Electric Glass Manufacturing Furnace

Abstract

To provide an electric glass furnace that allows heating of larger furnaces / reducing the number of electrodes. The present invention relates to an at least partially electric glass furnace (1), comprising a melting tank (2) made of refractory material suitable for containing a bath (3) of molten vitrifiable material, and a plurality of top-entry heating electrodes (An, Bn, Cn, Dn) immersed from the free surface of the bath (3) and supplied with electric current by an electric installation (4), the electric installation (4) being configured to generate a two-phase alternating current.

Description

[Technical Field]

[0001] The present invention belongs to the general field of glass production. The invention more particularly relates to an at least partially electric glass furnace suitable for melting vitrifiable material. The invention also relates to a method for melting vitrifiable material to enable glass to be produced. Particularly advantageous applications of the invention are found in, but are not limited to, the production of glass wool, rock wool, textile glass yarns and / or flat or hollow glass. [Background technology]

[0002] As used herein, "vitrifiable materials" or "raw materials" refers to all materials, natural or synthetic, and materials derived from recycling, such as cullet, that can be added to the composition fed to a glass furnace. This includes silica sand, but also all additives (sodium carbonate, limestone, dolomite, alumina, etc.), waste materials (including inorganic fibers) that may be produced from fiber manufacturing or construction or demolition sites, all possible liquid or solid fuels (composite or non-composite plastics, organic materials, coal), and any type of cullet. Also included are recyclable materials containing combustible (organic) elements, such as sized inorganic fibers with binders (such as those used for thermal or acoustic insulation or for reinforcing plastics), glazing laminated with sheets of polyvinyl butyral polymer, such as windshields, 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 glazing with a metal-containing coating. As used herein, "bath of vitrifiable material" or "glass bath" refers to the molten product of these raw materials.

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

[0004] In addition, the term "manufacturing" includes the essential step of melting the vitrifiable material and, if necessary, all subsequent steps of refining / conditioning the molten glass for its final shaping, in particular in the form of flat glass (glazing), hollow glass (bottles, jars), mineral wool (in particular rock wool or glass wool) used for its thermal or sound insulation properties, and also in the form of textile yarns used for reinforcement, etc.

[0005] Various examples of electric furnace designs are known from the prior art, in particular from patent EP 0 671 116 B1, in which the current is conducted in the bath of vitrifiable material by so-called "top-entry" electrodes, which are immersed in the bath from the free surface. This type of top-entry electrode differs in particular from so-called "submerged" electrodes, which are positioned vertically from the hearth into the bath or horizontally and pass through the side wall of the furnace. Compared to the latter, top-entry electrodes offer many advantages. Firstly, they avoid the difficulties associated with the passage of submerged electrodes through the bottom or side wall refractories, as well as the problems of replacing these electrodes when worn, as well as the problems of sealing the melting tank or even the problem of refractory wear due to the high temperatures and strong convection currents that occur in the vicinity of the electrodes during operation, which are particularly favorable for refractory attack.

[0006] These top-entry electrodes are usually supplied with three-phase current. Three-phase current offers many advantages, particularly in that it is the so-called "industrial" current that is customarily distributed to factories by energy suppliers, and therefore offers advantages in terms of equipment compatibility. Three-phase current also provides instantaneous power without pulse components, unlike, for example, single-phase current. However, it should be noted that the principle of phase balance tends toward a triangular or hexagonal arrangement of electrodes on the surface of the glass bath. While such geometric constraints do not seem to pose a theoretical challenge in the context of small electric furnaces, they do pose challenges in the context of large electric furnaces, where the glass bath is 25 m 2 Ultra, preferentially 40m 2 Over or even 100m 2 The tank extends over a distance of more than 100 m, with the width of the glass bath between its ends exceeding 5 m, preferentially exceeding 6.5 m. In such a configuration, taking into account the aforementioned geometric constraints, the current tends to concentrate between the electrodes at the same and / or adjacent tank ends, thus reducing the distance covered by the current in the glass bath and, therefore, the resistance of the glass bath to the passage of this current. For a given power corresponding to the energy required to melt the vitrifiable material, and in the context of a glass bath offering only reduced resistance, it becomes necessary to increase the intensity of the current being sent. However, with the intensity of the current being sent per electrode, wear on the electrodes and refractories that make up the tank increases. To overcome this wear problem, a natural solution is to distribute the current being sent among a greater number of electrodes. However, this has the drawback of increasing the operating costs of these electrodes, since there are more of them, and does not solve the specific problem of non-uniformity in the current distribution in the glass bath. Summary of the Invention [Problem to be solved by the invention]

[0007] The object of the present invention is to remedy some or all of the drawbacks of the prior art, in particular the drawbacks mentioned above. [Means for solving the problem]

[0008] To this end, according to a first aspect, the invention relates to an at least partly electric glass furnace, characterized in that it comprises a melting tank made of refractory material suitable for containing a bath of molten vitrifiable material, and a plurality of top-entering heating electrodes immersed from the free surface of the bath and supplied with electric current by an electrical installation, the electrical installation being adapted to generate a two-phase alternating current. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 shows a schematic side view of an electric glass furnace. [Figure 2] FIG. 2 shows a schematic top view of a glass bath and top-entry electrode of an electric furnace according to certain embodiments of the present invention. [Figure 3] FIG. 3 shows a schematic top view of a glass bath and top-entry electrode of an electric furnace in accordance with an alternative embodiment of the present invention. [Figure 4] FIG. 4 is a flow chart illustrating the sequence of steps in a manufacturing method according to a particular embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] For the purposes of the present invention, the term "two-phase alternating current" refers to a system having two phases of the same frequency and amplitude that are orthogonal, i.e., out of phase with each other by 90° or π / 2 radians.

[0011] In conventional situations, when current is distributed by an energy supplier in three-phase form, the implementation of an electrical installation adapted to convert this three-phase current into a two-phase current would theoretically imply unnecessary technical complexity and a non-negligible increase in the initial costs of this technical installation.

[0012] Despite these theoretical disadvantages that discourage their use, and in the specific context of supplying top-entry electrodes for glass furnaces, the inventors have found that such two-phase systems allow glass furnace designers to free themselves from certain geometric constraints and associated technical disadvantages inherent in three-phase systems, such as the large number of electrodes that need to be used and the uneven distribution of current within the bath of vitrifiable material.

[0013] In contrast, two-phase systems offer glass furnace designers the possibility of further spacing electrodes supplied by the same phase, for example by placing them near opposite ends of the melting tank. Compared to three-phase systems, for a given power, the resistance created by the glass bath (which increases with the distance covered by the current in the bath) is greater, which means a reduction in the current delivered. This intensity can then be distributed among a reduced number of electrodes and / or the intensity delivered to each electrode can be limited, thus increasing their service life.

[0014] According to a particular embodiment, the electrical installation comprises at least one two-phase transformer adapted to generate two single-phase output groups with a phase difference of 90° between each output group, each output group supplying at least one pair of electrodes.

[0015] For purposes of the present invention, the term "output group" refers to a set of phase-matched outputs of a two-phase transformer. Conventionally, as shown in Figure 2 and in the description of certain embodiments of the present invention, an output group comprises only a single output connected to multiple electrode pairs (three in the embodiment shown in Figure 2) supplying single-phase alternating current.

[0016] According to a particular embodiment, at least one output group of at least one two-phase transformer supplies a bundle of at least two electrode pairs, preferably three electrode pairs.

[0017] By connecting the output groups to bundles, or in other words to multiple pairs of electrodes, it is possible to distribute the current intensity between them, thus limiting their respective wear over time. Conversely, the use of a single pair of electrodes supplied by a group of outputs limits the initial cost of the installation.

[0018] According to a particular embodiment, at least one output group of at least one two-phase transformer comprises one or more outputs.

[0019] According to this alternative embodiment, which is particularly shown in Figure 3, the output group comprises several outputs, for example mounted in parallel, each connected to one or more pairs of electrodes, and in all cases the single-phase currents sent to each of these electrodes are phase-matched.

[0020] According to a particular embodiment, each electrode bundle is arranged in the bath of molten vitrifiable material so as to be centrosymmetric along a theoretical horizontal plane.

[0021] Retaining such axial symmetry ensures a more even distribution of current between the electrodes, thus limiting the possibility of one of these electrodes wearing out faster than the others.

[0022] According to a particular embodiment, the electrodes of the same output group are arranged near opposite walls of the tank.

[0023] This advantageous geometric arrangement of the electrode pairs is particularly well suited to two-phase operation, allowing the distance between electrodes connected to two terminals of the same output group to be increased without the risk of electrodes placed close to the same wall interacting with each other.

[0024] According to a particular embodiment, the electrode pairs powered by the same two-phase transformer are arranged in a quadrilateral, preferentially rectangular, preferentially square, shape along a theoretical horizontal plane in the bath of molten vitrifiable material.

[0025] This advantageous geometric arrangement of electrode pairs is particularly suited to two-phase operation and allows for current balancing. This quadrilateral arrangement contrasts particularly well with the triangular or hexagonal arrangements typical of three-phase systems.

[0026] According to a particular embodiment, the minimum distance between each electrode and the nearest tank wall is greater than 450 mm, preferentially greater than 600 mm, more preferentially greater than 800 mm, preferentially greater than 950 mm, preferentially greater than 1075 mm.

[0027] For purposes of the present invention, such minimum distance is measured along a normal to the tank wall nearest the electrode and passing through the electrode. Note that convective motion of the glass bath occurring near each electrode tends to erode the adjacent tank wall. Therefore, spacing the electrodes from the tank limits this premature wear of the tank wall.

[0028] According to a particular embodiment, each of the electrodes comprises a horizontally projecting arm, preferably of square cross section, the horizontal extension 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.

[0029] The use of electrode arms with a square cross section provides greater resistance to bending. This is particularly useful when the electrode arms are long. In particular, a long electrode arm allows the electrode to be moved further away from the adjacent tank wall, thereby limiting tank wall wear. This distance between the electrode and the tank wall is even more advantageous when the furnace power is increased. Since power depends on voltage and current, these two parameters are adjusted to higher values ​​as power increases. As a result, stronger glass bath convection motions occur near each electrode, which tend to corrode the adjacent tank wall. Moving the electrodes away from the tank wall limits this premature tank wall wear.

[0030] According to a particular embodiment, the electrical installation is adapted so that all pairs of electrodes connected to the same output group of the two-phase transformer are supplied with a current of the same voltage.

[0031] According to a particular embodiment, the glass furnace is fully electric and preferably includes a cold crown (5).

[0032] For the purposes of the present invention, a furnace is said to be "fully electric" in the sense that all heating energy supplied to the glass bath is of an electrical nature, and therefore such a furnace does not have heating burners.

[0033] According to a particular embodiment, the glass furnace comprises a plurality of two-phase transformers, preferably three transformers.

[0034] The use of multiple two-phase transformers is particularly suitable for powering large furnaces, in which the use of two-phase systems is particularly advantageous.

[0035] According to a particular embodiment, the melting tank contains a bath of molten vitrified material having a depth of 25 m 2 Larger surface area, preferentially 40m 2 Larger, preferentially 60m 2 Larger, preferentially 100m 2 It has a larger surface area and is preferentially dimensioned so that the distance between two opposing walls of the tank is greater than 5 m, preferably greater than 6.5 m.

[0036] Such dimensions relate to so-called large electric furnaces, and the use of a two-phase system is particularly advantageous for such large electric furnaces.

[0037] The construction of these so-called large electric furnaces usually poses a technical obstacle for those skilled in the art.

[0038] The first obstacle is the need for greater power to melt the vitrifiable material, which results in higher currents and voltages at the electrodes, increasing the convective motion of the glass bath generated near each electrode, which tends to corrode the adjacent tank walls.

[0039] The second obstacle is that the larger the area of ​​these furnaces, the greater the length and width of the chamber, so it is necessary to be able to deliver heating energy to any point, including the center of the furnace, which is the area farthest from the walls.

[0040] The present invention solves these obstacles by synergistically combining the use of two-phase systems with arms having a horizontal extension of more than 2000 mm, preferentially more than 2500 mm, preferentially more than 3000 mm, preferentially more than 3500 mm, preferentially more than 3700 mm, preferentially more than 3900 mm. This synergistic effect is based on the fact that, for a given power level, two-phase systems allow for less current in the electrodes than three-phase systems. This means that it is possible to obtain a higher power output for the same current. The possibility of having a higher power or even a higher current is associated with arms having a larger horizontal extension. These arms, due to their larger horizontal extension, allow the electrodes to be moved further away from the wall, thereby reducing the risk of corrosion of the tank wall and at the same time allowing heating of distant areas. In addition, the use of two-phase systems reduces the number of electrodes and therefore the cost of the installation. square meters (m 2 The number of electrodes per electrode is 0.1 to 0.45, preferably 0.15 to 0.4, and even more preferably 0.2 to 0.35.

[0041] According to certain embodiments, these so-called large furnaces are obtained by adding several basic modules. In this case, a basic module is considered to be the equivalent of a furnace whose tank has a defined length and width, and this basic module comprises a set of heating electrodes with a defined arrangement. Preferably, the basic module is square. A so-called large furnace comprises at least two basic modules arranged adjacently, i.e., a tank whose length and width dimensions are a multiple of the defined values ​​of the basic module. Thus, it is possible to easily obtain so-called large furnaces that can have various shapes, such as rectangular, square, L-shaped, or T-shaped.

[0042] According to a particular embodiment, the two-phase transformer supplies a number of electrodes equal to or less than 16, preferably equal to or less than 12, preferably equal to or less than 8.

[0043] Depending on whether each output group feeds four electrodes twice, three electrodes twice, or two electrodes twice, the total number of electrodes fed from a single two-phase transformer varies between 16, 12, and 8, respectively.

[0044] Compared to three-phase systems, for glass bath modules of equivalent surface area (and therefore equivalent power), two-phase systems offer the possibility of reducing the number of electrodes used in the furnace.

[0045] According to a particular embodiment, the invention relates to a method for melting vitrifiable material carried out by such a glass furnace, characterized in that it comprises at least one step of electrically heating the bath of molten vitrifiable material by means of the above-mentioned plurality of electrodes and by applying a two-phase alternating current in the bath.

[0046] According to a particular embodiment, all electrode pairs connected to the same output group of the two-phase transformer are supplied with current at the same voltage.

[0047] According to a particular embodiment, the present invention relates to a method for producing glass wool, rock wool, glass textile yarns and / or flat or hollow glass, characterized in that such a melting method is carried out.

[0048] 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 thereof. In the diagram: FIG. 1 shows a schematic side view of an electric glass furnace. FIG. 2 shows a schematic top view of a glass bath and top-entry electrode of an electric furnace according to certain embodiments of the present invention. FIG. 3 shows a schematic top view of a glass bath and top-entry electrode of an electric furnace in accordance with an alternative embodiment of the present invention. FIG. 4 is a flow chart illustrating the sequence of steps in a manufacturing method according to a particular embodiment of the present invention.

[0049] Figure 1 shows a schematic side view of an electric glass furnace 1. Such a glass furnace 1 comprises a melting tank 2 made of a refractory material suitable for containing a bath 3 of molten vitrifiable material, and a number of top-entry heating electrodes (An, Bn, Cn, Dn) (only one of which is shown in Figure 1 for the sake of simplicity), the arms of which have a square cross section, which are immersed in the bath 3 from its free surface and are supplied with electric current by an electrical installation 4. As is known, the part of the electrode in contact with the glass bath consists of molybdenum. The glass furnace 1 according to the invention is particularly characterized in that the electrical installation 4 is adapted to generate a two-phase alternating current.

[0050] According to the particular embodiment shown in FIG. 1, the furnace 1 is fully electric and comprises a cold crown 5 .

[0051] According to a particular embodiment, as shown 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). According to this particular embodiment, the output group includes only a single output (AB, CD) connected to a bundle of three electrode pairs ((An; Bn); (Cn; Dn) (n = 1, 2, 3) supplying a single-phase alternating current. The electrode bundle is arranged in the bath 3 in a substantially square shape and with central symmetry along a theoretical horizontal plane with respect to a point O located at the center of the bath 3.

[0052] According to this alternative embodiment shown in Figure 3, the first output group comprises several outputs (AB, A'-B') implemented in parallel, the first output AB being connected to a bundle of two electrode pairs ((An;Bn);(Cn;Dn), n = 1, 2), while the second output A'-B' is connected to one electrode pair (A3;B3). In all cases, the monophasic currents sent to each of these electrodes are phase-aligned.

[0053] In practice, a first single-phase current is generated by the transformer 6 at the terminals of the first output group AB and passes through the glass bath between electrodes A1, A2, A3 on the one hand and electrodes B1, B2, B3 on the other hand, thereby heating the bath 3 of vitrifiable material by the Joule effect. In parallel, a second single-phase current of the same frequency and amplitude as the first current but phase-shifted by 90° or π / 2 radians with respect to the first current is generated by the transformer 6 at the terminals of the second output group CD and passes through the glass bath between electrodes C1, C2, C3 on the one hand and electrodes D1, D2, D3 on the other hand, thereby heating the bath 3 of vitrifiable material by the Joule effect. In this way, the electrical installation 6 as a whole is adapted to generate a two-phase alternating current in the glass bath 3.

[0054] According to the embodiment shown in Figures 2 and 3, the electrical installation comprises only one two-phase transformer 6 supplying the "blocks" of electrodes (An, Bn, Cn, Dn). According to an alternative embodiment not shown, particularly for large electric furnaces, the electrical installation comprises several two-phase transformers respectively supplying several electrode blocks covering the surface of the glass bath 3.

[0055] FIG. 4 is a flow diagram illustrating the sequence of steps of a manufacturing method according to a particular embodiment of the invention, which includes a first step S1 of melting the vitrifiable material by electrically heating a bath 3 of vitrifiable material by means of a two-phase alternating current, and a second step S2 of producing glass wool, rock wool, glass textile yarns, and / or flat or hollow glass.

Claims

1. 1. An at least partially electric glass furnace (1), comprising a melting tank (2) made of a refractory material suitable for containing a bath (3) of molten vitrifiable material, and a plurality of top-entry heating electrodes (An, Bn, Cn, Dn) immersed in the bath (3) from a free surface and supplied with electric current by an electrical installation (4), the electrical installation (4) being configured to generate two-phase alternating current.

2. 2. The glass furnace (1) according to claim 1, characterized in that the electrical installation comprises at least one 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), each output group (A-B, C-D) supplying at least one pair of electrodes ((An; Bn); (Cn; Dn)).

3. 3. A glass furnace (1) according to claim 2, characterized in that at least one output group (A-B, C-D) of said at least one two-phase transformer (6) supplies a bundle of at least two electrode pairs ((An; Bn); (Cn; Dn)), preferentially three electrode pairs ((An; Bn); (Cn; Dn)).

4. 4. The glass furnace (1) according to claim 2, wherein at least one output group (A-B, C-D) of the at least one two-phase transformer (6) comprises one or more outputs.

5. 5. A glass furnace (1) according to claim 3 or 4, characterized in that each electrode bundle ((An; Bn); (Cn; Dn)) is arranged in the bath (3) of molten vitrifiable material so as to maintain centrosymmetrical alignment along a theoretical horizontal plane.

6. 6. A glass furnace (1) according to any one of claims 2 to 5, characterized in that the electrodes of the same output group (AB, CD) are arranged near opposite walls of the tank (2).

7. 7. A glass furnace (1) according to any one of claims 2 to 6, characterized in that the pairs of electrodes ((An; Bn); (Cn; Dn)) powered by the same two-phase transformer (6) are arranged in a quadrilateral, preferentially rectangular, preferentially square, arrangement along a theoretical horizontal plane in the bath of molten vitrifiable material (3).

8. 8. A glass furnace (1) according to any one of claims 1 to 7, characterized in that the minimum distance (dmin) between each electrode (An, Bn, Cn, Dn) and the nearest tank wall (2) is greater than 450 mm, preferably greater than 600 mm, preferentially greater than 800 mm, preferentially greater than 950 mm, preferentially greater than 1075 mm.

9. 9. A glass furnace (1) according to any one of claims 1 to 8, characterized in that each of the electrodes (An, Bn, Cn, Dn) comprises a horizontally projecting arm, preferably with a horizontal cross section, the horizontal extension 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.

10. 10. The glass furnace (1) according to any one of claims 2 to 9, characterized in that the electrical installation (4) is adapted to supply current of the same voltage to all electrode pairs connected to the same output group (A-B, C-D) of the two-phase transformer (6).

11. A glass furnace (1) according to any one of claims 1 to 10, characterized in that it is fully electric and preferably comprises a cold crown (5).

12. A glass furnace (1) according to any one of claims 2 to 11, characterized in that it comprises a plurality of said two-phase transformers (6), preferably three.

13. The melting tank (2) contains the bath (3) of molten vitrifiable material, the bath having a volume of 25 m ２ Larger, preferably 40m ２ Larger, preferably 60m ２ Larger, preferably 100m ２ 13. The glass furnace (1) according to any one of claims 1 to 12, which is dimensioned to have a larger surface area and preferably a distance between two opposite walls of the tank (2) greater than 5 m, preferentially greater than 6.5 m.

14. A glass furnace (1) according to any one of claims 2 to 13, characterized in that the two-phase transformer (6) supplies a number of electrodes not exceeding 16, preferably not exceeding 12, preferably not exceeding 8.

15. A glass furnace (1) according to any one of claims 2 to 13, characterized in that the number of electrodes per square meter is between 0.1 and 0.45, preferably between 0.15 and 0.4, even more preferably between 0.2 and 0.

35.

16. 16. A method for melting vitrifiable material using a glass furnace (1) according to any one of claims 1 to 15, characterized in that it comprises at least one step of electrically heating the bath (3) of molten vitrifiable material by means of the plurality of electrodes (An, Bn, Cn, Dn) and by applying a two-phase alternating current in the bath (3).

17. 17. A method for melting a vitrifiable material according to claim 16 by means of a glass furnace (1) according to claim 10, characterized in that all pairs of electrodes ((An; Bn); (Cn; Dn)) connected to the same output group (A-B, C-D) of the two-phase transformer (6) are supplied with currents of the same voltage.

18. 18. A method for producing glass wool, rock wool, glass textile fibers and / or flat or hollow glass, characterized in that the melting method according to claim 16 or 17 is carried out.

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