KR101050064B1 - Humidity Control System of Supply Gas and Recirculation Gas for Fuel Cell - Google Patents

Abstract

According to the present invention, in the humidity control of a fuel gas for a fuel cell, a measuring unit measuring a state of a gas, a thermoelectric control unit controlling a thermoelectric unit unit according to a result of the measuring unit, and a thermoelectric controlling a humidity of the fuel gas according to a signal of the thermoelectric control unit. A humidity control system for a fuel cell supply gas and a recirculation gas, which comprises a unit part, precisely controls the humidity of the fuel cell supply gas. In addition, in the control of the humidity of the recycle gas discharged after the reaction in the fuel cell stack, the humidity is controlled by using the same thermoelectric unit humidity control device as that of the supply gas. Therefore, in the humidity control of the supply gas and the recirculation gas of the fuel cell system through the present invention, the supply and residual recirculation gas is integrated humidity control device integrated into one device using a thermoelectric semiconductor without installing a separate control device To provide.

Fuel Cell, Supply Gas, Recirculation Gas, Humidity Control, Thermoelectric Semiconductor

Description

System of humidity control about supply and exhausted gas for fuel cell

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a humidity control system for a supply gas and a recirculation gas for a fuel cell. The control device, which has been installed and operated separately for a supply gas and a fuel gas that is recycled after a reaction, is a single integrated device using a thermoelectric semiconductor. To control technology.

Fuel cell is a power generation system that produces electric energy directly by using electrochemical reaction between fuel gas (hydrogen and oxygen). Compared with existing energy sources, fuel cell is more energy efficient and eco-friendly with few harmful emissions. It is expected to be an energy source. Fuel cells are classified into phosphate fuel cells, molten carbonate fuel cells, solid oxide fuel cells, and polymer electrolyte fuel cells according to the type of electrolyte used. The type of fuel used, the operating temperature, and the catalyst are different, but basically It is operated by the same principle.

In general, the fuel cell system is configured as follows. The fuel cell system includes a fuel cell stack 20 that generates electricity by an electrochemical reaction between hydrogen and oxygen, fuel gas, and a fuel processor (reformer & humidifier) 11 that reforms hydrogen gas using power generation materials. , An oxygen supply device for supplying oxygen to the fuel cell stack, a cooling device 14 for adjusting the temperature of the fuel cell stack, a power converter 13 for converting DC power produced in the fuel cell into AC power, and It consists of peripherals (BOP), among which fuel cell stacks are the key components responsible for producing the actual power.

The fuel cell stack is a stack structure consisting of a plurality of unit cells, and has a structure in which hydrogen and oxygen gas are supplied through the separator plate 43 with an electrode-electrolyte membrane (MEA) interposed therebetween. The supplied fuel gas (hydrogen) is separated into hydrogen ions and electrons by the catalytic reaction of the anode 42, and the ionized hydrogen gas passes through the electrolyte membrane 41 to move to the cathode 44. do. At this time, the hydrogen ions must move with the water molecules in order to pass through the electrolyte membrane, and for the performance of the fuel cell, the electrolyte membrane must maintain an excellent moisture content at all times and have excellent ion conductivity.

The gas (hydrogen, oxygen) supplied to the fuel cell stack must always supply more gas than is required for the electrochemical reaction because 100% of the gas is not involved in the reaction. Therefore, in order to increase the performance and efficiency of the fuel cell system, it is necessary to recycle residual hydrogen gas. However, since the electrolyte membrane and the feed gas are used in a humidified state in order to improve the ion conductivity of the electrolyte membrane, the residual gas that cannot participate in the reaction must always contain a certain amount of water. As such, the water contained in the recirculating gas has a problem in that a part of the residual water is condensed during the recirculation process, thereby reducing the pressure drop and the efficiency of the fuel cell system.

Therefore, in order to improve the performance of the fuel cell, it is necessary to precisely control the moisture content of the supply gas of the fuel cell and to remove sufficient moisture from the supply gas discharged after the stack reaction to improve the efficiency of the fuel cell system.

However, the existing fuel cell system installs a separate humidifier to humidify the supply gas and the electrolyte membrane, and supplies the reformed gas to the fuel cell stack by supplying the humidified gas to moisture condensation in the supply line between the humidifier and the fuel cell stack. In order to prevent additionally, a relative humidity is controlled by installing a heating device 12 such as a heater or using an absorbent material.

However, in the process of supplying the gas to the fuel cell stack through the humidifier, there is a possibility of condensation of moisture due to the change of temperature and pressure. Due to the complexity of the system configuration due to the installation, the consumption of additional energy for the heating device has a problem that the efficiency of the system is reduced.

In addition, even in the case of recirculated gas, condensed water is condensed through a separate cooling device 16 or a hygroscopic device is installed to prevent inflow of condensate into the fuel cell system, but in this case, precise humidity control is difficult as well. Since a separate control device is provided for each of the gas to be supplied and recycled, the entire fuel cell system is complicated.

Therefore, there is a need for a new control method that can achieve precise humidity control for fuel cell supply and recycle gas, simplify system configuration and achieve energy efficiency simultaneously.

Literature Information of the Prior Art

[Patent 1] Public Patent (Application No. 10-2004-0067818)

[Document 2] Registered Patent (Registration No.: 10-0835306)

[Document 3] Registered Patent (Registration No.: 10-0730400)

[Document 4] Registered Patent (Registration No.: 10-0657531)

[Document 5] Registered Patent (Registration No.: 10-0811806)

The present invention relates to a humidity control system of a fuel cell supply gas and a recirculation gas. The fuel cell supply gas must maintain an optimal hydration state to improve the conductivity of hydrogen ions. In order to prevent the deterioration of the fuel cell system's efficiency due to condensation, it should be recycled and used. Therefore, an object of the present invention is to maintain the optimum hydration state for the fuel cell supply gas through precise humidity control and to improve the efficiency of the fuel cell system through sufficient moisture removal for the recycle gas.

In addition, the control device, which is installed and installed separately in the fuel cell gas supply line and the recirculation line, is manufactured as a single integrated system using a thermoelectric semiconductor to overcome the complexity of the system structure and the difficulty of control and to improve the energy efficiency of the fuel cell system. It is an object of the present invention to make it possible.

In the humidity control system of the fuel gas and the recirculation gas of the fuel cell, the present invention provides a first measuring unit 32 for measuring a gas state before being supplied to a fuel cell stack, and a thermoelectric unit for adjusting a thermoelectric unit unit according to a gas state measurement value. The control unit 31, the thermoelectric control unit is composed of a thermoelectric unit unit 30 for controlling the humidity of the supply gas. The supply gas whose humidity is controlled through the thermoelectric unit part is supplied to the fuel cell stack 20, and the recycle gas discharged after the reaction from the fuel cell stack moves to the thermoelectric unit part again.

In the humidity control system of the high temperature and high humidity recycle gas discharged after the reaction in the fuel cell stack, the thermoelectric device receives the measurement value of the second measurement unit 33 and the second measurement unit to measure the gas state of the recycle gas discharged after the reaction. The humidity is controlled through the thermoelectric control unit 31 that controls the unit unit and the thermoelectric unit unit 30 that controls the humidity of the recirculating gas according to the signal of the thermoelectric control unit.

At this time, the supply gas and the recirculation gas are supplied and discharged through one thermoelectric semiconductor unit, and both ends of the thermoelectric unit part have a characteristic of being controlled separately according to the signal of the thermoelectric control unit.

The present invention is to enable the control of the humidity of the gas for the fuel cell using the humidity control system of the supply gas and the recirculation gas for the fuel cell. Through this, it is possible to improve the energy efficiency of the fuel cell system without additional energy consumption, to simplify the structure of the fuel cell system and to improve the performance of the fuel cell system by unifying the control system operated separately from the supply gas and the recirculation gas.

The present invention will now be described in detail with reference to the accompanying drawings.

1 is a block diagram showing the configuration of a conventional fuel cell system. Since the fuel cell system must be operated with sufficient water supply to prevent drying of the electrolyte membrane 41, the feed gas reformed through the fuel processing device 11 always passes through the humidifier and contains a large amount of water. The fuel cell stack 20 is supplied to the fuel cell stack 20 in a state. At this time, if the supply line between the humidifier and the fuel cell stack is long, condensation of moisture may occur due to temperature and pressure changes on the supply line, and in order to prevent this, the supply between the humidifier 11 and the fuel cell stack 20 A method of controlling humidity by using a heating device 12 such as a heater in a line may be used.

2 illustrates a structure of a fuel cell unit cell, in which a fuel cell stack 20 has a stacked structure of unit cells. The supply gas supplied to the fuel cell stack is supplied through the separator plate 43 of the fuel cell stack, and the hydrogen ions ionized at the anode 42 pass through the electrolyte membrane 41 to move to the cathode 44. . At this time, hydrogen ions and oxygen ions meet at the cathode to generate heat together with water by an electrochemical reaction, and the generated water is discharged to the outside or moved to a humidifier through an internal circulation system for recycling. In addition, the generated heat is controlled through a suitable cooling device 14 for maintaining the temperature of the fuel cell stack.

In addition, the gas that does not participate in the reaction in the fuel cell stack 20 is connected to the supply line through a recirculation line and used as a supply gas. At this time, the recirculating gas should be used in a state in which moisture in the gas is removed because it is a high temperature and high humidity state. For this purpose, it is common to use an absorbent such as silica or a cooling condenser 16.

However, it is difficult to control the humidity precisely by the conventional method as described above, and the separate humidity control devices 12 and 16 must be installed and operated in the supply line and the recirculation line, so that the volume of the system is increased and the heating and cooling devices are used. There are unreasonable points in terms of energy efficiency, such as extra energy consumption.

3 is a block diagram according to an embodiment of the present invention, a description of components of a general fuel cell system will be omitted, and only the contents according to the present invention will be described.

The supply gas containing sufficient moisture through the humidifier 11 of the fuel cell system passes through the first measuring unit 32 to measure temperature and humidity. The values measured by the first measuring unit 32 are sent to the thermoelectric control unit 31 and the thermoelectric control unit 31 calculates the measured values to calculate an appropriate relative humidity to prevent condensation of the supply gas.

The supply gas passing through the first measuring unit 32 is supplied to the fuel cell stack 20 in a controlled humidity while passing through the thermoelectric unit unit 30. The thermoelectric unit unit 30 is a thermoelectric control unit 31. In response to the signal of) serves to precisely control the relative humidity of the supply gas through the mutual conversion of the cooling and heating of the thermoelectric unit (30). At this time, the control of the thermoelectric unit 30 may be based on current or voltage, and one end 52, 53 of the thermoelectric unit unit may be cooled according to the polarity conversion direction of the current (voltage) applied to the thermoelectric semiconductor 51. 52) and the heating surface 53 can be switched and precise control within ± 0.1 ° C is possible through the control of the applied power supply with fast response speed.

In addition, since the thermoelectric unit unit 30 simultaneously implements cooling and heating at both ends 52 and 53 of the thermoelectric unit, the thermoelectric unit unit 30 supplies a supply line of the supply gas connected to the thermoelectric unit unit 30 according to the signal of the thermoelectric control unit 31. It may include the provision of the switching switch 34 that can be switched to the cooling unit or the heating unit. In addition, the supply gas passing through the thermoelectric unit part is supplied to the fuel cell stack 20 along the supply line. In this case, the supply line between the thermoelectric unit part 30 and the fuel cell stack 20 reduces the influence of the external environment. It is necessary to reduce the length of the supply line and to ensure sufficient warmth.

Residual (recycled) gas that has passed through the fuel cell stack contains a large amount of water, and is reused with sufficient water removal in order to be recycled. The recirculating gas exiting the fuel cell stack passes through the second measuring unit 33 to measure temperature and humidity conditions, and these measured values are sent to the thermoelectric control unit 31.

The thermoelectric control unit 31 sends a control signal to the thermoelectric unit unit based on the measured value for the recycle gas, and the thermoelectric unit unit 30 controls the humidity of the recycle gas based on the signal of the thermoelectric control unit. At this time, while passing through the thermoelectric unit, the recirculating gas is moved to the supply line with a large amount of water removed, and the water removed from the recirculating gas is discharged to the outside using a pump (36) or transferred to the humidifier (37). Can be used.

And in order to operate the thermoelectric unit, the power supply must be made, the thermoelectric unit is characterized in that it is driven only in the DC power source. Therefore, in the conventional fuel cell heating and cooling system, there was a difficulty in driving a separate power source from the outside, but as in the present invention, the humidity control system of the fuel cell supply gas and the recirculation gas according to the operation of the fuel cell is present. Since the generated direct current power source can be used, it is possible to improve the energy efficiency of the fuel cell system and the complexity of the system structure.

Figure 4 shows the configuration of the thermoelectric unit 30, the thermoelectric unit is characterized in that the cooling and heating at the same time occurs at both ends (52, 53), by converting the polarity of the power applied to the thermoelectric unit cooling (52) and There is a feature that the heating surface 53 can be switched. Therefore, in the case of the supply gas, the humidity of the supply gas can be controlled using the heating surface 53 of the thermoelectric unit, and in the case of the recirculating gas, the humidity can be used to remove moisture and control the humidity through the cooling surface 52. Alternatively, humidity control of the supply gas and the recirculation gas may be achieved by switching between the cooling and heating surfaces according to the measured values of the first 32 and the second measuring unit 33 according to the state of the gas.

And the contact surface with the gas of the thermoelectric unit portion is extruded fin type heat exchangers (52, 53) in Figure 4 for smooth heat exchange with the supply and recirculation gas, but brazing type such as louver fin or pipe heat exchange It is well known that various types of units can be configured, although the form is different.

As described in the embodiment of the present invention, the humidity control system using the thermoelectric semiconductor is possible to simultaneously control the supply gas and the recirculation gas of the fuel cell, while precise humidity control is possible to simplify the configuration of the fuel cell system The efficiency of the entire fuel cell system can be improved.

1 is a block diagram of a conventional general fuel cell system.

2 is a structural diagram of a unit cell for a fuel cell

3 is a configuration diagram of a fuel cell humidity control system according to the present invention;

4 is a side view of the thermoelectric unit unit according to the present invention;

Claims (4)

A first measuring unit measuring a state of the supply gas before being supplied to the fuel cell stack; A thermoelectric control unit controlling the thermoelectric unit unit according to the measured value of the first measurement unit; A thermoelectric unit unit for controlling the humidity of the supply gas by receiving a signal from the thermoelectric control unit; A second measuring unit measuring a state of the recycle gas after passing through the fuel cell stack; A thermoelectric control unit for controlling the thermoelectric unit unit according to the measured value of the second measurement unit; A humidity control system for a fuel cell supply gas and a recirculation gas, including a thermoelectric unit unit for controlling the humidity of the recirculation gas in response to a control signal of the thermoelectric control unit, which can simultaneously control the humidity of the fuel cell supply gas and the recycle gas. The method of claim 1, The thermoelectric unit part of the fuel cell supply gas and the recirculation gas provided with a thermoelectric semiconductor to control the humidity of the fuel cell supply gas through the fuel cell supply gas and the recirculation gas, and the moisture removal and humidity to the fuel cell recycle gas. Humidity control system. 3. The method of claim 2, A humidity control system for a fuel cell supply gas and a recirculation gas having a switch for switching a supply line of a supply gas connected to the thermoelectric unit to a cooling part or a heating part. The method of claim 1, The thermoelectric unit unit is a humidity control system of a fuel cell supply gas and a recirculation gas that is driven using the power generation power of the fuel cell without supplying additional power.

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