JP2010257645A - Control program of fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance water taking-in efficiency and to cover the whole amount of water necessary for operation in simple and compact constitution. <P>SOLUTION: The control program includes a control device 18 executing a first step detecting the amount of water stored in a water container 22; a second step detecting any one of the amount of water, the flow rate, temperature, humidity of oxidant gas, or the flow rate of fuel gas supplied to a fuel cell module; a third step calculating the whole amount of water supplied to the fuel cell module 16; a fourth step calculating the amount of water condensed from steam in exhaust gas exhausted from the fuel cell module 16; a fifth step calculating any one of temperature of the exhaust gas after heat exchange, exhausted from at least a condenser 24, or temperature of a coolant after heat exchange, exhausted from the condenser 24; and a sixth step adjusting the flow rate of the coolant supplied to the condenser 24. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a control program for a fuel cell system for controlling a fuel cell system including a fuel cell module, a control device, a water supply device, a water container and a condenser by a computer.

  Usually, a solid oxide fuel cell (SOFC) uses an oxide ion conductor, for example, stabilized zirconia, as a solid electrolyte. An electrolyte / electrode assembly in which an anode electrode and a cathode electrode are disposed on both sides of the solid electrolyte is sandwiched between separators (bipolar plates). This fuel cell is usually used as a fuel cell stack in which a predetermined number of electrolyte / electrode assemblies and separators are laminated.

  As the fuel gas supplied to the fuel cell, hydrogen gas generated from a hydrocarbon-based raw fuel by a reformer is usually used. In a reformer, generally, after obtaining a reforming raw material gas from a hydrocarbon-based raw fuel such as fossil fuel such as methane or LNG, the reforming raw material gas is subjected to, for example, steam reforming. The reformed gas (fuel gas) is generated.

  In the steam reforming described above, it is necessary to replenish water corresponding to the amount of steam used for the reforming reaction. For this reason, instead of a system that supplies the required amount of water from the outside, a water recovery system that completely circulates the water necessary for reforming (water self-sustained) by condensing exhaust gas generated by power generation of the fuel cell Attention has been paid.

  For example, a fuel cell system and a fuel gas supply method disclosed in Patent Document 1 are known. In Patent Document 1, as shown in FIG. 7, air heated through a heat exchanger 4a is supplied to the air electrode 2a of the solid oxide fuel cell 1a, and the fuel electrode 3a has The reformed fuel is supplied through the heat exchanger 5a and the reformer 6a.

  Fuel exhaust gas from the fuel electrode 3a is discharged to the exhaust gas passage 7a, and a distribution valve 8a is provided in the exhaust gas passage 7a to distribute the distribution pipe passage 9a. The distribution pipe 9a supplies the distributed fuel exhaust gas to the reformer 6a, the heat exchanger 4a, and the heat exchanger 5a.

  In addition, in the exhaust heat recovery system for a solid oxide fuel cell disclosed in Patent Document 2, as shown in FIG. 8, a solid oxide fuel cell 1b and a reformer 2b are arranged in a power generation chamber 3b. The power generation module 4b, and the exhaust gas discharged from the power generation chamber 3b circulate in the internal space 5b, and the exhaust heat recovery heat exchanger 7b in which the circulating water pipe 6b is inserted into the internal space 5b. ing.

  An outlet of condensed water is provided on the lower surface of the heat exchanger for exhaust heat recovery 7b, and a water storage tank 8b is disposed at the outlet. The water stored in the water storage tank 8b is supplied to the reformer 2b of the power generation module 4b via the water pump 9b.

JP 2006-156015 A JP 2007-234374 A

  However, in the above-mentioned Patent Document 1, since the distribution pipe 9a is branched from the exhaust gas flow path 7a, there is a problem that the whole system is increased in size and the heat radiation amount is increased. In addition, the number of parts increases and the manufacturing cost may increase. Moreover, since the distribution valve 8a is exposed to high-temperature fuel exhaust gas immediately after power generation, the heat resistance and durability of the distribution valve 8a are required. Thereby, there exists a problem that the cost of the distribution valve 8a rises.

  Moreover, in said patent document 2, although the water | moisture content in waste gas is taken out to the water storage tank 8b as condensed water with the heat exchanger 7b for waste heat collection | recovery, the collection | recovery amount of this condensed water cannot be adjusted. Therefore, there is a possibility that the water stored in the water storage tank 8b is significantly reduced or the water overflows from the water storage tank 8b.

  The present invention solves this type of problem, and has a simple and compact configuration, can improve water collection efficiency, and can control the total amount of water required for operation. The purpose is to provide.

  The present invention relates to a fuel cell module that generates electricity by an electrochemical reaction between a fuel gas and an oxidant gas by a computer, a water supply device that supplies water to the fuel cell module, and a water supply device that supplies water to the water supply device. A condenser for condensing water vapor in the exhaust gas and supplying condensed water to the water container by heat exchange between the container and the exhaust gas discharged from the fuel cell module and an externally supplied refrigerant body; The present invention relates to a fuel cell system control program for controlling a fuel cell system.

  The control program includes a first step of detecting the amount of water stored in the water container, the amount of water supplied to the fuel cell module, and at least the flow rate, temperature, and humidity of the oxidant gas supplied to the fuel cell module. Alternatively, a second step of detecting either the flow rate of the fuel gas supplied to the fuel cell module and a first step of calculating the total amount of water supplied to the fuel cell module based on the detection result of the second step. 3 and the water condensed from the water vapor in the exhaust gas discharged from the fuel cell module with the total water amount calculated in the third step as the upper limit based on the detection result of the first step. A fourth step of calculating the amount, and a temperature of the exhaust gas after heat exchange discharged from the condenser based on the calculation result of the fourth step Or the fifth step of calculating either the temperature of the refrigerant body after heat exchange discharged from the condenser, and the refrigerant body supplied to the condenser based on the calculation result of the fifth step And a sixth step of adjusting the flow rate of.

  In the control program, the fourth step is preferably executed by comparing the amount of water stored in the water container with a preset range of the amount of stored water. For this reason, an optimal amount of water can be secured in the water container, and the entire amount of water necessary for the operation of the fuel cell system can be covered in the fuel cell system.

  Accordingly, it is not necessary to supply water from the outside, and water self-sustained operation of the fuel cell system is performed. Here, water self-supporting means that the entire amount of water necessary for the operation of the fuel cell system is supplied from within the fuel cell system without being supplied from the outside.

  Further, in this control program, the fourth step is to condense from the water vapor in the exhaust gas discharged from the fuel cell module when it is determined that the amount of water stored in the water container is less than the range of the amount of stored water. The amount of water is preferably set to an amount that exceeds the amount of water supplied to the fuel cell module in the second step.

  As a result, when the amount of water stored in the water container is small, the water collection efficiency (the amount of water condensed from the water vapor in the exhaust gas discharged from the fuel cell module / the amount of water supplied to the fuel cell module)> 100%. Since the amount of water exceeds the amount of water supplied to the fuel cell module, an optimal amount of water is secured in the water container. For this reason, the entire amount of water required for the operation of the fuel cell system can be covered in the fuel cell system, and water supply operation of the fuel cell system is performed without the need for external water supply.

  Furthermore, in this control program, the fourth step is to condense from the water vapor in the exhaust gas discharged from the fuel cell module when it is determined that the amount of water stored in the water container exceeds the range of the amount of stored water. It is preferable to set the amount of water to be less than the amount of water supplied to the fuel cell module in the second step. Therefore, when the amount of water stored in the water container is large, the amount of condensed water is less than the amount of water supplied to the fuel cell module by setting the water collection efficiency <100%, so that an optimal amount of water is secured in the water container. Is done. As a result, the entire amount of water required for the operation of the fuel cell system can be covered in the fuel cell system, and the water cell autonomous operation of the fuel cell system is performed without the need for external water supply.

  Further, in this control program, the fourth step is to condense from the water vapor in the exhaust gas discharged from the fuel cell module when it is determined that the water storage amount in the water container is within the range of the water storage amount. The amount of water is preferably set to the same amount as the amount of water supplied to the fuel cell module in the second step. For this reason, by setting the water collection efficiency to 100%, an optimal amount of water is secured in the water container, and the entire amount of water necessary for the operation of the fuel cell system can be covered in the fuel cell system. Accordingly, it is not necessary to supply water from the outside, and water self-sustained operation of the fuel cell system is performed.

  Further, in this control program, the sixth step includes at least the temperature of the exhaust gas after heat exchange discharged from the condenser, the temperature of the exhaust gas calculated in the fifth step, or the heat discharged from the condenser. It is preferable that the temperature of the refrigerant body after replacement is compared with the temperature of the refrigerant body calculated in the fifth step. Thus, the total amount of water necessary for the operation of the fuel cell system is covered, and after the heat contained in the exhaust gas discharged from the fuel cell module is recovered well, the exhaust gas is discharged outside the fuel cell system. The For this reason, the thermal efficiency of the fuel cell system can be easily improved.

  Furthermore, in this control program, in the sixth step, the temperature of the exhaust gas after heat exchange discharged from the condenser exceeds the set range of the exhaust gas temperature calculated in the fifth step. When determined, it is preferable to increase the flow rate of the refrigerant supplied to the condenser. Therefore, when the temperature of the exhaust gas is high, the flow rate of the refrigerant supplied to the condenser is increased, and the temperature of the exhaust gas is lowered. Thereby, the amount of water condensed from the water vapor in the exhaust gas is always maintained at an optimal amount of water, and water shortage is reliably suppressed.

  In addition, the total amount of water necessary for the operation of the fuel cell system is covered, and after the heat contained in the exhaust gas discharged from the fuel cell module is recovered well, the exhaust gas is discharged outside the fuel cell system. . For this reason, the thermal efficiency of the fuel cell system can be easily improved.

  Further, in this control program, in the sixth step, it is determined that the temperature of the exhaust gas after heat exchange discharged from the condenser is equal to or less than the set range of the temperature of the exhaust gas calculated in the fifth step. In this case, it is preferable to reduce or maintain the flow rate of the refrigerant supplied to the condenser. Therefore, when the temperature of the exhaust gas is low, the flow rate of the refrigerant supplied to the condenser is reduced or maintained to increase or maintain the temperature of the exhaust gas. As a result, the amount of water condensed from the water vapor in the exhaust gas is always maintained at an optimal amount of water, and the surplus water is reliably suppressed.

  In addition, the total amount of water necessary for the operation of the fuel cell system is covered, and after the heat contained in the exhaust gas discharged from the fuel cell module is recovered well, the exhaust gas is discharged outside the fuel cell system. . For this reason, the thermal efficiency of the fuel cell system can be easily improved.

  Further, in this control program, in the sixth step, the temperature of the refrigerant body after the heat exchange discharged from the condenser exceeds the setting range of the temperature of the refrigerant body calculated in the fifth step. When it is determined, it is preferable to increase the flow rate of the refrigerant supplied to the condenser. Therefore, when the temperature of the refrigerant body is high, the flow rate of the refrigerant body supplied to the condenser is increased to lower the temperature of the exhaust gas. Thereby, the amount of water condensed from the water vapor in the exhaust gas is always maintained at an optimal amount of water, and water shortage is reliably suppressed.

  In addition, the total amount of water necessary for the operation of the fuel cell system is covered, and after the heat contained in the exhaust gas discharged from the fuel cell module is recovered well, the exhaust gas is discharged outside the fuel cell system. . For this reason, the thermal efficiency of the fuel cell system can be easily improved.

  Furthermore, in this control program, in the sixth step, the temperature of the refrigerant body after the heat exchange discharged from the condenser is less than the setting range of the temperature of the refrigerant body calculated in the fifth step. When the determination is made, it is preferable to reduce the flow rate of the refrigerant supplied to the condenser. Therefore, when the temperature of the refrigerant body is low, the flow rate of the refrigerant body supplied to the condenser is reduced to increase the temperature of the exhaust gas. As a result, the amount of water condensed from the water vapor in the exhaust gas is always maintained at an optimal amount of water, and the surplus water is reliably suppressed.

  In addition, the total amount of water necessary for the operation of the fuel cell system is covered, and after the heat contained in the exhaust gas discharged from the fuel cell module is recovered well, the exhaust gas is discharged outside the fuel cell system. . For this reason, the thermal efficiency of the fuel cell system can be easily improved.

  In this control program, the sixth step determines that the temperature of the refrigerant body after the heat exchange discharged from the condenser is within the setting range of the temperature of the refrigerant body calculated in the fifth step. When this is done, it is preferable to maintain the flow rate of the refrigerant supplied to the condenser. Accordingly, since the temperature of the refrigerant body is optimum, the flow rate of the refrigerant body supplied to the condenser is maintained, and the amount of water condensed from the water vapor in the exhaust gas can always be ensured optimally.

  In addition, the total amount of water necessary for the operation of the fuel cell system is covered, and after the heat contained in the exhaust gas discharged from the fuel cell module is recovered well, the exhaust gas is discharged outside the fuel cell system. . Thereby, the thermal efficiency of the fuel cell system can be easily improved.

  Further, in this control program, the fuel cell module is provided with a fuel cell in which an electrolyte / electrode assembly configured by sandwiching at least an electrolyte between an anode electrode and a cathode electrode, and a separator, and a plurality of the fuel cells are provided. In order to produce a fuel cell stack to be stacked, a heat exchanger for heating before supplying the oxidant gas to the fuel cell stack, and a mixed fuel of raw fuel and steam mainly composed of hydrocarbons, water is used. It is preferable to include an evaporator for evaporating and a reformer for reforming the mixed fuel to generate fuel gas.

  Therefore, it can be optimally applied to a fuel cell module that performs steam reforming in particular, and a good effect can be obtained.

  Furthermore, in this control program, the fuel cell module is preferably a solid oxide fuel cell module. Therefore, it can be optimally used for a high temperature fuel cell system, and a good effect can be obtained.

  According to the present invention, the total amount of water supplied to the fuel cell module is calculated based on the detection result of the amount of water stored in the water container, and the water vapor in the exhaust gas discharged from the fuel cell module with the total water amount as the upper limit. The amount of water to be condensed is calculated. As a result, the inside of the water container can always ensure an optimal amount of water, and with a simple and compact configuration, the water sampling efficiency of the fuel cell system (condensed from the water vapor in the exhaust gas discharged from the fuel cell module) It is possible to improve the amount of water / the amount of water supplied to the fuel cell module.

  For this reason, the entire amount of water required for the operation of the fuel cell system can be covered in the fuel cell system, and water supply operation of the fuel cell system is performed without the need for external water supply. Here, water self-supporting means that the entire amount of water necessary for the operation of the fuel cell system is supplied from within the fuel cell system without being supplied from the outside.

It is a schematic structure explanatory view of a fuel cell system for carrying out a control program concerning a 1st embodiment of the present invention. It is a circuit diagram of the fuel cell system. It is a flowchart explaining the control program which concerns on the said 1st Embodiment. It is explanatory drawing of the water level and coefficient (alpha) of a water container. It is a flowchart explaining the control program which concerns on the 2nd Embodiment of this invention. It is a flowchart explaining the control program which concerns on the 3rd Embodiment of this invention. 2 is an explanatory diagram of a fuel cell system of Patent Document 1. FIG. It is explanatory drawing of the waste heat recovery system of patent document 2. FIG.

  The fuel cell system 10 for executing the control program according to the first embodiment of the present invention is used for various purposes such as in-vehicle use as well as stationary use.

  The fuel cell system 10 includes a power generation unit 12 and a hot water storage unit 14 as schematically shown in FIG. The power generation unit 12 includes a fuel cell module 16 that generates power by an electrochemical reaction between a fuel gas (hydrogen gas) and an oxidant gas (air), and a control device (computer) that records a control program for controlling the fuel cell system 10. ) 18, a water supply device (including a water pump) 20 for supplying water to the fuel cell module 16, a water container 22 for supplying water to the water supply device 20, and the fuel cell module 16. A condenser 24 is provided that condenses water vapor in the exhaust gas and exchanges the condensed water to the water container 22 by heat exchange between the exhaust gas and a refrigerant body (for example, water) supplied from the outside.

  The hot water storage unit 14 includes a hot water storage tank 26. A refrigerant body is stored in the hot water storage tank 26, and the refrigerant body is circulated through the condenser 24 via the pump 28. City water is supplied to the hot water storage tank 26, while hot water is supplied from the hot water storage tank 26 to the home.

  More specifically, as shown in FIGS. 1 and 2, the power generation unit 12 includes a fuel cell module 16 and a fuel gas supply device (fuel) that supplies raw fuel (for example, city gas) to the fuel cell module 16. 32), an oxidant gas supply device (including an air pump) 34 for supplying an oxidant gas to the fuel cell module 16, a water supply device 20, a water container 22, a condenser 24, and the fuel. And a power converter 36 that converts DC power generated in the battery module 16 into required specification power. For example, a commercial power source 38 (or a load, a secondary battery, or the like) is connected to the power conversion device 36 (see FIG. 2).

  Although not shown, the fuel cell module 16 is, for example, an electrolyte / electrode joint configured by sandwiching a solid electrolyte (solid oxide) composed of an oxide ion conductor such as stabilized zirconia between an anode electrode and a cathode electrode. A solid oxide fuel cell 46 in which the body 42 and the separator 44 are stacked is provided, and a solid oxide fuel cell stack 48 in which the plurality of fuel cells 46 are stacked in the vertical direction is provided (see FIG. 2). ).

  On the upper end side (or lower end side) of the fuel cell stack 48 in the stacking direction, a heat exchanger 50 that heats the oxidant gas before being supplied to the fuel cell stack 48, raw fuel mainly composed of hydrocarbons, and steam In order to generate the mixed fuel, an evaporator 52 that evaporates the water and a reformer 54 that reforms the mixed fuel to generate a fuel gas (reformed gas) are disposed.

  On the lower end side (or upper end side) of the fuel cell stack 48 in the stacking direction, a load applying mechanism 56 for applying a tightening load to the fuel cells 46 constituting the fuel cell stack 48 along the stacking direction (arrow A direction). Is disposed.

The reformer 54 removes higher hydrocarbons (C ₂₊ ) such as ethane (C ₂ H ₆ ), propane (C ₃ H ₈ ) and butane (C ₄ H ₁₀ ) contained in the city gas (fuel gas). , A pre-reformer for steam reforming to a fuel gas mainly containing methane (CH ₄ ), and is set to an operating temperature of several hundred degrees Celsius.

  The operating temperature of the fuel cell 46 is as high as several hundred degrees C. In the electrolyte / electrode assembly 42, methane in the fuel gas is reformed to obtain hydrogen, and this hydrogen is supplied to the anode electrode.

  The heat exchanger 50 exchanges heat by flowing spent reaction gas (hereinafter also referred to as exhaust gas or combustion exhaust gas) discharged from the fuel cell stack 48 and air that is a fluid to be heated in opposite directions. The exhaust gas after the heat exchange is discharged to the exhaust pipe 60, while the air after the heat exchange is supplied to the fuel cell stack 48 as an oxidant gas.

  A double pipe is connected to the evaporator 52, and a raw fuel passage 62 and a water passage (water pipe) 64 are formed in the double pipe. The outlet of the evaporator 52 is connected to the inlet of the reformer 54, and the outlet of the reformer 54 communicates with a fuel gas supply communication hole (not shown) of the fuel cell stack 48. In order to discharge the exhaust gas supplied to the evaporator 52, a main exhaust pipe 65 is provided.

  A raw fuel passage 62 is connected to the fuel gas supply device 32. An air supply pipe 66 is connected to the oxidant gas supply device 34, and the air supply pipe 66 is connected to the heat exchanger 50.

  As shown in FIGS. 1 and 2, an exhaust pipe 60 and a main exhaust pipe 65 are connected to the condenser 24, and on the outlet side of the exhaust pipe 60 and the main exhaust pipe 65 from the condenser 24. The exhaust pipe 68 is connected.

  The hot water storage tank 26 is provided with a circulation pipe 70 connected to the pump 28. The circulation pipe 70 exchanges heat with the exhaust gas through the refrigerant body in the condenser 24, and returns the heated refrigerant body (hot water) to the upper side of the hot water storage tank 26.

  As shown in FIG. 1, the water passage 64 is provided with a flow meter 74 a located downstream of the water supply device 20. In the raw fuel passage 62, a flow meter 74b is disposed downstream of the fuel gas supply device 32, and in the air supply pipe 66, a flow meter 74c is disposed downstream of the oxidant gas supply device 34. Established.

  A temperature / humidity meter 76 is disposed on the inlet side of the oxidant gas supply device 34. A water level meter 78 for detecting the water level of the stored water in the water container 22 is disposed in the water container 22 at a predetermined height position.

  In the condenser 24, a thermocouple 80 a for detecting the exhaust temperature is disposed in the exhaust pipe 68, and the temperature of the heated refrigerant body is set on the outlet side of the circulation pipe 70 from the condenser 24. A thermocouple 80b for detection is provided.

  The control device 18 controls the water supply device 20, the fuel gas supply device 32, the oxidant gas supply device 34, and the pump 28. The control device 18 includes flow meters 74a to 74c, a temperature / humidity meter 76, and a water level meter. Each detection signal is input from 78 and thermocouples 80a and 80b.

  The operation of the fuel cell system 10 configured as described above will be described below.

Under the driving action of the fuel gas supply device 32, raw fuel such as city gas (including CH ₄ , C ₂ H ₆ , C ₃ H ₈ , and C ₄ H ₁₀ ) is supplied to the raw fuel passage 62. The On the other hand, under the driving action of the water supply device 20, water is supplied to the water passage 64, and oxidant gas is supplied to the air supply pipe 66 via the oxidant gas supply device 34, for example, air Is supplied.

In the evaporator 52, steam is mixed with the raw fuel flowing through the raw fuel passage 62 to obtain a mixed fuel, and this mixed fuel is supplied to the inlet of the reformer 54. The mixed fuel is subjected to steam reforming in the reformer 54, and C ₂₊ hydrocarbons are removed (reformed) to obtain a fuel gas mainly composed of methane. This fuel gas is introduced into the fuel cell stack 48 from the outlet of the reformer 54. Therefore, methane in the fuel gas is reformed to obtain hydrogen gas, and the fuel gas containing the hydrogen gas as a main component is supplied to an anode electrode (not shown).

  On the other hand, when the air supplied from the air supply pipe 66 to the heat exchanger 50 moves along the heat exchanger 50, heat exchange is performed with exhaust gas described later, and the air is preheated to a desired temperature. Has been. The air heated by the heat exchanger 50 is introduced into the fuel cell stack 48 and supplied to a cathode electrode (not shown).

  Therefore, in the electrolyte / electrode assembly 42, power generation is performed by an electrochemical reaction between fuel gas and air. The high-temperature (several hundred degrees Celsius) exhaust gas discharged to the outer periphery of each electrolyte / electrode assembly 42 exchanges heat with air through the heat exchanger 50, and heats the air to a desired temperature. A drop is triggered.

  This exhaust gas evaporates the water passing through the water passage 64. The exhaust gas that has passed through the evaporator 52 is sent to the condenser 24 via the main exhaust pipe 65 to condense the water vapor, while the exhaust gas component is discharged outside via the exhaust pipe 68. The condenser 24 is supplied with a refrigerant body from the hot water storage tank 26, the refrigerant body and the exhaust gas exchange heat, and the water vapor in the exhaust gas is condensed to obtain water.

  This water is introduced into a water container 22 arranged downstream of the condenser 24. Then, when the water supply device 20 disposed downstream of the water container 22 is driven, the water stored in the water container 22 is supplied to the fuel cell module 16 via the water passage 64.

  Next, a control program according to the first embodiment for controlling the fuel cell system 10 by the control device 18 will be described with reference to the flowchart shown in FIG.

  The control program first includes a step (first step) of detecting the amount of stored water stored in the water container 22 by the water level gauge 78 (step S1).

  The control device 18 sets the coefficient α based on the detected amount of stored water in the water container 22, that is, the water level. As will be described later, the coefficient α is a coefficient for calculating the target condensed water amount, and is set to a value shown in FIG. 4 depending on the water level of the water container 22.

  For example, if the detected water level is within the set range, the coefficient α is set to 0.95 ≦ α ≦ 1.05, whereas if the detected water level is less than the set range, the coefficient α is set to α> 1.05. Further, if the set range is exceeded, the coefficient α is set to α <0.95. Note that when maintaining a large amount of stored water in the water container 22, the coefficient α may be selected to be a large numerical value.

  In step S <b> 2 (second step), calculation of each moisture amount supplied to the fuel cell module 16 is executed.

  Specifically, the amount of water supplied to the fuel cell module 16 via the water supply device 20 is detected by the flow meter 74a. The flow rate of the oxidant gas supplied to the fuel cell module 16 via the oxidant gas supply device 34 is detected by the flow meter 74c, and the temperature and humidity of the oxidant gas are detected by the temperature and humidity meter 76. . The flow rate of the fuel gas supplied to the fuel cell module 16 via the fuel gas supply device 32 is detected via the flow meter 74b. Note that step S1 (first step) and step S2 (second step) may be performed in the reverse order.

  In step S3 (third step), the amount of water supplied to the fuel cell module 16 detected in the second step and at least the flow rate of the oxidant gas supplied to the fuel cell module 16, The total amount of water supplied to the fuel cell module 16 is calculated based on any one of temperature, humidity, and fuel gas flow rate.

  The control device 18 calculates the amount of water condensed from the water vapor in the exhaust gas discharged from the fuel cell module 16 with the total water amount calculated in step S3 as the upper limit based on the coefficient α determined in step S1. A step (fourth step) is executed (step S4).

  In this step S4, the amount of water condensed from the water vapor in the exhaust gas is set as the target condensed water amount, and the target condensed water amount = the input water amount × α is calculated. The amount of input water refers to the amount of water supplied from the water container 22 to the fuel cell module 16 via the water supply device 20.

  Next, it progresses to step S5 (5th step), and the exhaust gas temperature after the heat exchange discharged | emitted from the condenser 24, ie, target exhaust gas temperature T, is set based on the calculation result of step S4. Then, based on the target exhaust gas temperature T, a sixth step of adjusting the flow rate of the refrigerant body supplied to the condenser 24 is executed.

  In this sixth step, the temperature of the exhaust gas exhausted from the condenser 24 to the exhaust pipe 68 is detected via the thermocouple 80a (step S6). Here, if it is determined that the detected exhaust gas temperature is equal to or lower than the target exhaust gas temperature T (YES in step S6), the process proceeds to step S7, and the condensed water amount reduction / maintenance control by the condenser 24 is executed. The On the other hand, if it is determined that the detected exhaust gas temperature exceeds the target exhaust gas temperature T (NO in step S6), the process proceeds to step S8, and control for increasing the amount of condensed water by the condenser 24 is executed. .

  In this case, in the first embodiment, the total amount of water supplied to the fuel cell module 16 is calculated based on the detection result of the amount of water stored in the water container 22, and the total amount of water is set as the upper limit from the fuel cell module 16. The amount of water condensed from the water vapor in the exhaust gas discharged, that is, the target amount of condensed water is calculated. Thereby, the inside of the water container 22 can always ensure the optimal amount of water, and it becomes possible to improve the water collection efficiency of the fuel cell system 10 with a simple and compact configuration.

  Therefore, the entire amount of water necessary for the operation of the fuel cell system 10 can be covered within the fuel cell system 10, and the water supply operation of the fuel cell system 10 is performed without the need for external water supply. The effect that it is done is acquired.

  In step S4 (fourth step), the target condensate amount is calculated by comparing the amount of water stored in the water container 22 with a preset range of the amount of stored water. For this reason, an optimal amount of water can be secured in the water container 22, and the entire amount of water necessary for the operation of the fuel cell system 10 can be covered in the fuel cell system 10. Accordingly, it is not necessary to supply water from the outside, and the water self-sustaining operation of the fuel cell system 10 is performed.

  At that time, when it is determined that the amount of water stored in the water container 22 is less than the set range, the coefficient α is determined to exceed 1.05, for example (see FIG. 4). That is, the amount of water condensed from the water vapor in the exhaust gas discharged from the fuel cell module 16 (target condensed water amount) is the amount of water supplied from the water container 22 to the fuel cell module 16 via the water supply device 20. It is set to an amount that exceeds.

  As a result, when the amount of water stored in the water container 22 is small, the water collection efficiency is greater than 100% and the target condensed water amount exceeds the amount of water supplied to the fuel cell module 16. Water volume is secured. Therefore, the entire amount of water necessary for the operation of the fuel cell system 10 can be covered within the fuel cell system 10, and the water supply operation of the fuel cell system 10 is performed without the need for external water supply. Is done.

  On the other hand, when it is determined in step S4 that the amount of water stored in the water container 22 exceeds the set range, the target condensed water amount is less than the amount of water supplied to the fuel cell module 16 via the water supply device 20. The amount is set. Therefore, when the amount of stored water in the water container 22 is large, the target condensed water amount is less than the amount of water supplied to the fuel cell module 16 by setting the water collection efficiency <100%. Water volume is secured. As a result, the entire amount of water required for the operation of the fuel cell system 10 can be covered within the fuel cell system 10, and the water supply operation of the fuel cell system 10 is performed without the need for external water supply. Is done.

  In step S4, when it is determined that the amount of water stored in the water container 22 is within the set range, the target amount of condensed water is set to the same amount as the amount of water supplied to the fuel cell module 16. For this reason, by setting the water sampling efficiency = 100%, an optimal amount of water is secured in the water container 22, and the entire amount of water necessary for the operation of the fuel cell system 10 is covered in the fuel cell system 10. Can do. Accordingly, it is not necessary to supply water from the outside, and the water self-sustaining operation of the fuel cell system 10 is performed.

  Furthermore, in the sixth step, the temperature of the exhaust gas after heat exchange discharged from the condenser 24 is compared with the target exhaust gas temperature T, and the amount of condensed water is increased or decreased. Thereby, the total amount of water necessary for the operation of the fuel cell system 10 is covered, and after the heat contained in the exhaust gas discharged from the fuel cell module 16 is recovered well, the exhaust gas is external to the fuel cell system 10. To be discharged. For this reason, the thermal efficiency of the fuel cell system 10 can be easily improved.

  At that time, when it is determined that the temperature of the exhaust gas after heat exchange discharged from the condenser 24 is equal to or lower than the target exhaust gas temperature T (YES in step S6), the flow rate of the refrigerant supplied to the condenser 24 Is reduced or maintained. Therefore, when the temperature of the exhaust gas is low, the flow rate of the refrigerant supplied to the condenser 24 is reduced or maintained, and the temperature of the exhaust gas is increased or maintained. As a result, the amount of water condensed from the water vapor in the exhaust gas is always maintained at an optimal amount of water, and the surplus water is reliably suppressed.

  In addition, the total amount of water necessary for the operation of the fuel cell system 10 is covered, and after the heat contained in the exhaust gas discharged from the fuel cell module 16 is recovered well, the exhaust gas is transferred to the outside of the fuel cell system 10. Discharged. For this reason, the thermal efficiency of the fuel cell system 10 can be easily improved.

  On the other hand, when it is determined that the temperature of the exhaust gas after heat exchange discharged from the condenser 24 exceeds the target exhaust gas temperature T (NO in step S6), the refrigerant supplied to the condenser 24 The flow rate has been increased. Therefore, when the temperature of the exhaust gas is high, the flow rate of the refrigerant supplied to the condenser 24 is increased, and the temperature of the exhaust gas can be lowered. Thereby, the amount of water condensed from the water vapor in the exhaust gas is always maintained at an optimal amount of water, and water shortage is reliably suppressed.

  In addition, the total amount of water necessary for the operation of the fuel cell system 10 is covered, and after the heat contained in the exhaust gas discharged from the fuel cell module 16 is recovered well, the exhaust gas is transferred to the outside of the fuel cell system 10. Discharged. For this reason, the thermal efficiency of the fuel cell system 10 can be easily improved.

  Further, the fuel cell module 16 includes a fuel cell stack 48, a heat exchanger 50, an evaporator 52, and a reformer 54. Therefore, in particular, the fuel cell module 16 that performs steam reforming can be optimally used, and a good effect can be obtained.

  Furthermore, the fuel cell module 16 is configured with a high-temperature fuel cell system, for example, a solid oxide fuel cell (SOFC) module, so that a good effect is obtained. Moreover, it can be suitably used for other high-temperature fuel cell modules and medium-temperature fuel cell modules instead of the solid oxide fuel cell modules. For example, a molten carbonate fuel cell (MCFC), a phosphoric acid fuel cell (PAFC), a hydrogen separation membrane fuel cell (HMFC) and the like can be favorably employed.

  FIG. 5 is a flowchart for executing the control program according to the second embodiment of the present invention.

  Detailed descriptions of the same steps as those in the control program according to the first embodiment shown in FIG. 3 are omitted.

  In the second embodiment, first, steps S11 to S14 (first step to fourth step) are executed similarly to steps S1 to S4 of the first embodiment.

  Next, the process proceeds to step S15 (fifth step), and based on the target condensed water amount, the temperature of the refrigerant body after heat exchange discharged from the condenser 24, that is, the target refrigerant body upper limit temperature (MAX) and the lower limit temperature. (MIN) is set. Based on the target refrigerant body upper limit temperature (MAX) and the lower limit temperature (MIN), the flow rate of the refrigerant supplied to the condenser 24 is adjusted (sixth step).

  Specifically, in step S16, the temperature of the refrigerant body after the heat exchange discharged from the condenser 24 is detected by the thermocouple 80b, and the refrigerant body temperature and the target refrigerant body upper limit temperature (MAX) after the heat exchange are detected. Are compared. When it is determined that the refrigerant body temperature after heat exchange is equal to or lower than the target refrigerant body upper limit temperature (MAX) (YES in step S16), the process proceeds to step S17, and the refrigerant body temperature after heat exchange and the target cooling temperature are increased. The lower limit temperature (MIN) of the medium is compared.

  When it is determined that the refrigerant body temperature after heat exchange is equal to or higher than the target refrigerant body lower limit temperature (MIN) (YES in step S17), that is, the refrigerant body temperature after heat exchange is within a set range. If judged, the process proceeds to step S18, and the flow rate of the refrigerant supplied to the condenser 24 is maintained.

  On the other hand, if it is determined that the temperature of the refrigerant body after the heat exchange is lower than the target refrigerant body lower limit temperature (MIN) (NO in step S17), the process proceeds to step S19, and the refrigerant body temperature supplied to the condenser 24 is increased. The flow rate is reduced. In Step S16, when it is determined that the refrigerant body temperature after heat exchange exceeds the target refrigerant body upper limit temperature (MAX) (NO in Step S16), the process proceeds to Step S20, and the condenser 24 is supplied. The flow rate of the supplied refrigerant is increased.

  In this case, in the second embodiment, the temperature of the refrigerant body after the heat exchange discharged from the condenser 24 is within the target temperature range of the refrigerant body (the lower limit temperature (MIN) or higher and the upper limit temperature (MAX) or lower). ), The flow rate of the refrigerant supplied to the condenser 24 is maintained. Therefore, since the temperature of the refrigerant body is optimum, the flow rate of the refrigerant body supplied to the condenser 24 is maintained, and the amount of water condensed from the water vapor in the exhaust gas can always be ensured optimally. .

  In addition, the total amount of water necessary for the operation of the fuel cell system 10 is covered, and after the heat contained in the exhaust gas discharged from the fuel cell module 16 is recovered well, the exhaust gas is transferred to the outside of the fuel cell system 10. Discharged. Thereby, the thermal efficiency of the fuel cell system 10 can be easily improved.

  Further, when it is determined that the temperature of the refrigerant body after the heat exchange is less than the target refrigerant body lower limit temperature (MIN), for example, less than 60 ° C., the flow rate of the refrigerant body supplied to the condenser 24 is decreased. Therefore, when the temperature of the refrigerant body is low, the flow rate of the refrigerant body supplied to the condenser 24 is reduced and the temperature of the exhaust gas is set high. As a result, the amount of water condensed from the water vapor in the exhaust gas is always maintained at an optimal amount of water, and the surplus water is reliably suppressed.

  In addition, the total amount of water necessary for the operation of the fuel cell system 10 is covered, and after the heat contained in the exhaust gas discharged from the fuel cell module 16 is recovered well, the exhaust gas is transferred to the outside of the fuel cell system 10. Discharged. For this reason, the thermal efficiency of the fuel cell system 10 can be easily improved.

  Furthermore, when it is determined that the temperature of the refrigerant body after heat exchange discharged from the condenser 24 exceeds a target refrigerant body upper limit temperature (MAX), for example, 80 ° C., the refrigerant body 24 is supplied to the condenser 24. The flow rate of the refrigerant body is increased. Therefore, when the temperature of the refrigerant body is high, the flow rate of the refrigerant body supplied to the condenser 24 is increased, and the temperature of the exhaust gas is set low. As a result, the amount of water condensed from the water vapor in the exhaust gas is always maintained at an optimal amount of water, and water shortage is reliably suppressed.

  In addition, the total amount of water necessary for the operation of the fuel cell system 10 is covered, and after the heat contained in the exhaust gas discharged from the fuel cell module 16 is recovered well, the exhaust gas is transferred to the outside of the fuel cell system 10. Discharged. For this reason, the thermal efficiency of the fuel cell system 10 can be easily improved.

  FIG. 6 is a flowchart for executing the control program according to the third embodiment of the present invention.

  The detailed description of the same steps as those in the control programs according to the first and second embodiments is omitted.

  In the third embodiment, first, steps S31 to S35 (first step to fifth step) are executed in the same manner as steps S1 to S5 of the first embodiment. Next, when it is determined in step S36 that the detected exhaust gas temperature is equal to or lower than the target exhaust gas temperature T (YES in step S36), the process proceeds to step S37, and after the heat exchange exhausted from the condenser 24 is completed. The temperature of the refrigerant body is detected by the thermocouple 80b, and the refrigerant body temperature after the heat exchange is compared with the target refrigerant body upper limit temperature (MAX). And step S37-step S41 are performed similarly to step S16-step S20 of 2nd Embodiment.

  On the other hand, when it is determined in step S36 that the temperature of the exhaust gas after heat exchange discharged from the condenser 24 exceeds the target exhaust gas temperature T (NO in step S36), the process proceeds to step S41. The flow rate of the refrigerant supplied to the condenser 24 is increased.

  Thereby, in the third embodiment, the water container 22 can always ensure an optimal amount of water, improve the water collection efficiency of the fuel cell system 10, and perform the water self-sustained operation of the fuel cell system 10. The effect of being carried out is obtained. In addition, there is an advantage that heat recovery is performed well and the thermal efficiency of the fuel cell system 10 can be easily improved.

DESCRIPTION OF SYMBOLS 10 ... Fuel cell system 12 ... Power generation unit 14 ... Hot water storage unit 16 ... Fuel cell module 18 ... Control device 20 ... Water supply device 22 ... Water container 24 ... Condenser 26 ... Hot water storage tank 32 ... Fuel gas supply device 34 ... Oxidant gas Supply device 36 ... Power conversion device 46 ... Fuel cell 48 ... Fuel cell stack 50 ... Heat exchanger 52 ... Evaporator 54 ... Reformer 68 ... Exhaust pipe 70 ... Circulating pipe 74a-74c ... Flow meter 76 ... Temperature and humidity meter 78 ... Water level gauges 80a, 80b ... thermocouple

Claims (13)

A fuel cell module that generates electricity by an electrochemical reaction between a fuel gas and an oxidant gas by a computer;
A water supply device for supplying water to the fuel cell module;
A water container for supplying water to the water supply device;
A condenser for condensing water vapor in the exhaust gas by heat exchange between the exhaust gas discharged from the fuel cell module and an externally supplied refrigerant, and supplying condensed water to the water container;
A fuel cell system control program for controlling a fuel cell system comprising:
A first step of detecting the amount of water stored in the water container;
The amount of water supplied to the fuel cell module, and at least one of the flow rate, temperature, and humidity of the oxidant gas supplied to the fuel cell module or the flow rate of the fuel gas supplied to the fuel cell module. A second step of detecting;
A third step of calculating the total amount of water supplied to the fuel cell module based on the detection result of the second step;
Based on the detection result of the first step, the amount of water condensed from the water vapor in the exhaust gas discharged from the fuel cell module is calculated with the total water amount calculated in the third step as an upper limit. 4 steps,
Based on the calculation result of the fourth step, calculate at least either the temperature of the exhaust gas after heat exchange discharged from the condenser or the temperature of the refrigerant body after heat exchange discharged from the condenser And a fifth step
A sixth step of adjusting the flow rate of the refrigerant supplied to the condenser based on the calculation result of the fifth step;
A control program for a fuel cell system, characterized in that   2. The fuel cell system according to claim 1, wherein the fourth step is executed by comparing the water storage amount in the water container with a preset range of the water storage amount. 3. Control program.   3. The control program according to claim 2, wherein in the fourth step, in the exhaust gas discharged from the fuel cell module when it is determined that the water storage amount in the water container is less than the range of the water storage amount. The amount of water condensed from the water vapor is set to an amount that exceeds the amount of water supplied to the fuel cell module in the second step.   4. The control program according to claim 2, wherein in the fourth step, the water storage amount in the water container is discharged from the fuel cell module when it is determined that the water storage amount exceeds the range of the water storage amount. 5. A control program for a fuel cell system, wherein the amount of water condensed from water vapor in the exhaust gas is set to an amount less than the amount of water supplied to the fuel cell module in the second step.   5. The control program according to claim 2, wherein when the water storage amount in the water container is determined to be within the range of the water storage amount, the fourth step is the fuel. The amount of water condensed from water vapor in the exhaust gas discharged from the battery module is set to be the same as the amount of water supplied to the fuel cell module in the second step. System control program.   The control program according to any one of claims 1 to 5, wherein the sixth step is calculated by at least a temperature of the exhaust gas after heat exchange discharged from the condenser and the fifth step. And comparing the temperature of the exhaust gas or the temperature of the refrigerant body after heat exchange discharged from the condenser with the temperature of the refrigerant body calculated in the fifth step. A control program for a fuel cell system.   The control program according to any one of claims 1 to 6, wherein in the sixth step, the temperature of the exhaust gas after heat exchange discharged from the condenser is calculated in the fifth step. A control program for a fuel cell system, wherein the flow rate of the refrigerant supplied to the condenser is increased when it is determined that the temperature range of the exhaust gas is exceeded.   The control program according to any one of claims 1 to 7, wherein in the sixth step, the temperature of the exhaust gas after heat exchange discharged from the condenser is calculated in the fifth step. A control program for a fuel cell system, wherein when it is determined that the temperature of the exhaust gas is not more than a set range, the flow rate of the refrigerant supplied to the condenser is reduced or maintained.   The control program according to any one of claims 1 to 8, wherein in the sixth step, the temperature of the refrigerant body after heat exchange discharged from the condenser is calculated in the fifth step. A control program for a fuel cell system, wherein the flow rate of the refrigerant supplied to the condenser is increased when it is determined that the set temperature range of the refrigerant is exceeded.   The control program according to any one of claims 1 to 9, wherein in the sixth step, the temperature of the refrigerant body after heat exchange discharged from the condenser is calculated in the fifth step. A control program for a fuel cell system, wherein the flow rate of the refrigerant supplied to the condenser is reduced when it is determined that the temperature of the refrigerant is lower than a set range.   The control program according to any one of claims 1 to 10, wherein in the sixth step, the temperature of the refrigerant body after heat exchange discharged from the condenser is calculated in the fifth step. A control program for a fuel cell system, wherein the flow rate of the refrigerant body supplied to the condenser is maintained when it is determined that the temperature is within a set range of the temperature of the refrigerant body. The control program according to any one of claims 1 to 11, wherein the fuel cell module includes an electrolyte / electrode assembly configured by sandwiching at least an electrolyte between an anode electrode and a cathode electrode, and a separator. A fuel cell stack provided with a fuel cell, and a plurality of the fuel cells stacked;
A heat exchanger that heats the oxidant gas before supplying it to the fuel cell stack;
An evaporator for evaporating the water in order to produce a mixed fuel of raw fuel mainly composed of hydrocarbon and water vapor;
A reformer for reforming the mixed fuel to produce the fuel gas;
A control program for a fuel cell system, comprising:   The control program according to any one of claims 1 to 12, wherein the fuel cell module is a solid oxide fuel cell module.

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