WO2019008686A1

WO2019008686A1 - Fuel cell system

Info

Publication number: WO2019008686A1
Application number: PCT/JP2017/024550
Authority: WO
Inventors: 竹本　真典; 純迫田; 大視筒井
Original assignee: 三浦工業株式会社
Priority date: 2017-07-04
Filing date: 2017-07-04
Publication date: 2019-01-10

Abstract

This fuel cell system (1) is used in a building having, as building equipment; a hot water tank (4) which is installed on the ground or on a basement floor and replenished with room-temperature water via a water supply pipe (12); and a main heat source machine (6) that can heat the stored water inside the hot water tank (4). The fuel cell system (1) is provided with a fuel cell (7) that can supply power inside the building (2), and a preheating tank (5) disposed midway along the water supply pipe (12). In the preheating tank (5), heat recovery from an off gas of the fuel cell (7) causes the stored water to be preheated and the off gas to be cooled. The room-temperature water replenished via the water supply pipe (12) is used as the heat source for cooling the off gas in the preheating tank (5). Condensate water generated by cooling the off gas is reused in the fuel cell (7).

Description

Fuel cell system

The present invention relates to a fuel cell system used in a building.

A fuel cell that uses hydrocarbon fuel such as city gas as a raw fuel is a cogeneration system in which the energy of the fuel is converted into electricity and heat. When the fuel cell is used as a distributed power source for business establishments and various facilities, the electric mains thermal slave operation according to the power load is fundamental. The efficiency of the fuel cell (total efficiency) is determined by the sum of the power generation efficiency and the heat recovery efficiency. Therefore, if the off-gas waste heat generated with the power generation can not be used well, the overall efficiency will be reduced.

In addition, the fuel cell generates hydrogen gas by the steam reforming reaction of the raw fuel, and supplies the hydrogen gas to the cell stack to generate power. Under the present circumstances, the reforming water used for steam reforming reaction is ensured by condensing the water | moisture content in off-gas, as disclosed by following patent document 1 (water self-supporting). Therefore, if the off gas can not be cooled to the dew point temperature or less, the fuel cell can not continue the power generation.

As described above, in order to establish a fuel cell as a cogeneration system, it is necessary to simultaneously establish heat utilization and cooling of offgas waste heat in accordance with various heat utilization forms of business establishments and various facilities.

Patent No. 5593948 (FIG. 5)

For example, a hot water circulation system is known as a hot water supply system for a building. The hot water circulation facility is a facility provided with a hot water tank whose main heat source is a steam boiler or the like, and a hot water circulation pipe that sends hot water in the hot water tank to a hot water demand point. And in a building where such existing hot-water supply equipment exists, it may be desirable to install a fuel cell later. That is, there are cases where it is desired to enable heat recovery of the fuel cell while utilizing the existing hot water supply facility, and to establish water self-sustaining of the fuel cell.

As a system for meeting such a demand, the applicant has previously proposed the following system, and has already completed patent applications (Japanese Patent Application No. 2016-64802). That is, in the system of this prior application, the hot water produced by heat recovery of the fuel cell and the hot water produced by the main heat source unit can be supplied in parallel to the hot water supply circulation pipe, and the hot water on the fuel cell side is preferentially used. It is something to try. However, the following problems remain in this system.

(A) An auxiliary device (a pressure reducing valve, a pump, etc.) for preferentially using hot water on the fuel cell side is required. In addition, depending on the pressure loss and the power consumption by the auxiliary device, the efficiency of the entire system may be reduced.

(B) An auxiliary device (temperature sensor and shutoff valve) is required to shut off the water supply when the hot water in the fuel cell side runs out. The fuel cell is selected as a distributed power source based on the power generation output. Therefore, the amount of waste heat of the fuel cell, that is, the heat output, is not large, and there is a possibility that the hot water shortage occurs frequently in the facility having a large demand for hot water.

Therefore, the problem to be solved by the present invention is a fuel cell system that achieves both heat recovery of the fuel cell and water self-sustaining with a simple configuration that can utilize the existing facility environment without the need for the above-mentioned auxiliary equipment. To provide.

The present invention has been made to solve the above problems, and the invention according to claim 1 is a hot water tank which is installed on the ground or underground floor and to which normal temperature water is supplied via a water supply pipe and A fuel cell system used in a building having as a building facility a main heat source unit capable of heating stored water in the hot water tank, the fuel cell capable of supplying power into the building, the water supply pipe A preheating tank disposed in the middle, and the offgas can be cooled while preheating the stored water in the preheating tank by heat recovery of the offgas of the fuel cell, and the replenishment is performed via the water supply pipe The fuel cell system is characterized in that the normal temperature water used is used as a heat source for cooling the off gas in the preheating tank, and the condensed water generated by the cooling of the off gas is reused in the fuel cell.

According to the invention as set forth in claim 1, the water supply pipe to the hot water tank is provided with a preheating tank, and the stored water in the preheating tank and thus the water supply to the hot water tank is preheated by the waste heat of the fuel cell The off-gas of the battery can be cooled to achieve water self-sustaining. In addition, if hot water from the fuel cell and hot water from the main heat source unit can be discharged in parallel, the hot water on the fuel cell side is preferentially used, or water supply is interrupted when hot water on the fuel cell side runs out. In addition to preheating the water supply to the hot water tank with the waste heat of the fuel cell and enabling the stored water in the hot water tank to be heated by the main heat source unit, the fuel cell system has a simple structure. It is possible to obtain hot water that preferentially uses waste heat. In addition, an existing building installation of a building can also be used as a warm water tank, a main heat source machine, and a water supply pipe, and a fuel cell and a preheating tank may be newly built in the existing building installation.

In the invention according to claim 2, the fuel cell has a reformer, a cell stack, and an off-gas heat exchanger, and the off-gas heat exchanger exchanges the off-gas with a dew point by heat exchange between the off-gas and the coolant. It cools below, condenses the moisture in the off gas, re-supplys the condensed water to the reformer, and contains hydrogen by subjecting the raw fuel and the condensed water to a steam reforming reaction in the reformer The fuel cell system according to claim 1, wherein the fuel cell system generates a reformed gas, and generates hydrogen by chemically reacting hydrogen in the reformed gas and oxygen in air in the cell stack.

According to the invention as set forth in claim 2, in the off-gas heat exchanger, water is self-sustaining, which can be operated without makeup water from the outside by condensing the water in the off-gas and re-supplying the condensed water to the reformer. It becomes possible fuel cell system.

The invention according to claim 3 circulates the cooling fluid between a preheating heat exchanger for preheating the stored water in the preheating tank, the off gas heat exchanger and the preheating heat exchanger. 3. The fuel cell system according to claim 2, further comprising: a circulating fluid circuit.

According to the third aspect of the invention, the coolant is circulated between the off-gas heat exchanger on the fuel cell side and the preheating heat exchanger in the preheating tank. Then, the off gas heat exchanger exchanges heat between the off gas and the coolant to heat the coolant while cooling the off gas, and the heat of the heated coolant causes the inside of the preheating tank in the preheating heat exchanger. Storage water can be heated.

The invention according to claim 4 is the fuel cell system according to any one of claims 1 to 3, wherein the fuel cell is a solid oxide fuel cell.

Fuel cells include, in addition to solid oxide form (SOFC), phosphoric acid form (PAFC) and solid polymer form (PEFC). According to the invention of claim 4, SOFC is used. The SOFC has a high-temperature operating temperature of 650 to 800 ° C and a medium-temperature operating temperature of 450 to 650 ° C. Therefore, from the viewpoint of cell stack protection, the electric main heat secondary does not stop after startup / heating. It is basic to drive. Therefore, high overall efficiency can be maintained by enabling recovery of offgas waste heat that continues to be generated. However, SOFCs have higher power generation efficiency than PAFCs and PEFCs, so the off-gas waste heat quantity is small when compared at the same power generation output, and there is a possibility that they can not meet the hot water demand of buildings alone. However, by using off-gas waste heat for preheating the water supply to the hot water tank capable of heating the stored water with the main heat source unit, it is possible to construct a system that simultaneously satisfies the power demand of the building and the hot water demand.

Furthermore, according to the invention as set forth in claim 5, the building equipment is a hot water supply circulation pipe connected to the hot water tank so as to be able to circulate the hot water stored in the hot water tank; and the hot water supply pipe from the main pipe The fuel cell system according to any one of claims 1 to 4, further comprising a branch pipe for sending hot water to a demand point.

According to the invention of claim 5, by circulating the hot water stored in the hot water tank to the hot water supply circulation pipe (stem pipe), the hot water demand point via the branch pipe branched from the circulation pipe Hot water can be taken out quickly.

According to the present invention, it is possible to realize a fuel cell system that achieves both heat recovery of the fuel cell and water self-sustaining with a simple configuration that can utilize the existing facility environment.

FIG. 1 is a schematic view showing a fuel cell system according to an embodiment of the present invention.

Hereinafter, specific embodiments of the present invention will be described in detail based on the drawings.
FIG. 1 is a schematic view showing a fuel cell system 1 according to an embodiment of the present invention.

The fuel cell system 1 of the present embodiment is used as part of building equipment in a building 2 such as a public facility, an industrial facility, or a housing facility.

The building 2 is not particularly limited in its hierarchy, but is typically a low-rise building (1-2 hierarchy) or a middle-rise building (3-5 hierarchy). However, depending on the case, it may be a high-rise building (more than six levels). In the example of illustration, it is set as the building 2 of the basement 1 floor and 3 floors above the ground.

The building equipment refers to devices and devices integrated with the building 2 to perform various functions that are necessary for people to live their lives. The building equipment may include various equipment (for example, boiler equipment and communication equipment etc.) according to the needs of the building user, in addition to the equipment etc. defined in Building Standard Law Article 2, Item 3.

The building 2 of the present embodiment is, as building equipment, a water receiving tank 3 and a hot water tank 4 that can be supplied with water from a water supply source, a preheating tank 5 provided in a water supply system to the hot water tank 4, and storage in the hot water tank 4 A main heat source 6 capable of heating water, a fuel cell 7 in which off-gas waste heat is used to heat stored water in the preheating tank 5, and hot water circulation piping 8 for circulating hot water stored in the hot water tank 4 to each floor And a water supply pipe 9 for supplying normal temperature water stored in the water receiving tank 3 to each floor. Among these building facilities, the fuel cell 7 and the preheating tank 5 constitute the main part of the fuel cell system 1.

The water receiving tank 3, the hot water tank 4 and the preheating tank 5 are mounted on the floor of the basement floor (here, the first floor B1 in this case) in the present embodiment. However, one or more of the tanks 3 to 5 may be installed on the ground (outdoor or indoor), as the case may be. For example, in a building without a basement, these tanks 3 to 5 are mounted on the ground (typically, the first floor F1). In any case, it is preferable that the water receiving tank 3 and the hot water tank 4 be provided on the same floor.

The water receiving tank 3 is an open tank (a tank opened to the atmosphere) in the present embodiment. Tap water is supplied and stored in the water receiving tank 3 via the water supply pipe (first water supply pipe) 10. In the present embodiment, the presence or absence of water supply to the water receiving tank 3 is switched using the constant water level valve (ball tap) 11, and the inside of the water receiving tank 3 is maintained at a predetermined water level.

The hot water tank 4 is an open tank in this embodiment. Tap water is supplied and stored in the hot water tank 4 via the water supply pipe (second water supply pipe) 12. In the present embodiment, the presence or absence of water supply to the hot water tank 4 is switched using the constant water level valve (ball tap) 13, and the inside of the hot water tank 4 is maintained at a predetermined water level.

The first water supply pipe 10 to the water receiving tank 3 and the second water supply pipe 12 to the hot water tank 4 are formed as a common pipe line 14 on the upstream side. In other words, the water from the water distribution pipe (not shown) can be supplied to the water receiving tank 3 by the first water supply pipe 10 through the common pipeline 14, and to the hot water tank 4 by the second water supply pipe 12. It is possible to supply. In addition, a distribution pipe means the pipe which sends water from a distribution station to a water supply area, and the

water supply pipes

10 and 12 mean a pipe which branches from a distribution pipe and supplies water to consumers such as each household. Tap water (normally in the range of 5 to 30 ° C. in season) is supplied from the water distribution pipe to the

water supply pipes

10, 12.

By the way, in the case of this embodiment, even if the

water supply pipes

10 and 12 are not provided with a pump, if the constant

water level valves

11 and 13 are opened by the water pressure from the water distribution pipe, the

water supply pipes

10 and 12 to the

respective tanks

3 and 4 It can be watered. However, if necessary, a water pump may be provided in the common pipeline 14 (or the water supply pipes 10, 12).

The stored water in the hot water tank 4 can be heated by the main heat source unit 6. As described later, the water supplied to the hot water tank 4 is preheated using the off-gas waste heat of the fuel cell 7. However, even if this preheating is not performed (that is, even if the power generation of the fuel cell 7 is stopped) The machine 6 can maintain the water temperature in the warm water tank 4 as desired, and has a heating capacity that does not affect the warm water supply into the building 2. In other words, the main heat source unit 6 has a heat output that can meet the hot water demand of the building 2 alone.

The main heat source unit 6 is not particularly limited, but in the present embodiment, it is a steam boiler 6A. In this case, a steam heater (heat exchanger for steam from the steam boiler 6A and stored water in the hot water tank 4) 15 is incorporated in the hot water tank 4, and steam from the steam boiler 6A is supplied to the steam heater 15. And the stored water in the hot water tank 4 is heated. By automatically controlling the steam supply from the steam boiler 6A to the steam heater 15 based on the temperature of the stored water in the warm water tank 4, the stored water in the warm water tank 4 can be maintained at the set temperature. Thus, in the warm water tank 4, warm water to be supplied into the building 2 is stored. As described later, the hot water stored in the hot water tank 4 is circulated to the floors of the building 2 through the hot water supply circulation pipe 8. Therefore, from the viewpoint of hygiene such as prevention of Legionella contamination of circulating hot water, it is desirable to set the set temperature at the time of heating by the steam heater 15 to 60 ° C. or higher.

The preheating tank 5 is provided in the middle of the water supply pipe 12 to the hot water tank 4. The preheating tank 5 is a closed tank (a tank which is not open to the atmosphere) in the present embodiment. The preheating tank 5 is typically installed on the same floor as the hot water tank 4. However, if the piping from the water supply source to the hot water tank 4 via the preheating tank 5 does not have an open part to the atmosphere, the water pressure of the water supply source can supply water to the hot water tank 4, so the preheating tank 5 and the hot water tank 4 are on different floors It can also be installed. For example, while the preheating tank 5 may be installed on the ground floor, the hot water tank 4 may be installed on the basement floor.

The preheating tank 5 is connected to a water supply source (water distribution pipe) via the upstream water supply pipe 12A, and is connected to the hot water tank 4 via the downstream water supply pipe 12B. Therefore, water from the water supply source fills the preheating tank 5 via the upstream water supply pipe 12A, and can be supplied to the hot water tank 4 via the downstream water supply pipe 12B. As described above, the hot water tank 4 is provided with the constant water level valve 13. By opening the constant water level valve 13, the water from the water supply source can be divided into the upstream water supply pipe 12A, the preheating tank 5, and the downstream water supply pipe. It can be supplied to the hot water tank 4 via 12B. That is, by opening the constant water level valve 13, it is possible to supply water from the water supply source to the preheating tank 5 from the water supply source while supplying water from the preheating tank 5 to the hot water tank 4.

The stored water in the preheating tank 5 is heated using the off-gas waste heat of the fuel cell 7. At this time, temperature stratification (higher temperature in the upper part and lower temperature in the lower part) is formed in the preheating tank 5 . In order not to disturb the thermal stratification, the upstream side water supply pipe 12A from the water supply source is connected to the lower part of the preheating tank 5 as shown in the illustrated example, and the upper side is the downstream side water supply pipe 12B to the hot water tank 4 Are preferably connected.

The upstream water supply pipe 12A and the downstream water supply pipe 12B are optionally connected by a bypass pipe 12C. In this case, it is possible to switch whether water from the water supply source is supplied to the hot water tank 4 via the preheating tank 5 or supplied to the hot water tank 4 via the bypass pipe 12C without the preheating tank 5 . Therefore, in the present embodiment, the inlet valve 16 is provided in the upstream water supply pipe 12A downstream of the branch with the bypass pipe 12C, while the downstream water supply pipe 12B is provided with a junction with the bypass pipe 12C. An outlet valve 17 is provided upstream. Furthermore, a bypass valve 18 is provided in the bypass pipe 12C. The inlet valve 16, the outlet valve 17 and the bypass valve 18 are constituted by manual valves in this embodiment. And normally, while the bypass valve 18 is closed, the inlet valve 16 and the outlet valve 17 are maintained in the open state. Therefore, the water from the water supply source is supplied to the preheating tank 5 via the upstream water supply pipe 12A without via the bypass pipe 12C, and the water in the preheating tank 5 is supplied to the hot water tank via the downstream water supply pipe 12B. It is supplied to 4.

On the other hand, when desired, the bypass valve 18 is opened while the inlet valve 16 and the outlet valve 17 are closed, and water from the water supply source is transferred to the hot water tank 4 via the bypass pipe 12C without passing through the preheating tank 5 It is possible to supply. For example, when maintaining the preheating tank 5 and the circulating fluid circuit 19 described later, the bypass valve 18 may be opened while the inlet valve 16 and the outlet valve 17 may be closed. In that case, the hot water tank 4 can be supplied with water directly from the water supply source, and the main heat source unit 6 can produce hot water in the hot water tank 4, so that hot water to the hot water demand point can be prevented. .

The stored water in the preheating tank 5 can be heated using the off-gas waste heat of the fuel cell 7. Therefore, in the present embodiment, the off-gas heat exchanger 21 for exchanging heat between the off-gas of the fuel cell 7 (more specifically, the fuel cell main body 20 described later) and the coolant thereof, and 21 heating by the off-gas heat exchanger A preheating heat exchanger 22 for heating the stored water in the preheating tank 5 with the cooling fluid, and a circulating fluid circuit 19 for circulating the cooling fluid between the off gas heat exchanger 21 and the preheating heat exchanger 22; Prepare. The coolant circulating in the circulating fluid circuit 19 is water here, but may be another liquid (for example, antifreeze containing ethylene glycol as a main component).

The fuel cell 7 includes, in addition to the off-gas heat exchanger 21, a fuel cell body 20, a power conditioner (not shown), various accessories (not shown), and the like. The fuel cell main body 20 includes a reformer (not shown), a cell stack (not shown) and the like. Specifically, the fuel cell main body 20 is configured as a power generation module in which main devices used for power generation are accommodated in a heat insulation container, and the main devices include (I) an evaporation unit, a mixing unit, and a reforming unit. A reformer; (II) a cell stack composed of a plurality of power generation cells; (III) a combustor for burning the anode off gas and the cathode off gas; (IV) an air preheater for heat exchange between the combustion off gas and the anode air.

A raw fuel (city gas) G, air A, and water (reforming water) W are supplied to the fuel cell main body 20. Then, a reformed gas is produced by causing the raw fuel (city gas mainly containing methane gas) G and water (steam) W to undergo a steam reforming reaction to produce a reformed gas containing hydrogen, which is contained in the reformed gas. The hydrogen and oxygen in the air are chemically reacted in the cell stack to generate electricity. In the cell stack, an anode off gas and a cathode off gas are generated as the power is generated, but these gases are supplied to the combustor and then discharged as a combustion off gas. The combustion off gas is passed through an air preheater disposed upstream of the cell stack and used to preheat cathode air.

The cell output of the cell stack is fed into the building 2 after being conditioned by the power conditioner. The power conditioner is a DC / DC converter (boost circuit) that boosts the DC voltage output from the cell stack, and a system that converts the DC voltage boosted by the DC / DC converter into an AC voltage synchronized with the system power supply. It has an interconnection inverter (voltage conversion circuit) and an output current control unit (output control circuit) that controls the output current of the cell stack. The grid-connected inverter is electrically connected to the switchboard of the commercial power system installed in the building 2. The grid interconnection inverter and the switchboard can switch between parallel and parallel connection via a grid interconnection switch. A grid power supply and a plurality of distribution boards are electrically connected to the switchboard. The power distribution board is electrically connected to load devices such as lighting devices, power devices, and outlets used on each floor of the building.

The type of fuel cell main body 20 is not particularly limited, but is preferably in the form of solid oxide (SOFC). The SOFC has a high-temperature operating temperature of 650 to 800 ° C and a medium-temperature operating temperature of 450 to 650 ° C. Therefore, from the viewpoint of cell stack protection, the electric main heat secondary does not stop after startup / heating. It is basic to drive. Therefore, high overall efficiency can be maintained by enabling recovery of offgas waste heat that continues to be generated. However, SOFC (solid oxide form) has higher power generation efficiency compared to PAFC (phosphoric acid form) and PEFC (solid polymer form), so the off-gas waste heat quantity is small when compared with the same power generation output. It may not be possible to meet the demand for hot water. However, by using off-gas waste heat to preheat the feed water to the hot water tank 4 capable of heating the stored water by the main heat source unit 6, building a cogeneration system that simultaneously satisfies the power demand and the hot water demand of the building 2 Can.

The off-gas heat exchanger 21 is an indirect heat exchanger that exchanges heat without mixing the off-gas from the fuel cell body 20 and the coolant thereof. Therefore, the off gas is passed from the fuel cell main body 20 to the off gas heat exchanger 21 through the off gas pipe 23, and the circulating fluid in the circulating fluid circuit 19 is passed as a coolant for the off gas. As a result, in the off-gas heat exchanger 21, the off-gas is cooled by the circulating coolant, and the water (water vapor) in the off-gas is condensed. On the other hand, the circulating coolant in the circulating fluid circuit 19 is heated by exchanging heat with the off gas in the off gas heat exchanger 21.

The off-gas to be subjected to heat exchange in the off-gas heat exchanger 21 is an off-gas containing water vapor generated in the fuel cell main body 20. Specifically, (i) anode off gas discharged from the anode side of the cell stack; (ii) cathode off gas discharged from the cathode side of the cell stack; (iii) combustion off gas discharged from the combustor One or more can be the target of heat exchange. The off gas passed through the off gas heat exchanger 21 may be in a state after partial heat recovery by an air preheater or the like.

On the anode side of the SOFC cell stack, the anode off gas contains water vapor because a chemical reaction between hydrogen and oxygen takes place. Since the air supplied to the cathode side of the SOFC cell stack contains atmospheric water vapor, the cathode off gas also contains water vapor. The combustion off gas includes the water vapor derived from the anode off gas and the cathode off gas, as well as the water vapor generated by the combustion reaction of the residual hydrogen in the anode off gas and the residual oxygen in the cathode off gas. Therefore, even when any off-gas is subjected to heat exchange, condensed water can be obtained by cooling to a dew point temperature or lower.

A separator tank 24 is provided on the outlet side of the off gas from the off gas heat exchanger 21 so that the gas and liquid of the off gas passed through the off gas heat exchanger 21 can be separated. Then, the condensed water after gas-liquid separation can be re-supplied to the reformer of the fuel cell main body 20 via the supply pump 25 as reformed water W to the fuel cell main body 20. As a result, the fuel cell 7 is capable of water self-sustaining operation capable of continuing power generation without replenishment water from the outside. The anode off gas and the cathode off gas after gas-liquid separation are supplied to the combustor, and the combustion off gas after gas-liquid separation is discharged to the outside.

In the water self-sustaining operation of the fuel cell 7, in the reformer, after the condensed water as the reforming water W is vaporized in the evaporation unit, the raw fuel G and the water vapor are mixed in the mixing unit. Then, the mixed gas is supplied to the catalyst layer of the reforming unit to generate a reformed gas containing hydrogen. The reformed gas obtained in the reforming section is sent to the anode side of the cell stack as an anode fuel.

In addition, the off-gas heat exchanger 21 can perform the gas-liquid separation of the off-gas in the off-gas heat exchanger 21 instead of the separator tank by devising the structure and the flow of the fluid. In that case, a branch line for exhaust is connected to the outlet side of the off gas from the off gas heat exchanger 21.

The preheating heat exchanger 22 is disposed in the preheating tank 5 and performs indirect heat exchanger (for example, heat transfer) for exchanging heat without mixing the stored water in the preheating tank 5 with the circulating coolant from the off-gas heat exchanger 21. Coil). The preheating heat exchanger 22 is disposed so as to be able to heat at least a lower region (for example, a height region of 30 to 50% from the bottom) into which the normal temperature water flows in the inner region of the preheating tank 5. As a result, in the preheating heat exchanger 22, the stored water in the preheating tank 5 is heated, while the circulating coolant in the circulating fluid circuit 19 is cooled.

The circulating fluid circuit 19 circulates the coolant between the off-gas heat exchanger 21 and the preheating heat exchanger 22. Specifically, the cooling fluid is supplied from the preheating heat exchanger 22 to the off gas heat exchanger 21 via the cooling fluid feed passage 19A, and the cooling from the off gas heat exchanger 21 to the preheating heat exchanger 22 is performed. The coolant is returned through the liquid return path 19B. Then, the coolant is circulated between the off-gas heat exchanger 21 and the preheating heat exchanger 22 by operating the circulation pump 26 provided in the coolant feed passage 19A (or the coolant return passage 19B). it can.

In the present embodiment, a radiator 27 and a circulation pump 26 are provided in order from the heat exchanger 22 for preheating to the off gas heat exchanger 21 in the coolant delivery passage 19A. The circulation pump 26 may be provided in the cooling fluid return passage 19B instead of being provided in the cooling fluid feed passage 19A.

The radiator 27 is a heat exchanger for the coolant to the off-gas heat exchanger 21 and the ventilation by the fan 28. By operating the fan 28 of the radiator 27 when desired, the coolant supplied to the off-gas heat exchanger 21 can be cooled with the open air. For example, when the heat recovery of the off gas waste heat can not be sufficiently performed in the preheating tank 5, the off gas heat exchanger 21 is set by setting the temperature of the coolant to the off gas heat exchanger 21 below the dew point temperature of the off gas by the cooling action of the radiator 27. The water contained in the off-gas can be condensed in order to achieve water independence of the fuel cell 7.

The radiator 27 is preferably adjustable in ventilation rate. In the present embodiment, the drive motor of the fan 28 is a DC motor, and a plurality of radiators 27 are arranged in the coolant feed path 19A (an example of arrangement of only one is described in FIG. 1). In this configuration, the fan 28 is driven at a constant speed. By controlling the number of radiators 27 operated, that is, the number of fans 28 driven, the amount of ventilation can be adjusted.

Further, when the radiator 27 is configured as one unit, the drive motor of the fan 28 may be a brushless DC motor, and this DC motor may be configured to perform variable speed control by pulse width modulation (PWM). The amount of ventilation can be adjusted by changing the duty ratio of the drive voltage pulse of the DC motor while the fan 28 is operating.

When the radiator 27 is configured as one unit, the drive motor of the fan 28 may be an AC motor, and this AC motor may be configured to perform variable voltage variable frequency control (VVVF control) by an inverter device. While the fan 28 is operating, the amount of ventilation can be adjusted by changing the drive frequency or drive voltage of the AC motor.

The circulation pump 26 is preferably configured to be able to adjust the flow rate of the coolant. In this embodiment, the drive motor of the circulation pump 26 is a brushless DC motor, and this DC motor is configured to perform variable speed control by pulse width modulation (PWM). The circulation flow rate in the circulation fluid circuit 19 can be adjusted by changing the duty ratio of the drive voltage pulse of the DC motor while the circulation pump 26 is operating.

Further, the drive motor of the circulation pump 26 may be an AC motor, and this AC motor may be configured to perform variable voltage variable frequency control (VVVF control) by an inverter device. The circulation flow rate in the circulation fluid circuit 19 can be adjusted by changing the drive frequency or drive voltage of the AC motor while the circulation pump 26 is in operation.

Also, when driving the drive motor at a constant speed regardless of whether it is DC or AC, the coolant return path 19 B from the off gas heat exchanger 21 to the preheating heat exchanger 22 or the off gas from the preheating heat exchanger 22 A proportional control valve is provided in the coolant feed passage 19A to the heat exchanger 21. During operation of the circulation pump 26, the circulation flow rate in the circulation fluid circuit 19 can be adjusted by adjusting the opening degree of the proportional control valve.

In the coolant delivery passage 19A, a first temperature sensor 30 is provided on the outlet side of the radiator 27, and in the coolant return passage 19B, a second temperature sensor 31 is provided. The first temperature sensor 30 detects the temperature of the coolant on the inlet side of the off gas heat exchanger 21, and the second temperature sensor 31 detects the temperature of the coolant on the outlet side of the off gas heat exchanger 21.

When the fuel cell 7 is in operation, the circulation pump 26 is operated. As a result, the coolant is circulated between the off-gas heat exchanger 21 and the preheating heat exchanger 22. In the off-gas heat exchanger 21, the off-gas from the fuel cell main body 20 is cooled, while the coolant for the preheating heat exchanger 22 is heated. On the other hand, in the preheating heat exchanger 22, the stored water in the preheating tank 5 is heated by the cooling fluid from the off gas heat exchanger 21. In this manner, off-gas waste heat of the fuel cell 7 can be used to heat the stored water in the preheating tank 5 to recover heat.

During operation of the circulation pump 26, the number of driven fans 28 in the plurality of radiators 27 increases or decreases so that the temperature detected by the first temperature sensor 30 is maintained in the first target temperature range (for example, a setting range of 35 to 40.degree. C.). Be done. For example, feed forward control is used to increase or decrease the number of driving. Specifically, when the detected temperature of the first temperature sensor 30 becomes equal to or higher than the upper limit set value (for example, 40 ° C.) and the first set time (for example, 10 seconds) continues in that state, while one unit is activated, The temperature detected by the temperature sensor 30 becomes equal to or lower than the lower limit set value (for example, 35 ° C.), and one unit is stopped when the second set time (for example, 10 seconds) elapses in that state. Thereby, the temperature of the coolant can be prevented from rising excessively, and water self-sustaining can be reliably achieved. That is, the off gas can be cooled to the dew point temperature or less in the off gas heat exchanger 21 to condense the moisture in the off gas, and the condensed water can be resupplied to the reformer.

The drive motor output of the circulation pump 26, that is, the circulation flow rate, so as to maintain the temperature detected by the second temperature sensor 31 at the second target temperature (for example, a set value selected from 60 to 75 ° C.) Is adjusted. For the adjustment of the drive motor output, for example, feedback control based on a velocity type PID algorithm is used. Thus, the temperature of the circulating fluid supplied to the preheating heat exchanger 22 can be maintained at a predetermined temperature, and the stored water in the preheating tank 5 can be heated to a desired temperature.

The hot water in the hot water tank 4 is supplied to one or more hot water demand points in the building 2 and made available. In the present embodiment, a hot water supply circulation pipe 8 for circulating the hot water stored in the hot water tank 4 is laid in the building 2, and the hot water can be taken out from the hot water outlet 32 provided in the hot water supply circulation pipe 8 It is assumed.

The hot water supply circulation pipe 8 is a loop pipe for circulating the hot water in the hot water tank 4 to each floor of the building 2. In the present embodiment, the outgoing route 8A is laid from the underground warm water tank 4 toward the top floor, and the return route 8B is laid from the top floor toward the warm water tank 4. A circulation pump 33 which doubles as a pumping pump is provided at the outlet from the hot water tank 4 in the outward path 8A.

By the way, the hot water tank 4 is typically in the form of a substantially rectangular box, and the hot water supply port to the forward path 8A of the hot water supply circulation pipe 8 and the return port from the return path 8B are provided diagonally. preferable. Further, in the hot water tank 4, it is preferable that the water supply port from the water supply pipe 12 and the hot water outlet from the return path 8B of the hot water supply circulation pipe 8 be disposed adjacent to each other. Thus, it is possible to mix the makeup water from the water supply source through the preheating tank 5 and the hot water from the return path 8B of the hot water supply circulation pipe 8.

On each floor (or desired floor) of the building 2, a hot water outlet 32 to a hot water demand point is provided. In the present embodiment, on each floor of the first floor or more, the branch pipe 8X is provided, which uses the hot water supply circulation pipe 8 as a main pipe and sends hot water from the main pipe to a hot water demand point. At this time, normally, the branch pipe 8X is branched from the forward passage 8A of the main pipe. That is, the branch pipe 8 </ b> X is a construction facility associated with the hot water supply circulation pipe 8. In the illustrated example, only one branch pipe 8X is shown on each floor, but a plurality of branch pipes 8X may be provided. Also, if desired, one branch pipe 8X may be branched from one branch pipe 8X.

Each branch pipe 8X is a pipe for supplying the hot water from the trunk pipe (hot water supply circulation pipe 8) to the hot water discharge portion 32. The hot water outlet 32 is, for example, a mixing plug 32A provided in a wash basin, a bathroom, a kitchen or the like. In addition, the water supply piping 9 of cold water (normal temperature water) is separately laid from the water receiving tank 3 to each floor. Then, it is possible to supply hot water from the hot water tank 4 via the main pipe 8A and the branch pipe 8X and cold water from the water receiving tank 3 via the water supply pipe 9 to the mixing plugs 32A on each floor, and the mixing ratio The hot water of desired temperature can be discharged by adjusting. A water pump 34 is provided on the water receiving pipe 3 side of the water supply pipe 9. When the mixing valve 32A is opened in a state where the water pump 34 is operated, the water from the water receiving tank 3 is discharged. It can be done.

Next, the operation (operation) of the fuel cell system 1 of the present embodiment will be described.
The fuel cell 7 performs electric main heat secondary operation which constantly generates power while connecting to the grid, and according to the power demand in the building 2, the power generation output of the fuel cell 7 (cell output of the cell stack as power conditioner The output adjusted by) is adjusted. That is, the system power supply is used as a peak load power supply while using the fuel cell 7 as a base load power supply. Along with the operation of the fuel cell 7, the circulation pump 26 of the circulating fluid circuit 19 between the off-gas heat exchanger 21 and the preheating heat exchanger 22 operates. In addition, the number of driven fans 28 in the plurality of radiators 27 is increased or decreased and the detected temperature of the second temperature sensor 31 is set to the second target so that the temperature detected by the first temperature sensor 30 is maintained in the first target temperature range. As described above, the drive motor output of the circulation pump 26 is automatically controlled to maintain the temperature. As a result, in the off-gas heat exchanger 21, the off-gas can be cooled to the dew point temperature or lower, and reliable and stable water self-sustaining can be achieved. Further, in the preheating heat exchanger 22, the stored water in the preheating tank 5 can be heated by the circulating coolant at a predetermined temperature (second target temperature).

The stored water in the preheating tank 5 is heated up to the second target temperature by heat exchange in the preheating heat exchanger 22. The second target temperature is set to a temperature equal to or lower than the set temperature (the heating target temperature by the main heat source unit 6) in the hot water tank 4.

Water of a predetermined water level is stored in the hot water tank 4 by controlling the water supply by the constant water level valve 13. The preheating tank 5 is provided in the water supply pipe 12 to the hot water tank 4, and the off gas waste heat of the fuel cell 7 is recovered, whereby the preheated hot water can be supplied to the hot water tank 4. Moreover, the stored water in the hot water tank 4 is heated to the set temperature by the main heat source unit 6 and maintained.

In preparation for the hot water demand in the building 2, the circulation pump 33 of the hot water supply circulation pipe 8 continues to operate. Therefore, if the desired mixing stopper 32A on the desired floor is opened, hot water can be poured out immediately. At this time, by mixing normal temperature water from the water receiving tank 3 via the water supply pipe 9 with the hot water from the hot water tank 4, hot water can be discharged at a desired temperature.

By the way, in the preheating tank 5, the off gas waste heat of the fuel cell 7 is used for preheating the water supply to the hot water tank 4 to recover the heat, so that the off gas can be cooled while preheating the stored water in the preheating tank 5. . If this point is demonstrated concretely, the following case is assumed.

(A) If the tap water flowing through the upstream water supply pipe 12A does not exceed the dew point temperature of the off gas in other than the summer season, the off gas can be cooled to the dew point or less only by heat recovery in the preheating tank 5. In this case, in the circulating fluid circuit 19, the fan 28 of the radiator 27 may be stopped.

(B) In summer, when the tap water flowing through the upstream water supply pipe 12A exceeds the dew point temperature of the off gas (for example, when the upstream water supply pipe 12A laid outdoors) is heated by direct sunlight, By the heat recovery and the heat radiation in the radiator 27, the off gas is cooled to the dew point or less. However, even if it is a summer season, when there is a demand for hot water in the building 2, the tap water in the upstream water supply pipe 12A is frequently replaced, so the condition of (b) is basically rare. Therefore, if the water below the dew point temperature is secured for the makeup water to the preheating tank 5, it is possible to enhance the heat recovery efficiency while establishing the water independence by cold energy utilization of the makeup water.

When the demand for hot water in building 2 is small, sufficient heat recovery can not be performed regardless of the water temperature from the water supply source, so the fan 28 of the radiator 27 is operated to dissipate the off gas by heat dissipation to the outside air. It will be cooled below the dew point to establish water independence.

In the building 2 using the fuel cell system 1 of the present embodiment, the water supplied to the hot water tank 4 can be preheated with the waste heat of the fuel cell 7, and the stored water in the hot water tank 4 can be heated by the main heat source machine 6. Accordingly, it is possible to obtain warm water that preferentially uses the waste heat of the fuel cell 7 with a simple configuration. In addition, the existing building equipment of the building 2 can be used as the hot water tank 4, the main heat source machine 6 and the water supply pipe 12, and the fuel cell 7 and the preheating tank 5 are newly constructed in the existing building equipment Is also easy.

The fuel cell system 1 of the present invention is not limited to the configuration of the above embodiment, and can be changed as appropriate. In particular, a building 2 using the fuel cell system 1 is (a) installed on the ground or underground floor, and a warm water tank 4 to which normal temperature water is supplied via a water supply pipe 12; (b) a warm water tank The main heat source unit 6 capable of heating the stored water in 4 is provided as a building facility, and the fuel cell system 1 can supply (c) a fuel cell 7 capable of supplying power into the building 2; (d) water supply (E) cooling the off gas while preheating the stored water in the preheating tank 5 by recovering the heat of the off gas of the fuel cell 7 (f) ) If normal temperature water supplied via the water supply pipe 12 is used as a heat source for cooling off gas in the preheating tank 5 and (g) condensed water generated by cooling off gas is reused in the fuel cell 7 The other configurations can be changed as appropriate.

For example, in the above embodiment, the hot water tank 4 is constituted by the open tank, but in some cases it may be constituted by the closed tank. In that case, the installation of the constant water level valve 13 in the hot water tank 4 is unnecessary, and the hot water for the hot water supply is supplied to the hot water tank 4 via the preheating tank 5 along with the hot water at the hot water demand point.

Moreover, in the said Example, although the warm water tank 4 was maintained at the predetermined water level by the constant water level valve 13, based on the detection signal of the water level sensor provided in the warm water tank 4, the feedwater valve provided in the water supply pipe 12 is automatically controlled. You may This applies not only to the hot water tank 4 but also to the water receiving tank 3.

Moreover, in the said Example, although the preheating tank 5 was made into the closed type tank, you may be made into an open type tank depending on the case. In that case, as in the case where the hot water tank 4 is an open tank, the preheating tank 5 is provided with a constant water level valve or the upstream to the preheating tank 5 to maintain the water level in the preheating tank 5 at the set water level. The water supply valve provided in the side water supply pipe 12A may be automatically controlled.

In the above embodiment, the preheating heat exchanger 22 is installed in the preheating tank 5 to perform indirect heat exchange between the circulating coolant in the circulating fluid circuit 19 and the stored water in the preheating tank 5. The installation of the preheating heat exchanger 22 may be omitted, and the stored water itself in the preheating tank 5 may be circulated to and from the off-gas heat exchanger 21. That is, the stored water in the preheating tank 5 is supplied to the off-gas heat exchanger 21 as a coolant for the off-gas via the coolant feed path 19A, and is heated using the off-gas waste heat in the off-gas heat exchanger 21 The circulation to the preheating tank 5 may be repeated via the coolant return path 19B.

Moreover, in the said Example, although the receiving water tank 3 was installed in the building 2, you may install it in the outdoors (ground) adjacent to the building 2 depending on the case. In the above embodiment, only the first basement floor B1 is shown as the basement, but the second basement floor may be provided.

Moreover, in the said Example, although the receiving tank 3 was installed in the building 2, and water was supplied to each floor from the receiving tank 3, depending on the case, installation of the receiving tank 3 may be abbreviate | omitted and direct pressure direct pressure. Water may be supplied by a system or a direct compression system. The direct pressure direct pressure system is applied to buildings up to about 5 stories above the ground, and water is supplied to each floor only by the water pressure of the distribution pipe. The direct compression method is applied to buildings up to about 10 stories above the ground, and water is supplied to each floor while compensating for the insufficient pressure only by the water pressure of the distribution pipe with a booster pump provided in the middle of the water supply pipe.

Furthermore, in the said Example, although the main heat-source equipment 6 was comprised from the steam boiler 6A, you may be comprised from an electric heater, a burner, heat pump etc. depending on the case.

1 fuel cell system 2 building 3 water receiving tank 4 hot water tank 5 preheating tank 6 main heat source machine (6A: steam boiler)
7 fuel cell 8 hot water supply circulation piping (8A: outward path, 8B: return path, 8X: branch pipe)
9 water supply piping 10 water supply pipe 11 constant water level valve 12 water supply pipe (12A: upstream water supply pipe, 12B: downstream water supply pipe, 12C: bypass pipe)
13 Constant water level valve 14 Common pipeline 15 Steam heater 16 Inlet valve 17 Outlet valve 18 Bypass valve 19 Circulating fluid circuit (19A: Coolant feed path, 19B: Coolant return path)
DESCRIPTION OF SYMBOLS 20 Fuel cell main body 21 Off-gas heat exchanger 22 Heat exchanger for preheating 23 Off-gas piping 24 Separator tank 25 Supply pump 26 Circulation pump 27 Radiator 28 Fan 29 Flow control valve 30 1st temperature sensor 31 2nd temperature sensor 32 Hot water part (32A : Mixing stopper)
33 Circulating pump 34 Pumping pump

Claims

A building having a hot water tank installed on the ground or underground floor and supplemented with normal temperature water through a water supply pipe; and a main heat source unit capable of heating stored water in the hot water tank as a building facility A fuel cell system to be used,
A fuel cell capable of supplying electricity into the building;
And a preheating tank disposed in the middle of the water supply pipe,
It is possible to cool the off gas while preheating the stored water in the preheating tank by heat recovery of the fuel cell off gas;
The preheated tank utilizes normal temperature water supplied via the water supply pipe as a heat source for cooling the off gas,
A fuel cell system, wherein condensed water generated by the cooling of the off gas is reused in the fuel cell.
The fuel cell comprises a reformer, a cell stack and an off-gas heat exchanger,
In the off-gas heat exchanger, the off-gas is cooled to a dew point temperature or less by heat exchange between the off-gas and the coolant to condense water in the off-gas, and the condensed water is supplied again to the reformer.
In the reformer, a reformed gas containing hydrogen is generated by subjecting a raw fuel and the condensed water to a steam reforming reaction,
The fuel cell system according to claim 1, wherein in the cell stack, hydrogen in the reformed gas and oxygen in air are chemically reacted to generate power.
A preheating heat exchanger for preheating the stored water in the preheating tank;
The fuel cell system according to claim 2, further comprising: a circulating fluid circuit that circulates the cooling fluid between the off-gas heat exchanger and the preheating heat exchanger.
The fuel cell system according to any one of claims 1 to 3, wherein the fuel cell is a solid oxide fuel cell.
The building facility includes a hot water supply circulation pipe connected so as to be able to circulate the hot water stored in the hot water tank; and a branch pipe which sends the hot water from the main pipe to the hot water demand point using the hot water supply circulation pipe as a main pipe. The fuel cell system according to any one of claims 1 to 4, further comprising.