Hydrogen production apparatus

Abstract

To provide a hydrogen production apparatus that can be appropriately operated according to various requirements.SOLUTION: A hydrogen production apparatus has a reactor for producing hydrogen by thermally decomposing hydrocarbon gas as a raw material gas using a catalyst. The pressure inside the reactor is set in a range from 1 ata or more to 35 ata or less. The catalyst comprises fine solid particles and forms a catalyst layer inside the reactor. The reactor comprises a cylindrical body extending in the up-down direction and is configured so that the raw material gas is introduced from the lower part and product gas generated by thermal decomposition is led out from the upper part. A disperser having numerous holes is provided inside the reactor to partition the inside of the reactor into a reaction chamber and a wind chamber located below the reaction chamber. The catalyst layer is formed on the disperser in the reaction chamber. The catalyst forms a fluidized bed inside the reactor when the raw material gas is blown into the reaction chamber from below through the disperser.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a hydrogen production device. [Background technology]

[0002] Conventionally, there are known techniques for producing hydrogen by thermal decomposition of methane. For example, a hydrogen production apparatus disclosed in Patent Document 1 has a reactor containing a catalyst. Methane is introduced into the reactor. The methane is decomposed into hydrogen and carbon by contacting with the catalyst inside the reactor. A mixture of hydrogen, which is the product gas, and unreacted methane is taken out of the reactor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-73411 Summary of the Invention [Problem to be solved by the invention]

[0004] Hydrogen production equipment is required to operate appropriately in response to various demands. [Means for solving the problem]

[0005] A hydrogen production apparatus according to one aspect of the present disclosure includes a reactor that produces hydrogen by thermally decomposing a hydrocarbon gas, which is a feed gas, using a catalyst. The pressure inside the reactor is set to 1 ata or more and 35 ata or less. The catalyst is made of fine solid particles and forms a catalyst layer inside the reactor. The reactor is a vertically extending cylindrical body configured so that the feed gas is introduced from the bottom and the product gas generated by the thermal decomposition is discharged from the top. Inside the reactor, a distributor having a number of holes is provided, dividing the inside of the reactor into a reaction chamber and an air chamber located below the reaction chamber. The catalyst layer is formed on the distributor inside the reaction chamber. The catalyst forms a fluidized bed inside the reactor when the feed gas is blown into the reaction chamber from below through the distributor. [Effects of the Invention]

[0006] The hydrogen production device of the present invention can be appropriately operated in response to various demands. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a configuration diagram of an embodiment of a hydrogen production device. [Figure 2] 1 is a graph showing the relationship between the pressure of a reactor, the space velocity of a raw material gas, and the conversion rate of the raw material gas according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] An embodiment of the hydrogen production device will be described below. As shown in FIG. 1, the hydrogen production device 10 includes a pressure vessel 11 and a reactor 12. The pressure vessel 11 and the reactor 12 are each a cylindrical body having a circular cross section and extending in the vertical direction. The interior of the pressure vessel 11 is maintained at a predetermined pressure. The pressure is, for example, higher than atmospheric pressure. The reactor 12 is accommodated inside the pressure vessel 11 in a non-contact state. The inner diameter of the reactor 12 may be constant along its entire length.

[0009] A disperser 13 is provided inside the reactor 12. The disperser 13 is, for example, a plate-like body that extends in a direction perpendicular to the axial direction of the reactor 12 and has a large number of holes. The holes penetrate the disperser 13 in the plate thickness direction. The disperser 13 is disposed at a position closer to the lower end of the reactor 12 than the axial center position of the reactor 12. The disperser 13 divides the inside of the reactor 12 into two spaces, an upper space and an lower space. The upper space is the reaction chamber 12A, and the lower space is the air chamber 12B. The reaction chamber 12A and the air chamber 12B are in communication with each other via the holes in the disperser 13.

[0010] The catalyst 14 is deposited on the upper surface of the disperser 13. That is, the inside of the reaction chamber 12A is filled with the catalyst 14 up to a predetermined deposition height relative to the disperser 13. The upper surface is the surface of the disperser 13 on the reaction chamber 12A side. The catalyst 14 is, for example, iron (Fe) or fine solid particles containing iron as a main component. The catalyst 14 is heated by a heating device. The heating device is, for example, a heater or a jacket through which exhaust gas or steam flows.

[0011] An inlet pipe 15 is connected to the lower end of the reactor 12. The inlet pipe 15 penetrates the lower end of the pressure vessel 11. The inlet pipe 15 is a gas flow path for introducing a raw material gas into the reactor 12. The raw material gas is a hydrocarbon gas. The hydrocarbon gas is, for example, methane or a gas containing methane as a main component. The hydrocarbon gas is decomposed into hydrogen and carbon by coming into contact with the catalyst 14 inside the reactor 12. The carbon is in powder form.

[0012] An outlet pipe 16 is connected to the upper end of the reactor 12. The outlet pipe 16 passes through the upper end of the pressure vessel 11. The outlet pipe 16 is a gas flow path for discharging the produced gas to the outside of the reactor 12. The produced gas is a gas produced inside the reactor 12, and is a mixed gas of hydrogen produced by thermal decomposition and unreacted hydrocarbons.

[0013] The raw material gas is supplied to the reaction chamber 12A via the airflow chamber 12B and the disperser 13. The raw material gas is rectified and diffused by the disperser 13. This allows the raw material gas to flow uniformly into the reaction chamber 12A from below. When the raw material gas is blown into the reaction chamber 12A from below, the catalyst 14, which is a solid particle, is suspended to a certain height and moves around vigorously. In other words, a fluidized bed, which is a layer of the catalyst 14 that moves around vigorously, is formed. The fluidization of the catalyst 14 results in a good mixture of the catalyst 14 and the raw material gas. This promotes contact between the raw material gas and the catalyst 14. Therefore, the thermal decomposition reaction of the raw material gas by the catalyst 14 is promoted.

[0014] The reactor 12 is a fluidized bed reactor. The catalyst 14 is a fluidizing medium. The raw material gas is a fluidizing gas for fluidizing the catalyst 14. <Reaction temperature> When hydrogen is produced, the inside of the reactor 12, and therefore the catalyst 14, is heated to a predetermined reaction temperature. The reaction temperature is a temperature at which the thermal decomposition reaction of the raw material gas by the catalyst 14 proceeds efficiently. The reaction temperature is set to a value within a predetermined temperature range depending on product specifications, etc. The lower limit of the temperature range is set, for example, based on the starting temperature of thermal decomposition. The upper limit of the temperature range is set, for example, based on the heat resistance of the reactor 12.

[0015] If the reaction temperature is below the lower limit of the temperature range, the thermal decomposition reaction of the raw material gas may not proceed. This is because the reaction temperature is lower than the starting temperature of thermal decomposition, and the function of the catalyst 14 to decompose the raw material gas is not activated. The higher the reaction temperature, the more the thermal decomposition of the raw material gas proceeds. However, if the reaction temperature exceeds the upper limit of the temperature range, the reliability of the reactor 12 may not be ensured.

[0016] The temperature range is, for example, 700° C. to 950° C., with 700° C. being the lower limit of the temperature range and 950° C. being the upper limit of the temperature range. <Relationship between the pressure of the reactor 12 and the amount of hydrogen generated> Next, the relationship between the pressure in the reactor 12 and the amount of hydrogen generated will be described. The pressure is the pressure inside the reactor 12. The pressure inside the reactor 12 is a pressure that corresponds to the pressure of the raw material gas supplied into the reactor 12. Here, an example will be described in which the raw material gas is methane.

[0017] The thermal decomposition reaction of methane is expressed by the following formula (1): CH4→2H2+C …(1) Furthermore, regardless of the temperature and pressure of the reactor 12, the following formula (2) holds true.

[0018] P H2 2 / P CH4 = constant …(2) However, "P H2 2 " is the partial pressure of hydrogen inside the reactor 12, and is a pressure that depends on the amount of hydrogen generated. CH4 " is the partial pressure of methane inside the reactor 12, which is a pressure that depends on the pressure of the methane fed to the reactor 12. " / " indicates division.

[0019] If the pressure in reactor 12, i.e., the methane supply pressure, is increased fourfold, it would appear at first glance that the methane partial pressure and hydrogen partial pressure would also increase fourfold. However, according to equation (2) above, the hydrogen partial pressure would actually double. In other words, the amount of hydrogen generated would be half that before the pressure increase. Thus, when the pressure in reactor 12, i.e., the methane supply pressure, is increased, the amount of hydrogen generated, in terms of reaction equilibrium, would be less than that before the pressure increase. In other words, the methane conversion rate would decrease. The conversion rate is the degree of the thermal decomposition reaction in reactor 12 and indicates the conversion rate of the raw material gas, methane, to hydrogen.

[0020] The conversion rate of the raw material gas is determined by the temperature of the reactor 12, the pressure of the reactor 12, and the GHSV (Gaseous Hourly Space Velocity). The GHSV is the reciprocal of the time it takes for the raw material gas to pass through the catalyst under standard conditions of 1 atm and 0°C, and is one index that represents the catalyst passing speed in the reactor 12.

[0021] As shown by the first characteristic line L1 to the ninth characteristic line L9 in FIG. 2, the higher the pressure in the reactor 12, the lower the conversion rate of the raw material gas. Also, the higher the GHSV value, the lower the conversion rate of the raw material gas. As the pressure in the reactor 12 increases, the GHSV value gradually increases and eventually reaches a peak. After reaching its peak, the GHSV value gradually decreases as the pressure in the reactor 12 increases. The temperature of the reactor 12, i.e., the reaction temperature, is, for example, 800°C.

[0022] The first characteristic line L1 shows the relationship between pressure and GHSV when the conversion rate is 80%. The second characteristic line L2 shows the relationship between pressure and GHSV when the conversion rate is 75%. The third characteristic line L3 shows the relationship between pressure and GHSV when the conversion rate is 70%. The fourth characteristic line L4 shows the relationship between pressure and GHSV when the conversion rate is 65%. The fifth characteristic line L5 shows the relationship between pressure and GHSV when the conversion rate is 60%. The sixth characteristic line L6 shows the relationship between pressure and GHSV when the conversion rate is 55%. The seventh characteristic line L7 shows the relationship between pressure and GHSV when the conversion rate is 50%. The eighth characteristic line L8 shows the relationship between pressure and GHSV when the conversion rate is 45%. The ninth characteristic line L9 shows the relationship between pressure and GHSV when the conversion rate is 40%.

[0023] <First Advantage of High Pressure in Reactor 12> The first advantage of increasing the pressure in the reactor 12 is as follows. As shown in the following equation (3), the specific volume of all gases being handled is inversely proportional to the pressure. Specific volume is the volume occupied by a unit mass of a substance. Substances include gases.

[0024] V ∝ (1 / P) … (3) Where "V" is the specific volume and "P" is the pressure. By increasing the pressure of the hydrogen production facility, it is possible to reduce the diameters of various pressure vessels and piping according to the specific volume of the gas. The hydrogen production facility includes a hydrogen production device 10. In particular, when a fluidized-bed reactor 12 is used, the superficial velocity of the feed gas flowing through the reactor 12 and the hydrogen produced is important for the fluidity of the fluidized bed and, ultimately, the reaction efficiency of the thermal decomposition reaction of the feed gas. The superficial velocity is the flow rate of the feed gas calculated in the reactor 12 assuming that the catalyst 14, which is a packed particle, is not present.

[0025] The bottom area of ​​the fluidized bed is uniquely determined by the superficial velocity and the volumetric flow rate of the feed gas. The bottom area of ​​the fluidized bed is the area of ​​the boundary between the fluidized bed and the disperser 13. When the inner diameter of the reactor 12 is constant throughout its entire length, the bottom area of ​​the fluidized bed is equal to the area of ​​the inner part cut by a plane perpendicular to the axial direction of the reactor 12. By increasing the pressure of the reactor 12, it is possible to narrow the cross-sectional area of ​​the reactor 12 in inverse proportion to the pressure. The cross-sectional area is the cross-sectional area cut by a plane perpendicular to the axial direction of the reactor 12. This makes it possible to reduce the outer diameter of the reactor 12 and thereby make the reactor 12 more compact.

[0026] <Second Advantage of High Pressure in Reactor 12> The second advantage of increasing the pressure in the reactor 12 is as follows. The hydrogen production device 10 is used, for example, in a power generation facility that uses a gas turbine. The hydrogen produced by the hydrogen production device 10 is refined into pure hydrogen. The generated hydrogen is the fuel gas used as fuel for the gas turbine. To drive the gas turbine, a fuel gas pressure of at least 30 ata or more is required. Therefore, if the fuel gas pressure is insufficient, it is necessary to increase the fuel gas pressure, for example, using a compressor.

[0027] When the hydrogen production device 10, including the reactor 12, is pressurized, the pressure of the hydrogen produced also becomes sufficiently high. Therefore, the higher the hydrogen pressure, the more energy can be saved for the compressor, which also contributes to improving the efficiency of the power generation facility.

[0028] Furthermore, in the reactor 12, even if the flow rate of the raw material gas is the same, the higher the pressure, the higher the mass flow rate. The mass flow rate is the mass of raw material gas passing through the cross section of the reactor 12 per unit time. The cross section is a cross section cut along a plane perpendicular to the axial direction of the reactor 12. As a result, the GHSV can be set to a larger value. In other words, there is an operational advantage in that a smaller catalyst layer can be installed, thereby reducing the consumption of catalyst 14.

[0029] The hydrogen production facility may also have a device for moving the catalyst 14. Examples of such a device include a device for feeding the catalyst 14 into the reactor 12, a device for discharging the catalyst 14, or a device for transporting the catalyst 14. A reduction in the consumption of the catalyst 14 also reduces the amount of catalyst 14 supplied to the reactor 12. Therefore, a reduction in the consumption of the catalyst 14 contributes to a reduction in the power required for the device for moving the catalyst 14, and ultimately contributes to a reduction in the power required for the hydrogen production facility.

[0030] <Operation of hydrogen production unit 10> Table 1 compares the conversion rate of the feed gas, the consumption of the catalyst 14, the power of the pressure boosting equipment, and the power of the hydrogen production equipment between a low-pressure hydrogen production equipment 10 and a high-pressure hydrogen production equipment 10. The pressure boosting equipment includes a compressor that boosts the hydrogen pressure. The hydrogen production equipment includes the hydrogen production equipment 10 and equipment related to the movement of the catalyst 14. Low pressure is, for example, a pressure of 1 ata or more and 5 ata or less. High pressure is, for example, a pressure of 30 ata or more and 35 ata or less.

[0031] [Table 1]

[0032] As shown in Table 1, the conversion rate of the raw material gas increases when the pressure of the hydrogen production device 10 is lowered. The supply amount of catalyst 14 decreases when the pressure of the hydrogen production device 10 is higher. The power of the pressure boosting equipment and the power of the hydrogen production equipment each decrease when the pressure of the hydrogen production device 10 is higher.

[0033] The decision as to whether to use a low-pressure or high-pressure hydrogen production device 10 is made based on, for example, the following viewpoint. That is, when a reduction in environmental load is desired, the hydrogen production device 10 is made low-pressure. This is because the process of producing hydrogen by thermal decomposition of the raw material gas does not emit carbon dioxide (CO2), which meets the demand for carbon dioxide reduction. The lower the pressure in the reactor 12, the higher the conversion rate of the raw material gas and the greater the amount of hydrogen generated. It is also possible to produce highly useful solid carbon. Carbon has a spherical carbon structure with good crystallinity, such as carbon black.

[0034] When economical operation is desired while aiming for carbon neutrality, the hydrogen production device 10 is pressurized. This is because the higher the pressure in the reactor 12, the less catalyst 14 is consumed, i.e., the less catalyst 14 is supplied, thereby reducing the cost of the catalyst 14. Furthermore, the higher the pressure in the reactor 12, the less power is required for the pressure boosting equipment and the hydrogen production equipment. The reduced power consumption of the pressure boosting equipment and the hydrogen production equipment can be reduced accordingly.

[0035] In this way, the hydrogen production device 10 can be operated appropriately in response to various demands. <Effects of the embodiment> This embodiment has the following advantages.

[0036] (1) The hydrogen production device 10 has a reactor 12 that produces hydrogen by thermally decomposing a hydrocarbon gas, which is a feed gas, using a catalyst 14. The internal pressure of the reactor 12 is set to 1 ata or more and 35 ata or less. The lower the internal pressure of the reactor 12, the higher the conversion rate of the feed gas and the greater the amount of hydrogen generated. No carbon dioxide is emitted during the process of producing hydrogen by thermally decomposing the feed gas. Therefore, for example, when a reduction in environmental impact is desired, the internal pressure of the reactor 12 is set lower. In contrast, the higher the internal pressure of the reactor 12, the lower the conversion rate of the feed gas and the smaller the amount of hydrogen generated. However, the higher the pressure of the reactor 12, the less catalyst 14 is consumed, i.e., the less catalyst 14 is supplied, and therefore the cost of the catalyst 14 can be reduced. Therefore, when economical operation is desired, the internal pressure of the reactor 12 is set higher. In this way, the hydrogen production device 10 can be operated appropriately in response to various demands.

[0037] (2) The temperature inside the reactor 12 is set to 700°C or higher and 950°C or lower. This allows the thermal decomposition reaction of the hydrocarbon gas by the catalyst 14 to proceed. The higher the temperature inside the reactor 12, i.e., the temperature of the catalyst 14, the more the thermal decomposition of the raw material gas proceeds. Furthermore, by keeping the temperature inside the reactor 12 at 950°C or lower, the reliability of the reactor 12 can be ensured.

[0038] (3) The catalyst 14 is made of fine solid particles and forms a catalyst layer inside the reactor 12. The reactor 12 is a vertically extending cylindrical body configured so that the raw material gas is introduced from the bottom and the product gas generated by thermal decomposition is discharged from the top. With this configuration, the raw material gas is blown into the reactor 12 from the bottom, forming a fluidized bed, which is a layer of catalyst 14 that moves vigorously. The fluidization of the catalyst 14 promotes contact between the raw material gas and the catalyst 14. This allows the thermal decomposition reaction of the raw material gas by the catalyst 14 to proceed favorably.

[0039] (4) The hydrogen production device 10 is equipped with a distributor 13. The distributor 13 divides the interior of the reactor 12 into a reaction chamber 12A and an air chamber 12B located below the reaction chamber 12A. The distributor 13 has a large number of holes. A catalyst layer is formed on the distributor 13 within the reaction chamber 12A. With this configuration, the raw material gas is supplied to the reaction chamber 12A via the air chamber 12B and the distributor 13. The raw material gas is rectified and diffused by the distributor 13. As a result, the raw material gas flows uniformly into the reaction chamber 12A from below. This allows the catalyst 14, which is made up of fine solid particles, to be fluidized appropriately.

[0040] (5) The catalyst 14 is made of iron or contains iron as its main component. The catalyst 14 containing iron or iron as its main component is inexpensive, which allows the hydrogen production device 10 to be operated more economically.

[0041] (6) When the pressure inside the pressure vessel 11 is higher than atmospheric pressure, the reactor 12 is maintained in an externally pressurized state. This allows the thermal decomposition reaction of hydrocarbon gas by the catalyst 14 to be carried out more safely and stably.

[0042] <Other embodiments> This embodiment may be modified as follows. The catalyst 14 may be made of metals such as nickel and cobalt, or may be based on these metals.

[0043] The reactor 12 may be a fixed bed reactor in which the catalyst 14 is kept stationary. The hydrogen production device 10 may have a configuration in which the pressure vessel 11 is omitted. In this case, hydrogen is produced under atmospheric pressure. The atmospheric pressure is, for example, 1 ata.

[0044] As used herein, the term "cylinder" or "cylindrical" may refer to any structure having a peripheral wall. For example, but not limited to, the term "cylinder" or "cylindrical" may refer to any structure having a cross-sectional shape that is circular, oval, and polygonal with sharp or rounded corners. [Explanation of symbols]

[0045] 10...Hydrogen production equipment 12...Reactor 12A...Reaction chamber 12B…Wind room 13...distributor 14...Catalyst

Claims

1. A hydrogen production apparatus having a reactor for producing hydrogen by thermally decomposing a hydrocarbon gas as a raw material gas using a catalyst, The pressure inside the reactor is set to 1 ata or more and 35 ata or less, the catalyst is fine solid particles that form a catalyst layer inside the reactor; the reactor is a cylindrical body extending in a vertical direction, and is configured so that the raw material gas is introduced from a lower part thereof and a product gas generated by the pyrolysis is discharged from an upper part thereof; a distributor having a number of holes is provided inside the reactor, the distributor dividing the inside of the reactor into a reaction chamber and an air chamber located below the reaction chamber; the catalyst layer is formed on the distributor in the reaction chamber; The catalyst forms a fluidized bed inside the reactor when the raw material gas is blown into the reaction chamber from below through the disperser.

2. 2. The hydrogen production device according to claim 1, wherein the temperature inside the reactor is set to 700°C or higher and 950°C or lower.

3. 3. The hydrogen generating device according to claim 1, wherein the catalyst is iron or contains iron as a main component.

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