JP4187506B2 - Package type fuel cell power generator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention accepts raw fuel gas, reforms the raw fuel gas to obtain hydrogen gas, accepts the hydrogen gas generated from the reformer, and separately accepts oxygen gas. A working fuel cell, and an external output device for outputting power generated by the fuel cell to the outside,
The present invention relates to a package type fuel cell power generator in which the reformer, the fuel cell, and an external output device are accommodated in a package.
[0002]
[Prior art]
This type of packaged fuel cell power generation device is currently in a practical stage, and is installed in an on-site form, and is mounted on an automobile and fueled with city gas mainly composed of methane. This type of fuel cell power generator corresponds to this type.
[0003]
As a prior art of a package type fuel cell power generator, there is one disclosed in Patent Document 1. In this prior art, a raw fuel tank, a fuel reformer, a fuel cell, a power conversion device, etc. are provided in a predetermined package, and a heat insulating partition is provided to appropriately control the thermal influence on the control system and the like. Yes.
In this prior art, there is no mention of gas management (specifically, monitoring of leakage of raw fuel gas and hydrogen gas obtained after reforming) in the package.
[0004]
On the other hand, in the fuel cell, since hydrogen gas is used for power generation, conventionally, attempts have been made to suitably monitor the leakage of the hydrogen gas.
For example, in the technique disclosed in Patent Document 2, a hydrogen sensor that is preferable to be disposed in the vicinity of a hydrogen supply system to the fuel cell main body has been proposed.
In the technique disclosed in Patent Document 3, a hydrogen sensor having a similar purpose has been proposed, and an example applicable to a hydrogen gas detection device of a fuel cell system is shown.
In these technologies, hydrogen gas is monitored alone.
In the fuel cell power generation device, a reformer is provided in addition to the fuel cell, but it is also necessary to monitor the raw fuel gas supplied to the reformer. As a prior art for this problem, in the technique disclosed in Patent Document 4, a combustible gas detector (or fire detector) for detecting leakage of a combustible gas outside the reformer, It is disclosed to include a genital abnormality signal generating means. In this prior art, the gas type of the gas to be detected is not specified.
[0005]
[Patent Document 1]
Japanese Patent Application No. 5-290868 Specification [0006]
[Patent Document 2]
JP 2001-27626 A (Claim 7, paragraph number 0031)
[0007]
[Patent Document 3]
JP 2002-22700 A (paragraph number 0044)
[0008]
[Patent Document 4]
JP 2001-189161 A (paragraph number 0039)
[0009]
[Problems to be solved by the invention]
As described above, in the conventional fuel cell power generator, in which the fuel cell is housed in the package, there is no established technology for internal gas management, and hydrogen Gas, raw fuel gas, etc. were individually monitored.
[0010]
However, when hydrogen gas and raw fuel gas are detected separately, the number of sensors is increased and the installation space is increased. Further, since there are a plurality of detection systems for each gas, a relatively complicated determination structure is required, which is not preferable.
Considering that the package type fuel cell power generator is originally an on-site type and will be installed in the future in each home, etc., it is easy to maintain as much as possible, the structure is simple, and its lifetime Is preferably long.
[0011]
An object of the present invention is to obtain a device that is of a package type as a fuel cell power generation device and includes a gas detection system that can detect a gas that may leak into the package, along with its type, with a simple configuration.
[0012]
[Means for Solving the Problems]
The characteristic configuration of the packaged fuel cell power generator according to the present invention for achieving the above object is as described in claim 1.
A semiconductor gas sensor having selective sensitivity to the raw fuel gas and hydrogen gas is provided in the package, and detection means for detecting any one of the gases based on the electrical output of the semiconductor gas sensor. The raw fuel gas and the hydrogen gas can be detected.
[0013]
In the semiconductor type gas sensor used in the package type fuel cell power generator of the present application, the fuel of the fuel cell is sensitive to the raw fuel gas (for example, city gas mainly composed of methane) sent to the reformer. Some are sensitive to hydrogen gas.
And in this kind of thing, according to the gas kind, a sensitive form changes and both gas can be selectively detected by adjusting each time of detection.
[0014]
Therefore, in the present application, this type of semiconductor gas sensor is provided in the package, the electrical output is obtained, and each gas is detected by the detection means.
In this configuration, the gas that may leak into the package is detected by a single detection system, and as a result, sufficient gas monitoring for the fuel cell power generator can be performed while having a simple structure. Can be executed. In this case, since the system is simple, its maintenance and management are easy.
[0015]
Now, in the package type fuel cell power generator, as described in claim 2, the semiconductor gas sensor includes pulse energization means for energizing the semiconductor gas sensor, and energization of the semiconductor gas sensor is performed by a pulse energization method. In addition, it is preferable to perform gas detection within the pulse energization time.
[0016]
The semiconductor gas sensor detects gas in a state where the sensor element is heated. Therefore, it is also necessary to set the sensor temperature to a predetermined temperature range by using a sensor element as an energization method or the like. However, in the always energized state, the battery life is limited in the battery feeding method. On the other hand, in the fuel cell, since power generation is being performed, it may be possible to receive power supply from there, but when it is necessary to perform power generation and when gas leakage monitoring is required, It does not necessarily match. Therefore, although the battery type is selected, considering the life of the battery, the energization at all times is not preferable, and the pulse energization method is adopted.
[0017]
On the other hand, the sensitivity of the semiconductor gas sensor shows different sensitivity characteristics at different sensor temperatures with respect to the raw fuel gas and the hydrogen gas, and it is possible to perform selective detection by each gas type. Therefore, when the raw fuel gas and the hydrogen gas are detected in a plurality of temperature ranges until the predetermined heating state is reached, the pulse application mode is adopted, and the present application is aimed at until the sensor element is heated to a steady temperature. As a result, the object of the present application can be suitably achieved by detecting the two kinds of gases.
[0018]
That is, as described in claim 3, in the gas detection within a single pulse energization time,
A raw fuel gas detection time range for the raw fuel gas and a hydrogen gas detection time range for the hydrogen gas are provided separately,
The raw fuel gas may be detected in the raw fuel gas detection time region, and the hydrogen gas may be detected in the hydrogen gas detection time region.
[0019]
This point will be described in more detail. For example, hydrogen gas has high sensitivity when the temperature of the gas detection element has not yet risen. For raw fuel gas such as methane gas, the gas detection element is It reaches a predetermined heating state and exhibits its selection sensitivity. Therefore, by setting the detection time range for hydrogen gas and the detection time range for raw fuel gas separately, and looking at the sensitivity to both gases within a single pulse energization time, the possibility of leakage gas Can be reliably detected.
[0020]
The semiconductor gas sensor includes a tin oxide sintered body containing lanthanum and zirconium, and detects the hydrogen gas in a thermal initial transient response region. Preferably, the raw fuel gas is detected in a steady output region after the thermal initial transient response.
In the semiconductor type gas sensor, in the case where the sensitive part in contact with the gas to be detected includes a tin oxide sintered body containing, for example, lanthanum and zirconium, or a compound thereof as an oxide, Sensitive to methane. Therefore, by using this type of sensor, the detection object of the present application can be achieved, and the hydrogen gas detection time range and the raw fuel gas detection time range can be determined from the change in temperature of the sensor element during pulse energization. When specified, it becomes as described above, and similarly, hydrogen gas and raw fuel gas can be selectively detected.
[0021]
According to a fifth aspect of the present invention, the semiconductor gas sensor may include a tin oxide sintered body containing at least one alkaline earth element.
That is, in the case of a tin oxide sintered body in which at least one alkaline earth element or a compound thereof is contained, for example, as an oxide in the sensitive part that is in contact with the gas to be detected, this is sensitive to alcohol and hydrogen. To do. Therefore, the detection object of the present application can be achieved by using this type of sensor.
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described based on examples.
(Outline of package type fuel cell power generator)
FIG. 1 is a simplified elevational view showing a package type fuel cell power generator 1 according to an embodiment of the present invention.
[0022]
As shown in the figure, this package type fuel cell power generator 1 supplies raw fuel gas from a raw fuel gas tank 3 (specifically, a city gas tank) and raw fuel gas tank 3 in a predetermined package 2. Receiving reformer 4, fuel cell 5 that uses hydrogen gas generated by the reformer 4 as one gas, and power as an external output device that converts the power output from the fuel cell 5 into a predetermined alternating current A conversion device 6 and an exhaust heat recovery device 7 for utilizing the exhaust heat from each device are provided.
Furthermore, the control apparatus 9 which integrates the information from the measuring device (not shown) for detecting the operation state of these apparatuses, and outputs the control command to each apparatus is provided.
[0023]
One of these measuring instruments is provided with a gas detector 10 unique to the present application. When a shutoff output is output from the gas detector 10, the fuel cell power generator 1 is basically shifted to a stop operation. Configured to be started.
[0024]
Hereinafter, details of the gas detector 10 will be described with reference to FIGS.
(Outline of gas detector)
The gas detector 10 includes a semiconductor gas sensor 11, pulse energization means 12 for applying a pulse to the semiconductor gas sensor 11, and detection means 13 for detecting a gas based on an electrical output of the semiconductor gas sensor 11 in a pulse energization state. And is configured.
[0025]
The sequential energization drive of the pulse energization means 12, the processing of the detection result detected by the detection means 13, and the processing related to the cutoff output accompanying therewith are the main CPU 16 as the control means in the gas detector 10. Do these.
[0026]
(Semiconductor gas sensor)
The electrical resistance of the semiconductor gas sensor 11 changes due to contact with the detection target gas in an energized state. By detecting this change, the detection target gas (hydrogen gas and methane gas as the raw fuel gas) can be detected. The driving is performed by a battery, for example.
[0027]
In the gas detector 10, a change in the resistance value of the semiconductor gas sensor 11 (hereinafter simply referred to as “sensor 11”) is detected via a predetermined detection electric circuit 14 such as a Wheatstone bridge. The presence or absence of the detection target gas can be determined by comparing the detected value with data (threshold value) relating to the concentration or the like of the detection target gas obtained in advance.
[0028]
A sensor element used as the sensor 11 is similar to a combustible gas detection element disclosed in, for example, Japanese Patent Application Laid-Open No. 10-142183.
An outline of the sensor 11 is shown in FIG. The sensor 11 includes a tin oxide sintered body 11a obtained by applying a paste obtained by dispersing and mixing tin oxide in water to a platinum wire coil 11b, drying it, and firing it at 400 ° C. for 1 hour. ing.
[0029]
The tin oxide sintered body 11a is impregnated with a predetermined amount of a mixed solution of lanthanum nitrate and zirconyl nitrate. Thereby, the sensitive part 11c containing 0.9 mol% of the lanthanum compound in terms of lanthanum oxide (La ₂ O ₃ ) and 1.8 mol% of the zirconium compound in terms of zirconium oxide (ZrO ₂ ) is contained in the tin oxide sintered body. Is formed.
[0030]
(Gas detection)
The gas detector 10 is driven by the battery power supply 15 as described above. Therefore, in consideration of the life, a pulse energization method is used for heating the element in order to obtain a power saving effect.
[0031]
(Hydrogen gas detection and raw fuel gas detection)
Regarding pulse energization, a predetermined detection time set for each of hydrogen gas and methane gas during energization while repeating pulse-like energization (refer to the voltage pattern of “applied voltage” shown in FIG. 6) at a predetermined cycle. In the region, the electrical output of the sensor 11 is detected and gas detection is performed. That is, both the hydrogen gas detection that is performed on the hydrogen gas and the raw fuel gas detection that is performed on the methane gas are performed during the single pulse energization operation.
[0032]
3 and 4 show the form of pulse energization by the gas detector. FIG. 3 shows an operation state at the time of initial start, and FIG. 4 shows a normal operation state after the start is finished. Monitoring is performed in this normal operating state.
In these figures, the horizontal axis indicates time, and the vertical axis indicates the gas concentration or operation shown at the left end. In addition, each vertical bar shown in the pulse signal column corresponds to individual pulse energization.
[0033]
(Pulse energization operation at initial start)
As shown also in FIG. 3, at the time of initial start-up, it is executed by pulse energization every 10 seconds of the driving cycle. In this mode of operation, 1 minute is required for initial stabilization, and then a 2-minute inspection operation is performed. During this inspection, whether the gas detector works normally by blowing methane gas from a cylinder filled with methane gas, which is an inspection gas (appears as a normal lighter in appearance), to the specified location. Check whether it is correct. If there is no problem, the process proceeds to the normal operation shown in FIG.
[0034]
(Pulse energization during normal operation)
This will be described with reference to FIG.
This figure shows, from the top, “gas concentration change status”, “sensor drive status (specifically, change status of energization frequency of pulse energization)”, “alarm lighting status”, “cutoff output status” Is shown.
[0035]
As the “change state of gas concentration”, two forms of concentration increase are illustrated.
Since the first concentration increase has continued for a relatively long time, it represents a situation that actually requires a blocking operation.
The second increase in concentration represents a situation where there is a possibility of malfunction on the sensor side due to the short duration. These are basically separate examples.
[0036]
(Pulse energization control)
As can be seen from the figure showing the “sensor drive status”, the frequency control of the pulse energization is switched between a relatively rough “normal mode” and a dense “warning mode”. In the “normal mode”, pulse energization is repeated at a driving cycle of 60 s. In the “warning mode”, pulse energization is repeated at a driving cycle of 10 s.
In both modes, the single pulse energization is 2.5 s as will be described later.
Switching from “Normal mode” to “Warning mode” is executed when the gas concentration exceeds the warning level for a single pulse energization, and switching in the reverse direction does not exceed the “Warning level”. Is executed in a continuous four times. The switching of the operation mode is performed by the main CPU 16 as control means provided in the gas detector 10 described later.
[0037]
(Gas detection within pulse energization time)
Gas detection in each pulse energization will be described with reference to FIGS.
The energization time T0 of the pulse energization is 2.5 seconds as described above, and the pulse energization of this energization time is executed in the “normal mode” and the “warning mode”. The pulse energization is controlled by the pulse energization means 12, and the mode switching is performed by the main CPU 16.
[0038]
As shown by the “detection signal” in FIG. 6 or the vertical short dashed lines in FIGS. 5A and 5B, the sensor output is captured in a single pulse energization as follows.
In hydrogen gas detection, the sensor output is monitored until 1 second has elapsed after the start of energization, and the sensor output after 1 second (hydrogen gas detection time range) is captured. On the other hand, in the methane gas detection, the sensor output is monitored until 2.5 seconds after the start of energization, that is, until the end of energization, and the sensor output is taken in at the timing of the end of energization (methane gas detection time region).
These times can be set as appropriate according to the type of sensor 2 or the type of detection target gas.
[0039]
The reason why hydrogen gas detection and methane gas detection are performed in different time zones is as follows.
In FIG. 5, the horizontal axis represents time, and the vertical axis represents sensor output, indicating changes in sensor output. Among these, FIG. 5 (a) shows the aspect of the sensor output change in hydrogen gas detection, and FIG. 5 (b) shows the aspect of the sensor output change in methane gas detection.
The “surface temperature of the sensor”, “applied voltage”, and “detection signal / time” at the time of corresponding pulse energization are shown in FIG.
[0040]
0:00 indicates the start of pulse energization, and 2.5 sec indicates the end of pulse energization. In FIG. 5, a broken line extending in the transverse direction indicates a base output, that is, a sensor output in the air where no specific gas exists. The solid line shows the sensor output for 5000 ppm hydrogen. The alternate long and short dash line indicates the sensor output for 4000 ppm of methane. The numerical value of the concentration shown here is a value that is usually obtained when these gases are detected.
Further, as can be seen from the “surface temperature” shown in FIG. 6, a thermal transient response occurs from 0 o'clock to about 2 s with respect to the surface temperature, and thereafter, a steady output region is reached up to 2.5 s. I know that.
[0041]
When attention is paid to FIG. 5 (a), the sensitivity characteristics of the semiconductor gas sensor can be classified according to the gas to be detected.
One is to stabilize to a constant output value corresponding to the gas concentration through the initial rise s1 and the output drop s2 of the energization process. As this type of gas, methane indicated by a one-dot chain line is applicable. In this case, the sensor output becomes more stable as the energization time is longer.
[0042]
The other is that, after an initial rise and an output drop, a high sensitivity (time range showing a sensitivity higher than the sensitivity of methane gas) is shown in a relatively short time, and the sensitivity is eventually lowered. That is, this type of gas corresponds to a solid line hydrogen gas. In this case, an appropriate sensor output can be obtained only for a very short time before the temperature of the sensor sufficiently rises.
[0043]
As is clear from FIG. 5 (a), the output with respect to hydrogen gas is superior to the output with respect to methane gas in the initial energization time. As described above, the concentration of hydrogen gas and the concentration of methane gas are set to very general values here.
Therefore, in the initial stage of energization, hydrogen gas is detected with priority over methane gas.
Such a time region in which the output for hydrogen gas is higher than the output for methane gas is referred to as a high sensitivity time region Th. Therefore, the threshold value on the hydrogen gas side in this time zone is set to be larger than the output of methane gas having a general gas concentration.
[0044]
As is clear from FIGS. 5 (a) and 5 (b), when the high sensitivity time zone Th is exceeded, the methane gas can be preferentially detected with respect to the hydrogen gas until the energization is stopped. The threshold value on the methane gas side in this time range is set to be larger than the output of hydrogen gas having a general gas concentration.
[0045]
In the present application, detection using the above characteristics is performed by the detection means 13 provided in the gas detector 10.
The detection means 13 takes in an electrical output, performs conversion into data corresponding to the gas concentration, and outputs the data to the main CPU 16.
That is, when pulse energization starts, the sensor output in the time range indicated by the “detection signal” in FIG. 6 is taken in over time, and the sensor output in the hydrogen gas detection time range corresponds to hydrogen gas, and the methane gas detection time. The sensor output of the area is considered to correspond to methane gas.
[0046]
The detection mode is divided by the identification detection unit 130 provided inside the detection unit 13. Note that macro operation control of the pulse energizing means 12 and the detecting means 13 is performed by the main CPU 16.
[0047]
(Alarm to outside)
The gas detection signal obtained as described above is sent from the detection means to the main CPU 16, and in the main CPU 16, a warning level that is a preset threshold value for these signals is compared with each gas. Is done. That is, the sensor output captured in each detection time range is compared with a cutoff threshold value set separately for hydrogen gas and methane gas in advance.
[0048]
When any of the gases exceeds the cutoff threshold, the cutoff output is externally output via the external output means 18 as described above.
More specifically, as shown in the “shut-off output” column of FIG. 4, the shut-off output for executing the operation shut-off of each device provided in the package shifts to the alert mode and sets the alert level four times. It is configured to output at consecutive times. Therefore, a delay of 30 s occurs.
[0049]
(Alarm lights)
The main CPU 16 outputs a predetermined operation control command to each function unit based on the external determination result. As shown in FIG. 2, as the operation control command, for example, there is an output command for turning on the lighting warning output means 17. The lighting alarm output means 17 includes an LED 17a and an LED driving lighting alarm circuit 17b, and blinks the LED 17a at a predetermined interval in accordance with an output command from the main CPU 16. More specifically, the doting is performed once every 5 seconds.
As shown in the column of alarm lighting in FIG. 4, a lighting mode is adopted as the alarm, which is red when the gas concentration exceeds the warning level and green when the gas level does not exceed the warning level.
[0050]
(Cutoff output)
Further, the cutoff output is sent to the control device 9 of the fuel cell power generator, and this device 9 starts the operation stop sequence of the fuel cell.
[0051]
[Another embodiment]
(1) As a semiconductor type gas sensor, regarding the additive content, when the content of lanthanum oxide is 0.9 to 1.2 mol% and the content of zirconium oxide is 1.8 to 2.4 mol%, both gases Can exhibit high discrimination and detection ability.
[0052]
(2) Furthermore, in the above embodiment, the case where the main component of the raw fuel gas is methane has been shown. However, the present invention is a semiconductor gas sensor around the platinum wire coil as described above. A tin oxide sintered body provided with an alkaline earth oxide (for example, calcium oxide CaO or the like) may be used.
In this case, alcohol as raw fuel gas can be detected together with hydrogen detection. In addition, when this type of sensor is used, sensitivity to alcohol appears first, followed by sensitivity to hydrogen.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of a packaged fuel cell power generator of the present application. FIG. 2 is a functional block diagram of a gas detector used in the apparatus. 4] Illustration of pulse energization for semiconductor gas sensor [Fig. 5] Diagram showing changes in sensor output during pulse energization [Fig. 6] Diagram showing relationship between surface temperature and detection time range during pulse energization [Fig. 7] Diagram showing structure of gas sensor 【Explanation of symbols】
DESCRIPTION OF SYMBOLS 1 Package type fuel cell power generation device 2 Package 4 Reformer 9 Control device 10 Gas detector 11 Semiconductor type gas sensor 12 Pulse energization means 13 Detection means 15 Power supply battery 130 Identification detection means

Claims (5)

A reformer that receives raw fuel gas and reforms the raw fuel gas to obtain hydrogen gas; a fuel cell that receives the hydrogen gas generated from the reformer and receives oxygen gas; An external output device for outputting the electric power generated by the fuel cell to the outside,
A package type fuel cell power generator in which the reformer, the fuel cell and an external output device are housed in a package,
A semiconductor gas sensor having selective sensitivity to the raw fuel gas and the hydrogen gas is provided in the package, and any of the gases is detected based on an electrical output of the semiconductor gas sensor. A package type fuel cell power generator configured to detect the raw fuel gas and the hydrogen gas. 2. The package type fuel cell according to claim 1, further comprising pulse energization means for energizing the semiconductor gas sensor with a pulse, energizing the semiconductor gas sensor by a pulse energization method, and performing gas detection within a pulse energization time. Power generation device. In the gas detection within a single pulse energization time,
A raw fuel gas detection time range for the raw fuel gas and a hydrogen gas detection time range for the hydrogen gas are provided separately,
The package type fuel cell power generator according to claim 2, wherein the raw fuel gas is detected in the raw fuel gas detection time region, and the hydrogen gas is detected in the hydrogen gas detection time region. The semiconductor gas sensor includes a tin oxide sintered body containing lanthanum and zirconium, detects the hydrogen gas in a thermal initial transient response region, and outputs a steady output after the thermal initial transient response. The package type fuel cell power generator according to any one of claims 1 to 3, wherein the raw fuel gas is detected in a region. The package type fuel cell power generator according to any one of claims 1 to 3, wherein the semiconductor gas sensor includes a tin oxide sintered body containing at least one alkaline earth element.

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