Fuel cell system

Abstract

To provide a fuel cell system that can appropriately perform bacterium countermeasure operation of suppressing proliferation of bacteria.SOLUTION: A fuel cell system comprises a control device C that alternately sets operating periods, during which fuel gas generated by steam reforming in a fuel processing device 2 is supplied to a fuel cell 1, and stop periods, during which a reforming water supply unit L2 is stopped, water stored in a reforming water tank 4 is not supplied to the fuel processing device 2, and no steam reforming is performed in the fuel processing device 2; when starting a stop period, determines whether or not a bacterium countermeasure condition for suppressing proliferation of bacteria can be satisfied in the stop period; when it is determined that the bacterium countermeasure condition can be satisfied in the stop period, performs second processing of actuating a water circulation unit L3 in the stop period; and when it is determined that the bacterium countermeasure condition cannot be satisfied in the stop period, does not perform the second processing in the stop period.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a fuel cell system including a fuel cell, a fuel processing device that generates a fuel gas containing hydrogen to be supplied to the fuel cell by steam reforming, and an impurity removal device that performs an impurity removal process on water used as reforming water for steam reforming in the fuel processing device.

Background Art

[0002] In a fuel cell, for example, a fuel processing device (reformer) steam-reforms hydrocarbons such as city gas to generate hydrogen, and the hydrogen reacts with oxygen in the air in a cell stack to generate electricity. Pure water (reforming water) for the steam reforming reaction is supplied to the fuel processing device. In many systems, the water generated during the power generation reaction is recovered and used as water (reforming water) for steam reforming in the fuel processing device. Incidentally, if impurities (such as sulfate ions and ammonium ions in the air) are contained in this reforming water, the catalyst of the fuel processing device will be poisoned, so an impurity removal device such as an ion exchange resin is provided. Also, it is generally known that bacteria such as naturally-derived bacteria (for example, of the genus Pseudomonas) may grow in the flow path of the reforming water and narrow the flow path.

[0003] Patent Document 1 and Patent Document 2 describe performing an operation for suppressing the growth of bacteria on the water flowing through the flow path of the reforming water.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In some fuel cell systems, the antimicrobial operation to suppress bacterial growth can only be performed when the fuel cell is not generating power. For example, in fuel cell systems that perform SS operation (start-stop operation), which involves repeatedly starting and stopping the system periodically, the antimicrobial operation must be performed between the time power generation stops and the time the next power generation starts. Therefore, if the period between stopping and starting is short, it may not be possible to provide enough heat to suppress bacterial growth to the water targeted by the antimicrobial operation, and the antimicrobial operation may not be completed properly.

[0006] The present invention has been made in view of the above-mentioned problems, and its objective is to provide a fuel cell system that can appropriately perform antimicrobial operation to suppress the growth of bacteria. [Means for solving the problem]

[0007] The characteristic configuration of the fuel cell system according to the present invention for achieving the above objective is a fuel cell and A fuel treatment device that generates a hydrogen-containing fuel gas to be supplied to the aforementioned fuel cell by steam reforming, A battery cooling water tank for storing water used as battery cooling water to recover heat discharged from the fuel cell, A water tank for storing water used as reforming water in the aforementioned steam reforming, An impurity removal device that performs impurity removal treatment on the water used as the water for reforming, A battery cooling water circulation unit that circulates the water used as the battery cooling water between the fuel cell and the battery cooling water tank, A water reforming supply unit supplies the water used as reforming water to the fuel treatment device via the water reforming tank and the impurity removal device, A tank connection section connecting the battery cooling water tank and the reforming water tank, The water used as the battery cooling water and the water used for reforming is placed in the battery cooling water tank. 、 The tank connection part 、 The aforementioned water tank for modification 、 The impurity removal device ofA water circulation unit that circulates water in a sequential manner, Equipped with a control device, The control device is The first process involves operating the reforming water supply unit and supplying the water stored in the reforming water tank to the fuel treatment device, and the fuel treatment device supplying the fuel gas generated by the steam reforming to the fuel cell during an operating period, and alternating between this and a stop period in which the reforming water supply unit is stopped, the water stored in the reforming water tank is not supplied to the fuel treatment device, and the fuel treatment device does not perform the steam reforming. When commencing the aforementioned suspension period, it is determined whether or not the conditions for suppressing bacterial growth can be met during the suspension period. If it is determined that the conditions for preventing bacterial infection can be met during the aforementioned shutdown period, a second process is performed during the shutdown period to operate the water circulation unit. If it is determined that the conditions for controlling the bacteria cannot be met during the aforementioned suspension period, the second treatment will not be performed during that suspension period. In this case, the control device may determine that it can satisfy the bacterial control conditions if it determines that it can raise the temperature of the circulating water circulated by the water circulation unit to a predetermined target temperature or higher during the shutdown period.

[0008] According to the above characteristic configuration, if it is determined that the conditions for bacterial control can be met during the shutdown period, the second process is executed. As a result, the battery cooling water stored in the battery cooling water tank and the water stored in the reforming water tank are circulated by the water circulation unit as circulating water, and then the reforming water tank 、 Impurity removal equipment 、 Battery cooling water tank 、 Tank connection of The water flows and circulates sequentially. In other words, it is expected that the heat contained in the battery cooling water stored in the battery cooling water tank is transferred to the entire circulating water that is circulated by the water circulation unit in the second treatment, raising the temperature of the circulating water and suppressing the growth of bacteria in that circulating water. Furthermore, if it is determined that the conditions for bacterial control cannot be met during the shutdown period, the second treatment will not be performed during that shutdown period. As a result, it is possible to avoid the second treatment ending with insufficient temperature rise of the circulating water. Therefore, it is possible to provide a fuel cell system that can appropriately perform antimicrobial operation to suppress the growth of bacteria.

[0009] Another characteristic configuration of the fuel cell system according to the present invention is that the control device determines whether the overall temperature of the circulating water can be raised to or above the target temperature, based on the amount of circulating water circulated by the water circulation unit, the temperature at multiple points along the flow path of the circulating water before the start of the second treatment, and the ambient temperature.

[0010] If a second process is performed to operate the water circulation unit during the shutdown period, and assuming that the circulating water is properly mixed by the circulation, the overall temperature of the circulating water after mixing can be considered to be determined by the amount of circulating water, the temperature at multiple points along the flow path of the circulating water before the start of the second process, and the ambient temperature. Therefore, in this feature configuration, the control device can determine whether the temperature of the circulating water after mixing will be equal to or higher than the target temperature by predicting the overall temperature of the circulating water after mixing, based on the amount of circulating water, the temperature at multiple points along the circulating water flow path before the start of the second treatment, and the ambient temperature.

[0011] Another characteristic configuration of the fuel cell system according to the present invention is that it includes a heating device for heating the battery cooling water, The control device determines whether the overall temperature of the circulating water can be raised to or above the target temperature, based on the amount of circulating water circulated by the water circulation unit, the temperature at multiple points along the flow path of the circulating water before the start of the second process, the ambient temperature, and the amount of heat that the heating device can supply to the battery cooling water. Here, the control device may impose a constraint that when the heating device heats the battery cooling water, the temperature of the battery cooling water stored in the battery cooling water tank does not exceed a predetermined upper temperature.

[0012] When performing a second process of heating the battery cooling water with a heating device and operating a water circulation unit during a stop period, assuming that the circulating water is appropriately mixed by circulation, the overall temperature of the circulating water after mixing may be considered to be determined by the amount of the circulating water, the temperatures at a plurality of locations in the flow path of the circulating water before the start of the second process, the outside air temperature, and the amount of heat that the heating device can impart to the battery cooling water. Therefore, in this characteristic configuration, the control device can determine whether or not the temperature becomes equal to or higher than a target temperature by predicting the overall temperature of the circulating water after mixing based on the amount of the circulating water, the temperatures at a plurality of locations in the flow path of the circulating water before the start of the second process, the outside air temperature, and the amount of heat that the heating device can impart to the battery cooling water.

Brief Description of the Drawings

[0013] [Figure 1] It is a diagram showing the configuration of a fuel cell system. [Figure 2] It is a diagram showing the configuration of a fuel cell system. [Figure 3] It is a diagram showing the configuration of a fuel cell system. [Figure 4] It is a flowchart explaining the operation for countermeasures against bacteria. [Figure 5] It is a diagram explaining the temperature of water before the start of the second process and the temperature of water made uniform by the second process. [Figure 6] It is a diagram explaining the temperature of water before the start of the second process and the temperature of water made uniform by the second process. [Figure 7] It is a diagram explaining the temperature of water before the start of the second process and the temperature of water made uniform by the second process.

Mode for Carrying Out the Invention

[0014] <First Embodiment>[ Hereinafter, a fuel cell system according to a first embodiment of the present invention will be described with reference to the drawings. Figures 1 to 3 show the configuration of the fuel cell system. Details will be described later, but Figure 1 shows the state in which the first treatment is being performed, supplying water stored in the reforming water tank 4 to the fuel treatment device 2. Also, in the state shown in Figure 1, the fuel gas generated by the fuel treatment device 2 is supplied to the fuel cell 1, and the fuel cell 1 is also generating electricity. Figure 2 shows the water stored in the reforming water tank 4. 、 Ion exchange resin section 5 as an impurity removal device 、 Battery cooling water tank 3 、 Tank connection part 12 of Figure 1 shows the state during the second treatment, in which the fluid is circulated sequentially. Figure 3 shows the state during the second treatment and the heat treatment. In Figures 1 to 3, areas where fluids such as water are flowing are indicated by thick lines.

[0015] The ion exchange resin section 5 is provided to remove impurities that may be present in the reformed water (e.g., sulfate ions and ammonia ions from the air). However, naturally occurring bacteria (e.g., Pseudomonas species) may proliferate in the reformed water flow path including the ion exchange resin section 5, potentially narrowing the flow path. Therefore, in this embodiment of the fuel cell system, a bacterial control operation is performed on the water flowing through the reformed water flow path to suppress bacterial growth.

[0016] The fuel cell system comprises a fuel cell 1, a fuel treatment device 2, a battery cooling water tank 3, a reforming water tank 4, an ion exchange resin section 5, a battery cooling water circulation section L1, a reforming water supply section L2, a tank connection section 12, a water circulation section L3, and a control device C. In addition, the fuel cell system of this embodiment includes a heating device 23.

[0017] Fuel cell 1 is, for example, a polymer electrolyte fuel cell or a solid oxide fuel cell, and has an anode to which a fuel gas such as hydrogen is supplied and a cathode to which oxygen is supplied.

[0018] The fuel treatment device 2 generates hydrogen-containing fuel gas to be supplied to the fuel cell 1 by steam reforming. For example, the fuel treatment device 2 is supplied with a hydrocarbon gas such as methane and water (steam), and hydrogen-containing fuel gas is generated by steam reforming of the hydrocarbon gas. The fuel gas generated by the fuel treatment device 2 is supplied to the fuel cell 1 via the fuel gas supply passage 17.

[0019] The heat emitted from the fuel cell 1 is recovered by the battery cooling water. For example, the cooling water circulation path 6 is circulated by the cooling water pump 7 between the fuel cell 1 and the battery cooling water tank 3. In other words, the cooling water circulation path 6 and the cooling water pump 7 function as a battery cooling water circulation unit L1 that circulates the water used as battery cooling water between the fuel cell 1 and the battery cooling water tank 3. The battery cooling water tank 3 stores the battery cooling water that recovers the heat emitted from the fuel cell 1. The operation of the cooling water pump 7 is controlled by the control device C.

[0020] In addition, a heat exchange section 18 is provided in the cooling water circulation path 6, between the battery cooling water, which has recovered heat from the fuel cell 1, and the battery cooling water tank 3. Hot water taken from the hot water storage tank 21 flows into this heat exchange section 18, and after heat exchange in the heat exchange section 18, it returns to the hot water storage tank 21. In other words, the hot water circulates through the hot water circulation path 19, flowing sequentially through the hot water storage tank 21 and the heat exchange section 18. Hot water is pumped through the hot water circulation path 19 by a hot water pump 20. Therefore, the heat discharged from the fuel cell 1 is first transferred to the battery cooling water flowing through the cooling water circulation path 6, then transferred to the hot water in the heat exchange section 18, and then stored in the hot water storage tank 21. It should be noted that not all of the heat discharged from the fuel cell 1 is stored in the hot water storage tank 21; some is also stored in the battery cooling water tank 3. For example, the temperature of the battery cooling water stored in the battery cooling water tank 3 may reach temperatures of 60°C to 70°C. The operation of the hot and cold water pump 20 is controlled by the control device C.

[0021] A heating device 23 is provided between the heat exchange unit 18 and the battery cooling water tank 3 in the cooling water circulation path 6. The heating device 23 can heat the battery cooling water using heat generated by an electric heater or the like. The operation of the heating device 23 is controlled by the control device C.

[0022] The reforming water tank 4 stores water used as reforming water for steam reforming in the fuel treatment device 2. Additionally, recovered water from the fuel cell 1 via the water recovery path 16 flows into the reforming water tank 4. The battery cooling water tank 3 and the reforming water tank 4 are connected by a tank connection section 12. In other words, the water stored in the battery cooling water tank 3 (battery cooling water) flows into the reforming water tank 4.

[0023] The water (reformed water) from the reformed water tank 4 is supplied to the ion exchange resin section 5 through the reformed water channel 8a. The ion exchange resin section 5 is a device that removes ionic substances such as salts and ammonia that are ionized and dissolved in water. The reformed water channel 8 (8a, 8b) passes through the ion exchange resin section 5, the on-off valve 11, and the reformed water pump 10 to reach the fuel treatment device 2. The operation of the on-off valve 11 and the reformed water pump 10 is controlled by the control device C.

[0024] In other words, the reforming water channel 8, the on-off valve 11, and the reforming water pump 10 function as a reforming water supply unit L2 that supplies water used as reforming water to the fuel treatment device 2 via the reforming water tank 4 and the ion exchange resin unit 5.

[0025] Furthermore, the reforming water channel 8 branches off into a water return channel 13 at the branching point 9 downstream of the ion exchange resin section 5. The reforming water that flows into the water return channel 13 flows into the battery cooling water tank 3 through the on-off valve 15 and the water pump 14. The operation of the on-off valve 15 and the water pump 14 is controlled by the control device C.

[0026] In other words, the water reforming channel 8a, the water return channel 13, the on / off valve 15, the water pump 14, and the tank connection section 12 supply water used as battery cooling water and reforming water to the battery cooling water tank 3 、 Tank connection part 12 、 Water tank for treatment 4、 Ion exchange resin section 5 of It functions as a water circulation unit L3 that circulates water in a sequential manner.

[0027] The battery cooling water tank 3 is equipped with a temperature sensor T1 for measuring the temperature of the battery cooling water stored in the battery cooling water tank 3. The reforming water tank 4 is equipped with a temperature sensor T2 for measuring the temperature of the reforming water stored in the reforming water tank 4. The reforming water flow path 8a between the reforming water tank 4 and the ion exchange resin section 5 is equipped with a temperature sensor T3 for measuring the temperature of the reforming water flowing into the ion exchange resin section 5. In addition, an ambient temperature sensor 22 is provided for measuring the ambient temperature. The measurement results from temperature sensors T1, T2, T3 and ambient temperature sensor 22 are transmitted to the control device C.

[0028] As shown in Figure 1, when the first treatment is being performed, in which the reforming water supply unit L2 is operated and the water stored in the reforming water tank 4 is supplied to the fuel treatment device 2, the on-off valve 11 is opened, the reforming water pump 10 is operated, the on-off valve 15 is closed, and the water pump 14 is stopped. Therefore, the reforming water that flows out of the reforming water tank 4 flows from the branching section 9 towards the fuel treatment device 2, but does not flow into the water return path 13. In other words, the first treatment is a process in which the reforming water supply unit L2 is operated and the water stored in the reforming water tank 4 is supplied to the fuel treatment device 2 while it is necessary to supply the water stored in the reforming water tank 4 to the fuel treatment device 2.

[0029] As shown in Figure 2, while the second treatment is being performed, the water reforming supply unit L2 is stopped, and the water stored in the water reforming tank 4 is not supplied to the fuel treatment device 2. While the second treatment is being performed, the water stored in the battery cooling water tank 3 and the water stored in the water reforming tank 4 are supplied to the water reforming tank 4. 、 Ion exchange resin section 5 、 Battery cooling water tank 3 、 Tank connection part 12 ofThe water is circulated sequentially. In other words, the second process involves operating the water circulation unit L3 while it is not necessary to supply the water stored in the reforming water tank 4 to the fuel treatment device 2, thereby circulating the water stored in the battery cooling water tank 3 and the water stored in the reforming water tank 4. 、 Ion exchange resin section 5 、 Battery cooling water tank 3 、 Tank connection part 12 of This process involves sequentially flowing and circulating the materials. In this embodiment, the first and second processes are not performed simultaneously.

[0030] To elaborate on the second treatment, before the start of the second treatment, the temperature of the water stored in the battery cooling water tank 3 is high, for example, 60°C to 70°C, while the temperature of the water stored in the reforming water tank 4 is, for example, equivalent to the ambient temperature. In other words, before the start of the second treatment, there is a temperature distribution of highs and lows at multiple points along the flow path of the circulating water circulated by the water circulation unit L3. Therefore, if we assume that bacteria in the water are killed when the water temperature exceeds a predetermined target temperature, then bacteria will be killed in the parts of the circulating water where the temperature is above the target temperature, but not in the parts where the temperature is below the target temperature. However, since the temperature of the circulating water becomes uniform after a certain period of time when the water pump 14 is running, if the temperature of the circulating water becomes above the target temperature when the temperature of the circulating water is uniform, it can be assumed that bacteria will be killed in the entire circulating water.

[0031] As shown in Figures 5 and 6 described later, the control device C can predict the total temperature of the circulating water when the temperature is equalized by the second process, that is, the predicted equalization temperature, based on the amount of circulating water circulated by the water circulation unit L3, the temperature at multiple points along the flow path of the circulating water before the start of the second process, and the ambient temperature. In the following explanation, the temperature of the circulating water predicted by the control device C when the temperature is equalized by the second process may be referred to as the "predicted equalization temperature."

[0032] However, when the second treatment is performed, the temperature of the circulating water gradually equalizes while the water pump 14 is operating at the set output, so a predetermined period of time is required for the temperature of the circulating water to equalize. The control device C stores information about the time required for the temperature of the circulating water to equalize when the second treatment is performed. In the following explanation, the time required for the temperature of the circulating water to equalize due to the second treatment, as stored in the control device C, may be referred to as the "time required for equalization."

[0033] For example, the control device C stores a table showing the relationship between the current temperature of the circulating water measured by temperature sensors T1, T2, T3, etc., the current ambient temperature measured by the ambient temperature sensor 22, and the required period for uniformization. The control device C can then determine the required period for uniformization from the measurement results of temperature sensors T1, T2, T3, and the ambient temperature sensor 22.

[0034] Then, the control device C determines whether the conditions for bacterial control described later can be met, based on information about what the final temperature of the circulating water will be when the temperature is equalized by the second process (predicted equalization temperature) and information about the period required to equalize the temperature of the circulating water (duration required for equalization).

[0035] Figure 4 is a flowchart illustrating the bacterial control operation. Control device C repeatedly executes this flowchart at set timings.

[0036] The fuel cell system of this embodiment performs SS operation (start-stop operation), which involves periodically starting and stopping the system based on factors such as the load. Therefore, the control device C alternately sets the operating period and the stopping period. The operating period is the period during which the reforming water supply unit L2 is operated, the water stored in the reforming water tank 4 is supplied to the fuel treatment device 2 for a first process, and the fuel gas generated by steam reforming in the fuel treatment device 2 is supplied to the fuel cell 1, that is, the period during which the fuel cell 1 performs power generation operation. The stopping period is the period during which the reforming water supply unit L2 is stopped, the water stored in the reforming water tank 4 is not supplied to the fuel treatment device 2, and steam reforming is not performed in the fuel treatment device 2, that is, the period during which the power generation operation of the fuel cell 1 is stopped.

[0037] In step #10, the control device C determines whether or not it is time to start the bacterial control operation. For example, the control device C determines that it is time to start the bacterial control operation when the power generation operation of the fuel cell 1 is stopped and it is no longer necessary to supply the water stored in the reforming water tank 4 to the fuel treatment device 2, for example, when the reforming water pump 10 is stopped and the on-off valve 11 is closed. If the control device C determines that it is time to start the bacterial control operation, it proceeds to step #11; if it determines that it is not time to start the bacterial control operation, it terminates this flowchart.

[0038] In process #11, if the control device C initiates a shutdown period, it determines whether the conditions for suppressing bacterial growth during that shutdown period can be met. Specifically, the control device C determines the predicted uniformization temperature, which indicates the final temperature of the circulating water after the temperature has been uniformized by the second treatment, and the required uniformization period, which indicates the period required to uniformize the temperature of the circulating water. Furthermore, if the control device C initiates a shutdown period, it has predetermined the length of that shutdown period.

[0039] If the determined predicted homogenization temperature is above the target temperature, which is the temperature at which bacteria are killed, then after the required homogenization period, the temperature of the circulating water will reach the predicted homogenization temperature (i.e., above the target temperature), and it is expected that the bacteria living in the circulating water flow path will be killed after the required homogenization period. Therefore, the control device C determines that the conditions for bacterial control can be met if the predicted homogenization temperature is above the target temperature and the required homogenization period is less than or equal to the stop period. However, if the stop period is shorter than the required homogenization period, at least a portion of the temperature of the circulating water will not have reached the predicted homogenization temperature at the time the stop period has elapsed, and therefore it will not be possible to kill the bacteria living in the circulating water flow path.

[0040] If control device C determines that the bacterial control conditions can be met, it proceeds to process #12 and performs a second process during the stop period, which involves operating the water circulation unit L3. Conversely, if control device C determines that the bacterial control conditions cannot be met, it does not perform the second process during the stop period and terminates this flowchart.

[0041] Figures 5 and 6 illustrate the temperatures at multiple points along the circulating water flow path before the start of the second treatment, and the overall temperature of the circulating water after it has been homogenized by the second treatment. In this example, the target temperature of the circulating water required to kill the bacteria is assumed to be 40°C. Also, for the sake of simplifying the calculation, only the water stored in the battery cooling water tank 3 (1L) and the water stored in the reforming water tank 4 (2L) are considered, and the amount of water present in other water return paths 13, etc., is not considered.

[0042] In the example shown in Figure 5, since the ambient temperature is 25°C, the temperature of the water (2L) stored in the reforming water tank 4 is also 25°C, and the heat storage amount is 0kW. Also, since the water (1L) stored in the battery cooling water tank 3 is 70°C, the heat storage amount corresponding to the difference between 70°C and the ambient temperature of 25°C is approximately 3.1kW. If the second treatment is performed in this state, the temperature of the circulating water (3L) will be uniformly set to 40°C. In other words, the predicted uniformization temperature (40°C) is above the target temperature (40°C). Therefore, in step #11, the control device C determines that the bacterial control conditions can be met if the predicted uniformization temperature is above the target temperature and the required uniformization period is less than or equal to the stop period, and proceeds to step #12. On the other hand, in step #11, the control device C determines that although the predicted uniformization temperature is above the target temperature, if the required uniformization period is longer than the stop period, the bacterial control conditions cannot be met, and terminates this flowchart without performing the second treatment.

[0043] In the example shown in Figure 6, since the ambient temperature is 20°C, the temperature of the water (2L) stored in the reforming water tank 4 is also 20°C, and the heat storage amount is 0kW. Also, since the water (1L) stored in the battery cooling water tank 3 is 70°C, the heat storage amount corresponding to the difference between 70°C and the ambient temperature of 20°C is approximately 3.5kW. If the second treatment is performed in this state, the temperature of the circulating water (3L) will be uniformly set at 35°C. In other words, the predicted uniformization temperature (35°C) is not above the target temperature (40°C). Therefore, in step #11, the control device C determines that the bacterial control conditions cannot be met because the predicted uniformization temperature is not above the target temperature, and terminates this flowchart without performing the second treatment.

[0044] In process #12, the control device C operates the water circulation unit L3 to convert the circulating water into the water treatment tank 4. 、 Ion exchange resin section 5 、 Battery cooling water tank 3 、 Tank connection part 12 ofThe second process, which involves sequentially circulating the water, is initiated. Specifically, the control device C opens the on-off valve 15, which serves as the water circulation unit L3, and operates the water pump 14, thereby circulating the circulating water along the path shown by the thick line in Figure 2. As a result, as shown in Figure 5, the overall temperature of the circulating water circulated by the water circulation unit L3 reaches the target temperature of 40°C.

[0045] Subsequently, in step #13, the control device C determines whether it is time to end the bacterial control operation. If it is time to end the operation, it proceeds to step #14 and terminates the second process. For example, the control device C can determine that it is time to end the bacterial control operation when the water temperatures measured by temperature sensors T1, T2, and T3 are all above the target temperature. Alternatively, the control device C can determine that it is time to end the bacterial control operation after a predetermined time has elapsed following the water temperatures measured by temperature sensors T1, T2, and T3 being above the target temperature.

[0046] As described above, if it is determined that the conditions for bacterial control can be met during the shutdown period, the second process is executed. As a result, the battery cooling water stored in the battery cooling water tank 3 and the water stored in the reforming water tank 4 are circulated by the water circulation unit L3 as circulating water, and the reforming water tank 4 、 Ion exchange resin section 5 、 Battery cooling water tank 3 、 Tank connection part 12 of The water flows and circulates sequentially. In other words, it is expected that the heat contained in the battery cooling water stored in the battery cooling water tank 3 is transferred to the entire circulating water circulated by the water circulation unit L3 in the second treatment, raising the temperature of the circulating water and suppressing the growth of bacteria in that circulating water. Furthermore, if it is determined that the conditions for bacterial control cannot be met during the shutdown period, the second treatment will not be performed during that shutdown period. As a result, it is possible to avoid the second treatment ending with insufficient temperature rise of the circulating water.

[0047] <Second Embodiment> The fuel cell system of the second embodiment differs from the embodiment described above in the content of the second processing. The fuel cell system of the second embodiment will be described below, but the same configuration as in the embodiment described above will be omitted.

[0048] In the example shown in Figure 6 of the first embodiment described above, the control device C determined that the conditions for bacterial control could not be met because the predicted temperature of the circulating water (predicted uniform temperature) when the temperature is uniformized by the second process was not equal to or greater than the target temperature. However, the control device C can also perform a heat treatment to heat the battery cooling water using the heating device 23. For example, as shown in Figure 3, in the heat treatment, the cooling water pump 7 operates to circulate the battery cooling water through the cooling water circulation path 6, and the heating device 23 operates to heat the battery cooling water. In other words, the heat treatment provides heat to the battery cooling water stored in the battery cooling water tank 3, causing it to rise in temperature. In this case, the control device C can predict the total temperature of the circulating water (predicted uniform temperature) when the temperature is uniformized by the second process, based on the amount of circulating water circulated by the water circulation unit L3, the temperatures at multiple points along the circulating water flow path before the start of the second process, the ambient temperature, and the amount of heat that the heating device 23 can provide to the battery cooling water.

[0049] Figure 7 illustrates the temperature at multiple points along the circulating water flow path before the start of the second treatment, and the overall temperature of the circulating water after it has been homogenized by the second treatment, when heat treatment is performed. As shown in the figure, the control device C operates the heating device 23 and the cooling water pump 7 as part of the heat treatment, supplying battery cooling water heated from 70°C to 80°C to the battery cooling water tank 3. As a result, the water (1L) stored in the battery cooling water tank 3 is at 80°C, and the amount of heat stored corresponding to the difference between 80°C and the ambient temperature of 20°C is approximately 4.2kW. When the second treatment is performed in this state, the temperature of the circulating water (3L) is homogenized to 40°C, meeting the water temperature (40°C) required for bacterial control operation. In other words, the control device C determines that in order to make the temperature of the circulating water 40°C when the second treatment is performed, the water stored in the battery cooling water tank 3 needs to be at 80°C, and performs the heat treatment until the temperature of the battery cooling water measured by the temperature sensor T1 reaches 80°C.

[0050] However, if a predetermined upper temperature limit is set for the circulating water flowing into the ion exchange resin section 5, considering that the water stored in the battery cooling water tank 3 may flow into the ion exchange resin section 5, it is required that the temperature of the water stored in the battery cooling water tank 3 does not exceed that upper temperature limit. Alternatively, if a predetermined upper temperature limit is set for the battery cooling water flowing into the fuel cell 1, it is required that the temperature of the water stored in the battery cooling water tank 3 does not exceed that upper temperature limit. In such cases, the control device C sets a constraint that when the heating device 23 heats the battery cooling water, the temperature of the battery cooling water stored in the battery cooling water tank 3 does not exceed a predetermined upper temperature limit. For example, the upper temperature limit may be 80°C. In the case shown in Figure 7, this constraint is satisfied.

[0051] Thus, the control device C can predict the total temperature of the circulating water (predicted uniform temperature) that will be expected when the temperature is uniformized by the second process, based on the amount of circulating water circulated by the water circulation unit L3, the temperature at multiple points along the flow path of the circulating water before the start of the second process, the ambient temperature, and the amount of heat that the heating device 23 can supply to the battery cooling water. Then, in step #11, the control device C determines whether or not the conditions for bacterial control can be met, similar to the embodiment described above.

[0052] <Another Embodiment> <1> Although the configuration of the fuel cell system has been specifically described in the above embodiment, its configuration can be modified as appropriate.

[0053] For example, in the above embodiment, an example was described in which the heating device 23 is installed in the middle of the cooling water circulation path 6, but the heating device 23 may be installed in another location such as the battery cooling water tank 3. Furthermore, the heating device 23 is not limited to heating the circulating water using heat generated by an electric heater or the like, but may also heat the circulating water by heat exchange between the circulating water and another heat transfer medium.

[0054] Furthermore, although the above embodiment illustrates an ion exchange resin section 5 as an impurity removal device, an impurity removal device equipped with an adsorbent such as activated carbon to remove microorganisms and organic substances such as oil may also be used.

[0055] <2> In the above embodiment, the control device C may execute the second process during a period when the ambient temperature is high, within the period when it is not necessary to supply water stored in the reforming water tank 4 to the fuel treatment device 2 for executing the second process. For example, the control device C may determine that the above-described timing for starting the bacterial control operation is when it is within a period when it is predicted that the ambient temperature will be above a predetermined temperature, within the period when it is not necessary to supply water stored in the reforming water tank 4 to the fuel treatment device 2 for executing the second process.

[0056] During periods when the ambient temperature is relatively high, it is assumed that the temperature of the reforming water stored in the reforming water tank 4 is also high. In other words, as shown in Figure 5, the amount of heat required to raise the temperature of the circulating water circulated by the water circulation unit L3 in the second treatment to a predetermined temperature during periods when the ambient temperature is relatively high is preferable because it is less than the amount of heat required when the ambient temperature is relatively low, as shown in Figure 6. Therefore, if the shutdown period is longer than the period required for uniformization, the second treatment can be performed at some point during the shutdown period. For example, the ambient temperature during the shutdown period can be predicted, and the second treatment can be performed during the time period that includes the predicted peak ambient temperature. By performing the second treatment during periods when the ambient temperature is high, the temperature of the circulating water can be easily raised.

[0057] <3> In the above embodiment, an example was described in which the control device C determines that it is time to end the bacterial control operation when the water temperature measured by temperature sensors T1, T2, and T3 reaches or exceeds the target temperature. However, a different timing may be used to determine the end of the bacterial control operation. For example, the control device C may determine the end of the bacterial control operation as the timing when it is time to start the first treatment, that is, the timing when it becomes necessary to supply the water stored in the reforming water tank 4 to the fuel treatment device 2 in order to start the fuel cell 1 for power generation. In other words, the control device C may continue to perform the second treatment until it is time to start the first treatment.

[0058] Furthermore, the control device C may terminate the second process if the temperature of the circulating water measured by the temperature sensor T3 reaches the upper limit temperature mentioned above. For example, if an upper limit is set for the operating temperature of the ion exchange resin unit 5, the temperature of the circulating water must be kept below that upper limit. Therefore, the control device C may terminate the second process if the temperature of the circulating water measured by the temperature sensor T3 rises and reaches the upper limit for the operating temperature of the ion exchange resin unit 5. However, the upper limit for the operating temperature of the ion exchange resin unit 5 is higher than the target temperature mentioned above.

[0059] <4> In the above embodiment, an example was described in which the second treatment is performed after the heat treatment, but the heat treatment and the second treatment may be performed simultaneously. For example, the control device C may heat the battery cooling water circulating in the cooling water circulation path 6 by performing the heat treatment, while circulating the water in the water circulation unit L3. The control device C may then determine that it is time to end the second treatment when, for example, the temperature of the circulating water measured by the temperature sensor T3 reaches 40°C (the target temperature for suppressing bacterial growth).

[0060] <5> In the above embodiment, specific numerical values ​​were given for the water temperature, heat quantity, etc., but these values ​​are provided for illustrative purposes only and can be changed as appropriate.

[0061] <6> The configurations disclosed in the above embodiments (including other embodiments, the same applies hereinafter) can be applied in combination with configurations disclosed in other embodiments, as long as no inconsistencies arise. Furthermore, the embodiments disclosed herein are illustrative, and the embodiments of the present invention are not limited thereto and can be modified as appropriate without departing from the purpose of the present invention. [Industrial applicability]

[0062] This invention can be used in fuel cell systems that can appropriately perform antimicrobial operation to suppress the growth of bacteria. [Explanation of symbols]

[0063] 1:Fuel cell 2: Fuel treatment device 3: Battery cooling water tank 4: Water tank for treatment 5: Ion exchange resin section (impurity removal device) 12: Tank connection part 23: Heating device C: Control device L1:Battery cooling water circulation section L2: Water Reformation Supply Unit L3: Water circulation section

Claims

1. Fuel cells and A fuel treatment device that generates a hydrogen-containing fuel gas to be supplied to the aforementioned fuel cell by steam reforming, A battery cooling water tank for storing water used as battery cooling water to recover heat discharged from the fuel cell, A water tank for storing water used as reforming water in the aforementioned steam reforming, An impurity removal device that performs impurity removal treatment on the water used as the water for reforming, A battery cooling water circulation unit that circulates the water used as the battery cooling water between the fuel cell and the battery cooling water tank, A water reforming supply unit supplies the water used as reforming water to the fuel treatment device via the water reforming tank and the impurity removal device, A tank connection section connecting the battery cooling water tank and the reforming water tank, A water circulation unit that circulates the water used as the battery cooling water and the water used as the water for reforming in the following order: the battery cooling water tank, the tank connection unit, the water for reforming tank, and the impurity removal device. Equipped with a control device, The control device is The first process involves operating the reforming water supply unit and supplying the water stored in the reforming water tank to the fuel treatment device, and the fuel treatment device supplying the fuel gas generated by the steam reforming to the fuel cell during an operating period, and alternating between this and a stop period in which the reforming water supply unit is stopped, the water stored in the reforming water tank is not supplied to the fuel treatment device, and the fuel treatment device does not perform the steam reforming. When commencing the aforementioned suspension period, it is determined whether or not the conditions for suppressing bacterial growth can be met during the suspension period. If it is determined that the conditions for preventing bacterial infection can be met during the aforementioned shutdown period, a second process is performed during the shutdown period to operate the water circulation unit. A fuel cell system that, if it is determined that the conditions for preventing the bacteria cannot be met during the aforementioned shutdown period, does not perform the second treatment during that shutdown period.

2. The fuel cell system according to claim 1, wherein the control device determines that the temperature of the circulating water circulated by the water circulation unit during the shutdown period can be raised to a predetermined target temperature or higher, and determines that the conditions for preventing bacterial growth can be met.

3. The fuel cell system according to claim 2, wherein the control device determines whether the overall temperature of the circulating water can be raised to or above the target temperature based on the amount of circulating water circulated by the water circulation unit, the temperature at multiple points along the flow path of the circulating water before the start of the second treatment, and the ambient temperature.

4. The battery cooling water is heated by a heating device, The fuel cell system according to claim 2, wherein the control device determines whether the overall temperature of the circulating water can be raised to or above the target temperature based on the amount of circulating water circulated by the water circulation unit, the temperature at multiple points along the flow path of the circulating water before the start of the second treatment, the ambient temperature, and the amount of heat that the heating device can supply to the battery cooling water.

5. The fuel cell system according to claim 4, wherein the control device is constrained by the condition that when the heating device heats the battery cooling water, the temperature of the battery cooling water stored in the battery cooling water tank does not exceed a predetermined upper limit temperature.

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