CO2 capture process integrated into glass melting

Abstract

Title: CO2 capture method integrated into glass melting Glass melting method comprising: introducing a vitrifiable solid charge (11) into a furnace (1), heating and melting the charge (11) in the furnace (1) so as to obtain molten glass (17), removing the molten glass (17) from the furnace (1) and removing a gaseous effluent (20) containing CO2 from the furnace (1), the charge (11) comprising at least one carbonate undergoing a dissociation reaction and releasing gaseous CO2 (18) when the charge (11) is heated and melted, the gaseous effluent (20) removed from the furnace (1) being used to produce, by carbonation with the CO2 present in the gaseous effluent (20), at least one additive (33) in the form of an alkali metal or alkaline earth metal carbonate, at least a portion of which is incorporated into the charge (11) which is introduced into the oven (1). Figure of the abstract: Fig. 1

Description

Title of the invention: CO capture method 2 integrated into glass fusion

[0001] The present invention relates to the manufacture of glass.

[0002] Greenhouse gas emissions contribute significantly to the global warming. One of these greenhouse gases is CO2.

[0003] It is therefore important to reduce CO2 emissions into the atmosphere from industrial sites as much as possible.

[0004] Glass furnaces are among the industrial installations that emit CO2.

[0005] For the manufacture of glass, a vitrifiable solid charge with controlled composition and adapted to the nature of the glass to be produced is introduced into a furnace and melted there. The molten glass thus obtained is removed from the furnace and shaped according to the desired final product / its final application, for example flat glass, hollow glass, optical glass, etc. A gaseous effluent is also removed from the furnace.

[0006] Glass melting is energy intensive. In most cases, at least part of the energy required is provided by the combustion of fuels and in particular by the combustion of carbonaceous fuels such as natural gas, fuel oil and coal. The combustion of a carbonaceous fuel generates a flue gas containing CO2. Said flue gas is part of the off-gas discharged from the furnace. Other ingredients of the off-gas include: water vapor generated by the combustion as well as chemical species released by the charge in the furnace, said chemical species also including CO2.

[0007] Indeed, the vitrifiable solid filler is also a source of CO2 emissions. In addition to silicon oxide (SiO2), the filler typically also contains functional additives, such as fluxes, stabilizers, colorants, etc.

[0008] Some of these additives, including alkali metal and / or alkaline earth metal carbonates, dissociate inside the furnace releasing CO2 into the atmosphere above the charge in the furnace.

[0009] Therefore, even in the absence of combustion of a carbonaceous fuel in the furnace, or even in the absence of combustion at all in the furnace, CO2 is typically present in the gaseous effluent generated during glass melting.

[0010] For the future of our planet, it is important to reduce emissions, such as industrial emissions, of greenhouse gases, such as CO2.

[0011] Different processes have been developed allowing, by means of physical processes (for example: cryogenic separation) and / or chemical processes (for example: looping chemical), to capture CO2 present in gaseous effluents, and in particular in industrial gaseous effluents.

[0012] However, currently available CO2 capture processes are only cost-effective for the treatment of high flow rates of gaseous effluents, such as those generated by large industrial sites.

[0013] The quantities of off-gas generated by glass melting furnaces, including large continuous furnaces, such as so-called float furnaces (float glass manufacturing furnaces), are not large enough to allow such cost-effective CO2 capture with current technologies.

[0014] Since any CO2 emission contributes to the greenhouse gas effect, it would be desirable to be able to reduce CO2 emissions from glass melting installations for which CO2 capture by known CCUS processes is not cost-effective.

[0015] The present invention proposes to respond at least in part to this problem.

[0016] The present invention provides a method of melting glass comprising a step (called step a.) of introducing a vitrifiable solid charge into a furnace, a step (called step b.) of heating and melting the charge in the furnace so as to obtain molten glass, a step (called step c.) of removing the molten glass from the furnace and a step (called step d.) of removing a gaseous effluent from the furnace.

[0017] The charge introduced into the furnace in step a comprises at least one alkali or alkaline earth metal carbonate.

[0018] During step b., said at least one carbonate undergoes a dissociation reaction. Gaseous CO2 is then released.

[0019] The gaseous effluent discharged from the furnace during step d. contains CO2. The CO2 present in the gaseous effluent includes gaseous CO2 released following the dissociation described above of the carbonate(s) in the feedstock, but may also include gaseous CO2 of other origin, for example CO2 generated when a carbonaceous fuel is burned to heat the furnace.

[0020] According to the present invention, the method also comprises a step e., in which the gaseous effluent, discharged from the furnace during step d., is used to produce, by carbonation with the CO2 present in said gaseous effluent, at least one additive in the form of alkali metal or alkaline earth metal carbonate. At least a portion of the additive thus produced is incorporated into the charge which is introduced into the furnace in step a.

[0021] In this way, at least a portion of the CO2 present in the gaseous effluent discharged from the furnace is captured by the carbonation reaction and recycled to the furnace instead of being emitted into the atmosphere.

[0022] In the present context, the term 'functional additive' means an ingredient of the solid filler, other than sand (SiO2). Said functional additives are added to the filler in order to improve the melting and / or refining and / or forming of the glass (for example in the case of glass fibers), or in order to modify the properties of the solid glass product obtained (for example: the refractive index, the thermal shock resistance, the Young's modulus, etc.).

[0023] We can thus add to the charge: • sodium carbonate, if necessary accompanied by potassium carbonate, as a flux, • calcium carbonate, where appropriate accompanied by magnesium carbonate, as a stabilizer, • aluminum oxide to increase hydrolytic resistance, • lead oxide, to increase density, refractive index and glass shine, • boron oxide as a network former providing greater thermal stability, • metal oxides of transition elements and / or certain lanthanides as a colorant or decolorant, and • redox additives such as carbon and sodium sulfate.

[0024] The reactor in which the carbonation of step e. takes place is called a 'carbonator'. The carbonation is advantageously carried out by direct contact between the gaseous effluent discharged from the furnace with the oxide and / or hydroxide of the alkali metal or alkaline earth metal of the carbonate to be produced inside the carbonator.

[0025] Thus, the carbonation can be carried out by direct contact between the gaseous effluent and the oxide of the alkali metal or alkaline earth metal of the carbonate, by direct contact between the gaseous effluent and the hydroxide of the alkali metal or alkaline earth metal of the carbonate or even by direct contact between the effluent and a mixture of the oxide and the hydroxide of the alkali metal or alkaline earth metal of the carbonate.

[0026] For example, calcium carbonate can be produced as an additive by contacting the CO2-containing gaseous effluent with CaO and / or Ca(OH)2.

[0027] When, during step e., it is envisaged to produce carbonates of several alkali and / or alkaline earth metals, these carbonates can be produced in separate carbonators or gaseous effluent containing CO2 can be brought into contact with the oxide and / or hydroxide of several alkali and / or alkaline earth metals in the same carbonator.

[0028] The carbonator may be a batch carbonator, a fluidized bed carbonator or an entrained bed carbonator.

[0029] In order to accelerate carbonation, it is appropriate to maximize the contact surface between, on the one hand, the gaseous effluent and the CO2 it contains, and, on the other hand, the oxide / hydroxide of the alkali or alkaline-earth metal. Indeed, two phases are distinguished in the carbonation reaction: a first phase with very rapid reaction, at the contact surface between the gaseous CO2 and the solid oxide / hydroxide and a second phase with slower reaction, the speed of which is controlled by the diffusion of CO2 in the solid phase.

[0030] It is thus appropriate to use an oxide / hydroxide with a small particle size, for example a particle size of less than 1 mm, preferably between 100 and 200 pm. It is also possible to improve the contact between the gaseous effluent and the oxide by using a porous oxide, for example an oxide with a porosity of at least 0.078 cm3 / Â / g. Advantageously, an oxide having a specific surface area (BET) greater than 17 is used.

[0031] Carbonation / decarbonation is an equilibrium chemical reaction (reversible reaction). Therefore, reaction conditions should be chosen for the carbonator that favor carbonation over decarbonation. An important parameter in this context is the temperature in the carbonator. The temperature in the carbonator is kept below temperatures that favor decarbonation. Carbonation in the carbonator generally takes place at a temperature below 1050°C, preferably below 950°C. It has proven advantageous to carry out carbonation in the carbonator at a temperature between 500°C and 950°C, preferably between 550°C and 800°C, more preferably between 550°C and 700°C.This temperature can also be selected depending on the alkali or alkaline earth metal of the carbonate to be produced as well as depending on the use of the oxide or hydroxide of said metal as raw material for carbonation.

[0032] The temperature in the carbonator is, to a large extent, determined by the temperature at which the gaseous effluent is introduced into the carbonator. The temperature at which the gaseous effluent is introduced into the carbonator is advantageously between 600°C and 1000°C, preferably between 650°C and 950°C, more preferably between 700°C and 900°C.

[0033] The temperature of the gaseous effluent at the outlet of the furnace is generally such that it favors decarbonation rather than carbonation.

[0034] According to one embodiment of the invention, the gaseous effluent is cooled to a predetermined temperature or temperature range before its introduction into the carbonator. This predetermined temperature or said predetermined temperature range being, as indicated above, advantageously between 600°C and 1000°C, preferably between 650°C and 950°C, more preferably between 700°C and 900°C.

[0035] Before its introduction into the carbonator, the gaseous effluent may in particular be cooled in one or more heat exchangers.

[0036] In the present context, the term 'heat exchanger' is understood to mean an apparatus in which thermal energy is transferred from a first fluid, heat transfer fluid or fluid to be cooled, to a second fluid, fluid to be heated, the two fluids being separated from each other by one or more walls so that these fluids do not mix, the thermal energy being transferred from the first fluid to the second fluid through said wall or walls.

[0037] According to one embodiment of the invention, thermal energy extracted from the gaseous effluent during its cooling is recovered and used as an energy source. It is thus possible to use this thermal energy extracted from the gaseous effluent to heat an oxidant and / or a fuel.

[0038] It is thus possible to heat an oxidant and / or a fuel in the heat exchanger(s) used to cool the gaseous effluent, the gaseous effluent then being the first fluid, i.e. heat transfer fluid, and the oxidant, respectively the fuel being the second fluid, i.e. fluid to be heated.

[0039] The heat exchange between the gaseous effluent and the oxidant / fuel may be a direct heat exchange. In this case, the gaseous effluent and the oxidant, respectively the fuel, are located on one side and in direct contact with the wall(s) through which the thermal energy is transferred.

[0040] The heat exchange between the gaseous effluent and the oxidant / fuel can also be an indirect heat exchange, passing through an intermediate fluid. In this case, thermal energy is first transferred by direct heat exchange between the gaseous effluent and the intermediate fluid and the thermal energy thus transferred to and absorbed by the intermediate fluid is then transferred by direct heat exchange from the intermediate fluid to the oxidant, respectively the fuel.

[0041] As indicated above, it is known to heat the charge in a glass melting furnace at least partially by the heat generated by the combustion of a fuel with an oxidant.

[0042] When thermal energy extracted from the gaseous effluent is used as an energy source for heating an oxidant and / or a fuel, the heated oxidant and / or the heated fuel thus obtained is / are advantageously used to heat the charge in the furnace by combustion using the heated oxidant and / or the heated fuel as combustion reactant(s). By recycling thermal energy discharged from the furnace with the gaseous effluent in this way, the energy efficiency of the process according to the invention is improved.

[0043] In the context of the present application, the terms "oxidant" and "oxidizer" are synonymous and used interchangeably.

[0044] The fuel may be a carbon fuel, such as natural gas or biogas.

[0045] By using hydrogen as fuel, the generation of CO2 by its combustion is avoided. It is also possible to combine the combustion of a carbon fuel with the combustion of hydrogen.

[0046] In the context of limiting greenhouse gas emissions, the use of blue hydrogen or green hydrogen is preferred. A distinction is made between gray hydrogen, green hydrogen and blue hydrogen. The production of gray hydrogen has a CO2 emission intensity during hydrogen production of up to 9.3 kg CO2 / kg H2. Gray hydrogen can, for example, be produced by steam methane reforming without CCUS (Carbon Capture and Utilization or Sequestration). The production of blue hydrogen has a CO2 emission intensity of up to 0.97 kg CO2 / kg H2. Blue hydrogen can, for example, be produced by steam methane reforming with CCUS. The production of green hydrogen does not generate CO2 emissions. Green hydrogen can, for example, be produced by electrolysis of water using renewable energy (see van Cappellen, L., Croezen, H. & Rooijers, F. “Feasibility Study into Blue Hydrogen”. CE Delft, 2018).

[0047] The oxidant may be air, oxygen-enriched air, or industrial oxygen. In the present context, "industrial oxygen" means a gas having an oxygen content of 90 to 100% vol, preferably 95 to 100% vol. The oxidant may be supplied to the furnace as such or after being mixed with another gas. This is particularly the case when "artificial air" consisting of a mixture of industrial oxygen and an essentially inert gas, such as recycled off-gas, is supplied to the furnace. The use of such a mixture may in particular allow for better coverage of the charge by the flame(s) in the furnace.

[0048] It is also possible to provide at least part of the heat for heating the charge in step b. by electrical heating, for example by means of electrodes immersed in the molten charge. Such electrical heating may be the sole heat source of the furnace or may be combined with other heat sources, such as in particular the combustion of a fuel with an oxidant.

[0049] The method according to the invention applies to different glass melting furnaces. Thus, the furnace can be a batch furnace, a semi-batch furnace or a continuous furnace.

[0050] The additive produced in step e. of the present process and introduced into the furnace with the charge in step a. is generally a functional additive. In the furnace, the alkali or alkaline earth metal carbonate combines and reacts with the sand (SiO2), typically from 800°C.

[0051] The carbonate produced in step e. can thus be sodium carbonate, calcium carbonate, potassium carbonate, magnesium carbonate, lithium carbonate, barium carbonate or a mixture or combination of at least two of said carbonates.

[0052] For example, when sodium carbonate and calcium carbonate are added to the feed, the following reactions are observed: - from 800°C:

[0053] Na2CO3 + CaCO3 -> Na2Ca(CO3)2

[0054] Na2Ca(CO3)2 + 2SiO2 -> Na2SiO3 + CaSiO3 + 2CO2 - from 1000°C:

[0055] Na2CO3 + SiO2 -> Na2SiO3 + CO2

[0056] CaCO3 + SiO2 -> CaSiO3 + CO2

[0057] The silicates thus formed participate in the formation of glass in the molten phase.

[0058] The CO2, generated in significant quantity, partially solubilizes in the molten glass. Another part of the generated CO2 forms bubbles which escape from the molten glass in an upward movement and thus contribute to the refining of the molten glass.

[0059] In glass production, sodium carbonate is used as a flux: it lowers the melting temperature of the feedstock. Sodium carbonate can be produced in step e. by carbonation of Na2O and / or NaOH:

[0060] Na2O + CO2 Na2CO3

[0061] 2NaOH + CO2 Na2CO3 + H2O

[0062] Potassium carbonate is also a flux. Potassium carbonate can be produced in step e. by carbonation of K2O and / or KOH:

[0063] K2O + CO2 K2CO3

[0064] 2KOH + CO2 K2CO3 + H2O

[0065] Calcium carbonate is the main stabilizer of glass. It provides chemical protection to the glass and protects it in particular from the effects of water. Calcium carbonate can be produced in step e. by carbonation of CaO and / or Ca(OH)2:

[0066] CaO + CO2 CaCO3

[0067] Ca(OH)2 + CO2 CaCO3 + 2H2O

[0068] Magnesium carbonate increases the viscosity of the glass in the molten state and promotes the electrical resistivity, thermal stability and acid resistance of the glass. Magnesium carbonate can be produced in step e. by carbonation of MgO and / or Mg(OH)2:

[0069] MgO + CO2 MgCO3

[0070] Mg(OH)2 + CO2 MgCO3 + 2H2O

[0071] Lithium carbonate is another flux that can lower the melting temperature. It also helps to reduce the coefficient of thermal expansion of the glass. Lithium carbonate can be produced in step e. by carbonation of Li2O and / or LiOH:

[0072] Li2O + CO2 Li2CO3

[0073] 2LiOH + CO2 Li2CO3 + H2O

[0074] Barium carbonate is another flux used in glass manufacturing. It also acts as a matting agent to reduce the gloss of the finished product. Barium carbonate can be produced in step e. by carbonation of BaO and / or Ba(OH)2:

[0075] BaO + CO2 BaCO3

[0076] Ba(OH)2 + CO2 BaCO3 + 2H2O

[0077] During step e. of the process according to the invention, the CO2 present in the gaseous effluent discharged from the furnace can in particular be used to produce one or more of the following functional additives: sodium carbonate, calcium carbonate and potassium carbonate.

[0078] According to one embodiment of the invention, the method is used for the manufacture of soda-lime glass or borosilicate glass.

[0079] In the case of soda-lime glass, step e. of the process is advantageously used to produce at least one carbonate chosen from sodium carbonate, calcium carbonate and barium carbonate, preferably chosen from sodium carbonate and calcium carbonate, at least a portion of the carbonate(s) thus produced being added to the solid filler as a functional additive.

[0080] In the case of borosilicate glass, step e. of the process is advantageously used to produce at least one carbonate chosen from sodium carbonate, potassium carbonate, calcium carbonate and magnesium carbonate, preferably chosen from sodium carbonate and potassium carbonate, at least a portion of the carbonate(s) thus produced being added to the solid feedstock as a functional additive.

[0081] The molten glass discharged from the furnace in step c. of the process can be used for the manufacture of flat glass, such as glazing, hollow glass, such as glasses, bottles and flasks, or fiberglass, such as thermal insulation glass fibers, reinforcing glass fibers and optical glass fibers, each product having a glass composition suitable for its use. The carbonate produced in step e. of the process and added to the solid filler is advantageously chosen according to said composition.

[0082] The present invention and its advantages are illustrated by the following examples, reference being made to Figures 1 and 2, which are schematic representations of two embodiments of the method according to the invention.

[0083] In order to comply with environmental standards against global warming, industrial sites must reduce their greenhouse gas emissions into the atmosphere, such as CO2, as much as possible.

[0084] Glass furnaces are among the industries that emit CO2.

[0085] As already mentioned above, glass melting in the majority of cases uses the combustion of fossil carbon fuels such as natural gas, fuel oil or coal as an energy source to carry out melting and vitrification. This combustion produces CO2.

[0086] As also mentioned above, CO2 emissions from the process also come from the decarbonation of one or more carbonates present in the raw material.

[0087] Replacing fossil fuels with a non-carbon fuel, such as hydrogen, or with non-combustion heating, in particular electric heating, therefore makes it possible to reduce CO2 emissions from glass melting processes, but does not eliminate them.

[0088] For hollow glass which contains 11% CaO in its composition, 86.42 kg of CO2 is produced by the decomposition of CaCO3 per tonne of flint hollow glass produced.

[0089] For an average-sized furnace producing 300t / d of glass, this represents 26t / d of CO2 from the batch. For a flat glass furnace producing around 1000t / d, this CO2 emission amounts to 65t / d.

[0090] The need to reduce CO2 emissions from glass melting furnaces therefore remains relevant.

[0091] For fixed industrial sites emitting significant CO2 flows, CCS (Carbon Capture and Sequestration or Carbon Capture and Storage) is recommended. CCS is a process comprising the steps of capturing the CO2 present in the emissions, liquefying the captured CO2 and sequestering the liquefied CO2, for example in cavities that previously contained natural gas. It is commonly accepted that CO2 sequestration can only be a transitional solution before finding long-term solutions. An alternative to CCS is CCU (Carbon Capture and Utilization). CCU differs from CCS in that the liquefied carbon is not sequestered for an indefinite period, but is used in another industrial process, for example in the production of sparkling drinks.For industrial operation, CCS and CCU require not only flow rates. significant amounts of gaseous effluents containing CO2, but also that the effluents have a composition such that extraction and purification of the CO2 present in the effluents are possible without exorbitant costs.

[0092] Compared to thermal power generation plants, the amount of CO2 emitted by a glass melting furnace, with or without fossil fuel combustion, is relatively low. What is more, the gaseous effluent from a glass melting furnace contains components, including components also from the feedstock, making the capture of CO2 at the required purity difficult.

[0093] Under these circumstances, the investments required to organize CCS or CCU for a glass melting furnace are not profitable.

[0094] The present invention provides a more cost-effective means for reducing CO2 emissions from a glass melting furnace.

[0095] As illustrated in [Fig. 1], a charge 11 containing vitrifiable material and / or cullet, as well as functional additives, including in particular the stabilizer CaCO3, is introduced into a melting furnace 1.

[0096] Inside the furnace 1, the charge 11 is melted and forms a glass bath 15. Above the bath 15 is a gaseous atmosphere 16.

[0097] The molten glass present in the bath 15 is refined before being evacuated from the furnace 1 in the form of a flow of liquid glass 17 and being directed towards a forming installation (not illustrated in the figures) for the manufacture of the final product.

[0098] The furnace 1 is heated by combustion of a fuel 12 with an oxidant 13. The gases 14 generated by the combustion are evacuated from the furnace 1 in the form of a gaseous effluent 20.

[0099] Fuel 12 may be a carbon fuel. However, in the illustrated embodiment, fuel 12 is green hydrogen, thereby reducing CO2 emissions per ton of glass from the melting furnace by avoiding the generation of CO2 by combustion.

[0100] Despite this measure, CO2 is indeed present in the gaseous effluent 20 discharged from the furnace 1, more particularly because of the decarbonation during the melting of the charge 11 and the refining of the molten glass in the glass bath 15 of the carbonate(s) present in the charge 11, in particular calcium carbonate. This decarbonation generates gaseous CO2, at least a portion 18 of which passes into the gaseous atmosphere 16 and is therefore discharged from the furnace 1 by the gaseous effluent 20.

[0101] In order to further reduce CO2 emissions into the atmosphere without having to resort to expensive processes such as CCS or CCU, the gaseous effluent 20 discharged from the furnace 1 is used to produce, by carbonation with the CO2 present in the gaseous effluent 20, at least one additive in the form of alkali metal carbonate or of alkaline earth metal, at least part of which is introduced into furnace 1 with charge 11.

[0102] For this, the gaseous effluent 20 containing CO2 is introduced into a carbonator 30, in which the gaseous effluent 20 is brought into contact with CaO 31 under conditions, and in particular the temperature and residence time conditions, such that at least 50%, preferably at least 60% and more preferably at least 70% of the CO2 present in said effluent 20 reacts with the CaO 31 with the formation of CaCO3.

[0103] A single carbonator 30 is shown in [Fig.l]. The use of several carbonators is also possible. In the figure, the only carbonate formed by carbonation with the CO2 present in the gaseous effluent 20 is CaCO3. The CO2 present in the gaseous effluent 20 can, in a similar manner, be used for the production of another alkali or alkaline earth metal carbonate usable as a functional additive in the glass melting furnace 1, or even for the production of a combination of such carbonates.

[0104] The CO2-depleted residue 32 of the gaseous effluent is evacuated from the carbonator 30, as well as the carbonated product 33.

[0105] The conditions, and in particular the temperature and residence time conditions, in the carbonator 30 are chosen so that at least 50%, preferably at least 60% and more preferably at least 70% of the CO2 present in said effluent 20 reacts with the ground CaO 31 with formation of CaCO3.

[0106] The quantity of CaO 31 introduced into the carbonator 30 and its contact surface area with the gaseous effluent 20 are chosen so as to convert a maximum of CaO into CaCO3.

[0107] In order to increase this contact surface area, porous CaO in the form of particles is advantageously chosen.

[0108] Thus, in the embodiment illustrated in [Fig.l], porous CaO having a pore volume greater than 0.078 cm / A / g, also called "quicklime", and available on the market. This porous CaO is ground to a particle size less than 1 mm, preferably around 137 pm, so as to obtain a specific surface area (BET) greater than 17. This ground CaO 31 is then introduced into the carbonator 30. Inside said carbonator 30.

[0109] In the embodiment illustrated in [Fig.l], carbonator 30 is a "batch" carbonator. The duration of contact between the gaseous effluent 20 and the ground CaO 31 is greater than 4 minutes. The temperature in carbonator 30 is between 500°C and 650°C.

[0110] At least a portion of the carbonated product 33 discharged from the carbonator 30 is incorporated into the charge 11 which is introduced into the furnace 1, if necessary with a supplement 34 of CaCO3. A significant portion of the CO2 from the gaseous effluent 20 is thus trapped and the CaCO3 obtained will serve as raw material in furnace 1.

[0111] To the extent that the carbonation of the CaO is not complete and it proves necessary to limit the quantity of unconverted CaO that is added to the feedstock 11 and / or that the quantity of carbonate formed in the carbonator 30 exceeds the quantity to be added to the feedstock 11, a portion 35 of the carbonated product 33 is extracted from the recycle and is not added to the feedstock 11.

[0112] As indicated above, the temperature in the carbonator 30 is chosen so as to promote the reaction of the CO2 present in the effluent 20 with the CaO. This temperature is for example between 500°C and 650°C. However, the gaseous effluent 20 is evacuated from the furnace 1 at a temperature (typically between 1400°C and 1550°C, or even higher) promoting decarbonation rather than carbonation.

[0113] The temperature in the carbonator 30 is largely determined by the temperature of the gaseous effluent 20 at the inlet of the carbonator 30.

[0114] In order to ensure a suitable temperature in the carbonator 30, it is proposed to cool the gaseous effluent 20 between its exit from the furnace 1 and its entry into the carbonator 30.

[0115] In the embodiment illustrated in [Fig. 1], for this purpose, the gaseous effluent 20 passes through a heat exchanger 40 located on the flow path of the gaseous effluent 20 between the furnace 1 and the carbonator 30. The operation of said heat exchanger 40 is regulated so that the gaseous effluent 20 enters the carbonator 30 at a suitable temperature.

[0116] [Fig.2] shows an advantageous embodiment in which the thermal energy extracted from the gaseous effluent 20 in the heat exchanger 40 is used to preheat at least a portion of the fuel 12 and / or at least a portion of the oxidant 13 upstream of the furnace 1.

[0117] In order to regulate the portion 12a of the fuel 12 and / or the portion 13a of the oxidant 13 sent to the heat exchanger, a distribution valve 52 is installed on the flow path of the fuel 12 to the furnace 1 and / or a distribution valve 53 is installed on the flow path of the oxidant 13 to the furnace 1. The portion 12b of the fuel 12 and the portion 13b of the oxidant 13 which is not thus directed to the heat exchanger 40 is introduced into the furnace 1 without passing through the exchanger 40.

[0118] By thus regulating the portion 12a of the fuel 12 and / or the portion 13a of the oxidant 13 introduced into the exchanger 40, it is possible to regulate the cooling level of the gaseous effluent 20 in the exchanger 40 while reusing the thermal energy extracted from the gaseous effluent 20 in the glass melting furnace 1.

[0119] The distribution between the portions 12a and 12b and / or between the portions 13a and 13b can be regulated automatically, for example as a function of the temperature of the gaseous effluent 20 at the outlet of the exchanger 40 or at the inlet of the carbonizer 30.

[0120] It is thus possible to preheat both fuel 12a and oxidant 13a, for example in a single exchanger 40 or in two separate exchangers 40, or to preheat only fuel 12a or only oxidant 13a.

Claims

1. Claims Glass melting process comprising the following steps: a. introduction of a vitrifiable solid charge (11) into a furnace (1), this charge (11) comprising at least one carbonate, b. heating and melting the charge (11) in the furnace (1) so as to obtain molten glass (17), the at least one carbonate undergoing a dissociation reaction and releasing gaseous CO2 (18), c. evacuation of the furnace (1) of the molten glass (17), d. evacuation from the furnace (1) of a gaseous effluent (20) containing CO2, e. use of the gaseous effluent (20) discharged from the furnace (1) to produce, by carbonation with the CO2 present in the gaseous effluent (20), at least one additive (33) in the form of alkali metal or alkaline earth metal carbonate, by bringing the gaseous effluent (20) into contact in a carbonator (30) with the oxide (31) and / or the hydroxide of the alkali metal or alkaline earth metal corresponding to the carbonate to be produced, the gaseous effluent (20) being cooled in one or more heat exchangers (40) before being introduced into the carbonator (30), • at least a portion of said additive (33) produced in step e. being incorporated into the charge (11) which is introduced into the furnace (1) in step a., characterized: • in that the heat for heating the load (11) in step b. is supplied: • by combustion of a fuel (12) with an oxidant (13), the fuel (12) being hydrogen Or • by combustion of a fuel (12) with an oxidant (13), the fuel (12) being hydrogen and by electrical heating, • in that, before being introduced into the carbonator (30), the gaseous effluent (20) is cooled to a predetermined temperature or temperature range, said predetermined temperature or said predetermined temperature range being between 600°C and 1000°C • and in that, during the cooling of the gaseous effluent (20), thermal energy extracted from the gaseous effluent (20) is used to heat the oxidant (13) and / or the fuel (12), the heated oxidant (13) and / or the fuel (12) heated during the cooling of the gaseous effluent (20) being used to heat the charge (11) in the furnace (1) by combustion.

2. The method of claim 1, wherein the carbonator (30) is a batch carbonator, a fluidized bed carbonator or an entrained bed carbonator.

3. A method according to claim 1 or 2, wherein the carbonation takes place in the carbonator (30) at a temperature between 500°C and 950°C, preferably between 550°C and 800°C, more preferably between 550°C and 700°C.

4. A method according to one of claims 1 to 3, wherein the predetermined temperature or predetermined temperature range is between 650°C and 950°C, preferably between 700°C and 900°C.

5. Method according to one of the preceding claims, in which the oxidant (13) is chosen from air, oxygen-enriched air.

6. A method according to one of the preceding claims, wherein at least part of the heat for heating the load (11) in step b. is provided by electrical heating.

7. A method according to any preceding claim, wherein the furnace (1) is a batch furnace, a semi-batch furnace or a continuous furnace.

8. Method according to any one of the preceding claims, in which at least one additive (33) chosen from sodium carbonate, calcium carbonate, potassium carbonate, magnesium carbonate, lithium carbonate, barium carbonate is produced during step e.

9. A method according to claim 8, wherein at least one additive (33) selected from sodium carbonate, calcium carbonate and potassium carbonate is produced during step e.

10. A method according to one of the preceding claims, wherein the glass is selected from soda-lime glasses and borosilicate glasses.

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