Technical Field

[0001] The present invention relates broadly to a gas separation apparatus such as that suitable for extracting carbon dioxide from atmosphere. The invention is also broadly related to a method of gas separation and more particularly is directed to a method of directly capturing carbon dioxide from air.

Summary of Invention

[0002] According to a first aspect of the present invention there is provided a gas separation apparatus comprising: a plurality of gas chambers each containing an adsorbent structure adapted to directly adsorb carbon dioxide from gas exposed to the chamber; a gate assembly arranged to cooperate with the plurality of gas chambers, the gate assembly being movable from a first position to permit gas flow through at least one of the chambers for carbon dioxide adsorption whilst sealing closed the remaining of the chambers, to a second position to permit gas flow through at least said remaining of the chambers whilst sealing closed one of said at least one of the chambers; an actuator operatively coupled to the gate assembly to effect movement of the gate assembly from the first to the second positions.

[0003] Preferably each of the gas chambers is defined by a tubular housing being open at each of its ends. More preferably the tubular housing is in the form of a canister arranged to cooperate with the gate assembly at each of said open ends of the tubular housing for opening and sealing closure of the respective gas chambers.

[0004] Preferably the gate assembly includes a gate member dedicated to a common end of the canisters which are parallel and aligned with one another for simultaneously opening and sealing closure of select of the gas chambers in either the first or the second positions. More preferably the parallel canisters are equally spaced angularly relative to one another. Still more preferably the gate member includes a predetermined number of openings angularly separated to align with respective of said at least one of the chambers whilst the gate member blocks the remaining of the chambers in the first position. Even more preferably the gate member is arranged to rotate about the common end of the canisters for movement between the first and second positions, the canisters being angularly spaced relative to a rotational axis about which the gate member rotates wherein simultaneous opening and sealing closure of the select gas chambers is effected in either the first or the second positions.

[0005] Preferably the gate assembly includes biasing means operatively coupled to the gate member to urge it into sealing contact with the open end of the canister of the remaining of the chambers to promote sealing closure of said canister in the first position. More preferably each of the canisters at its open end is associated with a seal arranged for sealing contact with the gate member under the biasing influence of the biasing means.

[0006] Preferably the actuator includes a motor arranged to engage the gate member for rotation about its rotational axis between the first and second positions. More preferably the actuator also includes a clutch which on engagement deactivates the biasing means releasing it from the gate member releasing it from sealing contact with the canister of the select gas chamber whereupon rotation of the gate member is effected via the motor. Even more preferably the clutch is an electromagnetic clutch which on disengagement activates the biasing means urging it into contact with the gate member effecting its sealing contact with the canister of the select gas chamber.

[0007] Preferably the gate member is one of a pair of gate members dedicated to respective of the pair of open ends of the tubular housings. More preferably the actuator includes a pair of motors dedicated to respective of the pair of gate members. Even more preferably the pair of gate members are configured and the motors synchronised for simultaneous opening or closure of the open ends of the same tubular housings. Alternatively the actuator includes a shaft connected between the pair of gate members with a single motor coupled to the shaft for synchronised opening or closure of the tubular housings.

[0008] Preferably the gas separation apparatus also comprises a fan operatively coupled to at least one of the gas chambers to promote the gas flow through said chambers for carbon dioxide adsorption. More preferably the fan is one of a plurality of fans dedicated to respective of the plurality of gas chambers.

[0009] Preferably the gas separation apparatus further comprises a control device arranged to communicate with the actuator to control movement of the gate assembly from the first to the second positions after a predetermined period of time. More preferably the control device is arranged to communicate with the plurality of fans to deactivate the fan associated with the remaining of the chambers with the gate assembly in the first position.

[0010] Preferably the gas separation apparatus additionally comprises a purging assembly associated with the gas chambers for purging of gas from the remaining of the chambers with the gate assembly in the first position. More preferably the purging assembly includes a vacuum pump arranged for evacuation of gas from said remaining chambers.

[0011] Preferably the gas separation apparatus still further comprises a desorption assembly associated with the gas chambers for desorption of the carbon dioxide from the adsorbent structure to which it is directly adsorbed. More preferably the desorption assembly includes heating means operatively coupled to the gas chambers to elevate the temperature of the adsorbent structure for desorption of the carbon dioxide.

[0012] According to a second aspect of the invention there is provided a method of gas separation comprising the steps of: exposing gas to an adsorbent structure within a plurality of gas chambers for direct adsorption of carbon dioxide from the gas onto the adsorbent structure; moving a gate assembly arranged to cooperate with the plurality of gas chambers from i) a first position to permit gas flow through at least one of the chambers for carbon dioxide adsorption whilst sealing closed the remaining of the chambers, to ii) a second position to permit gas flow through at least said remaining of the chambers whilst sealing closed one of said at least one of the chambers. [0013] Preferably the step of exposing gas to an adsorbent structure involves promoting gas flow through a plurality of canisters each defining respective of the plurality of gas chambers.

[0014] Preferably the step of moving the gate assembly from the first to the second positions involves rotating a gate member dedicated to a common end of the canisters, the gate member including a predetermined number of openings arranged in the first position to align with respective openings of said at least one of the chambers of the corresponding canisters.

[0015] Preferably the gate assembly rotationally moves in substantially equal angular increments being equal to the angular offset of the canisters relative to one another. More preferably movement of the gate assembly is effected after substantially the same periods of time between the first and the second position, or consecutive positions, of the gate assembly. Still more preferably said periods of time are based on the time required for desorption of the carbon dioxide from the adsorbent structure onto which it is adsorbed.

[0016] Preferably the plurality of gas chambers in number is determined based on i) the total time (T) required for a full cycle of gas separation for one of the gas chambers, and ii) the time (ts) required for the desorption stage of that cycle. More preferably the number of chambers is calculated according to the equation T/(fs + tp) where tp is the time required for purging of the gas chamber.

Brief Description of Drawings

[0017] In order to achieve a better understanding of the nature of the present invention a preferred embodiment of a gas separation apparatus will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is a perspective view of a gas separation apparatus according to a preferred embodiment of the invention;

Figure 2 is an end elevational view of the gas separation apparatus of the embodiment of figure 1 ; Figure 3 is a perspective view shown exploded of the gas separation apparatus of the embodiment of figure 1 ;

Figure 4 is a sectional view taken longitudinally of the gas separation apparatus of the embodiment of the preceding figures.

Detailed Description

[0018] As best seen in figures 1 and 4, there is a gas separation apparatus 10 of a preferred embodiment of a first aspect of the invention. In this embodiment the gas separation apparatus is in the form of a direct air capture apparatus 10 generally comprising:

1 . a plurality of air or other gas chambers 12a to 12f each containing an adsorbent structure schematically depicted at 14a to 14f respectively;

2. a gate assembly 16 and 17 arranged to cooperate with each end of the plurality of air chambers 12a to 12f;

3. an actuator 18 and 19 operatively coupled to the gate assembly 16 and 17 to effect its movement.

[0019] In this example, the plurality of air chambers 12a to 12f are each defined by a tubular housing in the form of canisters 20a to 20f, respectively. The canisters such as 20a are open ended and arranged parallel to one another to cooperate with the gate assembly 16 and 17 for opening and sealing closure of the respective air chambers 12a to 12f. In this embodiment, the gate assembly 16 and 17 includes a pair of gate members 22 and 24 each dedicated to a common end of the canisters 20a to 20f. The gate members 22 and 24 are together movable from:

1 . a first position (as illustrated in all figures) to permit gas flow through at least one of the chambers such as 12a to 12e whilst sealing closed the remaining of the chambers 12f ;

2. to a second position (not illustrated) to permit gas flow through the remaining of the chambers 12f sealing closed one of said at least one of the chambers such as 12a. [0020] In this example, the canisters 20a to 20f are of substantially equal length and aligned with one another for simultaneous opening and sealing closure via the gate members 22 and 24 in either the first or the second positions. The parallel canisters 20a to 20f are as viewed from their common ends arranged in a circle and equally-spaced angularly relative to one another. The gate members such as 22 each include a predetermined number of openings, in this instance five openings 26a to 26e, angularly separated to align with respective of said at least one of the chambers 12a to 12e in the first position. The remaining of the chambers 12f is blocked or otherwise sealed by the gate members such as 22 and 24 in the first position.

[0021] In operation, the gate members 22 and 24 of this embodiment are arranged to rotate about respective ends of the canisters 20a to 20f for movement between the first and consecutive angular positions. The gate members 22 and 24 rotate about a rotational axis 30 about which the canisters 20a to 20f are equally spaced both radially and angularly. This means simultaneous opening and sealing closure of the select air chambers such as 12a is effected by rotation of the gate members 22 and 24 into either of the first or the consecutive positions.

[0022] As seen in the exploded view of figure 3, the gate assembly 17 includes biasing means in the form of springs 32a to 32f operatively coupled to the gate member 24 to urge it into sealing contact with the canister 20f of the remaining of the chambers 12f in the first position. In this example the springs 32a to 32f are mounted to an inside face of a housing plate 36 of the gate assembly 17. As seen at an opposite end of the apparatus 10, each of the canisters 20a to 20f is associated with a seal 38a to 38f arranged for sealing contact with the gate member 22 under the influence of the biasing means or springs such as 31 a. In this particular construction of the apparatus 10, the canisters 20a to 20f are mounted to end plates 39 and 40 having apertures such as 42a to 42f for receipt of the corresponding canister 20a to 20f. Each of the apertures such as 42a is rebated on an outer face of the end plate 39 for seating of the corresponding seal 38a.

[0023] As seen in figure 4, the actuator such as 18 includes a motor 46 arranged to engage the gate member 22 for rotation about its rotational axis 30. The actuator 18 or 19 also includes a clutch arrangement in the form or an electromagnetic clutch (not designated) which on engagement deactivates the biasing means or springs such as 31 a or 32a from the gate member 22 or 24. The gate member 22 or 24 thus retracts from its sealing contact with the canisters 20a to 20f whereupon rotation of the gate member 22 and 24 is effected via the corresponding motor 46 and 47. In this example, the gate member such as 22 is rotated anticlockwise (when viewed from the left hand end) from the first into the second position where the electromagnetic clutch on disengagement activates the biasing means or springs such as 31 a which urge the gate member 22 into sealing contact with the canisters 20a to 20f. In the second position, the canister 20a of the select air chamber 12a is sealed closed by the gate members 22 and 24 whereas the other canisters 20b to 20f are opened to atmosphere.

[0024] In this example, the motor 46 is one of a pair of the motors dedicated to respective of the pair of gate members 22 and 24. The pair of gate members 22 and 24 are configured and the motors 46 and 47 synchronised for simultaneous opening or closure of the canisters such as 32a to 32f. As seen in figure 3, the gas separation or direct air capture apparatus 10 also comprises a plurality of fans 52a to 52f dedicated to respective of the plurality of gas chambers 12a to 12f. The fans such as 52a are mounted to the housing plate 37 of the gate assembly 16and designed to promote gas flow through the corresponding chamber such as 12a for carbon dioxide adsorption.

[0025] The gas separation or direct air capture apparatus 10 further comprises a control device (not shown) arranged to communicate with the actuator 18 and 19 or in this example the motors 46 and 47. The control device controls movement of the gate assembly 16 and 17 or more particularly the gate members 22 and 24 from the first to the second positions, or other consecutive positions, after a predetermined period of time. The control device is also arranged to communicate with the fans 50a to 50f to deactivate the fan such as 52f associated with the remaining or sealed closed of the chamber 12fwith the gate assembly 18 and 19 in the first position.

[0026] The gas separation or direct air capture apparatus 10 additionally comprises a purging assembly (not shown) associated with each of the air chambers 12a to 12f for the purging of gas from the remaining or sealed closed of the chambers 12f with the gate assembly in the first position. In this example the purging assembly includes a vacuum pump (not shown) arranged for evacuation of gas from the sealed closed chamber 12f. The gas separation or direct air capture apparatus 10 still further comprises a desorption assembly (not shown) associated with the air chambers 12a to 12f for desorption of the carbon dioxide from the adsorbent structure 14a to 14f onto which it is directly adsorbed. In this embodiment the desorption assembly includes heating means operatively coupled to the sealed closed air chamber such as 12f to elevate the temperature of the corresponding adsorbent structure 14f for desorption of the carbon dioxide.

[0027] In a second aspect of the invention there is a method of gas separation or direct air capture which in this embodiment generally comprises the steps of:

1 . exposing air or another gas to an adsorbent structure within a plurality of air chambers for direct adsorption of carbon dioxide from the air onto the adsorbent structure;

2. moving a gate assembly arranged to cooperate with the plurality of air chambers to sequentially permit gas flow through at least one of the chambers whilst sealing closed the remainder of the chambers.

[0028] In this embodiment the method of gas separation or direct air capture will for convenience be described in the context of the apparatus 10 of the first aspect of the invention. It should be appreciated that the method of gas separation may be implemented by using another apparatus and nonetheless remain within the scope of this aspect of the present invention.

[0029] In this example, the adsorbent structure such as 14a is adapted to directly adsorb carbon dioxide from gas exposed to the chamber 12a. The adsorbent structure 14a includes a metal-organic framework (MOF) capable of directly adsorbing carbon dioxide from atmosphere. It will be understood that a typical cycle in gas separation or direct air capture of carbon dioxide from air involves the following stages:

1. adsorption of carbon dioxide from the air or other gas onto the MOF; 2. purging of residual air, typically by application of a vacuum;

3. desorption or release of the adsorbed carbon dioxide from the MOF, typically by heating the MOF to an elevated temperature;

4. cooling of the MOF, typically by exposing it to air or other gas at ambient temperature.

[0030] In this embodiment, the gate assembly 16 and 17 is sequentially moved from a first position as depicted in the various illustrations of the apparatus 10 of the preferred embodiment to a second and consecutive positions (not illustrated) synchronous with the typical cycle for gas separation or direct air capture of carbon dioxide as outlined in the preceding paragraph. In this example, the total time for a full cycle of gas separation for each of the canisters such as 20a is 30 minutes. The gate assembly 16 and 17 of the preferred embodiment of the apparatus 10 rotates from its first to the second or consecutive positions every five minutes wherein each of the canisters 20a to 20f experiences the total cycle time of 30 minutes. In the context of the apparatus 10 of the preferred embodiment, it will be understood that at the first position:

1 . canister 20a is open in the course of completing cooling at stage 4 and adsorption of carbon dioxide at stage 1 for a combined period of 25 minutes;

2. four canisters 20b to 20e are open in the course of stage 4 cooling and stage 1 adsorption for combined durations of 20, 15, 10, and 5 minutes, respectively;

3. canister 20f is sealed closed in the course of completing its purging of residual air at stage 2 and desorption of the adsorbed carbon dioxide at stage 3 for a combined period of 5 minutes.

[0031 ] The gate assembly 16 and 17 under the control of the actuator or motors 46 and 47 is rotated between consecutive positions every five minutes. In this case, the gate members 22 and 24 are rotated approximately 60 degrees anticlockwise each five minutes so that:

1 . the total cycle time for each of the canisters such as 20a is 30 minutes; and

2. the gate members 22 and 24 each rotate 360 degrees in the 30 minute cycle time. [0032] It will be apparent from the illustrations of the preferred embodiment that on stepped rotation of the gate members 22 and 24 to the second position:

1 . the canister 20a is sealed closed for stage 2 purging and stage 3 desorption;

2. canisters 20b to 20f are open for stage 4 cooling and stage 1 adsorption of carbon dioxide.

[0033] The apparatus 10 continues in this staged rotation of the gate assembly 16 and 17 whereby each of the canisters is sealed closed for purging and desorption for the requisite time. The total number of gas chambers (N) such as 12a or canisters 10a may be calculated based on the total time (T) required for a full cycle of gas separation or direct air capture according to the equation:

N = T/(fc/ + tp), where td is the time required for the desorption stage and tp is the time required for the purging stage.

[0034] For example, if the required time for purging and desorption is 10 minutes and the total cycle time is 60 minutes then the number of gas chambers will be six (6). Put differently, the time required for purging and desorption is a reciprocal fraction of the number of canisters of the apparatus. For example, if the apparatus consists of 10 canisters then one tenth of the time is dedicated to purging and desorption. If the total cycle time is 60 minutes this equates to 6 minutes for purging and desorption. In these variations, it is assumed that the gate member 22 or 24 includes N-1 or in this case openings 26a to 26e, where N is the number of gas chambers or corresponding canisters.

[0035] It is to be understood that carbon dioxide obtained from the apparatus such as 10 according to this cycle not only directly removes this greenhouse gas from the atmosphere but also provides carbon dioxide as a potential feedstock. For example, renewable methane may be synthesised by reacting carbon dioxide from the apparatus such as 10 with hydrogen from water hydrolysis powered by a renewable energy source. The applicant’s pending International patent publication No. W02020/000020 is directed to these technologies. [0036] Now that a preferred embodiment of the gas separation apparatus has been described it will be apparent to those skilled in the art that it has at least the following advantages:

1 . the apparatus with a given footprint provides increased exposure of air or other gas to the adsorbent structure for increased direct carbon dioxide adsorption;

2. the apparatus being of a modular construction lends itself to automation of the direct air capture of carbon dioxide;

3. the apparatus can be scaled up or down depending on the carbon dioxide requirement;

4. the apparatus can be reconfigured depending on the concentration of carbon dioxide in the air or other gas to which it is exposed where for example lower carbon dioxide concentrations require longer adsorption periods.

[0037] Those skilled in the art will appreciate that the invention as described herein is susceptible to variations and modifications other than those specifically described. For example, the canisters of the preferred embodiment may be of a linear rather than circular arrangement with gate members moving in a shuttle action across the ends of the aligned canisters. The specific construction of the apparatus may vary where for example the clutch and biasing means is not required where vacuum pressure alone maintains sealing closure of the gas chambers in the course of desorption of the adsorbed carbon dioxide. The gate member of the preferred or alternative embodiments may have more than one of the openings vacant for blocking or sealing of the same number of gas chambers or corresponding canisters of the apparatus. It is to be understood that the apparatus and method extend to other embodiments employing a combination of vacuum pressure swing and temperature swing driving the adsorption/desorption cycle which effects the required gas separation. The apparatus may be applied to gases other than air where carbon dioxide is adsorbed onto an adsorbent structure of the apparatus.

[0038] All such variations and modifications are to be considered within the scope of the present invention the nature of which is to be determined from the foregoing description.