JP2807635B2 - Temperature control method for fuel cell power generation equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the temperature of a fuel cell power generation system using a molten carbonate fuel cell.

[0002]

2. Description of the Related Art Molten carbonate fuel cells have features that are not found in conventional power generation devices, such as high efficiency and little impact on the environment, and have attracted attention as power generation systems following hydro, thermal and nuclear power. Are being researched and developed in various countries around the world. In particular, in a power generation facility using a molten carbonate fuel cell using natural gas as a fuel, as shown in FIG. 3, a reformer 10 for reforming a fuel gas 1 such as natural gas into an anode gas 2 containing hydrogen, A fuel cell 20 for generating electricity from the anode gas 2 and the cathode gas 3 containing oxygen; the anode gas 2 produced by the reformer is supplied to the fuel cell;
After consuming most of the fuel cell (for example, 80%) in the fuel cell, it enters the water removal device 30 as the anode exhaust gas 4,
The water is removed and supplied to the combustion chamber 10a of the reformer.
In the reformer 10, combustible components (hydrogen, carbon monoxide, methane, etc.) in the anode exhaust gas are burned in the combustion chamber 10a, and the reforming pipe 10b is heated by the high-temperature combustion gas to reform the fuel passing through the reforming pipe. I do. The combustion exhaust gas 5 that has exited the reforming chamber merges with the pressurized air 6 supplied from the pressure recovery device 40 to become the cathode gas 3 and supplies necessary carbon dioxide to the cathode side of the fuel cell. A part of the cathode gas (cathode exhaust gas 7) partially reacted in the fuel cell is circulated to the upstream side of the fuel cell by the blower 22, and the rest is collected by the pressure recovery device 40.
To recover the pressure, and the heat is recovered by the heat recovery device 50 and discharged out of the system.

[0003] The water removing device 30 comprises a condenser 32, a water separator 34, a blower 36, a water supply pump 38, and the like.
The water separated by the water separator 34 is supplied to the heat recovery device 50 by the water supply pump 38. The pressure recovery device 40 includes a turbine compressor device 44 (comprising the turbine 41, the compressor 42, and the generator 43) and an auxiliary combustor 46. The auxiliary combustor 46 heats the cathode exhaust gas 7 and supplies it to the turbine 41. I can do it. The heat recovery device 50 includes a feedwater heater 52, an evaporator 54, and a superheater 56, and heats and evaporates the feedwater from the feedwater pump 38 with the high-temperature exhaust gas that has exited the turbine 41, thereby forming a superheated steam 8
Generate. The generated steam 8 is supplied to the fuel gas 1 supplied to the fuel preheater 12 and used for the reforming reaction.

The fuel cell 20 uses a molten carbonate having a high melting point as an electrolytic solution. When the average temperature is 500 ° C. or lower, the electrolytic solution partially condenses, and when the average temperature exceeds 700 ° C., the electrolytic solution evaporates. And there is a problem that corrosion becomes severe. Therefore, conventionally, in the temperature control of the fuel cell, the maximum temperature (outlet temperature) is controlled by the amount of air from the compressor 42, and the minimum temperature (inlet temperature) is controlled by the amount of cathode gas circulated by the blower 22. That is, as shown in FIG. 3, the conventional fuel cell power generation equipment includes an inlet temperature control device 24 and an outlet temperature control device 48, detects the temperature of the cathode gas 3 entering the fuel cell, and adjusts the temperature to a predetermined range ( For example, 5
The flow rate of the circulating cathode gas is increased or decreased by controlling the blower 22 so as to be 50 to 600 ° C., the temperature of the cathode exhaust gas 7 is detected, and this temperature is set within a predetermined range (for example, 68 ° C.).
(0 to 700 ° C.) to control the pressure recovery device 40 to increase or decrease the amount of air from the compressor 42.

[0005]

The fuel cell exhibits power generation characteristics (relationship between current density and voltage) as illustrated in FIG. 4, and the current density and voltage are kept constant during normal rated operation (for example, (Point A: 150 mA / cm ² , 0.8 V / cell). However, when the battery performance decreases due to long-term operation, the internal resistance R increases, the voltage V decreases, and the same power P
Since the current I is increased (for example, point B) in order to obtain (= V × I), there is a problem that the calorific value (= I × R ² ) in the fuel cell rapidly increases. At this time, in order to maintain the fuel cell in a predetermined temperature range, the outlet temperature control device 48 described above is used.
When the air amount from the compressor 42 is increased by
There was a problem that the required air amount was excessive as compared with the normal rated operation. In addition, if the maximum flow rate of the compressor 42 is set to be large so as to cope with this situation, the flow rate of the compressor becomes about 80% or less of the maximum flow rate during normal rated operation, and there is a problem that surging occurs and the compressor cannot be used. Was. Further, in order to avoid this, when the compressor is operated at a flow rate at which surging does not occur (about 80% of the rating) and an excess amount of air is supplied to the auxiliary combustor 46 via the bypass line 6a (see FIG. 3), There has been a problem that the temperature of the cathode exhaust gas 7 supplied to the turbine 41 decreases, and the heat recovery device 50 cannot generate sufficient superheated steam 8. Further, the cathode exhaust gas 7 supplied to the turbine 41
To maintain the temperature of the fuel gas 1 in the auxiliary combustor 46.
Burning the fuel wastes the fuel gas 1 and degrades the power generation efficiency of the entire power generation facility.

The present invention has been made to solve such a problem. An object of the present invention, a fuel
Adjust the cathode gas inlet temperature, which directly affects battery performance.
It can always be kept in the optimal range (eg constant temperature)
In addition , the compressor does not generate surging during normal rated operation , and even if the battery performance deteriorates, the amount of air discharged from the compressor does not become excessive, and there is sufficient superheated steam in the heat recovery unit without wasting fuel gas. It is an object of the present invention to provide a method for controlling the temperature of a fuel cell power generation facility capable of generating the temperature.

[0007]

According to the present invention, there is provided a fuel cell for generating electricity from an anode gas containing hydrogen and a cathode gas containing oxygen, and a method for producing cathode exhaust gas passing through the fuel cell .
An exhaust gas circulator that circulates part of the fuel cell upstream,
With the remaining being driven by the cathode exhaust gas pressure recovery system for pressurizing the air, an air supply line to mix the pressurized air has an air cooling system for a fuel cell upstream side Kasotogasu, the exhaust gas circulation by exhaust gas circulation device By quantity
Control the temperature of the cathode gas entering the fuel cell,
A method for controlling the temperature of a fuel cell power generation facility is provided, wherein the pressurized air is cooled by an air cooling device in response to a decrease in the performance of the fuel cell.

According to a preferred embodiment of the invention, cathode
Blower that circulates part of the exhaust gas from the fuel cell upstream of the fuel cell
And inlet temperature to increase or decrease the flow rate of circulating cathode gas
A control device, a refrigerant flow control valve for controlling a refrigerant flow rate of the air cooling device, and an air temperature control device for controlling the refrigerant flow control valve ;
The temperature of the cathode gas entering the battery is detected and this temperature
Control the blower so that it is within a certain range, and at the same time,
The air temperature controller detects the temperature of the cathode exhaust gas and controls the refrigerant flow control valve to change the temperature of the pressurized air so that the temperature falls within a predetermined range. Further, it is preferable that the air cooling device is an indirect heat exchanger using air as a refrigerant.

[0009]

According to the method of the present invention described above, an air cooling device is provided in an air supply line for mixing pressurized air into the gusset gas on the upstream side of the fuel cell. To cool pressurized air,
Even if the cell performance deteriorates due to long-term operation and the calorific value in the fuel cell increases sharply, the low-temperature pressurized air flows into the gusset gas, thereby increasing the amount of cathode exhaust gas without increasing the amount of air from the pressure recovery device. The temperature can be reduced to a predetermined range. In addition, part of the cathode exhaust gas is
An exhaust gas circulating device circulating upstream of the pond is provided.
By controlling the amount of gas circulation, the amount of cathode gas entering the fuel cell
The temperature can be adjusted to the optimal temperature . That is, empty
Gas exhaust system keeps exhaust gas temperature of fuel cell within specified range
Controllable and at the same time the inlet temperature that constitutes the exhaust gas circulation device
The controller controls the temperature of the cathode gas entering the fuel cell.
It can be controlled within a predetermined range . Furthermore, with the exhaust gas circulation device
A large amount of cathode exhaust gas is circulated upstream of the fuel cell and
Since the battery inlet temperature is maintained within the specified range, air
The temperature of the pressurized air is greatly reduced by the cooling device and the cathode
Caso mixed with a large amount of circulating exhaust gas even if mixed with gas
Gas temperature can be prevented and the inlet temperature can be reduced.
Maintain the optimal range (eg, constant temperature) to prevent coagulation of the lysate
Can be

Therefore, there is a direct influence on the performance of the fuel cell.
Always keep the cathode gas inlet temperature in the optimal range (for example, constant temperature
Degree), and even if the battery performance decreases, the discharge air amount of the pressure recovery device (compressor) does not increase, and the maximum flow rate of the compressor can be the same as before, so that the normal rating There is no surging of the compressor during operation. Furthermore, since no surging occurs, the compressor can be operated at the flow rate required by the battery,
Excess air is not supplied to the auxiliary combustor, the temperature of the cathode exhaust gas is kept high, and sufficient superheated steam can be generated by the heat recovery device without fuel gas combustion.

[0011]

Preferred embodiments of the present invention will be described below with reference to the drawings. In the drawings, common portions are denoted by the same reference numerals and used, and redundant description will be omitted. FIG. 1 is an overall configuration diagram of a fuel cell power generation facility to which the method of the present invention is applied. In this figure, the fuel cell power generation equipment
A reformer 10, a fuel cell 20 that generates electricity from an anode gas 2 containing hydrogen and a cathode gas 3 containing oxygen, a moisture removing device 30, and a pressure recovery device that pressurizes air 6 driven by a cathode exhaust gas 7 that has passed through the fuel cell. 40, a heat recovery device 50, etc., the fuel gas 1 is reformed by the reformer 10, the power is generated by the fuel cell 20, the water in the anode exhaust gas 4 is removed by the water removal device 30, and the pressure recovery device 40 The pressure of the cathode exhaust gas 7 is recovered, and the heat recovery device 50 recovers exhaust heat. Further, the temperature of the blower 22 circulating a part of the cathode exhaust gas 7 upstream of the fuel cell 20 and the temperature of the cathode gas 3 entering the fuel cell are detected so that this temperature falls within a predetermined range (550 to 600 ° C.). And an inlet temperature control device 24 for controlling the blower 22 to increase or decrease the flow rate of the circulating cathode gas. Furthermore, an air supply line 14 is provided for mixing pressurized air into the gusset gas upstream of the fuel cell.

In the fuel cell power plant of FIG. 1, an air cooling device 62 is provided in the air supply line 14. The air cooling device 62 is preferably an indirect heat exchanger using air as a refrigerant, but may be a device using fresh water or seawater as a refrigerant. Further, the fuel cell power generation equipment of FIG. 1 further includes a refrigerant flow control valve 63 for controlling the refrigerant flow of the air cooling device, and an air temperature control device 64 for controlling the refrigerant flow control valve 63. With this configuration, the temperature of the cathode exhaust gas 7 is detected, and this temperature is set within a predetermined range (for example, 680 to 700).
° C) to control the temperature of the pressurized air by controlling the refrigerant flow control valve 63. The air temperature control device 64 is a conventional outlet temperature control device 48 (see FIG. 3).
The temperature of the cathode exhaust gas 7 may be detected to control both the refrigerant flow control valve 63 and the pressure recovery device 40 at the same time, or both may be selected and controlled according to the operation state. You may.

FIG. 2 is a configuration diagram of the main part of FIG. 1. The numbers enclosed by rectangles in the figure are approximate values of the flow weight Kg and the temperature ° C at the time of rated operation in the case of a 1000 kW power generation facility. In FIG. 2, the cathode exhaust gas 7 is about 6600
kg / h, 680-700 ° C., and the inflow air 6 has a flow weight of about 400 before entering the air cooling device 62 (upstream side).
0 kg / h, 100-300 ° C. Therefore, since the gas specific heat of air and cathode exhaust gas are almost equal,
Even when the temperature of the cathode exhaust gas 7 rises, for example, by about 50 ° C. due to deterioration of the fuel cell, the temperature rise of the cathode exhaust gas can be suppressed by cooling the inflow air by about 70 to 80 ° C. by the air cooling device 62. I understand. In this case, the cathode gas 3 flowing into the fuel cell 20
, The amount of circulating gas by the blower 22 is large as shown in FIG.
And the temperature control (increase in the amount of circulating gas) by the above-described inlet temperature control device 24 ,
Always optimizes the inlet temperature of cathode gas 3 which directly affects
It can be kept in a range (for example, a constant temperature).

As described above, according to the method of the present invention,
An air cooling device 62 is provided in the air supply line 14 for mixing the pressurized air 6 into the cathode gas on the upstream side of the fuel cell, and the pressurized air is cooled by the air cooling device 62 in response to the performance deterioration of the fuel cell. Even if the cell performance deteriorates due to long-term operation and the calorific value in the fuel cell increases sharply, the low-temperature pressurized air flows into the gusset gas without increasing the amount of air from the pressure recovery device 40. The temperature of the exhaust gas 7 can be reduced to a predetermined range.
Further, a part of the cathode exhaust gas 7 is transferred to the upstream side of the fuel cell 20 .
Exhaust gas circulation device (blower 22 and inlet temperature control
Device 24) to control the amount of exhaust gas circulation.
Optimizes the temperature of cathode gas 3 entering fuel cell 20
Temperature can be adjusted. That is, the air cooling device
62 allows the exhaust gas temperature of the fuel cell to be controlled within a predetermined range.
At the same time, the inlet temperature control device
The temperature of the cathode gas 3 entering the fuel cell 20 is determined by the device 24.
The degree can be controlled within a predetermined range. Furthermore, for exhaust gas circulation equipment
A larger amount of cathode exhaust gas 7 is provided upstream of the fuel cell 20
Circulate and maintain the fuel cell inlet temperature within the specified range
, The temperature of pressurized air is significantly reduced by the air cooling device 62
Down and mix with the cathode gas,
It is possible to prevent the temperature of the mixed cathode gas 3 from dropping.
The cathode gas inlet temperature flowing into the fuel cell
In the optimal range (eg, constant temperature) to prevent solidification of
Can be.

Accordingly, the performance of the fuel cell 20 is not directly affected.
The inlet temperature of a certain cathode gas 3 is always kept in an optimum range (for example,
(Constant temperature), and even if the battery performance deteriorates, the discharge air amount of the pressure recovery device 40 (compressor 42) does not increase, and the maximum flow rate of the compressor can be the same as the conventional one. There is no surging of the compressor during normal rated operation. Furthermore, since no surging occurs, the compressor can be operated at the flow rate required by the battery, no extra air is supplied to the auxiliary combustor 46, the temperature of the cathode exhaust gas is kept high, and heat is recovered without fuel gas combustion. The device can generate sufficient superheated steam.

It should be noted that the present invention is not limited to the above-described embodiment, but can be variously modified without departing from the gist of the present invention.

[0017]

As described above, the temperature control method for a fuel cell power generation system according to the present invention has a direct influence on the performance of the fuel cell.
Always keep the cathode gas inlet temperature in the optimal range (for example, constant temperature
), And the compressor does not generate surging during normal rated operation. Even if the battery performance deteriorates, the amount of air discharged from the compressor does not become excessive, and heat is consumed without wasting fuel gas. It has excellent effects such as sufficient generation of superheated steam in the recovery device.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a fuel cell power generation facility to which a method of the present invention is applied.

FIG. 2 is a configuration diagram of a main part of FIG. 1;

FIG. 3 is an overall configuration diagram of a conventional power generation facility using a molten carbonate fuel cell.

FIG. 4 is a power generation characteristic diagram of a fuel cell.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fuel gas 2 Anode gas 3 Cathode gas 4 Anode exhaust gas 5 Combustion exhaust gas 6 Air 7 Cathode exhaust gas 8 Steam 10 Reformer 10a Combustion chamber 10b Reforming pipe 12 Fuel preheater 14 Air supply line 20 Fuel cell 22 Blower 24 Inlet temperature control Apparatus 30 Water removal device 32 Condenser 34 Water separator 36 Blower 38 Feedwater pump 40 Pressure recovery device 41 Turbine 42 Compressor 43 Generator 44 Turbine compressor device 46 Auxiliary combustor 48 Outlet temperature control device 50 Heat recovery device 52 Feedwater heater 54 Evaporator 56 Superheater 62 Air cooling device 63 Refrigerant flow control valve 64 Air temperature control device

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuhiko Ito 3-1-1-15 Toyosu, Koto-ku, Tokyo Inside Ishikawa-Shimaharima Heavy Industries, Ltd.Higashiji Technical Center (72) Inventor Nobuo Nagasaki Sankomachi, Hitachi No. 1-1, Hitachi, Ltd. (72) Inventor Shinichi Ishida 3-10-10, Minami-Otsuka, Toshima-ku, Tokyo 6F, Nihon Seimei Minami-Otsuka Building Molten carbonate fuel cell power generation system technology research association (72) Inventor Yoshihiro Sawa 3-10-10 Minami-Otsuka, Toshima-ku, Tokyo 6F, Minami-Otsuka Building, Nihon Seimei Molten carbonate fuel cell power generation system technology research association (56) References JP-A-7- 288135 (JP, A) JP-A-58-164165 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01M 8/00-8/24

Claims (3)

(57) [Claims] 1. A fuel cell for generating electricity from an anode gas containing hydrogen and a cathode gas containing oxygen, and a part of the cathode exhaust gas passing through the fuel cell is circulated upstream of the fuel cell.
Exhaust gas circulating device, a pressure recovery device driven by the remaining cathode exhaust gas to pressurize air, and an air supply line having an air cooling device and mixing the pressurized air into the gusset gas upstream of the fuel cell, Enter the fuel cell according to the amount of exhaust gas circulated by the exhaust gas circulation device
Controlling the temperature of the cathode gas, and simultaneously cooling the pressurized air by an air cooling device in response to a decrease in the performance of the fuel cell. 2. A part of the cathode exhaust gas is transferred upstream of a fuel cell.
The flow rate of the circulating blower and the circulating cathode gas
An inlet temperature control device for increasing and decreasing, a refrigerant flow control valve for adjusting the refrigerant flow rate of the air cooling device, and an air temperature control device for controlling the refrigerant flow control valve , Cathode gas entering
Temperature, and adjust the temperature so that it is within the specified range.
Control the blower, and at the same time, by the air temperature control device,
2. The fuel cell power plant according to claim 1, wherein the temperature of the pressurized air is changed by detecting the temperature of the cathode exhaust gas and controlling the refrigerant flow control valve so that the temperature falls within a predetermined range. Temperature control method. 3. The method according to claim 1, wherein the air cooling device is an indirect heat exchanger using air as a refrigerant.