Glass melting process with very low to zero CO2 emissions

Abstract

The present invention relates to a method for melting a vitrifiable material to produce a sheet glass, the method comprising the steps of: (i) providing a furnace comprising at least one main melting tank with electrical heating means, at least one auxiliary melting tank, a fining tank with oxycombustion heating means, a neck separating the main melting tank and the fining tank; (ii) charging a vitrifiable material into the primary melting tank and / or into the secondary melting tank, the vitrifiable material comprising a raw material and cullet in a total amount of at least 10 wt% of the vitrifiable material; (iii) melting the vitrifiable material in the main melting tank by heating with an electrical heating device and flowing it through the neck to the fining tank; (iv) melting at least a portion of the cullet in the auxiliary melting tank and flowing it to the neck or to the fining tank wherein the electrical input fraction ranges from 50% to 85%; (v) clarifying the melt in the clarification tank by heating with an oxycombustion heating device supplied with a gas and / or hydrogen, (vi) flowing the melt from the clarification tank to the working zone, (vii) capturing CO2 from the flue gas, the steps comprising a compression and / or dehydration step, the flue gas having a CO2 concentration of at least 35%.

Description

TECHNICAL FIELD

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

[0002] The present invention more particularly relates to, but is not limited to, a melting process for flat glass which involves large-scale production capacities (i.e. up to 1000 tons / day or more). BACKGROUND

[0003] Global warming and the requirement to reduce CO2 emissions increase the pressure on glass manufacturers, but also the energy price and CO2 tax, which can soon seriously threaten the competitiveness of the glass industry.

[0004] In the context of the urgent action to reduce carbon emissions, the glass industry has invested a lot for many years in the decarbonization of its manufacturing process in order to produce glass goods suitable for a sustainable, resource-efficient, low-carbon society.

[0005] To achieve the transformation, the glass industry has identified many solutions / technologies to approach this ambitious goal, such as, for example, 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, the increase in the use of cullet as a raw material, heat recovery, CO2 capture utilization and storage (or CCUS),...

[0006] However, all these technologies are accompanied by serious drawbacks or problems in practical implementation, or are not economically viable. There is therefore still an urgent need for a glass melting process which allows a significant reduction in the amount of CO2 emissions, but at the same time remains economically acceptable for glass manufacturers.

[0007] Regarding the use of electricity as an energy source: it is known that furnaces for melting glass raw materials using electrical energy show a reduction in CO2 emissions, but also a reduction in total energy consumption. In such a configuration, the melting furnace comprises electrodes which allow an electric current / power to pass through the bath of molten glass and heat it from its bulk. However, when high-quality glass is required, glass melting furnaces in which the heating power is entirely supplied by electricity have not been adopted in flat glass technology due to serious temperature and glass convection / flow problems.

[0008] Consequently, conventional glass melting furnaces for flat glass are typically "fused" with electricity only, adopting a so-called "hybrid" configuration combining a combustion heating device (i.e. a burner) and an electric heating device (such as an immersed electrode). However, in such known "electrically fused combustion furnaces", the electric input fraction is limited to a maximum of 10-15% of the total energy input, thus hindering the full benefit of the energy consumption advantages of electric melting.

[0009] Recently, a specific design of a new furnace described in European patent application EP21200998.9 (which is hereby incorporated by reference) allows to reach a significantly higher electric input fraction in a "hybrid" furnace, i.e. more than 50%.

[0010] As regards the use of alternative and more environmentally friendly energy sources such as hydrogen H2 or biogas: even if it is clear that they would bring advantages in terms of environment / energy consumption / CO2 emissions, serious limitations hinder their widespread use in the glass industry (lack of availability of biogas, and high price of H2 which makes H2 so far an economically unfeasible solution as the only energy source for melting glass raw materials).

[0011] As regards heat recovery: the recovery of waste heat from flue gases has been widely applied in the glass industry for preheating combustion air entering the furnace at temperatures higher than 1000°C, or respectively gases and oxygen ("Hotox") at temperatures higher than 400°C and 500°C. In addition to this, waste heat from flue gases can also be used for preheating glassifiable materials, in particular cullet. However, it is known that preheating raw materials / cullet cannot be combined with electric melting, because in this case the flue gas temperature released by the raw materials is too low.

[0012] As regards the use of CO2 capture: typically, a CO2 capture process in an industrial process / plant consists of two steps: (i) separation of CO2 from a waste gas mixture by selective reaction with a separation material ("absorption" of CO2) and (ii) regeneration of the used material by the reverse reaction ("desorption" of CO2). The separation material can be reused for CO2 capture by repeating steps (i) and (ii) in sequence. Amines in the form of solvents or membranes or porous adsorbents are the most widely used materials in CO2 capture processes in industry so far, because the technology is mature and can effectively separate amines and CO2 via a reversible reaction. However, this amine approach (e.g. using aqueous MEA) is still a poor choice, especially in the specific context of the glass industry so far, at least for the following main reasons: - in known glass manufacturing processes, the combustion gases / flue gases show a low concentration of CO2 (generally lower than 30% by volume and often approximately 10-20%), and a low purity due to the presence of many other components (mainly N2, H2O, O2, NO x , SO x , etc.), greatly affecting the efficiency of the CO2 capture process; and - the amine-CO2 capture process requires a large amount of energy in order to regenerate the amine absorbent (desorption process), affecting the overall energy consumption (and, depending on the energy used, potentially CO2 emissions, which in the current situation are obviously counterproductive).

[0013] Furthermore, known glass manufacturing processes produce a very high flue gas volume or flow rate, which also directly affects the investment and operating costs when one wants to capture CO2 from those flue gases, regardless of the method used. Invention aims

[0014] The aim of the present invention is to overcome the drawbacks described above with regard to the prior art and to solve the technical problem, i.e. to provide a glass melting process for producing flat glass which shows a reduced overall energy consumption and reduced CO2 emissions compared to the classic melting furnace.

[0015] Another aim of the present invention is to provide a glass melting process for producing flat glass which shows a reduced overall energy consumption and reduced CO2 emissions compared to the classic melting furnace, i.e. which is economically viable.

[0016] Another aim of the present invention is to provide a glass melting process for producing flat glass which shows a reduced overall energy consumption and reduced CO2 emissions compared to the classic melting furnace, while allowing simple and cost-effective CO2 capture. SUMMARY

[0017] The present invention relates to a process for melting a glassifiable material to produce flat glass, comprising the following steps: - providing a melting furnace comprising (i) at least one main melting tank comprising electric heating means, (ii) at least one auxiliary melting tank, (iii) a fining tank provided with oxygen combustion heating means, (iv) at least one neck separating the at least one main melting tank and the fining tank, (v) inlet means located at the at least one main melting tank, (vi) outlet means located downstream of the fining tank; - charging a vitrifiable material into at least one main melting tank and / or into at least one auxiliary melting tank, the vitrifiable material comprising raw materials and cullet, the amount of cullet being at least 10% by weight of the total amount of the vitrifiable material; - melting the vitrifiable material in the at least one main melting tank by heating with electric heating means, and flowing the melt through a neck to a fining tank - melting at least a portion of the cullet in the at least one auxiliary melting tank; - fining the melt in the fining tank by heating with oxygen combustion heating means, the oxygen combustion heating means being fed with gas and / or hydrogen; - flowing the melt from the fining tank to a working area through outlet means; - capturing CO2 from a flue gas, the flue gas having a CO2 concentration of at least 35%; the electric input fraction thereof ranging from 50% to 85%; the step of capturing CO2 from the flue gas comprising a compression and / or dehydration step; and having the step of flowing the melt from the at least one auxiliary melting tank to the neck or to the fining tank.

[0018] The present application is therefore based on a novel and inventive method. In particular, the inventors have found that, in a glass melting method for producing flat glass, by combining: - the use of a furnace having a specific segmented design (separating an electrically heated main melting zone and a combustion heated fining zone), - the use of oxygen as combustion-supporting agent, - the use of gas and / or hydrogen as combustible, - the use of a minimum amount of cullet in the vitrifiable material, - the use of a step of at least partially melting the cullet in an auxiliary melter, which flows downstream of the melting tank (in particular into the neck or into the fining tank), and - the use of a specific electric input fraction, it is possible to simultaneously obtain: - a significant reduction of the overall energy consumption; and - a significant reduction of the overall production of CO2; and - a significant reduction of the flue gas volume and a significant increase of the CO2 concentration in said flue gas and of its purity, thus allowing the use of a simple, efficient and cost-effective CO2 capture process.

[0019] By implementing all the features of the present application, the method of the present application shows a very low CO2 footprint and is economically viable.

[0020] In the present specification and claims, it will be well understood by those skilled in the art that, as used herein, the terms "a", "an", or "the", unless otherwise expressly specified, are used indifferently and shall not be limited to "only one". Moreover, when indicating a range, the endpoints are included. Furthermore, all integer values and sub-domain values within a numerical range are clearly included as if expressly written. Finally, the terms "upstream" and "downstream" refer to the direction of flow of the glass and shall be understood in their usual meaning, i.e. meaning along the average direction of movement of the vitrifiable material / glass melt, from the inlet device(s) to the outlet device(s). The expression "upstream portion" shall be understood to mean the upstream portion of one third of the length, said length being positioned along the horizontal and longitudinal axes of the furnace. The expression "downstream portion" shall be understood to mean the downstream portion of the last third of said length.

[0021] Other characteristics and advantages of the application will become more clearly apparent from reading the following description of preferred embodiments, given as an indication and in no way limiting, in relation to the attached drawings.

[0022] Figure 1 is a flow chart of an embodiment of the method of the application.

[0023] According to the application and as illustrated in Figure 1 the method for melting a vitrifiable material to produce flat glass comprises the following steps: providing a furnace comprising (i) at least one main melting tank comprising electrical heating means, (ii) at least one auxiliary melting tank, (iii) a fining tank provided with oxygen combustion heating means, (iv) at least one neck separating the at least one main melting tank and the fining tank, (v) inlet means located at the at least one main melting tank, (vi) outlet means located downstream of the fining tank (for making the molten glass flow to a working zone).

[0024] According to the application and as generally adopted in the glass field, by "melting tank" is meant a tank delimiting a zone where the vitrifiable material (raw materials and / or cullet) is charged and melted by heating, and which, when the furnace is in operation, contains a "layer" of melt and of un-melted vitrifiable material floating on the melt and gradually melting.

[0025] According to the application and as generally adopted in the glass field, by "fining tank" is meant a tank delimiting a zone where there is no longer a "layer" of un-melted vitrifiable material floating on the melt, and in which the glass melt is heated at a temperature higher than the melting tank temperature (typically higher than 1400°C, or even higher than 1450°C), in order to refine the glass (mainly by eliminating most of the bubbles). Such a fining tank is also generally called "purification tank" in the art.

[0026] According to the present invention, the "neck" separating the at least one main melting tank and the fining tank means: - is narrower in width compared to the melting tank; - is narrower in width and (roof) height compared to the fining tank; and - the opening of the neck is only partially below the glass melt / layer free surface, leaving a free opening above the glass melt / layer.

[0027] The roof of the neck according to the present invention can be at a lower height than the roof of the main melting tank or substantially at the same height.

[0028] In addition to the advantages of the specific furnace design with a neck in combination with the other features of the present invention, the neck allows a wider opening and thus a lower glass velocity, leading to a lower corrosion and wear of the refractory material. This can advantageously increase the lifetime of the furnace. Furthermore, it provides a free surface which can be used to control the glass temperature flowing out of the neck (important for controlling the convective loop in the fining tank) and can introduce a skimmer rod / baffle introduced from the side of the neck (can be used to control the convection in the neck and can avoid backflow from the fining zone to the melting zone).

[0029] Furthermore, this furnace design with its specific segmentation of the main melting tank and the fining tank brings a lot of advantages in terms of energy consumption / CO2 emissions and in terms of mechanical stability / lifetime of the furnace. In particular, advantageously, the furnace with its specific segmented design allows, in the context of the present invention, to treat the flue gas from the main melting tank and the flue gas from the fining tank independently, if needed.

[0030] The invention of the segmented glass furnace described in European patent application EP21200998.9 and all its embodiments are incorporated herein by reference as embodiments of the present invention.

[0031] According to specific embodiments, the furnace of the present invention is defined by: 0.1 W2 ≤ W3i ≤ 0.6 W2; W1i ≥ 1.4 W3i; W1i is the width of the at least one main melting tank; W2 is the width of the fining tank; W3i is the width of the at least one neck.

[0032] This last specific design is advantageous to find a good compromise between, on the one hand, the neck between the melting zone and the fining zone ideally should be as narrow as possible in order to (1) reduce the opening between the melting upper structure / furnace roof and the fining upper structure / furnace roof, and (2) create an obstacle to the overall intensity of the glass melt convection in the main melting tank, and, on the other hand, the neck ideally should be as wide as possible in order to limit the glass velocity inside the neck, and thus limit the erosion / corrosion of the refractory walls of the neck.

[0033] According to the invention, the furnace can 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 extensively described in European patent application EP21200998.9, which is incorporated herein by reference.

[0034] For example, in the "two melting tanks" configuration, the furnace can comprise: (i) a first main melting tank, (ii) a second main melting tank; (iii) a fining tank, (iv) a neck Ni separating the first main melting tank and the fining tank; (v) a neck Nii separating the second main melting tank and the fining tank; (vi) at least one inlet device located at the first main melting tank; (vii) at least one inlet device located at the second main melting tank; (viii) at least one outlet device located at the fining tank.

[0035] According to this specific embodiment, the furnace can advantageously be defined by: 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 fining tank; W3i is the width of the neck Ni; W3ii is the width of the neck Nii.

[0036] Preferably, the total surface area of the main melting tank ranges from 25 m 2 to 400 m 2 . Also preferably, according to the application, the surface area of the refining tank ranges from 25 m 2 to 400 m 2 .

[0037] Preferably and as known in the art, the inlet device is located upstream of the at least one melting tank (on the width of the tank or laterally on its length), or at the top of the at least one melting tank ("top batcher").

[0038] In an advantageous embodiment of the application, the furnace comprises at least one melting tank that is laterally enlarged and equipped with at least two inlet devices, these inlet devices being located on both sides of the melting tank, laterally or as a top batcher, depending on the position of the neck.

[0039] According to the application and as illustrated in Figure 1 , the method for melting a glassifiable material to produce flat glass comprises the step of charging the glassifiable material into at least one main melting tank and / or at least one auxiliary melting tank, the glassifiable material comprising raw materials and cullet.

[0040] According to the application and as illustrated in Figure 1 , the method for melting a glassifiable material to produce flat glass comprises the step of melting at least a portion of the cullet in at least one auxiliary melting tank and flowing the melt (i.e. the molten cullet) to the neck or to the refining tank. For the sake of clarity, this means that the at least one auxiliary melting tank according to the application is connected to (or in other words, flows to) the neck or to the refining tank.

[0041] Advantageously, the method of the application comprises the step of melting at least a portion of the cullet in at least one auxiliary melting tank and flowing the melt to the neck. This allows the introduction of the molten cullet in a symmetrical manner with respect to the entire furnace, thereby producing better glass homogeneity in the refining tank and in the final glass product.

[0042] When the at least one auxiliary melting tank flows to (or is connected to) the refining tank, the at least one auxiliary melting tank is preferably connected at an upstream portion of the refining tank, and more preferably as far upstream as possible of the refining tank.

[0043] When the at least one auxiliary melting tank flows to (or is connected to) the refining tank, this can be done by a connection (preferably a throat or a neck) known in the art.

[0044] When the at least one auxiliary melting tank flows to (or is connected to) the neck, this is preferably done by a connection (such as a throat) known in the art.

[0045] Alternatively and advantageously, when at least one auxiliary melt tank flows toward (or is connected to) the neck, the flow can proceed from a height above the top of the neck, with the melt from the auxiliary melt tank flowing under gravity onto the upper surface of the melt already present in the neck (and from the main melt tank). This reduces the space required around the neck and facilitates operations within the neck (e.g., for equipment introduction). This can also be advantageously combined with purification processes, which can be gravity-flow processes.

[0046] According to embodiments, the furnace of the present invention may include more than one auxiliary molten pool, such as two or three auxiliary molten pools. In this case, each auxiliary molten pool may flow independently to / connect to the neck or refining pool. For example, if the furnace includes two auxiliary molten pools, one auxiliary molten pool flows to the neck and the other flows to the refining pool, or both flow to the neck, or both flow to the refining pool. In alternative embodiments, when the furnace of the present invention includes more than one auxiliary molten pool (e.g., two or three auxiliary molten pools), they may be arranged in series (one after another). For example, if the furnace includes three auxiliary molten pools arranged in series, the first auxiliary molten pool (at the very upstream of the neck or refining pool) flows to the second auxiliary molten pool, which flows to the last auxiliary molten pool, which ultimately flows to the neck or refining pool.

[0047] For clarity, according to the invention, the total amount of chopped glass fed into the furnace of the invention is entirely and solely fed into at least one auxiliary melting tank (meaning only the raw materials of the vitrifiable material of the invention are fed into at least one main melting tank), or alternatively, the total amount of chopped glass is diverted between at least one main melting tank and at least one auxiliary tank (meaning only a portion of the chopped glass is melted in at least one auxiliary melting tank, and the remaining portion of the chopped glass is melted in at least one main melting tank). According to this last embodiment, for example, the portion of the chopped glass considered "contaminated" or insufficiently clean is melted in at least one auxiliary melting tank, and the remaining "clean" portion of the chopped glass is fed together with the raw materials into at least one main melting tank and melted therein.

[0048] Also for the sake of clarity, according to the present application, at least a portion of the cullet (i.e. a portion of the total amount of cullet charged into the furnace of the present application) is charged into at least one auxiliary melting tank, which means that essentially the cullet is charged into at least one auxiliary melting tank. By "essentially the cullet" it is meant that the cullet is charged into at least one auxiliary melting tank alone or together with a small amount of compounds (e.g. up to 5 wt% or 10 wt% of the charged material) that help to adjust the properties of the melt in the auxiliary melting tank. For example, some soda and / or calcium oxide can be added with the cullet to adjust the viscosity of the melt / melted cullet without departing from the present application.

[0049] According to embodiments, the cullet is charged into the at least one main melting tank together with the raw materials (i.e. through the same inlet means), if any, or alternatively, independently from the raw materials, through different inlet means.

[0050] According to embodiments, the step of melting at least a portion of the cullet in the at least one auxiliary melting tank can comprise one or several steps of purifying said cullet. For example, by using a reducing agent (like coke or anthracite) to produce a molten metal, metal compounds present in the cullet can be eliminated in this auxiliary melting tank, the molten metal will be separated from the glass melt by decanting at the bottom of the auxiliary melting tank, while the obtained "purified" glass melt can flow from the top to the neck or fining tank.

[0051] According to embodiments of the present application, the at least a portion of the cullet that is melted in the at least one auxiliary melting tank represents at least 2% by weight, and preferably at least 5% by weight, or even at least 10% by weight, and more preferably at least 20% by weight of the total amount of cullet.

[0052] According to the present application, the step of melting at least a portion of the cullet in the at least one auxiliary melting tank can be performed with electric heating means (e.g. like an immersed electrode) and / or with combustion means (e.g. like an over-air burner or an immersed combustion means).

[0053] According to the present application, the amount of cullet is at least 10% by weight of the total amount of vitrifiable material. Preferably, the amount of cullet is at least 20% by weight of the total amount of vitrifiable material. More preferably, the amount of cullet is at least 30% by weight, or even very preferably at least 40% by weight of the total amount of vitrifiable material. This is advantageous as it allows to reduce the production / emission of CO2 of the method of the present application (due to the reduced emissions resulting from the decarburization of carbonate raw materials). Possibly, the amount of cullet is at most 90% by weight, or even at most 80% by weight of the total amount of vitrifiable material.

[0054] According to the present application and asFigure 1 As illustrated, the method for melting a glassifiable material to produce flat glass comprises a step of melting the glassifiable material in at least one main melting tank by heating with electric heating means.

[0055] The electric heating means according to the application can be located at the bottom of the at least one main melting tank and, in this case, are preferably constituted by immersed electrodes. The "bottom electrodes" are advantageously arranged in a grid pattern (checkerboard) in multiples of 3 or 2 in order to facilitate the connection to the transformer and the current balancing.

[0056] Alternatively, the electric heating means according to the application extend from the top of the at least one main melting tank (for example, generally held by a water-cooled holder) and are immersed. These "top electrodes" are advantageously positioned along the edges of the melting tank and / or at the corners.

[0057] In the present application, for example, the number of electrodes is designed so as to limit the maximum power of each electrode to 400 kW, while maintaining a maximum current density at the electrode surface of 1.5 A / cm2. For example, in the case of immersed electrodes, the height is between 0.3 and 0.8 times the height of the glass melt.

[0058] According to the application, the electric input fraction ranges from 50% to 85%. The "electric input fraction" according to the application means the portion of electric power for melting / fining in the total energy input of the method / furnace, i.e. electric power / (fuel + electric power), the total energy input being the total energy input of the method / furnace in standard / normal production mode, i.e. in its standard draw range (excluding periods of start-up, maintenance, hot repair, glass fragmentation...).

[0059] According to the application and as illustrated in Figure 1 As illustrated, the method for melting a glassifiable material to produce flat glass comprises a step of clarifying the melt in a refining tank by heating with oxygen combustion heating means, which are fed with a gas and / or hydrogen. The term "gas" herein includes, but is not limited to, natural gas, synthetic gas and biogas. For reasons of practicality, economy and availability, natural gas is currently the most widely used.

[0060] The "oxygen combustion means" according to the application means a combustion means supplied with gaseous oxygen (O2) as a combustion-supporting agent. Typically, the O2 gas combustion-supporting agent supplied to the glass melting furnace is at least 90% pure, or even at least 95% pure. The advantage of using gaseous oxygen as a combustion-supporting agent, compared to using air, is a substantial reduction in the so-called « NOx » pollutants that appear during the combustion process. Even if they can still be present in the flue gas (depending on the purity of the O2 and the amount of parasitic air), their amount will be very low.

[0061] The oxy-combustion heating device according to the application can be constituted by burners advantageously arranged along the side walls of the tank on each side of the tank so as to spread the flames almost over the entire width of the tank. The burners can be spaced apart from each other so as to distribute the energy supply over a portion of the tank, i.e. about 50% of the length. The burners are also generally arranged in rows on both sides of the tank.

[0062] According to the application, the oxy-combustion heating device is fed with gas and / or hydrogen. In an embodiment, the oxy-combustion heating device is fed with at least 50% of hydrogen, and preferably at least 80% of hydrogen. More preferably, the oxy-combustion heating device is fed with 100% of hydrogen. This is advantageous because it allows to significantly reduce the overall C02emissions of the process. In an alternative, the oxy-combustion heating device is fed with more than 50% of gas, preferably at least 80% of gas, or even at least 100% of gas. This is advantageous because it allows to reach higher C02concentrations in the flue gas, thus facilitating and improving the C02capture step, but also limiting the impact on the chemical properties of the glass and on the furnace refractory. In a particular and advantageous embodiment of the application, the oxy-combustion heating device is fed with 50% of gas and 50% of hydrogen.

[0063] According to the application and as shown in Figure 1 The method for melting a glassifiable material to produce flat glass according to the application comprises a step of passing the melt from the refining tank to a working zone through an outlet device.

[0064] According to the application, the outlet device is located downstream of the refining tank for the molten glass to reach the working zone. According to an embodiment, the outlet device is generally constituted by a neck so as to direct the melt towards the working zone, generally called "working end". Alternatively, the outlet device is constituted by a throat so as to direct the melt towards the working zone comprising for example a forehearth. The working zone according to the application can comprise for example a conditioning zone in which thermal conditioning by controlled cooling is performed before the glass melt leaves said zone through the outlet to reach a forming zone. Such forming zone can comprise for example a float facility and / or a rolling facility.

[0065] According to another advantageous embodiment, the furnace of the application can comprise a removable wall (for example a skimmer rod from the side wall of the neck) at the neck so as to (i) can stop unmelted glassifiable material that can reach the end of the melting tank, thus avoiding these unmelted glassifiable material to pass through the neck towards the refining tank, and (ii) control the intensity of the backflow of the melt from the refining tank towards the melting tank or eliminate the backflow of the melt from the refining tank towards the melting tank.

[0066] According to yet another advantageous embodiment of the application, the furnace can comprise a removable wall at the neck (e.g. a blind wall through the roof of the neck) in order to increase the segmentation of the melting tank and the refining tank in terms of atmosphere and thermal radiation.

[0067] According to the application and as shown in Figure 1 the method for melting a glassifiable material to produce flat glass further comprises a step of capturing CO2 from the flue gas.

[0068] According to the application, the flue gas (i.e. the flue gas which undergoes the CO2 capture step) has a CO2 concentration of at least 35%. The CO2 concentration according to the application is the concentration defined for a dry flue gas (i.e. a flue gas having all its components except water (H2O)). Preferably, the flue gas in the present application has a CO2 concentration of at least 40%, more preferably a CO2 concentration of at least 50%, or even more a CO2 concentration of at least 60%. This is advantageous because the higher the CO2 concentration of the flue gas, the easier and more efficient the CO2 capture applied on this flue gas.

[0069] According to the application and as shown in Figure 1 the step of capturing CO2 from the flue gas comprises a compression and / or a dehydration step. The dehydration step corresponds to a water condensation and / or a drying step of the flue gas. The compression step corresponds to an increase of the pressure of the CO2, usually by using a compressor. The dehydration step can precede the compression step, and / or the dehydration step can accompany the compression step.

[0070] In particular, the step of capturing CO2 from the flue gas according to the application can be performed using a CO2 compression and purification unit (or CPU) in a known manner.

[0071] The flue gas according to the application can be recovered from (i) at least one main melting tank, (ii) at least one main melting tank and at least one auxiliary melting tank, (iii) the refining tank or (iv) the entire furnace for the CO2 capture. In particular, if the oxy-combustion heating device according to the application is only fed with hydrogen, the flue gas is advantageously recovered from at least one melting tank only (the flue gas discharged from the refining tank does not contain CO2) or from at least one main melting tank and at least one auxiliary melting tank.

[0072] After the step of capturing CO2 according to the application, the CO2 product has a pressure of about 35 bars at a temperature of 5°C to 40°C in gaseous form, suitable for pipeline transport, or in liquid form, with a pressure of about 100 bars, suitable for pipeline transport but also for truck or railway transport. For transport with trucks, a value of 15 bars at -35°C is also known to be suitable.

[0073] This simple and efficient CO2 capture method is highly advantageous because it allows avoiding the use of any sorbent / chemical agent which would lead to operating / energy costs and environmental issues, and because it allows achieving a cost-effective CO2 capture, making the whole inventive method economically viable.

[0074] According to a preferred embodiment, the step of capturing CO2 from the flue gas essentially consists of a compression and / or dehydration step.

[0075] According to an advantageous embodiment, the method of the application further comprises a step of eliminating acidic components from the flue gas. This step of eliminating acidic components is performed before or simultaneously with the step of capturing CO2 (for example before or simultaneously / with the compression and / or dehydration step).

[0076] The step of eliminating acidic components can comprise a step of desulfurization (or removal of so-called « SOx » compounds) of the flue gas. It can also comprise a step of removal of so-called « NOx » compounds, which can still be present even if the amount of these compounds is very low due to the use of oxygen as oxidizer. This is advantageous because it allows removing corrosive compounds (SOx, NOx) before transport, storage and / or use.

[0077] After the step of capturing CO2 according to the application, the CO2 product (for example in liquid form) can be transported by pipeline to its final destination, then stored / sequestered (for example at great depth in the sea or in geological formations, such as aquifers with high salt content), or alternatively exploited (for example for enhanced oil recovery, or for food / beverage applications, or for firefighting applications), in a known manner. Advantageously, the CO2 product obtained after the step of capturing CO2 can be used locally, to limit transport. This can be considered if the amount of CO2 captured is not too high, so that it can be absorbed by the local market.

[0078] According to an advantageous embodiment of the application, the method further comprises a step of preheating the cullet at least partially by recovering heat from the furnace, before feeding said cullet into at least one main melting tank and / or at least one auxiliary melting tank. According to this embodiment, the heat recovery from the furnace can be performed from flue gases coming from (i) the melting tanks, or (ii) the fining tanks, or (iii) the whole furnace (thus including flue gases from the melting tanks (auxiliary melting tanks and / or main melting tanks) and the fining tanks).

[0079] According to this embodiment and advantageously, the CO2 capture step can be performed from the flue gases used in the cullet preheating step.

[0080] Also according to this embodiment, if only a part of the cullet is melted in the step of melting in the auxiliary melting tank, and if the remaining part of the cullet (to be charged into the main melting tank) is preheated, the raw materials are charged into the at least one main melting tank with the preheated cullet through the same inlet device (which therefore means that the two types of vitrifiable materials are mixed before charging) or independently of the preheated cullet through a different inlet device.

[0081] Preferably, according to this embodiment, the maximum temperature of the cullet during the step of preheating the cullet is 450°C. This allows to avoid clogging problems.

[0082] According to the embodiment, the step of preheating the cullet can be carried out in at least one cullet preheater, for example of the type of one of those described in US 5526580 or DE 3716687.

[0083] Advantageously, the at least one cullet preheater can be located at an upstream portion of the at least one main melting tank or of the at least one auxiliary melting tank, either on the width or laterally on the length of said tank. Advantageously and in particular for the at least one main melting tank, the step of preheating the cullet can be carried out in at least two cullet preheaters, for example located at an upstream portion of the main melting tank, either on the width or laterally on the length of the main melting tank, on both sides. For example, the step of preheating the cullet can be carried out in four cullet preheaters, located at an upstream portion of the main melting tank, distributed either on the width or laterally on the length of the main melting tank (for example two on each side). Also for example, the step of preheating the cullet can be carried out in six cullet preheaters, located at an upstream portion of the main melting tank, either on the width or laterally on the length of the main melting tank (for example three on each side), or also in eight cullet preheaters, located at an upstream portion of the main melting tank, either on the width or laterally on the length of the main melting tank (for example four on each side).

[0084] According to yet another advantageous embodiment of the application, the raw materials comprise less than 25% by weight of carbonate compounds. By "carbonate compounds" it is meant for example alkali metal carbonates and alkaline earth metal carbonates. Preferably, the raw materials comprise less than 20% by weight, more preferably less than 10% by weight, even less than 5% by weight of carbonate compounds. The raw materials can advantageously be free of any carbonate compounds.

[0085] This embodiment is advantageous in that it allows to reduce the fraction of CO2 emissions resulting from decarburization of raw materials compared to the classical glass melting process in which sodium and calcium are generally essentially sourced from sodium carbonate Na2CC>3, limestone CaCC>3 and dolomite CaMg(C03)2. According to this embodiment, the alkali and alkaline earth metal sources can advantageously be at least partially present in the form of oxides or hydroxides such as CaO, CaO.MgO (calcined dolomite), Ca(OH)2, Mg(OH)2, NaOH, KOH.

[0086] According to a very preferred embodiment of the application, the method for melting a glassable material to produce flat glass comprises the following steps: - providing a furnace comprising (i) at least one main melting tank comprising electric heating means, (ii) at least one auxiliary melting tank, (iii) a fining tank provided with oxygen combustion heating means, (iv) at least one neck separating the at least one main melting tank and the fining tank, (v) inlet means located at the at least one main melting tank, (vi) outlet means located downstream of the fining tank; - charging a glassable material into the at least one main melting tank and / or into the at least one auxiliary melting tank having the inlet means, said glassable material comprising (i) raw materials, the raw materials having less than 25% by weight of carbonate compounds, and (ii) cullet, the amount of cullet being at least 10% by weight of the total amount of glassable material, - prior to charging said cullet into the at least one main melting tank and / or into the at least one auxiliary melting tank, preheating the cullet at least partially by recovering heat from the furnace; - melting the glassable material in the at least one main melting tank by heating with the electric heating means, and flowing the melt through the neck to the fining tank, the electric input fraction of the method ranging from 50% to 85%; - melting at least a fraction of the cullet in the at least one auxiliary melting tank, and flowing the melt to the neck or to the fining tank; - fining the melt in the fining tank by heating with the oxygen combustion heating means, the oxygen combustion heating means being fed with a gas and / or hydrogen; - flowing the melt from the fining tank to a working area through the outlet means; - capturing CO2 from a flue gas having a CO2 concentration higher than 35%, the step comprising a compression and / or a dehydration step.

[0087] All the previously described specific embodiments related to each step of the method of the application are applicable to this last very preferred embodiment.

[0088] The person skilled in the art realizes that the present application is by no means limited to the preferred embodiments described above. Rather, many modifications and variations are possible within the scope of the appended claims. It should further be noted that the present application relates to all possible combinations of features and preferred features described herein and claimed in the claims.

Claims

1. A method for melting a vitrifiable material to produce flat glass, the method comprising the following steps: - Provide a furnace comprising (i) at least one main melting tank including an electric heating device, (ii) at least one auxiliary melting tank, (iii) a refining tank provided with an oxygen combustion heating device, (iv) at least one neck separating the at least one main melting tank and the refining tank, (v) an inlet device located at the at least one main melting tank, and (vi) an outlet device located downstream of the refining tank; - The vitrifiable material is fed into at least one main melting tank and / or at least one auxiliary melting tank having the inlet device, the vitrifiable material comprising raw materials and crushed glass, the amount of the crushed glass being at least 10% by weight of the total amount of the vitrifiable material; - The vitrifiable material is melted in the at least one main melting tank by heating with the electric heating device, and the melt is allowed to flow through the neck to the refining tank; - Melt at least a portion of the sharded glass in the at least one auxiliary melting tank; - The melt in the clarification tank is clarified by heating with the oxygen combustion heating device, which is supplied with gas and / or hydrogen; - Allow the melt to flow from the settling tank to the working area through the outlet device; - Capture CO2 from flue gas having a CO2 concentration of at least 35%; Its features are: - Its electrical input fraction ranges from 50% to 85%; -The steps for capturing CO2 from flue gas include compression and / or dehydration steps; The method includes the step of causing the melt to flow from the at least one auxiliary melting tank to the neck or the refining tank.

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

3. The method for melting vitrifiable materials according to the preceding claims, characterized in that, The oxygen combustion heating device is supplied with at least 50% hydrogen, and preferably at least 80% hydrogen.

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

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

6. The method for melting a vitrifiable material according to the preceding claims, characterized in that, The steps for capturing CO2 from flue gas consist essentially of compression and / or dehydration steps.

7. The method for melting vitrifiable materials according to the preceding claims, characterized in that, The method further includes the step of removing acidic components from the flue gas.

8. The method for melting a vitrifiable material according to the preceding claim, characterized in that, The step of removing acidic components from the flue gas is performed before or simultaneously with the step of capturing CO2.

9. The method for melting a vitrifiable material according to the preceding claims, characterized in that, The method further includes a step of preheating the cullet by recovering heat from the furnace, at least in part, before feeding the cullet into the at least one main melting tank and / or the at least one auxiliary melting tank.

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

11. The method for melting a vitrifiable material according to the preceding claim, characterized in that, The raw materials contain less than 25% carbonate compounds by weight.

12. A furnace for performing the method according to claims 1 to 11.

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