JP2007290942A - Method for stopping reforming system, and the reforming system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the phenomenon that, upon the stop of a reforming system, a closed system including a reforming means reaches a negative pressure region, and to protect the system. <P>SOLUTION: When the reforming system is stopped, at first, the feed of air for oxidation to a reforming means 1 is stopped, thereafter, the feed of a gaseous starting material is stopped, further, the feed of fuel to a water vapor generating means 30 is stopped, then, the gaseous starting material remaining in the reforming means 1 is purged with water vapor generated by the residual heat in the water vapor generating means 30, further, when the inside of the reforming means 1 reaches a negative pressure region or approaches a negative pressure region by the phenomenon that the water vapor at least present in a CO reducing means 17 and piping 16 communicated therefrom to the reforming means 1 is condensed by the reduction of temperature, a prescribed amount of water is fed to the reforming means 1, and the water is heated and evaporated by heat in the water vapor reforming means 1, thus the phenomenon that the inside of the reforming means 1 reaches a negative pressure state is prevented, and the system is protected. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for stopping a reforming system and a reforming system for producing a hydrogen-rich reformed gas by steam reforming a raw material and supplying the reformed gas to an additional facility such as a fuel cell. The present invention relates to a reforming system stopping method and a reforming system for preventing and protecting the reforming means and the like from becoming negative pressure when stopping.

Conventionally, there has been a reformer (reforming means) that generates a hydrogen-rich reformed gas by steam reforming a mixture of source gas and steam (hereinafter referred to as a source-steam mixture) in the presence of a reforming catalyst. Are known. The hydrogen-rich reformed gas obtained in the reformer reacts with residual oxygen (carbon monoxide) with an oxygen-containing gas in the presence of a catalyst to convert to CO ₂ (carbon dioxide), and operates at a particularly low temperature. For solid polymer electrolyte fuel cells, CO is reduced to the ppm level before being supplied as fuel.
As the source gas, hydrocarbons such as methane, aliphatic alcohols such as methanol, ethers such as dimethyl ether, city gas, and the like are used. In the reformer, the reaction formula of steam reforming when methane is used as a raw material gas can be expressed as CH ₄ + 2H ₂ O → CO ₂ + 4H ₂ , and the preferred reforming reaction temperature is 650 to 750 ° C. It is a range.

There are an external heating type and an internal heating type as a system for supplying heat necessary for the reaction of the reformer.
The external heating type reformer is provided with a heating unit outside, and a reformed gas is generated by reacting a raw material gas and water vapor with a heat source. The internal heating type reformer is provided with a partial oxidation reaction layer on the supply side (upstream side), and the steam reforming reaction layer disposed on the downstream side using the heat generated in the partial oxidation reaction layer is subjected to a steam reforming reaction. Heating is performed to a temperature, and a steam reforming reaction is performed in the heated steam reforming catalyst layer to generate a hydrogen-rich reformed gas.

The partial oxidation reaction can be represented by CH ₄ + 1/2 · O ₂ → CO + 2H ₂ , and the preferable partial oxidation reaction temperature is in the range of 250 ° C. or higher. For example, Patent Documents 1 and 2 describe a self-oxidation internal heating type reformer as an improvement of the internal heating type reformer. The reformers of Patent Documents 1 and 2 have a double structure including an outer pre-reforming chamber and an inner main reforming chamber communicating with the outer pre-reforming chamber, and the pre-reforming chamber is provided with a reforming catalyst layer. The main reforming chamber is provided with an oxidizing air supply pipe, a mixed catalyst layer in which the reforming catalyst and the oxidation catalyst coexist, a shift catalyst, and the like. A supply pipe for supplying the oxidizing air is extended to the central portion of the main reforming chamber, and an air ejection portion comprising a plurality of nozzles is formed at a portion where the supply pipe extends to the mixed catalyst layer.

The reforming catalyst layer is for steam reforming the raw material gas. For example, a Ni-based reforming reaction catalyst such as NiO—Al ₂ O ₃ or NiO—SiO ₂ · Al ₂ O ₃ or WO ₂ —SiO ₂ · Al _2. such as O ₃ or _{NiO-WO 2 · SiO 2 ·} Al 2 O 3 is used. The reforming catalyst constituting the mixed catalyst layer is the same as described above, and the oxidation catalyst uniformly dispersed therein is the temperature required for the steam reforming reaction by oxidizing the raw material gas in the raw material-steam mixture to generate heat. For example, platinum (Pt), rhodium (Rh), ruthenium (Ru), or palladium (Pd) is used.
The ratio of the oxidation catalyst to the reforming catalyst is selected in the range of about 1 to 15% depending on the type of the raw material gas to be steam reformed. For example, when methane is used as the raw material gas, about 5% ± 2%, In the case of methanol, the mixing ratio is about 2% ± 1%.

  In order to generate steam necessary for steam reforming of the reformer, the reforming system is provided with steam generating means. The water vapor generating means burns gaseous fuel or liquid fuel with a burner and heats water with the combustion gas to generate water vapor. The reformer is supplied with a raw material-water vapor mixture obtained by mixing the water vapor generated by the water vapor generating means and the raw material gas from the raw material gas supply means by the suction mixing means comprising an ejector.

  When stopping the reforming system, if the supply of raw material gas and oxidized air to the reformer is stopped, the internal temperature of the reformer does not drop rapidly, so the raw material gas remaining in the reformer Causes carbon deposition. In order to prevent the carbon deposition, for example, Patent Document 3 proposes a method of purging the raw material gas remaining inside the reformer with water vapor when the reforming system is stopped. The method for stopping the reforming system of Patent Document 3 is that after the raw material gas supply to the reformer is stopped, the raw material gas remaining in the reformer is purged with steam, and then left to natural cooling. The raw material gas is sealed inside the reformer when the temperature becomes lower than the carbon deposition temperature of the gas.

JP 2001-192201 A JP-A-2005-149860 JP 2002-151124 A

  In the conventional method of stopping the reforming system, after the raw material gas remaining in the reformer is purged with steam, the reformer is maintained in a sealed state to naturally cool the reformer. At that time, the piping from the reformer to the CO reduction means and the inside of the CO reduction means are cooled faster than the reformer, but the piping from the reformer to the CO reduction means and the inside of the CO reduction means are in the reforming system. Since the water vapor coexisting in the reformed gas at the time of operation remains, when the internal temperature falls to the dew point region of water, the remaining water vapor is condensed.

  Usually, since the reforming system including the reformer and the CO reduction means is maintained in a sealed state, the inside of the reforming system is in a negative pressure state due to the contraction and condensation of the sealed gas due to the cooling of the previous steam. However, if the inside of the reforming system is left in a negative pressure state, external air is sucked in from the connection part of the valve provided in the piping, the catalyst is oxidized and deteriorated, and safety such as explosion is hindered when mixed with fuel. A fear is born. In addition, water in the system such as piping may be drawn into the reactor and the internal catalyst layer may be submerged, accelerating catalyst deterioration such as pulverization and catalyst poisoning due to impurities.

  In the conventional reforming system shutdown method, the pipe from the reformer to the CO reduction means and the inside of the CO reduction means are rapidly cooled between the time when the reformer is purged with steam and the time when the raw material gas is sealed. As described above, the volume shrinkage of the sealed gas and the residual water vapor are condensed, and the inside of the reforming system is in a negative pressure state.

  In order to solve such a negative pressure state in the reforming system, for example, it is conceivable to supply new steam from the steam reforming means to the reformer. However, for that purpose, it is necessary to continue the operation of the steam generating means even during the operation of stopping the reforming system or to start the steam generating means every time the negative pressure state is reached. As described above, even when the reforming system is stopped, if the steam generating means is operated, the fuel is consumed accordingly, so that the thermal efficiency of the system is lowered.

  Accordingly, an object of the present invention is to solve such a problem in the conventional reforming system stopping method, and an object thereof is to provide a new reforming system stopping method and a reforming system therefor.

  The method for stopping the reforming system of the present invention that solves the above problems includes a steam generating means 30 that generates steam, and reforming a raw material gas with the steam generated by the steam generating means 30 to generate a hydrogen-rich reformed gas. This is a method for stopping a reforming system including a reforming unit 1 to be generated and a CO reduction unit 17 for reducing CO (carbon monoxide) contained in the generated reformed gas. When stopping the reforming system, first, the supply of the oxidizing air to the reforming means 1 is stopped, then the supply of the raw material gas is stopped and the fuel supply to the steam generating means 30 is stopped, and then the steam generation is performed. The raw material gas remaining in the reforming means 1 is purged by the steam generated by the residual heat of the means 30, and the temperature of the steam present in at least the CO reducing means 17 and the pipe 16 communicating with the reforming means 1 is lowered. When the inside of the reforming means 1 reaches or approaches the negative pressure region due to contraction and / or condensation, a predetermined amount of water is supplied to the reforming means 1 and the water is reformed. It is characterized in that the inside of the reforming means 1 is prevented from being in a negative pressure state by heating and evaporating with heat. (Claim 1)

  In the reforming system stopping method, the reformed gas whose CO has been reduced by the CO reducing means 17 is caused to flow into the water tank 60 by bubbling, and the water stored in the water tank 60 is supplied to the reforming means 1. can do. (Claim 2)

  Further, in the method for stopping the reforming system, the supply of a predetermined amount of water from the water tank 60 to the reforming unit 1 can be performed using a differential pressure between the water tank 60 and the reforming unit 1. it can. (Claim 3)

  In any one of the above reforming system stop methods, a predetermined amount of water is supplied to the heat exchange pipe 50 having a predetermined internal volume provided in the reforming means 1 to reform the steam generated by the heat exchange pipe 50. It can be supplied to the source gas supply unit 11 of the means 1. (Claim 4)

  The reforming system of the present invention that solves the above problems includes a steam generating unit 30 that generates steam, and a reformer that generates a hydrogen-rich reformed gas by reforming a raw material gas with the steam generated by the steam generating unit 30. The reforming system includes a quality control means 1 and a CO reduction means 17 for reducing CO (carbon monoxide) contained in the generated reformed gas. And the raw material supply part 11 which supplies the mixture (raw material-steam mixture) of the water vapor and the raw material gas provided in the reforming means 1, the heat exchange pipe 50 having a predetermined internal volume, and the outlet of the CO reduction means 17 A water tank 60 communicated to the side, and a pipe 51 for supplying the water of the water tank 60 to the inlet side of the heat exchange pipe 50, and the outlet side of the heat exchange pipe 50 and the raw material supply unit 11 are communicated with each other. It is characterized by that. (Claim 5)

  In the above reforming system, a gas-liquid separation chamber 61 for allowing the anode exhaust gas discharged from the fuel cell 15 to pass through and separating and recovering water contained therein can be provided in communication with the water tank 60. (Claim 6)

  In any one of the above reforming systems, a gas-liquid separation chamber 62 provided in communication with the upper portion of the water tank 60, and a hydrophilic packed bed 70 that sucks water from the water tank 60 into the gas-liquid separation chamber 62; A distribution unit 18a for supplying the reformed gas into the hydrophilic packed bed 70 and a supply unit 68 for supplying makeup water to the gas-liquid separation chamber 62 can be provided. (Claim 7)

  According to the method for stopping the reforming system of the present invention, at least the CO reducing means and the water vapor existing in the piping communicating with the reforming means 1 are reduced in temperature and contracted or condensed. When the interior of the reforming unit 1 reaches or approaches the negative pressure region, the water is heated at the temperature of the reforming unit 1 by supplying a predetermined amount of water to the reforming unit 1. Evaporation suppresses the reforming unit 1 from becoming a negative pressure state, and prevents the pressure from becoming higher than necessary (excessive positive pressure).

  In the above reforming system stop method, as described in claim 2, the reformed gas whose CO is reduced by the CO reducing means 17 is caused to flow into the water tank 60 by bubbling, and the water stored in the water tank 60 is stored. Is supplied to the reforming means 1, the water tank 60 can absorb the ammonia in the reformed gas into the tank water. In this way, the tank water containing the ammonia can be circulated and supplied as, for example, water of a steam generation source that supplies the reforming means 1, whereby the reforming means 1 can perform an equilibrium reaction between nitrogen gas and hydrogen gas. This makes it possible to suppress the amount of ammonia produced in step (1) and to supply the reformed gas with the produced ammonia sufficiently low to the fuel cell.

  In the method of stopping the reforming system, as described in claim 3, the supply of a predetermined amount of water from the water tank 60 to the reforming unit 1 is a difference between the water tank 60 and the reforming unit 1. Pressure can be used. This eliminates the need for a special water supply drive source.

In any one of the above reforming system stopping methods, as described in claim 4, a predetermined amount of water is supplied to the heat exchange pipe 50 having a predetermined internal volume provided in the reforming means 1 to perform heat exchange. The water vapor generated by the pipe 50 can be supplied to the raw material gas supply unit 11 of the reforming means 1.
In this way, when a predetermined amount of water is supplied to the heat exchange pipe 50 having a predetermined internal volume, only the minimum predetermined amount of water necessary for supplementing the reforming means to the target pressure is supplied to the heat exchange pipe. Since it is possible to heat and evaporate at 50, it is possible to increase the pressure of the reforming means to an appropriate pressure and, for example, the pressure in the reforming means becomes abnormally high (excessive positive pressure) due to excessive evaporation, for example. Unforeseen circumstances can be avoided.

The reforming system of the present invention reforms the raw material supply section 11 for supplying a mixture of steam and raw material gas (raw material-steam mixture) and the heat exchange pipe 50 having a predetermined internal volume as described in claim 5. The water tank 60 is connected to the outlet side of the CO reduction means 17 and provided with a pipe 51 for supplying water from the water tank 60 to the inlet side of the heat exchange pipe 50. The supply unit 11 is communicated. By configuring in this way, at least the CO reducing means and the water vapor existing in the piping communicating with the reforming means 1 are reduced in temperature and contracted or condensed, so that the interior of the reforming means 1 is brought into the negative pressure region. When the pressure reaches or approaches the negative pressure region, it is possible to supply the reforming unit 1 with water that generates water vapor necessary and sufficient to maintain the internal pressure of the reforming unit 1 at a predetermined pressure.
That is, when the inside of the reforming means 1 reaches the negative pressure region or approaches the negative pressure region, regardless of the internal volume of the water tank 60 (regardless of the fluctuation of the water amount accompanying the fluctuation of the water level of the water tank 60), A predetermined amount of water corresponding to the water level in the water tank 60 flows into the heat exchange pipe 50 having a predetermined internal volume, and reforms steam necessary and sufficient to maintain the internal pressure of the reforming means 1 at a predetermined pressure. A reforming system that can be supplied to the means 1 can be provided.

  In the above reforming system, a gas-liquid separation chamber 61 for allowing anode exhaust gas discharged from the fuel cell 15 to pass through and separating and recovering water contained therein is communicated with the upper portion of the water tank 60 as described in claim 6. Can be provided. If comprised in this way, while being able to use effectively the collection | recovery water of anode exhaust gas as a part of make-up water, a water system can be modularized and a simplification of a layout will be attained.

  In any one of the above reforming systems, as described in claim 7, a gas-liquid separation chamber 62 provided in communication with an upper portion of the water tank 60, and water in the water tank 60 is supplied to the gas-liquid separation chamber 62. A hydrophilic filling layer 70 sucked into the inside, a flow distribution section 18a for supplying the reformed gas into the hydrophilic filling layer 70, and a supply section 68 for supplying makeup water to the gas-liquid separation chamber 60 can be provided. With this configuration, the contact between the hydrophilic filling layer 70 containing sufficient water and the reformed gas containing ammonia is promoted, and ammonia in the reformed gas is efficiently absorbed into the water contained in the hydrophilic packed bed. Can be removed. Further, since the reformed gas smoothly passes through the hydrophilic packed bed 70 and rises, the pressure loss of the reformed gas is small and there is no pressure fluctuation, and the pressure inside the reforming means 1 during normal operation is reduced. It can be maintained stably.

  Next, the best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a process flow diagram of a reforming system for explaining an example of the stopping method of the present invention. The reforming means 1 is provided with an outer preliminary reforming chamber 2 and an inner main reforming chamber 3 which are arranged in a double manner, and the whole is formed thin. The preliminary reforming chamber 2 and the main reforming chamber 3 are elongated and have a flat cross section, and their cross sections are similar to each other. The preliminary reforming chamber 2 is formed between the outside and the inside, and the main reforming chamber 3 is formed on the inside.

  The reforming means 1 to which the present invention can be applied is not limited to such a double structure, and the pre-reforming chamber 2 and the main reforming chamber 3 are configured separately, or the pre-reforming chamber. The present invention can also be applied to a configuration in which steam reforming is performed only in the main reforming chamber 3 without having 2. Therefore, the reforming means 1 according to the present invention has a main reforming chamber 3 disposed separately from the main reforming chamber 3 arranged in the double structure as shown in FIG. It means that what has only the main reforming chamber 3 (single reforming chamber) which does not have the quality chamber 2 is included.

  A reforming catalyst layer 4 is provided in the preliminary reforming chamber 2 outside the dual structure, and a mixed catalyst layer 5 and a shift catalyst layer 6 in which the reforming catalyst and the oxidation catalyst coexist in the main reforming chamber 3 are arranged inside. Is provided, and the shift catalyst layer 6 includes a high temperature shift catalyst layer 7 and a low temperature shift catalyst layer 8. A supply pipe 9 for supplying oxidized air is extended to the mixed catalyst layer 5 along the central portion of the main reforming chamber 3, and an air ejection portion 10 is provided at an extended portion of the mixed catalyst layer 5. The supply pipe 9 is connected to a pipe 9a for supplying oxidation air, and a heat exchange section for preheating arranged in a CO reduction means (so-called PROX) 17 described later is provided in the middle of the pipe 9a.

  A raw material gas supply unit 11 (specifically, a raw material-steam mixture supply unit 11) is provided at the lower part of the preliminary reforming chamber 2, and a reformed gas discharge unit 12 is provided at the lower part of the main reforming chamber 3. It is done. A heating unit 1a including an electric heater is provided around the reformer 1, and the interior of the reformer 1 is kept at a temperature equal to or higher than the condensation temperature of water vapor (for example, about 100 to 120 ° C. or higher) while the reforming system is stopped. It is supposed to be.

  A preheater 13 for activation is connected to the upper part of the main reforming chamber 3. The preheater 13 oxidizes (combusts) fuel gas with oxidizing air to generate a high-temperature gas when the reforming system is started, and the high-temperature gas quickly and normally operates in the reforming means 1 including the mixed catalyst layer 5. In the interior, an electric heater is disposed and an oxidation catalyst such as platinum (Pt) or palladium (Pd) is filled.

  When the reforming system is started, a mixture of raw material gas (or fuel gas) and start air is supplied to the preheater 13 from the outlet side of the first suction mixing means 14 made of an ejector, and the raw material gas in the mixture is converted into an oxidation catalyst. Reacts with oxygen contained in the air in the presence of hot water, and high-temperature gas generated by the oxidation heat flows out to the mixed catalyst layer 5. The hot gas flowing into the mixed catalyst layer 5 is discharged from the discharge unit 12 to the outside of the reforming unit 1 while heating the inside of the reforming unit 1 including the mixed catalyst layer 5.

  The discharge unit 12 of the reforming unit 1 communicates with the inlet side of the CO reducing unit 17 through the pipe 16 and is mixed with the oxidizing air in a mixing unit 17a including an ejector provided on the inlet side. The CO reduction means 17 is provided with an oxidation catalyst layer filled with an oxidation catalyst such as platinum or carried on a honeycomb structure, where a small amount of CO (carbon monoxide) remaining in the reformed gas is reacted with oxygen to form carbon dioxide gas. Convert and reduce.

  The outlet side of the CO reduction means 17 communicates with the water tank 60 through a pipe 18 provided with an on-off valve 21d. The operation of the on-off valve 21d will be described later. The water tank 60 in the present embodiment removes the ammonia component contained in the reformed gas in a small amount by absorbing it into the water, and opens the tip of the pipe 18 into the water to eject the reformed gas by bubbling. ing. Thus, the front-end | tip part of the piping 18 is water-sealed by opening the front-end | tip of the piping 18 in water.

  The water tank 60 is separated into three chambers by partition walls 65 and 66. That is, the lower portions of the partition walls 65 and 66 extend to the water in the water tank 60 and separate the three gas-liquid separation chambers 61, 62, and 63, which are gas phase portions, with their lower ends at the water tank 60. The tank water is separated from the bottom surface by a predetermined distance, and the tank water can freely come and go through the gap between the bottom surface and the lower ends of the partition walls 65 and 66. Therefore, the gas-liquid separation chambers 61, 62, and 63 are sealed with water and separated from each other to prevent mixing between the gas phases and to ensure water circulation. A cooler 67b is provided at the bottom of the water tank 60 so that the tank water can be cooled to a predetermined temperature with the cooling water.

  The reformed gas supplied from the pipe 18 to the water tank 60 flows only into the gas-liquid separation chamber 62 which is one of the upper spaces of the water tank 60 by the function of the partition walls 65 and 66. The upper part of the gas-liquid separation chamber 62 communicates with the fuel cell 15 via a pipe 20 provided with an on-off valve 21a, and a bypass pipe provided with an on-off valve 21b that bypasses the fuel cell 15 is connected to the pipe 20. Further, a pipe for allowing the anode exhaust gas of the fuel cell 15 to flow out joins the bypass pipe via the on-off valve 21c. Cathode air is supplied to the fuel cell 15 from a pipe 22, and cooling water for cooling the fuel cell 15 circulates in a pipe 23 provided with a pump 25.

  The water produced by the reaction of hydrogen and oxygen in the fuel cell 15 is discharged to the cathode condenser 67a through the pipe 26, where it is cooled by heat exchange with the cooling water. The recovered water in the cathode condenser 67 a is supplied as makeup water to the recovery water tank 64 of the water tank 60 through the pipe 27, and the gas component contained in the makeup water is a gas-liquid separation chamber 63 provided in the upper part of the recovery water tank 64. And is discharged out of the system from a discharge unit (not shown). Note that an opening / closing valve may be provided in the pipe 27 as necessary, and the recovery water tank 64 may be configured so that makeup water can be replenished from the outside if necessary.

  A pipe 40 communicates with the gas-liquid separation chamber 61 of the water tank 60, and the anode exhaust gas is supplied to the second suction and mixing means 35 via the on-off valve 42. The anode exhaust gas flowing out from the fuel cell 15 is cooled by the cooling water in the anode exhaust gas condenser 67c provided on the downstream side of the junction with the bypass pipe. The anode exhaust gas flowing out from the anode exhaust gas condenser 67c flows into the gas-liquid separation chamber 61, and after separating the gas components contained therein, it flows into the second suction mixing means 35 from the pipe 40 provided with the on-off valve 42. From there, it is supplied as fuel to the combustion section of the water vapor generating means 30. The heat exchange efficiency of the condenser 67c and the condensers 67a and 67c can be improved by making the flow direction of the cooling water counter flow with respect to the medium to be cooled.

  The pipe 29a extends from the lower water between the partition walls 65 and 66 in the water tank 60 to the outside, and the tank water in the water tank 60 passes through the pipe 29a, the pump 32, the pipe 29, etc. to the water drum 31 of the water vapor generating means 30. Supplied. Note that the end of the pipe 29a opens above the portion where the reformed gas is bubbled from the pipe 18, and sucks water that has absorbed ammonia in the reformed gas from the periphery of the opening. As described above, the steam generating means 30 supplies steam to the reformer 1, and a combustion section 34 having a burner 33 is provided below the steam generator 30. The combustion section 34 is supplied with a mixture of fuel and primary air from a second suction mixing means 35 constituted by an ejector via a pipe 36 and further supplied with secondary air from a pipe 37. And the combustion gas produced | generated in the combustion part 34 is discharged | emitted from the piping 38 outside.

  Natural gas, city gas, or the like is supplied as fuel to the second suction mixing means 35 through the pipe 39, and anode exhaust gas containing hydrogen from the fuel cell 15 is supplied as fuel through the pipe 40. The fuel supply mode can be selected by opening and closing the on-off valve 41 provided on the pipe 39 and the on-off valve 42 provided on the pipe 40. If necessary, both gases can be burned together.

  The water vapor generated in the water drum 31 of the water vapor generating means 30 is supplied to the suction mixing means 14 through the pipe 31a. A pipe 43 for supplying a raw material gas to the reforming means 1 is connected to the first suction mixing means 14, and this pipe 43 is connected to a heat exchange section provided in the CO reduction means 17, and the raw material gas is preheated there. And flows into the first suction mixing means 14. A pipe 44 for supplying start air is further connected to the suction mixing means 14.

  A pipe 45 passing through a heat exchange section provided in the CO reduction unit 17 is connected to the outlet side of the suction mixing unit 14, and the pipe 45 is branched into a pipe 46 and a pipe 47. An on-off valve 48 is provided in the middle of one branched pipe 46, and the tip thereof communicates with the supply unit 11 of the reforming means 1. In addition, an on-off valve 49 is provided in the middle of the other branched pipe 47, and its tip communicates with the preheater 13.

  A heat exchange pipe 50 for evaporating water is provided on the outer wall of the outlet portion 12 of the shift catalyst layer 6 of the reforming means 1, and the inlet side of the heat exchange pipe 50 passes through a pipe 51 provided with an on-off valve 52. The water tank 60 communicates with the lower part of the water tank 60, and the outlet side of the heat exchange pipe 50 communicates with the supply unit 11 of the reforming means 1. By appropriately designing the positional relationship of the heating parts of the heat exchange pipe 50 provided in the reforming means 1 from the water tank 60 in advance, the internal pressure of the reactor can be arbitrarily set by simply opening the on-off valve 52 as will be described later.・ It can be adjusted.

  Next, the operation of the reforming system of FIG. 1 will be described. When the reforming system is operating normally, the anode exhaust gas from the fuel cell is supplied to the steam generating means 30 as fuel. The water vapor generated by the water vapor generating means 30 is supplied from the pipe 31a to the suction mixing means 14, where it is mixed with the raw material gas supplied from the pipe 43. The raw material-steam mixture flowing out from the suction mixing unit 14 is supplied to the supply unit 11 of the reforming unit 1 through the pipes 45 and 46.

  The raw material-steam mixture supplied to the supply unit 11 is partly reformed while passing through the reforming catalyst layer 4 in the preliminary reforming chamber 2 to form the mixed catalyst layer 5 in the main reforming chamber 3. Inflow. Oxidizing air is supplied to the mixed catalyst layer 5 from the air supply pipe 9, and a part of the pre-reformed gas reacts with oxygen to generate heat necessary for the reforming reaction. The remaining raw material gas is reformed in the mixed catalyst layer 5 to generate a hydrogen-rich reformed gas, and the reformed gas flows into the shift catalyst layer 6.

  While the reformed gas passes through the shift catalyst layer 6, most of the CO contained therein is removed and flows into the CO reduction means 17 from the discharge unit 12. The inflowing reformed gas is further reduced to a ppm order by the CO reduction means 17 and then the residual CO is bubbled from the pipe 18 to the water tank 60 where the ammonia contained therein is removed. The reformed gas from which the ammonia has been removed is supplied to the fuel cell 15 from the gas-liquid separation chamber 62 in the upper space of the water tank 60 through the pipe 20. The anode exhaust gas of the fuel cell 15 is supplied as fuel for the steam generating means 30 through the pipe 40 as described above, and the water containing the recovered ammonia in the water tank 60 is supplied as makeup water to the steam generating means 30 through the pipe 29. Is done.

  The water between the partition wall 65 and the partition wall 66 located above the bubbling portion of the water tank 60 into which the reformed gas flows in contains ammonia absorbed from the reformed gas, and the end of the pipe 29a is positioned below the water surface. The water that has sufficiently absorbed ammonia, that is, the water having the highest ammonia concentration in the water tank 60, is supplied as makeup water to the water vapor generating means 30 from the pipe 29a. As a result, since the ammonia in the tank water is efficiently discharged from the water tank 60, the ammonia concentration is maintained at a predetermined value or less that does not interfere with the system operation.

  On the other hand, ammonia contained in the supply water is supplied to the reforming means 1 while being mixed as a gas in the steam generated by the steam generating means 30. However, since the reforming reaction in the reforming means 1 is an equilibrium reaction, the concentration of ammonia contained in the generated reformed gas is suppressed. Accordingly, since ammonia in the reforming system is circulated while being maintained at an equilibrium concentration equal to or less than a predetermined amount, stable operation of the reforming system can be continued. When the operation of the reforming system is continued, the recovered water separated from the anode exhaust gas, the recovered water separated from the cathode exhaust gas, and the supplementary water from the outside are supplied to the partition walls 65 and 66 in the water tank of the gas-liquid separation chamber 61. Since the water is replenished through the gap between the lower end of the water tank and the bottom of the water tank, the ammonia concentration of the water supplied to the steam generating means 30 is kept fairly low.

  Next, a method for stopping the reforming system in FIG. 1 will be described. Based on the reforming system stop command, the supply of the oxidizing air from the pipe 9a to the mixed catalyst layer 5 of the reforming means 1 is first stopped and the supply of the raw material gas from the pipe 43 to the reforming means 1 is stopped. . At the same time, the supply of the oxidizing air to the CO reduction means 17 is stopped, and the fuel supply to the steam generation means 30 is stopped. On the other hand, the on-off valve 21a is closed to stop the supply of the reformed gas to the fuel cell 15, and at the same time, the on-off valve 21b is opened to bring the bypass line composed of the bypass pipe and the on-off valve 21b into communication.

  Even after the combustion of the steam generating means 30 is stopped, steam is generated by the residual heat for a while, and the raw material gas remaining in the reforming means 1 is purged by the generated steam. Needless to say, if necessary, water vapor can be additionally supplied by supplying the raw material gas and the combustion air to the combustion section 34 and tracking them. The purged source gas is bubbled together with water vapor from the pipe 16 through the CO reduction means 17 and from the pipe 18 to the water tank 60, and is guided to the outside through the on-off valves 21b and 42 and the pipes 36 and 38. Alternatively, the on-off valve 21a may be opened and supplied to the fuel cell side. The on-off valve 42 can be omitted.

When the steam purge is performed, the reforming means 1 becomes a steam atmosphere, but there are cases where the composition management of the reformed gas and steam mixed gas flowing into the gas-liquid separation chamber 62 at the upper part of the water tank 60 cannot be sufficiently performed. For example, the amount of steam flowing into the water tank 60 can be condensed and absorbed in the tank water as long as the inside of the system is steam purged with the steam generated by the residual heat of the steam generating means 30 as described above. It is considered that the line pressure of the pipe 20 to the fuel cell 15 is not greatly changed.
However, even after the reforming system is stopped, when the steam generating means 30 is operated for a short time, for example, and more steam purge is actively performed in the system, the steam flowing into the water tank 60 is sufficiently absorbed by the tank water. In some cases, condensation may not be possible, and the line of the pipe 20 may be filled with water vapor to expel the reformed gas downstream, and a large amount of moisture may be contained inside the line of the pipe 20. There is a possibility that the moisture in the piping 20 line condenses as the temperature drops, resulting in a negative pressure state.

Further, immediately after the reforming system is stopped, when the steam purging of the reforming unit 1 is not yet performed, the reforming unit 1, the CO reduction unit 17 and the gas / liquid separation chamber 61-pipe 40 line above the water tank 60 are connected. Is in a state in which the reformed gas at normal pressure remains sealed. When steam purge is performed in this state by steam purge, the internal pressure of the reforming means 1 rises and the reformed gas existing in the pipe 18 is pushed out to the water tank 60 all at once. The internal pressure of the pipe 20 on the side also rises and becomes a positive pressure state at the supplementary pressure level. That is, the appropriate predetermined pressure (reference pressure) inside the pipe 20 is increased under the influence of the level of the steam supplement pressure.
These mean that the gas-liquid separation chamber 62 in the upper part of the water tank 60 cannot be maintained at an appropriate predetermined pressure equal to or higher than the atmospheric pressure at the beginning of the steam supplementation, and becomes an excessive positive pressure level. For example, when the reforming unit 1 and the CO reduction unit 17 are boosted to about 50 kPa, for example, by steam supplement pressure, the reformed gas on the reforming unit 1 side moves from the bubbling portion of the water tank 60 to the gas-liquid separation chamber 62 side. Then, the pressure is increased, and the line pressure of the pipe 20 reaches about 50 kPa. That is, a situation occurs in which the appropriate reference pressure is shifted to an excessive positive pressure.

This phenomenon of excessive positive pressure can be solved by providing the system with means capable of absorbing it. That is, in the present embodiment, the installation level of the heat exchange pipe 50 is set within a predetermined range, thereby causing extra steam (including fluctuation to excessive positive pressure in the system) generated when the reforming system is stopped. It becomes possible to easily suppress the pressure fluctuation within a predetermined range. That is, when the position of the heat exchange pipe 50 with respect to the water tank 60 is set in advance to a position that maintains a predetermined relationship, and the on-off valve 52 is temporarily opened, the pressure difference between the water level of the water tank 60 and the heat exchange pipe 50 ( The tank water (predetermined amount of water) in the water tank 60 corresponding to the (water level difference) is temporarily sent to the heat exchange pipe 50 having a predetermined internal volume.
As a result, a predetermined amount of water is heated and evaporated in the heat exchange pipe 50, and the evaporation amount supplies the minimum amount of steam necessary for boosting / compensating the internal pressure of the reforming means 1 to an appropriate predetermined value range. To do. If the relationship between the predetermined amount of water and the pressure increase level is obtained in advance through experiments or the like, the excessive pressure as described above can be obtained either when the reforming system is stopped or before the steam purge is performed. It is possible to prevent the occurrence of the rise, and it is possible to automatically control the inside of the system to an appropriate supplemental pressure level.

The “predetermined amount of water” in the present invention is used to express “the minimum amount of water necessary for preventing excessive pressure increase in the system when the reforming system is stopped” as described above. However, in the present invention, as will be described later, it is also used to express “the amount of water to be supplied to the reforming means 1 in order to prevent the generation of negative pressure in the system”.
After the steam purge, the internal temperature of the reforming unit 1 gradually decreases, but the rate of decrease in the internal temperature of the piping 16 and the CO reduction unit 17 connected to the reforming unit 1 is larger than that. The water vapor remaining inside condenses relatively early. Since the tip of the pipe 18 on the outlet side of the CO reduction means 17 is sealed with a water tank 60, the reforming means 1, the pipe 16, the CO reduction means 17 and the pipe 18 form a closed system. The internal pressure decreases due to the contraction of the sealed gas and the condensation of the water vapor, and proceeds in the negative pressure direction.

When the internal pressure of the closed system gradually decreases to a negative pressure region, the atmosphere enters from an unillustrated on-off valve or device connection part constituting the closed system, or remains in the water tank 60 or the piping line. If water is sucked into the reactor and the catalyst is submerged, there is a fear of accelerating the deterioration due to oxidation of the catalyst or deterioration due to powdering or poisoning of the catalyst. Therefore, in the present embodiment, at least the CO reducing means 17 and the water vapor remaining in the piping 16 communicating with the reforming means 1 are condensed due to a temperature drop, and the reforming means 1 reaches the negative pressure region or the negative pressure region. When the temperature approaches, the on-off valve 52 is opened so that water is supplied from the water tank 60 to the heat exchange pipe 50 having a predetermined internal volume provided in the reforming means 1.
Here, the “predetermined internal volume” means “a sufficient internal volume that does not impair the negative pressure prevention function in the heat exchange pipe 50, or an excess in the system at the time of stopping the reforming system in the heat exchange pipe 50. It means a sufficient internal volume that does not impair the positive pressure prevention function.

  In order to automatically open the on-off valve 52 in order to supply water from the water tank 60 to the heat exchange pipe 50 of the reforming means 1, for example, the pressure of the reforming means 1 or the piping 16 is a pressure detecting means (not shown). And the detection signal is input to a control device (not shown), and when the detected pressure falls below a pressure preset in the control device (for example, atmospheric pressure or a pressure around it), the control device An open signal is output to the on-off valve 52.

  When the on-off valve 52 is opened, the pressure of the reforming means 1 reaches or approaches the negative pressure region, while the water tank 60 is maintained at the initial atmospheric pressure state as described above. Therefore, the water in the water tank is automatically sucked from the pipe 51 into the heat exchange pipe 50 of the reforming means 1 by the differential pressure (pressure difference) between the two. The water supplied to the heat exchange pipe 50 having a predetermined internal volume is heated and evaporated by the internal temperature of the reforming means 1 that is at a relatively high temperature at that time, and the generated predetermined amount of water vapor is the heat exchange pipe 50. From the outlet side to the supply unit 11 of the reforming means 1. Since the internal pressure of the closed system including the reforming unit 1 increases according to the amount of steam generated, it is possible to prevent the portion from being maintained in the negative pressure region.

  When the internal pressure of the closed system rises due to the generation of the water vapor, the internal pressure of the closed system including the reforming means 1 rises, so that the differential pressure decreases as the pressure rises. When the differential pressure decreases, the amount of water supplied from the water tank 60 to the heat exchange pipe 50 also decreases. In some cases, the supply automatically stops and the amount of water vapor generated also decreases.

  However, when the amount of generated water vapor decreases, the pressure reaches or approaches the negative pressure region again in the closed system, and the differential pressure also recovers accordingly, so that the water tank 60 transfers the heat exchange pipe 50 having a predetermined internal volume. Water supply is automatically started. Thus, by repeating automatic water supply and water vapor generation, it is possible to prevent a phenomenon in which the closed system including the reforming means 1 remains in the negative pressure region.

Here, the advantage of the present invention is that when the present invention is applied to a general reforming system for supplying reformed gas to, for example, a home or automobile fuel cell, heat exchange in the reforming means 1 is performed. The internal volume of the pipe 50 may be at most several milliliters, and the amount of water necessary for this supplemental pressure or prevention of negative pressure may be at most several milliliters. For example, 3 ml (3 g) of water turns into a little less than 4 liters of water vapor in a standard state (= 3 g / 18 * 22.4), so that the capacity of the heat exchange pipe 50 is enough for several milliliters.
Correspondingly, the evaporation part of the heat exchange pipe 50 may be the minimum necessary, and further evaporation of water will cause excessive pressure increase, which will induce pressure oscillation in the system, making stable supplemental pressure control difficult. . Thus, regardless of the relationship between the water level of the water tank 60 and the amount of water, it is possible to automatically control the required evaporation amount by simply adjusting and designing the water level relationship in advance. The above relationship does not change substantially even when the capacity of the reforming system is increased. Needless to say, the cathode recovery water may be laid separately.

As described above, when the reforming means 1 is in the negative pressure region, the heat exchange pipe 50 generates steam to maintain the system in the positive pressure region, but this operation has a time delay or some trouble. When this occurs, the tank water is sucked into the pipe 18 from the water tank 60 and the water may flow into the CO reduction means 17. Therefore, in this embodiment, a pressure detector (not shown) and a control device (not shown) for detecting the pressure in the pipe 18 are provided, and when the detected pressure falls below a preset value, the control device Control to close the on-off valve 21d provided in the pipe 18 is performed. Note that a check valve may be provided in the pipe 18 in place of the on-off valve 21d. In this case, the above-described pressure detector and control device are not necessary. Depending on the situation, the on-off valve 21d and the check valve can be omitted.
As shown in FIG. 1, in this embodiment, a check valve 52 a is provided in a pipe 51 that communicates a water tank 60 and a heat exchange pipe 50. During the normal operation of the reforming system, the reforming means 1 is in a positive pressure state. At this time, the check valve 52a is closed to prevent the reformed gas from the reforming means 1 from flowing out to the water tank 60. To do.

  FIG. 2 is a process flow diagram showing a modification of FIG. 2 is different from the example of FIG. 1 only in the water tank 60 and its peripheral part, and the rest is configured in the same manner. Therefore, in FIG. 2, the same parts as those in FIG. 1 are denoted by the same reference numerals as those in FIG. In the example of FIG. 1, the water tank 60 and the cathode recovery water tank 64 are integrally configured. However, in this embodiment, the water tank 60 and the cathode recovery water tank 64 are configured separately and are arranged adjacent to each other with a partition wall 66 therebetween.

The recovered water tank 64 collects cathode recovered water from the fuel cell 15 and externally supplied water, and the stored water in the recovered water tank 64 can be supplied as supply water from the supply unit 68 to the water tank 60 side. . Further, a flow distribution plate 69 is disposed inside the cathode recovery water tank 64 so as to flow out from the supply unit 68 to the water tank 60 side in a state where the cathode recovery water and the makeup water from the outside are uniformly mixed. ing.
The upper part of the water tank 60 is provided with gas-liquid separation chambers 61 and 62 partitioned by a partition wall 65, and the anode exhaust gas discharged from the fuel cell 15 flows into the gas-liquid separation chamber 61, and enters the gas-liquid separation chamber 62. Is provided with a hydrophilic filling layer 70. The hydrophilic filling layer 70 is made of a material having a three-dimensional network structure having hydrophilicity and water absorption such as an aggregate of hydrophilic particles such as ceramics or sintered glass, a nonwoven fabric having a cloth structure or a honeycomb structure, or a sponge. can do. The lower part of the hydrophilic filling layer 70 has a function of sucking up the tank water by extending below the water tank 60 and partially immersing it in the tank water. Further, the hydrophilic filling layer 70 has a structure that allows the reformed gas to pass three-dimensionally, and the reformed gas is hydrophilicly filled from the distribution section 18a having a plurality of ejection holes arranged immediately above the surface of the tank water. The layer 70 is supplied by being dispersed or diffusely penetrating.

  Next, the operation of the tank 60 will be described. The hydrophilic filling layer 70 sucks up water in the water tank and is always kept wet with water from the makeup water supply unit 68. The reformed gas supplied from the distribution section 18a comes into contact with the hydrophilic packed bed 70 containing water to disperse and rise in the inside thereof. At this time, the ammonia contained in the modified gas is contained in the hydrophilic packed bed 70. It is absorbed and removed by water. Cathode replenishment water in the cathode recovery tank 64 is supplied from the upper part of the hydrophilic packed bed 70 via the supply unit 68, and the ammonia absorbed from the reformed gas is efficiently washed down by the water dropped while being dispersed, and the water tank To recover. Thus, since the amount of ammonia absorbed per unit volume of the hydrophilic packed bed 70 is always suppressed to a predetermined value or less, the hydrophilic packed bed 70 can efficiently absorb and remove ammonia in the reformed gas for a long period of time. Further, unlike the conventional bubbling method, the flow of the reformed gas is maintained smoothly, the pressure fluctuation is suppressed, and the pressure loss can be kept small.

  The method for stopping a reforming system and the reforming system of the present invention can be used in a reforming system that generates a hydrogen-rich reformed gas by steam reforming a raw material gas and supplies it to additional equipment such as a fuel cell.

The process flow explanatory drawing for demonstrating the stop method of the reforming system of this invention, and its reforming system. Process flow explanatory drawing for demonstrating the stop method of the reforming system of this invention, and the modification of the reforming system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reforming means 2 Preliminary reforming chamber 3 Main reforming chamber 4 Reforming catalyst layer 5 Mixed catalyst layer 6 Shift catalyst layer 7 High temperature shift catalyst layer 8 Low temperature shift catalyst layer 9 Supply pipe 9a Piping 10 Jetting section 11 Supply section 12 Discharge Part 13 Preheater

14 1st suction mixing means 15 Fuel cell 16 Piping 17 CO reduction means 17a Mixing part 18 Piping 18a Distribution part 20 Piping 21a-21d On-off valve 22,23 Piping
25 Pump 26, 27 Piping 29, 29a Piping

30 Water vapor generating means 31 Water drum 31a Piping 32 Pump 33 Burner 34 Combustion part 35 Second suction and mixing means

36 to 40 Piping 41 and 42 On-off valve 43 to 47 Piping 48 and 49 On-off valve 50 Heat exchange pipe 51 Piping 52 On-off valve 52a Check valve 55 On-off valve

60 Water tank 61, 62, 63 Gas-liquid separation chamber 64 Recovery water tank 65, 66 Partition 67a Cathode condenser 67b Cooler 67c Anode exhaust gas condenser
68 Supply section 69 Distribution plate 70 Hydrophilic packed bed

Claims (7)

Included in the generated reformed gas, the steam generating means 30 for generating steam, the reforming means 1 for reforming the raw material gas with the steam generated by the steam generating means 30 to generate a hydrogen-rich reformed gas, and In a method for stopping a reforming system provided with CO reduction means 17 for reducing CO (carbon monoxide),
When stopping the reforming system, first, the supply of the oxidizing air to the reforming means 1 is stopped, then the supply of the raw material gas is stopped and the fuel supply to the steam generating means 30 is stopped, and then the steam generating means 30 is stopped. The raw material gas remaining in the reforming means 1 is purged with steam generated by the residual heat of
Further, at least the CO reducing means 17 and the water vapor existing in the piping 16 communicating with the reforming means 1 are lowered in temperature, contracted and / or condensed, so that the inside of the reforming means 1 reaches a negative pressure region or is negative. When a pressure region is approached, a predetermined amount of water is supplied to the reforming means 1 and the water is heated and evaporated by the heat of the reforming means 1 so that the inside of the reforming means 1 becomes a negative pressure state. A method for stopping a reforming system characterized in that   2. The reformed gas whose CO has been reduced by the CO reducing means 17 is caused to flow into the water tank 60 by bubbling, and the water stored in the water tank 60 is supplied to the reforming means 1. A method for stopping the reforming system.   3. The reforming process according to claim 2, wherein a predetermined amount of water is supplied from the water tank 60 to the reforming unit 1 by using a differential pressure between the water tank 60 and the reforming unit 1. How to stop the system.   4. The water vapor generated in the heat exchange pipe 50 is reformed by supplying a predetermined amount of water to the heat exchange pipe 50 having a predetermined internal volume provided in the reforming means 1 in any one of claims 1 to 3. A method for stopping a reforming system, characterized in that it is supplied to the raw material gas supply unit 11 of means 1. Included in the generated reformed gas, the steam generating means 30 for generating steam, the reforming means 1 for reforming the raw material gas with the steam generated by the steam generating means 30 to generate a hydrogen-rich reformed gas, and In the reforming system provided with CO reduction means 17 for reducing CO (carbon monoxide) generated,
On the outlet side of the CO reduction means 17, the raw material supply section 11 for supplying the steam and raw material gas mixture (raw material-steam mixture) provided in the reforming means 1 and the heat exchange pipe 50 having a predetermined internal volume. A water tank 60 communicated with the pipe 51 for supplying water from the water tank 60 to the inlet side of the heat exchange pipe 50, and the outlet side of the heat exchange pipe 50 and the raw material supply section 11 are in communication with each other; A characteristic reforming system.   6. The reforming process according to claim 5, wherein a gas-liquid separation chamber 61 for allowing the anode exhaust gas discharged from the fuel cell 15 to pass through and separating and recovering water contained therein is provided in communication with the water tank 60. system.   The gas-liquid separation chamber 62 provided in communication with the upper portion of the water tank 60, and the hydrophilic packed bed 70 that sucks up water from the water tank 60 into the gas-liquid separation chamber 62. The reforming system is characterized in that a distribution section 18a for supplying a reformed gas into the hydrophilic packed bed 70 and a supply section 68 for supplying makeup water to the gas-liquid separation chamber 62 are provided.

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