JP2005346951A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable to do away with hydrogen discharge from a hydrogen circulation channel due to purge, and efficiently remove impurities from anode offgas. <P>SOLUTION: A circulation channel of anode offgas is formed from an anode outlet 3b, to a hydrogen circulation channel 11, a hydrogen circulation pump 12, a hydrogen separation device 16 as well as a variable orifice 15 connected in parallel, a hydrogen circulation channel 17, a confluence 9 of a hydrogen supply channel 10 and the hydrogen circulation channel 11, the hydrogen supply channel 10, and an anode inlet 3a, in that order. A controller 24 controls a bypass flow rate by the variable orifice 15, so that a potential difference between an inlet and an outlet of the hydrogen separation device 16 be an optimum separation efficiency. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell system.

  In a fuel cell, a fuel gas such as hydrogen gas and an oxidizing gas containing oxygen are electrochemically reacted through an electrolyte, and electric energy is directly taken out between electrodes provided on both surfaces of the electrolyte. In particular, a polymer electrolyte fuel cell using a polymer electrolyte has attracted attention as a power source for electric vehicles because of its low operating temperature and easy handling. That is, a fuel cell vehicle is equipped with a hydrogen storage device such as a high-pressure hydrogen tank, a liquid hydrogen tank, or a hydrogen storage alloy tank in the vehicle, and reacts by supplying hydrogen supplied therefrom and air containing oxygen to the fuel cell. This is the ultimate clean vehicle that drives the motor connected to the drive wheels with the electric energy extracted from the fuel cell, and the only exhaust material is water.

  Usually, the anode and the cathode are supplied with a larger amount of hydrogen or air than the amount of the reaction gas consumed in the electrochemical reaction so that the reaction gas reaches the end cell of the fuel cell and the end of the power generation surface. A gas containing excess hydrogen gas called anode off-gas is discharged from the anode outlet. Since the anode off gas contains unreacted hydrogen gas, it is mixed with newly supplied hydrogen and supplied to the anode again. As described above, in the fuel cell having the function of circulating the anode off gas, the inert gas such as nitrogen or argon leaks from the cathode air to the anode through the electrolyte membrane and accumulates in the anode circulation path. Further, impurity gas contained in hydrogen as a fuel gas may accumulate in the anode circulation path.

  The amount of these impurities accumulated in the anode circulation path increases as the fuel cell operating time elapses, and the hydrogen partial pressure at the anode decreases, resulting in a decrease in power generation performance. For this reason, during the operation time, the anode off gas is sometimes discharged out of the system, and an operation called purging is performed to remove impurities from the anode circulation path. However, when performing the purge operation, unreacted hydrogen gas is also released, so that the fuel efficiency of the fuel cell is lowered.

  As a countermeasure, for example, according to Patent Document 1, a hydrogen separator having a hydrogen permeable membrane that selectively permeates hydrogen is disposed between a hydrogen supply source and a fuel cell, A fuel cell system is disclosed in which both supply gas (hydrogen-rich gas) is supplied simultaneously to a hydrogen separator, and hydrogen that has permeated through a hydrogen permeable membrane is supplied to the fuel cell.

Further, according to Patent Document 1, the concentration or amount of hydrogen remaining in the anode circulation system of the fuel cell is calculated, and a load current sufficient to use up all the remaining hydrogen during the purge is applied to the fuel cell, thereby being discharged during the purge. A method for reducing the amount of hydrogen to be reduced as much as possible is disclosed.
JP 2003-243020 A (page 4, FIG. 1)

  However, according to the conventional fuel cell system described above, the hydrogen separation from the anode off gas and the hydrogen separation from the supply gas are performed by the common hydrogen separation device, and therefore the amount of hydrogen separated from the anode off gas is the anode alone. Since this is less than the case of hydrogen separation from off-gas, there is a problem that the hydrogen separation efficiency is lowered.

  In addition, if the amount of hydrogen discharged is reduced by using up the remaining hydrogen in the hydrogen circulation system during the purge, there is a problem that the electrolyte membrane and electrode catalyst of the fuel cell may be deteriorated.

  In order to solve the above problems, the present invention provides a fuel cell body that generates electricity by an electrochemical reaction of hydrogen and an oxidant, a hydrogen supply path for supplying hydrogen to the anode inlet of the fuel cell body, An anode offgas circulation path for returning the anode offgas discharged from the anode outlet to the hydrogen supply path, and the anode offgas circulation upstream from the junction of the hydrogen supply path and the anode offgas circulation path The gist is that a hydrogen separator for separating hydrogen from the anode off-gas is provided on the path.

  According to the present invention, since the hydrogen separator dedicated to the anode off-gas is provided in the hydrogen circulation path, a hydrogen separator is provided upstream of the fuel cell to share one hydrogen separator from both the new supply gas and the anode off-gas. Thus, the amount of hydrogen that can be separated from the anode off-gas and the separation efficiency are improved compared to the case of hydrogen separation.

  Further, there is no need for purging itself, and there is no possibility of deterioration of the electrolyte membrane or electrode catalyst resulting from using up the remaining hydrogen in the hydrogen circulation system during purging.

BEST MODE FOR CARRYING OUT THE INVENTION

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a system schematic diagram illustrating the configuration of a fuel cell system according to a first embodiment of the present invention. In FIG. 1, a fuel cell system 1 includes a fuel cell main body 2 having an anode 3 and a cathode 4, an ammeter 5 that detects an output current of the fuel cell main body 2, and a load that consumes power generated by the fuel cell main body 2. An apparatus 6, a hydrogen supply source 7, a hydrogen pressure adjustment valve 8 that adjusts the pressure of hydrogen gas supplied from the hydrogen supply source 7, and a hydrogen supply path 10 that connects the hydrogen pressure adjustment valve 8 and the inlet 3 a of the anode 3. The hydrogen circulation path 11 connecting the outlet 3 b of the anode 3 and the inlet of the hydrogen circulation pump 12, the hydrogen circulation pump 12 that pumps the anode off-gas discharged from the anode outlet 3 b, and the downstream of the hydrogen circulation pump 12. Hydrogen circulation paths 13, 14, a variable orifice 15 disposed on the hydrogen circulation path 13, a hydrogen separator 16 disposed on the hydrogen circulation path 14, and under the hydrogen circulation paths 13 and 14 As a oxidant gas in the cathode 4, the junction 9 where the hydrogen circuit 17 joins the hydrogen supply path 10, the discharge path 18 for discharging impurities separated from the hydrogen separator 16, and the cathode 4. An air compressor 19 for supplying air, an air pressure regulating valve 20 for adjusting the pressure of air discharged from the cathode 4, a pressure sensor 21 for detecting the pressure of the anode inlet 3a, and an inlet pressure of the hydrogen separator 16 are detected. A pressure sensor 22 that detects the outlet pressure of the hydrogen separator 16, and a controller 24 that controls the fuel cell system 1.

  The fuel cell main body 2 is, for example, a solid polymer fuel cell including a solid polymer electrolyte. The hydrogen supply source 7 is a hydrogen storage device such as a high-pressure hydrogen tank, a hydrogen storage material tank, or a liquefied hydrogen storage device, or a fuel reformer that generates reformed hydrogen from raw fuel.

  The hydrogen separation device 16 is a device that separates hydrogen gas and impurity gas other than hydrogen from a gas containing hydrogen using a hydrogen permeable metal membrane, a molecular sieve carbon membrane, or the like. As a hydrogen separator using a hydrogen permeable metal membrane, a “hydrogen permeable membrane utilization device” described in JP-A-2003-334417 is known. As a hydrogen separation apparatus using a molecular sieve carbon membrane, “a method for purifying hydrogen using a molecular sieve carbon membrane” described in JP-A-2003-160308 can be applied. In particular, the molecular sieve carbon membrane exhibits excellent hydrogen separation characteristics under conditions of room temperature to 150 [° C.], and is therefore preferable for use in separating hydrogen from the anode offgas of a polymer electrolyte fuel cell.

  The variable orifice 15 is a bypass flow rate control means for adjusting the flow rate of the hydrogen circulation path 13 which is a bypass path arranged in parallel with the hydrogen circulation path 14 where the hydrogen separation device 16 is arranged. An adjustable valve may be used.

  The controller 24 controls the entire fuel cell system 1, demand load from the load device 6, fuel cell output current by the ammeter 5, anode supply pressure by the pressure gauge 21, and the hydrogen separator 16 by the pressure gauges 22 and 23. The differential pressure between the inlet and outlet of the gas is input, the reaction gas is controlled to the operating pressure corresponding to the required load, and the opening of the variable orifice 15 is controlled.

  Although not particularly limited, in this embodiment, the controller 24 is composed of a microprocessor having a CPU, a program ROM, a working RAM, and an input / output interface.

  Next, the operation of this embodiment having the above configuration will be described. Hydrogen is supplied from the hydrogen supply source 7 to the anode 3 of the fuel cell main body 2. Between the hydrogen supply source 7 and the fuel cell main body 2, a pressure regulating valve 8 for adjusting the pressure of the supplied hydrogen is provided, and the controller 24 regulates the pressure regulating valve so as to satisfy the required hydrogen supply amount according to the load. 8 is controlled to adjust the supply hydrogen pressure.

  In the anode 3 of the fuel cell main body 2, all of the supplied hydrogen does not react, and unreacted hydrogen that does not react with the anode catalyst is impure such as water vapor, nitrogen that has permeated from the cathode 4 to the anode 3, and argon. It is discharged with gas.

  The anode off gas mixed with unreacted hydrogen, water vapor, nitrogen, etc. discharged from the outlet 3b of the anode 3 is supplied from the hydrogen supply source 7 in order to improve fuel efficiency by reusing unreacted hydrogen and promote the reaction. It is constantly circulated to humidify dry hydrogen and to obtain a stable output by circulating excess hydrogen.

  The anode off-gas passes through the hydrogen circulation path 11 and is pumped by the hydrogen circulation pump 12, thereby joining at the junction 9 with the hydrogen supply path 10 via the hydrogen circulation path 17. The hydrogen circulation path downstream of the hydrogen circulation pump 12 branches into hydrogen circulation paths 13 and 14. A hydrogen separator 16 is disposed in the hydrogen circulation path 14, and a flow rate of the hydrogen circulation path 13 is controlled by a variable orifice 15 as a bypass flow rate control unit that bypasses the hydrogen separator 16.

  In the hydrogen separator 16, hydrogen is separated from the anode off-gas, and impure gases such as nitrogen and water vapor are discharged out of the system from the discharge path 18. The separated hydrogen reaches the junction 9 with the hydrogen supply path 10 via the hydrogen circulation path 17. The anode off gas whose flow rate is adjusted by the variable orifice 15 also reaches the junction 9 with the hydrogen supply path 10 via the hydrogen circulation path 17.

  When the output of the fuel cell main body 2 is large, the anode off-gas circulation flow rate required by the system may not be maintained due to the pressure loss of the hydrogen separator 16 or the like. In order to avoid this, a hydrogen circulation path 13 provided with a device capable of adjusting the flow rate such as a variable orifice 15 is provided as a path serving as a bypass path in parallel with the separation circuit 14 provided with the hydrogen separator 16. Yes.

  In order to achieve both the securing of the circulation flow rate of the anode off gas according to the changing load of the fuel cell and the maintenance of the optimum separation efficiency for the hydrogen separation device 16, the hydrogen separation device using the hydrogen circulation pump 12, the pressure regulating valve 8, and the variable orifice 15 The configuration is such that the correction control of the differential pressure between the 16 inlets and outlets can be performed.

  The controller 24 controls the discharge pressure of the hydrogen circulation pump 12 and the opening of the variable orifice 15 to optimally separate the differential pressure between the inlet pressure and the outlet pressure of the hydrogen separator 16 or the flow rate of the hydrogen separator. Adjust to differential pressure or flow rate that can achieve efficiency. However, when the output of the fuel cell is large, the opening of the variable orifice 15 on the hydrogen circulation path 13 is opened, and even if it deviates from the differential pressure or flow rate at which the optimum separation efficiency of the hydrogen separator 16 can be achieved, the fuel cell system Therefore, it is possible to secure the anode off-gas circulation flow rate required by the company.

  The impure gas separated by the hydrogen separator 16 does not contain hydrogen, and the main component is a gas that is harmless to the environment, such as water vapor, nitrogen, and argon, and therefore is always discharged from the discharge path 18 to the outside.

  In this embodiment, when the fuel cell is under a high load, that is, when the circulation flow rate of the anode off gas is large, the opening of the variable orifice 15 of the hydrogen circulation path 13 is increased due to the shortage of the anode off gas circulation flow rate due to the pressure loss of the hydrogen separator. This means that the separation performance (separation efficiency, pressure loss, operating flow range) of the hydrogen separator 16 can be applied without limitation. That is, if the separation performance of the hydrogen separator is sufficiently high, the anode offgas having the circulation flow rate required by the system is allowed to pass through the hydrogen separation device 16 without bypassing the anode offgas having increased circulation flow rate at the time of high output by the hydrogen circulation path 13. It goes without saying that it can be done.

  Next, control by the controller 24 in this embodiment will be described with reference to the flowchart of FIG. The flow chart of FIG. 3 has two inlets: an inlet for starting the fuel cell and an inlet called at every predetermined time (for example, every 10 [mS]) after the startup and the warm-up are completed.

  First, when the activation of the fuel cell system is started, the warm-up operation of the fuel cell main body 2 is started in step (hereinafter, step is abbreviated as S) 10. For this purpose, the air compressor 19 and the hydrogen circulation pump 12 are started, and the air pressure regulating valve 20 and the hydrogen pressure regulating valve 8 are set so that the hydrogen pressure at the anode and the air pressure at the cathode become predetermined warm-up operation pressures. Then, an output current for warm-up is taken out from the fuel cell main body 2.

  Next, at S12, the stack temperature Ts, which is the temperature of the fuel cell main body 2, is detected by a temperature sensor (not shown in FIG. 1), and at S14, Ts is a predetermined warm-up temperature T0 (for example, in the case of a polymer electrolyte fuel cell, 80 [° C.]) is determined. If Ts does not exceed T0 in the determination of S14, the process returns to S12.

  If it is determined in S14 that Ts exceeds T0, the warm-up is terminated and the process proceeds to S16. In S16, the required load Wr from the load device 6 is read into the controller 24, and in S18, the target current It to be output from the fuel cell main body 2 is calculated from the required load Wr. Next, in S20, the target operating pressure Pt is calculated from the target current It. For this purpose, a control map created based on an experiment in advance is stored in the controller 24, and the target operating pressure Pt is calculated from the target current It with reference to this control map.

  Next, in S22, the hydrogen pressure regulating valve 8 is controlled so that the anode inlet pressure detected by the pressure sensor 21 becomes the target operating pressure Pt. In S24, the hydrogen separation device 16 sets the opening of the variable orifice 15 to the optimum separation efficiency. Set to a predetermined differential pressure. At this time, the difference between the detected values of the pressure sensor 22 for detecting the inlet pressure of the hydrogen separator 16 and the pressure sensor 23 for detecting the outlet pressure is calculated as a differential pressure value between the inlet and outlet of the hydrogen separator 16. Then, the opening of the variable orifice 15, in other words, the bypass flow rate of the anode off gas through the hydrogen circulation path 13 is controlled so that this differential pressure value becomes a predetermined value at which the hydrogen separation device 16 set in advance has the maximum separation efficiency.

  Next, the anode inlet pressure P1 detected by the pressure sensor 21 is read into the controller 24 in S26, and it is determined in S28 whether or not the absolute value of the deviation between the target operating pressure Pt and the anode inlet pressure P1 is less than a predetermined error ε. To do. If it is determined in S28 that the absolute value of the deviation is equal to or larger than ε, the process returns to S22 to continue the control for further reducing the control error.

  If it is determined in S28 that the absolute value of the deviation is less than ε, the process proceeds to S30 within the control error range. In S <b> 30, the ammeter 5 detects the output current Io of the fuel cell and reads it into the controller 24. Next, in S32, it is determined whether or not the difference between the target current It and the output current Io is less than the allowable value α. If the difference between the target current It and the output current Io is less than the allowable value α, the process returns to the main routine. Thereafter, the processing from S16 onward is called and executed every predetermined time.

  If the difference between the target current It and the output current Io is greater than or equal to the allowable value α in the determination of S32, excess impurities accumulate in the hydrogen circulation path and the hydrogen partial pressure has decreased, so that the output current Io and the target current It are The flow proceeds to S34, the hydrogen pressure regulating valve 8 is adjusted to the target operating pressure, the variable orifice 15 is adjusted in S36, and the differential pressure at the inlet / outlet of the hydrogen separator 16 is reduced to hydrogen separation. The maximum impurity separation flow rate of the apparatus 16 is adjusted. As a result, impurities are rapidly removed from the anode off-gas circulation path, and the hydrogen partial pressure in the circulation path increases.

  Next, the output current Io of the fuel cell is detected by the ammeter 5 in S38 and read into the controller 24. In S40, it is determined whether or not the difference between the target current It and the output current Io is less than the allowable value α. If the difference between the target current It and the output current Io is less than the allowable value α, the process returns to the main routine. Thereafter, the processing from S16 onward is called and executed every predetermined time.

  If it is determined in S40 that the difference between the target current It and the output current Io is equal to or larger than the allowable value α, the process returns to S34, and control is performed so that both the operating pressure and the output current satisfy the target value.

  According to the present embodiment described above, in order to separate hydrogen from the anode offgas only from the anode offgas without supplying the mixed gas of hydrogen and anode offgas supplied from the hydrogen supply source to the hydrogen separator, Since all the hydrogen that can pass through the hydrogen separation membrane of the separator becomes hydrogen contained in the anode offgas, there is an effect that the recovery rate of unreacted hydrogen and the hydrogen circulation flow rate can be improved.

  Further, according to the present embodiment, the hydrogen circulation path 13 that bypasses the hydrogen separator 16 is provided, and the variable orifice 15 as the bypass flow rate control means for controlling the bypass flow rate is provided on the hydrogen circulation path 13. It is possible to supply the anode offgas flow rate at which the separation device 16 has the optimum separation efficiency to the hydrogen separation device 16 and to ensure the anode offgas circulation flow rate required by the system.

  FIG. 2 is a system schematic diagram illustrating the configuration of the fuel cell system according to the second embodiment of the present invention. In FIG. 2, the fuel cell system 1 includes a fuel cell body 2 having an anode 3 and a cathode 4, an ammeter 5 that detects an output current of the fuel cell body 2, and a load that consumes power generated by the fuel cell body 2. A device 6, a hydrogen supply source 7, a hydrogen pressure adjusting valve 8 that adjusts the pressure of hydrogen gas supplied from the hydrogen supply source 7, and a new hydrogen supplied from the hydrogen pressure adjusting valve 8 are used as a driving flow to circulate the anode off gas. Ejectors 31 and 32 that are fluid pumps, a hydrogen supply path 10 that connects a junction 9 a provided downstream of the ejectors 31 and 32, and an inlet 3 a of the anode 3 of the fuel cell body 2, and an outlet 3 b of the anode 3 The hydrogen circulation path 11 connected to the inlet of the water vapor removal apparatus 33, the hydrogen circulation paths 34, 35, and 36 branched from the outlet of the water vapor removal apparatus 33, and the hydrogen circulation path 34 are arranged. Separated from the hydrogen separator 16, the variable orifice 15 disposed on the hydrogen circulation path 35, the hydrogen separator 16 connected to the inlet pipes 37, 38 branched from the hydrogen circulation path 36, and the hydrogen separator 16. The discharge path 18 for discharging the impurities, the junction 9b where the hydrogen circulation path 41 on the outlet side of the hydrogen circulation pump 12 joins the hydrogen supply path 10, and the downstream of the variable orifice 15 and the suction port of the ejector 32 are connected. A hydrogen circulation path 40, a hydrogen circulation path 39 that connects the hydrogen outlet separated by the hydrogen separator 16 and the suction port of the ejector 31, an air compressor 19 that supplies air as an oxidant gas to the cathode 4, The air pressure regulating valve 20 that adjusts the pressure of the air discharged from the cathode 4, the pressure sensor 21 that detects the pressure at the anode inlet 3 a, and the inlet pressure of the hydrogen separator 16 are A pressure sensor 22 for output, a pressure sensor 23 for detecting the outlet pressure of the hydrogen separation device 16, and a controller 24 for controlling the fuel cell system 1.

  The difference between the present embodiment and the first embodiment is that it is provided with a water vapor removing device 33 that removes water vapor from the anode off gas, and is a fluid pump that performs hydrogen circulation at a high flow rate in addition to the hydrogen circulation pump 12 in the hydrogen circulation path. That is, ejectors 31 and 32 are provided. The constituent elements other than the above-described different constituent elements and the pipes associated therewith are the same as those in the first embodiment, and therefore the same constituent elements are given the same reference numerals and redundant description is omitted.

  For example, the water vapor removing device 33 cools the anode off gas below the dew point and removes the water vapor from the anode off gas, the air supplied from the air compressor 19 and the anode off gas through a moisture permeable hollow fiber membrane or the like. An apparatus for removing water vapor from the anode off-gas by exchanging water vapor can be applied.

  By removing the water vapor from the anode off-gas by the water vapor removing device, clogging of the separation membrane of the hydrogen separation device 16 disposed downstream thereof can be prevented, so that the hydrogen separation efficiency can be increased.

  Further, since the ejectors 31 and 32 which are fluid pumps that do not require external power are used as the driving force for anode off-gas circulation, energy consumption for hydrogen circulation can be reduced. The ejector 31 blows out the new hydrogen supplied from the hydrogen pressure control valve 8 from the nozzle as a driving flow, sucks the hydrogen separated by the hydrogen separator 16 from the suction port, and supplies the gas mixed with both from the discharge port to the hydrogen supply path 10 is sent out. The ejector 32 blows out the new hydrogen supplied from the hydrogen pressure regulating valve 8 from the nozzle as a driving flow, sucks in the anode off gas whose flow rate is adjusted by the variable orifice 15 from the suction port, and supplies the mixed gas to the hydrogen from the discharge port. It is sent out to the road 10.

  When a plurality of ejectors are arranged in series, each ejector nozzle section is finite and the amount of fluid that can pass through is limited, so the flow rate that can pass through the ejector nozzle section is limited. Yes. For this reason, if any one ejector obtains a large stoichiometry (total flow rate / driving flow rate) no matter how large the differential pressure is increased, other ejectors are subject to restrictions such as increasing or decreasing the ejector inlet flow rate. As a result, the amount of circulating water decreases, or a large negative pressure cannot be created due to a decrease in flow velocity, resulting in problems such as almost no stoichiometry.

  However, by arranging the ejectors 31 and 32 in parallel as in the present embodiment, the flow rate passing through the nozzles of each path is not limited by the flow rate passing through the other ejector nozzles, so the ejector inlet flow rate optimum for all ejectors. Thus, the stoichiometric value of each ejector can be maintained at an optimum value. Moreover, the differential pressure drop of the ejector per one by arranging a plurality of ejectors in parallel (increasing one ejector in parallel will increase the total nozzle cross-sectional area by one, This can be avoided by opening the pressure regulating valve located upstream, so that the pressure on the upstream side of the ejector can be raised, and it is possible to always ensure the optimum stoichiometry. .

  When the output of the fuel cell main body 2 is small, the driving force of the ejectors 31 and 32 due to the new hydrogen flow supplied from the hydrogen pressure regulating valve 8 is not sufficient. Try to get the amount. When the fuel cell output exceeds a certain level, the circulation function of the ejectors 31 and 32 is shifted, and the hydrogen circulation pump 12 is stopped.

  Such a configuration realizes a system that always maintains the optimum hydrogen separation efficiency for the hydrogen separator 16 and also ensures the required amount of hydrogen of the fuel cell body 2 at the same time. The variable orifice 15 provided in the hydrogen circuit 35 distributes the flow to the hydrogen circuits 36 and 35 so as to achieve optimum separation efficiency for the system.

  In addition, an open / close valve (not shown) is provided in each of the hydrogen circulation paths 39 and 40, and immediately after starting the fuel cell or during idling, the open / close valve is closed and the ejector sucks insufficiently when the flow rate of hydrogen is low, causing a reverse flow. May be prevented.

  The hydrogen circulation path 36 leading to the hydrogen separator 16 is branched into a circulation path 37 and a circulation path 38 at the inlet of the hydrogen separator 16. With this configuration, the flow rate is reduced only inside the hydrogen separator 16. Since the supply flow rate can be reduced without any delay, the amount of hydrogen diffusion increases and the hydrogen separation efficiency improves as the anode off-gas residence time in the hydrogen separation device increases. There is no pressure loss that prevents the ejector from being sucked by this effect.

  Next, control by the controller 24 in this embodiment will be described with reference to the flowchart of FIG. The flow chart of FIG. 4 has two inlets: an entrance for starting the fuel cell and an inlet called at every predetermined time (for example, every 10 [mS]) after the startup and warm-up is completed.

  First, when the start of the fuel cell system is started, the warm-up operation of the fuel cell main body 2 is started in S50. For this purpose, the air compressor 19 and the hydrogen circulation pump 12 are started, and the air pressure regulating valve 20 and the hydrogen pressure regulating valve 8 are set so that the hydrogen pressure at the anode and the air pressure at the cathode become predetermined warm-up operation pressures. Then, an output current for warm-up is taken out from the fuel cell main body 2.

  Next, at S52, the stack temperature Ts, which is the temperature of the fuel cell main body 2, is detected by a temperature sensor (not shown in FIG. 2), and at S54, Ts is a predetermined warm-up temperature T0 (for example, in the case of a polymer electrolyte fuel cell, 80 [° C.]) is determined. If Ts does not exceed T0 in the determination of S54, the process returns to S52.

  If it is determined in S54 that Ts exceeds T0, the warm-up ends and the process proceeds to S56. In S56, the required load Wr from the load device 6 is read into the controller 24, and in S58, the target current It to be output from the fuel cell main body 2 is calculated from the required load Wr. Next, in S60, the target operating pressure Pt is calculated from the target current It. For this purpose, a control map created based on an experiment in advance is stored in the controller 24, and the target operating pressure Pt is calculated from the target current It with reference to this control map.

  Next, in S62, it is determined whether or not the required load Wr is less than a predetermined load W0. This predetermined load W0 is a load corresponding to a hydrogen flow rate that determines that the ejectors 31 and 32 cannot obtain sufficient hydrogen circulation characteristics from the hydrodynamic characteristics of the hydrogen circulation path including the ejectors 31 and 32 and the fuel cell body 2. For example, the value obtained from the simulation of the fuel cell system is corrected based on the experimental data.

  If it is determined in S62 that the required load Wr is less than the predetermined load W0, the process proceeds to S64, and the hydrogen circulation pump 12 is operated to supplement the hydrogen circulation flow rate. If it is determined in S62 that the required load Wr is equal to or greater than the predetermined load W0, it is determined that a sufficient flow rate is required for suction of the ejectors 31 and 32, the process proceeds to S66, and the hydrogen circulation pump 12 is stopped.

  Next, in S68, the hydrogen pressure regulating valve 8 is controlled so that the anode inlet pressure detected by the pressure sensor 21 becomes the target operating pressure Pt. In S70, the hydrogen separator 16 sets the opening of the variable orifice 15 to the optimum separation efficiency. Set to a predetermined differential pressure. At this time, the difference between the detected values of the pressure sensor 22 for detecting the inlet pressure of the hydrogen separator 16 and the pressure sensor 23 for detecting the outlet pressure is calculated as a differential pressure value between the inlet and outlet of the hydrogen separator 16. Then, the opening of the variable orifice 15, in other words, the bypass flow rate of the anode off gas through the hydrogen circulation path 13 is controlled so that this differential pressure value becomes a predetermined value at which the hydrogen separation device 16 set in advance has the maximum separation efficiency.

  Next, the anode inlet pressure P1 detected by the pressure sensor 21 is read into the controller 24 in S72, and it is determined in S74 whether or not the absolute value of the deviation between the target operating pressure Pt and the anode inlet pressure P1 is less than a predetermined error ε. To do. If it is determined in S28 that the absolute value of the deviation is equal to or larger than ε, the process returns to S68 to continue the control for further reducing the control error.

  If it is determined in S74 that the absolute value of the deviation is less than ε, the process proceeds to S76 within the control error range. In S76, the ammeter 5 detects the output current Io of the fuel cell and reads it into the controller 24. Next, in S78, it is determined whether or not the difference between the target current It and the output current Io is less than the allowable value α. If the difference between the target current It and the output current Io is less than the allowable value α, the process returns to the main routine. Thereafter, the processing from S56 onward is called and executed every predetermined time.

  If the difference between the target current It and the output current Io is greater than or equal to the allowable value α in the determination of S78, excess impurities accumulate in the hydrogen circulation path and the hydrogen partial pressure has decreased, so that the output current Io and the target current It are The flow proceeds to S80, the hydrogen pressure regulating valve 8 is adjusted to the target operating pressure, the variable orifice 15 is adjusted in S82, and the differential pressure at the inlet / outlet of the hydrogen separator 16 is reduced to hydrogen separation. The maximum impurity separation flow rate of the apparatus 16 is adjusted. As a result, impurities are rapidly removed from the anode off-gas circulation path, and the hydrogen partial pressure in the circulation path increases.

  Next, in S84, the output current Io of the fuel cell is detected by the ammeter 5 and read into the controller 24. In S86, it is determined whether or not the difference between the target current It and the output current Io is less than the allowable value α. If the difference between the target current It and the output current Io is less than the allowable value α, the process returns to the main routine. Thereafter, the processing from S56 onward is called and executed every predetermined time.

  If it is determined in S86 that the difference between the target current It and the output current Io is equal to or greater than the allowable value α, the process returns to S80, and control is performed so that both the operating pressure and the output current satisfy the target value.

  Although various embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and it goes without saying that various configurations can be adopted without departing from the spirit of the present invention.

1 is a system configuration diagram illustrating the configuration of a first embodiment of a fuel cell system according to the present invention. FIG. It is a system block diagram explaining the structure of Example 2 of the fuel cell system which concerns on this invention. 3 is a flowchart illustrating control in the first embodiment. 6 is a flowchart illustrating control in the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel cell system 2 ... Fuel cell main body 3 ... Anode 4 ... Cathode 5 ... Ammeter 6 ... Load apparatus 7 ... Hydrogen supply source 8 ... Hydrogen pressure regulating valve 9 ... Junction point 10 ... Hydrogen supply path 11 ... Hydrogen circulation path 12 ... Hydrogen circulation pumps 13 and 14 ... Hydrogen circulation path 15 ... Variable orifice 16 ... Hydrogen separator 18 ... Discharge path 19 ... Air compressor 20 ... Air pressure regulating valves 21, 22, 23 ... Pressure sensor 24 ... Controller

Claims (6)

A fuel cell body that generates electricity by an electrochemical reaction of hydrogen and an oxidant; and
A hydrogen supply path for supplying hydrogen to the anode inlet of the fuel cell body;
An anode offgas circulation path for returning the anode offgas discharged from the anode outlet of the fuel cell main body to the hydrogen supply path,
A fuel cell system comprising a hydrogen separation device that separates hydrogen from anode offgas on the anode offgas circulation path upstream from a junction of the hydrogen supply path and anode offgas circulation path. A bypass path for bypassing the hydrogen separator;
Bypass flow rate control means for controlling the gas flow rate of the bypass path;
The fuel cell system according to claim 1, further comprising: A hydrogen circulation pump for pumping the anode off-gas discharged from the anode outlet of the fuel cell body;
3. The fuel cell system according to claim 2, wherein the hydrogen separator, the bypass path, and the bypass flow rate control means are disposed downstream of the hydrogen circulation pump.   2. The fuel cell system according to claim 1, wherein a plurality of anode off-gas circulation paths are provided between the anode outlet and the junction, and a hydrogen separator is disposed only in one of the paths. 4. The fuel cell system according to any one of items 3.   The fuel cell system according to any one of claims 1 to 4, wherein a path for supplying the anode off gas to the hydrogen separator is divided into two or more systems. A plurality of ejectors for recirculating the anode off gas discharged from the anode outlet of the fuel cell main body to the anode inlet;
The first ejector out of the plurality of ejectors joins the hydrogen separated by the hydrogen separator to the hydrogen supply path,
3. The fuel cell system according to claim 2, wherein an anode off-gas that has passed through the bypass path is joined to the hydrogen supply path by a second ejector of the plurality of ejectors.

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