JP2018129138A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system in which unreacted fuel gas can be used as a part of fuel gas of another fuel cell stack, a fuel cell stack for generating electric power can be arbitrarily selected, and it is possible to operate with high power generation efficiency by reducing loss of fuel gas used for power generation.SOLUTION: A fuel cell system 100 includes: a fuel gas supply unit 2-(1) to 2-(N) that is provided on fuel gas supply paths 3-(1) to 3-(N) and supplies fuel gas to the fuel cell stacks 10-(1) to 10-(N); unreacted fuel gas circulation paths 5-(1) to 5-(N) having conveying means 7-(1) to 7-(3) for supplying a fuel gas from unreacted fuel gas discharge paths 4-(1) to 4-(N) to fuel gas supply paths 3-(1) to 3-(N); and connection paths 6-(1) to 6-(N-1) connecting adjacent unreacted fuel gas discharge paths 4-(1) to 4-(N).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fuel cell system that generates power by supplying fuel gas to a plurality of fuel cell stacks.

  When an electrolyte layer is sandwiched between a fuel electrode and an air electrode to form a cell (single cell), a fuel gas containing hydrogen is supplied to the fuel electrode, and air containing oxygen is supplied to the air electrode. Electric energy is obtained. Since the generated voltage obtained by one unit cell is often less than 1 V, a practical fuel cell obtains a high voltage by stacking unit cells.

  In recent years, fuel cell systems have come to be used not only for general home use but also for in-vehicle and business use. In in-vehicle and business use, the amount of power generated is higher than that for general home use fuel cell systems. It has been demanded.

In order to realize a high power generation amount, it is generally known that a plurality of fuel cell stacks configured by stacking single cells are used in parallel, and used (for example, see Patent Document 1). )
FIG. 3 shows a block diagram of a conventional fuel cell system disclosed in Patent Document 1. In FIG. As shown in FIG. 3, the fuel cell system 300 includes a fuel gas supply source 1, a fuel gas supply path 3- (1), a fuel gas supply path 3- (2), a fuel gas supply path 3- (3), Reactive fuel gas discharge path 4- (1), unreacted fuel gas discharge path 4- (2), unreacted fuel gas discharge path 4- (3), fuel gas flow rate adjustment valve 8- (1), fuel gas flow rate adjustment It comprises a valve 8- (2), a fuel gas flow rate adjustment valve 8- (3), a fuel cell stack 10- (1), a fuel cell stack 10- (2), and a fuel cell stack 10- (3).

  The conventional fuel cell system 300 includes a fuel gas supply path 3- (1), a fuel gas supply path 3- (2), a fuel gas supply path 3- (3), an unreacted fuel gas discharge path 4- (1), Unreacted fuel gas discharge path 4- (2), Unreacted fuel gas discharge path 4- (3), Fuel cell stack 10- (1), Fuel cell stack 10- (2), Fuel cell stack 10- (3) Are configured in parallel, and the fuel gas flowing from the fuel gas supply source 1 through the fuel gas supply path 3- (1), the fuel gas supply path 3- (2), and the fuel gas supply path 3- (3) is used as the fuel gas. After adjusting the flow rate with the flow rate adjustment valve 8- (1), the fuel gas flow rate adjustment valve 8- (2), and the fuel gas flow rate adjustment valve 8- (3), the fuel cell stack 10- (1) and the fuel cell stack 10 -(2), supply to the fuel cell stack 10- (3) The fuel gas that has not been used in the fuel cell stack 10- (1), the fuel cell stack 10- (2), and the fuel cell stack 10- (3) is discharged into the unreacted fuel gas discharge path 4- (1). It was discharged out of the fuel cell system 300 via the route 4- (2) and the unreacted fuel gas discharge route 4- (3).

JP 2000-40518 A

However, the conventional fuel cell system 300 proposed in Patent Document 1 can obtain a large amount of power generation by arranging a plurality of fuel cell stacks 10- (1) to 10- (3) in parallel. In order to protect the reliability of the fuel cell stacks 10- (1) to 10- (3),
Fuel gas stack 10- (1) -10- (3) is supplied to fuel cell stack 10- (1) -10- (3) in an amount that is about 10-20% greater than the amount of fuel gas required for power generation. -It is necessary to prevent fuel gas deficiency in (3). The fuel gas that has not been used in the fuel cell stacks 10-(1) to 10-(3) is discharged out of the fuel cell system 300.

  The average fuel utilization rate Uf (%) of the fuel cell stack can be expressed by the following (Equation 1).

燃料電池システムの燃料利用率Ｕｆｓ（％）は以下の（数２）で表現できる。

The fuel utilization rate Ufs (%) of the fuel cell system can be expressed by the following (Equation 2).

特許文献１で提案されたものでは、燃料電池スタック１０−（１）〜１０−（３）で使用されなかった未反応燃料ガスは、未反応燃料ガス排出経路４−（１）〜４−（３）を通過して、燃料電池システム３００外へ排出していた。

In what was proposed by patent document 1, unreacted fuel gas which was not used by fuel cell stack 10- (1) -10- (3) is unreacted fuel gas discharge path 4- (1)-4- ( It passed through 3) and was discharged out of the fuel cell system 300.

  In this configuration, the fuel utilization rate Ufs of the fuel cell system 300 was obtained only the same value as the average fuel utilization rate Uf of the fuel cell stacks 10- (1) to 10- (3). Further, if the average fuel utilization rate Uf of the fuel cell stacks 10- (1) to 10- (3) is set too high, the fuel in the vicinity of the fuel outlets of the fuel cell stacks 10- (1) to 10- (3). Gas deficiency occurs and it is difficult to maintain the reliability of the fuel cell stacks 10- (1) to 10- (3).

  Therefore, the fuel utilization rate Ufs of the fuel cell system 300 can be set only to a value within a range in which the reliability of the fuel cell stacks 10- (1) to 10- (3) can be protected. A predetermined amount or more of the fuel gas is discharged out of the fuel cell system 300 as an unreacted fuel gas, and there is a problem that the fuel cell system 300 cannot be operated with high power generation efficiency.

  In the operation of the fuel cell system 300 having the plurality of fuel cell stacks 10- (1) to 10- (3), the specific fuel cell stacks 10- (1) to 10- (3) are preferentially operated. As a result, the operation time of the fuel cell stacks 10- (1) to 10- (3) may vary, resulting in a problem that durability is lowered.

  The present invention solves the above-described conventional problems, and can use unreacted fuel gas as a partial fuel gas of another fuel cell stack, arbitrarily select a fuel cell stack to generate power, It is an object of the present invention to provide a fuel cell system that can be operated with high power generation efficiency by reducing the loss of fuel gas used in the manufacturing process.

In order to solve the above-described conventional problems, the fuel cell system of the present invention includes first to Nth (N is an integer of 2 or more) fuel cell stacks that generate power by reacting a fuel gas and an oxidant, A predetermined amount of fuel gas is provided on the first to Nth stacks, provided on the first to Nth fuel gas supply paths for supplying fuel gas to the first to Nth fuel cell stacks, and on the first to Nth fuel gas supply paths. First to Nth fuel gas supply sections, first to Nth unreacted fuel gas discharge paths for discharging unreacted fuel gas from the first to Nth fuel cell stacks, and Kth unreacted fuel gas discharge A Kth unreacted fuel gas circulation path having a Kth transport means for supplying unreacted fuel gas to a Kth fuel gas supply path from a path (K is an integer of 1 ≦ K ≦ N), and Mth unreacted Fuel gas discharge path (M is all 1 ≦ M ≦ N−1) Is obtained by a second M connection path that connects the number) and the first M + 1 unreacted fuel gas circulation path.

  As a result, the Kth fuel cell stack can use unreacted fuel gas that has not been consumed in the K-1th fuel cell stack as fuel gas. In addition, since an appropriate number of fuel cell stacks can be selected to generate power according to the amount of power generation, if the fuel cell stacks are operated so that the power generation times are equalized, the endurance time of the fuel cell stack is maximized. Can be extended. Unreacted fuel gas that has not been consumed between selected fuel cell stacks can be used.

  Further, in the fuel cell stack located on the most downstream side in the selected fuel cell stack, the discharged unreacted fuel gas is circulated to the inlet of the fuel cell stack to generate power. Therefore, the amount of unreacted fuel gas discharged as a fuel cell system can be reduced, the fuel utilization rate Ufs of the fuel cell system can be increased, and the fuel cell system can be operated with high power generation efficiency.

  In addition, since any fuel cell stack can generate power according to the amount of power generated, the fuel cell stack can be operated by controlling the fuel cell stack so that the power generation time of each fuel cell stack is equalized. You can maximize your time.

  According to the fuel cell system of the present invention, an appropriate number of fuel cell stacks corresponding to the amount of power generation are connected, and unreacted fuel gas contained in the fuel exhaust gas is used for power generation, so that the operation of low power generation amount is achieved. In the fuel cell system, the fuel utilization rate Ufs of the fuel cell system can be increased independently of the average fuel utilization rate Uf of the fuel cell stack, and the fuel gas relative to the amount of fuel gas used in the fuel cell system can be increased. Since the supply amount can be reduced, the fuel cell system can be operated with high power generation efficiency.

  Furthermore, when generating a small number of fuel cell stacks that are configured in the fuel cell system, the fuel cell system is configured by operating the fuel cell system so that the power generation times of the plurality of fuel cell stacks are substantially uniform. As a fuel cell system, the durability (durability time) can be improved.

1 is a block diagram of a fuel cell system according to Embodiment 1 of the present invention. 1 is a block diagram of a fuel cell system including five fuel cell stacks according to Embodiment 1 of the present invention. Block diagram of a conventional fuel cell system

According to a first aspect of the present invention, fuel gas is generated in first to Nth (N is an integer greater than or equal to 2) fuel cell stacks that generate power by reacting a fuel gas with an oxidant, and fuel gas is supplied to the first to Nth fuel cell stacks. The first to Nth fuel gas supply paths for supplying a predetermined amount of fuel gas to the first to Nth stacks provided on the first to Nth fuel gas supply paths and the first to Nth fuel gas supply paths A first to Nth unreacted fuel gas discharge path for discharging unreacted fuel gas from the first to Nth fuel cell stacks, and a Kth unreacted fuel gas discharge path (K is 1 ≦ K ≦ N A Kth unreacted fuel gas circulation path having a Kth transport means for supplying unreacted fuel gas from all integers to a Kth fuel gas supply path, and an Mth unreacted fuel gas discharge path (M is 1 ≦ M ≦ all integers of N−1) and M + 1
A fuel cell system including an Mth connection path that connects an unreacted fuel gas circulation path.

  With this configuration, a large amount of power can be obtained during high power generation operation and unreacted fuel gas contained in the fuel exhaust gas can be used for power generation, and an appropriate number of fuels suitable for the amount of power generation can be used during low power generation operation. The battery stack can generate power, and unreacted fuel gas contained in the fuel exhaust gas can be used for power generation, and high power generation efficiency and stable power generation are possible even in low power generation operation.

  In addition, according to the fuel cell system of the present invention, when generating an appropriate number of fuel cell stacks according to the amount of power generation, by generating an arbitrary fuel cell stack for an appropriate time, a specific fuel cell stack can be generated. The fuel cell system can be operated without power generation time being biased.

  According to a second aspect of the present invention, the fuel cell system according to the first aspect includes a controller that controls the first to Nth fuel gas supply units and the first to Nth transport means, and the controller includes: The fuel gas supply unit corresponding to the fuel cell stack that does not generate power in the first to Nth fuel cell stacks is stopped, and the fuel cell stack that generates power in the first to Nth fuel cell stacks The amount of fuel gas supplied by the fuel gas supply unit corresponding to any one of the fuel cell stacks is set as a first predetermined amount, and another one of the fuel cell stacks to generate power is supplied to any one fuel cell stack. A fuel cell stack that supplies a first predetermined amount of fuel gas at the fuel gas supply unit among the fuel cell stacks that generate power, wherein the amount of fuel gas supplied by the corresponding fuel gas supply unit is a second predetermined amount; 2 Fuel gas supply unit for a predetermined amount of fuel gas The amount of fuel gas supplied by the fuel gas supply unit corresponding to the fuel cell stack excluding the fuel cell stack to be supplied is a third predetermined amount, and the relationship between the predetermined amounts is as follows: first predetermined amount> third predetermined amount> first 2 The fuel cell stack that does not generate electricity and the fuel cell stack that supplies the first predetermined amount of fuel gas at the fuel gas supply unit without supplying unreacted fuel gas at the second place The amount of unreacted fuel gas supplied by the transport means corresponding to the fuel cell stack that supplies a fixed amount of fuel gas at the fuel gas supply unit is set as the fourth predetermined amount, and the third predetermined amount of fuel gas is supplied at the fuel gas supply unit The amount of unreacted fuel gas supplied by the transport means corresponding to the fuel cell stack to be set is a fifth predetermined amount smaller than the fourth predetermined amount.

  With this configuration, at the time of low power generation operation, an appropriate number of fuel cell stacks corresponding to the power generation amount can be generated, and unreacted fuel gas contained in the fuel exhaust gas can be used for power generation. In the fuel cell stack that supplies the third predetermined amount of fuel gas at the fuel gas supply unit even if it is used for power generation, the unreacted fuel gas of one fuel cell stack is used for power generation, and the second predetermined amount In the fuel cell stack that supplies the fuel gas at the fuel gas supply unit, the unreacted fuel gas of the two fuel cell stacks can be circulated by power generation, which is high even in low power generation operation. Power generation efficiency and stable power generation are possible.

  Further, as described above, any fuel cell stack can be generated in accordance with the amount of power generation. Therefore, if the fuel cell system is operated by controlling the power generation time of each fuel cell stack to be equal, The endurance time of the battery stack can be maximized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 shows a block diagram of a fuel cell system according to Embodiment 1 of the present invention. In FIG. 1, a fuel cell system 100 includes N fuel cell stacks 10- (1) to 10- (N) that generate power by reacting a fuel gas and an oxidant, and a fuel cell stack 10- (1). ) To 10- (N) are provided on the fuel gas supply paths 3- (1) to 3- (N) and the fuel gas supply paths 3- (1) to 3- (N). The fuel gas supply units 2- (1) to 2- (N) for supplying a predetermined amount of fuel gas to the fuel cell stacks 10- (1) to 10- (N) and the fuel cell stacks 10- (1) to 10- (N) has an unreacted fuel gas discharge path 4- (1) to 4- (N) for discharging unreacted fuel gas, and a conveying means 7- (1) to 7- (N) on the path. Then, unreacted fuel gas is supplied from unreacted fuel gas discharge paths 4- (1) to 4- (N) to fuel gas supply paths 3- (1) to 3- Connection path 6 connecting unreacted fuel gas circulation paths 5- (1) to 5- (N) supplied to N) and adjacent unreacted fuel gas discharge paths 4- (1) to 4- (N). -(1) -6- (N-1) and the controller 11 are comprised. N is an integer of 2 or more.

  Here, reference numerals assigned to a plurality of identical elements will be described. For example, in the case of the fuel cell stack 10- (1), 10- (2), 10- (N), (1), (2), (N) are given to distinguish the same elements from each other. If there are N (N is an integer of 2 or more) fuel cell stacks 10- (1), 10- (2), 10- (N), the fuel cell stacks 10- (1), 10- (2) A serial number of 10- (N) is represented. The same applies to the other components, the fuel gas supply units 2- (1) to 2- (N), and the fuel gas supply paths 3- (1) to 3- (N).

  Moreover, the code | symbol which describes several identical element continuously is demonstrated. For example, when the fuel cell stacks 10- (1) to 10- (3) are described, the symbols “˜” indicate all 11- (1), 11- (2), and 11- (3). means. The same applies to other components.

  The fuel gas supply paths 3- (1) to 3- (N) supply fuel gas from the fuel gas infrastructure having a predetermined supply pressure to the fuel cell stacks 10- (1) to 10- (N), respectively. It is a piping path, using hydrogen gas as the fuel gas, and installing the fuel gas supply units 2- (1) to 2- (N) on the fuel gas supply paths 3- (1) to 3- (N), respectively To do.

  The fuel gas supply units 2- (1) to 2- (N) are configured by a flow meter and a pump that sends gas, and the pump pressurizes the fuel gas to supply fuel gas supply paths 3- (1) to 3 -Supply to (N). The flow meter measures the flow rate of the fuel gas in the fuel gas supply paths 3- (1) to 3- (N), and if there is excess or deficiency, returns the flow rate information to the controller 11, and the controller 11 instructs the pump to The capacity value is controlled to adjust the amount of fuel gas in the fuel gas supply paths 3- (1) to 3- (N).

  The controller 11 only needs to have a control function, and includes an arithmetic processing unit (not shown) and a storage unit (not shown) that stores a control program. A CPU is used as the arithmetic processing unit. A memory is used as the storage unit.

  The fuel cell stacks 10- (1) to 10- (N) generate power using fuel gas and an oxidizing gas supplied by an oxidizing gas supplier (not shown). A polymer electrolyte fuel cell is used as the fuel cell stack.

  The unreacted fuel discharge paths 4- (1) to 4- (N) are piping paths through which the fuel exhaust gas passes with the outlets of the fuel cell stacks 10- (1) to 10- (N) as one end. Reactive fuel gas circulation paths 5- (1) to 5- (N) are provided.

The other ends of the unreacted fuel gas circulation paths 5- (1) to 5- (N) are connected to the fuel gas supply sections 2- (1) to 2- (1) on the fuel gas supply paths 3- (1) to 3- (N). -(N) and fuel cell stack 10- (
1) to 10- (N), and includes conveying means 7- (1) to 7- (N) on the unreacted fuel gas circulation paths 5- (1) to 5- (N).

  The conveying means is constituted by a flow meter and a pump for sending gas, and the pump pressurizes the unreacted fuel gas and supplies it to the fuel gas supply paths 3- (1) to 3- (N).

  The connection paths 6- (1) to 6- (N-1) are unreacted fuel gas of one large fuel cell stack adjacent to the unreacted fuel gas discharge paths 4- (1) to 4- (N). It is a piping path that connects the circulation paths 5- (1) to 5- (N), the Mth connection path is the Mth unreacted fuel gas discharge path (M is an integer of 1 ≦ M ≦ N−1) ) And the (M + 1) th unreacted fuel gas circulation path.

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

  First, when the fuel cell system 100 operates, the following operation is performed. The optimum number of fuel cell stacks is determined according to the amount of power generation, and gas is supplied from the fuel supply units 2- (1) to 2- (N) corresponding to the fuel cell stacks 10- (1) to 10- (N) that generate power. The controller 11 controls the fuel supply units 2- (1) to 2- (N) corresponding to the fuel cell stacks 10- (1) to 10- (N) that supply a predetermined amount and do not generate power to stop the gas.

  When generating power with at least two fuel cell stacks 10- (1) to 10- (N), any one fuel cell among the fuel cell stacks 10- (1) to 10- (N) to be generated The amount (first predetermined amount) supplied by the fuel gas supply units 2- (1) to 2- (N) corresponding to the stacks 10- (1) to 10- (N) is the fuel cell stack 10 that generates power. -The largest amount of fuel gas supplied from (1) to 10- (N), and any one other fuel among the fuel cell stacks 10- (1) to 10- (N) that generate electricity The amount of fuel gas supply units 2- (1) to 2- (N) corresponding to the battery stacks 10- (1) to 10- (N) (the second predetermined amount) is the fuel cell stack that generates power. Fuel cell stack for generating power with the smallest amount of fuel gas supplied from 10- (1) to 10- (N) The fuel cell stacks 10- (1) to 10- (0- (1) to 10- (N) in which the first predetermined amount is supplied by the fuel gas supply units 2- (1) to 2- (N). N) and the fuel cell stack 10- except for the fuel cell stacks 10- (1) to 10- (N) that supply the second predetermined amount by the fuel gas supply units 2- (1) to 2- (N). (1) to 10- (N) corresponding to the fuel gas supply units 2- (1) to 2- (N) (the third predetermined amount) is supplied by the first predetermined amount> the third predetermined amount > Control is performed by the controller 11 so as to satisfy the relationship of the second predetermined amount.

  The fuel cell stack 10- (1) to 10- (N) that does not generate power and the fuel cell stack 10 that supplies the first predetermined amount of fuel gas by the fuel gas supply units 2- (1) to 2- (N) -The conveying means 7- (1) to 7- (N) corresponding to (1) to 10- (N) do not supply unreacted fuel gas, and supply a second predetermined amount of fuel gas to the fuel gas supply unit 2- (1) to 2- (N) of the unreacted fuel gas supplied by the transport means 7- (1) to 7- (N) corresponding to the fuel cell stacks 10- (1) to 10- (N) supplied Conveying means corresponding to the fuel cell stacks 10- (1) to 10- (N) in which the amount is the fourth predetermined amount and the third predetermined amount is supplied by the fuel gas supply units 2- (1) to 2- (N) The controller 11 controls the amount of unreacted fuel gas supplied in 7- (1) to 7- (N) to be a fifth predetermined amount smaller than the fourth predetermined amount. To.

By controlling in this way, the fuel cell stacks 10- (1) to 10- (N) that supply the first predetermined amount of fuel gas by the fuel supply units 2- (1) to 2- (N) are pure. The unreacted fuel gas discharged from all the fuel cell stacks 10- (1) to 10- (N) that generate power by supplying only the unreacted fuel gas is unreacted fuel gas discharge path 4- (1 ) To 4- (N) through the connection flow paths 6- (1) to 6- (N-1), the unreacted fuel gas circulation of the other fuel cell stacks 10- (1) to 10- (N) that generate electricity Among the fuel cell stacks 10- (1) to 10- (N) that generate power by the transfer means 7- (1) to 7- (N) installed in the paths 5- (1) to 5- (N). Fuel cell stack 10- (1) to supply a first predetermined amount of fuel gas by fuel gas supply units 2- (1) to 2- (N) Fuel cell stacks 10- (1) to 10- (N) other than 0- (N) are supplied to the fuel gas supply paths 3- (1) to 3- (N) to generate other power. (1) It is used for power generation of 10- (N).

  Here, in the fuel cell stacks 10- (1) to 10- (N) in which the third predetermined amount of fuel gas is supplied by the fuel gas supply units 2- (1) to 2- (N), other fuel cell stacks In the controller 11, the unreacted fuel gas for 10- (1) to 10- (N) is supplied by the unloading means 7- (1) to 7- (N) so as to be used for power generation. Control. The supply amount is the fifth predetermined amount.

  In the fuel cell stacks 10- (1) to 10- (N) in which the second predetermined amount of fuel gas is supplied by the fuel gas supply units 2- (1) to 2- (N), the other fuel cell stacks 10 -Fuel that supplies a second predetermined amount of fuel gas in the fuel gas supply units 2- (1) to 2- (N) in addition to the unreacted fuel gas for one of (1) to 10- (N) The unreacted fuel gas discharged by the battery stack 10- (1) to 10- (N) itself is supplied by the unloading means 7- (1) to 7- (N) so as to be used for power generation, and the supply amount ( The fourth predetermined amount) is controlled by the controller 11 so that the ratio of the unreacted fuel gas in the fuel gas used for power generation is greater than the fifth predetermined amount.

  On the other hand, when power is generated by one fuel cell stack 10- (1) to 10- (N), the unreacted fuel gas discharged from the fuel cell stack 10- (1) to 10- (N) to be generated is The fuel cell stack 10- (1) that generates power through the unreacted fuel gas circulation paths 5- (1) to 5- (N) corresponding to the fuel cell stacks 10- (1) to 10- (N) that generate power 10- (N) corresponds to the fuel cell stacks 10- (1) to 10- (N) that generate power so as to be supplied to the fuel gas supply paths 3- (1) to 3- (N) corresponding to The fuel gas supply units 2- (1) to 2- (N) supply a third predetermined amount of fuel gas and transfer means 7 corresponding to the fuel cell stacks 10- (1) to 10- (N) that generate power. In (1) to 7- (N), the controller 11 controls so as to supply the fifth predetermined amount of unreacted gas. To.

  Here, the fuel gas amount at the inlet portion of the fuel cell stack 10- (1) to 10- (N) is 10 L / min, and the fuel cell stack 10- in the fuel cell stack 10- (1) to 10- (N) is used. When the average fuel utilization rate Uf of (1) to 10- (N) is P (%), the amount of fuel gas used in the fuel cell stacks 10- (1) to 10- (N) is (P / 10 ) L / min, the amount of unreacted fuel gas at the exit portion of the fuel cell stack 10- (1) to 10- (N) is 10- (P / 10) L / min.

  Accordingly, the unreacted fuel to be supplied in the fuel cell stacks 10- (1) to 10- (N) in which the first predetermined amount of fuel gas is supplied by the fuel gas supply units 2- (1) to 2- (N). Since there is no gas, the amount (first predetermined amount) supplied by the fuel gas supply units 2- (1) to 2- (N) is 10 L / min.

  In the fuel cell stacks 10- (1) to 10- (N) in which the third predetermined amount of fuel gas is supplied by the fuel gas supply units 2- (1) to 2- (N), another fuel cell stack 10- ( 1) Since the unreacted fuel gas discharged from 10- (N) is supplied to the fuel gas supply paths 3- (1) to 3- (N), the fuel gas supply units 2- (1) to 2- The amount (third predetermined amount) supplied in (N) is first predetermined amount−fifth predetermined amount = 10− (10− (P / 10)) = P / 10 L / min.

In the fuel cell stacks 10- (1) to 10- (N) in which the second predetermined amount of fuel gas is supplied by the fuel gas supply units 2- (1) to 2- (N), another fuel cell stack 10- ( 1) Fuel that supplies unreacted fuel gas (fifth predetermined amount) and second predetermined amount of fuel gas discharged from 10- (N) by the fuel gas supply units 2- (1) to 2- (N) Since the unreacted fuel gas discharged from the battery stacks 10- (1) to 10- (N) itself is supplied to the fuel gas supply paths 3- (1) to 3- (N), the fuel gas supply unit 2- The amount (second predetermined amount) supplied by (1) to 2- (N) is the first predetermined amount-the fifth predetermined amount- (the second predetermined amount of fuel gas is supplied to the fuel gas supply unit 2- (1)- 2- (N) supplied fuel cell stack 10- (1) to 10- (N) unreacted fuel gas amount) = 10− (10− (P / 10) ) - (10- (P / 10)) = 2 × (P / 10) -10L / min, and it becomes smallest.

  Further, the transport means 7- (1) of the fuel cell stacks 10- (1) to 10- (N) for supplying the second predetermined amount of fuel gas by the fuel gas supply units 2- (1) to 2- (N). The flow rate (fourth predetermined amount) of the unreacted fuel gas supplied at ˜7- (N) is: fourth predetermined amount = fifth predetermined amount + (second predetermined amount of fuel gas is supplied to the fuel gas supply unit 2- ( 1) to 2- (N) supplied fuel cell stack 10- (1) to 10- (N) unreacted fuel gas amount) = 10− (P / 10) + 10− (P / 10) = 20−2 × (P / 10) L / min, and the fourth predetermined amount> the fifth predetermined amount.

  From the above, the amount of fuel gas supplied to all the fuel cell stacks 10- (1) to 10- (N) that generate electricity is equal to the number of fuel cell stacks 10- (1) to 10- (N) that generate electricity. In the case of a table, first predetermined amount + second predetermined amount + third predetermined amount × (Q−2) = 10 + 2 × (P / 10) −10+ (P / 10) × (Q−2) = Q × (P / 10).

  Therefore, when the number of fuel cell stacks 10- (1) to 10- (N) that generate power in the fuel cell system 100 is Q, the fuel utilization rate Ufs of the fuel cell system 100 can be expressed by the following (Equation 3). .

以上のように、本実施の形態の燃料電池システム１００では、燃料電池スタック１０−（１）〜１０−（Ｎ）の排出した未反応燃料ガスを再び燃料として利用するため、燃料電池システム１００の燃料利用率Ｕｆｓは１００％となり、Ｕｆの値に影響されることなく高い燃料利用率の燃料電池システム１００を提供することができる。

As described above, in the fuel cell system 100 according to the present embodiment, the unreacted fuel gas discharged from the fuel cell stacks 10- (1) to 10- (N) is used again as fuel. The fuel utilization rate Ufs is 100%, and the fuel cell system 100 with a high fuel utilization rate can be provided without being affected by the value of Uf.

  Note that when the fuel cell system 100 is operated, the fuel cell stacks 10- (1) to 10- (N) that generate power so that all the fuel cell stacks 10- (1) to 10- (N) can generate electric power at the same time. ) And switching the fuel cell stacks 10- (1) to 10- (N) that generate power at regular intervals, for example, some fuel cell stacks 10- (1) to 10- (N ) Can be prevented, and the life of the fuel cell system 100 can be extended.

  A more specific example of this embodiment will be described with reference to FIG. FIG. 2 is a block diagram of a fuel cell system including five fuel cell stacks according to Embodiment 1 of the present invention. In FIG. 2, the fuel cell system 200 shows a configuration for N = 5.

  In FIG. 2, the same components as those in FIG. 1 are denoted by the same reference numerals, and redundant description is omitted here.

  Among the fuel cell stacks 10- (1), 10- (2), 10- (3), 10- (4), 10- (5), 10- (2), 10- (4) 10- (5), and the average fuel utilization rate Uf of the fuel cell stacks 10- (2), 10- (4), 10- (5) is 80%. Fuel gas supply units 2- (1), 2- (3) and conveying means 7- (1), 7- (2), 7- (corresponding to the fuel cell stacks 10- (1), 10- (3) 3), gas is not supplied, and the amount of fuel gas at the entrance of the fuel cell stack 10- (2), 10- (4), 10- (5) is 10 L / min.

  At this time, since the amount of fuel gas consumed by the fuel cell stacks 10- (2), 10- (4), 10- (5) is 8 L / min, the fuel cell stacks 10- (2), 10- ( 4) The amount of unreacted fuel gas discharged from 10- (5) is 2 L / min.

  Therefore, the fuel gas is supplied at 10 L / min by the fuel gas supply unit 2- (2), and the unreacted fuel gas discharged through the fuel cell stack 10- (2) is connected to the connection paths 6- (2), 6- (3), the unreacted fuel gas circulation path 5- (4), the unreacted fuel gas of 2 L / min is transferred to the fuel cell stack 10- (4) by the transfer means 7- (4). 3-Supply to (4).

  The fuel gas supply unit 2- (4) supplies the fuel gas at 8 L / min. Thus, 10 ml / min of fuel gas can be supplied to the fuel cell stack 10- (4) together with the unreacted fuel gas of 2 ml / min. The unreacted fuel gas 2L / min discharged from the fuel cell stack 10- (4) passes through the unreacted fuel exhaust gas path 4- (4), passes through the connection path 6- (4), and passes through the unreacted fuel gas circulation path. 5- (5).

  On the other hand, the unreacted fuel gas 2 min / min discharged from the fuel cell stack 10- (5) is supplied to the unreacted fuel gas circulation path 5- (5) through the unreacted fuel exhaust gas path 4- (5). The

  Therefore, the unreacted fuel gas circulation path 5- (5) is supplied with the unreacted fuel exhaust gas from the two fuel cell stacks 10- (4) and 10- (5). -The amount of unreacted fuel gas supplied in (5) is 4 L / min, and the amount of fuel gas supplied in the fuel gas supply unit 2- (5) is 10-4 = 6 L / min.

  From the above, the amount of fuel gas supplied to the fuel cell system 200 is 10 + 8 + 6 = 24 L / min. In the fuel cell stacks 10- (2), 10- (4), and 10- (5), the total is 8 × 3 = 24 L / min. In the fuel cell system 200, the fuel utilization rate Ufs of the fuel cell system is 24/24. × 100 = 100%. Compared with 80%, which is the average fuel utilization rate Uf of the fuel cell stack, as the fuel cell system 200, the fuel utilization rate Ufs of the fuel cell system is increased by 20%.

As described above, in this embodiment, the fuel utilization rate Ufs of the fuel cell system 200 is set higher than the fuel utilization rates Uf of the fuel cell stacks 10- (2), 10- (4), and 10- (5). it can. In addition, when the fuel cell stack 10- (1), 10- (2), 10- (3), 10- (4), 10- (5) configured in the fuel cell system 200 is generated with a small number of units. When the fuel cell stack to be generated is switched so as to switch based on the power generation time, a plurality of fuel cell stacks 10- (1), 10- (2), 10- (3), 10- (4), 10- (
Since the power generation time of 5) can be made substantially uniform, the fuel cell stacks 10- (1), 10- (2), 10- (3), 10- (4) configured in the fuel cell system 200, The durability time 10- (5) becomes uniform, and the durability (durability time) of the fuel cell system 200 can be improved.

  As described above, the fuel cell system according to the present invention is configured to supply the fuel gas to another fuel cell stack after the unreacted fuel gas of the fuel cell stack is merged with the fuel gas from the fuel gas supply source. This makes it possible to use the unreacted fuel gas that has been exhausted as a part of the fuel cell stack, reduce the loss of fuel gas used for power generation, and operate with high power generation efficiency. This is useful as a fuel cell system capable of providing the same.

1 Fuel gas supply source 2- (1) to 2- (N) Fuel gas supply unit 3- (1) to 3- (N) Fuel gas supply path 4- (2) to 4- (N) Unreacted fuel gas Discharge route 5- (1) to 5- (N) Unreacted fuel gas circulation route 6- (1) to 6- (N-1) Connection route 7- (1) to 7- (N) Conveying means 10- ( 1) to 10- (N) Fuel cell stack 11 Controller 100, 200, 300 Fuel cell system

Claims (2)

First to Nth (N is an integer greater than or equal to 2) fuel cell stacks that generate power by reacting fuel gas and oxidant;
First to Nth fuel gas supply paths for supplying the fuel gas to the first to Nth fuel cell stacks;
A first to Nth fuel gas supply unit that is provided on the first to Nth fuel gas supply paths and supplies a predetermined amount of fuel gas to the first to Nth stacks;
First to Nth unreacted fuel gas discharge paths for discharging unreacted fuel gas from the first to Nth fuel cell stacks;
K-th unreacted fuel having K-th conveying means for supplying the unreacted fuel gas from the K-th unreacted fuel gas discharge path (K is an integer of 1 ≦ K ≦ N) to the K-th fuel gas supply path. A fuel gas circulation path;
An Mth connection path connecting the Mth unreacted fuel gas discharge path (M is an integer of 1 ≦ M ≦ N−1) and the M + 1th unreacted fuel gas circulation path;
A fuel cell system comprising: A controller for controlling the first to Nth fuel gas supply units and the first to Nth transport means;
The controller is
Stop the supply of the fuel gas at the fuel gas supply unit corresponding to the fuel cell stack that does not generate power among the first to Nth fuel cell stacks,
The amount of fuel gas supplied by the fuel gas supply unit corresponding to any one fuel cell stack among the fuel cell stacks that generate electric power among the first to Nth fuel cell stacks is set as a first predetermined amount,
The amount of fuel gas supplied by the fuel gas supply unit corresponding to another arbitrary one of the fuel cell stacks to generate power is set as a second predetermined amount,
Among the fuel cell stacks that generate power, a fuel cell stack that supplies the first predetermined amount of fuel gas by a fuel gas supply unit, and a fuel cell stack that supplies the second predetermined amount of fuel gas by a fuel gas supply unit The amount of fuel gas supplied by the fuel gas supply unit corresponding to the fuel cell stack except for the third and second fuel amounts is a third predetermined amount, and the relationship between the predetermined amounts is as follows: first predetermined amount> third predetermined amount> second predetermined amount ,
The unreacted fuel gas is not supplied by the transport means corresponding to the fuel cell stack that does not generate electricity and the fuel cell stack that supplies the first predetermined amount of fuel gas at the fuel gas supply unit,
The amount of unreacted fuel gas supplied by the conveying means corresponding to the fuel cell stack that supplies the second predetermined amount of fuel gas at the fuel gas supply unit is set as a fourth predetermined amount,
The amount of unreacted fuel gas supplied by the transport means corresponding to the fuel cell stack that supplies the third predetermined amount of fuel gas by the fuel gas supply unit is a fifth predetermined amount that is smaller than the fourth predetermined amount. The fuel cell system according to claim 1, wherein:

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