JP2008088033A - Fuel reforming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel reforming apparatus supplying a stable reformed gas to fuel cell by suppressing pulsation in a steam generator. <P>SOLUTION: The fuel reforming apparatus comprises a reformer 1 for steam-reforming a raw material fuel gas, a CO converter 2 for converting a reformed gas discharged from the reformer 1, and a CO remover 3 for selectively oxidizing the reformed gas discharged from the CO converter 2, wherein a steam generator 4 for evaporating water supplied from a water supply path 10 is provided in an inlet side of the reformer 1 and a buffer means 12 for suppressing any pulsation occurring when vaporizing the water is provided in the water supply path 10 located in the inlet side of the steam generator 4. The pulsation energy which is generated in the steam generator 4 by the cushioning function of the buffer means 12 can be absorbed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel reformer used by being incorporated in a fuel cell power generation system.

  A fuel cell power generation system supplies hydrogen gas or a reformed gas mainly composed of hydrogen to a fuel electrode (anode) in the fuel cell, and supplies oxygen gas or air to an air electrode (cathode). It is widely known to generate electricity by causing an electrochemical reaction through an electrolyte membrane disposed between the two. When the reformed gas is supplied to the fuel cell, a fuel reformer for reforming the hydrocarbon-based raw fuel gas into a reformed gas mainly composed of hydrogen is incorporated into the fuel cell power generation system and used. ing.

  The outline of a conventionally known fuel reformer will be described. For example, as shown in FIG. 10, a reformer 1 for steam reforming a hydrocarbon-based raw fuel gas, and a reformer discharged from the reformer 1 Generally, a CO converter 2 that converts gas and a CO remover 3 that selectively oxidizes the reformed gas discharged from the CO converter 2 are generally used.

  A reforming catalyst is accommodated in the reformer 1, and steam produced by the steam generator 4 is mixed with a hydrocarbon-based raw fuel gas and introduced into the reformer 1. Steam reforming while passing through the reforming catalyst layer in 1 generates a reformed gas mainly composed of hydrogen. This hydrogen-based reformed gas is not immediately supplied to the fuel cell, but is supplied to the fuel cell after removing CO contained in the reformed gas. If the CO concentration in the reformed gas is high, the catalyst in the fuel cell is poisoned and the power generation performance decreases.

  In order to remove CO in the reformed gas, the reformed gas output from the reformer 1 is introduced into the CO converter 2. The CO shifter 2 contains a shift catalyst, which is converted while passing through the shift catalyst layer to reduce the CO concentration in the reformed gas. Next, the reformed gas discharged from the CO converter 2 is introduced into the CO remover 3. An oxidation catalyst is accommodated in the CO remover 3 and is selectively oxidized while passing through the oxidation catalyst layer, so that the CO concentration in the reformed gas is reduced to approximately 10 ppm or less. Then, the reformed gas output from the CO remover 3 is supplied to the fuel electrode of the fuel cell 5.

  In this way, the reformed gas is supplied from the fuel reformer to the fuel cell, and it is required to supply a reformed gas whose flow rate and composition are always stable during power generation. However, according to the conventional fuel reformer, a pulsation phenomenon occurs when a part of the water boils in the steam generator 4. When such a state occurs, the flow rate of the water vapor coming out of the water vapor generator 4 and the raw fuel flow rate become non-uniform. As a result, the mixing ratio S / C (steam / carbon ratio) of the steam and the raw fuel gas changes, and it becomes impossible to generate a stable reformed gas in the reformer.

In order to solve such a problem, it is necessary to suppress the pulsation in the steam generator to make the steam flow rate and the raw fuel flow rate uniform. For this reason, for example, in FIG. 10, a configuration is disclosed in which the water supply path 6 is provided as a water supply preheating line, and the supply water throttling means 7 is provided between the CO remover 3 and the steam generator 4 in the water supply path 6. (Patent Document 1). According to this configuration, it is described that the pulsation accompanying the generation of steam can be suppressed by the throttle means 7.
JP 2002-241108 A

  An object of the present invention is to provide a fuel reformer that can supply a stable reformed gas to a fuel cell by improving the conventional fuel reformer and suppressing pulsation in a steam generator. And

  As means for achieving such an object, claim 1 of the present invention provides a reformer for steam reforming raw fuel gas, and a CO converter for transforming reformed gas discharged from the reformer. A fuel reformer comprising a CO remover that selectively oxidizes the reformed gas discharged from the CO converter, wherein a steam generator that superheats water supplied from a water supply path is provided at the inlet of the reformer And a fuel reforming device provided with buffer means for suppressing pulsation generated when water evaporates in the water supply path located on the inlet side of the steam generator.

  According to a second aspect of the present invention, in the fuel reformer of the first aspect, a throttle means is provided on the inlet side of the buffer means in the water supply path.

  According to a third aspect of the present invention, in the fuel reformer of the first or second aspect, the buffer means is a catalyst reaction vessel having a catalyst cooling function and a buffer function.

  According to a fourth aspect of the present invention, in the fuel reformer of the first or third aspect, a backflow prevention means is provided on the inlet side of the buffer means in the water supply path.

  According to a fifth aspect of the present invention, in the fuel reformer of the second aspect, a throttle means is provided in a steam path for supplying water vapor from the steam generator to the reformer.

  A sixth aspect of the present invention is the fuel reformer according to any one of the first to fifth aspects, wherein the buffer means has a volume of 1 to 4 times the amount of water flowing in the water supply path per unit time. To do.

  According to a seventh aspect of the present invention, in the fuel reformer of any one of the first to sixth aspects, the buffer means has a structure in which a large number of tubes are arranged in parallel.

  According to the first aspect of the present invention, even if pulsation occurs in the steam generator, the pressure fluctuation can be buffered and absorbed by the buffer means. As a result, the water supply side is not affected by pressure fluctuation due to pulsation, and can always supply a constant amount of water to the steam generator. Moreover, the boiling in the reforming reaction vessel can be suppressed by using a steam generator that converts to superheated steam.

  According to the invention of claim 2, even if pulsation occurs in the steam generator, the pressure fluctuation can be buffered and absorbed by the buffer means, and the pressure fluctuation can be prevented from being transmitted to the primary side by the throttle means. The pressure absorption effect by the buffer means can be improved.

  According to the invention of claim 3, since the catalyst reaction vessel having the catalyst cooling function and the buffer function is used as the buffer means, it is not necessary to separately provide a member having the buffer function. In this case, the catalyst reaction vessel may be a reaction vessel constituting a CO converter or a CO remover.

  According to the invention of claim 4, even if pulsation occurs in the steam generator, the pressure fluctuation can be buffered and absorbed by the buffer means, and the backflow can be prevented by the backflow prevention means. It is possible to prevent the pressure fluctuation from being transmitted and improve the pressure absorption effect by the buffer means.

  According to the invention of claim 5, even if pulsation occurs in the steam generator, the pressure fluctuation can be buffered and absorbed by the buffer means, and the pressure fluctuation can be prevented from being transmitted to the primary side by the throttle means. In addition, it is possible to prevent the pressure fluctuation from being transmitted to the junction with the reformed fuel by the throttle means on the outlet side of the steam generator.

  According to invention of Claim 6, the said buffer means can fully fulfill | perform the function as a buffer means by having a volume 1 to 4 times with respect to the amount of water which flows through the inside of a water supply path | route in unit time.

  According to the seventh aspect of the present invention, the buffer means can sufficiently fulfill the function as the buffer means by adopting a structure in which a large number of tubes are arranged in parallel.

  Next, an embodiment of a fuel reformer according to the present invention will be described with reference to the accompanying drawings. Here, for the sake of easy understanding, the same members as those in the conventional example are denoted by the same reference numerals.

  FIG. 1 is a schematic configuration diagram showing a first embodiment of a fuel reformer according to the present invention, wherein 1 is a reformer, 2 is a CO converter, and 3 is a CO remover. A burner 8 is attached below the reformer 1, and the reforming catalyst stored in the reformer 1 is heated by combustion of the burner 8 to heat a predetermined catalyst reaction temperature (for example, 600 to 700 ° C.). ). When the fuel cell system is started up, the burner 8 burns with the raw fuel gas as fuel to raise the temperature of the reforming catalyst to a predetermined catalytic action temperature. Since the reaction is an endothermic reaction, combustion is continued using off-gas discharged from the fuel cell as fuel in order to maintain the reaction at a predetermined catalytic reaction temperature.

  Reference numeral 4 denotes a steam generator 4 disposed above the reformer 1, and in this case, a steam generator that performs superheated vaporization (complete gas phase) is used. The steam generated by the steam generator 4 is supplied to the inlet side of the reformer 4, and hydrocarbon-based raw fuel gas is mixed in the steam path 9. As a result, the reformer 4 is supplied with a mixed gas in which water vapor and raw fuel gas are mixed. The supply of the mixed gas is performed after the reforming catalyst has been heated to the catalytic reaction temperature.

  The mixed gas supplied to the reformer 4 is steam-reformed while passing through the reforming catalyst layer housed therein to become a reformed gas mainly composed of hydrogen, and from the outlet side of the reformer 4 In addition to being discharged, it is introduced into the inlet side of the CO converter 2 through the steam generator 4. In this case, the high temperature reformed gas exchanges heat with water supplied to the steam generator 4 while passing through the steam generator 4.

  The reformed gas introduced into the CO converter 2 is converted while passing through the conversion catalyst layer housed therein, so that the CO concentration in the reformed gas is reduced and discharged from the outlet side of the CO converter 2. At the same time, it is introduced into the inlet side of the CO remover 3. The modified reformed gas introduced into the CO remover 3 is selectively oxidized while passing through the oxidation catalyst accommodated therein, and the CO concentration in the modified reformed gas is reduced to about 10 ppm. 3 and is supplied to the fuel electrode of a fuel cell (not shown).

  Reference numeral 10 denotes a water supply path provided for supplying water to the steam generator 4, and this water supply path 10 is a heat exchanger 11, a heat exchanger 3 a of the CO remover 3, and a heat of the CO transformer 2. By passing the replacement part 2a in this order, it is formed as a feed water preheating line that can gradually raise the temperature of the cold water.

  The heat exchanger 11 is configured so that combustion exhaust gas generated by the combustion of the burner 8 passes, and heat exchange is performed between the combustion exhaust gas and cold water supplied to the water supply path. Thereby, the exhaust heat of combustion exhaust gas can be used effectively. The water heated through the heat exchanger 11 undergoes heat exchange with the internal oxidation catalyst when passing through the CO remover 3. The catalytic reaction temperature of the oxidation catalyst is, for example, 100 to 180 ° C. This catalytic reaction is an exothermic reaction, so it is necessary to cool and maintain the catalytic reaction temperature during power generation of the fuel cell. The water in the water supply path 10 is used as the cold heat source, and the temperature of the water can be raised by heat exchange.

  The water heated by the CO remover 3 undergoes heat exchange with the internal shift catalyst when passing through the CO shift converter 2. The catalytic reaction temperature of the shift catalyst is, for example, 180 to 250 ° C., and this catalytic reaction is also an exothermic reaction. Therefore, it is necessary to maintain the catalytic reaction temperature by cooling during power generation of the fuel cell. The water in the water supply path 10 is used as the cold heat source, and the temperature of the water can be raised by heat exchange.

  In this way, the cold water supplied to the water supply path 10 is gradually preheated in three stages before reaching the steam generator 4 and then introduced into the steam generator 4. At this time, when water exceeds 100 ° C. in the middle of the water supply path 10 due to preheating, a part of the water boils, and pressure fluctuation occurs in the water supply path 10, thereby disturbing the flow of water. For this reason, although illustration is omitted, it is preferable to adjust the amount of water supply by providing a temperature sensor at an appropriate position in the water supply path to measure the water temperature and controlling the water supply pump based on the measured value.

  The present embodiment is characterized in that the buffer means 12 is provided on the inlet side of the water vapor generator 4 in the water supply path 10. As the buffer means 12, for example, a tank having a buffer function can be used.

  In the fuel reforming apparatus of the present invention configured as described above, the reforming water passes through the heat exchanger 11, the heat exchanger 3 a of the CO remover 3, and the heat exchanger 2 a of the CO converter 2 in the water supply path 10. In this case, it is preheated and further passes through the buffer means 12 and flows into the water vapor generator 4. The water flowing into the steam generator 4 is vaporized in a short time because the water temperature is close to 100 ° C., and is supplied to the reformer 1 through the steam path 9 as described above. Since the raw fuel gas is supplied in the middle of the steam path 9, the raw fuel gas is supplied to the inlet side of the reformer 1 in a state where water vapor and the raw fuel gas are mixed.

  When steam is generated in the steam generator 4, the pressure fluctuates, pulsation is generated in the water supply path 10 due to this pressure fluctuation, and the amount of water supplied into the steam generator 4 changes. However, since the buffer means 12 is provided on the inlet side of the steam generator 4, pulsation energy can be absorbed by the buffer function of the buffer means 12. Thereby, the change of the water supply amount which flows into the steam generator 4 can be suppressed small. Therefore, the change in the amount of steam supplied from the steam generator 4 to the reformer 1 can be kept small, and the mixing ratio S / C between the steam and the raw fuel gas can be kept substantially constant.

  FIG. 2 is a schematic block diagram showing a second embodiment of the fuel reforming apparatus according to the present invention. In place of the buffer means 12 in the first embodiment, a catalytic reaction having a structure having both a catalyst cooling function and a buffer function. The apparatus 13 is characterized in that it is provided on the inlet side of the steam generator 4.

  As the catalyst reactor 13, for example, one having a structure as shown in FIG. 3 can be used. In FIG. 3, 14 is a substantially cylindrical reactor main body, both ends are closed, and connection ports 14a and 14b for connecting to the water supply path 6 are provided at the center, and a partition plate is provided inside. 14c and 14d are provided with an appropriate interval. A plurality of small-diameter tubes 15 are arranged in parallel between the partition plates 14c and 14d, and these small-diameter tubes 15 communicate with both side portions P and Q partitioned by the partition plates 14c and 14d, respectively. . A catalyst layer 16 is formed by filling the central portion R provided with a plurality of small-diameter pipes 15 with a catalyst. Further, a gas inlet 14e is formed on one side in the central region of the reactor main body 14, and a gas is formed on the other side. Each outlet 14f is provided.

  The catalyst reactor 13 having the above-described configuration is connected to the water supply path 10 near the inlet side of the steam generator 4 through the connection ports 14a and 14b. Thereby, for example, water that has flowed into the one side Q from the water supply path 10 passes through the plurality of small-diameter pipes 15 and moves into the other side P, exits from the connection port 14a, and is again supplied with the water supply path. 10 flows into the steam generator 4 and is supplied to the steam generator 4. The reformed gas enters from the gas inlet 14e, passes through the catalyst layer 16, and is discharged from the gas outlet 14f.

  The water supplied to the steam generator 4 is vaporized in a short time as described above and supplied to the reformer 1 via the steam path 6. Since it is supplied, it is supplied to the inlet side of the reformer 1 in a state where water vapor and raw fuel gas are mixed.

  When steam is generated in the steam generator 4, the pressure fluctuates, pulsation is generated in the water supply path 10 due to this pressure fluctuation, and the amount of water supplied into the steam generator 4 changes. However, since the catalytic reactor 13 is provided on the inlet side of the steam generator 4, pulsation energy can be absorbed by the buffer function of the side portion P of the catalytic reactor 13. Thereby, the change of the water supply amount which flows into the steam generator 4 can be suppressed small. Therefore, the change in the amount of steam supplied from the steam generator 4 to the reformer 1 can be kept small, and the mixing ratio S / C between the steam and the raw fuel gas can be kept substantially constant.

  Here, the catalytic reactor 13 can be operated as the CO converter 2 in the first embodiment. In this case, the catalyst layer 16 may be formed of a shift catalyst. Since the shift catalyst is an exothermic reaction as described above, it can be cooled by exchanging heat with water passing through the small diameter tube 15. That is, the central portion R of the catalyst reactor 13 has a catalyst cooling function. Further, as described above, the side portion P of the catalytic reactor 13 has a buffer function. Although the catalytic reactor 13 can be operated as the CO remover 3 in the first embodiment, it is not preferable because it is located far from the steam generator 4.

  In the second embodiment, since the catalytic reactor 13 has a function as a CO converter, the CO converter 2 in the first embodiment can be omitted by providing the catalytic reactor 13. Since the catalytic reactor 13 has a buffer function, it is not necessary to provide a tank 12 having a buffer function, and the configuration can be simplified to reduce the cost and size of the fuel reformer.

  FIG. 4 is a schematic configuration diagram showing a third embodiment of the fuel reforming apparatus according to the present invention, which is characterized in that the first throttle means 17 is provided on the inlet side of the buffer means 12 in the first embodiment. It is what has. As the first throttle means 17, for example, a throttle valve, an orifice, a capillary tube or the like can be used.

In the third embodiment, when steam is generated in the steam generator 4, the pressure fluctuates. Due to this pressure fluctuation, pulsation is generated in the water supply path 10, and the amount of water supplied into the steam generator 4 changes. However, since the buffer means 12 is provided on the inlet side of the steam generator 4, the pulsating energy can be absorbed by the buffer function of the buffer means 12, and the steam generator is used by the first throttling means 17. The disturbance of the flow on the water supply side caused by the vibration of 4 can be adjusted. Thereby, while suppressing the change of the amount of water supply which flows into the steam generator 4, it can suppress a turbulent flow. Therefore, the change in the amount of steam supplied from the steam generator 4 to the reformer 1 can be kept small, and the mixing ratio S / C between the steam and the raw fuel gas can be kept substantially constant.
In the second embodiment, the present invention can also be applied to the case where the catalyst reactor 13 is used instead of the buffer means 12.

  FIG. 5 is a schematic configuration diagram showing a fourth embodiment of the fuel reformer according to the present invention, which is characterized in that a backflow prevention means 18 is provided on the inlet side of the buffer means 12 in the first embodiment. Is. As this backflow prevention means 18, a check valve can be used, for example.

In the fourth embodiment, when steam is generated in the steam generator 4, the pressure fluctuates. Due to this pressure fluctuation, pulsation is generated in the water supply path 10, and the amount of water supplied into the steam generator 4 changes. However, since the buffer means 12 is provided on the inlet side of the steam generator 4, the pulsation energy can be absorbed by the buffer function of the buffer means 12, and the backflow preventing means 18 allows the steam generator 4 to be absorbed. The influence of the flow to the water supply side caused by vibration can be prevented. Thereby, while suppressing the change of the amount of water supply which flows into the steam generator 4, it can suppress a turbulent flow. Therefore, the change in the amount of steam supplied from the steam generator 4 to the reformer 1 can be kept small, and the mixing ratio S / C between the steam and the raw fuel gas can be kept substantially constant.
In the second embodiment, the present invention can also be applied to the case where the catalyst reactor 13 is used instead of the buffer means 12.

  FIG. 6 is a schematic configuration diagram showing a fifth embodiment of the fuel reformer according to the present invention, which is characterized in that the second throttle means 19 is provided on the outlet side of the steam generator 4 in the fourth embodiment. It is what has. As the second throttling means 19, for example, a throttling valve, an orifice, a capillary tube or the like can be used in the same manner as the first throttling means 17.

  In the fifth embodiment, when steam is generated in the steam generator 4, the pressure fluctuates, and pulsation occurs in the steam path 9 for supplying steam from the steam generator 4 to the reformer 1 due to the influence of the pressure fluctuation. Since the second throttling means 19 is provided on the outlet side of the steam generator 4 in the steam path 9, the flow of water vapor is adjusted by the second throttling means 19. Further, since the buffer means 12 is provided on the inlet side of the steam generator 4 as described above, the pulsating energy generated in the steam generator 4 can be absorbed by the buffer function of the buffer means 12, and The first throttling means 17 can adjust the turbulence of the water supply side flow caused by the vibration of the water vapor generator 4. Thereby, while suppressing the change of the feed water amount which flows into the steam generator 4, it can suppress a turbulent flow, and can suppress the change of the steam amount supplied to the reformer 1 from the steam generator 4 small. It becomes possible to keep the mixing ratio S / C of water vapor and raw fuel gas substantially constant.

  Here, when the buffer function of the buffer means 12 was tested, it is sufficient if the buffer tank has a volume of about 1 to 4 times the amount of water flowing per minute on the water supply side. It turns out that the function is obtained. For example, when the flow rate is 10 cc / min, a buffer tank having a volume of 10 cc to 40 cc may be used. Further, as a buffer structure, a sufficient buffering function was obtained by increasing the number of flow paths, such as by arranging a large number of tubes in parallel. For example, it has been found that about ten pipes having a diameter of 6.35 mm may be used instead of the cylindrical buffer tank having a diameter of 25.4 mm.

  The pressure change state in the steam generator 4 was measured. FIG. 7 shows the pressure change in the comparative example (conventional example) in which no countermeasure is taken, FIG. 8 shows the pressure change in the configuration of the third embodiment, and FIG. 9 shows the fifth change. The pressure change in the thing of the structure of an Example is shown. Compared to the pressure change in the comparative example, it is recognized that the pressure change is suppressed to be small in the configuration of the third embodiment and the configuration of the fifth embodiment. When compared with that of the fifth embodiment, it can be seen that the configuration of the fifth embodiment further suppresses the pressure change. The configuration of the fifth embodiment can reduce the pressure fluctuation by about 20%.

  The fuel reforming apparatus according to the present invention can be applied particularly as a fuel reforming apparatus used by being incorporated in a fuel cell power generation system, and can suppress a change in the amount of feed water flowing into the steam generator, A change in the amount of steam supplied from the steam generator to the reformer can be kept small. As a result, the mixing ratio S / C between the water vapor and the raw fuel gas can be kept substantially constant, a stable reformed gas can be supplied to the fuel cell, and the power generation performance of the fuel cell can be improved.

1 is a schematic configuration diagram showing a first embodiment of a fuel reformer according to the present invention. It is a schematic block diagram which shows 2nd Example of the fuel reformer which concerns on this invention. It is a schematic perspective view which shows the catalyst reactor in 2nd Example of the fuel reformer which concerns on this invention. It is a schematic block diagram which shows 3rd Example of the fuel reformer which concerns on this invention. It is a schematic block diagram which shows 4th Example of the fuel reformer which concerns on this invention. It is a schematic block diagram which shows 5th Example of the fuel reformer which concerns on this invention. It is a graph which shows the pressure change of the steam generator in a prior art example. It is a graph which shows the pressure change of the steam generator in 3rd Example of the fuel reformer which concerns on this invention. It is a graph which shows the pressure change of the steam generator in 5th Example of the fuel reformer which concerns on this invention. It is a schematic block diagram which shows the conventional fuel reformer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reformer 2 CO converter 3 CO remover 4 Steam generator 5 Fuel cell 6 Water supply path 7 Throttle means 8 Burner 9 Steam path 10 Water supply path 11 Heat exchanger 12 Buffer means 13 Catalyst reactor 14 Reactor body 15 Small diameter Tube 16 Catalyst layer 17 First restricting means 18 Backflow preventing means 19 Second restricting means

Claims (7)

  A reformer for steam reforming the raw fuel gas, a CO converter for modifying the reformed gas emitted from the reformer, and a CO remover for selectively oxidizing the reformed gas emitted from the CO converter In the fuel reformer provided, a steam generator that superheats water supplied from the water supply path is provided on the inlet side of the reformer, and the water supply path located on the inlet side of the steam generator A fuel reformer comprising buffer means for suppressing pulsation generated when water evaporates.   2. The fuel reformer according to claim 1, wherein a throttle means is provided on an inlet side of the buffer means in the water supply path.   The fuel reformer according to claim 1 or 2, wherein the buffer means is a catalyst reaction vessel having a catalyst cooling function and a buffer function.   The fuel reformer according to claim 1 or 3, wherein a backflow prevention means is provided on an inlet side of the buffer means in the water supply path.   3. The fuel reformer according to claim 2, wherein a throttle means is provided in a steam path for supplying water vapor from the steam generator to the reformer.   6. The fuel reformer according to claim 1, wherein the buffer means has a volume of 1 to 4 times the amount of water flowing in the water supply path per minute.   The fuel reformer according to any one of claims 1 to 6, wherein the buffer means has a structure in which a large number of tubes are arranged in parallel.

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