JPH0881202A - Methanol reformer for fuel cell - Google Patents

Abstract

PURPOSE: To keep good reforming ratio and prevent efficiency of whole system from lowering by connecting a reforming reacting part through a heat pipe to a chemical heat source part. CONSTITUTION: A condensing part 11b of a heat pipe 11 is installed in a reforming reacting part 10 for generating hydrogen and an evaporating part 11a of the heat pipe 11 has a part 19 heated by oxidation heat of a discharge gas discharged from a fuel cell and a part bringing into contact with an electric heat source part 20 controlled to a prescribed temperature. Since, in this methanol the reforming reacting part of methanol is connected through a heat pipe having uniform temperature characteristics to a chemical heat source part, oxidation (combustion) heat generated in the chemical heat source part is transported under heating so as to keep the temperature of each part of the reforming reacting part to uniform temperature. Since electric heat source part for assisting the chemical heat source part is attached to the heat pipe, good reforming ratio is always kept in the reforming reactor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reforming reactor for reforming a raw material gas into a desired gas by using a catalyst, and specifically, a reforming reactor having an endothermic effect of obtaining a hydrogen-containing gas from methanol. The present invention relates to a reforming reactor configured so that thermal energy is supplied to accelerate the reaction.

[0002]

2. Description of the Related Art Development of an electric vehicle is underway as a vehicle for reducing pollution in terms of noise reduction and exhaust gas purification. A type using a storage battery as a source of energy and a type using a fuel cell have been attempted. However, when using a fuel cell, it is desirable to use hydrogen gas, which has a large amount of heat and whose exhaust gas generated by combustion is clean, as fuel. . However, even if hydrogen gas is packed in a cylinder, it is difficult to mount it on a vehicle as it is. Recently, it has been considered to obtain hydrogen gas by reforming hydrocarbon, specifically methanol, as a raw material. Has been.

The steam reforming reaction for obtaining hydrogen gas from methanol as a raw material is Cu-Zn at 200 to 300 ° C.
Is a reaction to obtain hydrogen and carbon dioxide by passing a mixed gas of methanol and water through a catalyst portion such as a Cu system or a Cu-Cr system,
This proceeds as represented by the equation below.

CH ₃ OH = 2H ₂ + CO-90 kJ / mol CO + H ₂ O = H ₂ + CO ₂ +40 kJ / mol Therefore, CH ₃ OH + H ₂ O = 3H ₂ + CO ₂ -50 kJ / mol This is an endothermic reaction. Therefore, it is necessary to heat the catalyst in order to maintain the catalyst temperature within a predetermined temperature range, but the progress of the reforming reaction is not always uniform over the entire catalyst, so the reforming rate in the low temperature part (supplied The ratio of the amount of reacted methanol to the amount of methanol) decreases, and as a result, a trace amount of unreacted methanol or carbon monoxide may be discharged together with hydrogen gas. Since these methanol and carbon monoxide contained in hydrogen gas adversely affect the fuel cell, it is desirable to make them as zero as possible. It is effective to maintain the range.

In general, the above-mentioned endothermic reforming reaction is
Most of the catalyst proceeds on the supply side of the raw material gas, and gradually progresses while the unreacted raw material gas flows through the catalyst, so the temperature on the so-called inlet side of the catalyst tends to decrease and there is much heat dissipation to the outside. The temperature at the location tends to drop. As a technique for suppressing such a partial decrease in temperature and increasing the reforming rate, the device disclosed in Japanese Patent Laid-Open No. 62-17002 has been known.

This will be briefly described with reference to FIG.
This equipment consists of a steam drum 1 and a methanol vaporizer 2
, Methanol reformer 3, low temperature shift converter 4
, A steam separator 5, a fuel cell 6 and a catalytic combustor 7
The heat pipe 8 is provided between the methanol reformer 3 and the catalytic combustor 7. This heat pipe 8
Is the evaporator 8a on the side of the catalytic combustor 7 and the methanol reformer 3
The side is a condensing part 8b, and the evaporating part 8a is provided with a temperature controller 9. That is, in this apparatus, the heat generated by the catalytic oxidation (combustion) reaction of the combustible gas in the catalytic combustor 7 is used for heating the methanol reforming reaction part by being transported through the heat pipe 8. At this time, the temperature controller 9 controls the temperature of the evaporation portion 8a of the heat pipe by burning the auxiliary fuel stepwise.

[0007]

According to the above-mentioned conventional apparatus, it is possible to correct the temperature variation of the reforming catalyst by the temperature equalizing characteristic of the heat pipe. However, when this device is operated in a variable manner, specifically,
When the reforming amount of methanol is changed in order to adjust the power generation amount in the fuel cell 6, the thermal load changes in the methanol reformer 3, so that even if the amount of the auxiliary fuel is adjusted,
Immediately, the amount of heat of combustion given to the evaporator 8a of the heat pipe is not controlled, so that it becomes difficult to maintain the temperature of the heat pipe within an appropriate range, and there is a disadvantage that the reforming rate of methanol is lowered.

Therefore, it is conceivable to heat the evaporation part of the heat pipe by using an electric heater which can be controlled relatively easily without using combustion heat which is difficult to control the temperature due to heat transfer. Since the electric power generated by the fuel cell, that is, the generated electric energy is used, there is a disadvantage that the power generation efficiency of the entire fuel cell device is lowered.

The present invention has been made in view of the above circumstances, and the reforming reaction is performed so that the temperature of the reforming catalyst is made uniform and a good reforming rate is maintained, and the efficiency of the entire system is not lowered. The purpose is to provide a container.

[0010]

In order to achieve the above-mentioned object, the invention described in claim 1 is for supplying hydrogen gas to a fuel cell which carries out an electrochemical reaction between hydrogen gas and oxygen gas. In a methanol reformer for a fuel cell that performs a steam reforming reaction of methanol, a reforming reaction unit that reforms methanol to generate hydrogen and a chemical heat source unit that generates heat by oxidation heat are generated by the latent heat of vaporization of a working fluid. It is characterized in that it is connected by a heat pipe for transporting heat, and an electric heat source part for assisting the chemical heat source part is attached so as to be able to exchange heat with the heat pipe.

According to a second aspect of the present invention, the reforming reaction section is composed of a reforming reaction tube which has a reforming catalyst for reforming methanol and is formed in a substantially U shape. The heat pipe is disposed inside the heat pipe.

[0012] The invention described in claim 3 is characterized in that the electric heat source portion is made of PTC ceramics.

[0013]

According to the invention described in claim 1, since the reforming reaction part of methanol and the chemical heat source part are connected through a heat pipe having a temperature equalizing characteristic, the oxidation generated in the chemical heat source part The (combustion) heat is transferred so that the respective parts of the reforming reaction part are soaked. Since the heat pipe is equipped with the electric heat source part that assists the chemical heat source part, a good reforming rate is always maintained in this reforming reactor. Specifically, when the reforming amount of methanol is increased in order to increase the power generation amount in the fuel cell, a reforming reaction involving many endothermic actions occurs in the reforming reaction part, and Although the temperature of the reforming reactor tends to decrease, the temperature of the reforming reaction section is quickly maintained at a predetermined temperature by the electric heat source section whose temperature control is easy and the temperature response is good. The reforming rate continues to be maintained. In other words, the electric heat source section is used as an auxiliary heat source for maintaining a good reforming rate in the reforming reactor, and the electric heat source section only adjusts the temperature of the reforming reaction section. The amount of electrical energy consumed is significantly reduced.

According to the invention described in claim 2, substantially U
The reforming reaction of methanol is performed inside the reforming reaction tube formed in a letter shape, and the reforming reaction tube absorbs heat from the outside. Since the reforming reaction tube is disposed inside the heat pipe, the outer peripheral portion of the reforming reaction tube functions as the condensing portion of the heat pipe. Therefore, the reforming reaction tube is heated to a uniform temperature due to the soaking property of the heat pipe. Therefore, this reforming reaction section continues to maintain a good reforming rate.

According to the invention described in claim 3, PT
C (Positive Temperature Coefficient) ceramics are ceramics that have the characteristic that they generate heat when energized and their electric resistance increases as the temperature rises. Thus, the portion of the heat pipe that exchanges heat with the PTC ceramics is quickly and accurately maintained at a predetermined temperature. Therefore, this reforming reaction section keeps a good reforming rate.

[0016]

EXAMPLES Examples of the present invention will be described below.
In each of the heat pipes described below, a condensable working fluid W that evaporates and condenses in a target temperature range is enclosed in a deaerated hermetic container, and the working fluid W evaporates in a portion with heat input. At the same time, the vapor flows to the heat radiation portion, and then the heat is taken away and condensed to mainly transport the heat as latent heat of vaporization of the working fluid W.

First, a first embodiment will be described with reference to FIGS. 1 and 2. The reforming reactor of the first embodiment includes a reforming reaction section 10 carrying a methanol reforming catalyst.
And a plurality of wick type heat pipes 11 and a heat source unit 12 for heating the heat pipes 11. The evaporating section 11 a of the heat pipe 11 is arranged in the heat source section 12, and the condensing section is arranged in the reforming reaction section 10. Here, the wick type heat pipe refers to a heat pipe of a system in which the condensed working fluid W in a liquid phase is circulated to the evaporation section by a wick having a capillary action, and the evaporation section and the condensation section are relatively free. It can be installed in.

In the reforming reaction section 10, a metallic honeycomb 13 carrying a Cu--Zn type reforming catalyst with a thickness of 30 to 80 μm is brazed or diffusion welded to the outer periphery of each heat pipe 11. The reforming flow path 14 is formed so as to be wound so as to be wound around. Then, as shown in FIG. 2, inside the case 15 having a substantially regular hexagonal cross section,
The plurality of reforming channels 14 are arranged in a staggered manner. A heat insulating material 16 is filled between the reforming passages 14 and between the reforming passages 14 and the case 15. At this time, vacuum heat insulation may be performed instead of the heat insulation material 16. The case 15 is provided with gas flow paths 17 and 18 communicating with the reforming flow path 14.
The reforming raw material gas, that is, methanol gas and water vapor are supplied from one of the flow paths 17 of 8, and the other flow path 18 of
Hydrogen gas as a fuel gas and carbon dioxide gas as a by-product are supplied to a fuel cell (not shown).

The heat source section 12 in which the evaporation section 11a of the heat pipe 11 is disposed includes an oxidation heat source section 19 and an electric heater 20 as an electric heat source. The oxidation heat source unit 19 communicates with the exhaust port of the fuel cell, and an inlet port 21 into which unused hydrogen gas and air (oxygen in air) flow.
And a discharge port 22 through which the gas after oxidation is discharged. And this oxidation heat source part 19
The fins 23 are brazed to the evaporation part 11a of the heat pipe 11 disposed inside the heat pipe 11, and the oxidation (combustion) catalyst, for example, a Pt-based catalyst having a thickness of 30 to 80 μm is attached to the surfaces of the fins 23 and the evaporation part 11a. It is carried by. A combustion system using a burner equipped with an ignition device without providing an oxidation catalyst may be used. Further, the electric heater 20 is arranged so as to come into contact with the evaporation portions 11a of all the heat pipes 11,
The evaporator 11a is configured to maintain a predetermined temperature according to an instruction from a temperature sensor (not shown) provided in the evaporator 11a. In addition, electric heater 2
0 can also be configured to apply a predetermined voltage to the PTC ceramics.

The operation of the first embodiment configured as described above will be described. The reforming raw material gas is introduced into the reforming flow path 14 formed of the metal honeycomb 13 through the gas flow path 17, contacts the reforming catalyst, and is reformed into hydrogen gas. In the fuel cell, this hydrogen gas is introduced to generate electricity, but about 20-50% of the hydrogen gas introduced in this fuel cell
However, it is discharged as unused without electrochemical reaction. This unused hydrogen gas is introduced into the oxidation heat source section 19 through the inlet 21. In the reforming reaction part 10, an attempt is made to lower the temperature of the reforming flow path 14, particularly the inlet part of the reforming flow path 14 and the condensing part 11b of the heat pipe 11 and hence the evaporating part 11a, by the heat absorption effect of the reforming reaction. . At this time, on the evaporation section 11a side of the heat pipe 11, the hydrogen gas introduced into the combustion heat source section 19 oxidizes with oxygen in the air on the surface of the evaporation section 11a and the like to generate oxidation heat, and this oxidation heat is The electric heater 20 is directly conducted to the evaporation part 11a.
The Joule heat generated from the heat pipe 11 is transported so as to maintain the entire temperature of the condensing portion 11b and the reforming flow path 14 at a predetermined temperature due to the uniform temperature characteristic of the heat pipe 11.

By the way, the amount of the reforming raw material gas introduced into the reforming reaction section 10 varies slightly even during steady operation. Therefore, the amount of heat absorbed by the reforming reaction also slightly changes. Therefore, the heat source unit 1 during this steady operation
If, for example, 5 to 20% of the amount of heat transferred from 2 to the reforming reaction unit 10 is configured to be obtained by the electric heater 20, the electric heater 20 can be used so as to correspond to the change in the temperature of the evaporation unit 11a due to the change in the heat absorption amount. Since the heater 20 operates quickly, temperature fluctuations in the condenser section 11b and the reforming reaction section 10 are suppressed, and the reforming rate of methanol in the reforming reaction section 10 does not fluctuate, that is, deteriorates. In other words,
Since the electric heater 20 only holds (adjusts) the temperature of the reforming reaction part as an auxiliary heat source for maintaining a good reforming rate, the electric heater 20 is used as an auxiliary energy source to generate electric energy generated by the fuel cell. Will not consume too much. Further, the power generation of the fuel cell can be operated not only in the upper limit direction but also in the lower limit direction within a range of approximately 5 to 20%.

Here, when the electric heater 20 is configured to apply a predetermined voltage to the PTC ceramics, the PTC ceramics heater generates heat by energization, and the electric resistance increases as the temperature rises, so that the electricity and heat are generated. Since it disappears, it operates so as to maintain a predetermined temperature. That is, the PTC ceramics heater and the evaporation part of the heat pipe in contact with the PTC ceramics heater have a self-temperature converging property, and a control means such as a temperature sensor is not required. Further, since the cross section of the reforming reaction section 10 is formed into a substantially regular hexagon and the heat pipes 11 are arranged in a zigzag pattern, the reforming reaction section 10 corresponding to the size of the reforming reactor, that is, the reforming reaction section is formed. Since the volumetric efficiency of the catalyst is high, the size of the reforming reactor can be reduced and the amount of the heat insulating material 16 provided can be reduced.

Next, a second embodiment of the present invention will be described with reference to FIG.
Will be described with reference to. The second embodiment uses a thermosyphon type heat pipe 11 in which a plurality of evaporation portions 11a that are arranged are integrally configured and gravity is used to recirculate the working fluid W. In the first embodiment, when a temperature drop occurs in any of the evaporating units 11a of the heat pipes 11 arranged, all the evaporating units 11a are heated. In the example, such a situation does not occur, and the amount of electric energy consumed by the electric heater 20 is further reduced as compared with the first embodiment. Further, since the thermosyphon type heat pipe is used, the wick is not required and the structure of the heat pipe 11 can be simplified.

Further, FIG. 4 shows the third embodiment of the present invention.
Will be described with reference to. The third embodiment uses a thermosyphon type heat pipe 11 as in the second embodiment. The diameter of the upper portion of the heat pipe 11 is formed to be larger than the diameter of the lower portion thereof, and a plurality of U-shaped tubes 24 are arranged inside the heat pipe 11. Further, the periphery of the upper portion is covered with a heat insulating material 16. Also,
The lower portion of the heat pipe 11 is arranged so as to penetrate the oxidation heat source portion 19, and the electric heater 20 is connected to the lower end portion of the protruding portion thereof. Also, a plurality of U-shaped tubes 24
Inside, the pellet-shaped reforming catalyst is filled,
One pipe port is connected to the reforming raw material gas flow channel 17, and the other pipe port is connected to the fuel gas flow channel 18.

The operation of the third embodiment will be described below.
The reforming raw material gas passes through the pellet-shaped catalyst packed in the U-shaped tube and is reformed into the fuel gas. At this time,
An endothermic reaction occurs inside the U-shaped tube 24, and the temperature of the outer surface of the U-shaped tube 24 tends to decrease.
Since the outer surface of the entire U-shaped tube 24, to be precise, the outer surface of the U-shaped tube 24 serves as a condensing portion, each part of all the U-shaped tubes 24 is heated to a predetermined temperature.

Unlike the first and second embodiments, the third embodiment described above does not require the metal honeycomb 13 and does not need to carry the reforming catalyst on the surface of the metal honeycomb 13. Therefore, the structure of the reforming reactor becomes simple. Therefore, the productivity of this reforming reactor is improved. Also,
Since the metal honeycomb 13 and the heat pipe 11 do not come into contact with each other, it is not necessary to consider the thermal stress of them. Further, unlike the first and second embodiments, it is not necessary to dispose a heat insulating material between the reformed gas flow passages, that is, between the U-shaped tubes 24, so that the size of the reforming reactor can be increased. The volumetric efficiency of the reforming reaction section 10, that is, the utilization rate of the reforming catalyst is very high, and the reforming reactor can be made smaller.

Since the present invention uses an electric heater which can easily control the temperature and has high responsiveness as an auxiliary heat source for finally maintaining the reforming reaction part at a predetermined temperature, As shown in the third embodiment, the location of the electric heater is not particularly limited, and it is suitable that the temperature sensor is provided in the condensing section or the reforming reaction section of the heat pipe. As a matter of course, the present invention only needs to use a heat pipe having a temperature equalizing characteristic.
That is, it goes without saying that it does not matter whether it is a wick type or a thermosyphon type.

[0028]

As described above, according to the invention described in claim 1, the temperature uniformity of the heat pipe makes the temperature of each part of the reforming reaction part uniform, and the temperature control is easy. The reforming reaction section is maintained at a predetermined temperature by the electric heat source section having good temperature responsiveness. That is, since the electric heat source section only adjusts the temperature of the reforming reaction section, it does not excessively consume the electric energy generated from the fuel cell, so that the power generation efficiency of the entire fuel cell power generator is improved. Further, since the reforming reaction section is quickly maintained at a predetermined temperature and the utilization rate of the reforming catalyst does not decrease, it is not necessary to upsize the fuel cell reforming reactor for variable operation.

In particular, according to the invention described in claim 2,
Since the reforming reaction section does not need a honeycomb structure and is very simple, the reforming reactor for a fuel cell becomes inexpensive and the production efficiency is improved.

Further, according to the invention described in claim 3, since the control device for maintaining the temperature of the reforming reaction part at a predetermined temperature is not required, the reliability is improved and at the same time,
The production efficiency is improved and it can be provided at a low cost.

[Brief description of drawings]

FIG. 1 is a first of a methanol reformer for a fuel cell according to the present invention.
It is sectional drawing which shows an Example schematically.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a second part of the methanol reformer for a fuel cell according to the present invention.
It is sectional drawing which shows an Example schematically.

FIG. 4 is a third part of the methanol reformer for a fuel cell of the present invention.
It is sectional drawing which shows an Example schematically.

FIG. 5 is a diagram schematically showing a conventional methanol reformer for a fuel cell.

[Explanation of symbols]

 10 Reforming Reaction Part 11 Heat Pipe 11a Evaporating Part 11b Condensing Part 12 Heat Source Part 19 Chemical (Oxidation) Heat Source Part 20 Electric Heat Source Part (Heater)

Claims (3)

[Claims] 1. A methanol reformer for a fuel cell that performs a steam reforming reaction of methanol to supply hydrogen gas to a fuel cell that performs an electrochemical reaction between hydrogen gas and oxygen gas, by reforming methanol. A reforming reaction section for generating hydrogen,
A chemical heat source part that generates heat by oxidation heat is connected by a heat pipe that transports heat by latent heat of vaporization of a working fluid, and an electric heat source part that assists the chemical heat source part is attached so as to be capable of exchanging heat with the heat pipe. A methanol reformer for a fuel cell, which is characterized in that 2. The reforming reaction section comprises a reforming reaction tube having a substantially U-shape, which contains a reforming catalyst for reforming methanol, and is disposed inside the heat pipe. It is provided, The methanol reformer for fuel cells of Claim 1 characterized by the above-mentioned. 3. The methanol reformer for a fuel cell according to claim 1, wherein the electric heat source section is made of PTC ceramics.