Direct air recovery system and method

Abstract

The direct air capture (DAC) system 100 comprises an absorber 106 configured to receive an air stream 102 and absorb at least a portion of the carbon dioxide present in the air stream 102. The DAC system 100 further comprises a mist eliminator 134, 434, 534, 634, 734 configured to receive at least a portion of the air stream 102 from the absorber 106. The DAC system 100 further comprises a cooling device 136, 436, 536, 636, 736 disposed in heat exchange relationship with the mist eliminator 134, 434, 534, 634, 734 and configured to cool a portion of the air stream 102.

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates to a direct air recovery system and a method of operating a direct air recovery system. [Background technology]

[0002] Direct air capture (DAC) of atmospheric carbon dioxide typically involves encouraging an incoming ambient air stream to interact with, for example, a sorbent capture medium under certain thermodynamic conditions. The sorbent capture medium can include a liquid medium or a solid medium. The sorbent capture medium absorbs some of the carbon dioxide from the air stream. Furthermore, the carbon dioxide can be separated from the sorbent capture medium during the desorption process, thereby enabling the carbon dioxide to be captured and stored.

[0003] DAC systems typically include an absorber. The absorption process occurs within the absorber of the DAC system. The absorber is an open system that removes carbon dioxide from an air stream while passing a large volume of air through it. Thus, carbon dioxide-depleted air can exit the absorber. The carbon dioxide-depleted air can have a different temperature and humidity than the incoming ambient air stream. Specifically, the temperature and humidity of the carbon dioxide-depleted air can be elevated compared to the incoming ambient air stream.

[0004] In instances where the sorbent capture medium is a liquid medium, conditions such as high temperatures within the absorber, high ambient temperatures, and low ambient humidity may increase drift and / or droplet shedding, increase the evaporation rate of the sorbent capture medium present in the airstream, and increase water loss in the absorber. Because the sorbent capture medium directly impacts the operating costs associated with a DAC system, increased drift and / or droplet shedding and increased evaporation rate of the sorbent capture medium may increase the operating costs of the DAC system. Summary of the Invention

[0005] In a first aspect, a direct air capture (DAC) system is provided. The DAC system includes an absorber configured to receive an air stream and absorb at least a portion of carbon dioxide present in the air stream. The DAC system further includes a mist eliminator configured to receive at least a portion of the air stream from the absorber. The DAC system further includes a cooling device disposed in heat exchange relationship with the mist eliminator and configured to cool a portion of the air stream.

[0006] The mist eliminator of the present disclosure can function as a drift and / or droplet capture structure that captures drift and / or droplets from the airflow before the airflow exits to the ambient. Additionally, the cooling device can reduce the temperature of the airflow, thereby reducing the evaporation rate of the sorbent capture medium present in the airflow before the airflow exits to the ambient. This phenomenon can also reduce water loss in the DAC system. Furthermore, the capture of drift and / or droplets and the reduction in the evaporation rate of the sorbent capture medium can reduce the operating costs of the DAC system. In one example, the mist eliminator and cooling device form a single, integrated structure that can reduce drift and / or droplets and reduce the temperature of the airflow.

[0007] In some embodiments, the cooling device is configured to cool the mist eliminator and cause condensation on the surfaces of the mist eliminator. The cooling device can define one or more flow paths for receiving a refrigerant for reducing the temperature of the airflow passing over the mist eliminator. In one example, the cooling device can be integrated with the mist eliminator. In another example, the cooling device can be separate from the mist eliminator and positioned downstream of the mist eliminator along the direction of the airflow.

[0008] In some embodiments, the mist eliminator comprises a filling structure. The cooling device comprises one or more tubes disposed in heat exchange relationship with the filling structure. In such examples, the cooling device and the filling structure may be embodied as a single, integral structure. Further, the tubes allow for the passage of a refrigerant to reduce the temperature of the airflow passing over the mist eliminator.

[0009] In some embodiments, the cooling device comprises a thermally conductive material, which in such embodiments can form the cooling device's fins that draw heat away from the airflow, thereby creating an effective cooling surface.

[0010] In some embodiments, the DAC system further comprises a cooling circuit disposed in fluid communication with the cooling device and configured to extract heat from the cooling device, the cooling circuit including a refrigerant flowing through one or more flow paths of the cooling device to reduce the temperature of the airflow flowing over the mist eliminator.

[0011] In some embodiments, the DAC system further comprises a controller configured to control the cooling cycle of the cooling circuit based on at least one of an environmental parameter, a pressure within the absorber, and a temperature within the absorber. In some examples, the environmental parameter can include the temperature, pressure, or humidity surrounding the DAC system. Because the cooling cycle is dynamically controlled according to current conditions inside and outside the absorber, the DAC systems described herein can eliminate unnecessary power consumption.

[0012] The controller can be configured to control the cooling circuit based on the humidity of the ambient air and the humidity of the air exiting the absorber to provide condensate to compensate for a portion of the water loss in the absorber by condensing on the mist eliminator surfaces, for example, at least 20% of the water loss, and more preferably, for example, to compensate for 30%, 50%, 70%, or 100% of the water loss.

[0013] In some embodiments, the refrigeration circuit comprises a heat pump and a heat exchanger disposed in heat exchange relationship with the heat pump, the heat pump capable of converting waste heat from the refrigeration of the chiller into useful heat that can be supplied to any heat exchanger / heating means associated with the DAC system.

[0014] In some embodiments, the heat exchanger comprises a heating means of the DAC system. In such instances, useful heat generated by the heat pump can be used to increase the temperature of an adsorbent lean stream flowing through the heating means. The heated adsorbent lean stream can then be used in a desorber of the DAC system.

[0015] In some embodiments, the DAC system further includes a first heat exchanger disposed downstream of the cooling device and configured to heat a portion of the airflow received from the cooling device, and a second heat exchanger disposed downstream of the first heat exchanger and configured to cool a portion of the airflow received from the first heat exchanger. In such embodiments, the mist eliminator and the cooling structure can each capture drift and / or droplets and reduce the evaporation rate of the sorbent capture medium. Furthermore, drift and / or droplets leaking through the mist eliminator can be captured by the first heat exchanger. The first heat exchanger is embodied as a high-temperature heat exchanger that can increase the temperature of the airflow, thereby evaporating the remaining droplets. Furthermore, the second heat exchanger is embodied as a low-temperature heat exchanger that can reduce the temperature of the airflow, thereby condensing the remaining sorbent capture medium present in the airflow before the airflow exits to the ambient.

[0016] In some embodiments, the DAC system further includes an additional cooling circuit disposed in fluid communication with the first heat exchanger and the second heat exchanger, the additional cooling circuit configured to provide heat exchange between the first heat exchanger and the second heat exchanger, the additional cooling circuit capable of converting waste heat from the cooling of the second heat exchanger into useful heat that can be used to heat the first heat exchanger and increase the temperature of the airflow passing over the first heat exchanger.

[0017] In some embodiments, the DAC system further comprises an electrostatic precipitator disposed downstream of the second heat exchanger. The electrostatic precipitator facilitates an effective impurity removal step. Specifically, the electrostatic precipitator can provide an air purification function, enabling the DAC system to remove any foreign matter, such as contaminants, from the airflow.

[0018] In some embodiments, the absorber, mist eliminator, and chiller are integrated into a single absorber unit, which can include a compact structure that can be retrofitted into existing DAC systems by replacing the existing absorber.

[0019] In a second aspect, a method is provided. The method includes removing at least a portion of carbon dioxide from an air stream via an absorber of a DAC system. The method further includes receiving at least a portion of the air stream from the absorber in a mist eliminator. The method further includes cooling a portion of the air stream passing over the mist eliminator via a cooling device.

[0020] The methods described herein can enable the capture of drift and / or droplets from an airflow before the airflow exits to the ambient. Additionally, the methods can reduce the temperature of the airflow and reduce the evaporation rate of the adsorbent capture medium present in the airflow before the airflow exits to the ambient. The methods can also reduce water loss in DAC systems. Additionally, the methods can reduce the operating costs of DAC systems due to the capture of drift and / or droplets and the reduced evaporation rate of the adsorbent capture medium.

[0021] In some embodiments, the method further includes extracting heat from the cooling device via a heat pump, which can convert waste heat from the cooling device into useful heat that can be used in any other heat exchangers associated with the DAC system.

[0022] In some embodiments, the method further includes heating a heating means of the DAC system via a heat pump. In such instances, useful heat generated by the heat pump can be used to increase the temperature of an adsorbent lean stream flowing through the heating means. The heated adsorbent lean stream can then be used in a desorber of the DAC system.

[0023] In some embodiments, the method further includes heating a portion of the airflow received from the cooling device through a first heat exchanger. The method further includes cooling a portion of the airflow received from the first heat exchanger through a second heat exchanger. The method further includes providing heat exchange between the first heat exchanger and the second heat exchanger through an additional cooling circuit. In such embodiments, the mist eliminator and the cooling structure can each capture drift and / or droplets and reduce the evaporation rate of the sorbent capture medium. Furthermore, drift and / or droplets that leak through the mist eliminator can be captured by the first heat exchanger. The first heat exchanger is embodied as a high-temperature heat exchanger that can increase the temperature of the airflow, thereby evaporating any remaining droplets. Furthermore, the second heat exchanger is embodied as a low-temperature heat exchanger that can reduce the temperature of the airflow, thereby condensing any remaining sorbent capture medium present in the airflow before the airflow exits to the ambient.

[0024] Those skilled in the art will understand that, except where mutually exclusive, any feature or parameter described in connection with any of the above embodiments may be applied to any of the other embodiments. Furthermore, except where mutually exclusive, any feature or parameter described herein may be applied to any embodiment and / or combined with any other feature or parameter described herein.

[0025] Embodiments will now be described, by way of example only, with reference to the drawings in which: [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 is a schematic diagram of a direct air capture (DAC) system according to one embodiment of the present disclosure. [Figure 2] FIG. 2 is a schematic perspective view of a mist eliminator and cooling device that can be used with the DAC system of FIG. 1 according to one embodiment of the present disclosure. [Figure 3] FIG. 2 is a schematic block diagram of the DAC system of FIG. 1 according to one embodiment of the present disclosure. [Figure 4] FIG. 2 is a schematic perspective view of a mist eliminator and cooling device that can be used with the DAC system of FIG. 1 according to another embodiment of the present disclosure. [Figure 5] FIG. 2 is a schematic perspective view of a mist eliminator and cooling device that can be used with the DAC system of FIG. 1 according to yet another embodiment of the present disclosure. [Figure 6] FIG. 2 is a schematic perspective view of a mist eliminator and cooling device that can be used with the DAC system of FIG. 1 according to yet another embodiment of the present disclosure. [Figure 7] FIG. 2 is a schematic diagram of a mist eliminator and a cooling device separate from the mist eliminator that can be used with the DAC system of FIG. 1 according to another embodiment of the present disclosure. [Figure 8] FIG. 10 is a schematic diagram of a DAC system including a first heat exchanger and a second heat exchanger according to another embodiment of the present disclosure. [Figure 9] 1 is a flowchart of a method of operating a DAC system according to one embodiment of the present disclosure. [Figure 10] 10 is two charts showing the effect of the system's operation on ambient conditions; DETAILED DESCRIPTION OF THE INVENTION

[0027] Aspects and embodiments of the present disclosure are discussed below with reference to the accompanying drawings. Further aspects and embodiments will be apparent to those skilled in the art.

[0028] FIG. 1 shows a schematic diagram of a direct air capture (DAC) system 100. The DAC system 100 operates to capture carbon dioxide (CO) from a gas stream containing CO. Herein, the DAC system 100 is embodied as an absorption liquid DAC system. Additionally, the CO-containing gas stream includes an air stream 102. The DAC system 100 includes a single absorber unit 104. The DAC system 100 includes an absorber 106 configured to receive the air stream 102 and absorb at least a portion of the CO present in the air stream 102. The absorber 106 is disposed within the absorber unit 104. The absorber unit 104 also includes a fan 108 configured to generate the air stream 102. The fan 108 can be disposed upstream or downstream of the absorber 106. In the embodiment shown in FIG. 1, the fan 108 is disposed downstream of the absorber 106. The air stream 102 entering the absorber 106 undergoes an absorption process within the absorber 106. Also, after flowing through the absorber 106, a CO2-depleted air stream 110 exits the absorber unit 104.

[0029] Additionally, a sorbent flows through the absorber 106 and interacts with the air stream 102 flowing through the absorber 106. The sorbent that captures CO2 may have a temperature-dependent equilibrium between a carbonate form and a CO2 solution state. The sorbent may be held in a solvent, such as water, which may contain additional additives that can act as catalysts, modify the physical properties of the solution, and / or reduce degradation or other desirable properties. The sorbent may include an alkaline absorbent such as a hydroxide or an organic sorbent. An alkaline sorbent may include, for example, potassium hydroxide or calcium hydroxide. An organic sorbent may include, for example, an amine or an amino acid. An amine may include, for example, ethanolamine. A preferred sorbent may include, for example, an amino acid or an alkaline salt solution of an amino acid. The amino acid may be from the group consisting of alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, histidine, isoleucine, leucine, lysine, methionine, ornithine, phenylalanine, proline, sarcosine, selenocysteine, serine, taurine, threonine, tryptophan, tyrosine, or valine. The amino acid may be a compound of an amino acid, such as methylamine or diethylamine. The preferred alkaline component of the amino acid salt is potassium or sodium. Examples of amino acid salts include sodium glycine, potassium lysine, and sodium taurine.

[0030] In the embodiment shown in FIG. 1 , a lean stream 114 of sorbent enters the absorber 106. The term “lean stream,” as used throughout this disclosure, refers to a stream of sorbent that is low in CO2. The lean stream 114 contacts the air stream 102 to absorb CO2 from the air stream 102, resulting in a rich stream 116. The term “rich stream,” as used throughout this disclosure, refers to a stream of sorbent that is high in CO2. The lean stream 114 is converted to the rich stream 116 based on the absorption of CO2 from the air stream 102. Additionally, a recycle stream 118 of sorbent can be recirculated within the absorber 106. The recycle stream 118 can increase the effective residence time of portions of the lean stream 114 of sorbent within the absorber 106.

[0031] DAC system 100 further includes heat exchange means 120. Heat exchange means 120 may include any conventional heat exchanger known in the art. Rich stream 116 passes through heat exchange means 120 to recover some heat from lean stream 114 returning from desorber 122 of DAC system 100. Based on the heat exchange in heat exchange means 120, the temperature of rich stream 116 exiting heat exchange means 120 is slightly increased. Further, desorber 122 receives rich stream 116 from heat exchange means 120 and heats it to a temperature at which CO2 is released from rich stream 116.

[0032] The DAC system 100 further includes a heating means 124, embodied herein as a reboiler. The heating means 124 increases the temperature of the rich stream 116 by circulating a heated adsorbent stream 126 through the desorber 122. The heating means 124 receives a portion of the lean stream 114 exiting the desorber 122. The heating means 124 heats the lean stream 114 to form the heated stream 126, which is introduced into the desorber 122. The heating means 124 may also generate steam to form vapor bubbles through which the desorbed CO2 can diffuse, returning the lean adsorbent stream 114 to the absorber 106 to repeat the absorption process. A mixture 128 of steam and desorbed CO2 exits the desorber 122. The DAC system 100 further includes a condensing medium 130 in fluid communication with the desorber 122. The condensing medium 130 receives the mixture 128 of steam and desorbed CO2 from the desorber 122 and can cool the mixture 128 to condense the steam, thereby causing a CO2 product stream 132 to exit the condensing medium 130.

[0033] The DAC system 100 further includes a mist eliminator 134 configured to receive at least a portion of the air flow 102 from the absorber 106. The mist eliminator 134 can function as a drift and / or droplet capture structure that captures drift and / or droplets from the air flow 102 before the air flow 102 exits the absorption unit 104. Additionally, the DAC system 100 includes a chiller 136 disposed in a heat exchange relationship with the mist eliminator 134 and configured to cool a portion of the air flow 102 before the air flow 102 exits the absorption unit 104. Furthermore, the chiller 136 can reduce the temperature of the air flow 102, thereby reducing the evaporation rate of the sorbent that absorbs CO2 from the air flow 102. This phenomenon can also reduce water loss in the DAC system 100. Furthermore, the capture of drift and / or droplets and the reduction in the evaporation rate of the sorbent can reduce the operating costs of the DAC system 100. In the embodiment shown in FIG. 1 , the absorber 106, the mist eliminator 134, and the cooling device 136 are integrated into a single absorber unit 104. Thus, the single absorber unit 104 can be operated to capture CO2, reduce drift and / or droplets, and reduce the temperature of the airflow 102. The single absorber unit 104 can include a compact structure that can be retrofitted into an existing DAC system by replacing the existing absorber. In the embodiment shown in FIG. 1 , the mist eliminator 134 and the cooling device 136 are located upstream of the fan 108. However, the mist eliminator 134 and the cooling device 136 may also be located downstream of the fan 108.

[0034] Figure 2 illustrates a schematic perspective view of a mist eliminator 134 and a cooling device 136 that can be used with the DAC system 100 of Figure 1 according to one embodiment of the present disclosure. In the embodiment illustrated in Figure 2, the cooling device 136 is configured to cool the mist eliminator 134 and cause condensation on a surface 138 of the mist eliminator 134. Furthermore, in the embodiment illustrated in Figure 2, the mist eliminator 134 includes a filling structure 140. The mist eliminator 134 is embodied herein as a cellular mist eliminator.

[0035] As shown in FIG. 2 , the filling structure 140 includes a plurality of structures 142 spaced apart from one another. Each structure 142 extends along direction D1. In some examples, the structures 142 can be made from an insulating material, such as a polymeric material, a metallic material, or a combination thereof. In one example, the polymeric material can include polyethylene or polyvinyl chloride. In one example, the metallic material can include stainless steel or aluminum. It should be noted that the structures 142 can include any shape or design that can maximize drift and / or droplet capture efficiency.

[0036] Further, in the embodiment shown in FIG. 2 , the cooling device 136 includes one or more tubes 144 disposed in a heat exchange relationship with the filling structure 140. The cooling device 136 may include a thermally conductive material. As shown in FIG. 2 , the cooling device 136 includes a plurality of tubes 144. Each tube 144 defines a flow path F1 for receiving a refrigerant for reducing the temperature of the airflow 102 flowing over the mist eliminator 134. Each tube 144 has a trapezoidal shape. Further, each tube 144 extends along a direction D1 and is parallel to the structure 142 of the filling structure 140. Alternatively, each tube 144 may be disposed at an angle relative to the structure 142. Furthermore, since the mist eliminator 134 and the cooling device 136 form a single component herein, each tube 144 of the plurality of tubes 144 is integral with the corresponding structure 142. Thus, the mist eliminator 134 and the cooling device 136 can collectively form a cooled mist eliminator. 2, each structure 142 has a corresponding tube 144 integral therewith. Thus, the total number of tubes 144 corresponds to the total number of structures 142 in the filling structure 140. In alternative embodiments, each structure 142 may define two or more tubes 144 without limitation. Furthermore, in some examples, the surface 138 of the mist eliminator 134 may be embodied as fins capable of drawing heat from the airflow 102, thereby forming an effective cooling surface. In other examples, the surface 138 may include a plurality of fins extending therefrom to form the cooling surface.

[0037] 1 and 2, the DAC system 100 includes a cooling circuit 146 disposed in fluid communication with the chiller 136 and configured to extract heat from the chiller 136. The cooling circuit 146 is configured to run a refrigerant cycle that cools the chiller 136. The cooling circuit 146 may include a refrigerant source (not shown) configured to direct refrigerant toward the chiller 136. Furthermore, each tube 144 of the chiller 136 is configured to allow the passage of refrigerant. The refrigerant flows through the tube 144 and exchanges heat with a portion of the airflow 102 flowing past the mist eliminator 134. Thus, the temperature of the airflow 102 decreases, thereby causing condensation of the adsorbent. The temperature of the refrigerant is lower than the dew point of the airflow exiting the absorber. Furthermore, the condensed adsorbent, along with any drift and / or droplets captured by the mist eliminator 134, may drip back into the absorber unit 104.

[0038] It is further understood that the thermophoresis effect causes the cooled mist eliminator 134 to capture more droplets from the airflow 102 than conventional mist eliminators. This weak effect provides an advantageous additional benefit.

[0039] The primary function of the cooling device 126 is to condense evaporated water by cooling the drift-fighting structure of the mist eliminator 134. Thermophoresis provides a welcome additional weak force to further improve particle rejection in the airflow 102.

[0040] In some embodiments, the refrigeration circuit 146 includes a heat pump 148 and a heat exchanger 150 disposed in a heat exchange relationship with the heat pump 148. Additionally, a refrigerant exits the chiller 136 and is introduced into the heat pump 148. The heat pump 148 extracts waste heat from the refrigerant to generate useful heat and directs the heat toward the heat exchanger 150. The heat exchanger 150 is embodied herein as the heating means 124 of the DAC system 100. In such an example, the useful heat generated by the heat pump 148 can be used to increase the temperature of the lean stream 114 flowing through the heating means 124. Alternatively, the heat exchanger 150 may be associated with any other component of the DAC system 100, or the heat exchanger 150 may be external to the DAC system 100.

[0041] 3 , in some embodiments, the DAC system 100 includes a controller 152 configured to control the cooling cycle of the cooling circuit 146 based on at least one of an environmental parameter, a pressure in the absorber 106 (see FIG. 1 ), and a temperature in the absorber 106. In some examples, the environmental parameter may include a temperature, pressure, or humidity surrounding the DAC system 100. Further, in some examples, a first sensor system 154 may be associated with the DAC system 100. The first sensor system 154 may include, for example, a temperature sensor, a pressure sensor, and / or a humidity sensor. In some examples, the DAC system 100 may include a second sensor system 156 associated with the absorber 106. The second sensor system 156 may include, for example, a temperature sensor or a pressure sensor. Each of the first sensor system 154 and the second sensor system 156 may be in communication with the controller 152. Based on the values ​​determined by the first sensor system 154 and the second sensor system 156, the controller 152 can determine whether a cooling cycle needs to be activated to reduce the temperature of the air stream 102 exiting the absorber unit 104 (see FIG. 1 ). For example, the cooling circuit 146 can be activated when environmental parameters, i.e., temperature, pressure, and / or humidity, or the temperature within the absorber 106, suggest that evaporation rates and / or water losses are high. Because the cooling cycle is dynamically controlled according to the current conditions inside and outside the absorber 106, the DAC system 100 can eliminate unnecessary power consumption.

[0042] The controller can be configured to control the cooling circuit based on the humidity of the ambient air and the humidity of the air exiting the absorber to provide condensate to replace a portion of the water loss in the absorber by condensing on the surfaces of the mist eliminator. The controller can calculate the absolute humidity based on sensor readings of relative humidity and temperature and calculate the cooling load required to condense water in the mist eliminator at a rate sufficient to replace a portion of the required water loss.

[0043] For example, the controller can control the cooling cycle to achieve near-zero net water loss from the absorber. Net water loss can include evaporation and drift losses from the absorber, as well as other incidental losses from the absorber circuit and desorber system. Net water loss can be reduced by more than 20% of the loss expected in the absence of mist eliminator cooling. Depending on climatic conditions, 100% of the loss can be recovered. Because the amount of water that can be economically recovered varies depending on the local costs of providing cooling, fan power, and water, in some environments, less than 100% water recovery may be desirable for economic reasons. Thus, the controller can be configured to vary the water recovery rate based on parameters indicative of ambient temperature and humidity, as well as water and power costs.

[0044] Figure 10 shows two charts illustrating the effect of controlling mist eliminator cooling in response to varying ambient conditions. Chart A shows the ambient conditions for a sample day, with the dotted line indicating relative humidity on the right axis and the dashed line indicating ambient temperature on the left axis. Chart B shows an example of energy use and water recovery as the plant was controlled over the course of the day, with the dotted line indicating water recovery on the right axis and the dashed line indicating the energy required by the cooler on the left axis. Both are expressed per ton of CO2 captured. As can be seen in Chart B, higher relative humidity in the afternoon of the day reduces water loss from the adsorbent in the absorber, allowing for reduced drift eliminator cooling and lower energy use.

[0045] In most cases, the controller can adjust heat pump operation to ensure that water loss is reduced to near zero. However, in practice, there are times when this is undesirable. At 21:00 on the graph, the controller recognizes that maintaining the zero water loss goal risks ice buildup in the chiller, so it limits the chiller's power at this point and allows for a small amount of water loss. Additional water can be temporarily stored at an earlier point when the chiller could have cooled a little more and efficiently captured some water from the more humid incoming air. One option is to use a feedforward controller to check the expected local weather (temperature, pressure, and humidity) and store a relatively small amount of water for several hours or days. On very hot, dry days, the heat pump may require a large amount of work, and in this case, the controller can again change its control goal from instantaneously achieving zero water loss to limiting water loss to a low value. Again, make-up water can be stored from another point when humidity levels were more favorable. The control objective is not to always achieve zero water loss instantaneously, but to limit water loss over a set period of time. With the option of temporarily storing water, the control objective can be to maximize cost savings, taking into account knowledge of the cost of purchasing make-up water and the cost of purchasing low-carbon energy. The heat pump system providing the cooling can transfer heat to other locations in the system, such as the desorber, which requires heat to separate the CO2 from the adsorbent. This can be done via a cascaded heat pump system that also recovers heat at different temperatures from other locations in the DAC plant.

[0046] The controller can vary the temperature of the drift eliminator so that the absolute humidity of the air leaving the mist eliminator is the same as or lower than the absolute humidity of the ambient air entering the absorber, the difference being sufficient to compensate for accidental and drift losses.

[0047] The controller can control the temperature of the refrigerant delivered to the chiller attached to the mist eliminator in response to psychometric sensor readings obtained around or within the absorber, which readings can include some or all of the temperature and humidity of the ambient air, the air exiting the absorber, or the air exiting the mist eliminator. Ambient air readings can be received from a local weather station.

[0048] The controller may obtain estimates of incidental losses elsewhere in the system by calculation or from tables of empirical water loss measurements. The controller may receive measurements of the total water volume in the system, for example, the height of adsorbent in a storage tank connected to the system, and may cycle control of the drift eliminator based on an indication that the adsorbent height is rising or falling.

[0049] The outlets of a group of absorbers can be connected to a common plenum and a mist eliminator can be incorporated within the plenum, so that the drift and evaporation from all the absorbers is concentrated in one location within the plenum, thereby reducing the number of cooling devices required.

[0050] The controller 152 may include one or more processors and one or more memories. It should be noted that the one or more processors may embody a single microprocessor or multiple microprocessors that receive various input signals. Many commercially available microprocessors may be configured to perform the functions of one or more processors. Each processor may further include a general-purpose processor, a central processing unit, an application-specific integrated circuit (ASIC), a digital signal processor, a field-programmable gate array (FPGA), a digital circuit, an analog circuit, a microcontroller, any other type of processor, or any combination thereof. Each processor may include one or more components that may be operable to execute computer-executable instructions or computer code that may be stored in and retrieved from one or more memories.

[0051] FIG. 4 illustrates another embodiment of a mist eliminator 434 and a cooling device 436 that may be associated with the DAC system 100 of FIG. 1. The mist eliminator 434 and the cooling device 436 form a single, integrated component herein. The mist eliminator 434 includes a filling structure 440. The mist eliminator 434 is embodied herein as a cellular mist eliminator. The filling structure 440 includes a plurality of spaced apart structures 442. Each structure 442 is similar in design and functionality to the structure 142 described in connection with FIG. 2.

[0052] Additionally, the cooling device 436 includes one or more tubes 444 disposed in a heat exchange relationship with the filling structure 440. The tubes 444 are similar in design and functionality to the tubes 144 described in connection with FIG. 2 . However, in the embodiment shown in FIG. 4 , the cooling device 436 includes two tubes 444. Specifically, only two of the structures 442 define corresponding tubes 444. While only two tubes 444 are shown here, it is contemplated that the cooling device 436 may include three or more tubes or a single tube without limitation. Thus, only some structures 442 may be provided with tubes 444, while other structures 442 may not have tubes 444. Furthermore, in some examples, the surface 438 of the mist eliminator 434 may be embodied as fins capable of drawing heat from the airflow 402, thereby forming an effective cooling surface. In other examples, the surface 438 may include multiple fins extending from the surface 438 to form a cooling surface.

[0053] FIG. 5 illustrates another embodiment of a mist eliminator 534 and a cooling device 536 that may be associated with the DAC system 100 of FIG. 1. The mist eliminator 534 and the cooling device 536 form a single, integrated component herein. The mist eliminator 534 includes a filling structure 540. The mist eliminator 534 is embodied herein as a cellular mist eliminator. The filling structure 540 includes a plurality of spaced apart structures 542. Each structure 542 is similar in design and functionality to the structure 142 described in connection with FIG. 2. Each structure 542 extends along a direction D2.

[0054] Additionally, the cooling device 536 includes one or more tubes 544 disposed in a heat exchange relationship with the filling structure 540. The tubes 544 are functionally similar to the tubes 144 described in connection with FIG. 2 . However, in the embodiment shown in FIG. 5 , the tubes 544 extend perpendicular to the direction D2. In other words, each tube 544 is perpendicular to the structure 542 of the filling structure 540. Alternatively, each tube 544 may be disposed at an oblique angle relative to the structure 542. The tubes 544 have a circular cross-section. Furthermore, although only two tubes 544 are shown here for illustrative purposes, the cooling device 536 may include three or more tubes 544. Furthermore, in some examples, the surface 538 of each tube 544 may be embodied as fins capable of drawing heat from the airflow 502, thereby forming an effective cooling surface. In other examples, the surface 538 may include multiple fins extending from the surface 538 to form the cooling surface.

[0055] FIG. 6 illustrates one embodiment of a mist eliminator 634 and a cooling device 636 that may be associated with the DAC system 100 of FIG. 1. The mist eliminator 634 and the cooling device 636 form a single, integrated component herein. The mist eliminator 634 is embodied herein as a mesh-type mist eliminator. The mist eliminator 634 includes a filling structure 640. The filling structure 640 includes a first mesh 658 and a second mesh 660 that are spaced apart from one another. Alternatively, the filling structure 640 may include three or more meshes based on the size of the absorber 106 (see FIG. 1).

[0056] The first mesh 658 and the second mesh 660 can be made of a metal material. Furthermore, each of the first mesh 658 and the second mesh 660 can be made of one or more mesh layers. Furthermore, the first mesh 658 and the second mesh 660 can be aligned with each other, or the first mesh 658 and the second mesh 660 can be offset / staggered. In some examples, it may be contemplated to combine a cellular-type mist eliminator (shown in FIGS. 2, 4, and 5) with a mesh-type mist eliminator (shown in FIG. 6) to improve drift and / or droplet capture efficiency.

[0057] Additionally, cooling device 636 includes a single tube 644 disposed in a heat exchange relationship with filling structure 640. Specifically, tube 644 is sandwiched between first mesh 658 and second mesh 660. Tube 644 is functionally similar to tube 144 described in connection with FIG. 2 . Here, tube 644 has a circular cross-section. Additionally, in some examples, surface 638 of tube 644 can be embodied as fins capable of drawing heat from airflow 602, thereby forming an effective cooling surface. In other examples, surface 638 can include multiple fins extending from surface 638 to form the cooling surface.

[0058] FIG. 7 illustrates another embodiment of a mist eliminator 734 and a cooling device 736 that may be associated with the DAC system 100 of FIG. 1. In the embodiment illustrated in FIG. 7, the mist eliminator 734 and the cooling device 736 are embodied as separate components disposed within the absorber unit 104. The cooling device 736 is disposed downstream of the mist eliminator 734 along the direction D3 of the airflow 702. The cooling device 736 may be embodied as a fin-and-tube heat exchanger, or the cooling device 736 may include any other design known in the art. Additionally, the mist eliminator 734 may comprise a packing structure that may be similar to any of the packing structures 140, 440, 540, and 640 described in connection with FIGS. 2, 4, 5, and 6, respectively. It should be noted that the mist eliminators 134, 434, 534, 634, 734 (see Figures 2, 4, 5, 6, and 7, respectively) and the cooling devices 136, 436, 536, 636, 736 (see Figures 2, 4, 5, 6, and 7, respectively) may include any other designs and / or combinations of components different from those described herein to achieve their intended functions.

[0059] FIG. 8 illustrates a DAC system 800 according to another embodiment of the present disclosure. The DAC system 800 has similar functionality to the DAC system 100 described in connection with FIGS. 1-3. Furthermore, the same parts are referred to by the same reference numerals herein. It should be noted that components having the same reference numerals in different figures have the same structural features and functions. The DAC system 800 includes the mist eliminator 134, the cooling device 136, the absorber 106, and the cooling circuit 146, as described in connection with FIGS. 1-3.

[0060] In the embodiment shown in FIG. 8 , the DAC system 800 further comprises a first heat exchanger 862 disposed downstream of the cooling device 136 and configured to heat a portion of the air flow 102 received from the cooling device 136. In the embodiment shown in FIG. 8 , the DAC system 800 further comprises a second heat exchanger 864 disposed downstream of the first heat exchanger 862 and configured to cool a portion of the air flow 102 received from the first heat exchanger 862. In such an embodiment, the mist eliminator 134 and the cooling device 136 can each capture drift and / or liquid droplets and reduce the evaporation rate of the adsorbent present in the air flow 102. Furthermore, drift and / or liquid droplets that leak through the mist eliminator 134 can be captured by the first heat exchanger 862. The first heat exchanger 862 is embodied as a high-temperature heat exchanger that can increase the temperature of the air flow 102 received from the cooling device 136, thereby evaporating any remaining drift and / or liquid droplets. Furthermore, the second heat exchanger 864 is embodied as a low-temperature heat exchanger that can reduce the temperature of the air flow 102 received from the first heat exchanger 862 to condense the adsorbent and water present in the air flow 102.

[0061] 8 , the DAC system 800 further includes an additional cooling circuit 866 disposed in fluid communication with the first heat exchanger 862 and the second heat exchanger 864. The additional cooling circuit 866 is configured to provide heat exchange between the first heat exchanger 862 and the second heat exchanger 864. In some examples, the additional cooling circuit 866 includes a heat pump 868 that converts waste heat from the cooling of the second heat exchanger 864 into useful heat. This useful heat can then be used to heat the first heat exchanger 862 and increase the temperature of the airflow 102 flowing over the first heat exchanger 862.

[0062] In some embodiments, the DAC system 800 further comprises an electrostatic precipitator 870 disposed downstream of the second heat exchanger 864. The electrostatic precipitator 870 is embodied as a low-loss filter. The electrostatic precipitator 870 can facilitate an effective impurity removal step. Specifically, the electrostatic precipitator 870 can provide an air cleaning function, enabling the DAC system 800 to remove any foreign matter, such as contaminants, from the airflow 102. In other embodiments, the electrostatic precipitator 870 can be omitted from the DAC system 800.

[0063] FIG. 9 illustrates a method 900 according to one embodiment of the present disclosure. Method 900 is directed to the operation of DAC systems 100, 800 described in connection with FIGS. 1-3 and 8, respectively. With reference to FIGS. 1-3 and 9, in step 902, absorber 106 of DAC system 100 removes at least a portion of CO2 from airflow 102. In step 904, mist eliminator 134 receives at least a portion of airflow 102 from absorber 106. In step 906, chiller 136 cools a portion of airflow 102 that flows over mist eliminator 134. In some embodiments, heat pump 148 extracts heat from chiller 136. In some embodiments, heat pump 148 heats heating means 124 of DAC system 100.

[0064] 8 and 9, in some embodiments, a portion of the airflow 102 received from the cooling device 136 is heated via a first heat exchanger 862. In some embodiments, a portion of the airflow 102 received from the first heat exchanger 862 is cooled via a second heat exchanger 864. In some embodiments, heat exchange between the first heat exchanger 862 and the second heat exchanger 864 is provided via an additional cooling circuit 866.

[0065] It will be understood that the present invention is not limited to the embodiments described above, and that various changes and modifications can be made without departing from the concepts described herein. Except where mutually exclusive, any of the features may be employed separately or in combination with any other feature, and the present disclosure extends to and includes all combinations and subcombinations of one or more features described herein.

Claims

1. A direct air recovery (DAC) system (100, 800) comprising: an absorber (106) configured to receive the air stream (102) and absorb at least a portion of the carbon dioxide present in the air stream (102); a mist eliminator (134, 434, 534, 634, 734) configured to receive at least a portion of the air flow (102) from the absorber (106); a cooling device (136, 436, 536, 636, 736) disposed in heat exchange relationship with the mist eliminator (134, 434, 534, 634, 734) and configured to cool the portion of the air flow (102); A DAC system comprising:

2. 2. The DAC system of claim 1, wherein the cooling device is configured to cool the mist eliminator and cause condensation on a surface of the mist eliminator.

3. 3. The DAC system of claim 2, wherein the mist eliminator comprises a filling structure, and the cooling device comprises one or more tubes disposed in a heat exchange relationship with the filling structure.

4. 4. The DAC system of claim 3, wherein the cooling device comprises a thermally conductive material.

5. 5. The DAC system (100, 800) of claim 2, further comprising a cooling circuit (146) disposed in fluid communication with the cooling device (136, 436, 536, 636) and configured to extract heat from the cooling device (136, 436, 536, 636).

6. 6. The DAC system of claim 5, further comprising a controller configured to control a cooling cycle of the cooling circuit based on at least one of an environmental parameter, a pressure in the absorber, and a temperature in the absorber.

7. 7. The DAC system of claim 6, wherein the controller is configured to control the cooling circuit based on the humidity of the ambient air and the humidity of the air exiting the absorber to provide condensate to compensate for a portion of the water loss in the absorber by the condensation on the surface of the mist eliminator.

8. 8. The DAC system (100, 800) of claim 5, wherein the cooling circuit (146) comprises a heat pump (148) and a heat exchanger (150) disposed in a heat exchange relationship with the heat pump (148).

9. 9. The DAC system (100, 800) of claim 8, wherein the heat exchanger (150) comprises a heating means (124) of the DAC system (100, 800).

10. DAC system (800) according to any one of claims 1 to 9, a first heat exchanger (862) disposed downstream of the cooling device (136) and configured to heat the portion of the air flow (102) received from the cooling device (136); a second heat exchanger (864) disposed downstream of the first heat exchanger (862) and configured to cool the portion of the air flow (102) received from the first heat exchanger (862); The DAC system further comprises:

11. 11. The DAC system (800) of claim 10, further comprising an additional cooling circuit (866) arranged in fluid communication with the first heat exchanger (862) and the second heat exchanger (864), the additional cooling circuit (866) configured to provide heat exchange between the first heat exchanger (862) and the second heat exchanger (864).

12. 12. The DAC system (800) of claim 10 or 11, further comprising an electrostatic precipitator (870) disposed downstream of the second heat exchanger (864).

13. 13. The DAC system (100, 800) of any one of claims 1 to 12, wherein the absorber (106), the mist eliminator (134, 434, 534, 634, 734), and the cooling device (136, 436, 536, 636, 736) are integrated into a single absorber unit (104).

14. 1. A method (900) comprising: removing at least a portion of the carbon dioxide from the air stream (102) via an absorber (106) of a direct air capture (DAC) system (100, 800); receiving at least a portion of the air flow (102) from the absorber (106) in a mist eliminator (134, 434, 534, 634, 734); cooling the portion of the airflow (102) passing over the mist eliminator (134, 434, 534, 634, 734) via a cooling device (136, 436, 536, 636, 736); A method comprising:

15. 15. The method of claim 14, further comprising controlling the cooling device based on the humidity of the ambient air and the humidity of the air exiting the absorber to provide sufficient condensate to compensate for a portion of the water loss in the absorber by condensation on the surface of the mist eliminator.

16. 16. The method (900) of claim 14 or 15, further comprising extracting heat from the cooling device (136, 436, 536, 636, 736) via a heat pump (148).

17. 17. The method (900) of claim 16, further comprising heating a heating means (124) of the DAC system (100, 800) via the heat pump (148).

18. A method (900) according to any one of claims 14 to 17, comprising: heating the portion of the airflow (102) received from the cooling device (136) via a first heat exchanger (862); cooling the portion of the airflow (102) received from the first heat exchanger (862) via a second heat exchanger (864); providing heat exchange between said first heat exchanger (862) and said second heat exchanger (864) via an additional cooling circuit (866); The method further comprises:

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