JP3050616B2 - Fuel cell - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel and an oxidizing agent,
The present invention relates to a structure of a fuel cell that generates power by these reactions.

[0002]

2. Description of the Related Art A fuel cell has a power generation section in which a fuel electrode and an oxidant electrode are alternately stacked via an electrolyte and a separator, and generates power by supplying fuel and an oxidant to each electrode plate. And is classified into several types depending on the constituent materials. At present, from a practical point of view, a phosphoric acid fuel cell using phosphoric acid as an electrolyte has reached the technically highest completed area.

FIG. 3 is a system diagram of a conventional example of this phosphoric acid type fuel cell, and FIG. 4 shows a configuration of a power generation unit. The conventional example includes a power generation unit 1, a reformer 2 supplied to the power generation unit 1 for producing a fuel gas containing hydrogen as a main component from a raw material gas, and a reformer 2 for operating the reformer 2 at a high temperature. A burner 3; a blower 4 for sending air to the burner 3 and sending air as an oxidizing gas to an oxidizing electrode 13 of each cell of the power generation unit 1; And a steam generator 5 for supplying steam.

[0004] The power generation unit 1 includes a fuel electrode 1 with an electrolyte 14 interposed therebetween.
1 and an oxidant electrode 13 are arranged in a large number, and a cooling plate 12 is provided for each of a fixed number of cells. 16 are provided. Water supplied from the water supply line 51 is supplied to the cooling plate 12 as cooling water through the steam generator 5 and the cooling water line 52, and after passing through the cooling plate 12, some of the cooling water is The steam is generated by the generator 5. At this time, the heat collected by the power generation unit 1 is used as heat necessary for generating steam. A raw material gas is supplied to the reformer 2 through a raw gas supply line 21, and steam from a steam generator 5 is mixed into the raw material gas through a steam supply line 53. As a result, methane gas or the like in the raw material gas is reformed in the reformer 2 into a gas containing hydrogen gas as a main component, and this gas is uniformly sent to the fuel electrode 11 of each cell through the fuel supply line 22. The exhaust gas from the fuel electrode 11 of each cell is supplied as fuel to the burner 3 through a fuel gas exhaust line 31.
Unreacted hydrogen in the exhaust gas is burned by the air from the blower 4. The blower 4 also serves to blow air for reaction,
Air to the oxidizer electrode 13 of each cell of the power generation unit 1 is supplied through an air supply line 41, and air after the reaction is discharged through an air discharge line 42.

In a conventional phosphoric acid type fuel cell, generally, hydrogen obtained by reforming a raw material such as city gas is used as a fuel and oxygen is used as an oxidizing agent, but the most familiar air source is oxygen. Is used. The temperature of the power generation unit 1 is maintained at about 190 ° C., and electric energy is obtained by the reaction between hydrogen and oxygen under such temperature conditions. At this time, the conversion efficiency of the supplied fuel energy to electric energy, that is, the power generation efficiency depends on the power generation output, but reaches a maximum of about 40%.

The relationship between the power output (load factor) of a fuel cell and the power generation efficiency is as shown in FIG.
%, The efficiency is reduced. Since the power generation efficiency of the fuel cell has such characteristics, it can be said that the fuel cell is suitable for applications such as on-site power generation that can be operated at the highest possible load factor. However, in recent years, with the spread of cogeneration systems that use not only the power of this power generation but also heat, a fuel cell with high power generation efficiency and clean exhaust gas has been installed in recent years. Is attracting attention.

[0007]

However, in the above-mentioned cogeneration system, the fluctuation of the daily load is large in the application to which the cogeneration system is to be applied. For example, there is a load fluctuation as shown in FIG. When a fuel cell is applied to such an application and all or most of the power is supplied from the fuel cell, a model having an output capable of supplying the maximum power of the load is installed. In this case, the power generated by the fuel cell changes following the load fluctuation. By the way, as described above, the power generation efficiency of a fuel cell is deeply related to the power generation output, and when the fuel cell is operated in an application having such a load fluctuation, the efficiency of the fuel cell during a time period when the required power of the load is small. Is extremely bad. That is, in such a state, there is a problem that the fuel consumption for the generated electric power is large, and the economic efficiency is deteriorated. Such a problem becomes more remarkable as the difference between the daytime load and the nighttime load becomes larger. When a fuel cell is applied to a cogeneration system, it becomes a serious obstacle from the viewpoint of overall economic efficiency.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the fuel cell, and has as its object to reduce the power required by the load in accordance with the required power of the load. Accordingly, it is an object of the present invention to provide a fuel cell capable of reducing the supply amount of a fuel gas and an oxidizing gas in accordance with the conditions, and constantly operating under conditions of high power generation efficiency.

[0009]

In order to achieve the above object, in a fuel cell according to the present invention, a power generation unit having a fuel electrode to which fuel gas is supplied and an oxidant electrode to which oxidant gas is supplied is provided. In a fuel cell that performs power generation, the power generation unit is divided into a plurality of power generation parts, the flow path of the fuel gas is divided corresponding to the power generation part, and each is connected to the power generation part through a valve. A flow path is provided corresponding to the power generation part, and a distribution means for supplying an oxidant is provided in each flow path, a power generation output required for the power generation unit is detected, and the valve and the delivery are provided in accordance with the power generation output. A control unit for controlling the operation of the means and controlling the number of operation of the power generation unit, wherein the power generation unit is operated at all times.
The cooling water is passed in series from one power generation part to another power generation part .

[0010]

In the fuel cell according to the present invention, the power generation section is divided into a plurality of power generation sections, the flow paths of the fuel gas and the oxidizing gas supplied to the power generation section are also divided correspondingly, and the divided flow paths are formed. A valve or a delivery means is provided to control the supply of the fuel gas and the oxidizing gas in accordance with the power generated by the control unit and to control the number of power generation units to be operated. As a result, the supply amounts of the fuel gas and the oxidizing gas are controlled in accordance with the required power of the load, and the load ratio of the operating power generation part is maintained at a high level to increase the power generation efficiency. And power generation
Cooling water from the inside power generation part to the stopped power generation part
The temperature required for operation of the stopped power generation part.
And restart power generation in response to increased load in a short time.
To get

[0011]

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

FIG. 1 is an overall system diagram of a fuel cell showing an embodiment of the present invention. In this embodiment, the power generation unit is 3
In this embodiment, a fuel gas containing hydrogen as a main component supplied to the power generation units 1, 1-1, 1-2 is used as a raw material. A reformer 2 produced from gas; a burner 3 for operating the reformer 2 at a high temperature; a blower 4 for feeding air to the burner 3 and the power generation unit 1; A steam generator 5 for supplying steam to be mixed into the gas;
Blowers 7, 8, 9 as delivery means for supplying reaction air to the two power generation units 1, 1-1, 1-2, and detecting the power output of the fuel cell and detecting the power of the blower 7,
Valves 10, 10-1, 10-2 provided in the fuel supply lines 22-1, 22-2, 22-3 to the power generation units 1, 1-1, 1-2 divided with the operation of 8, 9 And a control unit 6 for controlling the opening degree. The arrows shown on each line in the figure indicate the direction of the flow of the substance.

The basic configuration of each power generation unit is the same as that of the conventional example. That is, the power generation unit 1 (1-1, 1-2) is provided with the electrolyte 1
4 (14-1, 14-2) with the fuel electrode 11 (11-
1, 11-2) and the oxidizer electrode 13 (13-1, 13-2)
Are arranged in the separator 15 (15-
1, 15-2), a cooling plate 12 (12-1, 12-2) is provided for each fixed number of cells, and the poles 11 (11-1, 11-2), 13 ( 13-1, 13-
The group 2) is provided with electric output units 16 (16-1, 16-2). As described above, the power generation units 1-1 and 1-2 have the same structure as the power generation unit 1, and the power generation units 1, 1-1 and 1--1
Although both are configured to have the same output voltage, the power generation units 1-1 and 1-2 are configured such that the effective area of the electrode plate is smaller than that of the power generation unit 1 according to the power generation output. Water supplied from the water supply line 51 is supplied to the cooling plates 1212-1 and 12-2 as cooling water through the steam generator 5 and the cooling water line 52, and is supplied to the cooling plates 12-1 and 12-2.
After passing through 2-1 and 12-2 in series, some of the cooling water is turned into steam in the steam generator 5. At that time, part of the heat collected by the power generation unit is used as heat required for generating steam.

A raw material gas is supplied to the reformer 2 through a raw material gas supply line 21, and steam from a steam generator 5 is mixed into the raw material gas through a steam supply line 53. As a result, methane gas or the like in the raw material gas is reformed in the reformer 2 into a gas containing hydrogen gas as a main component, and this gas is supplied via the fuel supply line 22 to the fuel electrodes 11, 11-1 of each power generation unit. , 11-2. Therefore, three fuel supply lines 22 (22-1, 22-2, 22-
Branch to 3), and valves 10, 10-1, 10
-2 are provided and connected to the fuel electrodes 11, 11-1 and 11-2. Exhaust gas from each of the fuel electrodes 11, 11-1, and 11-12 is supplied as fuel to the burner 3 through a combustion gas discharge line 31, and unreacted hydrogen in the exhaust gas is burned by air from the blower 4. Therefore, each fuel electrode 11,
The fuel gas discharge lines 31 from 11-1 and 11-2 are combined and connected to the burner 3. On the other hand, the power generation units 1,1-1,
Regarding 1-2, the reaction air is sent from the blowers 7, 8, 9 through the reaction air supply lines 71, 81, 91, and the reacted air from the respective power generation units 1, 1-1, 1-2. Is discharged through the air discharge line 42 after the reaction.

The blowers 7, 8, and 9 described above are connected to the control unit 6 by a control signal line 6-1. The valves 10, 10-1 and 10-2 are connected to a control unit by a control signal line 6-2. 6, the operation or opening is adjusted under the control of the control unit 6.
The control unit 6 detects the power generation output of the fuel cell, adjusts its operation or opening according to the required power of the load, controls the power generation of the power generation units 1, 1-1, 1-2, and controls the fuel generation. Controls the amount of power generated by the entire battery.

A specific control operation and operation of the embodiment configured as described above will be described.

In the embodiment shown in FIG. 1, the electric output units 16, 16-1 and 16-2 are connected and used in a parallel state.
The outputs of 1, 1-2 are 100 kW and 5 respectively as an example.
The description will be made assuming 0 kw and 50 kw. In this case, the number of plates used in each of the power generation units 1, 1-1, and 1-2 is designed to be the same in order to make the output voltage at the maximum output the same, Is a power generation unit 1-1,
What is used in 1-2 is の of the power generation unit 1. In this case, since the maximum output of the fuel cell is 200 kW, when the load requires 200 kW, power is generated by all the power generation units. When the power required by the load decreases, the power generation unit 1-2 and the power generation unit 1-
The supply of fuel and air to 1 is stopped to stop power generation. Conversely, when the electric power of the load increases, the supply of the fuel and the air is started, and the power generation in the power generation unit 1-2 and the power generation unit 1-1 is started. At this time, each of the electrical output units 16, 16-1, 16-2
Are connected in parallel, the output can be adjusted by decreasing and increasing the generated current without causing a large voltage fluctuation even when the output section is switched. By such output adjustment, the supply amounts of the fuel gas and the oxidizing gas are controlled in accordance with the required power of the load, and the power generation units 1, 1-1, and 1-2 maintain a high load ratio, and the load of the load is maintained. Even when the required power is reduced, high power generation efficiency can be obtained.
Here, since the cooling water of the power generation unit communicates with each of the power generation units 1, 1-1, and 1-2 through the cooling water line 52, even if the power generation units 1-1 and 1-2 are stopped. The temperature required for operation is maintained, and power generation can be restarted with a load increase in a short time.

FIG. 2 shows the relationship between the power generation output and the efficiency by such fuel cell operation. Here, a fuel cell of a maximum of 200 kW is taken as an example as described above. That is, the output by the power generation of all the power generation units is shown by a solid line, and for power generation up to 100 kW, almost the same efficiency as the output (the broken line) by the power generation of only the power generation unit 1 is obtained. However, the efficiency gradually decreases below this level, and becomes 20% at 50 kW output.
It will be about. Therefore, when such a load situation is reached, specifically, when the load factor reaches the point A in FIG. In this system, even if half of the power generation unit is operated, the auxiliary equipment for operating the fuel cell (particularly, the blower that supplies air to the reformer) is not in the optimal design state for half of the power generation unit (that is, Equipment of a size of 200 kW is used, which is an excessive device when viewed as a 100 kW machine, and is not an optimal design in consideration of reduction in power consumption of auxiliary machines.) The efficiency at this time is slightly reduced because the power is connected to the suspended power generation unit. However, in the output region of 75 to 50 kW, power can be generated with higher efficiency than when all the power generation units are used.

The number of divisions of the power generation unit is not limited to the above-mentioned three, but may be two or four or more in consideration of the load variation.
As described above, the present invention can be variously applied according to the gist and can take various embodiments.

[0020]

As is apparent from the above description, according to the fuel cell of the present invention, the power generation section is divided into a plurality of power generation sections,
A structure that makes it possible to split each of the electrodes of each power generation unit content supplied separately oxidant and fuel, when the required power of the load receiving power supply from the fuel cell varies, the by controlling the supply of fuel and oxidizing agent, by increasing or decreasing the number of power generating unit amount of operating, it is possible to generate power by extremely high power generation efficiency operating conditions, the generator
Cooling water from the inside power generation part to the stopped power generation part
The temperature of the power generation part that is stopped
In a short time to restart power generation as load increases
You can do it . Therefore, the amount of fuel used is reduced as compared with a conventional fuel cell that does not implement such an invention. For example, when a fuel cell is applied to a cogeneration system, the operating cost is reduced, the cost is reduced , and the load is reduced.
A system with good responsiveness can be realized even with an increase in the number .

[Brief description of the drawings]

FIG. 1 is a system diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing power generation efficiency in the embodiment.

FIG. 3 is a system diagram showing a configuration of a conventional fuel cell.

FIG. 4 is a configuration diagram of a power generation unit of the conventional example.

FIG. 5 is a diagram showing the power generation efficiency of the conventional fuel cell.

FIG. 6 is a diagram showing an example of a change in load power per day.

[Explanation of symbols]

1, 1-1, 1-2: power generation unit, 2: reformer, 3: burner, 4: blower, 5: steam generator, 6: control unit, 6-1, 6-2: control signal line , 7,
8, 9 ... blower, 10, 10-1, 10-2 ... valve, 11, 11-1, 11-2 ... fuel electrode, 12, 12-
1, 12-2: cooling plate, 13, 13-1, 13-2: oxidizer electrode, 14, 14-1, 14-2: electrolyte, 16, 1
6-1, 16-2: electric output section, 21: raw gas supply line, 22, 22-1, 22-2, 22-3: fuel supply line, 31: fuel gas discharge line, 42: air discharge after reaction Line, 51: water supply line, 52: cooling water line, 53: steam supply line, 71, 81, 91: reaction air supply line.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Takashi Hasegawa Nippon Telegraph and Telephone Corporation, 1-6-1, Uchisaiwaicho, Chiyoda-ku, Tokyo (56) References JP-A-62-24570 (JP, A) JP-A Sho 62-150664 (JP, A) JP-A-61-206173 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 8/00-8/24

Claims (1)

(57) [Claims] 1. A fuel cell for generating electric power by the power generation unit fuel electrode and the oxidizer gas which fuel gas is supplied and an oxidant electrode supplied, by dividing the pre-Symbol generation unit to the plurality of power generation portion, connect the flow path of the previous SL fuel gas to the power generation portion through respectively divided corresponding valve to the power generation portion, the respective flow channel with the flow path of the previous SL oxidant gas provided in correspondence with the power generation portion delivery means for oxidizing agent supply is provided, controlling the number of operation of the power generation portion controls the operation of the delivery means and the valve according to the detected that the power generation output power output required before Symbol generation section Equipped with control unit
The power generation unit which is constantly operated among the power generation units is replaced with another power generation unit.
A fuel cell characterized by passing cooling water in series every minute .