JP2001176527A - Fuel cell system and fuel cell cogeneration system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system capable of recovering a large amount of exhaust heat. SOLUTION: This fuel cell system comprises a reform system for reforming a base fuel of a hydrocarbon system to produce a reformed gas including H2, a fuel cell 1 generating power by using H2 included in the reformed gas produced by the reforming system as the fuel, and a heat medium circuit 50 for recovering the exhaust heat produced in the reforming system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a fuel cell system.

[0002]

2. Description of the Related Art A fuel cell uses H2 gas fed to a hydrogen electrode.
Is generally known as a power generator in which oxygen is used as a fuel and O2 fed to an oxygen electrode is used as an oxidant, and these are reacted through an electrolyte. A fuel cell system including such a fuel cell is disclosed in Japanese Patent Application Laid-Open No. 10-308230.

In this fuel cell system, a hydrocarbon-based raw fuel is converted into H by a partial oxidation reaction represented by the following formula (1).
And a fuel reformer that reforms to CO and CO produced by the reforming by a water gas shift reaction represented by the following formula (2) to reduce the CO concentration and improve the yield of H2. A reforming system having a shift converter and a selective oxidation reactor for reducing remaining CO by oxidizing remaining CO by a selective oxidation reaction represented by the following formula (3) is provided. The raw fuel is reformed into H2 and sent to the hydrogen electrode. Air is fed into the oxygen electrode. Then, a cell reaction occurs in the fuel cell,
Electricity is generated.

CnHm + nH2O → nCO + (n + m / 2) H2 (1) CO + H2O → CO2 + H2 (2) CO + 1 / 2O2 → CO2 (3) By the way, the exhaust heat of the fuel cell system is used. There is a fuel cell cogeneration system (hereinafter referred to as "fuel cell cogeneration"). That is, the heat generated by the cell reaction occurring in the fuel cell is recovered as exhaust heat, and the recovered heat is used for raising the temperature of the water in the water heater.

[0005]

However, in the conventional fuel cell cogeneration, since the exhaust heat is recovered mainly from the fuel cell main body, the amount of heat that can be recovered is small. For example, the temperature of the water in the water heater only rises to about 60 ° C. There is a problem that you can not.

[0006] The present invention has been made in view of the above points, and an object of the present invention is to provide a fuel cell system capable of recovering a large amount of exhaust heat.

[0007]

SUMMARY OF THE INVENTION According to the present invention, waste heat in a so-called reforming system for reforming a hydrocarbon-based raw fuel to produce H2 is recovered by a heat medium circuit (50). It is.

Specifically, the invention of the present application provides a reforming system for reforming a hydrocarbon-based raw fuel to produce a reformed gas containing H2, and a reformed gas produced in the reforming system. H included
A fuel cell (1) that generates power using the fuel as a fuel and a heat medium circuit (50) that recovers exhaust heat generated in the reforming system.

According to the above configuration, a large amount of reaction heat released in the process of generating the reformed gas containing H2 from the raw fuel in the reforming system is recovered as exhaust heat by the heat medium circuit (50). Thus, a large amount of exhaust heat can be recovered as compared with the conventional case where exhaust heat is recovered only from the fuel cell. Then, by using this exhaust heat for the fuel cell cogeneration, it is possible to raise the temperature of the water in the water heater to 75 ° C. or more, for example. This waste heat can also be used for heating and evaporating water used for the water gas shift reaction in the reforming system. The heat medium circuit (50) includes a refrigerant circuit, a water circuit, and the like, and the heat medium includes water, antifreeze, and the like.

Here, the reforming system includes a fuel reformer (6) for producing a reformed gas containing H2 and CO from the raw fuel by a partial oxidation reaction, and a reformer (6). (7) for removing the CO contained in the reformed gas by a water gas shift reaction, and selection for further removing the residual CO contained in the reformed gas leaving the CO converter (7) by a CO selective oxidation reaction. If it has an oxidation reactor (8), the heat transfer medium circuit (50) is provided with the reformed gas after leaving the fuel reformer (6) and before entering the CO converter (7). Waste heat of the reformer gas after leaving the CO converter (7) and before entering the selective oxidation reactor (8), the selective oxidation reactor After leaving the exhaust heat and selective oxidation reactor (8) of (8) and the fuel cell (1)
What is necessary is just to be formed so as to collect at least one of the exhaust heat of the reformed gas before entering. Further, the CO transformer (7) may be configured in two stages of a high-temperature transformer and a low-temperature transformer, and the exhaust heat between the high-temperature transformer and the low-temperature transformer may be recovered. Further, the selective oxidation reactor (8) may be configured to be divided into two or more stages, and the exhaust heat between them may be recovered.

The first heat exchange for recovering the exhaust heat of the reformed gas after leaving the fuel reformer (6) and before entering the CO converter (7) to the heat medium circuit (50). Tableware (31)
The exhaust heat of the reformed gas after leaving the selective oxidation reactor (8) and before entering the fuel cell (1) is transferred to the heat medium circuit (5).
And a second heat exchanger (32) for recovery in 0). According to such a configuration, the temperature of the reformed gas at the inlet of the CO converter (7) and the temperature of the reformed gas at the inlet of the fuel cell (1) are each set to a predetermined temperature range by a simple method of providing a heat exchanger. Can be inside.

At least one of the temperature of the reformed gas at the inlet of the CO converter (7), the temperature of the CO converter (7) and the temperature of the reformed gas at the outlet of the CO converter (7) is a predetermined temperature. It may be configured to include a flow rate control unit that controls the flow rate of the heat medium flowing through the heat medium circuit (50) so as to fall within the range. According to this configuration, the amount of exhaust heat recovered can be controlled, and the temperature of the reformed gas entering the CO converter (7) can be adjusted even when the supply amount of the raw fuel fluctuates. (1) It is possible to stabilize the temperature and gas composition of the reformed gas entering. In this case, it is preferable that the flow rate of the heat medium is controlled by the rotation speed of the DC motor of the pump (71) driven by the DC motor. This is because control can be performed without using an expensive inverter. Further, it is preferable that the driving power of the DC motor is supplied from the power generated by the fuel cell (1). This is because the DC power generated by the fuel cell (1) can be used as it is, and there is no loss due to the orthogonal transform, which is efficient.

[0013] Further, the apparatus is configured to recover the heat of reaction of the water gas shift reaction occurring in the CO converter (7) and / or the reaction heat of the CO selective oxidation reaction occurring in the selective oxidation reactor (8) during the reaction. Is also good. According to such a configuration, the CO converter (7) and the selective oxidation reactor (8)
In each case, an exothermic reaction occurs, so that the reaction heat can be recovered as exhaust heat to stabilize each reaction. That is, for example, in the CO converter (7), there is a problem that as the reaction temperature increases, the CO conversion rate decreases and the CO concentration in the reformed gas exiting the reactor increases, and the selective oxidation reactor ( In 8), there is a problem that CH4 is generated by methanation when the reaction temperature increases. However, according to the above configuration, these problems are avoided.

Preferably, the heat medium circuit (50) is formed so that the heat medium flows in order from the one having the lowest exhaust heat temperature to recover the exhaust heat. This is because the exhaust heat recovery can be performed efficiently, and the temperature of the heat medium from which the exhaust heat has been recovered can be increased as compared with the related art.

In addition to the waste heat recovery in the reforming system,
It may be configured to recover exhaust heat of the fuel cell (1). According to this configuration, the exhaust heat recovery rate in the fuel cell system can be improved, and the temperature of the heat medium from which the exhaust heat has been recovered can be higher than in the related art.

In this case, the heat medium circuit (50)
May be configured such that the fuel cell (1) and the reforming system are connected in series, and the heat medium flows in the order of the fuel cell (1) and the reforming system to recover exhaust heat. This is because the exhaust heat is recovered in ascending order of the temperature, so that the exhaust heat can be efficiently recovered, and the temperature of the heat medium from which the exhaust heat has been recovered can be further increased.

Further, a configuration may be adopted in which a battery heat medium circuit (51) formed in a closed circuit and recovering exhaust heat of the fuel cell (1) is provided. According to this configuration, the sealed heat medium circulates in the heat medium circuit for battery (51), so that the scale does not adhere in the fuel cell (1) and the fuel cell (1) The service life is extended. In this case, the heat medium circuit for a battery (51)
Preferably, the heat medium is an antifreeze. This is because damage to the fuel cell (1) body due to freezing in winter is prevented.

When an off-gas burner (10) for burning the exhaust gas from the fuel cell (1) is provided, the exhaust heat of the off-gas burner (10) is recovered by a heat medium circuit (50). Is also good. According to such a configuration, the heat recovery rate of the fuel cell system is improved, and the temperature of the heat medium from which exhaust heat has been recovered can be higher than in the related art. In this case, the heat medium circuit (50)
Connects the reforming system and the off-gas burner (10) in series, and the heat medium is the reforming system and the off-gas burner (10).
It is preferable to be configured to circulate and recover exhaust heat in the following order. This is because the exhaust heat is recovered in ascending order of the temperature, so that the exhaust heat can be efficiently recovered, and the temperature of the heat medium from which the exhaust heat has been recovered can be further increased.

The heat medium circuit may be formed in a closed circuit. According to such a configuration, tap water or the like is not introduced into the heat medium circuit (50), heat exchange by silica and scale adhesion in the fuel cell (1) main body can be prevented, and the heat medium circuit (50) can be prevented. ) Will be stable over a long period of time. In this case, the heat medium circuit (50)
Preferably, the heat medium is an antifreeze. This is because damage to the heat medium circuit (50) due to freezing in winter is prevented.

The exhaust gas of the off-gas burner (10) may be recovered from exhaust heat. According to such a configuration, the condensed water can be recovered and used for supply to the reforming system.

In the fuel cell system for recovering the exhaust heat generated in the reforming system by the heat medium circuit (50), the temperature of the heat medium flowing through the heat medium circuit (50) is reduced to 75%.
It is also possible to raise the temperature to at least 0 ° C. (when the conventional fuel cell (1) is mainly used for exhaust heat recovery, this temperature becomes 6 ° C.).
It was about 0 ° C. ). As a result, the capacity of the hot water storage tank (60) required to store the same amount of heat can be reduced in size, and the fuel cell cogeneration can be used for adsorption-type air conditioning or the like.

Then, as a fuel cell cogeneration including a fuel cell system and a hot water storage tank (60) attached thereto, water in the hot water storage tank (60) is circulated through a heat medium circuit (50) as a heat medium and discharged. Heat is recovered, and the water is returned to the hot water storage tank (60) again so that the hot water storage tank (60)
That is configured to raise the temperature of water. According to such a configuration, since the water in the hot water storage tank (60) is used as the heat medium of the heat medium circuit (50), the system can be simplified as compared with the case where a separate heat medium is provided. it can. In addition, since the waste heat is directly recovered by the water in the hot water storage tank (60), the heat loss is reduced as compared with the case of indirect heat exchange. In this case, the water flows into the heat medium circuit (50) from the lower part of the hot water storage tank (60), and the water recovered by exhaust heat recovery by circulating through the heat medium circuit (50) returns to the upper part of the hot water storage tank (60). Is preferred. According to this configuration, a temperature stratification is formed in the hot water storage tank (60), so that the temperature of usable water in the upper part of the hot water storage tank (60) can be increased, and the lower part of the hot water storage tank (60) can be achieved. This means that low-temperature water is supplied to the circuit, so that the heat medium having a high heat absorption capacity circulates through the heat medium circuit (50), and the amount of heat recovered is further increased.

When the heat medium circuit (50) is formed in a closed circuit, heat exchange with the exhaust heat recovered by the heat medium circulating in the heat medium circuit (50) causes the hot water storage tank (60) to exchange heat. It may be configured to raise the temperature of water.

Further, when an off-gas burner (10) is provided, the exhaust heat of the exhaust gas of the off-gas burner (10) or the exhaust heat of the exhaust gas of the fuel cell (1) is stored in the hot water storage tank (6).
The water replenished in 0) may be recovered as a heat medium. According to such a configuration, the water (tap water) supplied to the hot water storage tank (60) is a low-temperature heat source,
Since the heat absorption capability is high, the amount of exhaust heat recovered can be increased, and the amount of condensed water that can be recovered can be increased accordingly.

[0025]

As described above, according to the invention of the present application, a large amount of reaction heat released in the reforming system is recovered as waste heat by the heat medium circuit (50), which is different from the conventional one. A large amount of exhaust heat can be recovered compared to a case where exhaust heat is recovered only from the fuel cell. Then, by using this exhaust heat for the fuel cell cogeneration, it is possible to raise the temperature of the water in the water heater to 75 ° C. or more, for example. This waste heat can also be used for heating and evaporating water used for the water gas shift reaction in the reforming system.

The reforming system comprises a fuel reformer (6),
If it has an O-transformer (7) and a selective oxidation reactor (8), after exiting the fuel reformer (6) and
After exiting the first heat exchanger (31) for recovering the exhaust heat of the reformed gas before entering the shifter (7) to the heat medium circuit (50) and the selective oxidation reactor (8), and Fuel cell (1)
And a second heat exchanger (32) for recovering the exhaust heat of the reformed gas before entering the heat medium circuit (50) by a simple method of providing a heat exchanger. The temperature of the reformed gas at the inlet of the CO converter (7) and the temperature of the reformed gas at the inlet of the fuel cell (1) can be respectively set within predetermined temperature ranges.

The temperature of the reformed gas at the inlet of the CO converter (7), the temperature of the CO converter (7), and the temperature of the CO converter (7)
By providing a flow control means for controlling the flow rate of the heat medium flowing through the heat medium circuit (50) so that at least one of the temperatures of the reformed gas at the outlet falls within a predetermined temperature range. In addition, the amount of exhaust heat recovered can be controlled, and the temperature of the reformed gas entering the CO converter (7) can be adjusted even when the supply amount of the raw fuel fluctuates, thereby entering the fuel cell (1). The temperature and gas composition of the reformed gas can be stabilized. Since the flow rate of the heat medium is controlled by the rotation speed of the DC motor of the pump (71) driven by the DC motor, it is not necessary to use an expensive inverter. Further, by supplying the driving power of the DC motor by the power generated by the fuel cell (1), the DC power generated by the fuel cell (1) can be used as it is, and there is no loss due to the orthogonal transformation. Be more efficient.

Also, by recovering the reaction heat of the water gas shift reaction occurring in the CO converter (7) and / or the reaction heat of the CO selective oxidation reaction occurring in the selective oxidation reactor (8) during the reaction. , The reaction heat in the CO converter (7) and the selective oxidation reactor (8) can be recovered as waste heat, and each reaction can be stabilized.

Further, the heat medium circuit (50) is formed so that the heat medium flows through the heat medium in order from the one having the lowest exhaust heat temperature to recover the exhaust heat. As a result, the temperature of the heat medium from which exhaust heat has been recovered can be made higher than in the past.

Further, in addition to the waste heat recovery in the reforming system,
By configuring so as to recover the exhaust heat of the fuel cell (1), it is possible to improve the exhaust heat recovery rate in the fuel cell system, and to increase the temperature of the heat medium from which the exhaust heat has been recovered as compared with the related art. be able to.

In this case, the fuel cell (1) and the reforming system are connected in series by the heat medium circuit (50), and the heat medium flows through the fuel cell (1) and the reforming system in this order, and is discharged. By configuring the heat medium circuit (50) to recover the heat, the waste heat is recovered in ascending order of the waste heat temperature, so that the waste heat can be efficiently recovered, and the recovered heat medium Can be further increased.

[0032] Further, by providing a structure having a battery heat medium circuit (51) formed in a closed circuit and recovering the exhaust heat of the fuel cell (1), the sealed heat medium can be used as the battery heat medium. Since it circulates in the circuit (51),
The scale does not adhere in the fuel cell (1), and the life of the fuel cell (1) can be extended. By using an antifreeze as the heat medium of the heat medium circuit for battery (51), it is possible to prevent the fuel cell (1) from being damaged by freezing in winter.

When an off-gas burner (10) for burning the exhaust gas of the fuel cell (1) is provided, the exhaust heat of the off-gas burner (10) is recovered by a heat medium circuit (50). In addition, the heat recovery rate of the fuel cell system can be improved, and the temperature of the heat medium from which exhaust heat has been recovered can be higher than in the related art. Then, the off-gas burner (10) and the reforming system are connected in series by a heat medium circuit (50), and the heat medium flows in the order of the off-gas burner (10) and the reforming system to recover exhaust heat. By configuring the heat medium circuit (50), waste heat recovery is performed in ascending order of the waste heat temperature, so that the waste heat recovery can be performed efficiently, and the temperature of the recovered heat medium can be further increased. Can be higher.

Further, by recovering the exhaust heat of the exhaust gas of the off-gas burner (10) or the exhaust heat of the exhaust gas of the fuel cell (1), condensed water can be recovered and supplied to the reforming system. Can be used for Then, the exhaust heat of the exhaust gas of the off-gas burner (10) or the exhaust heat of the exhaust gas of the fuel cell (1) is collected as water, which is supplied to a hot water storage tank (60) provided in the fuel cell system, as a heat medium. With this configuration, the amount of exhaust heat recovered can be increased, and the amount of condensed water that can be recovered can be increased accordingly.

Further, by employing a configuration in which the heat medium circuit is formed in a closed circuit, tap water or the like is not introduced into the heat medium circuit (50), and heat exchange with silica or the fuel cell (1) is prevented. 3.) It is possible to prevent scale adhesion in the main body and to stabilize the heat exchange characteristics of the heat medium circuit (50) for a long time. Then, the heat medium of the heat medium circuit (50) is frozen by using the antifreeze liquid as the heat medium of the heat medium circuit (50).
0) can be prevented.

Further, by increasing the temperature of the heat medium flowing through the heat medium circuit (50) to 75 ° C. or more, the capacity of the hot water storage tank (60) required to store the same amount of heat can be reduced in size. It can also be used as an air-conditioner of the adsorption type as a fuel cell cogeneration.

Then, as a fuel cell cogeneration including a fuel cell system and a hot water storage tank (60) attached thereto, water in the hot water storage tank (60) circulates through the heat medium circuit (50) as a heat medium and is discharged. Heat is recovered, and the water is returned to the hot water storage tank (60) again so that the hot water storage tank (60)
By increasing the temperature of the water, the water in the hot water storage tank (60) is used as the heat medium of the heat medium circuit (50). Can be simplified. Further, since the waste heat is directly recovered by the water in the hot water storage tank (60), the heat loss can be reduced as compared with the case of indirect heat exchange. And hot water storage tank (6
0) flows into the heat medium circuit (50) from the lower part, and circulates through the heat medium circuit (50) and recovers the waste heat.
By configuring so as to return to the upper part of the hot water storage tank (60), a temperature stratification is formed in the hot water storage tank (60). Since the low-temperature water is supplied to the circuit from the lower part of the hot water storage tank (60), the heat medium having a high heat absorption capacity circulates through the heat medium circuit (50),
The amount of heat recovered can be further increased.

When an off-gas burner (10) is provided, the exhaust heat of the exhaust gas of the off-gas burner (10) or the exhaust heat of the exhaust gas of the fuel cell (1) is stored in a hot water storage tank (60).
The water (tap water) supplied to the hot water storage tank (60) is a low-temperature heat source and has a high endothermic capacity, so that the amount of waste heat recovered is large. Accordingly, the amount of condensed water that can be recovered can be increased.

[0039]

Embodiments of the present invention will be described in detail with reference to the drawings. Embodiment 1 -Configuration of Fuel Cell System- FIG. 1 shows a schematic configuration of a fuel cell system according to Embodiment 1. This fuel cell 1 has an oxygen electrode (cathode) 2 which is a catalyst electrode and a hydrogen electrode (anode) which is also a catalyst electrode.
And 3 is a solid polymer membrane electrolyte type.

An air compressor 4 is connected to the oxygen electrode 2 by an air supply pipe 20.

Further, a fuel reformer 6 is connected to the hydrogen electrode 3 by a reformed gas supply pipe 24, and a hydrocarbon-based raw fuel source (city gas) is supplied to the fuel reformer 6. They are connected by a tube 25. In the reformed gas supply pipe 24, the first heat exchanger 31, the CO converter 7, the third heat exchanger 3
3. The selective oxidation reactor 8 and the second heat exchanger 32 are provided in order toward the fuel cell 1.

The fuel reformer 6 is filled with a catalyst (catalyst having Ru or Rh supported on Al 2 O 3) exhibiting an activity in the partial oxidation reaction, and the CO shift converter 7 is filled with a water gas shift reaction. (F)
_{e 2 O 3, Cr 2 O} 3, CuO, and ZnO, etc.) is filled, the selective oxidation reactor 8 is a catalyst (Ru, or Pt, which exhibits activity to the CO selective oxidation reaction is supported on Al2O3 or zeolite Catalyst).

Although not shown, the raw material gas supply pipe 25 has an air supply means for supplying air for the partial oxidation reaction and a steam supply means for supplying water vapor for the water gas shift reaction. An air supply means for supplying air for CO selective oxidation reaction is connected to a portion of the reformed gas supply pipe 24 upstream of the second heat exchanger 32.

An off-gas burner is provided downstream of the fuel cell 1 so that the exhaust gas of the oxygen electrode 2 and the exhaust gas of the hydrogen electrode 3 of the fuel cell 1 are guided to the off-gas burner 10 from the respective exhaust gas outlets. The tubing is connected.

The second heat exchanger 32 from the pump 71,
A water circuit 50 is provided as a heat medium circuit connected in series with the third heat exchanger 33 and the first heat exchanger 31 in this order, and water is used as the heat medium. Here, the pump 71 is driven by a DC motor, and the driving power is supplied from DC power before being generated by the fuel cell 1 and converted into AC power by the inverter 11.
The flow rate of the water flowing through the water circuit 50 by the pump 71 can be controlled by the rotation speed of the DC motor.

Further, the fuel cell system is provided with sensors for detecting a power generation amount, a fuel flow rate, an air flow rate, a reformed gas temperature at the inlet of the CO converter 7 and the like. Connected to —Operation of Fuel Cell System— The operation of the fuel cell system will be described.

The raw fuel is a fuel reformer 6 together with air and steam.
And a partial oxidation reaction of the raw fuel occurs on the catalyst of the fuel reformer 6 to generate H2 and CO (see the equation (1)). In addition, a water gas shift reaction occurs partially (see equation (2)).

The temperature of the reformed gas leaving the fuel reformer 6 is 80
The temperature is about 0 ° C., and the temperature is reduced to about 180 to 400 ° C. by the first heat exchanger 31. The reformed gas whose temperature has been lowered is sent to the CO converter 7, where the CO concentration is reduced by the water gas shift reaction occurring on the catalyst (see equation (2)).

The temperature of the reformed gas exiting the CO converter 7 is reduced to about 150 ° C. by the third heat exchanger 33.
The temperature-reduced reformed gas is sent to the selective oxidation reactor 8 where CO is oxidized by a CO selective oxidation reaction occurring on the catalyst.
The O concentration further decreases (see equation (3)).

The temperature of the reformed gas leaving the selective oxidation reactor 8 is reduced to about 80 ° C. by the second heat exchanger 32. The reformed gas whose temperature has been lowered is supplied to the hydrogen electrode 3 of the fuel cell 1.

On the other hand, the air sent from the air compressor 4 is
It is supplied to the oxygen electrode 2 as it is.

In the fuel cell 1, a cell reaction of 2H2 → 4H ++ 4e− on the electrode surface of the hydrogen electrode 3 and a cell reaction of O2 + 4H ++ 4e− → 2H2O on the electrode surface of the oxygen electrode 2 occur.
DC power is generated. The generated DC power is supplied to the inverter 11
Is converted into AC power. A part of the generated DC power is supplied as drive power for the pump 71 and the air compressor 4 provided in the water circuit 50.

At this time, excess air not used for the battery reaction as the exhaust gas of the oxygen electrode 2 and water vapor generated by the battery reaction are generated, while hydrogen not used for the battery reaction as the exhaust gas of the hydrogen electrode 3 is generated. , Carbon dioxide, nitrogen,
Unreformed raw fuel and steam are produced. Each exhaust gas from the oxygen electrode 2 and the hydrogen electrode 3 is supplied to an off-gas burner 10
It is burned and discharged by.

Then, the waste heat is recovered in the order of the second heat exchanger 32, the third heat exchanger 33, and the first heat exchanger 31 by the water flowing through the water circuit 50 by the pump 71.
At this time, the water returned through the water circuit 50 has a temperature of 75.
It is hot water of over ℃.

Further, the power generation amount detected by the sensor,
On the basis of the fuel flow rate, the air flow rate, the reformed gas temperature at the inlet of the CO converter 7 and the like, the control device operates the rotation speed of the DC motor of the pump 71 to adjust the flow rate of water flowing through the water circuit 50. Become. -Water Flow Control in Water Circuit 50- Next, a water flow control operation of the water circuit 50 in the exhaust heat recovery system of the present fuel cell system will be described with reference to FIGS. <First Control Flow> FIG. 2 shows a first control flow in the exhaust heat recovery system of the present fuel cell system. This first
The control flow is a control for controlling the temperature of the reformed gas entering the CO converter 7 within the range of the fixed upper and lower limit temperatures. That is, the control is performed during the steady operation of the fuel cell system.

First, in step ST1, the fuel cell system is started.

Then, from step ST2 to step ST
Water flow control up to 6 is executed.

That is, in step ST2, CO
The temperature of the reformed gas is detected by a temperature sensor provided at the inlet of the transformer 7, the temperature is read, and the process proceeds to step ST3. In step ST3, it is determined whether or not the temperature T of the reformed gas entering the CO converter 7 is higher than a set upper limit temperature Tmax. If T is higher than Tmax, the process proceeds to step ST4. In step ST4, the water circuit 50
Is increased, specifically, the electric power supplied from the fuel cell 1 to the pump 71 is increased,
The rotation speed of the motor of the pump 71 is increased. Therefore, the exhaust heat recovered in the first heat exchanger 31 increases, and the temperature of the reformed gas entering the CO converter 7 decreases. Then, the process returns to step ST2.

If T is equal to or smaller than Tmax in step ST3, the process proceeds to step ST5. In step ST5, it is determined whether or not the temperature T of the reformed gas entering the CO converter 7 is higher than a set lower limit temperature Tmin. If T is lower than Tmax, the process proceeds to step ST6. Step ST6
Then, the flow rate of the water flowing through the water circuit 50 is reduced. Specifically, the power supplied from the fuel cell 1 to the pump 71 is reduced, and the rotation speed of the motor of the pump 71 is reduced. Therefore, the exhaust heat recovered in the first heat exchanger 31 is reduced, and the temperature of the reformed gas entering the CO converter 7 is increased. Then, the process returns to step ST2.

If T is equal to or smaller than Tmax in step ST5, the process returns to step ST2. <Second Control Flow> FIG. 3 shows a second control flow in the exhaust heat recovery system of the present fuel cell system. This second
The control flow is a control for controlling the temperature of the reformed gas entering the CO converter 7 within a range of upper and lower limit temperatures set according to the power generation amount of the fuel cell 1, the fuel flow rate, the air flow rate, and the like. . That is, the control is performed at the time of the non-stationary operation of the fuel cell system in which the power generation amount fluctuates.

First, in step ST1 ', the fuel cell system is started.

Then, from step ST2 'to step S
Water flow control until T8 'is executed.

That is, in step ST2 ', the power generation amount, the fuel flow rate, the air flow rate, etc. are detected by the sensor.
After these are read, the process proceeds to step ST3 '.
In step ST3 ', C is determined based on the read calorific value and the like.
The upper limit temperature T'max and the lower limit temperature T'min of the temperature of the reformed gas entering the O shift converter 7 are determined, and the process proceeds to step ST4 '.

In step ST4 ', the CO transformer 7
The temperature of the reformed gas is detected by the temperature sensor provided at the inlet, and the temperature is read, and the process proceeds to step ST.
Go to 5 '. In step ST5 ', it is determined whether the temperature T' of the reformed gas entering the CO converter 7 is higher than the upper limit temperature T'max set in ST3 ', and if T' is higher than T'max. Proceed to step ST6 '. Step ST
In 6 ', the flow rate of the water flowing through the water circuit 50 is increased. Specifically, the power supplied from the fuel cell 1 to the pump 71 is increased, and the rotation speed of the motor of the pump 71 is increased. Therefore, the exhaust heat recovered in the first heat exchanger 31 increases, and the temperature of the reformed gas entering the CO converter 7 decreases. Then, the process returns to step ST2 '.

In step ST5 ', T' is changed to T'ma
If it is less than x, the process proceeds to step ST7 '. Step S
At T7 ', the temperature T of the reformed gas entering the CO converter 7 is S
It is determined whether or not the temperature is higher than the lower limit temperature T'min set in T3 ', and if T' is lower than T'max, step S is executed.
Proceed to T8 '. In step ST8 ′, the flow rate of the water flowing through the water circuit 50 is reduced. Specifically, the power supplied from the fuel cell 1 to the pump 71 is reduced, and the rotation speed of the motor of the pump 71 is reduced. . Therefore, the exhaust heat recovered in the first heat exchanger 31 is reduced, and the temperature of the reformed gas entering the CO converter 7 is increased. Then, the process returns to step ST2 '.

In step ST7 ', T' becomes T'ma
If it is less than x, the process returns to step ST2 '. -Operation / Effect- According to the fuel cell system having the above configuration, a large amount of reaction heat released in the process of generating the reformed gas containing H2 from the raw fuel in the reforming system is recovered by the water circuit 50 as exhaust heat. Thus, a large amount of exhaust heat can be recovered as compared with the conventional case where exhaust heat is recovered only from the fuel cell. Then, by using the exhaust heat for the fuel cell cogeneration, the temperature of the water in the water heater, which previously could only be raised to about 60 ° C., can be raised to 75 ° C. or more.
Further, it can be said that this waste heat is used for heating and vaporizing water supplied for the water gas shift reaction in the fuel reformer (6) or the CO shift converter (7).

The reformed gas exiting the fuel reformer 6 is the first gas.
Exhausted heat is recovered in the heat exchanger 31 to 180 to 400 ° C.
The reformed gas exiting the selective oxidation reactor 8 is the second
Exhausted heat is recovered in the heat exchanger 32 to about 80 ° C. That is, the temperature of the reformed gas entering each of the CO converter 7 and the fuel cell 1 is within a predetermined temperature range by a simple method of providing a heat exchanger.

By controlling the flow rate of water according to the flow shown in FIG. 2 or FIG. 3, the temperature of the reformed gas entering the CO converter 7 can be adjusted. However, the temperature and gas composition of the reformed gas entering the fuel cell 1 can be stabilized. Further, since the flow rate of water is controlled by the rotation speed of the DC motor of the pump 71 driven by the DC motor, it is not necessary to use an expensive inverter. Further, since the driving power of the DC motor is supplied by the power generated by the fuel cell 1, the DC power generated by the fuel cell 1 can be used as it is, and there is no loss due to the orthogonal transformation, which is efficient.

Further, since the exhaust heat recovery is performed in the order of the first heat exchanger 31, the third heat exchanger 33, and the second heat exchanger 32, that is, in order of the temperature, the efficiency of the exhaust heat recovery is good. Become.

Since the temperature of the water flowing through the water circuit 50 is 75 ° C. or higher as described above, the capacity of the hot water storage tank required to store the same amount of heat can be reduced. It can also be used for air conditioning of the adsorption type as a generation system. Embodiment 2 FIG. 4 shows a schematic configuration of a fuel cell system according to Embodiment 2. The same parts as those in the first embodiment are denoted by the same reference numerals.

In the fuel cell system according to Embodiment 2,
Heat exchange units 41 and 42 are provided inside the CO shift converter 7 and the selective oxidation reactor 8, respectively. The water circuit 50 is connected to the second heat exchanger 32 from the pump 71, the selective oxidation reactor 8, and the third heat exchange unit. , The inside of the CO transformer 7 and the first heat exchanger 3
1 are sequentially connected in series, and water is used as a heat medium. Therefore, the second heat exchanger 32, the inside of the selective oxidation reactor 8, the third heat exchanger 33, and the CO
Exhaust heat recovery is performed in the order of the inside and the first heat exchanger 31.
Other configurations are the same as those of the fuel cell system according to the first embodiment.

According to the fuel cell system having the above configuration, C
The reaction heat during the reaction of the water gas shift reaction occurring in the O shift converter 7 and the reaction heat during the reaction of the CO selective oxidation reaction occurring in the selective oxidation reactor 8 are both recovered as waste heat, thereby stabilizing each reaction. Can be planned. That is, for example, in the CO converter 7, a decrease in the CO conversion rate due to an increase in the reaction temperature is prevented. Further, in the selective oxidation reactor 8, CH increases due to an increase in the reaction temperature.
4 is prevented.

Other functions and effects are the same as those of the first embodiment. Third Embodiment FIG. 5 shows a schematic configuration of a fuel cell system according to a third embodiment. The same parts as those in the first embodiment are denoted by the same reference numerals.

In the fuel cell system according to Embodiment 3,
The heat exchange unit 43 is provided in the fuel cell 1, and the water circuit 50
The fuel cell 1, the second heat exchanger 32, the third heat exchanger 33, and the first heat exchanger 31 are sequentially connected in series, and water is used as a heat medium. Therefore, waste heat is recovered in the order of the fuel cell 1, the second heat exchanger 32, the third heat exchanger 33, and the first heat exchanger 31 by the water flowing through the water circuit 50 by the pump 71. Other configurations are the same as those of the fuel cell system according to the first embodiment.

According to the fuel cell system having the above-described structure, the exhaust heat of the fuel cell 1 can be recovered in addition to the recovery of the exhaust heat in the reforming system. Will be achieved.

Further, since the exhaust heat recovery is performed in the order of the fuel cell 1, the second heat exchanger 32, the third heat exchanger 33, and the first heat exchanger 31, that is, in order of decreasing temperature, the exhaust heat recovery is performed. The efficiency is good.

Other functions and effects are the same as those of the first embodiment. Embodiment 4 FIG. 6 shows a schematic configuration of a fuel cell system according to Embodiment 4. The same parts as those in the first embodiment are denoted by the same reference numerals.

In the fuel cell system according to Embodiment 4,
The off-gas burner 10 is provided with a heat exchange section 44, and the water circuit 50 includes a second heat exchanger 32, a third heat exchanger 33, and a first heat exchanger 33.
The heat exchanger 31 and the off-gas burner 10 are sequentially connected in series, and water is used as a heat medium. Therefore, the exhaust heat recovery is performed in the order of the second heat exchanger 32, the third heat exchanger 33, the first heat exchanger 31, and the off-gas burner 10 by the water flowing through the water circuit 50 by the pump 71. Other configurations are the same as those of the fuel cell system according to the first embodiment.

According to the fuel cell system having the above configuration, in addition to the recovery of exhaust heat in the reforming system, the off-gas burner 10
Waste heat can be recovered, and the heat recovery rate of the fuel cell system can be improved.

Further, the exhaust heat recovery is performed in the order of the second heat exchanger 32, the third heat exchanger 33, the first heat exchanger 31, and the off-gas burner 10, that is, in order of decreasing temperature.
Exhaust heat recovery efficiency is improved.

Other functions and effects are the same as those of the first embodiment. Embodiment 5 FIG. 7 shows a schematic configuration of a fuel cell system according to Embodiment 5. The same parts as those in Embodiments 4 and 5 are denoted by the same reference numerals.

In the fuel cell system according to Embodiment 5,
Heat exchange units 43 and 44 are provided in the fuel cell 1 and the off-gas burner 10, respectively.
2nd heat exchanger 32, 3rd heat exchanger 33, 1st heat exchanger 3
1 and the off-gas burner 10 are sequentially connected in series, and water is used as a heat medium. Therefore, the fuel cell 1, the second heat exchanger 32, and the third heat exchanger 3 are supplied by the water flowing through the water circuit 50 by the pump 71.
3. Exhaust heat recovery is performed in the order of the first heat exchanger 31 and the off-gas burner 10. That is, the present embodiment is a combination of the third embodiment and the fourth embodiment.

According to the fuel cell system having the above configuration, in addition to the recovery of the exhaust heat in the reforming system, the exhaust heat of the fuel cell 1 and the off-gas burner 10 can be recovered. Further improvement will be achieved.

Other functions and effects are the same as those of the third and fourth embodiments. <Fuel Cell Cogeneration 1> FIG.

In the fuel cell cogeneration 1, Embodiment 5
At the off-gas burner 10 to the fourth heat exchanger 34
The water circuit 5 returns to the first pump 71 via the
0 is formed. An antifreeze is used as a medium circulating in the water circuit 50. Then, water that has flowed out of the hot water storage tank 60 attached to the fuel cell system is sent to the fourth heat exchanger 34 by the second pump 72, and a closed circuit that returns to the hot water storage tank 60 is formed. Therefore, the antifreeze circulated through the water circuit 50 by the first pump 71 causes
Exhaust heat is recovered in the order of the fuel cell 1, the second heat exchanger 32, the third heat exchanger 33, the first heat exchanger 31, and the off-gas burner 10, and the recovered exhaust heat is circulated by the fourth heat exchanger 34. It is used for heating water in the hot water storage tank 60.

According to the fuel cell cogeneration 1 having the above configuration,
Since the water circuit 50 is a closed circuit, water in the hot water storage tank 60 is not introduced into the water circuit 50, and heat exchange with silica and scale adhesion in the fuel cell 1 main body can be prevented.
The heat exchange characteristics of the water circuit 50 will be stable for a long time.

Further, since the antifreeze liquid is used as a heat medium of the water circuit 50 forming the closed circuit, damage of the heat medium circuit 50 due to freezing in winter can be prevented. <Fuel Cell Cogeneration 2> FIG. 9 shows a schematic configuration of the fuel cell cogeneration 2. The same parts as those of the fuel cell cogeneration 1 are denoted by the same reference numerals.

In the fuel cell cogeneration system 2, in the fifth embodiment, the heat exchange unit 4 provided inside the hot water storage tank 60 attached to the fuel cell system is supplied from the off-gas burner 10.
5. The water circuit 50 returns to the pump 71 via the
Are formed. An antifreeze is used as a medium circulating in the water circuit 50. Therefore, the fuel cell 1,
2nd heat exchanger 32, 3rd heat exchanger 33, 1st heat exchanger 3
Exhaust heat recovery is performed in the order of 1 and the off-gas burner 10,
The recovered exhaust heat is used for heating water inside the hot water storage tank 60 by the heat exchange unit 45 provided inside the hot water storage tank 60. Other configurations are the same as the fuel cell cogeneration 1.

The operation and effects are described in the fuel cell cogeneration 1
Is the same as <Fuel Cell Cogeneration 3> FIG. The same parts as those of the fuel cell cogeneration 1 are denoted by the same reference numerals.

In the fuel cell cogeneration system 3, after exiting from the off-gas burner 10 in the fifth embodiment, the fuel cell cogeneration system enters the hot water storage tank 60 provided in the fuel cell system, and
The water circuit 50 is formed so as to form a closed circuit returning from 0 to the pump 71. That is, the water in the hot water storage tank 60 circulates in the water circuit 50. Here, water flows into the pump 71 from the lower part of the hot water storage tank 60, and the water circulated through the water circuit 50 returns to the upper part of the hot water storage tank 60. Further, a water supply pipe 26 for supplying tap water is connected to a lower portion of the hot water storage tank 60. Therefore, with the antifreeze circulated through the water circuit 50 by the pump 71, the exhaust heat is recovered in the order of the fuel cell 1, the second heat exchanger 32, the third heat exchanger 33, the first heat exchanger 31, and the off-gas burner 10, Hot water storage tank 60
Water is directly heated.

According to the fuel cell cogeneration 3, the water circuit 5
Since the water in the hot water storage tank 60 is used as the heat medium 0, the fuel cell cogeneration can be simplified as compared with the case where a separate heat medium is provided. Further, since the waste heat is directly recovered by the water in the hot water storage tank 60, the heat loss is reduced as compared with the case where the waste heat is indirectly recovered.

Further, the water circuit 5
0, and the water that has circulated through the water circuit 50 and recovered the exhaust heat returns to the upper part of the hot water storage tank 60.
Temperature stratification will be formed in the hot water storage tank 60,
The temperature of the available water in the upper part of the hot water storage tank 60 becomes higher. In addition, the water circuit 50
Is supplied to the water circuit, the heat medium having a high endothermic capacity circulates in the water circuit 50, and the amount of heat recovered is further increased. <Fuel Cell Cogeneration 4> FIG. 11 shows a schematic configuration of the fuel cell cogeneration 4. The same parts as those of the fuel cell cogeneration 1 are denoted by the same reference numerals.

In the fuel cell cogeneration 4, the fuel cell cogeneration 1 is provided with a battery water circuit 51 for recovering only the heat of the fuel cell 1. An antifreeze is used as a heat medium in the battery water circuit 51, and the third pump 7
3 allows the antifreeze to circulate the battery water circuit 51. The water circuit 50 and the battery water circuit 51 are connected via a fifth heat recovery unit 35. And
The waste heat is recovered in the order of the fifth heat exchanger 35, the second heat exchanger 32, the third heat exchanger 33, the first heat exchanger 31, and the off-gas burner 10 by the water flowing through the water circuit 50 by the first pump 71. Will be performed. Other configurations are the same as the fuel cell cogeneration 1.

According to the fuel cell cogeneration system 4 having the above configuration,
Since the sealed antifreeze circulates in the battery water circuit 51, the scale does not adhere in the fuel cell 1 and the life of the fuel cell 1 is extended.

Further, since the antifreeze is used as the heat medium of the battery water circuit 51, damage to the fuel cell 1 body due to freezing in winter can be prevented.

Other functions and effects are described in fuel cell cogeneration 1
Is the same as <Fuel Cell Cogeneration 5> FIG. The same parts as those of the fuel cell cogeneration 3 are denoted by the same reference numerals.

In the fuel cell cogeneration system 5, a fuel cell cogeneration system 3 is provided with a battery water circuit 51 for recovering only the heat of the fuel cell system 1. An antifreeze is used as a heat medium in the battery water circuit 51, and the third pump 7
3 allows the antifreeze to circulate the battery water circuit 51. The water circuit 50 and the battery water circuit 51 are connected via a fifth heat recovery device 35. And
The waste heat is recovered in the order of the fifth heat exchanger 35, the second heat exchanger 32, the third heat exchanger 33, the first heat exchanger 31, and the off-gas burner 10 by the water flowing through the water circuit 50 by the first pump 71. Will be done. Other configurations are the same as those of the fuel cell cogeneration 3.

Regarding the function and effect, see Fuel Cell Cogeneration 4
Is the same as <Fuel Cell Cogeneration 6> FIG. 13 shows a schematic configuration of the fuel cell cogeneration 6. The same parts as those of the fuel cell cogeneration 1 are denoted by the same reference numerals.

In the fuel cell cogeneration system 6 according to the fifth embodiment, the sixth heat exchanger 3 is provided downstream of the off-gas burner 10.
6 are provided. A hot water storage tank 60 is also provided in the fuel cell system, and a water supply pipe 26 for replenishing tap water is connected to a lower portion thereof via a sixth heat exchanger 36. Therefore, tap water is supplied to the sixth heat exchanger 36.
And recovers the latent heat to be supplied to the hot water storage tank 60. Further, the water supply pipe 26 is provided with a bypass 27 that does not pass through the sixth heat exchanger 36.

According to the fuel cell cogeneration 6 having the above configuration,
Condensed water can be recovered from the exhaust gas of the off-gas burner 10,
It can be used for feeding to the reforming system.

Further, the tap water supplied to the hot water storage tank 60 is a low-temperature heat source and has a high heat absorbing ability, so that the amount of exhaust heat recovered is large, and accordingly, a large amount of condensed water can be recovered.

[Brief description of the drawings]

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

FIG. 2 is a first control flow chart in the exhaust heat recovery system of the fuel cell system according to the first embodiment.

FIG. 3 shows a second control flow chart in the exhaust heat recovery system of the fuel cell system according to Embodiment 1.

FIG. 4 is a diagram showing a schematic configuration of a fuel cell system according to Embodiment 2.

FIG. 5 is a diagram showing a schematic configuration of a fuel cell system according to Embodiment 3.

FIG. 6 is a diagram showing a schematic configuration of a fuel cell system according to Embodiment 4.

FIG. 7 is a diagram showing a schematic configuration of a fuel cell system according to Embodiment 5.

FIG. 8 is a diagram showing a schematic configuration of a fuel cell cogeneration 1;

FIG. 9 is a diagram showing a schematic configuration of a fuel cell cogeneration 2.

FIG. 10 is a diagram showing a schematic configuration of a fuel cell cogeneration 3;

FIG. 11 is a diagram showing a schematic configuration of a fuel cell cogeneration 4;

FIG. 12 is a diagram showing a schematic configuration of a fuel cell cogeneration 5.

FIG. 13 is a diagram showing a schematic configuration of a fuel cell cogeneration 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fuel cell 2 Oxygen electrode 3 Hydrogen electrode 4 Air compressor 6 Fuel reformer 7 CO converter 8 Selective oxidation reactor 10 Off gas burner 11 Inverter 20 Air supply pipe 24 Reformed gas supply pipe 25 Source gas supply pipe 26 Water supply Pipe 27 Bypass 31 First heat exchanger 32 Second heat exchanger 33 Third heat exchanger 34 Fourth heat exchanger 35 Fifth heat exchanger 36 Sixth heat exchanger 41-45 Heat exchange unit 50 Water circuit 60 Hot water storage Tank 71-73 Pump

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[Procedure amendment]

[Submission date] December 17, 1999 (1999.12.
17)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction contents]

[Document Name] Statement

Patent application title: Fuel cell system and fuel cell cogeneration system

[Claims]

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a fuel cell system.

[0002]

2. Description of the Related Art Fuel cells use H ₂ gas fed to a hydrogen electrode.
Is generally known as a power generator in which O ₂ fed into the oxygen electrode is used as an oxidant and these are reacted through an electrolyte. A fuel cell system including such a fuel cell is disclosed in Japanese Patent Application Laid-Open No. 10-308230.

[0003] This fuel cell system comprises a fuel reformer for reforming a hydrocarbon-based raw fuel into H ₂ and CO by a partial oxidation reaction represented by the following equation (1), and a CO reformer produced during the reforming. Is oxidized by a water gas shift reaction shown in the following formula (2) to reduce the CO concentration and improve the yield of H ₂ , and further, the remaining CO is oxidized by a selective oxidation reaction shown in the following formula (3). And a selective oxidation reactor having a selective oxidation reactor for reducing residual CO,
The raw fuel supplied to the reforming system is reformed into H ₂ and sent to the hydrogen electrode. Air is fed into the oxygen electrode. Then, a cell reaction occurs in the fuel cell, and power is generated.

CnHm + nH ₂ O → nCO + (n + m / 2) H ₂ (1) CO + H ₂ O → CO ₂ + H ₂ (2) CO + 1 / 2O ₂ → CO ₂ (3) There is a fuel cell cogeneration system using the exhaust heat of such a fuel cell system (hereinafter referred to as "fuel cell cogeneration"). That is, the heat generated by the cell reaction occurring in the fuel cell is recovered as exhaust heat, and the recovered heat is used for raising the temperature of the water in the water heater.

[0005]

However, in the conventional fuel cell cogeneration system, since the exhaust heat is recovered mainly from the fuel cell main body, the amount of heat that can be recovered is small. For example, the temperature of the water in the water heater only rises to about 60 ° C. There is a problem that you can not.

[0006] The present invention has been made in view of the above points, and an object of the present invention is to provide a fuel cell system capable of recovering a large amount of exhaust heat.

[0007]

According to the present invention, waste heat in a so-called reforming system for reforming a hydrocarbon-based raw fuel to produce H ₂ is recovered by a heat medium circuit (50). Things.

Specifically, the invention of the present application relates to a reforming system for reforming a hydrocarbon-based raw fuel to produce a reformed gas containing H _2, and a reformed gas produced in the reforming system. H contained in
A fuel cell that generates ₂ as fuel (1), characterized in that it includes a heat medium circuit for recovering waste heat generated in the reforming system (50).

According to the above configuration, a large amount of reaction heat released in the process of generating the reformed gas containing H ₂ from the raw fuel in the reforming system is recovered by the heat medium circuit (50) as exhaust heat. As a result, a large amount of exhaust heat can be recovered as compared with the conventional case where exhaust heat is recovered only from the fuel cell. Then, by using this exhaust heat for the fuel cell cogeneration, it is possible to raise the temperature of the water in the water heater to 75 ° C. or more, for example. This waste heat can also be used for heating and evaporating water used for the water gas shift reaction in the reforming system. The heat medium circuit (50) includes a refrigerant circuit, a water circuit, and the like, and the heat medium includes water, antifreeze, and the like.

Here, the reforming system includes a fuel reformer (6) for generating a reformed gas containing H ₂ and CO from the raw fuel by a partial oxidation reaction, and a fuel reformer (6). A CO converter (7) for removing CO contained in the generated reformed gas by a water gas shift reaction, and a residual CO contained in the reformed gas exiting the CO converter (7) is further removed by a CO selective oxidation reaction. With the selective oxidation reactor (8), the heating medium circuit (50) is connected to the reforming unit after exiting the fuel reformer (6) and before entering the CO shift converter (7). Exhaust heat of gas, exhaust heat of CO converter (7), exhaust heat of reformed gas after leaving CO converter (7) and before entering selective oxidation reactor (8), selective oxidation reaction Waste heat of the reactor (8) and after exiting the selective oxidation reactor (8) and the fuel cell (1)
What is necessary is just to be formed so as to collect at least one of the exhaust heat of the reformed gas before entering. Further, the CO transformer (7) may be configured in two stages of a high-temperature transformer and a low-temperature transformer, and the exhaust heat between the high-temperature transformer and the low-temperature transformer may be recovered. Further, the selective oxidation reactor (8) may be configured to be divided into two or more stages, and the exhaust heat between them may be recovered.

The first heat exchange for recovering the exhaust heat of the reformed gas after leaving the fuel reformer (6) and before entering the CO converter (7) to the heat medium circuit (50). Tableware (31)
The exhaust heat of the reformed gas after leaving the selective oxidation reactor (8) and before entering the fuel cell (1) is transferred to the heat medium circuit (5).
And a second heat exchanger (32) for recovery in 0). According to such a configuration, the temperature of the reformed gas at the inlet of the CO converter (7) and the temperature of the reformed gas at the inlet of the fuel cell (1) are each set to a predetermined temperature range by a simple method of providing a heat exchanger. Can be inside.

At least one of the temperature of the reformed gas at the inlet of the CO converter (7), the temperature of the CO converter (7) and the temperature of the reformed gas at the outlet of the CO converter (7) is a predetermined temperature. It may be configured to include a flow rate control unit that controls the flow rate of the heat medium flowing through the heat medium circuit (50) so as to fall within the range. According to this configuration, the amount of exhaust heat recovered can be controlled, and the temperature of the reformed gas entering the CO converter (7) can be adjusted even when the supply amount of the raw fuel fluctuates. (1) It is possible to stabilize the temperature and gas composition of the reformed gas entering. In this case, it is preferable that the flow rate of the heat medium is controlled by the rotation speed of the DC motor of the pump (71) driven by the DC motor. This is because control can be performed without using an expensive inverter. Further, it is preferable that the driving power of the DC motor is supplied from the power generated by the fuel cell (1). This is because the DC power generated by the fuel cell (1) can be used as it is, and there is no loss due to the orthogonal transform, which is efficient.

[0013] Further, the apparatus is configured to recover the heat of reaction of the water gas shift reaction occurring in the CO converter (7) and / or the reaction heat of the CO selective oxidation reaction occurring in the selective oxidation reactor (8) during the reaction. Is also good. According to such a configuration, the CO converter (7) and the selective oxidation reactor (8)
In each case, an exothermic reaction occurs, so that the reaction heat can be recovered as exhaust heat to stabilize each reaction. That is, for example, in the CO converter (7), there is a problem that as the reaction temperature increases, the CO conversion rate decreases and the CO concentration in the reformed gas exiting the reactor increases, and the selective oxidation reactor ( In 8), there is a problem that CH ₄ is generated by methanation when the reaction temperature increases. However, according to the above configuration, these problems are avoided.

Preferably, the heat medium circuit (50) is formed so that the heat medium flows in order from the one having the lowest exhaust heat temperature to recover the exhaust heat. This is because the exhaust heat recovery can be performed efficiently, and the temperature of the heat medium from which the exhaust heat has been recovered can be increased as compared with the related art.

In addition to the waste heat recovery in the reforming system,
It may be configured to recover exhaust heat of the fuel cell (1). According to this configuration, the exhaust heat recovery rate in the fuel cell system can be improved, and the temperature of the heat medium from which the exhaust heat has been recovered can be higher than in the related art.

In this case, the heat medium circuit (50)
May be configured such that the fuel cell (1) and the reforming system are connected in series, and the heat medium flows in the order of the fuel cell (1) and the reforming system to recover exhaust heat. This is because the exhaust heat is recovered in ascending order of the temperature, so that the exhaust heat can be efficiently recovered, and the temperature of the heat medium from which the exhaust heat has been recovered can be further increased.

Further, a configuration may be adopted in which a battery heat medium circuit (51) formed in a closed circuit and recovering exhaust heat of the fuel cell (1) is provided. According to this configuration, the sealed heat medium circulates in the heat medium circuit for battery (51), so that the scale does not adhere in the fuel cell (1) and the fuel cell (1) The service life is extended. In this case, the heat medium circuit for a battery (51)
Preferably, the heat medium is an antifreeze. This is because damage to the fuel cell (1) body due to freezing in winter is prevented.

When an off-gas burner (10) for burning the exhaust gas from the fuel cell (1) is provided, the exhaust heat of the off-gas burner (10) is recovered by a heat medium circuit (50). Is also good. According to such a configuration, the heat recovery rate of the fuel cell system is improved, and the temperature of the heat medium from which exhaust heat has been recovered can be higher than in the related art. In this case, the heat medium circuit (50)
Connects the reforming system and the off-gas burner (10) in series, and the heat medium is the reforming system and the off-gas burner (10).
It is preferable to be configured to circulate and recover exhaust heat in the following order. This is because the exhaust heat is recovered in ascending order of the temperature, so that the exhaust heat can be efficiently recovered, and the temperature of the heat medium from which the exhaust heat has been recovered can be further increased.

The heat medium circuit may be formed in a closed circuit. According to such a configuration, tap water or the like is not introduced into the heat medium circuit (50), heat exchange by silica and scale adhesion in the fuel cell (1) main body can be prevented, and the heat medium circuit (50) can be prevented. ) Will be stable over a long period of time. In this case, the heat medium circuit (50)
Preferably, the heat medium is an antifreeze. This is because damage to the heat medium circuit (50) due to freezing in winter is prevented.

The exhaust gas of the off-gas burner (10) may be recovered from exhaust heat. According to such a configuration, the condensed water can be recovered and used for supply to the reforming system.

In the fuel cell system for recovering the exhaust heat generated in the reforming system by the heat medium circuit (50), the temperature of the heat medium flowing through the heat medium circuit (50) is reduced to 75%.
It is also possible to raise the temperature to at least 0 ° C. (when the conventional fuel cell (1) is mainly used for exhaust heat recovery, this temperature becomes 6 ° C.).
It was about 0 ° C. ). As a result, the capacity of the hot water storage tank (60) required to store the same amount of heat can be reduced in size, and the fuel cell cogeneration can be used for adsorption-type air conditioning or the like.

Then, as a fuel cell cogeneration including a fuel cell system and a hot water storage tank (60) attached thereto, water in the hot water storage tank (60) is circulated through a heat medium circuit (50) as a heat medium and discharged. Heat is recovered, and the water is returned to the hot water storage tank (60) again so that the hot water storage tank (60)
That is configured to raise the temperature of water. According to such a configuration, since the water in the hot water storage tank (60) is used as the heat medium of the heat medium circuit (50), the system can be simplified as compared with the case where a separate heat medium is provided. it can. In addition, since the waste heat is directly recovered by the water in the hot water storage tank (60), the heat loss is reduced as compared with the case of indirect heat exchange. In this case, the water flows into the heat medium circuit (50) from the lower part of the hot water storage tank (60), and the water recovered by exhaust heat recovery by circulating through the heat medium circuit (50) returns to the upper part of the hot water storage tank (60). Is preferred. According to this configuration, a temperature stratification is formed in the hot water storage tank (60), so that the temperature of usable water in the upper part of the hot water storage tank (60) can be increased, and the lower part of the hot water storage tank (60) can be achieved. This means that low-temperature water is supplied to the circuit, so that the heat medium having a high heat absorption capacity circulates through the heat medium circuit (50), and the amount of heat recovered is further increased.

When the heat medium circuit (50) is formed in a closed circuit, heat exchange with the exhaust heat recovered by the heat medium circulating in the heat medium circuit (50) causes the hot water storage tank (60) to exchange heat. It may be configured to raise the temperature of water.

Further, when an off-gas burner (10) is provided, the exhaust heat of the exhaust gas of the off-gas burner (10) or the exhaust heat of the exhaust gas of the fuel cell (1) is stored in the hot water storage tank (6).
The water replenished in 0) may be recovered as a heat medium. According to such a configuration, the water (tap water) supplied to the hot water storage tank (60) is a low-temperature heat source,
Since the heat absorption capability is high, the amount of exhaust heat recovered can be increased, and the amount of condensed water that can be recovered can be increased accordingly.

[0025]

As described above, according to the invention of the present application, a large amount of reaction heat released in the reforming system is recovered as waste heat by the heat medium circuit (50), which is different from the conventional one. A large amount of exhaust heat can be recovered compared to a case where exhaust heat is recovered only from the fuel cell. Then, by using this exhaust heat for the fuel cell cogeneration, it is possible to raise the temperature of the water in the water heater to 75 ° C. or more, for example. This waste heat can also be used for heating and evaporating water used for the water gas shift reaction in the reforming system.

The reforming system comprises a fuel reformer (6),
If it has an O-transformer (7) and a selective oxidation reactor (8), after exiting the fuel reformer (6) and
After exiting the first heat exchanger (31) for recovering the exhaust heat of the reformed gas before entering the shifter (7) to the heat medium circuit (50) and the selective oxidation reactor (8), and Fuel cell (1)
And a second heat exchanger (32) for recovering the exhaust heat of the reformed gas before entering the heat medium circuit (50) by a simple method of providing a heat exchanger. The temperature of the reformed gas at the inlet of the CO converter (7) and the temperature of the reformed gas at the inlet of the fuel cell (1) can be respectively set within predetermined temperature ranges.

The temperature of the reformed gas at the inlet of the CO converter (7), the temperature of the CO converter (7), and the temperature of the CO converter (7)
By providing a flow control means for controlling the flow rate of the heat medium flowing through the heat medium circuit (50) so that at least one of the temperatures of the reformed gas at the outlet falls within a predetermined temperature range. In addition, the amount of exhaust heat recovered can be controlled, and the temperature of the reformed gas entering the CO converter (7) can be adjusted even when the supply amount of the raw fuel fluctuates, thereby entering the fuel cell (1). The temperature and gas composition of the reformed gas can be stabilized. Since the flow rate of the heat medium is controlled by the rotation speed of the DC motor of the pump (71) driven by the DC motor, it is not necessary to use an expensive inverter. Further, by supplying the driving power of the DC motor by the power generated by the fuel cell (1), the DC power generated by the fuel cell (1) can be used as it is, and there is no loss due to the orthogonal transformation. Be more efficient.

Also, by recovering the reaction heat of the water gas shift reaction occurring in the CO converter (7) and / or the reaction heat of the CO selective oxidation reaction occurring in the selective oxidation reactor (8) during the reaction. , The reaction heat in the CO converter (7) and the selective oxidation reactor (8) can be recovered as waste heat, and each reaction can be stabilized.

Further, the heat medium circuit (50) is formed so that the heat medium flows through the heat medium in order from the one having the lowest exhaust heat temperature to recover the exhaust heat. As a result, the temperature of the heat medium from which exhaust heat has been recovered can be made higher than in the past.

Further, in addition to the waste heat recovery in the reforming system,
By configuring so as to recover the exhaust heat of the fuel cell (1), it is possible to improve the exhaust heat recovery rate in the fuel cell system, and to increase the temperature of the heat medium from which the exhaust heat has been recovered as compared with the related art. be able to.

In this case, the fuel cell (1) and the reforming system are connected in series by the heat medium circuit (50), and the heat medium flows through the fuel cell (1) and the reforming system in this order, and is discharged. By configuring the heat medium circuit (50) to recover the heat, the waste heat is recovered in ascending order of the waste heat temperature, so that the waste heat can be efficiently recovered, and the recovered heat medium Can be further increased.

[0032] Further, by providing a structure having a battery heat medium circuit (51) formed in a closed circuit and recovering the exhaust heat of the fuel cell (1), the sealed heat medium can be used as the battery heat medium. Since it circulates in the circuit (51),
The scale does not adhere in the fuel cell (1), and the life of the fuel cell (1) can be extended. By using an antifreeze as the heat medium of the heat medium circuit for battery (51), it is possible to prevent the fuel cell (1) from being damaged by freezing in winter.

When an off-gas burner (10) for burning the exhaust gas of the fuel cell (1) is provided, the exhaust heat of the off-gas burner (10) is recovered by a heat medium circuit (50). In addition, the heat recovery rate of the fuel cell system can be improved, and the temperature of the heat medium from which exhaust heat has been recovered can be higher than in the related art. Then, the off-gas burner (10) and the reforming system are connected in series by a heat medium circuit (50), and the heat medium flows in the order of the off-gas burner (10) and the reforming system to recover exhaust heat. By configuring the heat medium circuit (50), waste heat recovery is performed in ascending order of the waste heat temperature, so that the waste heat recovery can be performed efficiently, and the temperature of the recovered heat medium can be further increased. Can be higher.

Further, by recovering the exhaust heat of the exhaust gas of the off-gas burner (10) or the exhaust heat of the exhaust gas of the fuel cell (1), condensed water can be recovered and supplied to the reforming system. Can be used for Then, the exhaust heat of the exhaust gas of the off-gas burner (10) or the exhaust heat of the exhaust gas of the fuel cell (1) is collected as water, which is supplied to a hot water storage tank (60) provided in the fuel cell system, as a heat medium. With this configuration, the amount of exhaust heat recovered can be increased, and the amount of condensed water that can be recovered can be increased accordingly.

Further, by employing a configuration in which the heat medium circuit is formed in a closed circuit, tap water or the like is not introduced into the heat medium circuit (50), and heat exchange with silica or the fuel cell (1) is prevented. 3.) It is possible to prevent scale adhesion in the main body and to stabilize the heat exchange characteristics of the heat medium circuit (50) for a long time. Then, the heat medium of the heat medium circuit (50) is frozen by using the antifreeze liquid as the heat medium of the heat medium circuit (50).
0) can be prevented.

Further, by increasing the temperature of the heat medium flowing through the heat medium circuit (50) to 75 ° C. or more, the capacity of the hot water storage tank (60) required to store the same amount of heat can be reduced in size. It can also be used as an air-conditioner of the adsorption type as a fuel cell cogeneration.

Then, as a fuel cell cogeneration including a fuel cell system and a hot water storage tank (60) attached thereto, water in the hot water storage tank (60) circulates through the heat medium circuit (50) as a heat medium and is discharged. Heat is recovered, and the water is returned to the hot water storage tank (60) again so that the hot water storage tank (60)
By increasing the temperature of the water, the water in the hot water storage tank (60) is used as the heat medium of the heat medium circuit (50). Can be simplified. Further, since the waste heat is directly recovered by the water in the hot water storage tank (60), the heat loss can be reduced as compared with the case of indirect heat exchange. And hot water storage tank (6
0) flows into the heat medium circuit (50) from the lower part, and circulates through the heat medium circuit (50) and recovers the waste heat.
By configuring so as to return to the upper part of the hot water storage tank (60), a temperature stratification is formed in the hot water storage tank (60). Since the low-temperature water is supplied to the circuit from the lower part of the hot water storage tank (60), the heat medium having a high heat absorption capacity circulates through the heat medium circuit (50),
The amount of heat recovered can be further increased.

When an off-gas burner (10) is provided, the exhaust heat of the exhaust gas of the off-gas burner (10) or the exhaust heat of the exhaust gas of the fuel cell (1) is stored in a hot water storage tank (60).
The water (tap water) supplied to the hot water storage tank (60) is a low-temperature heat source and has a high endothermic capacity, so that the amount of waste heat recovered is large. Accordingly, the amount of condensed water that can be recovered can be increased.

[0039]

Embodiments of the present invention will be described in detail with reference to the drawings. Embodiment 1 -Configuration of Fuel Cell System- FIG. 1 shows a schematic configuration of a fuel cell system according to Embodiment 1. This fuel cell 1 has an oxygen electrode (cathode) 2 which is a catalyst electrode and a hydrogen electrode (anode) which is also a catalyst electrode.
And 3 is a solid polymer membrane electrolyte type.

An air compressor 4 is connected to the oxygen electrode 2 by an air supply pipe 20.

Further, a fuel reformer 6 is connected to the hydrogen electrode 3 by a reformed gas supply pipe 24, and a hydrocarbon-based raw fuel source (city gas) is supplied to the fuel reformer 6. They are connected by a tube 25. In the reformed gas supply pipe 24, the first heat exchanger 31, the CO converter 7, the third heat exchanger 3
3. The selective oxidation reactor 8 and the second heat exchanger 32 are provided in order toward the fuel cell 1.

The fuel reformer 6 is filled with a catalyst (catalyst in which Ru or Rh is supported on Al ₂ O ₃ ) exhibiting activity in the partial oxidation reaction.
A catalyst exhibiting activity for the water gas shift reaction (Fe _{2
O 3, Cr 2 O 3,} CuO, and ZnO, etc.) is filled, the selective oxidation reactor 8, is supported catalysts of the (Ru or Pt on Al ₂ O ₃ or a zeolite exhibiting activity CO selective oxidation reaction Catalyst).

Although not shown, the raw material gas supply pipe 25 has an air supply means for supplying air for the partial oxidation reaction and a steam supply means for supplying water vapor for the water gas shift reaction. An air supply means for supplying air for CO selective oxidation reaction is connected to a portion of the reformed gas supply pipe 24 upstream of the second heat exchanger 32.

An off-gas burner is provided downstream of the fuel cell 1 so that the exhaust gas of the oxygen electrode 2 and the exhaust gas of the hydrogen electrode 3 of the fuel cell 1 are guided to the off-gas burner 10 from the respective exhaust gas outlets. The tubing is connected.

The second heat exchanger 32 from the pump 71,
A water circuit 50 is provided as a heat medium circuit connected in series with the third heat exchanger 33 and the first heat exchanger 31 in this order, and water is used as the heat medium. Here, the pump 71 is driven by a DC motor, and the driving power is supplied from DC power before being generated by the fuel cell 1 and converted into AC power by the inverter 11.
The flow rate of the water flowing through the water circuit 50 by the pump 71 can be controlled by the rotation speed of the DC motor.

Further, the fuel cell system is provided with sensors for detecting a power generation amount, a fuel flow rate, an air flow rate, a reformed gas temperature at the inlet of the CO converter 7 and the like. Connected to —Operation of Fuel Cell System— The operation of the fuel cell system will be described.

The raw fuel is a fuel reformer 6 together with air and steam.
And a partial oxidation reaction of the raw fuel occurs on the catalyst of the fuel reformer 6 to generate H ₂ and CO (see the equation (1)). In addition, a water gas shift reaction occurs partially (see equation (2)).

The temperature of the reformed gas leaving the fuel reformer 6 is 80
The temperature is about 0 ° C., and the temperature is reduced to about 180 to 400 ° C. by the first heat exchanger 31. The reformed gas whose temperature has been lowered is sent to the CO converter 7, where the CO concentration is reduced by the water gas shift reaction occurring on the catalyst (see equation (2)).

The temperature of the reformed gas exiting the CO converter 7 is reduced to about 150 ° C. by the third heat exchanger 33.
The temperature-reduced reformed gas is sent to the selective oxidation reactor 8 where CO is oxidized by a CO selective oxidation reaction occurring on the catalyst.
The O concentration further decreases (see equation (3)).

The temperature of the reformed gas leaving the selective oxidation reactor 8 is reduced to about 80 ° C. by the second heat exchanger 32. The reformed gas whose temperature has been lowered is supplied to the hydrogen electrode 3 of the fuel cell 1.

On the other hand, the air sent from the air compressor 4 is
It is supplied to the oxygen electrode 2 as it is.

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.
A battery reaction of + 4H ⁺ + 4e ⁻ → 2H ₂ O occurs to generate DC power. The generated DC power is converted into AC power by the inverter 11. A part of the generated DC power is supplied to the pump 71 and the air compressor 4 provided in the water circuit 50.
Is supplied as the driving power for this.

At this time, excess air not used for the battery reaction as the exhaust gas of the oxygen electrode 2 and water vapor generated by the battery reaction are generated, while hydrogen not used for the battery reaction as the exhaust gas of the hydrogen electrode 3 is generated. , Carbon dioxide, nitrogen,
Unreformed raw fuel and steam are produced. Each exhaust gas from the oxygen electrode 2 and the hydrogen electrode 3 is supplied to an off-gas burner 10
It is burned and discharged by.

Then, the waste heat is recovered in the order of the second heat exchanger 32, the third heat exchanger 33, and the first heat exchanger 31 by the water flowing through the water circuit 50 by the pump 71.
At this time, the water returned through the water circuit 50 has a temperature of 75.
It is hot water of over ℃.

Further, the power generation amount detected by the sensor,
On the basis of the fuel flow rate, the air flow rate, the reformed gas temperature at the inlet of the CO converter 7 and the like, the control device operates the rotation speed of the DC motor of the pump 71 to adjust the flow rate of water flowing through the water circuit 50. Become. -Water Flow Control in Water Circuit 50- Next, a water flow control operation of the water circuit 50 in the exhaust heat recovery system of the present fuel cell system will be described with reference to FIGS. <First Control Flow> FIG. 2 shows a first control flow in the exhaust heat recovery system of the present fuel cell system. This first
The control flow is a control for controlling the temperature of the reformed gas entering the CO converter 7 within the range of the fixed upper and lower limit temperatures. That is, the control is performed during the steady operation of the fuel cell system.

First, in step ST1, the fuel cell system is started.

Then, from step ST2 to step ST
Water flow control up to 6 is executed.

That is, in step ST2, CO
The temperature of the reformed gas is detected by a temperature sensor provided at the inlet of the transformer 7, the temperature is read, and the process proceeds to step ST3. In step ST3, it is determined whether or not the temperature T of the reformed gas entering the CO converter 7 is higher than a set upper limit temperature Tmax. If T is higher than Tmax, the process proceeds to step ST4. In step ST4, the water circuit 50
Is increased, specifically, the electric power supplied from the fuel cell 1 to the pump 71 is increased,
The rotation speed of the motor of the pump 71 is increased. Therefore, the exhaust heat recovered in the first heat exchanger 31 increases, and the temperature of the reformed gas entering the CO converter 7 decreases. Then, the process returns to step ST2.

If T is equal to or smaller than Tmax in step ST3, the process proceeds to step ST5. In step ST5, it is determined whether or not the temperature T of the reformed gas entering the CO converter 7 is higher than a set lower limit temperature Tmin. If T is lower than Tmax, the process proceeds to step ST6. Step ST6
Then, the flow rate of the water flowing through the water circuit 50 is reduced. Specifically, the power supplied from the fuel cell 1 to the pump 71 is reduced, and the rotation speed of the motor of the pump 71 is reduced. Therefore, the exhaust heat recovered in the first heat exchanger 31 is reduced, and the temperature of the reformed gas entering the CO converter 7 is increased. Then, the process returns to step ST2.

If T is equal to or smaller than Tmax in step ST5, the process returns to step ST2. <Second Control Flow> FIG. 3 shows a second control flow in the exhaust heat recovery system of the present fuel cell system. This second
The control flow is a control for controlling the temperature of the reformed gas entering the CO converter 7 within a range of upper and lower limit temperatures set according to the power generation amount of the fuel cell 1, the fuel flow rate, the air flow rate, and the like. . That is, the control is performed at the time of the non-stationary operation of the fuel cell system in which the power generation amount fluctuates.

First, in step ST1 ', the fuel cell system is started.

Then, from step ST2 'to step S
Water flow control until T8 'is executed.

That is, in step ST2 ', the power generation amount, the fuel flow rate, the air flow rate, etc. are detected by the sensor.
After these are read, the process proceeds to step ST3 '.
In step ST3 ', C is determined based on the read calorific value and the like.
The upper limit temperature T'max and the lower limit temperature T'min of the temperature of the reformed gas entering the O shift converter 7 are determined, and the process proceeds to step ST4 '.

In step ST4 ', the CO transformer 7
The temperature of the reformed gas is detected by the temperature sensor provided at the inlet, and the temperature is read, and the process proceeds to step ST.
Go to 5 '. In step ST5 ', it is determined whether the temperature T' of the reformed gas entering the CO converter 7 is higher than the upper limit temperature T'max set in ST3 ', and if T' is higher than T'max. Proceed to step ST6 '. Step ST
In 6 ', the flow rate of the water flowing through the water circuit 50 is increased. Specifically, the power supplied from the fuel cell 1 to the pump 71 is increased, and the rotation speed of the motor of the pump 71 is increased. Therefore, the exhaust heat recovered in the first heat exchanger 31 increases, and the temperature of the reformed gas entering the CO converter 7 decreases. Then, the process returns to step ST2 '.

In step ST5 ', T' is changed to T'ma
If it is less than x, the process proceeds to step ST7 '. Step S
At T7 ', the temperature T of the reformed gas entering the CO converter 7 is S
It is determined whether or not the temperature is higher than the lower limit temperature T'min set in T3 ', and if T' is lower than T'max, step S is executed.
Proceed to T8 '. In step ST8 ′, the flow rate of the water flowing through the water circuit 50 is reduced. Specifically, the power supplied from the fuel cell 1 to the pump 71 is reduced, and the rotation speed of the motor of the pump 71 is reduced. . Therefore, the exhaust heat recovered in the first heat exchanger 31 is reduced, and the temperature of the reformed gas entering the CO converter 7 is increased. Then, the process returns to step ST2 '.

In step ST7 ', T' becomes T'ma
If it is less than x, the process returns to step ST2 '. - Operation and Effects - According to the fuel cell system of the invention, recovered by the water circuit 50 a large amount of reaction heat released in the process of generating the reformed gas containing H ₂ from the raw fuel in the reforming system as a waste heat Therefore, a large amount of exhaust heat can be recovered as compared with the conventional case where exhaust heat is recovered only from the fuel cell. Then, by using the exhaust heat for the fuel cell cogeneration, the temperature of the water in the water heater, which previously could only be raised to about 60 ° C., can be raised to 75 ° C. or more.
Further, it can be said that this waste heat is used for heating and vaporizing water supplied for the water gas shift reaction in the fuel reformer (6) or the CO shift converter (7).

The reformed gas exiting the fuel reformer 6 is the first gas.
Exhausted heat is recovered in the heat exchanger 31 to 180 to 400 ° C.
The reformed gas exiting the selective oxidation reactor 8 is the second
Exhausted heat is recovered in the heat exchanger 32 to about 80 ° C. That is, the temperature of the reformed gas entering each of the CO converter 7 and the fuel cell 1 is within a predetermined temperature range by a simple method of providing a heat exchanger.

By controlling the flow rate of water according to the flow shown in FIG. 2 or FIG. 3, the temperature of the reformed gas entering the CO converter 7 can be adjusted. However, the temperature and gas composition of the reformed gas entering the fuel cell 1 can be stabilized. Further, since the flow rate of water is controlled by the rotation speed of the DC motor of the pump 71 driven by the DC motor, it is not necessary to use an expensive inverter. Further, since the driving power of the DC motor is supplied by the power generated by the fuel cell 1, the DC power generated by the fuel cell 1 can be used as it is, and there is no loss due to the orthogonal transformation, which is efficient.

Further, since the exhaust heat recovery is performed in the order of the first heat exchanger 31, the third heat exchanger 33, and the second heat exchanger 32, that is, in order of the temperature, the efficiency of the exhaust heat recovery is good. Become.

Since the temperature of the water flowing through the water circuit 50 is 75 ° C. or higher as described above, the capacity of the hot water storage tank required to store the same amount of heat can be reduced. It can also be used for air conditioning of the adsorption type as a generation system. Embodiment 2 FIG. 4 shows a schematic configuration of a fuel cell system according to Embodiment 2. The same parts as those in the first embodiment are denoted by the same reference numerals.

In the fuel cell system according to Embodiment 2,
Heat exchange units 41 and 42 are provided inside the CO shift converter 7 and the selective oxidation reactor 8, respectively. The water circuit 50 is connected to the second heat exchanger 32 from the pump 71, the selective oxidation reactor 8, and the third heat exchange unit. , The inside of the CO transformer 7 and the first heat exchanger 3
1 are sequentially connected in series, and water is used as a heat medium. Therefore, the second heat exchanger 32, the inside of the selective oxidation reactor 8, the third heat exchanger 33, and the CO
Exhaust heat recovery is performed in the order of the inside and the first heat exchanger 31.
Other configurations are the same as those of the fuel cell system according to the first embodiment.

According to the fuel cell system having the above configuration, C
The reaction heat during the reaction of the water gas shift reaction occurring in the O shift converter 7 and the reaction heat during the reaction of the CO selective oxidation reaction occurring in the selective oxidation reactor 8 are both recovered as waste heat, thereby stabilizing each reaction. Can be planned. That is, for example, in the CO converter 7, a decrease in the CO conversion rate due to an increase in the reaction temperature is prevented. Further, in the selective oxidation reactor 8, CH increases due to an increase in the reaction temperature.
Generation of ₄ is prevented.

Other functions and effects are the same as those of the first embodiment. Third Embodiment FIG. 5 shows a schematic configuration of a fuel cell system according to a third embodiment. The same parts as those in the first embodiment are denoted by the same reference numerals.

In the fuel cell system according to Embodiment 3,
The heat exchange unit 43 is provided in the fuel cell 1, and the water circuit 50
The fuel cell 1, the second heat exchanger 32, the third heat exchanger 33, and the first heat exchanger 31 are sequentially connected in series, and water is used as a heat medium. Therefore, waste heat is recovered in the order of the fuel cell 1, the second heat exchanger 32, the third heat exchanger 33, and the first heat exchanger 31 by the water flowing through the water circuit 50 by the pump 71. Other configurations are the same as those of the fuel cell system according to the first embodiment.

According to the fuel cell system having the above-described structure, the exhaust heat of the fuel cell 1 can be recovered in addition to the recovery of the exhaust heat in the reforming system. Will be achieved.

Further, since the exhaust heat recovery is performed in the order of the fuel cell 1, the second heat exchanger 32, the third heat exchanger 33, and the first heat exchanger 31, that is, in order of decreasing temperature, the exhaust heat recovery is performed. The efficiency is good.

Other functions and effects are the same as those of the first embodiment. Embodiment 4 FIG. 6 shows a schematic configuration of a fuel cell system according to Embodiment 4. The same parts as those in the first embodiment are denoted by the same reference numerals.

In the fuel cell system according to Embodiment 4,
The off-gas burner 10 is provided with a heat exchange section 44, and the water circuit 50 includes a second heat exchanger 32, a third heat exchanger 33, and a first heat exchanger 33.
The heat exchanger 31 and the off-gas burner 10 are sequentially connected in series, and water is used as a heat medium. Therefore, the exhaust heat recovery is performed in the order of the second heat exchanger 32, the third heat exchanger 33, the first heat exchanger 31, and the off-gas burner 10 by the water flowing through the water circuit 50 by the pump 71. Other configurations are the same as those of the fuel cell system according to the first embodiment.

According to the fuel cell system having the above configuration, in addition to the recovery of exhaust heat in the reforming system, the off-gas burner 10
Waste heat can be recovered, and the heat recovery rate of the fuel cell system can be improved.

Further, the exhaust heat recovery is performed in the order of the second heat exchanger 32, the third heat exchanger 33, the first heat exchanger 31, and the off-gas burner 10, that is, in order of decreasing temperature.
Exhaust heat recovery efficiency is improved.

Other functions and effects are the same as those of the first embodiment. Embodiment 5 FIG. 7 shows a schematic configuration of a fuel cell system according to Embodiment 5. The same parts as those in Embodiments 4 and 5 are denoted by the same reference numerals.

In the fuel cell system according to Embodiment 5,
Heat exchange units 43 and 44 are provided in the fuel cell 1 and the off-gas burner 10, respectively.
2nd heat exchanger 32, 3rd heat exchanger 33, 1st heat exchanger 3
1 and the off-gas burner 10 are sequentially connected in series, and water is used as a heat medium. Therefore, the fuel cell 1, the second heat exchanger 32, and the third heat exchanger 3 are supplied by the water flowing through the water circuit 50 by the pump 71.
3. Exhaust heat recovery is performed in the order of the first heat exchanger 31 and the off-gas burner 10. That is, the present embodiment is a combination of the third embodiment and the fourth embodiment.

According to the fuel cell system having the above configuration, in addition to the recovery of the exhaust heat in the reforming system, the exhaust heat of the fuel cell 1 and the off-gas burner 10 can be recovered. Further improvement will be achieved.

Other functions and effects are the same as those of the third and fourth embodiments. <Fuel Cell Cogeneration 1> FIG.

In the fuel cell cogeneration 1, Embodiment 5
At the off-gas burner 10 to the fourth heat exchanger 34
The water circuit 5 returns to the first pump 71 via the
0 is formed. An antifreeze is used as a medium circulating in the water circuit 50. Then, water that has flowed out of the hot water storage tank 60 attached to the fuel cell system is sent to the fourth heat exchanger 34 by the second pump 72, and a closed circuit that returns to the hot water storage tank 60 is formed. Therefore, the antifreeze circulated through the water circuit 50 by the first pump 71 causes
Exhaust heat is recovered in the order of the fuel cell 1, the second heat exchanger 32, the third heat exchanger 33, the first heat exchanger 31, and the off-gas burner 10, and the recovered exhaust heat is circulated by the fourth heat exchanger 34. It is used for heating water in the hot water storage tank 60.

According to the fuel cell cogeneration 1 having the above configuration,
Since the water circuit 50 is a closed circuit, water in the hot water storage tank 60 is not introduced into the water circuit 50, and heat exchange with silica and scale adhesion in the fuel cell 1 main body can be prevented.
The heat exchange characteristics of the water circuit 50 will be stable for a long time.

Further, since the antifreeze liquid is used as a heat medium of the water circuit 50 forming the closed circuit, damage of the heat medium circuit 50 due to freezing in winter can be prevented. <Fuel Cell Cogeneration 2> FIG. 9 shows a schematic configuration of the fuel cell cogeneration 2. The same parts as those of the fuel cell cogeneration 1 are denoted by the same reference numerals.

In the fuel cell cogeneration system 2, in the fifth embodiment, the heat exchange unit 4 provided inside the hot water storage tank 60 attached to the fuel cell system is supplied from the off-gas burner 10.
5. The water circuit 50 returns to the pump 71 via the
Are formed. An antifreeze is used as a medium circulating in the water circuit 50. Therefore, the fuel cell 1,
2nd heat exchanger 32, 3rd heat exchanger 33, 1st heat exchanger 3
Exhaust heat recovery is performed in the order of 1 and the off-gas burner 10,
The recovered exhaust heat is used for heating water inside the hot water storage tank 60 by the heat exchange unit 45 provided inside the hot water storage tank 60. Other configurations are the same as the fuel cell cogeneration 1.

The operation and effects are described in the fuel cell cogeneration 1
Is the same as <Fuel Cell Cogeneration 3> FIG. The same parts as those of the fuel cell cogeneration 1 are denoted by the same reference numerals.

In the fuel cell cogeneration system 3, after exiting from the off-gas burner 10 in the fifth embodiment, the fuel cell cogeneration system enters the hot water storage tank 60 provided in the fuel cell system, and
The water circuit 50 is formed so as to form a closed circuit returning from 0 to the pump 71. That is, the water in the hot water storage tank 60 circulates in the water circuit 50. Here, water flows into the pump 71 from the lower part of the hot water storage tank 60, and the water circulated through the water circuit 50 returns to the upper part of the hot water storage tank 60. Further, a water supply pipe 26 for supplying tap water is connected to a lower portion of the hot water storage tank 60. Therefore, with the antifreeze circulated through the water circuit 50 by the pump 71, the exhaust heat is recovered in the order of the fuel cell 1, the second heat exchanger 32, the third heat exchanger 33, the first heat exchanger 31, and the off-gas burner 10, Hot water storage tank 60
Water is directly heated.

According to the fuel cell cogeneration 3, the water circuit 5
Since the water in the hot water storage tank 60 is used as the heat medium 0, the fuel cell cogeneration can be simplified as compared with the case where a separate heat medium is provided. Further, since the waste heat is directly recovered by the water in the hot water storage tank 60, the heat loss is reduced as compared with the case where the waste heat is indirectly recovered.

Further, the water circuit 5
0, and the water that has circulated through the water circuit 50 and recovered the exhaust heat returns to the upper part of the hot water storage tank 60.
Temperature stratification will be formed in the hot water storage tank 60,
The temperature of the available water in the upper part of the hot water storage tank 60 becomes higher. In addition, the water circuit 50
Is supplied to the water circuit, the heat medium having a high endothermic capacity circulates in the water circuit 50, and the amount of heat recovered is further increased. <Fuel Cell Cogeneration 4> FIG. 11 shows a schematic configuration of the fuel cell cogeneration 4. The same parts as those of the fuel cell cogeneration 1 are denoted by the same reference numerals.

In the fuel cell cogeneration 4, the fuel cell cogeneration 1 is provided with a battery water circuit 51 for recovering only the heat of the fuel cell 1. An antifreeze is used as a heat medium in the battery water circuit 51, and the third pump 7
3 allows the antifreeze to circulate the battery water circuit 51. The water circuit 50 and the battery water circuit 51 are connected via a fifth heat recovery unit 35. And
The waste heat is recovered in the order of the fifth heat exchanger 35, the second heat exchanger 32, the third heat exchanger 33, the first heat exchanger 31, and the off-gas burner 10 by the water flowing through the water circuit 50 by the first pump 71. Will be performed. Other configurations are the same as the fuel cell cogeneration 1.

According to the fuel cell cogeneration system 4 having the above configuration,
Since the sealed antifreeze circulates in the battery water circuit 51, the scale does not adhere in the fuel cell 1 and the life of the fuel cell 1 is extended.

Further, since the antifreeze is used as the heat medium of the battery water circuit 51, damage to the fuel cell 1 body due to freezing in winter can be prevented.

Other functions and effects are described in fuel cell cogeneration 1
Is the same as <Fuel Cell Cogeneration 5> FIG. The same parts as those of the fuel cell cogeneration 3 are denoted by the same reference numerals.

In the fuel cell cogeneration system 5, a fuel cell cogeneration system 3 is provided with a battery water circuit 51 for recovering only the heat of the fuel cell system 1. An antifreeze is used as a heat medium in the battery water circuit 51, and the third pump 7
3 allows the antifreeze to circulate the battery water circuit 51. The water circuit 50 and the battery water circuit 51 are connected via a fifth heat recovery unit 35. And
The waste heat is recovered in the order of the fifth heat exchanger 35, the second heat exchanger 32, the third heat exchanger 33, the first heat exchanger 31, and the off-gas burner 10 by the water flowing through the water circuit 50 by the first pump 71. Will be performed. Other configurations are the same as those of the fuel cell cogeneration 3.

Regarding the function and effect, see Fuel Cell Cogeneration 4
Is the same as <Fuel Cell Cogeneration 6> FIG. 13 shows a schematic configuration of the fuel cell cogeneration 6. The same parts as those of the fuel cell cogeneration 1 are denoted by the same reference numerals.

In the fuel cell cogeneration system 6 according to the fifth embodiment, the sixth heat exchanger 3 is provided downstream of the off-gas burner 10.
6 are provided. A hot water storage tank 60 is also provided in the fuel cell system, and a water supply pipe 26 for replenishing tap water is connected to a lower portion thereof via a sixth heat exchanger 36. Therefore, tap water is supplied to the sixth heat exchanger 36.
And recovers the latent heat to be supplied to the hot water storage tank 60. Further, the water supply pipe 26 is provided with a bypass 27 that does not pass through the sixth heat exchanger 36.

According to the fuel cell cogeneration 6 having the above configuration,
Condensed water can be recovered from the exhaust gas of the off-gas burner 10,
It can be used for feeding to the reforming system.

Further, the tap water supplied to the hot water storage tank 60 is a low-temperature heat source and has a high heat absorbing ability, so that the amount of exhaust heat recovered is large, and accordingly, a large amount of condensed water can be recovered.

[Brief description of the drawings]

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

FIG. 2 is a first control flow chart in the exhaust heat recovery system of the fuel cell system according to the first embodiment.

FIG. 3 shows a second control flow chart in the exhaust heat recovery system of the fuel cell system according to Embodiment 1.

FIG. 4 is a diagram showing a schematic configuration of a fuel cell system according to Embodiment 2.

FIG. 5 is a diagram showing a schematic configuration of a fuel cell system according to Embodiment 3.

FIG. 6 is a diagram showing a schematic configuration of a fuel cell system according to Embodiment 4.

FIG. 7 is a diagram showing a schematic configuration of a fuel cell system according to Embodiment 5.

FIG. 8 is a diagram showing a schematic configuration of a fuel cell cogeneration 1;

FIG. 9 is a diagram showing a schematic configuration of a fuel cell cogeneration 2.

FIG. 10 is a diagram showing a schematic configuration of a fuel cell cogeneration 3;

FIG. 11 is a diagram showing a schematic configuration of a fuel cell cogeneration 4;

FIG. 12 is a diagram showing a schematic configuration of a fuel cell cogeneration 5.

FIG. 13 is a diagram showing a schematic configuration of a fuel cell cogeneration 6;

[Description of Signs] 1 Fuel cell 2 Oxygen electrode 3 Hydrogen electrode 4 Air compressor 6 Fuel reformer 7 CO converter 8 Selective oxidation reactor 10 Off gas burner 11 Inverter 20 Air supply pipe 24 Reformed gas supply pipe 25 Source gas Supply pipe 26 Water supply pipe 27 Bypass 31 First heat exchanger 32 Second heat exchanger 33 Third heat exchanger 34 Fourth heat exchanger 35 Fifth heat exchanger 36 Sixth heat exchanger 41 to 45 Heat exchange unit 50 Water circuit 60 Hot water storage tank 71-73 Pump

Continuing on the front page (72) Inventor Shuji Ikegami 1304 Kanaokacho, Sakai-shi, Osaka Daikin Industries Inside the Sakai Plant Kanaoka Plant (72) Inventor Kazuo Yonemoto 1304 Kanaokacho, Sakai-shi, Osaka Daikin Industries Sakai F-term in the Kanaoka Plant (Reference) 4G040 EA03 EA07 EB14 EB23 EB32 EB44 EC02 EC03 4G075 AA42 AA43 AA44 AA45 AA63 BA06 BA08 CA52 DA01 5H027 AA06 BA01 BA16 BA17 DD06 KK41 MM16

Claims (22)

[Claims] 1. A reforming system for reforming a hydrocarbon-based raw fuel to generate a reformed gas containing H2, and a fuel for generating electricity using H2 contained in the reformed gas generated in the reforming system as a fuel A fuel cell system comprising: a battery (1); and a heat medium circuit (50) for recovering exhaust heat generated in the reforming system. 2. A fuel reformer for producing a reformed gas containing H2 and CO from a hydrocarbon-based raw fuel by a partial oxidation reaction, the fuel reformer comprising: (6)
A CO converter (7) for removing the CO contained in the reformed gas generated in the above by a water gas shift reaction, and a residual CO contained in the reformed gas exiting the CO converter (7) by a CO selective oxidation reaction. A selective oxidation reactor (8) for removal, wherein said heat transfer medium circuit (50) is after exiting said fuel reformer (6) and entering said CO converter (7). Waste heat of the previous reformed gas, waste heat of the CO converter (7), reformed gas after leaving the CO converter (7) and before entering the selective oxidation reactor (8) Of the exhaust gas, the exhaust heat of the selective oxidation reactor (8) and the exhaust heat of the reformed gas after leaving the selective oxidation reactor (8) and before entering the fuel cell (1). The fuel cell system according to claim 1, wherein the fuel cell system is formed so as to collect at least one. 3. The fuel reformer according to claim 1, wherein the temperature of the reformed gas at the inlet of the CO converter and the temperature of the reformed gas at the inlet of the fuel cell are within a predetermined temperature range. A first heat exchanger (31) for recovering the exhaust heat of the reformed gas after leaving the heat exchanger (6) and before entering the CO converter (7) to the heat medium circuit (50); A second heat exchanger (32) for recovering the exhaust heat of the reformed gas after leaving the selective oxidation reactor (8) and before entering the fuel cell (1) to the heat medium circuit (50). 3. The fuel cell system according to claim 2, comprising: 4. It is configured to recover heat of reaction of a water gas shift reaction occurring in the CO converter (7) and / or reaction heat of a CO selective oxidation reaction occurring in the selective oxidation reactor (8) during the reaction. The fuel cell system according to claim 2, wherein 5. The heat medium circuit according to claim 3, wherein the heat medium circuit is formed so that the heat medium flows in order from the one having a lower exhaust heat temperature to recover the exhaust heat. 3. The fuel cell system according to item 1. 6. The fuel cell system according to claim 1, wherein the system is configured to recover exhaust heat of the fuel cell. 7. The heat medium circuit (50) connects the fuel cell (1) and the reforming system in series, and the heat medium is in the order of the fuel cell (1) and the reforming system. 7. The apparatus according to claim 6, wherein the apparatus is configured to circulate and collect exhaust heat.
3. The fuel cell system according to item 1. 8. The fuel cell system according to claim 6, further comprising a battery heat medium circuit (51) formed in a closed circuit and recovering exhaust heat of the fuel cell (1). 9. The fuel cell system according to claim 8, wherein the heat medium of the heat medium circuit for a battery is an antifreeze. 10. An off-gas burner (10) for burning the exhaust gas of the fuel cell (1), and the exhaust heat of the off-gas burner (10) is recovered by the heat medium circuit (50). 2. The method according to claim 1, wherein
The fuel cell system according to claim 9. 11. The heating medium circuit (50) connects the reforming system and the off-gas burner (10) in series,
And the heat medium is the reforming system, the off-gas burner (10)
The fuel cell system according to claim 11, wherein the fuel cell system is configured to circulate in the following order to recover exhaust heat. 12. The fuel cell system according to claim 1, further comprising: a hot water storage tank (60) provided adjacent to the fuel cell system, wherein water in the hot water storage tank (60) is provided. Exhausted heat is recovered by circulating through the heat medium circuit (50) as a heat medium, and the water returns to the hot water storage tank (60) again.
0) A fuel cell cogeneration system configured to raise the temperature of water. 13. The heat medium circuit (50) flows into the heat medium circuit (50) from a lower portion of the hot water storage tank (60).
13. The fuel cell cogeneration system according to claim 12, wherein water recovered by exhaust heat recovery by circulating water is returned to an upper portion of the hot water storage tank (60). 14. The heating medium circuit according to claim 1, wherein the heating medium circuit is formed in a closed circuit.
The fuel cell system according to any one of the above. 15. The fuel cell system according to claim 14, wherein the heat medium of the heat medium circuit (50) is an antifreeze. 16. A fuel cell system according to claim 14 or 15, and a hot water storage tank (60) attached to the fuel cell system, wherein the heat medium circulates through the heat medium circuit (50). By the heat exchange with the recovered waste heat, the hot water storage tank (6
0) A fuel cell cogeneration system configured to raise the temperature of water. 17. An off-gas burner (10) for burning exhaust gas of the fuel cell (1), and configured to recover exhaust heat of exhaust gas of the off-gas burner (10). Item 2. The fuel cell system according to Item 1. 18. A fuel cell system having an offgas burner (10) for burning exhaust gas of the fuel cell (1), and a hot water storage tank provided in the fuel cell system, wherein the exhaust gas of the offgas burner (10) is provided. The exhaust heat of the fuel cell (1) or the exhaust heat of the exhaust gas of the fuel cell (1).
A fuel cell cogeneration system characterized in that the water replenished in 0) is recovered as a heat medium. 19. The temperature of the heat medium which has passed through the heat medium circuit (50) and has recovered the exhaust heat is 75 ° C. or higher, wherein the temperature of the heat medium is 75 ° C. or higher.
5. The fuel cell system according to any one of claims 17 to 17. 20. A fuel reformer for producing a reformed gas containing H2 and CO from a hydrocarbon-based raw fuel by a partial oxidation reaction, the fuel reformer comprising: A CO converter (7) for removing CO contained in the reformed gas generated in (6) by a water gas shift reaction, and the temperature of the reformed gas at the inlet of the CO converter (7); CO
The temperature of the heat medium flowing through the heat medium circuit (50) is adjusted so that at least one of the temperature of the reformer (7) and the temperature of the reformed gas at the outlet of the CO converter (7) falls within a predetermined temperature range. The fuel cell system according to any one of claims 1 to 19, further comprising a flow control means for controlling a flow rate. 21. The fuel cell system according to claim 20, wherein a flow rate of the heat medium is controlled by a rotation speed of the DC motor of a pump (71) driven by the DC motor. 22. The fuel cell system according to claim 21, wherein the drive power of the DC motor is supplied from the power generated by the fuel cell (1).