Patent Application
20250170524
The present application relates to the field of carbon capture. Embodiments of the present application provide systems, apparatuses, devices, and methods relating to metal hydroxide looping for capturing atmospheric carbon dioxide. Related systems for electrolytic production of acids and bases for chemical processing and materials handling are also described.
Carbon dioxide (CO2) makes up the vast majority of greenhouse gas emissions globally. Greenhouse gases trap heat and make the planet warmer. The contribution of CO2 to global warming is well-documented. Carbon dioxide is produced in a variety of sectors, including the transportation, electricity, industry, residential, commercial, and agricultural sectors. As of December 2022, the Mauna Loa observatory (NOAA, Hawaii) measured atmospheric CO2 to exceed 415 ppm. As CO2 emission continues, mitigation technologies will not be effective enough to avoid further increases in Earth's temperature, and CO2 levels may breach 450 ppm by mid-century. Atmospheric carbon dioxide removal and recycling is necessary to prevent catastrophic climate change.
Direct air capture of CO2 is a promising strategy for addressing concerns relating to greenhouse gases, particularly when the CO2 is permanently or semi-permanently prevented from re-entering the atmosphere. Another application of direct air capture is to supply recycled CO2 as a feedstock (alongside a source of hydrogen, H2) to synthesize low-carbon fuels or chemicals that displace demand for fossil fuels (e.g., methane, methanol, ethanol, plastics).
Direct air capture processes produce CO2 from air by cyclically absorbing CO2 with sorbents, then liberating (i.e., releasing) the sorbent's CO2 to regenerate the sorbent's CO2 uptake capacity. During direct air capture, sorbents in contact with air absorb CO2 with a certain CO2 uptake rate and approach a maximum CO2 uptake extent. Liberation and regeneration require a change in thermodynamic environment generated by changing temperature (i.e., heating), pressure (i.e., vacuum), moisture (i.e., humidity), electric charge (i.e., voltage or current), or some combination thereof. This step in a direct air capture process is usually the most energy intensive.
One direct air capture strategy is to use a sorbent comprised of alkali metal hydroxides or alkaline earth metal hydroxides that react with CO2 to obtain alkali metal carbonates or alkaline earth metal carbonates via a “carbonation” reaction. Some metal oxide direct air capture sorbents react with water to become metal hydroxides before reacting with CO2 at ambient air conditions (for example calcium oxide reacts with water to transform into calcium hydroxide before the carbonation reaction. A generalized reaction for metal (Me) hydroxides with monovalent or divalent cations is shown below:
aMex(OH)y+bCO2→xMea(CO3)b+(ay/2)H2O
Commercialization is ongoing for direct air capture technologies using metal hydroxides including sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca(OH)2), magnesium hydroxide (Mg(OH)2), among others.
One instantiation of direct air capture technology actively forces air through an air-liquid contactor to absorb CO2. The NaOH and/or KOH sorbent is dissolved in water, forms sodium or potassium carbonate upon CO2 uptake, and is subsequently reacted with Ca(OH)2 to produce CaCO3. This carbonate ion transfer regenerates the NaOH and/or KOH, but does not liberate CO2. Further treatment of CaCO3, for example in an oxygen-fired calciner at temperatures exceeding 900° C., is needed to release CO2 and regenerate the calcium source.
Another direct air capture process design passively contacts Ca(OH)2 with air moving with natural convection and diffusion. Similar high-temperature processing, including with electric calciners or steam calciners, is used to release CO2 and regenerate the sorbent due to the formation of CaCO3 upon CO2 uptake. However, the high-temperature processing forms calcium oxide which must be hydrated, or ‘slaked’, to reform the Ca(OH)2 sorbent.
This cyclical use of calcium for carbon capture is commonly referred to as “looping” or “calcium looping”. However, calcium looping has well-documented challenges with cyclic degradation of sorbent. The high temperatures used to liberate CO2 can sinter particles, reduce reactive surface area, and reduce CO2 uptake capacity. This degradation effect can limit the useful life of a sorbent, adding sorbent replacement, transport, and disposal costs. Furthermore, moisture improves carbonation reaction rates for low temperature calcium looping, but excess water reduces calcination efficiency, complicating operations.
Academic studies generally indicate that carbon capture processes designed to use metal hydroxides offer lower-than-average capital costs while claiming better-than-average supply chain infrastructure. Nevertheless, challenges remain. Current technologies for atmospheric carbon capture remain expensive and may be difficult to implement and scale. Calcium looping is an energy intensive process, and the high temperatures need consistent power for thermal efficiency and quality control. Supplying high temperatures with inexpensive, 24/7 carbon-free energy is not yet a reality. The most affordable carbon-free electricity options today are wind and solar photovoltaic power, but these sources are intermittent so are poorly suited to maintaining calcination temperatures. Therefore, there remains a need for more carbon capture technologies that are more compatible and cost-efficient with intermittent power.
Recognizing the need for better carbon capture technologies, the inventors of the present application have invented new systems, devices, and methods relating to metal hydroxide looping for capturing carbon dioxide.
In particular, certain embodiments of the present application provide aqueous processing for CO2 liberation from carbonates, as opposed to thermal processing, which is typically incompatible with many salts, including alkali salts, chloride salts, nitrate salts, fluoride salts, alkali hydroxides, etc. In a preferred embodiment, the system includes the use of a saturated salt or mixture of salts that mediate humidity during metal hydroxide carbonation, thereby enhancing metal hydroxide carbonation extent and carbonation rate. In a preferred embodiment, the system uses the same salt or mixture of salts as an electrolyte in a water electrolyzer used to produce acids and bases for aqueous processing.
Embodiments of the present application offer advantages over the state of the art leading to more cost-effective carbon capture. For example, embodiments of the present application provide for aqueous precipitation of highly reactive metal hydroxides with a mean particle size less than 1 micron and specific surface area-to-volume ratios superior to metal hydroxides produced by slaking subsequent to high-temperature metal carbonate processing. Furthermore, in certain embodiments metal hydroxides convert directly to metal carbonates in ambient air conditions, eliminating the intermediate metal oxide-to-hydroxide hydration step on the path to metal hydroxide carbonation. Additionally, aqueous precipitation avoids particle reactivity degradation due to sintering from prolonged or repeated thermal processing, extending the useful lifetime of sorbent feedstock. Aqueous processing is preferred to thermal processing for metal hydroxide carbon capture (also called “mineral looping” or, more specific to calcium-based sorbents, “calcium looping”), as thermal processing could require any number of additional processing steps that increase energy demand. These steps include drying, washing and/or rinsing solid carbonate of any water soluble salt or electrolyte, dewatering (or otherwise drying) and evaporating excess water from the solids produced or retained during ambient carbonation. Yet another advantage of aqueous processing is derived from lower operating temperatures as compared to thermal processing, as the high temperatures (900° C.) used in a thermal processing system are usually derived from combustion of fossil fuels. In comparison, aqueous processes are highly compatible with intermittently available renewable energy sources. Further advantages of embodiments of the present application will become apparent from the description below and from review of the figures of drawing.
In some embodiments, the application provides a system for capturing carbon dioxide from a gas (e.g., atmosphere or an air stream). In one embodiment, the system includes a metal hydroxide carbonation rack, for example racked trays of metal hydroxide undergoing carbonation in ambient air conditions (also called “mineral carbonation” or “weathering”), a liberation vessel, a regeneration vessel, a solid-liquid separation method, and a water electrolyzer operated in a manner consistent with chemical (acid and base) production and water splitting (hydrogen and oxygen production) required by the direct air capture system. The system optionally includes an energy recovery system, such as a fuel cell. In a preferred embodiment, the system includes the use of metal hydroxide particles with a saturated salt solution that mediates humidity to 25%-99%, or most preferably 50%-95%, and is distributed within and among the metal hydroxide particles which may enhance metal hydroxide carbonation extent and carbonation rate. In a preferred embodiment, the metal hydroxide looping system uses the same salt or mixture of salts as an electrolyte in the water electrolyzer referred to above.
In other embodiments, the application provides a method for capturing carbon dioxide from a gas (e.g., atmosphere or an air stream). In some embodiments, the method includes providing a metal hydroxide carbonation rack and converting a metal hydroxide to a metal carbonate, as discussed in the embodiments below. In some embodiments, the method includes providing liberation and regeneration vessels to liberate carbon dioxide from carbonate and regenerate a metal hydroxide, as discussed in the embodiments below. In some embodiments, the method includes providing a water electrolyzer for producing acidic and basic solutions, as discussed in the embodiments below. In some embodiments, the method includes providing an energy recovery system for recovering energy consumed by the system, e.g., by the water electrolyzer, by combining hydrogen and oxygen to form water, e.g., in a fuel cell or by combustion.
In other embodiments, the application provides a novel water electrolyzer for producing a continuous stream of acids, bases, hydrogen and oxygen. It should be understood that certain parts of each system or method may be combined for direct air capture, or may be used independently.
It should be understood the present application also encompasses the subprocesses and subcombinations of the embodiments discussed herein. Such subprocesses and subcombinations may be used independently or may be incorporated into larger systems or methods. It is the intent of the inventors that the present application shall encompass subprocesses and subcombinations as well as the larger systems and methods.
Further objects, features, and advantages of the present application will become apparent from the detailed description of preferred embodiments which is set forth below when considered together with the figures and drawings.
In the context of the present application, the terms “about” and “approximately” mean any value that is within ±10% of the value referred to.
The terms “mineral” and “metal hydroxide” and the terms containing these as sub parts are used interchangeably. For example, the terms “mineral carbonation rack” and “metal hydroxide carbonation rack” should be considered interchangeable.
The terms “liberation vessel” and “liberation tank” are used interchangeably and refer to the carbon dioxide liberation vessel discussed herein. The terms “regeneration vessel” and “regeneration tank” are used interchangeably and refer to the regeneration vessel discussed herein. The terms “settling vessel”, “settling tank”, “clarification vessel”, and “clarification tank” are used interchangeably and refer to the settling tank discussed herein. One of ordinary skill in the art would understand the term “vessel” to include any process container/reactor appropriate for the step discussed, including a fluidized reactor, pellet reactor, continuously stirred reactor, plug flow reactor, etc. It should be understood embodiments in the present application providing or discussing a settling tank may alternatively be provided using or embodied by any clarification equipment, including any hopper, basin, tank, baffled basin, baffled tank, hopper bottom tank, sedimentation tank, radial flow sedimentation tank, rectangular sedimentation tank, spiral flow sedimentation tank, etc.
The terms “electrolyzer” and “electrolyzer stack” are generally used interchangeably unless otherwise specified or unless referring to the construction, architecture, or components of an individual electrolyzer cell. Embodiments that include an “electrolyzer” or “electrolyzer stack” should be understood to relate to single and multiple-cell constructions.
The term “pellet” is used to refer to body of material and unless otherwise specified includes granules, granulates, spheronized granules, powders, extruded forms (such as strings, hollow tubes, and helicoids), as well as other geometries.
In some embodiments, the application provides a system for capturing carbon dioxide from a gas (e.g., atmosphere or an air stream). In one embodiment, the system includes a metal hydroxide carbonation rack, for example racked trays of metal hydroxide undergoing carbonation in ambient air conditions (also called “mineral carbonation” or “weathering”), a liberation vessel, a regeneration vessel, a solid-liquid separation method, and a water electrolyzer operated in a manner consistent with chemical (acid and base) production and water splitting (hydrogen and oxygen production) required by the direct air capture system. The system optionally includes an energy recovery system, such as a fuel cell. In a preferred embodiment, the system includes the use of metal hydroxide particles with a saturated salt solution that mediates humidity to roughly 50%-95% and is distributed within and among the metal hydroxide particles which may enhance metal hydroxide carbonation extent and carbonation rate. In a preferred embodiment, the metal hydroxide looping system uses the same salt or mixture of salts as an electrolyte in the water electrolyzer referred to above.
In other embodiments, the application provides a method for capturing carbon dioxide from a gas (e.g., atmosphere or an air stream). In some embodiments, the method includes providing a mineral carbonation rack and converting a metal hydroxide to a metal carbonate, as discussed in the embodiments below. In some embodiments, the method includes providing liberation and regeneration vessels to liberate carbon dioxide from carbonate and regenerate a metal hydroxide, as discussed in the embodiments below. In some embodiments, the method includes providing a water electrolyzer for producing acidic and basic solutions, as discussed in the embodiments below. In some embodiments, the method includes providing an energy recovery system for recovering energy consumed by the system, e.g., by the water electrolyzer, by combining hydrogen and oxygen to form water, e.g., in a fuel cell or by combustion.
In other embodiments, the application provides subprocesses and devices for accomplishing a portion of the systems and methods discussed herein. For example, it should be understood that certain parts of the entire system or entire method may be used independently of the entire system or method.
Certain embodiments of the present application include a mineral carbonation rack, for example racked trays of metal hydroxide undergoing mineral carbonation in ambient air conditions and related methods for capturing CO2 from a gas mixture, for example the atmosphere or an exhaust gas flow. The mineral carbonation rack may contain a plurality of racks and may be open to the atmosphere, partially enclosed (e.g., by a roof, which may protect from rain, gather rainwater, and/or support photovoltaic cells), or essentially fully enclosed. The mineral carbonation rack in some embodiments is configured to support photovoltaic cells. The mineral carbonation rack's trays may be spaced to minimize the pressure drop to allow wind and natural convection to circulate air or another gas containing CO2 through and over the metal hydroxide. The mineral carbonation rack may utilize fans or other air moving equipment or natural phenomena (e.g., atmospheric wind) to force, blow, or circulate air or another gas containing CO2 through and over the metal hydroxide. Some embodiments include racked trays of metal hydroxide undergoing mineral carbonation in ambient air conditions and related methods for capturing CO2 from a gas mixture (e.g., untreated exhaust gas from an upstream process, or exhaust gas from an incomplete upstream carbon capture process). In other embodiments, the mineral carbonation rack may provide other mechanical types of support for the metal hydroxides for permitting or preventing ambient air to flow over and/or around a pellets, granulates, extruded forms, or powder of metal hydroxide, for example rigid, semirigid, or flexible meshes or screens having various geometries. Mechanical structures may be added in some embodiments to block air flow, for example in circumstances where strong winds may be experienced. Some embodiments include an automated system for adjusting the spacing between racked trays in the mineral carbonation rack. Automated adjustment may be undertaken to increase air flow resistance, e.g. to protect against high wind conditions. It should be understood that routine adaptations of the mechanical support of the metal hydroxide are within the scope of the present disclosure.
In one embodiment, the mineral carbonation rack contains a metal hydroxide for capturing CO2 by producing a metal carbonate. In a preferred embodiment, the metal hydroxide is calcium hydroxide (Ca(OH)2), which produces calcium carbonate as shown in the reaction below. In other embodiments, the metal hydroxide is selected from the group consisting of (i) alkaline earth metal hydroxides, preferably calcium hydroxide, calcium magnesium hydroxide, magnesium hydroxide, and (ii) calcium silicate hydroxides/hydrates, including tobermorite, afwillite, jennite, and xonotlite, and (iii) magnesium carbonate hydroxides/hydrates, including magnesium carbonate hydroxide, dypingite, artinite, lansfordite, hydromagnesite, nesquehonite, barringtonite, and (iv) magnesium silicate hydroxides/hydrates, including lizardite, serpentine, talc, antigorite, and (v) mixtures thereof, including crystalline, non-crystalline or amorphous forms of the foregoing. Thus, in a particularly preferred embodiment, carbon dioxide is captured in the mineral carbonation racks according to the following carbonation reaction (1):
Ca(OH)2+CO2→CaCO3+H2O (1)
In some embodiments, the metal hydroxide is provided in the mineral carbonation racks or vessel in pellet form. In some embodiments, the pellets may be physically embodied as granules, spheronized granules, and/or extruded forms such as strings, hollow tubes, helicoids, etc. In some embodiments, the pellets have a mean radius preferably between 0.5 mm to 1 mm, or optionally between 100 nanometers and 1 micron, 1 micron and 10 microns, 10 microns to 0.1 mm, 0.1 mm to 0.5 mm, or 1 mm to 10 mm. When the mean pellet radius is less than 100 microns, it may be considered a powder or powderized. Without being bound by theory, embodiments of the present application include pellets designed to minimize CO2 diffusion distance and maximize surface area per unit of volume. In some embodiments, the mean diffusion distance is less than 10 mm. In some embodiments, the mean diffusion distance is less than 5 mm. In some embodiments, the mean diffusion distance is between 1-10 mm. In some embodiments, the mean diffusion distance is less than 1 mm. Thus, high surface area shapes with thin sub structures such as helicoids (fusilli/rotini pasta-shaped pellets) are preferred. In some embodiments, the pellets are arranged on trays inside the mineral carbonation racks and a CO2-containing gas is passed (e.g., passively by convection) between the pellets and/or flowed (e.g., actively with fans, pumps, etc.) over the pellets. In some embodiments, a plurality of trays is arranged inside the mineral carbonation racks. In some embodiments, the trays, or pallets of trays, may be rearranged inside the mineral carbonation racks manually or automatically to optimize carbon capture. In some embodiments, the trays may be manually or automatically removed and/or replaced to optimize carbon capture. In some embodiments, the pellets on the trays may be manually or automatically removed and/or replaced to optimize carbon capture. In some embodiments, the pellets on the trays may be automatically or manually rearranged, e.g., stirred, jostled, vibrated, blown, or otherwise moved mechanically, to optimize carbon capture. In some embodiments, the mineral carbonation racks or vessel contains a sensor for measuring a concentration of CO2 present in a region proximate to the metal hydroxide or in a stream exiting the mineral carbonation racks or vessel, wherein the sensor is optionally capable of activating a system for removing or rearranging the racks or pellets or providing a notification to an operator. In some embodiments, the mineral carbonation racks or vessel contains a sensor for determining an amount of metal carbonate produced, wherein the sensor is optionally capable of activating a system for removing or rearranging the racks or pellets or providing a notification to an operator.
In some embodiments, the carbonation reaction occurs in the presence of a salt. In some embodiments, the salt enhances and/or mediates the humidity in and around the carbonating metal hydroxides. In some embodiments, the salt may mediate humidity by reducing the evaporation rate or by absorbing moisture. In some embodiments, the salt is a hygroscopic salt (absorbing moisture, e.g., from the CO2 containing gas). In some embodiments, the salt is slightly hygroscopic or may exhibit deliquescence. In some embodiments, salts may reduce the freezing temperature of water and allow carbonation to continue below 0° C. In the preferred embodiment, the salt is sodium nitrate. In other embodiments, the salt is selected from the group consisting of potassium nitrate, sodium chloride, potassium chloride, sodium carbonate, potassium carbonate, sodium iodide, potassium iodide, magnesium chloride, calcium chloride, magnesium nitrate, calcium nitrate, and combinations or mixtures thereof. In some embodiments, the salt, e.g., potassium nitrate, is provided with a minimum concentration of 0.01M and a maximum concentration equivalent to a fully saturated solution. In other embodiments, the salt includes a fraction of alkali metal hydroxide selected from the group consisting of sodium hydroxide, potassium hydroxide, and combinations of mixtures thereof. In some embodiments, the ratio of salt to alkali metal hydroxide by weight is about 10:1, about 100:1, or between 10:1 and 100:1. In some embodiments, the ratio of salt to metal hydroxide potentially exceeds 1,000,000:1. In some embodiments, the ratio of salt to hydroxide by weight is about 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 15:1, 20:1, 25:1, 50:1, or 100:1. Without being bound by theory, it is believed the combined salt and alkali metal hydroxides enhance alkaline earth metal hydroxide carbonation by affecting the chemical and physical carbonation environment, improving CO2 uptake rate.
In some embodiments, water is intermittently added either directly, via spraying, misting, or soaking the trays or metal hydroxide pellets, or indirectly by controlling external humidity. In some embodiments, evaporated water is condensed and recovered while carbonation is occurring. In some embodiments, humid air condenses in the presence of the humidity mediating salts and water is collected instead of evaporated.
In some embodiments, a purified air stream passes out of the mineral carbonation racks. In some embodiments, the purified air stream contains essentially no CO2. In some embodiments, the purified air stream contains 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100% of the CO2 contained in the CO2-containing gas.
Some embodiments of the present application include a carbon dioxide liberation vessel and a metal hydroxide regeneration vessel. In some embodiments, these liberation and regeneration vessels are separate vessels. In some embodiments, these liberation and regeneration vessels are a single vessel. In the embodiments of the present application, the metal carbonate produced in the mineral carbonation rack is introduced into the liberation vessel, where carbon dioxide is liberated, and metal ions are produced in solution. In embodiments of the present application, the metal ions are fed to the regeneration vessel, where metal hydroxide is precipitated. In some embodiments, the metal carbonate is automatically introduced into the liberation vessel. In some embodiments, the metal carbonate is manually introduced into the liberation vessel. In some embodiments, the metal ions are automatically introduced into the regeneration vessel. In some embodiments, the metal ions are manually introduced into the regeneration vessel.
In some embodiments, a metal carbonate, optionally still partially wet, is fed to a liberation vessel. In some embodiments, the liberation vessel is operated at a temperature of 20-90° C., or preferably 30-80° C., or more preferably 40-70° C. In a preferred embodiment, an acidic solution is introduced to the liberation vessel. In some embodiments, the liberation vessel is a continuously stirred tank reactor (CSTR). In some embodiments, the solids from the racks are added to an acid in the liberation vessel, optionally produced in a water electrolyzer, to release CO2 gas, which is removed from the liberation vessel. A metal ion (e.g., Ca2+) rich solution is extracted—and in some embodiments, passed through metal carbonate to ensure full acid neutralization of the stream—before being introduced to a regeneration vessel. In some embodiments, a portion of the metal ion rich solution (e.g., Ca2+) can be mixed with the metal carbonate prior to introduction into the liberation vessel to suspend the metal carbonate solids (pellets, particles, etc.). In some embodiments, a portion of the metal ion solution may be passed through a vacuum degasser (e.g., with pressure below 1 atm) to liberate dissolved CO2. In some embodiments, the metal ion solution may be heated to liberate dissolved CO2. In some embodiments, the metal ion solution may be heated and passed through a vacuum degasser.
In some embodiments, the regeneration vessel is a continuously stirred tank reactor (CSTR). In the regeneration vessel, a basic solution, optionally produced in a water electrolyzer, is added and a metal hydroxide is precipitated. In some embodiments, the regeneration vessel is operated at a temperature of 20-90° C., or preferably 30-80° C., or more preferably 40-70° C. In some embodiments, the metal hydroxide is precipitated in an elevated ionic strength solution. In some embodiments, the elevated ionic strength solution contains salt concentrations between 1-3M. In a preferred embodiment, the ionic strength is elevated with a salt. In a preferred embodiment, the salt is sodium nitrate (NaNO3).
In some embodiments, after precipitation the metal hydroxide (which may be in the form of a particle suspension (“slurry”)) enters a solid-liquid separation process, which increases the weight % of solids. In some embodiments, the solid-liquid separation process is performed in a tank. In some embodiments, the solid-liquid separation process utilizes a settling tank to agglomerate the particles, sediment, and clarify the slurry. In some embodiments, the separation process utilizes a centrifuge, sedimentation, flotation, flocculation, spray drying, pellet reactor, sieving, filtration, or another similar method of solids liquid separation. In some embodiments, multiple techniques are used concurrently and/or sequentially. In some embodiments, the solid-liquid separation process may be open to a CO2 containing air stream and partial carbonation of metal hydroxide may occur before or during material handling or before pellets (or other solid metal hydroxide forms) enter the mineral carbonation rack. In some embodiments, the solid-liquid separation process may be repeated to incrementally remove liquid or increase wt. % of solids. In some embodiments, the solid-liquid separation process increases the wt. % of solids to at least 5 wt. %, 10 wt. %, 20 wt. %, or 55 wt. %.
In some embodiments, a thickened suspension (weight % of solids to at least 5 wt. %, 10 wt. %, 20 wt. %, or 55 wt. %) is pumped from the bottom of the settling tank and extruded or granulated to form pellets from the metal hydroxide suspension. In some embodiments, the still-warm pellets are contacted with flowing air to allow partial evaporation and drying of the pellets. In some embodiments, some shrinkage may occur upon drying, which may consolidate the metal hydroxide pellets to prevent substantial geometrical change to the pellets during transport to trays and on pallets to and from racks. In some embodiments, inert solids are added to the particle suspension as a thickening agent to enable extrusion or granulation or other pelletization. In some embodiments, pellets may be formed by coating inert particles. In some embodiments, the inert solids have negligible reactivity with respect to CO2. In some embodiments, the inert solids may include polymer beads, quartz, silica, sand, clays. In some embodiments, the inert solids may have particle sizes sufficiently large to simplify dewetting. In some embodiments, the inert solids may be graded to enhance material forming and water retention properties of the metal hydroxide pellets. In some embodiments, the inert solids have a density permitting density separation for reclaiming inert solids during processing (low density polymers floating in water or higher density quartz particles sinking/sedimenting).
In some embodiments, the liberation vessel is fed with an acidic solution and a metal carbonate discussed herein, preferably CaCO3. The liberation vessel may also be optionally fed with an acidic solution, a metal carbonate, and a salt discussed herein, preferably NaNO3, to reduce CO2 solubility. In a preferred embodiment, the acidic solution fed to the liberation is produced in a water electrolyzer, preferably a water electrolyzer according to the present application. In some embodiments, the acidic solution produced by the water electrolyzer contains the salt. In some embodiments, the concentration of the salt in the acid solution is between 0.01M and fully saturated, 0.5M-1.5M, 0.8-1.2M, or about 1M. In a preferred embodiment, the salt is present in a concentration preferably greater than 1 M (mol/L), but no less than 0.01 M.
In some embodiments, the acidic solution has a pH value of less than 4, and preferably less than 0. The acidic solution dissolves the metal carbonate and liberates CO2. In some embodiments, the liberated CO2 is produced as a high concentration CO2 gas stream. In a preferred embodiment, the liberation vessel is operated at elevated temperature, 20-90° C., preferably 30-80° C., or more preferably 40-70° C. In some embodiments, the liberation vessel is gas-tight to prevent undesired intrusion of air or loss of CO2 or liquids while also able to accept intentional solid and liquid inputs. In some embodiments, the liberation vessel is stirred. In some embodiments, the liberation vessel produces a high alkalinity solution containing metal ions, preferably Ca2+. The CO2 produced may optionally be processed with or without compression into products, such as carbonates, aggregates, supplementary cementitious materials (SCM), concrete, plastics, chemicals, fuels, building materials, etc. The CO2 produced may optionally be processed into storage mediums, including mine tailings, mining products, or injected into geologic storage, including basalt formations, saline aquifers, etc.
In some embodiments, the high alkalinity solution from the liberation vessel is fed to the regeneration vessel. The high alkalinity solution contains metal ions, preferably Ca2+ ions. The solution may also optionally contain a salt discussed herein, preferably NaNO3. In a preferred embodiment, the NaNO3 is present in high concentration, preferably greater than 1 M (mol/L), but no less than 0.01.M. In some embodiments, the concentration is between 1-3M. In a preferred embodiment, a basic solution is introduced into the regeneration vessel to cause oversaturated metal ions to precipitate metal hydroxide, preferably Ca(OH)2. In some embodiments, the pH of the basic solution is greater than 13, and more preferably greater than 14. In a preferred embodiment, the regeneration vessel is operated at elevated temperature, 20-90° C., preferably 30-80° C., or more preferably 40-70° C. In some embodiments, the regeneration vessel produces a metal hydroxide particle suspension of sub-micron metal hydroxide particles. Without being bound by theory, it is believed elevated temperatures and high ionic strength created from the sodium nitrate and alkali hydroxide contribute to such particle formation. The metal hydroxide produced may be used for CO2 capture in the mineral carbonation racks. The metal hydroxide and salt mixture may optionally be partially or fully de-watered/dried prior to being used for CO2 capture. As discussed above, inert solids may be added to the pellets and, in some embodiments, the inert solids may have particle sizes 10 to 100 microns, 100 microns to 1 mm, or a graded mixture to optimize pellet forming, simplify dewatering, and simplify reuse.
In some embodiments, inert solids are separated from the solution in the liberation vessel, prior to the solution being introduced into the liberation vessel, or downstream of the liberation vessel. In some embodiments, the inert solids are separated using density separation (e.g., low density polymers floating in water or higher density quartz particles sinking/sedimenting), or by using a flotation process in the acid environment of the liberation vessel. Thus, in some embodiments, particle reclamation is performed on the inert solids (e.g., removing particles from the top (skimming) or bottom of the tanks (pumping, raking, etc.). In some embodiments, the inert materials are of sufficiently large particle size to simplify a dewetting processes, for instance with a belt filter press. In some embodiments, density separation is performed using an additional sedimentation tank for inert particle separation after the liberation vessel and before the regeneration vessel. In some embodiments, inert particles may be physically separated from metal carbonates and salty acid with a separation process (e.g., sedimentation or flotation), then de-watered by filtering. Optionally, inert particles may be partially or fully dried (optionally with waste heat).
In some embodiments, the systems and methods of the present application include reservoirs for storing acids and/or bases. In some embodiments, this permits operational continuity in the event of a reduction or loss in electrical power (e.g., based on the use of intermittent renewable energy) or other input required to generate acids and bases. In some embodiments, the reservoirs are embodied as insulated containers or containers stored in an insulated environment, to maintain temperature and reduce energy loss.
In another aspect, the present application provides a novel water electrolyzer for producing a continuous stream of acids, bases, hydrogen and oxygen. The water electrolyzer may be used independently of the direct air capture equipment and methods discussed herein, or may be used together with such equipment and methods. For example, when used with direct air capture equipment and methods, the acidic and basic solutions used in the liberation and regeneration vessels may be produced using a water electrolyzer or an electrolyzer stack according to the present application. The H2 product from the electrolyzer may be provided for commercial or industrial applications including ammonia production, methanol production, direct reduction of iron for steel, other chemical processing operations, etc. The O2 product from the electrolyzer may be provided for commercial and industrial applications including for oxygen-fired combustion of hydrogen or hydrocarbons, medical applications, or other industrial uses.
In some embodiments, the water electrolyzer of the present application is a membrane-less water electrolyzer. In preferred embodiments, the water electrolyzer is operated with an electrolyte, preferably NaNO3. In some embodiments, the electrolyte is selected from the group consisting of sodium nitrate, potassium nitrate, sodium chloride, potassium chloride, sodium carbonate, potassium carbonate, sodium iodide, potassium iodide, magnesium chloride, calcium chloride, magnesium nitrate, calcium nitrate, and combinations or mixtures thereof. In other embodiments, the salt includes a fraction of alkali hydroxide selected from the group consisting of sodium hydroxide, potassium hydroxide, and combinations of mixtures thereof. In some embodiments, the salt has a minimum concentration of 0.01M and a maximum concentration equal to a fully saturated solution. In a preferred embodiment, the salt is NaNO3 and the concentration (entering electrolyzer or leaving regeneration vessel or settling tank) is 1-3M. In some embodiments, an acid and/or base produced by the electrolyzer has a lower salt concentration because a fraction of the salt entering the electrolyzer has been split to create the acid and base. In some embodiments, the alkali hydroxide is at a concentration of 0.01-0.1M or 0-0.5M. In preferred embodiments, the fraction of alkali hydroxide is controlled such that the pH of electrolyte entering the electrolyzer is between 7-14. In some embodiments, the pH of the electrolyte entering the electrolyzer is between 10-13. In some embodiments, the electrolyte entering the electrolyzer has been previously neutralized using an acid. Thus, in some embodiments, the electrolyte entering the electrolyzer is between 7-8.
In some embodiments, the membrane-less water electrolyzer is configured such that electrolyte flows by and/or through parallel or non-parallel electrodes spaced apart from one another in at least one dimension. In some embodiments, the membrane-less water electrolyzer is configured with a hybrid configuration such that electrolyte flows through and flows by parallel or non-parallel electrodes where each electrode pair is offset from another electrode pair in at least 1 dimension. In some embodiments, multiple sequential anode/cathode pairs are arranged from upstream to downstream (for example, 2, 3, 4, or 5 or more pairs), such that fluid passes each anode/cathode pair sequentially from a fluid inlet to the acid/base solution outlets. This configuration permits an increase in the conversion rate as water passes through each anode/cathode pair, instead of only one. In some embodiments, evolved H2 and O2 gases exit the electrolyzer with the acid/base solutions. In some embodiments, evolved H2 and O2 gases segregate from the acid/base solutions and exit through a separate conduit. Embodiments of this electrode architecture are shown in
In some embodiments, an electrolyzer cell is comprised of multiple electrode pairs. In some embodiments, these electrode pairs operate with non-matching potential differences. For example, a first pair of electrodes may operate at a potential difference lower than a second pair of electrodes, and the second pair of electrodes may operate at a potential difference lower than a third pair of electrodes, and so on. In some embodiments, an electrolyzer cell is made of more than one electrode pair operating in parallel. In some embodiments, an electrolyzer stack is made of electrolyzer cells which contain more than one electrode pair per cell.
In some embodiments, the electrodes in the water electrolyzer are constructed from a solid plate, porous plate, porous mesh, solid mesh, solid plate, wire, felt, foam, cylinder, mesh cylinder, or porous cylinder architecture. In some embodiments, the architecture is a combination of these architectures. In some embodiments, the architecture may include nested geometries, e.g., a smaller cylinder inside a larger cylinder. In some embodiments, the architecture may include electrodes with different dimensions, such as a different length or width. In some embodiments, the architecture includes pairs of flow-by plates (for both the anode and cathode) arranged at an offset angle to behave like a flow-through mesh. In some embodiments, each pair of flow by plates (anode/cathode) may have an independently adjustable voltage/potential. In some embodiments, at least one electrode is shaped as a ring, band, wire, disk, or plate.
In preferred embodiments, the water electrolyzer is operated with a pH gradient to produce an acidic solution and basic solution at the anode and cathode, respectively. In some embodiments, the pH gradient ΔpH is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16. In a preferred embodiment, the pH gradient is 13-16 or more preferably 14-15. In some embodiments, the operating voltage of the electrolyzer and the current density are dynamic and modulated to achieve a desired pH gradient. In particular, the operating voltage and current density may change over time as the ph gradient changes. In some embodiments, the operating voltage of the electrolyzer is between 1.5-5.0 volts. In some embodiments, the operating voltage of the electrolyzer is between 2.0-3.0 volts. In some embodiments, the pH gradient is modulated based on flow rate of water through the electrolyzer. In some embodiments, the flow rates are variable, or flow patterns are modulated to improve cell performance. Without being bound by theory, it is believed inducing turbulence in flow near an electrode surface affects the ionic diffusion layer, surface mixing, ion removal, and bubble removal to improve reaction kinetics. In some embodiments, this permits avoiding the use of platinum-group metals for the electrode materials.
In some embodiments, each electrode pair operates with a single potential difference. In some embodiments, some electrode pairs operate with a single potential difference, while others operate with a different potential difference. In some embodiments, individual electrode pairs may be switched on or off depending on operating conditions inside of the electrolyzer. In some embodiments, electrode pairs may be operated at near-zero voltage (well below the activation potential for water electrolysis), low voltage, voltage below the activation potential for water electrolysis, voltage above the activation potential for water (or far above the activation potential). In some embodiments, pairs of electrodes may be switched off during portions of operation depending on instantaneous operating conditions (water flow rate, pH, pH gradient, temperature, pressure, pressure drop, etc.).
Thus, pairs of electrodes may be activated based on availability of renewable energy. For example, when using a solar array to at least partially power the electrolyzer, electrode pairs operating at lower voltages may be switched on when only a moderate amount of sunshine powers the photovoltaic cells, whereas additional electrode pairs operating at higher voltages may be switched on when a greater amount of sunshine is available. When fewer electrode pairs are switched on, water flow may be limited to ensure production of acids and bases having desired pH. In an alternate embodiment, instead of switching off electrode pairs, all pairs may be operated at a lower voltage. In another embodiment, depending on available power, some electrodes may be switched on at lower voltage, whereas others are switched off completely. As more power becomes available, electrode pairs may be switched on and/or electrode pairs may be operated at a higher voltage. Water flow may be tailored to ensure production of acids and bases having desired pH during such operation. In some embodiments, the water electrolyzer is operated at elevated temperatures, 20-90° C., preferably 30-80° C., or more preferably 40-70° C. In some embodiments, this increases the kinetics of dissolution for less extreme pH gradients, enabling reduction in the operating voltage required to maintain a required pH gradient. In some embodiments, the operation temperature of the water electrolyzer is adjusted based on the pH gradient required to operate the liberation and regeneration vessels. Because ΔpH to operate the liberation and regeneration vessels changes with temperature, the operating temperature of the electrolyzer may be selected to minimize the required ΔpH. In preferred embodiments of the present application, the water electrolyzer operates within the closed loop system for CO2 capture, avoiding excessive heating and cooling inputs and outputs.
In some embodiments, the electrolyzer comprises a membraneless flow-through/flow-by reactor design. In some embodiments, the electrolyzer comprises a flow-through design, in which water/electrolyte flows through the electrodes. In some embodiments, the electrolyzer comprises a flow-by design, in which water/electrolyte flows by the electrodes. In some embodiments, the electrolyzer comprises a hybrid flow-through/flow by design containing aspects of each. In some embodiments, the membraneless reactor includes an upstream water inlet and two downstream outlets for acidic and basic solutions, respectively. In some embodiments, the membraneless flow-through reactor includes an anode and a cathode arranged obliquely relative to one another in a channel. In some embodiments, the anode and cathode (or anode and cathode pairs) are arranged in parallel rather than obliquely. In some embodiments, the angle between electrodes is defined as angle Θ. In some embodiments, when decreasing the angle between the electrodes, the distance between them also decreases, and as a result the uncompensated solution resistance decreases. In some embodiments, angle is selected from the group consisting of: 180°, 90°, 60°, 45°, 30°, and 0°. In some embodiments, the angle is between 0° and 180°.
2H2O+2e−⇄H2+2OH− (2)
2H2O⇄4H++O2+4e− (3)
In some embodiments, during operation, the products from reactions (2) and (3) are immediately swept downstream of the electrodes, preventing transport and recombination of the H+ and OH− ions that would normally occur in a stagnant electrolyte in the absence of a membrane or other means of separating these ions. In some embodiments, by varying operating parameters such as the electric current density of the electrodes, positioning of the electrodes and the flow rate of the electrolyte through the electrolyzer cell, it is possible to produce acid and base at a desired pH. The half-cell reactions (1) and (2) do not show the effect the electrodes have on the electrolyte. For instance, if NaNO3 is used as the salt, the full electrolytic reaction is shown in reaction (4) below.
6H2O+4NaNO3⇄2H2+O2+4HNO3+4NaOH (4)
As indicated previously, embodiments of the water electrolyzer of the present application may be used to supply acids and bases to the direct air capture equipment, systems, and methods of the present application. Thus, in one a preferred embodiment, an acidic solution containing salts produced at the anode may be used in the liberation vessel of the direct air capture system. Likewise, a basic solution containing salts produced at the cathode may be used in the regeneration vessel. The water electrolyzer also produces H2 and O2 gas. In some embodiments, the H2 and O2 gas are introduced into an energy recovery system as discussed herein. In contrast to other salt-splitting electrolyzers, embodiments of the present application do not produce other gases from corrosion of the electrolyte. For example, water electrolysis in the presence of sodium chloride may produce H2, O2, and Cl2, which may undergo secondary reactions to form HCl.
In some embodiments, a clarification effluent produced from the regeneration vessel, settling tank, and/or the de-watering step may optionally be recycled to the electrolyzer. Thus, in some embodiments, the clarification effluent is fed to an inlet in the electrolyzer. In some embodiments, the clarification effluent contains water and electrolyte and is weakly basic. In some embodiments, the clarification effluent has a pH between 7-14, 10-13, or 7-8. In some embodiments, the clarification effluent may be exposed to air during recycling to absorb CO2. In certain embodiments, the effluent containing absorbed CO2 is mixed with carbonated metal hydroxides to increase the extent of carbonation in a treatment step before carbonate solids enter the liberation vessel. In certain embodiments, the CO2 captured using the effluent is mixed with carbonated metal hydroxides to increase the extent of carbonation in a treatment step before carbonate solids enter the liberation vessel. In some embodiments, the otherwise sourced CO2 is mixed with carbonated metal hydroxides to increase the extent of carbonation in a treatment step before carbonate solids enter the liberation vessel. In some embodiments, the clarification effluent may be used as general feedwater to the electrolyzer. In some embodiments, the clarification effluent may be filtered of particles and used as general feedwater to the electrolyzer.
In some embodiments, the clarification effluent is treated with a water softening process to reduce alkalinity before being reused as feedwater to the electrolyzer. In some embodiments, alkalinity reduction includes ion exchange processes to remove metal ions, e.g., Ca2+ ions, which can prevent metal hydroxide precipitation on the electrolyzer's cathode, e.g., calcium hydroxide precipitation. In some embodiments, the ion exchange equipment is regenerated by flushing with electrolyte to recover Ca2+ ions for continued use in the CO2 capture process. In some embodiments, the basic clarification effluent is treated through a neutralization step, using acid produced by the electrolyzer, in order to reduce the overall pH before entering the electrolyzer.
In some embodiments, the water electrolyzer is configured as a cell stack comprising a plurality of cells, which may also be called an electrolyzer stack. Each cell in the stack may contain multiple electrode pairs as discussed previously. It shall be understood that the present application encompasses single and multiple cell electrolyzer designs. In some embodiments, the electrolyzer or electrolyzer stack contains the liberation and regeneration vessels. In some embodiments, the liberation and regeneration vessels contain the electrolyzer or electrolyzer stack. In a preferred embodiment, such an electrolyzer is operated using an electrolyte. In a preferred embodiment, the electrolyte is NaNO3 and water. In a preferred embodiment, the electrolyzer or electrolyzer stack is operated at elevated temperature. In some embodiments, the electrolyzer is operated at a temperature between 20-90° C., preferably 30-80° C., or more preferably 40-70° C.
In one embodiment, the metal carbonate produced in the metal hydroxide carbonation racks, preferably CaCO3, is introduced into the electrolyzer. In some embodiments, the metal carbonate is introduced into the electrolyzer proximate to the anode. In some embodiments, an acidic solution is present proximate to the anode and a basic solution is present proximate to the cathode due to the potential applied across the anode and cathode. Thus, in some embodiments, the electrolyzer liberates CO2 and O2 gas at the anode and produces an alkaline solution containing metal ions (e.g., Ca2+). In some embodiments, electrodialysis is used to move the metal ions towards a cathode. Such electrodialysis reduces the amount of unnecessary acid-base neutralization. Thus, the cathode liberates H2 gas and produces a metal hydroxide (e.g., Ca(OH)2) precipitate. Accordingly, in some embodiments, CO2 and O2 are produced in a first gas stream and H2 is produced in a second gas stream. The first and second gas streams are introduced into an energy recovery system as discussed herein to obtain CO2 and H2O, which may be separated by cooling, condensing, and/or dehydration processes.
In some embodiments, a fraction of H2 and O2 produced from the electrolyzer is stored (rather than directed immediately to the energy recovery system) to temporally shift the energy recovery process to generate electricity and maintain process power and continuity in subsystems, including particle suspension pumping and stirring, or to maintain electrolysis continuity.
In embodiments discussed herein, a metal hydroxide powder is obtained from a regeneration vessel. In further embodiments, the metal hydroxide powder is used to form pellets of metal hydroxide which are usable in the metal hydroxide carbonation racks or vessel discussed above. In some embodiments, waste heat produced in the liberation vessel or energy recovery system may be used for partial drying of metal hydroxide, for maintaining temperature in the regeneration vessel, or for warming feedstock for the water electrolyzer. In some embodiments, water is evaporated from the pellets (e.g., by flowing air over the pellets, or reducing pressure, to increase water evaporation while they are at elevated temperature), and subsequently condensed (e.g., from the flowing air stream) for recovery for re-use, for example in the water electrolyzer.
In some embodiments, a metal hydroxide powder is obtained from a settling tank. In further embodiments, the metal hydroxide powder is composed of agglomerated sub-micron Ca(OH)2 particles. In some embodiments, the agglomerated Ca(OH)2 powder is fully saturated with water. In further embodiments, the water saturating the metal hydroxide powder contains NaNO3 at concentrations between 0.01M and fully saturated concentrations. In further embodiments, the water saturating the metal hydroxide powder has a pH between 9 and 14 and contains alkali hydroxide, for example NaOH. In some embodiments, the concentration of alkali hydroxide is 0.00001-1M.
In further embodiments, the metal hydroxide powder is a slurry, paste, or particle suspension with water and other ions. In some embodiments, the metal hydroxide-water mixture is pumped from the settling tank, preferably the bottom. In some embodiments, the solid volume of metal hydroxide particles in the wet mixture is 10-50% by volume of the pumped mixture, or preferably 25-35% by volume.
In some embodiments, the metal hydroxide slurry, paste, or particle suspension is extruded. In some embodiments, the metal hydroxide slurry, paste, or particle suspension is further de-watered before extrusion. In further embodiments, inert particles are added to the metal hydroxide slurry, paste, or particle suspension before extrusion. In some embodiments, the addition of inert particles increases the solid volume fraction and improves pellet stability (e.g., prevents cracking upon drying, improves extrusion and lessens deformation, etc.). In some embodiments, pellets may be formed by coating inert particles.
Some embodiments of the present application include an energy recovery system. In preferred embodiments, H2 and O2 produced in the electrolyzer are consumed by the energy recovery system including a hydrogen-oxygen fuel cell or a combustion chamber/turbine for the same purpose. It should be understood that multiple fuel cells, combustion chambers, and/or turbines, and/or combustion cycles may be used. In some embodiments, the energy recovery system is used to separate CO2 and O2 produced in the liberation vessel. In some embodiments, the energy recovery system is used to separate CO2 and H2O produced in the energy recovery system. In some embodiments, liberated CO2 or a CO2/H2O mixture may be used as a diluent gas for H2 combustion to reduce flame temperature.
In a preferred embodiment, the energy produced in the energy recovery system is directed to electrolysis to reduce external energy demand. In some embodiments, waste heat produced in the energy recovery system is used to heat other processes (e.g., the regeneration vessel, or electrolyzer feedwater).
In some embodiments, heat is transferred from one location or subsystem to heat other processes (e.g., the regeneration vessel, or electrolyzer feedwater). In some embodiments, heat transfer occurs with a heat exchanger. In some embodiments, heat transfer occurs with a heat pump.
A gas stream (101) depicted as ambient air containing CO2 is passed into step (102) for capturing CO2. In step (102), Ca(OH)2 (optionally arranged as pellets in a plurality of trays) is reacted with the gas stream (101) under reaction (Ca(OH)2+CO2→CaCO3+H2O), producing carbonate and removing the carbon dioxide from the gas stream (101). A purified gas stream (not depicted) having a lower concentration of carbon dioxide exits step (102). In some embodiments, the purified gas stream may be passed through step (102) again to remove further CO2 until a desired concentration of CO2 in the purified gas stream is reached.
The mineral carbonation reaction products (102) are then fed into step (103) for a 2-step aqueous processing including the liberation of CO2 and the regeneration of Ca(OH)2 particles. In step (103), the products of (102) are first exposed to a concentrated acid and undergo an reaction (CaCO3+2HNO3→H2O+Ca2++CO2+2NO3−) and then exposed to a concentrated base, undergoing an reaction (Ca2++2NO3−+2NaOH→Ca(OH)2+2NaNO3). The CO2 evolved during the acidic dissolution of CaCO3 in (103) exits the liberation vessel and is optionally compressed (105) before the final captured CO2 product (106) is provided for use or storage. The regenerated product Ca(OH)2 precipitated in basic conditions in (103) is dewatered (104) and the resulting Ca(OH)2 is recovered and used again as a reactant in step (102). The water is recovered from step (104) is recycled through the process and used as the fluid medium for acid and base production in step (107) before returning to step (103).
The concentrated acids and based fed into the aqueous processing step (103) are obtained through water electrolysis (107), where water and an electrolyte (NaNO3 for this example) undergo an electrochemical reaction (3H2O+2NaNO3→H2+½O2+2NaOH+2HNO3). Power for step (107) is supplied as electricity, preferably from renewable power sources. The products H2+(½)O2 are then fed into step (108) for energy recovery. In step (108), such products undergo an exothermic reaction (H2+½O2→H2O) producing water and heat or power. Recovered electricity from step (108) may be used in step (107) to reduce the external power requirements. Waste heat produced in steps (105) and (108) may be used for dewatering or for other uses.
Ambient air (MC1) is passed into or through a mineral carbonation rack or vessel. Ca(OH)2 is added to a mineral carbonation rack, optionally with NaNO3 and H2O. Once prepared, Ca(OH)2+NaNO3+H2O composition (MC2), optionally in the form of pellets, is added to a plurality of mineral carbonation racks. The ambient air (MC1) reacts with composition (MC2) to generate CaCO3 and purified air (MC4). The purified air (MC4) exits the mineral carbonation racks.
A composition (MC5) containing CaCO3+Ca(OH)2+NaNO3+H2O is removed from the mineral carbonation rack or vessel, mixed with make-up CaCO3 for mass balance purpose (MC6), and is introduced into a liberation vessel. An acidic solution (MC8) containing H2O, HNO3, and NaNO3 is added to the liberation vessel. As a result, the liberation vessel liberates CO2 stream (MC9). The CO2 stream (MC9) is diverted for use and/or storage, and is optionally compressed.
An alkaline solution (MC10) of Ca2+ ions, NaNO3, H2O, and optionally Ca(OH)2 is pumped into a regeneration vessel. A basic solution (MC11) containing H2O, NaOH, and NaNO3 is added to the regeneration vessel. The regeneration vessel precipitates Ca(OH)2. The products (MC12) containing Ca(OH)2+NaNO3+H2O are passed to a de-watering/drying vessel or tank. The dewatered products (MC2) are optionally pelletized before being returned for mineral preparation and use in the mineral carbonation rack. Embodiment shows a forklift transporting the minerals from the de-water tank to the mineral carbonation racks, but this can be substituted by other manual or automated systems. A solution (MC14) of NaNO3+H2O is returned to an electrolyte tank for use in the water electrolyzer stack.
Water (E1) from a water tank and NaNO3 (E2) are added to the electrolyte tank (along with the solution (MC14) returned from the de-watering step). An electrolyte solution (E3) is pumped and added to an electrolyzer stack. The electrolyzer stack is operated with a pH gradient and produces acidic solution (E5) and basic solution (E6) referred to above, which are pumped from the electrolyzer stack to their respective destinations shown in
The energy recovery system in
Ambient air (MC1) is passed into or through a mineral carbonation rack or vessel. Ca(OH)2 is added to a mineral carbonation rack, optionally with NaNO3 and H2O. Once prepared, Ca(OH)2+NaNO3+H2O composition (MC2), optionally in the form of pellets, is added to a plurality of mineral carbonation racks. The ambient air (MC1) reacts with composition (MC2) to generate CaCO3 and purified air (MC4). The purified air (MC4) exits the mineral carbonation racks.
A composition (MC5) containing CaCO3+Ca(OH)2+NaNO3+H2O is removed from the mineral carbonation rack or vessel, mixed with make-up CaCO3 for mass balance purpose (MC6), and is introduced into a liberation vessel. An acidic solution (MC8) containing H2O, HNO3, and NaNO3 is added to the liberation vessel. As a result, the liberation vessel liberates CO2 stream (MC9). The CO2 stream (MC9) is diverted for use and/or storage, and is optionally compressed.
An alkaline solution (MC10) of Ca2+ ions, NaNO3, H2O, and optionally Ca(OH)2 is pumped into a regeneration vessel. A basic solution (MC11) containing H2O, NaOH, and NaNO3 is added to the regeneration vessel. The regeneration vessel precipitates Ca(OH)2. The products (MC12) containing Ca(OH)2+NaNO3+H2O are passed to a de-watering/drying vessel or tank. The dewatered products (MC2) are optionally pelletized before being returned for mineral preparation and use in the mineral carbonation rack. Embodiment shows a forklift to transport the minerals from the de-water tank to the mineral carbonation racks, but this can be substituted by an automatized system. A solution (MC14) of NaNO3+H2O is returned to an electrolyte tank for use in the water electrolyzer stack.
Water (E1) from a water tank and NaNO3 (E2) are added to the electrolyte tank (along with the solution (MC14) returned from the de-watering step). An electrolyte solution (E3) is pumped and added to an electrolyzer stack. The electrolyzer stack is operated with a pH gradient and produces acidic solution (E5) and basic solution (E6) referred to above, which are pumped from the electrolyzer stack to their respective destinations shown in
The energy recovery system in
The energy produced in the energy recovery system is optionally utilized to run the electrolyzer.
A gas stream (401) depicted as ambient air containing CO2 is passed into step (402) for capturing CO2. In step (402), Ca(OH)2 (optionally arranged as pellets in a plurality of trays) is reacted with the gas stream (401) under reaction (Ca(OH)2+CO2→CaCO3+H2O), producing carbonate and removing the carbon dioxide from the gas stream (401). A purified gas stream (not depicted) having a lower concentration of carbon dioxide exits step (402). In some embodiments, the purified gas stream may be passed through step (402) again to remove further CO2 until a desired concentration of CO2 in the purified gas stream is reached.
The mineral carbonation reaction products (402) are then fed into step (403) for a 2-step aqueous processing including the liberation of CO2 and the regeneration of Ca(OH)2 particles. In step (403), the products of (402) are first exposed to a concentrated acid and undergo an reaction (CaCO3+2HNO3→H2O+Ca2++CO2+2NO3−) and then exposed to a concentrated base, undergoing an reaction (Ca2++2NO3−+2NaOH→Ca(OH)2+2NaNO3). The CO2 evolved during the acidic dissolution of CaCO3 in (403) exits the liberation vessel and is optionally compressed (405) before the final captured CO2 product (406) is provided for use or storage. The regenerated product Ca(OH)2 precipitated in basic conditions in (403) is dewatered (404) and the resulting Ca(OH)2 is recovered and used again as a reactant in step (402). The water is recovered from step (404) is recycled through the process and used as the fluid medium for acid and base production in step (407) before returning to step (403). Waste heat produced in steps (405) may be used for dewatering or for other uses.
The concentrated acids and based fed into the aqueous processing step (403) are obtained through water electrolysis (407), where water and an electrolyte (NaNO3 for this example) undergo an electrochemical reaction (3H2O+2NaNO3→H2+½O2+2NaOH+2HNO3). Power for step (407) is supplied as electricity, preferably from renewable power sources. The products of (407) (H2+(½)O2) are then provided as separate gases for commercial or industrial uses.
Ambient air (MC1) is passed into or through a mineral carbonation rack or vessel. Ca(OH)2 is added to a mineral carbonation rack, optionally with NaNO3 and H2O. Once prepared, Ca(OH)2+NaNO3+H2O composition (MC2), optionally in the form of pellets, is added to a plurality of mineral carbonation racks. The ambient air (MC1) reacts with composition (MC2) to generate CaCO3 and purified air (MC4). The purified air (MC4) exits the mineral carbonation racks.
A composition (MC5) containing CaCO3+Ca(OH)2+NaNO3+H2O is removed from the mineral carbonation rack or vessel, mixed with make-up CaCO3 for mass balance purpose (MC6), and is introduced into a liberation vessel. An acidic solution (MC8) containing H2O, H+, NO3−, and NaNO3 is added to the liberation vessel. As a result, the liberation vessel liberates CO2 stream (MC9). The CO2 stream (MC9) is diverted for use and/or storage, and is optionally compressed.
An alkaline solution (MC10) of Ca2+ ions, NaNO3, H2O, and optionally Ca(OH)2 is pumped into a regeneration vessel. A basic solution (MC11) containing H2O, OH−, Na+, and NaNO3 is added to the regeneration vessel. The regeneration vessel precipitates Ca(OH)2. The products (MC12) containing Ca(OH)2+NaNO3+H2O are passed to a de-watering/drying vessel or tank. The heat from the dewatered products (16) Ca(OH)2+NaNO3+H2O is captured for re-use as discussed in embodiments herein. The dewatered products (MC2) are optionally pelletized before being returned for mineral preparation and use in the mineral carbonation rack. Embodiment shows a forklift to transport the minerals from the de-water tank to the mineral carbonation racks, but this can be substituted by an automatized system. A solution (MC14) of NaNO3+H2O is returned to an electrolyte tank for use in the water electrolyzer stack.
Water (E1) from a water tank and NaNO3 (E2) are added to the electrolyte tank (along with the solution (MC14) returned from the de-watering step). An electrolyte solution (E3) is pumped, heated to 80° C., and added to an electrolyzer stack. The electrolyzer stack is operated with a pH gradient and produces acidic solution (E5) and basic solution (E6) referred to above, which are pumped from the electrolyzer stack to their respective destinations shown in
A gas stream (701) depicted as ambient air containing CO2 is passed into step (702) for capturing CO2. In step (702), Ca(OH)2 (optionally arranged as pellets in a plurality of trays) is reacted with the gas stream (701) under reaction Rxn 3 (Ca(OH)2+CO2→CaCO3+H2O), producing carbonate and removing the carbon dioxide from the gas stream (701). A purified gas stream (not depicted) with having a lower concentration of carbon dioxide exits step (702). In some embodiments, the purified gas stream may be passed through step (702) again to remove further CO2 until a desired concentration of CO2 in the purified gas stream is reached.
The reaction products step (702) are then fed into step (703) for electrochemical liberation and regeneration. In step (703), such products undergo Rxn 1 (CaCO3+2H2O→Ca(OH)2+CO2+H2+½O2). The product Ca(OH)2 is dewatered (704) and the resulting Ca(OH)2 is recovered and used again as a reactant step (702). The water is recovered and used again as a reactant in step (703).
The products CO2+H2+(½)O2 are then fed into step (705) for energy recovery. In step (705), such products undergo exothermic reaction Rxn 2 (H2+½O2→H2O) producing water. The water and CO2 are then fed into step (706) for condensation to separate the water and CO2 and optional compression of the CO2 gas. Waste heat produced in steps (705) and (706) may be used for dewatering or for other uses.
A-1. A system for capturing atmospheric carbon dioxide, comprising: a mineral carbonation rack containing a metal hydroxide for capturing carbon dioxide by converting the metal hydroxide to metal carbonate;
A-2. The system of A-1,
A-3. The system of A-2,
A-4. The system of any of A-1 to A-3,
A-5. The system of any of A-1 to A-4,
A-6. The system of any of A-1 to A-5,
A-7. The system of any of A-1 to A-6,
A-8. The system of A-7,
A-9. The system of any of A-1 to A-8,
A-10. The system of A-9,
A-11. The system of A-10,
A-12. The system of A-1,
A-13. The system of A-12,
B-1. A method of capturing carbon dioxide from the atmosphere, comprising: providing a system according to any of A-1 to A-13;
C-1. A direct air capture system comprising:
C-2. The direct air capture system of C-1,
C-3. The direct air capture system of C-1,
C-4. The direct air capture system of C-1,
C-5. The direct air capture system of C-1 to C-4, further comprising:
C-6. The direct air capture system of C-1 to C-5, further comprising:
C-7. The direct air capture system of C-1 to C-6,
C-8. The direct air capture system of C-1 to C-7,
C-9. The direct air capture system of C-1 to C-8, further comprising:
D-1. A sorbent processing system for carbon dioxide liberation and metal hydroxide regeneration comprising:
D-2. The sorbent processing system of claim D-1, further comprising:
D-3. The sorbent processing system of claims D-1 to D-2, further comprising:
D-4. The sorbent processing system of D-1 to D-3,
D-5. The sorbent processing system of D-1 to D-4,
D-6. The sorbent processing system of D-2 to D-5,
D-7. The sorbent processing system of D-2 to D-6,
D-8. The sorbent processing system of D-2 to D-7, further comprising:
D-9. The sorbent processing system of D-2 to D-8, further comprising:
D-10. The sorbent processing system of D-2 to D-9,
D-11. The sorbent processing system of D-2 to D-10,
E-1. A water electrolyzer comprising:
E-2. The water electrolyzer of E-1, further comprising:
E-3. The water electrolyzer of E-1 to E-1, further comprising:
E-4. The water electrolyzer of E-1 to E-3,
E-5. The water electrolyzer of E-1 to E-4,
E-6. The water electrolyzer of E-1 to E-5,
E-7. The water electrolyzer of E-1 to E-6,
E-8. The water electrolyzer of E-1 to E-7,
E-9. The water electrolyzer of E-1 to E-8,
E-10. The water electrolyzer of E-1 to E-9,
E-11. The water electrolyzer of E-1 to E-10,
E-12. The water electrolyzer of E-1 to E-11, further comprising:
F-1. A system for capturing atmospheric carbon dioxide comprising:
G-1. A system for capturing atmospheric carbon dioxide comprising:
G-2. The system of G-1,
G-3. The system of G-1 to G-2,
G-4. The system of G-3,
G-5. The system of G-1 to G-4, further comprising:
G-6. The system G-5,
G-7. The system of G-1 to G-6, further comprising:
G-8. The system of G-1 to G-7, further comprising:
This application is based upon and claims the benefit of priority under 35 U.S.C. § 119(e) to U.S. Provisional Application No. 63/305,113, filed Jan. 31, 2022, the entire contents of all of which are incorporated herein by reference in their entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2023/012004 | 1/31/2023 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63305113 | Jan 2022 | US |
