JP2016090082A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a heat exchanger in which city water flows from being corroded by residual chlorine without entailing complication and cost increase of a fuel cell system.SOLUTION: A control device 15 for a fuel cell system comprises: a first-temperature high-water control unit 61 that controls a stored-hot-water circulation pump 22b so as to fill a hot water storage tank 21 with stored hot water, which is discharged from a heat exchanger 12, at a first temperature 2a corresponding to a first target temperature T1a lower than a second target temperature T1b of the stored hot water; and a second-temperature high-water control unit 62 that controls the stored-hot-water circulation pump 22b so as to fill the hot water storage tank 21 with the stored hot water at a second temperature T2b corresponding to a second target temperature T1b of the stored hot water discharged from the heat exchanger 12 after the hot water storage tank 21 is filled with the stored hot water at the first temperature T2a under the first-temperature high-water control unit 61.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a fuel cell system.

  As one type of fuel cell system, one shown in Patent Document 1 is known. As shown in FIG. 1 of Patent Document 1, the fuel cell system includes a stainless steel exhaust heat recovery heat exchanger 21 that is connected to the coolant circulation system 5 and recovers the exhaust heat of the coolant 7; The circulation path 22 of the intermediate heat transfer water 25 having a low ion concentration as the secondary heat medium, and the recovery heat of the intermediate heat transfer water connected to the circulation path to the outside with a high ion concentration (especially high residual chlorine concentration). A supply side heat exchanger 23 made of carbon steel that is transmitted to the heat transfer water 12. Thereby, even if it uses a tap water for external heat-medium water, the supply side heat exchanger 23 does not raise | generate a stress corrosion crack.

Japanese Patent Laid-Open No. 06-029036

  In the fuel cell system described in Patent Document 1 described above, the heat exchanger in which tap water having a high residual chlorine concentration flows does not corrode due to residual chlorine. However, the fuel cell system has a problem that the structure is complicated and the cost is increased.

  The present invention was made to solve the above-described problems, and in a fuel cell system, the heat exchanger through which tap water circulates is prevented from being corroded by residual chlorine without increasing complexity and cost. The purpose is to do.

  In order to solve the above problems, a fuel cell system according to a first aspect of the present invention includes a fuel cell that generates power using fuel and an oxidant gas, a hot water storage tank for storing hot water, and exhaust heat and hot water of the fuel cell. Is installed in the hot water circulation line formed to circulate the hot water between the hot water storage tank and the heat exchanger, and the hot water circulation line. And a control device for controlling the delivery amount of the delivery device, the control device corresponding to the first target temperature lower than the second target temperature of the hot water discharged from the heat exchanger. After the hot water tank is filled with the first temperature hot water by the first temperature hot water control part, and the first temperature full water control part that controls the delivery device to fill the hot water tank with the hot water of the first temperature, Second hot water derived from heat exchanger Comprises a second temperature-full level control unit for controlling the delivery device to the full level of the hot water storage tank, the by the hot water of the second temperature corresponding to the temperature.

  According to this, after the hot water storage tank is filled with the hot water of the first temperature by the first temperature full control unit, the hot water of the second temperature that is higher than the first temperature by the second temperature full control unit. Filled up. As a result, the concentration of residual chlorine contained in the tap water supplied to the hot water tank is lowered in the hot water tank raised to the first temperature, so that the tap water is circulated without causing complication and cost increase. It is possible to suppress the heat exchanger that is corroded by residual chlorine. Furthermore, since the hot water supplied from the hot water tank filled with the hot water at the first temperature is supplied to the heat exchanger after the residual chlorine concentration is lowered, the hot water is heated. Corrosion due to residual chlorine acting strongly is suppressed. Therefore, corrosion in the heat exchanger can be suppressed and exhaust heat recovery efficiency can be improved.

It is a schematic diagram showing an outline of one embodiment of a fuel cell system according to the present invention. It is a block diagram which shows the fuel cell system shown in FIG. 3 is a flowchart of a control program executed by the control device shown in FIGS. 1 and 2. It is a map which shows the relationship between the water temperature at the time of leaving the liquid containing a residual chlorine, and a residual chlorine concentration.

  Hereinafter, an embodiment of a fuel cell system according to the present invention will be described. As shown in FIG. 1, the fuel cell system includes a power generation unit 10 and a hot water storage tank 21. The power generation unit 10 includes a housing 10a, a fuel cell module 11 (30), a heat exchanger 12, an inverter device 13, a water tank 14, and a control device 15. The fuel cell module 11 (30), the heat exchanger 12, the inverter device 13, the water tank 14, and the control device 15 are accommodated in the housing 10a.

  As will be described later, the fuel cell module 11 includes at least a fuel cell 34. The fuel cell module 11 is supplied with reforming raw material, reforming water, and cathode air. Specifically, the fuel cell module 11 has one end connected to the supply source Gs and the other end of the reforming material supply pipe 11a to which the reforming material is supplied. The reforming material supply pipe 11a is provided with a material pump 11a1. Furthermore, the fuel cell module 11 has one end connected to the water tank 14 and the other end of the water supply pipe 11b to which the reforming water is supplied. The water supply pipe 11b is provided with a reforming water pump 11b1. Further, the fuel cell module 11 has one end connected to the cathode air blower 11c1 and the other end of the cathode air supply pipe 11c to which the cathode air is supplied.

  The heat exchanger 12 is supplied with combustion exhaust gas exhausted from the fuel cell module 11 and supplied with hot water from the hot water storage tank 21, and includes combustion exhaust gas (including exhaust heat from the fuel cell 34 and the reforming unit 33). Heat exchanger) and hot water storage. Specifically, the hot water storage tank 21 stores hot water, and is connected to a hot water circulation line 22 through which the hot water circulates (circulates in the direction of the arrow in the figure). On the hot water storage line 22, a radiator 22a, a hot water circulation pump 22b, a heat exchanger hot water introduction temperature sensor 22c, a heat exchanger 12, and a heat exchanger hot water derivation temperature sensor 22d are sequentially arranged from the lower end to the upper end. It is arranged. The heat exchanger 12 is connected (penetrated) with an exhaust pipe 11 d from the fuel cell module 11. The heat exchanger 12 is connected to a condensed water supply pipe 12 a connected to the water tank 14.

In the heat exchanger 12, the combustion exhaust gas from the fuel cell module 11 is introduced into the heat exchanger 12 through the exhaust pipe 11d, exchanged with the hot water, condensed and cooled. The condensed combustion exhaust gas is discharged to the outside through the exhaust pipe 11d. Moreover, the condensed condensed water is supplied to the water tank 14 through the condensed water supply pipe 12a. The water tank 14 purifies the condensed water with ion exchange resin.
The heat exchanger 12, the hot water tank 21, and the hot water circulation line 22 described above constitute an exhaust heat recovery system 20. The exhaust heat recovery system 20 recovers and stores the exhaust heat of the fuel cell module 11 in hot water storage.

The hot water tank 21 is a sealed container. The hot water tank 21 includes a pressure relief valve 21d. When the pressure in the hot water storage tank 21 becomes equal to or higher than a predetermined pressure, the pressure relief valve 21d is opened to release the pressure (internal gas) to the outside. The hot water tank 21 is a pressure-resistant container. The hot water tank 21 can withstand at least the pressure of tap water.
In the hot water tank 21, a hot water tank temperature state detection device 21b for detecting the temperature state of the hot water in the hot water tank 21 is provided. The hot water tank temperature state detection device 21b is composed of a plurality of (in this embodiment, five) temperature sensors 21b1, 21b2, 21b3, 21b4, and 21b5, and is equally spaced along the vertical direction (vertical direction) ( It is arranged at a distance of a quarter of the vertical height in the hot water tank 21). The temperature sensor 21b1 is disposed at the inner lower surface position (near 21a) of the hot water tank 21. Each temperature sensor 21b1, 21b2, 21b3, 21b4, 21b5 detects the temperature of the liquid (hot water or water) in the hot water storage tank 21 at that position. The amount of remaining hot water in the hot water storage tank 21, that is, the temperature state of the hot water stored in the hot water storage tank 21, is detected based on the detection result of the hot water temperature at each position by the temperature sensor group. The amount of remaining hot water represents the amount of heat stored in the hot water storage tank 21. In addition, you may make it the hot water tank inside temperature state detection apparatus 21b be comprised only by the temperature sensor 21b1 provided in the lowest part.
The temperature distribution in the hot water storage tank 21 is basically divided into two layers having different temperatures. The upper layer is a layer having a relatively high temperature (for example, 50 degrees or more), and the lower layer is a layer having a relatively low temperature (for example, 20 degrees or less (temperature of tap water)). The upper and lower layers are at substantially the same temperature.

The hot water storage tank 21 is provided with a derivation device 23 that adjustably supplies hot water from the hot water storage tank 21, and an introduction device 25 that introduces the water supplied from the water supply source 24 into the hot water storage tank 21.
The derivation device 23 is connected to a hot water use device 41 where hot water is used, and a hot water supply pipe 42 for supplying hot water to the hot water use device 41, and a hot water supply pipe 42 connected to the hot water supply pipe 42 to discharge the hot water to the outside. And a switching valve 44 provided on the draining pipe 43 and opening / closing the draining pipe 43 in accordance with an opening / closing command of the control device 15. Further, the derivation device 23 may be constituted by a hot water use device 41 and a hot water supply pipe 42. In addition, the hot water use apparatus 41 is comprised from the some hot water utilization apparatus and heat utilization apparatus, for example. There are bathtubs, showers, kitchens (kitchen faucets), and washrooms (toilet faucets). Examples of heat utilization devices include bathroom heating, floor heating, and hot water for bathtubs. There are two types of heat utilization devices: a type that circulates hot water and a type that discharges hot water after heat exchange.
The hot-water storage water supply pipe 42 is provided with a flow meter 42a that detects the supply amount of hot-water storage water that passes therethrough (water flow rate per unit time). The detection result of the flow meter 42 a is transmitted to the control device 15.

  The introduction device 25 includes a water supply pipe 51 that connects the water supply source 24 and the hot water storage tank 21. The water supply source 24 is a water pipe, for example. The water supply pipe 51 is provided with a pressure reducing device 52 that reduces the pressure of the supplied water to a predetermined pressure. The introduction device 25 includes a water supply pipe 51 and a pumping device such as a pump provided in the water supply pipe 51 when the water supply source 24 is not a water pipe having a relatively high pressure but a relatively low pressure supply source. You may make it do.

The radiator 22a is a cooling device that cools the heat medium (hot water) circulating through the hot water circulation line 22, and is controlled to be turned on / off by a command from the control device 15. The heat medium is cooled and turned off in the on state. It is not cooled when in the state. The radiator 22a includes a heat exchanging unit (not shown) in which heat is exchanged between the heat medium and air, and a cooling fan (not shown) for air-cooling the heat exchanging unit.
The hot water circulation pump 22b is a delivery device that sends out the heat medium (hot water) in the hot water circulation line 22 and circulates it in the direction of the arrow in the figure, and is controlled by the control device 15 to control its discharge amount (delivery amount). It is like that.

The heat exchanger hot water introduction temperature sensor 22 c is provided in the hot water circulation line 22 between the hot water outlet 21 a of the hot water tank 21 and the hot water inlet 12 b of the heat exchanger 12. The heat exchanger hot water introduction temperature sensor 22 c detects the temperature of the hot water introduced into the heat exchanger 12 and transmits it to the control device 15.
The heat exchanger hot water outlet temperature sensor 22 d is provided in the hot water circulation line 22 between the hot water outlet 12 c of the heat exchanger 12 and the hot water inlet 21 c of the hot water tank 21. The heat exchanger hot water outlet temperature sensor 22d is preferably provided in the vicinity of the hot water outlet 12c of the heat exchanger 12. The heat exchanger hot water derivation temperature sensor 22 d detects the temperature T1 of the hot water derived from the heat exchanger 12 and transmits it to the control device 15. In addition, instead of the heat exchanger hot water derivation temperature sensor 22d, the temperature of the hot water provided in the heat exchanger 12 and led out from the heat exchanger 12 (particularly on the hot water outlet 12c side of the heat exchanger 12). You may make it use the temperature sensor which detects (temperature).

  The inverter device 13 receives the DC voltage output from the fuel cell 34, converts it to a predetermined AC voltage, and supplies it to a power line 16b connected to an AC system power supply 16a and an external power load 16c (for example, an electrical appliance). Output. Further, the inverter device 13 receives an AC voltage from the system power supply 16 a via the power supply line 16 b, converts it to a predetermined DC voltage, and outputs it to the auxiliary machines (each pump, blower, etc.) and the control device 15. The control device 15 controls the operation of the fuel cell system by driving an auxiliary machine.

The fuel cell module 11 (30) includes a casing 31, an evaporation unit 32, a reforming unit 33, and a fuel cell 34. The casing 31 is formed in a box shape with a heat insulating material.
The evaporating unit 32 is heated by a combustion gas to be described later, evaporates the supplied reforming water to generate water vapor, and preheats the supplied reforming raw material. The evaporation section 32 mixes the steam generated in this way and the preheated reforming raw material and supplies the mixture to the reforming section 33. The reforming raw materials include natural gas (mainly composed of methane gas), gas fuel for reforming such as LP gas, and liquid fuel for reforming such as kerosene, gasoline, and methanol. I will explain.

  The other end of the water supply pipe 11 b whose one end (lower end) is connected to the water tank 14 is connected to the evaporation unit 32. The evaporating section 32 is connected to a reforming material supply pipe 11a having one end connected to the supply source Gs. The supply source Gs is, for example, a gas supply pipe for city gas or a gas cylinder for LP gas.

  The reforming unit 33 is heated by the combustion gas described above and supplied with heat necessary for the steam reforming reaction, so that the reformed gas is generated from the mixed gas (reforming raw material, steam) supplied from the evaporation unit 32. Is generated and derived. The reforming unit 33 is filled with a catalyst (for example, Ru or Ni-based catalyst), and the mixed gas reacts with the catalyst to be reformed to generate a gas containing hydrogen gas and carbon monoxide. (So-called steam reforming reaction). The reformed gas contains hydrogen, carbon monoxide, carbon dioxide, steam, unreformed natural gas (methane gas), and reformed water (steam) that has not been used for reforming. As described above, the reforming unit 33 generates reformed gas (fuel) from the reforming raw material (raw fuel) and the reformed water and supplies the reformed gas (fuel) to the fuel cell 34. The steam reforming reaction is an endothermic reaction.

  The fuel cell 34 is configured by laminating a fuel electrode, an air electrode (oxidant electrode), and a plurality of cells 34a made of an electrolyte interposed between the two electrodes. The fuel cell of this embodiment is a solid oxide fuel cell, and uses zirconium oxide, which is a kind of solid oxide, as an electrolyte. Hydrogen, carbon monoxide, methane gas, etc. are supplied to the fuel electrode of the fuel cell 34 as fuel. The operating temperature is about 400-1000 ° C.

  On the fuel electrode side of the cell 34a, a fuel flow path 34b through which the reformed gas as the fuel flows is formed. An air flow path 34c through which air (cathode air) that is an oxidant gas flows is formed on the air electrode side of the cell 34a.

The fuel cell 34 is provided on the manifold 35. A reformed gas (anode gas) from the reforming unit 33 is supplied to the manifold 35 via a reformed gas supply pipe 38. The lower end (one end) of the fuel flow path 34b is connected to the fuel outlet of the manifold 35, and the reformed gas led out from the fuel outlet is introduced from the lower end and led out from the upper end. . The cathode air sent out by the cathode air blower 11c1 is supplied via the cathode air supply pipe 11c, introduced from the lower end of the air flow path 34c, and led out from the upper end.
In the fuel cell 34, power generation is performed by the anode gas supplied to the fuel electrode and the cathode gas supplied to the air electrode.

  The combustion unit 36 is provided between the fuel cell 34, the evaporation unit 32, and the reforming unit 33. The combustion unit 36 heats the reforming unit 33 by burning the anode offgas (fuel offgas) from the fuel cell 34 and the cathode offgas (oxidant offgas) from the fuel cell 34.

  In the combustion unit 36, the anode off-gas is burned to generate a flame 37 (combustion gas). In the combustion section 36, the anode off gas is burned and the combustion exhaust gas is generated. The combustion unit 36 is provided with a pair of ignition heaters 36a1 and 36a2 for igniting the anode off gas.

  The control device 15 controls the overall operation of the fuel cell system. The control device 15 can adjust the delivery amount of the hot water circulating pump 22b. The control device 15 has a microcomputer (not shown). The microcomputer includes an input / output interface, a CPU, a RAM, and a ROM (all not shown) connected via a bus. The CPU performs the overall operation of the fuel cell system. The RAM temporarily stores variables necessary for execution of the control program, and the ROM stores the control program.

As shown in FIG. 2, the control device 15 includes a first temperature full control unit 61 and a second temperature full control unit 62.
The first temperature full water control unit 61 uses the hot water stored in the hot water at the first temperature T2a (hot water temperature) corresponding to the first target temperature T1a lower than the second target temperature T1b of the hot water derived from the heat exchanger 12. The hot-water storage water circulation pump 22b is controlled so as to fill the water 21 (the discharge amount of the hot-water storage water circulation pump 22b is controlled). The second temperature full control unit 62 uses the first temperature full control unit 61 to fill the hot water storage tank 21 with the hot water stored at the first temperature T2a, and then the second target temperature T1b of the hot water derived from the heat exchanger 12 is reached. The hot water circulation pump 22b is controlled so that the hot water storage tank 21 is filled with the hot water stored at the second temperature T2b (hot water tank temperature) corresponding to (the discharge amount of the hot water circulation pump 22b is controlled).

  For example, the first temperature T2a (hot water tank water temperature) is desirably set in the range of 50 to 70 ° C, and preferably in the range of 60 to 65 ° C. The first target temperature T1a is desirably set in the range of 60 to 80 ° C, and preferably in the range of 70 to 75 ° C. Also, the second temperature T2b (hot water tank water temperature) is desirably set in the range of 60 to 80 ° C, and preferably in the range of 70 to 75 ° C. The second target temperature T1b is desirably set in the range of 70 to 90 ° C, preferably in the range of 80 to 85 ° C.

  The first target temperature T1a corresponds to a first temperature (hot water tank water temperature) at which a residual chlorine concentration (for example, 2 ppm) of hot water in the hot water tank 21 becomes a predetermined concentration (for example, 0.5 ppm) or less after being left for a certain period of time. The temperature is set. The first temperature is derived based on a map in which the residual chlorine concentration decays (decreases) at each temperature. In this map, as shown in FIG. 4, the higher the water temperature, the shorter the time taken for the residual chlorine concentration to decrease to a predetermined concentration. In particular, when the water temperature is 70 ° C. or higher, the residual chlorine concentration decreases rapidly. Therefore, the necessary and sufficient time for the residual chlorine concentration to be 0.1 ppm or less at a water temperature of 70 ° C. is set to a certain time, and after standing for a certain time, the residual chlorine concentration is reduced to a predetermined concentration (for example, 0.5 ppm) or less. Select the water temperature to be used. For example, water temperatures of 70 ° C. and 80 ° C. are selected. Finally, when a water temperature of 70 ° C. is selected, the first target temperature T1a is set to a value (60 ° C.) that is smaller than the selected water temperature by a predetermined temperature (for example, 10 ° C.).

Residual chlorine is a combination of free residual chlorine and combined residual chlorine that must be present in tap water, and is a chlorine compound that can effectively act on the sterilization and oxidation reactions of substances contained in tap water. I mean. The free residual chlorine is, for example, hypochlorous acid (HClO), and the combined residual chlorine is, for example, monochloramine (NHCl) and dichloramine (NHCl ₂ ).

  Further, the second target temperature T1b is set to a maximum temperature at which water self-sustained that is derived from the reforming unit 33 by the heat exchanger 12 and covered with condensed water can be established. This is because when the second target temperature T1b is set to a value exceeding the maximum temperature, condensed water is hardly generated and water self-sustainability is not established.

The first temperature full control unit 61 includes a first heat exchanger derivation temperature control unit 61a and a first control stop unit 61b. The first heat exchanger derivation temperature control unit 61a controls the hot water circulating pump 22b so that the temperature T1 of the hot water detected by the heat exchanger hot water derivation temperature sensor 22d becomes the first target temperature T1a. When the discharge amount of the hot water circulating pump 22b decreases and the flow rate (per unit time) of the hot water flowing through (passing through) the heat exchanger 12 decreases, the temperature T1 of the hot water increases. On the other hand, when the discharge amount of the hot water circulating pump 22b increases and the flow rate (per unit time) of the hot water flowing through (passing through) the heat exchanger 12 increases, the temperature T1 of the hot water decreases.
Thus, the hot water circulating pump 22b is controlled, and the hot water having the first target temperature T1a is led out from the heat exchanger 12 and introduced into the hot water tank 21.
When the hot water storage tank temperature state detected by the hot water tank internal temperature state detection device 21b is in a first full water state where the hot water storage tank 21 is filled with hot water of the first temperature T2a, the first control stop unit 61b Then, the drive of the hot water circulating pump 22b is stopped.

The second temperature full water control unit 62 includes a second heat exchanger derived temperature control unit 62a and a second control stop unit 62b. The second heat exchanger derivation temperature controller 62a controls the hot water circulation pump 22b so that the temperature T1 of the hot water detected by the heat exchanger hot water derivation temperature sensor 22d becomes the second target temperature T1b. The hot water circulating pump 22b is controlled, and the hot water having the second target temperature T1b is led out from the heat exchanger 12 and introduced into the hot water tank 21.
When the hot water storage tank temperature state detected by the hot water tank internal temperature state detection device 21b is in a second full water state where the hot water storage tank 21 is filled with hot water of the second temperature T2b, the second control stop unit 62b Then, the drive of the hot water circulating pump 22b is stopped.

  The second temperature full control unit 62 also stores hot water derived from the heat exchanger 12 after a predetermined time has elapsed since the first temperature full control unit filled the hot water tank 21 with the hot water stored at the first temperature T2a. The hot water circulation pump 22b is controlled so that the hot water storage tank 21 is filled with hot water of the second temperature T2b corresponding to the second target temperature T1b of water.

  Moreover, the control apparatus 15 is as shown in FIG. The display unit 15b is connected to be communicable by wire or wireless. The display unit 15b receives a display signal from the control device 15 and displays the operating state (operating state) of the fuel cell system to the user. The display unit 15b is configured by a liquid crystal panel, for example. The display unit 15b may include an operation unit that inputs an instruction for the fuel cell system from the user.

Next, the operation of the fuel cell system described above will be described along the flowchart shown in FIG. The control device 15 repeatedly executes the program according to the flowchart every predetermined time (which may be a short time or a long time).
The controller 15 determines whether or not the flag F is 1 in step S102. The flag F is a flag indicating whether the hot water storage tank 21 is less than or equal to the first full water state. When the flag F is 0, it indicates that the hot water tank 21 is less than the first full water state, and when the flag F is 1, it indicates that the hot water tank 21 is equal to or higher than the first full water state. The hot water storage tank 21 being in the first full state is a state in which the hot water storage tank 21 is full of hot water stored at the first temperature T2a. For example, the hot water storage tank 21 being less than the first full state is a state in which the temperature of the hot water stored in the lower layer of the hot water tank 21 is lower than the first temperature T2a. When the hot water tank 21 is less than the first full state, the temperature of the hot water stored in the upper layer of the hot water tank 21 is equal to or higher than the first temperature T2a, and the temperature of the hot water stored in the lower layer of the hot water tank 21 is the first temperature. Also includes a state of less than T2a. In addition, the hot water storage tank 21 being in the first full water state or more is a state in which the hot water storage tank 21 is full of hot water having the first temperature T2a or higher.

  If the flag F is 0, the control device 15 determines “NO” in step S102, and advances the program to step S104. On the other hand, if the flag F is 1, the control device 15 determines “YES” in step S102, and advances the program to step S116.

  In step S104, the control device 15 determines whether or not the hot water storage tank 21 is at or above the first full water state. Specifically, the control device 15 determines that the temperature state of the hot water in the hot water tank 21 detected by the hot water tank temperature state detection device 21b is a temperature at which the hot water tank 21 is filled with the hot water at the first temperature T2a. When it is in the state, it is determined that the hot water storage tank 21 is in the first full state. On the other hand, the control device 15 determines that the temperature state of the hot water in the hot water tank 21 detected by the hot water tank temperature state detection device 21b is the hot water temperature in the upper layer of the hot water tank 21 is the first temperature T2a. When the temperature of the hot water stored in the lower layer 21 is lower than the first temperature T2a, it is determined that the hot water storage tank 21 is lower than the first full water state. Moreover, the state in which the hot water storage tank 21 is full with the hot water stored in the 1st temperature T2a or more determines with the hot water storage tank 21 being more than a 1st full water state.

  If the hot water storage tank 21 is less than the first full state, the control device 15 determines “NO” in step S104, and advances the program to step S106 and subsequent steps. That is, the control device 15 uses the hot water storage tank 21 with the hot water stored at the first temperature T2a corresponding to the first target temperature T1a of the hot water derived from the heat exchanger 12, similarly to the first temperature full control unit 61 described above. The hot water circulating pump 22b is controlled to fill the water.

  In step S106, the controller 15 sets the target temperature of the hot water (heat exchanger outlet hot water temperature) derived from the heat exchanger 12 to the first target temperature T1a. In step S108, similarly to the first heat exchanger derivation temperature control unit 61a described above, the controller 15 determines that the hot water temperature T1 detected by the heat exchanger hot water derivation temperature sensor 22d is the first target temperature T1a. As such, the hot water circulating pump 22b is controlled to adjust the discharge amount of the hot water circulating pump 22b.

Thus, when the hot water circulating pump 22b is controlled, the hot water having the first target temperature T1a is led out from the heat exchanger 12 and introduced into the hot water tank 21. As a result, when the hot water storage tank 21 becomes equal to or higher than the first full water state, the control device 15 determines “YES” in Step S104 and stops the drive of the hot water circulating pump 22b (Step S112). That is, in step S104, 112, the control apparatus 15 is the same as the 1st control stop part 61b mentioned above, and the hot water storage tank 21 is the temperature state of the hot water storage water detected by the hot water tank internal temperature state detection apparatus 21b. When the hot water stored at the temperature T2a is full, the hot water circulating pump 22b is stopped.
And the control apparatus 15 sets the flag F to 1 in step S114.

Since the flag F is set to 1 after the hot water storage tank 21 is in the first full state, the control device 15 determines “YES” in step S102 and advances the program to step S116.
When the predetermined time has not elapsed since the hot water storage tank 21 became the first full state, the control device 15 determines “NO” in step S116, advances the program to step S110, and temporarily executes the program. finish. When a predetermined time has elapsed since the hot water storage tank 21 is in the first full state, the control device 15 determines “YES” in step S116 and advances the program to step S118 and subsequent steps. The predetermined time is set to a time when the residual chlorine concentration of the hot water in the hot water tank 21 is not more than a predetermined concentration that does not corrode the heat exchanger 12 when the hot water in the hot water tank 21 is left unattended. Has been.

  In step S118, the control device 15 determines whether the hot water tank 21 is in the second full water state or more. Specifically, the control device 15 determines that the temperature state of the hot water stored in the hot water tank 21 detected by the hot water tank temperature state detection device 21b is such that the hot water tank 21 is filled with the hot water stored at the second temperature T2b. When it is in the state, it is determined that the hot water tank 21 is in the second full state. On the other hand, the control device 15 is configured such that the temperature state of the hot water in the hot water tank 21 detected by the hot water tank temperature state detection device 21b is the hot water temperature in the upper layer of the hot water tank 21 is the second temperature T2b. When the temperature of the hot water stored in the lower layer 21 is lower than the second temperature T2b, it is determined that the hot water storage tank 21 is lower than the second full water state. Moreover, it is determined that the hot water storage tank 21 is full of hot water stored at a temperature equal to or higher than the second temperature T2b.

  When the hot water storage tank 21 is less than the second full water state, the control device 15 determines “NO” in step S118 and advances the program to step S120 and subsequent steps. That is, the control device 15 uses the hot water storage tank 21 with the hot water stored at the second temperature T2b corresponding to the second target temperature T1b of the hot water derived from the heat exchanger 12 in the same way as the second temperature full control unit 62 described above. The hot water circulating pump 22b is controlled to fill the water.

  In step S120, the control device 15 sets the target temperature of the hot water (heat exchanger outlet hot water temperature) derived from the heat exchanger 12 to the second target temperature T1b. In step S122, similarly to the second heat exchanger derived temperature control unit 62a described above, the controller 15 determines that the temperature T1 of the stored hot water detected by the heat exchanger stored water derived temperature sensor 22d is the second target temperature T1b. As such, the hot water circulating pump 22b is controlled to adjust the discharge amount of the hot water circulating pump 22b.

Thus, when the hot water circulating pump 22b is controlled, the hot water having the second target temperature T1b is led out from the heat exchanger 12 and introduced into the hot water tank 21. As a result, when the hot water storage tank 21 becomes equal to or higher than the second full water state, the control device 15 determines “YES” in Step S118 and stops the drive of the hot water circulating pump 22b (Step S124). That is, in step S118, 124, the controller 15 determines that the temperature state of the hot water detected by the hot water tank temperature state detection device 21b is the same as that of the second control stop unit 62b described above. When the hot water stored at the temperature T2b is full, the hot water circulating pump 22b is stopped.
And the control apparatus 15 sets the flag F to 0 in step S126. The control device 15 performs normal exhaust heat recovery control. Normal waste heat recovery control is performed by controlling the amount of hot water circulating pump 22b (circulated flow rate of hot water) based on the temperature condition of hot water in the hot water tank 21 and the hot water outlet temperature of the heat exchanger 12. It is to control the exhaust heat recovery.

  As is clear from the above description, the fuel cell system of this embodiment includes a fuel cell 34 that generates power using fuel and an oxidant gas, a hot water storage tank 21 for storing hot water, and exhaust heat and hot water storage of the fuel cell 34. A heat exchanger 12 that exchanges heat with water, a hot water circulation line 22 that is configured to circulate hot water between the hot water tank 21 and the heat exchanger 12, and a hot water circulation line 22 are provided. And a hot water circulating pump 22b (delivery device) for delivering and circulating hot water, and a control device 15 for controlling the delivery amount of the hot water circulating pump 22b. The control device 15 circulates the hot water storage water so that the hot water storage tank 21 is filled with the hot water stored at the first temperature T2a corresponding to the first target temperature T1a lower than the second target temperature T1b of the hot water derived from the heat exchanger 12. A first temperature full control unit 61 that controls the pump 22b, and the hot water stored in the hot water tank 21 led out from the heat exchanger 12 after the hot water storage tank 21 is filled with the hot water stored at the first temperature T2a by the first temperature full control unit 61. A second temperature full control unit 62 that controls the hot water circulation pump 22b so as to fill the hot water tank 21 with the hot water stored at the second temperature T2b corresponding to the second target temperature T1b.

  According to this, the hot water storage tank 21 is filled with the hot water stored at the first temperature T2a by the first temperature full control unit 61, and then is hotter than the first temperature T2a by the second temperature full control unit 62. It is filled with hot water at temperature T2b. As a result, the residual chlorine concentration contained in the tap water supplied to the hot water tank 21 is lowered in the hot water tank 21 raised to the first temperature T2a. It can suppress that the heat exchanger 12 with which water circulates corrodes with residual chlorine. Furthermore, since the hot water supplied from the hot water storage tank 21 filled with the hot water of the first temperature T2a is supplied to the heat exchanger 12 after the residual chlorine concentration is lowered, the temperature of the hot water is increased. Corrosion due to residual chlorine which acts more strongly below is suppressed. Therefore, corrosion in the heat exchanger 12 can be suppressed and exhaust heat recovery efficiency can be improved.

Further, the fuel cell system of the present embodiment is provided in the hot water storage tank 21, and includes a hot water tank temperature state detection device 21b for detecting the temperature state of the hot water in the hot water storage tank 21, and a hot water circulation line 22 for heat exchange. The hot water storage water outlet temperature sensor 22d is provided between the hot water outlet 12c of the hot water tank 12 and the hot water inlet 21c of the hot water tank 21 and detects the temperature T1 of the hot water discharged from the heat exchanger 12. And further. The first temperature full water control unit 61 controls the hot water circulating pump 22b so that the temperature of the hot water detected by the heat exchanger hot water derivation temperature sensor 22d becomes the first target temperature T1a. When the hot water stored in the hot water tank detected by the controller 61a and the hot water tank temperature state detection device 21b is in a first full state where the hot water tank 21 is filled with hot water at the first temperature T2a, the hot water circulation is performed. A first control stop unit 61b for stopping the driving of the pump 22b. The second temperature full water control unit 62 controls the hot water circulating pump 22b so that the hot water temperature detected by the heat exchanger hot water derivation temperature sensor 22d becomes the second target temperature T1b in the hot water tank 21. When the temperature state of the stored hot water detected by the heat exchanger derivation temperature control unit 62a and the hot water tank temperature state detection device 21b becomes the second full water state filled with the hot water stored at the second temperature T2b, the hot water circulation pump And a second control stop unit 62b for stopping the drive of 22b.
According to this, when the hot water storage tank 21 is filled with the hot water stored at the first temperature T2a, the hot water is surely filled with the hot water stored at the first temperature T2a based on the detection result of the heat exchanger hot water derived temperature sensor 22d. In addition, the hot water storage tank 21 can be brought into the first full state based on the detection result of the hot water tank internal temperature state detection device 21b. Further, when the hot water storage tank 21 is filled with the hot water stored at the second temperature T2b, the hot water stored in the second temperature T2b is surely filled based on the detection result of the heat exchanger hot water derived temperature sensor 22d. At the same time, the hot water storage tank 21 can be brought into the second full water state based on the detection result of the hot water tank internal temperature state detection device 21b.

Further, the fuel cell system of the present embodiment includes a reforming unit 33 that generates fuel from the reforming raw material and reformed water and leads it to the fuel cell 34, a water tank 14 that stores the reformed water, and a fuel off-gas. And a combustion unit 36 that heats the reforming unit 33 by combusting the fuel off-gas with an oxidant gas, and the heat exchanger 12 includes combustion exhaust gas from the combustion unit 36 including exhaust heat of the fuel cell 34. Heat exchange is performed with the hot water storage, water vapor in the combustion exhaust gas is condensed and led to the water tank 14 as condensed water, and the second target temperature T1b The water self-supporting provided by the condensed water derived from the exchanger 12 is set to the highest temperature that can be established.
According to this, the fuel cell system can suppress the heat exchanger 12 in which the tap water circulates from being corroded by residual chlorine, and can establish water independence reliably.

Further, in the fuel cell system of the present embodiment, the first target temperature T1a is set to a temperature at which the residual chlorine concentration of the hot water in the hot water storage tank 21 becomes a predetermined concentration or less after being left for a certain period of time.
According to this, the residual chlorine concentration contained in the tap water supplied to the hot water tank 21 is surely lowered to a predetermined concentration or lower when left in the hot water tank 21 raised to the first temperature T2a for a certain period of time. Therefore, the heat exchanger 12 in which the tap water circulates can be more reliably suppressed from being corroded by residual chlorine without causing complication and cost increase. Further, the hot water supplied from the hot water tank 21 filled with the hot water of the first temperature T2a is supplied to the heat exchanger 12 and heated up after the residual chlorine concentration is more reliably lowered. In addition, the corrosive action due to residual chlorine that acts more strongly in a high-temperature environment is more reliably suppressed.

Further, in the fuel cell system of the present embodiment, the second temperature full control unit 62, after a predetermined time has elapsed since the first temperature full control unit 61 filled the hot water storage tank 21 with the hot water stored at the first temperature T2a. Then, the hot water circulating pump 22b is controlled so that the hot water storage tank 21 is filled with the hot water stored at the second temperature T2b corresponding to the second target temperature T1b of the hot water derived from the heat exchanger 12.
According to this, since the residual chlorine concentration contained in the tap water supplied to the hot water storage tank 21 is reliably lowered after a predetermined time in the hot water storage tank 21 raised to the first temperature T2a, it is complicated. -It can suppress more reliably that the heat exchanger 12 with which tap water circulates corrodes with residual chlorine, without causing cost increase.

  DESCRIPTION OF SYMBOLS 10 ... Electric power generation unit, 11 ... Fuel cell module, 12 ... Heat exchanger, 15 ... Control apparatus (1st temperature fullness control part, 2nd temperature fullness control part), 21 ... Hot water storage tank, 21b ... Temperature state detection in hot water storage tank Apparatus, 22 ... Hot water circulation line, 22b ... Hot water circulation pump (delivery device), 22d ... Heat exchanger hot water derivation temperature sensor, 23 ... Derivation apparatus, 24 ... Water supply source, 25 ... Introduction apparatus, 34 ... Fuel cell, 42a ... Flow meter, 44 ... On-off valve, 61 ... First temperature full control unit, 61a ... First heat exchanger derived temperature control unit, 61b ... First control stop unit, 62 ... Second temperature full control unit, 62a ... first Two heat exchanger derivation temperature control part, 62b ... 2nd control stop part.

Claims (5)

A fuel cell that generates electricity using fuel and oxidant gas;
A hot water storage tank for storing hot water,
A heat exchanger in which heat is exchanged between the exhaust heat of the fuel cell and the stored hot water;
A hot water circulation line formed to circulate the hot water between the hot water tank and the heat exchanger;
A delivery device provided in the hot water circulation line for delivering and circulating the hot water;
A control device for controlling the delivery amount of the delivery device,
The controller is
A first temperature full water that controls the delivery device to fill the hot water tank with hot water having a first temperature corresponding to a first target temperature lower than a second target temperature of the hot water derived from the heat exchanger. A control unit;
The hot water stored at the second temperature corresponding to the second target temperature of the stored hot water derived from the heat exchanger after the hot water storage tank is filled with the hot water stored at the first temperature by the first temperature full water control unit. A second temperature full control unit for controlling the delivery device to fill the hot water tank with
A fuel cell system comprising: A hot water tank temperature state detection device that is provided in the hot water tank and detects the temperature state of the hot water in the hot water tank;
Heat exchange that is provided in the hot water circulation line between the hot water outlet of the heat exchanger and the hot water inlet of the hot water tank and detects the temperature of the hot water drawn from the heat exchanger. A hot water outlet temperature sensor,
The first temperature full water control unit is
A first heat exchanger derived temperature control unit that controls the delivery device such that the temperature of the stored hot water detected by the heat exchanger stored water derived temperature sensor becomes the first target temperature;
When the temperature state of the stored hot water detected by the hot water tank internal temperature state detection device is in a first full state where the hot water tank is filled with hot water at the first temperature, the delivery device is driven. A first control stop unit to stop,
The second temperature full water control unit is
A second heat exchanger derived temperature control unit that controls the delivery device so that the temperature of the hot water detected by the heat exchanger stored water derived temperature sensor is equal to the second target temperature;
The second control stop that stops the driving of the delivery device when the temperature state of the hot water detected by the hot water tank temperature state detection device becomes a second full water state that is full by the hot water of the second temperature. And a fuel cell system according to claim 1. A reforming section for generating the fuel from the reforming raw material and reforming water and leading it to the fuel cell;
A water tank for storing the reformed water;
A combustion section that burns fuel off-gas that is an off-gas of the fuel with an oxidant gas and heats the reforming section,
The heat exchanger performs the heat exchange between the combustion exhaust gas from the combustion unit including the exhaust heat of the fuel cell and the hot water storage, condenses water vapor in the combustion exhaust gas, and condenses the water as condensed water. To the tank,
The second target temperature is set to a maximum temperature at which water self-supporting that covers the reformed water required in the reforming unit with the condensed water led out by the heat exchanger can be established. The fuel cell system according to claim 1 or 2.   The fuel according to any one of claims 1 to 3, wherein the first target temperature is set to a temperature at which a residual chlorine concentration of the hot water in the hot water tank is not more than a predetermined concentration after being left for a certain period of time. Battery system.   The second temperature full water control unit is a hot water discharged from the heat exchanger after a predetermined time has elapsed since the first temperature full water control unit filled the hot water storage tank with the first temperature hot water. The fuel cell system according to any one of claims 1 to 4, wherein the delivery device is controlled to fill the hot water storage tank with hot water having a second temperature corresponding to the second target temperature.

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