JP2003112905A - Fuel reforming system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel reforming system the contents of which can be purged without using an inert gas when the system is stopped. SOLUTION: This fuel reforming system is provided with a water vaporizer 4 for producing steam, a fuel vaporizer 1 for vaporizing fuel and mixing the vaporized fuel with steam to produce fuel gas, and a reformer 3 for producing hydrogen-rich reformed gas from the fuel gas by reformation reaction. When the system is stopped, the residual gas in the reformer 3 is purged by supplying only high-temperature steam from the vaporizer 4 to the reformer 3. After high-temperature steam is supplied, the moisture in the reformer 3 is purged by supplying air to the reformer 3. At this time, the hydrogen in a pure hydrogen layer 12 is also purged at the same time in the case that the reformer 3 is arranged in a membrane reactor 22.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to fuel reforming systems.

[0002]

2. Description of the Related Art As a fuel reforming system, it has been hitherto disclosed in
There is one disclosed in 7-37599. As shown in FIG. 1, the power is generated by a reformer 110 that produces a reformed gas (anode gas) containing hydrogen from a fuel gas containing steam, and an electrochemical reaction between a cathode gas as an oxidant and the anode gas. A fuel cell 120 and a duct burner 1 for combusting cathode exhaust gas of the fuel cell 120 to generate combustion gas.
43 and a steam generator 144 that generates steam by heat exchange with the combustion gas generated by the duct burner 143. Further, as a line connecting these respective components, a fuel gas supply line 161 for generating a fuel gas by mixing steam with a raw material gas and supplying the fuel gas to the reformer 110, and a steam generator 144. The steam line 151 that supplies the steam generated in step 1 to the fuel gas supply line 161, and the source gas line 153 that supplies the source gas to the duct burner 143 from the fuel gas supply line 161.
And an air supply line 157 for supplying air to the duct burner 143.

In such a fuel reforming system,
In order to prevent carbon deposition in the reformer 110 when the system is stopped, the following operation is performed using an inert gas. That is, when the stop command is issued, the reformer 1
The fuel supply to 10 is stopped and the duct burner 14
Fuel and air are supplied to and burned by the fuel cell 3, and the high temperature combustion gas generated thereby is supplied to the steam generator 144 to generate steam. Generated steam is steam supply line 151
To the fuel supply line 161, and then the reformer 1
Supply to 10. At the same time, in order to purge the residual gas in the fuel reforming system, the fuel gas supply line 161
N ₂ which is an inert gas is supplied to.

Since the steam is continuously supplied to the reformer 110 even after the fuel supply to the reformer 110 is stopped in this way, the raw material gas (mixed with the steam) remaining in the fuel gas supply line 161 is mixed. The previously evaporated fuel) is supplied to the reformer 110 in the form of fuel gas. As a result, it is possible to avoid mixing the raw material gas containing no steam into the reformer 110,
The deposition of carbon in the reformer 110 is prevented.

[0005]

[Problems to be solved by the invention] However,
In such a fuel reforming system, at the time of stop, N ₂
In order to perform the purging using an inert gas such as, it is necessary to provide a storage means such as a cylinder, the loading space efficiency is poor, and maintenance such as replacement of the cylinder has to be carried out, so There is a problem of being inappropriate.

Therefore, an object of the present invention is to provide a fuel reforming system which can perform purging without using an inert gas such as N ₂ .

[0007]

The first invention comprises a water evaporator for producing steam and a reformer for producing a hydrogen-rich reformed gas by a reforming reaction of fuel and water, When the system is stopped, only the steam generated by the water evaporator is supplied to the reformer, and after the steam generated by the water evaporator is supplied, air is supplied to the reformer.

In a second aspect based on the first aspect, the reformer is a membrane reactor composed of a reforming layer and a pure hydrogen layer which are adjacent to each other at least through the hydrogen separation membrane, and when the system is stopped, To supply steam to the reforming layer and the pure hydrogen layer so as to maintain a predetermined temperature at which hydrogen embrittlement of the hydrogen separation membrane can be avoided, and to purge residual gas in the reforming layer and the pure hydrogen layer. After supplying the required amount of water vapor, air is supplied.

In a third aspect based on the second aspect, means for detecting the presence or absence of hydrogen in the reformed layer and the pure hydrogen layer is provided, and the reformed layer and the pure hydrogen layer are supplied to the reformed layer and the pure hydrogen layer by supplying the steam. After detecting that the hydrogen was exhausted, the air supply was switched to.

A fourth invention is, in the second or third invention, for supplying the combustor formed in the membrane reactor and the combustion gas generated in the combustor to the reforming layer and the pure hydrogen layer. And a combustion gas line, and after supplying steam to the reforming layer and the pure hydrogen layer, supplying combustion gas and air.

A fifth aspect of the present invention is the fuel cell system according to the fourth aspect, further comprising means for supplying air to the combustion gas line, supplying steam to the reforming layer and the pure hydrogen layer, and then mixing the combustion gas and air. Supply gas, then air.

A sixth aspect of the present invention is the fuel cell system according to any one of the second to fifth aspects, wherein the reforming layer and the pure hydrogen layer are provided with a hydrogen partial pressure measuring device, and the temperature of the hydrogen separation membrane is increased while steam is being supplied. Is maintained above the temperature at which the hydrogen separation membrane is embrittled, which is determined by the pressure measured by the hydrogen partial pressure measuring device.

[0013]

According to the first aspect of the present invention, when the system is stopped, it is not necessary to perform the purging using the inert gas by performing the purging with the steam and the purging with the air. It is not necessary to provide a storage means, and the loading space efficiency can be improved when mounted on a vehicle.

According to the second aspect of the invention, when the residual gas such as hydrogen exists, the hydrogen separation membrane is maintained at a temperature at which hydrogen is not embrittled, so that hydrogen embrittlement of the hydrogen separation membrane can be prevented.

According to the third aspect of the present invention, the hydrogen detector or the means for detecting the hydrogen concentration is installed in the reforming layer and the pure hydrogen layer. It is possible to switch to the supply of water, and it is possible to shorten the time for purging the residual gas with water vapor and reduce the consumption of water vapor and fuel.

According to the fourth aspect of the invention, after purging the residual gas with steam, the moisture is purged with the high-temperature combustion gas, so that the time for purging the moisture can be shortened. Can be surely purged.

According to the fifth aspect of the present invention, by purging water with a mixed gas obtained by mixing combustion gas with air, it is possible to use a valve that does not have a high temperature specification and to reduce the cost of the valve. Moreover, since it is not necessary to supply extremely hot combustion gas to the reforming layer and the pure hydrogen layer, the durability of the reactor can be improved.

According to the sixth aspect of the present invention, by installing the hydrogen partial pressure measuring device in the reforming layer and the pure hydrogen layer, it is possible to set the temperature corresponding to the hydrogen partial pressure and supply the steam. Even if the difference becomes high, hydrogen embrittlement can be prevented.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 shows the configuration of the fuel reforming system according to the first embodiment.

A water evaporator 4 for evaporating water supplied by a water injector 7 and a gasoline evaporator 1 for evaporating gasoline supplied by a gasoline injector 2 in order to generate a fuel gas used for a fuel reforming reaction. Install. Water vapor generated in the water evaporator 4 is converted into gasoline vaporizer 1
Is supplied to the membrane reactor 22 for performing the reforming reaction through the steam supply line 24 after the fuel gas is generated by mixing with the steam of gasoline to generate the fuel gas.

The membrane reactor 22 to which the fuel gas is supplied is formed in a three-layer structure composed of the pure hydrogen layer 12, the reforming layer 3 and the combustor 8, and the fuel gas is located at the center of the three layers. Stratum 3
Supply to. In the reforming layer 3, a hydrogen-rich reformed gas is generated by a reforming reaction using the fuel gas. The hydrogen in the reformed gas passes through the hydrogen separation membrane 15 due to the hydrogen partial pressure difference between the reformed layer 3 and the pure hydrogen layer 12, and is supplied to the adjacent pure hydrogen layer 12. Hydrogen separated into the pure hydrogen layer 12 is supplied to the fuel cell 26, and electricity is generated by an electrochemical reaction.

On the other hand, in the combustor 8, combustion is performed by using the exhaust gas from the fuel cell 26 and the reforming layer 3 as fuel in order to generate heat necessary for the reforming reaction in the reforming layer 3. When the amount of heat required by the reforming layer 3 cannot be generated only by the exhaust gas, gasoline is supplied from the combustor injector 6 installed in the combustor 8 and burned. The high-temperature combustion gas generated by this combustion is supplied to the water evaporator 4, and heat exchange is performed to generate steam. A line for utilizing heat of the combustion gas downstream of the combustor 8 is referred to as a combustion gas line 17.

In such a fuel reforming system, when the system is stopped or restarted, the raw material gas containing no steam remaining in the steam supply line 24 is supplied to the reforming layer 3 so that carbon is deposited and reformed. The performance of the quality layer 3 may deteriorate. Further, when the temperature is low while the system is stopped, the hydrogen remaining in the reforming layer 3 and the pure hydrogen layer 12 may embrittle the hydrogen separation membrane 15. Therefore, it becomes necessary to purge the residual gas in the fuel reforming system.

Therefore, in the present embodiment, the residual gas is purged with water vapor, and then the water vapor is purged with air to remove the gas from the system.

For that purpose, a line for supplying steam to the reforming layer 3 and the pure hydrogen layer 12 and a line for supplying air are installed.

The above-mentioned steam supply line 24 is applied as a line for supplying steam to the reforming layer 3 when the system is stopped. By stopping the supply of gasoline by the gasoline injector 2 and operating only the water evaporator 4, only steam is supplied to the reforming layer 3. Further, an air purge line 23 for supplying air from the air compressor 14 to the pure hydrogen layer 12 via the air purge valve 13 is installed as a line for supplying air. This air purge valve 13
Above the air purge line 23 and the steam supply line 2
4 is provided with a communication line 25, and the line 2
A communication valve 11 is provided on the valve 5.

As a result, during operation of the system, the communication valve 11 is closed and the gasoline evaporator 1 and the water evaporator 4 are operated, whereby the fuel gas flowing through the steam supply line 24 can be supplied only to the reforming layer 3. . And when purging residual gas with steam when the system is stopped,
By stopping the supply of gasoline by the gasoline injector 2 while the water evaporator 4 is operating, closing the air purge valve 13 and opening the communication valve 11, steam can be supplied to the reforming layer 3 and the pure hydrogen layer 12. When purging water with air when the system is stopped, the supply of water by the water injector 7 is stopped, and the communication valve 11 and the air purge valve 13 are opened, so that the air compressor 14
Air from can be supplied to the reforming layer 3 and the pure hydrogen layer 12.

When purging or the like, the reforming layer 3 and the pure hydrogen layer 12 with hydrogen existing near the hydrogen separation membrane 15.
When the temperature decreases, the hydrogen separation membrane 15 becomes brittle. In order to prevent this, the temperature near the hydrogen separation membrane 15 (hydrogen separation membrane 1
5) The hydrogen separation membrane thermometer 5 for measuring T and the combustion gas thermometer 9 for measuring the temperature T of the combustion gas discharged from the combustor 8 are installed, and the measurement results are shown. Input to controller 10, water injector 7
The water supply amount (= steam generation amount) and the gasoline supply amount by the combustor injector 6 are controlled.

The control of the stop operation in the fuel reforming system executed by the controller 10 is shown in the flowchart of FIG.

When the stop operation is performed from the state where the output operation is performed (the air purge valve 13 and the communication valve 11 are closed), first, in step S1-1, the gasoline injector that supplies gasoline to the gasoline evaporator 1. Two
To stop. As a result, the mixed vapor (fuel gas) of gasoline and water was sent to the reforming layer 3 during the output operation, but only the water vapor from the water evaporator 4 is sent during the stop operation. Immediately after that, in step S1-2,
The communication valve 11 is opened to supply water vapor also to the pure hydrogen layer 12 so that H remaining in the reforming layer 3 and the pure hydrogen layer 12
Start purging of ₂ , CO, O ₂ and unreacted raw materials.

Next, in step S1-3, the hydrogen separation membrane temperature T and the combustion gas thermometer 9 are used.
And the combustion gas temperature T is measured. Measured temperature T,
Depending on T, the temperature of the combustion gas generated by the combustor 8 is adjusted by the combustor injector 6, and the amount and temperature of the steam generated by the combustion gas is adjusted by the water injector 7, and hydrogen separation during purging by steam is performed. The temperature of the film 15 is maintained at a temperature at which hydrogen embrittlement can be avoided.

At step S1-4, when a certain amount of water vapor is supplied to the reforming layer 3 and the pure hydrogen layer 12, H
_It is judged that ₂ , CO, O ₂ and unreacted fuel do not remain in these two layers. The amount of water vapor is obtained in advance by experiments or the like, and control is performed so that the flow rate will flow. Then, in step S1-5, the supply of water by the water injector 7 is stopped, and then the supply of gasoline by the combustor injector 6 is stopped. When the residual H ₂ in the two layers disappears, the hydrogen separation membrane 15 does not become embrittled by hydrogen, and therefore it is not necessary to keep the hydrogen separation membrane 15 at a high temperature. Therefore, the supply of water by the water injector 7 is stopped and the supply of steam is stopped. To stop.

Next, in step S1-6, the air purge valve 13 is opened, air is supplied from the air compressor 14 to the reforming layer 3 and the pure hydrogen layer 12, and the water content in these two layers is purged. As a result, the catalytic reaction can be instantaneously performed at the next startup, so that the startup can be performed in a short time.

After supplying the amount of air necessary for removing the moisture or after confirming that the moisture is sufficiently removed, the process proceeds to step S1-7, and the air purge valve 13
The communication valve 11 is closed and the supply of air to the reforming layer 3 and the pure hydrogen layer 12 is stopped. Finally, in step S1-8, the air compressor 14 is stopped and the operation ends.

When the stop command is issued in this way, for example, when the fuel cell 26 system is installed in a vehicle, if the ignition key is stopped, the supply of the raw material (gasoline) to the gasoline evaporator 1 is stopped. By continuing to supply only water, steam is supplied to the reforming layer 3 and the pure hydrogen layer 12.
At this time, since hydrogen exists in the reforming layer 3 and the pure hydrogen layer 12, the temperature and amount of water vapor are adjusted and supplied so that the temperatures of both layers are maintained at a temperature at which the hydrogen separation membrane 15 does not become hydrogen embrittlement.
As a result, H ₂ , CO, O ₂ , unreacted raw material in the reformed layer 3, or H ₂ in the pure hydrogen layer 12 can be purged without embrittlement of the hydrogen separation membrane 15. The purge time to previously obtain or H ₂ be allowed to flow how much water vapor in advance can be purged experimentally flows only that flow. Further, the water vapor remaining in the membrane reactor 22 at the time of system shutdown is adsorbed in the reforming layer 3 when cooled and condensed, and deteriorates the next startability. . This removes the water,
Next time, good startup will be possible. As described above, hydrogen embrittlement can be prevented and the purging can be performed without having a storage means for the inert gas such as N _2, so that a space-efficient fuel reforming system for vehicle can be realized.

The structure of the fuel reforming system in the second embodiment is shown in FIG.

In this embodiment, hydrogen concentration sensors 16 are provided in both the reforming layer 3 and the pure hydrogen layer 12 in the first embodiment, and the measured hydrogen concentration is input to the controller 10.
In the controller 10, the hydrogen concentration sensor 16 determines that the H _{2 in the} reforming layer 3 and the pure hydrogen layer 12 has disappeared, and switches from the steam-based purge to the air-based purge.

FIG. 5 shows a flow chart of the operation control during stop in the second embodiment.

Up to step S2-3, step S1-
As in the case up to 3, the reforming layer 3 and the pure hydrogen layer 12 are purged with water vapor at a temperature at which the hydrogen separation membrane 15 does not become hydrogen embrittlement. In step S2-4, the hydrogen concentration sensor 16 measures the hydrogen concentration of the reformed layer 3 and the pure hydrogen layer 12, and inputs the measured hydrogen concentration to the controller 10. Proceeding to step S2-5, the controller 10 determines from the measurement results whether H ₂ has been removed by purging. If H ₂ is not removed, the process returns to step S2-4 to continue purging with steam. When H ₂ is completely removed, the process proceeds to step S2-6, and the same control as step S1-5 and subsequent steps of the first embodiment is performed.

As described above, the purge flow rate of water vapor is not determined in advance, but it is confirmed by the hydrogen concentration sensor 16 that H ₂ is exhausted, and then the purge flow by air is performed to make the purge flow rate of water vapor accurate. The steam purging time can be shortened and the amount of fuel consumed for purging the steam can be reduced. When the purge amount is experimentally determined, the safety factor may be multiplied to determine the purge amount, and in that case, the steam may be wasted by the safety factor. In the present embodiment, since the residual H ₂ is exhausted and the purging of water vapor can be stopped, the amount of water vapor can be saved and the fuel consumption can be improved.

The structure of the fuel reforming system in the third embodiment is shown in FIG.

In this embodiment, in the second embodiment, the combustion gas generated in the combustor 8 when the system is stopped is used as the reforming layer 3
In order to supply both the pure hydrogen layer 12 and the pure hydrogen layer 12, the combustion gas line 17 on the downstream side of the combustor 8 is branched into a supply line to the water evaporator 4 and a line connected to the steam supply line 24.
Further, a water evaporator supply valve 19 is provided on the supply line to the water evaporator 4, and a combustion gas supply valve 18 is provided on the line connecting to the steam supply line 24.

In the fuel reforming system having such a structure, when the system is stopped, the combustion gas supply 18 valve is closed,
The water evaporator 4 is opened by opening the water evaporator supply valve 19.
Combustion gas can be supplied to the reforming layer 3 and the pure hydrogen layer 12 by supplying the combustion gas, closing the steam supply valve 19, and opening the combustion gas supply valve 18 and the communication valve 11.

Next, FIG. 7 shows a control flow of the stop operation in this embodiment.

After the stop operation is started, step S3-
Up to 5, the same control as that up to step S2-5 in the second embodiment is performed. When H ₂ is completely purged by the steam, the process proceeds to step S3-6, the water supply by the water injector 7 is stopped, and the generation of the steam is stopped. Subsequently, the combustion gas supply valve 18 is opened, while the water evaporator supply valve 19 is closed. Thereby, the high temperature combustion gas generated in the combustor 8 can be supplied to the reforming layer 3 and the pure hydrogen layer 12. Next, in step S3-7, the reforming layer 3 and the pure hydrogen layer 12 are dried by the high-temperature combustion gas to dry the reforming layer 3 and the pure hydrogen layer 12 in a shorter time than when air is used. be able to.

After the water in the reforming layer 3 and the pure hydrogen layer 12 is removed in step S3-8, the supply of gasoline by the combustion injector 6 is stopped and the supply of combustion gas is stopped. In step S3-9, the air purge valve 13 is opened, and the reforming layer 3 and the pure hydrogen layer 1 are removed from the air compressor 14.
2 is supplied with air and the combustion gas is purged. When the combustion gas is purged, the routine proceeds to step S3-10, the air purge valve 13 is closed, the combustion gas supply valve 18 and the communication valve 11 are closed, and then the routine proceeds to step S3-11, the air compressor 14 is stopped and the operation is terminated.

After the residual H ₂ purge with steam is completed, the combustion gas supply valve 18 is opened while the water evaporator supply valve 19 is closed to reform the combustion gas from the combustor 8. By sending it to the layer 3 and the pure hydrogen layer 12, the moisture remaining in both layers can be quickly purged to dry the inside of both layers, and the purge time can be shortened. Further, since the inside of the reformed layer 3 can be surely dried, the reforming reaction starts quickly at the next start-up, and good startability can be secured.

The structure of the fuel reforming system in the fourth embodiment is shown in FIG.

In this embodiment, in the third embodiment, one branched line of the combustion gas line 17 is connected not to the steam supply line 24 but to the air purge line 23 on the downstream side of the air purge valve 13. Further, a mixed gas supply valve 20 is provided in place of the combustion gas supply valve 18 on the air purge line 23 on the downstream side of the connection position of the combustion gas line 17 and the air purge line 23, and a communication line 25 with the air purge line 23 on the downstream side. Connect.

With such a structure, the combustion gas from the combustor 8 can be mixed with the air from the air compressor 14 and then supplied to the reforming layer 3 and the pure hydrogen layer 12.

The stopping procedure of this embodiment is shown in the flowchart of FIG. Up to step S4-5, the same control as up to step S3-5 of the third embodiment is performed.

When the removal of hydrogen in the reformed layer 3 and the pure hydrogen layer 12 is completed in step S4-5, step S4
Proceeding to -6, the supply of the water injector 7 is stopped and the air purge valve 13 is opened. Then, the mixed gas supply valve 20 is opened. As a result, the combustion gas and air are mixed in the air purge line 23, and the mixed gas supply valve 20
Reach Since the mixed gas at this time is air at room temperature, it is not as hot as the combustion gas, and the heat load given to the mixed gas supply valve 20 and the membrane reactor 22 can be reduced.

Next, in step S4-7, the modified layer 3
And after drying the water content of the pure hydrogen layer 12, step S
Proceeding to 4-8, the supply of gasoline by the combustor injector 6 is stopped, and the supply of the combustion mixed gas is stopped. Step
Proceeding to S4-9, the reforming layer 3 and the pure hydrogen layer 12 are purged from the air compressor 14 with only air. Then step S
In 4-10, the air purge valve 13 is closed, the mixed gas supply valve 20 and the communication valve 11 are closed, and finally, in step S4-11, the air compressor 14 is stopped and the operation is ended.

As described above, by mixing the combustion gas and the air to obtain the combustion mixed gas at a temperature at which the water content is purged, the mixed gas supply valve 20 is not limited to the high temperature specification, so that the cost can be reduced. . Further, since it is not necessary to supply an extremely hot combustion gas to the reforming layer 3 and the pure hydrogen layer 12, the heat load given to the membrane reactor 22 can be reduced and the durability can be improved.

The structure of the fuel reforming system in the fifth embodiment is shown in FIG.

In this embodiment, pressure sensors 21 are provided in the reforming layer 3 and the pure hydrogen layer 12 respectively in the fourth embodiment.

FIG. 11 shows a flowchart of the stopping procedure. In step S4-3 of the fourth embodiment,
In step S5-3 of the present embodiment, the hydrogen separation membrane temperature T is measured, the hydrogen partial pressure is calculated from the hydrogen concentration sensor 16 and the pressure gauge 21, and the combustion gas temperature T is maintained so that hydrogen embrittlement does not occur under the hydrogen partial pressure. Also, the water injector 7 is adjusted to control the hydrogen separation membrane temperature T.

FIG. 12 shows the relationship between the hydrogen embrittlement temperature of the hydrogen separation membrane 15 and the hydrogen partial pressure difference. As shown in FIG. 12, the smaller the partial pressure difference, the lower the maximum temperature at which hydrogen embrittlement occurs. Therefore, the pressure and hydrogen concentration of the reforming layer 3 and the pure hydrogen layer 12 are measured to calculate the respective hydrogen partial pressures, and the difference between them is used to determine the optimum temperature (the lowest temperature at which hydrogen embrittlement can be suppressed). By calculating and adjusting the combustion gas temperature T and the injector 7 so that the hydrogen separation membrane temperature T does not fall below the temperature at which the hydrogen separation membrane 15 becomes brittle, steam is supplied.

By controlling in this way, it is possible to prevent the water vapor temperature from being raised more than necessary, so that it is effective in improving fuel consumption.

It is needless to say that the present invention is not limited to the above embodiment, and various modifications can be made within the scope of the technical idea described in the claims.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a conventional fuel reforming system.

FIG. 2 is a configuration diagram of a fuel reforming system according to the first embodiment.

FIG. 3 is a flowchart of a stop operation in the fuel reforming system of the first embodiment.

FIG. 4 is a configuration diagram of a fuel reforming system according to a second embodiment.

FIG. 5 is a flowchart of a stop operation in the fuel reforming system of the second embodiment.

FIG. 6 is a configuration diagram of a fuel reforming system according to a third embodiment.

FIG. 7 is a flowchart of a stop operation in the fuel reforming system of the third embodiment.

FIG. 8 is a configuration diagram of a fuel reforming system according to a fourth embodiment.

FIG. 9 is a flowchart of a stop operation in the fuel reforming system of the fourth embodiment.

FIG. 10 is a configuration diagram of a fuel reforming system according to a fifth embodiment.

FIG. 11 is a flowchart of a stop operation in the fuel reforming system of the fifth embodiment.

FIG. 12 is a diagram showing a relationship between a temperature at which a hydrogen separation membrane is embrittled by hydrogen and hydrogen partial pressure.

[Explanation of symbols]

1 gasoline evaporator 3 Modified layer 4 water evaporator 5 Hydrogen separation membrane thermometer 8 Combustor 9 Combustion gas thermometer 11 Communication valve 12 Pure hydrogen layer 13 Air purge valve 15 Hydrogen separation membrane 16 Hydrogen concentration sensor 17 Combustion gas line 18 Combustion gas supply valve 20 Mixed gas supply valve 21 Pressure sensor 22 membrane reactor 23 Air purge line 24 Steam supply line 25 communication lines

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroshi Komatsu             Nissan, Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan             Inside the automobile corporation F term (reference) 4G040 EA03 EA06 EB11 EB33 EB43                       FA02 FC01 FE01                 5H027 AA02 BA01 BA20 KK42 MM08

Claims (6)

[Claims] 1. A water evaporator for producing steam, and a reformer for producing a hydrogen-rich reformed gas by a reforming reaction of fuel and water, wherein the water is fed to the reformer when the system is stopped. A fuel reforming system in which only steam generated by an evaporator is supplied, and after the steam generated by the water evaporator is supplied, air is supplied to the reformer. 2. The reformer is a membrane reactor composed of a reforming layer and a pure hydrogen layer which are adjacent to each other with at least the hydrogen separation membrane interposed therebetween. The steam is supplied so as to maintain a predetermined temperature at which hydrogen embrittlement of the hydrogen separation membrane can be avoided, and the amount of steam necessary for purging the residual gas in the reforming layer and the pure hydrogen layer is supplied, and then air is supplied. The fuel reforming system according to claim 1, which supplies the fuel. 3. A means for detecting the presence or absence of hydrogen in the reforming layer and the pure hydrogen layer is provided, and after detecting that the reforming layer and the pure hydrogen layer are depleted of hydrogen due to the supply of the steam. The fuel reforming system according to claim 2, wherein the fuel reforming system is switched to supply of air. 4. A reforming layer, comprising: a combustor formed in the membrane reactor; and a combustion gas line for supplying the combustion gas generated in the combustor to the reforming layer and the pure hydrogen layer. The fuel reforming system according to claim 2 or 3, wherein after supplying steam to the pure hydrogen layer, combustion gas is supplied and air is supplied. 5. A means for supplying air to the combustion gas line is provided, and after supplying steam to the reforming layer and the pure hydrogen layer, a mixed gas of combustion gas and air is supplied and then air is supplied. The fuel reforming system according to claim 4. 6. The hydrogen partial pressure measuring device is provided in the reforming layer and the pure hydrogen layer, and the temperature of the hydrogen separation membrane is determined from the pressure measured by the hydrogen partial pressure measuring device during supply of steam. The fuel reforming system according to any one of claims 2 to 5, which is maintained at a temperature at which the separation membrane becomes brittle or higher.