Metal particles used in a chemical loop combustion apparatus, and a method for manufacturing metal particles.

Abstract

The present invention provides metal particles that enable the stable operation of chemical loop combustion systems. [Solution] The metal particles used in the chemical loop combustion apparatus contain iron oxide and comprise an outer shell that forms the outer surface of the metal particle, and an inner body located inside the outer shell, with a gap formed between the outer shell and the inner body, and the iron oxide content [wt%] in the outer shell is greater than the iron oxide content [wt%] in the inner body.

Description

Technical Field

[0001] The present invention relates to metal particles for use in a chemical looping combustion apparatus, and a method for producing the metal particles.

Background Art

[0002] Metal particles for use in a chemical looping combustion apparatus are known, which comprises an air tower that reacts oxygen-containing air with metal particles to obtain oxidation heat, and a fuel tower that reduces the metal particles through a reaction between the metal particles oxidized in the air tower and a fuel (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of Invention

Problems to be Solved by the Invention

[0004] However, even with the above technique, there is still room for improvement in the technique for stabilizing the operation of a chemical looping combustion apparatus using metal particles.

[0005] The present invention has been made to solve at least part of the above-described problems, and an object of the present invention is to provide metal particles for further stabilizing the operation of a chemical looping combustion apparatus.

Means for Solving the Problems

[0006] The present invention has been made to solve at least part of the above-described problems, and can be implemented in the following embodiments.

[0007] (1) According to one embodiment of the present invention, metal particles for use in a chemical loop combustion apparatus are provided. These metal particles contain iron oxide and comprise an outer shell portion that constitutes the outer surface of the metal particles and a solid portion located inside the outer shell portion, with a gap formed between the outer shell portion and the solid portion, wherein the iron oxide content [wt%] in the outer shell portion is greater than the iron oxide content [wt%] in the solid portion.

[0008] This configuration allows for improved oxidation and reduction reactivity of metal particles. Therefore, stable operation of the chemical loop combustion system can be achieved from the start of operation.

[0009] (2) In the metal particles of the above form, the content [wt%] of iron oxide contained in the outer shell may be 50 wt% or more. This configuration allows for improved oxidation and reduction reactivity of metal particles. Therefore, a more stable chemical loop combustion system can be operated from the start of operation.

[0010] (3) In the metal particles of the above form, the size of the gap may be 5 μm or more and 10 μm or less. This configuration improves the reactivity of metal particles by enhancing their gas diffusivity. Therefore, it enables more stable operation of the chemical loop combustion system from the start of operation.

[0011] (4) In the metal particles of the above form, the surface area per gram of weight may be 0.75 m² or more. This configuration improves the reactivity of metal particles by enhancing their gas diffusivity. Therefore, it enables more stable operation of the chemical loop combustion system from the start of operation.

[0012] (5) In the metal particles of the above form, the content [wt%] of iron oxides in the whole may be 20 wt% or more. This configuration allows for improved oxidation and reduction reactivity of metal particles. Therefore, a more stable chemical loop combustion system can be operated from the start of operation.

[0013] Furthermore, the present invention can be realized in various forms, for example, as a chemical loop combustion system using these metal particles, a chemical loop combustion plant, apparatus and systems equipped therewith, a method for producing carbon dioxide, a method for synthesizing carbon dioxide, a control device for a metal particle production apparatus, a computer program for executing the control device and production method of the production apparatus, a server device for distributing this computer program, and a non-temporary storage medium storing the computer program. [Brief explanation of the drawing]

[0014] [Figure 1] This is a schematic cross-sectional diagram of a metal particle. [Figure 2] This is a diagram illustrating the characteristics of metal particles. [Figure 3] This is a diagram illustrating a metal particle manufacturing apparatus. [Figure 4] These are cross-sectional views of each sample. [Figure 5] This figure shows the metal oxide content of each sample overall. [Figure 6] This figure shows the specific surface area of ​​each sample. [Figure 7] This figure shows the content of each atom in the outer layer and the inner substance of each sample. [Figure 8] This figure shows the results of thermogravimetric analysis for each sample. [Figure 9] This is a schematic diagram showing the general configuration of a chemical loop combustion system. [Modes for carrying out the invention]

[0015] <First Embodiment> (Figure 1 is a schematic diagram of metal particles MP as the first embodiment of the present invention. The metal particles MP are used in a chemical looping combustion system described later, and are produced from ilmenite (FeTiO3) having a particle diameter of 50 to 250 μm. The metal particle MP has an outer skin part OM and an inner solid part IM, and has a gap G between the outer skin part OM and the inner solid part IM.

[0016] Figure 2 is a diagram for explaining the characteristics of the metal particles MP. The weight ratio [wt%] of the metal particles MP is 40 wt% or less for TiFe2O5, 30 wt% or more for TiO2, and 20 wt% or more for Fe2O3. Further, the weight ratio [wt%] of Fe2O3 in the outer skin part OM of the metal particles MP is 50% or more. The weight ratio [wt%] of Fe2O3 in the inner solid part IM is smaller than the weight ratio [wt%] of Fe2O3 in the outer skin part OM. That is, the weight ratio [wt%] of Fe2O3 in the outer skin part OM is larger than the weight ratio [wt%] of Fe2O3 in the inner solid part IM. In addition, the specific surface area per weight of the metal particles MP is 0.75 m^2 / g or more. Furthermore, the maximum value of the distance of the gap G between the outer skin part OM and the inner solid part IM is 5 μm or more and 10 μm or less. The maximum value of the distance of the gap G between the outer skin part OM and the inner solid part IM refers to the average value of the respective maximum values obtained by measuring the distance of the gap G in six randomly extracted metal particles MP. That is, the average value of the maximum values of the distance of the gap G in six randomly extracted metal particles MP falls within the range of 5 μm or more and 10 μm or less.

[0017] Since the content of Fe2O3 in the entire metal particles MP is 20 wt% or more, the amount of Fe component with high reactivity in gas increases, so that the reduction reactivity is enhanced. Next, the metal particle MP includes an outer shell part OM and an inner solid part IM. When the average value of the maximum distances of the gap G between the outer shell part OM and the inner solid part IM falls within the range of 5 μm to 10 μm, gas easily enters the gap G, gas diffusivity increases, and oxidation reactivity relatively increases. Regarding the distance of the gap G, gas more easily enters the gap G and gas diffusivity is higher when the distance is 5 μm or more than when it is less than 5 μm. If the distance of the gap G is larger than 10 μm, the outer shell part OM tends to break, and the outer shell part OM and the inner solid part IM tend to separate, which highly likely results in failure to obtain the effect of improving gas diffusivity. Further, in the metal particle MP, the content [wt%] of Fe₂O₃ in the outer shell part OM is larger than the content [wt%] of Fe₂O₃ in the inner solid part IM, so that the outer shell part OM contains more Fe component with high reactivity in gas than the inner solid part IM, leading to higher reduction reactivity. Furthermore, the content [wt%] of Fe₂O₃ in the outer shell part OM of the metal particle MP is 50% or more, the outer shell part OM contains a large amount of Fe component with high reactivity in gas, and reduction reactivity increases. In addition, since the specific surface area per unit weight of the metal particle MP is 0.75 m² / g or more, the area of the portion in contact with gas is large, which increases gas diffusivity and relatively increases oxidation reactivity.

[0018] <Manufacturing Apparatus> Figure 3 is a diagram for explaining the manufacturing apparatus 100 and the manufacturing method for the metal particles MP. The manufacturing apparatus 100 includes a reactor 110 and a heater 120. The reactor 110 is provided with a gas supply port 111 and a gas discharge port 112. The reactor 110 accommodates ilmenite (FeTiO₃) particles, which are the material of the metal particles MP, inside, causes the ilmenite particles to react with the gas supplied from the gas supply port 111, and discharges the reacted gas from the gas discharge port 112. The heater 120 heats the reactor 110 in the first step and the second step described below. An electric heater or the like can be used as the heater 120.

[0019] In the manufacturing process for metal particles MP, first, ilmenite particles, which will be the material for the metal particles MP, are prepared. The prepared ilmenite particles are placed in the reactor 110 of the manufacturing apparatus 100. After this, the manufacturing apparatus 100 repeatedly performs reduction and oxidation treatments to produce the metal particles MP.

[0020] <Examples> Figure 4 shows cross-sectional views of samples 1 to 3. Each cross-sectional view of samples 1 to 3 was obtained by embedding each sample in a transparent resin, exposing the particle cross-section by polishing, and then photographing it using an SEM (electron microscope). Sample 1 is a particle that has not been processed by the manufacturing device 100. Sample 2 is a particle that has undergone repeated reduction and oxidation treatment by the manufacturing device 100. Sample 3 is a particle that has undergone further reduction and oxidation treatment by the manufacturing device 100 in addition to sample 2.

[0021] As shown in the cross-sectional view of Sample 1, the particles of Sample 1 do not have a structure corresponding to an outer shell and an internal body. As shown in the cross-sectional view of Sample 2, the particles of Sample 2 consist of an outer shell and an internal solid part. The maximum gap between the outer shell and the internal solid part was less than 5 μm. As shown in the cross-sectional view of Sample 3, the particles of Sample 3 consist of an outer shell and an internal solid part. The maximum gap between the outer shell and the internal solid part was between 5 μm and 10 μm. Therefore, since Sample 2 has an outer shell and an inner solid, gas can enter the gap between the outer shell and the solid, resulting in higher gas diffusivity compared to Sample 1, and relatively higher oxidation reactivity. Furthermore, Sample 3 also has an outer shell and an inner solid, and the maximum value of the gap between the outer shell and the solid is 5 μm to 10 μm, which is larger than that of Sample 2. Therefore, since gas can enter more easily in Sample 3 than in Sample 2 due to the larger gap between the outer shell and the solid, gas diffusivity is further increased, and relatively higher oxidation and reduction reactivity. Note that if the gap between the outer shell and the solid is less than 5 μm, gas cannot easily enter the gap, and relatively lower gas diffusivity is achieved. If it is greater than 10 μm, the outer shell is more fragile, and the outer shell and the solid are more likely to separate, making it less likely that the effect of increased gas diffusivity will be obtained. Therefore, it is preferable that the maximum value of the gap between the outer shell and the solid is 5 μm to 10 μm.

[0022] Figure 5 shows the wt% content of metal oxides in the total metal particles of each sample. In the graph in Figure 5, the vertical axis represents the wt% content of each metal oxide in the total for each sample, and the horizontal axis represents each sample. Here, the wt% content of metal oxides in the total metal particles of each sample was measured by XRD (X-ray crystallography). The black circular marks on the graph represent the wt% content of Fe2O3 in each sample. The black triangular marks represent the wt% content of TiO2 in each sample. Furthermore, the black square marks represent the wt% content of TiFe2O5 in each sample.

[0023] In Sample 1, the TiFe2O5 content was 80 wt% or more, the TiO2 content was less than 20 wt%, and the Fe2O3 content was less than 1 wt%. In Sample 2, the TiFe2O5 content was 40 wt% or more, while the TiO2 and Fe2O3 content were both less than 30 wt%. In Sample 3, the TiFe2O5 and TiO2 content were both less than 40 wt%, while the Fe2O3 content was 20 wt% or more. In samples 2 and 3, the Fe2O3 content is 20 wt% or more. Therefore, samples 2 and 3 have a high proportion of Fe components, which are highly reactive in the gas, resulting in high reduction reactivity.

[0024] Figure 6 shows the specific surface area of ​​the metal particles in each sample. In the graph in Figure 6, the vertical axis represents the specific surface area [m^2 / g] of each sample, and the horizontal axis represents each sample. Here, the specific surface area of ​​each sample was measured by the amount of krypton gas adsorbed under normal temperature and pressure.

[0025] In Sample 1, the specific surface area is approximately 0.2 m² / g. In Sample 2, the specific surface area is 0.75 m² / g or more. In Sample 3, the specific surface area is 0.75 m² / g or more. Samples 2 and 3 have a specific surface area of ​​0.75 m² / g or more. Therefore, samples 2 and 3 have a large surface area in contact with the gas and high gas diffusivity, resulting in relatively higher oxidation and reduction reactivity.

[0026] Figure 7 shows the mass percentage (%) of each metal oxide in the outer and inner layers of metal particles for each sample. In the graph in Figure 7, the vertical axis represents the wt percentage (wt%) of each metal oxide in each sample, and the horizontal axis represents each sample. Here, the mass percentage (%) of each metal oxide in the outer and inner layers of metal particles for each sample was measured using EPMA (Electron Probe Microanalyzer). The black circular marks and dashed lines in the graph represent the mass percentage (mass%) of Fe2O3 in the inner layer of each sample. The black triangular marks and dashed lines represent the mass percentage (mass%) of TiO2 in the inner layer of each sample. The black square marks and dashed lines represent the mass percentage (mass%) of TiFe2O5 in the inner layer of each sample. The white circular marks and solid lines in the graph represent the mass percentage (mass%) of Fe2O3 in the outer layer of each sample. The white triangle marks and solid lines represent the mass percentage of TiO2 in the outer layer of each sample. The white square marks and solid lines represent the mass percentage of TiFe2O5 in the outer layer of each sample.

[0027] In Sample 1, since it does not consist of an outer layer and a solid core, it is considered to consist only of the solid core, with TiFe2O5 at approximately 40 mass%, and Fe2O3 and TiO2 both at approximately 30 mass%, respectively. In Sample 2, the internal structure contains over 20 mass% Fe2O3, less than 40 mass% TiO2, and over 40 mass% TiFe2O5. In the outer layer, Fe2O3 contains approximately 60 mass%, TiO2 contains less than 5 mass%, and TiFe2O5 contains over 35 mass%. In Sample 3, the internal structure contains approximately 20 mass% Fe2O3, 35 mass% TiO2, and 45 mass% TiFe2O5. In the outer layer, Fe2O3 contains approximately 55 mass%, TiO2 contains 5 mass% or more, and TiFe2O5 contains less than 40 mass%. Samples 2 and 3 have an outer layer, and the Fe2O3 content in the outer layer is 50 mass% or more. Therefore, because Samples 2 and 3 have a large amount of Fe component in the outer layer, which is highly reactive in gas, they exhibit high reduction reactivity.

[0028] Figure 8 shows the results of thermogravimetric analysis of metal particles in each sample. Figure 8 shows the results of thermogravimetric analysis for samples 1-3, where a reduction reaction with 10% H2 / N2 was carried out from time T1 to time T2, and an oxidation reaction with 20% O2 / N2 was carried out from time T2 to time T3. The vertical axis of the graph represents the weight change [mg] of each sample, and the horizontal axis represents time. The dashed line represents sample 1, the dashed line represents sample 2, and the solid line represents sample 3. In Sample 1, when the reduction reaction described above was carried out, the rate of weight loss was relatively slow, and the amount of weight loss was also relatively small. Conversely, when the oxidation reaction described above was carried out, the rate of weight increase was relatively slow. In Sample 2, when the reduction reaction described above was carried out, the rate of weight loss was faster than in Sample 1, and the amount of weight loss was also 1.7 to 1.8 times greater than in Sample 1. Furthermore, when the oxidation reaction described above was carried out, the rate of weight loss was similar to that of Sample 1. In Sample 3, when the reduction reaction described above was carried out, the rate of weight loss was even faster than in Sample 2, and the amount of weight loss was about twice that of Sample 1, which is greater than in Sample 2. Furthermore, when the oxidation reaction described above was carried out, the rate of weight increase was extremely faster than in Samples 1 and 2. Therefore, Sample 2 exhibits higher reduction reactivity than Sample 1. Furthermore, Sample 3 exhibits higher oxidation and reduction reactivity than both Sample 1 and Sample 2.

[0029] <Configuration of a chemical loop combustion system> Figure 9 is an explanatory diagram illustrating the configuration of a chemical loop combustion system 1 using the metal particles MP of the present invention. The chemical loop combustion system 1 is a system that generates heat through an oxidation reaction using metal particles MP circulating within the system, and generates carbon dioxide and the like through a reduction reaction using metal particles MP circulating within the system. The chemical loop combustion system 1 uses metal particles MP manufactured by the manufacturing method described above.

[0030] The chemical loop combustion system 1 comprises an air tower 10, a cyclone 20, a first loop seal section 30, a fuel tower 40, a second loop seal section 50, a circulation pipe 60, a dewaterer 70, and a control unit 80.

[0031] The air tower 10 is a tower that generates heat while oxidizing metal particles MP by reacting them with oxygen. The air tower 10 is provided with a supply port IG for supplying the processing gas and air to the inside of the air tower 10. A pipe (not shown) for circulating air is connected to the supply port IG. This pipe is also provided with an on-off valve (not shown) for adjusting the amount of air flowing through it. The opening degree of this on-off valve can be changed according to a control signal from the control unit 80. Inside the air tower 10, the metal particles MP are scattered by the supply of air, and the metal particles MP are sent to the side of the cyclone 20 (described later) which is connected to the upper part of the air tower 10 in the direction of gravity.

[0032] Inside the air tower 10, the metal particles MP are oxidized by reacting with oxygen (contained in the air supplied from the supply port IG). This oxidation of the metal particles MP generates heat of oxidation. In this embodiment, since the metal particles MP are ilmenite, the oxidation of the metal particles MP inside the air tower 10 is represented by the following equation (1). 8FeTiO3+2O2→4Fe2TiO5+4TiO2…(1) The reaction represented by equation (1) above generates heat. Furthermore, the removal of oxygen from the air during this reaction produces a high concentration of nitrogen gas as exhaust gas. For the reaction represented by equation (1) to proceed at a sufficient rate, a temperature of 800°C or higher is necessary. The gas supplied from the supply port IG does not have to be air. It may contain oxygen, or it may be oxygen alone.

[0033] Cyclone 20 is connected to the upper part of the air tower 10 in the direction of gravity, and separates the metal particles MP sent from the air tower 10 from the exhaust gas based on the difference in specific gravity. The exhaust gas, which is a high-concentration nitrogen gas, is sent out of cyclone 20 from the upper part of cyclone 20 in the direction of gravity.

[0034] The first loop seal section 30 is connected to the lower part of the cyclone 20 in the direction of gravity and receives metal particles MP separated from the exhaust gas in the cyclone 20. The first loop seal section 30 restricts the movement of gas between the air tower 10 and the fuel tower 40 by appropriately supplying water vapor as a sealing gas into its interior. This sealing gas also assists in the flow of the metal particles MP within the first loop seal section 30.

[0035] The fuel tower 40 is connected to the first loop seal section 30 via a first pipe 61, which will be described later. The fuel tower reacts metal particles MP oxidized in the air tower 10 with a hydrocarbon fuel to reduce the metal particles MP and discharges the gas generated by the reduction of the metal particles MP. Hydrocarbon fuel is a fuel that generates carbon dioxide and water when burned, and is not limited to hydrocarbons composed only of carbon and hydrogen atoms, but may also be a compound containing atoms other than carbon and hydrogen atoms (for example, oxygen atoms). In this embodiment, methane (CH4) is used as the hydrocarbon fuel. Alcohols such as methanol and ethanol may also be used as the hydrocarbon fuel. The fuel tower 40 is provided with a supply port IF for supplying hydrocarbon fuel to the inside of the fuel tower 40. A pipe (not shown) for circulating the hydrocarbon fuel is connected to the supply port IF. This pipe is also provided with an on-off valve (not shown) for adjusting the amount of hydrocarbon fuel flowing through it. The opening degree of this on-off valve can be changed according to a control signal from the control unit 80, which will be described later. The type of fuel is not limited to methane. Other hydrocarbon fuels, alcohol fuels, H2, and NH3 may also be used.

[0036] Inside the fuel tower 40, the metal particles MP are reduced by reacting with the hydrocarbon fuel. This reduction of the metal particles MP generates a gas containing only carbon dioxide and water. In this embodiment, since the metal particles MP are ilmenite, the reduction of the metal particles MP inside the fuel tower 40 is represented by the following equation (2). 4Fe2TiO5+4TiO2+CH4→8FeTiO3+CO2+2H2O…(2) To promote the reaction represented by formula (2) above, an electric heater may be provided to heat the inside of the fuel tower 40.

[0037] The gas (containing only carbon dioxide and water) generated by the reaction represented by the above formula (2) is discharged to the outside of the fuel tower 40 from the upper part of the fuel tower 40 in the direction of gravity.

[0038] The second loop seal section 50 is connected to the lower part of the fuel tower 40 in the direction of gravity and receives metal particles MP separated from the gas in the fuel tower 40. Similar to the first loop seal section 30, the second loop seal section 50 restricts the movement of gas between the air tower 10 and the fuel tower 40 by appropriately supplying water vapor as a sealing gas into its interior. This sealing gas also assists the flow of the metal particles MP within the second loop seal section 50.

[0039] The circulation piping 60 is a pipe that circulates metal particles MP between the air tower 10 and the fuel tower 40. The circulation piping 60 includes a first pipe 61 and a second pipe 62. The first pipe 61 is a pipe that connects the first loop seal section 30 and the fuel tower 40, and defines a flow path for metal particles MP to flow from the first loop seal section 30 to the fuel tower 40. Metal particles MP used in the reduction reaction in the fuel tower 40 are sent from the first loop seal section 30 to the fuel tower 40 via the first pipe 61. On the other hand, the second pipe 62 is a pipe that connects the second loop seal section 50 and the air tower 10, and defines a flow path for metal particles MP to flow from the second loop seal section 50 to the air tower 10. Metal particles MP used in the oxidation reaction in the air tower 10 are sent from the second loop seal section 50 to the air tower 10 via the second pipe 62.

[0040] The dewatering unit 70 is located above the fuel tower 40 in the direction of gravity and removes water from the gas discharged to the outside of the fuel tower 40. The dewatering unit 70 contains an adsorbent material capable of adsorbing moisture, such as silica gel. The gas that passes through the dewatering unit 70 is a gas containing only carbon dioxide. The dewatering unit 70 is not required. Furthermore, the configuration of the dewatering unit 70 and the method of dewatering are not limited to those described herein. Dewatering may also be performed by cooling the mixed gas.

[0041] The control unit 80 consists of an ECU (Electronic Control Unit) and controls the chemical loop combustion system 1. The control unit 80 controls the opening degree of the on-off valves that adjust the flow rate of VOCs and air through the supply port IG, and the opening degree of the on-off valves that adjust the flow rate of hydrocarbon fuels through the supply port IF.

[0042] As described above, the metal particle MP of this embodiment comprises an outer shell OM that contains Fe2O3 and constitutes the outer skin of the metal particle MP, and an inner solid IM located inside the outer shell OM, with a gap G formed between the outer shell OM and the inner solid IM. As shown in Figure 7, the Fe2O3 content [wt%] in the outer shell OM is 55 wt%, and the Fe2O3 content [wt%] in the inner solid IM is 20 wt%. In other words, the Fe2O3 content [wt%] in the outer shell OM is greater than the Fe2O3 content [wt%] in the inner solid IM. As a result, as shown in Figure 8, both oxidation reactivity and reduction reactivity are greatly improved. Therefore, in the chemical loop combustion system 1 shown in Figure 9, by using metal particle MP with high oxidation and reduction reactivity, it is possible to operate a highly stable chemical loop combustion system with sufficiently reactive metal particle MP from the start of operation.

[0043] Furthermore, according to the metal particle MP of this embodiment, as shown in Figure 7, the Fe2O3 content [wt%] in the outer layer OM is 50 wt% or more. Since Fe has higher reactivity than Ti in the gas, both oxidation reactivity and reduction reactivity are greatly improved, as shown in Figure 7. Therefore, by using metal particle MP with high oxidation and reduction reactivity in the chemical loop combustion system 1, it is possible to operate a highly stable chemical loop combustion system with sufficiently reactive metal particle MP from the start of operation.

[0044] Furthermore, in the metal particle MP of this embodiment, the size of the gap G between the outer shell OM and the inner body IM is 5 μm to 10 μm. This improves the gas diffusivity of the metal particle MP, thereby improving its reactivity. Therefore, by using highly reactive metal particle MP in the chemical loop combustion system 1, it becomes possible to operate a highly stable chemical loop combustion system with sufficiently reactive metal particle MP from the start of operation.

[0045] Furthermore, as shown in Figure 6, the specific surface area (surface area per gram of weight) of the metal particles MP in this embodiment is 0.75 m² or more. This improves the gas diffusivity of the metal particles MP, thereby improving reactivity. Therefore, by using highly reactive metal particles MP in the chemical loop combustion system 1, it becomes possible to operate a highly stable chemical loop combustion system with sufficiently reactive metal particles MP from the start of operation.

[0046] Furthermore, in the metal particle MP of this embodiment, as shown in Figure 5, the Fe2O3 content [wt%] in the total metal particle MP is 20 wt% or more. Since Fe has a higher reactivity than Ti in the gas, both oxidation reactivity and reduction reactivity are greatly improved, as shown in Figure 7. Therefore, by using metal particle MP with high oxidation and reduction reactivity in the chemical loop combustion system 1, it is possible to operate a highly stable chemical loop combustion system with sufficiently reactive metal particle MP from the start of operation.

[0047] <Modified form of this embodiment> The present invention is not limited to the embodiments described above, and can be implemented in various forms without departing from its spirit, for example, the following modifications are also possible.

[0048] [Example 1] While ilmenite particles were used as the material for the metal particles MP, this is not the only option. For example, instead of iron, materials containing copper, nickel, etc., may be used.

[0049] The embodiments of this specification have been described above based on the embodiments and modifications described above. The embodiments described above are for the purpose of facilitating understanding of this specification and do not limit it. This specification may be modified and improved without departing from its spirit and the scope of the claims, and equivalents thereof are included in this specification. Furthermore, any technical features that are not described as essential in this specification may be deleted as appropriate.

[0050] The present invention can also be realized in the following forms. [Application Example 1] Metal particles used in chemical loop combustion devices, The chemical loop combustion apparatus comprises an oxidation tower that generates a high-temperature gas using the heat of oxidation produced by the reaction of an oxidizing gas containing oxygen with the metal particles, and a reduction tower that reduces the metal particles oxidized in the oxidation tower by reaction with fuel. The aforementioned metal particles are It contains iron oxides, The metal particle comprises an outer shell portion that constitutes the outer shell of the metal particle, and an inner solid portion located inside the outer shell portion. A gap is formed between the outer shell and the inner body. The iron oxide content [wt%] in the outer layer is greater than the iron oxide content [wt%] in the inner layer. Metal particles characterized by the following features. [Application Example 2] The metal particles described in Application Example 1, The iron oxide content [wt%] in the outer layer is 50 wt% or more. Metal particles characterized by the following features. [Application Example 3] Metal particles as described in Application Example 1 or Application Example 2, The size of the gap is between 5 μm and 10 μm. Metal particles characterized by the following features. [Application Example 4] Metal particles as described in Application Example 1 or Application Example 2, The surface area per gram is 0.75 m² or more. Metal particles characterized by the following features. [Application Example 5] Metal particles as described in Application Example 1 or Application Example 2, The iron oxide content [wt%] in the total metal particles is 20 wt% or more. Metal particles characterized by the following features. [Application Example 6] A chemical loop combustion device, The system comprises metal particles as described in Application Example 1 or Application Example 2, an oxidation tower that generates a high-temperature gas using the heat of oxidation produced by the reaction of an oxidizing gas containing oxygen with the metal particles, and a reduction tower that reduces the metal particles oxidized in the oxidation tower using fuel. A chemical loop combustion apparatus characterized by the following features. [Application Example 7] A method for manufacturing metal particles used in a chemical loop combustion apparatus, The chemical loop combustion apparatus comprises an oxidation tower that generates a high-temperature gas using the heat of oxidation produced by the reaction of an oxidizing gas containing oxygen with the metal particles, and a reduction tower that reduces the metal particles oxidized in the oxidation tower using fuel. The aforementioned manufacturing method is A step of preparing the metal particles before use in the chemical loop combustion apparatus, The metal particles are subjected to a process of repeatedly performing reduction and oxidation reactions before being used in the chemical loop combustion apparatus. A method for producing metal particles, characterized by the following: [Explanation of Symbols]

[0051] MP…metal particles IM...Internal Affairs OM…Outer skin part G... Gap 1. Chemical loop combustion system 10...Air tower 20...Cyclone 30...First loop seal section 40...fuel tower 50...Second loop seal section 60...Circulation piping 61...First piping 62...Second piping 70...Dehydrator 80... Control Unit IF... Supply port IG…supply port 100...Manufacturing equipment 110... Reactor 111...Gas supply port 112...Gas outlet 120... Heater

Claims

1. Metal particles used in chemical loop combustion devices, The chemical loop combustion apparatus comprises an oxidation tower that generates a high-temperature gas using the heat of oxidation produced by the reaction of an oxidizing gas containing oxygen with the metal particles, and a reduction tower that reduces the metal particles oxidized in the oxidation tower by reaction with fuel. The aforementioned metal particles are It contains iron oxides, The metal particle comprises an outer shell portion that constitutes the outer shell of the metal particle, and an inner solid portion located inside the outer shell portion. A gap is formed between the outer shell and the inner body. The iron oxide content [wt%] in the outer layer is greater than the iron oxide content [wt%] in the inner layer. Metal particles characterized by the following features.

2. Metal particles according to claim 1, The iron oxide content [wt%] in the outer layer is 50 wt% or more. Metal particles characterized by the following features.

3. Metal particles according to claim 1 or claim 2, The size of the gap is between 5 μm and 10 μm. Metal particles characterized by the following features.

4. Metal particles according to claim 1 or claim 2, The surface area per gram of weight is 0.75 m² or more. Metal particles characterized by the following features.

5. Metal particles according to claim 1 or claim 2, The iron oxide content [wt%] in the total metal particles is 20 wt% or more. Metal particles characterized by the following features.

6. A chemical loop combustion device, The invention comprises metal particles according to claim 1 or claim 2, an oxidation tower that generates a high-temperature gas using the heat of oxidation produced by the reaction of an oxidizing gas containing oxygen with the metal particles, and a reduction tower that reduces the metal particles oxidized in the oxidation tower using fuel. A chemical loop combustion apparatus characterized by the following features.

7. A method for manufacturing metal particles used in a chemical loop combustion apparatus, The chemical loop combustion apparatus comprises an oxidation tower that generates a high-temperature gas using the heat of oxidation produced by the reaction of an oxidizing gas containing oxygen with the metal particles, and a reduction tower that reduces the metal particles oxidized in the oxidation tower using fuel. The aforementioned manufacturing method is A step of preparing the metal particles before use in the chemical loop combustion apparatus, The metal particles are subjected to a process of repeatedly performing reduction and oxidation reactions before being used in the chemical loop combustion apparatus. A method for producing metal particles, characterized by the following:

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