JP2006342003A - Hydrogen production apparatus and method for stopping the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To supply a purge gas containing few amount of oxygen and moisture for purging the residual gas in a hydrogen production apparatus without using special equipment. <P>SOLUTION: At the time of stopping the hydrogen production apparatus 1, the residual gas in the apparatus 1 can be purged with a purge gas of less oxygen and moisture content without using special equipment by supplying an exhaust gas of an auxiliary combustor 3 as the purge gas 33 to a reformer 4 after stopping the supply of fuel 14, air 16 and steam 17. Also abnormal temperature rising of a combustion catalyst at the time of restarting can be prevented by the stopping procedure of the hydrogen production apparatus 1 comprising stopping the fuel 14 and the air 16 while continuing supply of the steam 17, then supplying the air 16 again to burn and remove carbon deposited on the combustion catalyst 5. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a hydrogen production apparatus and a hydrogen production apparatus stop method.

  The hydrogen production apparatus, for example, mixes a hydrocarbon-based fuel, steam and air, burns a part of the fuel through the combustion catalyst layer, and supplies the fuel to the reforming catalyst layer. A reformer configured to generate reformed gas containing hydrogen by reforming, and a CO reducer that reduces CO in the reformed gas generated by the reformer and supplies it to the anode of the fuel cell Is done. The fuel cell generates power by reacting hydrogen in the reformed gas supplied from the CO reducer and oxygen in the air. For example, a solid polymer fuel cell is used.

When stopping the fuel cell system that generates power using the reformed gas produced by such a hydrogen production device, by purging the reformed gas containing hydrogen remaining in the hydrogen production device, abnormal combustion of the residual gas, Prevention of deterioration of the catalyst and the like due to condensation of water vapor has been performed. The purge gas, for example, water vapor, nitrogen gas (N _2), an inert gas etc. are used (Patent Document 1, Patent Document 2). However, if water vapor is used as the purge gas, the water vapor remaining in the apparatus after the hydrogen production apparatus is stopped may condense and the catalyst such as the reforming catalyst may deteriorate. Such a problem can be avoided if nitrogen is used as the purge gas, but it is necessary to store the nitrogen gas used only when the operation is stopped in the tank, and there is a problem that waste of storage facilities and the like is large.

  Patent Document 3 proposes that an exhaust gas obtained by burning a combustible gas such as an anode exhaust gas of a fuel cell is used as a purge gas. However, in order to generate combustion exhaust gas as purge gas that is used only when the operation is stopped, it is necessary to separately provide a combustion device, so that the equipment cost and the like cannot always be reduced.

  On the other hand, when a hydrocarbon-based fuel is used for the reforming reaction, carbon in the fuel decomposed during operation adheres to the combustion catalyst and the like, and when the hydrogen production apparatus is restarted, the adhering carbon burns temporarily. In particular, the temperature of the combustion catalyst may rise abnormally (for example, about 950 ° C. or more). Due to this temperature increase, there is a problem that the activity deterioration of the combustion catalyst using metal accelerates.

  As a problem similar to this adhering carbon, Patent Document 4 raises a problem that in a reformer using a liquid hydrocarbon fuel, carbon is deposited on the reforming catalyst and the reforming reaction is inhibited. Yes. According to this document, it is proposed that fuel supply is intermittently stopped, and oxidizing gas is supplied while the fuel supply is stopped to burn and remove the precipitated carbon.

  However, Patent Document 4 does not consider the problem that carbon adheres to the combustion catalyst or the like during operation, and the carbon burns and abnormally rises at the time of restart. In particular, if the supply of fuel is stopped intermittently, the generation efficiency of the reformed gas is lowered, so that it is difficult to adopt as a solution for removing carbon adhering to the combustion catalyst.

JP 2002-179401 A JP 2001-180908 A JP 2000-277137 A Japanese Patent Laid-Open No. 2004-262689

  An object of the present invention is to supply a purge gas for purging a residual gas of a hydrogen production apparatus without using a special apparatus with low oxygen content and water content.

  Another object of the present invention is to remove carbon adhering to the combustion catalyst and to avoid an abnormal rise in the temperature of the combustion catalyst when the hydrogen production apparatus is restarted.

  In order to solve the above-mentioned problems, the present invention presupposes a hydrogen production apparatus provided with an auxiliary combustor that burns anode exhaust gas of a fuel cell and heats at least one of fuel, water vapor, and air. When the fuel, the supply of fuel, air and water vapor are stopped, the exhaust gas of the auxiliary combustor is supplied to the reformer to purge the residual gas of the hydrogen production apparatus.

  That is, the combustion exhaust gas of the auxiliary combustor that improves the heat balance by heating the fuel necessary for the reforming reaction by the combustion heat of the anode exhaust gas of the fuel cell during normal operation is no longer present when the hydrogen production device is stopped. Since heating of fuel etc. becomes unnecessary, it is discharged into the atmosphere. Therefore, the present invention is characterized in that the combustion exhaust gas discharged from the auxiliary combustor to the atmosphere is used as a purge gas when the hydrogen production apparatus is stopped.

  In addition, since the discharge amount of the anode exhaust gas is rapidly reduced by stopping the hydrogen production apparatus, the auxiliary fuel is burned. Further, it is preferable to control the combustion air ratio to the auxiliary fuel in the range of 0.9 to 1.1. According to this, the oxygen concentration of the combustion exhaust gas used as the purge gas can be reduced, and the oxidation of the catalyst can be prevented.

  In order to solve the other problems described above, the present invention is characterized in that when the hydrogen production apparatus is stopped, the supply of fuel and air is stopped and the supply of water vapor is continued, and then the air is supplied again. To do. That is, by stopping the supply of fuel and air and continuously supplying water vapor, the reformed gas remaining in the reformer and the CO reducer is quickly purged. Even if the supply is resumed, abnormal combustion of the combustible gas can be prevented. Since carbon adhering to the combustion catalyst or the like is combusted and removed by restarting the supply of air, it is possible to avoid the combustion catalyst from becoming an abnormally high temperature at the next startup of the hydrogen production apparatus.

  Here, the timing of restarting the supply of air is after the residual gas has been purged, and the condition is that the temperature of the combustion catalyst is equal to or higher than the temperature at which the attached carbon can be combusted (for example, 550 ° C.). Further, in order to prevent the combustion catalyst from being deteriorated by heat generated during carbon combustion, the flow rate ratio of water vapor and air is controlled so that the temperature of the combustion catalyst layer is lower than a set temperature (for example, 900 ° C. or lower, preferably It is preferable to hold | maintain at 850 degrees C or less.

  In the above case, the exhaust gas of the auxiliary combustor can be used instead of water vapor as the purge gas. Nitrogen gas can also be used.

  In order to solve the above other problems, the present invention stops the supply of steam and water after stopping the supply of fuel and air when the hydrogen production apparatus is stopped. The supply of air is resumed, and the supply of air is stopped after the temperature of the combustion catalyst layer reaches the peak value.

  According to this, in addition to the above effect, it can be detected that the attached carbon has been burned and removed by the peak of the combustion temperature, so that excessive air supply can be prevented and deterioration of the CO selective oxidation catalyst due to oxygen can be prevented. be able to.

  According to the present invention, the purge gas for purging the residual gas of the hydrogen production apparatus can be supplied without using a special apparatus with a small oxygen content and water content.

  Further, according to the present invention, it is possible to remove carbon adhering to the combustion catalyst or the like in the reformer, and to avoid an abnormal increase in the temperature of the combustion catalyst when the hydrogen production apparatus is restarted.

  Hereinafter, the present invention will be described based on examples.

  FIG. 1 shows the configuration of a fuel cell system to which one embodiment of a method for stopping a hydrogen production apparatus of the present invention can be applied. As shown in the figure, a fuel cell system includes a small-sized hydrogen production apparatus 1 that generates a reformed gas containing hydrogen from a raw material gas, a solid polymer fuel cell 2 that generates power using hydrogen as a raw material, and a hydrogen production apparatus. 1 and an auxiliary combustor 3 that assists in raising the temperature of the gas supplied to the inside.

  The reforming reactor 4 constituting the hydrogen production apparatus 1 is arranged in a vertical cylindrical container in order from the bottom to the top, the combustion catalyst layer 5, the reforming catalyst layer 6, the CO shift catalyst layer 7, and the CO selection. An oxidation catalyst layer 8 is provided. An activation burner 9 is provided in the space below the combustion catalyst layer 5. Further, a steam generating heat exchanger 10 is provided in a space between the reforming catalyst layer 6 and the CO shift catalyst layer 7. A CO shift heat exchanger 11 is provided in the CO shift catalyst layer 7, and a CO selective oxidation heat exchanger 12 is provided in the CO selective oxidation catalyst layer 8.

  To the lower space of the reforming reactor 4 of the start burner 9, city gas 14 as fuel is supplied from the blower 13, combustion air 16 is supplied from the blower 15, and steam 17 is supplied from the steam generating heat exchanger 10. It has become so. Further, a thermocouple temperature sensor 18 is provided at the boundary between the combustion catalyst layer 5 and the reforming catalyst layer 6, and a thermocouple temperature sensor 19 is provided in the space between the reforming catalyst layer 6 and the steam generating heat exchanger 10. Is provided. Further, the air 20 can be introduced into the space between the CO shift catalyst layer 7 and the CO selective oxidation catalyst layer 8. Cooling water can be supplied from the water pumps 21 and 22 to the CO shift heat exchanger 11 and the CO selective oxidation heat exchanger 12 in order to adjust the catalyst temperature thereof.

  The reformed gas rich in hydrogen discharged from the top of the reforming reactor 4 configured as described above is supplied to the anode chamber of the fuel cell 2 through the reformed gas supply pipe 23. . Air 24 is supplied to the cathode chamber of the fuel cell 2. In the fuel cell 2, hydrogen in the reformed gas and oxygen in the air react via the electrolyte membrane to generate power. A cathode exhaust gas 25 containing unreacted oxygen is discharged from the cathode chamber, and an anode exhaust gas 26 containing unreacted hydrogen is discharged from the anode chamber. The anode exhaust gas 26 is guided to the auxiliary burner 27 of the auxiliary combustor 3 and burned.

  The auxiliary burner 27 of the auxiliary combustor 3 is supplied with city gas 14 as auxiliary fuel and air 16 as combustion air. A heat exchanger 28 is provided in the auxiliary combustor 3. The heat exchanger 28 is configured to heat the water supplied from the water pump 29 with the exhaust gas from the auxiliary combustor 3 and supply the water to the steam generating heat exchanger 10 of the reforming reactor 4. The exhaust gas 30 of the auxiliary combustor 3 can be released into the atmosphere via the switching valve 31. When the switching valve 31 is switched, the exhaust gas 30 can be supplied to the lower space of the activation burner 9 as the purge gas 33 via the dehumidifier 32. The dehumidifier 32 is for removing moisture in the purge gas 33, and can be omitted if the amount of moisture in the purge gas 33 is not a problem for the catalyst in the reforming reactor 4. .

  The controller 34 controls the entire hydrogen production apparatus 1. In the illustrated example, the controller 34 takes in the detected temperatures of the temperature sensors 18 and 19, and the blower 13 and the blower 15 according to the state of the hydrogen production apparatus 1. The water pump 29, the switching valve 31 and the like are controlled.

  The operation of this embodiment configured as described above will be described. The starter burner 9 is operated by supplying fuel 14 and air 16 to the lower space of the starter burner 9 of the reforming reactor 4. At startup, the air to fuel ratio is about 1.2. In the present embodiment, city gas mainly composed of methane is used as the fuel 14, but the fuel is not limited to this, and hydrocarbon fuels such as natural gas, LP gas, gasoline, and kerosene can be used. .

  When the temperature of the combustion catalyst layer 5 and the reforming catalyst layer 6 is sufficiently increased by the combustion gas of the starting burner 9, the steam 17 is supplied from the steam generating heat exchanger 10, and the reforming of the fuel 14 is performed in the reforming catalyst layer 6. Will be possible. Therefore, the reforming reaction is performed by lowering the air to fuel ratio (for example, 0.25 to 0.3).

  In the reforming catalyst layer 6, methane and water are converted into hydrogen mainly by the reforming reaction of the following formula (1), and simultaneously generated CO is further converted to hydrogen by the CO conversion reaction of the following formula (2). The CO concentration at this time is, for example, 2000 ppm to 3000 ppm.

CH ₄ + H ₂ O⇔CO + 3H ₂ (1)
CO + H ₂ O⇔CO ₂ + H ₂ (2)

   The reforming reaction of the formula (1) is a reaction that proceeds at a high temperature, and is an endothermic reaction that requires a large amount of energy. Therefore, in order to supply reaction heat, a part of the fuel methane is combusted in the combustion catalyst layer 5 to be supplemented. For example, the temperature distribution in the reforming reactor 4 is about 400 ° C. from the start burner 9 to the combustion catalyst layer 5, the combustion catalyst layer 5 is 750 ° C. to 850 ° C., and the reforming catalyst layer 6 is 550 ° C. to 750 ° C. It becomes ℃.

  The reforming reaction of the reforming catalyst layer 6 generates CO as a by-product. However, since the fuel cell 2 uses a platinum catalyst for the electrode, the electrode is covered when CO gas is contained in the fuel gas. Poisoning will reduce power generation performance. Therefore, CO generated in the reforming catalyst layer 6 is reduced by using the CO shift catalyst layer 7 and the CO selective oxidation catalyst layer 8. In the CO shift catalyst layer 7, CO is reduced by the CO conversion reaction of the formula (2). In the CO selective oxidation catalyst layer 8, the CO concentration is adjusted to about several ppm by the CO selective oxidation reaction of the following formula (3).

2CO + O ₂ → 2CO ₂ (3)

  Here, the temperature of the reformed gas generated from the reforming catalyst layer 6 (for example, 550 to 750 ° C.) is adjusted to the optimum operating temperature (for example, 250 to 300 ° C.) of the CO shift catalyst layer 7 to generate steam. It is reduced by the heat exchanger 10 for use. As described above, the steam 17 generated in the steam generating heat exchanger 10 is fed to the bottom of the reforming reactor 4 as raw material steam.

  In this manner, the reformed gas containing hydrogen treated by the CO selective oxidation catalyst 8 is supplied to the anode chamber of the fuel cell 2 through the reformed gas supply pipe 23 and reacts with the air supplied to the cathode chamber. To generate electricity.

  Since unreacted hydrogen remains in the exhaust gas in the anode chamber of the fuel cell 2, the anode exhaust gas 26 is guided to the auxiliary burner 27 of the auxiliary combustor 3 for combustion treatment. The temperature of the combustion exhaust gas in the auxiliary combustor 3 varies depending on the amount of unreacted hydrogen, but is, for example, 600 to 900 ° C. The combustion exhaust gas 30 of the auxiliary combustor 3 is discharged out of the system via the switching valve 31 during normal operation. On the other hand, auxiliary heat of water supplied from the water pump 29 is performed by the heat exchanger 28 provided in the auxiliary combustor 3, and the heated water is used as the steam generating heat exchanger 10 of the reforming reactor 4. As a result, the steam 17 is supplied to the bottom of the reforming reactor 4 as a raw material. Thus, according to the fuel cell system of the present embodiment, the hydrogen production apparatus 1 stably produces the reformed gas containing hydrogen, and stable power generation is performed in the fuel cell 2 by the reformed gas.

  Next, an embodiment of a method for stopping the hydrogen production apparatus 1 according to the features of the present invention will be described with reference to the flowchart of the stop process shown in FIG. 2 and the time chart of the operation state of each part shown in FIG. 2 is executed by the controller 34.

  As shown in FIGS. 2 and 3, during a steady operation from time Q to T (S 1), a predetermined amount of fuel 14, air 16, and water vapor 17 are supplied to the reforming reactor 4. Therefore, the reformer temperature detected by the temperature sensor 18 is constant. When a stop command is issued at time R (S2), the supply of fuel 14 and air 16 to the reforming reactor 4 is stopped in step S3 (FIG. 3 (a)), and the water pump 29 is stopped. Water supply to the steam generating heat exchanger 10 is stopped (FIG. 3B). However, the water vapor 17 supplied to the reforming reactor 4 stops after a slight delay as shown in FIG. On the other hand, the supply of the reformed gas to the anode exhaust gas 26 is stopped simultaneously with the stop operation at time B, so that the amount of the anode exhaust gas 26 introduced into the auxiliary combustor 3 quickly decreases (FIG. 3 (c)). Next, in step S4, the switching valve 31 is switched, and the combustion exhaust gas from the auxiliary combustor 3 is supplied as the purge gas 33 to the bottom of the reforming reactor 4 (FIG. 3 (f)). Supply of a set amount of fuel 14 and air 16 is started as fuel (S5). At this time, it is possible to keep the oxygen concentration in the purge gas 33 at 0% or in the vicinity of 0% by controlling the combustion air ratio to the auxiliary fuel in the range of 0.9 to 1.1. The purge gas 33 contains moisture from the combustion of the fuel 14 and remains in the reforming reactor 4, but it can be suppressed to a minimum amount as compared with the conventional purge by steam. Furthermore, if necessary, it is preferable to provide a dehumidifier 32 for dehumidification. The dehumidifier 32 condenses and removes moisture by cooling the purge gas 33 with, for example, cooling water.

  Next, in step S6, the exhaust gas temperature of the auxiliary combustor 3 is measured by a temperature sensor (not shown), the amount of fuel 14 and air 16 supplied to the auxiliary burner 27 is adjusted, and the exhaust gas temperature is controlled to be lower than the set temperature. (S7). In step S8, the temperature of the reforming catalyst layer 6 is detected by the temperature sensor 18, and the fuel 14 and air supplied to the auxiliary burner 27 so that the reforming catalyst temperature becomes a set temperature (for example, 100 ° C.). The amount of 16 is controlled (S9). Note that steps S6 and S7 can be omitted.

  When the reforming catalyst temperature falls below the set temperature, the timer is operated. When the timer set time is reached (S10), the supply of fuel 14 and air 16 supplied to the auxiliary burner 27 is stopped (S11), and the stop process is performed. finish.

  As described above, according to the present embodiment, the auxiliary combustor that burns the anode exhaust gas of the fuel cell and heats water or the like necessary for the reforming reaction becomes unnecessary when the hydrogen production apparatus is stopped. Since the combustion exhaust gas of the auxiliary combustor is used as the purge gas, the purge gas can be supplied without using a special device such as a nitrogen storage device.

  Further, since the combustion air ratio in the auxiliary combustor 3 is controlled in the range of 0.9 to 1.1, the oxygen concentration of the purge gas can be reduced and the oxidation of the catalyst can be prevented.

  Moreover, according to the purge by the combustion exhaust gas of the auxiliary combustor 3, the moisture in the purge gas can be suppressed to a small amount as compared with the conventional steam purge. At this time, if it is desired to further remove the moisture in the purge gas, the moisture can be removed by providing a dehumidifier 32.

  FIG. 4 shows a configuration of a fuel cell system according to another embodiment to which the hydrogen production apparatus stopping method of the present invention is applied. This embodiment differs from the embodiment of FIG. 1 in that it does not have a switching valve 31 and a dehumidifier 32 system for using the exhaust gas of the auxiliary combustor 3 as a purge gas, and a nitrogen gas 36 is used as the purge gas. 37, the air 16 can be supplied to the supply pipe. Since other configurations are the same as those of the embodiment of FIG. 1, the same reference numerals are given and the description thereof is omitted. In particular, the present embodiment is an embodiment characterized in that the hydrogen production apparatus 1 is stopped after removing carbon adhering to the combustion catalyst layer 5 in the reforming reactor 4.

  In the present embodiment, when the hydrogen production device 1 is restarted after the hydrogen production device 1 is stopped according to the embodiment of FIG. 1, the temperature of the combustion catalyst layer 5 rises abnormally as shown in FIG. It is a solution. That is, as shown in FIG. 5, the start burner 9 is ignited at time E, and fuel 14 and air 16 are supplied to the start burner 9 so that the air ratio becomes 1.2 from time E to H. To do. Thereby, a flame is formed by the start burner 9 and the temperature of the downstream combustion catalyst layer 5 and the reforming catalyst layer 6 is increased. The start-up mode is from time E to H. Then, it is confirmed that the temperature of the reforming catalyst layer 6 has reached the set temperature, and at time H, water is supplied to the steam generating heat exchanger 10 to generate steam 17 and supplied to the reforming reactor 4. . As a result, the reforming reactor 4 shifts to the reforming mode, and the hydrogen concentration in the reformed gas is increased to reach a steady operation.

  However, the inventors have found a phenomenon that the temperature of the combustion catalyst layer 5 temporarily becomes abnormally high (for example, 950 ° C. or higher) between time F and time G in the start mode. However, the abnormal rise in the temperature of the combustion catalyst layer 5 is temporary, and when the time G elapses, it drops to a temperature close to normal (for example, about 900 ° C.). In the reforming mode in which the supply of water vapor is started, the temperature of the combustion catalyst layer 5 gradually decreases and stabilizes at a steady operation temperature (for example, about 700 ° C.).

  Here, since the combustion catalyst layer 5 uses a metal, for example, when the temperature becomes 950 ° C. or more, there is a problem that the activity deterioration of the combustion catalyst is accelerated. Therefore, when the phenomenon in which the temperature of the combustion catalyst layer 5 abnormally rises in the start-up mode was examined, carbon in the fuel was thermally decomposed and adhered to the combustion catalyst layer 5 during the normal reforming operation. It was found that the cause was burning on restart.

By the way, it is considered that the reason why the attached carbon is generated is that the air ratio between the city gas and the air supplied to the combustion catalyst layer 5 during the reforming operation is low. That is, since the combustion catalyst layer 5 is for combusting a part of the city gas to supplement heat necessary for the reforming reaction, the air ratio is a low value necessary for partial combustion (for example, 0.25 to 0). .3). Thus, when the air ratio is low, partial oxidation combustion of city gas may occur. Here, the component of city gas is 85% or more of CH _4, but includes C ₂ H ₆ , C ₃ H _{8 and the} like.
FIG. 6 shows the relationship between the thermal decomposition temperature and decomposition amount of CH ₄ , C ₂ H ₆ , and C ₃ H ₈ contained in city gas. As shown in FIG. 6, it can be seen that C ₂ H ₆ and C ₃ H ₈ decompose at a relatively low temperature compared to CH ₄ . C ₃ H ₈ containing a large amount of C decomposes at the lowest temperature, decomposition proceeds from a temperature of about 500 ° C., and 23% decomposes at a temperature of 700 ° C. This decomposition will be described by taking the case of CH ₄ as an example. As shown in the following equation (4), CH ₄ is decomposed into H ₂ and C (carbon).

CH ₄ ⇒C + 2H ₂ (4)
In particular, carbon generation is more likely to occur at higher temperatures, lower steam flow rates, and lower air ratios. Therefore, in the vicinity of the combustion catalyst layer 5 during steady operation, the air ratio is low (for example, 0.3) and the temperature is high (for example, 700 ° C. or higher), so that carbon is easily generated.

  The carbon generated in this manner adheres to the catalyst surface of the combustion catalyst layer 5 and the attached carbon burns by the air set at a high air ratio supplied at the time of startup, so that the combustion catalyst layer 5 becomes abnormally high in temperature. It is considered to be.

  Therefore, in this embodiment, after the carbon adhering to the combustion catalyst layer 5 is burned and removed at the time of stopping, the hydrogen production apparatus 1 is stopped so as to avoid the abnormally high temperature of the combustion catalyst layer 5 at the time of startup. It is characterized by doing.

  A method for stopping the hydrogen production apparatus 1 of this embodiment will be described with reference to the time chart of FIG. In this embodiment, a stop procedure when steam is used as the purge gas is shown. In the figure, from time 0 to time B, steady operation is performed, and a predetermined amount of fuel 14, air 16, and water vapor 17 are supplied. When the stop operation is started at time B, a command to stop the fuel 14 and the air 16 almost simultaneously is output from the controller 34 to the blower 13 and the blower 15. On the other hand, since the inside of the reforming reactor 4 is purged, the supply of the steam 17 is continued to prevent abnormal combustion due to the residual gas. The temperature of the combustion catalyst layer 5 and the reforming catalyst layer 6 starts to decrease due to the purge of the steam 17, the interior of the reforming reactor 4 is replaced with steam, and the gas remaining in the reforming reactor 4 is supplemented. It is discharged out of the system from the combustor 3.

  In this embodiment, the water vapor 17 is supplied and purged at the same flow rate as in the steady operation, but it is also possible to purge at a lower flow rate than in the normal operation. In this embodiment, the hydrogen production apparatus 1 of the present embodiment has a space volume of about 6 L, and shows an example of purging at a steam flow rate of about 10 g / min. Accordingly, this corresponds to a flow rate at which the inside of the reforming reactor can be sufficiently replaced with a steam purge for 1 to 2 minutes. However, the purge time and the size of the hydrogen production apparatus 1 are not particularly limited.

  Next, at time C, air is supplied again into the reforming reactor 4 while supplying water vapor. The re-supply timing of the air is preferably controlled to a temperature (for example, 600 ° C. or more) in consideration of a margin before the temperature of the combustion catalyst layer 5 becomes a temperature at which carbon can be combusted (for example, 550 ° C.) or less. The Here, FIG. 8 shows the thermal decomposition characteristics of the carbon adhering to the combustion catalyst layer 5 in an oxidizing atmosphere. As is apparent from the figure, a decrease in the weight of carbon is confirmed from a temperature of 550 ° C., and it can be seen that the combustion of carbon has started. Therefore, during the period from time C to time E at which the air 16 is supplied, the temperature of the combustion catalyst layer 5 is maintained at a set temperature (for example, 850 ° C.) or less to prevent deterioration of the combustion catalyst layer 5. And the flow ratio of air 16 is controlled.

  In this embodiment, the supply of the air 16 is resumed when the temperature of the combustion catalyst layer 5 is 620 ° C., and gradually rises from 620 ° C. of the combustion catalyst layer 5 simultaneously with the start of the supply of air. It is 720 ° C. The reason why the temperature of the combustion catalyst layer 5 rises in this way is that the carbon adhering to the combustion catalyst layer 5 is combusted, and as a result, the temperature of the reforming catalyst layer 6 also rises.

  Here, in order to confirm whether or not the carbon inside the combustion catalyst layer 5 has completely combusted, the temperature sensor 18 measures the outlet temperature of the combustion catalyst layer 5, and when the measured value exceeds the peak value, It is determined that the carbon in the combustion catalyst layer 5 has burned. Then, with a margin, the supply of air is stopped at time E when the temperature of the combustion catalyst layer 5 has passed the peak. By the way, when the supply amount of air for carbon combustion is too large, there is a problem of deterioration of the CO selective oxidation catalyst layer 8 due to oxygen. Therefore, it is preferable to control the supply amount of air (oxygen) necessary for burning and removing carbon adhering to the combustion catalyst layer 5.

  FIG. 9 shows an example in which the air for carbon combustion is supplied more than necessary. The illustrated example is an example of restart when the hydrogen production apparatus 1 is stopped after supplying air for 5 minutes after the peak of the temperature of the combustion catalyst layer 5 during carbon removal. As shown in the figure, since the adhering carbon is removed, in the start-up mode, the temperature of the combustion catalyst layer 5 does not exceed 800 ° C., but the CO concentration in the reformed gas in the reforming operation becomes 2000 ppm or more. ing. It is the figure which showed the history of the temperature of the reformer at the time of restarting, and the CO density | concentration from a reformer. According to this, it is considered that since the excess air was supplied, the catalyst of the CO selective oxidation catalyst layer 8 was oxidized and the deterioration progressed.

  However, since the amount of carbon adhering to the combustion catalyst layer 5 cannot actually be detected, the time point when the temperature detected by the temperature sensor 18 for detecting the temperature of the combustion catalyst reaches a peak and then tends to decrease is taken as a guideline for stopping the air supply. It is preferable to do. In FIG. 7, the air supply stop time E is usually several minutes after the start of air supply, but stops after a set time (for example, 1-2 minutes) after the combustion catalyst temperature reaches its peak. It is preferable to do.

  FIG. 10 shows a time chart of the state of each part such as the catalyst temperature when the hydrogen production apparatus 1 is restarted after the hydrogen production apparatus 1 is stopped according to this embodiment. As shown in the figure, in the start-up operation, the temperature of the combustion catalyst does not exceed 800 ° C., and even when the reforming operation at time D is entered, the CO concentration temporarily becomes about 300 ppm. Can be maintained.

  As described above, according to this embodiment, the carbon adhering to the combustion catalyst layer 5 can be burned and removed during the stop operation, so that the combustion catalyst layer 5 is restarted when the hydrogen production apparatus 1 is restarted. The catalyst can be prevented from deteriorating due to an abnormal rise in temperature.

  Further, since the amount of air when the attached carbon is burned and removed is controlled based on the change in the temperature of the combustion catalyst, deterioration of the CO selective oxidation catalyst due to oxygen can be suppressed.

  If conditions such as the specifications of the hydrogen production apparatus 1 and the specifications of the fuel are determined, the times B, C, D, and E in FIG. 7 are determined almost uniquely, so that the temperature peak of the combustion catalyst is detected. Instead, the stop procedure of FIG. 7 can be realized by time control by a timer.

  In FIG. 11, the time chart of the other Example which stops the hydrogen production apparatus 1 after removing the carbon adhering to the combustion catalyst layer 5 in the reforming reactor 4 is shown. This embodiment differs from the embodiment of FIG. 7 in that nitrogen gas is applied instead of water vapor as the purge gas at the time of stoppage. That is, at time B, the supply of the fuel 14, air 16, and water vapor 17 is all stopped, and the regulating valve 36 is opened to supply nitrogen gas to the bottom of the reforming reactor 4. The other points are the same as in the embodiment of FIG.

  According to the present embodiment, in addition to the same effects as those of the second embodiment, when water vapor is used as the purge gas, it is possible to avoid problems associated with water vapor being condensed and moisture adsorbed on the catalyst.

  In addition, it cannot be overemphasized that it can replace with nitrogen gas and the combustion exhaust gas of the auxiliary | assistant combustor 3 shown in the Example of FIG. 1 can be used as purge gas.

  FIG. 12 shows a time chart of still another embodiment in which the hydrogen production apparatus 1 is stopped after the carbon adhering to the combustion catalyst layer 5 in the reforming reactor 4 is removed. The present embodiment is different from the embodiment of FIG. 7 in that the supply of the water vapor 17 is stopped at the time of air resupply in the stop process. The other points are the same as in the embodiment of FIG.

  According to the present embodiment, the steam is cut when the air is re-supplied, so that heat loss in the steam generating heat exchanger 10 necessary for generating steam is reduced, and the temperature of the combustion catalyst layer 5 is remarkably increased. It becomes easy to do. As a result, when the amount of carbon adhering to the combustion catalyst layer 5 is small, the peak of the combustion catalyst temperature can be clearly determined.

  The supply of the fuel 14 and the air 16 is stopped at time B in FIG. 12, and the hydrogen production apparatus 1 is purged with the steam 17 from time B to time C. At time C, the supply of the water vapor 17 is stopped, and at the same time, the supply of the air 16 is restarted. This resupply of air 16 is performed when the temperature of the combustion catalyst layer 5 is equal to or higher than the temperature at which carbon can be combusted, as in the case of FIG. Further, the flow rate of the water vapor 17 and the air 16 is controlled to adjust the temperature of the combustion catalyst layer 5 to a set temperature (for example, 900 ° C., preferably 850 ° C.) or less, thereby preventing deterioration of the combustion catalyst layer 5 due to heat.

  When the air was supplied again at time C, the temperature of the combustion catalyst suddenly increased at time D and reached, for example, 840 ° C. The peak temperature at that time is determined from the measured value of the temperature sensor 18, and the supply of the air 16 is stopped at time E after a predetermined time, and the process ends.

  It should be noted that the air flow rate and the steam flow rate in the stop operation can be fixed during the trial operation. However, when the combined operation of air and steam is performed in the initial stage and no significant history of the combustion catalyst temperature is obtained, the steam is stopped and only the air supply is performed as in this embodiment.

  Further, as described in the embodiment of FIG. 7, when the conditions such as the specifications of the hydrogen production apparatus 1 and the specifications of the fuel are determined, the times B, C, D, and E in FIG. 12 are determined almost uniquely. Thus, instead of detecting the temperature peak of the combustion catalyst, the stop procedure of FIG. 12 can be realized by time control by a timer.

It is a figure which shows the structure of the fuel cell system which can apply one Example of the stop method of the hydrogen production apparatus of this invention. It is a flowchart of the stop process of one Example of the stop method of the hydrogen production apparatus of this invention. 2 is a time chart showing a change in temperature of each part of the reforming reactor and a change in gas flow rate in the stopping step of the embodiment in FIG. It is a figure which shows the structure of the fuel cell system which can apply the other Example of the stop method of the hydrogen production apparatus of this invention. It is a figure explaining that the temperature of a combustion catalyst rises abnormally at the time of restart of a hydrogen production device. It is a figure which shows the relationship between the thermal decomposition temperature and decomposition amount of a hydrocarbon fuel. It is a time chart which shows the temperature change and gas flow rate change of each part of a reforming reactor in the stop process of other examples of the present invention. It is a figure which shows the thermal decomposition characteristic in the oxidation atmosphere of the carbon adhering to the combustion catalyst. FIG. 8 is a time chart for explaining the CO concentration at the time of restart when carbon combustion air is supplied more than necessary when the stop process of the embodiment of FIG. 7 is performed. FIG. 8 is a time chart showing a temperature change, a gas flow rate change, and a CO concentration change in each part of the reforming reactor when the hydrogen production apparatus is started after the stop process of the embodiment of FIG. 7 is performed. It is a time chart which shows the temperature change and gas flow rate change of each part of the reforming reactor in the stopping step of still another embodiment of the present invention. It is a time chart which shows the temperature change and gas flow rate change of each part of the reforming reactor in the stopping step of still another embodiment of the present invention.

Explanation of symbols

1: Hydrogen production device 2: Fuel cell 3: Auxiliary combustor 4: Reforming reactor 5: Combustion catalyst layer 6: Reforming catalyst layer 7: CO shift catalyst layer 8: CO selective oxidation catalyst layer 9: Startup burner 10: Steam generation heat exchanger 11: CO shift heat exchanger 12: CO selective oxidation heat exchanger 13, 15: Blower 14: Fuel 16, 20, 24: Air 17: Water vapor 18, 19: Temperature sensors 21, 22 , 29: water pump 23: reformed gas supply pipe 25: cathode exhaust gas 26: anode exhaust gas 27: auxiliary burner 28: heat exchanger 30: exhaust gas 31: switching valve 32: dehumidifier

Claims (12)

  A hydrocarbon-based fuel, water vapor, and air are mixed, and a part of the fuel is burned through the combustion catalyst layer, and then supplied to the reforming catalyst layer to reform the fuel with the water vapor to generate hydrogen. A reformer that produces reformed gas, a CO reducer that reduces the CO in the reformed gas produced by the reformer and supplies it to the anode of the fuel cell, and an anode exhaust gas of the fuel cell. In a hydrogen production apparatus stopping method comprising an auxiliary combustor that burns and heats at least one of the fuel, the water vapor, and the air, the supply of the fuel, the air, and the water vapor is stopped, and then the auxiliary A method for stopping a hydrogen production apparatus, wherein exhaust gas from a combustor is supplied to the reformer to purge residual gas from the hydrogen production apparatus.   The method of stopping a hydrogen production apparatus according to claim 1, wherein the auxiliary combustor burns auxiliary fuel during purging.   The method for stopping a hydrogen production apparatus according to claim 2, wherein the auxiliary combustor controls the flow rate ratio of the combustion air to the auxiliary fuel from 0.9 to 1.1.   A hydrocarbon-based fuel, water vapor, and air are mixed, and a part of the fuel is combusted through the combustion catalyst layer, and then supplied to the reforming catalyst layer, and the fuel is reformed by the water vapor to generate hydrogen. A reformer that produces reformed gas, a CO reducer that reduces the CO in the reformed gas produced by the reformer and supplies it to the anode of the fuel cell, and the anode exhaust gas of the fuel cell In the method for stopping a hydrogen production apparatus comprising an auxiliary combustor that heats at least one of the fuel, the steam, and the air, the supply of the fuel and the air is stopped and the supply of the steam is performed. A method for stopping a hydrogen production apparatus, characterized in that the method continues and then supplies the air again.   The method for stopping a hydrogen production apparatus according to claim 4, wherein the supply of the steam is stopped and the exhaust gas or nitrogen of the auxiliary combustor is supplied instead of continuing the supply of the steam.   5. The temperature of the combustion catalyst layer is maintained at a set temperature or lower by controlling a flow rate ratio of the water vapor or the inert gas and the air in the step of resupplying the air. Method for stopping the hydrogen production equipment.   A hydrocarbon-based fuel, water vapor, and air are mixed, and a part of the fuel is combusted through the combustion catalyst layer, and then supplied to the reforming catalyst layer, and the fuel is reformed by the water vapor to generate hydrogen. A reformer that produces reformed gas, a CO reducer that reduces the CO in the reformed gas produced by the reformer and supplies it to the anode of the fuel cell, and the anode exhaust gas of the fuel cell In the method for stopping a hydrogen production apparatus comprising an auxiliary combustor that heats at least one of the fuel, the steam, and the air, the supply of the fuel and the air is stopped and the supply of the steam is performed. The hydrogen production apparatus is characterized in that the supply of water vapor is stopped and then the supply of air is resumed, and the supply of air is stopped after the temperature of the combustion catalyst layer reaches a peak value. How to stop.   8. The method for stopping a hydrogen production apparatus according to claim 7, wherein the air supply is restarted when the temperature of the combustion catalyst layer is equal to or higher than a set temperature at which carbon can be reburned.   The method for stopping a hydrogen production apparatus according to claim 7, wherein the flow rate of the water vapor and the air is controlled to keep the temperature of the combustion catalyst layer at 900 ° C or lower, preferably 850 ° C or lower.   A hydrocarbon-based fuel, water vapor, and air are mixed, and a part of the fuel is combusted through the combustion catalyst layer, and then supplied to the reforming catalyst layer, and the fuel is reformed by the water vapor to generate hydrogen. A reformer that generates reformed gas, a CO reducer that reduces the CO in the reformed gas generated by the reformer and supplies it to the anode of the fuel cell, and the anode exhaust gas of the fuel cell In a hydrogen production apparatus comprising an auxiliary combustor for heating at least one of the fuel, the water vapor and the air, and a control means, exhaust gas from the auxiliary combustor is supplied to the reformer Supply means, and after the supply of the fuel and the air is stopped, the control means supplies the exhaust gas of the auxiliary combustor to the reformer and purges the residual gas of the hydrogen production apparatus. Hydrogen production equipment.   A hydrocarbon-based fuel, water vapor, and air are mixed, and a part of the fuel is combusted through the combustion catalyst layer, and then supplied to the reforming catalyst layer, and the fuel is reformed by the water vapor to generate hydrogen. A reformer that produces reformed gas, a CO reducer that reduces the CO in the reformed gas produced by the reformer and supplies it to the anode of the fuel cell, and the anode exhaust gas of the fuel cell In a hydrogen production apparatus comprising an auxiliary combustor that heats at least one of the fuel, the water vapor, and the air, and a control means, the control means stops supplying the fuel and the air Then, the supply of water vapor is continued, and then the hydrogen production apparatus is stopped after the air is resupplied. A hydrocarbon-based fuel, water vapor, and air are mixed, and a part of the fuel is combusted through the combustion catalyst layer, and then supplied to the reforming catalyst layer, and the fuel is reformed by the water vapor to generate hydrogen. A reformer that produces reformed gas, a CO reducer that reduces the CO in the reformed gas produced by the reformer and supplies it to the anode of the fuel cell, and the anode exhaust gas of the fuel cell In a hydrogen production apparatus comprising an auxiliary combustor for heating at least one of the fuel, the water vapor and the air, and a control means, the control means stops supplying the fuel and the air Then, the supply of the water vapor is continued, and then the supply of the water vapor is stopped to restart the supply of the air, and the supply of the air is stopped after the temperature of the combustion catalyst layer reaches a peak value. Characteristic hydrogen production equipment.

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