JP2019169443A - Fuel cell system and operation method thereof - Google Patents

Abstract

To solve the problem that an exhaust gas needs diluting to under a burnable range when discharging a gas flowing through an unreacted fuel gas circulation path in order to keep a nitrogen concentration of an anode at a predetermined range during power generation, which enlarges a fuel cell system.SOLUTION: A fuel cell system (100) comprises an unreacted fuel gas circulation flow path (4) for circulating hydrogen discharged from an anode (1a) through the anode. The fuel cell system regulates a fuel gas pressure regulating part (3) so that a nitrogen partial pressure in a fuel gas flowing through the anode becomes higher than a nitrogen partial pressure in an oxidant gas flowing through a cathode (1b) in a whole period or predetermined period during which a fuel cell stack (1) is generating electric power. Thus, nitrogen included in the fuel gas flowing through the anode can be made to transmit to the cathode through an electrolyte membrane of the fuel cell stack, and power generation can be performed without providing a diluter for diluting hydrogen to under a burnable range.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fuel cell system including a flow path for returning a hydrogen-containing gas discharged from an anode to the anode, and an operation method thereof.

  Conventionally, in this type of fuel cell system and its operation method, during power generation of the fuel cell system, nitrogen permeates from the cathode of the fuel cell stack to the anode through the electrolyte membrane, and the hydrogen-containing gas discharged from the anode is returned to the anode. The power generation performance decreases due to an increase in the nitrogen concentration of the gas flowing through the flow path. For this reason, in the fuel cell system, the nitrogen concentration of the gas flowing through the flow path for returning the hydrogen-containing gas discharged from the anode to the anode is calculated, and when the concentration exceeds a predetermined concentration, the nitrogen is discharged to the outside (for example, patent document) 1).

JP 2013-232407 A

  However, in the conventional configuration, since the hydrogen-containing gas discharged from the anode is continuously returned to the anode until the nitrogen concentration of the anode is reduced to a predetermined value during power generation, the gas is discharged from the anode. High-concentration hydrogen in the flow path for returning the hydrogen-containing gas to the anode will be discharged. For this reason, a diluter for diluting hydrogen to below the flammable range is required, and there is a problem that the fuel cell system becomes large.

  The present invention solves the above-mentioned conventional problem, and adjusts the nitrogen partial pressure of the anode during power generation, thereby discharging the nitrogen of the anode to the cathode through the electrolyte membrane of the fuel cell stack, and the nitrogen concentration of the anode Is reduced to a predetermined value. Accordingly, an object of the present invention is to provide a miniaturized fuel cell system that performs power generation without providing a diluter for diluting hydrogen to below the combustible range.

  In order to solve the above-described conventional problems, a fuel cell system according to the present invention includes a fuel cell stack that generates power using a fuel gas and an oxidant gas, and a fuel gas supply that supplies fuel gas to an anode of the fuel cell stack. A fuel gas pressure adjusting unit for adjusting the pressure of the fuel gas supplied to the anode, an unreacted fuel gas circulation passage for joining the unreacted fuel gas discharged from the anode to the fuel gas supply route, and a fuel cell An oxidant gas supply section for supplying an oxidant gas to the cathode of the stack, an oxidant gas supply path for connecting the cathode and the oxidant gas supply section, and an oxidant gas discharge path for discharging unreacted oxidant gas from the cathode; A control unit, wherein the control unit oxidizes the partial pressure of nitrogen in the fuel gas flowing through the anode during the entire period or a predetermined period during which the fuel cell stack is generating power. Is obtained by the adjusting the fuel gas pressure adjusting portion to be higher than the partial pressure of nitrogen gas.

  As a result, nitrogen contained in the fuel gas flowing through the anode is permeated to the cathode through the electrolyte membrane of the fuel cell stack, and power generation is performed without providing a diluter for diluting hydrogen to below the flammable range. It becomes.

  The fuel cell system operating method of the present invention includes a fuel cell stack for generating power using fuel gas and an oxidant gas, a fuel gas supply path for supplying fuel gas to the anode of the fuel cell stack, and an anode. A fuel gas pressure adjusting unit that adjusts the pressure of the supplied fuel gas, an unreacted fuel gas circulation passage that joins the unreacted fuel gas discharged from the anode to the fuel gas supply path, and an oxidation on the cathode of the fuel cell stack An oxidant gas supply path for supplying the oxidant gas, an oxidant gas supply means, and an oxidant gas discharge path for discharging the oxidant gas discharged from the cathode, and the fuel cell stack is in the entire power generation period Alternatively, the fuel gas pressure adjustment unit is adjusted so that the nitrogen partial pressure in the fuel gas flowing through the anode is higher than the nitrogen partial pressure in the oxidant gas flowing through the cathode for a predetermined period. It is intended to include the step of.

  As a result, nitrogen contained in the fuel gas flowing through the anode is permeated to the cathode through the electrolyte membrane of the fuel cell stack, and power generation is performed without providing a diluter for diluting hydrogen to below the flammable range. It becomes.

  In the fuel cell system and the operation method thereof according to the present invention, by adjusting the nitrogen partial pressure of the anode of the fuel cell stack during power generation, the nitrogen of the anode can pass through the electrolyte membrane of the stack and be discharged to the cathode. Thereby, since the nitrogen concentration of the anode can be reduced to a predetermined value, it is possible to realize a miniaturized fuel cell system by generating power without providing a diluter for diluting hydrogen below the flammable range.

  Further, since hydrogen as a fuel is not discharged out of the fuel cell system, a fuel cell system with higher safety can be realized.

1 is a block diagram of a configuration of a fuel cell system according to Embodiment 1 of the present invention. Flow chart of operation method of fuel cell system in Embodiment 1 of the present invention Block diagram of the configuration of the fuel cell system in Embodiment 2 of the present invention Flow chart of operation method of fuel cell system in Embodiment 2 of the present invention Block diagram of a configuration of a fuel cell system according to Embodiment 3 of the present invention Flow chart of operation method of fuel cell system in Embodiment 3 of the present invention Block diagram of the configuration of the fuel cell system in Embodiment 4 of the present invention Flow chart of operation method of fuel cell system in Embodiment 4 of the present invention Block diagram of the configuration of the fuel cell system in Embodiment 5 of the present invention Flow chart of operation method of fuel cell system in Embodiment 5 of the present invention

  A first invention includes a fuel cell stack that generates power using fuel gas and an oxidant gas, a fuel gas supply path that supplies fuel gas to the anode of the fuel cell stack, and the pressure of the fuel gas supplied to the anode A fuel gas pressure adjusting unit that adjusts the unreacted fuel gas, a non-reacted fuel gas circulation path that joins the unreacted fuel gas discharged from the anode to the fuel gas supply path, and an oxidant that supplies the oxidant gas to the cathode of the fuel cell stack A gas supply unit, an oxidant gas supply path for connecting the cathode and the oxidant gas supply unit, an oxidant gas discharge path for discharging unreacted oxidant gas from the cathode, and a control unit. Fuel gas so that the partial pressure of nitrogen in the fuel gas flowing through the anode is higher than the partial pressure of nitrogen in the oxidant gas flowing through the cathode during the entire period when the fuel cell stack is generating electricity or for a predetermined period. By adjusting the force adjusting unit, nitrogen contained in the fuel gas flowing through the anode is transmitted to the cathode through the electrolyte membrane of the fuel cell stack, and a diluter is provided for diluting hydrogen to below the flammable range. It is possible to generate electricity without any problems.

  The second invention is particularly the fuel cell system according to the first invention, wherein the fuel gas supply path is provided with pressure detection means, and the control unit is an oxidant gas in which the nitrogen partial pressure in the fuel gas flowing through the anode flows through the cathode By adjusting the fuel gas pressure adjustment unit so that it is higher than the nitrogen partial pressure inside, the pressure in the fuel gas flowing through the anode can be correctly controlled to a predetermined pressure, so that the nitrogen concentration of the fuel gas flowing through the anode can be accurately adjusted Can be adjusted. In this way, nitrogen contained in the fuel gas flowing through the anode is permeated to the cathode through the electrolyte membrane of the fuel cell stack, and power generation is performed without providing a diluter for diluting hydrogen to below the flammable range. be able to.

  The third aspect of the invention is particularly the fuel cell system of the first aspect of the invention, wherein the control unit estimates the nitrogen concentration in the fuel gas flowing through the anode based on the cell voltage of the fuel cell stack, and determines the anode from the nitrogen concentration. By estimating the nitrogen partial pressure in the flowing fuel gas and adjusting the fuel gas pressure adjusting unit so that the nitrogen partial pressure in the fuel gas flowing through the anode is higher than the nitrogen partial pressure in the oxidant gas flowing through the cathode The nitrogen concentration of the fuel gas flowing through the anode can be accurately adjusted because the pressure in the fuel gas flowing through the anode can be correctly controlled to a predetermined pressure based on the cell voltage. In this way, the nitrogen contained in the fuel gas flowing through the anode is accurately permeated to the cathode through the electrolyte membrane of the fuel cell stack, and power generation is performed without providing a diluter for diluting hydrogen below the flammable range. It can be performed.

  In the fourth invention, in particular, the fuel cell system according to the first invention is provided in the downstream side of the joining portion of the fuel gas supply path and the unreacted fuel gas circulation flow path, and is supplied to the anode. The nitrogen concentration in the fuel gas flowing through the anode is estimated from the nitrogen concentration detected by the anode nitrogen concentration detecting means, and the nitrogen partial pressure in the fuel gas flowing through the anode is By adjusting the fuel gas pressure adjustment unit so that it is higher than the nitrogen partial pressure in the oxidant gas flowing through the cathode, the pressure in the fuel gas flowing through the anode is correctly controlled to a predetermined pressure based on the measured nitrogen concentration This makes it possible to accurately adjust the nitrogen concentration of the fuel gas flowing through the anode. In this way, the nitrogen contained in the fuel gas flowing through the anode is accurately permeated to the cathode through the electrolyte membrane of the fuel cell stack, and power generation is performed without providing a diluter for diluting hydrogen below the flammable range. It can be performed.

  In particular, the fifth aspect of the invention provides the fuel cell system according to the first aspect of the present invention, which is provided in the unreacted fuel gas circulation passage and detects the nitrogen concentration in the fuel gas flowing through the unreacted fuel gas circulation passage. A detecting means is provided, and the anode nitrogen concentration detecting means detects the mixing ratio of the fuel gas flowing through the unreacted fuel gas circulation passage of the fuel gas supplied to the anode and the fuel gas supplied from the fuel gas supply path. Estimate the nitrogen partial pressure in the fuel gas flowing through the anode from the nitrogen concentration, and adjust the fuel gas pressure so that the nitrogen partial pressure in the fuel gas flowing through the anode is higher than the nitrogen partial pressure in the oxidant gas flowing through the cathode By adjusting the section, based on the estimated partial pressure, the pressure in the fuel gas flowing through the anode can be correctly controlled to a predetermined pressure, so that the nitrogen concentration of the fuel gas flowing through the anode can be accurately controlled. It can be an integer. In this way, the nitrogen contained in the fuel gas flowing through the anode is accurately permeated to the cathode through the electrolyte membrane of the fuel cell stack, and power generation is performed without providing a diluter for diluting hydrogen below the flammable range. It can be performed.

  According to a sixth aspect of the present invention, there is provided a fuel cell stack that generates power using fuel gas and oxidant gas, a fuel gas supply path that supplies fuel gas to the anode of the fuel cell stack, and the pressure of the fuel gas supplied to the anode A fuel gas pressure adjusting unit that adjusts the unreacted fuel gas, a non-reacted fuel gas circulation path that joins the unreacted fuel gas discharged from the anode to the fuel gas supply path, and an oxidant that supplies the oxidant gas to the cathode of the fuel cell stack An operating method of a fuel cell system, comprising: a gas supply path and an oxidant gas supply means; and an oxidant gas discharge path for discharging exhaust oxidant gas discharged from the cathode, wherein the fuel cell stack is generating power A process for adjusting the fuel gas pressure adjusting unit so that the nitrogen partial pressure in the fuel gas flowing through the anode is higher than the nitrogen partial pressure in the oxidant gas flowing through the cathode for a predetermined period. As a result, nitrogen contained in the fuel gas flowing through the anode is permeated to the cathode through the electrolyte membrane of the fuel cell stack, and power generation can be performed without providing a diluter for diluting hydrogen to below the flammable range. It can be carried out.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  Note that the present invention is not limited to the present embodiment.

(Embodiment 1)
FIG. 1 is a block diagram showing the configuration of the fuel cell system according to Embodiment 1 of the present invention.

  In FIG. 1, a fuel cell system 100 includes a fuel cell stack 1, a fuel gas supply path 2, a fuel gas pressure adjustment unit 3, an unreacted fuel gas circulation path 4, a mixed gas supply path 5, an ejector 6, An oxidant gas supply unit 7, an oxidant gas supply path 8, an oxidant gas discharge path 9, and a control unit 10 are provided.

  The fuel cell stack 1 generates power using fuel gas and oxidant gas. The fuel gas uses pure hydrogen gas and the oxidant gas uses air. The fuel cell stack 1 includes an anode 1a to which pure hydrogen gas is supplied, a cathode 1b to which air is supplied, and an electrolyte membrane that moves generated protons. The fuel cell stack 1 uses a polymer electrolyte fuel cell.

  The fuel gas supply path 2 is a path for supplying pure hydrogen gas from the outside of the fuel cell system 100 to the inside of the fuel cell system 100.

  The fuel gas pressure adjusting unit 3 is connected to the fuel gas supply path 2 and adjusts the pressure of pure hydrogen gas flowing through the fuel gas supply path 2. The pure hydrogen gas is supplied from the upstream side of the fuel gas pressure adjusting unit 3.

  The unreacted fuel gas circulation passage 4 is connected to the fuel gas supply path 2 from the downstream of the anode 1a, and is a path for mixing the gas discharged from the anode 1a with the pure hydrogen gas supplied from the fuel gas supply path 2. is there.

  The mixed gas supply path 5 is connected downstream of the fuel gas supply path 2, connected upstream of the anode 1a, and pure hydrogen gas flowing through the fuel gas supply path 2 and gas flowing through the unreacted fuel gas circulation path 4 are connected to each other. This is a path for supplying the mixed gas to the anode 1a. The gas flowing through the mixed gas supply path 5 is called a mixed gas. The gas flowing through the unreacted fuel gas circulation passage 4 is referred to as an unreacted mixed gas. By adjusting the pressure of the pure hydrogen gas flowing through the fuel gas supply path 2 by the fuel gas pressure adjusting unit 3, the pressure of the mixed gas flowing through the mixed gas supply path 5 can be adjusted, whereby the mixing flowing through the anode 1a. The gas pressure can be adjusted.

  The ejector 6 is connected to the joining portion of the fuel gas supply path 2 and the unreacted fuel gas circulation flow path 4 to mix pure hydrogen gas and unreacted mixed gas.

  The oxidant gas supply unit 7 supplies air to the cathode 1b.

  The oxidant gas supply path 8 is connected to the oxidant gas supply unit 7 and is a path for supplying air to the cathode 1b.

  The oxidant gas discharge path 8 is a path for discharging the air discharged from the cathode 1 b to the outside of the fuel cell system 100.

  The control part 10 should just have a control function, and is provided with an arithmetic processing part (not shown) and the memory | storage part (not shown) which memorize | stores a control program. An example of the arithmetic processing unit is a CPU. An example of the storage unit is a memory.

In the fuel cell stack 1, it is difficult to use all of the supplied mixed gas for power generation because of the gas diffusion performance of the gas flow path in the anode 1a, and the unreacted mixture that was not used for power generation from the anode 1a. Gas is exhausted. If the discharged unreacted mixed gas is discarded, the supplied pure hydrogen gas is wasted, and the efficiency of the fuel cell system 100 is reduced. Therefore, the control unit 10 mixes the unreacted mixed gas flowing in the unreacted fuel gas circulation passage 4 and the pure hydrogen gas flowing in the fuel gas supply path 2 by the ejector 6 and supplies the mixed gas to the anode 1a.
As a result, waste of pure hydrogen gas can be eliminated and the fuel cell system 100 can be made highly efficient.

  About the fuel cell system 100 comprised as mentioned above, the operation | movement and an effect | action are demonstrated below.

  FIG. 2 shows a flowchart of the operation method of the fuel cell system according to Embodiment 1 of the present invention. This operation is performed by the control of the control unit 10 when the fuel cell system 100 is generating power.

  The control unit 10 supplies air with the oxidant gas supply unit 7 and adjusts the pressure of the pure hydrogen gas flowing through the fuel gas supply path 2 with the fuel gas pressure adjustment unit 3 (S101). Here, the case where the pressure of air is set to 111.3 kPa and the pressure of pure hydrogen gas is set to 111.3 kPa is shown. The air component is oxygen: nitrogen: other gas = 21: 78: 1. At this time, the nitrogen partial pressure contained in the air supplied from the oxidizing gas supply unit 7 is 86.8 kPa. The component of pure hydrogen gas is hydrogen: nitrogen = 100: 0. At this time, the partial pressure of nitrogen contained in the pure hydrogen gas is 0 kPa. Since the nitrogen partial pressure of the air flowing through the cathode 1b is larger than the nitrogen partial pressure of the mixed gas flowing through the anode 1a, nitrogen contained in the air flowing through the cathode 1b passes through the electrolyte membrane of the fuel cell stack 1 to the anode 1a. . Therefore, the nitrogen concentration of the unreacted mixed gas discharged from the anode 1a increases, and the mixed gas supplied to the anode 1a is mixed with the pure hydrogen gas flowing through the fuel gas supply path 2 through the unreacted fuel gas circulation passage 4. Nitrogen concentration increases.

  Next, the control unit 10 determines whether a certain time has elapsed (S102). The predetermined time is a time set in advance so that the concentration of nitrogen contained in the mixed gas flowing through the anode 1a is not increased, and the power generation amount of the fuel cell system 100 is not reduced and the fuel cell stack 1 is not deteriorated. Here, the case of 30 minutes is shown.

  Next, the control unit 10 controls the fuel gas pressure adjusting unit 3 to an operation amount set in advance so that the nitrogen partial pressure of the mixed gas flowing to the anode 1a is higher than the nitrogen partial pressure of the air flowing to the cathode 1b. The pressure of pure hydrogen gas flowing through the supply path 2 is adjusted (S103). Here, the case where the nitrogen concentration of the mixed gas flowing through the anode 1a is reduced to 20% is shown. The nitrogen partial pressure of the air flowing through the cathode 1b is 86.8 kPa, and the pressure of the mixed gas at which the nitrogen partial pressure when the nitrogen concentration of the mixed gas is 20% is 86.8 kPa is 434 kPa. Therefore, when the pressure of the pure hydrogen gas flowing through the fuel gas supply path 2 is set to 434 kPa in the fuel gas pressure adjusting unit 3, the nitrogen concentration of the mixed gas exceeds 20% through the anode 1 a through the electrolyte membrane of the fuel cell stack 1. The mixed gas can be transmitted to the cathode 1b.

  Next, the control unit 10 determines whether a certain time has elapsed (S104). This fixed time is a preset time until the nitrogen concentration of the mixed gas is reduced by allowing nitrogen contained in the mixed gas to pass from the mixed gas flowing through the anode 1a to the cathode 1b. Here, the case of 10 minutes is shown. If 10 minutes have elapsed, the process returns to S101.

  Each step is shifted immediately after completion of each step without providing a waiting time.

  As described above, in the present embodiment, the nitrogen partial pressure of the mixed gas flowing to the anode 1a is made larger than the nitrogen partial pressure of the air flowing to the cathode 1b, so that the nitrogen contained in the mixed gas is reduced in the fuel cell stack 1. The air flowing to the cathode 1b through the electrolyte membrane is permeated, and it is not necessary to discharge the mixed gas from the fuel cell system 100 to reduce the nitrogen concentration of the mixed gas flowing to the anode 1a. A diluter for diluting below the range can be dispensed with.

  If the nitrogen partial pressure of the mixed gas flowing through the anode 1a is larger than the partial pressure of nitrogen in the air flowing through the cathode 1b, the permeation of nitrogen can be accelerated by that amount.

Further, here, the pressure of the pure hydrogen gas flowing through the fuel gas supply path 2 is adjusted only for a predetermined period, but it may be performed for the entire period during power generation.
(Embodiment 2)
FIG. 3 is a block diagram of the configuration of the fuel cell system according to Embodiment 2 of the present invention. In addition, the same code | symbol is provided about the component similar to Embodiment 1, and the description is abbreviate | omitted here.

  In FIG. 3, the fuel cell system 200 includes an unreacted fuel gas booster 11, a pressure detector 12, and a controller 13.

  The unreacted fuel gas pressure increasing unit 11 is connected to the unreacted fuel gas circulation channel 4 and adjusts the pressure of the unreacted mixed gas flowing through the unreacted fuel gas circulation channel 4.

  The pressure detection unit 12 is connected to the mixed gas supply path 5 and measures the pressure of the mixed gas flowing through the mixed gas supply path 5.

  The control part 13 should just have a control function, and is provided with an arithmetic processing part (not shown) and the memory | storage part (not shown) which memorize | stores a control program. An example of the arithmetic processing unit is a CPU. An example of the storage unit is a memory.

In the fuel cell stack 1, it is difficult to use all of the supplied mixed gas for power generation because of the gas diffusion performance of the gas flow path in the anode 1a, and the unreacted mixture that was not used for power generation from the anode 1a. Gas is exhausted. If the discharged unreacted mixed gas is discarded, the supplied pure hydrogen gas is wasted, and the efficiency of the fuel cell system 200 is reduced. Therefore, the control unit 13 pressurizes the unreacted mixed gas flowing through the unreacted fuel gas circulation passage 4 in the unreacted fuel gas boosting unit 11 and mixes the unreacted mixed gas and pure hydrogen gas flowing through the fuel gas supply path 2. And supplied to the anode 1a.
Thereby, waste of pure hydrogen gas can be eliminated and the fuel cell system 200 can be made highly efficient.

  The operation and action of the fuel cell system 200 configured as described above will be described below.

  FIG. 4 shows a flowchart of the operation method of the fuel cell system according to Embodiment 2 of the present invention. This operation is performed under the control of the control unit 13 when the fuel cell system 200 is generating power.

  The control unit 13 supplies air with the oxidant gas supply unit 7, adjusts the pressure of pure hydrogen gas with the fuel gas pressure adjusting unit 3, and increases the pressure of the unreacted mixed gas with the unreacted fuel gas pressurizing unit 11. (S201). Here, a case where the pressure of air is 111.3 kPa, the pressure of pure hydrogen gas is 111.3 kPa, and the pressure of unreacted mixed gas is 111.3 kPa is shown.

  Next, the control unit 13 determines whether a certain time has elapsed (S202). The predetermined time is a time set in advance so that the concentration of nitrogen contained in the mixed gas flowing through the anode 1a is not increased, and the power generation amount of the fuel cell system 200 is not reduced and the fuel cell stack 1 is not deteriorated. Here, the case of 30 minutes is shown.

  Next, the control unit 13 measures the pressure of the mixed gas at the pressure detection unit 12. The nitrogen partial pressure of the mixed gas supplied to the anode 1a is set to be higher than the nitrogen partial pressure of the air flowing to the cathode 1b (S203). Here, a case where the nitrogen concentration of the mixed gas is set to 30% or less is shown. The nitrogen partial pressure of the air flowing through the cathode 1b is 86.8 kPa, and the pressure of the mixed gas at which the nitrogen partial pressure when the nitrogen concentration of the mixed gas is 30% is 86.8 kPa is 289 kPa. Therefore, the pressure of the pure hydrogen gas flowing through the fuel gas supply path 2 is set to 289 kPa at the fuel gas pressure adjusting unit 3, and the pressure of the unreacted mixed gas flowing through the unreacted fuel gas circulation channel 4 is set to 289 kPa at the unreacted fuel gas boosting unit 11 By doing so, the nitrogen concentration of the mixed gas exceeding 30% can be transmitted from the anode 1 a to the cathode 1 b through the electrolyte membrane of the fuel cell stack 1.

  Next, the control unit 13 determines whether a certain time has elapsed (S204). This fixed time is a preset time until nitrogen contained in the mixed gas flowing through the anode 1a passes through the cathode 1b and the nitrogen concentration of the mixed gas decreases. Here, the case of 10 minutes is shown. If 10 minutes have elapsed, the process returns to S201.

  Each step is shifted immediately after completion of each step without providing a waiting time.

As described above, in the present embodiment, the fuel gas pressure adjusting unit 3 is set to a preset operation amount by making the nitrogen partial pressure of the mixed gas flowing to the anode 1a larger than the nitrogen partial pressure of the air flowing to the cathode 1b. In order to adjust the pressure by measuring the pressure of the mixed gas instead of adjusting the pressure of the pure hydrogen gas flowing through the fuel gas supply path 2 by controlling the fuel cell stack 1 Thus, the light is accurately transmitted to the cathode 1b through the electrolyte membrane. This eliminates the need to discharge the mixed gas from the fuel cell system 200 to reduce the nitrogen concentration of the mixed gas flowing to the anode 1a, and eliminates the need for a diluter for diluting the mixed gas to below the flammable range. Can do.

  If the nitrogen partial pressure of the mixed gas flowing through the anode 1a is larger than the partial pressure of nitrogen in the air flowing through the cathode 1b, the permeation of nitrogen can be accelerated by that amount.

Further, here, the pressure of the pure hydrogen gas flowing through the fuel gas supply path 2 is adjusted only for a predetermined period, but it may be performed for the entire period during power generation.
(Embodiment 3)
FIG. 5 is a block diagram of the configuration of the fuel cell system according to Embodiment 3 of the present invention. In addition, the same code | symbol is provided about the component similar to Embodiment 1, and the description is abbreviate | omitted here.

  In FIG. 5, the fuel cell system 300 includes a control unit 14.

  The control unit 14 has a control function, and includes an arithmetic processing unit (not shown) and a storage unit (not shown) that stores a control program. An example of the arithmetic processing unit is a CPU. An example of the storage unit is a memory. The voltage generated in the fuel cell stack 1 is called a cell voltage, and the cell voltage can be measured.

  The operation and action of the fuel cell system 300 configured as described above will be described below.

  FIG. 6 shows a flowchart of the operation method of the fuel cell system in Embodiment 3 of the present invention. This operation is performed under the control of the control unit 14 when the fuel cell system 300 is generating power.

  The control unit 14 supplies air with the oxidant gas supply unit 7 and adjusts the pressure of pure hydrogen gas flowing through the fuel gas supply path 2 (S301). Here, the case where the pressure of air is set to 111.3 kPa and the pressure of pure hydrogen gas is set to 111.3 kPa is shown.

  Next, the control unit 14 measures the cell voltage of the fuel cell stack 1. When the nitrogen concentration of the mixed gas supplied to the anode 1a increases, the cell voltage of the fuel cell stack 1 decreases and the fuel cell stack 1 deteriorates. It is determined whether or not the cell voltage is lower than a preset lower limit value of the cell voltage so that the power generation amount of the fuel cell system 400 does not decrease and the fuel cell stack 1 does not deteriorate (S302). The lower limit value of the cell voltage is that the normal cell voltage during power generation is 0.7 V, and 90% of the cell voltage is 0.63 V, which is the lower limit value of the cell voltage.

  Next, the control unit 14 causes the nitrogen partial pressure of the mixed gas flowing to the anode 1a to be higher than the nitrogen partial pressure of the air flowing to the cathode 1b (S303). Here, the case where the nitrogen concentration of the mixed gas is set to 32% or less is shown. The nitrogen partial pressure of the air flowing through the cathode 1b is 86.8 kPa, and the pressure of the mixed gas at which the nitrogen partial pressure when the nitrogen concentration of the mixed gas is 32% is 86.8 kPa is 271 kPa. Therefore, when the pressure of the pure hydrogen gas flowing through the fuel gas supply path 2 is 271 kPa in the fuel gas pressure adjusting unit 3, the nitrogen concentration of the mixed gas exceeds 32% from the anode 1 a to the cathode through the electrolyte membrane of the fuel cell stack 1. 1b can be transmitted.

  Next, the control unit 14 measures the cell voltage of the fuel cell stack 1 and determines whether the cell voltage is higher than 0.7 V (S304). If the cell voltage is greater than 0.7V, the process returns to S301.

  Each step is shifted immediately after completion of each step without providing a waiting time.

  As described above, in the present embodiment, the fuel gas pressure adjusting unit 3 is set to a preset operation amount by making the nitrogen partial pressure of the mixed gas flowing to the anode 1a larger than the nitrogen partial pressure of the air flowing to the cathode 1b. Instead of adjusting the pressure of pure hydrogen gas flowing through the fuel gas supply path 2 by controlling the fuel cell, the cell voltage is measured and the nitrogen concentration of the mixed gas is estimated, so that the nitrogen contained in the mixed gas is removed from the fuel cell. Through the electrolyte membrane of the stack 1, the light is accurately transmitted to the cathode 1b. This eliminates the need to discharge the mixed gas from the fuel cell system 300 to reduce the nitrogen concentration of the mixed gas flowing to the anode 1a, and eliminates the need for a diluter for diluting the mixed gas to below the flammable range. be able to.

  If the nitrogen partial pressure of the mixed gas flowing through the anode 1a is larger than the partial pressure of nitrogen in the air flowing through the cathode 1b, the permeation of nitrogen can be accelerated by that amount.

  Further, here, the pressure of the pure hydrogen gas flowing through the fuel gas supply path 2 is adjusted only for a predetermined period, but it may be performed for the entire period during power generation.

Note that the cell voltage to be measured may be the voltage of all or some of the cells of the fuel cell stack 1.
(Embodiment 4)
FIG. 7 is a block diagram of the configuration of the fuel cell system according to Embodiment 4 of the present invention. In addition, the same code | symbol is provided about the component similar to Embodiment 1, and the description is abbreviate | omitted here.

  In FIG. 7, the fuel cell system 400 includes an unreacted fuel gas booster 11, a nitrogen concentration detector 15, and a controller 16.

  The unreacted fuel gas pressure increasing unit 11 is connected to the unreacted fuel gas circulation channel 4 and adjusts the pressure of the unreacted mixed gas flowing through the unreacted fuel gas circulation channel 4.

  The nitrogen concentration detection unit 15 is connected to the mixed gas supply path 5 and measures the nitrogen concentration of the mixed gas flowing through the mixed gas supply path 5.

  The control part 16 should just have a control function, and is provided with the arithmetic processing part (not shown) and the memory | storage part (not shown) which memorize | stores a control program. An example of the arithmetic processing unit is a CPU. An example of the storage unit is a memory.

  The operation and action of the fuel cell system 400 configured as described above will be described below.

  FIG. 8 shows a flowchart of the operation method of the fuel cell system according to Embodiment 4 of the present invention. This operation is performed by the control of the control unit 16 when the fuel cell system 400 is generating power.

  The control unit 16 supplies air with the oxidant gas supply unit 7, adjusts the pressure of pure hydrogen gas flowing through the fuel gas supply path 2, and boosts the pressure of the unreacted mixed gas with the unreacted fuel gas booster 11. (S401). Here, a case where the pressure of air is 111.3 kPa, the pressure of pure hydrogen gas is 111.3 kPa, and the pressure of unreacted mixed gas is 111.3 kPa is shown.

  Next, the control unit 16 determines whether the nitrogen concentration measured by the nitrogen concentration detection unit 15 exceeds the preset nitrogen concentration so that the power generation amount of the fuel cell system 500 does not decrease and the fuel cell stack 1 does not deteriorate. Is determined (S402). Here, the nitrogen concentration 50% of the mixed gas flowing through the anode 1a is set as the upper limit value. If the measured nitrogen concentration is 50% or more, the nitrogen partial pressure of the mixed gas is set higher than the nitrogen partial pressure of air. Here, a case where the nitrogen concentration of the mixed gas is set to 33% or less is shown. The nitrogen partial pressure of the air flowing through the cathode 1b is 86.8 kPa, and the pressure of the mixed gas at which the nitrogen partial pressure when the nitrogen concentration of the mixed gas is 33% is 86.8 kPa is 263 kPa. Therefore, the pressure of the pure hydrogen gas flowing through the fuel gas supply path 2 is set to 263 kPa in the fuel gas pressure adjusting unit 3, and the pressure of the unreacted mixed gas flowing through the unreacted fuel gas circulation channel 4 is set to 263 kPa in the unreacted fuel gas booster 11. Thus, nitrogen having a nitrogen concentration of the mixed gas exceeding 33% can be transmitted from the anode 1 a to the cathode 1 b through the electrolyte membrane of the fuel cell stack 1.

  Next, the control unit 16 controls the fuel gas pressure adjusting unit 3 so that the pressure of the pure hydrogen gas becomes 263 kPa (S403).

  Next, the controller 16 determines whether the nitrogen concentration measured by the nitrogen concentration detector 15 is less than 36% (S404). Here, the range of + 3% is given to 33% of the nitrogen concentration of the mixed gas whose adjustment is desired. If the nitrogen concentration is less than 36%, the process returns to S401.

  Each step is shifted immediately after completion of each step without providing a waiting time.

  As described above, in the present embodiment, the fuel gas pressure adjusting unit 3 is set to a preset operation amount by making the nitrogen partial pressure of the mixed gas flowing to the anode 1a larger than the nitrogen partial pressure of the air flowing to the cathode 1b. By controlling the pressure of the pure hydrogen gas flowing through the fuel gas supply path 2, the nitrogen concentration of the mixed gas is measured to remove the nitrogen contained in the mixed gas from the electrolyte membrane of the fuel cell stack 1. Through the cathode 1b, it is not necessary to discharge the mixed gas from the fuel cell system 400 in order to reduce the nitrogen concentration of the mixed gas flowing to the anode 1a, and it is diluted to below the flammable range of the mixed gas. This eliminates the need for a diluter.

  If the nitrogen partial pressure of the mixed gas flowing through the anode 1a is larger than the partial pressure of nitrogen in the air flowing through the cathode 1b, the permeation of nitrogen can be accelerated by that amount.

Further, here, the pressure of the pure hydrogen gas flowing through the fuel gas supply path 2 is adjusted only for a predetermined period, but it may be performed for the entire period during power generation.
(Embodiment 5)
FIG. 9 is a block diagram of the configuration of the fuel cell system according to Embodiment 5 of the present invention. In addition, the same code | symbol is provided about the component similar to Embodiment 1, and the description is abbreviate | omitted here.

  In FIG. 9, the fuel cell system 500 includes a nitrogen concentration detection unit 17 and a control unit 18.

  The nitrogen concentration detection unit 17 is connected to the unreacted fuel gas circulation channel 4 and measures the nitrogen concentration of the unreacted mixed gas flowing through the unreacted fuel gas circulation channel 4.

  The control part 18 should just have a control function, and is provided with an arithmetic processing part (not shown) and the memory | storage part (not shown) which memorize | stores a control program. An example of the arithmetic processing unit is a CPU. An example of the storage unit is a memory.

  The operation and action of the fuel cell system 500 configured as described above will be described below.

  FIG. 10 shows a flowchart of the operation method of the fuel cell system according to Embodiment 5 of the present invention. This operation is performed by the control of the control unit 18 when the fuel cell system 500 is generating power.

  The control unit 18 supplies air from the oxidant gas supply unit 7 and adjusts the pressure of pure hydrogen gas flowing through the fuel gas supply path 2 (S501). Here, the case where the pressure of air is set to 111.3 kPa and the pressure of pure hydrogen gas is set to 111.3 kPa is shown.

  Next, the control unit 18 determines the pure hydrogen gas supplied from the fuel gas supply path 2 and the unreacted mixture flowing in the unreacted fuel gas circulation channel 4 from the nitrogen concentration of the unreacted mixed gas measured by the nitrogen concentration detection unit 17. The nitrogen partial pressure of the mixed gas after joining the gas is estimated (S502). First, pure hydrogen gas corresponding to the amount of power generation is supplied from the fuel gas supply path 2, and a predetermined flow rate is set to flow through the unreacted fuel gas circulation flow path 4. In the present embodiment, the pure hydrogen gas flow rate is 40 L / min, and the unreacted mixed gas flow rate is 60 L / min. Here, when the nitrogen concentration of the unreacted mixed gas measured by the nitrogen concentration detector 17 is 75%, the nitrogen concentration of the mixed gas is estimated to be 45%, and the nitrogen partial pressure is estimated to be 50.1 kPa. .

  Next, the control unit 18 determines whether the nitrogen partial pressure estimated in S502 is 50.1 kPa or more (S503).

  Next, the control unit 18 causes the nitrogen partial pressure of the mixed gas supplied to the anode 1a to be higher than the nitrogen partial pressure of the air supplied to the cathode 1b (S504). Here, a case where the nitrogen concentration of the mixed gas is set to 35% or less is shown. The nitrogen partial pressure of the air flowing through the cathode 1b is 86.8 kPa, and the pressure of the mixed gas at which the nitrogen partial pressure when the nitrogen concentration of the mixed gas is 35% is 86.8 kPa is 248 kPa. Therefore, when the pressure of the pure hydrogen gas flowing through the fuel gas supply path 2 is set to 248 kPa in the fuel gas pressure adjusting unit 3, the nitrogen concentration of the mixed gas exceeds 35% from the anode 1 a to the cathode through the electrolyte membrane of the fuel cell stack 1. 1b can be transmitted. The pressure of the pure hydrogen gas flowing through the anode 1a is controlled to be 248 kPa by the fuel gas pressure adjusting unit 3 so that the pressure is measured by the pressure detecting unit 12 and 248 kPa.

  Next, the control unit 18 measures the nitrogen concentration of the unreacted mixed gas at the nitrogen concentration detection unit 17 and estimates the nitrogen concentration of the mixed gas (S505).

  Next, the control unit 18 determines whether the nitrogen concentration estimated in S505 is less than 38% (S506). Here, the range of + 3% is given to 35% of the nitrogen concentration of the mixed gas whose adjustment is desired. If the nitrogen concentration is less than 38%, the process returns to S501.

  Each step is shifted immediately after completion of each step without providing a waiting time.

As described above, in the present embodiment, the fuel gas pressure adjusting unit 3 is set to a preset operation amount by making the nitrogen partial pressure of the mixed gas flowing to the anode 1a larger than the nitrogen partial pressure of the air flowing to the cathode 1b. Rather than adjusting the pressure of the pure hydrogen gas flowing through the fuel gas supply path 2 by controlling the flow rate, the nitrogen concentration of the unreacted mixed gas is measured and the nitrogen concentration contained in the mixed gas flowing to the anode 1a is estimated. Thus, the nitrogen contained in the mixed gas is accurately permeated to the cathode 1b through the electrolyte membrane of the fuel cell stack 1, and the mixed gas is supplied to the fuel cell system 500 in order to reduce the nitrogen concentration of the mixed gas flowing to the anode 1a. Therefore, a diluter for diluting to less than the combustible range of the mixed gas can be eliminated.

  If the nitrogen partial pressure of the mixed gas flowing through the anode 1a is larger than the partial pressure of nitrogen in the air flowing through the cathode 1b, the permeation of nitrogen can be accelerated by that amount.

  Further, here, the pressure of the pure hydrogen gas flowing through the fuel gas supply path 2 is adjusted only for a predetermined period, but it may be performed for the entire period during power generation.

  From the foregoing description, many modifications and other embodiments of the present invention are obvious to one skilled in the art. Accordingly, the foregoing description should be construed as illustrative only and is provided for the purpose of teaching those skilled in the art the best mode of carrying out the invention. The details of the structure and / or function may be substantially changed without departing from the spirit of the invention.

  As described above, the fuel cell system and the operation method thereof according to the present invention adjusts the nitrogen partial pressure of the anode of the fuel cell stack during power generation to allow the anode nitrogen to pass through the electrolyte membrane of the stack and to the cathode. Since it can discharge | emit, discharge | emission of hydrogen out of the system can be suppressed and a diluter becomes unnecessary. As a result, the fuel cell system can be miniaturized and the safety can be improved, so that it can be applied to a household fuel cell system, a commercial fuel cell system, and the like.

DESCRIPTION OF SYMBOLS 1 Fuel cell stack 1a Anode 1b Cathode 2 Fuel gas supply path 3 Fuel gas pressure adjustment part 4 Unreacted fuel gas circulation flow path 5 Mixed gas supply path 6 Ejector 7 Oxidant gas supply part 8 Oxidant gas supply path 9 Oxidant gas Exhaust path 10, 13, 14, 16, 18 Control unit 11 Unreacted fuel gas booster 12 Pressure detector 15 Nitrogen concentration detector 17 Nitrogen concentration detector 100, 200, 300, 400, 500 Fuel cell system

Claims (6)

A fuel cell stack that generates power using a fuel gas containing hydrogen and an oxidant gas;
A fuel gas supply path for supplying fuel gas to the anode of the fuel cell stack;
A fuel gas pressure adjusting unit for adjusting the pressure of the fuel gas supplied to the anode;
An unreacted fuel gas circulation passage for joining unreacted fuel gas discharged from the anode to the fuel gas supply path;
An oxidant gas supply unit for supplying an oxidant gas to the cathode of the fuel cell stack;
An oxidant gas supply path connecting the cathode and the oxidant gas supply unit;
An oxidant gas discharge path for discharging unreacted oxidant gas from the cathode;
A control unit,
The control unit is configured so that the partial pressure of nitrogen in the fuel gas flowing through the anode is higher than the partial pressure of nitrogen in the oxidant gas flowing through the cathode during the entire period when the fuel cell stack is generating power or for a predetermined period. A fuel cell system for adjusting the fuel gas pressure adjusting unit. The fuel gas supply path includes pressure detection means,
The said control part adjusts the said fuel gas pressure adjustment part so that the nitrogen partial pressure in the fuel gas which flows through the said anode may become higher than the nitrogen partial pressure in the oxidant gas which flows through the said cathode. Fuel cell system. The controller is
Estimating the nitrogen concentration in the fuel gas flowing through the anode based on the cell voltage of the fuel cell stack;
The nitrogen partial pressure in the fuel gas flowing through the anode is estimated from the nitrogen concentration, and the nitrogen partial pressure in the fuel gas flowing through the anode is higher than the nitrogen partial pressure in the oxidant gas flowing through the cathode. The fuel cell system according to claim 1, wherein the fuel gas pressure adjusting unit is adjusted. Provided with an anode nitrogen concentration detection means for detecting a nitrogen concentration in the fuel gas supplied to the anode, provided downstream of a junction between the fuel gas supply path and the unreacted fuel gas circulation path;
The nitrogen partial pressure in the fuel gas flowing through the anode is estimated from the nitrogen concentration detected by the anode nitrogen concentration detection means, and the nitrogen partial pressure in the fuel gas flowing through the anode is the nitrogen content in the oxidant gas flowing through the cathode. The fuel cell system according to claim 1, wherein the fuel gas pressure adjusting unit is adjusted to be higher than a pressure. An anode nitrogen concentration detecting means provided in the unreacted fuel gas circulation flow path for detecting the nitrogen concentration in the fuel gas flowing through the unreacted fuel gas circulation flow path;
The fuel gas flowing through the unreacted fuel gas circulation passage of the fuel gas supplied to the anode, the mixing ratio of the fuel gas supplied from the fuel gas supply path, and the nitrogen concentration detected by the anode nitrogen concentration detecting means The fuel gas pressure is estimated so that the nitrogen partial pressure in the fuel gas flowing through the anode is higher than the nitrogen partial pressure in the oxidant gas flowing through the cathode. The fuel cell system according to claim 1, wherein the adjustment unit is adjusted. A fuel cell stack that generates power using a fuel gas containing hydrogen and an oxidant gas;
A fuel gas supply path for supplying fuel gas to the anode of the fuel cell stack;
A fuel gas pressure adjusting unit for adjusting the pressure of the fuel gas supplied to the anode;
An unreacted fuel gas circulation passage for joining unreacted fuel gas discharged from the anode to the fuel gas supply path;
An oxidant gas supply path for supplying an oxidant gas to the cathode of the fuel cell stack and an oxidant gas supply means;
An oxidant gas discharge path for discharging an oxidant gas discharged from the cathode, and a method of operating a fuel cell system comprising:
The fuel gas pressure adjustment so that the partial pressure of nitrogen in the fuel gas flowing through the anode is higher than the partial pressure of nitrogen in the oxidant gas flowing through the cathode during the entire period of power generation by the fuel cell stack or for a predetermined period. A method for operating a fuel cell system, including a step of adjusting a section.

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