Electric glass furnace, processes of melting and manufacturing glass using said furnace

Abstract

Electric glass furnace, processes for melting and manufacturing glass using said furnace. The invention relates to an electric glass furnace (100) comprising a cold or semi-cold vaulted tank (110) and electrodes (150) for melting raw materials (130) introduced into the tank and thus obtaining a bath (120) of molten material. The tank has a side wall (112) with an opening (113) configured to allow the molten material to flow out of said tank. The furnace further comprises so-called "retarding" means (170, 180) immersed at least partially in the bath, positioned vertically above the opening and near the side wall of the tank, and configured to increase the residence time in the tank of the raw materials introduced near said retarding means. Figure for the abstract: Fig. 1

Description

Title of the invention: Electric glass furnace, methods for melting and manufacturing glass using said furnace. Prior art

[0001] The present invention relates to the general field of glass production. More particularly, it relates to an electric glass furnace configured to allow the melting of raw materials. It also relates to a process for melting raw materials implemented using this electric glass furnace, as well as a glass manufacturing process comprising a raw material melting step conforming to said melting process.

[0002] We know from the prior art various examples of design of furnaces for the manufacture of glass which depend in particular on the product to be manufactured, that is to say on the chemical composition of the glass and its final shaping (glass wool, rock wool, hollow glass or even flat glass).

[0003] In this description, "raw materials" means all materials, vitrifiable materials, natural ores or synthesized products, materials from recycling such as cullet, etc., which can be part of the composition used to feed a glass furnace.

[0004] Similarly, "glass" is understood to mean glass in the broad sense, that is to say, encompassing any material with a vitreous matrix, glass-ceramic or ceramic.

[0005] In addition, the term "manufacturing" includes the indispensable melting stage of the raw materials and, where applicable, all subsequent / complementary stages aimed at refining / conditioning the molten glass for its final shaping, in particular 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.

[0006] More particularly, it is known to use an electric glass furnace to achieve the melting of raw materials, so as to obtain a bath of vitrifiable materials, still commonly called "vitrifiable mixture" or "composition".

[0007] The vitrifiable mixture typically comes from raw materials comprising, for example, a mixture of sand, limestone (calcium carbonate), soda carbonate, dolomite for the manufacture of soda-lime glass (the most used glass for the manufacture of flat glass) or boron trioxide for the manufacture of borosilicate glass, and to which cullet (also called groisil) consisting of glass debris is advantageously added in order in particular to promote melting.

[0008] These raw materials are transformed into a liquid mass forming a bath of molten vitrifiable matter in which even the least miscible particles must dissolve, that is to say those richest in silicon dioxide or silica (SiO2) and poor in sodium oxide (Na2O).

[0009] The electric glass furnace conventionally comprises a refractory material tank for containing the molten material bath, the space above the tank being enclosed by a vault. The raw materials are introduced into the tank via its top, by means of a mechanical device capable of introducing them over all or part of the surface of the molten material bath. This surface acts as a thermal barrier, limiting the temperature above the bath. This type of furnace is also called a "cold vault" (or "semi-cold vault") furnace when the entire surface of the bath (or only a portion of the surface) is intended to be covered with raw materials.

[0010] The heating principle of an electric glass furnace relies in particular on the fact that the thermal energy required to melt the raw materials is supplied to the mass of molten glass (i.e., to the molten pool). More precisely, the electrical melting of glass is based on its property of becoming electrically conductive at temperatures of 800-900 °C, with conductivity increasing with temperature. The glass is therefore heated by the Joule effect, with the molten pool acting as the resistance. The electric current required to achieve this Joule effect is supplied by electrodes immersed in this pool.

[0011] The molten material is conventionally discharged from the tank through an opening in the lower part of the tank's side wall. This side opening is generally (but not necessarily) extended by a groove allowing the molten material to flow to other areas. These areas may be where refining, homogenization, heat conditioning, and final shaping of the glass are carried out (as in the manufacture of flat glass, hollow glass, etc.). Alternatively, when the product to be manufactured is glass in the form of mineral wool (in particular rock wool or glass wool), the molten material can be directly conveyed, from the groove outlet and after any necessary heat conditioning, to a suitable fiber-pulling station.

[0012] In practice, it has been observed that the raw materials introduced directly (i.e., vertically) into the lateral opening are those that are evacuated most rapidly. This rapid evacuation is due not only to the short distance separating the area where the raw materials are introduced from the opening in question, but also to the heat convection currents within the molten material bath.

[0013] Such rapid evacuation proves detrimental with regard to quality final stage of glass production. Indeed, since the raw materials introduced vertically through the side opening have a very short residence time in the molten bath, there is a significant risk that their fusion will not be complete when they leave the vat. The presence of unmelted (i.e., not completely melted) residues is known to alter the final quality of the glass (examples: presence of particles, viscosity variations, thickness variations in the finished product, etc.) in the case of flat and hollow glass production, but also to clog the fiber-laying plates, or even cause them to break, in the case of glass production in the form of mineral wool (particularly rock wool or glass wool). Description of the invention

[0014] The present invention aims to remedy all or part of the disadvantages of the prior art, in particular those set out above, by proposing a solution which makes it possible to greatly limit the presence of unmelted residues from raw materials introduced near the vertical of the opening formed in the side wall of an electric glass furnace comprising a cold or semi-cold vaulted tank.

[0015] To this end, and according to a first aspect, the invention relates to an electric glass furnace comprising a cold or semi-cold vaulted chamber and electrodes for melting raw materials introduced into the chamber and thus obtaining a bath of molten material. The chamber has a side wall with an opening configured to allow the molten material to flow out of said chamber. The furnace further comprises so-called "retarding" means, immersed at least partially in the bath, positioned vertically above the opening and near the side wall of the chamber, and configured to increase the residence time in the chamber of the raw materials introduced near said retarding means.

[0016] It should be noted that "in the vicinity of said retardation means" refers here not only to the area at the level of the bath surface directly vertically above the opening made in the side wall, but also to the area at the level of the bath surface which substantially precedes said retardation means when moving horizontally away from said side wall.

[0017] Thus, said delaying means prove to be particularly advantageous in that they allow, due to the increase in said residence time, to limit very strongly the risk of presence of unmelted material from raw materials introduced into the tank near the vertical of the opening in the side wall.

[0018] In particular embodiments, the oven may further comprise one or more of the following features, taken individually or in all their variations: technically possible combinations.

[0019] In particular embodiments, said retarding means comprise a plate including a layer made of refractory material and arranged in contact with or near the side wall of the tank, said plate extending in a substantially horizontal average plane in which it is held fixed.

[0020] Such a plate, due to its arrangement, therefore not only prevents raw materials from falling directly vertically from the opening, but also advantageously prevents raw materials which reach the bath in the vicinity of said plate from being carried too quickly by convection movements towards said opening.

[0021] In particular embodiments, the plate is substantially inclined, from the side wall, towards a lower wall of the tank.

[0022] Such arrangements are advantageous in that they prevent raw materials introduced vertically into the opening from accumulating above the plate. The inclination of the plate relative to the horizontal allows the materials thus introduced to slide towards the bath, moving away from the side wall.

[0023] In particular embodiments, said retarding means comprise a plate including a layer made of refractory material and arranged in contact with or near the side wall of the tank, said plate being retractable between two positions comprising a first substantially horizontal position and a second substantially vertical position.

[0024] Considering a retractable plate advantageously allows control of the times at which one actually wishes to increase the residence time in the tank of the raw materials introduced near said plate.

[0025] In particular embodiments, said plate is heated, the refractory material of said plate being a conductive material, for example molybdenum or platinum.

[0026] Heating the plate, particularly when the plate is in a vertical position, reverses the convection currents created in the bath and located locally opposite the side wall vertically above the opening, thus drawing the raw materials introduced into the tank near the plate towards the center of the bath. This results in an increased residence time of the introduced raw materials in the tank. Furthermore, heating the plate locally increases the temperature of the glass in the bath, which also contributes to improving the quality of the melting process.

[0027] In particular embodiments, said retarding means comprise a plate including a layer made of refractory material and arranged at contact or in the vicinity of the side wall of the tank, said plate extending in a substantially vertical average plane in which it is held fixed and being heated, the refractory material of said plate being a conductive material, for example molybdenum or platinum.

[0028] In particular embodiments, the plate is immersed in the molten material bath at a distance from the surface of said bath, preferably at a distance less than or equal to 10 centimeters from the surface of said bath.

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

[0030] Generally speaking, the dimensions of the plate are not limiting to the invention. However, the inventors have found that excellent results, in terms of increasing the residence time of the introduced raw materials in the tank, are obtained when the plate has a dimension greater than or equal to that of the opening in said transverse direction.

[0031] In particular embodiments, the plate extends, in said transverse direction, on either side of the opening, for example symmetrically, more particularly over a distance less than or equal to 20% of the dimension of said opening in said transverse direction.

[0032] In particular embodiments, the plate extends in said average plane (i.e. horizontally or vertically as the case envisaged) over a distance of between 30 centimeters and 50 centimeters.

[0033] In particular embodiments, said retardation means comprise at least one electrode, for example two electrodes, formed distinctly from a plate and arranged substantially vertically or substantially horizontally, said at least one electrode being distinct from the electrodes configured to melt the raw materials introduced into the tank.

[0034] Using at least one such electrode reverses the convection currents created in the bath and located locally opposite the side wall vertically above the opening, so as to draw the raw materials introduced into the tank near said electrodes back towards the center of the bath. This results in an increased residence time of the raw materials thus introduced in the tank. Furthermore, heating the plate locally increases the temperature of the glass in the bath, which also contributes to improving the quality of the melting.

[0035] In particular embodiments, the lateral opening is created by a barrier, for example a vertically removable barrier.

[0036] According to a second aspect, the invention relates to a process for melting raw materials implemented by means of an electric glass furnace according to the invention.

[0037] According to a third aspect, the invention relates to a method for manufacturing glass comprising a step of melting raw materials in accordance with a melting process according to the invention. Brief description of the drawings

[0038] 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:

[0039] [Fig-1] [Fig.1] schematically represents, in its environment, a mode particular of the realization of an electric glass furnace according to the invention;

[0040] [Fig.2] [Fig.2] schematically represents, in its environment, another particular method of embodiment of the electric glass furnace according to the invention;

[0041] [Fig.3] [Fig.3] schematically represents, in its environment, yet another another particular embodiment of the electric glass furnace according to the invention;

[0042] [Fig.4] [Fig.4] schematically represents, in its environment, yet another another particular embodiment of the electric glass furnace according to the invention;

[0043] [Fig.5] [Fig.5] schematically represents, in its environment, yet another another particular embodiment of the electric glass furnace according to the invention;

[0044] [Fig.6] [Fig.6] is a table allowing comparison of the efficiency of an oven in accordance with the invention with a traditional oven as known from the prior art.

[0045] Description of embodiments

[0046] Fig. 1 schematically represents, in its environment, a particular embodiment of an electric glass furnace 100 according to the invention.

[0047] In the following description, the horizontal, vertical and transverse orientations are considered without limitation in reference to the trihedron (H, V, T) shown in Figures 1 and 2. Also, the electric glass furnace 100 of [Fig.1] is shown there in a vertical section.

[0048] By convention, the terms "superior" and "inferior" or "top" and "bottom" or "above" and "below" are used with reference to the vertical orientation.

[0049] Said electric glass furnace 100 is configured to melt raw materials in order to form a bath of vitrifiable molten material. The molten material thus produced is intended for the manufacture of glass, the electric glass furnace 100 being integrated for this purpose into a glass manufacturing installation comprising, in areas other than those where the electric glass furnace 100 is located, various devices (not shown in the figures) capable of carrying out refining and / or homogenization and / or thermal conditioning and / or final shaping of the glass. Such steps are well known to those skilled in the art, and are therefore not described further here.

[0050] For the purposes of this description, the glass to be manufactured from the material melted in the electric glass furnace 101 is considered, without limitation, to be an insulating glass product. It is important to note, however, that considering the manufacture of such insulating glass is only one variant implementation of the invention. Therefore, and generally speaking, there are no limitations on the type of glass to be manufactured using the material melted in the electric glass furnace 100 according to the invention (e.g., flat glass, glass in the form of mineral wool, glass in the form of so-called textile fibers, etc.).

[0051] It should be noted that the composition of the raw materials used to manufacture a product of the insulating glass type is also well known to those skilled in the art and therefore not described in detail here. Of course, this observation also applies to all other types of glass that can be manufactured according to the invention.

[0052] In the embodiment illustrated by [Fig.1], the electric glass furnace 100 is parallelepiped in shape, and conventionally comprises a tank 110 in which the raw materials are melted so as to obtain the bath 120 of molten material.

[0053] The tank 110 has a lower wall 111 forming the floor of the electric glass furnace 100 and extending horizontally, as well as a side wall 112 rising vertically from said lower wall 111, the transverse axis T extending along said side wall 112. The tank 110 of the electric glass furnace 100 is here a cold vault tank, and is therefore surmounted by a vault (not shown in the figures) made of a material known per se, for example a clay material such as sillimanite.

[0054] The tank 110 (i.e., the walls of the tank 110) is made of refractory material, for example, alumina zirconia silica or chromium. The side wall 112 generally comprises an outer metal casing (also called the "reinforcement") in contact with the ambient air. This metal casing may include two partitions between which a cooling fluid, for example water, circulates (the so-called "water jacket" in the Anglo-Saxon literature).

[0055] The fact that an electric glass furnace is parallelepiped in shape and has a cold-vaulted chamber does not, of course, constitute a limitation of the invention. Thus, nothing precludes considering another shape, such as, for example, a cylindrical shape with a circular base, as well as a semi-cold-vaulted chamber.

[0056] Similarly, nothing excludes considering a lower wall 111 inclined with respect to the horizontal, for example in the form of a cone pointing downwards or an inclined plane, so as to promote the downward movement of the vat 110 of molten vitrifiable material at the beginning of melting.

[0057] The raw materials 130 useful for the manufacture of glass are introduced into the tank 110 is introduced via its top by means of a mechanical device 140 capable of introducing the molten material onto the surface of the bath 120, more specifically onto the entire surface of the bath 120, given that the tank 110 is considered here to have a cold vault. By way of a non-limiting example, and as illustrated by [Fig. 1], said mechanical device 140 corresponds to a loader with a rotating conveyor belt (also called a "boom" in English-language literature) that deposits the composition at any point on the surface of the bath.

[0058] The raw materials 130 thus introduced and not yet melted form a crust 121 on the surface of the bath 120 before melting and properly feeding the molten material of the bath 120.

[0059] The melting of the raw materials 130 introduced into the tank 110 is carried out by means of electrodes 150. In addition, the power dissipated around the electrodes 150 makes it possible to generate areas of strong convection in the bath 120, thus creating currents intense enough to bring the necessary heat to the boundary between the already molten material and the crust 121.

[0060] In the present embodiment, the electrodes 150 are arranged on the surface so as to immerse in the molten bath 120 through the crust 121. Furthermore, the immersing electrodes 150 extend vertically and, in the example of [Fig. 1], are two in number and made of a refractory material (resistant to temperatures above 1000°C), for example, molybdenum. It should also be noted that said electrodes 150 are conventionally distributed near the center of the bath 120.

[0061] Of course, other embodiments of the electrodes are conceivable, such as immersion electrodes extending obliquely, that is, inclined with respect to the vertical orientation. Furthermore, the number of immersion electrodes is not a limiting factor of the invention as long as it exceeds two.

[0062] As an alternative or in addition to electrodes 150 arranged on the surface of the bath 120 and immersed in it, it may also be envisaged to use rising electrodes (as opposed to immersing electrodes) arranged through the lower wall 111 so as to be immersed in the bath 120. Again, such rising electrodes may extend vertically or even obliquely.

[0063] Finally, possibly in addition to the previous variants, electrodes introduced through the vertical wall 110 can also be considered.

[0064] The side wall 112 of the tank 110 has an opening 113, also referred to as the "side opening 113" in the following description. This side opening 113 is configured to allow the molten material from the bath 120 to flow out of the tank 110. It should be noted that this side opening 113 does not cover the entire dimension of the side wall 112 in the transverse direction T.

[0065] More particularly, and as illustrated by [Fig. 1], the lateral opening 113 forms an outlet for the molten material which can then flow, via an evacuation channel 160 forming a groove, towards other areas in which refining and / or homogenization and / or thermal conditioning and / or final shaping of the glass are typically carried out.

[0066] In the present embodiment, the lateral opening 113 has a rectangular shape, of greater dimension (i.e. length) along the transverse direction T. It is understood, however, that this is only a particular variant of the embodiment, and that ultimately no limitation is attached to the shape of the lateral opening 113.

[0067] Furthermore, and as illustrated by [Fig. 1], it is considered here that the lateral opening 113 is arranged in the lower part of the lateral wall 112, at the level of the lower wall 111. That being said, it remains possible to consider other variants in which the lateral opening 113 is arranged at a level lower than that of the lower wall 111, or even in the upper part of the lateral wall 112 (i.e. closer to the surface of the bath 120 than to the lower wall 111).

[0068] According to the invention, the electric glass furnace 100 also includes so-called "delaying" means immersed at least in part in the bath 120, positioned vertically from the side opening 113 and in the vicinity of the side wall 112 of the tank 110, and configured to increase the residence time in the tank 110 of the raw materials 130 introduced near said delaying means.

[0069] It should be noted that by "in the vicinity of said retardation means", reference is made here not only to the area at the level of the surface of the bath 120 directly vertically from the lateral opening 113 (i.e. following the lateral wall 112 vertically), but also to the area at the level of the surface of the bath 120 which substantially precedes said retardation means when moving away horizontally (i.e. to the left in the horizontal direction H on the [Fig.1]) from said lateral wall 112, but also which extends substantially on either side of said retardation means in the transverse direction T.

[0070] By way of pure illustration, these two zones are contained in the space 122 delimited by a dotted boundary in [Fig.1], it being understood that this space 122 extends both in the horizontal direction H and also in the transverse direction T.

[0071] Such delaying means prove particularly advantageous in that they allow, due to the increase in said residence time, to limit very strongly the risk of presence of unmelted material from raw materials 130 introduced into the tank 110 near the vertical of the lateral opening 113.

[0072] It should also be noted that increasing the residence time in the tank 110 of the raw materials 130 introduced near said retarding means ultimately increases the minimum residence time of all the raw materials introduced into said tank 110 (and therefore, ultimately, gives them more time to melt).

[0073] In the embodiment of [Fig.1], said retardation means comprise a plate 170 including a layer made of refractory material (i.e. resistant to temperatures above 1000°C).

[0074] By way of non-limiting example, said refractory material is magnesia- and / or chromium-based, or is of the alumina-zirconia-silica type (electrofused or not). Yet another conceivable category is that of materials based on metals that withstand high temperatures (example: so-called refractory steels such as molybdenum or platinum) or are cooled.

[0075] In the present embodiment, said plate 170 is arranged in contact with the side wall 112 of the tank 110, here along its edge. It has a parallelepiped shape and comprises an upper face 171 and a lower face 172 opposite said upper face 171.

[0076] It is important to note that the shape of the plate 170 is chosen here to be parallelepiped-shaped, since the tank 110 is itself parallelepiped-shaped. However, it is understood that for another shape of tank 110, the shape of the plate 170 is advantageously adapted so that it is in contact with the lateral wall 112.

[0077] Furthermore, considering the plate 170 in contact with the side wall 112 is only one alternative implementation of the invention. Indeed, nothing precludes considering the plate 170 as arranged in the vicinity of said side wall 112. "In the vicinity" here refers to a distance of approximately 1 to 2 centimeters.

[0078] The plate 170 is further partially immersed in the molten material bath 120 and extends in a horizontal plane, referred to as the "average plane". More specifically, the plate 170 extends perpendicularly to the lateral wall 112 of the tank 110, and the upper face 171 (respectively the lower face 172) of the plate 170 is contained within the crust 121 (respectively is contained within the bath 120). The plate 170 is further held fixed in said average plane.

[0079] In the example of [Fig.1], the distance separating the lower face 172 of the plate 170 from the surface of the bath 120 is on the order of a centimeter, for example equal to 5 cm.

[0080] Furthermore, and by way of non-limiting example, the thickness of plate 170 is approximately 150 mm. However, nothing precludes considering other values ​​for the plate thickness. Moreover, and more generally, nothing precludes considering a thickness greater or less than that of crust 121, provided that that plate 170 is at least partially submerged.

[0081] Such a plate 170, due to its arrangement, therefore not only prevents raw materials from falling directly vertically from the lateral opening 113, but also advantageously prevents raw materials which reach the bath 120 in the vicinity of said plate 170 (see space 122 illustrated in [Fig. 1]) from being carried too quickly by convection movements towards said lateral opening 113.

[0082] Generally speaking, the horizontal and transverse dimensions of the plate 170 are not limiting to the invention. However, the inventors have found that excellent results, in terms of increasing the residence time in the tank 110 of raw materials introduced near said plate 170, are obtained when the plate 170 has: - a dimension greater than or equal to that of the lateral opening 113 in the transverse direction T, and / or - a horizontal dimension (along the direction H) greater than the vertical dimension (along the direction V) of the lateral opening 113.

[0083] By way of non-limiting example, the plate 170 may have dimensions between 800 mm and 1200 mm in the transverse direction T or in the horizontal direction H.

[0084] Preferably, the plate 170 extends, in said transverse direction T, on either side of the lateral opening 113, for example symmetrically, more particularly over a distance less than or equal to 20% of the dimension of said lateral opening 113 in said transverse direction T.

[0085] Of course, it is also possible to consider that the plate 170 extends, in said transverse direction T, only on one side of the lateral opening 113.

[0086] Furthermore, in the embodiment described here, the plate 170 extends horizontally (i.e. in the direction H) in said average plane over a distance between 30 cm and 50 cm, for example equal to 40 cm.

[0087] A person skilled in the art understands from the preceding provisions that the transverse and horizontal dimensions of the plate 170 can be advantageously adapted according to those of the lateral opening 113, the values ​​provided previously therefore not constituting in any way limitations of the invention.

[0088] Many other embodiments, listed below, are conceivable for the plate 170 as described so far with reference to the embodiment illustrated in [Fig. 1]. These other embodiments are all combinable with each other in any technically feasible combination.

[0089] Thus, according to one embodiment (not illustrated by the figures), the horizontal plate 170 is immersed in the bath 120 of molten material at a distance from the surface said bath, preferably at a distance less than or equal to 10 centimeters from the surface of said bath. In other words, in this mode, the plate 170 is completely immersed in the bath 120.

[0090] According to one embodiment (not illustrated in the figures), the horizontal plate 170 comprises, in addition to the layer made of refractory material, a layer made of metallic material to which said refractory material layer is attached. According to a further specific embodiment, an insulating layer may be arranged between said refractory and metallic layers.

[0091] According to one embodiment, the horizontal plate 170 is substantially inclined from the side wall 112 towards the lower wall 111. For example, this inclination is less than 30°, or even less than 15° in a more specific example. Moreover, in this embodiment, the bottom of the plate 170, that is, its lower face 172, remains immersed in the bath 120, which prevents the introduced raw materials 130 from flowing from the center of the furnace 100 towards the side wall 112 and passing under the plate 170.

[0092] Such arrangements are advantageous in that they allow the raw materials which are introduced vertically through the lateral opening 113 not to accumulate above the plate 170. The inclination of the plate 170 with respect to the horizontal allows the materials thus introduced to slide towards the bath 120 away from the lateral wall 112.

[0093] According to yet another embodiment (not shown in the figures), it is also possible to consider that the plate 170 is retractable between two positions comprising: - a first horizontal position (or substantially horizontal where appropriate) which corresponds to the position described so far for the arrangement of plate 170, - a second vertical position (or substantially vertical where appropriate) which corresponds to a position in which plate 170 is against (or substantially against) the side wall 112.

[0094] Considering a retractable plate 170 according to such arrangements advantageously allows control of the times at which one actually wishes to increase the residence time in the tank 110 of the raw materials 130 introduced near said plate 170.

[0095] Finally, it is also possible to consider other embodiments in which said plate 170 is heated.

[0096] The heating of the plate 170 is, for example, achieved by choosing a conductive material, such as molybdenum or platinum, for the refractory layer of the plate 170, and by connecting this layer to one of the electrodes 150. Such an embodiment is advantageously implemented when the plate 170 extends (Variously) vertically, but nothing, of course, precludes considering heating when the 170 plate extends (variously) horizontally. Furthermore, the heated 170 plate can be held fixed in its nominal position (i.e., vertically or horizontally), or, according to certain embodiments, be retractable between two positions, respectively vertical and horizontal.

[0097] It is noted that when the plate 170 is heated and extends (substantially) vertically, it can be immersed in the bath 120 by presenting an external part extending outside of said bath 120. This external part is for example used to fix the plate 170 to the side wall 112 and is made of a material other than the refractory material used for the complementary part located below the surface of the bath 120.

[0098] Considering the heating of the plate 170 when it extends (substantially) vertically allows the convection currents created in the bath 120 and located locally opposite the side wall 112 vertically above the side opening 113 to be reversed. Such a reversal of the convection currents is illustrated by way of no limitation in [Fig.2] in which the electric glass furnace 100 is shown in a vertical section. In [Fig.2], the convection currents are represented by means of the velocity field (arrows contained in the tank 110) of the molten material in the bath 120, and the said reversal of the convection currents can be clearly observed there (area 123 surrounded by dashed lines in [Fig.2]).The inversion in question therefore advantageously allows the raw materials introduced into the tank 110 near the plate 170 to be brought back towards the center of the bath 120, thus preventing them from being carried too quickly through the evacuation channel 160.

[0099] The invention has been described so far considering only embodiments in which the retarding means comprise said single plate 170. However, it is possible to consider other embodiments.

[0100] Thus, [Fig.3] schematically represents, in its environment, another particular embodiment of the electric glass furnace 100 according to the invention in which the retarding means comprise an electrode 180 arranged substantially vertically, more particularly immersed vertically in the bath 120. Said immersion electrode 180 is formed in a manner distinct from a plate (and is therefore a fortiori distinct from the plate 170) as well as partially immersed in the bath 120, but nothing excludes the possibility that it may be completely immersed.

[0101] To operate, this immersion electrode 180 is in the present embodiment connected to another electrode which corresponds to one of the electrodes 150 arranged in the middle of the bath and used to carry out the melting of the raw materials 130.

[0102] Furthermore, although it is considered here that the immersion electrode 180 equipping the furnace glass 110 in addition to the said electrodes 150 is arranged in a (substantially) vertical manner, it remains quite possible to consider that it is arranged in a (substantially) horizontal manner, from the lateral wall 112.

[0103] As illustrated by [Fig.3], the electrode 180 differs from the electrodes 150 in that it is positioned vertically from the lateral opening 113 and in the vicinity of the lateral wall 112 of the tank 110. In other words, the electrode 180 forming, in the present embodiment, said retardation means is placed much closer to the lateral wall 112 than are the electrodes 150 conventionally used to carry out the melting of the raw materials 130.

[0104] Using such an electrode 180 produces a technical effect similar to that described previously for the case where a vertical heating plate is used. Thus, the electrode 180 reverses the convection currents created in the bath 120 and located locally opposite the side wall 112 vertically above the side opening 113, so as to return the raw materials introduced into the tank 110 near said electrode 180 towards the center of the bath 120. This results in an increase in the residence time of the raw materials thus introduced in the tank 110.

[0105] Although the mode of [Fig. 3] has been described considering a single electrode 180, it is important to note that this number of electrodes is not limiting to the invention. Thus, nothing precludes, for example, considering that said immersion electrode 180 is connected to another electrode of the same type, in which case said electric glass furnace 100 comprises, in addition to the electrodes 150, two immersion electrodes of the same type as that illustrated in [Fig. 1].

[0106] The length of the electrode 180 is also not a limiting factor of the invention. Thus, according to a particular embodiment, the electrode 180 is configured to immerse in the bath 120 to a given depth of the tank 110, for example until one end is opposite the lateral opening 113.

[0107] It is important to note that, up to now, with reference to the method in [Fig. 3], it has been assumed that the delay means comprise only the electrode 180, the plate 170 not being present. These arrangements call for two remarks: 1) the plate 170, when heated as described above, can be seen as an electrode distinct from the electrodes 150 arranged in the middle of the bath and used to carry out the melting of the raw materials 130. In other words, in this mode, the heated plate 170 forms as such an electrode in the same way as the electrode 180 described with reference to [Fig.3]; 2) Nothing precludes considering other embodiments in which the plate 170, whether or not made of non-conductive refractory material, is combined with an electrode 180 to form said retarding means. For example, said electrode 180 can be arranged in a substantially horizontal manner by passing through said plate 170.

[0108] Finally, regardless of the embodiment envisaged for said delaying means, the invention has also been described so far considering the lateral opening 113 to be a cavity formed in the material of the lateral wall 112. However, other alternatives are conceivable, such as, for example, an alternative in which the lateral opening 113 is created by (results from) a dam 190, for example, a vertically removable dam. Conventionally, the width of the dam 190 is adapted to the width of the lateral opening 113, it being understood that the dam 190 does not extend beyond said lateral opening 113. Furthermore, the dam 190 is positioned directly above said opening 113.

[0109] Fig. 4 and Fig. 5 schematically illustrate embodiments in which such a barrier 190 is implemented, in cases where the retarding means comprise respectively a plate 170 (analogous to Fig. 1) and an electrode 180 (analogous to Fig. 3).

[0110] Said dam 190 is for example made of refractory material and / or includes a chamber allowing the circulation of a cooling liquid within it (“water jacket” in English).

[0111] It is noted that the dam 190 can be seen as forming part of the side wall 112 of the tank 110.

[0112] The construction of such a dam 190 is not described in more detail here, document WO 2013 / 098504 can be advantageously consulted for this purpose.

[0113] The invention also relates to a process for melting raw materials 130 implemented using the electric glass furnace 100 according to the invention. Said melting process (not illustrated in the figures) comprises a step of introducing raw materials 130 into the tank 110 and a step of melting the raw materials 130 thus introduced. Said melting process may further comprise, in a more specific implementation, a step of removing, through the lateral opening 113, the molten material obtained from the melting of the raw materials 130.

[0114] Finally, the invention also covers a glass manufacturing process (not illustrated in the figures) comprising a raw material melting step 130 in accordance with the melting process according to the invention. This manufacturing process also includes a final glass shaping step which, according to more specific implementation examples, may be preceded by refining and / or homogenization and / or heat conditioning steps using the molten material that flows out of the tank 110 through the side opening 113 and via the discharge channel 160.

[0115] We will now describe results obtained for a particular example of realization of the electric glass furnace 100, in terms of increasing the residence time in the tank 110 of the raw materials 130 introduced near the retarding means.

[0116] More particularly, for this specific embodiment, a parallelepiped-shaped electric glass furnace 100 with a rectangular lateral opening 113 is considered, said furnace 100 being intended for the production of insulating glass. The retarding means here are a plate 170 only, with a thickness of 150 mm, a width (measured in the transverse direction T) equal to the width of the lateral opening 113 plus 20%, and a length (measured in the horizontal direction H) equal to 70% of the width of the lateral opening 113. Furthermore, the plate 170 extends symmetrically, along the transverse direction T, on either side of the lateral opening 113. Finally, said plate 170 has a layer made of an electrofused alumina-zirconia-silica material.

[0117] The results obtained for this embodiment are listed in the table illustrated in [Fig. 6]. These are comparative results expressed in hours, allowing for an assessment of the performance in cases where plate 170 is used (reference "B" in the table) or not (reference "A" in the table): - the difference in minimum residence time T_MIN in tank 110, - the difference in average residence time T_MOY_1 of the 1% of glass that remained the shortest time in tank 110, - the difference in average residence time T_M0Y_5 of the 5% of glass that remained the shortest time in tank 110, - the difference in average residence time T_MOY_10 of the 10% of glass that stayed the shortest time in tank 110.

[0118] It appears from these results that the use of the plate 170 is particularly advantageous with regard to the underlying technical problem, since the residence time increases by 90%, 55%, 38% and 27% for respectively T_MIN, T_MOY_1, T_MOY_5 and T_MOY_10 when the electric glass furnace 100 is equipped with said plate 170.

Claims

Demands

1. Electric glass furnace (100) comprising a cold or semi-cold vaulted tank (110) and electrodes (150) for melting raw materials (130) introduced into the tank and thus obtaining a bath (120) of molten material, the tank comprising a side wall (112) comprising an opening (113) configured to allow the flow of the molten material out of said tank, the furnace being characterized in that it further comprises so-called "delaying" means (170, 180) immersed at least partially in the bath, positioned vertically above the opening and in the vicinity of the side wall of the tank, and configured to increase the residence time in the tank of the raw materials introduced into the area located at the level of the surface of the bath directly vertically above the opening made in the side wall,but also in the area located at the surface of the bath and which substantially precedes said retarding means when moving horizontally away from said lateral wall.

2. Oven (100) according to claim 1, wherein said retarding means comprise a plate (170) comprising a layer made of refractory material and arranged in contact with or near the side wall (112) of the vessel, said plate extending in a substantially horizontal average plane in which it is held fixed.

3. Oven (100) according to claim 2, in which the plate (170) is substantially inclined, from the side wall (112), towards a lower wall (111) of the tank (110).

4. Oven (100) according to claim 1, wherein said retarding means comprise a plate (170) comprising a layer made of refractory material and arranged in contact with or near the side wall (112) of the vessel, said plate being retractable between two positions comprising a first substantially horizontal position and a second substantially vertical position.

5. Oven (100) according to any one of claims 2 to 4, wherein said plate is heated, the refractory material of said plate being for example a conductive material, for example chromium or platinum.

6. Oven (100) according to claim 1, wherein said retarding means comprise a plate (170) including a layer made of refractory material and arranged in contact with or near the wall lateral (112) of the tank, said plate extending in a substantially vertical mean plane in which it is held fixed and being heated, the refractory material of said plate being a conductive material, for example molybdenum or platinum.

7. Furnace (100) according to any one of claims 2 to 6, wherein the plate (170) is immersed in the bath (120) of molten material at a distance from the surface of said bath, preferably at a distance less than or equal to 10 centimeters from the surface of said bath.

8. Oven (100) according to any one of claims 2 to 7, wherein the plate (170) has a dimension greater than or equal to that of the opening (113) in a transverse direction measured along the side wall (112) of the tank (110).

9. Oven (100) according to claim 8, wherein the plate (170) extends, in said transverse direction, on either side of the opening (113), for example symmetrically, more particularly over a distance less than or equal to 20% of the dimension of said opening in said transverse direction.

10. Oven (100) according to any one of claims 2 to 9, wherein the plate (170) extends in said mean plane over a distance of between 30 centimeters and 50 centimeters.

11. Oven (100) according to any one of claims 1 to 10, wherein said retarding means comprise at least one electrode (180), for example two electrodes), formed distinctly from a plate and arranged substantially vertically or substantially horizontally, said at least one electrode (180) being distinct from the electrodes (150) configured to melt the raw materials (130) introduced into the vessel.

12. Oven (100) according to any one of claims 1 to 11, wherein the opening (113) is created by a dam, for example a vertically removable dam.

13. A method for melting raw materials implemented using an electric glass furnace (100) according to any one of claims 1 to 12.

14. A method for manufacturing glass comprising a step of melting raw materials according to a melting process according to claim 13.

15. Glass, for example flat glass or insulating glass, obtained by means of a glass manufacturing process according to claim 14.

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