WO2023163182A1

WO2023163182A1 - Fuel cell system

Info

Publication number: WO2023163182A1
Application number: PCT/JP2023/007116
Authority: WO
Inventors: 大河村上; 秀貴渡邉; 浩一岡田; 亮介中村; 臻偉王; 海加藤; 堀内幸一郎
Original assignee: 株式会社アイシン
Priority date: 2022-02-28
Filing date: 2023-02-27
Publication date: 2023-08-31

Abstract

This fuel cell system is equipped with: a fuel cell; a reformer unit for reforming a starting material gas by using water vapor; a vaporization unit for generating water vapor by vaporizing the reformed water; a housing that has heat-insulating properties and houses the fuel cell, the reformer unit, and the vaporization unit; an anode off-gas flow passage for guiding anode off-gas from the fuel cell to the exterior of the housing; and a first heat exchanger and a second heat exchanger that are provided inside the housing. The first heat exchanger exchanges heat between the anode off-gas flowing through the anode off-gas flow passage and a fluid flowing toward the fuel cell on the upstream side of the fuel cell. The second heat exchanger exchanges heat between the reformed water and the anode off-gas flowing through the anode off-gas flow passage on the downstream side of the first heat exchanger.

Description

fuel cell system

This disclosure relates to a fuel cell system.

Conventionally, this type of fuel cell system is known to have a heat exchanger that exchanges heat between the anode off-gas from the fuel cell stack and another fluid. For example, Patent Document 1 describes a cell stack, a high-temperature housing that accommodates the cell stack and is covered with a heat insulating member, and a fuel off-gas (anode off-gas) from the cell stack that is led out of the high-temperature housing and then reintroduced into the high-temperature housing. a cooler located outside the hot housing of the fuel off-gas delivery channel to cool the fuel off-gas; and upstream within the hot housing of the fuel off-gas delivery channel. heat exchange between the fuel off-gas flowing on the side and the fuel off-gas flowing on the downstream side of the fuel off-gas delivery channel in the high-temperature housing (the portion that is again located in the high-temperature housing after being led out of the high-temperature housing) A fuel cell system is disclosed comprising:

Further, Patent Document 2 discloses a fuel processing device that steam reforms a raw material gas to generate a fuel gas, a fuel cell, a steam separation membrane that removes steam from the off-gas discharged from the fuel cell, and steam from the off-gas. and a regenerated fuel gas path for supplying the regenerated fuel gas from the fuel processing device to the fuel cell from the downstream side of the fuel processing device. Disclosed is a heat exchanger that exchanges heat between at least one of water and a fuel off-gas.

Japanese Patent Application Laid-Open No. 2020-47400 JP 2016-115496 A

In the fuel cell system described in Patent Document 1, fuel off-gas (anode off-gas) flowing downstream of the fuel off-gas supply channel in the high-temperature housing (portion again located in the high-temperature housing after being led out of the high-temperature housing) has a small heat capacity and cannot sufficiently cool the anode off-gas before it passes through the cooler, increasing the enthalpy of the anode off-gas carried out of the housing. Further, in the fuel cell system described in Patent Document 2, heat can be exchanged between the fuel off-gas and at least one of the regenerated fuel gas, raw material gas, air, water vapor, and water condensed from water vapor. There is no mention of whether the heat should be exchanged at , which is insufficient to improve the power generation efficiency of the system.

The main purpose of the fuel cell system of the present disclosure is to keep the temperature of the fuel cell at an appropriate temperature and reduce the enthalpy carried away by the anode off-gas, thereby further improving the power generation efficiency of the fuel cell system.

The fuel cell system of the present disclosure employs the following means to achieve the above-mentioned main purpose.

A first fuel cell system of the present disclosure includes:
a fuel cell that generates electricity through a reaction between an anode gas and a cathode gas;
a reforming unit that reforms the raw fuel gas into the anode gas using water vapor;
a vaporization unit that vaporizes the reforming water to generate the steam;
a housing that has heat insulation properties and accommodates the fuel cell, the reforming section, and the vaporization section;
a raw fuel gas supply unit that supplies the raw fuel gas to the vaporization unit;
a reformed water supply unit that supplies the reformed water to the vaporization unit;
a cathode gas supply unit that supplies the cathode gas to the fuel cell;
an anode off-gas flow path for leading the anode off-gas from the fuel cell to the outside of the housing;
a first heat exchanging part provided in the housing for exchanging heat between the anode off-gas flowing through the anode off-gas channel and the fluid flowing upstream of the fuel cell toward the fuel cell;
a second heat exchange section provided in the housing for exchanging heat between the reforming water and the anode offgas flowing downstream of the first heat exchange section in the anode offgas flow path;
The gist is to provide

The first fuel cell system of the present disclosure includes a first heat exchange section and a second heat exchange section provided within the housing. The first heat exchange section exchanges heat between the anode off-gas flowing through the anode off-gas channel and the fluid flowing upstream of the fuel cell toward the fuel cell. The second heat exchange section exchanges heat between the anode offgas flowing downstream of the first heat exchange section in the anode offgas channel and the reforming water. The temperature of the fuel cell can be maintained at a temperature suitable for its operation (high temperature state) by the fluid whose temperature has been raised by heat exchange with the anode off-gas in the first heat exchange section. In addition, since water has a relatively large heat of evaporation and can evaporate in a relatively low temperature range in the housing, the anode off-gas flowing downstream of the first heat exchange section is heat-exchanged with the reforming water. , the anode off-gas can be sufficiently cooled to reduce the enthalpy of the anode off-gas carried out of the housing. As a result, the power generation efficiency of the fuel cell system can be further improved.

In the first fuel cell system of the present disclosure, the fluid may be the cathode gas, and the first heat exchange section may exchange heat between the anode off-gas and the cathode gas. In this way, the temperature of the fuel cell can be maintained at a temperature suitable for its operation (high temperature state) by the cathode gas heated by heat exchange with the anode off-gas.

Further, in the first fuel cell system of the present disclosure, the second heat exchange section is provided in the vaporizer, and the anode off-gas and the raw fuel gas and reforming water respectively supplied to the vaporizer are exchanged. You may heat-exchange between. In this way, the anode off-gas can be sufficiently cooled by heat exchange with the reforming water, and the raw fuel gas can be preheated by heat exchange with the raw fuel gas. In addition, the apparatus can be made more compact by incorporating the second heat exchange section into the vaporization section.

A second fuel cell system of the present disclosure includes:
a fuel cell that generates electricity through a reaction between an anode gas and a cathode gas;
a reforming unit that reforms the raw fuel gas into the anode gas using water vapor;
a vaporization unit that vaporizes the reforming water to generate the steam;
a combustion section that heats the reforming section and the vaporization section with combustion heat;
a housing having heat insulating properties and housing the fuel cell, the reforming section, the vaporization section, and the combustion section;
a raw fuel gas supply unit that supplies the raw fuel gas to the vaporization unit;
a reformed water supply unit that supplies the reformed water to the vaporization unit;
a cathode gas supply unit that supplies the cathode gas to the fuel cell;
an anode off-gas flow path for introducing the anode off-gas from the fuel cell to the outside of the housing, introducing it into the housing, and supplying it to the combustion section;
a cooling unit provided outside the housing for cooling the anode off-gas flowing through the anode off-gas channel;
heat exchange between the anode off-gas provided in the housing and flowing upstream of the cooling portion of the anode off-gas channel and the anode off-gas flowing downstream of the cooling portion of the anode off-gas channel; a first heat exchange section to
A second heat exchanger is provided in the housing and exchanges heat between the reforming water and the anode offgas flowing downstream of the first heat exchange section and upstream of the cooling section of the anode offgas flow path. a heat exchange section;
The gist is to provide

In the second fuel cell system of the present disclosure, the first heat exchange section includes the anode offgas flowing upstream of the cooling section of the anode offgas channel and the anode offgas flowing downstream of the cooling section of the anode offgas channel. It exchanges heat with the anode off-gas. The second heat exchange section exchanges heat between the anode offgas and the reforming water that flow downstream of the first heat exchange section and upstream of the cooling section in the anode offgas flow path. By raising the temperature of the anode off-gas that has passed through the cooling section in the first heat exchange section and then supplying it to the combustion section, the temperatures of the reforming section, the vaporization section, and the fuel cell can be maintained at appropriate temperatures (high temperature state). In addition, since water has a relatively large heat of evaporation and can evaporate in a relatively low temperature range in the housing, the anode off-gas flowing downstream of the first heat exchange section is heat-exchanged with the reforming water. , the anode off-gas can be sufficiently cooled to reduce the enthalpy of the anode off-gas carried out of the housing. As a result, the power generation efficiency of the fuel cell system can be further improved.

Further, in the first or second fuel cell system of the present disclosure, the fuel cell is composed of a reversibly operating solid oxide cell, and has a power generation operation of generating power through a reaction between an anode gas and a cathode gas; It may be possible to switch between an electrolysis operation in which hydrogen is generated by steam electrolysis while power is supplied to the . In this way, even during the electrolysis operation, the hydrogen-containing off-gas discharged from the fuel electrode can be sufficiently cooled to reduce the enthalpy carried away by the off-gas to the outside of the housing. As a result, the power generation efficiency and the electrolysis efficiency can be further improved in a system capable of power generation and electrolysis. In this case, outside the housing, a recovery path communicating between the anode offgas flow path and the tank, an on-off valve provided in the recovery path, and a pump provided in the recovery path are provided, and the electrolysis operation is performed. A recovery unit may be provided for recovering the hydrogen-containing off-gas flowing through the anode off-gas flow path into the tank by opening the on-off valve and driving the pump at times. By doing so, hydrogen can be recovered during the electrolysis operation with a simple configuration. Further, in this case, a return path is provided which is connected to the anode off-gas flow path and returns the anode off-gas flowing through the anode off-gas flow path to the raw fuel gas supply section, and the recovery path branches off from the return path. may be connected to the tank through In this way, in a fuel cell system of the type in which the anode off-gas is recirculated to the raw fuel gas supply section, hydrogen can be recovered during the electrolysis operation using the recirculation path.

1 is a schematic configuration diagram of a fuel cell system according to an embodiment; FIG. FIG. 4 is a schematic configuration diagram of a fuel cell system of another embodiment; FIG. 4 is a schematic configuration diagram of a fuel cell system of another embodiment; FIG. 2 is a schematic configuration diagram of a fuel cell system that is a modified example of FIG. 1; FIG. 3 is a schematic configuration diagram of a fuel cell system that is a modified example of FIG. 2; FIG. 4 is a schematic configuration diagram of a fuel cell system that is a modification of FIG. 3;

A mode for carrying out the present invention will be described with reference to the drawings.

FIG. 1 is a schematic configuration diagram of the fuel cell system 10 of this embodiment. As shown in FIG. 1, the fuel cell system 10 of this embodiment includes a power generation module 20 including a fuel cell stack 21 that generates power through an electrochemical reaction between hydrogen in the anode gas and oxygen in the cathode gas; A raw fuel gas supply device 30 that supplies raw fuel gas (for example, natural gas or LP gas) as a raw material of anode gas to (vaporizer 22), and a power generation module 20 (vaporizer 22) from raw fuel gas to anode gas. and an air supply device 50 for supplying air as a cathode gas to the power generation module 20 (fuel cell stack 21). Prepare.

The power generation module 20 includes a fuel cell stack 21, a vaporizer 22, a reformer 23, a combustor 24, three heat exchangers (first, second and

third heat exchangers

25, 26, 27), These are housed in a box-shaped housing 29 having thermal insulation.

The fuel cell stack 21 includes a plurality of solid oxide single cells each having an electrolyte such as zirconium oxide and an anode and a cathode sandwiching the electrolyte. An anode gas passage is connected to the anode of each single cell. A cathode gas passage is connected to the cathode of each unit cell.

The vaporizer 22 and reformer 23 of the power generation module 20 are arranged above the fuel cell stack 21 inside the housing 29 . Between the fuel cell stack 21 and the vaporizer 22 and the reformer 23 is a combustor 24 that generates heat necessary for the operation of the fuel cell stack 21 and the reaction in the vaporizer 22 and the reformer 23. is arranged.

The raw fuel gas from the raw fuel gas supply device 30 and the reforming water from the reforming water supply device 40 flow into the vaporizer 22 . The raw fuel gas supply device 30 includes a raw fuel gas supply pipe 31 that connects a raw fuel supply source 1 that supplies the raw fuel gas and a vaporizer 22, an on-off valve 32 installed in the raw fuel gas supply pipe 31, It has an orifice 34 , a zero governor 35 , a gas pump 36 and a desulfurizer 38 . The raw fuel gas is pumped (supplied) from the raw fuel supply source 1 to the vaporizer 22 via the desulfurizer 38 by operating the gas pump 36 . The reforming water supply device 40 is installed in a reforming water tank 42 that stores reforming water, a reforming water supply pipe 41 that connects the reforming water tank 42 and the vaporizer 22 , and the reforming water supply pipe 41 . and a modified water pump 43 . By operating the reformed water pump 43 , the reformed water in the reformed water tank 42 is pumped (supplied) to the vaporizer 22 by the reformed water pump 43 .

The vaporizer 22 heats the inflowing raw fuel gas and reformed water with the heat (combustion heat) from the combustor 24 to preheat the raw fuel gas and evaporate the reformed water to generate steam. The raw fuel gas preheated by the vaporizer 22 is mixed with steam, and the mixed gas flows from the vaporizer 22 into the reformer 23 .

The reformer 23 has, for example, a Ru-based or Ni-based reforming catalyst filled therein, and in the presence of heat from the combustor 24, the mixed gas from the vaporizer 22 reacts with the reforming catalyst. A (steam reforming reaction) produces hydrogen gas and carbon monoxide. Furthermore, the reformer 23 produces hydrogen gas and carbon dioxide through a reaction (carbon monoxide shift reaction) between carbon monoxide produced in the steam reforming reaction and steam. As a result, the reformer 23 generates anode gas containing hydrogen, carbon monoxide, carbon dioxide, water vapor, unreformed raw fuel gas, and the like. The anode gas produced by the reformer 23 flows through the anode gas pipe 71 into the anode gas passage of each single cell of the fuel cell stack 21 and is supplied to the anode.

Also, air as cathode gas flows from the air supply device 50 through the cathode gas pipe 72 into the cathode gas passage of each unit cell of the fuel cell stack 21 and is supplied to the cathode. The air supply device 50 has an air supply pipe 51 connected to the cathode gas pipe 72 , an air filter 52 provided at the inlet of the air supply pipe 51 , and an air pump 53 installed in the air supply pipe 51 . By operating the air pump 53, air as the cathode gas is sucked into the air supply pipe 51 through the air filter 52 and pressure-fed (supplied) through the cathode gas pipe 72 to the fuel cell stack 21 (cathode). be.

Oxide ions (O ²⁻ ) are produced at the cathode of each single cell, and the oxide ions permeate the electrolyte and react with hydrogen and carbon monoxide at the anode to obtain electrical energy. The output terminal of the fuel cell stack 21 is connected to the input terminal of a power conditioner 90, and the output terminal of the power conditioner 90 is connected to the power line 3 from the power system 2 to the load 4 via a relay. there is By driving and controlling the power conditioner 90 , the power generated by the fuel cell stack 21 can be converted into AC power and supplied to the load 4 .

Anode gas containing components not used for the electrochemical reaction (power generation) in each unit cell (hereinafter referred to as “anode off-gas”) is once led out of the housing 29 through the anode off-gas pipe 73, and then out of the housing 29. It is supplied to the installed condenser 62 (cooler). Then, the anode off-gas is cooled by the condenser 62 to remove at least a part of the water vapor contained in the anode off-gas, and then introduced into the housing 29 through the anode off-gas pipe 74 to the combustor in the housing 29. 24.

The condenser 62 is connected to the hot water storage tank 61 via a circulation pipe 63 . The condenser 62 drives the circulation pump 64 to circulate the hot water stored in the hot water storage tank 61, thereby cooling the anode off-gas through heat exchange with the hot water and condensing water vapor in the anode off-gas. A condensed water pipe 44 and an anode off gas pipe 74 are connected to a passage outlet on the anode off gas side of the condenser 62, and the condensed water obtained by condensing water vapor in the anode off gas in the condenser 62 is It is introduced into the reforming water tank 42 through the condensed water pipe 44 . As a result, the condensed water can be used as the reforming water, and the operation of the fuel cell system 10 can be continued without supplying water from the outside (water independent operation). Further, as described above, the anode off-gas from which water vapor has been removed through the condenser 62 is supplied to the combustor 24 through the anode off-gas pipe 74 . Furthermore, a part of the anode off-gas from which water vapor has been removed by passing through the condenser 62 is supplied to the raw fuel gas supply pipe 31 (between the zero governor 35 and the gas pump 36) via a reflux pipe 81 branching from the anode off-gas pipe 74. is refluxed to The reflux pipe 81 is provided with an on-off valve 82 for opening and closing the reflux pipe 81 and an orifice 83 for adjusting the amount of reflux.

In addition, the cathode gas not used for the electrochemical reaction (power generation) in each single cell (hereinafter referred to as "cathode off-gas") is directly supplied to the combustor 24 through the cathode off-gas pipe 75.

The anode off-gas that has flowed into the combustor 24 is combustible gas containing fuel components such as hydrogen and carbon monoxide, and is mixed with the oxygen-containing cathode off-gas that has flowed into the combustor 24 . When the mixed gas (hereinafter referred to as "off-gas") is burned in the combustor 24, the combustion of the off-gas activates the fuel cell stack 21, preheats the raw fuel gas in the vaporizer 22, generates steam, and reforms it. Heat necessary for the steam reforming reaction or the like in the reformer 23 is generated. In addition, in the combustor 24, combustion exhaust gas containing unburned fuel is generated, and the combustion exhaust gas passes through the combustion exhaust gas pipe 76, passes through the combustion catalyst 28, and is discharged to the outside air. The combustion catalyst 28 is an oxidation catalyst for burning unburned fuel in the combustion exhaust gas.

The first, second and

third heat exchangers

25, 26, 27 are all installed inside the housing 29. The first heat exchanger 25 exchanges heat between the anode off-gas flowing upstream of the condenser 62 in the anode off-gas pipe 73 and the cathode gas flowing through the cathode gas pipe 72 . The second heat exchanger 26 includes anode offgas flowing downstream of the first heat exchanger 25 and upstream of the condenser 62 in the anode offgas pipe 73, and raw fuel gas and reforming gas flowing through the vaporizer 22. It exchanges heat with water. In this embodiment, the second heat exchanger 26 is built into the vaporizer 22 . Inside the vaporizer 22, an anode off-gas flow path is formed so that at least part of the reformed water flowing through the vaporizer 22 exchanges heat with the anode off-gas in a liquid phase state. The third heat exchanger 27 exchanges heat between the flue gas flowing through the flue gas pipe 76 and the cathode gas flowing downstream of the first heat exchanger 25 in the cathode gas pipe 72 .

As a result, the cathode gas supplied from the air supply device 50 to the cathode gas pipe 72 passes through the third heat exchanger 27 and the first heat exchanger 25 in order, and undergoes heat exchange between the combustion exhaust gas and the anode off-gas. The fuel is heated and sent to the fuel cell stack 21 . Therefore, a high-temperature cathode gas is supplied to the fuel cell stack 21, and the temperature of the fuel cell stack 21 is maintained at a temperature suitable for its operation (high temperature state).

Further, the anode off-gas that has passed through the first heat exchanger 25 is further cooled by being heat-exchanged with the reforming water in the second heat exchanger 26, and then discharged out of the housing 29 to the condenser 62. supplied. Since water has a relatively large heat of evaporation and can evaporate in a relatively low-temperature region within the housing, the anode off-gas can be sufficiently cooled by heat-exchanging the anode off-gas with the liquid-phase reforming water. That is, it is possible to reduce the enthalpy that the anode off-gas carries away to the outside of the housing 29 . Further, by sufficiently cooling the anode off-gas through heat exchange with the reforming water, the condensation of water vapor contained in the anode off-gas can be promoted in the condenser 62. is used as the reforming water to operate the fuel cell system 10 stably in a so-called water self-sustaining operation.

In the fuel cell system 10 of the present embodiment described above, the first heat exchanger 25 exchanges heat between the anode offgas flowing through the anode offgas pipe 73 and the cathode gas flowing through the cathode gas pipe 72 in the housing 29. and a second heat exchanger 26 that exchanges heat between the anode offgas flowing downstream of the first heat exchanger 25 in the anode offgas pipe 73 and the reforming water. By supplying the cathode gas heated by heat exchange with the anode off-gas to the fuel cell stack 21, the temperature of the fuel cell stack 21 can be maintained at a temperature suitable for its operation (high temperature state). Further, since water has a relatively large heat of evaporation and can evaporate in a relatively low-temperature region within the housing, the anode off-gas is sufficiently cooled within the housing 29 by further heat-exchanging the anode off-gas with the reforming water. , and the enthalpy carried away by the anode off-gas to the outside of the housing 29 can be reduced. As a result, the power generation efficiency of the fuel cell stack 21 can be improved.

In addition, in the fuel cell system 10 of the present embodiment, the second heat exchanger 25 exchanges heat between the anode off-gas and the raw fuel gas and reforming water flowing into the vaporizer 22, so that the raw fuel gas is preheated. It is possible to accelerate the vaporization of the reforming water. Furthermore, since the second heat exchanger 26 is built in the evaporator 22, the device can be made more compact.

In the embodiment described above, the first heat exchanger 25 exchanges heat between the anode off-gas and the cathode gas. However, the first heat exchanger is configured to have an anode off-gas flow path through which the anode off-gas flows inside the reformer 23, and the anode off-gas flowing through the anode off-gas flow path and the reformer 23 flow through the anode off-gas flow path. You may make it heat-exchange between gas. Also, the first heat exchanger may exchange heat between the anode off-gas and the anode gas flowing through the anode gas pipe 71 . Further, the first heat exchanger may exchange heat between the anode off-gas and the raw fuel gas flowing between the desulfurizer 38 and the vaporizer 22 in the raw fuel gas supply pipe 31 . All of these fluids are fluids that flow toward the fuel cell stack 21 on the upstream side of the fuel cell stack 21, and are supplied to the fuel cell stack 21 after being heated by heat exchange with the anode off-gas. The temperature of the fuel cell stack 21 can be maintained at a temperature suitable for its operation.

In the above-described embodiment, the fuel cell system 10 includes the first heat exchanger 25 that exchanges heat between the anode offgas and the cathode gas; and a second heat exchanger 26 that exchanges heat with water. However, as shown in the fuel cell system 110 of FIG. 2, in addition to the first heat exchanger 25 and the second heat exchanger 26, the anode off-gas and the reformed water alone (liquid phase) have passed through the second heat exchanger 26. ) may also be provided with a heat exchanger 126 for exchanging heat between the The heat exchanger 126 is installed in the housing 29 , and the anode offgas flowing downstream of the second heat exchanger 26 and upstream of the condenser 62 in the anode offgas pipe 73 and the reforming water supply pipe 41 . Heat is exchanged with the reformed water flowing upstream of the vaporizer 22 . By exchanging heat between the anode off-gas and the liquid reforming water, the anode off-gas can be further cooled, and the enthalpy carried away by the anode off-gas can be further reduced. When the heat exchanger 126 is provided, the second heat exchanger 26 may be configured such that the anode off-gas is heat-exchanged with the reforming water (water vapor) in the vapor phase state.

Also, as shown in the fuel cell system 210 of FIG. 3, a first heat exchanger 225 and a second heat exchanger 226 may be provided instead of the first heat exchanger 25 and the second heat exchanger 26. The first heat exchanger 225 exchanges heat between the anode off-gas flowing through the anode off-gas pipe 73 upstream of the condenser 62 and the anode off-gas flowing through the anode off-gas pipe 74 downstream of the condenser 62 . do The second heat exchanger 226 combines anode offgas, which flows downstream of the first heat exchanger 225 in the anode offgas pipe 73 and upstream of the condenser 62 , with the reforming water supply pipe 41 before the vaporizer 22 . heat exchange with the reformed water (liquid phase) flowing through. As a result, the anode off-gas cooled by the condenser 62 can be heated by the first heat exchanger 225 and then supplied to the combustor 24, thereby suppressing a temperature drop in the combustor 24 and vaporizing the gas. The temperature of the reactor 22, the reformer 23, and the fuel cell stack 21 can be maintained at appropriate temperatures. In addition, by heat-exchanging the anode off-gas that has passed through the first heat exchanger 225 with the liquid-phase reforming water, the anode off-gas can be sufficiently cooled and the enthalpy of the anode off-gas carried out of the housing 29 can be reduced. .

4, 5, and 6 are schematic configuration diagrams of

fuel cell systems

10B, 110B, and 210B, which are modifications of the

fuel cell systems

10, 110, and 210 of FIGS. 1, 2, and 3, respectively. Among the

fuel cell systems

10B, 110B, and 210B shown in FIGS. 4, 5, and 6, the same components as those of the

fuel cell systems

10, 110, and 210 shown in FIGS. A detailed description is omitted because it overlaps.

In the modified

fuel cell systems

10B, 110B, and 210B, the fuel cell stack 21B has the same configuration as the fuel cell stack 21, but is used as a reversible solid oxide cell stack. That is, the fuel cell stack 21B has, as an operation mode, an electric power generation operation (FC mode) in which electric power is generated by a reaction between hydrogen and oxygen, as in the

fuel cell systems

10, 110, and 210 of each embodiment, and an electric power generation operation (FC mode) between the power source and both electrodes. It has an electrolysis operation (EC mode) in which hydrogen is generated by high-temperature steam electrolysis while power is supplied to. The operating mode can be selected according to power demand. For example, the FC mode can be selected when load L is requesting power, and the EC mode can be selected when load L is not requesting power. In addition, in the

fuel cell systems

10B, 110B, and 210B with which the demand response contract has been concluded, when a lower DR that reduces the power demand is requested, the FC mode is selected, and a higher DR that increases the power demand is requested. EC mode can be selected.

Each of the modified

fuel cell systems

10B, 110B, and 210B includes a recovery pipe 91 branched from a reflux pipe 81 and connected to a hydrogen tank 95, a gas pump 92 installed in the recovery pipe 91, and a and an on-off valve 93 installed between the branch point with the reflux pipe 81 and the gas pump 93 . The on-off valve 93 is closed in FC mode and opened in EC mode. Furthermore, the fuel electrode (anode in FC mode, cathode in EC mode) side terminal and air electrode (cathode in FC mode, cathode in EC mode) in fuel cell stack 21B of

fuel cell systems

10B, 110B, 210B A power source (not shown) is connected to the terminal on the anode side so as to supply electric power at a voltage required for high-temperature steam electrolysis. As a power supply, a system power supply, renewable energy such as a solar power generation device, a storage battery, or the like can be used.

In the EC mode, water vapor and a small amount of hydrogen gas are introduced to the fuel electrode of the fuel cell stack 21B, and air is introduced to the air electrode of the fuel cell stack 21B. Then, when electric power of a predetermined voltage is supplied between the terminals of the fuel cell stack 21B (reversible solid oxide cell stack) from a power source, the water vapor introduced into the fuel electrode is converted into hydrogen and oxygen by electrolysis at the fuel electrode. It is decomposed into ions (O ^2- ). Oxygen gas is generated at the air electrode by the permeation of the oxygen ions through the electrolyte. Since a small amount of hydrogen gas is supplied to the fuel electrode together with water vapor, the fuel electrode is maintained in a reducing atmosphere, and oxidative deterioration of the fuel electrode can be suppressed. The hydrogen gas produced at the fuel electrode is discharged to the anode offgas pipe 73 as fuel electrode offgas together with water vapor that has not undergone electrolysis reaction, and is supplied to the condenser 62 . After water vapor is removed by the condenser 62 , the hydrogen-containing fuel electrode off-gas that has passed through the condenser 62 passes through the reflux pipe 81 and the recovery pipe 91 and is stored in the hydrogen tank 95 . The hydrogen gas stored in the hydrogen tank 95 may be used as anode gas in the FC mode, or may be used in the EC mode. A part of the fuel electrode off-gas that has passed through the condenser 62 is supplied to the combustor 24 through the anode off-gas pipe 74, and air containing oxygen gas is supplied from the air electrode to the combustor 24 through the cathode off-gas pipe 75. It is mixed with pole off-gas and combusted.

Here, in the fuel cell system 10B of the modified example of FIG. 4, in the EC mode, the fuel electrode off-gas containing hydrogen gas and water vapor discharged from the fuel electrode is 26 in order, and then supplied to the condenser 62 outside the module case 29 . In addition, combustion exhaust gas generated by combustion of the fuel electrode off-gas containing hydrogen gas introduced into the combustor 24 through the condenser 62 and the air electrode off-gas containing oxygen gas introduced from the air electrode into the combustor 24 passes through the third heat exchanger 27 and is discharged out of the module case 29 . As a result, in the fuel cell system 10B of the modified example, in the third heat exchanger 27 and the first heat exchanger 25, the air from the air pump 53 is used to heat the combustion exhaust gas and the fuel electrode off-gas discharged from the fuel electrode, respectively. It is possible to supply the air electrode of the fuel cell stack 21B after sequentially raising the temperature by the exchange. Further, in the vaporizer 22 including the second heat exchanger 26, the water (raw water) supplied from the reforming water tank 42 to the vaporizer 22 is mixed with the fuel electrode offgas after passing through the first heat exchanger 25. The steam can be converted into steam by heat exchange and the combustion heat of the combustor 24, and the steam can be heated and then supplied to the fuel electrode of the fuel cell stack 21B. By exchanging heat with relatively low-temperature water, the enthalpy that the fuel electrode off-gas carries out of the housing 29 can be reduced. As a result, the heat necessary for high-temperature steam electrolysis (the heat required for raising the temperature of the fuel cell stack 21B, the heat required for generating steam and raising the temperature, etc.) can be obtained, and the electrolysis efficiency can be further improved. can. In addition, since the first heat exchanger 25 is included in the evaporator 22, compared to a configuration in which the entire first heat exchanger 25 is provided outside the evaporator 22, the arrangement space for the first heat exchanger 25 is reduced. It is possible to reduce the size of the power generation module 20 (the fuel cell system 10) and suppress the increase in size.

In the fuel cell system 110B of the modified example of FIG. 5, in the EC mode, the fuel electrode off-gas containing hydrogen gas and water vapor discharged from the fuel electrode passes through the first heat exchanger 25, the second heat exchanger 26, and the heat After passing through the exchanger 126 in order, it is supplied to the condenser 62 outside the module case 29 . In addition, combustion exhaust gas generated by combustion of the fuel electrode off-gas containing hydrogen gas introduced into the combustor 24 through the condenser 62 and the air electrode off-gas containing oxygen gas introduced from the air electrode into the combustor 24 passes through the third heat exchanger 27 and is discharged out of the module case 29 . As a result, in the fuel cell system 110B of the modified example, in the third heat exchanger 27 and the first heat exchanger 25, the air from the air pump 53 is used to heat the combustion exhaust gas and the fuel electrode off-gas discharged from the fuel electrode, respectively. It is possible to supply the air electrode of the fuel cell stack 21B after sequentially raising the temperature by the exchange. Further, in the heat exchanger 126, the water (raw water ) can be converted to water vapor. Furthermore, in the vaporizer 22 including the second heat exchanger 26, by heat exchange with the fuel electrode offgas that has passed through the first heat exchanger 25 and before passing through the heat exchanger 126 and the combustion heat of the combustor 24 , the steam that has passed through the heat exchanger 126 can be heated and then supplied to the fuel electrode of the fuel cell stack 21B. By exchanging heat with relatively low-temperature water, the enthalpy that the fuel electrode off-gas carries out of the housing 29 can be reduced. As a result, the heat necessary for high-temperature steam electrolysis (the heat required for raising the temperature of the fuel cell stack 21B, the heat required for generating steam and raising the temperature, etc.) can be obtained, and the electrolysis efficiency can be further improved. can. In addition, since the first heat exchanger 25 is included in the evaporator 22, compared to a configuration in which the entire first heat exchanger 25 is provided outside the evaporator 22, the arrangement space for the first heat exchanger 25 is reduced. It is possible to reduce the size of the power generation module 20 (the fuel cell system 10) and suppress the increase in size.

In the fuel cell system 210B of the modified example in FIG. After passing through in order, it is supplied to the condenser 62 outside the module case 29 . After passing through the condenser 62 , the fuel electrode off-gas containing hydrogen gas is heated in the first heat exchanger 225 by heat exchange with the fuel electrode off-gas before passing through the condenser 62 . supplied to Further, the combustion exhaust gas generated by combustion of the fuel electrode off-gas containing hydrogen gas introduced into the combustor 24 and the air electrode off-gas containing oxygen gas introduced from the air electrode into the combustor 24 is transferred to the third heat exchanger. After passing through 27 , it is discharged out of the module case 29 . As a result, in the fuel cell system 210B of the modified example, in the third heat exchanger 27, the temperature of the air from the air pump 53 is raised by heat exchange with the combustion exhaust gas, and then supplied to the air electrode of the fuel cell stack 21B. can. In addition, in the second heat exchanger 226, the water (raw water) supplied from the reforming water tank 42 to the vaporizer 22 is converted into steam by heat exchange with the fuel electrode offgas after passing through the first heat exchanger 225. , and the temperature of the water vapor can be raised before being supplied to the fuel electrode of the fuel cell stack 21B. By exchanging heat with relatively low-temperature water, the enthalpy that the fuel electrode off-gas carries out of the housing 29 can be reduced. As a result, the heat necessary for high-temperature steam electrolysis (the heat required for raising the temperature of the fuel cell stack 21B, the heat required for generating steam and raising the temperature, etc.) can be obtained, and the electrolysis efficiency can be further improved. can.

The correspondence between the main elements of the embodiment and the main elements of the invention described in the column of Means for Solving the Problems will be explained. In the embodiment, the fuel cell stack 21 corresponds to the "fuel cell" of the present invention, the reformer 23 corresponds to the "reforming section", the vaporizer 22 corresponds to the "vaporization section", and the housing 29 corresponds to the " The raw fuel gas supply device 30 corresponds to the “raw fuel gas supply unit”, the reforming water supply device 40 corresponds to the “reforming water supply unit”, and the air supply device 50 corresponds to the “cathode gas supply unit”. The anode offgas pipe 73 corresponds to the "anode offgas channel", the first heat exchanger 25 corresponds to the "first heat exchange section", and the second heat exchanger 26 corresponds to the "second Equivalent to "heat exchange section". Further, the combustor 24 corresponds to the "combustion section", the

anode offgas pipes

73 and 74 correspond to the "anode offgas flow path", the condenser 62 corresponds to the "cooling section", and the first heat exchanger 225 It corresponds to the "first heat exchange section", and the second heat exchanger 226 corresponds to the "second heat exchange section". Also, the fuel cell stack 21B corresponds to a "reversible operation solid oxide cell stack". The recovery pipe 91 corresponds to the "recovery path", the hydrogen tank 95 to the "tank", the on-off valve 93 to the "on-off valve", and the gas pump 92 to the "pump". Also, the reflux pipe 81 corresponds to the "reflux path".

Note that the correspondence relationship between the main elements of the embodiment and the main elements of the invention described in the column of Means for Solving the Problem indicates that the embodiment implements the invention described in the column of Means to Solve the Problem. Since it is an example for specifically explaining the mode for solving the problem, it does not limit the elements of the invention described in the column of the means for solving the problem. That is, the interpretation of the invention described in the column of Means to Solve the Problem should be made based on the description in that column, and the embodiment should be based on the description of the invention described in the column of Means to Solve the Problem. This is only a specific example.

As described above, the mode for carrying out the present invention has been described using the embodiment, but the present invention is not limited to such an embodiment at all, and various forms can be used without departing from the scope of the present invention. Of course, it can be implemented.

The present invention can be used in the manufacturing industry of fuel cell systems.

1 raw fuel supply source, 2 power system, 3 power line, 4 load, 10, 110, 210, 10B, 110B, 210B fuel cell system, 20 power generation module, 21, 21B fuel cell stack, 22 vaporizer, 23 reformer vessel, 24 combustor, 25, 225 first heat exchanger, 26, 226 second heat exchanger, 27 third heat exchanger, 28 combustion catalyst, 29 housing, 30 raw fuel gas supply device, 31 raw fuel gas supply Pipe, 32 On-off valve, 33 Orifice, 35 Zero governor, 36 Gas pump, 38 Desulfurizer, 40 Reformed water supply device, 41 Reformed water supply pipe, 42 Reformed water tank, 43 Reformed water pump, 44 Condensed water pipe, 50 Air supply device, 51 Air supply pipe, 52 Air filter, 53 Air pump, 61 Hot water storage tank, 62 Condenser, 63 Circulation pipe, 64 Circulation pump, 71 Anode gas pipe, 72 Cathode gas pipe, 73, 74 Anode off gas pipe, 75 Cathode offgas piping, 76 Combustion exhaust gas piping, 81 Recirculation piping, 82 On-off valve, 83 Orifice, 90 Power conditioner, 91 Recovery piping, 92 Gas pump, 93 On-off valve, 95 Hydrogen tank, 126 Heat exchanger.

Claims

a fuel cell that generates electricity through a reaction between an anode gas and a cathode gas;
a reforming unit that reforms the raw fuel gas into the anode gas using water vapor;
a vaporization unit that vaporizes the reforming water to generate the steam;
a housing that has heat insulation properties and accommodates the fuel cell, the reforming section, and the vaporization section;
a raw fuel gas supply unit that supplies the raw fuel gas to the vaporization unit;
a reformed water supply unit that supplies the reformed water to the vaporization unit;
a cathode gas supply unit that supplies the cathode gas to the fuel cell;
an anode off-gas flow path for leading the anode off-gas from the fuel cell to the outside of the housing;
a first heat exchanging part provided in the housing for exchanging heat between the anode off-gas flowing through the anode off-gas channel and the fluid flowing upstream of the fuel cell toward the fuel cell;
a second heat exchange section provided in the housing for exchanging heat between the reforming water and the anode offgas flowing downstream of the first heat exchange section in the anode offgas flow path;
a fuel cell system.
The fuel cell system according to claim 1,
the fluid is the cathode gas;
The first heat exchange section exchanges heat between the anode off-gas and the cathode gas.
fuel cell system.
3. The fuel cell system according to claim 1 or 2,
The second heat exchange section is provided in the vaporizer and exchanges heat between the anode off-gas and the raw fuel gas and reforming water respectively supplied to the vaporizer.
fuel cell system.
a fuel cell that generates electricity through a reaction between an anode gas and a cathode gas;
a reforming unit that reforms the raw fuel gas into the anode gas using water vapor;
a vaporization unit that vaporizes the reforming water to generate the steam;
a combustion section that heats the reforming section and the vaporization section with combustion heat;
a housing having heat insulating properties and housing the fuel cell, the reforming section, the vaporization section, and the combustion section;
a raw fuel gas supply unit that supplies the raw fuel gas to the vaporization unit;
a reformed water supply unit that supplies the reformed water to the vaporization unit;
a cathode gas supply unit that supplies the cathode gas to the fuel cell;
an anode off-gas flow path for introducing the anode off-gas from the fuel cell to the outside of the housing, introducing it into the housing, and supplying it to the combustion section;
a cooling unit provided outside the housing for cooling the anode off-gas flowing through the anode off-gas channel;
heat exchange between the anode off-gas provided in the housing and flowing upstream of the cooling portion of the anode off-gas channel and the anode off-gas flowing downstream of the cooling portion of the anode off-gas channel; a first heat exchange section to
A second heat exchanger is provided in the housing and exchanges heat between the reforming water and the anode offgas flowing downstream of the first heat exchange section and upstream of the cooling section of the anode offgas flow path. a heat exchange section;
a fuel cell system.
5. The fuel cell system according to claim 1, 2 or 4,
The fuel cell is composed of a reversible solid oxide cell,
It is possible to switch between a power generation operation of generating electricity through a reaction between an anode gas and a cathode gas and an electrolysis operation of generating hydrogen by water vapor electrolysis while electric power is being supplied to the fuel cell.
fuel cell system.
A fuel cell system according to claim 5,
outside the housing, the anode offgas channel and the tank are communicated with each other; an on-off valve provided in the recovery path; and a pump provided in the recovery path. a recovery unit configured to recover off-gas containing hydrogen flowing through the anode off-gas channel into the tank by opening an on-off valve and driving the pump;
fuel cell system.
A fuel cell system according to claim 6,
a return path connected to the anode off-gas flow path for recirculating the anode off-gas flowing through the anode off-gas flow path to the raw fuel gas supply unit;
the recovery path is branched from the return path and connected to the tank;
fuel cell system.