Hydrogen production method

Abstract

A hydrogen production method and a hydrogen production device are provided that can suppress poor flow of catalyst particles in a reactor. [Solution] A hydrogen production method for producing hydrogen by directly decomposing hydrocarbons into carbon and hydrogen includes a forming step of forming a fluidized bed of the mixture inside a reactor by supplying a feed gas containing hydrocarbons to a mixture of low-reactivity particles, which are particulate matter made of a chemically inert, low-reactivity material, and a catalyst.

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing hydrogen. By law Regarding. [Background technology]

[0002] Currently, the production of various types of energy is heavily dependent on fossil fuels such as oil, coal, and natural gas, but from the perspective of global environmental conservation, the increase in carbon dioxide emissions released by the combustion of fossil fuels is seen as a problem. The Paris Agreement, agreed in 2015, calls for a reduction in carbon dioxide emissions in order to address the issue of climate change, and reducing carbon dioxide emissions from the combustion of fossil fuels is a key issue for thermal power plants and other facilities. While processes for separating and capturing emitted carbon dioxide are being actively studied, technologies for producing energy without emitting carbon dioxide by using alternative fuels to fossil fuels are also being considered.

[0003] Therefore, hydrogen, a clean fuel that does not emit carbon dioxide when burned, has been attracting attention as an alternative to fossil fuels. Hydrogen can be produced, for example, by steam reforming methane contained in natural gas. However, this production method produces carbon monoxide as a by-product, which is ultimately oxidized and emitted as carbon dioxide. Meanwhile, methods such as water electrolysis and photocatalysis have been investigated as methods for producing hydrogen from water without using fossil fuels, but these methods require a large amount of energy and are therefore economically problematic.

[0004] In response to this, methods for producing hydrogen and carbon by directly decomposing hydrocarbons (hereinafter referred to as "methods for direct decomposition of hydrocarbons") have been developed. For example, the applicant of the present disclosure has developed a method for direct decomposition of hydrocarbons using an unsupported catalyst that is an aggregate of multiple iron particles, as described in Patent Document 1. The characteristics of the method for direct decomposition of hydrocarbons are that it has the potential to produce hydrogen fuel without emitting carbon dioxide, and that because the carbon in the hydrocarbon feed gas can be recovered as solid by-product carbon after hydrogen production, it has the potential to be easier to handle and cheaper from the perspective of decarbonization than when gaseous carbon dioxide is recovered and stored. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 7089235 Summary of the Invention [Problem to be solved by the invention]

[0006] When a direct hydrocarbon cracking method is carried out using a catalyst (not limited to the unsupported iron catalyst as in Patent Document 1) in a fluidized bed, catalyst particles become smaller as the reaction progresses, and are dispersed from the reactor due to their terminal velocity becoming lower than the superficial velocity. Meanwhile, the smaller catalyst particles tend to loosely bond to each other through van der Waals forces, forming agglomerates that tend to remain in the bed. As the reaction progresses, the proportion of agglomerates in the bed increases. In the early stages of the reaction, relatively large catalyst particles are present in the fluidized bed, and collisions between these catalyst particles and the agglomerates disrupt the agglomerates, suppressing their growth. However, as the reaction progresses, the catalyst particles in the fluidized bed become smaller, and the number of large particles with sufficient kinetic energy to disrupt the agglomerates decreases, promoting the growth of agglomerates. Furthermore, because the agglomerates have a low apparent specific gravity and are soft, they are less likely to disintegrate when colliding with each other; in fact, they may even further aggregate together. As a result, the proportion of aggregates whose fluidization initiation velocity is equal to or greater than the superficial velocity increases, resulting in poor fluidity.

[0007] In view of the above circumstances, at least one embodiment of the present disclosure provides a hydrogen production method capable of suppressing poor flow of catalyst particles in a reactor. The law The purpose is to provide. [Means for solving the problem]

[0008] In order to achieve the above object, the present disclosure provides a hydrogen production method for producing hydrogen by directly decomposing hydrocarbons into carbon and hydrogen, the method comprising the steps of: For the direct decomposition of hydrocarbons into carbon and hydrogen inert Inactive The method includes a step of forming a fluidized bed of a mixture of particles and catalyst by supplying a feed gas containing a hydrocarbon to the mixture. fruit , In the reactor, the superficial velocity of the raw material gas is set to be equal to or higher than the fluidization initiation velocity of the inert particles and lower than the terminal velocity of the inert particles. . [Effects of the Invention]

[0010] The hydrogen production method of the present disclosure By law According to the inside of the reactor inertThe direct cracking reaction of hydrocarbons occurs in a state where the mixture of particles and catalyst forms a fluidized bed, and the catalyst particles that have become smaller as the reaction progresses and the carbon that has not adhered to the catalyst particles become fluidized. inert The particles are transported to the upper surface of the fluidized bed and are entrained in the gas flowing out of the reactor, and are efficiently scattered from the reactor, thereby suppressing an increase in the concentration of reduced-diameter catalyst particles in the fluidized bed, thereby suppressing poor fluidity of the catalyst particles in the reactor. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram illustrating the configuration of a hydrogen production device for carrying out a hydrogen production method according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, the hydrogen production method according to the embodiment of the present disclosure will be described. By law The following description will be given with reference to the drawings. The embodiment described below shows one aspect of the present disclosure, but does not limit the present disclosure and can be arbitrarily modified within the scope of the technical idea of ​​the present disclosure.

[0013] <Configuration of hydrogen production device according to one embodiment of the present disclosure> As shown in FIG. 1 , a hydrogen production device 1 according to an embodiment of the present disclosure includes a reactor 2. The reactor 2 is provided with a catalyst supply port 3 for supplying a catalyst 10 for a direct cracking reaction of hydrocarbons to the reactor 2, a raw material gas supply port 4 for supplying a raw material gas containing hydrocarbons to the reactor 2, and an outlet 5 for discharging the contents of the reactor 2 (described in detail below). Pipes 6, 7, and 8 may be connected to the catalyst supply port 3, the raw material gas supply port 4, and the outlet 5, respectively. A dispersion plate 9 is provided within the reactor 2 to divide the interior of the reactor 2 into two chambers, and the catalyst supply port 3 and the outlet 5 are located on the opposite side of the dispersion plate 9 from the raw material gas supply port 4. Low-reactivity particles 11, which are particulate matter made of a chemically inert, low-reactivity material, are contained within the reactor 2 so as to be placed on the dispersion plate 9, i.e., located on the opposite side of the dispersion plate 9 from the raw material gas supply port 4. The reactor 2 may also be provided with a low-reactivity particle supply port 12 for supplying the low-reactivity particles 11 to the reactor 2. In this case, a pipe 13 may be connected to the low-reactivity particle supply port 12 .

[0014] The catalyst 10 for the direct cracking reaction of hydrocarbons used in this embodiment may be, but is not limited to, an unsupported catalyst formed of an aggregate of multiple iron particles as described in Patent Document 1. For example, an unsupported catalyst formed of an aggregate of multiple particles of a nickel-based metal or a cobalt-based metal, an alloy thereof, or an oxide thereof, an aggregate of multiple particles made from a mineral containing at least one of an iron-based metal, a nickel-based metal, or a cobalt-based metal, or a supported catalyst in which at least one of an iron-based metal, a nickel-based metal, or a cobalt-based metal is supported on a carrier can also be used.

[0015] The low-reactivity particles 11 must be unaffected by the temperature at which the direct cracking reaction of hydrocarbons occurs in the reactor 2, and therefore must have a heat resistance temperature of 600°C or higher, preferably 650°C or higher, and more preferably 750°C or higher. Furthermore, as will be described in detail later, while the direct cracking reaction of hydrocarbons is occurring in the reactor 2, the low-reactivity particles 11 form a fluidized bed, and the catalyst 10 is supplied into this fluidized bed. Therefore, the catalyst 10 and the low-reactivity particles 11 rub against each other, and in order for the low-reactivity particles 11 to continue to form a fluidized bed, the low-reactivity particles 11 must be harder than the catalyst 10. Specifically, the Vickers hardness of the low-reactivity particles 11 needs to be greater than that of the catalyst 10. Depending on the type of metal constituting the catalyst 10, the Vickers hardness of the low-reactivity particles 11 is 10 Hv or higher, preferably 50 Hv or higher, and more preferably 70 Hv or higher. In this embodiment, when the catalyst 10 is a supported catalyst, the hardness of the catalyst 10 refers to the hardness of the support, and the Vickers hardness of the catalyst 10 refers to the Vickers hardness of the support. In addition, since the produced carbon generally has a lower hardness than the catalyst particles, by setting the hardness of the low-reactivity particles as described above, it is expected that the carbon deposited on the reactor wall surface and the layer inserts by the pyrolysis reaction will be worn and peeled off, thereby suppressing its growth.

[0016] The low-reactivity particles 11 are not particularly limited as long as they have the above-mentioned configuration and are made of a chemically inactive, low-reactivity material, and may be, for example, particles made of silicon dioxide such as silica sand, shirasu balloons, and silica balls; particles made of alumina such as alumina balls; particles made of a mixture of silicon dioxide and alumina such as blast furnace slag, coal gasification slag, and waste gasification melting furnace slag; or particles made of magnesia, calcium oxide, silicon carbide, silicon nitride, ytnia, titania, cordierite, etc.

[0017] The source gas may contain not only hydrocarbons but also one or both of a rare gas such as argon, an inert gas such as nitrogen, and hydrogen. The hydrocarbons contained in the source gas may be saturated hydrocarbons such as methane, ethane, or propane, or unsaturated hydrocarbons such as ethylene, propylene, or acetylene, or may be a mixture of at least two of these.

[0018] <Operation of the hydrogen production device according to one embodiment of the present disclosure> Next, the operation of the hydrogen production device (hydrogen production method) according to one embodiment of the present disclosure will be described. As shown in FIG. 1 , a fluidized bed of the mixture 14 is formed inside the reactor 2 by supplying a raw material gas to a mixture 14 of low-reactivity particles 11 and a catalyst 10. The operation of forming the fluidized bed of the mixture 14 is not particularly limited, and may be performed, for example, by the following operation. First, the low-reactivity particles 11 are supplied into the reactor 2. The low-reactivity particles 11 may be supplied to the reactor 2 through the low-reactivity particle supply port 12 if the reactor 2 has a low-reactivity particle supply port 12, or through the catalyst supply port 3 or outlet 5 if the reactor 2 does not have a low-reactivity particle supply port 12. Next, the raw material gas is supplied to the reactor 2 through the raw material gas supply port 4. The raw material gas supplied to the reactor 2 passes through the dispersion plate 9, further passes through a layer of low-reactivity particles 11, and then flows out of the reactor 2 through the outlet 5. When the raw material gas passes through the layer of the less reactive particles 11, the less reactive particles 11 are fluidized, thereby forming a fluidized bed of the less reactive particles 11 in the reactor 2.

[0019] A fluidized bed of the mixture 14 can also be formed by the operation exemplified below. The low-reactivity particles 11 and the catalyst 10 may be supplied into the reactor 2 (the order in which the low-reactivity particles 11 and the catalyst 10 are supplied to the reactor 2 is not limited, and they may be supplied simultaneously), and a raw material gas may be supplied to the reactor 2 containing the low-reactivity particles 11 and the catalyst 10. Alternatively, the catalyst 10 may be supplied into the reactor 2, the raw material gas may be supplied to the reactor 2 containing the catalyst 10, and then the low-reactivity particles 11 may be supplied to the reactor 2.

[0020] In order to form a fluidized bed of the mixture 14 in the reactor 2, the superficial velocity of the feed gas in the reactor 2 must be equal to or greater than the initiation velocity of the low-reactivity particles 11 and less than the terminal velocity of the low-reactivity particles 11. Preferably, the superficial velocity of the feed gas in the reactor 2 is at least three times the initiation velocity of the low-reactivity particles 11 and less than the terminal velocity of the low-reactivity particles 11. Since the initiation velocity and terminal velocity can be calculated using known methods, those skilled in the art can easily set the above conditions. Under these conditions, the reduced-diameter catalyst (described later) can be dispersed from the reactor 2, but the low-reactivity particles 11 can remain within the reactor 2. By selecting the low-reactivity particles 11 and the superficial velocity of the feed gas in the reactor 2 so as to satisfy these conditions, a fluidized bed of the mixture 14 can be formed in the reactor 2.

[0021] In the fluidized bed of the mixture 14 in the reactor 2, the hydrocarbons come into good contact with the catalyst 10, and the catalyst 10 exhibits good catalytic action for the direct cracking reaction of the hydrocarbons. Due to this catalytic action, the hydrocarbons are directly cracked into hydrogen and carbon.

[0022] Since the raw material gas is continuously supplied to the reactor 2, the hydrogen produced by the direct cracking reaction of hydrocarbons flows out from the reactor 2 together with unreacted hydrocarbons (and inert gases and hydrogen if the raw material gas contains them) via the outlet 5. The effluent gas flowing out from the reactor 2 via the outlet 5 can be purified by a hydrogen generator (not shown) to obtain a gas with a higher hydrogen concentration than the effluent gas.

[0023] A portion of the carbon produced by the direct cracking reaction of hydrocarbons adheres to the catalyst 10. The carbon that does not adhere to the catalyst 10 is transported to the upper surface of the fluidized bed by flowing together with the catalyst 10 and the low-reactivity particles 11. Because the carbon has a lower density than the low-reactivity particles 11, it is entrained in the gas flowing through the reactor 2 toward the outlet, and flows out of the reactor 2 through the outlet 5. The carbon entrained in the effluent gas flowing out of the reactor 2 can be separated from the effluent gas by a solid-gas separator (not shown) and recovered.

[0024] A portion of the carbon attached to the catalyst 10 is peeled off from the catalyst 10 due to friction between the catalyst 10 and the low-reactivity particles 11. The carbon peeled off from the catalyst 10 flows out of the reactor 2 and is collected in the same manner as the carbon not attached to the catalyst 10 described above.

[0025] The catalyst 10 is reduced in size by the catalytic action of the direct cracking reaction of hydrocarbons. The reduced-size catalyst particles are transported to the upper surface of the fluidized bed along with the flowing low-reactivity particles 11, and, like the carbon described above, are entrained in the gas flowing through the reactor 2 toward the outlet, and are discharged from the reactor 2 through the outlet 5. The catalyst particles entrained in the effluent gas discharged from the reactor 2 can be separated from the effluent gas by a solid-gas separator (not shown) and recovered.

[0026] In this way, the carbon and reduced-diameter catalyst particles are entrained in the effluent gas flowing out of the reactor 2 and are efficiently scattered from the reactor 2, and an increase in the concentration of reduced-diameter catalyst particles in the fluidized bed of the mixture 14 is suppressed, thereby suppressing poor fluidity of the catalyst particles in the reactor 2.

[0027] Regarding the particle size range in which the low-reactivity particles 11 can be used, the minimum average particle size is determined so that the low-reactivity particles 11 can be in a region where they can flow independently and avoid the C particle region (particles that are difficult to flow and are generally classified by particle size and density) and the terminal velocity is greater than the superficial velocity, and the maximum average particle size is determined so that the superficial velocity is at least three times the fluidization initiation velocity. For example, when the low-reactivity particles 11 are silica sand and methane at 600°C to 900°C is used at a superficial velocity of 0.05 m / sec to 0.2 m / sec, the average particle size of the low-reactivity particles 11 is preferably 20 μm to 300 μm.

[0028] The concentration of the low-reactivity particles 11 in the mixture 14 is preferably 20 wt % or more, and more preferably 40 wt % or more.

[0029] The contents described in each of the above embodiments can be understood, for example, as follows.

[0030] [1] A hydrogen production method according to one embodiment includes: A method for producing hydrogen by directly decomposing hydrocarbons into carbon and hydrogen, comprising: The method includes a formation step of forming a fluidized bed of a mixture (14) of a catalyst (10) and low-reactivity particles (11), which are particulate matter made of a chemically inert, low-reactivity material, in a reactor (2) by supplying a hydrocarbon-containing feed gas to the mixture (14).

[0031] According to the hydrogen production method of the present disclosure, a direct decomposition reaction of hydrocarbons occurs in a state in which a mixture of low-reactivity particles and catalyst forms a fluidized bed inside the reactor. As a result, the catalyst particles that have been reduced in size as the reaction progresses, and the carbon that has not adhered to the catalyst particles, are transported to the upper surface of the fluidized bed along with the flowing low-reactivity particles, and are efficiently scattered from the reactor along with the gas flowing out of the reactor. This prevents an increase in the concentration of reduced-size catalyst particles in the fluidized bed, thereby preventing poor fluidity of the catalyst particles within the reactor.

[0032] [2] A hydrogen production method according to another embodiment is the hydrogen production method according to [1], The forming step includes: supplying the low-reactivity particles (11) into the reactor (2); forming a fluidized bed of the less reactive particles (11) by supplying the feed gas to the reactor (2); supplying the catalyst (10) into the reactor (2) in which a fluidized bed of the low-reactivity particles is formed; Includes:

[0033] According to this method, for the same reason as in [1] above, poor fluidity of catalyst particles in the reactor can be suppressed.

[0034] [3] A hydrogen production method according to yet another embodiment is the hydrogen production method according to [1], The forming step includes: feeding the low-reactivity particles (11) and the catalyst (10) into the reactor (2); supplying the raw material gas to the reactor (2) containing the low-reactivity particles (11) and the catalyst (10); Includes:

[0035] According to this method, for the same reason as in [1] above, poor fluidity of catalyst particles in the reactor can be suppressed.

[0036] [4] A hydrogen production method according to yet another embodiment is the hydrogen production method according to [1], The forming step includes: feeding the catalyst (10) into the reactor (2); supplying the raw material gas to the reactor (2) containing the catalyst (10); supplying the low-reactivity particles (11) to the reactor (2) containing the catalyst (10); Includes:

[0037] According to this method, for the same reason as in [1] above, poor fluidity of catalyst particles in the reactor can be suppressed.

[0038] [5] A method for direct cracking of hydrocarbons according to yet another embodiment is the method for producing hydrogen according to any one of [1] to [4], The heat resistance temperature of the low-reactivity particles (11) is 600° C. or higher.

[0039] According to this method, the low-reactivity particles can form a fluidized bed without being affected by temperature even at temperatures at which direct cracking reactions of hydrocarbons occur, thereby suppressing poor fluidization of catalyst particles within the reactor.

[0040] [6] A method for direct cracking of hydrocarbons according to yet another embodiment is the method for producing hydrogen according to any one of [1] to [5], In the reactor (2), the superficial velocity of the raw material gas is set to be equal to or higher than the fluidization initiation velocity of the low-reactivity particles (11) and lower than the terminal velocity of the low-reactivity particles (11).

[0041] In this way, the reduced size catalyst particles can be dispersed from the reactor, while the less reactive particles remain within the reactor.

[0042] [7] A method for direct cracking of hydrocarbons according to yet another embodiment is the method for producing hydrogen according to any one of [1] to [5], In the reactor (2), the superficial velocity of the raw material gas is set to at least three times the fluidization initiation velocity of the low-reactivity particles (11) and less than the terminal velocity of the low-reactivity particles (11).

[0043] According to this method, the catalyst particles with reduced diameter can be scattered from the reactor, but the less reactive particles can be retained in the reactor, and a more stable fluidized bed can be formed and maintained.

[0044] [8] A method for direct cracking of hydrocarbons according to yet another embodiment is the method for direct cracking of hydrocarbons according to any one of [1] to [7], The Vickers hardness of the low-reactivity particles (11) is greater than the Vickers hardness of the catalyst (10).

[0045] According to this method, the low-reactivity particles and the catalyst do not break down due to friction between them, but rather the latter are reduced in size by the former, thereby promoting the direct cracking reaction of hydrocarbons. Also, because carbon is softer than catalyst particles, as the reaction progresses, the carbon is peeled off from the catalyst particles due to friction between the attached catalyst particles and the low-reactivity particles, allowing the carbon to be efficiently dispersed from the reactor.

[0046] [9] A hydrogen production device according to one aspect includes: A hydrogen production device (1) for producing hydrogen by directly decomposing hydrocarbons into carbon and hydrogen, comprising: A reactor (2), The reactor (2) contains a catalyst supply port (3) for supplying a catalyst (10) to the reactor (2); a raw material gas supply port (4) for supplying a raw material gas containing a hydrocarbon to the reactor (2); an outlet (5) for the contents of the reactor (2) to flow out; is formed, A mixture of the catalyst and low-reactivity particles (11), which are particulate matter made of a chemically inert, low-reactivity material, is contained in the reactor (2) so that a fluidized bed can be formed by the raw material gas supplied into the reactor (2).

[0047] According to the hydrogen production device of the present disclosure, a direct decomposition reaction of hydrocarbons occurs inside the reactor, with a mixture of low-reactivity particles and catalyst forming a fluidized bed. As a result, the catalyst particles that have been reduced in size as the reaction progresses, and the carbon that has not adhered to the catalyst particles, are transported to the upper surface of the fluidized bed along with the flowing low-reactivity particles, and are efficiently scattered from the reactor along with the gas flowing out of the reactor. This prevents an increase in the concentration of reduced-size catalyst particles in the fluidized bed, thereby preventing poor flow of the catalyst particles within the reactor.

[0048]

[10] A hydrogen production device according to another embodiment is the hydrogen production device according to [9], The reactor (2) further includes a low-reactivity particle supply port (12) for supplying the low-reactivity particles (11).

[0049] According to this configuration, it is possible to supply low-reactivity particles to the reactor even while the raw material gas and catalyst are being supplied to the reactor.

[0050]

[11] A hydrogen production device according to yet another embodiment is the hydrogen production device according to [9] or

[10] , The heat resistance temperature of the low-reactivity particles (11) is 600° C. or higher.

[0051] With this configuration, the low-reactivity particles can form a fluidized bed without being affected by temperature even at temperatures at which direct cracking reactions of hydrocarbons occur, thereby suppressing poor fluidization of the catalyst particles within the reactor.

[0052]

[12] A hydrogen production device according to yet another embodiment is the hydrogen production device according to any one of [9] to

[11] , The Vickers hardness of the low-reactivity particles (11) is greater than the Vickers hardness of the catalyst (10).

[0053] With this configuration, the low-reactivity particles and the catalyst do not break down due to friction between them, but rather the latter are reduced in particle size by the former, thereby accelerating the direct cracking reaction of hydrocarbons. Also, because carbon is softer than catalyst particles, as the reaction progresses, the carbon is peeled off from the catalyst particles due to friction between the attached catalyst particles and the low-reactivity particles, allowing the carbon to be efficiently dispersed from the reactor. [Explanation of symbols]

[0054] 1. Hydrogen production equipment 2. Reactor 3 Catalyst supply port 4. Raw material gas supply port 5 Outlet 10 Catalyst 11 Low-reactivity particles 12 Low-reactivity particle supply port 14 mixture

Claims

1. A method for producing hydrogen by directly decomposing hydrocarbons into carbon and hydrogen, comprising: The method includes a step of forming a fluidized bed of a mixture by supplying a feed gas containing hydrocarbons to a mixture of inert particles and a catalyst inert to a reaction for directly decomposing hydrocarbons into carbon and hydrogen in a reactor, a superficial velocity of the raw material gas in the reactor that is equal to or greater than a fluidization initiation velocity of the inert particles and less than a terminal velocity of the inert particles.

2. The forming step includes: feeding the inert particles into the reactor; forming a fluidized bed of the inert particles by supplying the feed gas to the reactor; feeding the catalyst into the reactor forming a fluidized bed of the inert particles; The method for producing hydrogen according to claim 1 , comprising:

3. The forming step includes: feeding the inert particles and the catalyst into the reactor; supplying the raw material gas to the reactor containing the inert particles and the catalyst; The method for producing hydrogen according to claim 1 , comprising:

4. The forming step includes: providing the catalyst into the reactor; supplying the raw material gas to the reactor containing the catalyst; supplying the inert particles to the reactor containing the catalyst; The method for producing hydrogen according to claim 1 , comprising:

5. 5. The method for producing hydrogen according to claim 1, wherein the inert particles have a heat resistance temperature of 600° C. or higher.

6. 5. The method for producing hydrogen according to claim 1, wherein, in the reactor, a superficial velocity of the raw material gas is set to be three times or more a fluidization initiation velocity of the inert particles and less than a terminal velocity of the inert particles.

7. 5. The method for producing hydrogen according to claim 1, wherein the inert particles have a Vickers hardness greater than that of the catalyst.

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