Thermochemical gas decomposition reactor system and method for thermochemical decomposition of gas

Abstract

Thermochemical gas decomposition reactor systems and methods of decomposing gas are disclosed herein. The system includes a reactor including a reaction zone comprising 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 a plurality of reactors. Methods may include providing one or more reactors, and performing one or more of oxidation and / or reduction processes using each of the reactors.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Application No. 63 / 410,177, filed on September 26, 2022, entitled “PRESSURE SWING REDOX PROCESSING TO SPLIT H2O / CO2,” and U.S. Provisional Application No. 63 / 425,617, filed on November 15, 2022, entitled “PRESSURE SWING REDOX PROCESSING TO SPLIT H2O / CO2,” the contents of which are hereby incorporated herein by reference.

[0003] STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0004] 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. Technical Field

[0005] The disclosure generally relates to thermochemical gas decomposition reactor systems and methods of decomposing gases, such as one or more of H2O and CO2. Background Art

[0006] The use of hydrogen as a renewable fuel has been hampered by the inability to produce it cleanly and economically. Conventional solar thermochemical approaches consider a two-step redox cycle using benchmark ceria or perovskites in a temperature-swinging configuration, where reduction occurs at much higher temperatures than oxidation. Isothermal redox cycling is feasible and avoids the solid-solid heat recovery and material stability challenges associated with large temperature swings; however, this has long been considered inefficient due to the thermodynamic disadvantages of operating the exothermic oxidation reaction at higher temperatures.

[0007] Furthermore, two-step thermochemical processes for the dissociation of H2O and / or CO2 (e.g., via solar heat) have historically performed the oxidation (fuel generation) step at ambient pressure, so in practice the work required for product compression is very large. Thus, improved methods and systems suitable for decomposing water (and / or carbon dioxide) in a relatively efficient manner are desired.

[0008] Any discussion set forth in this section (including discussion of problems and solutions) is included in the disclosure text only for the purpose of providing context for the disclosure text. Such discussion should not be considered as an admission that any or all of such information was known or otherwise constituted prior art at the time the present invention was made. Summary of the invention

[0009] This Summary is provided to introduce a selection of concepts. This Summary 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.

[0010] According to examples of the disclosure, a thermochemical gas decomposition reactor system and a method for decomposing a gas are provided. The system and method can be used, for example, to decompose water vapor (H2O) and / or carbon dioxide (CO2) in a relatively energy efficient and cost effective manner.

[0011] According to an exemplary embodiment of the disclosure, a thermochemical gas decomposition reactor system includes a reactor, the 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 connected to the gas heating zone, a gas outlet fluidly connected 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 in the reaction zone or reaction chamber to be greater than 1 bar during the gas decomposition step and to control the pressure in the reaction zone or reaction chamber to be less than or equal to 1 bar during the active material reduction step. According to aspects of these embodiments, the system includes a plurality of reactors that can be operated in reduction and / or oxidation modes to allow continuous operation and removal of products from the system. According to other aspects, the reactor and / or system is operated substantially isothermally. The reaction zone may include active materials. According to other aspects, the reactor includes an insulating wall contained in a pressure vessel. The gas distribution plate may be formed by one or more ceramic structures including alumina, zirconium oxide and / or silicon dioxide. According to other aspects, the gas distribution plate is configured to facilitate or allow flow substantially along the (eg, vertical) axis of the reactor. According to other aspects, the system can include one or more heaters or heat sources to heat or preheat the gas entering the reactor.

[0012] According to additional embodiments of the disclosure, a method for thermochemically decomposing a gas is provided. As described above, the gas to be decomposed may be or may include, for example, steam and / or carbon dioxide. The method includes: providing a reactor (e.g., a reactor as described above or elsewhere herein); providing a gas (e.g., one or more of H2O and CO2) to the reactor to a gas heating zone; heating the gas (e.g., one or more of H2O and CO2) in the gas heating zone; providing the heated gas (e.g., one or more of H2O and CO2) to the reaction zone through a gas distribution plate assembly; and decomposing the heated gas (e.g., one or more of H2O and CO2) 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 may also include performing an active material reduction step. During the active material reduction step, the pressure in the reaction zone or reaction chamber may be controlled to be less than or equal to 1 bar. The method may include continuously removing product gas from the reaction zone during the decomposition step and / or during the step of performing the active material reduction step. The exemplary method may also include heating the gas before the gas enters the reaction zone and / or before entering the reactor.

[0013] These and other embodiments will become apparent to those skilled in the art from the following detailed description of certain embodiments with reference to the attached figures; the disclosure is not limited to any particular embodiment disclosed. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] A more complete understanding of embodiments of the disclosure may be obtained by referring to the detailed description and claims when considered in conjunction with the following illustrative drawings.

[0015] Figure 1 A thermochemical gas decomposition reactor system according to at least one embodiment of the disclosure is shown.

[0016] Figure 2 Another thermochemical gas decomposition reactor system according to at least one embodiment of the disclosure is shown.

[0017] Figure 3 A multiple reactor system according to at least one embodiment of the disclosure is shown.

[0018] Figure 4 A gas distribution plate assembly according to at least one embodiment of the disclosure is shown.

[0019] Figure 5 A gas distribution plate assembly according to another embodiment of the disclosure is shown.

[0020] Figure 6 Thermochemical cycles of two candidate active materials according to examples of the disclosure are shown.

[0021] Figure 7 The cumulative production of CO according to an example of the disclosure is shown.

[0022] Figure 8 The peak generation rate after considering the effects of gas phase dispersion and mixing according to an example of the disclosure is shown.

[0023] Fig. 9 The undoped cerium dioxide (CeO 2-δ ) and ferrous aluminate Fe33Al67((Fe 1 / 3 Al 2 / 3 ) 3-δ The equilibrium oxygen content of O4) varies with the oxygen partial pressure at 1400°C.

[0024] Fig.10 The degree of Fe33Al67 oxidation measured at 1400°C is shown as a function of inlet oxidant composition (ie, CO2:CO ratio) and pressure, with each corresponding oxygen partial pressure determined from the carbon dioxide pyrolysis equilibrium presented in the top graph.

[0025] It should be understood that the elements in the drawings are shown for simplicity and clarity and are not necessarily drawn to scale. For example, the size of some elements in the drawings may be exaggerated relative to other elements to help improve the understanding of the illustrated embodiments of the disclosed text. DETAILED DESCRIPTION

[0026] Although certain embodiments and examples are disclosed below, it should be understood that the invention extends beyond the specifically disclosed embodiments and / or their uses and obvious modifications and equivalents thereof. Therefore, the scope of the disclosed invention is intended not to be limited by the specific disclosed embodiments described below.

[0027] The 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 variation to provide desired energy and / or cost efficiency while providing desired product throughput.

[0028] In the disclosure, "substantially isothermally" may mean that the temperature during the reduction phase and the temperature during the oxidation phase of a reduction and oxidation cycle or process during operation are within ±10°C or ±25°C or ±50°C or ±100°C or ±150°C of each other.

[0029] In the disclosure, "gas" may include materials that are gaseous at normal temperature and pressure, vaporized solids, and / or vaporized liquids, and may consist of a single gas or a mixture of gases, depending on the context. An inert gas may be a gas that does not participate in chemical reactions to a significant degree. Exemplary inert gases include nitrogen.

[0030] In the disclosure, "continuous" or "continuously" or "continuously" may refer to an uninterrupted timeline, without any material intervening step, without changing process conditions, or immediately following, as the next step, depending on the context.

[0031] In the open text, any two numerical values ​​of a variable can constitute the feasible range of the variable, and any range indicated can include or exclude endpoints. In addition, any value of the indicated variable (regardless of whether they are indicated with "about") can refer to an exact value or an approximate value and include equivalents, and in some embodiments, can refer to a mean value, a median, a representative value, a majority value, etc. In addition, in the open text, in some embodiments, the term "comprising", "consisting of ... " and "having" and variations thereof can independently refer to "generally including or widely including", "comprising", "essentially consisting of ... " or "consisting of ... " and variations thereof. According to the aspect of the open text, any limited meaning of a term does not necessarily exclude the common and customary meaning of a term.

[0032] Now turning to the attached figure, Figure 1 A thermochemical gas decomposition reactor system 100 according to an example of the disclosure is shown. 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.

[0033] Reactor 102 may be configured to operate at a temperature greater than 800° C. or greater than 1000° C. or between about 800° C. and about 1500° C. or between about 900° C. and about 1400° C. during the reduction phase and / or during the oxidation phase. 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.

[0034] 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 an example of the disclosure, the active material 120 includes a metal oxide. For example, the active material 120 may be or 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, active material 120 includes (M ζ Al 1-ζ ) 3-δ O4, wherein ζ is greater than 1 / 3 and M is one or more of Fe, Co, Ti, Mn, Mg, Zn, Ni, and Cr. As an example, the active material 120 may be or may include Co x Fe 1-x+y Al 2-y O4, wherein 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.

[0035] The reaction zone 104 can be configured as a fluidized bed reactor or a packed bed reactor. Thus, the active material 120 can be filled or fluidized during operation of the reactor 102.

[0036] The gas heating zone 106 may include one or more heat sources or elements 122 to heat the gas within the gas heating zone 106, e.g., the gas received from the gas inlet 110, before the gas enters the reaction zone 104. The heat source or element 122 may be or may include, for example, a concentrated solar radiation heater, a heat exchanger (e.g., where the heat exchanger is used to heat the gas within the gas heating zone, and optionally, the heat exchanger removes heat from the product gas removed from the reactor via the gas outlet), one or more (e.g., an array) of electrical resistance heaters, etc. In some cases, a ceramic protection tube 124 (e.g., formed of one or more of aluminum oxide, zirconium oxide, silicon carbide, boron nitride, silicon nitride) may be used to protect the heating element 122. The array of electrical resistance heaters may include about 2 to about 10 or about 10 to about 50 electrical resistance heaters.

[0037] The gas distribution plate assembly 108 can be used to support fluidized and / or packed bed particles, such as material 120. In addition, the gas distribution plate assembly 108 can be configured to facilitate and promote the flow of gas between the gas heating zone 106 and the reaction zone 104 in a direction along (e.g., vertical) axis 126. According to an example of the disclosure, the gas distribution plate assembly 108 includes one or more ceramic structures, and the one or more ceramic structures include a refractory material, such as one or more of alumina, zirconia, and / or silica. As discussed in more detail below, the gas distribution plate assembly 108 can include a plurality of holes, and the plurality of holes have a cross-sectional diameter between about 2.5 mm and about 0.5 mm and / or between about 200 microns and about 1 micron.

[0038] Figure 4 A gas distribution plate assembly 400 suitable for use as a gas distribution plate assembly 108 according to an example of the disclosure is shown. The gas distribution plate assembly 400 includes a porous ceramic frit and a plate 404. The porous ceramic frit 402 can be formed, for example, by zirconium oxide, etc. 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, by alumina, zirconium oxide, etc. The plate 404 can include holes having an average diameter or cross-section of about 200 microns to about 1 micron or about 40 microns to about 1 micron.

[0039] As shown, ceramic frit 402 may be adhered to one or more liners 406, 408 using adhesive 410. Liners 406, 408 may be formed, for example, of alumina, zirconia, etc. Adhesive 410 may be or may include, for example, a ceramic adhesive such as alumina. Liners 406 may be adhered to plate 404 and / or wall 130 using adhesive 412, which may be the same or similar to adhesive 410. Liners 408 may similarly be adhered to plate 404 and inlet tube 416 ( Figure 1 ), the adhesive may be the same as or similar to adhesive 410.

[0040] Figure 5Another gas distribution plate assembly 500 suitable for use as a gas distribution plate assembly 108 according to an example of the disclosed text is shown. 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 instead of the plate 404. The use of non-fluidized particles allows people to more easily adjust the pressure drop in the axial (vertical) direction of the bed, and thus achieve fluidization. The non-fluidized particles 502 can be formed of refractory materials, such as zirconium oxide, yttrium oxide, silicon nitride, etc. The average cross-sectional size of the non-fluidized particles 502 can be about 25 mm to about 1 mm or about 1 mm to about 0.03 mm. The active material 120 can reside on the non-fluidized particles 502.

[0041] return Figure 1 The gas inlet 110 can be connected to one or more gas sources including the gas to be decomposed. For example, the gas inlet 110 can be connected to a water and / or carbon dioxide source.

[0042] 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 may include any type of heater or heat exchanger, such as those described above in conjunction with the heating element 122.

[0043] The gas outlet 112 may be coupled to one or more gas collection vessels. According to an example of the disclosure, the product gas from the gas outlet 112 may be continuously compressed and collected.

[0044] According to the example shown, the reactor 102 also includes (e.g., refractory) insulating material 116 and (e.g., steel) pressure vessel 118. As shown, the insulating material 116 can surround (e.g., wrap) the reaction zone 104 and the gas heating zone 106. The insulating material 116 can be or can include, for example, silica refractory bricks. The pressure vessel 118 can be formed by, 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 wrap the insulating material 116 so that the insulating material 116 is contained in the pressure vessel 118.

[0045] The controller 114 is configured to operate the reaction zone 104 at the temperature as described above and to control the pressure within the reaction zone to be greater than 1 bar during the gas decomposition / oxidation step and to control the pressure within the reaction zone to be less than or equal to 1 bar during the active material reduction step. As discussed in more detail below, controlling the pressure within these mechanisms is believed to improve the efficiency of the thermochemical gas decomposition reactor system 100.

[0046] Figure 2Another thermal chemical gas decomposition reactor system 200 according to an example of the disclosure is shown. The thermal chemical gas decomposition reactor system 200 is similar to the thermal chemical gas decomposition reactor system 100, except that the thermal chemical gas decomposition reactor system 200 uses a heat exchanger within the system 200 to heat the gas before it enters the reaction zone.

[0047] In the example shown, the thermochemical gas decomposition reactor system 200 includes: a reactor 202, the reactor including a reaction zone 204, a gas heating zone 206, and a gas distribution plate assembly 208 inserted between the reaction zone 204 and the gas heating zone 206; a gas inlet 210, which is fluidly connected to the gas heating zone 206; a gas outlet 212, which is fluidly connected to the reaction zone 204; and a controller 214.

[0048] Reactor 202 can be similar to reactor 102 described above, and can be configured to operate at the above-described temperatures and pressures. 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 the same as gas distribution plate assembly 108.

[0049] In the example shown, the gas inlet 210 and the gas outlet 212 are at the same end of the reactor 202 to allow heat transfer from the product gas exiting the gas outlet 212 to the gas received through the gas inlet 210. As a specific example, the thermochemical gas decomposition reactor system 200 includes a first tube 213, which is fluidly coupled to the gas inlet 210 to deliver the gas received at the gas inlet 210 to the gas heating zone 206. The thermochemical gas decomposition reactor system 200 also includes a tube 215, which is fluidly coupled to the reaction zone 204 to receive the product gas and deliver the product gas to the gas outlet 212.

[0050] The tubes 213, 215 may be formed of any suitable material. For example, the tubes 213, 215 may be formed of a ceramic, such as aluminum oxide or silicon carbide. As shown, the tubes 213, 215 may be substantially concentric, wherein the first end 217 of the tube 213 extends 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 may include, for example, aluminum oxide or zirconium oxide or silicon carbide.

[0051] The thermochemical gas decomposition reactor system 200 may also include a controller 214, an insulating material 216, a pressure vessel 218, a material 220, a heating element 222, a protective tube 224 and an optional heat source 228, which may be the same or similar to the above-mentioned controller 114, insulating material 116, pressure vessel 118, material 120, heating element 122, protective tube 124 and heat source 128.

[0052] Figure 3 A system 300 is shown that includes multiple reactors 302, which can be the same or similar to the above-described thermochemical gas decomposition reactor systems 100, 200. The reactor 302 can be operated alternately and reversibly in a reduction mode and an oxidation mode to allow continuous capture of product gases from the system 300. As shown, the system 300 includes an inert gas (e.g., N2) input 304, a reactant gas (e.g., H2O and / or CO2) input 306, a heat exchanger 308, a membrane separator 310, a compressor 312, and recycle lines 314, 316. During operation, the oxidation products can be separated using the membrane separator 310, and the CO2 can be recycled back to the reactor 302. Similarly, the reduction products can be recycled back to the reactor 302 using the pipeline 318 and / or the source 304.

[0053] According to the additional examples of the disclosure, a method is provided herein. The exemplary methods described herein can be used for the thermochemical dissociation of water and / or carbon dioxide on the reduced metal oxide. For a long time, such reactions have been considered to be independent of total pressure because the moles of gaseous reactants (i.e., H2O and / or CO2) and gaseous products (i.e., H2 and / or CO) are equal. However, according to aspects of exemplary embodiments, in an open system where product gas is swept from the reaction zone, the equilibrium degree and rate of the aforementioned equimolar oxidation reaction are improved under elevated pressure. This not only enables the use of more earth-abundant materials, but also can facilitate the practical and efficient production of green hydrogen (or synthesis gas).

[0054] Thermochemical processes for the dissociation of H2O (and / or CO2) most commonly utilize alternating metal oxides (MO X ) Reduction-oxidation (redox) reactions divide the production of O2 and H2 (and / or CO) into different steps. The first step, which usually occurs at temperatures above 1400°C, involves the release of O2 from the crystal lattice of the metal oxide:

[0055]

[0056] Then, at the same temperature or lower, an oxidant gas is introduced to produce the desired fuel and to reduce the oxygen-deficient (or reduced) metal oxide (MO x-δ ) returns (or oxidizes back) to its original state:

[0057]

[0058] For simplicity, Equations 1 and 2 describe the following scenarios in which a binary metal oxide (such as ceria (i.e., CeO 2-δ However, it should be noted that there are alternative non-stoichiometric materials, including materials that have recently been shown to accommodate cation vacancies.

[0059] For candidate metal oxides, it has been well determined that the degree of reaction (δ) depends on both operating temperature and oxygen partial pressure. Therefore, in order to control material properties in the context of two-step thermochemical fuel production, variable temperature and / or variable partial pressure can be used to realize redox cycle. Considering extreme cases, variable temperature mode can greatly increase the thermochemical yield of metal oxide fuel production, but is subject to practical limitations, namely the significant heat loss and thermal stress caused by the thermal cycle between redox mechanisms. On the other hand, variable partial pressure (or isothermal) mode eliminates these concerns, at the cost of limiting the yield of metal oxide to the difference in oxygen chemical potential between the high-temperature oxidant and the inert environment established during reduction; therefore, the demonstration considering the variable partial pressure mode reports a lower oxidant conversion rate. Therefore, the combination of the two modes can usually be used for prototype or pilot-scale operation, in which case the energy efficiency and oxidant conversion rate of optimizing solar energy to fuel are prioritized.

[0060] To further reduce the oxygen partial pressure below that achievable by delivering only air or an inert purge gas, the reduction (Equation 1) is typically performed at subambient pressure, which is a non-equimolar reaction. Conversely, the oxidation (Equation 2) is an equimolar reaction that still needs to be evaluated at non-ambient pressure because, according to Le Chatelier's principle, one would not expect any benefit from driving the reaction differently. However, it is desirable to supply the generated fuel (i.e., hydrogen or syngas) at elevated pressure for further processing. For example, due to the low volumetric energy density of hydrogen (i.e., 10 kJ L -1), and therefore typically need to be compressed at high pressure for storage, and downstream processes (such as Haber-Bosch or Fischer-Tropsch) inherently operate at high pressure (i.e., above 30 bar). Despite this common understanding, solar-driven technologies that produce hydrogen or syngas (from H2O and / or CO2) by conventionally operating at ambient pressure have largely overlooked the work required for downstream compression when benchmarking performance (i.e., reporting solar-to-hydrogen or solar-to-fuel energy efficiencies). However, when considering the entire production chain for obtaining a ready-to-use fuel (e.g., renewable kerosene) from sunlight, H2O, and CO2, it becomes apparent that the energy penalties associated with downstream compression are actually significant, accounting for up to 10% of the solar input in a recent pilot-scale demonstration in which a two-step thermochemical cycle was employed. Importantly, such inefficiencies can be mitigated by implementing the process at elevated pressures (e.g., the oxidation step of a two-step thermochemical fuel generation) because it is more energy efficient (and more cost effective) to pressurize the upstream liquid reactants (i.e., HO) than to compress the downstream product gases (i.e., H2). Furthermore, it is expected that in the near future, high-pressure CO2 sources will be readily available, either delivered via pipeline infrastructure or by obtaining from commercial plants co-located with facilities capable of supplying high-concentration CO2 (e.g., direct air capture); thus, in this case, the work required for product compression can be avoided entirely.

[0061] It has surprisingly been found that carrying out the gas decomposition or oxidation at a pressure greater than 1 bar results in reduced energy requirements and reduced operating costs. Figure 6 Representative results using exemplary active materials are shown in and Table 1. Figure 7 The cumulative production of CO according to an example of the disclosure is shown. Figure 8 The peak generation rate after considering the effects of gas phase dispersion and mixing according to an example of the disclosure is shown.

[0062] Table 1. Further insights into material properties. Figure 6 The associated relevant metrics, namely, oxygen partial pressure (pO2) and redox yield, are quantified as a function of oxidant pressure.

[0063]

[0064] Notably, while ceria produces only slightly more CO at pressures above 1 atm, Fe33Al67 experiences a much larger effect, producing over 100% more CO when exposed to CO2 at 10 atm than at 1 atm (i.e., 768 ± 9.9 μmol g -1 and 356 ± 8.1 μmol g -1). In fact, for nearly 770 μmol g -1 The demonstration of CO represents one of the highest (if not the highest) reported yields of fuel produced by non-stoichiometric metal oxides under isothermal conditions, even surpassing the yields of promising perovskite and polycation oxide alternatives after temperature swings of several hundred degrees. Despite such different responses to changes in oxidant pressure, each improvement in fuel yield (i.e., degree of oxidation) is accompanied by a subsequent increase in the reduction rate, which produces additional oxygen release, given that the degree of reduction remains consistent. Thus, for Fe33Al67, the molar ratio of fuel produced (i.e., CO) to oxygen released remains near 2:1 (see Eqs. 1 and 2), with cyclic values ​​ranging from 1.8±0.1:1 to 2.1±0.1:1; on the other hand, for ceria, the molar ratio is lower, ranging from 1.0±0.1:1 to 1.2±0.1:1. Here, the deviation from the ideal 2:1 value is mainly attributed to the presence of pyrolysis-derived oxygen in the transition from oxidation to reduction, which, in particular, confounds the response of ceria due to its relatively small yield under the isothermal conditions considered. Another artifact—namely, axial dispersion and mixing in the gas phase (downstream of the reaction site)—is responsible for the apparent broadening of the kinetic profile. Once resolved, the intrinsic CO production rate of Fe33Al67 was found to increase, in concert with the yield, with increasing oxidant pressure. Importantly, the thermodynamic and kinetic benefits of increasing oxidant pressure are reproducible, as shown in four consecutive iron aluminate-based cycles in which the reduction and oxidation steps alternated between 1 and 5 atm, respectively.

[0065] The experimental results are further confirmed by using relevant extracts from well-established equilibrium diagrams, e.g. Fig. 9 As shown in Table 1, these equilibrium diagrams allow quantifying the thermochemical yield of oxides (Δδ) for a given set of thermodynamic states. For convenience, such states are usually defined with respect to temperature and oxygen partial pressure (the latter can be measured or calculated). Here, the oxygen partial pressure of the reduction step is determined by directly measuring the oxygen content in the effluent near the completion of the reaction (see Table 1). On the other hand, the oxygen partial pressure of the oxidation step is determined according to the equilibrium of the carbon dioxide pyrolysis in this case (i.e., CO2 → CO+ 1 / 2O2), the equilibrium depends on both temperature and pressure. For each of the defined thermodynamic states, it can be seen that at 1400°C, Fe33Al67 is able to achieve a much greater change in the extent of reaction than ceria; in contrast, ceria has a much higher standard partial molar reduction enthalpy (i.e., above 400 kJ mol O -1), and therefore favors its fully oxidized state (i.e., δ=0) over the same range of conditions. Thus, not only is the yield of ferroaluminate much greater in the conventional variable partial pressure mode (i.e., P=1 atm), but even more pronounced improvements in material properties are observed if the oxygen partial pressure of the inlet oxidant is further increased, e.g., when the oxidation step is effected at elevated pressure (e.g., P=5 atm). Here, the ability to even reach such higher oxygen partial pressures is attributed to the use of an open system reactor configuration, since each material is thereby exposed to the pressure-dependent chemical potential of the delivered oxidant, by effectively sweeping the gaseous products (and their effects) away from the reaction site.

[0066] To further understand this, additional experiments were performed with ferric aluminate to evaluate whether the aforementioned observations extend to conditions more representative of commercial practice, where the goal of maximizing oxidant conversion means that some of the active material will interact with the oxidant diluted by products produced elsewhere (i.e., H2 and / or CO); Fig.10 The results of this activity are presented in . As expected, the degree of oxidation of Fe33Al67 decreases when exposed to a less oxidizing gas mixture (i.e., CO2:CO<<∞), resulting in a decrease in yield. However, by increasing the oxidant pressure from 1atm to 5atm, it is possible to recover some of the reduced yield, which is a result of establishing a higher oxygen partial pressure at the reaction site as before. However, as more CO is introduced (i.e., CO2:CO decreases), the difference between the oxygen partial pressure that can be achieved during oxidation at 1atm and in this case 5atm decreases, and therefore the magnitude of the improvement observed decreases accordingly. Importantly, this reduction in yield can be compensated by further increasing the oxidant pressure or by considering materials that exhibit a greater delta change per unit change in oxygen partial pressure (such as Fe47Al53). In any case, it is clear that in addition to temperature, total pressure can also be used as a means to improve the degree of oxidation and therefore the oxidant conversion. Thus, candidate materials (eg, lanthanum manganate-based perovskites) or modes of operation (eg, variable partial pressure) that were previously rejected based on demonstrated inadequate conversion efficiency may be suitable for use with the systems and methods described herein.

[0067] As a specific example, a method according to the disclosure includes: providing a reactor containing a reaction, such as the reactor (or system) described herein; providing one or more of H2O and CO2 to a gas heating zone or reactor; heating one or more of H2O and CO2 in the gas heating zone; providing one or more of H2O and CO2 to the reaction zone through a gas distribution plate assembly; and decomposing one or more of H2O and CO2 in the reaction zone, wherein the temperature in the reaction zone is greater than about 1000° C. (e.g., a temperature range as provided 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 also include performing an active material reduction step in the reactor and / or in another reactor in the reactor system. During the reduction step, the pressure in the reaction zone may be less than or equal to 1 bar or between 1 bar and 1 mbar.

[0068] During the exemplary method, product gas can be continuously removed from the reaction zone during the decomposition step. According to some exemplary aspects, the decomposition step and the reduction step are substantially isothermal (e.g., performed substantially isothermally, as described above). In other cases, the temperature can vary, as described above.

[0069] The method may also include heating the reactant gas before the reactant gas enters the gas heating zone. In such cases, the heating step may include using a resistive heater (e.g., an array) to concentrate solar radiant heat, and / or recovering heat from the gas discharged from the reactor.

[0070] The exemplary embodiments of the disclosure described above do not limit the scope of the present invention, because these embodiments are merely examples of embodiments of the present invention. Any equivalent embodiments are intended to fall within the scope of the present invention. In fact, in addition to the embodiments shown and described herein, the various modifications of the disclosure (such as the replacement useful combination of the elements) can become apparent to those skilled in the art according to the description. Such modifications and embodiments are also intended to fall within the scope of the appended claims.

Claims

1. A thermochemical gas decomposition reactor system, comprising: A reactor, comprising: a reaction zone containing active materials; Gas heated areas; and a gas distribution plate assembly interposed between the reaction zone and the gas heating zone; 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 to be greater than 1 bar during the gas decomposition step and to be less than or equal to 1 bar during the active material reduction step.

2. The thermochemical gas decomposition reactor system of claim 1, wherein the reactor comprises an insulating material contained within a pressure vessel.

3. The thermochemical gas decomposition reactor system of claim 1, wherein the gas distribution plate assembly comprises one or more ceramic structures comprising alumina, zirconia, and / or silica.

4. The thermochemical gas decomposition reactor system of claim 1, wherein the gas distribution plate assembly comprises 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.

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

6. The thermochemical gas decomposition reactor system of claim 1, further comprising an array of resistive heaters, wherein the resistive heaters are used to heat the gas within the gas heating zone.

7. The thermochemical gas decomposition reactor system of claim 1, further comprising a heat exchanger, wherein the heat exchanger is used to preheat the gas in the gas heating zone.

8. The thermal chemical gas decomposition reactor system of claim 7, wherein the heat exchanger removes heat from product gas removed from the reactor via the gas outlet.

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

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

11. The thermochemical gas decomposition reactor system of claim 1, wherein the active material comprises (M ζ Al 1-ζ ) 3-δ O4, wherein ζ is greater than 1 / 3 and M is one or more of Fe, Co, Ti, Mn, Mg, Zn, Ni and Cr.

12. A method for thermochemical gas decomposition, the method comprising the following steps: providing a reactor comprising a reaction zone containing active material, a gas heating zone, and a gas distribution plate assembly interposed between the reaction zone and the gas heating zone; providing one or more of H2O and CO2 to the gas heating zone; heating said one or more of H2O and CO2 in said gas heating zone; providing heated one or more of H2O and CO2 to the reaction zone through the gas distribution plate assembly; and decomposing the heated one or more of H2O and CO2 in the reaction zone, wherein the temperature within the reaction zone is greater than about 1000°C and the pressure within the reaction zone is greater than 1 bar.

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

14. The process according to claim 13, wherein the pressure in the reaction zone during the reduction step is less than or equal to 1 bar.

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

16. The method of claim 12, wherein the decomposing step and the reducing step are substantially isothermal.

17. The method of claim 12, wherein the heating step comprises concentrated solar radiant heat.

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

19. The method of claim 12, wherein the heating step comprises recovering heat from gases exiting the reactor.

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