Glass melting furnace with lowered co2 emissions, processes thereof

Abstract

The invention concerns an advantageous glass furnace (1) comprising (i) a tank (2) with a melting zone (3) and a fining zone (4); (ii) inlet means (5,5'); (iii) fuel injection means (10); (iv) oxidizer injection means (11); (v) outlet means (17); (vii) fuel plasma devices (13) alimented with a fuel as working fluid and / or oxidizer plasma devices (14) alimented with an oxidizer as working fluid; wherein said plasma devices (13;14) are respectively in fluidic connection with said injection means (10;11).

Description

GLASS MELTING FURNACE WITH LOWERED CO2EMISSIONS, PROCESSES THEREOFFIELD OF THE INVENTION

[0001] The present invention relates to a glass furnace / process aimed at continuously supplying molten glass to glass forming installations such as float or rolling installations, to produce glass products. In particular, the present invention relates to a glass furnace / process that provides a lot of advantages, especially in terms of CO2emissions and energy consumption.

[0002] The invention is more particularly appropriate, but not limited, to glass furnaces for manufacturing glass, esp. flat glass, involving large production capacities, i.e. up to 1000 tons / day or more, and power demand up to 60 MW.BACKGROUND OF THE INVENTION

[0003] In the state of the art, vitrifiable materials or glass raw materials are melted in a glass furnace that commonly comprises :- a tank containing a melt when the furnace is in use;- inlet means located upstream of the furnace, for charging it with the glass raw materials / batch to be heated / melted;- heating means located in the tank for (i) melting the glass raw materials and (ii) downstream, for fining the melt, and finally,- an outlet for the melt to reach a processing zone or a working end.

[0004] In such glass furnaces, the melting and fining steps are commonly operated by heating through combustion (thanks to burners) or through electricity (thanks to electrodes).

[0005] In a combustion-type heating, a fuel source reacts when mixed in the tank with oxidizer (air or oxygen) in order to ignite and generate a combustion flame above the surface of the molten glass. Fuel may be, for example, fossil fuel, natural gas, methane, hydrocarbons, biogas or hydrogen. Flames coming from combustion are provided above the bath of molten glass / raw materials and heat it from the top.

[0006] In an electrical heating, electrodes are commonly immersed (partially / totally) and often located at the bottom of the tank, or inserted from the top of the glass melt, and allow an electric current / power to pass through and heat the bath from its bulk.

[0007] It is also known to combine, in a "hybrid furnace", combustion heating means (burners) and electrical heating means (electrodes) in the tank. In such known "electroboosted combustion furnaces", the electrical input fraction is commonly limited to 10-15% of the total energy input for flat glass furnaces. "Electrical input fraction" is commonly the part of electricity in the total energy input of the furnace for both the melting and fining, namely electricity / (fuel+electricity), the total energy input being that of the furnace in standard / normal production mode, i.e. at its standard pull range (excluding periods of startup, maintenance, hot repair, culleting, ...).

[0008] Finally, it is also known to melt glass raw materials or refine a glass melt in a tank equipped with plasma devices generating a plasma, inside the tank, which heats the melt from above in a radiative way. For example, WO2021225925A1 described a furnace equipped in the melting zone of plasma devices and immersed electrodes, rendering the melting step operated fully with electricity. For example also, international patent application PCT / EP2024 / 083498 (not yet published) describes a glass furnace with a segmented design (with a fining tank separated from a melting tank by a neck) comprising a plurality of torches, alimented with a working fluid, for refining the glass melt thanks to heating with a plurality of radiative plasma flames above the melt.

[0009] Moreover, it is to be noted that most of the proposed solutions / furnace designs requires generally high investments either in order to adapt an existing furnace (one talks generally about "retrofitting" or "revamping") or, worse, because it is needed to build a completely new installation, which represent a serious drawback. Moreover, as the lifetime of a glass furnace is generally around 20 years, this means that relatively young furnaces will continue to emit CO2 in their initial design during a long period if they cannot be retrofitted easily. Next to that, most of the proposed solutions / furnace designs brings significant changes regarding gas atmospheres in the furnace (gas flow, gas composition, etc.) which, in consequence, have a serious impact at various levels, notably the management / treatment of fumes / exhaust gas, the glass quality and the corrosion of refractories. Such an impact implies that further investments regarding exhaust gas treatment must generally be done for those solutions.

[0010] Though, despite the numerous options already described in the art to improve the carbon footprint of glass manufacturing processes, in the context of global warming that puts pressure on glass manufacturers as well as the energy prices and CO2 taxes that could become soon a severe threat on competitiveness in the glass business, there is still a need to propose an alternative and innovative solution for a glass furnace / process with decreased fossil energy and CO2 emissions, and which requires reduced investments for its implementation through an easy or limited revamping of existing installations. Moreover, such a solution should also have low or no impact on gas atmospheres compared to the retrofitted existing furnace.OBJECTIVE OF THE INVENTION

[0011] It is an objective of the present invention to overcome the disadvantages described above with respect to the state of the art and resolving the technical problem.

[0012] In particular, it is a further objective of the present invention to provide a glass melting furnace / process which shows a decreased CO2 emissions.

[0013] It is a further objective of the present invention to provide a glass furnace / process which shows a decreased fossil fuel consumption.

[0014] It is a further objective of the present invention to provide a glass furnace / process which requires significantly less investments for its implementation compared to solutions proposed in the prior art, especially by allowing an easy and limited retrofitting / revamping of an existing furnace / installation.

[0015] It is a further objective of the present invention to provide a glass furnace / process which has low or no impact on gas atmospheres, esp. compared to the retrofitted existing furnace.

[0016] It is a further objective of the present invention to provide a glass furnace / process which has low or no impact on glass composition and quality, especially compared to the retrofitted existing furnace.

[0017] It is a further objective of the present invention to provide a glass furnace / process which has low or no impact on furnace aging / refractories corrosion, esp. compared to the retrofitted existing furnace.DESCRIPTION OF THE INVENTION

[0018] The present invention relates to a furnace for melting vitrifiable materials, comprising a tank having side-walls and end-walls, and having a melting zone and a fining zone downstream of the melting zone; said tank comprising : inlet means configured to feed vitrifiable materials in said melting zone; fuel injection means for a fuel to be injected in said tank; oxidizer injection means for an oxidizer to be injected in said tank; outlet means; characterized in that said furnace further comprises : fuel plasma devices located outside said tank and alimented with a fuel as a working fluid; and / or oxidizer plasma devices located outside said tank and alimented with an oxidizer as a working fluid; wherein said fuel plasma devices are upstream of and in fluidic connection with said fuel injection means and / or said oxidizer plasma devices are upstream of and in fluidic connection with said oxidizer injection means.

[0019] Hence, the invention is based on a novel and inventive approach. In particular, the inventors have found that it is possible to reach the above-cited objectives by using, in a combustion-type furnace, plasma devices in order to provide energy to the fuel and / or the oxidizer (used as working fluid) before injection in the tank where they will undergo combustion / ignition. This energy will allow to pre-heat and / or ionize and / or excite and / or decompose the fuel and / or the oxidizer before it / they enter(s) the tank, so before it / they undergo combustion / ignition. In the tank, after plasma energizingof the fuel and / or the oxidizer, the fuel and the oxidizer will combine / mix and ignite to create combustion flame(s) that will heat the glass batch and / or the melt from above in a radiative way, to melt and / or to refine it. For the sake of clarity, the plasma devices in the invention do not act as direct heating means to melt / refine but these plasma devices serves to energize (pre-heat and / or ionize and / or excite and / or decompose) the fuel and / or the oxidizer before it / they enter(s) the tank where they will undergo ignition, thereby creating combustion flames inside said tank whose role is to heat glass batch and / or the melt, to melt and / or to refine it (through radiative heating).

[0020] Using the fuel and / or the oxidizer as a working fluid in a plasma devices to provide energy to the gas electrically before it enters the tank allows to reduce the gas consumption of the furnace, namely the amount of gas needed to melt and / or refine the melt. For example, for an air-gas glass furnace (fuel : natural gas, oxidizer : oxygen), energizing the natural gas in plasma devices before its injection esp. in the fining zone allows to decrease the gas consumption by almost 30% (and thereby generates less CO2 emissions) as well as to decrease a bit energy consumption for the fining step, e.g. by 5-10% (for example and as an illustration, 5MW natural gas injected through classical burners can be replaced by (i) 3.5MW natural gas and (ii) 1.21MWe electricity for plasma devices, which gives 4.71MW in total).

[0021] Moreover, the existing "burners" (which are roughly "injectors") in a classical combustion-type furnace are typically outside the tank, in port necks located at its side-walls, and it is therefore easy to adapt the furnace with the solution of the invention, namely the combination of plasma devices with injection means which are also mounted outside the tank.

[0022] Moreover, it has been discovered that the furnace of the invention allows to limit changes in the gas atmospheres. Indeed, using the fuel and / or the oxidizer as working fluid in the plasma devices brings a status-quo regarding the nature of the combustion products in the melting and / or the fining zone and limit also too high variations regarding gas flow esp. compared to whether an additional and classical working fluid is used in plasma torches but also compared to standard burners. This is advantageous as the solution of the invention does not then require any further investment for flue gas treatment when revamping an existing installation, and it limits also greatly impact on glass quality and corrosion of refractories. Finally, another advantage, compared to the use of standard plasm torches, is that the oxidizer and fuel (working fluid of the invention) are already available on site, when revamping an existing furnace.

[0023] The solution of the invention then shows a decreased fossil energetic consumption as well as a significant decreased CO2 emissions compared to classical combustion glass furnaces while requiring reduced investments for its implementation and / or allowing easy and limited revamping of existing installations.

[0024] The invention also relates to a process for melting vitrifiable materials, comprising steps of :(a) charging vitrifiable materials in a tank through inlet means, said tank having side-walls and end-walls, and having a melting zone and a fining zone downstream of the melting zone;(b) melting said vitrifiable materials in said melting zone, thereby providing a melt;(c) injecting in said tank a fuel with fuel injection means;(d) injecting in said tank an oxidizer with oxidizer injection means;(e) combustion of said fuel with said oxidizer, thereby generating combustion flames in said tank;(f) fining the melt in said fining zone, thereby providing a refined melt; and(g) flowing the refined melt to a working zone through outlet means; characterized in that it further comprises :(h) before the step (c) of injecting, a step of generating a plasma using said fuel as a working fluid in fuel plasma devices located outside said tank; and / or(i) before the step (d) of injecting, a step of generating a plasma using said oxidizer as a working fluid in oxidizer plasma devices located outside said tank.

[0025] Finally, the invention also relates to a process of revamping an existing combustion glass furnace to provide a revamped glass furnace, comprising the steps of :- providing an existing glass furnace with (i) a tank having side-walls and end-walls, and having a melting zone and a fining zone downstream of the melting zone; said tank comprising a plurality of combustion heating means;- replacing at least a part of said plurality of combustion heating means in said tank by new means comprising :(i) fuel plasma devices located outside of said tank and alimented with a fuel as a working fluid and / or oxidizer plasma devices located outside of said tank and alimented with an oxidizer as a working fluid;(ii) fuel injection means located at the tank;(iii) oxidizer injection means located at the tank; wherein said fuel plasma devices are upstream of and in fluidic connection with said fuel injection means and / or said oxidizer plasma devices are upstream of and in fluidic connection with said oxidizer injection means.

[0026] Other features and advantages of the invention will be made clearer from reading the following description of preferred embodiments as well as the following Figures, given by way of simple illustrative and non-restrictive examples:

[0027] FIG. 1 is a schematic plan view (horizontal cross-section) of an embodiment of a furnace according to the invention.

[0028] FIG. 2 is a schematic plan view (horizontal cross-section) of another embodiment of a furnace according to the invention.

[0029] FIG. 3 is a schematic plan view (horizontal cross-section) of another embodiment of a furnace according to the invention.

[0030] FIG. 4 is a schematic plan view (horizontal cross-section) of another embodiment of a furnace according to the invention.

[0031] FIG. 5 is a schematic plan view (horizontal cross-section) of another embodiment of a furnace according to the invention.

[0032] The sole function of reference signs in present specification and claims is to make the invention clearer and easier to understand. In particular, reference signs are not to be construed as limiting the extent of the matter protected.

[0033] In present specification and claims, it is well understood by the person skilled in the art that, as used herein the terms "a", "an" or "the" means at least "one" and should not be limited to "only one" unless explicitly indicated to the contrary. Also, when a range is indicated, the extremities are included. In addition, all the integral and subdomain values in the numerical range are expressly included as if explicitly written. Finally, the terms "upstream" and "downstream", unless otherwise specified, refer to the main flow direction of the glass in the tank and are to be understood with their common sense, namely herein as meaning along the averaged moving direction of the glass batch / the glass melt (defined herein as "glass stream"), from the inlet means to the outlet means, when operating the furnace according to the invention, that is to say along the direction going from the left to the right in FIGS. 1-5. By "width" in the invention, it is meant, unless otherwise specified, the dimension (in average) perpendicular to the glass stream.

[0034] The furnace (1) of the invention comprises a tank (2) having side-walls (generally two) and end-walls (generally two, one upstream and one downstream end-wall) and having a melting zone (3) and a fining zone (4) downstream of the melting zone (3).

[0035] According to the invention and as commonly adopted in the glass art, by "melting zone", it is meant a zone defined in the tank where the vitrifiable materials are charged and melt by heating, and comprising, when the furnace is in process, a melt and a "blanket" of unmelted vitrifiable materials that floats on the melt and is progressively melted and therefore reduced from upstream to downstream of the melting zone.

[0036] According to the invention and as commonly adopted in the glass art, by "fining zone", it is meant a zone defined in the tank where there is no more "blanket" of unmelted vitrifiable materials that floats on the melt and where the glass melt is heated at temperatures higher than melting tank temperatures (generally above 1400°C or even above 1450°C), in order to refine the glass (mainly by eliminating major part of bubbles). This fining zone is also commonly called "clarification zone" in the art.

[0037] As commonly known in the art, the fining zone (4) may comprise an immersed wall (or damwall), in order to reduce the flow of relatively cold glass coming back from the workingend to the fining zone (4) and melting zone (3) (good for energy consumption), and to stabilize the glass convection pattern in the melt (good for process stability).

[0038] As known in the art also, in the invention, the transition between the melting zone (3) and the fining zone (4) in the tank (2) may be done with bubblers (8), commonly arranged in the width of said tank (2), roughly in line(s), as illustrated in FIGS. 1, 2 and 4, 5.

[0039] Alternatively to the above embodiment, according to another embodiment, the transition between the melting zone (3) and the fining zone (4) in the tank (2) may be done with at least one neck (9) or throat, preferably a neck (9). In this embodiment, said melting zone (3) and said fining zone (4) are therefore separated by at least one neck (9) or throat, preferably a neck (9), giving a segmented tank (2). This embodiment is illustrated at FIG.3. In this embodiment, the tank (2) has therefore a melting zone (3) with two side-walls and two end-walls (upstream and downstream) and a fining zone (4) with two side-walls and two endwalls (upstream and downstream). According to this embodiment and as commonly accepted in the art, by a "neck" separating the melting zone and the fining zone, it is meant : (i) a narrowing in width and in (crown) height compared to the melting zone and the fining zone, together with (ii) an opening (of the neck) being only partially under the glass melt / batch blanket free surface, then leaving a free opening above the glass melt / batch blanket. According to the invention and as commonly accepted in the art, by a "throat" separating the melting zone and the fining zone, it is meant : (i) a narrowing in width compared to the meltingzone and the fining zone, together with (ii) an opening (of the throat) being completely under the glass melt / batch blanket free surface, thereby leaving no free space above the glass melt / batch blanket.

[0040] Such a neck (9) or throat separating the melting zone (3) and the fining zone (4) in this embodiment is advantageous, notably because it stabilizes the blanket of raw materials and avoid unmelted particles flowing directly towards the fining zone. This point can advantageously improve glass quality. Moreover, the presence of a neck (9) or a throat in the invention allows to deal with / treat independently exhaust gas from melting zone (3) independently from exhaust gas from fining zone (4). Finally, it also allows to use different sources of energy, if desired or needed, between melting and fining zones.

[0041] The furnace of the invention comprises inlet means (5;5') located at the tank (2), configured to feed vitrifiable materials in said melting zone (3).

[0042] According to the invention and as commonly adopted in the glass art, by "vitrifiable materials", it is meant the mixture of starting materials fed in the process of the invention. Vitrifiable materials according to the invention may comprise glass raw materials and / or cullet.

[0043] Any type of appropriate inlet means (5;5') may be considered in the invention. Preferably, the inlet means (5,5') of the invention are either located upstream of the melting zone (3) and / or located at the top of the melting zone (3).

[0044] In an embodiment, the inlet means (5;5') are located upstream of the melting zone (3), either in the width of said tank (2), at upstream end wall (as shown in FIGS. 1, 2 and 4, 5) or laterally in its length, at one or two side walls. In an alternative embodiment, the inlet means (5;5') are located at the top of the melting zone (3), as a "top batch charger" (5'), which allow advantageously to charge the vitrifiable materials directly on the top of glass melt, especially over the entire surface of the melting zone (3). It may advantageously be of the type "rotating batch charger" or "linear X-Y-batch charger" (e.g., in the form of a distributor arm that can move in both X-Y directions, namely in the length and width of the tank), located above the glass melt and below the crown of the tank. Such an embodiment is illustrated in FIG. 3 (inlet mean (5')).

[0045] The furnace of the invention comprises further fuel injection means (10) located at the tank (2), for a fuel to be injected in said tank (2). The furnace of the invention comprises also oxidizer injection means (11) located at the tank (2), for an oxidizer to be injected in said tank(2). Any appropriate injection means for injecting a gas may be considered in the invention, especially those commonly used in the glass furnace art, like, for example, injectors. The position inside port neck of the injection means (10; 11) in the invention may be, for example, of the type under-port or through-port or side-port. In the present text, when using "injection means (10;ll)", this means fuel injection means (10) and / or oxidizer injection means (11).

[0046] According to an embodiment, said injection means (10; 11) are located at at least one of the side-walls or at the downstream end-wall of the tank (2), preferably higher than the level of the batch blanket and / or glass melt.

[0047] In an embodiment where the oxidizer injected in the tank is air (even if it not preferred), as commonly known in the art for fuel-air furnaces, regenerators are present upstream of the oxidizer injection means (11).

[0048] In the invention, the injection of an oxidizer and of a fuel in the tank (2) leads, upon their mixture in said tank (2), to ignition which thereby generates combustion flames (12).

[0049] Preferably and as illustrated in FIGS. 1-5, the fuel injection means (10) and oxidizer injection means (11) are composed of pairs of individual injectors, one for the fuel and one for oxidizer, each pair injecting fuel and oxidizer, respectively, at a location close to each other, at the tank (2) and above the batch blanket and / or glass melt, where they will mix and ignite to give a combustion flame (12). More preferably, according to this embodiment, said pairs of individual injectors are arranged along the side-walls of the tank (2) on each side thereof, e.g. in rows, and spaced from one another in such a way so as to distribute the heat over a portion of the length of the zone to heat.

[0050] The furnace of the invention comprises further :(i) fuel plasma devices (13) located outside said tank (2) and alimented with a fuel as a working fluid; and / or(ii) oxidizer plasma device (14) located outside said tank (2) and alimented with an oxidizer as a working fluid.

[0051] In the furnace of the invention, said fuel plasma devices (13) are upstream of and in fluidic connection with said fuel injection means (10) and / or said oxidizer plasma devices (14) are upstream of and in fluidic connection with said oxidizer injection means (11). By the term "upstream" herein, it refers to the gas flow direction (fuel or oxidizer) and are to be understood with their common sense, namely as meaning along the averaged moving direction of the gas, when the furnace is operated.

[0052] In the present text, when using "plasma devices (13;14)", this means fuel plasma devices (13) and / or oxidizer plasma devices (14).

[0053] According to the invention, each plasma device (13;14) is able to generate a plasma from the working fluid (fuel or oxidizer) that is fed into said device and that is energized upon subjection to an energy source within the device. The plasma devices (13;14) may be preferably of the type that uses electricity as an energy source to generate the plasma, said source being for example arc-driven source with various current waveforms (DC, AC, pulse DC,...) or electromagnetic (EM) wave-driven source with various EM wave generation (microwaves, induction,...).

[0054] Advantageously, in the invention, each combination of a plasma device (13;14) fluidly connected to an injection mean (10;ll) may be obtained by using a plasma torch known in the art. Such a torch is commonly composed of :- a cylinder or main body where the working fluid is alimented and where the plasma is created, playing then the role of plasma device according to the invention, and- a downstream extremity, for example in the form of an orifice or a nozzle, playing the role of injection means (as the fluid / gas energized by the plasma will naturally be under pressure and thereby be ejected from the plasma torch through said orifice).

[0055] The fuel plasma devices (13) according to the invention uses the fuel as a working fluid to create a plasma and provide energy to the fuel electrically before it enters the tank (2) thanks to the fuel injection means (10).

[0056] The oxidizer plasma devices (14) according to the invention uses the oxidizer as a working fluid to create a plasma and provide energy to the oxidizer electrically before it enters the tank (2) thanks to the oxidizer injection means (11).

[0057] As already exposed, providing energy to the fuel and / or oxidizer in plasma devices before injection in the tank (2) allows to reduce the fuel consumption of the furnace, namely the amount of fuel needed to melt the glass batch or refine the melt (and thereby generates less CO2 emissions) as well as to decrease a bit energy consumption.

[0058] For the sake of clarity, the furnace of the invention then allows the following three configurations regarding the energizing of the combustion gas : the fuel is energized in fuel plasma devices (13) and is then passed to fuel injection means (10) to be injected in the tank (2) while the oxidizer is only (and commonly) passed to oxidizer injection means (10) to be injected, as illustrated at FIGS. 1, 3-5;or the oxidizer is energized in oxidizer plasma devices (14) and is then passed to oxidizer injection means (11) to be injected in the tank (2) while the fuel is only (and commonly) passed to fuel injection means (11) to be injected; or the fuel is energized in fuel plasma devices (13) and is then passed to fuel injection means (10) to be injected in the tank (2) and the oxidizer is also energized in oxidizer plasma devices (14) and is then passed to oxidizer injection means (11) to be injected, as illustrated at FIG.2.

[0059] By "energized" herein, it is meant notably heated and / or decomposed and / or excited and / or ionized in the plasma.

[0060] According to a first main embodiment of the invention, the injection means (10; 11) and the plasma devices (13; 14) are located at the fining zone (4). Said combustion flames (12) then allow to refine the melt. This embodiment is illustrated at FIGS. 1-3.

[0061] In this first main embodiment, the melting zone (3) comprises preferably melting heating means (6;6'), to melt said vitrifiable materials and thereby to provide a melt. The melting heating means (6;6' ) in the melting zone (3) may be any suitable heating means. They may comprise a plurality of combustion heating means (6) and / or a plurality of electrodes (6') and / or a plurality of plasma torches. This means that said melting heating means (6;6') may comprise the three precited types of heating, or two of them or only one type of them.

[0062] In said first main embodiment of the invention, and as illustrated at FIGS.1-2, said heating means (6;6') may comprise, or may consist in, a plurality of combustion heating means (6). A combustion heating mean is commonly called in the art as a "burner". It commonly comprises, or consists essentially, of two gas injectors, one for injecting the fuel and one for injecting the oxidizer in the melting zone (3), and are configured to emit a combustion flame (7) above the batch blanket / melt upon mixture of both injected gas (fuel and oxidizer). They may be supplied with fuel and air, or fuel and oxygen, or fuel and a gas that is enriched in oxygen. Fuel may be fossil fuel, natural gas, methane, hydrocarbons, biogas, hydrogen or mixture thereof. Preferably, said plurality of combustion heating means (6) (or burners) are arranged in the melting zone (3) along the side-walls of the tank (2) on each side thereof, e.g. in rows, , and spaced from one another in such a way so as to distribute the heat over a portion of the length of the melting zone (3).

[0063] In said first main embodiment of the invention and as illustrated at FIG. 3, said melting heating means (6;6') may comprise, or may consist in, a plurality of electrodes (6'). This is advantageous, notably in view of CO2 emissions, as this results in an electrical (potentially full electrical) melting step. Said plurality of electrodes (6') may be located at the bottom of the melting zone (3), as immersed electrodes or "bottom electrodes". Said plurality of electrodes (6') may be advantageously arranged according to a specific pattern (e.g., checkerboard), in order to facilitate connection to transformers and electric current balance. For example, in the case of immersed electrodes, their height is between 0.3 and 0.8 times glass melt height. Alternatively, the plurality of electrodes (6') may extend from the top of the melting zone (3) (forexample, maintained commonly by a water-cooled holder) and are immersed. These "top electrodes" may be advantageously located along the edge of the tank (2) and / or at the corner(s). The number of electrodes may be for example designed in order to limit maximum power for each electrode to 400kW, by respecting a maximum current density of 1.5A / cm2at the electrode surface.

[0064] In still said first main embodiment of the invention, advantageously, said heating means (6,6') may comprise, or may consist in, a plurality of electrodes (6') and said melting zone (3) and said fining zone (4) may be separated by at least one neck (8) or throat. This configuration is illustrated at FIG.3. Moreover and as illustrated at FIG.3, in such an embodiment where the furnace is segmented (namely with melting zone and fining zone separated by at least one neck / throat) and where the melting zone (3) is equipped with a plurality of electrodes (6'), it is advantageous that the inlet means (5;5') are located at the top of the melting zone (3), as a "top batch charger" (5') as described above.

[0065] In still said first main embodiment of the invention, the fining zone (4) may comprise, next to the injection means (10) and the plasma devices (13), additional heating means. For example, the fining zone (4) may comprise, next to the injection means (10) and the plasma devices (13), a plurality of electrodes, preferably upstream of the fining zone (4).

[0066] According to a second main embodiment of the invention, the injection means (10;ll) and the plasma devices (13; 14) are located at the melting zone (3). Said combustion flames (12) then allow to melt vitrifiable materials and thereby to provide a melt. This embodiment is illustrated at FIG. 4.

[0067] In this second main embodiment, the fining zone (4) comprises preferably fining heating means, to refine the glass melt and thereby to provide a refined melt. These finingheating means may be any suitable heating means. They may comprise a plurality of combustion heating means and / or a plurality of electrodes and / or a plurality of plasma torches. This means that said fining heating means may comprise the three precited types of heating, or two of them or only one type of them.

[0068] In said second main embodiment of the invention, and as illustrated at FIG.4, said fining heating means may comprise, or may consist in, a plurality of combustion heating means (15). A combustion heating mean commonly comprises, or consists essentially, of two gas injectors, one for injecting the fuel and one for injecting the oxidizer in the fining zone (4), and are configured to emit a combustion flame (16) above the melt upon mixture of both injected gas (fuel and oxidizer). They may be supplied with fuel and air, or fuel and oxygen, or fuel and a gas that is enriched in oxygen. Fuel may be fossil fuel, natural gas, methane, hydrocarbons, biogas, hydrogen or mixture thereof. Preferably, said plurality of combustion heating means (15) (or burners) are arranged in the fining zone (4) along the side-walls of the tank (2) on each side thereof, e.g. in rows, and spaced from one another in such a way so as to distribute the heat over a portion of the length of the fining zone (4).

[0069] In still said second main embodiment of the invention, said fining heating means may comprise, or may consist in, a plurality of electrodes. This is advantageous, notably in view of CO2 emissions, as this results in an electrical (potentially full electrical) fining step.

[0070] In still said first main embodiment of the invention, the melting zone (3) may comprise, next to the injection means (11) and the plasma devices (14), additional heating means. For example, the melting zone (3) may comprise, next to the injection means (11) and the plasma devices (13), a plurality of electrodes.

[0071] According to a third main embodiment of the invention, the injection means (10; 11) and the plasma devices (13; 14) are located at the melting zone (3) and at the fining zone (4). Said combustion flames (12) then allow to (i) melt vitrifiable materials and thereby to provide a melt and (ii) to refine the glass melt and thereby to provide a refined melt. This embodiment is illustrated at FIG.5.

[0072] In this third main embodiment of the invention, the melting zone (3) and / or the fining zone (4) may comprise, next to the injection means ( 10;ll) and the plasma devices (13; 14), additional heating means.

[0073] In said third main embodiment of the invention, the melting zone (3) may comprise, next to the injection means (11) and the plasma devices (14), additional heating means. Forexample, the melting zone (3) may comprise, next to the injection means (11) and the plasma devices (13), a plurality of electrodes.

[0074] In said third main embodiment of the invention, the fining zone (4) may comprise, next to the injection means (10) and the plasma devices (13), additional heating means. For example, the fining zone (4) may comprise, next to the injection means (10) and the plasma devices (13), a plurality of electrodes, preferably upstream of the fining zone (4).

[0075] The furnace (1) of the invention comprises further outlet means (17) located at said tank (2), preferably downstream of the fining zone (4). The outlet means (17) are configured to flow the refined melt from the fining zone (4) outside of the tank (2), especially to a working zone (18). According to an embodiment and as illustrated in Figs. 1-4, the outlet means (17) are composed of at least an outlet neck or, alternatively, at least an outlet throat, in order to lead the melt towards a working zone (18).

[0076] The working zone (18) (partially and schematically represented at FIGS. 1-5) may comprise, for example, a conditioning zone in which thermal conditioning by controlled cooling is carried out prior to glass melt leaving said zone through an outlet to a forming zone. Such a forming zone may comprise, for example, a float installation and / or a rolling installation, with the aim to manufacture flat glass products.

[0077] According to an advantageous embodiment, the furnace comprises further at least an extraction mean of exhaust gas in the melting zone (3).

[0078] According to another advantageous embodiment, the furnace comprises further at least an extraction mean of exhaust gas in the fining zone (4).

[0079] The invention also relates to a process for melting vitrifiable materials, comprising steps of :(a) charging vitrifiable materials in a tank (2) through inlet means (5), said tank (2) having side-walls and end-walls, and having a melting zone (3) and a fining zone (4) downstream of the melting zone (3);(b) melting said vitrifiable materials in said melting zone (3), thereby providing a melt;(c) injecting in said tank (2) a fuel with fuel injection means (10);(d) injecting in said tank (2) an oxidizer with oxidizer injection means (11);(e) combustion of said fuel with said oxidizer, thereby generating combustion flames (12) in said tank (2);(f) fining the melt in said fining zone (4), thereby providing a refined melt; and(g) flowing the refined melt to a working zone (18) through outlet means (17); characterized in that it further comprises :(h) before the step (c) of injecting, a step of generating a plasma using said fuel as a working fluid in fuel plasma devices (13) located outside said tank (2); and / or(i) before the step (d) of injecting, a step of generating a plasma using said oxidizer as a working fluid in oxidizer plasma devices (14) located outside said tank (2).

[0080] The process of the invention may be advantageously carried with the furnace (1) of the invention.

[0081] Features and embodiments described above in relation with the furnace, for example for the tank (2), the melting zone (3), the fining zone (4), the inlet means (5;5'), the outlet means (17), the working zone (18), the plasma devices (13;14), the injection means (10; 11), the melting heating means, the fining heating means, the fuel, the oxidizer and the vitrifiable materials, are applicable to the process of the invention.

[0082] By "before the step (c) (or (d)) of injecting", this means that the step (c) (or (d)) is carried out downstream of the step of generating a plasma, considering the gas flow (fuel or oxidizer) direction (then from plasma devices towards injection means).

[0083] For the sake of clarity, this means that the process of the invention allows the following three situations : the fuel is energized in fuel plasma devices (13) and is injected in the tank (2) while the oxidizer is only (and commonly) injected without plasma-energizing; or the oxidizer is energized in oxidizer plasma devices (14) and is then injected in the tank (2) while the fuel is only (and commonly) injected without plasma-energizing ; or the fuel is energized in fuel plasma devices (13) and is then injected in the tank (2) and the oxidizer is also energized in oxidizer plasma devices (14) and is injected in the tank (2).

[0084] According to an embodiment of the process of the invention, at the step of generating a plasma using said fuel, said fuel comprises natural gas, methane, hydrocarbons, biogas or hydrogen. In other words, this means that said fuel fed in the fuel plasma devices (13) as working fluid comprises natural gas, methane, hydrocarbons, biogas or hydrogen.

[0085] In an embodiment, at the step of generating a plasma using said fuel as working fluid, an inert gas (non-fuel, e.g. N2), sometimes called carrier gas in the art, may be added in addition to the fuel in the plasma device (13). This inert gas will act to protect the walls of the plasma device as known in the art, by making a vortex around said walls. Alternatively, at the step of generating a plasma using said fuel, said fuel consists essentially in natural gas, methane, hydrocarbons, biogas or hydrogen. By "consists essentially in", this means that said fuel may comprise, next to natural gas, biogas or hydrogen, some impurities in small amounts (usually found in the art for those gas). More preferably, at the step of generating a plasma using said fuel, said fuel consists essentially in natural gas.

[0086] It is to be noted that feeding natural gas, methane, hydrocarbons, or biogas in a plasma device will generate, next to ionization, some decomposition / cracking of the methane molecules leading to soot (and / or derived hydrocarbons species CxHy) formation in the created plasma (which will then be injected in the fining zone at the next step of the process). The presence of soot is another advantage of the invention, when using natural gas, methane, hydrocarbons, or biogas as fuel, as the soot will end up in the combustion flames (12) where it will emit as a black body and will :- increase radiation of the combustion flame and therefore improve energy transfer of the flame through the batch blanket / melt, in favour of energy consumption; and- decrease the combustion flame temperature, in favour of reducing NOx gas formation.

[0087] According to another embodiment of the process of the invention, at the step of generating a plasma using said oxidizer, said oxidizer comprises oxygen or air, preferably oxygen. In other words, this means that said oxidizer fed in the plasma devices as working fluid comprises oxygen or air.

[0088] In an embodiment, at the step of generating a plasma using said oxidizer as working fluid, an inert gas (e.g. N2), sometimes called carrier gas in the art, may be added in addition to the oxidizer in the plasma device (14). This inert gas will act to protect the walls of the plasma device as known in the art, by making a vortex around said walls. Alternatively, at the step of generating a plasma using said oxidizer, said oxidizer consists essentially in oxygen or air. By "consists essentially in", this means that said oxidizer may comprise, next to oxygen or air, some impurities in small amounts (usually found in the art forthose gas). For oxygen, such impurities may be present up to 10-15 %, esp. if said oxygen is produced on-site.

[0089] For example, in the invention, it may be considered the following advantageous combination of fuel / oxidizer : natural gas / air, natural gas / oxygen or hydrogen / oxygen.

[0090] According to an embodiment of the process of the invention, the vitrifiable materials comprise raw materials and cullet, preferably the amount of cullet being at least 10% in weight of the total amount of vitrifiable materials, or even at least 20% in weight of the total amount of vitrifiable materials. More preferably, the amount of cullet is at least 30% in weight of the total amount of vitrifiable materials, or even, very preferred, at least 40% in weight. This is advantageous as it allows to reduce further the CO2 production / emission of the process of the invention when operating (due to a reducing of the emission occurring from the decarbonization of the carbonate raw materials).

[0091] In an embodiment, the process of the invention comprises further a step of extracting exhaust gas from the melting zone (3) thanks to extracting means.

[0092] In another embodiment, the process of the invention comprises further a step of extracting exhaust gas from the fining zone (4) thanks to extracting means.

[0093] Finally, the invention also relates to a process of revamping an existing combustion glass furnace to provide a revamped glass furnace (1), comprising the steps of :- providing an existing glass furnace with (i) a tank (2) having side-walls and end-walls, and having a melting zone (3) and a fining zone (4) downstream of the melting zone (3); said tank comprising a plurality of combustion heating means;- replacing at least a part of said plurality of combustion heating means in said tank (2) by new means comprising :(i) fuel plasma devices (13) located outside of said tank (2) and alimented with a fuel as a working fluid and / or oxidizer plasma devices (14) located outside of said tank (2) and alimented with an oxidizer as a working fluid;(ii) fuel injection means (10) located at the tank (2) ;(iii) oxidizer injection means (11) located at the tank (2); wherein said fuel plasma devices (13) are upstream of and in fluidic connection with said fuel injection means (10) and / or said oxidizer plasma devices (14) are upstream of and in fluidic connection with said oxidizer injection means (13).

[0094] The solution of the invention is particularly advantageous as it allows an easy revamping / retrofitting of existing combustion furnaces. As classical burners / combustion heating means of classical combustion furnaces are located outside of the tank, it is relativelyeasy to replace those burners by the solution of the invention, namely the combination of fuel and / or oxidizer plasma devices with fuel and / or oxidizer injections means, without leading to too much modifications of the furnace structure and thereby with limited investments compared to other solutions from the prior art. Moreover, the oxidizer and fuel (working fluid of the invention) are already advantageously available on site.

[0095] The process of revamping an existing glass furnace according to the invention may be advantageously used to provide the furnace (1) according to the invention.

[0096] According to the process of revamping of the invention, said plurality of combustion heating means may be located in the melting zone (3) and / or in the fining zone (4).

[0097] According to the process of revamping of the invention, said plurality of combustion heating means are replaced at least partially by new means. For example, if the existing combustion glass furnace has combustion heating means at the melting zone and at the fining zone, only combustion heating means from the fining zone (or even at least a part of them) may be replaced by new means (leading to the configuration as illustrated at FIG.1-2). For example also, if the existing combustion glass furnace has combustion heating means at the melting zone and at the fining zone, only combustion heating means from the melting zone (or at least a part of them) may be replaced by new means (leading to the configuration as illustrated at FIG.4).

[0098] Preferably, the process of revamping according to the invention comprises a step of replacing the whole plurality of combustion heating means in said tank (2) by said new means (leading to the configuration as illustrated at FIGS.3, 5).

[0099] The person skilled in the art realizes that the present invention is by no means limited to the preferred embodiments described above. It is further noted that the invention relates to all possible combinations of features, and preferred features, described herein and recited in the claims.

Claims

CLAIMS1. Furnace (1) for melting verifiable materials, comprising a tank (2) having side-walls and end-walls, and having a melting zone (3) and a fining zone (4) downstream of the melting zone (3); said tank (2) comprising : inlet means (5,5') configured to feed vitrifiable materials in said melting zone (3); fuel injection means (10) for a fuel to be injected in said tank (2); oxidizer injection means (11) for an oxidizer to be injected in said tank (2); outlet means (17); characterized in that said furnace further comprises : fuel plasma devices (13) located outside said tank (2) and alimented with a fuel as a working fluid; and / or oxidizer plasma devices (14) located outside said tank (2) and alimented with an oxidizer as a working fluid; wherein said fuel plasma devices (13) are upstream of and in fluidic connection with said fuel injection means (10) and / or said oxidizer plasma devices (14) are upstream of and in fluidic connection with said oxidizer injection means (11).

2. Furnace according to claim 1, characterized in that said fuel injection means (10) and / or said oxidizer injection means (11) are located at at least one of the side-walls or at the downstream end-wall of the tank (2).

3. Furnace according to any of the preceding claims, characterized in that it comprises :- fuel plasma devices (13) located outside said tank (2) and alimented with a fuel as a working fluid; and- oxidizer plasma devices (14) located outside said tank (2) and alimented with an oxidizer as a working fluid.

4. Furnace according to any of the preceding claims, characterized in that the injection means (10;ll) and the plasma devices (13; 14) are located at the fining zone (4).

5. Furnace according to any of the preceding claim, characterized in that the injection means (10;ll) and the plasma devices (13; 14) are located at the melting zone (3).

6. Furnace according to any of claims 4 and 5, characterized in that the injection means (10;ll) and the plasma devices (13; 14) are located at the melting zone (3) and at the fining zone (4).

7. Furnace according to any of the preceding claims, characterized in that said melting zone (3) and said fining zone (4) are separated by at least one neck (9) or throat.

8. Process for melting vitrifiable materials, comprising steps of :(a) charging vitrifiable materials in a tank (2) through inlet means (5), said tank (2) having side-walls and end-walls, and having a melting zone (3) and a fining zone (4) downstream of the melting zone (3);(b) melting said vitrifiable materials in said melting zone (3), thereby providing a melt;(c) injecting in said tank (2) a fuel with fuel injection means (10);(d) injecting in said tank (2) an oxidizer with oxidizer injection means (11);(e) combustion of said fuel with said oxidizer, thereby generating combustion flames (12) in said tank (2);(f) fining the melt in said fining zone (4), thereby providing a refined melt; and(g) flowing the refined melt to a working zone (18) through outlet means (17); characterized in that it further comprises :(h) before the step (c) of injecting, a step of generating a plasma using said fuel as a working fluid in fuel plasma devices (13) located outside said tank (2); and / or(i) before the step (d) of injecting, a step of generating a plasma using said oxidizer as a working fluid in oxidizer plasma devices (14) located outside said tank (2).

9. Process according to the preceding claim, characterized in that, at the step (h) of generating a plasma using said fuel, said fuel comprises, or consists essentially in, natural gas, methane, hydrocarbons, biogas or hydrogen.

10. Process according to the preceding claim, characterized in that said fuel comprises, or consists essentially in natural gas.

11. Process according to any of claims 8-10, characterized in that, at the step (i) of generating a plasma using said oxidizer, said oxidizer comprises, or consists essentially in, oxygen or air.

12. Process of revamping an existing combustion glass furnace to provide a revamped glass furnace (1), comprising the steps of :- providing an existing glass furnace with (i) a tank (2) having side-walls and end-walls, and having a melting zone (3) and a fining zone (4) downstream of the melting zone (3); said tank comprising a plurality of combustion heating means;- replacing at least a part of said plurality of combustion heating means in said tank (2) by new means comprising :(i) fuel plasma devices (13) located outside of said tank (2) and alimented with a fuel as a working fluid and / or oxidizer plasma devices (14) located outside of said tank (2) and alimented with an oxidizer as a working fluid;(ii) fuel injection means (10) located at the tank (2) ; (iii) oxidizer injection means (11) located at the tank (2); wherein said fuel plasma devices (13) are upstream of and in fluidic connection with said fuel injection means (10) and / or said oxidizer plasma devices (14) are upstream of and in fluidic connection with said oxidizer injection means (11).

Images