Treatment of acid gas using molten alkali metal borate and related separation methods, as well as processes for regenerating adsorbents and related systems

Abstract

Generally, non-CO2 containing salts in molten form i Removal of acid gases (e.g., non-carbon dioxide acid gases) using an acid gas adsorbent, and related systems and methods, are described. Also generally described are processes and related systems for regenerating the adsorbent at elevated temperatures. Certain aspects relate to methods. In some embodiments, the method includes exposing a non-CO2 acid gas adsorbent comprising a salt in molten form to an environment containing non-CO2 acid gases, such that at least a portion of the non-CO2 acid gases interact with the non-CO2 acid gas adsorbent and at least a portion of the non-CO2 acid gases are removed from the environment.

Description

Technical Field

[0001] Related Applications This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No. 62 / 971,488, filed on February 7, 2020, for the invention entitled "Treatment of Acid Gases Using Molten Alkali Metal Borates, and Associated Methods of Separation"; U.S. Provisional Patent Application No. 62 / 988,436, filed on March 12, 2020, for the invention entitled "Processes for Regenerating Sorbents, and Associated Systems"; U.S. Provisional Patent Application No. 62 / 979,628, filed on February 21, 2020, for the invention entitled "Processes for Regenerating Sorbents, and Associated Systems"; and U.S. Provisional Patent Application No. 62 / 932,410, filed on November 7, 2019, for the invention entitled "Process for Regenerating Sorbents at High Temperatures", the entire contents of each of which are hereby incorporated by reference in their entireties for all purposes.

Background Art

[0002] Technical Field In one aspect, generally, the removal of acid gases other than carbon dioxide using non-CO2 acid gas sorbents comprising salts in molten form, as well as related systems and methods, are described. In another aspect, generally, processes for regenerating sorbents and related systems are described.

Summary of the Invention

Means for Solving the Problems

[0003] Abstract In general, the removal of acid gases other than carbon dioxide, as well as related systems and methods, using a non-CO2 acid gas adsorbent comprising a molten form of salt are described.

[0004] Certain embodiments relate to a method. In some embodiments, the method includes exposing a non-CO2 acid gas adsorbent comprising a molten form of salt to an environment containing a non-CO2 acid gas such that at least a portion of the non-CO2 acid gas interacts with the non-CO2 acid gas adsorbent and at least a portion of the non-CO2 acid gas is removed from the environment.

[0005] Also in general, processes for regenerating the adsorbent and related systems are described. Certain embodiments relate to the use of steam to remove one or more captured acid gases from the adsorbent.

[0006] Certain embodiments relate to a method. In some embodiments, the method includes regenerating an adsorbent exposed to an acid gas via exposure to steam such that at least a portion of the acid gas is separated from the adsorbent.

[0007] The subject matter of the present invention, in some cases, includes interrelated products, alternative solutions to particular problems, and / or multiple different uses of one or more systems and / or articles.

[0008] Other advantages and novel features of the present invention will become apparent from the following detailed description of various non-limiting embodiments of the invention when considered in conjunction with the accompanying drawings. In the event that the present specification and the incorporated documents include conflicting and / or inconsistent disclosures, the present specification shall prevail.

[0009] Non-limiting embodiments of the present invention are described by way of example with reference to the accompanying drawings, which are schematic and are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated is typically represented by a single reference numeral. For the sake of clarity, not all components are labeled in all of the drawings, nor are all components of each embodiment of the present invention shown to provide the illustration necessary for one of ordinary skill in the art to understand the present invention.

Brief Description of the Drawings

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[0032] Detailed Description In one aspect, generally, the removal of acid gases other than carbon dioxide, as well as related systems and methods, using a non-CO2 acid gas adsorbent containing a molten salt, are described. In another aspect, generally, a process for regenerating an adsorbent and related systems are described. Treatment of acid gases using molten alkali metal borates and related separation methods

[0033] The removal of acid gases (including carbon dioxide and acid gases other than carbon dioxide) from industrial streams can find use in the energy and chemical industries, particularly in environmentally responsible energy production from fossil fuels. Acid gases can become environmental pollutants as greenhouse gases or causative agents of acid rain, and in many cases, these acid gases can be severely harmful to human health. Streams often contain multiple acid gases at high temperatures, but in conventional systems, usually, multiple separate low-temperature processes are arranged in series and each acid gas is treated one by one. Therefore, a method that can capture and separate multiple acid gases at high temperatures without having a harmful effect on the performance of the system is of great interest and is described below and elsewhere in this specification.

[0034] In certain embodiments, the molten alkali metal borate is used as a non-CO2 acid gas adsorbent to remove acid gas(es) other than CO2 (also referred to herein as non-CO2 acid gas(es)) from a stream. Certain embodiments relate to the application of molten alkali metal borates in a continuous circulation system for the removal and separation of multiple acid gases at high temperatures. According to certain embodiments, each acid gas interacts differently with the molten alkali metal borate, such that each species can be separated from the other species at separate points in the high-temperature system. In certain embodiments, the product stream is concentrated at high temperature either by release as a gas or by physical separation of solids from a recirculating liquid.

[0035] Certain aspects of the present disclosure are directed to the removal of non-CO2 acid gases using non-CO2 acid gas adsorbents that include salts in a molten form. In some embodiments, the non-CO2 acid gas adsorbent can act as a sequestration material for one or more non-CO2 acid gases. In some embodiments, the removal of non-CO2 acid gases may be performed at elevated temperatures (e.g., at or above the melting temperature of the salt such that at least the unreacted molten salt is retained in a molten form). The inventors have recognized and understood that certain non-CO2 acid gas adsorbents described herein can remove various acid gases including carbon dioxide. In certain cases, a particular non-CO2 acid gas adsorbent can sequester non-CO2 acid gases. Further, in some embodiments, a particular non-CO2 acid gas adsorbent can preferentially sequester non-CO2 acid gases over carbon dioxide, which can advantageously be useful for separating carbon dioxide from non-CO2 acid gases.

[0036] While much of the disclosure herein focuses on the treatment of non-CO2 acid gases, it should be understood that the non-CO2 acid gas adsorbents described herein can also sequester carbon dioxide (in addition to non-CO2 acid gases).

[0037] According to certain embodiments, the non-CO2 acid gas adsorbent can be exposed to an environment containing non-CO2 acid gases. A non-CO2 acid gas is any acid gas that is not carbon dioxide. Non-limiting examples of non-CO2 acid gases include sulfur monoxide (SO), sulfur dioxide (SO2), nitrogen dioxide (NO2), hydrogen sulfide (H2S), sulfur trioxide (SO3), nitric oxide (NO), nitrous oxide (N2O), dinitrogen trioxide (N2O3), dinitrogen tetroxide (N2O4), dinitrogen pentoxide (N2O5), and / or carbonyl sulfide (COS). Also, exposure of the non-CO2 acid gas adsorbent to other acid gases (and removal of such acid gases) is possible.

[0038] According to certain embodiments, the non-CO2 acid gas adsorbent is exposed to non-CO2 acid gas under conditions favorable for the isolation of non-CO2 acid gas. For example, according to certain embodiments, a non-CO2 acid gas adsorbent comprising a salt in molten form can be exposed to an environment containing non-CO2 acid gas in a manner that promotes high contact between the two, e.g., the non-CO2 acid gas adsorbent can be flowed (continuously if desired) and / or sprayed during exposure of the non-CO2 acid gas adsorbent to the environment containing non-CO2 acid gas. By flowing and / or spraying the non-CO2 acid gas adsorbent during exposure of the non-CO2 acid gas adsorbent to the environment containing non-CO2 acid gas, the rate of non-CO2 acid gas capture by the non-CO2 acid gas adsorbent can be advantageously increased compared to the rate of non-CO2 acid gas capture by a completely solid non-CO2 acid gas adsorbent. For example, a non-CO2 acid gas adsorbent comprising a salt in molten form can be flowed and / or sprayed in one direction, while the environment containing non-CO2 acid gas is flowed in a different direction, e.g., the opposite direction, in a countercurrent or crosscurrent operation to maximize heat transfer and / or mass transfer between the non-CO2 acid gas adsorbent and the environment.

[0039] The uptake of non-CO2 acid gas by the non-CO2 acid gas adsorbent according to the present invention can be at any of various desired levels. Uptake by a non-CO2 acid gas adsorbent comprising a salt in molten form, including alkali metal cations and borate anions and / or their dissociated forms, can be 5 mmol or more per gram of non-CO2 acid gas adsorbent within 1 minute of exposure to an environment containing non-CO2 acid gas, which is a significantly faster uptake rate than that of a solid particle non-CO2 acid gas adsorbent of the same composition under similar conditions.

[0040] Furthermore, according to certain embodiments, the ability to flow a non-CO2 acid gas adsorbent comprising a molten form of a salt facilitates a continuous separation process for non-carbon dioxide acid gas(es), in which process, without stopping the process, over multiple cycles, a non-CO2 acid gas loaded non-CO2 acid gas adsorbent may be flowed from an adsorption vessel to a desorption vessel and / or an unloaded non-CO2 acid gas adsorbent may be flowed from the desorption vessel to the adsorption vessel. In some embodiments, continuous operation provides advantages including, but not limited to, a reduction in the duration of the non-CO2 acid gas capture process, a potential reduction in the input energy required in the non-CO2 acid gas capture process, and the ability to regenerate a poisoned non-CO2 acid gas adsorbent by purging rather than taking the unit offline. Also, as described elsewhere herein, the non-CO2 acid gas or mixture of non-CO2 acid gases may contain at least some carbon dioxide. Some of the methods described herein may be advantageously used to separate CO2 from non-CO2 acid gases and / or one type of non-CO2 acid gas from another type of non-CO2 acid gas.

[0041] According to certain embodiments, another important advantage associated with the use of a non-CO2 acid gas adsorbent comprising a molten form of a salt is the ability to use the non-CO2 acid gas adsorbent at elevated temperatures, e.g., at a temperature higher than or equal to the melting temperature of the non-CO2 acid gas adsorbent, e.g., greater than or equal to 200 °C. The temperature may be even higher, e.g., greater than or equal to 250 °C, greater than or equal to 300 °C, greater than or equal to 350 °C, greater than or equal to 400 °C, greater than or equal to 450 °C, or greater than or equal to 500 °C, or higher. In some embodiments where the non-CO2 acid gas adsorbent is used at elevated temperatures, any of a variety of suitable amounts of the non-CO2 acid gas adsorbent (e.g., greater than or equal to 1 wt% of the non-CO2 acid gas adsorbent, greater than or equal to 10 wt% of the non-CO2 acid gas adsorbent, greater than or equal to 50 wt% of the non-CO2 acid gas adsorbent, greater than or equal to 75 wt% of the non-CO2 acid gas adsorbent, greater than or equal to 90 wt% of the non-CO2 acid gas adsorbent, greater than or equal to 99 wt% of the non-CO2 acid gas adsorbent, or all) are within that elevated temperature (e.g., greater than or equal to 200 °C, greater than or equal to 250 °C, greater than or equal to 300 °C, greater than or equal to 350 °C, greater than or equal to 400 °C, greater than or equal to 450 °C, greater than or equal to 500 °C, and / or within the range of any of the other temperature ranges mentioned hereinabove or elsewhere). As used herein, the operating temperature refers to the temperature of the non-CO2 acid gas adsorbent itself, which may be essentially equal to or different from the temperature of the environment to which the non-CO2 acid gas adsorbent is exposed.

[0042] In certain embodiments, the process can be carried out in a pressure swing operation as needed. Generally, in the pressure swing operation in certain embodiments described herein, the non-CO2 acid gas adsorbent is exposed to an environment having a first partial pressure of non-CO2 acid gas during exposure of the non-CO2 acid gas adsorbent to an environment containing acid gas, and then the non-CO2 acid gas-loaded non-CO2 acid gas adsorbent is exposed to a second environment having a lower second partial pressure of non-CO2 acid gas (e.g., 0 bar of non-CO2 acid gas), and the unloaded non-CO2 acid gas adsorbent is regenerated. This pressure swing operation may be repeated over a plurality of cycles when the non-CO2 acid gas adsorbent is regenerated. In some embodiments, the first partial pressure of non-CO2 acid gas may be at least 0.000001 bar, at least 0.0001 bar, at least 0.01 bar, or at least 1 bar. In some embodiments, the first partial pressure of non-CO2 acid gas may be at most 30 bar, at most 20 bar, at most 10 bar, or at most 5 bar. Also, combinations of the above ranges are possible (e.g., between 0.000001 bar and 30 bar or equal thereto, between 0.01 bar and 20 bar or equal thereto, between 0.1 bar and 10 bar or equal thereto, between 1 bar and 5 bar or equal thereto). Also, other ranges are possible. In some embodiments, the second partial pressure of non-CO2 acid gas may be at least 0.000001 bar, at least 0.0001 bar, at least 0.01 bar, or at least 1 bar lower than the first partial pressure of non-CO2 acid gas. In some embodiments, the second partial pressure of non-CO2 acid gas may be at most 30 bar, at most 20 bar, at most 10 bar, or at most 5 bar lower than the first partial pressure of non-CO2 acid gas. Also, combinations of the above ranges are possible (e.g., between 0.001 bar and 30 bar or equally lower, between 0.01 bar and 20 bar or equally lower, between 0.1 bar and 10 bar or equally lower, between 1 bar and 5 bar or equally lower). Also, other ranges are possible.

[0043] The process can be carried out with a temperature swing operation as needed. Generally, in the temperature swing operation according to certain specific embodiments described herein, the non-CO2 acid gas adsorbent is exposed to a first temperature during the exposure of the non-CO2 acid gas adsorbent to an environment containing non-CO2 acid gas, and then the non-CO2 acid gas-loaded non-CO2 acid gas adsorbent is exposed to a higher second temperature in a second environment containing less or no non-CO2 acid gas, and the unloaded non-CO2 acid gas adsorbent is regenerated. This temperature swing operation may be repeated over a plurality of cycles when the non-CO2 acid gas adsorbent is regenerated. The first temperature may be higher than or equal to the melting temperature of the non-CO2 acid gas adsorbent, for example, greater than or equal to 200 °C. The first temperature may still be higher, for example, greater than or equal to 250 °C, greater than or equal to 300 °C, greater than or equal to 350 °C, greater than or equal to 400 °C, greater than or equal to 450 °C, or greater than or equal to 500 °C, or higher than that, and / or less than or equal to 1000 °C. In some embodiments, the second temperature is equal to the first temperature. In some embodiments, the second temperature may be at least 10 °C, at least 50 °C, at least 100 °C, at least 200 °C, at least 300 °C, at least 400 °C, or at least 500 °C higher than the first temperature. In some embodiments, the second temperature may be at most 1000 °C, at most 900 °C, at most 800 °C, at most 700 °C, or at most 600 °C higher than the first temperature. Also, combinations of the above ranges are possible (e.g., between 10 °C and 300 °C or equally higher, between 200 °C and 400 °C or equally higher, between 400 °C and 1000 °C or equally higher). Also, other ranges are possible.

[0044] Unless otherwise specified, the temperatures and other conditions described herein are at approximately atmospheric pressure, but it should be noted that while deviations from atmospheric pressure can occur, the objectives of the present invention can still be met. Those skilled in the art can select different pressures to achieve the results outlined herein.

[0045] Certain embodiments relate to non-CO2 acid gas adsorbent materials. As used herein, the phrase "non-CO2 acid gas adsorbent" is used to describe a material capable of removing non-CO2 acid gas (optionally along with CO2) from an environment containing non-CO2 acid gas. In some embodiments, the non-CO2 acid gas adsorbent can function as an isolation material.

[0046] Certain aspects relate to non-CO2 acid gas adsorbents comprising salts in a molten form, the composition of the salts being selected such that they have a lower melting temperature compared to other salts so that less energy is required to melt the salts. Further, the composition of the salts can be selected to adjust the melting point of the salts (e.g., the melting temperature at 1 atmosphere), for example, to approach or match the temperature at which the non-CO2 acid gas to which the salts are exposed is released from a source of non-CO2 acid gas.

[0047] In certain embodiments, the salt is in a molten form. For example, in some embodiments, a solid salt comprising an alkali metal cation and a boron oxide anion (and / or its dissociated form) can be heated above its melting temperature, such that the solid transitions to a liquid state. According to certain embodiments, a salt comprising an alkali metal cation and a boron oxide anion (and / or its dissociated form) is a salt having a melting point between 200°C and 1000°C (or equal thereto) (or between 200°C and 700°C) at atmospheric pressure. One of ordinary skill in the art will understand that a molten salt is different from a dissolved salt (i.e., a salt dissolved in a solvent).

[0048] The molten form of the salt can have several chemical compositions. According to certain embodiments, the molten form of the salt comprises at least one alkali metal cation, and at least one boron oxide anion and / or its dissociated form.

[0049] The term "alkali metal" is used herein to refer to the following six chemical elements of Group 1 of the periodic table: lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr).

[0050] In some embodiments, at least one alkali metal cation comprises cationic lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and / or cesium (Cs). In some embodiments, at least one alkali metal cation comprises cationic lithium (Li), sodium (Na), and / or potassium (K).

[0051] In some embodiments, the molten salt comprises at least one other metal cation. In some embodiments, at least one other metal cation comprises an alkali metal cation, an alkaline earth metal cation, or a transition metal cation. In some embodiments, the molten salt comprises at least two alkali metal cations (e.g., three alkali metal cations). In certain embodiments, the molten salt comprises cationic lithium and cationic sodium.

[0052] In some embodiments, salts in molten form that include cationic lithium and cationic sodium can provide advantages in temperature swing operations compared to, for example, similar salts in molten form that include cationic sodium or similar salts in molten form that include cationic lithium, cationic sodium, and cationic potassium. One advantage of salts in molten form that include cationic lithium and cationic sodium can be a higher non-CO2 acid gas uptake capacity than similar salts in molten form that include cationic sodium or similar salts in molten form that include cationic lithium, cationic sodium, and cationic potassium in a temperature range between 500 °C and 700 °C or equal thereto. Another advantage of salts in molten form that include cationic lithium and cationic sodium can be that a smaller temperature difference can be used in temperature swing operations for the same regeneration efficiency of non-CO2 acid gas capture and release compared to similar salts in molten form that include cationic sodium or similar salts in molten form that include cationic lithium, cationic sodium, and cationic potassium (e.g., between 0.25 and 0.5 times or equal to the temperature difference used for similar salts).

[0053] The term "alkaline earth metal" is used herein to refer to the six chemical elements in Group 2 of the periodic table: beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).

[0054] The "transition metal" elements are scandium (Sc), yttrium (Y), lanthanum (La), actinium (Ac), titanium (Ti), zirconium (Zr), hafnium (Hf), rutherfordium (Rf), vanadium (V), niobium (Nb), tantalum (Ta), dubnium (Db), chromium (Cr), molybdenum (Mo), tungsten (W), seaborgium (Sg), manganese (Mn), technetium (Tc), rhenium (Re), bohrium (Bh), iron (Fe), ruthenium (Ru), osmium (Os), hassium (Hs), cobalt (Co), rhodium (Rh), iridium (Ir), meitnerium (Mt), nickel (Ni), palladium (Pd), platinum (Pt), darmstadtium (Ds), copper (Cu), silver (Ag), gold (Au), roentgenium (Rg), zinc (Zn), cadmium (Cd), mercury (Hg), and copernicium (Cn).

[0055] In certain embodiments, the molten salt comprises an alkali metal cation and one other metal cation in a eutectic composition or a composition close thereto such that the melting temperature of the salt is lower than the melting temperature of salts having different compositions of the alkali metal cation and one other metal cation, which can be advantageous in reducing the energy required to achieve the separation operation(s) of non-CO2 acid gas(es) in the molten form of the salt.

[0056] Some of the non-CO2 acid gas adsorbents described herein have relatively low melting temperatures and can facilitate the separation (e.g., absorption) of non-CO2 acid gases at relatively low temperatures. For example, components capable of forming a eutectic composition with each other have a reduced melting point at the eutectic composition and compositions approximately at the eutectic composition compared to compositions in which the components are present in other relative amounts. As another example, compositions containing an alkali metal cation and / or an alkaline earth metal cation have a relatively low melting point compared to compositions containing other metal cations. The ability to absorb non-CO2 acid gases at relatively low temperatures can be advantageous as it can reduce, according to some but not necessarily all specific embodiments, the amount of energy required to absorb the acid gas.

[0057] In some embodiments, the non-CO2 acid gas adsorbent comprises at least two components (e.g., metal cations, alkali metal cations (plural possible)) that can form a eutectic composition with each other. As will be understood by those skilled in the art, a "eutectic composition" is a composition that melts at a temperature lower than the melting points of the components of the composition. In some eutectic compositions, the liquid phase is in equilibrium with both a first solid phase and a second solid phase different from the first solid phase at the eutectic temperature. A eutectic composition cooled from a temperature above the eutectic temperature to a temperature below the eutectic temperature under equilibrium cooling conditions may, in certain cases, undergo solidification at the eutectic temperature to simultaneously form the first solid phase and the second solid phase from the liquid. As will be understood by those skilled in the art, two components that can form a eutectic composition with each other may, in certain cases, also form a non-eutectic composition with each other. The non-eutectic composition often undergoes solidification over a range of temperatures because the liquid phase can be in equilibrium with the solid phase over a range of temperatures.

[0058] The term "borate anion" is used herein to refer to a negatively charged ion containing at least one boron and at least one oxygen. The borate anions of the molten form of the salt can be intact (e.g., anionic B w O z form, e.g., (BO3 3- )) and / or boron and oxygen can dissociate from each other (e.g., as B 3+ and O 2- such as, for example, to boron cations (plural possible) and oxygen anions (plural possible)).

[0059] According to some embodiments, at least one borate anion is anionic B w O zand / or its dissociated forms. In some embodiments, w is greater than 0 and less than or equal to 4. In certain embodiments, w is between 1 and 4, or equal thereto. In some embodiments, z is greater than 0 and less than or equal to 9. In certain embodiments, z is between 1 and 9, or equal thereto. In some embodiments, at least one boron oxide anion comprises anionic BO3, BO4, or B2O5, and / or its dissociated forms. In certain embodiments, it may be advantageous for the molten salt to have anionic BO3 and / or its dissociated forms. Potential advantages of anionic BO3 and / or its dissociated forms include higher acid gas uptake capacity of the molten salt during exposure to an environment containing acid gas, compared to salts having the same alkali metal cation (and any other cation), as well as anionic B2O5 and / or its dissociated forms. Another potential advantage of anionic BO3 and / or its dissociated forms is greater acid gas desorption of the molten salt during exposure to desorption conditions, compared to salts having the same alkali metal cation (and any other cation), as well as anionic BO4 and / or its dissociated forms.

[0060] In some embodiments, the boron oxide anion is B w O z and / or its dissociated forms, where w is greater than 0 and less than or equal to 4, and z is greater than 0 and less than or equal to 9.

[0061] In some embodiments, the stoichiometry of the salts described herein is M x B 1-x O y(Where x is the mixing ratio and is between 0 and 1). In some embodiments, the sub-stoichiometry is that of the salt in solid form, for example, before melting. In some embodiments, the sub-stoichiometry is that of the salt in molten form, for example, after melting. In certain embodiments, y = 1.5 - x. The "M" in this formula refers to the metal cation(s) (e.g., alkali metal cation, combination of alkali metal cation and at least one other metal cation) in the non-CO2 acid gas adsorbent described herein. For example, in some embodiments, the sub-stoichiometry of the salts described herein is A x B 1-x O y (Where 0 < x < 1 and A is an alkali metal (e.g., Li, Na, K)). In certain such embodiments, y = 1.5 - x.

[0062] As used herein, the term "mixing ratio" of an alkali metal cation or combination of metal cations in a non-CO2 acid gas adsorbent refers to the ratio of the moles of metal cation(s) in the non-CO2 acid gas adsorbent to the total moles of metal cation(s) and boron moles in the non-CO2 acid gas adsorbent. For example, the mixing ratio of sodium in Na3BO3 is 3 / (3 + 1) = 0.75, and (Li 0.5 Na 0.5) The mixing ratio of the alkali metal in 3BO3 is (0.5×3 + 0.5×3) / (3 + 1) = 0.75. In some embodiments, the mixing ratio is at least 0.5, at least 0.6, or at least 0.667. In some embodiments, the mixing ratio is at most 0.9, at most 0.835, at most 0.8, at most 0.75, or at most 0.7. Also, combinations of the above ranges are possible (e.g., between 0.5 and 0.9 or equal thereto, between 0.6 and 0.8 or equal thereto, between 0.7 and 0.8 or equal thereto). Also, other ranges are possible. Without wishing to be bound by theory, there may be a mixing ratio (for a particular alkali metal cation or combination of metal cations) below which the acid gas uptake capacity of the non-CO2 acid gas adsorbent becomes less than desirable. Without wishing to be bound by theory, there may be a mixing ratio (for a particular alkali metal cation or combination of metal cations) above which the regeneration efficiency of the non-CO2 acid gas adsorbent becomes less than desirable. In some embodiments, the alkali metal includes lithium (Li), sodium (Na), potassium (K), and / or mixtures thereof. In some embodiments, the alkali metal includes equal amounts of Li and Na.

[0063] Non-limiting examples of salts in molten form include molten Na3BO3 (e.g., can also be written as Na 0.75 B 0.25 O 0.75 ), Na5BO4 (e.g., can also be written as Na 0.83 B 0.17 O 0.67 ), Na4B2O5 (e.g., can also be written as Na2BO 2.5 ), K3BO3 (e.g., can also be written as K 0.75 B 0.25 O 0.75 ), (Li 0.5 Na 0.5 )3BO3, and / or (Li 0.33 Na 0.33 K 0.33 )3BO3, or combinations thereof, but are not limited thereto.

[0064] In some embodiments, the salts of the non-CO2 acid gas adsorbent in molten form may be accompanied by portions of that salt that are not molten. In other words, complete melting of all salt forms (plural) present in the molten form is not required in all embodiments. In some embodiments, at least 10 wt%, at least 20 wt%, at least 30 wt%, at least 40 wt%, at least 50 wt%, at least 60 wt%, at least 70 wt%, at least 80 wt%, at least 90 wt%, or more of the salts present in the non-CO2 acid gas adsorbent are molten. In some embodiments, less than 100 wt%, less than 99 wt%, less than 90 wt%, or less of the salts present in the non-CO2 acid gas adsorbent are molten. Also, combinations of the above ranges are possible (e.g., at least 10 wt% and less than 100 wt%). Other ranges are also possible.

[0065] In some embodiments, the non-CO2 acid gas adsorbent comprises at least one salt comprising at least one alkali metal cation and at least one boron oxide anion and / or its dissociated form (e.g., Na3BO3, Na5BO4, Na4B2O5, K3BO3, (Li 0.5 Na 0.5 )3BO3, and / or (Li 0.33 Na 0.33 K 0.33 )3BO3, including but not limited to), and at least 10 wt%, at least 20 wt%, at least 30 wt%, at least 40 wt%, at least 50 wt%, at least 60 wt%, at least 70 wt%, at least 80 wt%, at least 90 wt%, or more of that salt is molten. In some embodiments, the non-CO2 acid gas adsorbent comprises at least one salt comprising at least one alkali metal cation and at least one boron oxide anion and / or its dissociated form (e.g., Na3BO3, Na5BO4, Na4B2O5, K3BO3, (Li 0.5 Na 0.5 )3BO3, and / or (Li 0.33 Na 0.33 K 0.33) including, but not limited to, 3BO3, with less than 100 wt%, less than 99 wt%, less than 90 wt%, or less of the salts thereof being melted. Combinations of the above ranges are also possible. Other ranges are also possible.

[0066] In some embodiments, the non-CO2 acid gas adsorbent includes at least one alkali metal cation and at least one boron oxide anion and / or its dissociated form, and the total amount of all salts in the molten form is at least 10 wt%, at least 20 wt%, at least 30 wt%, at least 40 wt%, at least 50 wt%, at least 60 wt%, at least 70 wt%, at least 80 wt%, at least 90 wt%, or more. By way of non-limiting illustration, in some embodiments, the non-CO2 acid gas adsorbent may be a combination of 50 grams of Na3BO3, 50 grams of Na5BO4, and 50 grams of Na4B2O5, and in some such embodiments, at least 15 grams (i.e., 10 wt% of a total of 150 grams) of the total amount of Na3BO3, Na5BO4, and Na4B2O5 is melted. In certain embodiments, the non-CO2 acid gas adsorbent includes at least one alkali metal cation and at least one boron oxide anion and / or its dissociated form, and the total amount of all salts in the molten form is less than 100 wt%, less than 99 wt%, less than 90 wt%, less than 50%, less than 40%, less than 30%, less than 20%, or less. Combinations of the above ranges are also possible (e.g., at least 10 wt% and less than 100 wt%). Other ranges are also possible.

[0067] In some embodiments, the non-CO2 acid gas adsorbent further includes an additive. Examples of the types of additives that can be included in the non-CO2 acid gas adsorbent include, but are not limited to, corrosion inhibitors, viscosity modifiers, wetting agents, high-temperature surfactants, and scale inhibitors. In some embodiments, the non-CO2 acid gas adsorbent includes a plurality of additives (e.g., 2, 3, 4, or more).

[0068] In some embodiments, during exposure to an environment containing non-CO2 acid gas, at least a portion of the molten salt chemically reacts with at least a portion of the non-CO2 acid gas to form one or more products (e.g., including carbonates, nitrates, nitrites, sulfates, sulfites) within the non-CO2 acid gas adsorbent. These one or more products (e.g., carbonate product, nitrate product, nitrite product, sulfate product, sulfite product) may be in solid form or in liquid form depending on, for example, the temperature and / or composition of the salt (e.g., alkali metal borate).

[0069] In some embodiments, during exposure to an environment containing non-CO2 acid gas, at least a portion of the molten salt chemically reacts with at least a portion of the non-CO2 acid gas(es) to form solid particles (e.g., including carbonates, sulfates, sulfites, nitrates, nitrites) within the non-CO2 acid gas adsorbent, increasing the viscosity of the non-CO2 acid gas adsorbent. These solid particles loaded with non-CO2 acid gas(es) may be flowed to a desorption device within the molten residual salt using a slurry pump for regeneration (e.g., regeneration of the molten salt from the solid particles), or alternatively these solid particles may be regenerated within the same vessel in which the solid particles were formed.

[0070] In some embodiments, a relatively high percentage of the non-CO2 acid gas adsorbent is composed of salts in molten form. For example, in some embodiments, at least 10 weight percent (wt%), at least 20 wt%, at least 30 wt%, at least 40 wt%, at least 50 wt%, at least 60 wt%, at least 70 wt%, at least 80 wt%, at least 90 wt%, or more of the non-CO2 acid gas adsorbent is composed of salts in molten form. In some embodiments, up to 100 wt%, up to 99 wt%, or up to 90 wt% of the non-CO2 acid gas adsorbent is composed of salts in molten form. Also, combinations of the above ranges are possible (e.g., between 10 wt% and 100 wt% or equal thereto, between 20 wt% and 99 wt% or equal thereto, between 50 wt% and 90 wt% or equal thereto). Also, other ranges are possible. In some embodiments, all of the non-CO2 acid gas adsorbent is melted. In other embodiments, only a portion of the non-CO2 acid gas adsorbent is melted.

[0071] In some embodiments, a relatively high percentage of the non-CO2 acid gas adsorbent is chemically converted to non-CO2 acid gas-loaded solid particles during sequestration (e.g., absorption). For example, in some embodiments, at least 1 wt%, at least 10 wt%, or at least 20 wt% of the non-CO2 acid gas adsorbent is composed of non-CO2 acid gas-loaded solid particles. In some embodiments, up to 90 wt%, up to 80 wt%, or up to 50 wt% of the non-CO2 acid gas adsorbent is composed of non-CO2 acid gas-loaded solid particles. Also, combinations of the above ranges are possible (e.g., between 1 wt% and 90 wt% or equal thereto, between 10 wt% and 80 wt% or equal thereto, between 10 wt% and 50 wt% or equal thereto, between 20 wt% and 50 wt% or equal thereto). Also, other ranges are possible.

[0072] In some embodiments, the non-CO2 acid gas adsorbent also includes an alkali metal hydroxide. For example, in some embodiments, the non-CO2 acid gas adsorbent includes NaOH, KOH, and / or LiOH. According to certain embodiments, the alkali metal hydroxide can be formed as a byproduct of the reaction between the non-CO2 acid gas adsorbent and the non-CO2 acid gas.

[0073] According to certain embodiments, the non-CO2 acid gas adsorbent is capable of interacting with the non-CO2 acid gas such that a relatively large amount of the non-CO2 acid gas is sequestered. In certain embodiments, the non-CO2 acid gas adsorbent is capable of interacting with a mixture of non-CO2 acid gases. In some embodiments, the non-CO2 acid gas adsorbent can preferentially sequester the non-CO2 acid gas(es) over CO2 and thus can facilitate the separation of the non-CO2 acid gas from CO2. The interaction between the non-CO2 acid gas adsorbent and the acid gas (e.g., non-CO2 acid gas) can include a chemical reaction, adsorption, and / or diffusion. In some embodiments, multiple non-CO2 acid gases interact with the non-CO2 acid gas adsorbent such that at least a portion of the multiple non-CO2 acid gases is removed from the environment.

[0074] For example, in certain embodiments, the non-CO2 acid gas adsorbent is capable of interacting with non-CO2 acid gas such that at least 0.01 mmol of non-CO2 acid gas is sequestered per gram of non-CO2 acid gas adsorbent (e.g., from the environment, e.g., from the atmosphere, from a stream). In some embodiments, the non-CO2 acid gas adsorbent is capable of interacting with non-CO2 acid gas such that at least 0.1 mmol, at least 0.5 mmol, at least 2.0 mmol, or at least 10.0 mmol of non-CO2 acid gas is sequestered per gram of non-CO2 acid gas adsorbent (e.g., from the environment, e.g., from the atmosphere, from a stream). In certain embodiments, the non-CO2 acid gas adsorbent is capable of interacting with non-CO2 acid gas such that a maximum of 20.0 mmol, a maximum of 18.0 mmol, a maximum of 16.0 mmol, a maximum of 14.0 mmol, or a maximum of 12.0 mmol of acid gas is sequestered per gram of non-CO2 acid gas adsorbent (e.g., from the environment, e.g., from the atmosphere, from a stream). Combinations of the above ranges are also possible (e.g., between 0.1 mmol per gram and 20.0 mmol per gram or equal thereto, between 0.5 mmol per gram and 16.0 mmol per gram or equal thereto, between 2.0 mmol per gram and 12.0 mmol per gram or equal thereto).

[0075] According to certain embodiments, the non-CO2 acid gas adsorbent is capable of interacting with non-CO2 acid gas such that a relatively large amount of non-CO2 acid gas is sequestered even when the non-CO2 acid gas concentration in the environment (e.g., in the atmosphere, in a stream) is relatively low. For example, in some embodiments, the non-CO2 acid gas adsorbent, when exposed to a steady-state environment (e.g., the remainder of the environment is argon) containing non-CO2 acid gas at about 50 mol%, about 25 mol%, about 10 mol% or about 1 mol% less, is capable of sequestering at least 0.01 mmol, at least 0.1 mmol, at least 0.5 mmol, at least 2.0 mmol, at least 10.0 mmol, and / or up to 20.0 mmol, up to 18.0 mmol, up to 16.0 mmol, up to 14.0 mmol, or up to 12.0 mmol of non-CO2 acid gas per gram of non-CO2 acid gas adsorbent.

[0076] According to certain embodiments, the non-CO2 acid gas adsorbent is capable of interacting with non-CO2 acid gas such that a relatively large amount of non-CO2 acid gas is sequestered even at relatively low temperatures. For example, in some embodiments, the non-CO2 acid gas adsorbent, when the non-CO2 acid gas adsorbent is at a temperature of 1000 °C or less, 850 °C or less, 600 °C or less, 550 °C or less, or 520 °C or less (and / or at least 200 °C, at least 300 °C, at least 400 °C, at least 450 °C or at least 500 °C), is capable of sequestering at least 0.01 mmol, at least 0.1 mmol, at least 0.5 mmol, at least 2.0 mmol, at least 10.0 mmol, and / or up to 20.0 mmol, up to 18.0 mmol, up to 16.0 mmol, up to 14.0 mmol, or up to 12.0 mmol of non-CO2 acid gas per gram of non-CO2 acid gas adsorbent. Also, combinations of the above ranges are possible (e.g., between 200 °C and 1000 °C or equal thereto, between 200 °C and 600 °C or equal thereto, between 400 °C and 550 °C or equal thereto). Also, other ranges are possible.

[0077] According to certain embodiments, the salt of the non-CO2 acid gas adsorbent has a melting temperature within a range that is high enough to provide rapid isolation of non-CO2 acid gas(es) at 1 atmosphere, but not so high as to make the isolation of non-CO2 acid gas(es) an unduly energy-intensive process. In some embodiments, the salt of the non-CO2 acid gas adsorbent has a melting temperature of at least 200 °C, at least 300 °C, at least 400 °C, at least 450 °C, or at least 500 °C at 1 atmosphere. In some embodiments, the salt of the non-CO2 acid gas adsorbent has a melting temperature of at most 1000 °C, at most 850 °C, at most 600 °C, at most 550 °C, or at most 520 °C at 1 atmosphere. Also, combinations of the above ranges are possible (e.g., between 200 °C and 1000 °C or equal thereto, between 200 °C and 600 °C or equal thereto, between 400 °C and 550 °C or equal thereto). Also, other ranges are possible.

[0078] According to certain embodiments, the non-CO2 acid gas adsorbent is capable of interacting with non-CO2 acid gases such that relatively large amounts of non-CO2 acid gases are sequestered in a relatively short time. For example, in some embodiments, the non-CO2 acid gas adsorbent sequesters at least 0.01 mmol, at least 0.1 mmol, at least 0.5 mmol, at least 2.0 mmol, at least 10.0 mmol, and / or up to 20.0 mmol, up to 18.0 mmol, up to 16.0 mmol, up to 14.0 mmol, or up to 12.0 mmol of non-CO2 acid gas per gram of non-CO2 acid gas adsorbent when the non-CO2 acid gas adsorbent is exposed to an environment containing non-CO2 acid gas for 24 hours or less, 12 hours or less, 8 hours or less, 4 hours or less, 1 hour or less, 30 minutes or less, 10 minutes or less, or 2 minutes or less (and / or at least 10 seconds, at least 20 seconds, at least 30 seconds, or at least 1 minute). Combinations of the above ranges are also possible (e.g., between 10 seconds and 24 hours or equal thereto, between 20 seconds and 12 hours or equal thereto, between 30 seconds and 8 hours or equal thereto, between 1 minute and 4 hours or equal thereto, between 1 minute and 10 minutes or equal thereto, between 1 minute and 2 minutes or equal thereto). Other ranges are also possible.

[0079] The amount of non-CO2 acid gas sequestered by the non-CO2 acid gas adsorbent can be determined, for example, using thermogravimetric analysis.

[0080] In addition to the non-CO2 acid gas adsorbent, methods of capturing non-CO2 acid gases using the non-CO2 acid gas adsorbent are also described. For example, some of the non-CO2 acid gas adsorbents described herein can be used to remove non-CO2 acid gases from chemical process streams (e.g., exhaust streams of combustion systems) and / or from environments containing non-CO2 acid gases (e.g., environments within reactors or other unit operations).

[0081] In some embodiments, the method includes melting a solid non-CO2 acid gas adsorbent comprising a salt described herein (e.g., an alkali metal borate), and using the molten non-CO2 acid gas adsorbent to sequester non-CO2 acid gas. In some embodiments, the molten form of the salt (e.g., an alkali metal borate) comprises an alkali metal cation, a boron oxide anion, a boron cation, and / or an oxygen anion. In certain embodiments, all of these species are present in the molten form of the salt. In some embodiments, the molten form of the salt (e.g., an alkali metal borate) comprises an alkali metal cation, a boron cation, and an oxygen anion.

[0082] Certain aspects relate to a method of sequestering non-CO2 acid gas using a non-CO2 acid gas adsorbent described herein. Certain aspects are directed to a method that includes exposing a non-CO2 acid gas adsorbent described herein to an environment containing non-CO2 acid gas such that at least a portion of the non-CO2 acid gas interacts with the non-CO2 acid gas adsorbent and at least a portion of the non-CO2 acid gas is sequestered from the environment. In some such embodiments, a relatively high percentage of non-CO2 acid gas (e.g., at least 25 wt%, at least 50 wt%, at least 75 wt%, at least 90 wt%, at least 95 wt%, at least 99 wt%, at least 99.9 wt%, or more non-CO2 acid gas) is removed from the environment. In certain embodiments, essentially all of the non-CO2 acid gas is removed from the environment.

[0083] In certain embodiments, the method includes exposing a non-CO2 acid gas adsorbent to an environment containing non-CO2 acid gas at a temperature of at least 200° C. such that at least a portion of the non-CO2 acid gas interacts with the non-CO2 acid gas adsorbent and is sequestered from the environment.

[0084] Non-CO2 acid gas adsorbents can be exposed to an environment containing non-CO2 acid gas in several ways. For example, in some embodiments, the non-CO2 acid gas adsorbent can be added to an environment (e.g., an atmosphere, a stream) containing non-CO2 acid gas. According to certain embodiments, an environment containing non-CO2 acid gas can be transferred (e.g., poured) into a container holding the non-CO2 acid gas adsorbent. In certain embodiments, a non-CO2 acid gas adsorbent comprising a molten form of a salt can be flowed or sprayed through a container to which the environment belongs, and / or can be flowed in the same and / or opposite direction as the flow or spray direction of the non-CO2 acid gas adsorbent. Combinations of these methods are also possible. The non-CO2 acid gas to which the non-CO2 acid gas adsorbent is exposed is generally in a fluid form (e.g., in the form of a gas and / or a supercritical fluid). In certain embodiments, at least a portion of the non-CO2 acid gas to which the non-CO2 acid gas adsorbent is exposed is in the form of a subcritical gas.

[0085] The environment containing non-CO2 acid gas to which the non-CO2 acid gas adsorbent is exposed may be contained, for example, within a chemical processing unit operation. Non-limiting examples of such unit operations include reactors (e.g., packed bed reactors, fluidized bed reactors, falling film columns, bubble columns), separators (e.g., particulate filters such as diesel exhaust particulate filters), and mixers. According to certain embodiments, the environment containing non-CO2 acid gas is contained within a falling film column. According to certain embodiments, the environment containing non-CO2 acid gas is part of and / or derived from the product of a combustion process.

[0086] In certain embodiments, the method includes exposing a non-CO2 acid gas adsorbent to a stream containing non-CO2 acid gas (optionally also containing CO2). FIG. 1 is a schematic diagram of a non-CO2 acid gas adsorbent exposed to an environment containing non-CO2 acid gas according to certain embodiments. As shown in FIG. 1, method 100a may include exposing non-CO2 acid gas adsorbent 102 to a stream 104a containing non-CO2 acid gas. The stream to which the non-CO2 acid gas adsorbent is exposed can be, for example, part of and / or derived from a stream of a chemical process containing non-CO2 acid gas. For example, in some embodiments, the stream to which the non-CO2 acid gas adsorbent is exposed can be part of and / or derived from the product of a combustion process (e.g., an exhaust stream). FIG. 2 is a schematic diagram of a non-CO2 acid gas adsorbent exposed to an environment containing non-CO2 acid gas that is part of and / or derived from the product of a combustion process according to certain embodiments. As shown in FIG. 2, method 100b may include exposing non-CO2 acid gas adsorbent 102 to a stream 104b containing non-CO2 acid gas that is part of and / or derived from the product of combustion process 108. In some embodiments, at least a portion of the product stream of the combustion process is transported directly through the non-CO2 acid gas adsorbent. For example, as shown in FIG. 2, at least a portion of stream 104b of combustion process 108 is transported directly through non-CO2 acid gas adsorbent 102.

[0087] The stream to which the non-CO2 acid gas adsorbent is exposed can be transported, for example, through a chemical processing unit operation. Non-limiting examples of such unit operations include reactors (e.g., packed bed reactors, fluidized bed reactors, falling film columns, bubble columns), separators (e.g., particulate filters such as diesel exhaust particulate filters), and mixers. For example, referring again to FIG. 1, in some embodiments, non-CO2 acid gas adsorbent 102 is located within a reactor 110, if desired. According to certain embodiments, the stream to which the non-CO2 acid gas adsorbent is exposed is transported through a falling film column.

[0088] The non-CO2 acid gas adsorbents described in this specification can be used to remove non-CO2 acid gases produced by various systems. For example, in some embodiments, the non-CO2 acid gas adsorbent is used to remove non-CO2 acid gas from an exhaust stream from a boiler (e.g., of a power generation plant), from an exhaust stream from an integrated gasification combined cycle (IGCC) plant, from an exhaust stream from an internal combustion engine (e.g., from an automobile), from an exhaust stream from a pyrolysis processing furnace (e.g., as used in the cement industry), and / or from a stream from a hydrogen production process (e.g., by sorption enhanced steam reforming (SESR)).

[0089] The concentration of non-CO2 acid gas in the fluid to which the non-CO2 acid gas adsorbent is exposed may be within various ranges. In some embodiments, the environment (e.g., atmosphere, stream) to which the non-CO2 acid gas adsorbent is exposed contains non-CO2 acid gas in an amount of at least 1 ppm. In certain embodiments, the environment (e.g., atmosphere, stream) to which the non-CO2 acid gas adsorbent is exposed contains non-CO2 acid gas in an amount of at least 10 ppm, at least 1000 ppm, at least 0.01 mol%, at least 0.1 mol%, at least 1 mol%, at least 10 mol%, at least 50 mol%, or at least 99 mol%. In some embodiments, the non-CO2 acid gas adsorbent may be exposed to essentially pure non-CO2 acid gas. In some embodiments, the method includes exposing the non-CO2 acid gas adsorbent to an environment containing non-CO2 acid gas in an amount of at least 1 ppm.

[0090] Certain embodiments include exposing a non-CO2 acid gas adsorbent to an environment (e.g., an atmosphere, a stream) containing non-CO2 acid gas such that at least a portion of the non-CO2 acid gas interacts with the non-CO2 acid gas adsorbent and at least a portion of the non-CO2 acid gas is sequestered from the environment (e.g., from the atmosphere, from the stream). For example, as shown in FIG. 1, at least a portion of the non-CO2 acid gas in stream 104a interacts with non-CO2 acid gas adsorbent 102 and is sequestered from stream 104a such that it is not present in stream 106a. In certain embodiments, stream 106a may contain less non-CO2 acid gas than stream 104a after at least a portion of the non-CO2 acid gas in stream 104a has interacted with non-CO2 acid gas adsorbent 102 and been sequestered from stream 104a. The interaction between the sequestered non-CO2 acid gas and the non-CO2 acid gas adsorbent can take various forms. For example, in certain embodiments, the non-CO2 acid gas is absorbed into the non-CO2 acid gas adsorbent. In some embodiments, the non-CO2 acid gas is adsorbed onto the non-CO2 acid gas adsorbent. In some embodiments, the non-CO2 acid gas chemically reacts with the non-CO2 acid gas adsorbent. In some embodiments, the non-CO2 acid gas diffuses into the non-CO2 acid gas adsorbent. Combinations of two or more of these mechanisms (i.e., absorption, adsorption, chemical reaction, and / or diffusion) are also possible. In some embodiments, the sequestration of CO2 does not produce solid precipitates.

[0091] In some embodiments, the captured non-CO2 acid gas forms a solid suspended in a liquid non-CO2 acid gas adsorbent and is concentrated by physical separation. In some embodiments, the physical separation uses a crossflow filter. In some embodiments, the crossflow filter is operated at a temperature of at least 200 °C (or at least 400 °C, at least 600 °C, or at least 800 °C). In some embodiments, the crossflow filter is operated at a temperature of 1000 °C or less. In some embodiments, the separation includes centrifugation. In certain embodiments, the separation includes crystallization. In some embodiments, the separation includes sedimentation. Combinations of these are also possible.

[0092] According to certain embodiments, during exposure of the non-CO2 acid gas adsorbent to non-CO2 acid gas, a relatively large amount of non-CO2 acid gas is sequestered by the non-CO2 acid gas adsorbent (e.g., from the atmosphere, from a stream). For example, in certain embodiments, at least 0.01 mmol of non-CO2 acid gas per gram of non-CO2 acid gas adsorbent is sequestered (e.g., from the environment, e.g., from the atmosphere, from a stream). In some embodiments, at least 0.1 mmol, at least 0.5 mmol, at least 2.0 mmol, or at least 10.0 mmol of non-CO2 acid gas per gram of non-CO2 acid gas adsorbent is sequestered (e.g., from the environment, e.g., from the atmosphere, from a stream). In certain embodiments, at most 20.0 mmol, at most 18.0 mmol, at most 16.0 mmol, at most 14.0 mmol, or at most 12.0 mmol of non-CO2 acid gas per gram of non-CO2 acid gas adsorbent is sequestered (e.g., from the environment, e.g., from the atmosphere, from a stream). Also, combinations of the above ranges are possible (e.g., between 0.01 mmol per gram and 20.0 mmol per gram or equal thereto, between 0.1 mmol per gram and 18.0 mmol per gram or equal thereto, between 2.0 mmol per gram and 12.0 mmol per gram or equal thereto). Other ranges are also possible. In some embodiments, including some of the methods described herein, between 0.01 mmol and 20.0 mmol or equal thereto of non-CO2 acid gas per gram of non-CO2 acid gas adsorbent is sequestered from the environment.

[0093] According to certain embodiments, at least a portion of the non-CO2 acid gas interacts with the non-CO2 acid gas adsorbent over a time period of at least 10 seconds, at least 20 seconds, at least 30 seconds, or at least 1 minute, and is isolated from an environment containing the non-CO2 acid gas, such as an atmosphere or stream as described elsewhere herein. According to certain embodiments, at least a portion of the non-CO2 acid gas interacts with the non-CO2 acid gas adsorbent over a time period of 24 hours or less, 12 hours or less, 8 hours or less, 4 hours or less, 1 hour or less, or 30 minutes or less, 10 minutes or less, or 2 minutes or less, and is isolated from an environment containing the non-CO2 acid gas, such as an atmosphere or stream as described elsewhere herein. Combinations of the above ranges are also possible (e.g., between 10 seconds and 24 hours or equal thereto, between 20 seconds and 12 hours or equal thereto, between 30 seconds and 8 hours or equal thereto, between 1 minute and 4 hours or equal thereto, between 1 minute and 10 minutes or equal thereto, between 1 minute and 2 minutes or equal thereto). Other ranges are also possible.

[0094] In certain embodiments, at least 0.01 mmol of non-CO2 acid gas per gram of non-CO2 acid gas adsorbent is sequestered per 24 hours (e.g., from the atmosphere, from a stream). In some embodiments, at least 0.1 mmol, at least 0.5 mmol, at least 2.0 mmol, or at least 10.0 mmol of non-CO2 acid gas per gram of non-CO2 acid gas adsorbent is sequestered from the stream per 24 hours. According to some embodiments, a maximum of 20.0 mmol, a maximum of 18.0 mmol, a maximum of 16.0 mmol, a maximum of 14.0 mmol, or a maximum of 12.0 mmol of non-CO2 acid gas per gram of non-CO2 acid gas adsorbent is sequestered from the stream per 24 hours. Also, combinations of the above ranges are possible (e.g., between 0.01 mmol per gram and 20.0 mmol per gram or equal thereto, between 0.1 mmol per gram and 18.0 mmol per gram or equal thereto, between 2.0 mmol per gram and 12.0 mmol per gram or equal thereto). Also, other ranges are possible.

[0095] In certain embodiments, the temperature of the non-CO2 acid gas adsorbent is less than or equal to 1000 °C during at least a portion of the sequestration of the non-CO2 acid gas. In certain embodiments, the non-CO2 acid gas adsorbent is at a temperature higher than the melting temperature of the salt such that the salt is in a molten form during at least a portion of the sequestration of the non-CO2 acid gas. In certain embodiments, the temperature of the non-CO2 acid gas adsorbent is a maximum of 1000 °C, a maximum of 850 °C, a maximum of 600 °C, a maximum of 550 °C, or a maximum of 520 °C during at least a portion of the sequestration of the non-CO2 acid gas. In some embodiments, the temperature of the non-CO2 acid gas adsorbent is at least 200 °C, at least 300 °C, at least 400 °C, at least 450 °C, or at least 500 °C during at least a portion of the sequestration of the non-CO2 acid gas. Also, combinations of the above ranges are possible (e.g., between 200 °C and 1000 °C or equal thereto, between 200 °C and 600 °C or equal thereto, between 400 °C and 550 °C or equal thereto). Also, other ranges are possible.

[0096] In certain embodiments, the temperature of the environment containing non-CO2 acid gas is less than or equal to 1000 °C during at least a portion of the isolation of the non-CO2 acid gas. In certain embodiments, the temperature of the environment containing non-CO2 acid gas is at most 1000 °C, at most 850 °C, at most 600 °C, at most 550 °C, or at most 520 °C during at least a portion of the isolation of the non-CO2 acid gas. In some embodiments, the temperature of the environment containing non-CO2 acid gas is at least 200 °C, at least 300 °C, at least 400 °C, at least 450 °C, or at least 500 °C during at least a portion of the isolation of the non-CO2 acid gas. Also, combinations of the above ranges are possible (e.g., between 200 °C and 1000 °C or equal thereto, between 200 °C and 600 °C or equal thereto, between 400 °C and 550 °C or equal thereto). Also, other ranges are possible.

[0097] In some embodiments, a relatively high percentage of the non-CO2 acid gas adsorbent isolates the non-CO2 acid gas during the isolation. For example, in some embodiments, at least 0.01 wt%, at least 10 wt%, or at least 20 wt% of the non-CO2 acid gas adsorbent isolates the non-CO2 acid gas during the isolation. In some embodiments, at most 100%, at most 90 wt%, at most 80 wt%, or at most 50 wt% of the non-CO2 acid gas adsorbent isolates the non-CO2 acid gas during the isolation. Also, combinations of the above ranges are possible (e.g., between 0.01 wt% and 100 wt% or equal thereto, between 10 wt% and 90 wt% or equal thereto, between 10 wt% and 80 wt% or equal thereto, between 20 wt% and 50 wt% or equal thereto). Also, other ranges are possible.

[0098] In some embodiments, the method further includes regenerating the non-CO2 acid gas adsorbent by removing at least 50 mol% of the non-CO2 acid gas sequestered by the non-CO2 acid gas adsorbent from the non-CO2 acid gas adsorbent. In some embodiments, at least 60 mol%, at least 70 mol%, at least 80 mol%, at least 90 mol%, at least 95 mol%, at least 99 mol%, or at least 99.9 mol% of the non-CO2 acid gas sequestered by the non-CO2 acid gas adsorbent is removed from the non-CO2 acid gas adsorbent. In some embodiments, the non-CO2 acid gas adsorbent remains in a liquid state throughout the sequestration and regeneration processes. For example, in some embodiments, the salt remains in a liquid state throughout the sequestration and regeneration processes.

[0099] In certain embodiments, the method includes performing at least one sequestration / regeneration cycle (e.g., at least one temperature swing cycle, at least one pressure swing cycle). Each sequestration / regeneration cycle consists of a sequestration step (wherein the non-CO2 acid gas is sequestered by the non-CO2 acid gas adsorbent) followed by a regeneration step (wherein the non-CO2 acid gas is released by the non-CO2 acid gas adsorbent). According to certain embodiments, the non-CO2 acid gas adsorbent may be subjected to a relatively large number of sequestration / regeneration cycles while maintaining the ability to sequester and release a relatively large amount of non-CO2 acid gas.

[0100] The non-CO2 acid gas adsorbent may be exposed to any of the environments described herein (e.g., atmosphere, stream) during one or more (or all) of the isolation steps of one or more isolation / regeneration cycles. One or more (or all) of the regeneration steps of the isolation / regeneration cycle can be carried out using various suitable second environments (e.g., fluid, atmosphere, stream). In some embodiments, the regeneration of the non-CO2 acid gas adsorbent may be carried out by flowing an inert gas (e.g., argon, N2) over the non-CO2 acid gas adsorbent. Non-limiting examples of suitable environmental components that can be used during the regeneration step can include a 100 mol% N2 stream or gas stream.

[0101] In some embodiments, the gas space in the desorption vessel (further described elsewhere herein) contains non-CO2 acid gas, e.g., in the desorption vessel, a gas space greater than or equal to 0.0001 volume % is composed of non-CO2 acid gas(es). As will be understood by those skilled in the art, the volume % of the gas space composed of non-CO2 acid gas can be determined by dividing the partial pressure of the non-CO2 acid gas in the gas space by the total pressure of the gas in the gas space and multiplying by 100%. As used herein, the term "gas space" refers to the space or volume occupied by the gas in a vessel (e.g., adsorption vessel, desorption vessel). In some embodiments, the gas space in the desorption vessel is at the same pressure as the gas space in the adsorption vessel (further described elsewhere herein). In other embodiments, the gas space in the desorption vessel is at a different (e.g., lower) pressure than the gas space in the adsorption vessel.

[0102] In some embodiments, during the regeneration step, in a system configured for batch operation (further described elsewhere in this specification), the gas space in the vessel contains non-CO2 acid gas, e.g., in the vessel, a gas space greater than or equal to 0.0001 volume % is composed of non-CO2 acid gas(es). In some embodiments, during the regeneration step, in a system configured for batch operation, the gas space in the vessel is at the same pressure as the gas space in the vessel during the isolation step. In other embodiments, during the regeneration step, in a system configured for batch operation, the gas space in the vessel is at a different (e.g., lower) pressure than the gas space in the vessel during the isolation step.

[0103] According to certain embodiments, the method includes cycling a non-CO2 acid gas adsorbent at least 2 times (or at least 5 times, at least 10 times, at least 50 times, at least 100 times, at least 1000 times, or at least 10,000 times). In some such embodiments, between each of 2 (or 5, 10, 50, 100, 1000, and / or 10,000) isolation steps of the cycle, the amount of non-CO2 acid gas isolated by the non-CO2 acid gas adsorbent is at least 75%, at least 90%, at least 95%, at least 98%, at least 99%, or at least 99.9% of the amount of non-CO2 acid gas isolated by the non-CO2 acid gas adsorbent during the equivalent isolation step of the first cycle. In some such embodiments, between each of 2 (or 5, 10, 50, 100, 1000, and / or 10,000) regeneration steps of the cycle, the amount of non-CO2 acid gas released by the non-CO2 acid gas adsorbent is at least 75%, at least 90%, at least 95%, at least 98%, at least 99%, or at least 99.9% of the amount of non-CO2 acid gas released by the non-CO2 acid gas adsorbent during the equivalent regeneration step of the first cycle. In some such embodiments, the amount of non-CO2 acid gas released by the non-CO2 acid gas adsorbent during the regeneration step of the first cycle is at least 75%, at least 90%, at least 95%, at least 98%, at least 99%, or at least 99.9% of the amount of non-CO2 acid gas isolated by the non-CO2 acid gas adsorbent during the isolation step of the first cycle. In some such embodiments, the amount of non-CO2 acid gas isolated between the isolation steps of the first cycle, the tenth cycle, and / or the one-hundredth cycle is at least 0.01 mmol, at least 0.1 mmol, at least 0.5 mmol, at least 2.0 mmol, or at least 10.0 mmol (and / or a maximum of 20.0 mmol, a maximum of 18.0 mmol, a maximum of 16.0 mmol, a maximum of 14.0 mmol, or a maximum of 12.0 mmol) per gram of the non-CO2 acid gas adsorbent.In certain embodiments, the temperature of the non-CO2 acid gas adsorbent during the isolation / regeneration cycle is up to 1000 °C, up to 850 °C, up to 600 °C, up to 550 °C, or up to 520 °C (and / or at least 200 °C, at least 300 °C, at least 400 °C, at least 450 °C, or at least 500 °C). In certain embodiments, the time during which each of the isolation steps and each of the regeneration steps occur is 24 hours or less (or 12 hours or less, 8 hours or less, 4 hours or less, 1 hour or less, 30 minutes or less, 10 minutes or less, or 2 minutes or less, and / or at least 10 seconds, at least 20 seconds, at least 30 seconds, or at least 1 minute). In some embodiments, the steady-state concentration of non-CO2 acid gas in the environment to which the non-CO2 acid gas adsorbent is exposed during the isolation step of the isolation / regeneration cycle is a low acid gas on the order of 50 mol%, on the order of 25 mol%, on the order of 10 mol%, or on the order of 1 mol% (e.g., the remainder of the environment is argon or residual acid gas present after isolation of a particular acid gas).

[0104] In some embodiments, a system is provided for isolating non-CO2 acid gas using a non-CO2 acid gas adsorbent comprising a molten form of a salt. The systems described herein may be used to implement the methods described herein using the non-CO2 acid gas adsorbents described herein.

[0105] In some embodiments, a system configured to sequester non-CO2 acid gas in a batch operation is provided. The system configured for batch operation may include any of several suitable components. In some embodiments, the system configured for batch operation includes an inlet to a vessel, the vessel, and an outlet from the vessel. In some embodiments, during the sequestration step, the inlet is configured to receive a fluid rich in non-CO2 acid gas, and this fluid can flow from the inlet to the vessel. In certain embodiments, the vessel is configured to contain the non-CO2 acid gas adsorbent described herein. In some embodiments, during the regeneration step, the outlet is configured to receive from the vessel a fluid lean in non-CO2 acid gas having a lower mole percentage of non-CO2 acid gas than the fluid rich in non-CO2 acid gas, at least because some sequestration by the non-CO2 acid gas adsorbent occurs in the vessel. In some embodiments, during the regeneration step, the inlet is configured to receive energy or work (e.g., from heated and / or pressurized gas) that can flow from the inlet to the vessel. In some embodiments, during the regeneration step, the outlet is configured to receive from the vessel non-CO2 acid gas resulting from regeneration of the non-CO2 acid gas adsorbent in the vessel.

[0106] In some embodiments, a system configured to isolate non-CO2 acid gas in a continuous operation is provided. The system configured for continuous operation may include any of several suitable components. In some embodiments, the system configured for continuous operation includes an inlet to an adsorption vessel, the adsorption vessel, and an outlet from the adsorption vessel. In some embodiments, the system configured for continuous operation further includes an inlet to a desorption vessel, the desorption vessel, and an outlet from the desorption vessel. In some embodiments, the system for continuous operation further includes a first pipe between the adsorption vessel and the desorption vessel configured to transport a non-CO2 acid gas adsorbent loaded with non-CO2 acid gas from the adsorption vessel to the desorption vessel. In some embodiments, the system further includes a first pump configured inline with the first pipe to transport the loaded non-CO2 acid gas adsorbent. In certain embodiments, the first pump is a slurry pump. In some embodiments, the system for continuous operation further includes a second pipe between the adsorption vessel and the desorption vessel configured to transport an unloaded non-CO2 acid gas adsorbent from the desorption vessel to the adsorption vessel. In some embodiments, the system further includes a second pump configured inline with the second pipe to transport the unloaded non-CO2 acid gas adsorbent. In some embodiments, the system further includes a heat exchanger (e.g., configured for temperature swing operation) inline with the first pipe and / or the second pipe. In some embodiments, the system further includes a reboiler or heater (e.g., configured for temperature swing operation) fluidly connected to the desorption vessel and the pump. In some embodiments, the system further includes a compressor fluidly connected to the desorption vessel configured to produce a pure acid gas stream. The systems provided herein may include any suitable combination of components.

[0107] Also contemplated is a system that is a hybrid of a system configured for batch operation and a system configured for continuous operation.

[0108] As used herein, a "loaded" non-CO2 acid gas adsorbent refers to a non-CO2 acid gas adsorbent at least a portion of which (e.g., between 1 wt% and 90 wt% or equal thereto) has an isolated non-CO2 acid gas.

[0109] As used herein, an "unloaded" non-CO2 acid gas adsorbent refers to a non-CO2 acid gas adsorbent at least a portion of which (e.g., between 75 wt% and 100 wt% or equal thereto, between 85 wt% and 100 wt% or equal thereto, between 95 wt% and 100 wt% or equal thereto) has had the non-CO2 acid gas removed.

[0110] In some embodiments, the systems provided herein (e.g., a system for batch operation, a system for continuous operation) include at least one temperature controller configured to control the temperature of a vessel (e.g., an adsorption vessel, a desorption vessel). For example, the temperature controller can be used to set the temperature of the vessel at or above the melting temperature of the salt of the non-CO2 acid gas adsorbent to maintain at least a portion of the salt in a molten form during isolation.

[0111] The systems described herein (e.g., systems for batch operation, systems for continuous operation) can be used for pressure swing non-CO2 acid gas separation operations at high temperatures (e.g., between 200°C and 1000°C or equal thereto, between 500°C and 700°C or equal thereto) using the non-CO2 acid gas adsorbents described herein. For example, in some embodiments, during the isolation step (e.g., in the adsorption vessel), the partial pressure of the non-CO2 acid gas in the first environment to which the non-CO2 acid gas adsorbent is exposed is between 0.000001 bar and 20 bar or equal thereto (e.g., between 0.1 bar and 10 bar or equal thereto), and the total pressure of the first environment to which the non-CO2 acid gas adsorbent is exposed is between 1 bar and 30 bar or equal thereto, or between 1 bar and 50 bar or equal thereto. In some embodiments, the total pressure of the first environment to which the non-CO2 acid gas adsorbent is exposed can be at least 1 bar, at least 2 bar, at least 5 bar, at least 10 bar, at least 20 bar, at least 50 bar, at least 100 bar or higher. In certain embodiments, during the isolation step, the non-CO2 acid gas is between 1 ppm and 30 mol% of the first environment (e.g., the stream). In some embodiments, during the regeneration step (e.g., in the desorption vessel), the partial pressure of the non-CO2 acid gas in the second environment to which the non-CO2 acid gas adsorbent is exposed is between 0 bar and 0.2 bar or equal thereto, and the total pressure of the second environment to which the non-CO2 acid gas adsorbent is exposed is between 1 bar and 20 bar or equal thereto. In some embodiments, the total pressure of the second environment to which the non-CO2 acid gas adsorbent is exposed can be less than 20 bar, less than 10 bar, less than 5 bar, less than 2 bar, less than 1.5 bar, less than 1.2 bar, less than 1.1 bar, less than 1 bar, (e.g., under vacuum), less than 0.5 bar, less than 0.1 bar, or less than 0.01 bar. In some embodiments, the difference between the total pressure of the first environment and the total pressure of the second environment is between 0 bar and 20 bar or equal thereto.In certain embodiments, the difference between the total pressure of the first environment and the total pressure of the second environment is at least 0.1 bar, at least 1 bar, at least 5 bar, at least 10 bar, at least 50 bar, at least 100 bar, or higher. In some embodiments, the difference between the partial pressure of non-CO2 acid gas in the first environment and the partial pressure of non-CO2 acid gas in the second environment is between 1 bar and 20 bar or equal thereto. Also, other ranges are possible. For example, in a pressure swing operation, the non-CO2 acid gas adsorbent may be exposed to a first environment at a pressure of 30 bar where the partial pressure of non-CO2 acid gas is 1 bar during the isolation step, and the non-CO2 acid gas adsorbent may be exposed to a second environment at a pressure of 20 bar where the partial pressure of non-CO2 acid gas is 0 bar during the regeneration step.

[0112] The systems described herein (e.g., systems for batch operation, systems for continuous operation) can be used for temperature swing non-CO2 acid gas separation operations at high reference temperatures (e.g., between 200 °C and 900 °C or equal thereto). For example, in some embodiments, during the isolation step (e.g., in an adsorption vessel), the first temperature of the non-CO2 acid gas adsorbent is maintained between 200 °C and 900 °C or equal thereto. In some embodiments, during the regeneration step (e.g., in a desorption vessel), the second temperature of the non-CO2 acid gas adsorbent is maintained between 250 °C and 950 °C or equal thereto. In some embodiments, the difference between the second temperature and the first temperature is between 10 °C and 500 °C or equal thereto (e.g., between 20 °C and 400 °C, between 200 °C or equal thereto). For example, in a temperature swing operation, the non-CO2 acid gas adsorbent may be maintained at 500 °C during the isolation step and at 700 °C during the regeneration step.

[0113] In certain embodiments, at least a portion of the non-CO2 acid gas adsorbent containing at least a portion of the non-CO2 acid gas is removed from the environment. For example, in some embodiments (e.g., some embodiments where the non-CO2 acid gas adsorbent is neither concentrated nor regenerated), after the non-CO2 acid gas adsorbent captures the non-CO2 acid gas, the non-CO2 acid gas adsorbent containing the captured acid gas can be discarded.

[0114] In some embodiments, after the non-CO2 acid gas adsorbent captures the non-CO2 acid gas, a solution is added to the environment and at least a portion of the non-CO2 acid gas adsorbent precipitates. In some such embodiments, the solution contains calcium ions. In certain embodiments, as a result of adding the solution, CaSO4 precipitates. As an example, in some embodiments, lime water can be added to recover the aqueous non-CO2 acid gas adsorbent and gypsum.

[0115] U.S. Provisional Patent Application No. 62 / 971,488, filed on February 7, 2020, entitled "Treatment of Acid Gases Using Molten Alkali Metal Borates, and Associated Methods of Separation", is hereby incorporated by reference in its entirety for all purposes. Processes and related systems for regenerating adsorbents

[0116] Also disclosed herein are processes and related systems for regenerating adsorbents. Certain embodiments relate to the use of steam to remove one or more captured acid gases from the adsorbent. In some embodiments, the adsorbent can include a molten material such as a molten alkali metal borate material.

[0117] In particular, the use of steam as a sorbent regenerant at high temperatures can offer various advantages. For example, in some cases, after using steam to remove one or more acid gases from a sorbent, the steam (along with the removed acid gas) can be cooled so that the steam condenses while maintaining the acid gas in gaseous form. This can enable relatively easy separation of the steam and the acid gas. Further, steam is generally produced in many industrial processes that generate acid gases, making the source of the regenerant (e.g., steam) readily available.

[0118] The use of steam as a regenerant can be particularly useful in some cases in systems where the acid gas sorbent is at high temperature. For example, in certain embodiments, steam is used to regenerate a molten sorbent such as a molten alkali metal borate material. Generally, steam can remain chemically stable at such high temperatures, and as described above, the steam condensation cycle can enable relatively easy separation of the acid gas released during regeneration and the steam used during regeneration.

[0119] Certain embodiments relate to the regeneration of a sorbent. In some embodiments, the step of regenerating the sorbent includes exposing the sorbent to an environment containing steam. FIG. 9A is a schematic diagram illustrating one such process. In FIG. 9A, the sorbent 902 is exposed to steam within the headspace 904.

[0120] As used herein, "water vapor" refers to water (H2O) in its gaseous form (also referred to as its vapor form). Both subcritical water vapor and supercritical water vapor are considered to be within the scope of the term "water vapor" as used herein. In some embodiments, as a result of exposing an adsorbent to water vapor, at least a portion of the acid gas associated with the adsorbent is separated from the adsorbent. For example, in some embodiments, referring again to FIG. 9A, in some embodiments, water vapor within vessel 906 (e.g., within headspace 904 and / or flowing through adsorbent 902) can interact (e.g., physically interact) with adsorbent 902 such that at least a portion of the acid gas associated with adsorbent 902 is removed from adsorbent 902. In some embodiments, exposing an adsorbent having captured acid gas to water vapor can reduce the partial pressure of the acid gas in the environment around the adsorbent. This reduction in the partial pressure of the acid gas by water vapor can promote the release of the acid gas from the adsorbent (e.g., via a change in the capture equilibrium, e.g., a change in the adsorption equilibrium, absorption equilibrium, chemical reaction equilibrium, and / or diffusion equilibrium). Although FIG. 9A shows water vapor interacting with an adsorbent, it should be understood that in some embodiments, the water vapor does not interact with the adsorbent. In other words, in some embodiments, the adsorbent does not interact (e.g., physically interact, chemically interact) with the adsorbent. In some embodiments, the water vapor is chemically inert with respect to the adsorbent.

[0121] In some embodiments, water vapor can occupy a volume (e.g., headspace) close to the adsorbent during adsorbent regeneration. In some embodiments, for at least a portion of the time during which regeneration is performed, the headspace contains at least 75 wt%, at least 85 wt%, at least 95 wt%, at least 99 wt%, at least 99.9 wt% or more water vapor. In some embodiments, the amount of water vapor in the headspace does not decrease to less than 50 wt%, 25 wt%, 10 wt% or less than 1% during the regeneration step. In some embodiments, the remaining portion of the headspace not occupied by water vapor can be acid gas.

[0122] In some embodiments, the molar ratio of water vapor to acid gas in the adsorbent during adsorbent regeneration (i.e., the ratio between the number of moles of water vapor in the gas phase and the number of moles of acid gas retained in the adsorbent phase) can have a specific value. In some embodiments, for at least a portion of the time during which regeneration is carried out, the molar ratio of water vapor in the gas phase to acid gas in the adsorbent is at least 1, at least 10, at least 100, at least 1000, at least 10,000 or higher. In some embodiments, during the regeneration step, the molar ratio of water vapor to acid gas in the adsorbent does not drop below 0.5, below 0.1, below 0.01, or below 0.001. This molar ratio can be present within any part of the emission environment, for example, within the adsorbent contained within the emission environment. In some embodiments, the molar ratio of water vapor to the adsorbent is 0.1, 1, 10, 100, 1000, or in the range between these values.

[0123] In some embodiments, the inlet stream to the vessel containing the regenerated adsorbent can contain at least 75 mol%, at least 85 mol%, at least 95 mol%, at least 99 mol%, at least 99.9 mol%, or more of water vapor.

[0124] In some embodiments, the outlet stream from the vessel containing the regenerated adsorbent can contain at least 50 mol%, at least 75 mol%, at least 90 mol%, or more of water vapor. In certain embodiments, at least 75 mol%, at least 90 mol%, at least 95 mol%, at least 99 mol%, or at least 99.9 mol% of the outlet stream from the vessel containing the regenerated adsorbent is composed of water vapor and / or acid gas.

[0125] In some embodiments, the water vapor and the adsorbent can be separated from each other, and at least a portion of the acid gas removed from the adsorbent is associated with the water vapor, so that the acid gas is separated from the adsorbent. For example, referring to FIG. 9A, in some embodiments, the water vapor can be removed from the vessel 906 via the outlet 920. Since at least a portion of the acid gas removed from the adsorbent 902 is associated with the water vapor removed via the outlet 920, this portion of the acid gas is separated from the adsorbent 902.

[0126] The water vapor and / or the adsorbent can be introduced into each other in any of a variety of suitable ways. In some embodiments, the water vapor can be flowed into a vessel containing the adsorbent. As an example, the water vapor can be used (or a part thereof) as a sweep stream flowing across the adsorbent. For example, in FIG. 9A, the water vapor can be transported into the vessel 906 via the inlet stream 908. In some embodiments, the adsorbent can be fluid and can be transported through a vessel containing the water vapor. Also, other methods are possible.

[0127] In some embodiments, the acid gas released from the adsorbent can be derived from the exposure of the adsorbent to the acid gas. An example of the process is described in more detail below in connection with FIG. 10.

[0128] Examples of acid gases that can be captured by the adsorbent and then released are described in more detail below.

[0129] As used herein, the term "regeneration" refers to the removal of acid gas from the adsorbent such that the capacity of the adsorbent to capture acid gas increases. In some embodiments, the removal of acid gas from the adsorbent enables additional acid gas to be captured by the adsorbent and the adsorbent can be reused. In other words, regeneration may include the removal of an initial amount of acid gas such that the capacity of the adsorbent to capture subsequent amounts of acid gas increases. In some embodiments, regeneration can be performed in a regenerator (e.g., a vessel such as a desorber). In some embodiments, the adsorbent regeneration can be performed at least once, at least 10 times, at least 10 3times, at least 10 4 times, at least 10 6 times, or more, may be performed.

[0130] It should be understood that the regeneration includes both partial regeneration of the ability of the adsorbent to capture acid gas and complete regeneration of the ability of the adsorbent to capture acid gas. In some embodiments, at least 1 wt% (or at least 5 wt%, at least 10 wt%, at least 25 wt%, at least 50 wt%, at least 75 wt%, at least 90 wt%, at least 95 wt%, at least 99 wt%, at least 99.9 wt%, or more) of the adsorbent is regenerated during the regeneration step. In certain embodiments, at least 1 wt% (or at least 5 wt%, at least 10 wt%, at least 25 wt%, at least 50 wt%, at least 75 wt%, at least 90 wt%, at least 95 wt%, at least 99 wt%, at least 99.9 wt%, or more) of the adsorbent that has captured acid gas can be regenerated during the regeneration step.

[0131] Also, adsorbent regeneration can be described in terms of the amount of captured acid gas released from the adsorbent during regeneration. In some embodiments, the mole percentage of acid gas released from the adsorbent during regeneration is at least 1 mol% (or at least 5 mol%, at least 10 mol%, at least 25 mol%, at least 50 mol%, at least 75 mol%, at least 90 mol%, at least 95 mol%, at least 99 mol%, at least 99.9 mol%, or more). In certain embodiments, at least 1 mol% (or at least 5 mol%, at least 10 mol%, at least 25 mol%, at least 50 mol%, at least 75 mol%, at least 90 mol%, at least 95 mol%, at least 99 mol%, at least 99.9 mol%, or more) of the acid gas captured by the adsorbent can be regenerated during the regeneration step.

[0132] Any of a variety of suitable adsorbents can be used in the various embodiments disclosed herein. As used herein, the term "adsorbent" is used to describe a material capable of removing acid gas (e.g., any of the acid gases described elsewhere herein) from an environment containing the acid gas. In some embodiments, the adsorbent can function as a barrier material. In other words, the adsorbent can be capable of isolating the acid gas. In some embodiments, the adsorbent can further function as an absorption material. In other words, the adsorbent can be capable of absorbing the acid gas. In some embodiments, the adsorbent can function as an adsorbing material. In other words, the adsorbent can be capable of adsorbing the acid gas. In some embodiments, the adsorbent can chemically react with the acid gas. In some embodiments, the acid gas can diffuse into the adsorbent. Combinations of these mechanisms are also possible. For example, in some embodiments, the adsorbent can capture acid gas(es) via chemisorption. Other capture mechanisms may exist.

[0133] Regeneration of the adsorbent can include a process that is the reverse of the process used to capture the acid gas. For example, if the adsorbent captures acid gas(es) via a chemical reaction, regeneration of the adsorbent can, in certain cases, include reversing the chemical reaction used to capture the acid gas(es). In another example, if the adsorbent captures acid gas(es) via adsorption, regeneration of the adsorbent can include breaking the adsorption bond between the adsorbent and the captured acid gas(es).

[0134] In some embodiments, the adsorbent may include an alkali metal borate, which can be used as an adsorbent for removing acid gas from a stream (e.g., an inlet stream, an outlet stream). Specific examples of materials that can be used as adsorbents are provided in more detail below.

[0135] In some embodiments, the adsorbent can be fluid. For example, in some embodiments, the adsorbent can be in a molten form. One skilled in the art will understand that a molten material (e.g., molten salt) is different from a dissolved material (e.g., a salt dissolved in a solvent).

[0136] As an example, in some embodiments, the adsorbent comprises a molten alkali metal borate. In some embodiments, the molten alkali metal borate ensures an improvement in the approach employed for carbon capture by involving the liquid system process design at high temperatures in most of the CO2 emissions. At high temperatures, the high-quality thermal energy capacity of all the streams involved in the capture system can be efficiently recovered. The fluid adsorbent (e.g., molten alkali metal borate) further enables a simple and efficient liquid-liquid heat exchanger and generally provides the added benefit of their easy transport between vessels dedicated for capture and release via a transfer pump. In certain cases, the high working ability, ultra-fast kinetics and inherent regenerability of the molten alkali metal borate can endow it with extraordinary potential.

[0137] The use of certain adsorbents (e.g., adsorbents containing salts in molten form, or other fluid adsorbents) can provide the ability to use the adsorbent at elevated temperatures, i.e., at a temperature higher than or equal to the melting temperature of the adsorbent (e.g., a temperature greater than or equal to 200 °C). When using steam to remove acid gas (e.g., by using steam as a sweep gas), the subsequent separation of the acid gas and steam (e.g., via condensation of the steam) can be made relatively easy, and thus the use of adsorbents capable of operating at elevated temperatures can be particularly useful. The temperature may similarly be higher than the melting temperature of the adsorbent. In some embodiments, the temperature of the adsorbent (e.g., a salt in molten form) is at least 250 °C, at least 300 °C, at least 350 °C, at least 400 °C, at least 450 °C, or at least 500 °C, or higher. In some embodiments where the adsorbent is used at elevated temperatures, any of a variety of suitable amounts of the adsorbent (e.g., greater than or equal to 1 wt%, greater than or equal to 10 wt%, greater than or equal to 50 wt%, greater than or equal to 75 wt%, greater than or equal to 90 wt%, greater than or equal to 99 wt%, or all of the adsorbent) is within that elevated temperature (e.g., greater than or equal to 200 °C, greater than or equal to 250 °C, greater than or equal to 300 °C, greater than or equal to 350 °C, greater than or equal to 400 °C, greater than or equal to 450 °C, greater than or equal to 500 °C, and / or within the range of any of the other temperature ranges mentioned hereinabove or elsewhere). In certain embodiments, the process can be carried out in a pressure swing operation as needed. The operating temperature can refer to the temperature of the adsorbent itself, which may be essentially equal to or different from the temperature of the environment to which the adsorbent is exposed. In some embodiments, the environment in which the adsorbent is exposed to acid gas is at the same or similar temperature as the environment in which the adsorbent is regenerated.

[0138] As described above, regeneration of the adsorbent can include removing acid gas (e.g., a single acid gas, more than one acid gas) from the adsorbent. Non-limiting examples of acid gas include carbon dioxide (CO2), sulfur monoxide (SO), sulfur dioxide (SO2), nitrogen dioxide (NO2), hydrogen sulfide (H2S), sulfur trioxide (SO3), nitric oxide (NO), nitrous oxide (N2O), dinitrogen trioxide (N2O3), dinitrogen tetroxide (N2O4), dinitrogen pentoxide (N2O5) and / or carbonyl sulfide (COS). In some embodiments, the acid gas includes at least nitrogen oxides and CO2. In some embodiments, the acid gas includes at least CO2. Also, regeneration of the adsorbent from other acid gases is possible.

[0139] In some embodiments, regeneration of the adsorbent includes removing a single acid gas present in (e.g., trapped within) the adsorbent. In other embodiments, the adsorbent can trap multiple acid gases (e.g., CO2 and SO2; SO2 and NO2; CO2; SO2; and CO2; etc.).

[0140] When "acid gas" is described herein, it should be understood that a single acid gas may be present or multiple acid gases may be present, unless the contrary is clearly stated.

[0141] In some embodiments, the environment in which the water vapor is exposed to the adsorbent can be relatively hot (e.g., superheated). The use of a relatively high temperature can ensure that the water vapor does not condense during the exposure of the adsorbent to the water vapor during adsorbent regeneration. This can ensure that the water vapor and acid gas can be relatively easily removed from the adsorbent, while also retaining the ability to separate the water vapor from the acid gas at a downstream location. In some embodiments, the environment in which the water vapor is exposed to the adsorbent can be at a temperature of at least 200°C, at least 250°C, at least 300°C, at least 350°C, at least 400°C, at least 450°C, at least 500°C. Other temperatures are possible. In some embodiments, the temperature of the water vapor during the exposure of the adsorbent to the water vapor can be at least 200°C, at least 250°C, at least 300°C, at least 350°C, at least 400°C, at least 450°C, or at least 500°C. Also, other temperatures are possible.

[0142] The pressure of the regeneration environment can be within the range of any of various suitable pressures. In some embodiments, the pressure of the regeneration environment can be at least 0.01 bar, at least 0.1 bar, at least 1 bar, or at least 10 bar. In some embodiments, it may be advantageous not to use a vacuum or to use a relatively low vacuum (e.g., a pressure of at least 0.9 bar or higher) within the regeneration environment. By not using a vacuum or using a relatively low vacuum, the complexity can be reduced, and the energy consumption associated with the generation and / or maintenance of the vacuum can be reduced. In some embodiments, it may be advantageous to operate at a high pressure (e.g., a pressure exceeding 1.1 bar, 5 bar, 10 bar, or 20 bar). Operating at a high pressure can potentially improve heat recovery and also increase the electrical output of the water vapor turbine. In some embodiments, the pressure of the regeneration environment is 1 bar, 3 bar, 5 bar, 10 bar, 20 bar, 30 bar, 50 bar, or within the range between these pressures.

[0143] In some embodiments, the partial pressure of the gas (e.g., water vapor, acid gas) in the regeneration environment can be various suitable pressures. In some embodiments, the partial pressure of the gas in the regeneration environment is at least 0.000001 bar, at least 0.0001 bar, at least 0.01 bar, or at least 1 bar. By providing a specific partial pressure of the gas, sufficient driving force for the release of acid gas from the adsorbent can be provided.

[0144] The amount of the adsorbent containing water vapor and acid gas in the regeneration environment can establish any of various suitable molar ratios. In certain embodiments, the molar ratio of water vapor to acid gas in the adsorbent is at least 1, at least 10, at least 1000, or at least 10,000. The use of a relatively high ratio of water vapor to acid gas in the adsorbent can make it possible to remove a relatively large amount of acid gas from the adsorbent relatively efficiently. For example, a situation can be considered where a stream containing 15 moles of CO2 and 85 moles of N2 is brought into contact with the adsorbent and 15 moles of CO2 are captured by the adsorbent. Generally, when regenerating the adsorbent, the partial pressure of the acid gas in the regeneration stream needs to be reduced to at least less than the partial pressure of the acid gas present in the original CO2 / N2 stream to which the adsorbent was exposed. In this case, a supply of at least 85 moles of water vapor is required, and the ratio of water vapor to acid gas in the adsorbent needs to be at least 85 / 15 = 5.7. Supplying more water vapor helps to further drive the adsorbent regeneration.

[0145] Some embodiments may further include exposing the acid gas to an adsorbent such that the acid gas is captured by the adsorbent. In some embodiments, this may be done before the adsorbent is at least partially regenerated. Referring now to FIG. 9B, system 900 may include an inlet stream 910 in addition to the second inlet stream 908. The inlet stream 910 may enable the addition of acid gas to the adsorbent 902 such that the acid gas is captured by the adsorbent 902. As an example, an exhaust stream from an industrial process may be transported through inlet 910 and then the exhaust stream is exposed to the adsorbent 902. In some such embodiments, the adsorbent 902 can capture one or more acid gases from the exhaust stream of the industrial process and a relatively clean stream can be produced that exits the vessel 906 via outlet 920 (e.g., a stream in which the amount of one or more acid gases is reduced compared to the amount of one or more acid gases present in the exhaust stream from the industrial process).

[0146] In some such embodiments, it may be desirable to regenerate the adsorbent 902. Regeneration can be achieved, for example, by transporting steam to the vessel 906 such that the used adsorbent 902 is exposed to the steam (e.g., via inlet 908). In some such embodiments, as a result of the exposure of the adsorbent 902 to the steam, the acid gas is removed from the adsorbent 902 and thus the adsorbent 902 is regenerated. Optionally, the adsorbent 902 can then be reused in subsequent acid gas capture steps (e.g., by contacting the adsorbent 902 with an exhaust stream containing one or more acid gases for a second time).

[0147] In certain embodiments where the adsorbent is exposed to the acid gas and captures the acid gas, the temperature of the environment in which the adsorbent is exposed to the acid gas may be the same or similar to the temperature of the environment in which the adsorbent is regenerated. In certain embodiments, the temperature of the environment in which the adsorbent is exposed to the acid gas and captures the acid gas is within 200 °C (or within 100 °C, 50 °C, 10 °C, or 1 °C) of the temperature of the environment in which the adsorbent is regenerated.

[0148] In some embodiments, the adsorbent is exposed to the acid gas, and the temperature of the environment in which the acid gas is captured is greater than or equal to 200 °C, greater than or equal to 250 °C, greater than or equal to 300 °C, greater than or equal to 350 °C, greater than or equal to 400 °C, greater than or equal to 450 °C, greater than or equal to 500 °C, greater than or equal to 600 °C, greater than or equal to 700 °C, greater than or equal to 800 °C, or higher, and / or less than or equal to 1000 °C. In some embodiments, the environment is at a temperature of 800 °C, 700 °C, 600 °C, 500 °C, or greater than 200 °C, or in a range between these temperatures. Combinations of the above ranges are also possible (e.g., greater than or equal to 200 °C and up to 700 °C). Other ranges are possible.

[0149] In some embodiments, the water vapor used to regenerate the adsorbent may be subjected to downstream processing after adsorbent regeneration. For example, in some embodiments, after using water vapor to regenerate the adsorbent, the method further includes cooling a mixture of water vapor and acid gas such that the condensed water vapor is separated from the acid gas. As described above, the ability to condense water vapor while maintaining the acid gas in gaseous form can allow for relatively easy separation of the water vapor from the acid gas, resulting in a relatively pure acid gas stream and a relatively pure water stream. In some embodiments, the condensed water vapor can be recycled, converted back to water vapor, and reused for adsorbent regeneration.

[0150] In some embodiments, the acid gas can be recovered in a relatively pure form (e.g., in a relatively pure acid gas stream) when water vapor condenses out of the acid gas and steam mixture. In some embodiments, the acid gas is recovered with a purity greater than 50 wt%, greater than 60 wt%, greater than 70 wt%, greater than 80 wt%, greater than 90 wt%, greater than 95 wt%, greater than 99 wt%, or greater than 99.99 wt%. In some embodiments, the acid gas is recovered with a purity of 100 wt%. In some embodiments, the acid gas is recovered and subsequently compressed to ensure a purity greater than 50 wt%, greater than 60 wt%, greater than 70 wt%, greater than 80 wt%, greater than 90 wt%, greater than 95 wt%, greater than 99 wt%, or greater than 99.99 wt%.

[0151] In some embodiments, the mixture of acid gas and water vapor is cooled in a heat exchanger to generate useful energy. Cooling the mixture in the heat exchanger can increase the efficiency of energy use throughout the system for adsorbent regeneration. In certain embodiments, the mixture of acid gas and water vapor is cooled in a heat exchanger to generate useful energy prior to separation in a condenser. As an example, a turbine can be used to generate electrical energy as the water vapor is cooled.

[0152] In some embodiments, the condensed water vapor is heated and recycled back into the regeneration environment. In this way, the condensed water vapor may be recycled for further use. In some embodiments, adsorbent regeneration may be performed in multiple cycles. In some such embodiments, the water vapor used during one adsorbent regeneration step is condensed from the water vapor and acid gas mixture, reheated in a subsequent step, and reused during the next adsorbent regeneration step. In certain embodiments, the water vapor can be reused at least once, at least twice, at least ten times, at least one hundred times, at least one thousand times or more.

[0153] Steam quality can be maintained in a variety of ways. Generally, "steam quality" refers to the ratio of saturated steam (vapor) in a stream to the amount of condensate (liquid) in the stream. A steam quality of 100 indicates that the stream is 100% steam, and a steam quality of 0 indicates that the steam is 100% liquid. As used herein, steam quality is said to be "maintained" when at least some energy is input into the steam stream and / or the steam stream condensate. The energy input into the steam stream can be used, for example, to maintain or increase the temperature of the steam. The energy input into the steam stream condensate can be used, for example, to convert the condensed steam (water) back to steam.

[0154] Steam quality can be maintained via any number of sources (e.g., an energy source internal to the process or an energy source external to the process) compared to the adsorbent regeneration process.

[0155] In certain embodiments, steam quality is maintained, at least in part, by an energy source internal to the process that generates acid gas. An example of such an embodiment is shown in FIG. 11A. In FIG. 11A, acid gas source 1110 includes an energy source 1115 internal to the process that generates acid gas. Energy 1125 from energy source 1115 maintains the quality of the steam within steam source 1120. Acid gas from acid gas source 1110 can enter regenerator 1140 via acid gas inlet 1130, while steam, maintained at least in part by energy source 1115 internal to acid gas source 1110, can enter regenerator 1140 via steam inlet 1135. In some such embodiments, the energy source can be derived from fuel within the process that generates acid gas. In such cases, steam quality can be maintained, at least in part, by the energy capacity of the fuel within the process that generates acid gas. For example, in FIG. 11A, in some embodiments, energy source 1115 can be fuel from within acid gas source 1110. One such embodiment is shown in FIG. 16 and described in more detail in Example 3 below.

[0156] In some embodiments, the steam quality is maintained, at least in part, by an energy source external to the process that generates the acid gas. An example of such an embodiment is shown in FIG. 11B. In FIG. 11B, the process that generates the acid gas is the acid gas source 1110; however, here the energy source 1115 external to the acid gas source 1110 maintains the steam quality of the steam source 1120 via the energy exchange 1125. The acid gas from the acid gas source 1110 can enter the regenerator 1140 through the acid gas inlet 1130, while the steam, maintained at least in part by the energy source 1115 external to the acid gas source 1110, can enter the regenerator 1140 through the steam inlet 1135. In some embodiments, the steam quality is maintained, at least in part, by a steam cycle powered by a process separate from the process that generates the acid gas. For example, in FIG. 11B, in some embodiments, the energy source 1115 can be an external steam cycle power supply process. One such embodiment is shown in FIG. 15B and is described in more detail in Example 3 below.

[0157] In some embodiments, the environment in which regeneration occurs is part of an industrial process. An "industrial process" includes chemical, physical, electrical, or mechanical steps to assist in manufacturing one or more items and / or generating electricity. In some embodiments, the environment can be part of an industrial process that includes the combustion of fuels such as natural gas, oil, coal, biomass, or the manufacture of chemicals such as steel, cement, or hydrogen. Other things can exist. Additional non-limiting examples of industrial processes include power generation processes (e.g., within a power plant), chemical manufacturing processes, and equipment manufacturing processes. In some embodiments, the industrial process includes a natural gas combined cycle (NGCC) and / or a steam methane reforming (SMR) process with optional enhanced absorption reforming (SER). In certain embodiments, the industrial process includes an NGCC with carbon capture. In some embodiments, the industrial process includes cement manufacturing with carbon capture.

[0158] In some embodiments, the water vapor is taken directly from the water vapor cycle of a power plant that produces acid gas captured by the adsorbent (e.g., a coal power plant that can itself produce a significant amount of water vapor). In some embodiments, the water vapor is produced in another water vapor cycle using energy generated by a power plant (e.g., a natural gas power plant that may not itself produce much water vapor). In another embodiment, the water vapor is taken directly from the water vapor cycle of a power plant that does not produce the acid gas being captured (e.g., water vapor produced by a concentrating solar power plant for regenerating CO2 captured at a cement plant). In yet another embodiment, the water vapor can be produced in another water vapor cycle using externally generated energy (e.g., electrical energy from a wind turbine used to reheat the water vapor for regenerating CO2 captured at a cement plant).

[0159] As described above, any of the various adsorbents may be used according to a particular embodiment. According to a particular embodiment, the adsorbent comprises an alkali metal borate. Alkali metal borates generally contain at least one alkali metal, boron, and oxygen.

[0160] As described above, the term "alkali metal" is used herein to refer to the following six chemical elements in Group 1 of the periodic table: lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr).

[0161] In some embodiments, at least one alkali metal of the alkali metal borate comprises cationic lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and / or cesium (Cs). In some embodiments, at least one alkali metal comprises lithium (Li), sodium (Na), and / or potassium (K). In a particular embodiment, at least one alkali metal comprises equal amounts of Li and Na.

[0162] In some embodiments, the stoichiometry of the adsorbents described herein (e.g., salts, alkali metal borates, molten alkali metal borates) can be represented as A x B 1-x O 1.5-x (wherein A is one or more alkali metals (e.g., Li, Na, Li and Na), B is boron, O is oxygen, and x is between 0 and 1). In certain embodiments, x can refer to a mixing ratio as described below. In some embodiments, the stoichiometry is that of the adsorbent in solid form before melting the adsorbent. In some embodiments, the stoichiometry is that of the adsorbent after the adsorbent has melted. Consistent with its usage above, as used herein, the term "mixing ratio" of an alkali metal cation or combination of metal cations in an adsorbent refers to the ratio of the number of moles of metal cation(s) in the adsorbent to the total number of moles of metal cation(s) and moles of boron in the adsorbent. For example, the mixing ratio of sodium in Na3BO3 is 3 / (3 + 1)=0.75, and (Li 0.5 Na 0.5) The mixing ratio of the alkali metal in 3BO3 is (0.5×3 + 0.5×3) / (3 + 1) = 0.75. In some embodiments, the mixing ratio is at least 0.5, at least 0.6, or at least 0.667. In some embodiments, the mixing ratio is at most 0.9, at most 0.835, at most 0.8, at most 0.75, or at most 0.7. Also, combinations of the above ranges are possible (e.g., between 0.5 and 0.9 or equal thereto, between 0.6 and 0.8 or equal thereto, between 0.7 and 0.8 or equal thereto). Also, other ranges are possible. Without wishing to be bound by theory, there may be a mixing ratio (for a particular alkali metal cation or combination of metal cations) below which the acid gas uptake capacity of the adsorbent is less than desirable. Without wishing to be bound by theory, there may be a mixing ratio (for a particular alkali metal cation or combination of metal cations) above which the regeneration efficiency of the adsorbent is less than desirable. In some embodiments, the alkali metal includes lithium (Li), sodium (Na), potassium (K), and / or mixtures thereof. In some embodiments, the alkali metal includes equal amounts of Li and Na.

[0163] It should be understood that the embodiments disclosed herein are not limited to embodiments in which an alkali metal borate (molten or otherwise) is used as the adsorbent, and in other embodiments, other adsorbents may be used.

[0164] U.S. Provisional Patent Application No. 62 / 988,436, entitled "Processes for Regenerating Sorbents, and Associated Systems", filed on March 12, 2020; U.S. Provisional Patent Application No. 62 / 979,628, entitled "Processes for Regenerating Sorbents, and Associated Systems", filed on February 21, 2020; and U.S. Provisional Patent Application No. 62 / 932,410, entitled "Process for Regenerating Sorbents at High Temperatures", filed on November 7, 2019 are each hereby incorporated by reference in their entirety for all purposes.

Example

[0165] The following examples are intended to illustrate certain embodiments of the present invention and are not intended to illustrate the full scope of the present invention. (Example 1)

[0166] This example describes the removal of several non-CO2 acid gases compared to CO2 in both reducing and oxidizing environments.

[0167] An acid gas is any gas that forms an acidic solution with water. The ones most relevant to industrial emissions are sulfur (SO x ) and nitrogen (NO x) are various oxides, hydrogen sulfide (H2S), and carbon dioxide (CO2). Usually, acid gases are environmental pollutants such as greenhouse gases or causative substances of acid rain, and in some cases, are severely harmful to human health. The recent interest in capturing CO2 emissions to combat global warming overshadows the previous efforts to treat acid gas emissions more broadly, such as non-CO2 acid gases. From these successes, many lessons can be learned in terms of both the large-scale deployment strategies of emission control technologies and the specific technical challenges overcome. In fact, many of today's best options for carbon capture follow those pathways for the treatment of other acid gases (e.g., non-CO2 acid gases). For example, in natural gas treatment, it was originally desirable to remove H2S rather than CO2 with amines.

[0168] The capture method may be the same for each case. In the adsorber, the acid gas contacts the basic adsorbent to form a neutral salt, which is usually destabilized in the desorber by a change in conditions, such as temperature, and the recovered gas is sent for further treatment, storage, or utilization. The basicity of various adsorbents has been adjusted over decades to target specific acid gases and, more recently, to minimize the energy penalty of the release step among other process challenges. Real-world systems present both the challenge and the opportunity of containing multiple acid gases at various concentrations. The opportunity is to treat multiple acid gases simultaneously, thereby reducing equipment costs and system complexity. The challenge is to manage the products and maintain even stricter limits on acid gas emissions than before. A recent example of this trend can be seen in the shipping industry, where SO x emissions have been more strictly regulated since 2020, and this industry aims to reduce 70% of its CO2 emissions by 2050.

[0169] In understanding the relationship between various acid gases and specific industrial processes, it is convenient to distinguish between an oxidizing atmosphere in which an excess of oxidizing agent is present and a reducing atmosphere in which such an oxidizing agent is absent. When a sulfur-containing feedstock is treated in an oxidizing environment, sulfur is converted to SO xis emitted in the form of, among which SO2 is most centrally relevant. General examples include the combustion of coal, oil, natural gas, and biomass, the production of cement, and the smelting of ores. On the other hand, sulfur forms H2S in a reducing environment such as those associated with pre-combustion technologies, hydrogen production, and gas sweetening. Similarly, nitrogen is present in many feedstocks and gives rise to fuel NO x where NO2 and NO are most centrally relevant. Further, nitrogen is present in air and thermal NO x emissions penetrate particularly deeply into oxygen environments. However, in some embodiments, in a reducing atmosphere, nitrogen is typically emitted more than NO x . For various high-temperature sources, Table 1 below shows typical ranges of uncontrolled acid gas emissions.

Table 1

[0170] Typically, high-temperature capture at around 600 °C or 700 °C can offer many advantages over operation at lower temperatures, including efficient heat recovery, so-called "absorption enhancement" designs, and greater opportunities for faster kinetics and higher-capacity different chemistries. In some embodiments, the recent discovery of molten alkali metal borates (A x B 1-x O 1.5-x ) as high-temperature liquid-phase adsorbents for carbon capture shows significant advantages in realizing efficient low-cost carbon capture facilities. Without wishing to be bound by theory, two distinct reaction mechanisms have been identified, one in which the melt reacts to form a solid crystalline product and the other in which the melt reacts to form a melt product. In some embodiments, alkali metal borates with compositions of Na x B 1-x O 1.5-x (x = 0.75) and (Li 0.5 Na 0.5 ) x B 1-x O 1.5-x (x = 0.75) are representative examples of "liquid-solid" and "liquid-liquid" types of non-CO2 acid gas adsorbents, respectively.

[0171] As described herein, the interaction between other acid gases (e.g., non-CO2 acid gases) and this new class of high-temperature non-CO2 acid gas sorbents is discussed with a focus on the opportunities and challenges presented by real-world systems. In some embodiments, the performance of molten alkali metal borates at concentrations and mixtures applicable to real-world systems using SO2 as a representative example is described, then the reaction mechanisms of industrially important gases are described, and finally the relevance to the design of high-temperature capture facilities by comparison between the state of the art of carbon capture and molten alkali metal borates is further described below. Experiments and Methodology Sample Preparation

[0172] Lithium hydroxide (LiOH, 98%), sodium hydroxide (NaOH, 97%), and boric acid (H3BO3, 99.5%) were purchased from Sigma-Aldrich. Alkali metal borate samples, A x B 1-x O 1.5-x (where A is an alkali metal and x is the mixing ratio) were prepared from the mixed precipitate of alkali metal hydroxide and boric acid. The mixture was weighed and dissolved in 0.1 g / mL Milli-Q (Millipore) deionized water. The water was evaporated at 120 °C for several hours, followed by 400 °C for 2 hours to release residual moisture and CO2, and a final pretreatment step was carried out in-situ at 800 °C for 60 minutes to obtain the target composition. Performance Analysis

[0173] A mixture of 1 mol% acid gas of carbon dioxide (CO2), sulfur dioxide (SO2), hydrogen sulfide (H2S) and nitrogen dioxide (NO2), with the balance nitrogen (N2), was obtained (Airgas). 20% CO2 was mixed with 1 mol% acid gas to obtain various mixtures of 10 mol% CO2 and 0.5 mol% acid gas. The performance of the non-CO2 acid gas adsorbent was analyzed by the variation in the weight of the sample in a thermogravimetric analyzer (TGA, Q50 TA instrument) with respect to exposure to the gas stream. In each case, the sample mass was approximately 5 mg and the sample gas flow rate was approximately 30 mL / min. The final pretreatment step was carried out in the TGA under 200 mL / min N2. The weight change with respect to exposure to the acid gas was normalized by the sample mass after the final pretreatment to obtain the gas loading (mg) per gram of the non-CO2 acid gas adsorbent. In some cases, for better comparison, the weight change was converted to mmol of acid gas using the molecular weight of the gas. After the final pretreatment, a temperature gradient from 200 °C to 800 °C was carried out at 5 °C / min. Material Characterization

[0174] The phase composition and crystallographic characteristics were tested by powder X-ray diffraction (XRD) and high-temperature powder X-ray diffraction (HTXRD) (XRD: Cu-k α X-ray (λ = 1.541 Å) using a PANalytical X’Pert Pro multipurpose diffractometer) with the sample placed on a Pt sheet substrate. The peaks of the XRD spectra were identified by referring to the ICDD PDF-4+2016 RDB database. The samples were prepared ex-situ in a tubular furnace (GSL-1800, MTI Corp) for 60 minutes under a continuous flow of 1 mol% acid gas with the balance being N2. Results and Discussion

[0175] From Table 1 above, some industrially relevant acid gas concentrations can vary by an order of magnitude. In this example, SO2 was selected as a representative species at the higher concentration end values (1 mol%, 0.5 mol% and 0.1 mol%), the effect of the acid gas is most significant, and the comparison is made for CO2 capture at the same concentration.

[0176] At 600 °C, sodium borate for SO2 capturex B 1-x O 1.5-x (x = 0.75) had performance similar to CO2 capture on a molar basis (Figure 3A). For 1 mol% and 0.5 mol% acid gas concentrations, the capacity was consistent at approximately 6 mmol / g, but for 0.1 mol%, it was too low and the reaction did not reach completion in 60 minutes. However, even at this low concentration, there was an obvious interaction between the acid gas and the non-CO2 acid gas adsorbent. Exposure to nitrogen in the release step stimulated the pressure swing operation by reducing the partial pressure of the acid gas. At 600 °C, CO2 was released very slowly, while SO2 was retained by the non-CO2 acid gas adsorbent with a slight increase in the loading. As the acid gas concentration decreased from 0.1 mol% to 0% during exposure to nitrogen, the non-CO2 acid gas adsorbent continued to remove the remaining SO2 still present in the headspace, suggesting that concentrations substantially below 0.1 mol% could be effectively treated.

[0177] At 700 °C (Figure 3B), since CO2 was present in the melt below supersaturation conditions, the capacity of CO2 decreased at lower concentrations, while the capacity of SO2 increased. Although not wishing to be constrained by theory, the high SO2 loading suggested that different reactions occurred, which enabled a higher capacity at 700 °C compared to 600 °C. The release of CO2 was more favorable at 700 °C, but in each case, SO2 was retained at the capacity reached during the uptake step. This suggests that the reaction with CO2 was easily reversible, while the reaction with SO2 was irreversible up to at least 700 °C.

[0178] Lithium-sodium borate (Li 0.5 Na 0.5 ) x B 1-x O 1.5-x(x = 0.75) is the same (Figure 3C). At 600 °C, the initial reaction rate closely matched that of CO2, but the capacity was substantially higher. For lithium-sodium borate, CO2 in the melt is in equilibrium with CO2 in the gas stream, and the capacity will decrease stepwise with the CO2 concentration. Similar to sodium borate, for SO2, both at 1 mol% and 0.5 mol%, it reached the same approximately 11 mmol / g, and at below 0.1 mol%, 60 minutes was insufficient for the reaction to be completed. Also, the reaction with CO2 reversed upon exposure to nitrogen, but SO2 was retained.

[0179] At 700 °C (Figure 3D), the capacity of CO2 decreased as the release reaction became more favorable. For SO2, a similar uptake profile was observed in a second, slower process that occurs at high loadings, resulting in a stepwise increase beyond that seen at 600 °C. Again, without wishing to be bound by theory, the release profile at 700 °C confirms the irreversibility of SO2 uptake by both sodium borate and lithium-sodium borate. Acid gas mixture

[0180] In many real-world systems, multiple acid gases are present together, and with the increasing social environmental awareness, it is expected that future facilities will require strict control of all acid gas emissions. Therefore, a mixture of 10 mol% CO2 and 0.5 mol% SO2, similar to the worst-case scenario for a power plant burning high-sulfur bituminous coal, was tested.

[0181] To understand the effects of each acid gas and the possible interactions between the two species, several uptake experiments were carried out with each gas alone, 10 mol% CO2 (CO2) and 0.5 mol% SO2 (SO2), and both gases of 10 mol% CO2 and 0.5 mol% SO2 (CO2&SO2) together. In some variants, these were followed by a change to another mixture of acid gases. For example, following 10 mol% CO2, 0.5 mol% SO2 (CO2→SO2), following 0.5 mol% SO2, 10 mol% CO2 (SO2→CO2), and finally, following 10 mol% CO2, a mixture of 10 mol% CO2 and 0.5 mol% SO2 (CO2→CO2&SO2), etc. The difference between (CO2→SO2) and (CO2→CO2&SO2) is that the partial pressure of CO2 changes in the former while it does not change in the latter. Subsequently, the non-CO2 acid gas adsorbent was exposed to nitrogen in the release step. In the absence of a substitution step, the dashed line connects the uptake and release profiles. The loading is reported in mass rather than in molar basis because in the case of mixtures, it is not possible to determine which gas reacts and thus which molecular weight to apply.

[0182] Non-CO2 acid gas adsorbent Na at 600 °C x B 1-x O 1.5-xFor (x = 0.75) (Figure 4A), CO2 reacted rapidly and reached full capacity within just a few minutes. Since the concentration of SO2 was 1 / 20, the reaction was slower for SO2 alone, but the loading reached near full capacity as seen in Figure 3A within 60 minutes. For the mixture of both gases, the loading initially closely matched that of CO2 but then continued to increase. However, the capacity of SO2 alone was not reached in 60 minutes, suggesting that CO2 was slowly replaced by SO2. The same occurred when the non-CO2 acid gas adsorbent was first loaded with CO2 and then exposed to SO2, and when it was loaded with CO2 and then exposed to the mixture. These three cases were similar because at 600 °C, the change in the partial pressure of CO2 did not result in significant release of CO2. Under the release conditions at 600 °C, desorption was not favorable for any of the gases. The CO2 loading decreased slightly, but most other variations did not result in significant release. Without wishing to be bound by theory, it was confirmed that in the case of SO2 → CO2, the loading remained approximately constant, that SO2 reacted irreversibly with the non-CO2 acid gas adsorbent, and in some embodiments, could not be replaced by CO2.

[0183] The results at 700 °C were partially different from those at 600 °C because the release of CO2 was more favorable at higher temperatures. In Figure 4B, the gas mixture first followed the path of CO2 alone and then deviated and approached the capacity of SO2 alone. In the case of CO2 → SO2, a slight decrease in loading was seen because CO2 was released before the loading increased with the uptake of SO2. In some cases, the uptake rate of SO2 was faster for CO2 → SO2 than for SO2 and CO2 and for CO2 → CO2&SO2. The presence of CO2 slows down the substitution reaction because the carbonate product remains stable. As seen at 600 °C, CO2 does not replace SO2 in the SO2 → CO2 variation. Under the release conditions, CO2 alone was rapidly released while SO2 was not released. The change in loading for each variation thus indicates the relative proportions of CO2 and SO2 captured.

[0184] Lithium-sodium borate (Li 0.5 Na 0.5 ) x B 1-x O 1.5-x (x = 0.75) is different from sodium borate in that it has a higher capacity, the CO2 reaction is reversible at least at some temperatures, and the reaction product is liquid. In Figure 4C, at 600 °C, the mixture first follows the loading of CO2 alone, but then quickly replaces this CO2 with SO2 and follows the loading of SO2 alone. Without wishing to be bound by theory, carbonate ions stabilized in the melt by coordination with free lithium and sodium ions are thought to be more easily replaced than the solid sodium carbonate crystals in the case of sodium borate. Thus, in each variant, the capacity reached the capacity of SO2 alone, regardless of the presence of CO2 or the original loading amount. The complete replacement of CO2 by SO2 was supported by the release profile, which showed the release of CO2 alone but not the release of any other variant. Without wishing to be bound by theory, at 700 °C (Figure 4D), the capacity of CO2 decreased due to more favorable release conditions, but otherwise the profile of each variant was considered to be the same as the profile at 600 °C. Sulfur oxides, SO x

[0185] Figure 3A suggests that at 600 °C, the reaction proceeds in a similar manner for both SO2 and CO2 for Na x B 1-x O 1.5-x (x = 0.75). For CO2, it is known that the general reaction proceeds by conversion to sodium metaborate (NaBO2, x = 0.50) and sodium carbonate (Na2CO3).

Number

[0186] When this initial composition of sodium borate is x = 0.75, the stoichiometry of the reaction by conversion to x = 0.50 is Na3BO3 + CO2 → NaBO2 + Na2CO3 Equation 2 can be described as. The similarity between the uptake profiles at 600 °C implies that the SO2 reaction is similar Na3BO3 + SO2 → NaBO2 + Na2SO3 Equation 3 to that.

[0187] Assuming this is true, the complete reaction should correspond to a capacity of 501 mg / g. Figure 5A shows the loading as a function of temperature under 1 mol% SO2 with a stepwise temperature gradient of 5 °C / min for Na x B 1-x O 1.5-x (x = 0.75). Further, the capacities under the isothermal uptake conditions from Figure 3 above are indicated by points, and the dashed lines show the theoretical capacity values for a given reaction. For example, (x = 0.50, Na2SO3) corresponds to Equation 3, and the borate reacts with x = 0.50 (NaBO2) and the sulfur product Na2SO3. The difference between the temperature gradient and the isothermal capacity is due to relatively slow kinetics under 1 mol% SO2.

[0188] Figure 5A shows that the capacity at 600 °C was slightly lower but close to that predicted by Equation 3, supporting the view that this is a primary reaction mechanism. Further, XRD analysis, Figure 5B, revealed the main peaks corresponding to sodium metaborate (NaBO2) and sodium sulfite (Na2SO3). However, at 700 °C, the isothermal capacity exceeded this value, which cannot be explained by Equation 3. Without wishing to be bound by theory, the possibility is the occurrence of the following decomposition reaction 4Na2SO3 → 3Na2SO4 + Na2S Equation 4 which is known to occur around 700 °C.

[0189] Equation 4 explains the observation of sodium sulfate (Na2SO4) rather than sodium sulfite (Na2SO3) by XRD after reaction at 700 °C, Fig. 5B. Although not wishing to be bound by theory, in order to explain the increase in volume, the involvement of platinum from the platinum pan or platinum substrate may have caused sodium sulfide, Na2S, to react further with SO2 to produce platinum sulfide (PtS) and further sodium sulfate (Na2SO4). Na2S + 2SO2 + 2Pt → 2PtS + Na2SO4 Equation 4B is considered.

[0190] Although not wishing to be bound by theory, this reaction may increase the volume to about 630 mg / g, explaining the slower second increase in loading observed in the uptake experiment, Fig. 3B, and further the platinum sulfide peak observed by XRD after reaction at 700 °C, Fig. 5B.

[0191] Although not wishing to be bound by theory, a similar reaction may also explain the performance of lithium borate-sodium, Fig. 5C. However, at 600 °C, the volume exceeds that predicted by the equivalent of Equation 3, suggesting that considering the equivalent of Equation 4 plays an important role at both temperatures. Although not wishing to be bound by theory, the observation of a higher volume than expected by Equation 4 for lithium borate-sodium under isothermal uptake at 700 °C may be due to the formation of polysulfides or the conversion of lithium borate to a composition with x < 0.50, e.g., x = 0.25 (Li2B4O7), which has been proposed as a possible product of the reaction between lithium orthoborate (Li3BO3) and CO2.

[0192] XRD at 25 °C after reaction at 600 °C, Fig. 5D, supports the reaction to sulfate products with peaks corresponding to sodium sulfate (Na2SO4), lithium-sodium sulfate (LiNaSO4), and lithium metaborate (LiBO2). The expected instability of lithium sulfite (Li2SO3) and the absence of sodium borate peaks suggest that sodium is involved in the reaction with SOx This suggests that it is the main alkali metal in the reaction with [substance not specified]. Without wishing to be bound by theory, it is considered that both Equation 3 and Equation 4 occur as described and that sodium is involved in the reaction. Subsequently, sodium sulfate is formed, and a portion of the lithium present in the melt coordinates with the sulfate to form lithium-sodium sulfate.

[0193] Sodium sulfate melts at approximately 880 °C, which is [description continues but seems incomplete] for Na x B 1-x O 1.5-x (x = 0.75) suggested that the SO2 reaction mechanism is similar to that of CO2 in that the gas reacts with the liquid non-CO2 acid gas adsorbent to form a solid precipitate. However, in some embodiments, this may not be the case for lithium-sodium borate. With CO2, lithium-sodium borate, (Li 0.5 Na 0.5 ) x B 1-x O 1.5-x (x = 0.75) forms a eutectic such that both the borate and carbonate products are in the liquid phase above approximately 500 °C. In the case of SO2, HTXRD shows that at 600 °C, there are no peaks corresponding to alkali metal borates, suggesting that these species are present in the liquid phase. Only the lithium-sodium sulfate (LiNaSO4) phase remains as a solid crystal at approximately 600 °C, but at 700 °C, this compound also melts such that, except for platinum sulfide, all reaction products with SO2 are liquid at 700 °C, similar to the case of CO2.

[0194] The reactions and mechanisms proposed in this example may have an important effect on the design of high-temperature carbon capture facilities and are further considered below. However, here, in the oxidative environment of a real exhaust gas containing SO x , the consideration of two expected phenomena for the two purposes is included. First, without wishing to be bound by theory, sodium sulfide may not be stable in the presence of an oxidizing agent. For example, Na2S + 2O2 → Na2SO4 Equation 5

[0195] Thus, corrosion of the reactor vessel by sulfidation can be less likely than implied by the formation of transition metal sulfides in the above example. Second, at high temperatures, SO2 can react with an oxidant to become SO3, which typically constitutes 0.1 to 3 mol%. SO2 + 1 / 2O2 ←→ SO3 Equation 6

[0196] Although not explicitly mentioned and studied in this example, sulfur trioxide (SO3) is contemplated to form sulfate (A2SO4) that is efficiently captured by a more direct reaction with molten alkali metal borate (A3BO3), bypassing the formation of sulfite (A2SO3) and sulfide (A2S). A3BO3 + SO3 → ABO2 + A2SO4 Equation 7 Hydrogen sulfide, H2S

[0197] Hydrogen sulfide shows interesting similarities to sulfur oxides. SO x Similarly, the interaction between a basic non-CO2 acid gas adsorbent and an acidic gas is strong, resulting in efficient removal of the gas. Figure 6A shows the weight change of sodium borate Na x B 1-x O 1.5-x (x = 0.75) at a temperature gradient of 5 °C / min and under 1 mol% H2S. Note that in some cases, limited experiments were carried out with H2S due to its property of damaging the equipment used in the uptake experiments. However, the results for sodium borate can be sufficient to provide some useful insight into the reaction mechanism.

[0198] Unlike CO2 and SO2, the reaction with H2S started at approximately 430 °C, much lower than the melting point of the non-CO2 acid gas adsorbent (about 570 °C). Between 550 °C and 650 °C, the loading entered a plateau at approximately 350 mg / g and then increased further as the temperature rose. Typical reactions between metal oxides and H2S involve the formation of metal sulfides and water / water vapor. For example, Na3BO3 + H2S → NaBO2 + Na2S + H2O Equation 8

[0199] Although not wishing to be bound by theory, the theoretical capacity value for this reaction is only 126 mg / g, and although the uptake experiments immediately exceeded this, even complete conversion to x = 0 in the reaction products Na2S and B2O3 only resulted in a theoretical capacity value of 283 mg / g. However, the formation of polysulfide or sodium platinum sulfide (Na2PtS2) by conversion of the alkali metal borate to x = 0.50 can account for the loading in the range of 550 °C to 650 °C, for example, Na3BO3 + 2H2S → Na2PtS2 + H2O + H2 + NaBO2 Equation 9

[0200] This is supported by XRD, Figure 6B, which revealed peaks after reaction at 600 °C that can be attributed to Na2S, NaBO2, and Na2PtS2. In certain embodiments above 650 °C, the reaction can proceed to a conversion of less than x = 0.50, and extremely to x = 0, which results in a theoretical capacity value of about 1700 mg / g. In some cases, uptake experiments were not performed with lithium-sodium borate (Li 0.5 Na 0.5 ) x B 1-x O 1.5-x (x = 0.75), but XRD revealed that a reaction similar to Equation 9 may be due to products containing Na2PtS2 and Li6B4O9. Nitrogen oxides, NO x

[0201] Nitrogen oxides present a case of complex and difficult research. First, at high temperatures, the gas-phase chemistry plays a particularly important role because the desired NO2 is decomposed by an equilibrium reaction,

Number

[0202] Figure 7A shows the weight change of sodium borate Na x B 1-x O 1.5-x (x = 0.75) at a temperature gradient of 5 °C / min and 1 mol% NO2. Uptake starts at a low of about 300 °C, reaches a peak at 600 °C, after which release becomes favorable, the loading decreases, and at about 700 °C, a negative loading is observed, indicating mass loss from the original sodium borate. Without wishing to be bound by theory, sodium nitrate and sodium nitrite are liquid above about 300 °C and can catalyze their own reactions by providing a liquid surface that can react rapidly with solid sodium borate at a temperature far below the melting point of sodium borate, similar to the case of molten nitrate-promoted CO2 capture using metal oxides. The decomposition and vaporization of nitrates and nitrites are known to occur simultaneously at temperatures above 600 °C, which can account for the mass loss above about 700 °C. Based on theoretical capacity values, the reaction with NO x appears to have a stoichiometry close to Na3BO3 + NO2 + NO → NaBO2 + 2NaNO2 Equation 11 although in practice it is recognized that a number of gas-phase and liquid-phase reactions can lead to the net reaction shown by Equation 11.

[0203] After exposure to NO2 at 600 °C, peaks corresponding to sodium nitrite (NaNO2) and sodium metaborate (NaBO2) were observed. Figure 7B supported this net reaction for a particular embodiment. However, in some embodiments, unreacted trisodium borate (x = 0.75) and partially reacted disodium borate (x = 0.66) were also observed, indicating that the reaction did not proceed to the same extent in the tubular furnace. After the reaction at 800 °C, the peak attributable to sodium nitrite (NaNO2) was no longer present, leaving a mixture of trisodium borate (Na3BO3) and disodium borate (Na4B2O5). The decomposition to Na4B2O5 has a theoretical mass loss value of 243 mg / g and thus has a mixture of Na3BO3 and Na4B2O5, which could account for the observed loss value of approximately 150 mg / g. The decomposition of sodium nitrite involves several reactions including the generation of gaseous N2, O2, and NO, as well as solid Na2O, which could recombine with the borate melt in addition to vaporization.

[0204] Isothermal uptake and release were demonstrated for some embodiments in Figure 7C at 600 °C without the mass loss associated with higher temperatures. Similar to other acid gases, the behavior of lithium-sodium borate was similar to that of sodium borate as demonstrated by the temperature gradient in Figure 7D. The maximum loading was lower and the reaction did not go to completion, but significant uptake was observed even at 1 mol% NO2. Without wishing to be bound by theory, similar to sulfates / sulfites, lithium nitrate / nitrate is less stable than their sodium counterparts, so sodium is the major alkali metal involved in the above reaction and lithium may preferentially interact with borate species.

[0205] The understanding obtained above can affect the design of high-temperature carbon capture systems. The strong interaction between molten alkali metal borates and acid gases demonstrates that adsorbers designed for carbon capture can capture not only CO2 but also other acid gases present (e.g., non-CO2 acid gases). This can present opportunities for capturing multiple acid gases in a single adsorber or challenges in managing various corrosive or difficult-to-handle reaction products. The distinction between the opportunities and challenges is a matter of design, which is the topic of this section of the examples.

[0206] One of the main advantages of molten alkali metal borates is their fluid properties, which can facilitate transport between the adsorber and desorber at high temperatures in some embodiments, as shown in FIG. 8. Without modification, considering the plot in FIG. 8, after capturing acid gases other than CO2, either their accumulation in the system until their release into the CO2 product stream in the desorber or the replacement of the non-CO2 acid gas adsorbent may be required before the need for either. Note that when an excess amount of CO2 is present in the adsorber, other acid gases will be at a relatively low loading. Therefore, although not wishing to be bound by theory, it is expected that their presence will not significantly impede the pumping or fluidity of the bulk non-CO2 acid gas adsorbent unless they accumulate.

[0207] In many cases, the reaction with SO x is irreversible at appropriate temperatures, while the reaction with NO x easily reverses during pressure swing. Therefore, sulfur products are retained after the desorption step, while the products of the NO x reaction will be released into the CO2 product stream. For NO at temperatures below 700 °C xGas evolution from the product contains N2, O2 and NO, which may be acceptable in the product stream if in small amounts. To reduce the vaporization of nitrates / nitrites and thus the loss of alkali metals from the system, it was desirable to maintain a desorption temperature below 700 °C. The loss of alkali metals from the system can slightly decrease the mixing ratio, x, of the molten alkali metal borate circulating between the adsorber and the desorber. However, the mixing ratio can be increased by the addition of alkali metal hydroxides / carbonates. This approach can be simple and cost-effective when the loss is expected to be small and the main component is sodium rather than lithium.

[0208] Since sulfur products can accumulate in the system, different strategies may be useful for dealing with them. One option is to include a purge stream and intermittently replenish the non-CO2 acid gas adsorbent. However, the properties of the molten alkali metal borate may enable not only the simultaneous capture of multiple acid gases but also their efficient separation. Since the molten alkali metal borate is liquid and the sulfur products are usually solid, any number of liquid-solid separation techniques can be applied to the slip stream of the circulating non-CO2 acid gas adsorbent, as schematically shown in Figure 8, whereby the sulfur compounds are separated at high temperature.

[0209] Since the density difference between the melt and the sulfur product is relatively small, filtration may be superior to gravity separation methods. For example, cross-flow filtration by a metal mesh separator applied to the slip stream downstream of the desorber pump can be a suitably simple and robust method at the elevated temperatures involved. A large mesh size reduces the pressure drop and allows for a moderate amount of solid recycle. When concentrated, the sulfur compounds can be further purified and refined under ambient conditions to a marketable product. There are several options, including those at elevated temperatures that minimize heat loss. However, the value of lithium compared to all other species can potentially define the processing method. One option is to contact the concentrated sulfate stream with lime water, (Ca(OH)2(aq)), as schematically illustrated in Figure 8. Without wishing to be bound by theory, in the aqueous phase at ambient temperature, the sulfur species precipitate calcium sulfate (CaSO4). For example, Ca(OH) 2(aq) +NaLiSO 4(aq) →CaSO 4(s) +NaOH (aq) +LiOH (aq) Equation 12

[0210] The resulting gypsum (CaSO4·2H2O) can be sold as is customary in today's industry, and the residual ions in the solution, which can contain not only some borate species but more importantly useful lithium ions, can be returned to the high-temperature system. Evaporation of the water required for dissolution leaves mainly the alkali metal hydroxides, whereby the non-CO2 acid gas absorbent returns to its original mixing ratio, x.

[0211] Assuming that the reactor vessel can be protected from sulfidation, SO xA process similar to that described herein may be suitable for simultaneous H2S capture and separation. Solid Na2S may be filtered and processed. As with sulfates, the processing depends on the desired sulfur product, but in order to ensure the recovery of alkali metal and borate species, a reaction with oxygen to produce sulfates for subsequent processing may be preferred. In the case of a reducing environment, there is no oxidizing agent to protect the reactor vessel from sulfidation as in the case of an oxidizing environment. Sulfidation remains a major problem, especially in existing facilities that handle H2S at high temperatures. In fact, this is the main motivation for pretreatment in refineries and gas sweetening facilities. Sulfidation can be mitigated by material selection and the formation of a protective metal sulfide thin layer. This and other anti-corrosion techniques can enable the removal of H2S by molten alkali metal borates without unwanted reactions with metals present in the adsorber vessel walls or packing. In this regard, upstream desulfurization, such as natural gas sweetening, is still envisioned as being important for future carbon capture facilities operating in a reducing environment. Comparison with Others

[0212] The conceptual designs described elsewhere in this specification may, in some cases, be similar to some of the existing strategies used in amine and calcium loop systems that respectively represent the state of the art for low and high temperature carbon capture. However, molten alkali metal borates exhibit several advantages in the context of handling acid gas impurities briefly described below.

[0213] In certain embodiments, SO x reacts with the amine to form dissolved sulfite / sulfate in the aqueous phase, but since these species cannot be concentrated, most of the recycled amine solution needs to be periodically purged for treatment. There are several options, most established as thermal regeneration, amine evaporation and recovery. However, this approach usually results in amine losses due to thermal regeneration, so it is only cost-effective in upstream flue gas desulfurization, shows a relatively large energy penalty, and is contaminated with semi-solid products.

[0214] In some embodiments, NO x also reacts with amines to form dissolved nitrites / nitrates and nitrosamines / nitroamines. Depending on the amine, this absorption can result in a reasonable removal of NO x close to complete removal. These reactions can provide some benefits in NO x reduction, but the net effect is generally negative due to the health risks associated with some nitrosamines that will be present in the solid product and the relatively high cost of amines. As mentioned elsewhere herein, amines may be suitable for H2S capture in some cases, but may not be suitable for high-temperature applications such as pre-combustion carbon capture and hydrogen production as described herein. For a proper comparison with high-temperature non-CO2 acid gas sorbents, the inventors consider calcium oxide and the calcium looping process.

[0215] Calcium oxide can also remove SO x from the exhaust stream. However, in the calcium loop, CaO, CaCO3, and CaSO4 are all solids and cannot be easily separated, requiring periodic purging in the system. The situation is worsened by the nature of calcium sulfate, which blocks the internal pores of the solid non-CO2 acid gas sorbent and reduces its CO2 capacity. The generality and low cost of calcium compounds partially compensate for this drawback, but the results are not ideal. In a reducing environment, calcium oxide reacts with hydrogen sulfide (H2S) to form calcium sulfide (CaS), which is also purged when the non-CO2 acid gas sorbent decomposes. Without wishing to be bound by theory, calcium oxide does not have the property of reacting with NO x but by using oxy-combustion to generate most of the plant's electricity, there is a slightly lower NO x emission compared to a reference power plant. However, these emissions are still unacceptably high and downstream NO x scrubbing is required. Conclusion

[0216] The interaction between the various acid gases present (e.g., non-CO2 acid gases) and non-CO2 acid gas adsorbents designed for carbon capture is an important issue in state-of-the-art carbon capture and a major obstacle for less mature technologies. In this example and elsewhere in this specification, it has been demonstrated that molten alkali metal borates can greatly overcome this shortcoming and can do so in a manner that can be superior to both amines and calcium loops. This is not to say that there are no challenges. The importance of material selection, in particular the need for vessels and lines containing sulfides to be resistant to attack by sulfidation, has been demonstrated. In this regard, it is noted that an excess of oxygen is desirable as it helps to suppress the reaction pathway for sulfide formation, i.e., in some cases, the high-temperature reducing environment rich in H2S in upstream processes, such as natural gas sweetening, should be minimized as is customary in today's industry. Also, it should be noted that the temperature is limited to about 700 °C to minimize the vaporization of nitrate / nitrite species in some cases where the non-acid gas H2S is involved.

[0217] However, the net results are strongly biased by chance. The strong basicity of molten alkali metal borates means that acid gases can be removed at low concentrations and in mixtures relevant to real-world systems. The fluidity of molten alkali metal borates enables designs that take advantage of the efficient separation of sulfur products, which are normally solids, at high temperatures. The proposed designs for molten alkali metal borates appear to be superior when compared to the options available with amines and calcium loops, and support the advantages already obtained for this new class of non-CO2 acid gas adsorbents for carbon capture. Indeed, it can be demonstrated that molten alkali metal borates, along with associated system designs and methods, are efficient enough to generalize carbon capture to the broader issue of acid gas capture. (Example 2)

[0218] This example describes a process for regenerating an adsorbent using steam to remove acid gas (e.g., carbon dioxide) from the adsorbent. It also describes how the regeneration of the adsorbent can be carried out in multiple cycles (e.g., periodically) due to multiple interactions of the adsorbent regeneration. Experimental setup for bench-scale experiments

[0219] The bench-scale experiments were designed as follows. These bench-scale experiments can be introduced into the industrial-scale design of reactors such as those described in the future design of Example 3.

[0220] Nickel tubes (Nickel 200 / 201, Magellan Metals) with an outer diameter of 1 / 2 inch and an inner diameter of 0.41 inches (1 cm) were cut to size and bent into the desired shape by a tube bender to form tubular reactors. Each tubular reactor included a twist so that the molten sample spread uniformly along the base of the tube and was contained inside the furnace with the approximate dimensions shown in Figure 12A.

[0221] The tubes were inserted into a tubular furnace (OTF-1200, MTI Corp) that was thermally insulated from the outside with quartz wool and aluminum foil and connected to the upstream and downstream piping by stainless steel flareless tube fittings. A steady flow of CO2 at various concentrations was provided (Airgas) by an upstream digital mass flow controller (GFC17, Aalborg) and a mass flow meter (XFM17, Aalborg). For each CO2 concentration, the flow meter was calibrated against an adjustable gas setting flow meter (00412ML, ColeParmer). Pressure gauges (DPG409, Omegadyne) were placed upstream and downstream of the tubular reactor. Downstream, a filter (F504-02DHSS, Parker Watts) was cooled externally with ice to act as a separator to remove water vapor, and subsequently, the CO2 concentration was measured by infrared detection (CM-0154, CO2Meter). Adsorbent regeneration

[0222] The regeneration of adsorbents used for acid gas capture is an important part of the processes designed to reduce emissions. The examples provided herein mainly focus on the problems of global warming and CO2 emissions, but the processes and systems described herein can be extended to other acid gases such as SO x and NO x , as well as to other global issues such as acid rain.

[0223] The regeneration of adsorbents used for the capture of acid gases, particularly carbon dioxide, from industrial streams can find applications in the energy and chemical industries. Options for regeneration include temperature swing, pressure swing, and potential swing. In each case, capture is carried out under one set of conditions, e.g., at low temperature, and regeneration is carried out under a different set of conditions, e.g., at a higher temperature, in a different environment separated either spatially or temporally. Existing process designs are often inefficient because they cannot efficiently utilize the energy capacity of the various streams involved. In part, this is related to limitations inherent in the materials used for capture. However, the materials described elsewhere in this specification can provide highly efficient regeneration processes.

[0224] The inventors recognize and understand that an important improvement is to operate the system isothermally or nearly isothermally at high temperature, use steam to lower the partial pressure of the acid gas in the regenerator (e.g., desorber) to drive regeneration, and subsequently condense the steam from the mixture of acid gas and steam to produce a high-purity acid gas product. In this way, the energy capacity of both the separated acid gas and the steam used to lower the partial pressure can be recovered in a downstream heat exchanger. Without wishing to be bound by theory, it is believed that steam does not interact with the adsorbent itself and provides an entropy driving force to release the acid gas by lowering the partial pressure in the release environment. Unlike other gases (e.g., N2, argon) that can be used as sweep gases to lower the partial pressure, steam is easily separated from the acid gas in a condenser.

[0225] Molten alkali metal borates can be used as adsorbents throughout the regeneration process. These molten alkali metal borates can have many characteristics that make them promising adsorbents for carbon capture. One of these characteristics is their high working capacity under changes in CO2 partial pressure. For CO2 sources near ambient pressure, pressure swing can generally be driven by either vacuum suction, which is often very inefficient and tends to be difficult to maintain on a large scale, or a sweep gas. A sweep gas (e.g., N2, argon) can dilute rather than concentrate the product and thus may have limited use in low-temperature carbon capture systems. However, after a standard heat recovery unit, when the H2O / CO2 mixture is cooled, water vapor easily condenses, and thus a sweep gas that is convenient and advantageous at high temperatures is found in the water vapor.

[0226] Figure 12B schematically illustrates a block diagram demonstrating this concept. Equipment used in bench-scale experiments is shown in bold, and similar industrial-scale process units are shown in italics within parentheses. In the capture step, the CO2-containing stream is fed to a tubular reactor where CO2 is removed. As shown in Figure 12C, using 20% CO2 at 20 ml / min, approximately 90% of the incoming stream was removed. In the release step, the feed was switched to steam, which decreased the partial pressure of CO2 in the reactor and CO2 was extracted from the adsorbent. Subsequently, the combined H2O / CO2 mixture was cooled, and water vapor condensed in a separator to form a pure CO2 stream. The cycle schematically illustrated in Figure 12C is part of a series of cycles shown in the inset of Figure 12C, demonstrating the repeatability of capture and release over multiple cycles by this method.

[0227] The high-temperature carbon capture unit can operate isothermally and at ambient pressure without the need for oxygen combustion-driven release as is customary in existing calcium loop processes. Advantageously, the energy content of the H2O / CO2 mixture is recovered in a heat recovery steam generator (HRSG) before separation in the condenser, thereby recovering useful high-quality heat between both capture and release, resulting in a highly energy-efficient process. Without wishing to be bound by theory, steam does not interact with the sorbent itself and provides the entropy driving force for release, which is the same for a pure nitrogen stream. Thus, experiments using nitrogen more conveniently are directly comparable to experiments using steam as the sweep gas.

[0228] The processes described herein can be very efficient in separating and regenerating acid gas from industrial streams. Process designs applied to natural gas combined cycle (NGCC) power plants with carbon capture are shown in subsequent future examples. In an industry where significant effort and capital are invested to improve efficiency by just a few percentage points, the processes described herein are expected to substantially reduce the energy penalty for CO2 removal compared to existing systems in this field. Other applications of this process design are in chemical processes that emit CO2, such as other fuels like coal, oil or biomass, or metal smelting, cement manufacturing, and steam methane reforming for hydrogen production. Similar efficiency improvements are expected in these cases.

[0229] Molten sorbents, particularly molten alkali metal borates, are described in this example and elsewhere in this specification. However, other sorbents such as solid alkali metal borates may be used. Molten sorbents can have a high working capacity under pressure swing that occurs during regeneration (e.g., introduction of steam, release of acid gas from the sorbent). Further, molten sorbents can be very stable under high-temperature and isothermal operating conditions, thereby providing efficient heat recovery. The fluidity of molten sorbents can provide efficient heat exchange, seamless transport between capture and release environments, and the ability to compress to higher pressures.

[0230] Figures 12-13 detail the experiments conducted to demonstrate the underlying concepts and functional systems, while Figure 14 shows how the reactor can be spatially separated while continuously circulating between dedicated capture and release environments. This is in contrast to the fixed bed of Figure 12D where capture and release are temporally separated in a single reactor. As described in more detail in Example 3, Figures 15A-15B each show a block diagram of the process applied to a natural gas composite cycle and a steam methane reforming system, while Figures 16-18 schematically illustrate more detailed diagrams of the process design for a natural gas composite cycle, a steam methane reforming system, and a cement manufacturing plant, which are further described below. Adsorbent regeneration performance

[0231] The performance of the adsorbent was analyzed by examining the breakthrough behavior of a sample loaded inside a tubular reactor. The breakthrough behavior can be determined as follows. As schematically illustrated in Figures 12A and 12D, an empty tube can be filled with nitrogen gas and a stream of CO2 can be flowed through the tube. The CO2 detector at the end of the tube can measure nitrogen temporarily, and when the nitrogen is pushed out of the tube, then CO2 reaches or "breaks through" the detector and can be detected by the CO2 detector. In some cases, as shown in the "control" plot of Figure 12D, a "plug flow" can occur as a sharp change, but in reality, a more gradual breakthrough can be observed. When the tube contains an adsorbent, as in the "sample" plot of Figure 12D, the breakthrough is delayed because the adsorbent can capture some or all of the incoming CO2, and the sensor continues to detect only nitrogen. However, after some time, the adsorbent can reach its CO2 capacity and CO2 is pushed all the way through the tube to reach or break through the CO2 detector.

[0232] The sample (e.g., adsorbent) was weighed and inserted into the tube, and then pretreated at 800 °C under a N2 flow to melt the sample and remove residual H2O / CO2. The pretreatment was considered complete when the composition of the stream leaving the system dropped below about 0.1% CO2 at 800 °C.

[0233] At time = 0, the gas flow was switched from N2 to CO2 while monitoring the outlet CO2 concentration. Figure 12D shows a plot, where the dimensionless concentration is the outlet concentration divided by the inlet. Under non-capture conditions, for example, a control experiment flowing at room temperature is compared with the CO2 capture conditions where breakthrough is delayed. The area between the non-capture control and the capture experiment indicates the capacity of the adsorbent, which is calculated in mmol of CO2 per gram of adsorbent (mmol / g).

[0234] In addition to Figure 12D, the breakthrough profile can be represented as the bed volume of CO2 normalized by the sample mass. The bed volume is determined from the control experiment by integrating the area enclosed by the breakthrough curve at time = 0 on the x-axis, dimensionless concentration = 1, and a given flow rate. To avoid plotting the control for each case, one bed volume, i.e., the system volume, was then subtracted. Thus, the area enclosed by the breakthrough curve at time = 0 on the x-axis, dimensionless concentration = 1, and a given flow rate indicates the CO2 capacity in breakthrough plots other than those shown in Figure 12D.

[0235] The bed volume can be converted to the bed volume of CO2 by multiplying by the inlet CO2 concentration and then normalizing by the sample mass loaded onto the tube to obtain the normalized bed volume of CO2 (1 / g). The hygroscopic sample loses mass during the pretreatment step, and the mass loss can be determined by thermogravimetric analysis (Q-50, TA Instruments) and can be taken into account in the normalization and capacity calculations. Comparison of the Adsorbent Regeneration Performance of Water Vapor and Nitrogen

[0236] Next, it was shown that water vapor can be used to regenerate the adsorbent in a similar manner to an inert gas such as nitrogen. Figure 13 illustrates the performance of water vapor as a sweep gas compared to nitrogen gas. Before time zero, the sample (e.g., the adsorbent) was placed under 20% CO2 for 60 minutes and considered to be fully loaded with CO2. At time zero minutes, the gas flow was switched to either nitrogen or water vapor (water injection into the furnace). In both cases, the CO2 loading decreased similarly, suggesting that the method of release is similar for both sweep gases. This demonstrates that water vapor can be used to effect an entropy-driven release of acid gas from the adsorbent. In other words, although not wishing to be bound by theory, water vapor does not interact with the adsorbent and provides an entropy-driven force similar to nitrogen. However, unlike nitrogen, as already described elsewhere in this specification, water vapor can be readily condensed and removed from the acid gas. (Example 3)

[0237] The following provides future examples of processes for adsorbent regeneration. In some cases, adsorbent regeneration can be linked to an industrial process. Continuous circulation of the adsorbent between dedicated capture and release environments

[0238] As schematically illustrated in FIG. 14, the rich CO2 stream can contact the adsorbent in the capture environment, resulting in a treated lean CO2 stream and an adsorbent loaded with CO2. The CO2-loaded adsorbent can be pumped to the release environment via a transport pump and a heat exchanger. In the heat exchanger, the loaded adsorbent and the unloaded adsorbent can contact each other. The purpose of the heat exchanger is to maintain similar temperatures in both the capture and release environments. In certain cases, the heat exchanger alone may not be sufficient to equalize the temperatures of the capture and release environments. In some cases, to avoid this problem, one option is to place the release environment inside the capture environment. For example, the release environment can include a pipe passing through the capture environment. In the release environment, the CO2-loaded adsorbent contacts steam, and CO2 can be removed from the adsorbent, while the unloaded adsorbent can be returned to the capture environment via a transport pump and a heat exchanger. The steam-CO2 mixture can then be cooled, and CO2 can be separated from the water as the water condenses. The CO2 can then be sent for compression and delivery, while the water is vaporized and the cycle repeats. Carbon capture using steam methane reforming (SMR) with natural gas combined cycle (NGCC) and sorption enhanced reforming (SER)

[0239] For NGCC fuel at the plant level, air can be supplied to the gas turbine and hot flue gas can be generated. These hot flue gases can pass through the capture block along with steam, as schematically illustrated in Figure 15A, to produce a lean CO2 flue gas and a steam / CO2 mixture. The hot lean CO2 flue gas can then be used to drive the steam turbine and some of the steam is used to fill the capture block. Also, the steam / CO2 mixture can pass through the steam cycle as the CO2 and steam are separated. In the case of an absorption enhanced reforming plant, the fuel (usually methane) can be sent straight to the capture / conversion block (schematically shown in Figure 12B and more detailed in Figure 17). Steam is used both as a reactant and as a sweep gas (in separate vessels) to produce a hydrogen rich stream and a steam / CO2 mixture, which can be separated after a secondary heat recovery steam generator (HRSG). An external steam supply may be required to supply sufficient steam, which can be sourced from an adjacent power plant or a renewable resource. Detailed system-level design of NGCC with carbon capture

[0240] As shown in FIG. 16, natural gas can be supplied to the combustion chamber along with compressed air. The gas turbine can drive compression via a shaft and can also supply energy to a generator for conversion to electricity. The hot flue gas can be used to produce steam (or auxiliary steam production) and can be sent to the capture environment where the steam contacts the adsorbent and CO2 is removed. The flue gas then passes through the first HRSG where additional steam can be produced at various pressure levels (e.g., high, medium, low). These steam turbines can then generate electricity (as schematically shown in FIG. 16) or can support the supply of steam sweep gas (not shown). The condensate can then be returned to the HRSG via a supply pump and a cold reservoir may be required as a heat sink. The adsorbent then reaches a heat exchanger through the release environment via a transport pump where CO2 can be removed from the adsorbent using steam sweep gas. The adsorbent can then be returned to the capture environment to complete the cycle while the steam / CO2 mixture is passed through a second HRSG where additional steam can be produced at various pressure levels (e.g., high, medium, low). These steam turbines can then generate electricity (as schematically shown in FIG. 16) or can support the supply of steam sweep gas (not shown). In some embodiments, the second HRSG operates in the same manner as the first HRSG. As a final step, the cooled steam / CO2 mixture passes through a condenser to recycle the condensate and produce a CO2 stream ready for compression and delivery. Detailed System-Level Design of Steam Methane Reforming by Enhanced Absorption Reforming with Carbon Capture

[0241] Natural gas can be preheated, desulfurized, pre-reformed (i.e., mainly converted to methane) in a first HRSG as schematically illustrated in FIG. 17, and then further preheated in the first HRSG before being passed to a reactor (absorption enhanced reformer). Steam and adsorbent from the first HRSG can also be sent to the reactor to convert methane to hydrogen and CO2. As a result, an excess amount of steam and hydrogen products may exit the reactor as a gas, while CO2 is removed as a liquid by the adsorbent and passes through the emission environment. Steam in the emission environment can be used to release CO2 from the adsorbent, producing a steam / CO2 mixture that passes through a second HRSG. As the temperature drops, the steam can pass through a condenser where condensate can be separated, which can be recycled via a supply pump, and the CO2 product can be sent for compression and delivery. The steam generated can be used as a steam sweep gas and replenished by a supporting steam supply (e.g., a renewable resource). The hydrogen and steam mixture can drive the first HRSG, can be separated via a cooler, and the condensate is recycled through a supply pump. To ensure high-purity hydrogen products, a conventional pressure swing absorption (PSA) unit can be included and the off-gas is returned to the emission environment where further absorption enhanced reforming occurs. The hydrogen can then be compressed for delivery. Detailed system-level design of cement manufacturing with carbon capture

[0242] As schematically illustrated in FIG. 18, raw materials (e.g., limestone) can be supplied to a raw material mill, filtered to produce coarse powder. The coarse powder can then be preheated and sent to a calciner, where CO2 is removed from the limestone, mainly producing calcium oxide. The product can pass through a rotary kiln to produce clinker, which can be cooled in a clinker cooler and prepared for delivery. The process can be driven by fuel (usually, as one non-limiting example, coal), which can enter the rotary kiln and the calciner and be burned in the presence of air. The air can then be used as a refrigerant in the clinker cooler and is thus preheated before entering the rotary kiln and the calciner. Usually, the hot flue gas then passes through a preheater, but in the case of CO2 capture, the hot flue gas can first be used to produce steam in a steam sweep gas generator and CO2 can be captured as it passes through a capture environment. The cleaned hot flue gas can then pass through a preheater, a raw material mill, and a filter as in a conventional process. Additional fuel may be required to maintain the same level of preheating. The CO2-loaded adsorbent can then pass through a transport pump and a heat exchanger towards the release environment, as already described in the examples. Support steam may be required for release, which can be derived from an adjacent power plant or a renewable resource. The steam / CO2 mixture can then be separated in a condenser, the steam is recycled, and the CO2 is compressed for delivery.

[0243] Some embodiments of the present invention have been described and illustrated herein. Those skilled in the art can readily conceive of various other means and / or structures for performing the functions described herein and / or obtaining the results and / or one or more advantages, and such variations and / or modifications are considered to be within the scope of the present invention. More generally, those skilled in the art will recognize that all parameters, dimensions, materials, and spatial structures described herein are illustrative, and that the actual parameters, dimensions, materials, and / or spatial structures depend on the particular application in which the teachings of the present invention are used. Those skilled in the art can recognize and confirm many equivalents to the specific embodiments of the invention described herein using experiments that do not exceed the scope of routine experimentation. Accordingly, the foregoing embodiments are presented by way of example only, and it is to be understood that the present invention may be practiced otherwise than as specifically described and claimed, within the scope of the appended claims and their equivalents. The present invention is directed to each individual feature, system, article, material, and / or method described herein. Furthermore, any combination of two or more such features, systems, articles, materials, and / or methods is included within the scope of the present invention if such features, systems, articles, materials, and / or methods are not mutually inconsistent.

[0244] As used herein, the indefinite articles "a" and "an" in the specification and claims are to be understood to mean "at least one" unless the contrary is clearly indicated herein.

[0245] The phrase "and / or" in this specification and the claims is to be understood to mean "either or both" of the connected elements, i.e., elements that are connected in some cases and not connected in other cases. Other elements may optionally exist in addition to the elements specifically identified by the phrase "and / or", whether or not they are related to the specifically identified elements, unless the contrary is clearly indicated. Thus, a reference to "A and / or B" can, by way of non-limiting example, in one embodiment, refer to A without B (optionally including elements other than B) when used in conjunction with open-ended language such as "comprising"; in another embodiment, refer to B without A (optionally including elements other than A); and in yet another embodiment, refer to both A and B (optionally including other elements).

[0246] As used herein, and as used in the claims, the term "or" should be understood to have the same meaning as "and / or" as set forth above. For example, when separating items in a list, "or" or "and / or" is to be interpreted as inclusive, i.e., including the number of elements or at least one (including the case of more than one) of the list, and optionally further items not enumerated. Only terms where the contrary is clearly indicated, such as "only one of" or "exactly one of", or when used in the claims, "consisting of", refer to including exactly one of the number of elements or of the list. In general, the term "or", when used herein, is to be interpreted as exclusive only when preceded by terms such as "either", "one of", "only one of", or "exactly one of", i.e., indicating an exclusive alternative (i.e., "one or the other but not both"). When used in the claims, "consisting essentially of" has the ordinary meaning as used in the field of patent law.

[0247] As used herein, in this specification and in the claims, the phrase "at least one" refers to a list of one or more elements and is to be understood to mean at least one element selected from any one or more of the elements in the list of elements, but does not necessarily include at least one of each and every element specifically listed within the list of elements, and does not exclude any combination of elements in the list of elements. By this definition, an element may, as necessary, exist outside of the specifically identified elements within the list of elements referred to by the phrase "at least one", whether or not related to these specifically identified elements. Thus, by way of non-limiting example, "at least one of A and B" (or, equivalently, "at least one of A or B", or, equivalently, "at least one of A and / or B") can refer, in one embodiment, to at least one A, which includes more than one as necessary and where B does not exist (and includes other elements as necessary), or, in another embodiment, to at least one B, which includes more than one as necessary and where A does not exist (and includes other elements as necessary), or, in yet another embodiment, to at least one A, which includes more than one as necessary, and at least one B, which includes more than one as necessary (and includes other elements as necessary), and so on.

[0248] In the claims and in the above specification, all transitional phrases such as "comprising", "including", "carrying", "having", "containing", "involving", "holding", etc. should be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases "consisting of" and "consisting essentially of" are closed or semi-closed transitional phrases, respectively, as described in the United States Patent and Trademark Office Patent Examination Handbook, Section 2111.03. The present invention provides, for example, the following items. (Item 1) A non-CO 2 acid gas adsorbent containing a molten salt is exposed to an environment containing non-CO 2 acid gas such that at least a portion of the non-CO 2 acid gas interacts with the non-CO 2 acid gas adsorbent and at least a portion of the non-CO 2 acid gas is removed from the environment. (Item 2) The method according to Item 1, wherein the molten salt contains an alkali metal borate, M x B 1-x O 1.5-x [where M is one or more alkali metals, B is boron, O is oxygen, and x is a number such that 0 < x < 1]. (Item 3) The method according to Item 2, wherein the alkali metal contains lithium (Li), sodium (Na), potassium (K), and / or a mixture thereof. (Item 4) The method according to Item 3, wherein the alkali metal contains equal amounts of Li and Na. (Item 5) The method according to any one of Items 1 to 4, wherein the non-CO 2 acid gas contains sulfur monoxide (SO), sulfur dioxide (SO 2 ), nitrogen dioxide (NO 2 ), hydrogen sulfide (H 2 S), sulfur trioxide (SO 3 ), nitric oxide (NO), nitrous oxide (N 2 O), dinitrogen trioxide (N 2 O 3 ), dinitrogen tetroxide (N 2 O 4 ), dinitrogen pentoxide (N 2 O 5 ) and / or carbonyl sulfide (COS). (Item 6) The method according to any one of Items 1 to 5, wherein the environment is at a temperature of at least 200°C. (Item 7) The method according to any one of Items 1 to 6, wherein a plurality of non-CO 2 acid gases interact with the non-CO 2 acid gas adsorbent such that at least a portion of the plurality of non-CO 2 acid gases is removed from the environment. (Item 8) The method according to any one of Items 1 to 7, wherein the captured non-CO 2 acid gas is released and concentrated in the gas phase of another environment. (Item 9) The method according to Item 8, wherein the release is at least partly driven by a change in the partial pressure and / or temperature of the non-CO 2 acid gas in the second environment compared to the first environment. (Item 10) The captured non-CO 2 acid gas is in a liquid non-CO 2 A method according to any one of items 1 to 9, forming a solid suspended in an acid gas adsorbent and concentrated by physical separation. (Item 11) The method according to item 10, wherein the physical separation uses a cross-flow filter, centrifugation, crystallization and / or sedimentation. (Item 12) The method according to item 11, wherein the cross-flow filter is operated at a temperature of at least 200 °C. (Item 13) The non-CO 2 At least a part of the non-CO acid gas containing at least a part of the acid gas 2 The method according to any one of items 1 to 12, wherein at least a part of the acid gas adsorbent is removed from the environment. (Item 14) Adding a solution to the environment and further comprising the step of precipitating at least a part of the non-CO acid gas adsorbent, the method according to any one of items 1 to 13. 2 (Item 15) The method according to item 14, wherein the solution contains calcium ions. (Item 16) As a result of the step of adding the solution, CaSO The method according to any one of items 14 to 15, wherein is precipitated. 4 (Item 17) A method comprising the step of regenerating an adsorbent exposed to an acid gas through exposure to steam so that at least a part of the acid gas is separated from the adsorbent. (Item 18) The adsorbent according to item 17, wherein the adsorbent comprises an alkali metal borate, A [wherein A is one or more alkali metals, B is boron, O is oxygen, and x is a number such that 0 < x < 1]. x B 1-x O 1.5-x (Item 19) The method according to item 18, wherein the alkali metal comprises lithium (Li), sodium (Na), potassium (K), and / or a mixture thereof. (Item 20) The method according to item 19, wherein the alkali metal comprises equal amounts of Li and Na. (Item 21) The method according to any one of items 17 to 20, wherein the adsorbent is in a molten form. (Item 22) The acid gas according to item 17 to 21, wherein the acid gas comprises carbon dioxide (CO )), sulfur dioxide (SO 2 ), nitrogen dioxide (NO 2 ), hydrogen sulfide (H 2 S), sulfur trioxide (SO 2 ), nitric oxide (NO) and / or carbonyl sulfide (COS). 3 (Item 23) The method according to any one of items 17 to 22, wherein the step of regenerating the adsorbent comprises removing a plurality of acid gases present in the adsorbent. (Item 24) The method according to any one of items 17 to 23, wherein at least 1% by weight of the adsorbent is regenerated. (Item 25) (Item 25) The method according to any one of items 17 to 24, wherein at least 1 mol% of the acid gas is released from the adsorbent during regeneration. (Item 26) The method according to any one of items 17 to 25, wherein the environment in which the adsorbent is exposed to the acid gas is the same as or similar in temperature to the environment in which the adsorbent is regenerated. (Item 27) The method according to any one of items 17 to 26, wherein the environment in which the adsorbent is exposed to the water vapor is at a temperature above 200 °C. (Item 28) The method according to any one of items 17 to 27, wherein the pressure of the environment in which the adsorbent is exposed to the water vapor is at least 1 bar. (Item 29) The method according to any one of items 17 to 28, wherein the pressure of the environment in which the adsorbent is exposed to the water vapor is at least 1.1 bar. (Item 30) The method according to any one of items 17 to 29, wherein the molar ratio of water vapor to the adsorbent is at least 0.1. (Item 31) The method according to any one of items 17 to 30, wherein the molar ratio of water vapor to the acid gas in the adsorbent is at least 1. (Item 32) The method according to any one of items 17 to 31, wherein the environment in which the adsorbent is exposed to the water vapor is part of an industrial process. (Item 33) The method according to any one of items 17 to 32, further comprising the step of subsequently cooling a mixture of water vapor and acid gas such that the condensed water vapor is separated from the acid gas. (Item 34) The method according to any one of items 17 to 33, wherein the acid gas is recovered with a purity of more than 50% by weight. (Item 35) The method according to any one of items 33 to 34, wherein the mixture is cooled in a heat exchanger before separation in a condenser to generate energy. (Item 36) The method according to any one of items 33 to 35, wherein the condensed water vapor is heated and recycled back into the regeneration environment. (Item 37) The method according to any one of items 17 to 36, wherein the water vapor quality is maintained at least in part by an energy source inside the process that generates the acid gas. (Item 38) The method according to any one of items 17 to 37, wherein the water vapor quality is maintained at least in part by the energy capacity of the fuel in the process that generates the acid gas. (Item 39) The method according to any one of items 17 to 38, wherein the steam quality is maintained, at least in part, by an energy source external to the process that generates the acid gas. (Item 40) The method according to any one of items 17 to 39, wherein the steam quality is maintained, at least in part, by a steam cycle powered by a process separate from the process that generates the acid gas. (Item 41) The method according to any one of items 17 to 40, wherein the step of regenerating comprises reducing the partial pressure of the acid gas in the environment around the adsorbent. (Item 42) The method according to any one of items 17 to 41, wherein the steam is chemically inert with respect to the adsorbent.

Claims

1. A non-CO ２ acid gas adsorbent containing a salt in molten form is exposed to an environment containing non-CO ２ acid gas such that at least a portion of the non-CO ２ acid gas interacts with the non-CO ２ acid gas adsorbent and at least a portion of the non-CO ２ acid gas is removed from the environment, wherein the salt in molten form comprises an alkali metal borate, MxB1-xO1.5-x [wherein M is one or more alkali metals, B is boron, O is oxygen, and x is a number such that 0 < x < 1], the method.

2. The method according to claim 1, wherein the alkali metal comprises lithium (Li), sodium (Na), potassium (K), and / or a mixture thereof.

3. The method according to claim 2, wherein the alkali metal comprises equal amounts of Li and Na.

4. The non-CO ２ acid gas is sulfur monoxide (SO), sulfur dioxide (SO ２ ), nitrogen dioxide (NO ２ ), hydrogen sulfide (H ２ S), sulfur trioxide (SO ３ ), nitric oxide (NO), nitrous oxide (N ２ O), dinitrogen trioxide (N ２ O ３ ), dinitrogen tetroxide (N ２ O ４ ), dinitrogen pentoxide (N ２ O ５ ), and / or carbonyl sulfide (COS), the method according to any one of claims 1 to 3.

5. The method according to any one of claims 1 to 4, wherein the environment is at a temperature of at least 200°C.

6. A plurality of non-CO ２ acid gases, the plurality of non-CO ２At least a portion of the acid gas is removed from the environment so that the non-CO ２ The method according to any one of claims 1 to 5, which interacts with an acid gas adsorbent. **Claim 7** The captured non-CO ２ The method according to any one of claims 1 to 6, wherein the acid gas is released and concentrated in the gas phase of another environment. **Claim 8** At least in part, the release is driven by a change in the partial pressure and / or temperature of the non-CO ２ acid gas in the second environment compared to the first environment, according to the method of claim 7. **Claim 9** The captured non-CO ２ acid gas forms a solid suspended in a liquid non-CO ２ The method according to any one of claims 1 to 8, wherein the acid gas adsorbent is concentrated by physical separation. **Claim 10** The method according to claim 9, wherein the physical separation uses a cross-flow filter, centrifugation, crystallization and / or sedimentation. **Claim 11** The method according to claim 10, wherein the cross-flow filter is operated at a temperature of at least 200 °C. **Claim 12** The non-CO ２ At least a portion of the acid gas-containing non-CO ２ At least a portion of the acid gas adsorbent is removed from the environment, according to the method of any one of claims 1 to 11. **Claim 13** Further comprising adding a solution to the environment to precipitate at least a portion of the non-CO ２ acid gas adsorbent, according to the method of any one of claims 1 to 12. **Claim 14** The method according to claim 13, wherein the solution contains calcium ions. **Claim 15** As a result of adding the solution, CaSO ４The method according to any one of claims 13 to 14, wherein [it] precipitates.

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