Heated reformer and fuel cell system having the same

A fuel cell system is provided comprising: a reformer for generating hydrogen from hydrogen-containing fuel; and at least one electricity generator for generating electric energy through an electrochemical reaction of hydrogen and oxygen. The reformer includes a main body in which a plurality of reaction sections for generating hydrogen from hydrogen-containing fuel is integrally formed. A heating section is disposed in contact with the main body in order to supply different amounts of thermal energy to the plurality of reaction sections.

CROSS-REFERENCES TO RELATED APPLICATION

This application claims priority to and the benefit of Korean Patent Application Nos. 10-2004-0071668 filed on Sep. 8, 2004, and 10-2004-0077061 filed on Sep. 24, 2004, both applications filed in the Korean Intellectual Property Office, the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a fuel cell system and more particularly to a fuel cell system having an improved reformer.

BACKGROUND OF THE INVENTION

As is well known, a fuel cell is a system for generating electric energy through an electrochemical reaction between oxygen and hydrogen contained in hydrocarbon materials such as methanol, ethanol, and natural gas.

Recently developed polymer electrolyte membrane fuel cells (hereinafter, referred to as PEMFCs) exhibit excellent output characteristics, low operating temperatures, and fast starting and response characteristics. Therefore, the PEMFCs have a wide range of application including as mobile power sources for vehicles, as distributed power sources for homes or buildings, and as small-sized power sources for electronic apparatuses.

A fuel cell system employing the PEMFC scheme basically includes a stack, a reformer, a fuel tank, and a fuel pump. The fuel pump supplies fuel stored in the fuel tank to the reformer which reforms the fuel to generate hydrogen. The hydrogen and an oxygen supply such as air are fed to the stack which constitutes an electricity generator set having a plurality of unit cells.

In such a conventional fuel cell system, the reformer generates hydrogen from the hydrogen-containing fuel through a catalytic chemical reaction using thermal energy. Accordingly, the reformer generally includes a heat source for generating the thermal energy, a reforming reactor for absorbing the thermal energy and generating hydrogen gas from the fuel, and one or more carbon-monoxide reducing reactors for reducing the concentration of carbon monoxide in the hydrogen gas.

In such a conventional reformer, since the reforming reactor and the carbon-monoxide reducing reactors are separate from one another, the heat source should be separately provided to supply different ranges of thermal energy to the reforming reactor and the carbon-monoxide reducing reactor, respectively.

Therefore, since the structure of the reformer is complex, it is difficult to make the entire fuel cell system compact. In addition, since the heat exchange between the reaction parts is carried out through pipes, its heat delivery properties are inefficient.

SUMMARY OF THE INVENTION

The present invention is directed to a reformer having improved performance and a simple structure, and a fuel cell system having the reformer.

According to one embodiment of the present invention, a reformer for a fuel cell system comprises: a main body in which a plurality of reaction sections are provided in order to generate hydrogen from a hydrogen-containing fuel; and a heating section which is disposed in contact with the main body and which supplies different amounts of thermal energy to the different reaction sections.

The plurality of reaction sections may include a reforming reaction section for generating hydrogen gas from the hydrogen-containing fuel, and at least one carbon-monoxide reducing section for reducing the concentration of carbon monoxide contained in the hydrogen gas.

In one embodiment of the invention, the main body has a tubular shape of which the inner space is divided into a plurality of spaces. A reformer inlet may be formed at one end of the main body and a reformer outlet may be formed at the other end. The reaction sections are formed in the divided spaces.

In one embodiment of the invention, the heating section includes a resistance wire of a coil shape wound around the outer circumferential surface of the main body. The resistance wire may be wound around the outer circumferential surface of the main body at varying pitch to place different numbers of windings at each of the different reaction sections in order to provide a desired temperature profile to the reaction sections.

In one embodiment of the invention, the number of windings of the resistance wire in the area corresponding to the reforming reaction section is greater than that in the area corresponding to the carbon-monoxide reducing section.

The inner space of the main body may include one or more barriers for separating the different reaction sections. A suitable barrier is made of a mesh material.

The reformer may further comprise a heat insulating jacket surrounding the main body. The heat insulating jacket may include an inner wall and an outer wall surrounding the entire inner wall, the inner and outer walls being separated by a predetermined gap which in one embodiment of the invention, is maintained in a vacuum.

Suitable materials for construction of the inner wall and the outer wall include ceramics, stainless steel, and aluminum.

In another embodiment of the invention, the main body may be of a plate shape in which a channel for passing the fuel is formed. The channel generally includes a reformer inlet and a reformer outlet and may be provided as a sequence of U-bends which together form a serpentine shape.

According to this embodiment, the heating section may include a heating plate coupled to the channel-forming surface of the main body with a resistance wire pattern formed on one surface of the heating plate.

The resistance wire pattern in the area corresponding to the carbon-monoxide reducing section is configured to provide less heating than is provided to the area corresponding to the reforming reaction section in order to produce a desired temperature profile. This may be accomplished by providing different gaps, widths, or thicknesses in the resistance wire.

The gap of the resistance wire pattern in the area corresponding to the carbon-monoxide reducing section may be larger than that in the area corresponding to the reforming reaction section. Alternatively, the thickness or width of the resistance wire pattern in the area corresponding to the carbon-monoxide reducing section may be greater than that in the area corresponding to the reforming reaction section.

The plurality of reaction sections may further include a vaporization section for vaporizing the fuel before it is fed to the reformer section.

The carbon-monoxide reducing section may include a water-gas shift reaction section for reducing the concentration of carbon monoxide contained in the hydrogen gas through a catalytic water-gas shift reaction of the hydrogen gas.

The carbon-monoxide reducing section may alternatively or additionally include at least one CO oxidation section for reducing the concentration of carbon monoxide contained in the hydrogen gas through a preferential catalytic CO oxidation reaction.

The respective reaction sections may include catalyst provided in known configurations such as pellet-shaped catalyst or honeycomb-shaped catalyst.

The main body may be made of a material selected from the group consisting of stainless steel, aluminum, copper, and iron.

According to an embodiment of the present invention, a fuel cell system is provided comprising: a reformer as described above for generating hydrogen from a hydrogen-containing fuel; and at least one electricity generator for generating electric energy through an electrochemical reaction of hydrogen and oxygen.

The fuel cell system may further comprise a fuel supply unit for supplying the fuel to the reformer and an oxygen supply unit for supplying oxygen to the reformer and the electricity generator. The oxygen supply unit may include at least one air pump for supplying air to both the reformer and the electricity generator.

DETAILED DESCRIPTION

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the attached drawings such that the present invention can be easily put into practice by those skilled in the art. However, the present invention is not limited to the exemplary embodiments, but may be embodied in various forms.

FIG. 1is a block diagram schematically illustrating an entire construction of a fuel cell system according to an embodiment of the present invention.

Referring toFIG. 1, the fuel cell system100according to the present invention has a polymer electrode membrane fuel cell (PEMFC) scheme, in which a hydrogen-containing fuel is reformed to generate hydrogen which is electrochemically reacted with oxygen to generate electric energy.

The fuel used for generating electricity in the fuel cell system100may include any liquid fuel or gas fuel containing hydrogen such as methanol, ethanol, or natural gas. However, a liquid fuel is exemplified in the following description.

The fuel cell system100may utilize pure oxygen stored in an additional storage device as the oxygen that is reacted with the hydrogen, or may utilize air as the oxygen source. However, the latter is exemplified in the following description.

The fuel cell system100basically comprises at least one stack10for generating electric energy through an electrochemical reaction between hydrogen and oxygen, a reformer30for generating the hydrogen from the fuel, a fuel supply unit50for supplying the fuel to the reformer30, and an oxygen supply unit70for supplying oxygen to the stack10and the reformer30.

FIG. 2is an exploded perspective view illustrating the stack shown inFIG. 1. The stack10has an electricity generator set in which a plurality of electricity generators11are arranged in a stacked configuration.

The electricity generator is a unit fuel cell for generating electricity in which separators (also referred to as “bipolar plates” in the art)16are disposed on both sides of a membrane-electrode assembly (MEA)12.

The MEA12has a predetermined active area where the electrochemical reaction of hydrogen and oxygen occurs. The MEA12includes an anode electrode formed on one surface, a cathode electrode formed on the other surface, and an electrolyte membrane formed between both electrodes.

The anode electrode converts hydrogen into hydrogen ions (protons) and electrons through an oxidation reaction of the hydrogen. The cathode electrode generates heat and moisture of a predetermined temperature through a reduction reaction of the hydrogen ions and the oxygen. The electrolyte membrane performs an ion exchange function of moving the hydrogen ions generated from the anode electrode to the cathode electrode.

The separator16functions as a conductor for connecting an anode electrode with the adjacent cathode electrode in series, as well as for supplying hydrogen and oxygen to both sides of the MEA12throughout passages17formed on surfaces of the separator16.

The outermost sides of the stack10may be provided with additional pressing plates13and13′ for bringing a plurality of electricity generators11into close contact with each other. Alternatively, the stack10according to the present invention may be constructed such that the separators16located at the outermost sides of the plurality of electricity generators11function as the pressing plates.

One pressing plate13is provided with a first inlet13afor supplying the hydrogen generated from the reformer30to the electricity generators11and a second inlet13bfor supplying the air supplied from the oxygen supply unit70to the electricity generators11. The other pressing plate13′ is provided with a first outlet13cfor discharging the non-reacted hydrogen gas from the electricity generators11and a second outlet13dfor discharging the non-reacted air containing the moisture generated through the coupling reaction between hydrogen and oxygen from the electricity generators11.

In the present invention, the reformer30generates hydrogen from hydrogen-containing fuel through a catalytic chemical reaction using thermal energy. The structure of the reformer30will be described in detail later with reference toFIGS. 3 and 4.

The fuel supply unit50for supplying the fuel to the reformer30includes a fuel tank51for storing the liquid fuel, and a fuel pump53which is connected to the fuel tank51and which discharges the liquid fuel from the fuel tank51. An additional tank (not shown) supplying water to the reformer30may be further provided, and is within the scope of the present invention. Here, the reformer30and the fuel tank51are connected to each other through a first supply line91. The reformer30and the first inlet13aof the electricity generators11are connected to each other through a second supply line92.

The oxygen supply unit70includes at least one air pump71for supplying air with a predetermined pumping power to the reformer30and the electricity generators. The air pump71and the second inlet13bof the stack10are connected to each other through a third supply line93. The air pump71and the reformer30are connected to each other through a fourth supply line94.

A first embodiment of the reformer30according to the present invention will be described in detail with reference to the attached drawings.

FIG. 3is an exploded perspective view illustrating a reformer according to the first embodiment of the present invention andFIG. 4is a cross-sectional view of the reformer shown inFIG. 3.

Referring to the figures, the reformer30according to the present embodiment comprises a tubular main body31having an inner space, a plurality of reaction sections35formed in partitioned spaces of the inner space of the main body31and which generate hydrogen from fuel, and a heating section37which comes in contact with the outer circumferential surface of the main body31and which supplies the thermal energy necessary for reactions to occur in the respective reaction sections35. That is, a plurality of reaction sections35is integrally formed with the main body31.

In the present embodiment, the main body31has a reformer inlet32formed at one end and a reformer outlet33formed at the other end. The reformer inlet32and the fuel tank51of the fuel supply unit50are connected through the first supply line91. The reformer outlet33and the first inlet13aare connected through the second supply line92.

The main body31may be made of a material such as stainless steel, aluminum, copper, iron, or the like.

The inner space of the main body31is partitioned with barriers36and the reaction sections35are disposed in the partitioned spaces, respectively. The barriers36are formed as perforated disks with a plurality of bores36awhich allow the reaction gas to pass successively through the respective reaction sections35to the reformer outlet33while substantially partitioning the inner space of the main body31. It should be noted that while the barriers36are described as perforated disks, other arrangements such as a mesh configuration may also be used.

In this particular embodiment of the invention, the inner space of the main body31is partitioned into three spaces by the barriers36. A first reaction section41, a second reaction section42, and a third reaction section43are sequentially formed from the reformer inlet32to the reformer outlet33. However, this embodiment is not intended to limit the present invention. Accordingly, the inner space of the main body31may be partitioned into more or fewer spaces.

For this embodiment, the first reaction section41is a reforming reaction section for generating hydrogen gas from fuel through a catalytic steam reforming (SR) reaction of the fuel. The second reaction section42and the third reaction section43are carbon-monoxide reducing sections which substantially reduce the concentration of the carbon monoxide contained in the hydrogen gas.

The first reaction section41disposed in the vicinity of the reformer inlet32is supplied with the fuel from the fuel tank51through the first supply line91. The first reaction section41vaporizes the fuel and causes the steam reforming catalytic reaction to generate hydrogen from the vaporized fuel. The first reaction section41includes a reforming catalyst41afor promoting the steam reforming reaction of the fuel. The catalyst41ahas a pellet shape and is filled in the inner space of the main body31corresponding to the first reaction section41. The catalytic steam reforming reaction that takes place in the first reaction section41is an endothermic reaction and the reaction temperature ranges from about 300° C. to 600° C.

The second reaction section42is disposed successive to the first reaction section41and serves to primarily reduce the concentration of carbon monoxide contained in the hydrogen gas generated from the first reaction section41through a catalytic water-gas shift (WGS) reaction. The second reaction section42includes a second catalyst42apromoting the water-gas shift reaction of the hydrogen gas. The second catalyst42ahas a pellet shape and is filled in the inner space of the main body31corresponding to the second reaction section42. The water-gas shift reaction with the catalyst42ain the second reaction section42is an exothermic reaction and the reaction temperature ranges from about 200° C. to 300° C.

The third reaction section43is disposed successive to the second reaction section42in the vicinity of the reformer outlet33and serves to secondarily reduce the concentration of carbon monoxide contained in the hydrogen gas through a preferential catalytic CO oxidation (PROX) reaction. The third reaction section43includes a third catalyst43afor promoting the preferential CO oxidation reaction of the hydrogen gas and the air. The third catalyst43ahas a pellet shape and is filled in the inner space of the main body31corresponding to the third reaction section43. The preferential CO oxidation reaction that occurs in the third reaction section43is an exothermic reaction and the reaction temperature ranges from about 150° C. to 200° C.

The third reaction section43is connected to the air pump71of the oxygen supply unit70through a fourth supply line94.

The heating section37supplies thermal energy to the reaction section35, and is disposed to come in contact with the outer circumferential surface of the main body31and includes a resistance wire38for generating the thermal energy with a predetermined power.

In the present embodiment, the resistance wire38is wound around the outer circumferential surface of the main body31and is provided on the outer circumferential surface of the main body with different numbers of winding such that the plurality of reaction section35, can be maintained at the proper reaction temperatures necessary for the corresponding reactions of the respective reaction sections35. Various methods can be used to achieve this such as by adjusting the winding pitch.

In the present embodiment, the number of windings of the resistance wire38wound around the outer circumferential surface corresponding to the first reaction section41is greater than the number of windings of the resistance wire38wound around the outer circumferential surface corresponding to the second reaction section42. The number of windings of the resistance wire38around the outer circumferential surface corresponding to the second reaction section42is greater than the number of winding of the resistance wire38around the outer circumferential surface corresponding to the third reaction section43.

That is, since the first reaction section41should be kept at the highest temperature, the resistance wire38wound around the outer circumferential surface corresponding to the first reaction section41is disposed denser, thereby enhancing the heat delivery rate with the resistance wire38. Since the second reaction section42has a reaction temperature lower than that of the first reaction section41, the resistance wire38wound around the outer circumferential surface corresponding to the second reaction section42is looser than the resistance wire38wound around the outer circumferential surface corresponding to the first reaction section41. Since the third reaction43has a reaction temperature lower than that of the second reaction section42, the resistance wire38wound around the outer circumferential surface corresponding to the third reaction section43is looser than the resistance wire38wound around the outer circumferential surface corresponding to the second reaction section42.

According to the present embodiment, since the resistance wire38is wound around the outer circumferential surface of the main body31to have different numbers of windings corresponding to the different reaction sections35, it is possible to supply thermal energy of different temperature ranges to the respective reaction sections35.

In order to more efficiently deliver the thermal energy generated from the resistance wire38to the inside of the main body31, the reformer30may further include a heat insulating jacket39to reduce the leakage of the thermal energy generated from the resistance wire38. By forming the heat insulating jacket39, it is possible to further enhance the reaction efficiency and the thermal efficiency of the reformer30.

The heat insulating jacket39according to the present embodiment is formed in a cylindrical shape surrounding the entire main body31including the resistance wire38. The heat insulating jacket39includes an inner wall39asurrounding the main body31and an outer wall39bsurrounding the entire inner wall39awhile supporting the inner wall39aat a space apart from the inner wall39aby a predetermined gap. It is preferable that the space between the inner wall39aand the outer wall39bis kept under a vacuum.

The inner wall39aand the outer wall39bare made of a heat insulating material having a relatively small thermal conductivity, for example, a heat insulating metal material such as stainless steel, zirconium, or aluminum or a heat insulating non-metal material such as a ceramic material.

In the process, the thermal energy generated from the resistance wire38is blocked from leaking externally by the heat insulating jacket39. That is, the thermal energy generated from the resistance wire38is primarily blocked by the inner wall39aof the heat insulating jacket39and then is secondarily blocked by the outer wall39b. This helps to allow the heat insulating jacket39to minimize the loss of energy, thereby enhancing the reaction efficiency and the thermal efficiency of the whole reformer30.

Operations of the fuel cell system according to the first embodiment of the present invention will be now described in detail.

First, the resistance wire38that is wound around the outer circumferential surface of the main body31supplies the respective reaction sections35with the thermal energy for keeping the respective reaction sections35at the desired temperature ranges. Since the resistance wire38is wound in different numbers of windings around the respective reaction sections35, the first reaction section41can be kept at its reaction temperature of 300° C. to 600° C., the second reaction section42can be kept at its reaction temperature of 200° C. to 300° C., and the third reaction section43can be kept at its reaction temperature of 150° C. to 200° C.

In this state, the fuel pump53supplies the fuel stored in the fuel tank51to the inner space of the main body31through the first supply line91. Then, the first reaction section41absorbs the thermal energy from the resistance wire38and generates hydrogen gas containing carbon dioxide from the fuel through a steam reforming reaction using the thermal energy. At this time, it is difficult for the first reaction section41to completely carry out the steam reforming reaction and thus an amount of hydrogen gas containing carbon monoxide as a byproduct is generated.

Subsequently, the hydrogen gas is supplied to the second reaction section42through the bores36aof the barrier36. Then, the second reaction section42generates additional hydrogen through a water-gas shift reaction, thereby primarily reducing the concentration of carbon monoxide contained in the hydrogen gas.

Next, the hydrogen gas is supplied to the third reaction section43through the bores36aof the barrier36. The air pump71supplies air to the third reaction section43through the fourth supply line94. Then, the third reaction section43secondarily reduces the concentration of carbon monoxide contained in the hydrogen gas through the oxidation reaction of the hydrogen gas and the air.

The hydrogen generated from the fuel is discharged through the reformer outlet33of the main body31from the third reaction section43and is supplied to the electricity generators11of the stack10through the second supply line92. At this time, the air pump71supplies the air to the electricity generators11through the third supply line93.

Then, the hydrogen is supplied to the anode electrode of the membrane-electrode assembly12through the separators16of the electricity generators11. The air is supplied to the cathode electrode of the membrane-electrode assembly12through the separators16.

The anode electrode decomposes the hydrogen gas into electrons and protons (hydrogen ions) through an oxidation reaction. The protons are moved to the cathode electrode through the electrolyte membrane and the electrons are moved to the cathode electrode of the neighboring membrane-electrode assembly12through the separator16, but not through the electrolyte membrane. At this time, the flow of electrons causes a current to flow, and heat and water are also generated as byproducts.

That is, in the reformer30described above, a plurality of reaction sections35are formed on a main body31, the resistance wire38provides different amounts of thermal energy to each of the reaction sections35according to the numbers of windings at the reaction sections. Using this structure, it is possible to simplify the structure of the reformer and to make the entire fuel cell system compact. It is also possible to enhance the efficiency of the entire fuel cell system.

Modified examples of the first embodiment are described now. Elements of the modified examples substantially equal to those of the first embodiment are not described and shown in detail, but only elements of the modifies examples different from those of the first embodiment are described and shown in detail.

FIG. 5is a cross-sectional view illustrating a reformer according to a first modified example of the first embodiment of the present invention.

Referring toFIG. 5, the reformer30A according to the present modified example, includes main body31A which defines a reformer inlet32A and a reformer outlet33A, and the reaction sections35A are composed of a first reaction section41A for promoting the reforming reaction, a second reaction section42A for reducing the CO by the WGS reaction, and a third reaction section43A for reducing the CO by the PROX reaction, each having a honeycomb-shaped catalyst. Accordingly, the respective reaction sections35A have a structure that catalyst materials41b,42b, and43bare carried in a plurality of parallel penetrating holes41c,42c, and43c, that is, on the inner surfaces of ceramic or metal carrier cells. The penetrating holes41c,42c, and43cconstitute passages for passing the fuel and the catalyst materials41b,42b, and43bnecessary for the reaction specific to the respective reaction sections35A are formed on the inner surfaces of the passages.

FIG. 6is a cross-sectional view schematically illustrating a reformer of a second modified example of the first embodiment of the present invention.

Referring toFIG. 6, reformer30B includes a main body31B that includes a reformer inlet32B, and a reformer outlet33B. A first reaction section41B for promoting the reforming reaction, and at least two third reaction sections43B are also provided. The first reaction section41B and at least two third reaction sections43are sequentially disposed from the reformer inlet32B to the reformer outlet33B of the main body31B. The third reaction sections43B serve to reduce the concentration of carbon monoxide contained in the hydrogen gas generated from the first reaction section41B through the preferential CO oxidation catalytic reaction.

Although two third reaction sections43B are shown inFIG. 6, the present invention is not limited to this and more number of third reaction sections may be provided.

FIG. 7is a cross-sectional view schematically illustrating a reformer according to a third modified example in the first embodiment of the present invention.

Referring toFIG. 7, the reaction sections of the reformer30C according to the present modified example include a vaporization section45C, a first reaction section41C for promoting the reforming reaction, a second reaction section42C for reducing the CO content by the WGS reaction, and a third reaction section43C for reducing the CO content by the PROX reaction. The vaporization section45C, the first reaction section41C, the second reaction section42C, and the third reaction section43C are sequentially disposed from the reformer inlet32C to the reformer outlet33C of the main body31C.

The vaporization section45C vaporizes the fuel supplied through the reformer inlet32C and supplies the vaporized fuel to the first reaction section41C. The vaporization of fuel occurs at a temperature of about 700° C. The vaporization section45C is supplied with the thermal energy for keeping the temperature at about 700° C. using the resistance wire38C.

The resistance wire38C is wound in the most number of windings around the outer circumferential surface of the main body31C corresponding to the vaporization section45C. Here, the number of windings becomes smaller in the order of the first reaction section41C, the second reaction section42C, and the third reaction section43C.

FIG. 8is a cross-sectional view schematically illustrating a reformer according to a fourth modified example in the first embodiment of the present invention.

Referring toFIG. 8, the reaction sections of the reformer30D according to the present modified example include a vaporization section45D, a first reaction section41D for promoting the reforming reaction, and at least two third reaction sections43D for reducing the CO content by the PROX reaction. The vaporization section45D, the first reaction section41D, and the at least two third reaction sections43D are sequentially disposed from the reformer inlet32D to the reformer outlet33D of the main body31D.

Hereinafter, a reformer according to a second embodiment of the present invention and a reformer according to modified examples thereof will be described in detail. Elements substantially equal to those of the first embodiment are not described and shown and only elements different from those of the first embodiment are described and shown in detail.

FIG. 9is an exploded perspective view illustrating a reformer according to the second embodiment of the present invention andFIG. 10is a coupled cross-sectional view of the reformer shown inFIG. 9.

Referring to the figures, the reformer130according to this embodiment of the invention includes a reaction plate131which defines a channel131cfor enabling the flow of fuel and in which the catalytic reactions take place. A heating section137is provided that is closely coupled to the reaction plate131. The heating section137generates thermal energy to supply the thermal energy to the reaction plate131.

In the reaction plate131, the channel131cfor enabling the flow of fuel and air is formed on one surface of the main body131a. The channel131chas a structure that channels are disposed in a series of U-bends in a serpentine arrangement. The channel131cfurther defines a reformer inlet131fwhere the fuel enters the channel131c, and a reformer outlet131gwhere the hydrogen that is generated from the fuel is discharged.

The reaction plate131may be made of a material with good thermal conductivity such as metal. Exemplary metals include aluminum, copper, nickel, and iron.

In this embodiment of the invention, a plurality of reaction sections135is integrally formed on the reaction plate131which serves as a main body.

The heating section137supplies the thermal energy necessary for the reaction sections135formed on the reaction plate131. The heating section137may include a heating plate138closely disposed on one surface of the main body131aof the reaction plate131upon which a resistance wire pattern139is disposed on one surface. The resistance wire pattern139is supplied with predetermined power to supply the thermal energy to the respective reaction sections135.

The heating plate138is disposed in close contact with the surface of the reaction plate131on which the channel131cis formed, thereby forming a passage for passing the fuel. The heating plate138, like the reaction plate131, may be made of a material with good thermal conductivity. Examples include metals such as aluminum, copper, nickel, and iron.

The heating plate138can be coupled to the main body131aof the reaction plate131with conventional coupling means (not shown). The two may be fused to one another such as welding or frit, or may be fastened such as with nuts and bolts. However, the coupling means is not limited to such methods and the two may be coupled in various ways.

The resistance wire pattern139may be made of a material with good conductivity and which can generate heat of a predetermined temperature upon application of power. Exemplary materials include copper and nickel. The resistance wire pattern139may be formed on one surface of the heating plate138, for example, by using a conventional deposition method or a conventional etching method with a mask.

The resistance wire pattern139of this embodiment includes sequential U-bends that together form a serpentine arrangement similar to the flow channel131cof the reaction plate131. First portions139aare arranged parallel to one another and extend on one surface of the heating plate138. Second portions139balternately connect ends of the first portions139a, thereby forming the serpentine shape. However, the resistance wire pattern139is not limited to such a serpentine shape, and may include various other shapes.

In addition, since the heating plate138and the resistance wire pattern139are made of conductive materials, an insulating film (not shown) may be formed between the resistance wire pattern139and the heating plate138.

In the present embodiment, a plurality of reaction sections135is integrally formed on the reaction plate131. Accordingly, a plurality of reaction areas a, b, and c corresponding to the plurality of reaction sections135are formed on the reaction plate131.

The plurality of reaction areas a, b, and c can be divided into a first area a disposed on the surface of the reaction plate131close to the reformer inlet131fof the channel131c, a second area b disposed successive to the first area a, and a third area c disposed close to the reformer outlet131gand successive to the second area b.

Similarly to the first embodiment, the first reaction section141, the second reaction section142, and the third reaction section143of the reaction sections135are disposed in the first area a, the second area b, and the third area c, respectively.

The catalysts promoting the reactions of the reaction sections141,142, and143are formed in the form of catalyst layers141a,142a, and143a, respectively on the inner surface of the channel131c.

A reforming catalyst layer141ais provided on the inner surface of the channel131ccorresponding to the first area a in which the first reaction section141is formed. A water-gas shift catalyst layer142apromoting the water-gas shift reaction is formed on the inner surface of the channel131ccorresponding to the second area b in which the second reaction section142is formed. A preferential CO oxidation catalyst layer143apromoting the preferential CO oxidation reaction is formed on the inner surface of the channel131ccorresponding to the third area c in which the third reaction section143is formed.

Similar to the first embodiment, the reaction temperature of the first reaction section141ranges from 300° C. to 600° C., the reaction temperature of the second reaction section142ranges from 200° C. to 300° C., and the reaction temperature of the third reaction section143ranges from 150° C. to 200° C.

In the present embodiment, the first portions139aof the resistance wire pattern139are disposed with different gaps so as to supply different amounts of thermal energy to the reaction sections141,142, and143. A decrease in gap between the first portions139aof the resistance wire pattern139increases the number of passes of the resistance wire pattern139, thereby generating more thermal energy.

In the present embodiment, the first portions139aof the resistance wire pattern139are formed with a gap d1in the area corresponding to the first reaction section141which is smaller than the gap d2in the area corresponding to the second reaction section142. The gap d2in the area corresponding to the second reaction section142is smaller than the gap d3in the area corresponding to the third reaction section143.

That is, the heating section137supplies the first reaction section141with the most amount of thermal energy, supplies the second reaction section142with a less amount of thermal energy than the first reaction section141, and supplies the third reaction section143with a less amount of thermal energy than the second reaction section142.

Accordingly, the first reaction section141can be kept at a reaction temperature ranging from 300° C. to 600° C., the second reaction section142can be kept at a reaction temperature ranging from 200° C. to 300° C., and the third reaction section143can be kept at a reaction temperature ranging from 150° C. to 200° C.

For the reformer130described above, a plurality of reaction sections135are formed on the reaction plate131as a main body, the heating section137is integrally formed with the reaction plate131, and the resistance wire pattern139is disposed with different gaps, thereby generating different amounts of thermal energy. Accordingly, the respective reaction sections135can be kept at the desired reaction temperatures for the respective reactions.

According to such an embodiment, it is possible to simplify the structure of the reformer and to make the entire fuel cell system compact. It is also possible to enhance the efficiency of the entire fuel cell system.

FIG. 11is a cross-sectional view illustrating the reformer of this embodiment with a modified heating section237.

Referring toFIG. 11, in the reformer230according to the present modified example, the first portions of a resistance wire pattern239acorresponding to the respective reaction sections135are formed in different thicknesses, thereby supplying different amounts of thermal energy to the different reaction sections135. A smaller thickness for a given width of resistance wire results in a higher electrical resistance, and hence, a greater heat output.

Specifically, the thickness t1of the resistance wire pattern239ain the area corresponding to the first reaction section141is smaller than the thickness t2in the area corresponding to the second reaction section142. The thickness t2of the resistance wire pattern139ain the area corresponding to the second reaction section142is smaller than the thickness t3in the area corresponding to the third reaction section143.

FIG. 12is a cross-sectional view illustrating the reformer of this embodiment with yet another modified heating section337.

Referring toFIG. 12, in the reformer330according to the present modified example, the first portions of the resistance wire pattern339acorresponding to the respective reaction sections135are formed in different widths, thereby supplying different amounts of thermal energy to the respective reaction sections135. A smaller width for a given thickness of resistance wire results in a higher electrical resistance, and hence, a greater heat output.

Specifically, the width w1of the resistance wire pattern339ain the area corresponding to the first reaction section141is smaller than the width w2in the area corresponding to the second reaction section142. The width w2of the resistance wire pattern339ain the area corresponding to the second reaction section142is smaller than the width w3in the area corresponding to the third reaction section143.

FIG. 13is a cross-sectional view illustrating the reformer with yet a third modified heating section430.

Referring toFIG. 13, yet another embodiment is disclosed similar to that ofFIGS. 9-12. The reformer430according to the present modified example includes a reaction plate431as described above with a first reaction section441and at least two third reaction sections443. The at least two third reaction sections443both serve to reduce the concentration of carbon monoxide contained in the hydrogen gas generated from the first reaction section441through the preferential catalytic CO oxidation of the hydrogen gas and oxygen.

The heating section437according to the present modified example has a structure that different amounts of thermal energy are supplied to the respective reaction sections by making the resistance wire pattern different in gap, thickness, or width, similar to the second embodiment and the modified examples thereof. The structure of the resistance wire pattern has been described in the above-mentioned embodiments and thus description thereof is omitted.

Although two third reaction sections443are shown inFIG. 13, the present invention is not limited to it but may include more third reaction sections.

FIG. 14is a cross-sectional view illustrating a reformer according to still another modified example of a reformer with a reaction plate531as described above.

Referring toFIG. 14, the reformer530according to the present modified example includes a vaporization section545, a first reaction section541, a second reaction section542, and a third reaction section543. The vaporization section545, the first reaction section541, the second reaction section542, and the third reaction section543are sequentially disposed from the reformer inlet to the reformer outlet of the reaction plate531.

The vaporization section545vaporizes the fuel injected through the reformer inlet and supplies the vaporized fuel to the first reaction section541. The vaporization of fuel occurs at a temperature of about 700° C.

The vaporization section545is supplied with the thermal energy for keeping the temperature of about 700° C. from the resistance wire, vaporizes the fuel, and supplies the vaporized fuel to the first reaction section541.

The heating section537according to the present modified example has a structure that different temperatures of thermal energy are supplied to the respective reaction sections by varying the gap, thickness, or width of the resistance wire pattern, similarly to the previously mentioned embodiments of the invention. The thermal energy of about 700° C. is supplied to the vaporization section545. The structure of the resistance wire pattern has been described in the above-mentioned embodiments and thus description here is omitted.

FIG. 15is a cross-sectional view illustrating a reformer according to still another embodiment of the present invention.

Referring toFIG. 15, the reformer630according to the present modified example includes plate reactor631with a vaporization section645, a first reaction section641, and at least two reaction sections643. The vaporization section645, the first reaction section641, and the at least two third reaction sections643are sequentially disposed from the reformer inlet to the reformer outlet of the reaction plate631.

Although the exemplary embodiments of the present invention have been described, the present invention is not limited to the embodiments, but may be modified in various forms without departing from the scope of the appended claims, the detailed description, and the accompanying drawings of the present invention. Therefore, it is natural that such modifications belong to the scope of the present invention.