WO2008016257A1 - Fuel cell system and operating method - Google Patents

Fuel cell system and operating method Download PDF

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Publication number
WO2008016257A1
WO2008016257A1 PCT/KR2007/003694 KR2007003694W WO2008016257A1 WO 2008016257 A1 WO2008016257 A1 WO 2008016257A1 KR 2007003694 W KR2007003694 W KR 2007003694W WO 2008016257 A1 WO2008016257 A1 WO 2008016257A1
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WO
WIPO (PCT)
Prior art keywords
fuel cell
fuel
unit
cell stack
process unit
Prior art date
Application number
PCT/KR2007/003694
Other languages
French (fr)
Inventor
Ho-Suk Kim
Sang-Yong Lee
Hyung-Mok Cho
Byung-Sun Hong
Mee-Nam Shinn
Original Assignee
Fuelcell Power, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Fuelcell Power, Inc. filed Critical Fuelcell Power, Inc.
Priority to CN200780001131XA priority Critical patent/CN101356681B/en
Publication of WO2008016257A1 publication Critical patent/WO2008016257A1/en

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/06—Combination of fuel cells with means for production of reactants or for treatment of residues
    • H01M8/0606—Combination of fuel cells with means for production of reactants or for treatment of residues with means for production of gaseous reactants
    • H01M8/0612—Combination of fuel cells with means for production of reactants or for treatment of residues with means for production of gaseous reactants from carbon-containing material
    • H01M8/0618—Reforming processes, e.g. autothermal, partial oxidation or steam reforming
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04007—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids related to heat exchange
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04007—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids related to heat exchange
    • H01M8/04029—Heat exchange using liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04223—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids during start-up or shut-down; Depolarisation or activation, e.g. purging; Means for short-circuiting defective fuel cells
    • H01M8/04253—Means for solving freezing problems
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04007—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids related to heat exchange
    • H01M8/04014—Heat exchange using gaseous fluids; Heat exchange by combustion of reactants
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04082—Arrangements for control of reactant parameters, e.g. pressure or concentration
    • H01M8/04089—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants
    • H01M8/04097—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants with recycling of the reactants
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04082—Arrangements for control of reactant parameters, e.g. pressure or concentration
    • H01M8/04089—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants
    • H01M8/04119—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants with simultaneous supply or evacuation of electrolyte; Humidifying or dehumidifying
    • H01M8/04126—Humidifying
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Definitions

  • the present invention relates to a fuel cell system for generating power by an electrochemical reaction, and more particularly, to a fuel cell system for preventing internal constituent elements from being frozen by a low temperature below zero (for example, in winter) and an operation method thereof.
  • a fuel cell system 400 shown in FIG. 5 includes a fuel cell stack 410 for generating direct current power by an electrochemical reaction of hydrogen and oxygen, a fuel process unit 420 for reforming a hydrocarbon-based power generation fuel F such as liquefied natural gas (LNG) or liquefied petroleum gas (LPG) into a hydrogen-rich gas, an oxygen supply unit having an air pump 430 supplying oxygen to the fuel cell stack 410, a cooling unit 440 for cooling the fuel cell stack 410, a power converter 450 for converting the direct current power generated by the fuel cell stack 410 into alternating current power, and various balance of plants (BOP) and controllers.
  • LNG liquefied natural gas
  • LPG liquefied petroleum gas
  • a reforming reactor is required to be heated to a predetermined temperature so as to reform the power generation fuel F into the gas that is rich in hydrogen when the system starts operating, and therefore air and the power generation fuel F are supplied to a combustor 421 of the fuel process unit 420 to increase the temperature of the reforming reactor up to 650 0 C .
  • a reforming temperature e.g., about 650 " C
  • a predetermined amount of the power generation fuel F is supplied to the fuel process unit 420 through an electricity generation supply pipe, and at the same time, a predetermined amount of water used for performing a steam reforming reaction is supplied to the fuel process unit 420.
  • the fuel process unit 420 does not directly supply the reformed gas to the fuel cell stack 410 but supplies the reformed gas through a bypass line so as to be used by the combustor 421.
  • the fuel cell system 400 supplies the reformed gas to the fuel cell stack 410 after a predetermined time elapses (i.e., when the temperature of reactors in the fuel process unit 420 is stabilized), so that the fuel cell stack 410 generates the power.
  • the cooling unit 440 cools the fuel cell stack 410 to maintain internal temperatures of the fuel cell stack 410.
  • the fuel cell system 400 Since the fuel cell system 400 is usually located on a veranda or outside a building, it may be considerably affected by external environments. Particularly, in a fuel cell system 400 located where an external temperature is below zero (e.g., in winter), water in the fuel cell stack 410 or the fuel process unit 420 or various pipes may be frozen, and therefore performance of the constituent elements may be deteriorated or the pipes may freeze and burst. [Disclosure]
  • the present invention has been made in an effort to provide a fuel cell system for preheating internal constituent elements to a predetermined temperature so that a the fuel cell stack , a fuel process unit, a water tank of a cooling device, and various pipes may not be frozen when an external temperature decreases below zero, and a method thereof.
  • An exemplary fuel cell system includes: a fuel cell stack for generating direct current power by an electrochemical reaction of hydrogen and oxygen; a fuel process unit for reforming a power generation fuel into a hydrogen-included reformed gas to supply the reformed gas to the fuel cell stack; an oxygen supply unit for supplying oxygen to the fuel cell stack; a cooling unit for cooling the fuel cell stack; a temperature sensor provided in a system case including the fuel cell stack, the fuel process unit, the oxygen supply unit, and the cooling unit to measure a temperature; a cooling water heater provided in the cooling unit to heat cooling water flowing to the fuel cell stack; and a controller for controlling the cooling water heater and the fuel process unit according to a value obtained by the temperature sensor.
  • the exemplary fuel cell system further includes a space heater for heating an inside of the system case according to a control operation of the controller.
  • the exemplary fuel cell system further includes a preheating heater provided to reactors so that the reactors for generating the reforming reaction may be quickly heated in the fuel process unit
  • the exemplary fuel cell system further includes an auxiliary power source unit that is connected to the cooling unit and the fuel process unit to supply an operational power source to the cooling unit and the fuel process unit according to the control operation of the controller while system power is not supplied.
  • the exemplary fuel cell system further includes an air circulating fan that is provided in the system case to circulate air in the system case and that stops according to a control operation of the controller.
  • a temperature inside a system case is measured by a temperature sensor, and no additional process is performed when the measured temperature is higher than a preset low temperature value, while cooling water flowing to a fuel cell stack is heated by a cooling water heater provided in a cooling unit and reactors of the fuel process unit in which the reforming reaction is generated is preheated when the measured temperature is lower than the preset low temperature value.
  • the reactors of the fuel process unit are heated since a power generation fuel and combustion air are provided to a combustor of the fuel process unit and are combusted in the combustor.
  • the reactors of the fuel process unit are heated by a preheating heater provided to the reactors.
  • cooling unit and the fuel process unit receive power sources from an auxiliary power source unit while system power is not supplied.
  • FIG. 1 is a schematic diagram of a fuel cell system according to a first exemplary embodiment of the present invention.
  • FIG. 2 is a schematic diagram of a cooling unit of the fuel cell system shown in FIG. 1.
  • FIG. 3 is a schematic diagram of a fuel cell system according to a second exemplary embodiment of the present invention.
  • FIG. 4 is a schematic diagram of a fuel cell system according to a third exemplary embodiment of the present invention.
  • FIG. 5 is a schematic diagram of a conventional fuel cell system.
  • Fuel cell systems 100, 200, 300, 400: Fuel cell systems
  • Power converters 170, 270, 370 Air circulating fans [Best Mode]
  • FIG. 1 is a schematic diagram of a fuel cell system according to a first exemplary embodiment of the present invention.
  • a fuel cell system 100 includes a fuel cell stack 110 generating direct current power using an electrochemical reaction between hydrogen and oxygen, a fuel process unit 120 for reforming a hydrocarbon-based power generation fuel F such as liquefied natural gas (LNG) or liquefied petroleum gas into a reformed gas that is high in hydrogen and supplying the reformed gas to the fuel cell stack 110, an oxygen supply unit 130 having a humidifier and an air pump to supply air containing oxygen to the fuel cell stack 110, a cooling unit 140 for cooling the fuel cell stack 110, and a power converter 150 for converting the direct current power generated by the fuel cell stack into alternating current power.
  • a fuel process unit 120 for reforming a hydrocarbon-based power generation fuel F such as liquefied natural gas (LNG) or liquefied petroleum gas into a reformed gas that is high in hydrogen and supplying the reformed gas to the fuel cell stack 110
  • an oxygen supply unit 130 having a humidifier and an air pump to supply air containing oxygen to the fuel cell stack 110
  • the fuel cell system 100 includes a reformed gas supply pipe 160 for directing the reformed gas generated in the fuel process unit 120 to the fuel cell stack 110, a residual reformed gas discharge pipe 161 for returning residual reformed gas that is not consumed in the fuel cell stack 110 to a combustor 121 , a bypass pipe 162 connected between the reformed gas supply pipe 160 and the residual reformed gas discharge pipe 161 to alternatively supply the reformed gas to the residual reformed gas discharge pipe 161 without directly supplying the reformed gas into the fuel cell stack 110, and a filter 165 provided in the reformed gas supply pipe 160 so that the fuel cell stack 110 may not receive any impurities relating to catalysts.
  • the fuel cell system 100 further includes a variety of balance of plants (BOP) such as an air pump, a water pump, a power generation fuel gas compressor, a solenoid valve, a temperature sensor, and a pressure sensor that are related to the fuel cell stack 110 and the fuel process unit 120, and a controller for controlling operations of the variety of constituent elements.
  • BOP balance of plants
  • the cooling unit 140 of the fuel cell system 100 includes a water-cooled heat exchanger 142, a plurality of water pumps 143 for flowing cooling water, a water tank 144 for recovering waste heat by heat-exchanging with the cooling water, an air-cooled heat exchanger 145 for eliminating the heat that is not recovered by the water tank 144 by using a cooling fan, and an auxiliary burner 146 that is automatically driven when there is heat consumption greater than an amount of the waste heat recovered to the water tank 144.
  • the fuel cell system 100 includes a temperature sensor 180 provided in a system case including the fuel cell stack 110, the fuel process unit 120, the oxygen supply unit 130, the cooling unit 140, and the power converter 150 to measure a temperature in the system case, and a cooling water heater 141 provided in the cooling unit 140 to heat the cooling water flowing into the fuel cell stack 110.
  • the fuel cell system 100 further includes an air circulating fan 170 provided in the system case to circulate air in the system case and being stopped according to a control operation of the controller, a space heater 190 for heating the inside of the system case according to the control operation of the controller, and a preheating heater 122 provided to reactors so that the reactors including the reforming reactor, a desulfurizer, and a carbon monoxide eliminator may be quickly heated in the fuel process unit 120.
  • the controller is set to respectively control the cooling water heater 141 and the fuel process unit 120 according to a value measured by the temperature sensor 180.
  • the fuel cell system 100 may maintain a temperature in the system case to be a predetermined temperature (e.g., 3O 0 C - 4O 0 C) while generating the power, but water in the internal constituent elements may be frozen when the fuel cell system 100 stops for a long time in a situation where an external temperature is below zero in winter. That is, even when a heat insulation process is performed for the fuel cell stack 110, the fuel process unit 120, and the various pipes so that the fuel cell system 100 may not be sensitively affected by variation of the external temperature while maintaining heat balance, performance may be deteriorated and the internal constituent elements may freeze and burst when the remaining water in the internal constituent elements is frozen.
  • a predetermined temperature e.g., 3O 0 C - 4O 0 C
  • the cooling unit 140 is used to lower the temperature of the cooling water of the fuel cell stack 110 to lower than a predetermined temperature (e.g., approximately, 45 ° C).
  • a predetermined temperature e.g., approximately, 45 ° C.
  • the fuel cell system 100 supplies the air to the combustor 121 while supplying steam to the electricity generation supply line to reduce the temperatures of the combustor 121 of the fuel process unit 120 and the reforming reactor to be less than the predetermined temperature, and the fuel cell system 100 is finally stopped.
  • the temperature sensor 180 detects the temperature.
  • the fuel cell system 100 performs the following operations to prevent the remaining water in the fuel cell stack 110, the fuel process unit 120, the cooling unit 140, and the various pipes from being frozen. That is, in the first exemplary embodiment of the present invention, when the temperature in the system is lowered, the air circulating fan 170 is stopped, and the space heater 190 operates to maintain the temperature in the system to be greater than 5 ° C .
  • the cooling water heater 141 of the cooling unit 140 heats the cooling water so that the cooling water circulating by the cooling unit 140 maintains the fuel cell stack 110 at a predetermined temperature.
  • the preheating heater 122 of the fuel process unit 120 preheats the reactor to a temperature of about 90 0 C to 100 0 C , and when the temperature of the combustor 121 is reduced to 5 0 C , the stopped preheating heater 122 repeatedly performs the preheating operation to increase the temperature of the reformed gas in the fuel process unit 120.
  • the fuel cell system 100 uses system power to supply a power source that is required to prevent the space heater 190, the cooling water heater 141 of the cooling unit 140, and the preheating heater 122 of the fuel process unit 120 from being frozen.
  • a power source that is required to prevent the space heater 190, the cooling water heater 141 of the cooling unit 140, and the preheating heater 122 of the fuel process unit 120 from being frozen.
  • a fuel cell system 200 according to a second exemplary embodiment of the present invention shown in FIG. 3 is the same as that of the first exemplary embodiment of the present invention except that the fuel cell system 200 shown in FIG. 3 does not include the preheating heater 122. That is, the fuel cell system 100 shown in FIG. 1 additionally includes the preheating heater 122 to reduce an operation time of the fuel process unit 120. In the fuel cell system 200 shown in FIG.
  • a temperature of the combustor 221 is maintained at a predetermined temperature (e.g., approximately, 250 0 C), and a temperature of a reactor of a fuel process unit 220 is maintained at a temperature of 90 0 C to 100 0 C.
  • the fuel cell system 200 includes a fuel cell stack 210, an oxygen supply unit 230, a cooling unit 240, a water-cooled heat exchanger 241 , a power converter 250, a reformed gas supply pipe 260, a residual reformed gas discharge pipe 261 , a bypass pipe 262, a filter 265, an air circulating fan 270, a temperature sensor 280, and a space heater 290, and functions thereof are the same as those in the fuel cell system 100 shown in FIG. 1 and so detailed descriptions will be omitted.
  • a fuel cell system 300 according to a third exemplary embodiment of the present invention shown in FIG. 4 is the same as that of the fuel cell system 100 according to the first exemplary embodiment of the present invention shown in FIG. 1 except that the fuel cell system 300 additionally includes an auxiliary power source unit 390. That is, the fuel cell system 300 according to the third exemplary embodiment of the present invention includes the auxiliary power source unit 390 for supplying an operational power source to a fuel process unit 320 and a cooling unit 340 while the system power is not supplied.
  • the auxiliary power source unit 390 is charged by power generated by a fuel cell stack in a like manner of a storage battery in a normal situation, and it supplies the operational power source to each constituent element according to the control operation of the controller when the system power is not supplied.
  • the fuel cell system includes the fuel cell stack 310, the fuel process unit 320, a combustor 321 , an oxygen supply unit 330, a cooling unit 340, a water-cooled heat exchanger 341 , a power converter 350, a reformed gas supply pipe 360, a residual reformed gas discharge pipe 361 , a bypass pipe 362, a filter 365, an air circulating fan 370, and a temperature sensor 380, and functions thereof are the same as those in the fuel cell system 100 shown in FIG. 1 and so detailed descriptions will be omitted.
  • the fuel cell stack, the fuel process unit, the water tank in the cooling unit, and various pipes that include water may be prevented from being frozen and therefore durability may increase.

Abstract

The present invention relates to a fuel cell system for generating power by an electrochemical reaction and a method thereof. The fuel cell system includes a fuel cell stack for generating direct current power by an electrochemical reaction of hydrogen and oxygen, a fuel process unit for reforming a power generation fuel into a hydrogen-included reformed gas to supply the reformed gas to the fuel cell stack, an oxygen supply unit for supplying oxygen to the fuel cell stack, a cooling unit for cooling the fuel cell stack, a temperature sensor for measuring a temperature inside the system case, a cooling water heater for heating cooling water flowing to the fuel cell stack, and a controller for controlling the cooling water heater and the fuel process unit according to a value obtained by the temperature sensor. In the fuel cell system and the method thereof, since the internal constituent elements are heated when an external temperature decreases below zero and a temperature of the system is reduced to be lower than a predetermined temperature, the fuel cell stack, the fuel process unit, the water tank in the cooling unit, and various pipes that include water may be prevented from being frozen, and therefore durability may increase.

Description

[DESCRIPTION] [Invention Title]
FUEL CELL SYSTEM AND OPERATING METHOD [Technical Field] The present invention relates to a fuel cell system for generating power by an electrochemical reaction, and more particularly, to a fuel cell system for preventing internal constituent elements from being frozen by a low temperature below zero (for example, in winter) and an operation method thereof. [Background Art]
Generally, a fuel cell system has a configuration as shown in FIG. 5. A conventional fuel cell system 400 shown in FIG. 5 includes a fuel cell stack 410 for generating direct current power by an electrochemical reaction of hydrogen and oxygen, a fuel process unit 420 for reforming a hydrocarbon-based power generation fuel F such as liquefied natural gas (LNG) or liquefied petroleum gas (LPG) into a hydrogen-rich gas, an oxygen supply unit having an air pump 430 supplying oxygen to the fuel cell stack 410, a cooling unit 440 for cooling the fuel cell stack 410, a power converter 450 for converting the direct current power generated by the fuel cell stack 410 into alternating current power, and various balance of plants (BOP) and controllers.
In the conventional fuel cell system 400, a reforming reactor is required to be heated to a predetermined temperature so as to reform the power generation fuel F into the gas that is rich in hydrogen when the system starts operating, and therefore air and the power generation fuel F are supplied to a combustor 421 of the fuel process unit 420 to increase the temperature of the reforming reactor up to 6500C . When the reforming reactor reaches a reforming temperature (e.g., about 650 "C), a predetermined amount of the power generation fuel F is supplied to the fuel process unit 420 through an electricity generation supply pipe, and at the same time, a predetermined amount of water used for performing a steam reforming reaction is supplied to the fuel process unit 420. In addition, a small amount of air is supplied to a carbon monoxide removing unit. Since the temperature of the carbon monoxide removing unit is unstable after generating the reformed gas and highly concentrated carbon monoxide is included in the reformed gas, the fuel process unit 420 does not directly supply the reformed gas to the fuel cell stack 410 but supplies the reformed gas through a bypass line so as to be used by the combustor 421. In addition, the fuel cell system 400 supplies the reformed gas to the fuel cell stack 410 after a predetermined time elapses (i.e., when the temperature of reactors in the fuel process unit 420 is stabilized), so that the fuel cell stack 410 generates the power. In this case, the cooling unit 440 cools the fuel cell stack 410 to maintain internal temperatures of the fuel cell stack 410.
Since the fuel cell system 400 is usually located on a veranda or outside a building, it may be considerably affected by external environments. Particularly, in a fuel cell system 400 located where an external temperature is below zero (e.g., in winter), water in the fuel cell stack 410 or the fuel process unit 420 or various pipes may be frozen, and therefore performance of the constituent elements may be deteriorated or the pipes may freeze and burst. [Disclosure]
[Technical Problem]
The present invention has been made in an effort to provide a fuel cell system for preheating internal constituent elements to a predetermined temperature so that a the fuel cell stack , a fuel process unit, a water tank of a cooling device, and various pipes may not be frozen when an external temperature decreases below zero, and a method thereof. [Technical Solution]
An exemplary fuel cell system according to an embodiment of the present invention includes: a fuel cell stack for generating direct current power by an electrochemical reaction of hydrogen and oxygen; a fuel process unit for reforming a power generation fuel into a hydrogen-included reformed gas to supply the reformed gas to the fuel cell stack; an oxygen supply unit for supplying oxygen to the fuel cell stack; a cooling unit for cooling the fuel cell stack; a temperature sensor provided in a system case including the fuel cell stack, the fuel process unit, the oxygen supply unit, and the cooling unit to measure a temperature; a cooling water heater provided in the cooling unit to heat cooling water flowing to the fuel cell stack; and a controller for controlling the cooling water heater and the fuel process unit according to a value obtained by the temperature sensor.
In addition, the exemplary fuel cell system further includes a space heater for heating an inside of the system case according to a control operation of the controller.
Further, the exemplary fuel cell system further includes a preheating heater provided to reactors so that the reactors for generating the reforming reaction may be quickly heated in the fuel process unit Still further, the exemplary fuel cell system further includes an auxiliary power source unit that is connected to the cooling unit and the fuel process unit to supply an operational power source to the cooling unit and the fuel process unit according to the control operation of the controller while system power is not supplied. In addition, the exemplary fuel cell system further includes an air circulating fan that is provided in the system case to circulate air in the system case and that stops according to a control operation of the controller.
In an exemplary method for driving a fuel cell system for preventing internal constituent elements from being frozen, a temperature inside a system case is measured by a temperature sensor, and no additional process is performed when the measured temperature is higher than a preset low temperature value, while cooling water flowing to a fuel cell stack is heated by a cooling water heater provided in a cooling unit and reactors of the fuel process unit in which the reforming reaction is generated is preheated when the measured temperature is lower than the preset low temperature value.
In addition, in the performing no additional process, the heating the cooling water and preheating the reactors when the measured temperature value is lower than the preset low temperature value, an air circulating fan for circulating air inside the system case is stopped and the air inside the system case is heated by a space heater.
Further, in the performing of preheating the reactors when the measured temperature value is lower than the preset low temperature value, the reactors of the fuel process unit are heated since a power generation fuel and combustion air are provided to a combustor of the fuel process unit and are combusted in the combustor.
Still further, in the performing of preheating the reactors when the measured temperature value is lower than the preset low temperature value, the reactors of the fuel process unit are heated by a preheating heater provided to the reactors.
In addition, the cooling unit and the fuel process unit receive power sources from an auxiliary power source unit while system power is not supplied. [Advantageous Effects]
According to an exemplary embodiments of the present invention, since internal constituent elements are heated when an external temperature decreases below zero and a temperature of a system is reduced to be lower than a predetermined temperature, a fuel cell stack, a fuel process unit, a water tank in the cooling unit, and various pipes that include water may be prevented from being frozen and therefore durability may increase. [Description of Drawings] FIG. 1 is a schematic diagram of a fuel cell system according to a first exemplary embodiment of the present invention.
FIG. 2 is a schematic diagram of a cooling unit of the fuel cell system shown in FIG. 1.
FIG. 3 is a schematic diagram of a fuel cell system according to a second exemplary embodiment of the present invention.
FIG. 4 is a schematic diagram of a fuel cell system according to a third exemplary embodiment of the present invention.
FIG. 5 is a schematic diagram of a conventional fuel cell system.
^ Description of Reference Numerals Indicating Primary Elements in the Drawings ^
100, 200, 300, 400: Fuel cell systems
1 10, 210, 310, 410: Fuel cell stacks
120, 220, 320, 420: Fuel process units
130, 230, 330, 430: Oxygen supply units 140, 240, 340, 440: Cooling units
141 , 241 , 341 : Heaters
150, 250, 350, 450: Power converters 170, 270, 370: Air circulating fans [Best Mode]
In the following detailed description, only certain exemplary embodiments of the present invention have been shown and described, simply by way of illustration. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. < First exemplary embodiment >
FIG. 1 is a schematic diagram of a fuel cell system according to a first exemplary embodiment of the present invention.
As shown in FIG. 1 , a fuel cell system 100 according to the first exemplary embodiment of the present invention includes a fuel cell stack 110 generating direct current power using an electrochemical reaction between hydrogen and oxygen, a fuel process unit 120 for reforming a hydrocarbon-based power generation fuel F such as liquefied natural gas (LNG) or liquefied petroleum gas into a reformed gas that is high in hydrogen and supplying the reformed gas to the fuel cell stack 110, an oxygen supply unit 130 having a humidifier and an air pump to supply air containing oxygen to the fuel cell stack 110, a cooling unit 140 for cooling the fuel cell stack 110, and a power converter 150 for converting the direct current power generated by the fuel cell stack into alternating current power.
In addition, the fuel cell system 100 includes a reformed gas supply pipe 160 for directing the reformed gas generated in the fuel process unit 120 to the fuel cell stack 110, a residual reformed gas discharge pipe 161 for returning residual reformed gas that is not consumed in the fuel cell stack 110 to a combustor 121 , a bypass pipe 162 connected between the reformed gas supply pipe 160 and the residual reformed gas discharge pipe 161 to alternatively supply the reformed gas to the residual reformed gas discharge pipe 161 without directly supplying the reformed gas into the fuel cell stack 110, and a filter 165 provided in the reformed gas supply pipe 160 so that the fuel cell stack 110 may not receive any impurities relating to catalysts. The fuel cell system 100 further includes a variety of balance of plants (BOP) such as an air pump, a water pump, a power generation fuel gas compressor, a solenoid valve, a temperature sensor, and a pressure sensor that are related to the fuel cell stack 110 and the fuel process unit 120, and a controller for controlling operations of the variety of constituent elements.
As shown in FIG. 2, the cooling unit 140 of the fuel cell system 100 includes a water-cooled heat exchanger 142, a plurality of water pumps 143 for flowing cooling water, a water tank 144 for recovering waste heat by heat-exchanging with the cooling water, an air-cooled heat exchanger 145 for eliminating the heat that is not recovered by the water tank 144 by using a cooling fan, and an auxiliary burner 146 that is automatically driven when there is heat consumption greater than an amount of the waste heat recovered to the water tank 144.
Particularly, as shown in FIG. 1 and FIG. 2, the fuel cell system 100 according to the first exemplary embodiment of the present invention includes a temperature sensor 180 provided in a system case including the fuel cell stack 110, the fuel process unit 120, the oxygen supply unit 130, the cooling unit 140, and the power converter 150 to measure a temperature in the system case, and a cooling water heater 141 provided in the cooling unit 140 to heat the cooling water flowing into the fuel cell stack 110.
In addition, the fuel cell system 100 according to the first exemplary embodiment of the present invention further includes an air circulating fan 170 provided in the system case to circulate air in the system case and being stopped according to a control operation of the controller, a space heater 190 for heating the inside of the system case according to the control operation of the controller, and a preheating heater 122 provided to reactors so that the reactors including the reforming reactor, a desulfurizer, and a carbon monoxide eliminator may be quickly heated in the fuel process unit 120. In addition, the controller is set to respectively control the cooling water heater 141 and the fuel process unit 120 according to a value measured by the temperature sensor 180.
A method for preventing the fuel cell system 100 from being frozen will now be described.
The fuel cell system 100 according to the first exemplary embodiment of the present invention may maintain a temperature in the system case to be a predetermined temperature (e.g., 3O0C - 4O0C) while generating the power, but water in the internal constituent elements may be frozen when the fuel cell system 100 stops for a long time in a situation where an external temperature is below zero in winter. That is, even when a heat insulation process is performed for the fuel cell stack 110, the fuel process unit 120, and the various pipes so that the fuel cell system 100 may not be sensitively affected by variation of the external temperature while maintaining heat balance, performance may be deteriorated and the internal constituent elements may freeze and burst when the remaining water in the internal constituent elements is frozen. An operation of the fuel system 100 according to the first exemplary embodiment of the present invention to solve the above problem will now be described. When a user tries to stop the fuel cell system 100 according to the control operation of the controller, an operation of the power converter 150 is stopped, supply of the power generation fuel F to the fuel process unit 120 and supply of the combustion air to the carbon monoxide removing unit are stopped, and supply of the air to the fuel cell stack 110 is stopped. Subsequently, rather than supplying the reformed gas to the fuel cell stack 110, the reformed gas is directly supplied to the combustor 121 of the fuel process unit 120 through the bypass pipe 162. Then, the cooling unit 140 is used to lower the temperature of the cooling water of the fuel cell stack 110 to lower than a predetermined temperature (e.g., approximately, 45°C). The fuel cell system 100 according to the first exemplary embodiment of the present invention supplies the air to the combustor 121 while supplying steam to the electricity generation supply line to reduce the temperatures of the combustor 121 of the fuel process unit 120 and the reforming reactor to be less than the predetermined temperature, and the fuel cell system 100 is finally stopped.
When the temperature in the system is reduced to be lower than a low temperature (e.g., approximately, below 80C) while the fuel cell system 100 is maintained in a stopped state, the temperature sensor 180 detects the temperature. The fuel cell system 100 according to the first exemplary embodiment of the present invention performs the following operations to prevent the remaining water in the fuel cell stack 110, the fuel process unit 120, the cooling unit 140, and the various pipes from being frozen. That is, in the first exemplary embodiment of the present invention, when the temperature in the system is lowered, the air circulating fan 170 is stopped, and the space heater 190 operates to maintain the temperature in the system to be greater than 5°C . In addition, the cooling water heater 141 of the cooling unit 140 heats the cooling water so that the cooling water circulating by the cooling unit 140 maintains the fuel cell stack 110 at a predetermined temperature. Further, the preheating heater 122 of the fuel process unit 120 preheats the reactor to a temperature of about 900C to 1000C , and when the temperature of the combustor 121 is reduced to 50C , the stopped preheating heater 122 repeatedly performs the preheating operation to increase the temperature of the reformed gas in the fuel process unit 120.
In this case, the fuel cell system 100 uses system power to supply a power source that is required to prevent the space heater 190, the cooling water heater 141 of the cooling unit 140, and the preheating heater 122 of the fuel process unit 120 from being frozen. <Second exemplary embodiment
A fuel cell system 200 according to a second exemplary embodiment of the present invention shown in FIG. 3 is the same as that of the first exemplary embodiment of the present invention except that the fuel cell system 200 shown in FIG. 3 does not include the preheating heater 122. That is, the fuel cell system 100 shown in FIG. 1 additionally includes the preheating heater 122 to reduce an operation time of the fuel process unit 120. In the fuel cell system 200 shown in FIG. 3, since the preheating process is omitted and the power generation fuel F and the combustion air are combusted in a combustor 221 , a temperature of the combustor 221 is maintained at a predetermined temperature (e.g., approximately, 2500C), and a temperature of a reactor of a fuel process unit 220 is maintained at a temperature of 900C to 1000C.
In addition, the fuel cell system 200 according to the second exemplary embodiment of the present invention includes a fuel cell stack 210, an oxygen supply unit 230, a cooling unit 240, a water-cooled heat exchanger 241 , a power converter 250, a reformed gas supply pipe 260, a residual reformed gas discharge pipe 261 , a bypass pipe 262, a filter 265, an air circulating fan 270, a temperature sensor 280, and a space heater 290, and functions thereof are the same as those in the fuel cell system 100 shown in FIG. 1 and so detailed descriptions will be omitted. <Third exemplary embodiment
A fuel cell system 300 according to a third exemplary embodiment of the present invention shown in FIG. 4 is the same as that of the fuel cell system 100 according to the first exemplary embodiment of the present invention shown in FIG. 1 except that the fuel cell system 300 additionally includes an auxiliary power source unit 390. That is, the fuel cell system 300 according to the third exemplary embodiment of the present invention includes the auxiliary power source unit 390 for supplying an operational power source to a fuel process unit 320 and a cooling unit 340 while the system power is not supplied. The auxiliary power source unit 390 is charged by power generated by a fuel cell stack in a like manner of a storage battery in a normal situation, and it supplies the operational power source to each constituent element according to the control operation of the controller when the system power is not supplied.
In addition, the fuel cell system according to the third exemplary embodiment of the present invention includes the fuel cell stack 310, the fuel process unit 320, a combustor 321 , an oxygen supply unit 330, a cooling unit 340, a water-cooled heat exchanger 341 , a power converter 350, a reformed gas supply pipe 360, a residual reformed gas discharge pipe 361 , a bypass pipe 362, a filter 365, an air circulating fan 370, and a temperature sensor 380, and functions thereof are the same as those in the fuel cell system 100 shown in FIG. 1 and so detailed descriptions will be omitted. As described, according to the exemplary embodiments of the present invention, since the internal constituent elements are heated when an external temperature decreases below zero and a temperature of the system is reduced to be lower than a predetermined temperature, the fuel cell stack, the fuel process unit, the water tank in the cooling unit, and various pipes that include water may be prevented from being frozen and therefore durability may increase.
While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

[CLAIMS] [Claim 1 ]
A fuel cell system comprising: a fuel cell stack for generating direct current power by an electrochemical reaction of hydrogen and oxygen; a fuel process unit for reforming a power generation fuel into a hydrogen-included reformed gas to supply the reformed gas to the fuel cell stack; an oxygen supply unit for supplying oxygen to the fuel cell stack; a cooling unit for cooling the fuel cell stack; a temperature sensor provided in a system case including the fuel cell stack, the fuel process unit, the oxygen supply unit, and the cooling unit to measure a temperature; a cooling water heater provided in the cooling unit to heat cooling water flowing to the fuel cell stack; and a controller for controlling the cooling water heater and the fuel process unit according to a value obtained by the temperature sensor.
[Claim 2]
The fuel cell system of claim 1 , further comprising a space heater for heating an inside of the system case according to a control operation of the controller.
[Claim 3] The fuel cell system of claim 1 or claim 2, further comprising a preheating heater provided to reactors so that the reactors for generating the reforming reaction may be quickly heated in the fuel process unit.
[Claim 4] The fuel cell system of claim 1 or claim 2, further comprising an auxiliary power source unit that is connected to the cooling unit and the fuel process unit to supply an operational power source to the cooling unit and the fuel process unit according to the control operation of the controller while system power is not supplied.
[Claim 5]
The fuel cell system of claim 1 , further comprising an air circulating fan that is provided in the system case to circulate air in the system case and that is stopped according to a control operation of the controller.
[Claim 6] A method for driving a fuel cell system for preventing internal constituent elements from being frozen, the method comprising: measuring a temperature inside a system case by a temperature sensor; and performing no additional process when the measured temperature is higher than a preset low temperature value, and heating cooling water flowing to a fuel cell stack by a cooling water heater provided in a cooling unit and preheating reactors of the fuel process unit in which the reforming reaction is generated when the measured temperature is lower than the preset low temperature value.
[Claim 7]
The method of claim 6, wherein, in the performing of heating the cooling water and preheating the reactors when the measured temperature value is lower than the preset low temperature value, an air circulating fan for circulating air inside the system case is stopped and the air inside the system case is heated by a space heater.
[Claim 8] The method of claim 6 or claim 7, wherein, in the performing of preheating the reactors when the measured temperature value is lower than the preset low temperature value, the reactors of the fuel process unit are preheated since a power generation fuel and combustion air are provided to a combustor of the fuel process unit and are combusted in the combustor. [Claim 9]
The method of claim 6 or claim 7, wherein, in the performing of preheating the reactors when the measured temperature value is lower than the preset low temperature value, the reactors of the fuel process unit are preheated by a preheating heater provided to the reactors. [Claim 10]
The method of claim 6, wherein the cooling unit and the fuel process unit receive a power source from an auxiliary power source unit while system power is not supplied.
PCT/KR2007/003694 2006-08-04 2007-08-01 Fuel cell system and operating method WO2008016257A1 (en)

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