JP2021048096A - Fuel cell system and operational method of them - Google Patents

Abstract

To enable a suppression of a damage of a reproduction heat exchanger at an activation.SOLUTION: A fuel cell system (1) comprises: an SOFC (10) generating power by an electrochemical reaction of a fuel gas and an oxidant gas; a regenerative heat exchanger (40) that exchanges heat of the exhaust gas from the SOFC to the oxidant gas; and an adjustment valve (47) that executes a flow amount adjustment of the oxidant gas to the regenerative heat exchanger (40). A control part (60) is structured so that the flow amount adjustment is controlled in the adjustment valve so as to avoid a sudden change of an inlet temperature of the oxidant gas in the regenerative heat exchanger in one part of an activation time in the SOFC.SELECTED DRAWING: Figure 1

Description

The present invention relates to a fuel cell system and a method of operating the same.

In recent years, the development of solid oxide fuel cells (SOFCs) has been promoted. SOFC is a power generation mechanism in which oxide ions generated at the air electrode permeate the electrolyte and move to the fuel electrode, and the oxide ions react with hydrogen or carbon monoxide at the fuel electrode to generate electric energy. .. Among the currently known forms of fuel cells, SOFCs have the characteristics that the operating temperature of power generation is the highest (for example, 650 ° C. to 1000 ° C.) and the power generation efficiency is the highest.

Patent Document 1 includes a fuel cell system including a regenerative heat exchanger that exchanges heat of exhaust gas from SOFC with oxidant gas (air), an air preheater that heats the oxidant gas, and a start burner. It is disclosed. In this fuel cell system, at startup, the oxidant gas heated by the air preheater and the start burner is supplied to the SOFC to raise the temperature of the SOFC, and the exhaust gas discharged from the SOFC is introduced into the regenerated heat exchanger. There is. In the regenerative heat exchanger, a high-temperature exhaust gas is introduced on the high-temperature side, while an oxidant gas having an outside temperature is introduced on the low-temperature side, and the heat of the exhaust gas is reused as the oxidant gas.

Japanese Patent No. 6103127

In the above configuration, since the regenerative heat exchanger is heated by the high temperature exhaust gas and then the oxidant gas that becomes the outside air temperature is introduced into the regenerated heat exchanger, the low temperature side is also high temperature before the introduction of the oxidant gas. It will be in a sufficiently heated state as on the side. In this state, when the introduction of the oxidant gas to the low temperature side of the regenerative heat exchanger is started, the low temperature side is rapidly cooled by the oxidant gas that becomes the outside air temperature from the state of being heated to the high temperature. Due to such rapid cooling, the brazed portion of the regenerated heat exchanger is likely to be distorted, and there is a problem that the regenerated heat exchanger is damaged.

The present invention has been made in view of the above points, and one of the objects of the present invention is to provide a fuel cell system capable of suppressing damage to the regenerated heat exchanger at the time of starting and a method for operating the fuel cell system.

In one aspect of the fuel cell system of the present embodiment, the solid oxide fuel cell that generates power by the electrochemical reaction of the fuel gas and the oxidant gas and the heat of the exhaust gas from the solid oxide fuel cell are generated. A regenerated heat exchanger that exchanges heat with the oxidant gas supplied to the solid oxide fuel cell, a regulating valve that adjusts the flow rate of the oxidant gas to the regenerated heat exchanger, and the solid oxide fuel cell. It is characterized by having a control unit that controls the flow rate adjustment in the adjustment valve so as to avoid a sudden change in the inlet temperature of the oxidant gas in the regenerative heat exchanger during a part of the start-up time of the battery. There is.

In one aspect, the fuel cell system of the present embodiment includes a solid oxide fuel cell that generates power by an electrochemical reaction between a fuel gas and an oxidant gas, and the solid oxide fuel cell that heats the oxidant gas. And a heater arranged in parallel with the heater, the heat of the exhaust gas from the solid oxide fuel cell is exchanged with the oxidant gas supplied to the solid oxide fuel cell. It is characterized by having a heat exchanger and a supply line for supplying the oxidant gas heated by the heater to the inlet of the oxidant gas in the regenerated heat exchanger.

In one aspect of the operation method of the fuel cell system of the present embodiment, the solid oxide fuel cell that generates power by the electrochemical reaction of the fuel gas and the oxidant gas and the exhaust gas from the solid oxide fuel cell are used. A fuel having a regenerated heat exchanger that exchanges heat with the oxidant gas that supplies heat to the solid oxide fuel cell, and a regulating valve that adjusts the flow rate of the oxidant gas to the regenerated heat exchanger. A method of operating the battery system, in which the regulating valve is used so as to avoid a sudden change in the inlet temperature of the oxidant gas in the regenerative heat exchanger during a part of the start-up time of the solid oxide fuel cell. It is characterized by having an adjustment step for adjusting the flow rate.

According to the present invention, even if the oxidant gas is supplied to the inlet of the regenerative heat exchanger in which the inlet of the oxidant gas is also heated at the time of start-up, the supply flow rate is adjusted to avoid a sudden temperature change at the inlet. Or, the temperature of the oxidant gas supplied to the inlet via the supply line can be raised. As a result, it is possible to prevent the occurrence of distortion of the brazed portion in the regenerated heat exchanger due to rapid cooling, and it is possible to suppress damage to the regenerated heat exchanger.

It is a block diagram which shows the fuel cell system by 1st Embodiment. It is a figure for demonstrating the time change of the operation parameter of the fuel cell system by 1st Embodiment. FIG. 3A is a graph showing the time change of the temperature on the low temperature side in the regenerated heat exchanger, and FIG. 3B is a graph showing the time change of the opening degree in the adjusting valve for adjusting the flow rate of the reaction air with respect to the regenerated heat exchanger. is there. It is a block diagram which shows the fuel cell system by 2nd Embodiment.

[First Embodiment]
Hereinafter, the fuel cell system according to the first embodiment will be described in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing a fuel cell system according to the first embodiment. In FIG. 1, for convenience of explanation, only the components related to the present invention are shown. In FIG. 1, the flow path of a fluid such as fuel gas or oxidant gas is shown by a solid line, and the signal line of the control signal of the fuel cell system 1 is shown by a broken line (partially omitted). The fluid flow path in the SOFC 10 is indicated by a alternate long and short dash line for convenience.

As shown in FIG. 1, the fuel cell system 1 has a solid oxide fuel cell (SOFC: Solid Oxide Fuel Cell, hereinafter simply referred to as “SOFC”) 10. The SOFC 10 has a cell stack in which a plurality of cells are stacked or aggregated. Each cell has a basic configuration in which an electrolyte is sandwiched between an air electrode and a fuel electrode. Each cell in the cell stack is electrically connected in series. SOFC10 is a power generation mechanism in which oxide ions generated at the air electrode permeate the electrolyte and move to the fuel electrode, and the oxide ions react with hydrogen or carbon monoxide at the fuel electrode to generate electric energy. ..

The SOFC 10 has an oxidant gas flow path (cathode gas flow path) 12 and a fuel gas flow path (anode gas flow path) 14. The oxidant gas (air) taken in by the reaction air blower (oxidizer gas supply device) 20 and other gases are supplied to the inlet portion 12A of the oxidant gas flow path 12, and the outlet portion of the oxidant gas flow path 12 is supplied. From 12B, the cathode side exhaust gas (hereinafter, may be simply referred to as “exhaust gas”) is discharged. Fuel gas (fuel) and other gases from a fuel gas supply device (not shown) are supplied to the inlet portion 14A of the fuel gas flow path 14, and are discharged from the outlet portion 14B of the fuel gas flow path 14 on the anode side. Gas (sometimes referred to simply as "emissions" below) is emitted. A direct current is generated (generated electricity) by causing an electrochemical reaction between the oxidant gas supplied to the oxidant gas flow path 12 and the fuel gas supplied to the fuel gas flow path 14. The SOFC 10 is provided with a temperature detection unit 30 that detects the temperature of the SOFC 10 (module representative temperature).

The fuel cell system 1 supplies the air regenerating heat exchanger (hereinafter, simply referred to as “regenerating heat exchanger”) 40 and the oxidant gas taken in by the reaction air blower 20 to the inlet portion 12A of the oxidant gas flow path 12. It is provided with an air supply line 41. The regenerative heat exchanger 40 is provided in the reaction air supply line 41. The regenerative heat exchanger 40 is connected to a reaction air exhaust line 42 through which the cathode side exhaust gas from the outlet portion 12B of the oxidant gas flow path 12 passes. The regenerative heat exchanger 40 exchanges heat between the cathode side exhaust gas (mainly the oxidant gas) flowing through the reaction air exhaust line 42 and the oxidant gas flowing through the reaction air supply line 41, and introduces the oxidant gas into the SOFC 10. Heat (reaction air). Therefore, in the regenerated heat exchanger 40, the connection portion with the reaction air supply line 41 is on the low temperature side, while the connection portion with the reaction air exhaust line 42 is on the high temperature side, and the oxidant gas from the reaction air supply line 41 is discharged. The inlet to be introduced becomes particularly cold.

The reaction air exhaust line 42 is provided with a temperature detection unit (first temperature detection unit) 51 that detects the temperature in the vicinity of the outlet portion 12B of the oxidant gas flow path 12. The temperature detection unit 51 detects the temperature of the exhaust gas from the oxidant gas flow path 12 (SOFC10).

Although the oxidant gas flow path 12 is indicated by a straight line (dashed line) in the SOFC 10, the flow path may be set according to the shape of the cell stack.

A reaction air bypass line 43 branching from the reaction air supply line 41 is provided on the upstream side of the regenerative heat exchanger 40 in the reaction air supply line 41. The downstream end of the reaction air bypass line 43 is connected to the downstream side of the regenerated heat exchanger 40 in the reaction air supply line 41. The reaction air bypass line 43 is provided with an electric heater 44, a regulating valve 45, and a temperature detecting unit 46. The electric heater 44 is provided on the reaction air bypass line 43 and is arranged at a position parallel to the regenerated heat exchanger 40.

The electric heater 44 constitutes a heater, and heats the reaction air (oxidizing agent gas) flowing through the reaction air bypass line 43 from the reaction air blower 20. For example, the electric heater 44 heats the reaction air when the fuel cell system 1 is started. That is, the electric heater 44 constitutes an electric heater for starting the fuel cell system 1 (SOFC10). The output of the electric heater 44 is preferably 1/5 to 2/3 of the rated output of the SOFC 10.

The regulating valve 45 adjusts the amount of reaction air supplied from the reaction air blower 20 to the reaction air bypass line 43 (electric heater 44) by switching its own open / closed state. The opening degree of the regulating valve 45 is controlled by a control signal from the control unit 60, which will be described later.

The temperature detection unit 46 detects the temperature in the vicinity of the outlet of the electric heater 44 in the reaction air bypass line 43.

The reaction air supply line 41 is provided with a regulating valve 47 at a position parallel to the regulating valve 45 of the reaction air bypass line 43. The adjusting valve 47 adjusts the flow rate of the reaction air (oxidizing agent gas) supplied from the reaction air blower 20 to the reaction air supply line 41 (regenerated heat exchanger 40) by switching its own open / closed state. The opening degree of the regulating valve 47 is controlled by a control signal from the control unit 60, which will be described later.

The reaction air supply line 41 is provided with a temperature detection unit 48 that detects the temperature in the vicinity of the inlet portion 12A of the oxidant gas flow path 12. Further, the reaction air supply line 41 is provided with a temperature detection unit 49 for detecting the temperature in the vicinity of the outlet of the regenerative heat exchanger 40. The downstream end of the reaction air bypass line 43 is connected between the temperature detection units 48 and 49 in the reaction air supply line 41.

Further, a flow meter 50 for measuring the flow rate of the reaction air supplied from the reaction air blower 20 is provided on the outlet side of the reaction air blower 20 in the reaction air supply line 41. Further, the fuel cell system 1 includes a temperature detection unit (second temperature detection unit) 52 that detects the temperature of the reaction air (oxidizing agent gas) that becomes the outside air. Although FIG. 1 shows a case where the temperature detection unit 52 is provided on the inlet side of the reaction air blower 20, the installation position may be changed as long as the temperature of the reaction air supplied by the reaction air blower 20 can be detected. Good.

It is preferable that at least one of the regulating valves 45 and 47 controls the supply amount (flow rate) of the oxidant gas to both the reaction air bypass line 43 and the reaction air supply line 41 as a proportional control valve. Although the case where the reaction air bypass line 43 and the reaction air supply line 41 are provided with the regulating valves 45 and 47, respectively, is described here, the configuration of the regulating valves can be changed as appropriate. For example, a regulating valve having a three-pronged structure is provided at a branch point from the reaction air supply line 41 to the reaction air bypass line 43, and the amount of oxidant gas supplied to both the reaction air bypass line 43 and the reaction air supply line 41. May be controlled.

The fuel cell system 1 has a control unit 60 that controls the entire system. The control unit 60 is connected to temperature detection units 30, 46, 48, 49, 51, 52, regulating valves 45, 47, reaction air blower 20, electric heater 44, flow meter 50, and an operation unit (not shown). In FIG. 1, the signal line connecting the control unit 60 and the temperature detection unit 51 is omitted. The control unit 60 controls the connected equipment according to the instruction input from the operation unit and the detection results of the temperature detection units 30, 46, 48, 49, 51, 52, the flow meter 50, and the like.

Hereinafter, the starting operation (control content by the control unit 60) of the fuel cell system 1 will be described with reference to FIG. 2 in addition to FIG. FIG. 2 is a diagram for explaining time-dependent changes in operating parameters of the fuel cell system according to the present embodiment. The time during which the following startup operation is performed is defined as the "startup time" of the SOFC 10.

The control unit 60 executes control to open the regulating valve 45, close the regulating valve 47, and turn on the reaction air blower 20 and the electric heater 44, respectively. These controls may be executed substantially at the same time, or may be executed at staggered times. By these controls, the reaction air (oxidizer gas) taken in from the reaction air blower 20 is heated by the electric heater 44 and flows from the reaction air bypass line 43 to the oxidant gas flow path 12 through the reaction air supply line 41.

At this time, the temperature detected by the temperature detection unit 46 on the outlet side of the electric heater 44 (see FIG. 2A) gradually rises until the time t1, and the temperature detection unit at the inlet 12A of the oxidant gas flow path 12 on the downstream side thereof. Similarly, the temperature detected at 48 (see FIG. 2E) gradually rises to time t1. Then, the amount of heat of the reaction air supplied to the SOFC 10 via the oxidant gas flow path 12 (see FIG. 2G) gradually increases, the temperature of the SOFC 10 rises, and the temperature of the SOFC 10 detected by the temperature detection unit 30 (see FIG. 2F). ) Also gradually rises until time t1.

Here, in FIG. 2A, the temperature Ta is the heating temperature of the reaction air at the time of saturation output of the electric heater 44. When the temperature detected by the temperature detection unit 46 reaches the temperature Ta after the lapse of time t1, the control unit 60 increases the amount of reaction air supplied from the reaction air blower 20 based on the measured values of the flow meter 50 shown in FIG. 2B. Perform control. At the same time, as shown in FIG. 2C, the control unit 60 executes control to gradually open the regulating valve 47 from the closed state to the fully open state. Specific control of the opening degree adjustment of the adjusting valve 47 will be described later.

With this control, as shown in FIG. 2D, the temperature of the reaction air detected by the temperature detection unit 49 on the outlet side of the regenerative heat exchanger 40 gradually rises. At this time, the control unit 60 controls the opening degree of the adjusting valve 45 so that the temperature detected by the temperature detection unit 46 (see FIG. 2A), which is the outlet temperature of the reaction air of the electric heater 44, is maintained at the temperature Ta. To do. In other words, the control unit 60 controls the adjusting valve 45 according to the temperature detected by the temperature detection unit 46, and the output of the electric heater 44 is kept constant.

Since the reaction air heated by the regenerative heat exchanger 40 has a lower temperature than the reaction air heated by the electric heater 44, the temperature detected by the temperature detection unit 48 which is the inlet portion 12A of the oxidant gas flow path 12 ( (See FIG. 2E) slightly descends. However, the reaction air bypass line 43 joins the reaction air supply line 41, and the reaction air is supplied to the oxidant gas flow path 12. In other words, the reaction gas is heated by both the electric heater 44 and the regenerative heat exchanger 40 and simultaneously supplied to the oxidant gas flow path 12 (supply step) and supplied to the oxidant gas flow path 12 (SOFC10). The total amount of heat of the reaction air will be increased (see FIG. 2G). As a result, as shown in FIG. 2F, the temperature rise rate of the SOFC 10 which is the detection temperature of the temperature detection unit 30 is accelerated after the time t1 elapses as compared with the time before the time t1 elapses.

Here, the timing at which the detection temperature of the temperature detection unit 48 and the detection temperature of the temperature detection unit 30 are substantially the same is defined as the time t2, and the detection temperature is defined as the temperature Tb. Further, the timing at which the detection temperature of the temperature detection unit 30 becomes the temperature Tc which becomes the operating temperature (power generation preparation temperature) of the SOFC 10 is set as the time t3.

As shown in FIG. 2C, after the lapse of time t2, the adjusting valve 47 is adjusted to be gradually closed, and control is executed to maintain the state of a predetermined opening degree (for example, 50%) at time t3. At the same time, the control unit 60 executes control to reduce the amount of the reaction air supplied from the reaction air blower 20 to the time t3 and then maintain the constant value based on the measured value of the flow meter 50 shown in FIG. 2B. In the control of the change rate, the amount of change, and the control valve 45 in these controls, the temperature detected by the temperature detection unit 46 (see FIG. 2A) is adjusted via the control unit 60 so as to be maintained at the temperature Ta. By these controls, as shown in FIG. 2D, the temperature of the reaction air detected by the temperature detection unit 49 on the outlet side of the regenerative heat exchanger 40 rises to time t3 and is maintained constant.

By adjusting the opening degree of the regulating valve 47 after the time t2 as described above, the reaction air supplied to the regenerative heat exchanger 40 is reduced to a predetermined amount and supplied to the inlet portion 12A of the oxidant gas flow path 12. The reaction air is also reduced. In other words, the reaction air heated by the regenerative heat exchanger 40, which has a relatively low temperature in the reaction air supplied to the oxidant gas flow path 12, decreases, so that the temperature detection unit 48 after the lapse of time t2 The detection temperature of (see FIG. 2E) rises. At this time, the total amount of heat of the reaction air supplied to the oxidant gas flow path 12 (SOFC10) is substantially the same as or higher than the time t1 at the start of the reaction air supply from the regenerative heat exchanger 40 (FIG. See 2G). In this way, even after the time t2 has elapsed, the reaction air having a temperature higher than the temperature Tb is supplied to the oxidant gas flow path 12, and as shown in FIG. 2F, the SOFC 10 has a temperature detected by the temperature detection unit 30. The temperature is raised. By continuing this state until the time t3, the detection temperature of the temperature detection unit 30 becomes the operating temperature Tc of the SOFC 10, and the activation operation of the SOFC 10 is completed.

Next, with reference to FIG. 3, control of opening degree adjustment of the adjusting valve 47 in the starting operation will be described. FIG. 3A is a graph showing the time change of the temperature on the low temperature side in the regenerated heat exchanger, and FIG. 3B is a graph showing the time change of the opening degree in the adjusting valve for adjusting the flow rate of the reaction air with respect to the regenerated heat exchanger. is there.

When the time t1 elapses, as described above, the temperature detected by the temperature detection unit 46 reaches the temperature Ta (see FIG. 2A), that is, the heating temperature of the reaction air at the time of saturation output of the electric heater 44. Before the time t1 elapses, the SOFC 10 gradually rises in temperature (see FIG. 2F), and the exhaust gas flowing from the SOFC 10 through the reaction air exhaust line 42 also gradually rises in temperature. The temperature of 40 also gradually becomes high.

Immediately before time t1, the regulating valve 47 is closed and the supply of reaction air to the regenerating heat exchanger 40 is stopped. Therefore, the regenerating heat exchanger 40 is not only on the high temperature side but also on the low temperature side as well as on the high temperature side. (See FIG. 3A). Then, after the lapse of time t1, the regulating valve 47 is gradually opened from the closed state, and the reaction air is supplied to the reaction air inlet (connection portion with the reaction air supply line 41) on the low temperature side of the regenerative heat exchanger 40. To.

At this time, as a comparison method with respect to the present embodiment, for example, as shown by the alternate long and short dash line in FIG. 3B, the regulating valve 47 is opened. In the comparison method, after the lapse of time t1, the adjusting valve 47 is fully opened (valve opening 100%) in an extremely shorter time ts than reaching time t2. Then, as shown by the alternate long and short dash line in FIG. 3A, the reaction air inlet on the low temperature side of the regenerative heat exchanger 40 is cooled to the outside air temperature between the high temperature time t1 and the extremely short time ts. To. Therefore, there is a problem that a sudden temperature change occurs on the low temperature side, distortion or heat shrinkage occurs in the brazed portion of the regenerative heat exchanger 40, which causes damage to the regenerated heat exchanger 40.

Here, by introducing the outside air to the low temperature side of the regenerative heat exchanger 40 before the time t1, a sudden temperature change on the low temperature side can be avoided, but the high capacity of the reaction air blower 20 due to the increase in the air flow rate. The equipment burden will increase due to the increase in the output of the electric heater 44 and the increase in the output. In addition, problems such as a long heating time of SOFC 10 at startup occur, which is not preferable.

In this respect, in the present embodiment, the flow rate adjustment in the adjusting valve 47 is controlled by the control unit 60 so as to avoid a sudden change in the inlet temperature of the reaction air of the regenerating heat exchanger 40 (adjustment step). In such control, as shown in FIG. 3B, the opening adjustment time of the adjusting valve 47, which reaches the time t1 to the time t2, is set to be longer than the time t1 to the time ts. As a result, as shown by the solid line in FIG. 3A, the amount of temperature change per unit time becomes small, the temperature change is moderated at the inlet temperature of the reaction air of the regenerative heat exchanger 40, and the regenerative heat exchanger 40 is used. The occurrence of damage can be suppressed. As a result, it is possible to prevent the regenerative heat exchanger 40 from being unable to maintain airtightness due to damage, and it is possible to avoid a situation such as a system stop.

In such a temperature change, the opening degree of the adjusting valve 47 may be controlled by the control unit 60 so as to draw a curve shown in FIG. 3B. In the control of such an opening degree, the adjusting valve 47 is adjusted so that the value obtained by dividing the opening degree of the adjusting valve 47 by the elapsed time from the valve opening start (time t1) of the adjusting valve 47 increases as the elapsed time increases. Control. Therefore, in the graph of FIG. 3B, the slope of the curve showing the opening degree of the adjusting valve 47 gradually increases as time elapses from time t1. By controlling in this way, the amount of reaction air at the start of valve opening of the regulating valve 47 is reduced to avoid distortion of the regenerating heat exchanger 40, and the time until the regulating valve 47 is fully opened is shortened. The startup time of can be shortened.

Further, in the present embodiment, the control valve 47 can be controlled by the control unit 60 according to the detection results of the temperature detection units 51 and 52. In this case, the control unit 60 subtracts the detection result of the temperature detection unit 52, which is the temperature of the outside air, from the detection result of the temperature detection unit 51, which is the temperature of the outlet unit 12B in the oxidant gas flow path 12, and the temperature difference. Is calculated. Then, the control unit 60 adjusts to lengthen the opening degree adjusting time of the adjusting valve 47 as the temperature difference increases. In this way, the control unit 60 can increase or decrease the opening degree adjusting time of the adjusting valve 47 according to the temperature difference, avoiding a sudden temperature change on the low temperature side of the regenerating heat exchanger 40, and shortening the opening degree adjusting time. Can be better achieved at the same time.

As described above, in the fuel cell system 1, the electric heater 44 and the regenerative heat exchanger 40 are arranged in parallel. Then, the reaction air (oxidizing agent gas) is heated by both the electric heater 44 and the regenerative heat exchanger 40 from the time t1 to the time t2, which is a part of the start-up time of the SOFC 10, and is supplied to the SOFC 10.

Here, as a comparative example, when the reaction air is heated by the amount of heat of only the electric heater 44, the temperature is raised at a substantially constant rate as shown by the alternate long and short dash line in the graph of FIG. 2F. On the other hand, in the present embodiment, the amount of heat supplied to the SOFC 10 can be increased by supplying the heated reaction air from the regenerative heat exchanger 40 from the time t1 to the time t2. As a result, the rate of temperature rise of SOFC 10 can be accelerated, and the start-up time (time to reach the temperature Tc) can be shortened by the time tm in the graph of FIG. 2F.

Moreover, in the present embodiment, since the electric heater 44 and the regenerative heat exchanger 40 are arranged in parallel, the reaction air blower 20 as a supply mechanism for supplying the reaction air to them can be shared, and the supply can be made common. The number of installed mechanisms can be reduced. Further, the heating mechanism other than the regenerative heat exchanger 40 can be limited to the electric heater 44, and the conventional start burner can be omitted to reduce the size of the entire fuel cell system 1 and the equipment cost. ..

Here, in the above-mentioned start-up operation, the inlet temperature of the reaction air in the SOFC 10, that is, the detection result of the temperature detection unit 48 is controlled so as not to exceed the upper limit temperature (for example, 400 to 800 ° C., see FIG. 2E). That is, the control unit 60 acquires the detection result of the temperature detection unit 48, and adjusts the valve opening degrees of the adjusting valves 45 and 47 according to the detection result. By this adjustment, the supply amount of the reaction air to the electric heater 44 and the regenerative heat exchanger 40 is adjusted, and the high temperature reaction air is prevented from being supplied to the inlet portion 12A of the oxidant gas flow path 12. This makes it possible to prevent the SOFC 10 and its inlet from becoming too hot and damaged.

Further, since the valve opening degree of the adjusting valve 45 is adjusted according to the outlet temperature of the reaction air in the electric heater 44, that is, the detection result of the temperature detecting unit 46, the electric heater 44 becomes too hot and is damaged. Can be prevented.

Further, in the above embodiment, the internal temperature of the SOFC 10 (detection result of the temperature detection unit 30) and the temperature of the inlet portion 12A of the oxidant gas flow path 12 (detection result of the temperature detection unit 48) are substantially the same. After that, the regulating valve 47 is controlled to reduce the reaction air supplied to the regenerative heat exchanger 40 and then maintain the predetermined amount. Specifically, as shown in FIG. 2D, the temperature of the reaction air detected by the temperature detection unit 49 on the outlet side of the regenerative heat exchanger 40 is maintained constant after rising to time t3. As a result, it is possible to prevent the temperature of the regenerating heat exchanger 40 from becoming too high even after the reaction air heated by the regenerating heat exchanger 40 has been supplied to raise the temperature of the SOFC 10. As a result, it is possible to prevent the regenerated heat exchanger 40 from being damaged by the temperature difference from the reaction air having the same temperature (for example, about 20 ° C.) as the air temperature supplied through the reaction air blower 20.

[Second Embodiment]
Next, a second embodiment different from the first embodiment will be described with reference to FIG. FIG. 4 is a block diagram showing a fuel cell system according to the second embodiment. In the second embodiment, the same components as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 4, in the second embodiment, the configuration of the supply line 70 is added to the first embodiment. The upstream side of the supply line 70 branches from the outlet side of the electric heater 44 in the reaction air bypass line 43. The downstream side of the supply line 70 is connected between the branch position of the reaction air bypass line 43 in the reaction air supply line 41 and the regulating valve 47.

In the second embodiment, the oxidant gas heated by the electric heater 44 can be introduced to the upstream side of the regulating valve 47 in the reaction air supply line 41 via the supply line 70. Therefore, when the regulating valve 47 is opened, the oxidant gas heated by the electric heater 44 and the oxidant gas that becomes the outside air temperature from the reaction air blower 20 are mixed, and the oxidant gas in the regenerated heat exchanger 40 is mixed. Can be supplied to the entrance of. As a result, the oxidant gas supplied to the inlet of the regenerative heat exchanger 40 becomes higher than the outside air temperature, and even when the temperature of the inlet is raised, the sudden temperature change due to the supply of the oxidant gas is suppressed, and the regenerated heat is suppressed. Damage to the exchanger 40 can be avoided.

In each of the above embodiments, the case where the electric heater 44 is used as the heater has been described as an example, but other heating mechanisms may be used as the heater. For example, a burner.

Further, in each of the above embodiments, as shown in FIG. 2A, the output of the electric heater 44, which is the detection result of the temperature detection unit 46 after the time t1, is kept constant, but it depends on the output of the regenerative heat exchanger 40. The control unit 60 may perform control to reduce the output of the electric heater 44. In this case, the output of the electric heater 44 can be reduced by the output of the regenerative heat exchanger 40 for operation, and the start-up time may be slightly longer, but the power consumption at the time of start-up can be reduced. In other words, the effect of shortening the startup time and the effect of reducing power consumption can be obtained in a well-balanced manner.

Further, in the second embodiment, it is not necessary to control the regulating valve 47 shown by the solid line in the graph of FIG. 3 in the first embodiment, but it is better to carry out such control for regeneration. Damage to the heat exchanger 40 can be better suppressed.

The present invention is not limited to each of the above embodiments, and can be modified in various ways. In the above embodiment, the size, shape, function, and the like of the components shown in the accompanying drawings are not limited to this, and can be appropriately changed within the range in which the effects of the present invention are exhibited. In addition, it can be appropriately modified and implemented as long as it does not deviate from the scope of the object of the present invention.

The fuel cell system and its operating method of the present invention can suppress damage to the regenerated heat exchanger at the time of starting, and are suitable for application to the fuel cell system and its operating method in household, commercial and all other industrial fields. is there.

1 Fuel cell system 10 Solid oxide fuel cell (SOFC)
40 Regenerative heat exchanger 44 Electric heater (heater)
47 Control valve 51 Temperature detection unit (1st temperature detection unit)
52 Temperature detection unit (second temperature detection unit)
60 Control unit 70 Supply line

Claims (6)

Solid oxide fuel cells that generate electricity through the electrochemical reaction of fuel gas and oxidant gas,
A regenerative heat exchanger that exchanges heat from the exhaust gas from the solid oxide fuel cell with the oxidant gas supplied to the solid oxide fuel cell.
A regulating valve that adjusts the flow rate of the oxidant gas to the regenerated heat exchanger,
A control unit that controls the flow rate adjustment at the regulating valve so as to avoid a sudden change in the inlet temperature of the oxidant gas in the regenerative heat exchanger during a part of the start-up time of the solid oxide fuel cell.
A fuel cell system characterized by having. The control unit is characterized in that the regulating valve is controlled so that the value obtained by dividing the opening degree of the regulating valve by the elapsed time from the start of opening of the regulating valve increases as the elapsed time increases. The fuel cell system according to claim 1. A first temperature detection unit that detects the temperature of the exhaust gas from the solid oxide fuel cell, and
A second temperature detector that detects the temperature of the oxidant gas before it is supplied to the regenerative heat exchanger, and
With
The fuel cell system according to claim 1 or 2, wherein the control unit controls the adjustment valve according to the detection results of the first temperature detection unit and the second temperature detection unit. The control unit calculates a difference obtained by subtracting the detection result of the second temperature detection unit from the detection result of the first temperature detection unit, and increases or decreases the opening degree adjustment time of the adjustment valve according to the difference. The fuel cell system according to claim 3. Solid oxide fuel cells that generate electricity through the electrochemical reaction of fuel gas and oxidant gas,
A heater that heats the oxidant gas and supplies it to the solid oxide fuel cell,
A regenerative heat exchanger that is arranged in parallel with the heater and exchanges heat of the exhaust gas from the solid oxide fuel cell with the oxidant gas supplied to the solid oxide fuel cell.
A supply line for supplying the oxidant gas heated by the heater to the inlet of the oxidant gas in the regenerative heat exchanger.
A fuel cell system characterized by having. The solid oxide fuel cell that generates power by the electrochemical reaction of the fuel gas and the oxidant gas, and the oxidant gas that supplies the heat of the exhaust gas from the solid oxide fuel cell to the solid oxide fuel cell. A method of operating a fuel cell system, comprising: a regenerative heat exchanger that exchanges heat with the fuel cell, and a regulating valve that adjusts the flow rate of the oxidant gas with respect to the regenerated heat exchanger.
Having an adjustment step for adjusting the flow rate at the adjustment valve so as to avoid a sudden change in the inlet temperature of the oxidant gas in the regenerative heat exchanger at a part of the start-up time of the solid oxide fuel cell. A method of operating a fuel cell system characterized by.

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