Glass melting method with extremely low or zero CO2 emissions

Abstract

The present invention relates to a method for melting a glassifiable material for manufacturing sheet glass, comprising: (i) providing a furnace having a special divided design; (ii) charging a glassifiable material containing raw materials and cullets into a melting tank using inlet means, provided that the amount of cullets is at least 10% by weight of the total amount of the glassifiable material; (iii) preheating the cullets by recovering at least partially the heat from the furnace before charging the cullets into the melting tank; (iv) melting the glassifiable material in the 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 to a working zone through outlet means O; (vii) capturing CO2 from the exhaust gas having a CO2 concentration of at least 35%, wherein the electricity input rate is from 30% to 85%, and capturing CO2 includes compressing and / or dehydrating.

Description

Technical Field

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

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

Background Art

[0003] The requirements 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 been investing heavily in the decarbonization of manufacturing methods for many years to produce glass products that are sustainable, resource-efficient, and compatible with a low-carbon society in relation to emergency measures for reducing 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, an increased use of cullet as a raw material, heat recovery, carbon dioxide capture, utilization, and storage (or CCUS), etc.

[0006] Nevertheless, all of these technologies are associated with serious drawbacks or problems for practical implementation 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 not only to show a reduction in CO2 emissions but also to show a reduction in total energy consumption. Although demonstrated only for 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 being developed.

[0009] These furnaces are also called "cold top furnaces" as opposed to classical combustion furnaces called "hot top furnaces" (or "warm 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 (optionally down to 50 °C). All-electric furnaces have significant advantages. First, they have very low direct emissions of CO2, thermal NO x and SO x .

[0010] Furthermore, since the melting energy is basically transferred into the glass (for example, for electrodes that pass an electric current to heat the molten glass bath from its bulk), the heat losses of all-electric furnaces are much lower compared to hot top combustion furnaces where significant heat losses occur from the upper furnace structure and in the residual exhaust gases, even when using heat recovery systems, thus resulting in highly energy-efficient furnaces. Unfortunately, all-electric furnaces also have some disadvantages compared to combustion hot top furnaces.

[0011] In particular, such furnaces - The quality of the glass does not reach 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 corrosion of the bottom refractory and the walls of the glass tank, significantly shortening the furnace life (from typically over 15 years for conventional furnaces to less than 8 years, optionally down to 2 - 7 years).

[0012] Furthermore, the surface melting rate of the cold-top all-electric furnace, i.e., the amount of glass melted from the raw materials per unit time and per unit furnace area (T / d / m 2 as indicated) 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, a glass temperature of 1400 °C or higher or 1450 °C or higher is required, 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 . Instead, setting a low surface melting rate to avoid affecting the furnace life as much as possible means significantly increasing the melting area, which in turn has a great negative impact on the required investment and industrial floor area.

[0013] Finally, such cold-top furnaces have no flexibility in terms of energy (only electricity).

[0014] It is also known to combine combustion heating means and electric heating means in a "hybrid system". In such a configuration, which mainly operates in a "hot-top", the furnace is composed of burners and electrodes for power supply.

[0015] Such hybrid furnaces have great advantages in terms of energy flexibility and can adapt the electric input rate to various parameters in operation or assumptions.

[0016] Furthermore, compared with cold-top furnaces, if the bottom temperature is the same, the hot-top furnace can reach a higher surface melting rate (or if the surface melting rate is the same, it can reach a lower bottom temperature).

[0017] Next, there are several drawbacks to hybrid furnaces operated with a "warm top". In particular, (i) significant heat losses occur in 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 investments are required.

[0018] Furthermore, in such furnaces, the temperature of the crown / upper structure in the melting zone can become very low depending on the conditions (e.g., less than 1000 °C), significantly increasing the risk of alkali condensation (e.g., NaOH) in said zone and thus refractory corrosion of the crown.

[0019] Next, in these furnaces, especially for all-electric furnaces, due to the corrosion phenomena at the bottom and crown described above, the electrical input rate is generally limited to a maximum of 35% of the total energy input.

[0020] Among hybrid furnaces, some with special designs to increase the electrical input rate, for example, up to 80%, have recently been developed, but most of them are operated as cold top furnaces and have the problems that this brings.

[0021] Regarding the use of alternative and environmentally friendly energy sources such as hydrogen H2 or biogas: Even though it is clear that there are advantages in terms of environment / energy consumption / CO2 emissions, due to serious constraints (lack of availability of biogas, the high cost of hydrogen H2, which is an economically unfeasible solution as long as it is the only energy source for melting glass raw materials), its widespread use in the glass industry is hindered.

[0022] Regarding heat recovery:

[0023] 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, especially cullet. Nevertheless, in this case, it is known that the temperature of the exhaust gas discharged from the raw materials is too low, so the preheating of the raw materials / cullet cannot be combined with electric melting.

[0024] Regarding the use of CO2 capture:

[0025] 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 the 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 industrially most widely used 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 (for example, those using aqueous MEA) remain poor options, especially in the special circumstances of the glass industry, for at least the following main reasons: - The combustion gas / exhaust gas in known glass manufacturing methods has a low CO2 concentration (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 may affect the CO2 emissions depending on the energy source used, clearly having a reverse effect in this regard).

[0026] Furthermore, known glass manufacturing methods generate very high volumes or flows of exhaust gas. This also 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

[0027] An object of the present invention is to overcome the above-mentioned drawbacks with respect to the prior art and solve the 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.

[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 exhibits an acceptable surface melting rate (particularly greater than or better still greater than 2 2 T / d / m 2 or more preferably greater than 3 T / d / m

[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 provides sheet glass with an improved lifespan compared to classical "hot top" hybrid melting furnaces.

[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 enables simple and cost-effective CO2 capture.

[0031] 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 viable. Means for Solving the Problems

[0032] The present invention relates to a method for melting vitrifiable material for producing glass sheets, the method comprising: (i) a melting tank M comprising at least one upstream zone Z1 covered by a crown C1 and equipped with electrical heating means, a downstream zone Z2 covered by a crown C2 and equipped with combustion heating means and a transition zone T between the crowns C1 and C2, (ii) a refining tank F, covered with crown C4 and equipped with an oxygen combustion heating means; (iii) a neck N, covered by a crown C3, separating the melting tank M from the refining tank F; (iv) at least one inlet means X disposed in the melting tank M; (v) an outlet means O disposed downstream of the purification tank F; and (vi) at least one exhaust gas extraction means arranged in at least one upstream zone Z1

[0023] providing a furnace comprising: However, for furnaces, H1≦0.75 * The height H1 of the crown C1 defined by H2 (where H2 is the height of the crown C2) is 0.25 * (L1+L2)≦L1≦0.8 * At least one upstream zone Z1 has a length L1 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), - charging vitrifiable material, including raw materials and cullet, into the melting tank M by means of at least one inlet means X, with the amount of cullet being at least 10% by weight of the total amount of vitrifiable material; - preheating the cullet before it is charged into the melting tank M, at least in part by recovering heat from the furnace; - melting the vitrifiable material in a melting tank M by means of heating means; - refining the melt in a refining tank F by heating using oxy-combustion heating means supplied with gas and / or hydrogen; - flowing the melt from the refining 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.

[0033] Therefore, the present invention is based on a novel and innovative approach. In particular, the inventors have, in a glass melting method for manufacturing flat glass, - using a specially designed furnace including a combination of (i) separating a "hybrid" melting tank and a combustion refining 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 combustible substances, - using a minimum amount of cullet in the vitrifiable material, - using preheating of the cullet, and - using a specific high electricity input rate by combining, - 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, - being able to independently extract the exhaust gas generated from raw material decomposition (poor in NOx and SOx impurities) and the exhaust gas generated from combustion, and thereby, if necessary, separating and appropriately treating each of them, - 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 simultaneously obtain, thereby enabling the use of a simple, efficient and cost - effective CO2 capture method.

[0034] 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.

[0035] 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 also 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 general 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 portion" is understood to mean the first upstream one-third of the length, and said length is located along the horizontal longitudinal axis of the furnace. The expression "downstream portion" is understood to mean the last downstream one-third of said length.

[0036] Other features and advantages of the present invention will become more apparent by 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

[0042] According to the present invention, as shown in FIG. 1, a method for melting vitrifiable material to produce glass sheets includes first providing a specific furnace, said furnace 1 comprising: (i) a melting tank M comprising at least one upstream zone Z1 covered by a crown C1 and equipped with an electric heating means 2, a downstream zone Z2 covered by a crown C2 and equipped with a combustion heating means 3 and a transition zone T between the crowns C1 and C2, (ii) a refining tank F covered with a crown C4 and equipped with an oxygen combustion heating means 3'; (iii) a neck N, covered by a crown C3, separating the melting tank M from the refining tank F; (iv) at least one inlet means X disposed in the melting tank M; (v) an outlet means O disposed downstream of the purification tank F; and (vi) at least one exhaust gas extraction means arranged in at least one upstream zone Z1 and H1≦0.75 * The height H1 of the crown C1 defined by H2 (where H2 is the height of the crown C2) is 0.25 * (L1+L2)≦L1≦0.8 * At least one upstream zone Z1 has a length L1 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).

[0043] 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 materials and / or cullets) is charged and melted by heating. When the furnace is in operation, it includes the melt and a "blanket" of unmolten glassifiable material that floats on the melt and is gradually melted, thus decreasing from the upstream to the downstream of the melting tank.

[0044] 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 there is no longer a "blanket" of unmolten glassifiable material floating on the melt. The glass melt is heated at a temperature higher than the melting tank temperature (generally above 1400 °C or above 1450 °C) to refine the glass (mainly by removing the main part of the bubbles). This refining tank is generally also called a "purification tank" in the art.

[0045] According to the present invention, a "neck" that separates the melting tank and the refining tank means that the width and (crown) height are narrower compared to the downstream zone of the melting tank (zone Z2) and the upstream zone of the refining tank F. The opening of the neck according to the present invention can be partially below 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 unmolten 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 are reduced. Due to this point, the life of the furnace is advantageously improved.

[0046] Such a furnace design with a zone division of the melting and refining tanks combined with a height division of the melting crown brings many advantages in terms of energy consumption / CO2 emissions and the mechanical stability / life of the furnace.

[0047] In particular, by the combination of (i) separating the melting tank and the refining tank by a neck, and (ii) dividing the melting tank into two zones with different crown heights in a specific design (thereby providing a cooler upstream zone and a hotter downstream zone with a significant temperature difference), the total energy consumption of the furnace can be significantly reduced while maintaining a high electrical input rate (thereby reducing CO2 emissions), an acceptable surface melting rate is maintained, and the mechanical stability and lifespan of the furnace are improved.

[0048] The melting crowns C1 and C2 of the present invention take advantage of both the "cold top" zone and the "hot top" zone, and are specially designed to create a temperature gradient from a relatively low temperature (less than 1100 °C) upstream to a relatively high temperature (higher than 1300 °C) downstream.

[0049] In particular, the furnace of the present invention can fully control (i) the temperature of each zone and (ii) the exhaust gas re-division / extraction between the two zones of the melting tank and between the melting tank and the refining tank in order to optimize energy consumption, avoid alkali corrosion as much as possible, and optimize CO2 capture.

[0050] The furnace of the present invention is further advantageous in that it simultaneously generates a strong temperature difference between the upstream and downstream portions of the melting tank and avoids, as much as possible, the reverse flow of the exhaust gas generated from the refining tank towards the melting tank.

[0051] From the perspective of energy efficiency, - Dividing the atmosphere and blocking the heat radiation from the refining tank to the melting tank in order to efficiently confine energy in the zone where high temperature is required (refining zone), and - Extracting the exhaust gas from the upstream / exit at as low a temperature as possible in order to limit the waste heating of the gas released from the vitrifiable material and optionally maximize the heat transfer from the combustion gas to the vitrifiable material and the glass melt To enable this, the furnace of the present invention is advantageous.

[0052] From the point of view of surface melting rate, this is advantageous as it allows relatively high temperatures (>1300° C.) to be reached downstream of the melting tank in order to improve the melting rate of the vitrifiable material.

[0053] From a corrosion perspective, - Separation of the atmosphere between the melting tank and the refining tank limits / avoids the reflux of waste gases from the refining zone, which are rich in alkalis and therefore highly corrosive due to the high temperatures required for refining; - Having a restriction of the overall molten glass flow, which advantageously reduces the intensity of the glass convection in the melting tank, lowering the glass velocity and thus reducing wear and erosion of the bottom refractory. This is advantageous because it allows

[0054] Finally, the furnace of the present invention, with its specific division (via the neck) between the melting tank and the refining tank, also allows for a complete separation of the dimensions (length, width and crown height) and refractory properties of the melting and refining tanks, thus allowing for the optimization of each tank taking into account energy efficiency, glass quality, factory space constraints and mechanical / structural / other constraints.

[0055] 2 and 3 show an embodiment of a furnace 1 according to the invention (FIG. 2: vertical section, FIG. 3: horizontal section).

[0056] The furnace 1 of the invention includes a melting tank M, a neck N and a refining tank F. The assemblies M, N and F are generally made of refractory materials resistant to temperature, the corrosive effects of fumes and the aggressive action of the molten material. In Fig. 2 the glass melt level (excluding the batch blanket) in an exemplary tank is shown by a dashed line.

[0057] According to the invention, as shown in Figures 2-3, the furnace 1 comprises at least one inlet means X into the melting tank M for charging the vitrifiable raw materials (friction and / or cullet) into the furnace.

[0058] In order to improve distribution on the surface of the melt tank M, a plurality of inlet means, i.e. two or three inlet means, located upstream (in particular in zone Z1) of the melt tank M are advantageously provided. Preferably and as known in the art, at least one inlet means X is arranged upstream of the melt tank M (in particular in zone Z1) transversely across the width of said tank and / or across its length.

[0059] As shown in FIGS. 2-3, the furnace 1 of the present invention includes a melting tank M, which is at least one upstream zone Z1 covered by a crown C1 and equipped with electric heating means 2, a downstream zone Z2 covered by a crown C2 and equipped with electric heating means 2 and combustion heating means 3, - Transition zone T between crown C1 and crown C2 Includes.

[0060] According to an advantageous embodiment, the downstream zone Z2 comprises further electric heating means, as shown in FIGS.

[0061] The electric heating means 2 according to the invention are preferably arranged at the bottom of the melting tank M and also consist of electrodes, preferably immersed. 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 obtained. 2 The number of electrodes is designed to respect the above and limit the maximum power of each electrode to 200 kW. For example, the height of the immersed electrodes is also 0.3-0.8 times the height of the glass melt.

[0062] The combustion heating means 3 in the downstream zone Z2 of the melting tank M is particularly composed of burners. In particular, they are generally arranged in a row and are arranged on one side or, alternatively, on both sides along the side wall of the said zone, for example, to spread the flame over substantially the entire width of the said zone. They are alternatively or additionally arranged also on the crown C2, thereby promoting heat transfer to the batch, shortening the length of the batch, and being advantageous for avoiding the batch blanket reaching the end of the downstream zone Z2 and thus the downstream end of the melting tank.

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

[0064] According to an advantageous embodiment, at least one upstream zone Z1 can include further auxiliary combustion heating means (for example, burners, not shown) to enable control of the temperature of the crown C1 (for example, to limit temperature fluctuations along the zone Z1) and to raise the temperature when it drops below a specific level (for example, below 600 °C). In particular, these auxiliary combustion heating means can advantageously be arranged within the crown C1 to reduce the occupation of the free volume space above the melt / batch blanket.

[0065] 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.

[0066] According to the present invention, the height H1 of the crown C1 is defined by H1 ≦ 0.75 * H2, where H2 is the height of the crown C2. In the present invention, the change in height between the crowns C1 and C2 along the melting tank M means the transition zone T.

[0067] As used herein and throughout the claims, the "height" of the crown in the present invention means the average inner height (illustrated in Figure 2) from the inner surface of the crown to the glass melt (excluding the batch blanket if present). The height H1 of 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 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 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 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).

[0068] According to one embodiment of the present invention, the height H1 of crown C1 is such that H1≦0.7 * H2, preferably H1≦0.6 * H2, more preferably H1≦0.5 * is defined by H2. Thereby, the above-mentioned advantages of the present invention can be enhanced.

[0069] According to the present invention, 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), where L2 is the length of the downstream zone Z2.

[0070] As used herein and throughout the claims, "length" means the dimension along the flow of the glass.

[0071] According to another embodiment of the present invention, the length L1 of at least one upstream zone Z1 is such that 0.3 * (L1 + L2)≦L1, preferably 0.4 * (L1 + L2)≦L1, further 0.5 * is defined by (L1 + L2)≦L1. Thereby, the above-mentioned advantages of the present invention can also be enhanced.

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

[0073] It is worth mentioning that the total length of the melting tank may be slightly higher (e.g., on the order of 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") at the extreme upstream of the melting tank for the introduction of the vitrifiable material and the extrusion in the melting direction (not shown).

[0074] The crown C1 according to the present invention can be arch-shaped or round ceiling-shaped, or can be flat. Independently of the crown C1, the crown C2 according to the present invention can be arch-shaped or round ceiling-shaped, or can be flat.

[0075] Advantageously, the crown C1 can be composed of a refractory material essentially made of silica (e.g., high-purity silica). Silica refractories are known to be more vulnerable to corrosion (e.g., compared to alumina), but 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 melting tank.

[0076] The advantage of silica is its low coefficient of expansion when the temperature is higher than about 600°C, which allows it to withstand high temperature variations without disturbing the upper structure of the crown.

[0077] Alternatively, the crown C1 and / or the crown C2 can 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.

[0078] According to the present invention, as shown in FIG. 2, the furnace includes a melting tank M including at least one upstream zone Z1 and a downstream zone Z2 having different crown heights of C1 having a height H1 and C2 having a height H2.

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

[0080] 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 * is defined by (L1 + L2).

[0081] According to one embodiment, the transition zone T between the crown C1 and the crown C2 can be a breast wall. The breast wall according to one embodiment can be a vertical wall or a short inclined wall (allowing a gradual transition). In this embodiment, the crown C1 preferably has an inner surface substantially at the same height as or slightly lower than the lower edge of the breast wall. The breast wall can be composed of a suspended rear wall. The suspended rear wall according to the present invention is, for example, as described in U.S. Patent No. 5,011,402. Alternatively, the breast wall can lie on the outer surface of the crown C1.

[0082] 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 having 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 melting tank, better separates the exhaust gases emitted from Z1 and Z2, and has the advantage that the vitrifiable material extruded from the upstream can pass through the remaining free space. For example, this shadow wall can be an air-cooled suspended wall as known in the art. The shadow wall according to the present invention can be composed of, for example, a suspended U-shaped shadow wall as described in U.S. Patent No. 3399046A.

[0083] 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 including a first wife wall, a short crown at an intermediate height between H1 and H2, and a second wife 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.

[0084] 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).

[0085] According to an advantageous embodiment, the transition zone is composed of a refractory essentially made of silica.

[0086] Advantageously, according to another embodiment, in order to avoid expansion between materials and / or avoid corrosion between materials, the crown C1 and the transition zone T are made of the same refractory material. Preferably, it is composed of a refractory essentially made of silica.

[0087] Advantageously, according to another embodiment, the crown C1, the crown C2 and the transition zone T are also made of the same refractory material in order to avoid expansion between materials and / or corrosion between materials. Preferably, it is composed of a refractory essentially manufactured from silica.

[0088] According to the present invention, the furnace includes a refining tank F covered by a crown C4 and equipped with oxygen combustion heating means 3'.

[0089] The "oxygen combustion means" 3' according to the present invention means combustion means to which gaseous oxygen (O2) is supplied as a combustion agent. Generally, the O2 gas combustion agent supplied to a 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. Even if they are present in the exhaust gas (depending on the purity of O2 and the amount of parasitic air), they will be in a very small amount.

[0090] The oxygen combustion heating means 3' from the refining tank F according to the present invention can advantageously be composed of burners arranged along the side wall of the refining tank. Further, the burners are advantageously arranged at intervals from each other in order to disperse the energy supply to a part of the refining tank F, preferably the upstream part (for example, about 50% of the length). They are generally arranged in rows on one side or instead on both sides of the refining tank F, preferably arranged in a staggered pattern (in order to spread the flame over substantially the entire width of the tank).

[0091] The crown C4 according to the present invention is preferably arch-shaped or round ceiling-shaped.

[0092] According to an advantageous embodiment, the refining tank F may further include additional electric heating means (not shown), particularly in the upstream part of the refining tank (for example, about 50% of the length). Thereby, the electric input rate can be increased, and as a result, the energy efficiency can be improved and the CO2 emissions can be reduced.

[0093] According to the invention, the furnace includes a neck N, which is covered by a crown C3 and separates / divides a melting tank M and a refining tank F.

[0094] According to the invention, the "neck" separating the melting tank M and the refining tank F means a narrowing in width and (crown) height compared to the downstream zone of the 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.

[0095] 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 melting tank M. 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 F But, W F is the width of the purification tank F.

[0096] In the present invention, "width" means the dimension (average) perpendicular to the flow of glass throughout this specification and claims.

[0097] This furnace design with separate melting tank and refining tank offers many advantages in terms of energy consumption / CO2 emissions and is favorable for the mechanical stability / lifetime of the furnace. Particularly advantageously, the present invention allows the furnace with this particular split design to treat the off-gases from the melting tank (Zone 1 and / or Zone 2) and the off-gases from the refining tank independently, if necessary.

[0098] The base of the neck N in the present invention can be essentially located at the level of the floor / bottom of the melting tank M, or can be located above or below said level. Furthermore, the base of the neck N can be substantially located at the level of the floor / bottom of the refining tank F, or can be located above or below said level.

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

[0100] The crown C3 according to the present invention can be arch-shaped or round ceiling-shaped, or can 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 melting tank M. According to the definition of the neck according to the present invention, the crown C3 of the neck N also has a height H3 lower than the height H4 of the crown of the refining tank F.

[0101] According to yet another advantageous embodiment of the present invention, the furnace can include a removable wall (e.g., a skin bar coming from the side wall of the neck) located in the neck to (i) stop the unmelted vitrifiable material that can reach the end of the melting tank, thereby avoiding them from going through the neck towards the refining tank, and (ii) control or eliminate the intensity of the backflow of the glass melt from the refining tank towards the melting tank.

[0102] According to yet another advantageous embodiment of the present invention, the furnace can include a removable wall (e.g., a shadow wall passing through the crown of the neck part) located in the neck part to enhance the separation of the melting tank and the refining tank in terms of atmosphere and thermal radiation.

[0103] According to the present invention, the furnace includes outlet means O located downstream of the purification tank F so that the molten glass reaches the working zone. According to one embodiment, the outlet means O is usually composed of a neck to guide 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) to guide the melt to a working zone including, for example, a forehearth. The working zone according to the present invention may include, for example, a conditioning zone where thermal conditioning by controlled cooling is performed before the glass melt exits through the outlet into the forming zone. Such a forming zone may be composed of, for example, a float facility and / or a rolling facility.

[0104] According to the present 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, to recover heat and transfer it from the exhaust gas to the glass melt and / or the unmolten glassifiable material in the melting tank M.

[0105] According to one embodiment of the present invention, the furnace further includes 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).

[0106] If there is an extraction means in the zone Z2, this enables, advantageously, the extraction of exhaust gas from the downstream zone Z2, especially when the gas is alkali-rich (thereby avoiding condensation and subsequent corrosion in the zone Z1).

[0107] If there is an extraction means in the purification tank F, it is preferably arranged in the upstream part of the purification tank.

[0108] Preferably, in the present invention, the extraction means 4 is arranged on one or both side walls.

[0109] In particular, in the present invention, it is energetically advantageous for the exhaust gas to be extracted maximally from the upstream of the furnace, particularly from the upstream of the melting tank. For example, at least 25% of the combustion exhaust gas generated in the melting zone can be advantageously extracted from the upstream of the melting tank. Nevertheless, extracting a part of the exhaust gas from downstream of the melting tank can be advantageous for limiting the risk regarding the alkali attack of the crown refractory. In fact, the alkali evaporation increases with the temperature and the alkali concentration in the exhaust gas becomes higher in the downstream part of the melting zone. The exhaust gas with a higher alkali concentration may cause problems related to condensation in the lower temperature region of the superstructure / crown, so it is better to discharge it from the downstream. Furthermore, in its upstream zone, the exhaust gas essentially results from the gases released from the decomposition of the raw materials and is thus poor in alkali, so it is advantageous to extract a part of the exhaust gas from the upstream of the 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.

[0110] Furthermore, in the present invention, it is even more advantageous that the exhaust gas (at least its main part) generated from the decomposition of the raw materials at the upstream Z1 of the 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.

[0111] In an advantageous embodiment of the present invention shown in FIG. 4, the furnace of the present invention includes a melting tank M that is laterally enlarged and includes inlet means X' and X'' arranged in each lateral direction. The melting tank includes two different upstream zones Z1' and Z1'' and two transition zones T' and T'', and two opposing glass flows converge through the central downstream zone Z2.

[0112] In this configuration, - The height H1' of the melting 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 at least one upstream zone Z1’ is 0.25 * (L1’ + L2) ≦ L1’ ≦ 0.8 * is defined by (L1’ + L2), - The length L1’’ of at least one upstream zone Z1’’ is 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).

[0113] Also, in this configuration, - The melting tank includes one downstream crown C2 and two upstream crowns C1’ and C1’’. The crowns C1’ and C1’’ can each be independently configured according to any embodiment of the 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 melting tank includes two transition zones T’ and T’’. They can each be independently configured according to any embodiment of the invention related to the transition zone T.

[0114] 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.

[0115] 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 respectively according to the above description. Thus, for 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''. Furthermore, 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.

[0116] The design of a specific glass furnace having a neck-based division 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.

[0117] 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 is the width of at least one melting tank M, W F is the width of the refining tank F, W N is the width of at least one neck N.

[0118] This embodiment can enhance the above advantages of the present invention. 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 heat radiation shielding from the refining tank to the melting tank can be enhanced, - The overall restriction of the molten glass flow can be enhanced or the backflow can be eliminated.

[0119] Preferably, the furnace is 0.2 * W F ≦W N ≦0.6 * W F or 0.3 * W F ≦W N ≦0.5 * W F defined by. Thereby, a good compromise between the following two conflicting requirements can be found. On the one hand, (1) the opening between the melting superstructure / crown and the refining superstructure / crown is reduced, and (2) the neck between the melting zone and the refining zone should ideally be as narrow as possible in order to create an obstacle to the convection intensity of the total glass melt in the melting tank. On the other hand, the neck should ideally be as wide as possible in order to limit the glass velocity inside the neck and limit the wear / corrosion of the neck refractory wall.

[0120] Preferably, the furnace of the present invention is W M ≧1.5 * W N or W M ≧1.8 * W N also defined by. More preferably, the furnace of the present invention is defined by WM≧2 * W N This increases the width limitation of the neck N, improves the heat radiation shielding, enables better atmosphere separation, and restricts the molten glass flow.

[0121] 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 extensively described in European Patent Application Publication No. 21200998.9, which is incorporated herein by reference.

[0122] In the specific "two melting tanks" configuration shown in Figure 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).

[0123] This configuration is particularly advantageous compared to the configuration with one melting tank (Figure 3) because the following are possible: - It is possible to reduce the crown span of each melting tank for the same total melting tank area and furnace length (length is generally more restrictive than width). The reduction of the crown span results in (i) a reduction in the stress within the crown material, and then a reduction in the risk regarding creep and sagging of the material. As a result, it becomes possible to use refractories with higher resistance to corrosion such as alumina or spinel and lower resistance to creep, and it becomes possible to increase the life of the furnace, (ii) in the case of arch-shaped crowns C1 and / or C2, it is possible to reduce the average height of the crown, reduce the horizontal radiative transfer, and then, when the exhaust gas is extracted from the melting tank, achieve good heat transfer from the exhaust gas to the glass melt, - In the case of the same total neck width (W N’ +W N’’ ) and an arch-shaped neck crown C3, it is possible to reduce the opening area between the melting tank and the refining tank, - In the case of the same total neck width (W N’ +W N’’ ), it is possible to reduce the intensity of the glass convection within the melting tank, - It is possible to facilitate the maintenance of the furnace in the melting zone. In fact, when there are two melting tanks, it is possible to isolate and cool one melting tank from the other parts of the furnace and carry out production in the other melting tank. Therefore, by replacing the worn refractories in the melting zone, which is the most important area regarding wear / corrosion, it is possible to increase the life of the entire furnace.

[0124] In this configuration, the furnace comprises 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.

[0125] In this configuration, according to the present invention, - The height H1' of the fusion crown C1' is H1'≦0.75 * Defined by H2', - The height H1'' of the fusion crown C1'' is H1''≦0.75 * Defined by H2'', - The length L1' of the upstream zone Z1' is 0.25 * (L1'+L2')≦L1'≦0.8 * (L1'+L2'), and - The length L1'' of at least one upstream zone Z1'' is 0.25 * (L1''+L2'')≦L1''≦0.8 * (L1''+L2'', - The length LT' of the transition zone T' is LT'≦0.2 * (L1'+L2'), - The length LT of the transition zone T is LT≦0.2 * It is defined by (L1''+L2'').

[0126] According to this particular embodiment, the furnace advantageously comprises: 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''.

[0127] 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.

[0128] 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''.

[0129] Furthermore, the specific advantageous features described in relation to a furnace having one melting tank (e.g., those described in relation to C3, C4, F) are applied such that similar advantages are also present in this "two melting tanks" configuration.

[0130] 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 FIG. 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) and 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.

[0131] In the "two melting tanks" configuration, the two melting tanks are at the width W FWhen connected to the purification tank by a neck located at [the relevant 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 for enabling access to the maintenance work and the zone for tank wall overcoating.

[0132] In another embodiment of the present invention, the furnace has a configuration having three melting tanks, three necks and three inlet means. This embodiment is particularly advantageous compared to the configuration having 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.

[0133] The specific advantageous features described in relation to the furnaces having "one melting tank" and "two melting tanks" are also applicable to the configuration of "three melting tanks" and have the same advantages.

[0134] 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.

[0135] In all furnace configurations according to the present invention, that is, the "one melting tank", "two melting tanks" and "three melting tanks" configurations, in order to facilitate the distribution of the vitrifiable material into the charging, one or more charging means can be provided for each melting tank, that is, two charging means can be provided for each melting tank.

[0136] 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 m 2is.

[0137] According to the present invention, and as shown in FIG. 1, a method for producing sheet glass by melting a vitrifiable material includes charging a vitrifiable material including raw materials and cullet into at least one melting tank M using at least one inlet means X.

[0138] According to the present invention, the vitrifiable material includes raw materials and cullet, and both are preferably charged into the melting tank M together, i.e., through the same inlet means X. Alternatively, both are charged into the melting tank M separately through different inlet means X (for example, one inlet means for raw materials and one inlet means for cullet, or two inlet means for raw materials and two inlet means for cullet).

[0139] 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.

[0140] According to the present invention, as shown in FIG. 1, the method further includes preheating the cullet by recovering at least partially the heat from the furnace 1 before charging the cullet into the melting tank M. According to one embodiment, the heat recovery from the furnace 1 can be carried out from the exhaust gas coming from (i) the melting tank M, or (ii) the purification tank F, or (iii) the whole furnace (thereby including the exhaust gas from the melting tank and the purification tank).

[0141] Advantageously, the capture of CO2 can be carried out from the exhaust gas used by preheating the cullet.

[0142] According to one embodiment, in preheating the cullet, the raw materials are charged into the melting tank M through the same inlet means X together with the preheated cullet (thus, this suggests that the two vitrifiable materials are mixed before charging). Alternatively, the raw materials are charged into the melting tank M through different inlet means X independently of the preheated cullet.

[0143] Preferably, the maximum temperature of the cullet in preheating the cullet is also 450 °C. Thereby, the clogging problem can be avoided.

[0144] According to one embodiment, the preheating of the cullet can be carried out with at least one type of cullet preheater as described in, for example, U.S. Patent No. 5,526,580 or German Patent No. 3,716,687.

[0145] Advantageously, at least one cullet preheater can be arranged, for example, in the upstream part of the melting tank M, for example in zone Z1, either in the width of the tank or transversely in the longitudinal direction thereof. Advantageously, the preheating of the cullet can be carried out with at least two cullet preheaters arranged on both sides transversely in the width or in the longitudinal direction thereof in the upstream part of the melting tank M, for example in zone Z1. For example, the preheating of the cullet can be carried out with four cullet preheaters arranged dispersedly (for example, two on each side) transversely in the width or in the longitudinal direction thereof in the upstream part of the melting tank M, for example in zone Z1. For example, the preheating of the cullet can be carried out with six cullet preheaters arranged transversely in the width or in the longitudinal direction thereof (for example, three on each side) in the upstream part of the melting tank M, for example in zone Z1, or with eight cullet preheaters arranged transversely in the width or in the longitudinal direction thereof (for example, four on each side) in the upstream part of the melting tank, for example in zone Z1.

[0146] According to the present invention, as shown in FIG. 1, a method for melting a vitrifiable material for manufacturing sheet glass includes melting the vitrifiable material in a melting tank M by heating means, i.e., heating by electric heating means 2 and combustion heating means 3.

[0147] According to the present invention, as shown in FIG. 1, a method for melting a vitrifiable material for manufacturing sheet glass includes purifying the melt in a purification tank F by oxy-fuel combustion heating means 3' supplied with gas and / or hydrogen. The term "gas" as used herein includes, but is not limited to, natural gas, synthesis gas, and biogas. Natural gas is currently the most widely used for practical, economic, and available reasons.

[0148] According to the present invention, the oxy-fuel combustion heating means 3' is supplied with gas and / or hydrogen. In one embodiment, the oxy-fuel combustion heating means 3' is supplied with at least 50% hydrogen, preferably at least 80% hydrogen. More preferably, the oxy-fuel combustion heating means 3' is supplied with 100% hydrogen. This is advantageous because it can dramatically reduce the total CO2 emissions of the method. Alternatively, the oxy-fuel combustion heating means is supplied with more than 50%, preferably at least 80%, and further at least 100% gas. This is advantageous because it can reach a higher CO2 concentration in the exhaust gas, which not only facilitates and improves CO2 capture, but also suppresses the influence on the chemical properties of the glass and the furnace refractory materials. In a specific and advantageous embodiment of the present invention, the oxy-fuel combustion heating means 3' is supplied with 50% gas and 50% hydrogen.

[0149] According to the present invention, the electric input rate in the method is 30% to 85%. The "electric input rate" according to the present invention means the part of electricity in the total energy input of the method / furnace for melting / purifying, that is, electricity / (fuel + electricity), and the total energy input is that of the method / 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% to 85%, more preferably 40% to 85%.

[0150] According to the present invention, as shown in FIG. 1, a method for melting a vitrifiable material for producing sheet glass includes flowing the melt from a refining tank through an outlet means O into a working zone.

[0151] According to the present invention, the outlet means O is arranged downstream of the refining tank F such 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 a working zone generally called the "working end". Alternatively, the outlet means consists of a throat to direct the melt into a working zone including, for example, 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.

[0152] According to the present invention, as shown in FIG. 1, a method for melting a vitrifiable material for producing sheet glass includes capturing CO2 from the exhaust gas.

[0153] According to the present invention, the exhaust gas (i.e., the exhaust gas after CO2 capture) has a CO2 concentration of at least 35%. The CO2 concentration according to the present invention is a concentration defined for dry exhaust gas, i.e., exhaust gas containing 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, so this is advantageous.

[0154] 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.

[0155] 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).

[0156] 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 CO2 capture. 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 does not contain CO2).

[0157] 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 transportation through a pipeline, or has a pressure of about 100 bar and is in liquid form, suitable for transportation through a pipeline but also suitable for truck or rail transportation. It is also known that 15 barg at -35°C is suitable for transportation by truck.

[0158] This simple and effective method of CO2 capture can avoid the use of any adsorbents / chemical reagents that contribute to operating / energy costs and environmental problems, enabling cost-effective CO2 capture and making the overall method of the present invention economically viable, which is highly advantageous.

[0159] According to a preferred embodiment, capturing CO2 from the exhaust gas essentially involves compressing and / or dehydrating.

[0160] According to an advantageous embodiment, the method of the present invention further includes removing acidic components from the exhaust gas. Removing the acidic components is carried out before or simultaneously with (e.g., before or simultaneously with / along with compressing and / or dehydrating) capturing CO2.

[0161] Removing the acidic components may include desulfurizing the exhaust gas (or removing so-called "SOx" compounds). Since oxygen is used as a 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.

[0162] After the CO2 is captured according to the present invention, in a known method, the CO2 product (e.g., in liquid form) is transported through a pipeline to its final destination and then can be stored / reserved (e.g., in a formation such as deep under the sea or a saline aquifer) or utilized (e.g., for enhanced oil recovery, food / beverage applications, or fire protection applications). Advantageously, the CO2 product obtained after CO2 capture can be used locally to limit transportation. This can be considered when the amount of captured CO2 is not too high so that it can be absorbed in the local market.

[0163] According to an advantageous embodiment of the present invention, this method further comprises pre-melting at least a part of the cullet in an auxiliary melting tank and flowing the pre-melted cullet into a melting tank M (thus called the "main melting tank"). According to this embodiment, a part of the cullet to be pre-melted is charged into the auxiliary melting tank, and if there is a remaining cullet (not pre-melted), it is charged into the main melting tank M. This embodiment has the advantage of preventing a shortage of high-quality cullet in the method of the present invention because it enables the use of lower-quality 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, 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 resulting "purified" glass melt can be made to flow from the top towards the main melting tank. According to this embodiment, the auxiliary melting tank is preferably connected to the upstream part of the main melting tank M, more preferably as upstream as possible of the main melting tank M.

[0164] Also, according to this embodiment of the present invention, 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 M. Alternatively, the entire amount of the cullet is pre-melted in the auxiliary melting tank.

[0165] According to an embodiment of the present invention, it preferably includes preheating at least a part of the cullet by recovering at least partially the heat from the furnace 1 before charging it into the auxiliary melting tank.

[0166] An example of an auxiliary melting tank suitable for this embodiment is described in European Patent Application Publication No. 2137115A1.

[0167] According to another advantageous embodiment of the invention, the raw material comprises less than 25% by weight of carbonate compounds. By "carbonate compounds" is meant, for example, alkali carbonates and alkaline earth carbonates. Preferably, the raw material comprises less than 20% by weight, more preferably less than 10% by weight, even more preferably less than 5% by weight of carbonate compounds. The raw material may advantageously be free of any carbonate compounds.

[0168] 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.

[0169] 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 equipped with electrical heating means 2, a downstream zone Z2 covered by a crown C2 and equipped with 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 equipped with an oxygen combustion heating means 3'; (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 H1≦0.75 * The height H1 of the crown C1 defined by H2 (where H2 is the height of the crown C2) is 0.25 * (L1+L2)≦L1≦0.8 * At least one upstream zone Z1 has a length L1 defined by (L1+L2) (where L2 is the length of the downstream zone Z2) and LT≦0.2 * having a length LT of a transition zone T defined by (L1+L2), - charging vitrifiable material into the main melting tank M and / or into the auxiliary melting tank M by means of at least one inlet means, said vitrifiable material comprising (i) raw materials having a weight percentage of less than 25% carbonate compound, and (ii) cullet in an amount of at least 10% by weight of the total amount of vitrifiable material; - preheating the cullet before it is charged into the main melting tank M and / or into the auxiliary melting tank, at least in part by recovering heat from the furnace; - premelting at least a portion of the cullet in an auxiliary melting tank and flowing the premelted cullet into a main melting tank M; - melting the vitrifiable material in the main melting tank M by means of the heating means 2, 3; - refining the melt in a refining tank F by heating with oxy-combustion heating means 3' supplied with gas and / or hydrogen; - flowing the melt from the purification tank F through outlet means O into the working zone; - Capture CO2 from exhaust gases with a CO2 concentration of at least 35% However, the electricity input rate is between 30% and 85%, and capturing CO2 from the flue gas includes compression and / or dehydration.

[0170] All the specific embodiments described above relating to each step of the method of the invention apply to this last highly preferred embodiment.

[0171] 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. Further, 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 molten tank M including at least one upstream zone Z1 covered by a crown C1 and equipped with an electric heating means 2, a downstream zone Z2 covered by a crown C2 and equipped with a combustion heating means 3, and a transition zone T between the crown C1 and the crown C2. (ii) A purification tank F covered with a crown C4 and equipped with an oxygen combustion heating means 3', (iii) A neck N covered by a crown C3 and separating the melting tank M and the refining tank F, (iv) At least one inlet means X located in the molten tank M, (v) an outlet means O located downstream of the refining tank F, and (vi) 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 has 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 molten tank M using the at least one inlet means X, wherein the amount of cullet is at least 10% by weight of the total amount of the vitrifiable material. - Preheat the cullet by recovering at least partially the heat from the furnace before charging the cullet into the molten tank M. - Using the heating means 2 and 3, melt the vitrifiable material in the 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, characterized in that the maximum temperature of the cullet during preheating is 450°C.

10. A method for melting a vitrifiable material according to claim 1 or 2, further comprising pre-melting at least a portion of the cullet in an auxiliary melting tank, and flowing the pre-melted cullet into the melting tank M.

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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