Patent Application
20220355240
The present disclosure relates to selectively capturing a carbon containing gas from an input gas mixture. In particular, the present disclosure relates to an apparatus, system and method for selectively capturing the carbon containing gas from the input gas mixture by use of a thermal insulator and a media that has an affinity for the carbo-containing gas.
Atmospheric carbon dioxide (CO2) concentration cycled at about 235±50 ppm for about 400 millennia until around 1850. Currently atmospheric CO2 concentration is at about 420 ppm and rising at a rapid annual rate. The increased concentration of CO2 in the atmosphere is causing global planetary climate disruptions, habitat loss and various other threats to our planet. CO2 is regarded as a stable molecule such that its transformation into a non-greenhouse gas now poses a significant challenge.
It is known that the increasing atmospheric concentration levels of CO2 can be mitigated by the removal of CO2 from the air and/or by lowering the rate of emission of CO2 into the atmosphere. Known technologies that are intended to remove CO2 from the air that have been explored are costly, water and energy intensive and demonstrate little incentive for long-term storage of removed of CO2. For example, concentrated CO2 produced by air-capture membrane technologies is known to be used to make seltzer water, which re-releases the CO2 when consumed.
As another known example, concentrated CO2 produced by a precipitation/calcination method is currently injected to release fossil fuels, which has a limited capacity for storage, leaches back to the air, and releases CO2 to the air when the fossil fuels are consumed.
A further known example for mitigating the increasing atmospheric concentration levels of CO2 include converting CO2 to carbon and oxidation by molten carbonate electrolysis. A useful product generated by this process includes carbon nanomaterials. Carbon nanomaterials, including graphitic carbon nanomaterials, have great potential as a material resource, with applications ranging from reinforced composites, capacitors, lithium-ion batteries, woven textiles, nano-electronics, and catalysts, to the principal component of lightweight, high strength building materials due to their characteristic superior strength, electrical and thermal conductivity, flexibility and durability. However, technical challenges remain in order to capture sufficient amounts of CO2 so as to substantively decrease the atmospheric concentration levels of CO2 and the associated negative impacts on our planet.
Some embodiments of the present disclosure relate to a system for selectively transferring a carbon-containing gas from an input gas mixture. The system may include an optional permeable thermal insulator that permits a net selective passage therethrough of the carbon-containing gas from the input gas mixture at a first temperature and a plenum for housing a media at a second temperature that is greater than the first temperature. The media having a first affinity for carbon within the carbon-containing gas received from the optional thermal insulator and the media acts as a carbon sink. When used, the optional thermal insulator may be positioned between a source of the input gas mixture and the plenum.
Some embodiments of the present disclosure relate to a method for reducing a carbon-containing gas content of an input gas mixture. The method comprising the steps of: providing a media in fluid communication with a source of the input gas mixture, the media having an affinity to react with a carbon-containing gas of the input gas mixture; establishing a temperature differential whereby the media has a greater temperature than the input gas mixture; and reacting the media and carbon-containing gas together so that the media acts as a carbon sink for reducing the carbon-containing gas content of the input gas mixture.
Some embodiments of the present disclosure relate to an apparatus for capturing carbon dioxide (CO2) from an input gas mixture. The apparatus comprises an anode and cathode positioned within an electrolytic cell; a molten electrolyte media positioned between the anode and the cathode, wherein the molten electrolyte media defines an upper surface with a first surface area and wherein the upper surface is in fluid communication with a plenum containing the input gas mixture; and a thermal insulator that is positioned between the plenum containing the input gas mixture and the upper surface, wherein the thermal insulator is configured to facilitate the net selective passage of CO2 therethrough to the upper surface. The apparatus is configured to selectively heat and electrolytically split the captured CO2.
In some embodiments of the apparatus, the input gas mixture is air and the source of the input gas mixture is planet earth's atmosphere.
In some embodiments of the apparatus, the input gas mixture is an anthropogenic CO2-containing gas, an industrial waste-gas stream, a gas from a reservoir of sequestered CO2, an emission gas from an industrial plant, an emission gas from a chemical reactor, an emission gas from a power generating plant, an emission gas from a steam generation facility, an emission gas from a pyrolysis reactor, a CO2-containing gas product from combusting a fossil fuel, a CO2-containing gas product from transforming a fossil fuel, a CO2-containing gas product from heating, a CO2-containing gas product from transportation, a CO2-containing gas product from production of a polymer, a CO2-containing gas product from production of a plastic or combinations thereof.
In some embodiments of the apparatus, the thermal insulator has a surface area that is between 2 and 100 times greater than the first surface area of the upper surface of the molten electrolyte media within the electrolytic cell.
In some embodiments of the apparatus, the apparatus further comprises a housing positioned between the plenum containing the input gas mixture and the thermal insulator.
In some embodiments of the apparatus, the thermal insulator and the housing define an inter-insulation plenum with a first end, a second end and the cell is positioned therebetween and wherein the inter-insulation plenum receives the input gas mixture at the first end.
In some embodiments of the apparatus, the electrolytic cell comprises at least one metal wall that acts as the anode.
In some embodiments of the apparatus, the anode and the cathode are configured to select a relative amount of the constituent carbon nanostructures within the CNM product.
In some embodiments of the apparatus, the electrolysis current and voltage are configured to select a relative amount of the constituent carbon nanostructures within the CNM product.
In some embodiments of the apparatus, a metal salt, metal, or other additives are added to the electrolyte to select a relative amount of the constituent carbon nanostructures within the CNM product.
In some embodiments of the apparatus, the electrolyte comprises one or more carbonate salts to select a relative amount of the constituent carbon nanostructures within the CNM product.
In some embodiments of the apparatus, the electrolyte is configured for enhanced thermal properties that enhance selective capture of CO2 from the input gas mixture.
In some embodiments of the apparatus, electrolyte can store excess thermal energy.
In some embodiments of the apparatus, the input gas mixture is redirected through the apparatus using a wind lens or wind focus.
In some embodiments of the apparatus, heat is input to drive a heat engine or drive input gas mixture movement.
Some embodiments of the present disclosure relate to a system for capturing carbon dioxide (CO2) from an input gas mixture. The system comprises at least two apparatus, wherein each apparatus comprises: an anode and cathode positioned within an electrolytic cell; a molten electrolyte media positioned between the anode and the cathode, wherein the molten electrolyte media defines an upper surface with a first surface area and wherein the upper surface is in fluid communication with a plenum containing the input gas mixture; and a porous thermal insulator that is positioned between the plenum containing the input gas mixture and the upper surface, wherein the porous thermal insulator is configured to facilitate the net selective passage of CO2 therethrough to the upper surface. Each apparatus of the system is configured to selectively heat and electrolytically split the captured CO2 by an electrolysis process.
In some embodiments of the system, at least two apparatus are vertically arranged in a stack for lowering a physical footprint area of the system.
In some embodiments of the system, the system further comprises a source of heat and a source of electrical current that are operatively coupled to each apparatus.
In some embodiments of the system, the system further comprises a source of heat and a source of electrical current that are operatively coupled to the at least two apparatus.
Some embodiments of the present disclosure relate to a method for direct capture of carbon dioxide (CO2) from an input gas mixture within a plenum that comprises CO2. The method comprising the steps of: establishing fluid communication between the input gas mixture and an outer surface of a porous, thermal insulator; selectively capturing CO2 from the input gas mixture by passing CO2 through the thermal insulator into a second plenum; establishing fluid communication between an inner surface of the porous, thermal insulator and an electrolyte media within the second plenum, wherein the electrolyte media is configured to accentuate capture of CO2; and, collecting from an electrode within the second plenum a carbon nanomaterial product generated from the captured CO2.
In some embodiments of the apparatus, system and/or method, the input gas mixture comprises at least one carbon-containing gas.
In some embodiments of the apparatus, system and/or method, the input gas mixture is air, an anthropogenic CO2-containing gas, an industrial waste-gas stream, a gas from a reservoir of sequestered CO2, an emission gas from an industrial plant, an emission gas from a chemical reactor, an emission gas from a power generating plant, an emission gas from a steam generation facility, an emission gas from a pyrolysis reactor, a CO2-containing gas product from combusting a fossil fuel, a CO2-containing gas product from transforming a fossil fuel, a CO2-containing gas product from heating, a CO2-containing gas product from transportation, a CO2-containing gas product from production of a polymer, a CO2-containing gas product from production of a plastic or combinations thereof.
In some embodiments of the apparatus, system and/or method, an input rate of the input gas mixture, or an exit rate of the input gas mixture is accelerated by altering a pressure between a first and a second side of the porous thermal insulator by use of a diaphragm pump.
In some embodiments of the apparatus, system and/or method, an input rate of the input gas mixture, or an exit rate of the input gas mixture is accelerated by altering a pressure between a first and second side of the porous thermal insulator by use of a blower or a fan.
In some embodiments of the apparatus, system and/or method, further comprises a compressor mechanism for compressing the input gas mixture to a pressure greater than ambient pressure.
In some embodiments of the apparatus, system and/or method, the input gas mixture is pressurized.
In some embodiments of the apparatus, system and/or method, an off-gas generated in the second plenum is hotter than the input gas mixture.
In some embodiments of the apparatus, system and/or method, an off-gas generated in the second plenum is oxygen (O2).
In some embodiments of the apparatus, system and/or method, the off-gas product compensates or enhances an input rate of the input gas mixture and/or the CO2 capture in the internal second media.
In some embodiments of the method, the method further comprises a step of transferring thermal energy from the off-gas product to the input gas mixture.
In some embodiments of the apparatus, system and/or method, the porous thermal insulator is substantially completely porous and open to the input gas mixture.
In some embodiments of the apparatus, system and/or method, the porous thermal insulator is an open channel, thermal insulator that inhibits heat transfer between the second plenum and the input gas mixture.
In some embodiments of the apparatus, system and/or method, the porous thermal insulator is adjustable to adjust gas flow and heat transfer therethrough.
In some embodiments of the apparatus, system and/or method, the porous thermal insulator has a surface area that is between 1 and 100 times greater than a surface area of the internal second media. In some embodiments of the apparatus, system and/or method, the porous thermal insulator has a surface area that is between 2 and 20 times greater than a surface area of the internal second media.
In some embodiments of the apparatus, system and/or method, a ratio of the surface area of porous thermal insulator relative to a surface area of an electrolyte surface of the electrolyte media is adjustable.
In some embodiments of the apparatus, system and/or method, the inner surface of the porous thermal insulator directly contacts the electrolyte media.
In some embodiments of the apparatus, system and/or method, the inner surface of the porous thermal insulator is proximal to the electrolyte media with a gas space positioned therebetween.
In some embodiments of the method, the method further comprising a third step of positioning a non-porous housing for about the porous thermal insulator for defining an inter-insulation plenum, also referred to as a flow channel, with a first end, a second end and wherein the inter-insulation plenum is configured to receive the input gas mixture at the first end.
In some embodiments of the apparatus, system and/or method, the non-porous housing is a thermal insulator.
In some embodiments of the apparatus, system and/or method, excess heat generated by the method is used to heat or power external devices.
In some embodiments of the apparatus, system and/or method, a heat pump or a heat engine is used to heat the input gas mixture, the internal second media or a combination thereof.
In some embodiments of the apparatus, system and/or method, joule heat, industrial waste heat, solar heat, geothermal heat, exhaust heat or a combination thereof, is used to heat the input gas mixture, the internal second media or a combination thereof.
In some embodiments of the apparatus, system and/or method, further comprise a vortex tube, a heat pump, a heat engine and combinations thereof for increasing a concentration of the carbon-containing gases within the input gas mixture; increasing a flow rate of the input gas mixture; or combinations thereof.
In some embodiments of the apparatus, system and/or method, the thermal insulator is configured to enhance an exhaust flow of an off-gas product from the molten electrolyte media, to increase a rate at which the carbon-containing gas passes through the thermal insulator or combinations thereof.
In some embodiments of the apparatus, system and/or method, the thermal insulator is configured to selectively pass a greater amount of the carbon-containing gas therethrough as compared to other non-carbon-containing gases that are constituents of the input gas mixture.
In some embodiments of the apparatus, system and/or method, system further comprises one or more shiftable members that shift to shift their position to direct a flow of gas in a first direction or a second direction within the flow channel, wherein a first direction is towards an input aperture and the second direction is opposite and towards the output aperture.
Some embodiments of the apparatus, system and/or method further comprise situating a cover that is configured to regulate access to the captured CO2.
In some embodiments of the apparatus, system and/or method, one or more components of the selectively captured CO2 are mixed in the electrolyte media via mechanical mixing, agitation, stirring, convection, bubbling or a combination thereof.
In some embodiments of the apparatus, system and/or method, the input gas mixture comprises carbon-containing gases other than CO2, which the electrolyte media also has an affinity for.
In some embodiments of the method, the electrolyte media is a molten electrolyte media.
In some embodiments of the method, the method further comprises the additional steps of: heating an electrolyte to obtain the molten electrolyte media; disposing the molten electrolyte media between an anode and a cathode in an electrolytic cell; selectively heating the CO2 within the input gas mixture with at least the molten electrolyte media; applying an electrical current to the cathode and the anode in the cell for electrolytically splitting (splitting by an electrolysis process) the selectively heated CO2; and collecting a carbon nanomaterial product from the cathode of the cell.
In some embodiments of the method, the method further comprises a step of generating an oxygen (O2) product within the molten electrolyte media.
In some embodiments of the apparatus, system and/or method, the O2 product enhances a convective current within the molten electrolyte media for mixing the molten electrolyte media.
In some embodiments of the apparatus, system and/or method, the carbon nanomaterial product comprises one or more morphologies of graphitic nanocarbon such as, but not limited to: carbon nanotubes, carbon nano-onions, platelets, nano-scaffolds, nanohelices, nanoflowers, nanotrees, nanobelts, graphene, doped carbon nanomaterials, magnetic carbon nanomaterials, amorphous carbon or a combination thereof.
In some embodiments of the apparatus, system and/or method, a morphology of the carbon nanomaterial product may be adjusted by changing the electrolyte media temperature, CO2 rate, current, voltage, cathode composition, anode composition or electrolyte media composition.
In some embodiments of the apparatus, system and/or method, the molten electrolyte media comprises carbonates.
In some embodiments of the apparatus, system and/or method, the electrical current is supplied by a non-fossil energy source, including, but not limited to solar, wind, hydroelectric, geothermal, tidal, wave, nuclear power or combinations thereof.
In some embodiments of the method, the method further comprises a step of activating the electrolyte media.
In some embodiments of the apparatus, system and/or method, the electrolyte media comprises an added oxide.
In some embodiments of the apparatus, system and/or method, the electrolyte media is molten and reused to enhance the degree of CO2 conversion into a different chemical substance.
In some embodiments of the apparatus, system and/or method, the electrolyte media is molten and time equilibrated to enhance the degree of CO2 conversion.
In some embodiments of the apparatus, system and/or method, the upper surface of the electrolyte media is located close to the lower surface of the internal second media to enhance the degree of CO2 conversion.
In some embodiments of the apparatus, system and/or method, the electrical current is low to enhance the degree of CO2 conversion.
In some embodiments of the apparatus, system and/or method, the electrolytic cell is metal to enhance the degree of CO2 conversion.
In some embodiments of the apparatus, system and/or method, multiples of the CO2 capture apparatus are vertically stacked to reduce the horizontal footprint area of the method per unit of input gas mixture processed.
In some embodiments of the method, the method further comprises repeating steps a, b, c and d continuously.
In some embodiments of the method, the method further comprises repeating steps a, b, c and d and a step of replacing the internal media.
In some embodiments of the apparatus, system and/or method, the input gas mixture is accelerated using wind. In some embodiments of the apparatus, system and/or method, the input gas mixture is redirected using a wind lens or a wind focus.
In some embodiments of the apparatus, system and/or method further comprises a second layer of thermal insulation positioned between the source of the input gas mixture and a first side of the thermal insulator wherein the second layer of thermal insulation is substantially pore free and/or impermeable to the input gas mixture.
In some embodiments of the apparatus, system and/or method the electrolytic cell comprises at least one metal wall that acts as the anode.
In some embodiments of the apparatus, system and/or method the electrolytic cell the anode and the cathode are each adjusted to form a different carbon nanomaterial or to increase the amount of a desired carbon nanomaterial morphology within the carbon nanomaterial product.
In some embodiments of the apparatus, system and/or method the electrolytic cell the anode and the cathode are each adjusted to form a different carbon nanomaterial or to increase the amount of a desired carbon nanomaterial morphology within the carbon nanomaterial product.
In some embodiments of the apparatus, system and/or method a metal salt, metal, or other additives added to the electrolyte to form different carbon nanomaterial or to increase the amount of a desired carbon nanomaterial morphology within the carbon nanomaterial product.
In some embodiments of the apparatus, system and/or method the electrolyte media comprises one or more carbonate salts to form different carbon nanomaterial or to increase the amount of a desired carbon nanomaterial morphology within the carbon nanomaterial product.
In some embodiments of the apparatus, system and/or method the electrolyte is adjusted for enhanced thermal properties
In some embodiments of the apparatus, system and/or method the electrolyte is adjusted for to change the absorptivity of various gases from the input gas mixture.
In some embodiments of the apparatus, system and/or method the electrolyte can be used to store excess thermal energy.
Without being bound by any particular theory, the embodiments of the present disclosure provide an economical, scaleable and robust approach for selectively capturing carbon-containing gases from an input gas mixture by creating a temperature differential between the input gas mixture and a media with an affinity for reacting with the carbon-containing gas. In some embodiments, a source of the input gas mixture can be one or more anthropogenic sources of carbon-containing gas, such as CO2.
Embodiments of the present disclosure relate to one or more apparatus, one or more systems and one or more methods that are useful for selectively capturing carbon dioxide (CO2) from an input gas. The input gas may be a substantially pure gas, a pure gas or a combination of different gases and, therefore, the term “input gas” and “input gas mixture” can be used interchangeably herein. According to the embodiments of the present disclosure, the captured CO2 can be subjected to an electrolysis process, also referred to herein as the electrosynthesis process, for generating a carbon nanomaterial (CNM) product from the carbon within the CO2. The terms “carbon nanomaterial product” and “CNM product” are used herein to refer to a collection of nanocarbon, which may also be referred to as nano-scaled carbon, of one or more morphologies. The term “nanocarbon” is used herein to refer to carbon that is arranged into specific structures, such as graphitic nanocarbon structures, within the nanoscale. In particular, the CO2 that is selectively captured from the input gas mixture can be split into carbon and oxygen using the molten electrolyte media and a variety of electrolysis process configurations. The electrolysis process can cause a mass transfer of carbon from a gas phase into the molten electrolyte media, the solid CNM product or both. The CNM product can be a substantially pure, or pure, carbon nanomaterials (CNMs) including carbon nanotubes (CNTs). The CNM product may comprise one or more morphologies of CNM structures, such as carbon nanotubes, carbon nano-onions, nanoflowers, nanotrees, nanobelt, platelets, nano-scaffolds, helical carbon nanomaterials, graphene, doped carbon nanomaterials, amorphous carbon or a combination thereof. Optionally, one or more parameters of the electrolysis process may be adjusted in order to change the relative amount of a given morphology within the CNM product.
The vessel 1002 shown in
In some embodiments of the present disclosure, the media's affinity to react with the carbon-containing gas and the permeability properties of the thermal insulator 1008 can act in concert to deplete the carbon-containing gas content of the input gas 1006 and increase the carbon content of the media 1004. As in
CO2 is rapidly absorbed and spontaneously concentrated from air by an exothermic reaction with the molten electrolyte media by reacting with oxides in the molten salt. This continuously renews the molten carbonate electrolyte media, without being bound by any particular theory, as described by the following Equations 1, 2 and 3:
CO2(gas)+O2−fi CO32− (Equation 1)
The electrolysis reaction is in accord with equation (2) below:
CO32−fi C+O2+O2− (Equation 2)
In this process, CO2 is split by molten electrolysis, to produce the CNM carbon product and hot oxygen, and with the carbon as the CNM product as described by equation (3):
CO2fi CNMproduct+O2 (Equation 3)
As shown in
The experimental rapid rate of CO2 absorption in a 770° C. molten lithium carbonate media containing one molal lithium oxide is shown in FIG.3A.
CO32−fi Cnanomaterials+O2−+O2 (Equation 4a)
CO2+O2−fi CO32−; CO2+Li2O fi Li2CO3 (Equation 4b)
Regarding Equation 4a, the high rate of CO2 absorption, is due to its exothermic chemical reaction with one of the chemical species in the electrolyte media. Without being bound by any theory, the oxide that drives the fast reaction with CO2 is formed by chemical equilibration and by electrolysis of carbonate in the formation of a CNM product.
Regarding Equation 4b, without being bound by any theory, the oxide exothermically reacts with CO2 to continuously renew the carbonate in the electrolyte media, such as in Li2CO3, with the enthalpy of reaction calculated from that of the individual reactions species using the thermodynamic data available through the NIST Webbook and NIST-JANAF Thermochemical Tables.
The evolving O2 product rises through the electrolyte and enhances convective currents in the electrolyte media that facilitate mixing of incident CO2 and enhances the reaction rate. While the reaction rate from air CO2 into the electrolyte is very high, it will be lower compared to gases mixtures, such as flue gas, containing higher levels of CO2. Alternatively, with or without electrolysis, the rate of reactive absorption of CO2 in molten carbonate electrolyte media with oxide can further increase with enhanced convection, such as mechanical stirring or flowing of the electrolyte or rotating the electrodes, or agitation, or bubbling of the hot gas into the electrolyte.
A further physiochemical feature that allows for the CO2 portion within the input gas mixture to be selectively heated independent of the other components of the ambient air is the high conventional rate of CO2 diffusion in the air compared to the rate at which CO2 is consumed during the electrolysis.
Diffusion is traditionally described by Fick's Laws. Without being bound by an particular theory, a fundamentally equivalent, but simpler starting point is the Einstein-Smoluchowski equation describing the relationship between mean square displacement and diffusion. The Brownian motion mean square displacement of a species, i, by diffusion, <x2>, in time, t, is given in 1, 2 or 3 dimensions by Equation 5:
<x2>=qDit (Equation 5)
where q is the dimensionality factor (q=2, 4 or 6 for diffusion in 1, 2 or 3 dimensions); Di is the diffusion coefficient, and t is the time. Note, that molecular motion at interfaces can differ from this ideal case.
This translational displacement is converted to the average diffusion speed, <x2>/t, of CO2 as a function of temperature, see Equation 6:
nco2=<x2>0.5/t=(q×DCO2(T))0.5/tu (Equation 6)
where T is the temperature, and tu is unit time consistent with the diffusion coefficient.
Without being bound by any particular theory, the hot O2 generated by the electrolysis process, which may also be referred to as an off-gas product, could itself be used to produce oxidizing agents for various applications, including but not limited to: disinfectants, for various industrial and oxy-fuel processes and the like. Additionally, the hot O2 can be used to transfer some of its energy back into CO2 being absorbed or be used to pull in more reactant into the system as in a heat engine process. Some embodiments of the present disclosure relate to isolating the O2 off-gas product from the electrolysis cell, for example by way of a conduit that is in fluid communication with the gas space above the liquid-gas interface of carbonate electrolyte media within the electrolysis cell.
Heat may be preserved within the electrolyte media through the addition of a porous, thermal insulator surrounding the electrolysis cell. Note also that air within the gas space of the electrolysis cell—above the upper surface of the electrolyte media—as well as the air within the porous insulation, will contain a growing concentration of oxygen as the electrolysis process proceeds.
The addition of a porous, thermal insulator cover above the molten carbonate electrolyte media allows a gas phase CO2 to diffuse from the input gas mixture into the molten lithium carbonate electrolyte media, this is a further physiochemical feature by which the CO2 portion of input gas mixture can be selectively heated. Without being bound by any theory, in the absence of convection, the maximum rate of CO2 arriving as the reactant for the electrolysis is limited by the maximum one dimensional speed of CO2 in the direction orthonormal to the insulation surface as the CO2 travels towards the interior of a kiln containing the electrolysis cell. Without being bound by any theory, the one dimensional mean displacement per second, and the speed of CO2 in air trapped in the insulation nearest to the ambient air side at 20° C. is nco2−insulation=nco2(20° C.)=0.56 cm CO2 s−1.
When the input gas mixture is air sourced from the atmosphere, CO2 originates from ambient air, arriving as a reactant and passing into the porous thermal insulator for electrolytic splitting. The molar volume concentration of CO2 in ambient air (20*C), VM(CO2 in air) is determined from its 0.04% molar concentration and the molar volume of a gas; that is VM(CO2 in air)=VM(20° C.)/0.04% CO2=1 mol CO2 per 6.0×107 cm3 air. The molar flux of CO2 per cm2 through the external surface area of the porous insulation is given as f(CO2)insulation.
The average global speed of air (wind speed) is nair-average=330 cm/s (=11.9 kph=7.4 mph), and has been rising at 0.8% per year since 2010. In the Examples, 0.33%, 10% or 100% of this wind speed domain (1, 33 or 330 cm/s) were examined to demonstrate that natural wind, rather than an artificial blower, suffices to maintain CO2 for the embodiments of the present disclosure. Without being bound to any theory, to a first degree of approximation wind at an air speed of air orthogonally striking a one cm2 square area of insulation will be replenish the CO2 depleted by the diffusional mean square displacement at a proportional rate of Z=nair(cm/s)/nCO2. In principle, the air speed can be enhanced by a diaphragm that forces more air through a smaller area or that pressurizes the air. A wind speed increase in turn increases the mole concentration of CO2 striking the area to Z×VM(CO2 in air). The CO2 flux is driven by the concentration gradient between that at the exterior surface of the insulation and the concentration at the surface of the electrolyte media. CO2 uptake by the electrolyte media during the electrolysis is rapid; the rate of reaction is fast, expediting mass transfer of carbon into the electrolyte media.
Heat, (−Qin), is generated during the electrolysis and without being bound by any theory by (i) the heat of the reaction of CO2 with the Li2O as it reforms electrolyte media at ΔH=−158,000 J/mol (Equation 4), and (ii) the resistive heating from the electrolysis over-potential. Reactive heat released is the exothermic reaction of CO2 with the electrolytic Li2O, −ΔH (Equation 4) in accord with the moles of CO2 consumed. The resistive heating from the product of the electrolysis over-potential, h, and the electrolysis current. The rest potential for the electrolytic splitting of CO2 in molten carbonate electrolytes is ˜0.8V and varies with the electrolyte media composition and electrolysis electrodes. The additional over-potential to drive a constant current density, I, will vary with electrolyte media composition and electrode composition and texturing, and has been measured for planar electrodes. Heat loss from a system, Pout, is given by the thermal conductivity, the surface area of thermal contact, A, the difference of temperature across the insulator, ΔT, and the thickness of the insulation, □. Thermal conductivity, k, is often expressed in metric units (W/(mK)), while thermal resistance, R, is often expressed in British units (ft2 hr ° F./Btu) and includes the thickness of the insulator in inches.
Pout=kAΔT/□=AΔT/R (Equation 7)
The dual characteristics of a material which allows CO2 to enter the kiln and retain heat within the electrolysis chamber is achievable with porous thermal insulation. Such material has (i) an open porosity (as opposed to close pores or grains) materials, (ii) a high insulation factor, and (iii) can withstand the temperature of the electrolysis conditions in the appropriate temperature domain. The porosity dependence of thermal conductivity for high temperature refractory materials has been studied. Porous thermal insulators capable of withstanding the high temperature (>1150° C.) are alumina silicate and alumina calcium silicate blankets. Examples are various products including “ceramic fiber insulation for furnaces,” “alumina silica ceramic fiber,” “Durablanket®”, or “Cerablanket®”. The relevant thermal commercial products often regress to British rather than metric units, have similar available compositions (for example 46% Al2O3 and 54% Si2O), thicknesses (0.5, 1 or 2″ thick), and range of densities (4, 6 or 8 lbs/ft3=pcf).
Even the densest of these alumina silica fiber blankets is lightweight with a high porosity. As an example, the porosity of the 8 pcf density (=0.128 g/cm3) Cerablanket® may be estimated using the solid (pore free) average dsolid=3.2 g/cm3 density from 46% of the 4.0 g/cm3 density alumina and 54% of the 2.6 g/cm3 density Si2O. The porosity is estimated from the open space as (with dair=0.001225 g/cm3)):
p=100%×(dsolid−dcerablanket)/(dsolid−dair) with dair=0.001225 g/cm3 p(alumina silicate 8 pcf, example)=96% (Equation 8)
A readily available alumina silica fiber that is 2″ thick, 8 pcf, thermal fiber blanket that has rated insulation values respectively at 0° C. (extrapolated), 200° C., 400° C., 600° C. and 800° C. of k and (R) of 0.028 (10), 0.05 (5.7), 0.08 (3.6), 0.19 (2.2) NS 0.20 (1.4), for average thermal coefficients over the temperature range from Telectrolysis to Tair of k=0.52 W/(mK) (and R=3.8 ft2 hr F.° Btu−1). A mathematical convenience of the “R” expression of thermal resistance is approximate additivity with insulation layers. Hence, an 8″, rather than 2″, thickness of this insulator will have an R value of approximately 15.2 ft2 hr F.° Btu−1.
In an outer layer of insulation lower temperature compatible (less expensive and with higher R values) porous insulation, for example open faced fiberglass insulation, can be utilized. Such insulation is available from a variety of commercial manufactures. An example used here is 4″ thick unfaced Corning 710 fiber insulation with R=16.7 and a density of 1.5 pcf 0.024 g/cm3 composed of interwoven glass fibers. From the solid fiber glass density of 2.5 g cm−3, the porosity of this insulator is p(4″ C701)=99%. Combined, the insulating capability of 8″ of alumina silicate 8 pcf facing outward from the interior of the kiln and 4″ of C701 unfaced fiberglass insulation extending to the ambient air will be approximately additive, that is they will have an approximated combined R=(15.2+16.7)=31.9 ft2 hr F.° Btu−1.
Some embodiments of the present disclosure relate to an apparatus for selectively capturing CO2 from a carbon-containing input gas mixture and generating a CNM product from the captured CO2. The apparatus comprises a pair of electrodes, a cathode and an anode that define an inter-electrode space, which may also be referred to as an electrolysis space, which can receive and contain an electrolyte media. The apparatus also includes a thermal insulator positioned between the source of input gas mixture and the electrolyte media. The thermal insulator is porous and configured to facilitate selective capture of CO2 from the input gas mixture. The apparatus may further comprise a source of electric current, a source of heat a case to contain the electrodes and the electrolyte media and fluid communication with a source of a carbon-containing input gas mixture.
The plenum D that contains the input gas mixture can be Earth's atmosphere (with a CO2 content of about 420 ppm CO2) or it can be a plenum that houses concentrated anthropogenic CO2-containing gases such as industrial waste-gas streams or reservoirs of sequestered CO2. For example, the plenum D contains—or is the source of—the input gas mixture, which may be any gas that includes CO2 and, optionally, other carbon-containing gases. For example, the source of the input gas mixture may be various industrial plants including but not limited to: cement manufacturing plants; iron refining plants; steel manufacturing plants; plants that make or use one or more of ammonia, ethanol, magnesium, hydrogen, polymers, plastics, glass; waste water treatment plants, food processing plants. The source of the input gas mixture may also be chemical reactors including internal combustion engines and combustion of carbonaceous materials for heating or cooking. Emission gases from a power generating plant, steam generation facility, or pyrolysis reactors may also be a source of the input gas mixture. A CO2-containing gas emitted from these sources or in the production of any high carbon-footprint substance may also contribute to or constitute the input gas mixture. In addition, a CO2-containg gas product of the combustion or transformation of fossil fuels for heating, transportation, and carbon products such as polymers and plastics can also contribute to or constitute the input gas mixture. The temperature of the input gas mixture can range between about −90° C. and about 400° C. For example, if the source of the input gas mixture is the atmosphere, then the range of temperatures may range between about −90° C. and about 75° C. If the source of the input gas is anthropogenic, then the range of temperatures may range between about 50° C. and about 400° C. The case 12 is configured to be in fluid communication with the plenum D in order to receive the input gas mixture within the inter-electrode space B.
In some embodiments of the present disclosure, the anode 16 is formed as a planar structure, a wire structure, a screen, a porous structure, a conductive plate, a flat or folded shim, a coiled structure or the anode can form at least part of an inner side wall of the case 12. The anode 16 can be formed of various conductive materials so that the anode 16 may be oxygen generating or not. Such anode-forming materials include, but are not limited to: any conductive material that has a stable layer, or establishes, a highly stable oxide outer layer that is conducive to oxygen production during the electrolysis reactions performed according to the embodiments of the present disclosure, Ni, Ni alloys, galvanized (zinc coated) steel, titanium, graphite, iron, and a wide variety of metal which establish a highly stable oxide outer layer that is conducive to oxygen production. Further examples of suitable materials for forming the anode 16 include Nickel Alloy 36 (nickel without chromium, but with iron), Nichrome (nickel chromium based alloys) including stainless steels such as SS 304 or SS 316, and inconel alloys, such as Inconel 600, 625, and 718, alloy C-264, or Nichromes such as Chromel A, B or, as the co-nucleation of the alloy components are known to produce high quality CNTs. Binary and ternary transition metal nucleation agents may also be useful that include, but are not limited to: Ni, Cr, Sn, In, Fe, and Mo can also affect CNM product growth.
In some embodiments of the present disclosure, a transition metal may be added on the anode 16, which can be dissolved from the anode 16 to migrate through the electrolyte media 21 onto the cathode 18. The added transition metal can function as a nucleating agent, which may be selected from nickel, iron, cobalt, copper, titanium, chromium, manganese, zirconium, molybdenum, silver, cadmium, tin, ruthenium, zinc, antimony, vanadium tungsten, indium, gallium, or non-transition metals such as germanium or silicon, or a mixture thereof. The transition metal may also be introduced as a dissolved transition metal salt within the electrolyte media 21 directly to migrate onto the cathode 18. It is also possible to add the transition metal nucleating agent directly onto the cathode 18.
In some embodiments of the present disclosure, the cathode 18 is formed as a planar structure, a wire structure a screen, a porous structure, a conductive plate, a flat or folded shim, a sheet, a coiled structure or the cathode can form at least part of an inner side wall of the case 12. The cathode 18 can be formed of various conductive materials that reflect the need for variation of the nucleation point and the CNM product that forms on the cathode 18. Such cathode-forming materials include, but are not limited to: any conductive material, galvanized (zinc coated) steel, titanium, graphite, iron, an alloy that comprises copper and zinc, Monel (Ni 400, a Ni/Cu alloy), Inconel, stainless steel, iron, Nichrome, pure Cu, and brass alloys may also be suitable as materials for making the cathode 18.
The anode 16 and the cathode 18 may be aligned substantially parallel to each other within the case 12, such as a stainless steel case or a case made of substantially pure or pure alumina. The case 12 may be made of any material that is suitable to contain the molten electrolyte media 21 and to sustain the temperatures achieved by the apparatus 10A. The electrodes may be oriented in any orientation, including but not limited to substantially horizontally or substantially vertically, but spaced apart from each other so as to define the electrolysis space B therebetween. In some embodiments of the present disclosure, the electrolysis space B is between about 0.1 cm and about 10 cm. In some embodiments of the present disclosure, the electrolysis space B is about 1 cm. As will be appreciated by those skilled in the art, the dimensions of the electrolysis space B will be dictated by the scale of the apparatus 10A, such as the size of each electrode, the plenum defined within the case, the amount of electric current applied and combinations thereof.
The anode 16 and the cathode 18 are operatively connected to a source of electric current (not shown), which can be any source of an alternating current or a direct current, either constant or not, that provides a current density of between about 0.001 A/cm2 and 10 A/cm2. In some embodiments of the present disclosure, the current density provided between the electrodes is at least 0.02 A/cm2, 0.05 A/cm2, 0.1 A/cm2, 0.2 A/cm2, 0.3 A/cm2, 0.4 A/cm2, 0.5 A/cm2, 0.6 A/cm2, 0.7 A/cm2, 0.8 A/cm2, 0.9 A/cm2, 1.0 A/cm2 or greater. The power for the source of electric current may be any power source or combination of power sources, including electrical power sources, solar power sources and the like.
The source of heat (not shown) can be any source of heat that increases the temperature within the case 12 to a temperature that causes the electrolyte media 21 to transition to a molten phase. For example, the source of heat can achieve a temperature within the case 12 of between about 500° C. and about 850° C. or higher. In some embodiments of the present disclosure, the heating achieves a temperature between about 700° C. and about 800° C., between about 720° C. and about 790° C., or between about 750° C. and about 780° C. In some embodiments of the present disclosure, the heating achieves a temperature of 749-750° C., 751-752° C., 753-754° C., 755-756° C., 757-758° C., 759-760° C., 761-762° C., 763-764° C., 765-766° C., 767-768° C., 769-770° C., 771-772° C., 773-774° C., 775-776° C., 777-778° C., or 779-780° C. In some embodiments of the present disclosure, the temperature within the case 12 can be increased to about 800° C. or hotter. In some embodiments of the present disclosure, the source of heat is provided by, or is supplemented by, the exothermic reaction of CO2 absorption and conversion to carbonate (mass transfer from the gas phase to the solid phase CNM product), or an over potential of applied electrolysis current.
In some embodiments of the present disclosure, the electrolyte media may comprise a carbonate that can be heated by the heat source until it transitions to a molten phase. For example, the carbonate may be a lithium carbonate or lithiated carbonate. Molten carbonates, such as a lithium carbonate (Li2CO3), which has a melting point of 723° C., or lower melting point carbonates such as LiBaCaCO3, having a melting point of 620° C., when containing oxide includes spontaneous oxide formation that occurs upon melting, or that is a result of electrolysis or when mixed with highly soluble oxides, such as Li2O, Na2O and BaO, sustain rapid absorption of CO2 from the space above the molten electrolyte media. Suitable carbonates may include alkali carbonates and alkali earth carbonates. Alkali carbonates may include lithium, sodium, potassium, rubidium, cesium, or francium carbonates, or mixtures thereof. Alkali earth carbonates may include beryllium, magnesium, calcium, strontium, barium, or radium carbonates, or mixtures thereof. In some embodiments of the present disclosure, the electrolyte can be a mixed composition for example, a mix of alkali carbonates and alkali earth carbonates and one or more of an oxide, a borate, a sulfate, a nitrate, a chloride, a chlorate or a phosphate.
The embodiments of the present disclosure relate to providing the thermal insulator 22 between the plenum D that contains the input gas mixture and inside the case 12 that houses the molten electrolyte media 21. The thermal insulator 22 is configured to facilitate the net selective passage of CO2 therethrough from a first side 22C to and out a second side 22D. Other gases are inhibited from having a net selective passage through the thermal insulator as there is sink, no affinity for their consumption, in the higher temperature media. In some embodiments of the present disclosure, the thermal insulator 22 is made from a material that facilitates the flow of CO2 therethrough and that contributes towards maintaining the temperature within the insulated housing 20. In some embodiments of the present disclosure, the thermal insulator 22 material has: (i) an open pore structure; (ii) a high insulation factor; and (iii) it can withstand the high temperatures achieved within the case 22 and the insulated housing 20, as applicable. Non-limiting examples of suitable materials for the thermal insulator 22 include those capable of withstanding the high temperature (>1150° C.) such as: alumina silicate and alumina calcium silicate blankets. Examples of readily available materials for use as the thermal insulator 22 include, but are not limited to: fibrous or granular forms of permeable batts, mats or blankets; flexible or rigid boards or panels; and, permeable rigid blocks or bricks that permit passage of gas therethrough. Some insulator products used in construction may also be suitable for use as the thermal insulator 22 include, but are not limited to: low and mid-temperature insulation (used in outer walls) such as fiberglass, cellulose, cotton or woven fabrics; mid—temperature insulation (used in outer or middle walls) such as mineral wool; and, high-temperature insulation (used in outer, mid or inner walls) cements and ceramics such as aluminates (including carbonates), silicates (including calcium alumina silicates), derivatives thereof and combinations thereof. Examples of various readily available and suitable high-temperature ceramic products include, but are not limited to; “ceramic fiber insulation for furnaces”; “alumina silica ceramic fiber”; “Durablanket®”; “Cerablanket®” or “Superwool®”. Suitable insulator products may have similar compositions (for example about 46% Al2O3 and about 54% Si2O), thicknesses (0.5″, 1″ or 2″ thick), and a range of densities (4 lbs/ft3=pcf, 6 pcf or 8 pcf).
Even the densest of alumina silica fiber material can be lightweight with a high porosity. As an example, the porosity of the 8 pcf density (=0.128 g/cm3) Cerablanket® may be estimated using the solid (pore free) average dsolid=3.2 g/cm3density from 46% of the 4.0 g/cm3 density alumina and 54% of the 2.6 g/cm3 density Si2O. The porosity is estimated from the open space as (with dair=0.001225 g/cm3)): p=100%×(dsolid−dcerablanket)/(dsolid−dair) with dair=0.001225 g/cm3, (alumina silicate 8 pcf, example)=96% (open air pores). A readily available alumina silica fiber that is 2″ thick, 8 pcf, thermal fiber blanket that has rated insulation values respectively at 0° C. (extrapolated), 200° C., 400° C., 600° C. and 800° C. of k and (R) of 0.028 (10), 0.05 (5.7), 0.08 (3.6), 0.19 (2.2) NS 0.20 (1.4), for average thermal coefficients over the temperature range from Telectrolysis to Tair of k=0.52 W/(mK) (and R=3.8 ft2 hr F.° Btu−1). A mathematical convenience of the “R” expression of thermal resistance is approximate additivity with insulation layers. Hence, an 8″, rather than 2″, thickness of this insulator will have an R value of approximately 15.2 ft2 hr F.° Btu−1. The porosity and spacing between the insulating fibers are evident in the Scanning Electron Microscopy of a first material, Durablanket®, and a second material, Superwool®, each shown respectively in
In some embodiments of the present disclosure, the surface area of the thermal insulator 22 is between 1 and 100 times greater than the surface area of the upper surface 21A of the molten electrolyte media 21. In some embodiments of the present disclosure, the surface area of the thermal insulator 22 is between 2 and 20 times greater than the surface area of the upper surface 21A of the molten electrolyte media 21. In some embodiments of the present disclosure, in order to maximize net inward CO2 diffusion and minimize outward heat flow, the surface area of the thermal insulator 22 is larger on the outside (the first surface 22C), facing the input gas mixture, than on the inside (the second surface 22D) exposed to the higher temperature media.
In some embodiments of the present disclosure, the density and/or thickness of the thermal insulator may be subjected to a modification process to use with the embodiments of the present disclosure. For example, the thermal insulator may be compressed, or modified by other simple mechanical, chemical or structural means to in order to alter, increase or decrease the net passage of the carbon-containing gas through the thermal insulator, as compared to the unmodified thermal insulator.
The frame 22B shown in
The apparatus 10A may also be configured to establish a gas pressure differential between the electrolysis space B, above the upper surface 21A, and the plenum D. The gas pressure within the cell 12 may be lower than within the plenum D so that the established gas pressure differential may enhance the flow rate of carbon-containing gas through the thermal insulator 22 and into the cell 12. The pressure differential may be caused by various mechanisms, such as a diaphragm pump that decreases the relative gas pressure within the cell 12 as compared to the plenum D. Alternatively, or additionally, a blower or fan may also be used to increase the gas pressure within the plenum D.
In some embodiments of the present disclosure, the apparatus 10B and 10C are configured to establish a gas pressure differential between the plenum D and the plenum C, so as to enhance the movement of carbon-containing gases through the thermal insulator 22 into the plenum C. For example, the gas within the plenum D may be pressurized to a level greater than the gas pressure within the plenum C. A diaphragm pump, blower or fan can be used to facilitate establishing this gas pressure differential between the plenum D and the plenum C.
In some embodiments of the present disclosure, the cell 12 may be configured to cause mixing of the gas present between the inner surface 22C of the thermal insulator 22 and the upper surface 21A of the molten electrolyte media 21. For example, the cell 12 may include one or more mechanisms for mechanical mixing, agitation, stirring, convection, bubbling or a combination thereof to facilitate mixing of the gas above the upper surface 21A and the electrolyte media 21.
In some embodiments of the present disclosure, the apparatus 10A, 10B and 10C may further comprise a mechanism for concentrating the input gas mixture. For example, the apparatus 10A, 10B and 10C may further comprise a vortex tube, a heat pump or a heat engine in order to increase the concentration of carbon-containing gases within the input gas mixture.
Some embodiments of the present disclosure relate to one or more systems that are configured to selectively capture carbon-containing gases from an input gas mixture and then to generate a CNM product from the captured gas.
Some embodiments of the present disclosure relate to one or more methods for selectively capturing carbon-containing gases from an input gas mixture and generating a CNM product from the captured gas. In some embodiments of the present disclosure, the methods described herein may be operated using the apparatus and systems described herein, however, the various embodiments of the method are not limited to such apparatus and systems.
According to some embodiments of the present disclosure, the method 300 may further include a step of establishing a gas-pressure differential across the thermal insulator so that the gas pressure of the input gas mixture is higher than the captured gas within the second plenum. The gas pressure differential may be established by use of a diaphragm pump, a blower or a fan. Additionally or alternatively, the input gas mixture may be pressurized so as to establish the gas pressure differential. In some embodiments of the present disclosure, the off-gas generated in the second plenum may be hotter than the temperature of the input gas mixture. In some embodiments of the method, the off-gas product is O2. In some embodiments of the present disclosure, the off-gas product compensates or enhances an input rate of the input gas mixture and/or the selective capture and movement of CO2 into the second plenum. Some embodiments of the method 300 include a step of transferring thermal energy from the off-gas product to the input gas mixture. In some embodiments of the method 300, the porosity of the porous thermal insulator is adjustable so as to change the rate at which CO2 is selectively captured by moving through the thermal insulator and the rate at which heat may transfer through the thermal insulator.
In some embodiments of the method 300, the inner surface of the porous thermal insulator may directly contact the electrolyte media. In other embodiments of the method 300, the method 300 further comprises positioning the inner surface of the porous thermal insulator a predetermined distance from an upper surface of the electrolyte media.
Some embodiments of the present disclosure include a method step of positioning a non-porous outer wall media about the porous thermal insulator for defining an inter-insulation plenum with a first end, a second end and wherein the inter-insulation plenum is configured to receive the input gas mixture at a first end. Optionally, the non-porous outer wall media is also a thermal insulator.
In some embodiments of the present disclosure, the method 300 further comprises a step of using heat generated in the second plenum to heat or power external devices, such as a heat pump or a heat engine is used to heat the input gas mixture, the electrolyte media or a combination thereof. Additionally or alternatively, joule heat, industrial waste heat, solar heat, geothermal heat, exhaust heat or a combination thereof, may be used to heat the input gas mixture, the electrolyte media or a combination thereof.
In some embodiments of the present disclosure, the method 300 further comprises a step of mixing the gas content of the second plenum with the electrolyte media via mechanical mixing, agitation, stirring, convection, bubbling or a combination thereof.
In some embodiments of the present disclosure, the method 300 further comprises the steps of: heating an electrolyte to obtain the molten electrolyte media; disposing the molten electrolyte media between an anode and a cathode in an electrolysis cell within the second plenum; selectively heating the CO2 within the input gas mixture with at least the molten electrolyte media; applying an electrical current to the cathode and the anode in the cell for electrolytically splitting the selectively heated CO2; and, collecting the carbon nanomaterial product from the cathode of the cell.
In some embodiments of the present disclosure, the method 300 further comprises a step of generating an O2 product within the molten electrolyte media. Where the O2 product may enhance convective currents within the molten electrolyte media for mixing the molten electrolyte media.
In some embodiments of the present disclosure, the CNM product of the method 300 comprises carbon nanotubes, carbon nano-onions, nanoflowers, nanotrees, nanobelt, platelets, nano-scaffolds, helices, graphene, doped carbon nanomaterials, magnetic carbon nanomaterials, amorphous carbon or a combination thereof. In some embodiments of the present disclosure, the method 300 further comprises a step of selecting a relative amount of the constituent carbon nanostructures within the CNM product by changing the electrolyte media temperature, CO2 rate, current, voltage, cathode composition, anode composition or electrolyte media composition.
As used herein, the term “selecting a relative amount of the constituent carbon nanostructures within the CNM product” refers to any step that contributes to controlling the morphology of the electrosynthesis CNM product. In some embodiments of the present disclosure, the selected morphology of the CNM may include the following CNM morphologies: carbon nano-onions, carbon nano-scaffolds, carbon nano-spheres, carbon-nano-helices, carbon nano-platelets, graphene or combinations thereof. In some embodiments of the present disclosure, the step of selecting a nanomaterial morphology can result in an electrosynthesis CNM product that is partially, mostly, substantially all or all of a single CNM morphology. For example, the step of selecting a nanomaterial morphology can produce an electrosynthesis CNM product that is partially, mostly, substantially all or all of one of: carbon nano-onions, carbon nano-scaffolds, carbon nano-spheres, carbon-nano-helices, carbon nano-platelets or graphene.
In some embodiments of the present disclosure, the step of selecting a nanomaterial morphology comprises applying the electrical current to the cathode and anode as an alternating current (AC). For example, an AC electrolysis current may select for a CNM product with a nano-onion morphology.
In another embodiment, the step of selecting the nanomaterial morphology comprises adding ZnO to the molten carbonate electrolyte and applying an AC electrolysis current, which may select for a CNM product with a graphene platelet morphology.
In another embodiment, the step of selecting the nanomaterial morphology comprises adding MgO to the molten carbonate electrolyte and selecting an electrical current for a hollow carbon nano-sphere product.
Transition metal nucleated growth, such as the addition of nickel powder, can lead to clearly observable CNT walls. However, when these nucleation additives are purposely excluded during the synthesis, then the high yield synthesis of carbon nano-onions and graphene is accomplished. These differences in the parameters of the electrosynthesis process are but a few examples of how the electrosynthesis CNM product can be selected for.
In some embodiments of the present disclosure, the method 300 further comprises a step of suppling electrical current to the cell by a non-fossil energy source, including, but not limited to solar, wind, hydroelectric, geothermal, tidal, wave, nuclear power or combinations thereof.
In some embodiments of the present disclosure, the method 300 further comprises one or more steps of activating the molten electrolyte media, by pre-heating the electrolyte media, adding an oxide to the electrolyte media, re-using the electrolyte media for multiple electrolysis processes and time equilibrating the molten electrolyte media.
The examples and experiments described below relate to direct capture of CO2 from an input gas mixture, by a selective net passage of CO2 through a porous thermal insulator and the generation of a CNM product from the captured CO2. Without being bound by any particular theory, the selective net passage of CO2 is due, at least in part, to an affinity of a media for carbon that may be higher than an affinity of the media for the other constituent gases of the input gas mixture. These examples are offered to illustrate the embodiments of the present disclosure and are not to be construed in any way as limiting the scope of the present disclosure.
As shown in the upper panel
In the middle panel of
Without being bound by any particular theory a thicker, porous insulation layer may slow down the rate of CO2 concentration increases. Interestingly, the opposite was observed to occur. In the same test chamber, the 2″ layer of thermal insulator was replaced by 8″ (4 stacked 2″ layers) of thermal insulator separating the top and lower chambers (not shown). The CO2 from air in the upper compartment reached the 395 ppm level in about 20 minutes or 2.5 minutes respectively at the 0.624 or 6.2 L air/minute flow rates. Without being bound by any particular theory, the observed increase in CO2 concentration in the lower chamber 1006 over a shorter amount of time when the thicker insulator was used may be related to the substantially diminished height of the lower chamber 1006, which decreased the volume of the lower chamber 100B allowing for a more rapid replacement of the original N2.
The lower panel of
Without being bound by any particular theory, all of the experimental set ups shown in
For each of the subsequently described electrolysis processes, the theoretical change in mass before and after the electrolysis, is calculated using:
This experimental demonstration consists of two electrolysis configurations. As shown in
Specifically, the experiment without CO2 was conducted the configuration 400 was performed (as shown in
The combined mass of the cell, the electrolyte and the electrodes was measured before and after passage of 8.4 Amps×20 hours=168 Ah of electrolysis charge. 168 Ah is capable of reducing 1.567 moles of carbonate as calculated with mass=Q/nF in accordance with Equation 2 using n=4 and F=9.6485×104 As. In the sealed cell of configuration 400, without replacement of the CO2 the sealed cell should lose about 50 g of mass in accordance with Equation 2 due to the loss of O2 as 1.567 mol×32 g O2 mol−1. Subsequent to the electrolysis in the sealed cell, the measured cell mass loss was about 48 g amounting to 96% of the theoretical 50 g loss.
Without being bound to any theory, as oxide builds up in accord with Equation 3, it may be difficult to evolve the last remaining small portion of the O2, for example competitive equilibria may develop combining with O2+oxide or carbonate to develop species that inhibits the continue release of O2.
In a second configuration 400A (shown in
Using the unsealed configuration 400A with the porous insulator 412, consistent with Equation 2, which is the summation of Equations 1 and 2, the measured mass of the electrolysis cell 402, the electrodes 406 and carbonate electrolyte media 404 increased as CO2 was absorbed and reacted to renew the electrolyte media 404. From the input CO2, only O2 leaves the system. The electrolytically split CO2 remains as a solid CNM product on the cathode, and evolves as oxygen from the anode. During this electrolysis process the outside of the porous thermal insulation is observed to remain cool, that is near ambient air temperature, and the 48 g cell mass loss subsequent to the electrolysis process performed using the configuration 400 was prevented.
Further experiments were performed to investigate capturing CO2 from air and generating a CNM product by splitting of CO2 by electrolysis with a the operational parameters as follows:
These experiments consisted of measuring the mass of the cell before and after electrolysis. The mass of the cell included the mass of the cell, the electrolyte, and the electrode.
The ambient air temperature varied from 21° C. to 23° C. Masses were measured with a Radwag R Series Precision balance with 0.01 g resolution. The mass of the cell was elevated from the balance platform by thermal insulation, but the balance was heat sensitive accounting for several percent error in experimental mass change.
The theoretical mass gain due to the CNM product is: nF×FW(C) in accord with Equation 2 and 3. This is the same as theoretical cell mass gain for the full cell, including electrodes and electrolyte, only under the condition of the presence of sufficient CO2 to renew all consumed carbonate in accord with Equation 1. The theoretical mass loss due to O2 in accord with Equation 2 is: nF×FW(O2). This is the same as the theoretical cell mass loss only under the condition of the absence of any CO2 to renew the consumed carbonate in accord with Equation 1.
Electrolysis experiments gauging the relative reaction due to ingress and splitting of CO2 (reaction of Equation 3, from the net of Equation 1 and Equation 2), rather than just carbonate decomposition (Equation 2), may be analyzed compared to all CO2 absorbed (Equation 3), or as all CO2 blocked. The latter resulting in O2 evolution mass loss (Equation 2). This is measured as, dmcell, the change in cell mass before and after the electrolysis.
The extent of the dominance of CO2 splitting compared to carbonate decomposition is expressed here in two different manners. The first, expressed in Equation 9a and Equation 9b, is dmcell relative to the measured electrolysis charge converted to either carbon (CO2 absorption) or to the negative mass expected from oxygen evolution (carbonate decomposition). The second in Equation 10 measures the percent of CO2 absorbed compared to the CO2 required by the electrolysis. This is given by dmcell coupled with the maximum O2 loss possible, compared relative to the electrolysis charge converted to carbon plus oxygen (CO2). Equations 4a, 4b and 5 are shown below:
dC=100×dmcell/(nF×FW(C) (Equation 9a)
dO2=−100×dmcell/(nF×FW(O2) (Equation 9b)
dCO2=100×(dmcell+(nF×FW(O2))/(nF×FW(CO2) (Equation 10)
For the open configuration of apparatus 10A, the expected results were net electrolysis, without sufficient CO2 input, loss of cell mass in accordance with insufficient CO2, see Equation 11:
Li2CO3→CNMproduct(y)+Li2O(y)+O2↑;
y=stays in cell; ↑=gas leaves cell (Equation 11)
For the configuration of apparatus 10A, with a minimal portal for CO2 to enter the cell; that is only through a small section of porous insulator whose primary function is to allow the electrolysis off-gas product of O2 to leave the cell; the observed results were a pre-electrolysis cell mass of 2262.50 g and a post-electrolysis cell mass: 2257.50 g. The post-electrolysis mass loss was about 5 g lower than the pre-electrolysis cell mass.
The theoretical mass lost as O2 with minimal CO2 input:
32.00 g mol−1 O2×2A×9h/4F=5.37 g lost (as O2 evolved)
The change in oxygen, dO2, was about 93% (indicating oxygen generation).
The theoretical mass as CO2 is:
44.01 g mol−1 CO2×2A×9h/4F=7.38 g
The change in CO2, dCO472, was about 5% (indicating only a small47 absorption of the CO2). Without being bound by any particular theory, the CNM product remained on the cathode with n(e−)=4, but the anode produced O2 that evolved from cell 12.
Li2CO3→CCNT(y)+Li2O(y)+O2↑(gas out); y=stays in cell (Equation 12)
CO2(air)+Li2O(y)→Li2CO3 (Equation 13)
net: CO2(air)→CCNT(y)+O2↑ (Equation 14)
For the open configuration of apparatus 10B, with the frame 22A, the observed results were a pre-electrolysis cell mass of 2137.67 g and a post-electrolysis cell mass: 2138.81 g. As opposed to the measured mass loss incurred in Example 3A, this example resulted in a measured mass gain, and the post-electrolysis mass was about 1.14 g higher than the pre-electrolysis cell mass. The theoretical mass gain as C is:
12.01 g mol−1 C×2A×9h/4F=2.01 g gained (as CNM product)
Compared to the theoretical, the change in carbon, DC, was about 57%.
Furthermore, as compared to theoretical mass of CO2 calculated in Example 3A, the change in CO2, dCO2, was about 88%. Without being bound by any particular theory, the Li2CO3 within the electrolyte media 21 is renewed with carbon from CO2 that remains in cell 12. The CNM product remains on the cathode 18 with n(e−)=4, to account for the increase in cell mass.
For the open configuration of apparatus 10C the observed results were a pre-electrolysis cell mass of 2241.13 g and a post-electrolysis cell mass: 2243.16 g. The post-electrolysis mass was about 2.03 g higher than the pre-electrolysis cell mass. The change in change in carbon, dC, was about 101% and the change in CO2, dCO2, was about 100%. Without being bound by any theory, the rate of CO2 diffusion through the thermal insulator increases approximately linearly with decrease in insulator thickness, and insulator increases approximately linearly with decrease in insulator density. Therefore, use of a comparable, but 4 pcf, rather than 8 pcf insulator, with a thickness of 0.5″, rather than 2″, can increase sustainable current at a high dCO2 to approximately 16 Amps, rather than 2 Amps.
Without being bound by any particular theory, the increased cell mass may have been caused because the Li2CO3 within the electrolyte media 21 was at least partially renewed by the CO2 drawn into the cell 12 and the carbon from that CO2 remains in the cell 12 for generating the CNM product. The increased cell mass is due to increased CNM product derived from the CO2 within the plenum D, then plenum C and ultimately within the electrolysis space B.
The electrolyte media may require activation to initiate consumption of the CO2 captured from the input gas mixture. At 750° C., reaching equilibrium, pure Li2CO3 equilibrates with about 0.3 molal Li2O concentration in the Li2CO3, and there was no measured mass change for pure Li2CO3 mixed with 0.33 molal Li2O over a period of 4 hours. Hence, without being bound to any theory, the equilibrium is maintained in accordance with Equation 15:
Li2CO3CO2+Li2O (Equation 15)
This consumption may be driven by CO2 moving from the gas phase into the molten lithium carbonate electrolyte media, for example by Equation 1 and electrolytic consumption. Without being bound to any theory, if CO2 is not consumed then in accordance with Equation 2, the electrolyte media is consumed and is not renewed by CO2. The electrolyte media may electrolytically decompose and lose weight as oxygen is evolved in accordance with Equation 2 (rather than in accordance with the net of Equation 1 and Equation 2).
In an example without electrolyte activation, molten Li2CO3 contained in a high purity alumina (Al2O3) crucible acted inert to CO2 absorption during electrolysis in the molten electrolyte. Specifically fresh, melted Li2CO3 exhibited the need to be activated to initiate continuous electrolytic consumption of incident gas phase of CO2 in the air into the molten electrolyte. In an example, molten lithium carbonate open to hot air in a high purity alumina (Al2O3) crucible is inert to CO2 absorption during electrolysis with or without inclusion of a metal (12.5% cast iron) in the molten electrolyte. Specifically, fresh electrolyte, subsequent to a 4 hour electrolysis at 750° at 0.2 A/cm2 between a NiCr C anode and a Muntz brass cathode, displayed a good carbon deposition on the cathode as expected from equation 2, but the total mass of the cell measured before and after the electrolysis decreased, rather than grew as would be expected with sufficient CO2 absorption. The change in CO2 was in accordance with no oxygen absorption or CO2 per carbonate electrolyte renewal shown in Equation 1.
In a repeat 4-hour electrolysis in the cell, while reusing the same electrolyte (which can be considered to in the first stages of equilibration activation) CO2 was marginally absorbed (as measured by dCO2 which rose 3%). This 3% is indicated the start of CO2 continuous activation of the electrolyte, which is incomplete, to renew carbonate during the electrolysis. However, the pure Li2CO3 electrolyte was substantially activated when the electrolyte was heated at 750° C. for 24 hours (equilibration time) prior to electrode immersion and electrolysis. This activation step increased the change in CO2 to about 81%. Similarly, mixing the Li2CO3 with sufficient Li2O (5 wt %) in a stainless steel 304, rather than alumina, crucible without waiting for any equilibration subsequent to electrolysis time increased the change in CO2 to about 99%, indicating nearly complete CO2 absorption, in the fresh molten electrolyte. As with the electrolysis in pure Li2CO3 without any time equilibration activation, fresh Li2CO3 mixed with 10 wt % Na2CO3, or mixed with 3 and 1.3 wt % CaO, displayed no mass-based evidence of CO2 absorption during 4-hour electrolysis. The electrolyte can be modified by metal salt, metal, or other additives to affect both the rate of CO2 absorption and the CNM product
Two other examples of electrolyte activated absorption of CO2 are noted here. Reuse of electrolyte, which may provide greater time for electrolyte equilibration presumably leading to an observed increase in CO2 absorption, and specifically subsequent to electrolysis in 750° C. Li2CO3 with 1 wt % Li2O, the change in CO2 increased from 38% to 91% upon reuse of the electrolyte. Secondly, the upper surface of electrolyte relative to the top of the cell and proximity to the inward flow of CO2 directly relates to the observed measured change in CO2. When the gas phase interacted with electrolysis electrodes immersed in low levels of electrolyte (below the cell top), very low values of changes in CO2 are observed implying a “dead zone” that is depleted in CO2 immediately above the upper surface of the molten electrolyte media. Without being bound to any theory, this dead zone may be related to the flow of gas leaving (rising from the surface) during electrolysis without access to gas phase CO2 during the electrolysis. In one case, this depletion was observed to be so substantial that electrolyte decomposition beyond that attributed to Equation 2, electrolysis evidently occurred and the CO2 concentration was so low above the surface of the electrolyte media that, without being bound to any theory, the carbonate could further decompose in accord with Equation 11. This further carbonate decomposition, may lead to further mass loss and CO2 escape, rather than CO2 use by the electrolyte to generate the CNM product. In this case of electrolysis with low lying electrolyte in the crucible, the change in CO2 was measured at −39%.
Directing or enhancing the input gas flow (for example by directing wind, adding an additional fan, blower, wind lens, wind focus or driving a convection current) over the porous thermal insulator separated from the electrolyte media may also influence the consumption of carbon-containing input gas, such as airborne CO2, by the electrolysis process. Hence, as a related example the configuration used as in
Note in another example, the combined presence of (i) blowing air, (ii) a metal crucible and (iii) a low level of added Li2O (3⅓wt %) but using the electrolyte fresh, rather than time equilibrated, still resulted in a relatively low absorption of CO2 of about 8%.
The electrolysis current density, Jelectrolysis, also may affect the magnitude of change in CO2. A higher J requires a greater rate of CO2 influx. Hence under the previous conditions, with an incident air speed of 2.5 m/s the CO2 absorption was about 100% when the Jelectrolysis was 0.042 A/cm2, yet a CO2 absorption of 55% was measured when the Jelectrolysis was 0.15 A/cm2 with the same air speed.
The net passage of CO2 through the thermal insulator 22 and the absorption rate of CO2 into the media 21 may be increased by increasing the surface area of the first side 22C of the thermal insulator 22, for example by contouring the first side 22C. Maintaining a substantially flat second side 22D of the thermal insulator 22 may have the additional benefit of minimizing heat flow outward from plenum C. Increasing the surface area of the first side 22C may be accomplished by a wide variety of known contouring techniques, such as but not limited to: macroscopic (geometric), microscopic (surface roughening) and nanoscopic techniques/methods, such as bonding of molecular assemblies to the first side 22C. For example, the active surface area of the first side 22C of the thermal insulator 22 may be increased by adding a layer of “loose fill”, blown in fiberglass, borate coated cellulose or ceramic insulation. This layer may be distributed loosely on the first side 22C, and then confined by a flat or shape molded screen to maximize the surface area of the first side 22C.
Another example of contouring the first side 22C is macroscopic “dimple” surface enhancement. As shown in
The surface area of the two dimensional first side 22C may also be enhanced by macroscopic, microscopic, or nanoscopic methods. Non-limiting examples of methods for microscopic surface area enhancement include roughening the first side 22C by mechanical, physical, optical, electrical, electrochemical or thermal methods. The microscopic and nanoscopic increase of surface area can also be accomplished by a chemical treatment of the first side 22C, such as chemical deposition on, or chemical reaction, or chemical or electrochemical etching of, the first side 22C.
Without being bound by any particular theory, increasing the surface area of the first side 22C by macroscopic methods, microscopic methods or any combination thereof may increase the net, selective passage of CO2 from the first side 22C to the second side 22D and into the media 21 by providing a chemical affinity, a physical affinity or both for CO2 to enter into the thermal insulator 22. In turn, an increased net passage of CO2 through the thermal insulator 22 may increase the amount and/or rate at which the CO2 is absorbed into the media 21.
Additionally or alternatively, the first side 22C of the thermal insulator 22 may define one or more ridges 22E that extend towards the inner surface 24B and away from the second side 22D. The first side 22C may also define one or more valleys 22F that extend away from the inner surface 24B and towards the second side 22D.
The presence of ridges and/or valleys, as defined by the inner surface 24B of the housing 24, the first side 22C of the thermal insulator 22 or both, within the flow channel 26C may enhance the net, selective passage of CO2 through the thermal insulator 22 and into the media 21 by increasing the distance that the input gas mixture flows along the first side 22C. The flow channel 26C may be circuitous causing the flow of the input gas mixture within the flow channel 26C to change direction once or more times as it moves from the input aperture 26A (where the input gas mixture may have substantially the same constituent gases as the input gas mixture at the source) passing over the first side 22C of the thermal insulation 22 to exit by the output aperture 26B (where the gas in the flow channel 26C will be depleted of carbon-containing gas, such as CO2, and optionally supplemented with off-gas generated in the cell 12, such as hot O2. The changes in direction imposed by the circuitous flow channel 26C may induce turbulent flow within the input gas mixture and/or extend the flow path length. Each of turbulent flow and a greater flow path length, as compared to if the first side 22C and the inner surface 24B were substantially flat or smooth, may enhance interaction of the input gas mixture with the first side 22C of the thermal insulator 22 and enhance a net, selective passage of the carbon-containing gas to leave the flow channel 26A and enter into plenum C and ultimately into the media 21. A variety of channels or pathways to maximize this interaction are contemplated herein and the flow channel 26C shown
In some embodiments of the present disclosure, the thermal insulator 22 may be modified in order to preferentially or selectively allow a greater flow of the carbon-containing gas therethrough than the other constituent gases of the input gas mixture. For example, the molecular structure of the permeable thermal insulator may be chemically modified to selectively allow the carbon-containing gases to pass more easily therethrough as compared to when the thermal insulator 22 is not so modified, in comparison to the ease of passage of the other non-carbon containing constituent gases or combinations thereof. For example, the thermal insulator 22 may be modified so that certain non-carbon containing gases may absorb or adsorb on to the thermal insulator and, therefore, these non-carbon containing gases do not enter the plenum C to be absorbed by the media 21. In some embodiments of the present disclosure, the thermal insulator may be modified to incorporate molecular sieves that select which gases that are constituents in the input gas mixture can pass through the thermal insulator more easily than other constituent gases.
Without being bound by any particular theory, the Examples above demonstrate the selective capture of CO2 from an input gas mixture and the use of the carbon therein to generate a CNM product. The experiments were observed from start to end, including measurement of the cell mass before and the cell mass after the electrolysis. The calculations were compared with the experiments. The results were validated. The experiments showed the cell can access robust rates without the need to heat up all the input gas mixture. The porous thermal insulator with the high CO2 affinity higher temperature medium allows net selective passage/diffusion of CO2, which is at least one mechanism by which the selective capture of CO2 from the input gas mixture occurred. Surface adsorption and pore size both influenced CO2 diffusion for CO2/N2 mixtures across the porous thermal insulator. The porous structure of the thermal insulator facilitated interaction of the electrolyte media with the captured CO2 gas. The high affinity of the molten electrolyte for CO2 provided net selective transfer from the gas phase above the upper surface of the electrolyte media into the electrolyte media. The experiments and examples described herein demonstrate that the different configurations may influence the extent to which CO2 is absorbed within the cell. Experiments demonstrated configurations and operating conditions where CO2 is depleted and where there is sufficient CO2 from air for the given operation conditions of the cell.
As supported by the equations presented herein above, CO2 may be rapidly absorbed and spontaneously concentrated from the input gas mixture by an exothermic reaction with the electrolyte media through the reaction with oxides in the molten salts of the electrolyte media. The reaction of CO2 with the electrolyte media may continuously renews the carbonate electrolyte media, as described by Equation 1. The experimental results are in-line with the expected mass gain or loss, in accordance with the equations (as described in Section 2). Mass gain of the cell is observed to occur due to carbon built up—in the form of the CNM product—on the cathode, as described by the overall net equation (Equation 3). Hot O2 generated from the electrolysis could also be used. System features that may enhance the degree of CO2 conversion to cathode-associated CNM product during molten carbonate electrolysis include, but are not limited to: increased air or wind speed, using a lower current density, change of the porosity thermal insulation, adjusting the spacing between the thermal insulator and the upper surface of the electrolyte media, activation of the electrolyte by increased equilibration time, electrolyte re-use, increased oxide concentration, positioning the electrolyte media upper surface closer to the inner surface of the thermal insulator, use of a metal electrolysis cell, or a combination of these features.
This application claims priority to and the benefit of: U.S. Provisional Patent Application Ser. No. 63/179,778 filed on Apr. 26, 2021; U.S. Provisional Patent Application Ser. No. 63/305,544 filed on February 1, 2022; and, U.S. Provisional Patent Application Ser. No. 63/318,944 filed on Mar. 11, 2022, each of which are hereby incorporated by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63179778 | Apr 2021 | US | |
| 63305544 | Feb 2022 | US | |
| 63318944 | Mar 2022 | US |
