METHOD FOR MANUFACTURING HYDROGEN GENERATOR

Abstract

A method for manufacturing a hydrogen generator of the present invention is a method for manufacturing a hydrogen generator including: a water evaporator which has an inner tube, an outer tube, and a spacer disposed between the inner tube and the outer tube and in which a passage defined by the spacer is supplied with water and a raw material and heated to generate a material gas containing steam; and a reformer which has catalyst and in which the catalyst is heated to generate the material gas containing the steam from the material gas containing the steam, and the method includes: a disposing step (S2) of disposing the spacer between the inner tube and the outer tube; and a tube expanding step (S3) of expanding the inner tube to form the passage defined by the spacer.

Description

TECHNICAL FIELD

The present invention relates to a method for manufacturing a hydrogen generator, and particularly to a method for manufacturing a hydrogen generator including an inner tube, an outer tube, and a spacer disposed between the inner tube and the outer tube.

BACKGROUND ART

Generally used as a hydrogen generator for a fuel cell electric power generator is a hydrogen generator which reforms a raw material, i.e., a hydrocarbon compound, such as a natural gas, LPG gasoline, naphtha, kerosene, or methanol, using steam to generate a reformed gas mainly containing hydrogen.

The hydrogen generator is configured to include: a water evaporator which evaporates water; and a reformer which causes water evaporation and the material gas to react with each other at a high temperature of about 600 to 800° C. to generate the reformed gas.

Generally, the hydrogen generator includes: a water evaporator which has an inner tube, an outer tube, and a spacer disposed between the inner tube and the outer tube and in which a passage defined by the spacer is supplied with the water and the raw material and heated to generate a material gas containing steam; and a reformer which has catalyst and in which the catalyst is heated to generate a reformed gas containing hydrogen from the material gas containing the steam.

In Patent Document 1, Embodiment 2 and FIG. 1 disclose a water evaporator in which a passage of water or steam is constituted by a spacer. A time for which the water remains in the water evaporator increases depending on the configuration of the passage. In a case where the passage is formed in a spiral shape, a circumferential distribution of the water remaining is uniformized. Therefore, since the amount of heat transferred from a combustion gas to the water increases, it is possible to increase the amount of steam subjected to a steam-reforming reaction. That is, it is possible to increase a conversion ratio of the raw material and the amount of hydrogen in the reformed gas.

Patent Document 1: Japanese Laid-Open Patent Application Publication No. 2003-252604

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

The spacer disposed between the outer tube and the inner tube functions more effectively by causing the spacer to be joined to both the inner tube and the outer tube. To be specific, if a gap is formed between the spacer and the inner tube or between the spacer and the outer tube, the water leaks from the passage, and thereby the time for which the water remains in the water evaporator decreases. In addition, in a case where the passage is formed in a spiral shape, a circumferential temperature distribution becomes nonuniform, and thereby the increase in the amount of steam is suppressed.

Another method may be such that one tube, to which the spacer is joined, is pressed into the other tube. However, it is difficult to completely close a gap between the outer tube and a passage defining member and a gap between the inner tube and the passage defining member.

Moreover, since a space between two tubes, i.e., the inner tube and the outer tube is narrow, it is difficult to carry out an operation of causing the spacer to be air-tightly joined to walls of the tubes by joining means, such as welding or brazing. Moreover, even if the difficulty of this operation is overcome, the inner tube or the outer tube deforms by heat affect since the joining means, such as the brazing and the welding, needs to heat a joining portion. This reduces manufacturing accuracy of the hydrogen generator. Moreover, since the welding and the brazing require costs and labor, there is room for improvement in light of mass productivity.

The present invention was made to solve the above problems, and an object of the present invention is to provide a method for manufacturing a hydrogen generator which excels in mass productivity.

Means for Solving the Problems

In order to solve the above problems, a first method for manufacturing a hydrogen generator of the present invention is a method for manufacturing a hydrogen generator including: a water evaporator which has an inner tube, an outer tube, and a spacer disposed between the inner tube and the outer tube and in which a passage defined by the spacer is supplied with water and a raw material and heated to generate a material gas containing steam; and a reformer which has catalyst and in which the catalyst is heated to generate a reformed gas containing hydrogen from the material gas containing the steam, and the method includes: a disposing step of disposing the spacer between the inner tube and the outer tube; and a tube expanding step of expanding the inner tube to form the passage defined by the spacer. With this configuration, it is possible to improve mass productivity of the method for manufacturing the hydrogen generator.

In a second method for manufacturing a hydrogen generator of the present invention, the spacer may be a rod member having a spiral shape, and the passage having a spiral shape may be formed between the inner tube and the outer tube. With this configuration, it is possible to suppress nonuniformity of the temperature of the water evaporator in a circumferential direction.

In a third method for manufacturing a hydrogen generator of the present invention, the rod member may be a rod having a circular cross section or an oval cross section. With this configuration, it is possible to suppress damages of the outer tube and the inner tube.

In a fourth method for manufacturing a hydrogen generator of the present invention, a cross-sectional area of the passage, defined by the spacer, may be larger on a downstream side than on an upstream side. With this configuration, it is possible to ease the affect of pressure variation caused due to the water evaporation.

In a fifth method for manufacturing a hydrogen generator of the present invention, the disposing step may include: a first step of temporarily disposing the spacer on an inner peripheral surface of the outer tube; and a second step of disposing the inner tube on an inner peripheral side of the spacer after the first step. With this configuration, it is possible to more easily carry out the third step, and to suppress the occurrence of the damage in the third step.

In a sixth method for manufacturing a hydrogen generator of the present invention, the disposing step may include: a first step of temporarily disposing the spacer on an outer peripheral surface of the inner tube; and a second step of disposing the outer tube on an outer peripheral side of the spacer after the first step. With this configuration, it is possible to easily carry out the first step S1.

In a seventh method for manufacturing a hydrogen generator of the present invention, a material of the inner tube may have a higher stretching property than a material of the outer tube. With this configuration, in the third step S3, the rod member can be strongly joined between the outer tube and the inner tube.

EFFECTS OF THE INVENTION

As above, the method for manufacturing the hydrogen generator according to the present invention has an effect of being capable of improving mass productivity of the method for manufacturing the hydrogen generator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view schematically showing the configuration of a hydrogen generator of Embodiment of the present invention.

FIG. 2 is a flow chart showing a step of manufacturing a first evaporation chamber.

FIG. 3 is a cross-sectional view schematically showing a first step.

FIG. 4 is a cross-sectional view schematically showing a second step.

FIG. 5 is a cross-sectional view schematically showing a third step.

FIG. 6 is a cross-sectional view schematically showing Modification Example 1 of the third step, and shows a state before tube expansion.

FIG. 7 is a diagram showing a state after the tube expansion of FIG. 6.

FIG. 8 is a cross-sectional view schematically showing the first step of Modification Example 2.

FIG. 9 is a cross-sectional view schematically showing the second step of Modification Example 2.

FIG. 10 is a cross-sectional view schematically showing the third step of Modification Example 2.

EXPLANATION OF REFERENCE NUMBERS

• • 1 reformer
  • 2 water evaporator
  • 4 cover
  • 10 reforming chamber
  • 11 reforming gas passage
  • 12 combustion gas passage
  • 12A first portion
  • 12B second portion
  • 12C third portion
  • 12D fourth portion
  • 13 heat insulating member
  • 15 combustion gas outlet port
  • 16 burner
  • 17 combustion chamber
  • 18 first evaporation chamber
  • 19 raw material inlet port
  • 20 water inlet port
  • 22 second evaporation chamber
  • 26 communication passage
  • 27 reformed gas outlet port
  • 29 bottom wall
  • 30 passage
  • 31 rod member
  • 50 inner peripheral tube
  • 51 first separating tube
  • 52 second separating tube
  • 53 third separating tube
  • 54 outer peripheral tube
  • 61 radiating tube
  • 100 hydrogen generator
  • 101 fuel cell
  • 103 base

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the best mode for carrying out the present invention will be explained in reference to the drawings.

Embodiment

FIG. 1 is a cross-sectional view schematically showing the configuration of a hydrogen generator of Embodiment of the present invention. As shown in FIG. 1, a hydrogen generator 100 of the present embodiment is configured to include: a reformer 1 which is columnar; a water evaporator 2 which is cylindrical and disposed on an outer peripheral side of the reformer 1; a heat insulating wall 13 which is cylindrical and disposed between the reformer 1 and the water evaporator 2; and a cover 4 which covers the reformer 1 and the water evaporator 2 from above. The reformer 1 and the water evaporator 2 are configured to share a bottom wall 29.

The reformer 1 is configured such that a burner 16 which generates a combustion gas is disposed at a center of the bottom wall 29, and a lidded cylindrical reforming chamber 10 is disposed to cover the burner 16.

The reforming chamber 10 is disposed coaxially with the burner 16. A combustion chamber 17 is formed to be defined by a lower surface of a lid portion of the reforming chamber 10, an inner peripheral surface of the reforming chamber 10, and a bottom surface having the burner 16. In the combustion chamber 17, a radiating body 61 which is cylindrical and disposed coaxially with the burner 16. A first portion 12A of a combustion gas passage 12 is formed in a tubular space formed between the radiating body 61 and an inner peripheral surface of the reforming chamber 10. With this configuration, the combustion heat generated in the combustion chamber 17 can be efficiently radiated to the reforming chamber 10. Moreover, potential heat of the combustion gas flowing out from the combustion chamber 17 can be efficiently transferred to the reforming chamber 10.

The reforming chamber 10 stores a catalyst layer which is filled with a steam reforming catalyst. A communication passage 26 extending from an upper portion of the water evaporator 2 is connected to a center of the lid portion of the reforming chamber 10. With this configuration, the material gas containing steam supplied from the water evaporator 2 via the communication passage 26 is guided to an upper portion in the reforming chamber 10, and flows downward inside the reforming chamber 10. Then, the material gas containing the steam causes the steam-reforming reaction in the reforming chamber 10 by the catalysis caused by the heat applied from the combustion chamber. Thus, a reformed gas containing hydrogen is generated.

A reforming gas passage 11 is formed on an outer peripheral surface of the reforming chamber 10. The reforming gas passage 11 is formed to extend from a lower end of the reforming chamber 10 along the outer peripheral surface of the reforming chamber 10 up to an upper end of the reforming chamber 10 and further extend up to a reformed gas outlet port 27. With this configuration, the reformed gas generated in the reforming chamber 10 flows from the lower end of the reforming chamber 10 via the reforming gas passage 11 and is discharged from the reformed gas outlet port 27 to an outside of the hydrogen generator 100.

A second portion 12B of the combustion gas passage 12 is formed to extend from a region below the reforming chamber 10 to a region on an outer peripheral side of the reforming chamber 10 and a region above of the reforming chamber 10. The second portion 12B of the combustion gas passage is formed to extend from a gap between the bottom wall 29 having the burner 16 and a bottom surface of the reforming chamber 10, along an outer periphery of the reforming gas passage 11 up to the upper end of the reforming chamber 10 and further extend from a region above the heat insulating wall 13 to the water evaporator 2 disposed on an outer side of the heat insulating wall 13. With this configuration, the combustion gas suppresses temperature reduction of the reformed gas in the reforming gas passage 11, and is utilized as a heat source of the water evaporator 2. After the combustion gas flows through the water evaporator 2, it enters into the cover 4 disposed above the reformer 1 and the water evaporator 2, and is discharged from a combustion gas outlet port 15, formed on the cover 4, to an outside of the hydrogen generator 100.

The water evaporator 2 is configured such that a raw material inlet port 19 and a water inlet port 20 is formed at an upper portion of an outer circumference thereof, and the second portion 12B of the combustion gas passage is connected to an upper portion of an inner circumference thereof.

The water evaporator 2 has a multiple tube structure including a first separating tube 51, a second separating tube 52, and a third separating tube 53 between an outer peripheral tube 54 and an inner peripheral tube 50.

The outer peripheral tube 54 forms an outer peripheral surface of the hydrogen generator 100. The bottom wall 29 constituting a bottom portion of the hydrogen generator 100 is formed at a lower end of the outer peripheral tube 54. The cover 4 constituting a lid portion of the hydrogen generator 100 is formed at an upper end of the outer peripheral tube 54. The raw material inlet port 19 and the water inlet port 20 are formed at an upper portion of the outer peripheral tube 54.

The inner peripheral tube 50 is formed along an outer periphery of the heat insulating wall 13. An entire periphery of a lower end of the inner peripheral tube 50 is jointed to an edge portion of the bottom plate 29, and an upper end of the inner peripheral tube 50 extends up to a vicinity of an upper end of the heat insulating wall 13. The inner peripheral tube 50 may be omitted in a case where the heat insulating wall 13 is made of a material having airtightness.

The first separating tube 51 is disposed on an outer peripheral side of the inner peripheral tube 50, and a third portion 12C of the combustion gas passage is formed between the inner peripheral tube 50 and the first separating tube 51. An upper end of the first separating tube 51 extends to an inner peripheral side, and its entire periphery is joined to an upper end of the reforming chamber 10. At least a part of a lower end of the first separating tube 51 is spaced apart from the bottom wall 29. With this configuration, the second portion 12B of the combustion gas passage 12 extending up to an upper end of the reforming chamber 10 is connected to the third portion 12C of the combustion gas passage at a location above the heat insulating wall 13. To be specific, the combustion gas flows from an upper side to a lower side inside the third portion 12C of the combustion gas passage, and flows out from the lower end of the first separating tube 51 to an outer peripheral side of the first separating tube 51.

The second separating tube 52 is disposed on an outer peripheral side of the first separating tube 51, and a fourth portion 12D of the combustion gas passage is formed between the first separating tube 51 and the second separating tube 52. An upper end of the fourth portion 12D of the combustion gas passage is open. An upper end of the second separating tube 52 extends to an outer peripheral side, and its entire periphery is joined to the outer peripheral tube 54. An entire periphery of a lower end of the second separating tube 52 is joined to the bottom wall 29. With this configuration, the combustion gas passage 12 extending up to the lower end of the first separating tube 51 is connected to the third portion 12C of the combustion gas passage. To be specific, the combustion gas flowing out from the lower end of the first separating tube 51 flows from a lower side to an upper side inside a second combustion gas chamber 61, and flows out from the upper end of the second separating tube 52 to a space in the cover 4.

The third separating tube 53 is disposed between the outer peripheral tube 54 and the second separating tube 52. A first evaporation chamber 18 is formed between the third separating tube 53 and the outer peripheral tube 54. A second evaporation chamber 22 is formed between the second separating tube 52 and the third separating tube 53. Upper ends of the first water evaporation chamber 18 and the second water evaporation chamber 22 are sealed. The upper end of the second separating tube 52 extends to an outer peripheral side, and its entire periphery is joined to the outer peripheral tube 54. The entire periphery of a lower end of the second separating tube 52 is joined to the bottom wall 29. Moreover, an entire upper end of the third separating tube 53 extends to an outer peripheral side, and is joined to the outer peripheral tube 54. At least a part of a lower end of the third separating tube 53 is spaced apart from the bottom wall 29. With this configuration, a material gas passage is formed, through which fluids supplied from the raw material inlet port 19 and the water inlet port 20 flow downward inside the first evaporation chamber 18, and flows from the lower end of the third separating tube 53 to a lower end of the second evaporation chamber 22.

The communication passage 26 is formed on an upper portion of the second evaporation chamber 22 so as to extend and be joined to the center of the lid portion of the reforming chamber 10. The communication passage 26 is constituted by a duct-like member or a tubular member. With this configuration, the material gas flows upward from the lower end of the second evaporation chamber 22, and flows from the communication passage 26 to an upper portion of the reforming chamber 10.

The second separating tube 52 serves as a separating wall between the second evaporation chamber 22 and the fourth portion 12D of the combustion gas passage, and excess heat of the combustion gas is transferred to the first evaporation chamber 18 and the second evaporation chamber 22.

Here, a rod member (spacer) 31 is disposed in the first evaporation chamber 18 so as to be joined to both the outer peripheral tube 54 and the third separating tube 53. By disposing the rod member 31, a passage 30 of the raw material and the water is formed inside the first evaporation chamber 18. Moreover, by forming the passage 30, it is possible to extend the time for which the raw material and the water stay in the first evaporation chamber 18. Therefore, the amount of heat transferred from the combustion gas to the raw material and the water increases, and thereby it is possible to evaporate the water more efficiently.

The rod member 31 is a rod member having a spiral shape. Therefore, the passage 30 of the raw material and water in the first evaporation chamber 18 is configured in a spiral shape. With this configuration, nonuniformity of a circumferential distribution of the remaining raw material and water is suppressed.

Moreover, a cross-sectional area of the passage 30 is larger on a downstream side than on an upstream side. In a downstream portion of the passage 30, the water is converted into the steam, and its volume expands, thereby increasing the pressure loss of the passage. In a case where the pressure loss of the passage increases, an output of a water supplying unit which supplies water is affected, and the supply amount of water becomes unstable, thereby varying the amount of hydrogen generated in the reformer. Or, there is a possibility that in a case where the supply amount of water decreases as the pressure loss of the passage increases, the steam reforming cannot be adequately carried out in the reformer, so that carbon in the raw material is deposited to cause clogging of the passage. As a result, the operation cannot be continued.

Therefore, by making the cross-sectional area of the passage 30 on the downstream side larger than that of the passage 30 on the upstream side, it is possible to ease the affect of pressure variation in the passage 30 caused by the water evaporation.

A cross section of the rod member 31 may be of a shape of any one of a circle, an oval, and a polygon.

A rod member having a spiral shape may be disposed inside the second evaporation chamber 22. With this configuration, since a time for which the steam flowing inside the second evaporation chamber 22 stays can be increased, it is possible to further increase the temperature of the raw material.

Operations of the hydrogen generator 100 of the present embodiment configured as above will be explained.

The combustion gas generated in the burner 16 sequentially heats the reforming chamber 10, the reforming gas passage 11, and the combustion gas passage 12, and then it flows out to the cover 4 and is discharged from the combustion gas outlet port 15 to an outside of the hydrogen generator 100.

Water Y is supplied from the water inlet port 20, and a raw material X is supplied from the raw material inlet port 19. The raw material X and the water Y flow inside the first evaporation chamber 18 and the second evaporation chamber, and the water evaporates by the heat transferred from the third and fourth portions 12C and 12D of the combustion gas passage. Thus, the material gas containing the steam is generated. Moreover, the raw material also evaporates if the raw material is liquid. Here, it is desirable that the water inlet port 20 be disposed at as a high portion of the first evaporation chamber 18, i.e., the outer peripheral tube 54 as possible. With this, since the time for which the water Y stays in the first evaporation chamber 18 increases, it is possible to more efficiently generate the steam. Moreover, since the water of a liquid phase and saturated steam flow inside the first evaporation chamber 18, the temperature of the outer peripheral surface of the hydrogen generator 100, that is, the temperature of the outer peripheral tube 54 can be reduced to about 100° C. or lower. Since the amount of heat radiated to the circumference of the hydrogen generator 100 can be made small, the heat efficiency of the hydrogen generator 100 improves.

The material gas containing the steam generated in the water evaporator 2 is supplied from the second evaporation chamber 22 via the communication passage 26 to the reforming chamber 10. In the reforming chamber 10, the material gas is reformed into the reformed gas containing hydrogen by the steam-reforming reaction caused by the catalysis of the steam reforming catalyst. Note that the steam-reforming reaction is an endothermic reaction occurred at a high temperature of about 700° C., and is carried out by utilizing the heat radiated from the radiating tube 61 and the heat transferred from the combustion gas. The reformed gas generated as above flows through the reforming gas passage 11 and is discharged from the reformed gas outlet port 27 to an outside.

The concentration of carbon monoxide in the reformed gas discharged from the hydrogen generator 100 is further reduced, and then the reformed gas is supplied to a fuel cell 101 as an anode gas. Generally, a shift reaction or a carbon monoxide selective oxidation reaction is utilized to reduce carbon monoxide.

Here, in the method for manufacturing the hydrogen generator 100, a method for manufacturing the first evaporation chamber 18 that is a feature of the present invention will be explained.

In the method for manufacturing the first evaporation chamber 18, the outer peripheral tube 54 corresponds to an outer tube, and the third separating tube 53 corresponds to an inner tube.

FIG. 2 is a flow chart showing a step of manufacturing the first evaporation chamber.

In a first step S1, a rod member 31 is temporarily disposed at a predetermined position.

FIG. 3 is a cross-sectional view schematically showing the first step.

In FIGS. 3 to 10, the cross-sectional area of the passage 30 is uniform for convenience sake. The present manufacturing method can be carried out in a state in which the cross-sectional area of the passage 30 on the downstream side is made larger than that of the passage 30 on the upstream end by adjusting intervals of the spiral of the rod member 31.

As shown in FIG. 3, herein, the rod member 31 is prepared in advance, which bends in a spiral shape having an outer diameter substantially identical with an inner diameter of the outer peripheral tube 54. The rod member 31 is inserted into the outer peripheral tube (outer tube) 54, and is temporarily disposed in a spiral shape on an inner peripheral surface of the outer peripheral tube 54. Herein, the rod member 31 is joined to the inner peripheral surface of the outer peripheral tube 54 by spot welding or point welding at several portions of the entire rod member 31. It is rational that this joining is carried out at one portion for each loop of the rod member 31 having a spiral shape in order to achieve compatibility of the reliability of the joining and the ease of the processing. This is ideal since stress distribution after the tube expansion becomes uniform. In the drawings, a reference number 201 denotes a central axis of the outer peripheral tube 54.

In a second step S2, the third separating tube (inner tube) 53 and the outer peripheral tube (outer tube) 54 are coaxially disposed to form a double tube.

FIG. 4 is a cross-sectional view schematically showing the second step.

As shown in FIG. 4, the third separating tube 53 is disposed on an inner peripheral side of the outer peripheral tube 54 including the rod member 31. The third separating tube 53 and the outer peripheral tube 54 are disposed to be supported by a base 103. Moreover, the third separating tube 53 and the outer peripheral tube 54 are disposed coaxially with each other (coaxially with the central axis 201).

Through the first step S1 and the second step S2, the rod member 31 is disposed between the third separating tube 53 and the outer peripheral tube 54. That is, the first step S1 and the second step S2 constitute a disposing step.

In the third step (tube expanding step) S3, the third separating tube (inner tube) 53 is expanded.

FIG. 5 is a cross-sectional view schematically showing the third step.

As shown in FIG. 5, the third separating tube 53 is expanded by pressing of a tube expanding tool E from an inner side thereof.

Herein, the tube expanding tool E has a tip end of a truncated cone shape. The tip end of the tube expanding tool E moves along the central axis 201 of the third separating tube 53 in a state in which a peak of the truncated cone is located on a front side. Then, the tube expanding tool E enters into the third separating tube 53. Thus, the third separating tube 53 is expanded.

A diameter of a bottom surface of the truncated cone of the tube expanding tool E substantially conforms to an inner diameter of the third separating tube 53 in a state in which the rod member 31 is joined to both the outer peripheral tube 54 and the third separating tube 53. Specifically, a preferable diameter can be found by a trial of the third step. To be specific, a preferable size of the tube expanding tool E is such a size that the rod member 31 is joined to both the outer peripheral tube 54 and the third separating tube 53 so as to fill the gap between the outer peripheral tube 54 and the third separating tube 53.

Through the third step S3, the spiral-shape passage is formed in the first evaporation chamber 18.

Moreover, the tube expanding tool E substantially uniformly expands the diameter of the third separating tube 53 while maintaining the circular cross section of the third separating tube 53. Therefore, the rod member 31 can be surely joined to the outer peripheral tube 54 and the third separating tube 53 in the entire circumferential direction. That is, the leakage of the fluid from the spiral-shape passage is suppressed.

In the first step S1, the rod member 31 is disposed on an inner side of the outer tube 54 in advance. Thus, it is possible to facilitate the third step S3, i.e., the operation of expanding the inner tube 53. To be specific, since the amount of deformation of the inner tube 53 can be reduced as compared to a case where the rod member 31 is disposed on the inner tube (see Modification Example 2), it is possible to reduce the consumption energy in the third step S3, and to avoid the occurrence of the damage (crack) of the rod member 31 due to the deformation.

Moreover, the inner tube 53 and the outer tube 54 are made of different materials having different stiffness. The inner tube 53 may be made of a material having a higher stretching property than a material of the outer tube 54. For example, in a case where the inner tube 53 and the outer tube 54 is made of stainless steel, the inner tube 53 may be made of austenitic stainless steel having the high stretching property, and the outer tube 54 may be made of ferritic stainless steel which is higher in stiffness than the inner tube 53 and cheaper than the austenitic stainless steel. With this, in the third step S3, since the reactive force of the outer tube 54 with respect to the inner tube 53 becomes large, the rod member 31 can be strongly joined between the outer tube 54 and the inner tube 53.

Further, the third step excels in mass productivity since it is easier than the welding operation and the brazing operation.

It is preferable that the cross section of the rod member 31 be of a shape of circular or oval. With this configuration, the rod member 31 does not have any corners on a pressure-contact surface between the rod member 31 and the outer peripheral tube 54 and a pressure-contact surface between the rod member 31 and the third separating tube 53. Therefore, stress concentration with respect to walls of the outer peripheral tube 54 and the third separating tube 53 is suppressed, and thereby damages of the outer peripheral tube 54 and the third separating tube 53 are suppressed.

Moreover, the base 103 is removed in the process of the third step S3. With this, interference between the tube expanding tool E and the base 103 can be prevented, and the tube expanding tool E can penetrate through the third separating tube 53.

Then, a step of joining the upper end side of the third separating tube 53 and the upper end side of the outer peripheral tube 54 over the entire periphery, a step of joining the lower end side of the outer peripheral tube 54 to the bottom wall 29 over the entire periphery, and a step of forming the raw material inlet port 19 and the water inlet port 20 on the upper portion of the outer peripheral tube 54 are carried out in random order. Thus, the first evaporation chamber 18 is formed.

MODIFICATION EXAMPLE 1

In the present modification example, a splitter die K is disposed between the tube expanding tool E and the third separating tube 53 in the third step.

FIG. 6 is a cross-sectional view schematically showing Modification Example 1 of the third step, and shows a state before the tube expansion. FIG. 7 is a diagram showing a state after the tube expansion of FIG. 6.

As shown in FIG. 6, the splitter die (hereinafter simply referred to as a die) K is constituted by a predetermined number of split pieces (splitters). In a state in which these split pieces are disposed on a predetermined circumference of a circle at predetermined intervals in a circumferential direction, its entire shape (enveloping surface) forms a cylindrical shape. An outer diameter of the cylindrical shape is substantially the same as an inner diameter of the third separating tube 53, and an inner surface of the cylindrical shape has an inverted conic shape having the same taper shape as a conic surface of the tube expanding tool E.

In the second step S2, the predetermined number of split pieces of the die K are disposed on the base 103 together with the outer peripheral tube 54 and the third separating tube 53 (see FIG. 6). Moreover, the die K is disposed to contact an inner peripheral surface of the third separating tube 53 and such that the split pieces are disposed at the predetermined intervals in the circumferential direction.

Next, as shown in FIG. 6, the tube expanding tool E enters into the die K (predetermined number of split pieces) in the third step S3. As shown in FIG. 7, the conic surface of the tube expanding tool E contacts inner surfaces of respective split pieces of the die K. The tube expanding tool E proceeds while the conic surface presses the inner surfaces of the split pieces to press the die K in an outer circumferential direction. With this, the separating tube 53 is expanded. In accordance with the present modification example, since the die K presses the third separating tube 53 by a larger surface, it is possible to more quickly expand the third separating tube 53.

MODIFICATION EXAMPLE 2

In the first step S1, the rod member 31 may be disposed on an outer peripheral surface of the third separating tube 53.

FIG. 8 is a cross-sectional view schematically showing the first step of Modification Example 2.

As shown in FIG. 8, the rod member 31 is prepared in advance, which bends in a spiral shape having an outer diameter substantially identical with an outer diameter of the third separating tube 53. The rod member 31 is temporarily disposed in a spiral shape on the outer peripheral surface of the separating tube 53. Herein, the rod member 31 is joined to the outer peripheral surface of the third separating tube 53 by spot welding or point welding at several portions over the entire length of the rod member 31. With this, since the rod member 31 is easily accessible in the first step S1, it is possible to easily carry out the first step S1.

FIG. 9 is a cross-sectional view schematically showing the second step of Modification Example 2.

As shown in FIG. 9, the outer peripheral tube 54 is disposed on an outer peripheral side of the third separating tube 53 including the rod member 31. The third separating tube 53 and the outer peripheral tube 54 are disposed to be supported by the base 103. Moreover, the third separating tube 53 and the outer peripheral tube 54 are disposed coaxially with each other (coaxially with the central axis 201).

FIG. 10 is a cross-sectional view schematically showing the third step of Modification Example 2.

As shown in FIG. 10, the third separating tube 53 is expanded by pressing of the tube expanding tool E from the inner side thereof, and the rod member 31 is also deformed such that a spiral diameter thereof increases in size. Then, the rod member 31 is joined to the outer peripheral tube 54 and the third separating tube 53. Here, since the rod member 31 is joined to and supported by the outer peripheral tube 54 and the third separating tube 53, there is no problem if the spot welding or the point welding for temporarily disposition comes off at the time of tube expansion.

This method is especially effective in the case of using a material having a high stretching property (high stretch rate) as a material of the rod member 31.

The foregoing has explained the embodiment of the present invention, however the present invention is not limited to the above embodiment. For example, as with the first evaporation chamber 18, a spiral-shape passage may be formed in the second evaporation chamber 22 in the hydrogen generator of the present invention.

That is, in the method for manufacturing the second evaporation chamber 22, the third separating tube 53 corresponds to the outer tube, and the second separating tube 52 corresponds to the inner tube.

Specifically, after the spiral-shape passage is formed in the first evaporation chamber 18 of the outer peripheral side, a rod member having a spiral shape is temporarily disposed on an inner peripheral surface of the third separating tube 53 or on an outer peripheral surface of the second separating tube 52 as the first step S1.

Then, as the second step S2, the second separating tube 52 is disposed on an inner peripheral side of the third separating tube 53.

Then, the second separating tube 52 is expanded, and thereby the spiral-shape passage is formed in the second evaporation chamber 22.

Moreover, in the above-described embodiment, the first evaporation chamber 18 that is the water evaporator 2 is supplied with the raw material and the water, and the raw material and water flow to the reformer 1. That is, in the water evaporator, the water and the raw material evaporate to generate the material gas containing steam. In contrast, the raw material may not flow through the water evaporator 2 but flow through the other passage to reach the reformer 1. In this case, only the water is supplied to the first evaporation chamber 18. That is, in the water evaporator, the water evaporates to generate the steam.

INDUSTRIAL APPLICABILITY

The present invention is useful as a method for manufacturing a hydrogen generator capable of improving mass productivity.

Claims

1. A method for manufacturing a hydrogen generator comprising: a water evaporator which includes an inner tube, an outer tube, and a spacer disposed between the inner tube and the outer tube and in which a passage defined by the spacer is supplied with water and heated to generate steam; and a reformer which includes reforming catalyst and in which the steam and a raw material flow through the reforming catalyst to generate a reformed gas containing hydrogen, the method comprising:

a disposing step of disposing the spacer between the inner tube and the outer tube; and

a tube expanding step of expanding the inner tube to form the passage defined by the spacer.

2. The method according to claim 1, wherein: the spacer is a rod member having a spiral shape; and the passage having a spiral shape is formed between the inner tube and the outer tube.

3. The method according to claim 2, wherein the rod member is a rod having a circular cross section or an oval cross section.

4. The method according to claim 1, wherein a cross-sectional area of the passage, defined by the spacer, is larger on a downstream side than on an upstream side.

5. The method according to claim 1, wherein the disposing step includes: a first step of temporarily disposing the spacer on an inner peripheral surface of the outer tube; and a second step of disposing the inner tube on an inner peripheral side of the spacer after the first step.

6. The method according to claim 1, wherein the disposing step includes: a first step of temporarily disposing the spacer on an outer peripheral surface of the inner tube; and a second step of disposing the outer tube on an outer peripheral side of the spacer after the first step.

7. The method according to claim 1, wherein a material of the inner tube has a higher stretching property than a material of the outer tube.