JP2008063159A - Method for stopping reformer, reformer, and fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for stopping a reformer, a reformer, and a fuel cell system in which deterioration can be suppressed while reducing consumption of resources. <P>SOLUTION: A reformer 10 comprises a reforming part 21 for forming first reformed gas j which introduces material gas r and water s and is rich in hydrogen, a carbon monoxide reduction part 22 which produces second reformed gas g having low concentration of carbon monoxide from the first reformed gas j, a water pipe 25 which is disposed at a position to receive heat from the carbon monoxide reduction part 22 and flows water s to be supplied to the reforming part 21, and an air conduit 16 which is formed so that air a after flowing through a part adjoining the reforming part 21 flows a part adjoining the carbon monoxide reduction part 22 to move the heat of the reforming part 21 to the carbon monoxide reduction part 22. The reformer 10 evaporates the water s adjoining the carbon monoxide reduction part 22 to suppress the reduction of the internal pressure of the reforming part 21 and the carbon monoxide reduction part 22 which are sealed in the state that they are communicated with each other. The fuel cell system comprises the reformer 10 and a fuel cell. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a reformer stopping method, a reformer, and a fuel cell system, and more particularly to a reformer stopping method, a reformer, and this reformer that can suppress deterioration while reducing resource consumption. The present invention relates to a fuel cell system provided.

  A fuel cell that uses hydrogen and oxygen to generate electric power through these electrochemical reactions has attracted attention as an environmentally friendly power generator. Fuel cells require hydrogen for power generation, but because the infrastructure for supplying hydrogen itself is not widespread, it is relatively difficult to obtain, so reforming raw materials such as city gas and kerosene to generate power for fuel cells In many cases, a fuel cell system is built in which a reformer that generates a hydrogen-rich gas (reformed gas) containing hydrogen to be used in the fuel cell is attached to the fuel cell. An example of a reformer is one that introduces a raw material and water and reforms the raw material with steam at a high temperature of about 600 ° C. In general, the reformer is filled with a catalyst for promoting the reforming reaction.

When stopping the generation of reformed gas in the reformer, if the reformer cools and the water vapor in the interior dew condensation, the pressure in the reformer drops and air enters from the outside. The catalyst in the reformer may be deteriorated by the air or condensed water that has entered. In order to prevent the catalyst in the reformer from deteriorating without using a special device, when the reformer is stopped, the steam is supplied for a predetermined time after the supply of the raw material supplied with the steam is stopped. The reforming part is cooled by continuing the flow control while purging the reformed gas remaining in the reforming part, and when the supply of water vapor is stopped, the supply of the raw material is resumed and the raw material is supplied for a predetermined time. There is a reformer that prevents the water vapor remaining in the reforming unit from condensing in the reforming unit by continuing the supply of the gas while controlling the flow rate (see, for example, Patent Document 1).
JP 2003-288930 A (paragraph 0011 etc.)

  However, if the supply of the raw material is resumed when the catalyst of the reformer is at a high temperature, the raw material hydrocarbon is pyrolyzed and carbon is deposited, so that the performance of the reformer deteriorates. For this reason, if the steam is continuously supplied until the hydrocarbon of the raw material reaches a temperature at which thermal decomposition does not occur even after the reformer is stopped, extra resources are consumed. If the inside of the reformer becomes negative pressure before the raw material hydrocarbon is lowered to a temperature at which thermal decomposition does not occur, external air enters the reformer and the catalyst deteriorates.

  In view of the above-described problems, an object of the present invention is to provide a reformer stopping method, a reformer, and a fuel cell system that can suppress deterioration while reducing resource consumption.

  In order to achieve the above object, the reformer stopping method according to the invention described in claim 1 introduces a raw material gas r and water s and introduces the raw material gas r as shown in FIGS. A reforming unit 21 that generates a first reformed gas j rich in hydrogen by steam reforming, and a carbon monoxide concentration lower than that of the first reformed gas j by introducing the first reformed gas j. A carbon monoxide reduction unit 22 that generates the second reformed gas g, and a method of stopping the reformer 10; a step of stopping the supply of the raw material gas r and water s to the reforming unit 21 ( ST1); sealing the reforming unit 21 and the carbon monoxide reduction unit 22 in communication with each other (ST2); transferring the heat held by the reforming unit 21 to the carbon monoxide reduction unit 22, The water s in the water pipe 25 adjacent to the carbon oxide reduction unit 22 and communicating with the reforming unit 21 is vaporized and communicated with each other. And a step (ST5) to suppress a decrease in sealing the internal pressure of the reforming section 21 and the carbon monoxide reducing unit 22. Here, the state in which the reforming unit 21 and the carbon monoxide reduction unit 22 are in communication with each other means that at least when one internal pressure increases (decreases), the other internal pressure also increases (decreases). In this way, both are connected.

  When configured in this manner, the heat held by the reforming unit is transferred to the carbon monoxide reduction unit, the water in the water pipe adjacent to the carbon monoxide reduction unit and communicating with the reforming unit is vaporized, and communicated with each other The internal pressure of the reforming section and the carbon monoxide reduction section sealed with is suppressed, so that external air enters the reformer without newly supplying water and other resources. Thus, the catalyst can be prevented from deteriorating.

  Further, the reformer stopping method according to the invention described in claim 2 is, for example, as shown in FIGS. 1 and 3, in the reformer stopping method according to claim 1, the reformer is sealed in a state of being in communication with each other. A step (ST3) for detecting the internal pressure of the reforming unit 21 and the carbon monoxide reduction unit 22 that has been performed; and a step (ST4) for detecting the temperature of the reforming unit 21; When the temperature of the reforming unit 21 is equal to or higher than a predetermined temperature, the heat held by the reforming unit 21 is moved to the carbon monoxide reduction unit 22 (ST5), and the temperature of the reforming unit 21 is The raw material gas r is enclosed in the reforming section 21 when the temperature is lower than the predetermined temperature (ST6).

  With this configuration, since the raw material gas is sealed in the reforming unit when the temperature of the reforming unit is lower than a predetermined temperature, the reduction of the internal pressure is suppressed without causing thermal decomposition of the raw material gas with a simple configuration. can do.

  In order to achieve the above object, a reformer according to a third aspect of the present invention includes a raw material gas r and water s as shown in FIG. A reforming section 21 that generates a first reformed gas j rich in the gas; a second reformed gas that introduces the first reformed gas j and has a lower carbon monoxide concentration than the first reformed gas j. a carbon monoxide reduction unit 22 that generates g; and a water pipe 25 that is disposed at a position where heat is received from the carbon monoxide reduction unit 22 and flows water s supplied to the reforming unit 21; The air passage 16 is formed so as to be adjacent to the carbon oxide reduction unit 22 so that the air a after flowing through the portion adjacent to the reforming unit 21 flows through the portion adjacent to the carbon monoxide reduction unit 22. An air passage 16 is formed; heat of the reforming unit 21 is transferred to the carbon monoxide reduction unit 22 by the air a flowing through the air passage 16. It is configured to movement.

  With this configuration, the heat in the reforming section moves to the carbon monoxide reduction section by the air flowing through the air passage, the water in the water pipe received from the carbon monoxide reduction section is vaporized, and the pressure drop in the reforming section is reduced. It is suppressed and the catalyst can be prevented from deteriorating due to external air entering the reformer.

  Further, the reformer according to the invention described in claim 4 is the reformer 10 according to claim 3, for example, as shown in FIG. Combustion section 11 for generating reforming heat to be heated is provided; air path 16 is configured to serve as an exhaust gas path for flowing exhaust gas e generated by combustion in combustion section 11.

  If comprised in this way, since an air path serves as the exhaust gas path which flows the exhaust gas produced by the combustion in a combustion part, a reformer can be made compact.

  Further, the reformer according to the invention described in claim 5 supplies the raw material gas r to the reforming section 21 in the reformer 10 according to claim 3 or claim 4, for example, as shown in FIG. Raw material gas supply means 31; air supply means 32 for supplying air a to the air passage 16; sealing means 35, 36, 37, 38 for sealing the reforming section 21 and the carbon monoxide reduction section 22; Pressure detecting means 41 for detecting the pressure of at least one of the part 21 and the carbon monoxide reducing part 22; a temperature detecting means 42 for detecting the temperature of the reforming part 21; and the reforming part 21 and the carbon monoxide reducing part 22 When the pressure of the reforming unit 21 is less than or equal to a predetermined pressure in a sealed state, and the temperature of the reforming unit 21 is equal to or higher than the predetermined temperature, the air a is allowed to flow through the air passage 16 and the reforming unit When the temperature of 21 is lower than a predetermined temperature, the raw material gas r is sealed in the reforming section 21. As to, and a control unit 40 for controlling the raw material gas supply means 31, the air supply means 32, and the sealing means 35, 36, 37, 38.

  With this configuration, the reformer and the carbon monoxide reducing unit are sealed and the pressure of the reforming unit is equal to or lower than a predetermined pressure, and the temperature of the reforming unit is equal to or higher than the predetermined temperature. Sometimes air flows through the air passage, so that the air flowing through the air passage moves the heat of the reforming section to the carbon monoxide reduction section, and the water in the water pipe received from the carbon monoxide reduction section is vaporized. The pressure drop is suppressed. Further, when the reformer and the carbon monoxide reduction unit are sealed and the pressure of the reforming unit is equal to or lower than a predetermined pressure and the temperature of the reforming unit is lower than the predetermined temperature, reforming is performed. Since the raw material gas is sealed in the portion, it is possible to suppress a decrease in internal pressure without causing thermal decomposition of the raw material gas. As a result, it is possible to prevent the catalyst from deteriorating due to the outside air entering the reformer.

  In order to achieve the above object, a fuel cell system according to a sixth aspect of the present invention includes a reformer 10 according to any one of the third to fifth aspects as shown in FIG. A fuel that introduces a second reformed gas g and an oxygen-containing oxidant gas t, and generates electric power by an electrochemical reaction between hydrogen in the second reformed gas g and oxygen in the oxidant gas t A battery 60.

  If comprised in this way, the fuel cell system which can prevent deterioration of a reformer can be provided.

  According to the present invention, the heat in the reforming section is moved to the carbon monoxide reduction section by the air flowing through the air passage, and the water in the water pipe received from the carbon monoxide reduction section is vaporized to reduce the pressure in the reforming section. It is suppressed and the catalyst can be prevented from deteriorating due to external air entering the reformer.

  Embodiments of the present invention will be described below with reference to the drawings. In each drawing, the same or corresponding members are denoted by the same or similar reference numerals, and redundant description is omitted.

  First, a reformer 10 according to a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a longitudinal sectional view of the reformer 10. The reformer 10 includes a combustion section 11 that generates reforming heat used for steam reforming of the raw material gas r, and a first reformed gas j as a first reformed gas by steam reforming the raw material gas r. A reforming unit 21 to be generated, a carbon monoxide reducing unit 22 that generates a second reformed gas g as a second reformed gas having a reduced carbon monoxide concentration from the first reformed gas j, and a raw material gas r And a water pipe 25 through which water s used for steam reforming is supplied. The carbon monoxide reducing unit 22 converts the carbon monoxide in the first reformed gas j into a modified gas h in which the carbon monoxide is reduced from the first reformed gas j, and the modified gas h A selective oxidation unit 24 that selectively oxidizes carbon monoxide to generate a second reformed gas g in which carbon monoxide is further reduced from the modified gas h.

  The combustor 11 includes a burner 12 that combusts the combustion fuel f and a combustion chamber 13 that houses a flame generated by the combustion. The combustion chamber 13 is formed inside the inner cylinder 14 that is a cylindrical member. In the present embodiment, the burner 12 is accommodated in the inner cylinder 14, and the combustion chamber 13 is formed by the space at the tip of the burner 12 being surrounded by the inner cylinder 14. In the present embodiment, the inner cylinder 14 is disposed so that its axis is substantially parallel to the vertical direction. The length of the inner cylinder 14 is equal to or longer than the length in the vertical direction of the reforming unit 21 described later. The burner 12 is disposed in the inner cylinder 14 so that the flame is formed downward. The lower end of the inner cylinder 14 is an opening. On the other hand, the upper end 14a of the inner cylinder 14 is closed. The side of the burner 12 opposite to where the flame is formed penetrates the upper end 14 a of the inner cylinder 14 and is connected to the air fuel introduction pipe 29. The air fuel introduction pipe 29 forms a flow path through which the combustion fuel f flows. A cheese 29T is attached to the air fuel introduction pipe 29.

  The inner cylinder 14 is covered with an outer cylinder 15 that is a cylindrical member that is slightly larger than itself. The lower end 15b of the outer cylinder 15 is closed. The outer cylinder 15 is disposed so that its axis substantially coincides with the axis of the inner cylinder 14. Thus, an exhaust gas flow path 16 is formed between the outer side of the inner cylinder 14 and the inner side of the outer cylinder 15 for flowing the exhaust gas e after the combustion fuel f is burned by the burner 12. It is also possible to cause the combustion air a to flow through the exhaust gas flow channel 16 by supplying the combustion air a without supplying the combustion fuel f toward the burner 12. That is, the exhaust gas passage 16 of the present embodiment also serves as an air passage. The size of the outer cylinder 15 that is one size larger than the inner cylinder 14 may be appropriately determined in consideration of the flow rates of the exhaust gas e and the combustion air a flowing through the exhaust gas passage 16. The exhaust gas flow channel 16 is connected to the exhaust gas pipe 54 and configured to discharge the exhaust gas e to the outside of the system.

  The reforming unit 21 is configured by providing a reforming catalyst on the outer periphery excluding both ends and the upper portion of the outer cylinder 15. The reforming catalyst is held by a reforming catalyst holding cylinder 17 which is a cylindrical member coaxial with the inner cylinder 14 and the outer cylinder 15. In other words, the reforming catalyst is filled between the outer cylinder 15 and the reforming catalyst holding cylinder 17. The reforming catalyst is a catalyst that promotes the steam reforming reaction of the raw material gas r, and typically a nickel-based reforming catalyst or a ruthenium-based reforming catalyst is used. Further, the shape of the reforming catalyst is preferably granular, columnar, honeycomb, or monolithic in order to efficiently perform the steam reforming reaction. The steam reforming reaction is an endothermic reaction. Therefore, the combustion fuel f is burned in the combustion section 11 to generate reforming heat. The positional relationship between the reforming unit 21 and the burner 12 is configured such that the flame of the burner 12 is positioned approximately at the center in the vertical direction of the reforming unit 21. With such a positional relationship, the entire reforming unit 21 can be heated.

  The lower end of the reforming catalyst holding cylinder 17 is an opening. The reforming part 21 communicates with the transformation part 23 through this opening. On the other hand, the upper end of the reforming catalyst holding cylinder 17 is closed, and a raw material gas introduction pipe 26 for introducing the raw material gas r into the reforming section 21 is connected to a part of the upper end. In the upper part of the reforming part 21, a space not filled with the reforming catalyst is formed so that the source gas r introduced through the source gas introduction pipe 26 reaches the entire upper part of the reforming catalyst holding cylinder 17. . The source gas introduction pipe 26 extends in the direction opposite to the combustion unit 11 (that is, outward). A raw material gas shutoff valve 36 for shutting off the flow of the raw material gas r is disposed in the raw material gas introduction pipe 26. A water pipe 25, which will be described in detail later, is connected to the raw material gas introduction pipe 26 downstream of the raw material gas cutoff valve 36.

  The shift section 23 is configured by providing a shift catalyst on the outer periphery of the outer cylinder 15 above the reforming section 21 while leaving the upper portion of the outer cylinder 15. The shift catalyst also covers the upper part of the reforming catalyst holding cylinder 17. The portion where the shift catalyst covers the reforming catalyst holding cylinder 17 is partitioned by the reforming catalyst holding cylinder 17 and is not in communication with the reforming unit 21. The shift catalyst is a catalyst that promotes a shift reaction in which carbon monoxide contained in the first reformed gas j generated by the steam reforming reaction in the reforming section 21 is reacted with water. A chromium-based shift catalyst, a copper-zinc shift catalyst, a platinum shift catalyst, or the like is used. Further, the shape of the shift catalyst is preferably granular, columnar, honeycomb, or monolithic in order to efficiently perform the shift reaction. The metamorphic reaction shifts carbon monoxide to carbon dioxide. The modification reaction is an exothermic reaction.

  The selective oxidation unit 24 is configured by providing a selective oxidation catalyst on the outer periphery of the outer cylinder 15 above the shift unit 23. The boundary between the selective oxidation unit 24 and the transformation unit 23 may be partitioned by punching metal or the like, but the selective oxidation unit 24 and the transformation unit 23 are configured to communicate with each other. The selective oxidation catalyst is a catalyst that promotes a selective oxidation reaction in which carbon monoxide contained in the shift gas h generated by the shift reaction in the shift section 23 is reacted with oxygen, typically a platinum-based selective oxidation catalyst, A ruthenium-based selective oxidation catalyst, a platinum-ruthenium-based selective oxidation catalyst, or the like is used. Further, the shape of the selective oxidation catalyst is preferably a granular shape, a cylindrical shape, a honeycomb shape, or a monolith shape in order to efficiently perform a selective oxidation reaction. The selective oxidation reaction is an exothermic reaction.

  The shift catalyst and the selective oxidation catalyst are held by a CO reduction catalyst holding cylinder 18 which is a cylindrical member coaxial with the inner cylinder 14 and the like. In other words, the shift catalyst is filled between the outer cylinder 15 and a part of the reforming catalyst holding cylinder 17 and the CO reduction catalyst holding cylinder 18, and between the upper part of the outer cylinder 15 and the CO reduction catalyst holding cylinder 18. Are filled with a selective oxidation catalyst. The CO reducing catalyst holding cylinder 18 also extends below the shift unit 23 and covers the lower part of the reforming unit 21. The CO reduction catalyst holding cylinder 18 below the shift section 23 is formed to be slightly larger than the reforming catalyst holding cylinder 17. The lower end 18b of the CO reducing catalyst holding cylinder 18 is closed. The lower end of the reforming catalyst holding cylinder 17 is disposed so as not to contact the lower end 18b of the CO reducing catalyst holding cylinder 18. Thereby, the reforming unit 21 and the transformation unit 23 communicate with each other. A first reformed gas flow path 19 for flowing the first reformed gas j is formed between the outside of the reforming catalyst holding cylinder 17 and the inside of the CO reducing catalyst holding cylinder 18 below the shift portion 23. Yes. The first reformed gas flow path 19 extends radially outward so that the first reformed gas j spreads directly under the shift catalyst to the entire lower surface of the shift catalyst. The size of the CO reduction catalyst holding cylinder 18 that is slightly larger than the reforming catalyst holding cylinder 17 may be determined as appropriate in consideration of the flow rate of the first reformed gas j flowing through the first reformed gas flow path 19.

  A selective oxidation air introduction pipe 27 for introducing the selective oxidation air c into the selective oxidation unit 24 is connected to the CO reduction catalyst holding cylinder 18 at the selective oxidation unit 24 immediately adjacent to the shift unit 23. The selective oxidation air introduction pipe 27 extends outward. The selective oxidation air introduction pipe 27 is provided with a selective oxidation air shut-off valve 37 that blocks the flow of the selective oxidation air c. The CO reducing catalyst holding cylinder 18 is connected to a second reformed gas pipe 28 for deriving the second reformed gas g at the selective oxidation unit 24 opposite to the side adjacent to the shift unit 23. . The second reformed gas pipe 28 extends outward. The second reformed gas pipe 28 is provided with a second reformed gas shut-off valve 38 that shuts off the flow of the second reformed gas g.

  The water pipe 25 is arranged as follows. The outside of the CO reduction catalyst holding cylinder 18 is contacted from above the selective oxidation section 24, and the outside of the CO reduction catalyst holding cylinder 18 is spirally wound downward from above the selective oxidation section 24. When it is spirally wound downward and reaches a position about 2/3 from the top of the transformation section 23, it is separated from the CO reducing catalyst holding cylinder 18 and further turned upward to be connected to the raw material gas introduction pipe 26. To do. The water pipe 25 communicates with the reforming unit 21 by connecting the water pipe 25 to the raw material gas introduction pipe 26. When the water pipe 25 is arranged in this way, the water s flows from the side of the selective oxidation unit 24 to the side of the transformation unit 23 and receives heat from the selective oxidation unit 24 and the transformation unit 23 before flowing into the raw material gas introduction pipe 26. From liquid to gas. As shown in FIG. 1, if a part of the water pipe 25 is disposed so as to pass through the selective oxidation unit 24 and / or the transformation unit 23 and contact the outer cylinder 15, the amount of heat received increases. This is preferable. The water pipe 25 is provided with a water shut-off valve 35 that shuts off the flow of water s upstream from contacting the CO reducing catalyst holding cylinder 18.

  In the first reformed gas flow path 19, a pressure sensor 41 is disposed as pressure detecting means for detecting the pressure of the reforming unit 21. Since the reforming unit 21 communicates with the carbon monoxide reduction unit 22 (the transformation unit 23 and the selective oxidation unit 24), the pressure of the carbon monoxide reduction unit 22 is also detected by detecting the pressure of the reforming unit 21. can do. Further, the reforming catalyst holding cylinder 17 and the CO reduction catalyst holding cylinder 18 are attached with temperature sensors 42 as temperature detecting means for detecting the temperatures of the reforming section 21, the shift section 23, and the selective oxidation section 24, respectively. . The number of the temperature sensors 42 may be appropriately determined according to the sizes of the respective parts 21, 23, and 24. Each of the pressure sensor 41 and the temperature sensor 42 is connected to the control device 40 via a signal cable, and is configured to be able to transmit the detected pressure or temperature as a signal to the control device 40.

The outer periphery of the transformation unit 23 and the reforming unit 21 below the lowermost part of the water pipe 25 (in the present embodiment, a position about 2/3 from the top of the transformation unit 23) is covered with a heat insulating material 46. The outer circumferences of the transformation section 23 and the selective oxidation section 24 above the heat insulating material 46 are covered with a heat insulating material 47. Since each part 21, 23, 24 is covered with the heat insulating materials 46, 47, each part 21, 23, 24 can be maintained at a temperature suitable for reaction during operation, and the temperature of the outer periphery of the reformer 10 Can be made lower than the temperature of each part 21, 23, 24, and contribute to burn prevention and the like. Typically, the heat insulating material 46 is obtained by press dehydrating and molding a mixture of a raw material slurry containing a silica raw material, a lime raw material, and water, a heat ray reflective material, heat resistant fibers, and the like at a density of about 500 kg / m ³ or less. It is a molded inorganic porous body. Typically, the heat insulating material 47 is formed by foaming and curing a mixture of silica / alumina-based fine particle powder, alkali metal silicate, hydrogen peroxide, and heat ray reflective material at a density of about 500 kg / m ³ or less. Inorganic foam. The heat insulating materials 46 and 47 are covered with a surface material 48, and the appearance of the reformer 10 is formed in a substantially cylindrical shape. The surface material 48 is typically an inorganic short fiber felt obtained by molding inorganic short fibers into a felt shape.

  The above-described valves 35, 36, 37, 38 and the cheese 29T attached to the air fuel introduction pipe 29 are disposed outside the surface material 48. A source gas pipe 56 is connected to the source gas cutoff valve 36. A raw material gas blower 31 for pumping the raw material gas r is disposed in the raw material gas pipe 56. When the source gas r is pumped from outside the system at the same pressure as when the source gas blower 31 is started, the source gas blower 31 may not be provided. A selective oxidation air pipe 57 is connected to the selective oxidation air shut-off valve 37. The selective oxidation air pipe 57 is provided with a selective oxidation blower 33 for pumping the selective oxidation air c. A reformed gas pipe 68 is connected to the second reformed gas cutoff valve 38. A water supply pipe 55 is connected to the water cutoff valve 35. The water supply pipe 55 is provided with a water pump 34 that pumps water s. A combustion fuel pipe 59 for flowing the combustion fuel f is connected to one of the remaining connection ports of the cheese 29T attached to the air fuel introduction pipe 29, and a combustion air pipe 52 is connected to the other remaining connection ports. Is connected. The combustion air pipe 52 is provided with a combustion air blower 32 that pumps the combustion air a.

  The control device 40 is disposed outside the surface material 48 and controls the operation of the reformer 10. The control device 40 receives a pressure signal from the pressure sensor 41 and receives a temperature signal from the temperature sensor 42 from the temperature sensor 42. The control device 40 transmits an open / close signal to each of the valves 35, 36, 37, and 38 to control the open / close operation of each of the valves 35, 36, 37, and 38. Moreover, the control apparatus 40 adjusts the electric power supplied via the motive power system (not shown) connected to each blower 31, 32, 33, and starts / stops each blower 31, 32, 33, and fluid. Control the discharge rate.

  Next, a fuel cell system 100 according to a second embodiment of the present invention will be described with reference to FIG. FIG. 2 is a schematic system diagram of the fuel cell system 100. The fuel cell system 100 includes the reformer 10 described so far, a fuel cell 60 that generates electric power by an electrochemical reaction between hydrogen and oxygen, and a control device 70.

  The fuel cell 60 is typically a polymer electrolyte fuel cell. The fuel cell 60 includes an anode 61 for introducing the second reformed gas g, a cathode 62 for introducing the oxidant gas t, and a cooling unit (not shown) that removes heat generated by the electrochemical reaction. Has been. The oxidant gas t is typically air that has been humidified to a predetermined humidity. Although the fuel cell 60 is shown in a simplified manner in the figure, in practice, a single cell is formed by sandwiching a solid polymer membrane between an anode 61 and a cathode 62, and a plurality of cells are formed via a cooling unit. It is configured by stacking sheets. In the fuel cell 60, hydrogen in the second reformed gas g supplied to the anode 61 is decomposed into hydrogen ions and electrons, and the hydrogen ions move to the cathode 62 through the solid polymer film and the electrons are anodes. It moves to the cathode 62 through a conducting wire connecting 61 and the cathode 62 and reacts with oxygen in the oxidant gas t supplied to the cathode 62 to generate water, and heat is generated during this reaction. In this reaction, the direct current can be taken out by passing electrons through the conducting wire. The fuel cell 60 is typically electrically connected to a power conditioner (not shown) that converts DC power into AC power.

  In the anode 61 of the fuel cell 60, not all of the hydrogen in the introduced second reformed gas g is used for the above-described electrochemical reaction (power generation in the fuel cell 60), but some hydrogen is used. Is done. From the anode 61, the anode off gas p containing hydrogen that has not been used for the electrochemical reaction in the fuel cell 60 is discharged. The anode off gas p contains hydrogen, carbon dioxide, nitrogen and the like. At the cathode 62 of the fuel cell 60, not all of the oxygen in the introduced oxidant gas t is used for the above-described electrochemical reaction (power generation in the fuel cell 60), but some oxygen is used. . From the cathode 62, the cathode off gas q containing oxygen that has not been used for the electrochemical reaction in the fuel cell 60 is discharged.

  The anode 61 is connected to a reformed gas pipe 68 that supplies the second reformed gas g to the anode 61 and an anode offgas pipe 69 that discharges the anode offgas p. The reformed gas pipe 68 is connected to the second reformed gas cutoff valve 38. In the reformed gas pipe 68, a reformed gas cutoff valve 88 is disposed. The anode off gas pipe 69 is connected to a combustion fuel pipe 59 downstream of the combustion material shutoff valve 39. The combustion fuel pipe 59 is a pipe branched from the raw material gas pipe 56 between the raw material gas blower 31 and the raw material gas cutoff valve 36. By branching the combustion fuel pipe 59 from the source gas pipe 56, the source gas r can be led to the burner 12 as the combustion fuel f. An anode off gas shutoff valve 89 is disposed in the anode off gas pipe 69. A reformed gas pipe 68 upstream of the reformed gas cutoff valve 88 and an anode offgas pipe 69 downstream of the anode offgas cutoff valve 89 are connected by a bypass pipe 67. A bypass shutoff valve 87 is disposed in the bypass pipe 67. An oxidant gas pipe 65 that supplies the oxidant gas t to the cathode 62 and a cathode offgas pipe 66 that discharges the cathode offgas q are connected to the cathode 62. The oxidant gas pipe 65 is provided with an oxidant gas blower 64 that pumps the oxidant gas t. The oxidant gas blower 64 may also serve as the combustion air blower 32 and / or the selective oxidation air blower 33.

  The control device 70 controls the fuel cell system 100. The control device 70 is configured to transmit signals to the combustion raw material shut-off valve 39, the bypass shut-off valve 87, the reformed gas shut-off valve 88, and the anode off-gas shut-off valve 89 so as to open and close the respective valves. ing. Further, the control device 70 controls the oxidant gas blower 64. The control device 70 controls the reformer 10 in conjunction with the control device 40 (see FIG. 1) of the reformer 10. The control device 70 may be configured integrally with the control device 40 (see FIG. 1).

  With continued reference to FIGS. 1 and 2, the operation of the reformer 10 and the fuel cell system 100 will be described. Here, the operation of the reformer 10 will be described as part of the operation of the fuel cell system 100.

  When the fuel cell system 100 is stopped, the valves 35, 36, 37, 38, 88, and 89 are closed. When the fuel cell system 100 is started from a stopped state, the control device 70 opens the combustion material shut-off valve 39 and starts the material gas blower 31 and the combustion air blower 32. Then, the raw material gas r is supplied as the combustion fuel f to the burner 12 in the reformer 10, and the combustion air a is also supplied to the burner 12. The source gas r is typically a chain hydrocarbon such as methane or ethane (including city gas and natural gas), but carbonization of methanol, petroleum products (kerosene, gasoline, naphtha, LPG, etc.), etc. A hydrocarbon-based fuel such as a mixture containing hydrogen as a main component may be vaporized. When the combustion fuel f and combustion air a are supplied to the burner 12, the burner 12 is ignited and the reforming unit 21 is heated. The exhaust gas e generated by the combustion flows through the exhaust gas passage 16 and flows into the exhaust gas pipe 54 and is discharged out of the system. Further, the water shut-off valve 35 is opened and the water pump 34 is activated to feed the water s to the water pipe 25. At substantially the same time, the source gas cutoff valve 36 is opened to supply the source gas r to the source gas introduction pipe 26.

  The water s receives heat from the water pipe 25 and reaches the raw material gas introduction pipe 26 to become water vapor. The steam and the source gas r are mixed in the source gas introduction pipe 26 and reach the reforming section 21. In the reforming unit 21, the hydrocarbon in the raw material gas r and the water vapor evaporated from the water s react with the reforming heat obtained from the combustion unit 11 (steam reforming reaction), and contain hydrogen and carbon monoxide. One reformed gas j is generated. When the gas containing the carbon monoxide exceeding the allowable amount is supplied to the anode 61 of the fuel cell 60, the electrode catalyst is poisoned. Therefore, the reforming unit 21 reduces the carbon monoxide concentration in the first reformed gas j. The generated first reformed gas j is sent to the shift unit 23.

  The first reformed gas j sent to the shift unit 23 reacts with the water vapor in which the generated carbon monoxide remains (a shift reaction) to become hydrogen and carbon dioxide. That is, in the shift gas h generated in the shift section 23, compared with the first reformed gas j, carbon monoxide is reduced and hydrogen and carbon dioxide are increased. Although the modified gas h has a reduced carbon monoxide concentration compared to the first reformed gas j, it normally contains about 5,000 to 10,000 ppm of carbon monoxide during steady operation, and at this carbon monoxide concentration, The electrode catalyst of the fuel cell 60 may be poisoned. For this reason, in order to reduce the carbon monoxide concentration in the shift gas h, the shift gas h generated in the shift section 23 is sent to the selective oxidation section 24.

  When the modified gas h is sent to the selective oxidation unit 24, the control device 70 opens the selective oxidation air shut-off valve 37 and the second reformed gas shut-off valve 38 to activate the selective oxidation air blower 33 to generate the selective oxidation air c. This is supplied to the selective oxidation unit 24. The selective oxidizing air shut-off valve 37 and the second reformed gas shut-off valve 38 and the selective oxidizing air blower 33 may be activated simultaneously with the operation of the raw material gas shut-off valve 36 or the like, or the raw material gas shut-off valve It may be performed after a predetermined time has passed since opening 36. Further, the operations of the selective oxidation air cutoff valve 37 and the second reformed gas cutoff valve 38 may be performed at different timings.

  In the modified gas h sent to the selective oxidation unit 24, the remaining carbon monoxide reacts with oxygen in the supplied selective oxidation air c (selective oxidation reaction) to become carbon dioxide. The second reformed gas g generated by the selective oxidation reaction contains about 10 ppm or less of carbon monoxide during steady operation. With this level of carbon monoxide concentration, it is possible to avoid poisoning of the electrode catalyst of the fuel cell 60.

  In the steady operation of the reformer 10, the reforming unit 21, the shift unit 23, and the selective oxidation unit 24 are in a state where the temperatures are suitable for the reactions in the respective units. The temperature of each part at the time of steady operation is about 550 ° C. to 800 ° C. for the reforming unit 21, about 160 ° C. to 280 ° C. for the transformation unit 23, and about 100 ° C. to 250 ° C. for the selective oxidation unit. When each part 21, 23, 24 does not reach the temperature during steady operation at the initial start of the reformer 10, the composition of the second reformed gas g led out to the second reformed gas pipe 28 is stable. However, it contains carbon monoxide at a concentration at which the electrode catalyst of the fuel cell 60 may be poisoned. Therefore, the second reformed gas g whose composition is not stable is not supplied to the anode 61 of the fuel cell 60 but is guided to the combustion unit 11 and combusted as the combustion fuel f.

  The control device 70 opens the bypass shut-off valve 87, closes the combustion raw material shut-off valve 39, and converts the second reformed gas g whose composition is not stable into the reformed gas pipe 68, the bypass pipe 67, and the anode off gas. The burner 12 is supplied from the air fuel introduction pipe 29 via the pipe 69 and the combustion fuel pipe 59. At this time, the control device 40 detects the temperature of each part 21, 23, 24 by the temperature sensor 42. When the temperature of each part reaches the temperature during steady operation, the control device 70 opens the reformed gas cutoff valve 88 and the anode off-gas cutoff valve 89 and closes the bypass cutoff valve 87. By the operation of this valve, the second reformed gas g is supplied to the anode 61 of the fuel cell 60. When the second reformed gas g is supplied to the anode 61, the controller 70 activates the oxidant gas blower 64 and supplies the oxidant gas t to the cathode 62.

In the fuel cell 60, an electrochemical reaction is performed between hydrogen in the second reformed gas g introduced into the anode 61 and oxygen in the oxidant gas t introduced into the cathode 62. As for the electrochemical reaction, the reaction represented by the following formula (1) is performed at the anode 61, and the reaction represented by the following formula (2) is performed at the cathode 62.
2H ₂ → 4H ⁺ + 4e ⁻ (1)
O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O (2)
Electricity is generated by this electrochemical reaction, heat is generated, and moisture is generated. In further explanation, electric power can be obtained when electrons of the anode 61 move to the cathode 62 through the external electric circuit. Hydrogen ions of the anode 61 pass through the solid polymer film and move to the cathode 62, and combine with oxygen to generate moisture. As mentioned above, this electrochemical reaction is an exothermic reaction.

  The electric power obtained by the fuel cell 60 is direct-current power, which is converted into alternating-current power by a power conditioner (not shown) as necessary and transmitted to an electric power load (not shown). On the other hand, the heat generated in the fuel cell 60 is stored, for example, in a hot water storage tank (not shown), and is consumed in a heat load such as hot water supply or heating as necessary. By effectively using the heat generated in the fuel cell 60, the efficiency of the fuel cell system 100 is improved.

  During the operation of the fuel cell 60, the anode off gas p is discharged from the anode 61. The discharged anode off gas p is led to the combustion unit 11 of the reformer 10 and burned as the combustion fuel f. That is, the anode off gas p discharged from the anode 61 flows into the burner 12 from the air fuel introduction pipe 29 via the anode off gas pipe 69 and the combustion fuel pipe 59. By the combustion of the anode off gas p in the combustion unit 11, reforming heat used for reforming in the reforming unit 21 can be generated.

  When the fuel cell system 100 is stopped, the oxidant gas blower 64 is stopped and the shutoff valve (not shown) is closed so that the oxidant gas t is not supplied to the cathode 62. As a result, the solid polymer membrane of the fuel cell 60 is prevented from being dried and the catalyst is prevented from being oxidized, thereby preventing the performance of the fuel cell 60 from being lowered. Further, the blowers 31, 32, 33 and the water pump 34 are stopped, and the water shutoff valve 35, the raw material gas shutoff valve 36, the selective oxidation air shutoff valve 37, and the second reformed gas shutoff valve 38 are closed to perform reforming. The supply of water s, source gas r, and selective oxidation air c to the vessel 10 is stopped. As a result, the reforming unit 21 and the carbon monoxide reduction unit 22 of the reformer 10 are sealed with the first reformed gas j and the like. In this way, the reforming unit 21 and the carbon monoxide reduction unit 22 are sealed with the first reformed gas j and the like so as to have a positive pressure from the outside thereof, thereby the reforming unit 21 and the carbon monoxide reduction unit 22. Intrusion of outside air into the catalyst is prevented, and the reforming catalyst, shift catalyst, and selective oxidation catalyst are prevented from deteriorating due to contact with oxygen. When the fuel cell system 100 is stopped, the reformed gas cutoff valve 88 and the anode offgas cutoff valve 89 are closed.

  By the way, the temperature of the reformer 10 during the steady operation is as described above (for example, about 550 ° C. to 800 ° C. in the reforming unit 21), but the reformer 10 is stopped when the fuel cell system 100 is stopped. Then, the temperature of the reformer 10 decreases. When the temperature of the reformer 10 decreases, the pressure of the reforming unit 21 and the carbon monoxide reduction unit 22 decreases, and when negative pressure is reached, outside air enters and the catalyst of each unit 21, 22, particularly the shift catalyst, deteriorates. Become. In order to prevent this, when the pressures of the reforming unit 21 and the carbon monoxide reduction unit 22 are equal to or lower than a predetermined pressure, the source gas shut-off valve 36 is opened to start the source gas blower 31, and the source unit r is supplied to the reforming unit 21. To prevent pressure drop. If the reforming portion 21 and the like are maintained at a positive pressure using the raw material gas r, special equipment required when using other gases is not required, and the system can be simplified. However, when the hydrocarbon-based raw material gas r is introduced while the reforming section 21 is at a high temperature, the hydrocarbon is thermally decomposed to deposit carbon, and the performance of the reformer 10 is degraded. In order to avoid such an inconvenience, the control device 40 performs the following control.

  Here, with reference to the flowchart of FIG. 3 in addition to FIG. When the reformer 10 is stopped, the supply of the raw material gas r and water s to the reformer 10 is stopped (ST1), the valves 35, 36, 37, and 38 are closed, and the reformer 21 and the one are closed. When the carbon oxide reduction unit 22 is sealed (ST2), the control device 40 detects the pressure in the reforming unit 21 with the pressure sensor 41, and determines whether the internal pressure is equal to or lower than a predetermined pressure (ST3). . Here, the predetermined pressure is a pressure that allows for a margin in the pressure at which the outside air does not enter the reforming unit 21 and the carbon monoxide reduction unit 22, and is, for example, 15 kPa (gauge pressure) or 20 kPa (gauge pressure). It is. If the pressure is not lower than the predetermined pressure, the process returns to the step of determining whether the internal pressure is lower than the predetermined pressure (ST3).

  If the internal pressure is equal to or lower than the predetermined pressure, control device 40 determines whether or not the temperature of reforming unit 21 detected by temperature sensor 42 is equal to or higher than the predetermined temperature (ST4). The predetermined temperature is a temperature slightly lower than the temperature at which the raw material gas r undergoes thermal decomposition (a temperature that allows for a margin in the temperature at which the raw material gas r undergoes thermal decomposition), and is, for example, 400 ° C. If it is more than predetermined temperature, the control apparatus 40 will start the combustion air blower 32, and will supply the combustion air a to an air path (exhaust gas flow path 16) (ST5).

  By activating the combustion air blower 32, the combustion air a flows through the exhaust gas passage 16, reaches the exhaust gas pipe 54, and is discharged out of the system. When the combustion air a flows through the exhaust gas passage 16, the reforming unit 21 is cooled by the combustion air a. As a result, the temperature of the reforming unit 21 goes to a temperature at which the raw material gas r is not thermally decomposed even when the raw material gas r is introduced (a temperature lower than a predetermined temperature). Further, the combustion air a flowing through the exhaust gas flow channel 16 serves as a heat medium, and the heat of the reforming unit 21 is transmitted to the transformation unit 23 and the selective oxidation unit 24. Then, the water in the water pipe 25 adjacent to the transformation unit 23 and / or the selective oxidation unit 24 receives heat and a part thereof is evaporated. Thereby, it is possible to prevent the internal pressure of the reforming unit 21 and the like communicating with the water pipe 25 from rising and the inside of the reforming unit 21 and the carbon monoxide reduction unit 22 from being equal to or lower than a predetermined pressure. When the combustion air blower 32 is activated and the combustion air a is supplied to the air passage (exhaust gas passage 16), the flow returns to the step (ST3) for determining again whether the internal pressure is equal to or lower than the predetermined pressure. Continue.

  On the other hand, in the step (ST4) for determining whether or not the temperature of the reforming unit 21 is equal to or higher than a predetermined temperature, the raw material gas r is not thermally decomposed unless it is equal to or higher than the predetermined temperature. The gas r is supplied to the reforming unit 21 (ST6). Thereby, it can prevent reliably that the inside of the modification part 21 and the carbon monoxide reduction part 22 becomes below a predetermined pressure. When the raw material gas blower 31 is activated and the raw material gas r is supplied to the reforming unit 21, the flow returns to the step (ST3) for determining whether or not the internal pressure is equal to or lower than the predetermined pressure, and the subsequent flow is continued.

  As described above, according to the reformer 10 according to the present invention, the internal pressures of the reforming unit 21 and the carbon monoxide reduction unit 22 are reduced without providing special equipment regardless of the state of the reforming unit 21. And the deterioration of the reformer 10 can be prevented. The fuel cell system 100 according to the present invention including such a reformer 10 is a fuel cell system 100 having excellent durability.

  In the above description, in the step of supplying the combustion air a to the air passage (ST5), the combustion air a is flown. However, the air passage is formed separately from the exhaust gas passage 16 and is different from the combustion air a. Air may be supplied to the air path. However, the reformer 10 can be made compact by letting the combustion air a flow through the exhaust gas flow channel 16 in the step of supplying the air to the air flow channel (ST5).

  In the above description, the fuel cell 60 has been described as a polymer electrolyte fuel cell, but may be a fuel cell other than a polymer electrolyte fuel cell such as a phosphoric acid fuel cell. However, the polymer electrolyte fuel cell can be operated at a relatively low temperature and can be downsized, so that it is suitable for installation in a general household.

It is a longitudinal section of the reformer concerning a 1st embodiment of the present invention. FIG. 4 is a schematic system diagram of a fuel cell system according to a second embodiment of the present invention. It is a flowchart explaining the control at the time of a reformer stop.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Reformer 11 Combustion part 16 Air path 21 Reformation part 22 Carbon monoxide reduction part 25 Water pipe 31 Raw material gas blower 32 Combustion air blower 35 Water shutoff valve 36 Raw material gas shutoff valve 37 Selective oxidation air shutoff valve 38 Second reformed gas Shut-off valve 40 Control device 41 Pressure sensor 42 Temperature sensor 60 Fuel cell a Air e Exhaust gas f Fuel g Second reformed gas j First reformed gas r Raw material gas s Water

Claims (6)

A reforming section for introducing a source gas and water and steam-reforming the source gas to generate a first reformed gas rich in hydrogen; and introducing the first reformed gas to the first reformed gas A method of stopping a reformer having a carbon monoxide reduction unit that generates a second reformed gas having a lower carbon monoxide concentration than the gas;
Stopping the supply of the source gas and the water to the reforming section;
Sealing the reforming portion and the carbon monoxide reducing portion in communication with each other;
The heat held by the reforming unit is transferred to the carbon monoxide reduction unit, the water in the water pipe adjacent to the carbon monoxide reduction unit and communicating with the reforming unit is vaporized, and the two are in communication with each other A step of suppressing a decrease in internal pressure of the reforming section and the carbon monoxide reduction section sealed with
How to stop the reformer. Detecting the internal pressure of the reforming unit and the carbon monoxide reduction unit that are sealed in a state of communicating with each other;
Detecting the temperature of the reforming section;
When the internal pressure is equal to or lower than a predetermined pressure, and when the temperature of the reforming unit is equal to or higher than a predetermined temperature, the heat held by the reforming unit is transferred to the carbon monoxide reduction unit, Configured to enclose the raw material gas in the reforming section when the temperature of the reforming section is lower than the predetermined temperature;
The method for stopping a reformer according to claim 1. A reforming section for introducing a source gas and water and steam-reforming the source gas to generate a first reformed gas rich in hydrogen;
A carbon monoxide reduction unit that introduces the first reformed gas and generates a second reformed gas having a carbon monoxide concentration lower than that of the first reformed gas;
A water pipe that is disposed at a position to receive heat from the carbon monoxide reduction unit and that flows water supplied to the reforming unit;
An air passage formed so as to be adjacent to the reforming unit and the carbon monoxide reduction unit, wherein the air after flowing through a part adjacent to the reforming unit is adjacent to the carbon monoxide reduction unit The air passage is formed to flow through;
The heat of the reforming unit is transferred to the carbon monoxide reduction unit by the air flowing through the air path;
Reformer. A combustion section for introducing and burning fuel and generating reforming heat for heating the reforming section;
The air path is configured to serve as an exhaust gas path for flowing exhaust gas generated by combustion in the combustion section;
The reformer according to claim 3. Source gas supply means for supplying the source gas to the reforming section;
Air supply means for supplying air to the air passage;
Sealing means for sealing the reforming section and the carbon monoxide reduction section;
Pressure detecting means for detecting the pressure of at least one of the reforming unit and the carbon monoxide reducing unit;
Temperature detecting means for detecting the temperature of the reforming section;
When the reforming section and the carbon monoxide reducing section are sealed and the pressure of the reforming section is equal to or lower than a predetermined pressure, and the temperature of the reforming section is equal to or higher than a predetermined temperature. The raw material gas supply means, the air supply means, and the air gas are supplied to the reforming section when air is passed through the air passage and the temperature of the reforming section is lower than the predetermined temperature. A control device for controlling the sealing means;
The reformer according to claim 3 or 4. A reformer according to any one of claims 3 to 5;
A fuel cell that introduces the second reformed gas and an oxygen-containing oxidant gas and generates electric power by an electrochemical reaction between hydrogen in the second reformed gas and oxygen in the oxidant gas; Comprising:
Fuel cell system.

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