JPH05198309A - Fuel cell power generating system - Google Patents

Abstract

PURPOSE:To restrict the fluctuation of the output of a fuel cell to be caused by the condensation of the fuel gas at the time of starting the supply of the fuel or at the time of switching the fuel in a power generating system of a fuel cell using the reformed fuel gas, which is obtained by vaporizing the liquid fuel. CONSTITUTION:A vaporizer 1 for vaporizing the liquid fuel 43 and a reformer 9 for reforming the vaporized fuel gas to obtain the hydrogen rich gas and feeding this hydrogen rich gas to a fuel cell 22 are unified integrally. The exhaust heat of the reformer 9 is used to vaporize the liquid fuel 43, and the vaporized gas is supplied to the reformer 9 through a desulfurizing device 5 arranged near the reformer 9 for steam reforming without feeding the gas through a long distance pipeline. Condensation of the vaporized fuel gas is thereby prevented to restrict the fluctuation of the output of a fuel cell to be caused by shortage of the fuel gas due to the condensation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell power generation system which suppresses fluctuations in fuel cell output due to fuel gas shortage due to fuel gas condensation.

[0002]

2. Description of the Related Art As a fuel cell power generation system using a liquid fuel such as methanol as a fuel, a carburetor 1, a flow control valve 2, 7, a heat exchanger 3, as shown in the system diagram of FIG.
6, 11, 14, 16, 23, 27, 32, desulfurization device 5, steam separator 8, reformer 9, reformer burner 10, CO
Shift converter 13, condensers 15, 28, 33, fuel cell 22, control device 39, and various sensors 4, 12,
A system composed of 37 or the like has been proposed.

The structure and operation of this conventional fuel cell power generation system will be described below.

First, in a fuel supply system, a liquid fuel 43 such as methanol is vaporized in a vaporizer 1 and heated in a heat exchanger 3, and then a desulfurization unit together with a part of a hydrogen rich CO shift converter 13 outlet gas. 5, the sulfur content is removed (this desulfurization process is not necessary in the case of fuel containing no sulfur content such as methanol). The desulfurized fuel gas is
After the temperature is raised in the heat exchanger 6 together with the steam 44 generated in the steam separator 8, it is sent to the reformer 9 of the fuel reforming system.

In the fuel reforming system, the reforming device 9 causes a reforming reaction of the fuel to produce a hydrogen-rich reformed gas. The reformed gas that has exited the reformer 9 is sent to the CO shift converter 13 after being lowered in temperature by the heat exchanger 11, and carbon monoxide in the reformed gas is changed to carbon dioxide by the shift reaction ( The CO shift converter 13 is unnecessary in the case of a fuel in which the amount of carbon monoxide generated in the reforming reaction is small). The temperature of the gas leaving the CO shift converter 13 is lowered by the heat exchanger 14 and then sent to the condenser 15, where unreacted water vapor is condensed and removed. In addition, CO
A part of the gas leaving the shift converter 13 is recycled in order to supply the hydrogen required for the desulfurization reaction to the desulfurization device 5. The extracted water 36 separated by the condenser 15 is sent to the steam separator 8 and again supplied as steam 44 to the reformer 9. The gas discharged from the condenser 15 is heated by the heat exchanger 16 and then sent to the fuel electrode 19 of the fuel cell 22, and hydrogen in the gas is used for the cell reaction of the fuel cell 22.

The fuel cell 22 includes a fuel electrode 19 and an electrolyte 2.
In the cell reaction, hydrogen ions generated in the fuel electrode 19 move in the electrolyte 20 to the air electrode 21, and in the air 34 supplied as an oxidant from the oxidant supply system. Reacts with oxygen to produce water.
In the oxidant supply system, the air 34 is heated in the heat exchanger 23 and then sent to the air electrode 21 to be used in the cell reaction of the fuel cell 22. After the temperature of the air electrode exhaust gas 31 is lowered by the heat exchanger 32, it is sent to the condenser 33 and the produced water 35 is condensed and removed. The produced water 35 removed by the condenser 33 is also sent to the steam separator 8 and supplied to the reformer 9 as steam 44. The gas that has left the condenser 33 is discharged into the atmosphere as an exhaust gas 45. Since the cell reaction of the fuel cell 22 is accompanied by heat generation, although not shown in the figure, a cooling system for cooling the fuel cell 22 and peripheral devices is provided.

The DC power 18 generated by the fuel cell 22 is converted into AC power 30 by the inverter 29 and supplied to the load 38. Fuel electrode 19 of fuel cell 22
Since the hydrogen utilization rate is about 70 to 80%, the fuel electrode exhaust gas 24 contains unreacted hydrogen. The fuel electrode exhaust gas 24 containing unreacted hydrogen is sent to the reforming burner 10 for heating as the heating fuel 40 together with the combustion air 25, and the heat quantity required for the reforming reaction which is an endothermic reaction is supplied to the reforming device 9. Used for. In the reforming burner 10, a hydrogen combustion reaction occurs. Reforming burner 1 as when starting the fuel cell
When the supply amount of the fuel electrode exhaust gas that becomes 0 fuel is insufficient, a part of the desulfurization device 5 outlet gas is used as the auxiliary fuel 26 for the fuel of the reforming burner 10. The combustion gas 17 of the reforming burner 10 is cooled by the heat exchanger 27 and then sent to the condenser 28 to condense and remove the produced water 41. The produced water 41 removed by the condenser 28 is sent to the steam separator 8.
The steam 44 is supplied to the reformer 9. Condenser 28
The gas that has exited is discharged into the atmosphere as exhaust gas 42.

In such a fuel cell power generation system, the flow rate of the reformed gas supplied to the fuel cell 22 is adjusted by adjusting the flow rate of the fuel 43 by the fuel flow rate control valve 2. That is, the load current detection sensor 37 detects the load current and inputs it to the control device 39 as a signal a. The control device 39 sends a signal B to the fuel flow rate control valve 2, controls the opening of the fuel flow rate control valve 2, and supplies the fuel 43 corresponding to the hydrogen gas amount larger than the hydrogen gas amount corresponding to the load current. To do. Further, the supply amount of the steam 44 necessary for reforming the fuel 43 is detected by the fuel flow rate detection sensor 4 of the flow rate of the fuel 43 which has passed through the fuel flow rate control valve 2 and vaporized by the carburetor 1, and controls the signal c. To the device 39, and this control device 39 sends the signal A
To the steam flow rate control valve 7, and the steam flow rate control valve 7
It is adjusted by controlling the opening. The temperature of the reformer 9 is monitored by the temperature sensor 12 and input to the controller 39 as a signal b. The control device 39 controls the opening of the fuel flow control valve 2 so as to maintain the reformer temperature at a predetermined temperature by controlling the signal B sent to the fuel flow control valve 2 according to the reformer temperature. , The flow rate of the fuel 43 is adjusted.
The control device 39 receives the signal from each sensor, compares it with the set value stored in the control device 39, calculates based on the result, and controls the opening degree of each flow control valve described above. Sending a signal.

FIG. 8 is a graph showing changes over time in fuel flow rate and fuel cell output in the fuel cell power generation system using the conventional liquid fuel of FIG. 7 as fuel.

Further, as a fuel cell power generation system capable of switching the fuel from the liquid fuel to the spare fuel, a carburetor 1, a heat exchanger 3, 6, 11, as shown in the system diagram of FIG.
14, 16, 23, 27, 32, flow rate control valves 2, 7, desulfurization device 5, steam separator 8, reformer 9, CO shift converter 13, condensers 15, 28, 33, fuel cell 22,
Control device 39, flow divider 48, fuel electrode exhaust gas burner 4
A system including 9 and various sensors 4, 12, 37, 51, etc. has been proposed (Japanese Patent Application No. 63-22).
No. 0004). The basic configuration and operation of the fuel cell power generation system shown in FIG. 9 are the same as those of the fuel cell system using liquid fuel as the fuel described in FIG. 7, and the reference numerals shown in FIG. , The same part is shown. Therefore, here, the difference from the conventional example of FIG. 7 will be mainly described.

In the fuel cell power generation system capable of switching fuel shown in FIG. 9, when the supply of the fuel 43, which is the main fuel, is suddenly stopped due to a large earthquake, an accident, or the like, for example, the pressure or flow rate changes. Fuel supply abnormality detection sensor 51
This is detected and is input to the control device 39 as a signal d. The controller 39 controls the signal B, and the fuel flow rate control valve 3
And the signal D is sent to the auxiliary fuel flow rate adjusting valve 47, and the auxiliary fuel flow rate adjusting valve 47 is opened to supply the auxiliary fuel 46 which is a liquid fuel. Backup fuel flow control valve 4
7 and the steam flow rate control valve 7 are controlled so that the fuel flow rate and the steam flow rate are optimal for the auxiliary fuel 46 based on the data stored in the control device 39 in advance. Therefore, the power generation by the fuel cell 22 can be continued under the condition suitable for the reserve fuel 46.

In this conventional example, when city gas is used as the fuel and methanol is used as the auxiliary fuel (the heat of the reforming reaction required to obtain the same amount of hydrogen is less in methanol) When the reformer temperature rises, the auxiliary fuel flow rate control valve 47 is usually throttled to reduce the fuel supply amount. However, if the fuel cell output decreases due to insufficient fuel when the fuel supply amount is reduced by squeezing the reserve fuel flow rate control valve 47, the control device 39 sends the signal C to the flow divider 48, and becomes the heating fuel 40. A part of the polar exhaust gas 24 is divided by a flow diverter 48, burned by a burner 49 for the fuel electrode exhaust gas, and then discharged into the atmosphere as a combustion exhaust gas 50 (Japanese Patent Application No. 2-181260).

FIG. 10 is a graph showing the change over time in fuel flow rate and fuel cell output at the time of fuel switching of the fuel cell system in FIG. 9 in which the liquid fuel can be switched to the reserve fuel.

[0014]

However, the above-mentioned conventional fuel cell power generation systems have the following problems to be solved.

First, in the fuel cell power generation system using liquid fuel as a fuel of FIG. 7, a method of vaporizing the liquid fuel by utilizing high temperature exhaust heat has not been established, and it is made of a material having low heat resistance such as SUS. The vaporizer 1 is installed at a distance from the high temperature reformer 9 and is vaporized by electricity and hot water at a low temperature of about 100 ° C. Therefore, the vaporizer 1 is vaporized and then sent to the reformer 9. By the time the fuel supply is started, the fuel gas is condensed in the piping and the like, and the fuel supply amount pulsates as shown in FIG. 8 to change from the predetermined amount F ₁ and accordingly the fuel cell. There is a problem that the output also pulsates and changes from a predetermined amount of W ₁ .

Next, even in the fuel cell power generation system capable of switching the fuel from the liquid fuel to the reserve fuel in FIG. 9, a method of vaporizing the liquid fuel using high temperature exhaust heat has not been established.
The carburetor 1 made of a material having low heat resistance such as SUS is installed at a distance from the high temperature reformer 9 and is vaporized by using electricity and hot water at a low temperature of about 100 ° C. After the fuel is vaporized by the vaporizer 1, the reformer 9
Is condensed in a pipe or the like before being sent to the fuel cell, and the preliminary fuel supply amount pulsates as shown in FIG. 10, and it takes T ₁ time to reach a predetermined amount F ₄ . Along with this, the fuel cell output also temporarily decreases from a predetermined amount of W _{2 for} a time of T ₁ , and the fuel cell output also pulsates after the lapse of T ₁ time due to the pulsation of the preliminary fuel supply amount. was there.

The present invention has been made to solve the above-mentioned problems, and an object thereof is to prevent condensation of fuel gas when reforming fuel gas obtained by vaporizing liquid fuel,
An object of the present invention is to provide a fuel cell power generation system that suppresses fluctuations in fuel cell output.

[0018]

To achieve the above object, in a fuel cell power generation system of the present invention, a fuel cell main body and a vaporizer for vaporizing liquid fuel are provided, and fuel is supplied to the fuel cell main body. A fuel reforming system for reforming the fuel to produce a hydrogen-rich gas necessary for a cell reaction, an oxidant feeding system for feeding an oxidant to the fuel cell body, and the fuel cell In a fuel cell power generation system including a cooling system for cooling a main body and peripheral devices, and an auxiliary device, the vaporizer for vaporizing liquid fuel is integrated with the reforming device, and the vaporizer for vaporizing the liquid fuel is integrated with the vaporizer. The feature is that the exhaust heat of the reformer is used.

[0019]

In the fuel cell power generation system of the present invention, the vaporizer of liquid fuel and the reformer are integrated, the liquid fuel is vaporized by utilizing the exhaust heat of the reformer, and the long distance is maintained without the need for piping. It can be supplied to the reformer, and steam reforming is performed by the reformer. This prevents the vaporized fuel gas from condensing and suppresses the fluctuation of the fuel cell output due to the fuel gas shortage due to the condensation.

[0020]

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

FIG. 1 is a system diagram showing the configuration of the first embodiment to which the present invention is applied. This embodiment is an example of a fuel cell power generation system using liquid fuel as a fuel, and the basic configuration and operation of the fuel cell power generation system in this embodiment are the same as those of the conventional example described in FIG. The same symbols as those in FIG. 7 among the symbols shown in FIG. Therefore, here, the points different from the conventional example of FIG. 7 will be mainly described. In the conventional example of FIG. 7, the vaporizer 1 is integrated with the reformer 9 and the exhaust heat of the reformer 9 vaporizes the fuel 43, which is a liquid fuel, and the desulfurizer 5 is replaced with the vaporizer 1, that is, the reformer. The arrangement in the vicinity of 9 is very different. Note that FIG. 2 is a graph showing changes over time in fuel flow rate and fuel cell output in an embodiment of a fuel cell power generation system using a liquid fuel as a fuel to which the present invention is applied.

In this embodiment, the vaporizer 1 and the reformer 9 are integrated, and the fuel gas vaporized by the vaporizer 1 is directly supplied to the reformer 9 via the desulfurization device 5 adjacent to the vaporizer 1. As a result, it is possible to prevent the fuel gas from condensing, and as a result, as shown in FIG. 2, the fuel supply amount is maintained at a predetermined amount F ₁ and the fuel cell output is also a predetermined amount W _1. Can be kept constant. In the case of a liquid fuel containing no sulfur such as methanol, the fuel gas vaporized by the vaporizer 1 can be directly supplied to the reforming device 9, so vaporization and reforming are performed by the same device. be able to. Further, in the embodiment according to the present invention, the exhaust heat of the reformer 9 can be utilized for vaporizing the fuel gas, which is economical in terms of energy.

Next, a second embodiment to which the present invention is applied will be described. FIG. 3 is a system diagram showing the configuration. This embodiment is an example of a fuel cell power generation system capable of switching fuel from liquid fuel to auxiliary fuel, and the basic configuration and operation of the fuel cell power generation system in this embodiment are the same as those of the conventional example described in FIG. The same symbols as those in FIG. 9 among the symbols shown in FIG. 3 indicate the same parts. Therefore, the points different from the conventional example will be mainly described here. 9 is different from the conventional example of FIG. 9 in that the vaporizer 1 is integrated with the reformer 9 to vaporize the preliminary fuel 46 of liquid fuel by the exhaust heat of the reformer 9, and the desulfurizer 5 is arranged in the vicinity of the vaporizer 1. What you do is very different. In the configuration of FIG. 3, since the auxiliary fuel 46 is independently guided to the carburetor 1, the heat exchanger 52 and the auxiliary fuel flow rate detection sensor 53 are provided, but as shown in FIG. It is unnecessary if the fuel flow rate detection sensor 4 is also used. 4. FIG. 4 is a graph showing the change over time in fuel flow rate and fuel cell output at the time of fuel switching in an embodiment of a fuel cell power generation system capable of fuel switching from a liquid fuel to a backup fuel to which the present invention is applied.

Also in this embodiment, the vaporizer 1 and the reformer 9 are integrated, and the fuel gas vaporized by the vaporizer 1 is supplied to the reformer 9 through the desulfurizer 5 adjacent to the vaporizer 1. This makes it possible to prevent the fuel gas from condensing. As a result, as shown in FIG. 4, when the fuel is switched, the preliminary fuel supply amount is set to a predetermined amount of F ₄ by T ₂ shorter than T ₁ of FIG.
Quickly, and the reserve fuel supply is F
_The fuel cell output can be kept constant at ₄ , the decrease in fuel cell output due to the fuel shortage at the time of fuel switching can be suppressed, and the fuel cell output can be kept constant at a predetermined amount W ₂ .

Next, FIG. 5 shows an example of a vaporizer integrated with the reforming apparatus used in each of the above embodiments. Vaporizer 54
Is made of iron to withstand a high temperature of about 700 ° C. The vaporizer 54 is arranged so as to be entirely heated by the high temperature reformer combustion exhaust gas 57, and the liquid fuel 55 is sprayed from the nozzle 59 to the pipe wall inside the vaporizer 54 heated by the reformer fuel exhaust gas 57. Is vaporized. The vaporized fuel gas is sent to the reformer 58 (if the fuel gas 56 contains a sulfur content, it is sent to the reformer 58 via a desulfurization device).

FIG. 6 shows another example of the vaporizer integrated with the reformer. 6 that are the same as those in FIG. 5 indicate the same parts. Vaporizer 54 is 7
It is made of iron to withstand a high temperature of about 00 ° C. In this example, the entire vaporizer 54 is heated by the reformer combustion exhaust gas 57,
The liquid fuel 55 is supplied to the inside of the vaporizer 54 and is vaporized by the exhaust heat of the reformer 58. The vaporized fuel gas 56 is sent to the reformer 58 as it is (when the fuel gas 56 contains sulfur, it is sent to the reformer 58 via a desulfurization device).

Needless to say, the present invention can be applied to various types of fuel cell power generation systems. As described above, the present invention can be applied in various ways in accordance with the gist thereof and can take various embodiments.

[0028]

As described above, according to the fuel cell power generation system of the present invention, the vaporizer of the liquid fuel is integrated with the reformer, and the exhaust heat of the reformer is used to vaporize the reformer as it is. Since the fuel gas can be supplied to the device, it is possible to prevent the fuel gas from condensing, and it is possible to prevent the fuel cell output from varying due to the fuel gas shortage due to the fuel gas condensing.

[Brief description of drawings]

FIG. 1 is a system diagram showing a first embodiment of a fuel cell power generation system using a liquid fuel as a fuel to which the present invention is applied.

FIG. 2 is a graph showing changes over time in fuel flow rate and fuel cell output in the first embodiment of the fuel cell power generation system using liquid fuel as fuel.

FIG. 3 is a system diagram showing a second embodiment of a fuel cell power generation system capable of switching fuel from liquid fuel to backup fuel to which the present invention is applied.

FIG. 4 is a graph showing changes over time in fuel flow rate and fuel cell output during fuel switching in the second embodiment of the fuel cell power generation system capable of switching fuel from liquid fuel to backup fuel.

FIG. 5 is a configuration diagram showing an example of a vaporizer integrated with a reformer used in each of the above-described embodiments.

FIG. 6 is a configuration diagram showing another example of a vaporizer integrated with a reformer used in each of the above-described embodiments.

FIG. 7 is a system diagram of a fuel cell power generation system showing a conventional example using liquid fuel as fuel.

FIG. 8 is a graph showing changes over time in fuel flow rate and fuel cell output of the above fuel cell power generation system using liquid fuel as fuel.

FIG. 9 is a system diagram of a fuel cell power generation system showing another conventional example in which fuel can be switched from liquid fuel to backup fuel.

FIG. 10 is a graph showing a change over time in fuel flow rate and fuel cell output at the time of fuel switching of the fuel cell power generation system of another conventional example in which the fuel can be switched from the liquid fuel to the backup fuel.

[Explanation of symbols]

1 ... Vaporizer, 2 ... Fuel flow rate control valve, 3 ... Heat exchanger, 4 ...
Fuel flow rate detection sensor, 5 ... desulfurization device, 6 ... heat exchanger,
7 ... Steam flow rate control valve, 8 ... Steam separator, 9 ... Reforming device, 10 ... Reforming burner, 11 ... Heat exchanger, 12 ... Temperature sensor, 13 ... CO shift converter, 14 ... Heat exchanger, 15 … Condenser, 16… Heat exchanger, 17… Combustion gas,
18 ... DC power, 19 ... Fuel electrode, 20 ... Electrolyte, 21 ...
Air electrode, 22 ... Fuel cell, 23 ... Heat exchanger, 24 ... Fuel electrode exhaust gas, 25 ... Combustion air, 26 ... Auxiliary fuel, 27 ... Heat exchanger, 28 ... Condenser, 29 ... Inverter, 30 ... AC power, 31 ... Air electrode exhaust gas, 32 ... Heat exchanger, 33 ... Condenser, 34 ... Air, 35 ... Generated water, 36 ... Water extraction, 37 ...
Load current detection sensor, 38 ... Load, 39 ... Control device,
40 ... Heating fuel, 41 ... Generated water, 42 ... Exhaust gas, 43 ...
Fuel, 44 ... Steam, 45 ... Exhaust gas, 46 ... Spare fuel,
47 ... Reserve fuel flow rate control valve, 48 ... Flow divider, 49 ... Fuel electrode exhaust gas burner, 50 ... Combustion exhaust gas, 51 ... Fuel supply abnormality detection sensor, 52 ... Heat exchanger, 53 ... Preparatory fuel flow rate detection sensor, 54 ... Vaporizer, 55 ... Liquid fuel, 56
... fuel gas, 57 ... reformer combustion exhaust gas, 58 ... reformer, 59 ... nozzle.

Claims (1)

[Claims] 1. A fuel cell main body, a vaporizer for vaporizing a liquid fuel, a fuel supply system for supplying fuel to the fuel cell main body, and a reformer, which reforms the fuel and is necessary for cell reaction. In a fuel cell power generation system comprising a fuel reforming system for producing a hydrogen-rich gas, an oxidant supply system for supplying an oxidant to the fuel cell body, a cooling system for cooling the fuel cell body and peripheral devices, and an accessory device, A fuel cell power generation system, characterized in that the vaporizer for vaporizing liquid fuel is integrated with the reformer, and exhaust heat of the reformer is used for vaporizing the liquid fuel.