Modular radial adsorbent bed for direct air capture.

Abstract

A modular adsorber bed for mounting in a vacuum chamber for use in a vacuum temperature swing direct air capture process for extracting carbon dioxide from atmospheric air, the modular adsorber array comprising a plurality of axially parallel arrayable adsorber cartridges, each adsorber cartridge comprising a hollow cylinder housing an adsorber held in place between an outer gas permeable tube and an inner gas permeable tube defining an axially disposed void within the cartridge, each cartridge configured in use to receive a carbon dioxide adsorbing air flow passing radially through the adsorber towards the axially disposed void or passing radially away from the axially disposed void.

Description

[Technical field]

[0001] The present invention relates to adsorbent beds for direct air capture CO2 processes. [Background technology]

[0002] As climate change caused by human-induced CO2 emissions is increasingly recognized as a serious threat, there is a growing demand for technologies to reduce CO2 in the atmosphere.

[0003] These technologies include "direct air capture," which extracts CO2 directly from atmospheric air.

[0004] CO2 direct air capture technologies include vacuum temperature swing direct air capture. In this process, air is admitted into a vacuum chamber and passed through a sorbent bed located inside the vacuum chamber. The CO2 in this air is adsorbed by the sorbent layer. The vacuum chamber is then sealed, evacuated, and the sorbent bed is heated. This heating causes the CO2 to desorb from the sorbent bed in gaseous form and increases the pressure inside the vacuum chamber. The vacuum chamber is again evacuated, and the captured CO2 is removed. The captured CO2 can be used in processes that require CO2 or sequestered for long-term storage.

[0005] An example of a vacuum temperature swing direct air capture process using compressed air is described in Patent Document 1 (WO2020 / 157322). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2020 / 157322 Brochure Summary of the Invention [Problem to be solved by the invention]

[0007] To have a beneficial impact, for example, a process that uses vacuum temperature swing direct air capture to reduce the amount of CO2 in the atmosphere must overcome a number of technical challenges, including power consumption and "scalability." Obviously, to be practical, a CO2 capture process must require less electricity than the CO2 it captures. [Means for solving the problem]

[0008] According to a first aspect of the invention, there is provided a modular adsorber bed for mounting in a vacuum chamber for use in a vacuum temperature swing direct air capture process for extracting carbon dioxide from atmospheric air. The modular adsorber arrangement comprises a plurality of adsorbent cartridges which can be arranged in an axially parallel array. Each adsorbent cartridge comprises a hollow cylinder containing an adsorbent held in place between an outer gas permeable tube and an inner gas permeable tube which defines an axially disposed void within the cartridge, and in use each cartridge is configured to receive an air stream in which carbon dioxide is to be adsorbed passing radially through the adsorbent towards the axially disposed void or passing radially away from the axially disposed void.

[0009] Optionally, each adsorbent cartridge includes heat exchange means for providing thermal energy to the adsorbent during the regeneration stage of the vacuum temperature swing direct air capture process.

[0010] Optionally, within each adsorber cartridge, the heat exchange means is disposed between the outer and inner gas permeable tubes.

[0011] Optionally, each adsorbent cartridge is sealed at a first end and, in use, opens at a second end into a common airflow conduit such that, for each adsorbent cartridge, a pressure in the common airflow conduit that is lower than the pressure adjacent the exterior of each adsorbent cartridge drives air flow in a radial direction through the adsorbents toward the axially disposed voids, and a pressure in the common airflow conduit that is higher than the pressure adjacent the exterior of each adsorbent cartridge drives air flow in a radial direction through the adsorbents away from the axially disposed voids.

[0012] Optionally, within each sorbent cartridge, the outer gas permeable tube and the inner gas permeable tube of each sorbent cartridge comprise tubes of gas permeable material held tightly by a retaining tube.

[0013] Optionally, within each sorbent cartridge, the gas permeable material comprises a mesh.

[0014] Optionally, within each adsorbent cartridge, the retaining tube is made from a perforated sheet.

[0015] Optionally, the first end of each sorbent cartridge is sealed by an end cap.

[0016] Optionally, within each sorbent cartridge, the second end is terminated by an open end cap which encloses the sorbent material and includes an aperture which opens into a common airflow conduit.

[0017] Optionally, in each adsorber cartridge, the heat exchange means includes a conduit for receiving a heat exchange fluid.

[0018] Optionally, in each sorbent cartridge, the conduit comprises a plurality of connected tube sections.

[0019] Optionally, in each sorbent cartridge, each of the plurality of connected tubes is generally parallel to the axially disposed gap.

[0020] Optionally, in each adsorber cartridge, each tube is connected to one or more heat sink fins.

[0021] Optionally, in each adsorber cartridge, the heat exchange means of each adsorber cartridge is connected to a common heat exchange fluid source.

[0022] Optionally, within each sorbent cartridge, the cartridge contains sorbent particles.

[0023] According to a second aspect of the invention there is provided an adsorbent cartridge for use in a modular adsorbent bed according to the first aspect of the invention. The adsorbent cartridge comprises a hollow circular tube containing an adsorber held in place between an outer gas permeable tube and an inner gas permeable tube which defines an axially disposed void within the cartridge. In use the cartridge is configured to receive an air stream in which carbon dioxide is to be adsorbed, passing radially through the adsorbent towards the axially disposed void or passing radially through the adsorbent away from the axially disposed void.

[0024] According to a third aspect of the present invention, there is provided an apparatus for performing a vacuum temperature swing direct air capture process for extracting carbon dioxide from atmospheric air, the process comprising a carbon dioxide adsorption stage, an evacuation stage, a carbon dioxide desorption stage and a carbon dioxide extraction stage. The apparatus comprises a vacuum chamber, within whose internal volume a modular sorbent bed according to the first aspect is disposed. The apparatus further comprises a first sealable air conduit providing an air inlet to the internal volume of the vacuum chamber, a second sealable air conduit providing an air inlet to the vacuum chamber and connected to a common conduit connected via an airtight connection to an axially disposed gap of each adsorber cartridge of the modular adsorber bed, heating means configured to heat the adsorber cartridges of the modular adsorber bed during the carbon dioxide desorption stage, and a sealable carbon dioxide extraction conduit through which desorbed carbon dioxide is extracted during the carbon dioxide extraction stage. In a first operating mode, during the CO2 adsorption stage, the air to be treated is input to the vacuum chamber via the first sealable air conduit and output via the second sealable air conduit, and in a second operating mode, during the CO2 adsorption stage, the air to be treated is input to the vacuum chamber via the second sealable air conduit and output via the first sealable air conduit.

[0025] According to an embodiment of the present invention, there is provided a modular adsorber bed for use in a vacuum temperature swing direct air capture process for extracting carbon dioxide from atmospheric air. The modular adsorber bed includes a plurality of cylindrical adsorber cartridges arranged axially in parallel in use. Advantageously, the number and stacking pattern of cartridges can be readily selected to accommodate vacuum chambers of different sizes and geometries.

[0026] Furthermore, the cylindrical configuration of each cartridge, with the outer region of the adsorbent surrounding an inner axial void through which the airflow travels to adsorb CO2, provides a relatively large surface area of ​​the adsorbent with low resistance to airflow. As a result, the size of the adsorbent bed can be increased with an advantageously small increase in airflow resistance. As a result, less power is required to drive airflow through a system equipped with the adsorbent bed, reducing costs and energy consumption and facilitating system expansion. Furthermore, modular adsorbent beds according to embodiments of the present invention can be easily retrofitted into existing vacuum chambers and / or easily replace existing adsorbent beds, e.g., monolithic adsorbent beds, particularly conventional "axial" adsorbent beds that rely on axial airflow and generally have high airflow resistance.

[0027] Advantageously, in certain embodiments, due to the modular nature of the sorbent bed, each individual cartridge can be provided with its own individual heat exchange means for heating the sorbent, thereby increasing the rate at which the total amount of sorbent within the sorbent bed is heated and improving the degree to which the sorbent is heated uniformly.

[0028] Advantageously, in certain embodiments, each cartridge may be formed by first and second gas permeable tubes, each of which may be readily fabricated from a simple sheet of gas permeable material. Moreover, the dimensions of the cartridge so fabricated may be readily selected by simply varying the height and diameter of the first and second gas permeable tubes. In particular, the height, outer diameter, and diameter of the axial gap may all be readily selected by simply varying the dimensions of the sheet of gas permeable material.

[0029] Various further features and aspects of the present invention are defined in the claims. [Brief description of the drawings]

[0030] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which like parts are given corresponding reference numerals, and in which: [Figure 1] FIG. 1 shows a simplified schematic diagram of an adsorbent cartridge for use in a modular adsorbent bed constructed in accordance with certain embodiments of the present invention. [Diagram 2] FIG. 2 is a simplified schematic diagram showing the sorbent cartridge shown in FIG. 1 with the end caps removed. [Diagram 3] FIG. 2 is a simplified schematic diagram showing a cross section of the adsorbent cartridge shown in FIG. 1. [Figure 4] FIG. 2 is a simplified schematic diagram illustrating a heat exchanger configuration incorporated into an adsorbent cartridge according to certain embodiments of the present invention. [Diagram 5] FIG. 2 is a simplified schematic diagram showing inner and outer gas permeable tubes forming part of a sorbent cartridge according to certain embodiments of the present invention. [Figure 6a] FIG. 2 is a simplified schematic diagram illustrating the arrangement of end caps for an adsorbent cartridge according to certain embodiments of the present invention. [Figure 6b] FIG. 2 is a simplified schematic diagram illustrating the arrangement of end caps for an adsorbent cartridge according to certain embodiments of the present invention. [Figure 6c] FIG. 2 is a simplified schematic diagram illustrating an arrangement of an inner gas permeable tube within an outer gas permeable tube according to certain embodiments of the present invention. [Figure 7a] FIG. 2 is a simplified schematic diagram illustrating operation of an adsorbent cartridge according to a first mode of operation in accordance with certain embodiments of the present invention. [Figure 7b] FIG. 2 is a simplified schematic diagram illustrating operation of an adsorbent cartridge according to a second mode of operation in accordance with certain embodiments of the present invention. [Figure 8] FIG. 1 is a simplified schematic diagram illustrating a vacuum chamber equipped with a modular adsorbent bed according to certain embodiments of the present invention. [Figure 9a] 1 shows an example packing arrangement for a modular sorbent cartridge according to certain embodiments of the present invention. [Figure 9b]1 shows an example packing arrangement for a modular sorbent cartridge according to certain embodiments of the present invention. [Figure 10] 1A-1C are schematic diagrams showing an exemplary "axial bed" and an exemplary "radial bed", to which examples are referred to illustrate the improvements in reduced pressure drop resulting from the use of an adsorbent cartridge according to certain embodiments of the present invention. [Figure 11] 11 is a graph relating to the embodiment described with reference to FIG. 10. [Figure 12] 12a-d are simplified schematic diagrams showing examples of different configurations of cartridges with different heights, widths, inner and outer diameters, number of heating elements and types of heating elements according to certain embodiments of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] FIG. 1 is a simplified schematic diagram of a modular adsorbent cartridge 101 for use in a modular adsorbent bed according to certain embodiments of the present invention.

[0032] Modular sorbent cartridge 101 comprises an open end cap 102 and a sealed end cap 103. Open end cap 102 is open because it includes a central opening 104 that provides an opening to an axial cavity, as described further below.

[0033] The sealed end cap 103 is connected to a heat exchanger fluid inlet 105 and a heat exchanger fluid outlet 106 .

[0034] Modular adsorbent cartridge 101 has a cylindrical shape defined by an outer gas permeable tube 107 .

[0035] 1, in certain embodiments, the open end cap 102 is hexagonal in shape. The open end cap 102 further includes a plurality of fastener-receiving holes 111 disposed around the outer peripheral edge of the open end cap 102 for receiving fasteners to secure the modular adsorbent cartridge 101 in place during use.

[0036] FIG. 2 is another simplified schematic diagram showing a view of the modular sorbent cartridge 101 with the open end cap 102 omitted.

[0037] 2, the modular adsorbent cartridge 101 further comprises an inner gas permeable tube 108. The space between the outer gas permeable tube 107 and the inner gas permeable tube 108 is packed with adsorbent particles 109.

[0038] The sorbent particles 109 can be made from any suitable CO2 sorbent material, such as inorganic materials such as hybrid ultra-microporous materials, metal organic frameworks, metal covalent frameworks, mesoporous silica, zeolitic imidazolate framework materials, zeolites, silicates, aluminosilicates, and carbon-based materials.

[0039] The outer gas permeable tube 107 and the inner gas permeable tube 108 are substantially the same length, and the space within the inner gas permeable tube 108 opens into the central opening 104 of the open end cap 102, forming an axial gap 110 extending along the length of the adsorbent particles 109 packed between the outer gas permeable tube 107 and the inner gas permeable tube 108.

[0040] The axial gap 110 is open at one end by a central opening 104 in an open end cap 102. However, the opposite end of the axial gap 110 is sealed by a sealed end cap 103.

[0041] A heat exchanger is disposed between the outer gas permeable tube 107 and the inner gas permeable tube 108, as well as the adsorbent particles 109. This is depicted in FIG.

[0042] FIG. 3 is a simplified schematic diagram showing a cross section of modular adsorbent cartridge 101 taken along line A depicted in FIG.

[0043] The heat exchanger configuration includes a number of connected pipe sections 301, each connected to a pair of thermally conductive fins 302, 303. FIG. 3 shows an example of eight pipe sections. However, the actual number of pipe sections can vary depending on the size of the cartridge. Each pipe section is generally parallel to the axially disposed air gap. The pipe sections are typically made of a suitable thermally conductive material. Examples of suitable materials include, but are not limited to, copper and aluminum.

[0044] Figure 4 is an exploded view of the modular adsorber cartridge 101 with the outer gas permeable tube 107, sorbent particles 109 and open end cap 102 omitted, showing in more detail the pipe sections 301 and corresponding heating fins which together form the heat exchanger arrangement. Figure 4 also shows a first connection point 401 and a second connection point 402 which connect the connected pipe sections 301 to the heat exchanger fluid inlet 105 and the heat exchanger fluid outlet 106, respectively. In use, heated fluid flows into the connected pipe sections 301 via the heat exchanger fluid inlet 105 and flows out via the heat exchanger fluid outlet 106.

[0045] The heating fluid is usually provided by water heated to about 90° C. to 100° C. However, other suitable fluids can also be used, for example heating oil, which can be heated to higher temperatures.

[0046] In alternative embodiments, the heat exchanger arrangement can be replaced with alternative heating means for heating the sorbent particles. Such alternative heating means are known to those skilled in the art and include, for example, arrangements configured to flow heated nitrogen or steam over the sorbent particles.

[0047] FIG. 5 is a simplified schematic diagram showing the configuration of outer gas permeable tube 107 and inner gas permeable tube 108 in more detail.

[0048] 5, the outer gas permeable tube 107 comprises a gas permeable planar sheet that is rolled into a cylindrical shape and has its shape held at both ends by a first retaining ring 501 and a second retaining ring 502. The first retaining ring 501 and the second retaining ring 502 are typically machined from metal and welded to the outer gas permeable tube 107.

[0049] Similarly, the inner gas permeable tube 108 comprises a planar sheet of gas permeable material rolled into a cylindrical shape. At one end, the inner gas permeable tube 108 is held in shape by a third fastening ring 503. At the other end, the inner gas permeable tube 108 is held in shape by a mounting flange 504. The mounting flange 504 consists of a flange ring 505 and a plurality of circumferentially arranged bolt-receiving mounting points 506. In the example shown in FIG. 5, the mounting flange 504 includes four such mounting points 506.

[0050] 6a and 6b are simplified schematic diagrams showing how the open end cap 102 and the sealed end cap 103 are attached to the outer gas permeable tube 107 and the inner gas permeable tube 108. The open end cap 102 and the sealed end cap 103 are typically made from stainless steel, but may be formed from any suitable material as known to those skilled in the art.

[0051] As can be seen in Figure 6a, the open end cap 102 includes a circumferential mounting shoulder 601 that engages with the first fastening ring 501 of the outer gas permeable tube 107 and aligns the outer gas permeable tube 107 with the center of the open end cap 102. The mounting points 506 of the mounting flange 504 are secured to the open end cap 102 via bolts 602 that pass through bolt holes in the open end cap 102. This secures the inner gas permeable tube 108 to the open end cap 102 and aligns the axial gap 110 formed by the inner gas permeable tube 108 with the central opening 104 of the open end cap 102.

[0052] As can be seen in FIG. 6b, similar to the open end cap 102, the sealed end cap 103 includes a circumferential mounting shoulder 603 that engages with the second locking ring 502 of the outer gas permeable tube 107 and aligns the outer gas permeable tube 107 with the center of the sealed end cap 103.

[0053] The sealing end cap 103 includes an inner mounting shoulder 604 that engages with the third retaining ring 503 of the inner gas permeable tube 108 and aligns the inner gas permeable tube 108 to the center of the sealing end cap 103. The engagement between the inner mounting shoulder 604 and the third retaining ring 503 is typically a press-fit engagement that provides an air-tight seal.

[0054] For clarity, the heat exchange means has been omitted in FIGS. 6 a and 6 b , along with the heat exchange fluid inlet 105 and heat exchange fluid outlet 106 which pass through appropriate openings in the sealed end cap 103 .

[0055] The open end cap 102 is typically removable from the modular sorbent cartridge 101 so that the sorbent particles 109 can be easily inspected and replaced if necessary.

[0056] As mentioned above, outer gas permeable tube 107 and inner gas permeable tube 108 are each typically formed from a sheet of gas permeable material.

[0057] These sheets typically include a gas permeable mesh made from a suitable material, including, but not limited to, stainless steel, copper, titanium, brass, and the like. In one embodiment, the perforated sheet is stainless steel. In one example, the mesh has openings of about 0.18 mm to retain sorbent particles with a typical diameter of up to 0.2 mm. The gas permeable material sheet can be formed from any suitable material, such as, for example, synthetic materials such as fiberglass or polymers, or suitable metals such as copper or aluminum.

[0058] In an exemplary embodiment, each tube 107, 108 further comprises a support layer made from a sheet of perforated stainless steel, which provides the outer and inner gas permeable tubes 107, 108 with increased rigidity.

[0059] An example of this arrangement is shown in Figure 6c, which is a simplified schematic diagram depicting a cutaway view of how outer gas permeable tube 107 and inner gas permeable tube 108 are constructed. In particular, the outer layer is provided by a retaining mesh 605, which provides rigidity to an inner layer provided by gas permeable mesh layer 606.

[0060] 7a and 7b are simplified schematic diagrams illustrating the operation of a modular adsorber cartridge 101 in a vacuum temperature swing direct air capture process according to certain embodiments of the present invention.

[0061] For clarity, only a single modular adsorbent cartridge 101 is shown, however, as will be further described with reference to FIG. 8, in use the modular adsorbent cartridge 101 is part of an array of several other modular adsorbent cartridges, which form a modular adsorbent bed and are placed within the vacuum chamber of the vacuum temperature swing direct air capture system.

[0062] In one mode of operation, atmospheric air is drawn through the central opening 104. With a sealed end cap 103 sealing the other end of the axial gap 110, the air is drawn generally radially inwardly and toward the axial gap 110 through sorbent particles 109 packed between an outer gas permeable tube 107 and an inner gas permeable tube 108. As the air is drawn through the sorbent particles 109, atmospheric CO2 is adsorbed by the sorbent particles 109. This air flow is indicated by the arrows in FIG. 7a.

[0063] In another mode of operation, atmospheric air is driven through the central opening 104. With a sealed end cap 103 sealing the other end of the axial gap 110, the air is driven generally radially outwardly relative to the axial gap 110, away from the axial gap 110, through the sorbent particles 109 packed between the outer gas permeable tube 107 and the inner gas permeable tube 108. As the air is driven through the sorbent particles 109, the CO2 in the atmosphere is adsorbed by the sorbent particles 109. This air flow is shown by the arrows in FIG. 7b.

[0064] Once the CO2 has been adsorbed, a vacuum is applied to the modular adsorber cartridge 101. A hot fluid is then pumped through the connected pipe section 301 of the heat exchanger arrangement 701, dissipating (imparting) thermal energy to the adsorbent particles 109 through the fins of the heat exchanger arrangement 701. This heating of the adsorbent particles 109 causes the adsorbed CO2 to be released as a gas, regenerating the adsorbent particles 109. This released CO2 is removed from the vacuum chamber.

[0065] Advantageously, the modular adsorbent cartridge 101 presents a relatively "thin" bed of adsorbent material to the air flowing within the cartridge (either inwardly toward the axial gap 110 or outwardly away from the axial gap 110), thereby minimizing resistance to air flow while the overall contact surface area between the airflow and the adsorbent particles 109 is high given the total volume occupied by the modular adsorbent cartridge 101.

[0066] As a result, the size of the adsorbent bed can be increased with advantageously less increase in airflow resistance, which in turn reduces the power required to drive air through a system loaded with adsorbent beds, thereby reducing costs, energy consumption, and making such systems easier to scale up. This advantage is illustrated in the examples below.

[0067] For a packed bed (eg, a cartridge packed with sorbent particles), the pressure drop due to fluid flow can be calculated using the Ergun equation:

number

[0068] When air flows through the adsorbent cartridge, the density of the fluid (i.e., air) is 1.2 kg / m 3 , the dynamic viscosity of the fluid is 1.75×10 -5 Pa.s.

[0069] Further, for purposes of this illustration, a typical adsorbent bed for direct air capture has a void volume of about 0.4 m 3 / m 3 and the particle diameter can be assumed to be 1 mm.

[0070] These values ​​can be used to calculate the pressure drop across a sorbent cartridge of a given geometry for a given airflow, specifically, the pressure drop across a conventional sorbent bed where air enters the bed axially.

[0071] FIG. 10 shows a schematic diagram of an adsorbent bed arrangement 1001 according to a conventional design in which air flows axially into the adsorbent bed (an "axial bed").

[0072] FIG. 10 is another schematic diagram showing an adsorbent cartridge 1002 (a "radial bed") arranged in accordance with a particular embodiment of the present invention and including an internal axial void, with air passing radially into the cartridge.

[0073] For the purposes of this example, it is assumed that both the axial bed 1001 and the radial bed 1002 contain an adsorbent volume of 10 liters.

[0074] Air flow is 80m 3 / hr (22.2 liters / sec), the superficial velocity of the air in the axial bed 1001 is 1.257 m / sec.

[0075] In a radial bed 1002, the velocity of the air varies along the radial direction (i.e. the velocity varies depending on the distance from the central axis of the axial gap) and can be calculated at each point of the bed as shown in the graph of FIG.

[0076] The average velocity of the air entering the radial bed 1002 is calculated to be approximately 0.121 m / sec, as can be seen from the graph shown in FIG.

[0077] As can be seen, the radial bed 1002 produces air velocities that are over ten times lower than the axial bed 1001, although the overall shapes are very similar.

[0078] Applying these wind speed values ​​to the Ergun equation, the pressure drop across the axial bed is 28,329 Pa and the pressure drop across the radial bed is 104 Pa.

[0079] The work required by the compressor to move air through the bed, assuming the process is isothermal, is approximately:

number

[0080] For the axial bed 1001 the compressor work is 601 J / mol and for the radial bed 1002 the compressor work is 2.5 J / mol.

[0081] Therefore, in this example, it can be seen that the energy required to move the air through the radial bed 1002 is 240 times less than that required for the axial bed 1002.

[0082] As an additional advantage, the general configuration of the modular adsorber cartridge 101 provides useful design flexibility since the height of the modular adsorber cartridge 101 can be adapted simply by changing the lengths of the outer gas permeable tube 107 and the inner gas permeable tube 108, and the outer diameter and diameter of the axial gap 110 of the modular adsorber cartridge 101 can be easily adapted by changing the diameters of the outer gas permeable tube 107 and the inner gas permeable tube 108. As will be appreciated, these adaptations can be easily made by simply adapting the lengths of the edges of the sheets from which the outer gas permeable tube 107 and the inner gas permeable tube 108 are made, and by appropriately adapting the configurations of the open end cap 102 and the closed end cap 103.

[0083] The general configuration of the modular adsorber cartridge 101 means that the heat exchanger arrangement 701 can be easily integrated directly into the space in which the sorbent particles 109 are housed, leading to efficient heat transfer. Furthermore, the use of the heat exchanger arrangement 701 means that the sorbent particles 109 are indirectly heated. In other words, unlike many prior art techniques, the sorbent particles 109 are not heated by direct exposure to a heating medium such as steam or heated air. The use of such direct heating techniques typically results in a reduced durability of the sorbent and the need for more frequent replacement. Furthermore, the CO2 produced is generally of lower purity, as it is diluted with the direct heating medium. The result is an increased durability of the sorbent particles 109 and a higher purity of CO2 than would be expected if the modular adsorber cartridge 101 were heated with a direct heating medium.

[0084] FIG. 8 is a simplified schematic diagram illustrating a direct air capture apparatus 801 for extracting CO2 from atmospheric air using a vacuum temperature swing direct air capture process arranged in accordance with certain embodiments of the present invention.

[0085] Direct air capture device 801 comprises a modular adsorbent bed 802 comprising a plurality of modular adsorbent cartridges 803 of the type described above.

[0086] The modular adsorbent beds 802 are disposed within the interior volume of the vacuum chamber 804 in an axially parallel array. In other words, the axes of each of the modular adsorbent cartridges 803 are aligned parallel to one another.

[0087] The open end cap of each modular adsorber cartridge 803 is connected to an airflow conduit 805 to allow air to pass between the central opening of each modular adsorber cartridge 803 and the airflow conduit 805. The airflow conduit 805 is connected to a first sealable airflow conduit 806 which passes through a suitable opening in the wall of the vacuum chamber 804. Passing through a further opening in the wall of the vacuum chamber 804 is a second sealable air conduit 807. The first sealable air conduit 806 is provided with a first gas-tight valve 808 and the second sealable air conduit 807 is provided with a second gas-tight valve 809.

[0088] Typically, each modular adsorber cartridge 803 is positioned on a perforated plate 813 located on the outside of the airflow conduit 805 that provides perforations (holes) that open into the airflow conduit 805. Each perforated plate 813 is aligned with a central opening in the open end cap of each modular adsorber cartridge 803. Each modular adsorber cartridge 803 is secured in place by suitable fasteners 814 to ensure an airtight seal between the axial cavity of each modular adsorber cartridge 803 and the interior of the airflow conduit 805. This means that the only way air can move between the second sealable air conduit 807 and the first sealable air conduit 806 is through the adsorbent particles located between the inner and outer gas permeable tubes of the adsorber cartridge 803.

[0089] Typically, these fasteners 814 are provided by suitable bolts.

[0090] The heat exchanger fluid inlet and heat exchanger fluid outlet of each of the modular adsorber cartridges 803 are connected to a fluid flow conduit 810 for passing a heated fluid around the heat exchanger arrangement of each of the modular adsorber cartridges 803 .

[0091] A vacuum port 811 passes through a further opening in the wall of the vacuum chamber 804 for evacuating the vacuum chamber 804 during the CO2 capture process.

[0092] As described above, the vacuum temperature swing direct air capture process consists of four stages: in stage 1 (CO2 adsorption stage), atmospheric air is passed through the modular adsorber cartridges 803; in stage 2 (evacuation stage), the vacuum chamber 804 is evacuated; in stage 3 (desorption stage / regeneration stage), the adsorbent particles in each modular adsorber cartridge 803 are heated, the adsorbed CO2 is desorbed and the adsorbent particles are regenerated; and in stage 4 (CO2 extraction stage), the desorbed CO2 is extracted from the vacuum chamber.

[0093] In use, in one mode of operation, during the CO2 adsorption stage, the first gas tight valve 808 and the second gas tight valve 809 are set to an open position, and the fan 812 disposed in the first sealable air conduit 806 is operated to draw air from the vacuum chamber 804. This reduces the pressure in the air flow conduit 805, and consequently in the axial gap 110 of each modular adsorber cartridge 803. This means that the pressure in the axial gap of each modular adsorber cartridge 803 is lower than the pressure adjacent the exterior of each modular adsorber cartridge 803, and therefore air is drawn into the vacuum chamber 804 via the second sealable air conduit 807, and inwardly through the outer gas permeable tube, the adsorbent particles, and the inner gas permeable tube of each modular adsorber cartridge 803 in sequence. This air flow causes CO2 to be adsorbed onto the adsorbent particles of each modular adsorber cartridge 803.

[0094] Typically, the air entering the air capture device 801 directly via the second sealable air conduit 807 is ambient air. Typically, the incoming air undergoes particulate filtration to reduce the amount of solids entering the system. Such filtration typically filters out larger objects, such as small animals, and smaller objects, such as dust particles.

[0095] As will be appreciated, in alternative embodiments, the fan 812 may be positioned in alternative suitable locations, such as, for example, within the second sealable air conduit 807.

[0096] The direction of airflow in this mode of operation is indicated by the two arrows shown in FIG.

[0097] In another mode of operation, the direction of air flow is reversed during the CO2 adsorption phase. In this mode of operation, the first gas-tight valve 808 and the second gas-tight valve 809 are set to an open state, and the fan 812 located in the first sealable air conduit 806 is activated to draw air into the vacuum chamber 804. This increases the pressure in the air flow conduit 805, and thus in the axial gap 110 of each modular adsorber cartridge 803. This means that the pressure in the axial gap of each modular adsorber cartridge 803 is higher than the pressure adjacent the exterior of each modular adsorber cartridge 803, and therefore, in turn, air is pushed out of the vacuum chamber 804 via the second sealable air conduit 807. As will be appreciated, this draws air outwards through the outer gas permeable tube, the adsorbent particles and the inner gas permeable tube of each modular adsorber cartridge 803. This airflow causes the CO2 to be adsorbed onto the sorbent particles in each modular sorbent cartridge 803.

[0098] It will be appreciated that the modular adsorbent bed 802 may be used in substantially either mode of operation.

[0099] Once an appropriate amount of airflow has passed through modular adsorber cartridge 803, during an evacuation phase, first gas tight valve 808 and second gas tight valve 809 are closed, thereby sealing off vacuum chamber 804. A vacuum pump attached to vacuum port 811 is then activated to evacuate vacuum chamber 804 and create a vacuum within vacuum chamber 804. Once a sufficient vacuum has been established, the vacuum pump is stopped and vacuum port 811 is sealed off.

[0100] During the desorption stage, a heated fluid is passed through the heat exchanger arrangement of each of the modular adsorber cartridges 803, thereby desorbing CO2 previously adsorbed by the modular adsorber cartridges 803 and regenerating the adsorbent particles. As mentioned above, in alternative embodiments, alternative heating means may be provided, for example heating means configured to flow heated nitrogen or steam through the adsorbent particles of each modular cartridge.

[0101] As will be appreciated by those skilled in the art, the temperature of the heated water and the time the heat exchanger is activated will be determined by the temperature the sorbent particles must reach to desorb the adsorbed CO. In a typical embodiment, the heated fluid is at a temperature of 80-100° C., but can be as low as about 60° C. and as high as about 140° C. in certain embodiments.

[0102] This increases the pressure in the vacuum chamber 804, and once enough CO2 has been released, the vacuum pump is turned on again during the CO2 extraction stage, vacuum port 811 is opened, and CO2 is drawn out of the vacuum chamber 804. The CO2 is then compressed, typically in a liquid state, for either direct use in another process or for storage or later use.

[0103] The use of modular sorbent cartridges means that vacuum chambers of different sizes and configurations can be easily accommodated, as the number, position and size of cartridges can be easily adapted according to the spatial and geometric requirements of a particular vacuum chamber. Furthermore, the generally cylindrical configuration of each modular sorbent cartridge facilitates efficient packing within the vacuum chamber. FIG. 9a is a schematic diagram showing efficient packing of an array of modular sorbent cartridges within a vacuum chamber having a substantially circular cross section, and FIG. 9b is a schematic diagram showing efficient packing of an array of modular sorbent cartridges within a vacuum chamber having a substantially square cross section. Such efficient packing reduces the total volume of empty space within the vacuum chamber. This improves the purity of the CO2 produced in the direct air capture process, as less residual air is left in the vacuum chamber, resulting in a higher CO2 concentration. It also reduces the amount of energy required to generate the necessary vacuum within the vacuum chamber.

[0104] As can be seen from Figures 9a and 9b, advantageously, the use of a generally hexagonal open end cap for each modular adsorbent cartridge allows the modular adsorbent cartridges to be regularly spaced in a space-efficient hexagonal tiling pattern.

[0105] Additionally, the sorbent particles within any given modular sorbent cartridge can be easily accessed, inspected, and replaced, and as will be appreciated, inspecting and replacing sorbent particles in this manner is generally more convenient than in direct air capture systems consisting of a single monolithic sorbent bed.

[0106] Furthermore, a direct air capture system consisting of an array of modular adsorbent cartridges can be easily expanded in size and / or capacity by simply adding additional cartridges.

[0107] The dimensions of a modular adsorbent cartridge 101 according to embodiments of the present invention may vary depending on the intended use.

[0108] The number of modular adsorbent cartridges in a modular adsorbent bed according to embodiments of the present invention can vary depending on the intended application.

[0109] One of ordinary skill in the art will appreciate that the cartridge may take a variety of forms depending on the particular application. Figures 12a-d show illustrative cartridges of several different configurations, differing in height, width, inner and outer diameters, number of heating elements, and configurations of heating elements, in accordance with certain embodiments of the present invention.

[0110] Figure 12a shows an example cartridge with a height of 64 cm, an inner diameter of 5 cm, an outer diameter of 15 cm, and a bed thickness of 5 cm. It has a volume of 10 L and contains 8 heating elements, each of which consists of one pipe and two fins.

[0111] Figure 12b shows an example cartridge with a height of 200 cm, an inner diameter of 5 cm, an outer diameter of 15 cm, and a bed thickness of 5 cm. It has a volume of 31 L and six heating elements, each of which consists of one pipe and two fins.

[0112] Figure 12c shows an example cartridge with a height of 64 cm, an inner diameter of 2.5 cm, an outer diameter of 15 cm, and a bed thickness of 6.25 cm. It has a volume of 11 L and contains eight heating elements, each of which consists of one pipe and two fins.

[0113] Figure 12d shows an example cartridge with a height of 64 cm, an inner diameter of 5 cm, an outer diameter of 30 cm, and a bed thickness of 12.5 cm. The volume is 44 L and there are 10 heating elements, each of which consists of two pipes and three fins.

[0114] All features disclosed in this specification (including the accompanying claims, abstract and drawings), and / or all steps of any method or process so disclosed, may be combined in any combination, except combinations in which at least some of such features and / or steps are mutually exclusive. Each feature disclosed in this specification (including the accompanying claims, abstract and drawings), unless expressly stated otherwise, may be replaced with an alternative feature serving the same, equivalent or similar purpose. Thus, unless expressly stated otherwise, each feature disclosed is an example of a generic series of equivalent or similar features. The invention is not limited to the details of the foregoing embodiments. The invention extends to any novel or novel combination of features disclosed in this specification (including the accompanying claims, abstract and drawings), or any novel or novel combination of steps of any method or process disclosed.

[0115] With respect to the use of virtually any plural and / or singular term herein, one of ordinary skill in the art can translate from plural to singular and / or from singular to plural as appropriate to the context and / or application. Various singular / plural permutations may be expressly provided herein for clarity.

[0116] Those skilled in the art will understand that the terms used in this specification, in general, and in the appended claims, in particular, are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "includes but is not limited to," etc.). Moreover, those skilled in the art will understand that if a particular number of introduced claim recitations is intended, such intent will be expressly set forth in the claim, and in the absence of such recitation, no such intent exists. For example, to aid in understanding, the following appended claims may include the use of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed as meaning that the introduction of a claim recitation by the indefinite article "a" or "an" limits a particular claim that includes such introduced claim recitation to embodiments that include only one such recitation. This is true even if the same claim contains the introductory phrase "one or more" or "at least one" and the indefinite article "a" or "an" (e.g., "a" and / or "an" should be interpreted to mean "at least one" or "one or more"). The same applies to the use of definite articles used to introduce claim recitations. Moreover, even if a particular number is explicitly recited in the introduction to a claim recitation, one of ordinary skill in the art will recognize that such recitation should be interpreted to mean at least the recited number (e.g., a plain recitation of "two recited objects" without other modifiers means at least two recited objects, or more than two recited objects).

[0117] Various embodiments of the present disclosure have been described herein for purposes of illustration, and it will be understood that various changes may be made without departing from the scope of the present disclosure. Accordingly, the various embodiments disclosed herein are not intended to be limiting, with the true scope being indicated by the following claims.

Claims

1. 1. A modular adsorbent bed for mounting in a vacuum chamber for use in a vacuum temperature swing direct air capture process for extracting carbon dioxide from atmospheric air, said modular adsorbent bed comprising a plurality of adsorbent cartridges arrangable in an axially parallel array; a modular adsorbent bed, wherein each said adsorbent cartridge comprises a hollow cylindrical body containing an adsorbent held in place between an outer gas permeable tube and an inner gas permeable tube, the inner gas permeable tube defining an axially disposed void within the cartridge, and wherein, in use, each cartridge is configured to receive an air stream from which carbon dioxide is to be adsorbed, the air stream passing radially through the adsorbent towards the axially disposed void or passing radially away from the axially disposed void.

2. 10. The modular adsorbent bed of claim 1, wherein each adsorbent cartridge comprises heat exchange means for providing thermal energy to the adsorbent during a regeneration stage of the vacuum temperature swing direct air capture process.

3. 3. The modular adsorbent bed of claim 2, wherein within each adsorbent cartridge, the heat exchange means is disposed between the outer gas permeable tube and the inner gas permeable tube.

4. 2. The modular adsorbent bed of claim 1, wherein each adsorbent cartridge is sealed at a first end and, in use, opens at a second end to a common air flow conduit, the opening comprising, for each adsorbent cartridge: a pressure within the common air flow conduit that is less than the pressure adjacent the exterior of each sorbent cartridge drives air flow radially through the sorbent body toward the axially disposed voids; and wherein the modular adsorbent bed is open such that a pressure within the common air flow conduit, which is greater than the pressure adjacent the exterior of each adsorbent cartridge, drives air flow radially through the adsorbent and away from the axially disposed voids.

5. 10. The modular adsorbent bed of claim 1, wherein within each adsorbent cartridge, the outer gas permeable tube and the inner gas permeable tube of each adsorbent cartridge comprise tubes of gas permeable material held tightly by a retaining tube.

6. 6. The modular adsorbent bed of claim 5, wherein within each adsorbent cartridge, the gas permeable material comprises a mesh.

7. 7. A modular adsorbent bed according to claim 5 or 6, wherein within each adsorbent cartridge the holding tube is made from perforated sheet.

8. 5. The modular adsorbent bed of claim 4, wherein within each adsorbent cartridge, the first end is sealed by an end cap.

9. 5. The modular adsorbent bed of claim 4, wherein in each adsorbent cartridge, the second end is terminated by an open end cap, said open end cap enclosing the adsorbent material and including an aperture which, in use, opens to a common air flow conduit.

10. 4. A modular adsorbent bed according to claim 2 or 3, wherein within each adsorbent cartridge, the heat exchange means comprises a conduit for receiving a heat exchange fluid.

11. 11. The modular sorbent bed of claim 10, wherein within each sorbent cartridge, the conduit comprises a plurality of connected tubing sections.

12. 12. The modular adsorbent bed of claim 11, wherein within each adsorbent cartridge, the plurality of connected tube segments are substantially parallel to the axially disposed voids.

13. 12. The modular adsorbent bed of claim 11, wherein within each adsorbent cartridge, each of the tube sections is connected to one or more heat dissipation fins.

14. 11. The modular adsorbent bed of claim 10, wherein within each adsorbent cartridge, the heat exchange means of each adsorbent cartridge is connected to a common heat exchange fluid source.

15. 10. The modular adsorbent bed of claim 1, wherein in each adsorbent cartridge, the adsorbent comprises adsorbent particles.

16. 10. An adsorbent cartridge for a modular adsorbent bed according to claim 1, said adsorbent cartridge comprising:

1. An adsorbent cartridge comprising: a hollow cylinder containing an adsorbent held in place between an outer gas permeable tube and an inner gas permeable tube, the inner gas permeable tube defining an axially disposed void within the cartridge, the cartridge being configured, in use, to receive an air stream to be adsorbed of carbon dioxide passing radially through the adsorbent toward the axially disposed void or passing radially away from the axially disposed void.

17. 1. An apparatus for performing a vacuum temperature swing direct air capture process for extracting carbon dioxide from the atmosphere, the process including a carbon dioxide adsorption stage, a ventilation stage, a carbon dioxide desorption stage, and a carbon dioxide extraction stage, the apparatus comprising: a vacuum chamber having the modular adsorbent bed of claim 1 disposed within its interior volume; a first sealable air conduit providing an air inlet to the interior volume of the vacuum chamber; a second sealable air conduit providing an air inlet to the vacuum chamber and connected to a common conduit connected via an airtight connection to the axially disposed voids of each adsorbent cartridge of the modular adsorbent bed; heating means configured to heat the adsorbent cartridges of the modular adsorbent bed during the carbon dioxide desorption step; a sealable carbon dioxide extraction conduit through which carbon dioxide desorbed during the carbon dioxide extraction step is extracted, wherein in a first mode of operation during the carbon dioxide adsorption step, atmospheric air to be treated is input to the vacuum chamber via the first sealable air conduit and output via the second sealable air conduit, and in a second mode of operation during the carbon dioxide adsorption step, atmospheric air to be treated is input to the vacuum chamber via the second sealable air conduit and output via the first sealable air conduit.

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