Patent Application
20090064579
1. Field of the Invention
The present invention relates to a heat exchange reformer unit in which reforming reactions are caused by which reformate gas that contains hydrogen is obtained from reformation material, such as hydrocarbon, with heat supplied from a heating section to a reforming section. The present invention also relates to a reformer system including such a heat exchange reformer unit.
2. Description of the Related Art
A cross-flow heat exchange fuel reformer is available in which reforming passages for producing gas that contains hydrogen by reforming hydrocarbon material and combustion passages for burning fuel gas to supply heat, which is used in reforming reactions, to the reforming passages are alternately formed (see Japanese Patent Application Publication No. 2004-244230 (JP-A-2004-244230)). JP-A-2004-244230 describes a technology for setting a region in which catalyst is not supported between plates so that the distribution of heat generation caused by combustion reactions and the distribution of heat absorption by reforming reactions in the regions between the plates are adjusted to each other.
Although, in the cross-flow heat exchange fuel reformer according to the related art, the way to match the region in which a lot of heat is generated by combustion reactions, and the region in which a lot of heat is absorbed by reforming reactions is devised, there is room for improvement to enhance the heat exchange efficiency by matching the endothermic region and the exothermic region. In addition, because, in a fuel reformer, the difference between the reaction velocity of the reforming reactions (mainly, steam reforming reaction) in the reforming passages and the reaction velocity of the combustion reactions in the combustion passages is large, that is, the difference in the amount of reaction per volume between the reforming passages and the combustion passages is large, there has been a limit to the improvement in the reforming efficiency of the system when the configuration is adopted in which the reforming passages and combustion passages are merely alternately formed in the stacking direction as described above.
The present invention provides a heat exchange reformer unit of which the efficiency of heat exchange between a heating section and a reforming section is excellent. The present invention also provides a heat exchange reformer unit and a reformer system, which make it possible to improve reforming efficiency.
A heat exchange reformer unit according to a first aspect of the present invention includes: a reforming section, in which reforming catalyst for inducing reforming reactions is supported, for producing reformats gas, which contains hydrogen, from supplied reformation material through reforming reactions including steam-reforming reaction; a heating section, which is disposed adjacent to the reforming section with a separation wall interposed between the heating section and the reforming section so as to cause a gas flow in the same direction as that of a gas flow in the reforming section, and in which oxidizing catalyst for catalytic combustion is supported, for supplying, to the reforming section, heat generated by catalytically burning supplied fuel; a reformation material-introducing section, one end of which serves as a supply port of the reformation material, and the other end of which is integral with a reformation material inflow side of the reforming section; and a fuel-introducing section, one end of which serves as a supply port of the fuel, and the other end of which is integral with a fuel inflow side of the heating section, for introducing the fuel into the heating section in a flow direction different from a flow direction of the reformation material in the reformation material-introducing section.
In the heat exchange reformer unit according to the first aspect, reforming reactions are caused (promoted) in the reforming section by bringing supplied reformation material into contact with the reforming catalyst with heat supplied from the heating section, so that reformate gas that contains hydrogen is obtained. Reforming reactions create a highly endothermic region near the end portion on the upstream side (on the reformation material supply side) of the region in which the reforming catalyst is supported. Combustion reactions create a highly exothermic region near the end portion on the upstream side (on the fuel supply side) of the region in which the oxidizing catalyst is supported.
The direction in which the reformation material (or the reformate gas) flows in the reforming section, and the direction in which the fuel or fuel gas flows in the heating section are the same. In other words, the heating section and the reforming section constitute a parallel-flow heat exchange reformer unit. Accordingly, it is possible to create the highly endothermic region, which is created by the combustion reactions in the heating section, and the highly exothermic region, which is created by the reforming reactions in the reforming section, on the same side (upstream side) of the regions, in which the catalysts are supported, in the gas flow direction. Thus, it is possible to locate the region in which a large amount of heat is generated, close to the region in which endothermic demand is large (that is, to match the endothermic distribution and the exothermic distribution).
In this heat exchange reformer, the reformation material-introducing section, which is integral with the upstream side of the reforming section, and the fuel-introducing section, which is integral with the upstream side of the heating section in which the gas flow direction is parallel to that in the reforming passage (that is, the gas inlet ports of the reforming section and the heating section of, so to speak, the heat exchanger are positioned at virtually the same position), are constructed so as to cause gases to flow in directions different from each other. In other words, the reformation material-introducing section and the fuel-introducing section constitute a quasi cross-flow section. Thus, it is possible to allow the supply port of the reformation material and the supply port of the fuel to be open separately. Accordingly, it is made possible to separately supply reformation material and fuel to the same side of the reforming section and the heating section, and it is possible to construct a parallel-flow heat exchange reformer unit in which the region, in which a large amount of heat is generated, is located near the region, in which endothermic demand is large, as described above.
As described above, the heat exchange reformer unit according to the first embodiment has excellent efficiency of heat exchange between the heating section and the reforming section. In addition, because heat is exchanged between the reformation material flowing through the reformation material-introducing section and the fuel flowing through the fuel-introducing section, the stability (robustness) of operation is enhanced, and it is made possible to realize stable operation against fluctuations (variation in the temperature of the reformation material, for example).
In the heat exchange reformer unit according to this aspect, the entirety of the fuel-introducing section may be a region in which no oxidizing catalyst is supported.
In the heat exchange reformer unit according to this aspect, oxidizing catalyst is not supported in the fuel-introducing section, and therefore, catalytic combustion does not occur in the fuel-introducing section. Thus, the situation is prevented in which heat generated by catalytic combustion is not used in the reforming section and causes local high-temperature regions to occur. In particular, even in the case of adopting configurations in which reforming catalyst is supported in the reformation material-introducing section, local high-temperature regions can occur because the position of the highly endothermic region and the position of the highly exothermic region are not matched when oxidizing catalyst is supported in the fuel-introducing section, which, together with the reformation material-introducing section, forms a quasi cross-flow section described above. However, when oxidizing catalyst is not supported in the fuel-introducing section, occurrence of local high-temperature regions is effectively prevented.
In the heat exchange reformer unit according to this aspect, a plurality of the reforming sections and a plurality of the heating sections may be provided, and may be stacked with at least part of the plurality of the reforming sections being adjacent to at least part of the plurality of the heating sections, the reformation material-introducing section may be provided for each of the reforming sections, and surface planes of the reformation material supply ports may be substantially on the same plane, and the fuel-introducing section may be provided for each of the heating sections, and surface planes of the fuel supply ports may be substantially on the same plane.
In the heat exchange reformer unit according to this aspect, the plurality of the reforming sections and the plurality of the heating sections are stacked, and at least part of the reforming sections are adjacent to at least part of the heating sections. The number of the heating sections provided may be equal to or less than that of the reforming sections, and every heating section may be adjacent to the reforming section on each side of the heating section in the stacking direction. Because the reformation material-introducing sections that are open on the same surface plane are provided in the respective layers of the reforming sections, and the fuel-introducing sections that are open on the same surface plane are provided in the respective layers of the reforming sections, it is possible to separately supply reformation material and fuel to the same side of the reforming sections and the heating sections. Thus, it is possible to construct a parallel-flow heat exchange reformer unit, in which the region in which a large amount of heat is generated is located close to the region in which endothermic demand is large, with a multilayer structure showing excellent heat exchange efficiency.
In the heat exchange reformer unit according to this aspect, the heat exchange reformer unit may be constructed by stacking a plurality of reforming section-forming plate members and a plurality of heating section-forming plate members in a predetermined pattern. Each of the reforming section-forming plate members includes: a first flat-shaped plate portion; and a first standing wall provided on the first flat-shaped plate portion in a standing condition for guiding the reformation material in a predetermined direction, wherein a first heat exchanging section constituting the reforming section together with another plate portion is formed of part of the first flat-shaped plate portion, and wherein a reformation material guide section constituting the reformation material-introducing section together with another plate portion is formed of part of the first flat-shaped plate portion and the first standing wall that is formed adjacent to a reformation material supply-side of the first heat exchanging section. Each of the heating section-forming plate members includes: a second flat-shaped plate portion; and a second standing wall provided on the second flat-shaped plate portion in a standing condition for guiding the fuel in a direction intersecting the predetermined direction, wherein a second heat exchanging section constituting the heating section together with another plate portion is formed of part of the second flat-shaped plate portion, and wherein a fuel guide section constituting the fuel-introducing section together with another plate portion is formed of part of the second flat-shaped plate portion and the second standing wall that is formed adjacent to a fuel supply-side of the second heat exchanging section.
In the heat exchange reformer unit according to this aspect, the reforming section-forming plate members and the heating section-forming plate members are stacked in a predetermined pattern, so that the reforming sections and the heating sections are formed between the heat exchanging sections in the plate portions, and the reformation material-introducing sections and the fuel-introducing sections are formed between the reformation material guide sections and the fuel guide sections in the plate portions. Specifically, by stacking the reforming section-forming plate members and the heating section-forming plate members in a predetermined pattern, the reformation material-introducing sections and the fuel-introducing sections are integrally formed on the upstream side of the parallel-flow heat-exchanging sections, wherein the reformation material-introducing sections and the fuel-introducing sections have the reformation material supply ports and the fuel supply ports, respectively, which are open separately.
The heat exchange reformer unit according to this aspect may further include: a reformation material manifold, defining a collection space to which the reformation material supply ports of the plurality of the reformation material-introducing sections are open, for distributing the reformation material to the plurality of the reformation material-introducing sections; and a fuel manifold, defining a collection space to which the fuel supply ports of the plurality of the fuel-introducing sections are open, for distributing the fuel to the plurality of the fuel-introducing sections.
In the heat exchange reformer unit according to this aspect, the supply ports of the reformation material-introducing sections for introducing reformation material into the reforming sections of the respective layers are open to the reformation material manifold, and the supply ports of the fuel-introducing sections for introducing fuel into the heating sections of the respective layers are open to the fuel manifold. Thus, it is possible to evenly distribute reformation material from the reformation material manifold to the reforming sections of the respective layers through the reformation material-introducing sections of the respective layers. Similarly, it is possible to evenly distribute fuel from the fuel manifold to the heating sections of the respective layers through the fuel-introducing sections of the respective layers. In particular, by providing the fuel manifold with a mixer for mixing fuel and combustion-supporting gas, it is made possible to supply mixed gas, which is previously mixed immediately upstream of the heating sections of the respective layers, to the heating sections of the respective layers. In this case, occurrence of the regions in which fuel concentration is locally high is prevented, and thus, occurrence of local high-temperature regions in the heating sections is prevented.
The heat exchange reformer unit according to this aspect may further include: a reformate gas-discharging section, one end of which serves as a discharge port of the reformate gas, and the other end of which is integral with a reformate gas outflow side of the reforming section; and a combustion exhaust gas-discharging section, one end of which serves as a discharge port of combustion exhaust gas of the heating section, and the other end of which is integral with a combustion exhaust gas outflow side of the heating section, for introducing the combustion exhaust gas to the discharge port of the combustion exhaust gas in a flow direction different from a flow direction of the reformate gas in the reformate gas-discharging section.
In this heat exchange reformer according to this aspect, the reformate gas-discharging section, which is integral with the downstream side of the reforming section, and the combustion exhaust gas-discharging section, which is integral with the downstream side of the heating section in which the gas flow direction is parallel to that in the reforming passage (that is, the gas outlet ports of the reforming section and the heating section of, so to speak, the heat exchanger are positioned at virtually the same position), are constructed so as to cause gases to flow in directions different from each other. In other words, the reformate gas-discharging section and the combustion exhaust gas-discharging section constitute a quasi cross-flow section. Thus, it is possible to allow the discharge port of the reformate gas and the discharge port of the combustion exhaust gas to be open separately. Accordingly, it is made possible to separately discharge reformate gas and combustion exhaust gas to the same side of the reforming section and the heating section, and it is possible to construct a parallel-flow heat exchange reformer unit in which the region, in which a large amount of heat is generated, is located near the region in which endothermic demand is large, as described above.
In the configuration in which a plurality of reforming sections and a plurality of heating sections are stacked so that at least part of the reforming sections are adjacent to at least part of the heating sections, the reformate gas-discharging sections may be provided for the reforming sections of the respective layers, and the combustion exhaust gas-discharging sections may be provided for the heating sections of the respective layers. In particular, in the case of a configuration in which the reforming section-forming plate members and the heating section-forming plate members are stacked in a predetermined pattern, the configuration as described below may be adopted. Specifically, the reformate gas guide section is formed in the plate portion of the reforming section-forming plate member on the side of the heat-exchanging section opposed to the reformation material guide section. On the reformate gas guide section, the standing walls for guiding reformate gas in another predetermined direction are provided in a standing condition, and the reformate gas guide section constitutes the reformate gas-discharging section together with another plate portion. Meanwhile, the exhaust gas guide section is formed in the plate portion of the heating section-forming plate member on the side of the heat-exchanging section opposed to the fuel guide section. On the exhaust gas guide section, the standing walls for guiding combustion exhaust gas in a direction intersecting the another predetermined direction in the reforming section-forming plate member are provided in a standing condition, and the exhaust gas guide section constitutes the combustion exhaust gas-discharging section together with another plate portion. With this configuration, by stacking the reforming section-forming plate members and the heating section-forming plate members in a predetermined pattern, it is possible to separately provide the inlet port and the outlet port of the respective gas of a parallel-flow heat exchanger.
A heat exchange reformer according to a second aspect of the present invention includes: a plurality of reforming sections for producing reformate gas, in which reforming catalyst for inducing reforming reactions is supported; and a plurality of heating sections, in which reforming catalyst for catalytic combustion is supported, for supplying heat, which is generated by catalytically burning supplied fuel, to the reforming sections, wherein the number of the heating sections is less than the number of the reforming sections.
In the heat exchange reformer unit according to this aspect, reformate gas is obtained by bringing supplied reformation material into contact with the reforming catalyst in the reforming section with combustion heat supplied from the heating section to cause (promote) reformation reactions. In the meantime, because the reaction velocity of reforming reactions is lower than that of combustion reactions, reforming reactions require a reaction space (volume) larger than that of combustion reactions. In the heat exchange reformer unit according to this aspect, the number of layers of the reforming sections is greater than the number of layers of the heating sections, the difference in the amount of reaction per volume between the reforming passages and the combustion passages is compensated by the difference in the number of layers thereof (the volume of reaction space). That is, the amount of reaction is set according to the reaction field, and it is possible to increase the amount of reformate gas produced relative to the amount of reformation material supplied, or to the volume of the heat exchange reformer unit.
As described above, with the heat exchange reformer unit according to this aspect, it is possible to increase reforming efficiency. The reforming section may be a reaction section for producing reformate gas that contains hydrogen from supplied reformation material through reforming reactions including the steam-reforming reaction, for example.
A heat exchange reformer according to a third aspect of the present invention includes: a plurality of reforming sections for producing reformate gas, in which reforming catalyst for inducing reforming reactions is supported; and a plurality of heating sections, in which reforming catalyst for catalytic combustion is supported, for supplying heat, which is generated by catalytically burning supplied fuel, to the reforming reactions, wherein the plurality of the reforming sections and the plurality of the heating sections are stacked so that the surface area of the region in which the reforming catalyst is supported is greater than the surface area of the region in which the oxidizing catalyst is supported.
In the heat exchange reformer unit according to this aspect, reformate gas is obtained by bringing supplied reformation material into contact with the reforming catalyst in the reforming section with combustion heat supplied from the heating section to cause (promote) reformation reactions. In the heat exchange reformer unit according to this aspect, in the area in which heat is exchanged between the reforming sections and the heating sections, the surface area of the region in which the reforming catalyst is supported is greater than the surface area of the region in which the oxidizing catalyst is supported. For this reason, the amount of reforming reaction relative to the amount of combustion reaction is increased, and therefore, the difference in the amount of reaction between the reforming sections and the combustion sections is reduced (the difference in the amount of reaction per volume is compensated). That is, the amount of reaction is set according to the reaction field, and it is possible to increase the amount of reformats gas produced relative to the amount of reformation material supplied, or to the volume of the heat exchange reformer unit.
As described above, with the heat exchange reformer unit according to this aspect, it is possible to increase reforming efficiency. The reforming section may be a reaction section for producing reformate gas that contains hydrogen from supplied reformation material through reforming reactions including the steam-reforming reaction, for example.
A heat exchange reformer according to a fourth aspect of the present invention includes: a plurality of reforming sections for producing reformate gas, in which reforming catalyst for inducing reforming reactions is supported; and a plurality of heating sections, in which reforming catalyst for catalytic combustion is supported, for supplying heat, which is generated by catalytically burning supplied fuel, to the reforming reactions, wherein the plurality of the reforming sections and the plurality of the heating sections are stacked so that the amount of the reforming catalyst supported is greater than the amount of the oxidizing catalyst supported.
In the heat exchange reformer unit according to this aspect, reformate gas is obtained by bringing supplied reformation material into contact with the reforming catalyst in the reforming section with combustion heat supplied from the heating section to cause (promote) reformation reactions. In the heat exchange reformer unit according to this aspect, in the area in which heat is exchanged between the reforming sections and the heating sections, the amount of reforming catalyst supported is greater than the amount of oxidizing catalyst supported. For this reason, the amount of reforming reaction relative to the amount of combustion reaction is increased, and therefore, the difference in the amount of reaction between the reforming sections and the combustion sections is reduced (the difference in the amount of reaction per volume is compensated). That is, the amount of reaction is set according to the reaction field, and it is possible to increase the amount of reformate gas produced relative to the amount of reformation material supplied, or to the volume of the heat exchange reformer unit.
As described above, with the heat exchange reformer unit according to this aspect, it is possible to increase reforming efficiency. The reforming section may be a reaction section for producing reformats gas that contains hydrogen from supplied reformation material through reforming reactions including the steam-reforming reaction, for example.
A heat exchange reformer according to a fifth aspect of the present invention includes: a plurality of reforming sections for producing reformate gas, in which reforming catalyst for inducing reforming reactions is supported; and a plurality of heating sections, in which reforming catalyst for catalytic combustion is supported, for supplying heat, which is generated by catalytically burning supplied fuel, to the reforming reactions, wherein the plurality of the reforming sections and the plurality of the heating sections are stacked so that the total volume of the plurality of the reforming sections is greater than the total volume of the plurality of heating sections.
In the heat exchange reformer unit according to this aspect, reformate gas is obtained by bringing supplied reformation material into contact with the reforming catalyst in the reforming section with combustion heat supplied from the heating section to cause (promote) reformation reactions. In the meantime, because the reaction velocity of reforming reactions is lower than that of combustion reactions, reforming reactions require a reaction space (volume) larger than that of combustion reactions. In the heat exchange reformer unit according to this aspect, in the area in which heat is exchanged between the reforming sections and the heating sections, the total volume of the plurality of the reforming sections (volume, that is, passage cross section×passage length×number of layers) is greater than the total volume of the plurality of the combustion sections. For this reason, the difference in the amount of reaction per volume between the reforming passages and the combustion passages is compensated by the difference in the volume of the respective reaction spaces (volume ratio). That is, the amount of reaction is set according to the reaction field, and it is possible to increase the amount of reformate gas produced relative to the amount of reformation material supplied, or to the volume of the heat exchange reformer unit.
As described above, with the heat exchange reformer unit according to this aspect, it is possible to increase reforming efficiency. The reforming section may be a reaction section for producing reformats gas that contains hydrogen from supplied reformation material through reforming reactions including the steam-reforming reaction, for example.
In the heat exchange reformer unit according to this aspect, the heat exchange reformer unit may include a part in which two layers of the reforming sections are stacked per one layer of the heating section.
The heat exchange reformer unit according to this aspect includes a part in which the reforming sections and the heating sections are stacked so that the units are stacked in each of which two layers of the reforming sections are disposed on the same side of one layer of the heating section, or so that the units are stacked in each of which one layer of the heating section is sandwiched between a pair of layers of the reforming sections, for example. In such a part, two layers of the reforming sections are disposed between a pair of the heating sections. Specifically, in the part in which two layers of the reforming sections are stacked per one layer of the heating section, at least one side of each reforming section is adjacent to a heating section. In this way, it is possible to increase the volume of the reforming sections (the catalyst-supporting region surface area, or the amount of catalyst supported) with the heat transport distance between the heating sections and the reforming sections kept short as compared to that of the configuration in which the heating sections and the reforming sections are alternately stacked. For example, while the ratio of the volume of the reforming sections to the overall volume of the reformer unit is about 50% in the configuration in which the heating sections and the reforming sections are alternately stacked, it is possible to increase the ratio of the volume of the reforming sections to the overall volume of the reformer unit to about 67% in the above configuration.
In the heat exchange reformer unit according to this aspect, the heat exchange reformer unit may include a part in which three layers of the reforming sections are stacked per one layer of the heating section.
The heat exchange reformer unit according to this aspect includes a part in which the reforming sections and the heating sections are stacked so that the units are stacked in each of which three layers of the reforming sections are disposed on the same side of one layer of the heating section, for example. In such a part, three layers of the reforming sections are disposed between a pair of the heating sections. In this way, while the ratio of the volume of the reforming sections to the overall volume of the reformer unit is about 50% in the configuration in which the heating sections and the reforming sections are alternately stacked, for example, it is possible to increase the ratio of the volume of the reforming sections to the overall volume of the reformer unit to about 75% in the above configuration. It has been confirmed that, in this configuration, while a reforming section is formed that is not adjacent to any heating sections (the heat transport distance is long), the effect caused by the increase in the reaction space surpasses the effect caused by the increase in the heat transport distance under the operating conditions in which the operating temperature is low, for example.
In the heat exchange reformer unit according to this aspect, the heat exchange reformer unit may include a part in which four or more layers of the reforming sections are stacked per one layer of the heating section.
The heat exchange reformer unit according to this aspect includes a part in which the reforming sections and the heating sections are stacked so that the units are stacked in each of which four layers of the reforming sections are disposed on the same side of one layer of the heating section, for example. In such a part, four layers of the reforming sections are disposed between a pair of the heating sections. In this way, while the ratio of the volume of the reforming sections to the overall volume of the reformer unit is about 50% in the configuration in which the heating sections and the reforming sections are alternately stacked, for example, it is possible to increase the ratio of the volume of the reforming sections to the overall volume of the reformer unit to about 80% or more in the above configuration. It has been confirmed that, in this configuration, while a reforming section is formed that is not adjacent to any heating sections (the heat transport distance is long), the effect caused by the increase in the reaction space surpasses the effect caused by the increase in the heat transport distance under the operating conditions in which the operating temperature is low, for example.
The heat exchange reformer unit according to this aspect may further include a heat transfer-promoting portion for promoting heat transfer from the heating section to the adjacent reforming section.
In the heat exchange reformer unit according to the above aspect, thermal resistance between the heating sections and the reforming sections is reduced by the heat transfer-promoting portions, whereby the heat transport from the heating section to the reforming section is promoted. Thus, even in the case of the configuration in which the heat transport distance from part of the reforming sections is long (the configuration in which heat transfer-controlled effect is feared), such as in the case of the configuration in which three reforming sections per heating section are provided or four or more reforming sections per heating section are provided, for example, it is possible to efficiently supply heat to the reforming sections to which the heat transport distance is long. That is, it is possible to broaden the operating conditions (the range thereof) in which it is possible to enhance the reforming efficiency using the configuration in which three reforming sections per heating section are provided or four or more reforming sections per heating section are provided. As the heat transfer-promoting portion, a connecting wall or the like connecting between the separation walls each separating the reforming section and the heating section may be used, for example.
A reformer system according to a sixth aspect of the present invention includes: the heat exchange reformer unit according to the above aspect; and a water supply system for supplying water to the reforming section of the heat exchange reformer unit.
In the reformer system according to this aspect, the water supplied to the reforming section through the water supply system reacts with the reformation material in the reforming section, and reforms the reformation material into reformate gas that contains hydrogen. Specifically, reforming reactions including the steam-reforming reaction, which is endothermic reaction, occur in the reforming sections, and the heat required to cause the steam-reforming reaction is supplied from the heating sections to the reforming sections. Because the reformer system includes the heat exchange reformer unit according to the above aspect, the difference in the amount of reaction per volume between the reforming passages (reforming sections) and the combustion passages (heating sections) is compensated, and the reformer system increases the amount of reformate gas produced relative to the amount of reformation material supplied, or to the volume of the heat exchange reformer unit, despite the configuration in which steam-reforming reaction is caused that has reaction velocities lower than those of combustion reactions.
The heat exchange reformer unit and the reformer system according to the above aspects of the present invention have excellent efficiency of heat exchange between the heating sections and the reforming sections, and exhibit the advantageous effect that the reforming efficiency is enhanced.
The foregoing and further objects, features and advantages of the invention will become apparent from the following description of preferred embodiments with reference to the accompanying drawings, wherein like numerals are used to represent like elements and wherein:
A heat exchange reformer unit 10 according to a first embodiment of the present invention will be described with reference to
The fuel cell 12 is constructed with electrolyte (not shown) interposed between an anode electrode (fuel electrode) 14 and a cathode electrode (air electrode) 16, and is configured so as to generate electricity mainly by electrochemically reacting the hydrogen that is supplied to the anode electrode 14, and the oxygen that is supplied to the cathode electrode 16. Although various types of fuel cells may be used as the fuel cell 12, in this embodiment, a fuel cell having proton conductive electrolyte (such as a solid polymer fuel cell and a hydrogen membrane fuel cell) is used, which is operated at medium temperatures (about 300 to 700° C.), and in which water is produced at the cathode electrode 16 as electricity is generated.
As shown in
The reforming reactions in the reforming passage 18 includes reactions including the steam-reforming reaction expressed by the equation (1), as shown by the following equations (1) to (4). Accordingly, the reformate gas obtained through the reforming process contains combustible gas, such as hydrogen (H2), carbon monoxide (CO), methane (CH4), decomposed hydrocarbon and unreacted hydrocarbon material (CxHy), and incombustible gas, such as carbon dioxide (CO2) and water (H2O).
CnHm+nH2O?nCO+(n+m/2)H2 (1)
CnHm+n/2O2?nCO+m/2H2 (2)
CO+H2OCO2+H2 (3)
CO+3H2?CH4+H2O (4)
The steam-reforming reaction expressed by the equation (1), which is the principal reaction among these reforming reactions, is endothermic reaction, and, in the reforming passage 18, operation is performed at temperatures equal to or higher than a predetermined temperature to supply reformate gas to the fuel cell 12 that is operated at medium or high temperatures as described above. The combustion passage 20 is configured so as to supply heat used to maintain the reforming reactions and the working temperature in the reforming passage 18. The combustion passage 20 supports oxidizing catalyst 24, and is disposed adjacent to the reforming passage 18, so that the combustion passage 20 is configured so as to bring the supplied fuel and oxygen into contact with the oxidizing catalyst 24 to cause catalytic combustion. The partial oxidation reaction expressed by the equation (2) is exothermic reaction. The heat generated by the partial oxidation reaction is used in the steam-reforming reaction together with the heat supplied from the combustion passage 20.
The heat exchange reformer unit 10 is designed to supply the combustion heat obtained by catalytically burning fuel in the combustion passage 20 to the reforming passage 18 through a plate portion 52 described later. Thus, the heat exchange reformer unit 10 is configured so as to be able to directly supply heat to the reforming passage 18 without converting the heat into temperature as in the case of the configuration in which the reforming passage 18 is heated using heating medium (fluid), such as combustion gas.
The fuel cell system 11 includes a material pump 26 for supplying hydrocarbon material to the reforming passage 18. The discharge port of the material pump 26 is connected to a material inlet port 18A of the reforming passage 18 through a material supply line 28. The hydrocarbon material includes a very small amount of sulfur ingredients (sulfur compounds), which do not contribute to the reforming reactions described above. The hydrocarbon material is supplied to the reforming passage 18 in a gas phase or in an atomized form by a vaporizing device or the like (not shown), such as a vaporizer and an injector.
A reformate gas outlet 18B of the reforming passage 18 is connected to the upstream end of a reformate gas supply line 30, the downstream end of which is connected to a fuel inlet 14A of the anode electrode 14. Thus, the reformate gas produced in the reforming passage 18 is supplied to the anode electrode 14 of the fuel cell 12. The upstream end of an anode off-gas line 32 is connected to an off-gas outlet 14B of the anode electrode 14. The downstream end of the anode off-gas line 32 is connected to a fuel inlet 33A of a gas mixer 33. The gas mixer 33 substantially homogeneously mixes the anode off-gas and the coolant off-gas supplied through a combustion-supporting gas supply line 46 described later. A mixed gas outlet 33B of the gas mixer 33 is connected to a fuel (mixed gas) inlet 20A of the fuel passage 20.
In this way, the fuel cell system 11 is designed so that hydrogen in the reformate gas produced in the reforming passage 18 is used in the fuel cell 12, the remaining components, other than the used hydrogen, are introduced into the combustion passage 20 as an anode off-gas, and the combustible components therein (H2, CO, HC and CH4) are used as fuel in the combustion passage 20. An exhaust gas line 34 for discharging combustion exhaust gas out of the system is connected to an exhaust gas outlet 20B.
The fuel cell system 11 includes a cathode air pump 36 for supplying cathode air to the cathode electrode 16. Connected to the discharge port of the cathode air pump 36 is the upstream end of a cathode air supply line 38, the downstream end of which is connected to an air inlet 16A of the cathode electrode 16. The upstream end of a steam supply line 40 is connected to an off-gas outlet 16B of the cathode electrode 16, and the downstream end of the steam supply line 40 is connected to a steam inlet 18C of the reforming passage 18. Thus, the cathode off-gas that contains steam produced by the cathode electrode 16 and oxygen that is not used on the cathode electrode 16 are supplied to the reforming passage 18. The steam in the cathode off-gas is used in the steam-reforming reaction expressed by the equation (1), and oxygen is used in the partial oxidation reaction expressed by the equation (2). The heat exchange reformer unit 10 according to the first embodiment is configured so as to be operated under particular conditions in which the O/C ratio that is the ratio of the amount of supplied oxygen to the amount of carbon in the hydrocarbon material is set to a particular ratio by supplying cathode off-gas that contains oxygen to the reforming passage 18.
The fuel cell system 11 includes a cooling air pump 42 for supplying cooling air to the fuel cell 12. The discharge port of the cooling air pump 42 is connected to the upstream end of a cooling air supply line 44, the downstream end of which is connected to an inlet 12A of the coolant passage (not shown) of the fuel cell 12. An outlet 12B of the coolant passage is connected to the upstream end of a combustion-supporting gas supply line 46. The combustion-supporting gas supply line 46 is connected to a combustion-supporting gas inlet 33C of the gas mixer 33 so as to supply coolant off-gas that contains oxygen as combustion-supporting gas to the gas mixer 33. Thus, in the combustion passage 20, the mixed gas that is obtained by mixing the anode off-gas supplied through the anode off-gas line 32 and the coolant off-gas supplied through the combustion-supporting gas supply line 46 in the gas mixer 33, is brought into contact with the oxidizing catalyst 24 that the combustion passage 20 has therein, thereby causing catalytic combustion. It should be noted that, instead of the configuration in which the gas mixer 33 is provided, a configuration may be adopted in which the downstream end of the anode off-gas line 32 and the downstream end of the combustion-supporting gas supply line 46 are individually connected to the combustion passage 20, for example.
In the above configuration, the fuel cell 12 (cathode electrode 16) and the steam supply line 40 may be regarded as the water supply device of the present invention, and the fuel cell system 11 (more specifically, the part of the fuel cell system 11, which includes the heat exchange reformer unit 10, the cathode electrode 16, and the steam supply line 40) may be regarded as the reformer system of the present invention.
With regard to the fuel cell system 11, a configuration may be adopted in which the steam supply line 40 is provided with a separation membrane (a porous separation membrane made of polyimide and ceramic, for example) that selectively allows permeation of only the steam in the cathode off-gas, or in which the steam used in reforming is introduced from the outside of the system, so that oxygen is not supplied to the reforming passage 18, or that the ratio (O/C ratio) of the amount of supplied oxygen to the amount of carbon in the hydrocarbon material is small. In the case of such configurations, the main reaction of the reforming reactions in the heat exchange reformer unit 10 is the steam-reforming reaction, and therefore, the partial oxidation reaction is not caused, or the amount of heat generated by the partial oxidation reaction becomes very small.
The unit plate member 50 includes the plate portion 52 formed in a flat shape. The plate portion 52 is formed by integrally providing, at both ends in the longitudinal direction of a parallel flow portion 52 constituting a heat exchanging section formed in a rectangular shape, flow direction-changing sections 52B and 52C, when viewed from above. In this embodiment, the flow direction-changing sections 52B and 52C are formed in a triangular shape such that the bases thereof are made to coincide with the corresponding short sides of the parallel flow portion 52A (with a rectangular shape). Accordingly, the plate portion 52 as a whole is formed in a substantially hexagonal shape. Each unit plate member 50 includes outer walls 54, which are provided in a standing condition at edges of the plate portion 52 on the side thereof on which the reforming passages 18 are formed.
The outer walls 54 are provided in a standing condition all around the plate portion 52 except one side portion of each of the direction-changing sections 52B and 52C, so that the outer walls 54 function as spacers that define the reforming passages 18 between the stacked unit plate members 50 and 51, and also function as outer walls that prevent the outflow of gas from the reforming passages 18, and, at the same time, create a gas inlet 50A on the flow-direction changing section 52B-side, and a gas outlet 50B on the flow-direction changing section 52C-side. The gas inlet 50A and the gas outlet 50B are formed symmetrically with respect to the centroid of the plate portion 52, and the openings thereof are oriented in the directions indicated by the arrows C1 and C2 beside the flow-direction changing sections 52B and 52C, respectively, which are opposite to the direction of the parallel flow portion 52A, which extends along the longitudinal direction of the outer walls 54.
A plurality of standing walls (partition walls) 56 that divide the reforming passage 18 into a plurality of parallel passages are provided in a standing condition on the reforming passage 18-formed-side of the plate portion 52 of the unit plate members 50. The standing walls 56 are made substantially parallel with the outer walls 54 from the gas inlet 50A to the gas outlet 50B, and are configured so as to divide the reforming passage 18 into a plurality of divided passages (microchannels) 58. Each divided passage 58 is formed in a crank-like shape such that the length of the passages from the gas inlet 50A to the gas outlet 50B is substantially the same owing to the symmetrical arrangement of the gas inlet 50A and the gas outlet 50B described above.
The part of the divided passages 58 in the parallel flow portion 52A that are separated by partition wall portions 56A of the standing walls 56 lying along the longitudinal direction of the parallel flow portions 52A, serve as heat-exchanging passages 58A. Meanwhile, the part of the divided passages 58 between which inlet guide walls 56B are provided on the flow-direction changing section 52B in a standing condition, serve as reformation material guide passages 58B constituting a reformation material guide section. The inlet guide walls 56B are part of the standing walls 56, and lie along the direction indicated by the arrow C1. In addition, the part of the divided passages 58 between which outlet guide walls 56C are provided on the flow-direction changing section 52C in a standing condition, serve as reformate gas guide passages 58C constituting a reformate gas guide section. The outlet guide walls 56C are part of the standing walls 56, and lie along the direction indicated by the arrow C2.
The unit plate member 51 includes a plate portion 52 that has the same shape as that of the plate portion 52 constituting the unit plate member 50, and includes outer walls 60, which are provided in a standing condition at the periphery of the plate portion 52 on the side thereof on which the combustion passages 20 are formed. The outer walls 60 are provided in a standing condition all around the plate portion 52 except one side portion of each of the direction-changing sections 52B and 52C, so that the outer walls 60 function as spacers that form the combustion passages 20 between the stacked unit plate members 50 and 51, and also function as outer walls that prevent the outflow of gas from the combustion passages 20, and so that the outer walls 60 form a gas inlet 51A on the flow-direction changing section 52B-side, and a gas outlet 51B on the flow-direction changing section 52C-side.
The gas inlet 51A is formed on the same side of a parallel flow portion 52A in the longitudinal direction as the gas inlet 50A of the unit plate member 50 (that is, on the side indicated by the arrow A in
A plurality of standing walls (partition walls) 62 that divide the combustion passage 20 into a plurality of parallel passages are provided in a standing condition on the combustion passage 20-formed-side of the plate portion 52 of the unit plate members 51. The standing walls 62 are made substantially parallel with the outer walls 60 from the gas inlet 51A to the gas outlet 51B, and are configured so as to divide the combustion passage 20 into a plurality of divided passages (microchannels) 64. Each divided passage 64 is formed in a crank-like shape such that the length of the passages from the gas inlet 51A to the gas outlet 51B is substantially the same owing to the symmetrical arrangement of the gas inlet 51A and the gas outlet 51B described above.
The part of the divided passages 64 in the parallel flow portion 52A that are separated by partition wall portions 62A of the standing walls 62 lying along the longitudinal direction of the parallel flow portions 52A, serve as heat-exchanging passages 64A. Meanwhile, the part of the divided passages 64 between which inlet guide walls 62B are provided on the flow-direction changing section 52B in a standing condition, serve as mixed gas guide passages 64B constituting a fuel guide section. The inlet guide walls 62B are part of the standing walls 62, and lie along the direction indicated by the arrow D1. In addition, the part of the divided passages 64 between which outlet guide walls 62C are provided on the flow-direction changing section 52C in a standing condition, serve as combustion exhaust gas guide passages 64C constituting a combustion exhaust gas guide section. The outlet guide walls 62C are part of the standing walls 62, and lie along the direction indicated by the arrow D2.
In the heat exchange reformer unit 10 described above, the gas inlets 50A and 51A are positioned on the same side (that is, on the side indicated by the arrow A) of the parallel flow portion 52A (the heat-exchanging passages 58A and 64A), and the gas outlets SOB and SIB are positioned on the same side (that is, on the side indicated by the arrow B) of the parallel flow portion 52A as described above, so that the directions in which gas flows in the heat-exchanging passages 58A and 64A on the respective layers are set to the same direction (the direction indicated by the arrow F).
In each of the unit plate members 50 and 51 described above, the portions (the plate portion 52, the outer walls 54 and the standing walls 56; or the plate portion 52, the outer walls 60 and the standing walls 62) are integrally formed of metallic materials, such as stainless steel, or solid (not porous) ceramics, for example. The plurality of the unit plate members 50 and the plurality of the unit plate members 51 constitute the multilayer core unit 65 of the heat exchange reformer unit 10, wherein the plate members 52 and the outer walls 54 and 60 (the standing walls 56 and 62) are airtightly joined by brazing using brazing filler or by diffusion bonding, for example. As shown in
As shown in
The material inlet 18A and the steam inlet 18C for introducing reformation material (hydrocarbon) and steam (cathode off-gas), respectively, are provided in the reformation inlet manifold 66, and the reformats gas outlet 18B for discharging reformate gas is provided in the reformation outlet manifold 68. Meanwhile, the fuel inlet 20A for introducing mixed gas from the gas mixer 33 is provided in the combustion inlet manifold 70, and the exhaust gas outlet 20B for discharging combustion exhaust gas is provided in the combustion outlet manifold 72.
In the heat exchange reformer unit 10 (multilayer core unit 65) described above, the reforming catalyst 22 is supported on the inner surface of the divided passages 58 on the unit plate member 50, and the oxidizing catalyst 24 is supported on the inner surface of the divided passages 64 on the unit plate member 51. As shown in
More specifically, as shown in
With regard to the heat exchange reformer unit 10, as shown in
When the heat exchange reformer unit 10 is produced, as shown in
The multilayer core unit 65 in which the catalyst-supporting region position sensors 74 are set is immersed into the catalyst carrier 75 in the storage tank 76 from the gas outlet-SOB, or 51B-side. In consideration of the fact that, in the multilayer core unit 65 having a microchannel structure, the level of the surface of the catalyst carrier 75 in the divided passages 58 and 64 becomes higher than the level thereof in the storage tank 76 due to the capillary phenomenon, the multilayer core unit 65 is gradually (slowly) immersed into the catalyst carrier 75 until a notification is made by the notification device (until the catalyst-supporting region position sensor(s) 74 detects the catalyst carrier 75), as shown in
Subsequently, as shown in
Then, the reformation inlet manifold 66, the combustion inlet manifold 70, the reformation outlet manifold 68, and the combustion outlet manifold 72 are respectively joined to the opening portions of the gas inlets 50A and 51A, and the gas outlets 50B and 51B of the respective layers of the multilayer core unit 65. Thus, the production process of the heat exchange reformer unit 10 as shown in
Next, operations of the first embodiment will be described.
In the fuel cell system 11 with the above construction, operating the material pump 26 and the cathode air pump 36 causes hydrocarbon material and steam (cathode off-gas) to be introduced into the reforming passages 18 of the heat exchange reformer unit 10 through the material supply line 28. In the reforming passages 18 of the heat exchange reformer unit 10, the reforming reactions including the steam-reforming reaction expressed by the equation (1) and the partial oxidation reaction expressed by the equation (2) (see the above equations (1) to (4)) are caused by bringing the introduced hydrocarbon material and steam into contact with the reforming catalyst 22 with heat supplied from the combustion passages 20, so that reformate gas that contains hydrogen in high concentration is produced.
The reformate gas produced in the reforming passages 18 is supplied to the anode electrode 14 through the fuel inlet 14A of the anode electrode 14. In the fuel cell 12, hydrogen in the reformate gas supplied to the anode electrode 14 is turned into protons, and the protons migrate to the cathode electrode 16 through the electrolyte to react with oxygen in the air introduced onto the cathode electrode 16. As the protons migrate in this way, electrons flow from the anode electrode 14 toward the cathode electrode 16 through the external conductor, so that electricity is generated.
In the fuel cell 12, the generation of electricity uses hydrogen in the reformate gas supplied to the anode electrode 14 and oxygen in the cathode air supplied to the cathode electrode 16 in accordance with the amount of electricity generated (the electric power consumption of a load), and water (steam under operating temperature conditions) is produced at the cathode electrode 16. The gas that contains steam is expelled from the cathode electrode 16 to the steam supply line 40 as cathode off-gas as described above, and introduced into the reforming passage 18 through the steam inlet 18C.
The gas resulting after hydrogen in the reformate gas is used according to the amount of generated electricity as electricity is generated, is discharged from the anode electrode 14 as anode off-gas. The anode off-gas is supplied to the combustion passages 20 of the heat exchange reformer unit 10 through the anode off-gas line 32. In addition, the coolant off-gas after cooling the fuel cell 12 is supplied to the combustion passages 20 through the combustion-supporting gas supply line 46. In the combustion passages 20, catalytic combustion is caused by bringing the combustible components in the anode off-gas, which is fuel, into contact with the oxidizing catalyst 24 together with the oxygen in the coolant off-gas as the combustion-supporting gas. The heat produced by the catalytic combustion is supplied to the reforming passages 18 through the plate portions 52. Using the heat, in the reforming passages 18, the reforming reactions, which are endothermic reactions, are maintained, and the operating temperature (reformate gas temperature) is maintained at a temperature required to bring about reforming reactions.
In this way, the fuel cell system 11 supplies hydrocarbon material to the heat exchange reformer unit 10, and effectively uses various exhaust gases of the fuel cell 12 (the cathode off-gas that contains steam, the anode off-gas that contains combustible components, and the coolant off-gas that contains oxygen) to maintain the operation of the heat exchange reformer unit 10, which produces hydrogen that is supplied to the fuel cell 12.
The reforming reactions in the reforming passages 18 have an endothermic peak on the reformation material inlet side, that is, on the upstream-side catalyst-supporting region 22A-side of the region in which the reforming catalyst 22 is supported. The burning reactions in the combustion passages 20 have an exothermic peak on the fuel inlet side, that is, on the upstream-side catalyst-supporting region 24A-side of the region in which the reforming catalyst 24 is supported. Thus, in cross-flow heat exchange reformer units, for example, the gas flow directions in a reforming section and a heating section intersect with each other, and therefore, there is a problem that local high-temperature regions occur due to the structure. Meanwhile, in counter-flow heat exchange reformer units, for example, an endothermic peak and an exothermic peak in a reforming section and a heating section occur at opposite end portions with respect to the gas flow direction in a heat exchanging section, and therefore, counter-flow heat exchange reformer units are not suitable for the heat exchangers in reformers.
With regard to the heat exchange reformer unit 10, a parallel-flow heat exchanger, in which the gas flow direction in the heat-exchanging passages 58A of the reforming passage 18 and the gas flow direction in the heat-exchanging passages 64A of the combustion passage 20 are the same, is constructed, that is, it is possible to set an endothermic peak and an exothermic peak on the same side with respect to the gas flow direction, wherein, in the reforming reactions, the endothermic peak occurs on the gas inlet 50A-side to which reformation material is supplied, and, in the combustion reactions, the exothermic peak occurs on the gas inlet 51A-side to which fuel is supplied. Accordingly, the efficiency of heat exchange between the reforming passages 18 and the combustion passages 20 is enhanced. Thus, with the heat exchange reformer unit 10, it is possible to efficiently produce hydrogen by reforming, using heat generated in the combustion passage 20 effectively.
Thus, in the heat exchange reformer unit 10 according to the first embodiment, the efficiency of heat exchange between the combustion passages 20 and the reforming passages 18 is excellent.
In addition, in the heat exchange reformer unit 10, the reformation material guide passages 58B and the mixed gas guide passages 64B, which are located on the upstream side of the heat-exchanging passages 58A and 64A substantially constituting a parallel-flow heat exchanger, constitute a cross-flow heat exchanging section, so that the heat exchange therein enables stable operation against fluctuation (robustness is enhanced). An experimental example is shown in
In the heat exchange reformer unit 10, the reforming catalyst 22 and the oxidizing catalyst 24 are not supported in the cross-flow heat exchanging section, which is constituted of the reformation material guide passages 58B and the mixed gas guide passages 64B, and therefore, neither a reforming reaction nor a combustion reaction occurs in the reformation material guide passages 58B and the mixed gas guide passages 64B. Accordingly, the occurrence of local high-temperature regions due to the unbalance between the positions of the endothermic region and the exothermic region is prevented, which is a problem arising when a cross-flow heat exchange reformer unit is used. Experimental results have been obtained that show that, while, in the case where the reforming catalyst 22 and the oxidizing catalyst 24 are supported in the reformation material guide passages 58B and the mixed gas guide passages 64B, respectively, the maximum temperature in the reformation material guide passages 58B is about 800° C. when the temperature of the reformate gas discharged from the divided passages 58 (reformation outlet manifold 68) is controlled at 650° C., the maximum temperature in the reformation material guide passages 58B in the heat exchange reformer unit 10 is about 180° C. under the same conditions.
Thus, by providing the cross-flow heat exchanging section (quasi-cross-flow section), which is constituted of the reformation material guide passages 58B and the mixed gas guide passages 64B, upstream of the parallel-flow heat-exchanging section, which is constituted of the heat-exchanging passages 58A and the heat-exchanging passages 64A, it is made possible to realize an ideal reaction field (thermal balance) in the reforming passages 18 and the combustion passages 20, and in addition, the improvement in the robustness of the system is achieved.
In addition, because the region in which the catalyst carrier 75 is provided, that is, the region in which the reforming catalyst 22 and the oxidizing catalyst 24 are supported, is controlled using the catalyst-supporting region position sensor 74, it is possible to accurately form the upstream-side supporting region ends 22A and 24A of the reforming catalyst 22 and the oxidizing catalyst 24. Specifically, although, with regard to the multilayer core unit 65 in which multiple unit plate members 50 and 51 are stacked, it is infeasible to see the inside of the divided passages 58 and 64, it is possible to prevent the situation where catalyst is supported in the reformation material guide passages 58B and the mixed gas guide passages 64B as shown in
Moreover, in the multilayer core unit 65 of the heat exchange reformer unit 10, the reformation material guide passages 58B and the mixed gas guide passages 64B, which are positioned upstream of the heat-exchanging passages 58A and 64A substantially constituting a parallel-flow heat exchanger, constitute a cross-flow (quasi-cross-flow) section, so that it is possible to form the gas inlets 50A, whose surface planes in the respective layers are substantially on the same plane, and the gas inlet 51A, whose surface planes in the respective layers are substantially on the same plane, in the form of separate opening portions that are open toward different directions. Thus, a construction is realized, in which, while a parallel-flow configuration is adopted that shows an excellent balance between heat generation and heat absorption as described above, the reformation inlet manifold 66 that defines the collection space to which the gas inlets 50A of the respective layers are open is connected to the multilayer core unit 65, and the combustion inlet manifold 70 that defines the collection space to which the gas inlets 51A of the respective layers are open is connected to the multilayer core unit 65. Accordingly, it is possible to improve the homogeneity of the distribution of the amount of gas flowing into the divided passages 58 and 64, as compared to the configuration in which reformation material and mixed gas (anode off-gas as fuel) are supplied to the gas inlets 50A and 51A of the respective layers individually.
In particular, when the combustion inlet manifold 70 is provided, it is made possible to dispose the gas mixer 33, which supplies mixed gas to the divided passages 64 (combustion passages 20), immediately before the gas inlets 51A. When such a gas mixer 33 is structured in the form of a mixing space provided downstream of the microchannel structure, which is constructed by alternately stacking such unit plates as obtained by removing the flow direction-changing section 52C and the outlet guide walls 56C or 62C from the unit plate members 50 and 51, it is made possible to dispose, or form, the gas mixer 33 in the combustion inlet manifold 70 (or in a pipe with a rectangular cross-section connected to the combustion inlet manifold 70).
In the multilayer core unit 65 of the heat exchange reformer unit 10, the reformate gas guide passages 58C and the combustion exhaust gas guide passages 64C, which are positioned downstream of the heat-exchanging passages 58A and 64A substantially constituting a parallel-flow heat exchanger, constitute a cross-flow (quasi-cross-flow) section, so that it is possible to form the gas outlets 50B and 51B in the form of separate opening portions that are open toward different directions. Thus, a construction is realized, in which, while a parallel-flow configuration is adopted that shows an excellent balance between heat generation and heat absorption as described above, the reformation outlet manifold 68 that defines the collection space to which the gas outlets 50B of the respective layers are open is connected to the multilayer core unit 65, and the combustion outlet manifold 72 that defines the collection space to which the gas outlets 51B of the respective layers are open is connected to the multilayer core unit 65. Accordingly, in cooperation with the effect caused by providing the reformation inlet manifold 66 and the combustion inlet manifold 70 described above, it is possible to further improve the homogeneity of the distribution of the amount of gas flowing into the divided passages 58 and 64, as compared to the configuration in which reformate gas and combustion exhaust gas are discharged from the gas outlets 50B and 51B of the respective layers individually.
In addition, in the above embodiments, examples provided with the unit plate members 50 and 51 in each of which the substantially rectangular-parallel flow section 52A (the heat-exchanging passages 58A and 64A) is integrated with the substantially triangular-flow direction-changing sections 52B and 52C (the gas guide passages 58B and 58C, and 64B and 64C) are illustrated. However, the present invention is not limited to these examples, and the flow direction-changing sections 52B and 52C with various shapes may be provided. In addition, the configuration of the guide walls 56B and the like that constitute the gas guide passages 58B and the like together with the flow direction-changing section 52B and the like is not limited to a configuration having a straight shape. The guide walls 56B and the like may have a curved shape, for example.
A heat exchange reformer unit 10 according to a second embodiment of the present invention will be described with reference to
The unit plate member 50 includes the plate portion 52 formed in a flat shape. As shown in
The outer walls 54 are provided in a standing condition all around the plate portion 52 except one side portion of each of the direction-changing sections 52B and 52C, so that the outer walls 54 function as spacers that define the reforming passages 18 between the stacked unit plate members 50 and 51, and also function as outer walls that prevent the outflow of gas from the reforming passages 18, and, at the same time, create the gas inlet 50A on the flow-direction changing section 52B-side, and the gas outlet SOB on the flow-direction changing section 52C-side. The gas inlet 50A and the gas outlet 50B are formed symmetrically with respect to the centroid of the plate portion 52, and the openings thereof are oriented in the directions indicated by the arrows C1 and C2, respectively, which are opposite to the direction of the parallel flow portion 52A, which extends along the longitudinal direction of the outer walls 54, in the flow-direction changing sections 52B and 52C.
A plurality of standing walls (partition walls) 56 that divide the reforming passage 18 into a plurality of parallel passages are provided in a standing condition on the side of the plate portion 52 of the unit plate members 50 on which the reforming passage 18 is formed. The standing walls 56 are made substantially parallel with the outer walls 54 from the gas inlet 50A to the gas outlet 50B, and are configured so as to divide the reforming passage 18 into the plurality of divided passages (microchannels) 58. Each divided passage 58 is formed in a crank-like shape such that the length of the passages from the gas inlet 50A to the gas outlet SOB is substantially the same owing to the symmetrical arrangement of the gas inlet 50A and the gas outlet 50B described above.
The part of the divided passages 58 in the parallel flow portion 52A that are separated by partition wall portions 56A of the standing walls 56 lying along the longitudinal direction of the parallel flow portions 52A, serve as heat-exchanging passages 58A. Meanwhile, the part of the divided passages 58 between which inlet guide walls 56B are provided on the flow-direction changing section 52B in a standing condition, serve as reformation material guide passages 58B constituting a reformation material guide section. The inlet guide walls 56B are part of the standing walls 56, and lie along the direction indicated by the arrow C1. In addition, the part of the divided passages 58 between which outlet guide walls 56C are provided on the flow-direction changing section 52C in a standing condition, serve as reformate gas guide passages 58C constituting a reformate gas guide section. The outlet guide walls 56C are part of the standing walls 56, and lie along the direction indicated by the arrow C2.
The unit plate member 51 includes the plate portion 52 that has the same shape as that of the plate portion 52 constituting the unit plate member 50, and includes the outer walls 60, which are provided in a standing condition at the periphery of the plate portion 52 on the side thereof on which the combustion passages 20 are formed. The outer walls 60 are provided in a standing condition all around the plate portion 52 except one side portion of each of the direction-changing sections 52B and 52C, so that the outer walls 60 function as spacers that form the combustion passages 20 between the stacked unit plate members 50 and 51, and also function as outer walls that prevent the outflow of gas from the combustion passages 20, and so that the outer walls 60 form the gas inlet 51A on the flow-direction changing section 52B-side, and the gas outlet 51B on the flow-direction changing section 52C-side.
The gas inlet 51A is formed on the same side of a parallel flow portion 52A in the longitudinal direction as the gas inlet 50A of the unit plate member 50 (that is, on the side indicated by the arrow A in
The plurality of standing walls (partition walls) 62 that divide the combustion passage 20 into a plurality of parallel passages are provided in a standing condition on the combustion passage 20-formed-side of the plate portion 52 of the unit plate members 51. The standing walls 62 are made substantially parallel with the outer walls 60 from the gas inlet 51A to the gas outlet 51B, and are configured so as to divide the combustion passage 20 into the plurality of divided passages (microchannels) 64. Each divided passage 64 is formed in a crank-like shape such that the length of the passages from the gas inlet 51A to the gas outlet 51B is substantially the same owing to the symmetrical arrangement of the gas inlet 51A and the gas outlet 511B described above.
In the divided passages 64, the portions in the parallel flow portion 52A that are separated by partition wall portions 62A of the standing walls 62 lying along the longitudinal direction of the parallel flow portions 52A, are made to serve as heat-exchanging passages 64A. Meanwhile, the part of the divided passages 64 that are created by providing, as part of the standing walls 62, inlet guide walls 62B on the flow-direction changing section 52B in a standing condition that lie along the direction indicated by the arrow D1, are made to serve as mixed gas guide passages 64B constituting a fuel guide section. In addition, the part of the divided passages 64 that are created by providing, as part of the standing walls 62, outlet guide walls 62C on a flow-direction changing section 52C in a standing condition that lie along the direction indicated by the arrow D2, are made to serve as combustion exhaust gas guide passages 64C constituting a combustion exhaust gas guide section.
In the heat exchange reformer unit 10 described above, the multilayer core unit 65 is constructed by stacking the unit plate members 50 and 51 in the following manner: the gas inlets 50A and 51A are positioned on the same side (that is, on the side indicated by the arrow A) of the parallel flow portion 52A (the heat-exchanging passages 58A and 64A), and the gas outlets 50B and 51B are positioned on the same side (that is, on the side indicated by the arrow B) of the parallel flow portion 52A as described above, so that the directions in which gas flows in the heat-exchanging passages 58A and 64A on the respective layers are set to the same direction (the direction indicated by the arrow F).
As shown in
In each of the unit plate members 50 and 51 described above, the portions (the plate portion 52, the outer walls 54 and the standing walls 56; or the plate portion 52, the outer walls 60 and the standing walls 62) are integrally formed of metallic materials, such as stainless steel, or solid (not porous) ceramics, for example. The plurality of the unit plate members 50 and the plurality of the unit plate members 51 constitute the multilayer core unit 65 of the heat exchange reformer unit 10, wherein the plate members 52 and the outer walls 54 and 60 (the standing walls 56 and 62) are airtightly joined by brazing using brazing filler or by diffusion bonding, for example. As shown in
As shown in
Although not shown in the figures, the material inlet 18A and the steam inlet 18C for introducing reformation material (hydrocarbon) and steam (cathode off-gas), respectively, are provided in the reformation inlet manifold 66, and the reformate gas outlet 19B for discharging reformate gas is provided in the reformation outlet manifold 68. Meanwhile, the fuel inlet 20A for introducing mixed gas from the gas mixer 33 is provided in the combustion inlet manifold 70, and the exhaust gas outlet 20B for discharging combustion exhaust gas is provided in the combustion outlet manifold 72.
In the heat exchange reformer unit 10 (multilayer core unit 65) described above, the reforming catalyst 22 is supported on the inner surface of the divided passages 58 on the unit plate member 50, and the oxidizing catalyst 24 is supported on the inner surface of the divided passages 64 on the unit plate member 51. As shown in
More specifically, with regard to the reforming catalyst 22, an upstream-side supporting region end 22A that is the end on the upstream side (that is, on the side indicated by the arrow A) in the gas flow direction in which the reformation material is supplied, substantially coincides with the border between the heat-exchanging passages 58A (parallel flow section 52A) and the reformation material guide passages 58B (flow direction-changing section 52B) of the divided passages 58. With regard to the oxidizing catalyst 24, an upstream-side supporting region end 24A that is the end on the upstream side (that is, on the side indicated by the arrow A) in the gas flow direction, in which the fuel is supplied, substantially coincides with the border between the heat-exchanging passages 64A (parallel flow section 52A) and the mixed gas guide passages 64B (flow-direction changing section 52B) of the divided passages 64. It should be noted that the upstream-side supporting region end 24A of the oxidizing catalyst 24 coincides with the upstream-side supporting region end 22A of the reforming catalyst 22, or is positioned a bit further downstream than the upstream-side supporting region end 22A.
Next, the operations of the second embodiment will be described.
In the fuel cell system 11 with the above construction, operating the material pump 26 and the cathode air pump 36 causes hydrocarbon material and steam (cathode off-gas) to be introduced into the reforming passages 18 of the heat exchange reformer unit 10 through the material supply line 28. In the reforming passages 18 of the heat exchange reformer unit 10, the reforming reactions including the steam-reforming reaction expressed by the equation (1) and the partial oxidation reaction expressed by the equation (2) (see the above equations (1) to (4)) are caused by bringing the introduced hydrocarbon material and steam into contact with the reforming catalyst 22 with heat supplied from the combustion passages 20, so that reformate gas that contains hydrogen in high concentration is produced.
The reformate gas produced in the reforming passages 18 is supplied to the anode electrode 14 through the fuel inlet 14A of the anode electrode 14. In the fuel cell 12, hydrogen in the reformate gas supplied to the anode electrode 14 is turned into protons, and the protons migrate to the cathode electrode 16 through the electrolyte to react with oxygen in the air introduced onto the cathode electrode 16. As the protons migrate in this way, electrons flow from the anode electrode 14 toward the cathode electrode 16 through the external conductor, so, that electricity is generated.
In the fuel cell 12, the generation of electricity uses hydrogen in the reformate gas supplied to the anode electrode 14 and oxygen in the cathode air supplied to the cathode electrode 16 in accordance with the amount of electricity generated (the electric power consumption of a load), and water (steam under operating temperature conditions) is produced at the cathode electrode 16. The gas that contains steam is expelled from the cathode electrode 16 to the steam supply line 40 as cathode off-gas as described above, and introduced into the reforming passage 18 through the steam inlet 18C.
The gas resulting after hydrogen in the reformate gas is used according to the amount of generated electricity as electricity is generated, is discharged from the anode electrode 14 as anode off-gas. The anode off-gas is supplied to the combustion passages 20 of the heat exchange reformer unit 10 through the anode off-gas line 32. In addition, the coolant off-gas after cooling the fuel cell 12 is supplied to the combustion passages 20 through the combustion-supporting gas supply line 46. In the combustion passages 20, catalytic combustion is caused by bringing the combustible components in the anode off-gas, which is fuel, into contact with the oxidizing catalyst 24 together with the oxygen in the coolant off-gas as the combustion-supporting gas. The heat produced by the catalytic combustion is supplied to the reforming passages 18 through the plate portions 52. Using the heat, in the reforming passages 18, the reforming reactions, which are endothermic reactions, are maintained, and the operating temperature (reformate gas temperature) is maintained at a temperature required to bring about reforming reactions.
In this way, the fuel cell system 11 supplies hydrocarbon material to the heat exchange reformer unit 10, and effectively uses various exhaust gases of the fuel cell 12 (the cathode off-gas that contains steam, the anode off-gas that contains combustible components, and the coolant off-gas that contains oxygen) to maintain the operation of the heat exchange reformer unit 10, which produces hydrogen that is supplied to the fuel cell 12.
Because the combustion reactions in the combustion passage 20 have high reaction velocities, a reaction field is mainly created on the fuel inlet side, that is, on the upstream-side supporting region end 24A-side of the region in which the oxidizing catalyst 24 is supported, as shown in
In the heat exchange reformer unit 10, the number of the stacked layers (channels) of the reforming passages 18 is larger than the number of the stacked layers of the combustion passages 20. Thus, the increase in the volume (ratio) of the reforming passage 18 (divided passages 58) is achieved while keeping the overall volume (the sum of the total volume of the reforming passages 18 and the total volume of the combustion passages 20) unchanged. As a result, in the heat exchange reformer unit 10, the total amount of the reforming reaction in the reforming passages 18 and the total amount of the combustion reaction in the combustion passages 20 are matched (the amount of reforming reaction and the amount of combustion reaction are set according to the reforming reaction field), which realizes the operation at high space velocities, Assuming that the overall volume (m3) of the heat exchange reformer unit 10 is Va, the feed flow rate of the reformation material is Qr (m3/h), the total volume of the reforming passages 18 (all the divided passages 58) is Vr, and the total volume of the combustion passages 20 (all the divided passages 64) is Vc, the space velocity SV is defined by the equation, SV(1/h)=Qr/Va=Qr/(Vr+Vc). The operations and effects of the heat exchange reformer unit 10 will be described while comparing it with a comparative example shown in
A heat exchange reformer unit 200 according to the comparative example shown in
On the other hand, in the heat exchange reformer unit 10, two layers of the reforming passages 18 are stacked per one layer of the combustion passage 20, so that the ratio of the volume of the reforming passages 18 to the overall volume of the heat exchange reformer unit 10 increases to about 67% as shown in
As described above, with the heat exchange reformer unit 10, a higher space velocity as compared to that of the heat exchange reformer unit 200 is achieved, that is, a construction with which operation at high space velocities (increase in the amount of reformation material supplied) contributes to the improvement of the reforming efficiency, is realized.
As shown in
In this way, the heat exchange reformer unit 10 according to the second embodiment improves the reforming efficiency.
Next, other embodiments of the present invention will be described. It should be noted that basically the same components/portions as those of the second embodiment, or the foregoing construction are denoted by the same reference numerals as those of the second embodiment, or the foregoing construction, and the description thereof will be omitted. In some cases, the illustration thereof will also be omitted.
Specifically, in the multilayer core unit 82, three layers of the reforming passages 18 are disposed between a pair of the combustion passages 20, as shown in
As described above, in the multilayer core unit 82 in which three layers of the reforming passages 18 are stacked per one layer of the combustion passage 20, the ratio of the volume of the reforming passages 18 to the overall volume is about 75% as shown in
In the other points, the configuration of the heat exchange reformer unit 80 is the same as that of the heat exchange reformer unit 10. Accordingly, as in the case of the heat exchange reformer unit 10 according to the second embodiment, the heat exchange reformer unit 80 according to the third embodiment also makes it possible to match the total amount of the reforming reaction in the reforming passages 18 and the total amount of the combustion reaction in the combustion passages 20 (that is, to set the amount of reforming reaction and the amount of combustion reaction according to the reforming reaction field), and high space velocities are therefore achieved. That is, it is possible to improve reforming efficiency.
In
It is not illustrated herein but has been experimentally confirmed that, under the operating conditions in which, for example, the reforming reaction velocity is low (a larger reaction space is required), such as when the reformation material temperature is low, the effect of the increase in the volume of the reforming passages 18 (the surface area of the region in which the reforming catalyst 22 is supported) surpasses the effect of the reduction in the thermal performance, and the conversion ratio of the heat exchange reformer unit 80 is significantly greater than the conversion ratio of the heat exchange reformer unit 10.
In the fourth embodiment, the heat transfer-supporting ribs 92 are provided on the plate portions 52 in twos between the adjacent standing walls 56 (including between an outer wall 54 and the adjacent standing wall 56) and between the adjacent standing walls 62 (including between an outer wall 60 and the adjacent standing wall 62) in a standing condition so that the height of the standing walls 56 and 62 are equal to each other. The portions at which the heat transfer-supporting ribs 92 are provided in a standing condition are set substantially corresponding to the reaction field in which the combustion reactions mainly occur in the combustion passages 20, that is, the region in which a large amount of heat is generated.
When the plate portions 52 between the layers are regarded as heat transfer fins, wherein the width of the fin is W, the thickness of the connecting portions (the standing wall 56, the standing wall 64 and the heat transfer-supporting rib 92) is d, and the thermal conductivity is ?, as shown in
In the other points, the configuration of the heat exchange reformer unit 80 is the same as that of the heat exchange reformer unit 10. Accordingly, as in the case of the heat exchange reformer unit 10 according to the second embodiment, the heat exchange reformer unit 90 according to the fourth embodiment also makes it possible to match the total amount of the reforming reaction in the reforming passages 18 and the total amount of the combustion reaction in the combustion passages 20 (that is, to set the amount of reforming reaction and the amount of combustion reaction according to the reforming reaction field), and high space velocities are therefore achieved. That is, it is possible to improve reforming efficiency.
In the heat exchange reformer unit 90, the heat transfer-supporting ribs 92 promote heat transfer from the combustion passages 20 to the reforming passages 18, especially to the reforming passages 18 that are not adjacent to the combustion passages 20 on either side of each reforming passage 18, which cancels out the reduction in the thermal efficiency (heat-transfer controlled effect) caused in the case of the third embodiment. Thus, in the heat exchange reformer unit 90 (in which the ratio of the volume occupied by the reforming passages 18 is 75%), the conversion ratio exceeding that of the heat exchange reformer unit 10 is achieved under the operating conditions in which the space velocity is high and the temperature of the reformate gas is 650° C., as shown by the solid symbols in
The heat transfer-supporting thick portions 102 are set substantially corresponding to the reaction field in which the combustion reactions mainly occur in the combustion passages 20, that is, the region in which a large amount of heat is generated. Thus, when regarded as heat transfer fins shown in
In the other points, the configuration of the heat exchange reformer unit 100 is the same as that of the heat exchange reformer unit 80. Accordingly, as in the case of the heat exchange reformer unit 10 according to the second embodiment, the heat exchange reformer unit 100 according to the fifth embodiment also makes it possible to match the total amount of the reforming reaction in the reforming passages 18 and the total amount of the combustion reaction in the combustion passages 20 (that is, to set the amount of reforming reaction and the amount of combustion reaction according to the reforming reaction field), and high space velocities are therefore achieved. That is, it is possible to improve reforming efficiency.
In the heat exchange reformer unit 100, the heat transfer-supporting thick portions 102 promote heat transfer from the combustion passages 20 to the reforming passages 18, especially to the reforming passages 18 that are not adjacent to the combustion passages 20 on either side of each reforming passage 18, which cancels out the reduction in the thermal performance (heat-transfer controlled effect) caused in the case of the third embodiment. Thus, in the heat exchange reformer unit 100 (in which the ratio of the volume occupied by the reforming passages 18 is 75%), the conversion ratio exceeding that of the heat exchange reformer unit 10 is achieved under the operating conditions in which the space velocity is high and the temperature of the reformate gas is 650° C., as shown by the solid symbols in
The plate portion 112 is disposed except at the portions constituting the combustion passages 20, in other words, so as to separate the reforming passages 18 that are adjacent to each other in the stacking direction. The standing walls 114 are disposed at the positions such that the reforming passage 18 that is adjacent to a combustion passage 20 is divided into the divided passages 58. In
Thus, when regarded as heat transfer fins shown in
In the other points, the configuration of the heat exchange reformer unit 110 is the same as that of the heat exchange reformer unit 80. Accordingly, as in the case of the heat exchange reformer unit 10 according to the second embodiment, the heat exchange reformer unit 110 according to the sixth embodiment also makes it possible to match the total amount of the reforming reaction in the reforming passages 18 and the total amount of the combustion reaction in the combustion passages 20 (that is, to set the amount of reforming reaction and the amount of combustion reaction according to the reforming reaction field), and high space velocities are therefore achieved.
In the heat exchange reformer unit 110, the plate portions 112 and the standing walls 114 promote heat transfer from the combustion passages 20 to the reforming passages 18, especially to the reforming passages 18 that are not adjacent to the combustion passages 20 on either side of each reforming passage 18, which cancels out the reduction in the thermal efficiency (heat-transfer controlled effect) caused in the case of the third embodiment. Thus, in the heat exchange reformer unit 110 (in which the ratio of the volume occupied by the reforming passages 18 is 75%), the conversion ratio exceeding that of the heat exchange reformer unit 10 is achieved under the operating conditions in which the space velocity is high and the temperature of the reformate gas is 650° C., as shown by the solid symbols in
Specifically, in the multilayer core unit 122, four layers of the reforming passages 18 are disposed between a pair of the combustion passages 20, as shown in
As described above, in the multilayer core unit 122 in which four layers of the reforming passages 18 are stacked per one layer of the combustion passage 20, the ratio of volume of the reforming passages 18 to the overall volume is about 80%. In addition, because the volume of one layer of the reforming passage 18 is constant in the heat exchange reformer unit 120, the inner surface area, that is, the catalyst-supporting region area (supporting amount), of the combustion passages 20 is increased by about 60% as compared to that of the heat exchange reformer unit 200.
In the other points, the configuration of the heat exchange reformer unit 120 is the same as that of the heat exchange reformer unit 10. Accordingly, as in the case of the heat exchange reformer unit 10 according to the second embodiment, the heat exchange reformer unit 120 according to the seventh embodiment also makes it possible to match the total amount of the reforming reaction in the reforming passages 18 and the total amount of the combustion reaction in the combustion passages 20 (that is, to set the amount of reforming reaction and the amount of combustion reaction according to the reforming reaction field), and high space velocities are therefore achieved. That is, it is possible to improve reforming efficiency.
In the heat exchange reformer unit 120, in order to cancel out the reduction in the thermal performance (heat-transfer controlled effect) that results from the necessity to transport heat to two layers of the reforming passages 18 per one layer of the combustion passage 20, the heat transfer-supporting ribs 92, the heat transfer-supporting thick portion 102, or both of the plate portions 112 and the standing walls 114 (heat transfer-promoting portion) may be provided.
Although, in the above embodiments, examples are illustrated in which the heat exchange reformer unit is used in the fuel cell system, the present invention is not limited to these embodiments. The present invention is not limited by applications as long as the heat exchange reformer unit is one of various heat exchange reformer units for obtaining gas that contains hydrogen from reformation material. Accordingly, the present invention is not limited by the configuration of the water supply system. For example, a configuration in which a water tank, water pipes, water vaporizer etc. are provided as a water supply system may be adopted.
In addition, although, in the above embodiments, examples are illustrated in which the heat exchange reformer units 10, 80, 90, 100, 110 and 120 are each a parallel-flow heat exchange reformer unit, the present invention is not limited to the embodiments. The present invention may be applied to a cross-flow heat exchange reformer unit, for example.
Moreover, in the above embodiments, examples are illustrated in which one layer of the reforming passage 18 and one layer of the combustion passage 20 have the same volume (cross section of passage), the present invention is not limited to the embodiments. A configuration in which one layer of the reforming passage 18 and one layer of the combustion passage 20 have different volumes (cross section of passage), for example.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-119751 | Apr 2006 | JP | national |
| 2006-126407 | Apr 2006 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IB2007/001056 | 4/24/2007 | WO | 00 | 10/20/2008 |
