Patent Grant
7531016
This application is a U.S. National Phase Application under 35 USC 371 of International Application PCT/JP03/03364 filed Mar. 19, 2003.
The present invention relates to a chemical reaction apparatus and a power supply system including this chemical reaction apparatus and, more particularly, to a chemical reaction apparatus applied to a power supply system including a fuel cell which generates electric power by using fuel.
In the technical field of chemical reactions, chemical reaction apparatuses are known in which various fluidized material mixtures are supplied to flow paths to cause chemical reactions, i.e., catalyst reactions with catalysts placed in the flow paths, thereby producing desired fluid materials.
These chemical reaction apparatuses have various scales and structures in accordance with their applications. For example, in a certain relatively small-sized chemical reaction apparatus, a micron-order or millimeter-order flow path is formed in a silicon substrate by using the micropatterning technology developed in the technology for fabricating semiconductors such as semiconductor integrated circuits, and fluid is supplied to this flow path to cause a chemical reaction.
This chemical reaction apparatus includes a silicon substrate 1. On one surface of the silicon substrate 1, a fine zigzagged flow path 2 is formed by using the micropatterning technology developed in the semiconductor fabrication technology.
The two end portions of the flow path 2 are extended to substantially central portions of two predetermined end faces to form an inlet port 3 and outlet port 4. A catalyst layer 5 for performing a chemical reaction is formed on the inner wall surface of the flow path 2.
A glass substrate 6 is bonded to the above-mentioned surface of the silicon substrate 1. On the surface of the glass substrate 6 away from the surface opposite to the silicon substrate 1, a zigzagged thin-film heater 7 corresponding to the flow path 2 is provided.
The width of the thin-film heater 7 is made slightly smaller than that of the flow path 2. If the chemical reaction (catalyst reaction) in the chemical reaction apparatus induces an endothermic reaction under predetermined heat conditions, the thin-film heater 7 supplies predetermined thermal energy to the catalyst in the flow path 2 upon the chemical reaction.
A use example of this chemical reaction apparatus having the above arrangement will be explained below.
Recently, research and development for putting a power supply system using a fuel cell into practical use have been extensively done. A chemical reaction apparatus having the above arrangement can be used in this power supply system using a fuel cell. By this chemical reaction apparatus, as will be explained below, hydrogen can be produced from a power generation fuel gas and supplied to the fuel cell, and the power supply system using the fuel cell can be downsized.
While the thin-film heater 7 heats the interior of the flow path 2 to a predetermined temperature, the power generation fuel gas described above is supplied into the flow path 2 from the inlet port 3. This causes an endothermic reaction by the catalyst 5 in the flow path 2 to produce hydrogen and carbon dioxide as a byproduct. Of these products, only hydrogen can be produced by removing carbon dioxide from hydrogen. Electric power can be generated by supplying this hydrogen to the fuel cell.
In the above conventional chemical reaction apparatus, when the interior of the flow path 2 is heated by the thin-film heater 7, the two substrates 1 and 6 are also heated. Therefore, if the whole outer surfaces of these substrates 1 and 6 are exposed to the atmosphere, the thermal energy generated by the thin-film heater 7 is partially radiated to the outside from the surfaces of the substrates 1 and 6. This increases the thermal energy loss and worsens the energy utilization.
The present invention has the advantage that in a chemical reaction apparatus which includes a flow path for allowing fluid to flow and causes a heating element to heat the interior of the flow path to perform a desired chemical reaction, the energy utilization is improved by suppressing the thermal energy loss caused when the thermal energy generated by the heating element is partially radiated outside. The present invention also has the advantage that when this chemical reaction apparatus is applied to a power supply system using a fuel reforming type fuel cell, the loss of thermal energy required for heating for power generation can be reduced, the energy utilization can be increased, and the power supply system can be downsized.
To obtain the above advantages, a chemical reaction apparatus according to one aspect of the present invention comprises a plurality of substrates bonded to each other, at least one flow path formed in at least one of the plurality of substrates, heating element formed on at least one surface of at least one of the plurality of substrates to heat the flow path, and a heat radiation preventing film which covers at least a portion of an outermost surface of the plurality of substrates. The heat radiation preventing film can suppress radiation of heat from the outer surface of the substrate.
This chemical reaction apparatus further comprises a box member which covers all the outermost surfaces of the plurality of substrates including the heat radiation preventing film, wherein a space is formed in at least a portion between the box member and the outermost surfaces of the plurality of substrates including the heat radiation preventing film. The space is kept in a substantially vacuum state, or a gas having thermal conductivity lower than that of components of the box member is sealed in the space, so heat conduction to the outside from the outer surface of the substrate including the heat radiation preventing film can be suppressed. Accordingly, it is possible to suppress the thermal energy loss when the heating element heats the interior of the flow path, and increase the energy utilization.
The plurality of substrates include at least a first substrate in one surface of which the flow path is formed, and a second substrate bonded to one surface of the first substrate.
The heat radiation preventing film is one of a metal film made of Au, Al, or Ag, and a metal oxide film made of SnO2, InO3, or ZnO. This heat radiation preventing film is at least one of a first heat radiation preventing film which covers at least a portion of the other surface of the first substrate away from one surface, a second heat radiation preventing film which covers at least a portion of the other surface of the second substrate away from one surface which opposes the first substrate, a third heat radiation preventing film which covers at least a portion of those side surfaces of the first substrate, which are perpendicular to the other surface, and a fourth heat radiation preventing film which covers at least a portion of those side surfaces of the second substrate, which are perpendicular to the other surface.
The heating element comprises a thin-film heater. This thin-film heater has one of a zigzagged shape corresponding to the shape of the zigzagged flow path, and a rectangular shape covering substantially the whole of the flow path, and is formed on at least one of that one surface of the second substrate, which opposes the first substrate, the other surface of the second substrate away from one surface, and the other surface of the first substrate away from one surface. On the surface on which the thin-film heater is formed, the heating element has an insulating film which covers the thin-film heater and has a flat upper surface. The heat radiation preventing film may be formed on this insulating film. Alternatively, it is possible to include a third substrate which is bonded onto the insulating film and has a recess in a surface which opposes the thin-film heater, and form the heat radiation preventing film on the outer surface of this third substrate. The recess is in a substantially vacuum state, or a gas having thermal conductivity lower than that of the third substrate is sealed in the recess.
Also, as the heating element, it is possible to include a combustion flow path having a combustion catalyst layer formed in at least a portion thereof, and a supplying unit which supplies a combustion fluid to the combustion flow path, and a thermal energy generating unit which generates thermal energy in the combustion flow path by a combustion reaction on the combustion catalyst layer.
When the chemical reaction apparatus of the present invention is applied to a power supply system including a fuel reforming type fuel cell, it is possible, as a fuel vaporizer, to supply an aqueous solution of methanol as power generation fuel to the flow path, and vaporize the fluid in the flow path by heating the flow path by the heating element. As a reforming unit, it is possible to form a reforming catalyst layer in the flow path, and reform the power generation fuel in the flow path by heating the flow path by the heating element, thereby produce hydrogen. As a carbon monoxide removing unit, it is possible to form a selective oxidation catalyst layer in the flow path, and remove carbon monoxide from a gas mixture containing carbon monoxide by heating the flow path by the heating element. Electric power can be generated by supplying hydrogen produced by these units to the fuel cell, and causing hydrogen and oxygen to react with each other. It is also possible to form a heat radiation preventing film which covers the outermost surfaces of the plurality of substrates of the chemical reaction apparatus, and further comprises a box member which covers all the outermost surfaces of the plurality of substrates including the heat radiation preventing film, and forms, around the outermost surfaces of the plurality of substrates including the heat radiation preventing film, a space which is in a substantially vacuum state or in which a gas having low thermal conductivity is sealed. In this manner, it is possible to reduce the loss of thermal energy required for heating for power generation, increase the energy utilization, and downsize the power supply system.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention.
A chemical reaction apparatus according to the present invention and a power supply system including this chemical reaction apparatus will be described in detail below on the basis of embodiments shown in the drawings.
<Chemical Reaction Apparatus>
The chemical reaction apparatus 100 of the first embodiment of the present invention includes a rectangular, plate-like first substrate 11 having at least a flat upper surface and made of silicon. For example, the first substrate 11 has a length of about 15 to 35 mm, a width of about 10 to 25 mm, and a thickness of about 0.4 to 1.0 mm. In one surface, i.e., the upper surface of the first substrate 11, a fine zigzagged flow path 12 is formed by using the micropatterning technology developed in the semiconductor fabrication technology. For example, the flow path 12 has a width of about 0.2 to 0.8 mm, a depth of about 0.2 to 0.6 mm, and a total length of about 30 to 1,000 mm. The two end portions of the flow path 12 are extended to substantially central portions of two predetermined end faces of the first substrate 11 to form an inlet port 13 and outlet port 14. That is, the depth of the flow path 12 is set to be about half the substrate thickness.
For example, a reaction catalyst layer 15 for performing a desired chemical reaction is preferably formed on the entire inner wall surfaces of the flow path 12. The present invention is not limited to this form in which the reaction catalyst layer 15 is formed on the inner wall surfaces of the flow path 12. That is, an arrangement in which only the flow path 12 is formed and no reaction catalyst layer is formed is also possible.
A rectangular second substrate 21 which functions as a lid and is made of glass about 0.7 mm thick is adhered (bonded) on the upper surface of the first substrate 11, thereby forming a solid body by these two substrates. That surface of the second substrate 21, which faces the first substrate 11 or the lower surface of the second substrate 21 is flat. On substantially the whole of this surface (more specifically, the lower surface except for peripheral portions in this embodiment), a thin-film heater 22 made of a thin resistor film such as TaSiOx or TaSiOxN is formed as a heating element or heating element. This thin resistor film is formed by, e.g., sputtering.
As will be explained in the second to eighth embodiments described later, the heating element of the present invention, i.e., the thin-film heater 22 in this embodiment is not limited to the form in which it is formed on that surface of the second substrate 21, which opposes the first substrate 11. In short, this thin-film heater 22 need only be so designed as to supply predetermined thermal energy to the reaction catalyst layer 15 in the flow path 12, or to fluid flowing in the flow path 12, in order to progress a desired chemical reaction (catalyst reaction) in the flow path 12. When the thin-film heater 22 is formed on that surface of the second substrate 21, which faces the first substrate 11, i.e., when the thin-film heater 22 is formed immediately above or on the flow path 12 as in this first embodiment, the thermal energy can be efficiently supplied to the flow path 12. This relatively increases the thermal energy utilization.
In this first embodiment, the thin-film heater 22 is formed into a rectangular shape on substantially the whole of that surface of the second substrate 21, which opposes the first substrate 11. Therefore, the number of steps required for the formation of this thin-film heater 22 can be reduced, so the manufacturing cost can be reduced.
In this embodiment, as shown in
As shown in
These heat radiation preventing films 16 and 23 are made of a metal material such as Au, Al, or Ag having high heat ray reflectance, or a metal oxide such as SnO2, InO3, or ZnO.
As a method of forming this heat radiation preventing film, the following methods can be applied. That is, it is possible to apply: a method in which a member obtained by forming the metal material described above into a foil or film is coated with the metal oxide described above, or a film of the metal oxide is formed on the member, and the resultant film is adhered to the outer surfaces of each substrate; a method in which a thin film of any of the above materials is formed on the outer surfaces of each substrate by using a thin film formation technique such as deposition, sputtering, or plating; or a method in which the outer surfaces of each substrate are coated with fine grains of any of the above materials together with an appropriate solvent.
Also, as shown in
The inner and/or outer surface of the box 40 may be covered with a radiation preventing film or layer 40a, 40b for reflecting heat (infrared light) outwardly radiated from the apparatus 100 so that outwardly escaping of heat energy, that is, heat loss may be prevented or decreased.
Where the space 42 is vacuumed to increase the insulating efficiency, the lower the pressure in the space is, the higher the insulating efficiency is. Practically, for example, the pressure in the space 42 may be about 100 Pa, or made lower than about 100 Pa. Where the pressure is about 100 Pa, the power applied to the thin-film heater 22 may be decreased about 30% in comparison with the case where the pressure in the space 42 is atmosphere. Preferably, the pressure in the space 42 is set to about 10 Pa or set to lower than about 10 Pa. Where the pressure is set to about 10 Pa, the power applied to the thin-film heater 22 may lower by about half in comparison with the case where the pressure in the space 42 is atmosphere.
It can be understood that the embodiment as shown in
In the chemical reaction apparatus 100 according to this embodiment as described above, the heat radiation preventing films 16 and 23 are formed on the outer surfaces of the first and second substrates 11 and 21, respectively. Accordingly, radiation of heat to the outside from the outer surfaces of the first and second substrates 11 and 21 can be suppressed. In addition, heat conduction to the surroundings can be suppressed by forming the heat insulating space 42 around the chemical reaction apparatus 100. When the thin-film heater 22 heats the interior of the flow path 12, therefore, it is possible to suppress the thermal energy loss caused by a partial leak of the thermal energy to the outside, and thus, improve the energy utilization.
The second embodiment differs from the arrangement of the first embodiment in that a thin-film heater 22 formed on that surface of a second substrate 21, which opposes a first substrate 11 is formed into a zigzagged shape corresponding to a flow path 12 as shown in
In this arrangement, the thin-film heater 22 can be further approached to a reaction catalyst layer in the flow path 12, compared to the arrangement of the first embodiment described above. Therefore, the efficiency of supply of the thermal energy to the flow path 12 can be further increased, so the thermal energy utilization can be further increased.
In this second embodiment, the second substrate 21 is directly adhered (bonded) to one surface of the first substrate 11. These first and second substrates 11 and 21 may be adhered by using an adhesive, and may also be bonded by anodic bonding.
This anodic bonding process will be explained below.
The second substrate 21 is overlapped on the first substrate 11, and these first and second substrates 11 and 21 are used as an anode and cathode, respectively. While the first and second substrates 11 and 21 are heated to about 400 to 600° C., a DC voltage of about 1 kV is applied between the two electrodes. Consequently, cations as an impurity in the second substrate 21 move away from the first substrate 11, and a layer having a high oxygen ion concentration appears in that interface of the second substrate 21, which faces the first substrate 11. Accordingly, silicon atoms in that interface of the first substrate 11, which opposes the second substrate 21 and oxygen ions in that interface of the second substrate 21, which opposes the first substrate 11 are bonded, thereby forming a strong bonded interface.
In this process, when the first and second substrates 11 and 21 are heated to about 400 to 600° C. and a DC voltage of about 1 kV is applied between the two electrodes as described above, the speed at which cations as an impurity in the second substrate 21 move away from the first substrate 11 increases, so these cations can move within a short time period. This reduces the time required for the anodic bonding process.
When the first and second substrates 11 and 21 are bonded by anodic bonding as described above, strong bonding can be obtained. In addition, since no adhesive is necessary, no impurity such as an adhesive enters the flow path 12.
In this third embodiment, a thin-film heater 22 is formed on that surface of a second substrate 21, which faces a first substrate 11, as in the first embodiment described above. The third embodiment differs from the arrangement of the first embodiment in that an insulating film 24 made of silicon nitride or silicon oxide is additionally formed on that surface of the second substrate 21, which opposes the first substrate and includes the thin-film heater 22 embedded in the film 24, thereby forming a flat surface including the thin-film heater 22 on that surface of the second substrate 21, which opposes the first substrate 11.
As in the second embodiment described above, the thin-film heater 22 is formed into a zigzagged shape corresponding to a flow path 12. The second substrate 21 is adhered (bonded) to one surface of the first substrate 11 via the insulating film 24.
With the arrangement of the third embodiment, the thermal energy can be efficiently supplied from the thin-film heater 22 to the flow path 12 by arranging the thin-film heater 22 and flow path 12 close to each other. In addition, since the thin-film heater 22 is covered with the insulating film 24, a fluid flowing in the flow path 12 is not in direct contact with the thin-film heater 22. This avoids corrosion and deterioration of the thin-film heater 22 by the influence of the fluid flowing in the flow path 12.
This fourth embodiment differs from the arrangement of the third embodiment in that a thin-film heater 22 is formed on the outer surface or upper surface of a second substrate 21, and an insulating film 24 is formed on the outer surface of the second substrate 21 so as to cover the thin-film heater 22, thereby forming a flat upper surface including this thin-film heater 22, and that a heat radiation preventing film 23 is formed on this flat outer surface or upper surface of the insulating film 24.
In this arrangement, the thin-film heater 22 is formed into a zigzagged shape corresponding to a flow path 12, as in the second embodiment described above.
Since the thin-film heater 22 is formed outside the zigzagged flow path 12, the width of the thin-film heater 22 may be made substantially equal to that of the flow path 12, or the thin-film heater 22 may be made wider than the flow path 12. Furthermore, the thin-film heater 22 may be formed into a rectangular shape covering the whole flow path 12, as in the first embodiment shown in
In this fourth embodiment, the heat radiation preventing film 23 is formed on the outer surface or upper surface of the insulating film 24. This heat radiation preventing film 23 prevents radiation of heat from the thin-film heater 22 to the outside, and protects the thin-film heater 22.
The fifth embodiment differs from the arrangement of the fourth embodiment in that the formation position of a heat radiation preventing film 23 is changed, and a rectangular, plate-like third substrate 25 is adhered (bonded) to the outer surface of an insulating film 24.
This third substrate 25 has, e.g., a rectangular recess 26 in a central portion of the surface opposite to the outer surface of the insulating film 24, or of the lower surface. A peripheral portion around the recess 26 of the third substrate 25 is adhered (bonded) to the outer surface of the insulating film 24. This third substrate 25 is made of glass or aluminum. The heat radiation preventing film 23 is formed on the entire outer surfaces (side surfaces and upper surface) of the third substrate 25.
In this arrangement, the third substrate 25 further protects a thin-film heater 22. Also, in addition to suppression of the thermal energy loss by the heat radiation preventing film 23, heat diffusion from the thin-film heater 22 is further suppressed by the heat insulating function of the recess 26, so the heating efficiency can be further increased. For this purpose, a gas such as air, freon, or carbonic acid gas having thermal conductivity lower than that of the third substrate 25 may be sealed in the recess 26 of the third substrate 25, closed by the insulating film, thereby improving the heat insulating performance. The heat insulating performance may also be further improved by setting a substantially vacuum state in the recess 26 of the third substrate 25.
Where the recess 26 is vacuumed, the lower the pressure in the recess 26 is, the higher the insulating efficiency is. Practically, for example, the pressure in the recess 26 may be set to about 100 Pa, or set to a value lower than about 100 Pa, and preferably, set to about 10 Pa, or set to a value lower than about 10 Pa, so that the power applied to the thin-film heater 22 may be decreased.
This sixth embodiment differs from the first embodiment shown in
In this arrangement, as in the second embodiment described earlier, the thin-film heater 22 is formed into a zigzagged shape corresponding to a flow path 12.
In this sixth embodiment, the heat radiation preventing film 16 is formed on the outer surface of the insulating film 24. The heat radiation preventing film 16 prevents radiation of heat from the thin-film heater 22 to the outside, and protects the thin-film heater 22.
In this seventh embodiment, a third substrate 25 is adhered (bonded) to a flat outer surface of an insulating film 24 in addition to the arrangement of the sixth embodiment shown in
This third substrate 25 has a recess 26 in a central portion of the surface opposite to the outer surface of the insulating film 24. A peripheral portion of the third substrate 25 is adhered (bonded) to the outer surface of the insulating film 24. The third substrate 25 is made of glass or aluminum. A heat radiation preventing film 16 is formed on the outer surface of the third substrate 25.
In this arrangement, like the arrangement shown in
In each of the first to seventh embodiments described above, one thin-film heater 22 is formed. However, the present invention is not limited to these embodiments, and the embodiments may also be appropriately combined. For example, thin-film heaters 22 may be formed on the two sides of the flow path 12, i.e., on the lower surface of the first substrate and on the lower or upper surface of the second substrate. When the two thin-film heaters 22 are thus formed to sandwich the flow path 12 between them, the interior of the flow path 12 can be heated to a higher temperature by heat generated by these heaters. Therefore, this arrangement is suited to a case in which a chemical reaction in the flow path 12 requires a higher temperature.
A heating element of the present invention need only be capable of heating a flow path 12 to a predetermined temperature, thereby supplying a predetermined thermal energy to a reaction catalyst layer 15 in the flow path 12 or to a fluid flowing in the flow path 12. In the first to seventh embodiments, a thin-film heater is used as this heating element. Instead of using this thin-film heater as the heating element, it is also possible to use, e.g., thermal energy generated by a combustion reaction using a combustion catalyst layer.
In this eighth embodiment, a combustion catalyst layer is used as the heating element.
Similar to each of the above embodiments, the apparatus shown in
In this eighth embodiment, when a combustion fluid of a combustion gas, for example, hydrogen, and oxygen taken from the atmosphere is supplied into the combustion path 51 through an inlet port 53 as indicated by an arrow, this supplied combustion fluid combusts by a combustion reaction on the combustion catalyst layer 52, and thermal energy is generated by this combustion. The combusted gas is discharged to the atmosphere from an outlet port 54, as shown in an arrow. This apparatus has a structure in which the thermal energy generated by this combustion is supplied to a reaction catalyst layer 15 in the flow path 12.
In this arrangement, as in each of the above embodiments, a heat radiation preventing film 23 can be formed on the outer surfaces (upper surface and side surfaces) of the combustion substrate 50. This makes it possible to suppress radiation of heat from the outer surfaces of the combustion substrate 50, suppress the thermal energy loss, and increase the energy utilization.
<Power Supply System>
An arrangement in which the chemical reaction apparatus according to the present invention is applied to a power supply system using a fuel reforming type fuel cell will be described below.
The fuel unit 31 includes a fuel pack in which power generation fuel, e.g., an aqueous solution of methanol (CH3OH+H2O) is sealed, and a fuel pump, and supplies the power generation fuel to the fuel vaporizer 32.
The fuel vaporizer 32 vaporizes the power generation fuel supplied from the fuel unit 31. When the chemical reaction apparatus 100 having the arrangement of any embodiment described above is applied to this fuel vaporizer 32, no reaction catalyst layer 15 is formed in the flow path 12. Also, a glass substrate or aluminum substrate may be used as the first substrate 11 instead of a silicon substrate. When the power generation fuel is supplied from the fuel unit 31 into the flow path 12 of the fuel vaporizer 32 through the inlet port 13, this power generation fuel is vaporized as it is heated to a predetermined temperature, e.g., about 120° C. in the flow path 12 by the thin-film heater 22. The vaporized power generation fuel gas is discharged from the outlet port 14 and supplied to the reforming unit 33.
The reforming unit 33 produces hydrogen by reforming the power generation fuel gas supplied from the fuel vaporizer 32. When the chemical reaction apparatus 100 having the arrangement of any embodiment described above is applied to this reforming unit 33, a reaction catalyst layer 15 for reforming is provided in the flow path 12 of the first substrate 11. The reaction catalyst layer 15 is made of a reforming catalyst such as Cu, ZnO, or Al2O3. As the first substrate 11, a glass substrate may also be used instead of a silicon substrate. When the power generation fuel gas (e.g., an aqueous solution of methanol: CH3OH+H2O) is supplied from the fuel vaporizer 32 into the flow path 12 of the reforming unit 33 through the inlet port 13, this power generation fuel gas is heated to a predetermined temperature, e.g., about 280° C. in the flow path 12 by the thin-film heater 22. This induces an endothermic reaction as indicated by
CH3OH+H2O→3H2+CO2 (1)
and produces hydrogen and carbon dioxide as a byproduct. In the initial stages of this reaction, water (H2O) on the left side of formula (1) above may be water contained in the fuel in the fuel unit 31. It is also possible to collect water produced when the power generator 36 to be described later generates electric power, and supply this water to the reforming unit 33. The supply source of water (H2O) on the left side of formula (1) in the reforming unit 33 may be the power generator 36 alone, both the power generator 36 and fuel unit 31, or the fuel unit 31 alone. During the reaction, carbon monoxide is sometimes produced, albeit in a slight amount, in the reforming unit 33 as in a chemical reaction formula indicated by
2CH3OH+H2O→5H2+CO+CO2 (2)
The products (hydrogen and carbon dioxide) on the right side of formula (2) above and the slight amount of carbon monoxide are discharged from the outlet port 14 of the reforming unit 33. Of the products discharged from the outlet port 14 of the reforming unit 33, the vaporized hydrogen and carbon monoxide are supplied to the water shift reaction unit 34 and selective oxidation reaction unit 35 in this order. The carbon dioxide is separated and discharged to the atmosphere.
The water shift reaction unit 34 and selective oxidation reaction unit 35 form a carbon monoxide removing unit 38 which removes carbon monoxide produced by the reforming unit 33. When the chemical reaction apparatus 100 having the arrangement of any embodiment described above is applied to this water shift reaction unit 34, a reaction catalyst layer 15 for removing carbon monoxide is provided in the flow path 12 of the first substrate 11. This reaction catalyst layer 15 is made of a selective oxidation catalyst such as Pt or Al2O3. As the first substrate 11, a glass substrate or the like may also be used instead of a silicon substrate. When the vaporized hydrogen and carbon monoxide are supplied from the reforming unit 33 into the flow path 12 of the water shift reaction unit 34 through the inlet port 13, these vaporized hydrogen and carbon monoxide are heated to a predetermined temperature, e.g., about 180° C. by the thin-film heater 22. Consequently, of the hydrogen, carbon monoxide, and water supplied into the flow path 12, the carbon monoxide and water cause a water shift reaction with the catalyst to produce hydrogen and carbon dioxide as a byproduct as indicated by
CO+H2O→H2+CO2 (3)
In the initial stages of this reaction, water (H2O) on the left side of formula (3) above may be water contained in the fuel in the fuel unit 31. It is also possible to collect water produced when the power generator 36 generates electric power, and supply this water to the water shift reaction unit 34. The supply source of water (H2O) on the left side of formula (3) in the water shift reaction unit 34 may be the power generator 36 alone, both the power generator 36 and fuel unit 31, or the fuel unit 31 alone.
The selective oxidation reaction unit 35 performs a heat treatment for the gas mixture supplied from the water shift reaction unit 34. If a very slight amount of carbon monoxide is contained in this gas mixture supplied from the water shift reaction unit 34, the selective oxidation reaction unit 35 selects the residual carbon monoxide by a catalyst, and brings the selected carbon monoxide into contact with oxygen taken from the atmosphere, thereby reliably removing the carbon monoxide by producing carbon dioxide by a chemical reaction indicated by
CO+(1/2)O2→CO2 (4)
The fluid finally reaching the outlet port 14 of the selective oxidation reaction unit 35 mostly consists of hydrogen and carbon dioxide.
The products after the series of reactions described above are hydrogen and carbon dioxide. Of these products, the carbon dioxide is separated from the hydrogen and discharged to the atmosphere. Accordingly, only the hydrogen is supplied from the selective oxidation reaction unit 35 to the power generator 36.
A space 44 is formed outside the cathode 41. Hydrogen is supplied into the space 44 from the carbon monoxide removing unit 38, and this hydrogen is supplied to the cathode 41. Also, a space 45 is formed outside the anode 42. Oxygen taken from the atmosphere via a check valve is supplied into this space 45, and this oxygen is supplied to the anode 42.
On the side of the cathode 41, hydrogen ions (protons; H+) are generated by separating electrons (e−) from hydrogen and move to the anode 42 through the ion conductive film 43, and the electrons (e−) are extracted by the cathode 41 and supplied to the charger 37, as indicated by
3H2→6H++6e− (4)
On the side of the anode 42, the electrons (e−) supplied via the charger 37, the hydrogen ions (H+) passing through the ion conductive film 43, and oxygen react with each other to produce water as a byproduct, as indicated by
6H++(3/2)O2+6e−→3H2O (5)
The series of electrochemical reactions (formulas (4) and (5)) as described above progress in an environment at a relatively low temperature from about room temperature to about 80° C., and the only byproduct except for electric power is basically water. This water produced as a byproduct by the power generator 36 is collected. If at least a portion of the water produced by the power generator 36 is supplied to the reforming unit 33 as described previously, the amount of water initially sealed in the fuel unit 31 can be reduced, and the amount of water to be collected can also be reduced.
The electric power thus generated by the power generator 36 is supplied to the charger 37. The charger 37 includes a power holding means such as a secondary battery or capacitor, and charges this secondary battery or capacitor with the electric power supplied from the power generator 36, thereby temporarily holding the supplied power. In addition, the charger 37 supplies the held electric power to an apparatus which is driven by this power supply system.
Fuel applied to a fuel reforming type fuel cell currently being researched and developed is liquid fuel, liquefied fuel, or gas fuel containing at least a hydrogen element. This fuel need only be fuel with which the power generator 36 can generate electric energy at a relatively high energy conversion efficiency. In addition to methanol described above, it is possible to preferably use alcohol-based liquid fuel such as ethanol or butanol, liquid fuel such as dimethylether, isobutane, or natural gas (CNG) which is vaporized at room temperature and atmospheric pressure and made of hydrocarbon, or gas fuel such as hydrogen gas.
In
As shown in
As shown in
When this fuel pack 310 is connected to the holder unit 320, a fuel delivery pipe 350 provided to in the holder unit 320 pushes the fuel supply valve 340 downward, and the power generation fuel 330 is delivered from a fuel supply pipe 360 to the power generating unit 200 via the fuel delivery pipe 350 by the surface tension or the fuel pump.
The power generating unit 200 includes components corresponding to the fuel vaporizer 32, reforming unit 33, water shift reaction unit 34, selective oxidation reaction unit 35, power generator 36, and charger 37 shown in
The charger 37 is formed into a microchip or the like and placed in, e.g., a projecting terminal 250 or another space in the power generating unit 200.
The power generating unit 200 includes a plurality of ventilation holes (slits) 260 for supplying external air from the circumferential surface of the column of the power generating unit 200 to the anode 42 (
In the power supply system having the above arrangement, the chemical reaction apparatus 100 of the present invention is applied to the fuel vaporizer 32, reforming unit 33, water shift reaction unit 34, and selective oxidation reaction unit 35. This increases the utilization of the thermal energy required to heat the flow path, and downsizes the power generating unit 200.
In the present invention as has been explained above, a chemical reaction apparatus including a heating element for heating a flow path has a heat radiation preventing film which covers the outermost surfaces of the chemical reaction apparatus. This heat radiation preventing film can suppress radiation of heat from the outer surfaces of each substrate. Accordingly, it is possible to suppress the thermal energy loss when the heating element heats the interior of the flow path, and increase the energy utilization.
Furthermore, this chemical reaction apparatus is well applicable to a fuel vaporizer, reforming unit, or carbon monoxide removing unit of a power supply system using a fuel reforming type fuel cell. In this case, the heat radiation preventing film suppresses the loss of the thermal energy required for heating for power generation, and increases the energy utilization. As a consequence, the power supply system can be downsized.
In each embodiment, a means which generates thermal energy by an electrical or combustion reaction is used as the heating element or heater for heating the flow path to allow a reaction of the internal chemical medium to occur. However, it can be understood that it is also possible to use another means for generating thermal energy by, e.g., a physical or chemical principle, such as electromagnetic waves.
Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2002-094271 | Mar 2002 | JP | national |
| 2003-069442 | Mar 2003 | JP | national |
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