JP2004158340A - Package type fuel cell power plant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a package type fuel cell power plant equipped with a gas detecting system detecting gas which may leak in the power plant together with the kind of the gas in simple constitution. <P>SOLUTION: A semiconductor type gas sensor having individually selective sensitivity to material fuel gas supplied to a reformer and hydrogen gas is installed in a package, and gas leakage is detected based on an electrical output. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides a reformer for receiving a raw fuel gas, reforming the raw fuel gas to obtain hydrogen gas, and receiving the hydrogen gas generated from the reformer, and separately receiving oxygen gas. A working fuel cell, comprising an external output device that externally outputs power generated by the fuel cell,
The present invention relates to a packaged fuel cell power generator in which the reformer, the fuel cell, and the external output device are housed in a package.
[0002]
[Prior art]
This type of packaged fuel cell power generator is currently in the practical stage, and is installed in an on-site configuration. Corresponds to this type.
[0003]
As a conventional technology of a package type fuel cell power generation device, there is one disclosed in Patent Document 1. In this prior art, a raw fuel tank, a fuel reformer, a fuel cell, a power converter, and the like are provided in a predetermined package, and a heat insulating partition is provided to appropriately control a thermal influence on a control system and the like. I have.
In this prior art, there is no mention of gas management in the package (specifically, monitoring of leakage of raw fuel gas and hydrogen gas obtained after reforming).
[0004]
On the other hand, in a fuel cell, since hydrogen gas is used for power generation, attempts have conventionally been made to suitably monitor the leakage of hydrogen gas.
For example, in the technology disclosed in Patent Document 2, a hydrogen sensor that is preferable to be disposed near a hydrogen supply system to a fuel cell body has been proposed.
The technology disclosed in Patent Document 3 proposes a hydrogen sensor having a similar purpose, and shows an example in which the hydrogen sensor is applied to a hydrogen gas detection device of a fuel cell system.
In these technologies, hydrogen gas is independently monitored.
In a fuel cell power generator, a reformer is provided in addition to the fuel cell, and it is necessary to monitor raw fuel gas supplied to the reformer. As a conventional technique for solving this problem, in the technique disclosed in Patent Document 4, a flammable gas detector (or a fire detector) for detecting the leakage of flammable gas to the outside of the reformer is modified. It is disclosed that the apparatus comprises a quality abnormality signal generating means. In this conventional technique, the gas type of the gas to be detected is not specified.
[0005]
[Patent Document 1]
Japanese Patent Application No. 5-290868 specification
[Patent Document 2]
JP-A-2001-27626 (Claim 7, paragraph number 0031)
[0007]
[Patent Document 3]
JP-A-2002-22700 (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 a package, there is no established technology for internal gas management, and hydrogen Gas and raw fuel gas were monitored individually.
[0010]
However, when detecting hydrogen gas and raw fuel gas separately, there are a plurality of types of sensors and the installation space becomes large. Further, since a plurality of detection systems are provided for each gas, a relatively complicated determination structure is required, which is not preferable.
Considering that the packaged fuel cell power plant is originally an on-site type and will be installed in each household in the future, the maintenance and management are as simple as possible, the configuration is simple, Is preferably long.
[0011]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a device as a fuel cell power generation device which is of a package type and has a gas detection system capable of detecting, with a simple configuration, a gas which may leak into the package, together with its type.
[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 for each of raw fuel gas and hydrogen gas is provided in the package, and a detection unit for detecting any one of the gases based on an electrical output of the semiconductor gas sensor is provided. And a configuration in which the raw fuel gas and the hydrogen gas can be detected.
[0013]
The semiconductor gas sensor used in the packaged fuel cell power generation device of the present invention is sensitive to the raw fuel gas (for example, city gas containing methane as a main component) sent to the reformer, and has the fuel cell fuel cell. Some are sensitive to hydrogen gas.
In this type of gas, the response form differs according to the type of gas, and both gases can be selectively detected by adjusting the detection time.
[0014]
Therefore, in the present application, this type of semiconductor gas sensor is provided in a package, the electrical output is obtained, and each gas is detected by the detecting means.
In this configuration, by detecting a gas that may leak into the package with a single detection system, as a result, sufficient gas monitoring for the fuel cell power generator can be achieved with a simple structure. I can do it. In this case, since the system is simple, its maintenance and management are also easy.
[0015]
Now, in the package type fuel cell power generator, as described in claim 2, a pulse energizing means for energizing the semiconductor type gas sensor with a pulse is provided, and energization of the semiconductor type gas sensor is performed by a pulse energizing method. In addition, it is preferable to perform the gas detection within the pulse energization time.
[0016]
The semiconductor gas sensor detects gas when the sensor element is heated. Therefore, it is necessary to set the sensor temperature to a predetermined temperature range by using a sensor element as an energizing method or the like. However, in the always-on state, there is a limit to the battery life of the battery-powered type. On the other hand, in a fuel cell, since power is generated, it is conceivable that power is supplied from it.However, the time when it is desired to generate power and the time when gas leakage monitoring is required are: They are not necessarily the same. Therefore, the battery type is selected. However, considering the life of the battery, constant energization is not preferable, and a pulse energization type is adopted.
[0017]
On the other hand, the sensitivity of the semiconductor gas sensor shows different sensitivity characteristics to the raw fuel gas and the hydrogen gas at different sensor temperatures, and it is possible to selectively detect each gas type. Therefore, when detecting a raw fuel gas and a hydrogen gas in a plurality of temperature ranges until reaching a predetermined heating state, the present invention aims at adopting a pulse energization mode and heating the sensor element to a steady temperature. By detecting the two types of gases, the object of the present invention can be suitably achieved.
[0018]
That is, as described in claim 3, upon detecting the gas within a single pulse energizing 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 separately provided,
The raw fuel gas may be detected in the raw fuel gas detection time range, and the hydrogen gas may be detected in the hydrogen gas detection time range.
[0019]
To explain this point in more detail, for example, hydrogen gas has high sensitivity in a state where the temperature of the gas detection element has not yet risen, and for a raw fuel gas such as methane gas, the gas detection element Upon reaching a predetermined heating state, the selection sensitivity is exhibited. Therefore, the detection time range for hydrogen gas and the detection time range for raw fuel gas are set separately, and the sensitivity to both gases can be observed within a single pulse energization time, so that the possibility of leakage gas is increased. Can be reliably detected.
[0020]
Now, as described in claim 4, the semiconductor type gas sensor includes a tin oxide sintered body containing lanthanum and zirconium, and detects the hydrogen gas in a thermal initial transient response region. It is preferable that 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 portion which comes into contact with the gas to be detected is provided with a lanthanum and zirconium, or a tin oxide sintered body containing a compound thereof as, for example, an oxide, this includes hydrogen and Responds to methane. Therefore, by using this type of sensor, the detection purpose of the present application can be achieved, and the detection time range of the hydrogen gas and the detection time range of the raw fuel gas can be set based on the change in the temperature of the sensor element during the pulse current. If specified, it will be as described above. Similarly, hydrogen gas and raw fuel gas can be selectively detected.
[0021]
Further, as described in claim 5, the semiconductor gas sensor may be configured to include a tin oxide sintered body containing at least one of alkaline earth elements.
That is, in the case of a tin oxide sintered body containing at least one kind of alkaline earth element or a compound thereof as an oxide, for example, in a sensitive part that comes into contact with the gas to be detected, this is sensitive to alcohol and hydrogen. I do. Therefore, by using this type of sensor, the detection object of the present application can be achieved.
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described based on examples.
(Overview of packaged fuel cell power generator)
FIG. 1 is a simplified elevation view showing a package-type fuel cell power generator 1 according to an embodiment of the present invention.
[0022]
As shown in FIG. 1, the packaged fuel cell power generator 1 stores raw fuel gas tanks 3 (specifically, city gas tanks) in a predetermined package 2 and supplies raw fuel gas from the raw fuel gas tanks 3. Receiving a reformer 4, a fuel cell 5 that uses hydrogen gas generated by the reformer 4 as one gas, and an electric power as an external output device that converts the power output from the fuel cell 5 into a predetermined alternating current. It is provided with a conversion device 6, an exhaust heat recovery device 7 for utilizing exhaust heat from each device, and the like.
Further, there is provided a control device 9 that integrates information from a measuring instrument (not shown) for detecting the operation state of these devices and outputs a control command to each device.
[0023]
One of these measuring devices is provided with a gas detector 10 unique to the present application. When a shut-off output is output from the gas detector 10, basically, the fuel cell power generator 1 is shifted to a stop operation. It is 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, a pulse energizing unit 12 for energizing the semiconductor gas sensor 11 with a pulse, and a detecting unit 13 for detecting a gas based on an electrical output of the semiconductor gas sensor 11 in a pulse energized state. It is comprised including.
[0025]
The sequential energizing drive of the pulse energizing means 12, the processing of the detection result detected by the detecting means 13, and the processing related to the shutoff output accompanying the energizing driving are performed by the main CPU 16 as a control means in the gas detector 10. Do these.
[0026]
(Semiconductor gas sensor)
The electric resistance of the semiconductor gas sensor 11 changes due to contact with the gas to be detected in the energized state. By detecting this change, the detection target gas (hydrogen gas and methane gas as raw fuel gas) can be detected. The driving is performed by, for example, a battery.
[0027]
The gas detector 10 detects a change in the resistance value of a semiconductor gas sensor 11 (hereinafter simply referred to as “sensor 11”) via a predetermined detection electric circuit 14 such as a Wheatstone bridge. By comparing this detected value with data (threshold) relating to the concentration of the gas to be detected, which is obtained in advance, the presence / absence of the gas to be detected can be determined.
[0028]
The sensor element used as the sensor 11 is, for example, similar to the combustible gas detecting element disclosed in Japanese Patent Application Laid-Open No. 10-142183.
The outline of the sensor 11 is shown in FIG. The sensor 11 is provided with a tin oxide sintered body 11a obtained by dispersing and mixing tin oxide in water to form a paste and applying it to a platinum wire coil 11b, drying and firing 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, in the tin oxide sintered body, 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 provided. 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, in order to obtain a power saving effect, the element is heated by a pulse conduction method.
[0031]
(Hydrogen gas detection and raw fuel gas detection)
Regarding the pulse energization, a predetermined detection time set for the hydrogen gas and the methane gas at the time of energization while repeating the pulse-like energization (see the voltage pattern of “applied voltage” shown in FIG. 6) at a predetermined cycle. In the range, the electric output of the sensor 11 is detected to perform gas detection. In other words, pulse energization and accompanying gas detection are both performed during a single pulse energization operation, both for hydrogen gas detection for hydrogen gas and raw fuel gas detection for methane gas.
[0032]
3 and 4 show a form of pulse current application by the gas detector. FIG. 3 shows an operation state at the time of the initial start, and FIG. 4 shows a normal operation state after the end of the start. Monitoring is performed in this normal operation state.
In these figures, the horizontal axis indicates time, and the vertical axis indicates gas concentration or operation, respectively, shown at the left end. Each vertical bar shown in the column of the pulse signal corresponds to individual pulse energization.
[0033]
(Pulse energizing operation at initial startup)
As shown in FIG. 3, at the time of the initial startup, the operation is performed by pulse energization every 10 seconds of the driving cycle. In this operation mode, one minute is required for the initial stabilization, and thereafter, a two-minute inspection operation is performed. At the time of this inspection, the operator blows methane gas from a cylinder filled with methane gas, which is a gas for inspection (the appearance is no different from a normal lighter), to a predetermined location to check whether the gas detector works properly. Check whether it is. If there is no problem, the operation shifts to the normal operation shown in FIG.
[0034]
(Pulse energizing operation during normal operation)
A description will be given based on FIG.
This figure shows, from the top, “change state of gas concentration”, “drive state of sensor (specifically, change state of energization frequency of pulse energization)”, “lighting state of alarm”, “output state of cut-off output”. Is shown.
[0035]
As the “change state of the gas concentration”, two examples of the concentration increase mode are shown.
Since the first concentration increase has been continued for a relatively long time, it actually represents a situation where a shut-off operation is necessary.
The second increase in concentration is representative of a situation in which the sensor may malfunction due to a short duration. These are basically separate examples.
[0036]
(Pulse energization control)
As can be seen from the diagram showing the “driving state of the sensor”, the frequency control of the pulse energization is controlled to switch between a relatively coarse “normal mode” and a dense “alert 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 drive cycle of 10 s.
In both modes, the single pulse energization is 2.5 s as described later.
Switching from "normal mode" to "warning mode" is performed when the gas concentration exceeds the warning level for a single pulse energization cycle, and switching in the reverse direction does not exceed "warning level". Is executed four consecutive times. The switching of the operation mode is performed by a main CPU 16 as control means provided in the gas detector 10 described later.
[0037]
(Gas detection within the pulse energization time)
The detection of gas within each pulse energization will be described with reference to FIGS.
The energization time T0 of the pulse energization is set to 2.5 seconds as described above, and the pulse energization for this energization time is executed in the "normal mode" and the "alert mode". The pulse energization is controlled by the pulse energization means 12, and the mode is switched by the main CPU 16.
[0038]
As shown by the “detection signal” in FIG. 6 or the short vertical broken line in FIGS. 5A and 5B, the sensor output is captured in the single pulse energization as follows.
In the hydrogen gas detection, the sensor output is monitored until one second elapses after the start of energization, and the sensor output after one second elapses (hydrogen gas detection time range) is taken. On the other hand, in the methane gas detection, the sensor output is monitored until 2.5 seconds have elapsed since the start of energization, that is, until the end of energization, and the sensor output is captured just before the end of energization (methane gas detection time range).
These times can be set as appropriate according to the type of the sensor 2 or the type of the gas to be detected.
[0039]
The reason why the hydrogen gas detection and the methane gas detection are performed in different time zones as described above is as follows.
In FIG. 5, the horizontal axis indicates time, and the vertical axis indicates sensor output, and the change in sensor output is shown. Among them, FIG. 5A shows how the sensor output changes when detecting hydrogen gas, and FIG. 5B shows how the sensor output changes when detecting methane gas.
FIG. 6 shows “sensor surface temperature”, “applied voltage”, and “detection signal / time” at the time of corresponding pulse energization.
[0040]
0:00 indicates the start of the pulse energization, and 2.5 sec indicates the end of the pulse energization. In FIG. 5, the dashed line extending in the horizontal direction indicates the base output, that is, the sensor output in air in which no specific gas exists. The solid line shows the sensor output for 5000 ppm of hydrogen. The dashed line indicates the sensor output for 4000 ppm of methane. The numerical values of the concentrations shown here are values that are 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 0:00 to about 2 s with respect to the surface temperature, and thereafter, a steady output range is maintained until 2.5 s. It turns out that there is.
[0041]
Paying attention to FIG. 5A, the sensitivity characteristics of the semiconductor gas sensor can be classified into types 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 fall s2 of the energization process. As such a gas, methane indicated by a dashed line corresponds. In this case, the longer the energization time, the more stable the sensor output.
[0042]
The other is that, after an initial rise and a drop in output, a high sensitivity (a time region showing a sensitivity higher than the sensitivity of methane gas) is obtained in a relatively short time, and the sensitivity gradually decreases. That is, as this kind of gas, the hydrogen gas of the solid line corresponds. 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. 5A, the output for hydrogen gas is superior to the output for methane gas in the initial period of energization. As described above, here, the concentrations of the hydrogen gas and the methane gas are set to very general values.
Therefore, at the beginning of energization, hydrogen gas is detected with priority over methane gas.
Such a time zone in which the output for hydrogen gas is higher than the output for methane gas is referred to as a high sensitivity time zone Th. Therefore, the threshold value on the hydrogen gas side in this time range is larger than the output by methane gas having a general gas concentration.
[0044]
As apparent from FIGS. 5A and 5B, when the high sensitivity time range Th is exceeded, methane gas can be detected preferentially with respect to hydrogen gas until power supply is stopped. The threshold value on the methane gas side in this time range is larger than the output by 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 the electrical output, converts the data into data corresponding to the gas concentration, and outputs the data to the main CPU 16.
That is, when the pulse energization starts, the sensor output in the time range indicated by the “detection signal” in FIG. 6 is taken in as the time elapses, and the sensor output in the hydrogen gas detection time range corresponds to the hydrogen gas, and the methane gas detection time It is assumed that the sensor output in the region corresponds to methane gas.
[0046]
This detection mode is separated by the identification detection unit 130 provided inside the detection unit 13. The operation control of the macro of the pulse energizing means 12 and the detecting means 13 is performed by the main CPU 16.
[0047]
(External alarm)
The gas detection signal obtained as described above is sent from the detection means to the main CPU 16, and the main CPU 16 compares a warning level, which is a preset threshold value for these signals, with each gas. Is done. That is, the sensor outputs taken in the respective detection time ranges are compared with the cutoff thresholds set separately for the hydrogen gas and the methane gas in advance.
[0048]
When any one of the gases exceeds the cutoff threshold, the cutoff output is output to the outside via the external output means 18 as described above.
More specifically, as shown in the column of “interruption output” in FIG. 4, the interruption output for executing the operation interruption of each device provided in the package is shifted to the alert mode, and the alert level is increased four times. It is configured to output at successive points in time. Therefore, a delay of 30 s occurs.
[0049]
(Alarm lighting)
The main CPU 16 outputs a predetermined operation control command to each functional unit based on the result of the external determination. As shown in FIG. 2, the operation control command includes, for example, an output command for turning on the lighting warning output unit 17. The lighting alarm output means 17 includes an LED 17a and a lighting alarm circuit 17b for driving the LED, and blinks the LED 17a at predetermined intervals in accordance with an output command from the main CPU 16. Specifically, lighting 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, and the lighting is red when the gas concentration exceeds the alert level, and green when the gas concentration does not exceed the alert level.
[0050]
(Interrupt output)
Further, the cutoff output is sent to the control device 9 of the fuel cell power generation device, and the device 9 starts a fuel cell operation stop sequence.
[0051]
[Another embodiment]
(1) As a semiconductor type gas sensor, 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% with respect to the additive content, both gases are used. High discrimination detection ability can be exhibited.
[0052]
(2) Further, in the above-described embodiment, the case where the main component of the raw fuel gas is methane has been described. However, the present invention provides a semiconductor gas sensor around a platinum wire coil as described above. A structure having a tin oxide sintered body and containing an oxide of an alkaline earth element (for example, calcium oxide CaO) may be used.
In this case, alcohol as raw fuel gas can be detected together with hydrogen detection. Also, when using this type of sensor, the sensitivity to alcohol appears first, followed by the sensitivity to hydrogen.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of a packaged fuel cell power generation device of the present application; FIG. 2 is a functional block diagram of a gas detector used in the device; FIG. FIG. 4 is a diagram illustrating a form of pulse energization for a semiconductor gas sensor. FIG. 5 is a diagram illustrating a change in sensor output during pulse energization. FIG. 6 is a diagram illustrating a relationship between a surface temperature and a detection time region during pulse energization. Diagram showing structure of gas sensor [Explanation of symbols]
REFERENCE SIGNS LIST 1 Package type fuel cell power generator 2 Package 4 Reformer 9 Control device 10 Gas detector 11 Semiconductor gas sensor 12 Pulse energizing means 13 Detecting means 15 Power battery 130 Identification detecting means

Claims (5)

A reformer that receives a raw fuel gas and reforms the raw fuel gas to obtain hydrogen gas, and a fuel cell that receives the hydrogen gas generated from the reformer and separately works by receiving oxygen gas. An external output device that externally outputs power generated by the fuel cell,
A package-type fuel cell power generation device containing the reformer, a fuel cell, and an external output device 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 packaged fuel cell power generation apparatus, comprising: a detection unit that detects the raw fuel gas and the hydrogen gas. 2. The package type fuel cell according to claim 1, further comprising a pulse energizing means for energizing the semiconductor gas sensor with a pulse, performing energization of the semiconductor gas sensor by a pulse energizing method, and performing gas detection within a pulse energizing time. Power generator. Upon detecting the gas within a single pulse energizing 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 separately provided,
The package fuel cell power generator according to claim 2, wherein the raw fuel gas is detected in the raw fuel gas detection time range, and the hydrogen gas is detected in the hydrogen gas detection time range. 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 packaged 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-type gas sensor includes a tin oxide sintered body containing at least one of alkaline earth elements.

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