Electric glass-making furnace

Abstract

The invention relates to an at least partially electric glass-making furnace (1) comprising a melting tank (2) made of refractory materials that is configured to contain a bath (3) of molten batch materials, and a plurality of submerged heating electrodes (An, Bn, Cn, Dn) that are submerged from the free surface of said bath (3) and supplied with electric current by an electric apparatus (4), said furnace (1) being characterized in that said electric apparatus (4) is configured to generate a two-phase alternating current, said electric apparatus comprising a transformer module (6) configured 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), each output group (A-B, C-D) supplying a quartet ((An; Bn); (Cn; Dn)) of said electrodes.

Description

Description Title of the invention: Electric glass furnace

[0001] The present invention falls within the general field of glass production. More particularly, it relates to a glass furnace, at least partially electric, adapted for melting vitrifiable materials. It also relates to a process for melting vitrifiable materials to produce glass. The invention finds particularly advantageous, though not limiting, application in the production of glass wool, rock wool, textile glass yarns, and / or flat or hollow glass.

[0002] In this description, "vitrifiable materials" or "raw materials" refers to all materials, natural ores or synthesized products, recycled materials such as cullet, etc., that can be used in the composition of materials used to feed a glass furnace. This includes silica sand, but also all additives (sodium carbonate, limestone, dolomite, alumina, etc.), waste (including mineral fibers) that may originate from the production of said fibers or from construction or demolition sites, all liquid or solid fuels (plastic, composite or non-composite materials, organic matter, coal), and all types of cullet.Also included are recyclable materials containing combustible (organic) elements, such as, for example, coated mineral fibers with a binder (of the type used in thermal or acoustic insulation or in reinforcing plastics), laminated glass with polyvinyl butyral polymer sheets such as windshields, glass bottles (household cullet), or any type of composite material combining glass and plastics, such as certain bottles. Also recyclable are glass-metal composites or metallic composites, such as functionalized glass with coatings containing metals. In this description, the term "glass bath" refers to the product of melting these raw materials.

[0003] Similarly, "glass" is understood to mean glass in the broadest sense, that is to say, encompassing any material with a vitreous matrix, glass-ceramic or ceramic.

[0004] Furthermore, the term "manufacturing" includes the essential melting stage of the vitrifiable materials and, where applicable, all subsequent / complementary stages aimed at refining / conditioning the molten glass for its final shaping. particularly in the form of flat glass (windows), hollow glass (bottles, flasks), glass in the form of mineral wool (in particular rock wool or glass wool) used for its thermal or acoustic insulation properties, or even possibly glass in the form of so-called textile yarns used in reinforcement.

[0005] From the prior art, and in particular from patent EP0671116B1, we know of several examples of electric furnace designs in which the current is conducted in the bath of vitrifiable materials by so-called "immersion" electrodes, which are immersed from the free surface of the bath. This type of immersion electrode differs in particular from so-called "submerged" electrodes, which are arranged vertically in the bath from the furnace floor or horizontally, passing through the side walls of the furnace. Compared to the latter, immersion electrodes offer a number of advantages.First of all, they obviously avoid the difficulties associated with the passage of immersed electrodes through the refractory of the base or side walls, and also the problems of replacing these electrodes when worn, as well as the problems of sealing the melting tank or of wear of the refractories, in particular due to a high temperature which promotes the attack of the refractory and to powerful convection currents which develop near the electrodes during operation.

[0006] Typically, these immersion electrodes are powered by three-phase current. Three-phase current offers numerous advantages, foremost among them being the so-called "industrial" current commonly supplied to factories by energy providers, hence the resulting adaptation of machinery. Furthermore, three-phase current delivers instantaneous power without a pulsed component, unlike, for example, single-phase current. It should be noted, however, that the principle of phase balance tends towards a triangular or hexagonal arrangement of the electrodes on the surface of the glass bath. While such a geometric constraint may not seem a priori to pose a prohibitive problem in the context of a small electric furnace, it does present one in the context of a large electric furnace, where the glass bath extends over more than 25 m². 2 , preferably more than 40 m 2, or even more than 100m2 and in which the edge-to-edge width of the glass bath is greater than 5 m, preferably greater than 6.5 m. In such a configuration and in view of the aforementioned geometric constraints, the current tends to concentrate between the electrodes of the same tank edge and / or adjacent edges, thus reducing the distance traveled by the current within the glass bath and therefore the resistance of the glass bath to the passage of this current. For a predetermined electrical power corresponding to the energy required to melt the glassable materials, and in the context of a glass bath offering only low resistance, it is thus necessary to increase the intensity of the current delivered. However, the wear of the electrodes and the refractories constituting the tank increases with the intensity of the current delivered per electrode. In order to overcome this wear problem, the obvious solution is to distribute the delivered current among a larger number of electrodes, which, however, has the disadvantage of increasing the operating costs of these electrodes—since there are more of them—without resolving certain problems of inhomogeneity in the distribution of the electrical current within the glass bath. Summary of the invention

[0007] The present invention aims to remedy all or part of the drawbacks of the prior art, in particular those set out above.

[0008] To this end, the invention relates to a glass furnace, at least partly electric, comprising a melting tank made of refractory materials adapted to contain a bath of molten vitrifiable materials and a plurality of immersion heating electrodes, which are immersed from the free surface of said bath and supplied with electric current by an electrical installation, said furnace being characterized in that said electrical installation is adapted to generate a two-phase alternating current, said electrical installation comprising a transformer module adapted to generate two single-phase output groups with a phase difference of 90° between each output group, each output group supplying a quartet of said electrodes.

[0009] For the purposes of the invention, the expression "two-phase alternating current" designates a system with two phases of the same frequency and the same amplitude which are in quadrature, that is to say, out of phase with each other by 90° or n / 2 radians.

[0010] In a contemporary context where current is distributed by energy suppliers in three-phase form, the implementation of an electrical installation adapted to transform this three-phase current into a two-phase current implies a technical complexity that is a priori unnecessary and a significant increase in the initial cost of this technical installation.

[0011] Despite these seemingly insurmountable drawbacks, and in the specific context of supplying power to immersion electrodes in glass furnaces, the inventors observed that such a two-phase system allows a glass furnace designer to free themselves from certain geometric constraints inherent in three-phase systems and the technical disadvantages associated with them, including the large number of electrodes to be implemented and the inhomogeneous distribution of electric current within the bath of vitrifiable materials.

[0012] In contrast, a two-phase system allows a glass furnace designer to place the electrode(s) powered by the same phase further apart, for example, by positioning them near opposite edges of the melting tank. Compared to a three-phase system, and for a given electrical power, the resistance generated by the glass bath—which increases with the distance the current travels within it—is greater, thus requiring a reduction in the electrical current to be delivered. It is then possible to distribute this current among a smaller number of electrodes and / or limit the current delivered to each electrode, thereby increasing their lifespan.

[0013] According to one example, the transformer module includes at least one two-phase transformer or at least two two-phase transformers.

[0014] According to an example, at least one output group of said transformer module includes one or more outputs, preferably multiple outputs.

[0015] Thus, at least one output group of said transformer module may comprise a single output. Furthermore, this single output may power four electrodes. More specifically, the single output may be connected to a bundle of four pairs of electrodes.

[0016] According to another approach, at least one output group of the transformer module may include multiple outputs. Each of these outputs may, for example, be connected to one or more pairs of electrodes. For instance, an output group may include two outputs, each connected to a bundle of two pairs of electrodes.

[0017] In another example, one of the two output groups includes a single output, and the other of the two output groups includes multiple outputs.

[0018] In another example, each of the two output groups comprises multiple outputs. For instance, each of the two output groups might include two outputs connected to a bundle of two pairs of electrodes.

[0019] In the present invention, each output group supplies a "quartet" of electrodes. Thus, the "quartet" refers to a set of four electrodes and their associated electrodes, forming four pairs that allow the current to flow. The current passes through the bath of molten vitrifiable materials between two sets of four electrodes.

[0020] The term "bundle" can generally be used to refer to a grouping of several pairs of electrodes. Thus, a quartet of electrodes can be arranged as a single bundle of four pairs of electrodes or as several bundles of electrodes, for example, as 2 bundles of 2 pairs of electrodes each.

[0021] According to one example, each electrode bundle is arranged in the bath of molten vitrifiable materials in such a way as to respect a central symmetry along a theoretical horizontal plane.

[0022] According to one example, each quartet is arranged in the bath of molten vitrifiable materials in such a way as to respect a central symmetry according to a theoretical horizontal plane.

[0023] Maintaining such axial symmetry allows for a more homogeneous distribution of current between the electrodes, and therefore limits the probability of one of these electrodes wearing out faster than the others.

[0024] In one example, the electrodes of the same output group are arranged near opposite walls of the tank.

[0025] This advantageous geometric arrangement of electrode pairs is particularly suited to the two-phase regime, in which the distance between electrodes connected to the two terminals of the same output group can be increased without risk of electrodes located near the same wall exchanging with each other.

[0026] According to one example, the said quartet of electrodes supplied by the same two-phase transformer are arranged in a quadrilateral according to a theoretical horizontal plane, preferably in a rectangle, preferably in a square, in the bath of molten vitrifiable materials.

[0027] This advantageous geometric arrangement of the electrode pairs is particularly well-suited to two-phase flow and allows for current balancing. This quadrilateral arrangement contrasts in particular with the triangular or hexagonal arrangements, which are characteristic of three-phase systems.

[0028] According to an example, the minimum distance between each electrode and the nearest tank wall is greater than 250mm, preferably greater than 450mm, preferably greater than 600mm, preferably greater than 800mm, preferably greater than 950mm, preferably greater than 1075mm.

[0029] According to the invention, such a minimum distance is measured along the normal to the wall of the tank nearest to the electrode, and passing through the electrode. It should be noted that the convection currents of the glass bath generated near each electrode tend to corrode the adjacent tank wall. Therefore, moving the electrode further away from the tank helps to limit this premature wear of the tank wall.

[0030] According to one example, each of said electrodes comprises a horizontal projection arm, preferably of square cross-section, whose horizontal extent is greater than 2000 mm, preferably greater than 2500 mm, preferably greater than 3000 mm, preferably greater than 3500 mm, preferably greater than 3700 mm, preferably greater than 3900 mm.

[0031] The use of a square-section electrode arm provides it with greater resistance to bending. This is especially beneficial as the electrode arm lengthens. A long electrode arm allows, in particular, for a greater distance between the electrode and the adjacent furnace wall, thus limiting wear on the latter. This increased distance between the electrode and the furnace wall is particularly advantageous when the furnace power is increased. Indeed, power depends on voltage and current, and these two parameters are adjusted with increasing values ​​as power increases. This results in an intensification of the convection currents in the glass bath generated near each electrode, which tend to corrode the adjacent furnace wall. Increasing the distance between the electrode and the furnace wall helps to limit this premature wear of the furnace wall.

[0032] [According to an example, the said electrical installation is adapted so that all electrodes connected to the same output group of the said two-phase transformer are supplied with an electric current of the same voltage.

[0033] According to one example, the oven is totally electric, and preferably includes a cold vault.

[0034] For the purposes of this invention, a furnace is said to be "fully electric" in the sense that all the heating energy supplied to the glass bath is electrical in nature. Such a furnace is therefore devoid of heating burners.

[0035] According to one example, the oven includes a plurality of said two-phase transformers, preferably three.

[0036] The implementation of a plurality of two-phase transformers is particularly suitable for supplying electricity to large furnaces, for which the implementation of a two-phase system is particularly advantageous.

[0037] According to one example, the melting tank is sized so that the molten bath of vitrifiable materials has a surface area greater than 25 m² 2 , preferably greater than 40 m 2 , preferably greater than 60 m 2 , preferably greater than 100 m 2 , and preferably presents between two opposite walls of said tank a distance greater than 5 m, preferably greater than 6.5 m.

[0038] According to one example, the number of electrodes per square meter is between 0.05 and 0.45, preferably between 0.15 and 0.4 and even more preferably between 0.2 and 0.35.

[0039] According to one example, said tank is divided into at least two portions, each portion comprising two single-phase output groups with a phase difference of 90° between each output group, each output group supplying a quartet of said electrodes.

[0040] According to one example, each portion of the tank is equipped with a transformer module generating the two single-phase output groups with a phase difference of 90° between each output group, each output group supplying a quartet of said electrodes.

[0041] The invention further relates to a process for melting vitrifiable materials implemented by means of a glass furnace according to the invention, characterized in that it comprises at least one stage of electrically heating said bath of molten vitrifiable materials by means of said plurality of electrodes, and by applying within said bath a two-phase alternating current.

[0042] According to an example of the process for melting vitrifiable materials according to the invention, implemented using a glass furnace according to the invention, characterized in that the quartets of electrodes connected to the same output group of said two-phase transformer are supplied with an electric current of the same voltage.

[0043] The invention further relates to a method for manufacturing glass wool, rock wool, textile glass yarns and / or flat or hollow glass, characterized in that it implements a melting process according to the invention. Description of the figures

[0044] Other features and advantages of the present invention will become apparent from the description below, with reference to the accompanying drawings, which illustrate an example of an embodiment without being limiting in any way. In the figures: [Fig. 1] Figure 1 schematically represents, in profile view, an electric glass furnace; [Fig. 2] Figure 2 schematically represents, from a top view, the glass bath and the immersion electrodes of an electric furnace according to a particular embodiment of the invention; [Fig. 3] Figure 3 schematically represents, from a top view, the glass bath and the immersion electrodes of an electric furnace according to an alternative embodiment of the invention; [Fig. 4] Figure 4 is a flow diagram illustrating the successive steps of a manufacturing process according to a particular embodiment of the invention. [Fig. 5] Figure 5 schematically represents, from a top view, the glass bath and the immersion electrodes of an electric furnace comprising two portions according to a particular embodiment of the invention; [Fig. 6] Figure 6 schematically represents, from a top view, the glass bath and the immersion electrodes of an electric furnace comprising two portions according to an alternative embodiment of the invention. Description of the invention

[0045] Figure 1 schematically represents, in profile view, an electric glass furnace 1. Such a glass furnace 1 includes a melting tank 2 made of refractory materials adapted to contain a bath 3 of molten vitrifiable materials.

[0046] The melting pot is square or rectangular in shape. Its length and width determine its surface area. This surface area defines the quantity of glass produced by the furnace.

[0047] The melting chamber of the furnace according to the invention is dimensioned so that said bath of molten vitrifiable materials has an area of ​​less than 25 m² 2, or present 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 , preferably greater than 300 m 2 and preferably presents between two opposite walls of said tank a distance greater than 5 m, preferably greater than 6.5 m, preferably greater than 10 m.

[0048] In this particular embodiment, these so-called large furnaces are obtained by combining several elementary modules. An elementary module is considered equivalent to a furnace whose chamber has a defined length and width, and which includes a series of heating electrodes arranged in a defined configuration. Preferably, the elementary module is square. A large furnace thus comprises at least two contiguous elementary modules; that is, it includes a chamber whose length and width are multiples of the defined value of the elementary module. It is therefore possible to easily obtain a large furnace, which can have various shapes such as rectangular, square, L-shaped, or T-shaped.It is then understood that the chamber of a so-called large oven is divided into a plurality of portions, the portions having the same size and the same shape.

[0049] The glass furnace 1 further comprises a plurality of immersion heating electrodes (An, Bn, Cn, Dn) (only one is shown in Figure 1, for the sake of simplicity), the arms of which have a square cross-section, and which are immersed from the free surface of said bath 3 and supplied with electrical current by an electrical installation 4. As is known, the part of the electrode in contact with the glass bath is made of molybdenum. However, it can be made of any other suitable material.

[0050] A glass furnace 1 according to the invention is particularly characterized in that said electrical installation 4 is adapted to generate a two-phase alternating current.

[0051] For the purposes of the invention, the expression "two-phase alternating current" designates a system with two phases of the same frequency and the same amplitude which are in quadrature, that is to say, out of phase with each other by 90° or n / 2 radians.

[0052] The electrical installation includes a transformer module 6. This transformer module 6 includes at least one two-phase transformer suitable for generating two single-phase output groups with a phase difference of 90° between each output group.

[0053] Alternatively, the transformer module 6 includes at least two single-phase transformers to replace one two-phase transformer.

[0054] In the case of an oven comprising several portions, each portion is associated with a transformer module 6 or the portions are all associated with the same transformer module 6 as seen in figures 5 and 6.

[0055] For the purposes of this invention, the term "output group" refers to a set of outputs of the two-phase transformer that are phase-matched. Conventionally, and as illustrated in Figure 2 and in the description for a particular embodiment of the invention, an output group comprises a single output connected to the electrodes, which it supplies with single-phase alternating current. Alternatively, an output group may comprise several outputs, for example, connected in parallel, each output being connected to two pairs of electrodes. In this alternating configuration, notably illustrated in Figure 3, the single-phase current delivered to each of these electrodes is phase-matched.

[0056] According to the invention, each output group supplies a set of four electrodes. The presence of four pairs of electrodes per output group is advantageous because it allows for better current distribution. Indeed, with a single electrode, all the current is concentrated on that electrode, thus limiting the furnace's electrical power.

[0057] Supplying power to multiple electrodes allows the current to be distributed. This current distribution has two consequences. The first consequence is that it allows the current intensity in each electrode to be lowered. This reduction in intensity allows either for an increased lifespan of the electrode because it will be oversized relative to the current passing through it, or have electrodes with smaller dimensions which have a lower cost.

[0058] The second consequence is that it allows for an increase in the furnace's power output. Indeed, compared to a single electrode, the presence of multiple electrodes allows for the distribution of the current and also increases the furnace's electrical power. In fact, increasing the number of electrodes increases the power output because it is distributed across them.

[0059] The two consequences can combine. Indeed, in the case of a large furnace, the electrical power requirement is significant. Such a power requirement is characterized by a current exceeding 8000A, or even 9000A. Currently, electrodes are limited to 3000A to avoid overheating due to the Joule effect. With four electrodes, the current is distributed, which automatically reduces the current per electrode.

[0060] According to the particular embodiment illustrated in figure 1, the oven 1 is totally electric and is equipped with a cold vault 5.

[0061] According to a particular embodiment, and as illustrated in Figure 2, the electrical installation comprises a two-phase transformer 6 adapted to generate two single-phase output groups (AB, CD) with a phase difference of 90° between each output group (AB, CD). In this particular embodiment, each output group comprises a single output (AB, CD) connected to a bundle of four pairs of electrodes ((An; Bn); (Cn; Dn) with n=1,2,3,4), which it supplies with single-phase alternating current. The electrode bundles are arranged in bath 3 in a substantially square shape and in such a way as to maintain central symmetry about a theoretical horizontal plane, with respect to a point O located at the center of bath 3.For example, in the configuration of Figure 2, the current flows through the molten bath between electrodes A3 and Bl, A2 and B2, Al and B3, and A4 and B4, but also between electrodes Cl and D3, C2 and D2, C3 and Dl, and C4 and D4. Such symmetry makes it possible in particular to limit the distortion of the field lines both between the plurality of electrodes An and the plurality of electrodes Bn on the one hand (called here "1. er quartet”), and between the plurality of Cn electrodes and the plurality of Dn electrodes on the other hand (called here “2 e quartet").

[0062] According to the alternative embodiment illustrated in Figure 3, the first output group comprises several outputs (AB, A'-B') connected in parallel, the first output AB is connected to a bundle of two pairs of electrodes ((An; Bn) with n=1,2), while the second output A'-B' is connected to two pairs of electrodes ((An; Bn) with n=3, 4). In all cases, the single-phase current delivered to each of these electrodes is phase-matched. As illustrated in Figure 3, the second output group comprises only one output (CD), connected to a bundle of 4 pairs of electrodes ((Cn; Dn) with n=1,2,3,4). The electrode bundles are arranged in bath 3 in a roughly square shape and in such a way as to respect a central symmetry along a theoretical horizontal plane, with respect to a point O located at the center of bath 3. More particularly, in the configuration of figure 3, the current passes through the molten bath between electrodes Al and B2, A2 and Bl, A3 and B3, and A4 and B4 but also between electrodes Cl and D3, C2 and D2, C3 and Dl, and C4 and D4.Such symmetry makes it possible in particular to limit the distortion of the field lines both between the plurality of electrodes An and the plurality of electrodes Bn on the one hand ("1. er quartet”), and between the plurality of Cn electrodes and the plurality of Dn electrodes on the other hand (“ 2 e quartet").

[0063] In practice, a first single-phase current is generated by transformer 6 at the terminals of a first output group AB and flows through the glass bath between electrodes A1, A2, A3, A4 on one side, and electrodes B1, B2, B3, B4 on the other, thus heating the glass bath 3 of vitrifiable materials by Joule heating. In parallel, a second single-phase current, of the same frequency and amplitude as the first current, but phase-shifted by 90° or n / 2 radians relative to the latter, is generated by transformer 6 at the terminals of a second output group CD and flows through the glass bath between electrodes C1, C2, C3, C4 on one side, and electrodes D1, D2, D3, D4 on the other, thus heating the glass bath 3 of vitrifiable materials by Joule heating. Overall, the electrical installation 6 is thus adapted to generate a two-phase alternating current within the glass bath 3.

[0064] According to the embodiments illustrated in Figures 2 and 3, the electrical installation comprises only one two-phase transformer 6 which supplies a "block" of electrodes (An, Bn, Cn, Dn). According to alternative embodiments not illustrated, relating in particular to large electric furnaces, the electrical installation comprises a plurality of two-phase transformers which respectively supply a plurality of electrode blocks covering the surface of the glass bath 3.

[0065] Figure 4 is a flow diagram illustrating the successive stages of a manufacturing process according to a particular embodiment of the invention, which includes a first stage SI of melting vitrifiable materials by electrical heating of said bath 3 of vitrifiable materials by means of a two-phase alternating current, and a second stage S2 of manufacturing glass wool, rock wool, textile glass yarns and / or flat or hollow glass.

[0066] According to a particular embodiment, the minimum distance between each electrode and the nearest tank wall is greater than 250 mm, preferably greater than 450 mm, preferably greater than 600 mm, preferably greater than 800 mm, preferably greater than 950 mm, preferably greater than 1075 mm.

[0067] According to the invention, such a minimum distance is measured along the normal to the wall of the tank nearest to the electrode, and passing through the electrode. It should be noted that the convection currents of the glass bath generated near each electrode tend to corrode the adjacent tank wall. Therefore, moving the electrode further away from the tank helps to limit this premature wear of the tank wall.

[0068] According to a particular embodiment, each of said electrodes comprises a horizontal projection arm, preferably of square cross-section, whose horizontal extent is greater than 2000 mm, preferably greater than 2500 mm, preferably greater than 3000 mm, preferably greater than 3500 mm, preferably greater than 3700 mm, preferably greater than 3900 mm.

[0069] The use of a square-section electrode arm provides it with greater resistance to bending. This is especially beneficial as the electrode arm lengthens. A long electrode arm allows, in particular, for a greater distance between the electrode and the adjacent furnace wall, thus limiting wear on the latter. This increased distance between the electrode and the furnace wall is particularly advantageous when the furnace power is increased. Indeed, power depends on voltage and current, and these two parameters are adjusted with increasing values ​​as power increases. This results in an intensification of the convection currents in the glass bath generated near each electrode, which tend to corrode the adjacent furnace wall. Increasing the distance between the electrode and the furnace wall helps to limit this premature wear of the furnace wall.

[0070] The construction of so-called large electric furnaces usually encounters technical obstacles for the person skilled in the art.

[0071] The first obstacle lies in the need for greater electrical power to melt vitrifiable materials. This greater electrical power leads to an increase in current and voltage values ​​at the electrodes, and an intensification of convection movements in the glass bath generated near each electrode, which tend to corrode the adjacent wall of the tank.

[0072] The second obstacle is that if the surface area of ​​these furnaces is large, the resulting basin is longer and wider. It is therefore necessary to be able to supply heating energy to every point, including the center of the furnace, the area furthest from the wall.

[0073] The present invention overcomes these obstacles by synergistically combining the use of a two-phase system with arms whose horizontal span exceeds 2000 mm, preferably exceeding 2500 mm, preferably exceeding 3000 mm, preferably exceeding 3500 mm, preferably exceeding 3700 mm, and preferably exceeding 3900 mm. This synergy is based on the fact that a two-phase system, at a given power level, allows for lower current at the electrodes than a three-phase system. It is therefore understandable that it is possible to obtain higher power for the same current. This possibility of achieving higher power, or even higher current, is associated with arms having a greater horizontal span.These arms, with their greater horizontal reach, allow the electrodes to be positioned further from the walls, thus reducing the risk of corrosion to the tank walls while still enabling the heating of distant areas. Furthermore, the use of a two-phase system reduces the number of electrodes required and therefore lowers the installation cost. The number of electrodes per square meter (m²) is [not specified in the original text]. 2 ) is between 0.05 and 0.45, preferably between 0.15 and 0.4 and even more preferably between 0.2 and 0.35.

[0074] Of course, the present invention is not limited to the illustrated example but is susceptible to various variants and modifications which will become apparent to those skilled in the art.

[0075] Thus, many aspects and implementation methods are possible. Some of them are described below.

[0076] [Object 1]. Glass furnace (1) at least partly electric, comprising a melting tank (2) made of refractory materials adapted to contain a bath (3) of molten vitrifiable materials and a plurality of immersion heating electrodes (An, Bn, Cn, Dn), which are immersed from the free surface of said bath (3) and supplied with electric current by an electrical installation (4), said furnace (1) being characterized in that said electrical installation (4) is adapted to generate a two-phase alternating current, said electrical installation comprising a transformer module (6) adapted to generate two single-phase output groups (AB, CD) with a phase difference of 90° between each output group (AB, CD), each output group (AB, CD) supplying a quartet ((An ; Bn) ; (Cn ; Dn)) of said electrodes.

[0077] [Object 2]. Glass furnace (1) according to object 1, in which the transformer module (6) comprises at least one two-phase transformer or at least two single-phase transformers.

[0078] [Object 3] Glass furnace (1) according to objects 1 or 2, characterized in that at least one output group (AB, CD) of said transformer module (6) comprises one or more outputs.

[0079] [Object 4] Glass furnace (1) according to one of objects 1 to 3, characterized in that each electrode bundle ((An ; Bn) ; (Cn ; Dn)) is arranged in the bath (3) of molten vitrifiable materials so as to respect a central symmetry along a theoretical horizontal plane.

[0080] [Object 5] Glass furnace (1) according to any one of objects 1 to 4, characterized in that the electrodes of the same output group (AB, CD) are arranged near opposite walls of the tank (2).

[0081] [Object 6] Glass furnace (1) according to one of objects 1 to 5, characterized in that said quartet ((An ; Bn) ; (Cn ; Dn)) of electrodes supplied by the same two-phase transformer (6) are arranged in a quadrilateral according to a theoretical horizontal plane, preferably in a rectangle, preferably in a square, in the bath (3) of molten vitrifiable materials.

[0082] [Item 7] Glass furnace (1) according to any one of items 1 to 6, characterized in that the minimum distance (dmin) between each electrode (An, Bn, Cn, Dn) and the nearest wall of the tank (2) is greater than 450 mm, preferably greater than 600 mm, preferably greater than 800 mm, preferably greater than 950 mm, preferably greater than 1075 mm.

[0083] [Item 8] Glass furnace (1) according to any one of items 1 to 7, characterized in that each of said electrodes (An, Bn, Cn, Dn) comprises a horizontal projection arm, preferably of square cross-section, the horizontal extent of which is greater than 2000 mm, preferably greater than 2500 mm, preferably greater than 3000 mm, preferably greater than 3500 mm, preferably greater than 3700 mm, preferably greater than 3900 mm.

[0084] [Item 9] Glass furnace (1) according to any one of items 1 to 8, characterized in that said electrical installation (4) is adapted so that all electrodes connected to the same output group (AB, CD) of said two-phase transformer (6) are supplied with an electric current of the same voltage.

[0085] [Object 10] Glass furnace (1) according to one of objects 1 to 9, characterized in that it is totally electric, and preferably includes a cold vault (5).

[0086] [Object 11] Glass furnace (1) according to any one of claims 1 to 10, characterized in that it comprises a plurality of said two-phase transformers (6), preferably three.

[0087] [Item 12] Glass furnace (1) according to any one of items 1 to 11, characterized in that said melting tank (2) is dimensioned so that said bath (3) of molten vitrifiable materials has a surface area greater than 25 m² 2 , preferably greater than 40 m 2 , preferably greater than 60 m 2 , preferably greater than 100 m 2 , and preferably presents between two opposite walls of said tank (2) a distance greater than 5 m, preferably greater than 6.5 m.

[0088] [Item 13] Glass furnace (1) according to any one of items 1 to 12, characterized in that the number of electrodes per square meter is between 0.05 and 0.45, preferably between 0.15 and 0.4 and even more preferably between 0.2 and 0.35.

[0089] [Object 14] Glass furnace according to one of the preceding objects, characterized in that said vessel is divided into at least two portions, each portion comprising two single-phase output groups (AB, CD) with a phase difference of 90° between each output group (AB, CD), each output group (AB, CD) supplying a quartet ((An ; Bn) ; (Cn ; Dn)) of said electrodes.

[0090] [Object 15] Glass furnace according to the preceding object, characterized in that each portion of the tank is equipped with a transformer module generating the two single-phase output groups (AB, CD) with a phase difference of 90° between each output group (AB, CD), each output group (AB, CD) supplying a quartet ((An ; Bn) ; (Cn ; Dn)) of said electrodes.

[0091] [Item 16] A process for melting vitrifiable materials carried out using a glass furnace (1) according to any one of items 1 to 15, characterized in that it comprises at least one step of electrically heating said bath (3) of molten vitrifiable materials by means of said plurality of electrodes (An, Bn, Cn, Dn), and by applying within said bath (3) a two-phase alternating current.

[0092] [Object 17] A process for melting vitrifiable materials according to claim 16 implemented by means of a glass furnace (1) according to object 9, characterized in that the quartet ((An ; Bn) ; (Cn ; Dn)) of electrodes connected to the same output group (AB, CD) of said two-phase transformer (6) are supplied with an electric current of the same voltage.

[0093] [Item 18] A process for manufacturing glass wool, rock wool, textile glass yarns and / or flat or hollow glass, characterized in that it implements a melting process according to one of items 16 and 17.

Claims

Demands

1. Glass furnace (1) at least partly electric, comprising a melting tank (2) made of refractory materials adapted to contain a bath (3) of molten vitrifiable materials and a plurality of immersion heating electrodes (An, Bn, Cn, Dn), which are immersed from the free surface of said bath (3) and supplied with electric current by an electrical installation (4), said furnace (1) being characterized in that said electrical installation (4) is adapted to generate a two-phase alternating current, said electrical installation comprising a transformer module (6) adapted to generate two single-phase output groups (AB, CD) with a phase difference of 90° between each output group (AB, CD), each output group (AB, CD) supplying a quartet ((An ; Bn) ; (Cn ; Dn)) of said electrodes.

2. glass furnace (1) according to claim 1, wherein the transformer module (6) comprises at least one two-phase transformer or at least two single-phase transformers.

3. Glass furnace (1) according to claims 1 or 2, characterized in that at least one output group (AB, CD) of said transformer module (6) comprises one or more outputs, preferably several outputs.

4. Glass furnace (1) according to any one of claims 1 to 3, characterized in that at least one output group (AB, CD) of said transformer module (6) comprises a single output (AB, CD) connected to a bundle of four pairs of electrodes.

5. Glass furnace (1) according to any one of claims 1 to 4, characterized in that at least one output group (AB, CD) of said transformer module (6) comprises two outputs (AB, A'-B', CD, C'-D'), each of the two outputs being connected to a bundle of two pairs of electrodes.

6. Glass furnace (1) according to any one of claims 4 to 5, characterized in that each electrode bundle ((An ; Bn) ; (Cn ; Dn)) is arranged in the bath (3) of molten vitrifiable materials so as to respect a central symmetry along a theoretical horizontal plane.

7. Glass furnace (1) according to any one of claims 1 to 6, characterized in that the electrodes of the same output group (AB, CD) are arranged near opposite walls of the tank (2).

8. Glass furnace (1) according to any one of claims 1 to 7, characterized in that said quartet ((An ; Bn) ; (Cn ; Dn)) of electrodes supplied by the same two-phase transformer (6) are arranged in a quadrilateral along a theoretical horizontal plane, preferably in a rectangle, preferably in a square, in the bath (3) of molten vitrifiable materials.

9. Glass furnace (1) according to any one of claims 1 to 8, characterized in that the minimum distance (dmin) between each electrode (An, Bn, Cn, Dn) and the nearest wall of the tank (2) is greater than 450 mm, preferably greater than 600 mm, preferably greater than 800 mm, preferably greater than 950 mm, preferably greater than 1075 mm.

10. Glass furnace (1) according to any one of claims 1 to 9, characterized in that each of said electrodes (An, Bn, Cn, Dn) comprises a horizontal projection arm, preferably of square cross-section, the horizontal extent of which is greater than 2000 mm, preferably greater than 2500 mm, preferably greater than 3000 mm, preferably greater than 3500 mm, preferably greater than 3700 mm, preferably greater than 3900 mm.

11. Glass furnace (1) according to any one of claims 1 to 10, characterized in that said electrical installation (4) is adapted so that all electrodes connected to the same output group (AB, CD) of said two-phase transformer (6) are supplied with an electric current of the same voltage.

12. Glass furnace (1) according to any one of claims 1 to 11, characterized in that it is totally electric, and preferably comprises a cold vault (5).

13. Glass furnace (1) according to any one of claims 1 to 12, characterized in that it comprises a plurality of said two-phase transformers (6), preferably three.

14. Glass furnace (1) according to any one of claims 1 to 13, characterized in that said melting tank (2) is dimensioned such that said bath (3) of molten vitrifiable materials has a surface area greater than 25 m² 2 , preferably greater than 40 m 2 , preferably greater than 60 m 2 , preferably greater than 100 m 2 , and preferably presents between two opposite walls of said tank (2) a distance greater than 5 m, preferably greater than 6.5 m.

15. Glass furnace (1) according to any one of claims 1 to 14, characterized in that the number of electrodes per square meter is between 0.05 and 0.45, preferably between 0.15 and 0.4 and even more preferably between 0.2 and 0.

35.

16. Glass furnace according to any one of the preceding claims, characterized in that said tank is divided into at least two portions, each portion comprising two single-phase output groups (AB, CD) with a phase difference of 90° between each output group (AB, CD), each output group (AB, CD) supplying a quartet ((An ; Bn) ; (Cn ; Dn)) of said electrodes.

17. Glass furnace according to the preceding claim, characterized in that each portion of the tank is equipped with a transformer module generating the two single-phase output groups (AB, CD) with a phase difference of 90° between each output group (AB, CD), each output group (AB, CD) supplying a quartet ((An ; Bn) ; (Cn ; Dn)) of said electrodes.

18. A method for melting vitrifiable materials implemented using a glass furnace (1) according to any one of claims 1 to 17, characterized in that it comprises at least one step of electrically heating said bath (3) of molten vitrifiable materials by means of said plurality of electrodes (An, Bn, Cn, Dn), and by applying within said bath (3) a two-phase alternating current.

19. A method for melting vitrifiable materials according to claim 18 implemented by means of a glass furnace (1) according to claim 9, characterized in that the quartet ((An; Bn); (Cn; Dn)) of electrodes connected to the same output group (AB, CD) said two-phase transformer (6) are supplied with an electric current of the same voltage.

20. A method for manufacturing glass wool, rock wool, textile glass yarns and / or flat or hollow glass, characterized in that it implements a melting process according to one of claims 18 and 19.

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