JP2013222577A - Solid oxide type fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid oxide type fuel cell system that can continuously perform a water self-sustained operation while restraining a lack of modified water.SOLUTION: A solid oxide type fuel cell system comprises: a reformer 4 for vapor-modifying raw fuel; a solid oxide type fuel cell 6 for generating power by oxidizing and reducing modified fuel gas and an oxidation material; a blowing device 8 for supplying the oxidation material to the solid oxide type fuel cell 6; a fuel pump 34 for controlling a supply amount of the raw fuel; control means for controlling operations of the fuel pump 34 and the blowing device 8; condensation/recovery means 50 for condensing and recovering water vapor contained in combustion exhaust gas; and water supply means 52 for supplying the condensed and recovered water to the reformer 4. When an amount of the condensed and recovered water is smaller than a modification required amount, water self-sustained determination means determines that a water self-sustained operation is not satisfied, and the control means increases a power generation output of the solid oxide type fuel cell 6.

Description

  The present invention relates to a solid oxide fuel cell system that generates power by oxidation and reduction of a reformed fuel gas and an oxidizing material obtained by reforming raw fuel.

  2. Description of the Related Art Conventionally, there has been known a solid oxide fuel cell in which a solid oxide fuel cell using a solid electrolyte as a membrane for conducting oxide ions is accommodated in a storage container. In this solid oxide fuel cell, zirconia doped with yttria is generally used as a solid electrolyte, and a fuel electrode for oxidizing fuel gas is provided on one side of the solid electrolyte. An oxygen electrode for reducing oxygen in the air (oxidant) is provided on the side. The operating temperature of a solid oxide fuel cell (cell) is relatively high at about 700 to 1000 ° C. Under such a high temperature, hydrogen, carbon monoxide, hydrocarbons in fuel gas and oxygen in the air are electrically connected. Electricity is generated by causing a chemical reaction.

  In recent years, attention has been paid to a solid oxide fuel cell system using such a solid oxide fuel cell. In this solid oxide fuel cell system, a reformer for reforming raw fuel gas is provided. The reformer is supplied with raw fuel gas and water vapor, a part of the raw fuel gas and water vapor are reformed and reformed, and the reformed fuel gas subjected to water vapor reforming is a solid oxide fuel cell. To the fuel electrode side. Since the combustion exhaust gas generated in the solid oxide fuel cell contains water vapor, the water vapor in the combustion exhaust gas is condensed and stored in the water recovery tank, and the water stored in the water recovery tank is modified. There has been proposed a system that can be used for reforming reaction of raw fuel gas by being sent to a pristine device, enabling water to operate independently.

  Here, the condensation of water vapor in the combustion exhaust gas is performed by heat exchange performed between the circulating water fed from the hot water storage tank of the hot water storage system that stores the exhaust heat as hot water and the combustion exhaust gas. Although the temperature of the combustion exhaust gas is recovered as condensed water by being lowered to the dew point, when the ambient temperature is high such as in summer, the temperature is not sufficiently lowered even if the temperature of the circulating water is lowered using the heat radiation means. In such a state, it is difficult to condense the water vapor contained in the combustion exhaust gas, the moisture recovery from the water vapor in the combustion exhaust gas is reduced, and the water required for the water self-sustained operation may be insufficient.

  Therefore, conventionally, when there is a concern about the occurrence of water shortage, the power generation output of the solid oxide fuel cell is reduced, and the flow rate of the combustion exhaust gas is reduced by lowering the blower amount of the blower, so that the heat exchanger It has been proposed to secure a recovered amount of water vapor in the combustion exhaust gas by increasing the heat exchange efficiency in (see, for example, Patent Documents 1 and 2).

JP 2009-238467 A JP 2010-277773 A

  However, for example, when the power generation output is reduced from about 50% of the rated power generation output to about 0%, in order to obtain a stable operation, it is necessary to increase the air flow rate relative to the fuel gas. If the power generation output is reduced, it will be difficult for water to become independent. For this reason, when a user goes out at a time when the temperature is high and the temperature is high and the power generation output is low, there is a possibility that the operation cannot be continued without being able to stand on its own. The solid oxide fuel cell deteriorates when the frequency of start / stop increases, and the durability may be impaired. In addition, since it takes several hours to start, repeated start / stop of the fuel cell system is not preferable.

  An object of the present invention is to provide a solid oxide fuel cell system that can suppress the shortage of reformed water and can continue water self-sustained operation.

The solid oxide fuel cell system according to claim 1 of the present invention includes a reformer for steam reforming a raw fuel, a reformed fuel gas reformed by the reformer, and an oxidizing material. A solid oxide fuel cell that generates power by oxidation and reduction, a blower for supplying an oxidant to the solid oxide fuel cell, and a supply amount of raw fuel supplied to the reformer Fuel supply control means for controlling, control means for controlling operation of the fuel supply control means and the blower, and water vapor contained in combustion exhaust gas from the solid oxide fuel cell is condensed and recovered And a condensing / recovering means for supplying condensate / condensed water to the reformer, and the control means determines whether or not the water self-sustaining operation is established. Includes water independence judging means,
The water self-supporting determination means performs water self-sustained operation when the amount of condensed water condensed and collected by the condensing and collecting means is equal to or greater than the necessary amount of condensate reforming required for reforming raw fuel in the reformer If the water self-sustained operation is not established when it is determined that the amount of condensed water condensed and recovered by the condensation recovery means is smaller than the required amount of condensed water required for reforming the raw fuel in the reformer, Judgment,
When it is determined by the water independence determination means that water independence operation is not established, the control means increases the power generation output of the solid oxide fuel cell to increase the amount of condensed water to be condensed and recovered. It is characterized by.

In the solid oxide fuel cell system according to claim 2 of the present invention, the exhaust gas temperature detecting means for detecting the exhaust gas outlet temperature of the combustion exhaust gas discharged from the condensation recovery means, and the solid oxide fuel cell system A power measuring means for measuring the power generation output of the fuel cell; and a storage means for storing water independence map data.
The water self-supporting map data includes the exhaust gas outlet temperature of the combustion exhaust gas discharged from the condensation recovery means, the power generation output of the solid oxide fuel cell, and the amount of condensate reforming necessary for reforming the raw fuel. Map data showing the relationship between the excess and deficiency of the amount of condensed water collected and recovered with respect to
Whether the water self-sustained determination means is based on the exhaust gas outlet temperature detected by the exhaust gas temperature detecting means, the power generation output measured by the power measuring means, and the water self-sustained map data. It is characterized by determining whether or not.

Further, in the solid oxide fuel cell system according to claim 3 of the present invention, the exhaust gas treatment means for treating the combustion exhaust gas is provided in the combustion exhaust gas exhaust line through which the combustion exhaust gas from the solid oxide fuel cell flows. A warm-up heater means associated with the exhaust gas treatment means, a freeze prevention heater means for preventing the condensed water from freezing associated with the condensation recovery means, and the solid oxidation An ignition heater means for starting is provided in connection with the physical fuel cell, and the warm-up heater means, the anti-freezing heater means and the ignition heater means constitute an auxiliary machine of the solid oxide fuel cell. ,
When it is determined that the water self-sustained operation is not established by the water self-supporting determining means, the control means operates at least one auxiliary machine selected from a plurality of auxiliary machines to operate the solid oxide fuel cell. The power generation output is increased.

  In the solid oxide fuel cell system according to claim 4 of the present invention, each time the water self-sustained judging means judges that water self-sustaining operation is not established, the control means causes the plurality of auxiliary machines to It operates according to a predetermined order, and the power generation output of the solid oxide fuel cell is increased stepwise.

Furthermore, in the solid oxide fuel cell system according to claim 5 of the present invention, the solid oxide fuel cell system further comprises power determination means for determining whether or not the power generation output of the solid oxide fuel cell has increased, and the storage means , Storing the power generation output increased by the operation of the auxiliary machine,
The power determination means determines that the power generation output of the solid oxide fuel cell has increased when the power generation output measured by the power measurement means is greater than the power generation output stored in the storage means;
When the power determination means determines that the power generation output of the solid oxide fuel cell has increased, the control means stops the operation of the auxiliary machine.

  According to the solid oxide fuel cell system of the first aspect of the present invention, the amount of condensed water condensed and recovered by the condensation recovery means is equal to the reforming of condensed water required for reforming the raw fuel in the reformer. When the self-sustained operation determination means determines that the water self-sustained operation is not established because the required amount is insufficient, the control means increases the power generation output of the solid oxide fuel cell and increases the amount of condensed water that is condensed and recovered. Water self-sustained operation can be established, and operation stop due to lack of condensed water can be avoided.

  In the solid oxide fuel cell system according to claim 2 of the present invention, the water independence determining means determines whether or not the water independence operation is established based on the water independence map data. It is possible to accurately determine whether or not the independent operation is established.

  According to the solid oxide fuel cell system of claim 3 of the present invention, when it is determined that the water self-sustained operation is not established, one auxiliary machine selected from the plurality of auxiliary machines is operated. By doing so, the power generation output is increased, so that the amount of condensed water condensed and recovered can be increased. The auxiliary equipment includes an antifreeze heater means provided in connection with the condensation recovery means, a warm-up heater means provided in connection with the exhaust gas treatment means, and an ignition heater provided in connection with the solid oxide fuel cell. Means.

  Further, according to the solid oxide fuel cell system according to claim 4 of the present invention, when it is determined that the water self-sustaining operation is not established, the power generation output of the solid oxide fuel cell is increased stepwise. The power generation output can be increased according to the shortage of the condensed water condensed and recovered, and the amount of condensed water generated can be increased while avoiding an excessive increase in the power generation output.

  According to the solid oxide fuel cell system of claim 5 of the present invention, when it is determined that the power generation output of the solid oxide fuel cell has increased, the power generation output is increased by the operation of the auxiliary machine. Since the water self-sustained operation is established without increasing it, the operation of the auxiliary machine can be stopped and unnecessary power consumption can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a simplified diagram illustrating a configuration of a solid oxide fuel cell system according to an embodiment of the present invention. The block diagram which shows simply the control system of the solid oxide fuel cell system of FIG. The graph which shows the relationship between the temperature of combustion exhaust gas, and the excess and deficiency of condensed water. The figure which shows the operation | movement order data showing the operation | movement order of several auxiliary machines. The flowchart which shows the flow of control of the solid oxide fuel cell system of FIG.

  Hereinafter, an embodiment of a solid oxide fuel cell system according to the present invention will be described with reference to the accompanying drawings.

  1 and 2, a solid oxide fuel cell system 2 shown in the figure includes a reformer 4 for reforming a raw fuel gas (for example, natural gas) as a raw fuel, and a reformer. The solid oxide fuel cell 6 that generates power by oxidation and reduction of the reformed fuel gas and the oxidizing material reformed in 4, and the air blow for supplying air to the solid oxide fuel cell 6 The apparatus 8 and the control means 10 (FIG. 2) for controlling operation | movement of the solid oxide fuel cell 6 and the air blower 8 are provided.

  The solid oxide fuel cell 6 includes a solid oxide fuel cell stack 14, and the fuel cell stack 14 is disposed in a high-temperature space 18 defined by the shielding wall 16 of the cell housing 12. . The fuel cell stack 14 is configured by arranging a plurality of solid oxide fuel cells for generating power by an electrochemical reaction. The solid oxide fuel cell includes a solid electrolyte 20 that conducts oxygen ions, a fuel electrode (not shown) provided on one side of the solid electrolyte 20, and an oxygen electrode provided on the other side of the solid electrolyte 20. (Not shown) and, for example, zirconia doped with yttria is used as the solid electrolyte 20.

  The introduction side of the fuel electrode side 26 of the fuel cell stack 14 is connected to the reformer 4 via a reformed fuel gas supply line 28, and the reformer 4 is connected to the raw material via a raw fuel gas supply line 30. It is connected to a raw fuel gas supply source 32 (for example, a buried pipe or a storage tank) for supplying fuel gas. The raw fuel gas supply line 30 is provided with a fuel pump 34 (constituting fuel supply control means) for controlling the supply amount of the raw fuel gas, and the rotational speed of the fuel pump 34 increases (or decreases). Then, the supply flow rate of the raw fuel gas supplied through the raw fuel gas supply line 30 increases (or decreases). The introduction side of the oxygen electrode side 36 of the fuel cell stack 14 is connected to an air preheater 40 for preheating air via an air supply line 38, and the air preheater 40 is connected to an air supply line 42. To the blower 8. The blower device 8 is constituted by, for example, a blower fan. When the rotational speed of the blower fan increases (or decreases), the supply amount of air supplied through the air supply line 42 increases (or decreases).

  A combustion chamber 44 is provided on each discharge side of the fuel electrode stack 26 and the oxygen electrode side 36 of the fuel cell stack 14, and the reaction fuel gas (including residual fuel gas) discharged from the fuel electrode side 26 and the oxygen electrode side 36. The air (including oxygen) discharged from the fuel is supplied to the combustion chamber 44 and burned. The combustion chamber 44 is connected to an air preheater 40 via a combustion exhaust gas supply line 46, and a combustion exhaust gas discharge line 48 is connected to the air preheater 40. The combustion chamber 44 is provided with ignition heater means H2 for starting up the solid oxide fuel cell 6 (fuel cell stack 14), and at the time of startup, ignition combustion of the fuel gas is performed by the ignition heater means H2.

  Further, in the solid oxide fuel cell system 2, the condensation recovery means 50 for condensing and recovering water vapor contained in the combustion exhaust gas from the combustion chamber 44, and the condensed and recovered condensed water to the reformer 4. Water supply means 52 for supplying is provided. The condensation recovery means 50 includes a heat exchanger 54 for condensing water vapor contained in the combustion exhaust gas, an impurity removal means 56 for removing impurities contained in the condensed water, and condensed water from which impurities have been removed. And a water recovery tank 52 for storing water. The heat exchanger 54 is disposed in the combustion exhaust gas discharge line 48, and an impurity removing unit 56 and a water recovery tank 62 are connected to the heat exchanger 54 through a condensed water recovery line 58. The impurity removing means 56 is composed of, for example, an ion exchange membrane and removes impurities contained in the condensed water.

  In relation to the condensation recovery means 50, anti-freezing heater means are provided to prevent the condensed water from freezing. In this embodiment, the antifreeze heater means H1 includes first and second antifreeze heaters H1a and H1b. The first antifreeze heater H1a is provided in the impurity removing means 56, and the second antifreeze heater H1b collects water. A tank 62 is provided.

  The water feed means 52 includes a water feed line 78 for feeding the condensed water in the water recovery tank 62 to the reformer 4, and a feed pump 80 is disposed in the water feed line 78. The feed pump 80 feeds the condensed water in the water recovery tank 62 to the reformer 4 through the water feed line 78 as reforming water.

  Further, an exhaust gas processing means 73 for processing the exhaust gas to be discharged as required is provided at a portion downstream of the heat exchanger 54 of the combustion exhaust gas discharge line 48. It consists of a catalyst. In relation to the exhaust gas treatment means 73, a warm-up heater means H3 for warming up the exhaust gas treatment means 73 is provided. In this embodiment, the warm-up heater means H3 is a first warm-up heater H3a, Although it is comprised from two warm-up heaters of H3b, it can also comprise from one or three or more warm-up heaters. This warm-up heater means H3 constitutes part of the auxiliary equipment of the solid oxide fuel cell 6 together with the above-mentioned antifreeze heater means H1 and ignition heater means H2.

  The solid oxide fuel cell system 2 is further provided with a hot water storage system 60 for storing the exhaust heat of the combustion exhaust gas from the solid oxide fuel cell 6 as hot water. The hot water storage system 60 includes a hot water storage tank 64 for storing hot water, and the hot water storage tank 64 is connected to the heat exchanger 54 via a circulation channel 66. A circulation pump 68 is provided in the circulation channel 66, and the circulation pump 68 circulates water (circulation water) stored in the hot water storage tank 64 through the circulation channel 66. A water supply channel 74 is connected to the hot water storage tank 64, and an open / close valve 75 for controlling the supply of water (tap water) is disposed in the water supply channel 74. Hot water stored in the hot water storage tank 64 is discharged through a hot water supply line 76.

  The solid oxide fuel cell system 2 further includes power measuring means 24 for measuring the power generation output of the solid oxide fuel cell 6 (fuel cell stack 14). The combustion exhaust gas discharge line 48 (specifically, the downstream portion of the heat exchanger 54) is provided with exhaust gas temperature detection means 70 for detecting the temperature of the exhaust gas. The temperature of the exhaust gas discharged from the heat exchanger 54 (that is, the exhaust gas outlet temperature of the heat exchanger 54) is detected.

  The control means 10 is composed of, for example, a microprocessor, and includes an operation control means 81, a storage means 83, a water self-sustained determination means 85, a water self-sustained operation signal generation means 86, and a power determination means 87.

  The operation control means 81 controls operations of the solid oxide fuel cell 6 and the blower 8 as will be described later. The storage means 83 includes a water independence map data storage area 83a for storing the graph data (that is, water independence map data) shown in FIG. 3, an operation order data storage area 83b for storing operation order data shown in FIG. And a power generation output storage area 83c for storing the power generation output measured by the power measuring means 24. The graph (water independence map data) shown in FIG. 3 and the operation order data shown in FIG. 4 will be described later. The water self-supporting determination unit 85 includes the power generation output measured by the power measurement unit 24, the temperature of the combustion exhaust gas detected by the exhaust gas temperature detection unit 70 (that is, the exhaust gas outlet temperature of the heat exchanger 54), and the storage unit 83. Based on the water self-supporting map data stored in the water self-supporting map data storage area 83a, the amount of condensed water to be condensed and recovered is more than the necessary amount of condensate reforming required for reforming the raw fuel gas in the reformer 4. It is determined as described later whether there are many (that is, whether water self-sustained operation is established). The water self-sustained operation signal generating unit 86 generates a water self-sustained operation signal based on the determination data from the water self-supporting determination unit 85, and outputs the water self-supporting operation signal to the operation control unit 81. To operate. As will be described later, the power determination means 87 determines whether or not the power generation output has increased.

  The operation of the solid oxide fuel cell system 2 is performed as follows. Raw fuel gas from the raw fuel gas supply source 32 is supplied to the reformer 4 through the raw fuel gas supply line 30, and condensed water described later is supplied to the reformer 4 through the water supply line 78. In the reformer 4, a part of the raw fuel gas and water (condensed water) are reformed and reformed, and the reformed fuel gas thus reformed is reformed fuel gas supply line 28. To the fuel electrode side 26 of the fuel cell stack 14. In addition, air from the blower 8 is supplied to the air preheater 40 through the air supply line 42, heat is exchanged with the combustion exhaust gas in the air preheater 40 and heated, and then the air supply line 38. To the oxygen electrode side 36 of the fuel cell stack 14.

  The fuel electrode side 26 of the fuel cell stack 14 oxidizes the reformed reformed fuel gas, and its oxygen electrode side 36 reduces oxygen in the air, oxidation on the fuel electrode side 26 and reduction on the oxygen electrode side 36. Electricity is generated by an electrochemical reaction. The reaction fuel gas from the fuel electrode side 26 and the air from the oxygen electrode side 36 are respectively supplied to the combustion chamber 44, and excess fuel gas is combusted using oxygen in the air. The combustion exhaust gas from the combustion chamber 44 is supplied to the air preheater 40 through the combustion exhaust gas supply line 46, and is used for heat exchange with the air from the blower 8 in the air preheater 40 and passes through the combustion exhaust gas discharge line 48. It is fed to the heat exchanger 54. In the heat exchanger 54, heat exchange is performed between the water supplied from the hot water storage tank 64 through the circulation line 66 and the combustion exhaust gas flowing through the combustion exhaust gas discharge line 48. Water (warm water) heated by heat exchange is stored in the hot water storage tank 64 through the circulation line 66 by the action of the circulation pump 68. Further, the temperature of the combustion exhaust gas is lowered to the dew point by this heat exchange, so that the water vapor contained in the combustion exhaust gas is condensed and recovered. The condensed water is sent to the impurity removing unit 56 through the condensed water collecting line 58 and is stored in the water collecting tank 62 after the impurities are removed by the impurity removing unit 56. On the other hand, the flue gas after condensation recovery is sent to the flue gas treatment means 73 through the flue gas exhaust line 48, and harmful substances in the flue gas are treated as required by the flue gas treatment means 73 and then discharged to the atmosphere. . The condensed water stored in the water recovery tank 62 is fed to the reformer 4 through the water feed line 78 by the action of the feed pump 80, and the water self-sustained operation is performed in this way.

  Next, referring also to FIG. 3 and FIG. 4, it is determined whether or not the required amount of reformed condensed water collected and recovered with respect to the amount of condensed water required for reforming the raw fuel gas by the water self-supporting determining unit 85 Will be described.

  FIG. 3 shows the excess amount of condensed water (ml / min) and the temperature of the combustion exhaust gas discharged from the condensation recovery means 50 at each of the power generation outputs 700 W, 300 W, and 100 W (that is, the exhaust gas outlet temperature of the heat exchanger 54). The relationship with (° C.) is shown. As shown in FIG. 3, the higher the power generation output of the solid oxide fuel cell 6 (fuel cell stack 14), the greater the amount of condensed water that is condensed and recovered, which tends to increase the excess amount of condensed water. It is in. Further, as the exhaust gas temperature (exhaust gas outlet temperature of the heat exchanger 54) is lower, the amount of condensed water that is condensed and recovered increases, and this tends to increase the surplus amount of condensed water. On the other hand, when the excessive amount of condensed water is insufficient, water self-sustained operation cannot be established.

  Therefore, in the solid oxide fuel cell system 2, when the excess amount of the condensed water is insufficient, a plurality of auxiliary machines are sequentially activated to increase the power generation output of the solid oxide fuel cell 6 step by step. Therefore, the surplus amount of condensed water is secured and water self-sustained operation is established. In the present embodiment, as shown in FIG. 4, the antifreezing heater means H18 as the first stage auxiliary machine, the ignition heater means H2 as the second stage auxiliary machine, and the warm-up heater means as the third stage auxiliary machine. H3 is used. That is, when the water independence determination unit 85 determines that the water independence operation is not established, the water independence operation signal generation unit 86 generates a water independence operation signal and outputs it to the operation control unit 81. The operation control means 81 operates the freeze prevention heater means H1 as the first stage based on the water self-sustained operation signal, activates the ignition heater means H2 as the second stage, and activates the warm-up heater means H3 as the third stage. This increases the power generation output. Here, for example, the power consumption of the first antifreeze heater H1a and the second antifreeze heater H1b constituting the antifreeze heater means H1 is about 20 W, and the power consumption of the ignition heater means H2 is about 100 W. The power consumption of the first warm-up heater H3a and the second warm-up heater H3b constituting the warm-up heater means H3 is about 100W.

  With reference to FIG. 5 as well, the control flow of the solid oxide fuel cell system 2 will be described as follows. When the solid oxide fuel cell system 2 is operated, the operation control means 81 clears the power generation output storage area 83c of the storage means 83 (step S1), and then controls each device of the solid oxide fuel cell system 2. Then, normal operation according to the power load is performed (step S2). Next, the water self-supporting determination unit 85 is configured to detect the temperature of the combustion exhaust gas (the exhaust gas outlet temperature of the heat exchanger 54) detected by the exhaust gas temperature detection unit 70 and the solid oxide fuel cell 6 measured by the power measurement unit 24. A power generation output is acquired (step S3).

  The water independence determination unit 85 determines whether or not the water independence operation is established based on the exhaust gas temperature and the power generation output acquired in step S3 and the water independence map data stored in the storage unit 83 (that is, surplus water). It is determined whether or not the amount is sufficient (step S4). If the water independence determination unit 85 determines that the water independence operation is established, the process returns from step S4 to step S2. On the other hand, if it is determined that the water self-sustained operation is not established, the process proceeds from step S4 to step S5, and the power generation output of the first stage is increased. More specifically, the water self-sustained operation signal generation unit 86 generates a signal instructing the first-stage power generation output increase, and outputs the signal to the operation control unit 81. Thus, the operation control means 81 operates the first stage auxiliary machine, that is, the antifreezing heater means H1, based on the operation order data (FIG. 4) stored in the operation order data storage area 83b of the storage means 83. As a result, the power load of the solid oxide fuel cell 6 increases by the amount of power consumed by the freeze prevention heater means H1 (for example, about 40 W), and the power generation output of the solid oxide fuel cell 6 increases. Thus, the power measuring unit 24 measures the power generation output after such increase, and the operation control unit 81 stores the measured power generation output in the power generation output storage area 83c of the storage unit 83 (step S6).

  Thereafter, the water self-supporting determination unit 85 acquires the exhaust gas temperature (the exhaust gas outlet temperature of the heat exchanger 54) and the power generation output of the solid oxide fuel cell 6 similarly to steps S3 and S4 (step S7), and the water self-supporting determination is performed. The means 85 determines whether or not water self-sustained operation is established (step S8). As a result, when it is determined that the water self-sustaining operation is established, the power determination means 87 determines whether or not the power generation output has increased from step S8 (step S16). More specifically, the power determination unit 87 acquires the power generation output measured by the power measurement unit 24, the power generation output measured by the power measurement unit 24, and the power generation output stored in the power generation output storage area 83c. Compare As a result, if the power generation output measured by the power measuring unit 24 is larger, it is determined that the power generation output has increased, and the process returns from step S16 to step S1. However, if the power generation output measured by the power measurement unit 24 is equal to the power generation output stored in the power generation output storage area 83c, or if the power generation output measured by the power measurement unit 24 is smaller, It is determined that the output has not increased, and the process returns from step S31 to step S7.

  On the other hand, if it is determined in step S8 that the water self-sustaining operation is not established, the process proceeds from step S8 to step S9, and the power generation output of the second stage is increased. More specifically, the water self-sustained operation signal generation unit 86 generates a signal instructing the second-stage power generation output increase and outputs the signal to the operation control unit 81. Thus, the operation control means 81 operates the second stage auxiliary machine, that is, the ignition heater means H2, based on the operation order data (FIG. 4) stored in the operation order data storage area 83ba. As a result, the power load of the solid oxide fuel cell 6 increases by the amount of power consumed by the ignition heater means H2 (for example, about 100 W), thereby further increasing the power generation output of the solid oxide fuel cell 6. Therefore, when combined with the first stage, the power generation output increases by about 140 W, for example. The power measuring unit 24 measures the power generation output after the increase as described above, and the operation control unit 81 stores the measured power generation output in the power generation output storage area 83c (step S10).

  Next, the water self-supporting determination means 85 acquires the power generation output of the solid oxide fuel cell 6 and the temperature of the exhaust gas (the exhaust gas outlet temperature of the heat exchanger 54), similarly to steps S3 and S4 (step S12). It is determined whether or not water self-sustaining operation is established (step S12). As a result, when it is determined that the water self-sustained operation is established, the process proceeds from step S12 to step S17, and the power determination unit 87 determines whether or not the power generation output has increased by the same method as in step S16. If it is determined that the power generation output has increased, the process returns from step S17 to step S1, and if it is determined that the power generation output has not increased, the process returns from step S17 to step S11.

  On the other hand, if it is determined in step S12 that the water self-sustained operation is not established, the process proceeds from step S12 to step S13, and the power generation output at the third stage is increased (step S13). More specifically, the water self-sustained operation signal generation unit 86 generates a signal instructing the third-stage power generation output increase, and outputs this to the operation control unit 81. Thus, the operation control means 81 drives the third stage auxiliary machine, that is, the warm-up heater means H3, based on the operation order data (FIG. 4) stored in the operation order data storage area 83b. As a result, the power load of the solid oxide fuel cell 6 is increased by the amount of power consumed by the warm-up heater means H3 (for example, about 200 W), and the power generation output of the solid oxide fuel cell 6 is increased. Therefore, when combined with the first and second stages, the power generation output increases by 340 W, for example. The power measuring unit 24 measures the power generation output after the increase, and the operation control unit 81 stores the measured power generation output in the power generation output storage area 83c (step S14). Thereafter, the power determination means 87 determines whether or not the power generation output has increased by the same method as in step S16 (step S15). If it is determined that the power generation output has increased, the process returns from step S29 to step S1, and if it is determined that the power generation output has not increased, the process of step S15 is repeated.

  Here, if it is determined in step S16, S15, or S17 that the power generation output has increased, the process returns to step S2 via step S1, but normal operation is performed in step S2, and steps S5, S9, And / or the auxiliary machine started to operate in S13, that is, the operation of the antifreeze heater means H1, the ignition heater means H2, and / or the warm-up heater means H3 are all stopped.

  As described above, in the solid oxide fuel cell system 2 in the present embodiment, when it is determined that the water self-sustained operation is not established, it is condensed and recovered by increasing the power generation output of the solid oxide fuel cell 6. Increase the amount of condensed water. Here, as shown in FIG. 4, when the power generation output is 100 W, the water self-sustained operation cannot be established unless at least the exhaust gas temperature (exhaust gas outlet temperature of the heat exchanger 54) is cooled to 35 ° C. For example, when the outside air temperature is as high as 40 ° C, it is difficult to cool the exhaust gas temperature to 35 ° C, and in the method of suppressing the power generation output as in the above-described prior art, the operation is stopped due to insufficient condensed water. Cannot be avoided. On the other hand, in the present embodiment, the power generation output of the solid oxide fuel cell 6 can be increased up to 340 W by driving up to the third stage auxiliary machine, and the allowable exhaust gas temperature is thereby increased. It becomes high and water self-sustained operation can be easily established.

  As described above, in the solid oxide fuel cell system 2 according to the present embodiment, the water self-sustained operation can be easily established. Therefore, the operation of the solid oxide fuel cell system 2 is stopped due to the absence of the water self-sustained operation. Can be reliably avoided, and the durability of the solid oxide fuel cell system 2 can be maintained.

  Further, in the present embodiment, since the antifreeze heater means H1, the ignition heater means H2, and the warm-up heater means H3 are used as auxiliary machines, it is possible to reliably drive the auxiliary machines for the purpose of increasing the power generation output. . That is, the freeze prevention heater means H1, the ignition heater means H2, and the warm-up heater means H3 are normally always kept stopped during the continuous operation of the solid oxide fuel cell system 2 at a high temperature. Therefore, these can be reliably driven as necessary.

  Although various embodiments of the solid oxide fuel cell system according to the present invention have been described above, the present invention is not limited to such embodiments, and various modifications and corrections can be made without departing from the scope of the present invention. Is possible.

  For example, in the above embodiment, the antifreeze heater means H1, the ignition heater means H2, and the warm-up heater means H3 are used as auxiliary machines, but the auxiliary machines are not limited to these, and are provided in the hot water storage system 60, for example. The circulation pump 68 may be used, or a power conditioner for controlling the power generation output of the solid oxide fuel cell 6 (fuel cell stack 14) may be used. Further, the operation order of the auxiliary machines is not limited to the order described above. Further, the warm-up heater means H3 may be operated separately for the first warm-up heater H3a and the second warm-up heater H3b so that the warm-up heater means H3 has two stages. Furthermore, in the above embodiment, the power generation output increase stage is three stages, but it may be two stages or less or four stages or more.

DESCRIPTION OF SYMBOLS 2 Solid oxide fuel cell system 4 Reformer 6 Solid oxide fuel cell 8 Blower 10 Control means 24 Electric power measurement means 50 Condensation recovery means 52 Water supply means 54 Heat exchanger 56 Impurity removal means 62 Water recovery tank 70 Exhaust gas temperature detection means 83 Storage means H1 Antifreeze heater means H2 Ignition heater means H3 Warm-up heater means

Claims (5)

A reformer for steam reforming raw fuel, a solid oxide fuel cell that generates power by oxidation and reduction of the reformed fuel gas and the oxidant reformed in the reformer, and an oxidant A blower for feeding to the solid oxide fuel cell, a fuel supply control means for controlling the amount of raw fuel fed to the reformer, the fuel supply control means and the blower Control means for controlling the operation of the apparatus, condensation recovery means for condensing and recovering the water vapor contained in the combustion exhaust gas from the solid oxide fuel cell, and the condensed and recovered condensed water in the reformer Water supply means for supplying water, and the control means includes water self-supporting determination means for determining whether water self-supporting operation is established,
The water self-supporting determination means performs water self-sustained operation when the amount of condensed water condensed and collected by the condensing and collecting means is equal to or greater than the necessary amount of condensate reforming required for reforming the raw fuel in the reformer. If the water self-sustained operation is not established when it is determined that the amount of condensed water condensed and recovered by the condensation recovery means is smaller than the required amount of condensed water required for reforming the raw fuel in the reformer, Judgment,
When it is determined by the water independence determination means that water independence operation is not established, the control means increases the power generation output of the solid oxide fuel cell to increase the amount of condensed water to be condensed and recovered. A solid oxide fuel cell system. An exhaust gas temperature detecting means for detecting the exhaust gas outlet temperature of the combustion exhaust gas discharged from the condensation recovery means, an electric power measuring means for measuring the power generation output of the solid oxide fuel cell, and water self-supporting map data are stored. Storage means,
The water self-supporting map data includes the exhaust gas outlet temperature of the combustion exhaust gas discharged from the condensation recovery means, the power generation output of the solid oxide fuel cell, and the amount of condensate reforming necessary for reforming the raw fuel. Map data showing the relationship between the excess and deficiency of the amount of condensed water collected and recovered with respect to
Whether the water self-sustained determination means is based on the exhaust gas outlet temperature detected by the exhaust gas temperature detecting means, the power generation output measured by the power measuring means, and the water self-sustained map data. The solid oxide fuel cell system according to claim 1, wherein it is determined whether or not. The flue gas exhaust line through which the flue gas from the solid oxide fuel cell flows is provided with an exhaust gas treatment means for treating the flue gas, and a warm-up heater means is provided in relation to the exhaust gas treatment means, Antifreeze heater means for preventing freezing of the condensed water is provided in connection with the condensation recovery means, and ignition heater means for starting is provided in connection with the solid oxide fuel cell. Machine heater means, the antifreeze heater means and the ignition heater means constitute an auxiliary machine of the solid oxide fuel cell,
When it is determined that the water self-sustained operation is not established by the water self-supporting determining means, the control means operates at least one auxiliary machine selected from a plurality of auxiliary machines to operate the solid oxide fuel cell. The solid oxide fuel cell system according to claim 1 or 2, wherein the power generation output is increased.   Each time the water self-sustained determination means determines that the water self-sustained operation is not established, the control means operates the plurality of auxiliary devices in a predetermined order to stepwise the power generation output of the solid oxide fuel cell. The solid oxide fuel cell system according to claim 3, wherein the solid oxide fuel cell system is increased. It further comprises power determination means for determining whether or not the power generation output of the solid oxide fuel cell has increased, and the storage means stores the power generation output increased by the operation of the auxiliary machine,
The power determination means determines that the power generation output of the solid oxide fuel cell has increased when the power generation output measured by the power measurement means is greater than the power generation output stored in the storage means;
The said control means stops the operation | movement of the said auxiliary machine, when the said electric power determination means determines with the electric power generation output of the said solid oxide fuel cell having increased, The operation of the said auxiliary machine is characterized by the above-mentioned. Solid oxide fuel cell system.

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