METHOD FOR MANUFACTURING GLASS, HYBRID GLASS FURNACE FOR CARRYING OUT THE MANUFACTURING PROCESS

Description

Previous technique

[0001] The present invention belongs to the general field of glass manufacturing. More particularly, it relates to a manufacturing process comprising a step of melting vitrifiable materials to produce glass. It also relates to a hybrid glass furnace configured to implement said manufacturing process. The invention finds a particularly advantageous, though not limiting, application in the case where the glass to be produced is borosilicate glass.

[0002] In this description, "vitrifiable materials" means all materials, natural ores or synthesized products, materials from recycling such as cullet, etc., which can be used in the composition to feed a glass furnace intended for the manufacture of glass.

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

[0004] In addition, the term "manufacturing" includes the indispensable melting stage of the vitrifiable 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 (flaps, bottles), glass in the form of mineral wool (in particular rock wool or glass wool) used for its thermal or acoustic insulation properties, or even possibly glass in the form of so-called textile yarns used in reinforcement.

[0005] Several examples of furnace designs for melting vitrifiable materials are known from the prior art, producing a molten bath, commonly called a "vitrifiable mixture" or "composition," from which glass can be manufactured. More specifically, and particularly to address the environmental challenge of reducing carbon dioxide (CO2) emissions, a known method involves using a flame furnace (via burners) supplemented by electric heating (via electrodes immersed in the melt). A furnace of this design thus combines several energy sources: combustion energy, for example, from a fossil fuel (generally gas), and electrical energy. Such a furnace is also called a "hybrid" glass furnace.

[0006] A conventional hybrid glass furnace design comprises a hot-vaulted furnace, this furnace being divided (virtually or physically by means of a suitable vertical partition) into two heating zones. "Heating zones" refers to sections of the furnace, distributed from upstream to downstream according to the direction of flow of the vitrifiable materials introduced into the furnace, and differing between them with regard to the proportion of combustion energy (respectively electrical energy) used in each to heat the vitrifiable materials.

[0007] More specifically, the current design of a hybrid glass furnace consists of having an upstream heating zone intended for melting the vitrifiable materials and mainly powered by electrical energy, as well as a downstream heating zone more intended for refining the glass composition (i.e. improving the quality of the glass so that it contains as few unmelted particles as possible, or even as few bubbles) and mainly powered by combustion energy.

[0008] This design optimizes heating efficiency (or heat transfer) in both the upstream and downstream heating zones of the hybrid glass furnace. Electrical energy is prioritized in the upstream heating zone, which is dedicated to melting the glassable materials, because approximately 99% of the power is transferred from the electrodes to the glass bath. By comparison, the power transferred to the glassable materials by burners in the upstream heating zone is significantly lower, around 60%, varying depending on the fuel / oxidizer mixture, particularly the oxygen content and / or the use of preheating. This is one of the reasons why this type of hybrid glass furnace design has become the standard for glass manufacturing.

[0009] US4184863 A refers to a process for melting vitrifiable materials in a hybrid furnace. The first heating zone contains burners, and the second heating zone comprises electrodes immersed in the molten material bath. The proportion of combustion energy used to melt vitrifiable materials in the first zone is unknown, while the proportion of electrical energy used to melt vitrifiable materials in the second zone is 100%.

[0010] US5765489 A teaches a process for treating waste incinerator residues (e.g., slag) containing up to 5% unburned organic components, using a burner in an oxidizing atmosphere in the first part of a furnace and electrodes in the second part of the furnace, with heavy metals being separated at the bottom. The resulting purified slag pellets can be used in the construction industry.

[0011] US4584007 A sign to use multiple heating methods in one area.

[0012] During operation, the appearance of a phenomenon known as "foaming" on the surface of the molten material bath is commonly observed in a glass furnace. The presence of this foam results primarily from the content of the materials to be vitrified. Indeed, these materials typically contain, for recycling purposes, used materials such as household or flat cullet and / or glass wool (e.g., glass wool waste from a production line or end-of-life products). These used materials contribute to increasing the proportion of carbon chains (organic pollutants on bottle cullet, for example, or binders in mineral wool) as well as sulfate in the bath. Furthermore, particularly near electrodes, but not exclusively, the foaming phenomenon is thermo-activated; the sulfate desolubilizes by reacting with the added carbon, thus generating the foam in question.

[0013] The inventors have highlighted that the foam then forms a thermal barrier which is particularly detrimental to the overall heating efficiency of such a hybrid glass furnace for the reasons detailed below.

[0014] In the upstream heating zone, where foam formation is favored due to the predominant use of electrical energy for heating, the foam forms a thermal barrier at the interface between the glass bath and the floating, unmelted glassable materials. Consequently, this thermal barrier limits the transfer of heat generated by the electrodes to the newly introduced glassable materials on the surface of the glass bath. The melting of these materials in the tank is therefore only partial, which complicates tonnage control and increases the risk of the bath overflowing the tank.

[0015] Foam may also be present in the downstream heating zone. This can result from foam transfer from the upstream zone and / or the presence of unmelted material from the upstream heating zone, which maintains the foaming phenomenon, and / or the high temperatures reached in this downstream zone. Since combustion energy is used predominantly in this area, the problem of heat transfer from the burners to the bath is therefore significant. Indeed, the foam then forms a thermal barrier between the burners and the glass bath intended to be heated and refined in the downstream heating zone.

[0016] The following is a non-limiting example to illustrate the consequences of the screening effect resulting from the presence of foam, which forms said thermal screen. In the case of using air burners, for a power input of 200 kW / m², it is estimated that approximately 40 kW / m² (plus or minus + / - 10 kW / m²) will be transferred to the glass bath in the presence of foam forming said thermal screen, while this is, by comparison, approximately 120 kW / m² (plus or minus + / - 10 kW / m²) for the vitrifiable materials present on the surface of the glass bath.In the case of the use of electrodes, for a power input of 200 kW / m², it is known that approximately 198 kW / m² will be transferred to the glass bath (which is related to the aforementioned design of the hybrid glass furnace) but on the other hand it is estimated that only about 40 kW / m² (plus or minus + / - 10 kW / m²) will be transferred to the vitrifiable materials to be melted present on the surface of the bath and this again due to the thermal screen formed by the foam.

[0017] Thus, limiting the overall heating efficiency of the hybrid furnace means that the foaming phenomenon hinders the use of cullet-based products and / or glass wool as vitrifiable materials, i.e., their recycling. In other words, the foaming phenomenon limits the recycling capacity of a hybrid furnace and leads to significant overconsumption of energy, or even a temperature increase that contributes to the premature wear of the furnace refractories.

[0018] Current attempts to address this foaming problem are far from optimal, as they primarily involve implementing countermeasures such as adding solid oxidants like sodium nitrate (NaNO3) and manganese oxide (MnO2). Indeed, the use of oxidants is itself limited, particularly by NOx emissions and the need to maintain a biosoluble glass target. Consequently, increasing the quantity of oxidants is not feasible, thus limiting recycling in vitrifiable materials.

[0019] It should be noted that the foaming phenomenon described above, although present regardless of the composition of the vitrifiable materials, is more particularly problematic (in terms of the amount of foam generated) when the glass intended to be manufactured is a borosilicate glass. Description of the invention

[0020] 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 maximize the heating efficiency (or heat transfer) of each of the energies used (combustion, electricity) as well as the recycling capacity within a hybrid furnace.

[0021] To this end, and according to a first aspect, the invention relates to a glass manufacturing process comprising a step of melting vitrifiable materials intended for the manufacture of said glass, said vitrifiable materials containing a proportion of carbonaceous organic matter of between 0.5% and 10%, in which the step of melting the vitrifiable materials is carried out by means of a hybrid glass furnace comprising a hot-vaulted tank, said tank comprising from upstream to downstream: a first heating zone comprising combustion heating means, a second heating zone comprising electrodes immersed in the molten material bath, said melting step being implemented so that the share of combustion energy used to melt vitrifiable materials in the first zone is at least 50%, and the share of electrical energy used to melt vitrifiable materials in the second zone is at least 50%, prioritizing the use of combustion energy in the first heating zone in order to limit the foaming phenomenon in said first heating zone and, conversely, the use of electrical energy in the second heating zone in such a way as to maximize the heating efficiency of each of said energies used in the furnace.

[0022] Advantageously, the prioritization of combustion energy in the first heating zone and, conversely, of electrical energy in the second heating zone during the melting stage is determined according to the proportion of carbonaceous organic matter contained in the vitrifiable materials.

[0023] According to an important feature, the glassmaking process according to the invention implies, for those skilled in the art, a paradigm shift in the design of the glass furnace intended for its implementation. Indeed, as described above, the design of the hybrid glass furnace according to the prior art has established the principle of using electrical energy in the upstream heating zone and combustion energy in the downstream heating zone due to the respective efficiency of the heat transfer obtained.

[0024] Thus, the person skilled in the art is dissuaded from modifying such a design of furnace, moreover when the implementation of the invention leads him to a use of electrical and combustion energies in the heating zones of the tank which goes precisely against by reversing the majority energy in each, that is to say which is nothing less than the opposite.

[0025] The manufacturing process according to the invention therefore makes it possible to prioritize the use of combustion energy in the first heating zone, and, conversely, to prioritize the use of electrical energy in the second heating zone.

[0026] By proceeding in this way, the risk of the sulfate in the glassable materials interacting with the carbon chains also present in the glassable materials is greatly reduced, preventing the formation of very hot spots within the glass. In other words, this method effectively limits foaming in the initial heating zone.

[0027] Furthermore, if foam forms, the main heating means (burners or electrodes) of each zone is not then separated from what it must heat by a layer of foam forming a thermal screen, i.e. the screening or thermal screen previously present in the prior art.

[0028] Consequently, the invention maximizes the heating efficiency or heat transfer of each of the energy sources used in the furnace. Indeed, since foam formation is significantly limited in the first heating zone, the problem of poor heat transfer between the bath and the vitrifiable materials is also minimized, which greatly promotes the melting of the vitrifiable materials introduced into the furnace.

[0029] In the second heating zone, where the energy used is mainly electrical, the glass bath then contains almost no more carbonaceous vitrifiable materials and sulfate, so that the electric heating has a high efficiency without risk of poor heat transfer.

[0030] Furthermore, if a foam residue forms on the surface of the bath in the second heating zone, it will have no detrimental effect on glass production. On the contrary, this foam residue acts as a thermal barrier against the heat generated beneath the bath's surface by the electrodes, contributing to the bath's excellent thermal insulation. The thermal barrier formed by the foam, which was previously a drawback in the second heating zone with burners, becomes an advantage with electrodes.

[0031] In particular implementation modes, the share of combustion energy used to melt vitrifiable materials in the first zone is at least 60%, and the share of electrical energy used to melt vitrifiable materials in the second zone is at least 60%.

[0032] In specific implementation modes, the share of combustion energy used in the first zone is at least 70%.

[0033] In particular implementation modes, the fusion energy used in the first zone is solely combustion energy.

[0034] In particular modes of implementation, the first heating zone also includes electrodes immersed in the bath of molten material, the melting step being implemented in such a way that the proportion of electrical energy used in the first zone allows the temperature of the bath to be maintained above a given temperature, for example a devitrification temperature of the glass.

[0035] In specific implementation modes, the share of electrical energy used in the second zone is at least 70%.

[0036] In specific implementation modes, the fusion energy used in the second zone is solely electrical energy.

[0037] In particular modes of implementation, the second heating zone also includes means of heating by combustion, the melting stage being implemented in such a way that the proportion of combustion energy used in the second zone allows the temperature of the vault to be maintained above a given temperature, for example a condensation temperature of sodium borate.

[0038] In specific implementation modes, the share of combustion energy used in the first zone and the share of electrical energy used in the second zone are equal.

[0039] In particular modes of implementation, the share of combustion energy used in the first zone and the share of electrical energy used in the second zone are different, one being greater than the other or vice versa.

[0040] In specific implementation modes, the combustion energy in the first zone and / or in the second zone is obtained by combustion of hydrogen.

[0041] In specific implementation methods, vitrifiable materials are chosen to enable the manufacture of borosilicate glass.

[0042] In particular implementation methods, the proportion of carbonaceous organic matter contained in the vitrifiable materials, less than or equal to 10%, is between 0.75% and 10%, more preferably between 1% and 10%, even more preferably between 2% and 10%.

[0043] In specific implementation methods, vitrifiable materials include recycled materials, such as cullet, for example in a proportion less than or equal to 90%, and / or mineral wool in a proportion that can, for example, go up to 100%.

[0044] In particular modes of implementation, the combustion fumes produced in the first heating zone are evacuated to the second heating zone up to an exhaust chimney arranged downstream in said second heating zone so as to allow the temperature of the vault in said second heating zone to be maintained by means of said fumes above a given temperature, in particular a condensation temperature of sodium borate.

[0045] According to a second aspect, the invention relates to a hybrid glass furnace configured to implement a glass manufacturing process, said furnace comprising a control unit to control respectively at least the combustion heating means in the first heating zone and the electrodes immersed in the molten material bath in the second heating zone according to the proportion of carbonaceous organic matter contained in the vitrifiable materials, prioritizing the use of combustion energy in the first heating zone in order to limit the foaming phenomenon in said first heating zone and, conversely, the use of electrical energy in the second heating zone, so as to maximize the heating efficiency of each of said energies used in the furnace.

[0046] In certain embodiments, the oven includes a vertical partition configured to: block, at the level of the surface of the molten material bath, the circulation of molten material between the first and second zones, allow the molten material to circulate, at the level of the furnace floor, between the first and second zones.

[0047] The partition's ability (due to its optimized height) to block the flow of molten material between zones at the surface of the melting bath effectively prevents foam that forms in the second heating zone from migrating to the first. In other words, the presence of the vertical partition further optimizes the heating efficiency of the hybrid furnace.

[0048] In particular embodiments, the vault height in the second heating zone is less than the vault height in the first heating zone.

[0049] In particular embodiments, the bath height in the second heating zone is less than the bath height in the first heating zone.

[0050] In particular embodiments, the oven further comprises an exhaust chimney which, arranged in a downstream part of the second heating zone, is configured to evacuate combustion fumes produced in the first heating zone to the second heating zone. Brief description of the drawings

[0051] 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: there figure 1 schematically represents a particular embodiment of a hybrid glass furnace according to the invention; the figure 2 schematically represents another embodiment of a hybrid glass furnace according to the invention; the figure 3 schematically represents yet another embodiment of a hybrid glass furnace according to the invention; the figure 4 schematically represents yet another embodiment of a hybrid glass furnace according to the invention; the figure 5 schematically represents yet another embodiment of a hybrid glass furnace according to the invention. Description of implementation methods

[0052] There figure 1 schematically represents, within its environment, a particular embodiment of a glass furnace 100 according to the invention. More specifically, on the figure 1 , oven 100 is shown there in a side view.

[0053] In the following description, we will adopt, without limitation, the longitudinal, vertical and transverse orientations with reference to the trihedron (L, V, T) represented in the figures.

[0054] By convention, the terms "upstream" and "downstream," as well as "left" and "right," are used with reference to longitudinal orientation. The terms "upper" and "lower" or "top" and "bottom" are used with reference to vertical orientation.

[0055] More specifically, in this description, the terms "upstream" and "downstream" refer to the direction of glass flow in the furnace, with the glass flowing from upstream to downstream, or, put another way, from left to right with respect to the representation of furnace 100 on the figure 1 .

[0056] According to the invention, the furnace 100 comprises a hot vaulted chamber 110, typically made of refractory material, for example Alumina Zirconia Silica or chromium.

[0057] The concept of a "hot vault" in a glassmaking furnace is well known to those skilled in the art, so it is not explained further here. It is only recalled that, according to this design, the introduction of vitrifiable materials into the furnace 110 is carried out from its side (i.e., along its longitudinal orientation), typically by a loading device (not shown in the figures) also called a "loader".

[0058] In the implementation of the figure 1 The tank 110 has a lower wall 111 forming the floor of the furnace 100 and extending horizontally. However, nothing precludes considering, following other examples, a lower wall inclined relative 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 molten vitrifiable material in the tank 110 at the beginning of the melting process.

[0059] The furnace 100 is configured to melt the vitrifiable materials introduced into the tank 110, forming a bath 120 of molten vitrifiable material. This molten material is intended for glassmaking. The furnace 100 is integrated into a glassmaking installation which includes, in areas other than the one containing the furnace 100, various devices (not shown in the figures) capable of carrying out refining, homogenization, 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.

[0060] For the purposes of this description, the glass to be manufactured from the material melted in furnace 100 is considered, without limitation, to be borosilicate glass. However, considering the manufacture of such glass is merely one variant implementation of the invention. Therefore, and generally speaking, there are no limitations on the type of glass that can be manufactured using the material melted in furnace 100 according to the invention.

[0061] It should be noted that the composition of the vitrifiable materials used to manufacture borosilicate glass is 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. Furthermore, aspects related to the proportion of carbonaceous organic matter that can be contained in the vitrifiable materials used are described in more detail later.

[0062] According to the invention, the glass furnace 100 is of the hybrid type. In other words, the melting of the vitrifiable materials in the tank 110, to produce the bath 120, is carried out using two different energy sources, namely combustion energy and electrical energy. The use of each of these energy sources is achieved through suitable heating means of a type known per se, namely: aerial burners arranged between the vault of the furnace 110 and the surface of the bath 120 for the combustion energy, and electrodes, made of refractory material, for example molybdenum, and immersed in the bath 120 for the electrical energy.

[0063] Combustion can be achieved in a known way by combining different types of fuel and oxidizer. Thus, oxygen present in the air is generally used as the oxidizer; this air can be enriched with oxygen to obtain superoxygenated air. Pure oxygen can even be used as the oxidizer in the specific case of oxycombustion.

[0064] As for combustion, the fuel used is generally natural gas, or possibly other fossil products, such as petroleum products like fuel oil.

[0065] The use of fossil fuels naturally has direct consequences for the carbon footprint of glass manufacturing, particularly through the carbon dioxide (CO2) emissions generated by combustion. Therefore, to improve this carbon footprint, it is possible to use a biofuel (also known as a "green fuel") as an alternative to fossil fuels, specifically "biogas," which is a gas composed primarily of methane and carbon dioxide produced through methanation.

[0066] According to yet another alternative, the fuel used in all or part of furnace 100 can be hydrogen (H2) which, compared to biogas, advantageously contains no carbon.

[0067] In its general principle, the hybrid furnace 100 differs from the hybrid furnaces of the prior art in that the tank 110 has from upstream to downstream two heating zones, a first heating zone Z_1 and a second heating zone Z_2, configured to implement a melting step of vitrifiable materials of the glass manufacturing process according to the invention (not illustrated in the figures).

[0068] The execution of the melting step of vitrifiable materials intended for the manufacture of said glass, said vitrifiable materials containing a proportion of carbonaceous organic matter between 0.5% and 10%, is carried out in such a way that: the share of combustion energy used to melt vitrifiable materials in the first zone Z_1 is at least 50% (i.e. the total fusion energy used in the first zone Z_1 to melt vitrifiable materials includes at least 50% combustion energy), and the share of electrical energy used to melt vitrifiable materials in the second zone Z_2 is at least 50% (i.e. the total fusion energy used in the second zone Z_2 to melt vitrifiable materials includes at least 50% electrical energy).

[0069] More specifically, in the embodiment described here, the two heating zones Z_1, Z_2 are in fluidic communication, without any barrier intervening between them.

[0070] Furthermore, each of the aforementioned heating zones Z_1 and Z_2 is advantageously configured to allow the use of both combustion energy and electrical energy. Thus, and as illustrated by the figure 1 The first heating zone Z_1 has three air burners 130_1, 130_2, 130_3 and two electrodes 140_1, 140_2. The second heating zone Z_2, on the other hand, has a single air burner 150 and four electrodes 160_1, 160_2, 160_3, 160_4.

[0071] Burners 130_1, 130_2, 130_3, 150 are so-called transverse burners, commonly named as such because of their transverse arrangement, perpendicular to the flow of glass in furnace 100.

[0072] In the implementation of the figure 1 , electrodes 140_1, 140_2, 160_1, 160_2, 160_3, 160_4 are so-called rising electrodes, commonly called this because of their vertical arrangement from the sole 111 of the tank 110. That being said, nothing excludes the possibility that one or more of the electrodes may have a different orientation, for example oblique.

[0073] However, considering such a number of burners and electrodes in each of the heating zones Z_1 and Z_2 is only one implementation variant of the invention. Generally, there is no limitation on the number of burners and electrodes in each heating zone, provided that the proportion of combustion energy (or electrical energy) used in the first zone Z_1 (or the second zone Z_2) is at least 50%.

[0074] Implementing the melting stage of such a glass manufacturing process using the hybrid furnace 100 therefore makes it possible to prioritize the use of combustion energy in the first heating zone Z_1 in order to limit the foaming phenomenon in said first heating zone Z_1, and, conversely, to prioritize the use of electrical energy in the second heating zone Z_2, in order to maximize the heating efficiency (i.e. the heat transfer) of each of said energies used in the furnace 100.

[0075] By proceeding in this way, the risk of the sulfate contained in the vitrifiable materials becoming desolubilized near the electrodes of the first heating zone Z_1 and potentially interacting with the carbon chains also present in the vitrifiable materials is greatly reduced. In other words, this method advantageously limits the foaming phenomenon in the first heating zone Z_1, that is, the consequences of the thermal barrier formed by this foam.

[0076] As a result, the invention makes it possible to maximize the heating efficiency of each of the energies used in the furnace 100. Indeed, the appearance of foam being strongly limited in the first heating zone Z_1, the problem of poor heat transfer between the bath and the vitrifiable materials is also limited, which greatly promotes the melting of the vitrifiable materials introduced into the tank 110.

[0077] According to the invention, the energy source (combustion or electrical) is advantageously never separated from what it is to heat by foam, thereby remedying the disadvantages of the prior art described in the preamble related to the screening or a thermal screen formed by said foam.

[0078] Indeed, the foam—at least limited in the first heating zone—does not rise onto the vitrifiable materials to be melted and therefore no longer forms a thermal barrier, so the melting process, achieved according to the invention primarily by means of burners, is no longer affected. Similarly, in the second heating zone, where heating and refining are primarily achieved by means of electrodes, any foam present no longer acts as a thermal barrier to the (electrical) energy source, as was the case in the prior art with burners.

[0079] In the second heating zone Z_2, where the energy used is primarily electrical, bath 120 contains virtually no carbonaceous matter or sulfate, resulting in high efficiency of electric heating without risk of poor heat transfer. Furthermore, if a foam residue were to form on the surface of bath 120 in the second heating zone Z_2 (as illustrated, for example, in the figure 1 ), this will have no detrimental effect on glass production. On the contrary, this foam residue forms a thermal barrier against the heat generated under the surface of bath 120 by the electrodes, contributing to the good thermal insulation of said bath 120.

[0080] According to a more specific example of implementation of the melting stage, the share of combustion energy used to melt vitrifiable materials in the first zone is at least 60%, and the share of electrical energy used to melt vitrifiable materials in the second zone is at least 60%.

[0081] According to a more specific example of implementation of the fusion step, the share of combustion energy used in the first zone Z_1 is at least 70%, for example the share of combustion energy used in the first zone Z_1 is 75% or even 85%.

[0082] The melting stage can also be implemented so that the proportion of electrical energy used in the first zone Z_1 allows the bath temperature to be maintained above a given temperature, for example a glass devitrification temperature.

[0083] Generally, there is no limitation on the proportion of combustion energy used in zone Z_1, provided that it is greater than or equal to 50%. Thus, nothing precludes, for example, the fusion energy used in the first zone Z_1 from being solely combustion energy (i.e., combustion energy share = 100%). In this respect, it is understood that the presence of electrodes in the first heating zone Z_1 is not essential to the invention.

[0084] As for the second heating zone Z_2, in addition or not to the previous examples relating to the share of combustion energy used in the first heating zone Z_1, the share of electrical energy is at least 70%, for example the share of electrical energy used in the second zone Z_2 is 75% or even 85%.

[0085] Following a more particular implementation method, the melting stage can also be implemented so that the share of combustion energy used in the second zone Z_2 allows the temperature of the vault to be maintained above a given temperature.

[0086] As an example, the aforementioned temperature corresponds to the condensation temperature of sodium borate, approximately 1200 °C. This compound is indeed known for its corrosive properties and for its ability to condense on the walls of the vault if the temperature above bath 120 is not sufficient.

[0087] Generally, there is no limitation on the proportion of electrical energy used in the second zone Z_2, provided that it is greater than or equal to 50%. Thus, nothing precludes, for example, the fusion energy used in the second zone Z_2 from being solely electrical energy (i.e., electrical energy share = 100%). In this respect, it is understood that the presence of burners in the second heating zone Z_2 is not essential to the invention.

[0088] In addition to, or as an alternative to, maintaining the vault temperature above a given temperature via modulation of the combustion energy used in the second heating zone Z_2, the furnace may also include an exhaust chimney 180 configured to evacuate combustion fumes produced in the first heating zone Z_1 to the second heating zone Z_2.

[0089] Advantageously, the chimney 180 is arranged or connected to the downstream part of the second heating zone Z_2. However, there is no limitation attached to the configuration (shape, geometry, arrangement) of said chimney 180, which can for example take the form of openings made in the vault of the tank 110 so as to form a passage for the evacuation of fumes.

[0090] Such a chimney 180, via the evacuation of fumes in the second zone Z_2, also makes it possible to maintain the temperature above a given temperature, and can therefore also help to avoid corrosion effects linked to condensation of sodium borate on the vault of the furnace 100.

[0091] Advantageously, the circulation of fumes (from the first heating zone Z_1) through the second heating zone Z_2 before their evacuation downstream through chimney 180 makes it possible to maintain a vault temperature above a given temperature such as that of condensation of sodium borate, and may even make it possible to eliminate burner 130_4, which is then particularly favorable to a lowering of the vault height in the second heating zone Z_2 of furnace 100.

[0092] As mentioned previously, the melting stage of the glass manufacturing process according to the invention makes it possible to maximize the heating efficiency of each of the energies used in the furnace 100. Consequently, the invention makes it possible to consider an increased use of recycled materials compared to what is practiced in the prior art, so as to maximize the recycling capacity of the furnace 100.

[0093] Thus, according to a particular method of implementing the melting step, the proportion of carbonaceous organic matter contained in the vitrifiable materials introduced into tank 110 is less than or equal to 10%.

[0094] According to an important feature of the invention, the vitrifiable materials intended for the manufacture of glass contain a proportion of carbonaceous organic matter of between 0.5% and 10%, preferably between 0.75% and 10%, more preferably between 1% and 10%, even more preferably between 2% and 10%.

[0095] Vitrifiable materials intended for the manufacture of glass may, for example, contain recycled materials, such as cullet (e.g., household cullet, factory cullet, etc.), for example in a proportion less than or equal to 90%, and / or mineral wool in a proportion that may, for example, go up to 100% (e.g., loading vitrifiable materials corresponding to 100% glass wool to be recycled, which may contain up to 10% binder).

[0096] The furnace 100 includes a control unit UC to control respectively the combustion heating means 130_1, 130_2, 130_3 in the first heating zone Z_1 and the electrodes 160_1, 160_2, 160_3, 160_4 immersed in the bath 120 of molten materials in the second heating zone Z_2 according to the proportion of carbonaceous organic matter contained in the vitrifiable materials.

[0097] Preferably, and according to a first example, during the melting stage, the proportion of combustion energy used to melt vitrifiable materials in the first heating zone Z_1 is 50%, and the proportion of electrical energy used to melt vitrifiable materials in the second heating zone Z_2 is 50%, when the vitrifiable materials contain a proportion of carbonaceous organic matter on the order of 0.5%. In other words, the proportion of combustion energy and the proportion of electrical energy are respectively equal to 50% in each of the said heating zones Z_1 and Z_2.

[0098] Alternatively, the share of combustion energy and the share of electrical energy are not equal, for example the share of combustion energy in the first heating zone Z_1 is 50% and the share of electrical energy in the second heating zone Z_2 is greater than 50%, for example equal to 70%, or even 100%.

[0099] Of course, the share of combustion energy in the first zone Z_1 could alternatively be greater than the share of electrical energy in the second zone Z_2, in particular with a share of electrical energy of 50% and a share of combustion energy greater than 50%, for example equal to 70%, or even 100%.

[0100] Preferably, and according to a second example, during the melting stage, the proportion of combustion energy used to melt vitrifiable materials in the first heating zone Z_1 is 75%, and the proportion of electrical energy used to melt vitrifiable materials in the second heating zone Z_2 is 75%, when the vitrifiable materials contain a proportion of carbonaceous organic matter of approximately 5%. In other words, the proportion of combustion energy and the proportion of electrical energy are then respectively equal to 75% in each of the said heating zones Z_1 and Z_2.

[0101] Preferably, during the melting stage, the proportion of combustion energy used to melt vitrifiable materials in the first heating zone Z_1 is 100%, and the proportion of electrical energy used to melt vitrifiable materials in the second heating zone Z_2 is 100%, when the vitrifiable materials contain a proportion of carbonaceous organic matter equal to 10%.

[0102] In other words, the share of combustion energy and the share of electrical energy are then respectively equal to 100% in each of the said heating zones Z_1; Z_2.

[0103] According to the variants just described for the first example, the share of combustion energy and the share of electrical energy can be different for the second or third example, one being greater than the other or vice versa, each of said shares of energy being at least 50%.

[0104] Thanks to the UC control unit, the furnace 100 is able to be operated by prioritizing the use of combustion energy in the first heating zone Z_1 in order to limit the foaming phenomenon in said first heating zone Z_1 and, conversely, the use of electrical energy in the second heating zone Z_2 in order to maximize the heating efficiency (i.e. the heat transfer) of each of said energies used in the furnace 100.

[0105] We will describe below, by comparison with the embodiment illustrated by the figure 1 , other embodiments illustrated in figures 2 à 5 in which the UC control unit, or even the exhaust chimney, have not been shown, but only for the sake of simplicity, the oven according to the figures 2 à 5 which can of course include a control unit (CU) to control the prioritization of energies, or even a chimney for the evacuation of combustion fumes.

[0106] The hybrid furnace according to the invention has been described so far considering a particular geometry in which no physical separation exists between the two heating zones Z_1, Z_2. Other alternative embodiments are however conceivable.

[0107] There figure 2 schematically represents, in its environment, another particular embodiment of a glass furnace 200 according to the invention.

[0108] Following provisions similar to those described in reference to the figure 1 The hybrid furnace 200 comprises a tank 210 in which vitrifiable materials intended for glassmaking are melted to obtain a bath 220. More specifically, the tank 220 comprises two heating zones, Z_1 and Z_2, from upstream to downstream, the melting stage of the vitrifiable materials being carried out by means of: three air burners 230_1, 230_2, 230_3 and two electrodes 240_1, 240_2 in the first heating zone Z_1, one air burner 250 and four electrodes 260_1, 260_2, 260_3, 260_4 in the second heating zone Z_2.

[0109] Furthermore, in this other embodiment, and as illustrated without limitation by the figure 2 The oven includes a vertical partition 270 configured for: block, at the level of the surface of the molten material bath 220, the circulation of molten material between the first and second zones Z_1, Z_2, allow to circulate, at the level of the hearth 211 of the furnace 200, the molten material between the first and second zones Z_1, Z_2.

[0110] The vertical partition 270 is for example made of refractory material, for example based on magnesia and / or chromium, or of the Alumina-Zircone-Silica type (electrofused or not).

[0111] Alternatively, the vertical partition 270 may include an outer metal envelope (also called "frame"), which is formed of two partitions between which a cooling fluid circulates, for example water (wall called "water jacket" in Anglo-Saxon literature).

[0112] In other words, the vertical partition 270 is configured to create an opening in the lower part of the furnace 200, so that the molten materials in the first heating zone Z_1 can flow to the second heating zone Z_2, and then be evacuated out of the furnace 200.

[0113] It should be noted that the ability of partition 270 (due to its optimized height) to block the flow of molten material between zones Z_1 and Z_2 at the surface of the molten bath 220 effectively prevents foam that forms in the second heating zone Z_2 from migrating to the first heating zone Z_1. In other words, the presence of the vertical partition 270 further optimizes the heating efficiency of the hybrid furnace 200.

[0114] As mentioned previously, it is possible to consider that the melting energy used in the first zone Z_1 is solely combustion energy (i.e., combustion energy share = 100%). Such arrangements are advantageous in this alternative embodiment because they promote convection currents in the bath 220, thereby facilitating the circulation of the molten material between the first and second zones Z_1 and Z_2 at the hearth 211 of the furnace 200.

[0115] When the oven 200 has a smoke evacuation chimney similar to that 180 illustrated by the figure 1 , the vertical partition 270 is then provided in the upper part with at least one opening (not shown) to allow the circulation of said fumes from the first heating zone Z_1 to the second heating zone Z_2, up to said exhaust chimney arranged downstream.

[0116] There figures 3 et 4 schematically represent, in its environment, yet other particular modes of embodiment of glass furnaces 300, 400 according to the invention.

[0117] More specifically, furnace 300 (respectively furnace 400) differs from furnace 100 of the figure 1 (respectively from oven 200 of the figure 2 ) in that the vault height in the second heating zone Z_2 is less than the vault height in the first heating zone Z_1.

[0118] The hybrid oven according to the invention has also been described so far assuming that the bath height in the first zone Z_1 is identical to the bath height in the second zone Z_2. However, such provisions are not limiting to the invention, and nothing precludes embodiments in which the bath height in the second zone Z_2 is less than the bath height in the first zone Z_1. While maintaining such a difference in bath height between zones Z_1 and Z_2, the minimum bath height in the second zone Z_2 could, for example, be between 200 mm and 300 mm.

[0119] Having a lower glass height in the second zone Z_2 advantageously reduces the furnace construction cost, as the amount of refractory material required is minimized. Furthermore, this minimizes energy consumption because the volume of glass to be heated is reduced, thus minimizing heat loss through the refractory walls.

[0120] Preferably, when the bath height in the second zone Z_2 is less than the bath height in the first zone Z_1, the fusion energy used in the second zone Z_2 is only electrical energy, which may allow us to consider, for the second zone Z_2, a vault whose height is flush with the surface of the bath.

[0121] By no means as an exhaustive list, the figure 5 schematically represents another embodiment of a hybrid glass furnace 500 according to the invention, in which the bath height in the second zone Z_2 is less than the bath height in the first zone Z_1. As can be seen on the figure 5 The floor height of oven 500 differs between zones Z_1 and Z_2, which, in this embodiment, makes it possible to obtain the desired difference between bath heights.

[0122] According to yet another aspect, the invention also covers a glass manufacturing process (not illustrated in detail by the figures) which, in addition to the step of melting the vitrifiable materials, includes for example a final shaping step of the glass which may be preceded, according to more particular examples of implementation, by refining and / or homogenizing and / or thermal conditioning steps from the molten material which flows out of the tank.

Claims

1. A method for manufacturing glass, comprising a step of melting vitrifiable materials that are intended for the manufacture of said glass, said vitrifiable materials containing a proportion of carbon-containing organic matter of between 0.5% and 10%, wherein the step of melting the vitrifiable materials is implemented by means of a hybrid glass furnace (100) comprising a hot-top tank (110), said tank comprising, from upstream to downstream: - a first heating zone (Z_1) comprising combustion heating means (130_1, 130_2, 130_3), - a second heating zone (Z_2) comprising electrodes (160_1, 160_2, 160_3, 160_4) immersed in the bath (120) of molten materials, said melting step being implemented such that the proportion of combustion energy used for melting vitrifiable materials in the first zone is at least 50% and the proportion of electrical energy used for melting vitrifiable materials in the second zone is at least 50%, prioritizing the use of the combustion energy in the first heating zone (Z_1) in order to limit foaming in said first heating zone (Z_1) and, conversely, the use of the electrical energy in the second heating zone (Z_2) so as to maximize the heating efficiency of each of said energies used in the furnace.

2. The method according to claim 1, wherein the proportion of combustion energy used in the first zone (Z_1) is at least 70%.

3. The method according to claim 2, wherein the melting energy used in the first zone (Z_1) is solely combustion energy.

4. The method according to any one of claims 1 to 2, wherein the first heating zone (Z_1) further comprises electrodes (140_1, 140_2) immersed in the bath of molten materials, the melting step is implemented so that the proportion of electrical energy used in the first zone (Z_1) enables the bath temperature there to be maintained above a given temperature, for example a glass devitrification temperature.

5. The method according to any one of claims 1 to 4, wherein the proportion of electrical energy used in the second zone (Z_2) is at least 70%.

6. The method according to claim 5, wherein the melting energy used in the second zone (Z_2) is solely electrical energy.

7. The method according to any one of claims 1 to 5, wherein the second heating zone (Z_2) further comprises combustion heating means (130_4), the melting step being implemented in such a way that the proportion of combustion energy used in the second zone (Z_2) enables the temperature there of the crown to be maintained above a given temperature, for example a sodium borate condensation temperature.

8. The method according to any one of claims 1 to 7, wherein the proportion of combustion energy used in the first zone (Z_1) and the proportion of electrical energy used in the second zone (Z_2) are equal or different, one being greater than the other or vice versa.

9. The method according to any one of claims 1 to 8, wherein the combustion energy in the first zone (Z_1) and / or in the second zone (Z_2) is obtained by hydrogen combustion.

10. The method according to any one of claims 1 to 9, wherein the vitrifiable materials are chosen to enable the manufacture of borosilicate glass.

11. The method according to any one of claims 1 to 10, wherein the proportion of carbonaceous organic matter contained in the vitrifiable materials, less than or equal to 10%, is between 0.75% and 10%, more preferentially between 1% and 10%, even more preferentially between 2% and 10%.

12. The method according to any one of claims 1 to 11, wherein the vitrifiable materials comprise recycled materials, such as cullet, for example in a proportion less than or equal to 90%, and / or mineral wool in a proportion less than or equal to 100%.

13. The method according to any one of claims 1 to 12, wherein the combustion fumes produced in the first heating zone (Z_1) are discharged towards the second heating zone (Z_2) as far as an exhaust chimney (180) arranged downstream in said second heating zone (Z_2) so as to enable the temperature of the crown in said second heating zone (Z_2) to be maintained above a given temperature, in particular a sodium borate condensation temperature, by means of said fumes.

14. A hybrid glass furnace (100, 200, 300, 400, 500) configured to implement the method for manufacturing glass, according to any one of claims 1 to 13, said furnace comprising a control unit (UC) for respectively controlling at least the combustion heating means (130_1, 130_2, 130_3) in the first heating zone (Z_1) and the electrodes (160_1, 160_2, 160_3, 160_4) immersed in the bath (120) of molten materials in the second heating zone (Z_2) on the basis of the proportion of carbonaceous organic matter contained in the vitrifiable materials, prioritizing the use of the combustion energy in the first heating zone (Z_1) in order to limit foaming in said first heating zone (Z_1) and, conversely, the use of the electrical energy in the second heating zone (Z_2) so as to maximize the heating efficiency of each of said energies used in the furnace.

15. The furnace (200) according to claim 14, the furnace comprising a vertical partition (270) configured to: - block the flow of melt between the first and second zones (Z_1, Z_2) on the surface of the bath of molten materials, - allow melt to circulate between the first and second zones on the hearth (211) of the furnace.

16. The furnace (300, 400) according to any one of claims 14 to 15, wherein the crown height in the second heating zone (Z_2) is lower than the crown height in the first heating zone (Z_1).

17. The furnace (500) according to any one of claims 14 to 16, wherein the bath height in the second heating zone (Z_2) is lower than the bath height in the first heating zone (Z_1).

18. The furnace according to any one of claims 14 to 17, the furnace further comprising an exhaust chimney (180) which, arranged in a downstream portion of the second heating zone (Z_2), is configured to discharge combustion fumes produced in the first heating zone to the second heating zone.