JP2001155747A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system for supplying hot water prepared by waste heat accompanying generation of electricity that decreases the time required for starting a secondary burner by inhibiting generation of NOx due to the burning of the secondary burner. SOLUTION: The discharged gas from the hydrogen electrode (3) of a fuel cell (1) is introduced into a secondary burner (70) upon starting the secondary burner (70). The discharged gas includes hydrogen, which contacts the catalyst of the secondary burner (70), fired to start the secondary burner (70). Meanwhile, an electric heater (26) is made conducting electric current to preheat the raw gas. Thereafter, the secondary burner (70) supplies city gas, continuing to heat water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell system having a fuel cell for generating power and supplying hot water.

[0002]

2. Description of the Related Art In general, a fuel cell is known to generate electricity by using hydrogen fed to a negative electrode as fuel and oxygen fed to a positive electrode as an oxidizing agent, and reacting them through an electrolyte. Hydrogen used in this fuel cell can be generated by reforming hydrocarbons, methanol, and the like.

Conventionally, a fuel cell system has been disclosed in
There is one disclosed in Japanese Patent No. 308230. The fuel cell system includes a fuel reformer that reforms hydrocarbons into hydrogen by a partial oxidation reaction in the presence of a catalyst, a CO converter that oxidizes CO generated during the reforming by a water gas shift reaction, And a selective oxidizer for selectively oxidizing the remaining CO.

[0004] Conventionally, a system has been proposed in which not only power generation by a fuel cell but also hot water supply using waste heat of the fuel cell. This is a so-called cogeneration system. In this type of system, water heated using waste heat of a fuel cell is stored in a tank or the like, and hot water in the tank is supplied according to demand. In addition, in order to meet the demand for hotter water supply, a reburning burner may be provided. That is, when the hot water in the tank is supplied, the tank is further heated by the additional firing burner, and the relatively high-temperature hot water is supplied.

[0005]

However, when a fuel such as city gas is simply burned in a reburning burner,
NOx is generated during combustion. Therefore, this detracts from the advantage of the fuel cell system that no harmful substances are generated. In order to solve this problem, a countermeasure for performing catalytic combustion using a catalyst in a reburning burner is considered. That is, the use of the catalyst makes it possible to lower the combustion temperature of the fuel, thereby suppressing the generation of NOx during combustion.

However, when a catalyst is used in a reburning burner, the following disadvantages occur. That is, when performing catalytic combustion, there is a predetermined ignition temperature corresponding to the type of fuel. Therefore, it is necessary to raise the temperature of the fuel to the ignition temperature in advance. In the case of a general hydrocarbon-based fuel, the ignition temperature is much higher than the normal temperature. For example, in the case of city gas, the ignition temperature is about 450 ° C. For this reason, unless the fuel is preheated to the ignition temperature, the fuel cannot be burned by the reburning burner, and there is a problem that it takes time to start the reburning burner.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to suppress the generation of NOx due to the combustion of a reburning burner in a fuel cell system which performs hot water supply using waste heat as well as power generation. While reducing the time required to start up the reburning burner.

[0008]

A first solution of the present invention is to generate electric power by a fuel cell (1) and a fuel cell (1).
The present invention is directed to a fuel cell system for supplying hot water using waste heat. Further, a reburning burner (70) for heating hot water for hot water supply heated by waste heat of the fuel cell (1) by catalytic combustion of fuel is provided, while the fuel cell (1) is operating. When starting up the post-burning burner (70), the fuel is supplied after the exhaust gas from the fuel cell (1) containing hydrogen is supplied to the post-burning burner (70) and burned.

According to a second aspect of the present invention, in the first aspect, the raw material gas containing the hydrocarbon-based raw fuel is preheated by the heat of combustion of the exhaust gas from the fuel cell containing hydrogen. A hydrogen generator (60) for generating hydrogen from a raw material gas preheated by the preheat combustor (19) and supplying the hydrogen to a fuel cell (1); Reburning burner (70) during operation of battery (1)
When starting, the auxiliary fuel is supplied to the preheated combustor (19) such that the preheated combustor (19) generates a predetermined amount of heat.

According to a third aspect of the present invention, in the first aspect, the raw material gas containing the hydrocarbon-based raw fuel is preheated by the combustion heat of the exhaust gas from the fuel cell (1) containing hydrogen. A hydrogen generator (60) for generating hydrogen from the raw material gas preheated by the preheat combustor (19) and supplying the hydrogen to the fuel cell (1); The generator (60) includes the fuel cell (1)
And an electric heater (26) for heating the raw material gas to a predetermined state at the time of startup of the fuel cell (1) and at the time of startup of the reburning burner (70) during operation of the fuel cell (1). .

According to a fourth aspect of the present invention, in the first aspect, the raw material gas containing the hydrocarbon-based raw fuel is preheated by the combustion heat of the exhaust gas from the fuel cell containing hydrogen. A hydrogen generator (60) for generating hydrogen from a raw material gas preheated by the preheat combustor (19) and supplying the hydrogen to a fuel cell (1); Reburning burner (70) during operation of battery (1)
When starting up, the hydrogen generator (60) increases the amount of hydrogen generated so that a predetermined amount of hydrogen is supplied to the preheating combustor (19) and the reburning burner (70).

According to a fifth aspect of the present invention, there is provided a fuel cell (1) and a preheating combustor (19) for preheating a raw material gas containing a hydrocarbon-based raw fuel by heat of combustion of the fuel, A hydrogen generator (60) that generates hydrogen from the raw material gas preheated by the preheat combustor (19) and supplies the hydrogen to the fuel cell (1)
The present invention is directed to a fuel cell system that includes the above, and performs power generation by the fuel cell (1) and hot water supply using waste heat of the fuel cell (1). Further, a reburning burner (70) for heating hot water for hot water supply heated by waste heat of the fuel cell (1) by catalytic combustion of fuel is provided, while the reburning burner (70) is stopped. In the above, the combustion exhaust gas from the preheated combustor (19) is supplied to the additional firing burner (70).

A sixth solution taken by the present invention comprises a fuel cell (1) and a fuel reformer (5) for producing hydrogen by a partial oxidation reaction from a raw material gas containing a hydrocarbon-based raw fuel. A hydrogen generator (60) for supplying the hydrogen generated by the fuel reformer (5) to the fuel cell (1), and generating electricity by the fuel cell (1); It is intended for a fuel cell system that supplies hot water using waste heat. A reburning burner (70) for heating hot water for hot water supply heated by waste heat of the fuel cell (1) by catalytic combustion of fuel is provided, while the fuel cell (1) is stopped. When starting up the reheating burner (70), start the fuel reformer (5) of the hydrogen generator (60) and supply hydrogen from the fuel reformer (5) to the reheating burner (70). The fuel is supplied after the combustion.

A seventh solution taken by the present invention is a fuel cell (1) and a hydrogen generator for generating hydrogen from a raw material gas containing a hydrocarbon-based raw fuel and supplying the hydrogen to the fuel cell (1). (60), the power generation by the fuel cell (1),
The present invention is directed to a fuel cell system that supplies hot water using waste heat of the fuel cell (1). A reburning burner (70) for heating hot water for hot water supply heated by waste heat of the fuel cell (1) by catalytic combustion of fuel is provided, while the fuel cell (1) is stopped. Reburning burner (7
In the case of starting 0), the fuel that is supplied after the hydrogen remaining in the hydrogen generator (60) is supplied to the post-burning burner (70) and burned.

According to an eighth aspect of the present invention, there is provided the desulfurizer (16) according to any one of the first to seventh aspects, further comprising a desulfurizer (16) for removing sulfur from the raw fuel. 1
The raw fuel desulfurized in 6) is supplied as fuel to the additional firing burner (70).

-Operation- In the first solution, power is generated by the fuel cell (1). At the same time, waste water from the fuel cell (1) is used to heat water to supply hot water. The additional firing burner (70) further heats the hot water for hot water supply heated by the waste heat of the fuel cell (1) by the combustion heat of the fuel. As a result, hot water having a relatively high temperature is generated. The additional firing burner (70) burns fuel using a catalyst. Therefore,
The combustion temperature of the fuel in the additional firing burner (70) is lower than in the case where no catalyst is used, and the amount of generated NOx is suppressed.

The fuel cell (1) receives the supply of hydrogen and oxygen to generate power, but the supplied hydrogen is not always completely consumed in the fuel cell (1). Therefore, during operation of the fuel cell (1), exhaust gas containing hydrogen is normally discharged from the fuel cell (1). Therefore, if the fuel cell (1) is in operation, the exhaust gas of the fuel cell (1) containing hydrogen is supplied to the post-burning burner (70) when the post-burning burner (70) is started. Here, the ignition temperature in the case of catalytic combustion of hydrogen is approximately at room temperature. Therefore,
Hydrogen in the exhaust gas supplied to the reburning burner (70) immediately ignites and burns upon contact with the catalyst.

By the combustion of the hydrogen, the temperature of the catalyst of the reburning burner (70) reaches the ignition temperature of a general hydrocarbon fuel as a fuel. After that, reburn the burner (7
At 0), general fuel such as city gas is supplied to continue heating the water. That is, hydrogen is supplied first when the reburning burner (70) is started, and the hydrogen is immediately ignited and the reburning burner (70) is started up in a short time.

In the second, third, and fourth solving means, a hydrogen generator (60) for generating hydrogen from a raw material gas and supplying it to the fuel cell (1) is provided. The hydrogen generator (60) is provided with a preheating combustor (19) for preheating the raw material gas before reforming. The preheat combustor (19) performs preheating of the raw material gas using exhaust gas from the fuel cell (1).
That is, the exhaust gas from the fuel cell (1) contains hydrogen, and the heat of combustion of the hydrogen heats the source gas.

On the other hand, when the reburning burner (70) is started, the exhaust gas from the fuel cell (1) is also supplied to the reburning burner (70). For this reason, the amount of hydrogen supplied to the preheating combustor (19) decreases, and the amount of preheating of the raw material gas may be insufficient. On the other hand, each of the above solutions takes the following countermeasures.

First, in a second solution, a predetermined auxiliary fuel is separately supplied to a preheating combustor (19), and a preheating amount for the raw material gas is secured by the combustion heat of the auxiliary fuel.

In the third solution, a predetermined electric heater (26) is energized to heat the source gas. As a result, a preheating amount for the source gas is secured, and the source gas is heated to a predetermined state. The electric heater (26) is also energized when the fuel cell (1) is started. That is, for a while after startup, the amount of exhaust gas from the fuel cell (1) is insufficient, and the preheating amount of the raw material gas cannot be secured only by the preheating combustor (19). Therefore, when starting up the fuel cell (1), the electric heater (26) is used to secure a preheating amount for the source gas.

In the fourth solution, the amount of hydrogen generated in the hydrogen generator (60) is increased. For example, the supply amount of the raw material gas to the hydrogen generation device (60) is increased to increase the generation amount of hydrogen. Since the hydrogen consumption in the fuel cell (1) is almost constant, the hydrogen generator (6
When the amount of hydrogen generated in 0) is increased, the amount of hydrogen contained in the exhaust gas from the fuel cell (1) increases. Therefore, even in a state where the exhaust gas of the fuel cell (1) is supplied to both the post-heating burner (70) and the preheating combustor (19), the hydrogen supply amount to the preheating combustor (19) is ensured.

In the fifth, sixth and seventh solving means, a hydrogen generator (60) for generating hydrogen from a raw material gas is provided. The fuel cell (1) is supplied with hydrogen from the hydrogen generator (60) to generate power. At the same time, waste water from the fuel cell (1) is used to heat water to supply hot water.

The additional firing burner (70) further heats hot water for hot water supply heated by the waste heat of the fuel cell (1) by the combustion heat of the fuel. As a result, hot water having a relatively high temperature is generated. The additional firing burner (70) burns fuel using a catalyst. Therefore, the combustion temperature of the fuel in the additional firing burner (70) is lower than in the case where no catalyst is used, and the amount of NOx generated is suppressed.

In a fifth solution, the hydrogen generator (60) is provided with a preheat combustor (19) for preheating the raw material gas before reforming. The preheat combustor (19) performs preheating of the raw material gas using exhaust gas from the fuel cell (1). Here, the fuel cell (1) performs power generation by receiving supply of hydrogen and oxygen, but the supplied hydrogen is not always completely consumed. Therefore, during operation of the fuel cell (1), exhaust gas containing hydrogen is normally discharged from the fuel cell (1). Therefore, the preheated combustor (19) uses the fuel cell (1)
The raw material gas is heated by burning the hydrogen that has not been consumed in the above.

According to this solution, the combustion exhaust gas discharged from the preheating combustor (19) is supplied to the stopped reburning burner (70). Therefore, even during the stop of the post-heating burner (70), the catalyst of the post-heating burner (70) is continuously heated by the combustion exhaust gas from the preheating combustor (19). That is, during the operation of the fuel cell (1), the catalyst of the reburning burner (70) is constantly heated, and is maintained at a temperature equal to or higher than the ignition temperature of general hydrocarbon fuel. Therefore, the supplied fuel is immediately ignited even when the reburning burner (70) is started up, and the reburning burner (70) is started up in a short time.

According to a sixth solution, a fuel reformer (5) is provided in the hydrogen generator (60). The fuel reformer (5) generates hydrogen from a raw material gas by a partial oxidation reaction. Here, the fuel reformer (5) generally has a smaller heat capacity than the refired burner (70) in view of its use and function. Further, the partial oxidation reaction is an exothermic reaction, and the start-up of the fuel reformer (5) is completed in a very short time due to the heat generated during the reaction.

Therefore, in this solution, the fuel cell (1)
When the reburning burner (70) is started while the hydrogen generator (60) is stopped while the fuel reformer (5) is stopped before starting the reburning burner (70)
Start up. In the fuel reformer (5), the start-up is completed in a short time to generate hydrogen, and the generated hydrogen is supplied to the reburning burner (70). As described above, in the post-burning burner (70), hydrogen contacts the catalyst and immediately ignites, and the re-burning burner (70) rises in a short time. That is, by starting the fuel reformer (5), which starts up in a very short time, prior to the reburning burner (70), the time required for starting up the reburning burner (70) is reduced.

Further, in the seventh solution, when the reburning burner (70) is started while the fuel cell (1) is stopped and the hydrogen generator (60) is stopped, hydrogen generation is performed. The hydrogen remaining in the device (60) is supplied to the reburning burner (70). Here, even when the hydrogen generator (60) is stopped, hydrogen remains in the piping system of the hydrogen generator (60). Therefore, additional firing burner (70)
At the time of start-up, the hydrogen stored in the hydrogen generator (60) is sent to the additional firing burner (70).

As described above, in the post-burning burner (70), the hydrogen is ignited immediately upon contact with the catalyst. And
After the catalyst temperature of the reburning burner (70) is increased by the combustion of hydrogen, general fuel such as city gas is supplied to the reburning burner (70) to continue heating the water. That is, hydrogen is supplied first when the reburning burner (70) is started, and the hydrogen is immediately ignited and the reburning burner (70) is started up in a short time.

In the eighth solution, a desulfurizer (16) is provided. The desulfurizer (16) removes the sulfur content from the raw fuel, and then supplies the raw fuel to the hydrogen generator (60). The raw fuel from which the sulfur content has been removed by the desulfurizer (16) is also supplied as fuel to the reburning burner (70). That is, in the post-fired burner (70), the raw fuel after desulfurization comes in contact with the catalyst and burns.

[0033]

Therefore, according to the present invention, even in the case of using combustion by a catalyst in the reburning burner (70), the start-up of the reburning burner (70) can be completed in a short time. That is, according to the first to fifth solving means, the reburning burner (7) is operated during the operation of the fuel cell (1).
0) The time required for starting can be reduced. Further, according to the sixth and seventh solutions, the time required for starting up the additional firing burner (70) while the fuel cell (1) is stopped can be reduced. For this reason, the time required for starting up the reburning burner (70) can be reduced while suppressing the amount of NOx generated by lowering the combustion temperature of the fuel in the reburning burner (70) by using the catalyst. As a result, the performance of the reburning burner (70) can be sufficiently exhibited while suppressing generation of harmful substances.

In particular, according to the second to fourth solutions, even in a state where the exhaust gas from the fuel cell (1) is supplied to the reburning burner (70), the preheating of the raw material gas in the hydrogen generator (60) is performed. Quantity can be secured. For this reason, the preheating of the source gas can be reliably performed, and the hydrogen generator (6
0) to ensure the production of hydrogen, fuel cell (1)
, A predetermined power generation amount can always be secured.

Further, according to the eighth solution, the raw fuel after desulfurization can be burned in the reburning burner (70). Therefore, it is possible to prevent so-called poisoning of the catalyst, in which the action of the catalyst is impaired by the sulfur compound. As a result, the performance of the additional firing burner (70) can be reliably exhibited, and the reliability can be improved.

[0036]

Embodiment 1 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

As shown in FIG. 1, a fuel cell system has a solid polymer electrolyte having an oxygen electrode (cathode) (2) as a catalyst electrode and a hydrogen electrode (anode) (3) also as a catalyst electrode. Type fuel cell (1) is provided. The oxygen electrode (2) of this fuel cell (1) has an air compressor (4)
Is connected by an air supply pipe (10), and a fuel reformer (5) is connected to the hydrogen electrode (3) by a reformed gas supply pipe (20).

The fuel cell (1) has a first water pipe (4
5) is connected. When water is circulated through the first water pipe (45), the water is heated by waste heat from the fuel cell (1). Hot water obtained by this waste heat is stored in a hot water storage tank (not shown) and is used for hot water supply as appropriate.

A first heat exchanger (6), a high-temperature CO converter (7), a second heat exchanger (8),
An O low-temperature converter (9), a third heat exchanger (11), a CO selective oxidation reactor (12), and a fourth heat exchanger (13) are provided in order toward the fuel cell (1). The CO high-temperature converter (7) is filled with a catalyst that exhibits an activity in a water gas shift reaction at a high temperature (around 400 ° C.). Also,
The CO low-temperature shifter (9) is filled with a catalyst that exhibits an activity in a water gas shift reaction at a low temperature (around 180 ° C.). The CO selective oxidation reactor (12) is filled with a catalyst exhibiting activity in the selective oxidation reaction of CO.

The upstream of the first heat exchanger (6) in the reformed gas supply pipe (20) is provided with the water supply pipe (40) for spraying water for obtaining water vapor for the water gas shift reaction.
A branch pipe (41) branching from is connected. At a portion of the reformed gas supply pipe (20) upstream of the third heat exchanger (11), a pipe branched from the air supply pipe (10) to supply air for the selective oxidation reactor (12) is provided. It is connected.

Then, the reformed gas supply pipe (20) and the fuel reformer (5), the first heat exchanger (6),
CO high-temperature shifter (7), second heat exchanger (8), CO low-temperature shifter (9), third heat exchanger (11), CO selective oxidation reactor (12), and fourth heat exchanger (13) ) Constitute a hydrogen generator (60).

[0042] The fuel reformer (5) is provided with a catalyst exhibiting activity with respect to the partial oxidation reaction. Rhodium and ruthenium are preferred as the catalyst metal. These catalyst metals may be supported on a support in the form of a simple metal, an alloy, or a compound, for example, an oxide. Also,
Two or more catalyst metals (for example, rhodium and ruthenium
Species) may be supported on the same carrier, or a mixture of two or more catalyst metals supported on separate carriers.

A raw fuel source (city gas) (14) is connected to the fuel reformer (5) by a raw gas supply pipe (30). This source gas supply pipe (30) has a gas compressor (1
5) and a desulfurizer (16) are provided in order toward the fuel reformer (5). A branch pipe (29) branched from the air supply pipe (10) is connected to the fuel reformer (5) to supply air for the partial oxidation reaction from the air compressor (4). The water tank (17) is connected to the water supply pipe (4) to spray and supply water to obtain steam for the water gas shift reaction.
0). The water supply pipe (40) is provided with a pump (18).

As the hydrocarbon-based raw fuel, methane, propane, naphtha, kerosene and the like can be used in addition to city gas such as natural gas (including LNG) and liquefied petroleum gas (LPG).

The raw gas consisting of the raw fuel from the raw fuel source (14), the air from the air compressor (4) and the water vapor from the water tank (17) is heated by the preheating combustor (19) and then heated. It is supplied to the reformer (5). An electric heater (26) for heating the raw material gas is provided between the preheat combustor (19) and the fuel reformer (5).

The preheating combustor (19) is provided with a combustion catalyst. This preheated combustor (19)
The exhaust gas from the fuel cell (1) supplied through the fuel cell (0) is burned, and the raw material gas is preheated and supplied to the fuel reformer (5).

The electric heater (26) is provided to secure a preheating amount of the raw material gas at the time of starting the fuel cell system. That is, for a while after the start-up, the amount of exhaust gas from the fuel cell (1) is insufficient, so that the preheating combustor (19)
With only this, the preheating of the source gas becomes insufficient. For this reason, at the time of startup, the amount of preheating of the raw material gas is ensured by using the electric heater (26).

The exhaust gas from the fuel cell (1) is sent to a preheating combustor (19) as a combustion gas. Specifically, the exhaust gas of the oxygen electrode (2) and the exhaust gas of the hydrogen electrode (3) are combined after passing through the steam separators (21, 22), and the exhaust gas pipe (5
0) to be sent to the preheating combustor (19). The exhaust gas from the oxygen electrode (2) is supplied to the first valve (23)
By opening, it can be discharged to the atmosphere as appropriate.

The exhaust gas pipe (50) is arranged so as to pass through the fourth heat exchanger (13), the third heat exchanger (11), and the second heat exchanger (8) in this order. Exhaust gas from the fuel cell (1) is heated by heat exchange with the reformed gas in each of the heat exchangers (11, 8) and supplied to the preheat combustor (19). Accordingly, the reformed gas from the fuel reformer (5) is conversely cooled in each heat exchanger (6, 8, 11) and sent to the fuel cell (1).

However, a second water pipe (46) is connected to the first heat exchanger (6). When water flows through the second water pipe (46), the reformed gas from the fuel reformer (5) and the water from the second water pipe (46) pass through the first heat exchanger (6). Heat exchange. And in the first heat exchanger (6),
While the reformed gas from the fuel reformer (5) is cooled, the water from the second water pipe (46) is heated to become hot water. First
The hot water obtained in the heat exchanger (6) is stored in a hot water storage tank (not shown) and is appropriately used for hot water supply.

The fuel cell system is provided with a post-burning burner (70) in order to meet a high-temperature hot water supply demand.
That is, when hot water in the hot water storage tank is supplied, the hot water is further heated by the additional firing burner (70), thereby supplying relatively high-temperature hot water. The reburning burner (70) is provided with a catalyst for combustion. The additional firing burner (70) reheats the water with the heat obtained by catalytic combustion of the supplied fuel.

The reburning burner (70) has a fuel supply pipe (5
5) is connected. The fuel supply pipe (55) is connected to the desulfurizer (1
The city gas from which the sulfur content has been removed in 6) and into which air from the branch pipe (29) of the air supply pipe (10) has been further mixed is supplied as a fuel to the reburning burner (70). This fuel supply pipe (5
5) is provided with a second valve (56). Also, the second valve (56) in the fuel supply pipe (55) and the reburning burner (7
An exhaust gas branch pipe (51) is connected between 0).
One end of the exhaust gas branch pipe (51) is connected to the exhaust gas pipe (50), and supplies the exhaust gas from the hydrogen electrode (3) of the fuel cell (1) to the additional combustion burner (70). The exhaust gas branch pipe (51) is provided with a third valve (52).

The controller (80) is provided in the fuel cell system. This controller (80)
Performs a predetermined control operation when the reburning burner (70) is started.

-Operation-The operation of the fuel cell system will be described.

<< Operation at the time of power generation >> In the above fuel cell system, when the fuel reformer (5) is started, the temperature of the fuel reformer (5) is low, so that the electric heater (26) is operated until the temperature of the catalyst becomes active. , For example, to about 460 ° C. After a while, the electric heater (26) is stopped, and the raw material gas (mixed gas of raw fuel, air and steam) is only preheated by the preheat combustor (19).

The source gas is H ₂ O The supply amounts of the raw fuel, air and steam are adjusted so that the / C ratio becomes 0.5 to 3 and the O ₂ / C ratio becomes 0.45 to 0.75.
In addition, the temperature of the reformed gas at the outlet (32) of the fuel reformer (5) is separately adjusted so as not to rise to 800 ° C. or more. The most preferred operating conditions are the above H ₂ O / C ratio is 1.
0, the O ₂ / C ratio is 0.52 to 0.60 (preferably 0.
56), the outlet gas temperature of the fuel reformer (5) is 720 ° C.,
The CO ₂ / CO ratio of the outlet gas of the fuel reformer (5) is 0.4.

The raw fuel (city gas) is desulfurized in a desulfurizer (16), and then is supplied with an electric heater (26) together with air and spray water.
Or it is heated by a preheating combustor (19). This heating turns the spray water into steam. The raw material gas consisting of raw fuel, air and water vapor is preheated, and then the fuel reformer (5)
Flows into

In the fuel reformer (5), the raw material gas comes into contact with the catalyst, and hydrogen is generated by a partial oxidation reaction. Further, since water vapor is contained in the raw material gas, hydrogen is also generated in the fuel reformer (5) by the water gas shift reaction. That is, in the fuel reformer (5), the partial oxidation reaction and the water gas shift reaction sequentially proceed.

Specifically, the above sequential reaction is represented by the following formula.

C _n H _m + (n / 2) O ₂ → nCO + (m / 2) H ₂ ... <1> CO + H ₂ O → CO ₂ + H _2. The desired hydrogen is obtained by this reaction, and simultaneously generated CO is oxidized by the water gas shift reaction of the formula (2), and hydrogen is also generated at that time. Thereby, C in the reformed gas
O concentration decreases. At this time, the addition of steam as a raw material gas does not greatly affect the fuel conversion rate in the partial oxidation reaction of the formula (1), but the conversion easily causes the water gas shift reaction of the formula (2). For this reason (equilibrium tends to the production side), the yield of hydrogen increases.

The reformed gas leaving the fuel reformer (5) is
The temperature is reduced to about 400 ° C. by the heat exchanger (6) and sent to the CO high-temperature converter (7), where the water gas shift reaction occurring on the catalyst further reduces the CO concentration. The temperature of the reformed gas exiting the high-temperature CO converter (7) is reduced to about 180 ° C. by the second heat exchanger (8),
The CO gas is sent to the low-temperature shift converter (9), and the water gas shift reaction occurring on the catalyst further reduces the CO concentration. C
The reformed gas that has exited the O low-temperature converter (9) is supplied to the third heat exchanger (1
The temperature is reduced to about 140 ° C. by 1) and sent to the CO selective oxidation reactor (12), where CO generated on the catalyst is generated.
The CO concentration is further reduced by the selective oxidation reaction of. C
The temperature of the reformed gas exiting the O selective oxidation reactor (12) is lowered to about 80 ° C. by the fourth heat exchanger (13) and enters the hydrogen electrode (3) of the fuel cell (1).

In the fuel cell (1), 2H ₂ → 4H ⁺ + 4e ^{− on} the electrode surface of the hydrogen electrode (3) and O 2 on the electrode surface of the oxygen electrode (2).
₂ ⁺ 4H + + 4e ^- → causing cell reaction 2H ₂ O. Therefore, the exhaust gas from the oxygen electrode (2) contains surplus air not used in the battery reaction and water vapor generated by the battery reaction. On the other hand, the exhaust gas from the hydrogen electrode (3) contains hydrogen not used for the battery reaction, unreformed raw fuel, air and water vapor.

The exhaust gas from the oxygen electrode (2) and the exhaust gas from the hydrogen electrode (3) merge through the steam separators (21, 22) to form a fourth heat exchanger (13) and a third heat exchanger (11). ) And the second heat exchanger (8)
Is heated by heat exchange and sent to the preheat combustor (19). Hydrogen and oxygen contained in the exhaust gas react by the action of the combustion catalyst in the preheating combustor (19), and the reaction heat serves as a preheating source for the raw material gas. The unreformed raw fuel contained in the exhaust gas also burns at the same time and becomes a preheating source.

<< Operation at Hot Water Supply >> In the fuel cell system,
During the power generation by the fuel cell (1), hot water is generated by flowing water through the first water pipe (45) and the second water pipe (46).
Then, the generated hot water is stored in a hot water storage tank (not shown), and hot water is appropriately supplied. When there is a demand for high-temperature hot water supply, the additional heating burner (70) is started up, and the hot water in the hot water storage tank is further heated by the additional heating burner (70) before hot water is supplied. When the additional firing burner (70) is started, a predetermined operation is performed based on the control operation of the controller (80).

First, an operation for starting up the reheating burner (70) during the operation of the fuel cell (1) will be described. First, the third valve (52) is opened according to an instruction from the controller (80). At this time, the second valve (56) is closed. In this state, the exhaust gas from the hydrogen electrode (3) of the fuel cell (1) is supplied to the reheating burner (70) through the exhaust gas branch pipe (51). As described above, the exhaust gas from the hydrogen electrode (3) contains hydrogen. In the case of catalytic combustion, hydrogen ignites at almost normal temperature. Therefore, the hydrogen in the exhaust gas supplied to the reburning burner (70) is immediately ignited by contact with the catalyst, and the reburning burner (70) is started up in a short time.

Here, when the third valve (52) is opened, the exhaust gas from the hydrogen electrode (3) is supplied to both the reburning burner (70) and the preheating combustor (19). For this reason, in the preheating combustor (19), the supply amount of exhaust gas serving as a preheating source decreases,
There is a possibility that the amount of preheating of the source gas may be insufficient. On the other hand, in the first embodiment, power is supplied to the electric heater (26) according to an instruction from the controller (80). Therefore, the amount of decrease in the amount of preheating due to the decrease in the amount of exhaust gas supplied is determined by the electric heater
And the amount of preheating for the source gas is ensured.

When the supply of the exhaust gas to the reburning burner (70) is continued for a predetermined time, the third valve (52) is closed and the second valve (56) is opened according to an instruction from the controller (80).
Further, the power supply to the electric heater (26) is stopped. At this point, the temperature of the catalyst of the post-fired burner (70) has reached the ignition temperature of city gas due to the combustion of hydrogen. Therefore, the city gas supplied to the reburning burner (70) through the fuel supply pipe (55) by opening the second valve (56) is immediately ignited, and the heating of the water by catalytic combustion is continued. Also,
The use of the catalyst lowers the combustion temperature of city gas, and suppresses the amount of NOx generated in the post-fired burner (70).

Next, an operation for starting up the reheating burner (70) while the fuel cell (1) is stopped will be described. While the fuel cell (1) is stopped, the hydrogen generator (60) including the fuel reformer (5) is also stopped. However, the reformed gas supply pipe (20) of the hydrogen generator (60) and the fuel reformer (5)
And the like, hydrogen is retained even during shutdown.
Therefore, in the first embodiment, the stopped hydrogen generator (6
The reburning burner (70) is started up using the hydrogen accumulated in 0).

Specifically, the third valve (52) is opened according to an instruction from the controller (80), and the gas compressor (1) is opened.
5) and the air compressor (4) are operated. At this time, the second
Valve (56) is closed. In this state, city gas, which is the raw fuel, mixed with air is supplied to the reformed gas supply pipe (2
0), whereby the reformed gas supply pipe (20)
Hydrogen accumulated in the water is pushed out. The extruded hydrogen passes through the fuel cell (1) and is supplied to the reburning burner (70) through the exhaust gas branch pipe (51). Then, in the reburning burner (70), the supplied hydrogen immediately ignites,
The additional firing burner (70) starts up in a short time.

When the supply of the exhaust gas to the reburning burner (70) is continued for a predetermined time, the third valve (52) is closed and the second valve (56) is opened according to an instruction from the controller (80).
At this point, the temperature of the catalyst of the post-fired burner (70) has reached the ignition temperature of city gas due to the combustion of hydrogen.
Accordingly, the city gas supplied to the refire burner (70) through the fuel supply pipe (55) by the solution of the second valve (56) is immediately ignited, and the heating of the water by the catalytic combustion is continued.

According to the first embodiment, the start-up of the reheating burner (70) can be completed in a short time even when the combustion by the catalyst is used in the reheating burner (70). Becomes possible. At that time, regardless of whether the fuel cell (1) is operating or not, the predetermined operation of the controller (80) can start up the reheating burner (70) in a short time. For this reason, the time required for starting up the additional firing burner (70) can be shortened while reducing the combustion temperature of the fuel in the additional firing burner (70) by using the catalyst and suppressing the generation amount of NOx. As a result, the performance of the reburning burner (70) can be sufficiently exhibited while suppressing generation of harmful substances.

When the reburning burner (70) is started, the electric heater (26) is energized.
For this reason, the amount of preheating for the raw material gas can always be ensured, and the generation of hydrogen in the hydrogen generator (60) can be reliably performed, and the predetermined power generation amount in the fuel cell (1) can always be ensured.

Further, city gas after desulfurization in the desulfurizer (16) is supplied to the reburning burner (70). Therefore, the town gas after desulfurization can be burned in the post-burning burner (70). The so-called poisoning of the catalyst, in which the action of the catalyst is impaired by the sulfur compound, can be prevented. As a result, the performance of the additional firing burner (70) can be reliably exhibited, and the reliability can be improved.

-Modification of Embodiment 1- In Embodiment 1 described above, when the reburning burner (70) is started during operation of the fuel cell (1), the electric heater (26) is energized to preheat the raw material gas. I try to secure the amount. On the other hand, by the following operation,
The amount of preheating for the source gas can be secured.

That is, the hydrogen electrode (3) is supplied to the reburning burner (70).
During the supply of the exhaust gas, the gas discharge amount of the gas compressor (15) and the air discharge amount of the air compressor (4) may be increased instead of energizing the electric heater (26). .
Thereby, the amount of the raw material gas supplied to the hydrogen generator (60) increases, and the amount of hydrogen generated in the hydrogen generator (60) increases. On the other hand, the hydrogen consumption in the fuel cell (1) is almost constant. For this reason, the hydrogen generator (6
When the amount of hydrogen generated in 0) is increased, the amount of hydrogen contained in the exhaust gas from the hydrogen electrode (3) increases.

Therefore, even in a state where the exhaust gas of the fuel cell (1) is supplied to both the post-heating burner (70) and the preheating combustor (19), the hydrogen supply amount to the preheating combustor (19) is ensured. That is, the amount of preheating of the raw material gas by the preheating combustor (19) is secured.

[0077]

Embodiment 2 Embodiment 2 of the present invention differs from Embodiment 1 in that a predetermined fuel branch pipe (57) is added and the control operation of the controller (80) is changed. Hereinafter, a configuration different from the first embodiment will be described.

As shown in FIG. 2, the fuel branch pipe (57)
The fuel supply pipe (55) branches off from the upstream of the second valve (56). The fuel branch pipe (57) is connected to the preheat combustor (19), and is provided with a fourth valve (58) in the middle thereof. The fuel branch pipe (57) supplies the city gas desulfurized by the desulfurizer (16) and further added with air to the preheat combustor (19).

The controller (80) according to the second embodiment is different from the controller (80) according to the first embodiment in the control operation for starting up the reheating burner (70) during the operation of the fuel cell (1). The following operation is performed instead of energizing the power supply. The control operation of the controller (80) is otherwise the same as in the first embodiment.

Specifically, with the third valve (52) opened, the controller (80) opens the fourth valve (58) to introduce the city gas into the preheated combustor (19). As described above, when the third valve (52) is opened, the exhaust gas from the hydrogen electrode (3) is reheated to the burner (70) and the preheated combustor (1).
Since it is supplied to both 9), the amount of preheating of the raw material gas in the preheating combustor (19) may be insufficient.

On the other hand, in the first embodiment, the fourth valve (58) is opened according to the instruction of the controller (80), and city gas is supplied to the preheating combustor (19). Therefore, the decrease in the preheat amount accompanying the decrease in the exhaust gas supply amount is compensated for by the combustion heat of the supplied city gas, and the preheat amount for the raw material gas is secured. In the preheating combustor (19), the city gas is burned using a catalyst.
There is no generation of Ox. That is, according to the second embodiment, the same effect as that of the first embodiment can be obtained.

[0082]

Embodiment 3 Embodiment 3 of the present invention differs from Embodiment 1 in that a predetermined flue gas pipe (53) is added and the control operation of the controller (80) is changed. Hereinafter, a configuration different from the first embodiment will be described.

As shown in FIG. 3, the flue gas pipe (53)
Has one end connected to the preheating combustor (19), and the other end connected to the additional firing burner (70). The combustion exhaust pipe (53) is provided with a fifth valve (54). The combustion exhaust gas pipe (53) supplies the combustion exhaust gas generated by the combustion in the preheat combustor (19) to the additional firing burner (70).

The controller (80) of the third embodiment differs from that of the first embodiment in the control operation for starting up the reheating burner (70) during the operation of the fuel cell (1). Performs the same operation.

When the fuel cell (1) is in operation and the reburning burner (70) is in a stopped state, the fifth valve (54) is opened by an instruction from the controller (80). At this time, the second
The valve (56) and the third valve (52) are closed. In this state, the high-temperature combustion exhaust gas generated in the preheat combustor (19) is introduced into the reheating burner (70) through the combustion exhaust gas pipe (53). Therefore, the catalyst of the reburning burner (70) is continuously heated by the combustion exhaust gas from the preheating combustor (19). In other words, during operation of the fuel cell (1), even when the reburning burner (70) is stopped, the reburning burner (7
The catalyst of 0) is constantly heated and maintained at or above the ignition temperature of city gas.

When the reburning burner (70) is to be started, the second valve (5) is instructed by the controller (80).
6) is opened and the third valve (52) is closed. In this state, city gas is supplied to the refire burner (70) through the fuel supply pipe (55). At this time, the catalyst of the reburning burner (70) is already at or above the ignition temperature of city gas. Therefore, even when the reburning burner (70) is started, the supplied city gas is immediately ignited, and the reburning burner (70) is started up in a short time. That is, according to the third embodiment,
The same effects as in the first embodiment can be obtained.

[0087]

Other Embodiments of the Invention Regarding each of the above embodiments, the control operation of the controller (80) when starting up the reheating burner (70) while the fuel cell (1) is stopped will be described.
The following may be performed.

That is, the hydrogen generator (60) is started up before the additional firing burner (70) is started, and the hydrogen generated by the hydrogen generator (60) is supplied to the additional firing burner (70) to start up. May be performed. Specifically, in the present modified example, when the reburning burner (70) is started while the fuel cell (1) is stopped, an instruction from the controller (80)
The gas compressor (15) and the air compressor (4) are operated to start the hydrogen generator (60).

Here, the fuel reformer (5) of the hydrogen generator (60) has an extremely small heat capacity as compared with the refired burner (70). In the fuel reformer (5), hydrogen is generated by a partial oxidation reaction. This partial oxidation reaction is an exothermic reaction, and the start-up of the fuel reformer (5) takes a very short time due to the heat generated during the reaction. Complete.

Therefore, in a modified example, a reburning burner (70)
Before starting, the hydrogen generator (60) is started to generate hydrogen. Then, by the instruction of the controller (80),
Open the third valve (52). The hydrogen generated by the hydrogen generator (60) passes through the fuel cell (1) and passes through the exhaust gas branch pipe (5
It is supplied to the reburning burner (70) through 1). In the refire burner (70), the hydrogen comes into contact with the catalyst and immediately ignites, and the refire burner (70) starts up in a short time. Thereafter, city gas is supplied to the additional firing burner (70) through the fuel supply pipe (55), and heating of the water is continued by burning the city gas. Therefore, by starting the fuel reformer (5) which starts up in an extremely short time prior to the reburning burner (70), the time required for starting up the reburning burner (70) is reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a fuel cell system according to a first embodiment.

FIG. 2 is a schematic configuration diagram of a fuel cell system according to Embodiment 2.

FIG. 3 is a schematic configuration diagram of a fuel cell system according to Embodiment 3.

[Explanation of symbols]

 (1) Fuel cell (5) Fuel reformer (16) Desulfurizer (19) Preheating combustor (26) Electric heater (60) Hydrogen generator (70) Reburning burner

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yasunori Okamoto 1304 Kanaoka-cho, Sakai-shi, Osaka Daikin Industries, Ltd. Sakai Seisakusho Kanaoka Factory F-term (reference) 5H027 AA06 BA01 BA09 BA10 BA16 BA17 CC06 DD06 MM01 MM13 MM21

Claims (8)

[Claims] A fuel cell system for generating electricity by a fuel cell (1) and supplying hot water using waste heat of the fuel cell (1), wherein the hot water heated by the waste heat of the fuel cell (1) is provided. A reburning burner (70) for heating hot water for use by catalytic combustion of fuel is provided, and when the reburning burner (70) is started during operation of the fuel cell (1), the reburning burner (70) is used. A fuel cell system that supplies fuel after supplying and burning the exhaust gas from hydrogen-containing fuel cell (1) to 70). 2. The fuel cell system according to claim 1, further comprising a preheat combustor (19) for preheating a raw material gas containing a hydrocarbon-based raw fuel by heat of combustion of exhaust gas from the fuel cell (1) containing hydrogen. A hydrogen generator (60) for generating hydrogen from the raw material gas preheated by the preheat combustor (19) and supplying the hydrogen to the fuel cell (1), while the fuel cell (1) is operating. A fuel cell system for supplying auxiliary fuel to the preheated combustor (19) such that the preheated combustor (19) generates a predetermined amount of heat when the reheating burner (70) is started. 3. The fuel cell system according to claim 1, further comprising a preheat combustor (19) for preheating the raw material gas containing the hydrocarbon-based raw fuel by the heat of combustion of the exhaust gas from the fuel cell (1) containing hydrogen. A hydrogen generator (60) that generates hydrogen from the raw material gas preheated by the preheat combustor (19) and supplies the generated hydrogen to the fuel cell (1); and the hydrogen generator (60) includes: An electric heater (26) is provided for heating the raw material gas to a predetermined state when the fuel cell (1) is started and when the reburning burner (70) is started while the fuel cell (1) is operating. Fuel cell system. 4. The fuel cell system according to claim 1, further comprising a preheat combustor (19) for preheating a raw material gas containing a hydrocarbon-based raw fuel by heat of combustion of exhaust gas from the fuel cell (1) containing hydrogen. A hydrogen generator (60) for generating hydrogen from the raw material gas preheated by the preheat combustor (19) and supplying the hydrogen to the fuel cell (1), and during operation of the fuel cell (1). When starting up the reburning burner (70), the hydrogen generator (60) adjusts the amount of hydrogen generated so that a predetermined amount of hydrogen is supplied to the preheating combustor (19) and the reburning burner (70). Increasing fuel cell system. 5. A fuel cell (1), and a preheat combustor (19) for preheating a raw material gas containing a hydrocarbon-based raw fuel by the heat of combustion of the fuel. A hydrogen generator (60) that generates hydrogen from the raw material gas and supplies the hydrogen to the fuel cell (1), using the power generation by the fuel cell (1) and the waste heat of the fuel cell (1). A fuel cell system for supplying hot water, wherein a reburning burner (70) for heating hot water for hot water supply heated by waste heat of the fuel cell (1) by catalytic combustion of fuel is provided. A fuel cell system that supplies the combustion exhaust gas from the preheated combustor (19) to the reburning burner (70) when the reburning burner (70) is stopped. 6. A fuel reformer (5) comprising: a fuel cell (1); and a fuel reformer (5) for generating hydrogen from a raw material gas containing a hydrocarbon-based raw fuel by a partial oxidation reaction. A hydrogen generator (60) for supplying the hydrogen generated in step (1) to the fuel cell (1), the fuel being used for power generation by the fuel cell (1) and hot water supply using waste heat of the fuel cell (1) A refueling burner (70) for heating hot water for hot water supply heated by waste heat of the fuel cell (1) by catalytic combustion of a fuel, wherein the fuel cell (1) When starting up the reheating burner (70) during the stop of the fuel, the fuel reformer (5) of the hydrogen generator (60) is started, and the fuel reformer (5) is supplied to the reheating burner (70). A fuel cell system that supplies fuel after supplying and burning hydrogen from a fuel cell. 7. A fuel cell comprising: a fuel cell (1); and a hydrogen generator (60) for generating hydrogen from a raw material gas containing a hydrocarbon-based raw fuel and supplying the hydrogen to the fuel cell (1). A fuel cell system for performing power generation by (1) and hot water supply using waste heat of the fuel cell (1), wherein hot water for hot water supply heated by waste heat of the fuel cell (1) is used as fuel. While a reburn burner (70) for heating by catalytic combustion is provided, when the reburn burner (70) is started while the fuel cell (1) is stopped, the above reburn burner (70) is provided. A fuel cell system that supplies fuel after supplying and burning hydrogen remaining in the hydrogen generator (60). 8. The fuel cell system according to claim 1, further comprising a desulfurizer (16) for removing a sulfur content from the raw fuel, wherein the raw fuel desulfurized by the desulfurizer (16) is used. Additional firing burner (70)
Fuel cell system for supplying fuel to the