Method for producing sodium carbonate solution

Abstract

A process for making a sodium carbonate solution. A process for producing a sodium carbonate solution by electrodialysis of sodium chloride using a stack of electrodialyzer units comprising several chambers, wherein an aqueous solution comprising sodium carbonate is fed to one of the chambers.

Description

[0001] The present invention relates to a method for producing sodium carbonate (Na2CC>3) and / or sodium bicarbonate (NaHCC>3) with reduced fossil carbon dioxide (CO2) emissions by electrodialysis of sodium chloride using an electrodialyzer cell stack comprising several compartments, wherein one of the compartments is fed with an aqueous solution comprising sodium carbonate.

[0002] Advantageously, in the method, the electrodialyzer uses a voltage provided by electricity having a reduced fossil CO2 footprint.

[0003] More advantageously, at least a part of the aqueous solution for the carbonated alkali compartment outlet to obtain a carbonated liquid is partially or completely of biological origin, or from a biological origin source, or not derived from fossil carbon or not derived from fossil carbon dioxide.

[0004] The method enables a sensitive reduction of the CO2 fossil footprint when producing sodium carbonate or sodium bicarbonate compared to known methods and is a way to achieve net zero emissions for such manufacturing and the obtained product. TECHNICAL FIELD

[0005] Sodium carbonate (Na2CC>3) or soda ash is one of the largest quantities of basic alkali products manufactured worldwide, with a total production of more than 65 million tons in 2022. The main uses of sodium carbonate are in the glass, chemicals, detergent industry, non-ferrous metallurgy, and also in the sodium bicarbonate production industry.

[0006] Sodium bicarbonate is also a basic chemical produced worldwide, mainly for food and feed, acid fume abatement, and pharmaceutical uses.

[0007] The main methods for manufacturing sodium carbonate production are the Solvay ammonia synthesis method, the ammonium chloride method, and methods based on sodium carbonate or sodium bicarbonate ores.

[0008] The Solvay ammonia synthesis process (including one of its alternatives: the 'double process' (or HOU process)) is the main process used worldwide (two-thirds of the world production). This process consists in treating an aqueous ammonia containing sodium chloride with a gas containing carbon dioxide. Sodium bicarbonate precipitates from this solution, which is recovered and calcined to obtain sodium carbonate. More details on the Solvay ammonia soda process and production of refined bicarbonate are described in Ullmann's Encyclopedia of Industrial Chemistry ["Sodium Carbonate" chapter, volume 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 abundant raw materials in the world as starting materials, these raw materials being: sodium chloride (NaCI) as a source of sodium, and limestone (CaC03) as a source of CO2 (or carbonate).

[0009] The source of carbonate in the ammonia soda process can be partially or totally replaced by CO2 from other industries or by biogenic CO2. Moreover, limestone (CaC03) which is used as a source of alkalinity at calcination can be replaced by non-fossil alkali. One limitation of the Solvay process at present is that it uses thermal energy (about 9 GJ / ton of soda ash), part of which is used at high temperature for limestone calcination. This high temperature energy source is not easily replaced by green energy such as rapidly developing solar photovoltaic or wind power.

[0010] The main alternative process to produce sodium carbonate (soda ash) at present is those using minerals containing sodium carbonate (such as fossil trona), which represent one third of the world soda ash production. The mined ores related to alkaline volcanic activity exist in a limited number of countries: mainly the USA, Turkey, China. The limited number of countries where such deposits exist leads to heavy intercontinental transportation, and the limited exploitable reserves of the deposits that have been identified. The available quantity of the deposits in Turkey represents about 20 to 40 years of production, while for the Wyoming deposits in the USA it is several centuries. Moreover, the CO2 content of the sodium carbonate or bicarbonate produced from such ores is totally fossil and is released in the atmosphere when used in the glass or metallurgical industry. This makes such processes not long-term sustainable and unable to achieve net zero emissions of fossil CO2 and greenhouse gases to comply with the COP21 commitments.

[0011] Therefore, there is a need for improved sodium carbonate and sodium bicarbonate manufacturing processes that are suitable for the use of sustainable green energy and that can integrate non-fossil CO2 sources or captured fossil CO2 from other industries to meet net-zero emission requirements immediately or stepwise. Such improved processes should meet the need for large-scale use of green and sustainable energy. Indeed, the International Energy Agency Net Zero 2050 Outlook 2023 forecasts that 70% of the total primary energy supply will be renewable, about 10% will be nuclear, and less than 10% will be oil and coal fossil primary energy (compared to 80% globally in 2021 for fossil fuels, including natural gas), and less than 10% will be other energy sources.

[0012] US 6554990 (from Solvay) discloses a process for the manufacture of an alkali metal hydroxide, such as sodium hydroxide, according to which an aqueous solution of an alkali metal halide is circulated in a brine compartment of an electrodialysis unit delimited between an anion membrane and a cation membrane, and the alkali metal halide is introduced in an acid compartment of the unit delimited between the anion membrane and the cationic face of a bipolar membrane, and an aqueous solution of the alkali metal hydroxide is extracted from a base compartment of the unit delimited between the cation membrane and the anionic face of the bipolar membrane. However, the process results in the production of an acid solution comprising hydrochloric acid and sodium chloride. This makes the hydrochloric acid difficult to use for other purposes. SUMMARY

[0013] The present invention relates to a process for the manufacture of a sodium carbonate solution by electrodialysis of sodium chloride using an electrodialyzer unit stack comprising several compartments, wherein one of the compartments is fed with an aqueous solution comprising sodium carbonate.

[0014] The present invention also relates to the above process, wherein the electrodialyzer unit stack comprises at least three compartments, wherein one compartment is a salt compartment, the second compartment is a base compartment and the third compartment is an acid compartment, and the process comprises: - feeding an aqueous solution comprising sodium chloride into the salt compartment, the salt compartment being delimited between an anion membrane and a cation membrane, - feeding an aqueous solution comprising sodium carbonate into the base compartment, the base compartment being delimited between the cation membrane and the anionic face of a bipolar membrane, - feeding an aqueous solution into the acid compartment, the acid compartment being delimited between the cationic face of the bipolar membrane and the anion membrane, - the generation of sodium hydroxide (NaOH) in the base compartment and hydrochloric acid (HC1) in the acid compartment is performed by splitting water molecules into hydroxide anions (OH ) in the base compartment and into hydronium cations (H+) in the acid compartment by means of a bipolar membrane, by means of a cation selective membrane to transfer sodium ions (Na+) to the base compartment, and by means of an anion membrane to transfer chloride ions (CI ) to the acid compartment by using the voltage between the salt compartment and the acid compartment, - removing from the base compartment an outlet aqueous solution comprising sodium hydroxide and sodium carbonate, - removing from the salt compartment a sodium chloride-depleted outlet aqueous solution comprising sodium chloride, - removing from the acid compartment an outlet aqueous solution comprising hydrochloric acid, and - carbonating at least a part of the outlet aqueous solution of the base compartment with a gas comprising carbon dioxide (C02) to obtain a carbonated liquid, wherein at least a part or all of the sodium hydroxide is converted into sodium carbonate and water.

[0015] The inventors of the present invention found that when manufacturing a sodium carbonate solution by electrodialysis of sodium chloride using an electrodialyzer unit stack comprising several compartments, wherein one of the compartments is fed with an aqueous solution comprising sodium carbonate, the membrane defining said compartment has a significantly increased operational lifetime compared to the same membrane defining said compartment when present in a base compartment without sodium carbonate, at the same molar concentration of the aqueous sodium hydroxide solution.

[0016] Furthermore, compared to the production of caustic soda and chlorine gas by membrane electrolysis of a sodium chloride solution, the use of electrodialysis to convert a sodium chloride solution into caustic soda (NaOH) and hydrochloric acid (HC1) to produce sodium carbonate has a significantly reduced electrical consumption. The reduction in energy consumption by electrodialysis is as low as about 30% compared to electrolysis. This easily reduces the C02footprint of the electrical power required for the reaction and switches to 'green energy'.

[0017] Furthermore, the use of electrodialysis to convert sodium chloride solution into sodium hydroxide and sodium carbonate (in the base compartment) and into hydrochloric acid (in the acid compartment) works well in synergy with the use of gaseous bio-source CO2 or CO2 from bio-source origin as impurity level requirements in the CO2 gas fed to the electrodialyzer, where at least part of the caustic soda (NaOH) is replaced by sodium carbonate with lower pH, resulting in less precipitation of divalent and trivalent metal impurities compared to sodium hydroxide of the same molar concentration, thereby also preserving the expected operational lifetime of the membranes used in the electrodialyzer, and reducing the amount of sodium hydroxide solution and hydrochloric acid used for purifying the aqueous solution containing sodium chloride fed to the salt compartment, such as the sodium hydroxide solution and hydrochloric acid used for the secondary purification of the brine in the ion exchange unit (as described in EU - BAT reference document for chlor-alkali production - 2014 - edited by Joint Research Center Institute - doi: 10.2791 / 13138 - 2.5 Salt water purification and 2.5.3.3.).

[0018] The present invention also relates to a process, wherein a part of the carbonated liquid obtained from the outlet solution of the base compartment of the above process is further processed to crystallize sodium carbonate crystals or sodium bicarbonate crystals.

[0019] The present invention also relates to sodium carbonate crystals, wherein at least 25% of its carbon content is bio-source carbon, and these crystals contain at most 20 mg of calcium or magnesium per kg of sodium carbonate crystals. The present invention also relates to sodium bicarbonate crystals, wherein at least 25% of its carbon content is bio-source carbon, and these crystals contain at most 20 mg of calcium or magnesium per kg of sodium bicarbonate crystals. Indeed, the inventors have found that even in case of low impurity levels (such as calcium and magnesium) of the sodium carbonate obtained from the process of the invention, the attrition of the obtained sodium carbonate is acceptable for the main end-uses, and enables them to reduce the fossil CO2 emissions in the scopes 1, 2 and 3 as defined by the Greenhouse Gas Protocol organization.

[0020] The present invention also relates to sodium carbonate crystals or sodium bicarbonate crystals manufactured according to the process of the invention, and wherein at least 25% of the electrical energy used by the electrodialyzer is provided by electrical power selected from the group consisting of: hydroelectric power, solar photovoltaic power, wind power, waste-to-energy power, power generated from biomass combustion, power generated from biogas combustion, power generated from hydrogen combustion, geothermal power, power generated from compressed air (such as compressed air stored in underground caverns), nuclear power, or mixtures thereof.

[0021] In fact, the good synergy of the combination of electrodialysis and sodium carbonate or sodium bicarbonate crystallization presents a surprisingly optimal effect for reducing the CO2 fossil footprint of manufacturing sodium carbonate or sodium bicarbonate and achieving net zero fossil emissions.

[0022] Definitions For the purposes of the present specification, certain terms are intended to have the following meanings.

[0023] The term ‘electrodialysis’ refers to an electrochemical process that enables the at least partial or complete extraction of salt ions from one solution to another by means of ion exchange membranes placed under an electric field.

[0024] The term ‘electrodialyzer cell stack’ refers to the equipment in which the electrodialysis process can be carried out. It generally comprises several cells delimited by ion exchange membranes (also known as ion-selective permselective membranes).

[0025] The term ‘biogenic carbon’ or ‘biogenic carbonate’ is carbon or carbonate whose carbon source is directly in equilibrium with atmospheric CO2. In the present specification, the biogenic (also known as ‘bio-based’) carbon content is measured according to ASTM D6866-22, Standard Test Methods for Determining the Bio-based Content of Solid, Liquid, and Gaseous Samples Using Radiocarbon Analysis. This method provides accurate bio-based / biogenic carbon content results: it uses Isotope Ratio Mass Spectrometry (IRMS) technology to quantify the bio-based or biogenic content of a given product based on the measurement of the carbon 14 isotope of the sample. Instrumental error of the method is typically within 0.1-0.5% (relative standard deviation).

[0026] The term ‘green energy’, also known as ‘renewable energy’, generally refers to energy from renewable natural resources that replenish on the human timescale. This encompasses solar energy (both thermal or photovoltaic electrical energy), wind power, hydroelectric power, bioenergy (derived from biomass, typically from land or from marine sources), and geothermal energy. In the present specification, in addition to the ‘green energy’ listed above, low-fossil CO2 footprint energy includes heat or cold recovered by heat pumps and nuclear energy.

[0027] The term ‘green electricity’, also known as ‘renewable electricity’, generally refers to electricity produced from renewable natural resources that replenish on the human timescale. This encompasses solar energy (from thermal energy or from photovoltaic electrical energy), wind power, hydroelectric or hydrokinetic power, marine power, electricity derived or produced from bioenergy (i.e. from biomass, and typically from land or from marine sources), and electricity derived from geothermal energy. In the present specification, in addition to the ‘green energy’ listed above, low-fossil CO2 footprint electricity includes nuclear electricity (electricity produced from nuclear energy).

[0028] The term "purge" refers to a stream withdrawn from a part of the process in order to limit the impurities concentration in the process.

[0029] The expression "derived from", for example "the sodium chloride derived from the solar pond" means a stream of sodium chloride withdrawn from the solar pond as it is, or a stream that has been subjected to one or several chemical engineering operations (such as: purification, concentration, thermal conversion, decantation, centrifugation, crystallization, filtration, evaporation, drying, dilution, heating, cooling operations) downstream of the crystallizer, or a stream that has been mixed with one or more other streams, but still retains at least a part of the sodium chloride withdrawn from the solar pond. derived from

[0030] The term "impurities" refers to chemical compounds different from the sodium carbonate and / or bicarbonate salt to be produced.

[0031] The term "carbonation" refers to the action of increasing the total amount of carbonates (i.e. carbonate and bicarbonate) of a stream.

[0032] The term "bicarbonation" refers to the action of increasing the amount of bicarbonate of a stream.

[0033] The term "comprising" encompasses "consisting essentially of" as well as "consisting of".

[0034] In the present specification, the terms "%", "wt%", "wt%", "wt. %", "weight percent" or "percent by weight" are used interchangeably, unless the "%" term is explicitly referring to another physical unit (such as for example "mole%" or "mol. %", "volume%" or "vol. %", and the like).

[0035] A plurality of elements includes two or more elements.

[0036] The phrase 'A and / or B' refers to the following choices: element A; or element B; or a 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' is equivalent to at least one of A and B.

[0037] The phrase 'A1, A2,..., and / or An' (where n > 3) includes the following choices: any single element Ai (i = 1, 2,..., n); or any sub-combination of from two to (n-1) elements selected from A1, A2,..., An; or a combination of all elements Ai (i = 1, 2,..., n). For example, the phrase 'A1, A2, and / or A3' refers to the following choices: A1; A2; A3; A1 + A2; A1 + A3; A2 + A3; or A1 + A2 + A3. ​

[0038] In this specification, the description of a series of values ​​for a variable defined by a lower limit, or an upper limit, or by both a lower limit and an upper limit also includes embodiments in which the variable is selected correspondingly within that range of values: excluding the lower limit, or excluding the upper limit, or excluding both the lower limit and the upper limit.

[0039] In this specification, the description of several consecutive ranges of values ​​for the same variable also includes descriptions of embodiments in which the variable is selected from any other intermediate ranges included in these consecutive ranges. Thus, for illustrative purposes, when stating "Element X is typically at least 10, advantageously at least 15," this specification also includes another embodiment in which a new minimum value can be selected between 10 and 15, for example: where "Element X is at least 11," or additionally where "Element X is at least 13.74," etc.; 11 or 13.74 are values ​​included between 10 and 15. Also for illustrative purposes, when indicating "Element X is typically at most 15, advantageously at most 10," this specification also includes another embodiment in which a new maximum value can be selected between 10 and 15.

[0040] In this specification, where an element or component is referred to as being included in and / or selected from a list of enumerated elements or components, it should be understood that in the relevant embodiments explicitly considered herein, the element or component may also be any one of these individually enumerated elements or components, or may also be a group consisting of any two or more of these explicitly listed elements or components.

[0041] For example, when the selection of elements from a set of elements is described in the embodiments, the following embodiments are also explicitly described: - Select two or more elements from this group. - Select features from a subgroup of features that has had one or more features removed from it.

[0042] The singular 'a' or 'one' used in this article includes the plural unless otherwise expressly indicated.

[0043] If the term “about” is used before a numerical value, it corresponds to a variation of ±10% of the nominal value, unless otherwise indicated. Attached Figure Description

[0044] Figure 1 (Fig. 1) schematically illustrates the function of an electrodialysis unit in one embodiment of the method of the present invention.

[0045] Figure 2 (Fig. 2) schematically illustrates an apparatus for implementing an embodiment of the method according to the invention. DETAILED DESCRIPTION

[0046] Electrodialysis refers to an electrochemical process that is able to extract salt ions from one solution to another through ion exchange membranes placed under an electric field.

[0047] Electrodialysis techniques are known: they are mainly used in electroseparation processes, such as the production of drinking water, the treatment of industrial waste water, the recovery of acids or bases in the metal plating industry, food and pharmaceutical processes. The principle of electrodialysis is detailed in, for example, Ullmann’s Encyclopedia of Industrial Chemistry (2011 edition, Wiley -VCH Verlag GmbH & Co, volume 12, pages 273-313, Electrochemistry) or Technique de l’Ingénieur Encyclopedia (2006 edition, Electrodialysis chapter, J2840 V1, 2006, pages 1-15 and technical appendix pages 1-3).

[0048] In a preferred mode of the application, the electrodialysis operates in an electrodialysis cell stack comprising a combination of bipolar ion exchange membranes with anion and / or cation exchange membranes within a set of contiguous compartments.

[0049] An anion membrane is an ion exchange membrane permeable to anions and ideally impermeable to cations. A cation membrane is itself permeable to cations and impermeable to anions. A bipolar membrane is an ion exchange membrane comprising a cationic face and an anionic face. Such a membrane can be produced by joining a cation membrane and an anion membrane. A bipolar membrane can be produced, for example, by the method described in WO 01 / 79335 in the name of Solvay.

[0050] Within a bipolar membrane, under the action of a sufficient local electric field, water that has diffused into it dissociates into its H + and OH - ions, which then migrate on both sides of the membrane. Thus, acidification exists in one of the compartments adjacent to the bipolar membrane and alkalization exists in the other adjacent compartment. Sequential bipolar membranes are separated by cationic or anionic unipolar membranes. When an electrodialyzer has only bipolar membranes and one type of unipolar membrane (cationic or anionic), it is said to have two (types of) compartments. The electrodialyzer used in the method of the application preferably has only bipolar membranes and anion membranes.

[0051] The compartment located between the anionic face of the bipolar membrane and the cationic membrane constitutes the alkaline compartment. In this compartment, OH -The supply of ions. In the method of the invention, an aqueous solution comprising sodium carbonate is fed to the base compartment. OH - The ions will provide alkalinity to thus absorb acidic carbon dioxide to form a carbonated solution.

[0052] In an advantageous embodiment, the electrodialyser used in the invention comprises at least three compartments, one of which is a salt compartment, the second compartment is a base compartment and the third compartment is an acid compartment.

[0053] A first advantage of the invention is that the operating time of the membrane in contact with the base compartment into which an aqueous solution comprising sodium carbonate is introduced, before acid washing or replacement, is increased compared to the same equipment without sodium carbonate in the compartments.

[0054] A second advantage of the invention is that the electrical energy consumption of the method for producing sodium carbonate or sodium bicarbonate is reduced compared to the equivalent method in which an electrolyser would be used instead of an electrodialyser, thus reducing the CO2 footprint linked to the production of electrical energy whatever the source of electrical energy, thus easily enabling the sodium carbonate or sodium bicarbonate produced to achieve a near-zero CO2 footprint.

[0055] A third advantage of the invention is the possibility of using renewable or low-fossil-CO2-footprint energy to replace the high-temperature step of the conventional method (calcination of limestone into lime, which is used in both the soda-ammonia process and the trona solution mining process, usually using coal) and to replace it with electrical power with a reduced fossil-CO2 footprint, said electrical power being preferably selected from the group consisting of hydroelectric power, photovoltaic power, wind power, waste-to-energy power, power generated from biogas, power generated from biomass combustion, power generated from hydrogen combustion, geothermal power, power generated from compressed air (such as compressed air stored in underground caverns), nuclear power and mixtures thereof. This also contributes to the near-zero CO2 footprint of the sodium carbonate or sodium bicarbonate produced.

[0056] A fourth advantage of the invention is the ease of capturing CO2 from flue gases, or from other industries, or from the atmosphere, since the sodium hydroxide produced has a high reactivity, capturing said CO2 even at low concentrations (with a CO2 concentration lower than 30% vol. or even lower than 10% vol. based on dry gas), or even for efficiently capturing CO2 from the Earth's atmosphere (about 420 ppm by volume) and increasing the circularity of the CO2 resource by manufacturing sodium carbonate or sodium bicarbonate.

[0057] A fifth advantage of the invention is the ability to use low purity limestone (CaCCb) of 60% to 85% CaCCb when CO2 capture or CO2 from other industries is not available locally (this is not recommended at all in the ammonia-soda process because mineral impurities of limestone, mainly clay and aluminum or iron silicates, form insoluble substances with hydrated lime Ca(OH)2, which causes loss of calcium hydroxide and severe fouling in the still).

[0058] A sixth advantage of the invention is the use of other by-products (such as concentrated brines from desalination discharges of reverse osmosis or of multiple-effect evaporation plants from areas of the world where there is a lack of drinking water) by synergistic addition and their use as NaCl raw material of the process of the invention, and by doing so, the pressure on existing natural resources is reduced.

[0059] A seventh advantage of the invention is the possibility of treating the sodium carbonate solution that leaves the lye compartment, even if it contains traces of sodium chloride generated by the leakage of chloride ions from the salt compartment to the lye compartment through the cation membrane of the electrodialyzer, because the sodium chloride will then be separated during the crystallization of sodium carbonate or bicarbonate and will remain in the mother liquor of the crystallizer. Said sodium chloride, which is then washed with part of the sodium carbonate, can be recycled to the front end of the brine (NaCl solution) for purifying the impurities of said brine (such as calcium) before feeding it to the salt compartment, avoiding or reducing the loss of sodium carbonate and enabling the production of useful synergies between the electrodialyzer section and the crystallization of sodium carbonate or bicarbonate.

[0060] Thus, the process of the invention enables to improve the circularity of the use of raw materials such as sodium chloride or limestone and optimizes, by synergistic effect, the reduction of the CO2 footprint of the manufacture of sodium carbonate or bicarbonate paving the way for net zero emissions.

[0061] The invention relates to several advantageous embodiments which are described hereinafter as ‘items’.

[0062] Item 1. A process for the manufacture of a sodium carbonate solution by electrodialysis of sodium chloride using an electrodialyzer unit stack comprising several compartments, wherein one of said compartments is fed with an aqueous solution comprising sodium carbonate.

[0063] Item 2. The process according to item 1, wherein at least 25 wt.%, more advantageously at least 40 wt% of the carbon comprised in the sodium carbonate is of biological origin or from a biological origin source.

[0064] Item 3. The process according to item 2, wherein at least 80 wt.% or at least 90 wt.% of the carbon comprised in the sodium carbonate is of biological origin or from a biological origin source.

[0065] Project 4. The method according to one of the preceding projects, wherein the electrodialysis unit comprises at least two chambers, one of which is a salt chamber and the second chamber is an alkali chamber.

[0066] Project 5. The method according to one of the preceding projects, wherein the electrodialysis unit comprises at least three chambers, one of which is a salt chamber, the second chamber is an alkali chamber, and the third chamber is an acid chamber.

[0067] Project 6. A method according to one of the preceding projects, wherein one of the chambers is a salt chamber defined between an anion exchange membrane and a cation exchange membrane.

[0068] Project 7. The method according to one of the preceding projects, wherein one of these chambers is an alkaline chamber defined between the anion side of a cation membrane and a bipolar membrane.

[0069] Project 8. The method according to one of the preceding projects, wherein one of these chambers is an acid chamber defined between the cation side of the bipolar membrane and the anion side of the bipolar membrane.

[0070] Project 9. The method according to one of the preceding projects, wherein the aqueous solution containing carbonate is fed into the alkali chamber.

[0071] Item 10. The method according to one of the preceding items, wherein the cation membrane and / or the anion membrane is selective for monovalent ions. In this specification, 'selective for monovalent ions' means selective permeation of the cation or anion membrane, allowing either monovalent cations or monovalent anions to permeate, and preventing or reducing the permeation of divalent or trivalent cations or anions. This is particularly advantageous in the present invention because it further limits the permeation of impurities such as divalent ions: calcium (Ca). 2 + ), magnesium (Mg) 2+ ), sulfate (SO4 -- ), nitrate (NO3-), silicate (SiO3-) 2- ), or trivalent ions (Fe 3+ Al 3+ ...), borate (BO3) 3- Ions migrate from the salt chamber to the alkali chamber, thus increasing the purity of the produced sodium carbonate or sodium bicarbonate solution. It also reduces scaling of insoluble precipitates (such as CaCO3, Mg(OH)2, or silicates of iron, aluminum, or calcium) in the membrane.

[0072] Item 11. A method according to one of the preceding items, wherein the electrodialysis unit stack comprises at least three chambers, one chamber being a salt chamber, a second chamber being an alkali chamber, and a third chamber being an acid chamber, and the method comprising: - feeding an aqueous solution comprising sodium chloride into a salt compartment, said salt compartment being delimited between an anion membrane and a cation membrane, - feeding an aqueous solution comprising sodium carbonate into a base compartment, said base compartment being delimited between the cation membrane and the anion face of the bipolar membrane, - feeding an aqueous solution into an acid compartment, said acid compartment being delimited between the cation face of the bipolar membrane and the anion membrane, - the generation of sodium hydroxide (NaOH) in the base compartment and of hydrochloric acid (HC1) in the acid compartment is performed by splitting water molecules into hydroxide anions (OH ) in the base compartment and into hydronium cations (H+) in the acid compartment using the bipolar membrane, by transferring sodium ions (Na+) to the base compartment through the cation selective membrane, and by transferring chloride ions (CI ) to the acid compartment through the anion membrane using the voltage between the salt compartment and the acid compartment, - removing an outlet aqueous solution comprising sodium hydroxide and sodium carbonate from the base compartment, - removing an outlet aqueous solution comprising sodium chloride from the salt compartment, which is sodium chloride depleted, - removing an outlet aqueous solution comprising hydrochloric acid from the acid compartment, and - carbonating at least part of the outlet aqueous solution of the base compartment with a gas comprising carbon dioxide (C02) to obtain a carbonated liquid, wherein at least part or all of the sodium hydroxide is converted into sodium carbonate and water.

[0073] Item 12a. The method according to one of the preceding claims, wherein the electrodialyzer cell stack comprises at least one acid compartment, and wherein the aqueous solution fed into the acid compartment comprises less than 1 g calcium per kg of aqueous solution. This embodiment enables valorization of the hydrochloric acid produced in the acid compartment in more uses.

[0074] Item 12b. The method according to one of the preceding claims, wherein the electrodialyzer cell stack comprises at least one acid compartment, and wherein the aqueous solution fed into the acid compartment comprises at least 2 wt% or at least 4 wt% of calcium (expressed by weight of calcium). This can be calcium dissolved as calcium chloride (CaCI2). This embodiment enables co-production of calcium chloride from the acid compartment, in addition to sodium carbonate or sodium bicarbonate of the present invention.

[0075] Item 13. The method according to one of items 4 to 12b, wherein the aqueous solution comprising sodium chloride fed into the salt compartment comprises less than 20 g of calcium, preferably less than 8 g of calcium, per kg of aqueous solution.

[0076] Item 14. The method according to one of items 4 to 13, wherein the aqueous solution comprising sodium chloride fed into the salt compartment comprises less than 2.5 g of magnesium, preferably less than 0.5 g of magnesium, per kg of aqueous solution.

[0077] Item 15. The method according to one of items 4 to 13, wherein the aqueous solution comprising sodium chloride fed into the salt compartment comprises less than 20 microgram Ca + Mg per liter of cumulative weight of calcium and magnesium.

[0078] Item 16. The method according to one of items 11 to 15, wherein a part of the carbonated liquid obtained from carbonating the outlet solution of the base compartment is further processed to crystallize sodium carbonate crystals. This can for example be done by removing a part of the water of the carbonated solution in order to reach the solubility limit of sodium carbonate and to crystallize crystals of sodium carbonate.

[0079] Item 17. The method according to one of items 11 to 16, wherein a part of the carbonated liquid obtained from carbonating the outlet solution of the base compartment comprises sodium bicarbonate and is further processed to crystallize sodium bicarbonate crystals. Examples of such further processing can be: - by removing a part of the water in the bicarbonate solution to reach the solubility limit of sodium bicarbonate and to crystallize crystals of sodium bicarbonate; - or alternatively by controlling the concentrations of sodium carbonate and sodium hydroxide of the outlet aqueous solution from the base compartment such that when said outlet aqueous solution is further bicarbonated by reacting the solution with CO2, the solubility limit of sodium bicarbonate is reached and crystals of sodium bicarbonate are crystallized.

[0080] Item 18. The method according to one of items 11 to 17, or alternatives thereof, wherein the carbonated liquid obtained from carbonation of the outlet aqueous solution of the base compartment is partially recycled back into the electrodialyzer unit stack as an aqueous solution comprising sodium carbonate.

[0081] Item 19. The method according to one of items 11 to 18, wherein the outlet aqueous solution comprising sodium hydroxide and sodium carbonate removed from the alkaline compartment has a molar ratio of alkaline sodium from sodium hydroxide to alkaline sodium from sodium carbonate of less than 0.5, preferably less than 0.2. This is particularly advantageous to limit the aging of the membrane present in the alkaline compartment and to increase the operating life of said membrane, or to increase the operating time of said membrane between two pickling operations in one or more alkaline compartments to limit the overvoltage across said membrane. In the method of the present invention, the concentration of sodium hydroxide and sodium carbonate in the outlet aqueous solution removed from the alkaline compartment is not particularly limited. However, too dilute a solution leads to a large energy consumption for the recovery or concentration of the sodium carbonate subsequently produced. And whereas too great a concentration can lead to solubility limitations of the sodium carbonate salt, with the risk of encrustation of the compartment and of the membrane contained therein.

[0082] Item 20. The method according to one of items 11 to 19, wherein the outlet liquid of the alkaline compartment 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 alkaline compartment.

[0083] Item 21. The method according to one of items 11 to 20, wherein the outlet aqueous solution comprising hydrochloric acid from the acid compartment comprises at least 1 wt% and preferably at most 8 wt% of HC1.

[0084] Item 22. The method according to one of items 11 to 21, wherein the outlet aqueous solution comprising hydrochloric acid is further processed to concentrate it into a concentrated aqueous solution of hydrochloric acid.

[0085] Item 23. The 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.

[0086] Item 24. The method according to one of items 11 to 23, wherein the sodium chloride from the aqueous sodium chloride solution originates from: solar pond salt, or sea salt, rock salt, or dissolved salt from geological salt caverns, or industrial vacuum crystallized salt, or residual or by-product sodium chloride from other industries, or a seawater desalination unit.

[0087] Item 25. The method according to one of the preceding items, wherein the electrodialyzer uses electricity, and said electricity is provided by electricity having a reduced fossil CO2 footprint, preferably selected from the group consisting of: hydroelectric power, solar photovoltaic power, wind power, waste-to-energy power, power generated from biomass combustion, power generated from biogas combustion, power generated from hydrogen combustion, geothermal power, power generated from compressed air (such as compressed air stored in underground caverns), nuclear power, or mixtures thereof.

[0088] Item 26. The method according to one of the preceding items, wherein the electrodialyzer cell stack comprises at least five chambers: one anode chamber, one acid chamber, one salt chamber, one base chamber, one cathode chamber.

[0089] Item 27. The method according to one of the preceding items, wherein the carbon dioxide (CO2) used to carbonate the outlet aqueous solution of the base chamber to obtain a carbonated liquid is at least partially of biological origin, or is entirely of biological origin, not derived from fossil carbon or not derived from fossil carbon dioxide. Advantageously, carbon dioxide (CO2) comprising CO2 of biological origin can be produced from a concentration or purification process that increases its CO2 concentration. This can include concentration methods such as: amine-based methods, ammonia-based methods, pressure swing adsorption (PSA) methods, temperature swing adsorption (TSA) methods, cryogenic methods, or membrane methods.

[0090] Item 28. The method according to one of the preceding items, wherein at least part of the carbon dioxide (CO2) used to carbonate the outlet aqueous solution of the base chamber to obtain a carbonated liquid is from CO2 captured from air, or is derived from the combustion of fossil carbonaceous fuels, or is derived from fossil carbon dioxide.

[0091] Item 29. The method according to any of items 11 to 28, wherein the carbon dioxide (CO2) is partially or entirely derived from smoke or gas generated by a plant or equipment thereof selected from the group consisting of: a power plant, a glass plant, a steel or sintering plant, a waste plant or waste-to-energy plant, a pulp plant, a paper plant, an oil refinery, a petrochemical 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 chemical fertilizer plant, a biochar plant, a biogas plant, and combinations thereof.

[0092] Item 30. The method according to one of the preceding items, wherein the carbon dioxide (CO2) of at least part of the outlet aqueous solution of the base chamber used to carbonate is generated by acid erosion of limestone (CaCCb) or of a rock comprising carbonate material such as dolomite, and the acid erosion is performed with hydrochloric acid generated in or derived from the electrodialyzer cell stack.

[0093] Item 31. A method for manufacturing sodium carbonate crystals from sodium chloride and green electricity or electricity with a reduced fossil CO2 footprint, the method comprising: (a) providing solid sodium chloride or a brine comprising sodium chloride and water, (b) optionally pre-treating the brine to reduce impurities detrimental to a selective permeation membrane selected from the group of a cation selective permeation membrane, an anion selective permeation membrane, a bipolar membrane, and combinations thereof, for producing a purified brine comprising sodium chloride and water, (d) manufacturing a sodium carbonate solution according to the method of any one of the preceding items 1 to 30, wherein the brine or the optional purified brine is used as an aqueous solution comprising sodium chloride fed to a salt compartment, and wherein the voltage is provided by green electricity or by electricity with a reduced fossil CO2 footprint, (e) concentrating the sodium carbonate solution by removing a portion of the water content of the sodium carbonate solution so as to produce sodium carbonate crystals and a mother liquor, (f) separating the sodium carbonate crystals from the mother liquor, (g) optionally drying the sodium carbonate crystals to obtain dried sodium carbonate crystals.

[0094] Item 32. The method 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, a sodium carbonate anhydrous crystallizer, a sodium carbonate sesquihydrate crystallizer, and combinations thereof.

[0095] Item 33. The method according to the preceding item, wherein the sodium carbonate crystallizer is a sodium carbonate monohydrate evaporator crystallizer using mechanical vapor recompression, and wherein preferably the mechanical vapor recompression uses green electricity or electricity with a reduced fossil CO2 footprint.

[0096] Item 34. The method according to any one of items 31 to 33, wherein the solid sodium chloride, or the brine comprising sodium chloride and water, is derived from: solar pond salt, or sea salt, rock salt, or dissolved salt from geological salt caverns, or industrial vacuum crystallized salt, or residual or by-product sodium chloride from other industries, or a seawater desalination unit.

[0097] Item 35. A sodium carbonate crystal or a sodium bicarbonate crystal: - 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 - the crystals comprise at most 20 mg of calcium and / or at most 20 mg of magnesium per kg of crystals, preferably at most 8 mg of calcium and / or at most 8 mg of magnesium per kg of crystals.

[0098] Item 36. The sodium carbonate crystals or sodium bicarbonate crystals according to the preceding items, comprising at most 10 mg of iron (Fe) per kg of crystals, preferably at most 4 mg of iron (Fe) per kg of crystals.

[0099] Item 37. The sodium carbonate crystals or sodium bicarbonate crystals according to item 35 or 36, wherein at least 25% of the electrodialytic electric power used to manufacture said sodium carbonate or sodium bicarbonate crystals is selected from the list of item 25, and preferably from: solar photovoltaic electric power, wind electric power, hydroelectric power, and mixtures thereof.

[0100] Item 38. The sodium carbonate crystals or sodium bicarbonate crystals according to the preceding items, wherein at least 60% or at least 70% of the electrodialytic electric power used to manufacture said sodium carbonate or sodium bicarbonate crystals is selected from the list of item 25, and preferably from: solar photovoltaic electric power, wind electric power, hydroelectric power, and mixtures thereof.

[0101] Item 39. The sodium carbonate crystals or sodium bicarbonate crystals according to the preceding items, wherein at least 10% by weight of the crystals exceed 50 pm, or exceed 200 pm.

[0102] Item 40. The sodium carbonate crystals or sodium bicarbonate crystals according to one of the preceding items, wherein at most 10% by weight of the crystals exceed 1800 pm, or exceed 1100 pm.

[0103] Item 41. The sodium carbonate crystals or sodium bicarbonate crystals according to one of the preceding items, wherein the median size (D50) by weight is comprised between 200 and 600 pm, preferably comprised between 300 and 500 pm.

[0104] Item 42. The sodium carbonate crystals or sodium bicarbonate crystals according to one of the preceding items, wherein the fraction of crystals having a particle size below 125 pm is less than 8 wt%, preferably less than 4 wt%, more preferably less than 1 wt.%.

[0105] The following examples are merely intended to illustrate the present application and are not intended to limit the scope of the claimed invention.

[0106] Example Example 1 Figure 1 (Fig. 1) illustrates schematically the functioning of an electrodialyzer in one embodiment of the method of the present application, illustrating a favorable configuration of the electrodialysis cell stack. In this example, the electrodialyzer cell stack comprises three consecutive compartments: a base compartment, an acid compartment, and a salt compartment.

[0107] A sodium carbonate containing aqueous solution is fed into the base compartment, which is delimited between a cation-selective permeable membrane and the anion-selective permeable face of a bipolar membrane.

[0108] The aqueous solution is fed into the acid compartment, which is delimited between the cation face of the bipolar membrane and the anion membrane, The aqueous solution comprising sodium chloride is fed into the salt compartment, which is delimited between one anion membrane and one cation membrane, The production of sodium hydroxide (NaOH) in the base compartment and of hydrochloric acid (HC1) in the acid compartment is performed by splitting water molecules into hydroxide anions (OH") in the base compartment and into hydronium cations (H+) in the acid compartment with the bipolar membrane, by transferring sodium ions (Na+) to the base compartment through the cation selective membrane, and by transferring chloride ions (CI") to the acid compartment through the anion membrane by using the voltage between the salt and acid compartments.

[0109] The outlet aqueous solution comprising sodium hydroxide and sodium carbonate is removed from the base compartment and can be used as shown in example 2. The sodium chloride-depleted outlet aqueous solution comprising sodium chloride is removed from the salt compartment and the sodium chloride can be reconcentrated by dissolution of solid sodium chloride and optionally brine purification, or if the initial brine comes from a desalination unit, it is released to the sea. It thus avoids the local concentration of sodium chloride in the sea or in a salted pool and thus limits the environmental impact of such a release in the environment. It also enables the valorization of a part of the sodium chloride leaving said desalination unit in a cyclic manner.

[0110] The outlet aqueous solution comprising hydrochloric acid is removed from the acid compartment, so as to be valorized as mentioned in the above examples.

[0111] Example 2 Figure 2 (Fig. 2) schematically illustrates the setup for implementing an advantageous embodiment of the method according to the application. Figure 2 The setup schematically illustrated in Fig. 1 comprises an electrodialysis unit (1), a carbonation tower (2), an evaporator-crystallizer (3) and a dryer (4).

[0112] The electrodialysis unit is a multi-compartment unit type comprising an acid compartment, a base compartment and a salt compartment, with a combination of cation membranes, anion membranes and bipolar membranes. This type of unit is well known in the electrolysis technology and is widely used for the industrial production of aqueous solutions of bases and acids starting from aqueous solutions of the corresponding salts (Ullmann's Encyclopedia, Sodium Hydroxide, page 376).

[0113] According to the present invention, an aqueous sodium chloride solution (6) is introduced into the salt compartment of an electrodialysis unit, while a diluted aqueous hydrochloric acid solution (9) and a diluted aqueous solution containing sodium carbonate and caustic soda (11) are introduced into the acid and base compartments of the unit, respectively. During the operation of the electrodialysis unit, hydrochloric acid and sodium hydroxide are generated in the acid and base compartments, respectively, while sodium chloride is gradually depleted in the salt compartment. An outlet aqueous solution depleted in sodium chloride containing sodium chloride is extracted from the salt compartment. At the same time, an outlet aqueous solution enriched in sodium hydroxide containing sodium carbonate and sodium hydroxide is extracted from the base compartment and an outlet solution enriched in hydrochloric acid is extracted from the acid compartment, respectively. The aqueous sodium chloride solution fed to the electrodialysis unit and the outlet aqueous solution depleted in sodium chloride extracted from the unit constitute a sodium chloride solution loop. The outlet aqueous solution depleted in sodium chloride is partially washed (7). Another aqueous sodium chloride solution (5) is fed to the loop to increase the sodium chloride concentration. Similarly, the aqueous hydrochloric acid solution fed to the electrodialysis unit and the outlet aqueous solution enriched in hydrochloric acid extracted from the unit constitute a hydrochloric acid solution loop. The outlet aqueous solution enriched in hydrochloric acid from the system is partially washed for downstream use (10). Water (8) is fed to the hydrochloric acid solution loop to adjust the hydrochloric acid concentration. In the same way, the aqueous solution containing sodium carbonate and sodium hydroxide fed to the electrodialysis unit and the outlet aqueous solution enriched in sodium hydroxide containing sodium carbonate and sodium hydroxide extracted from the unit constitute a sodium hydroxide and sodium carbonate solution loop. A first part (12) of the outlet aqueous solution enriched in sodium hydroxide containing sodium carbonate and sodium hydroxide extracted from the unit is recirculated in the sodium hydroxide and sodium carbonate solution loop, where another part (13) is sent to a carbonation column (2), where a gas containing carbon dioxide (14) (where 82% of its carbon content is of biological origin) is generated from a waste-to-energy unit using waste biomass material and the CO2 gas is sent to the carbonation column to obtain a carbonated liquid, where sodium hydroxide is converted into sodium carbonate and water. The carbonated liquid is partially recirculated in this sodium hydroxide and sodium carbonate solution loop (15), where another part of it is sent to an evaporator-crystallizer. In this unit, the slurry is subjected to controlled evaporation to crystallize sodium carbonate. In the same device, sodium carbonate crystals (17) and mother liquor (18) are separated. The sodium carbonate crystals are then sent to a drying unit for final processing, resulting in dry sodium carbonate crystals as the final product (19).

[0114] The following example is used to illustrate the present invention. It refers to Figure 2 . An electrodialysis stack with a 3-compartment configuration (1) was assembled by alternating bipolar membranes, anion membranes and cation membranes (100 of 1 m 2 2 ​of 1.2 t / h of substantially saturated brine (5) containing 250 g of sodium chloride per kg is fed into the sodium chloride solution loop. At the same time, 22 t / h of aqueous sodium chloride solution (6) containing 155 g of sodium chloride per kg is introduced into the salt compartment of the electrodialysis unit. At the same time, 23 t / h of aqueous solution containing sodium carbonate and sodium hydroxide (11) containing 139 g of sodium carbonate and 45 g of sodium hydroxide per kg and 20.4 t / h of aqueous hydrochloric acid solution (9) containing 34 g of hydrochloric acid per kg are fed into the base compartment and the acid compartment of the unit, respectively.

[0115] At the outlet of the electrodialysis unit, the following are obtained: - 20.9 t / h of depleted or dilute brine containing 150 g of sodium chloride per kg; - 20.5 t / h of a solution enriched in hydrochloric acid containing 40 g of hydrochloric acid per kg; - 23.8 t / h of aqueous solution containing sodium carbonate and sodium hydroxide containing 134 g of sodium carbonate and 50 g of sodium hydroxide per kg.

[0116] In order to control the concentration of the hydrochloric acid solution, 3.2 t / h of water (8) is fed into the hydrochloric acid solution loop. From the hydrochloric acid solution loop, 3.3 t / h of hydrochloric acid solution containing 40 g of hydrochloric acid per kg (10) is extracted. Similarly, from the sodium chloride solution loop, 0.15 t / h of depleted or dilute brine containing 150 g of sodium chloride per kg is extracted.

[0117] The 20.5 t / h of aqueous outlet solution containing sodium carbonate and sodium hydroxide is recirculated to the sodium hydroxide and carbonate solution loop (12), of which 3.3 t / h is sent to the carbonation column (2). Here, 90 kg / h of carbon dioxide (14) is also fed in to obtain a carbonated liquid containing 180 g of sodium carbonate per kg. 1 t / h of carbonated liquid (16) is introduced into the evaporator-crystallizer (3), of which 168 kg / h of sodium carbonate crystals (17) are separated from the mother liquor (18) containing 100 g of sodium carbonate per kg and sent to the drier (4), obtaining 160 kg / h of dried sodium carbonate crystals (19).

[0118] The mother liquor (18) is mainly recycled at the front end of the evaporator-crystallizer (3) feed, except for its following part: washed out of the crystallizer to control and limit the concentration of soluble impurities (mainly sodium chloride and sodium sulfate) in the mother liquor present in the crystallizer (3) and adjusted according to the specification content of said impurities to be achieved in the dried sodium carbonate crystals (19). The wash liquid is then recycled at the brine purification section, where the sodium chloride brine is purified before feeding the electrodialysis unit (1). This enables valorization and electrolysis of the sodium chloride part of the wash liquid and thus avoids losses. Sodium carbonate and optionally sodium sulfate are also valorized and not lost as they can be used as precipitants of calcium ions (as gypsum and / or calcium carbonate) in the purification section of the raw brine containing sodium chloride and its impurities before purification and then used in the electrodialysis unit (1) as feed to the salt compartments in stream (6). This enables a drastic reduction of the amount of washed brine and a near zero loss of sodium carbonate in the washed mother liquor from the evaporator-crystallizer (3) section.

[0119] The sodium carbonate crystals thus obtained over a 1 month operating test time have an excellent purity with calcium and magnesium content less than 20 ppm, iron content (Fe) less than 10 mg / kg, with most of the samples having less than 8 ppm of calcium, same magnesium content, and less than 4 ppm of iron content, respectively. The production of sodium bicarbonate crystals from the outlet aqueous solution containing sodium hydroxide and sodium carbonate would enable to obtain a crystal purity comparable to when using carbon dioxide gas, as the occlusion of impurities is similar for sodium carbonate and sodium bicarbonate, and the impurity partitioning in the crystal and mother liquor is generally even more favorable for sodium bicarbonate than for sodium carbonate crystals, and also considering the lower molar content of basic sodium per mole of sodium bicarbonate compared to the same ratio per mole of sodium carbonate.

[0120] Moreover, the obtained sodium carbonate crystals surprisingly present a good particle size distribution, with less than 10% of the crystal weight exceeding 1100 pm, the median particle size (D50) by weight comprised between 320 pm and 600 pm, and for most of the samples, a particle size fraction through 125 pm sieve of less than 1 wt.%. Moreover, the attrition behavior of such sodium carbonate is similar to the attrition behavior of Solvay ammonia process, which meets market requirements. The fossil CO2 footprint of said sodium carbonate is reduced by 3 to more than 5 times compared to existing soda ammonia process and trona ore process when using green electricity.

Claims

1. A method for producing a sodium carbonate solution by electrodialysis of sodium chloride using a stack of electrodialysis unit comprising several chambers, wherein an aqueous solution containing sodium carbonate is fed into one of the chambers.

2. The method according to claim 1, wherein, The sodium carbonate contains at least 25 wt.% or at least 40 wt% of the carbon, which is of biological origin.

3. The method according to claim 2, wherein, The sodium carbonate contains at least 80 wt.% or at least 90 wt% of the carbon, which is of biological origin.

4. The method according to any one of the preceding claims, wherein, The electrodialysis unit includes at least two chambers, one of which is a salt chamber and the second chamber is an alkali chamber.

5. The method according to any one of the preceding claims, wherein, The electrodialysis unit includes at least three chambers, one of which is a salt chamber, the second chamber is an alkali chamber, and the third chamber is an acid chamber.

6. The method according to any one of the preceding claims, wherein, The aqueous solution containing carbonate is fed into the alkali chamber.

7. The method according to any one of the preceding claims, wherein, The cation exchange membrane and / or the anion exchange membrane are more permeable to monovalent ions than to polyvalent ions.

8. The method according to any one of the preceding claims, wherein, The electrodialysis unit stack includes at least three chambers, one of which is a salt chamber, the second chamber is an alkali chamber, and the third chamber is an acid chamber, and the method includes: - An aqueous solution containing sodium chloride is fed into the salt chamber, which is defined between an anion exchange membrane and a cation exchange membrane. - The aqueous solution containing sodium carbonate is fed into the alkali chamber, which is defined between the cation exchange membrane and the anion exchange surface of the bipolar membrane. - An aqueous solution is fed into the acid chamber, which is defined between the cation and anion sides of the bipolar membrane. The formation of sodium hydroxide (NaOH) in the alkaline chamber and hydrochloric acid (HCl) in the acidic chamber is achieved by the following: water molecules are split into hydroxide anions (OH-) in the alkaline chamber using the bipolar membrane. - And in this acid chamber, it splits into hydrated hydrogen cations (H+). + Sodium ions (Na) are separated by this cation-selective membrane. + The chloride ions (Cl-) are transferred to the alkali chamber, and the chloride ions (Cl-) are transferred through the anion membrane by the voltage between the salt chamber and the acid chamber. - ) transferred to the acid chamber, - Remove the outlet aqueous solution containing sodium hydroxide and sodium carbonate from this alkali chamber. - Remove the sodium chloride-depleted outlet aqueous solution containing sodium chloride from the salt chamber. - Remove the outlet aqueous solution containing hydrochloric acid from the acid chamber, and - Carbonate at least a portion of the outlet aqueous solution of the alkali chamber with a gas containing carbon dioxide (CO2) to obtain a carbonated liquid, wherein at least a portion or all of the sodium hydroxide is converted into sodium carbonate and water.

9. The method according to the preceding claim, wherein, A portion of the carbonated liquid obtained from the outlet solution of the carbonated alkali chamber is further processed to crystallize sodium carbonate crystals.

10. The method according to any one of claims 8 or 9, wherein, A portion of the carbonated liquid obtained from the outlet solution of the carbonated alkali chamber contains sodium bicarbonate and is further processed to crystallize sodium bicarbonate crystals.

11. The method according to any one of claims 8 to 10, wherein, The effluent aqueous solution containing sodium hydroxide and sodium carbonate removed from the alkali chamber has a molar ratio of less than 0.5, preferably less than 0.2, of alkaline sodium from sodium hydroxide to alkaline sodium from sodium carbonate.

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

13. The method according to any one of claims 4 to 12, wherein, The sodium chloride from this aqueous solution originates from: solar pool salt, or sea salt, rock salt, or dissolved salt from geological salt cavities, or industrial vacuum crystallized salt, or sodium chloride residue or byproduct from other industries, or seawater desalination units.

14. The method according to any one of the preceding claims, wherein, The electrodialysis unit uses voltage, and the voltage is provided by electricity with a reduced fossil CO2 footprint, preferably selected from the group consisting of: hydroelectric power, solar photovoltaic power, wind power, waste-to-energy power, electricity generated by biomass combustion, electricity generated by biogas combustion, electricity generated by hydrogen combustion, geothermal power, electricity generated by compressed air (such as compressed air stored in underground cavities), nuclear power, or mixtures thereof.

15. The method according to any one of the preceding claims, wherein, At least a portion of the outlet aqueous solution used to carbonate the alkali chamber, and the carbon dioxide (CO2) used to obtain the carbonated liquid, is at least partially or entirely biologically derived.

16. The method according to any one of the preceding claims, wherein, At least a portion of the outlet aqueous solution used for carbonateding of the alkali chamber contains carbon dioxide (CO2) from which the carbonated liquid is obtained, either from CO2 captured from the air, or from the combustion of fossil carbonaceous combustibles, or from fossil carbon dioxide.

17. The method according to any one of claims 8 to 16, wherein, The carbon dioxide (CO2) is a fumes or gas produced by a factory or its equipment, which is partly or wholly derived from the group consisting of: power plants, glass factories, steel or sintering plants, waste plants or waste-to-energy plants, pulp mills, paper mills, oil refineries, petrochemical plants, coal gasification plants, cement plants, tile manufacturing plants, brick manufacturing plants, mining processes, mineral processing plants, lime plants, ammonia plants, fertilizer plants, biochar plants, biogas plants, and combinations thereof.

18. The method according to any one of the preceding claims, wherein, At least a portion of the carbon dioxide (CO2) in the outlet aqueous solution used for carbonated alkaline chamber is generated by acid etching of limestone (CaCO3) or rocks containing carbonated materials, such as dolomite, and the acid etching is carried out with hydrochloric acid generated in or derived from the electrodialysis unit stack.

19. A sodium carbonate crystal or sodium bicarbonate crystal: - Wherein at least 25 wt.% of its carbon content is bio-derived carbon, preferably at least 80 wt.% of its carbon content is bio-derived carbon; and - Contains up to 20 mg of calcium (Ca) and / or up to 20 mg of magnesium (Mg) per kilogram of crystals, preferably up to 8 mg of calcium and / or up to 8 mg of magnesium per kilogram of crystals.

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

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