Carbon dioxide capture system and carbon dioxide capture method

Abstract

To provide a carbon dioxide recovery system and a carbon dioxide recovery method capable of improving carbon dioxide recovery efficiency without needing much energy in a DAC.SOLUTION: This carbon dioxide recovery system comprises: a carbon dioxide separation unit that stores a first material enabling separation of a carbon dioxide contained in a gas; and a preprocessing unit positioned upstream of the carbon dioxide separation unit and connected to the carbon dioxide separation unit through a first pipeline. The preprocessing unit includes a storage container and a second material stored in the storage container. The second material has a Si / Al mol ratio of 0.7-1.3 and a peak near 2θ=20, 26, 35, 39° in a powder X-ray diffraction pattern using Cu as an X-ray source, and contains a low crystalline laminar clay mineral having a peak caused by OH-Si-(OAl)3 in a 29Si solid NMR spectrum and a peak observed within the range of -84 to -94 ppm, and an aluminum silicate composite containing an amorphous aluminum silicate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a carbon dioxide capture system and a method for capturing carbon dioxide. [Background technology]

[0002] Direct air capture (DAC) technology is known, which directly captures carbon dioxide contained in the atmosphere. For example, Patent Document 1 describes a carbon dioxide capture system that includes multiple capture structures for capturing carbon dioxide. Patent Document 1 describes that the capture structures are formed by impregnating a porous material with an adsorbent, such as an amine compound.

[0003] Patent Document 2 discloses a carbon dioxide adsorbent having a specific Si / Al ratio, 29 The paper discloses a carbon dioxide adsorbent made of amorphous aluminum silicate that has a peak in a specific range in the Si solid-state NMR spectrum. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-502736 [Patent Document 2] International Publication No. 2008 / 129968 Brochure Summary of the Invention [Problem to be solved by the invention]

[0005] Further improvement in the carbon dioxide capture efficiency of DAC is desired. At the same time, reducing energy consumption is an issue for commercialization of DAC. In other words, further improvement in the energy efficiency of DAC is also desired. Therefore, one of the objectives of the present disclosure is to provide a carbon dioxide capture system that can improve the carbon dioxide capture efficiency in DAC without requiring a large amount of energy. Another objective is to provide a carbon dioxide capture method that can improve the carbon dioxide capture efficiency in DAC without requiring a large amount of energy. [Means for solving the problem]

[0006] A carbon dioxide capture system according to the present disclosure includes a carbon dioxide separation unit that accommodates a first material capable of separating carbon dioxide contained in a gas, and a pretreatment unit that is located upstream of the carbon dioxide separation unit and is connected to the carbon dioxide separation unit via a first pipe. The pretreatment unit includes a container and a second material accommodated in the container. The second material has a Si / Al molar ratio of 0.7 to 1.3, and has peaks at around 2θ=20, 26, 35, and 39° in a powder X-ray diffraction pattern using Cu as an X-ray source. 29 It contains an aluminum silicate complex consisting of a low-crystalline layered clay mineral and amorphous aluminum silicate, which has a peak due to OH-Si-(OAl)3 and a peak observed in the range of -84 to -94 ppm in the Si solid-state NMR spectrum.

[0007] A method for recovering carbon dioxide according to the present disclosure includes: a carbon dioxide separation unit that accommodates a first material capable of separating carbon dioxide contained in a gas; and a pretreatment unit that is located upstream of the carbon dioxide separation unit, is connected to the carbon dioxide separation unit via a first pipe, and accommodates a second material that is capable of adsorbing moisture, wherein the second material has a Si / Al molar ratio of 0.7 to 1.3, and has peaks at around 2θ=20, 26, 35, and 39° in a powder X-ray diffraction pattern using Cu as an X-ray source; 29The carbon dioxide recovery system includes an aluminum silicate complex made of amorphous aluminum silicate and a low-crystalline layered clay mineral having a peak due to OH-Si-(OAl)3 and a peak observed in the range of -84 to -94 ppm in a Si solid-state NMR spectrum, and includes a pretreatment step of circulating a gas containing moisture and carbon dioxide through the pretreatment step, and a carbon dioxide separation step of circulating the gas from the pretreatment step through the carbon dioxide separation section via the first pipe. [Effects of the Invention]

[0008] According to the carbon dioxide capture system, the carbon dioxide capture efficiency can be improved in the DAC without requiring a large amount of energy. According to the carbon dioxide capture method, the carbon dioxide capture efficiency can be improved without requiring a large amount of energy. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of a carbon dioxide capture system according to the present disclosure. [Figure 2] FIG. 2 is a control flow showing an example of control of the pretreatment section in the carbon dioxide capture system. [Figure 3] FIG. 3 is a schematic diagram showing the configuration of a test device used in a demonstration test of a carbon dioxide capture system according to the present disclosure. [Figure 4] FIG. 4 is a graph showing the results of a first practical test example of the carbon dioxide capture system according to the present disclosure. [Figure 5] FIG. 5 is a graph showing the results of Comparative Test Example 1 of the carbon dioxide capture system according to the present disclosure. [Figure 6] FIG. 6 is a graph showing the results of Comparative Test Example 2 of the carbon dioxide capture system according to the present disclosure. [Figure 7] FIG. 7 is a graph showing the results of a second practical test example of a carbon dioxide capture system according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Outline of implementation] First, embodiments of the present disclosure will be listed and explained. A carbon dioxide capture system according to the present disclosure includes a carbon dioxide separation unit that accommodates a first material capable of separating carbon dioxide contained in a gas, and a pre-treatment unit that is located upstream of the carbon dioxide separation unit and is connected to the carbon dioxide separation unit via a first pipe. The pre-treatment unit includes a storage container and a second material that is stored in the storage container. The second material has a Si / Al molar ratio of 0.7 to 1.3, and has peaks at around 2θ=20, 26, 35, and 39° in a powder X-ray diffraction pattern using Cu as an X-ray source, 29 It contains an aluminum silicate complex consisting of a low-crystalline layered clay mineral and amorphous aluminum silicate, which has a peak due to OH-Si-(OAl)3 and a peak observed in the range of -84 to -94 ppm in the Si solid-state NMR spectrum.

[0011] Technologies for practical application of DAC are being investigated. Conventional DAC systems use physical adsorption, chemical adsorption, carbon dioxide separation membranes, and combinations of these as means for separating carbon dioxide from gas. Because the carbon dioxide concentration in the gas to be treated in DAC is relatively low, on the order of several hundred ppm or less, it is desirable to be able to efficiently separate carbon dioxide from the gas to be treated, regardless of the method used. Against this background, methods for improving the carbon dioxide separation efficiency have been investigated. It has been thought that moisture contained in the gas to be treated is one of the factors that inhibit carbon dioxide separation during carbon dioxide separation.

[0012] Therefore, the idea of ​​providing a pretreatment section in a DAC system to remove moisture from the gas to be treated before supplying the gas to the carbon dioxide separation section was conceived. Conventional devices for removing moisture from gases, such as cooling dehumidifiers, require a lot of energy to remove moisture from large volumes of gas to be treated. Therefore, the use of adsorbents capable of adsorbing moisture in gases for dehumidification was considered. However, it was found that adsorbents adsorb carbon dioxide along with moisture, resulting in carbon dioxide loss before the gas to be treated reaches the carbon dioxide separation section. Therefore, a search was conducted for an adsorbent that selectively removes moisture from gases containing both moisture and carbon dioxide. It was found that an adsorbent with a specific chemical structure can selectively adsorb moisture from gases containing both moisture and carbon dioxide, dehumidify the gas without requiring a lot of energy, and minimize carbon dioxide loss in the pretreatment section.

[0013] The carbon dioxide capture system according to the present disclosure is provided with a pretreatment unit upstream of a carbon dioxide separation unit, and the pretreatment unit has a Si / Al molar ratio of 0.7 to 1.3, and in a powder X-ray diffraction pattern using Cu as an X-ray source, has peaks at around 2θ=20, 26, 35, and 39°, 29The present invention includes an aluminum silicate composite (second material) composed of a low-crystalline layered clay mineral having a peak due to OH-Si-(OAl)3 and a peak observed in the range of -84 to -94 ppm in the Si solid-state NMR spectrum, and an amorphous aluminum silicate. By using this specific second material in pretreatment, it is possible to remove moisture from the gas to be treated without requiring a large amount of energy. At the same time, carbon dioxide loss in the pretreatment section is minimal, making it possible to supply a gas containing carbon dioxide to the carbon dioxide separation section, thereby improving the carbon dioxide recovery efficiency in the DAC system. The aluminum silicate composite, which is the second material, includes a material known as HASClay (registered trademark). HASClay (registered trademark) was known as a material that adsorbs both carbon dioxide and moisture, but the selectivity between carbon dioxide and moisture discovered in this disclosure was not known, and its use as a pretreatment agent in DAC was not anticipated.

[0014] In the carbon dioxide capture system, the first material and the second material may be different materials. By using different materials for the material for carbon dioxide separation in the carbon dioxide separation section (first material) and the moisture adsorption material in the pretreatment section (second material), the carbon dioxide adsorption efficiency can be further improved, and the effects of the present disclosure can be reliably obtained.

[0015] In the carbon dioxide recovery system, the pre-treatment section includes the storage vessel and the No. a first pre-treatment unit including the container and the first material; No.and a second pretreatment unit different from the first pretreatment unit. The pretreatment unit may further include: a second pipe different from the first pipe, connecting the first pretreatment unit and an outlet side of the carbon dioxide separation unit and equipped with a first switching mechanism capable of switching between a state in which the first pretreatment unit and the carbon dioxide separation unit are in communication with each other and a state in which the first pretreatment unit and the carbon dioxide separation unit are not in communication with each other; and a third pipe connecting the second pretreatment unit and the outlet side of the carbon dioxide separation unit and equipped with a second switching mechanism capable of switching between a state in which the second pretreatment unit and the carbon dioxide separation unit are in communication with each other and a state in which the second pretreatment unit and the carbon dioxide separation unit are not in communication with each other. By configuring the pretreatment unit to include multiple units, it is possible to perform pretreatment while switching between the multiple units, and carbon dioxide adsorption can be performed continuously. Furthermore, by providing piping that connects the outlet side of the carbon dioxide separation section with each pretreatment unit, the exhaust gas discharged from the carbon dioxide separation section can be used to regenerate the moisture absorbent material (second material) in the pretreatment section.

[0016] In the carbon dioxide capture system, the first material may be a material that captures carbon dioxide by physical adsorption. Physical adsorption carbon dioxide capture is believed to be susceptible to moisture contained in the energy processing gas. Therefore, the configuration according to the present disclosure, which includes a pre-processing section that removes moisture from the gas and minimizes carbon dioxide loss, can more reliably achieve the effects of the present disclosure.

[0017] A method for recovering carbon dioxide according to the present disclosure includes: a carbon dioxide separation unit that accommodates a first material capable of separating carbon dioxide contained in a gas; and a pretreatment unit that is located upstream of the carbon dioxide separation unit, is connected to the carbon dioxide separation unit via a first pipe, and accommodates a second material that can adsorb moisture, wherein the second material has a Si / Al molar ratio of 0.7 to 1.3, and has peaks at around 2θ=20, 26, 35, and 39° in a powder X-ray diffraction pattern using Cu as an X-ray source; 29A carbon dioxide capture system includes an aluminum silicate composite composed of an amorphous aluminum silicate and a low-crystalline layered clay mineral having a peak due to OH-Si-(OAl)3 and a peak observed in the range of -84 to -94 ppm in a Si solid-state NMR spectrum, and the system includes a pretreatment step of passing a gas containing moisture and carbon dioxide through the pretreatment step, and a carbon dioxide separation step of passing the gas from the pretreatment step through the carbon dioxide separation step. This capture method achieves DAC with high carbon dioxide capture efficiency and low energy consumption.

[0018] In the pretreatment step, the pressure of the gas supplied to the pretreatment section may be 90 kPaA or more and 300 kPaA or less, and the treatment temperature in the pretreatment section may be 0°C or more and 50°C or less. According to a system having the above configuration, in the pretreatment step, the moisture content in the gas to be treated can be reduced at a temperature near atmospheric pressure and 100°C or less (particularly, 50°C or less). According to this method, it becomes possible to capture carbon dioxide while further suppressing energy consumption.

[0019] The carbon dioxide recovery method may further include a pretreatment unit regeneration step of circulating the gas that has passed through the carbon dioxide separation unit through the pretreatment unit. The second material used in the pretreatment unit of the recovery method according to the present disclosure can be easily regenerated by adsorbing moisture and then contacting it with air at a relatively low temperature of 100°C or less. This recovery method makes it possible to recover carbon dioxide continuously with low energy consumption.

[0020] [Specific example of embodiment] An example of a carbon dioxide capture system and capture method according to the present disclosure will be described in more detail below with reference to the drawings: Figure 1 is a diagram showing an example of the configuration of a carbon dioxide capture system.

[0021] (Carbon dioxide capture system) Referring to FIG. 1, a carbon dioxide recovery system 1 is a system used in DAC. The raw material gas G0 is mainly atmospheric air. The raw material gas G0, which is the gas to be treated, typically contains nitrogen (N2), oxygen (O2), moisture (H2O), carbon dioxide (CO2), and other components. When the raw material gas G0 is atmospheric air, it usually contains approximately 300 ppm to 500 ppm of carbon dioxide, but is not limited to this range. For example, the carbon dioxide content in the raw material gas may be approximately 300 ppmv to 5000 ppmv. The carbon dioxide contained in the raw material gas G0 is separated and recovered by the carbon dioxide recovery system 1 and extracted as recovered gas G3.

[0022] The carbon dioxide capture system 1 includes a pretreatment section 10, a carbon dioxide separation section 20, and a blower 30. The blower 30 may be, for example, a blower or a fan. The blower 30 and the pretreatment section 10 are connected to each other via a pipe 51. The pretreatment section 10 is arranged to reduce the moisture content of the raw material gas G0 sent by the blower 30. The pretreatment section 10 may include multiple pretreatment units. In the example of FIG. 1, the pretreatment section 10 includes two pretreatment units 10A and 10B. The pipe 51 includes a first branch pipe 51A connected to the first pretreatment unit 10A and a second branch pipe 51B connected to the second pretreatment unit 10B. A valve V1 is provided in the first branch pipe 51A, which can be switched between a state in which the blower 30 and the first pretreatment unit 10A are connected and a closed state. A valve V2 is provided in the second branch pipe 51B, which can switch between a state in which the blower 30 and the second pre-processing unit 10B are in communication with each other and a closed state. The first pre-processing unit 10A and the second pre-processing unit 10B preferably have the same configuration. In the example of Fig. 1, the blower 30 is provided upstream of the pre-processing unit 10, but in another embodiment, a pump can be provided downstream of the pre-processing unit 10, and the raw material gas G0 can be sucked into the pre-processing unit 10 by suction with the pump.

[0023] The pretreatment units 10A and 10B in the pretreatment section 10 include storage containers 11A and 11B, and moisture absorbents 12A and 12B as second materials stored in the storage containers 11A and 11B, respectively. The storage containers 11A and 11B may be absorption towers. The moisture absorbents 12A and 12B are moisture absorbents that adsorb moisture and adsorb a small amount of carbon dioxide. In the carbon dioxide capture system 1 according to the present disclosure, the moisture absorbents 12A and 12B have a Si / Al molar ratio of 0.7 to 1.3, and in a powder X-ray diffraction pattern using Cu as the X-ray source, have peaks at around 2θ=20, 26, 35, and 39°, 29 One of the features of this system is the use of an aluminum silicate complex consisting of a low-crystalline layered clay mineral that has a peak due to OH-Si-(OAl)3 and a peak observed in the range of -84 to -94 ppm in the Si solid-state NMR spectrum, and amorphous aluminum silicate. Details of the moisture absorbents 12A and 12B will be described later. The pretreatment units 10A and 10B may be equipped with a heating or cooling device for temperature control, a pump or fan for pressure control, etc.

[0024] The pretreatment unit 10 and the carbon dioxide separation unit 20 are connected via a pipe 52 serving as a first pipe. in The pipe 52 includes a first branch pipe 52A that connects to the first pretreatment unit 10A, and a second branch pipe 52B that connects to the second pretreatment unit 10B. A valve V3 that can switch between a state in which the first pretreatment unit 10A and the carbon dioxide separation section 20 are connected and a closed state is provided midway along the first branch pipe 52A. A valve V4 that can switch between a state in which the second pretreatment unit 10B and the carbon dioxide separation section 20 are connected and a closed state is provided midway along the second branch pipe 52B.

[0025] The carbon dioxide separation unit 20 separates carbon dioxide contained in the gas G1 that has passed through the pretreatment unit 10 and has had its moisture content reduced. The carbon dioxide separation unit 20 may include a carbon dioxide separation device used in DAC. Examples of the carbon dioxide separation device used in DAC may include a physical adsorption device that physically adsorbs carbon dioxide, a chemical adsorption device that chemically adsorbs carbon dioxide, an intermediate device between these, a membrane separation device that separates carbon dioxide by membrane separation, a cooling device that separates carbon dioxide by utilizing a phase change, etc.

[0026] In the example of FIG. 1 , the carbon dioxide separation unit 20 includes a storage container 21 and a carbon dioxide adsorbent 22 as a first material stored in the storage container 21. The carbon dioxide capture system 1 according to the present disclosure includes a pretreatment unit 10, and moisture is removed from the gas to be treated in the pretreatment unit 10, so the effect of moisture on the carbon dioxide separation unit 20 is small. Therefore, when carbon dioxide separation is performed using physical adsorption in the carbon dioxide separation unit 20, a decrease in carbon dioxide adsorption efficiency due to the presence of moisture can be suppressed. Examples of carbon dioxide adsorbents 22 using physical adsorption include zeolite, metal-organic frameworks (MOFs), and HASClay (registered trademark). Examples of carbon dioxide adsorbents 22 using chemical adsorption include solid adsorbents in which a porous material is impregnated with an amine compound, liquid amine compounds, and those using inorganic alkali compounds such as calcium hydroxide. The carbon dioxide separation unit 20 may also include a heating or cooling device for temperature adjustment, a pump or fan for pressure adjustment, etc.

[0027] In the carbon dioxide capture system 1, the pretreatment unit 10 and the carbon dioxide separation unit 20 are connected via a pipe 53 as a second pipe, which is separate from the pipe 52 as a first pipe. outand the pretreatment section 10 are connected via piping 53. The piping 53 constitutes a regeneration system for regenerating the moisture absorbents 12A and 12B in the pretreatment section 10. The piping 53 includes a first branch piping 53A connected to the first pretreatment unit 10A and a second branch piping 53B connected to the second pretreatment unit 10B. A valve V5 is provided in the first branch piping 53A, which can switch between a state in which the first pretreatment unit 10A and the carbon dioxide separation section 20 are connected and a closed state. A valve V6 is provided in the second branch piping 53B, which can switch between a state in which the second pretreatment unit 10B and the carbon dioxide separation section 20 are connected and a closed state.

[0028] The first pre-treatment unit 10A is further connected to a pipe 54A that discharges gas to the outside of the carbon dioxide capture system 1. Similarly, the second pre-treatment unit 10B is further connected to a pipe 54B that discharges gas to the outside of the carbon dioxide capture system 1. The pipes 54A and 54B are exhaust pipes. A valve V7 is provided midway along the pipe 54A. The valve V7 is switchable between a state in which the first pre-treatment unit 10A is connected to the outside and a state in which the communication between the first pre-treatment unit 10A and the outside is closed. The valve V8 is switchable between a state in which the second pre-treatment unit 10B is connected to the outside and a state in which the communication between the second pre-treatment unit 10B and the outside is closed.

[0029] A pipe 55, which is an extraction pipe, is connected to the carbon dioxide separation unit 20. Through the pipe 55, the recovered gas G3 containing the carbon dioxide separated in the carbon dioxide separation unit 20 is extracted from the carbon dioxide recovery system 1 and recovered.

[0030] (moisture absorbent) The moisture absorbent (moisture absorbent 12A, 12B) used in the carbon dioxide capture system according to the present disclosure has a Si / Al molar ratio of 0.7 to 1.3, and in a powder X-ray diffraction pattern using Cu as an X-ray source, has peaks at around 2θ=20, 26, 35, and 39°, 29This paper describes an aluminum silicate complex consisting of a low-crystalline layered clay mineral and amorphous aluminum silicate, which exhibits a peak due to OH-Si-(OAl)3 and a peak observed in the range of -84 to -94 ppm in the Si solid-state NMR spectrum. The moisture absorbent includes an inorganic porous material M known as HASClay (registered trademark). The main constituent elements of inorganic porous material M are silicon (Si), aluminum (Al), oxygen (O), and hydrogen (H). Inorganic porous material M is a complex of hydrated aluminum silicate and a clay mineral, assembled through numerous Si-O-Al bonds.

[0031] While not particularly limited as long as the effects of the present disclosure can be obtained, the moisture absorbents 12A and 12B can contain 90% or more of the inorganic porous material M relative to the entire moisture absorbents 12A and 12B, preferably 95% or more, and more preferably 100%. To reliably obtain the effects of the present disclosure, the moisture absorbents 12A and 12B preferably contain 95% or more of the inorganic porous material M relative to the entire moisture absorbents 12A and 12B. In addition to the inorganic porous material M, the moisture absorbents 12A and 12B may also contain, for example, alumina, zeolite, silica gel, activated carbon, etc.

[0032] The inorganic porous material M may be in a granular form. The size and shape of the granulated material are not particularly limited, but may be, for example, pellets of about 0.5 mm to 10 mm. The density of the inorganic porous material M in a dry state is, for example, 0.3 g / cm 3 ~0.6g / cm 3 The specific surface area of ​​the inorganic porous material M may be, for example, 500 m 2 / g~1000m 2 / g The porosity of the inorganic porous material M may be, for example, 40% to 70%.

[0033] The inorganic porous material M has a high moisture adsorption capacity at around atmospheric pressure. Specifically, the water vapor adsorption capacity at a relative humidity of 40% (100°C) is about 28 wt%, and the moisture adsorption capacity at a relative humidity of 60% (100°C) is 45 wt% or more. Furthermore, the inorganic porous material M has a low carbon dioxide adsorption capacity at around atmospheric pressure. For example, at an absolute pressure of 100 kPaA, the carbon dioxide adsorption capacity of HASClay (registered trademark) is about 6 wt%.

[0034] The inorganic porous material M can be industrially produced, for example, by mixing a solution of an inorganic silicon compound with a solution of an inorganic aluminum compound, polymerizing the silicon and aluminum, and then performing heat aging and desalting and washing. Specifically, it can be obtained by mixing an aqueous monosilicic acid solution with an aluminum solution so that the Si / Al ratio is 0.7 to 1, adjusting the pH to 6 to 8 by adding an acid or alkali, and then heating. Specific examples of monosilicic acid that can be used include sodium orthosilicate, sodium metasilicate, and amorphous colloidal silicon dioxide (e.g., Aerosil). The aluminum source to be bonded to the silicate molecules may be aluminum ions. Specific examples include aluminum compounds such as aluminum chloride, aluminum nitrate, and sodium aluminate.

[0035] These raw materials are dissolved in an appropriate aqueous solution to prepare a solution of a predetermined concentration. The silicon / aluminum ratio is mixed to be 0.7 to 1.0. The silicon compound concentration in the solution can be 1 to 1,000 mmol / L. The aluminum compound solution can be 1 to 1,400 mmol / L. It is preferable to mix a silicon compound solution of 1 to 800 mmol / L with an aluminum compound solution of 1 to 1,200 mmol / L. Based on these ratios and concentrations, the silicon compound solution is mixed with the aluminum compound solution to form a precursor, and the pH is then adjusted to 6 to 8. Next, thermal synthesis is performed, followed by desalting and washing by centrifugation, filtration, membrane separation, etc., to obtain the inorganic porous material M.

[0036] The inorganic porous material M can be industrially produced, for example, by mixing water glass with an aqueous aluminum sulfate solution, polymerizing silicon and aluminum under acidic conditions, and then desalination and heating. Specifically, the inorganic porous material M can be produced by mixing water glass with an aqueous aluminum sulfate solution so that the Si / Al molar ratio is 0.7 to 1.3 and the pH at the time of mixing is 3.5 to 4.8, stirring the mixture, adding an alkali to adjust the pH to 6 to 10, and then desalination and heating at 120 to 300°C.

[0037] For example, the inorganic porous material M obtained by the above method exhibits broad peaks at around 2θ=20, 26, 35, and 39° in the powder X-ray diffraction pattern using Cu as the X-ray source. The peaks at 20° and 35° are due to reflections from the hk0 plane of the layered clay mineral, and since the 00l reflections commonly seen in layered clay minerals are not observed, it is presumed to be a layered clay mineral with low crystallinity and almost no thickness in the stacking direction. Furthermore, the broad peaks at around 2θ=26° and 39° are peaks characteristic of amorphous aluminum silicates. Furthermore, by the CP / MAS method, 29 In the Si solid-state NMR spectrum, there is a peak due to OH-Si-(OAl)3 and a peak observed in the range of -84 to -94 ppm. The peak due to OH-Si-(OAl)3 is observed around -76 to -78 ppm.

[0038] (Carbon dioxide capture method) A carbon dioxide recovery method according to the present disclosure will be described. The carbon dioxide recovery method according to the present disclosure is preferably a method carried out in the carbon dioxide recovery system described above. The raw material gas to be treated in the carbon dioxide recovery method according to the present disclosure is a gas containing moisture and carbon dioxide. The moisture content in the raw material gas is not particularly limited, but may be, for example, about 1 vol% to 10 vol%. The carbon dioxide content in the raw material gas is not particularly limited, but may be, for example, about 300 ppmv to 5000 ppmv.

[0039] The carbon dioxide recovery method according to the present disclosure includes a pretreatment step of passing a gas containing moisture and carbon dioxide through a pretreatment section to reduce the moisture content in the gas, and a carbon dioxide separation step of passing the gas from the pretreatment section through a carbon dioxide separation section. The pretreatment section is a dehumidification section containing the inorganic porous material M described above.

[0040] In the pretreatment step, the pressure of the gas supplied to the pretreatment section is preferably 90 kPaA or more and 300 kPaA or less. The treatment temperature in the pretreatment may be 100°C or less, and is preferably 0°C or more and 50°C or less. The treatment temperature here refers to the temperature of the raw material gas G0 circulating in the pretreatment section. In the carbon dioxide recovery method according to the present disclosure, the pretreatment step can be carried out at near atmospheric pressure and in the room temperature range or a temperature range close to room temperature, typically in a temperature range of 100°C or less. Therefore, the energy required in the pretreatment step can be reduced compared to, for example, when dehumidification is performed by heating. Furthermore, compared to, for example, when a porous adsorbent such as zeolite is used, less carbon dioxide is adsorbed, and moisture can be selectively adsorbed from the gas to be treated.

[0041] Following the pretreatment step, a carbon dioxide separation step is carried out in which the gas discharged from the pretreatment section is passed through a carbon dioxide separation section. Appropriate conditions for the carbon dioxide separation step can be selected depending on the carbon dioxide separation method. In the carbon dioxide capture method according to the present disclosure, the moisture content of the gas supplied to the carbon dioxide separation section is reduced. Therefore, a carbon dioxide separation method that is susceptible to moisture (for example, when zeolite is used as a carbon dioxide adsorbent) can also be suitably used.

[0042] A carbon dioxide recovery step can be carried out following the carbon dioxide separation step or simultaneously with the carbon dioxide separation step. The carbon dioxide recovery step is a step of recovering the carbon dioxide separated in the carbon dioxide separation section. When physical adsorption and / or chemical adsorption is used as the carbon dioxide separation method in the carbon dioxide separation section, the carbon dioxide separation step and the carbon dioxide recovery step can be carried out using, for example, a temperature swing method, a pressure swing method, or a humidity swing method.

[0043] The carbon dioxide capture method according to the present disclosure can include a regeneration step of regenerating the moisture absorbent in the pretreatment section. In the regeneration step, the treated gas discharged from the carbon dioxide separation section can be used. Furthermore, when the pretreatment section includes multiple pretreatment units, dehumidification of the raw gas and regeneration of the moisture absorbent can be carried out in parallel.

[0044] Fig. 2 is a control flow showing an example of control of a pretreatment unit in a carbon dioxide capture system according to the present disclosure. The flow shown in Fig. 2 shows an example of control of the carbon dioxide capture system 1 shown in Fig. 1, and the reference numerals in Fig. 2 correspond to the components shown in Fig. 1.

[0045] First, the device is started (START). Next, among the valves, V1, V3, V6, and V8 are opened, and V2, V4, V5, and V7 are closed (S10). By this operation, the blower 30 and the first pre-treatment unit 10A are communicated with each other, and the first pre-treatment unit 10A and the carbon dioxide separation section 20 are communicated with each other, and the outlet side 20 of the carbon dioxide separation section 20 is out The second pre-treatment unit 10B communicates with the first pre-treatment unit 10A, and the second pre-treatment unit 10B communicates with the exhaust port 55B.

[0046] Next, the blower 30 and the separation device of the carbon dioxide separation section 20 are turned on (S20). The blower 30 sends a raw material gas G0 containing nitrogen, oxygen, moisture, and carbon dioxide to the first pretreatment unit 10A. The gas G1, whose moisture content has been reduced in the first pretreatment unit 10A, is supplied to the carbon dioxide separation section 20, where the carbon dioxide is separated. The carbon dioxide separation section 20 supplies dry air G2 containing nitrogen and oxygen to the second pretreatment unit 10B. In this way, dehumidification is performed in the first pretreatment unit 10A, and regeneration of the moisture absorbent 12B is performed in the second pretreatment unit 10B (S30). The exhaust gas G4, which contains nitrogen, oxygen, and moisture and has been used to regenerate the moisture absorbent 12B, is discharged to the outside from the exhaust port 55B. Specifically, the regeneration of the moisture absorbent 12B in the second pre-treatment unit 10B is carried out by feeding dry air G2, adjusted for example to a pressure of about 101 kPaA to 300 kPaA and a temperature of about 60°C to 100°C, into the second pre-treatment unit 10B to desorb moisture from the moisture absorbent 12B. The temperature of the dry air G2 used in the regeneration step may be, for example, 20°C to 100°C, and is more preferably 60°C to 100°C.

[0047] A decrease in dehumidification performance in the first pre-treatment unit 10A is determined (S40). The dehumidification performance can be determined, for example, by measuring the humidity of the gas exiting the first pre-treatment unit 10A at the outlet side of the first pre-treatment unit 10A. Specific means are not limited as long as the dehumidification performance can be determined by other methods. If it is not determined that the dehumidification performance in the first pre-treatment unit 10A has decreased (NO in S40), dehumidification in the first pre-treatment unit 10A and regeneration in the second pre-treatment unit 10B are continued (S30).

[0048] If it is determined that the dehumidification performance of the first pre-treatment unit 10A has decreased (YES in S40), among the valves, V1, V3, V6, and V8 are closed, and V2, V4, V5, and V7 are opened (S60). By this operation, the blower 30 and the second pre-treatment unit 10B are communicated with each other, the second pre-treatment unit 10B is communicated with the carbon dioxide separation section 20, and the outlet side 20 of the carbon dioxide separation section 20 is opened. out The first pre-treatment unit 10A communicates with the first pre-treatment unit 10A, and the first pre-treatment unit 10A communicates with the exhaust port 55A.

[0049] The raw material gas G0 is sent from the blower 30 to the second pre-treatment unit 10B. The gas G1, whose moisture content has been reduced in the second pre-treatment unit 10B, is supplied to the carbon dioxide separation section 20, where the carbon dioxide is separated. The dried air G2 from which the carbon dioxide has been separated is supplied to the first pre-treatment unit 10A. In this manner, dehumidification is carried out in the second pre-treatment unit 10B, and regeneration is carried out in the first pre-treatment unit 10A (S60). The exhaust gas G4, which contains nitrogen, oxygen, and moisture and has been used to regenerate the moisture absorbent 12A, is discharged to the outside from the exhaust port 55A.

[0050] A determination is made as to whether the dehumidification performance of the second pre-treatment unit 10B has decreased (S70). If it is not determined that the dehumidification performance of the second pre-treatment unit 10B has decreased (NO in S70), dehumidification in the second pre-treatment unit 10B and regeneration in the first pre-treatment unit 10A are continued (S60). If it is determined that the dehumidification performance of the second pre-treatment unit 10B has decreased (YES in S70), valves V1, V3, V6, and V8 are opened, and valves V2, V4, V5, and V7 are closed (S80), and dehumidification in the first pre-treatment unit 10A and regeneration in the second pre-treatment unit 10B are carried out (S30).

[0051] The above-described control method allows dehumidification in one pretreatment unit and regeneration in the other pretreatment unit to be carried out in parallel. Furthermore, the pretreatment units can be regenerated using the dry gas obtained after carbon dioxide separation, resulting in a carbon dioxide capture system with excellent energy efficiency.

[0052] [Test Example 1] The pretreatment step (dehumidification step) according to the present disclosure was demonstrated by the following test. <Test equipment> An overview of the test equipment is shown in Figure 3. As shown in Figure 3, an adsorption tower was constructed by filling a column with moisture absorbent material, and the adsorption of moisture and carbon dioxide in the adsorption tower was measured. A column with a diameter of 60 mm and a length of 1000 mm was used. 490.41 g (1 L) of HASClay (registered trademark) (product number: HASClay GI-Z, manufactured by Ishihara Sangyo Kaisha, Ltd., pellet-shaped particles with a diameter of 4 mm and a length of 6 mm) was filled into the column as the moisture absorbent material. The HASClay used was dried at 110°C. A carbon dioxide concentration meter (Ondotori TR-76Ui-S, manufactured by T&D Co., Ltd.) and a thermo-hygrometer (Ondotori TR-72nw-S, manufactured by T&D Co., Ltd.) were installed at the inlet and outlet of the adsorption tower to measure the carbon dioxide concentration, temperature, and humidity. During adsorption, a pump (MP-30, manufactured by AS ONE Co., Ltd.) was installed at the outlet of the adsorption tower, and the gas to be treated was introduced into the adsorption tower by suction, allowing it to pass through.

[0053] <Test Method> After filling the column with 1 L of moisture absorbent material, nitrogen gas generated by a nitrogen generator (M4NT-0.8-5, manufactured by Kofloc Corporation) was introduced into the test equipment. The column was equilibrated by circulating nitrogen gas until the carbon dioxide concentration measured at the outlet side was 10 ppm or less. This was the preliminary preparation. After the preparatory steps were completed, the raw gas, which was the ambient air to which moisture had been added by bubbling in water, was introduced into the column. The raw gas had a relative humidity of 80-90% RH and a carbon dioxide concentration of 500-600 ppm. The flow rate of the raw gas was 25 L / min.

[0054] <Test Results> Figure 4(a) shows the time-dependent changes in relative humidity and carbon dioxide concentration at the inlet side of the adsorption tower, and Figure 4(b) shows the time-dependent changes in relative humidity and carbon dioxide concentration at the outlet side of the adsorption tower. As shown in Figures 4(a) and 4(b), while the relative humidity in the feed gas was 80-90% RH, the relative humidity at the outlet side of the adsorption tower was reduced to 5% RH and maintained this state for up to 100 minutes. Even at 110 minutes, the relative humidity at the outlet side was below 10% RH. Furthermore, while the carbon dioxide concentration in the feed gas was 450-500 ppm, the carbon dioxide concentration at the outlet side of the adsorption tower maintained a state of approximately 420-500 ppm. These results confirmed that HASClay selectively adsorbs moisture from gases containing carbon dioxide and moisture. When HASClay is used as a pretreatment for DAC, it is thought that there will be less carbon dioxide loss in the gas supplied to the DAC device, and that the dehumidification process can be carried out at room temperature and pressure.

[0055] [Comparative Test Example 1] In the apparatus of Example Test 1, zeolite (Molecular Sieve 4A, product number: 141302, manufactured by Union Showa Co., Ltd., 3.2 mm pellet particles) was used as the moisture absorbent instead of HASClay. The zeolite was dried at 200°C and 784.57 g (1 L) was packed in the column. Otherwise, the test was carried out in the same manner as in Example Test 1.

[0056] <Result> Figure 5(a) shows the time-dependent changes in relative humidity and carbon dioxide concentration at the inlet side of the adsorption tower, and Figure 5(b) shows the time-dependent changes in relative humidity and carbon dioxide concentration at the outlet side of the adsorption tower. As shown in Figures 5(a) and 5(b), the relative humidity in the feed gas was 77-80% RH, whereas the relative humidity at the outlet side of the adsorption tower was reduced to 5% RH and maintained this state for 150 minutes. Meanwhile, while the carbon dioxide concentration in the feed gas was 525-600 ppm, the carbon dioxide concentration at the outlet side of the adsorption tower was close to 0 ppm for approximately 50 minutes and then gradually increased until 150 minutes. These results confirmed that zeolite not only adsorbs water but also carbon dioxide. When zeolite is used as a pretreatment for DAC, carbon dioxide loss is expected to occur in the gas supplied to the DAC system.

[0057] [Comparative Test Example 2] In the apparatus of Example Test 1, alumina gel (activated alumina D201, product number: 00918500, manufactured by Union Showa Co., Ltd., 5-8 mesh, bead-shaped particles) was used as the moisture absorbent instead of HASClay. The activated alumina was dried at 200°C, and 855.74 g (1 L) was packed into the column. Otherwise, the test was carried out in the same manner as in Example Test 1.

[0058] <Result> Figure 6(a) shows the time-dependent changes in relative humidity and carbon dioxide concentration at the inlet side of the adsorption tower, and Figure 6(b) shows the time-dependent changes in relative humidity and carbon dioxide concentration at the outlet side of the adsorption tower. As shown in Figures 6(a) and 6(b), the relative humidity in the feed gas was 80–85% RH, whereas the relative humidity at the outlet side of the adsorption tower was reduced to approximately 5–7% RH and maintained this state for up to 120 minutes. Meanwhile, while the carbon dioxide concentration in the feed gas was 490–580 ppm, the carbon dioxide concentration at the outlet side of the adsorption tower remained below 10 ppm for approximately 40 minutes, then gradually increased until 120 minutes, remaining at approximately 270 ppm. These results confirmed that alumina gel not only adsorbs water but also carbon dioxide. It is believed that using alumina gel as a pretreatment for DAC results in carbon dioxide loss in the gas supplied to the DAC system.

[0059] [Test Example 2] The pretreatment treatment section regeneration process (desorption process) according to the present disclosure was demonstrated by the following test. <Test equipment> An overview of the test equipment is shown in Figure 3(b). As shown in Figure 3(b), an adsorption tower was constructed by filling a column with moisture absorbent material, and the desorption of moisture and carbon dioxide in the adsorption tower was measured. The same column as in Example 1 was used, and the column after adsorbing moisture in Example 1 was used for the desorption test. A carbon dioxide concentration meter (Ondotori TR-76Ui-S, manufactured by T&D Co., Ltd.) and a thermo-hygrometer (Ondotori TR-72nw-S, manufactured by T&D Co., Ltd.) were installed at the inlet and outlet sides of the adsorption tower to measure the carbon dioxide concentration, temperature, and humidity.

[0060] <Test Method> Nitrogen gas generated by a nitrogen generator (M4NT-0.8-5, manufactured by Kofloc Corporation) was introduced into the column used in the adsorption test in Experimental Example 1. The flow rate of the raw material gas was set to 10.0 L / min.

[0061] <Test Results> The time-dependent changes in relative humidity and carbon dioxide concentration at the desorption inlet side are shown in Figure 7(a), and the time-dependent changes in relative humidity and carbon dioxide concentration at the desorption outlet side are shown in Figure 7(b). As shown in Figures 7(a) and (b), when nitrogen at a temperature of approximately 22°C to 25°C and a relative humidity of approximately 5% RH is fed, it was confirmed that gas with a relative humidity of approximately 80 to 40% RH is discharged at the outlet side of the moisture absorption tower. From these results, it was thought that moisture can be desorbed from HASClay using dry air at room temperature, and that the regeneration process of the pre-treatment unit can be carried out at room temperature and normal pressure.

[0062] It should be understood that the embodiments disclosed herein are illustrative in all respects and are not limiting in any respect. The scope of the present invention is defined not by the above meaning but by the scope of the claims, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0063] 1 Carbon dioxide capture system, 10 Pretreatment unit, 10A First pretreatment unit, 10B Second pretreatment unit, 11A, 11B Storage container, 12A, 12B Moisture absorbent, 20 Carbon dioxide separation unit, 21 Storage container, 22 Carbon dioxide adsorbent, 30 Blower, 51, 52, 53, 54, 55 Piping, 55A, 55B Exhaust port, V1, V2, V3, V4, V5, V6, V7, V8 Valves.

Claims

1. A carbon dioxide capture system that captures carbon dioxide by direct air capture (DAC), comprising: a carbon dioxide separation unit containing a first material capable of separating carbon dioxide contained in a gas; a pretreatment unit located upstream of the carbon dioxide separation unit and connected to the carbon dioxide separation unit via a first pipe; Equipped with The pre-treatment unit A storage container; A second material contained in the container; Including, The second material is The Si / Al molar ratio is 0.7 to 1.3, and in a powder X-ray diffraction pattern using Cu as an X-ray source, the powder X-ray diffraction pattern has peaks at 2θ=approximately 20, 26, 35, and 39°, ２９ In the Si solid state NMR spectrum, OH-Si-(OAl) ３ and a peak observed in the range of -84 to -94 ppm. Carbon dioxide capture system.

2. The first material and the second material are different materials. The carbon dioxide capture system of claim 1 .

3. The pre-treatment unit a first pre-processing unit including the container and the second material; a second pre-treatment unit that includes the container and the second material and is different from the first pre-treatment unit; a second pipe different from the first pipe, which connects the first pretreatment unit and the outlet side of the carbon dioxide separation unit and is provided with a first switching mechanism that can switch between a state in which the first pretreatment unit and the carbon dioxide separation unit are in communication with each other and a state in which the first pretreatment unit and the carbon dioxide separation unit are not in communication with each other; a third pipe that connects the second pretreatment unit and the outlet side of the carbon dioxide separation unit and is provided with a second switching mechanism that can switch between a state in which the second pretreatment unit and the carbon dioxide separation unit are in communication with each other and a state in which the second pretreatment unit and the carbon dioxide separation unit are not in communication with each other; Further provided with The carbon dioxide recovery system according to claim 1 or 2.

4. A method for capturing carbon dioxide by direct air capture (DAC), comprising: a carbon dioxide separation unit containing a first material capable of separating carbon dioxide contained in a gas; a pretreatment section located upstream of the carbon dioxide separation section, connected to the carbon dioxide separation section via a first pipe, and accommodating a second material capable of adsorbing moisture; Equipped with the second material has a Si / Al molar ratio of 0.7 to 1.3, and has peaks at 2θ=approximately 20, 26, 35, and 39° in a powder X-ray diffraction pattern using Cu as an X-ray source; ２９ In the Si solid state NMR spectrum, OH-Si-(OAl) ３ and a peak observed in the range of -84 to -94 ppm. a pretreatment step of passing a gas containing moisture and carbon dioxide through the pretreatment step; A carbon dioxide separation step of circulating the gas discharged from the pretreatment section in the carbon dioxide separation section. Carbon dioxide capture methods.

5. In the pretreatment step, The pressure of the gas supplied to the pretreatment unit is 90 kPaA or more and 300 kPaA or less, The temperature of the pre-treatment section is 0°C or higher and 50°C or lower. The method for recovering carbon dioxide according to claim 4.

6. In the carbon dioxide recovery method, Further, a pretreatment unit regeneration step of circulating the gas that has passed through the carbon dioxide separation unit through the pretreatment unit is included. The method for recovering carbon dioxide according to claim 4 or claim 5.

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