Hybrid glass melting furnace with excellent energy efficiency and durability

Abstract

The present invention relates to a furnace for melting a vitrifiable material, comprising: (i) a melting tank (M) including at least one upstream zone (Z1) covered by a crown (C1) and having electric heating means, a downstream zone (Z2) covered by a crown (C2) and having combustion heating means, and a transition zone (T) between (C1) and (C2); (ii) a refining tank (F) having combustion heating means; (iii) a neck (N) covered by a crown (C3) and separating the melting tank (M) from the refining tank (F); (iv) at least one inlet means (X) disposed in the melting tank; (v) an outlet means (O); and (vi) exhaust gas extraction means in the zone (Z1), wherein the height (H1) of the crown (C1) is defined by H1 ≦ 0.75 * H2, where H2 is the height of the crown (C2), and the length (L1) of the zone (Z1) is defined by 0.25 * (L1 + L2) ≦ L1 ≦ 0.8 * (L1 + L2), where (L2) is the length of the zone (Z2), and the length (LT) of the transition zone is defined by LT ≦ 0.2 * (L1 + L2). This furnace enables reduction of the overall energy consumption while maintaining a high electric input rate (thereby reducing CO2 emissions), maintaining an acceptable surface melting rate, and improving the furnace life.

Description

Technical Field

[0001] The present invention relates to a glass melting furnace for continuously supplying molten glass to a glass forming facility such as a float or rolling facility. In particular, the present invention relates to a glass melting furnace that offers many advantages, particularly in terms of energy consumption, CO2 emissions, flexibility of the method, and durability.

[0002] More particularly, the present invention relates to a melting furnace for sheet glass with a large production capacity, i.e., a maximum of over 1000 tons / day and a maximum power requirement of 60 MW, although not limited thereto.

Background Art

[0003] In current technology, glassifiable materials are generally - a tank covered by a crown containing molten glass when the furnace is in use, and - at least one inlet disposed upstream of the furnace for charging the furnace with the glassifiable material to be heated, and - heating means disposed within the tank, and - at least one downstream outlet for the molten glass to reach the processing zone or the end point of the operation and melted in a glass melting furnace comprising.

[0004] In such a glass melting furnace, the glass is generally melted by a flame generated from combustion by burners provided above the glass surface, whereby a bath of molten glass / raw material can be heated from above. Glass melting furnaces using oxy-fuel combustion or air-fuel combustion are well known. The fuel can be a fossil fuel, natural gas, biogas, or hydrogen.

[0005] The requirements for global warming and CO2 emissions reduction are increasing the pressure on glass manufacturers, and energy prices and CO2 taxes can immediately pose a serious threat to the competitiveness in the glass industry.

[0006] Electric melting can be part of the solution. It has only been demonstrated for small capacities, i.e., less than 300 tons per day (scaling up above 600 tons per day is still under development), but glass melting furnaces with all heating provided electrically are actually known and being developed in relation to this.

[0007] 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 melt surface, forming an insulating batch "blanket", so the temperature above the blanket drops from about 1400 °C of the glass melt to less than 500 °C (optionally up to 50 °C).

[0008] All-electric furnaces have significant advantages. First, they have very low direct emissions of CO2, thermal NO x , SO x . Furthermore, since the melting energy is basically transmitted into the glass (e.g., thanks to electrodes passing current to heat the molten glass bath from its bulk), 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 residual exhaust gases, even when using, for example, a heat recovery system. Therefore, they are highly energy-efficient furnaces.

[0009] Unfortunately, all-electric furnaces also have some disadvantages compared to combustion hot top furnaces.

[0010] In particular, such furnaces - The quality of the glass does not meet 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 refractories and the walls of the glass tank, significantly shortening the furnace life (typically from over 15 years for conventional furnaces to less than 8 years, optionally down to 2 - 7 years).

[0011] 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, needs to be targeted, 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, as much as possible, the impact on furnace life 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] It is also known to combine heating combustion means and electric heating means in a "hybrid system". In such a configuration, which mainly operates in a "warm-top", the furnace is composed of burners and electrodes for supplying power.

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

[0015] Furthermore, compared to cold-top furnaces, for the same bottom temperature, a hot-top furnace can reach a higher surface melting rate (or for the same surface melting rate, a lower bottom temperature can be reached).

[0016] Next, the hybrid furnace operated with a "warm top" has several drawbacks. In particular, (i) significant heat losses occur in the crown and wall of the melting zone, and (ii) in the high-temperature exhaust gas / exhaust gas 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 a furnace, the temperature of the crown / upper structure in the melting zone becomes very low depending on the conditions (for example, less than 1000 °C), and the risk of alkali condensation (for example, NaOH) in the zone, and thus the corrosion of the crown refractory, increases significantly.

[0018] Next, in these furnaces, especially for all-electric furnaces, due to the limitations described above, namely the corrosion phenomena at the bottom and the 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 to, for example, 80% have recently been described, but most of them are operated in cold top furnaces, which pose problems.

[0020] Therefore, in order to solve the above problems and maintain a high electric input rate while showing an acceptable surface melting rate together with high energy efficiency and long life, an evolution of the design of existing glass melting furnaces is required, by combining a combustion burner and an electrode as heating means. Summary of the Invention Problems to be Solved by the Invention

[0021] An object of the present invention is to overcome the drawbacks described above with respect to the prior art and solve the technical problems.

[0022] In particular, it is an object of the present invention to provide a glass melting furnace that combines combustion burners and electrodes as heating means, and that has improved energy efficiency (in other words, reduced specific energy consumption), especially compared to conventional "hot top" hybrid melting furnaces.

[0023] A further object of the present invention is to provide a method for producing a material having an acceptable surface melting rate (especially 2T / d / m 2 More than or better than 3T / d / m 2 The object of the present invention is to provide a glass melting furnace which combines a combustion burner and an electrode as a heating means and exhibits a surface melting rate of 10 ...

[0024] It is a further object of the present invention to provide a glass melting furnace combining combustion burners and electrodes as heating means, which has an improved life span compared to classical hot-top hybrid melting furnaces.

[0025] It is a further object of the present invention to provide a glass melting furnace that combines a combustion burner and an electrode as a heating means, and that achieves improved energy efficiency, an acceptable surface melting rate, and an extended lifespan while maintaining a high electric input rate (particularly 30% to 85%). [Means for solving the problem]

[0026] The present invention relates to a furnace for melting a vitrifiable material, comprising: (i) a melting tank M, at least one upstream zone Z1 covered by a crown C1 and equipped with electric heating means, a downstream zone Z2 covered by a crown C2 and equipped with combustion heating means, - Transition zone T between crown C1 and crown C2 A melting tank M including (ii) a refining tank F covered with a crown C4 and equipped with a combustion heating means; (iii) a neck N, surrounded by a crown C3, separating the melting tank M from the refining tank F; (iv) At least one inlet means X arranged in the melting tank M for charging the glassifiable material to be heated into the melting tank M, (v) At least one outlet means O arranged downstream of the refining tank F so that the molten glass flows into the working zone, (vi) At least one exhaust gas extraction means arranged in at least one upstream zone Z1 In a furnace comprising: - The height H1 of the crown C1 is defined by H1 ≦ 0.75 * H2 (where H2 is the height of the crown C2), - The length L1 of at least one upstream zone Z1 is such that 0.25 * (L1 + L2) ≦ L1 ≦ 0.8 * (L1 + L2) (where L2 is the length of the downstream zone Z2), and - The length LT of the transition zone T is defined by LT ≦ 0.2 * (L1 + L2), characterized in that it relates to a furnace.

[0027] Accordingly, the present invention is based on a novel and innovative approach. In particular, the inventors have found that by a combination of (i) separating the electric melting tank and the combustion 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 lower temperature upstream zone and a higher temperature downstream zone with a significant temperature difference, it is possible to significantly reduce the total energy consumption of the furnace (thereby reducing CO2 emissions) while maintaining a high electric input rate, maintaining an acceptable surface melting rate, and improving the mechanical stability and lifespan of the furnace.

[0028] The melting crowns C1 and C2 of the present invention are specifically designed by the inventors to take advantage of both the "cold top" zone and the "hot top" zone and create a temperature gradient from a relatively low temperature (less than 1100 °C) upstream to a relatively high temperature (higher than 1300 °C) downstream.

[0029] The inventors have demonstrated that the furnace of the present invention offers many advantages in terms of energy consumption / CO2 emissions, surface melting rate, and mechanical stability / lifetime of the furnace.

[0030] 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 both zones of the melting tank and between the melting tank and the purification tank in order to optimize energy consumption and avoid alkali corrosion as much as possible.

[0031] The furnace of the present invention is further advantageous in that it simultaneously generates a significant temperature difference between the upstream and downstream portions of the melting tank and, as much as possible, avoids the reverse flow of the exhaust gas generated from the purification tank towards the melting tank.

[0032] From the perspective of energy efficiency, - Dividing the atmosphere and blocking the heat radiation from the purification tank to the melting tank in order to efficiently confine the energy in the zone that requires high temperature (purification zone), and - Extracting the exhaust gas from the upstream portion / 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.

[0033] From the perspective of the surface melting rate, this is advantageous because it enables reaching a relatively high temperature (>1300 °C) in the downstream portion of the melting tank in order to improve the melting rate of the vitrifiable material.

[0034] From the perspective of corrosion, - By separating the atmosphere between the melting tank and the purification tank, it is possible to limit / avoid the reflux of the exhaust gas from the purification zone, which is rich in alkali due to the high temperature required for purification and thus highly corrosive. - Having an overall restriction of the molten glass flow that advantageously reduces the intensity of glass convection in the melting tank, reduces the glass velocity, and thereby reduces wear and corrosion of the bottom refractory This is advantageous in order to enable

[0035] Finally, the furnace of the present invention having a specific division (through a neck) between the melting tank and the refining tank also makes it possible to completely separate the dimensions (length, width and crown height) of the melting tank and the refining tank and the properties of the refractories, and thus to optimize each tank taking into account energy efficiency, glass quality, factory space constraints and mechanical / structural / other constraints.

[0036] 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 ranges are 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 direction of glass flow, and are understood in their general sense, i.e., along the average direction of movement of the vitrifiable material / molten glass (defined herein as "glass flow") from the inlet means to the outlet means, i.e., along the direction from left to right in FIGS. 1-2 for example.

[0037] According to the present invention, and as generally adopted in the glass technology field, "melting tank" means a tank that defines a zone where a vitrifiable material is charged and melted by heating, and when the furnace is in operation, it includes the melt and a "blanket" of unmolten vitrifiable material that floats on the melt and is gradually melted, and thus decreases from the upstream to the downstream of the melting tank.

[0038] According to the present invention, and as generally adopted in the glass technology field, a "refining tank" means a tank in which there is no longer a "blanket" of unmelted glassifiable material floating on the melt, and the glass melt defines a zone that is heated at a temperature higher than the melt tank temperature (generally a temperature exceeding 1400 °C or exceeding 1450 °C) in order to purify the glass (mainly by removing the main part of the bubbles). This refining tank is also generally called a "purification tank" in the art.

[0039] The furnace of the present invention is particularly suitable for the production of flat glass sheets.

[0040] The present invention relates to a method for melting a glassifiable material for producing flat glass, comprising: - providing a furnace according to the present invention and its embodiments; - charging the glassifiable material into the melting tank M using the inlet means X; - melting the glassifiable material in the melting tank M; - purifying the obtained melt in the refining tank F; - flowing the melt through the outlet means O from the refining tank F into the working zone The method also relates to a method, wherein the electrical input rate of the furnace is 30% - 85%, preferably 35 - 85%.

[0041] According to the present invention, the electrical input rate in the method is 30% - 85%. The "electrical input rate" according to the present invention means the part of electricity in the total energy input of the method / furnace for melting / refining, 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 periods such as startup, maintenance, high-temperature repair, caulking, etc.).

[0042] According to an embodiment, in the method according to the present invention, the vitrifiable material includes raw materials and cullet, and the amount of the cullet is at least 10% by weight of the total amount of the vitrifiable material, preferably at least 30% by weight of the total amount of the vitrifiable material.

[0043] Other features and advantages will become clearer by referring to the following description of the preferred embodiments and the drawings as simple illustrative and non-limiting examples.

Brief Description of the Drawings

[0044]

Figure 1

[0045]

Figure 2

[0046]

Figure 3

Figure 4

Figure 5

[0047]

Figure 6

[0048]

Figure 7

Mode for Carrying Out the Invention

[0049] Figures 1 and 2 show an embodiment of a furnace 1 according to the invention (Figure 1: vertical section, Figure 2: horizontal section). The furnace 1 in Figures 1-2 comprises a melting tank M, a neck N and a refining tank F. The assembly of M, N and F is generally made of refractory materials that are resistant to temperature, the corrosive effects of smoke and the aggressive action of the molten material. An illustration of the level of the glass melt in the tank (excluding the batch blanket) is shown by a dashed line in Figure 1.

[0050] According to the invention, as shown in FIGS. 1-2, a furnace 1 is provided in which vitrifiable raw materials (glass frit and / or cullet) are fed in a melting tank M by at least one inlet means X.

[0051] In order to improve distribution on the surface of the melt tank M, several inlet means, ie two or three inlet means, located upstream of the melt tank M (in particular in zone Z1) can advantageously be provided.

[0052] Preferably, and as known in the art, at least one inlet means X is arranged upstream of the melting tank M (particularly in zone Z1) transversely across the width of said tank and / or across its length.

[0053] According to the present invention, and as shown in Figs. 1-2, the furnace includes a melting tank M, 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 combustion heating means 3, - Transition zone T between crown C1 and crown C2 Includes.

[0054] According to another advantageous embodiment, the downstream zone Z2 further comprises electric heating means, as shown in FIGS.

[0055] 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.

[0056] The combustion heating means 3 in the downstream zone Z2 of the 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 side thereof or alternatively on both sides in order to spread the flame over substantially the entire width of said zone. They are alternatively or additionally also arranged in the crown C2, which is advantageous in order to promote the heat transfer to the batch and 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 melting tank.

[0057] The burner 3 may be supplied with fuel and air, or fuel and oxygen, or fuel and oxygen enriched gas. The fuel may be fossil fuel, natural gas, biogas, hydrogen, ammonia, syngas or a mixture thereof.

[0058] According to an advantageous embodiment, at least one upstream zone Z1 may be equipped with auxiliary combustion heating means (e.g. burners, not shown) to allow control of the temperature of crown C1 (e.g. limiting the temperature variation 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 be advantageously located within crown C1 in order to reduce the occupation of the free volume of space above the melt / batch blanket.

[0059] The upstream zone Z1 according to the invention is covered by a crown C1, while the downstream zone Z2 according to the invention is covered by a crown C2.

[0060] According to the present invention, the height H1 of the crown C1 is such that H1 ≦ 0.75 * is defined by 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.

[0061] The "height" of the crown in the present invention means, throughout this specification and the claims, the average inner height (illustrated in FIG. 1) 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 (for example, 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 (for example, in the case of an arch / round ceiling crown).

[0062] According to one embodiment of the present invention, the height H1 of the 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.

[0063] According to the present invention, the length L1 of at least one upstream zone Z1 is 0.25 * (L1 + L2) ≦ L1 ≦ 0.8 * is defined by (L1 + L2), where L2 is the length of the downstream zone Z2.

[0064] "Length" means, throughout this specification and the claims, the dimension along the flow of the glass.

[0065] 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-mentioned advantages of the present invention can also be enhanced.

[0066] 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).

[0067] 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 referred to as a "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).

[0068] 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.

[0069] Advantageously, the crown C1 can be composed of a refractory 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.

[0070] The advantage of silica is that its coefficient of expansion is low when the temperature is higher than about 600°C, whereby it can withstand high temperature changes without disturbing the upper structure of the crown.

[0071] Alternatively, the crown C1 and / or the crown C2 may be composed of refractories essentially made of alumina or AZS (alumina-zirconia-silica), which have better resistance to corrosion and thus a longer lifespan.

[0072] According to the present invention, as shown in FIG. 2, the furnace includes a melting tank M having at least one upstream zone Z1 and a downstream zone Z2 with different crown heights of C1 having a height H1 and C2 having a height H2.

[0073] In the present invention, the change in height between the crowns C1 and C2 along the melting tank M means a transition zone T.

[0074] 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 * (L1 + L2). For the sake of clarity, it is obvious from the concept of the present invention that the said transition zone T is present / essential in the furnace of the present invention. That is, LT shall not be a length having a zero value, or in other words, the value LT = 0 is implicitly excluded from the scope of the present invention.

[0075] FIGS. 3, 4 and 5 are schematic views of embodiments of the transition zone between Z1 and Z2 according to the present invention. In these figures, only the glass melt and the batch blanket are shown for illustrative purposes. The heating means are not shown.

[0076] 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 (such as shown in FIG. 3) or a short inclined wall (enabling a gradual transition). In this embodiment, the crown C1 preferably has an inner surface that is 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 A. Alternatively, the breast wall can lie on the outer surface of the crown C1.

[0077] 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 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. A configuration example of the shadow wall is shown in FIG. 4. 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. 3,399,046 A.

[0078] According to a further embodiment, the transition zone T between the crown C1 and the crown C2 includes at least one step. In the configuration having one step shown in FIG. 5, the change in height between the crown C1 and the crown C2 is obtained, for example, by a transition zone T including: 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 advantages of facilitating the creation of the transition between the crown C1 and the crown C2 and enhancing stability.

[0079] 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 wall thickness (even when lying on and / or overlapping the crown C1 and / or the crown C1).

[0080] According to an advantageous embodiment, the transition zone is composed of a refractory essentially made of silica.

[0081] Advantageously, according to another embodiment, in order to avoid expansion between materials and / or 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.

[0082] 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 made of silica.

[0083] According to the present invention and as shown in FIGS. 1 to 2, the furnace includes a refining tank F covered by a crown C4 and provided with combustion heating means 3'.

[0084] The crown C4 according to the present invention is preferably in an arch shape or a round ceiling shape.

[0085] The oxy-combustion heating means 3' from the refining tank F according to the invention in particular consist of burners arranged in particular along the side walls of said tank. Moreover, the burners are advantageously spaced apart from one another in order to distribute 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 also arranged in a row on one or alternatively both sides of the refining tank F, preferably in a staggered arrangement (to spread the flame over substantially the entire width of said tank). The burners can be supplied with fuel and air, or with fuel and oxygen, or with fuel and oxygen-enriched gas. The fuel can be fossil fuel, natural gas, biogas, hydrogen, ammonia, synthesis gas or a mixture thereof.

[0086] According to an advantageous embodiment, the purification tank may further comprise electric heating means (not shown), particularly in the upstream part of said purification tank (e.g. about 50% of its length), which allows to increase the electricity input rate and thus improve energy efficiency and reduce CO2 emissions.

[0087] According to the invention and as shown in FIGS. 1-2, the furnace includes a neck N, surrounded by a crown C3, separating / dividing a melting tank M and a refining tank F.

[0088] 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.

[0089] 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 is also, W F is the width of the purification tank F.

[0090] In the present invention, the "width" means the dimension (average) perpendicular to the flow of the glass throughout this specification and the claims.

[0091] This design of the furnace in which the melting tank and the purification tank are 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 melting tank and the exhaust gas from the purification tank can be treated independently as required.

[0092] 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. Further, the base of the neck N can be substantially located at the level of the floor / bottom of the purification tank F, or can be located above or below said level.

[0093] According to one embodiment, the neck N does not include any heating means, for example, any electric heating means.

[0094] 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 purification tank F.

[0095] According to yet another advantageous embodiment of the present 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 to (i) stop the unmelted vitrifiable material that can reach the end of the melting tank, thereby avoiding their passage 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.

[0096] According to yet another advantageous embodiment of the present 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 to enhance the separation of the melting tank and the refining tank in terms of atmosphere and thermal radiation.

[0097] According to the present invention and as shown in FIGS. 1 to 3, the furnace includes at least one outlet means O located downstream of the refining tank F for the molten glass to reach the working zone. According to one embodiment, the outlet means O generally consists of a neck, usually, to guide the melt to a working zone, also commonly referred to as the "working end", or "flare", or "conditioning zone". Alternatively, the outlet means O may consist 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 to the forming zone. Such a forming zone may consist of, for example, a float facility and / or a rolling facility.

[0098] According to an advantageous embodiment of the present invention, the furnace is 0.1 * W F ≦W N ≦0.7 * W F 、 W M ≧1.4 * W N (where W M is the width of the melting tank M, W F is the width of the refining tank F, W N is the width of the neck N) is defined by

[0099] With 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.

[0100] Preferably, the furnace is 0.1 * W F ≤W N ≤0.6 * W F is defined by. More 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 is defined by. Thereby, a good compromise point between two conflicting requirements can be found. On the one hand, in order to (1) reduce the opening between the melting superstructure / crown and the refining superstructure / crown and (2) create 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, in order 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.

[0101] Preferably, the furnace of the present invention has W M ≥1.5 * W N or W M ≥1.8* W N is also defined by. More preferably, the furnace of the present invention satisfies WM≧2 * W N is defined by. As a result, the width limitation of the neck N becomes larger, the blocking of heat radiation is improved, better atmosphere separation becomes possible, and the flow of the molten glass is restricted.

[0102] According to the present invention and as shown in FIGS. 1 and 2, 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, for recovering heat and transferring it from the exhaust gas to the glass melt and / or the material capable of being vitrified but not yet vitrified in the melting tank M.

[0103] According to an 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).

[0104] When there is an extraction means in the zone Z2, advantageously, when the gas is alkali-rich, the exhaust gas can be extracted from the downstream zone Z2 (thereby avoiding condensation and subsequent corrosion in the zone Z1).

[0105] When there is an extraction means in the purification tank F, it is preferably arranged in the upstream part of the purification tank.

[0106] Preferably, in the present invention, the extraction means 4 is arranged on one or both side walls.

[0107] In particular, in the present invention, it is energetically advantageous for the exhaust gas to be extracted maximally from upstream of the furnace, in particular 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 upstream of the melting tank. Nevertheless, extracting a part of the exhaust gas from downstream of the melting tank can be advantageous in order to limit 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 is 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 therefore poor in alkali, so it is advantageous to extract a part of the exhaust gas from upstream of the melting tank. Finally, the temperature required for purification is higher and the exhaust gas from the purification tank contains more alkali, so it is also advantageous to extract a part of the exhaust gas from the purification tank.

[0108] In an advantageous embodiment of the invention shown in FIG. 6, the furnace for melting the vitrifiable material 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.

[0109] In this configuration, - The height H1' of the melting crown C1' is H1'≤0.75 * defined by H2, - The height H1'' of the melting crown C1'' is H1''≤0.75 * defined by H2, - The length L1' of at least one upstream zone Z1' is 0.25 * (L1'+L2)≤L1'≤0.8 * defined by (L1'+L2), - The length L1'' of at least one upstream zone Z1'' is 0.25* (L1’’ + L2) ≤ L1’’ ≤ 0.8 * Defined by (L1’’ + L2), - The length LT’ of the transition zone T’ satisfies LT’ ≤ 0.2 * Defined by (L1’ + L2), and - The length LT’’ of the transition zone T’’ satisfies LT’’ ≤ 0.2 * Defined by (L1’’ + l2).

[0110] 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 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 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.

[0111] In this configuration, for example, the combustion heating means 3 is arranged, as shown in FIG. 6, on the melting tank wall facing the neck, for example, like two burners. Alternatively, for example, the burner 3 is arranged on the crown C2.

[0112] In this advantageous configuration / embodiment, each upstream zone, each upstream crown and each inlet means are according to the 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 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''. 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.

[0113] In the embodiment of the invention shown in FIG. 7, the furnace for melting the vitrifiable material comprises 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).

[0114] This configuration is particularly advantageous compared to the configuration with one melting tank (FIG. 2) 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 that are more resistant to corrosion such as alumina or spinel and less resistant 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, to provide good heat transfer from the exhaust gas to the glass melt, - For the same total neck width (W N’ +W N’’) and arched neck crown C3, it is possible to reduce the open 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 the 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. It is therefore possible to increase the life of the entire furnace by replacing worn refractories in the melting zone, which is the most critical area in terms of wear / corrosion.

[0115] 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.

[0116] In this configuration, - 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'' satisfies LT'' ≤ 0.2 * and is defined by (L1'' + L2'').

[0117] Also, in this configuration, - The upstream zone and the downstream zone can be independently configured according to any embodiment of the present invention related to Z1 and Z2, respectively. - The crowns C1' and C1'' can 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'' can 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'' can be independently configured according to any embodiment of the present invention related to the transition zone T, respectively.

[0118] 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 present invention and its embodiments and can be designed independently of the other melting tanks, upstream zones, downstream zones, transition zones, necks, and inlet means according to the above description. Therefore, for clarity, the features described above in relation to M are independently applied to M' and M'', the features described above in relation to Z1 are independently applied to Z1' and Z1'', the features described above in relation to C1 are independently applied to C1' and C1'', the features described above in relation to Z2 are independently applied to Z2' and Z2'', the features described above in relation to C2 are independently applied to C2' and C2'', the features described above in relation to T are independently applied to T' and T'', and the features described above in relation to X are independently applied to X' and X''.

[0119] Furthermore, the specific advantageous features described in connection with a furnace having one melting tank (e.g., those described in connection with C3, C4, F) are applied such that the "two melting tanks" configuration also has similar advantages.

[0120] 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. 7). 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 upstream of the purification tank near the length (right or left side) 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.

[0121] In the "two melting tanks" configuration, when the two melting tanks are connected to the purification tank by necks located at the width W F of the purification tank, the distance D between the two melting tanks is preferably at least 1 m, more preferably at least 2 m, even more preferably at least 3 m. This is advantageous to allow access to the maintenance work and the zones for tank wall overcoating.

[0122] In another embodiment of the present invention, a furnace for melting a vitrifiable material has a configuration with three melting tanks, three necks and three inlet means. This embodiment is particularly advantageous compared to a 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.

[0123] Certain advantageous features described in connection with a furnace having "one melting tank" and "two melting tanks" also apply to a configuration of "three melting tanks" and have the same advantages.

[0124] In a "three melting tanks" furnace according to one embodiment, when at least two melting tanks are connected to the refining tank by a neck located in the width W F of the refining tank, 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.

[0125] In all furnace configurations according to the present invention, i.e., the "one melting tank", "two melting tanks" and "three melting tanks" configurations, in order to facilitate the distribution to the charging of the vitrifiable material, one or more charging means can be provided for each melting tank, i.e., two charging means can be provided for each melting tank.

[0126] In all furnace configurations according to the present invention, 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 refining tank is 25 - 400 m 2 is.

[0127] 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 and preferred features described herein and recited in the claims.

[0128] The following examples are provided for illustrative purposes and are not intended to limit the scope of the present invention.

Example

[0129] Examples of furnaces according to the present invention and comparative examples of furnaces according to the prior art were calculated by well-known methods.

[0130] The optimization and design of melting furnaces are difficult, risky, and very time-consuming without mathematical modeling. In fact, the furnaces are very expensive, and their lifespan is longer than 15 years and, in some cases, exceeds 20 years. Therefore, there are few opportunities to conduct research and design changes, and there is a high level of stress to reduce the risks associated with these changes. Therefore, the mathematical modeling of the melting method in operating glass furnaces is well-developed in glass manufacturing technology and is well-known to glass manufacturers. By using mathematical models, detailed temperature and velocity fields of the glass melt in the tank and the gas in the combustion / purification space can be obtained. The results of these existing mathematical models have been verified by comparison with measured values (thermocouples and infrared cameras) in many operating furnaces.

[0131] The following furnaces with the same glass production rate (90 tons / day) and furnace area were considered by default in this calculation (unless otherwise specified). - Melting tank with a width of 7 m (W M ) and a total length of 7 m, - Refining tank F with a width of 6 m (W F ) and a length of 8 m, - Glass outlet means at the center on the downstream side of the refining tank, - Average crown height H4 of the refining tank equal to 3.5 m. - Furnace 1 (comparison): A "cold top" glass melting furnace having a neck between the refining tank and the glass melting tank, and comprising the following: - Cold top melting tank with a suspended flat crown, - Vertical charging of glassifiable materials in the melting tank, - Neck with a width (W N ) of 2.4 m and a length of 3.0 m separating the melting tank and the refining tank, - Electrodes in the melting tank, - Oxygen burners in the refining tank to which pure oxygen and natural gas are supplied, - Exhaust gas extraction openings arranged in the melting tank, - Exhaust gas extraction openings arranged in the upstream part of the refining tank. - Furnace 2 (comparison): A conventional "hot top" glass melting furnace having a neck between the melting tank and the refining tank, the glass melting furnace comprising: - A hot top melting tank having a standard arch-shaped crown with an average height equal to 1.7 m, - Horizontal charging of raw materials in the melting tank from upstream, - A neck separating the melting tank and the refining tank with a width (W N ) of 2.4 m and a length of 3.0 m, - Electrodes in the melting tank, - An oxygen burner in the melting tank to which pure oxygen and natural gas are supplied, - An oxygen burner in the refining tank to which pure oxygen and natural gas are supplied, - Two exhaust gas extraction openings in the melting tank, one from upstream and the other from downstream, - An exhaust gas extraction opening arranged in the upstream part of the refining tank. - Furnace 3: A furnace according to the present invention, the furnace comprising: - A melting tank having two zones Z1 and Z2 respectively covered by arch-shaped crowns C1 and C2, - The average height H1 of C1 equal to 0.8 m and the average height H2 of C2 equal to 2.3 m, and - A length L1 equal to 3.8 m and a length L2 equal to 2.0 m, - A gable wall in contact with the outer surface of crown C1, a transition zone between crowns C1 and C2 having a length LT equal to 0.5 m having a furnace. - (In zone Z1) Horizontal charging of raw materials in the melting tank from upstream, - A neck separating the melting tank and the refining tank with a width (W N ) of 2.4 m and a length of 3.0 m, - Electrodes in the melting tank (in zone Z1 and zone Z2), - An oxygen burner in zone Z2 to which pure oxygen and natural gas are supplied, - An oxygen burner (two opposing staggered burners at about 50% of the length) in the purification tank, to which pure oxygen and natural gas are supplied, - Two exhaust gas extraction openings, one upstream (within zone Z1) and the other downstream (within zone Z2), arranged in the melting tank, - An exhaust gas extraction opening arranged in the upstream part of the purification tank. - Furnace 4 (comparison): A furnace with a split at the height of the melting crown and no neck between the melting tank and the purification tank, comprising: - A melting tank having two zones Z1 and Z2 covered by arch-shaped crowns C1 and C2 of the same design as furnace 3, - Horizontal feeding of raw materials in the melting tank from upstream, - Electrodes in the melting tank (in zones Z1 and Z2, arranged the same as in furnace 3), - An oxygen burner in zone Z2, to which pure oxygen and natural gas are supplied (arranged the same as in furnace 3), - An oxygen burner in the purification tank, to which pure oxygen and natural gas are supplied (arranged the same as in furnace 3), - Two exhaust gas extraction openings, one from upstream and the other from downstream, arranged in the melting tank, - An exhaust gas extraction opening arranged in the upstream part of the purification tank. TIFF2025523629000002.tif123170

[0132] The results obtained are shown in the following table for furnaces 1 to 4.

[0133] These results show that, in combination with the neck separating the melting tank and the purification tank, the energy efficiency is improved for the same electrical input rate due to the split at the height of the upper structure / crown of the melting tank. For example, when the electrical input rate is about 36%, comparing furnace 3 with furnace 2, the specific consumption of the split furnace is 13% lower.

[0134] On the one hand, at the same electric input rate, in the furnace of the present invention, the molten bottom temperature becomes significantly lower. For example, when the electric input rate is about 36%, the maximum bottom temperature is 1390 °C in the case of a standard hot top upper structure and neck (furnace 2), and 1415 °C in the case of no neck (furnace 4) which divides the height of the molten crown, while it is 1350 °C in furnace 3 according to the present invention.

[0135] In the case of furnace 1 where only power is used in the melting zone, the power input and the glass temperature are directly determined by the desired melting rate and there is no flexibility. In this example, the required bottom surface temperature is equal to 1410 °C, and the corrosion and wear of the refractory are accelerated.

Claims

1. A furnace for melting materials that can be vitrified, (i) A melting tank M, - At least one upstream zone Z1 covered by a crown C1 and equipped with an electric heating means, - Downstream zone Z2, which is covered by crown C2 and has combustion heating means, - Transition zone T between Crown C1 and Crown C2 A molten tank M containing, (ii) A refining tank F covered with a crown C4 and equipped with a combustion heating means, (iii) Covered by a crown C3, and a neck N that separates the melting tank M and the refining tank F, (iv) at least one inlet means X provided in the molten tank M for loading a vitrifiable material to be heated into the molten tank M, (v) At least one outlet means O positioned downstream of the refining tank F so that the molten glass flows into the work zone, (vi) At least one exhaust gas extraction means 4 located in the at least one upstream zone Z1 and In a furnace including, - The height H1 of the crown C1 is H1 ≤ 0.75 ＊ Defined by H2 (where H2 is the height of the crown C2), - The length L1 of the at least one upstream zone Z1 is 0.25 ＊ (L1+L2)≦L1≦0.8 ＊ Defined by (L1 + L2) (where L2 is the length of the downstream zone Z2), and - The length LT of the transition zone T is LT ≤ 0.2 ＊ A furnace characterized by being defined by (L1 + L2).

2. The height H1 of the molten crown C1 is H1 ≤ 0.5 ＊ The furnace according to claim 1, characterized in that it is defined by H2.

3. The length L1 of the at least one upstream zone Z1 is L1 ≤ 0.7 ＊ The furnace according to claim 1 or 2, characterized in that it is defined by (L1 + L2).

4. The length L1 of the at least one upstream zone Z1 is 0.5 ＊ The furnace according to claim 1 or 2, characterized in that it is defined by (L1 + L2) ≤ L1.

5. The length LT of the transition zone T is LT ≤ 0.15 ＊ The furnace according to claim 1 or 2, characterized in that it is defined by (L1 + L2).

6. The furnace according to claim 1 or 2, wherein the downstream zone Z2 further comprises an electric heating means.

7. The furnace according to claim 1 or 2, further comprising at least one exhaust gas extraction means in the downstream zone Z2.

8. The furnace according to claim 1 or 2, characterized in that the purification tank F further includes at least one exhaust gas extraction means.

9. The furnace, 0.1 ＊ W Ｆ ≦W Ｎ ≦0.7 ＊ W Ｆ 、 W Ｍ ≧1.4 ＊ W Ｎ (In the formula, W Ｍ This is the width of the molten tank M, W Ｆ This is the width of the refining tank F, W Ｎ (This is the width of the neck N.) The furnace according to claim 1, characterized by being defined by

10. W Ｍ ≥ 1.5 ＊ W Ｎ The furnace according to claim 9, characterized by being defined by

11. 0.2 ＊ W Ｆ ≤W Ｎ ≤ 0.6 ＊ W Ｆ The furnace according to claim 9 or 10, characterized by being defined by

12. A furnace according to claim 1 or 2 for manufacturing a plate glass sheet.

13. A method for melting a vitrifiable material for manufacturing plate glass, - To provide the furnace described in claim 1 or 2, - The vitrifiable material is loaded into the melting tank using the inlet means. - Melting the vitrifiable material in the melting tank, - The obtained molten material is purified in the purification tank. - The molten material is flowed from the refining tank through the outlet means to the work zone. A method comprising the above, characterized in that the power input rate of the furnace is 30% to 85%, preferably 35% to 85%.

14. The method according to claim 13, characterized in that the vitrifiable material includes raw materials and cullet, and the amount of cullet is at least 10% by weight of the total amount of the vitrifiable material, preferably at least 30% by weight of the total amount of the vitrifiable material.

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