JPH11317239A - Energy supply system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continuously operate a reformer without largely decreasing energy efficiency even in a time band when the amount of hydrogen consumption by a fuel cell is smaller than the amount of hydrogen generation by the reformer. SOLUTION: A system control device 76 opens a flow control valve 68, supplies reactant gas corresponding to an amount of surplus hydrogen to a burner part 70 of a hot water device 14 for the reformer 10, and ignites the burner part 70, when the consumption of hydrogen by a fuel cell 12 becomes smaller than the generation of hydrogen by the reformer 10. The hot water device 14 for a reformer heats water in a tank part 46 to high-temperature hot water by combustion heat of the reactant gas. Thereby, the water recovering the combustion heat of surplus hydrogen is supplied to the reformer 10 together with natural gas to save fuel consumption by the reformer 10 for supplying heat of reaction to the natural gas and the water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an energy supply system for supplying electric energy and heat energy using natural gas or the like as a raw material and hydrogen produced by a reformer as a fuel.

[0002]

2. Description of the Related Art In recent years, an energy supply system combining a reformer and a fuel cell has been developed. In such an energy supply system, a natural gas or the like supplied as a hydrogen source is reformed into hydrogen by a reformer, and a fuel cell generates electric energy using the hydrogen as a fuel. Further, since the exhaust gas discharged from the reformer and the fuel cell has a high temperature, if the thermal energy is recovered from the exhaust gas, the thermal energy can be used for hot water supply, heating, and the like. Therefore, according to such an energy supply system, for example, electric energy and heat energy can be supplied to a house or a temporary facility provided in an area where power supply from a power company cannot be received. The system generates electricity only during the daytime hours when power demand is high, and receives power from the power company during the nighttime when power demand is low, responding to social demands for leveling power demand during the daytime and nighttime. You can also.

[0003] A reformer applied to the above energy supply system includes a catalyst container containing a metal catalyst.
By supplying a hydrogen source and water (steam) into a catalyst container maintained at a high temperature (for example, 700 to 800 ° C.), methane or the like contained in the hydrogen source reacts with water on the metal catalyst to produce hydrogen. Generate.

[0004]

Therefore, every time the reformer is stopped / operated, a large thermal stress acts on the metal catalyst, and this thermal stress promotes the deterioration of the metal catalyst and shortens the life of the reformer. Become. For this reason, in order to prevent the life of the reformer from being shortened, it is necessary to operate the reformer continuously for as long as possible and reduce the frequency at which a large thermal stress acts on the reformer. . However, if the operation is performed without stopping the reformer, hydrogen generated from the reformer may become excessive during a time period such as midnight when power demand is low. It is conceivable that this hydrogen is wasted and stored in a tank or the like in order not to lower the energy use efficiency of the system. However, in order to store a sufficient amount of hydrogen, the capacity of the tank is increased and the system becomes large.

An object of the present invention is to take the above facts into consideration and to reduce the amount of hydrogen consumed by a fuel cell even when the amount of hydrogen generated by the reformer is small without significantly lowering the energy utilization efficiency. An object of the present invention is to provide a small energy supply system that can be operated continuously.

[0006]

According to the first aspect of the present invention, there is provided an energy supply system for supplying a predetermined heat of reaction to a hydrogen raw material and water to cause a hydrocarbon or alcohol contained in the hydrogen raw material to react with water to generate hydrogen. A reformer, a fuel cell that reacts hydrogen supplied from the reformer with oxygen in the air to generate electric energy, and stores water to be supplied to the reformer in a tank. When the amount of hydrogen consumed by the fuel cell is small with respect to the amount of hydrogen generated by the fuel cell, surplus hydrogen generated by the reformer and not consumed by the fuel cell is burned to supply water supplied from the tank to the reformer. And a reforming water heater for raising the temperature.

[0007] According to the energy supply system having the above configuration, during the period when the hydrogen consumption by the fuel cell is smaller than the hydrogen generation by the reformer, the water stored in the reforming hot water device is heated by the combustion heat of the excess hydrogen. Since the temperature can be raised and the heated water can be supplied to the reformer together with the hydrogen raw material, the fuel consumed by the reformer to supply reaction heat to the hydrogen raw material and water can be reduced. As a result, the reformer can be continuously operated even during a time period when the power demand is small, without significantly lowering the energy use efficiency of the entire system. The life can be prevented from being shortened or suppressed. Also, since there is no need to provide a tank or the like for storing excess hydrogen, a small energy supply system can be realized.

Here, the period in which the amount of hydrogen consumed by the fuel cell is smaller than the amount of hydrogen generated by the reformer includes a period in which the operation of the fuel cell is stopped. Further, the reformer has a built-in metal catalyst made of a Ni-based or Cu-based alloy, and when the metal catalyst is cooled / heated with the stop / operation of the reformer,
Large thermal stress acts on the metal catalyst. If the thermal stress acts frequently, the metal catalyst is damaged, such as cracks and peeling, which limits the life of the entire reformer.

[0009] The energy supply system according to claim 2 is the energy supply system according to claim 1,
When water to be supplied to the outside of the system is stored in a tank, and when the amount of hydrogen consumed by the fuel cell device is smaller than the amount of hydrogen generated by the reformer, surplus hydrogen generated by the reformer and not consumed by the fuel cell And a hot water supply device for raising the temperature of water supplied from the tank to the outside of the system.

[0010] According to the energy supply system having the above configuration, during the period in which the hydrogen consumption by the fuel cell is smaller than the hydrogen generation by the reformer, the water stored in the hot water supply device is raised by the combustion heat of the excess hydrogen. Since the heated water can be heated and supplied to the outside of the system as hot water, the amount of fuel consumed by the hot water supply device to produce hot water can be reduced.
As a result, compared with the case where excess hydrogen is consumed only by the reforming hot water device, the time during which the reformer can be continuously operated can be extended in a time period during which power demand is low without greatly reducing energy use efficiency. It is possible to further reduce the frequency of the thermal stress associated with the shutdown / operation of the reformer.

According to a third aspect of the present invention, in the energy supply system according to the second aspect,
Until the water stored in the tank of the reforming hot water device is heated to a predetermined temperature, the excess hydrogen is preferentially supplied to the hot water supplying device to the hot water supplying device. It has gas supply control means.

According to the energy supply system having the above structure, during the period in which the amount of hydrogen consumed by the fuel cell is smaller than the amount of hydrogen generated by the reformer, the water of the reforming water heater is heated to a predetermined temperature by the combustion heat of the excess hydrogen. As the temperature is raised preferentially, the energy of the surplus hydrogen is preferentially recovered as heat energy in the water of the reforming water heater, and the reformer consumes the heat energy of the water of the reforming water heater. Since fuel can be saved, a decrease in energy use efficiency can be reliably suppressed.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

(Structure of Embodiment) FIGS. 1 and 2 show an energy supply system according to an embodiment of the present invention. This energy supply system is capable of supplying electric energy and heat energy such as hot water according to the demand of a home or the like. As shown in FIG.
0, polymer electrolyte fuel cell 12, reforming water heater 14
And a hot water supply device 16 for hot water supply. The reformer 10
Natural gas containing methane as a main component is supplied to the reformer 10 through the gas supply pipes 18 and 20, which are connected to a gas cylinder and gas supply facilities of a gas company by two gas supply pipes 18 and 20. You. The reformer 10 includes a reaction vessel 22 and a gas burner 24 as shown in FIG. A hollow catalyst reaction tube 26 is disposed in the reaction vessel 22, and a Ni-based metal catalyst (not shown) for reforming methane into hydrogen is loaded in the catalyst reaction tube 26. The gas burner 24 is disposed at the bottom of the reaction vessel 22 and burns natural gas and the like in the reaction vessel 22.

A flow control valve 28 is disposed in the gas supply pipe 18 in the middle of the pipe, and is connected to a gas burner 24 of the reformer 10 as shown in FIG. The gas burner 24 has an air supply pipe 30 in parallel with the gas supply pipe 18.
Are connected, and a blower 32 is
Is supplied. Gas supply pipe 2
Numeral 0 branches into a plurality of tubes in the reaction vessel 22, and these branch tubes are inserted into the catalyst reaction tubes 26, respectively.
As shown in FIG. 1, a flow control valve 34, a desulfurizer 36, an ejector 38, and a heat exchanger 40 are arranged in the gas supply pipe 20 from the upstream side. Here, the ejector 38
Is connected to a tank 46 of the reforming hot water device 14 by a water supply pipe 44 in which a pump 42 is disposed.
At the time of driving 2, the water stored in the tank 46 through the water supply pipe 44 is supplied to the ejector 38. Further, the water supply pipe 44 is provided with a heat exchange section 44A for flowing water along the side wall of the reaction vessel 22, and the heat exchange section 44A supplies heat from inside the reaction vessel 22 to water flowing through the water supply pipe 44. Is done.

The exhaust pipe 4 extends from the reaction vessel 22 of the reformer 10.
8 extends, and the exhaust pipe 48 is connected to a heat exchanger 50 arranged in the hot water supply device 16. This allows
The high-temperature combustion gas discharged from the reaction vessel 22 at the time of gas combustion by the gas burner 24 is supplied to the heat exchanger 50, and supplies heat to the water stored in the tank 52 of the hot water supply device 16. Further, as shown in FIG. 2, a reaction gas supply pipe 54 extends from the catalyst reaction tube 26 of the reformer 10, and the reaction gas supply pipe 54 passes through the heat exchanger 40 as shown in FIG. Connected to the fuel cell 12. In the reaction gas supply pipe 54, a CO converter 56 and a CO remover 58 are arranged between the heat exchanger 40 and the fuel cell 12, and the air blown from the blower 60 is sent to the carbon monoxide remover 58. An air supply pipe 62 for supply is connected.

The reaction gas supply pipe 54 has two branch pipes 64, 66 extending from between the CO remover 54 and the fuel cell 12, and one of the branch pipes 64 extends through a flow control valve 68. The other branch pipe 66 is connected to the burner 70 of the reforming water heater 14, and the other branch pipe 66 is connected to the hot water heater 1 via a flow control valve 72.
6 is connected to the burner section 74.

A system controller 76 for controlling the entire system opens the flow control valve 28 to a predetermined initial opening at the start of operation of the system, supplies natural gas to the gas burner 24 through the gas supply pipe 18, and ignites the gas burner 24. I do. Thereby, the natural gas is burned by the gas burner 24, and the temperature in the reaction vessel 22 rises. Gas burner 24
The high-temperature exhaust gas is supplied from the reaction vessel 22 to the heat exchanger 50 through the exhaust pipe 48 to raise the temperature of the water in the hot water supply device 16. When the temperature inside the reaction vessel 22 is raised to 700 to 800 ° C., the system control device 76 opens the flow control valve 34 and drives the pump 42. Thereby, the natural gas desulfurized by the desulfurizer 36 is supplied into the catalytic reaction tube 26 through the gas supply pipe 20, and water in the tank 46 of the reforming hot water device 14 is supplied to the ejector 38 through the water supply pipe 44. Supplied. At this time, the water supplied to the ejector 38 is supplied to the tank 46 by the hot water supply device 14.
The temperature is increased in the inside, and the heat is further supplied by the heat exchange section 44A, so that the ejector 38 is turned into superheated steam.
It is injected into and mixed with natural gas. The natural gas and the steam are supplied with heat by the heat exchanger 40 and supplied into the catalytic reaction tube 26.

In the catalytic reaction tube 26, when a predetermined heat of reaction is supplied to natural gas and water vapor, methane in the natural gas chemically reacts with water vapor on the metal catalyst to produce hydrogen, carbon dioxide, carbon monoxide and the like. Is generated. This reaction gas is supplied to the CO converter 56 via the heat exchanger 40 at a high temperature. The CO converter 56 converts most of the carbon monoxide in the reaction gas to carbon dioxide. At this time, the system controller 76 drives the blower 60 in advance in synchronization with the opening of the flow control valve 34. Therefore, CO
The remover 58 is supplied with the reaction gas from the CO converter 56 and the air from the blower 60. The CO remover 58 reacts carbon monoxide in the mixed gas with oxygen in the air to further reduce the carbon monoxide concentration. Also, the system controller 76
Adjusts the opening of the flow control valve 28 so that the temperature inside the reaction vessel 22 is maintained at 700 to 800 ° C. On this occasion,
As the temperature of natural gas and water supplied to the catalytic reaction tube 26 of the reformer 10 is lower, it is necessary to increase the opening of the flow control valve 28 and supply a larger amount of natural gas to the gas burner 24.

As shown in FIG. 1, the fuel cell 12 is connected to a blower 80 by an air supply pipe 78, and a water storage tank 86 storing pure water through a water supply pipe 84 in which a pump 82 is disposed.
Connected to Further, a DC / DC converter 88 is connected to the fuel cell 12, and this DC / DC converter 8
8, a DC / AC inverter 90 and a secondary battery 92 are connected in series.

When the supply of the reaction gas from the reformer 10 to the fuel cell 12 is started, the system controller 76
0 and the pump 82 are started to drive, and the opening of the flow control valve 34 is adjusted in accordance with the power load on the fuel cell 12. As a result, pure water and a reaction gas corresponding to the electric power load are supplied to the hydrogen electrode in the fuel cell 12, and air is supplied to the air electrode. The fuel cell 12 reacts hydrogen in the reaction gas with oxygen in the air to output DC power according to an external load. DC power output from the fuel cell 12 is DC / D
After being converted to a predetermined voltage by the C converter 88,
The DC / AC inverter 90 converts the AC power into AC power and supplies the AC power to the outside of the system. Further, the DC power stored in the secondary battery 92 is supplied to the system control device 76, and is used by the system control device 76 for controlling and driving the electric components constituting the system.

As shown in FIG. 1, a drain pipe 94, an air exhaust pipe 96, and a gas exhaust pipe 98 are connected to the fuel cell 12. At the air electrode of the fuel cell 12, oxygen in the air supplied by the blower 80 reacts with the hydrogen that has moved from the hydrogen electrode to generate water. Drainage from the hydrogen electrode is returned to the water storage tank 86 through the drain pipe 94. here,
Pure water is supplied from the outside of the system so that the water storage tank 86 always stores a predetermined amount or more of water. Fuel cell 12
The air discharged from the air electrode is discharged into the atmosphere through an air discharge pipe 96. On the other hand, at the hydrogen electrode of the fuel cell 12, only hydrogen in the reaction gas is consumed, and other unreacted gases (carbon dioxide, carbon monoxide, water vapor) are passed through the gas discharge pipe 98 as shown in FIG. The gas is supplied to the ten gas burners 24, and the gas burners 24 completely burn carbon monoxide together with natural gas.

The water storage tank 86 is connected to the tank section 4 of the reforming hot water device 14 by a water supply pipe 100 in which a pump 99 is disposed.
6. Further, an air supply pipe 104 of a blower 102 is connected to a burner section 70 of the reforming hot water device 14 together with a branch pipe 64 for supplying a reaction gas. Here, a water level sensor 46A for detecting the water level in the tank and a water temperature sensor 46B for detecting the water temperature are arranged in the tank section 46. When the system control device 76 determines that the water in the tank 46 has fallen below the predetermined lower limit water level based on the detection signal from the water level sensor 46A, the system controller 76 drives the pump 99 for a certain period of time and Water is supplied to the section 46.

On the other hand, the tank 52 of the hot water supply device 16
Is provided with a water temperature sensor 52A for detecting the water temperature in the tank, and is connected to a hot water supply pipe 110 in which a water pipe 106 and an on-off valve 108 are disposed. Here, when the on-off valve 108 is opened, the hot water in the tank 52 is supplied to the outside of the system, and the same amount of hot water flowing out of the tank 52 is supplied to the tank 52 through the water pipe 106. Further, an air supply pipe 114 of a blower 112 is connected to a burner section 74 of the hot water supply device 16 together with a branch pipe 66 for supplying a reaction gas.

(Operation of the Embodiment) The operation and operation of the energy supply system of the embodiment configured as described above will be described.

The system controller 76 controls the opening of the flow control valve 34 in accordance with the power load on the fuel cell 12 during the operation of the system as described above. Thereby, the amount of hydrogen generated by the reformer 10 is adjusted to an amount corresponding to the power load of the fuel cell 12. However, during operation of the reformer 12, the reformer 10, the CO shifter 56, the CO remover 58
In order to maintain the internal temperature within a proper temperature range, it is necessary to continuously supply a certain amount or more of natural gas to the catalyst reaction tube 26, and the flow control valve 34 cannot be narrowed below a predetermined minimum opening. Therefore, the system controller 76 reduces the power demand outside the system and narrows the opening of the flow control valve 34, but when the power demand falls below a predetermined level, the system control device 76 sets the flow control valve 34 to the minimum opening. Also fuel cell 1
2 is less than the amount of hydrogen generated by the reformer 10, and surplus hydrogen is generated. Further, when the fuel cell 12 is stopped during a time period such as midnight when the power demand decreases, the hydrogen is not consumed by the fuel cell 12 and the total amount of hydrogen generated by the reformer 10 becomes excessive.

Next, a control routine by the system controller 76 during a period when the hydrogen consumption of the fuel cell 12 is smaller than the hydrogen generation of the reformer 10 will be described with reference to FIG.

If it is determined in step 200 that the amount of hydrogen consumed by the fuel cell 12 is smaller than the amount of hydrogen generated by the reformer 12, the flow control valve 68 is opened in step 202 to supply the reaction gas to the reforming hot water device 14. Supply to the burner 70,
The burner unit 70 is ignited. At this time, the opening degree of the flow control valve 68 is adjusted so that an amount of reaction gas containing an excess amount of hydrogen with respect to the fuel cell 12 is supplied to the burner unit 70. Thereby, the reforming hot water device 14 raises the temperature of the water in the tank 46 by the combustion heat of the reaction gas supplied to the burner 70.

When it is determined in step 204 that the water in the tank 46 has been raised to the target temperature from the signal from the water temperature sensor 46B, in step 206, the water in the tank 46 is within the target temperature range (for example, 90 degrees). The opening of the flow control valve 68 is maintained at a temperature of
Feedback control is performed based on the signal from 6A.

In step 208, the flow control valve 72 is opened simultaneously with the start of the feedback control in step 206, and the reaction gas is supplied to the burner section 74 of the hot water supply hot water device 16, and the burner section 74 is ignited. At this time, the flow control valve 7
The opening degree of the reaction gas 2 is such that the amount of the reaction gas including the amount of excess hydrogen with respect to the reforming hot water device 14 and the fuel cell 12 is
4 is adjusted. Accordingly, the hot water supply device 16 raises the temperature of the water in the tank 52 by the combustion heat of the reaction gas supplied to the burner 74. Step 2
At 10, the tank unit 52 receives a signal from the water temperature sensor 52 </ b> A.
When it is determined that the temperature of the water inside has risen to the target temperature, the flow control valve 68 and the flow control valve 72 are closed in step 212 to stop the operation of the reformer 10 urgently.

However, even if any of the processes in steps 200 to 212 is being executed, the system
Is monitored at regular intervals. When the amount of hydrogen consumed by the fuel cell 12 exceeds the amount of hydrogen generated by the reformer 10 by the flow control valve 34, the flow control valves 68 and 7 are immediately
2 is closed to interrupt the control routine described above. If the amount of surplus hydrogen generated during the period in which the amount of hydrogen consumed by the fuel cell 12 is smaller than the amount of hydrogen generated by the reformer 10 can be predicted in advance, the amount of combustion heat of the surplus hydrogen is reduced by the amount of combustion heat in the tank unit. The tank units 46 and 52 are so heated as to increase the amount of heat required to raise the water in the tanks 46 and 52 to the target temperature.
If the total amount of water to be stored is set, the reformer 10 can be continuously operated without an emergency stop.

According to the energy supply system of the present embodiment described above, during the period when the hydrogen consumption by the fuel cell 12 is smaller than the hydrogen generation by the reformer 10, the excess hydrogen is supplied to the burner of the reforming hot water device 14. The water stored in the tank 46 is preferentially heated to a predetermined target temperature by the heat of combustion of the surplus hydrogen, and the water stored in the tank 46 is heated to the target temperature. And supplying the surplus hydrogen to the burner section 74 of the hot water supply hot water device 16 and raising the temperature of the water stored in the tank section 52 to a predetermined target temperature by the heat of combustion of the surplus hydrogen. Can be supplied to the reformer together with the natural gas, the fuel consumed by the reformer 10 to supply heat of reaction to the natural gas and the water can be reduced, and the water in the tank 46 can be reduced. Heated Since the water supplied to the outside of the system by the heat of combustion of the excess hydrogen can be heating, the hot water supply water heater 16 can be reduced fuel consumption in order to make the hot water supplied to the system outside. As a result, the reformer 10 can be continuously operated for a long time even during a time period when the power demand is small, without greatly reducing the energy use efficiency of the entire system. It is possible to prevent or suppress that the metal catalyst in the catalyst reaction tube 26 is damaged by the thermal stress and the life of the reformer 10 is shortened. Further, in the energy supply system of the present embodiment, it is not necessary to provide a tank or the like for storing excess hydrogen, so that a small energy supply system can be realized.

In the energy supply system of the present embodiment, only the case where a polymer electrolyte fuel cell is used as the fuel cell 12 has been described. A fuel cell of a carbonate type, a solid electrolyte type, an alkaline type, or the like is also applicable. Further, in addition to the reformer 10 using natural gas as a hydrogen source, a reformer using alcohol such as methanol as a hydrogen source can be applied to the energy supply system of the present embodiment.

[0034]

As described above, according to the energy supply system of the present invention, the energy use efficiency of the entire system can be increased even during the period when the hydrogen consumption by the fuel cell is smaller than the hydrogen generation by the reformer. Since the reformer can be continuously operated for a long time without lowering, the shortening of the life of the reformer due to the thermal stress accompanying the stop / operation of the reformer is prevented or suppressed, and the energy use efficiency is reduced. A high energy supply system can be realized. Further, since there is no need to provide a tank or the like for storing excess hydrogen in the system, the size of the system can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an energy supply system according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a configuration of a reformer in the energy supply system according to the embodiment of the present invention.

FIG. 3 is a flowchart showing a control routine by the system control device during a period when the hydrogen consumption of the fuel cell according to the embodiment of the present invention is smaller than the hydrogen generation amount of the reformer.

[Explanation of symbols]

 Reference Signs List 10 reformer 12 fuel cell 14 reforming hot water device 16 hot water supply hot water device 22 reaction vessel 26 catalyst reaction tube 46 tank section 52 tank section 54 reaction gas supply pipe 64 branch pipe 66 branch pipe 68 flow control valve (gas supply control Means) 70 Burner section 72 Flow control valve (gas supply control means) 74 Burner section 76 System controller (gas supply control means)

Claims (3)

[Claims] 1. A reformer for supplying predetermined heat of reaction to a hydrogen raw material and water to react hydrocarbons or alcohols contained in the hydrogen raw material with water to generate hydrogen, and hydrogen supplied from the reformer. A fuel cell that generates electrical energy by reacting with the oxygen in the air; and a tank that stores water to be supplied to the reformer, and the amount of hydrogen consumed by the fuel cell with respect to the amount of hydrogen generated by the reformer. When the amount is small, a reforming hot water device for burning excess hydrogen generated by the reformer and not consumed by the fuel cell to raise the temperature of the water supplied from the tank to the reformer, And energy supply system. 2. A system according to claim 1, wherein water supplied to the outside of the system is stored in a tank, and when the amount of hydrogen consumed by said fuel cell device is smaller than the amount of hydrogen produced by said reformer, the amount of hydrogen generated by said reformer is reduced by a fuel cell. 2. A hot water supply device for burning excess hydrogen that is not consumed to raise the temperature of water supplied from the tank to the outside of the system.
An energy supply system as described. 3. The water heater for hot water supply is given priority to the hot water heater for reforming until the water stored in the tank of the water heater for reforming is heated to a predetermined temperature. 3. The energy supply system according to claim 2, further comprising gas supply control means for supplying surplus hydrogen.