Voltage-change process for carbon dioxide removal using porous carbons

Abstract

A method and system for carbon dioxide separation by voltage switching is provided. The method can include the separation of carbon dioxide from a gas mixture by physisorption through the application of a positive electrical charge to a sorbent to increase the selectivity and adsorption of the sorbent, as well as the release of the carbon dioxide from the sorbent by removing the positive charge and applying a desorption process to the sorbent.

Description

BACKGROUND

[0001] The present invention relates generally to the field of global warming mitigation and, more particularly, to carbon dioxide capture.

[0002] As the planet warms, technological advances are becoming increasingly important to mitigate the accumulation of carbon dioxide in the Earth's atmosphere. One promising technology area that has the potential to have a significant impact is carbon dioxide capture. Carbon dioxide capture is the process of capturing or removing carbon dioxide from the atmosphere before it enters the atmosphere. Carbon dioxide can be captured and separated from gas mixtures using a variety of different means, including absorption, adsorption, chemical looping, membrane gas separation, and gas hydrogenation. However, the field faces numerous challenges before carbon dioxide capture can have a significant impact on atmospheric carbon dioxide levels. SUMMARY

[0003] According to at least one embodiment, a method and system for carbon dioxide capture using a voltage swing process is provided. The present invention may include removing carbon dioxide from a gas mixture using physisorption by applying electrical charges to a sorbent to increase the selectivity and adsorption of the sorbent, and releasing the carbon dioxide from the sorbent by removing the charges from the sorbent and applying a desorption process to the sorbent. BRIEF DESCRIPTION OF THE DIFFERENT VIEWS OF THE DRAWINGS

[0004] These and other objects, features, and advantages of the present invention will become apparent from the following detailed description of illustrative embodiments thereof, which should be read in conjunction with the accompanying drawings. The various features of the drawings are not to scale, as the illustrations are provided for clarity by aiding a person skilled in the art to understand the invention in conjunction with the detailed description. In the drawings: illustrated Fig. 1 illustrates an exemplary system for voltage cycling carbon dioxide capture according to at least one embodiment; is Fig. 2 is an operational flow diagram illustrating a process for voltage cycling carbon dioxide capture according to at least one embodiment; illustrated Fig. 3A illustrates an exemplary system for voltage cycling carbon dioxide capture according to at least one embodiment; illustrated Fig. 3B illustrates an exemplary system for voltage cycling carbon dioxide capture according to at least one embodiment; and is Fig. 4 is an operational flow diagram illustrating a process for voltage cycling carbon dioxide capture according to at least one embodiment. DETAILED DESCRIPTION

[0005] Detailed embodiments of the claimed structures and methods are disclosed herein; however, it should be understood that the disclosed embodiments are merely illustrative of the claimed structures and methods, which may be embodied in various forms. This invention may be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. Details of well-known features and techniques may be omitted from the description to avoid unnecessarily obscuring the disclosed embodiments.

[0006] As described above, technological advances are becoming increasingly important to mitigate the accumulation of carbon dioxide in the Earth's atmosphere. One promising technology field that has the potential to have a significant impact is carbon dioxide capture. Carbon dioxide capture refers to the process of capturing carbon dioxide (e.g., in the flue gas from a power plant) before it enters the atmosphere, or of filtering carbon dioxide out of the atmosphere. Carbon dioxide can be captured and separated from gas mixtures by a variety of different means, e.g., absorption, adsorption, chemical looping, membrane gas separation, and gas hydrogenation. However, the field faces numerous challenges before carbon dioxide capture can have a significant impact on atmospheric carbon dioxide levels.

[0007] Adsorption is an important, state-of-the-art technology for carbon dioxide capture. Adsorption refers to the attachment of atoms, ions, or molecules from a gas, liquid, or dissolved solid to a surface made of an adsorbent material called a sorbent. The attachment of the atoms, ions, or molecules to the sorbent can occur via a non-bonding electrostatic interaction (accompanied by van der Waals interaction), known as physisorption, or via chemical bonding, known as chemisorption.To be an effective sorbent, a material must possess a property known as selectivity, which is the ability of a sorbent to preferentially adsorb one gas over another. Materials with low selectivity are largely unable to separate carbon dioxide and are therefore ineffective for carbon dioxide capture. Furthermore, sorbents require a regeneration step to remove carbon dioxide from the sorbent after it has accumulated there, allowing the sorbent to be reused. An example sorbent is the metal-organic framework (MOF), which captures carbon dioxide by physisorption or chemisorption based on the porous atomic structure of a MOF.The carbon dioxide is then removed from the MOF in a regeneration step using temperature swing adsorption or pressure swing adsorption. However, MOFs can be very expensive, costing up to $500 per pound at the time of writing. Another example sorbent is activated carbon, or amorphous carbon. Activated carbon is highly porous, so one gram of activated carbon can have a surface area of ​​more than 3,000 square meters, resulting in a very high capacity for carbon dioxide capture. Activated carbon is also inexpensive, costing only a few dollars per pound at the time of writing. Activated carbon is also prone to chemical modification: n- or beta-doping, oxidation, hydrogenation, metal doping, polymer functionalization, etc. However, unmodified activated carbon is not very selective, which reduces its suitability for carbon dioxide capture applications.

[0008] Another technology for carbon dioxide capture is absorption, which is the transfer of atoms, ions, or molecules from a gas, liquid, or dissolved solid into a liquid solution consisting of an absorbent material called a solvent. One absorption process is amine gas treatment, which is a group of processes that use aqueous solutions of various alkylamines to remove carbon dioxide from gases. However, amine gas treatment absorbs carbon dioxide by forming chemical bonds between the solvent and the carbon dioxide (chemisorption); accordingly, chemisorption requires significant amounts of energy to break the chemical bond and desorb the carbon dioxide from a sorbent or solvent, resulting in high energy costs for regenerating the sorbent or solvent.

[0009] Carbon can also be removed using membrane gas filters, which employ a number of permeable membranes to block molecules of a particular gas while allowing others to pass. However, the performance of membrane gas filters is limited by the trade-off between permeability and selectivity, and vice versa. This makes membrane gas filters unsuitable for separating carbon dioxide from flue gas streams, as achieving a degree of selectivity sufficient to preferentially separate carbon dioxide over other gases would require a membrane gas filter to suffer such a significant loss in permeability that an impractically large number of gas filters would be required to achieve a useful level of carbon dioxide removal. As a result, mass transport of filters would become a limiting factor, and regeneration of spent filters would become very expensive.

[0010] It may therefore be advantageous, among other things, to implement a system that electrostatically removes carbon dioxide using physisorption, resulting in significantly lower energy costs for regenerating the sorbent than is the case with electrochemical methods using chemisorption. It may also be advantageous to implement a system that uses a voltage swing process for activated carbon to improve its selectivity to enable removal from ambient air and significantly improve adsorption, thus overcoming the major drawback of activated carbon and enabling the system to benefit from the low cost and high storage capacity associated with activated carbon.It may further be advantageous to use the voltage swing process in the regeneration step to reduce the selectivity of the activated carbon and thereby reduce the energy requirement for the release of captured carbon dioxide in the regeneration step.

[0011] According to at least one embodiment, the invention is a method for removing carbon dioxide from a gas mixture by applying a voltage to a sorbent to increase the selectivity and adsorption of the sorbent, and, after the sorbent is saturated under applied external conditions (e.g., pressure and temperature), reducing the voltage to decrease the selectivity and adsorption of the sorbent to enable low-energy release of the removed carbon dioxide molecules during a regeneration step. Although activated carbon is contemplated in embodiments of this invention, it will be apparent to those skilled in the art that any conductive sorbent has the same adsorption and selectivity advantages as activated carbon. However, activated carbon may have additional advantages related to cost and low environmental impact.

[0012] In some embodiments of the invention, the gas mixture may be any combination of two or more gases, one of which comprises carbon dioxide. For example, the gas mixture may comprise a flue gas that predominantly comprises a combination of nitrogen and carbon dioxide. The gas mixture may also be atmospheric air, which may be a combination of nitrogen, oxygen, carbon dioxide, etc. In some embodiments of the invention, the system may be used in industrial plants, cement factories, and / or chemical plants where carbon dioxide is released and should be separated and captured from the air.

[0013] In some embodiments of the invention, the voltage swing process is a process of changing the properties of activated carbon by applying a charge to the activated carbon. For porous carbon, as the charge per carbon atom increases above zero, the adsorption loading of carbon dioxide increases sharply with voltage, from a loading of around 5 moles per kilogram at a charge of 0.0 electrons per atom to a loading of over 20 moles per kilogram at a charge of 0.1 electrons per atom. And because the adsorption loading is so low at or below zero charge density, it may not be necessary to actively remove the adsorbed gas from the porous carbon at such charge densities.Furthermore, selectivity increases with increasing charge density; unmodified activated carbon has a selectivity of less than 20, but when the charge density increases to 0.1 electrons per atom, the selectivity jumps to approximately 1000 (based on our computer modeling), a 50-fold increase. Thanks to the high selectivity of charged activated carbon for adsorbing molecules with a large charge quadrupole moment (due to the favorable interaction between charge and quadrupole moment), the adsorption of carbon dioxide exceeds that of nitrogen. The selectivity of carbon dioxide over nitrogen can be further increased by releasing the first-time adsorbed gas into a second chamber containing charged amorphous carbon, followed by a second adsorption and release; the second-time adsorbed gas has an even higher purity.In charged activated carbon, charges can be located at spike ends or defects; such a heterogeneous charge distribution generates stronger local electric fields than a homogeneous charge, and these stronger fields can enable higher carbon dioxide selectivity and adsorption.

[0014] In some embodiments of the invention, the voltage cycling process is a process of changing the properties of a sorbent by applying a charge to the sorbent; any conductive sorbent may have the same adsorption and selectivity advantages as activated carbon.

[0015] In some embodiments of the invention, the sorbent can be any solid that adsorbs carbon dioxide by physisorption and exhibits increased carbon dioxide adsorption when the substance is electrically charged. In other words, any sorbent in which carbon dioxide binds to the sorbent due to electrical and / or van der Waals forces rather than by chemisorption, where an electrochemical means is used to form molecular bonds between the sorbent and the carbon dioxide. The sorbent can be activated carbon, certain metal-organic frameworks (MOFs), or any other suitable sorbent.

[0016] The amount of activated carbon required to remove carbon dioxide from a gas mixture can be expressed as follows: The number of moles of adsorbed carbon dioxide can be represented as MCO2 = C (mol / kg activated carbon) * m (kg activated carbon mass). If this is set equal to the number of moles of carbon dioxide in the feed chamber, the following equation results: MCO2 = V (volume of the chamber in m 3 ) *f (CO2 fraction of the input gas) / 0.0224 (m 3 / mol at SPT). Thus, the volume of air required to pressurize the activated carbon with carbon dioxide is: V = 0.0224 cm / f.

[0017] In an exemplary embodiment where the system separates carbon dioxide from flue gas, f = 0.1, according to our calculations, V = 4.48m 3per kilogram of activated carbon for C = 20 mol / kg. Since most of the carbon dioxide is adsorbed on the activated carbon, the remainder consists of almost pure nitrogen, which can be released into the air. The activated carbon is contaminated by nitrogen. At a selectivity of S, the ratio of CO2 to N2 adsorbed on the activated carbon is Sf. At S ~ 1000 (see above) and f = 0.1, the ratio of CO2 to N2 adsorbed on the activated carbon is 100, so the CO2 is 99% pure.

[0018] In some embodiments of the invention, after carbon dioxide has been adsorbed onto the sorbent by the carbon dioxide removal methods mentioned herein or any other methods, the system can release the first-time adsorbed residual gas into a second chamber containing charged amorphous carbon, followed by a second adsorption and release to increase the sorbent's selectivity for carbon dioxide over nitrogen; the second-time adsorbed gas has an even higher purity. For example, if the system removes carbon dioxide from the atmosphere via ambient air removal, f = 0.0004, the volume of air required to contain enough carbon dioxide to load one kilogram of activated carbon is 1120 m 3, and the ratio of CO2 to N2 in the activated carbon is 4. One kilogram of activated carbon spread over a one-square-meter area would, for example, have a thickness of 0.4 mm at a typical density of 2.5 gm / cc. For such a large volume of air, a fan would have to blow the air over the activated carbon in order to absorb 1120 m of carbon dioxide per kilogram during the time it takes for the activated carbon to adsorb the carbon dioxide. 3 In this case, the activated carbon may still be heavily contaminated with nitrogen, which is why the system can direct the separated carbon dioxide and nitrogen mixture to another filter unit, in which the carbon dioxide fraction deposited on the second activated carbon is multiplied by the carbon dioxide fraction deposited on the first activated carbon by a factor of S. 2 f = 400. In the second filter unit, the CO2 is then 99.75% pure.

[0019] The exemplary embodiments described below provide a system, method, and program product for carbon dioxide capture in a gas mixture by increasing the selectivity of a sorbent by applying an electrical charge, attaching carbon dioxide to the sorbent by physisorption, and then removing the captured carbon dioxide by reducing the charge of the sorbent.

[0020] With reference to Fig. 1 illustrates an exemplary voltage-cycling carbon dioxide capture system 100 according to at least one embodiment. Here, the voltage-cycling carbon dioxide capture system 100 includes four chambers: a first chamber 102 having an inlet 104 for receiving a high-pressure gas mixture, an outlet 106 for venting nitrogen, and a valve 110 connecting the first chamber 102 to a second chamber 108. The second chamber 108 has an outlet 112 for venting carbon dioxide and a first capacitor plate 114. The first capacitor plate 114 may include a sorbent that can be charged, for example, by a battery. The first capacitor plate 114 may include any conductive sorbent, including activated carbon, a metal-organic framework (MOF), zeolite, etc.The first chamber 102 is mirrored by a third chamber 116, which has an inlet 118 for receiving a high-pressure gas mixture, an outlet 120 for venting nitrogen, and a valve 124 connecting the third chamber 116 to a fourth chamber 122. The fourth chamber 122 has an outlet 126 for venting carbon dioxide and a second capacitor plate 128. The second capacitor plate 128 may include a sorbent that can be charged, for example, by a battery. The first capacitor plate 128 may include any conductive sorbent.The voltage-swapping carbon dioxide capture system 100 may further include a voltage regulator 130 that electrically connects to the two capacitor plates 114, 128 and regulates charges applied thereto. The capacitor plates 114, 128 may be part of a single capacitor and / or connected such that when one carries a negative charge, the other carries a positive charge, and vice versa. The voltage regulator 130 may be connected to a power source such as a battery or a wall outlet.In some embodiments of the invention, for example, when the voltage cycling carbon dioxide capture system 100 captures carbon dioxide from atmospheric air, the outlet 106 may be for removing a residual gas, where the residual gas may comprise a gas mixture from which all or a majority of the carbon dioxide has been removed by the voltage cycling carbon dioxide capture process.

[0021] With reference to Fig. 2, an operational flowchart illustrating a voltage-cycling carbon dioxide capture process 200 is shown, according to at least one embodiment. The voltage-cycling carbon dioxide capture process 200 uses a voltage-cycling carbon dioxide capture system 100 to alternately charge the two sides 114 and 128 of a capacitor plate. At 202, the voltage-cycling carbon dioxide capture system 100 positively charges a first capacitor plate located within a second chamber and negatively charges a second capacitor plate located within a fourth chamber.Here, the voltage-cycling carbon dioxide capture system 100 may positively charge a first capacitor plate 114 located within a second chamber 108 to improve the selectivity and carbon dioxide capture rate of the first capacitor plate 114, and may simultaneously negatively charge or discharge a second capacitor plate 128 located within a fourth chamber 122 to release captured carbon dioxide from the second capacitor plate 128. The capacitor plates 114, 128 may be sorbents, which may be any conductive solid that adsorbs carbon dioxide by physisorption. In other words, the carbon dioxide binds to the sorbent due to electrical and / or van der Waals forces, rather than by chemisorption, which uses an electrochemical means to form molecular bonds between the sorbent and the carbon dioxide.The sorbent can be activated carbon, conductive metal-organic frameworks (MOFs), or any other suitable sorbent. By positively charging the capacitor plate 114, the voltage-swing carbon dioxide capture system 100 increases the selectivity and adsorption of the capacitor plate 114, allowing the capacitor plate 114 to adsorb a high proportion and quantity of carbon dioxide from the gas mixture in the second chamber 108. By negatively charging, or grounding, the second capacitor plate 128, the voltage-swing carbon dioxide capture system 100 decreases the selectivity and adsorption charge of the second capacitor plate 128, allowing carbon dioxide molecules to be more easily removed from the second capacitor plate 128, thereby regenerating the second capacitor plate 128.

[0022] The voltage swing carbon dioxide capture system 100 may utilize any number or type of desorption processes in conjunction with the voltage swing, such as temperature swing adsorption or pressure swing adsorption. Temperature swing adsorption may involve heating the sorbent to add sufficient heat energy so that captured molecules can be released from the surface of the sorbent, while pressure swing adsorption may involve reducing the pressure around the sorbent to cause desorption from the sorbent. For example, the high-pressure gas mixture may be configured to create a pressure swing system if the feedstock gases (carbon dioxide, nitrogen, residual gas) are maintained at or below atmospheric pressure, in which case the voltage swing carbon dioxide capture system 100 would include high-pressure adsorption and low-pressure desorption.

[0023] At 204, the voltage-cycling carbon dioxide capture system 100 flows high-pressure gas comprising nitrogen and carbon dioxide into a first chamber 102 and a second chamber 108. At this time, the voltage-cycling carbon dioxide capture system 100 may close the outlet 106 and open the inlet 104 and the valve 110, allowing the gas mixture to flow into the first chamber 102 and the second chamber 108, and separating the carbon dioxide from the gas mixture in the first chamber 102 and the second chamber 108. The outlets 106 and 112 may remain closed at this time.The voltage swing carbon dioxide capture system 100 allows the gas mixture to flow through the valve 110 from the first chamber 102 into the second chamber 108, so that the gas mixture comes into contact with the positively charged first capacitor plate 114. The positively charged first capacitor plate 114 can then begin to adsorb carbon dioxide from the gas mixture in the first chamber 102 and the second chamber 108, as molecular diffusion ensures uniform movement of the molecules of the gas mixture in the chambers 102 and 108. The gas mixture can be a flue gas, which can be a combination of nitrogen and carbon dioxide. The gas mixture can also be atmospheric air, which can be a combination of nitrogen, oxygen, carbon dioxide, etc.The gas mixture may be pressurized to facilitate its movement into the voltage-swing carbon dioxide capture system 100, and the voltage-swing carbon dioxide capture system 100 may reduce the pressure within the first chamber 102 and / or the second chamber 108 to further facilitate the movement of the gas mixture. The voltage-swing carbon dioxide capture system 100 may maintain the positive charge on the first capacitor plate 114 while admitting the high-pressure gas mixture to adsorb as much carbon dioxide from the gas mixture as possible.After the first capacitor plate 114 reaches a threshold carbon dioxide saturation level, the voltage cycling carbon dioxide capture system 100 may close the valve 110 to isolate the first chamber 102 and the second chamber 108 from each other, thereby trapping nitrogen within the first chamber 102 and ensuring that upon desorption of carbon dioxide from the first capacitor plate 114, the carbon dioxide remains trapped and isolated within the second chamber 108; the voltage cycling carbon dioxide capture system 100 may further close the inlet 104 to prevent further inflow of the gas mixture.

[0024] At 206, the voltage-cycling carbon dioxide capture system 100 expels released carbon dioxide from the fourth chamber 122 and nitrogen from the third chamber 116. Here, the previously captured carbon dioxide has been desorbed from the second capacitor plate 128 as a result of the negative charge or grounding and additional desorption processes applied. Thus, the fourth chamber 122 may be filled with nearly pure carbon dioxide. This carbon dioxide may be discharged from the system, for example, by opening the outlet 126. Once released into some type of container, the carbon dioxide may be stored, for example, for sequestration or industrial use. The voltage-cycling carbon dioxide capture system 100 may maintain the negative or neutral charge of the second capacitor plate 128 during the duration of the carbon dioxide expulsion in order to re-adsorb as little desorbed carbon dioxide as possible.The voltage cycling carbon dioxide capture system 100 may release the nitrogen from the third chamber 116 by opening the outlet 120. The nitrogen in the third chamber 116 may be a gas mixture from which the positively charged second capacitor plate 128 has removed all or a majority of the carbon dioxide. Nitrogen may alternatively be referred to herein as a nitrogen-rich residual gas remaining after the carbon dioxide has been removed from the gas mixture, which may be released to the atmosphere or captured and stored. Once the carbon dioxide has been expelled from the fourth chamber 122 and the nitrogen has been expelled from the third chamber 116, as determined, for example, by sensor data or inferred after a predetermined period of time, the voltage cycling carbon dioxide capture system 100 may close the outlets 126 and 120.

[0025] At 208, the voltage-swinging carbon dioxide capture system 100 negatively charges the first capacitor plate 114 and positively charges the second capacitor plate 128. Here, the voltage-swinging carbon dioxide capture system 100 may switch the polarity of the voltage regulator 130 to negatively charge or ground the capacitor plate 114 to release captured carbon dioxide and to positively charge the second capacitor plate 128 located within the fourth chamber 122 to capture carbon dioxide.Here, by negatively charging or grounding the first capacitor plate 114, the voltage-cycling carbon dioxide capture system 100 reduces the selectivity and adsorption of the first capacitor plate 114, thereby reducing the energy required to more easily remove carbon dioxide molecules from the second capacitor plate 114 and thereby reducing the energy required to regenerate the first capacitor plate 114. By positively charging the second capacitor plate 128, the voltage-cycling carbon dioxide capture system 100 increases the selectivity and adsorption of the second capacitor plate 128, allowing the second capacitor plate 128 to adsorb a high proportion and quantity of carbon dioxide when it comes into contact with the gas mixture.

[0026] The voltage swing carbon dioxide capture system 100 may utilize any number or type of desorption techniques in conjunction with negative charging or grounding, such as temperature swing or pressure swing. Temperature swing adsorption may involve heating the sorbent to add sufficient heat energy so that captured molecules can be released from the surface of the sorbent, while pressure swing adsorption may involve reducing the pressure around the sorbent to cause desorption from the sorbent.

[0027] At 210, the voltage-cycling carbon dioxide capture system 100 expels released carbon dioxide from the second chamber 108 and nitrogen from the first chamber 102. Here, the previously captured carbon dioxide has been desorbed from the first capacitor plate 114 as a result of the negative or zero charge and any additional desorption processes applied. Thus, the second chamber 108 may be filled with nearly pure carbon dioxide. The voltage-cycling carbon dioxide capture system 100 may release this carbon dioxide from the third chamber 116 by opening the outlet 112, after which the carbon dioxide may be stored, for example, for sequestration or industrial use.After a large portion of the carbon dioxide has been adsorbed, the voltage-cycling carbon dioxide capture system 100 may now open the outlet 106 to release nitrogen remaining after the carbon dioxide was adsorbed into the first capacitor plate 114 from the first chamber 102. Once the carbon dioxide has been expelled from the second chamber 108 and the nitrogen has been expelled from the first chamber 102, as determined, for example, by sensor data or inferred after a predetermined period of time, the voltage-cycling carbon dioxide capture system 100 may close the outlets 106 and 112.

[0028] At 212, the voltage swing carbon dioxide capture system 100 allows high-pressure gas comprising nitrogen and carbon dioxide to flow into the third chamber 116. Here, both the second chamber 108 and the fourth chamber 122 have been emptied of carbon dioxide, the former by purging and the latter by adsorption. The voltage swing carbon dioxide capture system 100 opens the inlet 118 and the valve 124, allowing the gas mixture to flow into the third chamber 116 and then via the valve 124 into the fourth chamber 122, causing the gas mixture to contact the second capacitor plate 128.The gas mixture may be pressurized to facilitate its movement into the voltage-swing carbon dioxide capture system 100, and the voltage-swing carbon dioxide capture system 100 may reduce the pressure within the third chamber 116 and / or the fourth chamber 122 to further facilitate the movement of the gas mixture. The voltage-swing carbon dioxide capture system 100 may maintain the positive charge on the second capacitor plate 128 while flowing the high-pressure gas mixture to adsorb as much carbon dioxide from the gas mixture as possible.In some embodiments of the invention, after the second capacitor plate 128 reaches a threshold carbon dioxide saturation level, the voltage cycling carbon dioxide removal system 100 may close the valve 124 to isolate the fourth chamber 122 and the third chamber 116 from each other, thereby trapping nitrogen within the third chamber 116 and ensuring that upon desorption of carbon dioxide from the second capacitor plate 128, the carbon dioxide remains trapped and isolated within the fourth chamber 122; the voltage cycling carbon dioxide removal system 100 may further close the inlet 118 to prevent further inflow of the gas mixture.

[0029] At 214, the voltage cycling carbon dioxide capture system 100 determines whether the carbon dioxide capture cycle has terminated. In some embodiments of the invention, the voltage cycling carbon dioxide capture system 100 may be cycled as long as a carbon dioxide gas mixture is produced, which may be as long as a power plant combusts fuel or an industrial facility produces a gas mixture. Thus, the voltage cycling carbon dioxide capture system 100 may operate continuously until it receives a termination command. The voltage cycling carbon dioxide capture system 100 may receive a termination command from an authorized user, where the authorized user may be a user whose authorization has been verified in one or a combination of ways.The termination command may be a digital transmission received by the voltage-cycling carbon capture system 100 over a network, and / or it may be a specific input entered on a user interface device integrated with the voltage-cycling carbon capture system 100. According to one implementation, if the voltage-cycling carbon capture system 100 determines that the carbon capture cycle has not received a termination command and thus has not terminated (step 214, branch "NO"), the voltage-cycling carbon capture system 100 may proceed to step 202 to positively charge a first capacitor plate 114 located within a second chamber 108 and negatively charge a second capacitor plate 128 located within a fourth chamber 122.If the voltage cycling carbon capture system 100 determines that the voltage cycling carbon capture system 100 has received a termination command from an authorized user and the carbon capture cycle has consequently terminated (step 214, branch "YES"), the voltage cycling carbon capture system 100 may terminate the voltage cycling carbon capture process 200.

[0030] With reference to Fig. 3A, an exemplary voltage-cycling carbon dioxide capture system 300 is illustrated in accordance with at least one embodiment. Here, the voltage-cycling carbon dioxide capture system 300 includes two chambers: a first chamber 302 having an inlet 304 for a gas mixture, which may be atmospheric air or flue gas, and an outlet 306 for removing residual gas, and a second chamber 308 having an outlet 310 for regenerated gas. Within the first chamber is a porous carbon adsorbent 312, which may be an activated carbon sorbent, and which may in turn be located within a conductive container 314 that is movable between the first chamber 302 and the second chamber 308. The voltage-cycling carbon dioxide capture system 300 may be electrically connected to a voltage source 316 and a ground 318.

[0031] With reference to Fig. 3B, an exemplary system 300 for voltage cycling carbon dioxide capture is illustrated in accordance with at least one embodiment. Fig. illustrates the voltage cycling carbon dioxide capture system 300 in a state during the voltage cycling carbon dioxide capture process, with the porous carbon adsorbent 312 displaced from the first chamber 302 to the second chamber 308.

[0032] With reference to Fig. 4, an operational flow diagram illustrating a voltage-swing carbon dioxide capture process 400 is shown, according to at least one embodiment. The voltage-swing carbon dioxide capture process 400 moves a porous carbon adsorbent 312 between the two chambers 302, 308, thereby moving carbon dioxide from the first chamber 302 to the second chamber 308. At 402, the voltage-swing carbon dioxide capture system 300 loads a porous carbon adsorbent 312 located within the first chamber 302.Here, the voltage-cycling carbon dioxide capture system 300 can apply a uniform positive electrical charge to the porous carbon adsorbent 312 via the voltage source 316. For example, the voltage-cycling carbon dioxide capture system 300 can charge the porous carbon adsorbent 312 with a charge of 0.1 electrons per atom, increasing the adsorption to approximately 20 mol / kg according to our computer modeling. Since 20 mol / kg is close to the saturation value, further increasing the charge does not necessarily result in much more carbon dioxide being captured. However, the charge at saturation could be different for different activated carbon structures, so deviations from this value are conceivable without departing from the scope of the invention.

[0033] At 404, the voltage-swing carbon dioxide capture system 300 admits a gas mixture into the first chamber 302. The gas mixture may be flue gas or atmospheric air. Here, the voltage-swing carbon dioxide capture system 300 opens the inlet 304 to admit the gas mixture, which may be pressurized to facilitate its movement through the voltage-swing carbon dioxide capture system 300. This gas mixture may then contact the charged porous carbon adsorbent 312, which may adsorb the carbon dioxide from the gas mixture. During this phase, the outlet 306 may be closed.

[0034] At 406, the voltage-cycling carbon dioxide capture system 300 moves the loaded porous carbon adsorbent 312 into a second chamber 308. The loaded porous carbon adsorbent 312 may be disposed within a conductive container 314 that may be moved between the first chamber 302 and the second chamber 308 using pneumatic, motorized, or any other means. The loaded porous carbon adsorbent 312 may be moved when the loaded porous carbon adsorbent 312 is saturated with carbon dioxide, which may be confirmed by sensors or estimated at regular intervals for each cycle depending on the input gas mixture input rate and the adsorption rate of the loaded porous carbon adsorbent 312.The voltage cycling carbon dioxide capture system 300 can thus transport the captured carbon dioxide from the first chamber 302 and leave behind a residual gas that has the original gas mixture but does not contain carbon dioxide.

[0035] At 408, the voltage-swing carbon dioxide capture system 300 regenerates the gas in the second chamber 308 by removing the voltage from the porous carbon adsorbent 312. Here, the porous carbon adsorbent 312 is saturated with carbon dioxide from the first chamber 302. The voltage-swing carbon dioxide capture system 300 discharges the porous carbon adsorbent 312, reducing its electrical charge to zero, which in turn reduces the selectivity and adsorption of the porous carbon adsorbent 312 and reduces the energy cost of releasing the captured carbon dioxide from the surface of the porous carbon adsorbent 312, which in turn reduces the efficiency and rate at which the porous carbon adsorbent 312 re-adsorbs carbon dioxide previously released from it.The voltage swing carbon dioxide capture system 300 can remove the captured carbon dioxide from the surface of the porous carbon adsorbent 312 using any number or combination of desorption methods, such as pressure swing adsorption and temperature swing adsorption. The voltage swing carbon dioxide capture system 300 can fill the second chamber 308 with the released carbon dioxide gas by desorbing / regenerating the porous carbon adsorbent 312.

[0036] At 410, the voltage swing carbon dioxide capture system 300 expels residual gas from the first chamber 302 by reducing the pressure in the first chamber 302. Here, the first chamber 302 may contain residual gas, which may be the remainder of the original gas mixture after the porous carbon adsorbent 312 adsorbs and removes the carbon dioxide from the gas mixture. The voltage swing carbon dioxide capture system 300 may release this residual gas, for example, by opening the outlet 306. The residual gas may be vented directly to the atmosphere, captured for sequestration, or used for other purposes. The voltage swing carbon dioxide capture system 300 may expel the residual gas by reducing the pressure beyond the outlet 306, causing the gas to exit.

[0037] At 412, the voltage-swing carbon dioxide capture system 300 moves the porous carbon adsorbent 312 into the first chamber 302. Here, the voltage-swing carbon dioxide capture system 300 moves the discharged and newly regenerated porous carbon adsorbent 312 from the second chamber 308 into the first chamber 302 so that it is recharged and begins to adsorb additional carbon dioxide from the gas mixture.

[0038] At 414, the voltage-swing carbon dioxide capture system 300 expels carbon dioxide from a second chamber 308 by reducing the pressure beyond the outlet 310. Here, the voltage-swing carbon dioxide capture system 300 opens the outlet 310 to release the contents of the chamber 308, which may be carbon dioxide desorbed from the porous carbon adsorbent 312 during the regeneration process. The carbon dioxide may be sequestered or used in industrial applications.

[0039] At 416, the voltage-swing carbon dioxide capture system 300 determines whether the efficiency of the porous carbon adsorbent 312 has decreased below a threshold. The threshold may represent the efficiency with which the porous carbon adsorbent 312 separates carbon dioxide from the gas mixture and may be measured by measuring the proportion of carbon dioxide remaining in the residual gas exhausted from the outlet 306. If the voltage-swing carbon dioxide capture system 300 determines, according to one implementation, that the efficiency of the porous carbon adsorbent 312 has not decreased below a threshold (step 416, branch "NO"), the voltage-swing carbon dioxide capture system 300 may proceed to step 402 to charge the porous carbon adsorbent 312 located within the first chamber.If the voltage cycling carbon capture system 400 determines that the efficiency of the porous carbon adsorbent 312 has decreased below a threshold (step 416, branch "YES"), the voltage cycling carbon capture system 300 may terminate the voltage cycling carbon capture process 400. In some embodiments of the invention, the voltage cycling carbon capture system 300 may alternatively or additionally determine whether the carbon capture cycle has ended by determining whether the voltage cycling carbon capture system 300 has received a termination command from an authorized user.

[0040] It should be clear that the Fig.1 to 4 merely provide illustrations of particular implementations and do not imply any limitations on the implementation of various embodiments. Numerous changes may be made to the illustrated environments based on design and implementation requirements. For example, in at least one embodiment of the invention, only one side of the voltage cycling carbon dioxide capture system 100 may be used, including chambers 102 and 108, inlet 104, valve 110, and outlets 106 and 112. The capacitor plate 114 may cycle between a positive charge and a negative or zero charge, with adsorption of carbon dioxide occurring during the positive charge phase and desorption of carbon dioxide occurring during the negative or zero charge phase.The inlet 104 and valve 110 may be opened and the outlets 106 and 112 closed during the positive charge phase to admit high pressure gas comprising nitrogen and carbon dioxide, while the inlet 104 and valve 110 may be closed and the outlets 106 and 112 opened during the negative or zero charge phase to release the separated gases.

[0041] The descriptions of the various embodiments of the present invention have been presented for illustrative purposes and are not intended to be exhaustive or limited to the disclosed embodiments. Those skilled in the art will appreciate that numerous modifications and variations are possible without departing from the spirit and scope of the described embodiments. The terminology used herein has been chosen to best explain the principles of the embodiments, practical application, or technical improvement over current technologies, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

[1] A process for carbon dioxide capture, the process comprising: Removing carbon dioxide from a gas mixture by applying a positive electrical charge to a sorbent to increase the selectivity and adsorption of the sorbent; and Releasing the carbon dioxide from the sorbent by removing the positive electrical charge from the sorbent and applying a desorption process to the sorbent. [2] The method of claim 1, wherein the sorbent comprises activated carbon, a conductive metal-organic framework, metal-organic framework, MOF, or a conductive zeolite. [3] The method of claim 1, wherein the sorbent separates carbon dioxide from the gas mixture by physisorption. [4] The method of claim 1, wherein the desorption processes include pressure cycling and temperature cycling. [5] A process according to claim 1, wherein the gas mixture is flue gas or atmospheric air. [6] The method of claim 1, wherein the separating occurs in response to determining that an efficiency of the sorbent does not fall below a threshold. [7] The method of claim 1, wherein the sorbent comprises activated carbon and the positive electrical charge has a charge density of 0.1 electrons per atom in the sorbent. [8] A process for carbon dioxide capture, the process comprising: Charging a capacitor having two oppositely charged plates such that when a first of the two plates becomes negatively charged, the second of the two plates becomes positively charged, and when the first of the two plates becomes positively charged, the second of the two plates becomes negatively charged; Separating carbon dioxide from a gas mixture by using the positively charged side of the capacitor; Desorbing previously captured carbon dioxide by using the negatively charged side of the capacitor and one or more desorption processes; and Changing the charge of the two capacitor plates at regular intervals. [9] The method of claim 8, wherein the sorbent comprises activated carbon, a conductive metal-organic framework, MOF, or a conductive zeolite. [10] The method according to claim 8, wherein the sorbent separates carbon dioxide from the gas mixture by physisorption. [11] A method according to claim 8, wherein the desorption processes include pressure cycling and temperature cycling. [12] A method according to claim 8, wherein the gas mixture is flue gas or atmospheric air. [13] The method of claim 8, wherein the separating occurs in response to determining that an efficiency of the sorbent does not fall below a threshold. [14] The method of claim 8, wherein the sorbent comprises activated carbon and the positive electrical charge has a charge density of 0.1 electrons per atom of the sorbent. [15] A process for carbon dioxide capture, the process comprising: Removing carbon dioxide from a gas mixture to produce a residual gas by applying a positive electrical charge to a sorbent within a first chamber to increase the selectivity and adsorption of the sorbent; Moving the loaded sorbent into a second chamber; Unloading the loaded sorbent; Desorbing the separated carbon dioxide into the second chamber from the discharged sorbent; Expelling the residual gas from the first chamber; Moving the discharged sorbent into the first chamber; and Expulsion of the absorbed carbon dioxide from the second chamber. [16] The method of claim 15, wherein the sorbent comprises activated carbon, a conductive metal-organic framework, MOF, or a conductive zeolite. [17] The method of claim 15, wherein the sorbent separates carbon dioxide from the gas mixture by physisorption. [18] The method of claim 15, wherein the desorption processes include pressure cycling and temperature cycling. [19] A method according to claim 15, wherein the gas mixture is flue gas or atmospheric air. [20] The method of claim 15, wherein the separating occurs in response to determining that an efficiency of the sorbent does not fall below a threshold.

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