METHOD FOR CAPTURE OF CARBON DIOXIDE FROM AMBIENT AIR AND CORRESPONDING ADSORBER STRUCTURES WITH A PLURALITY OF PARALLEL SURFACES

Abstract

A DAC method as well as a unit containing an adsorber structure having an array of adsorber elements with a support layer and on both sides thereof a sorbent layer (1, 2), wherein the adsorber elements are parallel and spaced apart forming parallel fluid passages for flow-through of ambient atmospheric air and steam. The method involves the following sequential and repeating steps: (a) adsorption by flow-through; (b) isolating the sorbent; (c) injecting a stream of saturated steam through the parallel fluid passages and inducing an increase of the temperature; (d) extracting desorbed carbon dioxide from the unit and separating it from steam; (e) bringing the sorbent material to ambient temperature conditions wherein in step (a) the speed of the air is in the range of 2-8 m/s, and wherein at least in step (d) the speed of the steam is at least 0.2 m/s.

Claims

1. A method for separating gaseous carbon dioxide from ambient atmospheric air containing said gaseous carbon dioxide as well as further gases different from gaseous carbon dioxide, by cyclic adsorption/desorption using a sorbent material adsorbing said gaseous carbon dioxide, using a unit containing an adsorber structure with said sorbent material, the adsorber structure being able to sustain a temperature of at least 60° C. for the desorption of at least said gaseous carbon dioxide and the unit being openable to flow-through of the ambient atmospheric air and for contacting it with the sorbent material for the adsorption step, wherein the adsorber structure comprises an array of individual adsorber elements, each adsorber element comprising at least one support layer and at least one sorbent layer comprising or consisting of at least one sorbent material, where said sorbent material offers selective adsorption of CO.sub.2 over other major non-condensable gases in air in the presence of moisture or water vapor, wherein the adsorber elements in the array are arranged essentially parallel to each other and spaced apart from each other forming parallel fluid passages for flow-through of at least one of ambient atmospheric air and steam, wherein the method comprises at least the following sequential and in this sequence repeating steps (a) - (e): (a) contacting said ambient atmospheric air with the sorbent material to allow at least said gaseous carbon dioxide to adsorb on the sorbent material by flow-through through said parallel fluid passages under ambient atmospheric pressure conditions and ambient atmospheric temperature conditions in an adsorption step; (b) isolating said sorbent with adsorbed carbon dioxide in said unit from said flow-through while maintaining the temperature in the sorbent; (c) injecting a stream of saturated or superheated steam by flow-through through said parallel fluid passages and thereby inducing an increase of the temperature of the sorbent to a temperature between 60 and 110° C., starting the desorption of CO.sub.2; (d) extracting at least the desorbed gaseous carbon dioxide from the unit and separating gaseous carbon dioxide from steam by condensation in or downstream of the unit, while still contacting the sorbent material with steam by injecting and/or partial circulating saturated or superheated steam into said unit, thereby flushing and purging both steam and CO.sub.2 from the unit at a molar ratio of steam to carbon dioxide between 4:1 and 40:1, while regulating the extraction and steam supply or both to essentially maintain the temperature in the sorbent at the end of the preceding step (c) or to essentially maintain the pressure in the sorbent at the end of the preceding step (c), or both; (e) bringing the sorbent material to ambient atmospheric temperature conditions; wherein in step (a) the flow speed of the ambient atmospheric air through the adsorber structure is in the range of 2-9 m/s, and wherein at least in step (d) the flow speed of the steam through the adsorber structure is at least 0.2 m/s, wherein essentially exclusive use or fully exclusive use of steam is made in steps (c) and (d) for the delivery of heating energy during the desorption process.

2. The method according to claim 1, wherein in step (a) the flow speed of the ambient atmospheric air through the adsorber structure is in the range of 2-9 m/s, or wherein at least in step (d) the flow speed of the steam through the adsorber structure is in the range of 0.3-6 m/s.

3. The method according to claim 1, wherein in step (a) the specific flow rate of the ambient atmospheric air through the adsorber structure, as a function of the mass of the sorbent, is in the range of 20 - 10′000 m3/h/kg, or wherein in step (a) the specific flow rate of the ambient atmospheric air through the adsorber structure, as a function of the volume of the sorbent, is in the range of 4′000-500′000 m3/h/m3, or wherein at least in step (d) the specific flow rate of the steam through the adsorber structure, as a function of the mass of the sorbent, is in the range of 1 - 500 kg/h/kg , or wherein at least in step (d) the specific flow rate of the steam through the adsorber structure, as a function of the volume of the sorbent, is in the range of 200-15 ′000 kg/h/m3.

4. The method according to claim 1, wherein the carbon dioxide capture fraction, defined as the percentage of carbon dioxide captured from the ambient atmospheric air in an adsorption step by the sorbent material is in the range of 10 - 75%, or wherein the amount of carbon dioxide captured on the sorbent per gram sorbent is at least 0.1 for an adsorption time span of at least 5 or at least 10 minutes, or wherein the normalized amount of carbon dioxide captured on the sorbent per gram sorbent per hour is in the range of 0.5 - 10 mmol/g/h.

5. The method according to claim 1, wherein the adsorber structure comprises an array of individual adsorber elements, each adsorber element comprising a central carrier layer or porous support and on both sides thereof at least one porous or permeable sorbent layer with chemically attached carbon dioxide capture moieties.

6. The method according to claim 1, wherein the adsorber elements in the array are arranged essentially parallel to each other and spaced apart by spacer elements from each other forming parallel fluid passages for flow-through of at least one of ambient atmospheric air and steam, or wherein the spacing (b.sub.spacer) between the adsorber elements is in the range of 0.2 - 5 mm, or wherein each adsorber element has the form of a plane with a thickness (b.sub.element) in the range of 0.1 - 1 mm.

7. The method according to claim 1, wherein said unit is evacuable to a vacuum pressure of 400 mbar(abs) or less, and wherein step (b) includes isolating said sorbent with adsorbed carbon dioxide in said unit from said flow-through while maintaining the temperature in the sorbent and then evacuating said unit to a pressure in the range of 20-400 mbar(abs), wherein in step (c) injecting a stream of saturated or superheated steam is also inducing an increase in internal pressure of the reactor unit, and wherein step (e) includes bringing the sorbent material to ambient atmospheric pressure conditions and ambient atmospheric temperature conditions.

8. A device for carrying out a method for separating gaseous carbon dioxide from a gas mixture in the form of ambient air, containing said gaseous carbon dioxide as well as further gases different from gaseous carbon dioxide by cyclic adsorption/desorption using a sorbent material adsorbing said gaseous carbon dioxide, said device comprising a steam source; at least one unit containing an adsorber structure with said sorbent material, the adsorber structure being heatable to a temperature of at least 60° C. for the desorption of at least said gaseous carbon dioxide and the unit being openable to flow-through of the ambient atmospheric air and for contacting it with the sorbent material for an adsorption step, wherein the adsorber structure comprises an array of individual adsorber elements each adsorber element comprises at least one sorbent layer comprising or consisting of at least one sorbent material, where said sorbent material offers selective adsorption of CO.sub.2 over other major non-condensable gases in air in the presence of moisture or water vapor, wherein the adsorber elements in the array are arranged essentially parallel to each other and spaced apart from each other, forming parallel fluid passages for flow-through of at least one of ambient atmospheric air and steam, at least one device for separating carbon dioxide from water.

9. The device according to claim 8, wherein the spacing width (b.sub.spacer) is in the range of 0.4-5 mm or wherein the element length (L) is in the range of 100-3000 mm.

10. The device according to claim 8, wherein the element length (L) is given as a function of the spacing width (b.sub.spacer), and as a function of the element thickness (b.sub.element) by the following equation $L = \frac{K_{g l o b a l} \cdot b_{s p a c e r}^{2}}{(1 + \frac{b_{e l e m e n t}}{b_{s p a c e r}})}$ wherein K.sub.global is in the range of 70-2500 mm^-1.

11. The device according to claim 8, wherein the adsorber elements comprise a central carrier layer and on both sides thereof at least one sorbent layer (1, 2), or wherein the adsorber structure comprises an array of individual adsorber elements each adsorber element comprising a central porous carrier layer or porous support and on one or both sides thereof at least one porous and/or permeable sorbent layer or wherein the adsorber structure comprises an array of individual adsorber elements, each adsorber element comprising a central carrier or support layer and on both sides thereof at least one porous and/or permeable sorbent layer with chemically attached carbon dioxide capture moieties.

12. The device according to claim 8, wherein the adsorber elements in the array are arranged essentially parallel to each other and spaced apart by spacer elements from each other forming parallel fluid passages for flow-through of ambient atmospheric air and/or steam, or wherein the spacing between the adsorber elements is in the range of 0.2 - 5 mm.

13. The device according to claim 8, wherein it is suitable and adapted such that in the adsorption step (a) the flow speed of the ambient atmospheric air through the adsorber structure is in the range of 2-9 m/s, or wherein it is suitable and adapted such that in a steam flow through step (d) the flow speed of the steam through the adsorber structure is in the range of at least 0.2 m/s, or wherein it is suitable and adapted such that in the adsorption step (a) the flow speed of the ambient atmospheric air through or at the inlet into the adsorber structure is in the range of 4-7 m/s, or wherein it is suitable and adapted such that in a steam flow through step (d) the flow speed of the steam through the adsorber structure is in the range of 0.3-6 m/s.

14. The device according to claim 8, wherein it comprises means for directing the steam in a steam flow through step (d) along a different flow direction than the flow direction of the flow-through direction of the ambient atmospheric air in the adsorption step (a).

15. The method according to claim 1 carried out for direct air capture or for recovery of carbon dioxide from ambient atmospheric air.

16. The method according to claim 2, wherein at least in step (d) the flow speed of the steam through the adsorber structure is in the range of 0.3-1.0 m/s if the flow of the ambient atmospheric air in step (a) and the flow of the steam in step (d) are essentially along the same flow path, or wherein at least in step (d) the flow speed of the steam through the adsorber structure is in the range of 1-6 m/s if the flow of the ambient atmospheric air in step (a) and the flow of the steam is step (d) are along different flow path flows, or if the flow of steam in step (d) is essentially orthogonal to that of the ambient atmospheric air in step (a).

17. The method according to claim 1, wherein in step (a) the specific flow rate of the ambient atmospheric air through the adsorber structure, as a function of the mass of the sorbent, is in the range of 100-7′000 m3/h/kg, or wherein in step (a) the specific flow rate of the ambient atmospheric air through the adsorber structure, as a function of the volume of the sorbent, is in the range of 10′000-300′000 m3/h/m3 or wherein at least in step (d) the specific flow rate of the steam through the adsorber structure, as a function of the mass of the sorbent, is in the range of 50-250 kg/h/kg, or wherein at least in step (d) the specific flow rate of the steam through the adsorber structure , as a function of the volume of the sorbent, is in the range of 500-10 ′000 kg/h/m3.

18. The method according to claim 1, wherein the carbon dioxide capture fraction, defined as the percentage of carbon dioxide captured from the ambient atmospheric air in an adsorption step by the sorbent material is in the range of 30-60% or wherein the amount of carbon dioxide captured on the sorbent per gram sorbent is in the range of 0.1- 1.8 mmol/g for an adsorption time span of at least 5 or at least 10 minutes, or wherein the normalized amount of carbon dioxide captured on the sorbent per gram sorbent per hour is in the range of 1 - 6 mmol/g/h.

19. The method according to claim 1, wherein the adsorber structure comprises an array of individual adsorber elements, each adsorber element comprising a central carrier layer or porous support and on both sides thereof at least one porous and/or permeable sorbent layer with chemically attached carbon dioxide capture moieties, in the form of amine groups, wherein the porous sorbent layer is in the form of a woven or non-woven, fibre based structure, wherein said carrier or porous support layer can be based on at least one of metal, polymer, carbon, carbon molecular sieve and graphene material.

20. The method according to claim 1, wherein the the spacing (b.sub.spacer) between the adsorber elements is in the range of 0.4 - 3 mm, or wherein each adsorber element has the form of a plane with a thickness (b.sub.element) in the range of 0.2 - 0.5 mm.

21. The method according to claim 1, wherein said unit is evacuable to a vacuum pressure of 400 mbar(abs) or less, and wherein step (b) includes isolating said sorbent with adsorbed carbon dioxide in said unit from said flow-through while maintaining the temperature in the sorbent and then evacuating said unit to a pressure in the range of 20-400 mbar(abs), wherein in step (c) injecting a stream of saturated or superheated steam is also inducing an increase in internal pressure of the reactor unit, and wherein step (e) includes bringing the sorbent material to ambient atmospheric pressure conditions and ambient atmospheric temperature conditions, and wherein after step (d) and before step (e) the following step is carried out: (d1) ceasing the injection and, if used, circulation of steam, and evacuation of the unit to pressure values between 20 - 500 mbar(abs), or in the range of 50-250 mbar(abs) in the unit, thereby causing evaporation of water from the sorbent and both drying and cooling the sorbent, wherein step (e) is carried out exclusively by contacting said ambient atmospheric air with the sorbent material under ambient atmospheric pressure conditions and ambient atmospheric temperature conditions to evaporate and carry away water in the unit and to bring the sorbent material to ambient atmospheric temperature conditions or wherein said ambient atmospheric air in step (a) flows through said parallel fluid passages essentially along a first direction, and wherein said steam in at least one or both of steps (c) and (d) flows essentially along that same first direction or a direction essentially opposite to said first direction or wherein said ambient atmospheric air in step (a) flows through said parallel fluid passages essentially along a first direction, and wherein said steam at least one or both of steps (c) and (d) flows essentially along a direction orthogonal to said first direction through said parallel fluid passages.

22. The device according to claim 8 for carrying out a method for separating gaseous carbon dioxide from a gas mixture in the form of ambient air, containing said gaseous carbon dioxide as well as further gases different from gaseous carbon dioxide by cyclic adsorption/desorption using a sorbent material adsorbing said gaseous carbon dioxide, said device comprising a steam source; at least one unit containing an adsorber structure with said sorbent material, the adsorber structure being heatable to a temperature of at least 60° C. for the desorption of at least said gaseous carbon dioxide and the unit being openable to flow-through of the ambient atmospheric air and for contacting it with the sorbent material for an adsorption step, wherein the unit is evacuable to a vacuum pressure of 400 mbar(abs) or less wherein the adsorber structure comprises an array of individual adsorber elements, in the form of layers, each adsorber element, comprising at least one support layer, comprises at least one sorbent layer comprising or consisting of at least one sorbent material, where said sorbent material offers selective adsorption of CO.sub.2 over other major non-condensable gases in air in the presence of moisture or water vapor, wherein the adsorber elements in the array are arranged essentially parallel to each other and spaced apart from each other, essentially equally spaced apart from each other, forming parallel fluid passages for flow-through of ambient atmospheric air and/or steam.

23. The device according to claim 8, wherein the individual adsorber elements have an element length (L) along the flow-through direction of the ambient atmospheric air in an adsorption step (a), wherein the individual adsorber elements have an element thickness (b.sub.element) along a direction orthogonal to said flow-through direction, and wherein the spacing between the adsorber elements has a spacing width (b.sub.spacer), and wherein further the spacing width (b.sub.spacer) is in the range of 0.4-5 mm, and the element length (L) is in the range of 100-3000 mm;.

24. The device according to claim 8, wherein the at least one device for separating carbon dioxide from water is a condenser.

25. The device according to claim 8, wherein at the gas outlet side of said device for separating carbon dioxide from water, there is at least one of, or both of a carbon dioxide concentration sensor and a gas flow sensor for controlling the desorption process.

26. The device according to claim 8, wherein the spacing width (b.sub.spacer) is in the range of 0.5-3 mm, or wherein the element length (L) is in the range of 200-2000 mm.

27. The device according to claim 8, wherein the element length (L) is given as a function of the spacing width (b.sub.spacer), and as a function of the element thickness (b.sub.element) by the following equation $L = \frac{K_{g l o b a l} \cdot b_{s p a c e r}^{2}}{(1 + \frac{b_{e l e m e n t}}{b_{s p a c e r}})}$ wherein K.sub.global is in the range of 200-1000 mm^-1, or wherein b.sub.element is in the range of 0.1-1 mm, or in the range of 0.1-0.5 mm or wherein b.sub.spacer is in the range of 0.4-5 mm, or 0.5-3 mm.

28. The device according to claim 8, wherein the adsorber elements comprise a central carrier layer and on both sides thereof at least one sorbent layer, or wherein the adsorber structure comprises an array of individual adsorber elements, each adsorber element comprising a central porous carrier layer or porous support and on one or both sides thereof at least one porous and/or permeable sorbent layer, with chemically attached carbon dioxide capture moieties, in the form of amine groups, wherein the porous sorbent layer is in the form of a woven or non-woven, fibre based structure, wherein said carrier or porous support layer can be based on at least one of metal, polymer, carbon, carbon molecular sieve and graphene material, or wherein the adsorber structure comprises an array of individual adsorber elements , each adsorber element comprising a central carrier or support layer and on both sides thereof at least one porous and/or permeable sorbent layer with chemically attached carbon dioxide capture moieties, in the form of amine groups, wherein the porous sorbent layer can be in the form of a woven or non-woven, fibre based structure, or wherein said support or carrier layer is based on at least one of metal, polymer, carbon, carbon molecular sieve and graphene material, and is porous.

29. The device according to claim 8, wherein the spacing between the adsorber elements is in the range of 0.5 - 3 mm, and wherein each adsorber element has the form of a plane with a thickness in the range of 0.2 - 0.5 mm.

30. The device according to claim 8, comprising means for directing the steam in a steam flow through step (d) along a different flow direction than the flow direction of the flow-through direction of the ambient atmospheric air in the adsorption step (a), along a flow direction orthogonal to the flow-through direction of the ambient atmospheric air in the adsorption step (a), wherein at least in a steam flow through step (d) the flow speed of the steam through the adsorber structure is in the range of 1-6 m/s if the flow of the gas mixture in step (a) and the flow of the steam in step (d) are along different flow path flows, further if the flow of steam in step (d) is essentially orthogonal to that of the gas mixture in step (a).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0150] Preferred embodiments of the invention are described in the following with reference to the drawings, which are for the purpose of illustrating the present preferred embodiments of the invention and not for the purpose of limiting the same. In the drawings,

[0151] FIG. 1 shows a schematic representation of required and optional steps for the method presented to attain CO.sub.2 in an economically feasible cyclic adsorption and desorption process;

[0152] FIG. 2 shows a schematic of a single adsorber element, as comprising a porous support and at least one sorbent layer;

[0153] FIG. 3 shows a schematic of a single adsorber element, as comprising a carrier layer and at least one sorbent layer on either side;

[0154] FIG. 4 shows an exemplary schematic of an adsorber structure comprising a plurality of parallel adsorber elements thus forming a plurality of parallel fluid passages;

[0155] FIG. 5 shows a schematic realization of a reactor unit with the required inlets and outlets for the method presented;

[0156] FIG. 6 shows a schematic of the adsorber structure with the adsorber elements and subsequent parallel fluid passages in vertical orientation, with an indication of the axial, mostly horizontal flow direction of the multi-component flow during adsorption, and a horizontal counter-flow arrangement for the steam during purge;

[0157] FIG. 7 shows a schematic of the adsorber structure with the adsorber elements and subsequent parallel fluid passages in vertical orientation, with an indication of the axial, mostly horizontal flow direction of the multi-component flow during adsorption, and a vertical orthogonal-flow arrangement for the steam during purge;

[0158] FIG. 8 shows a schematic of the adsorber structure with the adsorber elements and subsequent parallel fluid passages in horizontal orientation, with an indication of the axial, mostly horizontal flow direction of the multi-component flow during adsorption, and a horizontal counter-flow arrangement for the steam during purge;

[0159] FIG. 9 shows a schematic of the adsorber structure with the adsorber elements and subsequent parallel fluid passages in horizontal orientation, with an indication of the axial, mostly horizontal flow direction (a) of the multi-component flow during adsorption, and a horizontal orthogonal-flow arrangement (d) for the steam during purge;

[0160] FIG. 10 shows laboratory testing results of an adsorber structure (1″ x ½” by 40 mm) for different adsorption conditions, delivering 1.2 - 1.6 mmol/g;

[0161] FIG. 11 shows average breakthrough curves (top curves) and average CO.sub.2-loading (bottom curves) for experimental operation of embodiment 1, with an adsorber structure (360 mm × 360 mm by 100 mm) with parallel passages in vertical orientation and a process including evacuation steps to below 200 mbar(abs);

[0162] FIG. 12 shows relative breakthrough curves (top curves) and CO.sub.2-loading (bottom curves) for experimental operation of embodiment 2, with an adsorber structure (360 mm × 360 mm by 100 mm) with parallel passages in vertical orientation and a process without any evacuation steps;

[0163] FIG. 13 shows a summary of experimental results with an insufficiently long adsorber structure according to embodiment 1;

[0164] FIG. 14 shows a schematic plant layout as can be used for carrying out the proposed method

[0165] FIG. 15 shows the pressure drop measured and calculated for various spacer heights and superficial velocities;

[0166] FIG. 16 shows, for different spacer heights in mm, the maximum length of the laminate as a function of the speed in the free air for a pressure drop of 300 Pa;

[0167] FIG. 17 shows, for different spacer heights in mm, the mass of laminate sheets per square meter inlet area as a function of the speed in the free air (inlet velocity prior to parallel passages) for a pressure drop of 300 Pa;

[0168] FIG. 18 shows, for different spacer heights in mm, the time until uptake of 1 mmol/g as a function of speed in the free air for a pressure drop of 300 Pa and capture fraction of 60%;

[0169] FIG. 19 shows a comparative production rate as a function of the speed in free air for different spacer heights in mm for a pressure drop of 300 Pa;

[0170] FIG. 20 shows the ratio of characteristic time of advection and diffusion as a function of the speed in the free air for different spacer heights for a pressure drop of 300 Pa;

[0171] FIG. 21 shows the maximum length of laminate as a function of the speed in the free air for different spacer heights and the DAC window for a pressure drop of 300 Pa;

[0172] FIG. 22 shows the capture rate and the capture capacity as a function of the adsorption time for a given set of parameters.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0173] The embodiments of the present invention presented below describe the proposed method in terms of a variable set of process steps, which an adsorber structure is exposed to in a dedicated reaction unit and can be run through in various sequences. The process steps of the method for the preferred embodiments include: [0174] 1. CO.sub.2 capture by adsorption of CO.sub.2 onto the adsorber structure by contacting the sorbent layers with sufficient amounts of ambient atmospheric air, with a capture fraction between 10% and 75% (adsorption step (a), mandatory). [0175] 2. Isolating the adsorber structure in the reactor from external ambient atmospheric air (isolation step (b), mandatory). [0176] 3. Establishing a pressure typically between 50-400 mbar(abs) in the reactor unit by means of evacuation (evacuation step within (b), optional). [0177] 4. Flushing the reactor unit of non-condensable gases by an initial flow of non-condensable steam while holding the pressure of step 3 or not allowing the adsorber structure temperature to exceed 75° C. (flushing with steam step (b1), optional). [0178] 5. Injecting a stream of saturated or superheated steam at a temperature of typically at least 45° C. and, if evacuation in step 3 took place, inducing an increase in internal pressure of the reactor unit, and an increase of the temperature of the adsorber structure to a temperature between 60 and 110° C., preferably according to the saturation temperature for the current reactor pressure, facilitating the desorption and release of CO.sub.2 (heat up with steam step (c), mandatory). [0179] 6. Opening of the reactor unit outlet while still injecting steam, thus flushing and purging both steam and CO.sub.2 from the adsorber structure and reactor unit, typically at a molar ratio of steam to CO.sub.2 between 4:1 and 40:1, while preferably regulating the outflow in such a way to maintain to a degree the pressure achieved at the end of the previous step (purge step with steam (d), mandatory). [0180] 7. After ceasing the injection of steam, reduction of unit pressure to values between 50-250 mbar(abs) in the reactor unit by means of evacuation, which causes evaporation of water from the adsorber structure subsequently both drying and cooling the sorbent material (vacuum cool/dry step (d1), optional). [0181] 8. Breaking the isolation of the reactor to the ambient atmospheric air and re-pressurizing the reactor unit if required (step of breaking isolation and re-pressurisation (e), mandatory). [0182] 9. Drying of the adsorber structure with warm air between 40° C. and 100° C. (step of air drying (e1), optional). Continue cyclic operation with step 1.

[0183] A schematic illustration of this sequence of steps is given in FIG. 1.

[0184] One embodiment of the composition of the individual adsorber elements is shown in FIG. 2. The individual adsorber element 5a comprises at least one sorbent layer 1a on a porous support layer 3a, where said sorbent layer comprises at least one sorbent material containing a selective porous solid adsorbent for CO.sub.2 capture, thus forming a sheet or laminate. The spacing and arrangement of multiple elements is achieved by the insertion of spacer elements 4 on one or both planar sides of the element.

[0185] Another embodiment of the composition of the individual adsorber elements is shown in FIG. 3. The individual adsorber element 5b comprises a layer structure with a central carrier layer 3b, adjacent to which on both sides there is provided a first sorbent layer 1b and a second sorbent layer 2b, respectively. Each individual adsorber element has a thickness b.sub.element, and a length L along the flow direction in adsorption. More specifically, in the embodiments used here, the individual adsorber element 5b comprises a sheet or laminate - comprising at least one layer containing a selective porous solid adsorbent for CO.sub.2 capture and, if need be, a central porous support layer. The spacing and arrangement of multiple elements is achieved by the insertion of spacer elements 4 on one or both planar sides of the element.

[0186] FIG. 4 shows, how individual adsorber elements 5 are combined to form an adsorber structure 6, by arranging them as an array of parallel layers, between which there are fluid passages 7 for the passage of the air in the adsorption step, and for the steam in the desorption step, each passage bound by the sorbent layer of one adsorber element 1.sup.N and another sorbent layer of the next adsorber element 2.sup.N+1. The width of these flow passages is b.sub.spacer.

[0187] An illustration of the reactor unit and the necessary flow and inlets and outlets is schematically given by FIG. 5. In this case, the flow of ambient air during the adsorption is along a direction orthogonal to the direction of flow of steam during the desorption. To allow that flow scheme using the layer structure of the adsorber structure the individual adsorber elements in a reactor according to this scheme need to be parallel to the paper plane.

[0188] In an embodiment 1, the adsorber structure is positioned such that the adsorber elements 5 and parallel passages 7 are orientated vertically, illustrated in FIG. 6. In step 1, the sorbent layers are contacted with an adsorption flow a for a duration of 5 min to 40 min along a main flow direction perpendicular to the largest adsorber structure perimeter surface available, such that a through flow of air is possible along the parallel passages at a velocity of between 2 m/s to 9 m/s.

[0189] After this adsorption step 1, the reactor unit containing the adsorber structure is closed off in step 2. The pressure within the reactor unit is then reduced to a pressure between 50 mbar (abs) and 400 mbar(abs) in the evacuation step 3.

[0190] Subsequently, in the heat-up step 5 the adsorber structure is brought to a temperature between 60° C. and 110° C. by the injection of steam until the necessary reactor pressure is achieved to attain the desired adsorber structure temperature by condensation and adsorption of steam on the adsorber structure within 0.5 min to 15 min.

[0191] In the subsequent purge step 6, steam flows through the parallel passages in the same plane as the adsorption flow of step 1, either in the same flow direction or in the opposing direction (shown as d) at a velocity preferably between 0.3-1 m/s for a duration of 0.5 min to 15 min, purging the parallel passages of desorbed CO.sub.2 in a ratio ranging from 4 to 40 moles of steam per mole of CO.sub.2.

[0192] In a following step 7, the injection of steam is ceased and the reactor unit evacuated is to a pressure of 50-250 mbar(abs). In the final step 8, the reactor unit is opened to the ambient conditions before the cycle recommences with step 1.

[0193] An embodiment 2, is essentially embodiment 1, but the flow of steam during step 5 and step 6 is introduced, such that it can pass fully through the parallel passages in a plane orthogonal to the adsorption flow, preferably at a velocity between 1 m/s and 6 m/s. For the vertical orientation of the adsorber elements and parallel passages, this essentially entails a steam flow from top to bottom or bottom to top, as indicated in FIG. 7.

[0194] An embodiment 3, shown in FIG. 8, is essentially embodiment 1, but where the adsorber structure is positioned such that the adsorber elements and parallel passages are orientated horizontally - as indicated in FIG. 8.

[0195] An embodiment 4, is essentially embodiment 3, but the flow of steam during step 5 and step 6 is introduced, such that it can pass fully through the parallel passages in a plane orthogonal to the adsorption flow, preferably at a velocity between 1 m/s and 6 m/s. For the vertical orientation of the adsorber elements and parallel passages, this essentially entails a steam flow from left to right or right to left, as indicated in FIG. 9.

[0196] In an embodiment 5 without evacuation, the adsorber structure is positioned such that the adsorber elements and parallel passages are orientated vertically, as illustrated in FIG. 6. In step 1, the sorbent layers are contacted with an adsorption flow a for a duration of 5 min to 40 min along a main flow direction perpendicular to the largest adsorber structure perimeter surface available, such that a through flow of air is possible along the parallel passages at a velocity of between 2 m/s to 9 m/s.

[0197] After this adsorption step 1, the reactor unit containing the adsorber structure is closed off in step 2.

[0198] Subsequently, in a steam purge step the adsorber structure is brought to a temperature between 60° C. and 110° C. by the injection of steam under ambient pressure until the local vapor pressure within the adsorber structure increases the adsorber structure temperature by condensation and adsorption of steam on the adsorber structure within 0.5 min to 30 min or 0.5 - 15 min, while the reactor outlet is open to allow the extraction of gases initially present after step 2 and then the extraction of CO.sub.2 and steam. Steam flows through the parallel passages in the same plane as the adsorption flow of step 1, either in the same flow direction or in the opposing direction (shown as d) at a velocity preferably between 0.3-1 m/s for a duration of 0.5 min to 30 min or 0.5 - 15 min, purging the parallel passages of desorbed CO.sub.2 in a ratio ranging from 4 to 40 moles of steam per mole of CO.sub.2.

[0199] In the final step 8, the reactor unit is opened to the ambient conditions before the cycle recommences with step 1.

[0200] Embodiment 5 can equally be carried out using the flow conditions and adsorber structure arrangement of embodiments 2-4, again without evacuation

[0201] FIG. 10 shows loading curves gained from extensive hot air purge at 95° C. after adsorption at the conditions indicated on the figure on a lab-scale breakthrough analyzer and is considered to indicate the maximum potential for such an adsorber structure with current sorbent materials embedded in the first and/or second sorbent layer, reaching loadings of 1.2 to 1.6 mmol/g.

[0202] Successful operation of embodiment 1 is shown in FIG. 11. At an adsorption through-flow velocity within the parallel passages of approximately 4 m/s an average CO.sub.2 yield of 0.4 mmol/g was achievable within 10 min at sufficiently dry ambient conditions, increasing to 0.8 mmol/g after 40 min. The evacuation pressure for step 3 and step 7 was 150 mbar(abs), the pressure after heat-up step 5 of 2 min and during purge step 6 of 3 min lay between 850 and 950 mbar(abs). The steam flow during these steps took the same path as the initial adsorption flow, at a (mean) velocity of 0.72 m/s within the parallel passages.

[0203] Successful operation of embodiment 5 is shown in FIG. 12. Three cycles according to embodiment 5 were run in sequence and yielded between 0.8 and 0.9 mmol/g of CO.sub.2.

[0204] A summary of experimental results from embodiment 1 is given in FIG. 13, indicating successful cyclical operation over at least 10 cycles for several ambient conditions. The results are very promising and considerable improvements are expected with an optimization of the adsorber structure and sorbent material for DAC purposes.

[0205] FIG. 14 shows a general scheme of a plant layout suitable and adapted for carrying out the method described.

[0206] The plant comprises T major units as required for the desired plant capacity.

[0207] Each unit comprises X subunits, where X:1 is the relation between total cycle time and the time required for desorption / regeneration. For example, in tower N there is an adsorber structure with 6 subunits, one of them is desorbing and the rest of them is adsorbing. Each subunit comprises one or multiple reaction chambers acting in unison and undergoing the same process steps.

[0208] Each subunit can be sealed off mechanically from the surrounding ambient by way of a valve, flap or door.

[0209] Each subunit can be in size similar to a 40 foot shipping container, primarily concerning length (12.2 m) and height (2.6 m).

[0210] Each reaction chamber contains the adsorber structure, which in this case is the above laminate stack. To the extent that the inflow to the adsorber is the largest open surface provided by the subunit, therefore less than length × height (12.2 m × 2.6 m).

[0211] For example, considering six reaction chambers, a viable inlet section is six adsorber structure inlets of length 1.6 m to 2 m by height 1.6 m to 2.4 m.

[0212] The volume of the adsorber structure behind this inlet for the entire subunit ranges from 1.5 m3 (1.6 m × 1.6 m × 6 × 0.1 m) to 60 m3 (just more than 2 m × 2.4 m × 6 × 2 m).

[0213] The adsorber structure mass of one subunit is in the range 75 kg to 3000 kg, depending on the optimal configuration.

[0214] Each subunit is supplied with steam in the range of 6 tons to 20 tons per hour.

[0215] An adsorption airflow can be generated at each subunit of 100 ′000 m3/h to 650 ′000 m3/h.

Specific Example 1

[0216] The results shown in FIGS. 11, 12 and 13 were obtained on an experimental rig in April and May of 2020. The adsorber structure was operated as given in embodiment 1 and FIG. 6, with dimensions of 360 mm × 360 mm × 100 mm, where the gas flow inlet and outlet was the respective largest surface given by the 360 mm by 360 mm area. The adsorber elements comprised at least one layer of functionalized silica for CO.sub.2 adsorption, and had a width of approximately 0.25 mm. The spacer employed provided a spacing between parallel adsorber elements of approximately 0.5 mm. The entire adsorber structure consisted therefore of approximately 480 individual adsorber elements.

[0217] The operational embodiment with results shown in FIG. 11 employed an adsorption step 1 with duration of 10 min and 40 min and flow velocity within the parallel passages of 4 m/s. In step 2 and 3, the reactor unit was isolated and evacuated to 150 mbar(abs). In the heat-up step 5, steam injection increased chamber pressure to 950 mbar(abs) within less than 2 min, before an steam purge step 6 with flow velocities in the channel of 0.72 m/s at a pressure of 850 mbar(abs) is conducted for 3 min. In step 7, the injection of steam is ceased and the pressure in the reactor unit is reduced to 150 mbar(abs). Before the unit is repressurized to ambient in step 8.

[0218] The operational embodiment with results shown in FIG. 11 employed an adsorption step 1 with duration of 40 min and flow velocity within the parallel passages of 4 m/s. In step 2, the reactor unit was isolated but no evacuation occurred. No dedicated heat-up step was foreseen; instead, an immediate steam purge step 6 with flow velocities in the channel of 0.72 m/s at ambient pressure is conducted for 6 min resulting in simultaneous heat-up and purge of the adsorber structure. The injection of steam is ceased and the isolation of the unit broken before the unit again recommences with adsorption.

[0219] As pointed out above, the pressure drop across such an adsorber structure can be estimated by the following equation:

[00005] $\frac{Δ P}{L} = K \cdot (U_{i n l e t}) \cdot {(b_{s p a c e r})}^{- 2.27}$

Here: [0220] ΔP is the pressure drop across the structure in Pa [0221] L is the length of the parallel passage the gas flows across in cm [0222] K is a roughness factor to be determined experimentally, typically in the range of 1 to 10. [0223] U.sub.inlet is the velocity on the inlet plane of the adsorber structure (not yet the velocity in the parallel passage) in m/s. [0224] b.sub.spacer is the height of the spacers determining the width of the parallel passages in mm.

[0225] FIG. 15 indicates such pressure drop calculated for various spacer heights and superficial velocities.

[0226] An exemplary configuration for flue gas capture entails a system with length of 2 m, and spacing of 0.35 mm at a superficial velocity of 5 m/s. Such a configuration results in a pressure drop of well above 3 bar. Such a pressure drop might be feasible for flue gas system operating at elevated pressures, but not for DAC applications.

[0227] DAC applications are generally limited by the viable pressure drop of commercially available fan and ventilator systems. For axial fans, this leads to a maximum pressure drop around 300 Pa is substantial volume flows are still to be achieved, and for radial fans this can be increased to 600 Pa or 700 Pa, at most up to 1200 Pa. Using this correlation, a map of the maximum flow path and therefore laminate length can be determined for a given adsorber type and spacer height as a function of the inlet flow velocity, also termed the superficial velocity,or velocity in free air to achieve a target pressure drop across the adsorber, see FIG. 16.

[0228] Given this length of the adsorber structure, the thickness and density of individual adsorber sheets as well as the height of the spacers, a mass of adsorber structure per inlet area can be determined (see also FIG. 17):

[00006] $\frac{m}{A} = L \cdot ρ_{e l e m e n t} \cdot \frac{b_{e l e m e n t}}{b_{e l e m e n t} + b_{s p a c e r}}$

Additionally, by knowing the flow and assuming a capture fraction, that is portion of the total CO.sub.2 passing the contactor that is captured, in this case 60%, a time until a certain loading of the sorbent is achieved can be estimated (see also FIG. 18).

[0229] The ratio of the mass of adsorber structure and achieved CO.sub.2 loading per unit area divided by the time required for adsorption is an indicative and directly comparative parameter for the CO.sub.2 production rate, see FIG. 19.

[0230] This is the same for all spacer heights, as it is assuming a constant capture fraction for the ingoing air, and therefore linearly increases with velocity. This assumption would be verified or adjusted once specific kinetic and geometric parameters of the sorbent and structure are known. Another parameter is required to adjudge which spacer height to best use for such a system. This can be achieved by analyzing the kinetics involved in the adsorption process. This is done by comparing a characteristic time of advection T.sub.adv- which describes the time frames associated with the flow - with a characteristic time of diffusion T.sub.diff - which describes the time frames associated with the diffusion of CO.sub.2 into the sorbent layer.

[0231] Here

[00007] $τ_{a d v} = \frac{L}{U_{i n t e r s t i t i a l}} = \frac{L}{U_{i n l e t}} \cdot \frac{b_{s p a c e r}}{b_{e l e m e n t} + b_{s p a c e r}}$

And the characteristic time of diffusion is the sum of the characteristic time of film diffusion and pore diffusion into the adsorptive layer:

[00008] $τ_{d i f f} = τ_{f i l m} + τ_{p o r e}$

Where the characteristic time of film diffusion is given as a function of the spacer height and the film mass transfer coefficient k.sub.f:

[00009] $τ_{f i l m} = \frac{b_{s p a c e r / 2}}{k_{f}}$

The characteristic time of pore diffusion is given as a function of the element thickness and the pore mass transfer coefficient k.sub.p:

[00010] $τ_{p} = \frac{b_{e l e m e n t} / 2}{k_{p}}$

[0232] With these correlations, an analysis of the ratio of advection to diffusion characteristic times can be carried out, as shown in FIG. 20.

[0233] The important aspect here is, that larger spacing solutions, that are in this case still attributed to the length assigned to maintain a desired pressure drop, show a smaller advection to diffusion time ratio, indicating more time for diffusion compared to smaller spacer heights associated with shorter beds. The efficiency of the capture process during adsorption is largely determined and limited by diffusion into the sorbent.

[0234] Therefore, the above realization shows for DAC, that larger spacer heights and longer beds are producing better adsorption results than a theoretically similar solution with tighter spacing and shorter beds. Therefore, DAC applications (see FIG. 21) are optimally operated at larger spacer heights, the technically feasible range seemingly between 0.4 and 3 mm, and technically realizable inlet velocities of 2-6 m/s, resulting in bed lengths of 100 to 3000 mm. At this stage, another factor to be considered beside the practical and technical implementation is to be mentioned - the cost of such adsorber structures: larger spacing structures inherently require more initial sorbent material and the increased investment cost drives the trade-off from the other direction in most practical implementations.

Specific Example 2

[0235] An adsorber structure based on parallel passages from which the maximum capture capacity is sought must consider a number of factors: allowable pressure drop, sorbent capacity, effective sorbent density and kinetics of capture. A sorbent for example having high capacity requires a lot of air to fully load which correspondingly requires wide channels to respect the pressure drop limitation. Correspondingly, such systems will have likely lower sorbent density limiting the potential capture capacity.

[0236] In this example associated with FIG. 22, the operation of an adsorber structure along this invention is numerically investigated for a direct air capture process with a particular sorbent and adsorber structure. A limiting pressure drop of 750 Pa is assumed acceptable for a specific sorbent material having a surface density of 230 g/m2, a parallel passage spacing width b.sub.spacer of 1.7 mm, an inflow air speed of 7 m/s in the passages and a length L of 1.2 m. The capture process was numerically simulated with a linear driving force model and mass transfer formulations for CO2 air and the optimum capture capacity was determined (in tonsCO2capture/m2 inlet air/yr) by varying the adsorption duration with an associated desorption process duration. It is seen that the optimum adsorption process duration for this case can be found at 840s (14 min) and corresponds to an average capture rate of just under 2 mmol/g/h. This point falls well within the ranges of interest specified in this invention.

TABLE-US-00002 LIST OF REFERENCE SIGNS 1 first sorbent layer adsorber structure 2 second sorbent layer K.sub.surface roughness factors 3a porous support layer K.sub.linear linear roughness factors 3b carrier layer k.sub.f film mass transfer coefficient 4 spacer elements k.sub.p pore mass transfer coefficient 5 individual adsorber element L length of the adsorber element along the flow-through direction in adsorption 6 complete adsorber structure 7 fluid passage, bound on one side by a first sorbent layer (1.sup.N) from one adsorber element, and a second sorbent layer (2.sup.N+1) from a neighboring adsorber element m mass of the adsorber structure ρ.sub.element density of individual adsorber sheets T.sub.adv characteristic time of advection A inlet area a flow direction of the multi-component flow during adsorption T.sub.diff characteristic time of diffusion T.sub.film characteristic time of film diffusion b.sub.element element thickness of the adsorber element T.sub.pore characteristic time of pore diffusion b.sub.spacer spacing width U.sub.inlet velocity on the inlet plane of the adsorber structure d flow direction of the steam flow during desorption U.sub.interstitial velocity between the plates in the channels ΔP pressure drop across the

METHOD FOR CAPTURE OF CARBON DIOXIDE FROM AMBIENT AIR AND CORRESPONDING ADSORBER STRUCTURES WITH A PLURALITY OF PARALLEL SURFACES

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