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Publication numberUS20020022204 A1
Publication typeApplication
Application numberUS 09/925,655
Publication dateFeb 21, 2002
Filing dateAug 10, 2001
Priority dateAug 11, 2000
Publication number09925655, 925655, US 2002/0022204 A1, US 2002/022204 A1, US 20020022204 A1, US 20020022204A1, US 2002022204 A1, US 2002022204A1, US-A1-20020022204, US-A1-2002022204, US2002/0022204A1, US2002/022204A1, US20020022204 A1, US20020022204A1, US2002022204 A1, US2002022204A1
InventorsSusumu Nagano, Katsuyuki Ohsawa
Original AssigneeKabushiki Kaisha Toyota Chuo Kenkyusho
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Catalytic combustor
US 20020022204 A1
Abstract
The present invention provides a small-sized and lightweight catalytic combustor which can operate stably against variations of members to be heated. The catalytic combustor includes a heat-conductive separator for defining a combustion chamber and conducting heat to a member to be heated, the separator has projections and depressions in at least one part of a surface facing the combustion chamber, and an oxidation catalyst is supported on at least one part of the projections and depressions of the heat-conductive separator. By providing the projections and depressions in the surface of the heat-conductive separator, which faces the combustion chamber, a flow of a mixture of combustible materials and combustion-assisting materials can partly stay around the projections and depressions to enable a stable combustion thereof even at various flow rates.
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Claims(11)
What is claimed is:
1. A catalytic combustor comprising:
a heat-conductive separator for defining a combustion chamber and conducting heat to a member to be heated, at least one part of a surface of said heat-conductive separator, which faces said combustion chamber, having projections and depressions; and
an oxidation catalyst which is supported on at least one part of said projections and depressions of said heat-conductive separator.
2. A catalytic combustor as claimed in claim 1, wherein said projections and depressions have configurations which generate swirls in a flow of fluid within said combustion chamber.
3. A catalytic combustor as claimed in claim 1, wherein the height from projecting ends of said projections to bottoms of said depressions ranges from 0.4 to 1.0 mm.
4. A catalytic combustor as claimed in claim 1, wherein the number of sets of one of said projections and one of said depressions per unit length of said surface of said heat-conductive separator ranges from 0.5 to 10/cm.
5. A catalytic combustor as claimed in claim 1, further comprising a wall which is arranged so as to face said heat-conductive separator at a predetermined distance therefrom for defining said combustion chamber, said wall having a supply port for supplying at least one of a combustible material and a combustion-assisting material for burning said combustible material, to said combustion chamber.
6. A catalytic combustor as claimed in claim 5, wherein said supply port supplies said combustible material, and said combustion-assisting material is supplied via an end of a space defined by said surface of said heat-conductive separator, which has said projections and said depressions, and said wall which faces said heat-conductive separator.
7. A catalytic combustor as claimed in claim 5, wherein said supply port is composed of a plurality of supply ports which are arranged in multiple stages toward a downstream side of said combustion chamber.
8. A catalytic combustor as claimed in claim 1, wherein at least one part of a surface of said heat-conductive separator, which defines said member to be heated, has said projections and said depressions.
9. A catalytic combustor as claimed in claim 1, wherein said member to be heated is a heating chamber for reforming organic compounds to gas which contains hydrogen.
10. A catalytic combustor as claimed in claim 5, wherein at least one of said combustible material and said combustion-assisting material, which is supplied from said supply port, is injected toward said heat-conductive separator.
11. A catalytic combustor as claimed in claim 10, wherein said supply port supplies said combustible material, and said combustion-assisting material is supplied via an end of a space defined by said surface of said heat-conductive separator, which has said projections and said depressions, and said wall which faces said heat-conductive separator.
Description
BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a catalytic combustor for heating members to be heated.

[0003] 2. Description of Related Art

[0004] Fuel reformers for use in fuel cells generate hydrogen by bringing organic compounds into contact with fuel reforming catalysts in high temperature atmospheres. To keep high temperature atmospheres, some heating devices are required. The heating devices are auxiliary facilities of the fuel reformers, and accordingly it is preferable to make the heating devices as small and light as possible. Where the fuel cells are used in motor vehicles or the like, it is much required to make the heating devices small and light. The output of the fuel cells greatly varies with the operating conditions of motor vehicles, and accordingly, it is preferable that the fuel reforming rate of the fuel reformers, as well as the energy generated by the heating devices can greatly vary with the output of the fuel cells. More specifically, the heating devices for the fuel reformers are required to have reduced size and weight and to operate stably when the operating conditions varies. Such performance is also required in general heating devices as well as heating devices for the fuel reformers.

[0005] Examples of the conventional heating devices for heating members to be heated with combustion heat of fuel include a combustor having fuel injection ports which are distributed in multiple stages within a combustion chamber packed with catalyst pellets (Publication of unexamined Japanese patent application No. Hei 3-208803), a combustor in which a combustion catalyst is supported on surfaces of slit grooves which are formed in plates, and previously mixed fuel and air are supplied to combustion chambers (Publication of unexamined Japanese patent application No. Hei 6-111838) and a combustor in which a combustion catalyst is packed between a corrugated plate and a heat-conductive plate and previously mixed fuel and air are supplied to a combustion chamber (Publication of unexamined Japanese patent application No. Hei 9-255304).

[0006] These combustors as the conventional heating devices, however, have disadvantages as follows. In the combustors disclosed in Publications of unexamined Japanese patent applications Nos. Hei 3-208803 and Hei 9-255304, the combustion catalysts are packed in the combustion chambers. Accordingly, to make the combustors small and light, the diameter of the combustion catalysts or pellets which support the combustion catalyst must be decreased for improving the activity of the combustion catalysts. With this arrangement, however, the miniaturized combustion catalysts cause the increment of pressure loss with the result that fuel and air are required to be supplied under high pressure. Consequently, power of pumps or the like must be raised, and additional thermal heat capacity for the packed catalysts and pellets supporting catalysts is required.

[0007] The combustor disclosed in Publication of unexamined Japanese patent application No. Hei 6-111838 does not have a serious problem concerning pressure loss, but, where the supply rate of fuel or the like is varied for temperature adjustment, or where incombustible materials such as water is mixed with fuel in the case of exhaust gases of fuel cells being used as fuel, etc., it is impossible to keep the stable combustion, and consequently, flame failure may occur. In this case, uniform heating cannot be performed. In addition, the combustion chambers having slits-like configurations make it difficult to supply fuel to every combustion chamber uniformly, and accordingly, uniform heating of the members to be heated becomes impossible.

SUMMARY OF THE INVENTION

[0008] It is an object of the present invention to provide a catalytic combustor of a small size and light weight, which is capable of operating stably against variations of a member to be heated.

[0009] The present inventors have earnestly studied to achieve the above-described object, and as a result, they have completed the present invention.

[0010] The catalytic combustor in accordance with the present invention includes a heat-conductive separator for defining a combustion chamber and conducting heat to a member to be heated. At least one part of a surface of the heat-conductive separator, which faces the combustion chamber, has projections and depressions. And the catalytic combustor in accordance with the present invention further includes an oxidation catalyst which is supported on at least one part of the projections and depressions of the heat-conductive separator.

[0011] With the catalytic combustor in accordance with the present invention, pressure loss is small even with a reduced size and weight. And by supporting the oxidation catalyst on at least one part of the surface of the heat-conductive separator, heat can be conducted to the members to be heated prior to other members. In addition, the projections and depressions provided in the surface of the heat-conductive separator, which faces the combustion chamber, enable a flow of a mixture of combustible materials and combustion-assisting materials to partly stay therearound, whereby stable combustion can be effected even at widely ranged flow rates. Furthermore, if combustion-blocking materials such as water enter the combustion chamber in such a case that the catalytic combustor in accordance with the present invention is used in the fuel reformer, the projections and depressions provided in the heat-conductive separator enable the diffusion range of the combustion-blocking materials to be reduced. Accordingly, the risk of flame failure decreases, and, even if flame failure occurs, the diffusion range thereof becomes narrow.

[0012] The catalytic combustor in accordance with the present invention will be explained in detail. The following explanation will be made with reference to the catalytic combustor for heating a fuel reformer which is used in generating hydrogen to be supplied to a fuel cell. The catalytic combustor in accordance with the present invention is not limited to the catalytic combustor for the fuel reformer. The catalytic combustor in accordance with the present invention can be used in other general heating devices. Where the catalytic combustor in accordance with the present invention is used for heating the fuel reformer for a fuel cell, the performance of improved stability against load variations of the fuel cell, and the reduced size and weight is sufficiently achieved, which is preferable. Where the catalytic combustor in accordance with the present invention is used as a catalytic heater for a fuel reformer, it is preferable to arrange the fuel reformer by alternately layering the catalytic combustors of the present embodiment, fuel evaporating chambers (as members to be heated) and fuel reforming chambers (heating chambers) which support fuel reforming catalysts, considering the thermal efficiency. In this case, the fuel to be reformed can be also used as the fuel for the catalytic combustor.

[0013] The catalytic combustor in the present embodiment includes a heat-conductive separator and an oxidation catalyst. With the present catalytic combustor, a fluid of combustible materials such as hydrogen, alcohol of which one example is methanol, and/or hydrocarbon of which examples include town gas, gasoline, light oil, kerosene and heavy oil, along with combustion-assisting materials such as air flows into the combustion chamber, and reacts with an oxidation catalyst to generate heat. In the present embodiment, hydrogen which has been unable to use in fuel cells during normal operation, for example, can be used as the combustible material. In starting the fuel cells, hydrogen may not exist sufficiently so that fuel to be reformed is available. Of course, fuel to be reformed can be also used during normal operation, if required. Where the catalytic combustor of the present invention is used in devices other than fuel cells, other proper fuel can be used. Examples of the combustible materials further include carbon monoxide, butane, propane, ammonia, pulverized coal-containing gas, vegetable fat and oil, hydrogen sulfide in addition to the above-described hydrogen, alcohol, town gas, gasoline, light oil, kerosene and heavy oil. An oxygen gas and air are used as the combustion-assisting material. In addition, to use energy effectively, exhaust gases from air electrodes of fuel cells can be used as the combustion-assisting material.

[0014] The heat-conductive separator is a member defining a combustion chamber, having projections and depressions in at least one part of a surface thereof, which faces the combustion chamber, and conducting heat to members to be heated. The heat-conductive separator serves to combust the combustible materials by supporting a later-described oxidation catalyst on at least one part of the projections and depressions thereof. Accordingly, in the surface of the heat-conductive separator, oxidation reaction occurs positively. Thus, the heat-conductive separator is a member which is heated directly.

[0015] The combustion chamber is defined by the heat-conductive separator and other walls. Since the heat-conductive separator is a member which is heated directly, to heat the members to be heated efficiently, it is preferable to provide the heat-conductive separator on at least one side where the member to be heated exists. With this arrangement, heat generated by the oxidation catalyst is conducted directly to the member to be heated via the heat-conductive separator. For example, where the member to be heated exists on only one side of the combustion chamber, it is preferable to provide the heat-conductive separator on only such side. If the heat-conductive separator is provided on only the side where the member to be heated exists, oxidation reaction is not promoted on the other walls so that generated heat is conducted to the member to be heated prior to other members, which is preferable.

[0016] The material of the heat-conductive separator is not limited specifically. Any metal, ceramics, semiconductor, and resin composite material will do as far as the thermal conductivity is high and stability is good at normally operating temperatures of the catalytic combustor. The configuration of the combustion chamber defined by the heat-conductive separator is not limited specifically. Any configuration such as a film-like configuration or groove-like configuration will do. For the view of easy manufacturing it is preferable that the combustion chambers, each having a rectangular film-like configuration, and members to be heated are alternately layered.

[0017] The heat-conductive separator has projections and depressions in at least one part of a surface thereof, which defines the combustion chamber. The projections and depressions provided in the surface of the heat-conductive separator enable heat generated due to the oxidation reaction in the oxidation catalyst to be conducted efficiently, and affect the flow of the fluid within the combustion chamber to achieve the micro flame-holding function. Consequently, the combustion efficiency of the combustible materials is improved and the efficient operation becomes possible. Since the surface of the heat-conductive separator, which faces the combustion chamber, is divided by the projections and the depressions, foreign substances such as water, which are intermixed, are prevented from diffusing on the surface of the heat-conductive separator, which has projections and depressions, thereby reducing the effect on the catalyst function to the minimum. Furthermore, to obtain the micro flame-holding function to the maximum, it is preferable that the projections and the depressions have such configurations as to generate swirls in a fluid flow within the combustion chamber. The micro flame-holding function is achieved by forming disorder of the fluid flow as well as small-sized recycling areas of fluid on rear sides of the projections and depressions of the surface of the heat-conductive separator with respect to the fluid flow. For example, the projections and depressions can have configurations provided with angular parts, such as rectangular, trapezoidal, columnar, or triangular pyramid-like configuration or the like, with respect to the fluid flow. In particular, it is preferable to have such angular parts on rear sides of the projections and depressions with respect to the fluid flow.

[0018] The arrangement of the projections and depressions is not limited specifically. Examples thereof include a combination of continuous depressions and scattering projections, and a combination of continuous projections and scattering depressions. The preferred combination is composed of continuous depressions and scattering projections, considering the pressure loss. The arrangement of the projections and depressions in the surface of the heat-conductive separator may be regular or irregular. For reducing the pressure loss, it is preferable to arrange them so as not to resist the fluid flow as far as possible. Accordingly, it is preferable to adjust the arrangement of the projections and depressions so as to form passages in parallel to the fluid flow. For example, they may be arranged in the direction along the fluid flow, or they may be arranged at identical intervals. With these arrangements, the resistance to the fluid flow can be reduced. Therefore, it is preferable to decrease the length of each of the projections and depressions in directions perpendicular to the fluid flow, because the passage for fluid flow can be enlarged. However, if the length in the directions perpendicular to the fluid flow is too short, the effect of generating disordered flows decreases. Accordingly, it is preferable to adjust such length to a proper length in accordance with the using conditions.

[0019] The preferred height from projecting ends of the projections to bottoms of the depressions ranges from 0.4 to 1.0 mm. In the case of less than 0.4 mm, the effect resulted from the projections and depressions decreases. In the case of more than 1.0 mm, the increase of such effect is small. The most suitable height from the projecting ends of the projections to the bottoms of the depressions is greatly affected by the configurations of the projections and depressions. The preferred number of sets of one projection and one depression per unit length of the surface of the heat-conductive separator ranges from 0.5 to 10/cm. Outside this range, the effect resulted from the projections and depressions decreases. The density of these projections and depressions is also affected greatly by the configurations thereof.

[0020] These projections and depressions may be provided by forming them integrally with the heat-conductive separator with pressing, etching, cutting or the like method, or by previously forming projections, and securing the projections to a surface of a member for defining the heat-conductive separator, thus forming an integral heat-conductive separator.

[0021] In addition, it is preferable to further provide projections and depressions in a surface of the heat-conductive separator, which faces a member to be heated. By providing these projections and depressions, the thermal conductivity is improved. When the member to be heated is fluid such as gas and liquid, the heat can be conducted efficiently. In particular, this arrangement is preferable where the member to be heated is a heating chamber for reforming organic compounds to hydrogen-containing gas, and the heat-conductive separator defines the heating chamber, too. The configurations of these projections and depressions formed in the surface facing the member to be heated do not differ from those formed in the surface facing the combustion chamber. The effect of disordering the fluid is not needed. It is sufficient to enlarge the specific surface area. The method for forming these projections and depressions is similar to the case where they are formed in the surface facing the combustion chamber.

[0022] The configuration of walls other than the heat-conductive separator, which define the combustion chamber, is not limited specifically. It is preferable that the wall which faces the heat-conductive separator is provided with supply ports for supplying at least one of combustible materials and combustion-assisting materials to the combustion chamber. By previously arranging these supply ports in accordance with the arrangement of the members to be heated and the heating conditions such as a heating temperature, which were required by the member to be heated, or by arranging these supply ports adjustably in accordance with the variations of these heating conditions, more precise heating can be effected. For example, by arranging the supply ports uniformly to enable the combustible materials to be supplied to the heat-conductive separator uniformly, the heat-conductive separator is heated uniformly. By arranging the supply ports so as to correspond to parts of the member to be heated, which are required to be heated, efficient heating can be effected. It is preferable that these supply ports have a reduced opening diameter. The reduced opening diameter thereof enables the increment of the supply flow rate, and accordingly the possibility of backfire decreases even when heating is carried out with a low output. The increase of the pressure of the combustible materials supplied into the combustion chamber, which is caused by the reduced opening diameter of these supply ports, can be prevented by increasing the number of supply ports. With this arrangement, a proper pressure can be obtained. The configuration of the supply ports is not limited specifically. It is preferable to have such a configuration as to enable the combustible materials or the like which are supplied into the combustion chamber to flow in directions approximately perpendicular to the heat-conductive separator. By supplying the combustible materials so as to inject toward the heat-conductive separator, the combustible materials can reach oxidation catalysts more surely, and consequently a precise temperature control can be performed.

[0023] Supply ports for supplying the combustible materials or the like into the combustion chamber can be provided in walls other than the wall facing the heat-conductive separator. Where no supply port is provided in the wall facing the heat-conductive separator, other walls must have such supply ports. The heat-conductive separator and walls other than the wall facing the heat-conductive separator can have such supply ports. Where the combustion chamber is a rectangular configuration, such supply ports can be provided at an end of a space defined between the surface of the heat-conductive separator, which has projections and depressions, and the wall facing the heat-conductive separator. With this arrangement, the fluid flow can be directed in parallel with the heat-conductive separator to improve the disordered flows-generating effect due to the projections and depressions. Accordingly, the combustion stabilizing effect can be preferably achieved.

[0024] In addition, outlet ports for discharging gas after reacting with the oxidation catalyst can be provided in the heat-conductive separator or other walls. The positions for providing the outlet ports are not limited specifically.

[0025] The oxidation catalyst is supported on at least one part of the surface of the heat-conductive separator, which has projections and depressions and faces the combustion chamber, and serves to generate the reaction of the combustible materials and the combustion-assisting materials. The oxidation catalyst is not required to be supported on the entire surface of the heat-conductive separator, which has projections and depressions, and may be supported on surfaces other than the surface of the heat-conductive separator, which has projections and depressions. By supporting the oxidation catalyst on the surface having projections and depressions, precise heating adjustment can be achieved, as described above. The supporting amount of the oxidation catalyst is not limited specifically. A proper amount of oxidation catalyst may be supported. The preferred positions in which the oxidation catalyst is supported, and the preferred supporting amount of the oxidation catalyst will be explained in accordance with following four types of operating conditions. {circle over (1)} Where the catalytic combustor may start slowly and frequently operates under a normal state of 200° C. or more, and if water or other materials which obstruct the combustion is not greatly intermixed, the oxidation catalyst may operate only around the supply ports, and a small amount of the oxidation catalyst may be supported only around the supply ports. {circle over (2)} Where the catalytic combustor may start slowly, but the load variation after starting is large, even if the action of oxidation catalyst at each gas recycling area of the rear side of projections and depressions against fluid flow is small, it does not greatly affect the heat adjustment. Accordingly, it is unnecessary that the each rear side of the projections and depressions supports a large amount of oxidation catalyst. {circle over (3)} As the conditions {circle over (2)} approach the conditions {circle over (1)}, it is possible to further decrease the supporting amount of oxidation catalyst gradually from lateral sides of the projections and depressions against the fluid flow in order. {circle over (4)} Where the starting speed is rapid, load drastically varies, and water drops or other materials which obstruct combustion are expected to be intermixed, it is preferable that the entire surface having the projections and depressions supports the oxidation catalyst.

[0026] Examples of the elements which can operate as the oxidation catalyst include alloys or mixtures of one or more of Pt, Pd, Rh, Re, Ru, Au, Ag, Cu, Ni, Co, Fe, Cr, La, Ce, Mo, Nb, V, Zr, Y, Sr, K, Ca, Mg, Na and Ba. These elements can be used as simple substances or compounds.

[0027] The oxidation catalyst is generally used by supporting it on a support, and is used with a promoter, as required. Examples of the support and promoter include oxides and simple metals of Al, Mg, Fe, Co, Ni, Zn, Ti, V, Cr, Ce, La, Li, Na, K, Ca, Sr, Y, Nb, Mo and Ba, and include composite bodies or mixtures of one or more kinds thereof.

[0028] To support the oxidation catalyst on the surface having projections and depressions, a well-known method can be adopted. For example, first, a support is formed on the surface having projections and depressions into a layer to obtain a support layer. By forming the support layer, the surface area increases and the efficiency of the catalyst is enhanced. Then, the oxidation catalyst is supported on the support layer. To form the support layer, and to support the oxidation catalyst on the support layer, well-known methods can be adopted. In addition, by using the heat-conductive separator of which the surface is composed of a porous material, the oxidation catalyst can be supported on the heat-conductive separator without forming any support layer.

[0029] The combustible materials and combustion-assisting materials may be supplied to the combustion chamber as a mixture thereof, or separately. It is preferable to supply them separately, because there does not occur backfire of the combustion of the combustion chamber via the supply ports. The preferred method for supplying the combustible materials and the combustion-assisting materials includes the steps of supplying the combustion-assisting materials such as air into the space defined by the heat-conductive separator and the wall which faces the separator in parallel with these members, and supplying the combustible materials from the supply ports provided in the wall which faces the separator according to demand. With this method, the combustion temperature can be precisely adjusted, and backfire or the like can be prevented. And the combustible materials need not be supplied to the combustion chamber uniformly. It is desirable to vary the supply amount of the combustible materials in accordance with the requirement by the member to be heated. The supplying phase of the combustible materials can be arbitrarily varied in accordance with the condition of the combustible materials. If the combustible materials are initially liquid, for example, the supplying phase thereof may be not varied or may be varied into gas by heating. If the combustible materials are initially gas, they may be supplied in a gas phase.

[0030] The catalytic combustor in accordance with the present invention can achieve the operational effect that the combustion state in the combustion chamber can be readily controlled, and a stable operation can be effected against the variations of the members to be heated.

[0031] In addition, the catalytic combustors in accordance with the present invention can achieve the operational effect that the catalytic combustor can be made small and light as required under conditions capable of restraining the degradation of the various performance of the catalytic combustors to a minimum.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032]FIG. 1 is a schematic view explaining the constructions of catalytic combustors of one embodiment of the present invention and a comparative example;

[0033] FIGS. 2(a), 2(b), 2(c) and 2(d) are contour maps of combustion efficiencies, each showing the result of a combustion efficiency test of hydrogen in a catalytic combustor of the present invention;

[0034] FIGS. 3(a), 3(b), 3(c) and 3(d) are contour maps of combustion efficiencies, each showing the result of a combustion efficiency test of methanol in a catalytic combustor of the present invention;

[0035] FIGS. 4(a) and 4(b) are views, each showing a surface of a heat-conductive separator, which has projections and depressions, in catalytic combustors of third and fourth embodiments of the present invention; and

[0036]FIG. 5 is a graph showing the result of a temperature distribution measuring test in a catalytic combustor of one embodiment of the present invention.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EXEMPLARY EMBODIMENTS

[0037] [Embodiment]

[0038] Hereinafter, the catalytic combustor in accordance with the present invention will be explained in more detail based on several embodiments.

[0039] [Catalytic Combustor]

[0040] The catalytic combustor which was used in tests is schematically illustrated in FIG. 1. The catalytic combustor of the present embodiment includes a heat-conductive separator 1 which has projections and depressions in one part 10 (78 mm×49 mm) of a surface which faces a combustion chamber, a catalyst layer (not shown) which is supported on the part 10, a wall 2 which has supply ports 21 (opening diameter 0.3 mm, 12 ports) for supplying fuel toward the part 10, faces the heat-conductive separator 1, and defines the combustion chamber with the heat-conductive separator 1, a plate-like member 3 which is located to face the wall 2 on the opposite side of the combustion chamber and defines one part (52) of a fuel supply passage, an air supply passage 4 which is communicated with a supply port which opens at one end of the heat-conductive separator 1, and a gas discharge passage 6 which is communicated with an outlet port of a combustion gas, which opens at the other end of the heat-conductive separator 1.

[0041] To support a catalyst on the surface having projections and depressions, a mixture of AL2O3 and Pt was supported by a thickness of 50 μm toward the part 10 with a normal supporting method. A resultant layer contains 100 parts by weight of AL2O3 and 10 parts by weight of Pt.

[0042] The height of the projections in the part 10, which was denoted by H, in each of the catalytic combustors of the embodiments and a conventional catalytic combustor was 0.4 mm, 0.6 mm, 0.75 mm (Embodiments 1 to 3), 0 mm (Comparative example). The width of each of the projections and depressions was 1 mm (5 sets of projection and depression/cm), and the distance between each projecting end and the wall 2 was all 0.5 mm. And, the length of each of the projections and the depressions in directions perpendicular to the fluid flow was 1 mm, and the distance between adjacent two projections or depressions was 1 mm.

[0043] In addition, a catalytic combustor of which H was 0.75 mm and the supply ports was six was prepared as the catalytic combustor of a fourth embodiment.

[0044] [Measurement of Combustion Efficiency]

[0045] The combustion efficiency of fuel in the present catalytic combustor was measured using two kinds of model fuel: {circle over (1)} exhaust gas (hydrogen/carbon dioxide=38%/62% (volume ratio) from a fuel electrode of a fuel cell of which the hydrogen utilization factor is 80% and {circle over (2)}100% methanol.

[0046] [Measuring Method]

[0047] With respect to the model fuel {circle over (1)}, air and model fuel were respectively supplied to the air supply passage 4 and fuel supply passage 51 of each of the catalytic combustors of Embodiments 1 to 4, and Comparative example in predetermined air and fuel flow rates. Next, the fuel concentration in the exhaust gas which is discharged from the gas discharge passage 6 was measured with gas chromatography, and the combustion efficiency was measured from the measured fuel concentration in the exhaust gas and the fuel concentration of an inlet gas. At the same time, pressure loss in each of the air supply passage 4 and the fuel supply passage 51 was measured.

[0048] With respect to the model fuel {circle over (2)}, air and model fuel were respectively supplied to the air supply passage 4 and fuel supply passage 51 of each of the catalytic combustors of Embodiments 1 to 3 in predetermined air and fuel flow rates, and a mixture gas containing air and fuel in a predetermined mixing ratio was supplied to the catalytic combustor of Embodiment 3 via the fuel supply passage 51.

[0049] [Measurement Result]

[0050] The measurement result of the combustion efficiency of the model fuel {circle over (1)} is shown in FIG. 2 (a: comparative example, b: Embodiment 1, c: Embodiment 2, d: Embodiment 3), and the measurement result of the combustion efficiency of the model fuel {circle over (2)} is shown in FIG. 3 (a: Embodiment 1, b: Embodiment 2, c: Embodiment 3, d: Embodiment 3 (mixture gas)). In FIG. 2, the hydrogen flow rate in ordinate is the flow rate in terms of hydrogen element in the standard state. And in FIG. 3, the methanol flow rate in ordinate is the flow rate in terms of liquid methanol in the standard condition.

[0051] The measurement result concerning the model gas {circle over (1)} shows that as H increases from 0 mm (comparative example) to 0.6 mm (Embodiment 2) via 0.4 mm (Embodiment 1), the range wherein the combustion efficiency is high enlarges drastically. Furthermore, when H increases to 0.75 mm (Embodiment 3), the range wherein the combustion efficiency is high further enlarges, as compared with the range of Embodiment 2, but the enlarging speed was gentle. Accordingly, it is considered that the elevation of the combustion efficiency is saturated when H is about 0.6 to 0.75 mm.

[0052] The measurement result concerning the model gas {circle over (2)} shows that as H increases from 0.4 mm (Embodiment 1) to 0.75 mm (Embodiment 3), the range wherein the combustion efficiency is high enlarges drastically.

[0053] Although the measurement result is not shown, the range of fuel air ratio (that is the range wherein the combustion efficiency is high) which was measured using vapor phase burners with similar fuel gas was remarkably narrow, as compared with the case of the catalytic combustor of the present invention.

[0054] With respect to the model gas {circle over (1)}, the pressure loss in the comparative example was about 0.15 N/cm2 in the air flow rate of 4 L/min, and about 0.20 N/cm2 in the air flow rate of 6 L/min. On the other hand, the pressure loss in the present embodiment was as low as about 0.15 N/cm2 in the air flow rate of 3 L/min, and about 0.20 N/cm2 in the air flow rate of 5 L/min, and a large lowering of the pressure loss was not observed, as compared with that of the comparative example. With respect to the pressure loss on the fuel side, a large lowering thereof was not observed in the catalytic combustors of both the comparative example and the present embodiment.

[0055] Accordingly, with the catalytic combustor of the present embodiment, it was possible to keep the combustion at a high efficiency even when the operating conditions (flow rate of air and fuel, and mixing ratio thereof) are greatly varied. And, this effect can be achieved without a large increment of pressure loss. Accordingly, it has been clarified that only a small amount of energy is required by an auxiliary power such as pumps for operating the present catalytic combustor.

[0056] The projections and depressions formed in the part 10 of the heat-conductive separator 1 of the catalytic combustors of the embodiments 3 and 4 were observed. As a result, as shown in FIG. 4, combusted areas (a: Embodiment 3, b: Embodiment 4) were observed. This observation result shows that combustion was carried out approximately uniformly around each supply port.

[0057] [Temperature Distribution Measuring Test]

[0058] Testing Methods and Testing Conditions

[0059] The catalytic combustor of Embodiment 3 was operated under following three operating conditions, and the temperature of the surface 11 of the separator 1, which faces the heating chamber, was measured at each of seven measuring points 111 to 117.

[0060] {circle over (1)} A gas obtained by mixing methanol and air such that the flow rate of methanol is 0.6 ml/min and the flow rate of air is 3 L/min was supplied from the air supply passage 4. {circle over (2)} A gas obtained by mixing methanol and air such that the flow rate of methanol is 0.6 ml/min and the flow rate of air is 3 L/min was supplied from the fuel supply passage 51. {circle over (3)} A gas containing hydrogen and carbon dioxide in the composition ratio of 38% to 62% (volume ratio) was supplied to the fuel supply passage 51 in the flow rate of 0.5 L/min in terms of hydrogen element under the standard state, and air was supplied from the air supply passage 4 in the flow rate of 3 L/min.

[0061] [Result]

[0062] The testing result is shown in FIG. 5. As is apparent from FIG. 5, in the operating conditions {circle over (2)} and {circle over (3)} wherein fuel is supplied from the supply ports of the wall 2 which faces the heat-conductive separator 1, variations in the resultant temperature distributions were small. In contrast, in the operating condition {circle over (1)} wherein fuel is supplied from one side of the combustion chamber, the temperatures at the measuring points 112 to 114 were high whereas those at the measuring points 115 and 116 were low, whereby there occurred a great difference in temperature distribution. The reason for these results is considered as follows. In the method of supplying fuel from one side of the combustion chamber, as the fuel passes the measuring points 112 through 116, the combustion thereof is completed so that the combustion cannot be maintained. In addition, upon measuring the temperature of the oxidation catalyst, and that of the fuel supply passage 52, the temperature of the oxidation catalyst did not much differ from that of the surface 11 which faces the heating chamber, and the temperature on the side of the fuel supply passage 52 was as low as about 100 to 200° C. These results show that the combustion heat was conducted to the side of the heating chamber prior to other sides.

[0063] Small variations in the temperature distributions in the conditions {circle over (2)} and {circle over (3)} are considered to be caused by the supply ports being uniformly distributed in the wall 2 facing the separator 1. And by properly adjusting the fuel supply rate and air supply rate, the temperature can be controlled freely.

[0064] Accordingly, by supplying fuel from the supply ports of the wall 2, the temperature distribution as well as the temperature can be freely adjusted as required. In addition, by adjusting the arrangement of the heat-conductive separator 1, thermal conduction can be also controlled.

[0065] While the invention has been described in connection with what are considered presently to be the most practical and preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US7096671Oct 14, 2003Aug 29, 2006Siemens Westinghouse Power CorporationCatalytic combustion system and method
US8039157Dec 1, 2005Oct 18, 2011Nissan Motor Co., Ltd.Startup method for fuel cell stack structure, temperature control method for fuel cell stack structure, and fuel cell stack structure
US8609295Oct 21, 2005Dec 17, 2013Nissan Motor Co., Ltd.Solid-electrolyte fuel cell and stack structure
Classifications
U.S. Classification431/7, 431/268
International ClassificationH01M8/06, B01J23/42, F23D11/40, F23C13/00
Cooperative ClassificationF23C13/00
European ClassificationF23C13/00