JP2007173060A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system having an activated carbon regenerator applicable to a smaller fuel cell system. <P>SOLUTION: This fuel cell system is provided with a fuel cell 14 generating power by supply of hydrogen and air, a hydrogen supply system supplying hydrogen to the fuel cell 14, and an air supply system supplying air to the fuel cell 14. In the air supply system provided with a compressor 3 and a catalyst (a combustor and a reductor) 9, a circulation passage including a chemical filter 2, a compressor 3, and the catalyst 9 is construed. Harmful gas adsorbed by the chemical filter 2 is desorbed by combustion heat of hydrogen fed to the circulation passage from the hydrogen supply system, and the desorbed gas is reduced. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell system, and more particularly, to a fuel cell system including an activated carbon regeneration device that is smaller and adaptable to a fuel cell system.

  The fuel cell system supplies hydrogen as a fuel gas to the fuel electrode of the fuel cell, supplies air as the oxidant gas to the oxidant electrode of the fuel cell, and causes the hydrogen and oxygen in the air to react electrochemically. To obtain generated power. Such a fuel cell system is highly expected to be put into practical use, for example, as a power source for automobiles, and research and development for practical use are being actively carried out.

  As a fuel cell used in a fuel cell system. For example, a solid polymer type fuel cell is known as being suitable for mounting in an automobile. A solid polymer type fuel cell is provided with a solid polymer membrane as an electrolyte membrane between a fuel electrode and an oxidant electrode. In this solid polymer type fuel cell, the solid polymer membrane functions as an ion conductor, a reaction occurs in which hydrogen is separated into hydrogen ions and electrons at the fuel electrode, and oxygen and hydrogen in the air at the oxidant electrode. A reaction for generating water from ions and electrons is performed.

  In such a fuel cell system, in an air supply system that supplies air to the oxidant electrode of the fuel cell, an impurity gas component such as an organic solvent contained in the supply air is adsorbed on a chemical filter made of activated carbon or the like, and the fuel cell Prevents stack deterioration. This chemical filter needs to be regenerated moderately to ensure its function.

  Here, as a conventional activated carbon regeneration apparatus, for example, there is a “low concentration NOx treatment apparatus” disclosed in JP-A-8-318127. This is a NOx treatment device for exhaust gas installed in tunnels, underground highways, etc., and performs the regeneration operation of the activated carbon adsorbent in an oxygen concentration atmosphere without risk of ignition.

In this conventional example, the exhaust gas discharged from the tunnel is sucked by the exhaust gas fan, passed through the gate valve to the activated carbon adsorbent in the low concentration NOx treatment device, and then released into the atmosphere through the gate valve. . The activated carbon adsorbent whose adsorbent has sufficiently adsorbed and removed the low-concentration NOx after long-term use continues to be regenerated. When this activated carbon is regenerated, it is sent into a closed loop consisting of an adsorbent, a circulation fan, a denitration device, and a heater. Start the nitrogen generator, close the gate valve, supply nitrogen to the low-concentration NOx treatment device, and if the oxygen concentration measured by the oximeter is 5% or less, circulate the gas with the circulation fan in the closed loop Then, the heater is started to raise the temperature of the gas in the system and the regeneration of the activated carbon adsorbent is started. The generated NOx is decomposed by the denitration device and used again as the regeneration gas for the adsorbent.
JP-A-8-318127

  However, the technique disclosed in Patent Document 1 described above is applied to a NOx treatment apparatus for exhaust gas installed in tunnels, underground highways, and the like, and is a polymer electrolyte fuel cell that supplies hydrogen directly. This cannot be applied to the system as it is. That is, in a fuel cell system, since high temperature heat is not emitted so as to desorb activated carbon, a separate heating device is necessary, and the system is enlarged.

  The present invention has been made in view of the above-described conventional circumstances, and an object thereof is to provide a fuel cell system including an activated carbon regeneration device that is smaller and adaptable to a fuel cell system.

  In order to solve the above-described object, the present invention provides a fuel cell that generates power by supplying fuel gas and oxidant gas, a fuel gas supply system that supplies fuel gas to the fuel cell, and oxidant gas to the fuel cell. An oxidant gas supply system for supplying a fuel cell system, wherein the oxidant gas supply system has a chemical filter for removing harmful gas components, and combustion heat of the fuel gas supplied from the fuel gas supply system Is applied to the chemical filter to desorb the harmful gas adsorbed by the chemical filter, and the chemical filter is regenerated.

  In the fuel cell system according to the present invention, in the polymer electrolyte fuel cell system that directly supplies hydrogen, the fuel gas necessary for power generation is also used for the regeneration of the chemical filter, so that the chemical filter is not enlarged. Can be regenerated and the life of the chemical filter can be extended.

  Hereinafter, embodiments of the fuel cell system of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a configuration diagram of a fuel cell system according to an embodiment of the present invention. The fuel cell system of this embodiment is used as a driving power source of a fuel cell vehicle, for example, and includes a fuel cell 14 that generates power by supplying hydrogen and air as shown in FIG.

  The hydrogen supply system (fuel gas supply system) includes a hydrogen tank 11, a hydrogen supply valve 12, a switching valve 13, and a power generation channel (hydrogen supply channel) 20. As shown in the figure, a hydrogen circulation path is provided, and hydrogen that has not been consumed in the fuel cell 14 is circulated to the hydrogen supply system by a circulation means (not shown) of an ejector or a circulation pump.

  As an air supply system (oxidant gas supply system), an intake valve 1, a chemical filter 2, a compressor (compressor) 3, a dust filter 4, a pressure sensor 5, a temperature sensor 6, a NOx sensor 7, a switching valve 8, and a catalyst (Combustor and reduction device) 9, switching valve (exhaust valve) 10, circulation passages 15 and 16, exhaust passage 17, hydrogen supply passage 18, power generation passage (air supply passage) 19 and exhaust passage 21. . Here, air is supplied to the fuel cell 14 by the intake valve 1, the chemical filter 2, the compressor 3, the dust filter 4, the pressure sensor 5, the temperature sensor 6, the NOx sensor 7, the switching valve 8, the power generation passage 19 and the exhaust passage 21. A supply system is configured, and a circulation path including a chemical filter 2, a compressor 3, a dust filter 4, a pressure sensor 5, a temperature sensor 6, a NOx sensor 7, a switching valve 8, a catalyst 9, a switching valve 10, and circulation paths 15 and 16. The intake valve 1, the hydrogen supply path 18 and the exhaust path 17 constitute a system for regenerating the chemical filter 2 and the dust filter 4.

  Here, the chemical filter 2 adsorbs and removes gas components harmful to the fuel cell such as carbon monoxide and sulfur, and the dust filter 4 removes dust components such as dust. The NOx sensor 7 detects the concentration of nitrogen oxides. Furthermore, the catalyst 9 has both a combustion catalyst and a NOx reduction catalyst, and functions as a combustor and a reduction device.

  Note that the fuel cell system of this embodiment includes a controller (not shown), and the controller is based on the hydrogen supply system and the air supply system based on various sensors and detection signals from various other sensors. Control each component of the supply system.

  The fuel cell 14 includes a fuel cell (anode) supplied with hydrogen as a fuel gas and an oxidant electrode (cathode) supplied with air as an oxidant gas, with an electrolyte interposed therebetween, thereby forming a power generation cell. In addition, it has a stack structure in which a plurality of power generation cells are stacked in multiple stages, and converts chemical energy into electrical energy by an electrochemical reaction based on hydrogen and oxygen in the air. In each power generation cell of the fuel cell 14, a reaction occurs in which hydrogen supplied to the fuel electrode is separated into hydrogen ions and electrons, the hydrogen ions pass through the electrolyte, and the electrons generate power through an external circuit, Each moves to the oxidizer electrode. At the oxidizer electrode, hydrogen in the supplied air reacts with hydrogen ions and electrons that have moved through the electrolyte to produce water, which is discharged to the outside.

  In order to generate power with the fuel cell 14, it is necessary to supply hydrogen as fuel gas or air as oxidant gas to the fuel electrode (anode) or oxidant electrode (cathode) of each power generation cell. As a mechanism for this, a hydrogen supply system and an air supply system are provided.

  In the hydrogen supply system, hydrogen supplied from the hydrogen tank 11 serving as a hydrogen supply source is depressurized by the hydrogen supply valve 12 and sent to the fuel electrode of the fuel cell 14 through the power generation channel (hydrogen supply channel) 20. The fuel electrode pressure of the fuel cell 14 is detected by a pressure sensor (not shown), and the controller feeds back the detected value of the pressure sensor to control the operation of the pressure control valve (not shown). The anode pressure is maintained at a desired pressure.

  In the air supply system, the air supply to the oxidant electrode of the fuel cell 14 is a system for supplying air to the fuel cell 14 (that is, the intake valve 1, the chemical filter 2, the compressor 3, the dust filter 4, the pressure). Sensor 5, temperature sensor 6, NOx sensor 7, switching valve 8, power generation channel 19 and exhaust channel 21). The air pressure of the oxidant electrode of the fuel cell 14 is controlled by driving the pressure control valve (not shown) by feeding back the air pressure detected by the pressure sensor 5 by the controller.

  Furthermore, the controller is configured as a microcomputer having, for example, a CPU, ROM, RAM, peripheral interface, and the like, and based on detection signals from the fuel cell 14, various sensors of the hydrogen supply system and air supply system, and other various instruments. Then, each component of the hydrogen supply system and the air supply system is controlled (by driving various actuators, etc.), and operation control (power generation control, filter regeneration control, etc.) of the fuel cell system is performed.

  Next, the filter regeneration function that is a feature of the present invention will be described in detail.

  First, when the fuel cell 14 generates power, if the NOx sensor 7 detects the concentration of NOx (nitrogen oxide) greater than or equal to a predetermined value, it is assumed that the gas adsorption performance of the chemical filter 2 has reached its limit, and the next startup is performed. The filter regeneration mode is set before power generation at the time or after power generation at the time of stop.

  In the filter regeneration mode, the circulation path is configured by switching the hydrogen supply path of the hydrogen supply system and the air supply path of the air supply system. That is, a circulation path is constituted by the chemical filter 2, the compressor 3, the dust filter 4, the pressure sensor 5, the temperature sensor 6, the NOx sensor 7, the switching valve 8, the catalyst 9, the switching valve 10, and the circulation passages 15 and 16. Hydrogen is supplied to the catalyst 9 via the hydrogen supply path 18 by the control of the valve 13, and air is supplied to the catalyst 9 via the circulation flow path 15 by the control of the switching valve 8. To do.

  In the following description, a case will be described in which the filter regeneration mode is set before power generation at start-up and the chemical filter 2 and the dust filter 4 are regenerated.

  First, before starting power generation at the time of start-up, the controller closes the intake valve 1, switches the switching valve 8 so that air flows into the circulation channel 15, and causes gas from the catalyst 9 to flow into the circulation channel 16. By switching the switching valve 10 to, a circulation path is made. At this time, air is circulated through the circulation path by operating the compressor 3. Note that the compressor 3 in the filter regeneration mode simply operates as a blower in the circulation path.

  Next, the controller calculates the oxygen amount in the circulation path based on the outputs of the pressure sensor 5 and the temperature sensor 6 and the volume in the circulation path, and calculates the hydrogen amount that reacts with the oxygen amount without excess or deficiency. Then, the switching valve 13 is switched so that hydrogen flows into the hydrogen supply path 18, and the hydrogen supply valve 12 is opened to supply hydrogen for the calculated hydrogen amount.

  At this time, the amount of hydrogen to be supplied is adjusted so that the temperature in the circulation path and the oxygen concentration are optimal for burning the dust in the dust filter 4. That is, by creating a hydrogen lean state in the circulation path, oxygen necessary for the combustion of dust can be secured, a reliable dust combustion treatment can be performed, and regeneration of the dust filter 4 can be promoted.

  Hydrogen supplied via the switching valve 13 and the hydrogen supply path 18 is combusted by the catalyst 9 which serves both as combustion and NOx reduction. Gases (NOx, SOx, H2S, etc.) harmful to the fuel cell adsorbed by the chemical filter 2 are desorbed by the heat generated at this time, and dust trapped by the dust filter 4 is also burned. The chemical filter 2 and the dust filter 4 are regenerated while flowing through the circulation circuit several times, and then hydrogen is supplied to react with oxygen in the circulation circuit without excess or deficiency. Thereby, insufficient supply or excessive supply of hydrogen can be prevented. Thereafter, the oxygen concentration in the circulation path becomes lean, and an environment suitable for reduction of NOx desorbed from the chemical filter 2 is obtained.

  Here, hydrogen is supplied to the circulation path little by little while detecting the output of the NOx sensor 7. When the concentration becomes lower than a certain concentration, the supply of hydrogen is stopped, and the switching valve 10 is switched so that the gas flows into the exhaust passage 17. Next, while detecting the output of the pressure sensor 5, the intake valve 1 is opened when the pressure in the circulation path decreases to near atmospheric pressure so that the hot gas in the circulation path is not exhausted from the intake port.

  In addition, if the switching valve 8 is switched to flow to the power generation flow path 19 in this state, the high temperature residual gas in the circulation path may flow into the fuel cell 14, so that the intake valve is detected while detecting the output of the temperature sensor 6. 1 is opened and air is allowed to flow into the exhaust passage 17 so that the gas flows into the circulation passage 16 after the temperature has dropped to a temperature that does not adversely affect the fuel cell 14. After switching the switching valve 10, the switching valve 8 is switched so that air flows into the power generation flow path 19, and air is supplied to the fuel cell 14 via the intake valve 1, the chemical filter 2, the compressor 3, and the dust filter 4. The system is configured, and the control proceeds to the start control of the fuel cell 14.

  As described above, in the fuel cell system of the present embodiment, the fuel cell 14 that generates power by supplying hydrogen (fuel gas) and air (oxidant gas), and the hydrogen supply system that supplies hydrogen to the fuel cell 14 ( In a fuel cell system comprising a fuel gas supply system) and an air supply system (oxidant gas supply system) for supplying air to the fuel cell 14, the combustion heat of hydrogen supplied from the hydrogen supply system is converted into oxidant gas. The chemical filter 2 that removes harmful gas components from the supply system is applied to desorb the harmful gas adsorbed by the chemical filter 2 to regenerate the chemical filter 2. As a result, in the polymer electrolyte fuel cell system that supplies hydrogen directly, the hydrogen necessary for power generation can also be used for the regeneration of the filter, and the chemical filter 2 can be regenerated without enlarging the system. The life of the filter 2 can be extended.

  In this embodiment, the air supply system is provided with a compressor (compressor) 3 and a catalyst (combustor and reduction device) 9, and a circulation path including the chemical filter 2, the compressor 3 and the catalyst 9 is configured, and the circulation The harmful heat adsorbed by the chemical filter 2 is desorbed by the combustion heat of hydrogen supplied from the hydrogen supply system to the passage, and the desorbed gas is reduced. As a result, the heating and oxygen concentration reduction steps required for removing the harmful gas desorbed from the chemical filter 2 can be achieved in one step of burning hydrogen, and the system can be miniaturized.

  Further, in this embodiment, when the air supply system includes the dust filter 4 for removing dust components, the dust filter 4 is included in the circulation path, and the combustion of hydrogen supplied from the hydrogen supply system to the circulation path is performed. The dust captured by the dust filter 4 was burned by heat, and the dust filter 4 was regenerated. Thereby, the chemical filter 2 and the dust filter 4 can be regenerated at once, and the life of the dust filter 4 can be extended.

  In this embodiment, before the power generation at the time of start-up (or after the end of power generation at the time of stoppage), the hydrogen supply path of the hydrogen supply system and the air supply path of the air supply system are switched to form a circulation path, and the chemical filter 2 The dust filter 4 was regenerated. Thereby, by burning hydrogen in the closed flow path, the oxygen concentration is lowered, and the desorbed harmful gas undergoes a reduction reaction, so that the harmful gas can be treated without being released to the atmosphere.

  In the present embodiment, the air supply system (circulation path) is provided with a pressure sensor 5 for detecting the air pressure and a temperature sensor 6 for detecting the air temperature. After the circulation path is configured, the circulation path The amount of hydrogen that reacts with the amount of oxygen without excess or deficiency is determined from the amount of oxygen determined based on the volume of the gas and the detected pressure and temperature, and fuel hydrogen corresponding to the amount of hydrogen is supplied into the circulation path from the hydrogen supply system. It was. This prevents the reduction of harmful gases due to insufficient hydrogen supply and the increase in exhaust hydrogen concentration due to excessive supply of hydrogen, enabling reliable reduction of harmful gases and reduction of exhaust hydrogen concentration. It becomes.

  In the present embodiment, the air supply system (circulation path) is provided with a NOx sensor 7 for detecting the concentration of nitrogen oxides, and the fuel from the hydrogen supply system to the circulation path is based on the detected value of the NOx sensor 7. It was decided to determine when to stop supplying gas. Thereby, the reduction degree of NOx desorbed from the chemical filter 2 and the reduction completion timing can be detected, and the optimum timing for stopping the hydrogen supply can be found.

  In this embodiment, the oxidant gas supply system (circulation path) is provided with a switching valve (exhaust valve) 10 and an intake valve 1, and after the supply of hydrogen from the hydrogen supply system is stopped in the circulation path, The switching valve 10 is switched so as to flow into the exhaust flow path 17 (the exhaust valve is opened), and the intake valve 1 is opened after the air pressure in the circulation path is reduced. Thereby, the hot gas in the circulation path is prevented from flowing back to the intake port, and safe exhaust is possible.

  Further, in this embodiment, after opening the intake valve 1, it is determined when to switch the switching valve 10 (close the exhaust valve) so as to flow into the circulation flow path 16 based on the temperature detected by the temperature sensor 6 of the circulation path. Then, after switching the switching valve 10 (closing the exhaust valve), a system for supplying air to the fuel cell 14 via the chemical filter 2, the compressor 3 and the dust filter 4 is configured. Thereby, it is possible to prevent the high-temperature gas remaining in the circulation path from flowing into the fuel cell 14, and to prevent failure and performance deterioration of the fuel cell 14.

  Furthermore, in this embodiment, the regeneration of the dust filter 4 is promoted by creating a lean fuel gas state in the circulation path. Thereby, oxygen required for the combustion of dust is ensured, and a reliable dust combustion process becomes possible.

  In the specific description of the present embodiment, the filter regeneration mode before power generation at the time of start-up has been described. However, when the NOx sensor 7 detects the concentration of NOx equal to or greater than a predetermined value during power generation of the fuel cell 14. The filter regeneration may be performed by setting the filter regeneration mode at the stop after the end of the power generation.

  Moreover, in the structure of FIG. 1, although it was set as the structure provided with the chemical filter 2 and the dust filter 4 one each, it is good also as a structure provided with multiple each. In this case, one chemical filter and dust filter are used in a system for supplying air to the fuel cell 14 to generate power by the fuel cell 14, while another chemical filter and dust filter are incorporated in the circulation path. The exhaust gas of the fuel cell 14 is supplied to the chemical filter and the dust filter to regenerate the fuel cell 14. In other words, since it is possible to realize a configuration having an intake passage used for power generation of the fuel cell 14 and a circulation path used for regeneration of the filter, the filter can be regenerated during power generation.

1 is a configuration diagram of a fuel cell system according to an embodiment of the present invention.

Explanation of symbols

1 Intake valve 2 Chemical filter 3 Compressor
4 Dust filter 5 Pressure sensor 6 Temperature sensor 7 NOx sensor 8 Switching valve 9 Catalyst (combustor and reduction device)
10 Switching valve (exhaust valve)
DESCRIPTION OF SYMBOLS 11 Hydrogen tank 12 Hydrogen supply valve 13 Switching valve 14 Fuel cell 15, 16 Circulation flow path 17 Exhaust flow path 18 Hydrogen supply path 19, 20 Power generation flow path 21 Exhaust flow path

Claims (10)

A fuel cell that generates power by supplying fuel gas and oxidant gas;
A fuel gas supply system for supplying fuel gas to the fuel cell;
An oxidant gas supply system for supplying an oxidant gas to the fuel cell;
In a fuel cell system having
The oxidant gas supply system has a chemical filter that removes harmful gas components,
A fuel cell system for regenerating the chemical filter by applying combustion heat of the fuel gas supplied from the fuel gas supply system to the chemical filter to desorb the harmful gas adsorbed by the chemical filter. The oxidant gas supply system includes a compressor, a combustor, and a reduction device,
The chemical filter, the compressor, the combustor, and the recirculation path including the reduction device are configured, and the chemical filter adsorbs the combustion heat of the fuel gas supplied from the fuel gas supply system to the circulation path. The fuel cell system according to claim 1, wherein the gas is desorbed and the desorbed gas is reduced. The oxidant gas supply system has a dust filter for removing dust components,
The circulation path includes the dust filter, and the dust captured by the dust filter is burned by the combustion heat of the fuel gas supplied from the fuel gas supply system to the circulation path to regenerate the dust filter. The fuel cell system according to claim 2, wherein:   Before the power generation at the time of starting or after the end of the power generation at the time of stopping, the fuel gas flow path of the fuel gas supply system and the oxidant gas flow path of the oxidant gas supply system are switched to configure the circulation path, and the chemical filter 4. The fuel cell system according to claim 2, wherein the dust filter is regenerated. The oxidant gas supply system is connected to the circulation path.
A pressure sensor for detecting the pressure of the oxidant gas;
A temperature sensor for detecting the temperature of the oxidant gas,
After configuring the circulation path, from the amount of the oxidant gas obtained based on the volume of the circulation path and the detected pressure and temperature, the amount of fuel gas that reacts with the amount of the oxidant gas without excess or deficiency is obtained, and the fuel gas The fuel cell system according to any one of claims 2 to 4, wherein the supply system supplies fuel gas corresponding to the amount of the fuel gas into the circulation path. The oxidant gas supply system has a NOx sensor for detecting the concentration of nitrogen oxides in the circulation path,
The fuel according to any one of claims 2 to 5, wherein a stop timing of fuel gas supply from the fuel gas supply system to the circulation path is determined based on a detection value of the NOx sensor. Battery system. The oxidant gas supply system has an exhaust valve and an intake valve in the circulation path,
3. The exhaust valve is opened after the fuel gas supply from the fuel gas supply system is stopped in the circulation path, and the intake valve is opened after the oxidant gas pressure in the circulation path is reduced. The fuel cell system according to any one of claims 6 to 6.   After opening the intake valve, it is determined when to close the exhaust valve based on the temperature detected by the temperature sensor of the circulation path, and after closing the exhaust valve, the chemical filter, the compressor and / or the dust 8. The fuel cell system according to claim 7, wherein a system for supplying an oxidant gas to the fuel cell via a filter is configured.   The fuel cell system according to any one of claims 3 to 8, wherein regeneration of the dust filter is promoted by creating a lean fuel gas state in the circulation path.   When power generation is performed by the fuel cell using a plurality of the chemical filter or the dust filter and using the one chemical filter or the dust filter in a system for supplying an oxidant gas to the fuel cell, the other chemical filter The filter or the dust filter is incorporated in the circulation path, and exhaust gas of the fuel cell is supplied to the circulation path to regenerate the chemical filter or the dust filter. The fuel cell system according to any one of claims 5 to 9.

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