JP5033379B2 - Starting method of fuel cell power generation system - Google Patents

Description

  The present invention relates to a method for starting a fuel cell power generation system, and more particularly to a method for starting a fuel cell power generation system that reduces loss of power energy on the commercial power source side during startup.

  When the raw fuel is a hydrocarbon fuel such as natural gas, city gas, LPG, etc., the fuel cell power generation system reforms the hydrocarbon fuel into a hydrogen-based reformed gas using a fuel reformer. In addition to supplying the reformed gas to the fuel electrode of the fuel cell, the air taken in from the outside is supplied as the oxidant gas to the air electrode of the fuel cell to generate an electrochemical reaction through the electrolyte membrane. Is what you do.

The fuel reformer includes a reformer that reforms a hydrocarbon-based raw fuel into a reformed gas mainly composed of steam, and CO contained in the reformed gas discharged from the reformer. A CO converter that converts CO ₂ to reduce CO concentration and a CO remover that selectively oxidizes the modified reformed gas emitted from the CO converter to further reduce CO concentration (less than 10 ppm) are provided. It is common.

  At the time of starting the fuel cell power generation system, since the temperature of the catalyst layer housed in each reactor of the reformer of the fuel reformer, the CO converter, and the CO remover is low, the generated reformer The composition of the gas is not stable and this reformed gas cannot be supplied to the fuel cell. For this reason, for example, in Patent Document 1, until the reformed gas composition is stabilized, the generated reformed gas having an unstable composition is introduced into a gas burner called a PG burner and burned. Yes. Then, after the reformed gas composition is stabilized, the valve is switched to supply the reformed gas to the fuel cell.

Also, a fuel cell that has started generating electricity by supplying reformed gas does not immediately enter a stable steady state. The power output is low while the temperature of the fuel cell is low. For this reason, an electric load is started after the start of power generation, the current is increased by applying the maximum load within a range not damaging the fuel cell, the temperature of the fuel cell is raised to an appropriate temperature by self-heating by reaction heat, and as short as possible. Transition to steady operation in time.
JP 2001-291525 A

  In the conventional fuel cell power generation system, an auxiliary power source for operating auxiliary machinery such as a solenoid valve and a pump is provided, and electric power is supplied to the auxiliary power source by wiring from the commercial power source side at the time of startup. An AC / DC converter is provided in the middle of the wiring path, and electric power converted into direct current (24V) by the AC / DC converter is supplied to the auxiliary power source. The power supply from the side is stopped and switched so that a part of the DC power generated by the fuel cell is supplied to the supplementary power source.

  The power supply from the commercial power supply side to the auxiliary power supply must be continued from the start of the fuel cell power generation system to the transition to the steady operation of the fuel cell. For this reason, there has been a problem that a loss of power energy on the commercial power source side occurs at the time of startup.

  The present invention has been made to solve the above problems, and provides a method for starting a fuel cell power generation system that suppresses loss of power energy on the commercial power source side when the fuel cell power generation system is started. Objective.

As means for achieving the above object, claim 1 of the present invention provides:
A method for starting a fuel cell power generation system including a fuel reformer,
Supplying the reformed gas reformed by the fuel reformer to the fuel cell at start-up;
Ri by the power generation in the early stage of the fuel cell, when exceeding a voltage value which the cell block voltage is preset in units of a plurality of cells in the stack of the fuel cell, the and the total voltage exceeds the specified voltage, start the connected auxiliary converter to the fuel cell by energizing the auxiliary power supply via the auxiliary converter,
When power generation of the fuel cell is started and the total voltage of the fuel cell exceeds a predetermined voltage higher than the specified voltage, the commercial power source side is connected via an AC / DC converter connected to the auxiliary power source. The power supply to the supplementary power supply is cut off , and the DC / DC converter and the grid-connected inverter connected to the fuel cell are started, so that the power from the fuel cell is fed to the distribution board side and the steady state of the fuel cell Enter the driving action,
When the total voltage of the fuel cell does not exceed the predetermined voltage greater than the specified voltage after the fuel cell power generation is started, the fuel cell power generation system is emergency stopped.
It is characterized by that.

Claim 2 of the present invention is the starting method of the fuel cell power generation system of claim 1,
The fuel cell is in a solid polymer form,
The fuel cell stack is heated by self-heating by increasing a power generation load until the temperature of the fuel cell stack reaches a predetermined temperature after entering the steady operation. To do.

  According to the first aspect of the present invention, when the fuel cell power generation system is started, the reformed gas reformed by the fuel reformer is supplied to the fuel cell to generate power, and the total amount of power generated in the initial stage of the fuel cell is generated. When the voltage exceeds the specified voltage, the auxiliary converter is activated to energize the auxiliary power supply from the fuel cell side, and the power supply from the commercial power supply side to the auxiliary power supply is cut off via the AC / DC converter. . As a result, it is possible to cut off the supply of commercial power to the auxiliary power supply by supplying power to the auxiliary power supply at a relatively early power generation stage of the fuel cell at the time of startup, and to reduce the power energy loss on the commercial power supply side at the time of startup. Can be suppressed.

Further, according to the invention of claim 1, exceeds the voltage value cell block voltage of the fuel cell is set in advance, and since the total voltage activates the auxiliary converter when exceeding the specified voltage, the fuel cell Power can be supplied to the auxiliary power supply after the initial power generation state is accurately determined.

Further, according to the invention of claim 1, when the total voltage of the fuel cell exceeds a greater predetermined voltage than the specified voltage, the DC / DC converter and system interconnection inverter of the power conditioner connected to the fuel cell activation Therefore, it is possible to switch to power feeding to the system after the power generation state of the fuel cell is almost stabilized.

  Next, an embodiment showing a method for starting a fuel cell power generation system according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram showing a fuel cell power generation system to which the start-up method of the present invention is applied. The fuel cell power generation system includes a reformer 1, a CO converter 2, and a CO remover 3. Is provided with a heating burner 4. Reference numeral 5 denotes a desulfurizer. The desulfurizer 5 desulfurizes the hydrocarbon-based raw fuel and introduces it into the reformer 1. The burner 4 is supplied with a part of the desulfurized raw fuel at the time of start-up and burns. After the steady operation, the burner 4 is supplied with off-gas discharged from the fuel electrode of the fuel cell 8 and burns. The burner 4 is supplied with air taken in from outside via the air pump AP1 for combustion.

  A water vapor generator 6 supplies a part of the water stored in the water tank 7 by the water pump WP1, and exchanges heat between this water and the high-temperature combustion exhaust gas generated by the combustion of the burner 4. Steam is generated by this, and this steam is mixed into the raw fuel. Thereby, the raw fuel desulfurized by the desulfurizer 5 is introduced into the reformer 1 in a state where steam is mixed.

  The hydrogen-based reformed gas steam-reformed in the reformer 1 is cooled to an appropriate temperature through the first heat exchanger H1 and then introduced into the CO converter 2, where it is transformed. As a result, the CO concentration in the reformed gas is reduced. A water circulation path is provided between the first heat exchanger H1 and the water tank 7, and a part of the water in the water tank 7 is circulated by the water pump WP2 and modified by the first heat exchanger H1. Heat exchange with quality gas.

  The reformed gas transformed by the CO transformer 2 is cooled to an appropriate temperature through the second heat exchanger H2, and then mixed with the air taken in from the outside via the air pump AP2 to the CO remover 3. The CO concentration in the reformed gas is reduced to approximately 10 ppm or less by being introduced and selectively oxidized by the CO remover 3. A water circulation path is also provided between the second heat exchanger H2 and the water tank 7, and a part of the water in the water tank 7 is circulated by the water pump WP3 to generate heat in the second heat exchanger H2. Let them exchange.

  The reformed gas thus reformed is heated up to the reaction temperature of the catalyst contained in the reactors of the reformer 1, the CO converter 2, and the CO remover 3 at the time of startup. Therefore, the reformed gas composition is not stable. For this reason, conventionally, the unstable reformed gas discharged from the CO remover 3 was introduced into the PG burner and burned as described above. However, in the present invention, the PG burner is not provided. In the present invention, a heater 3 a is disposed in the CO remover 3, and the reformed gas is heated by the heater 3 a to change the gas composition to a substantially stable gas and supply it to the fuel electrode of the fuel cell 8. The CO transformer 2 is also provided with a heater 2a.

  Into the water tank 7, air taken in from the outside through the air pump AP3 is introduced into the water, is humidified by bubbling, and then supplied to the air electrode of the fuel cell 8. Further, a water circulation path is provided between the water tank 7 and the cooling part of the fuel cell 8, and a part of the water in the water tank 7 is circulated by the water pump WP4 during the steady operation to cool the fuel cell 8. In this case, when the fuel cell 8 is a polymer electrolyte fuel cell, the fuel cell 8 is cooled to maintain an appropriate temperature (about 80 ° C.) during steady operation.

  FIG. 2 is a schematic configuration diagram showing a power supply circuit in the embodiment of the start-up method of the fuel cell power generation system according to the present invention. A power conditioner 9 is connected to the fuel cell 8, and this power conditioner 9 is not shown. It is connected to a distribution board (for example, a residential distribution board). The distribution board is connected to a commercial power source via a power meter (not shown).

  The power conditioner 9 includes a DC / DC converter 9a connected to the fuel cell 8 and a grid-connected inverter 9b connected to the DC / DC converter 9a. The power conditioner 9 converts DC power generated by the fuel cell 8 to DC / DC. The voltage is boosted by the DC converter 9a, converted into AC power by the grid interconnection inverter 9b, and transmitted to the distribution board via the grid relay 9c and ELB (switch). Then, power is supplied from the distribution board to each load in the home.

  Reference numeral 10 denotes an auxiliary power source, and an AC / DC converter 11, a relay 12, and a main power switch 13 are connected in series in this order. The main power switch 13 is connected to the interconnection relay 9c in the power conditioner 9 and the ELB. Connected between. Accordingly, when the main power switch 13 is turned on at the time of starting the fuel cell power generation system, commercial power flows from the distribution board side, and the AC / DC converter 11 is energized via the relay 12, and this AC / DC conversion is performed. The power is converted to DC power (24V) by the device 11 and supplied to the auxiliary power source 10. The auxiliary power source 10 is connected to a plurality of auxiliary devices such as the air pumps AP1 to AP3, the water pumps WP1 to WP3, and a solenoid valve, and can be operated by supplying power from the auxiliary power source 10, respectively. .

  Reference numeral 14 denotes an auxiliary converter, which is connected to connect the downstream side of the fuel cell 8 and the upstream side of the auxiliary power supply 10 as shown in FIG. When the fuel cell power generation system is started, when the total voltage becomes equal to or higher than the specified voltage in the initial power generation by the fuel cell 8, the auxiliary power source 10 is connected from the fuel cell 8 side via the auxiliary converter 14. While supplying electricity, the said relay 12 is opened and the electric power feeding from the commercial power source side to the auxiliary machine power supply 10 is interrupted | blocked via the AC / DC converter 11.

  Reference numeral 15 denotes a surplus power processor, and a part of power from the fuel cell 8 flows as surplus power during steady operation of the fuel cell 8, and the DC heater connected to the surplus power processor 15 is energized. The DC heater is not shown in FIG. 1, but is, for example, a heater for heating water to be fed into a hot water storage tank (not shown) or a heater (not shown) provided in the water tank 7.

  Next, a method for starting the fuel cell power generation system according to the present invention will be described. 3 to 5 are schematic diagrams showing a flowchart at the time of starting the fuel cell power generation system. When the main switch of the system is turned on at the start shown in FIG. 3, an operation command signal is output from a control device (not shown) (steps). S1), temperature raising start of the reformer, temperature raising start of the fuel cell, heater control start, reforming system pressure control start, water supply, drainage control start, etc. are performed (step S2). Each of these start operations is performed by a command signal from the control device, and power is supplied to each device from the commercial power supply side.

  At the start stage, the electromagnetic valve V on the raw fuel supply side shown in FIG. 1 is opened, the raw fuel is supplied to the desulfurizer 5 and desulfurized, and then supplied to the burner 4 of the reformer 1, and the air pump Combustion air is supplied from the AP 1 and burned by ignition of the burner 4. At this time, the fuel pump FP is held in the off state. Then, the temperature of the reforming catalyst layer housed in the reactor of the reformer 1 starts to be increased by the combustion gas of the burner 4. The temperature of the catalyst layer housed in the reactor is increased by the CO converter 2 by the heater 2a and the CO remover 3 by the heater 3a, respectively. The heaters 2a and 3a, the solenoid valve V, and the like are also operated by command signals from the control device, and are supplied with power from the commercial power source side.

  When a temperature sensor (not shown) detects that the catalyst layer temperature of the CO converter 2 exceeds 150 ° C. (step S3), the water pump WP1 for supplying water from the water tank 7 to the steam generator 6 is turned on. . Thereby, the said water pump WP1 act | operates and supplies a small amount of water to the steam generator 6. FIG.

  Thereafter, the temperature sensor detects that the catalyst bed temperature of the reformer 1 exceeds 620 ° C., the catalyst bed temperature of the CO converter 2 exceeds 160 ° C., and the steam generator 6 exceeds 95 ° C. When detected (step S5), the fuel pump FP is operated to supply the raw fuel after desulfurization to the reformer 1, and steam is supplied from the steam generator 6 almost simultaneously with the supply of the raw fuel. When the mixed gas with the raw fuel is supplied to the reformer 1, reforming of the raw fuel gas is started (step S6).

  The reformed gas steam-reformed by the reformer 1 is introduced into the CO converter 2 through the first heat exchanger H 1 and is converted by the CO converter 2. Further, the air pump AP is operated to supply air to the CO remover 3, and the reformed gas introduced into the CO remover 3 through the second heat exchanger H is selectively oxidized (step S7).

  The reformed gas selectively oxidized by the CO remover 3 is supplied to the fuel electrode of the fuel cell 8, the air pump AP 3 is operated to supply air to the water tank 7, and is bubbled in the water tank 7. The humidified air is supplied as an oxidant gas to the air electrode of the fuel cell 8 (step S8).

  Thereby, power generation is started in the fuel cell 8, and after the start of power generation, the cell block voltage is measured for each of a plurality of cells (for example, three cells) in the stack of the fuel cell 8, and the total voltage of the fuel cell 8 is measured. Then, it is determined whether the cell block voltage exceeds 1.8V and the total voltage exceeds 43V (step S9). In this case, the cell block voltage 1.8V is a 3-cell block voltage and is a preset voltage value, and the total voltage 43V is a specified voltage and is the minimum operating voltage value of the auxiliary converter 14.

  If YES in step S9, the auxiliary converter 14 is started (step S10), and if NO, the process waits until the total voltage exceeds 43V. Thereafter, whether or not the state where the cell block voltage exceeds 1.8V is maintained (step S11), if YES, it is determined whether or not the total voltage exceeds 52V (step S12). Stops auxiliary converter 14 and returns to step S9. The total voltage 52V is a predetermined voltage, and is a voltage for maintaining the single cell voltage at 0.8V or less, and has a relationship of a prescribed voltage <predetermined voltage.

  If YES in step S12, the AC / DC converter 11 energizing the auxiliary power supply 10 is stopped (step S13). If NO, an abnormality has occurred in the power generation of the fuel cell 8. Emergency stop because of expectation. When the AC / DC converter 11 is stopped, the supply of AC power from the commercial power supply side to the AC / DC converter 11 is stopped, and the DC power generated by the fuel cell 8 is converted to 24V DC by the auxiliary converter 14. Auxiliary power supply 10 is supplied. For this reason, it is possible to cut off the supply of commercial power to the auxiliary power source 10 at a relatively early stage at the time of start-up, and to suppress loss of commercial power energy. In addition, since the interconnection relay 9c of the power conditioner 9 is open, no DC power flows from the fuel cell 8 to the power conditioner 9 side.

  After the AC / DC converter 11 is stopped, the interconnection relay 9c is closed and the DC / DC converter 9a and the grid interconnection inverter 9b are activated (step S14). As a result, the DC power generated by the fuel cell 8 also flows to the power conditioner 9 side and is boosted by the DC / DC converter 9a, and converted to AC by the grid interconnection inverter 9b to be linked to the grid relay 9c and ELB. Power is supplied to the distribution board side through (step S15).

  After starting the power supply to the system, it is measured by a timer (not shown) and waits for one minute (step S16), and it is detected that the power generation output of the fuel cell 8 is increased to about 6.5A (step S17).

  In step S17, it is detected that the power generation output of the fuel cell 8 is increased to about 6.5A, and then measured by a timer and waits for 5 minutes (step S18). The load increase is started and the fuel cell 8 is rated 17A. It is detected that the output is increased up to (step S19). In this case, since the fuel cell 8 is a solid polymer type, the temperature is still low (about 50 to 60 ° C.), and a sufficient output cannot be obtained. When a load is applied, the temperature of the fuel cell 8 is increased by self-heating, and when the temperature reaches 67 to 70 ° C., a rated current can be obtained. The electrochemical reaction due to the power generation of the fuel cell 8 is an exothermic reaction, and the temperature further increases with the power generation. Since the battery temperature during steady operation is 70 to 80 ° C., the water pump WP4 is operated so that the battery temperature does not rise any further, and cooling water is supplied from the water tank 7 to the cooling part of the fuel cell 8, As a result, the fuel cell 8 is cooled and maintained at an appropriate operating temperature.

  When the fuel cell 8 reaches a predetermined temperature and each of the reaction temperatures of the fuel reformer reaches a specified temperature, a predetermined start condition is established, and the target output of the fuel cell 8 is confirmed (step S20). To do. Thereafter, the fuel cell 8 shifts to the steady operation mode.

  The starting method of the fuel reformer according to the present invention can be applied to a fuel reformer used by being incorporated in a fuel cell power generation system.

It is a schematic block diagram which shows the fuel cell power generation system to which the starting method of this invention is applied. It is a schematic block diagram which shows the power supply circuit in embodiment of the starting method of the fuel cell power generation system which concerns on this invention. It is a part of flowchart at the time of starting in embodiment of the starting method of the fuel cell power generation system which concerns on this invention. It is a continuation part of the flowchart in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reformer 2 CO converter 3 CO remover 4 Burner 5 Desulfurizer 6 Steam generator 7 Water tank 8 Fuel cell 9 Power conditioner 9a DC / DC converter 9b System connection inverter 9c System connection relay 10 Auxiliary power supply 11 AC / DC converter 12 Relay 13 Main power switch 14 Auxiliary converter

Claims (2)

A method for starting a fuel cell power generation system including a fuel reformer,
Supplying the reformed gas reformed by the fuel reformer to the fuel cell at start-up;
Ri by the power generation in the early stage of the fuel cell, when exceeding a voltage value which the cell block voltage is preset in units of a plurality of cells in the stack of the fuel cell, the and the total voltage exceeds the specified voltage, start the connected auxiliary converter to the fuel cell by energizing the auxiliary power supply via the auxiliary converter,
When power generation of the fuel cell is started and the total voltage of the fuel cell exceeds a predetermined voltage higher than the specified voltage, the commercial power source side is connected via an AC / DC converter connected to the auxiliary power source. The power supply to the supplementary power supply is cut off , and the DC / DC converter and the grid-connected inverter connected to the fuel cell are started, so that the power from the fuel cell is fed to the distribution board side and the steady state of the fuel cell Enter the driving action,
When the total voltage of the fuel cell does not exceed the predetermined voltage greater than the specified voltage after the fuel cell power generation is started, the fuel cell power generation system is emergency stopped.
A method for starting a fuel cell power generation system. The fuel cell is in a solid polymer form,
The fuel cell stack is heated by self-heating by increasing a power generation load until the temperature of the fuel cell stack reaches a predetermined temperature after entering the steady operation. The starting method of the fuel cell power generation system according to claim 1.

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