CN118251366A

CN118251366A - Hybrid glass preparation furnace using electrofusion for supplying float units

Info

Publication number: CN118251366A
Application number: CN202280076131.0A
Authority: CN
Inventors: A·萨格特; P·德迪亚努斯; A·勒弗热; J-M·孔布
Original assignee: Saint Gobain Glass France SAS
Current assignee: Saint Gobain Glass France SAS
Priority date: 2021-11-18
Filing date: 2022-11-15
Publication date: 2024-06-25

Abstract

The invention relates to a hybrid glass preparation furnace (10) for supplying a unit for floating glass on a bath of molten metal, said hybrid furnace (10) comprising, from upstream to downstream: -an electrofusion zone (100) having a cold roof (140) comprising electrodes (110) for melting the vitrifiable mixture to obtain a glass bath (130); -a refining and homogenizing zone (200) with a hot top comprising a first convection loop (210) and a second convection loop (220); and-a zone (300) for cooling the glass formed by a conditioning tank (310), said conditioning tank (310) being traversed by said second convection loop (220) and connected to at least one flow channel (400), characterized in that the hybrid furnace (10) comprises at least one tank neck (160), called a first tank neck, comprising a bottom plate (165) and connecting the electric melting zone (100) to the refining and homogenizing zone (200) of the glass, and in that said hybrid furnace (10) comprises "non-return" separation means (170) located at said first tank neck (160) designed to prevent the molten glass in the refining and homogenizing zone (200) from returning to the melting zone (100).

Description

Hybrid glass preparation furnace using electrofusion for supplying float units

Field of the invention

The present invention relates to a hybrid glass preparation furnace using electrofusion for supplying a float unit.

More particularly, the present invention relates to a hybrid glass making furnace using electrofusion for supplying float units, further comprising an electrofusion zone with cold roof for melting the vitrifiable mixture, which is connected by a first trough neck to a refining and homogenizing zone with hot roof, which comprises two glass convection loops in order to obtain a suitable amount of high quality glass.

The hybrid glass production furnace according to the invention is not only capable of providing high quality glass with less than 0.1 bubbles per liter, but also capable of providing such glass at a pull rate of at least 400 tons per day in order to supply a float glass unit on a molten metal bath intended for producing sheet glass.

Technical Field

Different example designs of furnaces for producing glass are known from the prior art, which depend inter alia on the product to be produced, i.e. the final shaping of the glass.

Thus, different furnace designs are distinguished depending on whether the planned production involves glass fiber, industrial hollow glass forming or sheet glass.

One of the industrial challenges in glass furnace design is the ability to obtain glass whose quality requirements depend on the product. In this respect, sheet glass production is one of the relatively most demanding productions.

The very large volume of sheet glass is used in a wide variety of applications due to its versatility. It is widely used in the electronic (flat screen), architectural and automotive fields, where it can be processed using a variety of techniques (bending, tempering, etc.) making it the base glass for a full range of glass products.

In view of the quality and quantity concerns involved, the present invention is particularly directed to glass production for industrially shaping such sheet glass, which is conventionally obtained by means of a glass float unit on a bath of molten metal (usually tin), which is why such sheet glass is still known as float glass.

For the production of sheet glass, it is desirable to be able to supply high quality glass to the float unit, i.e. glass containing as few bubbles as possible, i.e. glass generally having less than 0.5 bubbles per liter.

The glass quality is determined in particular, but not exclusively, by the number of bubbles present in the glass, expressed as "bubbles/liter". The smaller the number of bubbles per liter in the glass, the higher the quality thereof is considered.

It should also be remembered that the presence of bubbles (or gaseous defects) in the glass is inherent to the glass production process, wherein there are typically three successive steps or stages: melting, refining and homogenizing, and heat conditioning of glass.

The presence of bubbles in the glass occurs during the melting step during which the vitrifiable mixture, also known as a "batch" (composition) is melted. The vitrifiable mixture consists of raw materials comprising, for example, a mixture of sand, limestone (calcium carbonate), soda ash and dolomite for the preparation of soda lime glass, the glass most commonly used for the preparation of flat glass, to which cullet consisting of broken glass is advantageously added to promote melting.

The vitrifiable mixture is converted into a liquid mass in which even the least miscible particles, i.e. the particles most rich in silica or silica (SiO ₂) and low in sodium oxide (Na ₂ O), are dissolved.

Sodium carbonate (Na ₂CO₃) starts to react with sand at 775 ℃ releasing carbon dioxide (CO ₂) bubbles into the liquid, which becomes more and more viscous as the carbonate is converted to silicate. Likewise, the conversion of limestone particles into lime and the decomposition of dolomite also results in the emission of carbon dioxide (CO ₂).

When no solid particles are present in the molten glass liquid anymore, the melting phase is completed, the molten glass liquid has become highly viscous and this phase of the preparation process is filled with air and bubbles.

The refining and homogenizing steps then make it possible to eliminate the bubbles present in the molten glass. It is known to use advantageously during this stage "refining agents", i.e. substances of low concentration, which supply the gases that cause the expansion of the bubbles by decomposing at the melting temperature of the bath, thus accelerating their rise to the glass surface.

The thermal conditioning stage of the preparation method then makes it possible to reduce the temperature of the glass, since at the beginning of the forming operation the viscosity of the glass must generally be at least ten times the viscosity during refining.

Each step of preparing glass, which has just been described, naturally corresponds to the structure of the furnace used to carry out these steps.

Typically, glass melters of this type include a melting zone in which the glass batch material is melted to form a glass bath, followed by a refining and homogenizing zone to eliminate glass bubbles, and finally a heat conditioning zone to cool the glass to its forming temperature, which is well below the temperature that the glass experiences during its production.

From the above mentioned glass manufacturing process we can see that the melting phase is accompanied by the emission of carbon dioxide (CO ₂), one of the main greenhouse gases involved in climate change.

For this reason, efforts are underway to use increasingly higher proportions of cullet to reduce these direct carbon dioxide (CO ₂) emissions, as well as indirect carbon dioxide (CO ₂) emissions associated with the raw materials used in the vitrifiable mixture.

In fact, in addition to the industrial challenges of high quality glass production and achieving high productivity with the lowest possible furnace construction and operation costs, one of the other major challenges currently the glass industry must face is ecology, i.e. the need to find solutions to reduce the carbon footprint (or CO ₂ footprint) of the glass production process.

In order to achieve carbon neutralization, the overall approach (a global approach to the process) to the process is preferred, which seeks to act in a variety of ways to reduce direct and indirect emissions during production, as well as upstream and downstream emissions in the value chain, such as emissions associated with the transportation of upstream materials and downstream products.

Thus, these various approaches include product design and material composition, improving energy efficiency of industrial processes, using renewable and decarbonized energy sources, cooperating with raw material suppliers and carriers to reduce their emissions, and finally exploring technologies for capturing and sequestering residual emissions.

In addition to the direct emissions inherent in the above-described glass manufacturing process, the type of energy used, particularly for the high temperature melting stage (exceeding 1500 ℃), accounts for the largest share of the carbon footprint of the glass manufacturing process, since it generally involves fossil fuels, the most common of which is natural gas or even petroleum products such as fuel oil.

Thus, research into new furnace designs must not only meet industry challenges related to glass quality, but also reduce the carbon footprint of the glass manufacturing process, in terms of direct and indirect carbon dioxide (CO ₂) emissions, especially by reducing fossil fuel usage.

Glass production is performed in a furnace that has evolved from the first pot (or crucible) furnace, gradually to a siemens furnace, which is generally considered an ancestor of today's large continuous melting glass furnaces, such as a transverse flame furnace that can produce up to 1,200 tons of float glass per day.

Thus, the choice of energy for the melt has led to two common large furnace designs for glass production, flame and electric, respectively.

According to a first design, flame melters generally use fossil fuels, particularly natural gas for the burner; thus, heat energy is transferred to the glass by heat exchange between the flame and the glass bath surface.

The above-described cross flame furnace is an example of a furnace conforming to the first design, and is widely used for supplying molten glass to a float unit intended for producing flat glass.

According to a second design, the electric melter is one in which thermal energy is generated by the joule effect in the volume of molten glass.

In fact, glass is an insulating substance at room temperature, becoming conductive at high temperatures, so that it is conceivable to heat them by the joule effect within the glass melt.

However, electric melters are used, for example, for producing special glasses, such as opal glass containing fluorine or lead crystals, or are generally used for producing glass fibers for thermal insulation.

In fact, it is widely recognized by those skilled in the art that such electric melters are not capable of supplying a float glass unit on a molten metal bath for producing flat glass with a sufficient quantity or quality of glass (less than 0.5 bubbles per liter as a reminder).

The prior art electric melters known to the applicant are capable of providing a glass pull rate of at most 200-250 tons/day with hundreds, more generally thousands, of bubbles per liter, which may be suitable for forming hollow glass, typically bottles, but is in no way suitable for the case of making sheet glass, and thus is not suitable for supplying float units.

This is why flame furnaces (e.g. cross flame furnaces) are still the only furnaces that are capable of supplying such float glass units.

However, flame melters rely on the use of fossil fuels (primarily natural gas) such that their carbon footprint is nearly incompatible with the goal of reducing carbon dioxide (CO ₂) emissions (i.e., the carbon footprint of glass production processes).

To complete the description of the design of a furnace for the production of glass according to the prior art, reference will be made to a "third design" of the furnace, which has recently been subjected to known changes in particular with respect to the ecological problem of reducing carbon dioxide (CO ₂) emissions.

A third furnace design is based on flame furnaces but uses electric auxiliary heating, in particular in order to immediately increase the yield of the furnace or to improve the quality of the glass.

Thus, such furnaces are also referred to as "electric flame-assisted furnaces".

Thus, the furnace according to this third design combines multiple energy sources, fossil fuel and electricity, respectively, and is therefore also referred to as a "hybrid" furnace.

The addition of electrically assisted heating makes it possible to improve the melting capacity of the flame furnace, which is limited by the heat transfer that occurs between the flame and the glass bath surface.

However, the operation of such hybrid furnaces is always mainly based on the use of fossil fuels (usually natural gas), so that the impact finally obtained on improving the carbon footprint of the glass production process is still limited.

In fact, the power is used here only as auxiliary heater, so its effect is proportional. Furthermore, to effectively improve the carbon footprint, the power used must still be so-called "green" power, i.e. power produced from renewable and decarbonized energy sources.

The object of the present invention is in particular to propose a new design of glass production furnace which is capable of providing high quality glass and of supplying float glass units for producing flat glass, the energy consumption level of which is such that a significantly reduced emission of carbon dioxide (CO ₂) from the glass production process can be obtained.

Disclosure of Invention

To this end, the invention proposes a hybrid glass preparation furnace for supplying units for floating glass on a bath of molten metal, comprising, from upstream to downstream:

-an electrofusion zone with a cold roof comprising electrodes for melting the vitrifiable mixture to obtain a glass bath;

-a refining and homogenizing zone with a hot top comprising a first convection loop and a second convection loop; and

A zone for cooling the glass formed by a conditioning tank (conditioningtank) traversed by the second convection circuit and connected to at least one flow channel,

Characterized in that the hybrid melting furnace comprises at least one trough neck, called a first trough neck, which comprises a bottom plate and connects the electric melting zone with the refining and homogenizing zone of the glass, and in that the hybrid melting furnace comprises "non-return" separating means, which are located at the first trough neck and are designed to prevent the molten glass in the refining and homogenizing zone from returning to the melting zone.

Advantageously, the first tank neck of the hybrid furnace, which, in combination with the separation device, participates in controlling the temperature of the glass, is achieved by: it makes it possible to ensure that the glass flowing from the electrofusion zone to the glass refining and homogenizing zone is cooled, so that control of the first and second convection loops is obtained, to finally facilitate the production of the desired quantity of high quality glass.

Advantageously, the hybrid furnace comprises means for cooling the glass, which are able to selectively cool the glass in the neck of the first tank. Preferably, the hybrid furnace comprises an air circulation cooling device.

Advantageously, the tool for cooling glass can ensure a variable cooling, i.e. the cooling is adjustable, in particular determined as a function of the temperature of the glass.

The hybrid furnace according to the invention makes it possible to combine, on the one hand, a high-performance vitrifiable mixture melt in the melting zone with, on the other hand, temperature control of the glass introduced into the refining and homogenizing zone, in particular to obtain a flow of glass therein using the first and second convection loops, respectively, thereby obtaining in particular a high quality glass.

In fact, the separating device limits the amount of molten glass flowing downstream from the melting zone, thereby promoting cooling of the glass in the first trough neck and why there is a synergy between the separating device and the first trough neck.

In addition, the separation device prevents glass from returning to the first trough neck, from the refining and homogenizing zone to the melting zone, thereby enabling the molten glass to cool in the first trough neck and then to refine in the refining and homogenizing zone comprising the first and second convection loops.

Advantageously, the separation means ensuring the function of preventing the glass from returning to the electrofusion zone comprise at least one elevation (elevation) of the weir (dam) and/or of the bottom plate of the first trough neck, depending on the embodiment.

According to the invention, the overall design of the hybrid furnace (with an electrofusion zone and a refining zone with two convection loops, and a first trough neck connecting them together) together with a separation device (in other words, the combination of both) makes it possible not only to obtain a high quality glass with less than 0.1 bubbles/liter, but also to provide a quantity of such glass with a lifting rate greater than or equal to 400 tons/day, in order in particular to be able to supply a float unit.

Thus, the hybrid furnace according to the invention is able to provide the glass with a forming zone consisting of a float glass unit on a molten metal bath for the production of flat glass.

Advantageously and contrary to the assumptions of the person skilled in the art, the hybrid furnace according to the invention thus enables to combine high quality glass with a high yield of glass, which is achieved with a cold top electrofusion zone (and no longer a flame fusion zone).

Thus, in the present invention, the electric power accounts for more than 60%, or even 80%, and even more of the total energy used in the hybrid furnace for the glass production process.

By analogy with the third furnace design described above, the furnace according to the invention is referred to as "hybrid", as a result of the use of two different energy sources (electric energy and fuel energy, respectively), the term "hybrid" is therefore used to qualify it.

However, analogy to the present invention does not fall outside this scope, as electrical energy is the only energy source used to melt glass when making glass, and fuel energy, fossil fuel or equivalent is therefore used only in furnaces for refining and homogenizing the glass.

Advantageously, the hybrid melting furnace according to the invention combines, on the one hand, an electric melting zone with a cold roof and, on the other hand, a refining and homogenizing zone for glass using a flame (i.e. by combustion, preferably with electric auxiliary heating), said melting zone and refining zone being separated by a so-called "non-return" separation device, keeping the glass away from the melting zone.

By means of such a combination, in particular a device for separating and controlling the temperature of the glass entering the refining and homogenizing zone, the hybrid furnace according to the invention makes it possible to obtain a high quality glass, i.e. containing less than 0.1 bubbles per liter, while at the same time being able to provide the glass in a large quantity, so that it is possible to advantageously supply a float glass unit for the production of flat glass.

Accordingly, the present invention is not to be construed as limited by the assumption of those skilled in the art that electric melting furnaces would not allow such large amounts of such high quality glass to be obtained.

In the present invention, a high quality glass is obtained in particular by means of this refining and homogenizing step, which is carried out after the electrofusion step, said step being advantageously controlled by the cooling of the glass effected by the first trough neck, which cooling participates in obtaining two convection loops (when controlling the guiding of the glass).

Advantageously, a high quality glass can also be obtained by means of said separation device, which is arranged in the first trough neck of the hybrid furnace and is constructed such that the molten glass does not return from the refining and homogenizing zone to the melting zone.

By means of this separation device, the flow of glass in the neck of the first trough is a "plug" flow.

Advantageously, the separation means are formed by a weir and/or a raised portion of the floor of the neck of the first trough, which are able to prevent, separately or together, the return of molten glass from the refining and homogenizing zone of the hybrid melting furnace according to the invention to the electrofusion zone.

In the hybrid furnace according to the invention, no convection loop or glass recirculation loop extends from the refining and homogenizing zone to the melting zone by means of the separation device.

In contrast, the submerged throat connecting the melting and refining zones does not ensure this function of preventing glass from returning to the furnace. In fact, there is a back flow of glass in such an immersed throat, in particular due to wear of the material.

Furthermore, the glass flowing in the immersed throat is not in contact with the atmosphere, so that it is also not cooled in a controlled and variable manner on the surface, in particular by means of an air-circulation cooling device.

The first trough neck additionally allows glass to flow at a pull rate corresponding to the feed float unit, as compared to an immersed throat whose cross section is structurally limited.

According to the invention, the step of refining and homogenizing the glass is performed on glass advantageously containing little or no unmelted portions, in particular by means of a "non-return" separation device, which makes it possible to increase the residence time of the glass in the electrofusion zone.

The hybrid melting furnace according to the invention is constituted by a combination of features rather than by juxtaposition, since there is an interaction, synergy between the technical features, in particular between the electrofusion zone and the refining and homogenizing zone with two convection loops, thanks to the first tank neck and the relative separating means, respectively, which are able to allow the glass to cool and prevent the glass from returning to the melting zone.

By means of the first trough neck and the separating device, the temperature of the glass can be controlled separately and precisely in the electrofusion zone on the one hand and in the refining and homogenizing zone on the other hand.

Preferably, the length of the neck of the first trough is configured to achieve a cooling function to reduce the temperature of the glass that subsequently flows into the refining and homogenizing zone.

In fact, molten glass obtained by electrofusion generally has a higher temperature, in particular compared to flame fusion.

For example, the temperature of the glass in the melting zone is about 1450 ℃, while the desired temperature of the glass in the downstream portion of the first trough neck is more about 1300 ℃ to 1350 ℃.

Advantageously, the hybrid furnace comprises glass cooling means arranged in the neck of the first tank in order to selectively cool the glass, i.e. to control the cooling so as to actively regulate the glass temperature.

Preferably, the cooling means are formed by at least one air circulation cooling device, air being introduced into the atmosphere of the neck of the first tank to come into contact with the surface of the glass bath and being extracted to remove the heat (calories) transferred from the glass into the air.

Alternatively, the cooling tool is immersed in the glass flowing through the neck of the first trough from upstream to downstream to allow it to cool.

Such cooling means immersed in the glass are for example formed by a weir forming all or part of the separation means and cooled by a cooling circuit (in particular a "water jacket" type circuit) with a heat transfer fluid.

According to another embodiment, the cooling means are formed by vertical studs arranged in the neck of the first tank and immersed in the glass, which are cooled by a cooling circuit with a heat transfer fluid to remove the heat transferred by the glass.

According to another embodiment, the cooling means are able to cool the structure of the first groove neck in contact with the glass, the cooling being carried out from outside the structure of the first groove neck.

Of course, the cooling means associated with the first tank neck can be implemented alone or in combination, according to the various examples just given.

Advantageously, the means for cooling the glass associated with the first channel neck allows for selective control of the temperature of the glass, which is likely to vary, particularly as the rate of draw varies, as an increase in the rate of draw results in an increase in the temperature of the glass.

Such variable glass cooling would not be possible using an immersed throat as compared to such tools for cooling glass associated with the first trough neck.

Advantageously, the hybrid furnace according to the invention employs electrical energy for melting the vitrifiable mixture and relies on the increasing availability of "green" power, for example obtained from wind energy, solar energy, etc., rather than from fossil fuels such as coal or petroleum.

Advantageously, the fuel energy source used in the burner of the refining and homogenizing zone is not a fossil fuel such as natural gas, but another equivalent fuel energy source, preferably hydrogen, or alternatively biomethane.

Accordingly, the hybrid furnace according to the present invention can solve not only the problems of high quality and pulling rate of glass required for supplying a float unit, respectively, but also the ecological problems so as to allow the reduction of the carbon footprint of the glass manufacturing process.

Other features of the furnace according to the invention:

-the separation device comprises a weir intended to be partially immersed in a glass bath;

The separation device consists only of a weir capable of preventing the molten glass from returning from the refining and homogenizing zone to the melting zone, preferably at the upstream end of the neck of the first trough;

-said separating means comprise at least one elevation of the floor of the first tank neck;

the separating means consist only of the raised portion of the bottom plate, which prevents the molten glass from returning from the refining and homogenizing zone to the melting zone;

the separating means ensuring the function of preventing the glass from returning to the melting zone comprise at least one elevation of the weir and/or bottom plate;

-the separating means ensuring the function of preventing the glass from returning to the melting zone comprise a weir in combination with at least one elevation of said bottom plate;

-at least one elevation of the soleplate comprises, from upstream to downstream, at least one rising section, a top section and a descending section;

-the weir is arranged at the neck of the first trough above the top section of the raised portion of the floor;

-at least one of the rising and falling sections of the at least one elevation of the floor is inclined with respect to the horizontal plane and/or comprises a top section;

-the at least one elevation has a maximum height that wholly or partly determines the passage cross-section of the molten glass in the neck of the first trough;

-mounting the weir so as to be vertically movable to allow adjustment of its depth of immersion in the glass bath;

-the weir, alone or in combination with the at least one elevation, determining a cross-section of a channel of molten glass that is variable as a function of the depth adjustment of the weir;

The weir is removable, that is to say detachable, so as to allow its replacement and facilitate maintenance of the furnace, in particular in the event of wear;

The hybrid furnace comprises at least one atmosphere separation means, for example a vertical partition, able to separate the atmosphere of the electrofusion zone with cold roof from the atmosphere of the refining and homogenizing zone with hot roof;

-the hybrid furnace comprises a blocking means arranged at the upstream end of the first tank neck, which is capable of maintaining the layer of vitrifiable mixture in the electrofusion zone such that the vitrifiable mixture present on the surface of the glass bath does not penetrate into the first tank neck;

-means for blocking the layer of vitrifiable mixture are formed by the weir;

-the blocking means are formed by isolating means, the free ends of which extend to the surface of the glass bath or are immersed in the glass bath;

-the blocking means is different from the isolating means, the blocking means being attached to or remote from the isolating means;

the hybrid furnace comprises means for cooling the glass, which means are able to cool the glass in the neck of the first tank, in particular at least one air circulation cooling device;

-the hybrid furnace comprises a charging zone in which charging means are arranged to introduce the vitrifiable mixture into the electrofusion zone;

-configuring the charging device to deposit a vitrifiable mixture over the entire surface of the glass bath so as to form an insulating layer between the glass bath and the top of the melting zone;

-electrodes are arranged on the surface so as to be immersed in the vitrifiable mixture, the submerged electrodes preferably extending vertically;

-the electrodes are arranged through the floor of the melting zone so as to be immersed in the vitrifiable mixture, the rising electrodes preferably extending vertically;

-the hybrid furnace comprises a submerged electrode and/or a rising electrode;

said electrofusion zone advantageously comprises a zone of low convection, known as buffer zone, located between the free end of the immersed electrode and the bottom plate of the fusion zone;

-configuring the melting zone to have a determined depth so as to obtain the low convection buffer zone, preferably a depth greater than 600mm, or even preferably greater than 800mm;

-the first convection loop and the second convection loop are separated by a loop inversion zone, which is defined by a hot spot or source corresponding to the hottest spot of glass;

-the refining and homogenizing zone comprises at least one burner arranged to obtain the hot spot determining the loop inversion zone;

-the hybrid furnace comprises a barrier arranged in the loop reversal region;

The hybrid furnace comprises a variation in the depth of the bottom plate relative to the glass surface, preferably at least one elevation, or even a variation in the level, in the refining and homogenizing zone, said depth variation being located in the portion comprising the first convection loop and/or the portion comprising the second convection loop;

The hybrid furnace comprises conditioning means, such as electrically assisted heating and/or bubblers, arranged in the refining and homogenizing zone, capable of making it possible to adjust the convection of the circuit in order to drive the preparation of the glass;

the conditioning tank of the cooling zone comprises, from upstream to downstream, a tank neck, called second tank neck, then working end;

-no back flow occurs after the conditioning tank in a flow channel intended to supply high quality glass to a forming zone containing the float unit; in other words, the flow of glass within the channel is a "piston" type flow;

-configuring the hybrid furnace to supply glass to the float glass unit intended to produce flat glass with a lift rate of greater than or equal to 400 tons/day, preferably 600-900 tons/day, or even 1000 tons/day or more, the high quality glass having less than 0.1 bubbles/liter, preferably less than 0.05 bubbles/liter.

The invention also proposes an assembly for producing flat glass, comprising a hybrid glass production furnace and a downstream float glass unit located on a molten metal bath, which float glass unit is supplied with glass by the furnace via at least one flow channel.

Brief description of the drawings

Further features and advantages of the present invention will become apparent upon reading the following detailed description, for an understanding of which reference is made to the drawings in which:

FIG. 1 is a side view showing a hybrid glass preparation furnace according to a first embodiment of the present invention, the hybrid glass preparation furnace comprising an electrofusion zone with a cold roof connected by a first trough neck to a refining and homogenizing zone with a hot roof, the refining and homogenizing zone comprising a first convection loop and a second convection loop, and then a cooling zone traversed by the second convection loop, and further showing a weir arranged at the first trough neck forming a "non-return" separation device;

FIG. 2 is a top view showing the furnace according to FIG. 1 and showing the electrofusion zone connected to the refining and homogenizing zone by a first trough neck in which weirs are disposed, the weirs being designed to prevent molten glass from returning from the refining and homogenizing zone to the electrofusion zone;

FIG. 3 is a side view similar to FIG. 1 showing a hybrid melting furnace according to a second embodiment of the invention wherein the separation device is formed by at least one raised portion of the weir and the floor of the first trough neck, and showing the weirs associated with the raised portions, respectively configured to prevent molten glass from returning from the refining and homogenizing zone of the furnace to the electric melting zone;

FIG. 4 is a top view similar to FIG. 2 showing the hybrid furnace according to FIG. 3 and showing a preferably movable weir associated with the raised portion of the bottom plate in the first trough neck connecting the melting zone to the refining and homogenizing zone;

Fig. 5 is a side view similar to fig. 1 and 3, showing a hybrid furnace according to a third embodiment of the invention, in which the separating means are formed by only the raised portion of the floor of the first trough neck, and which thus shows a raised portion having a higher height than in the second embodiment, said separating means being configured to prevent molten glass from returning without a weir,

Fig. 6 is a side view showing in detail a part of the hybrid furnace according to fig. 5 and showing a variant embodiment of the elevation of the bottom plate of the first trough neck, comprising a descending section forming an inclined plane, able to ensure a gradual change of the depth of the molten glass towards the refining and homogenizing zone.

Detailed Description

In the remainder of this description, longitudinal, vertical and transverse directions will be used with reference to the shafting (L, V, T) shown in fig. 1-6, without limitation.

The terms "upstream" and "downstream" will also be used, but are not limited to, when referring to a longitudinal direction, and "upper" and "lower" or "top" and "bottom" when referring to a vertical direction, and finally "left" and "right" when referring to a transverse direction.

In this specification, the terms "upstream" and "downstream" correspond to the direction of flow of glass in the furnace, with the glass flowing from upstream to downstream (upstream from A and downstream from A ') along the longitudinal central axis A-A' of the hybrid furnace shown in FIGS. 2 and 4.

Furthermore, the term "loop" is used herein in connection with the recirculation of glass in a furnace, as is well known to those skilled in the art, as is the concept of "cold roof" and "hot roof" for glass making furnaces.

Fig. 1 and 2 are side and top views, respectively, of a hybrid glass production furnace 10 (which is not drawn to scale) illustrating a first embodiment of the present invention.

As noted above, similar to the third furnace design described above, the term "hybrid" is used herein to refer to a furnace according to the present invention because two different energy sources, electrical and fuel energy, respectively, are used during the glass making process in the furnace.

However, a solution similar to the present invention does not fall outside this range, since on the one hand electric energy (constituting the first source) is the only energy source for obtaining glass melting, and on the other hand fossil or equivalent type of fuel energy (constituting the second source) is only used for refining and homogenizing the glass.

The hybrid furnace 10 according to the invention is particularly useful for supplying float glass units on a bath of molten metal (typically tin) to produce sheet glass.

As shown in fig. 1 and 2, the hybrid furnace 10 includes at least one electric melting zone 100, a refining and homogenizing zone 200, and a glass cooling zone 300 in this order from upstream to downstream along a longitudinal central axis A-A' of the furnace. .

According to a first feature of the hybrid furnace 10 of the present invention, the melting zone 100 of the hybrid furnace 10 is powered.

Advantageously, the electrofusion zone 100 is of the "cold top" type.

Advantageously, the step of melting the glass is achieved by using only electric energy during the preparation of the glass, compared to prior art hybrid furnaces, in which the melting step is achieved by a source of fuel energy and electric energy as auxiliary heater.

The electrofusion zone 100 includes electrodes 110 for melting a vitrifiable mixture (or "batch") composed of raw materials and cullet to obtain a glass bath 130.

In a known manner, the cullet consists of glass cullet pieces obtained by recovering glass, which are ground and cleaned before being subsequently added to the raw material to produce the glass again.

Advantageously, the cullet promotes melting, that is to say the vitrifiable glass mixture is transformed by melting.

Furthermore, by recycling the waste glass (glass is infinitely recyclable), cullet allows the waste glass to be upgraded, thereby reducing the amount of raw materials required to make the glass and helping to reduce the carbon footprint in the glass making process.

The hybrid furnace 10 comprises a charging zone 120 in which a charging device 12 (also referred to as a batch charger) is arranged, which is intended to introduce a vitrifiable mixture into the electric melting zone 100, said charging device 12 being schematically shown by an arrow in fig. 1.

Advantageously, the loading device 12 is configured to deposit the vitrifiable mixture on the entire surface of the glass bath 130 so as to form an insulating layer 112 between the glass bath 130 and the top 140 of the electrofusion zone 100, which is why the latter is referred to as "cold-top".

Preferably, the glass bath 130 is uniformly covered with a layer 112 consisting of a vitrifiable mixture, for example of thickness 10cm to 40cm, under which a complex chemical reaction occurs, which, as stated in the preamble of the present application, causes the obtaining of molten glass.

In the cold top electrofusion zone 100, the power dissipated around the electrode 110 creates a high convection zone 132, which high convection zone 132 contains in particular a very strong upward flow, which provides the necessary heat at the boundary between cast iron and the formation of the vitrifiable mixture layer 112.

In the glass manufacturing method according to the related art, besides carbon dioxide (CO ₂), the decomposition of raw materials and the use of fossil energy as fuel for the melting step are also pollution emission sources mainly composed of nitrogen oxides (NO _x), sulfur oxides (SO _x), halogens and dust.

Advantageously, the absence of combustion (flame) in the cold top electrofusion zone 100 of the hybrid furnace 10 according to the present invention results in relatively very low rates of NO _x and SO _x contamination.

Furthermore, although permeable to carbon dioxide (CO ₂), the layer 112 of vitrifiable mixture present on the surface of the bath 130 advantageously makes it possible to trap, by condensation or by chemical reaction, the vapours emitted by the molten glass, which are sometimes toxic depending on the composition.

Advantageously, the electrode 110 is arranged on the surface so as to penetrate the layer 112 covering the surface of the glass bath 130, immersed in the glass bath 130, as shown in fig. 1.

Preferably, the submerged electrode 110 extends vertically. Alternatively, the submerged electrode 110 extends obliquely, i.e., is inclined, so as to have a given angle with respect to the vertical direction.

Alternatively, the electrodes 110 are arranged through the floor 150 of the electrofusion zone 100 so as to be immersed in the bath 130, the rising electrodes (as opposed to the submerged electrodes) preferably extending vertically, or obliquely.

The submerged electrode 110 also allows for easier control of its wear state and causes dissipation of electrical energy (which is advantageously closer to the melting interface) from the vitrifiable mixture layer 112 than electrodes disposed through the floor 150.

Advantageously, the submerged electrode 110 makes it possible to keep the floor 150 of the electrofusion zone 100 free of any openings, compared to the rising electrode.

Preferably, the floor 150 of the electrofusion zone 100 is planar, as shown in FIG. 1.

As a variation, the floor 150 includes at least one variation in depth relative to the surface of the glass bath 130, including at least one elevation and/or at least one level variation.

Preferably, the melting electrode 110 is uniformly distributed in the bath 130. Furthermore, the number of nine electrodes 110 shown in fig. 1 and 2 is merely an illustrative example, and thus is in no way limiting.

Alternatively, the electrofusion zone 100 may cumulatively contain a submerged electrode and a rising electrode.

According to another alternative arrangement, the electrode 110 passes through at least one side wall defining the electrofusion region 100, when the electrode 110 extends horizontally and/or obliquely.

Advantageously, the electrode 110 is made of molybdenum, which refractory metal can withstand temperatures of 1700 ℃, and is particularly suitable for melting glass by the joule effect, since glass becomes conductive only at high temperatures.

Advantageously, the electrofusion zone 100 comprises a low convection zone, referred to as buffer zone 134, located between the free end of the submerged electrode 110 and the bottom plate 150.

Thus, the electrofusion zone 100 is configured to have a depth (P) below the submerged electrode 110 that is determined to achieve such a low convection buffer zone 134.

Preferably, the depth (P) between the free end of the submerged electrode 110 and the bottom plate 150 is greater than 600mm, preferably greater than 800mm.

Such a low convection buffer zone 134 constitutes another reason why the submerged electrode 110 is preferred over a rising electrode passing through the floor 150.

Advantageously, the presence of the low convection buffer zone 134 directly participates in obtaining high quality glass by promoting a longer residence time of the glass in the melting zone 100.

Advantageously, the electrofusion zone 100 and the zone 200 for refining and homogenizing glass are connected to each other by a first trough neck 160 (i.e., a zone of reduced width), as shown in FIG. 2.

Advantageously, said first trough neck 160 of the hybrid melting furnace makes it possible to ensure cooling of the glass as it flows from the electrofusion zone 100 to the zone 200 for refining and homogenizing the glass.

Because the first trough neck has a large length, cooling of the glass will be more pronounced, as the glass from the melting zone 100 cools naturally during its flow from upstream to downstream through the first trough neck 160.

Advantageously, the hybrid furnace 10 includes a tool 500 for cooling glass that is capable of selectively cooling glass in the first trough neck 160.

In addition to cooling the glass during its flow through the first trough neck 160 connecting the melting zone 100 and refining zone 200, such a cooling tool 500 makes it possible to further enhance the cooling and in particular to modify it, whereby the temperature regulation of the glass is advantageously achieved at this time.

Preferably, the tool 500 for cooling glass in the first channel neck 160 comprises at least one air circulation cooling device 510.

An exemplary embodiment of a cooling device 510 is described below, as shown more particularly schematically in fig. 3 and 4, which show a second embodiment, and in fig. 5 and 6, which show a third embodiment and variant, respectively, so that reference will advantageously be made to the accompanying drawings.

Such an air cooling device 510 for glass comprises, for example, at least an air intake means 512 for introducing cooling air into the atmosphere of said first trough neck 160 of the hybrid furnace 10.

Preferably, the means 510 for cooling glass comprises a discharge means 514 arranged in the first tank neck 160 to discharge the hot air and ensure that it is refreshed with fresh cooling air.

Alternatively, the discharge means are formed by extraction means (not shown) located downstream of the first tank neck 160, intended to extract the fumes. Advantageously, the hot air is then exhausted through the extraction means together with the fumes, without the need for equipping the hybrid furnace 10 with additional means.

The air intake means 512 and the air discharge means 514 of the glass cooling device 510 are formed, for example, by one or more openings present in the side wall supporting the top of the first tank neck 160.

The at least one inlet opening and the at least one outlet opening, which are schematically shown in fig. 3 and above, are for example arranged longitudinally opposite each other, the inlet opening being arranged in an upstream portion of the first tank neck 160 and the outlet opening being arranged in a downstream portion of the first tank neck 160.

The air inlet means 512 and the air outlet means 514 are for example arranged laterally on both sides of the first slot neck 160 or on only one side of the first slot neck 160.

Advantageously, the temperature of the cooling air introduced into the first tank neck 160 is lower than the temperature of the hot air located inside said first tank neck 160, the circulated cooling air forming a heat transfer fluid.

Preferably, the cooling air used is atmospheric air taken from outside the hybrid furnace 10, or even outside the housing of the building in which the hybrid furnace 10 is installed (supplying the float unit).

Advantageously, the temperature of the atmospheric air used is controlled so that it can be regulated. For example, the air may be pre-cooled or reheated to control its temperature before being introduced.

Glass cooling is mainly achieved by convection, wherein the incoming cooling air heats up when in contact with the glass surface and is then carried away with the heat (calories) transferred by the glass.

Advantageously, the circulation of air can be controlled by blowing means (not shown), such as a fan, associated with said intake and/or exhaust means, which can be controlled to vary the flow rate of the air circulation.

According to another embodiment, the tool 500 for cooling glass is immersed in the glass flowing through the first trough neck 160 from upstream to downstream so as to allow it to cool.

Such cooling tools are formed, for example, by vertical studs immersed in the glass, which are cooled by a cooling circuit with a heat transfer fluid in order to expel the heat transferred to the studs through the glass.

According to yet another embodiment, the cooling tool 500 is capable of cooling the structure of the first channel neck 160 in contact with the glass, the cooling being from outside the structure of the first channel neck 160.

Of course, the cooling tool 500 associated with the first slot neck 160 (e.g., cooling tool according to various examples just described) can be implemented alone or in combination.

Advantageously, the means 500 for cooling the glass associated with the first channel neck 160 allows for selective control of the temperature of the glass, which is likely to vary, particularly as the pull rate varies, as an increase in the pull rate results in an increase in the glass temperature.

Fig. 2 shows an example of a first tank neck 160 connecting the electrofusion zone 100 with a refining and homogenizing zone 200.

The passage from the electrofusion zone 100 to the first trough neck 160 involves a sudden narrowing of the width and passage cross section of the glass, for example here by walls 162 and 163 forming an angle of 90 ° with the longitudinal central axis A-A' of the furnace.

The passage from said first trough neck 160 to the zone 200 for refining and homogenizing glass involves a sudden widening of the glass passage section, for example here by walls 262 and 263 forming an angle of 90 ° with the longitudinal centre axis A-A' of the furnace.

Alternatively, the angle at the inlet of the first trough neck 160 may have a value greater than 90 ° such that the narrowing of the width is less abrupt and more gradual, and as such, the value of the angle at the outlet of the first trough neck 160 may be selected such that the widening along the median longitudinal axis A-A' of the furnace is also less abrupt and more gradual.

Advantageously, molten glass flowing from upstream to downstream via the first trough neck 160 is withdrawn from the lower portion of the electrofusion zone 100, or from the bottom, as opposed to where the glass is "cooler" than the glass in the high convection zone 132 between the electrodes 110.

In this first embodiment, the first channel neck 160 comprises a preferably flat floor (not shown) such that the floor of the first channel neck 160 extends horizontally in the extension of the flat floor 150 of the electrofusion zone 100.

According to the present invention, the hybrid furnace 10 includes a "no-return" separation device 170 at the first trough neck 160 that is configured to prevent molten glass from returning from the refining and homogenizing zone 200 to the melting zone 100.

The separation device 170 according to the first embodiment of the hybrid furnace 10 shown in fig. 1 and 2 will be described in more detail later.

According to a second feature of the hybrid melting furnace 10 of the present invention and in contrast to the cold top electrofusion zone 100, the refining and homogenizing zone 200 of the hybrid melting furnace 10 is of the "hot top" type.

The refining and homogenizing zone 200 of the hybrid furnace 10 is configured to eliminate bubbles (or gaseous defects) present in the molten glass from the electrofusion zone 100 to obtain high quality glass, and this in particular allows for supply to a float glass unit.

To this end, the refining and homogenizing zone 200 comprises a first convection loop 210, referred to as an upstream recirculation loop, and a second convection loop 220, referred to as a downstream recirculation loop.

Preferably, the first convection loop 210 (referred to as the upstream recirculation loop) is longitudinally shorter than the second convection loop 220, as shown in fig. 1.

Advantageously, convection stirring of the glass in the glass corresponding to the circuits 210, 220 eliminates bubbles and increases the residence time of the glass in the refining and homogenizing zone 200, thereby helping to obtain high quality glass.

The first convection loop 210 and the second convection loop 220 are separated by a reversal zone 230 of the loops 210, 220, the reversal zone 230 being defined by a hot spot (also referred to as a "source point") that corresponds to the hottest spot of glass in the refining and homogenizing zone 200, typically at a temperature above 1500 ℃.

The refining and homogenizing zone 200 comprises at least one burner 215, here preferably two aerial burners 215, arranged below an arched roof 240 to obtain the hot spot defining the inversion zone 230 of the circuit 210, 220.

In the refining and homogenizing zone 200, a portion of the thermal energy released by the combustion is transferred directly to the glass by radiation and convection, another portion is transferred by dome-shaped roof 240, dome-shaped roof 240 returns thermal energy to the glass by radiation, and it is referred to as a "hot roof" for this reason, among other reasons.

Preferably, the burner 215 of the refining and homogenizing zone 200 is a cross-flame burner schematically shown in fig. 2.

Thus, the heating of the glass in the refining and homogenizing zone 200 is achieved by the flame of the burner 215, which flame is created by combustion above the surface S of the glass.

In the hybrid furnace 10 according to the present invention, the step of melting glass performed in the melting zone 100 after it is used for the preparation is implemented using only electric energy.

Advantageously, the heating of the glass at the surface in said zone 200 by burning fossil energy or equivalent fuel is therefore only intended to carry out the steps of refining and homogenizing the glass withdrawn from said melting zone 100.

In contrast, particularly with the hybrid furnace according to the third design described above, the equivalent fossil energy source or fuel used by the burner 215 for combustion does not participate in the melting step, so that in the present invention, this fuel energy source is used as a "booster" with respect to the electrical energy further used for melting.

The hybrid furnace 10 according to the invention thus makes it possible to significantly reduce the proportion of fuel energy relative to electrical energy in the glass production process, wherein electrical energy is the primary energy source and fuel energy is the secondary or auxiliary energy source.

Advantageously, the electric power represents more than 60%, or even 80% and even more of the total energy used in the hybrid furnace for the glass production process.

It will thus be appreciated that the design of the hybrid furnace 10 according to the present invention is particularly advantageous for reducing the carbon footprint when the combustible energy source is fossil energy, such as natural gas, on the one hand, and the electrical energy is wholly or partially "green" electrical power derived from renewable and decarbonized energy, on the other hand.

The refining and homogenizing zone 200 can comprise more than two burners 215, in particular burners located upstream and/or downstream of said inversion zone 230, which are also located above the surface S of the glass, capable of heating said surface S of the glass in order to achieve refining and homogenizing of the glass by removing the bubbles (or gas defects) present in the molten glass.

In fact, by adjusting the power of the burner 215, it is possible to adjust the longitudinal distribution of the temperature and thus the position of the hot spot, which is an important parameter of the furnace operation.

The burner 215 produces a flame by combustion, which can be accomplished by combining different types of fuels and oxidants in a known manner, but the choice of fuel and oxidant can also directly affect the carbon footprint of the glass production or the direct and indirect emission of greenhouse gases associated with the production of the product, particularly carbon dioxide emissions (CO ₂).

For the combustion of the burner 215 in the refining and homogenizing zone 200, oxygen present in the air is generally used as oxidant, which can be enriched with oxygen to obtain peroxygen air, or even almost pure oxygen in the specific case of oxygen combustion.

Typically, the fuel used is natural gas. However, in order to further improve the carbon balance, it would be advantageous to use biofuels, in particular "biogas", i.e. a gas consisting mainly of methane and carbon dioxide produced by methanation (i.e. the fermentation of organic materials in the absence of oxygen), or even preferentially use "biomethane" (CH ₄).

More preferably, a hydrogen fuel (H ₂) will be used, which advantageously does not contain carbon compared to biogas.

Advantageously, the hybrid glass production furnace 10 according to the present invention may comprise a regenerator or air/flue gas metal exchanger (also known as regenerator) made of refractory material (e.g. in pairs and in opposite directions) that uses the heat contained in the flue gas resulting from the production, respectively, to preheat the gas and thereby improve combustion.

As noted above, the hybrid furnace 10 according to the present invention includes a separation device 170 configured to prevent molten glass from returning from the refining and homogenizing zone 200 to the melting zone 100.

The separation device 170 is located at the first trough neck 160, i.e., between the refining and homogenizing zone 200 and the melting zone 100, to ensure the "check" function of the glass from the first convection loop 210 of glass.

In this first embodiment, the separation device 170 includes a weir 172, the weir 172 being adapted for partial immersion in the molten glass bath 130, as shown in FIGS. 1 and 2.

More specifically, the separation device 170 according to the first embodiment is constituted only by the weir 172, which advantageously makes it possible to prevent the molten glass from returning from the refining and homogenizing zone 200 to the melting zone 100.

Preferably, the weir 172 is located at the upstream end of the first trough neck 160.

Advantageously, forming the weir 172 of the separation device 170 allows for an increase in the residence time of the glass in the electrofusion zone 100, which helps to achieve a high quality glass.

Preferably, the weir 172 extends laterally across the width of the first trough neck 160, as shown in fig. 2.

Advantageously, the weir 172 is mounted for vertical movement so that the depth of immersion in the glass bath 130 can be adjusted so that the cross section 180 of the underlying molten glass channel can vary as a function of the depth adjustment of the weir 172.

Alternatively, the weir 172 is fixed such that the cross-section 180 of the molten glass channel is now constant, i.e., determined by the depth of immersion of the weir 172 into the glass bath 130.

Advantageously, the weir 172 disposed upstream of the first trough neck 160 ensures the securement of the layer 112 of glass mixture (relative to the hot top refining and homogenizing zone 200) overlying the glass bath 130 in the cold top electrofusion zone 100.

Preferably, the definition of the layer 112 of vitrifiable mixture is thus ensured by the weir 172, the weir 172 extending vertically above the surface of the glass bath 130 to this end, as shown in fig. 1.

Preferably, the weir 172 is removable, that is, detachable, so that the weir 172 can be replaced or repaired, particularly due to wear occurring upon contact with the glass, thereby facilitating maintenance of the hybrid furnace 10.

The weir 172 is for example made of a non-refractory metal or alloy, in which case the weir 172 can be cooled by a cooling fluid cooling circuit (not shown), in particular a water jacket type circuit.

Advantageously, the weir 172 helps cool the glass in the first trough neck 160 by restricting flow in the first trough neck 160 and by virtue of a water jacket cooling fluid cooling circuit that removes some of the heat (calories) transferred to the weir 172 by the glass.

Alternatively, the weir 172 is made of a refractory material, typically a ceramic, such as an electro-fused refractory material "AZS" (abbreviation for alumina-zircon-silica) or a refractory metal (e.g., molybdenum).

The hybrid furnace 10 also includes at least one separation means 174 for separating the atmosphere from the cold top electrofusion zone 100 from the atmosphere (including in particular fumes) of the hot top refining and homogenizing zone 200.

Advantageously, such a separation tool 174 makes it possible to isolate the atmosphere from the first tank neck 160 from the atmosphere of the melting zone 100, particularly when an air cooling device is used as a tool for cooling the glass in the first tank neck 160.

Preferably, the partition means 174 is formed of a partition plate (or curtain) constituting an element attached to the upper structure of the hybrid furnace 10.

A set of blocks in contact with glass is commonly referred to as a "substructure" and a "superstructure" is all the material disposed above the substructure.

Since the upper structural material above the trough blocks of the lower structure is not in contact with the glass but in contact with the atmosphere within the furnace, the upper structural material generally has different properties than the tank blocks of the lower structure.

Even though the material used for the upper structure is the same as the material of the lower structure, for example in the case of hot tops, the two parts of the furnace structure are often different from each other.

Alternatively, the divider 174 is formed from a portion of the superstructure, such as an outwardly opening double U-shaped baffle.

Advantageously, the weir 172 is then installed between the two wings of the "U" shape of the baffle, or in the empty bottom connecting them.

Preferably, in this first embodiment, the weir 172 and the atmospheric barrier 174 are structurally distinct, independent elements.

Preferably, the divider 174 is not in contact with the glass surface, but rather in contact with the weir 172 to establish the separation.

Advantageously, the baffle 174 is located behind the weir, i.e. downstream of the weir, as shown in fig. 1, for example.

Alternatively, the divider 174 is located forward of the weir 172, i.e., upstream of the weir 172, or in the same vertical plane.

Alternatively, the weir 172 and the baffle 174 are made of a single piece, thereby ensuring a dual function, on the one hand, a first function of separating the glass between the melting zone 100 and the refining and homogenizing zone 200, and on the other hand, a function of separating the atmosphere of the melting zone 100 with the cold roof 140 from the atmosphere of the refining and homogenizing zone 200 with the hot roof 240.

Alternatively (not shown), if the weir 172 is not arranged upstream of the first trough neck 160 as shown in fig. 1, the hybrid furnace 1 then advantageously includes a blocking means (also referred to as a "skimmer (skimming)") capable of retaining the layer 112 of vitrifiable mixture in the electrofusion zone 100.

Preferably and similar to the weir 172, a blocking means is disposed at the upstream end of the first trough neck 160 such that the vitrifiable mixture on the surface of the glass bath 130 does not penetrate into the first trough neck 160.

In the first embodiment, the weir 172 ensures the function of such a blocking means by advantageously retaining the layer 112 of vitrifiable mixture in the electrofusion zone 100 in addition to the backflow prevention function of the glass.

Exemplary embodiments of such blocking means will be described in more detail below with reference numeral 176 in the second embodiment shown by fig. 3 and 4 and in the third embodiment shown in fig. 5.

In the first embodiment shown by fig. 1 and 2, the hybrid furnace 10 advantageously comprises a barrier 260 or weir wall disposed in the loop reversal region 230.

Preferably, the barrier 260 extends vertically from the floor 250 of the refining and homogenizing zone 200.

As shown in fig. 1, the barrier 260 includes a platform portion submerged below the glass surface S that determines the passage of glass from the first convection loop 210 (referred to as the upstream recirculation loop) toward the second convection loop 220 (referred to as the downstream recirculation loop).

Preferably, the hybrid furnace 10 includes a conditioning tool (not shown), such as an electrically assisted heating and/or bubbler disposed in the refining and homogenizing zone 200, which enables the convection currents of the circuits 210, 220 to be sequentially adjusted to facilitate the glass making process.

Advantageously, the brewing means thus comprise electrically assisted heating (i.e. additional electrically heated means comprising electrodes) and/or a bubbler, i.e. a system for injecting at least one gas (e.g. air or nitrogen) at the soleplate, the bubbles of which then create an upward movement of the glass.

Preferably, the hybrid furnace 10 includes at least one variation 270 in the depth of the bottom plate 250 relative to the glass surface S in the refining and homogenizing zone 200.

The depth variation 270 is located in the portion containing the first convection loop 210 and/or in the portion containing the second convection loop 220.

Advantageously, the depth change 270 of the glass is constituted, for example, by at least one elevation of the bottom plate 250, or even here by a plurality of elevations as shown in fig. 1. Alternatively, depth variation 270 is comprised of at least one level difference of floor 250.

The raised portion of the floor 250 (i.e., where the depth decreases) forming the depth variation 270 is constituted, for example, by at least one step 272 or even two steps.

The depth variation 270 may be more or less gradual, for example, by a straight section 274 in the case of two steps 272 located upstream of the barrier 260, or alternatively, for example, by an inclined section 276 as shown in the case of a step 322 located downstream of the barrier 260, at the intersection of the refining and homogenizing zone 200 and the glass cooling zone 300.

Preferably, the cooling zone 300 thus also includes a depth variation 370 formed by the raised portions.

As shown in fig. 1, the depth variation 370 in the cooling zone 300 includes, for example, a step 322 in the second slot neck 320 (the angled connection 276 leading from the floor 250 to the step 320) and another step 332 in the working end 330 downstream of the step 322.

The step 322 is also gradually connected to the other step 332 by an inclined portion 376 at the junction between the second slot neck 320 and the working end 330.

Alternatively, the respective straight and inclined portions, which have just been described with reference to fig. 1, may be interchanged between the step 272 on the one hand and the steps 322, 332 on the other hand, or of just the same type, that is to say either straight or inclined.

As shown in fig. 1, and as just described for the continuous steps 322 and 332, the cooling zone 300 includes a floor 350 configured such that the depth relative to the glass surface S gradually decreases from upstream to downstream from the barrier 260.

According to a third feature of the invention, the hybrid furnace 10 comprises, downstream of the refining and homogenizing zone 200, said zone 300 for cooling the glass, through which a second convection loop 220, called downstream recirculation loop, passes.

The cooling zone 300 is formed by a conditioning trough 310, the conditioning trough 310 being in communication with at least one flow channel 400 intended to supply high quality glass, a float glass unit on a molten metal bath (not shown) located downstream forming a forming zone.

Advantageously, conditioning tank 310 of cooling zone 300 comprises, from upstream to downstream, a second tank neck 320, then a working end 330.

Advantageously, the atmosphere of the refining and homogenizing zone 200 and the cooler atmosphere of the cooling zone 300 are separated from each other by a heat shield 360, which heat shield 360 extends vertically from the top 340 to near the surface S of the glass, preferably without tempering in the glass.

Advantageously, in any vertical plane transverse to the longitudinal central axis A-A' of the furnace, there is a point (in glass) in conditioning tank 310 with a longitudinal velocity component from downstream to upstream.

After conditioning the trough 310, no back flow occurs in the flow channel 400 for supplying glass to the forming zone, in other words, the glass flow in the channel 400 is a "plug" flow.

Advantageously, the hybrid furnace 10 according to the present invention is capable of providing less than 0.1 bubbles per liter, preferably less than 0.05 bubbles per liter, of high quality glass that is particularly suitable for supply to a float glass unit on a molten metal bath.

Advantageously, the hybrid furnace 10 is capable of supplying high quality glass with less than 0.1 bubbles per liter to a float glass unit on a molten metal bath at a pull rate of greater than or equal to 400 tons per day, preferably between 600 and 900 tons per day, or even 1000 tons per day or more.

Advantageously, the hybrid furnace 10 according to the present invention is capable of providing a pull rate similar to a flame furnace with or without an electric auxiliary heater, thereby being capable of supplying high quality glass to a float unit.

The hybrid furnace 10 for glass production according to the present invention supplies a float glass unit to a bath of molten metal (e.g., tin) for producing flat glass via a flow channel 400.

Advantageously, the method for preparing glass in a hybrid furnace 10 of the type just described with reference to fig. 1 and 2 comprises, in sequence, the following steps:

(a) -melting the vitrifiable mixture in a cold top electrofusion zone to obtain molten glass;

(b) Collecting the molten glass flowing from the melting zone to the refining and homogenizing zone through a first trough neck provided with separation means;

(c) -refining and homogenizing the molten glass in a refining and homogenizing zone with a hot top, comprising a first convection loop (called upstream recirculation loop) and a second convection loop (called downstream recirculation loop);

(d) -cooling the glass in a cooling zone formed by a conditioning tank, through which cooling zone a second convection loop passes.

Advantageously, the temperature of the molten glass collected in the melting zone 100 is reduced during passage through the first trough neck 160, the first trough neck 160 containing a separation device 170 formed by a weir 172 and/or raised portion 161 of a floor 165.

Advantageously, according to this embodiment, the method comprises an adjustment step (e) consisting of: the depth of the movable weir 172 is adjusted, and the movable weir 172 immersed in the glass is disposed in the first trough neck 160 connecting the electric melting zone 100 and the refining and homogenizing zone 200 to control the flow rate of the molten glass collected in the melting zone 100.

Advantageously, the adjustment of step (e) makes it possible to vary the quantity of molten glass transferred from the electrofusion zone 100 to the refining and homogenizing zone 200, for example as a function of the rate of lift.

After cooling step (d) in conditioning tank 310, the glass flows into flow channel 400 which is intended to supply high quality glass to the float glass unit.

Advantageously, the method comprises the step of regulating the cooling of the glass in the first channel neck 160, in particular by selectively controlling the means 500 for cooling the glass, for example the at least one air cooling device 510.

Advantageously, the amount of cooling air introduced into the first tank neck 160 by the air inlet means 512 of the air cooling device 510 is controlled in particular as a function of the temperature of the glass.

A second embodiment of the hybrid furnace 10 shown in fig. 3 and 4 is described below by comparison with the first embodiment.

In fact, the hybrid furnace 10 according to this second embodiment is similar to the hybrid furnace described above with reference to fig. 1 and 2, so that the description given thereby also applies to this second embodiment, except as described in detail below.

One of the differences with respect to the first embodiment is that the first channel neck 160 comprises a floor, indicated as 165, which floor 165 is not flat, which floor 165 does not extend in the extension of the flat floor 150 of the electrofusion zone 100.

In fact, as shown in fig. 3, the floor 165 of the first slot neck 160 is configured to form at least one raised portion 161.

Advantageously, the elevation 161 extends longitudinally more than half the length of the first slot neck 160, or even more than three-quarters of said length.

In this second embodiment, the first trough neck 160 of the hybrid furnace 10 advantageously has a length that is greater than the length of the first embodiment, as can also be seen by comparing fig. 2 and 4.

Advantageously, the length of the first trough neck 160 is configured to cool the glass intended to flow into the refining and homogenizing zone 200, since molten glass obtained by electric melting generally has a higher temperature than flame melting in particular.

For example, the glass temperature in the melting zone is about 1450 ℃, while the desired glass temperature in the downstream portion of the neck of the first trough is more about 1300 ℃ to 1350 ℃.

According to a feature of the second embodiment, the at least one raised portion 161 of the bottom plate 165 of the first trough neck 160 forms part of the separation device 170, thereby ensuring the function of preventing glass from returning to the melting zone 100.

Advantageously, the separating apparatus 170 according to this second embodiment comprises a weir 172, respectively, similar to the weir of the first embodiment, associated with the at least one raised portion 161 of the floor 165 of the first trough neck 160.

However, the weir 172 is not positioned upstream of the first trough neck 160, but rather is positioned inside the first trough neck 160 containing the at least one raised portion 161 of the floor 165 longitudinally between its upstream and downstream ends.

Preferably, the separating apparatus 170 here comprises a single elevation 161 of the floor 165.

By contrast to the barrier (or weir wall), the raised portion 161 is formed directly from the floor 165 and is not attached to the floor 165 such that the raised portion 161 is composed of a refractory material that forms the lower structure of the floor 165 of the first trough neck 160. In addition, the barrier is a narrow structure, with a small thickness, which is subject to significant wear, so that it cannot be permanently ensured that the glass does not return to the melting zone.

As mentioned above, the raised portion 161 is wider, extending longitudinally over a substantial portion of the length of the first channel neck 160, the raised portion 161 advantageously participating in cooling of the glass in the first channel neck 160.

An exemplary embodiment of the raised portion 161 of the base plate 165 as shown in fig. 3 will be described in more detail below.

In fig. 3, the elevation 161 comprises, in order from upstream to downstream, at least a first ascending section 164, a second top section 166 and a third descending section 168.

Advantageously, the raised portion 161 extends laterally across the width of the first slot neck 160.

Of course, such elevation 161 may have many geometric variations in its overall shape, its dimensions, and in particular, in terms of the configuration of the various segments 164, 166 and 168 that make up it.

Preferably, the rising section 164 is inclined at a determined angle (α) to form a ramp that is capable of rising the molten glass toward the top section 166 of the raised portion 161, as shown in FIG. 3.

Preferably, the rising section 164 is an inclined plane, for example having an acute angle (α) comprised between 20 ° and 70 °, said angle (α) being expressed (for greater readability, see fig. 6) as the angle between the rising section 164 of the elevation 161 and the horizontal, here referenced to the flat floor 150 of the melting zone 100.

As a variant (not shown), the rising section 164 is stepped, for example in the form of a staircase, with at least one step, or even two or more steps, the height and/or length dimensions of which may be identical or different.

Preferably, the top section 166 is planar, forming a horizontal platform. Advantageously, the top section 166 thus extends longitudinally for a given length, preferably here greater than or equal to half the total length of the first slot neck 160.

The top section 166 determines the maximum height H1 of the raised portion 161 and this also determines the channel cross section 180 of the molten glass in the first trough neck 160 (due only in part to the weir 172).

Preferably, the lower section 168 of the raised portion 161 extends vertically and connects at right angles to the downstream end of the horizontally extending plateau section 166.

According to another embodiment, such as shown in FIG. 6, as will be described later, the drop leg 168 is configured to gradually accompany the flow of molten glass from the first trough neck 160 to the refining and homogenizing zone 200.

Such a section 168 is formed, for example, by an inclined plane, which may or may not be stepped, in particular stepped as described above for the alternative embodiment of the rising section 164.

In addition to the at least one elevation 161, which has just been described, in this second embodiment the separation device 170 also comprises at least one weir 172 as in the first embodiment, said weir 172 being partially submerged in the molten glass.

The weir 172 and the raised portion 161, which in combination form the separation device 170, prevent molten glass from returning from the refining and homogenizing zone 200 to the electrofusion zone 100, that is, from the first convection loop 210 of glass.

Advantageously, the weir 172 in combination with the at least one raised portion 161 allows for a common increase in the residence time of the glass in the electrofusion zone 100, which helps to achieve a high quality glass.

Advantageously, the weir 172 can have the same features as described above for the first embodiment.

Likewise, the weir 172 is for example made of a non-refractory metal or alloy, said weir 172 being now capable of being cooled by a cooling fluid cooling circuit (not shown), in particular a water jacket type circuit.

As shown in fig. 3, the at least one weir 172 is disposed longitudinally between the downstream and upstream ends of the first trough neck 160.

Preferably, the weir 172 is positioned vertically above the top section 166 of the raised portion 161.

Preferably, the weir 172 extends laterally across the width of the first trough neck 160, as shown in fig. 4.

Advantageously, the weir 172 is mounted for vertical movement so that the depth of immersion in the glass bath 130 can be adjusted so that the cross-section 180 of the molten glass channel above the top section 166 of the raised portion 161 can vary as a function of the adjustment of the depth of the weir 172 (relative to the depth P1 of the glass determined by the height H1).

Advantageously, the hybrid furnace 10 also comprises at least one separation means 174, for example a partition, to separate the atmosphere coming from the electrofusion zone 100 from the atmosphere of the refining and homogenizing zone 200, which in particular comprises flue gas.

As shown in fig. 3 and 4, a separation tool 174 is disposed at the upstream end of the first tank neck 160 adjacent the electrofusion zone 100.

In this second embodiment, separation means 174 (here formed by a spacer) is in contact with the glass surface, or even submerged at its free end, to not only establish the atmosphere barrier, but also to retain the vitrifiable mixture layer 112 in the electrofusion zone 100.

Advantageously, the separation means 174 thus provides another function, namely the function of the blocking means 176, so that the layer 112 of vitrifiable mixture present on the surface of the glass bath 130 does not penetrate into the first tank neck 160.

In this second embodiment, the blocking means 176 are thus formed by the free end of the separating means 174, which separating means 174 consist of a partition which extends for this purpose to the bath surface 130 or even preferably is immersed in the glass bath 130.

Alternatively, the means 176 for blocking layer 112 is structurally different from the separation means 174, in which case the blocking means 176 can be adjacent to or remote from the separation means 174.

Such a variant is also shown in fig. 5 or 6, which represents a third embodiment, which will be described in more detail later.

The separating means 174 is located, for example, downstream of the blocking means 176, that is to say at a distance therefrom. Alternatively, a separation tool 174 is attached to the blocking tool 176.

Thus, in contrast to the first embodiment, the definition of the vitrifiable mixture layer 112 is not ensured here by the weir 172, but by the free end of the separating means 174 in the second embodiment shown in fig. 3 and 4, or by the separate blocking means 176 in the third embodiment shown in fig. 5 or 6.

A third embodiment shown by fig. 5 (and fig. 6 showing an alternative embodiment of the elevation), most particularly in comparison to the second embodiment, will be described below.

In this third embodiment, as compared to the second embodiment shown in fig. 3 and 4 or even to the first embodiment, the so-called "non-return" separating means 170 consist only of at least one elevation 161 of the floor 165 of the first trough neck 160, thus leaving no movable weir 172.

Preferably, the hybrid furnace 10 comprises a raised portion 161 of the floor 165 having a height H2, indicated in fig. 5 with respect to a horizontal line at the flat floor 150 of the melting zone 100 as reference, said height H2 being relatively greater than the height H1 indicated in fig. 3.

Advantageously, the raised portion 161 of the bottom plate 165 of the first slot neck 160 has the same shape as described above with reference to fig. 3, i.e. is composed of an ascending section 164, a top section 166 and a descending section 168 in sequence.

As shown in fig. 5, the depth P2 between the surface S of the molten glass and the top section 166 of the raised portion 161 of the bottom plate 165 is less than the depth P1.

In this third embodiment, the channel section 180 of the molten glass is thus not determined by the advantageously movably mounted weir 172, but only by said height 161 of the bottom plate 165, so that said channel section 180 cannot be changed in particular.

Without the weir 172, the hybrid furnace 10 nevertheless includes at least one separation means 174 as in the first and second embodiments that is capable of separating the atmosphere from the electrofusion zone 100 and the atmosphere from the refining and homogenizing zone 200, respectively.

Furthermore, and as described above as a variation of the second embodiment, the blocking means 176 is preferably different and separate from said separating means 174.

Alternatively and as in the second embodiment, the blocking means 176 is formed by a separation means 174, the free end of the separation means 174 (i.e. the lower end here) preferably being immersed in the glass bath 130.

According to an alternative embodiment of the raised portion 161 of the floor 165 of the first trough neck 160 shown in fig. 6, the lowered section 168 is configured to gradually accompany the flow of molten glass toward the refining and homogenizing zone 200.

Such a segment 168 is formed, for example, by an inclined plane, which may or may not be stepped, particularly stair-like.

Preferably, the segment 168 is inclined at a determined angle (β) to form a ramp that enables the molten glass to gradually descend toward the floor 250 of the refining and homogenizing zone 200.

For the descending section 168, the angle (β) is an obtuse angle, which may for example have a value between 90 ° and 145 °, which corresponds to the internal angle marked at the connection of the top section 166 and the descending section 168 in fig. 6.

As a variant (not shown), the rising section 168 is not flat but stepped, for example in the form of a staircase, with at least one step, or even two or more steps, the height and/or length dimensions of which may be identical or different.

As shown, the depth of the glass here is not the same longitudinally on both sides of the at least one elevation 161, between the flat floor 150 of the electrofusion zone 100 and the beginning of the floor 250 of the refining and homogenizing zone 200 (downstream of the first trough neck 160), respectively, the refining and homogenizing zone 200 may have at least one depth variation.

As previously mentioned, such elevation 161 may have a wide variety of geometric variations with respect to its overall shape, its dimensions, particularly in terms of the configuration of each of the different segments 164, 166, and 168 that make up it.

Claims

1. A hybrid glass production furnace (10) for producing glass for supplying a unit for floating glass on a bath of molten metal, said hybrid furnace (10) comprising, from upstream to downstream:

-an electrofusion zone (100) having a cold roof (140) comprising electrodes (110) for melting the vitrifiable mixture to obtain a glass bath (130);

-a refining and homogenizing zone (200) with a hot top comprising a first convection loop (210) and a second convection loop (220); and

-A zone (300) for cooling glass formed by a conditioning tank (310), said conditioning tank (310) being traversed by said second convection loop (220) and connected to at least one flow channel (400),

Characterized in that the hybrid furnace (10) comprises at least one trough neck (160), called a first trough neck, which comprises a bottom plate (165) and connects the electric melting zone (100) to the refining and homogenizing zone (200) of the glass, and in that the hybrid furnace (10) comprises a "non-return" separating device (170) located at the first trough neck (160), which is designed to prevent molten glass in the refining and homogenizing zone (200) from returning to the melting zone (100).

2. Furnace according to claim 1, characterized in that the separation device (170) comprises a weir (172) intended to be partially immersed in the glass bath (130).

3. Furnace according to claim 1 or 2, characterized in that the separating means (170) comprise at least one elevation (161) of the floor (165) of the first trough neck (160).

4. A furnace according to claim 3, characterized in that the at least one elevation (161) of the floor (165) comprises, from upstream to downstream, at least one rising section (164), a top section (166) and a descending section (168).

5. Furnace according to claim 4 presented in combination with claim 2, characterized in that the weir (172) is arranged in the first trough neck (160) above the top section (166) of the raised portion (161) of the floor (165).

6. Furnace according to claim 4 or 5, characterized in that at least one of the rising (164) and falling (168) sections of the at least one elevation (161) of the floor (165) is inclined with respect to the horizontal and/or comprises a top section (166).

7. Furnace according to any one of claims 3 to 6, characterized in that the at least one elevation (161) has a maximum height (H1, H2) which wholly or partly determines the molten glass channel cross-section (180) in the first trough neck (160).

8. The furnace according to any one of claims 2 to 7, characterized in that the weir (172) is movably mounted vertically to allow adjustment of the immersion depth in the glass bath (130).

9. Furnace according to any one of claims 2 to 8, characterized in that the weir (172) is removable, that is to say, detachable, in order to allow in particular its replacement in case of wear and to facilitate maintenance of the furnace.

10. Furnace according to any one of the preceding claims, characterized in that the hybrid furnace (10) comprises at least one atmosphere separation means (174), such as a vertical partition, capable of separating the atmosphere of the electrofusion zone (100) with cold roof from the atmosphere of the refining and homogenizing zone (200) with hot roof.

11. Furnace according to any one of the preceding claims, characterized in that the hybrid furnace (10) comprises a blocking means (176) arranged at the upstream end of the first bath neck (160) capable of holding the layer (112) of vitrifiable mixture in the electrofusion zone (100) such that the vitrifiable mixture present on the surface of the glass bath (130) does not penetrate into the first bath neck (160).

12. Furnace according to claim 11, presented in combination with claim 2, characterized in that the means (176) for blocking the layer (112) of vitrifiable mixture are formed by a weir (172).

13. Furnace according to claim 11, presented in combination with claim 10, characterized in that the blocking means (176) are formed by separation means (174), the free end of the separation means (174) extending to the surface of the glass bath (130) or being immersed in the glass bath (130).

14. Furnace according to claim 11 presented in combination with claim 10, wherein the blocking means (176) is separate from the separating means (174), with the blocking means (176) being connected to the separating means (174) or remote from the separating means (174).

15. Furnace according to any one of the preceding claims, characterized in that the hybrid furnace (10) comprises means (500) for cooling glass, which are capable of cooling glass in the first trough neck (160), in particular at least one air circulation cooling device (510).

16. Furnace according to any of the preceding claims, characterized in that the electrodes (110) are arranged on a surface so as to be immersed in the vitrifiable mixture, the submerged electrodes (110) preferably extending vertically.

17. Furnace according to any one of claims 1 to 15, characterized in that the electrode (110) is arranged through a floor (150) of the melting zone (100) so as to be immersed in the vitrifiable mixture, the rising electrode (110) preferably extending vertically.

18. Furnace according to claim 16, characterized in that the electrofusion zone (100) comprises a low convection zone, called buffer zone (134), located between the free end of the submerged electrode (110) and the bottom plate (150) of the fusion zone (100).

19. Furnace according to claim 18, characterized in that the melting zone (100) is configured to have a determined depth (P) in order to obtain the low convection buffer zone (134), preferably the depth (P) is greater than 600mm, or even preferably greater than 800mm.

20. Furnace according to any one of the preceding claims, characterized in that the first convection loop (210) and the second convection loop (220) are separated by a reversal zone (230) of the loops (210, 220), which reversal zone is defined by a hot spot or heat source corresponding to the hottest spot of glass, and in that the refining and homogenizing zone (200) comprises at least one burner (215) arranged to obtain the hot spot defining the loop reversal zone (230).

21. The furnace according to claim 20, characterized in that the hybrid furnace (10) comprises a barrier (260) arranged in the loop reversal zone (230).

22. Furnace according to any one of the preceding claims, characterized in that the hybrid furnace (10) comprises a conditioning means, such as an electrically assisted heating and/or bubbler arranged in the refining and homogenizing zone (200), which is capable of conditioning the convection of the circuits (210, 220) to facilitate the glass production process.

23. The furnace according to any of the preceding claims, characterized in that the conditioning tank (310) of the cooling zone (300) comprises, from upstream to downstream, a second tank neck (320) and then a working end (330).

24. Furnace according to any of the preceding claims, characterized in that the hybrid furnace (10) is configured to supply glass to the float glass unit with a pulling rate of greater than or equal to 400 tons/day, preferably 600 to 900 tons/day, or even 1000 tons/day or more, the high quality glass having less than 0.1 bubbles/liter, preferably less than 0.05 bubbles/liter.

25. An assembly for producing flat glass, comprising a hybrid furnace (10) for producing glass according to any of the preceding claims and a float glass unit arranged downstream on a molten metal bath, the float glass unit being supplied with glass by the furnace (10) through the at least one flow channel (400).