JP6900004B2 - Hydrogen generator - Google Patents

Description

The present invention relates to a hydrogen generator. In particular, the present invention relates to a hydrogen generating apparatus in which the yield of hydrogen is high and the amount of hydrogen produced can be easily controlled.

There is a demand for a technology that produces high-purity hydrogen and stably supplies it to fuel cells and the like. As a method for producing hydrogen, for example, a method of steam reforming a hydrocarbon gas is known. However, steam reforming of hydrocarbons has a problem that carbon is precipitated and the catalyst is deactivated when the molar ratio of steam to the raw material becomes low. Therefore, it is necessary to strictly control the process conditions according to the amount of hydrogen produced.

The inventors invented a method and an apparatus for generating hydrogen as plasma by discharging ammonia, and disclosed it as Patent Document 1. Patent Document 1 discloses a hydrogen generator including a plasma reactor, a high voltage electrode, and a ground electrode. In the hydrogen generator of Patent Document 1, the hydrogen separation membrane functions as a high-voltage electrode, and the hydrogen separation membrane discharges a dielectric barrier from the ground electrode under the condition of normal temperature and atmospheric pressure, and the supplied gas. High-purity hydrogen is produced by converting the ammonia contained in the substance into plasma. In the hydrogen generator of Patent Document 1, the raw material gas is discharged between the facing high voltage electrodes and the ground electrode to be in a plasma state, so that the volumes of the raw material gas that has been turned into plasma are such that the electrodes face each other. It becomes substantially the same as the volume of the part.

In the hydrogen generator using the plasma discharge of Patent Document 1, it is necessary to increase the electric power for uniformly plasmaizing the raw materials in the cylindrical reaction vessel according to the capacity of the reaction vessel. Larger reaction vessels can be less energy efficient than smaller reaction vessels, which can result in lower hydrogen yields when mass production of hydrogen is required.

Japanese Unexamined Patent Publication No. 2014-70012

The present invention has been made in view of the present situation, and has solved the problem of providing a hydrogen generating apparatus capable of easily controlling the amount of hydrogen produced and constantly producing high-purity hydrogen in a high yield. It was done as an issue to be done.

The hydrogen generator of the present invention includes a dielectric, an electrode, a hydrogen separation membrane, and a high voltage power supply. The dielectric is a flat plate-shaped dielectric having a first surface formed as a continuous groove in which the raw material gas flow path is formed and a second surface substantially parallel to the first surface. The electrodes are arranged so as to face the second surface of the dielectric, and the hydrogen separation membrane is arranged on the first surface side of the dielectric to cover the groove openings of the raw material gas flow path. The high voltage power supply supplies power to the hydrogen separation membrane or electrodes to generate an electric discharge. The hydrogen generating apparatus of the present invention is characterized in that the electrode and the hydrogen separation membrane are arranged at positions asymmetric with respect to the dielectric.

In the hydrogen generating apparatus of the present invention, the raw material gas flow path is formed as a groove on the dielectric, and the hydrogen separation membrane is arranged so as to cover the opening of the groove. When power is supplied to either the hydrogen separation membrane or the electrode facing the hydrogen separation membrane with the dielectric sandwiched between them, an electric discharge is generated in the raw material gas flow path, the raw material gas becomes plasma, and hydrogen is generated. Generate.

In the hydrogen generating apparatus of the present invention, it is preferable that the hydrogen separation membrane covers the entire first surface of the dielectric. Further, the area of the portion of the electrode facing the second surface is preferably 1% or more and 60% or less of the area of the hydrogen separation membrane.

Hydrogen generated in the raw material gas flow path is separated from the raw material gas by passing through the hydrogen separation membrane covering the opening of the raw material gas flow path due to the plasma conversion of the raw material gas by the discharge between the hydrogen separation membrane and the electrode. .. It is possible to efficiently decompose the raw material gas into hydrogen and separate the generated hydrogen from the raw material gas, and it is possible to generate hydrogen gas in a high yield.

In the hydrogen generator of the present invention, the hydrogen separation membrane and the electrode are arranged asymmetrically with respect to the dielectric. As a result, the plasma generated by the electric discharge spreads from the upstream to the downstream of the raw material gas flow path in which the electrodes do not face each other, starting from the electrode, and the region where the plasma is generated expands.

The dielectric of the hydrogen generating apparatus of the present invention has, in addition to the cross-sectional shape of the groove which is the flow path of the raw material gas, the total length of the raw material gas flow path, the contact area with the hydrogen separation membrane, the supply rate of the raw material gas, and the applied voltage. The amount of hydrogen produced can be controlled by appropriately changing the arrangement of the electrodes.

The hydrogen generating apparatus of the present invention can efficiently generate plasma of the raw material gas and control the amount of hydrogen generated in the presence of a flow of the raw material gas.

In the hydrogen generator of the present invention, the electrode facing the hydrogen separation membrane is made smaller than the hydrogen separation membrane, and the area where the electrode faces the dielectric is 1% to 60% of the area of the hydrogen separation membrane. As a result, the capacitance between the hydrogen separation membrane and the electrode can be reduced, plasma can be generated with a small amount of power, and the power saving of the high voltage power supply can be achieved.

In the hydrogen generating apparatus of the present invention, although the area of the electrode facing the hydrogen separation membrane is smaller than the area of the hydrogen separation membrane, the portion where the raw material gas is turned into plasma with respect to the entire raw material gas flow path. The ratio of is large. Since the area converted to plasma is large, the decomposition of ammonia progresses, and the proportion of hydrogen molecules generated by the decomposition of ammonia becoming hydrogen atoms increases. As a result, it is possible to control the amount of hydrogen produced and increase the capacity.

FIG. 1 is a perspective view schematically showing a hydrogen generating apparatus according to an embodiment of the present invention. FIG. 2 is an exploded perspective view of a hydrogen generating apparatus according to an embodiment of the present invention. FIG. 3 is an exploded perspective view of a hydrogen generating apparatus according to an embodiment of the present invention. FIG. 4 is a drawing-substituting photograph showing the state of the raw material gas plasmalized by the hydrogen generating apparatus of the present invention.

The hydrogen generating apparatus of the present invention is characterized in that the electrode and the hydrogen separation membrane are arranged at positions asymmetric with respect to the dielectric. The asymmetrical arrangement referred to here includes the following two types of arrangement.
That is, the arrangement in which the area of the electrode facing the dielectric is different from the area of the hydrogen separation membrane facing the dielectric and the position of the electrode and the hydrogen separation membrane with respect to the dielectric are relative to any position of the dielectric. The arrangement is neither plane symmetric, line symmetric, nor point symmetric.

In the hydrogen generator of the present invention, although the area of the electrode facing the hydrogen separation membrane is smaller than the area of the hydrogen separation membrane, the region where the raw material gas becomes plasma in the raw material gas flow path is larger. Therefore, plasma is generated in the entire raw material gas flow path. Since the area of plasma formation is wide, the proportion of hydrogen molecules generated by decomposition of ammonia and decomposition from ammonia becomes hydrogen atoms, which makes it possible to control the amount of hydrogen produced and increase the capacity. In the prior art, since the ground electrode and the high voltage electrode facing each other are discharged to a plasma state, the region to be plasmaized is substantially the same as the volume between the facing electrodes. On the other hand, in the present invention, the plasma spreads from the electrode facing the hydrogen separation membrane in the flow path direction in which the electrodes do not face, that is, from the upstream to the downstream of the raw material gas, and the area of the plasma is expanded. .. Here, in the hydrogen generator, as the flow rate of the raw material gas is reduced, the spread of the plasma in the direction of the raw material gas flow path decreases. When the raw material gas flow rate is zero, the plasma does not spread in the flow path direction, and plasma is generated only in the direction perpendicular to the hydrogen separation membrane from the electrode. That is, the hydrogen generating apparatus of the present invention is an apparatus suitable for efficiently generating plasma and controlling the amount of hydrogen produced in the presence of a flow of raw material gas. In particular, it is particularly effective that the electrode facing the hydrogen separation membrane is smaller than the hydrogen separation membrane and has an area of 1% to 60% of the hydrogen separation membrane. When the area of the electrode facing the hydrogen separation film becomes small, the capacitance between the hydrogen separation film and the electrode becomes small, plasma can be generated with a small amount of electric power, and the power saving of the high voltage power supply can be achieved. ..

The preferred embodiments of the present invention are listed below.
(1) The raw material gas preferably used in the hydrogen generating apparatus can be ammonia, a hydrocarbon-based gas such as methane, or a mixed gas of ammonia and an inert gas instead of ammonia alone. Further, it can be a simple substance of ammonia generated from liquefied ammonia or urea, or a mixed gas of the ammonia and an inert gas.
(2) A hydrogen flow path plate for deriving the generated hydrogen is arranged adjacent to the hydrogen separation membrane. The hydrogen flow path plate is provided with a hydrogen flow path for receiving hydrogen that has passed through the hydrogen separation membrane and a hydrogen outlet.
(3) The hydrogen separation membrane functions as a high-voltage electrode when connected to a high-voltage power supply. When the hydrogen separation membrane functions as a high voltage electrode, the electrode arranged so as to face the second surface of the dielectric functions as a ground electrode. At this time, the insulating spacer is arranged between the hydrogen separation membrane and the hydrogen flow path plate.
(4) When the hydrogen separation membrane is grounded, it functions as a ground electrode. When the hydrogen separation membrane functions as a ground electrode, the electrode arranged so as to face the second surface of the dielectric functions as a high voltage electrode. At this time, the insulating spacer is arranged outside the high voltage electrode.
(5) The high-voltage electrode and the ground electrode face each other with a dielectric material in between, and the raw material gas in the raw material gas flow path is converted into atmospheric pressure non-equilibrium plasma by the dielectric barrier discharge. The high voltage power supply applies a bipolar pulse waveform to the high voltage electrode.
(6) The dielectric is formed of glass such as quartz glass, ceramics such as alumina, barium titanate, polycarbonate, acrylic and other highly insulating resins.
(7) The electrode is formed in a flat plate shape or a rod shape, and the area of the portion facing the dielectric is smaller than the area of the second surface of the dielectric.

(Example 1)
Hereinafter, preferred examples of the hydrogen generating apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a perspective view schematically showing a hydrogen generating apparatus 1 according to an embodiment of the present invention. FIG. 2 is an exploded perspective view showing the front surface, the upper surface surface, and the right side surface of each component of the hydrogen generation device 1. In the following description, the terms of up / down / left / right indicating the relative positional relationship correspond to the directions of up / down / left / right shown in the drawings.

The hydrogen generation device 1 includes a dielectric 2, an electrode 3, a hydrogen flow path plate 4, a hydrogen separation membrane 5, a high voltage power supply 6, and an insulating spacer 7. The dielectric 2, the hydrogen flow path plate 4, and the insulating spacer 7 are formed in a rectangular shape having substantially the same aspect ratio on the side surfaces. The aspect ratio of the hydrogen separation membrane 5 is also substantially the same as that of the dielectric 2.

The dielectric 2 is a flat plate made of quartz glass having a first surface 11 on which the raw material gas flow path 13 is formed and a second surface 12 substantially parallel to the first surface 11. It is a member. As shown in FIG. 2, a raw material gas flow path 13 is formed on the first surface 11 of the dielectric 2 as a groove having an opening. The pattern in which the raw material gas flow path 13 is formed can be appropriately set in consideration of the flow rate of the raw material gas and the voltage applied to the raw material gas. In FIG. 2, as an example, an outward path portion 16 communicating with the raw material gas inlet 14 and extending linearly parallel to the upper surface of the dielectric 2 and a return path portion 17 that folds back from the outward path portion 16 and extends parallel to the outward path portion 16. And are shown alternately as raw material gas flow paths 13 connected a plurality of times at uniform intervals.

In this embodiment, the electrode 3 is a flat plate-shaped electrode having a length in the vertical direction substantially the same as that of the dielectric 2 and a length of approximately 1/3 of the dielectric 2 in the depth direction. One surface of the electrode 3 faces the second surface 12 of the dielectric 2. The electrode 3 is grounded and functions as a ground electrode.

The hydrogen separation membrane 5 is arranged so as to be in contact with the first surface 11 of the dielectric 2 and covers the entire opening of the raw material gas flow path 13. The dielectric 2 and the hydrogen separation membrane 5 define a wall surface having a closed cross section of the raw material gas flow path 13. The hydrogen separation membrane 5 does not allow the raw material gas in the raw material gas flow path 13 to permeate, but allows only hydrogen generated from the raw material gas to permeate and separate.

The hydrogen separation film 5 includes a palladium alloy thin film, a zirconium-nickel (Zr-Ni) -based alloy thin film, a vanadium-nickel (V-Ni) -based alloy thin film, a niobium-nickel (Nb-Ni) -based alloy thin film, and niobium (Nb-Ni) -based alloy thin film. Nb), one or more metals selected from the group consisting of nickel (Ni), cobalt (Co) and molybdenum (Mo), vanadium (V), titanium (Ti), zirconium (Zr), tantalum (Ta). It can also be formed of a thin film made of an alloy with one or more metals selected from the group consisting of hafnium (Hf) and the like. As the hydrogen separation membrane 5 of this example, a palladium alloy thin film can be particularly preferably used. The hydrogen separation membrane 5 can be formed by a single-layer membrane made of these metals or by laminating two or more metals selected from these metals. It is also possible to use non-metals such as silica-based separation membranes, zeolite-based separation membranes, polyimide separation membranes, and polysulfone separation membranes as hydrogen separation membranes, but in that case, the strength is higher in order to maintain the shape. It is necessary to bond the high support with the hydrogen separation membrane 5.

The hydrogen flow path plate 4 is a plate-shaped member having an aspect ratio substantially the same as that of the dielectric 2 and the hydrogen separation membrane 5. The hydrogen flow path plate 4 includes a hydrogen flow path 18 that is open on the left side surface side and a hydrogen outlet 19 that communicates with the hydrogen flow path 18, and the hydrogen flow path plate 4 is a dielectric material. It is arranged on the right side of the hydrogen separation membrane 5 on the outside of the raw material gas flow path 13 so as to sandwich and hold the insulating spacer 7 and the hydrogen separation membrane 5 between the two. The hydrogen flow path 18 is provided with an opening at a position facing the raw material gas flow path 13 of the dielectric 2, and the opening is covered by the hydrogen separation membrane 5.

The high voltage power supply 6 is a power supply for generating an electric discharge in the raw material gas flow path 13 between the hydrogen separation membrane 5 and the electrode 3. In this embodiment, the high voltage power supply 6 is connected to the hydrogen separation film 5, and a high voltage is applied to the hydrogen separation film 5 to cause the hydrogen separation film 5 to function as a high voltage electrode. The insulating spacer 7 is arranged between the hydrogen separation membrane 5 and the hydrogen flow path plate 4. The high-voltage power supply 6 can increase the electron energy density by applying a bipolar pulse waveform having an extremely short waveform holding time of 10 μs.

In this embodiment, the dielectric 2, the electrode 3, the hydrogen flow path plate 4, the hydrogen separation membrane 5, and the insulating spacer 7 are overlapped and bonded by bolts and nuts. Then, the electrode 3 is coupled to the central portion of the second surface of the dielectric 2 in a state where the positions in the height direction are aligned. In order to reliably seal the raw material gas flow path 13 and the hydrogen flow path 18, a gasket is additionally arranged or a sealing material is additionally applied.

Ammonia is most preferably used as a raw material in the hydrogen generating apparatus 1 of this embodiment. The reaction formula when hydrogen is produced from ammonia as a raw material is shown in the following formula 1.

2NH ₃ + e → N ₂ + 3H ₂ + e (Equation 1)

A method of generating hydrogen using ammonia as a raw material gas in the hydrogen generating apparatus 1 will be described. The raw material supply means (not shown) includes a flow velocity control means for controlling the flow velocity of the raw material gas, and is supplied to the raw material gas flow path 13 at a predetermined speed via the raw material gas flow path inlet 14 of the dielectric 2. When the high voltage power supply 6 applies a voltage to the hydrogen separation membrane 5, a dielectric barrier discharge is generated between the hydrogen separation membrane 5 and the electrode 3. Due to the discharge, the ammonia in the raw material gas flow path 13 becomes atmospheric pressure non-equilibrium plasma.

FIG. 4 shows a drawing-substituting photograph of a state in which ammonia, which has become atmospheric pressure non-equilibrium plasma, is emitting light by the hydrogen generating apparatus 1 of this embodiment. As is clear from this figure, plasma is generated in the entire raw material gas flow path 13. The expansion of the plasma region occurs when the plasma starts from the electrode 3 facing the hydrogen separation membrane 5 and spreads in the flow path direction in which the electrode 3 does not face, that is, from the upstream to the downstream of the raw material gas.

In this embodiment, the area of the portion of the electrode 3 facing the dielectric 2 is 1/3 of the area of the hydrogen separation membrane 5. However, the area where the ammonia plasma is generated is larger than the area where the area of the electrode facing the dielectric 2 is the same as that of the hydrogen separation membrane 5.

Hydrogen generated from the atmospheric pressure non-equilibrium plasma of ammonia is adsorbed on the hydrogen separation membrane 5 in the form of hydrogen atoms, passes through the hydrogen separation membrane 5 while diffusing, and enters the hydrogen flow path 18 of the hydrogen flow path plate 4. It reaches and recombines into a hydrogen molecule. In this way, the hydrogen separation membrane 5 allows only hydrogen to pass through the hydrogen flow path 18 side, and hydrogen is separated.

Ammonia passing through the raw material gas flow path 13 can secure a time to be exposed to electric discharge by controlling the flow velocity, and approximately 100% of the hydrogen contained in the ammonia is separated as hydrogen into the hydrogen flow path 18. It is possible to introduce it. Further, by optimizing the pattern of the raw material gas flow path 13 and the arrangement of the electrodes 3, hydrogen can be generated from ammonia in a high yield even when the flow rate of ammonia is increased.

(Example 2)
FIG. 3 shows the hydrogen generator 21 of this embodiment. The electrode 3'in this embodiment has substantially the same length in the vertical direction as the dielectric 2 and has a length of 1/4 of the dielectric 2 in the depth direction. The electrodes 3'face each other from the upper end to the lower end at the center of the second surface 12 of the dielectric 2. In this embodiment, the electrode 3'is connected to the high voltage power supply 6 and functions as a high voltage electrode. The insulating spacer 9 is arranged outside the electrode 3'.

In this embodiment, the hydrogen separation membrane 5 is grounded and functions as a ground electrode. When the high voltage power supply 6 applies a voltage to the electrode 3', a dielectric barrier discharge is generated in the raw material gas flow path 13 between the hydrogen separation film 5 and the electrode 3'. By the electric discharge, the ammonia in the raw material gas flow path 13 becomes atmospheric pressure non-equilibrium plasma, and hydrogen can be generated in high yield.

The area of the portion where the electrode 3'of this embodiment faces the dielectric 2 is 1/4 of the area of the hydrogen separation membrane 5. However, as in Example 1, the area where the ammonia plasma is generated is larger than the area where the area of the electrode 3'opposing the dielectric 2 is the same as that of the hydrogen separation membrane 5.

In the hydrogen generating devices 1 and 21 described in the examples, the size and arrangement of the electrodes with respect to the dielectric 2 can be changed as appropriate. In the embodiment, in the case where the hydrogen separation membrane covers the entire first surface of the dielectric, the area of the electrode facing the second surface is 1/3 of the area of the hydrogen separation membrane. Although the case of 1/4 has been described, it has been confirmed that the plasma generation area becomes large when the electrode area is 1% or more and 60% or less.

In the embodiment, an example in which the dielectric 2 is arranged so as to be in contact with the central portion of the dielectric 2 has been described, but it may be arranged at the end portion of the dielectric 2 so as to be along any side. It is also possible to arrange a plurality of electrodes, for example, small electrodes can be arranged at the four corners of the dielectric. The yield of hydrogen can be further increased by changing the arrangement of the raw material gas flow path according to the arrangement of the electrodes.

1, 21 Hydrogen generator 2 Dielectric 3, 3'Electrode 4 Hydrogen flow path plate 5 Hydrogen separation membrane 6 High voltage power supply 7, 9 Insulation spacer 11 First surface 12 Second surface 13 Raw material gas flow path 14 Raw material gas Flow path inlet 15 Raw material gas flow path outlet 16 Outward path part of raw material gas flow path 17 Return path part of raw material gas flow path 18 Hydrogen flow path 19 Hydrogen outlet

Claims (2)

A flat-plate-shaped dielectric having a first surface formed as a continuous groove in which the raw material gas flow path is formed, and a second surface substantially parallel to the first surface.
An electrode arranged to face the second surface of the dielectric and
A hydrogen separation membrane arranged on the first surface side of the dielectric and covering the opening of the groove of the raw material gas flow path, and a hydrogen separation membrane.
A high-voltage power supply that supplies electric power to the hydrogen separation membrane or the electrode to generate an electric discharge,
Is equipped with
A hydrogen generating apparatus characterized in that the electrode and the hydrogen separation membrane are arranged at positions asymmetric with respect to the dielectric. The hydrogen separation membrane covers the entire first surface of the dielectric.
The hydrogen generating apparatus according to claim 1, wherein the area of the portion where the electrode faces the second surface is 1% or more and 60% or less of the area of the hydrogen separation membrane.

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