JP5309799B2 - Reformer and fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress emission to be low or blowing out by stabilizing combustion at a burner during a starting operation in a reforming apparatus and a fuel cell system. <P>SOLUTION: The reforming apparatus includes: a reforming portion to generate a reformed gas by supplying a reforming fuel and reforming water; an evaporating portion to supply steam produced by evaporating the supplied reforming water to the reforming portion; a burner to burn at least the reformed gas supplied from the reforming portion with an oxidizer gas for combustion during the starting operation; and a burning portion to heat the reforming portion by a combustion gas exhausted from the burner. Combustion at the burner is stopped (step 110) by a control unit in the reforming apparatus when the generation of steam is detected at the evaporating portion (step 106) during the combustion at the burner in the starting operation. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a reformer and a fuel cell system.

As one type of reformer, the one shown in Patent Document 1 is known. As shown in FIG. 1 of Patent Document 1, the reformer includes a reforming unit that is supplied with reforming fuel and reforming water to generate reformed gas, is supplied with reforming water, and An evaporation section for evaporating the reformed water and supplying it to the reforming section; and a burner for supplying at least the reformed gas from the reforming section during the start-up operation and combusting the reformed gas with the oxidizing gas for combustion. And a combustion section that heats the reforming section with the combustion gas discharged from the burner. In this reformer, when the start-up operation is started, the burner is ignited, and the reforming section and the evaporation section are heated by the combustion gas from the burner. After a predetermined time has elapsed after the burner ignition, supply of reforming water to the evaporation section is started. When the generation of water vapor is detected in the evaporation section, reforming fuel is supplied to the reforming section, reformed gas is generated, and the reformed gas is supplied to the burner and burned. When the warming-up of the reformer is completed, the start-up operation is terminated, the reformed gas is supplied to the fuel cell, and the power generation operation is started.
JP 2008-91094 A

During the start-up operation of the reformer described in Patent Document 1 described above, when steam is generated in the evaporation section, the steam is supplied to the burner through the reforming section. At this time, the gas existing in the reforming section, the piping between the reforming section and the burner and the member is pressed by the water vapor and flows into the burner. If the gas present is combustible gas, the combustible gas is decreased combustion λ to become flow into the burner during combustion, emissions (NO _X concentration, CO concentration) becomes unstable combustion or increased, blown May disappear. In addition, when the gas present is an inert gas (N _{2 or the} like), the combustion λ increases, and similarly, the combustion becomes unstable and there is a risk of increasing emission or blowing off. Combustion λ is an air ratio (actual amount of combustion air input / ideal amount of combustion air input) and is (actual air / fuel ratio / theoretical air / fuel ratio). The air-fuel ratio is obtained by dividing the mass of input air by the mass of combustible gas input. The stoichiometric air-fuel ratio is the air-fuel ratio when oxygen in the air and the combustible gas react without excess or deficiency.

  The present invention has been made to solve the above-described problems, and in a reformer and a fuel cell system, combustion of a burner during start-up operation is stabilized, emission is suppressed to a low level, and blow-off is suppressed. With the goal.

In order to solve the above-mentioned problem, the structural feature of the reformer according to claim 1 is that a reforming unit that generates reformed gas by being supplied with reforming fuel and reforming water, and reforming An evaporating unit that supplies water to evaporate the reformed water and supplies the reformed water to the reforming unit; and at least a reformed gas is supplied from the reforming unit during start-up operation, and the reformed gas is used as a combustion oxidizing gas A combustion section that has a burning burner and that heats the reforming section with combustion gas discharged from the burner, and during the start-up operation and combustion of the burner after the first ignition of the burner, the evaporation section When the generation of water vapor is detected, combustion of the burner is stopped, and the supply of reforming water is continued until a predetermined time has elapsed from the time when water vapor generation is detected. From the point of time, supply of reforming fuel is started and the burner It is that the ignition is performed.

Further, the feature in construction of the invention of the reforming apparatus according to claim 2 includes a reformer for reforming fuel and reforming water to generate is supplied reformed gas, reforming water is supplied該改An evaporation section that evaporates the quality water and supplies it to the reforming section; and a burner that is supplied with at least the reformed gas during the start-up operation and burns the reformed gas with the combustion oxidant gas. A combustion section that heats the reforming section with a combustion gas, and during the start-up operation, when the combustion of the burner is stopped after the first ignition of the burner, the generation of water vapor in the evaporation section is detected the, from the occurrence detection time of steam until a predetermined time has elapsed to continue the supply of the reforming water, and re-ignition of the burner is prohibited, from the point of elapse of a predetermined time after occurrence detection time of the steam, the re-ignition of the burner is performed by starting the supply of the reforming fuel A.

The structural feature of the invention the reforming apparatus according to claim 3, in the reforming apparatus according to claim 1 or claim 2, wherein the evaporation unit and heat combustion section after the combustion gas is reformer and heat exchanger The replacement is performed, and only the oxidizing gas for combustion is supplied to the burner from the time when the generation of water vapor is detected until the burner is ignited (including re-ignition).
Further, the structural feature of the invention of the reformer according to claim 4 is that, in the reformer according to claim 3, the supply amount of the combustion oxidant gas supplied to the burner is from immediately before the detection of the generation of water vapor. Is to be increased.

  The fuel cell system according to claim 5 is characterized in that the fuel cell system includes a fuel cell in which fuel gas is supplied to the fuel electrode and oxidant gas is supplied to the oxidant electrode to generate electric power. The reformed gas generated by the reformer according to any one of claims 1 to 4 is used as a fuel gas.

In the invention of the reformer according to claim 1 configured as described above, if the generation of water vapor is detected in the evaporation section during start-up operation and combustion of the burner, combustion of the burner is performed. Stopped. According to this, during start-up operation, when steam is generated in the evaporation section and the steam is supplied to the burner through the reforming section, the piping and members in the reforming section and between the reforming section and the burner Even if the gas present inside is compressed by water vapor and flows into the burner, the combustion of the burner is stopped. Therefore, even if the gas present is a combustible gas, the gas flows into the burner during which combustion is stopped. In other words, the gas existing in the reforming section, the piping between the reforming section and the burner and the member during combustion can be prevented from flowing into the burner. Thereby, the combustion of the burner does not become unstable, and the emission (NO _X concentration, CO concentration) can be increased, or blow-off can be suppressed.
In addition to this, the burner is re-ignited after a predetermined time has elapsed since the detection of the generation of water vapor. Thus, after a sufficient time (predetermined time) has passed from the detection of water vapor in the evaporation section, the gas present in the reforming section, the piping between the reforming section and the burner and the member is pressed by the steam. By performing reignition of the burner, instability of combustion during reignition can be further suppressed.

In the invention of the reformer according to claim 2 configured as described above, the generation of water vapor in the evaporation section is detected during the start-up operation and during the combustion stop of the burner after the first ignition of the burner. time when the can, from occurrence detection time of steam until a predetermined time has elapsed, which continues to supply the reforming water, and re-ignition of the burner is prohibited, and predetermined time has elapsed from the occurrence detection point of the water vapor Then , the supply of reforming fuel is started and the burner is re- ignited. According to this, during the start-up operation, when steam is generated in the evaporation section while the combustion of the burner is stopped and the steam is supplied to the burner through the reforming section, the reforming section, the reforming section and the burner are Combustion of the burner is stopped even if the gas existing in the pipes and members between them is compressed by water vapor and flows into the burner. Therefore, even if the gas present is a flammable gas, it will not be burned even if the gas flows into the burner where combustion is stopped, so combustion will not become unstable and emissions (NO _X concentration, CO concentration) will increase. Or blow out. Furthermore, the burner after a sufficient time (predetermined time) for the gas existing in the reforming unit, the piping between the reforming unit and the burner and the gas present in the member to be pressed by the steam is detected from the steam detection in the evaporation unit. By performing this ignition, combustion instability upon ignition can be further suppressed.

In the invention according to claim 3 configured as described above, in claim 1 or claim 2 , the combustion section exchanges heat with the evaporation section after the combustion gas exchanges heat with the reforming section. Until the burner is ignited (including re-ignition) from the time of occurrence detection, only the oxidant gas for combustion is supplied to the burner. As a result, even if the combustion of the burner is stopped, the heat of the reformed portion that has been heated and heated to a certain degree is applied to the evaporation portion by the combustion oxidant gas discharged from the burner. Generation of water vapor can be promoted. In addition to this, the gas supplied to the burner while the combustion is stopped (the gas existing in the reforming part, the piping between the reforming part and the burner and the member) is diluted with the oxidizing gas for combustion and discharged. Can do.
In the invention according to claim 4 configured as described above, in claim 3, the supply amount of the combustion oxidant gas supplied to the burner is increased from immediately before the detection of the generation of water vapor.

  In the invention of the fuel cell system according to claim 5 configured as described above, in the fuel cell system including the fuel cell in which the fuel gas is supplied to the fuel electrode and the oxidant gas is supplied to the oxidant electrode to generate electric power. The reformed gas generated by the reformer according to any one of claims 1 to 4 is used as a fuel gas. Thereby, the fuel cell system provided with the reformer which exhibits the effect mentioned above can be provided.

  Hereinafter, an embodiment of a fuel cell system to which a reformer according to the present invention is applied will be described. FIG. 1 is a schematic diagram showing an outline of this fuel cell system. 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. 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. Furthermore, the temperature sensor 21 d is provided at the outlet of the reforming unit 21 and detects the outlet temperature of the reforming unit 21. Specifically, the temperature sensor 21d is provided at a position away from the outlet of the filling portion of the catalyst 21b (the outlet of the reforming portion 21) by a predetermined distance in the gas flow direction. The temperature of the temperature sensor 21d is equal to the fluid temperature at the outlet of the reforming unit 21. The detection results of the temperature sensors 21c and 21d are 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 burner 25 generates combustion gas for heating the reforming unit 21 and supplying heat necessary for the steam reforming reaction, and a lower end portion is inserted into the inner peripheral wall of the reforming unit 21 to form a space. Is placed. 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 of the first injection ports 25c1 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 the combustion reaction (oxidation reaction) of the burner fuel gas (for example, anode off gas) 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 22 to generate water vapor.

  A combustion section 27 is configured by the burner 25 and the combustion gas flow path 26 described above. The combustion unit 27 includes a burner 25 that is supplied with at least the reformed gas from the reforming unit 21 during the start-up operation and burns the reformed gas with combustion air (combustion oxidant gas), and is discharged from the burner 25. The reforming section 21 is heated with the combustion gas generated.

  The combustion air supply pipe 64 is provided with a combustion air pump (combustion oxidant gas supply means) 65 and a combustion air valve 66, as shown in FIG. The combustion air pump 65 sucks combustion air from the atmosphere and discharges it 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 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. The temperature sensor 28a is preferably provided at the downstream portion (exit side) in the evaporation portion 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, 21d, 23c, 24b, 25e, 28a, the pumps 42, 53, 62, 65, 68, and the like. 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. Based on the temperature from the temperature sensors 21c, 21d, 23c, 24b, 25e, 28a, etc., the CPU is responsible for the pumps 42, 53, 62, 65, 68, the valves 43, 45, 54, 63, 66, 69, The operation of the fuel cell system is controlled by controlling 74, 75, 76 and the ignition electrode 25g. The RAM temporarily stores variables necessary for executing the program, and the ROM stores the program.

  Next, an outline of the operation of the above-described fuel cell system 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 section 21 and the evaporation section 28 while passing through the combustion gas passage 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 from the time point when the generation of water vapor is detected, the generated water vapor is a gas (in the present embodiment) that is present in the reformer 20 during the shutdown of the fuel cell system. Is a gas mainly composed of reforming fuel enclosed or purged in the stop operation), that is, reforming that remains (residual) from the inside of the evaporation section 28 to the second reformed gas valve 76 of the bypass pipe 73. The gas containing the main 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 the supply amount A-1, and when a predetermined time ΔTM-a has elapsed. Then, the charging of the reforming fuel is started and 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. 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, the case where generation | occurrence | production of water vapor | steam is detected during the combustion of the burner 25 or a combustion stop is explained in full detail. First, the case where the generation of water vapor is detected during combustion of the burner 25 will be described with reference to FIGS. A form according to FIGS. 4 to 6 is a first embodiment. In FIG. 5, the same processes as those in FIG. Moreover, the upper stage of FIG. 6 shows the evaporation part temperature T1 and the combustion part temperature T3, the next stage shows the gas flow rate of gas flowing into the burner 25 from the off-gas supply pipe 72 and its components, and the next stage is for combustion. The flow rate of air is shown, the next stage shows the type and flow rate of the combustible gas supplied to the reformer 20, and the lower stage shows on / off of the ignition electrode (igniter) 25g.

  When main power (not shown) is turned on, control device 30 starts the program at step 200 and advances the program to step 102. In step 102, the control device 30 determines whether or not to start operation of the system.

  The start-up sequence in this case is: i) igniting the burner 25 with combustion fuel, ii) charging the reforming water when the combustion section 27 reaches a predetermined temperature (300 ° C.), and iii) generating steam in the evaporation section 28 When started, the reforming fuel is introduced to switch the combustion of the burner 25 by the combustion fuel to the combustion by the reformed gas, and iv) warm up the CO shift section 23 and thereafter. It is.

  When there is a start instruction, control device 30 starts a start sequence (time TM0 in FIG. 6). That is, the control device 30 opens the combustion air valve 66 and drives the combustion air pump 65 to supply combustion air to the burner 25 (purging with combustion air, step 202). At this time, the combustion air is supplied by a standard amount (supply amount A-0). Then, the control device 30 starts driving an ignition device (not shown) and energizes the ignition electrode 25g of the burner 25 (step 204). 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 (step 206). Thereby, the burner 25 is ignited. In the present embodiment, energization of the ignition electrode 25g is continued for a predetermined time from the time TM0.

  After the burner 25 has ignited, the control device 30 starts to supply reforming water when the temperature T3 of the combustion section 27 reaches a predetermined temperature (for example, 300 ° C.) (determined as “YES” in step 208). (Step 210. Time TM1 in FIG. 6). In step 208, it is determined whether or not the combustion section temperature T3 is higher than a predetermined temperature (for example, 300 ° C.).

  In step 210, 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.

  After igniting the burner 25 and introducing the reforming water, the control device 30 detects (determines) the presence or absence of the generation of water vapor 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 equal to or higher than a predetermined temperature T1-a (for example, 100 ° C.). The unit 28 is not warmed up and does not detect the generation of water vapor.

  In the reformer 20, the combustion of the burner 25 continues, and the reforming unit 21 and the evaporation unit 28 are heated by the combustion gas discharged from the burner 25. Until the temperature of the evaporator 28 rises and the evaporator temperature T1 reaches the predetermined temperature T1-a, the control device 30 determines “NO” in step 106 and continues the activation sequence.

  If the evaporation section temperature T1 becomes equal to or higher than the predetermined temperature T1-a during the start-up sequence, the control device 30 detects that water vapor has been generated (time TM2 in FIG. 6), and advances the program to step 110. That is, when the controller 30 detects the generation of water vapor in the evaporation unit 28 after starting the introduction of the reforming water (determined as “YES” in step 106), the control device 30 advances the program to step 110.

  When the controller 30 detects the generation of water vapor in the evaporation section 28 during the combustion of the burner 25, in step 110, the control apparatus 30 stops combustion in the burner 25 and purges the combustion section 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 at this time 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).

  Control device 30 continues the combustion air purge mode described above until a predetermined time ΔTM-a elapses from the time when the generation of water vapor is detected (time TM3 in FIG. 6) (in step 112, the determination of “NO” is repeated). ). 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 from the time point when the generation of water vapor is detected, the generated water vapor is a gas (in the present embodiment) that is present in the reformer 20 during the shutdown of the fuel cell system. Is a gas mainly composed of reforming fuel enclosed or purged in the stop operation), that is, reforming that remains (residual) from the inside of the evaporation section 28 to the second reformed gas valve 76 of the bypass pipe 73. A gas containing the main fuel as a main component is scavenged (pushed) to flow into the burner 25, discharged from the burner 25 to the combustion gas passage 26, and then discharged to the outside.

  When a predetermined time ΔTM-a has elapsed from the time when the generation of water vapor is detected (“YES” in step 112, time TM3 in FIG. 6), control device 30 ends the combustion air purge mode and restarts the startup sequence. The re-ignition of the burner 25 is started. Specifically, the control device 30 starts energization to the ignition electrode 25g from time TM3 while continuing to supply the reforming water (supply amount W-1) (step 212). This energization is continued for a time set longer than time TM4. The time required for at least the reformed gas to reach the combustion space 25d of the burner 25 is continued.

  Further, the control device 30 starts to supply the reforming fuel at time TM3. Specifically, the control device 30 opens the reforming fuel valve 43 and keeps the combustion fuel valve 45 closed, and starts driving the fuel pump 42 (step 214). Note that the supply amount of combustion air is changed from A-1 to A-2 at the start of charging of the reforming fuel (time TM3). The supply amount A-2 is a value smaller than the supply amount A-1, and a value close to the supply amount A-0. A-0 and A-2 are set to optimum flow rates for burning the combustion fuel and the reforming fuel.

  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 water vapor is mainly supplied to the burner 25 from time TM3 to time TM4. In addition, the time required for the reforming fuel to flow into the reforming section 21 and the reformed gas generated in the reforming section 21 from when the reforming fuel is supplied until the reformed gas flows into the combustion space 25d. It takes a total time with the time required for the reformed gas to flow into the combustion space 25d of the burner 25. Accordingly, the burner 25 is re-ignited at the time (at time TM4 in FIG. 6) when at least the total time described above 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. In addition, after the re-ignition of the burner 25 (time TM4), what flows into the burner 25 is a reforming fuel, a combustible gas containing a reformed gas, and an incombustible gas such as water vapor or carbon dioxide. At this stage (stage where the warming-up of the reforming unit 21 is not sufficient), the reforming is not sufficiently advanced, and the reforming fuel flows into the burner 25 as it is without being reformed. Therefore, the main component of the combustible gas at this stage is the reforming fuel. A part of the reforming fuel is reformed, and the reformed gas also flows into the burner 25. When the reforming unit 21 is heated and reforming progresses, the reforming fuel is reformed, the reformed gas flowing in increases, and the reforming fuel that flows into the burner 25 without being reformed. Decrease.

  As indicated by the solid line in the second stage of FIG. 6, the gas remaining in the reformer 20 and the piping is scavenged and flows into the burner 25 due to the generation of water vapor from time TM2. When all of the gas is scavenged, water vapor flows into the burner 25 so that the gas is replaced. At time TM3, only water vapor flows into the burner 25. When the introduction of the reforming fuel is started from time TM3, the reforming unit 21 generates reformed gas (including hydrogen, steam, carbon monoxide, carbon dioxide) by the reforming reaction in the reforming unit 21. Then, the reformed gas scavenges water vapor remaining in the reformer 20 and the piping. Thereby, the remaining water vapor flows into the burner 25. When all the remaining water vapor is scavenged, the reformed gas flows into the burner 25 after time TM4. The reformed gas is a combustible gas mainly composed of hydrogen gas and an incombustible gas such as water vapor or carbon dioxide. The broken line in the second stage in FIG. 6 indicates the total flow rate of the gas (gas) that flows after all the gas remaining in the reformer 20 and the piping has been scavenged, and the one-dot broken line indicates a change in the total flow rate. The flow of combustible gas when the quality gas starts to flow is shown. As for the flow rate of the inflowing gas, the total flow rate increases after the reforming fuel is input. Note that the conversion rate of reforming increases as the temperature of the reforming unit 21 increases, and the total flow rate and the ratio of combustible gas to inert gas change accordingly. The conversion rate is low immediately after reignition, and then increases.

  After re-igniting the burner 25 by the introduction of the reforming fuel, the controller 30 completes the start-up sequence (completion of the warm-up operation), and determines each temperature (any temperature) of the CO shift unit 23 and the CO purification unit 24. But it can be determined. 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 (step 216).

  If control device 30 determines that the activation sequence has been completed, it starts the power generation operation. 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 (step 216).

As is clear from the above-described embodiment, if the generation of water vapor in the evaporator 28 is detected during the start-up operation of the fuel cell system (reformer 20) and the burner 25 is burning, the burner is detected. The combustion of 25 is stopped. According to this, during the start-up operation, when steam is generated in the evaporation section 28 and the steam is supplied to the burner 25 through the reforming section 21, the reforming section 21 and the burner Even if the gas existing (residual) in the pipes and members between 25 is compressed by water vapor and flows into the burner 25, the combustion of the burner 25 is stopped. Therefore, even if the existing (residual) gas is a combustible gas, the gas flows into the burner 25 in which combustion is stopped. In other words, during combustion of the burner 25, it is possible to suppress the gas existing in the reforming unit 21, the piping between the reforming unit 21 and the burner 25 and the members from flowing into the burner 25. Thereby, the combustion of the burner 25 does not become unstable, and the emission (NO _X concentration, CO concentration) can be increased, or blow-off can be suppressed.

  Further, when a predetermined time (ΔTM-a) has elapsed from the time point when the generation of water vapor is detected (time TM2 in FIG. 6), the burner 25 is re-ignited. Thereby, from the detection of the generation of water vapor in the evaporation unit 28, a sufficient time (predetermined) for the gas existing in the reforming unit 21, the piping between the reforming unit 21 and the burner 25, and the member to be compressed by the water vapor. When the burner 25 is re-ignited after a lapse of time, combustion instability during re-ignition can be further suppressed.

  Further, in the fuel cell system including the fuel cell 10 that generates power by supplying the fuel gas to the fuel electrode 11 and supplying the oxidant gas to the oxidant electrode 12, the reformed gas generated by the reformer 20 is used as the fuel. Use as gas. Thereby, the fuel cell system provided with the reformer 20 which exhibits the effect mentioned above can be provided.

  Next, a case where the generation of water vapor is detected while combustion of the burner 25 is stopped will be described with reference to FIGS. A form according to FIGS. 7 to 9 is a second embodiment. 7 and 8, the same processes as those in FIGS. 4 and 5 are denoted by the same reference numerals, and the description thereof is omitted. Moreover, the upper stage of FIG. 9 shows the evaporation part temperature T1 and the combustion part temperature T3, the next stage shows the gas flow rate of the gas flowing into the burner 25 from the off-gas supply pipe 72 and its components, and the next stage is for combustion. The flow rate of air is shown, the next stage shows the type and flow rate of the combustible gas supplied to the reformer 20, and the lower stage shows on / off of the ignition electrode (igniter) 25g.

  When main power (not shown) is turned on, control device 30 starts the program at step 300 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 it is determined that the system operation is to be started, the control device 30 starts the activation sequence.

  In parallel with this, when the main power supply (not shown) is turned on, the control device 30 starts the program in step 400 and advances the program to step 402. In step 402, the control device 30 determines whether or not to start the activation sequence. When it is determined that the activation sequence is to be started, the control device 30 executes the processing from step 404 and starts the activation operation.

  When there is an instruction to start the activation sequence, the control device 30 starts the activation sequence (time TM0 in FIG. 9). That is, the control device 30 opens the combustion air valve 66 and drives the combustion air pump 65 to supply combustion air to the burner 25 (purging with combustion air; step 404). At this time, the combustion air is supplied by a standard amount (supply amount A-0). Then, the control device 30 starts driving an ignition device (not shown) and energizes the ignition electrode 25g of the burner 25 (step 406). 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 (step 408). Thereby, the burner 25 is ignited. In the present embodiment, energization of the ignition electrode 25g is continued for a predetermined time from the time TM0.

  After the burner 25 has ignited, the control device 30 starts to add reforming water when the temperature T3 of the combustion section 27 reaches a predetermined temperature (for example, 300 ° C.) (determined as “YES” in step 410). (Step 412. Time TM1 in FIG. 9). In step 410, it is determined whether or not the combustion section temperature T3 is higher than a predetermined temperature (for example, 300 ° C.).

  In step 412, the control device 30 opens the reforming water valve 54 and drives the reforming water pump 53 as in step 210. 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.

  The control device 30 ignites the burner 25 and feeds the reformed water. When the temperature T3 of the combustion unit 27 reaches a predetermined temperature T3-a (for example, 600 ° C.) (determined as “YES” in step 414), Combustion of the burner 25 is stopped (step 416, time TM2 in FIG. 9). The control device 30 stops driving the fuel pump 42, closes the combustion fuel valve 45, stops the supply of combustion fuel to the burner 25, and keeps the combustion air valve 66 open to maintain combustion air. The driving of the pump 65 is continued and the supply of combustion air 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).

  When combustion of the burner 25 is stopped, the temperature of the combustion part 27 also falls. When the combustion section temperature T3 becomes lower than a predetermined temperature T3-b (for example, 400 ° C.) that is lower than the predetermined temperature T3-a, the control device 30 returns the program to step 406 and reignites the burner 25 with the combustion fuel. . At this time, the combustion air is returned to the supply amount A-0. It should be noted that by repeating the processing of steps 406 to 418, the combustion section 27 is maintained in an appropriate temperature range, thereby suppressing the caulking of the catalyst of the reforming section 21 and the high-temperature deterioration of the reforming section material, the catalyst, and the like. Can do.

  The control device 30 executes the startup sequence shown in FIG. 8 until the generation of water vapor in the evaporation unit 28 is detected. 8 is a sequence between step 302 and step 304 shown in FIG.

  In parallel with this activation sequence, the control device 30 ignites the burner 25 and introduces reformed water (after starting the activation sequence (after time TM0)), in step 106, the evaporation unit 28 generates steam. Detect (determine) the presence or absence of. 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 equal to or higher than a predetermined temperature T1-a (for example, 100 ° C.). The unit 28 is not warmed up and does not detect the generation of water vapor.

  Until the temperature of the evaporator 28 rises and the evaporator temperature T1 reaches the predetermined temperature T1-a, the control device 30 determines “NO” in step 106 and continues the activation sequence (step 304). If the evaporation part temperature T1 becomes equal to or higher than the predetermined temperature T1-a during the start-up 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 evaporation unit 28 during the startup sequence (determined as “YES” in step 106), the control device 30 advances the program to step 110.

  Here, it is assumed that it is detected that water vapor is generated at time TM3 in FIG. 9 while the start-up sequence is continuing and combustion of the burner 25 is stopped. When the controller 30 detects the generation of water vapor in the evaporation section 28 while the combustion of the burner 25 is stopped, in step 110, the control apparatus 30 stops the combustion in the burner 25 and purges the combustion section 27 with combustion air (for combustion). Air purge mode). At this time, since the combustion has already been stopped, the combustion stop is maintained.

  The control device 30 stops driving the fuel pump 42 and keeps the combustion fuel valve 45 closed, and keeps the combustion air valve 66 open and continues to drive the combustion air pump 65 to burner 25. Continue to supply combustion air to In the present embodiment, the supply amount of combustion air at this time 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).

  Control device 30 continues the combustion air purge mode described above until a predetermined time ΔTM-a elapses from the time when the generation of water vapor is detected (time TM5 in FIG. 9) (the determination of “NO” is repeated in step 112). ). Since the process of the flowchart of FIG. 7 is preferentially executed from time TM4 to time TM5, according to the process of the flowchart of FIG. 8, if the combustion section temperature T3 is equal to or lower than the predetermined temperature T3-b ( Time TM4 in FIG. 9) The burner 25 should be re-ignited, but its re-ignition is prohibited.

  When a predetermined time ΔTM-a has elapsed since the detection of water vapor generation (determined as “YES” in step 112, time TM5 in FIG. 9), control device 30 ends the combustion air purge mode and restarts the startup sequence. The re-ignition of the burner 25 is started. Specifically, the control device 30 starts energization to the ignition electrode 25g from time TM5 while continuing to supply the reforming water (supply amount W-1) (step 212). This energization is continued for a time set longer than time TM6. The time required for at least the reformed gas to reach the combustion space 25d of the burner 25 is continued.

  Furthermore, the control device 30 starts to supply the reforming fuel at time TM5 in FIG. 9 (step 214). Note that the supply amount of combustion air is changed from A-1 to A-2 at the start of charging the reforming fuel (time TM5). The supply amount A-2 is a value smaller than the supply amount A-1, and a value close to the supply amount A-0. A-0 and A-2 are set to optimum flow rates for burning the combustion fuel and the reforming fuel.

  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 water vapor is mainly supplied to the burner 25 from time TM5 to time TM6. In addition, the time required for the reforming fuel to flow into the reforming section 21 and the reformed gas generated in the reforming section 21 from when the reforming fuel is supplied until the reformed gas flows into the combustion space 25d. It takes a total time with the time required for the reformed gas to flow into the combustion space 25d of the burner 25. Therefore, the burner 25 is re-ignited at the time (at time TM6 in FIG. 9) when at least the total time described above has elapsed from the time when the reforming fuel is started. When it is confirmed that the burner 25 has re-ignited, the supply amount of combustion air is returned from A-1 to A-0.

  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. Further, after the reignition of the burner 25 (time TM6), what flows into the burner 25 is a reforming fuel, a combustible gas containing a reformed gas, and an incombustible gas such as water vapor or carbon dioxide. At this stage (stage where the warming-up of the reforming unit 21 is not sufficient), the reforming is not sufficiently advanced, and the reforming fuel flows into the burner 25 as it is without being reformed. Therefore, the main component of the combustible gas at this stage is the reforming fuel. A part of the reforming fuel is reformed, and the reformed gas also flows into the burner 25. When the reforming unit 21 is heated and reforming progresses, the reforming fuel is reformed, the reformed gas flowing in increases, and the reforming fuel that flows into the burner 25 without being reformed. Decrease.

  As indicated by the solid line in the second stage of FIG. 9, the gas remaining in the reformer 20 and the piping is scavenged and flows into the burner 25 due to the generation of water vapor from time TM3. When all of the gas is scavenged, water vapor flows into the burner 25 so that the gas is replaced. At time TM5, only water vapor flows into the burner 25. When the introduction of the reforming fuel is started from time TM5, the reforming unit 21 generates reformed gas (including hydrogen, steam, carbon monoxide, carbon dioxide) by the reforming reaction in the reforming unit 21. Then, the reformed gas scavenges water vapor remaining in the reformer 20 and the piping. Thereby, the remaining water vapor flows into the burner 25. When all the remaining water vapor is scavenged, the reformed gas flows into the burner 25 after time TM6. The reformed gas is a combustible gas mainly composed of hydrogen gas and an incombustible gas such as water vapor or carbon dioxide. The broken line in the second stage in FIG. 6 indicates the total flow rate of the gas (gas) that flows after all the gas remaining in the reformer 20 and the piping has been scavenged, and the one-dot broken line indicates a change in the total flow rate. The flow of combustible gas when the quality gas starts to flow is shown. As for the flow rate of the inflowing gas, the total flow rate increases after the reforming fuel is input. Note that the conversion rate of reforming increases as the temperature of the reforming unit 21 increases, and the total flow rate and the ratio of combustible gas to inert gas change accordingly. The conversion rate is low immediately after reignition, and then increases.

  After re-igniting the burner 25 by the introduction of the reforming fuel, the controller 30 completes the start-up sequence (completion of the warm-up operation), and determines each temperature (any temperature) of the CO shift unit 23 and the CO purification unit 24. But it can be determined. 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 (step 216).

  If control device 30 determines that the activation sequence has been completed, it starts the power generation operation. 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 (step 216).

As is clear from the above-described embodiment, when the generation of water vapor is detected in the evaporation unit 28 during the start-up operation of the fuel cell system (reformer 20) and the combustion of the burner 25 being stopped, The reignition of the burner 25 is prohibited until the predetermined time ΔTM-a has elapsed from the time point when the generation of water vapor is detected (time TM3 in FIG. 9). Is done. According to this, during the start-up operation, when the steam is generated in the evaporation section 28 while the combustion of the burner 25 is stopped, and the steam is supplied to the burner 25 through the reforming section 21, Even if the gas existing in (remaining in) the piping and members between the reforming section 21 and the burner 25 is compressed by the water vapor and flows into the burner 25, the combustion of the burner 25 is stopped. Therefore, even if the existing (residual) gas is a flammable gas, it will not be burned even if the gas flows into the burner 25 where combustion is stopped, so that the combustion does not become unstable and the emission (NO _X concentration, CO 2 Density) can be increased, and blowout can be suppressed. Furthermore, from the detection of water vapor in the evaporation unit 28, a sufficient time (predetermined time) for the gas present in the reforming unit 21, the piping between the reforming unit 21 and the burner 25 and the member to be compressed by the water vapor. When the burner 25 is re-ignited after the elapse of time, instability of combustion during re-ignition can be further suppressed.

  The combustion unit 27 exchanges heat with the evaporation unit 28 after the combustion gas exchanges heat with the reforming unit 21, and burns to the burner 25 until the burner 25 is re-ignited from the time when the steam is detected. Only the oxidant gas is supplied. Thereby, even if the combustion of the burner 25 is stopped, the heat of the reforming unit 21 that is heated to a certain high temperature is applied to the evaporation unit 28 by the combustion oxidant gas discharged from the burner 25. The generation of water vapor in the evaporation unit 28 can be promoted. In addition to this, the gas supplied to the burner 25 during combustion stop (gas in the reforming section, piping between the reforming section and the burner and the member) is diluted with the oxidant gas for combustion and discharged. be able to.

  Further, in the fuel cell system including the fuel cell 10 that generates power by supplying the fuel gas to the fuel electrode 11 and supplying the oxidant gas to the oxidant electrode 12, the reformed gas generated by the reformer 20 is used as the fuel. Use as gas. Thereby, the fuel cell system provided with the reformer 20 which exhibits the effect mentioned above can be provided.

  The present invention can also be applied to the case where the combustion and stop of combustion of the burner 25 are repeated during the startup sequence, and the generation of water vapor is detected while the combustion of the burner 25 is stopped.

  In the above-described embodiment, the vapor is generated in the evaporation unit 28 using the combustion gas. However, the present invention can be applied to a configuration in which the water vapor is generated using another heat source such as a heater. . In this case (when steam is generated by a separate heat source), the burner 25 may be ignited for the first time, not for reignition. That is, after the start of the reforming water, it is only necessary to control the burner 25 to be ignited after the evaporation section temperature T1 is heated to a predetermined temperature T1-a or higher by another heat source.

  In this case, the control device 30 is in the start-up operation and the combustion of the burner 25 is stopped, and when the generation of water vapor in the evaporation unit 28 is detected (the evaporation unit temperature T1 is a separate heat source and is equal to or higher than the predetermined temperature T1-a). In this case, ignition of the burner 25 (first ignition) is prohibited until a predetermined time ΔTM-a has elapsed from the time when the occurrence of water vapor is detected, and a predetermined time ΔTM-a has elapsed since the time when the occurrence of water vapor was detected. Then, the burner 25 may be ignited. At this time, only the combustion air (combustion oxidant gas) may be supplied to the burner 25 from the time when the generation of water vapor is detected until the burner 25 is ignited. The start-up operation in this case refers to the start-up operation period after the time when the start instruction is received, and the ignition / non-ignition of the burner 25 is not relevant.

  In addition, the detection of the generation of water vapor in the evaporation unit 28 is performed by measuring the temperature of the evaporation unit 28 and using the evaporation unit temperature T1 as described above. The outlet temperature may be measured and the outlet temperature may be used. In this case, the control device 30 may determine that the generation of water vapor has started when the rate of temperature increase at the outlet of the reforming unit 21 has reached a predetermined value or more. Further, the temperature of the combustion gas passage 26 may be measured and the temperature of the combustion part may be used. In this case, the control device 30 may determine that the generation of water vapor has been started when the temperature decrease rate of the combustion gas flow path 26 becomes equal to or higher than a predetermined value.

1 is a schematic diagram showing an outline of an embodiment of a fuel cell system to which a reformer 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 an example of the control program performed with the control apparatus shown in FIG. It is a time chart which shows operation | movement of a fuel cell system when the water vapor | steam generation | occurrence | production in an evaporation part is detected during combustion of a burner. It is a flowchart which shows an example of the control program performed with the control apparatus shown in FIG. It is a flowchart which shows an example of the control program performed with the control apparatus shown in FIG. It is a time chart which shows operation | movement of a fuel cell system when the water vapor | steam generation | occurrence | production in an evaporation part is detected during the combustion stop of a burner.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Fuel cell, 11 ... Fuel electrode, 12 ... Air electrode, 20 ... Reformer, 21 ... Reformer, 22 ... Cooling part (heat exchange part), 23 ... Carbon monoxide shift reaction part (CO shift part) 24 ... carbon monoxide purification unit (CO purification unit), 25 ... burner, 25a ... base, 25b ... combustion cylinder, 25b1 ... partition plate, 25b2 ... second outlet, 25c ... off-gas nozzle, 25c1 ... first outlet 25e ... temperature sensor, 25g ... ignition electrode, 26 ... combustion gas flow path, 27 ... combustion part, 28 ... evaporation part, 29 ... heat insulation part, 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 ... Feed water pipe, 53 ... Reforming water pump, 54 ... Reforming 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 ... first reformed gas valve, 75 ... off gas valve, 76 ... second reformed gas valve, 81, 82 ... exhaust pipe 89 ... Connection pipe.

Claims (5)

A reforming unit that is supplied with reforming fuel and reforming water to generate reformed gas;
An evaporating unit that is supplied with the reforming water, evaporates the reforming water, and supplies the reforming unit to the reforming unit;
During the start-up operation, at least the reformed gas is supplied from the reforming section, and the reforming section is heated by the combustion gas discharged from the burner having a burner that burns the reformed gas with a combustion oxidant gas. And a combustion section that
During the start-up operation and during the combustion of the burner after the first ignition of the burner, when the generation of water vapor in the evaporation section is detected, the combustion of the burner is stopped ,
Until the elapse of a predetermined time from the generation detection time of the steam, the supply of the reforming water is continued,
A reformer characterized in that supply of the reforming fuel is started and the burner is re-ignited from the time when the predetermined time has elapsed from the time when the generation of steam is detected . A reforming unit that is supplied with reforming fuel and reforming water to generate reformed gas;
An evaporating unit that is supplied with the reforming water, evaporates the reforming water, and supplies the reforming unit to the reforming unit;
A combustion section that has a burner that is supplied with at least the reformed gas during start-up operation and burns the reformed gas with a combustion oxidant gas, and that heats the reformed section with the combustion gas discharged from the burner; With
During the start-up operation and when the combustion of the burner after the first ignition of the burner is stopped, when the generation of water vapor in the evaporation section is detected, a predetermined time has elapsed from the time when the water vapor generation was detected. until the continued supply of the reforming water, and re-ignition of the burner is prohibited, from the point of elapse of a predetermined time after occurrence detection point of the water vapor, starting the supply of fuel for the reformer reforming apparatus characterized in that the re-ignition takes place in the burner Te. Before SL combustion unit is to carry out the evaporation section and the heat exchanger after the combustion gas is heat-exchanged the reforming section,
3. The reformer according to claim 1 , wherein only the combustion oxidant gas is supplied to the burner from the time when the generation of the water vapor is detected until the burner is ignited.   The reformer according to claim 3, wherein the supply amount of the combustion oxidant gas supplied to the burner is increased immediately before the detection of the generation of the water vapor. In a fuel cell system including a fuel cell in which fuel gas is supplied to the fuel electrode and oxidant gas is supplied to the oxidant electrode to generate electric power,
A fuel cell system using the reformed gas generated by the reformer according to any one of claims 1 to 4 as the fuel gas.

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