JP2020128311A - Hydrogen generation system and operation method thereof - Google Patents

Abstract

To suppress reduction of hydrogen purification efficiency due to reverse transmission of hydrogen generated on a cathode of an electrochemical device of a hydrogen generation system to an anode side.SOLUTION: A hydrogen generation system 100 comprises: gas supply means 30 for supplying a hydrogen containing gas to an anode 7; a power supply 40 for supplying a current to a space between the anode 7 and a cathode 8 of an electrochemical device 1; a controller 60 for controlling the power supply 40; and the electrochemical device 1. On a cathode side separator 16 of the electrochemical device 1, a cathode side outlet 18 for discharging hydrogen generated on a cathode side gas channel 17 and the cathode 8 is provided, and the cathode side gas channel 17 stores water.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a hydrogen generation system that uses an electrochemical device to generate high-purity hydrogen from a hydrogen-containing gas supplied from a gas supply device, and a method for operating the same.

The hydrogen generation system is a system that generates high-purity hydrogen by utilizing an electrochemical reaction from a hydrogen-containing gas. This hydrogen generation system is, for example, an electrochemical method in which an electrolyte membrane-electrode assembly (MEA) in which an anode and a cathode are provided on both sides of an electrolyte membrane that selectively transports hydrogen ions (protons) is sandwiched by separators. Equipped with a device.

By supplying a humidified hydrogen-containing gas (including impurities in addition to hydrogen) to the anode, and flowing a current in a predetermined direction (current flowing from the anode to the cathode through the electrolyte membrane) between the anode and the cathode, At the anode, an oxidation reaction occurs in which hydrogen shown in (Chemical formula 1) dissociates into protons (H ⁺ ) and electrons, and at the cathode, a reduction reaction in which hydrogen is generated from protons (H ⁺ ) shown in (Chemical formula ² ) and electrons occurs. Occur.

以上の反応により、アノードに供給された水素含有ガスから、カソードにおいて水素を生成することができる。

Through the above reaction, hydrogen can be generated at the cathode from the hydrogen-containing gas supplied to the anode.

The hydrogen generated by this is compressed and stored at high pressure, liquefied and stored at low temperature, stored by adsorbing/adsorbing on metal or the like, or converted to another substance and stored, or stored as gas at high pressure. To use.

The hydrogen-containing gas supplied to the hydrogen generation system is subjected to steam reforming, partial oxidation reforming, or autothermal reforming of a hydrocarbon-based fuel such as 13A gas or propane gas by a fuel processor, for example. Generated.

Such a hydrogen production power generation system (hereinafter referred to as a hydrogen generation system) includes a fuel cell-ion pump combination (hereinafter referred to as an electrochemical device) that generates high-purity hydrogen from a hydrogen-containing gas.

The electrochemical device is an electrolyte membrane-electrode structure (MEA) in which an anode-side electrode (hereinafter, referred to as an anode) and a cathode-side electrode (hereinafter, referred to as a cathode) are provided on both sides of an electrolyte membrane made of a polymer ion exchange membrane. Equipped with.

Further, the electrochemical device includes an electrochemical cell (hereinafter referred to as a cell) in which the electrolyte membrane-electrode structure is sandwiched by separators.

Electromagnetic valves are respectively provided in the cathode off-gas passage connected to the cathode side inlet and the hydrogen gas passage connected to the cathode side outlet of this electrochemical device.

When the hydrogen generation system is started in the hydrogen production mode, purified hydrogen gas (hereinafter referred to as hydrogen) purified on the cathode side of the electrochemical device is accompanied by low-purity hydrogen remaining on the cathode side from the cathode off-gas passage. It is discharged to the catalytic combustor via the cathode purge flow path. This ensures that the low-purity hydrogen remaining on the cathode side is purged from the cathode side.

Therefore, it is possible to reliably prevent low-purity hydrogen containing nitrogen gas and the like from being supplied to the dehumidifying and refining unit disposed downstream of the cathode side outlet and the compressing unit that compresses hydrogen, thereby ensuring high purity. Hydrogen can be supplied (see, for example, Patent Document 1).

JP, 2009-123432, A

However, in the above-described conventional configuration, high-purity hydrogen discharged from the cathode side outlet of the electrochemical device is sent to the compression unit that compresses hydrogen via the dehumidification and purification unit arranged on the downstream side. When the pressure on the cathode side is increased, a pressure difference is generated on the anode side, and hydrogen generated at the cathode reversely permeates to the anode through the space of the electrolyte membrane. Therefore, there is a problem that the amount of hydrogen discharged from the cathode side outlet is reduced and the hydrogen purification efficiency is lowered.

Here, the reverse permeation is a phenomenon in which hydrogen generated at the cathode of the electrochemical device permeates to the anode through the electrolyte membrane. The hydrogen purification efficiency is the ratio of the energy of hydrogen discharged from the cathode side outlet to the electric energy input to the electrochemical device.

When the reverse permeation is small, a part of the hydrogen generated at the cathode of the electrochemical device permeates to the anode through the electrolyte membrane, and the amount of hydrogen discharged from the cathode side outlet of the electrochemical device increases. Therefore, the hydrogen purification efficiency becomes high. On the other hand, if the reverse permeation is large, a part of hydrogen generated at the cathode permeates to the anode, and the amount of hydrogen exhausted from the cathode side outlet of the electrochemical device decreases, so that the hydrogen purification efficiency decreases.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a hydrogen generation system and a method for operating the same, which can suppress a decrease in hydrogen purification efficiency due to reverse permeation of hydrogen generated at the cathode to the anode side. And

In order to solve the conventional problems, the hydrogen generation system of the present invention is an electrolyte membrane composed of an electrolyte membrane and an anode arranged on one surface with the electrolyte membrane sandwiched therebetween and a cathode arranged on the other surface. -It comprises an electrode assembly, an anode-side separator and a cathode-side separator that are arranged on both outsides of the anode and the cathode, supplies a hydrogen-containing gas to the anode, and supplies a current in a predetermined direction between the anode and the cathode. The electrochemical device for generating hydrogen at the cathode by flowing the gas, a gas supply means for supplying a hydrogen-containing gas, a power supply for flowing an electric current between the anode and the cathode, and a controller. The side separator has an anode-side gas flow path formed on the surface in contact with the anode and through which hydrogen-containing gas flows, and the cathode-side separator is formed on the surface in contact with the cathode, and the hydrogen generated in the cathode flows through the cathode. Has a side gas flow path and a cathode side outlet for discharging hydrogen from the cathode, and the controller generates hydrogen at the cathode in a state where water is stored in the cathode side gas flow path of the cathode side separator. It is what makes me.

As a result, in a state where water is stored in the cathode-side gas flow path of the electrochemical device, the hydrogen-containing gas is supplied to the anode, and a current in a predetermined direction is caused to flow between the anode and the cathode to generate water at the cathode. Hydrogen quickly becomes bubbles in water and becomes difficult to contact with the electrolyte membrane. As a result, hydrogen can be prevented from permeating from the cathode side to the anode side, and a reduction in hydrogen purification efficiency can be suppressed.

Since the hydrogen generation system of the present invention can suppress a decrease in hydrogen purification efficiency, the electric power cost at the time of hydrogen generation can be suppressed low. This makes it possible to provide an economical hydrogen production system.

1 is a schematic configuration diagram of a hydrogen generation system according to Embodiment 1 of the present invention. Enlarged view of part A in FIG.

A first invention is an electrolyte membrane-electrode assembly including an electrolyte membrane and an anode arranged on one surface with the electrolyte membrane sandwiched therebetween and a cathode arranged on the other surface, and both an anode and a cathode. An electricity generator that includes an anode-side separator and a cathode-side separator that are disposed outside, supplies hydrogen-containing gas to the anode, and causes a current in a predetermined direction to flow between the anode and the cathode to generate hydrogen at the cathode. A chemical device, a gas supply means for supplying a hydrogen-containing gas, a power supply for passing an electric current between the anode and the cathode, and a controller are provided, and the anode-side separator is formed on the surface that contacts the anode. And a cathode-side separator that discharges hydrogen from the cathode, and a cathode-side gas flow channel in which hydrogen generated in the cathode flows in the cathode-side separator, and a cathode-side gas flow channel in which the hydrogen-containing gas flows. The hydrogen generating system is characterized in that the controller has a cathode-side outlet for producing hydrogen in the cathode in a state where water is stored in the cathode-side gas flow path of the cathode-side separator.

As a result, the hydrogen generation system supplies the hydrogen-containing gas to the anode while flowing water in the cathode-side gas flow path of the electrochemical device and causes a current in a predetermined direction to flow between the anode and the cathode to cause the cathode to flow. The hydrogen generated in step (3) quickly becomes bubbles in water, making it difficult to contact with the electrolyte membrane. As a result, hydrogen can be prevented from permeating from the cathode side to the anode side, and a reduction in hydrogen purification efficiency can be suppressed.

A second invention is an electrolyte membrane-electrode assembly including an electrolyte membrane and an anode arranged on one surface with the electrolyte membrane sandwiched therebetween and a cathode arranged on the other surface, and both an anode and a cathode. An electricity generator that includes an anode-side separator and a cathode-side separator that are disposed outside, supplies hydrogen-containing gas to the anode, and causes a current in a predetermined direction to flow between the anode and the cathode to generate hydrogen at the cathode. A chemical device, a gas supply means for supplying a hydrogen-containing gas, and a power supply for supplying an electric current between the anode and the cathode, and the anode-side separator is a hydrogen-containing gas formed on a surface in contact with the anode. The cathode side separator has a cathode side gas flow path through which hydrogen generated in the cathode flows, and a cathode side for discharging hydrogen from the cathode. An operating method of a hydrogen generation system having an outlet, characterized in that hydrogen is generated at the cathode in a state where water is stored in the cathode gas flow path of the cathode separator.

As a result, the hydrogen generation system can supply hydrogen-containing gas to the anode and supply a current in a predetermined direction between the anode and the cathode while water is stored in the cathode-side gas flow path of the electrochemical device. Hydrogen is produced at the cathode.

The hydrogen generated at the cathode quickly becomes bubbles in water, making it difficult to contact the electrolyte membrane. As a result, hydrogen can be suppressed from permeating from the cathode side to the anode side, and operation can be performed to suppress a decrease in hydrogen purification efficiency.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to this embodiment.

(Embodiment 1)
1 is a schematic configuration diagram of a hydrogen generation system according to Embodiment 1 of the present invention, and FIG. 2 is an enlarged view of part A of FIG.

As shown in FIG. 1, the hydrogen generation system 100 is provided with an electrochemical device 1, a gas supply unit 30, a power supply 40, and a controller 60.

In the electrochemical device 1, an electrolyte membrane-electrode assembly 9 in which an anode 7 is provided on one main surface of an electrolyte membrane 6 and a cathode 8 is provided on the other main surface of the electrolyte membrane 6, a pair of anode side separators 11 is provided. It is configured to be sandwiched by the cathode side separator 16.

Here, as the electrolyte membrane 6, a perfluorocarbon sulfonic acid-based polymer electrolyte membrane having a sulfonic acid group is used. For the anode 7 and the cathode 8, carbon particles carrying platinum are applied and formed on a carbon felt. The anode-side separator 11 and the cathode-side separator 16 are made of compressed carbon, which is a conductive member having no gas permeability.

The anode-side separator 11 has an anode-side inlet 13 for supplying a hydrogen-containing gas to the anode 7, and an anode-side gas flow path formed in a groove shape on a surface in contact with the anode 7 and having one end communicating with the anode-side inlet 13. 15 and an anode-side outlet 14 that communicates with the other end of the anode-side gas flow path 15 and discharges the hydrogen-containing gas.

On the other hand, the cathode-side separator 16 has a cathode-side gas flow path 17 formed on the surface in contact with the cathode 8 and through which hydrogen generated in the cathode 8 flows. It is stored so as to fill the range in which it comes into contact with 8.

Further, the cathode-side separator 16 has a cathode-side outlet 18 above the cathode-side gas flow channel 17 in the vertical direction to discharge hydrogen generated in the cathode 8 from the cathode-side gas flow channel 17.

The gas supply means 30 for supplying the humidified hydrogen-containing gas to the anode side inlet 13 of the electrochemical device 1 is composed of a pump capable of supplying the hydrogen-containing gas containing the humidified carbon dioxide and hydrogen.

The electrochemical device 1 is provided with a power source 40 for flowing a current in a predetermined direction (current flowing from the anode 7 to the cathode 8 through the electrolyte membrane 6) between the anode 7 and the cathode 8.

As the power supply 40, a DC power supply whose positive terminal is electrically connected to the anode 7 and whose negative terminal is electrically connected to the cathode 8 is used. Further, the gas supply means 30 and the power source 40 are connected to the controller 60, respectively.

Although not shown, the hydrogen discharged from the cathode side outlet 18 of the electrochemical device 1 is sent to a compression unit that compresses hydrogen via a dehumidification and purification unit.

Further, FIG. 2 shows a state in which hydrogen is generated when a current in a predetermined direction is applied between the anode 7 and the cathode 8 of the electrochemical device 1.

At the anode 7, the hydrogen in the hydrogen-containing gas dissociates into protons (H ⁺ ) and electrons to cause an oxidation reaction, the protons (H ⁺ ) move to the electrolyte membrane 6, and the inside of the electrolyte membrane 6 moves to the cathode 8 side. Further, in the cathode 8, a reduction reaction occurs in which hydrogen is generated from protons (H ⁺ ) that have moved from the anode 7 through the electrolyte membrane 6 to the cathode 8 and electrons that have moved from the anode 7 through the power supply 40 to the cathode 8. ..

At this time, water is stored in the cathode-side gas flow passage 17 in the range where the hydrogen is generated and comes into contact with the cathode 8. The generated hydrogen quickly becomes bubbles and leaves the cathode 8, and the inside of the cathode-side gas flow passage 17 is closed. Be thrown into the water.

The operation and action of the hydrogen generation system 100 configured as above in the first embodiment will be described with reference to FIGS. 1 and 2.

First, water is stored in advance in the cathode-side gas flow path 17 in a range in which the hydrogen of the electrochemical device 1 contacts the cathode 8 so that the range of the cathode 8 is watertight.

Next, from the gas supply means 30, the gas temperature is 85° C., the relative humidity is 80%, the dew point is 79.4° C., the carbon dioxide content is 12%, the hydrogen content is 46%, A hydrogen-containing gas having a water vapor content ratio of 42% is supplied to the anode 7 via the anode-side inlet 13 and the anode-side gas flow path 15 of the electrochemical device 1.

Although not shown, the electrochemical device 1 is adjusted by a temperature controller so that the temperature becomes 85° C., and a current of 40 A from a power supply 40 is passed from the anode 7 of the electrochemical device 1 to the cathode 8 through the electrolyte membrane 6. ..

Here, in the water stored in the cathode-side gas flow path 17, hydrogen is generated from the hydrogen-containing gas at the cathode 8 and quickly becomes hydrogen bubbles. The hydrogen bubbles generated in the water move in the cathode side gas flow path 17 and are discharged from the cathode side outlet 18.

The hydrogen-containing gas that has not been used in the oxidation reaction at the anode 7 is discharged from the anode-side outlet 14 and reused. Further, since hydrogen discharged from the cathode side outlet 18 is boosted to 40 kPa, the inside of the cathode side gas passage 17 is boosted to 40 kPa.

By the way, the hydrogen purification efficiency of the hydrogen generation system 100 is represented by the ratio of the energy of hydrogen obtained from the hydrogen generation system 100 to the energy supplied to the power source 40 of the electrochemical device 1.

The hydrogen energy obtained here is the energy of hydrogen obtained from the cathode side outlet 18 of the electrochemical device 1. The electric energy W(W) per unit time applied to the power source of the electrochemical device can be expressed by the following (Equation 1) from the current value I(A) and the voltage V(V).

また、電気化学デバイス１のカソード側出口１８から得られる水素エネルギーＸ（Ｗ）は、電流値Ｉ（Ａ）によって決まる水素ガス流量をＱ（ＮＬ／ｓ）、水素の高位発熱量を２８５８００（Ｊ／ｍｏｌ）とすると、下記（数２）で表すことができる。

Further, the hydrogen energy X(W) obtained from the cathode side outlet 18 of the electrochemical device 1 has a hydrogen gas flow rate Q(NL/s) determined by the current value I(A) and a higher heating value of hydrogen of 285800(J). /Mol), it can be expressed by the following (Equation 2).

また、水素生成システム１００の水素純化効率Ｙは、（数１）で求めた電気エネルギーＷ（Ｗ）と（数２）で求めた水素エネルギーＸ（Ｗ）から、下記の（数３）で表すことができる。

Further, the hydrogen purification efficiency Y of the hydrogen generation system 100 is expressed by the following (Equation 3) from the electric energy W(W) obtained by (Equation 1) and the hydrogen energy X(W) obtained by (Equation 2). be able to.

本実施の形態では、８５℃に設定した電気化学デバイス１には、電流Ｉ＝９０（Ａ）を流しており、カソード側出口１８から得られる水素ガス流量は、０．００９４５（ＮＬ／ｓ）となり、電圧は、０．０３（Ｖ）となる。

In the present embodiment, a current I=90 (A) is passed through the electrochemical device 1 set at 85° C., and the hydrogen gas flow rate obtained from the cathode side outlet 18 is 0.00945 (NL/s). And the voltage becomes 0.03 (V).

Therefore, the hydrogen purification efficiency of the hydrogen generation system 100 is 44.7 according to (Equation 3).

Here, when a current I=90 (A) is passed through the electrochemical device 1 set at 85° C. in a state where water is not stored in the cathode side gas flow path 17 of the electrochemical device 1, the cathode 8 The hydrogen generated in 1 is in contact with the cathode 8 in a gaseous state.

In this state, the pressure on the cathode side is increased to 40 MPa. Due to the partial pressure difference between the hydrogen on the anode side and the hydrogen on the cathode side, hydrogen permeates back from the cathode side to the anode side, and the generated hydrogen returns to the anode side. The efficiency is 44.0.

From this, in the present embodiment, the hydrogen purification efficiency is improved by 0.7 as compared with the case where water is not stored on the cathode side.

As described above, the electrochemical device 1 of the hydrogen generation system 100 according to the present embodiment has a structure in which the electrolyte membrane-electrode assembly 9 is sandwiched between the pair of anode-side separators 11 and cathode-side separators 16.

The anode-side separator 11 has an anode-side gas flow path 15 formed on the surface in contact with the anode 7, through which the hydrogen-containing gas flows. Further, the cathode side separator 16 includes a cathode side gas passage 17 formed on a surface in contact with the cathode 8 through which hydrogen generated in the cathode 8 flows, and a cathode side outlet 18 for discharging hydrogen from the cathode 8. have.

The hydrogen generation system 100 supplies the hydrogen-containing gas to the anode 7 in a state where water is stored in the cathode-side gas flow path 17 of the cathode-side separator 16 of the electrochemical device 1, and between the anode 7 and the cathode 8. Hydrogen is generated at the cathode 8 by flowing a current in a predetermined direction.

As a result, the hydrogen generated in the cathode 8 quickly becomes bubbles in the water, making it difficult to contact the electrolyte membrane 6. As a result, hydrogen can be prevented from permeating from the cathode side to the anode side, and a reduction in hydrogen purification efficiency can be suppressed.

Further, since water is stored in the cathode side gas flow path 17, the water content of the electrolyte membrane 6 of the electrochemical device 1 can be increased, and a decrease in the proton conductivity of the electrolyte membrane 6 can be suppressed. Thereby, the resistance of the electrolyte membrane 6 is suppressed from increasing, and the hydrogen generation system 100 capable of further suppressing the reduction of the hydrogen purification efficiency can be provided.

In the present embodiment, the composition of the hydrogen-containing gas is carbon dioxide and hydrogen, but it is not limited to this as long as it contains hydrogen.

In this embodiment, water is stored in advance in the cathode-side gas flow path 17 of the electrochemical device 1, but a water supply valve may be provided at the cathode-side outlet 18 to enter it. Further, the stored water may be circulated, as long as the surface contacting the cathode 8 is watertight. Further, the stored water can be discharged by providing a drain outlet on the cathode side separator 16.

As described above, in the hydrogen generation system according to the present invention, it is possible to suppress reverse permeation of hydrogen from the cathode side to the anode side, so that it is possible to suppress a decrease in hydrogen purification efficiency, and further increase the water content of the electrolyte membrane. Can be made. Further, since it is also possible to suppress the decrease in the proton conductivity of the electrolyte membrane, it is possible to suppress the increase in the resistance of the electrolyte membrane of the electrochemical device, and to use it in applications such as a hydrogen filling device that can further suppress the decrease in hydrogen purification efficiency. Can also be adapted.

DESCRIPTION OF SYMBOLS 1 Electrochemical device 6 Electrolyte membrane 7 Anode 8 Cathode 9 Electrolyte membrane-electrode assembly 11 Anode side separator 13 Anode side inlet 14 Anode side outlet 15 Anode side gas flow channel 16 Cathode side separator 17 Cathode side gas flow channel 18 Cathode side outlet 30 gas supply means 40 power supply 60 controller 100 hydrogen generation system

Claims (2)

An electrolyte membrane-electrode assembly composed of an electrolyte membrane and an anode arranged on one surface with the electrolyte membrane sandwiched therebetween and a cathode arranged on the other surface, and arranged on both outer sides of the anode and the cathode. Is provided with an anode-side separator and a cathode-side separator, and hydrogen is generated in the cathode by supplying a hydrogen-containing gas to the anode and passing a current in a predetermined direction between the anode and the cathode. An electrochemical device,
Gas supply means for supplying the hydrogen-containing gas,
A power supply for flowing the current between the anode and the cathode,
And a controller,
The anode-side separator has an anode-side gas flow path in which the hydrogen-containing gas is formed, which is formed on a surface in contact with the anode,
The cathode-side separator has a cathode-side gas flow path formed on the surface in contact with the cathode, through which the hydrogen generated in the cathode flows, and a cathode-side outlet for discharging the hydrogen from the cathode. Then
The hydrogen generation system, wherein the controller causes the cathode to generate hydrogen in a state where water is stored in the cathode side gas flow path of the cathode side separator. An electrolyte membrane-electrode assembly composed of an electrolyte membrane and an anode arranged on one surface with the electrolyte membrane sandwiched therebetween and a cathode arranged on the other surface, and arranged on both outer sides of the anode and the cathode. Is provided with an anode-side separator and a cathode-side separator, and hydrogen is generated in the cathode by supplying a hydrogen-containing gas to the anode and passing a current in a predetermined direction between the anode and the cathode. An electrochemical device,
Gas supply means for supplying the hydrogen-containing gas,
A power supply for flowing the current between the anode and the cathode,
The anode-side separator has an anode-side gas flow path in which the hydrogen-containing gas is formed, which is formed on a surface in contact with the anode,
The cathode-side separator has a cathode-side gas flow path formed on the surface in contact with the cathode, through which the hydrogen generated in the cathode flows, and a cathode-side outlet for discharging the hydrogen from the cathode. A method of operating a hydrogen generation system,
A method of operating a hydrogen generation system, wherein the hydrogen is generated in the cathode in a state where water is stored in the cathode side gas passage of the cathode side separator.

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