Systems and methods for converting carbon dioxide in a gas stream into commercially desirable chemical products

Abstract

An effective system and method for reducing the amount of carbon dioxide contained in a gas stream. The carbon dioxide absorption and mineralization unit is configured to produce at least one of carbonate and bicarbonate and ammonium chloride from carbon dioxide, an ammoniated solvent, and at least one metal chloride in the gas stream. The mineral separation unit is configured to separate carbonates and bicarbonates from ammonium chloride. The solvent regeneration unit is configured to use a catalyst to produce chlorine and ammonium hydroxide from ammonium chloride, heat, and oxygen.

Description

[Technical Field]

[0001] REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 63 / 484,194, filed February 10, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a system and method for capturing carbon dioxide (CO2) from dilute gas streams, such as flue gases or fermentation off-gases, and using the captured CO2 to produce minerals or other commercially useful chemical products. [Background technology]

[0003] Carbon capture, utilization, and storage (CCUS) can be an effective tool to help achieve net-zero emissions in industrial sectors where emissions reductions are difficult. Conventional methods involve capturing carbon dioxide before it is emitted into the atmosphere, and these include "carbon capture and geological storage (CCS)" and "carbon capture and utilization (CCU)," collectively referred to as CCUS.

[0004] These methods typically involve the application of carbon capture technologies to power plants or industrial processes to remove carbon before it is emitted. Carbon capture technologies are generally classified into three types: (i) post-conversion capture, which separates emitted carbon dioxide from gas streams; (ii) pre-conversion capture, which removes carbon dioxide as a by-product produced during the process; and (iii) oxy-combustion capture, which burns fuel under pure oxygen to produce high-purity carbon dioxide free of nitrogen compounds. Pre- and post-conversion capture employ techniques such as absorption by chemical absorbents or adsorption onto porous organic materials.

[0005] After carbon dioxide is captured, it is typically compressed and prepared for transport, geological storage, or other uses. While geological formations are the most common storage location, many challenges remain before CCS can function as a solution to the excess CO2 in the atmosphere, including storage methods and the cost of injecting it into rock. The lack of sufficient economic incentives for gas storage, particularly as an economic barrier, is one of the reasons for the slow adoption of CCS. However, carbon dioxide, when captured and activated, can become a useful chemical feedstock for a variety of industrial sectors.

[0006] One proposed alternative to geological carbon dioxide storage is to use CO2 as a chemical feedstock. The benefit of this approach is that it provides economic incentives for industry to adopt these technologies. Using CO2 as a sustainable feedstock can produce useful petrochemicals or other commercial chemical products, helping to reduce excess CO2 in the atmosphere.

[0007] However, for these processes to be commercially viable, higher production efficiency, lower energy consumption, and lower carbon emissions must be achieved. As environmental raw material resources become more scarce, CO2 recycling becomes an increasingly attractive option for industry. Therefore, innovative solutions for capturing CO2 and providing it as a chemical feedstock offer significant value from both environmental and economic perspectives. This invention relates to systems and methods for capturing and mineralizing CO2 from dilute gas streams to produce important chemical products, such as Cl2 (chlorine). Cl2 is a key feedstock for many industrial applications, including water treatment, and is traditionally produced via the chlor-alkali process, which presents environmental challenges. In the United States, more than 75% of chlor-alkali production uses asbestos diaphragm cell technology, raising concerns about worker and environmental exposure to asbestos fibers. Meanwhile, in Germany, a complete ban on asbestos use has been implemented by law since 1994 due to these risks.

[0008] Furthermore, the chlor-alkali process, particularly the mercury cell method, is one of the most energy-intensive processes in the chemical industry, requiring approximately 3,500 kWh of electricity per ton of chlorine. By transitioning to membrane cell technology, energy savings of more than 15% per ton of product are expected, resulting in significant energy savings.

[0009] These processes also have a significant environmental impact, and mercury cell processes have historically been a source of mercury pollution. Older facilities have released large amounts of mercury into the environment. Furthermore, the chemical industry, including chlor-alkali production, is highly dependent on fossil fuels and is the third largest industrial producer of greenhouse gases.

[0010] These challenges highlight the urgent need for the chlor-alkali industry to adopt new, safer and more energy-efficient technologies. Summary of the Invention

[0011] All examples and features shown below can be combined in any way that is technically possible.

[0012] As an example of the present disclosure, a system and process for the capture and mineralization of carbon dioxide (CO2) from a dilute gas stream is disclosed. The example includes an absorption and mineralization step in which carbon dioxide from a CO2-rich gas stream (e.g., flue gas or fermentation by-product gas) is reacted with a solvent. The solvent is composed of water, ammonium hydroxide, and an X-chloride salt, where the cation X is Ca. 2+ , Mg + , Na + , or K +In this process, the CO2 is mineralized to produce solid X-carbonate and aqueous ammonium chloride, which are mixed and exit the absorber as the output stream. The CO2-depleted gas then leaves the process entirely. After the absorption and mineralization steps, the output stream enters a separation unit that removes the solid X-carbonate and ammonium chloride. The X-carbonate is removed from the process, and the ammonium chloride is sent to a regeneration process. In the regeneration process, the ammonium chloride reacts with oxygen (which may be present in the air) to remove chlorine and release ammonium hydroxide. This newly produced ammonium hydroxide is returned to the absorber to combine with new X-chloride.

[0013] The present disclosure relates to systems and methods for capturing and mineralizing carbon dioxide (CO) from dilute CO gas streams, such as flue gases or fermentation by-product gases, to produce commercially useful products. The disclosed methods involve converting CO to metal carbonates using a high-salinity solution and ammonia gas, with the primary products being CaCO, NaHCO, KHCO, or similar carbonates and bicarbonates, and NHCl. In some embodiments, the bicarbonates produced are further processed and converted to carbonates. In other embodiments, NHCl can be converted to NH and HCl by heating. In other embodiments, NHCl can be converted to NH and NaCl, KCl, CaCl, or the like by adding hydroxides such as NaOH, KOH, or Ca(OH).

[0014] In one embodiment, the disclosed method uses brine (aqueous sodium chloride solution) and ammonia gas to capture and convert CO to primary products including sodium carbonate (NaCO), HCl (or Cl), HO, and / or NH4Cl. In another embodiment, the disclosed method uses aqueous potassium chloride solution and ammonia gas to capture and convert CO to primary products including potassium carbonate (KCO), HCl (or Cl), HO, and / or NH4Cl.

[0015] In some embodiments, the disclosed method uses brine (aqueous sodium chloride solution) and ammonia gas to capture and convert CO into primary products including sodium bicarbonate (NaHCO), HCl (or Cl), HO, and / or NH4Cl.

[0016] In some embodiments, the disclosed method uses aqueous potassium chloride solution and ammonia gas to capture and convert CO into primary products including potassium bicarbonate (KHCO), HCl (or Cl), HO, and / or NH4Cl.

[0017] In some embodiments, the disclosed method uses an aqueous calcium chloride solution and ammonia gas to capture and convert CO into primary products including calcium carbonate (CaCO), HCl (or Cl), HO, and / or NH4Cl.

[0018] In some embodiments, the sodium bicarbonate, potassium bicarbonate, calcium carbonate, or similar carbonate / bicarbonate salts produced by the disclosed methods are separated from the aqueous ammonium chloride solution.

[0019] In some embodiments, the sodium bicarbonate or potassium bicarbonate produced by the disclosed methods is heated and converted to sodium carbonate or potassium carbonate, respectively.

[0020] In some embodiments, the ammonium chloride produced by the disclosed methods is converted to hydrochloric acid and ammonia. The resulting mixture of hydrochloric acid and ammonia gas can be separated, and the ammonia then recycled for reuse in the disclosed methods.

[0021] In another embodiment, ammonium chloride is isolated as a product for use in fertilizers or fermentation processes, and the ammonia used in the disclosed methods is used as a precursor to ammonium chloride production.

[0022] In one embodiment, a system and method for reducing the amount of carbon dioxide contained in a gas stream includes a carbon dioxide absorption and mineralization package configured to produce carbonates and / or bicarbonates and ammonium chloride from carbon dioxide, an ammoniated solvent, and at least one metal chloride in the gas stream; a mineral separation package configured to separate the carbonates and bicarbonates from the ammonium chloride; and a solvent regeneration package configured to use a catalyst, heat, and oxygen to produce chlorine and ammonium hydroxide from the ammonium chloride.

[0023] Some examples include one or any combination of the above or below features.

[0024] In some examples, the solvent regeneration package is configured to separate HCl from the output of the mineral separation package and react the HCl with metal chloride-based catalyst X and oxygen to form XCl and water. In some examples, the solvent regeneration package is configured to regenerate catalyst X by decomposing XCl in the presence of a hot inert gas to produce Cl. In some examples, the solvent regeneration package is configured to regenerate catalyst X by reacting XCl with carbon monoxide to produce phosgene. In some examples, the solvent regeneration package is configured to regenerate catalyst X by reacting XCl with water to form HCl and oxygen.

[0025] Some examples include one or any combination of the above or below features. In some examples, the molar ratio of ammonia to HCl in the solvent regeneration package is greater than 1. In some examples, the solvent regeneration package is configured to separate the HCl from the gas stream using membrane separation. In some examples, the system also includes a salt dissolution unit. In some examples, the salt dissolution unit is configured to mix water and salt to form a high-salinity solution that is input to the carbon dioxide absorption and mineralization package. In some examples, the high-salinity solution is an aqueous solution of CaCl2, MgCl2, NaCl, KCl, or a mixture of two or more thereof. In some examples, the salt dissolution unit is configured to mix seawater, brackish water, or wastewater with salt to form a high-salinity solution that is input to the carbon dioxide absorption and mineralization package. In some examples, the high-salinity solution is an aqueous solution of CaCl2, MgCl2, NaCl, KCl, or a mixture of two or more thereof.

[0026] Some examples include one or any combination of the above or below features. In one example, the solvent regeneration package includes an ammonia absorber configured to mix ammonia from the separation package with a high-salt solution to form an ammoniaated high-salt solution. The carbon dioxide absorption and mineralization package is configured to mix the ammoniaated high-salt solution from the ammonia absorber with a carbon dioxide-containing gas stream to form an aqueous ammonium chloride solution and carbonate and / or bicarbonate salts. The mineral separation package includes a solid-liquid separator configured to separate at least a portion of the carbonate and / or bicarbonate salts from the aqueous ammonium chloride solution, where the carbonate and / or bicarbonate salts can be hydrated or anhydrous. The solvent regeneration package further includes a heater configured to evaporate water from the aqueous ammonium chloride solution and decompose the ammonium chloride to form a mixture containing ammonia and HCl, and a water condenser configured to condense water vapor generated by use of the heater to produce liquid water.

[0027] Some examples include one or any combination of the above or below features. In some examples, the solvent regeneration package includes an ammonia absorber configured to mix ammonia with brine to form an ammoniated brine. In some examples, the carbon dioxide absorption and mineralization package is configured to mix the ammoniated brine with a carbon dioxide-containing gas stream to form an aqueous ammonium chloride solution and carbonates and / or bicarbonates. In some examples, the mineral separation package includes a solid-liquid separator configured to separate at least a portion of the carbonates and / or bicarbonates from the aqueous ammonium chloride solution, where the carbonates and / or bicarbonates can be hydrated or anhydrous. In some examples, the system also includes a dryer configured to remove at least a portion of the water from the hydrated carbonates and / or bicarbonates separated in the solid-liquid separator. In some examples, the solvent regeneration package further includes a heater configured to evaporate water from the aqueous ammonium chloride solution and decompose the ammonium chloride to form ammonia and HCl. In some examples, the solvent regeneration package further includes a water condenser configured to condense water vapor generated by use of the heater.

[0028] Various aspects of at least one embodiment will now be described with reference to the accompanying drawings, which are not intended to be drawn to scale. The drawings are included to explain and provide a further understanding of various aspects and embodiments of the invention, and constitute a part of this specification, but do not limit the scope of the invention. In the drawings, identical or nearly identical components in different views may be represented by the same reference characters or numerals. For clarity, not every component is labeled in every view. [Brief explanation of the drawings]

[0029] [Figure 1] FIG. 1 is a schematic diagram of the general configuration of the system and process of the present invention.

[0030] [Figure 2] FIG. 2 is a detailed schematic diagram of a non-limiting example of a specific application of a system and process for producing calcium carbonate (CaCO) and chlorine gas (Cl) using calcium chloride.

[0031] [Figure 3] FIG. 3 shows the conversion rate from CaCl2 to CaCO3 for flue gases with different carbon dioxide concentrations.

[0032] [Figure 4] FIG. 4 shows the ammonia production rate in experiments carried out under different temperature conditions.

[0033] [Figure 5] FIG. 5 shows the average and maximum rates of ammonia production in packed and fluidized bed reactions carried out under identical conditions.

[0034] [Figure 6] FIG. 6 shows the amount of ammonia and hydrochloric acid dissolved in the solution as measured over time by ion chromatography.

[0035] [Figure 7] FIG. 7 shows the average and maximum rates of chlorine production in experiments carried out under the same conditions but at different temperatures.

[0036] [Figure 8] FIG. 8 shows the average and maximum rates of chlorine production in packed and fluidized bed reactions carried out under identical conditions.

[0037] [Figure 9] FIG. 9 shows the average and maximum rates of chlorine production under different catalyst loadings, run at the minimum oxygen flow rate required for fluidization for each bed size.

[0038] [Figure 10] Figure 10 shows the estimated total amount of chlorine produced based on 7% solubility of chlorine gas in water and the number of moles of chlorine dissolved in solution. DETAILED DESCRIPTION OF THE INVENTION

[0039] The example materials, systems, methods, and devices described herein are not limited to the structural details set forth below or the arrangement of components illustrated in the accompanying drawings. These systems, methods, and devices may be implemented in other examples and may be practiced or operated in various ways. The particular examples are provided for illustrative purposes only and are not to be construed as limiting. In particular, features, components, elements, and characteristics described in connection with one or more examples are not intended to exclude that they may play a similar role in other examples.

[0040] Examples disclosed herein may be combined with other examples in a manner consistent with at least one principle of the disclosure, and the terms "in one example," "in some examples," "in another example," "in various examples," "in one example," and the like are not mutually exclusive and are intended to indicate that particular features, structures, or characteristics may be included in at least one example, and all occurrences of these terms are not necessarily referring to the same example.

[0041] Furthermore, phrases and terminology used herein are for descriptive purposes and should not be construed as limiting. When computer program product, system, and method examples, components, elements, acts, or functions referred to herein are referred to in the singular, they may also encompass plural embodiments. Also, plural references may encompass singular embodiments. Thus, singular or plural references are not intended to limit the systems or methods, components, acts, or elements disclosed herein. As used herein, terms such as "comprise," "include," "have," "includes," "involving," and variations thereof are meant to encompass the items listed thereafter and equivalents thereof, as well as additional items. Also, "or" is intended to be inclusive and may include one, more than one, or all of the described items.

[0042] Described herein are systems and methods for the capture and conversion of carbon dioxide, such as CO2, contained in exhaust gases and / or fermentation off-gases into commercially viable chemical products. The disclosed methods involve the use of high-salt solutions and ammonia gas to capture and convert CO2 to CaCO3, MgCO3, NaHCO3, KHCO3, or other similar carbonate or bicarbonate salts, and NH4Cl. In some embodiments, the bicarbonate may be further processed and converted to carbonate. In some embodiments, NH4Cl may be converted to NH3 and HCl by heating. In other embodiments, NH4Cl may be converted to NH3 and NaCl, KCl, CaCl2, or similar products by adding NaOH, KOH, Ca(OH)2, or similar hydroxides.

[0043] The systems and methods disclosed in this invention allow for the regeneration of CO2 absorbents, improving efficiency and minimizing by-product production.

[0044] Figure 1 shows a general process 10 for converting a CO2-enriched gas stream into a CO2-depleted gas stream and commercially valuable chemical products. Process 10 consists of three major equipment packages / steps: step 12, CO2 absorption and mineralization to produce X-carbonate and ammonium chloride ("Product A"); step 14, separation of X-carbonate and ammonium chloride from the mineralization product stream; and step 16, reconversion of ammonium chloride to solvent and product for reuse in step 12. The numbered boxes in Figure 1 represent the equipment and processing for carrying out these processes, and one skilled in the art will understand that some processes may be integrated within a single unit.

[0045] In some embodiments, brine (aqueous sodium chloride solution) and ammonia gas are used to capture and convert CO2 to produce sodium carbonate (Na2CO3), hydrochloric acid (or chlorine), water, and / or ammonium chloride (NH4Cl) as primary products in step 12.

[0046] In some embodiments, aqueous potassium chloride solution and ammonia gas are used to capture and convert CO2, producing potassium carbonate (K2CO3), hydrochloric acid (or chlorine), water, and / or ammonium chloride (NH4Cl) as primary products in step 12. In embodiments in which flue gas is captured and converted, additional products of step 12 may include potassium nitrate (KNO3), potassium nitrite (KNO2), potassium sulfite (K2SO3), potassium bisulfite (KHSO3), potassium bisulfite (KHSO4), and potassium sulfate (K2SO4).

[0047] In some embodiments, brine (aqueous sodium chloride solution) and ammonia gas are used to capture and convert CO2 to produce sodium bicarbonate (NaHCO3), hydrochloric acid (or chlorine), water, and / or ammonium chloride (NH4Cl) as primary products in step 12. In some embodiments, aqueous potassium chloride solution and ammonia gas are used to capture and convert CO2 to produce potassium bicarbonate (KHCO3), hydrochloric acid (or chlorine), water, and / or ammonium chloride (NH4Cl) as primary products in step 12.

[0048] In some embodiments, an aqueous calcium chloride solution and ammonia gas are used to capture and convert CO to produce calcium carbonate (CaCO), hydrochloric acid (or chlorine), water, and / or ammonium chloride (NHCl) as primary products in step 12.

[0049] In some embodiments, the sodium bicarbonate, potassium bicarbonate, calcium carbonate, or similar carbonate or bicarbonate salt produced using the disclosed method in step 12 is separated from the aqueous ammonium chloride solution in step 14.

[0050] In some embodiments, the sodium bicarbonate or potassium bicarbonate produced using the disclosed method in step 12 is heated to convert it to sodium carbonate or potassium carbonate, respectively.

[0051] In some embodiments, the ammonium chloride produced using the disclosed method in step 12 is separated from the solution and converted to hydrochloric acid and ammonia in step 14. The resulting gas mixture of hydrochloric acid and ammonia is separated in step 16, and the ammonia is recycled for reuse.

[0052] With respect to process 10 shown in FIG. 1, in some embodiments, the inputs to step 12 are a gas stream containing carbon dioxide, an absorbent (e.g., NHOH), and a high salt concentration solution (X-Cl). Additionally, separation process gases (including reactant gases) used in steps 14 and 16 are also input. In some embodiments, the gases used in the separation process may be N2 and O2. In some embodiments, the gases used in the separation process may be CO and O2. The outputs of the process are carbonates and / or bicarbonates (e.g., sodium bicarbonate and calcium carbonate), chlorine (Cl2), water, N2, and O2. In some embodiments, the products may include hydrochloric acid (HCl). In some embodiments, the products may include phosgene (COCl2).

[0053] In some embodiments, a salt dissolver (not shown) is used to mix salt with water to produce a high-salt solution. This high-salt solution is also referred to herein as a brine solution or brine. The salt used can be pure NaCl, CaCl2, KCl, or MgCl2, or a mixture thereof. In some embodiments, calcium chloride is added to the salt dissolver in the form of anhydrous CaCl2, CaCl2·2H2O, or CaCl2·4H2O. In some embodiments, magnesium chloride is added to the salt dissolver in the form of anhydrous MgCl2 or MgCl2·6H2O. In some embodiments, the process output is a saturated solution of salt at the operating temperature. The salt dissolver can operate over a wide temperature range from 15 to 70°C, with a preferred operating temperature range being 25 to 60°C.

[0054] In some embodiments, seawater or brackish water can be used as the medium in the salt dissolver, and thus the disclosed method can also be used in desalination or water treatment processes, since fresh water is obtained as a by-product.

[0055] Before processing the carbon dioxide-containing gas stream, the temperature of the gas stream may be reduced by transferring heat to other process equipment. For example, in some embodiments, heat may be transferred to a catalytic process (step 16) that produces aqueous ammonia and chlorine (Cl2). After the temperature of the gas stream is reduced, it enters step 12, an absorption and mineralization process.

[0056] In some embodiments, the components involved in step 12 are a carbon dioxide-containing gas stream, NH4OH, and a high-salt aqueous solution containing NaCl, CaCl2, KCl, or mixtures thereof. In some embodiments, these salts are mixed with water in a continuously stirred reactor to produce the high-salt aqueous solution. In some embodiments, the high-salt aqueous solution and ammonia are mixed in an ammonia absorber to produce an ammoniaated solution, and the ammoniated brine solution is passed through a CO2 absorber tower (step 12) from top to bottom, countercurrently contacting the CO2-enriched gas stream entering the tower at the bottom. The reaction between the high-salt solution, aqueous ammonia, and CO2 produces NaHCO3, KHCO3, CaCO3, or other carbonate or bicarbonate salts with NH4Cl according to one of the following reactions (depending on the composition of the high-salt solution): NaCl(aq)+NH4OH+CO2→NaHCO3(s)+NH4Cl (aq) (1) CaCl2(aq)+2NH4OH+CO2→CaCO3(s)+2NH4Cl (aq) (2) MgCl2(aq)+2NH4OH+CO2→MgCO3(s)+2NH4Cl (aq) (3) KCl(aq)+NH4OH+CO2→KHCO3(s)+NH4Cl (aq) (4)

[0057] In one embodiment, the absorption and mineralization unit (step 12) is configured to operate over a wide temperature range of 10-70° C., with a preferred operating temperature range being 15-60° C. As a result of CO2 absorption in the absorption and mineralization unit, the amount of CO2 in the gas stream may be reduced by at least 30% and up to 99%.

[0058] In one embodiment, biogas is the gas stream fed to step 12. As a result of absorption and mineralization, the gas exiting the absorber is a methane-enriched gas stream, which in one embodiment can be used commercially as renewable natural gas (RNG).

[0059] The solution exiting the bottom of absorber 12 contains aqueous NH4Cl and carbonate / bicarbonate salts (e.g., CaCO3, NaHCO3, KHCO3, MgCO3), which is sent to separation process / unit 14, where the carbonate and / or bicarbonate salts are separated and the aqueous NH4Cl salt is sent to the heater (regenerator) of catalytic process / unit 16. In one embodiment, the absorber step 12 discharges carbonate and / or bicarbonate solids at a rate of 10-50% by weight, which are fed to a solid-liquid separator in step 14, which may include or consist of a filter or centrifuge.

[0060] In step 14, ammonium salts are separated from the aqueous NH4Cl solution remaining from the solid-liquid separation in another separator. In one embodiment, this separator can be a crystallizer or an evaporator. In some embodiments, a single unit separates both carbonate / bicarbonate and NH4Cl from the product from step 12. The NH4Cl concentrated stream from step 14 is fed to a catalytic process, step 16.

[0061] In step 16, a catalytic process, NH4Cl is decomposed at elevated temperatures to produce NH3 and HCl. The reaction is as follows: NH4Cl → HCl(g) + NH3(g) (5)

[0062] In one embodiment, in step 16, NH is recovered by a catalyst regeneration process, a membrane separation process, or other separation method. In the catalyst regeneration process, HCl is reacted with catalyst (X) and oxygen to recover NH via the following reaction: 4HCl(g) + O2(g) + 4X → 4XCl + 2H2O (6)

[0063] In one embodiment, the catalyst (X) is a metal chloride such as nickel chloride, cobalt chloride, CuCl, or FeCl2.

[0064] In another embodiment, the catalyst (X) is a mixture of a molten alkali metal chloride, such as KCl, NaCl, CuCl, or KiCl2, and a metal oxide, such as Fe, Ni, Co, or Cu, as described in U.S. Pat. No. 3,627,471(A).

[0065] In another embodiment, the catalyst (X) is an activated form of a mixture of sesquioxides of a metal selected from Mn, Fe, Co, Cu, Ni, potassium chloride, and cuprous chloride, as described in US Pat. No. 3,410,657.

[0066] In yet another embodiment, the catalyst is a metal oxide (MO), such as nickel oxide, cobalt oxide, or CuO (preferably CuO), as described in US Patent US4959202A. In this case, the reaction is as follows: 4HCl(g) + 2MO → 2MCl2+ 2H2O (7)

[0067] In some embodiments, the catalyst is impregnated onto a support such as alumina, silica, or molecular sieve material, as described in U.S. Patent No. 4,959,202, which provides a surface structure that influences the reaction rate of the catalyst.

[0068] The ammonia recovery step operates over a wide temperature range from 180 to 450°C, preferably from 180 to 300°C. The pressure ranges from 1 to 20 bar.

[0069] In the catalyst regeneration step, a hot inert gas (such as N) is used to release Cl from the catalyst and regenerate it via the following reaction: 2XCl → 2X + Cl2(8)

[0070] If a metal oxide (e.g., CuO) is used to separate NH3, the catalyst is regenerated with oxygen according to the following reaction: 2MCl2 + O2(g) → 2MO + Cl2(9)

[0071] In some embodiments, superheated steam is used to produce HCl: 4XCl + 2H2O → 4X + 2HCl + O2(g) (10)

[0072] The reaction to produce phosgene (COCl2) using CO is as follows: 2XCl + CO → 2X + COCl2(11)

[0073] The catalyst regeneration is carried out at a temperature in the range of 300 to 800° C., preferably 300 to 500° C., and at a pressure of 1 to 20 bar.

[0074] The catalytic process produces an ammonia-containing stream having an ammonia to HCl molar ratio greater than 1 and a chlorine-containing stream having an ammonia to chlorine molar ratio less than 2.

[0075] Alternatively, an ammonia-containing stream and an HCl-containing stream having an ammonia to HCl molar ratio greater than 1 and less than 1 are produced.

[0076] In another embodiment, a phosgene-containing stream is obtained having a molar ratio of ammonia to phosgene of less than 1.

[0077] The ammonia-containing stream from the catalytic process is dissolved in water to produce a new solvent (NH4OH) for the absorption and mineralization step according to the following reaction: NH3(g) + H2O → NH4OH(aq) (12)

[0078] Before being recycled, the gas stream's temperature is lowered by heat transfer to another process unit, for example, to return heat to a catalytic process. After the temperature is reduced, it enters the ammonification reactor to complete the catalytic process and regenerate the solvent.

[0079] Figure 2 is a non-limiting example illustrating the process of Figure 1 in more detail. Absorption and mineralization unit 12a includes a mineralizer / mineralizer 32, where a CO2-enriched gas stream (such as flue gas or fermentation exhaust) is contacted with NH4OH solvent mixed with CaCl2 to produce CaCO3, NH4Cl, and a CO2-depleted gas. The CO2-depleted gas is vented to the outside. After step 32, the solid CaCO3 is separated from the aqueous NH4Cl solution in a physical separation step (e.g., filtration) (step 34), and the CaCO3 slurry is dried in dryer 35 for industrial use. The NH4Cl solution exiting separation step 34 is sent to crystallizer 36, which produces a concentrated NH4Cl slurry and water. The water is sent to mixer 42. Separation unit 14a includes filter 34, crystallizer 36, and optional dryer 35.

[0080] The slurry from crystallizer 36 is heated to 200-350°C in sublimation unit 38, where NH4Cl is sublimated to produce NH3 and HCl. Unit 38 contains a condenser, which condenses the water vapor and sends it to unit 42. In regeneration unit 40, HCl reacts with the catalyst in the presence of oxygen to release ammonia. The recovered ammonia exits the regeneration unit as a gas. The catalyst is heated to 400-500°C to produce chlorine. Water from units 36 and 38 is mixed with CaCl2 to produce an aqueous solution in mixer 42. The ammonia released from step 40 is mixed with the aqueous CaCl2 solution in mixer 42 in the ammonification unit in step 44 to produce new solvent for step 32. Catalytic process 16a consists of sublimation 38, regeneration 40, mixer 42, and ammonification 44.

[0081] The numbered boxes in Figure 2 represent the equipment and processes used in each process. Some processes can be performed in integrated equipment, as would be understood by one skilled in the art.

[0082] Example

[0083] Example 1: Mineralization Reaction

[0084] The first parameter evaluated was the effect of solvent composition. This was tested by conducting mineralization reactions using different solvents in PVC columns 3 inches in diameter and 36 inches in height. For each mineralization reaction, the column was packed with ceramic pellets to help evenly distribute the gas and liquid flows. The CO2-enriched feed gas was introduced through a bubbler at the bottom of the reactor, and the solvent was added at the top of the column and allowed to flow down to the outlet at the bottom. This configuration was operated in semi-batch mode, with the solvent continuously recirculated while fresh CO2 was fed to the column. The entire experiment was carried out at room temperature, and conversion was monitored using pH. The mineralization reaction was continued until the pH stopped changing or began to increase. Calibration samples were also prepared to determine the pH as a function of calcium chloride conversion.

[0085] The ideal concentrations of CaCl2 (calcium chloride) and NH4OH (ammonium hydroxide) in the solvent were found to be 2.51 mol and 10.56 mol, respectively (110% stoichiometric excess of NH4OH). However, when the concentrations of each were individually reduced by a factor of 10 (2.51 mol of CaCl2 and 1.06 mol of NH4OH, resulting in a 374% excess of CaCl2, or 0.251 mol of CaCl2 and 10.56 mol of NH4OH, resulting in a 1,995% excess of NH3), undesirable by-products were formed. This was confirmed by running samples based on the predicted conversion of the limiting reagent using a pH calibration curve. At both CaCl2 and NH4OH excesses, the samples reached estimated conversions of 190% and 135%, respectively, suggesting further pH shifts due to by-product formation. Table 1 shows the predicted starting pH, predicted pH at 100% conversion, actual starting pH, and actual final pH for each solvent composition. The standard solvent composition was within the predicted pH range, but the final pH for the two solvents with a large stoichiometric excess was outside the predicted range. [Table 1]

[0086] Next, the effect of CO2 concentration in the feed gas was examined. CO2 compositions of 100%, 75%, and 25% by volume were tested. It was found that, at a constant total flow rate, the CaCO3 production rate decreased as the CO2 concentration decreased. This is expected, as a decrease in CO2 concentration slows the rate of CO2 inflow into the mineralization column. Figure 3 compares the CaCO3 production rate at each fluogas concentration. Analysis of the mineralization product composition by CHN (carbon, hydrogen, nitrogen) elemental analysis revealed that the feed CO2 concentration did not affect the purity of the CaCO3 produced. Table 2 shows the purity of the CaCO3 produced at each fluogas concentration. The slight differences in purity are due to variations in the sample washing process. [Table 2]

[0087] Example 2: Crystallization

[0088] Ammonium chloride (NH4Cl) is less soluble in water than calcium chloride (CaCl2), so crystallization can be used to supersaturate the ammonium chloride in solution while keeping the calcium chloride dissolved. Once the ammonium chloride is supersaturated, it forms solid crystals that can be easily separated from the spent solvent and sent to a regeneration unit.

[0089] To test this hypothesis, a bench-scale forced circulation crystallizer was constructed. The solution was introduced into the crystallizer from below the liquid surface upward, and the crystal-rich stream flowed out the bottom of the crystallizer into an open reservoir. The solution in the reservoir was circulated by a pump through a boiling water heat exchanger and then returned to the crystallizer. The crystallizer was run for 1 hour at different heat exchanger temperatures. When crystal formation was confirmed visually, the run was terminated, the final solution was collected, and the crystals were separated by centrifugation.

[0090] After the crystallization process, salt crystals formed on the surface near the outlet, and the remaining solution was centrifuged to remove any floating crystals. The liquid sample was then analyzed by ion chromatography (IC) to measure the concentrations of ammonium, calcium, and chloride ions. The IC results supported the hypothesis and are shown in Table 3. The ammonium concentration decreased in the post-crystallization sample, confirming that the ammonium was precipitated and removed as solid crystals. Meanwhile, the calcium concentration increased due to the decrease in solvent volume (evaporation during the crystallization process). [Table 3]

[0091] By accounting for solvent loss due to evaporation, the molar amounts of calcium chloride and ammonium chloride in the sample before and after crystallization can be determined. Table 4 shows that the amount of calcium chloride remained fairly constant (0.4%) during crystallization, while the amount of ammonium chloride decreased by 65.7%. This indicates that the ammonium chloride crystallized to form solid crystals, while the calcium chloride remained dissolved in the solvent. These solid crystals were recovered by filtration, resulting in a 65.7% recovery of ammonium chloride. [Table 4]

[0092] Example 3: Solvent Regeneration

[0093] Various parameters can affect the solvent regeneration process. The following factors were investigated experimentally: temperature, reactor bed configuration, and salt condition at the time of loading. These factors were investigated using two experimental setups. The first was a fixed-bed reactor, in which catalyst-impregnated alumina beads were packed into the reactor and ammonium chloride was placed in the center. The reactor was heated to various temperatures and oxygen gas was passed through. The second was a fluidized-bed setup, in which pure catalyst and salt were mixed, fluidized with oxygen, and heated under the same temperature conditions as the fixed-bed setup. In both experiments, the produced ammonia gas was absorbed into water, and the amount of ammonia produced was measured by monitoring the pH change. Measurements were continued until the pH change stopped or began to decrease.

[0094] The effect of temperature was evaluated in a fixed-bed reactor over the range of 190°C to 240°C. It was observed that the ammonia production rate increased as the temperature increased. The production rates at 190°C, 210°C, 230°C, and 240°C are shown in Figure 4 and Table 5. While the performance improvement was minimal from 190°C to 230°C, increasing the temperature from 230°C to 240°C resulted in a ten-fold increase in the average and maximum instantaneous rates. This efficiency improvement is likely due to a significant increase in the sublimation rate of ammonium chloride between 230°C and 240°C, which provides a larger supply of hydrochloric acid available for reaction. [Table 5]

[0095] Solvent regeneration was also evaluated in a fluidized bed using cuprous chloride (CuCl) as the catalyst. Compared to a fixed bed, the fluidized bed produced approximately two times the average production rate and approximately three times the maximum production rate. These results are shown in Figure 5. Additionally, samples from the fluidized bed were analyzed by ion chromatography, confirming the presence of the expected ions in solution. Figure 6 shows that the amount of ammonia increased over time while the amount of chlorine remained constant. This indicates that the catalyst captured the chlorine, and the ammonia passed through the reactor unchanged. A slight increase in the hydrochloric acid concentration toward the end of the experiment suggested that the amount of hydrochloric acid produced exceeded the catalyst's capacity at 90 minutes, necessitating catalyst regeneration.

[0096] Example 4: Catalyst regeneration

[0097] Cupric chloride (CuCl2) is thermally decomposed into cuprous chloride (initial catalyst) and chlorine gas (process product). The rate of this thermal decomposition is affected by various factors. Experimental evaluations included temperature, fluidization, bed size, grind size, and pre-drying. As with solvent regeneration, the process was tested using two types of equipment: a fixed bed and a fluidized bed. The main differences were the reaction temperature (>400 °C) and the absence of ammonium chloride. In the fixed bed, the catalyst impregnated on alumina beads was held in the reactor and operated at various temperatures in a flowing oxygen atmosphere. In the fluidized bed, the pure catalyst was similarly heated while fluidized with oxygen. In both conditions, the chlorine produced was absorbed in water, and the amount produced was measured by monitoring the pH change.

[0098] Catalyst regeneration is performed by pyrolysis, so temperature is the dominant parameter. Regeneration was performed over a range of temperatures from 400°C to 450°C. The reaction proceeded even at the lowest temperature of 400°C, but efficiency improved as the temperature increased. Figure 7 compares the average and maximum regeneration activity rates at 400°C, 430°C, and 450°C.

[0099] Furthermore, we confirmed that fluidizing the system significantly increased the chlorine production rate. This is due to two reasons: first, the catalyst particles are smaller in a fluidized bed, increasing the surface area in the reactor bed. Second, fluidization improves mixing, increasing the interaction between the catalyst and the heated section of the reactor wall. This resulted in an approximately ten-fold increase in chlorine production rate. In a comparison of performance under identical conditions (fluidized with oxygen at 400°C), the average production rate in the fixed bed was 0.108 mg / min per gram of catalyst, with a maximum of 0.354 mg / min, compared with 1.896 mg / min and 7.392 mg / min, respectively, in the fluidized bed. These results are shown in Figure 8.

[0100] After confirming that a fluidized bed could achieve higher chlorine production rates, the maximum amount of catalyst that could be used in one regeneration was investigated. To test this, the catalyst load was doubled from 10 g to 20 g, and the oxygen flow rate required for fluidization was also increased. As a result, the average production rate per gram of catalyst remained nearly the same (1.896 → 1.794 mg / min), but the maximum production rate decreased by approximately 20% (7.392 → 5.880 mg / min). Figure 9 compares the average and maximum production rates for different initial catalyst loads. The results show that increasing the catalyst load slightly decreases the chlorine production rate per gram of catalyst.

[0101] With respect to the above-described embodiments, various changes, modifications, and improvements will readily occur to those skilled in the art. These modifications and improvements are part of this disclosure and are intended to be included within the scope of the invention. Therefore, the above description and drawings are merely exemplary, and the scope of the invention should be properly interpreted in accordance with the appended claims and their equivalents.

Claims

1. 1. A system for reducing the amount of carbon dioxide contained in a gas stream, comprising: a carbon dioxide absorption and mineralization unit configured to produce at least one of a carbonate and a bicarbonate and ammonium chloride from carbon dioxide, an ammoniated solvent, and at least one metal chloride in the gas stream; a mineral separation unit configured to separate carbonates and bicarbonates from ammonium chloride; A solvent regeneration unit configured to use a catalyst to produce chlorine and ammonium hydroxide from ammonium chloride, heat, and oxygen.

2. 10. The system of claim 1, wherein the solvent regeneration unit is configured to separate HCl from the output of the mineral separation unit by reacting it with a metal chloride-based catalyst, X, and oxygen to form XCl and water.

3. 3. The system of claim 2, wherein the solvent regeneration unit decomposes XCl in the presence of a hot inert gas to produce Cl. ２ The catalyst X is regenerated by generating

4. 3. The system of claim 2, wherein the solvent regeneration unit is configured to regenerate catalyst X by reacting XCl with carbon monoxide to produce phosgene.

5. 3. The system of claim 2, wherein the solvent regeneration unit is configured to regenerate catalyst X by reacting XCl with water to form HCl and oxygen.

6. 10. The system of claim 1, wherein the molar ratio of ammonia to HCl in the solvent regeneration unit is greater than 1.

7. 7. The system of claim 6, wherein the solvent regeneration unit is configured to separate HCl from the gas stream by membrane separation.

8. 10. The system of claim 1, further comprising a salt dissolving unit.

9. 9. The system of claim 8, wherein the salt dissolution unit is configured to mix water and salt to form a high salinity solution and supply it to the carbon dioxide absorption and mineralization unit.

10. 10. The system of claim 9, wherein the high salt solution comprises CaCl ２ , MgCl ２ , NaCl, KCl or a mixture of two or more thereof.

11. 9. The system of claim 8, wherein the salt dissolution unit is configured to mix seawater, brackish water, or wastewater with salt to form a high-salinity solution and supply it to the carbon dioxide absorption and mineralization unit.

12. 12. The system of claim 11, wherein the high salt solution comprises CaCl ２ , MgCl ２ , NaCl, KCl or a mixture of two or more thereof.

13. 12. The system of claim 11, wherein: The solvent regeneration unit includes an ammonia absorber that mixes the ammonia from the separation unit with the high salt solution to form an ammoniated high salt solution; the carbon dioxide absorption and mineralization unit is configured to mix the ammoniated high-salinity solution from the ammonia absorber with the carbon dioxide-containing gas stream to form an aqueous ammonium chloride solution and carbonate and / or bicarbonate salts; the mineral separation unit includes a solid-liquid separator and is configured to separate at least a portion of the carbonate and / or bicarbonate from the aqueous ammonium chloride solution, where the carbonate and / or bicarbonate may be either hydrated or anhydrous; The solvent regeneration unit further includes a heater that vaporizes water from the aqueous ammonium chloride solution and decomposes the ammonium chloride to form a mixture containing ammonia and HCl, and a water condenser that condenses the water vapor produced by the heater to produce liquid water.

14. 10. The system of claim 1, wherein the solvent regeneration unit includes an ammonia absorber that mixes ammonia with a saltwater solution to form an ammoniated brine.

15. 15. The system of claim 14, wherein the carbon dioxide absorption and mineralization unit is configured to mix the ammoniated brine with the carbon dioxide-containing gas stream to form an aqueous ammonium chloride solution and carbonate and / or bicarbonate salts.

16. 16. The system of claim 15, wherein the mineral separation unit comprises a solid-liquid separator that separates at least some of the carbonates and / or bicarbonates from the aqueous ammonium chloride solution, the carbonates and / or bicarbonates being either hydrated or anhydrous.

17. 17. The system of claim 16, further comprising a dryer for removing at least a portion of the water from the hydrated carbonates and / or bicarbonates separated in the solid-liquid separator.

18. 16. The system of claim 15, wherein the solvent regeneration unit further comprises a heater for vaporizing water from the aqueous ammonium chloride solution and decomposing the ammonium chloride to form ammonia and HCl.

19. 20. The system of claim 18, wherein the solvent regeneration unit further comprises a water condenser for condensing water vapor produced by the heater.

20. 1. A method for reducing the amount of carbon dioxide contained in a gas stream, comprising: producing at least one of a carbonate and a bicarbonate and ammonium chloride from carbon dioxide, an ammoniated solvent, and at least one metal chloride in the gas stream; Separating the carbonate and bicarbonate from ammonium chloride; Using a catalyst to produce chlorine and ammonium hydroxide from ammonium chloride, heat, and oxygen.

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