Glass melting method with very little or zero CO2 emissions

Abstract

The present invention relates to a method for melting a glassifiable material for producing sheet glass, comprising: (i) providing a furnace with a special design; (ii) charging the glassifiable material containing raw materials and cullet into a main melting tank using at least one inlet means and / or into an auxiliary melting tank, provided that the amount of cullet is at least 10% by weight of the total amount of the glassifiable material; (iii) pre-melting at least a part of the cullet in the auxiliary melting tank and flowing the pre-melted cullet into the main melting tank; (iv) melting the glassifiable material in the main melting tank; (v) purifying the melt in a purification tank by heating with oxygen combustion heating means supplied with gas and / or hydrogen; (vi) flowing the melt from the purification tank through an outlet means into a working zone; (vii) capturing CO2 from exhaust gas having a CO2 concentration of at least 35%, the electric input rate being 30% to 85%, and capturing CO2 including compressing and / or dehydrating.

Description

Technical Field

[0001] The present invention relates to a glass melting method for continuously supplying molten glass to a sheet glass forming facility such as a float or rolling facility. In particular, the present invention relates to a glass melting method that provides many advantages, especially in terms of CO2, especially its emission and capture.

[0002] More particularly, the present invention relates to a method for melting sheet glass with a large production capacity, i.e., up to 1000 tons / day or more, without limitation.

Background Art

[0003] The demands for global warming and CO2 emission reduction are increasing the pressure on glass manufacturers, and energy prices and CO2 taxes can immediately pose a serious threat to competitiveness in the glass sector.

[0004] The glass industry has invested heavily in the decarbonization of manufacturing methods for many years in order to manufacture glass products that are sustainable, resource-efficient, and compatible with a low-carbon society in connection with emergency measures to reduce carbon emissions.

[0005] To enable the transition, the glass sector has already identified many solutions / technologies to approach its ambitious goals, such as the use of electricity as an energy source, the use of alternative and more environmentally friendly energy sources such as H2 or biogas, the use of alternative raw materials, increased use of cullet as a raw material, heat recovery, carbon dioxide capture utilization storage (or CCUS), etc.

[0006] Nevertheless, all of these technologies are associated with serious drawbacks or problems for practical application or are infeasible from an economic perspective. Therefore, there is still an urgent need for a glass melting method that can dramatically reduce the amount of CO2 emitted and is economically acceptable to glass manufacturers.

[0007] Regarding the use of electricity as an energy source:

[0008] Furnaces that use electrical energy to melt glass raw materials are known to not only show a reduction in CO2 emissions but also a reduction in total energy consumption. Although it has only been demonstrated in the case of small capacities, i.e., less than 300 tons per day (scaling up above 600 tons per day is still under development), glass melting furnaces with all heating power supplied electrically are known and are being developed.

[0009] In contrast to classical combustion furnaces called "hot top furnaces" (or "warm top furnaces"), these furnaces are also called "cold top furnaces". This is because the raw materials are dispersed on the glass melting surface, forming a heat-insulating batch "blanket", so that the temperature above the blanket drops from about 1400 °C of the glass melt to less than 500 °C (in some cases up to 50 °C). All-electric furnaces have significant advantages. First of all, they have very little direct emissions of CO2, thermal NO x , SO x .

[0010] Furthermore, (thanks to, for example, electrodes that pass an electric current to heat the molten glass bath from its bulk), the melting energy is basically transferred into the glass, so the heat loss of all-electric furnaces is much lower compared to hot top combustion furnaces where significant heat loss occurs from the upper furnace structure and in the residual exhaust gases, even when using, for example, a heat recovery system. Therefore, they are furnaces with high energy efficiency. Unfortunately, all-electric furnaces also have some disadvantages compared to combustion hot top furnaces. In particular, such furnaces - The quality of the glass has not reached the specifications of general sheet glass, especially regarding the small bubble density. - The temperature at the bottom where the electrodes are placed is very high (e.g., > 1400 °C), which promotes the corrosion of the bottom refractory and the walls of the glass tank, and significantly shortens the furnace life (typically from over 15 years of conventional furnaces to less than 8 years, and in some cases down to 2 - 7 years).

[0011] Furthermore, 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 surface area (T / d / m 2 displayed) is a direct function of the glass temperature. To achieve an acceptable surface melting rate (about 2 - 3 T / d / m 2 ) in such a furnace, it is necessary to target a glass temperature of 1400 °C or higher, or 1450 °C or higher, which further negatively affects the furnace life. For comparison, the surface melting rate of a classical combustion furnace is typically about 5 T / d / m 2 . Alternatively, setting the surface melting rate low to avoid the impact on furnace life as much as possible means significantly increasing the melting area, which in turn has a major adverse impact on the required investment and industrial floor area.

[0012] Finally, such cold-top furnaces have no flexibility in terms of energy (only electricity).

[0013] Also, in a "hybrid system", it is known to combine heating combustion means and electric heating means. In such a configuration, which mainly operates in a "hot-top", the furnace is composed of burners and electrodes for supplying power.

[0014] Such hybrid furnaces have a great advantage in terms of energy flexibility and can adapt the electric input rate to various operating or assumed parameters.

[0015] Furthermore, compared with cold-top furnaces, if the bottom temperature is the same, hot-top furnaces can reach a higher surface melting rate (or, if the surface melting rate is the same, can reach a lower bottom temperature).

[0016] Next, there are several drawbacks to hybrid furnaces operated with a "warm top". In particular, (i) significant heat losses occur at the crown and walls of the melting zone, as well as (ii) in the high-temperature exhaust gas / exhaust fumes generated during melting, thereby reducing the energy efficiency of the furnace. Although a heat recovery system can be considered to suppress the heat lost by the exhaust gas, this problem cannot be solved and special investment is required.

[0017] Furthermore, in such furnaces, the temperature of the crown / upper structure in the melting zone can become very low under certain conditions (e.g., less than 1000 °C), significantly increasing the risk of alkali condensation (e.g., NaOH) in said zone and thus corrosion of the crown refractories.

[0018] Next, in these furnaces, especially for all-electric furnaces, due to the limitations described above, namely the corrosion phenomena at the bottom and crown, the electric input rate is generally limited to a maximum of 35% of the total energy input.

[0019] Among hybrid furnaces, some with special designs to increase the electric input rate, for example up to 80%, have recently been described, but most of them are operated as cold top furnaces, which pose problems.

[0020] Regarding the use of alternative and environmentally friendly energy sources such as hydrogen H2 or biogas, although it is clear that there are advantages in terms of the environment / energy consumption / CO2 emissions, extensive use in the glass industry is inhibited due to serious constraints (lack of availability of biogas, high cost of hydrogen H2 which is an economically unfeasible solution as the sole energy source for melting glass raw materials).

[0021] Regarding heat recovery,

[0022] Waste heat recovery from exhaust gas is already widely applied in the glass industry to preheat combustion air entering the furnace at temperatures above 1000°C or gas and oxygen ( "Hotox") at temperatures above 400°C and 500°C, respectively. It is also possible to utilize the waste heat of the exhaust gas to preheat vitrifiable materials, particularly cullet. Nevertheless, in this case, it is known that the temperature of the exhaust gas discharged from the raw materials is too low, so that preheating of the raw materials / cullet cannot be combined with electric melting.

[0023] Regarding the use of CO2 capture:

[0024] Generally, the CO2 capture method 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), (ii) regeneration of the used material by reverse reaction ( "desorption" of CO2). The separation material can be reused for CO2 capture by sequentially repeating steps (i) and (ii). Amines in the form of solvents, membranes or porous adsorbents are materials that have been most widely used industrially in CO2 capture methods so far because the technology is mature and effective separation of amines and CO2 by reversible reactions is possible. Nevertheless, such amine methods (e.g., those using aqueous MEA) remain poor options, especially in the special circumstances of the glass industry, for at least the following main reasons: - In the combustion gas / exhaust gas in known glass manufacturing methods, the CO2 concentration is low (generally less than 30% by volume, often about 10 - 20% by volume), and the purity is low due to the presence of many other components (mainly N2, H2O, O2, NO x , SO x etc.), which greatly affects the efficiency of the CO2 capture method. - The amine - CO2 capture method requires a lot of energy to regenerate the amine adsorbent (desorption method), which affects the total energy consumption (and can affect the CO2 emissions depending on the energy source used, and clearly has a reverse effect in this regard).

[0025] Furthermore, known glass manufacturing methods generate very high volumes or flows of exhaust gas. This directly affects the investment and operating costs when attempting to capture CO2 from the exhaust gas, regardless of the method used. Summary of the Invention Problems to be Solved by the Invention

[0026] An object of the present invention is to overcome the above-mentioned drawbacks with respect to the prior art and solve technical problems by providing a glass melting method for manufacturing sheet glass using combustion and electric heating means, which shows a reduction in total energy consumption and a reduction in CO2 emissions compared to conventional melting furnaces, particularly conventional "hot top" hybrid furnaces.

[0027] A further object of the present invention is to provide a glass melting method for manufacturing sheet glass using combustion and electric heating means, which shows an acceptable surface melting rate (particularly higher than 2 T / d / m 2 more preferably higher than 3 T / d / m 2 higher surface melting rate).

[0028] A further object of the present invention is to provide a glass melting method for manufacturing sheet glass using combustion and electric heating means, which has an improved lifespan compared to classical hot top hybrid melting furnaces.

[0029] A further object of the present invention is to provide a glass melting method for manufacturing sheet glass using combustion and electric heating means, which enables simple and cost-effective CO2 capture.

[0030] A further object of the present invention is to provide a glass melting method for manufacturing sheet glass using combustion and electric heating means, which is economically feasible. Means for Solving the Problems

[0031] The present invention relates to a method for melting vitrifiable material for producing glass sheets, the method comprising: (i) a main melting tank M including at least one upstream zone Z1 covered by a crown C1 and including electrical heating means, a downstream zone Z2 covered by a crown C2 and including combustion heating means, and a transition zone T between the crowns C1 and C2; (ii) Auxiliary melting tanks; (iii) a refining tank F, covered with Crown C4 and including an oxygen combustion heating means; (iv) a neck N, covered by a crown C3, separating the main melting tank M from the refining tank F; (v) at least one inlet means X disposed in the main melter tank M; (vi) an outlet means O disposed downstream of the purification tank F; and (vii) at least one exhaust gas extraction means arranged in at least one upstream zone Z1;

[0023] providing a furnace comprising: However, the furnace has a capacity of H1≦0.75 * The height H1 of crown C1 defined by H2 (H2 is the height of crown C2), 0.25 * (L1+L2)≦L1≦0.8 * At least one upstream zone Z1 has a length L1 defined by (L1+L2) (L2 being the length of the downstream zone Z2), and LT≦0.2 * The transition zone T has a length LT defined by (L1+L2), - charging vitrifiable material, including raw materials and cullet, into the main melting tank M by means of at least one inlet means X and / or into the auxiliary melting tank, with the amount of cullet being at least 10% by weight of the total amount of vitrifiable material, - premelting at least a portion of the cullet in an auxiliary melting tank and flowing the premelted cullet into a main melting tank; - melting the vitrifiable material in the main melting tank M by heating using a heating means; - Purifying the melt in the purification tank F by heating using oxygen combustion heating means supplied with gas and / or hydrogen, - Flowing the melt from the purification tank F through the outlet means O into the working zone, - Capturing CO2 from the exhaust gas having a CO2 concentration of at least 35%, However, the electricity input rate is 30% - 85%, and capturing CO2 from the exhaust gas includes compressing and / or dehydrating.

[0032] Therefore, the present invention is based on a novel and innovative approach. In particular, the inventors, in a glass melting method for manufacturing sheet glass, - Using a specially designed furnace including a combination of (i) separating the "hybrid" melting tank and the combustion purification zone by a neck, and (ii) dividing the melting tank into two zones having different crown heights (thereby providing a cooler upstream zone and a hotter downstream zone with a significant temperature difference), - Using oxygen as a combustion agent, - Using gas and / or hydrogen as a combustible substance, - Using a minimum amount of cullet in the vitrifiable material, - Using the pre - melting of at least a part of the cullet, and - Using a specific high electricity input rate By combining these, - An acceptable surface melting rate, - An extended furnace life, - A significant reduction in the total energy consumption, - A significant reduction in the total amount of CO2 generated, - It is possible to independently extract the exhaust gas generated from raw material decomposition (poor in NOx and SOx impurities) and the exhaust gas generated from combustion, whereby, if necessary, each can be separated and appropriately treated, - A significant reduction in the exhaust gas volume and a significant increase in the CO2 concentration and its purity in the exhaust gas It has been found that it is possible to obtain them simultaneously, thereby enabling the use of a simple, efficient and cost-effective CO2 capture method.

[0033] By implementing all the features of the present invention, the method of the present invention exhibits a very low CO2 fingerprint and is economically viable.

[0034] In this specification and the claims, it is well understood by those skilled in the art that the terms "a", "an" or "the" as used herein mean "at least one" and should not be limited to "only one" unless the contrary is explicitly stated. When a range is indicated, the endpoints are included. Further, all integer values and subdomain values included in a numerical range are explicitly included as if they were explicitly recited. Finally, the terms "upstream" and "downstream" mean the flow direction of the glass and are understood in their ordinary sense, i.e., along the average movement direction of the vitrifiable material / glass melt from the inlet means to the outlet means. The expression "upstream section" is understood to mean the first upstream one-third of the length, said length being located along the horizontal longitudinal axis of the furnace. The expression "downstream section" is understood to mean the last downstream one-third of said length.

[0035] Other features and advantages of the present invention will become more apparent upon reading the following description of the preferred embodiments and figures given by way of simple illustrative and non-limiting examples.

Brief Description of the Drawings

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Figure 1

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Figure 2

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Figure 3

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Figure 4

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Figure 5

[0041] According to the present invention, as shown in FIG. 1, a method for melting vitrifiable material to produce glass sheets includes firstly providing a specific furnace, said furnace 1 comprising: (i) a main melting tank M including at least one upstream zone Z1 covered by a crown C1 and including electrical heating means, a downstream zone Z2 covered by a crown C2 and including combustion heating means, and a transition zone T between the crowns C1 and C2; (ii) Auxiliary melting tanks; (iii) a refining tank F, covered with Crown C4 and including an oxygen combustion heating means; (iv) a neck N, covered by a crown C3, separating the main melting tank M from the refining tank F; (v) at least one inlet means X disposed in the main melter tank M; (vi) an outlet means O disposed downstream of the purification tank F; and (vii) at least one exhaust gas extraction means arranged in at least one upstream zone Z1; Including, The furnace has a temperature of H1≦0.75 * The height H1 of crown C1 defined by H2 (H2 is the height of crown C2), 0.25 * (L1+L2)≦L1≦0.8 * At least one upstream zone Z1 has a length L1 defined by (L1+L2) (L2 being the length of the downstream zone Z2), and LT≦0.2* It has a length LT of the transition zone T defined by (L1 + L2).

[0042] According to the present invention, and as generally adopted in the glass technology field, a "melting tank" means a tank that defines a zone where a glassifiable material (raw material and / or cullet) is charged and melted by heating. When the furnace is in operation, it includes the melt and a "blanket" of un-melted glassifiable material that floats on the melt and is gradually melted, and thus decreases from the upstream to the downstream of the melting tank.

[0043] According to the present invention, and as generally adopted in the glass technology field, a "refining tank" means a tank that defines a zone where no "blanket" of un-melted glassifiable material floating on the melt exists. The glass melt is heated at a temperature higher than the melting tank temperature (generally a temperature exceeding 1400 °C or exceeding 1450 °C) in order to refine the glass (mainly by removing the main part of the bubbles). This refining tank is also generally called a "clarifying tank" in the art.

[0044] According to the present invention, a "neck" that separates the main melting tank and the refining tank means that the width and (crown) height are narrower compared to the downstream zone (zone Z2) of the melting tank and the upstream zone of the refining tank F. The opening of the neck according to the present invention can be partially under the glass melt / blanket-free surface, leaving a free opening above the glass melt / blanket. This is advantageous because, firstly, it can stabilize the blanket of raw materials and prevent un-melted particles from flowing directly towards the refining tank, and secondly, it can prevent potential defects generated at the contact part of the glass, refractory and atmosphere from flowing directly into the refining tank. Due to these points, the quality of the glass can be advantageously improved. Furthermore, since a wide opening is possible, the glass velocity decreases and the corrosion and wear of the refractory decrease. Due to this point, the life of the furnace is advantageously improved.

[0045] Such a furnace design, with height segmentation of the melting crown combined with zone segmentation of the melting and refining tanks, offers many advantages in terms of energy consumption / CO2 emissions and the mechanical stability / lifetime of the furnace.

[0046] In particular, the combination of (i) separating the main melting tank and the refining tank by a neck, and (ii) dividing the main melting tank into two zones with different crown heights in a specific design (thereby providing a significant temperature difference, a cooler upstream zone and a hotter downstream zone), allows the total energy consumption of the furnace to be significantly reduced while maintaining a high electrical input rate (thereby reducing CO2 emissions), maintaining an acceptable surface melting rate, and improving the mechanical stability and lifetime of the furnace.

[0047] The melting crowns C1 and C2 of the present invention take advantage of both the "cold top" and "hot top" zones and are specially designed to create a temperature gradient from the relatively cool upstream (less than 1100 °C) to the relatively hot downstream (higher than 1300 °C).

[0048] In particular, the furnace of the present invention can fully control (i) the temperature of each zone and (ii) the exhaust gas re - splitting / extraction between the two zones of the main melting tank and between the main melting tank and the refining tank in order to optimize energy consumption, avoid alkali corrosion as much as possible, and optimize CO2 capture.

[0049] The furnace of the present invention is further advantageous in that it simultaneously creates a strong temperature difference between the upstream and downstream parts of the main melting tank and, as much as possible, avoids the reverse flow of the exhaust gas generated from the refining tank towards the melting tank.

[0050] From the perspective of energy efficiency, - dividing the atmosphere and blocking the heat radiation from the refining tank to the main melting tank in order to efficiently confine energy in the zone where high temperature is required (refining zone), and To limit the wasteful heating of the gases released from the vitrifiable material and, optionally, to maximize the heat transfer from the combustion gases to the vitrifiable material and the glass melt, the exhaust gas is extracted from the upstream section / exit at the lowest possible temperature. For this reason, the furnace of the present invention is advantageous.

[0051] From the viewpoint of the surface melting rate, this is advantageous because it enables the melting rate of the vitrifiable material to reach a relatively high temperature (>1300 °C) downstream of the melting tank, thus improving the melting rate of the vitrifiable material.

[0052] From the viewpoint of corrosion - By separating the atmosphere between the main melting tank and the refining tank, the reflux of the exhaust gas from the refining zone, which is rich in alkali and thus highly corrosive due to the high temperature required for refining, can be restricted / avoided. - Having a restriction on the overall molten glass flow that advantageously reduces the intensity of the glass convection in the melting tank, reduces the glass velocity, and thereby reduces the wear and corrosion of the bottom refractory. For this reason, this is advantageous.

[0053] Finally, the furnace of the present invention with a specific division (via a neck) between the main melting tank and the refining tank also makes it possible to completely separate the dimensions (length, width, and crown height) of the main melting tank and the refining tank and the properties of the refractories, and thus to optimize each tank considering energy efficiency, glass quality, factory space constraints, and mechanical / structural / other constraints.

[0054] Figures 2 and 3 show an embodiment of the furnace 1 of the present invention (Figure 2: vertical cross-sectional view, Figure 3: horizontal cross-sectional view).

[0055] The furnace 1 of the invention includes a main melting tank M, a neck N and a refining tank F. The M, N and F assemblies are generally made of refractory materials resistant to temperature, the corrosive effects of fumes and the aggressive action of molten materials. In Fig. 2, the glass melt level (excluding the batch blanket) in an exemplary tank is shown by a dashed line.

[0056] According to the invention, as shown in Figures 2-3, the furnace 1 comprises at least one inlet means X in the main melting tank M for charging the vitrifiable raw materials (friction and / or cullet) into the furnace.

[0057] In order to improve distribution on the surface of the main melting tank M, several inlet means, i.e. two or three inlet means, located upstream of the main melting tank M (in other words in zone Z1), are advantageously provided. Preferably, and as known in the art, at least one inlet means X is arranged upstream of the main melting tank M, transversely across the width of said tank and / or across its length.

[0058] As shown in Figures 2-3, the furnace 1 of the present invention includes a main melting tank M and an auxiliary melting tank (not shown), the main melting tank: - at least one upstream zone Z1 covered by a crown C1 and comprising an electric heating means 2; - a downstream zone Z2 covered by a crown C2 and comprising an electric heating means 2 and a combustion heating means 3; - Transition zone T between crown C1 and crown C2 Includes.

[0059] According to an advantageous embodiment, the downstream zone Z2 comprises further electric heating means, as shown in FIGS.

[0060] The electric heating means 2 according to the invention are preferably placed at the bottom of the main melting tank M and preferably consist of immersed electrodes. The electrodes are advantageously arranged in a grid (checkerboard) of multiples of 3 or 2 to facilitate connection to the transformer and current balancing. For example, a maximum current density of 1.5 A / cm2 on the electrode surface is required. 2 The number of electrodes is designed so as to respect the above and limit the maximum power of each electrode to 200 kW. Also, for example, the height of the immersed electrodes is 0.3-0.8 times the height of the glass melt.

[0061] The combustion heating means 3 in the downstream zone Z2 of the main melting tank M consist in particular of burners. In particular, they are generally arranged in a row and are arranged along the side walls of said zone, for example on one or alternatively on both sides thereof, in order to spread the flame over substantially the entire width of said zone. They are also, alternatively or additionally, arranged in the crown C2, which promotes the heat transfer to the batch and is also advantageous in order to shorten the length of the batch and to avoid the batch blanket reaching the end of the downstream zone Z2 and thus the downstream end of the main melting tank.

[0062] Fuel and air, or fuel and oxygen, or fuel and oxygen enriched gas can be supplied to the combustion heating means 3. The fuel can be a fossil fuel, natural gas, biogas, hydrogen, ammonia, synthetic gas, or a mixture thereof.

[0063] According to an advantageous embodiment, at least one upstream zone Z1 may comprise further auxiliary combustion heating means (e.g. burners, not shown) to allow control of the temperature of crown C1 (e.g. to limit the temperature variations along zone Z1) and to increase the temperature if it falls below a certain level (e.g. below 600° C.). In particular, these auxiliary combustion heating means may advantageously be located within crown C1 in order to reduce the occupation of the free volume of space above the melt / batch blanket.

[0064] According to one embodiment, an auxiliary melting tank (not shown) is preferably connected to the upstream part (e.g., zone Z1) of the main melting tank M, more preferably to the uppermost possible upstream part (in particular, zone Z1) of the main melting tank M, in order to achieve better homogeneity / mixing of the pre-melt and the melt.

[0065] An example of an auxiliary melting tank suitable in the present invention is described in European Patent Application Publication No. 2137115A1.

[0066] The upstream zone Z1 according to the present invention has a crown C1. The downstream zone Z2 according to the present invention has a crown C2.

[0067] According to the present invention, the height H1 of the crown C1 is H1 ≦ 0.75 * is defined by H2; H2 is the height of the crown C2. In the present invention, the change in height between the crowns C1 and C2 along the main melting tank M means the transition zone T.

[0068] The "height" of the crown in the present invention means, throughout this specification and the claims, the average inner height (shown in FIG. 2) from the inner surface of the crown to the glass melt (excluding the batch blanket if present). The height H1 of the crown C1 may be substantially constant along the length of the crown, or may vary along the length of the crown. The height H1 of the crown C1 may be substantially constant along the width of the crown, or may vary along the width of the crown (e.g., in the case of an arch / round ceiling crown). The height H2 of the crown C2 may be substantially constant along the length of the crown, or may vary along the length of the crown. The height H2 of the crown C2 may be substantially constant along the width of the crown, or may vary along the width of the crown (e.g., in the case of an arch / round ceiling crown).

[0069] According to one embodiment of the present invention, the height H1 of the crown C1 is H1 ≦ 0.7 *H2, preferably H1 ≤ 0.6 * H2, more preferably H1 ≤ 0.5 * It is defined by H2. Thereby, the above-described advantages of the present invention can be enhanced.

[0070] According to the present invention, the length L1 of at least one upstream zone Z1 is 0.25 * (L1 + L2) ≤ L1 ≤ 0.8 * It is defined by (L1 + L2), and L2 is the length of the downstream zone Z2.

[0071] Throughout this specification and the claims, "length" means the dimension along the flow of the glass.

[0072] According to another embodiment of the present invention, the length L1 of at least one upstream zone Z1 is 0.3 * (L1 + L2) ≤ L1, preferably 0.4 * (L1 + L2) ≤ L1, more preferably 0.5 * It is defined by (L1 + L2) ≤ L1. Thereby, the above-described advantages of the present invention can also be enhanced.

[0073] According to another embodiment of the present invention, the length L1 of at least one upstream zone Z1 is L1 ≤ 0.75 * (L1 + L2), preferably L1 ≤ 0.7 * It is defined by (L1 + L2).

[0074] It is worth mentioning that the total length of the main melting tank M may be slightly higher (on the order of, for example, 10% - 15%) than the total (L1 + L2). In fact, in the art, it is common to provide a first zone Z0 (commonly called the "doghouse") for introducing the vitrifiable material and extruding it in the melting direction at the extreme upstream part of the main melting tank (not shown).

[0075] The crown C1 according to the present invention may be of an arch type or a round ceiling type, or may be flat. Independently of the crown C1, the crown C2 according to the present invention may be of an arch type or a round ceiling type, or may be flat.

[0076] Advantageously, the crown C1 may be composed of a refractory material essentially made of silica (e.g., high-purity silica). Although silica refractories are known to be more vulnerable to corrosion (e.g., compared to alumina), in the present invention, since there is a neck separating the melting tank and the refining tank, there is less alkali in the fumes present in the main melting tank.

[0077] The advantage of silica is that it has a low coefficient of expansion when the temperature is higher than about 600 °C, whereby it can withstand high temperature changes without disturbing the superstructure of the crown.

[0078] Alternatively, the crown C1 and / or the crown C2 may be composed of a refractory material essentially made of alumina or AZS (alumina-zirconia-silica), which has better resistance to corrosion and thus a longer lifespan.

[0079] According to the present invention, as shown in FIG. 2, the furnace includes a main melting tank M including at least one upstream zone Z1 and a downstream zone Z2 having different crown heights of C1 with a height H1 and C2 with a height H2.

[0080] In the furnace provided by the method according to the present invention, the change in height between the crowns C1 and C2 along the main melting tank M means a transition zone T.

[0081] According to the present invention, the length LT of the transition zone T is LT ≦ 0.2 * (L1 + L2), preferably LT ≦ 0.15 * (L1 + L2), and further LT ≦ 0.1 * defined by (L1 + L2).

[0082] According to one embodiment, the transition zone T between the crown C1 and the crown C2 may be a breast wall. The breast wall according to one embodiment may be a vertical wall or a short inclined wall (which allows for a gradual transition). In this embodiment, the crown C1 preferably has an inner surface that is substantially at the same height as the lower edge of the breast wall or slightly lower than it. The breast wall can be composed of a suspended back wall. The suspended back wall according to the present invention is, for example, as described in U.S. Patent No. 5,011,402A. Alternatively, the breast wall may lie on the outer surface of the crown C1.

[0083] According to another embodiment, the transition zone T between the crown C1 and the crown C2 is a shadow wall. The "shadow wall" in the present invention means a wall that has a lower end extending below the inner surface of the crown C1, thereby being close to the glass melt but leaving a free space above the glass melt. This embodiment further reduces the radiative heat exchange between the upstream zone and the downstream zone of the main melting tank, better separates the exhaust gases emitted from Z1 and Z2, while having the advantage that the glassifiable material extruded from the upstream can pass through the remaining free space. For example, this shadow wall may be an air-cooled suspended wall, as known in the art. The shadow wall according to the present invention may be composed of, for example, a suspended U-shaped shadow wall as described in U.S. Patent No. 3,399,046A.

[0084] According to a further embodiment, the transition zone T between the crown C1 and the crown C2 includes at least one step. In a configuration having one step, the change in height between the crown C1 and the crown C2 is obtained by a transition zone T that includes: a first breast wall, a short crown at the intermediate height between H1 and H2, and a second breast wall from C1 to C2. This configuration has the advantage of facilitating the creation of the transition between the crown C1 and the crown C2 and enhancing stability.

[0085] The "length of the transition zone" means, throughout this specification and the claims, the dimension of said zone along the flow of the glass, including the thickness of the wall (even if it lies on and / or overlaps the crown C1 and / or the crown C1).

[0086] According to an advantageous embodiment, the transition zone is composed of refractory material essentially made from silica.

[0087] Advantageously, according to another embodiment, the crown C1 and the transition zone T are made from the same refractory material in order to avoid expansion between materials and / or to avoid corrosion between materials. Preferably, it is composed of refractory material essentially made from silica.

[0088] Also advantageously, according to another embodiment, the crown C1, the crown C2 and the transition zone T are made from the same refractory material in order to avoid expansion between materials and / or to avoid corrosion between materials. Preferably, it is composed of refractory material essentially made from silica.

[0089] According to the invention, the furnace comprises a refining tank F covered by a crown C4 and comprising oxygen combustion heating means 3'.

[0090] The "oxygen combustion means" 3' according to the invention means combustion means to which gaseous oxygen (O2) is supplied as a combustion agent. Generally, the O2 gas combustion agent supplied to the glass melting furnace has a purity of at least 90% or at least 95%. The advantage of using gaseous oxygen as a combustion agent is that the so-called corrosive "NOx" pollutants generated during combustion are significantly reduced compared to the case of using air. (Depending on the purity of O2 and the amount of parasitic air), even if they are present in the exhaust gas, it will be in a very small amount.

[0091] The oxy-combustion heating means 3' from the refining tank F according to the invention may advantageously consist of burners arranged along the side walls of the refining tank. Moreover, the burners are advantageously spaced apart from one another in order to distribute the energy supply over a portion of the refining tank F, preferably over the upstream portion (for example about 50% of the length). Also, they are generally arranged in a row on one side of the refining tank F, or alternatively on both sides, preferably in a staggered arrangement (to spread the flame over substantially the entire width of said tank).

[0092] The crown C4 according to the invention is preferably arched or vaulted.

[0093] According to an advantageous embodiment, the purification tank F may comprise further electric heating means (not shown), particularly in the upstream part of said purification tank (for example about 50% of its length), which allows to increase the electric input rate and thus improve the energy efficiency and reduce CO2 emissions.

[0094] According to the invention, the furnace includes a neck N, which is covered by a crown C3 and separates / divides a main melting tank M and a refining tank F.

[0095] According to the invention, the "neck" separating the main melting tank M and the refining tank F means a narrowing in width and (crown) height compared to the downstream zone of the main melting tank (zone Z2) 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 glass melt / batch blanket free surface and then leaves a free opening above the glass melt / batch blanket.

[0096] According to the definition of the neck according to the present invention, the width W of the neck N N is as follows: N <W M And W M is the width of the main melting tank M. According to the definition of the neck in this invention, the width W of the neck N is N is as follows: N <WF where W F is the width of the refining tank F.

[0097] In the present invention, the "width" means the dimension (average) perpendicular to the flow of the glass throughout this specification and the claims.

[0098] This furnace design with the melting tank and the refining tank separated brings many advantages in terms of energy consumption / CO2 emissions and is preferable for the mechanical stability / lifetime of the furnace. Particularly advantageously, in the present invention, with a furnace having this specific separation design, the exhaust gas from the main melting tank M (zone 1 and / or zone 2) and the exhaust gas from the refining tank can be independently processed as required.

[0099] The base of the neck N in the present invention may be essentially located at the level of the floor / bottom of the main melting tank M, or may be located above or below said level. Further, the base of the neck N may be substantially located at the level of the floor / bottom of the refining tank F, or may be located above or below said level.

[0100] According to one embodiment, the neck N does not include any heating means, for example, any electric heating means.

[0101] The crown C3 according to the present invention may be arch-shaped or round ceiling-shaped, or may be flat. According to the definition of the neck according to the present invention, the crown C3 of the neck N has a height H3 lower than the height H2 of the crown C2 of the main melting tank M. Also according to the definition of the neck according to the present invention, the crown C3 of the neck N has a height H3 lower than the height H4 of the crown of the refining tank F.

[0102] According to yet another advantageous embodiment of the invention, the furnace may include a removable wall (e.g., a skin bar coming from the side wall of the neck) located at the neck in order to (i) stop unmolten vitrifiable materials that can reach the ends of the main melting tank, thereby avoiding their passage through the neck towards the purification tank, and (ii) control or eliminate the intensity of the reverse flow of the glass melt from the purification tank towards the main melting tank.

[0103] According to yet another advantageous embodiment of the invention, the furnace may include a removable wall (e.g., a shadow wall passing through the crown of the neck section) located at the neck section in order to enhance the separation of the melting tank and the purification tank in terms of atmosphere and thermal radiation.

[0104] According to the invention, the furnace includes outlet means O located downstream of the purification tank F for the molten glass to reach the working zone. According to one embodiment, the outlet means O is usually composed of a neck in order to direct the melt to a working zone, which is generally also called the "working end" or "flare" or "conditioning zone". Alternatively, the outlet means O is composed of a throat (i.e., an opening that is completely immersed in the glass melt and leaves no free surface thereon) in order to direct the melt to a working zone including, for example, a forehearth. The working zone according to the invention may include, for example, a conditioning zone where thermal conditioning by controlled cooling is performed before the glass melt exits through the outlet to the forming zone. Such a forming zone may be composed of, for example, a float facility and / or a rolling facility.

[0105] According to the invention (as shown in FIGS. 2 and 3), the furnace includes at least one upstream zone Z1, preferably at least one exhaust gas extraction means 4 arranged in the vicinity of the inlet means X, in order to recover heat and transfer it to the glass melt and / or the unmolten vitrifiable materials in the main melting tank M from the exhaust gas.

[0106] According to one embodiment of the present invention, the furnace further comprises at least one exhaust gas extraction means in the downstream zone Z2 and / or at least one exhaust gas extraction means in the purification tank F (not shown).

[0107] When there is an extraction means in zone Z2, this can advantageously extract exhaust gas from the downstream zone Z2, particularly when the gas is alkali-rich (thereby avoiding condensation and subsequent corrosion in zone Z1).

[0108] When there is an extraction means in the purification tank F, it is preferably arranged upstream of the purification tank.

[0109] Preferably, in the present invention, the extraction means 4 is arranged on one or both side walls.

[0110] In particular, in the present invention, it is energetically advantageous for the exhaust gas to be extracted as much as possible from upstream of the furnace, particularly upstream of the main melting tank. For example, at least 25% of the combustion exhaust gas generated in the melting zone can be advantageously extracted from upstream of the main melting tank. Nevertheless, extracting a part of the exhaust gas from downstream of the main melting tank can be advantageous for limiting the risk of alkali attack on the crown refractory. In fact, alkali evaporation increases with temperature, and the alkali concentration in the exhaust gas is higher in the downstream part of the melting zone. Exhaust gas with a higher alkali concentration can cause problems related to condensation in the cooler regions of the superstructure / crown, so it is better to discharge it from downstream. Furthermore, in its upstream zone, the exhaust gas essentially results from the gases released from the decomposition of the raw materials and is therefore poor in alkali, so it is advantageous to extract a part of the exhaust gas from upstream of the main melting tank. Finally, since the temperature required for purification is higher and the exhaust gas from the purification tank contains more alkali, it is also advantageous to extract a part of the exhaust gas from the purification tank.

[0111] Furthermore, in the present invention, it is further advantageous that the exhaust gas (at least its main part) generated from the raw material decomposition at the upstream Z1 of the main melting tank can be extracted (and thereby treated) almost independently of the exhaust gas coming from the combustion (in zone Z2 and / or the purification tank). In fact, the exhaust gas generated in zone Z1 is poor in NOx and SOx, so the recovery of CO2 is easy.

[0112] In an advantageous embodiment of the invention shown in FIG. 4, the furnace of the invention includes a main melting tank M that is expanded in the lateral direction and includes inlet means X' and X'' arranged in each lateral direction. The main melting tank includes two different upstream zones Z1' and Z1'', and two transition zones T' and T'', such that two opposing glass flows converge through a central downstream zone Z2.

[0113] In this configuration, - The height H1' of the melting crown C1' is defined by H1' ≤ 0.75 * H2; - The height H1'' of the melting crown C1'' is defined by H1'' ≤ 0.75 * H2; - The length L1' of at least one upstream zone Z1' is such that 0.25 * (L1'+L2) ≤ L1' ≤ 0.8 * is defined by (L1'+L2); - The length L1'' of at least one upstream zone Z1'' is such that 0.25 * (L1''+L2) ≤ L1'' ≤ 0.8 * is defined by (L1''+L2); - The length LT' of the transition zone T' is such that LT' ≤ 0.2 * is defined by (L1'+L2); and - The length LT'' of the transition zone T'' is such that LT'' ≤ 0.2 * is defined by (L1''+l2).

[0114] Also, in this configuration, - The main melting tank includes one downstream crown C2 and two upstream crowns C1' and C1''. The crowns C1' and C1'' can be independently configured according to any embodiment of the present invention related to the crown C1. For example, the upstream crowns C1' and C1'' can have the same or different heights H1' and H1''; - The main melting tank includes two transition zones T' and T''. They can be independently configured according to any embodiment of the present invention related to the transition zone T.

[0115] Also, in this configuration, for example, the combustion heating means 3 is arranged, as shown in FIG. 4, on the melting tank wall facing the neck, for example, like two burners. Alternatively, for example, the combustion heating means 3 is arranged on the crown C2.

[0116] In this advantageous configuration / embodiment, each upstream zone, each upstream crown, and each inlet means are according to the present invention and its embodiments and can be designed independently of the other upstream zones, upstream crowns, and inlet means according to the above description. Therefore, for the sake of clarity, the features described above in relation to Z1 are independently applicable to Z1' and Z1'', the features described above in relation to C1 are independently applicable to C1' and C1'', the features described above in relation to T are independently applicable to T' and T'', and the features described above in relation to X are independently applicable to X' and X''. Further, the specific advantageous features described in relation to M, C2, C3, C4, N, F, etc. are also applicable to this specific configuration and have the same advantages.

[0117] Also, in this configuration, an auxiliary melting tank (not shown in FIG. 4) can be arranged / connected upstream of one of the upstream parts of the main melting tank M (for example, within the zone Z1'), more preferably as upstream as possible of the main melting tank M (especially within the zone Z1'). Alternatively, the furnace can include two auxiliary melting tanks, one in each upstream part of the main melting tank M (for example, within the zones Z1' and Z1''), more preferably one in each upstream zone Z1' and Z1''.

[0118] The design of a specific glass furnace having a division by a neck between a melting tank and a refining tank is described in European Patent No. 21200998.9, which is incorporated herein by reference as an embodiment of the present invention.

[0119] According to a specific embodiment, the furnace of the present invention 0.1 * W F ≦W N ≦0.6 * W F 、 W M ≧1.4 * W N is defined by W M which is the width of at least one melting tank M, W F which is the width of the refining tank F, W N which is the width of at least one neck N.

[0120] According to this embodiment, the above advantages of the present invention can be enhanced. In particular, - The atmosphere between the melting tank and the refining tank can be better separated, and the reflux of corrosive fumes from the refining tank to the melting tank can be restricted. - The blocking of heat radiation from the refining tank to the melting tank can be strengthened. - The restriction of the overall molten glass flow can be strengthened, or the backflow can be eliminated.

[0121] Preferably, the furnace is 0.2 * W F ≦W N ≦0.6 * W F 、 or 0.3 * W F ≦W N ≦0.5 * W FIt is defined by this. Thereby, a good compromise between the following two conflicting requirements can be found. On the one hand, (1) to reduce the opening between the melting upper structure / crown and the refining upper structure / crown, and (2) to cause an obstacle to the convection intensity of the entire glass melt in the melting tank, the neck between the melting zone and the refining zone should ideally be as narrow as possible. On the other hand, to limit the glass velocity inside the neck and limit the wear / corrosion of the neck refractory wall, the neck should ideally be as wide as possible.

[0122] Also preferably, the furnace of the present invention is W M ≧1.5 * W N or W M ≧1.8 * W N defined by. More preferably, the furnace of the present invention is WM≧2 * W N defined by. Thereby, the width limitation of the neck N becomes large, the blocking of heat radiation is improved, better atmosphere separation becomes possible, and the restriction of the molten glass flow occurs.

[0123] According to an embodiment, the furnace may include one melting tank and one neck or two melting tanks and two necks or even three melting tanks and three necks. These embodiments are widely described in European Patent Application Publication No. 21200998.9, which is incorporated herein by reference.

[0124] In the specific "two melting tanks" configuration shown in FIG. 5, the furnace for melting the vitrifiable material includes two melting tanks M' and M'', two necks N' and N'' (one for each melting tank), and at least two inlet means X' and X'' (one for each melting tank).

[0125] This configuration is particularly advantageous compared to the configuration with one melting tank (FIG. 3) because the following are possible: - The crown span of each melt tank can be reduced for the same total melt tank area and furnace length (length is generally more of a constraint than width). By reducing the crown span, (i) stresses within the crown material are reduced, which in turn reduces the risk of material creep and crown sagging, allowing the use of refractories with higher resistance to corrosion and lower resistance to creep, such as alumina or spinel, thus increasing the life of the furnace; (ii) in the case of arched crowns C1 and / or C2, it is possible to reduce the average height of the crowns, lowering the horizontal radiation transfer and resulting in a better heat transfer from the exhaust gases to the glass melt when the exhaust gases are then extracted from the melting tank; - Same overall neck width (W N’ +W N’’ ) and arched neck crown C3, it is possible to reduce the opening surface area between the melting tank and the refining tank; - Same overall neck width (W N’ +W N’’ ) it is possible to reduce the strength of glass convection in the melting tank; - It is possible to facilitate furnace maintenance in the melting zone. In fact, if there are two melting tanks, it is possible to isolate and cool one melting tank from the rest of the furnace while production takes place in the other melting tank. And it is possible to increase the life of the whole furnace by replacing worn refractories in the melting zone, which is the most critical area in terms of wear / corrosion.

[0126] In this configuration, the furnace has two melting tanks M', M'', each having its upstream zone, Z1' or Z1'', its upstream crown, C1' or C1'', its downstream zone, Z2' or Z2'', its transition zone, T' or T'', and its inlet means, X' or X''. Furthermore, each melting tank M' and M'' is separated from the refining tank F by a neck N' and N'', respectively.

[0127] Also, in this configuration, the auxiliary melting tank (not shown in FIG. 5) may be disposed / connected at one of the upstream portions of the main melting tank M' (e.g., within the zone Z1'), more preferably at the most upstream portion possible of the main melting tank M' (particularly within the zone Z1'). Alternatively, the furnace may include two auxiliary melting tanks, one at each upstream portion of the main melting tanks M' and M'', more preferably one at each of the upstream zones Z1' and Z1''.

[0128] In this configuration, according to the present invention, - The height H1' of the molten crown C1' is such that H1' ≤ 0.75 * is defined by H2', - The height H1'' of the molten crown C1'' is such that H1'' ≤ 0.75 * is defined by H2'', - The length L1' of the upstream zone Z1' is such that 0.25 * (L1' + L2') ≤ L1' ≤ 0.8 * is defined by (L1' + L2'), and - The length L1'' of at least one upstream zone Z1'' is such that 0.25 * (L1'' + L2'') ≤ L1'' ≤ 0.8 * is defined by (L1'' + L2''), - The length LT' of the transition zone T' is such that LT' ≤ 0.2 * is defined by (L1' + L2'), - The length LT'' of the transition zone T'' is such that LT'' ≤ 0.2 * is defined by (L1'' + L2'').

[0129] According to this specific embodiment, the furnace preferably has 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’’ may be defined by W M’ is the width of at least one melting tank M', W M’’ is the width of at least one melting tank M'', W F is the width of the purification tank F, W N’ is the width of the neck N', W N’’ is the width of the neck N''.

[0130] Also, in this configuration, - The upstream zone and the downstream zone may be independently configured according to any embodiment of the present invention related to Z1 and Z2, respectively. - The crowns C1' and C1'' may be independently configured according to any embodiment of the present invention related to the crown C1, respectively. For example, the upstream crowns C1' and C1'' may have the same or different heights H1' and H1''. - The crowns C2' and C2'' may be independently configured according to any embodiment of the present invention related to the crown C2, respectively. For example, the crowns C2' and C2'' may have the same or different heights H2' and H2''. - The transition zones T' and T'' may be independently configured according to any embodiment of the present invention related to the transition zone T, respectively.

[0131] In this advantageous configuration / embodiment, each melting tank, each upstream zone, each downstream zone, each transition zone, each neck and each inlet means are according to the invention and its embodiments and can be designed independently of the other melting tanks, upstream zones, downstream zones, transition zones, necks and inlet means respectively, according to the above description. Thus, for the sake of clarity, the features described above in relation to M are applied independently to M' and M'', the features described above in relation to Z1 are applied independently to Z1' and Z1'', the features described above in relation to C1 are applied independently to C1' and C1'', the features described above in relation to Z2 are applied independently to Z2' and Z2'', the features described above in relation to C2 are applied independently to C2' and C2'', the features described above in relation to T are applied independently to T' and T'', and the features described above in relation to X are applied independently to X' and X''.

[0132] Furthermore, the specific advantageous features described in relation to a furnace having one melting tank (for example those described in relation to C3, C4, F) are applied such that they have similar advantages in this "two melting tanks" configuration.

[0133] In a "two melting tanks" furnace according to one embodiment, the two melting tanks M', M'' are preferably connected to the purification tank F by two necks N', N'' located at the width W F of the purification tank F (illustrated in Figure 5). Alternatively, in the "two melting tanks" configuration, the first melting tank is connected to the purification tank by a neck located at the width W F of the purification tank, and the second melting tank is connected to the purification tank by a neck located at the length of the purification tank (right or left) close to the upstream of the purification tank (i.e., the first third of its length). This last configuration is advantageous, for example, when the space available in the plant housing the furnace is not sufficient to arrange the two melting tanks side by side.

[0134] In the "two melting tanks" configuration, the two melting tanks are at the width W of the said purification tank FWhen connected to the purification tank by a neck located at [location not specified in the original, assumed as 'a certain position'], the distance D between the two melting tanks is preferably at least 1 m, more preferably at least 2 m, and even more preferably at least 3 m. This is advantageous as it allows access to the maintenance work and the zone for tank wall overcoating.

[0135] In another embodiment of the present invention, the furnace has a configuration with three melting tanks, three necks, and three inlet means. This embodiment is particularly advantageous compared to the configuration with one melting tank, similar to the 'two melting tanks' configuration. In this 'three melting tanks' configuration, each neck, each melting tank, and each inlet means are according to the present invention and its embodiments, and can be designed independently of the other necks, melting tanks, and inlet means according to the above description.

[0136] The specific advantageous features described in relation to the furnaces having 'one melting tank' and 'two melting tanks' are also applicable to the 'three melting tanks' configuration and have the same advantages.

[0137] In a 'three melting tanks' furnace according to an embodiment, when at least two melting tanks are connected to the purification tank by a neck located at the width W of the purification tank F the distance D between two adjacent melting tanks is preferably at least 1 m, more preferably at least 2 m, and even more preferably at least 3 m.

[0138] In all furnace configurations according to the present invention, i.e., the 'one melting tank', 'two melting tanks', and 'three melting tanks' configurations, one or more charging means can be provided for each melting tank to facilitate the distribution of the vitrifiable material into the charge, i.e., two charging means can be provided for each melting tank.

[0139] Preferably, the total surface area of the melting tank is 25 - 400 m 2 Similarly preferably, according to the present invention, the surface area of the purification tank is 25 - 400 m2 is.

[0140] According to the present invention and as shown in FIG. 1, a method for producing sheet glass by melting a vitrifiable material includes charging the vitrifiable material, which includes raw materials and cullet, into at least one main melting tank M using at least one inlet means X or into an auxiliary melting tank.

[0141] According to the present invention, the amount of cullet is at least 10% by weight of the total amount of the vitrifiable material. Preferably, the amount of cullet is at least 20% by weight of the total amount of the vitrifiable material. More preferably, the amount of cullet is at least 30% by weight of the total amount of the vitrifiable material, and even more preferably at least 40% by weight. This is advantageous because it can reduce the CO2 generation / emission of the method of the present invention (for reducing the emissions resulting from the decarbonation of carbonate raw materials). Preferably, the amount of cullet is at most 90% by weight or at most 80% by weight of the total amount of the 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 the vitrifiable material.

[0142] According to the present invention and as shown in FIG. 1, this method further includes pre-melting at least a part of the cullet in an auxiliary melting tank and flowing the pre-melted cullet into the main melting tank.

[0143] According to the present invention, a part of the cullet to be pre-melted is charged into the auxiliary melting tank, and if there is the remaining cullet (not pre-melted), it is charged into the main melting tank. This embodiment has the advantage of preventing the shortage of high-quality cullet in the method of the present invention in order to enable the use of lower-quality cullet or contaminated cullet. In fact, in this embodiment, at least a part of the cullet is pre-“digested” in the auxiliary melting tank. For example, the metal compounds present in the cullet can be removed in this auxiliary melting tank by using a reducing agent (such as coke or anthracite), and the molten metal is separated from the glass melt by decanting at the bottom of the auxiliary melting tank, while the obtained “purified” glass melt can flow from the upper part towards the main melting tank.

[0144] According to one embodiment, if there is the remaining part of the cullet (not pre-melted), it is charged into the main melting tank together with the raw materials, that is, through the same inlet means X, or through different inlet means X separate from the raw materials.

[0145] Also, according to one embodiment, only a part of the cullet is pre-melted in the auxiliary melting tank. For example, the part of the cullet considered to be “contaminated” or not clean enough is pre-melted in the auxiliary melting tank, and the remaining “clean” part of the cullet is charged into the main melting tank. Alternatively, the entire amount of the cullet is pre-melted in the auxiliary melting tank.

[0146] According to one embodiment of the present invention, at least a part of the cullet pre-melted in at least one auxiliary melting tank accounts for at least 2% by weight, preferably at least 5% by weight, more preferably at least 10% by weight, and even more preferably at least 20% by weight of the total amount of the cullet. According to another embodiment of the present invention, at least a part of the cullet pre-melted in at least one auxiliary melting tank accounts for at most 60% by weight, preferably at most 50% by weight, more preferably at most 40% by weight of the total amount of the cullet.

[0147] Alternatively, the entire amount of cullet is preliminarily melted in the auxiliary melting tank (i.e., only the vitrifiable raw materials of the present invention are charged into the main melting tank).

[0148] According to the present invention, at least a part of the cullet can be preliminarily melted in the auxiliary melting tank by using electric heating means such as immersion electrodes and / or combustion means such as air burners or immersion combustion means.

[0149] According to one embodiment, at least a part of the cullet can be preliminarily melted in two auxiliary melting tanks.

[0150] According to the present invention and as shown in FIG. 1, a method for melting a vitrifiable material to produce sheet glass includes melting the vitrifiable material in the melting tank M by heating using heating means, i.e., electric heating means 2 and combustion heating means 3.

[0151] According to the present invention and as shown in FIG. 1, a method for melting a vitrifiable material to produce sheet glass includes purifying the melt in the purification tank F by heating using oxygen combustion heating means 3' supplied with gas and / or hydrogen. In this specification, the term "gas" includes, but is not limited to, natural gas, synthesis gas, and biogas. From the viewpoints of practicality, economy, and availability, natural gas is currently the most widely used.

[0152] According to the present invention, the oxy-fuel heating means 3' is supplied with gas and / or hydrogen. In one embodiment, the oxy-fuel heating means 3' is supplied with at least 50% hydrogen, preferably at least 80% hydrogen. More preferably, the oxy-fuel heating means 3' is supplied with 100% hydrogen. This is advantageous because it can dramatically reduce the total CO2 emissions of the process. Alternatively, the oxy-fuel heating means is supplied with more than 50%, preferably at least 80%, and even at least 100% gas. This can reach a higher CO2 concentration in the exhaust gas, not only facilitating and improving the CO2 capture process, but also suppressing the influence on the chemical properties of the glass and the furnace refractory materials, which is advantageous. In a specific and advantageous embodiment of the present invention, the oxy-fuel heating means 3' is supplied with 50% gas and 50% hydrogen.

[0153] According to the present invention, the electric input rate in the process is 30% - 85%. The "electric input rate" according to the present invention means the portion of electricity in the total energy input of the process / furnace for melting / purifying, that is, electricity / (fuel + electricity), and the total energy input is that of the process / furnace in the standard / normal production mode, that is, in its standard pull range (excluding the periods of startup, maintenance, high-temperature repair, and caulking). Preferably, the electric input rate is 35% - 85%, more preferably 40% - 85%.

[0154] According to the present invention and as shown in FIG. 1, a method for melting a vitrifiable material to produce sheet glass includes flowing the melt from the refining tank F through the outlet means O into the working zone.

[0155] According to the present invention, the outlet means O is arranged downstream of the refining tank F so that the molten glass reaches the working zone. According to one embodiment, the outlet means generally consists of a neck, usually to direct the melt towards the working zone, commonly referred to as the "working end". Alternatively, the outlet means consists of a throat to direct the melt towards a working zone, for example including a forehearth. The working zone according to the present invention may include, for example, an adjustment zone where thermal adjustment by controlled cooling is performed before the glass melt exits through the outlet into the forming zone. Such a forming zone may include, for example, a float facility and / or a rolling facility.

[0156] According to the present invention and as shown in FIG. 1, a method for producing sheet glass by melting a vitrifiable material includes capturing CO2 from the exhaust gas.

[0157] According to the present invention, the exhaust gas (i.e., the exhaust gas that has undergone CO2 capture) has a CO2 concentration of at least 35%. The CO2 concentration according to the present invention is the concentration defined for the dry exhaust gas, i.e., the exhaust gas including all components except water (H2O). Preferably, the exhaust gas in the present invention has a CO2 concentration of at least 40%, more preferably at least 50%, and even more preferably at least 60%. The higher the CO2 concentration of the exhaust gas, the easier and more effective the CO2 capture applied to this exhaust gas, which is advantageous.

[0158] According to the present invention, capturing CO2 from the exhaust gas includes compressing and / or dehydrating. Dehydrating corresponds to compressing and / or drying the water in the exhaust gas. Compressing generally corresponds to increasing the pressure of CO2 by using a compressor. Dehydrating can be before compressing, and / or dehydrating can be simultaneous with compressing.

[0159] In particular, capturing CO2 from the exhaust gas according to the present invention can be carried out in a known manner using a CO2 compression purification unit (or CPU).

[0160] As shown in FIG. 1, the exhaust gas according to the present invention can be recovered from the melting tank M or the purification tank F or both for the capture of CO2. In particular, when only hydrogen is supplied to the oxy-fuel heating means 3' according to the present invention, the exhaust gas is preferably recovered only from the melting tank M (the exhaust gas generated from the purification tank F does not contain CO2).

[0161] After the capture of CO2 according to the present invention, the CO2 product has, for example, a pressure of about 35 bar at a temperature of 5°C to 40°C and is in gaseous form, suitable for transport through a pipeline or has a pressure of about 100 bar and is in liquid form, suitable for transport through a pipeline, but also suitable for truck or rail transport. It is also known that 15 barg at -35°C is suitable for transport by truck.

[0162] This simple and effective CO2 capture method can avoid the use of any adsorbent / chemical reagent that contributes to operating / energy costs and environmental problems, enabling the achievement of cost-effective CO2 capture and making the entire method of the present invention economically viable, which is very advantageous.

[0163] According to a preferred embodiment, capturing CO2 from the exhaust gas essentially includes compressing and / or dehydrating.

[0164] According to an advantageous embodiment, the method of the present invention further includes removing acidic components from the exhaust gas. Removing acidic components is carried out before or simultaneously with (e.g., before or simultaneously with / both during compressing and / or dehydrating) capturing CO2.

[0165] Removing acidic components may include desulfurizing the exhaust gas (or removing so-called "SOx" compounds). Since oxygen is used as the combustion-supporting substance, it may also include removing so-called "NOx" compounds that may be present even in very small amounts. This is advantageous because corrosive compounds (SOx, NOx) can be removed before transportation, storage, and / or utilization.

[0166] After the capture of CO2 according to the present invention, in known methods, the CO2 product (for example, in liquid form) is transported through a pipeline to its final destination and can then be stored / reserved (for example, in a formation such as a deep seabed or saline aquifer) or utilized (for example, for enhanced oil recovery, food / beverage applications or fire protection applications). Advantageously, the CO2 product obtained after the capture of CO2 can be used locally to limit transportation. This can be considered if the amount of captured CO2 is not too high so that it can be absorbed in the local market.

[0167] According to an advantageous embodiment of the present invention, the method further comprises preheating the cullet by recovering heat from the furnace 1 at least partially before loading the cullet into at least one main melting tank M. According to this embodiment, the heat recovery from the furnace 1 can be carried out from the exhaust gas exiting from (i) the main melting tank M, or (ii) the purification tank F, or (iii) the entire furnace (including the exhaust gas from the melting tank and the purification tank).

[0168] According to this embodiment, advantageously, the capture of CO2 can be carried out from the exhaust gas used for preheating the cullet.

[0169] According to this embodiment, the raw materials are loaded into the main melting tank M together with the preheated cullet through the same inlet means (thus, this means that both types of vitrifiable materials are mixed before loading). Alternatively, the raw materials are loaded into the main melting tank M through different inlet means independently of the preheated cullet.

[0170] Preferably, according to this embodiment, the maximum temperature of the cullet in preheating the cullet is 450 °C. This can avoid the problem of clogging.

[0171] According to this embodiment, preheating the cullets can be carried out, for example, in at least one type of cullet preheater described in U.S. Patent No. 5,526,580 or German Patent No. 3,716,687.

[0172] Advantageously, at least one cullet preheater can be arranged either transversely to the width or the length of the tank upstream of the melting tank. Advantageously, preheating the cullets can be carried out, for example, with at least two cullet preheaters arranged on both sides transversely to the width direction or the length of the melting tank upstream thereof. For example, preheating the cullets can be carried out with four cullet preheaters distributed (e.g., two on each side) transversely to the width direction or the length of the melting tank upstream thereof. For example also, preheating the cullets can be carried out with six cullet preheaters arranged (e.g., three on each side) transversely to the width or the length of the melting tank upstream thereof or similarly with eight cullet preheaters arranged (e.g., four on each side) transversely to the width or the length of the melting tank upstream thereof.

[0173] According to another embodiment of the invention, the method further comprises preheating at least a part of the cullets by recovering heat from the furnace 1 at least partially before charging the auxiliary melting tank.

[0174] According to another advantageous embodiment of the invention, the raw material contains less than 25% by weight of carbonate compounds. "Carbonate compounds" means, for example, alkali carbonates and alkaline earth carbonates. Preferably, the raw material contains less than 20% by weight, more preferably less than 10% by weight, and even more preferably less than 5% by weight of carbonate compounds. Advantageously, the raw material may not contain any carbonate compounds.

[0175] This embodiment is advantageous since it allows to reduce some of the CO2 emissions resulting from the decarbonation of the raw materials compared to classical glass melting processes, where sodium carbonate Na2CO3, limestone CaCO3 and dolomite CaMg(CO3)2 are generally essentially used as sodium, calcium and magnesium sources. According to this embodiment, the alkali and alkaline earth sources may advantageously be present at least partially in the form of oxides or hydroxides such as CaO, CaO·MgO (dolomite), Ca(OH)2, Mg(OH)2, NaOH, KOH, etc.

[0176] According to a highly preferred embodiment of the present invention, a method of melting vitrifiable material to produce glass sheets comprises: (i) a main melting tank M comprising at least one upstream zone Z1 covered by a crown C1 and comprising an electrical heating means 2, a downstream zone Z2 covered by a crown C2 and comprising a combustion heating means 3, and a transition zone T between the crowns C1 and C2; (ii) Auxiliary melting tanks; (iii) a refining tank F covered with a crown C4 and including an oxygen combustion heating means 3'; (iv) a neck N, covered by a crown C3, separating the main melting tank M and the refining tank F; (v) at least one inlet means X disposed in the main melter tank M; (vi) an outlet means O disposed downstream of the purification tank F; and (vii) at least one exhaust gas extraction means arranged in at least one upstream zone Z1;

[0023] providing a furnace comprising: However, the furnace has a capacity of H1≦0.75 * The height H1 of crown C1 defined by H2 (H2 is the height of crown C2), 0.25 * (L1+L2)≦L1≦0.8 * At least one upstream zone Z1 has a length L1 defined by (L1+L2) (L2 being the length of the downstream zone Z2), and LT≦0.2 *having a length LT of the transition zone T defined by (L1 + L2), - charging a vitrifiable material into the main melting tank and / or into the auxiliary melting tank using at least one inlet means, provided that the vitrifiable material comprises (i) a raw material having a carbonate compound weight of less than 25%, and (ii) cullet in an amount of at least 10% by weight of the total amount of the vitrifiable material, - preheating the cullet by recovering heat from the furnace at least partially before charging the cullet into the main melting tank and / or into the auxiliary melting tank, - pre-melting at least a part of the cullet in the auxiliary melting tank and flowing the pre-melted cullet into the main melting tank, - melting the vitrifiable material in the main melting tank by heating means 2, 3, - purifying the melt in the purification tank F by heating with oxygen combustion heating means 3' supplied with gas and / or hydrogen, - flowing the melt from the purification tank F through the outlet means O into the working zone, - capturing CO2 from the exhaust gas having a CO2 concentration of at least 35%; provided that the electricity input rate is 30% - 85%, and capturing CO2 from the exhaust gas includes compressing and / or dehydrating.

[0177] All of the specific embodiments described above related to each step of the method of the present invention apply to this last very preferred embodiment.

[0178] Those skilled in the art will understand that the present invention is in no way limited to the above-described preferred embodiments. Rather, many modifications and variations are possible within the scope of the appended claims. Furthermore, it should be noted that the present invention relates to all possible combinations of the features described herein and the preferred features recited in the claims.

Claims

1. A method for melting a vitrifiable material for manufacturing plate glass, comprising the following: (i) A main melting tank M comprising at least one upstream zone Z1 covered by a crown C1 and including an electric heating means 2, a downstream zone Z2 covered by a crown C2 and including a combustion heating means 3, and a transition zone T between the crown C1 and the crown C2. (ii) Auxiliary melting tank, (iii) A purification tank F covered with a crown C4 and including an oxygen combustion heating means 3', (iv) A neck N covered by a crown C3 and separating the main melting tank M and the refining tank F, (v) At least one inlet means X located in the main melting tank M, (vi) an outlet means O located downstream of the refining tank F, and (vii) At least one exhaust gas extraction means located in the at least one upstream zone Z1 To provide a furnace 1 including, However, the furnace is H1 ≤ 0.75 ＊ The height of the crown C1 is defined by H1 (where H2 is the height of the crown C2), H1, 0.25 ＊ (L1+L2)≦L1≦0.8 ＊ The length L1 of the at least one upstream zone Z1 is defined by (L1 + L2) (where L2 is the length of the downstream zone Z2), and LT ≤ 0.2 ＊ The transition zone T has a length LT defined by (L1 + L2); - The vitrifiable material, including the raw materials and cullet, is charged into the main melting tank M using the at least one inlet means X and / or into the auxiliary melting tank, wherein the amount of cullet is at least 10% by weight of the total amount of the vitrifiable material. - Pre-melting at least a portion of the cullet in the auxiliary melting tank, and flowing the pre-melted cullet into the main melting tank, - By heating using the heating means 2 and 3, the vitrifiable material is melted in the main melting tank M. - The molten material is purified in the purification tank F by heating using the oxygen combustion heating means 3' supplied with gas and / or hydrogen. - The molten material is flowed from the refining tank F through the outlet means O to the work zone. - At least 35% CO ２ CO from exhaust gas with concentration ２ To capture, However, the electricity input rate is 30% to 85%, and CO2 is released from the exhaust gas. ２ Capturing includes compressing and / or dehydrating.

2. The method for melting a vitrifiable material according to claim 1, characterized in that the amount of cullet is at least 30% by weight of the total amount of the vitrifiable material.

3. The method for melting a vitrifiable material according to claim 1 or 2, characterized in that the oxygen combustion heating means is supplied with at least 50% hydrogen, preferably at least 80% hydrogen.

4. The exhaust gas contains at least 40% CO ２ A method for melting a vitrifiable material according to claim 1 or 2, characterized by having a concentration.

5. The exhaust gas has at least 50% CO ２ A method for melting a vitrifiable material according to claim 4, characterized in that it has a concentration.

6. CO from exhaust gases ２ A method for melting a vitrifiable material according to claim 1 or 2, characterized in that capturing essentially includes compressing and / or dehydrating.

7. A method for melting a vitrifiable material according to claim 1 or 2, further comprising removing acidic components from the exhaust gas.

8. Removing acidic components from the aforementioned exhaust gas is CO ２ A method for melting a vitrifiable material according to claim 7, characterized in that it takes place before or simultaneously with capturing the material.

9. A method for melting a vitrifiable material according to claim 1 or 2, further comprising preheating the cullet by recovering heat from the furnace at least partially before charging the cullet into the melting tank M.

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

11. A method for melting a vitrifiable material according to claim 1 or 2, characterized in that the raw material contains less than 25% by weight of a carbonate compound.

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