JP4878466B2 - Fuel reformer for fuel cell - Google Patents

Description

  The present invention relates to a fuel reformer for a fuel cell.

  As is well known, a fuel cell is one of power generation devices, and generates power by supplying hydrogen as fuel and oxygen (or air) and causing an electrochemical reaction through an electrolyte. Hydrogen used as fuel is sometimes supplied directly from a hydrogen cylinder to a fuel cell, but carbon-based raw fuel such as natural gas is reformed into a reformed gas mainly composed of hydrogen by a fuel reformer, In many cases, this reformed gas is supplied to the fuel cell.

The fuel reformer usually includes a desulfurizer, a reformer, a CO converter, and a CO remover. After the carbon-based raw fuel gas is sent to the desulfurizer and desulfurized, the reformer performs steam reforming. The reformed gas is mainly composed of hydrogen. Since this reformed gas contains high-concentration CO, it is converted to CO ₂ by a CO converter, and then selectively oxidized by a CO remover to produce a CO concentration. The process of decreasing is performed. If the reformed gas contains high-concentration CO, the catalyst in the electrode part of the fuel cell is poisoned, and the cell performance is degraded, so the CO concentration needs to be reduced.

In a household combined heat and power system incorporating a fuel cell, for example, a stationary case incorporating a fuel cell and a fuel reformer and a hot water storage tank separate from the stationary case are prepared. The stationary case is preferably small because of the installation space, and the fuel reformer incorporated in the case is required to be small and compact. For this reason, a fuel reformer in which a reformer, a CO converter, and a CO remover are integrated in a multi-cylindrical structure is conventionally known (for example, Patent Document 1).
JP 2005-15292 A

  In the conventional fuel reformer, a reformer is disposed inside a cylindrical heat insulating container, and a burner is disposed at the bottom of the cylindrical heat insulating container, and the burner is burned to generate a flame in an upward direction. The reforming catalyst generated and heated in the reformer is heated. Since the reforming catalyst usually reacts in a temperature range of 700 ° C. to 750 ° C., it is necessary to burn the burner at the time of start-up and to raise the temperature, and for the endothermic reaction, the burner must continue to burn during operation and be heated. In this case, the flame of the burner is located inside the cylindrical heat insulating container, but the case incorporating the burner is located outside the cylindrical heat insulating container. For this reason, the heat dissipation from the burner case escapes to the outside, and there is a problem that the heat efficiency is lowered because the heat cannot be effectively used.

  The present invention is made to solve such problems in the prior art, and provides a fuel reformer for a fuel cell in which heat efficiency is improved by effectively using heat radiation from a combustion device including a burner. With the goal.

As a means for achieving the above object, a fuel reformer for a fuel cell according to claim 1 includes a reformer for steam reforming a carbon-based raw fuel gas, and a reformer reformed by the reformer. A CO converter that converts CO into gas is integrated into a multi-cylindrical unit to form a unit, and a space part that is partitioned into a central space region and an outer peripheral space region by a housing is provided at the top of the unit. A fuel reformer for a fuel cell having a structure in which a combustion device including a burner at a lower portion is built in and built in the unit,
A first heat exchanger for generating water vapor from water by exchanging heat with the combustion gas generated in the combustion device is disposed in the outer peripheral space region, and is reformed by the reformer in the central space region. A second heat connected to the first heat exchanger for exchanging the reformed gas and flowing in, and exchanging heat between the reformed gas and the steam generated in the first heat exchanger. Arranging an exchanger , mixing water vapor generated through the first heat exchanger and the second heat exchanger and the carbon-based raw fuel gas, and supplying the mixed gas to the reformer;
The reformed gas is flown into the CO converter for CO conversion.

  The fuel reformer for a fuel cell according to claim 2 is the fuel reformer for a fuel cell according to claim 1, wherein the combustion device including the burner is disposed inside the CO converter via a heat insulating material. It is characterized by that.

According to the first aspect of the present invention, the reformer for steam reforming the carbon-based raw fuel gas and the CO converter for converting CO to the reformed gas reformed by the reformer are formed in a multi-cylinder shape. The unit is formed as a unit, and a space part partitioned into a central space region and an outer peripheral space region by a housing is provided in the upper part of the unit, and a combustion device including a burner is incorporated in the unit at the lower part of the unit. A fuel reformer for a fuel cell having a built-in structure,
A first heat exchanger for generating water vapor from water by exchanging heat with the combustion gas generated in the combustion device is disposed in the outer peripheral space region, and is reformed by the reformer in the central space region. A second heat connected to the first heat exchanger for exchanging the reformed gas and flowing in, and exchanging heat between the reformed gas and the steam generated in the first heat exchanger. Arranging an exchanger , mixing water vapor generated through the first heat exchanger and the second heat exchanger and the carbon-based raw fuel gas, and supplying the mixed gas to the reformer;
Since this reformed gas has a structure that flows into the CO converter that converts CO, the heat released from the combustion device can be used effectively without being dissipated to the outside, and the reformer has been reformed by the reformer. The sensible heat of the reformed gas can also be used effectively, thereby producing a remarkable effect that the thermal efficiency can be improved.

  According to the second aspect of the invention, since the combustion device including the burner is disposed inside the CO transformer via the heat insulating material, the heat radiation from the combustion device is reduced by the temperature difference between the inside and the outside of the heat insulating material. Heat transfer to the transformer side is possible. Thereby, at the time of start-up, the CO converter can be heated by heat radiation from the combustion device, and the temperature of the CO converter catalyst can be raised to the reaction temperature region, thereby shortening the operation start time.

  Next, an embodiment of a fuel reformer for a fuel cell according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic longitudinal sectional view showing an embodiment of a fuel reformer for a fuel cell according to the present invention. In FIG. 1, reference numeral 1 denotes a unit in which a reformer 2 and a CO converter 3 are integrated into a multi-cylinder shape, and a combustion device 4 including a burner is incorporated.

  The reformer 2 is disposed at the center of the unit 1, and a fixed amount of the reforming catalyst A is filled between the inner cylinder 2a and the outer cylinder 2b. As the reforming catalyst A, for example, a nickel catalyst can be used. A bottom plate 2c such as a mesh plate is attached to the bottom of the catalyst storage portion filled with the reforming catalyst A to prevent the reforming catalyst A from falling. A partition plate 2d is attached to the upper end portion of the inner cylinder 2a in the reformer 2, and an introduction port 5 for raw fuel gas is formed by attaching a cover plate 2e having a small hole above the partition plate 2d. Yes. A top plate 2f is attached to the upper end portion of the outer cylinder 2b. A raw fuel gas supply pipe 6 is attached through the top plate 2f and the cover plate 2e, and its lower end portion opens into the introduction port 5. is doing.

  The combustion device 4 is disposed below the reformer 2, and a combustion cylinder 4 a erected on the upper side of the reformer 2 enters the internal space of the reformer 2. A combustion gas passage 7 is provided on the outer periphery of the reformer 2. The combustion gas passage 7 includes an inner cylinder 7a and an outer cylinder 7b. A bottom plate 7c is attached to the bottom of the outer cylinder 7b, and a bottom plate 7d having a round hole in the center is formed at the bottom of the inner cylinder 7a. It is attached. The combustion cylinder 4a passes through the bottom plate 7c and protrudes into the internal space of the reformer 2 through a round hole in the bottom plate 7d. The bottom edge of the inner cylinder 2a of the reformer 2 is attached to the edge of the round hole with respect to the bottom plate 7d. Further, a reformed gas first passage 8 is formed with a gap between the inner cylinder 7 b of the combustion gas passage 7 and the outer cylinder 2 b of the reformer 2.

  A cylindrical partition wall 9 is provided on the outer periphery of the combustion gas passage 7, and a heat insulating material 10 is interposed between the cylindrical partition wall 9 and the outer cylinder 7 b of the combustion gas passage 7. The heat insulating material 10 covers the entire outer peripheral portion of the combustion device 4 except the bottom portion of the case 4b and the vicinity of the lower end portion of the combustion cylinder 4a. Note that the bottom of the case 4b is preferably covered with the heat insulating material 10. As the heat insulating material 10, what consists of a high functional heat insulating material (WDS) by Wacker Chemie company can be used, for example.

  The CO transformer 3 is disposed on the outer peripheral portion of the cylindrical partition wall 9. The CO converter 3 includes an inner cylinder 3a and an outer cylinder 3b, and a predetermined amount of CO conversion catalyst B is filled between them. As the reforming catalyst B, for example, an iron-based catalyst or a copper-based catalyst can be used. A bottom plate 3c such as a mesh plate is attached to the bottom of the catalyst storage portion filled with the CO conversion catalyst B to prevent the CO conversion catalyst B from falling. A reformed gas second passage 11 is formed with a gap between the inner cylinder 3a of the CO transformer 3 and the cylindrical partition wall 9. The outer peripheral portion of the CO transformer 3 is generally covered with a heat insulating material (not shown).

  A space 1a is provided in the upper part of the unit 1 by a housing, and a heat exchanger 12 is disposed in the space 1a. A water supply pipe 13 is provided at the start end of the pipe line in the heat exchanger 12. At the same time, the end of the pipe is connected to the raw fuel gas supply pipe 6. Further, a connecting pipe 12 a is attached to an intermediate portion of the pipe line in the heat exchanger 12.

  A connecting pipe 14 that connects the space portion 1a of the unit 1 and the catalyst storage portion of the CO converter 3 is fixed at one end to the space portion 1a side and fixed at the other end through the flange portion of the unit 1. It is attached. As a result, the reformed gas flowing from the reformed gas first passage 8 into the space 1 a of the unit 1 flows into the catalyst storage section of the CO converter 3 through the connecting pipe 14. A reformed gas discharge pipe 15 is fixed to the flange portion of the unit 1, and a lower end portion thereof communicates with the upper merge space of the reformed gas second passage 11. Thereby, the reformed gas passing through the reformed gas second passage 11 can be discharged from the reformed gas discharge pipe 15 to the outside. A punching metal plate 3d is attached to the upper end of the CO transformer 3.

  The space portion 1a of the unit 1 is partitioned into a central space region and an outer peripheral space region by a cylindrical partition wall 1b, and an upper end portion of the combustion gas passage 7 communicates with the outer peripheral space region in the space portion 1a. A combustion exhaust gas pipe 16 is attached to the upper end portion of the outer peripheral space region of the space portion 1a. A part of the pipe line of the heat exchanger 12 is located in the outer peripheral space region of the space 1a, and in this outer peripheral space region, between the water supplied from the water supply pipe 13 and the high-temperature combustion exhaust gas. Then, heat is exchanged, water becomes steam and enters the raw fuel gas supply pipe 6, and the combustion exhaust gas is cooled and exhausted from the combustion exhaust gas pipe 16 to the outside.

  Near the upper end of the unit 1, a flange 1d is attached to the housing forming the space 1a, and a corresponding flange 9a is attached to the upper end of the cylindrical partition wall 9, and these flanges sandwich a sealing material. And fixed by welding or bolts. At the lower end of the unit 1, a flange 9b is attached to the lower end of the cylindrical partition wall 9, and a sealing material is sandwiched between the flange 9b and the bottom plate 1e of the unit and fixed by welding or bolts. The combustion apparatus 4 is connected to a fuel pipe 4c, an offgas pipe 4d, and a combustion air pipe 4e. In this embodiment, the CO remover is not incorporated in the unit 1 and is formed separately from the unit 1.

  The fuel cell fuel reformer according to the present embodiment configured as described above supplies carbon-based raw fuel gas from the fuel pipe 4c at the time of start-up, and sends air from the combustion air pipe 4e to burner ( Ignite (not shown). When the burner burns, a flame rises inside the combustion cylinder 4a, the combustion gas flows into the internal space of the reformer 2 and heats the reformer 2 from the inside, and the combustion gas flows into the combustion cylinder 4a. While descending between the cylinder 2 a and flowing into the combustion gas passage 7, the combustion gas passage 7 is elevated and flows into the outer peripheral space region of the space portion 1 a of the unit 1. And combustion gas is exhausted outside from the said combustion exhaust gas pipe 16 attached to the outer peripheral space area | region of the space part 1a. Thereby, the temperature of the reforming catalyst A of the reformer 2 is increased by the combustion heat of the burner, and heating is continued until, for example, about 700 ° C.

In the present embodiment, since the outer peripheral portion of the combustion device 4 is covered with the heat insulating material 10 as described above, the heat radiation from the case 4b in the combustion device 4 does not escape to the outside. In the lower layer of the heat insulating material 10, the temperature inside the combustion device 4 facing the case 4b side is high, and the temperature outside the gas facing the CO transformer 3 side is low. Due to this temperature difference, heat radiation from the case 4b is transferred from the case 4b side to the CO transformer 3 side through the heat insulating material 10. Further, in the middle layer and the upper layer of the heat insulating material 10, since the high-temperature combustion gas moves upward in the combustion gas passage 7, the inner temperature facing the combustion gas passage 7 side is high, and the CO transformer 3 side is high. The opposing outside temperature is low. Due to this temperature difference, the heat radiation from the combustion gas passage 7 side is transferred to the CO transformer 3 side through the heat insulating material 10. As a result, the temperature of the CO shift catalyst B of the CO shift converter 3 is increased, and heating is continued until, for example, 250 ° C. to 300 ° C. In this way, the heat radiation from the combustion device 4 can be effectively used as a heat source for heating the CO transformer 3. At the time of start-up, the CO starter 3 is heated by heat radiation from the combustion device 4 and the temperature of the CO shift catalyst B is raised to the reaction temperature range, so that the operation start time can be shortened.

  When the reforming catalyst A of the reformer 2 and the CO conversion catalyst of the CO converter 3 are heated to a predetermined temperature, the carbon-based raw fuel gas desulfurized through a desulfurizer (not shown) is supplied from the raw fuel gas supply pipe 6. In addition, water is supplied from the water supply pipe 13. The water supplied from the water supply pipe 13 undergoes heat exchange with the combustion gas in the outer peripheral space region of the space portion 1a of the unit 1 while passing through the pipe line of the heat exchanger 12, and is steam. To change. The water vapor travels through the pipe line of the heat exchanger 12 and flows into the raw fuel gas supply pipe 6 from the terminal end of the pipe line. Thereby, in the raw fuel gas supply pipe 6, the raw fuel gas and water vapor are mixed and supplied to the raw fuel gas inlet 5.

  The mixed gas of the raw fuel gas and water vapor supplied to the raw fuel gas inlet 5 moves upward through the small hole of the cover plate 2e. At this time, the mixed gas is diffused due to a pressure loss. The diffused mixed gas is reflected by the top plate 2 f of the reformer 2, flows into the catalyst storage portion of the reformer 2, and flows down in the reforming catalyst A. As a result, the mixed gas is steam reformed by the reforming catalyst A and reformed into a reformed gas mainly composed of hydrogen.

The reformed gas that has come out from under the catalyst storage part rises in the reformed gas first passage 8 and rises in the housing forming the space part 1a of the unit 1 in the junction pipe 1c provided. Merge and flow into the central space region in the space 1 a of the unit 1. Furthermore, it flows into the catalyst storage part of the CO converter 3 through the connecting pipe 14. While the reformed gas that has flowed into the catalyst storage section of the CO converter 3 flows down through the CO converter catalyst B, CO contained in the reformed gas is converted into CO ₂ by a shift reaction.

  The reformed gas that has come out from under the catalyst storage section of the CO converter 3 moves up the reformed gas second passage 11 and flows into the upper space of the CO converter 3, and from the reformed gas discharge pipe 15. It is discharged outside. Since the reformed gas discharged to the outside still has a considerably high CO concentration, it is introduced into a CO remover (not shown) and selectively oxidized to reduce the CO concentration to about 10 ppm or less. The reformed gas discharged from the CO remover is supplied to the fuel electrode of the stack in the fuel cell (not shown). In this case, since the CO remover is not incorporated in the unit 1, the catalyst exchange of the CO remover can be easily performed.

  In a fuel cell, power is generated by an electrochemical reaction that occurs via an electrolyte between hydrogen gas in the reformed gas supplied to the fuel electrode and oxygen gas in the air supplied to the air electrode, for example. . The off-gas that has not reacted at the fuel electrode during the power generation is supplied to the fuel device 4 through the off-gas pipe 4d and used as a combustion gas for the burner. Since the steam reforming in the reformer 2 is an endothermic reaction, it is necessary to burn the burner and maintain the reforming catalyst A at the reaction temperature even during power generation. At the time of startup, since no offgas is generated, the raw fuel gas is supplied from the fuel pipe 4c and the burner is burned. However, it is possible to switch to offgas supply during power generation.

  The present invention can be used for a fuel reformer for a fuel cell having a multi-cylinder shape, and a combustion apparatus disposed below the reformer is disposed inside a CO converter 3 via a heat insulating material 10. However, by incorporating it in the unit, it is possible to effectively use the heat radiation from the combustion device that has been wasted in the past. In particular, the heat radiation from the combustion device can be used as a heat source for heating the CO transformer during startup.

1 is a schematic longitudinal sectional view showing an embodiment of a fuel reformer for a fuel cell according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Unit 1a Space part 2 Reformer 3 CO converter 4 Combustion device 4a Combustion cylinder 4b Case 5 Inlet 6 Raw fuel gas supply pipe 7 Combustion gas passage 8 Reformed gas first passage 9 Cylindrical partition wall 10 Heat insulation material 11 Reformation Gas second passage 12 Heat exchanger 13 Water supply pipe 14 Connection pipe 15 Reformed gas discharge pipe 16 Combustion exhaust gas pipe
A reforming catalyst
B CO conversion catalyst

Claims (2)

A unit is formed by integrating a reformer for steam reforming a carbon-based raw fuel gas and a CO converter for CO reforming of the reformed gas reformed by the reformer into a multi-cylinder shape, A fuel cell having a structure in which a space part partitioned into a central space region and an outer peripheral space region by a housing is provided at an upper part of the unit, and a combustion device including a burner is incorporated in the unit and incorporated in the lower part of the unit A fuel reformer,
A first heat exchanger for generating water vapor from water by exchanging heat with the combustion gas generated in the combustion device is disposed in the outer peripheral space region, and is reformed by the reformer in the central space region. A second heat connected to the first heat exchanger for exchanging the reformed gas and flowing in, and exchanging heat between the reformed gas and the steam generated in the first heat exchanger. Arranging an exchanger , mixing water vapor generated through the first heat exchanger and the second heat exchanger and the carbon-based raw fuel gas, and supplying the mixed gas to the reformer;
A fuel reformer for a fuel cell, wherein the reformed gas reformed by the reformer flows into the CO converter for CO conversion.   2. The fuel reformer for a fuel cell according to claim 1, wherein the combustion apparatus including the burner is disposed inside the CO converter via a heat insulating material. 3.

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