Long-life high-oxygen decoupling oxygen carrier and preparation method and application thereof

Abstract

The application discloses a long-life high-oxygen decoupling oxygen carrier and a preparation method and application thereof, and comprises the following steps: S1, precursor preparation; S2, solid-phase reaction calcination; S3, phase separation induction calcination; S4, cyclic activation decomposition; and S5, densification re-calcination. The oxygen carrier prepared by the application utilizes the alpha-Al2O3 skeleton formed by high-temperature calcination to provide extremely high mechanical strength, and through a specific activation step, copper species is completely released from the spinel lattice, and the excellent oxygen decoupling capacity of CuO is restored. The oxygen carrier can release about 50% of the total oxygen carrying capacity within 2 minutes under a nitrogen atmosphere at 900 DEG C, and is suitable for the fields of chemical looping oxygen decoupling combustion and chemical looping heat storage.

Description

Technical Field

[0001] This invention specifically relates to the fields of energy, chemical engineering and materials science and technology, and in particular to a long-life, high-oxygen decoupled oxygen carrier, its preparation method and application. Background Technology

[0002] Currently, chemical looping combustion (CLC) is limited by the slow gasification kinetics of solid fuels, making it difficult to achieve efficient conversion. However, existing technologies propose chemical looping oxygen decoupled combustion (CLOU), which releases gaseous O2 through oxygen decoupling of the oxygen carrier, transforming the solid-solid reaction into rapid gas-solid combustion, significantly improving efficiency. Simultaneously, chemical looping thermal storage (CLHS) utilizes the high enthalpy change of metal oxides to achieve high-density thermal storage (1000–2000 MJ / m³). 3 Copper-based materials are ideal candidates for CLOU / CLHS due to their theoretical oxygen carrying capacity of 21wt% and reaction enthalpy change of 263kJ / molO2. However, they tend to form a thermodynamically stable CuAl2O4 spinel phase with Al2O3 support at temperatures above 800℃. This phase hardly releases oxygen within the range of 850–950℃, forming "dead copper" and resulting in loss of activity.

[0003] Traditional preparation methods face a dilemma: low-temperature calcination suppresses spinel formation but fails to yield high-strength α-Al₂O₃ with poor wear resistance; high-temperature calcination enhances mechanical stability but exacerbates spinel formation. The synergistic regulation of activity and stability has become a key bottleneck for the industrialization of copper-based oxygen carriers.

[0004] Therefore, this application proposes a long-life, high-oxygen decoupled oxygen carrier, its preparation method, and its application. Summary of the Invention

[0005] To overcome the problem that existing copper-based oxygen carriers easily form difficult-to-decompose copper-aluminum spinel at high temperatures, resulting in poor oxygen decoupling performance and difficulty in balancing mechanical strength, a long-life oxygen carrier with high oxygen decoupling, its preparation method, and its application are proposed.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a long-life, high-oxygen decoupled oxygen carrier includes the following steps: S1: Precursor preparation: copper-containing precursor is impregnated onto an alumina support and dried to obtain precursor material particles; S2: Solid-state reaction calcination. The precursor material obtained in S1 is placed in a muffle furnace for the first heat treatment at a temperature of 600℃-900℃ for 4-6 hours, so that the copper and aluminum components can react in a solid-state reaction to form copper aluminate spinel phase, thus obtaining the intermediate material. S3: Phase separation induced calcination, the intermediate material containing copper aluminate obtained in S2 is subjected to a second heat treatment at a temperature of 1000℃-1200℃ to induce partial phase separation of copper aluminate; S4: Cyclic activation and decomposition. The material obtained in S3 is subjected to chemical looping combustion oxidation-reduction cycle reaction in a fluidized bed reactor at a temperature of 900℃-950℃. This allows the material to undergo multiple oxidation-reduction cycles to fully decompose the residual copper aluminate and form independent copper oxide and aluminum oxide. S5: Densification and reheating. The material treated by S4 is subjected to a third heat treatment at a temperature of 1000℃-1200℃. Copper species are used to promote the shrinkage and densification of the alumina lattice, resulting in the final high-hardness copper-based oxygen carrier.

[0007] Furthermore, in S4, the oxidation-reduction cycle is a gas-solid reaction, and the reducing gas used contains hydrogen, while the oxidizing gas contains oxygen or air.

[0008] Based on the aforementioned scheme, in S4, the number of oxidation-reduction cycles is 15-25.

[0009] As a further embodiment of the present invention, in processes S3 and S5, the calcination time is 1 hour to 6 hours.

[0010] A long-life, high-oxygen decoupled oxygen carrier is a product prepared using the aforementioned oxygen carrier preparation method.

[0011] Based on the aforementioned scheme, the oxygen carrier is composed of CuO and α-Al2O3, with the standard being that no diffraction peak of CuAl2O4 phase can be detected by X-ray diffraction analysis.

[0012] As a further embodiment of the present invention, after the oxygen carrier is fully oxidized, it has the ability to spontaneously decouple oxygen under an inert atmosphere at 900°C, and releases 45%-55% of the total oxygen load within 2 minutes.

[0013] Furthermore, the alumina matrix of the oxygen carrier is a high-temperature stable α phase.

[0014] Applications of long-life, high-oxygen decoupled oxygen carriers in the fields of chemical looping oxygen decoupled combustion or chemical looping thermal storage.

[0015] The beneficial effects of this invention are as follows: 1. Superior oxygen decoupling performance, i.e., CLOU characteristics: Traditional copper aluminate phases have almost no oxygen decoupling ability. This invention, through a unique "generation-decomposition-activation" process route, forcibly "squeezes" copper oxide out of the stable copper aluminate lattice. Experiments show that the oxygen carrier prepared by this invention can spontaneously release about 50% of its total oxygen load within 2 minutes at 900℃ in an inert atmosphere, such as nitrogen, i.e., CuO is converted to Cu2O. The oxygen release rate is extremely fast, perfectly solving the problem of reduced oxygen release capacity caused by copper-aluminum interaction.

[0016] 2. Extremely high mechanical strength and long service life: After high-temperature calcination at 1000-1200℃, the alumina matrix in the oxygen carrier is completely transformed into the thermodynamically stable α–Al2O3, resulting in extremely high hardness. Combined with the stable microstructure after cyclic activation, this oxygen carrier exhibits extremely low wear rate in high-speed fluidized beds, making it suitable for long-term industrial operation.

[0017] 3. Dual application areas: This material is not only suitable for solid fuels, such as coal and biomass, chemical looping oxygen decoupling combustion, but also has a huge reaction enthalpy change due to its efficient and reversible transformation based on CuO / Cu2O. It is also suitable for high-temperature chemical looping thermal storage systems to achieve efficient storage and release of thermal energy.

[0018] 4. Anti-sintering and high dispersibility: Unlike simple physical mixing or low-temperature impregnation, this invention first allows copper to enter the aluminum lattice to form spinel, and then precipitates it through high temperature and activation. This "in-situ precipitation" mechanism makes the CuO active sites more uniformly distributed on the alumina framework, effectively preventing the agglomeration and sintering of copper particles at high temperatures, and ensuring stable performance after multiple cycles. Attached Figure Description

[0019] Figure 1 XRD patterns of samples taken after different cycles following the first high-temperature calcination; Figure 2 Thermogravimetric analysis (TGA) of the oxygen carrier material of this invention in a fluidized bed after 24 hours of long-term circulation; Figure 3 This is a thermogravimetric analysis of oxygen decoupling of the oxygen carrier of the present invention under a nitrogen atmosphere at 920°C. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0021] Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this patent, and should not be construed as limiting this patent.

[0022] In the description of this patent, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection or setting, a detachable connection or setting, or an integral connection or setting. Those skilled in the art can understand the specific meaning of the above terms in this patent according to the specific circumstances.

[0023] Reference Figure 1-3 A method for preparing a long-life, high-oxygen decoupled oxygen carrier, comprising: S1: Precursor preparation; Weigh 100g of γ-Al2O3 microspheres and 80g of Cu(NO3)2·6H2O in a mass ratio of 1:0.8; dissolve copper nitrate in 500mL of deionized water, add alumina microspheres for impregnation, and stir in a water bath until the water is completely evaporated to obtain a dried precursor.

[0024] S2: Solid-phase reaction calcination; The dried precursor obtained from S1 was placed in a muffle furnace and heated to 800°C at 5°C / min, and held at 800°C for 5 h. Then it was cooled to room temperature at 5°C / min and the particles were removed. This step was intended to remove nitrate and promote the formation of CuAl2O4.

[0025] S3: Phase separation induced calcination; After cooling, the material was transferred to a high-temperature muffle furnace and heated to 900°C at 5°C / min, then to 1200°C at 2°C / min, and held at 1200°C for 2 hours. After that, the temperature was reduced to 900°C at 2°C / min, and then the furnace was stopped for rapid cooling. At this time, some CuAl2O4 began to decompose.

[0026] S4: Cyclic activation decomposition; The above-mentioned particles were placed in a fluidized bed reactor with the following fluidization parameters: furnace temperature 920℃, reducing gas H2, oxidizing gas O2, and purge gas and carrier gas N2. The N2 flow rate was 7.5 L / min, the O2 flow rate was 1.0 L / min, and the H2 flow rate was 500 mL / min. Twenty redox cycles were performed.

[0027] S5: Densification and re-firing; The S4-treated material was subjected to a third heat treatment at a temperature of 1000℃-1200℃ to promote the shrinkage and densification of the alumina lattice using copper species, resulting in the final high-hardness copper-based oxygen carrier.

[0028] Test results: The XRD pattern of the final product is attached. Figure 1 The results showed that the CuAl2O4 diffraction peaks disappeared, and only sharp α–Al2O3 and CuO diffraction peaks were observed.

[0029] The oxygen carrier was subjected to thermogravimetric analysis (TGA) in a 900°C N2 gas stream after complete oxidation. The results are attached. Figure 3 The material showed a rapid decrease in mass within 2 minutes, and calculations showed that it released approximately 52% of the total theoretical oxygen load, demonstrating an excellent oxygen decoupling rate.

[0030] Compressive strength tests showed that the average crushing strength of the particles exceeded 50N, and the wear rate was <0.05% / h in a 24-hour fluidized bed abrasion test. (See attached...) Figure 2 As shown.

[0031] XRD characterization Materials with different Redox cycle numbers after the second calcination were characterized by XRD, such as... Figure 2 As shown, in the initial stage of the reaction, the material contains a large number of copper aluminate diffraction peaks. However, after approximately 20 cycles, the material contains almost no copper aluminate phase, while the peak heights of copper oxide and aluminum oxide phases increase. This indicates that after about 20 cycles, the copper aluminate in the material almost completely separates into aluminum oxide and copper oxide.

[0032] Long redox performance The prepared oxygen carrier underwent a redox cycle test lasting 24 hours. The test was conducted on an analytical instrument combining a fluidized bed and a thermogravimetric analyzer. The reducing gas used was H2, the oxidizing gas was O2, and both the purge gas and carrier gas were N2. The N2 flow rate was 7.5 L / min, the O2 flow rate was 1.0 L / min, the H2 flow rate was 500 mL / min, and the furnace temperature was 920 °C.

[0033] Characterization tests of oxygen carriers - compressive strength test The particles after cyclic activation (step S4) and before the third calcination (step S5), as well as the particles after the third calcination (step S5), were characterized using a compressive strength tester. Three particles from each condition were randomly tested and designated as test group 1-1, test group 1-2, test group 1-3, test group 1-4, test group 1-5, and test group 1-6, respectively. The comparison showed that the material hardness was significantly improved after the third calcination.

[0034] The results of the compressive strength test are shown in Table 1.

[0035] Table 1. Particle strength test in Example 1 ; Oxygen decoupling performance The oxygen decoupling performance of the prepared oxygen carrier was tested. A certain weight of material was weighed and placed in a fluidized bed thermogravimetric analyzer. At 920℃, an oxygen-nitrogen-hydrogen-nitrogen gas cycle was introduced to allow the material to react fully, and the theoretical oxygen carrying capacity (ag) was calculated. Then, oxygen was introduced to fully oxidize the material, followed by switching to nitrogen. It was observed that the material mass decreased by approximately bg within two minutes, b / a ≈ 51.8%. This indicates that the material possesses good oxygen decoupling ability, and that spontaneous oxygen decoupling under an inert atmosphere can reach approximately 50% of its theoretical oxygen carrying capacity.

[0036] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a long-life, high-oxygen decoupled oxygen carrier, characterized in that, Includes the following steps: S1: Precursor preparation: copper-containing precursor is impregnated onto an alumina support and dried to obtain precursor material particles; S2: Solid-state reaction calcination. The precursor material obtained in S1 is placed in a muffle furnace for the first heat treatment at a temperature of 600℃-900℃ for 4-6 hours, so that the copper and aluminum components can react in a solid-state reaction to form copper aluminate spinel phase, thus obtaining the intermediate material. S3: Phase separation induced calcination, the intermediate material containing copper aluminate obtained in S2 is subjected to a second heat treatment at a temperature of 1000℃-1200℃ to induce partial phase separation of copper aluminate; S4: Cyclic activation and decomposition. The material obtained in S3 is subjected to chemical looping combustion oxidation-reduction cycle reaction in a fluidized bed reactor at a temperature of 900℃-950℃. This allows the material to undergo multiple oxidation-reduction cycles to fully decompose the residual copper aluminate and form independent copper oxide and aluminum oxide. S5: Densification and reheating. The material treated by S4 is subjected to a third heat treatment at a temperature of 1000℃-1200℃. Copper species are used to promote the shrinkage and densification of the alumina lattice, resulting in the final high-hardness copper-based oxygen carrier.

2. The method for preparing a long-life, high-oxygen decoupled oxygen carrier as described in claim 1, characterized in that: In S4, the oxidation-reduction cycle is a gas-solid reaction, and the reducing gas used contains hydrogen, while the oxidizing gas contains oxygen or air.

3. The method for preparing a long-life, high-oxygen decoupled oxygen carrier as described in claim 1, characterized in that: In S4, the number of oxidation-reduction cycles is 15-25.

4. The method for preparing a long-life, high-oxygen decoupled oxygen carrier as described in claim 1, characterized in that: In processes S3 and S5, the calcination time is 1 hour to 6 hours.

5. A long-life, high-oxygen decoupled oxygen carrier, characterized in that: The oxygen carrier is a product prepared by the oxygen carrier preparation method according to any one of claims 1-4.

6. The long-life, high-oxygen decoupled oxygen carrier as described in claim 5, characterized in that: The oxygen carrier is composed of CuO and α-Al2O3, and the standard is that no diffraction peak of CuAl2O4 phase can be detected by X-ray diffraction analysis.

7. The long-life, high-oxygen decoupled oxygen carrier as described in claim 5, characterized in that: After being fully oxidized, the oxygen carrier has the ability to spontaneously decouple oxygen under an inert atmosphere at 900°C, releasing 45%-55% of the total oxygen load within 2 minutes.

8. The long-life, high-oxygen decoupled oxygen carrier as described in claim 5, characterized in that: The alumina matrix of the oxygen carrier is a high-temperature stable α phase.

9. The application of a long-life, high-oxygen decoupled oxygen carrier as described in claim 5 in the fields of chemical looping oxygen decoupled combustion or chemical looping thermal storage.

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