CN114229910A - Calcium-iron dual-function composite oxygen carrier and large-scale preparation method thereof - Google Patents

Calcium-iron dual-function composite oxygen carrier and large-scale preparation method thereof Download PDF

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CN114229910A
CN114229910A CN202111315798.5A CN202111315798A CN114229910A CN 114229910 A CN114229910 A CN 114229910A CN 202111315798 A CN202111315798 A CN 202111315798A CN 114229910 A CN114229910 A CN 114229910A
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oxygen carrier
cafe
oxygen
calcium
iron
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郭庆杰
韩梓恒
马晶晶
郭欣桐
袁妮妮
康慧芬
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Ningxia University
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G49/00—Compounds of iron
    • C01G49/0018—Mixed oxides or hydroxides
    • C01G49/0036—Mixed oxides or hydroxides containing one alkaline earth metal, magnesium or lead
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/002—Mixed oxides other than spinels, e.g. perovskite
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/78—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with alkali- or alkaline earth metals
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
    • C10J3/00—Production of combustible gases containing carbon monoxide from solid carbonaceous fuels
    • C10J3/72—Other features
    • C10J3/725—Redox processes
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/30—Three-dimensional structures
    • C01P2002/32—Three-dimensional structures spinel-type (AB2O4)
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/80—Particles consisting of a mixture of two or more inorganic phases
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
    • C10J2300/00—Details of gasification processes
    • C10J2300/09—Details of the feed, e.g. feeding of spent catalyst, inert gas or halogens
    • C10J2300/0983—Additives
    • C10J2300/0996—Calcium-containing inorganic materials, e.g. lime
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/50—Improvements relating to the production of bulk chemicals
    • Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts

Abstract

The invention relates to the technical field of large-scale preparation of oxygen carriers in chemical looping gasification and chemical looping hydrogen production systems, in particular to a calcium-iron dual-functional composite oxygen carrier and a large-scale preparation method thereof. The method is characterized in that: the oxygen carrier is made of CaFe with a spinel structure2O4And Ca of double perovskite structure2Fe2O5Composition of and wherein CaFe2O4：Ca2Fe2O5The mass ratio of (1): 0.5-4. The composite oxygen carrier provided by the invention has the double functions of oxygen carrying and catalysis. The oxygen carrier developed is CaFe with spinel structure2O4Ca of double perovskite structure2Fe2O5Has the advantages of high reaction rate, high oxygen carrying capacity and stable cycle performance, and can be used for treating CO2Decomposition ofHas the promoting effect, and can prepare high-concentration hydrogen-rich synthesis gas in the coal chemical looping gasification technology.

Description

Calcium-iron dual-function composite oxygen carrier and large-scale preparation method thereof
Technical Field
The invention relates to the technical field of large-scale preparation of oxygen carriers in chemical looping gasification and chemical looping hydrogen production systems, in particular to a calcium-iron dual-functional composite oxygen carrier and a large-scale preparation method thereof.
Background
Along with the increasing consumption of fossil energy, the development of a cleaner and more efficient utilization mode of fossil energy is always a key problem concerned by scholars at home and abroad. Chemical chain gasification is a novel gasification technology, and the oxygen transfer process is completed by utilizing lattice oxygen or molecular oxygen released by an oxygen carrier, so that air separation equipment is not needed, and the equipment cost is reduced to a great extent; and high-quality synthesis gas can be produced by adjusting the mixing ratio of the oxygen carrier and the fuel. Meanwhile, the oxygen carrier can realize the self-heating operation of the whole reaction system through the circulation between the fuel reactor and the air reactor without providing additional heat. Therefore, the development of oxygen carriers with excellent reaction performance, excellent cycling stability and low cost is the key of the chemical-looping gasification technology.
So far, most oxygen carriers are mainly composed of transition metal elements in the fourth period of the periodic table, such as: fe2O3、CuO、CaSO4And the like. The reaction performance of the iron-based oxygen carrier is poor, the copper-based oxygen carrier is easy to sinter, and the quality of the synthesis gas can be influenced by sulfur-containing gas released in the reaction process of the calcium-based oxygen carrier. In order to overcome the defect of the single metal oxygen carrier, the double metal oxygen carrier is produced. In recent years, CaFe2O4With Ca2Fe2O5Oxygen carrier for its combination of CaO and Fe2O3The advantages of the two metal oxides are widely concerned in the chemical-looping gasification and the chemical-looping hydrogen production processes. However, the conventional calcium-iron oxygen carrier prepared by the coprecipitation method, the sol-gel method and the impregnation method usually adopts metal nitrate as a raw material, and a coprecipitator and a gel agent are added to prepare a precursor, so that the preparation period is long, the raw material is expensive, and the oxygen carrier is prepared by the methodPoor cycle stability, insufficient mechanical strength and the like. According to the method, low-price ores are used as raw materials, the raw materials are directly put into a colloid mill to be uniformly mixed, an oxygen carrier precursor is prepared without extra additives, and oxygen carrier particles are obtained after suction filtration, calcination and crushing. Liu et al found Ca prepared by sol-gel method2Fe2O5The oxygen carrier has the phenomenon of serious abrasion along with the increase of the cycle number in the experimental process, so that the cycle stability of the oxygen carrier is poor. Hu et al found Ca prepared by the impregnation method2Fe2O5The oxygen carrier gradually shows phase separation along with the increase of the cycle number to generate Fe2O3The performance in oxygen carriers is severely affected. Therefore, the method which is simple in development process and can be used for preparing the calcium-iron oxygen carrier with stable performance on an industrial scale has important practical significance.
Disclosure of Invention
The invention aims to provide a calcium-iron dual-functional composite oxygen carrier with dual functions of oxygen carrying and catalysis, and has the advantages of high reaction rate, high oxygen carrying capacity and stable cycle performance;
the second purpose of the invention is to provide a large-scale preparation method of the oxygen carrier.
A calcium-iron bifunctional composite oxygen carrier is characterized in that: the oxygen carrier is CaFe with a spinel structure2O4Or Ca of a double perovskite structure2Fe2O5。
A calcium-iron bifunctional composite oxygen carrier is characterized in that: the oxygen carrier is made of CaFe with a spinel structure2O4And Ca of double perovskite structure2Fe2O5Composition of and wherein CaFe2O4：Ca2Fe2O5The mass ratio of (1): 05-4.
A large-scale preparation method of a calcium-iron bifunctional composite oxygen carrier is characterized by comprising the following steps:
(1) preparation of CaFe2O4: according to n (Fe)2O3)/n(CaCO3)＝2-3:1，Putting limestone and iron ore into a feeder; adding water, feeding into a colloid mill, and uniformly mixing at a certain rotating speed for a certain time; sending the mechanically mixed solution to a vacuum suction filter for suction filtration, sending a filter cake after suction filtration into a drying box, drying at the temperature of 110-120 ℃ for 12-18h, then placing in a calcining furnace for calcining at the constant temperature of 1000-1100 ℃ for 3-6h, sending an oxygen carrier to a crusher when the temperature in the furnace is reduced to room temperature, crushing and screening to obtain CaFe2O4Oxygen carrier particles;
(2) preparation of Ca2Fe2O5: according to n (Fe)2O3)/n(CaCO3) Adding limestone and hematite into a feeder at a ratio of 0.5-2: 1; adding water, feeding into a colloid mill, and uniformly mixing at a certain rotating speed for a certain time; sending the mechanically mixed solution to a vacuum suction filter for suction filtration, sending a filter cake after suction filtration into a drying box, drying at the temperature of 110-120 ℃ for 12-18h, then placing in a calcining furnace for calcining at the constant temperature of 1000-1100 ℃ for 3-6h, sending an oxygen carrier to a crusher when the temperature in the furnace is reduced to room temperature, crushing and screening to obtain Ca2Fe2O5Oxygen carrier particles;
(3) respectively taking the CaFe obtained in the step (1)2O4Oxygen carrier particles and Ca obtained in step (2)2Fe2O5Oxygen carrier particles according to CaFe2O4：Ca2Fe2O5The mass ratio of (1): 05-4, and mixing.
The certain rotating speed and time in the step (1) are specifically 2000rpm/min and 20 min; the certain rotating speed and time in the step (2) are specifically 2000rpm/min and 20 min.
The invention provides a method for preparing a calcium-iron oxygen carrier on an industrial scale, which adopts limestone and hematite which are low in price and rich in reserves as raw materials and adjusts Fe2O3With CaCO3The molar ratio of (A) to (B) of (B) is determined, namely CaFe is obtained2O4With Ca2Fe2O5An oxygen carrier. The composite oxygen carrier provided by the invention has the double functions of oxygen carrying and catalysis. The oxygen carrier developed is CaFe with spinel structure2O4Ca of double perovskite structure2Fe2O5Has the advantages of high reaction rate, high oxygen carrying capacity and stable cycle performance, and can be used for treating CO2Has the promotion function of decomposition, and can prepare high-concentration hydrogen-rich synthesis gas in the coal chemical looping gasification technology. In addition, the invention directly adopts limestone and hematite as raw materials, and other reagents are not needed in the process. The method solves the problem of adopting calcium nitrate and ferric nitrate as raw materials, and simultaneously solves the problem that a coprecipitator and a gelling agent need to be added during the preparation of the coprecipitation method and the sol-gel method, so that the whole preparation process is simple and easy to obtain, the production cost is obviously reduced, and the economic benefit is obvious in the industrial production process.
Drawings
FIG. 1 is a flow chart of a large-scale preparation of a calcium-iron composite oxygen carrier;
FIG. 2 shows the CaFe that has been produced2O4With Ca2Fe2O5XRD spectrograms of the two oxygen carriers;
FIG. 3 is a trend graph of gas content of an oxygen carrier in a coal chemical looping gasification process along with time;
FIG. 4 is a trend graph of gas content of an oxygen carrier in a coal chemical looping gasification process along with time;
FIG. 5 is a trend graph of gas content of an oxygen carrier in a coal chemical looping gasification process along with time;
FIG. 6 is an XRD (X-ray diffraction) spectrum of the composite oxygen carrier after five times of cycle tests;
fig. 7 is an XRD (X-ray diffraction) spectrum of the composite oxygen carrier after five times of cycle tests.
Detailed Description
The invention relates to the technical field of large-scale preparation of oxygen carriers in chemical looping gasification and chemical looping hydrogen production systems. The oxygen carrier of the invention takes limestone and iron ore as main raw materials, and can prepare CaFe with a spinel structure by adjusting the proportion of the limestone and the iron ore in a feeder, mechanically mixing by a colloid mill, decompressing and filtering, drying, calcining, crushing and screening2O4And Ca of a double perovskite structure2Fe2O5An oxygen carrier. The invention has the advantages of simple preparation method and good oxygen carrier preparation effectThe period is short, the prepared oxygen carrier is low in price and excellent in reaction performance, and the crystal form of the oxygen carrier can be controlled by adjusting the proportion of the raw materials. The invention provides a method for preparing a calcium-iron oxygen carrier in a large scale with industrial application prospect, which solves the problems of high cost and difficulty in batch preparation of the calcium-iron oxygen carrier prepared by a sol-gel method, a coprecipitation method and an impregnation method at present.
Further, the invention takes limestone and hematite as raw materials, and the oxygen carrier with high reactivity and high mechanical strength can be obtained after the steps of uniform mixing in a colloid mill, decompression, suction filtration, drying and calcination. The invention can realize the large-scale preparation of the calcium-iron oxygen carrier, and the prepared oxygen carrier has low price and H pair2Has better selectivity with CO, and is simultaneously suitable for the chemical-looping hydrogen production and the chemical-looping gasification process. Through performance tests, the prepared composite oxygen carrier shows high oxygen carrying capacity, the content of the synthetic gas in the gasification product is about 75%, and H is2The ratio of/CO can reach more than 5. Compared with the original gasification, CaFe2O4In the chemical chain gasification process, H in the gasification product is consumed2Promoting CO and CH in gasification products4Reducing the rate at which the syngas is consumed. Ca2Fe2O5Peripheral O2-Has better activity, is easy to escape from crystal lattices and accelerates Fe3+With Fe2+Easily form spinel-structured Fe3+Fe2+[Fe3+O4]. Oxygen deficient Fe formed in the reaction3O4With catalytic decomposition of CO2The function of (1). The method specifically comprises the following steps: first of all CO and H2With Ca2Fe2O5Reacting to reduce it to Fe3O4(ii) a Then Fe3+Then continuing reduction to generate low-valence oxide similar to FeO, and finally converting the low-valence oxide into Fe simple substance along with the increase of the reaction temperature. Oxygen vacancies CaFe formed in this process2O4-δ、CaFe2O5-δWith catalytic decomposition of CO2Especially the formation of a lower oxide pair CH similar to FeO4And CO2The reforming effect is very significant. In addition, the carrierThe carbon deposition on the surface of the oxygen body is less, and the cycle performance is stable. After ten cycles of experiments, H2The reduction amount is stabilized within 10 percent, the increase amount of CO is stabilized about 1.5 percent, and the oxygen carrier has good reaction performance and catalytic performance.
The technical scheme for realizing the invention is as follows:
the raw materials of the composite oxygen carrier are from limestone and hematite, and are formed by mechanical mixing after being calcined in different proportions; when the composite oxygen carrier is applied to chemical chain gasification, CaFe2O4And Ca2Fe2O5In cooperation with each other, the catalyst can supplement and transfer lattice oxygen and still has catalytic action after the lattice oxygen is consumed and lost. CaCO with raw material in composite oxygen carrier3、CaO、Fe2O3The composite oxygen carrier plays a role in carrying active components when being applied to chemical looping hydrogen production.
CaFe2O4The preparation method of the oxygen carrier comprises the following steps:
(1) according to n (Fe)2O3)/n(CaCO3) Putting limestone and iron ore into a feeder 2;
(2) adding water, feeding into a colloid mill, and uniformly mixing at a certain rotating speed for a certain time;
(3) sending the mechanically mixed solution to a vacuum suction filter for suction filtration, sending a filter cake after suction filtration into a drying box, drying for 12h at 110 ℃, then placing in a calcining furnace for calcining for 3h at constant temperature of 1100 ℃, sending an oxygen carrier to a crusher after the temperature in the furnace is reduced to room temperature, crushing and screening to obtain CaFe2O4Oxygen carrier particles.
Ca2Fe2O5The preparation method of the oxygen carrier comprises the following steps:
(1) according to n (Fe)2O3)/n(CaCO3) 1, putting limestone and hematite into a feeder;
(2) adding water, feeding into a colloid mill, and uniformly mixing at a certain rotating speed for a certain time;
(3) sending the mechanically mixed solution to a vacuum suction filter for suction filtration, sending the filter cake after suction filtration into a drying oven,drying at 110 deg.C for 12h, calcining at 1100 deg.C for 3h, cooling to room temperature, feeding oxygen carrier to crusher, crushing, and sieving to obtain Ca2Fe2O5Oxygen carrier particles.
Finally, the two oxygen carriers are mechanically mixed according to the mass ratio of CaFe2O4：Ca2Fe2O5Weighing 1:0.5-4, and uniformly stirring and mixing to form the composite oxygen carrier.
Ca in the invention2Fe2O5The oxygen carrier is easy to realize Fe due to the structural particularity of the oxygen carrier0To Fe3+The change of the method has obvious advantages in the process of preparing hydrogen by chemical looping, an air reactor in the process of preparing hydrogen by chemical looping can be omitted, and the whole hydrogen preparation process can be realized by only two reactors.
The invention provides a method for preparing calcium-iron oxygen carrier in scale with industrial application prospect, which is further explained by combining the attached drawings and the embodiment.
According to the preparation flow chart shown in figure 1, limestone and hematite are fed into a colloid mill through a feeder for uniform mixing, after full mixing, the mixture of colloid mill coal is fed into a vacuum suction filter for decompression suction filtration, the filter cake after suction filtration is fed into a drying box for drying at 110 ℃ for 12h, and is calcined in a calcining furnace at the constant temperature of 1100 ℃ for 3h, and finally, a crusher is used for crushing to obtain calcium-iron oxygen carrier particles.
The principle of preparing the calcium-iron oxygen carrier by using a mechanical mixing method comprises the following steps: limestone can release CO at high temperature2Formation of CaO, CaO and Fe in hematite2O3The calcium-iron oxygen carrier is obtained by reaction at high temperature, so that the aim of controlling the structure of the oxygen carrier can be achieved only by adjusting the proportion of the calcium source and the iron source in the raw materials. The specific synthetic mechanism is as follows:
1)CaCO3(s)＝CaO(s)+CO2(g)；
2)CaO(s)+Fe2O3(s)＝CaFe2O4(s)；
3)2CaO(s)+Fe2O3＝Ca2Fe2O5(s)；
the following examples are set forth to further illustrate:
example 1:
according to n (Fe)2O3)/n(CaCO3) 2, hematite (Fe)2 O 355%) (industrial pure, particle size < 100 μm, Nanjing Steel works), and limestone (CaCO)3 Content 90%) (industrial purity, unique rich mineral products of inner Mongolia with particle size less than 100 μm) was fed out of the feeder, the mixed raw materials were fed into a colloid mill, and a certain amount of water was added through a water pump, the rotation speed of the colloid mill was set to 2000rpm/min, and uniformly and mechanically mixed for 15 min. After the mechanical mixing is finished, the mixture is sent to a drying box for drying at 110 ℃ for 12h, then is placed in a calcining furnace for calcining at the constant temperature of 1100 ℃ for 3h, when the temperature in the furnace is reduced to room temperature, the oxygen carrier is sent to a crusher, and the crushing and screening particle size is 150-2O4Oxygen carrier particles.
Example 2:
according to n (Fe)2O3)/n(CaCO3) 1, hematite (Fe)2 O 355%) (industrial pure, particle size < 100 μm, Nanjing Steel works), and limestone (CaCO)3 Content 90%) (industrial purity, unique rich mineral products of inner Mongolia with particle size less than 100 μm) was fed out of the feeder, the mixed raw materials were fed into a colloid mill, and a certain amount of water was added through a water pump, the rotation speed of the colloid mill was set to 2000rpm/min, and uniformly and mechanically mixed for 15 min. After the mechanical mixing is finished, the mixture is sent to a drying box for drying for 12h at 110 ℃, then is placed in a calcining furnace for calcining for 3h at the constant temperature of 1100 ℃, the oxygen carrier is sent to a crusher when the temperature in the furnace is reduced to room temperature, and the Ca is obtained after the crushing and screening of the particle size of 150-2Fe2O5Oxygen carrier particles.
Example 3:
according to n (Fe)2O3)/n(CaCO3) 1/2, mixing hematite (Fe)2 O 355%) (industrial pure, particle size < 100 μm, Nanjing Steel works), and limestone (CaCO)3 Content 90%) (industrial purity, particle size < 100 μm special rich mineral products of inner Mongolia Co., Ltd.)) And (3) feeding the mixed raw materials into a colloid mill, adding a certain amount of water through a water pump, setting the rotating speed of the colloid mill to 2000rpm/min, and uniformly and mechanically mixing for 15 min. After the mechanical mixing is finished, the mixture is sent to a drying box for drying at 110 ℃ for 12h, then is placed in a calcining furnace for calcining at the constant temperature of 1100 ℃ for 3h, when the temperature in the furnace is reduced to room temperature, the oxygen carrier is sent to a crusher, and the CaO & Ca is obtained after the crushing and screening of the particle size is 150-2Fe2O5Oxygen carrier particles.
Example 4:
according to n (Fe)2O3)/n(CaCO3) 3, mixing hematite (Fe)2 O 355%) (industrial pure, particle size < 100 μm, Nanjing Steel works), and limestone (CaCO)3 Content 90%) (industrial purity, unique rich mineral products of inner Mongolia with particle size less than 100 μm) was fed out of the feeder, the mixed raw materials were fed into a colloid mill, and a certain amount of water was added through a water pump, the rotation speed of the colloid mill was set to 2000rpm/min, and uniformly and mechanically mixed for 15 min. After the mechanical mixing is finished, the mixture is sent to a drying box for drying for 12h at 110 ℃, then is placed in a calcining furnace for calcining for 3h at the constant temperature of 1100 ℃, the oxygen carrier is sent to a crusher when the temperature in the furnace is reduced to room temperature, and the crushing and screening particle size is 150-2O3·Ca2Fe2O5Oxygen carrier particles. And mixing the mixed oxygen carrier particles with the oxygen carrier prepared in the embodiment 3 according to the mass ratio of 1:1 to obtain the mixed oxygen carrier particles which can be used in the chemical looping hydrogen production process.
FIG. 2 shows CaFe prepared in example 1 and example 22O4With Ca2Fe2O5XRD spectrograms of the two oxygen carriers, and CaFe appears in the spectrograms2O4With Ca2Fe2O5Characteristic diffraction peak of (1). It is confirmed that the high performance oxygen carrier can be prepared according to the flow of fig. 1. The modified method has short preparation process and potential economic value. CaFe2O4With Ca2Fe2O5With provision of lattice oxygen and catalytic decomposition of CO2Of dual function, CaFe2O4With CO, H2The reaction loses lattice oxygen to generate metallic iron oxide,oxygen vacancies and Fe formed in the reaction3O4With catalytic decomposition of CO2The function of (1).
FIG. 3 shows the oxygen carriers prepared in examples 1 and 2, and the particle size of the oxygen carrier is controlled at 150-270 μm. When the gas velocity is 1500ml/min at 900 ℃, adopting nitrogen as fluidizing gas, CO is generated in the chemical chain gasification process2Trend graph of content over time. CO 22The content of the oxygen carrier increases with time and then decreases, and when the oxygen carriers prepared in the example 1 and the example 2 are adopted, the oxidation capability is weaker, so that less CO can be obviously generated2。
FIG. 4 shows the oxygen carriers prepared in examples 1 and 2, and the particle size of the oxygen carrier is controlled at 150-270 μm. And (3) a trend graph of the change of the CO content with time in the chemical chain gasification process at 900 ℃ and a gas speed of 1500ml/min by using nitrogen as a fluidizing gas. The increase of the CO content with time shows a trend of increasing firstly and then decreasing, and when the oxygen carriers prepared in the examples 1 and 2 are adopted, the solid CO yield is obviously increased due to better selectivity to CO.
FIG. 5 shows the oxygen carriers prepared in examples 1 and 2, and the particle size of the oxygen carrier is controlled at 150-270 μm. When the gas velocity is 1500ml/min at 900 ℃ and nitrogen is taken as fluidizing gas, H is generated in the chemical chain gasification process2Trend graph of content over time. H2The content of the oxygen carrier prepared in the embodiment 1 and the embodiment 2 shows a trend of increasing firstly and then decreasing when the content increases with time, because the oxygen carrier is used for H2The selectivity is good, and simultaneously, the valence state of the iron element in the oxygen carrier is easily realized by Fe under the action of water vapor0To Fe3+So that more H can be generated via the iron-water reaction2Thus H in the course of the reaction2The yield is obviously improved by 6 percent compared with the pure iron-based oxygen carrier H2.
FIG. 6 is CaFe prepared via example 12O4Oxygen carrier, and the particle size of the oxygen carrier is controlled at 150-270 mu m. An XRD pattern of the oxygen carrier after five times of cycle tests at 900 ℃ and under the condition of adopting nitrogen as the fluidizing gas with the gas velocity of 1500ml/min, wherein the crystalline phase of the oxygen carrierStable, small amount of CaFe2O4Slight phase separation occurs to form Fe2O3With CaO in a new phase. It is shown that the generated Fe and CaO can further catalyze the reaction after the active lattice oxygen is exhausted. The composite oxygen carrier shows good reaction performance and catalytic performance.
FIG. 7 shows Ca prepared in example 22Fe2O5Oxygen carrier, and the particle size of the oxygen carrier is controlled at 150-270 mu m. At 900 ℃, nitrogen is adopted as the fluidizing gas, the gas velocity is 1500ml/min, and after five times of cycle experiments, the XRD pattern of the oxygen carrier is obtained, wherein the crystalline phase of the oxygen carrier is kept stable, and the oxygen carrier can still keep a complete structure without phase separation.

Claims (4)

1. A calcium-iron bifunctional composite oxygen carrier is characterized in that: the oxygen carrier is CaFe with a spinel structure2O4Or Ca of a double perovskite structure2Fe2O5。
2. A calcium-iron bifunctional composite oxygen carrier is characterized in that: the oxygen carrier is made of CaFe with a spinel structure2O4And Ca of double perovskite structure2Fe2O5Composition of and wherein CaFe2O4：Ca2Fe2O5The mass ratio of (1): 0.5-4.
3. A large-scale preparation method of a calcium-iron bifunctional composite oxygen carrier is characterized by comprising the following steps:
(1) preparation of CaFe2O4: according to n (Fe)2O3)/n(CaCO3) Putting limestone and iron ore into a feeder at a ratio of 2-3: 1; adding water, feeding into a colloid mill, and uniformly mixing at a certain rotating speed for a certain time; sending the mechanically mixed solution to a vacuum suction filter for suction filtration, sending a filter cake after suction filtration into a drying box, drying at the temperature of 110-120 ℃ for 12-18h, then placing in a calcining furnace for calcining at the constant temperature of 1000-1100 ℃ for 3-6h, sending an oxygen carrier to a crusher when the temperature in the furnace is reduced to room temperature,crushing and screening to obtain CaFe2O4Oxygen carrier particles;
(2) preparation of Ca2Fe2O5: according to n (Fe)2O3)/n(CaCO3) Adding limestone and hematite into a feeder at a ratio of 0.5-2: 1; adding water, feeding into a colloid mill, and uniformly mixing at a certain rotating speed for a certain time; sending the mechanically mixed solution to a vacuum suction filter for suction filtration, sending a filter cake after suction filtration into a drying box, drying at the temperature of 110-120 ℃ for 12-18h, then placing in a calcining furnace for calcining at the constant temperature of 1000-1100 ℃ for 3-6h, sending an oxygen carrier to a crusher when the temperature in the furnace is reduced to room temperature, crushing and screening to obtain Ca2Fe2O5Oxygen carrier particles;
(3) respectively taking the CaFe obtained in the step (1)2O4Oxygen carrier particles and Ca obtained in step (2)2Fe2O5Oxygen carrier particles according to CaFe2O4：Ca2Fe2O5The mass ratio of (1): 0.5-4 of the above-mentioned raw materials.
4. The large-scale preparation method of the calcium-iron bifunctional composite oxygen carrier according to claim 3, which is characterized by comprising the following steps: the certain rotating speed and time in the step (1) are specifically 2000rpm/min and 20 min; the certain rotating speed and time in the step (2) are specifically 2000rpm/min and 20 min.
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