GLASS MANUFACTURING PROCESS WITH THE BLUE SODA LOOP

Abstract

The invention relates to a process for producing soda glass with steps involving melting a batch of glass including sodium carbonate and refining the molten glass, producing CO2-containing emissions, which includes the following steps, in order and in series: (a) a step where this emissions are heated to a temperature above 250°C and brought into contact with a sodium source, producing sodium carbonate; (b) a step where the sodium carbonate is collected; and (c) a step where at least a portion of the collected sodium carbonate is used as a raw material in the glass batch. This process has the advantage of reducing CO2 emissions.

Description

GLASS MANUFACTURING PROCESS WITH A GREEN SODA LOOPFIELD OF THE INVENTION

[0001] The present invention relates to a glass manufacturing process aimed at continuously supplying glass products (for example, a float or rolling installation to produce flat glass) and involving melting of raw materials especially raw materials including soda ash. In particular, the present invention relates to a glass manufacturing process that provides a lot of advantages, especially in terms of CO2 emissions.

[0002] The invention is more particularly related, but not limited, to glass manufacturing process involving large production capacities, i.e. up to 1000 tons / day or more.BACKGROUND OF THE INVENTION

[0003] The global warming and the requirements for CO2 emissions reduction increase the pressure on glass manufacturers, as well as CO2 taxes that could become soon a severe threat on competitiveness in the glass sector.

[0004] In that context of urgent action to reduce carbon emissions, the glass industry has invested a lot since years in the decarbonization of its manufacturing processes, with the view to produce glass goods that are fit for a sustainable, resource-efficient, low-carbon society.

[0005] The GHG (Green House Gas) Protocol Corporate Standard classifies a company's GHG emissions into three "scopes" :Scope 1 emissions are direct emissions from owned or controlled sources. For glass industry, it corresponds to direct emissions that occur from fossil fuel combustion and raw materials decarbonization;Scope 2 emissions are indirect emissions from the generation of purchased energy. For glass industry, it corresponds to indirect emissions from the generation of acquired and consumed electricity;Scope 3 emissions are indirect emissions (not included in scope 2) that occur upstream or downstream in the value chain of the company. For glass industry, it corresponds to indirect emissions coming, for example, from raw materials production and transport, fuel extraction and supply and product transport.

[0006] Scope 1 emissions represent a major part (~50%) of CO2 emissions in a glass manufacturing activities.

[0007] For the emissions attributed to fossil fuel combustion which represents about 35 % of scope 1 emissions, the glass sector has already identified and even implemented numerous solutions / technologies to reduce its carbon footprint. Some plays on the energy consumption of the furnace, other plays on the energy source itself. One may cite, as examples, the use of electricity as energy source (in a full or hybrid configuration), the use of alternative and greener sources of energy like H2 or biogas, the use of specific furnace designs with a higher energy efficiency and the implementation of heat recovery.

[0008] For the emissions attributed to raw material decarbonization which represents about 15 % of scope 1 emissions of a glass manufacturing activity, some initiatives have also emerged with the use of alternative raw materials and also the increased use of cullet as a raw material (which also plays positively on energy consumption). Those emissions occur during melting from burning conventional carbonated raw materials necessary to glass production, esp. soda-lime glass, like limestone (or calcium carbonate), dolomite (or calciummagnesium carbonate) and soda ash (or sodium carbonate). Some specific solutions have been proposed in the glass sector to reduce their carbon impact. For example, it is already known to replace them by their corresponding decarbonated compounds.

[0009] As far as calcium and / or magnesium sources are concerned : it is indeed described in the art to replace limestone by its corresponding oxide ("quicklime" or CaO). Even if quicklime is produced industrially by burning limestone and thereby releasing CO2 (shifting the emissions from scope 1 to scope 3), it is manufactured in a furnace called "lime kiln" which is known to show a higher energy efficiency than a glass furnace, thereby implying a lower level of CO2 emissions coming from fuel combustion in the kiln. Moreover, it is also known that using calcium oxide instead of calcium carbonate improves the melting kinetics of the glass batch, which implies that, in a given glass furnace at a given temperature, the energy consumption as well as the CO2 emission is consequently decreased.

[0010] However, this solution is not easy and straightforward as replacing limestone by quicklime in a glass batch leads to serious issues related to the high reactivity of quicklime with water, its fine granulometry in general and consequently dust issues that this brings during conveying, weighting, furnace loading, etc.

[0011] As far as sodium sources are concerned : it is also known, but in a less extent than for calcium, to replace soda ash (sodium carbonate) by its corresponding oxide, Na2O (sometimes called "calcined soda"), with similar advantages on energy consumption and CO2 emissions than for the replacement of limestone by quicklime.

[0012] Nevertheless, this sodium source has also severe issues regarding its high reactivity with water (even higher than for calcium oxide), generating a strongly exothermic reaction producing the corresponding corrosive hydroxide (NaOH) with serious risks of safety for structures and workers.

[0013] Moreover, it is also worth to note that those solutions of using decarbonated materials (e.g., oxides) do not play positively on scope 3 emissions and even, have a negative impact thereon. Indeed, using oxides instead of carbonates, as explained above, shifts a part of CO2 emissions from scope 1 to scope 3 (global benefit comes mainly from the better energy efficiency of the specific furnace, e.g. lime kiln) and moreover, raw materials transport is still to take into account.

[0014] Next to the already known solutions (mainly using oxides instead of carbonated raw materials), due to their drawbacks, there is still room for the glass manufacturers to act on the scope 1 emissions coming from carbonated raw materials, especially from the carbonated sodium source (namely, sodium carbonate or soda ash), while avoiding the severe issue of water reactivity of the existing described solutions and while having no impact on scope 3 emissions or even a positive impact, contrary to the use of decarbonated raw materials like calcium and / or sodium oxides (negative impact on scope 3 emissions).

[0015] Finally, it is also worth to note that, next to actions aimed at reducing CO2 emissions (scope 1-2-3), some initiatives have also been launched in order to develop CO2 capture, utilization and storage (also known as "CCUS") in a glass manufacturing process. However, the proven techniques to capture CO2 (i.e. amine capture) are still energy-demanding and not really satisfying when applied to exhaust gas occurring in a glass manufacturing process. Indeed, such exhaust gas show a low concentration in CO2 and, above all, a lot of impurities / poisoning compounds like NOX, SOXand O2, affecting greatly the efficiency of the capture process.OBJECTIVE OF THE INVENTION

[0016] It is an objective of the present invention to overcome the disadvantages described above with respect to the state of the art and resolving the technical problem, i.e. by providing a glass manufacturing process, showing a global decrease in CO2 emissions compared to a classical process, especially a decrease of scope 1 emissions.

[0017] It is a further objective of the present invention to provide a glass manufacturing process, showing a global decrease of the scope 1 emissions due to decarbonization of raw materials, while showing no impact or even a positive impact on scope 3 emissions.

[0018] It is a further objective of the present invention to provide a glass manufacturing process, showing a global decrease of the scope 1 emissions due to decarbonization of raw materials, while avoiding the severe issue of water reactivity when using an oxide raw materials.

[0019] It is a further objective of the present invention to provide a glass manufacturing process which allows a simple and cost-effective solution to reduce effectively the scope 1 emissions due to decarbonization of raw materials.DESCRIPTION OF THE INVENTION

[0020] The present invention relates to a manufacturing process of a soda glass comprising steps of melting a raw materials glass batch including sodium carbonate and fining a glass melt, thereby generating at least an exhaust gas comprising CO2, said process comprising further the following steps, in order and carried out on-line :(a) a step of contacting said exhaust gas at a temperature higher than 250°C with a source of sodium, thereby producing solid sodium carbonate;(b) a step of collecting, to collect said solid sodium carbonate; and(c) a step of using at least a part of solid sodium carbonate collected at step (b) as a raw material in said glass batch.

[0021] Hence, the invention is based on a novel and inventive approach. In particular, the inventors have found that by combining, in a glass manufacturing process including melting a glass batch having sodium carbonate thereby generating an exhaust gas comprising CO2, the specific steps (a) to (c) in order and on-line, it is possible to have at the same time a decrease of scope 1 emissions due to the suppression of emissions coming from soda source and noimpact on scope 3 emissions or even a positive impact, as the production of the sodium source according to the invention has a lower CO2 footprint than commercial sodium carbonate (especially if it is manufactured according to a classical process, whether it is an extraction or a chemical process). This is even more the case if the sodium source is produced usually by electrolysis using green(er) energy (e.g., electricity). Moreover, the process of the invention avoids the reactivity issue of using a decarbonated sodium raw materials (e.g. Na2O), as the sodium raw material in the process of the invention is a sodium carbonate produced on-line through steps (a) to (c). Finally, the invention allows using the exhaust gas roughly at the temperature it is generated / as such (through the on-line process), without any cooling down or heating up, in favour of the global consumption of the furnace.

[0022] In other words, the invention provides the advantage of using sodium carbonate as raw material (thereby benefiting from its stability towards water) but while avoiding its drawback of CO2 emission when it is calcined / decarbonized during the melting. Hence, the invention provides an efficient green soda loop, as it allows to use sodium carbonate as a raw material for the melting while recycling / reforming it on-line by using its CO2 release.

[0023] Finally, the solution of the invention may be implemented easily in existing furnace installations, without huge investments or plant adaptations.

[0024] In summary, by implementing all the features of the invention, the glass manufacturing process shows a lowered carbon footprint by acting on sodium raw material, without undergoing the issues related to the use of oxides.

[0025] Other features and advantages of the invention will be made clearer from reading the following description of preferred embodiments and figures, given by way of simple illustrative and non-restrictive examples.

[0026] FIG. 1 is a flowchart of an embodiment of the process of the invention.

[0027] FIG. 2 is a flowchart of an embodiment of the process of the invention.

[0028] In present specification and claims, it is well understood by the person skilled in the art that, as used herein the terms "a", "an" or "the" means "at least one" and should not be limited to "only one" unless explicitly indicated to the contrary. Also, when a range is indicated, the extremities are included. In addition, all the integral and subdomain values in the numerical range are expressly included as if explicitly written.

[0029] The terms "upstream" and "downstream", as used herein and unless otherwise specified, refer to the flow direction of said exhaust gas and are to be understood with theircommon sense, namely as meaning along the moving direction of said gas in the process / installation.

[0030] The manufacturing process of the invention is advantageous to produce any form of glass. For example, it may be used to manufacture glass articles like flat glass, fiber glass or hollow glass (e.g., glassware or glass containers / bottles). The manufacturing process of the invention is particularly of interest to produce flat glass.

[0031] By "soda glass", it is meant herein any glass comprising sodium (meaning that said glass comprises, in its chemical composition, > 0 % in weight of sodium, generally expressed as Na2O). One may cites soda-lime glass, borosilicate glass and aluminosilicate glass, as examples. As long the glass comprises sodium, even in a very small amount, it may be produced advantageously by the process of the invention.

[0032] According to the invention and as illustrated at FIG.l, the process comprises steps of melting a raw materials glass batch including sodium carbonate and fining a glass melt.

[0033] By a "step of melting", it is meant herein and as commonly accepted in the art, a step during which the glass batch (including commonly raw materials and, optionally, cullet) is melt by heating thanks to heating means using, for example, combustion and / or electricity, thereby producing a glass melt. The combustion heating means at the step of melting, if any, may be supplied with fuel and air, or fuel and oxygen, or fuel and a gas that is enriched in oxygen. Fuel may be fossil fuel, natural gas, biogas, hydrogen, synthetic gas, ammonia, or mixture thereof.

[0034] By a "step of fining", it is meant herein and as commonly accepted in the art, a step during which the glass melt is treated at temperatures higher than melting temperatures (generally above 1450-1500°C or even above 1550°C), thanks to heating means using for example combustion and / or electricity, in order to refine the glass (mainly by eliminating major part of bubbles). This fining step is also sometimes called "clarification step".

[0035] Considering steps of melting and / or fining generating an exhaust gas that has a high temperature (like for example, when using combustion, at least partially) is advantageous to carry out the step (a) of contacting according to the invention.

[0036] According to the invention and as illustrated at FIG.l, the steps of melting and fining generates at least an exhaust gas comprising CO2. Such an exhaust gas may also be called "flue gas" or "fumes" or "combustion gas" in the art. Such a gas may comprise, next to CO2(coming essentially from air and from decarbonization of raw materials, if carbonates are present), other gaseous compounds like N2, H2O, O2, NOXand SOX.

[0037] According to the invention, the at least an exhaust gas comes from the melting step or from the fining step or, preferably, from the whole furnace (including gas generated at the melting and the fining step). In an embodiment, said exhaust gas has a CO2 concentration of from 5 vol%, preferably of from 10 vol%. The CO2 concentration according to the invention is the concentration defined for the exhaust gas on a dry basis, namely the exhaust gas with all its components except water (H2O). The process of the invention is very advantageous as it allows to treat efficiently exhaust gas from low concentrations in CO2 (e.g. from 5 vol%) and to create the sodium loop.

[0038] The raw materials glass batch according to the invention includes sodium carbonate (also named "soda ash" in the art). The amount of sodium carbonate in the glass batch depends on the targeted glass composition and may vary e.g., from 0.5 wt% to 25 wt% (expressed as Na2O).

[0039] Said glass batch may also comprise silica sand, that is needed in the case of a silica glass (soda-silicate, aluminosilicate, borosilicate, etc.). Said glass batch may also comprise other compounds, in nature and amounts depending on the targeted glass composition and properties. Examples of possible raw materials for the glass batch are potash, salt cake (or sodium sulfate, Na2SO4), feldspar, boron oxide, barium oxide, cullet, selenium, metallic oxides (cobalt oxide, chromium oxide,...), clarifying agents (cerium oxide,..), oxidizers (sodium nitrate,...), reducing agents (graphite, coke, pyrite,...).

[0040] According to the invention, the steps (a) to (c) are carried out on-line, which means, as commonly understood in the art, that those steps take place continuously and on the same production line during the process, by opposition to off-line steps. In particular, in the glass manufacturing art, an on-line process involves an exhaust gas flow in the range of 60000 to 100000 Nm3 / h, which implies that the step of contacting said exhaust gas with a source of sodium is carried out in the invention in a very short time, i.e. lower than 1 minute and usually, below 10 seconds and even below 5 seconds.

[0041] As illustrated at FIG.l, the process of the invention comprises a step (a) of contacting said exhaust gas at a temperature higher than 250°C with a source of sodium, thereby producing solid sodium carbonate. Preferably, said exhaust gas is at a temperature higher than 300°C, or even higher than 350°C. More preferably, said exhaust gas is at a temperaturehigher than 400°C.. Preferably also, said exhaust gas is at a temperature lower than 900°C, or even lower than 850°C. More preferably, said exhaust gas is at a temperature lower than 800°C, or even lower than 700°C.

[0042] The source of sodium according to the invention may be any appropriate source able to react with CO2 at high temperature in order to produce sodium carbonate. Preferably, said source of sodium is sodium hydroxide or sodium chloride. In a very preferred embodiment, said source of sodium is sodium hydroxide. When using sodium hydroxide, the global reaction occurring at the step of contacting, between the sodium source and the gaseous CO2 comprised in the exhaust gas, is as follows : 2 NaOH + CO2 (g)Na2COs (s) + H2O (g) (for the sake of clarity, herein: (s) means a solid state and (g) means a gaseous state). The by-product of this reaction at the step of contacting is therefore advantageously water, which is gaseous at the contacting temperature and which will easily escape with the remaining exhaust gas.

[0043] According to an embodiment of the invention, at the step (a) of contacting, said exhaust gas is brought into contact with said sodium source by injecting said sodium source as a solution, preferably an aqueous solution, into a pipe through which said exhaust gas travels. When using sodium hydroxide as a sodium source in the invention, it is advantageous to use it as an aqueous solution, for example an aqueous solution with a concentration between 1 and 55wt% in NaOH, preferably between 5 and 55 wt%, more preferably between 5 and 30 wt%.

[0044] As illustrated at FIG.l, the process of the invention comprises a step (b) of collecting, to collect said solid sodium carbonate. According to the invention, this step is carried out downstream of the step (a) of contacting.

[0045] Advantageously, the step (b) of collecting is carried out in a gas-solid separator, in order to separate the formed solid sodium carbonate from the exhaust gas. Preferably, the step (b) of collecting may be carried out using mechanical filtration (e.g. bag filter or ceramic collector), electrostatic filtration and / or cyclonic filtration. Those techniques allow to collect efficiently a solid from an exhaust gas, even when the solid is in a significant amount.

[0046] As illustrated at FIG.l, the process of the invention comprises a step (c) of using at least a part of sodium carbonate collected at step (b) (or "collected sodium carbonate") as a raw material in said glass batch. According to the invention, this step is carried out downstream of the step (b) of collecting. This step (c) allows to reach the targeted "loop" andto recycle sodium carbonate as a raw material, without releasing its CO2 and while avoiding that this CO2 weights on the CO2 footprint of the global glass manufacturing process.

[0047] According to step (c) of the invention, either a part of or all the collected sodium carbonate is used as a raw material in the loop of the invention. In the event where only a part of the collected sodium carbonate is used as a raw material at step (c), then the remaining part may be valorized off-line. For example, it may stocked at the place of the manufacturing process and be used / injected as a raw material later on the same installation, or it may be transferred to another (glass) manufacturing installation / furnace, or it may be commercially valorized (e.g., sold or exchanged).

[0048] According to an advantageous embodiment of the process of the invention, when the exhaust gas comprises further SOXgas:- the step (a) of contacting produces further solid sodium sulfate, and- the step (b) of collecting is further to collect said solid sodium sulfate.

[0049] When the exhaust gas comprises SOX(which is often the case in soda glass production) next to CO2, this represent an additional advantage as the invention thereby allows SOXelimination together with the targeted sodium loop, and then allows to avoid the use of the additional common step of desulphurization of exhaust gas (namely, a step of removing the so-called acidic SOxgas, also called "DeSox" process) and of a dedicated installation. Moreover, this SOXelimination together with the targeted sodium loop of the invention is particularly effective, and allows to obtain an almost complete or complete removal of SOXin said exhaust gas (this is not the case with a classical desulphurization process).

[0050] When the exhaust gas comprises further SOXgas and when using sodium hydroxide at the step (a) of contacting, other reactions occur between the sodium source and the gaseous SOXcomprised in the exhaust gas. For example, with SO3, it is as follows : 2Na2SO4 (s) + H2O (g). The by-product of this reaction at the step of contacting is therefore advantageously also gaseous water, which will easily escape with the remaining exhaust gas.

[0051] It is to be noted that, when the exhaust gas comprises SOXnext to CO2, at the step (a) of contacting, the sodium source reacts first with SOXand then with CO2.

[0052] For the sake of clarity, when the exhaust gas comprises further SOXgas, the step (b) of collecting allows to collect solid sodium carbonate together with solid sodium sulfate.

[0053] According to an advantageous embodiment, when the exhaust gas comprises further SOXgas, the process comprises further, after the step (b) of collecting, a step of using at leasta part of said collected sodium sulfate as a raw material in said glass batch. This embodiment is illustrated at FIG. 2. In practice, as a (small) part of the sulfate introduced in the glass batch is consumed / stays in the final glass articles, the produced and collected sodium sulfate at the steps of contacting / collecting of the invention (coming from the SOXgas) is generally in default compared to the need in the glass batch, so that the total amount, or almost the total amount, of collected sodium sulfate is advantageously used / recycled as a raw material in said glass batch. Next to the use of collected sodium sulfate according to the invention, as it is in default compared to the need in the glass batch, a complement (to reach the need) of commercial sodium sulfate (external to the loop of the invention) may be added to the glass batch.

[0054] In the invention, advantageously, the amount of the source of sodium is adjusted in order to correspond, on a stoichiometric basis : at least to the amount of sodium carbonate required in the glass batch; or if said exhaust gas comprises SOXgas, at least to the total amount of (i) sodium carbonate required in the glass batch and of (ii) SOXpresent in said exhaust gas.

[0055] The amount of sodium carbonate required in the glass batch is based on the final sodium content targeted for the final glass. The amount of SOXpresent in exhaust gas may be determined by common analysis of said gas or by determining the difference between the sulfate introduced in the glass batch and that observed / analyzed in the final glass.

[0056] In practice, the reaction of sodium carbonate formation has a specific kinetics and may not be complete when the exhaust gas comes to the step (b) of collecting. Therefore, it may occur that, even if the amount of sodium source was adjusted to reach, on a stoichiometric basis, the amount of sodium carbonate required in the glass batch, it is not produced in a sufficient amount at the step of contacting. In such an event, all the collected sodium carbonate is used as a raw material at step (c) and the glass batch may be supplemented with a sodium raw materials (in minor amounts then, e.g. sodium carbonate or oxide).

[0057] Preferably, to alleviate the issue of reaction kinetics, the amount of sodium source is adjusted to be in slight excess, namely to correspond, on a stoichiometric basis, to a value slightly higher than the amount of sodium carbonate required in the glass batch (e.g. higher than 5 wt% or 10 wt%).

[0058] In an alternative embodiment, the amount of the source of sodium is adjusted in order to correspond, on a stoichiometric basis, to a value higher than the amount of sodium carbonate required in the glass batch (or, if said exhaust gas comprises SOXgas, to a valuehigher than the total amount of (i) sodium carbonate required in the glass batch and of (ii) SOXpresent in said exhaust gas). In such case, as CO2 is also emitted in the exhaust gas from other sources than the sodium raw material (e.g. calcium carbonate and / or fuel combustion), sodium carbonate will be formed at step (a) and collected at step (b) in excess compared to what is required for the glass batch. In such a case also, only a part of the collected sodium carbonate is used as a raw material in the loop of the invention. And, as already explained above, the remaining part of sodium carbonate (that in excess) may be valorized off-fine (stocked, transferred to another installation, sold, etc.)

[0059] According to an embodiment, the process of the invention may advantageously comprises, downstream of the step (b) of collecting, a step of removing the NOXgaseous compounds (also called "DeNOx"), preferably according to a SCR process (selective catalytic reduction) using ammonia. Such gas are indeed generally present in exhaust gas from a glass furnace, even if in some cases it is in very low amounts (e.g. if use of oxygen as comburant in a combustion process). This is very advantageous as those NOXgas are very corrosive. Moreover, when considering a step of removing the NOXgaseous compounds downstream of the process of the invention and if the exhaust gas comprise SOXgas that is collected according to the invention, there is an additional advantage in the invention. Indeed, removing SOXgas upstream allows decreasing the operating temperature of the standard "DeNOx" step (which usually requires temperatures of about 300°C to avoid the formation of ammonium bisulfate or ABS that poisons the process due to clogging).

[0060] According to another embodiment, the process of the invention may advantageously comprises a step of carbon capture applied on said exhaust gas, preferably downstream of the step (b) of collecting and, if the process comprises a step of removing the « NOx » gaseous compounds, downstream of this step. This step of capture carbon is advantageous as it allows to reduce further the CO2 footprint of the process, by further reducing the scope 1 emissions. This carbon capture may be done, for example, through dehydration / compression and / or through an amine adsorption / desorption process, or through any other appropriate technique.

[0061] Finally, the invention also relates to :- a sodium carbonate obtained by the process according to the invention and its embodiments exposed above; and- a sodium sulfate obtained by the process according to the invention and its relevant embodiments exposed above.

[0062] The person skilled in the art realizes that the present invention is by no means limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims. It is further noted that the invention relates to all possible combinations of features, and preferred features, described herein and recited in the claims.

Claims

CLAIMS1. Manufacturing process of a soda glass comprising steps of melting a raw materials glass batch including sodium carbonate and fining a glass melt, thereby generating at least an exhaust gas comprising CO2, characterized in that it comprises further the following steps, in order and carried out online :(a) a step of contacting said exhaust gas at a temperature higher than 250°C with a source of sodium, thereby producing solid sodium carbonate;(b) a step of collecting, to collect said solid sodium carbonate; and(c) a step of using at least a part of solid sodium carbonate collected at step (b) as a raw material in said glass batch.

2. Process according to claim 1, characterized in that, at the step of contacting, said exhaust gas is at a temperature higher than 300°C.

3. Process according to claim 1 or 2, characterized in that, at the step of contacting, said exhaust gas is at a temperature lower than 900°C.

4. Process according to any of the preceding claims, characterized in that said source of sodium is sodium hydroxide or sodium chloride.

5. Process according to the preceding claim, characterized in that said source of sodium is sodium hydroxide.

6. Process according to any of the preceding claims, characterized in that, at the step of contacting, said exhaust gas is brought into contact with said sodium source by injecting said sodium source as a solution, preferably an aqueous solution, into a pipe through which said exhaust gas travels.

7. Process according to any of the preceding claims, characterized in that the step of collecting is carried out in a gas-solid separator using mechanical filtration, electrostatic filtration and / or cyclonic filtration.

8. Process according to any of the preceding claims, characterized in that said exhaust gas comprises further SOXgas, and in that :- the step of contacting produces further solid sodium sulfate, and- the step of collecting is further to collect said solid sodium sulfate.

9. Process according to the preceding claim, characterized in that it comprises further, after the step of collecting, a step of using at least a part of said collected sodium sulfate as a raw material in said glass batch.

10. Process according to any of the preceding claims, characterized in that the amount of said source of sodium is adjusted in order to correspond, on a stoichiometric basis : at least to the amount of sodium carbonate required in the glass batch; or if said exhaust gas comprises SOXgas, at least to the total amount of (i) sodium carbonate required in the glass batch and of (ii) SOXpresent in said exhaust gas.

11. Process according to any of the preceding claims, characterized in that the exhaust gas has a CO2 concentration of from 5 vol%, preferably of from 10 vol%.

12. Process according to any of the preceding claims, characterized in that it further comprises a step of carbon capture applied on said exhaust gas.

13. Process according to any of the preceding claims, characterized in that it comprises further, downstream of the step (b) of collecting, a step of removing the NOx gaseous compounds, preferably according to a selective catalytic reduction process using ammonia.

14. Sodium carbonate characterized in that it is produced by the process according to any of claims 1 to 13.

15. Sodium sulfate characterized in that it is produced by the process according to any of claims 8 to 13.

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