Method for manufacturing a sodium carbonate solution

Abstract

Method for manufacturing a sodium carbonate solution A method for manufacturing a sodium carbonate solution by the electrodialysis of sodium chloride, using an electrodialyzer cellstack comprising several chambers, wherein one of said chambers is fed with an aqueous solution comprising sodium carbonate.

Description

[0001] Method for manufacturing a sodium carbonate solution

[0002] The present invention relates to a method for producing sodium carbonate (Na2COs) and / or sodium bicarbonate (NaHCCh) with reduced fossil carbon dioxide (CO2) emission, by electrodialysis of sodium chloride, using an electrodialyzer cellstack comprising several chambers, wherein one of said chambers is fed with an aqueous solution comprising sodium carbonate.

[0003] Advantageously, in said method the electrodialyzer uses an electrical tension which is provided with electricity having a reduced fossil CO2 footprint. More advantageously, the carbon dioxide (CO2) used for carbonating at least part of the aqueous outlet solution of the base chamber to obtain a carbonated liquid is partly, or totally, biogenic, or from biogenic origin, or not deriving from fossil carbon or not deriving from fossil carbon dioxide.

[0004] The said method enables sensitively a reduction of the CO2 fossil footprint when producing sodium carbonate or bicarbonate, compared to known processes and is a way to achieve net zero emission for such manufacturing and for the obtained products.

[0005] Technical field

[0006] Sodium carbonate (ISfeCCh), or soda ash, is one of the largest volume essential alkali product made worldwide with a total production in 2022 of more than 65 million tons. Sodium carbonate finds major use in the glass, chemicals, detergents industries, non-ferrous metallurgy, and also in the sodium bicarbonate production industry.

[0007] Sodium bicarbonate is also an essential chemical produced worldwide finding main uses in food and feed, acidic fumes mitigation, and pharmaceuticals uses.

[0008] The main processes for manufacturing sodium carbonate production are the Solvay ammonia synthetic process, the ammonium chloride process, and sodium carbonate or bicarbonate ore-based processes.

[0009] The SOLVAY ammonia synthetic process including one of its alternative the ‘dual process’ (or HOU process), is the main one used worldwide (two thirds of the world production). This process consists in treating an ammoniacal brine comprising sodium chloride with a gas containing carbon dioxide. From the solution, sodium bicarbonate precipitates, is recovered and calcined to obtain sodium carbonate. More details of the Solvay ammonia soda process and of the production of refined bicarbonate, is described in Ullmann's Encyclopedia of Industrial Chemistry (“Sodium carbonate” chapter, Vol. 33, pages 299-317, 2012 edition, Wiley -VCH Verlag GmbH & Co, paragraphs 1.4.1 and 1.4.2). One major advantage of the Solvay ammonia soda process is that it uses, as starting materials, worldwide abundant ones, which are: sodium chloride (NaCl) as source of sodium, and lime stone (CaCOs) as source of CO2 (or of the carbonate).

[0010] Said sourcing of carbonate in the ammonia soda process may be replaced partially or totally with CO2 from other industries or with biogenic CO2. And limestone (CaCCh), as source of alkalinity when calcined, can be substitute with non-fossil alkalis. One limit of the present Solvay process is that it uses thermic energy (about 9 GJ / ton of soda ash), part of it at high temperatures for limestone calcination. This high temperature energy is not easy to substitute with green energy such as fast developing solar photovoltaic or wind electrical power.

[0011] The main present alternative processes to produce sodium carbonate (soda ash) are those using sodium carbonate-containing minerals, such as fossil Trona, which represent one third of the world production of soda ash. The exploited ores related to alkaline volcanism, occur in a limited number of countries: mainly the USA, Turkey, China. The limited number of countries where such ore deposits occur, induces heavy intercontinental transports, and the exploitable reserves of identified deposits are limited. Availabilities of said ore deposits in Turkey represent about 20 to 40 years production, and a few centuries for the Wyoming USA deposit. Moreover, the CO2 content of the manufactured sodium carbonate or bicarbonate from such ores, is totally fossil and is freed in the atmosphere when used in the glass or metallurgy industries. This avoid such processes to be sustainable in long term and meet net zero emission of fossil CO2 and of greenhouse gasses to be in line with COP21 commitments.

[0012] There is therefore a need to improve sodium carbonate and bicarbonate manufacturing processes so that to be fitted to the use of sustainable green energy and which can integrate non-fossil CO2 sourcing or captured fossil CO2 from other industries to meet at once or progressively, net zero emissions requirements. Such improved processes should meet the need to massively use green and sustainable energy. Indeed the International Energy Agency net zero 2023 perspective for year 2050, forecasts as achievable: 70% of total primary energy supply being renewable energy, about 10% nuclear energy, and less than 10% oil and coal fossil primary energy (compared to 80% of fossil fuels in 2021 including natural gas, at worldwide scale), and less than 10% others.

[0013] US6554990 (from Solvay) discloses a process for the manufacture of alkali metal hydroxide such as sodium hydroxide, according to which an electrodialysis cell containing three chambers is used, an aqueous alkali metal halide solution is circulated in a saline chamber of the cell, delimited between an anionic membrane and a cationic membrane, and an alkali metal halide is introduced into an acidic chamber of the cell, delimited between the anionic membrane and a cationic face of a bipolar membrane and an aqueous alkali metal hydroxide solution is extracted from an alkaline chamber of the cell, delimited between the cationic membrane and an anionic face of the bipolar membrane. Though said process induces the production of acid solutions of hydrochloric acid which comprise sodium chloride. This makes it difficult the use of said hydrochloric acid for other uses.

[0014] Brief description of the invention

[0015] The present invention relates to a method for manufacturing a sodium carbonate solution by the electrodialysis of sodium chloride, using an electrodialyzer cellstack comprising several chambers, wherein one of said chambers is fed with an aqueous solution comprising sodium carbonate.

[0016] The present invention relates also to the above method wherein the electrodialyzer cellstack comprises at least three chambers one of which is a salt chamber, a second one is a base chamber and a third one is an acid chamber, and said method comprising:

[0017] - feeding an aqueous solution comprising sodium chloride into the salt chamber, said salt chamber being bounded between one anionic membrane and one cationic membrane,

[0018] - feeding the aqueous solution comprising sodium carbonate into the base chamber, said base chamber being bounded between the cationic membrane and an anionic face of a bipolar membrane,

[0019] - feeding an aqueous solution into the acid chamber, said acid chamber being bounded between a cationic face of the bipolar membrane and an anionic membrane,

[0020] - generating in the base chamber sodium hydroxide (NaOH) and in the acid chamber hydrochloric acid (HC1), by splitting water molecules with the bipolar membrane into hydroxide anions (OH-) in the base chamber and into hydronium cations (H+) in the acid chamber, transferring sodium ions (Na+) to the base chamber through the cation selective membrane and transferring chloride ions (C1-) to the acid chamber through the anionic membrane by using an electrical tension between the salt chamber and the acid chamber,

[0021] - removing an aqueous outlet solution comprising sodium hydroxide and sodium carbonate from the base chamber,

[0022] - removing an aqueous outlet solution comprising sodium chloride depleted in sodium chloride from the salt chamber,

[0023] - removing an aqueous outlet solution comprising hydrochloric acid from the acid chamber, and

[0024] - carbonating at least part of the aqueous outlet solution of the base chamber with a gas comprising carbon dioxide (CO2) to obtain a carbonated liquid wherein at least part of, or the totality of, the sodium hydroxide is transformed into sodium carbonate and water.

[0025] The present inventors found that when manufacturing a sodium carbonate solution by the electrodialysis of sodium chloride, using an electrodialyzer cellstack comprising several chambers, wherein one of said chambers is fed with an aqueous solution comprising sodium carbonate, the membranes delimiting said chambers have an operation life which is sensitively increased compared to same membranes delimiting said chambers when sodium hydroxide aqueous solution at the same molarity is present in the base chamber without sodium carbonate.

[0026] Moreover the production of sodium carbonate using electrodialysis of sodium chloride solutions into caustic soda (NaOH) and hydrochloric acid (HC1) has an electricity consumption sensitively decreased compared to the production of caustic soda and chlorine by membrane electrolysis of sodium chloride solutions. The decrease of energy consumption is about 30% less by electrodialysis compared to electrolysis. This eases to decrease the CO2 footprint for the needed electrical power for said reaction, and to switch to ‘green energy’.

[0027] Moreover use of electrodialysis of sodium chloride solution into sodium hydroxide and sodium carbonate (in base chamber) and into hydrochloric acid (in acid chamber) gives good synergies with the use of gaseous biogenic CO2, or from biogenic origin, as impurities level requirements in the CO2 gas feeding an electrodialyzer, wherein at least part of the caustic soda (NaOH) is replaced by sodium carbonate with a lower pH, causes less precipitation of divalent and trivalent metal impurities than with sodium hydroxide at same molarity, preserving in this also the operation life expectancy of the used membranes in the electrodialyzer, and decreasing the sodium hydroxide solution and hydrochloric acid used for purifying the aqueous solution comprising sodium chloride fed in the salt chamber, such as the sodium hydroxide solution and hydrochloric acids used for secondary purification of brine in ion-exchange unit (as described in EU - BAT Reference document for the Production of Chloralkali - 2014 - edited by the Joint Research Center Institute - doi: 10.2791 / 13138 - § 2.5 Brine purification, and § 2.5.3.3).

[0028] The invention relates also to a method wherein part of the carbonated liquid obtained from carbonating the outlet solution of the base chamber of the above method is further processed to crystallize sodium carbonate crystals or sodium bicarbonate crystals.

[0029] The invention relates also to sodium carbonate crystals in which at least 25% of its carbon content is biogenic carbon, and comprise at most 20 mg calcium or magnesium per kilogram of sodium carbonate crystals. The invention relates also to sodium bicarbonate crystals in which at least 25% of its carbon content is biogenic carbon, and comprise at most 20 mg calcium or magnesium per kilogram of sodium bicarbonate crystals. Indeed the inventors have discovered that even with low impurities levels such as calcium and magnesium made from the method of said invention, attrition of the obtained sodium carbonate is acceptable for main final uses and enable them to reduce scopes 1, 2 and 3, emissions of fossil CO2 as defined by the Greenhouse Gas Protocol organization.

[0030] The invention relates also to sodium carbonate crystals or the sodium bicarbonate crystals made according to the present method and in which at least 25% of the used electrical energy for the electrodialyzer is provided with electricity selected from the group consisting of: hydraulic electricity, solar photovoltaic electricity, wind electricity, waste to energy electricity, electricity generated from biomass combustion, electricity generated from biogas combustion, electricity generated from hydrogen combustion, geothermal electricity, electricity generated by compressed air such as from compressed air stored in underground cavities, nuclear electricity, or mixtures thereof.

[0031] Indeed the good synergy of the combination of electrodialysis and sodium carbonate or bicarbonate crystallization presents a surprising optima for decreasing the CO2 fossil footprint and achieve net zero fossil emission for manufacturing sodium carbonate or sodium bicarbonate. Definitions

[0032] For purposes of the present specification, certain terms are intended to have the following meanings.

[0033] The term ‘electrodialysis’ refers to an electrochemical process which enables to at least partially or totally extract salt ions from one solution through an ion-exchange membrane subjected to an electric field to another solution.

[0034] The term ‘electrodialyzer cellstack’ refers to an equipment wherein an electrodialysis process may be performed. It generally comprises several cells delimited by ion exchange membranes (also called ion perm-selective membranes).

[0035] The term ‘biogenic carbon’ or ‘biogenic carbonate’ is carbon or carbonate whose carbon source was directly in equilibrium with CO2 in the atmosphere. In the present specification the biogenic (also called ‘biobased’) carbon content is measured according to ASTM D6866-22 Standard Test Method for determining the biobased content of solid, liquid, and gaseous samples using Radiocarbon Analysis. Said method provides accurate biobased / biogenic carbon content results: the method uses Isotope Ratio Mass Spectrometry (IRMS) techniques to quantify the biobased or biogenic content of a given product, based on carbon 14 isotope measurement of said sample. Instrumental error of the method is typically within 0.1-0.5 % (on relative standard deviation).

[0036] The term ‘green energy’ also called ‘renewable energy’ refers commonly to energy from renewable natural resources that are replenished on a human timescale. This encompasses solar energy (both thermic or photovoltaic electricity energy), wind power, hydropower, bioenergy (derived from biomass (generally from terrestrial of from marine origin), and geothermal energy. In present specification low fossil CO2 footprint energy in complement of the ‘green energy’ listed above, includes heat or cold recovered by heat pumps, and nuclear energy.

[0037] The term ‘green electricity’ also called ‘renewable electricity’ refers commonly to electricity produced from renewable natural resources that are replenished on a human timescale. This encompasses solar energy (either from thermic, or from photovoltaic electricity energy), wind power, hydropower or hydraulic electricity, marine power, electricity deriving or produced from bioenergy (ie. derived from biomass, and generally from terrestrial of from marine origin), and electricity derived from geothermal energy. In present specification low fossil CO2 footprint electricity in complement of the ‘green energy’ listed above, includes nuclear power (electricity produced from nuclear energy).

[0038] The term "purge” refers to a stream withdrawn from a part of a process to limit impurity concentration in this process.

[0039] The expression “derived from” for instance “sodium chloride derived from: a solar pond salt or from sea” refers to a sodium chloride stream withdrawn as such from said solar pond or sea, or to a stream that have been subjected to one or several chemical engineering operation downstream the said crystallizer (such as: purifying, concentrating, thermally transforming, decanting, centrifuging, crystallizing, filtering, evaporating, drying, diluting, heating, cooling operations), or that has been mixed with one or more other stream(s), though keeping at least one part of the sodium chloride withdrawn from said solar pond or sea.

[0040] The term "impurity” refers to a compound different from the sodium carbonate and / or the sodium bicarbonate salt to be produced.

[0041] The term “carbonating” refers to the action of increasing the amount of total carbonate (i.e. carbonate and bicarbonate) of a stream.

[0042] The term “bicarbonating” refers to the action of increasing the amount of bicarbonate of a stream.

[0043] The term "comprising" includes "consisting essentially of and also "consisting of.

[0044] In the present specification, the terms “%”, “% by weight”, “wt%”, “wt. %”, “weight percentage”, or “percentage by weight” can be used interchangeably, unless the “%” term is explicitly referred to an other physical unit (such as for instance “% in mole”, or mol. %”, “% in volume” or “vol. %”, etc....).

[0045] A plurality of elements includes two or more elements.

[0046] The phrase ‘A and / or B’ refers to the following selections: element A; or element B; or combination of elements A and B (A+B). The phrase ‘A and / or B’ is equivalent to at least one of A and B. The phrase ‘A and / or B’ equates to at least one of A and B.

[0047] The phrase ‘Al, A2, . . . and / or An’ with n > 3 includes the following choices: any single element Ai (i= 1, 2, . . .n); or any sub-combinations of from two to (n-1) elements chosen from Al, A2, . . ., An; or combination of all elements Ai (i=l, 2, ... n). For example, the phrase ‘Al, A2, and / or A3’ refers to the following choices: Al; A2; A3; A1+A2; A1+A3; A2+A3; or A1+A2+A3. In the present specification, the description of a range of values for a variable, defined by a bottom limit, or a top limit, or by a bottom limit and a top limit, also comprises the embodiments in which the variable is chosen, respectively, within the value range: excluding the bottom limit, or excluding the top limit, or excluding the bottom limit and the top limit.

[0048] In the present specification, the description of several successive ranges of values for the same variable also comprises the description of embodiments where the variable is chosen in any other intermediate range included in the successive ranges. Thus, for illustration purpose, when it is stated that "the element X is generally at least 10, advantageously at least 15", the present description also includes another embodiment where a new minimum can be selected between 10 and 15, for example: where "the element X is at least 11", or also where: "the element X is at least 13.74", etc.; 11 or 13.74 being values included between 10 and 15. Also for illustration purpose, when it is indicated that "the element X is generally at most 15, advantageously at most 10", the present description also includes another embodiment where a new maximum can be selected between 10 and 15.

[0049] In the present description, wherein an element or composition is said to be included in and / or selected from a list of recited elements or components, it should be understood that in related embodiments explicitly contemplated here, the element or component can also be any one of the individual recited elements or components, or can also be selected from a group consisting of any two or more of the explicitly listed elements or components.

[0050] For example, when in an embodiment the choice of an element from a group of elements is described, the following embodiments are also explicitly described:

[0051] - the choice of two or more elements from the group,

[0052] - the choice of an element from a subgroup of elements consisting of the group of elements from which one or more elements have been removed.

[0053] The use of the singular ‘a’ or ‘one’ herein includes the plural unless specifically stated otherwise.

[0054] If the term "about" is used before a quantitative value, this corresponds to a variation of ± 10% of the nominal quantitative value, unless otherwise indicated.

[0055] Brief description of the figures Figure 1 (Fig. 1) shows schematically the function of the electrodialyzer in one embodiment of the method of the present invention.

[0056] Figure 2 (Fig. 2) shows schematically an equipment for implementing an embodiment of the method according to the invention.

[0057] Detailed description of the invention

[0058] Electrodialysis refers to electrochemical processes which enable to extract salt ions from one solution through an ion-exchange membrane subjected to an electrical field to another solution.

[0059] Electrodialysis technologies are known: they are mainly used for electroseparation processes, such as the production of drinkable water, industrial waste water treatments, acid or alkali recovery in metal plating industries, food and pharmaceuticals processes. Electrodialysis principles are well described for instance in Ullmann’s Encyclopedia of Industrial Chemistry (2011 edition, Wiley -VCH Verlag GmbH & Co, Vol. 12 pp 273-313, Electrochemistry), or in Technique de 1’Ingenieur Encyclopedia (2006 edition, Chapter Electrodialyse, J2840 VI, 2006, pp 1-15 and Technical appendixes pp 1-3).

[0060] In a preferred mode of the present invention, the electrodialysis is operated in an electrodialysis cellstack which comprises combining, within a set of adjoining chambers, bipolar ion-exchange membranes with anionic and / or cationic ion-exchange membranes.

[0061] The anionic membranes are ion-exchange membranes that are permeable to anions and, ideally, impermeable to cations. The cationic membranes are themselves permeable to cations and impermeable to anions. A bipolar membrane is an ion-exchange membrane comprising a cationic face and an anionic face. Such membranes may be produced by joining a cationic membrane and an anionic membrane. The bipolar membrane may for example be produced by the process described in WO 01 / 79335 in the name of Solvay.

[0062] Within the bipolar membrane, under the action of a sufficient local electric field, the dissociation of the water that has diffused therein, to its H+and OH' ions takes places, which ions then migrate on both sides of this membrane. There is therefore acidification in one of the chambers adjacent to the bipolar membrane and alkalinization in the other adjacent chamber. Successive bipolar membranes are separated by cationic or anionic monopolar membranes. When the electrodialyzer only possesses bipolar membranes and one type of monopolar membranes (cationic or anionic), they are said to have two (types of) chambers. The electrodialyzer used in the method of the present invention possesses preferably only bipolar and anionic membranes.

[0063] The chamber located between the anionic face of the bipolar membrane and a cationic membrane constitutes a base chamber. In this chamber there is a supply of OH' ions originating from the bipolar membrane. In the method of the present invention, the base chamber is fed with an aqueous solution comprising sodium carbonate. The OH' ions supplied from the bipolar membrane will provide alkalinity to absorb then acidic carbon dioxide to form a carbonated solution.

[0064] In an advantageous embodiment the electrodialyzer used in present invention comprises at least three chambers one of which is a salt chamber, a second one is a base chamber and a third one is an acid chamber.

[0065] A first advantage of the present invention is the increased operation time before acid washing or before replacement, of the membranes in contact with the base chamber wherein the aqueous solution comprising sodium carbonate is introduced compared to same equipment without sodium carbonate in said chamber.

[0066] A second advantage of the present invention is the reduced electrical energy consumption of the method to produce sodium carbonate or bicarbonate compared to an equivalent process wherein an electrolyzer would be used rather than an electrodialyzer, decreasing as such the CO2 footprint related to the electrical energy production, whatever the electrical energy origin, easing as such a near-zero CO2 foot-print of the produced sodium carbonate or bicarbonate.

[0067] A third advantage of the present invention is the possibility to use renewable energy or low fossil CO2 footprint energy, replacing high temperature steps of conventional processes (limestone calcination into lime used in both Soda ammonia process and Trona solution mining process using generally coal) and replacing it with electricity having a reduced fossil CO2 footprint, said electricity being preferably selected among the group consisting of: hydraulic electricity, photovoltaic electricity, wind electricity, waste to energy electricity, electricity generated from biogas, electricity generated from biomass combustion, electricity generated from hydrogen combustion, geothermal electricity, electricity generated by compressed air such as from compressed air stored in underground cavities, nuclear electricity, and mixtures thereof. This contributes also to a near-zero CO2 foot-print of the produced sodium carbonate or bicarbonate. A fourth advantage of the present invention is to ease CO2 capture from fumes, or from other industries, or from the atmosphere, as the produced sodium hydroxide is highly reactive to capture said CO2 even at low concentration (with CO2 at concentrations lower than 30% vol. or even lower than 10% vol. on dry gases), or even for capturing efficiently CO2 from Earth atmosphere (a. 420 ppm by volume) and to increase the circularity of CO2 resources by manufacturing sodium carbonate or bicarbonate.

[0068] A fifth advantage of the present invention is when CO2 capture, or CO2 from other industries, are not available locally to be able to use limestone (CaCCh) of low purity at 60 to 85% CaCCh (which is not at all recommended in Ammonia soda process, as mineral impurities of limestone mainly clays and aluminum or iron silicates form with hydrated lime Ca(OH)2 insoluble matters, generating a loss of calcium hydroxide, and heavy incrustations in distillers).

[0069] A sixth advantage of the present invention is to increase by synergy the use of other by-products, such as concentrated brines from desalination discharge from reverse osmosis or from multiple effects evaporation equipment in regions of the world were drinkable water is scarce, and to use it as NaCl raw material for the present method and by so-doing, reducing the stress on existing natural resources.

[0070] A seven advantage of the present invention is the possibility to process the sodium carbonate solution exiting from the base chamber, even if the said sodium carbonate solution comprises traces of sodium chloride generated by the leakage of chlorides ions from the salt chamber to the base chamber through the cationic membrane of the electrodialyzer, as sodium chloride will be then separated during crystallization of sodium carbonate or bicarbonate and will remain in the mother liquor of the crystallizers. Said sodium chloride then purged with part of sodium carbonate can be recycled upfront the brine (NaCl solution) to be used for purifying said brines in impurities such as calcium, before feeding it to the salt chamber, avoiding or reducing sodium carbonate loss and enabling a useful synergy between electrodialyzer sector and the crystallization of sodium carbonate or bicarbonate.

[0071] Therefore, the method of the present invention enables to improve the circularity of the use of raw materials such as sodium chloride or limestone, and optimizes by synergy, a decrease of the CO2 fossil footprint of the manufacture of sodium carbonate or bicarbonate, paving the way to net zero emission. The present invention relates to several advantageous embodiments which are described hereafter as ‘Items’.

[0072] Item 1. A method for manufacturing a sodium carbonate solution by the electrodialysis of sodium chloride, using an electrodialyzer cellstack comprising several chambers, wherein one of said chambers is fed with an aqueous solution comprising sodium carbonate.

[0073] Item 2. The method according to item 1, wherein at least 25 wt.%, more advantageously at least 40 wt% of the carbon comprised in the sodium carbonate is biogenic or from biogenic origin.

[0074] Item 3. The method according to Item 2, wherein at least 80 wt.% or at least 90 wt% of the carbon comprised in the sodium carbonate is biogenic or from biogenic origin.

[0075] Item 4. The method according to one of the preceding items, wherein the electrodialyzer comprises at least 2 chambers, one of which is a salt chamber, a second one is a base chamber.

[0076] Item 5. The method according to one of the preceding items, wherein the electrodialyzer comprises at least 3 chambers, one of which is a salt chamber, a second one is a base chamber and a third one is an acid chamber.

[0077] Item 6. The method according to one of the preceding items, wherein one of the chambers is a salt chamber bounded between one anionic membrane and one cationic membrane.

[0078] Item 7. The method according to one of the preceding items, wherein one of the chambers is a base chamber bounded between one cationic membrane and an anionic face of a bipolar membrane.

[0079] Item 8. The method according to one of the preceding items, wherein one of the chambers is an acid chamber bounded between a cationic face of a bipolar membrane and an anionic membrane.

[0080] Item 9. The method according to one of the preceding items, wherein the aqueous solution comprising carbonate is fed to the base chamber.

[0081] Item 10. The method according to one of the preceding items, wherein the cationic membrane and / or the anionic membrane is / are selective of monovalent ions. In present specification the expression ‘selective of monovalent ions’ refers to permselective cationic or anionic membranes permeable to respectively monovalent cations or monovalent anions, and not, or less, permeable to divalent or trivalent cations or anions. This is particularly advantageous in present invention as it further limit the migration of impurities such as divalent ions : calcium (Ca2+), magnesium (Mg2+), sulfate (SOT'), nitrates (NO3— ), , silicates (SiCh2'), or trivalent ions (Fe3+, Al3+,. . .) borate (BO33) ions from the salt chamber to the base chamber, and increase as such purity of the manufactures sodium carbonate or bicarbonate solution. It also reduces the incrustation in membranes of insoluble precipitates such as CaCCh, Mg(0H)2, or silicates of iron, aluminum or calcium.

[0082] Item 11. The method according to one of the preceding items, wherein the electrodialyzer cellstack comprises at least three chambers one of which is a salt chamber, a second one is a base chamber and a third one is an acid chamber, and said method comprising:

[0083] - feeding an aqueous solution comprising sodium chloride into the salt chamber, said salt chamber being bounded between one anionic membrane and one cationic membrane,

[0084] - feeding the aqueous solution comprising sodium carbonate into the base chamber, said base chamber being bounded between the cationic membrane and an anionic face of a bipolar membrane,

[0085] - feeding an aqueous solution into the acid chamber, said acid chamber being bounded between a cationic face of the bipolar membrane and an anionic membrane,

[0086] - generating in the base chamber sodium hydroxide (NaOH) and in the acid chamber hydrochloric acid (HC1), by splitting water molecules with the bipolar membrane into hydroxide anions (OH-) in the base chamber and into hydronium cations (H+) in the acid chamber, transferring sodium ions (Na+) to the base chamber through the cation selective membrane and transferring chloride ions (C1-) to the acid chamber through the anionic membrane by using an electrical tension between the salt chamber and the acid chamber,

[0087] - removing an aqueous outlet solution comprising sodium hydroxide and sodium carbonate from the base chamber,

[0088] - removing an aqueous outlet solution comprising sodium chloride depleted in sodium chloride from the salt chamber,

[0089] - removing an aqueous outlet solution comprising hydrochloric acid from the acid chamber, and

[0090] - carbonating at least part of the aqueous outlet solution of the base chamber with a gas comprising carbon dioxide (CO2) to obtain a carbonated liquid wherein at least part of, or the totality of, the sodium hydroxide is transformed into sodium carbonate and water. Item 12a. Method according to one of the preceding claims, wherein the electrodialyzer cellstack comprises at least one acid chamber, and wherein the aqueous solution fed into the acid chamber comprises less than 1 g of calcium per kg of aqueous solution. This embodiment enables to valorize in more uses the produced hydrochloric acid in the acid chamber.

[0091] Item 12b. Method according to one of the preceding claims, wherein the electrodialyzer cellstack comprises at least one acid chamber, and wherein the aqueous solution fed into the acid chamber comprises at least 2 wt%, or at least 4 wt% of calcium (expressed as weight of calcium). This may be for instance calcium dissolved as calcium chloride (CaCh). This embodiment enables to coproduce a calcium chloride from the acid chamber, in complement of the sodium carbonate or bicarbonate of the present invention.

[0092] Item 13. Method according to one of the items 4 to 12b, wherein the aqueous solution comprising sodium chloride fed into the salt chamber, comprises less than 20 g of calcium, preferably less than 8 g of calcium per kg of aqueous solution.

[0093] Item 14. Method according to one of the items 4 to 13, wherein the aqueous solution comprising sodium chloride fed into the salt chamber, comprises less than 2.5 g of magnesium, preferably less than 0.5 g of magnesium per kg of aqueous solution.

[0094] Item 15. Method according to one of the items 4 to 13 wherein the aqueous solution comprising sodium chloride fed into the salt chamber, comprises a cumulated weight of calcium and magnesium to less 20 pg Ca +Mg per liter.

[0095] Item 16. Method according to one of the items 11 to 15 wherein part of the carbonated liquid obtained from carbonating the outlet solution of the base chamber is further processed to crystallize sodium carbonate crystals. For instance this can be done by removing part of the water of the carbonated solution so that to reach the solubility limit of sodium carbonate and crystallizing crystals of sodium carbonate.

[0096] Item 17. Method according to one of the items 11 to 16 wherein part of the carbonated liquid obtained from carbonating the outlet solution of the base chamber comprises sodium bicarbonate and is further processed to crystallize sodium bicarbonate crystals. Examples of such further processing may be: - by removing part of the water of the bicarbonated solution so that to reach the solubility limit of sodium bicarbonate and crystallizing crystals of sodium bicarbonate;

[0097] - or alternatively by controlling the concentration of sodium carbonate and sodium hydroxide from the aqueous outlet solution of the base chamber so that when said aqueous outlet solution is further bicarbonated by reacting the solution with CO2, the solubility limit of sodium bicarbonate is obtained and crystallizing crystals of sodium bicarbonate.

[0098] Item 18. Method according to one of the items 11 to 17, or of their alternatives, wherein the carbonated liquid obtained from the carbonation of the aqueous outlet solution of the base chamber is partly recycled back to the electrodialyzer cellstack as the aqueous solution comprising sodium carbonate.

[0099] Item 19. Method according to one of the items 11 to 18, wherein the removed aqueous outlet solution comprising sodium hydroxide and sodium carbonate from the base chamber has a molar ratio of alkaline sodium from sodium hydroxide to the alkaline sodium from sodium carbonate is less than 0.5, preferably less than 0.2. This is particularly advantageous for limiting aging of the membranes present in the base chamber and increasing operation lifetime of said membranes, or increasing operation time between two acidic washing operations of said membranes in the base chamber(s), to limit overvoltage across said membranes. In the present method, the concentrations of sodium hydroxide and sodium carbonate in the removed aqueous outlet solution from the base chamber are not particularly limited. However too diluted solutions leads to important energy consumption for recovering or concentrating the then generated sodium carbonate. And also a too important concentration may leads to the solubility limit of sodium carbonate salt, with the risk to encrust said chamber and the membranes comprised therein.

[0100] Item 20. Method according to one of the items 11 to 19, wherein the outlet liquid of the base chamber has a molar concentration of alkaline sodium from sodium carbonate and sodium hydroxide of at least 1, preferably at least 2 mol Na+ per kg of outlet liquid. Advantageously, in said embodiment the molar concentration of alkaline sodium from sodium carbonate and sodium hydroxide is at most 3 mol Na+ per kg of outlet liquid of the base chamber.

[0101] Item 21. Method according to one of the items 11 to 20, wherein the aqueous outlet solution comprising hydrochloric acid from the acid chamber comprises at least 1 wt% and preferably at most 8 wt% HC1. Item 22. Method according to one of the items 11 to 21, wherein the aqueous outlet solution comprising hydrochloric acid is further processed to concentrate it into a concentrated aqueous solution of hydrochloric acid.

[0102] Item 23. Method according to the preceding item, wherein the concentrated aqueous solution of hydrochloric acid (HC1) comprises at least 6%, preferably at least 9%, more preferably at least 30% by weight of HC1.

[0103] Item 24. Method according to one of the items 11 to 23, wherein the sodium chloride from the sodium chloride aqueous solution derives from: a solar pond salt, or sea salt, rock-salt, or a dissolved salt from a geological salt cavity, or industrial vacuum crystallized salt, or a residual or a co-product sodium chloride resulting from an other industry, or a sea-water desalination unit.

[0104] Item 25. Method according to one of the preceding items, wherein the electrodialyzer uses an electrical tension, and said electrical tension is provided with electricity having a reduced fossil CO2 footprint, preferably selected from the group consisting of: hydraulic electricity, solar photovoltaic electricity, wind electricity, waste to energy electricity, electricity generated from biomass combustion, electricity generated from biogas combustion, electricity generated from hydrogen combustion, geothermal electricity, electricity generated by compressed air such as from compressed air stored in underground cavities, nuclear electricity, or mixtures thereof.

[0105] Item 26. Method according to one of the preceding items, wherein the electrodialyzer cellstack comprises at least five chambers: one anode chamber, one acid chamber, one salt chamber, one base chamber, one cathode chamber.

[0106] Item 27. Method according to one of the preceding items, wherein carbon dioxide (CO2) used for carbonating the aqueous outlet solution of the base chamber to obtain a carbonated liquid is at least partly biogenic, or totally biogenic not deriving from fossil carbon or not deriving from fossil carbon dioxide. Advantageously, the carbon dioxide (CO2) including biogenic CO2 may result from concentration or purification processes which increase its CO2 concentration. This may include concentration processes such as: an amine based process, an ammonia based process, a Pressure Swing Absorption (PSA) process, a Temperature Swing Absorption (TSA) process, a cryogenic process, or a membrane process.

[0107] Item 28. Method according to one of the preceding items, wherein carbon dioxide (CO2) used for carbonating at least part of the aqueous outlet solution of the base chamber to obtain a carbonated liquid is from CO2 captured from the air, or deriving from the combustion of fossil carbonaceous combustibles, or deriving from fossil carbon dioxide.

[0108] Item 29. Method according to any items 11 to 28, wherein the carbon dioxide (CO2) derives partly or totally from fumes or gases generated by plants or equipment thereof, selected from the group consisting of: a power plant, a glass plant, a steel or sinter plant, a waste plant or a waste-to-energy plant, a pulp plant, a paper plant, an oil refinery, a petro-chemical plant, a coal gasification plant, a cement plant, a tile manufacturing plant, a brick manufacturing plant, a mining process, a mineral processing plant, a lime plant, an ammonia plant, a fertilizer plant, a biochar plant, a biogas plant, and combinations thereof.

[0109] Item 30. Method according to one of the preceding items, wherein carbon dioxide (CO2) used for carbonating at least part of the aqueous outlet solution of the base chamber is generated by acid attack of limestone (CaCO3) or of a rock comprising carbonated minerals such as dolomite, and the acid attack is made with hydrochloric acid generated in, or derived from, the electrodialyzer cell stack.

[0110] Item 31. Process for manufacturing sodium carbonate crystals, from sodium chloride and, green electricity or electricity with a reduced fossil CO2 footprint, comprising:

[0111] (a) providing solid sodium chloride or a brine comprising sodium chloride and water,

[0112] (b) optionally pre-treating the brine to reduce detrimental impurities to permselective membranes selected from the group of: cationic permselective membrane, anionic permselective membrane, bipolar membrane and combinations thereof, for producing a purified brine comprising sodium chloride and water,

[0113] (d) manufacturing a sodium carbonate solution according to the method of any of the preceding items 1 to 30, wherein the brine or the optional purified brine is used as the aqueous solution comprising sodium chloride feeding the salt chamber, and wherein the electric tension is provided with green electricity or with electricity with a reduced fossil CO2 footprint,

[0114] (e) concentrating the sodium carbonate solution by removing part of its water content so that to produce sodium carbonate crystals and a mother liquor,

[0115] (f) separating the sodium carbonate crystals from the mother liquor, (g) optionally drying the sodium carbonate crystals to obtain dried sodium carbonate crystals.

[0116] Item 32. Process according to the preceding item wherein step (e) comprises using a crystallizer selected from the group consisting of: a sodium carbonate decahydrate crystallizer, a sodium carbonate monohydrate crystallizer, an anhydrous sodium carbonate crystallizer, a sodium sesqui carb onate crystallizer, and combination therefrom.

[0117] Item 33. Process according to the preceding item wherein the sodium carbonate crystallizer is a sodium carbonate monohydrate evaporator crystallizer using mechanical steam recompression, and wherein preferably the mechanical steam recompression uses green electricity or electricity with a reduced fossil CO2 footprint.

[0118] Item 34. Process according to any of items 31 to 33, wherein the solid sodium chloride, or the brine comprising sodium chloride and water, derives from: a solar pond salt, or sea salt, rock-salt, or a dissolved salt from a geological salt cavity, or industrial vacuum crystallized salt, or a residual or a co-product sodium chloride resulting from an other industry, or a sea-water desalination unit.

[0119] Item 35. Sodium carbonate crystals or sodium bicarbonate crystals:

[0120] - wherein at least 25 wt.% of its carbon content is biogenic carbon, preferably at least 80 wt. % of its carbon content is biogenic carbon; and

[0121] - comprising at most 20 mg calcium and / or at most 20 mg magnesium per kilogram of crystals, preferably at most 8 mg calcium and / or at most 8 mg magnesium per kilogram of crystals.

[0122] Item 36. Sodium carbonate crystals or sodium bicarbonate crystals according to the preceding item comprising at most 10 mg iron (Fe), preferably at most 4 mg iron (Fe) per kilogram of crystals.

[0123] Item 37. Sodium carbonate crystals or sodium bicarbonate crystals according to item 35 or 36, wherein at least 25% of the electrodialysis electrical power to manufacture said sodium carbonate or bicarbonate crystals, is selected among the list of item 25, and preferably is selected among: solar photovoltaic electricity, wind electricity, hydraulic electricity, and mixtures thereof.

[0124] Item 38. Sodium carbonate crystals or sodium bicarbonate crystals according to the preceding item, wherein at least 60% or at least 70% of the electrodialysis electrical power to manufacture said sodium carbonate or bicarbonate crystals, is selected among the list of item 25, and preferably is selected among: solar photovoltaic electricity, wind electricity, hydraulic electricity, and mixtures thereof.

[0125] Item 39. Sodium carbonate crystals or sodium bicarbonate crystals according to the preceding item wherein at least 10% in weight of the crystals are above 50 pm, or above 200 pm.

[0126] Item 40. Sodium carbonate crystals or sodium bicarbonate crystals according to one of the preceding items wherein at most 10% in weight of the crystals are above 1800 pm, or above 1100 pm

[0127] Item 41. Sodium carbonate crystals or sodium bicarbonate crystals according to one of the preceding items wherein the medium size in weight (D50) is comprised between 200 and 600 pm, preferably comprised between 300 and 500 pm.

[0128] Item 42. Sodium carbonate crystals or sodium bicarbonate crystals according to one of the preceding items wherein the crystals have a size fraction passing a 125 pm sieve is less than 8 wt%, preferably less than 4 wt%, more preferably less than 1 wt. %.

[0129] The following examples are intended only to exemplify the invention and are not intended to limit the scope of the claimed invention.

[0130] Examples

[0131] Example 1

[0132] Figure 1 (Fig. 1) shows schematically the function of the electrodialyzer in one embodiment of the method of the present invention, illustrating an advantageous configuration of the electrodialysis cellstack. In this example, the electrodialyzer cellstack comprises a succession of 3 chambers: base chamber, acid chamber, salt chamber.

[0133] An aqueous solution comprising sodium carbonate is fed into the base chamber, bounded between a cationic permselective membrane and an anionic permselective face of a bipolar membrane.

[0134] An aqueous solution is fed into the acid chamber, said acid chamber being bounded between a cationic face of the bipolar membrane and an anionic membrane,

[0135] An aqueous solution comprising sodium chloride is fed into the salt chamber, said salt chamber being bounded between one anionic membrane and one cationic membrane,

[0136] In the base chamber sodium hydroxide (NaOH) and in the acid chamber hydrochloric acid (HC1) are generated, by splitting water molecules with the bipolar membrane into hydroxide anions (OH-) in the base chamber and into hydronium cations (H+) in the acid chamber, transferring sodium ions (Na+) to the base chamber through the cation selective membrane and transferring chloride ions (C1-) to the acid chamber through the anionic membrane by using an electrical tension between the salt chamber and the acid chamber, An aqueous outlet solution comprising sodium hydroxide and sodium carbonate from the base chamber is removed and cane be used as illustrated in Example 2. An aqueous outlet solution comprising sodium chloride depleted in sodium chloride is removed from the salt chamber, and may be re-concentrated with sodium chloride by dissolving solid sodium chloride with an optional brine purification, or be released in the sea if the initial brine was coming from a desalination unit. As such it avoids concentrating locally the sodium chloride in the sea or in brackish ponds and to limit therefore the environmental impact of such release in the environment. It enables also to valorize part of the sodium chloride exiting said desalination unit in a circular way.

[0137] An aqueous outlet solution comprising hydrochloric acid is removed from the acid chamber, so that to be valorize as mentioned in the above described embodiments.

[0138] Example 2

[0139] Figure 2 (Fig. 2) schematically shows an installation for implementing an advantageous embodiment of the method according to the invention. The installation shown schematically in Figure 2 comprises an electrodialysis cell (1), a carbonation tower (2), an evaporator-crystallizer (3) and a dryer (4).

[0140] The electrodialysis cell is a multichamber cell type with a combination of cation, anion, and bipolar membranes comprising acid, base and salt chambers. Cells of this type are well known in electrolytic technique and widely used for the industrial production of aqueous solutions of a base and an acid starting from aqueous solutions of the corresponding salt (Ullmann’s Encyclopedia, Sodium Hydroxide, p. 376).

[0141] According to the invention, an aqueous solution of sodium chloride (6) is introduced into the salt chamber of the electrodialysis cell, while a diluted aqueous hydrochloric acid solution (9) and a diluted aqueous solution comprising sodium carbonate and caustic soda (11) are introduced into the acid and base chambers of the cell, respectively. During electrodialysis cell operation, hydrochloric acid and sodium hydroxide are generated in the acid and base chambers, respectively, while sodium chloride is gradually depleted in the salt chamber. An aqueous outlet solution comprising sodium chloride depleted in sodium chloride is extracted from the salt chamber. Simultaneously, an aqueous solution comprising sodium carbonate and sodium hydroxide enriched in sodium hydroxide and a hydrochloric acid solution enriched in hydrochloric acid are extracted from the base and the acid chamber, respectively. The aqueous solution of sodium chloride fed to the electrodialysis cell and the outlet aqueous solution depleted in sodium chloride extracted from the cell constitute a sodium chloride solution loop. The outlet aqueous solution depleted in sodium chloride is partially purged (7). Another aqueous solution of sodium chloride (5) is fed to the loop in order to raise the sodium chloride concentration. Similarly, the aqueous solution of hydrochloric acid fed to the electrodialysis cell and the outlet aqueous solution enriched in hydrochloric acid extracted from the cell constitute a hydrochloric acid solution loop. The outlet aqueous solution enriched in hydrochloric acid is partially purged from the system for downstream use (10). Water (8) is fed to the hydrochloric acid solution loop in order to regulate the hydrochloric acid concentration. In the same way, the aqueous solution comprising sodium carbonate and sodium hydroxide fed to the electrodialysis cell and the outlet aqueous solution comprising sodium carbonate and sodium hydroxide enriched in sodium hydroxide extracted from the cell constitute a sodium hydroxide and sodium carbonate solution loop. A first portion of the outlet aqueous solution comprising sodium carbonate and sodium hydroxide enriched in sodium hydroxide extracted from the cell (12) is recycled in the sodium hydroxide and sodium carbonate solution loop, wherein another portion (13) is sent to a carbonation tower (2), where a gas comprising carbon dioxide (14) of which 82% of its carbon content is biogenic, generated from a waste to energy unit using waste biomass material, and said CO2 gas is to the carbonation tower to obtain a carbonated liquid, wherein the sodium hydroxide is transformed into sodium carbonate and water. Said carbonated liquid is partly recycled in the sodium hydroxide and sodium carbonate solution loop (15), wherein another portion of the same is sent to an evaporator-crystallizer. In this unit, the slurry is subjected to controlled evaporation to crystallize sodium carbonate. In the same apparatus the crystals of sodium carbonate (17) and a mother liquor (18) are separated. Sodium carbonate crystals are then sent to a drying unit for final processing, giving dry sodium carbonate crystals as the end product (19). - 1 -

[0142] The example below serves to illustrate the invention. It refers to Figure 2. An electrodialysis stack (1) with a 3 chambers configuration, consisting of 100 unitary cells with 1 m2surface area, was assembled by alternating bipolar, anionic and cationic membranes at a current density of 1500 A / m2. 1.2 t / h of a substantially saturated brine (5), containing, per kg, 250 g of sodium chloride, are fed to the sodium chloride solution loop. Simultaneously, 22 t / h of an aqueous solution of sodium chloride (6) containing, per kg, 155 g of sodium chloride is introduced into the salt chamber of the electrodialysis cell. At the same time, 23 t / h of an aqueous solution comprising sodium carbonate and sodium hydroxide (11) containing per kg, 139 g of sodium carbonate and 45 g sodium hydroxide and 20.4 t / h of an aqueous solution of hydrochloric acid (9) containing per kg, 34 g of hydrochloric acid are fed to the base and acid chamber of the cell, respectively.

[0143] At the outlet of the electrodialysis cell, the following are obtained:

[0144] - 20.9 t / h of depleted or dilute brine, containing per kg, 150 g of sodium chloride;

[0145] - 20.5 t / h of an enriched hydrochloric acid solution, containing per kg, 40 g of hydrochloric acid;

[0146] - 23.8 t / h of an aqueous solution comprising sodium carbonate and sodium hydroxide containing per kg, 134 g of sodium carbonate and 50 g sodium hydroxide.

[0147] In order to control the concentration of the hydrochloric acid solution, 3.2 t / h of water (8) are fed to the hydrochloric acid solution loop. 3.3 t / h of a hydrochloric acid solution containing, per kg, 40 g of hydrochloric acid (10) are extracted from the hydrochloric acid solution loop. Similarly, 0.15 t / h of depleted or dilute brine, containing, per kg, 150 g of sodium chloride are extracted from the sodium chloride solution loop.

[0148] 20.5 t / h of the outlet aqueous solution comprising sodium carbonate and sodium hydroxide are recycled to sodium hydroxide and sodium carbonate solution loop (12), wherein 3.3 t / h are sent to a carbonation tower (2). Here, 90 kg / h of carbon dioxide (14) are also fed to obtain a carbonated liquid containing, per kg, 180 g of sodium carbonate. 1 t / h of carbonated liquid (16) are introduced into the evaporator-crystallizer (3), where 168 kg / h of sodium carbonate crystals (17) are separated from the mother liquor (18), containing per kg, 100 g of sodium carbonate, and sent to a dryer (4) obtaining 160 kg / h of dried sodium carbonate crystals (19). The mother liquor (18) is recycled mostly up-front at the evaporator-crystallizer (3) feed, except a part of it which is purged from the crystallizer to control and limit the concentration of soluble impurities (mainly sodium chloride and sulfate) in the mother liquor present in the crystallizer (3) and adjusted according to the specifications content of said impurities to be achieved in the dried sodium carbonate crystals (19). The purge is then recycled at the brine purification sector wherein sodium chloride brine is purified before feeding the electrodialysis cell (1). This enables to valorize the sodium chloride part of the purge and be electrolyzed and so avoiding to be lost. Sodium carbonate and optionally sodium sulfate are also valorized and not lost, as they can be used as precipitating agent of calcium ions (as gypsum and / or calcium carbonate) at the purification sector of the raw brine comprising sodium chloride and its impurities, before being purified and then used in the electrodialysis cell (1) feeding the salt chamber as stream (6). This enables to achieve a sharp decrease in purged brine quantity and to approach a near-zero loss of sodium carbonate in the purged mother liquor from the evaporator-crystallizer (3) sector.

[0149] The sodium carbonate crystals obtained thereto on a 1 month operation testing time, is of excellent purity with a calcium and a magnesium content of less than 20 ppm, an iron content (Fe) of less than 10 mg / kg, with most samples having respectively less than 8 ppm regarding calcium, same for magnesium content, and less than 4 ppm for the iron content. A manufacturing of sodium bicarbonate crystals from the outlet aqueous solution comprising sodium hydroxide and sodium carbonate would enable to obtain comparable crystal purities with the used carbon dioxide gas, as the occlusion of impurities are similar for sodium carbonate and bicarbonate, with generally an even more favorable impurity split in crystals and mother liquor for sodium bicarbonate compared to sodium carbonate crystals for said impurities taking into account also the lesser content of mol of alkaline sodium per mol of sodium bicarbonate compared to same ratio per mol of sodium carbonate.

[0150] Moreover the obtained sodium carbonate crystals present surprisingly a good particle size distribution, with less than 10% in weight of the crystals above 1100 pm, a medium particle size in weight (D50) comprised between 320 and 600 pm, and a size fraction passing a 125 pm sieve of less than 1 wt. % for most samples. Moreover the attrition behavior of such sodium carbonate is similar to the one of the Solvay ammonia process, meeting market requests. The fossil CO2 footprint of said sodium carbonate is reduced when using green electricity of a factor 3 to more than 5 compared to existing soda ammonia process and trona ore process.

[0151] 5

Claims

1. A method for manufacturing a sodium carbonate solution by the electrodialysis of sodium chloride, using an electrodialyzer cellstack comprising several chambers, wherein one of said chambers is fed with an aqueous solution comprising sodium carbonate.

2. The method according to claim 1, wherein at least 25 wt.% or at least 40 wt% of the carbon comprised in the sodium carbonate is biogenic.

3. The method according to claim 2, wherein at least 80 wt.% or at least 90 wt% of the carbon comprised in the sodium carbonate is biogenic.

4. The method according to one of the preceding claims, wherein the electrodialyzer comprises at least 2 chambers, one of which is a salt chamber, a second one is a base chamber.

5. The method according to one of the preceding claims, wherein the electrodialyzer comprises at least 3 chambers, one of which is a salt chamber, a second one is a base chamber and a third one is an acid chamber.

6. The method according to one of the preceding claims, wherein the aqueous solution comprising carbonate is fed to the base chamber.

7. The method according to one of the preceding claims, wherein the cationic membrane and / or the anionic membrane is / are more permeable to monovalent ions than multivalent ions.

8. The method according to one of the preceding claims,, wherein the electrodialyzer cellstack comprises at least three chambers one of which is a salt chamber, a second one is a base chamber and a third one is an acid chamber, and said method comprising:- feeding an aqueous solution comprising sodium chloride into the salt chamber, said salt chamber being bounded between one anionic membrane and one cationic membrane,- feeding the aqueous solution comprising sodium carbonate into the base chamber, said base chamber being bounded between the cationic membrane and an anionic face of a bipolar membrane,- feeding an aqueous solution into the acid chamber, said acid chamber being bounded between a cationic face of the bipolar membrane and an anionic membrane,- generating in the base chamber sodium hydroxide (NaOH) and in the acid chamber hydrochloric acid (HC1), by splitting water molecules with the bipolar membrane into hydroxide anions (OH ) in the base chamber and into hydronium cations (H+) in the acid chamber, transferring sodium ions (Na+) to the base chamber through the cation selective membrane and transferring chloride ions (Cl’) to the acid chamber through the anionic membrane by using an electrical tension between the salt chamber and the acid chamber,- removing an aqueous outlet solution comprising sodium hydroxide and sodium carbonate from the base chamber,- removing an aqueous outlet solution comprising sodium chloride depleted in sodium chloride from the salt chamber,- removing an aqueous outlet solution comprising hydrochloric acid from the acid chamber, and- carbonating at least part of the aqueous outlet solution of the base chamber with a gas comprising carbon dioxide (CO2) to obtain a carbonated liquid wherein at least part of, or the totality of, the sodium hydroxide is transformed into sodium carbonate and water.

9. Method according to the preceding claim, wherein part of the carbonated liquid obtained from carbonating the outlet solution of the base chamber is further processed to crystallize sodium carbonate crystals.

10. Method according to one of the claims 8 or 9, wherein part of the carbonated liquid obtained from carbonating the outlet solution of the base chamber comprises sodium bicarbonate and is further processed to crystallize sodium bicarbonate crystals.

11. Method according to one of the claims 8 to 10, wherein the removed aqueous outlet solution comprising sodium hydroxide and sodium carbonatefrom the base chamber has a molar ratio of alkaline sodium from sodium hydroxide to the alkaline sodium from sodium carbonate is less than 0.5, preferably less than 0.2.

12. Method according to one of the claims 8 to 11, wherein the outlet liquid of the base chamber has a molar concentration of alkaline sodium from sodium carbonate and sodium hydroxide of at least 1, preferably at least 2 mol Na+ per kg.

13. Method according to one of the claims 4 to 12, wherein the sodium chloride from the sodium chloride aqueous solution derives from: a solar pond salt, or sea salt, rock-salt, or a dissolved salt from a geological salt cavity, or industrial vacuum crystallized salt, or a residual or a co-product sodium chloride resulting from an other industry, or a sea-water desalination unit.

14. Method according to one of the preceding claims, wherein the electrodialyzer uses an electrical tension, and said electrical tension is provided with electricity having a reduced fossil CO2 footprint, preferably selected from the group consisting of: hydraulic electricity, solar photovoltaic electricity, wind electricity, waste to energy electricity, electricity generated from biomass combustion, electricity generated from biogas combustion, electricity generated from hydrogen combustion, geothermal electricity, electricity generated by compressed air such as from compressed air stored in underground cavities, nuclear electricity, or mixtures thereof.

15. Method according to one of the preceding claims, wherein carbon dioxide (CO2) used for carbonating at least part of the aqueous outlet solution of the base chamber to obtain a carbonated liquid is at least partly biogenic, or totally biogenic.

16. Method according to one of the preceding claims, wherein carbon dioxide (CO2) used for carbonating at least part of the aqueous outlet solution of the base chamber to obtain a carbonated liquid is from CO2 captured from the air, or deriving from the combustion of fossil carbonaceous combustibles, or deriving from fossil carbon dioxide.

17. Method according to any claims 8 to 16, wherein the carbon dioxide (CO2) derives partly or totally from fumes or gases generated by plants orequipment thereof, selected from the group consisting of: a power plant, a glass plant, a steel or sinter plant, a waste plant or a waste-to-energy plant, a pulp plant, a paper plant, an oil refinery, a petro-chemical plant, a coal gasification plant, a cement plant, a tile manufacturing plant, a brick manufacturing plant, a mining process, a mineral processing plant, a lime plant, an ammonia plant, a fertilizer plant, a biochar plant, a biogas plant, and combinations thereof.

18. Method according to one of the preceding claims, wherein carbon dioxide (CO2) used for carbonating at least part of the aqueous outlet solution of the base chamber is generated by acid attack of limestone (CaCCh) or of a rock comprising carbonated minerals such as dolomite, and the acid attack is made with hydrochloric acid generated in, or derived from, the electrodialyzer cell stack.

19. Sodium carbonate crystals or sodium bicarbonate crystals:- wherein at least 25 wt.% of its carbon content is biogenic carbon, preferably at least 80 wt. % of its carbon content is biogenic carbon; and- comprising at most 20 mg calcium (Ca) and / or at most 20 mg magnesium (Mg) per kilogram of crystals, preferably at most 8 mg calcium and / or at most 8 mg magnesium per kilogram of crystals.

20. Sodium carbonate crystals or sodium bicarbonate crystals according to the preceding claim comprising at most 10 mg iron (Fe), preferably at most 4 mg iron per kilogram of crystals. .

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