Glass melting process with very low to zero CO2 emissions

Abstract

The present invention relates to a method for melting a vitrifiable material to produce a sheet glass, the method comprising the steps of: (i) providing a furnace having a specific segmented design; (ii) charging vitrifiable materials comprising raw materials and cullet in an amount of at least 10% by weight of the total amount of vitrifiable materials, and the raw materials comprising less than 25% by weight of carbonate compounds, into the melting tank using an inlet device; (iii) melting the vitrifiable material in the melting tank; (iv) clarifying the melt in the clarification tank by heating with an oxycombustion heating device supplied with a gas and / or hydrogen; (v) flowing the melt from the clarification tank to a working zone through an outlet device; (vi) capturing CO2 from a flue gas, said flue gas having a CO2 concentration of at least 35%; the electrical input fraction ranges from 30% to 85%, and the step of capturing CO2 comprises a compression and / or dehydration step.

Description

Technical Field

[0001] The present invention relates to a glass melting method which is intended to continuously supply molten glass to a flat glass forming facility such as a float facility or a rolling facility. In particular, the present invention relates to a glass melting method which offers many advantages, especially in terms of CO2, especially CO2 emissions and capture.

[0002] The present invention more particularly relates, but is not limited to, a fusion process for flat glass involving large-scale production capabilities (ie, up to 1000 tons / day or more). Background Art

[0003] Global warming and the need to reduce CO2 emissions are increasing pressure on glass manufacturers, and rising energy prices and CO2 taxes could soon seriously threaten the competitiveness of the glass industry.

[0004] Against the backdrop of urgent action to reduce carbon emissions, the glass industry has over the years invested heavily in the decarbonization of its manufacturing processes in order to produce glass products suitable for a sustainable, resource-efficient, low-carbon society.

[0005] To achieve the transformation, the glass industry has identified many solutions / technologies to approach this ambitious goal, such as, for example, using electricity as energy, using alternative and greener energy sources like H2 or biogas, using alternative raw materials, increasing the use of cullet as raw material, heat recovery, CO2 capture utilization and storage (or CCUS), …

[0006] However, all these techniques are accompanied by serious disadvantages or problems in practical implementation or are not feasible from an economic point of view. Therefore, there is still an urgent need for a glass melting method that allows a substantial reduction in CO2 emissions but at the same time remains economically acceptable to glass manufacturers.

[0007] On using electricity as energy:

[0008] It is known that furnaces which use electrical energy to melt the raw glass materials show a reduction in CO2 emissions and also show a reduction in overall energy consumption. Glass melting furnaces in which the heating power is supplied entirely by electricity are known and have been developed, although they are well proven only for small-scale capacities, i.e. less than 300 t / day (scale-ups to more than 600 t / day remain to be developed).

[0009] In contrast to the classic combustion furnaces known as "hot top furnaces" (or "warm top furnaces"), these furnaces are also known as "cold top furnaces" because the raw materials are distributed above the glass melting surface to form an insulating batch "thin layer" that reduces the temperature from about 1400°C in the glass melt to less than 500°C (perhaps to 50°C) at and above the thin layer. All-electric furnaces offer significant advantages. First, all-electric furnaces have low direct CO2 emissions, thermal NO x or SO x Very low emissions.

[0010] Furthermore, since the melting energy is substantially transferred to the glass (e.g., since the electrodes allow the current to pass through and heat the bath of molten glass from their volume), heat losses in an all-electric furnace are much lower, making it an energy-efficient furnace, for example, compared to a hot-top fired furnace, where significant heat losses still occur in the furnace superstructure and residual exhaust gases, even if a heat recovery system is used. Unfortunately, all-electric furnaces also exhibit some disadvantages compared to fired hot-top furnaces.

[0011] In particular, in this furnace: - The glass quality does not meet typical flat glass specifications, especially in terms of small bubble density; and - The temperature at the bottom where the electrodes are located is very high (e.g. greater than 1400°C), which can lead to a significant reduction in the furnace life (typically from more than 15 years for conventional furnaces to less than 8 years, sometimes even to 2 to 7 years) due to accelerated corrosion of the bottom refractory and glass tank walls.

[0012] In addition, the surface melting rate of the cold top all-electric furnace, that is, the amount of glass melted from the raw materials per unit time and per unit furnace area (in T / d / m 2 In order to achieve an acceptable surface melting rate for this furnace (approximately 2T / d / m 2 Up to 3T / d / m 2 ), it is necessary to set the glass temperature above 1400°C, or even above 1450°C, which will further adversely affect the furnace life. In contrast, the surface melting rate of a classic combustion furnace is typically about 5T / d / m 2 Alternatively, if a lower surface melting rate is targeted in order to avoid affecting the furnace life as much as possible, this would mean that the melting area would need to be significantly increased, which would have a significant negative impact on the required investment and the industrial space occupied.

[0013] Finally, such cold-top furnaces lack flexibility in terms of energy (electricity only).

[0014] It is also known to combine combustion heating and electrical heating in a "hybrid system". In this configuration, which primarily operates with a "hot top", the furnace comprises a burner and electrodes to which electricity is supplied.

[0015] This hybrid furnace offers great advantages in terms of energy flexibility, allowing the electrical input fraction to be adapted according to different parameters (operating or speculative).

[0016] Furthermore, a hot top furnace allows a higher surface melting rate to be achieved for the same bottom temperature compared to a cold top furnace (or alternatively, a hot top furnace has a lower bottom temperature for the same surface melting rate).

[0017] Apart from this, hybrid furnaces with "hot top" operation show some disadvantages. In particular, significant heat losses occur (i) at the roof and walls of the melting zone and (ii) in the hot waste / flue gases produced during melting, which reduces the energy efficiency of the furnace. The use of heat recovery systems to limit heat losses with the flue gases can be considered, but this does not completely solve the problem and requires specific investments.

[0018] Furthermore, in such furnaces the temperature of the roof / superstructure in the melting zone may under some conditions become very low (e.g. less than 1000°C), which may lead to a significantly increased risk of alkaline condensation (e.g. NaOH) in said zone, leading to refractory corrosion of the roof.

[0019] Besides, in these furnaces, especially due to the limitations described above for all-electric furnaces (ie bottom and roof corrosion phenomena), the electrical input fraction is usually limited to a maximum of 35% of the total energy input.

[0020] Recently, some hybrid furnaces have been described with specific designs in order to increase the electrical input fraction (e.g. up to 80%), but for most of them they operate with cold tops and this poses some problems. Regarding the use of alternative and more environmentally friendly energy sources like hydrogen H2 or biogas:

[0021] Even though it is clear that they would bring advantages in terms of environment / energy consumption / CO2 emissions, serious limitations prevent their widespread use in the glass industry (lack of availability of biogas, and the high price of H2 (which makes H2 an economically unfeasible solution as the only energy source for melting glass raw materials so far)).

[0022] About heat recovery:

[0023] The recovery of waste heat from flue gases is already widely used in the glass industry for preheating the combustion air entering the furnace at temperatures above 1000°C or for preheating gases and oxygen at temperatures above 400°C and 500°C, respectively ("Hotox"). Apart from this, waste heat from flue gases can also be used for preheating vitrifiable materials, in particular cullet. However, it is known that preheating raw materials / cullet cannot be combined with electric melting, since the temperature of the flue gases released by the raw materials in this case is too low.

[0024] On the use of CO2 capture:

[0025] Typically, the CO2 capture process in industrial processes / plants consists of two steps: (i) separation of CO2 from the exhaust gas mixture by selective reaction with a separation material ("absorption" of CO2) and (ii) regeneration of the used material by a reverse reaction ("desorption" of CO2). The separation material can be reused for CO2 capture by repeating steps (i) and (ii) in sequence. Amines in the form of solvents or membranes or porous adsorbents are by far the most widely used materials in CO2 capture processes in industry, as the technology is mature and amines and CO2 can be effectively separated via a reversible reaction. However, this amine approach (e.g., using aqueous MEA) remains a poor choice, especially in the specific context of the glass industry to date, for at least the following main reasons: - In known glass manufacturing processes, the combustion gases / flue gases exhibit low concentrations of CO2 (generally, less than 30% by volume and usually about 10% to 20%), as well as a high concentration of CO2 due to the presence of many other components (mainly N2, H2O, O2, NO x 、SO x etc.), which has low purity, thus greatly affecting the efficiency of the CO2 capture process; and - The amine-CO2 capture process requires a large amount of energy in order to regenerate the amine adsorbent (desorption process), thus affecting the overall energy consumption (and potentially CO2 emissions depending on the energy used, which is obviously counterproductive in the current situation).

[0026] Furthermore, known glass manufacturing processes generate very high flue gas volumes or flow rates, which also directly impacts investment and operating costs when one wants to capture CO2 from those flue gases, regardless of the process used. Purpose of the Invention

[0027] The object of the present invention is to overcome the disadvantages described above with respect to the prior art and to solve the technical problem, namely, by providing a glass melting method for producing flat glass using a combustion heating device and an electric heating device, which glass melting method shows reduced overall energy consumption and reduced CO2 emissions compared to classical melting furnaces, in particular compared to classical "hot top" hybrid melting furnaces.

[0028] Another object of the present invention is to provide a glass melting method which uses a combustion heating device and an electric heating device to produce flat glass and which exhibits an acceptable surface melting rate (particularly higher than 2T / d / m 2 , or better than 3T / d / m 2 surface melting rate).

[0029] Another object of the present invention is to provide a glass melting method for producing flat glass, which uses a combustion heating device and an electric heating device and has a longer life than a classical hot top hybrid melting furnace.

[0030] Another object of the present invention is to provide a glass melting method for producing flat glass using a combustion heating device and an electric heating device, which allows simple and cost-effective CO2 capture.

[0031] Another object of the present invention is to provide a glass melting method for producing flat glass using a combustion heating device and an electric heating device, which glass melting method is economically feasible. Summary of the invention

[0032] The present invention relates to a method for melting a vitrifiable material to produce flat glass, the method comprising the following steps: -Providing a furnace, the furnace comprising: (i) a melting tank M comprising at least one upstream zone Z1 covered by the furnace roof C1 and equipped with an electric heating device, a downstream zone Z2 covered by the furnace roof C2 and equipped with a combustion heating device 3, and a transition zone T between the furnace roofs C1 and C2; (ii) a clarifier tank F, which is covered by a furnace roof C4 and equipped with an oxygen-combustion heating device; (iii) a neck N which is covered by the furnace roof C3 and separates the melting tank M from the refining tank F; (iv) at least one inlet device X located at the melting tank M; (v) an outlet device O located downstream of the clarification tank F; and (vi) at least one flue gas extraction device located at at least one upstream zone Z1; The height H1 of the furnace roof C1 of the furnace is defined by: H1≤0.75*H2; H2 is the height of the furnace roof C2, the length L1 of at least one upstream zone Z1 is defined by: 0.25*(L1+L2)≤L1≤0.8*(L1+L2); L2 is the length of the downstream zone Z2, and the length LT of the transition zone T is defined by: LT≤0.2*(L1+L2), - charging vitrifiable materials into the melting tank M by means of at least one inlet device X, these vitrifiable materials comprising raw materials and cullet, the amount of cullet being at least 10% by weight of the total amount of vitrifiable materials, and the raw materials comprising less than 25% by weight of carbonate compounds; - melting the vitrifiable material in a melting tank M using a heating device; - fining the melt in the fining tank F by heating with an oxycombustion heater supplied with gas and / or hydrogen; - allowing the melt to flow from the clarification tank F to the working area through the outlet device O; - Capturing CO2 from flue gases having a CO2 concentration of at least 35%; Wherein the electricity input fraction ranges from 30% to 85%, and wherein the step of capturing CO2 from the flue gas comprises a compression and / or a dehydration step.

[0033] The present invention is therefore based on a novel and inventive method. In particular, the inventors have found that in a glass melting process for producing flat glass, by combining: - using a furnace with a specific design that includes a combination of (i) a "mixing" melt tank and a combustion and fining zone separated by a neck, and (ii) segmenting the melt tank into two zones with different furnace top heights (thus providing a cooler upstream zone and a warmer downstream zone with significant temperature differences), -Use oxygen as a combustion aid, - use of gases and / or hydrogen as combustibles, - use of a minimum amount of cullet in the vitrifiable material, - use of a minimum amount of decarbonized raw materials in the vitrifiable material, and - Using a specific and high electrical input fraction, You can also get: - acceptable surface melting rate, - extended furnace life, - Significant reduction in total energy consumption; - Significant reduction in total CO2 production; - the flue gases from the decomposition of raw materials (low in NOx and SOx impurities) and from the combustion can be extracted independently, allowing the separation and appropriate treatment of each, if necessary; and - A significant reduction in the volume of flue gases and a significant increase in the CO2 concentration in said flue gases and its purity, allowing the use of a simple, efficient and cost-effective CO2 capture process.

[0034] By implementing all the features of the present invention, the method of the present invention shows a very low CO2 fingerprint and is economically feasible.

[0035] In the present specification and claims, it should be well understood by those skilled in the art that, unless explicitly indicated to the contrary, as used herein, the term "a / an" or "the" means "at least one", and should not be limited to "only one". In addition, when a range is indicated, the endpoints are included. In addition, all integer values ​​and sub-domain values ​​within the numerical range are clearly included as if explicitly written. Finally, the terms "upstream" and "downstream" refer to the flow direction of the glass and should be understood in their usual sense, i.e., meaning along the average moving direction of the vitrifiable material / glass melt, from (multiple) inlet devices to (multiple) outlet devices. The expression "upstream portion" should be understood to mean the upstream portion of the first third of the length, which is located along the horizontal axis and the longitudinal axis of the furnace. The expression "downstream portion" should be understood to mean the downstream portion of the last third of the length.

[0036] Other characteristics and advantages of the invention will appear more clearly from a reading of the following description of a preferred embodiment given by way of simple illustrative and non-limiting example and of the accompanying drawings.

[0037] Figure 1 is a flow chart of an embodiment of the method of the present invention.

[0038] Figure 2 is a schematic plan view (vertical section) of an embodiment of the melting furnace of the present invention.

[0039] Figure 3 is a schematic plan view (horizontal cross section) of an embodiment of the melting furnace of the present invention.

[0040] Figure 4 is a schematic plan view (horizontal cross section) of an embodiment of the melting furnace of the present invention.

[0041] Figure 5 is a schematic plan view (horizontal cross section) of an embodiment of the melting furnace of the present invention.

[0042] According to the present invention and Figure 1The method presented for melting a vitrifiable material to produce flat glass comprises a first step of providing a specific furnace, said furnace 1 comprising: (i) a melting tank M comprising at least one upstream zone Z1 covered by a furnace roof C1 and equipped with an electric heating device 2, a downstream zone Z2 covered by a furnace roof C2 and equipped with a combustion heating device 3, and a transition zone T between the furnace roofs C1 and C2; (ii) a clarification tank F, which is covered by a furnace roof C4 and equipped with an oxygen combustion heating device 3', (iii) a neck N which is covered by the furnace roof C3 and separates the melting tank M from the refining tank F, (iv) at least one inlet device X located at the melting tank M; (v) an outlet device O located downstream of the clarification tank F; and (vi) at least one flue gas extraction device located at at least one upstream zone Z1; And the height H1 of the furnace top C1 of the furnace is defined as follows: H1≤0.75*H2; H2 is the height of the furnace top C2, the length L1 of at least one upstream zone Z1 is defined as follows: 0.25*(L1+L2)≤L1≤0.8*(L1+L2); L2 is the length of the downstream zone Z2, and the length LT of the transition zone T is defined as follows: LT≤0.2*(L1+L2).

[0043] According to the present invention and as generally adopted in the glass field, "melting tank" refers to a tank defining a zone where vitrifiable material (raw material and / or cullet) is fed and melted by heating, and when the furnace is in operation, the tank includes a melt and a "thin layer" of unmelted vitrifiable material, which floats on the melt and gradually melts and thus decreases from upstream to downstream of the melting tank.

[0044] According to the present invention and as generally used in the glass field, a "fining tank" refers to a tank defining a zone in which there is no longer a "thin layer" of unmelted vitrifiable material floating on the melt, the glass melt being heated at a temperature higher than the melting tank temperature (generally higher than 1400° C., or even higher than 1450° C.) in order to refine the glass (mainly by eliminating most of the bubbles). Such a fining tank is also generally referred to in the art as a "purification tank".

[0045] According to the invention, the "neck" separating the melting tank from the refining tank is narrowed in width and (roof) height compared to the downstream zone (zone Z2) of the melting tank and compared to the upstream zone of the refining tank F. The opening of the neck according to the invention is only partially below the free surface of the glass melt / thin layer, thus leaving a free opening above the glass melt / thin layer.

[0046] This furnace design with separate segmentation of the melting tank and the refining tank and with a high segmentation of the melting furnace roof brings many advantages with regard to energy consumption / CO2 emissions and with regard to the mechanical stability / lifetime of the furnace.

[0047] In particular, by combining the following two points in a specific design, namely, (i) separating the melting tank and the refining tank by a neck-shaped portion and (ii) segmenting the melting tank into two zones with different furnace top heights (thereby providing a cooler upstream zone and a warmer downstream zone with a significant temperature difference), the overall energy consumption of the furnace can be significantly reduced while maintaining a high electrical input fraction (thereby reducing CO2 emissions), maintaining an acceptable surface melting rate, and improving the mechanical stability and life of the furnace.

[0048] The melting furnace roofs C1 and C2 in the present invention are specifically designed to utilize the advantages of both the "cold roof" and "hot roof" zones and create a temperature gradient from the relatively low temperature upstream (below 1100°C) to the relatively high temperature downstream (above 1300°C).

[0049] In particular, the furnace of the present invention allows full control of (i) the temperature in each zone and (ii) the flue gas redistribution / extraction between the two zones of the melting tank and between the melting tank and the refining tank, so as to optimize energy consumption, avoid alkali corrosion as much as possible, and also optimize CO2 capture.

[0050] Furthermore, the furnace of the invention facilitates the creation of a strong temperature difference between the upstream and downstream parts of the melting tank, while avoiding as much as possible the backflow of flue gases emerging from the clarification tank towards the melting tank.

[0051] From the point of view of energy efficiency, the furnace of the present invention is advantageous because it allows: - segmenting the atmosphere and cutting off the heat radiation from the fining tank towards the melting tank(s) in order to effectively limit the energy in the zone requiring high temperature (fining zone); and - Extracting the flue gases from the upstream portion / outlet at the lowest possible temperature in order to limit useless heating of the gases released from the vitrifiable material and in order to optionally maximize the heat transfer from the combustion gases to the vitrifiable material and the glass melt.

[0052] From the point of view of surface melting rate, the furnace of the invention is advantageous because it allows to reach relatively high temperatures (greater than 1300° C.) in the downstream part of the melting tank in order to improve the melting kinetics of the vitrifiable material.

[0053] From a corrosion point of view, the furnace of the present invention is advantageous because it allows: - separation of the atmosphere between the melting tank and the refining tank allows limiting / avoiding the return flow of flue gases from the refining zone, which are rich in alkalis and therefore very corrosive due to the high temperatures required for refining; and - Having a restriction on the overall flow of molten glass will advantageously reduce the intensity of glass convection in the melting tank and reduce glass velocity, thereby reducing wear and erosion of the bottom refractory material.

[0054] Finally, the furnace of the present invention, through its specific segmentation between the melting tank and the fining tank (through the neck), also allows the melting tank and the fining tank to be completely decoupled in terms of dimensioning (length, width and furnace top height) and refractory properties, thereby optimizing each tank taking into account energy efficiency, glass quality, equipment space limitations and mechanical / structural / other limitations.

[0055] Figure 2 and Figure 3 An embodiment of the furnace 1 of the present invention is shown ( Figure 2 : vertical section, Figure 3 : horizontal section).

[0056] The furnace 1 of the present invention comprises a melting tank M, a neck portion N and a refining tank F. The components of M, N and F are generally made of refractory materials that are resistant to high temperatures, fumes and the corrosive effects of molten materials. An illustrative glass melt level in the tank (excluding a thin layer of batch material) is Figure 2 The dotted line in FIG.

[0057] According to the present invention and Figures 2 to 3 As shown, the furnace 1 comprises at least one inlet device X at the melting tank M for charging the furnace with vitrifiable material (raw glass material and / or cullet).

[0058] In order to improve the distribution over the surface of the molten tank M, several inlet devices, i.e. two or three inlet devices, are advantageously provided upstream of the molten tank M (or in other words, in the zone Z1). Preferably, and as is known in the art, at least one inlet device X is upstream of the molten tank M in terms of its width and / or laterally in terms of its length.

[0059] like Figures 2 to 3 As shown, the melting furnace 1 of the present invention comprises a melting tank M, which comprises: - at least one upstream zone Z1 covered by the roof C1 and comprising electric heating means 2; - a downstream zone Z2 covered by the furnace roof C2 and comprising the electric heating device 2 and the combustion heating device 3; - Transition zone T between furnace roof C1 and furnace roof C2.

[0060] According to an advantageous embodiment, the downstream zone Z2 comprises further electric heating means, such as Figure 2 and Figure 3 What is shown.

[0061] The electric heating device 2 according to the present invention is preferably located at the bottom of the molten tank M and is also preferably composed of immersed electrodes. The electrodes are advantageously arranged in a grid pattern (checkerboard) of multiples of 3 or 2 to facilitate connection with the transformer and current balancing. For example, the number of electrodes is designed so as to limit the maximum power of each electrode to 200kW while maintaining a maximum current density of 1.5A / cm at the electrode surface. 2 Furthermore, for example, the immersion electrode height is between 0.3 and 0.8 times the height of the glass melt.

[0062] The combustion and heating means 3 in the downstream zone Z2 in the melting tank M are constituted in particular by burners. In particular, these burners can be arranged generally in a row and along the side walls of the zone, for example on one side thereof or alternatively on each side thereof, so that the flame spreads over almost the entire width of the zone. Alternatively or additionally, these burners can also be located in the furnace roof C2, which promotes the heat transfer to the batch material, which in turn helps to reduce the batch material length, avoiding a thin layer of batch material reaching the end of the downstream zone Z2 and thus avoiding reaching the downstream end of the melting tank.

[0063] The combustion heating device 3 can be supplied with fuel and air, or fuel and oxygen, or fuel and oxygen-rich gas. The fuel can be fossil fuel, natural gas, biogas, hydrogen, ammonia, synthesis gas or a mixture thereof.

[0064] According to an advantageous embodiment, at least one upstream zone Z1 may comprise additional auxiliary combustion heating means (for example burners, not shown in the figure) in order to allow controlling the temperature of the furnace roof C1 (for example limiting the temperature variation along the zone Z1) and to increase the temperature when the temperature of the furnace roof drops below a certain level (for example below 600° C.). In particular, these auxiliary combustion heating means may advantageously be located in the furnace roof C1 in order to reduce the space occupation in the free volume above the melt / batch thin layer.

[0065] The upstream zone Z1 according to the invention has a furnace roof C1. The downstream zone Z2 according to the invention has a furnace roof C2.

[0066] According to the present invention, the height H1 of the furnace roof C1 is defined as follows: H1≤0.75*H2; H2 is the height of the furnace roof C2. In the present invention, the change in height between the furnace roofs C1 and C2 along the melting tank M means a transition zone T.

[0067] The "height" of the furnace roof in the present invention refers to the average inner height (e.g., the height from the inner surface of the furnace roof to the glass melt (excluding the batch material thin layer if any) from the inner surface of the furnace roof to the glass melt (e.g., the height from the inner surface of the furnace roof to the glass melt if any) from the inner surface of the furnace roof to the glass melt (excluding the batch material thin layer if any). Figure 2 1 ). The height H1 of the furnace roof C1 may be substantially constant along the length of the furnace roof, or alternatively, the height may vary over the length of the furnace roof. The height H1 of the furnace roof C1 may be substantially constant along the width of the furnace roof, or alternatively, the height may vary over the width of the furnace roof (e.g. in the case of an arched / dome-shaped furnace roof). The height H2 of the furnace roof C2 may be substantially constant along the length of the furnace roof, or alternatively, the height may vary over the length of the furnace roof. The height H2 of the furnace roof C2 may be substantially constant along the width of the furnace roof, or alternatively, the height may vary over the width of the furnace roof (e.g. in the case of an arched / dome-shaped furnace roof).

[0068] According to an embodiment of the present invention, the height H1 of the furnace roof C1 is defined by: H1≤0.7*H2, preferably H1≤0.6*H2, or even H1≤0.5*H2. This allows enhancing the above advantages of the present invention.

[0069] According to the invention, the length L1 of at least one upstream zone Z1 is defined by: 0.25*(L1+L2)≤L1≤0.8*(L1+L2); L2 is the length of the downstream zone Z2.

[0070] "Length" herein and throughout the specification and claims refers to the dimension taken along the flow of glass.

[0071] According to another embodiment of the invention, the length L1 of at least one upstream zone Z1 is defined by: 0.3*(L1+L2)≤L1, preferably 0.4*(L1+L2)≤L1, or even 0.5*(L1+L2)≤L1. This also allows enhancing the above advantages of the invention.

[0072] According to another embodiment of the invention, the length L1 of the at least one upstream zone Z1 is defined by: L1 ≤ 0.75*(L1 + L2), preferably L1 ≤ 0.7*(L1 + L2).

[0073] It is worth mentioning that the total length of the melting tank can be slightly higher than the sum of (L1+L2) (e.g., about 10% to 15% higher). In fact, it is common in the art to provide a first zone Z0 (usually called "feeding chamber") (not shown) at the most upstream part of the melting tank for introducing vitrifiable materials and pushing these vitrifiable materials in the direction of the melt.

[0074] The furnace roof C1 according to the invention may be arched or domed, or alternatively, it may be flat. Independently of the furnace roof C1, the furnace roof C2 according to the invention may be arched or domed, or alternatively, it may be flat.

[0075] Advantageously, the furnace roof C1 may be constructed of a refractory material substantially made of silica, for example high purity silica. Silica refractory materials are known to be more sensitive to corrosion, for example compared to alumina, but due to the presence of the neck separating the melting tank from the refining tank, there is less alkali in the flue gas present in the melting tank.

[0076] The advantage of silicon dioxide is its low coefficient of expansion at temperatures above about 600° C., which allows high variations in temperature to be tolerated without disturbing the furnace roof superstructure.

[0077] Alternatively, the furnace roof C1 and / or the furnace roof C2 may consist of refractory materials substantially made of alumina or AZS (alumina-zirconia-silica), which have better corrosion resistance and therefore better lifespan.

[0078] According to the present invention and Figure 2 As shown, the melting furnace comprises a melting tank M comprising at least an upstream zone Z1 and a downstream zone Z2 having different furnace roof heights, the furnace roof C1 having a height H1 and the furnace roof C2 having a height H2.

[0079] In the melting furnace provided in the method according to the present invention, the change in height along the melting tank M between the furnace roof C1 and the furnace roof C2 means a transition zone T.

[0080] According to the invention, the length LT of the transition zone T is defined by: LT≤0.2*(L1+L2), preferably LT≤0.15*(L1+L2), or even LT≤0.1*(L1+L2).

[0081] According to an embodiment, the transition zone T between the furnace roof C1 and the furnace roof C2 may be an end wall. The end wall according to an embodiment may be a vertical wall or a short inclined wall (allowing a gradual transition). In this embodiment, the furnace roof C1 preferably has an inner surface that is substantially at the same level as the lower edge of the end wall or slightly below the lower edge. The end wall may be composed of a suspended rear wall. The suspended rear wall according to the present invention may be, for example, a suspended rear wall described in patent application US 5011402 A. Alternatively, the end wall may be located on the outer surface of the furnace roof C1.

[0082] According to another embodiment, the transition zone T between the furnace roof C1 and the furnace roof C2 is a shielding wall. The "shielding wall" in the present invention refers to a wall whose lower edge extends below the inner surface of the furnace roof C1 and is thus closer to the glass melt, but the wall leaves a free space above the glass melt. The advantage of this embodiment is to further reduce the radiation heat exchange between the upstream and downstream zones of the melting tank, and better separate the flue gases released from Z1 and Z2, while allowing free space for the vitrifiable material pushed from the upstream to pass through. For example, as is known in the art, the shielding wall can be an air-cooled suspended wall. The shielding wall according to the present invention can be composed of a suspended U-shaped shielding wall (as described, for example, in patent application US 3399046 A).

[0083] According to another embodiment, the transition zone T between the furnace roof C1 and the furnace roof C2 comprises at least one step. In the configuration with one step, the change in height of the furnace roofs C1 and C2 is obtained by the transition zone T, which comprises from C1 to C2: a first end wall, a short furnace roof with a height between H1 and H2, and a second end wall. The advantage of this configuration is that it facilitates the production of the transition between the furnace roofs C1 and C2 and increases the stability of the transition.

[0084] "Length of the transition zone" herein and throughout the specification and claims refers to the dimension of said zone along the glass flow, which dimension includes the thickness of the wall(s) (even if located on and / or overlapping the furnace roof C1 and / or furnace roof C1).

[0085] According to an advantageous embodiment, the transition zone consists of a refractory material substantially made of silicon dioxide.

[0086] Advantageously, according to another embodiment, the roof C1 and the transition zone T are made of the same refractory material in order to avoid expansion between the materials and / or to avoid corrosion between the materials. Preferably, they consist of a refractory material substantially made of silicon dioxide.

[0087] Also advantageously, according to another embodiment, the roof C1 , the roof C2 and the transition zone T are made of the same refractory material in order to avoid expansion between the materials and / or to avoid corrosion between the materials. Preferably, they consist of a refractory material substantially made of silicon dioxide.

[0088] According to the invention, the furnace comprises a refining tank F covered by a roof C4 and equipped with oxygen-combustion heating means 3 ′.

[0089] The "oxy - combustion device" 3' according to the present invention refers to a combustion device supplied with gaseous oxygen (O₂) as a combustion aid. Generally, the O₂ gas combustion aid supplied to the glass melting furnace has a purity of at least 90%, or even at least 95%. Compared with using air, the advantage of using gaseous oxygen as a combustion aid is that it greatly reduces the so - called corrosive <NOx> pollutants that occur during combustion. Even if they can still be present in the flue gas (depending on the purity of O₂ and the amount of parasitic air), the amount will be very low.

[0090] The oxy - combustion heating device 3' in the clarification tank F according to the present invention can be constituted by burners, which are advantageously arranged along the side walls of the clarification tank. In addition, the burners are advantageously spaced apart from each other in order to distribute the energy supply over a part of the clarification tank F, preferably the upstream part (e.g., over about 50% of the length). These burners are also generally arranged in rows on one side of the clarification tank F, or alternatively on each side of the clarification tank, and are preferably arranged in a staggered manner (so that the flames spread over almost the entire width of the tank).

[0091] The furnace roof C4 according to the present invention is preferably arched or domed.

[0092] According to an advantageous embodiment, the clarification tank F can include additional electric heating devices (not shown in the figures), especially in the upstream part of the clarification tank (e.g., over about 50% of its length). This allows increasing the fraction of electrical input and thus improving the energy efficiency, thereby reducing CO₂ emissions.

[0093] According to the present invention, the furnace includes a neck - like part N, which is covered by the furnace roof C3 and separates / segments the melting tank M from the clarification tank F.

[0094] According to the present invention, the "neck - like part" that separates the melting tank M from the clarification tank F means that it is narrower in width and (furnace - roof) height compared to the downstream zone (zone Z2) of the melting tank and compared to the upstream zone of the clarification tank F. The opening of the neck - like part according to the present invention is only partially below the free surface of the glass melt / batch thin layer, thus leaving a free opening above the glass melt / batch thin layer.

[0095] Based on the definition of the neck - like part according to the present invention, the width W of the neck - like part N N is as follows: W N <W M and W M is the width of the melting tank M. Also based on the definition of the neck - like part according to the present invention, the width W of the neck - like part N N is as follows: W N <W F and W F is the width of the clarification tank F.

[0096] "Width" in the context of the present invention refers herein and throughout the specification and claims to the (average) dimension perpendicular to the glass flow.

[0097] This furnace design with segmentation of the melting tank and the refining tank brings many advantages, both in terms of energy consumption / CO2 emissions and in terms of the mechanical stability / lifetime of the furnace. In particular, advantageously, in the context of the present invention, this furnace with its specific segmented design allows, if necessary, to independently treat the flue gases from the melting tank (zone Z1 and / or zone Z2) and the flue gases from the refining tank.

[0098] The base of the neck-shaped portion N in the present invention may be substantially at the level of the floor / bottom of the melting tank M, or above the level, or below the level. In addition, the base of the neck-shaped portion N may be substantially at the level of the floor / bottom of the clarification tank F, or above the level, or below the level.

[0099] According to an embodiment, the neck N does not comprise any heating means, such as any electric heating means.

[0100] The furnace roof C3 according to the present invention may be arched or dome-shaped, or alternatively, the furnace roof may be flat. Based on the definition of the neck-shaped portion according to the present invention, the height H3 of the furnace roof C3 of the neck-shaped portion N is lower than the height H2 of the furnace roof C2 of the melting tank M. Also based on the definition of the neck-shaped portion according to the present invention, the height H3 of the furnace roof C3 of the neck-shaped portion N is lower than the height H4 of the furnace roof of the clarification tank F.

[0101] According to yet another advantageous embodiment of the present invention, the furnace may include a removable wall located at the neck (e.g., a scraper rod from the side wall of the neck) so that (i) unmelted vitrifiable material that may reach the end of the melting tank can be blocked, thereby avoiding these unmelted vitrifiable materials from passing through the neck toward the clarification tank, and (ii) the intensity of the reverse flow of the glass melt from the clarification tank toward the melting tank is controlled or the reverse flow of the glass melt from the clarification tank toward the melting tank is eliminated.

[0102] According to yet another advantageous embodiment of the invention, the furnace may comprise a removable wall at the neck (eg a shielding wall through the roof of the neck) in order to increase the segmentation of the melting and refining tanks in terms of atmosphere and heat radiation.

[0103] According to the present invention, the melting furnace comprises an outlet device O, which is located downstream of the clarification tank F and is used to allow the molten glass to reach the working area. According to an embodiment, the outlet device O is generally composed of a neck-shaped portion so as to guide the melt to the working area, which is generally referred to as the "working end" or also referred to as "pressure steaming" or also referred to as "regulation zone". Alternatively, the outlet device O is composed of a throat-shaped portion (i.e., an opening completely immersed in the glass melt, with no free surface left above it) so as to guide the melt to a working area including, for example, (multiple) forehearths. The working area according to the present invention may include, for example, a regulation zone, in which, before the glass melt leaves the zone through the outlet to reach the forming zone, thermal regulation is performed by controlled cooling. Such a forming zone may include, for example, a float facility and / or a rolling facility.

[0104] According to the present invention (such as Figure 2 and Figure 3 As shown), the furnace comprises at least one flue gas extraction device 4, which is located in at least one upstream zone Z1, preferably close to (multiple) inlet devices X, so as to recover heat from the flue gases and transfer the heat to the glass melt and / or unmelted vitrifiable material in the melting tank M.

[0105] According to an embodiment of the invention, the furnace further comprises at least one flue gas extraction device in the downstream zone Z2 and / or at least one flue gas extraction device in the clarifier F (not shown in the figures).

[0106] When extraction means are present in zone Z2, this advantageously allows extracting flue gases from the downstream zone Z2 if the flue gases in this downstream zone are rich in alkali (thus avoiding condensation and the ensuing corrosion in zone Z1).

[0107] When an extraction device is present in the clarification tank F, it is preferably located in the upstream part of the clarification tank.

[0108] Preferably, in the present invention, the extraction device(s) 4 are located on the side wall (the side wall on one side or both sides).

[0109] In particular, it is energetically advantageous in the present invention to extract the flue gas to the greatest extent from upstream of the furnace, in particular from upstream of the melting tank. For example, at least 25% of the flue gas produced in the melting zone can be advantageously extracted from upstream of the melting tank. However, it may be advantageous to extract a portion of the flue gas from downstream in the melting tank in order to limit the risks associated with alkali attack of the furnace roof refractory. In fact, alkali evaporation increases with temperature, so the alkali concentration in the flue gas in the downstream part of the melting zone will be higher. Flue gas with a higher alkali concentration may cause problems related to condensation in the cooler areas of the superstructure / furnace roof, so it is more appropriate to discharge the flue gas from downstream. In addition, it may be advantageous to extract a portion of the flue gas from upstream in the melting tank, because in this upstream zone, the flue gas is substantially composed of gases released from the decomposition of the raw materials, and therefore the alkali content is low. Finally, it may also be advantageous to extract a portion of the flue gas from the clarification tank, because the flue gas in the clarification tank contains even more alkali due to the higher temperature required for clarification.

[0110] Moreover, it is further advantageous in the present invention that the flue gases (at least a large part thereof) resulting from the decomposition of the raw materials in the upstream Z1 of the melting tank can be extracted (and thus treated) almost independently of the flue gases coming from the combustion (in the zone Z2 and / or the clarifier tank). In fact, the flue gases emerging in the zone Z1 are low in NOx and SOx content, thus facilitating CO2 capture.

[0111] In an advantageous embodiment of the invention, Figure 4 As shown, the furnace of the present invention includes a melting tank M, which is laterally expanded and is equipped with (multiple) inlet devices X' and X", located at each lateral side, so that the melting tank includes two different upstream zones Z1' and Z1", and two transition zones T' and T", in which two relative glass flows converge through a central downstream zone Z2.

[0112] In this configuration: - The height H1' of the melting furnace roof C1' is defined by: H1'≤0.75*H2; - The height H1" of the melting furnace roof C1" is defined by: H1"≤0.75*H2; - the length L1' of at least one upstream zone Z1' is defined by: 0.25*(L1'+L2)≤L1'≤0.8*(L1'+L2); - the length L1″ of at least one upstream zone Z1″ is defined by: 0.25*(L1″+L2)≤L1″≤0.8*(L1″+L2); - the length LT' of the transition zone T' is defined by: LT'≤0.2*(L1'+L2); and - The length LT" of the transition zone T" is defined by: LT"≤0.2*(L1"+L2).

[0113] Additionally, in this configuration: - the melting tank comprises a downstream furnace roof C2 and two upstream furnace roofs C1' and C1". The furnace roofs C1' and C1" can each be independently configured according to any embodiment of the present invention related to the furnace roof C1. For example, the upstream furnace roofs C1' and C1" can have the same or different heights H1' and H1"; The molten tank comprises two transition zones T′ and T″. The two transition zones can each be configured independently according to any embodiment of the invention with respect to the transition zone T.

[0114] In addition, in this configuration, for example, the combustion heating device 3 is Figure 4 Shown are, for example, two burners located in the melting tank wall facing the neck. Alternatively, for example, the combustion heating device 3 is located in the furnace roof C2.

[0115] In this advantageous configuration / embodiment, each upstream zone, each upstream furnace roof and each inlet device is according to the present invention and its embodiments, and can be designed independently of other upstream zones, other upstream furnace roofs and other inlet devices according to the above description. Therefore, for the sake of clarity, the features described above with respect to Z1 apply independently to Z1' and Z1", the features described above with respect to C1 apply independently to C1' and C1", the features described above with respect to T apply independently to T' and T", and the features described above with respect to X apply independently to X' and X". In addition, the specific advantageous features described with respect to M, C2, C3, C4, N, F, etc. also apply to this specific configuration, and the advantages are the same.

[0116] A specific glass melting furnace design with segmentation between the melting tank and the refining tank by a neck is described in European patent application EP 21200998.9, which is incorporated herein by reference as an embodiment of the present invention.

[0117] According to a particular embodiment, the furnace of the present invention is defined by: 0.1*W F ≤W N ≤0.6*W F ; W M ≥1.4*W N ; W M is the width of the molten groove M; W F is the width of the clarification tank F; W N is the width of the neck N.

[0118] This embodiment allows enhancing the above-mentioned advantages of the present invention, as follows: - better separation of the atmosphere between the melting tank and the refining tank, thus limiting the backflow of corrosive fumes from the refining tank to the melting tank; - Enhanced cut-off of heat radiation from the clarification tank toward the melting tank; - Increase restriction on the overall flow of molten glass or even eliminate reverse flow.

[0119] Also preferably, the furnace is 0.2*W F ≤W N ≤0.6*W F , or even 0.3*W F ≤W N ≤0.5*W F This allows to find a good compromise between two opposing requirements: on the one hand, the neck(s) between the melting zone and the refining zone should ideally be as narrow as possible in order to (1) reduce the opening between the melting superstructure / roof and the refining superstructure / roof and (2) create an obstacle to the overall strength of the glass melt convection in the melting tank, and on the other hand, the neck should ideally be as wide as possible in order to limit the glass velocity inside the neck and thus limit the wear / erosion of the refractory wall of the neck.

[0120] Also preferably, the furnace of the present invention is composed of W M ≥1.5*W N , or even W M ≥1.8*W N More preferably, the furnace of the present invention is composed of W M ≥2*W N This allows a higher width limitation to be achieved at the neck N and allows improved cut-off of thermal radiation, better separation of the atmosphere and the creation of a limitation on the flow of molten glass.

[0121] According to an embodiment, the furnace may comprise one melting tank and one neck; or two melting tanks and two necks; or even three melting tanks and three necks. These embodiments are extensively described in European patent application EP 21200998.9, which is incorporated herein by reference.

[0122] exist Figure 5 In the particular "double melt tank" configuration shown, the furnace for melting vitrifiable material comprises two melt tanks M' and M", two necks N' and N" (one neck for each melt tank) and at least two inlet devices X' and X" (one inlet device for each melt tank).

[0123] Configuration with single melting tank ( Figure 3 ) is particularly advantageous because it allows: - Reduce the roof span of each melting tank with the same total melting tank area and furnace length (length is usually more constrained than width). The reduction in the roof span allows: (i) Reducing stresses within the furnace roof material, thereby reducing the risk of material creep and furnace roof sagging. It will then be possible to use refractory materials with higher corrosion resistance and lower creep resistance, such as alumina or spinel, thereby extending the furnace life; (ii) in the case of a vaulted furnace roof C1 and / or C2, the average height of the furnace roof is reduced, thereby resulting in a lower horizontal radiation transfer and, subsequently, in the case of flue gases being extracted from the melting tank, a better heat transfer from the flue gases to the glass melt; - At the same total neck width (W N' +W N” ) and in the case of an arched neck-shaped furnace roof C3, reducing the opening surface between the melting tank and the clarification tank; - At the same total neck width (W N' +W N” ) to reduce the intensity of glass convection in the melting tank; - Makes furnace maintenance in the melting zone easier. In fact, with two melting tanks, one melting tank can be isolated from the rest of the furnace and allowed to cool, while production is carried out with the other melting tank. The overall life of the furnace can then be extended by replacing worn refractory materials in the melting area (which is the most critical area in terms of wear / corrosion).

[0124] In this configuration, the furnace has two melting tanks M', M", each melting tank having its upstream zone Z1' or Z1", its upstream furnace top C1' or C1", its downstream zone Z2' or Z2", its transition zone T' or T", and its inlet device X' or X". In addition, each melting tank M' and M" is separated from the fining tank F by a neck portion N' and N", respectively.

[0125] In this configuration, according to the present invention: - The height H1' of the melting furnace roof C1' is defined as follows: H1'≤0.75*H2'; - The height H1" of the melting furnace roof C1" is defined by: H1"≤0.75*H2"; - the length L1' of the upstream zone Z1' is defined by: 0.25*(L1'+L2')≤L1'≤0.8*(L1'+L2'); and - the length L1″ of at least one upstream zone Z1″ is defined by: 0.25*(L1″+L2″)≤L1″≤0.8*(L1″+L2″); - the length LT' of the transition zone T' is defined by: LT'≤0.2*(L1'+L2'); and - The length LT" of the transition zone T" is defined by: LT"≤0.2*(L1"+L2").

[0126] Furthermore, in this configuration, the furnace may advantageously be defined by: 0.1*W F ≤W N' ≤0.6*W F ; 0.1*W F ≤W N” ≤0.6*W F ; W M' ≥1.4*W N' ; W M' ≥1.4*W N” ; W M' is the width of the molten groove M'; W M” is the width of the molten groove M”; W F is the width of the clarification tank F; W N' is the width of the neck N'. W N' is the width of the neck N".

[0127] Additionally, in this configuration: - The upstream zone and the downstream zone may each be independently configured according to any embodiment of the invention in relation to Z1 and Z2. - the furnace roofs C1 ′ and C1 ″ can each be configured independently according to any embodiment of the invention related to the furnace roof C1 . For example, the upstream furnace roofs C1 ′ and C1 ″ can have the same or different heights H1 ′ and H1 ″; - the furnace roofs C2' and C2" can each be independently configured according to any embodiment of the invention related to the furnace roof C2. For example, the furnace roofs C2' and C2" can have the same or different heights H2' and H2"; and The transition zones T′ and T″ can each be independently configured according to any embodiment of the invention related to the transition zone T.

[0128] In this advantageous configuration / embodiment, each melt groove, each upstream zone, each downstream zone, each transition zone, each neck-shaped portion and each inlet device are according to the present invention and its embodiments, and can be designed independently of other melt grooves, other upstream zones, other downstream zones, other transition zones, other neck-shaped portions and other inlet devices according to the above description. Therefore, for the sake of clarity, the features described above with respect to M apply independently to M' and M", the features described above with respect to Z1 apply independently to Z1' and Z1", the features described above with respect to C1 apply independently to C1' and C1", the features described above with respect to Z2 apply independently to Z2' and Z2", the features described above with respect to C2 apply independently to C2' and C2", the features described above with respect to T apply independently to T' and T", and the features described above with respect to X apply independently to X' and X".

[0129] Furthermore, certain advantageous features described with respect to furnaces having a single melt tank (such as those described with respect to C3, C4, F) apply to this "dual melt tank" configuration, and the advantages are the same.

[0130] In the "double melting tank" furnace according to the embodiment, the two melting tanks M' and M" are preferably located at the width W of the refining tank F. F The two necks N', N" are connected to the clarification tank F (such as Figure 5 Alternatively, in a "double melt tank" configuration, one melt tank is located across the width W of the fining tank. F The first melting tank is connected to the clarifier tank by a neck in the middle of the length of the clarifier tank (on the right or left side) and the second melting tank is connected to the clarifier tank by a neck located in the middle of the length of the clarifier tank (on the right or left side) and close to the upstream of the clarifier tank (i.e. in the first third of the length of the clarifier tank). This latter configuration may be advantageous, for example, when there is insufficient space in the equipment housing the melting furnace to place two melting tanks side by side.

[0131] In the "double melting tank" configuration, the two melting tanks are located at the width W of the clarification tank. F In the case of a neck-shaped section connected to a fining tank, the distance D between the two melting tanks is preferably at least 1 m, more preferably at least 2 m, or better still at least 3 m. This is advantageous because it allows access to this area for maintenance operations and coating of the tank wall exterior.

[0132] In an alternative embodiment of the invention, the furnace is in a configuration with three melting grooves, three necks and three inlet devices. This embodiment is particularly advantageous compared to a configuration with a single melting groove, in the same manner as a "double melting groove" configuration. In this "three melting groove" configuration, each neck, each melting groove and each inlet device is in accordance with the invention and embodiments thereof, and can be designed independently of the other necks, other melting grooves and other inlet devices, respectively, as described above.

[0133] The specific advantageous features described with respect to the furnace having a "single melt tank" configuration and having a "double melt tank" configuration are applicable to the "triple melt tank" configuration, and the advantages are the same.

[0134] In the "three-melting tank" furnace according to the embodiment, at least two melting tanks pass through the width W of the clarification tank. F In the case where the neck portion in the melting tank is connected to the refining tank, the distance D between two adjacent melting tanks is preferably at least 1 m, more preferably at least 2 m, or better still at least 3 m.

[0135] In all furnace configurations according to the present invention (i.e., the "single melt tank" configuration, the "double melt tank" configuration and the "triple melt tank" configuration), in order to facilitate the distribution of the vitrifiable material to be charged, more than one inlet device can be provided for each melt tank, i.e., two inlet devices for each melt tank.

[0136] Preferably, the total surface area of ​​the melting tank(s) is in the range of 25 m 2 Up to 400m 2 Also preferably, according to the present invention, the surface area of ​​the clarification tank F is in the range of 25 m 2 Up to 400m 2 .

[0137] According to the present invention and Figure 1 The method for melting vitrifiable materials to produce flat glass comprises the steps of charging vitrifiable materials, including raw materials and cullet, into a melting tank using at least one inlet device.

[0138] According to the present invention, since the vitrifiable material includes raw materials and cullets, the raw materials and cullets are preferably charged into the melting tank M together, that is, charged into the melting tank through the same (multiple) inlet devices X. Alternatively, the raw materials and cullets are independently charged into the melting tank M through different (multiple) inlet devices X (e.g., one inlet device for the raw materials, one inlet device for the cullets, or two inlet devices for the raw materials, and two inlet devices for the cullets).

[0139] According to the invention, the amount of cullet is at least 10% by weight of the total amount of vitrifiable material. Preferably, the amount of cullet is at least 20% by weight of the total amount of vitrifiable material. More preferably, the amount of cullet is at least 30% by weight, or even very preferably at least 40% by weight of the total amount of vitrifiable material. This is advantageous because it allows to reduce the production / emission of CO2 of the process of the invention (due to the reduction of emissions resulting from the decarbonization of carbonate raw materials). Also preferably, the amount of cullet is at most 90% by weight, or even at most 80% by weight of the total amount of vitrifiable material. More preferably, the amount of cullet is at most 70% by weight, or even at most 60% by weight of the total amount of vitrifiable material.

[0140] According to the invention, the raw material contains less than 25% by weight of carbonate compounds. "Carbonate compounds" means, for example, alkali metal carbonates and alkaline earth metal carbonates. Preferably, the raw material contains less than 20% by weight, more preferably less than 10% by weight, even less than 5% by weight of carbonate compounds. The raw material may advantageously be free of any carbonate compounds.

[0141] This is advantageous because it allows reducing the portion of CO2 emissions resulting from the decarbonization of the raw materials compared to the classical glass melting process in which sodium carbonate Na2CO3, limestone CaCO3 and dolomite CaMg(CO3)2 are generally used as sources of sodium, calcium and magnesium. According to this embodiment, the alkali and alkaline earth metal sources can advantageously be present at least partially in the form of oxides or hydroxides such as CaO, CaO.MgO (calcined dolomite), Ca(OH)2, Mg(OH)2, NaOH, KOH.

[0141] According to the present invention and Figure 1 As shown, the method for melting a vitrifiable material to produce a flat glass includes the step of melting the vitrifiable material in a melting tank M by heating with a heating device (ie, an electric heating device 2 and a combustion heating device 3).

[0142] According to the present invention and Figure 1 The method for melting vitrifiable material to produce flat glass as shown comprises a step of refining the melt in a refining tank F by heating with an oxygen combustion heating device 3' supplied with gas and / or hydrogen. The term "gas" herein includes but is not limited to natural gas, synthesis gas and biogas. Natural glass is currently the most widely used due to practical, economic and availability reasons.

[0143] According to the present invention, the oxygen combustion heating device 3' is supplied with gas and / or hydrogen. In an embodiment, the oxygen combustion heating device 3' is supplied with at least 50% hydrogen, preferably at least 80% hydrogen. More preferably, the oxygen combustion heating device 3' is supplied with 100% hydrogen. This is advantageous because it allows a substantial reduction in the overall CO2 emissions of the method. In an alternative, the oxygen combustion heating device is supplied with more than 50% gas, preferably at least 80% gas, or even at least 100% gas. This is advantageous because it allows a higher CO2 concentration to be achieved in the flue gas, thereby facilitating and improving the CO2 capture step, and limiting the impact on the chemical properties of the glass and the refractory materials of the furnace. In a specific and advantageous embodiment of the present invention, the oxygen combustion heating device 3' is supplied with 50% gas and 50% hydrogen.

[0144] According to the invention, the fraction of electricity input in the process ranges from 30% to 85%. "Fraction of electricity input" according to the invention refers to the portion of electricity used for melting / refining in the total energy input of the process / furnace, i.e. electricity / (fuel+electricity), the total energy input being the total energy input of the process / furnace in standard / normal production mode, i.e. the total energy input at its standard withdrawal range (excluding the time periods of start-up, maintenance, thermal repair, culletizing, ...). Preferably, the fraction of electricity input ranges from 35% to 85%, more preferably from 40% to 85%.

[0145] According to the present invention and Figure 1 As illustrated, the method for melting vitrifiable material to produce flat glass comprises the step of causing the melt to flow from a refining tank F through an outlet device O to a working area.

[0146] According to the present invention, the outlet device O is located downstream of the clarification tank F for allowing the molten glass to reach the working area. According to an embodiment, the outlet device is generally composed of a neck-shaped portion so as to guide the melt to the working area, which is generally referred to as the "working end". Alternatively, the outlet device is composed of a throat-shaped portion so as to guide the melt to a working area including, for example, (multiple) forehearths. The working area according to the present invention may include, for example, a conditioning area, in which, before the glass melt leaves the area through the outlet to reach the forming area, thermal conditioning is performed by controlled cooling. Such a forming area may include, for example, a float facility and / or a rolling facility.

[0147] According to the present invention and Figure 1 As presented, a method for melting vitrifiable material to produce flat glass comprises the step of capturing CO2 from flue gases.

[0148] According to the present invention, the flue gas (i.e. the flue gas that undergoes the CO2 capture step) has a CO2 concentration of at least 35%. The CO2 concentration according to the present invention is a concentration defined for dry flue gas (i.e. flue gas with all its components except water (H2O)). Preferably, the flue gas in the present invention has a CO2 concentration of at least 40%, more preferably a CO2 concentration of at least 50%, or even a higher CO2 concentration of at least 60%. This is advantageous because the higher the CO2 concentration of the flue gas, the easier and more effective the CO2 capture applied on the flue gas.

[0149] According to the invention, the step of capturing CO2 from flue gas comprises a compression and / or dehydration step. The dehydration step corresponds to a water condensation and / or drying step of the flue gas. The compression step corresponds to increasing the pressure of the CO2, usually by using a compressor. The dehydration step may precede the compression step, and / or the dehydration step may accompany the compression step.

[0150] In particular, the step of capturing CO 2 from flue gases according to the invention can be carried out in a known manner using a CO 2 compression and purification unit (or CPU).

[0151] like Figure 1 As shown, the flue gas according to the invention can be recovered from the melting tank M, or from the clarification tank F, or from both for CO2 capture. In particular, if the oxygen combustion heating device 3' according to the invention is only supplied with hydrogen, the flue gas is advantageously recovered only from the melting tank M (the flue gas discharged from the clarification tank F does not contain CO2).

[0152] After the CO2 capture step according to the invention, the CO2 product has, for example, a pressure of about 35 bar at a temperature of 5° C. to 40° C., in gaseous form, suitable for transport by pipeline, or about 100 bar, in liquid form, suitable for transport by pipeline but also suitable for transport by truck or rail. For transport by truck, a value of 15 bar gauge at -35° C. is known to be suitable.

[0153] This simple and effective CO2 capture method is very advantageous because it allows avoiding the use of any adsorbents / chemical reagents that would lead to operating / energy costs and environmental issues, and because it allows cost-effective CO2 capture, making the entire inventive method economically viable.

[0154] According to a preferred embodiment, the step of capturing CO2 from the flue gases substantially consists of a compression and / or a dehydration step.

[0155] According to an advantageous embodiment, the method of the invention further comprises a step of eliminating acidic components from the flue gas. This step of eliminating acidic components is performed before or simultaneously with the step of capturing CO2 (e.g. before or simultaneously with / together with the compression and / or dehydration step).

[0156] The step of eliminating acidic components may include a step of flue gas desulfurization (or removal of so-called "SOx" compounds). It may also include a step of removing so-called "NOx" compounds, which may still be present even if the amount is very low due to the use of oxygen as an oxidant. This is advantageous because it allows the removal of corrosive compounds (SOx, NOx) before transport, storage and / or use.

[0157] After the step of capturing CO2 according to the invention, in a known manner, the CO2 product (e.g., in liquid form) can be transported by pipeline to its final destination and then stored / sequestered (e.g., deep in the seabed or in geological formations, such as groundwater layers with a high salt water content), or alternatively utilized (e.g., for enhanced oil recovery, or for food / beverage applications, or for firefighting applications). Advantageously, the CO2 product obtained after the step of capturing CO2 can be used locally to limit transportation. This can be considered if the amount of CO2 captured is not too high so that it can be absorbed by the local market.

[0158] According to an advantageous embodiment of the invention, the method further comprises a step of preheating the cullet, at least in part, by recovering heat from the furnace 1, before charging said cullet into the melting tank M. According to this embodiment, the recovery of heat from the furnace 1 can be carried out from flue gases from (i) the melting tank M or (ii) the refining tank F, or (iii) from the entire furnace (thereby comprising flue gases from the melting tank and the refining tank).

[0159] According to this embodiment and advantageously, the CO2 capture step can be performed from the flue gases used in the cullet preheating step.

[0160] Also according to this embodiment, the raw materials are charged into the melting tank M together with the preheated cullet through the same inlet device(s) X (which therefore means that the two types of vitrifiable materials are mixed before charging). Alternatively, the raw materials are charged into the melting tank M independently of the preheated cullet through different inlet devices(s) X.

[0161] Preferably, according to this embodiment, in the cullet preheating step, the maximum temperature of the cullet is 450° C. This allows to avoid clogging problems.

[0162] According to an embodiment, the step of cullet preheating may be performed in at least one cullet preheater, for example of the type of one of those described in US5526580 or DE 3716687.

[0163] Advantageously, the at least one cullet preheater may be located at the upstream portion of the trough on the width of the melting trough or laterally on its length. Advantageously, the step of cullet preheating may be performed in at least two cullet preheaters, which are located at the upstream portion of the melting trough on both sides, for example, on the width of the melting trough or laterally on its length. For example, the step of cullet preheating may be performed in four cullet preheaters, which are located at the upstream portion of the melting trough, distributed on the width of the melting trough or laterally on its length (e.g., two on each side). Also for example, the step of cullet preheating may be performed in six cullet preheaters, which are located at the upstream portion of the melting trough on the width of the melting trough or laterally on its length (e.g., three on each side), or the step of cullet preheating may also be performed in eight cullet preheaters, which are located at the upstream portion of the melting trough on the width of the melting trough or laterally on its length (e.g., four on each side).

[0164] According to another advantageous embodiment of the present invention, the method further comprises the step of pre-melting at least a portion of the cullets in an auxiliary melting tank and flowing the pre-melted cullets to the melting tank (then referred to as the "main melting tank"). According to this embodiment, the portion of the cullets to be pre-melted is charged into the auxiliary melting tank, and the remaining portion of the cullets (the portion that is not pre-melted, if any) is charged into the main melting tank. Since this embodiment allows the use of poor quality cullets or contaminated cullets in the method of the present invention, this embodiment has the advantage of avoiding the lack of available high-quality cullets. In fact, in this embodiment, at least a portion of the cullets is "digested" in advance in the auxiliary melting tank. For example, by using a reducing agent (such as coke or anthracite) to produce molten metal, the metal compounds present in the cullets can be eliminated in the auxiliary melting tank, the molten metal will be separated from the glass melt by decantation at the bottom of the auxiliary melting tank, and the obtained "purified" glass melt can flow from the top to the main melting tank.

[0001] According to this embodiment, the auxiliary melting groove is preferably connected at an upstream portion of the main melting groove M, more preferably as upstream as possible of the main melting groove M.

[0165] Also according to this embodiment of the invention, only a portion of the cullet is pre-melted in the auxiliary melting tank. For example, a portion of the cullet that is considered "contaminated" or not clean enough is pre-melted in the auxiliary melting tank, and the remaining "clean" portion of the cullet is charged into the main melting tank. Alternatively, the total amount of cullet is pre-melted in the auxiliary melting tank.

[0166] Also according to this embodiment of the invention, preferably, the method comprises the step of preheating at least a portion of the cullet at least partly by recovering heat from the melting furnace 1 before charging at least a portion of the cullet into the auxiliary melting tank.

[0167] One example of an auxiliary melt tank suitable for use in embodiments of the present invention is described in patent application EP 2137115 A1.

[0168] According to a very preferred embodiment of the present invention, the method for melting a vitrifiable material to produce flat glass comprises the following steps: -Providing a furnace, the furnace comprising: (i) a main melting tank M, which comprises at least one upstream zone Z1 covered by the furnace roof C1 and equipped with an electric heating device 2, a downstream zone Z2 covered by the furnace roof C2 and equipped with a combustion heating device 3, and a transition zone T between the furnace roofs C1 and C2; (ii) an auxiliary melting tank, (iii) a clarification tank F, which is covered by a furnace roof C4 and equipped with an oxygen combustion heating device 3', (iv) a neck N which is covered by the furnace roof C3 and separates the main melting tank M from the refining tank F, (v) at least one inlet device X located at the main melting tank M; (vi) an outlet device O located downstream of the clarification tank F; and (vii) at least one flue gas extraction device located at at least one upstream zone Z1; The height H1 of the furnace roof C1 of the furnace is defined by: H1≤0.75*H2; H2 is the height of the furnace roof C2, the length L1 of at least one upstream zone Z1 is defined by: 0.25*(L1+L2)≤L1≤0.8*(L1+L2); L2 is the length of the downstream zone Z2, and the length LT of the transition zone T is defined by: LT≤0.2*(L1+L2), - charging a vitrifiable material into a main melting tank M having at least one inlet device and / or into an auxiliary melting tank, the vitrifiable material comprising (i) a raw material having less than 25% by weight of carbonate compounds and (ii) cullet in an amount of at least 10% by weight of the total amount of the vitrifiable material, - preheating the cullet at least in part by recovering heat from the furnace before charging the cullet into the main melting tank M and / or the auxiliary melting tank; - pre-melting at least a portion of the cullet in the auxiliary melting tank, and allowing the pre-melted cullet to flow to the main melting tank M; - melting the vitrifiable material in the main melting tank M using the heating devices 2, 3; - fining the melt in the fining tank F by heating with an oxygen combustion heating device 3 ′, which is supplied with gas and / or hydrogen; - allowing the melt to flow from the clarification tank F to the working area through the outlet device O; - Capturing CO2 from flue gases having a CO2 concentration of at least 35%; Wherein the electricity input fraction ranges from 30% to 85%, and wherein the step of capturing CO2 from the flue gas comprises a compression and / or a dehydration step.

[0169] All previously described specific embodiments in connection with each step of the method of the invention apply to this last, very preferred embodiment.

[0170] Those skilled in the art will recognize that the present invention is by no means limited to the preferred embodiments described above. On the contrary, within the scope of the appended claims, many modifications and variations are possible. It should be further noted that the present invention relates to all possible combinations of features and preferred features described herein and stated in the claims.

Claims

1. A method for melting a vitrifiable material to produce flat glass, the method comprising the following steps: - Providing a furnace 1, said furnace comprising: (i) a melting tank M, comprising at least one upstream zone Z1 covered by a furnace roof C1 and equipped with an electric heating device 2, a downstream zone Z2 covered by a furnace roof C2 and equipped with a combustion heating device 3, and a transition zone T between the furnace roofs C1 and C2; (ii) a clarification tank F, which is covered by a furnace roof C4 and is equipped with an oxygen combustion heating device 3', (iii) a neck portion N, which is covered by the furnace roof C3 and separates the melting tank M from the refining tank F, (iv) at least one inlet device X located at the melting tank M; (v) an outlet device O located downstream of the clarification tank F; and (vi) at least one flue gas extraction device located at said at least one upstream zone Z1; The height H1 of the furnace roof C1 of the furnace is defined by: H1≤0.75*H2; H2 is the height of the furnace roof C2, the length L1 of the at least one upstream zone Z1 is defined by: 0.25*(L1+L2)≤L1≤0.8*(L1+L2); L2 is the length of the downstream zone Z2, and the length LT of the transition zone T is defined by: LT≤0.2*(L1+L2), - charging the vitrifiable material into the melting tank M by means of the at least one inlet device X, the vitrifiable material comprising raw materials and cullet, the amount of cullet being at least 10% by weight of the total amount of the vitrifiable material, and the raw materials comprising less than 25% by weight of carbonate compounds; - melting the vitrifiable material in the melting tank M using the heating device 2; 3; - fining the melt in the fining tank F by heating with the oxygen combustion heating device 3 ′, the oxygen combustion heating device being supplied with gas and / or hydrogen; - allowing the melt to flow from the clarification tank F to the working area through the outlet device O; - Capturing CO2 from flue gas, said flue gas having a CO2 concentration of at least 35%; wherein the electricity input fraction ranges from 30% to 85%, and wherein the step of capturing CO2 from the flue gas comprises a compression and / or dehydration step.

2. Method for melting a vitrifiable material according to the preceding claim, characterized in that The amount of cullet is at least 30% by weight of the total amount of vitrifiable material.

3. The method for melting a vitrifiable material according to the preceding claim, characterized in that The oxy-combustion heating device is supplied with at least 50% hydrogen, preferably at least 80% hydrogen.

4. Method for melting a vitrifiable material according to the preceding claim, characterized in that The flue gas has a CO2 concentration of at least 40%.

5. Method for melting a vitrifiable material according to the preceding claim, characterized in that The flue gas has a CO2 concentration of at least 50%.

6. Method for melting a vitrifiable material according to the preceding claim, characterized in that The steps of capturing CO2 from flue gases generally consist of a compression and / or a dehydration step.

7. Method for melting a vitrifiable material according to the preceding claim, characterized in that The method further comprises the step of eliminating acidic components from the flue gas.

8. Method for melting a vitrifiable material according to the preceding claim, characterized in that Said step of eliminating acidic components from said flue gas is carried out before or simultaneously with said step of capturing CO2.

9. Method for melting a vitrifiable material according to the preceding claim, characterized in that The method further comprises the step of preheating the cullet before charging the cullet into the melting tank M, at least in part by recovering heat from the melting furnace.

10. The method for melting a vitrifiable material according to claim 9, characterized in that The maximum temperature of the cullet in the cullet preheating step is 450°C.

11. Method for melting a vitrifiable material according to the preceding claim, characterized in that The method further comprises the steps of pre-melting at least a portion of the cullet in an auxiliary melting tank and allowing the pre-melted cullet to flow to the melting tank M.

12. Method for melting a vitrifiable material according to the preceding claim, characterized in that The raw material contains less than 10% by weight of carbonate compounds.

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