JP2007161553A - Hydrogen generating apparatus and fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform reforming of a raw material and generation of hydrogen with a small amount of a fuel in a short time after starting by suppressing an unnecessary warming-up operation. <P>SOLUTION: At the starting time, it is determined whether the temperature of a PSR (Pressure Swing Reforming) type reformer 10, in which the catalyst temperature is higher (the heat storage quantity is larger), is lower or not lower than a temperature T at which reforming reaction occurs. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a hydrogen generator that performs a fuel reforming reaction using a catalyst and a regeneration reaction for heating and regenerating the catalyst, and a fuel cell system including the same.

  A conventional electric vehicle is equipped with a fuel cell as a power source for driving the vehicle, and with hydrogen or a raw fuel for generating hydrogen, which is a fuel for causing the fuel cell to perform a power generation operation.

  When the hydrogen itself is mounted, the hydrogen gas is compressed and packed in a high-pressure cylinder or liquefied and filled into a tank, or mounted using a hydrogen storage alloy or a hydrogen adsorbing material. However, in the case of high-pressure filling, the volume of hydrogen is small because the container wall thickness is thick and large, but in the case of liquefied filling with liquid hydrogen, vaporization loss is unavoidable and it is very difficult to liquefy. Requires energy. Further, hydrogen storage alloys and hydrogen adsorbing materials have insufficient hydrogen storage density required for electric vehicles and the like, and it is difficult to control hydrogen storage / adsorption. In addition, when the raw fuel is installed, there is a method of obtaining hydrogen by steam reforming the fuel, but since the reforming reaction is endothermic, a separate heat source is required, and an electric heater or the like was used as the heat source. The system cannot improve the overall energy efficiency, and it is inevitable that the amount of hydrogen can be secured stably under all environmental conditions.

  The actual hydrogen supply method has not yet been technically established, but it is expected that a hydrogen supply method will be established in light of the anticipated increase in hydrogen utilization in various devices in the future. ing.

  As a technology related to the above, when a predetermined condition is established using a catalyst, the steam reforming reaction of the fuel that is an endothermic reaction and the regeneration reaction that regenerates the catalyst temperature decreased by the steam reforming reaction are switched. A fuel reformer that can perform the above has been proposed (see, for example, Patent Document 1).

In this fuel reformer, two catalysts are combined into one set, and when one catalyst undergoes a reforming reaction, the other catalyst undergoes a regenerative reaction, and these two reactions are alternately switched so that the reforming performance can be maintained. In particular, it is suitable for reforming liquid fuel or the like from which sulfur content is not completely removed.
US 2003-235529

  However, the reformable temperature is high, and the reforming reaction is performed using the heat stored in the reactor. Therefore, after the catalyst has cooled down at the time of start-up, the amount of heat in the reactor is insufficient. Therefore, warming up is necessary, and it takes a long time to raise the temperature to the required temperature to reform and produce the desired amount of hydrogen, and there is a problem that startup cannot be performed in a short time.

  Even if the catalyst has cooled to such an extent that the reforming reaction is impossible, if a certain amount of heat storage remains before the start-up, that heat storage amount is not used effectively at the start-up, which is a problem in terms of energy efficiency. There is also.

  In particular, when a fuel cell system combined with a fuel cell is configured and mounted on a vehicle, the fuel cell is reformed and generated until the fuel cell can be shifted to normal power generation operation, that is, the fuel reformer. As a result, it is necessary to supply power until the amount of hydrogen supplied to the fuel cell reaches the required amount of power generation using a separate large-scale power storage device, etc. There are also problems in mounting such as power supply performance and space in the vehicle.

  The present invention has been made in view of the above, and provides a hydrogen generator and a fuel cell system that can perform reforming and generation of hydrogen in a short amount of fuel from startup without performing unnecessary warm-up operation. It is an object to achieve this purpose.

The present invention relates to a steam reforming reaction of fuel, which is an endothermic reaction, and an exothermic reaction (hereinafter referred to as “regeneration reaction”) for recovering the reforming reactivity on the catalyst by recovering the catalyst temperature lowered by the steam reforming reaction. )), The start-up control taking into account the reforming reaction environment at the start-up and switching the reforming / regeneration reaction in consideration of the heat storage amount of the reformers is the reforming productivity. It has been achieved based on the knowledge that it is effective in improving the above.
The exothermic reaction in the present invention includes a combustion reaction and the like.

  In order to achieve the object, the hydrogen generator according to the first invention comprises a catalyst, and when the reforming raw material is supplied, the reforming raw material is reformed on the heated catalyst, When the exothermic fuel is supplied, the exothermic reaction of the exothermic fuel causes the exothermic reaction to heat the catalyst, and the heat storage selected from the at least two reformer reactors at startup Determining means for determining whether or not the temperature condition of the reforming reactor having the largest amount has reached a state in which the reforming reaction is possible.

  The state in which the reforming reaction is possible refers to a state in which a certain reforming efficiency is maintained and a stable reforming reaction can be maintained for 1 second or more without generation of soot and the like.

  The hydrogen generator according to the present invention includes at least two reforming units capable of alternately switching between a steam reforming reaction of fuel using heat storage and a regeneration reaction for recovering the heat storage amount reduced by the steam reforming reaction. A reactor (hereinafter also referred to as “PSR (Pressure swing reforming type reformer)”) is provided, and at least one of the reactors performs a steam reforming reaction of the fuel, and at least one of the other reactors performs a regeneration reaction. (Hereinafter, this hydrogen generator is sometimes referred to as a “PSR reformer”).

The reforming reaction according to the present invention includes a steam reforming reaction that is an endothermic reaction and a partial oxidation reaction that is an exothermic reaction, as described below. In the reforming reaction in the present invention, the following steam reforming reaction (1) is mainly performed.
_{C n H 2n + 2 + nH} 2 O → (2n + 1) H 2 + nCO ... (1)
C _n H _{2n + 2} + (n / 2) O ₂ → (n + 1) H ₂ + nCO (2)
CO + H ₂ O⇔CO ₂ + H ₂ (3)
CO + 3H ₂ ＣＨCH ₄ + H ₂ O (4)

  For example, when there are two reforming reactors, one of them performs a steam reforming reaction that is an endothermic reaction by using heat storage in the chamber, and the other side performs a regeneration reaction that is an exothermic reaction. When the amount of stored heat is reduced by the steam reforming reaction, one of the two is converted into a regeneration reaction by switching means for switching the reforming raw material flow path and the exothermic fuel flow path to the two reforming reactors. In addition to switching, the other side switches from the regeneration reaction to the reforming reaction so that the fuel reforming is performed by the heat stored by the regeneration reaction. This eliminates the need for a separate heater and enables continuous hydrogen generation with high use efficiency of heat energy.

In the first invention, at the time of start-up, with respect to the reforming reactor having the largest amount of heat storage among the plurality of reforming reactors, it is determined whether or not the temperature condition has reached a state where the reforming reaction is possible. Therefore, it is possible to determine whether or not it is necessary to warm up in accordance with the start-up, so that unnecessary warm-up operation and unnecessary warm-up time at the start-up can be reduced. Fuel consumption can also be reduced.
In addition, when warming up, it is possible to shorten the startup time required for hydrogen reforming and generation from startup.

  According to a first aspect of the present invention, there is provided switching means for switching a reforming raw material supply flow path and a heat generating fuel supply flow path to the reforming reactor, and a temperature condition of the reforming reactor having the largest amount of heat storage by the determination means. Switching control to switch the supply flow path by switching means so that the reforming raw material is supplied to the reforming reactor with the largest amount of heat storage when it is determined that the reforming reaction is possible. Further means can be provided.

  When it is determined that the temperature condition of the reforming reactor having the largest amount of heat storage among the plurality of reforming reactors has already reached a state where the reforming reaction is possible, hydrogen gas is supplied when the reforming raw material is supplied. The temperature of the reforming reactor is in a temperature environment where the reforming reaction can be performed, and the reforming reactor is controlled by switching the supply flow path to perform the reforming reaction. Without this, reforming production of hydrogen gas can be started quickly.

  Further, in the switching control means, when it is determined by the determination means that the temperature condition of the reforming reactor having the largest amount of heat storage has not reached the state capable of the reforming reaction, the reforming reactor having the largest amount of heat storage is set. It is desirable to control the switching means to switch the supply flow path so that the fuel for heat generation is supplied.

  When it is determined that the temperature condition of the reforming reactor with the largest amount of heat storage has not yet reached the state in which the reforming reaction is possible, reforming and generation of more than the desired amount of hydrogen gas is achieved even if the reforming raw material is supplied. Although it is in a low temperature environment that can not be done, the reforming reactor with the largest amount of heat storage is the target of supply, and control is performed to supply the exothermic fuel to the reforming reactor with the largest amount of heat storage, thus shortening the warm-up time be able to.

  The hydrogen generator according to the first aspect of the present invention further includes detection means for detecting the temperature (catalyst temperature) of the catalyst provided in the reforming reactor, and the catalyst temperature detected by the detection means by the switching control means. The supply flow path can be switched so that the reforming raw material or fuel for fuel is supplied to the reforming reactor having the largest amount of heat storage selected based on the above.

  That is, the reforming reactor having the largest heat storage amount is selected based on the temperature of the catalyst provided in each reforming reactor, and the reforming reaction having the highest catalyst temperature among the plurality of reforming reactors is performed. As a reforming reactor having the largest amount of heat storage, when it is determined that the catalyst temperature has reached a temperature at which the reforming reaction is possible, the reforming raw material is in a temperature environment capable of reforming and generating hydrogen gas. Conversely, when it is determined that the catalyst temperature has not reached the temperature at which the reforming reaction is possible, a low temperature environment in which more than a desired amount of hydrogen gas cannot be reformed and produced even when the reforming raw material is supplied Therefore, since the fuel for heat generation is configured to be supplied, the reformed generation of hydrogen gas can be started promptly or without a warm-up time after start-up.

  A fuel cell system according to a second aspect of the invention comprises a hydrogen generator according to the first aspect of the invention and a fuel cell that generates electric power by supplying a hydrogen-containing gas reformed and produced by the hydrogen generator.

  As described above, it is necessary to warm up at the time of start-up by determining whether or not the temperature condition of the reforming reactor having the largest amount of heat storage has reached a state in which the reforming reaction is possible. Therefore, it is possible to reduce the unnecessary warm-up operation and unnecessary warm-up time at start-up, and to start the reforming reaction quickly from start-up. Fuel consumption associated with driving can also be reduced.

  In the second invention, it is effective to use a fuel cell including an electrolyte in which an electrolyte layer is laminated on at least one side of a hydrogen permeable metal layer. Such a fuel cell including an electrolyte in which an electrolyte layer is laminated on at least one side of a hydrogen permeable metal layer has an operating temperature range of 300 to 600 ° C. The hydrogen rich gas produced by reforming can be supplied in the operating temperature range of the fuel cell, and the off-gas on the anode side and cathode side of the fuel cell is directly returned to the PSR reformer for regeneration, etc. Therefore, it is particularly suitable in terms of system configuration and effective use of thermal energy. In addition, preheating before supply is unnecessary.

  In the present invention, when a reforming reaction is performed by using a heat storage amount stored in a reformer to form a fuel cell system, the reformed and generated hydrogen is supplied to the fuel cell and is reduced by steam reforming of the fuel. When the reformer's heat storage amount is recovered by performing an exothermic reaction (regeneration reaction) and the reforming reaction and the regeneration reaction are switched alternately, the reformer with the most heat storage amount reforms. When possible temperature conditions are met, the system can be started without unnecessary warm-up operation, and when it is configured to give priority to the reformer with the most heat storage, the unnecessary fuel consumption can be reduced in a short time. It is possible to build a system that can be started.

  According to the present invention, it is possible to provide a hydrogen generator and a fuel cell system that can perform reforming and generation of hydrogen with a low amount of fuel in a short time after startup without performing unnecessary warm-up operation.

  Hereinafter, with reference to FIGS. 1 to 4, embodiments of the fuel cell system of the present invention will be described in detail, and details of the hydrogen generator of the present invention will also be specifically described through the description. In the following embodiment, a case where combustion fuel is used as the heat generating fuel will be mainly described.

  The fuel cell system of the present embodiment is an electric vehicle equipped with a hydrogen separation membrane fuel cell (HMFC) using an electrolyte membrane in which proton conductive ceramics are laminated on the membrane surface of a hydrogen permeable metal membrane. Equipped with the hydrogen generator of the present invention, and at the start of the system, the catalyst temperature of the reforming reactor constituting the hydrogen generator is detected, and the reforming reaction having the highest detected catalyst temperature (the largest amount of heat storage) It is configured to supply the reforming fuel or the combustion fuel by determining whether or not the temperature condition of the reactor has reached a state where the reforming reaction is possible.

  Regarding the hydrogen generator, gasoline (or a mixed gas of gasoline and steam) as a reforming raw material to be reformed by a reforming reaction is discharged from the hydrogen electrode side of the fuel cell as a combustion fuel to be combusted during the regeneration reaction. In the following description, the anode off-gas (and gasoline or hydrogen gas, if necessary) is used. However, the present invention is not limited to the following embodiment.

  As shown in FIG. 1, the hydrogen generator of the present embodiment is provided with an injection device that includes a catalyst and at least injects gasoline, and can alternately perform reforming reaction and regeneration reaction. When the first PSR reformer 10 and the second PSR reformer 11 are provided and hydrogen (hydrogen rich gas) is reformed and generated in each PSR reformer, the reformed and generated hydrogen Is supplied to a hydrogen separation membrane fuel cell (HMFC) 200 connected to the PSR reformer.

  The mutual switching between the reforming reaction and the regeneration reaction in the PSR reformer 10 and the PSR reformer 11 is performed by a flow path for supplying gasoline (reforming raw material) to the PSR reformer, an anode ( Hydrogen electrode; the same applies hereinafter) A flow path for supplying off-gas (fuel for heat generation) to the PSR reformer, a flow path for discharging the reformed hydrogen-rich gas from the PSR reformer, and a regeneration reaction Switching means for switching the flow path for discharging the exhaust gas from the PSR reformer, specifically, a plurality of valves (valves V1 to V9) can be controlled by the control device 100. Yes.

  At one end of the first PSR reformer 10, an injection device 15 for injecting gasoline (or a mixed gas of gasoline and water vapor) that is a reforming raw material is attached. A supply pipe 102 having a valve V1 is connected at one end, and one end of a discharge pipe 105 having a valve V4 is further connected. In addition, an injection device 17 for injecting a mixed gas of gasoline and steam, which is a reforming raw material, is attached to one end of the second PSR reformer 11, and a valve V2 is provided via the injection device 17. Is connected at one end, and one end of a discharge pipe 104 provided with a valve V3 is further connected. Each of the other ends of the supply pipes 102 and 103 includes a mixer 117 and is connected to a fuel supply pipe 101 that mixes gasoline with water vapor and supplies a mixed gas (reforming raw material). Valves V1 to V4 are connected to each other. By automatically switching, the raw material for reforming is selectively supplied to the reforming side PSR reformer to be reformed and generated from the regeneration side PSR reformer to be regenerated. Combustion gas (hereinafter also referred to as “combustion off gas”) can be discharged.

  Further, the other ends of the discharge pipes 104 and 105 are connected to one end of a discharge pipe 106 for discharging the combustion off gas to the outside so that the combustion off gas can be discharged.

  At the other end of the first PSR reformer 10, air supplied for combustion (combustion air) is supplied from a hydrogen separation membrane fuel cell (hereinafter also simply referred to as “fuel cell”) 200. An injection device 16 for injecting together with the anode off-gas and, if necessary, gasoline, hydrogen gas, etc., is attached, and a discharge pipe 107 provided with a valve V6 and a supply pipe 110 provided with a valve V8 via the injection device 16 respectively. Connected at one end.

  An injection for injecting air supplied for combustion (combustion support air) to the other end of the second PSR reformer 11 together with anode off-gas from the fuel cell 200 and, if necessary, gasoline or hydrogen gas. An apparatus 18 is attached, and a discharge pipe 108 provided with a valve V7 and a supply pipe 109 provided with a valve V5 via an injection device 18 are connected at one end of each.

  Each of the other ends of the discharge pipes 107 and 108 is connected to one end of a hydrogen supply pipe 111 that supplies hydrogen-rich gas reformed and generated by a PSR reformer connected at one end to the hydrogen separation membrane fuel cell 200. Has been. The other ends of the supply pipes 109 and 110 are connected to a connection pipe 118 to which one end of an air supply pipe 120 to which a pump P1 and a mixer 119 are attached is connected. The mixer 119 is connected to one end of a supply pipe 112 for supplying anode off gas to a PSR reformer to which supply pipes 109 and 110 are connected at one end, so that anode off gas and the like can be supplied together with supply of combustion support air. It is like that.

  By switching valves V5 to V8, combustion support air and anode off-gas (and gasoline or hydrogen gas, if necessary) are selectively supplied to the regeneration-side PSR reformer, and the reforming-side PSR reformer The hydrogen-rich gas generated and discharged in can be supplied to the fuel cell 200 as a fuel for power generation.

  The injectors 15 and 17 inject a mixed gas of gasoline and steam (reforming raw material) at a wide angle when the PSR reformer to which each is attached causes a reforming reaction, and the injectors 16 and 18 When the PSR reformer to which each is attached is subjected to a regeneration reaction, combustion support air and anode off-gas (and gasoline, hydrogen gas, etc., if necessary) are injected into a wide angle to be installed in the PSR reformer. Further, the supply and reaction on the catalyst 12 can be performed.

  The hydrogen supply pipe 111 is further configured to store hydrogen in a hydrogen storage tank (for example, a hydrogen storage device) to which extra hydrogen rich gas is separately attached, and when the hydrogen demand varies due to start-up, low load, or load fluctuation. The hydrogen amount may be appropriately increased or decreased by removing the hydrogen from the hydrogen storage tank, or the hydrogen in the anode off-gas supplied to the PSR reformer by temporarily changing the hydrogen supply amount (for combustion It is also possible to adjust the increase / decrease of the fuel amount as appropriate.

  The supply pipe 112 is provided with a valve V9, and an external supply pipe 113 and an air supply pipe 116 are connected via the valve V9, and gasoline, hydrogen gas, or the like is additionally supplied as combustion fuel through the external supply pipe 113. Air can be replenished from the outside, and air (combustion air) for burning hydrogen or the like (combustion fuel) in the anode off-gas can be supplied by the air supply pipe 116 and the amount of air can be controlled. It has become. Further, a pipe for inserting a cathode (oxygen electrode; hereinafter the same) off-gas from the fuel cell 200 is connected to the supply pipe 109, 110 or 112 or directly to the PSR reformer to control the amount of combustion support air. At the same time, the temperature may be adjusted by additionally supplying a relatively high temperature cathode off gas.

  The supply pipe 112 is provided with a throttle valve and a hydrogen buffer tank (for example, a hydrogen storage device, a high-pressure hydrogen tank, etc.) that adjust the anode off-gas amount according to the opening, and drive the throttle valve and supply hydrogen from the hydrogen buffer tank. Thus, the supply amount to the PSR reformer can be controlled so as not to be linked to the power generation operation state.

  On the anode (hydrogen electrode) side, the hydrogen separation membrane fuel cell 200 is connected to the other end of the hydrogen supply pipe 111 and the other end of the supply pipe 112 through which the anode off-gas can be discharged and inserted. On the (oxygen electrode) side, an air supply pipe 114 for supplying air (oxidant gas) having a high oxygen content for power generation operation, and a discharge pipe 115 for discharging the cathode off-gas generated by the battery reaction, Are each connected at one end. In this way, the fuel cell 200 is configured to perform a power generation operation when the reformed and generated hydrogen and air are supplied, and after the power generation, off gas (anode off gas and cathode off gas) can be discharged to the outside of the cell, Further, the discharged anode off gas can be supplied mainly to the regeneration side PSR reformer through the supply pipe 112.

  The other end of the discharge pipe 115 is connected by a mixer 117 provided in the fuel supply pipe 101, and circulates moisture (and residual oxygen) contained in the cathode offgas as a water vapor source necessary for the reforming reaction. It is configured to be available.

  The fuel cell 200 is provided with a cooling pipe through which cooling air (cooling medium) supplied from the atmosphere is inserted so that the inside of the battery can be cooled by heat exchange with the cooling air. Supply piping 109, 110 or 112 or directly connected to the PSR reformer on the regeneration side, supplying cooling air discharged from the cooling pipe to enable temperature control and flow rate control, as well as regeneration reaction You may make it utilize as combustion support air used for combustion at the time.

  As shown in FIG. 3, the first PSR reformer 10 includes a cylindrical body 13 having a circular cross-section with both ends closed, and a catalyst (catalyst supporting section) 12 supported on the inner wall surface of the cylindrical body 13. The cylindrical body 13 forms a space for carrying out the reaction and functions as a catalyst carrier.

  The cylindrical body 13 is a hollow body that is formed into a cylindrical shape having a circular cross section with a diameter of 10 cm using a ceramic honeycomb and has both ends in the longitudinal direction of the cylinder closed. As the cross-sectional shape and size, an arbitrary shape and size such as a rectangle other than a circle and an ellipse can be selected according to the purpose and the like.

  The catalyst 12 does not carry a catalyst in a region of a predetermined distance A from both ends in the length direction of the cylindrical body toward the in-cylinder direction, that is, from the both ends in the length direction, of the curved surface of the cylindrical body wall. The catalyst non-supporting portions 12A and 12B are left (see FIG. 1) and are supported on the entire surface excluding the catalyst non-supporting portion. For the catalyst 12, metals such as Pd, Ni, Pt, Rh, Ag, Ce, Cu, La, Mo, Mg, Sn, Ti, Y, and Zn can be used.

  When the reforming reaction is performed by the catalyst 12, the reformed and generated hydrogen rich gas is cooled by the catalyst non-supporting portion 12 </ b> A on the downstream side in the gas discharge direction, and the hydrogen rich gas can be supplied close to the operating temperature of the fuel cell 200. On the contrary, when the reforming reaction is switched to the regeneration reaction, the catalyst unsupported portion 12A is in a state of being heated by heat exchange with the hydrogen rich gas, and the combustion supplied in the direction opposite to the discharge direction of the hydrogen rich gas The fuel can be supplied to the catalyst 12 after being preheated by the catalyst non-supporting portion 12A. Thereby, a temperature distribution in which the amount of heat storage becomes higher is formed near the center of the cylindrical body 13 on which the catalyst 12 is supported, which is advantageous in terms of reactivity. The tubular body 13 is attached with a temperature sensor 19 for measuring the temperature of the catalyst.

  The second PSR reformer 11 is configured in the same manner as the first PSR reformer 10, and is a reaction (reforming reaction or regeneration reaction) performed by the first PSR reformer 10. Therefore, it is possible to switch between the reforming reaction and the regeneration reaction.

As shown in FIG. 4, the hydrogen separation membrane fuel cell (HMFC) 200 includes a battery membrane 51 having a dense hydrogen permeable membrane using a hydrogen permeable metal, and an oxygen electrode (O ₂₎ sandwiching the battery membrane 51. Electrode) 52 and a hydrogen electrode (H ₂ electrode) 53. When the hydrogen-rich gas reformed and generated by the PSR reformer 10 is supplied, hydrogen can be selectively permeated to perform power generation operation. It has become so.

  Between the oxygen electrode 52 and the battery film 51, an air flow path 59 a for passing, that is, supplying and discharging air (Air) as an oxidant gas is formed. A fuel flow path 59b for passing, that is, supplying and discharging hydrogen-rich fuel gas (here, reformed and generated hydrogen-rich gas) is formed. The oxygen electrode 52 and the hydrogen electrode 53 are made of various materials such as carbon (for example, carbon powder carrying platinum or an alloy composed of platinum and other metals) or an electrolyte solution (for example, Nafion Solution manufactured by Aldrich Chemical). Can be formed.

The battery film 51 has a five-layer structure including a dense substrate (dense hydrogen permeable layer made of a hydrogen permeable metal) 56 formed of vanadium (V). The palladium (Pd) layers (dense hydrogen permeable layers made of a hydrogen permeable material) 55 and 57 are provided so as to sandwich the base material 56 from both sides, and are opposite to the side of the one Pd layer 55 in contact with the base material 56. On the side surface, an electrolyte layer 54 made of BaCeO ₃ (solid oxide) is further provided in a thin layer shape. Further, a cathode layer 58 made of lanthanum cobaltite is provided in a thin layer on the surface of the electrolyte layer 54 opposite to the side in contact with the Pd layer 55. The Pd layer 57 and the cathode layer 58 function as a current collector plate.

  The base material 56 can be suitably formed using niobium, tantalum, and an alloy containing at least one of these in addition to vanadium (V). These have high hydrogen permeability and are relatively inexpensive.

Electrolyte layer (BaCeO ₃ layer) 54 can be configured by using a SrCeO ₃ based ceramic proton conductor other than BaCeO _3. Further, the cathode layer 58 can be formed using a conductive material such as lanthanum manganate, silver, platinum, platinum-supported carbon, in addition to lanthanum cobaltite.

  Examples of the hydrogen permeable metal include, in addition to palladium, vanadium, niobium, tantalum, an alloy containing at least one of these, and a palladium alloy. The electrolyte membrane can be protected by providing a dense layer using these.

  The dense layer (coating film) made of a hydrogen permeable metal includes, for example, vanadium (vanadium alone and an alloy such as vanadium-nickel) in that the oxygen electrode side generally has high hydrogen permeability and is relatively inexpensive. ), Niobium, tantalum, and alloys containing at least one of these are preferably used. Although these can be applied on the hydrogen electrode side, the oxygen electrode side is desirable in terms of avoiding hydrogen embrittlement. On the hydrogen electrode side, it is preferable to use, for example, palladium or a palladium alloy because hydrogen permeability is relatively high and hydrogen embrittlement is difficult.

  As shown in FIG. 4, a sandwich structure composed of three layers of Pd layer 55 / base material 56 / Pd layer 57, that is, a laminated structure of two or more layers composed of different metals (dense layer composed of hydrogen permeable material). When it has, you may make it provide the metal diffusion suppression layer which suppresses the spreading | diffusion of this different metal in at least one part of the contact interface of a different metal (for example, refer FIG.5 and FIG.6). The metal diffusion suppressing layer is described in paragraphs [0015] to [0016] of JP-A No. 2004-146337.

  As described above, the sandwich layer may be provided as a five-layer structure such as Pd / tantalum (Ta) / V / Ta / Pd in addition to palladium (Pd) / vanadium (V) / Pd. is there. As described above, V has a faster proton or hydrogen atom permeation rate than Pd and is inexpensive, but has a low ability to dissociate hydrogen molecules into protons and the like. By providing on one or both sides of the layer, the transmission performance can be improved. In this case, by providing a metal diffusion suppressing layer between the metal layers, mutual diffusion between different metals can be suppressed, and a decrease in hydrogen permeation performance and hence a decrease in electromotive force of the fuel cell can be suppressed.

  The electrolyte layer 54 is made of a solid oxide, and a reaction suppression layer that suppresses the reaction between oxygen atoms in the electrolyte layer and Pd may be provided at least at a part of the interface with the Pd layer 55 ( For example, the reaction suppression layer 65 in FIG. This reaction suppression layer is described in paragraphs [0024] to [0025] of JP-A No. 2004-146337.

  The battery membrane 51 includes a vanadium base material, which is a dense hydrogen permeable metal, and an inorganic electrolyte layer formed on the cathode side of the fuel cell, so that the electrolyte layer can be made thin. The operating temperature of the high-temperature solid oxide fuel cell (SOFC) can be lowered to a temperature range of 300 to 600 ° C. As a result, the fuel cell system of the present invention that supplies the cathode off-gas discharged from the fuel cell directly to the PSR reformer that undergoes the reforming reaction can be suitably configured.

In the hydrogen separation membrane fuel cell 200, when a hydrogen-rich gas having a high hydrogen (H ₂ ) density is supplied to the fuel flow path 59b and air containing oxygen (O ₂ ) is supplied to the air flow path 59a, the following formula ( The electrochemical reaction (battery reaction) represented by 1) to (3) is caused to supply electric power to the outside. Equations (1) and (2) represent reactions on the anode side and cathode side, respectively, and equation (3) represents the total reaction in the fuel cell.
H ₂ → 2H ⁺ + 2e ⁻ (1)
(1/2) O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O (2)
H ₂ + (1/2) O ₂ → H ₂ O (3)

  The PSR reformers 10 and 11, the hydrogen separation membrane fuel cell (HMFC) 200, the valves V1 to V9, the injectors 15 to 18, the temperature sensor 19, and the mixers 117 and 119 are electrically connected to the controller 100. The operation timing is controlled by the control device 100. The control device 100 controls the output of the fuel cell by adjusting the amount of hydrogen gas and air according to the magnitude of a load (not shown) connected to the hydrogen separation membrane fuel cell. In addition to the control, it also controls the reforming reaction and the regeneration reaction in the PSR reformer.

  Here, a control routine performed by the control device 100 of the fuel cell system will be described with reference to FIG. 2, particularly focusing on a startup control routine performed when the fuel cell is started.

FIG. 2 shows a startup control routine. When the ignition (IG) switch is turned on and this routine is executed, in step 100, temperature sensors 19 attached to the PSR reformer (PSR1) 10 and the PSR reformer (PSR2) 11 respectively. from the catalyst temperature ^{t 2} of the catalyst temperature ^{t 1} and PSR2 of PSR1 it is captured.

Next, in step 120, the captured catalyst temperatures t ¹ and t ² are compared, and the highest temperature T ^max , here, the catalyst temperature T ^{max of the} higher one of t ¹ and t ² (for example, t ^1). Hereinafter, the case where t ¹ > t ² will be described as an example.) Is selected, and it is determined whether or not the catalyst temperature t ¹ is equal to or higher than the reformable temperature T.

  Here, the reformable temperature is a temperature capable of maintaining a certain reforming efficiency and maintaining a stable reforming reaction for 1 second or more without generation of soot and the like. The reformable temperature differs depending on the system configuration and conditions (fuel, catalyst, steam / carbon (S / C) ratio, oxygen / carbon (O / C) ratio, required load, etc.).

In step 120, when the catalyst temperature t ¹ is determined to have reached the above reformable temperature T, when PSR1 gasoline is supplied to the reforming reactor of the reforming side performing reforming reaction PSR1 Since the reformed generation of hydrogen gas is possible, it is next determined in step 140 whether or not continuous operation is possible, that is, whether or not the reforming reaction can be maintained for the required time without warming up. Is done.

  Here, the “necessary time” is a time required for the regeneration-side PSR reformer (here, for example, the PSR reformer 11 [PSR2]) to reach the reformable temperature T or higher.

  In step 140, for example, PSR1 is used as a reforming reactor on the high temperature side (that is, reforming side), and PSR2 is used as the reforming reactor on the low temperature side (regeneration side) to maintain the catalyst temperature T1 at which PSR1 can perform the reforming reaction. Possible maintenance time is estimated based on various conditions (fuel, catalyst, water vapor / carbon (S / C) ratio, oxygen / carbon (O / C) ratio, required load, etc.), and PSR1 of PSR2 (especially catalyst) Is estimated based on various conditions (reactor heat capacity, warming heat quantity, warming efficiency, etc.) and it is determined that T2 ≧ reformable temperature T is satisfied. It may be determined that continuous operation is possible.

  If it is determined in step 140 that the reforming reaction for the necessary time in PSR1 can be maintained, in the next step 160, whether or not the high temperature side PSR1 is set in the reforming side reforming reactor. Is determined. If it is determined in step 160 that PSR1 is set in the reforming reactor on the reforming side, this routine is terminated and the routine proceeds to normal power generation operation described later. As described later, at the time of transition to normal power generation operation, the reforming reaction is started in the high-temperature side PSR1, and the system can be started as it is. At this time, the regeneration reaction is started in PSR2.

  As described above, since the reforming reaction is started using the heat storage amount of the high-temperature side PSR1, the system can be quickly started up without performing unnecessary warm-up at the time of startup.

On the other hand, if it is determined in step 120 that the catalyst temperature t ¹ is lower than the reformable temperature T, the reforming of hydrogen cannot be performed even if gasoline is supplied, and therefore the routine proceeds to step 200.

  Further, when it is determined in step 140 above that it is impossible to maintain the reforming reaction for the required time in PSR1, the catalyst by the reforming reaction can be started even if the reforming reaction is started by supplying gasoline. Since the temperature drop of the fuel is so great that the desired hydrogen production may not be performed over the required time, the routine proceeds to step 200 without supplying gasoline.

Then, in the next step 200, since the situation that can not be satisfactorily continue the reforming reaction even PSR1 on the high temperature side as the catalyst temperature t ^1, PSR1 catalyst temperature t ¹ is reproduced by causing a combustion reaction ( It is determined whether or not the regeneration-side reforming reactor is set to perform warm-up. If it is determined in step 200 that PSR1 is not set to the regeneration-side reforming reactor, the next step At 220, PSR1 is set as the reforming reactor on the regeneration side. Conversely, when it is determined in step 200 that PSR1 has already been set in the reforming reactor on the regeneration side, the process proceeds to step 240 as it is. At this time, the PSR 2 is set as a reforming reactor on the reforming side that performs the reforming reaction.

  In step 240, the valves V1 and V6 are opened, and gasoline and combustion support air are supplied as combustion fuel to the regeneration side PSR1, and the PSR2 having a lower catalyst temperature than the PSR1 set on the reforming side V2 and V5 are opened and gasoline is supplied as combustion fuel, and at the same time, warm-up is started.

After the start of warm-up at step 240 or when it is determined at step 160 that PSR1 is not set in the reforming reactor on the reforming side, the initial catalyst temperature is PSR2 (t ¹ ) with PSR2 (t ¹ ). higher than t ^2), since the after starting the warm-up can reach the reformable temperature T faster is PSR1 side, in step 260, again PSR1 the reforming reactor of the reforming side, modifying the playback side PSR2 Set to quality reactor. Then, after switching, this routine is terminated and the routine proceeds to normal power generation operation. Also in this case, as will be described later, at the time of transition to normal power generation operation, it is possible to operate the system by performing a reforming reaction in PSR1, and at this time, the regeneration reaction is continued in PSR2.

  As described above, the system can be started up in a short time while suppressing fuel consumption by warming up using the heat storage amount of the high-temperature side PSR1.

  Next, the normal power generation operation of the fuel cell system after starting as described above will be specifically described.

  When the PSR reformer 10 performs the reforming reaction and the PSR reformer 11 performs the regeneration reaction, the fuel supply pipe 101 and the supply pipe 102 are opened by opening the valve V1 and the valve V6 and closing the valve V2 and the valve V7. The discharge pipe 107 and the hydrogen supply pipe 111 are communicated with each other, and the valve V3 and the valve V5 are opened and the valve V4 and the valve V8 are closed, so that the supply pipe 109 and the supply pipe 112, the discharge pipe 104 and the discharge pipe 106 are communicated with each other. Let At this time, a mixed gas of gasoline and water vapor (reforming raw material) is supplied to the PSR reformer 10 and subjected to a water vapor reforming reaction, and combustion supporting air from the pump P1 and anode off gas from the fuel cell 200 are supplied. Is supplied to the PSR reformer 11 and subjected to a combustion reaction. The gas mixture which is a reforming raw material is generated by mixing gasoline and water vapor (moisture) in the cathode off-gas from the discharge pipe 115 in the mixer 117, and sent to the PSR reformer 10.

  In the PSR type reformer 10, the heat storage amount is increased due to the regeneration reaction before the reforming reaction switching, and the mixed gas (reforming raw material) of gasoline and steam is inserted from the injection device 15 through the supply pipe 102. When injected and supplied onto the catalyst 12, steam reforming of gasoline is performed at the catalyst 12 to generate hydrogen-rich synthesis gas (hydrogen-rich gas). The reforming reaction is desirably performed under heat storage at 300 to 1100 ° C.

The hydrogen-rich gas generated by reforming as described above is cooled in advance by the catalyst non-supporting portion 12A on the side to which the discharge pipe 107 of the PSR reformer 10 is connected, and then inserted through the discharge pipe 107 and the hydrogen supply pipe 111. Then, it is supplied to the anode side of the hydrogen separation membrane fuel cell 200, and further, air is supplied from the air supply pipe 114 provided on the cathode side, and a power generation operation (cell reaction) is performed. When the supplied hydrogen-rich gas is consumed in the power generation operation, it is then discharged as an anode off gas to the supply pipe 112 and is injected from the injection device 18 through the supply pipe 112 and the supply pipe 109. The anode off gas mainly includes residual hydrogen that has not been subjected to the cell reaction, and CO and CH ₄ .

  At this time, if the anode off gas alone is small in the amount of combustion and a sufficient heat storage amount cannot be obtained, or if heat storage cannot be performed in a short time, the valve V9 is connected so that the external supply pipe 113 communicates with the supply pipe 112. Can be switched, and gasoline or hydrogen gas for combustion can be additionally supplied from the outside. Further, by switching the valve V9, it is also possible to supply combustion supporting air for burning hydrogen or the like in the anode off gas from the air supply pipe 116.

  When combustion-supporting air and anode off-gas are supplied from the injector 18 to the PSR reformer 11, hydrogen injected on the catalyst 12 is combusted, and the amount of heat stored by combustion heating, that is, the catalyst temperature is recovered. it can. At this time, the catalyst non-supporting portion 12A on the side of the PSR reformer 11 to which the anode off gas or the like is supplied is heated in the reforming reaction before the regeneration reaction is started in the same manner as described above. Heat is returned to the catalyst 12 again by heat exchange with the supplied anode off gas or the like, so that heat can be used effectively.

  As described above, when the heat storage amount of the PSR reformer 10 undergoing the reforming reaction, that is, the catalyst temperature is lowered and the hydrogen reforming production efficiency is lowered, the PSR reformer 10 The reforming reaction is switched to the regeneration reaction, and the regeneration reaction in the PSR reformer 11 is switched to the reforming reaction.

  Specifically, by opening the valve V2 and the valve V7 and closing the valve V1 and the valve V6, the fuel supply pipe 101 and the supply pipe 103, the discharge pipe 108 and the hydrogen supply pipe 111 are communicated with each other, and the valve V8 and the valve V4 are connected. By closing the opening valve V5 and the valve V3, the supply pipe 110 and the air supply pipe 120, the discharge pipe 105, and the discharge pipe 106 are communicated with each other. At this time, a mixed gas of gasoline and water vapor (reforming raw material) is supplied to the PSR reformer 11, and the anode off-gas is used as a combustion fuel for the regenerative reaction together with combustion support air and the PSR reformer 10. To be used for each reaction.

  In the case of switching as described above, the PSR reformer 11 is in a state where the heat storage amount has increased due to the regeneration reaction before the reforming reaction switching, and the gasoline and water vapor are mixed from the injector 17 through the supply pipe 103. When gas (reforming raw material) is injected and supplied onto the catalyst 12, the catalyst 12 performs steam reforming of gasoline to generate hydrogen-rich synthesis gas (hydrogen-rich gas). The reaction temperature of the reforming reaction is the same as described above. The hydrogen-rich gas reformed and generated by the PSR reformer 11 is cooled in advance by the catalyst non-supporting portion 12A on the side to which the exhaust pipe 108 of the PSR reformer 11 is connected, and then the exhaust pipe 108 and the hydrogen The gas is supplied to the anode side of the hydrogen separation membrane fuel cell 200 through the supply pipe 111 and is supplied to the power generation operation (cell reaction) together with the air supplied from the air supply pipe 114. After the supplied hydrogen-rich gas is consumed and discharged as the anode off-gas to the supply pipe 112, the anode off-gas is supplied from the injector 16 together with the combustion supporting air from the supply pipe 112 via the air supply pipe 120 and the supply pipe 110. Be injected.

  At this time, similarly to the above, when the anode off gas alone is small in combustion amount and a sufficient heat storage amount cannot be obtained or heat storage cannot be performed in a short time, the gasoline V or hydrogen for combustion is switched by switching the valve V9. Gas can be additionally supplied from the outside. Similarly, combustion support air is supplied from the air supply pipe 116.

  Combustion air and anode off-gas are supplied from the injection device 16 to the PSR reformer 10, and the amount of heat stored (that is, the catalyst temperature) can be recovered again by burning hydrogen or the like supplied on the catalyst 12. . At this time, the catalyst non-supporting portion 12A on the side of the PSR reformer 10 to which the anode off gas or the like is supplied is in a state where the temperature has been raised in the reforming reaction before the regeneration reaction is started in the same manner as described above. The heat is exchanged with the anode off gas or the like, so that the heat is returned to the catalyst 12 again and used effectively. The combustion off gas generated by the regeneration reaction in the PSR reformer 10 is exhausted through the exhaust pipe 105.

  In the fuel cell system of the present invention, as a fuel cell, a hydrogen separation membrane provided with an electrolyte membrane in which an electrolyte layer is laminated on at least one side of a dense hydrogen permeable membrane (hydrogen permeable metal layer) using a hydrogen permeable metal. Type fuel cells (which may be either proton-conductive solid oxide type or solid polymer type) can be selected according to the purpose.

  For example, (1) an electrolyte membrane having a hydrogen permeable metal and an inorganic electrolyte layer (especially proton conductive ceramics) formed on at least one side of the metal, and hydrogen provided on one surface of the electrolyte membrane A fuel supply part for supplying power generation fuel to the electrode and the hydrogen electrode, an oxygen electrode provided on the other surface of the electrolyte membrane, and an oxidant gas supply part for supplying an oxidant gas to the oxygen electrode Hydrogen separation membrane fuel cell, or (2) an electrolyte membrane having a proton conductive electrolyte layer and a hydrogen permeable metal sandwiching the electrolyte layer from both sides, a hydrogen electrode provided on one surface of the electrolyte membrane, and the A solid polymer comprising a fuel supply unit for supplying power generation fuel to the hydrogen electrode, an oxygen electrode provided on the other surface of the electrolyte membrane, and an oxidant gas supply unit for supplying an oxidant gas to the oxygen electrode Type hydrogen separation membrane fuel cell, etc. It can be used to apply.

  5 to 6 show other specific examples of the hydrogen separation membrane fuel cell constituting the fuel cell system of the present invention. For details about other specific examples, reference can be made to the description in Japanese Patent Application Laid-Open No. 2004-146337.

FIG. 5 shows a battery film 61 having a six-layer structure including a dense substrate 66 formed of vanadium (V), an oxygen electrode (O ₂ electrode) 62 and a hydrogen electrode (H ₂ electrode) sandwiching the battery film 61. ) 63 and a hydrogen separation membrane fuel cell 60 provided with a metal diffusion suppression layer and a reaction suppression layer. The battery film 61 includes a dense metal diffusion suppression layer 67 and a palladium (Pd) layer 68 in this order from the surface side of the base electrode 66 on the hydrogen electrode (anode) 63 side. On the surface of the cathode 62 side, a dense reaction suppressing layer (for example, proton conductor, mixed conductor, or insulator layer) 65 and a thin electrolyte layer (for example, perovskite layer) made of solid oxide are sequentially formed from the surface side. A single metal oxide SrCeO ₃ layer 64) and a cathode layer 69. The Pd layer 68 and the cathode layer 69 function as a current collector plate. The reaction suppression layer 65 has a function of suppressing the reaction between oxygen atoms in the electrolyte layer 64 and the base material (V) 66. In the same manner as described above, an air channel 59a and a fuel channel 59b are formed between the oxygen electrode or hydrogen electrode and the electrolyte membrane. Details of the metal diffusion suppression layer and the reaction suppression layer are as described above.

FIG. 6 includes a battery film 71 having a dense hydrogen permeable layer using a hydrogen permeable metal, and an oxygen electrode (O ₂ electrode) 72 and a hydrogen electrode (H ₂ electrode) 73 sandwiching the battery film 71. The solid polymer type hydrogen separation membrane fuel cell 70 is shown. The battery membrane 71 has, for example, a multilayer structure in which both surfaces of an electrolyte layer 76 made of a solid polymer membrane such as a Nafion (registered trademark) membrane are sandwiched between dense hydrogen permeable metal layers. A palladium (Pd) layer (dense layer) 77 is provided on the hydrogen electrode (anode) side surface of 76, and a vanadium-nickel serving as a base material in order from the surface side on the oxygen electrode (cathode) side surface of the electrolyte layer 76. An alloy (V—Ni) layer (dense layer) 75 and a Pd layer (dense layer) 74 are provided. Note that an air flow path 59a and a fuel flow path 59b are respectively formed between the oxygen electrode or the hydrogen electrode and the battery membrane 71 in the same manner as described above. Also in the present fuel cell, a metal diffusion suppression layer can be provided between the V-Ni layer 75 and the Pd layer 74, and a reaction occurs between the V-Ni layer 75 or the Pd layer 77 and the electrolyte layer 76. A suppression layer can be provided.

  In the polymer electrolyte fuel cell shown in FIG. 6, by forming a hydrogen permeable layer using a hydrogen permeable metal so as to sandwich the water-containing electrolyte layer, moisture evaporation and membrane resistance of the electrolyte layer at a high temperature are achieved. It is possible to suppress the increase, and in general, the operating temperature of a low-temperature polymer electrolyte fuel cell (PEFC) can be improved to a temperature range of 300 to 600 ° C. This is suitable for the configuration of the fuel cell system of the present invention in which the cathode off-gas discharged from the fuel cell is directly supplied to the PSR reformer that undergoes the reforming reaction.

  In the above embodiment, the case where gasoline (or a mixed gas of gasoline and steam) is used as the reforming raw material has been described. However, the same applies to the case where a hydrocarbon fuel other than gasoline is used.

  In the above description, the fuel cell system is mainly described in the form of the two PSR reformers 10 and 11. However, three or more PSR reformers may be provided. Moreover, although it comprised with the two PSR type reformers which make a pair, you may be comprised with the form provided with three or more PSR type reformers.

1 is a schematic configuration diagram showing a fuel cell system according to an embodiment of the present invention. It is a flowchart which shows the starting time control routine performed at the time of starting in the fuel cell system which concerns on embodiment of this invention. It is a perspective view which shows schematic structure of the PSR type reformer which concerns on embodiment of this invention. 1 is a schematic cross-sectional view showing a hydrogen separation membrane fuel cell (HMFC) according to an embodiment of the present invention. It is a schematic sectional drawing which shows the other specific example of the fuel cell which comprises the fuel cell system of this invention. It is a schematic sectional drawing which shows the other specific example of the fuel cell which comprises the fuel cell system of this invention.

Explanation of symbols

10, 11 PSR reformer 12 Catalyst (catalyst support)
DESCRIPTION OF SYMBOLS 19 ... Temperature sensor 30, 60, 70, 200 ... Hydrogen separation membrane type fuel cell 100 ... Control apparatus V1-V9 ... Valve

Claims (6)

When the reforming raw material is supplied, the reforming raw material is reformed on the heated catalyst, and when the exothermic fuel is supplied, the exothermic fuel is exothermicly reacted. At least two reforming reactors for heating
Determining means for determining whether the temperature condition of the reforming reactor having the largest amount of heat storage selected from the at least two reforming reactors has reached a state in which the reforming reaction is possible at the time of start-up;
A hydrogen generation apparatus comprising: Switching means for switching the reforming raw material supply flow path and the heat generating fuel supply flow path to the reforming reactor;
When it is determined by the determination means that the temperature condition of the reforming reactor having the largest amount of heat storage has reached a state where a reforming reaction is possible, the reforming reactor having the largest amount of heat storage is used for the reforming Switching control means for switching the supply flow path by the switching means so that the raw material is supplied;
The hydrogen generator according to claim 1, further comprising:   The switching control means, when it is determined by the determination means that the temperature condition of the reforming reactor having the largest amount of heat storage has not reached a state capable of reforming reaction, the reforming reaction having the largest amount of heat storage. The hydrogen generation apparatus according to claim 2, wherein the supply passage is switched by the switching unit so that the heat-generating fuel is supplied to a vessel. It further comprises detection means for detecting the temperature of the catalyst,
The switching control means switches the supply flow path so that the supply is performed to the reforming reactor having the largest amount of heat storage selected based on the temperature detected by the detection means. 4. The hydrogen generator according to 3.   A fuel cell system comprising: the hydrogen generator according to any one of claims 1 to 4; and a fuel cell that generates electric power by supplying a hydrogen-containing gas reformed and generated by the hydrogen generator.   The fuel cell system according to claim 5, wherein the fuel cell includes an electrolyte in which an electrolyte layer is stacked on at least one side of a hydrogen permeable metal layer.

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