JP2016207500A - Fuel battery system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel battery system that can reduce the probability of deposition of carbon in a reformer and suppress occurrence of evaporation vibration of water caused by water level variation of an evaporator.SOLUTION: A fuel battery system 100 includes: a reformer 5 that generates hydrogen-containing gas by reforming reaction using fuel and water vapor; an evaporator 4 for evaporating water to generate water vapor to be supplied to the reformer 5; a water level detector 50 for detecting the water level of the evaporator 4; a cathode and an anode; a fuel battery 6 for generating electric power using oxidant gas supplied to the cathode and hydrogen-containing gas supplied from the reformer 5 to the anode; a combustor 7 for generating combustion exhaust gas by burning anode off-gas exhausted from the anode; a heating unit 8 for heating the evaporator 4 by heat of combustion exhaust gas; a heating amount adjuster 9 for adjusting the amount of heating to the evaporator 4; and a controller 11 for controlling the heating amount adjuster 9 until the water level of the evaporator 4 reaches a preset position due to variation of the heating amount to the evaporator 4.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a fuel cell system.

  In general, a hydrogen-containing gas that is a fuel of a fuel cell system is generated by subjecting a hydrocarbon fuel to, for example, steam reforming or oxidative steam reforming. Such a fuel cell system includes a combustor and an evaporator, and steam for reforming reaction is generated by heating the evaporator with the heat of combustion exhaust gas of the combustor. For this reason, when the power generation output of the fuel cell system changes, the flow rate of hydrocarbon fuel and the flow rate of water sent to the evaporator increase and decrease together with the current taken out from the fuel cell.

  Here, when the power generation output of the fuel cell system increases, the flow rate of water supplied to the evaporator increases. Then, the problem that the evaporation vibration of water occurs when the water surface of an evaporator rises is already known (for example, refer patent document 1). In addition, when the water oscillation occurs, there is a possibility that the flow control of the gas system of the fuel cell system may be hindered, and the amount of water necessary for the reforming reaction of the reformer may not be covered.

  With respect to such a problem, in Patent Document 1, the position of the water surface of the evaporator is kept constant by changing the ratio of the amount of raw fuel supplied to the reformer and the amount of water vapor supplied to the reformer. It has been proposed to

International Publication No. 2011-122419

  However, in the conventional example, the problem in the case where the ratio of the amount of raw fuel supplied to the reformer and the amount of water vapor supplied to the reformer changes is not sufficiently studied.

  One aspect of the present disclosure has been made in view of such circumstances, and can reduce the possibility of carbon deposition in a reformer as compared with the prior art. A fuel cell system capable of suppressing the occurrence of evaporation vibration is provided.

  In order to solve the above problems, a fuel cell system according to one embodiment of the present disclosure generates a reformer that generates hydrogen-containing gas by a reforming reaction using fuel and steam, and steam that is supplied to the reformer. An evaporator for evaporating water, a water level detector for detecting the water level of the evaporator, a cathode and an anode, and an oxidant gas supplied to the cathode and supplied from the reformer to the anode A fuel cell that generates electric power using the hydrogen-containing gas, a combustor that generates combustion exhaust gas by burning the anode off-gas discharged from the anode, and a heating unit that heats the evaporator by heat of the combustion exhaust gas A heating amount adjuster that adjusts the heating amount to the evaporator, and the heating amount adjuster until the water level of the evaporator reaches a preset position by changing the heating amount to the evaporator And a control unit for controlling.

  According to the fuel cell system of one aspect of the present disclosure, it is possible to reduce the possibility that carbon is deposited in the reformer as compared with the conventional case, and it is possible to suppress the occurrence of water evaporation vibration due to the water level change of the evaporator.

FIG. 1 is a block diagram showing an example of a schematic configuration of the fuel cell system according to the first embodiment. FIG. 2 is a diagram illustrating an example of a peripheral portion of the evaporator of the fuel cell system according to the example of the first embodiment. FIG. 3A is a diagram illustrating an example of the water surface height of the evaporator of the fuel cell system according to the example of the first embodiment. FIG. 3B is a diagram illustrating an example of the water surface height of the evaporator of the fuel cell system according to the example of the first embodiment. FIG. 3C is a diagram illustrating an example of the water surface height of the evaporator of the fuel cell system according to the example of the first embodiment. FIG. 4 is a diagram illustrating an example of the relationship between the water level of the evaporator and the heater energization amount of the fuel cell system according to the example of the first embodiment. FIG. 5 is a block diagram showing an example of a schematic configuration of the fuel cell system according to the second embodiment. FIG. 6 is a diagram illustrating an example of the relationship between the water surface height of the evaporator and the fuel utilization rate of the fuel cell system according to the second embodiment. FIG. 7 is a block diagram showing an example of a schematic configuration of a fuel cell system according to the third embodiment. FIG. 8 is a diagram showing an example of the relationship between the water surface height of the evaporator and the air utilization rate of the fuel cell system according to the third embodiment.

  The inventors diligently studied the problem in the case where the ratio of the amount of raw fuel supplied to the reformer and the amount of steam supplied to the reformer changes, and obtained the following knowledge.

  In Patent Document 1, when the water surface position in the evaporator rises above a preset range, the water surface position of the evaporator is lowered by decreasing the set value of the reformer S / C. It is described that the supply amount is set (paragraph 0042 of Patent Document 1). Thereby, it is supposed that the water surface position of the evaporator can be controlled within a preset range.

  However, reducing the set value of the S / C of the reformer increases the possibility that carbon will precipitate in the reformer.

  Therefore, the fuel cell system according to the first aspect of the present disclosure includes a reformer that generates hydrogen-containing gas by a reforming reaction using fuel and steam, and water for generating steam to be supplied to the reformer. An evaporator that evaporates, a water level detector that detects the water level of the evaporator, a cathode and an anode, and an oxidant gas supplied to the cathode and a hydrogen-containing gas supplied to the anode from the reformer A fuel cell for generating electricity, a combustor that generates combustion exhaust gas by combustion of anode off-gas discharged from the anode, a heating unit that heats the evaporator with the heat of the combustion exhaust gas, and a heating amount to the evaporator are adjusted A heating amount adjuster, and a controller that controls the heating amount adjuster until the water level of the evaporator reaches a preset position by changing the amount of heating to the evaporator.

  According to such a configuration, it is possible to reduce the possibility of carbon deposition in the reformer as compared with the conventional case, and it is possible to suppress the occurrence of water evaporation vibration due to the change in the water level of the evaporator. For example, when the power generation output of the fuel cell system is increased, the heating amount to the evaporator can be increased by the heating amount regulator. As a result, by slowing the rising speed of the water surface of the evaporator, the wall surface near the upper surface of the evaporator can be cooled to a suitable temperature in a timely manner by heat conduction between the water in the water pool of the evaporator and the wall surface. . For this reason, even if the water level of the evaporator rises, the temperature difference between the temperature of the wall surface of the evaporator and the temperature of water in contact with the main wall surface can be reduced, so that the possibility of bumping in the evaporator can be reduced. Therefore, generation | occurrence | production of the water evaporation vibration by the water surface change of an evaporator can be suppressed.

  The fuel cell system according to the second aspect of the present disclosure is the fuel cell system according to the first aspect. The fuel cell system according to the first aspect includes a heater that heats the evaporator as a heating amount adjuster, and the controller controls an energization amount to the heater. By changing, the heater is controlled until the water level of the evaporator reaches a preset position.

  According to such a configuration, for example, when the power generation output of the fuel cell system is increased, the amount of heat to the evaporator is increased by the heater, so that the water level of the evaporator can be gradually raised, and bumping occurs in the evaporator. The possibility of doing so can be reduced. Therefore, generation | occurrence | production of the water evaporation vibration by the water surface change of an evaporator can be suppressed. Further, since the heating amount to the evaporator is controlled by the heater, it is not necessary to reduce the set value of the reformer S / C. Therefore, the possibility that carbon is deposited in the reformer can be reduced as compared with the conventional case.

  Further, the fuel cell system according to the third aspect of the present disclosure is the fuel cell system according to the first aspect or the second aspect, wherein the fuel supply system supplies the fuel to the reformer as a heating amount adjuster. A water supply unit that supplies the water to the evaporator, and the controller changes the fuel utilization rate of the fuel cell while maintaining a constant ratio between the flow rate of the fuel and the flow rate of the water. The fuel supply device and the water supply device are controlled until the water level reaches a preset position.

  According to such a configuration, for example, when the power generation output of the fuel cell system is increased, the water surface of the evaporator can be gradually increased by changing the fuel utilization rate, so that the possibility of bumping in the evaporator can be reduced. . Therefore, generation | occurrence | production of the water evaporation vibration by the water surface change of an evaporator can be suppressed. Further, since the fuel utilization rate of the fuel cell is changed in a state where the ratio between the flow rate of the fuel and the flow rate of water is kept constant, the possibility of carbon deposition in the reformer can be reduced as compared with the conventional case.

  A fuel cell system according to a fourth aspect of the present disclosure is the fuel cell system according to any one of the first aspect, the second aspect, and the third aspect. An oxidant gas supply device that supplies oxidant gas is provided, and the controller controls the oxidant gas supply device until the water level of the evaporator reaches a preset position by changing the oxidant gas utilization rate of the fuel cell. To do.

  According to such a configuration, for example, when the power generation output of the fuel cell system is increased, the water level of the evaporator can be gradually increased by changing the oxidant gas utilization rate. Can be reduced. Therefore, generation | occurrence | production of the water evaporation vibration by the water surface change of an evaporator can be suppressed. Moreover, since the oxidant gas utilization factor of the fuel cell that does not affect the S / C of the reformer is changed, the possibility that carbon is deposited in the reformer can be reduced as compared with the conventional case.

  The fuel cell system according to the fifth aspect of the present disclosure is the fuel cell system according to any one of the first aspect, the second aspect, the third aspect, and the fourth aspect, wherein the controller is a fuel cell system. The heating amount adjuster is controlled until the water level of the evaporator reaches a preset position based on the power generation output fluctuation command.

  According to this configuration, the heating amount to the evaporator can be appropriately controlled by the heating amount adjuster based on the power generation output fluctuation command of the fuel cell system.

  Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. Each of the following embodiments shows a specific example of the present disclosure. Numerical values, shapes, materials, constituent elements, arrangement positions of constituent elements, order of connection forms, and the like shown in the embodiments are merely examples, and do not limit the above-described aspect of the present disclosure. In addition, among the constituent elements in the embodiment, constituent elements that are not described in the independent claims indicating the highest concept of the present disclosure are described as arbitrary constituent elements. In the drawings, the same reference numerals are sometimes omitted. In addition, the drawings schematically show each component for easy understanding, and there are cases where the shape and dimensional ratio are not accurately displayed.

(First embodiment)
[Device configuration]
FIG. 1 is a block diagram showing an example of a schematic configuration of the fuel cell system according to the first embodiment.

  The fuel cell system 100 of the first embodiment includes an evaporator 4, a water level detector 50, a reformer 5, a fuel cell 6, a combustor 7, a heating unit 8, a heating amount adjuster 9, And a controller 11.

  The reformer 5 generates a hydrogen-containing gas by a reforming reaction using fuel and steam. The reforming reaction may be in any form. Examples of the reforming reaction include a steam reforming reaction and an oxidative steam reforming reaction. Although not shown in FIG. 1, equipment required for each reforming reaction is provided as appropriate. For example, if the reforming reaction is an oxidative steam reforming reaction, an air supply unit for supplying air to the reformer 5 is provided.

  A reforming catalyst is provided inside the reformer 5. The reforming reaction proceeds by the reforming catalyst, and a hydrogen-containing gas can be generated from the fuel and water vapor. Generally, at least one selected from the group consisting of noble metal catalysts such as Pt, Ru, Rh, and Ni is preferably used as the reforming catalyst. In this embodiment, a reforming catalyst containing Ru is used.

  Further, as the fuel, city gas and natural gas mainly composed of methane, and gas containing an organic compound composed of at least carbon and hydrogen such as LPG can be used. Further, kerosene and alcohols such as methanol and ethanol can be used as fuel. City gas refers to gas supplied from a gas company to each household through piping.

  In the evaporator 4, water for generating water vapor supplied to the reformer 5 evaporates. Specifically, in the evaporator 4, the water supplied from the supply path by the water supplier evaporates, and the steam is supplied to the reformer 5. A specific configuration of the evaporator 4 will be described in an embodiment.

  The water level detector 50 detects the water level of the evaporator 4. The water level detector 50 may have any configuration as long as the water level of the evaporator 4 can be detected or estimated. A specific configuration of the water level detector 50 will also be described in the embodiment.

  The fuel cell 6 includes a cathode and an anode, and generates power using an oxidant gas supplied to the cathode and a hydrogen-containing gas supplied from the reformer 5 to the anode. The fuel cell 6 may be any type of fuel cell. Examples of the fuel cell 6 include a polymer electrolyte fuel cell (PEFC), a solid oxide fuel cell, and a phosphoric acid fuel cell. If the fuel cell 6 is a solid oxide fuel cell, the reformer 5 and the fuel cell 6 may be built in one container. Examples of the oxidant gas include air and oxygen gas.

  The fuel cell 6 may include a cell stack in which a plurality of cells are stacked. For the cell, for example, a known configuration using yttria-stabilized zirconia (YSZ) as an electrolyte may be employed. As the material of the cell, zirconia doped with yttrium or scandium, or a lanthanum gallate solid electrolyte can also be used. In a cell using yttria-stabilized zirconia, a power generation reaction is performed in a temperature range of about 600 ° C. to 1000 ° C., for example, depending on the thickness of the electrolyte.

  The cell stack may be, for example, a flat plate stack in which members such as flat cells and interconnectors are stacked, or a cylindrical stack in which members such as cylindrical cells and interconnectors are bundled (fixed in a bundle). It's okay.

  The electric power obtained by the power generation of the fuel cell 6 is supplied to an external load via two terminals provided in the cell stack. A DC / DC converter or a DC / AC inverter may be provided between this terminal and an external load.

  In the present embodiment, a solid oxide fuel cell is used as the fuel cell 6. In this case, in the fuel cell 6, electric power is generated by the following electrochemical reaction between hydrogen in the hydrogen-containing gas supplied to the anode and oxygen in the oxidant gas (air) supplied to the cathode.

H ₂ + 1 / 2O ₂ → H ₂ O
CO + 1 / 2O ₂ → CO ₂
In the solid oxide fuel cell, oxygen ions move from the cathode to the anode through the electrolyte, and the above reaction is performed at the anode. H ₂ O, CO ₂ generated by these reactions, and the hydrogen-containing gas that has not been consumed by the above reactions are discharged from the anode of the fuel cell 6 as anode off-gas. The anode off gas is supplied to the combustor 7.

  The combustor 7 generates combustion exhaust gas by burning the anode off-gas discharged from the anode of the fuel cell 6. In the present embodiment, the cathode off-gas discharged from the cathode of the fuel cell 6 is used as the oxidant gas used for the combustion. The flue gas discharged from the combustor 7 is supplied to the heating unit 8 through the flue gas passage.

  The heating unit 8 heats the evaporator 4 with the heat of the combustion exhaust gas. The heating unit 8 may have any configuration as long as the evaporator 4 can be heated by the heat of the combustion exhaust gas. A specific configuration of the heating unit 8 will also be described in the embodiment.

  Note that the reformer 5 may be heated with combustion exhaust gas discharged from the combustor 7. The combustion exhaust gas may pass through the heating unit 8 of the evaporator 4 after heating the reformer 5, or may heat the reformer 5 after passing through the heating unit 8.

  The heating amount adjuster 9 adjusts the heating amount to the evaporator 4. The heating amount adjuster 9 may have any configuration as long as the amount of heating to the evaporator 4 can be adjusted. Specific examples of the heating amount adjuster 9 will be described in Examples, Second Embodiment, and Third Embodiment.

  The controller 11 controls the heating amount adjuster 9 until the water level of the evaporator 4 reaches a preset position by changing the heating amount to the evaporator 4. In the present specification, the preset position in the water level of the evaporator 4 is the amount of water supplied to the evaporator 4 and the amount of water evaporated in the evaporator 4 in the stable power generation state of the fuel cell system 100. The water surface height of the evaporator 4 that is substantially the same may be used, or a desired range based on such a water surface height may be used.

  The controller 11 may have any configuration as long as it has a control function. For example, the controller 11 may include an arithmetic processing unit (not shown) and a storage unit (not shown) that stores a control program. Examples of the arithmetic processing unit include one or a plurality of arithmetic circuits (not shown). Examples of the arithmetic circuit include an MPU (microprocessor) and a CPU. Examples of the storage unit include one or a plurality of storage circuits (not shown). Examples of the memory circuit include a semiconductor memory. The controller 11 may be composed of a single controller that performs centralized control, or may be composed of a plurality of controllers that perform distributed control in cooperation with each other.

  As described above, it is possible to reduce the possibility that carbon is deposited in the reformer 5 as compared with the conventional case, and it is possible to suppress the occurrence of water evaporation vibration due to the water surface change of the evaporator 4.

  Specifically, for example, when the power generation output of the fuel cell system 100 is increased by a command from the controller 11, the flow rate of water supplied to the evaporator 4 increases. At this time, the water surface of the evaporator 4 may rise rapidly. In this case, the temperature of the upper part of the wall surface of the evaporator 4 heated by the heating unit 8 that is not in contact with the water pool may be a high temperature close to the temperature of the combustion exhaust gas. When a sudden contact occurs, the temperature difference between the wall surface temperature and the water temperature contacting the main wall surface is large. Then, film boiling of water in the evaporator 4 and, consequently, bumping occur, and water evaporation vibration occurs.

  Therefore, in the present embodiment, for example, when the power generation output of the fuel cell system 100 is increased, the heating amount to the evaporator 4 can be increased by the heating amount adjuster 9. As a result, the rising speed of the water surface of the evaporator 4 is moderated so that the wall surface near the upper surface of the evaporator 4 can be appropriately heated in a timely manner by heat conduction between the water in the water pool of the evaporator 4 and the wall surface. Can be cooled. For this reason, even if the water level of the evaporator 4 rises, the temperature difference between the temperature of the wall surface of the evaporator 4 and the temperature of the water in contact with the main wall surface can be reduced. Can be reduced. Therefore, generation | occurrence | production of the water evaporation vibration by the water surface change of the evaporator 4 can be suppressed.

(Example)
[Device configuration]
FIG. 2 is a diagram illustrating an example of a peripheral portion of the evaporator of the fuel cell system according to the example of the first embodiment. In FIG. 2, it is assumed that gravity acts from “upper” to “lower”.

  The fuel cell system 100 of this embodiment includes a heater 9 </ b> A that heats the evaporator 4 as the heating amount adjuster 9. That is, the evaporator 4 includes a container for storing water for generating water vapor to be supplied to the reformer 5, and a heater 9 </ b> A that is an example of the heating amount adjuster 9 is provided in the evaporator 4. For example, as shown in FIG. 2, the heater 9 </ b> A is provided in a water reservoir near the lower end of the evaporator 4.

  The heating unit 8 includes a flow path member 8A that is provided on the side wall of the container and through which combustion exhaust gas passes from the upper end to the lower end of the container. That is, as the heating unit 8, a heat exchanger in which high-temperature combustion exhaust gas is a heating fluid and water is a heat receiving fluid is illustrated. In addition, the heating part 8 is not limited to this example, For example, the structure which is provided with the tube which passes the water sump of the container of the evaporator 4 and a combustion exhaust gas flows into this tube may be sufficient.

  Further, the fuel cell system 100 of the present embodiment includes a plurality of temperature detectors 50A, 50B, 50C, and 50D provided in the evaporator 4 as the water level detector 50. The temperature detectors 50A, 50B, 50C, and 50D may have any configuration as long as the temperature inside the container of the evaporator 4 can be detected directly or indirectly. That is, temperature detectors 50A, 50B, 50C, and 50D may be provided at appropriate locations (for example, the container wall surface of the evaporator 4) that correlate with such temperatures, and this temperature may be detected indirectly, The temperature detectors 50A, 50B, 50C, and 50D may be inserted to directly detect this temperature. In the present embodiment, the temperature detectors 50A, 50B, 50C, and 50D are provided on the container wall surface. As shown in FIG. 2, a plurality (four in this embodiment) of temperature detectors 50 </ b> A, 50 </ b> B, 50 </ b> C, 50 </ b> D are vertically arranged between the upper end portion and the lower end portion of the container of the evaporator 4. Are distributed almost evenly.

  In addition, as a temperature detector 50A, 50B, 50C, 50D, a thermocouple etc. can be illustrated, for example.

  Thereby, the controller 11 can determine the water level of the evaporator 4 based on the detected temperatures of the temperature detectors 50A, 50B, 50C, and 50D. For example, when the temperature detected by the temperature detector 50A is 100 ° C. or higher, the controller 11 can determine that the water surface height of the evaporator 4 is lower than the temperature detector 50A. When the temperature detected by the temperature detector 50A is less than 100 ° C., it can be determined that the water surface height of the evaporator 4 is higher than the temperature detector 50A. The same applies to the other temperature detectors 50B, 50C, 50D. Therefore, the controller 11 has, for example, the temperature detected by the lower temperature detector 50A of the pair of temperature detectors 50A and 50B adjacent in the vertical direction is less than 100 ° C. and the upper temperature detector 50B. When the detected temperature is 100 ° C. or higher, as shown in FIG. 2, it can be determined that the water surface height of the evaporator 4 exists between the pair of temperature detectors 50A and 50B.

[Operation]
Hereinafter, the operation of the fuel cell system 100 of the present embodiment will be described with reference to the drawings.

In this example, Japanese city gas “13A” as fuel (composition ratio of city gas “13A” is, for example, CH ₄ : 88.9%, C ₂ H ₆ : 6.8%, C ₃ H ₈ : 3.1%, C ₄ H ₁₀ : 1.2%) and air as the oxidant gas will be described. Further, a case will be described in which the power generation output of the fuel cell system 100 increases from a low output (for example, 500 W) to a high output (for example, 1000 W) due to demand on the power load side (not shown).

  3A, 3B, and 3C are diagrams showing an example of the water surface height of the evaporator of the fuel cell system according to the example of the first embodiment.

  FIG. 4 is a diagram illustrating an example of the relationship between the water level of the evaporator and the heater energization amount of the fuel cell system according to the example of the first embodiment.

  The following operation is performed based on the detected temperature of the temperature detector 50A by executing a control program in the controller 11.

  As shown in FIG. 3A, when the power generation output of the fuel cell system 100 is a stable power generation state of 500 W, the water surface height of the evaporator 4 is stable between a pair of temperature detectors 50A and 50B adjacent in the vertical direction. ing. Here, when the controller 11 obtains a power generation output fluctuation command for raising the power generation output of the fuel cell system 100 to 1000 W, the flow rate of the city gas and water supplied to the reformer 5, the fuel cell 6 The flow rate of the supplied air and the current value extracted from the fuel cell 6 are changed to the set values when the power generation output is 1000 W. Each of these numerical values is set in advance corresponding to the power generation output of the fuel cell system 100.

  With such a change in the set value, the flow rate of water supplied to the evaporator 4 increases. Then, as shown to FIG. 3B, the water surface height of the evaporator 4 rises. Then, in the power generation stable state where the power generation output of the fuel cell system 100 is 1000 W, the water surface height of the evaporator 4 is stabilized between the pair of temperature detectors 50C and 50D adjacent in the vertical direction, which is shown in FIG. 3C. Thus, the water surface height of the evaporator 4 reaches the above-mentioned stable position.

  Here, as described above, high-temperature combustion exhaust gas circulates in the heating unit 8. Hereinafter, the temperature distribution of the container wall surface of the evaporator 4 heated by the combustion exhaust gas will be described in detail.

  First, the container wall surface at a position equal to or lower than the water surface of the evaporator 4 is strongly influenced by the temperature of the water in the water reservoir of the evaporator 4 and therefore has a temperature of 100 ° C. or lower.

  In addition, the container wall near the upper surface of the evaporator 4 is affected by the temperature of the water in the reservoir due to the heat conduction between the water in the reservoir of the evaporator 4 and the wall of the container. (For example, about 400 ° C.), the temperature is about 100 ° C. to 200 ° C.

  On the other hand, on the container wall surface above the water surface of the evaporator 4 (for example, the position of the temperature detector 50D when the water surface height of the evaporator 4 in FIG. Temperature.

  Due to the temperature distribution of the container wall surface, the temperature difference between the wall surface temperature near the upper surface of the evaporator 4 and the water temperature is not so large. For this reason, for example, when the water surface of the evaporator 4 gradually rises, the container wall near the upper surface of the evaporator 4 is heated in a timely manner by heat conduction between the water in the reservoir of the evaporator 4 and the container wall. Can be cooled. Therefore, in this case, even if the water surface of the evaporator 4 rises, film boiling of water hardly occurs and the possibility of bumping is low.

  However, when the water surface of the evaporator 4 rises rapidly, for example, the cooling of the vessel wall surface cannot follow the rise of the water surface of the evaporator 4, and the temperature of the upper vessel wall surface separated from the water surface of the evaporator 4 However, the water in the evaporator 4 may come into contact with the vessel wall surface heated to about 400 ° C., which is substantially equal to the combustion exhaust gas temperature, for example. Therefore, in this case, since the temperature difference between the wall surface temperature of the container and the water temperature is large, water film boiling is likely to occur, and there is a high possibility that bumping will occur.

  Therefore, in this embodiment, the controller 11 controls the heater 9A until the water level of the evaporator 4 reaches a preset position by changing the energization amount to the heater 9A. For example, the controller 11 controls the heater 9 </ b> A so that the energization amount of the heater 9 </ b> A provided in the evaporator 4 increases at the same time as obtaining the fluctuation command for increasing the power generation output. That is, by controlling the energization amount of the heater 9A, the heating amount to the evaporator 4 is increased, and the water level of the evaporator 4 gradually rises while keeping the evaporation amount of water in the evaporator 4 at a set value. It is controlled so that the water surface of the evaporator 4 does not move upward from the arrangement position of the temperature detector 50D.

  Specifically, after a change command for increasing the power generation output of the fuel cell system 100 is issued, energization of the heater 9A is started as shown in FIG. And, as the water surface height of the evaporator 4 approaches the position corresponding to the temperature detector 50C, the water surface of the evaporator 4 tends to rise slowly, so that the water surface height corresponding to the temperature detector 50C is increased. As the distance approaches, the amount of current supplied to the heater 9A is decreased. For example, as shown in FIG. 4, the energization amount to the heater 9A is zero (OFF) at the water surface height corresponding to the temperature detector 50C.

  Note that the correlation between the water surface height of the evaporator 4 and the energization amount to the heater 9A when the power generation output of the fuel cell system 100 is increased is based on a condition in which bumping does not occur in the evaporator 4 that has been verified in advance by experiments. It is good to be determined. Further, the control of the energization amount to the heater 9A may be ON / OFF control, or may be control to increase or decrease the energization amount to the heater 9A. In addition, specific numerical values and the like in the above operation are examples and are not limited to this example. For example, in the present embodiment, the energization amount to the heater 9A is set to zero (OFF) at the water surface height corresponding to the temperature detector 50C, but a preset desired energization amount is given to the heater 9A. It doesn't matter.

  As described above, for example, when the power generation output of the fuel cell system 100 is increased, the water level of the evaporator 4 can be gradually increased by increasing the amount of heating to the evaporator 4 by the heater 9A. It is possible to reduce the possibility of occurrence. Therefore, generation | occurrence | production of the water evaporation vibration by the water surface change of the evaporator 4 can be suppressed. Moreover, since the heating amount to the evaporator 4 is controlled by the heater 9A, it is not necessary to reduce the set value of S / C of the reformer 5. Therefore, the possibility that carbon is deposited in the reformer 5 can be reduced as compared with the conventional case. In this embodiment, since the temperature of the evaporator 4 is directly controlled by the heater 9A, the controllability (responsiveness) of the water level of the evaporator 4 is also good.

(Second Embodiment)
[Device configuration]
FIG. 5 is a block diagram showing an example of a schematic configuration of the fuel cell system according to the second embodiment.

  The fuel cell system 100 according to the second embodiment includes a fuel supplier 1, a water supplier 2, an evaporator 4, a water level detector 50, a reformer 5, a fuel cell 6, a combustor 7, A heating unit 8 and a controller 11 are provided.

  The fuel cell system 100 according to the second embodiment is different from the first embodiment in that a fuel supply device 1 and a water supply device 2 are provided as the heating amount adjuster 9 in FIG. The fuel cell system 100 of the second embodiment may be configured in the same manner as the fuel cell system 100 of the first embodiment except for the above points. The description of the same configuration as that of the first embodiment is omitted.

  The fuel supplier 1 supplies fuel to the reformer 5. The fuel supplier 1 may have any configuration as long as fuel can be supplied to the reformer 5. The fuel supply device 1 is constituted by, for example, a booster and a flow rate adjustment valve, but may be constituted by any one of these. For example, a pump or a blower is used as the booster, but the booster is not limited to this. The fuel is supplied from a fuel supply source (not shown). The fuel supply source has a predetermined supply pressure. Examples of the fuel supply source include a fuel cylinder and a fuel infrastructure.

  The water supplier 2 supplies water to the evaporator 4. The water supply device 2 may have any configuration as long as it can supply water to the evaporator 4. Examples of the water supply device 2 include displacement pumps such as a gear pump and a plunger pump.

[Operation]
Hereinafter, the operation of the fuel cell system 100 according to the second embodiment will be described with reference to the drawings.

  In the second embodiment, similarly to the fuel cell system 100 of the example of the first embodiment, the city gas “13A” is used as the fuel, the air is used as the oxidant gas, and the power load (not shown) is applied to the fuel cell system 100. The case where the power generation output of the fuel cell system 100 increases from a low output (for example, 500 W) to a high output (for example, 1000 W) due to demand on the side will be described.

  The contents of FIGS. 3A to 3B and the temperature distribution on the vessel wall surface of the evaporator 4 heated by the combustion exhaust gas are the same as those of the fuel cell system 100 of the example of the first embodiment, and thus the description thereof is omitted. .

  FIG. 6 is a diagram illustrating an example of the relationship between the water surface height of the evaporator and the fuel utilization rate of the fuel cell system according to the second embodiment. The following operation is performed based on the detected temperature of the temperature detector 50A by executing a control program in the controller 11.

  Here, in the present embodiment, the controller 11 changes the fuel utilization rate Uf of the fuel cell 6 while keeping the ratio of the fuel flow rate to the water flow rate constant, thereby changing the water level of the evaporator 4. The fuel supply device 1 and the water supply device 2 are controlled until reaching a preset position.

  For example, when the power generation output of the fuel cell system 100 increases from a low output (for example, 500 W) to a high output (for example, 1000 W), the current taken out from the fuel cell 6 is maintained at a preset current increase. The fuel flow rate is increased from a preset flow rate increase. That is, the fuel utilization rate Uf is reduced from the set value at 1000 W. As a result, the amount of combustion heat of the combustor 7 increases, so that the temperature of the combustion exhaust gas for heating the evaporator 4 can be raised in a timely manner. That is, by reducing the fuel utilization rate Uf, the amount of heating to the evaporator 4 is increased, and the water level of the evaporator 4 is controlled to rise gradually while maintaining the amount of water evaporation in the evaporator 4 at a set value. Thus, the water surface of the evaporator 4 is controlled so as not to move above the position where the temperature detector 50D is disposed.

  Specifically, after a change command for increasing the power generation output of the fuel cell system 100 is issued, the fuel flow rate is increased from a flow rate set in advance at 1000 W, as shown in FIG. And, as the water surface height of the evaporator 4 approaches the position corresponding to the temperature detector 50C, the water surface of the evaporator 4 tends to rise slowly, so that the water surface height corresponding to the temperature detector 50C is increased. As it approaches, the fuel flow rate is brought close to the value set in advance at 1000 W. That is, the fuel flow rate is decreased. For example, as shown in FIG. 6, the fuel flow rate is a value set in advance at 1000 W at the water surface height corresponding to the temperature detector 50C.

  Regarding the correlation between the water surface height of the evaporator 4 and the fuel flow rate (fuel utilization rate Uf) when the power generation output of the fuel cell system 100 is increased, a condition in which bumping does not occur in the evaporator 4 verified in advance by experiments. It may be determined based on In addition, specific numerical values and the like in the above operation are examples and are not limited to this example.

  As described above, for example, when the power generation output of the fuel cell system 100 is increased, the water surface of the evaporator 4 can be gradually increased by changing the fuel utilization rate Uf. Therefore, there is a possibility that bumping may occur in the evaporator 4. Can be reduced. Therefore, generation | occurrence | production of the water evaporation vibration by the water surface change of the evaporator 4 can be suppressed. Further, since the fuel utilization rate Uf of the fuel cell 6 is changed in a state where the ratio of the flow rate of fuel and the flow rate of water is kept constant, the possibility of carbon deposition in the reformer 5 is reduced compared to the conventional case. obtain. And in this embodiment, since the fuel flow rate of the combustor 7 is directly controlled, the controllability (responsiveness) of the combustion exhaust gas temperature, and hence the water level controllability (responsiveness) of the evaporator 4 is also good. .

(Third embodiment)
[Device configuration]
FIG. 7 is a block diagram showing an example of a schematic configuration of a fuel cell system according to the third embodiment.

  The fuel cell system 100 according to the third embodiment includes an oxidant gas supply device 3, an evaporator 4, a water level detector 50, a reformer 5, a fuel cell 6, a combustor 7, and a heating unit 8. And a controller 11.

  The fuel cell system 100 of the third embodiment is different from the first embodiment in that an oxidant gas supply device 3 is provided as the heating amount adjuster 9 of FIG. The fuel cell system 100 of the third embodiment may be configured in the same manner as the fuel cell system 100 of the first embodiment except for the above points. The description of the same configuration as that of the first embodiment is omitted.

  The oxidant gas supply unit 3 supplies oxidant gas to the cathode of the fuel cell 6. The oxidant gas supply unit 3 may have any configuration as long as the oxidant gas can be supplied to the cathode of the fuel cell 6. For example, a pump, a blower, or the like is used as the oxidant gas supply device 3, but the oxidant gas supply device 3 is not limited thereto.

[Operation]
Hereinafter, the operation of the fuel cell system 100 according to the third embodiment will be described with reference to the drawings.

  In the third embodiment, similarly to the fuel cell system 100 of the example of the first embodiment, the city gas “13A” is used as the fuel, the air is used as the oxidant gas, and the power load (not shown) is applied to the fuel cell system 100. The case where the power generation output of the fuel cell system 100 increases from a low output (for example, 500 W) to a high output (for example, 1000 W) due to demand on the side will be described.

  The contents of FIGS. 3A to 3B and the temperature distribution on the vessel wall surface of the evaporator 4 heated by the combustion exhaust gas are the same as those of the fuel cell system 100 of the example of the first embodiment, and thus the description thereof is omitted. .

  FIG. 8 is a diagram showing an example of the relationship between the water surface height of the evaporator and the air utilization rate of the fuel cell system according to the third embodiment. The following operation is performed based on the detected temperature of the temperature detector 50A by executing a control program in the controller 11.

  Here, in the present embodiment, the controller 11 changes the oxidant gas utilization rate (here, air utilization rate Ua) of the fuel cell 6 until the water level of the evaporator 4 reaches a preset position. The oxidant gas supply unit 3 is controlled.

  For example, when the power generation output of the fuel cell system 100 increases from a low output (for example, 500 W) to a high output (for example, 1000 W), the current taken out from the fuel cell 6 is maintained at a preset current increase. The air flow rate is decreased from a preset flow rate increase. That is, the air utilization rate Ua is increased from the set value at 1000 W. Thereby, since the air which dilutes the combustion exhaust gas from the combustor 7 decreases, the combustion exhaust gas temperature which heats the evaporator 4 can be raised timely. That is, by increasing the air utilization rate Ua, the amount of heating to the evaporator 4 is increased, and the water level of the evaporator 4 is gradually increased while keeping the amount of water evaporated in the evaporator 4 at a set value. It is controlled so that the water surface of the evaporator 4 does not move upward from the arrangement position of the temperature detector 50D.

  Specifically, after a fluctuation command for increasing the power generation output of the fuel cell system 100 is issued, the air flow rate is reduced from a flow rate set in advance at 1000 W, as shown in FIG. And, as the water surface height of the evaporator 4 approaches the position corresponding to the temperature detector 50C, the water surface of the evaporator 4 tends to rise slowly, so that the water surface height corresponding to the temperature detector 50C is increased. As the distance approaches, the air flow rate approaches the value set in advance at 1000 W. That is, the air flow rate is increased. For example, as shown in FIG. 8, at the water surface height corresponding to the temperature detector 50C, the air flow rate is a value set in advance at 1000W.

  Regarding the correlation between the water surface height of the evaporator 4 and the air flow rate (air utilization rate Ua) when the power generation output of the fuel cell system 100 is increased, a condition in which bumping does not occur in the evaporator 4 verified in advance by experiments. It may be determined based on In addition, specific numerical values and the like in the above operation are examples and are not limited to this example.

  As described above, for example, when the power generation output of the fuel cell system 100 is increased, the water surface of the evaporator 4 can be gradually increased by changing the air utilization rate Ua, so that the possibility of bumping in the evaporator 4 is generated. Can be reduced. Therefore, generation | occurrence | production of the water evaporation vibration by the water surface change of the evaporator 4 can be suppressed. Further, since the air utilization rate Ua of the fuel cell 6 that does not affect the S / C of the reformer 5 is changed, the possibility that carbon is deposited in the reformer 5 can be reduced as compared with the conventional case. And in this embodiment, since the air flow rate with a small influence on the power generation efficiency of the fuel cell system 100 is controlled, this power generation efficiency fall can also be suppressed.

  From the above description, many modifications and other embodiments of the present disclosure are apparent to persons skilled in the art. Accordingly, the foregoing description is to be construed as illustrative only and is provided for the purpose of teaching those skilled in the art the best mode of carrying out the disclosure. Details of the structure and / or function may be substantially changed without departing from the spirit of the present disclosure.

  For example, as a method of controlling the heating amount to the evaporator 4, a method of controlling the energization amount to the heater 9A of the example of the first embodiment, a method of controlling the fuel utilization rate Uf of the second embodiment, and a third method Although the method for controlling the air utilization rate Ua of the embodiment has been described, the heating amount of the evaporator 4 may be controlled by appropriately combining these methods.

  Further, the oxidant gas such as air used for the combustion of the combustor 7 is not limited to the cathode off gas. For example, air (fresh air) taken from the outside of the fuel cell system 100 may be burned together with the anode off gas in the combustor 7. In this case, the combustion exhaust gas discharged from the combustor 7 and the cathode off gas may be mixed and circulated through the combustion gas flow path.

  In addition, the controller 11 controls the amount of heating to the evaporator 4 at the same time as acquiring the fluctuation command for increasing the power generation output of the fuel cell system 100, but is not limited thereto. For example, when the power generation output fluctuation of the fuel cell system 100 is not an operation that follows external load fluctuations but an operation that can be grasped in advance, the heating amount to the evaporator 4 before a predetermined time prior to the increase of the power generation output. May be controlled. Thereby, the controllability (responsiveness) of the water level of the evaporator 4 is further improved.

  One embodiment of the present disclosure can reduce the possibility of carbon deposition in a reformer as compared with the conventional case, and can suppress the occurrence of water evaporation vibration due to a change in the water level of the evaporator. Therefore, one embodiment of the present disclosure can be used in, for example, a fuel cell system.

DESCRIPTION OF SYMBOLS 1: Fuel supply device 2: Water supply device 3: Oxidant gas supply device 4: Evaporator 5: Reformer 6: Fuel cell 7: Combustor 8: Heating part 8A: Flow path member 9: Heating amount regulator 9A : Heater 11: Controller 50: Water level detector 50A: Temperature detector 50B: Temperature detector 50C: Temperature detector 50D: Temperature detector 100: Fuel cell system

Claims (5)

A reformer that generates hydrogen-containing gas by a reforming reaction using fuel and steam; and
An evaporator in which water for generating water vapor to be supplied to the reformer evaporates;
A water level detector for detecting the water level of the evaporator;
A fuel cell comprising a cathode and an anode, and generating electricity using an oxidant gas supplied to the cathode and a hydrogen-containing gas supplied from the reformer to the anode;
A combustor that generates combustion exhaust gas by burning off the anode off-gas discharged from the anode;
A heating section for heating the evaporator with heat of the combustion exhaust gas;
A heating amount adjuster for adjusting the heating amount to the evaporator;
A fuel cell system comprising: a controller that controls the heating amount adjuster until a water level of the evaporator reaches a preset position by changing a heating amount to the evaporator. The heating amount adjuster includes a heater for heating the evaporator,
2. The fuel cell system according to claim 1, wherein the controller controls the heater until a water level of the evaporator reaches a preset position by changing an energization amount to the heater. As the heating amount adjuster, a fuel supply device that supplies the fuel to the reformer, and a water supply device that supplies the water to the evaporator,
The controller changes the fuel utilization rate of the fuel cell in a state where the ratio of the flow rate of the fuel and the flow rate of the water is kept constant, so that the water level of the evaporator becomes a preset position. The fuel cell system according to claim 1, wherein the fuel supplier and the water supplier are controlled. As the heating amount adjuster, comprising an oxidant gas supply device for supplying the oxidant gas to the cathode of the fuel cell,
4. The controller according to claim 1, wherein the controller controls the oxidant gas supply unit until a water level of the evaporator reaches a preset position by changing an oxidant gas utilization rate of the fuel cell. 5. The fuel cell system described in 1.   The controller acquires a power generation output fluctuation command to the fuel cell system and controls the heating amount regulator until the water level of the evaporator reaches a preset position based on the power generation output fluctuation command. The fuel cell system according to any one of claims 1 to 4.

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