A glass melting method with low CO2 emissions

Abstract

The present invention relates to a method for melting a vitrifiable material for manufacturing plate glass, the method comprising: (i) preparing a furnace comprising at least one main melting tank equipped with an electric heating means, at least one auxiliary melting tank, a refining tank equipped with an oxygen combustion heating means, and a neck separating the main melting tank and the refining tank; (ii) charging a vitrifiable material, comprising raw material and optionally cullet, into the main melting tank; (iii) charging cullet into the auxiliary melting tank; and (iv) heating with the electric heating means. The process includes the steps of: (v) melting the vitrifiable material charged in the main melting tank and flowing it through the neck to the refining tank; (v) melting the charged cullet in an auxiliary melting tank and flowing it through the neck or to the refining tank; (vi) refining the molten material in the refining tank by heating with an oxygen combustion heating means supplied with gas and / or hydrogen; and (vii) flowing the molten material from the refining tank to the working zone, wherein the electrical input ratio of the furnace is in the range of 50% to 85%, and the total amount of cullet is at least 10% by weight of the total amount of vitrifiable material.

Description

Technical Field

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

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

Background Art

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

[0004] The glass industry has invested heavily in decarbonizing 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 to reduce carbon emissions.

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

[0006] Nevertheless, all of these technologies are associated with serious drawbacks or problems for practical 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, furnaces that use electrical energy to melt glass raw materials are known to reduce not only CO2 emissions but also overall energy consumption. In such configurations, the melting furnace includes electrodes that heat the molten glass bath from its entirety through electric current / electricity. However, glass melting furnaces that are entirely electrically powered for heating have not been adopted in plate glass technology where high-quality glass is required due to serious temperature and glass convection / flow problems.

[0008] Therefore, conventional glass melting furnaces for plate glass generally employ a so-called "hybrid" configuration that combines combustion heating means (i.e., burners) and electric heating means (i.e., immersed electrodes), with only electric "boost" being utilized. However, in such known "electric boost combustion furnaces," the electric input ratio is limited to a maximum of 10-15% of the total energy input, and the benefits of electric melting in terms of energy consumption cannot be fully realized.

[0009] More recently, a new specific furnace design described in European Patent Application No. 21200998.9 (which is incorporated herein by reference) makes it possible to achieve a significantly higher electrical input ratio, i.e., an electrical input ratio exceeding 50%, in a “hybrid” furnace.

[0010] While the advantages of using alternative and environmentally friendly energy sources such as hydrogen (H2) or biogas in terms of environmental impact, energy consumption, and CO2 emissions are clear, their widespread use in the glass industry is hindered by serious constraints (lack of biogas availability and the high cost of hydrogen (H2), which makes it an economically unfeasible solution as long as it is the only energy source for melting glass raw materials).

[0011] Regarding heat recovery: Waste heat recovery from exhaust gases is already widely applied in the glass industry to preheat combustion air entering the furnace at temperatures exceeding 1000°C or gas and oxygen ("Hotox") at temperatures exceeding 400°C and 500°C, respectively. Waste heat from exhaust gases can also be used to preheat vitrifiable materials, particularly cullet. Nevertheless, it is known that in this case, the temperature of the exhaust gases emitted from the raw materials is too low to combine the preheating of the raw materials / cullet with electric melting. [Overview of the project] [Problems that the invention aims to solve]

[0012] The objective of the present invention is to overcome the above-mentioned drawbacks of the prior art and solve the technical problems. Specifically, it is to provide a glass melting method for manufacturing plate glass that shows a reduction in overall energy consumption and CO2 emissions compared to conventional melting furnaces.

[0013] A further object of the present invention is to provide a glass melting method for producing plate glass that exhibits improved lifespan compared to conventional melting furnaces, reduces glass defects caused by refractories, and demonstrates a reduction in overall energy consumption and CO2 emissions.

[0014] A further object of the present invention is to provide a glass melting method for producing plate glass that exhibits excellent sustainability (particularly by using it as part of a material that can be vitrified even if the cullet is of poor quality) and reduces overall energy consumption and CO2 emissions. [Means for solving the problem]

[0015] The present invention relates to a method for melting a vitrifiable material for manufacturing plate glass, - Steps to prepare a furnace comprising: (i) at least one main melting tank equipped with an electric heating means; (ii) at least one auxiliary melting tank; (iii) a refining tank equipped with an oxygen combustion heating means; (iv) at least one neck separating at least one main melting tank from the refining tank; (v) an inlet means located in at least one main melting tank; and (vi) an outlet means located downstream of the refining tank; - A step of charging a vitrifiable material, which optionally includes raw materials and cullet, into at least one main molten tank using an inlet means; - A step of charging cullet into at least one auxiliary melting tank; - A step of melting the vitrifiable material charged in at least one main melting tank by heating it with an electric heating means, and flowing the molten material through the neck into a refining tank; - A step of melting the charged cullet in at least one auxiliary melting tank; - A step of purifying the molten material in a purification tank by heating it in an oxygen combustion heating means supplied with gas and / or hydrogen; - A step of flowing the molten material from the refining tank through the outlet means into the work zone; Includes, (i) The electrical input ratio of the furnace is in the range of 50% to 85%, (ii) The total amount of cullet is at least 10% by weight of the total amount of vitrifiable material, (iii) The step of flowing the molten material from at least one auxiliary melting tank to the neck or refining tank is further included. Regarding the method.

[0016] Therefore, the present invention is based on a novel and original approach. In particular, the inventors have developed a glass melting method for manufacturing plate glass, - Use of a furnace with a specific segment design (separating the electric heating main melting zone from the combustion heating refining zone), - Use of oxygen as a combustion agent, - Use of gas and / or hydrogen as flammable substances, - Use of a minimum amount of cullet as raw material, - Use of the step of at least partially melting the cullet in an auxiliary melting furnace flowing downstream of the melting tank (particularly in the neck or refining tank), and - Use of a specific electrical input ratio By combining, - A significant reduction in the total energy consumption, - A significant reduction in the total amount of CO2 generated, - Excellent sustainability (by using, in particular, as part of a material that can be vitrified even with insufficient-quality cullet) It has been found that it is possible to obtain simultaneously.

[0017] In this specification and the claims, it is well understood by those skilled in the art that the terms "a", "an" or "the" 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 described. 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 part" is understood to mean the first upstream third of the length, and the said length is located along the horizontal longitudinal axis of the furnace. The expression "downstream part" is understood to mean the last downstream third of the said length.

[0018] The present invention relates to a method for melting a vitrifiable material to produce sheet glass. In this specification, the "vitrifiable material" means the raw materials and cullet charged and melted in the entire furnace (i.e., at least one main melting tank and at least one auxiliary melting tank).

[0019] Other features and advantages of the present invention will become more apparent upon reading the following description of the preferred embodiments and figures, which are given by way of simple illustrative and non-limiting examples.

Brief Description of the Drawings

[0020] [Figure 1] It is a flowchart of an embodiment of the method of the present invention.

Embodiments for Carrying Out the Invention

[0021] According to the present invention, as shown in FIG. 1, the method comprises the steps of preparing a furnace comprising: (i) at least one main melting tank equipped with electric heating means; (ii) at least one auxiliary melting tank; (iii) a refining tank equipped with oxygen combustion heating means; (iv) at least one neck separating at least one main melting tank and the refining tank; (v) inlet means disposed in at least one main melting tank; and (vi) outlet means (for flowing the molten glass to the working zone) disposed downstream of the refining tank.

[0022] According to the present invention, as generally adopted in the field of glass technology, a "melting tank" means a tank that defines a zone where a glassifiable material (i.e., raw materials and / or cullets) is charged and melted by heating. When the furnace is in the process of the method steps, it includes the melt and a "blanket" of unmelted material that floats on the melt and is gradually melted.

[0023] According to the present invention, as generally adopted in the field of glass technology, a "refining tank" means a tank that defines a zone where the "blanket" of unmelted glassifiable material floating on the melt no longer exists and the glass melt is heated to a temperature (generally above 1400 °C or above 1450 °C), optionally higher than the temperature of the melting tank, in order to purify the glass (mainly by removing the main part of the bubbles). This refining tank is generally also called a "clarifying tank" in the art.

[0024] According to the present invention, the "neck" separating at least one main melting tank and a purification tank is, - It is narrower in width compared to a molten tank; - Compared to refining tanks, it is narrower in width and (crown) height; - The neck opening is only partially present beneath the glass molten / blanket-free surface, leaving a free opening above the glass molten / blanket. It means a part.

[0025] The crown of the neck according to the present invention may be lower in height than the crown of the main melting tank, or may be substantially the same height. In addition to the advantages of a particular furnace design having a neck, combined with other features of the present invention, the neck allows for a wider opening, thereby reducing the glass flow rate and reducing corrosion and wear of the refractory. This can favorably improve the lifespan of the furnace. Furthermore, it provides a free surface, which can be used to control the temperature of the glass flowing out of the neck (important for controlling the convection loop in the refining tank) and, optionally, to introduce skin bars / barriers introduced from both sides of the neck (usable to control convection in the neck and, optionally, to prevent backflow from the refining zone to the melting zone).

[0026] This furnace design, which segments the main melting tank and the refining tank, offers numerous advantages in terms of energy consumption / CO2 emissions and the furnace's mechanical stability / lifespan. Particularly advantageous in relation to the present invention, this furnace, due to its specific segmented design, allows for the independent treatment of exhaust gases from the main melting tank and the refining tank as needed.

[0027] The invention of the segmented glass furnace and all embodiments thereof described in European Patent Application No. 21200998.9 are incorporated herein by reference as embodiments of the present invention.

[0028] According to a particular embodiment, the furnace of the present invention is defined by the following: 0.1*W2≦W3i≦0.6*W2; W1i ≥ 1.4 * W3i; W1i is the width of at least one main melting tank. W2 is the width of the refining tank. W3i is the width of at least one neck.

[0029] This last particular design is advantageous in finding an excellent compromise between two conflicting requirements. On the one hand, the neck between the melting zone and the refining zone should ideally be as narrow as possible to (1) reduce the opening between the molten superstructure / crown and the refining superstructure / crown, and (2) create an obstruction to the overall convection intensity of molten glass in the main melting tank; on the other hand, the neck should ideally be as wide as possible to limit the flow velocity of glass within the neck and suppress wear / corrosion of the neck refractory wall.

[0030] According to the present invention, the furnace may comprise one main melting tank and one neck, or two main melting tanks and two necks, or even three main melting tanks and three necks. Embodiments of these specific designs are described in detail in European Patent Application No. 21200998.9, which is incorporated herein by reference.

[0031] For example, in a "two-molten-tank" configuration, the furnace may include the following: (i) First main melting tank, (ii) Second main melting tank, (iii) Refining tank, (iv) Neck Ni separating the first main melting tank and the purification tank, (v) Neck Nii separating the second main melting tank and the refining tank. (vi) at least one inlet means located in the first main melting tank, (vii) at least one inlet means located in the second main melting tank, (viii) At least one outlet means located in the refining tank.

[0032] According to this particular embodiment, the furnace can be advantageously defined by the following formula: 0.1*W2≦W3i≦0.6*W2; 0.1*W2≦W3ii≦0.6*W2; W1i ≥ 1.4 * W3i; W1ii≧1.4*W3ii; W1i is the width of the first main melting tank. W1ii is the width of the second main melting tank. W2 is the width of the refining tank. W3i is the width of the neck Ni. W3ii is the width of the Nii neck.

[0033] Preferably, the total surface area of ​​the main melting tank(s) is 25-400 m². 2 It is within the range of . Similarly preferably, according to the present invention, the surface area of ​​the purification tank is 25 to 400 m 2 It is within the range.

[0034] In an advantageous embodiment of the present invention, the furnace includes at least one main melting tank that is laterally extended and has at least two inlet means, the inlet means being located on both sides of the melting tank, laterally on the sides or as an upper batch charger, based on the position of the neck.

[0035] Preferably, and as is known in the art, the inlet means is located upstream of at least one melting tank (laterally in the widthwise or lengthwise direction of the tank) or located above at least one melting tank ("upper batch charger").

[0036] According to the present invention, as shown in Figure 1, the method includes the step of charging a vitrifiable material, which comprises raw materials and optionally cullet, into at least one main melting tank using an inlet means.

[0037] According to one embodiment, when cullet is charged into at least one main melting tank, this can be done from the same inlet means as those used for the raw materials, or from a different inlet means independently of the raw materials.

[0038] According to the present invention, as shown in Figure 1, the method includes the step of charging cullet into at least one auxiliary melting tank.

[0039] According to the present invention, the total amount of cullet is at least 10% by weight of the total amount of vitrifiable material (i.e., vitrifiable material charged in at least one main melting tank and cullet charged in at least one auxiliary melting tank). Preferably, the total amount of cullet is at least 20% by weight of the total amount of vitrifiable material. More preferably, the total amount of cullet is at least 30% by weight of the total amount of vitrifiable material, and very preferably at least 40% by weight. This is advantageous because it can reduce the CO2 generation / emissions of the method of the present invention (due to the reduction in emissions resulting from the decarbonization of the raw materials, which are carbonates). The amount of cullet may be up to 90% by weight, and even more preferably up to 80% by weight, of the total amount of vitrifiable material.

[0040] To clarify, according to the present invention, either the entire amount of cullet to be charged into the furnace of the present invention is entirely charged into at least one auxiliary melting tank (i.e., only the raw material derived from the vitrifiable material of the present invention is charged into at least one main melting tank), or the entire amount of cullet is divided among at least one main melting tank and at least one auxiliary melting tank (meaning that only a portion of the cullet is melted in at least one auxiliary melting tank, and the remaining portion of the cullet is melted in at least one main melting tank). According to this last embodiment, for example, any portion of the cullet deemed to be "contaminated" or not sufficiently clean is melted in at least one auxiliary melting tank, and the remaining "clean" portion of the cullet is charged into at least one main melting tank along with the raw material and melted there.

[0041] To clarify here as well, according to the present invention, at least a portion of the cullet (i.e., a portion of the total amount of cullet charged into the furnace of the present invention) is charged into at least one auxiliary melting tank. That is, essentially cullet is charged into at least one auxiliary melting tank. "Essentially cullet" means that either only cullet is charged into at least one auxiliary melting tank, or it is charged together with a small amount of compound (e.g., up to 5% or 10% by weight of the charged material, i.e., useful for adjusting the properties of the molten material in the auxiliary melting tank). For example, sodium and / or calcium oxides may be added with the cullet to adjust the viscosity of the molten material / molten cullet, and this does not depart from the present invention.

[0042] In an embodiment in which the entire amount of cullet is divided into at least one main melting tank and at least one auxiliary melting tank, the cullet charged into at least one auxiliary melting tank accounts for at least 2% by weight, preferably at least 5% by weight, more preferably at least 10% by weight, and even more preferably at least 20% by weight of the total amount of cullet charged into the furnace of the present invention.

[0043] According to the present invention, as shown in Figure 1, the method includes the steps of melting the charged cullet in at least one auxiliary melting tank and flowing the molten material (i.e., molten cullet) to a neck or purification tank. For clarity, this means that at least one auxiliary melting tank according to the present invention is connected to (i.e., in other words, flowing through) the neck or purification tank.

[0044] A configuration in which at least one auxiliary melting tank flows downstream of the main melting tank, i.e., to the neck or refining tank, is advantageous at various levels: - This improves energy efficiency: The molten material leaving / flowing from the auxiliary melting tank (typically 1350°C) is generally cooler than the molten material present in the main melting tank (typically 1450°C). The molten material present in the main melting tank is then cooled (typically to 1450°C-1350°C) before or upon entering the refining tank. From an energy standpoint, it is inefficient to flow the molten cullet into the main melting tank, reheat it there (+100°C), and then cool it (-100°C) before or upon entering the refining tank. By flowing the molten cullet directly into the refining zone, it is brought to the target temperature directly without requiring the aforementioned heating / cooling cycle; - This reduces the flow rate of molten glass through the main melting tank, as a portion of the vitrifiable material (i.e., in cullet form) is charged downstream (in the auxiliary melting tank). As a result, the residence time of the glass in the main melting tank increases, accelerating the melting of the raw materials (and optionally the cullet) and promoting the removal of bubbles from the molten glass present in the main melting tank. Furthermore, the average velocity of the glass in contact with the refractory materials (walls and bottom) in the main melting tank decreases, reducing wear and corrosion of these refractories. Consequently, the furnace life is increased, and defects caused by refractories in the final glass product are reduced. - This avoids the possibility of gas generation when mixing two glass melts with different oxidation-reduction states / compositions in the case of a cold-top melting tank (where the melt flows from an auxiliary melting tank to the main melting tank). In fact, such gas generation can adversely affect the melting method because a gas layer may form between the glass melt and the vitrifiable material layer. In that case, this gas layer can act as an insulator, significantly reducing the melting rate and thereby increasing energy consumption.

[0045] Advantageously, the method of the present invention includes the step of melting the cullet charged in at least one auxiliary melting tank and flowing the molten material into the neck. This allows for a symmetrical introduction of the molten cullet / molten material with respect to the entire furnace, improving the homogeneity of the glass in the refining tank and the final glass product.

[0046] If at least one auxiliary melting tank flows into (or is connected to) the purification tank, the at least one auxiliary melting tank is preferably connected to the upstream part of the purification tank, and more preferably as far upstream as possible.

[0047] If at least one auxiliary melting tank flows into (or is connected to) the refining tank, this can be done via a connection known in the art, preferably a throat or neck.

[0048] If at least one auxiliary melting tank flows into (or is connected to) the neck, this is preferably done via a connection commonly known in the art, such as a throat.

[0049] Alternatively, and advantageously, if at least one auxiliary melting tank flows into (or is connected to) the neck, the inflow may be from a height higher than the top of the neck, and the melt from the auxiliary melting tank flows by gravity over the melt already present in the neck (and the melt from the main melting tank). This embodiment reduces the required space around the neck at ground level and facilitates operations inside the neck (e.g., introduction of equipment). This can also be advantageously combined with a refining method which may be a gravity flow method.

[0050] According to one embodiment, the furnace of the present invention may comprise a plurality of auxiliary melting tanks, for example, two or three auxiliary melting tanks. In such a case, each auxiliary melting tank can independently flow into / connect to a neck or a refining tank. For example, if the furnace comprises two auxiliary melting tanks, one auxiliary melting tank may flow into the neck and the other auxiliary melting tank may flow into a refining tank, or both may flow into the neck, or both may flow into a refining tank. In another embodiment, if the furnace of the present invention comprises a plurality of auxiliary melting tanks, for example, two or three auxiliary melting tanks, they may be arranged in series (continuously). For example, if the furnace comprises three auxiliary melting tanks arranged in series, the first tank (the upstreammost from the neck or refining tank) flows into the second tank, the second tank flows into the last tank, and the last tank eventually flows into the neck or refining tank.

[0051] According to the present invention, the step of melting the charged cullet in at least one auxiliary melting tank can be carried out using, for example, an electric heating means such as an immersed electrode and / or a combustion means such as an air burner or an immersed combustion means.

[0052] According to one embodiment, the step of melting cullet in at least one auxiliary melting tank according to the present invention may include one or more steps of purifying the cullet. For example, metal compounds present in the cullet can be removed in the auxiliary melting tank by generating molten metal using a reducing agent (such as coke or anthracite), which is separated from the glass molten material by decanting at the bottom of the auxiliary melting tank, while the resulting "purified" glass molten material can flow from the top toward the neck or a purification tank.

[0053] According to the present invention, as shown in Figure 1, the method includes the steps of melting a charged vitrifiable material, which includes raw materials and optionally cullet, by heating it with an electric heating means in at least one main melting tank, and flowing the molten material through a neck to a refining tank.

[0054] The electric heating means according to the present invention can be positioned at the bottom of at least one main melting tank, and in such cases, preferably consists of immersed electrodes. The “bottom electrodes” are advantageously arranged in a grid (checkerboard pattern) of three or multiples of two to facilitate connection to the transformer and current balancing.

[0055] Alternatively, the electric heating means according to the present invention extends from and is immersed in at least one main melting tank (for example, typically held by a water-cooled holder). These “upper electrodes” are advantageously positioned along the edges and / or corners of the melting tank.

[0056] The number of electrodes in this invention is, for example, based on the maximum current density of the electrode surface of 1.5 A / cm². 2 Respecting this principle, the design limits the maximum power of each electrode to 400kW. For example, in the case of immersed electrodes, the height is 0.3 to 0.8 times the height of the molten glass.

[0057] According to the present invention, the electrical input ratio is in the range of 50% to 85%. In this invention, "electrical input ratio" means the electrical portion of the total energy input of the method / furnace for melting / purification, i.e., electricity / (fuel + electricity). The total energy input is that of the method / furnace in standard / normal production mode, i.e., in its standard pull range (excluding startup, maintenance, high-temperature repair, and caletting periods).

[0058] According to the present invention, as shown in Figure 1, the method includes the step of purifying the molten material (i.e., the molten material obtained from the main molten tank and the auxiliary molten tank) in a purification tank by heating in an oxygen combustion heating means supplied with gas and / or hydrogen. In this specification, the term “gas” includes, but is not limited to, natural gas, synthesis gas, and biogas. Natural gas is currently the most widely used in terms of practicality, economy, and availability.

[0059] The "oxygen combustion means" according to the present invention refers to a combustion means in which gaseous oxygen (O2) is supplied as a combustion agent. Typically, the O2 gas combustion agent supplied to a glass melting furnace has a purity of at least 90%, and moreover, at least 95%. The advantage of using gaseous oxygen as a combustion agent is that, compared to using air, so-called "NO" is produced during combustion. x "The result is a significant reduction in pollutants. (Depending on the purity of O2 and the amount of parasitic air) even if they are present in the exhaust gas, the amount will be very small."

[0060] The oxygen combustion heating means according to the present invention can, advantageously, consist of burners positioned along the side walls on both sides of the tank to spread the flame substantially across the entire width of the tank. The burners can be spaced apart from each other to distribute the energy supply to a portion of the purification tank (i.e., about 50% of its length). They can also commonly be arranged in rows on both sides of the tank.

[0061] According to the present invention, the oxygen combustion heating means is supplied with gas and / or hydrogen. In one embodiment, the oxygen combustion heating means is supplied with at least 50% hydrogen, preferably at least 80% hydrogen. More preferably, the oxygen combustion heating means is supplied with 100% hydrogen. This is advantageous because it can significantly reduce the overall CO2 emissions of the method. Alternatively, the oxygen combustion heating means is supplied with more than 50%, preferably at least 80%, and even more preferably at least 100% gas. This is advantageous because it can minimize the impact on the chemical properties of the glass and the refractory materials of the furnace. In a particularly advantageous embodiment of the present invention, the oxygen combustion heating means is supplied with 50% gas and 50% hydrogen.

[0062] According to the present invention, as shown in Figure 1, the method includes the step of flowing the molten material from the purification tank through an outlet means to a work zone.

[0063] According to the present invention, the outlet means is positioned downstream of the refining tank so that the molten glass reaches a work zone. According to one embodiment, the outlet means typically consists of a neck to guide the molten material toward a work zone generally called a “work end.” Alternatively, the outlet means consists of a throat to guide the molten material toward a work zone, for example, including a fore hearth. The work zone according to the present invention may include, for example, a conditioning zone where thermal adjustment by controlled cooling is performed before the molten glass exits the outlet into the molding zone. Such a molding zone may include, for example, a float facility and / or a rolling facility.

[0064] In another advantageous embodiment, the furnace of the present invention may include a removable wall (e.g., a skin bar extending from the side wall of the neck) positioned at the neck to (i) prevent as much as possible any unmelted vitrifiable material (cullet) that could reach the end of the molten tank, thereby preventing them from going through the neck to the refining tank, and (ii) to control or eliminate the intensity of backflow of molten glass from the refining tank to the molten tank.

[0065] According to yet another advantageous embodiment of the present invention, the furnace may include a removable wall located at the neck (e.g., a shadow wall passing through the crown of the neck) to improve the segmentation of the melting tank and the refining tank in terms of atmosphere and thermal radiation.

[0066] According to an advantageous embodiment of the present invention, the method further includes a cullet preheating step by recovering heat from the furnace at least partially before charging the cullet into at least one main melting tank and / or at least one auxiliary melting tank. According to this embodiment, the recovery of heat from the furnace can be carried out from (i) the melting tank, or (ii) the refining tank, or (iii) the exhaust gas from the entire furnace (including the exhaust gas from the auxiliary melting tank and / or the main melting tank, as well as the refining tank).

[0067] Similarly, according to this embodiment, if only a portion of the cullet is melted in the melting step in the auxiliary melting tank and the remaining portion of the cullet (the portion to be charged into the main melting tank) is preheated, the vitrifiable material is charged into at least one main melting tank through the same inlet means together with the preheated cullet (which thus means that both types of material are mixed before charging), or through a different inlet means independently of the preheated cullet.

[0068] Preferably, according to this embodiment, the maximum temperature of the cullet in the cullet preheating step is 450°C. This helps to avoid clogging problems.

[0069] According to one embodiment, the cullet preheating step can be carried out in at least one cullet preheater of one type, for example, as described in U.S. Patent No. 5,526,580 or German Patent No. 3,716,687.

[0070] Advantageously, at least one cullet preheater may be positioned upstream of at least one main melting tank and / or at least one auxiliary melting tank, either in the width direction or transversely to the length direction of the tank. Advantageously, particularly in at least one main melting tank, the cullet preheating step may be carried out with, for example, at least two cullet preheaters positioned on both sides upstream of the main melting tank in the width direction or transversely to its length. For example, the cullet preheating step may be carried out with four cullet preheaters distributed (e.g., two on each side) upstream of the main melting tank in the width direction or transversely to its length. Alternatively, the cullet preheating step may be carried out with six cullet preheaters positioned upstream of the main melting tank in the width direction or transversely to its length (e.g., three on each side), or similarly with eight cullet preheaters positioned upstream of the main melting tank in the width direction or transversely to its length (e.g., four on each side).

[0071] According to yet another advantageous embodiment of the present invention, the raw materials in the vitrifiable material contain less than 25% by weight of a carbonate compound. "Carbonate compound" means, for example, alkali carbonates and alkaline earth carbonates. Preferably, the vitrifiable material contains less than 20% by weight of a carbonate compound, more preferably less than 10% by weight, and even more preferably less than 5% by weight. The vitrifiable material may, advantageously, not contain any carbonate compound at all.

[0072] This embodiment is advantageous because it can reduce some of the CO2 emissions resulting from the decarboxylation of raw materials compared to classical glass melting methods in which sodium carbonate (Na2CO3), limestone (CaCO3), and dolomite (CaMg(CO3)2) are generally used as sodium and calcium sources. According to this embodiment, the alkali source and alkaline earth source may, at least partially, exist in the form of oxides or hydroxides such as CaO, CaO·MgO (dolomite), Ca(OH)2, Mg(OH)2, NaOH, and KOH.

[0073] According to a very preferred embodiment of the present invention, a method for melting a vitrifiable material to produce plate glass is: - A step of preparing a furnace comprising: (i) at least one main melting tank equipped with an electric heating means; (ii) at least one auxiliary melting tank; (iii) a refining tank equipped with an oxygen combustion heating means; (iv) at least one neck separating at least one main melting tank and the refining tank; (v) an inlet means located in at least one main melting tank; and (vi) an outlet means located downstream of the refining tank; - A step of charging a vitrifiable material, which optionally includes raw materials and cullet, into at least one main molten tank using an inlet means; - A step of charging cullet into at least one auxiliary melting tank; - A cullet preheating step by recovering at least partially of the heat from the furnace before the cullet is charged into at least one main melting tank and / or one auxiliary melting tank; - A step of melting the vitrifiable material charged in at least one main melting tank by heating it with an electric heating means, and flowing the molten material through the neck into a refining tank; - A step of melting the charged cullet in at least one auxiliary melting tank and flowing the molten material into a neck or refining tank; - A step of purifying the molten material in a purification tank by heating it in an oxygen combustion heating means supplied with gas and / or hydrogen; - A step of flowing the molten material from the refining tank through the outlet means into the work zone; Includes, The method has an electrical input ratio in the range of 50% to 85%, and the vitrifiable material comprises (i) a raw material having less than 25% by weight of a carbonate compound, and (ii) cullet in an amount of at least 10% by weight of the total amount of the vitrifiable material.

[0074] All of the specific embodiments described above relating to each step of the method of the present invention apply to this last, highly preferred embodiment.

[0075] Those skilled in the art will understand that the present invention is not limited to the preferred embodiments described above. Rather, many modifications and changes are possible within the scope of the appended claims. Furthermore, it should be noted that the present invention relates to all possible combinations of the features and preferred features described herein and in the claims.

Claims

1. A method for melting a vitrifiable material for manufacturing plate glass, - Steps to prepare a furnace comprising: (i) at least one main melting tank equipped with an electric heating means; (ii) at least one auxiliary melting tank; (iii) a refining tank equipped with an oxygen combustion heating means; (iv) at least one neck separating the at least one main melting tank from the refining tank; (v) an inlet means located in the at least one main melting tank; and (vi) an outlet means located downstream of the refining tank; - A step of charging a vitrifiable material, which optionally includes raw materials and cullet, into the at least one main melting tank using the inlet means; - A step of charging cullet into at least one auxiliary melting tank; - A step of melting the vitrifiable material placed in the at least one main melting tank by heating it with the electric heating means, and flowing the molten material through the neck to the refining tank; - A step of melting the charged cullet in at least one of the auxiliary melting tanks; - A step of purifying the molten material in the purification tank by heating in the oxygen combustion heating means to which gas and / or hydrogen is supplied; - A step of flowing the molten material from the refining tank through the outlet means to the work zone; In a method including, (i) The electrical input ratio is in the range of 50% to 85%; (ii) The total amount of cullet is at least 10% by weight of the total amount of vitrifiable material; (iii) The method includes the step of flowing the molten material from the at least one auxiliary melting tank to the neck or the refining tank. A method characterized by the following features.

2. The method according to claim 1, characterized in that the total amount of cullet is at least 20% by weight of the total amount of vitrifiable material.

3. The method according to claim 2, characterized in that the total amount of cullet is at least 40% by weight of the total amount of vitrifiable material.

4. The method according to any one of claims 1 to 3, characterized in that the method includes the step of melting cullet charged in at least one auxiliary melting tank and flowing the molten material into the neck.

5. The method according to any one of claims 1 to 4, characterized in that the cullet charged into the at least one auxiliary melting tank accounts for at least 2% by weight of the total amount of cullet charged into the furnace.

6. The method according to claim 5, characterized in that the cullet charged into the at least one auxiliary melting tank accounts for at least 10% by weight of the total amount of cullet charged into the furnace.

7. The method according to any one of claims 1 to 6, characterized in that at least 50% hydrogen, preferably at least 80% hydrogen, is supplied to the oxygen combustion heating means.

8. The method according to any one of claims 1 to 7, further comprising a cullet preheating step of recovering at least partially heat from the furnace before charging the cullet into the at least one main melting tank and / or the at least one auxiliary melting tank.

9. The method according to claim 8, characterized in that the maximum temperature of the cullet in the cullet preheating step is 450°C.

10. The method according to claim 9, characterized in that the vitrifiable material contains less than 25% by weight of a carbonate compound.

11. A furnace for carrying out the method according to any one of claims 1 to 10.

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