Carbon dioxide adsorbents, use of carbon dioxide adsorbents, carbon dioxide separation methods, carbon dioxide capture and storage plants, and carbon dioxide capture and storage methods.

Abstract

This invention provides a carbon dioxide adsorbent that can be used in a high-temperature pressure swing CO2 separation process in a hydrocarbon gasification process. [Solution] A carbon dioxide adsorbent is provided, on which at least one alkali metal element selected from the group consisting of lithium, rubidium, and cesium is supported on a carrier. This carbon dioxide adsorbent can be used in a high-temperature pressure swing CO2 separation process in a hydrocarbon gasification process.

Description

[Technical Field]

[0001] This invention relates to carbon dioxide adsorbents, the use of carbon dioxide adsorbents, carbon dioxide separation methods, carbon dioxide capture and storage plants, and carbon dioxide capture and storage methods. This application claims priority based on Japanese Patent Application No. 2022-164639, filed in Japan on October 13, 2022, and the contents of that application are incorporated herein by reference. [Background technology]

[0002] With the progression of global warming, reducing carbon dioxide (CO2) emissions has become an urgent necessity. While the use of renewable energy is being considered as a solution, it is currently difficult to meet all energy needs solely through these sources due to cost and power generation efficiency considerations. Energy supply methods that are expected to reduce CO2 emissions include power generation with CO2 separation and recovery from hydrocarbon fuels, and hydrogen production with CO2 separation and recovery from hydrocarbons (blue hydrogen). Both methods use combustible gas containing carbon monoxide (CO) and hydrogen (H2) generated by gasifying hydrocarbons, and when combined with CCS (Carbon Dioxide Capture and Storage) for CO2 recovery and storage, it becomes possible to supply energy while reducing CO2 emissions. One method for separating and recovering CO2 involves using an absorbent solution such as an amine aqueous solution. However, this method requires sufficient thermal energy to dissociate the chemically bonded CO2 during recovery from the absorbent solution. Therefore, there is a need for separation and recovery technologies that can be performed with lower energy consumption.

[0003] Patent Document 1 describes a carbon dioxide recovery technology that is excellent in energy saving and economic efficiency and can recover high concentrations of carbon dioxide with high processing capacity by the PSA method, which includes a carbon dioxide recovery apparatus having a separation device that separates carbon dioxide from gas by utilizing the adsorption and desorption of carbon dioxide to an adsorbent due to pressure fluctuations, and a carbon dioxide recovery method having a separation process that separates carbon dioxide from gas by utilizing the adsorption and desorption of carbon dioxide to an adsorbent due to pressure fluctuations.

[0004] Patent Document 2 describes a pressure swing adsorption method for removing light hydrocarbons from a hydrogen stream. This pressure swing adsorption method includes the steps of (a) passing a feed stream containing carbon dioxide and hydrocarbons over an adsorbent containing a metal-organic framework (MOF) material in an adsorption zone with a temperature and adsorption pressure sufficient to adsorb at least a portion of the carbon dioxide in the feed stream, and thereby continuing to pass the feed stream over the adsorbent for a time until the adsorbent substantially reaches its adsorption capacity, thereby generating an effluent hydrocarbon stream with reduced carbon dioxide content; (b) reducing the pressure in the adsorption zone to a sufficient desorption pressure for a time sufficient to desorb at least a portion of the carbon dioxide from the adsorption zone, and then extracting a desorbed effluent stream rich in carbon dioxide; and repressurizing the adsorption zone to the adsorption pressure, and repeating steps (a) and (b).

[0005] Patent Document 3 describes a method for recovering carbon dioxide, characterized by passing a gas containing water vapor and carbon dioxide through a porous material that has been dried by supporting 2K2CO3·3H2O in its pores.

[0006] Patent Document 4 describes a carbon dioxide adsorbent for adsorbing and separating carbon dioxide from a gas containing carbon dioxide, characterized in that the support for the carbon dioxide adsorbent is formed of mesoporous silica, and at least one element selected from the group consisting of Mg, Ca, Sr, Ba, Y, and La is supported on this support. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2016-040025 [Patent Document 2] Japan Special Publication No. 2009-521320 [Patent Document 3] Japanese Patent Publication No. 8-040715 [Patent Document 4] Japanese Patent Application Publication No. 2010-184229 [Overview of the project] [Problems that the invention aims to solve]

[0008] When recovering CO2 during energy supply from hydrocarbon fuels, the generated combustible gas (H2, CO) is converted to CO2 and H2 via an aqueous shift reaction, and the CO2 is recovered. Since the gas after the shift reaction is at high temperature and pressure, a high-temperature pressure swing CO2 adsorbent that adsorbs and desorbs by changing the pressure at high temperature is considered advantageous. In addition to pressure swing adsorbents, there are also temperature swing adsorbents, but they consume energy due to heating when desorbing CO2. On the other hand, since the gas from which CO2 is separated in the hydrocarbon gasification process is at high pressure, it is considered that adsorption and desorption can be performed with low energy because there is no need to pressurize the gas again to adsorb CO2 when using a pressure swing adsorbent.

[0009] The object of this invention is to provide a carbon dioxide adsorbent that can be used in a high-temperature pressure swing CO2 separation process in a hydrocarbon gasification process. [Means for solving the problem]

[0010] [1] A carbon dioxide adsorbent having at least one alkali metal element selected from the group consisting of lithium, rubidium, and cesium supported on a carrier. [2] The carbon dioxide adsorbent according to [1], wherein the carrier is further supported with at least one metal element selected from the group consisting of alkali metal elements other than lithium, rubidium, and cesium, alkaline earth metal elements, and transition metal elements. [3] The carbon dioxide adsorbent according to [1] or [2], wherein the carrier contains at least one metal element selected from the group consisting of alkali metal elements other than lithium, rubidium, and cesium, alkaline earth metal elements, group 13 metal elements, and transition metal elements. [4] The carbon dioxide adsorbent according to any one of [1] to [3], wherein the carrier is a carrier formed of a mesoporous material. However, mesoporous materials are porous materials that have pores with a diameter of 2 to 50 nm. [5] The carbon dioxide adsorbent according to [4], wherein the mesoporous material is mesoporous alumina. [6] The carbon dioxide adsorbent according to [4], wherein the mesoporous material is mesoporous silica. [7] The carbon dioxide adsorbent according to any one of [1] to [3], wherein the carrier is a metal-containing material that is not a mesoporous material. [8] The carbon dioxide adsorbent according to any one of [1] to [3], wherein the carrier is an aluminum-containing material that contains boehmite in at least part of it. [9] A carbon dioxide adsorbent consisting of a metal-containing material containing 35% by mass or more of alkali metal carbonates. However, carbonates refer to carbonates, bicarbonates, or compounds containing either or both carbonate ions and / or bicarbonate ions.

[10] The carbon dioxide adsorbent according to [9], wherein the alkali metal is at least one selected from the group consisting of cesium, rubidium, and sodium.

[11] The carbon dioxide adsorbent according to [9], wherein the alkali metal comprises at least one selected from the group consisting of cesium and rubidium, and at least one selected from the group consisting of lithium, sodium, and potassium.

[12] Use of alkali metal carbonates as carbon dioxide adsorbents.

[13] A carbon dioxide adsorbent according to any one of [1] to

[11] for separating and adsorbing carbon dioxide from a gas containing carbon dioxide and water.

[14] A carbon dioxide adsorbent according to any one of [1] to

[11] used in a pressure swing adsorption method.

[15] The carbon dioxide adsorbent according to

[14] , wherein carbon dioxide adsorption and desorption are performed at 80 °C or higher.

[16] Use of a carbon dioxide adsorbent according to any one of [1] to

[11] in a pressure swing adsorption method.

[17] The use according to

[16] , wherein carbon dioxide adsorption and desorption are performed at 80 °C or higher.

[18] A carbon dioxide separation method in a pressure swing adsorption method for separating carbon dioxide from a mixed gas containing carbon dioxide and water vapor, wherein a gas containing water vapor at a relative pressure of 0.10 or higher is introduced into an adsorption tower filled with a carbon dioxide adsorbent.

[19] A carbon dioxide separation method for adsorbing carbon dioxide to a carbon dioxide adsorbent under coexistence conditions of high-temperature and high-pressure steam with a total pressure of 1 MPa or higher, 10 vol% or more of water vapor, and a temperature of 100 °C or higher.

[20] The carbon dioxide separation method according to

[18] , using a carbon dioxide adsorbent having a characteristic that the carbon dioxide adsorption amount increases due to the presence of water vapor.

[21] The carbon dioxide separation method according to

[19] , using a carbon dioxide adsorbing material having a characteristic that the carbon dioxide adsorption amount increases due to the presence of water vapor.

[22] The carbon dioxide separation method according to

[20] , using a carbon dioxide adsorbent according to any one of [1] to

[11] as a carbon dioxide adsorbent having a characteristic that the carbon dioxide adsorption amount increases due to the presence of water vapor.

[23] The carbon dioxide separation method according to

[21] , using a carbon dioxide adsorbent according to any one of [1] to

[11] as a carbon dioxide adsorbent having a characteristic that the carbon dioxide adsorption amount increases due to the presence of water vapor.

[24] A gasification facility for gasifying a hydrocarbon fuel to produce a synthesis gas containing carbon monoxide and hydrogen, A gas purification facility for purifying the synthesis gas, A shift reaction apparatus is provided to obtain a mixed gas containing carbon dioxide, hydrogen, and water by subjecting the purified synthesis gas to a water-gas shift reaction. The system includes a pressure fluctuation adsorption type carbon dioxide separation and recovery facility that separates carbon dioxide from the aforementioned mixed gas and a hydrogen-rich gas containing hydrogen and water. In the pressure fluctuation adsorption type carbon dioxide separation and recovery equipment, the carbon dioxide separation method described in any of

[18] to

[23] is carried out. Carbon dioxide capture and storage plant.

[25] The carbon dioxide recovery and storage plant according to

[24] , wherein the pressure of the carbon dioxide supplied to the next process for utilizing or transporting the carbon dioxide discharged from the pressure fluctuation adsorption type carbon dioxide separation and recovery equipment is 0.5 to 1.0 MPaG.

[26] The carbon dioxide recovery and storage plant according to

[24] or

[25] , wherein the temperature of the mixed gas supplied from the shift reaction equipment to the pressure fluctuation adsorption type carbon dioxide separation and recovery equipment is 150 to 350°C and the pressure is 2.5 to 8.0 MPaG.

[27] Furthermore, the facility is equipped with a gas turbine combined cycle power generation system. A carbon dioxide capture and storage plant according to any one of

[24] to

[26] , wherein hydrogen separated from the mixed gas is supplied to the gas turbine combined cycle power generation equipment. A carbon dioxide capture and storage method using a carbon dioxide capture and storage plant described in any of

[28]

[24] to

[27] .

[29] A gasification facility that gasifies hydrocarbon fuels to produce synthesis gas containing carbon monoxide and hydrogen, A gas purification facility for purifying the aforementioned synthesis gas, A shift reaction apparatus is provided to obtain a mixed gas containing carbon dioxide, hydrogen, and water by subjecting the purified synthesis gas to a water-gas shift reaction. The system includes a pressure fluctuation adsorption type carbon dioxide separation and recovery facility that separates carbon dioxide from the aforementioned mixed gas and a hydrogen-rich gas containing hydrogen and water. The pressure fluctuation adsorption type carbon dioxide separation and recovery equipment has an adsorption tower filled with a carbon dioxide adsorbent described in any of [1] to

[11] , Carbon dioxide capture and storage plant.

[30] The carbon dioxide recovery and storage plant according to

[29] , wherein the pressure of the carbon dioxide supplied to the next process for utilizing or transporting the carbon dioxide discharged from the pressure fluctuation adsorption type carbon dioxide separation and recovery equipment is 0.5 to 1.0 MPaG.

[31] The carbon dioxide recovery and storage plant according to

[29] or

[30] , wherein the temperature of the mixed gas supplied from the shift reaction equipment to the pressure fluctuation adsorption type carbon dioxide separation and recovery equipment is 150 to 350°C and the pressure is 2.5 to 8.0 MPaG.

[32] Furthermore, the facility is equipped with a gas turbine combined cycle power generation system, A carbon dioxide capture and storage plant according to any one of

[29] to

[31] , wherein hydrogen separated from the mixed gas is supplied to the gas turbine combined cycle power generation equipment. A carbon dioxide capture and storage method using a carbon dioxide capture and storage plant described in any of

[33]

[29] to

[32] . [Effects of the Invention]

[0011] According to the present invention, a carbon dioxide adsorbent can be used in a high-temperature pressure swing CO2 separation process in a hydrocarbon gasification process. Furthermore, according to the present invention, it is possible to provide a carbon dioxide capture and storage plant and a carbon dioxide capture and storage method using the above-mentioned carbon dioxide adsorbent. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a diagram illustrating the estimated mechanism of carbon dioxide adsorption and release by a carbon dioxide adsorbent according to an example of an embodiment of the present invention. [Figure 2] Figure 2 is a schematic diagram of a carbon dioxide capture and storage plant, which is an example of an embodiment of the present invention. [Figure 3] Figure 3 illustrates the manufacturing procedure for mesoporous alumina (121_MAl) in an experimental example. [Figure 4]Figure 4 illustrates the manufacturing procedure for mesoporous alumina (121_MAl_3) supported with Cs2CO3 in an experimental example. [Figure 5] Figure 5 is a graph showing the CO2 adsorption isotherm per gram of Cs2CO3-supported mesoporous alumina in an experimental example. [Figure 6] Figure 6 illustrates the manufacturing procedure for mesoporous alumina (122_MAl_1) supported with Cs2CO3 and Na2CO3 in an experimental example. [Figure 7] Figure 7 is a graph showing the PSA measurement results for Experiment Example 3. [Figure 8] Figure 8 is a graph showing the PSA measurement results for Experimental Example 4. [Figure 9] Figure 9 shows the XRD measurement results of the adsorbent in Experimental Example 4 before PSA measurement. [Figure 10] Figure 10 shows the XRD measurement results after PSA measurement of the adsorbent in Experimental Example 4. [Figure 11] Figure 11 is a graph showing the PSA measurement results for Experiment Example 5. [Modes for carrying out the invention]

[0013] The embodiments of the present invention will be described in detail below. However, the present invention is not limited to the embodiments described later, and various modifications are possible as long as they do not depart from the spirit of the invention.

[0014] In this invention, when a numerical range is indicated using "~", that numerical range includes the values ​​at both ends.

[0015] [Carbon dioxide adsorbent] <First Embodiment> The carbon dioxide adsorbent of the first embodiment of the present invention (hereinafter also referred to as "CO2 adsorbent") has at least one alkali metal element selected from the group consisting of lithium (Li), rubidium (Rb), and cesium (Cs) (hereinafter sometimes referred to as "first alkali metal element") supported on a carrier.

[0016] Alkali metal elements are metallic elements belonging to Group 1 of the periodic table (https: / / iupac.org / what-we-do / periodic-table-of-elements / ), specifically lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr).

[0017] The first alkali metal element may be an elemental element or a compound element. Examples of the first alkali metal element compound include carbonates, citrates, acetates, nitrates, sulfates, chlorides, oxides, and superoxides, and at least one selected from the group consisting of these compounds is preferred, with carbonates being more preferred. Furthermore, the first alkali metal element may be an alloy of the first alkali metal elements, or an alloy of the first alkali metal element with the first alkali metal element described later.

[0018] In addition to the first alkali metal element, the CO2 adsorbent of this embodiment may also have at least one metal element selected from the group consisting of alkali metal elements other than the first alkali metal element (hereinafter also referred to as the "second alkali metal element"), alkaline earth metal elements, and transition metal elements (hereinafter also referred to as the "metal element other than the first alkali metal") supported on the carrier.

[0019] Furthermore, the CO2 adsorbent of this embodiment may contain at least one metal element selected from the group consisting of alkali metal elements other than lithium, rubidium, and cesium, alkaline earth metal elements, group 13 metal elements, and transition metal elements in the carrier.

[0020] The aforementioned metal elements can be added during the adsorbent manufacturing process using compounds containing those elements as raw materials, but it is also effective to incorporate them into the support beforehand as constituent elements of the support. For example, to add aluminum, it is possible to use a support containing aluminum and then subject it to heat treatment, steam treatment, or heated steam treatment under actual usage conditions to enhance the performance of the adsorbent.

[0021] The second alkali metal element is a metal element belonging to Group 1 of the periodic table (shown above), excluding lithium (Li), rubidium (Rb), and cesium (Cs), specifically sodium (Na), potassium (K), and francium (Fr). The second alkali metal element is preferably at least one selected from the group consisting of sodium (Na) and potassium (K), with sodium being more preferred.

[0022] The aforementioned alkaline earth metal elements are elements belonging to Group 2 of the periodic table (shown above), specifically beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). The alkaline earth metal element is preferably at least one selected from the group consisting of magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba). The alkaline earth metal element can be used alone or in combination of two or more.

[0023] The aforementioned Group 13 metallic elements are elements belonging to Group 13 of the periodic table (shown above) whose elemental form possesses metallic properties (for example, metallic luster, excellent electrical and thermal conductivity, and readily forming positive ions). Specifically, these include aluminum (Al), gallium (Ga), indium (In), and thallium (Tl).

[0024] The aforementioned transition metal elements are elements belonging to groups 3 through 12 of the periodic table (shown above), specifically including scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), technetium (Tc), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), cadmium (Cd), lanthanides, hafnium (Hf), tantalum (Ta), tungsten (W), rhenium (Re), osmium (Os), iridium (Ir), platinum (Pt), gold (Au), and mercury (Hg). The transition metal element is preferably at least one selected from the group consisting of scandium (Sc), yttrium (Y), transition metals of the fourth period of the periodic table (so-called 3d transition metals), and among these, manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), and lanthanides. The transition metal element can be used alone or in combination of two or more.

[0025] The aforementioned lanthanides are elements with atomic numbers from 57 to 71, that is, from lanthanum to ruthenium, specifically lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and ruthenium (Lu). The lanthanide is preferably at least one selected from the group consisting of lanthanum (La), cerium (Ce), neodymium (Nd), samarium (Sm), and ytterbium (Yb). The lanthanide can be used alone or in combination of two or more.

[0026] In the CO2 adsorbent of this embodiment, the alkali metals and other elements supported on the carrier do not adsorb CO2 molecules on their surface, but rather the entire supported amount undergoes a chemical reaction with CO2. Therefore, in principle, a larger amount of these elements is preferable, as it greatly affects the performance of the adsorbent. The amount of alkali metals and other elements supported is preferably 5 to 100, more preferably 20 to 100, and even more preferably 45 to 100, where [number of moles of the first alkali metal element / (total number of moles of the first alkali metal element and other metal elements)] × 100.

[0027] In the CO2 adsorbent of this embodiment, the amount of alkali metal elements supported on the carrier is not particularly limited, but the mass of the alkali metals, when converted to the weight of the corresponding carbonate, is preferably 15 to 95% by mass, more preferably 20 to 95% by mass, even more preferably 25 to 90% by mass, even more preferably 35 to 90% by mass, and even more preferably 50 to 90% by mass, relative to the total mass of the CO2 adsorbent. When the CO2 adsorbent of this embodiment has metal elements other than alkali metals supported on a mesoporous material, the amount of metal elements other than alkali metals, as the net mass of the metal elements, is preferably 3 to 95% by mass, more preferably 5 to 60% by mass, even more preferably 8 to 60% by mass, and even more preferably 10 to 60% by mass, relative to the total mass of the metal elements.

[0028] The carrier may be made of a mesoporous material, or it may be made of a metal-containing material that is not a mesoporous material.

[0029] The mesoporous material is a material containing pores with a pore diameter of 2 to 50 nm. The mesoporous material only needs to contain pores within this range, and may also contain a large amount of larger pores. Generally, catalyst supports manufactured and used for industrial catalysts, i.e., supports made of metal oxides such as silica, alumina, silica-alumina, zirconia, and titania, generally contain a large amount of pores with a diameter of 50 nm or more (referred to as "macropores"). These industrial catalyst supports are also suitable for use as the CO2 adsorbent in this embodiment if the ratio of the total volume of pores with a pore diameter of 2 to 50 nm to the total pore volume is 2% or more, preferably 5% or more, more preferably 10% or more, even more preferably 20% or more, even more preferably 30% or more, even more preferably 40% or more, even more preferably 50% or more, even more preferably 60% or more, even more preferably 70% or more, and particularly preferably 80% or more.

[0030] The mesoporous material is not particularly limited, but mesoporous alumina or mesoporous silica is preferred, and mesoporous alumina is more preferred.

[0031] The average pore size of the pores in the mesoporous material is preferably 2 to 50 nm, more preferably 2 to 20 nm, and even more preferably 2 to 10 nm. Here, the average pore size is a value obtained by analyzing nitrogen gas adsorption isotherms using the BJH method (Barrett-Joyner-Halenda method).

[0032] The pore volume of the aforementioned mesoporous material is 0.01 to 3.0 cm³. 3 A value of / g is preferred, and the size is 0.1 to 2.0 cm. 3 / g is more preferable, 0.2~1.5cm 3 / g is even more preferable. Here, the pore volume is a value obtained by measurement using the nitrogen gas adsorption method.

[0033] The specific surface area of ​​the aforementioned mesoporous material is 20 to 2000 m². 2 / g is preferred, and 50-1500m2 / g is more preferable, 100-1200m 2 / g is even more preferable. Here, the specific surface area is a value obtained by measurement using the nitrogen gas adsorption method.

[0034] The aforementioned mesoporous material can be manufactured by conventionally known methods. For example, mesoporous alumina can be produced by mixing an ethanol solution of Pluronic P123 with an ethanol solution of aluminum isopropoxide (Al(Oi-Pr)3) to which nitric acid has been added, and then drying and calcining the mixture. However, the production method is not limited to this method.

[0035] The metal-containing material that is not a mesoporous material is a metal-containing material other than the mesoporous material described above, and is, for example, a metal-containing material that is not a "porous material having pores with a diameter of 2 to 50 nm". The metal-containing material may be an elemental metal, or a compound such as an oxide, nitride, or carbide.

[0036] Examples of the metal-containing material include aluminum, aluminum alloys, and aluminum compounds such as aluminum oxide (alumina).

[0037] As a metal-containing material other than the aforementioned mesoporous material, an aluminum-containing material containing boehmite in part is preferred. As a carrier made of the aforementioned metal-containing material, an aluminum-containing material containing boehmite in at least part is preferred. Examples of the aforementioned aluminum-containing material include aluminum and various aluminum alloys. Boehmite is an aluminum hydrated oxide produced by holding aluminum or an aluminum alloy in high-temperature water or pressurized steam.

[0038] The loading of metallic elements such as cesium onto the aforementioned carrier can be carried out, for example, by immersing a mesoporous material in an aqueous solution of a salt of the metallic element and then drying it. However, this method is not limited to this method.

[0039] <Second Embodiment> The CO2 adsorbent of the second embodiment of the present invention consists of a metal-containing material containing 35% by mass or more, preferably 50% by mass or more, of an alkali metal compound.

[0040] The alkali metals mentioned above refer to metallic elements belonging to Group 1 of the periodic table (https: / / iupac.org / what-we-do / periodic-table-of-elements / ), specifically lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr).

[0041] Examples of alkali metal compounds include alkali metal carbonates. Here, carbonates mean carbonates, bicarbonates, or compounds containing either or both carbonate ions and bicarbonate ions. The carbonates may also contain other anions such as hydroxide ions. Examples of alkali metal carbonates include cesium, rubidium, or sodium carbonates, with at least one selected from the group consisting of cesium, rubidium, and sodium carbonates being preferred, at least one selected from the group consisting of cesium and rubidium carbonates being more preferred, and cesium carbonates being even more preferred.

[0042] Furthermore, it is preferable that the alkali metal carbonates include, as the alkali metal, at least one selected from the group consisting of cesium and rubidium, and at least one selected from the group consisting of lithium, sodium, and potassium.

[0043] Unlike the CO2 adsorbent of the first embodiment, the CO2 adsorbent of the present invention does not require a carrier.

[0044] The CO2 adsorbents of the first and second embodiments of the present invention described above are preferably used in the pressure swing adsorption method. In this case, the temperature (adsorption-desorption temperature) of CO₂ adsorption and desorption of the CO₂ adsorbent of the present embodiment is preferably 80°C or higher, more preferably 100°C or higher, further preferably 120°C, still more preferably 150°C or higher, even more preferably 160°C or higher, even more preferably 170°C or higher, and even more preferably 200°C or higher. The upper limit of the adsorption-desorption temperature is not particularly limited, but is preferably 400°C or lower, more preferably 350°C, and further preferably 300°C or lower.

[0045] <Estimated mechanism of CO₂ adsorption and release> Figure 1 is a diagram for explaining the estimated mechanism of CO₂ adsorption and release of the CO₂ adsorbent of the present invention. Taking the case where cesium carbonate (cesium carbonate, Cs₂CO₃) is supported on mesoporous alumina as an example, the mechanism of CO₂ adsorption and release of the CO₂ adsorbent of the present embodiment is not limited to the following explanation. First, under pressure, in the pores of mesoporous alumina supporting cesium carbonate (Cs₂CO₃), Cs₂CO₃ dissolves in the water formed by the condensation of water vapor in the mixed gas to form an aqueous Cs₂CO₃ solution. CO₂ in the mixed gas is absorbed by this aqueous Cs₂CO₃ solution to form an aqueous cesium hydrogen carbonate (CsHCO₃) solution. Thereby, CO₂ adsorption to the CO₂ adsorbent is performed. Next, under reduced pressure, as H₂O evaporates from the aqueous CsHCO₃ solution, CsHCO₃ precipitates and decomposes, generating CO₂. Thereby, the release of CO₂ from the CO₂ adsorbent is performed. The compound supported on the adsorbent may be any compound that can be converted into carbonates under the adsorption reaction conditions, and includes carbonates, bicarbonates, compounds containing carbonate ions or bicarbonate ions, and hydroxides. On the other hand, there may also be a mechanism in which carbonates adsorb (or absorb) and desorb CO₂ while remaining solid without the condensation and evaporation of water as shown in Figure 1.

[0046] <Function and effect> The carbon dioxide adsorbent of the present invention has the following characteristics (A) to (E). (A) The PSA process utilizes the change in water vapor partial pressure for separation. In other words, during CO2 adsorption, CO2 is adsorbed when water vapor comes into contact with the adsorbent, and during CO2 desorption, the water vapor partial pressure decreases by releasing the pressure, causing CO2 to desorb. (B) This control of water vapor partial pressure is achieved by introducing water vapor from the shift reactor into the PSA adsorption tower without intentionally removing it. During adsorption, the water vapor partial pressure is high, and after CO2 adsorption is complete, simply removing the gas reduces the water vapor partial pressure. (C) A necessary element for realizing this process is that the carbon dioxide adsorbent has the characteristic of adsorbing CO2 in the presence of water vapor and releasing CO2 when the partial pressure of water vapor decreases. (D) One mechanism that realizes this property is the mechanism shown in Figure 1. (E) Another way to achieve (C) above is to utilize a chemical reaction in which both CO2 and H2O react. Substance A+CO2+H2O⇔Substance B This is precisely the chemical reaction that occurs when cesium carbonate is present on its own. Cs2CO3 + CO2 + H2O ⇔ 2Cs(HCO3) In this invention, CO2 can be recovered simply by slightly reducing the pressure (releasing the pressure) without changing the temperature, thus significantly reducing the energy required for recovery compared to conventional methods.

[0047] [Carbon dioxide separation method] The present invention relates to a carbon dioxide separation method, which is a pressure swing adsorption method for separating carbon dioxide from a mixed gas containing carbon dioxide and water vapor, characterized in that a gas containing water vapor at a relative pressure of 0.10 or higher is introduced into an adsorption tower filled with a carbon dioxide adsorbent. The relative pressure of water vapor is not particularly limited as long as it is 0.10 or higher, but 0.20 or higher is preferable, and 0.40 or higher is more preferable. The upper limit of the relative pressure of water vapor is not particularly limited, but 0.90 or lower is preferable, and 0.85 or lower is more preferable. The saturated water vapor pressure is 1.15 MPa at 200°C, 3.98 MPa at 250°C, and 16.5 MPa at 350°C.

[0048] In this embodiment, the carbon dioxide separation method preferably involves adsorbing carbon dioxide onto the carbon dioxide adsorbent under high-temperature, high-pressure water vapor conditions, with a total pressure of 1 MPaG or higher, a water vapor content of 10% by volume or higher, and a temperature of 100°C or higher. The total pressure is not particularly limited as long as it is 1 MPa or higher, but is preferably 1.5 MPaG or higher, and more preferably 2.0 MPaG or higher. The upper limit of the total pressure is not particularly limited, but is preferably 8.0 MPaG or lower, and more preferably 3.5 MPaG or lower. The proportion of water vapor is not particularly limited as long as it is 10% by volume or more, but 15% by volume or more is preferred, and 20% by volume or more is more preferred. The upper limit of the proportion of water vapor is not particularly limited, but 90% by volume or less is preferred, and 70% by volume or less is more preferred. The temperature is not particularly limited as long as it is 100°C or higher, but 120°C or higher is more preferred, 150°C or higher is even more preferred, 160°C or higher is even more preferred, 170°C or higher is even more preferred, and 200°C or higher is even more preferred. The upper limit of the temperature is not particularly limited, but 400°C or lower is preferred, 350°C or lower is more preferred, and 300°C or lower is even more preferred.

[0049] In the carbon dioxide separation method of this embodiment, the carbon dioxide adsorbent used is preferably one that has the characteristic of increasing carbon dioxide adsorption capacity in the presence of water vapor, and the carbon dioxide adsorbent described above is more preferable.

[0050] [Carbon dioxide capture and storage plants and carbon dioxide capture and storage methods] The carbon dioxide capture and storage plant of this embodiment shown in Figure 2 comprises: a gasification facility 11 that gasifies hydrocarbon fuels such as coal, natural gas, and biomass to produce synthesis gas containing CO and H2; a gas purification facility 12 that purifies the synthesis gas containing carbon monoxide and hydrogen produced in the gasification facility 11 to remove sulfur, soot, etc.; a shift reaction facility 13 that subjects the purified synthesis gas to a water-gas shift reaction to produce a mixed gas containing CO2, H2, and water vapor; a pressure fluctuation adsorption type CO2 separation and recovery facility 16 that separates and recovers CO2 and hydrogen-rich gas (H2-rich gas) containing H2 and water vapor from the mixed gas; a combined cycle power generation facility 14 to which the H2-rich gas at a pressure of 2.5 to 8.0 MPaG and a temperature of 150 to 300°C, which is supplied after being heated and pressurized, and a chimney 15 that discharges exhaust gas from the combined cycle power generation facility 14.

[0051] The gasification facility 11 includes a gasifier that gasifies hydrocarbon fuels such as coal, natural gas, and biomass. To gasify coal, for example, in the gasifier, the coal is first crushed and dried in a pulverizer and then fed into the gasifier along with an oxidizer. In the gasifier, a high-temperature combustible gas (synthesis gas) mainly composed of CO and H2 is produced. There are three types of gasifiers used to gasify coal: (1) fixed bed or moving bed, (2) fluidized bed, and (3) jet bed. These differ in coal particle size, partial combustion temperature, and other factors. A fixed-bed gasifier is a method that gasifies coal placed on a grate over time, with coal lumps of 5-30 mm being fed in from the top and oxidizing agents such as oxygen supplied from the bottom of the furnace. Fluidized bed gasification is a method that uses relatively coarse particles with a diameter of several millimeters, and partially burns them while fluidizing them with air or other fluids to produce gas. Because combustion takes place at a relatively low temperature of around 1000°C, it is suitable for coal with a high ash melting point, and is also suitable for low-grade coal such as high-ash coal. Furthermore, because it can handle coarse particles, it is also effective for the utilization of waste and biomass. Jet-bed gasifiers use fine particles with a diameter of 0.1 mm or less and perform partial combustion at high temperatures of around 1800°C. Due to the small particle size, the specific surface area is large, and the reaction rate is extremely fast due to the high temperature. Furthermore, because the gasifier's design follows the cube law, it can be compact, achieve high output, and be highly economical. There are two methods of coal supply: dry (dry feed) and wet (slurry feed). In the wet method, coal is mixed with water to form a slurry, which can then be supplied to the gasifier via pipeline. Gasifying agents include oxygen (oxygen-blown) and air (air-blown). Oxygen-blown gas is suitable for hydrogen production because the resulting gas does not contain nitrogen. However, the power required for the air separation unit (ASU) used to produce oxygen as a gasifying agent is high, reducing the efficiency of the power plant. Therefore, for integrated coal gasification combined cycle (IGCC) power generation, air-blown gas is more efficient. When using hydrocarbon fuels, gaseous hydrocarbons such as natural gas or liquid hydrocarbons such as petroleum are mixed with air or oxygen. Biomass is pulverized and atomized before being mixed with air or oxygen, and partial combustion is carried out at around 1800°C.

[0052] The gas purification equipment 12 includes a gas heater 121, a water washing tower 122, a COS converter 123, and a desulfurization unit 124. The synthesis gas produced in the gasification facility 11 is mainly composed of CO and H2, but it also contains impurities such as nitrogen compounds (NH3) and sulfur compounds (H2S and COS), which are removed in the gas purification facility 12. In the washing tower 122, dust, trace components, and NH3 are removed. Since the sulfur compounds in synthesis gas are mainly in the forms of H2S (hydrogen sulfide) and COS (carbonyl sulfide), COS is converted to H2S by a catalytic reaction in the COS converter 123 to enable absorption in the amine aqueous solution. Then, in the desulfurization unit 124, the synthesis gas is passed through the amine aqueous solution to absorb H2S and remove sulfur.

[0053] In the shift reaction facility 13, CO and H2O (water vapor) are reacted at 200-400°C in the presence of a transition metal oxide such as iron oxide (Fe3O4 (magnetite)) or a catalyst such as platinum to produce CO2 and H2. The H2O (water vapor) can be the water vapor contained in the H2-rich gas separated in the pressure fluctuation adsorption type CO2 separation and recovery facility 16. The mixed gas containing CO2, H2, and water vapor produced in the shift reaction facility 13 is at a temperature of approximately 200-350°C and a pressure of approximately 2.5-3.5 MPaG. This mixed gas is introduced into the pressure fluctuation adsorption type CO2 separation and recovery facility 16 in a high-temperature, high-pressure state without any cooling or depressurization operations.

[0054] The pressure fluctuation adsorption type CO2 separation and recovery equipment 16 includes a pressure fluctuation adsorption type CO2 separation device. This pressure fluctuation adsorption type CO2 separation device has an adsorption tower filled with the carbon dioxide adsorbent described above.

[0055] The pressure of the CO2 supplied to the next process for utilizing or transporting the CO2 extracted from the pressure fluctuation adsorption type CO2 separation and recovery equipment 16 is not particularly limited, but it is preferably set to 0.5 to 1.0 MPaG.

[0056] The carbon dioxide capture and storage plant of this embodiment may further include a CO2 liquefaction unit 17 for liquefying the CO2 released from the pressure fluctuation adsorption type CO2 separation and recovery unit 16. By setting the pressure of the CO2 supplied to the next process for utilization or transport of the CO2 released from the pressure fluctuation adsorption type CO2 separation and recovery unit 16 to 0.5 to 1.0 MPaG, it can be used in the next process.

[0057] The H2-rich gas separated by the pressure fluctuation adsorption type CO2 separation and recovery equipment 16 is partially used in the shift reaction equipment 13, and the rest is heated to 300-350°C by the heat generated in the shift reaction equipment 13 before being supplied to the combined cycle power generation equipment 14, where it is used as the driving force for the gas turbine 141, and then the heat is recovered to the maximum extent possible in the waste heat recovery boiler 142 (HRSG: Heat Recovery Steam Generator). This heat is recovered as steam and becomes the power source for the steam turbine 143. The exhaust from the waste heat recovery boiler 142 is discharged through the chimney 15.

[0058] Furthermore, it is also preferable to implement the carbon dioxide separation method of the present invention described above in the pressure fluctuation adsorption type carbon dioxide separation and recovery equipment.

[0059] <Effects and Effects> In the carbon dioxide capture and storage plant of the present invention, by setting the pressure of the CO2 supplied to the next process for utilization or transport of the CO2 derived from the pressure fluctuation adsorption type CO2 separation and recovery equipment 16 to 0.5 to 1.0 MPaG, the CO2 can be supplied to the next process without further compression, making it possible to utilize the CO2 by partially omitting the compression process. [Examples]

[0060] The present invention will be described in more detail below with reference to experimental examples. However, the present invention is not limited to the experimental examples described later.

[0061] [Experimental Example 1] The manufacturing procedure for the mesoporous alumina (121_MAl) carrier is shown in Figure 3, and the manufacturing procedure for the mesoporous alumina (121_MAl_3) supported with Cs2CO3 is shown in Figure 4. Amount of Cs2CO3 supported on mesoporous alumina (121_MAl): 1.498 g per gram of MPA (mesoporous alumina) (4.598 mmol per gram of MPA) · Mass percentage of MPA relative to the total weight of the adsorbent: 40.03% by mass • Pore volume per gram of MPA: 0.05553 / 0.4003 = 0.1387 cm³3 / g ·Decrease in pore volume per MPa: 0.2789 - 0.1387 = 0.1402 cm 3 / g ·Assuming that the decrease in pore volume is due to the loading of Cs2CO3 Density of Cs2CO3: 4.072 g / cm 3 From this, per 1 g of MPA, (Cs2CO3 in pores) 1.752 mmol; (Cs2CO3 outside pores) 2.846 mmol: per 1 g of adsorbent, (Cs2CO3 in pores) 0.7014 mmol; (Cs2CO3 outside pores) 1.139 mmol

[0062] The CO2 adsorption amount of 121_MAl_3 was measured using a PSA device. The CO2 adsorption isotherm per 1 g of adsorbent for the 121_MAl_3 sample is shown in Fig. 5. Following the plot of the adsorption isotherm, it becomes like the solid line. <Conditions> Temperature of reaction tube and thermostat: 200 °C, He:CO2:H2O = 1:1:1 PSA lower limit pressure: 0.08 MPaG (at total pressure) Adsorption time: (Run 19, 21 - 28) 600 sec, (Run 20) 3600 sec Weight of adsorbent used: (121_MAl_3) 0.1075 g In Fig. 5, Run indicates the order of measurement. For this sample, measurements were carried out in the order from Run19 to Run28. Run19 was the first measurement with an adsorption time of 600 seconds, but the adsorption amount was not very high. Therefore, the adsorption time was extended, and when measured at 3600 seconds, the adsorption amount increased (Run20). After that, when measuring the low CO2 partial pressure part (Run21, 22) with the adsorption time returned to 600 seconds, a result with a higher adsorption amount than Run19 with a high CO2 partial pressure at the same 600 seconds was obtained. When measuring the adsorption amount at a CO2 partial pressure of 1 MPaG again with an adsorption time of 600 seconds, it was the same as the adsorption amount in Run20 with an adsorption time of 3600 seconds (Run24). These results suggest that the sample may have changed due to exposure to high-temperature water vapor in the adsorption gas. One possible reason for the increase in adsorption is that Cs2CO3, which was supported outside the pores, may have been incorporated into the pores and contributed to adsorption. It is also possible that aluminum, a constituent element of the alumina support, was added to the supported compound through heat treatment and water vapor treatment, improving the performance of the adsorbent. A large change in adsorption amount of 0.5 mol / kg was obtained with a narrow pressure range of 0.8 MPaG to 0.6 MPaG. An S-shaped adsorption isotherm, which allows for large changes in adsorption amount with small pressure changes, is ideal but was previously impossible. The CO2 partial pressure on the horizontal axis is gauge pressure (MPaG). The adsorption amount measured under the same conditions as Run24, except for the absence of water vapor, was approximately 0.2 mmol per gram of adsorbent, and the adsorption amount decreased significantly in the absence of water vapor compared to when water vapor was present (Run24).

[0063] Table 1 shows the adsorption amount per gram of MPA for Run 19 and 20, and the amount of Cs2CO3 inside and outside the pores of the sample.

[0064] [Table 1]

[0065] Table 1 shows that in Run 19 (the first measurement), the amount of adsorption per gram of MPA is less than the amount of Cs2CO3 in the pores (Cs2CO3 + CO2 + H2O → 2CsHCO3, so Cs2CO3 and CO2 react in a 1:1 ratio), but in Run 20, the amount of adsorption per gram of MPA is greater than the amount of Cs2CO3 in the pores.

[0066] [Experimental Example 2] Samples supporting both Cs2CO3 and Na2CO3 were prepared with the expectation that using Na2CO3, which has a lower molecular weight than Cs2CO3, would increase the amount of adsorption per gram of adsorbent. 122_MAl_1 was prepared by supporting Cs2CO3 and Na2CO3 on mesoporous alumina 122_MAl. 122_MAl was prepared using the same procedure as 121_MAl. The preparation procedure for 122_MAl_1 is shown in Figure 6. Since Na2CO3 has lower solubility than Cs2CO3, it was not possible to create a solution as concentrated as that of Cs2CO3, so the solution was added dropwise and dried twice.

[0067] Table 2 shows the pore diameter, pore volume, and BET specific surface area values ​​for 122_MAl and 122_MAl_1. The pore volume in Table 2 is the value per gram of adsorbent.

[0068] [Table 2]

[0069] Regarding 〇122_MAl_1 (MPA: ) • Amount of Cs2CO3 and Na2CO3 supported on 122_MAl: Cs2CO3 2.343 mmol per 1 g of mesoporous alumina (MPA); Na2CO3 2.344 mmol per 1 g of MPA • Mass percentage of MPA relative to the total weight of the adsorbent: 49.71% by mass • Pore volume per gram of MPA: 0.051072 / 0.4971 = 0.1027 cm³ 3 / g • Decrease in pore volume per MPA: 0.3217 - 0.1027 = 0.2190 cm³ 3 / g The decrease in pore volume corresponds to the loading of Cs2CO3 and Na2CO3, and assuming that Cs2CO3 and Na2CO3 are loaded in a 1:1 ratio within the pores, the density of Cs2CO3 is 4.072 g / cm³. -3 The density of Na2CO3 is 2.533 g / cm³. 3 twist, Per 1g of MPA, there are 1.80 mmol each of (intrapore Cs2CO3, Na2CO3) and 0.55 mmol each of (extrapore Cs2CO3, Na2CO3). Per gram of adsorbent, 0.89 mmol each of (intrapore Cs2CO3, Na2CO3) and 0.27 mmol each of (extrapore Cs2CO3, Na2CO3) are present. The amount of Cs+Na (122_MAl_1) supported per gram of MPA was similar to that of Cs (121_MAl_3), but the amount contained within the pores was greater in the Cs+Na sample. Using this adsorbent, the amount of CO2 adsorbed was measured under the same conditions as in Figure 5. The amount of adsorbed CO2 at a partial pressure of 1 MPaG reached 800 μmol.

[0070] [Experimental Example 3] We compared the CO2 adsorption performance of alumina carriers with pores (pore-containing) and alumina carriers without pores (pore-free). Alumina supports with the characteristics shown in Table 3 were used, and PSA measurements were performed in the same manner as in Experimental Example 1.

[0071] [Table 3]

[0072] The PSA measurement results are shown in Figure 7. Alumina carriers with pores (pored) and alumina carriers without pores (non-pored) showed nearly equivalent CO2 adsorption performance in terms of maximum adsorption capacity. On the other hand, the dependence of CO2 adsorption capacity on CO2 partial pressure changed depending on the presence or absence of pores.

[0073] XRD analysis of the alumina support (without pores) after PSA measurement revealed the formation of boehmite on the alumina support. This boehmite was produced by the reaction of alumina with water.

[0074] [Experimental Example 4] <PSA measurement of cesium carbonate alone> Cesium carbonate, which had been dissolved and reprecipitated, was individually packed into a 1 / 4-inch reaction tube, and PSA measurement was performed.

[0075] (Measurement conditions) Reaction tube temperature during high-temperature phase: 200℃, He:CO2:H2O=1:1:1 PSA lower limit pressure (total pressure): 0.3 MPaG Adsorption time: 600 seconds (3600 seconds for Run 5 only) Mass of adsorbent (cesium carbonate): 0.0594g

[0076] The PSA measurement results are shown in Figure 8. High adsorption was achieved only in Run 1, and the adsorption decreased thereafter. Runs 1-3 and Runs 4-7 are data measured on separate days. In Run 5, the adsorption time was extended to 3600 seconds, and the adsorption amount increased compared to Run 6, which had an adsorption time of 600 seconds, but it did not reach the adsorption amount of Run 1.

[0077] Cesium carbonate is thought to adsorb CO2 through the following reaction. Cs2CO3 + H2O + CO2 → 2CsHCO3 Since 1 g of cesium carbonate is 3069 μmol, the reaction rate of Cs2CO3 in Run 1 was 59%.

[0078] Figure 9 shows the XRD measurement results of the adsorbent before PSA measurement, and Figure 10 shows the XRD measurement results after PSA measurement. Cs2CO3 showed different peaks before and after PSA measurement.

[0079] [Experimental Example 5] <PSA measurement using rubidium carbonate alone> Using rubidium carbonate that had been dissolved and reprecipitated, PSA measurements were performed in the same manner as in Experimental Example 4.

[0080] (Measurement conditions) Reaction tube temperature during high-temperature phase: 200℃, He:CO2:H2O=1:1:1 PSA lower limit pressure (total pressure): 0.3 MPaG Adsorption time: 600 seconds Mass of adsorbent (rubidium carbonate): 0.0563g Dead volume: 0.497cm before PSA measurement 3, after PSA measurement 0.598cm 3 Number of moles in 1g of rubidium carbonate: 4330 μmol

[0081] The PSA measurement results are shown in Figure 11. After measuring PSA levels, the dead volume was remeasured and found to be approximately 0.1 cm³. 3 The amount of CO2 absorbed had increased. Therefore, two values ​​were plotted for CO2 absorption: the value obtained by subtracting the amount of CO2 leaching out from the dead volume before PSA measurement (gray rectangle) and the value obtained by subtracting the amount of CO2 leaching out from the dead volume after PSA measurement (white rectangle). Compared to an adsorbent with rubidium carbonate supported on a mesoporous alumina carrier (data not shown), the adsorbent made of rubidium carbonate alone showed increased CO2 adsorption.

[0082] [Experimental Example 6] <Repeated PSA measurements using cesium carbonate alone> The following experiment was conducted to measure the adsorption performance of cesium carbonate itself, which is a type of carbonate.

[0083] 0.1041 g of cesium carbonate (Cs2CO3) was packed into a reaction tube, and the gas composition was set to CO2:H2O:He = 1:1:1 (molar ratio). Adsorption was carried out at a temperature of 200°C and a total pressure of 3.0 MPaG for 600 seconds. After that, the total pressure was reduced to 0.3 MPaG, and the amount of CO2 desorbed from the adsorbent was quantified. This operation was repeated 12 times, and the amount of adsorption per gram of adsorbent was determined, yielding the results shown in Table 4. From these results, it was found that cesium carbonate itself has a sufficient adsorption capacity.

[0084] [Table 4]

[0085] [Experimental Example 7] <PSA measurement of cesium bicarbonate alone> The following experiment was conducted to measure the adsorption performance of cesium bicarbonate itself, which is a type of carbonate.

[0086] 0.1002 g of cesium bicarbonate (CsHCO3) was packed into a reaction tube, and the gas composition was set to CO2:H2O:He = 1:1:1 (molar ratio). Adsorption was carried out at a temperature of 200°C and a total pressure of 3.0 MPaG for 600 seconds. After that, the total pressure was reduced to 0.3 MPaG, and the amount of CO2 desorbed from the adsorbent was quantified. This operation was repeated 12 times, and the amount of adsorption per gram of adsorbent was determined, yielding the results shown in Table 5. From these results, it was found that cesium bicarbonate itself has a sufficient adsorption capacity.

[0087] [Table 5]

[0088] [Experimental Example 8] <PSA measurement of cesium bicarbonate alone> The amount of CO2 adsorbed onto cesium bicarbonate itself was measured under conditions without water vapor. 0.1029 g of cesium bicarbonate (CsHCO3) was packed into a reaction tube, and the gas composition was set to CO2:H2O:He=1:0:1 (molar ratio). Adsorption was carried out at a temperature of 200°C and a total pressure of 2.0 MPaG for 600 seconds. After that, the total pressure was reduced to 0.3 MPaG, and the amount of CO2 desorbed from the adsorbent was quantified. The same procedure was performed twice, and in both cases the quantitative results were below the detection limit (within the measurement error). From these experimental results, it was concluded that in the absence of water vapor, the adsorption of CO2 to cesium bicarbonate and the desorption of CO2 from cesium bicarbonate do not occur. [Explanation of symbols]

[0089] 11…Gasification equipment 12…Gas purification equipment 121... Gas heater 122…Water washing tower 123...COS converter 124...Desulfurization equipment 13… Shift reaction equipment 14…Combined cycle power generation equipment 141... Gas turbine 142... Heat recovery boiler 143... Steam Turbine 15… Chimney 16…Pressure fluctuation adsorption type CO2 separation and recovery equipment 17…CO2 liquefaction equipment 20... Compressor

Claims

1. A carbon dioxide adsorbent used in pressure swing adsorption, consisting of a metal-containing material containing 35% by mass or more of alkali metal carbonates. However, carbonates refer to carbonates, bicarbonates, or compounds containing either or both carbonate ions and / or bicarbonate ions.

2. The carbon dioxide adsorbent according to claim 1, wherein the alkali metal is at least one selected from the group consisting of cesium, rubidium, and sodium.

3. The carbon dioxide adsorbent according to claim 1, wherein the alkali metal comprises at least one selected from the group consisting of cesium and rubidium, and at least one selected from the group consisting of lithium, sodium, and potassium.

4. Use of alkali metal carbonates as carbon dioxide adsorbents in pressure swing adsorption.

5. A carbon dioxide adsorbent according to any one of claims 1 to 3, for separating and adsorbing carbon dioxide from a gas containing carbon dioxide and water.

6. The carbon dioxide adsorbent according to claim 1, wherein carbon dioxide adsorption and desorption occur at temperatures of 80°C or higher.

7. The use of a carbon dioxide adsorbent according to any one of claims 1 to 3, wherein carbon dioxide adsorption and desorption are performed at 80°C or higher in a pressure swing adsorption method.

8. A pressure swing adsorption method for separating carbon dioxide from a mixed gas containing carbon dioxide and water vapor, wherein a gas containing water vapor at a relative pressure of 0.10 or higher is introduced into an adsorption tower filled with a carbon dioxide adsorbent.

9. A carbon dioxide separation method using a pressure swing adsorption method, in which carbon dioxide is adsorbed onto a carbon dioxide adsorbent under high-temperature, high-pressure water vapor conditions, with a total pressure of 1 MPa or more, a water vapor content of 10% by volume or more, and a temperature of 100°C or higher.

10. The carbon dioxide separation method according to claim 8, wherein a carbon dioxide adsorbent is used that has the characteristic of increasing carbon dioxide adsorption capacity in the presence of water vapor.

11. The carbon dioxide separation method according to claim 9, wherein a carbon dioxide adsorbent is used that has the characteristic of increasing carbon dioxide adsorption capacity in the presence of water vapor.

12. The carbon dioxide separation method according to claim 10, wherein the carbon dioxide adsorbent described in any one of claims 1 to 3 is used as a carbon dioxide adsorbent characterized by an increased carbon dioxide adsorption capacity in the presence of water vapor.

13. The carbon dioxide separation method according to claim 11, wherein the carbon dioxide adsorbent described in any one of claims 1 to 3 is used as a carbon dioxide adsorbent characterized by an increased carbon dioxide adsorption amount in the presence of water vapor.

14. A gasification facility that gasifies hydrocarbon fuels to produce synthesis gas containing carbon monoxide and hydrogen, A gas purification facility for purifying the aforementioned synthesis gas, A shift reaction apparatus is provided to obtain a mixed gas containing carbon dioxide, hydrogen, and water by subjecting the purified synthesis gas to a water-gas shift reaction. The system includes a pressure fluctuation adsorption type carbon dioxide separation and recovery facility that separates carbon dioxide from the aforementioned mixed gas and a hydrogen-rich gas containing hydrogen and water. In the pressure fluctuation adsorption type carbon dioxide separation and recovery equipment, the carbon dioxide separation method described in claim 8 or 9 is implemented. Carbon dioxide capture and storage plant.

15. The carbon dioxide recovery and storage plant according to claim 14, wherein the pressure of the carbon dioxide supplied to the next process for utilizing or transporting the carbon dioxide discharged from the pressure fluctuation adsorption type carbon dioxide separation and recovery equipment is 0.5 to 1.0 MPaG.

16. The carbon dioxide recovery and storage plant according to claim 14, wherein the temperature of the mixed gas supplied from the shift reaction equipment to the pressure fluctuation adsorption type carbon dioxide separation and recovery equipment is 150 to 350°C and the pressure is 2.5 to 8.0 MPaG.

17. Furthermore, it is equipped with a gas turbine combined cycle power generation facility. The carbon dioxide capture and storage plant according to claim 14, wherein hydrogen separated from the mixed gas is supplied to the gas turbine combined cycle power generation equipment.

18. A method for capturing and storing carbon dioxide using the carbon dioxide capture and storage plant described in claim 14.

19. A gasification facility that gasifies hydrocarbon fuels to produce synthesis gas containing carbon monoxide and hydrogen, A gas purification facility for purifying the aforementioned synthesis gas, A shift reaction apparatus is provided to obtain a mixed gas containing carbon dioxide, hydrogen, and water by subjecting the purified synthesis gas to a water-gas shift reaction. The system includes a pressure fluctuation adsorption type carbon dioxide separation and recovery facility that separates carbon dioxide from the aforementioned mixed gas and a hydrogen-rich gas containing hydrogen and water. The pressure fluctuation adsorption type carbon dioxide separation and recovery equipment has an adsorption tower filled with the carbon dioxide adsorbent described in any one of claims 1 to 3. Carbon dioxide capture and storage plant.

20. The carbon dioxide recovery and storage plant according to claim 19, wherein the pressure of the carbon dioxide supplied to the next process for utilizing or transporting the carbon dioxide discharged from the pressure fluctuation adsorption type carbon dioxide separation and recovery equipment is 0.5 to 1.0 MPaG.

21. The carbon dioxide recovery and storage plant according to claim 19, wherein the temperature of the mixed gas supplied from the shift reaction equipment to the pressure fluctuation adsorption type carbon dioxide separation and recovery equipment is 150 to 350°C and the pressure is 2.5 to 8.0 MPaG.

22. Furthermore, it is equipped with a gas turbine combined cycle power generation facility. The carbon dioxide capture and storage plant according to claim 19, wherein hydrogen separated from the mixed gas is supplied to the gas turbine combined cycle power generation equipment.

23. A method for capturing and storing carbon dioxide using the carbon dioxide capture and storage plant described in claim 19.

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