Hydrogen-producing apparatus

Abstract

To provide a hydrogen-producing apparatus capable of producing hydrogen with less power.SOLUTION: A hydrogen-producing apparatus 1 comprises: an ammonia tank 2 in which ammonia is stored; a plasma reactor 3 for decomposing the ammonia supplied from the ammonia tank 2 into nitrogen and hydrogen; a first separation film 5 for separating undecomposed ammonia, and nitrogen and oxygen from a mixture of the undecomposed ammonia, the nitrogen and the oxygen, that is supplied from the plasma reactor 3; a second separation film 6 for separating the undecomposed ammonia and the nitrogen from a mixture of the undecomposed ammonia and the nitrogen that are separated by the first separation film 5; and an ammonia return line 14 for supplying the undecomposed ammonia separated by the second separation film 6 to the plasma reactor 3.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] In recent years, from the perspective of environmental protection, hydrogen fuel has attracted attention. Such hydrogen fuel is produced, for example, by a fuel reformer. In the fuel reformer, ammonia is decomposed into nitrogen and hydrogen, and the decomposed hydrogen is extracted.

[0003] As such a fuel reformer, for example, a fuel reformer equipped with a reformer that reforms ammonia by plasma to generate high-concentration hydrogen gas has been proposed (see, for example, Patent Document 1 below).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] On the other hand, there is a demand for producing hydrogen with less power consumption.

[0006] The present invention provides a hydrogen production device that can produce hydrogen with less power consumption.

Means for Solving the Problems

[0007] The hydrogen production device of the present invention [1] comprises an ammonia tank for storing ammonia, a plasma reactor for decomposing the ammonia supplied from the ammonia tank into nitrogen and hydrogen, a first separation membrane for separating undissociated ammonia and nitrogen from hydrogen from a mixture of undissociated ammonia, nitrogen and hydrogen supplied from the plasma reactor, a second separation membrane for separating undissociated ammonia and nitrogen from the mixture of undissociated ammonia and nitrogen separated by the first separation membrane, and an ammonia return line for supplying the undissociated ammonia separated by the second separation membrane to the plasma reactor.

[0008] According to such a configuration, a part of the ammonia is decomposed into hydrogen by the plasma reactor, and the remaining ammonia (undissociated ammonia) is supplied again to the plasma reactor via the ammonia return line. That is, in this hydrogen production device, the ammonia is decomposed in several stages. Therefore, the power of the plasma reactor required for one decomposition can be suppressed, and as a result, the total power of the plasma reactor can be suppressed.

Advantages of the Invention

[0009] According to the hydrogen production device of the present invention, hydrogen can be produced with less power consumption.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0011] <Hydrogen production device> Referring to FIG. 1, an embodiment of the hydrogen production device of the present invention will be described in detail.

[0012] The hydrogen production device 1 is, for example, a fuel supply device connected to a fuel cell 100 (see the dashed line in FIG. 1). Examples of the fuel cell 100 include a fuel cell vehicle and a household fuel cell. Further, the hydrogen production device 1 and the fuel cell 100 constitute a fuel cell system. That is, the fuel cell system includes the hydrogen production device 1 and the fuel cell 100.

[0013] The hydrogen production device 1 includes an ammonia tank 2, a plasma reactor 3, an ammonia supply line 11, a vaporizer 4, a first mass flow meter 21, a pressure gauge 41, a first separation membrane 5, a mixture supply line 12, a second separation membrane 6, an undecomposed ammonia supply line 13, a back pressure valve 42, an ammonia return line 14, a second mass flow meter 22, a nitrogen discharge line 15, a catalyst unit 7, a hydrogen supply line 16, a third mass flow meter 23, and a control unit 8. Further, the hydrogen production device 1 includes a pump (not shown) at an appropriate position. By driving the pump, ammonia, hydrogen, and nitrogen described later can be supplied.

[0014] <Ammonia tank> The ammonia tank 2 is a tank for storing ammonia (liquid).

[0015] <Plasma reactor> The plasma reactor 3 decomposes ammonia supplied from the ammonia tank 2 into nitrogen and hydrogen. Although details will be described later, in the plasma reactor 3, based on a predetermined ammonia decomposition rate, a part of the ammonia supplied from the ammonia tank 2 is decomposed into nitrogen and hydrogen.

[0016] The plasma reactor 3 includes a casing 30 and a plurality of electrodes 31.

[0017] The casing 30 has a hollow cylindrical shape and is arranged such that its longitudinal direction is along the flow direction of ammonia. The plurality of electrodes 31 are arranged in the casing 30 along the longitudinal direction of the casing 30. Further, the plurality of electrodes 31 are arranged at intervals from each other along the direction orthogonal to the longitudinal direction of the casing 30.

[0018] The electrode 31 includes a conductor 32, a dielectric 33 covering the conductor 32, and an ammonia adsorption member 34 covering the dielectric 33.

[0019] Examples of the material of the conductor 32 include tungsten. Examples of the material of the dielectric 33 include alumina.

[0020] The ammonia adsorption member 34 is a layer formed by applying an ammonia adsorbent on the surface of the dielectric 33. Examples of the ammonia adsorbent include zeolite.

[0021] <Ammonia supply line> The ammonia supply line 11 supplies ammonia from the ammonia tank 2 to the plasma reactor 3.

[0022] The upstream end in the ammonia supply direction of the ammonia supply line 11 is connected to the ammonia tank 2. The downstream end in the ammonia supply direction of the ammonia supply line 11 is connected to the plasma reactor 3.

[0023] <Vaporizer> The vaporizer 4 is a vaporizer that vaporizes ammonia (liquid) supplied from the ammonia tank 2.

[0024] The vaporizer 4 is interposed in the middle of the ammonia supply line 11 in the ammonia supply direction.

[0025] <First Mass Flow Meter> The first mass flow meter 21 measures the mass flow rate of the ammonia vaporized by the vaporizer 4.

[0026] The first mass flow meter 21 is interposed between the vaporizer 4 and the plasma reactor 3 in the middle of the ammonia supply direction of the ammonia supply line 11.

[0027] <Pressure Gauge> The pressure gauge 41 measures the pressure of the ammonia (gas) between the vaporizer 4 and the plasma reactor 3.

[0028] The pressure gauge 41 is interposed between the vaporizer 4 and the first mass flow meter 21 in the middle of the ammonia supply direction of the ammonia supply line 11.

[0029] <First Separation Membrane> The first separation membrane 5 separates unreacted ammonia and nitrogen from hydrogen in the mixture of unreacted ammonia, nitrogen, and hydrogen supplied from the plasma reactor 3. That is, the first separation membrane 5 is a hydrogen separation membrane, and examples thereof include, for example, a palladium membrane.

[0030] <Mixture Supply Line> The mixture supply line 12 supplies a mixture of unreacted ammonia, nitrogen, and hydrogen from the plasma reactor 3 to the first separation membrane 5.

[0031] The upstream end in the mixture supply direction of the mixture supply line 12 is connected to the plasma reactor 3. The downstream end in the mixture supply direction of the mixture supply line 12 is connected to the first separation membrane 5.

[0032] <Second Separation Membrane> The second separation membrane 6 separates unreacted ammonia and nitrogen from the mixture of unreacted ammonia and nitrogen separated by the first separation membrane 5. The second separation membrane 6 is not particularly limited as long as it can separate unreacted ammonia and nitrogen, and examples thereof include, for example, a polymer separation membrane.

[0033] <Undissociated ammonia supply line> The undissociated ammonia supply line 13 supplies a mixture of undissociated ammonia and nitrogen from the first separation membrane 5 to the second separation membrane 6.

[0034] The upstream end of the undissociated ammonia supply line 13 in the undissociated ammonia supply direction is connected to the first separation membrane 5. The downstream end of the undissociated ammonia supply line 13 in the undissociated ammonia supply direction is connected to the second separation membrane 6.

[0035] <Back pressure valve> The back pressure valve 42 adjusts the pressure in the undissociated ammonia supply line 13.

[0036] The back pressure valve 42 is interposed in the middle of the undissociated ammonia supply line 13 in the undissociated ammonia supply direction.

[0037] <Ammonia return line> The ammonia return line 14 supplies the undissociated ammonia separated by the second separation membrane 6 to the plasma reactor 3.

[0038] The upstream end of the ammonia return line 14 in the ammonia supply direction is connected to the second separation membrane 6. The downstream end of the ammonia return line 14 in the ammonia supply direction is connected to the plasma reactor 3 (specifically, the upstream end of the plasma reactor 3).

[0039] <Second mass flow meter> The second mass flow meter 22 measures the mass flow rate of the undissociated ammonia separated by the second separation membrane 6.

[0040] The second mass flow meter 22 is interposed in the middle of the ammonia return line 14 in the ammonia supply direction.

[0041] <Nitrogen discharge line> The nitrogen discharge line 15 discharges the nitrogen separated by the second separation membrane 6 into the atmosphere.

[0042] The upstream end portion of the nitrogen discharge line 15 in the nitrogen discharge direction is connected to the second separation membrane 6. The downstream end portion of the nitrogen discharge line 15 in the nitrogen discharge direction is open to the atmosphere.

[0043] <Catalyst unit> The catalyst unit 7 is a storage tank that stores a known ammonia decomposition catalyst for decomposing ammonia.

[0044] The catalyst unit 7 is interposed in the middle of the nitrogen discharge line 15 in the nitrogen discharge direction.

[0045] <Hydrogen supply line> The hydrogen supply line 16 supplies the hydrogen separated by the first separation membrane 5 to the fuel cell 100.

[0046] The upstream end portion of the hydrogen supply line 16 in the hydrogen supply direction is connected to the first separation membrane 5. The downstream end portion of the hydrogen supply line 16 in the hydrogen supply direction is connected to the fuel cell 100.

[0047] <Third mass flowmeter> The third mass flowmeter 23 measures the mass flow rate of the hydrogen separated by the first separation membrane 5.

[0048] The third mass flowmeter 23 is interposed in the middle of the hydrogen supply line 16 in the hydrogen supply direction.

[0049] <Control unit> The control unit 8 is a unit (e.g., ECU: Electronic Control Unit) that executes electrical control in the hydrogen production device 1, and is composed of a microcomputer equipped with an arithmetic processing unit, a memory, and the like. The control unit 8 stores MAP1 to MAP3, which will be described later, in the memory of the microcomputer. As shown by the dashed line in FIG. 1, the control unit 8 is electrically connected to the plasma reactor 3, the vaporizer 4, the first mass flow meter 21, the second mass flow meter 22, the third mass flow meter 23, the back pressure valve 42, and a pump (not shown). Thus, although details will be described later, the control unit 8 controls the hydrogen flow rate F 水素 (described later) and the ammonia flow rate F アンモニア (described later) to enable hydrogen production with lower power consumption.

[0050] <Operation of Hydrogen Production Device> The operation of the hydrogen production device 1 will be described in detail.

[0051] The operation of the hydrogen production device 1 is controlled by the control unit 8.

[0052] In the hydrogen production device 1, first, the power generation power and the ammonia decomposition rate are input to the control unit 8.

[0053] Next, the control unit 8 sets the ammonia flow rate (ammonia flow rate F アンモニア ) according to the power generation power and the ammonia decomposition rate. Specifically, first, the hydrogen flow rate F 水素 required to generate the input power generation power is set. The hydrogen flow rate F 水素 is set based on MAP1 (FIG. 2A) showing the relationship between the power generation power and the hydrogen flow rate F 水素 . The hydrogen flow rate F 水素 is the flow rate of hydrogen supplied to the fuel cell 100 and is the flow rate measured by the third mass flow meter 23.

[0054] Next, the control unit 8 determines the ammonia flow rate F 水素 based on the set hydrogen flow rate F アンモニアSet it. Specifically, the ammonia flow rate F アンモニア is set based on MAP2 (Figure 2B) showing the relationship between the hydrogen flow rate F 水素 and the ammonia flow rate F アンモニア at the input ammonia decomposition rate. The ammonia flow rate F アンモニア is the flow rate of ammonia supplied to the plasma reactor 3 (the total flow rate of ammonia supplied via the ammonia supply line 11 and ammonia returned via the ammonia return line 14), and is the flow rate measured by the first mass flow meter 21 and the second mass flow meter 22.

[0055] Thus, the ammonia flow rate F アンモニア is set.

[0056] Next, the control unit 8 controls a pump and a valve (not shown) to supply ammonia from the ammonia tank 2 to the plasma reactor 3.

[0057] In the plasma reactor 3, based on the input ammonia decomposition rate, a part of the ammonia supplied to the plasma reactor 3 is decomposed by the plasma reactor 3 into nitrogen and hydrogen.

[0058] The decomposition rate of ammonia is, for example, 15% or more, preferably 20% or more, more preferably 30% or more, and, for example, less than 40%. If the decomposition rate of ammonia is within the above range, hydrogen can be produced with lower power consumption.

[0059] Then, the mixture of the remaining ammonia (undecomposed ammonia) and nitrogen and hydrogen (nitrogen and hydrogen obtained by the decomposition of the plasma reactor 3) is supplied to the first separation membrane 5 via the mixture supply line 12.

[0060] The first separation membrane 5 separates nitrogen and undissociated ammonia from a mixture of undissociated ammonia, nitrogen, and hydrogen, and separates hydrogen therefrom. The separated nitrogen and undissociated ammonia are supplied to the second separation membrane 6 via the undissociated ammonia supply line 13. On the other hand, the separated hydrogen is supplied to the fuel cell 100 via the hydrogen supply line 16. The fuel cell 100 generates electricity based on the supplied hydrogen. The electricity obtained by the power generation can also be used to start the plasma reactor 3.

[0061] Then, the nitrogen and undissociated ammonia separated by the first separation membrane 5 are separated into undissociated ammonia and nitrogen by the second separation membrane 6. The separated undissociated ammonia is supplied to the plasma reactor 3 via the ammonia return line 14. That is, such ammonia is decomposed again by the plasma reactor 3.

[0062] On the other hand, the separated nitrogen is released into the atmosphere via the nitrogen discharge line 15. Note that ammonia discharged via the nitrogen discharge line 15 without being separated by the second separation membrane 6 is decomposed by the catalyst unit 7.

[0063] Also, in the operation of the hydrogen production apparatus 1 described above, the control unit 8 monitors the first mass flow meter 21, the second mass flow meter 22, and the third mass flow meter 23 to make the set ammonia flow rate F アンモニア such that it becomes アンモニアBased on MAP3 (Fig. 2C) showing the relationship with the pressure value of the first separation membrane 5, the back pressure valve 42 is adjusted. Specifically, the pressure of ammonia (gas) is the same as the pressure applied to the first separation membrane 5. That is, the pressure value of the first separation membrane 5 can be obtained by measuring the pressure of ammonia (gas) with the pressure gauge 41. As the pressure of the first separation membrane 5 increases, the discharge rate of the plasma reactor 3 decreases, but the amount of hydrogen separated (permeated) by the first separation membrane 5 can be increased. As will be described in detail later, it can be seen that when the decomposition rate of ammonia is 40% or more, even if the power of the plasma reactor 3 is further increased, the decomposition rate of ammonia tends to be difficult to increase. Ammonia flow rate F アンモニア When it increases, it takes time to produce hydrogen at a decomposition rate of less than 40% of ammonia. Therefore, as the ammonia flow rate F アンモニア increases, by increasing the pressure of the first separation membrane 5, the amount of hydrogen separated (permeated) by the first separation membrane 5 can be increased, and more hydrogen can be produced.

[0064] The control unit 8 repeats the above-described operation until the input generated power is generated or a stop signal for the hydrogen production apparatus 1 is input.

[0065] <Advantages and effects> According to the hydrogen production apparatus 1, hydrogen can be produced with less power consumption. Specifically, according to the hydrogen production apparatus 1, a part of ammonia is decomposed into hydrogen by the plasma reactor 3, and the remaining part of ammonia (undecomposed ammonia) is supplied again to the plasma reactor 3 via the ammonia return line 14. That is, in this hydrogen production apparatus 1, ammonia is decomposed in several stages. Therefore, the power of the plasma reactor 3 required for one decomposition can be suppressed, and as a result, the total power of the plasma reactor 3 can be suppressed.

[0066] More specifically, FIG. 3 shows the relationship between the decomposition rate of ammonia and the power of the plasma reactor 3. According to FIG. 3, when the decomposition rate of ammonia is less than 40%, increasing the power of the plasma reactor 3 tends to efficiently decompose ammonia. On the other hand, when the decomposition rate of ammonia is 40% or more, it can be seen that even if the power of the plasma reactor 3 is further increased, the decomposition rate of ammonia tends not to increase easily. Such a tendency is presumably because when the power of the plasma reactor 3 is increased too much, hydrogen and nitrogen obtained by the decomposition of ammonia recombine to generate ammonia once again.

[0067] And according to the above tendency, in order to increase the decomposition rate of ammonia (specifically, so that the decomposition rate is 40% or more), rather than increasing the power of the plasma reactor 3, it is found that reducing the power of the plasma reactor 3 so that the decomposition rate of ammonia is less than 40% and suppressing the power of the plasma reactor 3 required for one decomposition can suppress the total power of the plasma reactor 3.

[0068] <Modification Example> In the modification example, for members and steps similar to those in an embodiment, the same reference numerals are given, and detailed descriptions thereof are omitted. Further, the modification example can achieve the same operational effects as those in an embodiment unless otherwise specified. Furthermore, an embodiment and its modification example can be combined as appropriate.

[0069] In one embodiment, the hydrogen production device 1 supplies hydrogen to the fuel cell 100, but the supply destination is not limited. The hydrogen production device 1 can also supply hydrogen, for example, as fuel for hydrogen power generation.

[0070] In one embodiment, the downstream end of the ammonia return line 14 in the ammonia supply direction is connected to the plasma reactor 3 (specifically, the upstream end of the plasma reactor 3). The ammonia return line 14 is a line for supplying the undissociated ammonia separated by the second separation membrane 6 to the plasma reactor 3. As long as the undissociated ammonia is supplied to the plasma reactor 3, the downstream end of the ammonia return line 14 in the ammonia supply direction does not have to be directly connected to the plasma reactor 3. For example, it may be connected to the ammonia supply line 11.

Explanation of Signs

[0071] 1 Hydrogen production device 2 Ammonia tank 3 Plasma reactor 5 First separation membrane 6 Second separation membrane 14 Ammonia return line

Claims

【Claim 1】 An ammonia tank for storing ammonia, A plasma reactor that decomposes ammonia supplied from the ammonia tank into nitrogen and hydrogen, A first separation membrane that separates undissociated ammonia and nitrogen from hydrogen from a mixture of undissociated ammonia, nitrogen, and hydrogen supplied from the plasma reactor, A second separation membrane that separates undissociated ammonia and nitrogen from a mixture of undissociated ammonia and nitrogen separated by the first separation membrane, A hydrogen production apparatus comprising an ammonia return line for supplying the undissociated ammonia separated by the second separation membrane to the plasma reactor.

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