JP4556305B2 - Fuel reformer and hydrogen production method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel reformer and a hydrogen production method, and more particularly to an apparatus for reforming a hydrocarbon fuel to produce hydrogen and a method for producing hydrogen from the hydrocarbon fuel.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as an apparatus for producing hydrogen, a fuel reformer that reforms a hydrocarbon fuel to generate a hydrogen rich gas is known. Such a fuel reformer is used together with a fuel cell, for example. Here, the hydrogen-rich gas generated by the fuel reformer is supplied to the fuel cell, and the fuel cell uses this hydrogen-rich gas as the fuel gas to obtain an electromotive force by an electrochemical reaction.
[0003]
When the hydrogen-rich gas is generated from the hydrocarbon-based fuel by the reforming reaction, carbon monoxide is generated along with the reforming reaction, and a predetermined amount of carbon monoxide remains in the hydrogen-rich gas. As described above, when hydrogen rich gas is supplied to the fuel cell as fuel gas, carbon monoxide is adsorbed on the catalyst provided in the fuel cell and has the property of inhibiting the electrochemical reaction. Therefore, it is required to sufficiently suppress the carbon monoxide concentration in the hydrogen rich gas. Therefore, the fuel reformer usually includes a device for reducing the carbon monoxide concentration in the hydrogen-rich gas produced by the reformer in addition to the reformer that proceeds with the reforming reaction. Yes.
[0004]
For example, in Japanese Patent Laid-Open No. 1-265461, hydrogen rich gas obtained by reforming a fuel is supplied to a shift unit, and the hydrogen rich gas is oxidized by a shift reaction that generates carbon dioxide and hydrogen from carbon monoxide and water. A technique for reducing the carbon concentration and supplying the hydrogen-rich gas with the reduced carbon monoxide concentration to the phosphoric acid fuel cell is disclosed. Since the shift reaction is an exothermic reaction, in order for the shift reaction to proceed sufficiently, it is necessary to cool the shift portion to remove excess heat and to maintain the inside of the shift portion in a desired temperature range. In the configuration disclosed in the above publication, cooling of the shift unit is performed using cooling water that has been heated by indirectly transferring heat generated in the fuel cell. With such a configuration, a hydrogen-rich gas whose carbon monoxide concentration is reduced to several percent or less can be supplied to the fuel cell.
[0005]
[Problems to be solved by the invention]
However, when a solid polymer fuel cell is used instead of the phosphoric acid fuel cell as a fuel cell that receives supply of a hydrogen rich gas obtained by reforming the fuel, the carbon monoxide concentration in the hydrogen rich gas is further increased. It is necessary to keep it low (for example, below several ppm). In such a case, a carbon monoxide selective oxidation unit is further provided in addition to the shift unit to further reduce the carbon monoxide concentration in the hydrogen rich gas.
[0006]
The carbon monoxide selective oxidation unit is a member that includes a carbon monoxide selective oxidation catalyst and advances a carbon monoxide selective oxidation reaction that oxidizes carbon monoxide in preference to hydrogen. This carbon monoxide selective oxidation reaction is an exothermic reaction similar to the shift reaction, and the carbon monoxide selective oxidation part also needs to remove the generated heat by cooling and maintain the inside in a desired temperature range. Here, as the carbon monoxide selective oxidation catalyst, a noble metal-based catalyst including platinum, palladium, and rhodium is known, and the carbon monoxide selective oxidation reaction unit including such a catalyst is a monoxide. In order to maintain the activity of the carbon selective oxidation reaction sufficiently high, it is necessary to maintain the internal temperature (catalyst temperature) in the range of about 100 to 200 ° C.
[0007]
As a method for cooling the carbon monoxide selective oxidation unit, for example, a method of circulating cooling water in the carbon monoxide selective oxidation unit is conceivable. Here, since the carbon monoxide selective oxidation reaction generates a larger amount of heat than the shift reaction, it is necessary to perform cooling with higher efficiency. However, when the above-described carbon monoxide selective oxidation catalyst is used, the desirable reaction temperature at which the activity of the reaction is sufficiently high is close to the boiling point of water (condensation temperature), so that the hydrogen rich gas to be generated in the fuel reformer When the amount of heat fluctuates and the calorific value in the carbon monoxide selective oxidation reaction section fluctuates, when trying to cope with the large heat generation associated with the carbon monoxide selective oxidation reaction, the cooling temporarily becomes excessive. Thus, the internal temperature of the carbon monoxide selective oxidation reaction part is partially below 100 ° C., and condensed water may be generated. When condensed water is generated in the carbon monoxide selective oxidation reaction section, the condensed water may cover the surface of the carbon monoxide selective oxidation catalyst and inhibit the carbon monoxide selective oxidation reaction. Therefore, a configuration for sufficiently cooling the carbon monoxide selective oxidation reaction section without overcooling and maintaining the activity of the carbon monoxide selective oxidation reaction sufficiently without impairing the energy efficiency of the entire fuel reformer. It was desired.
[0008]
The fuel reforming apparatus and the hydrogen production method of the present invention are made for the purpose of solving such problems and providing a cooling method for sufficiently maintaining the activity of the reaction in the carbon monoxide selective oxidation reaction section. Adopted composition.
[0009]
[Means for solving the problems and their functions and effects]
The fuel reformer of the present invention is a fuel reformer that reforms a hydrocarbon-based fuel to produce hydrogen,
A reformer that includes a reforming catalyst that promotes a reforming reaction, receives a supply of the hydrocarbon-based fuel, and proceeds with the reforming reaction to generate a hydrogen-rich gas;
Heat exchange between the hydrogen-rich gas discharged from the reformer and a predetermined fluid, a heat exchange unit that lowers the temperature of the hydrogen-rich gas and raises the temperature of the fluid;
A carbon monoxide selective oxidation catalyst that promotes a carbon monoxide selective oxidation reaction that oxidizes carbon monoxide in preference to hydrogen, receives the supply of a hydrogen-rich gas via the heat exchange unit, and the carbon monoxide selective oxidation A carbon monoxide selective oxidation part that reduces the carbon monoxide concentration in the hydrogen-rich gas by advancing the reaction;
A cooling means for cooling the carbon monoxide selective oxidation unit using the heated fluid;
It is a summary to provide.
[0010]
The fuel reformer of the present invention configured as described above is a reformer including a reforming catalyst that promotes a reforming reaction, receives the supply of the hydrocarbon-based fuel, and proceeds with the reforming reaction. A hydrogen-rich gas is generated, and heat exchange is performed between the hydrogen-rich gas discharged from the reformer and a predetermined fluid in a heat exchanging unit to lower the temperature of the hydrogen-rich gas and raise the temperature of the fluid. In addition, in the carbon monoxide selective oxidation unit including a carbon monoxide selective oxidation catalyst that promotes a carbon monoxide selective oxidation reaction that oxidizes carbon monoxide in preference to hydrogen, supply of a hydrogen-rich gas via the heat exchange unit In response, the carbon monoxide concentration is reduced by advancing the carbon monoxide selective oxidation reaction. At this time, the carbon monoxide selective oxidation unit is cooled using the fluid whose temperature has been increased.
[0011]
The hydrogen production method of the present invention is a hydrogen production method for reforming a hydrocarbon fuel to produce hydrogen,
(A) proceeding with a reforming reaction to generate a hydrogen-rich gas from the hydrocarbon-based fuel;
(B) performing heat exchange between the hydrogen-rich gas and a predetermined fluid to lower the temperature of the hydrogen-rich gas and raise the temperature of the fluid;
(C) Using a carbon monoxide selective oxidation catalyst that promotes a carbon monoxide selective oxidation reaction that oxidizes carbon monoxide in preference to hydrogen, in the hydrogen-rich gas lowered in temperature by the carbon monoxide selective oxidation reaction. Reducing the carbon monoxide concentration;
With
The step (c)
(C-1) The gist is to include a step of cooling the carbon monoxide selective oxidation catalyst using the fluid heated in the step (b).
[0012]
According to such a fuel reforming apparatus and a hydrogen production method of the present invention, carbon monoxide selective oxidation is performed using a fluid whose temperature has been raised by exchanging heat with the hydrogen-rich gas generated by the reforming reaction. Since the catalyst is cooled, the operation of keeping the carbon monoxide selective oxidation catalyst in a desired temperature range can be more easily performed without overcooling the carbon monoxide selective oxidation catalyst. Since the carbon monoxide selective oxidation catalyst is not overcooled, the activity of the carbon monoxide selective oxidation reaction can be maintained sufficiently high, and a hydrogen-rich gas having a sufficiently low carbon monoxide concentration can be stably obtained. it can.
[0013]
Here, as the hydrocarbon fuel, in addition to hydrocarbons such as methane and gasoline, alcohol or ether such as methanol, aldehyde, or the like generates hydrogen rich gas by proceeding with a steam reforming reaction at a predetermined high temperature. Various hydrocarbon compounds can be used as long as they can be used.
[0014]
In the fuel reformer of the present invention,
The fluid is water,
Water supply means for supplying the water used for cooling the carbon monoxide selective oxidation unit in the cooling means to the reformer so as to be in a steam state in the reformer; In addition,
The reformer may generate a hydrogen rich gas by a steam reforming reaction using the hydrocarbon fuel and the water.
[0015]
In the hydrogen production method of the present invention,
The fluid is water;
In the step (a), the water used for cooling the carbon monoxide selective oxidation catalyst in the step (c-1) is reacted with the hydrocarbon fuel, and a hydrogen-rich gas is formed by a steam reforming reaction. It is good also as a process of generating.
[0016]
With such a configuration, the water supplied to the steam reforming reaction is heated in advance by performing heat exchange with the hydrogen-rich gas and cooling the carbon monoxide selective oxidation catalyst. The heat required for heating water when subjected to the steam reforming reaction can be reduced, and the energy efficiency can be improved. That is, when the steam reforming reaction proceeds on the reforming catalyst, it is necessary to evaporate the supplied water and raise the temperature to a predetermined temperature corresponding to the reaction temperature of the steam reforming reaction. However, the heat required for this vaporization and temperature rise can be reduced.
[0017]
In such a fuel reformer of the present invention, the heated fluid may be in a gas-liquid two-phase state to cool the carbon monoxide selective oxidation unit in the cooling means.
[0018]
Further, in the hydrogen production method of the present invention, in the step (c-1), the carbon monoxide selective oxidation is performed using the fluid that has become a gas-liquid two-phase state by raising the temperature in the step (b). The catalyst may be cooled.
[0019]
According to the fuel reformer and the hydrogen production method of the present invention, the gas-liquid two-phase fluid has a large heat capacity and can exchange a predetermined amount of heat without causing a temperature change, thereby preventing overcooling. In addition, the carbon monoxide selective oxidation catalyst can be sufficiently cooled, and the carbon monoxide selective oxidation catalyst can be easily maintained in a desired temperature range.
[0020]
Furthermore, in the fuel reformer of the present invention, the temperature at which the reforming reaction proceeds in the reformer is higher than the temperature at which the carbon monoxide selective oxidation reaction proceeds in the carbon monoxide selective oxidation unit. Also good.
[0021]
In the hydrogen production method of the present invention, the temperature at which the reforming reaction proceeds in the step (a) may be higher than the temperature at which the carbon monoxide selective oxidation reaction proceeds in the step (c). .
[0022]
With such a configuration, the temperature of the fluid can be sufficiently raised when exchanging heat with the hydrogen-rich gas obtained by the reforming reaction, and the overcooling of the carbon monoxide selective oxidation catalyst can be easily prevented. can do.
[0023]
Furthermore, in the fuel reformer of the present invention,
A catalyst for proceeding a shift reaction that generates carbon dioxide and hydrogen from carbon monoxide and water is received in the hydrogen-rich gas by receiving the supply of the hydrogen-rich gas via the heat exchange unit and proceeding with the shift reaction. Further comprising a shift unit for reducing the carbon monoxide concentration of
The carbon monoxide selective oxidation unit may be supplied with a hydrogen-rich gas whose carbon monoxide concentration is reduced by the shift unit.
[0024]
In the hydrogen production method of the present invention,
(D) The carbon monoxide concentration in the hydrogen-rich gas lowered in the step (b) is reduced prior to the step (c) by a shift reaction that generates carbon dioxide and hydrogen from carbon monoxide and water. It is good also as providing the process to do.
[0025]
In the fuel reformer of the present invention described above,
The temperature at which the reforming reaction proceeds in the reformer is 600 ° C. or higher,
The temperature at which the shift reaction proceeds in the shift portion is in the range of 200 ° C. to 400 ° C.,
The temperature at which the carbon monoxide selective oxidation reaction proceeds in the carbon monoxide selective oxidation section may be in the range of 100 ° C to 200 ° C.
[0026]
In the above-described hydrogen production method of the present invention.
In step (a), the temperature at which the reforming reaction proceeds is 600 ° C. or higher,
The temperature at which the shift reaction proceeds in the step (d) is in the range of 200 ° C. to 400 ° C.,
In the step (c), the temperature at which the carbon monoxide selective oxidation reaction proceeds may be in the range of 100 ° C to 200 ° C.
[0027]
With such a configuration, since the difference between the temperature of the reforming reaction and the temperature of the shift reaction is sufficiently large, the hydrogen-rich gas generated by the reforming reaction is transferred between a predetermined fluid prior to the shift reaction. When the temperature is lowered by heat exchange, the fluid can be sufficiently heated. Further, since the temperature of the carbon monoxide selective oxidation reaction is sufficiently lower than the reaction temperature of the reforming reaction, the operation of cooling the carbon monoxide selective oxidation catalyst while preventing overcooling by the heated fluid. It can be done easily.
[0028]
In the fuel reformer of the present invention, the hydrocarbon fuel may be natural gas or gasoline.
[0029]
In the hydrogen production method of the present invention, the hydrocarbon fuel may be natural gas or gasoline.
[0030]
Since natural gas and gasoline have a sufficiently high reaction temperature when performing a steam reforming reaction using these as fuel, heat exchange with the reformed gas is performed to cool the carbon monoxide selective oxidation catalyst. The temperature of the fluid can be sufficiently raised, and the operation of cooling the carbon monoxide selective oxidation catalyst can be easily performed while preventing overcooling.
[0031]
The fuel cell of the present invention is a fuel cell device comprising a fuel cell that obtains an electromotive force by an electrochemical reaction,
A fuel reformer according to any one of claims 1 to 7,
The gist of the fuel cell is that the electrochemical reaction proceeds using hydrogen generated by the fuel reformer.
[0032]
According to such a fuel cell of the present invention, by providing the fuel reformer of the present invention, a hydrogen-rich gas with a sufficiently reduced carbon monoxide concentration can be stably supplied to the fuel cell. There is no possibility that the catalyst provided in the fuel cell is poisoned by carbon monoxide, and the performance of the fuel cell is not impaired due to the carbon monoxide.
[0033]
The method for warming up the fuel reformer of the present invention is as follows.
A reformer equipped with a reforming catalyst for promoting a reforming reaction, and a carbon monoxide selective oxidation unit comprising a carbon monoxide selective oxidation catalyst for promoting a carbon monoxide selective oxidation reaction for oxidizing carbon monoxide in preference to hydrogen. A hydrogen rich gas is generated from a hydrocarbon-based raw fuel by the reforming reaction in the reformer, and a carbon monoxide concentration of the hydrogen rich gas by the carbon monoxide selective oxidation reaction in the carbon monoxide selective oxidation unit. A method for warming up a fuel reformer to reduce
(A) heating the reformer while supplying a predetermined gas to the reformer;
(B) heat exchange between the heated gas discharged from the reformer heated in the step (a) and a predetermined fluid to raise the temperature of the fluid;
(C) heating the carbon monoxide selective oxidation unit using the fluid heated in the step (b);
It is a summary to provide.
[0034]
According to such a warming-up method of the fuel reformer, the carbon monoxide selective oxidation unit is heated using the fluid that is heated and exchanged heat with the gas discharged from the reformer. Therefore, the carbon monoxide selective oxidation unit can be heated to a desired temperature earlier, and the time required for warming up the fuel reformer can be shortened. In the fuel reformer, the reformer is a member positioned upstream of the carbon monoxide selective oxidation unit in the gas flow, and when the heated gas is discharged from the reformer, this reformer selects the carbon monoxide. The temperature of the carbon monoxide selective oxidation unit is transmitted to the oxidation unit, but by using the fluid, the heat of the upstream reformer is more effectively transmitted to the carbon monoxide selective oxidation unit of the downstream side. The time required for warming up the carbon monoxide selective oxidation unit can be shortened.
[0035]
DETAILED DESCRIPTION OF THE INVENTION
In order to further clarify the configuration and operation of the present invention described above, embodiments of the present invention will be described in the following order based on examples.
1. Overall configuration of the fuel cell device 10
2. Configuration related to cooling of CO selective oxidation section
3. Operation at start-up of the fuel cell device 10
4). Fuel cell device 110 of the second embodiment
[0036]
(1) Overall configuration of the fuel cell device 10:
FIG. 1 is a block diagram showing an outline of the configuration of a fuel cell device 10 according to a preferred embodiment of the present invention. The fuel cell device 10 includes a fuel tank 20 that stores natural gas, a water tank 22 that stores water, a desulfurizer 24 that removes sulfur in the natural gas, a burner 28 that generates combustion gas, and an evaporation that includes the burner 28. Unit 26, reformer 30 that generates a hydrogen-rich gas by a reforming reaction, heat exchange unit 32 that lowers the temperature of the hydrogen-rich gas discharged from the reformer 30, and the carbon monoxide (CO) concentration in the hydrogen-rich gas by a shift reaction A shift unit 34 for reducing, a CO selective oxidation unit 36 for reducing the concentration of carbon monoxide in the hydrogen-rich gas by an oxidation reaction, a fuel cell 40 for obtaining an electromotive force by an electrochemical reaction, and a blower for compressing air and supplying the fuel cell 40 38. A control unit 50 constituted by a computer is a main component. Hereinafter, each component will be described in order.
[0037]
Natural gas stored in the fuel tank 20 is supplied to the desulfurizer 24 and the burner 28. A valve 25 is provided in the fuel flow path 60 that connects the fuel tank 20 and the desulfurizer 24, and a valve 21 is provided in the branch path 61 that branches from the fuel flow path 60 and communicates with the burner 28. . The valves 25 and 21 are connected to the control unit 50, are driven by a signal output from the control unit 50, and control the amount of natural gas supplied to the desulfurizer 24 and the burner 28.
[0038]
The desulfurizer 24 removes sulfur contained in an odorant such as mercaptan added to the supplied natural gas. Since the sulfur content lowers the activity of the reforming catalyst provided in the reformer 30 and inhibits the reforming reaction, the fuel cell apparatus 10 is provided with a desulfurizer 24 prior to the reformer 30 to provide the sulfur content. Is removed. The desulfurized gas from which the sulfur content has been removed by the desulfurizer 24 is supplied to the evaporator 26 via the fuel flow path 63.
[0039]
Further, a water flow path 62, which is a flow path through which water supplied from the water tank 22 passes, is connected to the fuel flow path 63. The water passing through the water flow path 62 is mixed with the desulfurization gas passing through the fuel flow path 63 at this connecting portion, and supplied to the evaporation section 26 together with the desulfurization gas. The water flow path 62 is provided with a pump 23. The pump 23 is connected to the control unit 50, is driven by a signal output from the control unit 50, and adjusts the amount of water supplied to the evaporation unit 26 via the water channel 62. The water that passes through the water flow path 62 and merges with the desulfurization gas in the fuel flow path 63 passes through the heat exchange section 32 and the CO selective oxidation section 36 before joining with the desulfurization gas. The refrigerant functions as a refrigerant for cooling the exchange unit 32 and the CO selective oxidation unit 36. The cooling operation will be described in detail later.
[0040]
The evaporation unit 26 is a device that vaporizes the water supplied from the water tank 22, and receives a supply of desulfurization gas and water as described above to form a mixed gas composed of water vapor and desulfurization gas. Raise the temperature to discharge. The mixed gas discharged from the evaporation unit 26 is supplied to the reformer 30 via the fuel gas channel 64. The evaporator 26 is provided with a burner 28 as a heat source for vaporizing water. The burner 28 is supplied with fuel for combustion from the anode side of the fuel cell 40 and the fuel tank 20. The fuel cell 40 performs an electrochemical reaction using a hydrogen rich gas generated by reforming methane in natural gas by the reformer 30 as a fuel gas, but all the hydrogen supplied to the fuel cell 40 is subjected to an electrochemical reaction. The fuel exhaust gas containing hydrogen that is not consumed but remains without being consumed is discharged to the fuel discharge path 78. The burner 28 is connected to the fuel discharge path 78 to receive supply of fuel exhaust gas, and completely burns hydrogen remaining without being consumed, thereby improving the fuel utilization rate. Normally, such exhaust fuel alone is insufficient as fuel for the combustion reaction in the burner 28. Therefore, the fuel corresponding to this shortage and the supply of exhaust fuel from the fuel cell 40 at the time of startup of the fuel cell device 10 are supplied. When the fuel cannot be received, the fuel for the combustion reaction in the burner 28 is supplied from the fuel tank 20 via the branch passage 61 described above.
[0041]
The reformer 30 reforms the mixed gas composed of the supplied desulfurized gas and water vapor to generate a hydrogen-rich fuel gas. The main component of natural gas is methane, and the reformer 30 generates hydrogen from methane by a steam reforming reaction. The reaction formula showing the steam reforming reaction of methane is shown below.
[0042]
CH _Four + 2H ₂ O → 4H ₂ + CO ₂ -165.13 (kJ / mol) (1)
CH _Four + H ₂ O → CO + 3H ₂ -206.2 (kJ / mol) (2)
CO + H ₂ O → CO ₂ + H ₂ +40.5 (kJ / mol) (3)
[0043]
When the steam reforming reaction of methane proceeds, first, the decomposition reaction of methane shown in the formula (2) proceeds, and methane reacts with water (steam) to generate carbon monoxide and hydrogen. The carbon monoxide generated here reacts with water according to the shift reaction shown in the formula (3) to generate carbon dioxide and hydrogen, and the reaction shown in the formula (1) proceeds as a whole. In the present embodiment, the reformer 30 is also provided with a blower 31, and air (oxygen) is supplied to the reformer 30 from the blower 31. Therefore, in the reformer 30, using this oxygen, a partial oxidation reaction of methane shown in the following formula (4), an oxidation reaction of carbon monoxide shown in the formula (5), and a formula (6) The oxidation reaction of hydrogen proceeds.
[0044]
CH _Four + (1/2) O ₂ → CO + 2H ₂ +44 (kJ / mol) (4)
CO + (1/2) O ₂ → CO ₂ +279.5 (kJ / mol) (5)
H ₂ + (1/2) O ₂ → H ₂ O + 240 (kJ / mol) (6)
[0045]
As shown in the formula (1), the steam reforming reaction of methane is an endothermic reaction, and it is necessary to apply heat to advance the reaction. In this embodiment, air is supplied to the reformer 30. As a result, the oxidation reactions shown in the above equations (4) to (6) are advanced in the reformer 30, and the heat generated by these oxidation reactions is utilized in the steam reforming reaction.
[0046]
Here, the reaction of the formula (5) is a reaction for oxidizing the carbon monoxide generated by the decomposition reaction of methane shown in the formula (2) and the partial oxidation reaction of methane shown in the formula (4). Further, the reaction of the formula (6) is a reaction that consumes the hydrogen generated by the reactions shown in the formulas (1) to (4) by oxidation. The degree to which each oxidation reaction shown in the equations (4) to (5) proceeds can be controlled by adjusting the amount of air supplied to the reformer 30. In the reformer 30 of this embodiment, hydrogen is consumed while balancing the heat required for the steam reforming reaction of methane and the heat generated by the oxidation reaction shown in the formula (1). The amount of air to be supplied is adjusted so that the oxidation reaction does not proceed excessively.
[0047]
The reformer 30 includes a reforming catalyst having an activity of promoting the steam reforming reaction and the oxidation reaction described above. As the reforming catalyst, for example, a noble metal catalyst such as a rhodium catalyst or a platinum / iridium alloy catalyst, a nickel catalyst, or the like can be used. Various shapes can be selected as the shape for holding the reforming catalyst in the reformer 30. For example, pellets formed in a particle shape by supporting the reforming catalyst are formed inside the reformer. Alternatively, the reformer may be formed in a honeycomb shape and the reforming catalyst may be supported on the surface thereof. In the reformer 30 of this example, the reforming catalyst is supported on the honeycomb.
[0048]
The reaction that proceeds on the reforming catalyst can obtain sufficiently high activity by maintaining the catalyst temperature within a predetermined temperature range. Each of the above reforming catalysts has a temperature showing a sufficient activity for promoting the above-described reaction at 600 ° C. or higher. Therefore, in the evaporation unit 26, when water is vaporized to generate a mixed gas composed of water vapor and desulfurized gas, mixing is performed so as to correspond to a predetermined temperature of 600 ° C. or higher which is the reaction temperature in the reformer 30. The temperature of the gas is sufficiently raised and discharged to the reformer 30 side.
[0049]
In the fuel cell device 10 of the present embodiment shown in FIG. 1, a blower 31 is provided in the reformer 30 to supply air to the reformer 30, and the heat required for the steam reforming reaction is generated by the heat generated by the oxidation reaction. However, the reformer 30 may generate hydrogen only by the steam reforming reaction without performing the oxidation reaction. In the case of such a configuration, a heating device such as a heater may be provided in the reformer 30 in order to supply heat required for the steam reforming reaction. Alternatively, when the oxidation reaction proceeds in the reformer 30, the steam reforming reaction has higher efficiency of generating hydrogen than the partial oxidation reaction. The amount of (oxygen), that is, the amount of progressing oxidation reaction may be suppressed, and the insufficient heat may be compensated by the heating device as described above. Alternatively, the temperature of the mixed gas may be raised to a higher temperature in the evaporation unit 26 to supplement the heat required for the steam reforming reaction from the evaporation unit 26 side.
[0050]
The hydrogen-rich fuel gas generated in the reformer 30 is supplied to the heat exchanging unit 32 via the gas flow path 65, and is cooled here, and then supplied to the shift unit 34 via the gas flow path 66. The The shift unit 34 is a device that reduces the carbon monoxide concentration in the hydrogen-rich gas. That is, in the reformer 30, the hydrogen-rich gas produced by the above-described reaction using a mixed gas composed of desulfurized gas and water vapor contains a predetermined amount (about 10%) of carbon monoxide. In the shift unit 34, the reduction of the carbon monoxide concentration in the hydrogen-rich gas is reduced.
[0051]
The shift unit 34 is a device that reduces the carbon monoxide concentration by advancing the shift reaction shown in the above-described equation (3), and includes a catalyst that promotes the shift reaction. As a catalyst for promoting such a shift reaction, a copper-based catalyst including copper, an iron-based catalyst including iron, or the like can be used. Under such a catalyst, the shift reaction proceeds well in the temperature range of 200 ° C to 400 ° C.
As described above, the reaction temperature in the reformer 30 is 600 ° C. or higher, and the temperature of the hydrogen-rich gas discharged from the reformer 30 is a high temperature corresponding to this reaction temperature. In the fuel cell apparatus 10, the heat exchange unit 32 is provided between the reformer 30 and the shift unit 34, and the temperature of the hydrogen rich gas is sufficiently lowered in the heat exchange unit 32 and then supplied to the shift unit 34. Yes. The configuration related to the cooling of the hydrogen rich gas in the heat exchange unit 32 will be described in detail later.
[0052]
Although the shift reaction is an exothermic reaction as shown in the equation (3), in this embodiment, the shift reaction that is an exothermic reaction is performed by sufficiently reducing the temperature of the hydrogen-rich gas in the heat exchanging unit 32. Even if it progresses, it is possible to keep the inside of the shift portion 34 within the desirable temperature range. Of course, it is possible to further provide a cooling means in the shift section 34 to adjust the temperature in the shift section 34. The hydrogen rich gas whose carbon monoxide concentration has been reduced by the shift unit 34 is supplied to the CO selective oxidation unit 36 via the flow path 67.
[0053]
The CO selective oxidation unit 36 is a device for further reducing the carbon monoxide concentration in the hydrogen-rich gas supplied from the shift unit 34. That is, in the shift unit 34, the carbon monoxide concentration in the hydrogen-rich gas is reduced to about several percent, while in the CO selective oxidation unit 36, the carbon monoxide concentration is reduced to about several ppm. The reaction that proceeds in the CO selective oxidation unit 36 is a carbon monoxide selective oxidation reaction that oxidizes carbon monoxide in preference to hydrogen abundantly contained in the hydrogen-rich gas. The CO selective oxidation unit 36 is filled with a carrier carrying a platinum catalyst, a ruthenium catalyst, a palladium catalyst, a gold catalyst, or an alloy catalyst using these as a first element, which is a selective oxidation catalyst for carbon monoxide. Under such a carbon monoxide selective oxidation catalyst, the carbon monoxide selective oxidation reaction proceeds well by maintaining the reaction temperature at 100 ° C. to 200 ° C.
[0054]
Note that a blower 37 is provided in the CO selective oxidation unit 36 in order to supply oxygen required for the carbon monoxide selective oxidation reaction that proceeds in the CO selective oxidation unit 36. The blower 37 takes in air from the outside, compresses it, and supplies it to the CO selective oxidation unit 36. The blower 37 is connected to the control unit 50, and the amount of air (oxygen) supplied to the CO selective oxidation unit 36 is adjusted by the control unit 50.
[0055]
Note that the carbon monoxide selective oxidation reaction that proceeds in the CO selective oxidation unit 36 is a reaction shown in the equation (5), which is an exothermic reaction. Therefore, the CO selective oxidation unit 36 includes a heat exchanging unit 39 in order to maintain the internal temperature (catalyst temperature) at the desired reaction temperature. The configuration related to the cooling of the CO selective oxidation unit 36 by the heat exchange unit 39 will be described in detail later.
[0056]
The hydrogen-rich gas whose carbon monoxide concentration has been lowered in the CO selective oxidation unit 36 as described above is guided to the fuel cell 40 by the fuel gas flow path 68 and is used as a fuel gas for the cell reaction on the anode side. The fuel exhaust gas after being subjected to the cell reaction in the fuel cell 40 is discharged to the fuel discharge path 78 and guided to the burner 28 as described above, and the hydrogen remaining in the fuel exhaust gas is used as fuel for combustion. As consumed. On the other hand, the oxidizing gas related to the cell reaction on the cathode side of the fuel cell 40 is supplied as compressed air through the oxidizing gas channel 69 by the blower 38 that outputs a drive signal from the control unit 50. The remaining oxidizing exhaust gas used for the battery reaction is discharged to the outside.
[0057]
The fuel cell 40 is a solid polymer electrolyte type fuel cell, and is configured by laminating a plurality of single cells each including an electrolyte membrane, an anode, a cathode, and a separator. The electrolyte membrane is a proton-conductive ion exchange membrane formed of a solid polymer material such as a fluorine-based resin. Both the anode and the cathode are made of carbon cloth woven from carbon fibers. In addition, a catalyst layer including a catalyst that promotes an electrochemical reaction is provided between the electrolyte membrane and the anode or the cathode. As such a catalyst, platinum or an alloy made of platinum and another metal is used. The separator is formed of a conductive member having gas impermeability, such as dense carbon which has been made impermeable to gas by compressing carbon, or a metal having excellent corrosion resistance. In addition, the separator forms a flow path of fuel gas and oxidizing gas between the anode and the cathode. The fuel cell 40 is supplied with hydrogen rich gas as a fuel gas and compressed air as an oxidizing gas to the flow path, and generates an electromotive force by proceeding an electrochemical reaction. The electric power generated by the fuel cell 40 is supplied to a predetermined load connected to the fuel cell 40. The electrochemical reaction that proceeds in the fuel cell 40 is shown below. Formula (7) represents the reaction on the anode side, Formula (8) represents the reaction on the cathode side, and the reaction shown in Formula (9) proceeds in the entire battery.
[0058]
H ₂ → 2H ⁺ + 2e ^- ... (7)
(1/2) O ₂ + 2H ⁺ + 2e ^- → H ₂ O ... (8)
H ₂ + (1/2) O ₂ → H ₂ O ... (9)
[0059]
The control unit 50 is configured as a logic circuit centered on a microcomputer. Specifically, the CPU 54 executes predetermined calculations according to a preset control program, and controls necessary for executing various calculation processes by the CPU 54. A ROM 56 in which programs and control data are stored in advance, a RAM 58 in which various data necessary for performing various arithmetic processes in the CPU 54 are temporarily read and written, detection signals from various sensors provided in the fuel cell device 10, The input / output port 52 and the like for inputting information related to the load connected to the fuel cell and outputting a drive signal to each of the blowers and valves described above according to the calculation result in the CPU 54 are provided. The controller 50 controls the operation state of the entire fuel cell device 10 by inputting and outputting various signals in this way.
[0060]
(2) Configuration relating to cooling of CO selective oxidation unit:
Next, the structure regarding the cooling in the CO selective oxidation part 36 with which the said fuel cell apparatus 10 is provided is demonstrated. The water flow path 62 that guides the water stored in the water tank 22 to the evaporation section 26 passes through the water flow path 62 via the heat exchange section 32 and the heat exchange section 39 before being connected to the fuel flow path 63. The water to be used exchanges heat with the hydrogen-rich gas passing through the heat exchange unit 32 and the CO selective oxidation unit 36, and functions as a refrigerant for cooling them.
[0061]
The heat exchange unit 32 is a device that lowers the hydrogen-rich gas generated from the natural gas by the reforming reaction in the reformer 30 to a temperature suitable for supplying to the shift unit 34. As described above, the reformer 30 ensures that the activity of the reforming reaction is sufficiently high by keeping its internal temperature at a predetermined temperature of 600 ° C. or higher. A high temperature gas of about 600 ° C. is discharged. The shift reaction that proceeds in the shift unit 34 exhibits high activity by maintaining the internal temperature of the shift unit 34 at a predetermined temperature in the range of 200 ° C. to 400 ° C. When a gas having a very high temperature is supplied, The internal temperature of the shift unit 34 may exceed the above temperature range, which may cause a decrease in the activity of the shift reaction, an increase in an undesired reaction, or a deterioration of the catalyst that promotes the shift reaction. Therefore, the heat exchange unit 32 is provided prior to the shift unit 34, and after the temperature of the hydrogen rich gas is sufficiently lowered by heat exchange with water passing through the water flow path 62, the hydrogen rich gas is shifted in the shift unit 34. It is used for the reaction. By exchanging heat with the hydrogen rich gas in the heat exchanging section 32, the temperature of the water passing through the water flow path 62 is raised.
[0062]
As described above, the water flow path 62 forms the heat exchange part 39 in the CO selective oxidation part 36, and the water passing through the flow path forming the heat exchange part 39 and the inside of the CO selective oxidation part 36 Heat exchange is possible with (the carbon monoxide selective oxidation catalyst provided in). The carbon monoxide selective oxidation reaction is an exothermic reaction, but by performing heat exchange with the cooling water in the heat exchanging section 39, the CO selective oxidizing section 36 maintains its inside in a desired temperature range, and the monoxide is oxidized. The activity of the carbon selective oxidation reaction is maintained sufficiently high.
[0063]
The efficiency of the heat exchange performed in the heat exchange unit 32 and the heat exchange unit 39 includes the shape of the heat exchange unit, the flow rate of the cooling water passing through the cooling water flow path included in the heat exchange unit, and the temperature between the cooling water and the surroundings. It depends on the difference. In the fuel cell device 10 of this embodiment, when the fuel cell 40 is operating in a steady state, an amount of water to be supplied to the reformer 30 via the evaporator 26 in order to generate a desired amount of fuel gas. Is passed through the water flow path 62, the hydrogen-rich gas passing through the heat exchange section 32 is sufficiently cooled to a temperature suitable for the shift reaction (for example, up to about 200 ° C.). At this time, the water (cooling water) passing through the water flow path 62 is heated by heat exchange with the hydrogen-rich gas, and becomes a gas-liquid two-phase state (that is, a state of boiling water). It is supplied to the exchange unit 39 and cools the CO selective oxidation unit 36. Of course, a configuration for maintaining a gas-liquid two-phase state in the cooling water passing through the heat exchanging portion 39, for example, passing through a water flow path in the heat exchanging portion 32 in accordance with the temperature rise state of the cooling water in the heat exchanging portion 32. A configuration for controlling the flow rate of the cooling water to be performed may be further provided.
[0064]
According to the fuel cell apparatus 10 of the present embodiment configured as described above, the CO selective oxidation unit 36 is cooled by the cooling water that has passed through the heat exchange unit 32, and this cooling water is used as the reformer 30. Since the temperature is raised by exchanging heat with the hydrogen-rich gas discharged from the CO, it is possible to prevent the CO selective oxidation unit 36 from being overcooled. When the amount of hydrogen-rich gas generated in the reformer 30 and supplied to the CO selective oxidation unit 36 or the amount of cooling water passing through the heat exchange unit 39 fluctuates, the internal temperature of the CO selective oxidation unit 36 is cooled. However, overcooling can be prevented by cooling the CO selective oxidation unit 36 using cooling water preliminarily warmed with a hydrogen-rich gas having a sufficiently high temperature. That is, even when the amount of hydrogen rich gas or the amount of cooling water fluctuates, it is possible to prevent the internal temperature of the CO selective oxidation unit 36 from excessively or partially decreasing. Therefore, the activity of the carbon monoxide selective oxidation reaction can always be kept sufficiently high in the CO selective oxidation unit 36, and hydrogen-rich gas with a sufficiently reduced carbon monoxide concentration can be stably supplied to the fuel cell 40. it can.
[0065]
In particular, in this embodiment, the heat exchange unit 32 exchanges heat with the hydrogen-rich gas so that the cooling water that cools the CO selective oxidation unit 36 is in a gas-liquid two-phase state, and cooling in a gas-liquid two-phase state is performed. Since water has a larger heat capacity than liquid or gas, the operation of keeping the inside of the CO selective oxidation unit 36 in a desired temperature range can be made easier. That is, when liquid (water) or gas (water vapor) is used as a refrigerant, if heat exchange is performed with substances having different temperatures, the temperature of the refrigerant itself immediately rises and falls, but the gas-liquid two-phase state The cooling water in the water can exchange a predetermined amount of heat with the surroundings (substance to be heat exchanged) while maintaining a temperature state of 100 ° C.
[0066]
As described above, the desirable operating temperature of the CO selective oxidation unit 36 is in the temperature range of 100 ° C. to 200 ° C. However, as in the present embodiment, heat exchange is performed in the heat exchange unit 32 and a gas-liquid two-phase state ( By cooling the CO selective oxidation unit 36 using the cooling water in the state of boiling water), the internal temperature of the CO selective oxidation unit 36 is always kept at 100 ° C. or more, and the activity of the carbon monoxide selective oxidation reaction Can be sufficiently maintained. That is, in the case where cooling water in a gas-liquid two-phase state is used in the CO selective oxidation unit 36, the CO selective oxidation unit is caused by some cause such as a change in the state of the carbon monoxide selective oxidation reaction that proceeds in the CO selective oxidation unit 36. Even when the amount of heat generated in 36 decreases and the internal temperature of the CO selective oxidation unit 36 decreases, if the ambient temperature begins to drop below 100 ° C, heat is applied from the refrigerant that maintains the state of 100 ° C. It is possible to prevent the activity of the carbon oxide selective oxidation catalyst from being lowered.
[0067]
Note that when the temperature of the carbon monoxide selective oxidation catalyst is lower than 100 ° C., not only the activity of the carbon monoxide selective oxidation reaction is lowered, but also water vapor is condensed in the CO selective oxidation unit 36, and the resulting condensed water is produced. May cover the surface of the catalyst and reduce the performance of the catalyst. When the CO selective oxidation unit 36 is cooled using the cooling water in the gas-liquid two-phase state as in this embodiment, there is no possibility of overcooling as in the case of using liquid cooling water, and the CO selective oxidation is performed. It is possible to always keep the internal temperature of the part 36 at 100 ° C. or higher and prevent inconvenience due to the generation of condensed water.
[0068]
Furthermore, since the gas-liquid two-phase cooling water has a much higher heat exchange efficiency than the case where gas is used as the refrigerant, the CO selective oxidation unit 36 can be sufficiently cooled. Therefore, even when the flow rates of the hydrogen rich gas and the cooling water fluctuate, it is possible to suppress the internal temperature of the CO selective oxidation unit 36 from becoming an undesirably high temperature (200 ° C. or higher). In addition, since the operation of keeping the inside of the CO selective oxidation unit 36 within a desired temperature range is facilitated in this way, the configuration of the heat exchange unit 39 can be made more compact.
[0069]
The reforming catalyst provided in the reformer 30, the catalyst provided in the shift unit 34 to promote the shift reaction, and the carbon monoxide selective oxidation catalyst provided in the CO selective oxidation unit 36 are in a desired temperature range (depending on the type of catalyst used). The temperature range in which the activity is sufficiently high) is different. In this embodiment, the reaction temperatures in the reformer 30, the shift unit 34, and the CO selective oxidation unit 36 are 600 ° C. or higher, 200 to 400 ° C., and 100 to 200 ° C., respectively. Thus, prior to supplying the hydrogen-rich gas to the shift section having a reaction temperature lower than that of the reformer, the temperature of the hydrogen-rich gas is lowered by performing heat exchange with the cooling water, and the temperature is increased by the heat exchange. By cooling the CO selective oxidation unit 36 in which the exothermic reaction proceeds at a reaction temperature lower than that of the shift unit using warm cooling water, heat exchange can be efficiently performed in the entire apparatus.
[0070]
Moreover, in the said Example, in order to use the water used for the steam reforming reaction which advances with the reformer 30 as cooling water for cooling the reformed gas discharged | emitted from the reformer 30, and the CO selective oxidation part 36 In addition, there is an effect that it is possible to reduce the energy required to heat the water in the evaporating unit 26 prior to the supply to the reformer 30. That is, the evaporation unit 26 is a member for vaporizing and raising the temperature of the water before supplying it to the reformer 30, but the water supplied to the evaporation unit 26 passes through the heat exchange unit 32. As a result, the gas-liquid two-phase state is obtained, and further heating is performed via the heat exchanging unit 39, so that the energy consumed for vaporizing water in the evaporation unit 26 can be greatly reduced, Energy efficiency can be improved.
[0071]
In the above embodiment, in order to sufficiently reduce the carbon monoxide concentration in the fuel gas, and to suppress the reduction in the efficiency of hydrogen generation when the carbon monoxide concentration is reduced, the reformer The shift unit 34 is provided between the CO 30 and the CO selective oxidation unit 36. That is, the shift reaction generates hydrogen when carbon monoxide reacts as shown in equation (3), but the oxidation reaction of carbon monoxide that proceeds in the CO selective oxidation unit 36 is expressed in equation (5). As shown, the reaction does not involve the generation of hydrogen. Therefore, when reducing the carbon monoxide in the hydrogen-rich gas, it is possible to secure a higher hydrogen concentration by using the shift reaction rather than the oxidation reaction. it can. In addition, although carbon monoxide is oxidized in preference to hydrogen in the CO selective oxidation unit 36, if the oxidation reaction of carbon monoxide proceeds more, the amount of hydrogen being oxidized increases accordingly. There is a risk of causing a decrease in the hydrogen concentration in the hydrogen-rich gas. Therefore, in the above embodiment, after the carbon monoxide concentration is reduced to some extent by the shift reaction accompanied by the generation of hydrogen, the carbon monoxide concentration is more sufficiently reduced by the carbon monoxide selective oxidation reaction. Here, when the carbon monoxide concentration in the reformed gas generated by the reformer 30 is sufficiently low, the shift unit 34 may not be provided. Also in this case, if the operation temperature of the reformer 30 is sufficiently higher than the operation temperature of the CO selective oxidation unit 36, the heat exchange unit lowers the reformed gas before supplying it to the CO selective oxidation unit 36. By providing the cooling water that is heated by passing through the heat exchange section 32 and cooling the CO selective oxidation section 36, the above-described effects can be obtained.
[0072]
Moreover, in the said Example, although the cooling water which cools the CO selective oxidation part 36 was made into the gas-liquid two-phase state, it is good also as a different structure. For example, the inside of the water channel 62 may be pressurized, and the hydrogen rich gas or the carbon monoxide selective oxidation catalyst may be cooled by the heat exchange unit 32 and the heat exchange unit 39 using pressurized water. If cooling water in a gas-liquid two-phase state is used as the refrigerant, it is desirable that the heat capacity of the refrigerant is sufficiently increased and the internal temperature of the CO selective oxidation unit 36 can be easily maintained at 100 ° C. or higher. Even if the configuration is different, the above-described effects can be obtained by cooling the CO selective oxidation unit 36 with the refrigerant heated by heat exchange with the hydrogen rich gas heated by the reformer 30.
[0073]
In the above-described embodiment, a special structure for cooling the shift unit 34 is not provided as the hydrogen-rich gas is sufficiently cooled before being supplied to the shift unit 34. However, in the shift unit 34, further cooling is performed. It is good also as providing the structure for.
[0074]
(3) Operation at startup of the fuel cell device 10:
In the above description, the operation related to the cooling of the hydrogen rich gas and the CO selective oxidation unit 36 when the fuel cell 40 performs a steady operation has been described. However, the fuel cell device 10 of the above-described embodiment has already been described at the time of startup. Warming up can be performed more quickly by utilizing the configuration related to cooling. That is, when the fuel cell device is started up, the heated gas is supplied from the upstream side, so that the warm-up sequentially proceeds from the upstream member. In the fuel cell device 10 of this embodiment, such heating is performed. In addition to the warming-up from the upstream side by the gas, the downstream member can be actively warmed by the cooling water described above. Below, the warm-up operation at the time of start-up in the fuel cell device 10 will be described.
[0075]
When the fuel cell device 10 is started, first, supply of natural gas from the fuel tank 20 to the burner 28 and the evaporation unit 26 is started, and water is supplied from the water tank 22 to the evaporation unit 26 via the water channel 62. Supply is started. When the supply of natural gas is started, the burner 28 starts combustion immediately, and the natural gas and water supplied through the fuel flow path 63 are heated. Due to the combustion of the burner 28, the temperature of the evaporator 26 immediately rises, and in the evaporator 26, a sufficiently heated gas mixture is generated.
[0076]
When the gas mixture sufficiently heated is supplied from the evaporation unit 26 to the reformer 30, the inside of the reformer 30 is heated by the gas mixture. Further, when compressed air is supplied from the blower 31 to the reformer 30, the oxidation reaction of methane gradually proceeds in the reformer 30 as the temperature of the catalyst rises. The inside of the reformer 30 is further warmed by the generated heat.
[0077]
Thus, the temperature rising gas that has passed through the reformer 30 in which warm-up proceeds (the gas in which the reforming reaction has proceeded according to the warm-up state of the reformer 30) is converted into the heat exchange unit 32, the shift unit 34, and the CO. After passing through the selective oxidation unit 36, these members are sequentially warmed by the temperature rising gas, and the warm-up of the members downstream from the reformer 30 also proceeds sequentially from the upstream side. In addition, if the desulfurizer 24 provided upstream of the evaporation unit 26 is provided with a heating device for startup, the desulfurization operation in the desulfurizer 24 can be made faster and steady. it can.
[0078]
Thus, when the fuel cell device is started up, warm-up proceeds sequentially from the upstream member, but in the fuel cell device 10 of the present embodiment, the flow path for supplying water from the water tank 22 to the evaporation unit 26 includes: Since it passes through the heat exchanging unit 32 and the heat exchanging unit 39, the heat generated on the upstream side is transmitted to the downstream CO selective oxidation unit 36 by the cooling water without passing through the gas. That is, when the temperature-raising gas is discharged from the reformer 30 when the fuel cell device 10 is started up, the heat exchanging unit 32 causes the temperature rising gas to pass between the cooling water passing through the heat exchanging unit 32 and the temperature-raising gas. Heat exchange is performed, and the cooling water heated by the temperature raising gas is supplied to the CO selective oxidation unit 36, and the CO selective oxidation unit 36 is allowed to warm up.
[0079]
Therefore, according to the fuel cell device 10 of the present embodiment, the CO selective oxidation unit 36 can be warmed up faster than when warming up only with the gas that sequentially passes through each member, and the fuel cell device 10 as a whole. Can complete the warm-up faster. When warming up only with the gas transmitted from the upstream side, the warming up of the reformer 30 proceeds to some extent, and the sufficiently heated gas is discharged from the reformer 30. The warming of the CO selective oxidation unit 36 is not started until the shift unit 34 is warmed by the heated gas and the gas whose temperature has been raised to some extent is discharged from the shift unit 34. On the other hand, in the fuel cell device 10 of the present embodiment, when the gas whose temperature has been raised to some extent is discharged from the reformer 30, the cooling water heated in the heat exchanging unit 32 by this gas is converted to CO selective oxidation. This is transmitted to the heat exchanging unit 39 of the unit 36, and warming up of the CO selective oxidation unit 36 is started. Therefore, when the warm-up of the shift unit 34 is completed, the warm-up of the CO selective oxidation unit 36 is also progressing, and the warm-up of the entire fuel cell device 10 is completed more quickly.
[0080]
As described above, the fuel cell device 10 according to the present embodiment can promote the warm-up of the CO selective oxidation unit 36 at the start-up by the configuration provided for cooling the CO selective oxidation unit 36 during the steady operation. In the present embodiment, in particular, when the CO selective oxidation unit 36 is warmed up using the cooling water that has been heated by heat exchange with a predetermined high temperature part, the temperature is raised at an early stage of the warm-up operation. Since the heat of the gas discharged from the mass device 30 is used, the effect of shortening the warm-up time of the fuel cell device 10 can be remarkably obtained. Further, when the CO selective oxidation unit 36 is warmed up, a gas discharged from the reformer 30 performing a normal warming-up operation is used, so that no special heat source is required, and the CO selective oxidation unit 36 is used. By promoting the warm-up of the fuel cell device 10, there is no possibility of causing a decrease in energy efficiency in the fuel cell device 10.
[0081]
When the CO selective oxidation unit 36 is warmed up in this way, the internal temperature (catalyst temperature) of the CO selective oxidation unit 36 is detected by a predetermined temperature sensor, and the catalyst has a certain degree of activity to promote the oxidation reaction. When the internal temperature rises to a higher temperature, the blower 37 is driven to supply compressed air to the CO selective oxidation unit 36 to advance the oxidation reaction, thereby further promoting the warm-up of the CO selective oxidation unit 36. It is also good to do.
[0082]
In the fuel cell device 10 shown in FIG. 1, the cooling water that has passed through the heat exchanging unit 32 and the heat exchanging unit 39 is supplied to the evaporating unit 26 as it is after the warm-up is started, and the desulfurizer 24 is supplied. The mixed gas is supplied to the reformer 30 as a mixed gas together with the natural gas passed through, but water is not supplied to the reformer 30 until at least the warming up of the reformer 30 proceeds to some extent. In 30, only the oxidation reaction may be performed. In the case of such a configuration, the cooling water is not supplied between the heat exchange unit 32 and the CO selective oxidation unit 36 without being supplied to the evaporation unit 26 until the warm-up of the reformer 30 proceeds to some extent. It may be circulated. Such a configuration is a second embodiment, and a fuel cell device 110 of the second embodiment is shown in FIG.
[0083]
(4) Fuel cell device 110 of the second embodiment:
The fuel cell device 110 of the second embodiment has substantially the same configuration as that of the fuel cell device 10, and common members are denoted by the same reference numerals and detailed description thereof is omitted. In the fuel cell device 110, the water channel 62 that supplies the water stored in the water tank 22 to the evaporation unit 26 includes a pump 70, valves 72 and 74, and a bypass channel 76 that communicates between the valves 72 and 74. ing. The pump 70 and the valves 72 and 74 are connected to the control unit 50 and are driven according to a drive signal output from the control unit 50. When the fuel cell device 110 performs a steady operation, the valves 72 and 74 are switched, and the water stored in the water tank 22 cools the heat exchange unit 32 and the heat exchange unit 39 in the same manner as the fuel cell device 10. As a result, the water is not supplied to the evaporation section 26 and the water does not flow through the bypass passage 76.
[0084]
When the fuel cell device 110 is activated, the valves 72 and 74 are switched so that the valves 72 and 74 communicate with each other via the bypass flow path 76, and the heat exchange unit 32 and the water tank 22 are respectively connected by the valves 72 and 74. In addition, the flow of water in the water flow path 62 is blocked between the heat exchange unit 39 and the evaporation unit 26. At this time, the pump 70 is driven. As a result, the water flow path 62 forms a closed flow path via the bypass flow path 76, and water (cooling water) in the flow path is newly pumped from the water tank 22 or is sent to the evaporation section 26. It is circulated between the heat exchange unit 32 and the heat exchange unit 39 without being supplied.
[0085]
At this time, water is not supplied to the evaporation unit 26, and the reformer 30 is supplied with the gas heated by the evaporation unit 26 via the desulfurizer 24 and the compressed air from the blower 31. As a result, in the reformer 30, the oxidation reaction of methane proceeds. Therefore, the reforming catalyst is further heated by heat generated by the oxidation reaction in addition to the heat of the gas supplied from the evaporation unit 26. As the temperature of the reforming catalyst rises, a gas having a high temperature is discharged from the reformer 30, and the downstream shift unit 34 and the like are warmed by this gas. Further, when a gas having a high temperature is discharged from the reformer 30, the heat is exchanged with the water circulating in the closed flow path in the heat exchanging section 32, and the gas is raised. Let warm. The heated water circulates in the water flow path and passes through the heat exchange unit 39 to warm the CO selective oxidation unit 36.
[0086]
In the fuel cell device 110 that performs such an operation at startup, temperature sensors are provided in the reformer 30, the CO selective oxidation unit 36, the closed flow path, and the like, and the warm-up state of each unit is monitored to When the machine advances to some extent, the valves 72 and 74 are switched, and the water flow is changed so that the water stored in the water tank 22 is supplied to the evaporation unit 26 via the heat exchange units 32 and 39. do it.
[0087]
According to the fuel cell device 110 of the second embodiment configured as described above, like the fuel cell device 10 of the first embodiment, the cooling water warmed with the reformed gas is used when performing steady operation. As a result, the above-described effects of cooling the CO selective oxidation unit 36 can be obtained, and at the time of start-up, the warming up of the CO selective oxidation unit 36 is promoted by using the cooling water heated through the heat exchange unit 32. The effects described above can be obtained.
Furthermore, at the time of start-up, the cooling water flow path is a closed flow path, and the cooling water circulates between the heat exchange unit 32 and the heat exchange unit 39. The temperature of water can be raised more quickly by the accumulation of heat that can be given from the gas in the heat exchanging section 32, and the effect of warming up the CO selective oxidation section 36 can be enhanced.
[0088]
In addition, since water is not supplied to the evaporation unit 26 until the warm-up has progressed to some extent, the heat supplied from the burner 28 to the evaporation unit 26 is vaporized until the supply of water to the evaporation unit 26 is started. The natural gas supplied via the desulfurizer 24 can be sufficiently heated immediately and the reformer 30 can be warmed up more quickly. Furthermore, the steam reforming reaction that is an endothermic reaction does not proceed in the reformer 30 until only the oxidation reaction that is an exothermic reaction proceeds in the reformer 30 until the supply of water to the evaporation unit 26 is started. The time required for warming up 30 can be further shortened.
[0089]
In the first and second embodiments described above, the natural gas is stored in the fuel tank 20 and the water is stored in the water tank 22, but different configurations may be used. For example, the fuel flow path 60 may be connected to a supply line for natural gas supplied as commercial gas instead of the fuel tank 20. Similarly, the water channel 62 may be connected to a water supply line instead of the water tank 22. When fuel and water for reforming are stored in a tank as in this embodiment, the fuel cell device is mounted on a moving body such as an electric vehicle, and the fuel cell 40 is used as a power source for driving the moving body. be able to.
[0090]
In the above-described embodiments, natural gas is used as the fuel for the reforming reaction, but a different fuel may be used. For example, other types of hydrocarbon fuel that can generate hydrogen by a steam reforming reaction, such as gasoline, can be used. If the reaction temperature of the reforming reaction proceeding in the reformer is sufficiently high and the hydrogen-rich gas discharged from the reformer is cooled and then supplied to the downstream member, it is discharged from the reformer. The effect described above can be obtained by cooling the CO selective oxidation unit using the refrigerant whose temperature is increased by exchanging heat with the hydrogen-rich gas. In particular, natural gas and gasoline have a high reforming reaction temperature of 600 ° C. or higher, and heat exchange with the hydrogen-rich gas discharged from the reformer makes it easy to change the cooling water into a gas-liquid two-phase state. It can be desirable.
[0091]
In the first and second embodiments described above, the hydrogen-rich gas discharged from the CO selective oxidation unit 36 is supplied to the polymer electrolyte fuel cell as a fuel gas. Hydrogen rich gas may be supplied. By applying the present invention, the operation of keeping the carbon monoxide selective oxidation catalyst in the CO selective oxidation unit within a desirable temperature range becomes easier, and a hydrogen-rich gas with a sufficiently low carbon monoxide concentration can always be supplied to the fuel cell. Therefore, in a fuel cell including a noble metal catalyst such as platinum, it is possible to suppress a decrease in cell performance due to carbon monoxide. Furthermore, the apparatus for supplying the hydrogen-rich gas by the fuel reformer of the present invention is not limited to the fuel cell, and the hydrogen-rich gas may be supplied to other types of apparatuses that consume hydrogen.
[0092]
Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and it is needless to say that the present invention can be implemented in various modes without departing from the gist of the present invention.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an outline of the configuration of a fuel cell device 10 according to a preferred embodiment of the present invention.
FIG. 2 is an explanatory diagram showing a schematic configuration of a fuel cell device 110. FIG.
[Explanation of symbols]
10, 110 ... Fuel cell device
20 ... Fuel tank
21, 25 ... Valve
22 ... Water tank
23, 70 ... Pump
24 ... desulfurizer
26 ... evaporation part
28 ... Burner
30 ... reformer
31, 37, 38 ... Blower
32, 39 ... heat exchange section
34 ... Shift section
36 ... CO selective oxidation part
40 ... Fuel cell
50. Control unit
52 ... I / O port
54 ... CPU
56 ... ROM
58 ... RAM
60 ... Fuel flow path
61 ... Branch
62 ... Water channel
63 ... Fuel flow path
64 ... Fuel gas flow path
65, 66 ... gas flow path
67 ... Flow path
68 ... Fuel gas flow path
69 ... Oxidizing gas flow path
72, 74 ... Valve
76: Bypass flow path
78 ... Fuel discharge path

Claims (11)

A fuel reformer that generates hydrogen by reforming a hydrocarbon-based fuel,
A reformer that includes a reforming catalyst that promotes a reforming reaction, receives a supply of the hydrocarbon-based fuel, and proceeds with the reforming reaction to generate a hydrogen-rich gas;
Heat exchange between the hydrogen-rich gas discharged from the reformer and a predetermined fluid, a heat exchange unit that lowers the temperature of the hydrogen-rich gas and raises the temperature of the fluid;
Provided with a catalyst for proceeding with a shift reaction that generates carbon dioxide and hydrogen from carbon monoxide and water, and receiving a supply of hydrogen rich gas via the heat exchange section, the shift has a lower reaction temperature than the reforming reaction A shift unit that reduces the carbon monoxide concentration in the hydrogen-rich gas by advancing the reaction;
Includes a carbon monoxide selective oxidation catalyst to accelerate the carbon monoxide selective oxidation reaction for oxidizing carbon monoxide in preference to hydrogen, by receiving the supply of hydrogen rich gas concentration of carbon monoxide in the shift portion is reduced, the than the shift reaction is to proceed the reaction temperature is lower the carbon monoxide selective oxidation reaction, carbon monoxide selective oxidizing unit that reduces carbon monoxide concentration in the hydrogen-rich gas,
A fuel reformer comprising: cooling means for cooling the carbon monoxide selective oxidation unit using the fluid whose temperature has been raised. The fuel reformer according to claim 1, wherein
  The fluid is water;
  The temperature at which the carbon monoxide selective oxidation reaction proceeds in the carbon monoxide selective oxidation portion is in the range of 100 ° C. to 200 ° C.,
  The water that has been heated is in a gas-liquid two-phase state, and the cooling means cools the carbon monoxide selective oxidation unit.
  Fuel reformer. The fuel reformer according to claim 2 , wherein
The water used to cool the carbon monoxide selective oxidation unit before Symbol cooling means, the relative reformer, the reformer in supplying water supplier so that the state of the water vapor Further comprising
The reformer generates a hydrogen rich gas by a steam reforming reaction using the hydrocarbon fuel and the water. The fuel reformer according to claim 2 or 3 , wherein
The temperature at which the reforming reaction proceeds in the reformer is 600 ° C. or higher,
The temperature at which the shift reaction proceeds Ru Der range from 200 ° C. to 400 ° C. In the shift unit
Fuel reformer. The fuel reformer according to any one of claims 1 to 4 , wherein the hydrocarbon fuel is natural gas or gasoline. A method for producing hydrogen by reforming a hydrocarbon fuel to produce hydrogen,
(A) proceeding with a reforming reaction to generate a hydrogen-rich gas from the hydrocarbon-based fuel;
(B) performing heat exchange between the hydrogen-rich gas and a predetermined fluid to lower the temperature of the hydrogen-rich gas and raise the temperature of the fluid;
(C) The concentration of carbon monoxide in the hydrogen-rich gas lowered in the step (b) by a shift reaction having a reaction temperature lower than that of the reforming reaction and generating carbon dioxide and hydrogen from carbon monoxide and water. Reducing the process,
( D ) By using the carbon monoxide selective oxidation catalyst that promotes the carbon monoxide selective oxidation reaction that oxidizes carbon monoxide in preference to hydrogen, by the carbon monoxide selective oxidation reaction having a reaction temperature lower than that of the shift reaction. And (c) reducing the carbon monoxide concentration in the hydrogen-rich gas whose carbon monoxide concentration has been reduced in the step (c) ,
The step ( d )
( D- 1) A hydrogen production method comprising a step of cooling the carbon monoxide selective oxidation catalyst using the fluid heated in the step (b). The hydrogen production method according to claim 6,
  The fluid is water;
  The temperature at which the carbon monoxide selective oxidation reaction proceeds in the step (d) is in the range of 100 ° C. to 200 ° C.,
  In the step (d-1), the carbon monoxide selective oxidation catalyst is cooled by using the water that has become a gas-liquid two-phase state by raising the temperature in the step (b).
  Hydrogen production method. The hydrogen production method according to claim 7 ,
Before Symbol (a) step, the (d -1) and water used to cool the carbon monoxide selective oxidation catalyst in the process, by reacting the hydrocarbon-based fuel, hydrogen by steam reforming reaction A method for producing hydrogen, which is a process of generating rich gas. The method for producing hydrogen according to claim 7 or 8 , comprising:
In step (a), the temperature at which the reforming reaction proceeds is 600 ° C. or higher,
The temperature at which the shift reaction proceeds Ru Der range from 200 ° C. to 400 ° C. In the step (c)
Hydrogen production method. The hydrocarbon-based fuels, hydrogen production method according to any one of claims 6 to 9 which is natural gas or gasoline. A fuel cell device comprising a fuel cell that obtains an electromotive force by an electrochemical reaction,
A fuel reformer according to any one of claims 1 to 5 ,
The fuel cell device proceeds with the electrochemical reaction using hydrogen generated by the fuel reformer.

Images