Electric glass furnace and method for melting and producing glass using said furnace

Abstract

The present invention relates to an electric glass furnace (100) comprising a tank (110) with a cold or semi-cold top and an electrode (150) for melting raw materials (130) introduced into the tank, thereby obtaining a bath (120) of molten material, the tank having a side wall (112) with an opening (113) configured to allow the molten material to flow out of the tank. The furnace further comprises means, called "delay" means (170, 180), at least partially immersed in the bath and arranged adjacent to the side wall of the tank in vertical alignment with the opening, configured to increase the residence time, in the tank, of raw materials introduced adjacent to the delay means.

Description

[Technical field]

[0001] The present invention belongs to the general field of glass production. It more particularly relates to an electric glass furnace adapted to melt raw materials. It also relates to a method for melting raw materials carried out using this electric glass furnace, and to a method for producing glass comprising a step of melting raw materials according to said melting method. [Background technology]

[0002] Various examples of furnace designs for glass production are known, in particular depending on the article to be produced, i.e. the chemical composition of the glass and its final shape (glass wool, rock wool, hollow glass or even flat glass).

[0003] In the present specification, "raw materials" is understood to mean all materials, vitrifiable materials, natural ores or synthetic products, materials of recycled origin, such as cullet, that may enter the composition fed to the glass furnace.

[0004] Similarly, "glass" is understood to mean glass in the broad sense, i.e., to include any material having a vitreous, glass-ceramic, or ceramic matrix.

[0005] Furthermore, the term "manufacturing" includes the essential steps of melting the raw materials 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 heat or sound insulation properties, or even optionally in the form of fiber threads used for reinforcement.

[0006] More particularly, it is known to carry out the melting of raw materials using electric glass furnaces, thereby obtaining a bath of vitrifiable material, commonly called "vitrifiable mixture" or "composition".

[0007] Vitrifiable mixtures are derived from raw materials that typically include, for example, a mixture of sand, limestone (calcium carbonate), soda ash, and dolomite for the production of soda-lime glass (the glass most commonly used in flat glass production), or boron trioxide for the production of borosilicate glass, to which cullet, made of broken glass, is advantageously added to facilitate melting.

[0008] These raw materials are converted into a liquid mass that forms a bath of molten vitrifiable material that dissolves even the least miscible particles, i.e., those richest in silicon dioxide or silica (SiO2) and poorest in sodium oxide (Na2O).

[0009] Said electric glass furnaces conventionally have a tank made of refractory material intended to contain a bath of molten material, the space above the tank being closed by an arch. The raw materials are introduced into the tank through its top by a mechanical device capable of carrying out this introduction over all or part of the surface of the bath of molten material. This surface constitutes a heat shield making it possible to limit the temperature above the bath. This type of furnace is also called "cold top" (respectively "semi-cold top") when the entire surface of the bath (respectively only a part of the bath surface) is intended to be covered with raw materials.

[0010] The heating principle of electric glass furnaces is based on the fact that the thermal energy required, in particular, for the melting of the raw materials is provided in a mass of molten glass (i.e. in a bath of molten material). More precisely, the electric melting of glass is based on its property that it becomes electrically conductive from 800-900 °C onwards, and its conductivity increases with temperature. The glass is therefore heated by the Joule effect, with the bath of molten material constituting the resistor. The current required to obtain this Joule effect is provided, in part, by electrodes embedded in this bath.

[0011] The material thus molten leaves the tank through an opening, conventionally made in the lower part of the tank's side wall. This side opening is generally (but not necessarily) extended by a throat that allows the flow of the molten material to other areas. These may be the areas where refining, homogenization or thermal conditioning steps and the final glass shaping (as in the production of flat glass, hollow glass, etc.) are carried out. Alternatively, if the article to be produced is glass in the form of inorganic wool (in particular rock wool or glass wool), the molten material may be conveyed directly at the throat outlet and, optionally after thermal conditioning, to a suitable fiberization station.

[0012] It should be noted that in practice, raw material introduced in line with the side opening (i.e. vertically) will be discharged as quickly as possible, due not only to the short distance separating the introduction area of ​​the raw material from said opening, but also to the thermal convection movements prevailing in the bath of molten material.

[0013] Such discharge rates prove to be detrimental to the final quality of the glass to be produced. Indeed, in so far as the raw materials thus introduced vertically into the side opening have a very short residence time in the bath of molten material, there is a great risk that their melting may be incomplete when they leave the tank. However, the presence of unmelted (i.e. not completely melted) residues is known to alter the final quality of the glass (for example the presence of particles, variations in viscosity, variations in the thickness of the finished product, etc.) in the case of the production of flat and hollow glass, and to clog or even break fiberizing spinners in the case of the production of glass in the form of inorganic wool (in particular rock wool or glass wool). Summary of the Invention [Problem to be solved by the invention]

[0014] The object of the present invention is to remedy all or some of the drawbacks of the prior art, in particular those mentioned above, by proposing a solution which makes it possible to very largely limit the presence of unmelted residues originating from the raw materials introduced in the vertical vicinity of the openings made in the side walls of an electric glass furnace having a cold or semi-cold top tank. [Means for solving the problem]

[0015] To this end, according to a first aspect, the invention relates to an electric glass furnace, which also comprises a cold or semi-cold top tank and electrodes for melting raw materials introduced into the tank, thus obtaining a bath of molten material, the tank having a side wall with an opening configured to allow the molten material to flow out of the tank. The furnace further comprises means, called "delay" means, which are at least partially immersed in the bath, and are arranged in vertical alignment with the opening and adjacent to the side wall of the tank, configured to increase the residence time in the tank of the raw materials introduced adjacent to the delay means.

[0016] It should be noted that "adjacent to the delay means" in this context means not only adjacent to a zone located at the surface of the bath in direct vertical alignment with the opening made in the side wall, but also adjacent to a zone located at the surface of the bath and which substantially precedes said delay means when moving horizontally away from said side wall.

[0017] Said delay means therefore prove to be particularly advantageous in that they make it possible, due to the increase in residence time, to very significantly reduce the risk of the presence of unmelted material resulting from raw materials being introduced into the tank in close proximity to the vertical direction of the opening in the side wall.

[0018] In certain embodiments, the furnace may further comprise some of the following features, taken alone or in any technically possible combination:

[0019] In a particular embodiment, the delay means comprises a plate, the plate having a layer made of a fire-resistant material and arranged in contact with or near a side wall of the tank, the plate extending in a substantially horizontal mid-plane, where it remains fixed.

[0020] Such a plate, by its positioning, therefore not only makes it possible to prevent the raw material from falling directly vertically onto the opening, but also advantageously prevents raw material that reaches the bath in the vicinity of said plate from being pulled too quickly by convective motion in the direction of said opening.

[0021] In certain embodiments, the plate is substantially sloped from the side wall towards the lower wall of the tank.

[0022] Such an arrangement is advantageous in that raw material introduced in vertical alignment with the openings can be prevented from accumulating above the plate: the inclination of the plate relative to the horizontal actually allows material introduced in this manner to slide away from the side walls and towards the bath.

[0023] In a particular embodiment, the delay means comprises a plate having a layer made of a fire-resistant material and disposed in contact with or near a side wall of the tank, the plate being retractable between two positions including a first substantially horizontal position and a second substantially vertical position.

[0024] The consideration of a retractable plate advantageously makes it possible to control the moment at which it is actually desired to increase the residence time in the tank of the raw material introduced close to said plate.

[0025] In certain embodiments, the plates are heated and the refractory material of the plates is a conductive material such as molybdenum or platinum.

[0026] The heating of the plate, especially when it is in a vertical position, makes it possible to reverse the convection currents that occur in the bath and that are located locally against the side wall that is vertically aligned with the opening, thereby making it possible to move the raw materials introduced into the tank near said plate back towards the center of the bath, thus increasing the residence time in the tank of the raw materials thus introduced. Furthermore, the heating of the plate makes it possible to locally increase the temperature of the glass in the bath, which also contributes to improving the quality of the melt.

[0027] In a particular embodiment, the delay means comprises a plate having a layer made of a refractory material and arranged in contact with or near a side wall of the tank, the plate extending in a substantially vertical mid-plane where it is kept fixed and heated, the refractory material of the plate being a conductive material, such as molybdenum or platinum.

[0028] In a particular embodiment, the plate is immersed in the bath of molten material at a distance from the surface of said bath, preferentially at a distance of 10 centimetres or less from the surface of said bath.

[0029] In certain embodiments, the plate has a dimension in a transverse direction measured along the side wall of the tank that is equal to or greater than the dimension of the opening.

[0030] In general, the dimensions of the plates are not limiting to the invention, however, the inventors have found that superior results are obtained, in terms of increasing the residence time in the tank of the raw material introduced, when the plates have dimensions in said transverse direction equal to or greater than the dimensions of the openings.

[0031] In certain embodiments, the plates extend, for example symmetrically, on either side of the opening in said transverse direction, more particularly over a distance of no more than 20% of the dimension of said opening in said transverse direction.

[0032] In a particular embodiment, the plate extends in said mid-plane (ie horizontally or vertically, depending on the case considered) over a distance between 30 centimetres and 50 centimetres.

[0033] In a particular embodiment, the delay means comprises at least one electrode, e.g. two electrodes, formed in a manner other than a plate and arranged substantially vertically or substantially horizontally, said at least one electrode being separate from the electrode configured to melt the raw material introduced into the tank.

[0034] The use of at least one such electrode reverses the convection currents occurring in the bath and located locally against the side wall vertically aligned with the opening, thereby making it possible to move the raw materials introduced into the tank near said electrode back towards the center of the bath, thus increasing the residence time in the tank of the raw materials thus introduced. Furthermore, the heating of the plate makes it possible to locally increase the temperature of the glass in the bath, which also contributes to improving the quality of the melt.

[0035] In certain embodiments, the side opening is formed by a dam, for example a vertically removable dam.

[0036] According to a second aspect, the invention relates to a method for melting raw materials carried out by an electric glass furnace according to the invention.

[0037] According to a third aspect, the present invention relates to a method for producing glass comprising the step of melting raw materials according to the melting method according to the invention.

[0038] Other characteristics and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, which show an exemplary embodiment thereof, without any limiting characteristics, in which: [Brief description of the drawings]

[0039] [Figure 1] FIG. 1 shows, in its environment, a particular embodiment of an electric glass furnace according to the invention, diagrammatically;

[0040] [Diagram 2] FIG. 2 shows, in its environment, another particular embodiment of an electric glass furnace according to the invention, diagrammatically;

[0041] [Diagram 3] FIG. 3 shows, in its environment, yet another particular embodiment of an electric glass furnace according to the invention, diagrammatically;

[0042] [Figure 4] FIG. 4 shows, in its environment, yet another particular embodiment of an electric glass furnace according to the invention, diagrammatically;

[0043] [Diagram 5] FIG. 5 shows, in its environment, yet another particular embodiment of an electric glass furnace according to the invention, diagrammatically;

[0044] [Figure 6] FIG. 6 is a table for comparing the effectiveness of the furnace according to the invention with conventional furnaces known from the prior art. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] FIG. 1 shows, in its environment, a particular embodiment of an electric glass furnace 100 according to the invention.

[0046] In the remaining description, horizontal, vertical and transverse directions are used without limitation with respect to the axial system (H,V,T) shown in Figures 1 and 2. Also, the electric glass furnace 100 in Figure 1 is shown in vertical cross section.

[0047] By convention, the terms "upper" and "lower", or "top" and "bottom", or "above" and "below" are used in relation to the vertical direction.

[0048] Said electric glass furnace 100 is configured to carry out the melting of raw materials with the purpose of forming a bath of vitrifiable molten material. The material thus melted is intended for the production of glass, and for this purpose the electric glass furnace 100 is integrated into a glass production installation comprising various devices (not shown) capable of carrying out steps of refining and / or homogenization and / or thermal conditioning and / or final shaping of the glass in zones other than the zone in which the electric glass furnace 100 is implemented. Such steps are well known to those skilled in the art and will not be described further here.

[0049] In the remaining description, it is considered in a non-limiting manner that the glass intended to be produced from the molten material in the electric glass furnace 101 is an insulating glass type article. However, it should be noted that considering the production of such insulating glass is only one alternative embodiment of the present invention. Thus, in general, no limitations are placed on the type of glass (e.g., flat glass, glass in the form of mineral wool, glass in the form of fiber yarn, etc.) intended to be produced by the molten material in the electric glass furnace 100 according to the present invention.

[0050] It should be noted that the composition of the raw materials making it possible to manufacture an article of the insulation glass type is also well known to those skilled in the art and will therefore not be detailed here, this remark of course also applies to all other types of glass that can be manufactured according to the invention.

[0051] In the embodiment shown in FIG. 1, the electric glass furnace 100 is of parallelepiped shape and conventionally comprises a tank 110 in which the raw materials are melted, thereby obtaining a bath 120 of molten material.

[0052] The tank 110 has a horizontally extending lower wall 111 forming the bottom of the electric glass furnace 100, and a side wall 112 rising vertically from said lower wall 111, along which the transverse axis T extends. The tank 110 of the electric glass furnace 100 is here a cold-top tank and is therefore covered by a top (not shown in the figures) made of a material known per se, for example a clay material, such as sillimanite.

[0053] The tank 110 (i.e. the walls of the tank 110) are made of a refractory material, for example alumina-zirconia-silica (AZS) or chrome. The side wall 112 typically has an outer metal casing (also called "stiffener") in contact with the surrounding air. This metal casing may have two compartments through which a cooling fluid circulates, for example water (so-called "water jacket" walls).

[0054] The consideration of an electric glass furnace with a cold top tank of parallelepiped shape does not of course constitute a limitation of the invention, and therefore does not prevent the consideration of other shapes, such as a cylindrical shape with a circular base, and a semi-cold top tank, etc.

[0055] Similarly, it is not precluded to consider that the lower wall 111 is inclined with respect to the horizontal, for example in the form of a downwardly pointing cone or other inclined plane, thereby promoting the movement of the molten vitrifiable material towards the bottom of the tank 110 at the start of melting.

[0056] Raw materials 130 useful for the manufacture of glass are introduced into the tank 110 through its top by a mechanical device 140 capable of carrying out the introduction onto the surface of the bath 120 of molten material, and more particularly over the entire surface of the bath 120, considering the tank 110 here as the cold top. As a non-limiting example, as illustrated by Figure 1, said mechanical device 140 corresponds to a batch charger having a rotating mat (also called a "boom") that deposits the composition anywhere on the bath surface.

[0057] The raw material 130 thus introduced and not yet melted forms a crust 121 on the surface of the bath 120 before melting and providing the actual molten material of the bath 120 .

[0058] The melting of the raw material 130 introduced in the tank 110 is carried out by means of the electrode 150. Moreover, the power dissipated around the electrode 150 makes it possible to generate an area of ​​strong convection in the bath 120, thus generating currents strong enough to provide the necessary amount of heat at the interface between the already molten material and the crust 121.

[0059] In this embodiment, the electrodes 150 are arranged on the surface so as to be submerged in the bath 120 of molten material through the crust 121. Moreover, the submerged electrodes 150 extend vertically, are two in number in the example of Fig. 1, and are made of a refractory material (resistant to temperatures above 1000°C), such as molybdenum. It should also be noted that said electrodes 150 are conventionally distributed near the center of the bath 120.

[0060] Of course, other alternative embodiments of the electrodes may be envisaged, such as submerged electrodes extending obliquely, i.e. inclined to the vertical, etc. Furthermore, the number of submerged electrodes, if it is greater than two, does not constitute a limiting factor of the invention.

[0061] Alternatively, or in addition to the electrode 150 disposed on the surface of and immersed in the bath 120, it may be envisioned to use a raised electrode (as opposed to a submerged electrode) disposed through the lower wall 111 and thereby immersed in the bath 120. Again, such a raised electrode may extend vertically or, alternatively, obliquely.

[0062] Finally, optionally in addition to the previous variants, electrodes introduced through the vertical wall 110 can also be envisaged.

[0063] The sidewall 112 of the tank 110 has an opening 113, also referred to elsewhere herein as "side opening 113." The side opening 113 is configured to allow the molten material of the bath 120 to flow out of the tank 110. It should be noted that the side opening 113 does not cover the entire dimension of the sidewall 112 in the transverse direction T.

[0064] More specifically, as shown in FIG. 1, the side opening 113 forms an outlet for the molten material so that it may flow via an outlet channel 160 forming a throat to another area where the steps of refining and / or homogenization and / or thermal conditioning and / or final shaping of the glass are typically performed.

[0065] In this embodiment, the side opening 113 has a rectangular shape with a relatively large dimension (i.e., length) in the transverse direction T. However, it will be understood that this is merely a variation of the particular embodiment, and ultimately, no limitations are placed on the shape of the side opening 113.

[0066] 1, it is considered here that the side opening 113 is arranged in the lower part of the side wall 112, in the lower wall 111. However, other variants may be envisaged, in which the side opening 113 is arranged at a level lower than the level of the lower wall 111, or else in an upper part of the side wall 112 (i.e. closer to the surface of the bath 120 than the lower wall 111).

[0067] According to the present invention, the electric glass furnace 100 also has a so-called "delay" means, which is at least partially immersed in the bath 120 and is positioned near the side wall 112 of the tank 110 in vertical alignment with the side opening 113 and configured to increase the residence time in the tank 110 of raw material 130 introduced near said delay means.

[0068] It should be noted that "adjacent to the delay means" here means not only adjacent to a zone located at the surface of the bath 120 that is directly vertically aligned with the side opening 113 (i.e. along the vertical side wall 112), but also adjacent to a zone located at the surface of the bath 120 that substantially precedes the delay means when moving horizontally away from the side wall 112 (thus to the left in the horizontal direction H in Figure 1) and also extends substantially on both sides of the delay means in the transverse direction T.

[0069] Purely by way of example, these two zones are contained within a space 122 bounded by a dotted boundary in FIG. 1, it being understood that this space 122 extends in both the horizontal direction H and the transverse direction T.

[0070] Such a delay means proves to be particularly advantageous in that, due to the increase in residence time, it makes it possible to greatly limit the risk of the presence of unmelted material resulting from raw materials 130 being introduced into the tank 110 close to the vertical of the side opening 113.

[0071] It should also be noted that increasing the residence time in tank 110 of the raw materials 130 introduced near the delay means ultimately makes it possible to increase the minimum residence time of all raw materials introduced into tank 110 (and thus ultimately give them more time to melt).

[0072] In the embodiment of FIG. 1, the retardation means comprises a plate 170 having a layer made of a refractory material (ie capable of withstanding temperatures above 1000° C.).

[0073] By way of non-limiting example, said refractory materials are based on magnesia and / or chromium, or else of the alumina-zirconia-silica type (electrofused or not), etc. Yet another category is envisaged: materials based on metals at high temperatures (e.g. so-called refractory steels, such as molybdenum or platinum) or materials that are cooled.

[0074] In this embodiment, the plate 170 is placed in contact with the side wall 112 of the tank 110, here along its edge. It has a parallelepiped shape and has an upper side 171 and a lower side 172 opposite the upper side 171.

[0075] It should be noted that the shape of the plate 170 is here chosen to be parallelepipedal insofar as the tank 110 itself is parallelepipedal in shape. However, it is understood that in the case of a tank 110 of another shape, the shape of the plate 170 is advantageously adapted so that the plate 170 is in contact with the side wall 112.

[0076] Moreover, considering the plate 170 in contact with the side wall 112 constitutes only one alternative embodiment of the invention. In fact, nothing prevents considering the plate 170 to be located in the vicinity of said side wall 112. The term "in the vicinity" here refers to a distance of about 1-2 centimeters.

[0077] Plate 170 is further partially immersed in bath 120 of molten material and extends in a horizontal plane, referred to as the "mid-plane". More specifically, plate 170 extends perpendicular to side wall 112 of tank 110, with upper side 171 (and lower side 172, respectively) of plate 170 being contained within crust 121 (and respectively contained within bath 120) and plate 170 being fixed within said mid-plane.

[0078] In the embodiment of FIG. 1, the distance separating the lower surface 172 of the plate 170 from the surface of the bath 120 is approximately 1 cm, for example equal to 5 cm.

[0079] Moreover, by way of non-limiting example, the thickness of the plate 170 is substantially equal to 150 mm. However, other values ​​for the thickness of the plate are not excluded. Moreover, in a more general manner, it is not excluded to consider a thickness that is greater or less than the thickness of the crust 121, while the plate 170 is at least partially immersed.

[0080] Such a plate 170, by its positioning, therefore not only makes it possible to prevent raw materials from falling vertically directly onto the side opening 113, but also advantageously makes it possible to prevent raw materials arriving at the bath 120 in the vicinity of said plate 170 (see space 122 shown in FIG. 1 ) from being pulled too quickly by convection movements in the direction of said side opening 113.

[0081] In general, the horizontal and transverse dimensions of plate 170 are not limiting of the present invention. However, the inventors have found that superior results are obtained in terms of increasing the residence time in tank 110 of ingredients introduced proximate said plate 170 when plate 170 has the following: a dimension in the transverse direction T that is greater than or equal to the dimension of the lateral opening 113, and / or The side opening 113 has a horizontal dimension (direction H) that is greater than its vertical dimension (direction V).

[0082] As a non-limiting example, the plate 170 may have dimensions in the transverse direction T or in the horizontal direction H of 800 mm and 1200 mm.

[0083] Preferably, the plate 170 extends in said transverse direction T on both sides of the side opening 113, for example symmetrically, and more particularly over a distance of less than or equal to 20% of the dimension of said side opening 113 in said transverse direction T.

[0084] Of course, it is also conceivable that the plate 170 extends in said transverse direction T to only one side of the lateral opening 113 .

[0085] Furthermore, in the embodiment described here, the plate 170 extends horizontally (ie in the direction H) in said mid-plane over a distance between 30 cm and 50 cm, for example equal to 40 cm.

[0086] A person skilled in the art will understand that in the above arrangement, the transverse and horizontal dimensions of the plate 170 can advantageously be adapted as a function of those of the side opening 113, and therefore the values ​​provided above do not constitute any limitation to the invention.

[0087] Again, other embodiments, listed below, may be envisaged for the plate 170 described above with reference to the embodiment shown in Fig. 1. All these other embodiments may be combined with one another according to all technically feasible combinations.

[0088] Thus, according to one embodiment (not shown), the horizontal plate 170 is immersed in the bath 120 of molten material at a distance from the surface of said bath, preferentially at a distance of 10 centimeters or less from the surface of said bath. In other words, in this embodiment, the plate 170 is completely immersed in the bath 120.

[0089] According to one embodiment (not shown), the horizontal plate 170 has, in addition to a layer made of fire-resistant material, a layer made of metallic material to which the layer made of fire-resistant material is attached. According to a further particular embodiment, a barrier layer may be disposed between the fire-resistant layer and the metallic layer.

[0090] According to one embodiment, the horizontal plate 170 is substantially inclined from the side wall 112 towards the lower wall 111. For example, said inclination is less than 30°, or even more particularly less than 15°. Moreover, in this embodiment, the bottom of the plate 170, i.e. its bottom surface 172, remains submerged in the bath 120, which makes it possible to prevent the raw material 130 introduced from circulating from the center of the furnace 100 to the side wall 112 and passing under the plate 170.

[0091] Such an arrangement is advantageous in that it allows raw material introduced in vertical alignment with the side openings 113 to not accumulate above the plate 170. The inclination of the plate 170 relative to the horizontal actually allows material introduced in this manner to slide away from the side walls 112 and towards the bath 120.

[0092] According to yet another embodiment (not shown), the plate 170 may be considered to be retractable between two positions having the following: a first horizontal (or substantially horizontal) position, corresponding to the positions previously described for the placement of the plate 170; a second vertical (or substantially vertical, if desired) position, which corresponds to the position in which the plate 170 is adjacent (or substantially adjacent) to the side wall 112 .

[0093] Considering a retractable plate 170 in such an arrangement advantageously makes it possible to control the moment at which it is actually desired to increase the residence time in the tank 110 of the raw material 130 introduced near said plate 170.

[0094] Finally, other embodiments may be envisaged in which the plate 170 is heated.

[0095] Heating of the plate 170 is for example carried out by choosing a conductive material, such as molybdenum or platinum, for the refractory layer of the plate 170 and connecting it to one of the electrodes 150; such an embodiment is advantageously carried out when the plate 170 extends (substantially) vertically, although of course heating when the plate 170 extends (substantially) horizontally is not excluded. Furthermore, the heating plate 170 may remain fixed in its nominal position (i.e. vertical or horizontal) or else, according to an embodiment, it may be retractable between two respective vertical and horizontal positions.

[0096] It should be noted that if the plate 170 is heated and extends (substantially) vertically, it may be immersed in the bath 120 by having an outer portion extending outside said bath 120. This outer portion may be used, for example, to fasten the plate 170 to the side wall 112 and may be made of a material other than the refractory material used for the auxiliary portion located below the surface of the bath 120.

[0097] Considering the heating of the plate 170 in the case where it extends (substantially) vertically allows to reverse the convection currents that arise in the bath 120 and are located locally against the side wall 112 vertically aligned with the side opening 113. Such a reversal of the convection currents is represented as a non-limiting example in FIG. 2, which shows the electric glass furnace 100 in a vertical section. In FIG. 2, the convection currents are represented by the velocity field of the molten material of the bath 120 (arrows contained in the tank 110), where a reversal of the convection currents is clearly observed (zone 123, enclosed by a dotted line in FIG. 2). Said reversal therefore advantageously allows the raw materials introduced in the tank 110 near the plate 170 to be returned to the center of the bath 120, thus preventing them from being drawn too quickly through the discharge channel 160.

[0098] The invention has been described so far considering only the embodiment in which the delay means comprises the above-mentioned single plate 170. However, further embodiments may be envisaged.

[0099] 3 thus diagrammatically represents another particular embodiment of an electric glass furnace 100 according to the invention, in whose environment the delay means have an electrode 180 arranged substantially vertically, more particularly immersed ("submerged") vertically in the bath 120. Said submerged electrode 180 is formed in a different manner to a plate (and therefore more different from the plate 170) and is partially immersed in the bath 120, although it is not prevented from imagining that it is completely immersed.

[0100] To operate, this submerged electrode 180 is connected to another electrode, which in this embodiment corresponds to one of the electrodes 150 , located in the center of the bath and used to carry out the melting of the raw material 130 .

[0101] Furthermore, here, the submerged electrode 180, which the glass furnace 110 is equipped with in addition to the above-mentioned electrode 150, is considered to be arranged (substantially) vertically, but it is also quite possible to consider this to be (substantially) horizontal when viewed from the side wall 112.

[0102] 3, electrode 180 differs from electrode 150 in that it is vertically aligned with side opening 113 and is located near side wall 112 of tank 110. In other words, in this embodiment, electrode 180 forming the delay means is located much closer to side wall 112 than electrode 150 conventionally used to melt raw material 130.

[0103] The use of such an electrode 180 produces the same technical effect as described above for the case where a heated vertical plate is used. The electrode 180 thus makes it possible to reverse the convection currents occurring in the bath 120 and located locally opposite the side wall 112 vertically aligned with the side opening 113, thereby returning the raw materials introduced in the tank 110 in the vicinity of said electrode 180 towards the center of the bath 120. This results in a longer residence time in the tank 110 of the raw materials thus introduced.

[0104] It should be noted that although the embodiment of Fig. 3 is described considering a single electrode 180, this number of electrodes is not a limitation of the invention. Thus, for example, it is not precluded to consider that the submerged electrode 180 is connected to another electrode of the same kind, in which case the electric glass furnace 100 has, in addition to the electrode 150, two submerged electrodes of the same kind as shown in Fig. 1.

[0105] The length of electrode 180 does not represent a limiting factor of the present invention. Thus, according to certain embodiments, electrode 180 is configured to be submerged within bath 120 to a predetermined depth in tank 110, for example, until it has an end opposite side opening 113.

[0106] It should be noted that up until now, with reference to the embodiment of figure 3, it has been considered that the delay means only comprise the above-mentioned electrodes 180, and that the plate 170 is absent for its part. These arrangements lead to two observations: (1) The plate 170, when heated as described above, may be viewed as a separate electrode of the electrode 150 that is placed in the center of the bath and that is used to carry out the melting of the raw material 130. In other words, in this embodiment, the heating plate 170 is formed as such an electrode, similar to the electrode 180 described with reference to FIG. 3; (2) It is not precluded to consider further embodiments in which a plate 170, made or not of a non-conductive refractory material, is combined with an electrode 180 to form said delay means. For example, said electrode 180 may be arranged substantially horizontally by passing through said plate 170.

[0107] Finally, independently of the embodiment envisaged for said delay means, the invention has also been described so far considering that the side opening 113 is a cavity made of the material of the side wall 112. However, other alternatives may be envisaged, such as an alternative in which the side opening 113 is (eventually) formed by a dam 190, such as a vertically removable dam. Conventionally, it is understood that the width of the dam 190 matches the width of the side opening 113, the dam 190 not extending beyond said side opening 113. Furthermore, the dam 190 is arranged in a straight line with said opening 113.

[0108] 4 and 5 show diagrammatically an embodiment in which such a dam 190 is implemented in the case where the delay means comprises a plate 170 (similar to FIG. 1) and an electrode 180 (similar to FIG. 3), respectively.

[0109] The dam 190 may, for example, be made of a fire-resistant material and / or have a container (a "water jacket") that allows for the circulation of a cooling liquid therein.

[0110] The dam 190 may be considered to be part of the sidewall 112 of the tank 110 .

[0111] The creation of such a dam 190 will not be described in detail here, but for this purpose reference is advantageously made to WO 2013 / 098504.

[0112] The present invention also relates to a method for melting raw materials 130 carried out using the electric glass furnace 100 according to the present invention. Said melting method (not shown) comprises the steps of introducing raw materials 130 into the tank 110 and melting the raw materials 130 thus introduced. Said melting method may further comprise, in a more particular embodiment, the step of discharging the molten material resulting from the melting of the raw materials 130 through the side opening 113.

[0113] Finally, the invention also concerns a method for producing glass (not shown), comprising a step of melting raw materials 130 according to the melting method according to the invention. Said method also comprises a step of final shaping of the glass, which according to a more particular embodiment may be preceded by a step of refining and / or homogenization and / or thermal conditioning from the molten material that leaves the tank 110 through the side opening 113 and via the discharge channel 160.

[0114] A specific example of an embodiment of the electric glass furnace 100 is then described with respect to the results obtained in terms of increasing the residence time in the tank 110 of the raw material 130 introduced proximate to the delay means.

[0115] More specifically, in this particular embodiment, a parallelepiped shaped electric glass furnace 100 with a rectangular side opening 113 is considered, said furnace 100 intended for the production of barrier glass. The retardation means is here a plate 170 with a thickness equal to 150 mm, a width (measured in the transverse direction T) equal to the width of the side opening 113 increased by 20% and a length (counted in the transverse direction H) equal to 70% of the width of the side opening 113. Furthermore, the plate 170 extends symmetrically along the transverse direction T on both sides of the side opening 113. Finally, said plate 170 has a layer made of electrofusion material of the alumina-zirconia-silica type.

[0116] The results obtained for this exemplary embodiment are set out in the table shown in Figure 6. These are comparative results, expressed in units of time, which make it possible to evaluate the case when plate 170 is used (reference "B" in the table) or when it is not used (reference "A" in the table): - the difference in the minimum residence time T_MIN in the tank 110, - the difference in the mean residence time of the 1% of glass that had the shortest residence time in tank 110, T_MOY_1; - the difference in the mean residence time of the 5% of glasses that had the shortest residence time in tank 110, T_MOY_5; - The difference in the average residence time of the 10% of glass that had the shortest residence time in tank 110, T_MOY_10.

[0117] From these results, it can be seen that when the electric glass furnace 100 is equipped with the above-mentioned plate 170, the residence times increase by 90%, 55%, 38%, and 27% for T_MIN, T_MOY_1, T_MOY_5, and T_MOY_10, respectively, so that the use of the plate 170 is particularly advantageous with respect to the underlying technical problem.

Claims

1. 1. An electric glass furnace (100) comprising a tank (110) with a cold top or semi-cold top, the tank (110) further comprising electrodes (150) for melting raw materials (130) introduced into the tank to obtain a bath (120) of molten material, the tank (110) having a sidewall (112) with an opening (113) configured to allow the molten material to flow out of the tank; The electric glass furnace (100) is characterized in that the furnace further comprises so-called "delay" means (170, 180) that are at least partially immersed in the bath, are positioned vertically aligned with the opening and adjacent to the side wall of the tank, and are configured to increase the residence time in the tank of the raw materials introduced into a zone vertically aligned with the opening in the side wall and located directly at the surface of the bath, and into a zone located at the surface of the bath and substantially preceding the delay means when moving horizontally from the side wall.

2. 2. The furnace (100) of claim 1, wherein the delay means comprises a plate (170) having a layer made of refractory material and arranged in contact with or near the side wall (112) of the tank, the plate extending in a substantially horizontal mid-plane and maintained fixed therein.

3. 3. The furnace (100) of claim 2, wherein the plate (170) is substantially sloped from the side wall (112) toward the bottom wall (111) of the tank (110).

4. 2. The furnace (100) of claim 1, wherein the delay means comprises a plate (170) having a layer made of refractory material and positioned in contact with or near the side wall (112) of the tank, the plate being retractable between two positions including a first substantially horizontal position and a second substantially vertical position.

5. A furnace (100) according to any one of claims 2 to 4, wherein the plates are heated and the refractory material of the plates is for example a conductive material, such as chromium or platinum.

6. 2. The furnace (100) of claim 1, wherein the delay means comprises a plate (170) having a layer made of refractory material and arranged in contact with or near the side wall (112) of the tank, the plate extending in a substantially vertical mid-plane where it is maintained fixed and heated, and the refractory material of the plate is a conductive material, such as molybdenum or platinum.

7. 7. The furnace (100) according to any one of claims 2 to 4 and 6, wherein the plate (170) is immersed in the bath (120) of molten material at a distance from the surface of the bath, preferentially at a distance of 10 centimeters or less from the surface of the bath.

8. The furnace (100) of any one of claims 2 to 4 and 6, wherein the plate (170) has a dimension in a transverse direction measured along the side wall (112) of the tank (110) that is equal to or greater than a dimension of the opening (113).

9. 9. The furnace (100) of claim 8, wherein the plates (170) extend on both sides of the opening (113) in the transverse direction, for example symmetrically, and more particularly over a distance of not more than 20% of the dimension of the opening in the transverse direction.

10. The furnace (100) of any one of claims 2 to 4 and 6, wherein the plate (170) extends over a distance of between 30 centimeters and 50 centimeters at the mid-plane.

11. 7. The furnace (100) according to any one of claims 2 to 4 and 6, wherein the delay means comprises at least one electrode (180), such as two electrodes, formed in a manner other than a plate and arranged substantially vertically or substantially horizontally, the at least one electrode (180) being different from the electrode (150) configured to melt the raw material (130) introduced into the tank.

12. The furnace (100) according to any one of claims 1 to 4 and 6, wherein the opening (113) is formed by a dam, such as a vertically removable dam.

13. A method for melting raw materials, carried out using an electric glass furnace (100) according to any one of claims 1 to 4 and 6.

14. A method for producing glass, comprising melting raw materials according to the melting method of claim 13.

15. 15. Glass, such as flat glass or insulating glass, obtainable by the method for producing glass according to claim 14.

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