JPH117972A - Fuel-cell power generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel-cell power generator which is used effectively irrespective of fluctuations in power demand and the thermal output of which is used effectively even in its low-load operation, and a control method for the power generator. SOLUTION: The exhaust gas out of a fuel electrode 15 inside a fuel cell body is lead to the burner of a reformer 11, where it is used as the fuel of the reformer burner. Excessive hydrogen is taken out from a midway of a line 114 connecting the fuel electrode outlet of the fuel cell body to the burner inlet of the reformer to be stored or utilized in other apparatuses. Gaseous hydrogen as the fuel reacts with air as the oxidizer in fuel cell body to generate heat, which is fed to a hot heat-recovering heat exchanger 20 by means of a circulating heating medium and is taken out as hot thermal output. The water after the heat recover in the heat exchanger is returned to a flush tank 23 and flushed steam is mainly taken out as hot thermal output and a part of it is mixed as the reforming steam with crude fuel through a line 113 to produce excessive hydrogen in the reformer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a fuel cell power generator. Further, the present invention relates to a control method of the fuel cell power generator.

[0002]

2. Description of the Related Art Conventionally, as schematically shown in FIG. 5, a fuel cell power generator 1 is produced by a reformer 2 and a CO shift converter 3 using hydrocarbons such as natural gas and propane gas as raw fuel. This is a device that generates DC electricity in the fuel cell main body 4 by the hydrogen and oxygen in the air, and converts the DC electricity into AC electricity by the inverse converter 5, and outputs the AC electricity. Further, as by-products, the heat generated in the fuel cell 4 and the calorific value of the fuel gas in the reformer 2 are recovered by the heat exchanger 7 for high-temperature heat recovery and the heat exchanger 6 for low-temperature heat recovery, and the high-temperature heat output and Low temperature heat output. In this case, the exhaust gas 8 containing the unreacted components discharged from the fuel electrode of the fuel cell is sent to the reformer burner and reused.

[0003]

[Problems to be solved by the invention]

(1) When the power demand is high only in a specific time zone of the day and the power demand is relatively low in other time zones, for example, when the fuel cell power generation device is installed in an office or the like, the power demand in the daytime Because of the high power consumption, they are operated at the rated output, but at night there is little power demand and they are often operated at low load. For this reason, the average load factor becomes low, and there is a case where the effective use is not performed.

(2) The reformer is the hottest device in the fuel cell power generator, and is the device most subjected to a heat cycle due to a change in load. In the conventional apparatus, when the electric output changes, the load of the reformer also changes accordingly. When the load of the reformer changes, the amount of heat transfer in the reformer changes, so that the temperature distribution in the reformer changes greatly. For this reason, the reformer is subjected to a heat cycle every time the electric output changes, and there is a problem that the life of the reformer is shortened.

(3) In the conventional fuel cell power generator, since each flow rate such as a raw fuel flow rate is controlled in accordance with the electric output, the heat output also fluctuates in accordance with the electric output. At the time of rated operation, the ratio of electric output and heat output is about 50:50,
It is difficult to change this ratio in the conventional fuel cell device, and there is a drawback that the heat output is not effectively used.

Accordingly, an object of the present invention is to provide a fuel cell power generator that can be used effectively even when the power demand fluctuates.

It is another object of the present invention to provide a fuel cell power generator which does not generate a heat cycle even if the electric output changes.

A further object of the present invention is to provide a fuel cell power generator capable of effectively utilizing a heat output even during a load operation lower than a rated operation.

Still another object of the present invention is to provide a fuel cell power generator capable of outputting an amount of heat commensurate with the demand without changing the electric output when the heat demand is smaller than the heat output. And

[0010]

In order to solve the above-mentioned problems of the present invention, a fuel cell power generator according to the first aspect of the present invention reforms raw fuel to produce hydrogen, A part or the whole is supplied to the fuel electrode of the fuel cell to be used for the power generation reaction of the fuel cell, and a part or all of the unreacted hydrogen discharged from the fuel electrode of the fuel cell is used as reformer combustion hydrogen as reformer hydrogen. In the fuel cell power generation device supplied to the burner, surplus hydrogen that does not contribute to any of the power generation reaction of the fuel cell and the combustion of the reformer burner out of the hydrogen generated in the reformer is converted into a fuel cell power generation device. Means are provided for storing outside or inside the apparatus or supplying the outside to the fuel cell power generation apparatus.

According to a second aspect of the present invention, in the fuel cell power generator according to the first aspect, the means includes a line connecting the reformer, the CO converter, and the fuel cell body. It is characterized by being provided in at least one place.

According to a third aspect of the present invention, in the fuel cell power generator according to the first aspect, the means is connected to a line connecting a fuel electrode outlet of the fuel cell and a reformer burner inlet. It is characterized by being.

A fuel cell power generator according to a fourth aspect of the present invention is the fuel cell power generator according to any one of the first to third aspects, wherein the flow rate of the raw fuel supplied to the reformer is constant and the output of the fuel cell is constant. The flow rate of the reforming combustion hydrogen supplied to the reforming burner is made constant by changing the amount of the surplus hydrogen extracted to the outside according to the fluctuation.

According to a fifth aspect of the present invention, there is provided a fuel cell power generating apparatus for supplying exhaust heat of the fuel cell to the outside as a heat output, and reforming at least a part of steam of the steam separator as reforming steam. Means for supplying heat to the vessel, wherein when the heat output exceeds the heat demand and an excess amount of heat is output, the amount of steam that corresponds to part or all of the excess amount of heat is added. Steam is used as the reforming steam, and a surplus hydrogen is reformed by increasing a flow rate of raw fuel supplied to the reformer in accordance with an increase in the steam.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) FIG. 1 is a schematic block diagram of a fuel cell power generator according to an embodiment of the present invention. As shown in FIG. 1, raw fuel is charged to the reformer 11 through a line 100,
The air is partially burned using air sent from the air compressor 12 via the line 101 to generate heat, and the heat reforms the raw fuel. The reformed fuel gas is sent to the CO converter 13 via a line 102 and is reformed to generate hydrogen gas. The generated hydrogen gas enters the fuel electrode (hydrogen electrode) 15 of the fuel cell body 14 through the line 103. On the other hand, the air sent from the air compressor 16 through the line 104 enters the cathode 17 of the fuel cell body 14. Hydrogen gas as fuel and air as oxidant react in the fuel cell body to generate DC electricity and heat. The DC electricity is converted into AC by the inverter 18 and is taken out of the system. The generated heat is sent to the high-temperature heat recovery heat exchanger 20 by the heat medium circulating through the line 105 by the pump 19,
The water as a heat medium circulating in the line 106 is taken out as a high-temperature heat output. The exhaust gas from the cathode 17 is sent to the condenser 21 through the line 107, where
The heat is exchanged by the heat medium (water) circulating through the flow path 08 to be taken out as a low-temperature heat output. After the heat exchange, the exhaust gas is condensed into water, which is sent to the steam separator 22 by the pump 22 through the line 109. Gas content is line 11
It is released into the atmosphere through zero. Exhaust gas from the reformer burner is sent to a condenser 21 as a low-temperature heat recovery exchanger through a line 111. The water after the heat recovery by the high-temperature heat recovery exchanger returns to the steam separator 23, and the remaining heat is further used for steam separation. The steam generated in the steam separator 23 is extracted as high-temperature heat output in the form of steam through a line 112. A part of the steam passes through the line 113 and is mixed with the raw fuel as reforming steam, and is used to generate hydrogen in the reformer. On the other hand, the exhaust gas from the fuel electrode 15 of the fuel cell body is sent to the burner of the reformer 11 through the line 114, and is used as a reformer burner fuel.

In the fuel cell power generator according to the first aspect of the present invention, a line 115 is provided which branches off in the middle of a line 114 extending from the fuel electrode outlet of the fuel cell main body 14 to the burner inlet of the reformer 11. It is characterized in that, of the hydrogen generated in the reformer 1 through the line 115, surplus hydrogen that is not used as a power generation reaction of the fuel cell and fuel for the reforming burner can be taken out. The surplus hydrogen extracted in this manner may be temporarily stored for reuse, and may be effectively used by another device, or may be returned to the fuel cell power generator at the peak of power demand. Alternatively, it can be used as fuel for another fuel cell power generator.

The removal of surplus hydrogen is carried out at line 114.
In addition to the above, a line 102 between the reformer 11 and the CO converter 13 or a line between the reformer 13 and the fuel cell body 14
A branch line may be provided at any of the lines 103 between the fuel cell and the fuel cell, but it is preferable to take out the fuel between the fuel electrode outlet and the reformer burner inlet.

Further, in the above-described fuel cell power generator according to the first invention of the present application, when the power demand at night or the like is small, the electric output is changed (decreased) according to the demand.
The fuel (hydrogen) that is no longer consumed by the fuel cell is taken out without changing (reducing) the load on the reformer 11 and the CO converter 13. Natural gas used as raw fuel,
Hydrogen, which has a higher added value than propane gas and is easier to store than electricity, can be generated and stored for use when needed, so that the fuel cell power generator can always be used effectively.

FIG. 2 is a block diagram showing a surplus hydrogen amount control device. As shown in FIG.
Are the surplus hydrogen amount control means 31, storage means 32, raw fuel flow rate setting device 33, electric output setting device 34, reformer temperature setting device 35, reformer temperature measuring device 36, raw fuel flow rate adjusting means (valve). 37, a surplus hydrogen receiving device 38 is provided. The raw fuel flow rate is always set to a constant value in the raw fuel flow rate setting device 33,
That is, the flow rate is set according to the rated electric output. The raw fuel flow rate setting unit 33 sends the raw fuel flow rate set value signal S1 to the surplus hydrogen amount control means 31. The surplus hydrogen control means 31 sends a signal S2 to the raw fuel flow control means 37 based on the signal S1, and controls the opening of the flow control valve. As a result, the load on the reformer 11 (FIG. 1) becomes constant, and the amount of hydrogen produced by the reformer also becomes constant. The surplus hydrogen control means 31 stores data based on past reaction examples in the storage means 32, and based on the data D, the raw fuel flow rate set value signal S1
Is calculated, the reformer-generated hydrogen amount data D1 is generated, and stored in the storage means 32. On the other hand, the electric output measuring device 34 measures the changing electric output and sends the measured value to the surplus hydrogen amount control means 31 as an electric output set value signal S3. Based on the data D stored in the storage unit 32, the surplus hydrogen amount control unit 31 calculates the amount of hydrogen consumed by the fuel cell corresponding to the electric output value, and stores it in the storage unit 32 as fuel cell consumed hydrogen amount data D2. The reformer temperature setter 35 sets the reformer temperature to a predetermined value, that is, a temperature to be realized when the reactor is operated to generate hydrogen according to the rated electric output. S4 is sent to the surplus hydrogen amount control means 31. The value of the set temperature value signal S4 is stored as the temperature data T1 in the storage unit 3.
2 is stored. When the electric output changes, the amount of hydrogen produced by the reformer is constant as described above, but the amount of hydrogen consumed by the fuel cell changes, and ΔD = D1−D2 changes. Based on the value of ΔD, a signal S5 corresponding to this ΔD is output to the surplus hydrogen receiving device 3
Send to 8. The surplus hydrogen receiving device 38 extracts or feeds the amount of hydrogen indicated by the signal S5 from the line 115 (FIG. 1). As a result, a change in electric output can be absorbed by increasing or decreasing the amount of excess hydrogen without changing the load on the reformer 11.

Further, in the present invention, even when the amount of hydrogen consumed by the fuel cell changes with the electric output, the amount of surplus hydrogen taken out of the system from the line 115 is changed while the raw fuel flow rate is kept constant. It is possible to maintain a constant amount of combustion hydrogen in the porcelain. By keeping the raw fuel flow rate and reformer combustion hydrogen amount constant in this way, it is possible to keep the reformer load and reformer temperature constant even when the electric output changes. Therefore, the occurrence of a heat cycle can be prevented.

FIG. 3 is a block diagram summarizing the reformer temperature control flow described above.

(Embodiment 2) Next, an embodiment according to the second invention of the present application will be described.

As described above, conventionally, the raw fuel flow rate is controlled so as to correspond to the electric output (the raw fuel flow rate is controlled so as not to generate excess hydrogen), and the heat output is controlled by the electric power. Even if the heat demand is smaller than the heat output, the heat output can not be reduced unless the electric output is reduced, and the excess heat output was eventually discarded without being used . The second invention of this application intends to make effective use of this.

FIG. 4 is a block diagram showing a surplus hydrogen amount control flow according to the second invention of the present application. The reforming steam required for the raw fuel reforming is supplied from the steam separator 23 shown in FIG. 1 to the reformer 11 via the line 113. One heat demand) is further supplied as reforming steam and supplied to the reformer 11. Then, the flow rate of the raw fuel is increased in accordance with the increase in the amount of the reforming steam, and excess hydrogen is generated by the increased amount of the reforming steam and the raw twisting material.

The surplus hydrogen is supplied to the line 102 or 103 between the reformer 11 and the fuel cell 14 shown in FIG.
4 to be taken out and stored by providing a branch line in any one of the lines 114 from the fuel electrode outlet to the burner inlet of the reformer 11 for use when power demand increases or for use in other equipment. Can be used.

As described above, when the surplus heat is supplied to the generation of surplus hydrogen as reforming steam, the heat output is reduced by that amount. Therefore, in the fuel cell power generator of the present invention, even when the heat demand is small, the electric power output is reduced. Can be reduced without changing the heat output, and the excess heat can be effectively used without discarding the surplus heat.

[0027]

According to the present invention, when the power demand is small, the electric output changes according to the demand, but the load of the reformer and the CO converter does not change, and the portion which is no longer consumed by the fuel cell is taken out. By doing so, it generates and stores hydrogen, which has higher added value than natural gas and propane gas currently used as raw fuel, and is easier to store than electricity,
It can be used when necessary, and the fuel cell power generator can always be used effectively.

Further, by always controlling the raw fuel at a flow rate corresponding to the rated electrical output (always generating hydrogen according to the rated electrical output), the load on the reformer is kept constant, and the change in electrical output is caused by excess hydrogen. By increasing or decreasing the amount of absorption, the temperature of the reformer can be kept constant and a heat cycle can be prevented, so that the service life of the reformer can be extended.

Further, the high-temperature heat output is maximum when the raw fuel flow rate is controlled to a flow rate corresponding to the electric output (in a state where there is no surplus hydrogen output), so when the heat demand is smaller than the heat output, By using surplus heat (heat output-heat demand) as steam for reforming and generating surplus hydrogen, it is possible to change the heat output without changing the electric output, Heat can be used effectively.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a fuel cell power generator according to one embodiment of the present invention.

FIG. 2 is a block diagram showing a surplus hydrogen amount control device of the fuel cell power generator according to one embodiment of the present invention.

FIG. 3 is a block diagram showing a reformer temperature control flow of the fuel cell power generator according to one embodiment of the present invention.

FIG. 4 is a block diagram showing a control flow of a surplus hydrogen amount of the fuel cell power generator according to one embodiment of the present invention.

FIG. 5 is a block diagram showing a schematic configuration of a conventional fuel cell power generator.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 fuel cell power generator 2 reformer 3 CO transformer 4 fuel cell body 5 inverter 6 heat exchanger for low-temperature heat recovery 7 heat exchanger for high-temperature heat recovery 8 exhaust gas 11 reformer 12 air compressor 13 CO conversion Device 14 Fuel cell body 15 Fuel electrode (hydrogen electrode) 16 Air compressor 17 Air electrode 18 Inverter 19 Pump 20 Heat exchanger for high-temperature heat recovery 21 Condenser 22 Pump 23 Steam separator 30 Excess hydrogen control device 31 Excess hydrogen Quantity control means 32 Storage means 33 Raw fuel flow rate setting device 34 Electric output setting device 35 Reformer temperature setting device 36 Reformer temperature measuring device 37 Raw fuel flow rate adjusting means (valve) 38 Surplus hydrogen receiving device 100-115 line D1 Data D2 Fuel cell hydrogen consumption data S1 Raw fuel flow rate set value signal S2 signal S3 Electric output set value signal S4 Set temperature Value signal S5 signal T1 Temperature data T2 Temperature data

Claims (5)

[Claims] 1. A reformer reforms a raw fuel to produce hydrogen, and supplies a part or all of the hydrogen to a fuel electrode of a fuel cell for a power generation reaction of the fuel cell. In a fuel cell power generator in which part or all of unreacted hydrogen discharged from a fuel electrode is supplied to a reformer burner as reformer combustion hydrogen, of the hydrogen generated by the reformer, the fuel cell Surplus hydrogen that does not contribute to any of the power generation reaction and the combustion of the reformer burner is stored outside or inside the fuel cell power generator or supplied to the outside of the fuel cell power generator. Fuel cell power plant. 2. The method according to claim 1, wherein the means includes: a reformer; a CO converter;
2. The fuel cell power generator according to claim 1, wherein the fuel cell power generator is provided at at least one location of a line connecting the fuel cell main body. 3. The fuel cell power generator according to claim 1, wherein said means is connected to a line connecting a fuel electrode outlet of the fuel cell and a reformer burner inlet. 4. The reformed combustion hydrogen flow rate supplied to the reformer burner by keeping the raw fuel flow rate supplied to the reformer constant and changing the amount of the surplus hydrogen taken out in accordance with the output fluctuation. The fuel cell power generator according to any one of claims 1 to 3, wherein 5. A fuel cell power generator comprising: means for supplying the exhaust heat of the fuel cell to the outside as heat output; and means for supplying at least a part of the steam of the steam separator to the reformer as reforming steam. In the case where the heat output exceeds the heat demand and an excess amount of heat is output, a steam of an amount obtained by adding steam corresponding to part or all of the excess amount of heat is used as the reforming steam, and A fuel cell power generation device characterized by increasing the flow rate of raw fuel supplied to a reformer in accordance with an increase in the amount to reform surplus hydrogen.