JP2008105892A - Stopping method for fuel reformer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stopping method for a fuel reformer preventing lowering of catalytic performance and generation of hazardous substances or the like. <P>SOLUTION: After a fuel reformer is stopped and while the temperatures of catalyst layers of both a first reactor 22 and a second reactor 23 are lowered to the cracking temperature of a raw fuel gas or below, steam is flown through the first reactor 22 and the second reactor 23 to purge residual reformed gas and raw fuel gas. After the temperatures of catalyst layers of both first reactor 22 and second reactor 23 are lowered to the cracking temperature of the raw fuel gas or below and while the temperature of catalyst layer of either the first reactor 22 or the second reactor 23 is lowered to the condensation temperature of steam or below, the raw fuel gas is flown through the first reactor 22 and the second reactor 23 to purge residual steam. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for stopping a fuel reformer that reforms raw fuel into a reformed gas containing hydrogen.

  Hydrogen is expected as clean energy, and its use is being studied in various industrial fields. For example, in a fuel cell, a pair of electrodes are arranged with an electrolyte layer in between, a fuel gas containing hydrogen is supplied to one electrode (anode side), and an oxidizing gas containing oxygen is supplied to the other electrode (cathode side) Is a power generation system that obtains an electromotive force by utilizing an electrochemical reaction that occurs between the two electrodes, and can achieve high energy efficiency, and can also be used for nitrogen oxide (NOx), sulfur oxide (SOx), etc. As the amount of air pollutants emitted is small, it is expected to be used as a clean energy supply method.

  Usually, in these fuel cells, air is used as an oxidizing gas, and a gas containing hydrogen obtained by steam reforming a raw material fuel of a hydrocarbon such as natural gas is used as a fuel gas. Therefore, a fuel cell power generation apparatus including such a fuel cell is provided with a hydrogen generator such as a fuel reformer, and a desulfurizer and reformer in which hydrocarbons such as natural gas are continuously provided. Thus, desulfurization and steam reforming are performed to obtain a reformed gas mainly composed of hydrogen, and this reformed gas is supplied to the fuel cell after the CO concentration is reduced to 1% or less by a CO converter. . For example, in a polymer electrolyte fuel cell having a lower operating temperature of 60 to 80 ° C., the CO concentration is reduced to 1% or less by a CO converter, and further the CO concentration is reduced to 10 ppm or less by a CO remover. After that, the fuel cell is supplied.

  On the other hand, the fuel cell power generation apparatus is so-called DSS (Daily Start and Stop) operation that starts and stops according to the demand for electric power, and the fuel reforming apparatus is repeatedly started and stopped in response to this. ing.

  However, if the operation of the fuel reformer is stopped while water vapor, reformed gas, or the like remains in the fuel reformer, the water vapor is condensed and water is retained in the fuel reformer. There is a problem that the catalyst is deteriorated and performance is lowered, and it is difficult to quickly raise the temperature to a target temperature upon restart.

  For this reason, when stopping the operation of the fuel reformer, it is necessary to drain off the water vapor and the reformed gas remaining in the fuel reformer. At that time, various attempts have been made to change the type of purge gas to be introduced into the reformer depending on the temperature of the catalyst layer to prevent the catalyst layer from being oxidized and to form a dew condensation atmosphere, and to carry out the operation more economically. For example, in Patent Document 1 below, after the reformed gas in the reformer is purged with steam, the temperature of the reforming catalyst layer is equal to or lower than the temperature at which the raw material gas does not thermally decompose, and It is disclosed that after the temperature of the water vapor condenses below the temperature, the raw material gas is introduced and the water vapor in the reformer is purged to stop the operation of the fuel reformer.

  In addition, in Patent Document 2 below, when steam is supplied into the reformer and the temperature in the reformer decreases to the condensation temperature of steam or the vicinity thereof, the steam supply to the reformer is stopped, An inert gas is supplied to the reformer to replace water vapor remaining in the interior with the inert gas, and then an inert gas is supplied to the reformer so that the internal pressure does not become a negative pressure value. Disclosing the operation of the fuel reformer is disclosed.

In addition, hydrocarbons in the raw fuel are decomposed by the reforming reaction, and CO is produced as a by-product. However, CO reacts with Ni under a temperature condition of approximately 200 ° C. or less, and is volatile and toxic. New nickel carbonyl may be formed. For this reason, when a Ni-based catalyst is used in the catalyst layer of each reactor, it is necessary to prevent the formation of nickel carbonyl from the viewpoint of the environment and safety. It is disclosed that the temperature of the purge gas introduced into the disposed catalyst layer is maintained at 200 ° C. or higher.
JP 2002-151124 A JP 2004-137108 A JP 2005-506659 A

  As long as the purge gas is introduced into the fuel reformer and the water vapor and the reformed gas staying inside are flushed, the reformer, CO Purge is performed in the order of the transformer, the CO remover, or the order of the CO remover, the CO converter, and the reformer.

  Therefore, in the configuration in which the purge gas is introduced from the reformer side of the fuel reformer and the water vapor is washed away, the CO converter and the CO remover are also washed away in order.

  However, since the individual reactors have different operating temperatures, there is a difference in the temperature drop rate after the fuel reformer is stopped.

  For this reason, it is necessary to determine the purge conditions while monitoring the catalyst layer temperature of each reactor, but until now, the type of purge gas introduced into the reformer is appropriately changed based on the temperature change in the reformer. Therefore, depending on conditions such as the operating temperature and the type of catalyst layer of each reactor, water may remain in the downstream CO converter or CO remover.

  Ni-based catalysts are relatively inexpensive, have high performance and high durability, but Ni may react with CO under the temperature condition of 200 ° C. or less to produce volatile and toxic nickel carbonyl. There is. For this reason, when a Ni-based catalyst is used, it is necessary to prevent the formation of nickel carbonyl from the viewpoint of environment and safety.

  However, in the method disclosed in Patent Document 3, a relatively high temperature purge gas is introduced into the catalyst layer on which the Ni-based catalyst is arranged, so that the cooling efficiency of the reactor is poor, and the purge gas is relatively low. There were many economic problems.

  Accordingly, an object of the present invention is to provide a method for stopping a fuel reforming apparatus that can solve the above-described problems and prevent the deterioration of catalyst performance and the generation of harmful substances.

  In order to achieve the above object, a method for stopping a fuel reformer according to the present invention includes a first reactor for generating a reformed gas by a steam reforming reaction between steam and raw fuel gas, and the first reactor. And a second method of stopping the fuel reformer, the second reactor being connected to the second reactor for reducing the concentration of impurities contained in the reformed gas to obtain a refined reformed gas, Until the temperature of the catalyst layer of both the first reactor and the second reactor becomes equal to or lower than the decomposition temperature of the raw fuel gas, steam is circulated through the first reactor and the second reactor. The remaining reformed gas and raw fuel gas are flowed away, and after the temperature of the catalyst layer of both the first reactor and the second reactor becomes equal to or lower than the decomposition temperature of the raw fuel gas, the first reactor And until the temperature of the catalyst layer of any of the second reactors is equal to or lower than the condensation temperature of water vapor During characterized by causing runoff water vapor remaining in the raw fuel gas is circulated to the first reactor and the second reactor.

  According to the present invention, after the fuel reformer is stopped, the first reactor and the temperature of the catalyst layers of both the first reactor and the second reactor become lower than the decomposition temperature of the raw fuel gas. Since the remaining reformed gas and raw fuel gas are caused to flow away by circulating water vapor through the second reactor, the remaining raw fuel gas is thermally decomposed to deposit carbon, resulting in performance deterioration due to carbon poisoning of the catalyst. It is possible to prevent nickel carbonyl, which is a highly volatile harmful substance, from reacting with Ni when the temperature of CO in the remaining reformed gas decreases. Then, after the temperature of the catalyst layer of both the first reactor and the second reactor becomes equal to or lower than the decomposition temperature of the raw fuel gas, the temperature of the catalyst layer of either the first reactor or the second reactor is steam. The condensed water stays in the fuel reforming device by flowing the raw fuel gas through the first reactor and the second reactor and allowing the remaining water vapor to flow out until the temperature becomes below the condensation temperature. It is possible to prevent the catalyst performance from being deteriorated by the condensed water, and to quickly raise the temperature to the target temperature upon restart.

  Further, the method for stopping the fuel reformer of the present invention includes the first reactor and the method until the temperature of the catalyst layer of the first reactor becomes 500 ° C. or less after the fuel reformer is stopped. It is preferable to circulate water vapor through the second reactor. By passing water vapor through the first reactor and the second reactor until the temperature of the catalyst layer of the first reactor becomes 500 ° C. or less, the remaining reformed gas and raw fuel gas are washed away, It is possible to suppress the decomposition of the remaining raw fuel gas and the deposition of carbon, and it is possible to prevent the catalyst performance from being deteriorated due to the carbon poisoning of each catalyst layer.

  Further, the fuel reforming apparatus stopping method of the present invention is characterized in that the first reformer and the second reactor are circulated with water vapor to flow out the remaining reformed gas and raw fuel gas, and then the first reactor and the second reactor. Until the temperature of the catalyst layer of both the reactor and the second reactor is equal to or lower than the decomposition temperature of the raw fuel gas, the inside of the flow path of the first reactor and the second reactor is sealed, It is preferable that water vapor is intermittently introduced into the flow path so that the internal pressure of the flow path maintains a positive pressure with respect to the outside air. When the internal pressure in the first reactor and the second reactor becomes negative with respect to the outside air, the atmosphere flows into the fuel reformer and the catalyst layer of each reactor may be oxidized and deteriorated. By introducing water vapor intermittently into the flow path so that the internal pressure in one reactor and the second reactor is kept positive with respect to the outside air, the inflow of air into the fuel reformer is reduced. It can prevent, and the fall of the catalyst performance of each catalyst layer can be prevented.

  Further, the fuel reforming apparatus stopping method of the present invention seals the flow paths of the first reactor and the second reactor after the temperature of the catalyst layer of the first reactor becomes 500 ° C. or less. Until the temperature of the catalyst layer of the first reactor becomes 400 ° C. or lower so that the internal pressure of the flow path maintains a positive pressure with respect to the outside air. Until the temperature of the catalyst layer of the first reactor is 400 ° C. or lower and 350 ° C. or lower, water vapor and / or raw fuel gas is intermittently introduced into the flow path. Is preferred. According to this aspect, while preventing the inflow of air into the fuel reformer, the temperature is increased until the temperature of the catalyst layers of both the first reactor and the second reactor becomes equal to or lower than the decomposition temperature of the raw fuel gas. Can be reduced.

  In addition, the method for stopping the fuel reforming apparatus of the present invention is performed until the temperature of the catalyst layer of the first reactor becomes 200 ° C. or less after the temperature of the catalyst layer of the first reactor becomes 350 ° C. or less. In the meantime, it is preferable to flow the raw fuel gas through the first reactor and the second reactor and to drain the remaining water vapor. According to this aspect, it is possible to prevent the condensed water from staying in the fuel reformer by causing the water vapor to flow away, to prevent deterioration of the catalyst performance due to the condensed water, and to quickly reach the target temperature at the time of restart. The temperature can be raised to. Further, thermal decomposition does not occur even when raw fuel gas is circulated.

  Further, the method for stopping the fuel reformer of the present invention is for heating the first reactor and the second reactor with the raw fuel gas circulated through the first reactor and the second reactor. It is preferable to send the gas to a non-ignition combustion device, dilute with the air introduced into the combustion device, and exhaust. According to this aspect, the raw fuel gas circulated for running off the water vapor can be sufficiently diluted and safely exhausted.

  In the method for stopping a fuel reforming apparatus of the present invention, it is preferable that the first reactor includes a reforming catalyst in which Ni is supported on alumina and / or zirconia. According to this aspect, since the catalyst cost can be reduced, the material cost of the fuel reformer can be reduced.

  According to the method for shutting down the fuel reforming apparatus of the present invention, the catalyst layer reacts with Ni when performance deterioration occurs due to carbon poisoning or oxidation, or when the CO in the remaining reformed gas is lowered in temperature. The formation of nickel carbonyl, which is a highly volatile harmful substance, can be prevented. Further, since the condensed water can be prevented from staying in the fuel reformer, the catalyst performance can be prevented from being deteriorated by the condensed water, and the temperature can be quickly raised to the target temperature upon restart.

  Hereinafter, an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic configuration diagram of a fuel cell power generator capable of applying a method for stopping a fuel reformer according to the present invention.

  The fuel cell main body 10 is mainly composed of an electrolyte 11 and a fuel electrode 12 and an air electrode 13 disposed on both sides thereof.

  The reformed gas supply side of the fuel electrode 12 is connected to a pipe L <b> 1 extending from the opening 31 a of the reformed gas switching valve 31.

  From the off-gas discharge side of the fuel electrode 12, the pipe L <b> 2 extends and is connected to the combustion raw material inlet 21 a of the combustion device 21 of the fuel reformer 20. An off-gas cutoff valve 32 is arranged in the middle of the pipe L2. In addition, a part of the pipe line between the off-gas cutoff valve 32 and the combustion device 21 of the pipe L2 is branched and extends from the opening 31c of the reformed gas switching valve 31. It is connected to the arranged pipe L3.

  The oxidant gas supply side of the air electrode 13 is connected to a pipe L4 extending from the oxidant gas supply source. A first oxidant gas supply pump 41 is disposed in the middle of the pipe L4.

  From the off-gas discharge side of the air electrode 13, the pipe L <b> 5 extends so that the oxidant gas used in the electrode reaction can be discharged to the outside air or used in the next process (not shown).

  The fuel reformer 20 is mainly composed of a first reactor 22 and a second reactor 23.

  The first reactor 22 is a reactor that generates a reformed gas mainly composed of hydrogen from a raw fuel of hydrocarbons such as naphtha, natural gas, coal gas, and alcohols by a steam reforming reaction. What is called a reformer is preferably employed.

  The first reactor 22 is provided with a combustion device 21 that heats the reforming catalyst layer filled with the reforming catalyst and supplies reaction heat for performing the reforming reaction.

  A piping L6 for taking in combustion air is connected to the combustion raw material inlet 21a of the combustion device 21, and a combustion air blower 42 is arranged in the middle.

  Further, a piping L7 for exhausting the combustion exhaust gas extends from the combustion exhaust gas discharge port 21b of the combustion device 21 so that it can be processed in the next process (not shown) or released to the atmosphere.

  The reforming raw material input side of the first reactor 22 is connected to a pipe L8 extending from the raw fuel source. The pipe L8 is provided with a raw fuel supply valve 34, a desulfurizer 24, and a raw fuel supply pump 43 on the way, so that the raw fuel gas supplied from the raw fuel source can be desulfurized by the desulfurizer 24. Has been. The pipe L8 is partially branched, extends from the reforming water source, and is connected to the pipe L9 in which the reforming water supply pump 44 is disposed in the middle.

  Further, a temperature sensor 51 that measures the temperature of the catalyst layer and a pressure sensor 52 that measures the pressure are disposed inside the first reactor 22.

The second reactor 23 is a reactor for purifying by reducing the impurity concentration in the reformed gas. For example, the second reactor 23 reacts with CO in the reformed gas with water vapor to form hydrogen and CO ₂ . A CO converter that performs modification (water gas shift reaction; exothermic reaction), a CO remover that selectively oxidizes CO contained in the reformed gas (selective oxidation reaction; exothermic reaction) to form CO _2, and the like are preferably employed. .

  In this embodiment, the second reactor 23 is divided into a lower reaction chamber and an upper reaction chamber, and the lower reaction chamber is filled with a shift catalyst to form a CO converter 23a, and the upper reaction chamber. The chamber is filled with a CO selective oxidation catalyst to form a CO remover 23b. Further, temperature sensors 53 and 54 for measuring the temperature of each catalyst layer are arranged in each of the CO converter 23a and the CO remover 23b.

  The CO remover 23b is connected to a pipe L10 for taking in an oxidant gas such as air necessary for the oxidation reaction in the CO remover 23b, and a second oxidant gas supply pump 45 is disposed on the way. ing. The upper end of the CO remover 23b is provided with a pipe L11 for sending purified reformed gas with reduced impurities such as CO, and is connected to the opening 31b of the reformed gas switching valve 31 via the filter 25. is doing.

  As the second reactor 23, the type of fuel cell to be applied, the type of raw fuel supplied to the first reactor 22, the type of catalyst charged in the first reactor 22, and the like are required. Depending on the purity of the refined reformed gas, the reactor to be used can be appropriately selected, and only the CO converter 23a may be used. Further, a reactor other than the CO converter 23a and the CO remover 23b may be used, or the CO converter 23a and / or the CO remover 23b may be used in combination with another reactor. In addition to the reactor using the selective oxidation reaction that selectively reacts CO with oxygen in the air to reduce the CO concentration, the CO remover can react with CO and hydrogen to cause methanation to reduce the CO concentration. It may be a reactor using a methanation reaction to be reduced.

  Next, the operation of the fuel cell power generator including the method for stopping the fuel reformer of the present invention will be described.

  This fuel cell power generator is repeatedly started and stopped according to the amount of power demand.

  During startup, the off-gas cutoff valve 32 and the raw fuel supply valve 34 are opened, and the reformed gas cutoff valve 33 is closed. The reformed gas switching valve 31 closes the valve of the opening 31c and opens the valve of the opening 31a and the valve of the opening 31b. That is, the pipe L1 and the pipe L11 are connected. Further, the first oxidant gas supply pump 41, the combustion air blower 42, the raw fuel supply pump 43, the reforming water supply pump 44, and the second oxidant gas supply pump 45 are operated. Further, the combustion device 21 is set in an ignition state.

  The raw fuel gas supplied from the raw fuel source is first introduced into the desulfurizer 24 to remove sulfur components contained in the raw fuel gas. The raw fuel gas from which the sulfur component has been removed is mixed with the reforming water supplied from the pipe L9 and supplied to the first reactor 22 to generate a hydrogen-rich reformed gas by the reforming reaction. Since the above reforming reaction is an endothermic reaction, combustion air 21 and off-gas are supplied from the piping L6 and the off-gas from the piping L2 to the combustion device 21 in an ignition state, and these are combusted to produce the first reactor 22. The catalyst layer is heated.

  And the reformed gas produced | generated by the 1st reactor 22 reduces the carbon monoxide density | concentration with a 2nd reactor (CO converter 23a, CO removal device 23b), Then, it lets the filter 25 pass, and is piping L1 is supplied to the fuel electrode 12 of the fuel cell body 10.

  In the fuel cell main body 10, the reformed gas supplied to the fuel electrode 12 and the oxidant gas supplied to the air electrode 13 are electrochemically reacted to generate power, and this power generation output is an inverter unit (not shown). Etc., and converted to AC power of a predetermined voltage and linked to the power system.

  The off gas discharged from the fuel electrode 12 is supplied to the combustion device 21 through the pipe L2 and used as a combustion source.

  On the other hand, when the demand amount of electric power falls and it becomes necessary to stop a fuel cell power generation device, the off-gas cutoff valve 32, the reformed gas cutoff valve 33, and the raw fuel supply valve 34 are closed. The reformed gas switching valve 31 closes the valve of the opening 31a and opens the valve of the opening 31b and the valve of the opening 31c. That is, the pipes L3 and L11 are connected. Further, the first oxidant gas supply pump 41, the combustion air blower 42, the raw fuel supply pump 43, and the second oxidant gas supply pump 45 are stopped. Further, the combustion device 21 is set to a non-ignition state.

  If the second oxidant gas supply pump 45 is stopped before the reformed gas switching valve 31 is switched, high-concentration CO may be supplied to the fuel electrode 12 and the fuel electrode 12 may be poisoned by CO. Therefore, it is preferable to stop the second oxidant gas supply pump 45 in view of the timing at which the path of the reformed gas switching valve 31 is switched. That is, it is preferable to stop at the same time when the path of the reformed gas switching valve 31 is switched or after the path of the reformed gas switching valve 31 is switched.

  Thus, immediately after the stop, only the reforming water is supplied to the fuel reforming device 20 in a state where each pipeline is sealed. Then, it is steamed in the fuel reformer 20.

  If the temperature of the catalyst layer of the first reactor 22 is sufficiently high, almost all of the supplied reformed water evaporates and is vaporized, so that the pressure in the fuel reformer 20 is unlikely to decrease. However, since the temperature of the catalyst layer of the first reactor decreases with the passage of time, it becomes difficult to be gradually steamed, and the pressure in the fuel reformer 20 tends to gradually decrease.

  Therefore, the supply of reforming water to the fuel reformer 20 may be continuous until the temperature of the catalyst layer of the first reactor 22 is 500 ° C. or lower, or may be intermittently supplied. However, after the temperature of the catalyst layer of the first reactor 22 becomes 500 ° C. or less, the reforming water is used until the temperature of the first reactor 22 becomes 400 ° C. or less, preferably 350 ° C. or less. Is intermittently supplied to the first reactor 22 to generate steam and expand the volume in the fuel reformer 20.

  By supplying the reforming water in this way, the pressure in the fuel reformer 20 can be maintained at a positive pressure with respect to the outside air, and the inflow of air into the fuel reformer 20 is prevented. The temperature of the catalyst layers of both the first reactor 22 and the second reactor 23 can be lowered to a temperature below the decomposition temperature of the raw fuel gas.

  The supply of the reforming water to the fuel reformer 20 is controlled based on the index of the pressure sensor 52 installed in the first reactor so that the reforming water is supplied when a pressure drop occurs. May be. Further, the correlation between temperature and pressure may be acquired as data in advance, and control may be performed so that reforming water is supplied at regular intervals when the temperature of the first reactor 22 falls to a predetermined temperature.

  And after the temperature of the catalyst layer of both the 1st reactor 22 and the 2nd reactor 23 became below the decomposition temperature of raw fuel gas, specifically, the temperature of the catalyst layer became 350 degrees C or less. Thereafter, preferably after the temperature reaches 300 ° C. or less, the raw fuel supply valve 34 is opened, the raw fuel supply pump 43 is operated, and the reforming water supply pump 44 is stopped. The raw fuel supply pump 43 may be operated continuously or intermittently. That is, the supply of the raw fuel gas to the fuel reformer 20 may be a continuous supply or an intermittent supply.

  Next, the reformed gas shut-off valve 33 is opened, the combustion air blower 42 is operated, and the water vapor retained in the fuel reformer 20 is washed away with the raw fuel gas and introduced into the combustor 21. It is diluted with combustion air supplied from the pipe L6 and exhausted from the pipe L7 to the outside of the system.

  In the present invention, until the temperature of the catalyst layer of either the first reactor 22 or the second reactor 23 is equal to or lower than the condensation temperature of water vapor, preferably the temperature of the catalyst layer of the first reactor 22 is Before the temperature reaches 200 ° C. or lower, the raw fuel gas is circulated through the first reactor 22 and the second reactor 23 to cause the water vapor remaining in the fuel reformer 20 to flow away.

  The raw fuel gas is allowed to flow through the first reactor 22 and the second reactor 23 until the temperature of the catalyst layer of either the first reactor 22 or the second reactor 23 becomes equal to or lower than the condensation temperature of water vapor. By flowing away the remaining water vapor, it is possible to prevent the generation of condensed water in the fuel reforming device 20, to prevent the performance of the catalyst from being deteriorated by the condensed water, and to quickly reach the target temperature upon restarting. The temperature can be raised.

  Ni-based catalysts are relatively inexpensive, have high performance and high durability as reforming catalysts, but if gas containing CO stays at a temperature of 200 ° C. or lower, Ni and CO May react to produce volatile and harmful nickel carbonyl. On the other hand, since the raw fuel gas is decomposed in the presence of water vapor to produce CO, in the water vapor staying in the fuel reformer 20, CO produced by the reforming reaction is slightly present. However, it may be included. Therefore, the production of nickel carbonyl can be suppressed by causing the water vapor remaining in the fuel reformer 20 to flow out until the temperature becomes 200 ° C. or lower.

  Then, after the water vapor remaining in the fuel reformer 20 is drained, the reformed gas cutoff valve 33 and the raw fuel supply valve 34 are closed, and the raw fuel supply pump 43 is stopped. That is, the raw fuel gas is sealed in the fuel reformer 20.

  By doing so, the catalyst layer reacts with Ni when the performance deterioration due to carbon poisoning, oxidation, etc. occurs or the temperature of the CO in the remaining reformed gas decreases, and it is a highly volatile harmful substance. The formation of certain nickel carbonyl can be prevented. Further, since it is possible to prevent the generation of condensed water in the fuel reformer, it is possible to prevent the catalyst performance from being deteriorated by the condensed water and to quickly raise the temperature to the target temperature upon restart.

  At the time of restart, since the raw fuel gas stays in the fuel reformer 20, if the raw fuel gas continues to be heated as it is, there is a possibility that the raw fuel gas is decomposed and carbon is deposited. Before the temperature rises to a temperature that is easy to do, it is preferable to circulate the raw fuel gas by circulating water vapor.

  Examples will be described in detail below. The raw fuel was reformed using the fuel reformer shown in FIG.

  When the stop operation of the fuel reformer was started, the off-gas cutoff valve 32, the reformed gas cutoff valve 33, and the raw fuel supply valve 34 were closed. In the reformed gas switching valve 31, the valve of the opening 31a is closed, and the valve of the opening 31b and the valve of the opening 31c are opened. Then, after supplying the reforming water from the reforming water supply pump 44 to the fuel reformer at a supply rate of 5 g / min for 60 seconds, the reforming water supply pump 44 is stopped and the catalyst layer of the first reactor 22 is stopped. When the temperature of the water becomes 400 ° C. or lower and 350 ° C. or lower, the reforming water supply pump is operated again, and the reforming water is supplied with reforming water at a supply rate of 5 g / min for 60 seconds. After supplying to the reformer, the reforming water supply pump 44 was stopped.

  When the temperature of the catalyst layer of the first reactor 22 becomes 300 ° C. or less, the raw fuel supply valve 34 is opened, the raw fuel supply pump 43 is operated, and the supply amount of the raw fuel is 300 cc / min. For 330 seconds. During this time, the reformed gas shut-off valve 33 is opened, the combustion air blower 42 is operated, water vapor remaining in the fuel reformer 20 is washed away with the raw fuel gas, and introduced into the combustor 21. It diluted with the combustion air supplied from the piping L6, and exhausted out of the system from the piping L7. After the raw fuel supply pump 43 was stopped, the reformed gas shutoff valve 33 was closed and the combustion air blower 42 was stopped. When the temperature of the catalyst layer of the first reactor 22 becomes 280 ° C. or lower, the raw fuel supply pump 43 is operated to supply the raw fuel at an interval of 30 minutes at a supply rate of 300 cc / min for 60 seconds. Then, when the temperature of the catalyst layer became 150 ° C. or lower, the raw fuel was supplied at a supply rate of 300 cc / min for 60 seconds at an interval of 60 minutes.

In this way, the reforming ratio from raw fuel to hydrogen when the fuel reforming apparatus is stopped and repeated starting and stopping, and the content of each component (H ₂ , CH ₄ , CO ₂ , CO) in the reformed gas The amount was measured. The results are shown in FIG.

  As can be seen from FIG. 2, according to the method for stopping the fuel reforming apparatus of the present invention, even if the start and stop of the fuel reforming apparatus are repeated, the reforming performance is hardly lowered.

It is a schematic block diagram of the fuel cell power generator which enabled it to apply the stop method of the fuel reformer of this invention. Changes in the reforming rate from raw fuel to hydrogen and the contents of H ₂ , CH ₄ , CO ₂ and CO contained in the resulting reformed gas when the method for stopping the fuel reformer of the present invention is applied. It is a chart shown.

Explanation of symbols

10: Fuel cell body 11: Electrolyte 12: Fuel electrode 13: Air electrode 20: Fuel reformer 21: Combustion device 22: First reactor 23: Second reactor 24: Desulfurizer 25: Filter 31: Reformed gas Switching valve 32: Off-gas cutoff valve 33: Reformed gas cutoff valve 34: Raw fuel supply valve 41: First oxidant gas supply pump 42: Combustion air blower 43: Raw fuel supply pump 44: Reformed water supply pump 45: First Dioxidant gas supply pumps 51, 53, 54: Temperature sensor 52: Pressure sensor

Claims (7)

A first reactor that generates a reformed gas by performing a steam reforming reaction between steam and raw fuel gas, and a refinement reformer that is connected to the first reactor and reduces the concentration of impurities contained in the reformed gas. A method for stopping a fuel reformer having a second reactor as a gas,
After the fuel reformer is stopped, the first reactor and the first reactor are heated until the temperature of the catalyst layers of both the first reactor and the second reactor becomes equal to or lower than the decomposition temperature of the raw fuel gas. The remaining reformed gas and raw fuel gas are caused to flow by passing steam through the two reactors,
After the temperature of the catalyst layer of both the first reactor and the second reactor becomes equal to or lower than the decomposition temperature of the raw fuel gas, the temperature of the catalyst layer of either the first reactor or the second reactor The fuel reformer is stopped until the raw fuel gas is circulated through the first reactor and the second reactor and the remaining steam is allowed to flow out until the temperature becomes equal to or lower than the condensation temperature of the steam. Method.   The method of stopping a fuel reformer according to claim 1, wherein water vapor is circulated through the first reactor and the second reactor until the temperature of the catalyst layer of the first reactor becomes 500 ° C or lower. .   After flowing the steam through the first reactor and the second reactor to remove the remaining reformed gas and raw fuel gas, the catalyst layers of both the first reactor and the second reactor Until the temperature becomes equal to or lower than the decomposition temperature of the raw fuel gas, the flow paths in the first reactor and the second reactor are sealed, and the pressure in the flow path maintains a positive pressure with respect to the outside air. Thus, the method for stopping the fuel reformer according to claim 1 or 2, wherein water vapor is intermittently introduced into the flow path.   After the temperature of the catalyst layer of the first reactor becomes 500 ° C. or less, the flow paths of the first reactor and the second reactor are sealed, and the flow path pressure is positive with respect to the outside air. In order to maintain the pressure, steam is intermittently introduced into the flow path until the temperature of the catalyst layer of the first reactor becomes 400 ° C. or lower, and the catalyst layer of the first reactor The method for stopping a fuel reformer according to claim 3, wherein steam and / or raw fuel gas are intermittently introduced into the flow path until the temperature is 400 ° C or lower and 350 ° C or lower.   After the temperature of the catalyst layer of the first reactor becomes 350 ° C. or lower and before the temperature of the catalyst layer of the first reactor becomes 200 ° C. or lower, the first reactor and the second reactor The method for stopping the fuel reformer according to any one of claims 1 to 4, wherein the raw fuel gas is circulated to cause residual water vapor to flow out.   The raw fuel gas passed through the first reactor and the second reactor is sent to a non-ignition combustion device for heating the first reactor and the second reactor, and introduced into the combustion device. The method of stopping a fuel reformer according to any one of claims 1 to 5, wherein the exhaust gas is diluted with exhausted air and exhausted.   The said 1st reactor is the stop method of the fuel reformer as described in any one of Claims 1-6 provided with the reforming catalyst formed by carrying | supporting Ni on an alumina and / or zirconia.