JP2014214050A - Hydrogen generator and fuel cell system - Google Patents

Abstract

An object of the present invention is to provide a hydrogen generator and a fuel cell system capable of eliminating an oxygen deficiency state of off-combustion gas in a combustor and accurately detecting defective combustion of a flame with a gas sensor. An off-combustion gas path 12 is disposed upstream of a gas sensor 17 and includes a buffer tank 14 for storing off-combustion gas. The combustion of combustor 1b generates off-combustion gas that generates a large amount of CO. When the combustion state deteriorates, the off-combustion gas can be prevented from becoming deficient, and the detection failure of the gas sensor 17 can be prevented. [Selection] Figure 1

Description

  The present invention relates to a hydrogen generator of a fuel cell system that provides a configuration for preventing a detection failure of a gas sensor.

  In a fuel cell system, a source gas such as city gas is reformed by a catalytic reaction into a hydrogen-rich fuel gas in a hydrogen generator. A combustor is provided for supplying the hydrogen generator with heat energy necessary to heat the hydrogen generator to a temperature at which a reforming reaction is possible. The combustor burns a raw material gas or off-fuel gas (a gas containing a combustible component after being reacted from the fuel cell) and gives heat to the hydrogen generator. At this time, the combustor takes in fresh air from the outside of the fuel cell system as combustion air to ensure a stable combustion state. Off-combustion gas generated by combustion in the combustor is discharged to the outside of the fuel cell system from an exhaust port provided in the casing as off-combustion gas.

  This off-burning gas usually contains almost no carbon monoxide (hereinafter also referred to as “CO”). However, when the amount of oxygen supplied to the combustor is insufficient, the off-combustion gas contains CO. For example, when the entire fuel cell system is covered and sealed with a cover member, fresh air is not taken into the combustor. Therefore, incomplete combustion occurs in the combustor, and CO is gradually included in the off-combustion gas, so that the CO concentration inside the cover member is further increased. Due to this high concentration of CO, problems such as a decrease in the amount of power generation in the fuel cell system, system shutdown, or system failure occur.

  For this reason, in order to detect the quality of the combustion state in the combustor, a CO sensor that detects the concentration of carbon monoxide generated at the time of poor combustion may be disposed in the off-combustion gas path (see, for example, Patent Document 1). .

  In Patent Document 1, an air supply pipe that introduces dilution air into the off-combustion gas from the upstream side of the CO sensor is provided, and the air supply pipe is provided with combustion air blowing means, independent introduction air supply means, or the like. By supplying air, when the combustion state of the combustor where a large amount of CO is generated is deteriorated, the off-combustion gas is prevented from becoming in an oxygen deficient state, so that CO concentration detection failure of the CO sensor can be prevented. It is configured.

JP 2006-282425 A

  However, in the conventional configuration, it is necessary to newly provide an air supply pipe for introducing dilution air into the off-combustion gas from the upstream side of the CO sensor in order to prevent oxygen deficiency of the off-combustion gas. There was a problem in the simplification of the configuration. Moreover, since it is necessary to supply air to the air supply pipe from the combustion air blowing means or the independent introduction air supply means, etc., the capacity of the air supply means is increased or newly introduced, and the power for supplying the air Therefore, there are problems in reducing the cost and power saving of the air supply means.

In the present invention, as described above, in the case of preventing the CO concentration detection failure of the CO sensor, it is possible to accurately detect the combustion failure of the combustor using the CO sensor while simplifying the configuration of the hydrogen generator and saving power. It is an object of the present invention to provide a hydrogen generator and a fuel cell system which are well performed.

  In order to solve the above-described conventional problems, a hydrogen generator of the present invention includes a reformer that generates a fuel gas containing hydrogen by a reforming reaction of a source gas, and a reformer that burns the source gas or the fuel gas. A combustor that heats, an off-combustion gas path that discharges off-combustion gas generated in the combustor, and a gas sensor that is disposed in the off-combustion gas path and detects the specific gas by burning the specific gas contained in the off-combustion gas And a buffer tank that is disposed upstream of the gas sensor in the off-combustion gas path and stores off-combustion gas.

  As a result, in the combustion of the combustor of the hydrogen generator, even when the off-combustion gas that generates a large amount of CO deteriorates, the off-combustion gas is prevented from suddenly becoming deficient, and the CO concentration detection failure of the gas sensor Can be prevented.

  According to the hydrogen generator of the present invention, it is possible to prevent an oxygen-deficient state of the off-combustion gas of the combustor, to prevent a CO concentration detection failure of the gas sensor, and to prevent a decrease in detection accuracy.

1 is a block diagram schematically showing a schematic configuration of a hydrogen generator according to Embodiment 1 of the present invention. The block diagram which shows typically schematic structure of the hydrogen generator which concerns on Embodiment 2 of this invention The internal block diagram of the buffer tank which concerns on Embodiment 1 of this invention

  The first invention includes a reformer that generates a fuel gas containing hydrogen by a reforming reaction of a raw material gas, a combustor that burns the raw material gas or the fuel gas and heats the reformer, and an off-state generated in the combustor. An off-combustion gas path for discharging the combustion gas; a gas sensor disposed in the off-combustion gas path for detecting the specific gas by burning the specific gas contained in the off-combustion gas; and an upstream side of the gas sensor in the off-combustion gas path And a buffer tank that stores off-burning gas. With this configuration, the combustion of the combustor of the hydrogen generator prevents the off-combustion gas from rapidly becoming deficient even when the off-combustion gas that generates a large amount of CO deteriorates, and the CO concentration detection of the gas sensor Defects can be prevented.

  According to a second aspect of the invention, in particular, the hydrogen generator of the first aspect of the invention further includes an off-oxidant gas path for discharging off-oxidant gas of the fuel cell, and the off-oxidant gas path is included in the off-combustion gas path. The gas sensor is connected upstream. With this configuration, in the combustion of the combustor of the hydrogen generator, the off-combustion gas is in an oxygen-deficient state while the off-oxidant gas of the fuel cell is being supplied even when the off-combustion gas in which a large amount of CO is generated is deteriorated. It becomes possible to prevent the CO sensor from being detected poorly.

  In a third aspect of the invention, in particular, the hydrogen generator of the second aspect of the invention is configured such that the off-oxidant gas path is connected downstream of the buffer tank in the off-combustion gas path. With this configuration, the gas flowing through the buffer tank can be only off-burning gas, and it is possible to suppress an increase in pressure loss due to an increase in gas flow rate due to the flow of off-oxidant gas through the buffer tank. Become.

According to a fourth aspect of the present invention, in particular, the buffer tank according to any one of the first to third aspects of the present invention is provided with a gas diffusion mechanism that promotes the homogenization of components in a cross section perpendicular to the flow direction of off-combustion gas. A generator. With this configuration, even when the off-combustion gas in which a large amount of CO is generated deteriorates in the combustion of the combustor of the hydrogen generator, the generated off-combustion gas having a low oxygen concentration and the high oxygen concentration stored in the buffer tank are reduced. The off-burning gas having a high oxygen concentration stored in the buffer tank can be effectively used by uniformly mixing the off-burning gas with the cross section perpendicular to the flow direction and supplying the mixed gas to the gas sensor.

  According to a fifth aspect of the present invention, in particular, the buffer tank according to any one of the first to fourth aspects of the present invention is a hydrogen generator provided with a drain port for discharging water contained in the off-combustion gas. With this configuration, even when moisture contained in the off-combustion gas is condensed and generated as condensed water, clogging of the off-combustion gas path due to the condensed water is suppressed, and the CO concentration detection failure of the gas sensor can be prevented stably. It becomes possible.

  In the sixth aspect of the invention, the concentration of CO in the off-combustion gas of the hydrogen generator is increased by mounting the hydrogen generator of any one of the first to fifth aspects of the invention in the fuel cell system. Sometimes, it is possible to eliminate the oxygen deficiency state of the off-burning gas, prevent the detection failure of the gas sensor, and perform the fuel cell system stop process with high accuracy.

  Hereinafter, embodiments of the present invention will be specifically exemplified. In all the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted. Further, in all the drawings, only components necessary for explaining the present invention are extracted and illustrated, and other components are not illustrated. Furthermore, the present invention is not limited to the following embodiment.

(Embodiment 1)
FIG. 1 is a block diagram schematically showing a schematic configuration of a fuel cell system 100 including a hydrogen generator 1 according to the first embodiment.

  As shown in FIG. 1, a fuel cell system 100 includes a hydrogen generator 1, a reformer 1a, a combustor 1b, a raw material supply unit 2, a water supply unit 3, a fuel gas supply path 4a, an off fuel gas path 4b, a fuel Battery 5, blower 6, oxidant gas path 7, exhaust gas heat exchanger 8, exhaust air heat exchanger 9, air supplier 10, air flow meter 11, off-combustion gas path 12, off-oxidant gas path 13, buffer tank 14, a gas sensor 17, an exhaust heat recovery water path 18, and a controller 101.

  The hydrogen generator 1 has a reformer 1a and a combustor 1b for heating the reformer.

  The reformer 1a is configured to generate a fuel gas containing hydrogen by causing a reforming reaction between the raw material gas and water. The fuel gas generated by the reformer 1a is supplied to the anode (not shown) of the fuel cell 5 through the fuel gas supply path 4a. A raw material supply unit 2 and a water supply unit 3 are connected to the reformer 1 a of the hydrogen generator 1. The raw material supply unit 2 is configured to supply a raw material gas, which is a gaseous raw material, to the reformer 1a while adjusting the flow rate. As the raw material supply part 2, for example, a flow rate adjusting valve and a pump may be configured, or a flow rate adjustable pump may be configured.

  The combustor 1b is connected to an off-fuel gas path 4b that allows the fuel cell 5 and the combustor 1b to communicate with each other. The combustor 1b burns off-fuel gas that is fuel gas discharged from the fuel cell 5 via the off-fuel gas path 4b to generate off-combustion gas. In addition, you may directly form the path | route for supplying a raw material separately in the combustor 1b. Here, the raw material means a gas or liquid having at least hydrocarbon as a component, for example, natural gas, coal, petroleum, fossil fuel such as methane hydrate, and city gas.

Here, the off-combustion gas generated by the combustor 1 b of the hydrogen generator 1 is heated to the reformer 1 a and then discharged to the off-combustion gas path 12, and the fuel cell system 100 passes through the off-combustion gas path 12. Discharged outside. The off combustion gas contains oxygen, carbon dioxide, nitrogen, carbon monoxide, and nitrogen oxides.
The water supply unit 3 supplies condensed water stored in a condensed water tank (not shown) to the reformer 1a. The water supply device 3 may be in any form as long as it is configured to supply condensed water while adjusting the flow rate to the reformer 1a. It may be comprised, and may be comprised with the pump which can adjust flow volume. Since the condensed water stored in the condensed water tank contains some impurities, it is purified through a purifier (not shown) provided with an ion exchange resin and supplied to the water supplier 3.

  The fuel cell 5 has an anode and a cathode (not shown). As the fuel cell 5, various fuel cells such as a polymer electrolyte fuel cell, a direct internal reforming solid oxide fuel cell, and an indirect internal reforming solid oxide fuel cell can be used. In the first embodiment, the hydrogen generator 1 and the fuel cell 5 are separately configured. However, the present invention is not limited to this, and the hydrogen generator 1 and the fuel cell 5 are not limited to this. The fuel cell 5 may be integrally formed. In this case, the hydrogen generator 1 and the fuel cell 5 are configured as one unit covered with a common heat insulating material, and the combustor 1b of the hydrogen generator 1 heats not only the reformer 1a but also the fuel cell 5. To do. Moreover, in the direct internal reforming solid oxide fuel cell, the anode of the fuel cell 5 has the function of the reformer 1a, so that the anode of the fuel cell 5 and the reformer 1a of the hydrogen generator 1 are connected. You may be comprised integrally. Furthermore, since the structure of the fuel cell 5 is the same as that of a general fuel cell, its detailed description is omitted.

  The cathode of the fuel cell 5 is supplied with an oxidant gas containing oxygen (air is used in the present embodiment) from the blower 6 through the oxidant gas path 7. Then, the fuel gas supplied to the anode and the oxidant gas supplied to the cathode react to generate water, and electricity and heat are generated. The fuel gas that has not been used in the fuel cell 5 is supplied to the combustor 1b of the hydrogen generator 1 through the off-fuel gas path 4b as off-fuel gas. The oxidant gas that has not been used in the fuel cell 5 is discharged out of the fuel cell system 100 via the off-oxidant gas path 13. The generated electricity is supplied to an external power load (for example, home electrical equipment) by a power regulator (not shown). The generated heat is recovered by cooling water (not shown) flowing through the fuel cell 5.

  The buffer tank 14 is disposed on the off-combustion gas path 12 so that the off-combustion gas discharged from the combustor 1 b is supplied to the buffer tank 14. Further, by disposing the exhaust gas heat exchanger 8 on the upstream side of the buffer tank 14, water vapor contained in the off combustion gas is condensed in the exhaust gas heat exchanger 8, and the condensed off combustion gas is supplied to the buffer tank 14. It becomes possible to do. For this reason, it is possible to suppress clogging of the off-combustion gas path 12 due to condensed water.

  Further, the buffer tank 14 may be configured to include a gas diffusion plate 15 that promotes the homogenization of the components of the cross section perpendicular to the flow direction of the off combustion gas. FIG. 3 illustrates a cross-sectional view illustrating the internal structure of the buffer tank 14. In this example, three gas diffusion plates 15 are provided in the buffer tank 14, but any number of gas diffusion plates 15 can be used as long as the components can be made uniform in a cross section perpendicular to the flow direction of the off combustion gas. It may be configured to be diffused by a synergistic effect of forced convection caused by flowing off combustion gas from the side surface of the buffer tank 14 and natural convection caused by a temperature difference. With this configuration, even when the off-combustion gas in which a large amount of CO is generated deteriorates in the combustion of the combustor 1b of the hydrogen generator 1, the generated off-combustion gas having a low oxygen concentration and the high stored in the buffer tank 14 can be obtained. The off-combustion gas having an oxygen concentration can be uniformly mixed in a cross section perpendicular to the flow direction, and the off-combustion gas having a high oxygen concentration stored in the buffer tank 14 can be used effectively.

  Further, the buffer tank 14 may further include a drain port 16. With this configuration, water vapor contained in the off-combustion gas after flowing through the buffer tank 14 condenses and can also be generated as condensed water, which can be discharged from the drain port 16 and condensed in the off-combustion gas path 12. It becomes possible to suppress clogging with water. Further, the capacity of the buffer tank 14 may be changed in accordance with the reaction rate of the gas sensor 17. With this configuration, it is possible to minimize the capacity of the buffer tank 14 in accordance with the reaction speed of the gas sensor 17 to be used, and to obtain the minimum necessary capacity. Furthermore, the capacity | capacitance of the buffer tank 14 is good also as a structure which changes a capacity | capacitance according to the amount of off combustion gas generated in the combustor 1b. With this configuration, it is possible to minimize the capacity of the buffer tank 14 in accordance with the amount of off-burning gas from the combustor 1b, so that the required capacity is minimized.

  The gas sensor 17 is disposed downstream of the buffer tank 14 in the off-combustion gas path 12, and the off-oxidant gas path 13 is connected to the upstream of the gas sensor 17 in the off-combustion gas path 12. Yes. With this configuration, the gas flowing through the buffer tank 14 can be limited to off-burning gas, and an increase in pressure loss due to an increase in gas flow rate due to the flow of off-oxidant gas through the buffer tank 14 is suppressed. It becomes possible to do.

  The gas sensor 17 takes a part of the off combustion gas from the off combustion gas path 12 and directly measures the component. The gas sensor 17 includes a contact combustion type CO sensor, measures the CO concentration in the off-combustion gas, and sends the signal to the controller 101. The controller 101 evaluates the combustion state by converting the amount of CO generated from the flame in the combustor 1b according to the magnitude of the signal, and when the CO amount exceeds a predetermined threshold value and the combustion state is determined to be defective. The supply of the raw material from the raw material supply unit 2 is stopped, and an instruction to stop the combustor 1b is issued. When the gas sensor 17 is attached to the off-combustion gas path 12, the detection part at the tip thereof is inserted into the off-combustion gas path 12, and the signal and power connection part are exposed to the outside to promote heat dissipation and increase in temperature. Is preventing.

  In the contact combustion type, CO in the off-combustion gas is contact-combusted at the detection portion, and the temperature rise is converted into electric resistance and taken out as a voltage output. As a result, no matter what fuel gas the combustor 1b burns, or even if the flow rate of the fuel gas changes and the temperature of the off-combustion gas increases or decreases, the CO concentration in the high-temperature off-combustion gas is measured. The combustion state can be evaluated.

  The exhaust heat recovery water path 18 is provided so that a part thereof is located outside the fuel cell system 100. The exhaust heat recovery water path 18 is provided with an exhaust gas heat exchanger 8 and an exhaust air heat exchanger 9 in this order. Then, the first heat medium in the exhaust heat recovery water path 18 flows through each heat exchanger while exchanging heat with the other heat medium. As the first heat medium, water or an antifreeze liquid (for example, an ethylene glycol-containing liquid) can be used.

  The exhaust gas heat exchanger 8 is provided so as to contact the exhaust heat recovery water path 18 and the off combustion gas path 12, and the first heat medium and the off combustion gas path 12 flowing through the exhaust heat recovery water path 18. It is configured to exchange heat with the off-combustion gas flowing therethrough. In addition, by exchanging heat with the first heat medium in the exhaust gas heat exchanger 8, the water vapor in the off-combustion gas is condensed and condensed water is generated. The produced condensed water is collected in a condensed water tank (not shown) through an exhaust gas condensed water path (not shown). The off-combustion gas after the condensed water is recovered is discharged out of the fuel cell system 100 via the off-combustion gas path 12.

Further, the exhaust air heat exchanger 9 is provided so as to contact the exhaust heat recovery water path 18 and the off-oxidant gas path 13, and the first heat medium flowing through the exhaust heat recovery water path 18 is off-oxidized. It is configured to exchange heat with the off-oxidant gas flowing through the agent gas path. In addition, by exchanging heat with the first heat medium in the exhaust air heat exchanger 9, the water vapor in the off-oxidant gas is condensed and condensed water is generated. The produced condensed water is collected in a condensed water tank (not shown) through an off-oxidant gas condensed water path (not shown). The off-oxidant gas after the condensed water is recovered is discharged out of the fuel cell system 100 via the off-oxidant gas path.
[Operation of Gas Sensor 17]
Next, the operation of the hydrogen generator 1 of the fuel cell system 100 according to Embodiment 1 will be described with reference to FIG. The power generation operation in the fuel cell system 100 is performed in the same manner as the power generation operation of a general fuel cell system, and thus detailed description thereof is omitted.

  In the fuel cell system 100, the raw material gas is supplied to the combustor 1b and burned. Thereby, the reformer 1a is heated. When the temperature of the reformer 1a reaches the temperature required for reforming the source gas, the source gas is also supplied to the reformer 1a. Further, water is supplied from the water supply unit 3 to the reformer 1a as moisture necessary for the reforming reaction. Then, the raw material gas is reformed in the reformer 1a, and a hydrogen-rich fuel gas is generated. During power generation by the fuel cell system 100, off-fuel gas discharged as the remainder of the fuel gas supplied from the hydrogen generator 1 to the fuel cell 5 is used as the fuel gas, and the catalyst layer (see FIG. (Not shown) is heated to promote the steam reforming reaction.

  At this time, the gas sensor 17 continuously measures the CO concentration in the off-combustion gas, and evaluates the state of the flame in the combustor 1b. For example, when the air supply 10 becomes exhausted or the supply air is blocked and the flame becomes air shortage and generates CO, the gas sensor 17 detects it and sends the signal to the controller 101. The controller 101 determines that the combustion state of the combustor 1b is defective when the signal exceeds a predetermined value (for example, a threshold signal corresponding to the maximum amount of CO emission defined by JIS or the like), and combustor An instruction to stop 1b is given. The controller 101 also instructs the hydrogen generator 1 and the fuel cell system 100 to perform a stop operation. Further, even if the flame becomes excessive air and CO is generated due to a decrease in the supply amount due to a decrease in temperature or a supply failure of the raw material gas, the signal of the gas sensor 17 is similarly evaluated and the combustion state is determined. I have to.

  The gas sensor 17 detects CO and sends the signal to the controller 101. The controller 101 outputs a signal having a threshold value corresponding to a predetermined value (for example, the maximum discharge amount of CO defined by JIS or the like). ), The combustion state of the combustor 1b is determined to be defective, and an instruction to stop the combustor 1b is given. However, the controller 101 controls the air supply device 10 so that the signal of the gas sensor 17 is lower than a predetermined value (for example, CO is increased by increasing the amount of air even if the CO value is lower than the predetermined value). This operation is repeated every time the concentration is reduced and the CO concentration is increased.) When the gas sensor 17 exceeds the predetermined value when the capacity of the air supply device 10 is reached, the combustor 1b is stopped. It is also possible to make it.

  As described above, in the first embodiment, the buffer tank 14 is introduced on the upstream side of the gas sensor 17 that detects the component of the off-combustion gas in the combustor 1b, thereby eliminating the oxygen-deficient state of the off-combustion gas. Thus, the detection failure of the gas sensor 17 can be prevented.

(Embodiment 2)
FIG. 2 is a block diagram schematically showing a schematic configuration of the fuel cell system 100 including the hydrogen generator 1 according to the second embodiment.

  As shown in FIG. 2, the fuel cell system 100 according to Embodiment 2 of the present invention is different only in that an oxidant gas path 7 is added to the path communicating with the buffer tank 14.

As described above, also in the second embodiment, the buffer tank 14 is introduced upstream of the gas sensor 17 that detects the off-burning gas component of the combustor 1b as in the first embodiment. It is possible to eliminate the oxygen deficiency state of the gas and prevent the detection failure of the gas sensor 17.

  In the hydrogen generator according to the present invention, when the combustion state of the combustor is detected, the oxygen deficiency state of the off-combustion gas is resolved and detected by the gas sensor, so that the fuel from the off-combustion gas discharged from the fuel cell system is detected. Since it is possible to detect defective combustion of gas and it can be applied to a heat source of a water heater or a heater, it is useful in the fields of a fuel cell, a water heater, and a heater.

DESCRIPTION OF SYMBOLS 1 Hydrogen generator 1a Reformer 1b Combustor 2 Raw material supply part 3 Water supply device 4a Fuel gas supply path 4b Off-fuel gas path 5 Fuel cell 6 Blower 7 Oxidant gas path 8 Exhaust gas heat exchanger 9 Exhaust air heat exchanger DESCRIPTION OF SYMBOLS 10 Air supply device 11 Air flowmeter 12 Off combustion gas path 13 Off oxidant gas path 14 Buffer tank 15 Gas diffusion plate 16 Drain port 17 Gas sensor 18 Waste heat recovery water path 100 Fuel cell system 101 Controller

Claims (6)

A reformer that generates a fuel gas containing hydrogen by a reforming reaction of the raw material gas;
A combustor that burns the raw material gas or the fuel gas and heats the reformer;
An off combustion gas path for discharging off combustion gas generated in the combustor;
A gas sensor that is disposed in the off-combustion gas path and detects the specific gas by burning the specific gas contained in the off-combustion gas;
A buffer tank that is disposed upstream of the gas sensor in the off-combustion gas path and stores the off-combustion gas;
A hydrogen generator. An off-oxidant gas path for discharging the off-oxidant gas of the fuel cell;
The hydrogen generator according to claim 1, wherein the off-oxidant gas path is connected upstream of the gas sensor in the off-combustion gas path.   The hydrogen generator according to claim 2, wherein the off-oxidant gas path is connected downstream of the buffer tank in the off-combustion gas path.   4. The hydrogen generator according to claim 1, wherein the buffer tank includes a gas diffusion mechanism that promotes homogenization of a component having a cross section perpendicular to a flow direction of the off-combustion gas.   The hydrogen generator according to any one of claims 1 to 4, wherein the buffer tank includes a drain port that discharges moisture contained in the off-combustion gas.   The fuel cell system carrying the hydrogen generator of any one of Claim 1 to 5.

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