JP2019169368A - Fuel battery system - Google Patents

Abstract

To provide a fuel battery system capable of controlling a generation amount of drain water.SOLUTION: A fuel battery system 10 comprises: a reformer 14 for performing water vapor reforming on raw material gas to generate fuel gas; a fuel battery (fuel battery cell stack 22) for making the fuel gas supplied from the reformer 14 react with oxidation gas to generate power; a separation membrane 26C for making water vapor move to sweep gas from off-gas discharged from the fuel battery; a water tank 32 to which the water vapor moved to the sweep gas or condensed water obtained by condensing water vapor is to be input; and a control device 68 for adjusting at least one of an amount of water vapor or an amount of condensed water to be input to the water tank 32 to keep an amount of water in the tank within a predetermined range.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fuel cell system.

  Patent Document 1 listed below discloses a multistage fuel cell system that generates a fuel gas containing hydrogen by steam reforming a raw material gas. The multistage fuel cell system includes a water vapor separation membrane that separates water vapor from off-gas discharged from the first fuel cell. The water vapor separated by the water vapor separation membrane is condensed and stored in a water tank.

JP-A-2006-115495

  In the multistage fuel cell system described in Patent Document 1, when a predetermined amount or more of water has accumulated in the water tank, this water is drained from the drain pipe. That is, in order to drain water from the water tank, it is necessary to provide a drain pipe for drainage.

  An object of the present invention is to provide a fuel cell system capable of controlling the amount of drain water generated in consideration of the above facts.

  The fuel cell system according to claim 1 is a fuel that performs power generation by reacting a raw material gas with steam reforming to produce a fuel gas, and a reaction between the fuel gas produced in the reforming unit and an oxidizing gas. A battery, a separation membrane that moves water vapor from the off-gas discharged from the fuel cell to a sweep gas, and the water vapor that has been moved to the sweep gas or condensed water that is condensed with the water vapor are used as water to be used in the system. A water tank to be stored; and a control device that adjusts at least one of the amount of water vapor and the amount of condensed water charged into the water tank and maintains the amount of water in the water tank within a predetermined range.

  According to the fuel cell system of claim 1, the control device adjusts at least one of the amount of water vapor and the amount of condensed water charged into the water tank. For example, when the amount of water in the water tank reaches a predetermined upper limit value, the amount of water vapor or condensed water introduced into the water tank is reduced. As a result, the amount of water in the water tank can be maintained within a predetermined range, and drainage from the water tank can be reduced.

  The “reforming part” refers to both a reformer provided separately from the fuel cell and a part where a reforming reaction is performed in the fuel cell. The “condensed water” charged into the water tank is, for example, water (liquid phase) condensed by cooling water vapor on the upstream side of the water tank. Further, “water vapor” charged into the water tank is water (gas layer) that is not condensed on the upstream side of the water tank and maintains a gaseous state.

  The fuel cell system according to claim 2 is a fuel that generates electric power by reacting a reforming section that generates a fuel gas by steam reforming a raw material gas, and the fuel gas and the oxidizing gas supplied from the reforming section. A battery, a separation membrane for moving water vapor from off gas discharged from the fuel cell to a sweep gas, a water tank in which condensed water condensed from the water vapor moved to the sweep gas is stored as water used in the system, Adjusting the amount of condensed water discharged from the water tank to the water supply pipe by adjusting a water supply pipe for supplying the condensed water stored in the water tank to the reforming unit via a vaporizer; And a control device for maintaining the amount of water in the tank within a predetermined range.

  According to the fuel cell system of claim 2, the control device adjusts the amount of condensed water discharged from the water tank to the water supply pipe. For example, when the amount of water in the water tank reaches a predetermined upper limit, the amount of condensed water discharged from the water tank to the water supply pipe is increased. As a result, the amount of water in the water tank can be maintained within a predetermined range, and drainage from the water tank can be reduced.

  A fuel cell system according to claim 3 is the fuel cell system according to claim 1 or 2, wherein a reseparation membrane that moves the water vapor from the sweep gas to the source gas upstream of the water tank, and a transfer to the source gas A steam supply path for supplying the steam to the reforming section.

  According to the fuel cell system of claim 3, the water vapor moves from the sweep gas to the raw material gas by the reseparation membrane. Further, the raw material gas and the water vapor are supplied to the reforming section through the water vapor supply path. Thereby, the water vapor is supplied to the reforming section without being condensed and consumed by the reforming reaction. For this reason, compared with the case where water vapor | steam is condensed, the calorie | heat amount for re-evaporating the condensed water is unnecessary, and energy efficiency is high.

  A fuel cell system according to a fourth aspect is the fuel cell system according to any one of the first to third aspects, further comprising a sweep gas flow rate adjusting mechanism for adjusting a flow rate of the sweep gas supplied to the separation membrane. The control device controls the sweep gas flow rate adjusting mechanism to adjust the amount of water vapor introduced into the water tank.

  According to the fuel cell system of claim 4, the control device adjusts the flow rate of the sweep gas supplied to the separation membrane. For example, when the amount of water in the water tank reaches a predetermined upper limit, the flow rate of the sweep gas supplied to the separation membrane is reduced. As a result, the amount of water vapor transferred from the off gas to the sweep gas is reduced, and the amount of water vapor introduced into the water tank is reduced. In this way, the amount of water vapor introduced into the water tank can be easily adjusted simply by adjusting the flow rate of the sweep gas.

  The fuel cell system according to claim 5 is the fuel cell system according to any one of claims 1 to 4, further comprising a bypass valve for discharging the sweep gas without passing through the water tank, The control device controls the bypass valve to adjust the amount of water vapor introduced into the water tank.

  According to the fuel cell system of the fifth aspect, the control device controls the bypass valve for discharging the sweep gas without going through the water tank. For example, when the amount of water in the water tank reaches a predetermined upper limit value, the bypass valve is opened and the sweep gas containing water vapor is discharged out of the system. This reduces the amount of water vapor charged into the water tank. In this way, the amount of water vapor introduced into the water tank can be adjusted with a simple structure provided with a bypass valve.

  The fuel cell system according to claim 6 is the fuel cell system according to any one of claims 1 to 5, wherein the sweep gas is cooled in the upstream side of the water tank or in the water tank, and the water vapor. The control device controls the cooling mechanism to adjust the amount of condensed water charged into the water tank.

  According to the fuel cell system of the sixth aspect, the control device controls the cooling mechanism for condensing water vapor by cooling the sweep gas in the upstream side of the water tank or in the water tank. For example, when the amount of water in the water tank reaches a predetermined upper limit value, the cooling function is suppressed to reduce the amount of condensation of water vapor contained in the sweep gas. Thereby, the amount of condensed water thrown into the water tank can be reduced.

  The fuel cell system according to claim 7 is the fuel cell system according to claim 1 or 2, wherein the sweep gas is a raw material gas, and one of the water vapor is changed from the raw material gas to the re-sweep gas upstream of the water tank. A re-separation membrane for moving the part, and a raw material gas supply path for supplying the raw material gas in which a part of the water vapor has moved to the re-sweep gas to the reforming part.

  According to the fuel cell system of the seventh aspect, a part of the water vapor that has moved from the off gas discharged from the fuel cell to the raw material gas as the sweep gas moves to the re-sweep gas by the re-separation membrane. Thereby, water vapor | steam required for a reforming reaction remains, and excess water vapor | steam can be removed from raw material gas.

  The fuel cell system according to claim 8 is the fuel cell system according to claim 7, further comprising a re-sweep gas flow rate adjusting mechanism for adjusting a flow rate of the re-sweep gas supplied to the re-separation membrane, and the control device includes: The re-sweep gas flow rate adjusting mechanism is controlled to adjust the amount of water vapor introduced into the water tank.

  According to the fuel cell system of the eighth aspect, the control device adjusts the flow rate of the re-sweep gas supplied to the separation membrane. For example, when the amount of water in the water tank reaches a predetermined upper limit, the flow rate of the re-sweep gas supplied to the separation membrane is reduced. As a result, the amount of water vapor transferred from the source gas to the re-sweep gas is reduced, and the amount of water vapor introduced into the water tank is reduced. In this way, the amount of water vapor introduced into the water tank can be easily adjusted simply by adjusting the flow rate of the re-sweep gas.

  A fuel cell system according to claim 9 is the fuel cell system according to claim 7 or 8, further comprising a bypass valve for discharging the re-sweep gas without passing through the water tank, A bypass valve is controlled to adjust the amount of water vapor introduced into the water tank.

  According to the fuel cell system of the ninth aspect, the control device controls the bypass valve for discharging the re-sweep gas without going through the water tank. For example, when the amount of water in the water tank reaches a predetermined upper limit, the bypass valve is opened and the re-sweep gas containing water vapor is discharged out of the system. This reduces the amount of water vapor charged into the water tank. In this way, the amount of water vapor introduced into the water tank can be adjusted with a simple structure provided with a bypass valve.

  The fuel cell system according to claim 10 is the fuel cell system according to any one of claims 7 to 9, wherein the re-sweep gas is cooled in an upstream side of the water tank or in the water tank. A cooling mechanism for condensing water vapor is provided, and the control device controls the cooling mechanism to adjust the amount of condensed water charged into the water tank.

  According to the fuel cell system of the tenth aspect, the control device controls the cooling mechanism for condensing the water vapor by cooling the re-sweep gas in the upstream side of the water tank or in the water tank. For example, when the amount of water in the water tank reaches a predetermined upper limit value, the cooling function is suppressed to reduce the amount of condensation of water vapor contained in the re-sweep gas. Thereby, the amount of condensed water thrown into the water tank can be reduced.

  The fuel cell system according to claim 11 is the fuel cell system according to any one of claims 1 to 10, wherein a water level sensor is provided in the water tank, and the control device includes the water level sensor. Based on the information from the above, the amount of water in the water tank is maintained within a predetermined range.

  According to the fuel cell system of the eleventh aspect, since the water level sensor is provided in the water tank, the water level of the water tank can be accurately measured. It is easy to maintain the amount of water in the water collecting tank within a predetermined range.

  A fuel cell system according to a twelfth aspect of the present invention is the fuel cell system according to any one of the first to eleventh aspects, further comprising a raw material gas flow rate adjusting mechanism for adjusting an input amount of the raw material gas, and the control device includes: The power generation amount is adjusted by controlling the raw material gas flow rate adjusting mechanism.

  According to the fuel cell system of the twelfth aspect, the control device can control the raw material gas flow rate adjusting mechanism to control the input amount of the raw material gas. For example, when the amount of water in the water tank reaches a predetermined upper limit value, the input amount of the raw material gas is reduced to reduce the power generation amount. As a result, the generation of water vapor accompanying the power generation reaction is suppressed, and the amount of water vapor introduced into the water tank is reduced.

  A fuel cell system according to a thirteenth aspect is the fuel cell system according to any one of the first to twelfth aspects, wherein power is generated by reacting an unreacted fuel gas and an oxidizing gas contained in the off gas. A rear fuel cell is provided, and the control device controls the power generation amount of at least one of the fuel cell and the rear fuel cell to adjust the amount of water vapor introduced into the water tank.

  According to the fuel cell system of the thirteenth aspect, the control device controls the power generation amount of at least one of the fuel cell and the rear fuel cell. For example, when the amount of water in the water tank reaches a predetermined upper limit value, the power generation amount in the fuel cell is reduced, and the generation amount of off-gas and water vapor contained in the off-gas is reduced. In addition, the power generation amount in the rear fuel cell is increased, and the reduction in the power generation amount of the entire fuel cell system is suppressed. Thereby, the amount of water vapor introduced into the water tank can be reduced.

  A fuel cell system according to a fourteenth aspect is the fuel cell system according to the thirteenth aspect, wherein the rear-stage fuel cell is disposed on the downstream side of the water tank.

  According to the fuel cell system of the fourteenth aspect, the control device can maintain the power generation amount of the entire system by reducing the power generation amount in the fuel cell and simultaneously increasing the power generation amount of the subsequent fuel cell.

  According to the fuel cell system of the present invention, the amount of drain water generated can be controlled.

1 is a block diagram illustrating an example of an overall configuration of a fuel cell system according to a first embodiment of the present invention. It is a block diagram which shows an example of the whole structure of the fuel cell system which concerns on 2nd Embodiment of this invention. It is a block diagram which shows an example of the whole structure of the fuel cell system which concerns on 3rd Embodiment of this invention. It is a block diagram which shows an example of the whole structure of the fuel cell system which concerns on 4th Embodiment of this invention.

[First Embodiment]
<Fuel cell system>
As shown in FIG. 1, the fuel cell system 10 according to the first embodiment of the present invention includes a vaporizer 12, a reformer 14, a combustor 16, a first fuel cell stack 22, and a second fuel cell stack 24. , A fuel regenerator 26, water tanks 32 and 34, flow dividing valves 42A, 42B, 44A and 44B, cooling mechanisms 52 and 54, pumps 62 and 64, flow rate adjusting mechanisms 66 and 67, and a control device 68.

(Vaporizer)
The vaporizer 12 is connected to one end of a source gas pipe P1, which is a pipe through which source gas flows. A flow rate adjusting mechanism 67 that adjusts the flow rate of the raw material gas supplied to the vaporizer 12 is provided in the middle of the raw material gas pipe P1. As the flow rate adjustment mechanism 67, a flow rate adjustment valve is used as an example.

  In addition, one end of a water supply pipe P2, which is a pipe through which water flows, is connected to the vaporizer 12, and the other end side of the water supply pipe P2 branches into two flow paths P2A and P2B, respectively. The tanks 32 and 34 are connected. Water is stored in the water tanks 32 and 34.

  The pumps 62 and 64 pump water from the water tanks 32 and 34 through the water supply pipe P2. The pumps 62 and 64 supply the water to the vaporizer 12 by sending the pumped water to the vaporizer 12 through the water supply pipe P2.

  The vaporizer 12 vaporizes the water supplied from the water supply pipe P2. For the vaporization, heat from the combustor 16 or the like is used.

  The vaporizer 12 supplies the raw material gas and water vapor to the reformer 14 by sending the raw material gas and water vapor to the reformer 14 through the pipe P3.

(Reformer)
The reformer 14 generates a reformed gas by steam reforming the raw material gas. One end of a pipe P3 is connected to the reformer 14. As a result, the raw material gas and the water vapor are supplied to the reformer 14 through the pipe P3.

When methane, which is an example of a raw material gas, is steam reformed in the reformer 14, carbon monoxide and hydrogen are generated by the reaction of the following formula (1).
CH ₄ + H ₂ O → CO + 3H ₂ (1)

Furthermore, when carbon monoxide is shift-reformed, hydrogen and carbon dioxide are generated by the reaction of the following formula (2).
CO + H ₂ O → H ₂ + CO ₂ (2)

  In the present embodiment, methane is adopted as an example of the raw material gas. However, the gas is not particularly limited as long as it can be reformed, and a hydrocarbon fuel can be used. Examples of the hydrocarbon fuel include natural gas, LP gas (liquefied petroleum gas), coal reformed gas, lower hydrocarbon gas, and the like. Examples of the lower hydrocarbon gas include lower hydrocarbons having 4 or less carbon atoms such as methane, ethane, ethylene, propane, and butane, and methane used in the present embodiment is preferable. The hydrocarbon fuel may be a mixture of the above-described lower hydrocarbon gas, and the above-mentioned lower hydrocarbon gas is a gas such as natural gas, city gas, LP gas, biogas, etc. Also good. Further, the raw material gas may be a mixed gas thereof.

  One end of a reformed gas supply pipe P4 is connected to the reformer 14. The other end of the reformed gas supply pipe P4 is connected to an anode (not shown) in the first fuel cell stack 22. As a result, the reformed gas generated in the reformer 14 is supplied to the first fuel cell stack 22 through the reformed gas supply pipe P4. The reformed gas contains unreacted methane, carbon dioxide generated by the reformer 14, hydrogen, unreacted carbon monoxide, water vapor, and the like.

(Fuel battery cell stack)
The first fuel cell stack 22 is a solid oxide fuel cell stack, for example, and has a plurality of stacked fuel cells (not shown). Each fuel cell has an electrolyte layer, and a cathode and an anode laminated on the front and back surfaces of the electrolyte layer, respectively. The first fuel cell stack 22 may be a dissolved carbonate type fuel cell stack.

  One end of an oxidizing gas pipe P5, which is a pipe through which oxidizing gas flows, is connected to the cathode of the first fuel cell stack 22. An oxidizing gas (for example, air) is supplied to the cathode via the oxidizing gas pipe P5. At the cathode, as shown in the following formula (3), oxygen in the oxidizing gas reacts with electrons to generate oxygen ions. The generated oxygen ions reach the anode through the electrolyte layer.

1 / 2O ₂ + 2e ⁻ → O ²⁻ (3)

  On the other hand, in the anode, as shown in the following formulas (4) and (5), oxygen ions that have passed through the electrolyte layer react with hydrogen and carbon monoxide, which are fuel gases in the reformed gas, and water ( Steam), carbon dioxide and electrons are produced. Electrons generated at the anode move from the anode to the cathode through an external circuit, thereby generating power in each fuel cell. Each fuel cell generates heat during power generation.

H ₂ + O ²⁻ → H ₂ O + 2e ⁻ (4)

CO + O ²⁻ → CO ₂ + 2e ⁻ (5)

  One end of an anode offgas pipe P6 that is a pipe through which anode offgas flows is connected to the anode of the first fuel cell stack 22, and the anode offgas is discharged to the anode offgas pipe P6. The anode off gas contains unreacted hydrogen, unreacted carbon monoxide, carbon dioxide, water vapor, and the like.

  One end of a cathode offgas pipe P7 that is a pipe through which the cathode offgas flows is connected to the cathode of the first fuel cell stack 22, and the cathode offgas is discharged to the cathode offgas pipe P7. The cathode off gas contains unreacted oxidizing gas and the like.

  The other end of the anode off gas pipe P6 is connected to the inflow portion 26A of the fuel regenerator 26, and the other end of the cathode off gas pipe P7 is connected to the cathode (not shown) of the second fuel cell stack 24.

  The configuration of the second fuel cell stack 24 is the same as that of the first fuel cell stack 22 and will not be described in detail. However, as described above, the cathode of the second fuel cell stack 24 is connected to the cathode offgas pipe P7. Are connected at one end. Further, one end of a regeneration gas pipe P8 described later is connected to the anode of the second fuel cell stack 24.

  Furthermore, one end of a cathode offgas pipe P11 that is a pipe through which the cathode offgas flows is connected to the cathode of the second fuel cell stack 24, and the cathode offgas is discharged to the cathode offgas pipe P11. The cathode off gas contains unreacted oxidizing gas and the like, and the cathode off gas is supplied to the combustor 16 via the cathode off gas pipe P11.

  One end of an anode offgas pipe P13 that is a pipe through which the anode offgas flows is connected to the anode of the second fuel cell stack 24, and the anode offgas is discharged to the anode offgas pipe P13. The anode off gas contains unreacted hydrogen, unreacted carbon monoxide, carbon dioxide, water vapor, and the like, and the anode off gas is supplied to the combustor 16 through the anode off gas pipe P13.

(Fuel regenerator)
The fuel regenerator 26 includes an inflow portion 26A and a permeation portion 26B, and the inflow portion 26A and the permeation portion 26B are partitioned by a separation membrane 26C.

  The anode off gas discharged from the anode of the first fuel cell stack 22 flows into the inflow portion 26A via the anode off gas pipe P6.

  The air supplied from the oxidizing gas pipe P9 branched from the oxidizing gas pipe P5 flows into the permeation portion 26B as a sweep gas. Thereby, the partial pressure of the water vapor in the permeation part 26B is lowered, and the water vapor easily passes through the separation membrane 26C from the inflow part 26A and moves to the permeation part 26B. One end of a pipe P10 is connected to the transmission part 26B. The sweep gas is sent from the permeation section 26B to the pipe P10 as permeation section exhaust gas together with the water vapor that has passed through the separation membrane 26C.

  A flow rate adjusting mechanism 66 that adjusts the flow rate of air supplied to the fuel regenerator 26 is provided in the middle of the oxidizing gas pipe P9. The flow rate adjusting mechanism 66 is configured using, for example, a flow rate adjusting valve.

  The gas from which water vapor or the like has been removed in the inflow portion 26A flows into the anode of the second fuel cell stack 24 as a regeneration gas via the regeneration gas pipe P8.

(Combustor)
The combustor 16 uses the used gas supplied from the cathode and anode of the second fuel cell stack 24 for incineration. One end of an exhaust pipe P12 is connected to the combustor 16, and exhaust gas after combustion is sent to the exhaust pipe P12. A midway portion of the exhaust pipe P12 is disposed in the vaporizer 12, and in the vaporizer 12, water is vaporized by the heat of the exhaust pipe P12.

(water tank)
The permeate portion exhaust gas (sweep gas) sent from the permeate portion 26B of the fuel regenerator 26 flows into the water tank 32 via the pipe P10. The other end side of the pipe P10 having one end connected to the transmission part 26B is branched into two flow paths P10A and P10B. A flow dividing valve 42A and a cooling mechanism 52 are provided in the flow path P10A, and an end of the flow path P10A is inserted into the water tank 32. The cooling mechanism 52 is provided downstream of the flow dividing valve 42A. The flow path P10B is provided with a flow dividing valve 42B, and the end of the flow path P10B is open to the outside air. Furthermore, the other end of the flow path P10C having one end inserted into the water tank 32 is connected to the flow path P10B. The diversion valves 42A and 42B are examples of bypass valves in the present invention.

  Inside the water tank 32, a water level sensor 32S is provided. The water level sensor 32S can detect the water level in the water tank 32 in order to maintain the amount of water in the water tank 32 within the range of the predetermined upper limit value and lower limit value. In the water tank 32, an end portion of the flow path P2A in the water supply pipe P2 is connected below the lower limit position of the water level. The water supply pipe P2 sends the water in the water tank 32 to the vaporizer 12 when the pump 62 is driven. The lower ends of the flow paths P10A and P10C are disposed above the upper limit of the water level of the water level sensor 32S.

  The predetermined lower limit value in the water level sensor 32S is appropriately determined depending on, for example, the amount of reforming water required when starting up the fuel cell system 10 and the amount of reforming water required when increasing the power generation amount.

  Similarly, the exhaust gas sent from the combustor 16 flows into the water tank 34 through the exhaust pipe P12. The other end of the exhaust pipe P12 whose one end is connected to the combustor 16 is branched into two flow paths P12A and P12B. The flow path P12A is provided with a flow dividing valve 44A and a cooling mechanism 54, and an end of the flow path P12A is inserted into the water tank 34. The cooling mechanism 54 is provided downstream of the flow dividing valve 44A. The flow path P12B is provided with a diversion valve 44B, and the end of the flow path P12B is open to the outside air. Furthermore, the other end of the flow path P12C having one end inserted into the water tank 34 is connected to the flow path P12B.

  Inside the water tank 34, a water level sensor 34S is provided. The water level sensor 34S can detect the water level in the water tank 34 in order to maintain the amount of water in the water tank 34 within the range of the predetermined upper limit value and lower limit value. In the water tank 34, the end of the flow path P2B in the water supply pipe P2 is connected below the lower limit of the water level. The water supply pipe P2 sends the water in the water tank 34 to the vaporizer 12 when the pump 64 is driven.

(Cooling mechanism)
The cooling mechanism 52 is a device that cools the permeate exhaust gas (sweep gas) flowing through the flow path P10A in the pipe P10, and is a heat exchanger as an example. In the water tank 32, water obtained by condensation by the cooling operation when the cooling mechanism 52 is driven is discharged and stored. For example, the cooling mechanism 52 heat-exchanges the oxidizing gas flowing through the oxidizing gas pipe P5 and the permeated portion exhaust gas flowing through the flow path P10A to cool the permeated portion exhaust gas.

  Similarly, the cooling mechanism 54 is a heat exchanger that cools the exhaust gas flowing through the flow path P12A in the exhaust pipe P12. In the water tank 34, the water obtained by condensation by the cooling operation when the cooling mechanism 54 is driven is discharged and stored. The cooling mechanism 54 cools the exhaust gas, for example, by exchanging heat between the source gas flowing through the source gas pipe P1 and the exhaust gas flowing through the flow path P12A.

(Control device)
The control device 68 includes a first fuel cell stack 22, a second fuel cell stack 24, water level sensors 32S and 34S, flow dividing valves 42A, 42B, 44A and 44B, cooling mechanisms 52 and 54, pumps 62 and 64, and flow rate adjustment. It is electrically connected to the mechanisms 66 and 67. The control device 68 and the first fuel cell stack 22 are connected via a power conditioner that controls current and the like. The same applies to the control device 68 and the second fuel cell stack 24.

  The control device 68 controls the flow rate adjusting mechanism 66 based on the water level information of the water tanks 32 and 34 received from the water level sensors 32S and 34S, and adjusts the amount of sweep gas supplied to the permeation part 26B of the fuel regenerator 26. be able to.

  The control device 68 can adjust the driving state of the cooling mechanisms 52 and 54 based on the water level information of the water tanks 32 and 34 received from the water level sensors 32S and 34S.

  Further, the control device 68 can adjust the open / close state of the diversion valves 42A, 42B, 44A, 44B based on the water level information of the water tanks 32, 34 received from the water level sensors 32S, 34S.

  Moreover, the control apparatus 68 can adjust the drive state of the pumps 62 and 64 based on the water level information of the water tanks 32 and 34 received from the water level sensors 32S and 34S.

  Further, the control device 68 can adjust the power generation amount in the first fuel cell stack 22 and the second fuel cell stack 24 based on the water level information of the water tanks 32 and 34 received from the water level sensors 32S and 34S. .

  Further, the control device 68 can control the flow rate adjusting mechanism 67 based on the water level information of the water tanks 32 and 34 received from the water level sensors 32S and 34S to adjust the input amount of the raw material gas to the vaporizer 12. .

<Action and effect>
In the fuel cell system 10 according to the first embodiment, the water supplied from the water supply pipe P2 is consumed by the reforming reaction of the reformer 14 [formulas (1) and (2)]. Further, water is generated by the power generation of the first fuel cell stack 22 and the second fuel cell stack 24 [Equation (4)]. When the current value is high, the amount of water generated in the first fuel cell stack 22 and the second fuel cell stack 24 is larger than the amount of water consumed in the reformer 14. For this reason, the water in the system increases through the reforming reaction and the power generation reaction.

  Water generated by the power generation reaction circulates in the system. A part of the water is stored in the water tank 32 via the separation membrane 26C and supplied to the water supply pipe P2. Others are stored in the water tank 34 and supplied to the water supply pipe P2. The water supplied to the water supply pipe P2 is consumed again by the reforming reaction.

  In order to reduce water (liquid phase) in the system, water is discharged out of the system as water vapor from the exhaust pipe P12 or the pipe P10. In the fuel cell system 10, the control device 68 controls the water discharge amount and the power generation amount to adjust the water amount in the system. The amount of water in the system is determined by the amount of water in the water tanks 32 and 34.

  In order to reduce the water (liquid phase) in the system without discharging it outside the system, the water is discharged as “steam” from the exhaust pipe P12 or the pipe P10 to the outside of the system. In the fuel cell system 10, the control device 68 includes the first fuel cell stack 22, the second fuel cell stack 24, the diversion valves 42A, 42B, 44A, 44B, the cooling mechanisms 52, 54, the pump 62, and the flow rate adjusting mechanism. The amount of water vapor discharged outside the system is adjusted by appropriately controlling 66 and 67 in combination. Thereby, the water (liquid phase) in the system can be reduced without being discharged out of the system. The amount of water in the system is determined by the amount of water in the water tanks 32 and 34.

  Specifically, when the amount of water in the water tanks 32 and 34 is small (when the water level reaches the lower limit value of the water level sensors 32S and 34S), it is determined that there is insufficient water in the system, and the power generation amount is increased. Thus, the amount of condensed water in the water tanks 32 and 34 is increased. Or the cooling intensity | strength of the cooling mechanisms 52 and 54 is strengthened, and the amount of condensed water thrown into the water tanks 32 and 34 is increased. Thereby, for example, the reforming water required at the time of starting the system can be secured.

  The cooling mechanism 52 cools the permeated portion exhaust gas by exchanging heat between, for example, the oxidizing gas flowing through the oxidizing gas pipe P5 and the permeated portion exhaust gas flowing through the flow path P10A. In order to control the cooling strength of the cooling mechanism 52, a bypass path and a control valve (not shown) are provided in the flow path P10A, and the amount of permeable portion exhaust gas to be “heat exchanged” with the oxidizing gas flowing through the oxidizing gas pipe P5; Adjust the amount of exhaust gas in the permeation section that does not allow heat exchange. Alternatively, a bypass path may be provided in the oxidant gas pipe P5 to adjust the amount of oxidant gas that exchanges heat with the permeate exhaust gas.

  Also in the cooling mechanism 54, a bypass (not shown) is provided in the flow path P12A. Thus, for example, when cooling is performed using the raw material gas pipe P1, the amount of exhaust gas that is “heat exchanged” with the raw material gas and the amount of exhaust gas that is not “heat exchanged” are adjusted.

  In addition to the embodiment using the fluid in the system as described above, the cooling mechanisms 52 and 54 may use a cooling fan or cooling water outside the system drawn from the outside. When a cooling fan or cooling water is used, there is no need to provide a bypass path.

  Further, when the amount of water in the water tanks 32 and 34 is large (when the water level reaches the upper limit value of the water level sensors 32S and 34S), it is determined that there is excess water in the system, and the exhaust pipe P12 or the pipe P10 The amount of condensed water in the water tanks 32 and 34 is reduced by increasing the amount of water vapor discharged. Thereby, even if it does not use the drain pipe which discharges condensed water to the water tanks 32 and 34, water can be reduced from a system.

  In the following paragraphs, a method for adjusting the amount of condensed water in the water tanks 32 and 34 will be described for each control target by the control device 68.

  First, an example of a method for increasing the amount of power generation and increasing the amount of condensed water in the water tanks 32 and 34 will be described.

(Adjustment of raw material gas input)
The control device 68 can control the flow rate adjusting mechanism 67 based on the water level information of the water tanks 32 and 34 received from the water level sensors 32S and 34S, and can adjust the input amount of the raw material gas to the vaporizer 12. For example, the amount of power generation can be increased by increasing the input amount of the source gas.

  When the control device 68 obtains information from the water level sensor 32S that the water level (water amount) of the water tank 32 has reached a predetermined lower limit value, the control device 68 controls the flow rate adjusting mechanism 67 to input the amount of raw material gas to the vaporizer 12. Adjust. Specifically, the input amount of the raw material gas is increased, and the input amount of the reforming water, the power generation amount in the first fuel cell stack 22 and the second fuel cell stack 24 are appropriately selected according to the increase in the raw material gas. The amount of power generation and the amount of oxidant gas (air) input to the first fuel cell stack 22 are increased. Thereby, the amount of anode offgas in the first fuel cell stack 22 and the amount of water vapor contained in the anode offgas are increased. In addition, the amount of water vapor charged into the water tank 32 can be increased. Thereby, the amount of water stored in the water tank 32 can be increased.

  Similarly, when the control device 68 obtains information from the water level sensor 34S that the water level (water amount) of the water tank 34 has reached a predetermined lower limit value, the control device 68 controls the flow rate adjusting mechanism 67 to supply the raw material gas to the vaporizer 12. Adjust the input amount. As a result, the amount of anode offgas in the second fuel cell stack 24 and the amount of water vapor contained in the anode offgas are increased. In addition, the amount of water vapor charged into the water tank 34 can be increased. Thereby, the amount of water stored in the water tank 34 can be increased.

  Next, an example of a method for reducing the amount of condensed water in the water tanks 32 and 34 by increasing the amount of water vapor discharged from the exhaust pipe P12 or the pipe P10 will be described.

(Control of flow adjustment mechanism)
The control device 68 controls the flow rate adjusting mechanism 66 based on the water level information of the water tanks 32 and 34 received from the water level sensors 32S and 34S, and adjusts the amount of sweep gas supplied to the permeation part 26B of the fuel regenerator 26. be able to.

  For example, when the control device 68 receives information from the water level sensor 32S that the water level (water amount) of the water tank 32 has reached a predetermined “upper limit value”, the control device 68 controls the flow rate adjusting mechanism 66 to transmit the fuel regenerator 26. The amount of sweep gas supplied to the section 26B is reduced. Alternatively, the supply of the sweep gas is stopped. As a result, the amount of water vapor transferred from the anode off gas to the sweep gas in the inflow portion 26A is reduced, and the amount of water vapor input to the water tank 32 is reduced. For this reason, the amount of condensed water condensed inside the water tank 32 can be reduced.

  When the control device 68 obtains information from the water level sensor 32S that the water level (water amount) of the water tank 32 has reached a predetermined “lower limit value”, the control device 68 controls the flow rate adjusting mechanism 66 to control the fuel regenerator 26. The amount of sweep gas supplied to the transmission part 26B is increased. As a result, the amount of water vapor that moves from the anode off gas to the sweep gas in the inflow portion 26A increases, and the amount of water vapor that enters the water tank 32 increases. For this reason, the amount of condensed water condensed inside the water tank 32 can be increased.

  In this way, the amount of condensed water condensed inside the water tank 32 can be reduced or increased by the control of the flow rate adjusting mechanism 66 by the control device 68. Thereby, the amount of water in the water tank 32 can be maintained within a predetermined range. Therefore, drainage from the water tank 32 can be controlled.

  Further, when the control device 68 obtains information from the water level sensor 34S that the water level (water amount) of the water tank 34 has reached a predetermined upper limit value, the control device 68 controls the flow rate adjusting mechanism 66 to control the permeation section of the fuel regenerator 26. Increase the amount of sweep gas supplied to 26B. As a result, the amount of water vapor that moves from the anode off gas to the sweep gas in the inflow portion 26A increases, and the amount of water vapor that enters the water tank 34 decreases. For this reason, the amount of condensed water condensed inside the water tank 34 can be reduced.

(Control of cooling mechanism)
The control device 68 can adjust the driving state of the cooling mechanisms 52 and 54 based on the water level information of the water tanks 32 and 34 received from the water level sensors 32S and 34S.

  For example, when receiving information from the water level sensor 32S that the water level (water amount) of the water tank 32 has reached a predetermined upper limit value, the control device 68 controls the cooling mechanism 52 to weaken the cooling intensity. Alternatively, the drive is stopped. Thereby, it is suppressed that the water vapor | steam contained in the permeation | transmission part exhaust gas (sweep gas) which flows through the flow path P10A in the piping P10 is condensed. For this reason, the amount of condensed water thrown into the water tank 32 can be reduced.

  In addition, the non-condensed water vapor | steam thrown into the water tank 32 is discharged | emitted out of the system via flow paths P10C and P10B except for a part condensed inside the water tank 32. For this reason, the amount of condensed water stored in the water tank 32 can be reduced.

  Similarly, when the control device 68 receives information from the water level sensor 34S that the water level (water amount) of the water tank 34 has reached a predetermined upper limit value, the control device 68 controls the cooling mechanism 54 to weaken the cooling strength. Alternatively, the drive is stopped. Thereby, it is suppressed that the water vapor | steam contained in the exhaust gas which flows through the flow path P12A in the exhaust pipe P12 is condensed. For this reason, the amount of condensed water thrown into the water tank 34 can be reduced.

  The non-condensed water vapor introduced into the water tank 34 is discharged out of the system via the flow paths P12C and P12B, except for a part that condenses inside the water tank 34. For this reason, the amount of condensed water stored inside the water tank 34 can be reduced.

(Control of shunt valve)
The control device 68 can adjust the open / close state of the diversion valves 42A, 42B, 44A, 44B based on the water level information of the water tanks 32, 34 received from the water level sensors 32S, 34S.

  For example, when the control device 68 obtains information from the water level sensor 32S that the water level (water amount) of the water tank 32 has reached a predetermined upper limit value, the control device 68 controls the diversion valves 42A and 42B to control the water tank of the permeation unit exhaust gas. The inflow amount to 32 is adjusted. Specifically, for example, the diversion valve 42A is closed and the diversion valve 42B is opened. As a result, the permeation portion exhaust gas and the water vapor contained in the permeation portion exhaust gas are exhausted outside the system and are prevented from flowing into the water tank 32. For this reason, the amount of condensed water condensed inside the water tank 32 can be reduced.

  Note that the control device 68 does not need to completely close the diversion valve 42A and completely open the diversion valve 42B. For example, the degree of opening of the diversion valve 42A and the diversion valve 42B may be adjusted so that at least a part of the permeation portion exhaust gas flowing through the pipe P10 is directly discharged from the flow path P10B without flowing into the water tank 32. . The same applies to the control of the diversion valves 44A and 44B described below.

  Further, when the control device 68 obtains information from the water level sensor 34S that the water level (water amount) of the water tank 34 has reached a predetermined upper limit value, the control device 68 controls the diversion valves 44A and 44B to control the exhaust gas water tank 34. Adjust the amount of inflow. Specifically, for example, the diversion valve 44A is closed and the diversion valve 44B is opened. As a result, the exhaust gas and the water vapor contained in the exhaust gas are exhausted outside the system and are prevented from flowing into the water tank 34. For this reason, the amount of condensed water condensed inside the water tank 34 can be reduced.

(Pump control)
The control device 68 can adjust the driving state of the pumps 62 and 64 based on the water level information of the water tanks 32 and 34 received from the water level sensors 32S and 34S.

  For example, when the control device 68 obtains information from the water level sensor 32S that the water level (water amount) of the water tank 32 has reached a predetermined upper limit value, the control device 68 controls the pump 62 to flow from the water tank 32 to the water supply pipe P2. The amount of condensed water discharged to the path P2A is adjusted. Specifically, the driving force of the pump 62 is increased, and the amount of condensed water discharged from the water tank 32 is increased. Thereby, the amount of condensed water inside the water tank 32 can be reduced.

  Similarly, when the control device 68 obtains information from the water level sensor 34S that the water level (water amount) of the water tank 34 has reached a predetermined upper limit value, the control device 68 controls the pump 64 to control the water supply pipe P2 from the water tank 34. The amount of condensed water discharged to the flow path P2B is adjusted. Specifically, the driving force of the pump 64 is increased, and the amount of condensed water discharged from the water tank 34 is increased. Thereby, the amount of condensed water inside the water tank 34 can be reduced.

(Control of fuel cell stack)
The control device 68 can adjust the power generation amount of at least one of the first fuel cell stack 22 and the second fuel cell stack 24 based on the water level information of the water tanks 32 and 34 received from the water level sensors 32S and 34S. it can.

  As an example, when the control device 68 obtains information from the water level sensor 32S that the water level (water amount) of the water tank 32 has reached a predetermined upper limit value, the control device 68 controls the first fuel cell stack 22 to control the first fuel cell. The power generation amount of the battery cell stack 22 is adjusted. Specifically, the power generation amount of the first fuel cell stack 22 is reduced, and the amount of anode offgas and the amount of water vapor contained in the anode offgas are reduced. Thereby, the water vapor amount thrown into the water tank 32 can be reduced.

  At this time, by increasing the power generation amount in the second fuel cell stack 24, it is possible to suppress a reduction in the power generation amount of the entire fuel cell system.

  As another example, when the control device 68 obtains information from the water level sensor 32S that the water level (water amount) of the water tank 34 has reached a predetermined upper limit value, the control device 68 controls the second fuel cell stack 24 to (2) The power generation amount of the fuel cell stack 24 is adjusted. Specifically, the power generation amount of the second fuel cell stack 24 is reduced, and the anode off-gas amount of the second fuel cell stack 24 and the amount of water vapor contained in the anode off-gas are reduced. Thereby, the water vapor amount thrown into the water tank 34 can be reduced.

  In addition, when the power generation amount of the second fuel cell stack 24 is reduced, if the power generation amount of the first fuel cell stack 22 is increased, the reduction of the power generation amount of the entire fuel cell system 10 can be suppressed. However, when the amount of power generation in the first fuel cell stack 22 is increased, the amount of water vapor of the anode off gas discharged from the first fuel cell stack 22 is increased. Therefore, in order to suppress an increase in the amount of water vapor flowing into the second fuel cell stack 24, for example, the flow rate adjusting mechanism 66 is controlled to reduce the amount of sweep gas supplied to the permeation portion 26B of the fuel regenerator 26. It is preferable to increase. Thereby, water vapor can be removed from the anode off-gas discharged from the first fuel cell stack 22.

  The control device 68 controls the flow rate adjusting mechanisms 66 and 67, controls the cooling mechanisms 52 and 54, controls the flow dividing valves 42A, 42B, 44A and 44B, controls the pumps 62 and 64, and the first fuel cell stack 22. And the control of the second fuel cell stack 24 can be appropriately combined and executed. By combining these controls, the effect of adjusting the amount of water vapor or condensed water introduced into the water tanks 32 and 34 can be enhanced. Or the control apparatus 68 can also perform any control independently.

  As described above, according to the fuel cell system 10 according to the first embodiment, the flow rate adjusting mechanisms 66 and 67, the cooling mechanisms 52 and 54, the diversion valves 42A, 42B, 44A and 44B, the pumps 62 and 64, and the first fuel. By controlling the battery cell stack 22 and the second fuel battery cell stack 24, the amount of water in the system can be adjusted.

  Further, according to the fuel cell system 10, the control device 68 adjusts the amount of water vapor or condensed water introduced into the water tanks 32, 34. Thereby, the amount of water in the water tanks 32 and 34 can be maintained within a predetermined range. Therefore, drainage from the water tanks 32 and 34 can be controlled.

  Further, the control device 68 adjusts the amount of condensed water discharged from the water tanks 32 and 34 to the water supply pipe P2. Thereby, the amount of water in the water tanks 32 and 34 can be maintained within a predetermined range. Accordingly, drainage from the water tanks 32 and 34 can be reduced. Furthermore, drainage from the water tanks 32 and 34 can be eliminated, and facilities and construction for drainage can be omitted.

[Second Embodiment]
<Fuel cell system>
The fuel cell system 70 according to the second embodiment shown in FIG. 2 is the fuel according to the first embodiment in that the vaporizer 12, the water supply pipe P2, the pump 62, and the pump 64 shown in FIG. 1 are not provided. Different from the battery system 10. Furthermore, the fuel cell system 70 differs from the fuel cell system 10 according to the first embodiment in that a heat exchanger 72, a water vapor separator 74, and an aggregation tank 76 shown in FIG. 2 are provided.

  The fuel cell system 70 is the same as the fuel cell system 10 according to the first embodiment in that air is used as the sweep gas supplied to the fuel regenerator 26. Note that in the second embodiment, the same components as those in the fuel cell system 10 according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted. Also, the description of the same effect by the same configuration as the fuel cell system 10 according to the first embodiment is omitted.

(Heat exchanger)
The heat exchanger 72 exchanges heat between the high-temperature exhaust gas discharged from the combustor 16 to the exhaust pipe P12 and the raw material gas containing water vapor sent from the water vapor separator 74, which will be described later, to the water vapor supply pipe P14. Raise the temperature of the gas. One end of a water vapor supply pipe P17 is connected to the heat exchanger 72, and the raw material gas is discharged to the water vapor supply pipe P17. The other end of the water vapor supply pipe P17 is connected to the reformer 14.

(Steam separator)
The steam separator 74 is disposed between the fuel regenerator 26 and the water tank 32, that is, on the upstream side of the water tank 32 in the flow path of the permeate exhaust gas (sweep gas) discharged from the fuel regenerator 26. Yes.

  Similarly to the fuel regenerator 26, the water vapor separator 74 includes an inflow portion 74A and a permeation portion 74B, and the inflow portion 74A and the permeation portion 74B are partitioned by a separation membrane 74C. The separation membrane 74C is an example of a re-separation membrane in the present invention.

  The permeation portion exhaust gas (sweep gas) discharged from the permeation portion 26B of the fuel regenerator 26 flows into the inflow portion 74A of the water vapor separator 74 via the pipe P16. Further, the raw material gas supplied from the raw material gas pipe P15 flows into the permeation portion 74B of the water vapor separator 74 as a sweep gas. As a result, the partial pressure of water vapor in the permeation part 74B decreases, and the water vapor and the like easily move from the inflow part 74A through the separation membrane 74C to the permeation part 74B. A flow rate adjusting mechanism 67 for adjusting the flow rate of the raw material gas supplied to the water vapor separator 74 is provided in the middle of the raw material gas pipe P15.

  One end of a water vapor supply pipe P14 is connected to the transmission part 74B. Thereby, the raw material gas containing water vapor is sent to the heat exchanger 72 through the water vapor supply pipe P14. Further, the permeation portion exhaust gas (sweep gas in the fuel regenerator 26) is sent from the inflow portion 74A to the pipe P10.

(Aggregation tank)
The aggregation tank 76 is provided at a position lower than the water tanks 32 and 34, and an overflow pipe P20 connected to the water tank 32 and an overflow pipe P21 connected to the water tank 34 are inserted therein. The overflow pipes P20 and 21 send the condensed water to the collecting tank 76 when the water level of the condensed water in the water tanks 32 and 34 reaches a certain level. For this reason, the water tanks 32 and 34 are not provided with the water level sensors 32S and 34S shown in FIG.

  Inside the collecting tank 76, a partition plate 76A and a water level sensor 76S are provided. The partition plate 76A is joined to the aggregation tank 76 so as to constitute two air chambers into which the overflow pipes P20 and 21 are inserted, respectively. More specifically, the upper end surface and the side end surface of the partition plate 76A are joined to the inner surface of the aggregation tank 76, and the lower end surface of the partition plate 76A is disposed below a predetermined water level lower limit value. Thereby, the lower end part of 76 A of partition plates is inserted in condensed water, and it is difficult to mix the gas in two air chambers.

  The water stored in the collecting tank 76 is used as, for example, reforming water necessary for starting up the fuel cell system 70 or reforming water necessary for increasing the power generation amount.

<Action and effect>
In the fuel cell system 70 according to the second embodiment, the water vapor is transferred from the permeated portion exhaust gas (sweep gas in the fuel regenerator 26) to the raw material gas by the water vapor separator 74. Further, the raw material gas and water vapor are supplied to the reformer 14 through the water vapor supply pipes P14 and P17. Thereby, the steam is supplied to the reformer 14 without being condensed and consumed by the reforming reaction. For this reason, compared with the case where water vapor | steam is condensed, the calorie | heat amount for re-evaporating the condensed water is unnecessary, and energy efficiency is high. Also, the vaporizer can be omitted.

  Note that the control device 68 uses the flow level adjustment mechanisms 66 and 67, the cooling mechanisms 52 and 54, the diversion valves 42A, 42B, 44A, and the like based on the water level information of the collecting tank 76 received from the water level sensor 76S, as in the first embodiment. 44B, the first fuel cell stack 22 and the second fuel cell stack 24 are appropriately combined and controlled. Thereby, the waste_water | drain from the aggregation tank 76 can be reduced.

[Third Embodiment]
<Fuel cell system>
The fuel cell system 80 according to the third embodiment shown in FIG. 3 is the fuel cell according to the first embodiment in that the vaporizer 12, the water supply pipe P2, the pump 62, and the pump 64 shown in FIG. 1 are not provided. Different from system 10. The fuel cell system 80 is different from the fuel cell system 10 according to the first embodiment in that a heat exchanger 72 shown in FIG. 3 is provided. Furthermore, the fuel cell system 80 is different from the fuel cell system 10 according to the first embodiment in that the raw material gas is used as the sweep gas supplied to the fuel regenerator 26.

  Note that in the third embodiment, the same components as those in the fuel cell systems 10 and 70 according to the first and second embodiments are denoted by the same reference numerals, and the description thereof is omitted. Also, the description of the same effect by the same configuration as the fuel cell systems 10 and 70 according to the first and second embodiments is omitted.

(Fuel regenerator)
In the fuel cell system 80 according to the third embodiment, the raw material gas supplied from the raw material gas pipe P22 is supplied to the permeation portion 26B of the fuel regenerator 26 as a sweep gas. Thereby, the partial pressure of water vapor in the permeation portion 26B is lowered, and the water vapor or the like permeates through the separation membrane 26C from the inflow portion 26A and easily moves to the permeation portion 26B. One end of a pipe P10 is connected to the transmission part 26B. Note that a flow rate adjusting mechanism 67 for adjusting the flow rate of the raw material gas supplied to the fuel regenerator 26 is provided in the middle of the raw material gas pipe P22.

(water tank)
The raw material gas sent from the permeation part 26B of the fuel regenerator 26 flows into the water tank 32 through the pipe P10. The other end side of the pipe P10 having one end connected to the transmission part 26B is branched into two flow paths P10A and P10B. The end of the flow path P10A is inserted into the water tank 32. The flow path P <b> 10 </ b> B is connected at one end to a water vapor supply pipe P <b> 23 inserted into the water tank 32. The other end of the water vapor supply pipe P23 is connected to the heat exchanger 72.

<Action and effect>
In the fuel cell system 80 according to the third embodiment, the raw material gas is supplied to the permeation portion 26B of the fuel regenerator 26 as a sweep gas. Then, the raw material gas and water vapor are supplied to the water tank 32 or the water vapor supply pipe P23 through the pipe P10.

  For example, when the control device 68 closes the flow dividing valve 42A and opens the flow dividing valve 42B, the raw material gas and water vapor are supplied to the reformer 14 through the water vapor supply pipe P23. Thereby, the steam is supplied to the reformer 14 without being condensed and consumed by the reforming reaction. For this reason, compared with the case where water vapor | steam is condensed, the calorie | heat amount for re-evaporating the condensed water is unnecessary, and energy efficiency is high. Also, the vaporizer can be omitted.

  Note that the control device 68, based on the water level information of the water tanks 32, 34 received from the water level sensors 32S, 34S, as in the first and second embodiments, the flow rate adjusting mechanism 67, the cooling mechanisms 52, 54, the diversion valve 42A, 42B, 44A, 44B, the first fuel cell stack 22 and the second fuel cell stack 24 are appropriately combined and controlled. Thereby, the waste_water | drain from the water tanks 32 and 34 can be decreased.

[Fourth Embodiment]
<Fuel cell system>
A fuel cell system 90 according to the fourth embodiment shown in FIG. 4 is different from the fuel cell system 80 according to the third embodiment in that a water vapor separator 92 and an aggregation tank 76 are provided. The fuel cell system 90 is the same as the fuel cell system 80 according to the third embodiment in that the raw material gas is used as the sweep gas supplied to the fuel regenerator 26.

  Note that in the fourth embodiment, the same components as those of the fuel cell systems 10, 70, and 80 according to the first, second, and third embodiments are denoted by the same reference numerals, and description thereof is omitted. Also, the description of the same effect by the same configuration as the fuel cell systems 10, 70, 80 according to the first, second, and third embodiments is omitted.

(Steam separator)
The steam separator 92 is disposed between the fuel regenerator 26 and the water tank 32. Similar to the fuel regenerator 26, the water vapor separator 92 includes an inflow portion 92A and a permeation portion 92B, and the inflow portion 92A and the permeation portion 92B are partitioned by a separation membrane 92C. Note that the separation membrane 92C in the present embodiment is an example of a re-separation membrane in the present invention.

  The raw material gas (sweep gas) discharged from the permeation part 26B of the fuel regenerator 26 flows into the inflow part 92A of the water vapor separator 92 through the pipe P24. Further, the air supplied from the sweep gas pipe P26 flows into the permeation portion 92B of the water vapor separator 92 as the sweep gas. As a result, the partial pressure of water vapor in the permeation part 92B is reduced, and the water vapor or the like permeates through the separation membrane 92C from the inflow part 92A and easily moves to the permeation part 92B. The air supplied from the sweep gas pipe P26 is an example of the re-sweep gas in the present invention.

  A flow rate adjusting mechanism 66 that adjusts the flow rate of the air supplied to the water vapor separator 92 is provided in the middle of the sweep gas pipe P26. The flow rate adjusting mechanism 66 in the present embodiment is an example of a re-sweep gas flow rate adjusting mechanism in the present invention.

  One end of a water vapor supply pipe P25 is connected to the inflow portion 92A. The other end of the water vapor supply pipe P25 is connected to the heat exchanger 72. Thereby, the raw material gas from which the water vapor has been removed is sent to the heat exchanger 72 via the water vapor supply pipe P25. Moreover, the air as the sweep gas is sent from the transmission part 92B to the pipe P10.

<Action and effect>
In the fuel cell system 90 according to the fourth embodiment, the raw material gas (sweep gas) containing water vapor discharged from the permeation part 26B of the fuel regenerator 26 is passed through the inflow part 92A of the water vapor separator 92 and the reformer. 14 flows into.

  For this reason, if the control device 68 controls the flow rate adjusting mechanism 66 to reduce the amount of air supplied to the permeation part 92B of the water vapor separator 92, the amount of water vapor moving from the inflow part 92A to the permeation part 92B decreases. The amount of water vapor introduced into the water tank 32 can be reduced. For this reason, the amount of condensed water thrown into the collecting tank 76 is reduced. Therefore, drainage from the collecting tank 76 can be reduced.

  Further, if the amount of air supplied to the permeation portion 92B of the water vapor separator 92 is reduced, the amount of water vapor contained in the raw material gas flowing through the water vapor supply pipe P25 is increased. The steam is consumed by the reforming reaction without being condensed. For this reason, a vaporizer can be omitted.

  Note that the control device 68 uses the flow level adjustment mechanisms 66 and 67, the cooling mechanisms 52 and 54, the diversion valves 42A, 42B, 44A, and the like based on the water level information of the collecting tank 76 received from the water level sensor 76S, as in the first embodiment. 44B, the first fuel cell stack 22 and the second fuel cell stack 24 are appropriately combined and controlled. Thereby, the waste_water | drain from the aggregation tank 76 can be reduced.

[Other Embodiments]
In each of the above embodiments, the water tank 34 is connected to the exhaust pipe P12, but the embodiment of the present invention is not limited to this. For example, the water tank 34 may not be provided, and the steam may be directly exhausted from the exhaust pipe P12. If the water tank 34 is not provided, it is not necessary to provide the diversion valves 44A and 44B and the cooling mechanism 54, so the configuration of the fuel cell system can be simplified. Furthermore, if the water tank 34 is not provided, the collecting tank 76 in the second and fourth embodiments can be omitted. If the aggregation tank 76 is omitted, a water level sensor may be provided in the water tank 32.

  Moreover, in each said embodiment, although it is set as the multistage type fuel cell system provided with the 1st fuel cell stack 22 and the 2nd fuel cell stack 24, embodiment of this invention is not restricted to this. For example, the second fuel cell stack 24, the cathode offgas pipe P11 and the anode offgas pipe P13 shown in FIG. 1 are omitted, the regeneration gas pipe P8 is connected to the pipe P3 and the reformed gas supply pipe P4, and the regeneration gas pipe P8 is branched. A circulating fuel cell system in which the branched branch pipe connected to the combustor 16 and the cathode offgas pipe P7 connected to the combustor 16 may be used.

  Further, in the fuel cell system 10 according to the first embodiment shown in FIG. 1, when the control device 68 adjusts the amount of water vapor or condensed water supplied to the water tanks 32, 34, it is not always necessary to provide the pumps 62, 64. There is no. In this case, the water supply pipe P2 is not necessarily connected to the water tanks 32 and 34, and the reformed water may be introduced from the outside of the fuel cell system 10. Even if the water supply pipe P2 is not connected to the water tanks 32, 34, the amount of water discharged from these water tanks 32, 34 can be reduced by adjusting the amount of water vapor or condensed water supplied to the water tanks 32, 34. Can do.

  In the fuel cell system 10, when the control device 68 controls the pumps 62 and 64 to adjust the amount of condensed water discharged from the water tanks 32 and 34 to the water supply pipe P <b> 2, the control device 68 is not necessarily limited to the water tank. It is not necessary to adjust the amount of water vapor or the amount of condensed water supplied to 32 and 34. In this case, the flow rate adjusting mechanisms 66 and 67, the diversion valves 42A, 42B, 44A, and 44B and the cooling mechanisms 52 and 54 may not be provided. Even if the controller 68 does not adjust the amount of water vapor or condensed water supplied to the water tanks 32 and 34, the amount of condensed water discharged from the water tanks 32 and 34 to the water supply pipe P2 can be adjusted to adjust the amount of water. Drainage from the tanks 32 and 34 can be reduced.

  Further, in the fuel cell system 70 according to the second embodiment shown in FIG. 2, the condensed water in the water tanks 32 and 34 is concentrated in the aggregation tank 76, but the embodiment of the present invention is not limited to this. For example, as shown in FIG. 1, water level sensors 32S and 34S are provided in water tanks 32 and 34, and further water supply pipes P2 (flow paths P2A and P2B) are connected to supply water to the reformer 14 via the vaporizer 12. You may supply. In this case, it is preferable that pumps 62 and 64 are provided in the flow paths P2A and P2B and controlled by the control device 68. In this way, it is arbitrary whether or not the aggregation tank 76 is provided. For example, the aggregation tank 76 may be provided in the fuel cell system 80 according to the third embodiment shown in FIG. 3, or the fourth embodiment shown in FIG. The aggregation tank 76 of the fuel cell system 90 according to the above may be omitted.

  Moreover, in each said embodiment, although the cooling mechanisms 52 and 54 are provided in the upstream of the water tanks 32 and 34, embodiment of this invention is not restricted to this. For example, the cooling mechanisms 52 and 54 may be provided inside the water tanks 32 and 34.

  Moreover, in each said embodiment, although the fuel cell stack is comprised in two steps, embodiment of this invention is not restricted to this. For example, an arbitrary number of fuel cell stacks of three or more stages may be used.

  Moreover, in each said embodiment, although the reformer 14 for producing | generating fuel gas is provided, embodiment of this invention is not restricted to this. For example, the reformer 14 may not be provided, and the steam and the raw material gas may be supplied to the first fuel cell stack 22. In this case, the reforming reaction is performed in the first fuel cell stack 22. Thus, the “reformer” in the present invention refers to both the reformer 14 provided separately from the fuel cell and the part where the reforming reaction is performed in the fuel cell. As described above, the present invention can be implemented in various modes.

10, 70, 80, 90 Fuel cell system 12 Vaporizer 14 Reformer (reformer)
22 First fuel cell stack (fuel cell)
24 Second fuel cell stack (second-stage fuel cell)
26C Separation membrane 32 Water tank 32S Water level sensors 42A, 42B Flow dividing valve (bypass valve)
52 Cooling mechanism 66 Flow rate adjustment mechanism (sweep gas flow rate adjustment mechanism, re-sweep gas flow rate adjustment mechanism)
67 Flow rate adjustment mechanism (Raw material gas flow rate adjustment mechanism)
68 Controller 74C Separation membrane (re-separation membrane)
92C separation membrane (re-separation membrane)
P2 Water supply pipe (water supply pipe)
P14 Water vapor supply pipe (water vapor supply path)

Claims (14)

A reforming section for generating fuel gas by steam reforming the raw material gas;
A fuel cell that generates electricity by reacting the fuel gas and the oxidizing gas generated in the reforming section;
A separation membrane for transferring water vapor from off gas discharged from the fuel cell to sweep gas;
A water tank that is charged with the water vapor that has been moved to the sweep gas or condensed water in which the water vapor has been condensed, and is stored as water to be used in the system;
A controller that adjusts at least one of the amount of water vapor and the amount of condensed water charged into the water tank and maintains the amount of water in the water tank in a predetermined range;
A fuel cell system comprising: A reforming section for generating fuel gas by steam reforming the raw material gas;
A fuel cell that generates electricity by reacting the fuel gas and the oxidizing gas generated in the reforming section;
A separation membrane for transferring water vapor from off gas discharged from the fuel cell to sweep gas;
A water tank in which condensate obtained by condensing the water vapor transferred to the sweep gas is stored as water used in the system;
A water supply pipe for supplying the condensed water stored in the water tank to the reforming unit via a vaporizer;
A controller for adjusting the amount of condensed water discharged from the water tank to the water supply pipe, and maintaining the amount of water in the water tank in a predetermined range;
A fuel cell system comprising: A reseparation membrane that moves the water vapor from the sweep gas to the source gas upstream of the water tank;
A water vapor supply path for supplying the water vapor moved to the source gas to the reforming unit;
The fuel cell system according to claim 1 or 2, further comprising: A sweep gas flow rate adjusting mechanism for adjusting the flow rate of the sweep gas supplied to the separation membrane;
4. The fuel cell system according to claim 1, wherein the control device controls the sweep gas flow rate adjusting mechanism to adjust an amount of water vapor introduced into the water tank. 5. A bypass valve for discharging the sweep gas without passing through the water tank;
The fuel cell system according to any one of claims 1 to 4, wherein the control device controls the bypass valve to adjust an amount of water vapor introduced into the water tank. A cooling mechanism for condensing the water vapor by cooling the sweep gas upstream of the water tank or in the water tank;
The fuel cell system according to any one of claims 1 to 5, wherein the control device controls the cooling mechanism to adjust an amount of condensed water to be introduced into the water tank. The sweep gas is a source gas,
A re-separation membrane that moves part of the water vapor from the source gas to the re-sweep gas upstream of the water tank;
A raw material gas supply path for supplying the raw material gas in which a part of the water vapor has moved to the re-sweep gas to the reforming unit;
The fuel cell system according to claim 1 or 2, further comprising: A re-sweep gas flow rate adjusting mechanism for adjusting a flow rate of the re-sweep gas supplied to the re-separation membrane;
The fuel cell system according to claim 7, wherein the control device controls the re-sweep gas flow rate adjusting mechanism to adjust an amount of water vapor introduced into the water tank. A bypass valve for discharging the re-sweep gas without passing through the water tank;
9. The fuel cell system according to claim 7, wherein the control device controls the bypass valve to adjust an amount of water vapor introduced into the water tank. A cooling mechanism for condensing the water vapor by cooling the re-sweep gas upstream of the water tank or in the water tank;
The fuel cell system according to any one of claims 7 to 9, wherein the control device controls the cooling mechanism to adjust an amount of condensed water to be supplied to the water tank. The water tank is provided with a water level sensor,
The fuel cell system according to any one of claims 1 to 10, wherein the control device maintains the amount of water in the water tank within a predetermined range based on information from the water level sensor. A source gas flow rate adjusting mechanism for adjusting the amount of the source gas charged,
The fuel cell system according to any one of claims 1 to 11, wherein the control device controls the raw material gas flow rate adjusting mechanism to adjust a power generation amount. A post-stage fuel cell that generates power by reacting an unreacted fuel gas and an oxidizing gas contained in the off-gas,
The control device according to any one of claims 1 to 12, wherein the control device controls a power generation amount of at least one of the fuel cell and the rear-stage fuel cell to adjust an amount of water vapor input to the water tank. The fuel cell system described.   The fuel cell system according to claim 13, wherein the rear-stage fuel cell is disposed on the downstream side of the water tank.