JP2000357527A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely prevent the generation of dispersion of a mixing ratio caused by the temperature difference between liquid fuel and water by simple constitution. SOLUTION: The fuel cell system has a mixing tank 16 for mixing and storing methanol and water and supplying a mixture to a reformer 12, a methanol supply device 18 for supplying methanol to the mixing tank 16, a water supply device 20 for supplying water to the mixing tank 16, and a heat exchanger 22 arranged between the methanol supply device 18 and the water supply device 20 and for adjusting the temperature difference between methanol and water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell system for supplying hydrogen gas generated from a liquid mixture of liquid fuel and water to an anode electrode constituting a fuel cell unit.

[0002]

2. Description of the Related Art For example, a fuel cell stack has been developed in which a plurality of fuel cells, each having an anode electrode and a cathode electrode opposed to each other with a solid polymer electrolyte membrane interposed therebetween, are sandwiched by a separator and stacked. Are being put to practical use for various applications.

[0003] This type of fuel cell stack uses, for example, a reformed gas (fuel gas) containing hydrogen gas produced by reforming a mixed liquid (aqueous methanol solution) of a liquid fuel such as methanol and water and an anode. By supplying the oxidant gas (air or oxygen gas) to the cathode side electrode while supplying the hydrogen gas to the electrode, the hydrogen gas is ionized and flows through the solid polymer electrolyte membrane. Is obtained.

Incidentally, various fuel cell systems having a structure in which a predetermined amount of liquid fuel and water are mixed and a mixed liquid is supplied to a reformer have been proposed.
2. Description of the Related Art A fuel cell system disclosed in Japanese Patent Application Publication No. 2-14747 is known. In this prior art, a reformer (reformer)
A mixing tank is openably and closably connected to the storage tank inlet side connected to the storage tank, and three level sensors are provided in the mixing tank.

When the mixture of the liquid fuel and water in the mixing tank falls below the first specified level, the liquid fuel is supplied from the fuel source into the mixing tank until the mixture reaches the second specified level. Thereafter, water is supplied into the mixing tank until a third prescribed level is reached. Thus, after the liquid fuel and water are mixed in the mixing tank at a specified mixing ratio, the mixture is supplied from the mixing tank to the storage tank.

[0006]

However, in the above prior art, when water discharged from the fuel cell system is used, the temperature of the water and the temperature of the liquid fuel are affected by operating conditions, environmental temperatures, and the like. Changes in various ways. As a result, it has been pointed out that the level sensor disposed in the mixing tank cannot accurately obtain a desired mixing ratio (molar ratio) of water and liquid fuel due to a difference in volume expansion rate. .

The present invention solves this kind of problem, and is capable of mixing liquid fuel and water at a desired mixing ratio with high accuracy without being affected by temperature changes, and achieving good power generation. It is an object to provide a fuel cell system capable of obtaining performance.

[0008]

In a fuel cell system according to a first aspect of the present invention, a liquid fuel supply device for supplying liquid fuel to a mixing tank and a water supply device for supplying water to the mixing tank are provided. A heat exchange device for adjusting a temperature difference between the liquid fuel and the water before being supplied to the mixing tank. For this reason, even if the water temperature changes due to the operating state of the fuel cell system, environmental temperature change, etc., the water temperature and the temperature of the liquid fuel can be controlled to a constant temperature, and the mixing tank can be reliably maintained at the specified mixing ratio. Can be supplied to

Further, in the fuel cell system according to the second aspect, the heat exchange device includes a cooling medium pipe provided from the condenser for recovering moisture to the liquid fuel supply device. By controlling the temperature of the cooling medium flowing through the cooling medium pipe, the temperature of the water recovered through the condenser and the temperature of the liquid fuel in the liquid fuel supply device can be kept at a constant temperature with a simple configuration. It can be controlled reliably.

In a fuel cell system according to a third aspect of the present invention, the heat exchange device includes a fuel tank provided in the liquid fuel supply device and a water supply device which supplies water to the mixing tank. A water passage pipe disposed in the fuel tank. Therefore, when water is supplied from the water supply device to the water passage pipe, heat exchange is performed between the liquid fuel in the fuel tank in which the water passage pipe is disposed and the water, and the water and the liquid fuel are exchanged. Can be adjusted to a predetermined temperature. Therefore, with a simple configuration, it is possible to effectively prevent the variation in the mixing ratio between the liquid fuel and water due to the temperature.

Further, in the fuel cell system according to claim 4 of the present invention, the water supply device includes a condenser for recovering at least moisture, and the heat exchange device is provided in the liquid fuel supply device. A fuel tank is provided in the condenser. Thereby, heat exchange between the liquid fuel and water is effectively performed in the condenser, and the liquid fuel and the water can be supplied to the mixing tank at a desired mixing ratio with a simple configuration.

[0012]

FIG. 1 is a schematic configuration diagram of a fuel cell system 10 according to a first embodiment of the present invention.

The fuel cell system 10 includes a hydrocarbon-based liquid.
Body fuel such as methanol (CH _ThreeOH) and water
Fuel reformer that generates reformed gas containing hydrogen gas from the combined liquid
12 and the reformer 12 as a fuel gas from the reformer 12.
Fuel cell 14 to which the fuel is supplied, and the methanol
While storing the mixture with the water, the mixture is
A mixing tank 16 for supplying to the reformer 12;
Methanol for supplying the methanol to the mixing tank 16
Supply device (liquid fuel supply device) 18 and the mixing tank
16, a water supply device 20 for supplying the water,
Between the water supply device 18 and the water supply device 20.
The methanol before being supplied to the mixing tank 16
And a heat exchange device 22 for adjusting the temperature difference of the water.
You.

A first level sensor 24 for detecting the level of the mixed liquid is provided in the mixing tank 16, and a fuel path 26 is provided in the mixing tank 16.
A first pump 28 and a first regulator 30 are arranged on the way of the fuel path 26, and a return path 32 for returning the mixture to the mixing tank 16 is connected to the first regulator 30.

The fuel path 26 is connected to an evaporator 34, and combustion heat is supplied to the evaporator 34 from a combustor 36. The outlet side of the evaporator 34 is connected to the reformer 12 and the C
The fuel cell stack 40 is connected via an O (carbon monoxide) remover 38.

The fuel cell stack 40 includes the fuel cell 1
4 and a plurality of separators 42 are alternately laminated. The fuel cell 14 includes a solid polymer electrolyte membrane 44.
And a hydrogen electrode (anode side electrode) 46 and an air electrode (cathode side electrode) 48 opposed to each other with the solid polymer electrolyte membrane 44 interposed therebetween.
Are connected to a load 50 such as an electric motor.

The fuel cell stack 40 is connected to an air compressor 52 for supplying atmospheric air (or oxygen gas), which is an oxidizing gas, to the air electrode 48. The fuel cell stack 40 has first and second discharge paths 54 for discharging exhaust components from the fuel cell stack 40,
One end of a gas supply port 56 is connected to the first discharge path 54, and a condenser (gas condenser) constituting the water supply device 20 for separating the discharged components into a gas component and moisture and supplying water to the mixing tank 16. The second discharge path 56 joins a gas path 60 that communicates with the combustor 36 from the condenser 58 while a liquid separator 58 is connected.

The condenser 58 includes a methanol supply device 18.
Medium piping 6 that constitutes heat exchange device 22 over
2 are provided. A second pump 64 is provided in the pipe 62.
A cooling medium, for example, cooling water is circulated through,
A radiator 66 and a cooling fan 68 are provided on the inlet side of the second pump 64. Inside the condenser 58, a second level sensor 70 for detecting a water level and a first temperature sensor 71 for detecting a water temperature are arranged, and a drain valve 72 is provided at the bottom of the condenser 58. I have.

A water tank 76 is connected to the bottom of the condenser 58 via a water path 74, and the water tank 76 is connected to the mixing tank 16. As shown in FIG. 2, the water tank 76 constitutes a constant volume container, and a first opening / closing valve 78 and a second opening / closing valve 80 are provided at an inlet on an upper side and an outlet on a lower side, respectively. The water tank 76 is provided with a second temperature sensor 82 for detecting the temperature of the water once stored therein.

The methanol supply device 18 includes a methanol storage tank 84 having a relatively large capacity, and a methanol path 86 is connected to the methanol storage tank 84. A third pump 88 and a second pump
A regulator 90 is connected, and the methanol path 86 is connected to the mixing tank 16 via a methanol tank (fuel tank) 92.

The methanol tank 92 is a constant-volume container integrally formed with the water tank 76, and a third on-off valve 94 and a fourth on-off valve 96 are connected to the inlet side and the outlet side thereof. A third temperature sensor 98 for detecting the temperature of methanol once stored in the methanol tank 92 is arranged, and a pipe 62 is continuously arranged in the methanol tank 92 from inside the condenser 58. ing.

The fuel cell system 10 includes an ECU 100 as a control circuit, and the ECU 100 controls the driving of the fuel cell system 10 as a whole.

The fuel cell system 1 configured as described above
The operation of 0 will be described below.

First, at the time of startup, a liquid mixture of methanol and water, which is a liquid fuel, stored in the mixing tank 16 passes through the fuel path 26 by a predetermined amount by the first regulator 30 under the action of the first pump 28. And supplied to the evaporator 34. The liquid mixture vaporized by the heat of combustion from the combustor 36 in the evaporator 34 is sent to the reformer 12 to be reformed. As a result, a reformed gas (fuel gas) containing hydrogen gas and carbon dioxide gas is obtained. After the reformed gas is subjected to carbon monoxide removal by the CO remover 38, each hydrogen electrode 46 of the fuel cell stack 40 is removed. Supplied to

On the other hand, each air electrode 4 of the fuel cell stack 40
At 8, air (or oxygen gas) in the atmosphere is introduced from an air compressor 52 as an oxidizing gas. Therefore,
In each fuel cell 14, the hydrogen gas contained in the reformed gas is ionized (hydrogen ionization) and solid polymer electrolyte membrane 4
4 flows toward the air electrode 48 side, and the hydrogen ions react with oxygen and electrons at the air electrode 48 to generate water. The electrons generated when the hydrogen gas is ionized become electric energy for driving the load 50, while the hydrogen electrode 46
The exhaust component discharged from the air electrode 48 is introduced into the first and second discharge paths 54 and 56.

The exhaust component discharged to the first discharge path 54 is introduced into the condenser 58 and separated into water and a gas component, and this gas component is passed through the gas path 60 to the combustor 36.
Sent to The discharged components introduced into the second discharge path 56 join the gas path 60 and are sent to the combustor 36.

In the condenser 58, when the temperature detected by the first temperature sensor 71 becomes higher than a preset temperature, first, the second pump 64 is driven to circulate the cooling water in the pipe 62, Further, when the temperature in the condenser 58 is higher than a predetermined temperature, the cooling fan 68 is driven to forcibly cool the cooling water flowing in the radiator 66 and circulate through the pipe 62. As a result, in the condenser 58, the discharged components are separated into water and gas components, and water at a predetermined temperature is generated in the condenser 58.

Next, a procedure for mixing methanol and water at a predetermined mixing ratio and storing the mixed water in the mixing tank 16 will be described with reference to the flowchart shown in FIG.

First, with the second and fourth on-off valves 80 and 96 closed, the third on-off valve 94 is opened (step S1), and the methanol stored in the methanol storage tank 84 is removed by the third on-off valve. The water is supplied to a methanol tank 92 via a methanol path 86 under the action of a pump 88.
The condenser 5 detected by the first temperature sensor 71
When the temperature in the chamber 8 becomes higher than the predetermined temperature t ₁ (YES in step S2), the first on-off valve 78 is opened, and the water generated in the condenser 58 passes through the water path 74 to the water tank 76. (Step S3).

Through the second level sensor 70, the condenser 5
8 has a predetermined water level h ₁More than
If it is determined (YES in step S4) that the
Proceeding to step S5, a predetermined time T1 is measured. others
Therefore, the methanol tank 92 and the water tank 76
Each would be filled with methanol and water.

Here, in the methanol tank 92, a pipe 62 is disposed integrally from the condenser 58. Cooling water circulated in the pipe 62 is sent from the condenser 58 to the methanol tank 92. The heat exchange is performed with the methanol stored in the methanol tank 92. that time,
The cooling water in the pipe 62 is used to generate water in the condenser 58. By passing the cooling water through the methanol tank 92, the temperature of the water generated in the condenser 58 and the temperature of the water The temperature of the methanol stored in the methanol tank 92 becomes the same or an approximate value.

Then, the process proceeds to step S6, in which the water temperature and the methanol temperature are set to the predetermined temperatures t _{2 to} t ₃ via the second and third temperature sensors 82 and 98 provided in the water tank 76 and the methanol tank 92, respectively. When it is detected that the value falls within the range, the first and third on-off valves 78 and 94 are closed (step S7), and then the second and fourth on-off valves 80 and 96 are opened (step S8). .

Therefore, the supply of the water in the water tank 76 and the methanol in the methanol tank 92 to the mixing tank 16 is started, and when the time T2 elapses (YES in step S9), the water tank 76 and the methanol are stopped. Water and methanol, each of which has been fixedly filled in the methanol tank 92, are mixed in the mixing tank 1 at a desired mixing ratio.
6 is introduced. Further, proceeding to step S10,
The second and fourth on-off valves 80 and 96 are closed.

During this time, water is being generated in the condenser 58, and the second level sensor 70 outputs the water to the condenser 5.
The water level in the 8 to be the predetermined water level h ₂ or more height (in step S11, YES), the time the drainage valve 72 is predetermined T3
And the drainage is performed until the time elapses (step S
12 and S13). Then, the process proceeds to step S14,
It is determined whether or not the power generation of the fuel cell system 10 is stopped, and when the power generation is continued, the process returns to step S1 to perform a mixing operation of water and methanol.

In this case, in the first embodiment, the condenser 5
A pipe 62 disposed in the condenser 8 for generating water is disposed in the condenser 58 in the methanol tank 92, and cooling water is circulated in the pipe 62. For this reason, the cooling water having substantially the same temperature as the temperature of the water generated in the condenser 58 is used for heat exchange with the methanol stored in the methanol tank 92. It can be adjusted to the same or similar temperature as the water temperature inside.

Thus, the water tank 76 and the methanol tank 92 are filled with water and methanol, respectively, which are adjusted to a constant temperature, and after the first and third on-off valves 78 and 94 are closed, And the fourth on-off valve 8
By opening 0 and 96, it is possible to obtain an effect that water and methanol set at a constant mixing ratio (molar ratio) can always be reliably supplied into the mixing tank 16.

Further, the condenser 58 is provided in the heat exchanger 22.
6 arranged from the tank to the methanol tank 92
2, the structure can be simplified at a stroke, and a rise in manufacturing cost can be effectively suppressed. Furthermore, the water tank 76 and the methanol tank 92 each constitute a fixed-capacity container, so that it is possible to reliably adjust water and methanol to a desired mixing ratio. At this time, the water tank 76 and the methanol tank 92 are integrally formed, and the water tank 76 and the methanol tank 92 themselves have a heat exchange function. Therefore, variation in the mixing ratio due to the temperature difference between water and methanol can be prevented as much as possible.

Further, the temperature of the cooling water circulating in the pipe 62 is controlled by the control of the second pump 64 and the cooling fan 68. For this reason, it is possible to control the respective temperatures of the water generated in the condenser 58 and stored in the water tank 76 and the methanol stored in the methanol tank 92 to a constant temperature.

In the first embodiment, the pipe 62 is disposed integrally from the condenser 58 to the methanol tank 92. However, heat exchange between the water tank 76 and the methanol tank 92 is ensured. In this case, the pipe 62 need not be disposed in the methanol tank 92. Further, the pipe 62 disposed in the condenser 58 and the pipe 62 disposed in the methanol tank 92 are formed in separate circuits, and the water and the methanol are controlled by controlling water and methanol to respective target temperatures. May be adjusted to a constant value.

Further, a temperature detecting means (third temperature sensor 98) is provided only in the methanol tank 92. Then, without using the first and second temperature sensors 71 and 82, it is also possible to perform a mixing operation of water and methanol by time management.

FIG. 4 is a schematic structural explanatory view of a heat exchanger 122 constituting a fuel cell system 120 according to a second embodiment of the present invention. The same components as those of the fuel cell system 10 according to the first embodiment are denoted by the same reference numerals, and a detailed description thereof will be omitted.

The heat exchange device 122 includes a water passage tube 124 that is spirally disposed in the methanol tank 92 instead of the water tank 76. The water passage pipe 124 is connected to the condenser 5
8 and the mixing tank 16, and a constant volume container similar to the water tank 76 is formed between the first on-off valve 78 and the second on-off valve 80.

In the second embodiment configured as described above, the cooling water whose temperature is controlled flows through the pipe 62 to generate water in the condenser 58, and this water is introduced into the water passage pipe 124. You. Here, since the second on-off valve 80 is closed, water is temporarily stored in the water passage pipe 124. On the other hand, when the fourth on-off valve 96 is closed, methanol is temporarily stored in the methanol tank 92.

At this time, since the water passage pipe 124 is disposed in the methanol tank 92, heat exchange is performed between the water stored in the water passage pipe 124 and methanol in the methanol tank 92. Will be Then, it is determined that the temperature of the water in the water passage pipe 124 and the temperature of the methanol in the methanol tank 92 are the same or similar.
And third temperature sensors 82 and 98, the first and third on-off valves 78 and 94 are closed, the second and fourth on-off valves 80 and 96 are opened, and water is supplied to the mixing tank 16. And methanol are supplied.

In this case, in the second embodiment, the temperatures of water and methanol are controlled to be constant, and the volume of the water passage pipe 124 and the volume of the methanol tank 92 have a predetermined mixing ratio. It is set as follows. As a result, there is obtained an effect that the mixing ratio of water and methanol does not vary, and the mixture is reliably sent to the mixing tank 16 at a predetermined mixing ratio. Moreover, the configuration of the heat exchange device 122 is effectively simplified, and
Can be manufactured economically.

As the temperature detecting means, only the third temperature sensor 98 may be used. Alternatively, the temperature may be circulated in the pipe 62 based on the temperature signals detected from the second and third temperature sensors 82 and 98. The temperature of the water and methanol can be controlled to the target temperature by changing the temperature of the cooling water.

FIG. 5 is a schematic structural explanatory view of a heat exchanger 132 constituting a fuel cell system 130 according to a third embodiment of the present invention. The same components as those of the fuel cell system 10 according to the first embodiment are denoted by the same reference numerals, and a detailed description thereof will be omitted.

This heat exchange device 132 has a methanol tank 136 disposed inside the condenser 134. The methanol tank 136 forms a constant volume container,
The volumes of the water tank 76 and the methanol tank 136 are set so that a prescribed mixing ratio of methanol and water is obtained at a predetermined temperature of, for example, 30 ° C. or higher. The methanol tank 136 may be provided with irregularities on its surface to improve the efficiency of heat exchange with water in the condenser 134.

In the third embodiment configured as described above, the humidified gas flows through the pipe 6 in the condenser 134.
The water is separated into water and gas components by the cooling water circulating through the cooling water 2, and water is generated in the condenser 134. Here, by controlling the temperature and the amount of the cooling water, the temperature of the water generated in the condenser 134 is adjusted to be constant. On the other hand, in the methanol tank 136, the fourth on-off valve 96 is closed, and the methanol 136 is filled with methanol.

Therefore, until a predetermined amount of water is accumulated in the condenser 134, the temperature of the methanol stored in the methanol tank 136 is equal to the temperature of the water accumulated in the condenser 134. Becomes And the water tank 7
When it is detected that the water temperature in the water tank 6 and the methanol temperature in the methanol tank 136 have reached a predetermined temperature, the water and methanol in the water tank 76 and the methanol tank 136 are adjusted to a prescribed mixing ratio. It is supplied to the mixing tank 16 in a state where it is in a state of being closed. Thereby, the mixing ratio of water and methanol does not vary, and the mixing ratio can be reliably supplied to the mixing tank 16 at a desired mixing ratio. The same effect as in the embodiment can be obtained.

[0051]

According to the fuel cell system of the present invention, the liquid fuel and the water are provided between a liquid fuel supply device for supplying liquid fuel to the mixing tank and a water supply device for supplying water to the mixing tank. A heat exchange device that adjusts the temperature difference is provided, and the liquid fuel and the water can always be supplied to the mixing tank in a state where the mixing ratio is surely adjusted to a specified mixing ratio. This makes it possible to effectively prevent the variation in the mixing ratio between the liquid fuel and water due to temperature with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a fuel cell system according to a first embodiment of the present invention.

FIG. 2 is a schematic explanatory view of a heat exchange device constituting the fuel cell system.

FIG. 3 is a flowchart for obtaining a mixture of methanol and water.

FIG. 4 is a schematic explanatory diagram of a heat exchange device constituting a fuel cell system according to a second embodiment of the present invention.

FIG. 5 is a schematic explanatory diagram of a heat exchange device constituting a fuel cell system according to a third embodiment of the present invention.

[Explanation of symbols]

10, 120, 130 ... fuel cell system 12 ... fuel reformer 14 ... fuel cell 16 ... mixing tank 18 ... methanol supply device 20 ... water supply device 22, 122, 132
... Heat exchangers 24,70 ... Level sensor 34 ... Evaporator 36 ... Combustor 40 ... Fuel cell stack 42 ... Separator 44 ... Solid polymer electrolyte membrane 46 ... Hydrogen electrode 48 ... Air electrode 50 ... Load 54,56 ... Discharge route 58, 134 ... condenser 62 ... piping 28, 64, 88 ... pump 66 ... radiator 68 ... cooling fan 71, 82, 98 ... temperature sensor 76 ... water tank 78, 80, 94, 9
6 On-off valve 84 Methanol storage tank 92 136 Methanol tank 100 ECU 124 Water passage pipe

Claims (4)

[Claims] 1. A fuel cell comprising a fuel reformer for generating a reformed gas containing hydrogen gas from a liquid mixture of liquid fuel and water, wherein an anode electrode and a cathode electrode are opposed to each other with an electrolyte interposed therebetween. A fuel cell system for supplying the reformed gas to the anode electrode, wherein the liquid fuel and the water are mixed and stored.
A mixing tank for supplying the mixed liquid to the fuel reformer; a liquid fuel supply device for supplying the liquid fuel to the mixing tank; a water supply device for supplying the water to the mixing tank; A heat exchange device disposed between the fuel supply device and the water supply device to adjust a temperature difference between the liquid fuel and the water before being supplied to the mixing tank. Battery system. 2. The fuel cell system according to claim 1, wherein the water supply device includes a condenser for recovering at least water discharged from the fuel cell, and the heat exchange device includes the condenser. A fuel cell system, comprising: a cooling medium pipe disposed from the liquid fuel supply device to the liquid fuel supply device. 3. The fuel cell system according to claim 1, wherein the heat exchange device is provided in a fuel tank provided in the liquid fuel supply device, and is provided in the water supply device, and supplies the water to the mixing tank. And a water passage tube disposed in the fuel tank. 4. The fuel cell system according to claim 1, wherein the water supply device includes a condenser for recovering at least water discharged from the fuel cell, and the heat exchange device includes the liquid fuel. A fuel tank provided in the supply device and disposed in the condenser.