JP2010257823A - Combustion device of fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect blow-out of a burner surely without inviting increase in cost in a combustion device of a fuel cell system. <P>SOLUTION: The combustion device of the fuel cell system is applied for the fuel cell system equipped with a fuel cell in which power generation is carried out by a fuel supplied to a fuel electrode and an oxidizer gas supplied to an oxidizer electrode. It includes a combustion part equipped with the burner to burn the fuel for the burner by the oxidizer gas for combustion and a combustion gas flow passage in which a combustion gas generated by the burner is circulated, a temperature sensor to detect a temperature of the combustion part, and a sending means of the oxidizer gas for combustion to the burner. As for this combustion device, a combustion instruction is carried out for the burner (step 402), and when the target sending amount is increased or maintained constant, in the case it is detected that the temperature of the combustion part drops and a pressure loss in the front and rear of the burner is reduced (step 405, 406), it is determined that the burner is blown out (step 408). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a combustion apparatus for a fuel cell system.

  As a type of a combustion apparatus for a fuel cell system, one disclosed in Patent Document 1 is known. As shown in FIG. 1 of Patent Document 1, the combustion apparatus of the fuel cell system is provided with a flame detector 12 that detects off-gas as fuel and detects the ionic current of the flame 11 formed in the combustion chamber 9. The fan 10 is controlled so that the temperature sensor 20 provided in the hydrogen generator 6 is below a predetermined temperature. In this combustion apparatus, since the hydrogen generator 6 is controlled to be equal to or lower than a predetermined temperature, the conversion rate of the raw material fuel by the reforming reaction of the hydrogen generator 6 can be reduced to a predetermined value or less, and is used for combustion. The hydrocarbon can be set to a predetermined value or more, and the ionic current of the flame 11 increases as the amount of hydrocarbon increases, so that the detection voltage at the flame detector 12 can be increased, and ignition and misfire can be ensured. It can be detected.

  As another type of combustion apparatus for a fuel cell system, one disclosed in Patent Document 2 is known. As shown in FIG. 1 of Patent Document 2, in the combustion apparatus of the fuel cell system, the burner 3 of the combustion apparatus 4 includes a flame temperature measuring thermometer 9, and the fuel burned in the burner 3 is a hydrocarbon-based fuel. Temperature thresholds (T1, T2, T3) corresponding to the case of only fuel, the mixture of exhaust hydrogen gas and hydrocarbon fuel, and the case of only exhaust hydrogen gas, respectively, are detected by the thermometer 9. And the temperature threshold value can be compared to solve the problem.

JP 2002-75412 A JP 2004-200020 A

  In the combustion apparatus described in Patent Document 1 described above, although the flame detection unit 12 can determine misfire (blown out) of the combustion chamber 9 based on the ion current, a dedicated detection unit for misfire determination ( It was expensive to provide the flame detector 12). Moreover, in the combustion apparatus described in Patent Document 2 described above, the flame temperature measurement thermometer 9 provided in the burner 3 determines the misfire (blown out) of the burner 3 based on the temperature detected by the thermometer 9. Although it can be performed, it is expensive because a dedicated detection unit (flame temperature measurement thermometer 9) for misfire determination is provided.

  The present invention has been made to solve the above-described problems, and it is an object of the present invention to reliably detect burn-out of a burner without incurring high costs in a combustion apparatus of a fuel cell system.

  In order to solve the above-mentioned problem, the constitutional feature of the invention according to claim 1 is that a fuel cell system including a fuel cell that generates electric power using a fuel supplied to the fuel electrode and an oxidant gas supplied to the oxidant electrode. Combustion device applied to the above, a combustion section comprising a burner for burning burner fuel with combustion oxidant gas, a combustion gas flow path through which combustion gas generated in the burner flows, and the temperature of the combustion section , A combustion oxidant gas delivery means for delivering combustion oxidant gas to the burner, a pressure loss reduction detection means for detecting a decrease in pressure loss before and after the burner, and a combustion oxidant A delivery amount detection means for detecting the delivery amount of the combustion oxidant gas delivered from the gas delivery means; an actual delivery amount actually detected by the delivery amount detection means; and a target delivery amount of the combustion oxidant gas delivery means. Based on , An instruction value deriving means for deriving a control instruction value to the combustion oxidant gas delivery means, and a combustion instruction when the combustion instruction is given to the burner and the target delivery amount is increased or kept constant. And a blow-off detection means for determining that the burner has blown out when it is detected that the temperature of the burner has decreased and the pressure loss before and after the burner has decreased.

  According to a second aspect of the present invention, the fuel cell system according to the first aspect further includes a reforming unit that is supplied with reforming fuel and generates reformed gas, and the fuel electrode of the fuel cell. In other words, the reformed gas is supplied as fuel, and the burner is supplied with any one of combustion fuel, reformed gas, and anode off gas as burner fuel.

  According to a third aspect of the present invention, there is provided a structural feature of the invention according to claim 1, wherein the burner uses an anode off-gas directly derived from the fuel electrode of the fuel cell as the oxidant gas for combustion. It is configured to burn with cathode off gas derived directly from the pole.

  Further, the structural feature of the invention according to claim 4 is that, in any one of claims 1 to 3, the pressure loss before and after the burner when the control instruction value derived by the instruction value deriving means decreases. It is to judge that has decreased.

  In the invention according to claim 1 configured as described above, the pressure loss reduction detecting means detects that the pressure loss before and after the burner in which the burner fuel is burned with the combustion oxidant gas is reduced. The delivery amount detection means detects the delivery amount of the combustion oxidant gas delivered from the combustion oxidant gas delivery means. The instruction value deriving means derives a control instruction value to the combustion oxidant gas delivery means based on the actually measured delivery amount actually detected by the delivery amount detection means and the target delivery amount of the combustion oxidant gas delivery means. . When the blow-off detection means gives a combustion instruction to the burner, and the target delivery amount is increased or maintained constant, the temperature of the combustion section decreases and the pressure loss before and after the burner decreases. When this is detected, it is determined that the burner has blown out. By the way, if the burner is in combustion, the burner fuel (at least the anode off gas) is supplied to the burner and the combustion oxidant gas is sent out by the combustion oxidant gas delivery means, and the burner burns (flame). Since pressure is generated, large pressure loss occurs before and after the burner. On the other hand, when the burner is blown off, the pressure due to combustion is not generated in the burner, and the pressure loss is reduced. By utilizing this phenomenon, it can be determined that the burner has blown out when it is detected that the pressure loss before and after the burner has decreased. Therefore, according to the present invention, it is possible to reliably detect the blow-out of the burner without providing a dedicated blow-off detection unit as in the prior art, that is, without increasing the cost.

  In the invention according to claim 2 configured as described above, in claim 1, the fuel cell system further includes a reforming section that is supplied with reforming fuel and generates reformed gas, and the fuel for the fuel cell The electrode is supplied with reformed gas as fuel, and the burner is supplied with any one of combustion fuel, reformed gas, and anode off-gas as burner fuel. As a result, in a fuel cell system equipped with a so-called polymer electrolyte fuel cell, it is possible to reliably detect the burn-out of the burner without being expensive and suitable for the system.

  In the invention according to claim 3 configured as described above, in claim 1, the burner uses the anode off-gas directly derived from the fuel electrode of the fuel cell as the oxidant gas for combustion. It is configured to burn with cathode off-gas derived directly from the agent electrode. As a result, in a fuel cell system including a so-called solid oxide fuel cell, it is possible to reliably detect the burn-out of the burner without being expensive and suitable for the system.

  In the invention according to claim 4 configured as described above, the pressure before and after the burner when the control instruction value derived by the instruction value deriving means decreases in any one of claims 1 to 3. Judge that the loss has decreased. Thereby, during the start-up operation of the fuel cell system, it is possible to easily and reliably detect the burn-out of the burner with a simple configuration based on the control instruction value to the combustion oxidant gas delivery means.

1 is a schematic diagram showing an outline of a first embodiment of a fuel cell system to which a combustion apparatus according to the present invention is applied. It is sectional drawing which shows the burner shown in FIG. It is a block diagram which shows the fuel cell system shown in FIG. It is a flowchart which shows the outline | summary of the control program performed with the control apparatus shown in FIG. It is a flowchart which shows the outline | summary of the control program (program for target sending amount setting) performed with the control apparatus shown in FIG. It is a flowchart which shows the outline | summary of the control program (program for carrying out feedback control of the sending amount of the combustion air) performed with the control apparatus shown in FIG. It is a flowchart which shows the outline | summary of the control program (program of the burner blow-off determination during starting driving | running | working) performed with the control apparatus shown in FIG. It is a flowchart which shows the outline | summary of the control program (program of the burner blow-off determination during electric power generation operation) performed with the control apparatus shown in FIG. It is a schematic diagram which shows the outline | summary of 2nd Embodiment of the fuel cell system to which the combustion apparatus by this invention is applied. FIG. 10 is a partial cross-sectional view of the fuel cell (cell and cell connection body) shown in FIG. 9.

1) First Embodiment Hereinafter, a first embodiment of a fuel cell system to which a combustion apparatus according to the present invention is applied will be described. FIG. 1 is a schematic diagram showing an outline of a fuel cell system including a polymer electrolyte fuel cell. The fuel cell system includes a fuel cell 10 and a reformer 20 that generates a reformed gas (fuel gas) containing hydrogen gas necessary for the fuel cell 10.

  The fuel cell 10 includes a fuel electrode 11, an air electrode 12 that is an oxidant electrode, and an electrolyte 13 interposed between the electrodes 11 and 12, and supplies the reformed gas supplied to the fuel electrode 11 and the air electrode 12. Electric power is generated using air (cathode air), which is the oxidant gas. The electrolyte 13 is a polymer electrolyte, and the fuel cell 10 is a polymer electrolyte fuel cell. Note that air-enriched gas may be supplied instead of air.

  The reformer 20 steam reforms the reforming fuel and supplies a hydrogen-rich reformed gas to the fuel cell 10. The reformer 20 includes a reforming unit 21, a cooling unit 22, a carbon monoxide shift reaction unit (hereinafter referred to as a “carbon monoxide shift reaction unit”). , A CO shift unit) 23, a carbon monoxide purification unit (hereinafter referred to as a CO purification unit) 24, a combustion unit 27, and an evaporation unit 28. Examples of the reforming fuel include natural gas, gas fuel for reforming such as LPG, and liquid fuel for reforming such as kerosene, gasoline, and methanol. In the present embodiment, description will be made on natural gas.

  The reforming unit 21 generates and derives a reformed gas from a mixed gas that is a reforming raw material in which reforming water is mixed with the reforming fuel. The reforming portion 21 is formed in a bottomed cylindrical shape, and includes an annular folded channel 21a extending along the axis in the annular cylindrical portion.

  The return channel 21 a of the reforming unit 21 is filled with a catalyst 21 b (for example, a Ru or Ni-based catalyst) and introduced from the reforming fuel introduced from the cooling unit 22 and the steam supply pipe 51. The gas mixture with the steam reacts and is reformed by the catalyst 21b to generate hydrogen gas and carbon monoxide gas (so-called steam reforming reaction). At the same time, a so-called carbon monoxide shift reaction occurs in which carbon monoxide generated in the steam reforming reaction reacts with steam to transform into hydrogen gas and carbon dioxide. These generated gases (so-called reformed gas) are led to a cooling unit (heat exchange unit) 22. The steam reforming reaction is an endothermic reaction, and the carbon monoxide shift reaction is an exothermic reaction.

  The temperature sensor 21 c is provided near the wall surface in the reforming unit 21 (near the wall surface in contact with the combustion gas flow path 26), and detects the wall surface temperature of the reforming unit 21. Although the temperature sensor 21c detects the temperature of the reforming part 21, since it is installed in the place where the combustion gas from the burner 25 hits, the temperature detected by the temperature sensor 21c is the temperature of the combustion gas (combustion part). Is well reflected. The detection result of the temperature sensor 21 c is transmitted to the control device 30.

  The cooling unit 22 is a heat exchanger (heat exchange unit) in which heat exchange is performed between the reformed gas derived from the reforming unit 21 and a mixed gas of reforming fuel and reformed water (steam). The temperature of the reformed gas having a high temperature is lowered by the mixed gas having a low temperature and led to the CO shift unit 23, and the temperature of the mixed gas is raised by the reformed gas and led to the reforming unit 21. Yes.

  Specifically, a reforming fuel supply pipe 41 connected to a fuel supply source (not shown) (for example, a city gas pipe) is connected to the cooling unit 22. The reforming fuel supply pipe 41 is provided with a fuel pump 42, a desulfurizer 46, and a reforming fuel valve 43 in order from the upstream. The reforming fuel valve 43 opens and closes the reforming fuel supply pipe 41. The fuel pump 42 is reforming fuel supply means for supplying reforming fuel and adjusting the supply amount. The desulfurizer 46 reduces the sulfur content (for example, sulfur compound) in the fuel. Of the fuel supplied from the fuel supply source, the fuel supplied to the reforming unit 21 and reformed is called reforming fuel, and the fuel supplied to the burner 25 and combusted is called combustion fuel.

  A combustion fuel supply pipe 44 connected to a combustion air supply pipe 64 connected to the burner 25 is connected between the desulfurizer 46 and the reforming fuel valve 43 of the reforming fuel supply pipe 41. ing. A combustion fuel valve 45 is provided in the combustion fuel supply pipe 44. The combustion fuel valve 45 opens and closes the combustion fuel supply pipe 44. When the fuel pump 42 is driven and the reforming fuel valve 43 is closed and the combustion fuel valve 45 is opened, combustion fuel is supplied to the burner 25, and the fuel pump 42 is driven and the reforming fuel valve. When 43 is opened and the combustion fuel valve 45 is closed, the reforming fuel is supplied to the reforming unit 21.

  Further, a steam supply pipe 51 connected to the evaporation section 28 is connected between the reforming fuel valve 43 and the cooling section 22 of the reforming fuel supply pipe 41. The steam supplied from the evaporation unit 28 is mixed with the reforming fuel, and the mixed gas is supplied to the reforming unit 21 through the cooling unit 22.

  The CO shift unit 23 is a unit that reduces carbon monoxide in the reformed gas supplied from the reforming unit 21 through the cooling unit 22, that is, a carbon monoxide reducing unit. The CO shift unit 23 includes a folded channel 23a extending along the vertical direction. The return channel 23a is filled with a catalyst 23b (for example, a Cu—Zn-based catalyst). In the CO shift unit 23, a so-called carbon monoxide shift reaction in which carbon monoxide and water vapor contained in the reformed gas introduced from the cooling unit 22 react with the catalyst 23b to be converted into hydrogen gas and carbon dioxide gas. Has occurred. This carbon monoxide shift reaction is an exothermic reaction.

  In the CO shift unit 23, a temperature sensor 23c that measures the temperature in the CO shift unit 23 is provided. The detection result of the temperature sensor 23 c is transmitted to the control device 30.

  The CO purifying unit 24 further reduces the carbon monoxide in the reformed gas supplied from the CO shift unit 23 and supplies it to the fuel cell 10, that is, a carbon monoxide reducing unit. The CO purification unit 24 is formed in a cylindrical shape, and is provided so as to cover the outer peripheral wall of the evaporation unit 28. The inside of the CO purification unit 24 is filled with a catalyst 24a (for example, a Ru or Pt catalyst).

  Further, a temperature sensor 24 b that measures the temperature in the CO purification unit 24 is provided in the CO purification unit 24. The detection result of the temperature sensor 24 b is transmitted to the control device 30.

  A connecting pipe 89 connected to the CO shift unit 23 and a reformed gas supply pipe 71 connected to the fuel electrode 11 of the fuel cell 10 are connected to the lower side wall surface and the upper side wall surface of the CO purification unit 24, respectively. Yes. An oxidation air supply pipe 61 is connected to the connection pipe 89. As a result, the reforming gas from the CO shift unit 23 and the oxidizing air from the atmosphere are introduced into the CO purification unit 24. The oxidizing air supply pipe 61 is provided with an oxidizing air pump 62 and an oxidizing air valve 63 in order from the upstream. The oxidizing air pump 62 supplies oxidizing air and adjusts the supply amount. The oxidation air valve 63 opens and closes the oxidation air supply pipe 61.

  Therefore, carbon monoxide in the reformed gas introduced into the CO purification unit 24 reacts (oxidizes) with oxygen in the oxidizing air to become carbon dioxide. This reaction is an exothermic reaction and is promoted by the catalyst 24a. Thereby, the reformed gas is derived by further reducing the carbon monoxide concentration (10 ppm or less) by the oxidation reaction, and is supplied to the fuel electrode 11 of the fuel cell 10.

  The CO purification unit 24 is connected to the inlet of the fuel electrode 11 of the fuel cell 10 via a reformed gas supply pipe 71, and the burner 25 is connected to the outlet of the fuel electrode 11 via an offgas supply pipe 72. Has been. The bypass pipe 73 bypasses the fuel cell 10 and directly connects the reformed gas supply pipe 71 and the offgas supply pipe 72. The reformed gas supply pipe 71 is provided with a first reformed gas valve 74 between the branch point of the bypass pipe 73 and the fuel cell 10. The off gas supply pipe 72 is provided with an off gas valve 75 between the junction with the bypass pipe 73 and the fuel cell 10. A second reformed gas valve 76 is provided in the bypass pipe 73.

  During the start-up operation, the first reformed gas valve 74 and the offgas valve 75 are closed to avoid the supply of the reformed gas having a high carbon monoxide concentration from the reformer 20 to the fuel cell 10. During the steady operation (power generation operation), the first reformed gas valve 74 and the offgas valve 75 are opened to supply the reformed gas from the reformer 20 to the fuel cell 10 during the steady operation (power generation operation). Is closed.

  A cathode air supply pipe 67 is connected to the inlet of the air electrode 12 of the fuel cell 10, and an exhaust pipe 82 is connected to the outlet of the air electrode 12. Air is supplied to the air electrode 12, and off-gas is exhausted. The cathode air supply pipe 67 is provided with a cathode air pump 68 and a cathode air valve 69 in order from the upstream. The cathode air pump 68 supplies cathode air and adjusts the supply amount. The cathode air valve 69 opens and closes the cathode air supply pipe 67.

  The combustion unit 27 is supplied with at least the anode off-gas from the fuel electrode 11 and burns the anode off-gas with combustion air (combustion oxidant gas), and the combustion gas generated in the burner 25 evaporates the reforming unit 21 and evaporates. And a combustion gas passage 26 that circulates while heating the portion 26. In the present embodiment, the burner 25 is supplied with any of combustion fuel, reformed gas, and anode off gas.

  The lower end of the burner 25 is inserted into the inner peripheral wall of the reforming part 21 and is arranged with a space. As shown in FIG. 2, the burner 25 includes a base 25a, a cylindrical combustion cylinder 25b provided on the base 25a and communicating with the base 25a, an off-gas nozzle 25c, a temperature sensor 25e, an ignition electrode (igniter). ) 25g.

  A combustion air supply pipe 64 is connected to the side surface of the base 25a, and combustion air is introduced into the space 25a1 in the base 25a. The upper end (one end) of the combustion cylinder 25b is connected to the lower plate portion of the base portion 25a, and the lower side (the other end) is opened. A disc-shaped partition plate 25b1 is provided in the middle of the combustion cylinder 25b in the longitudinal direction (for example, the lower end side from the middle), and partitions the combustion cylinder 25b in the longitudinal direction.

  The base end portion of the off-gas nozzle 25c is connected to the inner wall surface of the upper plate portion of the base portion 25a and communicates with the connection path 25a2. The connection path 25a2 communicates with the off gas supply pipe 72. The tip portion of the off-gas nozzle 25c passes through the center of the partition plate 25b1 and extends to the combustion space 25d. The tip portion of the off-gas nozzle 25c is closed, and a first injection port 25c1 is provided on a side surface portion slightly away from the tip. The first injection port 25c1 has a substantially circular cross section, and a plurality (four in this embodiment) are provided.

  The temperature sensor 25e detects the radiation temperature of the flame 25f generated in the combustion space 25d of the burner 25 and transmits the detection result to the control device 30 (for example, a radiation thermometer). The temperature sensor 25e is a sheath thermocouple, and is inserted into the combustion space 25d through the upper plate portion of the base portion 25a and through the partition plate 25b1. The tip portion (slightly behind the tip 25e1) is a temperature measurement unit. The tip 25e1 of the temperature sensor 25e is provided so as to be closer to the partition plate 25b1 than the end 25c2 of the first injection port 25c1 on the partition plate 25b1 side, but is not limited thereto. Any position where the temperature measuring unit of the temperature sensor 25e can measure the radiation temperature of the flame 25f may be used. Specifically, it suffices if it is outside the flame surface 25f1 of the flame 25f inside the combustion space 25d. Here, the flame surface refers to a boundary surface between a portion where a combustion reaction (oxidation reaction) of a burner fuel gas (for example, anode off gas) as a burner fuel occurs and the other portion. The combustion space 25d is a portion provided for burning the burner fuel gas, and is a space on the side where the tip of the off-gas nozzle 25c of the partition plate 25b1 protrudes in the combustion cylinder 25b. In the present embodiment, a thermocouple is used as the temperature sensor 25e, but a thermistor may be used.

  A plurality of second injection ports 25b2 (20 in the embodiment) are provided around the off-gas nozzle 25c of the partition plate 25b1. The anode off-gas and the reformed gas are supplied from the off-gas supply pipe 72 through the connection path 25a2 to the off-gas nozzle 25c, and are introduced into the combustion space 25d from the first injection port 25c1. Combustion air is supplied from the combustion air supply pipe 64 to the space 25a1 in the base 25a, passes between the combustion cylinder 25b and the off-gas nozzle 25c, and is introduced into the combustion space 25d from the second injection port 25b2. The anode off gas (or reformed gas) introduced into the combustion space 25d is burned by the combustion air to form a flame 25f. The off-gas nozzle 25c is used not only for off-gas but also for reformed gas that bypasses the fuel cell 10. On the other hand, the combustion fuel is premixed with air and supplied from the combustion air supply pipe 64.

  According to the burner 25 having such a configuration, it is possible to perform diffusion combustion in which the anode off-gas or the reformed gas introduced from the first injection port 25a1 is burned by the combustion air input from the second injection port 25a2. . Further, it is possible to perform premixed combustion in which combustion fuel is mixed with combustion air in advance and injected from the second injection port 25a2 for combustion.

  The ignition electrode 25g penetrates the upper plate portion of the base portion 25a and penetrates the partition plate 25b1. The front end portion of the ignition electrode 25g extends to the combustion space 25d, and is arranged at a distance where sparks fly to the front end portion of the off-gas nozzle 25c. The ignition power 25g is insulated and fixed at the upper plate portion of the base portion 25a and the penetrating portion of the partition plate 25b1, and sparks fly from the tip portion of the ignition electrode 25g to the off-gas nozzle 25c. The ignition electrode 25g is controlled by a command from the control device 30 so that a spark can fly. The burner 25 is ignited by the ignition electrode 25g in accordance with a command from the control device 30.

  Combustion fuel, reformed gas, or anode off-gas supplied to the burner 25 (these are combustible gas and burner fuel gas) are combusted by the combustion air supplied to the burner 25 and are heated to a high temperature. Combustion gas is generated. As shown in FIG. 1, this combustion gas is formed between the burner 25 and the reforming unit 21, between the reforming unit 21 and the heat insulating unit 29, and between the heat insulating unit 29 and the evaporation unit 28. The gas flows through the combustion gas passage 26 disposed so as to heat the mass portion 21 and the evaporation portion 28, and is discharged to the outside through the exhaust pipe 81 as combustion exhaust gas. The combustion gas channel 26 is a folded channel. The combustion gas heats the reforming catalyst 21a of the reforming unit 21 so as to be in the activation temperature range, and heats the evaporation unit 28 to generate water vapor.

  As shown in FIG. 1, the combustion air supply pipe 64 is provided with a combustion air pump (combustion oxidant gas delivery means) 65, a flow meter 64a, and a combustion air valve 66. The combustion air pump 65 sucks combustion air from the atmosphere and discharges (sends) the combustion air to the burner 25, and adjusts the amount of combustion air supplied to the burner 25 in accordance with a command from the control device 30. The flow meter 64 a is for measuring the volume or mass of the combustion air flowing through the combustion air supply pipe 64 per unit time, and the detection result is sent to the control device 30. . Since the flow meter 64 a is provided on the discharge side of the combustion air pump 65, the flow meter 64 a is a delivery amount detection means for detecting the delivery amount of the combustion air sent from the combustion air pump 65. The combustion air valve 66 opens and closes the combustion air supply pipe 64 in accordance with a command from the control device 30.

  The evaporation unit 28 evaporates the supplied reforming water to generate water vapor, and supplies it to the reforming unit 21 via the cooling unit 22. The evaporating section 28 is formed in a cylindrical shape so as to cover and contact the outer peripheral wall of the combustion gas passage 26 (outermost combustion gas passage).

  A water supply pipe 52 connected to a reforming water tank (not shown) is connected to a lower portion (for example, a lower portion of the side wall surface and a bottom surface) of the evaporation section 28. A steam supply pipe 51 is connected to the upper part of the evaporation unit 28 (for example, the upper part of the side wall surface). The reformed water introduced from the reformed water tank is heated by the heat from the combustion gas and the heat from the CO purifying unit 24 in the course of flowing through the evaporation unit 28 to become water vapor and the steam supply pipe 51 and It is led out to the reforming unit 21 via the cooling unit 22. The water supply pipe 52 is provided with a reforming water pump 53 and a reforming water valve 54 in order from the upstream. The reforming water pump 53 supplies reforming water to the evaporation unit 28 and adjusts the reforming water supply amount. The reforming water valve 54 opens and closes the water supply pipe 52.

  In addition, the evaporation unit 28 is provided with a temperature sensor 28 a that detects the temperature in the evaporation unit 28. It is desirable to provide the temperature sensor 28a in the downstream part (exit side) in the evaporation part 28. The temperature sensor 28a needs to be provided on the outlet side of the portion of the evaporation unit 28 where liquid water is present. Specifically, the temperature sensor 28 a is provided in a portion above the water surface in the evaporation unit 28. The temperature sensor 28a may be provided in the vaporizer outlet provided above the water surface in the evaporator 28 or in the steam supply pipe 51 near the evaporator outlet. The detection result of the temperature sensor 28 a is transmitted to the control device 30.

  The fuel cell system also includes a control device 30. The control device 30 includes the temperature sensors 21c, 23c, 24b, 25e, and 28a, the flow meter 64a, and the pumps 42, 53, 62, 65, and 68 described above. The valves 43, 45, 54, 63, 66, 69, 74, 75, and 76 and the ignition electrode 25g are connected (see FIG. 3). The control device 30 includes a microcomputer (not shown), and the microcomputer includes an input / output interface, a CPU, a RAM, and a ROM (all not shown) connected through a bus. The CPU, based on the temperature from the temperature sensors 21c, 23c, 24b, 25e, 28a, the flow rate from the flow meter 64a, etc., each pump 42, 53, 62, 65, 68, each valve 43, 45, 54, 63. , 66, 69, 74, 75, 76 and the ignition electrode 25g are controlled to control the operation of the fuel cell system. The RAM temporarily stores variables necessary for executing the program, and the ROM stores the program.

  Next, an outline of the operation of the fuel cell system described above will be described with reference to FIG. When main power (not shown) is turned on, control device 30 starts the program at step 100 and advances the program to step 102. In step 102, the control device 30 determines whether or not to start operation of the system. When the start switch (not shown) is pressed and the operation is started, or when the operation is started according to the operation plan, the control device 30 determines “YES” in step 102 as an instruction to start the system. The warming-up (startup sequence) of the reformer 20 is started (step 104). Otherwise, the determination of “NO” is repeatedly executed at step 102.

  The start-up sequence is start-up control in which the start-up operation (warm-up operation) is performed by starting the operation of the fuel cell system and the reformer 20. The start-up operation (warm-up operation) is an operation for warming up the reformer 20, that is, warms up the catalysts 21b, 23b, and 24a of the reforming unit 21, the CO shift unit 23, and the CO purification unit 24 to the active temperature range. The operation is performed until the carbon monoxide concentration in the reformed gas derived from the reformer 20 is reduced to a predetermined concentration or less and the reformed gas can be supplied to the fuel cell 10 (power generation operation). is there.

  In the startup sequence, processing from ignition of the burner 25 to completion of warming up of the reformer 20 is performed. In this starting sequence, i) the burner 25 is ignited by the fuel for combustion, ii) the reforming water is introduced when the combustion unit 27 reaches a predetermined temperature (300 ° C.), and iii) when the vaporization unit 28 starts generating steam. The reforming fuel is introduced to switch the combustion of the burner 25 by the combustion fuel to the combustion by the reformed gas. Iv) The CO shift unit 23 and the subsequent parts are warmed up.

  When there is an activation instruction, the control device 30 starts an activation sequence in step 104. That is, the control device 30 opens the combustion air valve 66 and drives the combustion air pump 65 to supply the combustion air to the burner 25. Then, the control device 30 energizes the ignition electrode 25g of the burner 25. Further, the control device 30 opens the combustion fuel valve 45 and drives the fuel pump 42 to supply the combustion fuel to the burner 25. Thereby, the burner 25 is ignited. Thereafter, the control device 30 executes the processes after ii) of the above-described activation sequence.

  When the burner 25 ignites, the control device 30 detects (determines) whether or not water vapor is generated in the evaporation unit 28 in step 106. The control device 30 detects the temperature of the evaporation unit 28, and detects that water vapor is generated if the temperature (evaporation unit temperature T1) is higher than a predetermined temperature T1-a (for example, 100 ° C.). . Before the water vapor is generated, the evaporation unit temperature T1 is equal to or lower than the predetermined temperature T1-a, and therefore no water vapor is generated. Therefore, the control device 30 determines “YES” in step 106 and continues the activation sequence ( Step 108).

  In step 108, the control device 30 starts to add reforming water when the temperature T3 of the combustion unit 27 reaches a predetermined temperature (for example, 300 ° C.). At this time, the control device 30 opens the reforming water valve 54 and drives the reforming water pump 53. Further, the control device 30 also opens the second reformed gas valve 76 to allow the reforming device 20 (CO purification unit 24) to communicate with the burner 25 and thus communicate with the atmosphere. As a result, when water vapor starts to be supplied from the evaporation unit 28 to the reforming unit 21, the water vapor passes through the cooling unit 22, the CO shift unit 23, and the CO purification unit 24 to the burner 25 via the bypass pipe 73. The gas is supplied and discharged to the outside through the combustion gas flow path 26 and the exhaust pipe 81.

  The control device 30 continues the combustion of the burner 25 by the fuel for combustion until the generation of water vapor in the evaporation unit 28 is detected after the start of the reforming water (the determination of “YES” is repeated in step 106) (intermittent). The start-up sequence is continued (step 108). It should be noted that the start of charging the reforming water may be performed in step 104 instead of step 108. In step 108, the combustion of the burner 25 by the combustion fuel and the introduction of reforming water are continued.

  When the burner 25 is ignited, the combustion gas heats the reforming unit 21, the evaporation unit 28, and the CO purification unit 24 while passing through the combustion gas channel 26. Therefore, the evaporator temperature T1 also increases. If the evaporation part temperature T1 becomes higher than the predetermined temperature T1-a during the startup sequence, the control device 30 detects that water vapor has been generated and advances the program to step 110. That is, when the controller 30 detects the generation of water vapor in the evaporating unit 28 after starting the introduction of the reforming water (determined “NO” in step 106), the control device 30 advances the program to step 110.

  In step 110, the control device 30 stops combustion in the burner 25 and purges the combustion unit 27 with combustion air (combustion air purge mode). Specifically, the control device 30 stops driving the fuel pump 42, closes the combustion fuel valve 45, stops the supply of the fuel for combustion to the burner 25, and keeps the combustion air valve 66 open. The combustion air pump 65 is continuously driven and the combustion air supply to the burner 25 is continued. In the present embodiment, the supply amount of combustion air is set to a value (the supply amount is A-1) larger than the supply amount (supply amount A-0). By increasing the supply amount, the combustion unit 27 can be efficiently purged and the heat of the reforming unit 21 can be efficiently transferred to the evaporation unit 28. In addition, the supply amount of the reforming water at this time is maintained at the supply amount W-1. The reforming unit 21 communicates with the atmosphere through the burner 25 (opened).

  The control device 30 continues the combustion air purge mode described above until the predetermined time ΔTM-a has elapsed from the time when the generation of water vapor is detected (the determination of “NO” is repeated in step 112). The predetermined time ΔTM-a is set to a value corresponding to the time until the first (tip) portion of the water vapor generated in the evaporation section 28 passes through the burner 25 at least. According to this, when a predetermined time ΔTM-a has elapsed since the detection of the generation of water vapor, the generated water vapor is a gas (in the present embodiment, present in the reformer 20 while the fuel cell system is shut down). , Gas mainly composed of reforming fuel enclosed or used for purging in the stop operation), that is, for reforming remaining (residual) from the inside of the evaporation section 28 to the second reformed gas valve 76 of the bypass pipe 73. A gas containing fuel as a main component is discharged from the burner 25 to the combustion gas passage 26 and then discharged to the outside.

  In step 112, the control device 30 determines whether or not the elapsed time ΔTM from the time when the combustion air purge mode is started, that is, when the generation of water vapor in the evaporator 28 is detected is equal to or longer than the predetermined time ΔTM-a. Determine.

  When a predetermined time ΔTM-a has elapsed from the time when the generation of water vapor is detected (determined as “YES” in step 112), the control device 30 ends the combustion air purge mode, restarts the start-up sequence, and restarts the burner 25. Ignition is started (step 114). Specifically, the control device 30 continues to supply the reforming water (supply amount W-1) to decrease the supply amount of combustion air from A-1 to A-0, and the predetermined time ΔTM-a has elapsed. At this point, the reforming fuel starts to be fed and the energization to the ignition electrode 25g is started.

  When charging of the reforming fuel into the reforming unit 21 is started, generation of reformed gas is started in the reforming unit 21 by the reforming reaction described above, and the generated reformed gas passes through the bypass pipe 76. It is supplied to the burner 25. Note that the time required for the reforming fuel to flow into the reforming unit 21 and the reformed gas generated in the reforming unit 21 from when the reforming fuel is started to flow into the combustion space 25d. It takes at least the total time with the time required for the reformed gas to flow into the combustion space 25d of the burner 25. Therefore, the ignition by the burner 25 is performed at least when the above-mentioned total time has elapsed since the start of the charging of the reforming fuel.

  As described above, the reformer 20, that is, the reforming unit 21, the CO shift unit 23, and the CO purifier is generated by generating the reformed gas by supplying the reforming fuel and burning by reignition of the burner 25 by the reformed gas. The part 24 is warmed up.

  The control device 30 determines completion of the start-up sequence (completion of warm-up operation) based on the temperatures (any temperature) of the CO shift unit 23 and the CO purification unit 24. When the temperature of each of the CO shift unit 23 and the CO purification unit 24 (any temperature) is equal to or higher than a predetermined temperature, the control device 30 causes the carbon monoxide concentration in the reformed gas to be equal to or lower than the predetermined concentration. As a result, it is determined that the activation sequence has been completed.

  If control device 30 determines that the startup sequence has been completed (determined as “YES” in step 116), it starts power generation operation (step 118). Specifically, the control device 30 opens the first reformed gas valve 74 and the off-gas valve 75 and closes the second reformed gas valve 76 to connect the CO purification unit 24 to the inlet of the fuel electrode 11 of the fuel cell 10. The outlet of the fuel electrode 11 is connected to the burner 25. During the power generation operation, the control device 30 generates power so as to follow the user load within a range of the maximum output or less.

  In a fuel cell system during power generation operation, when a stop switch (not shown) is pressed and the operation is stopped, or when the operation is stopped according to the operation plan, it is determined that there is an instruction to stop the system, and the control device 30 Determines “YES” in step 120 and performs a stop operation (step 122). The control device 30 stops driving the fuel pump 42, stops the supply of reforming fuel, and closes the reforming fuel valve 43. The control device 30 stops the driving of the reforming water pump 53, stops the supply of the reforming water, and closes the reforming water valve 54. The control device 30 stops the driving of the oxidizing air pump 62, stops the supply of the oxidizing air, and closes the oxidizing air valve 63. The control device 30 stops the driving of the combustion air pump 65 after cooling the temperature of the reforming unit 21 and the like to a predetermined temperature by the combustion air purge, stops the supply of the combustion air, and closes the combustion air valve 66. . Then, the control device 30 closes the first reformed gas valve 74, the offgas valve 75, and the second reformed gas valve 76. Thereby, the power generation of the fuel cell 10 is stopped.

  Thereafter, when the temperature of the reforming apparatus 20 is lowered and the inside becomes a negative pressure, the reforming fuel valve 43 is opened and the fuel pump 42 is driven to supply the reforming fuel to the reforming apparatus 20. Thereby, the inside of the reformer 20 is sealed with the reforming fuel. Further, instead of this sealing, the reformer 20 may be purged with reforming fuel. In any case, since the inside of the reformer 20 is filled with the reforming fuel while the fuel cell system is stopped, the catalyst and the like can be protected from the oxidizing atmosphere.

  Furthermore, blow-off detection (determination) of the burner 25 will be described in detail with reference to FIGS. The control device 30 sets (derived) a target delivery amount of the combustion air pump 65 that sends combustion air to the burner 25. When the main power supply (not shown) is turned on, the control device 30 starts the program in step 200 shown in FIG. 5 and executes the processing of step 202 every predetermined short time. In step 202, the control device 30 sets a target delivery amount.

In the start-up operation mode, the target delivery amount is set based on whether the burner 25 is in combustion or is in a state where combustion is stopped (blown out). The target delivery amount (for example, the supply amount A-1 described above) while combustion is stopped (blow-off) is set to a value larger than the target delivery amount during combustion (for example, the supply amount A-0 described above). Any target delivery amount is stored in the control device 30 in advance.
In the power generation operation mode, the target delivery amount is set based on the power consumption, that is, the amount of reforming fuel input.

  Next, the control device 30 drives the combustion air pump 65 by feedback control. That is, the combustion pump 65 is driven so that the actual delivery amount (actual delivery amount) of the combustion pump 65 becomes the target delivery amount. When the main power supply (not shown) is turned on, the control device 30 starts the program at step 300 shown in FIG. 6 and executes the processing after step 302 every predetermined short time. In step 302, the control device 30 reads the set target delivery amount, and in step 304, reads the actual flow rate (actual flow rate) of the combustion air measured by the flow meter 64a. It is assumed that the actual flow rate measured by the flow meter 64a is equal to the actually measured delivery amount. This is because the flow meter 64 a is installed near the discharge port of the combustion air 65.

  When the actual flow rate is equal to the target delivery amount, the control device 30 instructs the combustion air pump 65 to maintain the delivery amount at that time (step 308). When the actual flow rate is smaller than the target delivery amount, the control device 30 instructs the combustion air pump 65 to increase the delivery amount (step 310). The increase amount is set to a predetermined value. That is, the instruction value is increased by a predetermined value. When the actual flow rate is larger than the target delivery amount, the control device 30 instructs the combustion air pump 65 to reduce the delivery amount (step 312). The decrease amount is set to a predetermined value. That is, the indicated value is decreased by a predetermined value.

  In this manner, the control device 30 controls the control command value (simply the command value) to the combustion air pump 65 based on the actually measured delivery amount actually detected by the flow meter 64a and the target delivery amount of the combustion air pump 65. (Indicated value deriving means).

  And the control apparatus 30 performs the blow-off detection process of the burner 25. FIG. First, blow-off detection during start-up operation will be described with reference to FIG. When the main power supply (not shown) is turned on, the control device 30 starts the program at step 400 shown in FIG. 7, and executes the processing after step 402 every predetermined short time. In step 402, control device 30 determines whether there is a combustion instruction for burner 25. The combustion instruction is an instruction issued to burn the burner 25. For example, this combustion instruction is issued together with the start instruction in the start operation mode, or is issued at the time of re-ignition. However, no combustion instruction is issued in the combustion air purge mode.

  In the combustion air purge mode and the stop operation mode, since it is not necessary to burn the burner 25, no combustion instruction is issued. Therefore, the control device 30 determines “NO” in step 402, and advances the program to step 412. This flowchart is temporarily ended. On the other hand, in the case where the burner 25 is burned in the start-up operation mode or in the power generation operation mode, a combustion instruction is issued to burn the burner 25. Therefore, the control device 30 determines “YES” in step 402 and executes the program. Proceed to step 404.

  During the blow-off detection, the control device 30 keeps the target delivery amount of the combustion air pump 65 constant or increases it by a predetermined amount so as to keep the delivery amount of the combustion air pump 65 constant or Increase (step 404). Then, the control device 30 detects the pressure loss reduction before and after the burner 25, that is, detects the blow-off of the burner 25. Although the delivery amount of the combustion air pump 65 is increased, the supply amount of the burner fuel gas such as the combustion fuel is not changed, and the supply amount up to that is maintained. Further, it is desirable that the blow-off detection process is performed after the flame is stabilized after the burner 25 is ignited. Moreover, maintaining constant means maintaining the target sending amount just before the start of blow-off detection. Further, it is desirable that the predetermined amount to be increased is set to a value smaller than the actual flow rate that increases when the burner 25 blows off. This is because if the value is set to a large value, the instruction value may be increased by feedback control.

  During the start-up operation, the control device 30 keeps the target delivery amount constant or increases the combustion part temperature during the increase control within a predetermined rate of increase, and the instruction value to the combustion air pump 65 decreases. Judged to blow out.

  That is, in step 405, the controller 30 reads the temperature of the combustion unit 27 detected by the temperature sensor 25e in step 405, and the temperature of the combustion unit 27 temporarily decreases based on the read temperature (step 405). It is determined whether or not (decrease). Control device 30 determines “YES” when it descends, advances the program to step 406, otherwise determines “NO”, and advances the program to step 410.

  In step 406, the control device 30 detects (determines) that the pressure loss before and after the burner 25 has decreased by determining whether or not the indicated value to the combustion air pump 65 has decreased. For example, the instruction value read last time is compared with the instruction value read this time, and if the current instruction value is small, it is determined that the instruction value has decreased. When the indicated value to the combustion air pump 65 has decreased, the control device 30 determines “YES” in step 406, that is, detects (determines) that the pressure loss before and after the burner 25 has decreased. (Pressure loss reduction detection means). Eventually, the control device 30 determines in step 408 that the burner 25 has been blown off (blow-off detection means). On the other hand, if the indicated value to the combustion air pump 65 has not decreased, the control device 30 determines “NO” in step 406, that is, detects that the pressure loss before and after the burner 25 has not decreased. (judge. As a result, the control apparatus 30 determines in step 410 that the burner 25 is not blown out.

  That is, as a result of feedback control of the amount of combustion air delivered, the control device 30 causes the flame of the burner 25 to disappear if the indicated value of the combustion air pump 65 decreases, thereby causing a pressure loss before and after the burner 25. Is determined to have decreased, and it is detected that the burner 25 has blown off. On the other hand, if the indicated value of the combustion air pump 65 has not decreased, it is determined that the flame of the burner 25 is maintained, the pressure loss before and after the burner 25 has not decreased, and the burner 25 has not blown out. Detect the effect.

  This is due to the following reason. If the burner 25 is in combustion, the burner fuel gas (at least the anode off-gas) is supplied to the burner 25 and combustion air is sent out by the combustion air pump 65, and the pressure due to combustion (flame) in the burner 25 is increased. Because of this, a large pressure loss occurs before and after the burner 25. On the other hand, if the burning burner 25 is blown off, combustion (flame) disappears in the burner 25, so that the pressure loss before and after the burner 25 decreases more rapidly than before. That is, the combustion air having a relatively high pressure that exists between the combustion air pump 65 and the burner 25 flows toward the burner 25 vigorously. Therefore, the actual flow rate measured by the flow meter 64a is a larger value than before. Then, the actual flow rate becomes larger than the target delivery amount. Further, since the control instruction value to the combustion air pump 65 is feedback-controlled, the instruction value is decreased if the actual flow rate becomes larger than the target delivery amount.

  Next, blow-off detection during power generation operation will be described with reference to FIG. Basically, the process is the same as the blow-off detection during the start-up operation, and the same process is denoted by the same reference numeral and the description thereof is omitted. Note that the blow-off detection during the power generation operation is not desirably performed when the power generation fluctuates, and is desirably performed while maintaining the power generation amount constant.

  In the flowchart shown in FIG. 8, the process of step 502 is performed instead of the process of step 404 of the flowchart shown in FIG.

  During the power generation operation, the control device 30 keeps the target delivery amount constant or the combustion part temperature decreases during the increase control within a predetermined increase rate, and the indicated value to the combustion air pump 65 decreases. Judged to blow out.

  That is, in step 502, the control device 30 determines whether or not the target delivery amount is fixed for a predetermined time (predetermined time). If “YES”, the program proceeds to step 504, and if “NO”, the program is executed. Proceed to END (step 412). Since this flow is always executed during the power generation operation, it is executed again from START in step 400. In this embodiment, it is determined at step 502 that the target delivery amount is fixed, but it may be increased within a predetermined rate of increase. Further, during the power generation operation, the state of the target delivery amount is detected and determined. On the other hand, during the start-up operation, the target delivery amount is actively controlled so as to be constant or increased.

  When the target delivery amount of the combustion air pump 65 is kept constant for a certain period of time and the temperature of the combustion unit 27 decreases (when it is determined “YES” in steps 502 and 504, respectively), the control device 30 ), Pressure loss reduction before and after the burner 25, that is, blow-off detection of the burner 25 is detected. When increasing the delivery amount of the combustion air pump 65, the supply amount of the burner fuel gas such as combustion fuel is not changed, and the supply amount up to that time is maintained. Further, it is desirable that the blow-off detection process is performed after the flame is stabilized after the burner 25 is ignited. Also, the increase in the delivery amount at this time is preferably set to a value smaller than the actual flow rate that increases as the burner 25 blows off, as in the case of the start-up operation.

  In step 504, the control device 30 reads the temperature of the combustion unit 27 detected by the temperature sensor 25e, and determines whether or not the temperature of the combustion unit 27 has once decreased (decreased) based on the read temperature. For example, the past data is stored, and it is determined whether or not the data once descends from the data and rises again. As the temperature of the combustion unit 27, the temperature detected by the temperature sensor 21c (the reforming unit wall surface temperature) may be used.

  Steam supplied to the burner 25 by increasing the delivery amount of the combustion air without changing the supply amount of the fuel gas for the burner and, as a result, the temperature of the combustion section 27 is once lowered as a condition for detecting blow-off. The influence by the fluctuation | variation of the pressure loss accompanying the fluctuation | variation of quantity can be suppressed. Therefore, blow-off can be detected even during the power generation operation.

  As is clear from the above-described embodiment, the pressure loss reduction detecting means (step 406) is supplied with anode off-gas, reformed gas, and combustion fuel from the fuel electrode 11, and burns the burnable combustible gas with combustion air. It is detected that the pressure loss before and after the burner 25 is reduced. The delivery amount detection means (flow meter 64a) detects the delivery amount of the combustion oxidant gas sent from the combustion oxidant gas delivery means (combustion air pump 65). The instruction value deriving means (flow chart of FIG. 6) is based on the actual delivery amount actually detected by the delivery amount detection means (flow meter 64a) and the target delivery amount of the combustion oxidant gas delivery means combustion air pump 65. Then, the control instruction value to the combustion air pump 65 is derived. When the blow-off detection means (step 408) gives a combustion instruction to the burner 25 and the target delivery amount is increased or kept constant, the temperature of the combustion section 27 decreases and the burner 25 When it is detected that the pressure loss in the front and rear is reduced, it is determined that the burner 25 has blown out. By the way, if the burner 25 is in combustion, the burner fuel (at least the anode off gas) is supplied to the burner 25 and the combustion oxidant gas is sent out by the combustion oxidant gas delivery means and burned in the burner 25 ( A large pressure loss occurs before and after the burner 25 because of the pressure generated by the flame. On the other hand, when the burner 25 is blown off, the pressure due to combustion is not generated in the burner 25, and therefore the pressure loss is reduced. By utilizing this phenomenon, it can be determined that the burner 25 has blown out when it is detected that the pressure loss before and after the burner 25 has decreased. Therefore, according to the present invention, it is possible to reliably detect the blow-off of the burner 25 without providing a dedicated blow-off detection unit as in the prior art, that is, without increasing the cost.

It should be noted that the feature of the present invention is that, even during start-up operation and power generation operation, the target delivery amount is kept constant or the combustion section temperature decreases during the increase control within a predetermined increase rate, and the pump instruction value decreases. If it is, it is determined that it has blown out. “The temperature of the combustor is decreased” means that the temperature is detected at predetermined time intervals and it can be determined that the temperature is decreasing. For example, the temperature T _n at time t _n is the temperature T _n-1 lower than immediately before time t _n-1 is determined to be lowered and continues a predetermined time. The “combustion instruction” is a control state during combustion.

  The fuel cell system further includes a reforming unit 21 that is supplied with reforming fuel and generates reformed gas. The fuel electrode 11 of the fuel cell 10 is supplied with reformed gas as fuel, and the burner 25 Is supplied with any one of combustion fuel, reformed gas and anode off-gas as burner fuel. As a result, in the fuel cell system including the so-called polymer electrolyte fuel cell, it is possible to detect the blow-off of the burner 25 without fail in conformity with the system and without increasing the cost.

  Further, when the control instruction value derived by the instruction value deriving means (the flowchart of FIG. 6) decreases (determined as “YES” in step 406), it is determined that the pressure loss before and after the burner 25 has decreased. Thereby, during the start-up operation of the fuel cell system, the burner 25 can be blown out easily and reliably with a simple configuration based on the control instruction value to the combustion oxidant gas delivery means (combustion air pump 65). Can be detected.

2) Second Embodiment Next, a second embodiment of the fuel cell system to which the combustion apparatus according to the present invention is applied will be described. FIG. 9 is a schematic diagram showing an outline of a fuel cell system including a solid oxide fuel cell. In addition, about the structural member similar to 1st Embodiment mentioned above, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  This fuel cell system includes a fuel cell module 100. The fuel cell module 100 includes a casing 101, an evaporation unit 128, a reforming unit 121, and a fuel cell 110.

  The casing 101 is formed in a box shape with a heat insulating material. An evaporation unit 128, a reforming unit 121, and a fuel cell 110 are disposed in the casing 101. At this time, the evaporation unit 128 and the reforming unit 121 are disposed above the fuel cell 110.

  The evaporation unit 128 is heated by a combustion gas, which will be described later, evaporates the supplied reforming water to generate water vapor, and preheats the supplied reforming fuel. The evaporation unit 128 mixes the steam generated in this way and the preheated reforming fuel and supplies the mixture to the reforming unit 121. Examples of the reforming fuel include natural gas, gas fuel for reforming such as LPG, and liquid fuel for reforming such as kerosene, gasoline, and methanol. In the present embodiment, description will be made on natural gas.

  The evaporation section 128 is connected to the other end of a water supply pipe 52 whose one end (lower end) is connected to a water tank (not shown). A reforming water pump 53 is provided in the water supply pipe 52. The reforming water pump 53 supplies reforming water to the evaporation unit 128 and adjusts the reforming water supply amount.

  The evaporating unit 128 is supplied with reforming fuel from a fuel supply source (not shown) via the reforming fuel supply pipe 41. The reforming fuel supply pipe 41 is provided with a pair of raw material valves (not shown), a fuel pump 42, and a desulfurizer 46 in order from the upstream. The raw material valve is an electromagnetic on-off valve that opens and closes the reforming fuel supply pipe 41. The fuel pump 42 adjusts the amount of fuel supplied from the fuel supply source. The desulfurizer 46 removes a sulfur content (for example, a sulfur compound) in the reforming fuel.

  The reforming unit 121 is heated by a combustion gas described later and supplied with heat necessary for the steam reforming reaction, so that the reformed gas is converted from the mixed gas (reforming fuel, steam) supplied from the evaporation unit 128. Is generated and derived. The reforming unit 121 is filled with a catalyst (for example, a Ru or Ni-based catalyst), and the mixed gas reacts and is reformed by the catalyst to generate hydrogen gas and carbon monoxide gas (so-called so-called). Steam reforming reaction). At the same time, a so-called carbon monoxide shift reaction occurs in which carbon monoxide generated in the steam reforming reaction reacts with steam to transform into hydrogen gas and carbon dioxide. These generated gases (so-called reformed gas) are led to the fuel electrode 111 of the fuel cell 110. The reformed gas contains hydrogen, carbon monoxide, carbon dioxide, water vapor, and unreformed natural gas (methane gas). The steam reforming reaction is an endothermic reaction, and the carbon monoxide shift reaction is an exothermic reaction.

  The fuel cell 110 includes a fuel electrode 111, an air electrode 112 (oxidant electrode), and an electrolyte 113 interposed between the electrodes 111 and 112, and a plurality of cells 110a formed in a columnar shape having an elliptical cross section. Configured.

  As shown in FIG. 10, the cell 110a includes a conductive support substrate 114 having a flat cross section and an elliptical column shape as a whole. In the conductive support substrate 114, a plurality of fuel gas passages 114a are formed penetrating in the axial direction at appropriate intervals. The conductive support substrate 114 is gas permeable to allow the fuel gas flowing through the fuel gas passage 114a to pass to the fuel electrode 111, and is conductive to collect current via the interconnector 115. Is required. In order to satisfy this requirement, the conductive support substrate 114 is formed of a composite made of a metal (for example, an iron group metal component) and a rare earth oxide.

  The conductive support substrate 114 includes two flat portions facing each other and arc-shaped portions at both ends of both flat portions. A fuel electrode 111 is formed in layers so as to cover one flat portion and the arc-shaped portions on both sides. Further, an electrolyte 113 is laminated so as to cover the fuel electrode 111, and an air electrode 112 is laminated on the electrolyte 113 so as to face the fuel electrode 111. An interconnector 115 is formed on the other flat portion where the fuel electrode 111 and the electrolyte 113 are not stacked. The fuel electrode 111 and the electrolyte 113 extend to both sides of the interconnector 115, and are configured so that the surface of the conductive support substrate 114 is not exposed to the outside.

The fuel electrode 111 is formed of porous conductive ceramics (for example, nickel-containing stabilized zirconia). The air electrode 112 is formed of porous conductive ceramics (for example, ABO ₃ type perovskite oxide). The electrolyte 113 is formed of ceramics having gas impermeability and insulating properties (for example, zirconia in which a rare earth element is dissolved). The interconnector 115 is formed of ceramics having gas permeability and conductivity (for example, perovskite oxide (LaCrO ₃ oxide)).

  Two adjacent cells 110a are provided with a space therebetween and are electrically connected by a cell connector 110b. This space penetrates vertically and is used as a cathode air (oxidant gas) flow path 110c. The cell connector 110b is made of a metal material. The cell connector 110b connects the air electrode 112 of the cell 110a and the interconnector 115 of the cell 110a.

  The fuel cell 110 is provided on the anode manifold 117. The reformed gas from the reforming unit 121 is supplied to the anode manifold 117 via the reformed gas supply pipe 71. Each fuel gas passage 114a of the cell 110a has a lower end (one end) connected to the fuel outlet of the anode manifold 117, and the reformed gas led out from the fuel outlet is introduced from the lower end and led out (spout) from the upper end. ).

  Further, a cathode air introduction section 116 is provided on the side of the fuel cell 110. A cathode air supply pipe 67 is connected to the cathode air introduction section 116 so that cathode air is supplied. The cathode air supplied to the cathode air introduction section 116 is introduced from the lower end of the cathode air passage 110c and led out (spouted) from the upper end.

  In addition, between the fuel cell 110 and the evaporation unit 128 (or the reforming unit 121) (combustion space), the anode off gas ejected from the cell 110a is ignited by the cathode off gas ejected from the cathode air flow channel 110c. An ignition means 125g (ignition heater) is provided. The ignition means 125g is turned on / off in accordance with an instruction from the control device 30 in the same manner as the ignition electrode 25g.

  Thereby, the anode off gas ejected from the cell 110a can be burned with the cathode off gas ejected from the cathode air flow path 110c. That is, the fuel cell 110 can function as the burner 125.

  The combustion space is provided with a temperature sensor 125e that detects the combustion temperature of the space. The temperature sensor 125e detects the temperature of the combustion space in the same manner as the temperature sensor 25e, and the detection result is sent to the control device 30.

  The cathode air supply pipe 67 is provided with a flow meter 67a similar to the flow meter 64a described above. The flow meter 67 a is for measuring the volume or mass per unit time of the combustion air flowing through the cathode air supply pipe 67, and the detection result is sent to the control device 30. . Since the flow meter 67 a is provided on the discharge side of the cathode air pump 68, the flow meter 67 a is a delivery amount detection means for detecting the delivery amount of cathode air sent from the cathode air pump 68.

In the fuel cell 110, power generation is performed by the fuel supplied to the fuel electrode 111 and the oxidant gas supplied to the air electrode 112. That is, the reaction shown in chemical formula 1 and chemical formula 2 below occurs in the fuel electrode 111, and the reaction shown in chemical formula 3 below occurs in the air electrode 112. That is, oxide ions (O ²⁻ ) generated at the air electrode 112 permeate the electrolyte 113 and react with hydrogen at the fuel electrode 111 to generate electric energy. Therefore, the reformed gas and the oxidant gas (air: cathode off gas) that have not been used for power generation are led out from the fuel gas passage 114a and the cathode air passage 110b.

(Chemical formula 1)
H ₂ + O ²⁻ → H ₂ O + 2e ⁻

(Chemical formula 2)
CO + O ²⁻ → CO ₂ + 2e ⁻

(Chemical formula 3)
1 / 2O ₂ + 2e ⁻ → O ²⁻

  Then, the reformed gas and the oxidant gas (air) that are derived from the fuel gas passage 114a and the cathode air passage 110b and that are not used for power generation are between the fuel cell 110 and the evaporation section 128 (the reforming section 121). The evaporating section 128 and the reforming section 121 are heated by the combustion gas. Furthermore, the inside of the fuel cell module 100 is heated to the operating temperature. Thereafter, the combustion gas passes through the space between the fuel cell 110 and the casing 101 (this space is the combustion gas flow path 126), and is exhausted out of the fuel cell module 100 through the exhaust pipe 81.

  In the combustion operation of the burner 125 of the fuel cell system including the solid oxide fuel cell configured as described above, the same control as the combustion of the burner 25 of the fuel cell system including the polymer electrolyte fuel cell described above is performed. Since it is performed, the same operation and effect can be obtained. The control target is the cathode air pump 68 instead of the combustion air pump 65.

  Further, the burner 125 burns the anode off gas directly derived from the fuel electrode 111 of the fuel cell 110 with the cathode off gas (utilized as the oxidant gas for combustion) directly derived from the oxidant electrode 112 of the fuel cell 111. Configured as follows. As a result, in a fuel cell system including a so-called solid oxide fuel cell, it is possible to reliably detect (determine) the burn-out of the burner without being expensive and suitable for the system.

  DESCRIPTION OF SYMBOLS 10,110 ... Fuel cell, 11, 111 ... Fuel electrode, 12, 112 ... Air electrode, 20 ... Reformer, 21, 121 ... Reformer, 22 ... Cooling part (heat exchange part), 23 ... Carbon monoxide Shift reaction part (CO shift part), 24 ... Carbon monoxide purification part (CO purification part), 25, 125 ... Burner, 25a ... Base part, 25b ... Combustion cylinder, 25b1 ... Partition plate, 25b2 ... Second outlet, 25c ... off-gas nozzle, 25c1 ... first outlet, 25e, 125e ... temperature sensor, 25g, 125g ... ignition electrode, 26,126 ... combustion gas flow path, 27 ... combustion part, 28,128 ... evaporation part, 29 ... insulation , 30 ... control device, 41 ... fuel supply pipe, 42 ... fuel pump, 43 ... reforming fuel valve, 44 ... combustion fuel supply pipe, 45 ... combustion fuel valve, 46 ... desulfurizer, 51 ... steam supply Pipe, 52 ... water supply pipe, DESCRIPTION OF SYMBOLS 3 ... Reform water pump, 54 ... Reform water valve, 61 ... Oxidation air supply pipe, 62 ... Oxidation air pump, 63 ... Oxidation air valve, 64 ... Combustion air supply pipe, 65 ... Combustion air pump , 66 ... Combustion air valve, 67 ... Cathode air supply pipe, 68 ... Cathode air pump, 69 ... Cathode air valve, 71 ... Reformed gas supply pipe, 72 ... Off gas supply pipe, 73 ... Bypass pipe, 74 ... 1st reformed gas valve, 75 ... Off gas valve, 76 ... 2nd reformed gas valve, 81, 82 ... Exhaust pipe, 89 ... Connecting pipe. DESCRIPTION OF SYMBOLS 100 ... Fuel cell module, 101 ... Casing, 110a ... Cell, 110b ... Cell connection body, 110c ... Cathode air flow path, 114 ... Conductive support substrate, 114a ... Fuel gas passage, 115 ... Interconnector, 116 ... For cathode Air introducing member, 117... Anode manifold.

Claims (4)

A combustion apparatus applied to a fuel cell system including a fuel cell that generates electricity by using a fuel supplied to a fuel electrode and an oxidant gas supplied to an oxidant electrode,
A combustion section comprising a burner for burning the burner fuel with a combustion oxidant gas, and a combustion gas flow path through which the combustion gas generated in the burner flows;
A temperature sensor for detecting the temperature of the combustion section;
Combustion oxidant gas delivery means for delivering the combustion oxidant gas to the burner;
Pressure loss decrease detecting means for detecting that the pressure loss before and after the burner has decreased,
A delivery amount detection means for detecting a delivery amount of the combustion oxidant gas delivered from the combustion oxidant gas delivery means;
Deriving an instruction value for deriving a control instruction value to the combustion oxidant gas delivery means based on the actual delivery quantity actually detected by the delivery quantity detection means and the target delivery quantity of the combustion oxidant gas delivery means Means,
The combustion instruction is given to the burner, and when the target delivery amount is increased or kept constant, the temperature of the combustion section is lowered and the pressure loss before and after the burner is reduced. A blow-off detection means for determining that the burner has blown off when detected,
A combustion apparatus for a fuel cell system comprising: The fuel cell system according to claim 1, further comprising a reforming unit that is supplied with reforming fuel and generates reformed gas,
The reformed gas is supplied to the fuel electrode of the fuel cell as the fuel,
A combustion apparatus of a fuel cell system, wherein any one of combustion fuel, reformed gas, and anode off-gas is supplied to the burner as the burner fuel.   2. The burner according to claim 1, wherein the burner is a cathode off-gas directly derived from an oxidant electrode of the fuel cell that uses the anode off-gas directly derived from the fuel electrode of the fuel cell as the oxidant gas for combustion. A combustion apparatus for a fuel cell system, characterized by being configured to burn. 4. The fuel according to claim 1, wherein when the control command value derived by the command value deriving means decreases, it is determined that the pressure loss before and after the burner has decreased. Battery system combustion device.

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