetic field (B1) and adapted to generate a magnetic reverse field (B2).

2. The glass melting furnace (1) according to claim 1, characterized in that, It comprises a single reverse reaction device (8) arranged in said first magnetic field (B1) of each single-phase conductor (7) and adapted to generate a magnetic reverse field (B2).

3. The glass melting furnace (1) according to any one of claims 1 and 2, characterized in that, Said reverse reaction device (8) comprises a closed loop (9), at least a part (10) of said closed loop (9) being made of a conductive metallic material selected from the group comprising copper, aluminum and iron, said part (10) being arranged in said first magnetic field (B1) and adapted to generate said magnetic reverse field (B2).

4. The glass melting furnace (1) according to claim 3, characterized in that, Said part (10) of said closed loop (9) is in the form of a cable, a metal bar or a box.

5. The glass melting furnace (1) according to any one of claims 3 and 4, characterized in that, Said closed loop (9) is grounded at a single point.

6. The glass melting furnace (1) according to any one of claims 3 to 5, characterized in that, Said closed loop (9) comprises a current control system having a cut-off threshold for said closed loop (9).

7. The glass melting furnace (1) according to any one of claims 3 to 6, characterized in that, Said part (10) of said closed loop (9) is arranged at a distance from said single-phase conductor (7) less than 1.0 m, preferably less than 0.5 m, preferably less than 0.3 m.

8. The glass melting furnace (1) according to any one of claims 3 to 7, characterized in that, Said part (10) of said closed loop (9) is arranged at a distance from said single-phase conductor (7) more than 0.1 m, preferably more than 0.2 m, and / or is characterized in that said single-phase conductor (7) is coated with an electrical insulator, preferably plastic.

9. The glass melting furnace (1) according to any one of claims 1 to 8, characterized in that, The melting bath (2) is dimensioned such that the bath (3) of the molten vitrifiable material has a surface area greater than 25 m 2 , preferably greater than 40 m 2 , preferably greater than 60 m 2 , preferably greater than 100 m 2 , and preferably has a distance between two opposite walls of the bath (2) greater than 5 m, preferably greater than 6.5 m.

10. The glass melting furnace (1) according to any one of claims 1 to 9, characterized in that, Said electrical device (4) is adapted to generate two-phase or three-phase alternating current.

11. The glass melting furnace (1) according to any one of claims 1 to 10, characterized in that, At least one heating electrode (An, Bn, Cn, Dn), preferably all heating electrodes (An, Bn, Cn, Dn), are immersed from the surface of the bath (3) of molten vitrifiable material.

12. The glass melting furnace (1) according to any one of claims 10 and 11, characterized in that, Said transformer (6) is two-phase and supplies a plurality of electrodes less than or equal to 16, preferably less than or equal to 12, preferably less than or equal to 8.

13. The glass melting furnace (1) according to any one of claims 1 to 12, characterized in that, Said transformer (6) is adapted to generate single-phase alternating current with a current value greater than 1000 A, preferably greater than 4000 A, preferably greater than 6000 A at each output group.

14. A method for melting a vitrifiable material by means of a glass melting furnace (1) according to any one of claims 1 to 13, characterized in that, It comprises at least one step of electrically heating said bath (3) of molten vitrifiable material by means of said plurality of electrodes (An, Bn, Cn, Dn) supplied with alternating current by said electrical device (4).

15. The method for melting a vitrifiable material according to claim 14, which is carried out by means of a glass melting furnace (1) according to claim 13, is characterized in that, The current value of said alternating current is greater than 1000 A, preferably greater than 4000 A, preferably greater than 6000 A.

16. A method for manufacturing glass wool, rock wool, textile glass filaments, and / or flat or hollow glass, characterized in that, It implements the melting method according to any one of claims 14 and 15.

Images