Catalytic converter

Abstract

The problem that the technology disclosed herein aims to solve is to suppress variations in the decomposition of a raw material gas from the upstream to the downstream of the flow path in a catalytic device that decomposes a raw material gas into a reaction gas. [Solution] The catalyst apparatus 1 for decomposing a raw material gas into a reaction gas has a flow path 3 and a catalyst 10. The flow path 3 includes a constant cross-sectional area 5 with a substantially constant cross-sectional area. The catalyst 10 is granular and is contained in the constant cross-sectional area 5. By passing through the catalyst 10, the raw material gas is decomposed into a reaction gas and the total number of gas molecules increases. The catalyst 10 has a first average particle size 12a in the upstream area 13 of the constant cross-sectional area 5. The catalyst 10 has a second average particle size 12c which is larger than the first average particle size 12a in the downstream area 15 downstream of the upstream area 13.

Description

Technical Field

[0001] The present invention relates to a catalyst device for decomposing a raw material gas into a reaction gas.

Background Art

[0002] Patent Document 1 discloses a catalyst structure for decomposing ammonia to produce hydrogen. Metal fine particles are used as a catalyst for decomposing ammonia. The catalyst structure is constituted by supporting the catalyst inside a porous carrier of a zeolite-type compound. Ammonia is decomposed into hydrogen and nitrogen. Hydrogen contained in the mixed gas of hydrogen and nitrogen is used as fuel for a fuel cell.

[0003] The catalyst is disposed as a catalyst layer in a flow path through which the raw material gas and the generated mixed gas flow. Considering the thermal efficiency of heating the catalyst layer with a heater from the outside of the flow path and the compactness of the catalyst device, it is desirable that the flow path has a substantially constant cross-sectional area from the upstream to the downstream. On the other hand, since the total number of molecules of the raw material gas and the total number of molecules of the generated mixed gas are not the same, pressure variations occur from the upstream to the downstream in the flow path with a substantially constant cross-sectional area of the conventionally provided catalyst device. For example, the total number of molecules of the generated mixed gas of hydrogen and nitrogen increases to twice the total number of molecules of ammonia of the raw material gas. Therefore, the pressure in the downstream region of the flow path is higher than that in the upstream region. Due to the pressure difference between the upstream and downstream regions, variations also occur in the decomposition of the raw material gas between the upstream and downstream regions. As a result, there is a risk of a decrease in the working efficiency of decomposing the raw material gas and a decrease in the amount of the reaction gas generated because the raw material gas cannot be sufficiently decomposed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The problem that the technology disclosed herein aims to solve is to suppress variations in the decomposition of a raw material gas from the upstream to the downstream of the flow path in a catalytic device that decomposes a raw material gas into a reaction gas. [Means for solving the problem]

[0006] According to one feature of this disclosure, a catalytic device for decomposing a raw material gas into a reaction gas comprises a flow channel and a catalyst. The flow channel includes a constant cross-sectional area having a substantially constant cross-sectional area. The catalyst is granular and contained within the constant cross-sectional area. By passing through the catalyst, the raw material gas is decomposed into a reaction gas, increasing the total number of gas molecules. The catalyst has a first average particle size in the upstream region of the constant cross-sectional area. The catalyst has a second average particle size that is larger than the first average particle size in the downstream region downstream of the upstream region.

[0007] Therefore, a catalyst with a first average particle size is placed in the upstream region of the constant cross-sectional area where the proportion of raw material gas is high and the proportion of reaction gas is low. A catalyst with a second average particle size is placed in the downstream region of the constant cross-sectional area where the proportion of raw material gas is low and the proportion of reaction gas is high. As a result, the void area in the cross-section is larger on average in the downstream region of the constant cross-sectional area than in the upstream region. The total number of molecules, including both raw material gas and reaction gas, increases in regions where the proportion of reaction gas is high. By making the void area in the cross-section larger in the downstream region where the proportion of reaction gas is high than in the upstream region, the increase in pressure in the downstream region relative to the upstream region can be suppressed. This suppresses pressure variation from upstream to downstream of the flow path and suppresses variation in the decomposition of the raw material gas.

[0008] According to other features of this disclosure, the catalyst has a minimum average particle size in the uppermost region including the inlet of the constant cross-sectional area. The catalyst has a maximum average particle size in the lowermost region including the outlet of the constant cross-sectional area. The catalyst has an intermediate average particle size that is larger than the minimum average particle size and smaller than the maximum average particle size in the middle region between the uppermost and lowermost regions.

[0009] Therefore, the intermediate average particle size of the catalyst in the middle reaches is made larger than the minimum average particle size in the uppermost reaches. As a result, the average void area in the cross-section is larger in the middle reaches of the constant cross-section region than in the uppermost reaches. The maximum average particle size of the catalyst in the lowermost reaches is made smaller than the intermediate average particle size in the middle reaches. As a result, the average void area in the cross-section is larger in the lowermost reaches of the constant cross-section region than in the middle reaches. Thus, it is possible to suppress the increase in pressure in the middle reaches relative to the uppermost reaches, and to suppress the increase in pressure in the lowermost reaches relative to the middle reaches. As a result, pressure variations can be suppressed between the uppermost, middle, and lowermost reaches of the flow path, and variations in the decomposition of the raw material gas can be suppressed.

[0010] According to other features of this disclosure, the average particle size of the catalyst gradually increases from upstream to downstream along the entire length of the constant cross-sectional area. Therefore, the average particle size of the catalyst gradually increases as the proportion of the reaction gas increases from the inlet to the outlet of the constant cross-sectional area. This allows for more efficient suppression of pressure variations and variations in the decomposition of the raw material gases along the entire length of the constant cross-sectional area.

[0011] According to other features of this disclosure, the constant cross-sectional area has a first average void area in the upstream area. The constant cross-sectional area has a second average void area in the downstream area that is larger than the first average void area. Therefore, granular catalysts are arranged in the upstream and downstream areas respectively such that the second average void area in the downstream area of ​​the constant cross-sectional area is larger than the first average void area in the upstream area. This makes it possible to more reliably suppress pressure variations between the upstream and downstream areas of the constant cross-sectional area.

[0012] According to other features of this disclosure, the average void area over a predetermined length of the constant cross-sectional area gradually increases from upstream to downstream along the entire length of the constant cross-sectional area. Therefore, the average void area gradually increases as the proportion of reaction gas increases from the inlet to the outlet of the constant cross-sectional area. This makes it possible to more reliably and efficiently suppress pressure variations along the entire length of the constant cross-sectional area.

[0013] According to other features of this disclosure, the raw material gas is ammonia. Therefore, even when the total number of molecules in the reaction gas, which is a mixture of hydrogen and nitrogen, increases to twice the total number of molecules in the raw material gas ammonia, variations in pressure and variations in the decomposition of the raw material gas can be suppressed from the upstream to the downstream of the flow path. [Brief explanation of the drawing]

[0014] [Figure 1] This is a block diagram of a fuel cell system equipped with a catalyst device related to this disclosure. [Figure 2] This is a schematic longitudinal cross-sectional view showing a catalyst device according to the first embodiment. [Figure 3] This figure shows cross-sections of the uppermost, middlemost, and lowermost regions of the catalytic converter. [Figure 4] This graph shows the number of molecules in the source gas and reaction gas from upstream to downstream. [Figure 5] This is a schematic longitudinal cross-sectional view showing a catalyst device according to the second embodiment. [Figure 6] This is a schematic longitudinal cross-sectional view showing a catalyst device according to the third embodiment. [Figure 7] This is a schematic longitudinal cross-sectional view showing a catalyst device according to the fourth embodiment. [Figure 8] This is a schematic longitudinal cross-sectional view showing a catalyst device according to the fifth embodiment. [Figure 9] This is a schematic longitudinal cross-sectional view showing a catalyst device according to the sixth embodiment. [Figure 10] This is a schematic longitudinal cross-sectional view showing a catalyst device according to the seventh embodiment. [Modes for carrying out the invention]

[0015] Hereinafter, a first embodiment of the catalyst device of the present disclosure will be described based on FIGS. 1 to 4. The same reference numerals in the description denote the same elements having the same functions without redundant description. As shown in FIG. 1, the catalyst device 1 is provided in the fuel cell system 20. The fuel cell system 20 has an ammonia storage 21 upstream of the catalyst device 1. The fuel cell system 20 has an adsorption device 22 downstream of the catalyst device 1, and a fuel cell (FC) 23 is arranged further downstream.

[0016] As shown in FIG. 1, ammonia (NH3) as a raw material gas is introduced from the ammonia storage 21 into the catalyst device 1. In the catalyst device 1, ammonia is decomposed into hydrogen (H2) and nitrogen (N2), and a reaction gas containing hydrogen and nitrogen is generated. A mixed gas containing the reaction gas and a small amount of ammonia that was not decomposed is discharged from the catalyst device 1 to the adsorption device 22. The adsorption device 22 adsorbs the ammonia contained in the mixed gas. A purified gas from which ammonia has been removed from the mixed gas is introduced into the fuel cell 23. The fuel cell 23 generates electricity using hydrogen contained in the purified gas as fuel.

[0017] As shown in FIG. 2, the catalyst device 1 has a substantially cylindrical housing 2. A flow path 3 is provided inside the housing 2. A raw material gas inlet 3a communicating with the flow path 3 is provided at the upstream end of the housing 2. Ammonia as the raw material gas is introduced from the upstream ammonia storage 21 (see FIG. 1) into the flow path 3 of the catalyst device 1 through the raw material gas inlet 3a. A reaction gas outlet 3b communicating with the flow path 3 is provided at the downstream end of the housing 2. A mixed gas containing hydrogen and nitrogen as the reaction gas is discharged from the flow path 3 to the downstream adsorption device 22 (see FIG. 1) through the reaction gas outlet 3b.

[0018] As shown in Fig. 2, most of the flow path 3 is a constant cross-section area region 5 with a substantially constant cross-sectional area orthogonal to the flow direction. The cross-sectional area is substantially constant from the inlet 5a at the upstream end to the outlet 5b at the downstream end of the constant cross-section area region 5. In the present disclosure, the substantially constant cross-sectional area means that the maximum cross-sectional area is, for example, +10% or less, +5% or less, +3% or less with respect to the minimum cross-sectional area of the constant cross-section area region 5. A heater 4 is provided on the radially outer side of the housing 2. The heater 4 heats the constant cross-section area region 5 substantially uniformly. The radially outer periphery of the heater 4 is covered with a heat insulating material (not shown).

[0019] As shown in Fig. 2, the constant cross-section area region 5 is a catalyst layer in which a plurality of catalysts 10 are accommodated. The catalyst 10 is in a substantially spherical granular or块状 form. The plurality of catalysts 10 are provided in generally the same shape. A void 11 is formed between the plurality of catalysts 10. The catalyst 10 is formed by mixing metal fine particles etc. that function as the catalyst itself with a carrier and baking them. Metal fine particles etc. are supported and exposed on the surface of the catalyst 10. The material of the metal fine particles etc. may be, for example, at least one of ruthenium, nickel, cobalt, palladium, but is not limited thereto and may be other metals, alloys, etc. For the sake of easy viewing of the figure, the catalyst 10 filled only in a partial region of the constant cross-section area region 5 is shown in the figure, but actually the catalyst 10 is filled over the entire length of the constant cross-section area region 5. Also, the size of the catalyst 1 that in the figure schematically shows the relative size relationship of each of the plurality of catalysts 10, for example, does not specifically specify the size ratio of each catalyst 10, nor does it specify the size ratio of the catalyst 10 to the housing 2, for example.

[0020] As shown in Figure 2, the constant cross-sectional area 5 includes the uppermost region 13, which includes the inlet 5a; the lowermost region 15, which includes the outlet 5b; and the middle region 14 between the uppermost region 13 and the lowermost region 15. The uppermost region 13 is filled with catalyst 10 with a particle size of 10a. The average particle size 12 of the catalyst 10 in the uppermost region 13 is approximately the same diameter as particle size 10a, which is the uppermost average particle size 12a. The middle region 14 is filled with catalyst 10 with a particle size of 10b. Particle size 10b is larger in diameter than particle size 10a. The average particle size 12 of the catalyst 10 in the middle region 14 is approximately the same diameter as particle size 10b and is larger in diameter than the uppermost average particle size 12a, which is the middle average particle size 12b. The lowermost region 15 is filled with catalyst 10 with a particle size of 10c. Particle size 10c is larger in diameter than particle size 10b. The average particle size 12 of the catalyst 10 in the downstream region 15 is approximately the same diameter as the particle size 10c and is larger than the midstream average particle size 12b, resulting in a downstream average particle size 12c.

[0021] As shown in Figure 2, the second average particle size in the lower reaches is larger than the first average particle size in the upper reaches. When the uppermost reaches 13 are considered the upper reaches and the lowermost reaches 15 are considered the lower reaches, the second average particle size, the lowermost average particle size 12c, is larger than the first average particle size, the uppermost average particle size 12a. When the uppermost reaches 13 are considered the upper reaches and the middle reaches 14 are considered the lower reaches, the second average particle size, the middle reaches average particle size 12b, is larger than the first average particle size, the uppermost average particle size 12a. When the middle reaches 14 are considered the upper reaches and the lowermost reaches 15 are considered the lower reaches, the second average particle size, the lowermost average particle size 12c, is larger than the first average particle size, the middle reaches average particle size 12b.

[0022] As shown in Figure 2, the average particle size 12 of the catalyst 10 gradually increases from upstream to downstream, in the uppermost reaches 13, middle reaches 14, and lower reaches 15, with the uppermost average particle size being 12a, the middle reaches 12b, and the lower reaches 12c. The uppermost average particle size 12a in the uppermost reaches 13 is the smallest among the average particle sizes 12 in each of the constant cross-sectional area 5. The lowermost average particle size 12c in the lower reaches 15 is the largest among the average particle sizes 12 in each of the constant cross-sectional area 5. The middle reaches average particle size 12b in the middle reaches 14 is an intermediate average particle size that is larger than the smallest average particle size, the uppermost average particle size 12a, and smaller than the largest average particle size, the lower reaches average particle size 12c.

[0023] As shown in Figure 3, the average void area obtained by averaging the area of ​​voids 11 in each cross-section of the uppermost reaches 13 across the entire uppermost reaches 13 is approximately the same size as the area of ​​voids 11 in a cross-section at a predetermined location in the uppermost reaches 13. The average void area obtained by averaging the area of ​​voids 11 in each cross-section of the middle reaches 14 across the entire middle reaches 14 is approximately the same size as the area of ​​voids 11 in a cross-section at a predetermined location in the middle reaches 14. The average void area obtained by averaging the area of ​​voids 11 in each cross-section of the lowermost reaches 15 across the entire lowermost reaches 15 is approximately the same size as the area of ​​voids 11 in a cross-section at a predetermined location in the lowermost reaches 15. The average void area in each region of the fixed cross-section area 5 gradually increases from upstream to downstream, starting with the uppermost reaches 13, the middle reaches 14, and the lowermost reaches 15.

[0024] As shown in Figure 3, the second average void area in the lower reaches is larger than the first average void area in the upper reaches. When the uppermost reaches 13 are considered the upper reaches and the lowermost reaches 15 are considered the lower reaches, the second average void area in the lowermost reaches 15 is larger than the first average void area in the uppermost reaches 13. When the uppermost reaches 13 are considered the upper reaches and the middle reaches 14 are considered the lower reaches, the second average void area in the middle reaches 14 is larger than the first average void area in the upper reaches 13. When the middle reaches 14 are considered the upper reaches and the lowermost reaches 15 are considered the lower reaches, the second average void area in the lowermost reaches 15 is larger than the first average void area in the middle reaches 14.

[0025] Ammonia is decomposed into hydrogen and nitrogen as shown in the following chemical equation (1). As shown in Figure 4, if the total number of ammonia molecules in the raw material gas is n, and all of the ammonia is decomposed into hydrogen and nitrogen, the total number of molecules in the reaction gas mixture of hydrogen and nitrogen increases to 2n. Therefore, the total number of molecules per unit volume, including both the raw material gas and the reaction gas, increases as you move downstream from the constant cross-sectional area 5 (see Figure 2). By increasing the void 11 downstream of the constant cross-sectional area 5 compared to upstream, the pressure increase due to the increase in the total number of molecules can be suppressed. 2NH3 → 3H2 + N2 ... (1)

[0026] As described above, the catalyst apparatus 1 for decomposing the raw material gas into a reaction gas has a flow path 3 and a catalyst 10, as shown in Figure 2. The flow path 3 includes a constant cross-sectional area 5 with a substantially constant cross-sectional area. The catalyst 10 is granular and is contained within the constant cross-sectional area 5. By passing through the catalyst 10, the raw material gas is decomposed into a reaction gas, increasing the total number of gas molecules. The catalyst 10 has a first average particle size 12a in the upstream area (upstreammost area) 13 of the constant cross-sectional area 5. The catalyst 10 has a second average particle size 12c, which is larger than the first average particle size 12a, in the downstream area (downstreammost area) 15 downstream from the upstream area 13.

[0027] Therefore, a first catalyst 10 with an average particle size of 12a is placed in the upstream region 13 of the constant cross-sectional region 5, where the proportion of raw material gas is high and the proportion of reaction gas is low. A second catalyst 10 with an average particle size of 12c is placed in the downstream region 15 of the constant cross-sectional region 5, where the proportion of raw material gas is low and the proportion of reaction gas is high. As a result, the downstream region 15 of the constant cross-sectional region 5 has a larger average void area in the cross-section than the upstream region 13. The higher the proportion of reaction gas, the greater the total number of molecules of the raw material gas and reaction gas combined. By making the void area in the cross-section larger in the downstream region 15, where the proportion of reaction gas is high, than in the upstream region 13, it is possible to suppress the increase in pressure in the downstream region 15 relative to the upstream region 13. This suppresses pressure variation from upstream to downstream of the flow path 3, and thus suppresses variation in the decomposition of the raw material gas.

[0028] As shown in Figure 2, catalyst 10 has a minimum average particle size 12a in the uppermost region 13, which includes the inlet 5a of the constant cross-sectional region 5. Catalyst 10 has a maximum average particle size 12c in the lowermost region 15, which includes the outlet 5b of the constant cross-sectional region 5. Catalyst 10 has an intermediate average particle size 12b in the middle region 14 between the uppermost region 13 and the lowermost region 15, which is larger than the minimum average particle size 12a and smaller than the maximum average particle size 12c.

[0029] Therefore, the intermediate average particle size 12b of the catalyst 10 in the middle reaches 14 is made larger than the minimum average particle size 12a in the uppermost reaches 13. As a result, the average void area in the cross-section of the middle reaches 14 of the constant cross-section region 5 is larger than that of the uppermost reaches 13. The maximum average particle size 12c of the catalyst 10 in the lowermost reaches 15 is made smaller than the intermediate average particle size 12b in the middle reaches 14. As a result, the average void area in the cross-section of the lowermost reaches 15 of the constant cross-section region 5 is larger than that of the middle reaches 14. Thus, the increase in pressure in the middle reaches 14 relative to the uppermost reaches 13 can be suppressed, and the increase in pressure in the lowermost reaches 15 relative to the middle reaches 14 can be suppressed. As a result, pressure variations can be suppressed between the uppermost reaches 13, the middle reaches 14, and the lowermost reaches 15 of the flow path 3, and variations in the decomposition of the raw material gas can be suppressed.

[0030] As shown in Figures 2 and 3, the average particle size 12 of the catalyst 10 gradually increases from upstream to downstream along the entire length of the constant cross-sectional area 5. Therefore, as the proportion of reaction gas increases from the inlet 5a to the outlet 5b of the constant cross-sectional area 5, the average particle size 12 of the catalyst 10 is gradually increased. This allows for more efficient suppression of pressure variations and variations in the decomposition of the raw material gas along the entire length of the constant cross-sectional area 5.

[0031] As shown in Figures 2 and 3, the constant cross-sectional area 5 has a first average void area in the upstream area 13. The constant cross-sectional area 5 has a second average void area in the downstream area 15 that is larger than the first average void area. Therefore, granular catalyst 10 is placed in the upstream area 13 and the downstream area 15 respectively so that the second average void area in the downstream area 15 of the constant cross-sectional area 5 is larger than the first average void area in the upstream area 13. This makes it possible to more reliably suppress pressure variations between the upstream area 13 and the downstream area 15 of the constant cross-sectional area 5.

[0032] As shown in Figures 2 and 3, the average void area over a predetermined length of the constant cross-sectional area 5 gradually increases from upstream to downstream along the entire length of the constant cross-sectional area 5. Therefore, the average void area gradually increases as the proportion of reaction gas increases from the inlet 5a to the outlet 5b of the constant cross-sectional area 5. This makes it possible to more reliably and efficiently suppress pressure variations along the entire length of the constant cross-sectional area 5.

[0033] As shown in Figure 4, the raw material gas is ammonia. Therefore, even when the total number of molecules in the reaction gas, which is a mixture of hydrogen and nitrogen, increases to 2n, which is twice the total number of molecules of ammonia in the raw material gas (n), it is possible to suppress pressure variations and variations in the decomposition of the raw material gas from the upstream to the downstream of the flow path 3.

[0034] A second embodiment of the catalyst apparatus of this disclosure will be described below with reference to Figure 5. In the second embodiment, the constant cross-sectional area 5 of the catalyst apparatus 30 has, in order from upstream, an uppermost area 32, a middle upper area 33, a middle lower area 34, and a lowest cross-sectional area 35, instead of the uppermost area 13, middle upper area 14, and lowest cross-sectional area 15 shown in Figure 2. The uppermost area 32 includes the inlet 5a of the constant cross-sectional area 5. The lowest cross-sectional area 35 includes the outlet 5b of the constant cross-sectional area 5. In the following description, only the parts that differ from the first embodiment will be described in detail.

[0035] As shown in Figure 5, the uppermost region 32 is filled with catalyst 10 with a particle size of 10a. The average particle size 31 of the catalyst 10 in the uppermost region 32 is the uppermost average particle size 31a, which is approximately the same diameter as particle size 10a. The middle and upper regions 33 are filled with catalyst 10 of two different sizes, particle size 10a and particle size 10b. The catalyst 10 with particle size 10a and the catalyst 10 with particle size 10b are mixed fairly uniformly within the middle and upper regions 33. In the following description, catalysts of multiple sizes within the same region are mixed fairly uniformly with each other. The average particle size 31 of the catalyst 10 in the middle and upper regions 33 is the middle and upper average particle size 31b, which is larger than particle size 10a and the uppermost average particle size 31a, and smaller than particle size 10b. The middle and lower regions 34 are filled with catalyst 10 of two different sizes, particle size 10b and particle size 10c. The average particle size 31 of the catalyst 10 in the middle and lower reaches 34 is larger than the middle and upper average particle size 31b, larger than particle size 10b, and smaller than particle size 10c, which is the middle and lower average particle size 31c. The furthest downstream reach 35 is filled with catalyst 10 with a particle size of 10c. The average particle size 31 of the catalyst 10 in the furthest downstream reach 35 is approximately the same diameter as particle size 10c and larger than the middle and lower average particle size 31c, which is the furthest downstream average particle size 31d.

[0036] As shown in Figure 5, when the uppermost reaches 32 are considered the upper reaches, and the middle upper reaches 33, middle lower reaches 34, or the lowest reaches 35 are considered the lower reaches, the second average particle size, which is the middle upper reaches average particle size 31b, the middle lower reaches average particle size 31c, or the lowest reaches average particle size 31d, is greater than the first average particle size, which is the uppermost reaches average particle size 31a. When the middle upper reaches 33 are considered the upper reaches, and the middle lower reaches 34 or the lowest reaches 35 are considered the lower reaches, the second average particle size, which is the middle lower reaches average particle size 31c, or the lowest reaches average particle size 31d, is greater than the first average particle size, which is the middle upper reaches average particle size 31b. When the middle lower reaches 34 are considered the upper reaches, and the lowest reaches 35 are considered the lower reaches, the second average particle size, which is the lowest reaches average particle size 31d, is greater than the first average particle size, which is the middle lower reaches average particle size 31c.

[0037] As shown in Figure 5, the average particle size 31 of the catalyst 10 gradually increases from upstream to downstream, starting with the uppermost average particle size 31a, the middle-uppermost average particle size 31b, the middle-downpermost average particle size 31c, and the lowermost average particle size 31d. The uppermost average particle size 31a is the smallest, and the lowermost average particle size 31d is the largest. The middle-uppermost average particle size 31b and the middle-downpermost average particle size 31c are intermediate average particle sizes that are larger than the smallest average particle size (uppermost average particle size 31a) and smaller than the largest average particle size (lowestmost average particle size 31d).

[0038] As shown in Figure 5, the average void area in each region of the constant cross-sectional area 5 gradually increases from upstream to downstream, starting with the uppermost region 32, then the middle upper region 33, the middle lower region 34, and finally the lowest region 35, as the average grain size in each region increases. When the uppermost region 32 is considered the upper region, and the middle upper region 33, or the middle lower region 34, or the lowest region 35 is considered the lower region, the second average void area of ​​each lower region is larger than the first average void area of ​​the uppermost region 32. When the middle upper region 33 is considered the upper region, and the middle lower region 34, or the lowest region 35 is considered the lower region, the second average void area of ​​each lower region is larger than the first average void area of ​​the middle upper region 33. When the middle lower region 34 is considered the upper region, and the lowest region 35 is considered the lower region, the second average void area of ​​the lowest region 35 is larger than the first average void area of ​​the middle lower region 34.

[0039] The catalyst device 30 of the second embodiment described above provides the same effects as the first embodiment. For example, pressure variations can be suppressed from the upstream to the downstream of the flow path 3, and variations in the decomposition of the raw material gas can be suppressed.

[0040] A third embodiment of the catalyst apparatus of this disclosure will be described below with reference to Figure 6. In the third embodiment, the constant cross-sectional area 5 of the catalyst apparatus 40 has, in order from upstream, an uppermost area 42, a middle area 43, and a lowermost area 44, instead of the uppermost area 13, middle area 14, and lowermost area 15 shown in Figure 2. The uppermost area 42 includes the inlet 5a of the constant cross-sectional area 5. The lowermost area 44 includes the outlet 5b of the constant cross-sectional area 5. In the following description, only the parts that differ from the first embodiment will be described in detail.

[0041] As shown in Figure 6, the uppermost region 42 is filled with catalyst 10 of two different sizes, particle size 10a and particle size 10b. The average particle size 41 of the catalyst 10 in the uppermost region 42 is the uppermost average particle size 41a, which is larger than particle size 10a and smaller than particle size 10b. The middle region 43 is filled with catalyst 10 of particle size 10b. The average particle size 41 of the catalyst 10 in the middle region 43 is the middle average particle size 41b, which is approximately the same diameter as particle size 10a and larger than the uppermost average particle size 41a. The lowermost region 44 is filled with catalyst 10 of two different sizes, particle size 10b and particle size 10c. The average particle size 41 of the catalyst 10 in the lowermost region 44 is the lowermost average particle size 41c, which is larger than particle size 10b and the middle average particle size 41b and smaller than particle size 10c.

[0042] As shown in Figure 6, when the uppermost reaches 42 are considered the upper reaches and the middle reaches 43 or the lower reaches 44 are considered the lower reaches, the second average particle size, the middle reaches average particle size 41b or the lower reaches average particle size 41c, is larger than the first average particle size, the upper reaches average particle size 41a. When the middle reaches 43 are considered the upper reaches and the lower reaches 44 are considered the lower reaches, the second average particle size, the lower reaches average particle size 41c, is larger than the first average particle size, the middle reaches average particle size 41b. The average particle size 41 of the catalyst 10 gradually increases from upstream to downstream, with the upper reaches average particle size 41a, the middle reaches average particle size 41b, and the lower reaches average particle size 41c. The upper reaches average particle size 41a is the smallest, and the lower reaches average particle size 41c is the largest. The middle reaches average particle size 41b is an intermediate average particle size that is larger than the minimum average particle size, the upper reaches average particle size 41a, and smaller than the maximum average particle size, the lower reaches average particle size 41c.

[0043] As shown in Figure 6, the average void area in each region of the constant cross-sectional area 5 gradually increases from upstream to downstream, starting with the uppermost reaches 42, then the middle reaches 43, and finally the lower reaches 44, as the average grain size in each region increases. When the uppermost reaches 42 is considered the upper reaches and the middle reaches 43 or the lower reaches 44 is considered the lower reaches, the second average void area of ​​each lower reaches is larger than the first average void area of ​​the uppermost reaches 42. When the middle reaches 43 is considered the upper reaches and the lower reaches 44 is considered the lower reaches, the second average void area of ​​the lower reaches 44 is larger than the first average void area of ​​the middle reaches 43.

[0044] The catalyst device 40 of the third embodiment described above provides the same effects as the first embodiment. For example, pressure variations can be suppressed from the upstream to the downstream of the flow path 3, and variations in the decomposition of the raw material gas can be suppressed.

[0045] A fourth embodiment of the catalyst apparatus of this disclosure will be described below with reference to Figure 7. In the fourth embodiment, the constant cross-sectional area 5 of the catalyst apparatus 50 has, in order from upstream, an uppermost area 52, a middle area 53, and a lowermost area 54, instead of the uppermost area 13, middle area 14, and lowermost area 15 shown in Figure 2. The uppermost area 52 includes the inlet 5a of the constant cross-sectional area 5. The lowermost area 54 includes the outlet 5b of the constant cross-sectional area 5. In the following description, only the parts that differ from the first embodiment will be described in detail.

[0046] As shown in Figure 7, the uppermost reaches 52, the middle reaches 53, and the lowermost reaches 54 are all filled with catalysts 10 of two different sizes: particle size 10a and particle size 10c. The proportion of catalysts 10 with a small diameter of particle size 10a decreases from upstream to downstream in the uppermost reaches 52, middle reaches 53, and lowermost reaches 54. The average particle size 51 of the catalysts 10 in the uppermost reaches 52 is the uppermost average particle size 51a, which is larger than particle size 10a and smaller than particle size 10c. The average particle size 51 of the catalysts 10 in the middle reaches 53 is the middle average particle size 51b, which is larger than particle size 10a, larger than the uppermost average particle size 51a, and smaller than particle size 10c. The average particle size 51 of the catalysts 10 in the lowermost reaches 54 is the lowermost average particle size 51c, which is larger than particle size 10a, larger than the middle average particle size 51b, and smaller than particle size 10c.

[0047] As shown in Figure 7, when the uppermost reaches 52 are considered the upper reaches and the middle reaches 53 or the lower reaches 54 are considered the lower reaches, the second average particle size, the middle reaches average particle size 51b or the lower reaches average particle size 51c, is larger than the first average particle size, the upper reaches average particle size 51a. When the middle reaches 53 are considered the upper reaches and the lower reaches 54 are considered the lower reaches, the second average particle size, the lower reaches average particle size 51c, is larger than the first average particle size, the middle reaches average particle size 51b. The average particle size 51 of the catalyst 10 gradually increases from upstream to downstream, with the upper reaches average particle size 51a, the middle reaches average particle size 51b, and the lower reaches average particle size 51c. The upper reaches average particle size 51a is the smallest, and the lower reaches average particle size 51c is the largest. The middle reaches average particle size 51b is an intermediate average particle size that is larger than the minimum average particle size, the upper reaches average particle size 51a, and smaller than the maximum average particle size, the lower reaches average particle size 51c.

[0048] As shown in Figure 7, the average void area in each region of the constant cross-sectional area 5 gradually increases from upstream to downstream, starting with the uppermost reaches 52, then the middle reaches 53, and finally the lower reaches 54, as the average grain size in each region increases. When the uppermost reaches 52 is considered the upper reaches and the middle reaches 53 or the lower reaches 54 is considered the lower reaches, the second average void area in each lower reaches is larger than the first average void area in the uppermost reaches 52. When the middle reaches 53 is considered the upper reaches and the lower reaches 54 is considered the lower reaches, the second average void area in the lower reaches 54 is larger than the first average void area in the middle reaches 53.

[0049] The catalyst device 50 of the fourth embodiment described above provides the same effects as the first embodiment. For example, pressure variations can be suppressed from the upstream to the downstream of the flow path 3, and variations in the decomposition of the raw material gas can be suppressed.

[0050] A fifth embodiment of the catalyst apparatus of this disclosure will be described below with reference to Figure 8. In the fifth embodiment, the constant cross-sectional area 5 of the catalyst apparatus 60 has, in order from upstream, an uppermost area 62, a middle area 63, and a lowermost area 64, instead of the uppermost area 13, middle area 14, and lowermost area 15 shown in Figure 2. The uppermost area 62 includes the inlet 5a of the constant cross-sectional area 5. The lowermost area 64 includes the outlet 5b of the constant cross-sectional area 5. In the following description, only the parts that differ from the first embodiment will be described in detail.

[0051] As shown in Figure 8, both the uppermost reaches 62 and the middle reaches 63 are filled with catalyst 10 with a particle size of 10a. The middle reaches 63 is continuous with the uppermost reaches 62 and can also be described as being included in the uppermost reaches 62. The average particle size 61 of the catalyst 10 in the uppermost reaches 62 and the middle reaches 63 is approximately the same diameter as particle size 10a, with the uppermost average particle size 61a and the middle reaches average particle size 61b. The lowermost reaches 64 is filled with catalyst 10 with a particle size of 10c. The average particle size 61 of the catalyst 10 in the lowermost reaches 64 is approximately the same diameter as particle size 10c and the lowermost average particle size 61c, which is larger than the uppermost average particle size 61a and the middle reaches average particle size 61b.

[0052] As shown in Figure 8, when the uppermost reaches 62 or the middle reaches 63 are considered the upper reaches and the lowermost reaches 64 are considered the lower reaches, the second average particle size, the lowermost average particle size 61c, is larger than the first average particle size, the uppermost average particle size 61a or the middle reaches average particle size 61b. The average particle size 61 of the catalyst 10 is approximately the same diameter or larger from upstream to downstream, corresponding to the uppermost average particle size 61a, the middle reaches average particle size 61b, and the lowermost average particle size 61c. The uppermost average particle size 61a and the middle reaches average particle size 61b are the minimum average particle sizes, and the lowermost average particle size 61c is the maximum average particle size.

[0053] As shown in Figure 8, the average void area in each region of the constant cross-sectional area 5 increases or becomes approximately the same from upstream to downstream, in the uppermost region 62, middle region 63, and lowermost region 64, as the average particle size in each region increases. If the uppermost region 62 or middle region 63 is considered the upper region and the lowermost region 64 is considered the lower region, then the second average void area in the lowermost region 64 is larger than the first average void area in the uppermost region 62 or middle region 63.

[0054] The catalyst device 60 of the fifth embodiment described above provides the same effects as the first embodiment. For example, pressure variations can be suppressed from the upstream to the downstream of the flow path 3, and variations in the decomposition of the raw material gas can be suppressed.

[0055] Hereinafter, a sixth embodiment of the catalyst apparatus of this disclosure will be described with reference to Figure 9. In the sixth embodiment, the constant cross-sectional area 5 of the catalyst apparatus 70 has, in order from upstream, an uppermost area 72, a middle upper area 73, a middle upper area 74, a middle lower area 75, and a lowest cross-sectional area 76, instead of the uppermost area 13, middle area 14, and lowest cross-sectional area 15 shown in Figure 2. The uppermost area 72 includes the inlet 5a of the constant cross-sectional area 5. The lowest cross-sectional area 76 includes the outlet 5b of the constant cross-sectional area 5. In the following description, only the parts that differ from the first embodiment will be described in detail.

[0056] As shown in Figure 9, the uppermost region 72 is filled with catalyst 10 with a particle size of 10b. The average particle size 71 of the catalyst 10 in the uppermost region 72 is approximately the same diameter as particle size 10b, which is the uppermost average particle size 71a. The middle and upper regions 73 are filled with catalyst 10 with a particle size of 10a. The average particle size 71 of the catalyst 10 in the middle and upper regions 73 is approximately the same diameter as particle size 10a, which is the middle and upper average particle size 71b. The middle region 74 is filled with catalyst 10 with a particle size of 10b. The average particle size 71 of the catalyst 10 in the middle region 74 is approximately the same diameter as particle size 10b and is larger than the middle and upper average particle size 71b, which is the middle average particle size 71c. The middle and lower regions 75 are filled with catalyst 10 with a particle size of 10c. The average particle size 71 of the catalyst 10 in the middle and lower regions 75 is approximately the same diameter as particle size 10c and is larger than the middle average particle size 71c, which is the middle and lower average particle size 71d. The downstream region 76 is filled with catalyst 10 with a particle size of 10d. The average particle size 71 of the catalyst 10 in the downstream region 76 is approximately the same diameter as particle size 10d and is greater than the mid-to-downstream average particle size 71d, resulting in a downstream average particle size 71e.

[0057] As shown in Figure 9, when the uppermost reaches 72 are considered the upper reaches and the middle / lower reaches 75 or the lowermost reaches 76 are considered the lower reaches, the second average particle size, the middle / lower reaches average particle size 71d or the lowermost reaches average particle size 71e, is greater than the first average particle size, the uppermost reaches average particle size 71a. When the middle / upper reaches 73 are considered the upper reaches and the middle reaches 74, the middle / lower reaches 75, or the lowermost reaches 76 are considered the lower reaches, the second average particle size, the middle reaches average particle size 71c, the middle / lower reaches average particle size 71d, or the lowermost reaches average particle size 71e, is greater than the first average particle size, the middle / upper reaches average particle size 71b. When the middle reaches 74 are considered the upper reaches and the middle / lower reaches 75 or the lowermost reaches 76 are considered the lower reaches, the second average particle size, the middle / lower reaches average particle size 71d or the lowermost reaches average particle size 71e, is greater than the first average particle size, the middle reaches average particle size 71c. If the middle and lower reaches 75 are considered the upper reaches and the very lower reaches 76 are considered the lower reaches, then the second average particle size, the very lower reaches average particle size 71e, is greater than the first average particle size, the middle and lower reaches average particle size 71d.

[0058] As shown in Figure 9, the average particle size 71 of the catalyst 10 gradually increases from the upper and middle reaches 73 downstream to the upper and middle reaches average particle size 71b, the middle reaches average particle size 71c, the lower and middle reaches average particle size 71d, and the lower reaches average particle size 71e. The lower and middle reaches average particle size 71d is an intermediate average particle size that is larger than the upper reaches average particle size 71a and smaller than the lower reaches average particle size 71e.

[0059] As shown in Figure 9, the average void area in each region of the constant cross-sectional area 5 gradually increases from the middle and upper reaches 73 downstream as the average particle size in each region increases. When the uppermost reaches 72 are considered the upper reaches and the middle and lower reaches 75 or the lowermost reaches 76 are considered the lower reaches, the second average void area of ​​each lower reaches is greater than the first average void area of ​​the uppermost reaches 72. When the middle and upper reaches 73 are considered the upper reaches and the middle reaches 74, the middle and lower reaches 75, or the lowermost reaches 76 are considered the lower reaches, the second average void area of ​​each lower reaches is greater than the first average void area of ​​the middle and upper reaches 73. When the middle reaches 74 are considered the upper reaches and the middle and lower reaches 75 or the lowermost reaches 76 are considered the lower reaches, the second average void area of ​​each lower reaches is greater than the first average void area of ​​the middle reaches 74. When the middle and lower reaches 75 are considered the upper reaches and the lowermost reaches 76 are considered the lower reaches, the second average void area of ​​the lowermost reaches 76 is greater than the first average void area of ​​the middle and lower reaches 75.

[0060] The catalyst device 70 of the sixth embodiment described above provides the same effects as the first embodiment. For example, pressure variations can be suppressed from the upstream to the downstream of the flow path 3, and variations in the decomposition of the raw material gas can be suppressed.

[0061] Hereinafter, a seventh embodiment of the catalyst apparatus of this disclosure will be described with reference to Figure 10. In the seventh embodiment, the constant cross-sectional area 5 of the catalyst apparatus 80 has, in order from upstream, an uppermost area 82, a middle area 83, and a downstream area 84, instead of the uppermost area 13, middle area 14, and downstream area 15 shown in Figure 2. The uppermost area 82 includes the inlet 5a of the constant cross-sectional area 5. The downstream area 84 includes the outlet 5b of the constant cross-sectional area 5. In the following description, only the parts that differ from the first embodiment will be described in detail.

[0062] As shown in Figure 10, both the uppermost region 82 and the lowermost region 84 are filled with catalyst 10 with a particle size of 10a. The average particle size 81 of the catalyst 10 in the uppermost region 82 and the lowermost region 84 is approximately the same diameter as particle size 10a, with the uppermost average particle size 81a and the lowermost average particle size 81c. The middle region 83 is filled with catalyst 10 with a particle size of 10c. The average particle size 81 of the catalyst 10 in the middle region 83 is approximately the same diameter as particle size 10c and is larger than the uppermost average particle size 81a and the lowermost average particle size 81c, with the middlemost average particle size 81b. If the uppermost region 82 is considered the upper reaches and the middle region 83 is considered the lower reaches, the second average particle size, the middlemost average particle size 81b, is larger than the first average particle size, the uppermost average particle size 81a. The average particle size 81 of the catalyst 10 increases from the uppermost region 82 to the middle region 83, with the uppermost average particle size 81a and the middlemost average particle size 81b.

[0063] As shown in Figure 10, the average void area in each region of the constant cross-sectional area 5 increases as the average particle size increases from the uppermost region 82 to the middle region 83. If the uppermost region 82 is considered the upper reaches and the middle region 83 is considered the lower reaches, the second average void area in the middle region 83 is larger than the first average void area in the uppermost region 82.

[0064] The catalyst device 80 of the seventh embodiment described above provides the same effects as the first embodiment. For example, pressure variations can be suppressed from the upstream to the downstream of the flow path 3, and variations in the decomposition of the raw material gas can be suppressed.

[0065] The technologies disclosed herein are not limited to the embodiments described above and are subject to various modifications. A catalytic apparatus for decomposing ammonia is provided as an example. However, the technologies are applicable to all decomposition processes in which a source gas is broken down into a reaction gas, thereby increasing the total number of molecules. While the decomposition of ammonia, which doubles the total number of molecules, is provided as an example, the rate of increase is not limited to this; it may be less than or greater than double.

[0066] In this example, a catalyst 10 is provided in which metal nanoparticles are mixed with a support, exposing the metal nanoparticles on the surface. Alternatively, for example, the surface of the support may be coated with metal nanoparticles. For example, a metal that functions as the catalyst body may be formed into particulate form and used as a catalyst. The catalyst 10 is illustrated as having a roughly spherical shape, but is not limited to this. When the catalyst is not spherical, "particle size" may be replaced with, for example, the maximum length of the granular catalyst, or the average value of the maximum and minimum lengths.

[0067] The diameter and length of the fixed cross-section area 5 are not limited to those exemplified and may be changed as appropriate. The proportions of each region, such as the uppermost reaches, upper middle reaches, middle reaches, lower middle reaches, and lower reaches, are not limited to those exemplified and may be changed as appropriate. The division of the fixed cross-section area 5 is not limited to the 3 to 5 regions exemplified; for example, it may consist of 2 regions, such as the uppermost reaches and lower reaches, or it may consist of 6 or more regions.

[0068] While particle sizes 10a, 10b, 10c, and 10d are given as representative particle sizes for catalyst 10, the ratio and types of particle sizes are not limited to those given as examples. An embodiment is given in which catalyst 10 of one or two particle sizes is contained in one region. Alternatively, catalysts of three or more particle sizes may be contained in one region. A constant cross-sectional area 5 in which catalysts 10 of multiple sizes are mixed substantially uniformly is given as an example. Alternatively, the distribution of catalysts 10 of multiple sizes may be biased, for example, by arranging small-diameter catalysts 10 on the radially outer side of the constant cross-sectional area 5 and large-diameter catalysts 10 on the radially inner side of the constant cross-sectional area 5.

[0069] The increase in average particle size and average void area from upstream to downstream may be appropriately adjusted depending on the rate of increase in the total number of molecules due to the decomposition of the raw material gas and the location of the decomposition peak region. The average particle size and average void area in the uppermost region do not need to be the minimum. The average particle size and average void area in the lowermost region do not need to be the maximum. [Explanation of Symbols]

[0070] 1…Catalyst device (first embodiment) 2… Housing 3…Flow path, 3a…Raw material gas inlet, 3b…Reaction gas outlet 4… Heater 5... Constant cross-sectional area (catalyst layer), 5a... Inlet, 5b... Outlet 10...Catalyst, 10a, 10b, 10c, 10d...Particle size 11...Void 12...Average particle size, 12a...Uppermost average particle size (first average particle size, minimum average particle size) 12b...Midstream mean particle size (first mean particle size, second mean particle size, intermediate mean particle size) 12c...Lowest-most average particle size (second average particle size, maximum average particle size) 13... Uppermost basin (upstream basin) 14…Midstream area (upstream area, downstream area) 15…Lowest region (downstream region) 20…Fuel cell systems 21…Ammonia storage 22...Adsorption device 23…fuel cell 30…Catalyst device (second embodiment) 31...Average particle size, 31a...Uppermost average particle size (first average particle size, minimum average particle size) 31b...Mid-to-upstream average particle size (first average particle size, second average particle size, intermediate average particle size) 31c...Mid-to-downstream average particle size (first average particle size, second average particle size, intermediate average particle size) 31d...Lowest-most average particle size (second average particle size, maximum average particle size) 32... Uppermost basin (upstream basin) 33…Mid-upstream area (upstream area, downstream area) 34…Mid-downstream area (upstream area, downstream area) 35…lowest stream area (downstream area) 40…Catalyst device (third embodiment) 41...Average particle size, 41a...Uppermost average particle size (first average particle size, minimum average particle size) 41b...Midstream mean particle size (first mean particle size, second mean particle size, intermediate mean particle size) 41c...Lowest-most average particle size (second average particle size, maximum average particle size) 42... Uppermost basin (upstream basin) 43…Midstream area (upstream area, downstream area) 44…Lowest region (downstream region) 50…Catalyst device (fourth embodiment) 51...Average particle size, 51a...Uppermost average particle size (first average particle size, minimum average particle size) 51b...Midstream mean particle size (first mean particle size, second mean particle size, intermediate mean particle size) 51c...Lowest-most average particle size (second average particle size, maximum average particle size) 52... Uppermost basin (upstream basin) 53…Midstream area (upstream area, downstream area) 54…lowest stream area (downstream area) 60…Catalyst device (5th embodiment) 61...Average particle size, 61a...Uppermost average particle size (first average particle size, minimum average particle size) 61b...Midstream mean particle size (first mean particle size, minimum mean particle size) 61c...Lowest-most average particle size (second average particle size, maximum average particle size) 62... Uppermost basin (upstream basin) 63...middle area (upstream area) 64…lowest stream area (downstream area) 70…Catalyst device (6th embodiment) 71...Average particle size, 71a...Uppermost average particle size (first average particle size) 71b...Average particle size in the middle and upper reaches (1st average particle size, 2nd average particle size) 71c...Midstream mean particle size (first mean particle size, second mean particle size) 71d...Mid-to-downstream average particle size (1st average particle size, 2nd average particle size) 71e...Lowest-most mean particle size (second mean particle size) 72... Uppermost basin (upstream basin) 73…Mid-upstream area (upstream area, downstream area) 74…Midstream area (upstream area, downstream area) 75…Mid-downstream area (upstream area, downstream area) 76…Lowest region (downstream region) 80... Catalyst device (7th embodiment) 81...Average particle size, 81a...Uppermost average particle size (first average particle size) 81b...Midstream mean particle size (second mean particle size), 81c...Far downstream mean particle size 82... Uppermost basin (upstream basin) 83...Midstream area (upstream area) 84…Lowest region (downstream region)

Claims

1. A catalytic device that decomposes a raw material gas into a reaction gas, A flow channel that includes a constant cross-sectional area with a substantially constant cross-sectional area, The catalyst has granular material contained within the aforementioned constant cross-sectional area, By passing through the catalyst, the raw material gas is decomposed into the reaction gas, increasing the total number of gas molecules. The catalyst apparatus wherein the catalyst has a first average particle size in the upstream region of the constant cross-sectional area, and a second average particle size that is larger than the first average particle size in the downstream region downstream of the upstream region.

2. A catalyst apparatus according to claim 1, The catalyst apparatus has a catalyst having a minimum average particle size in the uppermost region including the inlet of the constant cross-sectional area, a maximum average particle size in the lowermost region including the outlet of the constant cross-sectional area, and an intermediate average particle size in the middle region between the uppermost and lowermost regions that is larger than the minimum average particle size and smaller than the maximum average particle size.

3. A catalyst apparatus according to claim 2, A catalyst apparatus in which the average particle size of the catalyst gradually increases from upstream to downstream over the entire length of the constant cross-sectional area.

4. A catalyst apparatus according to any one of claims 1 to 3, The catalyst apparatus wherein the constant cross-sectional area has a first average void area in the upstream region and a second average void area in the downstream region that is larger than the first average void area.

5. A catalyst apparatus according to claim 4, A catalytic device in which the average void area over a predetermined length of the constant cross-sectional area gradually increases from upstream to downstream along the entire length of the constant cross-sectional area.

6. A catalyst apparatus according to any one of claims 1 to 3, A catalyst apparatus in which the raw material gas is ammonia.

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