Fuel cell system

Abstract

To provide a fuel cell system that reduces costs and is easy to maintain by reviewing the configuration of a water supply line.SOLUTION: A fuel cell system includes a first tank 3 and a second tank 4 that store water used for operating a fuel cell 11, an exhaust heat exchanger 2 that heats a heat medium with exhaust heat discharged from the fuel cell 11, a hot water heat exchanger 6 that heats water supplied from an external water supply source using a heat medium, a mixing valve 33 that mixes the water heated by the hot water heat exchanger 6 and the water supplied from the water supply source, a hot water supply line 30 connecting a water supply port 50a, the hot water heat exchanger 6, the mixing valve 33, and a hot water outlet 50b, a first water replenishment line 35 that replenishes the first tank 3 with water from the water supply source, and a second water replenishment line 36 that replenishes the second tank 4 with water from the water supply source, and the first replenishment line 35 and the second replenishment line 36 are connected between the hot water supply heat exchanger 6 and the mixing valve 33.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a fuel cell system.

Background Art

[0002] There is known a fuel cell system that generates electricity using a fuel gas containing hydrogen and an oxygen-containing gas (air) and supplies electricity to the outside. In such a fuel cell system, a heat storage tank for storing a heat medium is provided, and heat is recovered from the exhaust gas generated by the power generation of the fuel cell and stored in the heat storage tank, and this is used to efficiently utilize energy by performing hot water supply. A hot water supply line is connected to the fuel cell system, and hot water is generated from the water supplied from the outside and the heat medium in the heat storage tank and sent to a hot water supply device (for example, Patent Document 1).

[0003] In addition, since the exhaust gas discharged from the fuel cell contains water vapor, so-called water self-sufficient operation is generally performed in which the water vapor is condensed and recovered by cooling the exhaust gas and used as reformed water. The recovered condensed water is stored in a condensed water tank.

[0004] Before installing the fuel cell system and starting the power generation operation, water filling is carried out to store water in the heat storage tank and the condensed water tank. In addition, when the water in the tank is insufficient during the power generation operation, water replenishment is performed. Therefore, a water replenishment line is connected to the tank, and water is supplied from a water supply source outside the device through the water replenishment line.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Thus, fuel cell systems are equipped with both a hot water supply line and a water replenishment line as lines for supplying water from an external source. This results in longer piping lengths for the water supply lines, leading to increased component costs. Furthermore, the increased complexity of the system's internal configuration could potentially reduce maintainability.

[0007] The present invention aims to solve the above problems by providing a fuel cell system that is cost-effective and easy to maintain by reviewing the configuration of the water supply line. [Means for solving the problem]

[0008] This invention relates to a fuel cell that generates electricity using a fuel gas and an oxygen-containing gas, A first tank and a second tank for storing water used in the operation of the fuel cell, A heat exchanger that heats a heat transfer medium with waste heat discharged from the aforementioned fuel cell, A hot water heat exchanger that heats water supplied from an external water source using the aforementioned heat transfer medium, A mixing valve that mixes water heated by the hot water heat exchanger with water supplied from the water source, A hot water supply line connecting the water inlet, the hot water heat exchanger, the mixing valve, and the hot water outlet, The first tank is provided with a first water supply line for supplying water from the water source, The second tank is provided with a second water supply line for supplying water from the water source. The first water supply line and the second water supply line are the hot water supply line hot water This is a fuel cell system connected between the exchanger and the mixing valve. [Effects of the Invention]

[0009] By configuring the system as described above, the water supply line is partially shared with the hot water supply line, allowing for a shorter piping length. This reduces costs and improves maintainability. [Brief explanation of the drawing]

[0010] [Figure 1] This is a system configuration diagram of the fuel cell system of this embodiment. [Figure 2] This is a diagram showing the main components related to water supply in this embodiment. [Figure 3] This figure shows the connection structure around the joint in this embodiment. [Figure 4] This is a cross-sectional view of the joint. [Modes for carrying out the invention]

[0011] A preferred embodiment of the present invention will be briefly described by illustrating its operation.

[0012] The present invention comprises a first tank and a second tank for storing water used in the operation of a fuel cell; a waste heat exchanger for heating a heat transfer medium with waste heat discharged from the fuel cell; a hot water heat exchanger for heating water supplied from an external water source with the heat transfer medium; a mixing valve for mixing the water heated in the hot water heat exchanger with the water supplied from the water source; a hot water line connecting the water inlet, the hot water heat exchanger, the mixing valve, and the hot water outlet; a first water supply line for supplying water from the water source to the first tank; and a second water supply line for supplying water from the water source to the second tank. The first and second water supply lines are connected between the hot water heat exchanger and the mixing valve of the hot water line. Since the first and second water supply lines are connected in the middle of the hot water line rather than directly to the external water source, they are partially shared with the hot water line, allowing for a shorter piping length. This reduces costs and improves maintainability.

[0013] Furthermore, the first and second water supply lines are connected to the hot water supply line via a cross-shaped joint. Because each line is connected around the joint, it can be easily connected, resulting in excellent workability.

[0014] Further, the joint has a first axis and a second axis that are orthogonal to each other. A hot water supply line is connected to the first axis, a first makeup water line is connected to one end of the second axis via a first makeup water valve, and a second makeup water line is connected to the other end of the second axis via a second makeup water valve. As a result, the first makeup water valve and the second makeup water valve can also be easily attached, resulting in better workability.

[0015] Further, it includes a holding fixture that holds the first makeup water valve and the second makeup water valve, and the holding fixture is fixed to the first axis. This prevents the makeup water valves from rotating.

[0016] Also, the pipes connecting the hot water heat exchanger and the joint, and the pipes connecting the mixing valve and the joint are made of resin. Since the joint can be rotated starting from the connection part with the pipe, it is possible to secure a working space during maintenance etc., improving workability.

[0017] Also, an orifice is formed in the second axis. Since the resin joint has excellent workability, the orifice can be easily formed, reducing the cost of manufacturing the parts.

Embodiment

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0019] FIG. 1 is a system configuration diagram of the fuel cell system of this embodiment. The fuel cell system 100 includes a fuel cell module 1, and a plurality of auxiliary machines such as an exhaust heat exchanger 2, a heat storage tank 3, a condensed water tank 4, a radiator 5, an air supply device 14, a fuel supply device 15, and a reformed water supply device 16 for operating the fuel cell module 1 are housed in a housing 50. It is not necessary to house all of the above-mentioned devices in the housing 50. For example, the exhaust heat exchanger 2 or the heat storage tank 3 may be provided outside the housing 50. Also, a fuel cell system with some of the above-mentioned devices omitted is also possible.

[0020] The fuel cell module 1 is constructed by housing a fuel cell 11 that generates electricity using fuel gas and oxygen-containing gas, and a reformer 12 that generates the fuel gas supplied to the fuel cell 11, inside a box-shaped storage container 10.

[0021] The configuration of the fuel cell 11 is not particularly limited, but for example, it may have a cell stack structure in which multiple fuel cell cells are arranged. The fuel cell 11 with a cell stack structure is constructed, for example, by fixing the lower end of each fuel cell to a manifold using an insulating bonding material such as a glass seal material.

[0022] The reformer 12 steam reforms raw fuel gases such as natural gas and LPG to produce fuel gas supplied to the fuel cell 11. The reformer 12 is connected to a fuel supply device 15 that supplies raw fuel gas and a reformed water supply device 16 that supplies reformed water. The raw fuel gas and reformed water undergo a reforming reaction in the heated reformer 12 to produce fuel gas containing hydrogen.

[0023] The fuel cell 11 is supplied with fuel gas produced in the reformer 12 and air (oxygen-containing gas) introduced by the air supply device 14. As the fuel gas passes through the fuel cell cell, it reacts with the oxygen-containing gas to generate electricity. The fuel gas and oxygen-containing gas that are not used for power generation merge and burn at the top of the fuel cell 11. This combustion of fuel gas generates high-temperature exhaust gas, which heats the reformer 12. The exhaust gas generated in this way within the fuel cell module 1 is supplied to the exhaust heat exchanger 2.

[0024] The exhaust heat exchanger 2 is connected to a heat storage tank 3, a heat transfer pump P1, and a radiator 5 via piping, forming a first heat transfer circulation line HC1. A heat transfer medium is introduced into this first heat transfer circulation line HC1, and in the exhaust heat exchanger 2, heat exchange takes place between this heat transfer medium and the aforementioned exhaust gas, heating the heat transfer medium. The heat storage tank 3 stores the heat transfer medium whose temperature has risen due to the heat exchange. The heat transfer medium stored in the heat storage tank 3 is sent to the radiator 5 to be cooled, and after exchanging heat with the exhaust gas again in the exhaust heat exchanger 2, it is returned to the heat storage tank 3. As a result, the heat transfer medium with the highest temperature is stored in the heat storage tank 3 from the top, forming a temperature stratification.

[0025] Furthermore, a condensate tank 4 is connected to the exhaust heat exchanger 2 via a condensate recovery path 20. When the exhaust gas generated by the fuel cell module 1 is cooled by heat exchange, the water vapor contained in the exhaust gas is separated into water and gas, and the separated water is recovered in the condensate tank 4 through the condensate recovery path 20. In the condensate tank 4, impurities are removed from the recovered water through an ion exchanger (not shown) and the like to produce pure water. The purified water is supplied to the reformer 12 by a water supply device 16 and used as reformed water. On the other hand, the gas from which the water has been removed is discharged outside the housing 50 after passing through the exhaust path 21.

[0026] In this embodiment, water is used as the heat transfer medium, with the heat storage tank 3 corresponding to the first tank and the condensate tank 4 corresponding to the second tank. However, if the fuel cell system 100 is equipped with tanks other than those described above, the first and second tanks are not limited to these. The first and second tanks can be any tanks to which water is supplied.

[0027] The fuel supply device 15, which supplies raw fuel to the reformer 12, is equipped with auxiliary equipment such as a first solenoid valve V1, a pressure sensor PS, a desulfurizer DS, a gas flow meter FM1, a fuel pump B1, and a second solenoid valve V2 on the raw fuel flow path 22 connected to the fuel supply source. The reformed water supply device 16, which supplies reformed water to the reformer 12, is equipped with auxiliary equipment such as a reformed water pump P3 on the reformed water flow path 23 connected to the condensate tank 4. The air supply device 14, which supplies oxygen-containing gas to the fuel cell module 1, is equipped with auxiliary equipment such as an air flow meter FM2 and a blower B2 on the oxygen-containing gas flow path 24. Note that the auxiliary equipment listed here is just an example, and other configurations with other auxiliary equipment are also possible.

[0028] Furthermore, the fuel cell system 100 is equipped with a control device 7 that controls the operation of various devices, as well as a power supply adjustment unit (power conditioner) 8 that converts the DC power generated by the fuel cell module 1 into AC power and adjusts the amount of the converted electricity supplied to the external load.

[0029] Furthermore, the fuel cell system 100 is equipped with a second heat transfer medium circulation line HC2 and a hot water supply line 30, and hot water is generated by heat exchange between the high-temperature heat transfer medium stored in the heat storage tank 3 and tap water supplied from the outside in the hot water heat exchanger 6. The housing 50 is provided with a water inlet 50a to which an external water supply source is connected and a hot water outlet 50b to which a flow path leading to a reheating device such as a water heater is connected, and hot water can be sent from the hot water outlet 50b to the reheating device such as an external water heater.

[0030] The second heat transfer medium circulation line HC2 consists of a hot water heat exchanger 6, a heat supply pump P2 that circulates the heat transfer medium from the heat storage tank 3, and piping connecting these components.

[0031] The hot water supply line 30 comprises a water supply channel 31 through which water flows from the water inlet 50a toward the hot water heat exchanger 6, a supply channel 32 through which heated water flows after passing through the hot water heat exchanger 6 toward the hot water outlet 50b, a mixing valve 33 provided in the supply channel 32, and a mixing channel 34 that branches off from the water supply channel 31 and connects to the mixing valve 33. The mixing valve 33 has a hot water inlet 33a, a cold water inlet 33b, and an outlet 33c. Hot water that has passed through the hot water heat exchanger 6 flows into the hot water inlet 33a, and water that has passed through the mixing channel 34 flows into the cold water inlet 33b. Hot water mixed with hot water that has flowed in from the hot water inlet 33a and cold water that has flowed in from the cold water inlet 33b is discharged from the outlet 33c. By adjusting the opening degree of the mixing valve 33, the mixing ratio of hot water flowing in from the hot water side inlet 33a and cold water flowing in from the cold water side inlet 33b is changed, thereby controlling the temperature of the hot water discharged from the hot water outlet 50b.

[0032] Furthermore, in the hot water supply line 30, a heat medium replenishment channel 35 (first replenishment line) for supplying water to the heat storage tank 3 and a reformed water replenishment channel 36 (second replenishment line) for supplying water to the condensate tank 4 are connected between the hot water heat exchanger 6 and the mixing valve 33. Before installing the fuel cell system 100 and starting power generation operation, water is supplied to the heat storage tank 3 and the condensate tank 4 via the heat medium replenishment channel 35 and the reformed water replenishment channel 36. Also, if the water in the heat storage tank 3 or the condensate tank 4 becomes insufficient during power generation operation, water replenishment is performed. The heat medium replenishment channel 35 is equipped with a heat medium replenishment valve 37 (first replenishment valve) and is connected to the top surface of the heat storage tank 3. The reformed water replenishment channel 36 is equipped with a reformed water replenishment valve 38 (second replenishment valve) and is connected to the top surface of the condensate tank 4.

[0033] The heat transfer fluid replenishment channel 35 and the reformed water replenishment channel 36 are not directly connected to an external water source, but are connected in the middle of the hot water supply line 30. Therefore, the heat transfer fluid replenishment channel 35 and the reformed water replenishment channel 36 are partially shared with the hot water supply line 30, allowing for a reduction in piping length. This leads to cost reduction and improved maintainability.

[0034] Figure 2 is a diagram showing the main components related to water supply in this embodiment. A cross-shaped joint 40 is positioned between the hot water heat exchanger 6 and the mixing valve 33 of the hot water supply line 30. The joint 40 is a resin component and has a first shaft 41 and a second shaft 42 that are perpendicular to each other, with the hot water supply line 30 connected to the first shaft 41. A heat medium replenishment channel 35 is connected to one end of the second shaft 42, and a reformed water replenishment channel 36 is connected to the other end. In other words, since the heat medium replenishment channel 35 and the reformed water replenishment channel 36 are connected to the hot water supply line 30 via the cross-shaped joint 40, they can be easily connected to the hot water supply line 30, resulting in excellent workability.

[0035] Alternatively, the heat transfer fluid replenishment valve 37 may be connected to one end of the second shaft 42, so that the heat transfer fluid replenishment channel 35 is connected to the joint 40 via the heat transfer fluid replenishment valve 37. Similarly, the reformed water replenishment valve 38 may be connected to the other end of the second shaft 42, so that the reformed water replenishment channel 36 is connected to the joint 40 via the reformed water replenishment valve 38. This allows the heat transfer fluid replenishment valve 37 and the reformed water replenishment valve 38 to be easily installed, resulting in improved workability.

[0036] In the above configuration, when supplying hot water, the heat transfer fluid replenishment valve 37 and the reformed water replenishment valve 38 are closed, and the mixing valve 33 is opened. Furthermore, the heat supply pump P2 is driven to circulate the hot water in the heat storage tank 3 through the second heat transfer fluid circulation line HC2. The water flowing into the hot water supply line 30 from the water inlet 50a flows through the water supply channel 31 to the hot water heat exchanger 6, where it is heated by heat exchange, and then flows from the supply channel 32 through the joint 40 to the mixing valve 33. In the mixing valve 33, the water is mixed with the water flowing in from the mixing water channel 34 to adjust the temperature, and then the hot water is discharged from the hot water outlet 50b.

[0037] On the other hand, when supplying water to the heat storage tank 3 and the condensate tank 4, such as for filling or replenishing, the heat medium replenishment valve 37 and the reformed water replenishment valve 38 are opened, and the mixing valve 33 is closed. At this time, the heat supply pump P2 is not driven. The water flowing in from the water inlet 50a flows through the water supply channel 31 to the hot water heat exchanger 6, but since the hot water in the heat storage tank 3 is not circulating in the hot water heat exchanger 6, no heat exchange takes place and the water temperature hardly rises. The water that has passed through the hot water heat exchanger 6 flows through the joint 40 to the heat medium replenishment channel 35 and the reformed water replenishment channel 36. The heat storage tank 3 and the condensate tank 4 are equipped with water level sensors (not shown), and when a predetermined water level is detected, the heat medium replenishment valve 37 and the reformed water replenishment valve 38 are closed, and the water supply to the tanks is stopped.

[0038] In this way, by controlling the opening and closing of the mixing valve 33, the heat transfer fluid replenishment valve 37, and the reformed water replenishment valve 38, hot water supply and water supply to the tank can be performed.

[0039] Figure 3 shows the connection structure around the joint in this embodiment. The joint 40 is arranged inside the housing 50 with the first shaft 41 extending vertically and the second shaft 42 extending horizontally. The heat transfer fluid replenishment valve 37 and the reformed water replenishment valve 38 are directly connected to both ends of the second shaft 42 and fixed with quick fasteners 45a and 45b, respectively. Furthermore, a retaining bracket 44 is provided to hold the heat transfer fluid replenishment valve 37 and the reformed water replenishment valve 38, and this retaining bracket 44 prevents the heat transfer fluid replenishment valve 37 and the reformed water replenishment valve 38 from rotating. The retaining bracket 44 is fixed to the first shaft 41 by screw fastening.

[0040] In this embodiment, the retaining bracket 44 is configured to fix both the heat transfer fluid replenishment valve 37 and the reformed water replenishment valve 38 with a single component, but the shape of the retaining bracket 44 is not particularly limited. As long as the retaining bracket 44 is fixed to the first shaft 41, it is possible to prevent the heat transfer fluid replenishment valve 37 and the reformed water replenishment valve 38 from rotating. Furthermore, the fixing method is not limited to screw fastening; it may also be fixed by locking it to the first shaft 41.

[0041] Furthermore, the piping 39a connecting the hot water heat exchanger 6 to the fitting 40, and the piping 39b connecting the mixing valve 33 to the fitting 40, are also made of resin. The fitting 40 can be rotated from the connection point with these pipes, which allows for more workspace during maintenance and improves work efficiency.

[0042] Figure 4 is a cross-sectional view of the joint. An orifice 43 with a narrowed flow path diameter is formed on the second shaft 42 of the joint 40. By forming the orifice 43 in the joint 40 rather than providing it as a separate part, the cost of the parts is reduced. In addition, since the joint 40 is made of resin, it has excellent processability, and the orifice 43 can be easily formed, which also reduces the cost of manufacturing. [Explanation of Symbols]

[0043] 2 Waste heat heat exchanger 3. Heat storage tank (Tank 1) 4. Reconditioned water tank (second tank) 6. Hot water heat exchanger 11 Fuel Cell 30 Hot water supply lines 33 Mixing valve 35. Heat transfer fluid supply channel (first supply line) 36. Modified water replenishment channel (second replenishment line) 37. Heat transfer fluid replenishment valve (first replenishment valve) 38. Water treatment valve (second water treatment valve) 40 fittings 41 1st axis 42 2nd axis 44 Retaining hardware 43 Orifice 50a water inlet 50b Hot water outlet

Claims

1. A fuel cell that generates electricity using fuel gas and oxygen-containing gas, A first tank and a second tank for storing water used in the operation of the fuel cell, A heat exchanger that heats a heat transfer medium with waste heat discharged from the aforementioned fuel cell, A hot water heat exchanger that heats water supplied from an external water source using the aforementioned heat transfer medium, A mixing valve that mixes water heated by the hot water heat exchanger with water supplied from the water source, A hot water supply line connecting the water inlet, the hot water heat exchanger, the mixing valve, and the hot water outlet, The first tank is provided with a first water supply line for supplying water from the water source, The second tank is provided with a second water supply line for supplying water from the water source. A fuel cell system in which the first water supply line and the second water supply line are connected between the hot water heat exchanger and the mixing valve of the hot water supply line.

2. The fuel cell system according to claim 1, wherein the first water supply line and the second water supply line are connected to the hot water supply line via a cross-shaped joint.

3. The fuel cell system according to claim 2, wherein the joint has a first shaft and a second shaft that are perpendicular to each other, the hot water supply line is connected to the first shaft, the first water supply line is connected to one end of the second shaft via a first water supply valve, and the second water supply line is connected to the other end of the second shaft via a second water supply valve.

4. The system includes a retaining fitting that holds the first water supply valve and the second water supply valve, The fuel cell system according to claim 3, wherein the retaining bracket is fixed to the first shaft.

5. The fuel cell system according to claim 3 or 4, wherein the fitting, the piping connecting the hot water heat exchanger and the fitting, and the piping connecting the mixing valve and the fitting are made of resin.

6. The fuel cell system according to claim 5, wherein an orifice is formed on the second axis.

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