JP5593808B2 - Fuel cell hot water supply system - Google Patents

Description

  The present invention relates to a fuel cell hot water supply system comprising a fuel cell unit and a hot water storage unit that collects exhaust heat from the fuel cell unit and stores hot water, and in particular, by supplying drain water from the hot water storage unit side. It relates to the technology to ensure sufficient water used on the side.

  Conventionally, heat generated from a combined heat and power supply device is stored in hot water storage tanks as hot water, and this hot water is used for hot water supply to hot water supply destinations such as kitchens and baths and hot water for hot water heating. In addition, a system has been proposed in which auxiliary heating is performed using a latent heat recovery type auxiliary heat source device when the hot water storage cannot provide heat necessary for hot water supply or the like (see, for example, Patent Document 1).

JP 2009-236411 A

  By the way, exhaust heat is recovered from the exhaust gas generated during power generation by the fuel cell and stored in the hot water storage unit. On the other hand, the drain water (condensed water) generated during the exhaust heat recovery is used as a raw material for water treatment. It is used for power generation by a battery. For example, in solid oxide fuel cells (SOFCs), steam reforming is performed in which steam is reacted with hydrocarbon fuel under high temperature conditions to convert it into hydrogen and carbon monoxide. The drain water is used for the steam reforming. However, it is expected that various inconveniences will arise if the water used for the steam reforming is insufficient.

  For example, as illustrated in FIG. 2 in which a fuel cell unit is provided with a hot water storage unit 100, the drain water generated in the heat exchanger 102 for exhaust heat recovery is stored in the water tank 103 on the fuel cell unit 101 side. Water is used for steam reforming in the fuel cell 104, while the hot water storage unit 100 circulates and supplies the cold water in the hot water storage tank 105 to the exhaust heat recovery heat exchanger 102 to exhaust gas. After the heat exchange is heated by the exhaust heat, the hot water is returned to the hot water storage tank 105 and stored.

  However, since the heat exchanger for exhaust heat recovery 102 functions as a drain water recovery heat exchanger for securing steam reforming water, it is circulated and supplied from the hot water storage unit 100 to exchange heat with the exhaust gas. The hot water in the hot water storage tank 105 needs to be sufficiently low in temperature. For this reason, when the hot water in the hot water storage tank 105 has become relatively hot due to the exhaust heat recovery so far, the hot water is circulated and supplied to the exhaust heat recovery heat exchanger by operating the cooling radiator 106. It is necessary to perform operation control to lower the temperature of the battery, and energy consumption (power consumption) for this purpose is required.

  On the other hand, if the drain water is not sufficiently recovered, the water for steam reforming may be depleted, which may lead to a situation that may cause problems for the fuel cell 104 itself, and the deterioration of the fuel cell 104 may occur. There is a possibility of promoting this.

  The present invention has been made in view of such circumstances, and an object of the present invention is to secure water used in the fuel cell unit from other than the fuel cell unit without incurring new energy consumption. The object is to provide a fuel cell hot water supply system.

In order to achieve the above object, in the present invention, a fuel cell unit provided with a fuel cell, and a hot water storage unit that stores heat in a hot water storage tank as hot water storage by exhaust heat recovery using the exhaust heat of the fuel cell as a heat source and uses it for hot water supply or the like The following specific items were provided for a fuel cell hot water supply system equipped with: The hot water storage unit is provided with a latent heat recovery type heat source device as an auxiliary heat source device, and drain water generated by operation of the auxiliary heat source device is recovered and supplied to the fuel cell unit as water used in the fuel cell unit. A drain water supply circuit is provided . In addition, the fuel cell unit includes an exhaust heat recovery heat exchanger that recovers exhaust heat for storing heat as hot water storage in the hot water storage tank by heat exchange heating using the exhaust gas from the fuel cell as a heat source, and the exhaust heat In the heat exchanger for recovery, a water tank for storing drain water generated by condensation of moisture in the exhaust gas by the heat exchange heating, and purifying the water in the water tank into pure water before supplying it to the fuel cell A water treatment unit to be treated is provided. The water tank is configured such that drain water generated in the exhaust heat recovery heat exchanger and drain water supplied by the drain water supply circuit are introduced and stored (claim). Item 1).

In the case of this invention, the drain water supply circuit can supply the drain water generated by the auxiliary heat source unit of the hot water storage unit to the fuel cell unit. For this reason, it becomes possible to secure the water used in, for example, steam reforming in the fuel cell unit by supplying water from other units other than the fuel cell unit in the same system. Thus, although originally in the fuel cell unit has been secured to use water in the fuel cell units by the recovery of P caused drain water to heat recovery in the waste heat recovery heat exchanger, the hot-water storage unit by drain water supply circuit By adding drain water supply to the water tank, it is possible to ensure sufficient water in the same system as water in the water tank that can be purified to pure water and supplied to the fuel cell in the water treatment unit. become able to. Along with the drain water supply is also added from such the drain water supply circuit, minutes of their need for drain water recovery from exhaust heat recovery heat exchanger is reduced, the hot water storage temperature in the hot water storage tank Even if the temperature is higher than the set temperature, for example, the necessity for cooling operation by a cooling radiator or the like is reduced, and the consumption of electric power energy for the driving is reduced. As a result, overall efficiency can be improved without incurring new energy consumption.

  In the present invention, the drain water supply circuit may be provided with a drain water supply path and a drain pump for pumping the drain water to the fuel cell unit through the drain water supply path (Claim 2). By doing in this way, the structure which concerns on drain water supply can be actualized. The drain water supply circuit includes a drain tank for storing drain water, and the fuel cell unit supplies drain water supplied from the drain water supply circuit to the fuel cell. A water tank that stores the used water as the water used, and the control means is configured to control the operation of the drain pump according to the stored water level in the water tank or the stored water level in the drain tank. (Claim 3). By doing so, it becomes possible to maintain the stored water level in the water tank of the fuel cell unit at an appropriate level or more, and it is possible to stably continue operation such as power generation on the fuel cell unit side. Become. For example, if the stored water level in the water tank decreases, the drain pump is controlled to supply drain water from the drain tank, or if the stored water level in the drain tank becomes full, the drain pump is controlled to operate. By supplying drain water from the tank, it is possible to solve both problems of securing the amount of water in the water tank on the fuel cell unit side and avoiding inconvenience such as overflow avoidance due to full water in the drain tank on the hot water storage unit side It will be.

In the present invention, the water tank can be connected to a drainage channel for draining after draining the internal drain water (Claim 4). By doing in this way, drain water can be discharged after neutralizing drain water in the water tank at the time of maintenance or operation stop. Furthermore , in the present invention, the drain water supply path is attached to at least one of the circulation pipes piped for exhaust heat recovery from the hot water storage unit to the fuel cell unit to which hot water after heat recovery is returned. (Claim 5 ). By doing so, the drain water supply path is also kept warm by the heat of the hot water after heat recovery, and in particular, the drain water supply path is prevented from freezing in winter and the like. Installation can be omitted, and not only the electric heater itself but also electric energy consumption for driving can be reduced or eliminated.

As described above, according to the fuel cell hot water supply system of the present invention, the drain water generated by the auxiliary heat source unit of the hot water storage unit can be supplied to the fuel cell unit by the drain water supply circuit. The water used for, for example, steam reforming in the fuel cell unit can be secured by the supply water from other units other than the fuel cell unit in the same system. Thus, although originally in the fuel cell unit has been secured to use water in the fuel cell units by the recovery of P caused drain water to heat recovery in the waste heat recovery heat exchanger, the hot-water storage unit by drain water supply circuit By adding drain water supply to the water tank, it is possible to ensure sufficient water in the same system as water in the water tank that can be purified to pure water and supplied to the fuel cell in the water treatment unit. become able to. Along with the drain water supply is also added from such the drain water supply circuit, minutes of their need for drain water recovery from exhaust heat recovery heat exchanger is reduced, the hot water storage temperature in the hot water storage tank Even if the temperature is higher than the set temperature, for example, it is not necessary to perform a cooling operation with a cooling radiator or the like, and it is possible to reduce power energy consumption for driving. As a result, overall efficiency can be improved without incurring new energy consumption.

  In particular, according to claim 2, by providing a drain water supply path and a drain pump as the drain water supply circuit, the configuration relating to the drain water supply can be embodied, and in claim 3, According to this, by controlling the operation of the drain pump according to the stored water level of the water tank or the stored water level of the drain tank by the control means, the stored water level in the water tank of the fuel cell unit can be maintained at an appropriate amount or more. As a result, power generation and the like on the fuel cell unit side can be continued stably.

According to claim 4, the water tank is connected to a drainage channel for draining after neutralizing the drain water inside, so that the water tank can be maintained during maintenance or when the operation is stopped. The drain water can be drained after being neutralized. Furthermore , according to the fifth aspect , the drain water supply path is disposed along the pipe line to which at least the hot water after the heat recovery is returned in the circulation pipe for the recovery of the exhaust heat. The drain water supply path can be kept warm by the heat of the hot water, and in particular, the drain water supply path can be prevented from freezing in winter. As a result, installation of an electric heater or the like for preventing freezing can be omitted, and consumption of electric energy not only for the electric heater itself but also for driving it can be reduced or eliminated.

It is a schematic diagram which shows embodiment of the fuel cell hot-water supply system of this invention. FIG. 2 is a diagram corresponding to FIG. 1 illustrating an example of a fuel cell hot water supply system for illustrating the problems of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a fuel cell hot water supply system according to an embodiment of the present invention. This fuel cell hot water supply system includes a fuel cell unit 2, a hot water storage unit 3, and a drain water supply circuit 4 that collects and supplies drain water from the hot water storage unit 3 to the fuel cell unit 2. Hereinafter, a case where water in a water tank 71 described later is used as water for steam reforming will be described by taking as an example a case where the fuel cell unit 2 is configured by a solid oxide fuel cell (SOFC).

  The fuel cell unit 2 includes a fuel cell 5, an exhaust heat recovery heat exchanger 6, and a water supply processing circuit 7. The hot water storage unit 3 includes a hot water storage tank 8, a circulation circuit 9 that circulates and supplies hot water between the hot water storage tank 8 and the exhaust heat recovery heat exchanger 6, and a water inlet passage that allows water from the outside to enter the hot water storage tank 8. 10. Hot water outlet 11 for hot water supply for hot water supply from the top of the hot water storage tank 8, auxiliary heat source machine 12 for auxiliary heating when hot water in the hot water storage tank 8 is lower than the temperature required for hot water supply, and auxiliary heat source machine 12 is provided with an auxiliary heating hot water supply passage 13 for introducing hot water from the hot water storage tank 8 and performing auxiliary heating to discharge the hot water.

  The fuel cell 5 is connected to an air supply system 51 and a fuel gas supply system 52, and includes, for example, a reformer that converts a city gas into a hydrogen-rich fuel gas by steam reforming, a fuel cell, and the like. It is. The fuel battery cell includes a fuel electrode and an air electrode formed of ceramics containing a metal oxide such as Ni, and is formed of a solid oxide such as YSZ (yttrium stabilized zirconia) as an electrolyte. In the fuel cell, cathode air is supplied to the air electrode, oxygen in the cathode air becomes oxygen ions, passes through the electrolyte, and reacts with hydrogen of the fuel gas at the fuel electrode to generate water (water vapor). On the other hand, electricity generated at that time is repeatedly generated by moving to the air electrode side through the circuit and ionizing oxygen again. After the fuel gas supplied to the fuel electrode is used for the above reaction, unused hydrogen-rich off-gas is used as fuel for combustion in the reformer burner, and the exhaust gas after combustion is exhausted through the exhaust gas passage 61. It is introduced into the heat recovery heat exchanger 6.

  The heat exchanger 6 for exhaust heat recovery heats and heats the water circulated and supplied from the circulation circuit 9 on the hot water storage unit 3 side using the exhaust gas introduced from the exhaust gas passage 61 as a heat source. The hot water heated and heated by the heat exchange with the exhaust gas is returned to the hot water storage tank 8 and stored. Thereby, exhaust heat recovery from the exhaust gas introduced from the exhaust gas passage 61 is achieved, and the recovered heat is stored in the hot water storage tank 8 in the form of hot water. Also, drain water (condensed water) generated by condensation of moisture in the exhaust gas by heat exchange with the water in the exhaust heat recovery heat exchanger 6 is recovered in the water tank 71 through the drain water recovery path 62. On the other hand, the exhaust gas after heat exchange is discharged through the exhaust passage 63.

  The water supply processing circuit 7 collects drain water in which moisture contained in the exhaust gas is condensed in the heat exchanger 6 for exhaust heat recovery, purifies the recovered water into pure water, and uses the pure water as the fuel cell 5. It is designed to be reused. That is, the water supply processing circuit 7 includes a water tank 71 for storing drain water, a water treatment unit 72 for purifying the water in the water tank 71 into pure water, and the water-treated pure water for steam reforming. A supply pump 73 for supplying the fuel cell 5 is provided. In the water tank 71, the drain water recovered from the exhaust heat recovery heat exchanger 6 through the drain water recovery path 62 and the drain water supplied by the drain water supply circuit 4 are introduced and stored. It has become. The water tank 71 is provided with a water level sensor 711 as a water level detecting means for detecting that the stored water level in the water tank 71, in particular, the water level has dropped to the set low water level and outputting it to the controller 14 described later. Reference numeral 74 in FIG. 1 denotes a drainage channel, and the drainage channel 74 is drained after neutralizing drain water in the water tank 71 at the time of maintenance or operation stop.

  Next, the hot water storage unit 3 side will be described. A circulation pump 91 and a cooling radiator 92 are interposed in the circulation circuit 9. When the circulation pump 91 is actuated, hot water is taken out from the bottom of the hot water storage tank 8 and then sent to the exhaust heat recovery heat exchanger 6 through the circulation forward passage 93. The exhaust heat recovery heat exchanger 6 exhausts the exhaust gas. The hot water heated to the high temperature by heat exchange with the water is circulated so as to be returned to the top of the hot water storage tank 8 through the circulation return path 94. The cooling radiator 92 is activated when the temperature of the hot water in the hot water storage tank 8 becomes higher than the set upper limit temperature set in relation to the temperature of the exhaust gas supplied to the exhaust heat recovery heat exchanger 6, and is used for exhaust heat recovery. In the heat exchanger 6, the temperature of the circulating hot water is lowered so that drain water is effectively collected. The operation of the circulation pump 91 and the operation of the cooling radiator 92 are controlled by a controller 14 described later.

  The auxiliary heat source unit 12 is constituted by a latent heat recovery type heat source unit, and in addition to the sensible heat recovery heat exchanger 122 that performs heat exchange heating by the combustion heat (sensible heat) of the combustion burner 121, combustion after sensible heat recovery A latent heat recovery heat exchanger 123 is provided for recovering the latent heat of the exhaust gas to increase the efficiency of the heat recovery. The hot water led out from the hot water storage tank 8 is first passed through the latent heat recovery heat exchanger 123 and preheated by the latent heat recovery of the exhaust gas, and then passed through the sensible heat recovery heat exchanger 122 for heat exchange heating. Thus, after the auxiliary heating to the predetermined temperature, the hot water is discharged for hot water supply through the auxiliary heating hot water supply passage 13.

  The drain water supply circuit 4 collects and stores the drain water generated by heat exchange with the exhaust gas in the latent heat recovery heat exchanger 123, and supplies the drain water from the drain tank 41 to the drain water. And a drain pump 43 that supplies the water tank 71 on the fuel cell unit 2 side through the passage 42. The drain tank 41 is provided with a water level sensor 411 serving as a water level detecting means for detecting that the stored water level in the drain tank 41, in particular, the water level has risen to the set high water level and outputting it to the controller 14 described later. In addition, the drain water supply path 42 is in a state where it is attached to the circulation forward path 93 and the circulation return path 94 of the circulation circuit 9 at least in a range where piping is connected between the fuel cell unit 2 and the hot water storage unit 3. It is piped. That is, the three pipes 44 are formed by bundling and integrating the three pipes of the drain water supply path 42, the circulation forward path 93, and the circulation return path 94. Thereby, in particular, the drain water supply passage 42 is prevented from freezing in winter or the like by the heat of hot water that has become hot after the exhaust heat recovery flowing in the circulation return passage 94. As a result, energy saving is realized such that installation of an electric heater or the like for preventing freezing can be omitted, or not only the electric heater itself but also electric energy consumption for driving can be reduced or eliminated. be able to. Even if the main pipe is not used, the drain water supply path 42 may be provided at least along the circulation return path 94.

  Each operation of the fuel cell unit 2, the hot water storage unit 3 and the drain water supply circuit 4 is controlled by a controller 14. In particular, the controller 14 includes a drain water supply control unit 141 as control means for controlling the operation of the drain water supply circuit 4. This drain water supply control unit 141 receives the output of the water level detection signal from the water level sensor 711 of the water tank 71 and the water level detection signal from the water level sensor 411 of the drain tank, and controls the operation of the drain pump 43. The storage amount in the water tank 71 is maintained and secured at an appropriate amount or more (a set water level or more).

  That is, when it is detected that the stored water level in the water tank 71 has decreased to the set low water level based on the water level detection signal from the water level sensor 711, the drain water supply control unit 141 controls the operation of the drain pump 43 to Drain water is supplied from the tank 41 to the water tank 71 to raise the stored water level of the water tank 71. In this case, if the water level sensor 711 detects that the inside of the water tank 71 has risen to the set high water level or the water level sensor 411 detects that the inside of the drain tank 41 has fallen to the set low water level, the operation of the drain pump 43 is performed. It is supposed to stop. On the other hand, when it is detected that the stored water level of the drain tank 41 has risen to the set high water level based on the water level detection signal from the water level sensor 411, the drain water supply control unit 141 controls the drain pump 43 in the same manner as described above. The operation is controlled so that drain water is supplied from the drain tank 41 to the water tank 71. In this case, if the water level sensor 411 detects that the inside of the drain tank 41 has been lowered to the set low water level, or if the water level sensor 711 has detected that the inside of the water tank 71 has risen to the set high water level, the operation of the drain pump 43 is performed. It is supposed to stop. As described above, it is possible to realize both of securing the amount of water in the water tank 71 on the fuel cell unit 2 side and avoiding inconvenience such as overflow avoidance due to full water in the drain tank 41 on the hot water storage unit 3 side.

  In the case of the above embodiment, the water tank 71 of the fuel cell unit 2 not only secures water on the fuel cell unit 2 side, that is, drain water recovery from the exhaust heat recovery heat exchanger 6, but also assists the hot water storage unit 3. It is also possible to supply drain water generated by the heat source unit 12 and to secure water from the hot water storage unit 3 side constituting the fuel cell hot water supply system other than the fuel cell unit 2. Sufficient water can be secured in the same system as water used for reforming. As the drain water supply is added from the auxiliary heat source unit 12 as well, the necessity for drain water recovery from the exhaust heat recovery heat exchanger 6 is reduced correspondingly, and the hot water storage temperature in the hot water storage tank 8 is reduced. Even if the temperature is higher than the set temperature, the necessity of operating the cooling radiator 92 is reduced, and the power consumption for driving can be reduced. As a result, the overall efficiency can be improved. In addition, by controlling the operation of the drain pump 43 by the drain water supply control unit 141, the stored water level in the water tank 71 can be maintained at an appropriate amount or more, and thereby operation such as power generation on the fuel cell unit 2 side can be performed. Can be continued stably.

<Other embodiments>
In addition, this invention is not limited to the said embodiment, Various other embodiments are included. That is, in the above-described embodiment, the case where the water in the water tank 71 is used as water for steam reforming will be described by taking as an example the case where the fuel cell unit 2 is configured by a solid oxide fuel cell (SOFC). However, the present invention is not limited to this, and the present invention is applied when, for example, the fuel cell unit is configured by a polymer electrolyte fuel cell (PEFC), and the water in the water tank is used as water for cell humidification of the fuel cell. You may do it.

  Further, the drain tank 41 may be installed in the auxiliary heat source unit 12, and the drain pump 43 may be installed in the auxiliary heat source unit 12, or may be installed in a drain water supply path 42 other than the hot water storage unit 3. You may interpose in the part which is.

2 Fuel Cell Unit 3 Hot Water Storage Unit 4 Drain Water Supply Circuit 5 Fuel Cell 8 Hot Water Storage Tank 12 Auxiliary Heat Source Machine (Latent Heat Recovery Type Heat Source Machine)
41 Drain tank 42 Drain water supply path 43 Drain pump 71 Water tank 93 Circulation forward path (circulation pipeline)
94 Circulation return path (pipe for returning hot water after heat recovery)
141 Drain water supply control part (control means)
411 Water level sensor 711 Water level sensor

Claims (5)

A fuel cell hot water system comprising: a fuel cell unit including a fuel cell; and a hot water storage unit that stores heat in a hot water storage tank as hot water by exhaust heat recovery using the exhaust heat of the fuel cell as a heat source, and is used for hot water supply, etc.
The hot water storage unit has a latent heat recovery type heat source machine as an auxiliary heat source machine,
E Bei drain water supply circuit for supplying to the fuel cell unit as used water collected drain water generated by the operation operation of the auxiliary heat source machine the drain water in the fuel cell unit,
The fuel cell unit includes an exhaust heat recovery heat exchanger for recovering exhaust heat for storing heat as hot water storage in the hot water storage tank by heat exchange heating using exhaust gas from the fuel cell as a heat source, and heat for recovering the exhaust heat. A water tank for storing drain water generated by condensation of moisture in the exhaust gas by heat exchange heating in the exchanger, and water to be purified into pure water before supplying the water in the water tank to the fuel cell A processing unit,
In the water tank, drain water generated in the heat exchanger for exhaust heat recovery and drain water supplied by the drain water supply circuit are introduced and stored .
A fuel cell hot water supply system characterized by that. The fuel cell hot water supply system according to claim 1,
The drain water supply circuit includes a drain water supply path and a drain pump for pumping drain water to the fuel cell unit through the drain water supply path. The fuel cell hot water supply system according to claim 2,
The drain water supply circuit includes a drain tank for storing drain water, and the fuel cell unit uses the drain water supplied from the drain water supply circuit in the fuel cell. It has a water tank that stores it as water,
The fuel cell hot water supply system, wherein the control means is configured to control the operation of the drain pump in accordance with a stored water level in the drain tank or a stored water level in the water tank. A fuel cell hot water supply system according to any one of claims 1 to 3,
A fuel cell hot water supply system, wherein the water tank is connected to a drainage channel for draining after neutralizing drain water inside. The fuel cell hot water supply system according to any one of claims 1 to 4 ,
The drain water supply path is disposed along a pipe line in which at least hot water after heat recovery is returned from among circulation pipes piped for exhaust heat recovery from the hot water storage unit to the fuel cell unit. , Fuel cell hot water system.

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