Manufacturing method of oxygen carrier material and oxygen carrier material

Abstract

To provide a manufacturing method of an oxygen carrier material with improved reaction activity.SOLUTION: A manufacturing method of the present disclosure is a manufacturing method of an oxygen carrier material containing an alkaline earth metal-added ilmenite, including the following steps: (A) a blend of ilmenite and an alkali metal compound is fired to obtain a fired material; and (B) a blend of the fired material and an alkaline earth metal compound is fired to obtain the oxygen carrier material. The alkali metal compound may be potassium carbonate. The alkaline earth metal compound may be calcium hydroxide.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a method for making an oxygen carrier material and to an oxygen carrier material. [Background technology]

[0002] Chemical looping combustion (CLC), which enables the separation and capture of CO2, is attracting attention due to its efficiency and low cost. Chemical looping is an energy conversion system that utilizes the oxidation-reduction reaction of metal oxides, which act as oxygen carriers.

[0003] The chemical looping method is an energy conversion system that produces heat or hydrogen as well as carbon dioxide and nitrogen gas by circulating metal particles and metal oxides between an oxidation reaction system that oxidizes the metal particles and a reduction reaction system that reduces the metal oxides.Instead of directly burning fuel with air, the system uses the lattice oxygen in the metal oxide as the oxygen source, dividing the combustion reaction into two parts: "oxidation of metal particles" and "reduction of metal oxide," and links the two through physical particle circulation.The fuel and air do not come into direct contact, and pure oxygen is exchanged using the metal as a medium.

[0004] Figure 1 is a schematic diagram showing an example of a chemical looping method using iron oxide as an oxygen carrier. Note that Figure 1 merely shows an example of the use of the chemical looping method. Figure 1 does not intend to limit the method to the one shown. The chemical looping method shown in Figure 1 has a hydrogen generation tower, an air reaction tower, and a fuel reaction tower.

[0005] In the hydrogen generation tower, FeO (II) as an oxygen carrier is oxidized to FeO (II, III) using steam (HO), and hydrogen (H) is discharged. In the air reaction tower, FeO (II, III) as an oxygen carrier is oxidized to FeO (III) using oxygen in the air, and N and heat are discharged. In the fuel reaction tower, FeO as an oxygen carrier is reduced to FeO using a fuel such as biomass, and CO and steam (HO) are discharged. The discharged CO may be recovered and stored, for example. Hydrogen can be produced by the method shown in Figure 1.

[0006] The most important factor in improving the energy efficiency of chemical looping is the oxygen carrier.

[0007] Over the past few decades, numerous oxygen carriers have been investigated, including artificial particles such as NiO and CuO, as well as various natural ores. Low-cost natural ores are likely to be more practical for large-scale power plant operation. Among these, ilmenite (FeTiO3) has attracted attention as a natural ore with advantages such as low cost, abundant supply, and durability. However, its reactivity is not as high as that of artificial particles. Therefore, research into improving the reactivity of ilmenite-based oxygen carriers is needed.

[0008] In this regard, Patent Document 1 discloses a method for producing an oxygen carrier material suitable for a chemical looping process that has high activity and stability, is advantageous in terms of material cost, and is suitable for a chemical looping process. Specifically, Patent Document 1 discloses a method for producing an oxygen carrier material containing alkaline earth metal-doped ilmenite, which includes the steps of calcining ilmenite (FeTiO) to obtain ilmenite oxide (FeTiO and TiO), adding an alkaline earth metal compound to the ilmenite oxide to obtain a mixture, and calcining the mixture to obtain alkaline earth metal-doped ilmenite.

[0009] Non-Patent Document 1 describes iron-doped calcium titanate (CaTi) formed within particles by adding Ca to ilmenite using the solid-phase method and melt impregnation method. 1-x Fe x It has been disclosed that the use of O3:CTFO) improves reaction activity and redox stability.

[0010] Non-Patent Document 2 discloses that uniform micropores are generated inside the particles of K-doped ilmenite after it has undergone several tens of CLC oxidation-reduction cycles. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Publication No. 2018-20913 [Non-patent literature]

[0012] [Non-Patent Document 1] Kazuyuki Miya, Junichiro Otomo. “Improvements in reaction kinetics and stability of ilmenite as oxygen carrier by surface modification with calcium titanate in redox cycles of chemical-looping systems”, Chem. Eng. J., 327 257-267 (2017) [Non-patent document 2] Jinhua Bao, Zhenshan Li, and Ningsheng Cai. “Promoting the Reduction Reactivity of Ilmenite by Introducing Foreign Ions in Chemical Looping Combustion”, Ind. Eng. Chem. Res., 52, 6119-6128 (2013) Summary of the Invention [Problem to be solved by the invention]

[0013] There is a need to further improve the reaction activity of ilmenite-based oxygen carriers.

[0014] That is, an object of the present disclosure is to provide a method for producing an oxygen carrier material with improved reaction activity and such an oxygen carrier material. [Means for solving the problem]

[0015] The present inventors have found that the above object can be achieved by the following means: <<Aspect 1>> 1. A method for producing an oxygen carrier material containing alkaline earth metal doped ilmenite, comprising the steps of: (A) calcining a mixture of ilmenite and an alkali metal compound to obtain a calcined product; and (B) calcining the mixture of the calcined product and an alkaline earth metal compound to obtain the oxygen carrier material. <<Aspect 2>> 2. The method of claim 1, wherein the alkali metal compound is potassium carbonate, potassium oxide, or potassium hydroxide. Aspect 3 3. The method of claim 1 or 2, wherein the alkaline earth metal compound is calcium carbonate, calcium oxide, or calcium hydroxide. Aspect 4 A method according to any one of aspects 1 to 3, wherein in step (A), the firing temperature is 600°C to 1000°C. Aspect 5 A method according to any one of aspects 1 to 4, wherein in step (A), the mass percent concentration of the alkali metal (calculated as alkali metal oxide) relative to the total mass of the fired product is 1 mass % to 15 mass %. Aspect 6 A method according to any one of aspects 1 to 5, wherein in step (B), the firing temperature is 700°C to 1400°C. Aspect 7 The method according to any one of Aspects 1 to 6, wherein in step (B), the mass percent concentration of the alkaline earth metal (calculated as alkaline earth metal oxide) relative to the total mass of the oxygen carrier material is 10 mass % to 30 mass %. Aspect 8 1. An oxygen carrier material comprising alkaline earth metal doped ilmenite, The alkaline earth metal-doped ilmenite is a complex containing TiO2, Fe2TiO5, iron oxide, and alkaline earth metal titanate; When the oxygen carrier material is chemically reacted with water vapor at 900°C, the maximum hydrogen production rate per 1 g of the alkaline earth metal-doped ilmenite is 1.60 μmol / sec or more. Oxygen carrier materials. Aspect 9 9. The oxygen carrier material of claim 8, wherein when chemically reacted with water vapor at 900°C, the amount of hydrogen produced per gram of the alkaline earth metal-doped ilmenite is 0.80 mmol or more within 600 seconds from the start of the reaction. Aspect 10 10. A system for performing chemical looping combustion or chemical looping reforming to obtain carbon dioxide simultaneously with heat or hydrogen by circulating an oxygen carrier material between an oxidation reaction system that oxidizes the oxygen carrier material and a reduction reaction system that reduces the oxygen carrier material, wherein the oxygen carrier material is the oxygen carrier material of aspect 8 or 9. [Effects of the Invention]

[0016] According to the present disclosure, a method for producing an oxygen carrier material with improved reaction activity and such an oxygen carrier material can be provided. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic diagram showing an example of chemical looping combustion. [Figure 2] FIG. 2 is a diagram showing an example of step (A) in the production method of the present disclosure. [Figure 3] FIG. 3 is a diagram showing an example of step (B) in the production method of the present disclosure. [Figure 4] FIG. 4 is a graph showing the results of an X-ray diffraction test on the samples of Example 1, Comparative Example 1, and Comparative Example 5. [Figure 5] FIG. 5 is a graph showing the results of thermogravimetric analysis (TGA) tests of the samples of Example 1 and Comparative Examples 1 to 5. [Figure 6] FIG. 6 shows energy dispersive X-ray spectroscopy (SEM-EDX) images of the samples of Comparative Examples 2 to 4 after the thermogravimetric analysis test. [Figure 7] FIG. 7 shows energy dispersive X-ray spectroscopy (SEM-EDX) images of the samples of Example 1 and Comparative Example 1 before and after the thermogravimetric analysis test. [Figure 8] FIG. 8 is a graph showing the hydrogen generation rates when the samples of Example 1, Comparative Examples 1, 5, and 6 were brought into contact with water vapor under predetermined conditions. [Figure 9] FIG. 9 is a graph showing the total amount of hydrogen produced when the samples of Example 1, Comparative Examples 1, 5, and 6 were brought into contact with water vapor under predetermined conditions. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present disclosure will be described in detail. Note that the present disclosure is not limited to the following embodiments, and various modifications can be made within the scope of the present disclosure.

[0019] 1. Manufacturing Method of the Present Disclosure The present disclosure relates to a method for producing an oxygen carrier material containing alkaline earth metal-doped ilmenite. The disclosed method for producing an oxygen carrier material includes the following steps: (A) calcining a mixture of ilmenite and an alkali metal compound to obtain a calcined product; and (B) calcining the mixture of the calcined product and an alkaline earth metal compound to obtain the oxygen carrier material.

[0020] The oxygen carrier material produced by the manufacturing method of the present disclosure is suitable for use in a chemical looping process. The oxygen carrier material containing alkaline earth metal-doped ilmenite is suitable for use in a chemical looping process. The alkaline earth metal-doped ilmenite is preferably iron-doped alkaline earth metal titanate, such as iron-doped calcium titanate (CaTi 1-x Fe x O3:CTFO) improves reaction activity and redox cycling stability.

[0021] Such oxygen carrier materials can be produced by a solid-state method, as disclosed in, for example, Patent Document 1 and Non-Patent Document 1. However, in the methods described in these documents, the alkaline earth metal segregates to the surface of the ilmenite particles, so that the iron-doped alkaline earth metal titanate is ubiquitous on the surface of the ilmenite particles. Therefore, the effect of improving the reaction activity and the stability during repeated oxidation-reduction cycles is limited.

[0022] Such oxygen carrier materials can also be produced by the melt impregnation method, as disclosed in Non-Patent Document 1. Oxygen carrier materials produced by this method can have alkaline earth metals dispersed even inside the ilmenite particles. However, the melt impregnation method uses Ca(NO3)2·4H2O to introduce Ca into ilmenite, which generates NOx during the production process. In addition, oxygen carrier materials produced by this method are required to have improved reactivity and oxidation-reduction cycle stability.

[0023] In contrast, the production method of the present disclosure includes the above steps (A) and (B), and therefore makes it possible to obtain an oxygen carrier material with improved reaction activity.

[0024] Without being limited by theory, it is believed that in the above step (A), the ilmenite particles are doped with the alkali metal by firing a mixture of ilmenite and an alkali metal compound, thereby generating uniform micropores inside the ilmenite particles. Then, in the above step (B), when the mixture of ilmenite particles having uniform micropores and an alkaline earth metal compound is fired, the presence of the micropores makes it easier for the alkaline earth metal to be doped even into the interior of the ilmenite particles. Therefore, in the oxygen carrier material produced by the production method of the present disclosure, the alkaline earth metal is dispersed in the ilmenite particles, preferably uniformly, even inside the particles. As a result, the oxygen carrier material produced by the production method of the present disclosure has high reactivity.

[0025] 1-1. Process (A) Step (A) in the manufacturing method of the present disclosure is to calcinate a mixture of ilmenite (FeTiO3) and an alkali metal compound to obtain a calcined product.

[0026] The alkali metal compound may be, for example, a metal salt of lithium, sodium, or potassium. The metal salt may be a carbonate, nitrate, or hydroxide. The alkali metal compound may be potassium carbonate (K2CO3), potassium hydroxide (KOH). Potassium hydroxide may be a hydrate. The alkali metal compound may also be an alkali metal oxide, for example, potassium oxide (KO).

[0027] Here, "calcining a mixture of ilmenite and an alkali metal compound" may mean either providing a mixture of ilmenite and an alkali metal compound and calcining the mixture, or calcining the mixture while mixing ilmenite and an alkali metal compound. When a mixture of ilmenite and an alkali metal compound is provided in advance, the mixture may be obtained, for example, by mixing ilmenite and an alkali metal compound using a ball mill or the like. When the mixture is obtained using a ball mill, it may be obtained by mixing in the ball mill for a predetermined time, for example, 5 to 20 hours, and then drying.

[0028] The mixing time using a ball mill may be 5 hours or more, 6 hours or more, 7 hours or more, 8 hours or more, 9 hours or more, 10 hours or more, 11 hours or more, or 12 hours or more. The mixing time using a ball mill may be 20 hours or less, 19 hours or less, 18 hours or less, 17 hours or less, 16 hours or less, 15 hours or less, 14 hours or less, 13 hours or less, or 12 hours or less.

[0029] The mixture of ilmenite and an alkali metal compound may be fired at a temperature of 600°C to 1000°C for a predetermined time, for example, 4 hours to 12 hours. The firing may be carried out in air. The above temperature range is preferable from the viewpoint of the effect of promoting the reduction reaction in the finally obtained oxygen carrier material.

[0030] The firing temperature may be 600° C. or higher, 650° C. or higher, 700° C. or higher, 750° C. or higher, 800° C. or higher, 850° C. or higher, or 900° C. The firing temperature may be 1000° C. or lower, 950° C. or lower, or 900° C. or lower.

[0031] The baking time may be 4 hours or more, 5 hours or more, 6 hours or more, 7 hours or more, or 8 hours or more. The baking time may be 12 hours or less, 11 hours or less, 10 hours or less, 9 hours or less, or 8 hours or less.

[0032] In step (A), the calcined product may contain ilmenite oxide (Fe2TiO5 and TiO2).

[0033] In step (A), the mass percent concentration of the alkali metal (calculated as alkali metal oxide) relative to the total mass of the fired product is 1 mass % to 15 mass %. Here, the alkali metal oxide equivalent is the proportion of the alkali metal converted into alkali metal oxide. For example, when the alkali metal is potassium, it is the proportion calculated by converting it into KO. That is, the mass percent concentration of potassium can be calculated as follows: mass of KO / (mass of KO + mass of ilmenite) × 100.

[0034] The mass percent concentration of the alkali metal compound (calculated as alkali metal oxide) relative to the total mass of the fired product may be 1% by mass to 15% by mass. This mass percent concentration range is preferable from the viewpoint of uniformity of the alkali metal distribution within the fired product produced in step (A). The mass percent concentration may be 1% by mass or more, 2% by mass or more, 3% by mass or more, 4% by mass or more, 5% by mass or more, 6% by mass or more, 7% by mass or more, 8% by mass or more, 9% by mass or more, or 10% by mass or more. The mass percent concentration may be 15% by mass or less, 14% by mass or less, 13% by mass or less, 12% by mass or less, 11% by mass or less, 10% by mass or less, 9% by mass or less, 8% by mass or less, 7% by mass or less, or 6% by mass or less.

[0035] In step (A), ilmenite (FeTiO3) can be completely or partially converted into ilmenite oxide (Fe2TiO5 and TiO2) by calcination.

[0036] Fig. 2 is a diagram showing an example of step (A) in the manufacturing method of the present disclosure. As shown in Fig. 2, in one example of step (A), a slurry in which potassium carbonate particles and ilmenite particles are dispersed in ethanol as a solvent is first subjected to a ball mill treatment using zirconia balls for 12 hours, and then stirred and dried at 150°C to provide a mixture of potassium carbonate particles and ilmenite particles. The mixture is then calcined in air at 800°C for 8 hours to obtain a calcined product, i.e., an oxygen carrier material precursor. The calcined product may be pulverized and classified into particles with a particle size of 150 μm to 300 μm using a sieve or the like before being used in step (B).

[0037] In the production method of the present disclosure, after step (A) and before step (B), the fired product may be subjected to the following oxidation-reduction cycle treatment.

[0038] A cycle of alternately passing a reducing atmosphere and an oxidizing atmosphere at a temperature of 600°C to 1000°C may be performed 5 to 20 times. The flow rate of each atmosphere may be 200 ml / min to 400 ml / min. The time for passing each atmosphere may be 10 minutes to 60 minutes. When switching between the flow of a reducing atmosphere and the flow of an oxidizing atmosphere, Ar gas may be passed for 1 minute to 15 minutes.

[0039] The oxidation-reduction cycle treatment may be carried out using, for example, a fluidized bed apparatus (manufactured by Tokyo Motoyama Shokai Co., Ltd.) Specifically, the fluidized bed apparatus is composed of a cylindrical fluidized bed reactor made of quartz with a diameter of 2 cm and a tubular furnace.

[0040] 1-2. Process (B) Step (B) in the production method of the present disclosure is to calcinate the mixture of the calcined product obtained in step (A) and an alkaline earth metal compound to obtain an oxygen carrier material.

[0041] The alkaline earth metal compound may be a metal salt of beryllium, magnesium, or calcium. The metal salt may be a carbonate, nitrate, or hydroxide. The alkaline earth metal compound may be calcium carbonate (CaCO3) or calcium hydroxide (Ca(OH)2). The alkali metal compound may also be an alkali metal oxide, such as calcium oxide (CaO).

[0042] The mixture of the calcined product and alkaline earth metal compound obtained in step (A) may be obtained by mixing the calcined product and the alkaline earth metal compound, for example, in a ball mill, etc. When the mixture is obtained by a ball mill, the mixture may be obtained by mixing in the ball mill for a predetermined time, for example, 5 to 20 hours, and then drying.

[0043] The mixing time using a ball mill may be 5 hours or more, 6 hours or more, 7 hours or more, 8 hours or more, 9 hours or more, 10 hours or more, 11 hours or more, or 12 hours or more. The mixing time using a ball mill may be 20 hours or less, 19 hours or less, 18 hours or less, 17 hours or less, 16 hours or less, 15 hours or less, 14 hours or less, 13 hours or less, or 12 hours or less.

[0044] The mixture of the calcined product obtained in step (A) and the alkaline earth metal compound may be calcined at a temperature of 1200°C to 1400°C for a predetermined time, for example, 1 hour to 10 hours. The calcination may be carried out in air. The above temperature range is preferable from the viewpoint of the effect of promoting the reduction reaction in the finally obtained oxygen carrier material.

[0045] The firing temperature may be 700° C. to 1400° C. The firing temperature may be 700° C. or higher, 800° C. or higher, 900° C. or higher, 1000° C. or higher, 1100° C. or higher, 1200° C. or higher, 1250° C. or higher, or 1300° C. or higher. The firing temperature may be 1400° C. or lower, 1350° C. or lower, or 1300° C. or lower.

[0046] The baking time may be 1 hour or more, 2 hours or more, 3 hours or more, 4 hours or more, or 5 hours or more. The baking time may be 10 hours or less, 9 hours or less, 8 hours or less, 7 hours or less, or 6 hours or less.

[0047] If ilmenite (FeTiO3) is not completely converted into ilmenite oxide (Fe2TiO5 and TiO2) in step (A), it is preferable that ilmenite (FeTiO3) is completely converted into ilmenite oxide (Fe2TiO5 and TiO2) by firing in step (B).

[0048] In step (B), the oxygen carrier material can contain Fe2TiO5 and TiO2. In step (B), the oxygen carrier material can further contain an alkaline earth metal titanate. When the alkaline earth metal is calcium, the alkaline earth metal titanate can be calcium titanate (CaTiO3).

[0049] In step (B), the mass percent concentration of the alkaline earth metal compound (calculated as alkaline earth metal oxide) relative to the total mass of the oxygen carrier material is 10% to 30% by mass. This mass percent concentration range is preferable from the viewpoints of the stability of the particle structure of the finally obtained alkaline earth metal-doped ilmenite and the stability of the reduction reaction rate. For example, when the alkaline earth metal is calcium, the mass percent concentration is calculated in terms of CaO. That is, it can be calculated as follows: mass percent concentration of calcium = mass of CaO / (mass of CaO + mass of ilmenite) × 100. The mass percent concentration may be 10% by mass or more, 12% by mass or more, 14% by mass or more, 16% by mass or more, 18% by mass or more, or 20% by mass or more. The mass percent concentration may be 30% by mass or less, 28% by mass or less, 26% by mass or less, 24% by mass or less, 22% by mass or less, or 20% by mass or less.

[0050] Fig. 3 is a diagram showing an example of step (B) in the manufacturing method of the present disclosure. As shown in Fig. 3, in one example of step (B), a slurry of calcium carbonate particles and ilmenite particles dispersed in ethanol as a solvent is first subjected to a ball mill treatment using zirconia balls for 12 hours, and then stirred and dried at 150°C to provide a mixture of potassium carbonate particles and ilmenite particles. The mixture is then calcined in air at 800°C for 8 hours, and then pulverized to a particle size of approximately 150 to 300 µm to obtain a calcined product, i.e., an oxygen carrier material precursor. The oxygen carrier material precursor may be pulverized and classified to a particle size of 150 to 300 µm using a sieve or the like.

[0051] 2. Oxygen Carrier Materials of the Present Disclosure The oxygen carrier material of the present disclosure is an oxygen carrier material that contains alkaline earth metal-doped ilmenite, and that, when chemically reacted with water vapor at 900°C, has a maximum hydrogen production rate per 1 g of alkaline earth metal-doped ilmenite of 1.60 μmol / sec or more.

[0052] The oxygen carrier material of the present disclosure has a high reaction rate, with the maximum hydrogen production rate per gram of alkaline-earth metal-doped ilmenite being 1.60 μmol / s or more, and therefore has a very high hydrogen production rate, enabling the oxygen carrier material of the present disclosure to exhibit high redox reaction properties as an oxygen carrier material in a chemical looping method.

[0053] The maximum hydrogen generation rate may be 1.60 μmol / sec to 3.00 μmol / sec. The maximum hydrogen generation rate may be 1.60 μmol / sec or more, 1.65 μmol / sec or more, or 1.70 μmol / sec or more. The maximum hydrogen generation rate may be 3.00 μmol / sec or less, 2.95 μmol / sec or less, or 2.92 μmol / sec or less.

[0054] As another indicator, the oxygen carrier material of the present disclosure may have a hydrogen production rate of 1.60 μmol / sec or more, 1.65 μmol / sec or more, or 1.70 μmol / sec or more and 3.00 μmol / sec or less, 2.95 μmol / sec or less, or 2.92 μmol / sec or less within 200 seconds from the start of the chemical reaction with water vapor.

[0055] Furthermore, when the oxygen carrier material of the present disclosure is chemically reacted with water vapor at 900°C, the amount of hydrogen produced per 1 g of alkaline earth metal-doped ilmenite may be 0.80 mmol or more for 600 seconds from the start of the reaction.

[0056] The amount of hydrogen produced per gram of alkaline earth metal-added ilmenite from the start of the reaction until 600 seconds may be 0.80 mmol to 1.20 mmol. The amount of hydrogen produced may be 0.80 mmol or more, 0.85 mmol or more, 0.90 mmol or more, or 0.95 mmol or more. The amount of hydrogen produced may be 1.20 mmol or less, 1.10 mmol or less, 1.05 mmol or less, or 1.00 mmol or less.

[0057] Here, the chemical reaction between the oxygen carrier material and water vapor may be carried out by, for example, bringing them into physical contact with each other. The chemical reaction between the oxygen carrier material and water vapor may be carried out using a fluidized bed device.

[0058] More specifically, the chemical reaction between the oxygen carrier material and water vapor may be carried out in the following manner:

[0059] One gram of oxygen carrier material was placed in the reaction tube of a small quartz fluidized bed reactor (Tokyo Motoyama Shokai Co., Ltd.). Pretreatment was performed by alternately flowing 1.5% H (remainder Ar gas) and 50% air (remainder Ar gas) at 900°C for 40 minutes at a flow rate of 500 ml / min five times. When switching between 1.5% H (remainder Ar gas) and 50% air (remainder Ar gas), Ar gas was passed through as a purge gas for 3 minutes. The small fluidized bed reactor consisted of a cylindrical quartz fluidized bed reactor with a diameter of 2 cm and a tubular furnace.

[0060] Next, reducing gas (7.5% CO / 10% CO 2 / balance N 2 ) is passed through the reaction tube at a flow rate of 500 ml / min for 90 minutes.

[0061] Finally, steam (7.5% H2O / balance N2) is passed through the reaction tube at a flow rate of 500 ml / min for 90 minutes.

[0062] The rate of hydrogen production can be measured, for example, by gas chromatography. For gas chromatography, a VARIAN-490-GC (micro-GC) can be used. The amount of hydrogen produced can also be measured, for example, by gas chromatography.

[0063] The oxygen carrier material of the present disclosure has a specific surface area of ​​10.0 m 2 / g or less. The specific surface area is 10.0 m 2 / g or less, 9.0m 2 / g or less, 7.0m 2 / g or less, 5.0m 2 / g or less, or 3.0m 2 / g or less.

[0064] The oxygen carrier material of the present disclosure contains alkaline earth metal-doped ilmenite. Here, the alkaline earth metal-doped ilmenite may be a composite containing TiO, FeTiO, iron oxide, and alkaline earth metal titanate. The iron oxide may contain at least one selected from the group consisting of FeO, FeO, and FeO, depending on the oxidation state of the oxygen carrier material.

[0065] The oxygen carrier material of the present disclosure also preferably has the alkaline earth metal titanate uniformly dispersed inside the ilmenite particles.

[0066] Without being bound by theory, it is believed that in the oxygen carrier material of the present disclosure, alkaline earth metals are dispersed, preferably uniformly, inside the ilmenite particles. Therefore, in the oxygen carrier material of the present disclosure, a layer of alkaline earth metal titanate is formed even inside the ilmenite particles. Therefore, O2 - It is believed that a conductor is formed, which has the effect of promoting the oxidation-reduction reaction.

[0067] In addition to alkaline earth metal-doped ilmenite, the oxygen carrier material of the present disclosure may contain a porous agent, a binder, etc. Examples of the porous agent that can be used include graphite and activated carbon, and examples of the binder that can be used include ethyl cellulose and terpineol.

[0068] The oxygen carrier material of the present disclosure can be produced, for example, by the manufacturing method of the present disclosure.

[0069] 3. The system of the present disclosure The system of the present disclosure is a system for performing chemical looping combustion or chemical looping reforming in which carbon dioxide is obtained simultaneously with heat or hydrogen by circulating an oxygen carrier material between an oxidation reaction system in which the oxygen carrier material is oxidized and a reduction reaction system in which the oxygen carrier material is reduced, wherein the oxygen carrier material is the oxygen carrier material of the present disclosure.

[0070] The system disclosed herein is a system for performing chemical looping combustion or chemical looping reforming, which generates heat or hydrogen by circulating metal particles and metal oxides between an oxidation reaction system that oxidizes the metal particles and a reduction reaction system that reduces the metal oxides. A typical example of such a chemical looping combustion system is the system disclosed in Japanese Patent Laid-Open No. 2015-81203.

[0071] The disclosed system utilizes the disclosed oxygen carrier material in such a chemical looping process.

[0072] In the chemical looping combustion system and chemical looping reforming system disclosed herein, an oxidation reaction device that controls the oxidation reaction system and a reduction reaction device that controls the reduction reaction system are installed as separate facilities, and may further include a transport system that transports metal particles and metal oxides between the two devices.

[0073] In chemical looping combustion, fuel is supplied to a reduction reaction device, and the exhaust gas components carbon dioxide and water are emitted through a reduction reaction. In the chemical looping method (chemical looping combustion system and chemical looping reforming system) disclosed herein, hydrocarbons such as methane, petroleum, solid fuels, liquid fuels, biomass, etc. can be used as fuel. [Example]

[0074] 1. Sample Preparation 1-1. Example 1 (1) Process (A) Australian ilmenite was used as the ilmenite. K2CO3 was added to the ilmenite so that the mass percent concentration of K relative to the total mass of the fired product was 5 mass% converted to KO, and the mixture was mixed in a ball mill for 12 hours using ethanol as a dispersion medium and zirconia balls. The resulting slurry was dried at 150°C. The solid was then fired at 900°C for 8 hours in an air atmosphere. The fired material was pulverized and further classified using a sieve to obtain particles with a particle size of 150 nm to 300 nm, yielding a fired product.

[0075] The resulting fired product was subjected to 10 oxidation-reduction cycles using a differential thermal / thermogravimetric simultaneous measurement device Thermo plus Evo2 TG 8121 (manufactured by Rigaku Corporation). The reaction conditions were as follows: Temperature: 900℃ Reducing atmosphere: 3% H2 (balance Ar), flow rate 150 ml / min, flow time 30 min Oxidizing atmosphere: air, flow rate 300 ml / min, flow time 30 min Flush: Ar gas, flow rate 300 ml / min, flow time 10 min The fired product treated by the oxidation-reduction cycle was used in the following step (B).

[0076] (2) Process (B) CaCO3 was added to the fired material obtained in step (A) so that the mass percent concentration of Ca relative to the total mass of the oxygen carrier material was 30 mass% in terms of CaO, and the mixture was mixed in a ball mill using ethanol as a dispersion medium and zirconia balls for 12 hours. The resulting slurry was dried at 150°C. The solid was then fired in an air atmosphere at 1300°C for 5 hours. The fired material was pulverized and further classified using a sieve to obtain particles with a particle size of 150 nm to 300 nm, thereby obtaining the oxygen carrier material of Example 1.

[0077] 1-2. Comparative Example 1 CaCO3 was added to the calcined ilmenite so that the mass percent concentration of Ca relative to the total mass of the oxygen carrier material was 30 mass% in terms of CaO, and the mixture was mixed in a ball mill using ethanol as a dispersion medium and zirconia balls for 12 hours. The resulting slurry was dried at 150°C. The solid matter was then calcined in an air atmosphere at 1300°C for 5 hours. The calcined material was pulverized and further classified using a sieve to obtain particles with a particle size of 150 nm to 300 nm, thereby obtaining the oxygen carrier material of Comparative Example 1.

[0078] The ilmenite was fired in air at 950°C for 24 hours.

[0079] 1-3. Comparative Examples 2 to 4 The oxygen carrier material of Comparative Example 2 was prepared by carrying out only step (A) in Example 1. Oxygen carrier materials of Comparative Examples 3 and 4 were obtained in the same manner as in Comparative Example 2, except that the mass percent concentrations of K relative to the total mass of the fired material were 10 mass% and 15 mass%, respectively, calculated as KO.

[0080] 1-4. Comparative Example 5 The calcined Australian ilmenite itself was used as the oxygen carrier material of Comparative Example 5. The ilmenite was calcined in air at 950°C for 24 hours.

[0081] 1-5. Comparative Example 6 The calcined ilmenite of Comparative Example 5 was impregnated with Ca(NO3)2·4H2O to obtain the oxygen carrier material of Comparative Example 6.

[0082] 2. X-ray diffraction test An X-ray diffraction (XRD) test was performed on the oxygen carrier materials of Example 1, Comparative Example 1, and Comparative Example 5. For the XRD, a SmartLab (manufactured by Rigaku Co., Ltd.) was used. The results of the X-ray diffraction test are shown in FIG.

[0083] As shown in FIG. 4, the X-ray diffraction pattern of the oxygen carrier material of Example 1 confirmed the formation of Fe2TiO5, TiO2, Fe2O3, and CaTiO3.

[0084] Similarly, the X-ray diffraction pattern of the oxygen carrier material of Comparative Example 1 also confirmed that Fe2TiO5, TiO2, Fe2O3, and CaTiO3 were formed.

[0085] The X-ray diffraction pattern of the oxygen carrier material of Comparative Example 5 confirmed the presence of Fe2TiO5 and TiO2.

[0086] 3. Thermogravimetric analysis test The oxidation-reduction reaction properties of the oxygen carrier materials of Example 1 and Comparative Examples 1 to 5 were evaluated by thermogravimetric analysis (TGA) using a differential thermal-thermogravimetric simultaneous measurement device Thermo plus Evo2 TG 8121 manufactured by Rigaku Co., Ltd. The reaction conditions are as follows.

[0087] Pretreatment: The temperature was raised to 900°C at a rate of 20°C / min in a N2 atmosphere and maintained for 30 minutes or more until the mass change became constant.

[0088] Reaction rate measurement: At 900°C, a reducing atmosphere (5% H2 (remainder: N2), flow rate: 300 ml / min, flow time: 5 min), an oxidizing atmosphere (50% air (remainder: N2), flow rate: 300 ml / min, flow time: 5 min), and a purge (N2, flow rate: 150 ml / min, flow time: 30 sec) were repeated 10 times.

[0089] The results of thermogravimetric analysis (TGA) are shown in Figure 5 and Table 1. In Table 1, the mass % of KCO3 is the mass percent concentration of K in the entire fired material in step (A), converted into KO. The mass % of CaCO3 is the mass percent concentration of Ca in the entire oxygen carrier material in step (B), converted into CaO. The mass reduction rate (%) in Table 1 indicates the mass reduction rate of the oxygen carrier material at the 10th reduction cycle in thermogravimetric analysis (TGA) relative to the mass before TGA.

[0090] [Table 1]

[0091] 4. Scanning Electron Microscope Observation The cross-sections of the oxygen carrier material before and after the oxidation-reduction treatment in the thermogravimetric analysis (TGA) in 6 above were observed using a scanning electron microscope and energy dispersive X-ray analysis (SEM-EDX).

[0092] Fig. 6 shows energy dispersive X-ray spectroscopy (SEM-EDX) images of the samples of Comparative Examples 2 to 4 after thermogravimetric analysis testing, and Fig. 7 shows energy dispersive X-ray spectroscopy (SEM-EDX) images of the samples of Example 1 and Comparative Example 1 before and after thermogravimetric analysis testing.

[0093] 6, it can be seen that K is dispersed even inside the ilmenite particles in the oxygen carrier materials of Comparative Examples 2 to 4. This suggests that K is dispersed even inside the ilmenite particles by step (A).

[0094] As shown in Figure 7, it can be seen that Ca is dispersed even inside the ilmenite particles in the oxygen carrier material of Example 1. It is thought that in step (A), K is dispersed even inside the ilmenite particles to form a microstructure, which makes it easier for Ca to be dispersed even inside the ilmenite particles in the subsequent step (B). On the other hand, it can be seen that Ca is dispersed only near the surface of the ilmenite particles in the oxygen carrier material of Comparative Example 1.

[0095] 5. Measurement of specific surface area The specific surface area was measured for each of the oxygen carrier materials of Example 1, Comparative Example 1, Comparative Example 5, and Comparative Example 6. The measurement results are shown in Table 2 below.

[0096] [Table 2]

[0097] 6. Measurement of the Hydrogen Evolution Reaction The oxygen carrier materials of Example 1, Comparative Example 1, Comparative Example 5, and Comparative Example 6 were each introduced into a small fluidized bed (manufactured by Tokyo Motoyama Shokai Co., Ltd.), and the hydrogen production reaction rate of the sample was evaluated using gas chromatography (VARIAN-490-GC (micro-GC)).

[0098] Specifically, the following was done:

[0099] The oxygen carrier material was placed in the reaction tube of a small fluidized bed device (Tokyo Motoyama Shokai Co., Ltd.), and pretreatment was performed by alternately flowing 1.5% H2 (with the remainder being Ar gas) and 50% air (with the remainder being Ar gas) at a flow rate of 500 ml / min five times for 40 minutes at 900°C. Note that when switching between 1.5% H2 (with the remainder being Ar gas) and 50% air (with the remainder being Ar gas), Ar gas was passed through as a purge gas for 3 minutes.

[0100] Next, reducing gas (7.5% CO / 10% CO 2 / balance N 2 ) is passed through the reaction tube at a flow rate of 500 ml / min for 90 minutes.

[0101] Finally, steam (7.5% H2O / balance N2) is passed through the reaction tube at a flow rate of 500 ml / min for 90 minutes.

[0102] The rate and amount of hydrogen production were measured using gas chromatography (VARIAN-490-GC (micro-GC)).

[0103] The measurement results are shown in FIGS.

[0104] 8 and 9, the oxygen carrier material of Example 1 completed its chemical reaction with hydrogen in a shorter time of about 600 seconds from the start of the reaction than the other examples. Furthermore, the oxygen carrier material of Example 1 produced about 1.00 mmol of hydrogen per gram of oxygen carrier material 600 seconds after the start of the reaction, and the hydrogen production rate per gram of oxygen carrier material was about 2.91 μmol / s at the start of the reaction and about 1.70 μmol / s 200 seconds later. Other examples did not achieve such high values.

Claims

1. 1. A method for producing an oxygen carrier material containing alkaline earth metal doped ilmenite, comprising the steps of: (A) calcining a mixture of ilmenite and an alkali metal compound to obtain a calcined product; and (B) calcining the mixture of the calcined product and an alkaline earth metal compound to obtain the oxygen carrier material.

2. The method according to claim 1 , wherein the alkali metal compound is potassium carbonate, potassium oxide, or potassium hydroxide.

3. The method according to claim 1 or 2, wherein the alkaline earth metal compound is calcium carbonate, calcium oxide, or calcium hydroxide.

4. The method according to claim 1 or 2, wherein in the step (A), the firing temperature is 600°C to 1000°C.

5. 3. The method according to claim 1, wherein in the step (A), the mass percent concentration of the alkali metal compound (in terms of alkali metal oxide) relative to the total mass of the fired product is 5 mass% to 15 mass%.

6. The method according to claim 1 or 2, wherein in the step (B), the firing temperature is 700°C to 1400°C.

7. 3. The method according to claim 1, wherein in step (B), a mass percent concentration of the alkaline earth metal compound (in terms of alkaline earth metal oxide) relative to the total mass of the oxygen carrier material is 10 mass% to 30 mass%.

8. 1. An oxygen carrier material comprising alkaline earth metal doped ilmenite, The alkaline earth metal-doped ilmenite is TiO ２ , Fe ２ TiO ５ , iron oxide, and alkaline earth metal titanate, When the oxygen carrier material is chemically reacted with water vapor at 900°C, the maximum hydrogen generation rate per 1 g of the alkaline earth metal-doped ilmenite is 1.60 μmol / sec or more. Oxygen carrier materials.

9. 9. The oxygen carrier material according to claim 8, wherein when chemically reacted with water vapor at 900°C, the amount of hydrogen produced per 1 g of the alkaline earth metal-doped ilmenite from the start of the reaction to 600 seconds is 0.80 mmol or more.

10. 10. A system for performing chemical looping combustion or chemical looping reforming in which carbon dioxide is obtained simultaneously with heat or hydrogen by circulating an oxygen carrier material between an oxidation reaction system in which the oxygen carrier material is oxidized and a reduction reaction system in which the oxygen carrier material is reduced, wherein the oxygen carrier material is the oxygen carrier material described in claim 8 or 9.

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