JP2012233609A - Hot water storage tank for fuel cell, and power generation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve the self-sustained operation of water in a fuel cell system and the continuation of long-term operation by efficiently recovering heat through a heat exchanger and lowering a water temperature of exhaust heat recovery water from a hot water storage tank to the fuel cell system.SOLUTION: A coiled exhaust heat recovery water heat exchanger 21 is arranged in the hot water storage tank 20, and the surface area per unit height of the upstream portion of the exhaust heat recovery water heat exchanger 21 is made larger than the surface area per unit height of the downstream portion thereof. At an upper side in the hot water storage tank 20, an area with the surface of the exhaust heat recovery water heat exchanger 21 brought into contact with city water in the hot water storage tank 20 is enlarged, thereby efficiently recovering the heat and lowering the temperature of the exhaust heat recovery water supplied to a fuel cell. Since the temperature of the exhaust heat recovery water is kept low, moisture contained in exhaust gas and exhaust air is recovered by condensation, the self-sustained operation of water in the fuel cell system is performed, and the continuation of the long-term operation is performed.

Description

  The present invention relates to a hot water storage tank for a fuel cell used in a fuel cell system for generating electricity by reacting hydrogen and oxygen and a power generation system using the same.

  Conventionally, a fuel cell system capable of high-efficiency small-scale power generation is easy to build a system for using thermal energy generated during power generation. Development is underway as a power generation system.

  The fuel cell system includes a fuel cell as a main body of the power generation unit. In this fuel cell, hydrogen (hydrogen gas) is usually used as a fuel for power generation. However, the means for supplying hydrogen necessary for power generation by this fuel cell is not currently established as an infrastructure. Therefore, the conventional fuel cell system is provided with a hydrogen generator for generating hydrogen necessary for power generation. In this hydrogen generator, fossil fuel such as natural gas is reformed by a predetermined reforming reaction, and thereby hydrogen is generated from the fossil fuel. That is, in the conventional fuel cell system, hydrogen generated by the hydrogen generator is supplied to the fuel cell as fuel for power generation. In the fuel cell, hydrogen supplied from the hydrogen generator is used to generate power to output predetermined power.

  In general, a steam reforming reaction is used as a reforming reaction used for generating hydrogen in a hydrogen generator. In this steam reforming reaction, hydrogen is generated from the fossil fuel by reforming the fossil fuel using steam. Therefore, during the power generation operation of the fuel cell system, water for generating water vapor is supplied to the hydrogen generator. In other words, in order to obtain a predetermined power using the fuel cell system, it is indispensable to secure a water supply source at the place where the fuel cell system is installed.

  Usually, water is suitably used as the water supply means for supplying water to the fuel cell system. Here, when water supply is used as the water supply means, it is necessary to sufficiently remove components such as calcium and chlorine from the water supplied by the water supply. The reason is that when water containing a component such as calcium or chlorine is supplied, the performance of the fuel cell system deteriorates with time due to accumulation of calcium, corrosion of piping due to chlorine, or the like. Therefore, the conventional fuel cell system is provided with a water purifier including an ion exchange resin or the like in order to sufficiently remove components such as calcium and chlorine from the water supplied by the water supply.

  By the way, according to a water purifier provided with an ion exchange resin or the like, it is possible to sufficiently remove components such as calcium and chlorine contained in water, but the water purification performance of the ion exchange resin and the like deteriorates depending on the use time. To do. That is, in the configuration using this ion exchange resin or the like, it is necessary to frequently maintain the water purifier. This becomes a factor that deteriorates the running cost of the fuel cell system. Therefore, in the conventional fuel cell system, the water generated by the power generation in the fuel cell or the condensed water obtained by cooling the gas containing moisture discharged from the fuel cell is recovered and used. In many cases, a self-supporting form is adopted. According to this water self-sustained supply mode, a water purifier is unnecessary, or the load on the water purifier is reduced and the frequency of maintenance can be reduced, so that the running cost of the fuel cell system can be improved. (See Patent Document 1).

The fuel cell system is generally used as a cogeneration system that comprehensively improves thermal efficiency by using thermal energy generated during power generation for hot water supply or the like. FIG. 5 shows a configuration diagram of a conventional fuel cell system. The fuel cell system 100 includes a hot water storage tank 20 having an exhaust heat recovery water heat exchanger 21 therein. Heat generated during power generation in the fuel cell power generation unit 5 is recovered into the exhaust heat recovery water in the exhaust heat recovery water path 9 through the cooling water heat exchanger 13 provided in the cooling water circulation path 7. The heat of the waste heat recovery water is transmitted to the city water in the hot water storage tank 20 via a coiled exhaust heat recovery water heat exchanger 21 disposed in the exhaust heat recovery water path 9 in the hot water storage tank 20 for cooling. The exhausted heat recovered water is recovered again by the exhaust gas heat exchanger 11, the exhaust air heat exchanger 12, and the cooling water heat exchanger 13.

  In the fuel cell cogeneration system, in order to effectively use energy, a hot water storage / hot water supply system that recovers hot water obtained by heat exchange of exhaust heat energy of the fuel cell can be considered. The heat generated in the fuel cell is recovered via a heat medium, and the heat is transmitted to the hot water storage tank via the heat medium.

  As a method for increasing the efficiency of hot water storage and hot water supply, it has been proposed to arrange a heat exchange coil above the hot water storage tank (see Patent Document 2).

JP 2005-243623 A JP 2003-214711 A

  However, in the conventional configuration (Patent Document 1), when the temperature of the exhaust heat recovery water supplied to the fuel cell system is high, the moisture in the exhaust gas in the fuel cell system cannot be sufficiently recovered. Insufficient water is used for the reforming reaction. That is, there is a problem that the operation cannot be continued because the self-sustained supply form of water cannot be taken in the fuel cell system. Here, the exhaust heat recovery water is a heat medium that flows in a coiled heat exchanger disposed in the hot water storage tank, recovers the exhaust heat energy of the fuel cell, and transmits it to the city water in the hot water storage tank. It takes on a role.

  Therefore, as a result of intensive studies, the present inventors have found that there is still room for improvement from the viewpoint of water independence. That is, when the technique of Patent Document 1 is applied to Patent Document 2, exhaust heat recovery water that is a heat medium circulating through a coiled heat exchanger in the hot water storage tank and water in the hot water storage tank are efficiently heated. It has been found that there is a problem that the temperature of the exhaust heat recovery water supplied to the fuel cell system cannot be sufficiently lowered because the replacement cannot be performed.

  The present invention solves the above-described conventional problems, and efficiently recovers heat energy generated in the fuel cell system in a hot water storage tank incorporating a coiled heat exchanger and is supplied to the fuel cell system. By reducing the water temperature of the exhaust heat recovery water, water is recovered from the exhaust air in the fuel cell power generation section and the combustion exhaust gas in the reforming heating section inside the hydrogen generation section by condensation, and the water in the fuel cell system is self-supporting. It is an object of the present invention to provide a hot water storage tank for a fuel cell that can be operated for a long time.

In order to solve the conventional problems, a hot water storage tank for a fuel cell according to the present invention includes a heat exchanger having a coiled path and a hot water storage tank having the heat exchanger therein. In the tank, the heat exchanger is arranged such that a downstream portion which is a portion on the outlet side of the heat exchanger is disposed below a gravity direction from an upstream portion which is a portion on the inlet side of the heat exchanger, The surface area of the upstream part of the heat exchanger is larger than the surface area of the downstream part of the heat exchanger.

  Here, one end on the upstream side of the heat exchanger is defined as an upstream end, and the other end on the downstream side of the heat exchanger is defined as a downstream end, and is located in the middle of the height direction of the upstream end and the height of the downstream end. When the point is an intermediate point of the heat exchanger, the upstream part is a part of the heat exchanger upstream from the intermediate point, and the downstream part is a part of the heat exchanger downstream from the intermediate point. .

  In the hot water storage tank, a temperature laminated structure with a high temperature layer on the upper side and a low temperature layer on the lower side is generated due to the difference in specific gravity, but the upstream part on the inlet side of the heat exchanger is arranged on the upper side, and in the downstream part. Compared to the surface area of the hot water storage tank, the surface area of the coiled heat exchanger and the water in the tank come into contact with each other. Since the water is sufficiently cooled below the hot water storage tank, the temperature of the exhaust heat recovery water supplied to the fuel cell system can be lowered. In addition, by actively recovering heat above the hot water storage tank, the surface area per unit height on the upstream and downstream sides of the heat exchanger can be increased in a short time above the hot water storage tank. Since a high temperature layer can be generated, it is possible to shorten the time from the start of power generation of the fuel cell until the use of hot water supply becomes possible. Furthermore, by separating the city water and waste heat recovery water paths in the hot water storage tank, the city water in the hot water storage tank will not be stirred by the momentum of the exhaust heat recovery water, so the temperature lamination structure is kept stable. As a result, the temperature during hot water supply is also stabilized.

  By reducing the temperature of the exhaust heat recovery water supplied to the fuel cell system, the exhaust air discharged from the cathode side of the fuel cell power generation unit and the combustion exhaust gas in the reforming heating unit inside the hydrogen generation unit , Through the exhaust air heat exchanger and the exhaust gas heat exchanger, respectively, heat exchange with the exhaust heat recovery water, water necessary for generating hydrogen in the hydrogen generator can be recovered by condensation, Water in the fuel cell system can become independent, and operation can be continued for a long time.

  The hot water storage tank for a fuel cell according to the present invention efficiently recovers heat through a coiled heat exchanger and lowers the temperature of the exhaust heat recovery water supplied to the fuel cell system. By collecting moisture by condensation and enabling the water in the fuel cell system to be independent, it is possible to provide a fuel cell system capable of continuing operation for a long time.

1 is a configuration diagram of a fuel cell system according to Embodiment 1 of the present invention. Configuration diagram of a fuel cell system according to Embodiment 2 of the present invention Configuration diagram of fuel cell system according to Embodiment 3 of the present invention Configuration diagram of fuel cell system according to Embodiment 4 of the present invention Configuration diagram of conventional fuel cell system

  1st invention is a hot water storage tank for fuel cells provided with the heat exchanger which has a coil-shaped path | route, and the hot water storage tank which has the said heat exchanger inside, The said heat exchanger is the said heat exchanger. The downstream part which is a part on the outlet side is disposed below the upstream part which is a part on the inlet side of the heat exchanger in the gravity direction, and the surface area of the upstream part of the heat exchanger is the surface area of the heat exchanger. By using a hot water storage tank for fuel cells that is larger than the surface area of the downstream part, the area where the surface of the coiled heat exchanger and the water in the tank are in contact with each other is increased. Thus, heat recovery can be performed efficiently, and the water is sufficiently cooled below the hot water storage tank, so that the temperature of the exhaust heat recovery water supplied to the fuel cell system can be lowered.

  Here, one end on the upstream side of the heat exchanger is defined as an upstream end, and the other end on the downstream side of the heat exchanger is defined as a downstream end, and is located in the middle of the height direction of the upstream end and the height of the downstream end. When the point is an intermediate point of the heat exchanger, the upstream part is a part of the heat exchanger upstream from the intermediate point, and the downstream part is a part of the heat exchanger downstream from the intermediate point. .

  In particular, the second invention has a path in which the upstream portion and the downstream portion of the heat exchanger are wound in a coil shape, and the upstream portion of the heat exchanger By making the fuel cell hot water storage tank having an outer diameter larger than the outer diameter of the downstream portion of the heat exchanger, the surface of the coiled heat exchanger and the water in the tank are in contact with each other above the hot water storage tank. Therefore, heat recovery can be performed efficiently in the upper part of the hot water tank, and the water is sufficiently cooled below the hot water tank. Therefore, the temperature of the exhaust heat recovery water supplied to the fuel cell system should be lowered. Can do.

  Here, the outer diameter of the upstream portion is the outer diameter of the path in a cross section perpendicular to the traveling direction of the fluid flowing inside the upstream portion, and the outer diameter of the downstream portion is the progression of the fluid flowing inside the downstream portion. It is the outer diameter of the path in a cross section perpendicular to the direction.

  In particular, the third invention has a path in which the upstream portion and the downstream portion of the heat exchanger are wound in a coil shape in the heat exchanger of the first invention, and the upstream portion of the heat exchanger An area where the surface of the coiled heat exchanger and the water in the tank are in contact with each other above the hot water storage tank by forming a hot water storage tank for the fuel cell, the number of windings being larger than the number of windings in the downstream portion of the heat exchanger. Therefore, heat recovery can be performed efficiently in the upper part of the hot water tank, and the water is sufficiently cooled below the hot water tank. Therefore, the temperature of the exhaust heat recovery water supplied to the fuel cell system should be lowered. Can do. Moreover, since only the number of turns of the coiled heat exchanger is changed depending on the position, and it is not necessary to change the coil diameter in the middle of the heat exchanger, the manufacturing cost can be suppressed.

  Here, the number of turns in the upstream part is the number of turns in the coiled path in the upstream part, and the number of turns in the downstream part is the number of turns in the coiled path in the downstream part.

  In particular, the fourth aspect of the invention includes the heat exchanger according to the first aspect of the invention having a path in which the upstream part and the downstream part of the heat exchanger are wound in a coil shape, and the upstream part of the heat exchanger. The surface of the coiled heat exchanger and the water in the tank are in contact with each other above the hot water storage tank by using a hot water storage tank for the fuel cell that has a winding radius larger than that of the downstream portion of the heat exchanger. Since the area increases, heat recovery can be efficiently performed in the upper part of the hot water tank, and the water is sufficiently cooled below the hot water tank, so that the temperature of the exhaust heat recovery water supplied to the fuel cell system is lowered. be able to. Further, the winding radius of the coiled heat exchanger is merely changed depending on the position, and it is not necessary to change the coil diameter in the middle of the heat exchanger, so that the manufacturing cost can be suppressed.

  Here, the winding radius of the upstream part is the winding radius of the coiled path in the upstream part, and the winding radius of the downstream part is the winding radius of the coiled path in the downstream part.

In particular, the fifth invention uses a hot water storage tank for a fuel cell according to any one of the first to fourth inventions, and a fuel gas and an oxidant gas generated from a reforming reaction between a raw material gas and condensed water. A fuel cell device for generating electric power and supplying electric power and heat; a condenser for generating condensed water by cooling a gas containing water discharged from the fuel cell; and circulating the heat medium, the condenser And a heat utilization path for recovering heat from the fuel cell, wherein one end of the heat utilization path communicates with an upstream portion of the heat exchanger, and the other end communicates with a downstream portion of the heat exchanger. With the power generation system configured as described above, heat recovery can be efficiently performed in the upper part of the hot water storage tank, and the water is sufficiently cooled in the lower part of the hot water storage tank. Since the temperature of the heat recovery water can be lowered, From the exhaust air exhausted from the cathode side of the battery power generation unit and the combustion exhaust gas in the reforming heating unit inside the hydrogen generation unit, the exhaust heat recovery water passes through the exhaust air heat exchanger and the exhaust gas heat exchanger, respectively. The water necessary for generating hydrogen in the hydrogen generator can be recovered by condensation, so that the water in the fuel cell system can become independent and the operation can be continued for a long time. it can.

  Also, by actively recovering heat above the hot water tank, a high-temperature layer is generated above the hot water tank in a short time compared to a constant surface area on the upstream and downstream sides of the heat exchanger. Therefore, it is possible to shorten the time from the start of power generation by the fuel cell until the hot water supply can be used. Furthermore, the city water in the hot water storage tank and the exhaust heat recovery water are separated from each other, so that the city water in the hot water storage tank is not stirred by the momentum of the exhaust heat recovery water. By leaning, the temperature at the time of hot water supply is also stabilized.

  According to a sixth aspect of the invention, in particular, the power generation system of the fifth aspect of the invention is arranged on the heat utilization path, supplies the heat medium to an upstream portion of the heat exchanger, and supplies the heat medium to the heat exchanger. By providing the heat medium circulation device for discharging from the downstream part, heat recovery can be efficiently performed in the upper part of the hot water tank, and the water is sufficiently cooled in the lower part of the hot water tank, so it is supplied to the fuel cell system. Since the temperature of the exhaust heat recovered water can be lowered, the exhaust air discharged from the cathode side of the fuel cell power generation unit and the combustion exhaust gas in the reforming heating unit inside the hydrogen generation unit are respectively discharged. The fuel cell system is capable of recovering the water necessary for generating hydrogen in the hydrogen generator by condensation through the air heat exchanger and the exhaust gas heat exchanger, and collecting the moisture necessary for generating hydrogen in the hydrogen generator. The independence of water in Becomes a function, it is possible to continue the long-term operation. Furthermore, the temperature of the fuel cell can be adjusted to an appropriate temperature by adjusting the flow rate of the exhaust heat recovery water by the heat medium circulation device, so that the fuel cell system can be stably operated.

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

(Embodiment 1)
FIG. 1 shows a configuration diagram of a fuel cell system according to Embodiment 1 of the present invention. In FIG. 1, the solid lines between the components constituting the fuel cell system indicate piping, and the arrows marked on the solid lines indicate normal times such as water and reformed gas flowing in the piping. The flow direction in is shown.

As shown in FIG. 1, the fuel cell system 100 according to the present embodiment includes a hydrogen generator 1. This hydrogen generation unit 1 uses a raw material containing water and steam containing organic compounds composed of at least carbon and hydrogen, such as natural gas, hydrocarbon components such as LPG, alcohols such as methanol, or naphtha components. The reforming reaction to be performed mainly proceeds, and this reforming reaction generates a reformed gas rich in hydrogen. Here, although not particularly shown in FIG. 1, the hydrogen generating unit 1 is provided with a reforming unit for advancing the reforming reaction described above and carbon monoxide in the reformed gas discharged from the reforming unit. A carbon monoxide shifter (hereinafter simply referred to as a shifter) and a carbon monoxide removal unit (hereinafter simply referred to as a purifier) for reduction are provided. The reforming unit combusts a part of the raw material for supplying the reforming catalyst for proceeding the reforming reaction and the heat necessary for proceeding the reforming reaction, or the reformed gas A flame burner for burning off-gas (excess reformed gas or off-hydrogen gas) returned from a supply destination (that is, a fuel cell) and a sirocco fan for supplying combustion air are provided. The shift section includes a shift catalyst for reacting carbon monoxide and steam in the reformed gas discharged from the reforming section. The purification unit also includes a CO removal catalyst for oxidizing or methanating carbon monoxide in the reformed gas discharged from the shift unit. In order to effectively reduce the carbon monoxide contained in the reformed gas, these shift and purification sections are each operated under a temperature condition suitable for each chemical reaction. It should be noted that here, a detailed description of the configuration other than the above-described reforming unit, transformation unit, and purification unit inside the hydrogen generation unit 1 is omitted.

  Further, as shown in FIG. 1, the fuel cell system 100 includes a raw material supply unit 2. The raw material supply unit 2 supplies a raw material such as natural gas used for generating hydrogen to the hydrogen generation unit 1 described above. In the present embodiment, the raw material supply unit 2 is configured to supply natural gas as a raw material from a natural gas infrastructure. In the present embodiment, the mode of using natural gas as a raw material for generating hydrogen is described. However, the present invention is not limited to this mode, and as described above, hydrocarbon-based components such as LPG. Any raw material may be used as long as it is a raw material containing an organic compound composed of at least carbon and hydrogen exemplified by alcohols such as methanol or naphtha components. For example, when LPG is used as a raw material, an LPG tank is disposed in the raw material supply unit 2.

  The fuel cell system 100 includes a water supply path 3. The water supply path 3 supplies water for generating steam used for the reforming reaction toward the hydrogen generator 1 described above. Here, in the present embodiment, the water supply path 3 includes a plunger pump, and water is sent out toward the hydrogen generator 1 by the operation of the plunger pump. Further, the pumped water is purified by a water purification unit (not shown) and then supplied to the hydrogen generation unit 1. Here, the water purification unit includes activated carbon and an ion exchange resin. The impurity removing member used in the water purification section is not limited to activated carbon and ion exchange resin, and any impurity removing member capable of removing impurities such as ions and organic substances in water can be made of zeolite, ceramic, etc. Any impurity removing member may be used.

  The fuel cell system 100 includes a fuel cell power generation unit 5 as a main body of the power generation unit. The fuel cell power generation unit 5 is sucked by a reformed gas rich in hydrogen discharged from the hydrogen generation unit 1 and supplied to the anode side (fuel electrode side) of the fuel cell power generation unit 5 and a blower 6 described later. Using the air supplied to the cathode side (air electrode side) of the fuel cell power generation unit 5, power generation is performed so as to output predetermined power. Here, in the present embodiment, the fuel cell power generation unit 5 includes a solid polymer fuel cell. The fuel cell power generation unit 5 has a configuration in which the air supplied to the cathode side is humidified using moisture contained in exhaust air after being used for power generation inside the fuel cell power generation unit 5. Has been. Further, in the fuel cell power generation unit 5, when the humidification of the air supplied to the cathode side is insufficient, a part of the cooling water stored in the cooling water circulation path 7 is transferred to the inside of the fuel cell power generation unit 5. By evaporating in step (b), the humidification is adjusted to be an appropriate humidification. In addition, as shown in FIG. 1, the reformed gas produced | generated in the hydrogen production | generation part 1 is supplied to the anode side of the fuel cell power generation part 5 via the hydrogen supply path | route 4a. The surplus reformed gas that has not been used for power generation and is discharged from the fuel cell power generation unit 5 is returned to the hydrogen generation unit 1 through the off-hydrogen gas path 4b. Excess reformed gas returned to the hydrogen generator 1 via the off-hydrogen gas path 4b is supplied to a flame burner in the reformer, and is burned in order to advance the reforming reaction in the flame burner. Further, the configuration of the fuel cell power generation unit 5 is the same as the configuration of a general fuel cell power generation unit, and therefore, a detailed description of a further internal configuration is omitted here.

  The fuel cell system 100 includes a blower 6. The blower 6 supplies air to the cathode side of the fuel cell power generation unit 5 by sucking air. A sirocco fan or the like is preferably used as the blower 6.

  The fuel cell system 100 includes a cooling water circulation path 7. In the present embodiment, the cooling water circulation path 7 includes a small water storage tank (not shown) for storing the cooling water and a water supply pump (not shown) for circulating the cooling water. Due to the circulation of the cooling water, the cooling water circulation path 7 recovers heat generated during power generation in the fuel cell power generation unit 5, thereby cooling the fuel cell power generation unit 5.

  The fuel cell system 100 includes a water recovery unit 8. The water recovery unit 8 is configured to remove exhaust air heat from each of exhaust air discharged from the cathode side of the fuel cell power generation unit 5 and the hydrogen generation unit 1 and combustion exhaust gas in the reforming heating unit inside the hydrogen generation unit 1. Heat exchange with exhaust heat recovery water is performed via the exchanger 12 and the exhaust gas heat exchanger 11, and moisture is recovered by condensation. At this time, the lower the temperature of the exhaust heat recovery water, the more the condensed water can be recovered, so that the water for generating the steam used for the reforming reaction is stably directed toward the hydrogen generation unit 1 described above. Can be supplied to.

  The fuel cell system 100 includes a hot water storage tank 20 having an exhaust heat recovery water heat exchanger 21 therein. Heat generated during power generation in the fuel cell power generation unit 5 is recovered into the exhaust heat recovery water in the exhaust heat recovery water path 9 through the cooling water heat exchanger 13 provided in the cooling water circulation path 7. The heat of the waste heat recovery water is transmitted to the city water in the hot water storage tank 20 via a coiled exhaust heat recovery water heat exchanger 21 disposed in the exhaust heat recovery water path 9 in the hot water storage tank 20 for cooling. The exhausted heat recovered water is recovered again by the exhaust gas heat exchanger 11, the exhaust air heat exchanger 12, and the cooling water heat exchanger 13.

  The fuel cell system 100 also includes a control unit 101 for appropriately controlling the operation of each component constituting the fuel cell system 100. The control unit 101 includes, for example, a storage unit, a central processing unit (C P U) and the like, which are not particularly illustrated in FIG. A program relating to the operation of each component of the fuel cell system 100 is stored in advance in the storage unit of the control unit 101, and the control unit 101 controls the fuel cell system 100 based on the program stored in the storage unit. Is appropriately controlled.

  Next, the operation of the fuel cell system according to Embodiment 1 of the present invention will be described in detail with reference to the drawings.

  The fuel cell system 100 performs the following operation under the control of the control unit 101. Here, in this specification, the power generation operation of the fuel cell system 100 refers to the start operation (start mode) of the power generation operation, the subsequent steady power generation operation (power generation mode), and the end of the subsequent power generation operation. An operation including an operation (stop mode). The start operation (start-up mode) of the power generation operation is an operation for starting up the fuel cell system 100 stably for the power generation operation. The power generation operation end operation refers to an operation for stably stopping the fuel cell system 100 from the power generation operation.

  First, when the power generation operation of the fuel cell system 100 shown in FIG. 1 is started, in order to generate the reformed gas containing abundant hydrogen necessary for the power generation operation of the fuel cell power generation unit 5, the hydrogen generation unit 1 Is activated. Specifically, natural gas as a raw material for generating hydrogen is supplied from the raw material supply unit 2 to the reforming unit of the hydrogen generation unit 1. In addition, the water supply path 3 is activated to supply water to the reforming section of the hydrogen generating section 1 in order to generate steam for advancing the reforming reaction. This water passes through the water purification unit by the operation of the water supply path 3 and is then supplied to the reforming unit of the hydrogen generation unit 1 while the supply amount is controlled. At this time, in order to advance the reforming reaction, the reforming catalyst provided in the reforming section is heated by heat generated by burning off-hydrogen gas in the flame burner. In order to burn off the off-hydrogen gas, air is supplied from a sirocco fan for supplying combustion air to the flame burner. As a result, the reforming unit of the hydrogen generating unit 1 generates a reformed gas rich in hydrogen by the steam reforming reaction. The reformed gas generated in the reforming section of the hydrogen generating section 1 is then supplied to the shift section and the purification section. And in this metamorphic part and purification | cleaning part, the carbon monoxide contained in reformed gas is reduced and removed effectively. Then, the reformed gas from which carbon monoxide has been effectively reduced and removed in the transformation unit and the purification unit is supplied to the anode side of the fuel cell included in the fuel cell power generation unit 5.

  When reformed gas containing abundant hydrogen is supplied from the hydrogen generator 1 to the anode side of the fuel cell of the fuel cell power generation unit 5 and air is supplied from the blower 6 to the cathode side, the fuel cell power generation unit 5 Then, the reformed gas and air supplied to the anode side and the cathode side are used, and power generation is performed to output predetermined power. The surplus reformed gas that has not been used for power generation is discharged from the anode side of the fuel cell and then returned to the hydrogen generator 1. And it supplies to the flame burner which this hydrogen production | generation part 1 has, and it burns in order to advance a reforming reaction in this flame burner. As will be described later, the exhaust air discharged from the cathode side of the fuel cell is condensed via the exhaust air heat exchanger 12 and supplied to the water recovery unit 8 in order to recover the moisture.

  During the power generation operation, the fuel cell power generation unit 5 generates heat due to power generation because the fuel cell generates heat due to an electrochemical reaction for power generation. The heat generated in the fuel cell power generation unit 5 is recovered into exhaust heat recovery water through a cooling water heat exchanger 13 provided in the cooling water circulation path 7. The heat of the waste heat recovery water is transmitted to the city water in the hot water storage tank 20 via a coiled exhaust heat recovery water heat exchanger 21 disposed in the exhaust heat recovery water path 9 in the hot water storage tank 20 for cooling. The exhausted heat recovered water is recovered again by the exhaust gas heat exchanger 11, the exhaust air heat exchanger 12, and the cooling water heat exchanger 13. At this time, the city water in the hot water storage tank 20 heated by the heat exchanger is moved upward due to the density difference caused by the temperature difference from the low temperature hot water charged in the hot water storage tank 20. Moving. In this configuration, the city water in the hot water storage tank 20 and the exhaust heat recovery water are separated from each other, so that the city water in the hot water storage tank 20 is not stirred by the momentum of the exhaust heat recovery water. The temperature at the time of hot water supply is also stable. City water is supplied to the hot water storage tank 20 from a replenishing port provided on the bottom surface side, and hot water is supplied to an external hot water supply load such as a water heater or a heater from a hot water supply port provided on the upper surface side.

  Further, during the power generation operation, the fuel cell power generation unit 5 discharges exhaust air containing water generated along with power generation. In addition, combustion exhaust gas containing moisture is discharged from the hydrogen generator 1. These exhaust air and combustion exhaust gas exchange heat with exhaust heat recovery water via the exhaust air heat exchanger 12 and exhaust gas heat exchanger 11, respectively, and the water recovery unit 8 recovers the moisture. That is, the water recovery unit 8 recovers the water contained in the exhaust air and the combustion exhaust gas by condensing. The water recovery unit 8 supplies water recovered from the exhaust air and the combustion exhaust gas to the reforming unit of the hydrogen generation unit 1.

  The water sent from the water recovery unit 8 is supplied to the water purification unit by the operation of the water supply path 3. And the impurity in water is removed by the water purification function which the activated carbon and ion exchange resin of a water purification part have. Thereafter, the supply amount of the water from which impurities have been removed is controlled and supplied to the hydrogen generator 1. As described above, in the fuel cell system 100 according to the present embodiment, the water recovered by the water recovery unit 8 described above is supplied to the hydrogen generation unit 1 to continuously generate power without replenishing water from the outside. Operation is performed.

  As described above, the basic power generation operation of the fuel cell system 100 according to the present embodiment is the same as the power generation operation of the conventional fuel cell system. That is, in the same manner as in the case of the conventional fuel cell system, also in the fuel cell system 100 shown in the present embodiment, the power generation operation is performed in the self-sustained supply form of water using the water collected therein.

At this time, in the hot water storage tank 20 used for recovering the heat generated in the fuel cell power generation unit 5, the surface area per unit height of the upstream portion of the coiled exhaust heat recovery water heat exchanger 21 in the hot water storage tank 20 is as follows. By increasing the surface area per unit height of the downstream portion, the area where the surface of the exhaust heat recovery water heat exchanger 21 and the city water in the hot water storage tank 20 are in contact with each other above the hot water storage tank 20 is increased. In the hot water storage tank 20, heat can be recovered efficiently and the hot water storage tank 20
Since the water is sufficiently cooled below, the temperature of the exhaust heat recovery water supplied to the fuel cell system can be lowered. Thereby, from each of the exhaust air discharged from the cathode side of the fuel cell power generation unit and the combustion exhaust gas in the reforming heating unit inside the hydrogen generation unit, through the exhaust air heat exchanger and the exhaust gas heat exchanger, respectively. Heat exchange with the exhaust heat recovery water is performed, and the water necessary to generate hydrogen in the hydrogen generator can be recovered by condensation, so that the water in the fuel cell system can be self-supported and operated for a long time. Can continue. In addition, by actively recovering heat above the hot water storage tank, the surface area per unit height on the upstream and downstream sides of the heat exchanger can be increased in a short time above the hot water storage tank. Since a high temperature layer can be generated, it is possible to shorten the time from the start of power generation of the fuel cell until the use of hot water supply becomes possible.

  In addition, the downstream part which is a part on the outlet side of the heat exchanger is arranged below the gravity direction from the upstream part which is a part on the inlet side of the heat exchanger, and the surface area of the upstream part is the downstream part. The exhaust heat recovery water heat exchanger 21 does not need to be disposed over almost the entire area in the direction of gravity in the hot water storage tank 20, for example, below the center in the hot water storage tank 20. It may be arranged. Furthermore, a plurality of heat exchangers of different systems that recover heat (for example, a boiler or the like) other than the fuel cell power generation unit may exist in the hot water storage tank 20. The heat exchanger of another system may be arranged side by side with the exhaust heat recovery water heat exchanger in the gravitational direction, or may be disposed concentrically with the exhaust heat recovery water heat exchanger with a different winding radius. At that time, in order to lower the temperature of the exhaust heat recovery water supplied to the fuel cell system, the downstream of the exhaust heat recovery water heat exchanger 21 with respect to another heat exchanger in the hot water storage tank 20. The side is preferably located below the gravitational direction.

(Embodiment 2)
FIG. 2 shows a configuration diagram of a fuel cell system according to the second embodiment of the present invention. The coil-shaped exhaust heat recovery water heat exchanger 21 arranged in the hot water storage tank 20 has a number of windings per unit height upstream of the exhaust heat recovery water heat exchanger 21 so that the unit height of the downstream portion is high. By increasing the number of turns of the winning path, the area where the coiled heat exchanger and the water in the hot water tank 20 come into contact with each other in the upper part of the hot water tank 20 is increased. Recovery can be performed, and the water is sufficiently cooled below the hot water storage tank 20, so that the temperature of the exhaust heat recovery water supplied to the fuel cell system can be lowered. Thereby, from each of the exhaust air discharged from the cathode side of the fuel cell power generation unit and the combustion exhaust gas in the reforming heating unit inside the hydrogen generation unit, through the exhaust air heat exchanger and the exhaust gas heat exchanger, respectively. Heat exchange with the exhaust heat recovery water is performed, and the water necessary to generate hydrogen in the hydrogen generator can be recovered by condensation, so that the water in the fuel cell system can be self-supported and operated for a long time. Can continue.

(Embodiment 3)
FIG. 3 shows a configuration diagram of a fuel cell system according to the third embodiment of the present invention. The coiled exhaust heat recovery water heat exchanger 21 disposed in the hot water storage tank 20 has a coiled heat above the hot water storage tank 20 by making the winding radius of the upstream path larger than the radius of the downstream part. Since the area of contact between the exchanger and the water in the hot water storage tank 20 is larger than that below the hot water storage tank 20, heat recovery can be performed efficiently above the hot water storage tank 20. Therefore, the temperature of the exhaust heat recovery water supplied to the fuel cell system can be lowered. Thereby, from each of the exhaust air discharged from the cathode side of the fuel cell power generation unit and the combustion exhaust gas in the reforming heating unit inside the hydrogen generation unit, through the exhaust air heat exchanger and the exhaust gas heat exchanger, respectively. Heat exchange with the exhaust heat recovery water is performed, and the water necessary to generate hydrogen in the hydrogen generator can be recovered by condensation, so that the water in the fuel cell system can be self-supported and operated for a long time. Can continue.

(Embodiment 4)
FIG. 4 shows a configuration diagram of a fuel cell system according to a fourth embodiment of the present invention. The exhaust heat recovery water is supplied to the upstream portion of the exhaust heat recovery water heat exchanger 21 on the exhaust heat recovery water path 9, and the exhaust heat recovery water is discharged from the downstream portion of the exhaust heat recovery water heat exchanger 21. By providing the exhaust heat recovery water circulation pump 22, it is possible to efficiently recover heat above the hot water storage tank 20 by adjusting the flow rate of the exhaust heat recovery water, and sufficiently cool water below the hot water storage tank 20. Therefore, the temperature of the exhaust heat recovery water supplied to the fuel cell system can be lowered. Thereby, from each of the exhaust air discharged from the cathode side of the fuel cell power generation unit and the combustion exhaust gas in the reforming heating unit inside the hydrogen generation unit, through the exhaust air heat exchanger and the exhaust gas heat exchanger, respectively. Heat exchange with the exhaust heat recovery water is performed, and the water necessary to generate hydrogen in the hydrogen generator can be recovered by condensation, so that the water in the fuel cell system can be self-supported and operated for a long time. Can continue.

  As described above, the fuel cell hot water storage tank of the present invention efficiently recovers heat through the coiled heat exchanger, and lowers the temperature of the exhaust heat recovery water supplied to the fuel cell system. Continues operation for a long time by recovering moisture from the exhaust air in the fuel cell power generation unit and the combustion exhaust gas in the reforming heating unit inside the hydrogen generation unit, allowing water in the fuel cell system to become independent Therefore, it can be applied to various types of fuel cell systems.

DESCRIPTION OF SYMBOLS 1 Hydrogen production | generation part 2 Raw material supply part 3 Water supply path 4a Hydrogen supply path 4b Off-hydrogen gas path 5 Fuel cell power generation part 6 Blower 7 Coolant circulation path 8 Water recovery part 9 Waste heat recovery water path 11 Exhaust gas heat exchanger 12 Exhaust air Heat exchanger 13 Cooling water heat exchanger 20 Hot water storage tank 21 Waste heat recovery water heat exchanger 22 Waste heat recovery water circulation pump 100 Fuel cell system 101 Control unit

Claims (6)

In a hot water storage tank for a fuel cell comprising a heat exchanger having a coiled path, and a hot water storage tank having the heat exchanger inside,
In the heat exchanger, a downstream portion that is a portion on the outlet side of the heat exchanger is disposed below a gravity direction from an upstream portion that is a portion on the inlet side of the heat exchanger, and the heat exchanger The hot water storage tank for a fuel cell, wherein the surface area of the upstream portion is larger than the surface area of the downstream portion of the heat exchanger. The heat exchanger has a path in which an upstream part and a downstream part of the heat exchanger are wound in a coil shape,
The hot water storage tank for a fuel cell according to claim 1, wherein an outer diameter of an upstream portion of the heat exchanger is larger than an outer diameter of a downstream portion of the heat exchanger. The heat exchanger has a path in which an upstream part and a downstream part of the heat exchanger are wound in a coil shape,
The hot water storage tank for a fuel cell according to claim 1, wherein the number of turns in the upstream portion of the heat exchanger is greater than the number of turns in the downstream portion of the heat exchanger. The heat exchanger has a path in which an upstream part and a downstream part of the heat exchanger are wound in a coil shape,
The hot water storage tank for a fuel cell according to claim 1, wherein a winding radius of an upstream portion of the heat exchanger is larger than a winding radius of a downstream portion of the heat exchanger. Electricity is generated by using the hot water storage tank for a fuel cell according to any one of claims 1 to 4, a fuel gas generated from a reforming reaction between a raw material gas and condensed water, and an oxidant gas to generate electric power and heat. A fuel cell device for supplying
A condenser for generating condensed water by cooling a gas containing moisture discharged from the fuel cell;
A heat utilization path for circulating a heat medium and recovering heat from the condenser and the fuel cell, and
One end of the heat utilization path communicates with an upstream portion of the heat exchanger, and the other end communicates with a downstream portion of the heat exchanger.   The heat medium circulation device which is arranged on the heat utilization path, supplies the heat medium to the upstream part of the heat exchanger, and discharges the heat medium from the downstream part of the heat exchanger. 5. The power generation system according to 5.

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