JP4088945B2 - Fuel cell evaporator - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an evaporator of methanol and water used for a fuel reforming system of a polymer electrolyte fuel cell.
[0002]
[Prior art]
A polymer electrolyte fuel cell (PEFC) uses a polymer membrane 1 having proton (H ⁺ ) conductivity as an electrolyte and is thin on both sides of the membrane as shown in the principle diagram of FIG. It has a structure with a porous Pt catalyst electrode 2 (anode and cathode). Supplying H ₂ and O ₂ to the respective electrodes, operating at around room temperature to 100 ° C., H ₂ is oxidized to H ⁺ with H _2-pole (anode), H ⁺ is moved to the film O ₂ Reach the pole (cathode). On the other hand, e ⁻ reaches the O ₂ pole after performing electrical work through an external circuit. At the O ₂ electrode, O ₂ reacts with the reached H ⁺ and e ⁻ and is reduced to H ₂ O.
[0003]
A structural example of PEFC is shown in FIG. In PEFC, one cell is configured with a membrane / electrolyte assembly 4 sandwiched between separators 5. The membrane / electrolyte assembly 4 is obtained by disposing a porous electrode 2 made of Pt black or Pt-supported carbon and a support current collector 3 made of carbon paper or carbon cloth on both surfaces of the ion exchange membrane 1. The separator 5 is a conductive plate having a groove for flowing gas on both sides and a groove for flowing cooling water inside. In the example of FIG. 5, the internal cooling groove is formed by joining two separators.
[0004]
A stack (laminated battery) is formed by alternately laminating a plurality of separators 5 and membrane / electrolyte assemblies 4. Gas or cooling water is often sealed with a rubber sheet or a Teflon sheet sandwiched between them, but sometimes the film itself is sealed by utilizing the elasticity of the ion exchange membrane. In addition, metal current collector plates (not shown) are arranged at both ends of the stack to serve as external current extraction terminals, and further, a clamping plate is arranged through an insulating plate, and the whole is integrated by tightening with bolts or the like. .
Since the polymer electrolyte fuel cell (PEFC) described above operates at a low temperature of 100 ° C. or less, it has the advantage of reducing heat dissipation and making the system compact, and it is vigorous in various countries as a portable power source for electric vehicles. Has been studied.
[0005]
FIG. 6 is a configuration diagram of a portable power source using methanol as a fuel and combining a methanol reformer and a PEFC. In this figure, in a methanol reformer, hydrogen and carbon dioxide are produced from methanol and water by a reaction of CH ₃ OH + H ₂ O → 3H ₂ + CO ₂ . The reaction temperature is about 300 ° C., and the heat required for the evaporation and reforming reaction of water and methanol is supplied by burning fuel exhaust gas containing unused hydrogen of the fuel cell and air. Such a small portable power source can be used as a power source for a vehicle such as an electric vehicle.
[0006]
[Problems to be solved by the invention]
A power source for a vehicle such as an electric vehicle is particularly required to have a small size and start-up characteristics. That is, in the PEFC power source shown in FIG. 6, the evaporator requires a larger amount of heat than the reforming reaction, so that the evaporator tends to be large and hinders the miniaturization of the PEFC power source itself. In addition, it is necessary to start / stop the vehicle power supply in a short time, and there has been a demand for shortening the start / stop time of the evaporator.
As a conventional evaporator, for example, “Methanol reformer evaporator” (Japanese Patent Publication No. 2-42762) is disclosed. In this evaporator, a methanol aqueous solution is flowed into an evaporation tube and heated by a burner from the outside. In addition, similarly, the liquid to be evaporated is caused to flow in the heat transfer tube, and an electric heater and one heated by the combustion gas from the outside thereof, and an electric heater and a heating tube heated by the combustion gas are placed in the liquid to be evaporated in the container. What is heated by this heating tube is known.
[0007]
However, these conventional evaporators have a problem that the heat transfer area and the heat transfer coefficient on the liquid side are particularly small and it is difficult to reduce the size. Further, the conventional evaporator has a problem that it takes a long time to start up due to its large heat capacity, and a large amount of excess steam remains after it stops. Furthermore, the conventional evaporator has a problem that pressure control and flow rate control are complicated.
[0008]
The present invention has been developed to solve the above-described problems. That is, the object of the present invention is that the heat transfer area and heat transfer coefficient on the liquid side are large and can be reduced in size, can be started up in a short time, and the amount of residual steam after stopping is small, and pressure control and flow control It is an object of the present invention to provide a fuel cell evaporator that is easy to achieve.
[0009]
[Means for Solving the Problems]
According to the present invention, the inner tube (11) and outer tube (12) and the double tube consisting of a (13), the inner tube and to contact the outer tube sintered metal tube clamped a cylindrical therebetween (14 The inner tube and / or the outer tube are heated, the liquid to be evaporated is permeated into the sintered metal tube and evaporated, and the liquid to be evaporated is supplied spirally to the outer surface of the sintered metal tube (14). As described above, a spiral groove (12a) is provided on the inner surface of the outer tube (12), and a steam flow path (11a) extending in the axial direction is provided on the outer surface of the inner tube (11). A fuel cell evaporator is provided.
[0010]
According to the configuration of the present invention, the liquid to be evaporated is spirally supplied from the spiral groove (12a) on the inner surface of the outer pipe (12) to the outer surface of the sintered metal pipe (14), and the liquid to be evaporated is supplied to the sintered metal pipe. This is permeated and evaporated in the sintered metal tube by heat transfer from the heated inner tube and / or outer tube, and through a steam channel (11a) provided on the outer surface of the inner tube (11). , And can be supplied to a reformer for a fuel cell.
The sintered metal tube has a thermal conductivity close to that of a solid metal material and has a large specific surface area. Therefore, the sintered metal tube has a large substantial heat transfer area even though the apparent volume is small. In addition, the liquid to be evaporated (methanol or water, or a mixture thereof) can be held inside by surface tension and can be evaporated and discharged inside, so that it has a high heat transfer coefficient. Therefore, the heat transfer area and the heat transfer coefficient on the liquid side are large and downsizing is possible.
Further, since the sintered metal tube can be heated by heating the inner tube and / or the outer tube, it is possible to heat from the inner surface using a heat medium at the start-up, and from the outer surface using a combustion gas in a steady state. Or one or both can be used together.
Further, by holding the sintered metal tube in a preheated state and supplying the required amount of liquid to be evaporated, it is possible to start up in a short time and to reduce the amount of remaining steam after stopping.
[0011]
The outer pipe (12) has a plurality of heat transfer fins (12b) on the outer periphery thereof, and further includes a hollow cylindrical shell (16) surrounding the double pipe (13), and a plurality of insides of the shell. And baffles (17) each having a through hole (17a), and hot gas is supplied into the shell. Further, a heated heat medium is supplied to the inside of the inner pipe (11).
With this configuration, high-temperature gas (for example, combustion gas) can be sequentially brought into contact with the heat transfer fins (12b) around the outer pipe (12) through the through hole (17a) of the baffle (17). ) Through which the sintered metal tube can be efficiently heated. In addition, by supplying a heated heat medium to the inner tube (11), the sintered metal tube can be heated through the inner tube, and one of them can be used at the time of start-up or steady operation, or both. Can be used together.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In each drawing, common parts are denoted by the same reference numerals.
FIG. 1 is an overall configuration diagram of a fuel cell evaporator according to the present invention. As shown in this figure, a fuel cell evaporator 10 according to the present invention includes a hollow cylindrical shell 16 surrounding a double pipe 13, and a baffle 17 that partitions the inside of the shell 16 into a plurality of spaces and has through holes 17a. With. A plurality of heat transfer fins 12 b are attached to the outer peripheral portion of the outer tube 12 constituting the double tube 13. Both ends of the shell 16 are closed by a flat plate or a mirror plate, and the double tube 13 passes through the flat plate or the mirror plate. The baffle 17 is a partition plate perpendicular to the axis of the shell 16 and partitions the inside of the shell 16 into a plurality of substantially equal spaces (five in this figure). The through holes 17a of the baffle 17 are alternately provided at the end portions in the width direction of the partitioned spaces. In addition, supply / discharge ports 16 a and 16 b for supplying and discharging the high temperature gas 7 are provided in spaces positioned at both ends of the shell 16, respectively. In this figure, reference numeral 9a denotes a liquid to be evaporated (methanol or water, or a mixture thereof), and methanol or water may be evaporated alone, or a mixture of water and methanol may be evaporated. Moreover, 9b is the vapor | steam which the to-be-evaporated liquid evaporated.
[0013]
With this configuration, by supplying the high temperature gas 7 into the shell 16, the high temperature gas 7 (for example, combustion gas) is sequentially passed around the outer tube 12 through the through hole 17a of the baffle 17 as shown by the broken arrow in the figure. The heat transfer fins 12b can be brought into contact with each other, and the inside (sintered metal tube described later) can be efficiently heated through the outer tube 12.
Further, as shown in FIG. 1, in this embodiment, the heated heat medium 8 is supplied to the inside of the inner tube 11 constituting the double tube 13. With this configuration, the inside of the double pipe 13 (sintered metal pipe to be described later) can be heated through the inner pipe 11, and one of them can be used at the start-up and steady state, or both can be used together. Can do.
[0014]
2 is an enlarged cross-sectional view of a portion A in FIG. 1, and FIG. 3 is a cross-sectional view taken along line BB in FIG. As shown in FIGS. 1 and 2, the fuel cell evaporator 10 of the present invention is in close contact with a double pipe 13 composed of an inner pipe 11 and an outer pipe 12, and the inner pipe 11 and the outer pipe 12. The cylindrical sintered metal tube 14 is sandwiched. As shown in FIG. 2, the inner tube 11 and the outer tube 12 are airtightly joined by welding or the like at their ends. As described above, a plurality of heat transfer fins 12b are attached to the outer peripheral portion of the outer tube 12 at a sufficiently small pitch.
[0015]
The sintered metal tube 14 is filled with metal particles, formed into a desired shape (in this case, a cylindrical shape), further sintered at a high temperature, and partially sintered between the particles. The sintered metal tube 14 used in the present invention uses metal particles having high thermal conductivity, allows the liquid to be evaporated to penetrate into the gaps between the particles with surface tension, and holds the particles with the surface tension inside. The average gap is set so that
[0016]
As shown in FIGS. 1 and 2, in the fuel cell evaporator 10 of the present invention, the evaporated liquid 9 a is further spirally supplied to the outer surface of the sintered metal tube 14. A spiral groove 12a is provided. The liquid to be evaporated 9a is supplied to the spiral groove 12a from a liquid supply pipe 12c attached to the end of the outer pipe 12.
Further, a steam flow passage 11 a extending in the axial direction is provided on the outer surface of the inner tube 11. With this configuration, the inner tube 11 and / or the outer tube 12 can be heated, and the liquid 9a to be evaporated can penetrate into the sintered metal tube 14 to be evaporated.
[0017]
According to the configuration of the present invention described above, the evaporating liquid 9a is supplied spirally from the spiral groove 12a on the inner surface of the outer tube 12 to the outer surface of the sintered metal tube 14, and the surface tension of the evaporating liquid 9a is applied to the sintered metal tube 14. (Capillary phenomenon) is permeated and vaporized in the sintered metal tube 14 by heat transfer from the heated inner tube 11 and / or outer tube 12, and a steam flow provided on the outer surface of the inner tube 11 The steam 9b can be supplied to a reformer for a fuel cell or the like via the path 11a.
The sintered metal tube 14 has a thermal conductivity close to that of a solid metal material and has a large specific surface area. Therefore, the sintered metal tube 14 has a large substantial heat transfer area even though the apparent volume is small. Further, since the liquid to be evaporated 9a (methanol or water, or a mixture thereof) can be held inside by surface tension and can be evaporated and discharged inside, it has a high heat transfer coefficient. . Therefore, the heat transfer area and the heat transfer coefficient on the liquid side are large and downsizing is possible.
[0018]
Further, since the inner tube 11 and / or the outer tube 12 can be heated to heat the sintered metal tube 14, the heating medium 8 is used for heating from the inner surface during startup, and the outer surface is used using the combustion gas 7 during steady operation. Can be heated, or one or both can be used together.
In addition, by holding the sintered metal tube 14 in a preheated state and supplying the required amount of the liquid 9a to be evaporated, it is possible to start up in a short time and to reduce the amount of remaining steam after stopping. Further, since the entire amount of the supplied liquid 9a is evaporated as it is, pressure control and flow rate control can be easily performed.
[0019]
In addition, this invention is not limited to embodiment mentioned above, Of course, it can change variously in the range which does not deviate from the summary of this invention.
[0020]
【The invention's effect】
As described above, the fuel cell evaporator of the present invention has a large heat transfer area and heat transfer coefficient on the liquid side, can be downsized, can be started up in a short time, and has a small amount of remaining steam after being stopped. Further, it has excellent effects such as easy pressure control and flow rate control.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a fuel cell evaporator according to the present invention.
FIG. 2 is an enlarged cross-sectional view of a portion A in FIG.
3 is a cross-sectional view taken along line BB in FIG.
FIG. 4 is a principle diagram of a polymer electrolyte fuel cell.
FIG. 5 is a structural diagram of a polymer electrolyte fuel cell.
FIG. 6 is a configuration diagram of a portable power source combining a conventional methanol reformer and PEFC.
[Explanation of symbols]
1 Ion exchange membrane (polymer membrane)
2 Electrode 3 Support current collector 4 Membrane / electrolyte assembly 5 Separator 7 Hot gas 8 Heat medium 9a Evaporated liquid (methanol or water, or a mixture thereof)
9b Steam 11 Inner pipe 11a Steam flow path 12 Outer pipe 12a Spiral groove 12b Heat transfer fin 12c Liquid supply pipe 13 Double pipe 14 Sintered metal pipe 16 Shell 17 Baffle 17a Through hole

Claims (3)

It from the inner tube (11) outer tube (12) from become double pipe (13), contact and sintered metal tube a cylindrical sandwiched therebetween on the inner tube and the outer tube (14), the inner The tube and / or the outer tube is heated, the liquid to be evaporated is permeated into the sintered metal tube and evaporated ;
A spiral groove (12a) is provided on the inner surface of the outer tube (12) so as to supply the liquid to be evaporated spirally to the outer surface of the sintered metal tube (14), and a shaft is formed on the outer surface of the inner tube (11). An evaporator for a fuel cell, characterized in that a steam flow path (11a) extending in a direction is provided .   The outer pipe (12) has a plurality of heat transfer fins (12b) on the outer periphery thereof, and further includes a hollow cylindrical shell (16) surrounding the double pipe (13), and a plurality of spaces in the shell. 2. The fuel cell evaporator according to claim 1, further comprising a baffle (17) having a partition and a through hole (17 a), wherein a high-temperature gas is supplied into the shell.   2. The fuel cell evaporator according to claim 1, wherein a heated heat medium is supplied to the inside of the inner pipe (11). 3.

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