Thermochemical gas decomposition reactor system and method for thermochemically decomposing gases

Abstract

A thermochemical gas decomposition reactor system and method for decomposing gases are disclosed. The system includes a reactor including a reaction zone containing an active material, a gas heating zone, and a gas distribution plate assembly interposed between the reaction zone and the gas heating zone. An exemplary system may include multiple reactors. The method may include providing one or more of the reactors and performing one or more of an oxidation process and / or a reduction process using each of the reactors.

Description

[Technical Field]

[0001] [CROSS REFERENCE TO RELATED APPLICATIONS] This application claims priority to U.S. Provisional Application No. 63 / 410,177, entitled "PRESSURE SWING REDOX PROCESSING TO SPLIT HO / CO2," filed September 26, 2022, and U.S. Provisional Application No. 63 / 425,617, entitled "PRESSURE SWING REDOX PROCESSING TO SPLIT HO / CO2," filed November 15, 2022, the contents of which are incorporated herein by reference.

[0002] [STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT] This invention was made with government support under Grant No. DGE1650115 awarded by the National Science Foundation. The government has certain rights in this invention.

[0003] [Field of Disclosure] The present disclosure generally relates to thermochemical gas decomposition reactor systems and methods for decomposing gases such as one or more of H2O and CO2. [Background technology]

[0004] The use of hydrogen as a renewable fuel has been hampered by the inability to produce it cleanly and economically. Traditional solar thermochemical methods consider a two-step redox cycle of standard ceria or perovskite in a temperature swing configuration, where reduction occurs at a significantly higher temperature than oxidation. Isothermal redox cycling, while feasible and avoids the solid-solid heat recovery and material stability challenges associated with large temperature swings, has long been considered inefficient due to the thermodynamic disadvantages of dealing with an exothermic oxidation reaction at high temperatures.

[0005] Furthermore, two-step thermochemical processes for dissociation of HO and / or CO (e.g., via solar heat) have historically performed the oxidation (fuel-producing) step at ambient pressure, resulting in significant work required to compress the products in practice. Accordingly, improved methods and systems suitable for splitting water (and / or carbon dioxide) in a relatively efficient manner are desirable.

[0006] Any discussion in this section, including any discussion of problems and solutions, has been included in this disclosure solely for the purpose of providing a context for the disclosure. Such discussion should not be construed as an admission that any or all of the information was publicly known at the time the invention was made or otherwise constitutes prior art. Summary of the Invention

[0007] This Summary is provided to introduce a selection of concepts and is not intended to necessarily identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

[0008] According to disclosed embodiments, a thermochemical gas decomposition reactor system and method for decomposing gases are provided that can be used, for example, to decompose water vapor (H2O) and / or carbon dioxide (CO2) in a relatively energy-efficient and cost-effective manner.

[0009] According to exemplary embodiments of the disclosure, a thermochemical gas decomposition reactor system includes a reactor including a reaction zone, a gas heating zone, and a gas distribution plate assembly interposed between the reaction zone and the gas heating zone. The thermochemical gas decomposition reactor system also includes a gas inlet fluidly coupled to the gas heating zone, a gas outlet fluidly coupled to the reaction zone, and a controller configured to operate the reaction zone at a temperature greater than about 1000°C and to control the pressure within the reaction zone or chamber to a pressure greater than 1 bar during the gas decomposition step and to a pressure less than or equal to 1 bar during the active material reduction step. According to aspects of these embodiments, the system includes multiple reactors operable in reduction and / or oxidation modes to enable continuous operation and product removal from the system. According to further aspects, the reactors and / or system operate substantially isothermally. The reaction zone can include an active material. According to further aspects, the reactor includes an insulating wall contained within a pressure vessel. The gas distribution plate may be formed from one or more of a ceramic structure including alumina, zirconia, and / or silica. According to a further aspect, the gas distribution plate is configured to facilitate or enable flow substantially along the (e.g., vertical) axis of the reactor. According to a further aspect, the system may include one or more heaters or heat sources for heating or preheating gases entering the reactor.

[0010] According to an additional embodiment of the disclosure, a method for thermochemically decomposing a gas is provided. As noted above, the gas to be decomposed can be or include, for example, steam and / or carbon dioxide. The method includes providing a reactor (e.g., as described above or elsewhere herein), providing gases (e.g., one or more of HO and CO) to the reactor in a gas heating zone, heating the gases (e.g., one or more of HO and CO) in the gas heating zone, providing the heated gases (e.g., one or more of HO and CO) through a gas distribution plate assembly and to a reaction zone, and decomposing the heated gases (e.g., one or more of HO and CO) in the reaction zone, wherein the temperature in the reaction zone is greater than about 1000°C and the pressure in the reaction zone is greater than 1 bar. The method can further include performing an active material reduction step. The pressure in the reaction zone or chamber during the active material reduction step can be controlled to 1 bar or less. The method may include continuously removing product gas from the reaction zone during the decomposing step and / or during the active material reduction step. Exemplary methods may further include heating the gas before it enters the reaction zone and / or before it enters the reactor.

[0011] These and other embodiments will become readily apparent to those skilled in the art from the following detailed description of several embodiments with reference to the figures; the disclosure is not limited to any particular embodiments disclosed. [Brief explanation of the drawings]

[0012] A more complete understanding of the embodiments of the present disclosure may be had by reference to the detailed description and appended claims when considered in conjunction with the following illustrative figures. [Figure 1] 1 illustrates a thermochemical gas decomposition reactor system in accordance with at least one embodiment of the disclosure. [Figure 2] 1 illustrates another thermochemical gas decomposition reactor system in accordance with at least one embodiment of the disclosure. [Figure 3]1 illustrates a multiple reactor system in accordance with at least one embodiment of the disclosure. [Figure 4] 1 illustrates a gas distribution plate assembly in accordance with at least one embodiment of the disclosure. [Figure 5] 10 illustrates a gas distribution plate assembly according to another embodiment of the disclosure. [Figure 6] 1 illustrates thermochemical cycling of two candidate active materials according to disclosed embodiments. [Figure 7] 1 illustrates cumulative CO production according to an embodiment of the disclosure. [Figure 8] 1 illustrates the peak rate of production after accounting for the effects of gas phase dispersion and mixing in accordance with an embodiment of the disclosure. [Figure 9] 1 illustrates the equilibrium oxygen content of undoped ceria CeO2-δ and iron aluminate Fe33Al67(Fe1 / 3Al2 / 3)3-δO4 as a function of oxygen partial pressure at 1400° C., according to disclosed embodiments. [Figure 10] The measured degree of oxidation of Fe33Al67 (i.e., CO2:CO ratio) as a function of input oxidant composition and pressure at 1400 °C is shown, with the corresponding oxygen partial pressure determined by the equilibrium of the thermal decomposition of carbon dioxide and displayed in the upper box.

[0013] It will be understood that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of the illustrated embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0014] Although several embodiments and examples are disclosed below, it is understood that the invention extends beyond the specifically disclosed embodiments and / or uses thereof and obvious modifications and equivalents thereof. Accordingly, it is not intended that the scope of the disclosed invention should be limited by the specific embodiments disclosed below.

[0015] The present disclosure provides improved methods and systems for decomposing gas-phase reactants using reduction and oxidation (redox) reactions. As described in more detail below, in some cases, the methods and systems can be operated under substantially isothermal conditions or within a specified temperature swing to provide desired energy efficiency and / or cost-effectiveness while providing desired production throughput.

[0016] In this disclosure, substantially isothermal may mean that the temperature during the reduction phase and the temperature during the oxidation phase of the reduction and oxidation cycle or process are within ±10°C or ±25°C or ±50°C or ±100°C or ±150°C of each other during operation.

[0017] In this disclosure, gas may include a substance that is a gas at standard temperature and pressure, a vaporized solid, and / or a vaporized liquid, depending on the context, and may consist of a single gas or a mixture of gases. An inert gas may be a gas that does not appreciably participate in chemical reactions. Exemplary inert gases include nitrogen.

[0018] In this disclosure, continuous or consecutive can refer, depending on the context, to an uninterrupted timeline, without any intervening material in the step, without changing process conditions, or immediately thereafter as the next step.

[0019] In this disclosure, the number of any two variables may constitute a range valid for that variable, and any range specified may or may not include the endpoints. Additionally, any numerical value of a specified variable (whether or not marked "about," "approximately") may refer to the exact or approximate numerical value and may include equivalents, and in some embodiments may refer to the average, median, representative, majority, etc. Furthermore, in this disclosure, the words "comprise," "consist," and "have," and variations thereof, may independently refer in some embodiments to "typically or generally include," "comprise," "consist essentially of," or "consist," and variations thereof. According to aspects of the present disclosure, a defined meaning of a term does not necessarily exclude the ordinary and accustomed meaning of that term.

[0020] 1 illustrates a thermochemical gas decomposition reactor system 100 according to an embodiment of the disclosure. The thermochemical gas decomposition reactor system 100 includes a reactor 102 including a reaction zone 104, a gas heating zone 106, and a gas distribution plate assembly 108 interposed between the reaction zone 104 and the gas heating zone 106; a gas inlet 110 fluidly coupled to the gas heating zone 106; a gas outlet 112 fluidly coupled to the reaction zone 104; and a controller 114.

[0021] The reactor 102 may be configured to operate during the reduction phase and / or the oxidation phase at temperatures greater than 800° C., or greater than 1000° C., or at temperatures between about 800° C. and about 1500° C., or between about 900° C. and about 1400° C. In some cases, the reduction phase and the oxidation phase may be within about ±400° C., or within about ±300° C., or within about ±200° C. of each other, or may be operated substantially isothermally.

[0022] As shown, the reaction zone 104 includes an active material 120. The active material 120 includes a material that is reduced during a reduction phase or process and oxidized during an oxidation phase or process. According to disclosed embodiments, the active material 120 includes a metal oxide. For example, the active material 120 may include an iron aluminate-based spinel (e.g., Fe33Al67), a lanthanum manganate-based perovskite (e.g., LSMA6464), and / or a ceria-based oxide (e.g., Ce 0.80 Zr 0.20 O 2-δ In some cases, the active material 120 can be or include (M ζ Al 1-ζ ) 3-δ O4, ζ is greater than 1 / 3, and M is one or more of Fe, Co, Ti, Mn, Mg, Zn, Ni, and Cr. x Fe 1-x+y Al 2-y 04, where x is between 0 and 0.4 or between 0.4 and 1.0 and y is between 0 and 0.4 or between 0.4 and 1.

[0023] The reaction zone 104 may be configured as a fluidized bed reactor or as a packed bed reactor. Thus, the active material 120 may be packed or fluidized during operation of the reactor 102.

[0024] The gas heating zone 106 may include one or more heat sources or elements 122 for heating the gas in the gas heating zone 106, such as the gas received from the gas inlet 110, before the gas enters the reaction zone 104. The heat sources or elements 122 may be or include, for example, concentrated solar radiant heaters, heat exchangers (e.g., one in which the gas in the gas heating zone is heated using a heat exchanger, and optionally, one in which a heat exchanger removes heat from the product gas removed from the reactor via a gas outlet), one or more resistive heaters (e.g., an array of resistive heaters), or others. In some cases, a ceramic protection tube 124 (e.g., formed from one or more of alumina, zirconia, silicon carbide, boron nitride, silicon nitride) may be used to protect the heating elements 122. The array of resistive heaters may include from about 2 to about 10 or from about 10 to about 50 resistive heaters.

[0025] The gas distribution plate assembly 108 can be used to support fluidized and / or packed bed particles, such as material 120. Additionally, the gas distribution plate assembly 108 can be configured to facilitate and promote gas flow in a direction along an axis 126 (e.g., a vertical axis) between the gas heating zone 106 and the reaction zone 104. According to disclosed embodiments, the gas distribution plate assembly 108 includes one or more ceramic structures including a refractory material, such as one or more of alumina, zirconia, and / or silica. As described in more detail below, the gas distribution plate assembly 108 can include a plurality of holes having a cross-sectional diameter between about 2.5 mm and about 0.5 mm and / or between about 200 microns and about 1 micron.

[0026] FIG. 4 illustrates a gas distribution plate assembly 400 suitable for use as the gas distribution plate assembly 108 according to a disclosed embodiment. The gas distribution plate assembly 400 includes a porous ceramic frit and plate 404. The porous ceramic frit 402 can be formed, for example, from zirconia. The porous ceramic frit 402 can include an average pore size of about 2.5 mm to about 0.5 mm, or about 0.5 mm to about 0.1 mm. The porosity of the ceramic frit 402 can be between about 10 PPI (pores per inch) and about 45 PPI, or between about 45 PPI and about 250 PPI. The plate 404 can be formed, for example, from alumina, zirconia, or the like. The plate 404 can include pores with an average diameter or cross-section of about 200 microns to about 1 micron, or about 40 microns to about 1 micron.

[0027] As shown, ceramic frit 402 may be attached to one or more of liners 406, 408 using adhesive 410. Liners 406, 408 may be formed from, for example, alumina, zirconia, etc. Adhesive 410 may be or include a ceramic adhesive, such as, for example, alumina. Liner 406 may be attached to plate 404 and / or wall 130 using adhesive 412, which may be the same as or similar to adhesive 410. Liner 408 may likewise be attached to plate 404 and inlet tube 416 (not shown separately in FIG. 1 ) using adhesive 414, which may be the same as or similar to adhesive 410.

[0028] FIG. 5 illustrates another gas distribution plate assembly 500 suitable for use as the gas distribution plate assembly 108 according to disclosed embodiments. The gas distribution plate assembly 500 is similar to the gas distribution plate assembly 400, except that the gas distribution plate assembly 500 includes non-fluidized particles 502 rather than plates 404. The use of non-fluidized particles allows for easier adjustment of the pressure drop across the axial (vertical) direction of the bed, thereby enabling fluidization. The non-fluidized particles 502 may be formed from a refractory material such as zirconia, yttria, silicon nitride, etc. The average cross-sectional dimension of the non-fluidized particles 502 may be from about 25 mm to about 1 mm, or from about 1 mm to about 0.03 mm. The active material 120 may be in the non-fluidized particles 502.

[0029] 1, the gas inlet 110 may be coupled to one or more of the gas sources containing the gas to be decomposed. For example, the gas inlet 110 may be coupled to a water source and / or a carbon dioxide source.

[0030] As shown, the system 100 may include a heat source 128 to heat the gas prior to the gas inlet 110. The heat source 128 may be or include any type of heater or heat exchanger, such as those described above in connection with the heating element 122.

[0031] The gas outlet 112 may be coupled to one or more of the gas collection vessels. According to the disclosed embodiments, the product gas from the gas outlet 112 may be continuously compressed and collected.

[0032] According to the illustrated embodiment, the reactor 102 further includes an insulating material 116 (e.g., refractory) and a pressure vessel 118 (e.g., made of steel). As shown, the insulating material 116 can surround, e.g., encase, the reaction zone 104 and the gas heating zone 106. The insulating material 116 can be or include, for example, silica refractory brick. The pressure vessel 118 can be formed from, for example, stainless steel or carbon steel. The thickness of the wall 130 of the pressure vessel 118 can be between about 2 mm and about 5 mm, or between about 5 mm and about 30 mm. The pressure vessel 118 can surround or encase the insulating material 116 such that the insulating material 116 is contained within the pressure vessel 118.

[0033] The controller 114 is configured to operate the reaction zone 104 at a temperature as described above and to control the pressure in the reaction zone to greater than 1 bar during the gas decomposition / oxidation step and to less than 1 bar during the active material reduction step. As described in more detail below, controlling the pressure during these processes is believed to improve the efficiency of the thermochemical gas decomposition reactor system 100.

[0034] 2 illustrates another thermochemical gas decomposition reactor system 200 according to an embodiment of the disclosure. Thermochemical gas decomposition reactor system 200 is similar to thermochemical gas decomposition reactor system 100, except that thermochemical gas decomposition reactor system 200 uses heat exchangers within system 200 to heat the gas before it enters the reaction zone.

[0035] In the illustrated embodiment, the thermochemical gas decomposition reactor system 200 includes a reactor 202 including a reaction zone 204, a gas heating zone 206, and a gas distribution plate assembly 208 positioned between the reaction zone 204 and the gas heating zone 206, a gas inlet 210 fluidly coupled to the gas heating zone 206, a gas outlet 212 fluidly coupled to the reaction zone 204, and a controller 214.

[0036] Reactor 202 can be similar to reactor 102 described above and can be configured to operate at the temperatures and pressures described above. Similarly, reaction zone 204 and gas heating zone 206 can be similar to reaction zone 104 and gas heating zone 106 described above. Gas distribution plate 208 can be identical to gas distribution plate assembly 108.

[0037] In the illustrated embodiment, gas inlet 210 and gas outlet 212 are at the same end of reactor 202 to enable heat transfer from product gas exiting gas outlet 212 to gas received through gas inlet 210. As a particular example, thermochemical gas decomposition reactor system 200 includes a first tube 213 fluidly coupled to gas inlet 210 for conveying gas received at gas inlet 210 to gas heating zone 206. Thermochemical gas decomposition reactor system 200 also includes a tube 215 fluidly coupled to reaction zone 204 for receiving product gas and conveying the product gas to gas outlet 212.

[0038] The tubes 213, 215 may be formed from any suitable material. For example, the tubes 213, 215 may be formed from a ceramic such as alumina or silicon carbide. As shown, the tubes 213, 215 may be substantially concentric, with the first end 217 of the tube 213 extending beyond the first end 219 of the second tube 215. The second end 221 of the first tube 213 may also extend beyond the second end 223 of the second tube 215. The tubes 213, 215 may be coated with or include a porous ceramic foam 225, which may be or include, for example, alumina, zirconia, or silicon carbide.

[0039] Thermochemical gas decomposition reactor system 200 may also include a controller 214, insulating material 216, pressure vessel 218, material 220, heating element 222, protective tube 224, and optionally, heat source 228, which may be the same as or similar to controller 114, insulating material 116, pressure vessel 118, material 120, heating element 122, protective tube 124, and heat source 128 described above.

[0040] 3 illustrates a system 300 that includes multiple reactors 302 and may be the same or similar to the thermochemical gas decomposition reactor systems 100, 200 described above. The reactors 302 may be selectively and reversibly operated between a reduction mode and an oxidation mode to allow for continuous production of product gas from the system 300. As shown, the system 300 includes an inert gas (e.g., N) input 304, a reactant gas (e.g., HO and / or CO) input 306, a heat exchanger 308, a membrane separator 310, a compressor 312, and recycle lines 314, 316. During operation, oxidation products may be separated using the membrane separator 310, and CO may be recycled back to the reactor 302. Similarly, reduction products may be recycled back to the reactor 302 using line 318 and / or source 304.

[0041] According to additional examples of the disclosure, methods are provided. The exemplary methods described herein can be used for the thermochemical dissociation of reduced metal oxides to water and / or carbon dioxide. Such reactions have long been considered independent of overall pressure due to the equal moles of gaseous reactants (i.e., HO and / or CO) and gaseous products (i.e., H and / or CO). However, according to aspects of the exemplary embodiment, in an open system where product gas is removed from the reaction zone, operation at elevated pressure improves both the degree of balance and the rate of the above-described equimolar oxidation reaction. This not only enables the use of more earth-abundant materials, but also facilitates the production of green hydrogen (or syngas), which is both practical and efficient.

[0042] Thermochemical processes for the dissociation of H2O (and / or CO2) are most commonly implemented using metal oxides (MOs) to separate the production of O2 and H2 (and / or CO) into distinct steps. x The first step, which typically occurs at temperatures above 1400°C, involves the release of O from the metal oxide crystal lattice:

number

[0043] Thereafter, at the same or lower temperature, the desired fuel is produced to form oxygen-deficient (i.e., reduced) metal oxides (MO x-δ ) is introduced to return it to its original state (i.e., oxidize it):

number

[0044] Briefly, Equations 1 and 2 represent the relationship between ceria (i.e., CeO 2-δ This represents a thermochemical cycle in which binary metal oxides that accommodate oxygen vacancies, such as SiO2, SiO2, and SiO2, are used. However, it should be noted that alternative non-stoichiometric materials exist, including materials that have recently been shown to accommodate cation vacancies.

[0045] For candidate metal oxides, it is widely accepted that the reaction progress (δ) depends on both the operating temperature and the oxygen partial pressure. Therefore, to control material performance in the context of two-step thermochemical fuel production, redox cycles can be implemented using temperature swings and / or partial pressure swings. Considering extreme cases, the temperature swing mode can significantly increase the thermochemical capacity of metal oxides for fuel production, but it has practical limitations, namely, the large heat losses and thermal stresses imposed by temperature cycling during the redox process. On the other hand, the partial pressure swing (or isothermal) mode overcomes these concerns at the cost of limiting the metal oxide's capacity to the difference in oxygen chemical potential between the hot oxidant and the inert environment established during reduction. Therefore, experiments considering the partial pressure swing mode report lower oxidant conversion. Consequently, a combination of both modes can be commonly used for prototype or pilot-scale operations, where optimization of both solar-to-fuel energy efficiency and oxidant conversion is a priority.

[0046] Reduction (Equation 1), a non-equimolar reaction, is often performed at subambient pressure to further reduce the oxygen partial pressure below that which would otherwise be achievable by simply delivering air or an inert sweep gas. Conversely, oxidation (Equation 2), an equimolar reaction, has not yet been evaluated at pressures other than ambient, since no benefit is expected by running the reaction differently according to Le Châtelier's principle. Nevertheless, it is desirable for the fuel produced (i.e., hydrogen or syngas) to be delivered at elevated pressure for further processing. For example, hydrogen is often used at elevated pressures due to its low volumetric energy density (i.e., 10 kJ / L). -1), often require high-pressure compression for storage, and downstream processes such as the Haber-Bosch or Fischer-Tropsch processes inherently operate at high pressures (i.e., above 30 bar). Despite this universal understanding, solar-powered technologies for producing hydrogen or syngas (from H2O and / or CO2) traditionally operate at ambient pressure, thereby largely downplaying the downstream compression effort when assessing performance (i.e., reporting solar-to-hydrogen energy efficiency or solar-to-fuel energy efficiency). However, when considering the entire chain of events involved in producing drop-in fuel (i.e., renewable kerosene) from sunlight, H2O, and CO2, recent pilot-scale experiments using a two-step thermochemical cycle reveal that the energy losses associated with downstream compression are indeed significant, accounting for up to 10% of the input solar energy. Importantly, such inefficiencies can be reduced by running the process at increased pressure (e.g., an oxidation step for two-step thermochemical fuel production), since pressurizing the liquid reactant (i.e., HO) upstream is significantly more energy efficient (and cost-effective) than compressing the product gas (i.e., H) downstream. Furthermore, it is expected that sources of high-pressure CO2 will become readily available in the near future, whether through pipeline infrastructure or by co-locating commercial plants with facilities capable of supplying high-concentration CO2 (e.g., direct air capture); therefore, in such a scenario, product compression operations could be avoided entirely.

[0047] Surprisingly, it has been discovered that conducting gas decomposition or oxidation above 1 bar reduces energy requirements and reduces operating costs. Representative results using exemplary active materials are illustrated in Figure 6 and Table 1. Figure 7 illustrates cumulative CO production according to disclosed embodiments. Figure 8 illustrates peak rates of production after accounting for gas phase dispersion and mixing effects according to disclosed embodiments.

[0048] Table 1. Further insight into material performance The relevant metrics associated with Figure 6, namely oxygen partial pressure (pO2) and redox yield, are quantified as a function of oxidant pressure. [Table 1]

[0049] Notably, ceria produced slightly more CO at pressures above 1 atm, while Fe33Al67 was significantly more effective, i.e., it produced over 100% more CO when exposed to CO2 at 10 atm compared to CO2 at 1 atm (i.e., 768 ± 9.9 μmol g, respectively). -1 and 356±8.1 μmol g -1 ) In fact, 770 μmol g -1The nearby CO experiment demonstrated one of the highest (if not the highest) reported capacities for fuel production from nonstoichiometric metal oxides under isothermal conditions, even exceeding that of perovskite and polycationic oxide alternatives observed after a temperature swing of several hundred degrees. Despite these different responses to changes in oxidant pressure, each improvement in fuel yield (i.e., degree of oxidation) was achieved by subsequently increasing the rate of reduction, resulting in additional oxygen release given that the degree of reduction was held constant. Thus, for Fe33Al67, the molar ratio of fuel produced (i.e., CO) to oxygen released remained approximately 2:1 (see Equations 1 and 2), with cycle values ​​ranging from 1.8±0.1:1 to 2.1±0.1:1, whereas the molar ratio for ceria was lower, ranging from 1.0±0.1:1 to 1.2±0.1:1. Here, deviations from the ideal 2:1 ratio are primarily due to the presence of oxygen from thermal decomposition during the oxidation-to-reduction transition, rather than specifically to the reaction of ceria, given its relatively small capacity under the isothermal conditions considered. Another product, namely axial dispersion and mixing in the gas phase (downstream of the reaction site), is responsible for the apparent broadening of the kinetic profile. Upon decomposition, the intrinsic rate of CO production for Fe33Al67, along with the yield, was found to increase with increasing oxidant pressure. Importantly, the thermodynamic and kinetic benefits of increasing oxidant pressure were repeatable, as seen in four consecutive iron aluminate cycles in which the reduction and oxidation steps alternated between 1 and 5 atm, respectively.

[0050] The experimental results were further supported with relevant excerpts from well-established equilibrium maps, which allow the quantification, for a given set of thermodynamic states, of the thermochemical capacity of the oxide (Δδ), as shown in Figure 9. For convenience, such states are often defined in terms of temperature and oxygen partial pressure, which can be measured or calculated. Here, the oxygen partial pressure for the reduction step was determined by directly measuring the oxygen content in the effluent near reaction completion (see Table 1). On the other hand, the oxygen partial pressure for the oxidation step was determined according to the equilibrium of the thermal decomposition of carbon dioxide (i.e., CO → CO + 1 / 2O), which in this case depends on both temperature and pressure. With each thermodynamic state defined, it can be seen that Fe33Al67 is capable of significantly greater changes in reaction progress than ceria at 1400 °C; in contrast, ceria exhibits a significantly higher standard partial molar enthalpy of reduction (i.e., 400 kJ mol O -1 (exceeding δ = 0), and as a result, tend primarily toward the fully oxidized state (i.e., δ = 0) throughout the same range of conditions. Thus, not only is the capacity of iron aluminate significantly greater under conventional partial pressure swing mode (i.e., P = 1 atm), but even more significant improvements in material performance are observed when the oxygen partial pressure of the input oxidant is further increased, as when the oxidation step is carried out at elevated pressure (e.g., P = 5 atm). Here, even the ability to access such higher oxygen partial pressures is due to the use of an open-system reactor configuration, since each material is exposed to the pressure-dependent chemical potential of the delivered oxidant, effectively sweeping the gaseous products (and their effects) away from the reaction site.

[0051] To further this understanding, additional experiments were performed on iron aluminate to assess whether the above observations could be extended to conditions more representative of commercial practice, where the goal of maximizing oxidant conversion implies that a portion of the active material interacts with an oxidant diluted with products generated elsewhere (i.e., H and / or CO). The results of the experiments are shown in Figure 10. As expected, exposure to a less oxidizing gas mixture (i.e., CO:CO << ∞) reduced the extent of oxidation of Fe33Al67, resulting in lower yields. However, by increasing the oxidant pressure from 1 atm to 5 atm, some of this reduced yield could be recovered as a result of establishing a higher oxygen partial pressure at the reaction site, as described above. However, as more CO (i.e., a lower CO2:CO ratio) was introduced, the difference in oxygen partial pressure achievable during oxidation between 1 atm and, in this case, 5 atm, decreased, and therefore the magnitude of the observed improvement concomitantly decreased. Importantly, this reduction in capacity can be compensated for by either further increasing the oxidant pressure or by considering materials such as Fe47Al53, which exhibit a larger change in δ per unit change in oxygen partial pressure. In either case, it is clear that total pressure, in addition to temperature, can be exploited as a means to induce an improvement in the degree of oxidation and thus in oxidant conversion. Thus, candidate materials (e.g., lanthanum manganate perovskite) or operating modes (e.g., partial pressure swing) previously rejected because they exhibited insufficient conversion may be suitable for use in the systems and methods described herein.

[0052] As a specific example, a method according to the present disclosure includes providing a reactor containing a reaction, such as a reactor (or system) described herein, providing one or more of HO and CO to a gas heating zone or reactor, heating one or more of HO and CO in the gas heating zone, providing the heated one or more of HO and CO through a gas distribution plate assembly and to a reaction zone, and decomposing the heated one or more of HO and CO in the reaction zone, wherein the temperature in the reaction zone is greater than about 1000°C (e.g., in the temperature ranges presented herein), and the pressure in the reaction zone is greater than 1 bar, or between greater than 1 bar and about 10 bar, or between 10 bar and 35 bar. The method may further include performing an active material reduction step in the reactor and / or another reactor in the reactor system. The pressure in the reaction zone during the reduction step may be less than 1 bar or between 1 bar and 1 mbar.

[0053] In exemplary methods, product gas may be continuously removed from the reaction zone during the decomposing step. According to some exemplary embodiments, the decomposing and reducing steps may be substantially isothermal (e.g., may be carried out substantially isothermally as described above). In other cases, the temperature may vary as described above.

[0054] The method may also include heating the reaction gas prior to entering the gas heating zone. In such cases, the heating step may include concentrating solar radiant heat using a resistive heater (e.g., an array of resistive heaters) and / or recovering heat from gases exiting the reactor.

[0055] The exemplary embodiments of the disclosure above do not limit the scope of the invention, as these embodiments are merely examples of embodiments of the invention. Any equivalent embodiments are intended to be within the scope of the invention. Indeed, modifications of the disclosure, such as alternative useful combinations of the described elements, in addition to the embodiments shown and described herein may become apparent to those skilled in the art from this description. Such modifications and embodiments are also intended to fall within the scope of the appended claims.

Claims

1. 1. A thermochemical gas decomposition reactor system comprising: A reactor comprising: a reaction zone containing an active material; a gas heating zone; and a gas distribution plate assembly interposed between the reaction zone and the gas heating zone; the reactor comprising: a gas inlet fluidly coupled to the gas heating zone; a gas outlet fluidly coupled to the reaction zone; a controller configured to operate the reaction zone at a temperature greater than about 1000°C and configured to control the pressure in the reaction zone to a pressure greater than 1 bar during the gas decomposition step and to a pressure less than or equal to 1 bar during the active material reduction step; Including, 1. The thermochemical gas decomposition reactor system.

2. 10. The thermochemical gas decomposition reactor system of claim 1, The reactor includes an insulating material contained in a pressure vessel.

1. The thermochemical gas decomposition reactor system.

3. 10. The thermochemical gas decomposition reactor system of claim 1, the gas distribution plate assembly includes one or more ceramic structures including alumina, zirconia, and / or silica; 1. The thermochemical gas decomposition reactor system.

4. 10. The thermochemical gas decomposition reactor system of claim 1, the gas distribution plate assembly includes a plurality of holes having a cross-sectional diameter between about 2.5 mm and about 0.5 mm and / or between about 200 microns and about 1 micron; 1. The thermochemical gas decomposition reactor system.

5. 10. The thermochemical gas decomposition reactor system of claim 1, further comprising a concentrated solar radiant heater, wherein the gas is preheated using the concentrated solar radiant heater before entering the gas heating zone; 1. The thermochemical gas decomposition reactor system.

6. 10. The thermochemical gas decomposition reactor system of claim 1, further comprising an array of resistive heaters, wherein the gas in the gas heating zone is heated using the resistive heaters.

1. The thermochemical gas decomposition reactor system.

7. 10. The thermochemical gas decomposition reactor system of claim 1, a heat exchanger, wherein the gas in the gas heating zone is preheated using the heat exchanger; 1. The thermochemical gas decomposition reactor system.

8. 8. The thermochemical gas decomposition reactor system of claim 7, comprising: the heat exchanger removes heat from the product gas removed from the reactor via the gas outlet; 1. The thermochemical gas decomposition reactor system.

9. 10. The thermochemical gas decomposition reactor system of claim 1, the active material comprises a metal oxide; 1. The thermochemical gas decomposition reactor system.

10. 10. The thermochemical gas decomposition reactor system of claim 9, the active material comprises an iron aluminate-based spinel, a lanthanum manganate-based perovskite, and / or a ceria-based oxide; 1. The thermochemical gas decomposition reactor system.

11. 10. The thermochemical gas decomposition reactor system of claim 1, The active material is (M ζ Al １－ζ ) ３－δ O ４ wherein ζ is greater than 1 / 3 and M is one or more of Fe, Co, Ti, Mn, Mg, Zn, Ni, and Cr; 1. The thermochemical gas decomposition reactor system.

12. 1. A method for thermochemical gas decomposition comprising: providing a reactor including a reaction zone containing an active material, a gas heating zone, and a gas distribution plate assembly interposed between the reaction zone and the gas heating zone; The gas heating zone ２ O and CO ２ providing one or more of: In the gas heating zone, H ２ O and CO ２ heating said one or more of: H through the gas distribution plate assembly and into the reaction zone. ２ O and CO ２ providing heated one or more of: H in the reaction zone ２ O and CO ２ decomposing said heated one or more of: Including, the temperature in the reaction zone is greater than about 1000°C and the pressure in the reaction zone is greater than 1 bar; The thermochemical gas decomposition method.

13. 13. The method of claim 12, Further comprising performing an active material reduction step; The method.

14. 14. The method of claim 13, the pressure in the reaction zone during the reduction step is 1 bar or less; The method.

15. 13. The method of claim 12, During the decomposing step, product gas is continuously removed from the reaction zone. The method.

16. 13. The method of claim 12, the decomposing and reducing steps are substantially isothermal; The method.

17. 13. The method of claim 12, the heating step includes concentrating solar radiation. The method.

18. 13. The method of claim 12, the heating step comprises resistive heating; The method.

19. 13. The method of claim 12, the heating step includes recovering heat from gases exiting the reactor; The method.

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