MATERIAL FOR STORING AND RELEASING OXYGEN

Description

[0001] The invention relates to a material for storing and releasing oxygen with the features of claim 1.

[0002] Oxide ceramic systems for oxygen generation or air separation are known. For example, ceramics with a perovskite crystal structure have the property that they can reversibly incorporate oxygen into their crystal lattice or allow it to diffuse through their volume.

[0003] There are two approaches being pursued to utilize perovskite ceramics for air separation. Firstly, ceramic membranes are produced from these compounds, which, due to their chemical properties, allow oxygen to diffuse through their crystal lattice from an oxygen-rich to an oxygen-poor gas phase at temperatures of approximately 800 °C. The oxygen-poor gas phase is referred to as the sweep side, and the oxygen-rich gas phase as the feed side. Conversely, an electrical charge equalization in the opposite direction occurs through the ceramic. Due to the large number of possible ion combinations, a variety of such mixed-ionic-electronic conductors (MIECs) exist.

[0004] Oxygen diffusion can be used for the continuous production of ultrapure oxygen, provided the oxygen partial pressure difference between the two sides is kept constant. This is technically implemented in the form of commercially available ion transport membrane systems. However, this method is not suitable for nitrogen or inert gas production, as the driving force—the oxygen partial pressure difference between the feed and sweep sides—approaches zero as the oxygen content of the feed stream decreases.

[0005] The second approach to the technical application of perovskite ceramic systems for oxygen separation is their use as oxygen storage materials (OSMs). In addition to their oxygen-conducting properties, perovskite ceramics also possess the ability to absorb and release oxygen more or less uniformly throughout their entire volume. This results in two limiting states for these ceramics, which are described as "discharging" and "charging."

[0006] For technical applications, perovskite ceramics are introduced into a reactor as a fixed-bed material and alternately exposed to heated air or a vacuum. When the ceramic is unloaded, it absorbs oxygen from the surrounding air. It is thus gradually loaded with oxygen. Once the ceramic is fully loaded, the airflow is stopped and the reactor is evacuated. The ceramic then releases the oxygen it had previously absorbed. This discontinuous process can be repeated continuously. By operating at least two of these reactors in parallel and in opposite directions, a continuous air separation process can be generated. This process is sometimes referred to as high-temperature pressure swing adsorption (HSA) and is therefore a high-temperature variant of the HSA process. An example of this is disclosed in US Patent 6,361,584 B1.However, the term "adsoption" is not entirely correct in this context, since it is essentially an absorption process in which the oxygen not only remains on the surface of the ceramic, but is absorbed into the ceramic.

[0007] Another example of the application of a ceramic oxygen carrier is the so-called CLC technology (Chemical Looping Combustion). In this process, a fuel is brought into contact with the ceramic oxygen carrier, in the form of oxide ceramic particles, in a fluidized bed reactor. The oxygen carrier releases some of its oxygen to the fuel, oxidizing it and thus enabling combustion in the absence of air. The discharged oxide ceramic particles are then transferred to a second fluidized bed reactor, where they are surrounded by air and recharged with oxygen. Once this has occurred, they are returned to the combustion reactor, allowing combustion to occur again.

[0008] In the CLC process, tiny particles of the oxygen storage materials swirl in the gas phase and must be constantly transported back and forth between reactors. This currently represents one of the biggest problems in CLC technology, as the particles often agglomerate at the prevailing temperatures, are no longer sufficiently swirled, and sometimes even clog the system.

[0009] Other such ceramics are also known from the prior art: The publication "Preparation and physical properties of the solid solutions Cu1+xMn1-xO2 (0 ≤ x ≤ 0,2)" (M. Trari, J. Töpfer et al., Journal of Solid State Chemistry 178 (2005) 2751-2758) investigates the thermal stability of crednerite in air. A reaction involving the uptake of oxygen to form spinel and tenorite is observed. With increasing temperature, a reaction from spinel and tenorite back to crednerite is observed, with the release of oxygen.

[0010] German patent DE 10 2012 025 205 A1 discloses a ceramic oxygen storage material that has spinel and / or delafossite phases and can reactively absorb and release oxygen. The patent application teaches the use of this oxygen storage material for oxygen generation over very long process times of 1 to 2 hours.

[0011] EP 2 853 306 A1 discloses a system for using oxygen storage materials in so-called high-temperature PSA systems. The teaching mentioned therein aims at the use of perovskite ceramics as oxygen storage materials.

[0012] US Patent 6,361,584 B1 discloses a method and system for using various oxide ceramic materials for oxygen separation from a feed gas stream in a high-temperature PSA plant. The teaching disclosed therein addresses a wide variety of ceramic structures. All of these structures are characterized by being non-reactive ceramics. In particular, they do not undergo phase transitions and can therefore only absorb and release oxygen within the limits of their phase widths.

[0013] US patent 2010 278719 A1 discloses a process in which a copper-free material consisting of iron-manganese oxides is used for high-temperature oxygen production.

[0014] US 2015 290627 A1 and US 2016 361711 A1 disclose copper-manganese spinels as oxygen storage materials and their use for exhaust aftertreatment in motor vehicles.

[0015] The materials known to date for oxygen storage and generation exhibit several disadvantages. These are primarily due to the fact that these materials either have a relatively limited oxygen storage capacity, oxygen storage and release involve long loading and unloading times, and their energy efficiency is too low for economical use. Furthermore, these materials can only be used under very limited process conditions, unfortunately precluding universal and flexible application. Finally, they are relatively prone to wear or insufficiently corrosion-resistant, resulting in a decrease in efficiency after a certain number of process cycles and a certain period of use.

[0016] The task therefore arises to specify a material for oxygen storage or separation, its application, and a system for its use, with which the aforementioned disadvantages can be eliminated. In particular, the aim is to ensure the shortest possible process times combined with a long service life and the broadest possible range of applications.

[0017] The problem is solved by a material for storing and releasing oxygen with the features of claim 1. The dependent claims contain advantageous embodiments and configurations of the material, as well as uses and applications of the material.

[0018] According to the invention, the material for storing and releasing oxygen consists of a reactive ceramic made of copper, manganese and iron oxides.

[0019] According to the invention, the reactive ceramic can be introduced into a reactor vessel as a loose packing of fragments, pellets or granulated bodies on a material carrier or as an applied layer of material on a material carrier.

[0020] According to the invention, the copper, manganese and iron oxides of the reactive ceramic form different compounds with each other depending on the oxygen content bound in the material, so that individual oxides can be present side by side, but also mixed oxides or combinations of both at the same time.

[0021] As a further essential feature of the invention, the reactive ceramic has a chemical composition in which the stoichiometric ratio between the proportion of copper and the combined proportion of manganese and iron is between 0.7 / 0.3 and 0.4 / 0.6 and the stoichiometric ratio between manganese and iron is between 0.2 / 0.8 and 0.99 / 0.01.

[0022] A further essential aspect of the invention is that the reactive ceramic comprises the phases crednerite / CuMn 1-x Fe x O 2 with 0 ≤ x ≤ 0.75 and delafossite / CuFe 1-x Mn x O 2 with 0 ≤ x < 0.25, spinel / CuMn 2(1-x) Fe 2x O 4 with 0 ≤ x ≤ 1, tenorite / CuO, hausmannite / Mn 3 O 4 , cuprite / Cu 2 O , wherein the ratio of the individual phases to each other depends on the oxygen loading of the ceramic material.

[0023] According to the invention, the reactive ceramic exhibits, depending on the oxygen partial pressure of an surrounding atmosphere and / or an ambient temperature, a transition zone between a discharge limit state consisting of a three-phase crednerite / cuprite / hausmannite mixed ceramic and a loading limit state consisting of a two-phase spinel / tenorite mixed ceramic, which can be traversed any number of times. A passage through the transition zone from the discharge limit state towards the loading limit state is associated with oxygen uptake, and a passage through the transition zone from the loading limit state towards the discharge limit state is associated with oxygen release.

[0024] The direction and course of the reaction are influenced by the combination of the oxygen partial pressure of the surrounding atmosphere and the temperature of the material, with reaction times for charging and discharging the reactive ceramics ranging from a few seconds to minutes.

[0025] According to the invention, the reactive ceramic exhibits self-porosity as a result of oxygen release when passing through the transition zone towards the discharge limit state, with a porosity in the reactive ceramic ranging from 25 volume % to 50 volume %.

[0026] The material according to the invention thus consists of various copper, manganese, and iron oxides, which form different compounds with each other depending on the oxygen content of the material. Individual oxides can coexist, but mixed oxides or combinations of both can also be present simultaneously. The structures crednerite and delafossite, spinel, tenorite, hausmannite, and cuprite can occur. The ratio of the individual phases to each other depends on the oxygen loading state of the ceramic material, resulting in the aforementioned loading and discharging limit states. Between these two limit states, a transition region exists in which all intermediate states occur, depending on the oxygen loading state of the material. The ceramic is therefore a reactive ceramic because the processes of oxygen loading and oxygen discharge are associated with a structural remodeling within the ceramic.

[0027] There is therefore a gradual transition from the discharged to the charged limit state during oxygen uptake and vice versa during oxygen release. This transition is characterized by oxidation and reduction reactions of the ceramic components. In the discharge limit state, the material consists essentially of the phases crednerite, hausmannite, and cuprite, and in the charging limit state, essentially of the phases spinel and tenorite. The transition region is thus bounded in its limit states by a mixed system that is, on the one hand, three-phase and, on the other hand, two-phase.

[0028] According to the invention, as mentioned, the reactive ceramic has a chemical composition in which the stoichiometric ratio between the proportion of copper and the combined proportion of manganese and iron is between 0.7 / 0.3 and 0.4 / 0.6 and the stoichiometric ratio between manganese and iron is between 0.2 / 0.8 and 0.99 / 0.01.

[0029] The reactive ceramic thus formed exhibits a high oxygen storage capacity of 4.0 to 6.5 wt% compared to known oxygen storage materials.

[0030] In one embodiment of the reactive ceramic, the passage through the transition zone between the discharge limit state and the charging limit state in both directions is possible in a temperature range of 400°C to 1200°C.

[0031] As mentioned, according to the invention, the reactive ceramic exhibits self-porosity as a result of oxygen release when passing through the transition region towards the discharge limit state, with a porosity in the reactive ceramic ranging from 25 volume % to 50 volume %.

[0032] This self-porosity according to the invention prevents compaction and agglomeration of the reactive ceramic and, in conjunction with the charging and discharging with oxygen, simultaneously ensures a structure that is exceptionally conducive to gas exchange with the surrounding atmosphere. Importantly, this ensures that the functionality of the reactive ceramic is maintained even during continuous operation and that it essentially regenerates itself.

[0033] In a further embodiment, the reactive ceramic contains an addition of up to 25 mol% aluminum, nickel, cobalt, chromium, and / or lithium. These additions allow for advantageous modification of the reactive ceramic's corrosion resistance to various gases, as well as the ability to tailor its temperature stability and reaction characteristics to specific requirements.

[0034] Furthermore, the reactive ceramic is corrosion-resistant to gases containing carbon oxides and / or sulfur oxides. It can therefore be used in harsh or corrosive environments.

[0035] The reactive ceramic can be used in various ways. According to the invention, the reactive ceramic is introduced into a reactor vessel as a loose packing of fragments, pellets or granulated bodies onto a material carrier or applied as a material layer onto a material carrier.

[0036] In reactive ceramics, the passage through the transition zone from the loading limit state towards the discharge limit state can also be induced by applying a vacuum or by exposure to water vapor and / or other oxygen-poor or oxygen-free gases.

[0037] Reactive ceramics can be used for various purposes.

[0038] One possible application is in a device for generating inert gas from an oxygen-containing gas mixture, in particular from air, wherein the reactive ceramic is used to remove the oxygen content present in the gas mixture.

[0039] Another possible use is in a device for extracting oxygen from an oxygen-containing gas mixture, in particular from air, wherein the reactive ceramic is used to extract and temporarily store the oxygen and to subsequently release the oxygen into a separate gas volume.

[0040] Furthermore, the use of the reactive ceramic in a device for oxygen enrichment and oxygen depletion in gas mixtures, especially in air, is possible.

[0041] It is also possible to use the reactive ceramic in a device for the catalytic flameless combustion of gaseous fuels.

[0042] A facility for the use of the the aforementioned The system, which uses reactive ceramics for storing and releasing oxygen, comprises a reactor with a reaction chamber filled with the reactive ceramic, a heating system for heating the reaction chamber, a valve assembly for controlling the gas flow into and out of the reaction chamber and / or for separating the usable gas from the exhaust gas, and pumps for generating positive and / or negative pressure in the reaction chamber. In one embodiment of the system, at least two reactors are connected in parallel and operated in opposite directions, enabling continuous oxygen separation through the counter-rotating reactions.

[0043] The material for storing and releasing oxygen will be described in more detail below using exemplary embodiments and uses.

[0044] The following serve to illustrate this. Figure 1 and 2 It shows: Fig. 1 an exemplary plant with a reactor containing the reactive ceramic, Fig. 2 An exemplary circuit consisting of two reactors operating alternately.

[0045] The material for storing and releasing oxygen is a ceramic oxygen storage material based on copper, manganese, and iron oxides. This oxygen storage material is a reactive mixed ceramic with a variable phase composition. When the phase composition changes, it undergoes a transition, absorbing or releasing oxygen. The current phase composition of the reactive mixed ceramic thus depends on the oxygen content, i.e., the oxygen loading state of the storage material. Two limit states can be defined for the reactive mixed ceramic, which encompass a transition range in which oxygen loading and unloading can occur. These limit states are, firstly, the discharge limit state and, secondly, the loading limit state.In the discharge limit state, the reactive ceramic is maximally discharged and has released all possible oxygen, and in the loading limit state, the reactive ceramic is maximally loaded and can no longer absorb any more oxygen.

[0046] Both the discharge limit state and the loading limit state are clearly identifiable in reactive ceramics by the presence of distinct phases and can be defined by these phases. In the material presented here, the discharge limit state is defined by the phases crednerite, hausmannite, and cuprite, with a possible proportion of delafossite, while the loading limit state is defined by the phases spinel and tenorite. The transition between the two limit states is gradual and is determined by the oxygen partial pressure of the surrounding atmosphere and the temperature of the oxygen storage material. It is accompanied by oxygen uptake or release from the surrounding atmosphere.

[0047] The oxygen storage material has a wide range of applications, such as the separation of oxygen from oxygen-containing gas mixtures. By using this oxygen storage material, it is possible to separate air into oxygen and oxygen-free inert gas (i.e., nitrogen, along with its noble and trace gas components) and to provide both the oxygen and the inert gas separately. It is also possible to enrich or deplete air or other gas mixtures with oxygen.

[0048] The use of the ceramic oxygen storage material is made possible by a system consisting at least of the ceramic oxygen storage material, a reactor, heater, heat exchanger, gas pump, vacuum pump, valves, and a control unit. This system functions in various configurations as an oxygen generator, nitrogen generator, air separation unit, or oxygen metering unit.

[0049] The material consists of various copper, manganese, and iron oxides, which form different compounds with each other depending on the oxygen content bound within the material. Individual oxides can exist side by side, as well as mixed oxides or combinations of both simultaneously. The following structures can occur: crednerite (CuMn 1-x Fe x O 2 with 0 ≤ x ≤ 0.75) and delafossite (CuFe 1-x Mn x O 2 with 0 ≤ x < 0.25) – collectively known as Cu(Mn,Fe)O 2 ; spinel Cu(Mn,Fe) 2 O 4 (CuMn 2(1-x) Fe 2x O 4 with 0 ≤ x ≤ 1 ); tenorite (CuO); hausmannite (Mn 3 O 4 ); and cuprite (Cu 2 O). The ratio of the individual phases to each other depends on the loading state of the ceramic material.

[0050] The phases copper-manganese crednerite (CuMnO₂) and copper-iron delafossite (CuFeO₂) can exist individually side by side or as mixed phases Cu(Mn,Fe)O₂. If an increasing proportion of manganese is added to delafossite, it gradually transforms into a crystallographically distorted crednerite. If one starts with pure copper-manganese crednerite and gradually adds iron, it gradually transforms into delafossite. This results in a continuous solid solution series between crednerite and copper-iron delafossite.

[0051] According to the invention, crednerite is now used, whereby a higher oxygen storage capacity of the reactive ceramic is achieved when using crednerite compared to delafossite.

[0052] Reactive ceramics can exist as oxygen storage materials in two limiting states: the discharge limiting state and the charging limiting state. Between these two limiting states, all intermediate states exist, depending on the material's state of charge. Thus, there is a continuous transition from the discharged to the charged limiting state, both during oxygen uptake and vice versa during oxygen release. This transition is characterized by oxidation or reduction reactions of the ceramic components. The material is therefore a reactive ceramic in which oxygen is absorbed via chemical bonds or released by breaking these bonds.

[0053] In the discharge limit state, the material consists of the phases crednerite, hausmannite, and cuprite with a certain, but not necessarily present, proportion of delafossite, while in the loading limit state, the phases spinel and tenorite are detectable. The reactive ceramic thus undergoes a transition between a three-phase and a two-phase state during oxygen uptake and release.

[0054] Specifically, the following reactions occur between the discharge limit state and the charging limit state in the reactive ceramic with oxygen uptake and release: with 0 ≤ x ≤ 0.5.

[0055] The reaction equation describes, from left to right, the charging and thus the passage through the transition region towards the charging limit state, and from right to left, the discharging and thus the passage through the transition region towards the discharging limit state.

[0056] The molar ratio between manganese and iron in the ceramic (Mn,Fe) can be adjusted depending on the application and requirements of the material by the molar ratio of the starting materials in the production of the oxygen storage material according to the invention with an iron content of 0 ≤ Fe / (Fe+Mn) ≤ 1 (molar).

[0057] The composition, i.e., the phase ratio of the discharged reactive ceramic and thus the value of the variable x, depends on the conditions of the discharge (temperature, oxygen partial pressure and time) as well as the molar ratio of the elements iron and manganese, i.e. Fe / (Fe+Mn).

[0058] One embodiment of the reactive ceramic involves the oxygen storage material having an excess of copper in the following ratio: Cu / (Cu + Fe + Mn) > 0.5 (molar). This leads to an increase in the oxygen storage capacity of the material, as the copper plays a key role in the redox reactions involved in oxygen uptake and release.

[0059] Another way to develop reactive ceramics is to add aluminum, nickel, cobalt, chromium, lithium, or combinations thereof. This allows the temperature stability, reaction rate, oxygen storage capacity, reactivity, porosity, stability, and / or strength to be tailored to the specific requirements of an application.

[0060] The reactive ceramic oxygen storage material described here exhibits an oxygen storage capacity in the range of 4.0 to 6.5 wt% based on the mass of the discharged ceramic. Charging occurs via oxygen uptake from the surrounding atmosphere, preferably in the temperature range of 400 to 900 °C, and discharging via oxygen release to the surrounding atmosphere takes place in the temperature range of 650 to 1150 °C. At reaction temperatures of 400 to 1150 °C, reaction rates of up to 20 l O₂ / (min*kg ceramic) are achieved.

[0061] The reaction times for charging and discharging the reactive ceramic range from a few seconds to minutes; they are very short compared to the reaction times of materials known from the prior art. These reaction times can be significantly influenced by the control variables of temperature and the oxygen partial pressure of the surrounding atmosphere.

[0062] The direction and course of the reaction are influenced by the combination of factors including the oxygen partial pressure of the surrounding atmosphere and the temperature of the material. At lower temperatures and higher oxygen partial pressures, oxygen loading is favored, while at higher temperatures and lower oxygen partial pressures, oxygen discharge is favored.

[0063] It has proven very advantageous for the use of the oxygen storage material described here, especially with regard to its application for oxygen separation, to lower the partial pressure of oxygen by creating a negative pressure or applying a vacuum to the surrounding atmosphere, thereby discharging the material and releasing the oxygen from it. Furthermore, the partial pressure of oxygen can be reduced by purging the material with oxygen-poor or oxygen-free gases (e.g., Ar, CO₂, H₂O).

[0064] The loading process can be facilitated by creating an overpressure in the oxygen-containing atmosphere around the oxygen storage material.

[0065] Surprisingly, it has been shown that the oxygen storage material according to the invention undergoes a self-porosity process, which is directly caused by the incorporation and removal of oxygen and the associated reactive remodeling of the ceramic. It has been shown that an equilibrium porosity of 25 to 50 vol.% can be established over the material's service life. This porosity ensures consistent oxygen storage properties and is regenerated by the use of the reactive ceramic itself.

[0066] The corrosion resistance of the ceramic oxygen storage material has proven to be a highly advantageous property. No corrosion products are observed upon contact with carbon dioxide or sulfur oxides. This enables exceptionally versatile applications for the reactive ceramic. It can therefore be used, in particular, for oxygen enrichment or reduction in exhaust or process gases.

[0067] A further advantage of the reactive ceramic oxygen storage material according to the invention is its ease of preparation compared to other ceramic oxygen storage materials. The reactive ceramic is primarily produced from harmless copper, manganese, and iron oxides by powder and solid preparation. The embodiment of the oxygen storage material according to the invention intended for technical use is available as fragments, granulated bodies, or in the form of pellets, which can be filled as a loose bulk material into a suitable reaction chamber. It is also possible to apply the reactive ceramic as a coating to a material carrier. In such a case, a grid-like or lamellar material carrier is recommended to ensure the largest possible coated surface area.

[0068] To use the reactive ceramic oxygen storage material according to the invention, it is placed accordingly in a reaction chamber of a reactor. The reaction chamber is heated to the respective reaction temperature and supplied with the appropriate reaction-promoting atmosphere, which favors passage through the transition region in one of the two directions, i.e., to one of the two limiting states.

[0069] The use of reactive ceramic oxygen storage material for oxygen separation makes it possible to produce oxygen, technical nitrogen, or oxygen-free inert gas. Furthermore, oxygen-containing gas mixtures can be enriched or depleted of oxygen, and oxygen-free gas mixtures can also be enriched with oxygen. This application is particularly important for use in so-called oxyfuel processes and for oxygen enrichment of combustion air. The latter is used, for example, in general combustion optimization and for the combustion of low-calorific-value gases such as landfill gas or raw biogas.

[0070] Furthermore, the ceramic oxygen storage material according to the invention is suitable for catalytic flameless combustion of gaseous fuels.

[0071] The following describes a system for the use of ceramic oxygen storage material, enabling the technical utilization of the oxygen-storing properties of the reactive ceramic. The excellent oxygen-storing properties of the reactive ceramic described here allow the system to be operated for a variety of purposes: namely, oxygen extraction, gas separation, and inert gas production. All these applications are performed with equal effectiveness, which explains the universal applicability of the system and, above all, of the reactive ceramic described here.

[0072] The Figure 1 and 2 Here are exemplary designs for such systems. Fig. 1 This shows a system with a reactor and thus a reaction chamber. Fig. 2 shows a connection of two reactors and reaction chambers.

[0073] The respective functional core of the in the Figure 1 and 2 The depicted system forms a reaction chamber, which can consist of one or more reactors 2. Each reactor 2 contains the previously described ceramic oxygen storage material 1. Within the reaction chamber, the oxygen storage material is bathed with oxygen-containing gases for charging or surrounded by a reduced pressure or vacuum for discharging, or bathed with an oxygen-free or oxygen-deficient gas. To achieve the temperature level required for the reactions within the reaction chamber, each reactor is surrounded by a heating system 3. The heating system can be operated electrically, by means of a combustion system, or with other heat sources.

[0074] The heating system 3 can be arranged around the reactor or passed through it in various ways to ensure an even distribution of heating power and optimal heating of the reaction chamber with the oxygen storage material.

[0075] In the reaction chamber, the reactive ceramic oxygen storage material 1 is placed either loosely as a bed in the form of pellets, crushed stone, or granulated bodies, with or without auxiliary devices, or as a layer of material on a material carrier. These auxiliary devices can be intermediate trays, sieves, or packing materials. The aim is to achieve optimal flowability through the material and, if necessary, to combine this with a modular reactor design.

[0076] Since the overall process of using the ceramic oxygen storage material for oxygen separation is a high-temperature process, a heat recovery / transfer system is provided at the reaction chamber. In this example, this system is designed as a heat exchanger 4. The task of this heat exchanger is to transfer the heat carried by the gases flowing out of the reaction chamber back to the incoming gases. Recuperative or regenerative systems, as well as a combination of both, are suitable for this purpose.

[0077] The reactor 2 containing the oxygen storage material 1, the heating system 3, and the heat exchanger 4 can be combined to form a reactor module. Such a reactor module constitutes a functional and structural unit within the system according to the invention for utilizing the reactive ceramic oxygen storage material for oxygen separation.

[0078] The reactor module is completely enclosed by thermal insulation 10, which minimizes heat losses and thus enables energy-efficient operation of the system according to the invention.

[0079] To introduce the required gases into the reaction chamber and generate the correct pressure therein, a gas pump 5 is provided, which can generate a continuous gas flow, the pressure of which is preferably close to ambient pressure. This incoming gas flow is controlled by a first valve 8. A second valve 7, located downstream of the reactor module in the direction of flow, controls the outgoing gas flow.

[0080] A vacuum pump 6 is provided to generate the negative pressure or vacuum in the reaction chamber and to transport the product gas out.

[0081] Downstream of the vacuum pump is a third valve 9, which enables the separation of the usable gas O2 and the exhaust gas X. This eliminates the negative effects of a switching delay or the inertia of the system when changing from loading to unloading and ensures high gas purity.

[0082] The entire system is automatically switched by an electronic control unit, but can also be manually controlled if necessary.

[0083] The system according to the invention is characterized by a wide variety of applications. It can be used as an oxygen separation system for the production of oxygen with an adjustable purity of more than 99 vol% and for the production of inert gas (i.e., nitrogen and the oxygen-free residual gas components such as argon) with an adjustable residual oxygen content of less than 1 vol%, as well as for a combination of both. Furthermore, with a further development of the system according to the invention, it is possible to generate a gas stream with an adjustable oxygen content of 0 to 100 vol%.

[0084] An advantageous embodiment of the system according to the invention is in the form of a parallel circuit consisting of several reactors or reactor modules according to Fig. 2This enables the continuous production of all gases simultaneously. Since an oxygen separation cycle consists of two sub-cycles—the charging and discharging of the oxygen storage material—a continuous oxygen separation process can be generated by operating several of these sub-cycles in reverse, alternating directions.

[0085] It has proven highly advantageous that the system shown here, using the described reactive oxygen storage material, can produce comparatively large quantities of product gases with high purity levels, despite its very small size and low operating costs, compared to systems known in the prior art. Furthermore, due to its high efficiency, the system exhibits very low specific energy consumption and therefore low operating costs for gas production. This latter advantage results, among other things, from the fact that no high-performance and energy-intensive compressed air technology is required for operating the system according to the invention, since the charging process is preferably carried out at near ambient pressure. The pump technology used can therefore preferably be implemented using small, energy-saving diaphragm pumps.

[0086] Furthermore, the aforementioned system has the advantage that, due to its design, technology and the use of small, low-noise pump technology, it causes hardly any noise emissions and can therefore also be used for soundproofed applications.

[0087] The following are possible examples of the implementation of the reactive ceramic and the corresponding system. a) Mixed series Cu-Mn-O / Cu-Mn-Fe-O / Cu-Fe-O

[0088] It has been shown that reactive ceramic oxygen storage materials based on copper, manganese, and iron oxides form a continuous series of mixtures between copper-manganese oxides and copper-iron oxides. This series can be prepared from the individual oxides CuO, Mn₂O₃, and Fe₂O₃ and investigated for their oxygen-storing and oxygen-separating properties. Surprisingly, it was found that, in principle, the entire series is suitable as an oxygen storage material. However, this is associated with different phase compositions, reaction conditions, and properties. This means that, depending on the application criteria, the material can be specifically adapted to the requirements. b) Increasing the operating temperature by adding aluminium oxide

[0089] Adding gamma-aluminum oxide to the ceramic oxygen storage material according to the invention allows its operating temperature to be raised. For example, adding 10 wt% aluminum increases the operating temperature by up to 200 K. c) Excess copper in the oxygen storage material

[0090] Adding an equal amount of tenorite to the already present oxygen storage material results in a mass loss of approximately 6.5 wt% during discharge at a temperature of 1000 °C. The oxygen storage capacity of the ceramic material can thus be further increased. d) Air separation plant

[0091] One system demonstrates the functionality of the material, process, and system. Using different compositions of oxygen storage materials, a continuous oxygen flow with a purity > 98 vol.% and a nitrogen flow with a residual oxygen content < 2 vol.% could be generated from the air.

[0092] Further embodiments are described in the dependent claims. Reference symbol list

[0093] 1 Oxygen storage material 2 Reactor 3 Heating system 4 Heat exchanger 5 Gas pump 6 Vacuum pump 7 Valve for outgoing gas flow 8 Valve for incoming gas flow 9 Valve for separating useful gas and exhaust gas 10 Thermal insulation

Claims

1. Material for storing and releasing oxygen, consisting of a reactive ceramic made of copper, manganese, and iron oxides, which can be introduced, as a loose fill of fragments, pellets, or granulated bodies on a material carrier or as an applied material layer on a material carrier, into a reactor vessel, which form different compounds with one another depending on the oxygen content bound in the material, so that individual oxides adjacent to one another, but also mixed oxides or combinations of both can be present simultaneously, wherein the reactive ceramic comprises a chemical composition, in which the substance amount ratio between the proportion of copper and the unified proportion of manganese and iron is between 0.7 / 0.3 and 0.4 / 0.6 and the substance amount ratio between manganese and iron is between 0.2 / 0.8 and 0.99 / 0.01, wherein the reactive ceramic comprises the phases crednerite / CuMn1-xFexO2 with 0 ≤ x ≤ 0.75 and delafossite / CuFe1-xMnxO2 with 0 ≤ x ≤ 1, spinel / CuMn2(1-x)Fe2xO4 with 0 ≤ x ≤ 1, tenorite / CuO, hausmannite / Mn3O4, cuprite / Cu2O, wherein the ratio of the individual phases to one another depends on the load state of the ceramic material with oxygen, wherein the reactive ceramic, depending on the oxygen partial pressure of a surrounding atmosphere, and / or an ambient temperature, displays a transition range which can be passed through arbitrarily often between on unloaded limit state made up of a three-phase crednerite / cuprite / hausmannite mix ceramic and a loaded limit state made up of a two-phase spinel / tenorite mixed ceramic, wherein a pass through the transition range from the unloaded limit state in the direction of the loaded limit state is connected to an oxygen absorption and a pass through the transition range from the loaded limit state in the direction of the unloaded limit state is connected to an oxygen release, wherein the reaction direction and the reaction course is influenced by the combination of the influencing variables of the oxygen partial pressure of the surrounding atmosphere and the temperature of the material, wherein the reaction times for loading and unloading the reactive ceramics are in the range of a few seconds to minutes, and the reactive ceramic has a self-porosification as a result of the oxygen discharge upon the pass through the transition range in the direction of the unloaded limit state, wherein a porosity in the range of 25 vol.-% to 50 vol.-% results in the reactive ceramic.

2. Material according to claim 1, characterized in that the reactive ceramic has an oxygen storage capacity of 4.0 to 6.5 mass-%.

3. Material according to any one of the preceding claims, characterized in that in the reactive ceramic, the pass through the transition range between the unloaded limit state and the loaded limit state in both directions can be carried out in a temperature range from 400°C to 1200°C.

4. Material according to any one of the preceding claims, characterized in that the reactive ceramic comprises an additive of up to 25 mol-% aluminum, nickel, cobalt, chromium, and / or lithium.

5. Material according to any one of the preceding claims, characterized in that the reactive ceramic is corrosion resistant to gases containing carbon oxides and / or sulfur oxides.

6. Material according to any one of the preceding claims, characterized in that in the reactive ceramic, the pass through the transition range from the loaded limit state in the direction of the unloaded limit state can be induced by applying a vacuum or by subjecting it to water vapor and / or other oxygen-poor or oxygen-free gases.

7. Use of a reactive ceramic according to any one of claims 1 to 6 in a device for producing inert gas from an oxygenated gas mixture, wherein the reactive ceramic is used to withdraw the oxygen component present in the oxygenated gas mixture.

8. Use of a reactive ceramic according to any one of claims 1 to 6 in a device for obtaining oxygen from an oxygenated gas mixture, wherein the reactive ceramic is used to withdraw and temporarily store the oxygen and to subsequently discharge the oxygen into a separate gas volume.

9. Use of a reactive ceramic according to any one of claims 1 to 6 in a device for oxygen regulation in a gas mixture, wherein the reactive ceramic is used, by way of the withdrawal, temporary storage, and / or discharge of the oxygen, for an oxygen depletion and / or oxygen enrichment in the gas mixture.

10. Use of a reactive ceramic according to any one of claims 1 to 6 in a device for catalytic flameless combustion of gaseous fuels.

11. Facility for the use of a reactive ceramic for storing and releasing oxygen according to any one of claims 1 to 6, containing a reactor (2) having a reaction chamber filled with the reactive ceramic (1), a heating system (3) for heating the reaction chamber, a valve device for controlling a gas flow (7, 8) flowing into and out of the reaction chamber and / or for separating useful gas and exhaust gas (9), a gas pump (5) for generating a gas flow in the reaction chamber, and a vacuum pump (6) for generating a negative pressure in the reaction chamber.

12. Facility according to claim 11, characterized in that at least two reactors (2), which are connected in parallel and are operated in opposition in their work cycle, are provided, wherein a continuous oxygen separation can be carried out by the reactions operated in opposition.