Recovery of potassium and ammonium salts by precipitation induced with CO2

Abstract

This disclosure provides a method for recovering solid potassium / ammonium salts, the method comprising: introducing an aqueous stream containing at least one of ammonium cations or potassium cations and at least one of carbonate anions or bicarbonate anions into a processing unit; introducing a carbon dioxide stream containing CO2 into the processing unit; contacting the aqueous stream with the carbon dioxide stream to form a mixture; removing heat from the processing unit to control the temperature of the mixture; forming a slurry from the mixture, the slurry comprising water and at least one of solid potassium salts or solid ammonium salts; removing the slurry from the processing unit as a treated aqueous stream; and introducing the treated aqueous stream into a separator to generate a brine stream, and a recovered potassium and / or ammonium salt stream containing at least one of the solid potassium salts or solid ammonium salts.

Description

Background Technology

[0001] Carbon dioxide is a major driver of global climate change; therefore, reducing its emissions is crucial. The mixed salt process (MSP) uses an aqueous mixture of potassium carbonate and ammonium salts as a solvent and is a promising technology for CO2 capture. However, under certain operating conditions, some available process configurations require significant replenishment of potassium carbonate and ammonia due to the need for stream purging to maintain mass balance in continuous operations. Unfortunately, this increases the cost of process operation associated with chemical consumption and liquid waste treatment. Furthermore, there is a continued need for energy-efficient MSP methods for CO2 capture. Summary of the Invention

[0002] A method for recovering potassium and / or ammonium salts includes: introducing an aqueous stream containing at least one of ammonium cations or potassium cations and at least one of carbonate anions or bicarbonate anions into a processing unit; introducing a carbon dioxide stream containing CO2 into the processing unit; contacting the aqueous stream with the carbon dioxide stream to form a mixture; removing heat from the processing unit to control the temperature of the mixture; forming a slurry from the mixture, the slurry containing water and at least one of solid potassium or solid ammonium salts; removing the slurry from the processing unit as a treated aqueous stream; and introducing the treated aqueous stream into a separator to generate a brine stream and a recovered potassium and / or ammonium salt stream containing at least one of the solid potassium or solid ammonium salts.

[0003] As used herein, an absorber may comprise a single absorber unit or several interconnected absorber units. Each absorber unit may independently generate a CO2-containing solution. A method for capturing CO2 includes: contacting a CO2-rich gas with an aqueous absorbent solution in an absorber of a system comprising a single absorber unit or interconnected absorber units to generate one or more CO2-containing solutions and a CO2-lean gas stream; providing one or more CO2-lean aqueous solutions from a regenerator; transferring heat from the one or more CO2-lean aqueous solutions to the one or more CO2-containing solutions; introducing the heat-exchanged one or more CO2-containing solutions into the regenerator, which generates a CO2 gas stream and the one or more CO2-lean aqueous solutions; introducing about 0.1 vol% to about 3 vol% of any one of the heat-exchanged one or more CO2-lean aqueous solutions as a group of aqueous streams into a treatment unit; introducing about 0.1 vol% to about 5 vol% of the CO2 gas stream generated by the regenerator as a carbon dioxide stream into the treatment unit; and recovering solid potassium and / or ammonium salts according to the method described above. Attached Figure Description

[0004] The following description should not be considered as limiting in any way. Referring to the accompanying drawings, similar element numbers are similar:

[0005] Figure 1 This illustrates the use of K + or NH4 + At least one of them and CO3 2- or HCO3 -1 A simplified embodiment of a method for recovering solid potassium and / or ammonium salts from at least one of aqueous feed streams;

[0006] Figure 2 This is a simplified embodiment of a method for recovering solid potassium and / or ammonium salts from an aqueous stream purged by a regenerator using a portion of the carbon dioxide stream generated by the regenerator; and

[0007] Figure 3 This is a simplified embodiment of an implementation of a method for recovering solid potassium and / or ammonium salts in the context of a potential MSP layout for CO2 capture. Detailed Implementation

[0008] The inventors of this paper have discovered an efficient method for recovering potassium and / or ammonium salts from a purged aqueous stream of a mixed salt process by inducing salt precipitation with CO2 and controlling temperature.

[0009] This method has low complexity in terms of equipment setup. The key reagent, CO2, used to induce the recovery of potassium and / or ammonium salts, is readily available as a product at the MSP plant. Compared to conventional evaporation / vacuum crystallization methods, the method described herein has the added advantage of also recovering ammonia-based salts. This method is also more energy-efficient than conventional evaporation / vacuum crystallization methods.

[0010] The salt recovered from this method can be recycled for further CO2 capture in the MSP plant or sold to the external market as a valuable product. The cost of recovering potash and / or ammonium salts using the disclosed method can be lower than the price of commercially available potash and ammonium salt feedstocks.

[0011] This method provides a reliable solution for recovering potassium and / or ammonium salts and helps reduce waste from the MSP as well as the replenishment of solvents, potassium carbonate and ammonia, thereby transforming the MSP's operating range to lower energy-cost operating conditions and improving the overall plant's economics and sustainability.

[0012] Detailed descriptions of one or more embodiments of the disclosed method are presented herein by way of example rather than limitation, with reference to the accompanying drawings.

[0013] refer to Figure 1The method for recovering potassium and / or ammonium salts includes introducing an aqueous stream (10) containing dissolved potassium and / or ammonium salts into a processing unit (30); introducing a carbon dioxide stream (20) into the processing unit (30); contacting or mixing the aqueous stream (10) and the carbon dioxide stream (20) in the processing unit (30) to generate a mixture; removing heat from the processing unit (30) to control the temperature of the mixture; forming a slurry from the mixture, the slurry comprising water and at least one of solid potassium or solid ammonium salts; and introducing the slurry as a processed aqueous stream (40) into a separator (50) to generate a recovered potassium and / or ammonium salt stream (70) and a brine stream (60). Advantageously, the method is a continuous method.

[0014] The aqueous stream (10) contains dissolved potassium and / or ammonium salts, for example, the aqueous stream (10) contains at least one of potassium cation or ammonium cation, and at least one of carbonate anion or bicarbonate anion. In one aspect, the aqueous stream (10) contains both potassium cation and ammonium cation, and one or both of carbonate anion or bicarbonate anion. The aqueous stream (10) may also contain at least one of dissolved ammonia, carbamate anion or hydroxide anion.

[0015] The potassium cation content in the aqueous stream (10) may be from about 0.1 molal to about 10 molal or from about 1 molal to about 10 molal (mol / kg solvent, m). The ammonia (NH3 and ammonia-containing ions) content may be from about 0.05 molal to about 10 molal, from about 0.1 molal to about 8 molal or from about 0.1 molal to about 6 molal. Based on the total weight of the aqueous stream, the water content in the aqueous stream (10) may be from about 55% by weight to about 95% by weight or from about 80% by weight to about 90% by weight.

[0016] In the aqueous stream, cations and anions dissociate from each other. On the one hand, each based on the total weight of the aqueous stream, the aqueous stream (10) contains less than about 20% by weight of solids, less than about 15% by weight of solids, less than about 10% by weight of solids, less than about 5% by weight of solids, less than about 0.5% by weight of solids, or less than 0.1% by weight of solids. The aqueous stream may be free of solids.

[0017] The aqueous stream (10) may have a temperature of about 25°C to about 60°C, preferably about 25°C to about 50°C, or about 25°C to about 45°C. The aqueous stream may have a pressure of more than 1 bar, for example, about 1.5 bar to about 35 bar.

[0018] The carbon dioxide stream (20) may contain more than about 80% by volume, more than about 85% by volume, or more than 95% by volume of CO2 based on the total volume of the carbon dioxide stream.

[0019] The carbon dioxide stream (20) may have a temperature of about 5°C to about 45°C, preferably about 5°C to about 40°C, more preferably about 5°C to about 35°C. The carbon dioxide stream (20) may have a pressure of about 1 bar to about 40 bar, about 5 bar to about 30 bar, or about 10 bar to about 20 bar.

[0020] The carbon dioxide stream (20) and the aqueous stream (10) can be introduced into the treatment unit (30) separately. Alternatively, the carbon dioxide stream (20) and the aqueous stream (10) can be combined before being introduced into the treatment unit (30).

[0021] The processing unit (30) can be a mixer having means for mixing the aqueous stream (10) and the carbon dioxide stream (20) and controlling the temperature of the mixture to change the solubility of salt and gaseous CO2. The processing unit (30) can also be a vertically oriented tower. The aqueous stream (10) can be introduced in the upper section of the tower and the CO2 stream (20) can be introduced in the lower section of the tower to promote the dissolution of carbon dioxide in the aqueous stream (10).

[0022] In the treatment unit (30), the aqueous stream (10) is brought into contact with or mixed with CO2. During the contact or mixing, at least a portion of the CO2 from the carbon dioxide stream dissolves in the aqueous stream. The aqueous stream may be saturated with CO2 in the treatment unit.

[0023] The processing unit (30) has a cooling device (300) to cool the aqueous stream (10) upon contact with the carbon dioxide stream (20), thereby promoting the dissolution of CO2 in the liquid phase, which in turn promotes the precipitation of solids. Alternatively or otherwise, the cooling device (300) may remove heat that may be generated during the reaction for forming potassium and / or ammonium salts, thereby further promoting the formation and precipitation of solids. During the method, the temperature of the mixture of the aqueous stream (10) and the carbon dioxide stream (20) in the processing unit (30) may be controlled to about 30°C, or about 2°C to about 30°C, or about 5°C to about 25°C, based on the freezing point of the mixture. As used herein, about the freezing point of the mixture means that the temperature may be about 0.5°C, about 1°C, or about 2°C higher than the freezing point of the mixture.

[0024] The cooling device (300) is not particularly limited and is known to those skilled in the art. For example, the processing unit (30) may have a jacket with a circulating fluid that carries away heat from the processing unit (30). In one aspect, the processing unit (30) may be a cooling mixer.

[0025] The pressure in the processing unit can be atmospheric pressure or higher, for example, about 1 bar to about 40 bar or about 1 bar to about 30 bar. Pressure can be generated by the flow of liquids and gases.

[0026] By contacting an aqueous stream with a carbon dioxide stream, and optionally further cooling the aqueous stream, solid potassium salts, solid ammonium salts, or combinations thereof can precipitate from the aqueous stream, thereby forming a slurry. The solid salts may be present in particulate form. The slurry may have a temperature of about 30°C (about the slurry's freezing point), about 2°C to about 30°C, or about 5°C to about 25°C.

[0027] Not wanting to be bound by theory, it is believed that according to equations (1) and (2), CO2 dissolves in water to form bicarbonate ions, carbonate ions, or combinations thereof.

[0028] CO2 (aqueous solution) + 2H2O (l) HCO3 - (Aqueous solution) + H3O + (Aqueous solution)(1)

[0029] HCO3 - (Aqueous solution) + H₂O (l) CO3 2- (Aqueous solution) + H3O + (Aqueous solution)(2)

[0030] An increase in the concentration of carbonate and / or bicarbonate ions shifts the equilibrium equations (3)-(6) to the left, thereby forming a slurry containing at least one of a solid potassium salt or a solid ammonium salt.

[0031] K2CO3 (solid) 2K + (Aqueous solution) + CO3 2- (Aqueous solution)(3)

[0032] KHCO3 (solid) K + (Aqueous solution) + HCO3 - (Aqueous solution)(4)

[0033] (NH4)2CO3 (solid) 2NH4 + (Aqueous solution) + CO3 2- (Aqueous solution)(5)

[0034] NH4HCO3 (solid) NH4 +(Aqueous solution) + HCO3 - (Aqueous solution)(6)

[0035] On one hand, the slurry contains both solid potassium salts and solid ammonium salts. Examples of solid potassium salts include potassium carbonate and potassium bicarbonate. Examples of solid ammonium salts include ammonium carbonate and ammonium bicarbonate. The slurry may contain more than one solid salt and / or its hydrated form.

[0036] The solids content of the slurry can vary based on the aqueous stream to be treated and the temperature of the slurry. In one respect, based on the total weight of the slurry, the solids content of the slurry is from about 0.1 wt% to about 45 wt%, from about 0.1 wt% to about 40 wt%, or from about 0.1 wt% to about 35 wt%.

[0037] The generated slurry is taken out from the treatment unit (30) as a treated aqueous stream (40) and can be introduced into a separator (50) where the solids are separated from the aqueous phase, thereby generating a recovered potassium and / or ammonium salt stream (70) and a brine stream (60).

[0038] Any separator that effectively separates solids from liquids can be used. Examples of separators may include centrifuges, filters, gravity settlers, hydrocyclones, and screens. Other suitable solid / liquid separators known in the art may also be used. In one aspect, the separator may be a hydrocyclone. Known hydrocyclones can be used. A hydrocyclone may include a cylindrical feed section with tangential feed; an overflow section with an eddy current detector; and a conical section with a apex. The aqueous stream (40) being processed may be tangentially fed into the hydrocyclone at a pressure (e.g., about 1 bar to about 45 bar or about 1 bar to about 40 bar). This generates centrifugal motion, thereby pushing the heavier phase (potassium salt and / or ammonium salt) outward and downward along the wall of the conical section. The reduced diameter in the conical section increases the velocity and thus enhances the separation. The concentrated solids, as a potassium salt and / or ammonium salt stream (70), are discharged through the apex. The eddy current detector in the overflow section generates a rapid upward spiral motion of fluid in the center of the conical shell, and the fluid is discharged as brine flow (60) through the overflow outlet.

[0039] The recovered potassium and / or ammonium salt stream (70) contains at least one of solid potassium or solid ammonium salts as described herein in the context of slurry.

[0040] The carbon dioxide feed stream (20) used to induce potassium and / or ammonium salt recovery is readily available at the MSP plant. Reference Figure 2The carbon dioxide feed stream (20) can be generated in the regenerator (80) from a CO2-containing solution (100). The CO2-containing solution (100) may contain water, dissolved carbon dioxide, and ions such as potassium ions, ammonium ions, carbonate ions, and / or bicarbonate ions.

[0041] In the regenerator (80), a CO2-containing solution (100) is subjected to a high temperature of about 110°C to about 200°C or about 160°C to about 200°C, thereby releasing a CO2 gas stream (90) and generating a CO2-lean aqueous solution (110). The pressure within the regenerator (80) can be about 2 bar to about 20 bar or about 2 bar to about 40 bar. The regenerator (80) can have different zones, each with a different operating temperature and / or a different pressure.

[0042] Approximately 0.1% to approximately 1% or approximately 0.1% to approximately 5% of the carbon dioxide generated by the regenerator (80) can be introduced into the processing unit (30) as a carbon dioxide feed stream (20). If necessary, the carbon dioxide generated by the regenerator can be cooled before being introduced into the processing unit (30).

[0043] About 0.1% to about 3% of the lean CO2 aqueous solution (110) from the regenerator (80) is purged to avoid water accumulation in the plant. The purged aqueous stream, or simply aqueous stream (10), can be introduced into the treatment unit (30) to recover potassium and / or ammonium salts.

[0044] The methods for recovering potassium and ammonium salts described herein can be integrated into potential MSP (Multi-Service Provider) layouts. References Figure 3 The recovered potassium and / or ammonium salt stream (70) obtained from the separator (50) can be diluted with a lean CO2 aqueous solution (110) and then returned to the absorber (95) from which lean CO2 gas (120) is generated by the enriched CO2 gas (150). Although not shown, it should be understood that the method may use more than one absorber and / or more than one regenerator. Furthermore, an absorber may also have multiple zones / units with different absorbent solutions, such as absorbent solutions with different concentrations of adsorbent or absorbent solutions with different temperatures.

[0045] refer to Figure 3The method for capturing CO2 includes contacting a CO2-rich gas (150) with an absorbent solution in an absorber (95) to generate a CO2-containing solution (100) and a CO2-lean gas stream (120). The CO2-containing solution (100) is introduced into a heat exchanger (500) and then into a regenerator (80), where a CO2 gas stream (90) and a CO2-lean aqueous solution (110) are generated. The CO2-lean aqueous solution (110) generated from the regenerator (80) is also introduced into the heat exchanger (500), where the CO2-lean aqueous solution (110) transfers heat to the CO2-containing solution (100) before entering the regenerator (80). Approximately 0.1% to approximately 3% by volume of the CO2-lean aqueous solution (110) leaving the heat exchanger is introduced as an aqueous stream (10) into a treatment unit (30). Approximately 0.1% to 5% by volume of the CO2 gas stream (90) generated by the regenerator (80) is introduced as a CO2 stream (20) into the treatment unit (30). Solid potassium and / or ammonium salts can then be recovered according to the methods described herein. The recovered potassium and / or ammonium salt stream (70) can be returned to the absorber (95) after dilution in a lean CO2 aqueous solution (110) leaving the heat exchanger (500). Advantageously, the method can be a continuous method.

[0046] Since the absorber may include one absorber unit or several interconnected absorber units, and each absorber unit can independently generate a CO2-containing solution, in one aspect, the method for capturing CO2 includes: contacting CO2-rich gas with an aqueous absorbent solution in an absorber of a system comprising one or more interconnected absorber units to generate one or more CO2-containing solutions and a CO2-lean gas stream; providing one or more CO2-lean aqueous solutions from a regenerator; transferring heat from the one or more CO2-lean aqueous solutions to the one or more CO2-containing solutions; introducing the heat-exchanged one or more CO2-containing solutions into the regenerator, which generates a CO2 gas stream and the one or more CO2-lean aqueous solutions; introducing about 0.1 vol% to about 3 vol% of any one of the heat-exchanged one or more CO2-lean aqueous solutions as a group of aqueous streams into a treatment unit; introducing about 0.1 vol% to about 5 vol% of the CO2 gas stream generated by the regenerator as a carbon dioxide stream into the treatment unit; and recovering solid potassium and / or ammonium salts according to the methods described herein.

[0047] CO2-rich gas may include flue gas streams from power plants or other industrial CO2 sources. The absorbent solution may contain water; ammonia, ammonium hydroxide, ammonium salts such as ammonium carbonate, ammonium bicarbonate, or combinations thereof; and potassium salts such as potassium carbonate and potassium bicarbonate. Based on the total weight of the absorbent solution, the total concentration of inorganic salts in the absorber may be from about 5% to about 40% by weight or from 30% to 40% by weight. The absorber may operate at about 20°C to about 40°C and at about 1 atm.

[0048] Example

[0049] according to Figure 1 The method shown treats an aqueous stream at 41°C and 1 bar pressure with a carbon dioxide stream at 15 bar pressure. The aqueous stream contains 85.8 mol% H₂O, 3.1 mol% dissolved NH₃, 6.1 mol% potassium ions, 0.4 mol% ammonium ions, 2.0 mol% carbonate ions, 0.4 mol% bicarbonate ions, and 2.1 mol% carbamate ions (NH₂COO₃). - The results are shown in the table below.

[0050]

[0051] The method disclosed in this paper requires less energy to recover potassium salts than evaporation / vacuum crystallization methods.

[0052] The following illustrates some of the aspects disclosed above:

[0053] Aspect 1. A method comprising: introducing an aqueous stream containing at least one of an ammonium cation or a potassium cation and at least one of a carbonate anion or a bicarbonate anion into a processing unit; introducing a carbon dioxide stream containing CO2 into the processing unit; contacting the aqueous stream with the carbon dioxide stream to form a mixture; removing heat from the processing unit to control the temperature of the mixture; forming a slurry from the mixture, the slurry containing water and at least one of a solid potassium salt or a solid ammonium salt; removing the slurry from the processing unit as a treated aqueous stream; and introducing the treated aqueous stream into a separator to generate a brine stream and a recovered potassium salt and / or ammonium salt stream containing at least one of the solid potassium salt or the solid ammonium salt.

[0054] Aspect 2. The method according to any of the preceding aspects, wherein the method is a continuous method.

[0055] Aspect 3. The method according to any of the preceding aspects, wherein the aqueous stream has a temperature of up to 60°C before being introduced into the processing unit.

[0056] Aspect 4. The method according to any of the preceding aspects, wherein the mixture in the processing unit has a temperature of about 30°C, for example, about 2°C to about 30°C, which is about the freezing point of the mixture.

[0057] Aspect 5. The method according to any of the preceding aspects, wherein the carbon dioxide feed stream comprises more than 80% by volume of CO2.

[0058] Aspect 6. The method according to any of the preceding aspects, wherein the carbon dioxide stream has a pressure of up to 40 bar.

[0059] Aspect 7. The method according to any of the preceding aspects, the method further comprising generating a carbon dioxide feed stream from a CO2-containing solution in a regenerator.

[0060] Aspect 8. The method according to any of the preceding aspects, further comprising generating the aqueous stream from a CO2-containing solution in a regenerator. The regenerator produces a CO2-lean aqueous solution, which is introduced into a heat exchanger to transfer heat to the CO2-containing solution before it enters the regenerator, and wherein approximately 0.1 vol% to approximately 3 vol% of the CO2-lean aqueous stream exiting the heat exchanger is introduced as the aqueous stream into the processing unit.

[0061] Aspect 9. The method according to any of the preceding aspects, the method further comprising, after dilution in a CO2-deficient aqueous solution, returning the recovered potassium and / or ammonium salt stream to the absorber.

[0062] Aspect 10. A method comprising: contacting a CO2-rich gas with an aqueous absorbent solution in an absorber to generate one or more CO2-containing solutions and a CO2-lean gas stream; providing one or more CO2-lean aqueous solutions from a regenerator; transferring heat from the one or more CO2-lean aqueous solutions to the one or more CO2-containing solutions; introducing the heat-exchanged one or more CO2-containing solutions into the regenerator, the regenerator generating a CO2 gas stream and the one or more CO2-lean aqueous solutions; introducing about 0.1 vol% to about 3 vol% of any one of the heat-exchanged CO2-lean aqueous solutions as a set of aqueous streams into a treatment unit; introducing about 0.1 vol% to about 5 vol% of the CO2 gas stream generated by the regenerator as a carbon dioxide stream into the treatment unit; and recovering solid potassium and / or ammonium salts according to the method described in any of the preceding aspects. The method may further include returning the recovered potassium and / or ammonium salt streams to the absorber after dilution in the CO2-lean aqueous solution. The method may be a continuous method.

[0063] In the context of describing the invention (particularly in the context of the appended claims), the terms “a” and “the”, and similar designations, should be interpreted to cover both the singular and the plural, unless otherwise specified herein or clearly contradicted by the context. The terms “about,” “substantially,” and “generally” are intended to include a degree of error associated with a specific number of measurements based on the equipment available at the time of filing. For example, “about” and / or “substantially” and / or “generally” can include a range of ±8% for a given value.

[0064] Although the invention has been described with reference to one or more exemplary embodiments, those skilled in the art will understand that various changes can be made and equivalents can be substituted for elements therein without departing from the scope of the invention. Furthermore, many modifications can be made to adapt particular situations or materials to the teachings of the invention without departing from the basic scope of the invention. Therefore, it is contemplated that the invention is not limited to the specific embodiments disclosed as the best mode contemplated for carrying out the invention, but rather that the invention will encompass all embodiments falling within the scope of the claims. Additionally, exemplary embodiments of the invention have been disclosed in the drawings and detailed descriptions, and although specific terminology has been used, it is used in a general and descriptive sense only, and not for limiting purposes, unless otherwise specified; therefore, the scope of the invention is not limited thereto.

Claims

1. A method for recovering solid potassium salts and / or ammonium salts, characterized in that: An aqueous stream (10) containing at least one of ammonium cation or potassium cation and at least one of carbonate anion or bicarbonate anion is introduced into the treatment unit (30); A carbon dioxide feed stream (20) containing CO2 is introduced into the processing unit (30); The aqueous stream (10) is brought into contact with the carbon dioxide stream (20) to form a mixture; Heat is removed from the processing unit (30) to control the temperature of the mixture; The mixture forms a slurry, the slurry comprising water and at least one of a solid potassium salt or a solid ammonium salt; The slurry is removed from the processing unit (30) as a water-based material stream (40) for processing; and The aqueous stream (40) of the treatment is introduced into the separator (50) to generate a brine stream (60) and a recovered potassium and / or ammonium stream (70) containing at least one of the solid potassium salt or the solid ammonium salt.

2. The method according to claim 1, wherein the method is a continuous method.

3. The method according to claim 1, wherein the aqueous stream (10) has a temperature of up to 60°C before being introduced into the processing unit (30).

4. The method of claim 1, wherein the mixture in the processing unit has a temperature of about 30°C, which is approximately the freezing point of the mixture.

5. The method of claim 1, wherein the mixture in the processing unit has a temperature of about 2°C to about 30°C.

6. The method according to claim 1, wherein the carbon dioxide feed stream (20) contains more than 80% by volume of CO2.

7. The method according to claim 1, wherein the carbon dioxide stream (20) has a pressure of up to 40 bar.

8. The method according to claim 1, further comprising generating the carbon dioxide stream (20) from a CO2-containing solution (100) in a regenerator (80).

9. The method according to claim 1, further comprising generating the aqueous stream (10) from a CO2-containing solution (100) in a regenerator (80).

10. The method according to claim 9, wherein the regenerator (80) generates a CO2-lean aqueous solution (110), the CO2-lean aqueous solution is introduced into a heat exchanger (500) to transfer heat to the CO2-containing solution (100) before the CO2-containing solution (100) enters the regenerator (80), and wherein about 0.1 vol% to about 3 vol% of the CO2-lean aqueous solution (110) leaving the heat exchanger is introduced into the processing unit (30) as the aqueous feed stream (10).

11. The method according to any one of claims 1 to 10, the method further comprising returning the recovered potassium and / or ammonium salt stream (70) to the absorber (95) after dilution in a CO2-poor aqueous solution (110).

12. A method for capturing CO2, characterized in that: The CO2-rich gas (150) is contacted with an aqueous absorption solution in an absorber (95) to generate one or more CO2-containing solutions (100) and a CO2-lean gas stream (120). One or more CO2-lean aqueous solutions (110) are supplied from the regenerator (80); Heat is transferred from one or more CO2-poor aqueous solutions (110) to one or more CO2-containing solutions (100). The heat-exchanged one or more CO2-containing solutions (100) are introduced into the regenerator (80), which generates a CO2 gas stream (90) and the one or more CO2-lean aqueous solutions (110). Approximately 0.1% to approximately 3% by volume of one or more of the heat-exchanged lean CO2 aqueous solutions (110) are introduced into the treatment unit (30) as a group of aqueous feed streams (10); The CO2 gas stream (90) generated by the regenerator (80) is introduced into the processing unit (30) as a carbon dioxide stream, with an amount of approximately 0.1% to approximately 5% by volume. The aqueous stream and the carbon dioxide stream are brought into contact in the processing unit (30) to form a mixture; Heat is removed from the processing unit (30) to control the temperature of the mixture; The mixture forms a slurry, the slurry comprising water and at least one of a solid potassium salt or a solid ammonium salt; The slurry is removed from the processing unit (30) as a water-based material stream (40) for processing; and The aqueous stream (40) of the treatment is introduced into the separator (50) to generate a brine stream (60) and a recovered potassium and / or ammonium stream (70) containing at least one of the solid potassium salt or the solid ammonium salt.

13. The method according to claim 12, further comprising, after dilution in the CO2-poor aqueous solution (110), returning the recovered potassium and / or ammonium salt stream (70) to the absorber (95).

14. The method according to claim 12, wherein the aqueous stream (10) has a temperature of about 25°C to about 60°C before being introduced into the processing unit (30).

15. The method according to any one of claims 12 to 14, wherein the mixture in the processing unit has a temperature of about 2°C to about 30°C.

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