JP2006062884A - Fuel reformer and fuel reforming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel reformer simple in equipment constitution and good in the production efficiency of hydrogen, and a fuel reforming method. <P>SOLUTION: The fuel reformer of the invention is for steam reforming of methanol, and provided with a reaction vessel 14, which stores a mixture liquid 21 constituted of a methanol aqueous solution 20 and a fine powdery reforming catalyst 31, a fine bubble generating means 23 for generating fine bubbles 26 in the mixture liquid 21 inside the reaction vessel 14, and a heating means 15 for heating the reaction vessel 14. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel reforming apparatus and a fuel reforming method that perform steam reforming of methanol to generate hydrogen gas.

  In recent years, hydrogen has attracted attention as a new energy source to replace fossil fuels as global environmental problems increase. There is a polymer electrolyte fuel cell (hereinafter referred to as PEFC (Polymer Electrolyte Fuel Cell)) that generates electricity by electrochemically reacting hydrogen and oxygen with this hydrogen as a fuel.

  Hydrogen for PEFC is generally produced from city gas mainly composed of methane, natural gas, liquefied petroleum gas (LPG), alcohol such as methanol, naphtha and the like. Of these fuel gases, methanol is an inexpensive liquid fuel that is easily synthesized from fossil fuels, and has the advantage that hydrogen can be produced relatively easily by using a catalyst. As a hydrogen source for As PEFC using methanol, there are a methanol reformed PEFC and a direct methanol fuel cell (hereinafter referred to as DMFC (Direct Methanol Fuel Cell)).

A methanol reforming fuel cell reforms methanol using a reformer to produce hydrogen, and uses this hydrogen as fuel. As a typical methanol reforming method,
a) steam reforming,
b) Partial oxidation reforming,
c) Autothermal reforming (also called Oxygen Steam Reforming),
Is mentioned.

  In the steam reforming reaction of a), as shown in the formula (1), methanol and steam are mixed and reacted at a temperature of about 150 to 300 ° C. to decompose methanol into hydrogen and carbon dioxide (for example, , See Patent Document 1).

CH ₃ OH + H ₂ O → 3H ₂ + CO ₂ Formula (1)
In the partial oxidation reforming of b), as shown in the formula (2), methanol is reacted halfway with a small amount of air (oxygen) to decompose methanol into hydrogen and carbon dioxide.

CH ₃ OH + 1 / 2O ₂ → CO ₂ + 2H ₂ (2)
In the autothermal reforming of c), since the steam reforming reaction shown in the formula (1) is a relatively large endothermic reaction, the above formula (2), the following formula (3) , In combination with a partial oxidation reaction of at least one methanol represented by formula (4), the methanol is decomposed into hydrogen and carbon dioxide.

CH ₃ OH + 1 / 2O ₂ → CO + H ₂ + H ₂ O Formula (3)
CH ₃ OH + O ₂ → CO ₂ + H ₂ + H ₂ O (4)
On the other hand, DMFC directly separates H of methanol molecules (CH ₃ OH) one by one at the fuel electrode without using a reformer, and reacts the remaining CO with water (H ₂ O) to produce carbon dioxide ( CO ₂ ), which uses methanol directly as fuel.

JP 2002-542143 A

The steam reforming of a) absorbs heat from the outside and generates three hydrogen molecules from one methanol molecule, so the generated hydrogen is larger in energy than the original methanol, and energy efficiency Has the advantage of being good. However, since the steam reforming reaction is an endothermic reaction, it is necessary to heat to about 150 to 300 ° C. with an electric heater or a methanol burner at the time of starting. For this reason, there was a problem that startability and responsiveness were inferior. Further, even in a steady state, it is necessary to heat with a heater or a burner in order to maintain the reaction temperature, and accordingly, energy loss and energy efficiency decrease. Furthermore, during the reforming reaction, carbon monoxide (CO) that causes a drop in the performance of the fuel cell is partially generated, so that an oxidizer or the like is required to selectively CO react with CO ₂ to obtain CO ₂ . That is, since a device such as a vaporizer, a reformer, and an oxidizer for gasifying methanol and water is required, there is a problem that the device configuration becomes complicated.

  The partial oxidation reforming b) is an exothermic reaction, and has an advantage of good startability and responsiveness because the reaction proceeds spontaneously even if heat is not supplied from the outside. However, since only two hydrogen molecules are generated from one methanol molecule, there is a problem that energy efficiency is not so good. Further, since nitrogen in the air remains in the reformed product gas, there is a problem that the hydrogen concentration is low.

  In c) autothermal reforming, the partial oxidation reforming ratio is increased at start-up or when the load increases, and the steam reforming ratio is increased at steady state or when the heat supply is sufficient to operate the fuel cell. Yes. That is, it has both the advantage that the energy efficiency of a) is good, and the advantage that b) the startability and responsiveness are good. However, since the steam reforming reaction is performed in a steady state, it is necessary to heat with a heater or a burner in order to maintain the reaction temperature, and energy loss and energy efficiency are reduced accordingly. Moreover, since energy is required to activate the reforming catalyst, energy is lost. Furthermore, an oxidizer that oxidizes carbon monoxide (CO) is required. Further, since nitrogen in the air remains in the reformed product gas, there is a problem that the hydrogen concentration is low.

On the other hand, since DMFC does not require a reformer, the configuration of the apparatus is simple, and since it operates at almost normal temperature and normal pressure, startability and responsiveness are good. However, since the reaction rate of methanol at the fuel electrode is slow and the electrode activity is low, there is a problem that a part of unreacted methanol passes through the polymer membrane as it is, so-called “methanol crossover” occurs. . There is also a problem that the catalyst supported on the electrode surface of the fuel electrode is very expensive. Furthermore, there has been a problem that the reaction between carbon monoxide (CO) and water (H ₂ O) at the fuel electrode is slow. If this reaction is slow, the reaction for separating H from methanol molecules will be slow. Therefore, it is necessary to activate the catalyst of the fuel electrode, but energy is required for that purpose, resulting in energy loss.

  An object of the present invention created in view of the above circumstances is to provide a fuel reforming apparatus and a fuel reforming method that have a simple apparatus configuration and good hydrogen generation efficiency.

To achieve the above object, a fuel reformer according to the present invention is a fuel reformer that performs steam reforming of methanol,
A reaction tank in which a mixed liquid composed of a methanol aqueous solution and a finely powdered reforming catalyst is stored;
Microbubble generating means for generating microbubbles in the mixed liquid inside the reaction vessel,
Heating means for heating the reaction vessel;
It is equipped with.

  Here, the microbubble generating means may be an ultrasonic oscillator. The heating means is preferably a fuel cell using hydrogen gas as fuel. It is preferable to arrange porous particles at the bottom of the reaction vessel. The porous granule may be a tablet-like reforming catalyst. The heating and heat transfer surface inner wall of the reaction tank may be formed on an uneven surface.

The fuel reformer according to the present invention is a fuel reformer that performs steam reforming of methanol,
A reaction tank in which a mixed liquid composed of a methanol aqueous solution and a finely powdered reforming catalyst is stored;
A circulating means for circulating the mixed liquid in the reaction tank;
Heating means for heating at least a part of the circulating means and heating the mixed liquid circulating inside the circulating means;
Microbubble generating means for generating microbubbles in the heated mixed liquid;
It is equipped with.

  Here, the circulating means may have a head part for discharging and dropping the mixed liquid into the mixed liquid pool inside the reaction tank at the end of the last flow side, and the micro-bubble generating means may be provided in the head part. The microbubble generating means may be an ultrasonic oscillator. The fine bubble generating means may be a foam forming mesh member provided at the liquid mixture discharge port of the head portion. The heating means is preferably a fuel cell using hydrogen gas as fuel. The circulation means preferably includes a heating heat exchanger. The heating and heat transfer surface inner wall of the circulation means may be formed on the uneven surface.

On the other hand, the polymer electrolyte fuel cell system according to the present invention is:
The fuel reformer described above;
Supply means for supplying an aqueous methanol solution into the reaction tank of the fuel reformer;
A hydrogen line that extracts hydrogen gas and methanol mist generated inside the reaction tank, heat-exchanges the gas mixture, gas-liquid separation, and a hydrogen line that supplies only hydrogen gas to the fuel cell;
It is equipped with.

On the other hand, the fuel reforming method according to the present invention is a fuel reforming method for performing steam reforming of methanol,
Using an ultrasonic oscillator to ultrasonically vibrate a mixed solution composed of an aqueous methanol solution and a fine powdery reforming catalyst stored in the reaction vessel, and generating cavitation in the mixed solution; ,
Heating the liquid mixture inside the reaction vessel by boiling heat transfer to form microbubbles with cavitation as a nucleus in the liquid mixture;
A step of reforming methanol inside the microbubbles formed by adhering a reforming catalyst around it to generate hydrogen gas; and
Is included.

  Here, it is preferable to heat the reaction vessel so that the liquid temperature of the mixed solution becomes 60 to 85 ° C.

The fuel reforming method according to the present invention is a fuel reforming method for performing steam reforming of methanol,
Extracting a part of the mixed solution composed of the aqueous methanol solution stored in the reaction tank and the finely powdered reforming catalyst using a circulation means;
Heating the liquid mixture flowing inside the circulation means to subcool the liquid mixture;
Re-feeding the mixed liquid after subcooled boiling into the reaction vessel;
Forming microbubbles in the mixture using the microbubble generating means;
A step of reforming methanol inside the microbubbles formed by adhering a reforming catalyst around it to generate hydrogen gas; and
Is included.

  Here, it is preferable to heat the circulation means so that the liquid temperature of the mixed liquid flowing inside the circulation means becomes 60 to 85 ° C. When returning the mixed liquid after subcooled boiling to the inside of the reaction vessel, the ultrasonically oscillated liquid mixture is used to generate cavitation in the mixed liquid, and the mixed liquid is discharged into the mixed liquid reservoir. It may be dropped. When returning the mixed liquid after subcooled boiling to the inside of the reaction tank, the mixed liquid is discharged and dropped into the mixed liquid reservoir via the foam forming mesh member provided at the return port, and cavitation is generated in the mixed liquid. You may let them.

  According to the present invention, it is possible to obtain an excellent fuel reforming apparatus that has a simple apparatus configuration and is inexpensive.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a preferred embodiment of the invention will be described with reference to the accompanying drawings.

(First embodiment)
A schematic diagram of a fuel reformer according to a preferred embodiment of the present invention is shown in FIG.

As shown in FIG. 1, the fuel reformer according to the present embodiment is
A reaction tank 14 in which a mixed liquid 21 composed of a methanol aqueous solution 20 and a fine powdery reforming catalyst 31 (see FIG. 3) is stored;
An ultrasonic oscillation device (microbubble generating means) 23 for generating microbubbles 25 in the liquid mixture 21 inside the reaction tank 14;
PEFC (heating means) 15 for heating the reaction vessel 14 and heating and boiling the mixed solution 21;
It is equipped with.

PEFC15 includes a fuel electrode (anode) 15a which hydrogen gas G _H is introduced, and an air electrode (cathode) 15b which air G _A is introduced, the electrolyte is interposed between the fuel electrode 15a and an air electrode 15b And a membrane (ion exchange membrane) 15c. The fuel electrode 15a and the air electrode 15b are electrically connected via a load 15d. The fuel electrode 15a has a hydrogen line 17 (described later), an air supply line 18 at one end of the air electrode 15b (left end in FIG. 1), and an air supply line 18 at the other end (right end in FIG. 1). Line 19 is connected. The PEFC 15 having such a configuration is provided in a state where the air electrode 15 b side is in contact with the bottom surface of the reaction tank 14.

  The ultrasonic oscillator 23 includes an oscillator 24a and a vibrator (main body) 24b. The ultrasonic oscillating device 23 is provided in a state where the vibration surface (left surface in FIG. 1) of the vibrator 24 b is in contact with the side wall of the reaction vessel 14.

  Porous particles are disposed at the bottom of the reaction vessel 14. This porous particle is composed of a tablet-like reforming catalyst 22 (or boiling stone). Here, instead of arranging the porous particles at the bottom of the reaction vessel 14, the heating and heat transfer surface inner wall (bottom inner wall in FIG. 1) of the reaction vessel 14 is changed to an uneven surface (surface having a rough surface). You may form in. For example, the surface roughness is adjusted so that the average roughness Ra of the inner wall of the heating and heat transfer surface is 1 to 100 μm.

  The amount of the finely powdered reforming catalyst 31 does not decrease with fuel reforming. For this reason, a supply means for the reforming catalyst 31 is not particularly required. However, if necessary, the reforming catalyst 31 may be supplied into the reaction tank 14 via a catalyst supply line (not shown) connected to the reaction tank 14. Good.

  Here, the constituent materials of the reforming catalysts 22 and 31 are not particularly limited, and all conventional methanol reforming catalysts can be applied, and examples thereof include Cu / Zn-based and Pd / Zn-based. .

  The average particle diameter of the fine powdery reforming catalyst 31 constituting the mixed liquid 21 is set to 1000 to 1 nm, preferably 10 to 1 nm.

  The average size of the tablet-like reforming catalyst 22 disposed at the bottom of the reaction tank 14 is 50 to 5 mm in diameter and 10 to 1 mm in height, preferably 10 to 5 mm in diameter and 5 to 1 mm in height. The

  The length of the ultrasonic vibration direction (the left-right direction in FIG. 1) in the reaction tank 14 needs to be longer than the wavelength (λ (= c / f), c: speed of sound, f: frequency). This is because the generation of cavitation, which will be described later, occurs at the node of the ultrasonic wave. Further, the length of the reaction tank 14 in the direction perpendicular to the ultrasonic vibration direction (direction perpendicular to the drawing of FIG. 1) is appropriately determined according to the volume of the reaction tank 14, and is particularly limited. is not.

  In the fuel reformer according to the present embodiment, the case where the PEFC 15 is attached to the bottom of the reaction vessel 14 and the ultrasonic oscillator 23 is attached to the side wall of the reaction vessel 14 has been described. There is no particular limitation. For example, as shown in FIG. 4, the ultrasonic oscillator 23 may be attached to the bottom of the reaction vessel 14 and the PEFC 15 may be attached to the side wall of the reaction vessel 14. In this case, the attachment position of the PEFC 15 on the side wall of the reaction tank 14 is preferably as low as possible below the reaction tank 14.

In the fuel reformer according to the present embodiment having the above-described configuration, supply means for supplying the aqueous methanol solution 20 into the reaction tank 14 of the fuel reformer, hydrogen generated in the reaction tank 14 and methanol mist ( withdrawn mixture G _M of methanol vapor + water vapor), is obtained by connecting the recovery heat exchanger 13 for condensing and recovering the hydrogen line 17, and methanol mist supplying hydrogen gas G _H to the fuel electrode 15a of PEFC15, present The PEFC system 10 according to this embodiment is used.

The supply means connects the methanol tank 12 that temporarily stores the methanol aqueous solution 20 and performs gas-liquid separation, the supply device 11 that supplies the methanol aqueous solution 20 to the methanol tank 12, the methanol tank 12, and the reaction tank 14. And a supply line 16 through which 20 flows. Here, it is preferable that the supply device 11 includes a backflow prevention means (for example, a check valve) so that the hydrogen gas _GH in the methanol tank 12 is not released to the atmosphere.

Hydrogen line 17 connects the methanol tank 12 and the reaction vessel 14, constituted by a line 17a to the air-fuel mixture G _M flows, connected to the fuel electrode 15a of the methanol tank 12 and PEFC15, and line 17b through which hydrogen gas G _H Is done.

The recovery heat exchanger 13 is provided in the middle of the supply line 16 and the line 17a. The recuperator, sensible heat of the gas mixture G _M flowing through the line 17a is collected, the aqueous methanol solution 20 flowing in the supply line 16 is heated.

  Next, a fuel reforming method using the PEFC system 10 according to the present embodiment will be described based on the attached drawings.

  In a typical steam reforming reaction environment, the reaction temperature is 150 to 250 ° C., and the reaction pressure (differential pressure from atmospheric pressure (= about 0.1 MPa)) is 0.3 MPa. As a result of intensive studies by the present inventors, the reaction environment of the liquid mixture 21 in the reaction vessel 14 is steam reformed by utilizing the fact that the pressure rise and the temperature rise due to the surface tension inside the microbubbles having a diameter of about several μm. It has been found that even if the reaction environment is not satisfied, steam reforming can be locally generated in the microbubbles generated in the mixed liquid 21.

  In the fuel reforming method according to the present embodiment, first, an aqueous methanol solution 20 is supplied from the methanol tank 12, and a mixed liquid composed of the aqueous methanol solution 20 and the finely powdered reforming catalyst 31 in the reaction tank 14. 21 is stored. Here, the mixing ratio of methanol in the methanol aqueous solution 20 is not particularly limited as long as the same number of molecules of methanol and water can be collected to form a stable cluster. For example, 20 to 90 wt% , Preferably 35-60 wt%. Moreover, when supplying the methanol aqueous solution 20 from the methanol tank 12, it can supply, without using electric power, for example by utilizing the level difference of the methanol tank 12 and the reaction tank 14. FIG.

  Since the steam reforming reaction is an endothermic reaction, it is necessary to heat the liquid mixture 21 in order to advance the reaction. In the fuel reforming method according to the present embodiment, the mixed liquid 21 is heated using the heat of chemical reaction in the PEFC 15. At the time of start-up, since the chemical reaction heat of PEFC 15 cannot be used, the mixed liquid 21 in the reaction tank 14 is heated using a methanol burner or the like. If sufficient heat of chemical reaction is generated in the PEFC 15 after starting, heating with a methanol burner or the like becomes unnecessary. Here, the liquid temperature of the mixed liquid 21 is in the range of 60 to 85 ° C., preferably 35 to 75 ° C. where the incidence of cavitation by ultrasonic waves described later is high, and more than the boiling point of methanol (64.65 ° C.), that is, 64.65. It is set to -75 degreeC, More preferably, it is set as 70-75 degreeC which is easy to produce boiling of methanol.

  In parallel with this heating, the reaction vessel 14 is subjected to ultrasonic vibration using the ultrasonic oscillator 23 to generate cavitation in the liquid mixture 21 (cavitation generation step). Here, the frequency oscillated from the ultrasonic oscillator 23 is preferably 20 to 40 kHz, which has a high cavitation rate.

  Using this cavitation as a “boiling nucleus”, bubbles are generated by nucleate boiling, and methanol boiling bubbles (microbubbles 26) are generated (microbubble formation step). At this time, water vapor and methanol vapor are enclosed in the microbubbles 26, and the fine powdery reforming catalyst 31 is adsorbed and attached around the microbubbles 26 by the interfacial force.

  The pressure and temperature in the microbubbles 26 generated in the mixed liquid 21 are increased by the surface tension. At this time, as shown in FIG. 2, if the bubble diameter of the microbubbles 26 is 5 μm or less (shaded area A in FIG. 2), a differential pressure of 0.05 MPa or more is generated with respect to the atmospheric pressure. When in contact with the reforming catalyst 31, even if the reaction environment of the liquid mixture 21 is a reaction temperature of 80 ° C. or less and a reaction pressure as small as 0.05 MPa, the water vapor represented by the formula (1) inside the microbubbles 26 The reforming reaction proceeds.

CH ₃ OH + H ₂ O → 3H ₂ + CO ₂ Formula (1)
Therefore, as shown in FIG. 3, the hydrogen gas _GH is reformed and generated in the microbubbles 26 rising and rising in the mixed liquid 21 (hydrogen gas generation step). In the following, “microbubble 26” refers to a microbubble having a bubble diameter of 5 μm or less unless otherwise specified.

As the microbubbles 26 rise and rise, the internal temperature gradually decreases and contracts. Some of the microbubbles 26 that have reached the liquid level of the mixed liquid 21 due to rising and floating are further collected and combined. As a result, the surface tension is reduced, the microbubbles 26 are repelled, and the generated hydrogen gas _GH is released. At this time, together with the hydrogen gas _GH , unreacted methanol vapor and water vapor that did not contribute to the reaction are also released. That is, on the liquid surface of the mixture 21 inside the reaction vessel 14, there is air-fuel mixture G _M hydrogen gas G _H and methanol mist (methanol vapor + water vapor).

Mixture G _M in the reaction vessel 14 is withdrawn through the hydrogen line 17. Mixture G _M, first flows through the front side of the line 17a in the hydrogen line 17, in the recuperator 13, is heat exchanged with the methanol aqueous solution 20 flowing through the supply line 16. The by heat exchange sensible heat of the mixed gas G _M is cooled is recovered and condense each of methanol and water becomes the dew point or less. Methanol solution 20 flowing in the supply line 16, after being heated to 80 ° C. Near utilizing the sensible heat of the gas mixture G _M, is fed to the reaction vessel 14.

Thereafter, the mixture G _M is introduced into the methanol tank 12 is separated into a hydrogen gas G _H and liquid (methanol aqueous solution). Since this separation is gas-liquid separation, it can be easily separated without using a special separation device such as a gas separation device. The separated aqueous methanol solution is collected in the methanol tank 12. Hydrogen gas G _H after separation flows through the second-stage of the line 17b in the hydrogen line 17, is supplied to the fuel electrode 15a of PEFC15.

The hydrogen gas _GH supplied to the fuel electrode 15a is ionized as shown in equation (5). Hydrogen atoms (protons) that have lost the electrons (e ⁻ ) are supplied to the air electrode 15b through the electrolyte membrane 15c. Further, the electrons are supplied to the air electrode 15b through the load 15d. In the air electrode 15b, first, protons and air G _A supplied via the air supply line 18 react to form water without electrons, and then react with electrons to obtain the equation (6). Water W is obtained. The generated water W, together with the unreacted surplus air G _A, and is discharged from the discharge line 19.

_{^{2H 2 → 4H + + 4e -}} ... formula (5)
O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O (6)

  Since the finely powdered reforming catalyst 31 in the mixed liquid 21 is stirred by ultrasonic vibration, it is uniformly dispersed in the mixed liquid 21 without being agglomerated. Further, bubbles due to nucleate boiling generated on the surface of the porous reforming catalyst 22 having a tablet shape are efficiently separated from the reforming catalyst 22 by being shaken by ultrasonic vibration.

  If the generated microbubbles 26 are too small, the microbubbles 26 cannot easily rise and float in the mixed liquid 21. However, some of the bubbles generated by nucleate boiling are immediately gathered and coalesced by ultrasonic vibration. As a result, the generated microbubbles 26 have a certain size (for example, 5 μm or less), and the retention time (steam reforming reaction time) of the microbubbles 26 in the mixed liquid 21 is sufficiently secured. The microbubbles 26 can be efficiently lifted and floated.

  As time elapses from the start of the start, the temperature of the mixed liquid 21 gradually rises and finally reaches 70 to 75 ° C., and in some cases close to 80 ° C. When the temperature difference between the mixed liquid 21 and the PEFC 15 is reduced, heat transfer is less likely to occur. Therefore, when the mixed solution 21 is heated by the PEFC 15, it is important how the heat of the PEFC 15 is transferred to the mixed solution 21 in the reaction tank 14.

  Therefore, in the fuel reformer according to the present embodiment, the porous reforming catalyst 22 having a tablet shape is disposed on the heat transfer surface. As a result, the reforming catalyst 22 has the function of a boiling stone as well as the reforming action. Therefore, the mixed liquid 21 is not overheated, and nucleate boiling is surely generated on the heat transfer surface. As a result, regardless of the temperature difference between the mixed liquid 21 and the PEFC 15, boiling heat transfer is performed on the heat transfer surface, so that the heat transfer effect from the PEFC 15 increases, that is, the heat removal / cooling effect of the PEFC 15 increases. Therefore, it is possible to suppress a decrease in the progress rate of the chemical reaction at the air electrode 15b of the PEFC 15.

Since the microbubbles 26 generated in the mixed liquid 21 in the reaction tank 14 are microbubbles having a bubble diameter of 5 μm or less, the surface area per unit volume of the microbubbles 26 becomes very large. For this reason, when the reforming catalyst 31 is adsorbed by the microbubbles 26, the contact area between the microbubbles 26 and the reforming catalyst 31 becomes very large, and the steam reforming reaction is further promoted. As a result, the chemical reaction of the formula (1) described above can be made to proceed completely, so that the intermediate product CO is not generated, and CO ₂ is generated. Therefore, an oxidizer for selectively oxidizing CO is not required, and the apparatus configuration is simplified.

  The reforming catalyst 31 of the mixed liquid 21 is adsorbed by the microbubbles 26 and floated and separated, and is settled by natural convection accompanying the boiling of methanol, so that it is uniformly distributed in the reaction tank 14. Therefore, the steam reforming reaction occurs uniformly in the reaction vessel 14.

  The PEFC system 10 using the fuel reformer according to the present embodiment includes a portable information terminal, for example, a fuel cell such as a notebook personal computer or a PDA, a fuel cell vehicle, and a power generator for home / portable and distributed power sources. It becomes a system suitable for such as.

  Next, another embodiment of the present invention will be described with reference to the accompanying drawings.

(Second Embodiment)
FIG. 5 shows a schematic diagram of a fuel reformer according to another preferred embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the member similar to FIG. 1, and description is abbreviate | omitted about these members.

As shown in FIG. 5, the fuel reformer according to the present embodiment is
A reaction vessel 14 in which a liquid mixture 21 is stored;
A circulating means 51 for circulating the mixed liquid 21 inside the reaction tank 14;
PEFC (heating means) 15 for heating at least a part of the circulation means 51 and heating and boiling the mixed liquid 21 circulating inside the circulation means 51;
An ultrasonic oscillation device (microbubble generating means) 23 for generating microbubbles in the heated mixed liquid 21;
It is equipped with.

  The circulation means 51 extracts the mixed liquid 21 from the reaction tank 14 and returns it to the reaction tank 14 again, a circulation line 52 provided in the middle of the circulation line 52, a pump 53 that pressurizes and circulates the mixed liquid 21, and a circulation A heating heat exchanger 54 is provided in the middle of the line 52 and performs heat exchange between the PEFC 15 and the mixed liquid 21.

  The heat transfer surface inner wall (the surface in contact with the PEFC 15) 54a in the heating heat exchanger 54 may be formed as an uneven surface (a surface having a rough surface). For example, the surface roughness of the uneven surface is adjusted so that the average roughness Ra of the heat transfer surface inner wall 54a is 1 to 100 μm.

  In the fuel reformer according to the present embodiment, the case where the ultrasonic oscillator 23 is attached to the side wall of the reaction tank 14 has been described, but the attachment position is not particularly limited. For example, the ultrasonic oscillating device 23 may be attached to the downstream side of the heating heat exchanger 54 in the circulation line 52.

  The fuel reformer according to the present embodiment is connected to a supply means (methanol tank 12, supply device 11, and supply line 16), a hydrogen line 17, and a recovery heat exchanger 13, which is the present embodiment. This PEFC system 50 is used.

  Next, a fuel reforming method using the PEFC system 50 according to the present embodiment will be described based on the attached drawings.

  Similar to the fuel reforming method according to the first embodiment, first, the methanol aqueous solution 20 is supplied from the methanol tank 12, and the mixed solution 21 is stored in the reaction tank 14.

  In the fuel reforming method according to the present embodiment, the mixed liquid 21 stored in the reaction tank 14 is once extracted through the circulation line 52 (mixed liquid extracting step), and the extracted mixed liquid 21 is heated. . Specifically, the mixed liquid 21 is extracted through the circulation line 52, flows inside the circulation line 52, and is circulated. The circulated mixed liquid 21 is heated in the heating heat exchanger 54 by transferring the chemical reaction heat of the PEFC 15 as sensible heat. At the time of start-up, since the heat of chemical reaction of PEFC 15 cannot be used, the circulating liquid mixture 21 is heated using a methanol burner or the like. If sufficient heat of chemical reaction is generated in the PEFC 15 after starting, heating with a methanol burner or the like becomes unnecessary.

  At this time, in the heat transfer surface inner wall 54a of the heating heat exchanger 54, the methanol aqueous solution 20 constituting the mixed solution 21 undergoes nucleate boiling to generate boiling bubbles. However, the boiling bubbles are immediately cooled and disappeared by the liquid mixture 21 flowing in the vicinity of the heat transfer surface inner wall 54a one after another. That is, “subcool boiling” in which boiling bubbles are generated only in the vicinity of the heat transfer surface inner wall 54a occurs in the heat transfer surface inner wall 54a (subcool boiling step). Thus, heat transfer is performed on the inner wall 54a of the heat transfer surface with efficiency several times that of forced convection heat transfer. The circulation speed of the mixed liquid 21 by the pump 53 is appropriately adjusted so that subcool boiling occurs favorably on the heat transfer surface inner wall 54a.

  After that, the heat-exchanged mixed solution 21 is supplied again to the reaction tank 14 (mixed solution resupply step), and is ultrasonically excited by the ultrasonic oscillator 23. At this time, the boiling bubbles that have disappeared during the subcooling boiling are actually present in the liquid mixture 21 as very small bubbles. Therefore, this ultrasonic vibration produces methanol microbubbles 26 with microbubbles as nuclei (microbubble formation step). At this time, water vapor and methanol vapor are enclosed in the microbubbles 26, and the fine powdery reforming catalyst 31 is adsorbed and adhered around the microbubbles 26.

Thereafter, similarly to the fuel reforming method according to the first embodiment, a steam reforming reaction occurs inside the microbubbles 26 to generate hydrogen gas _GH (hydrogen gas generation step). Mixture G _M hydrogen gas G _H and methanol mist in the reaction vessel 14 (methanol vapor + water vapor) is withdrawn via a line 17a, the heat exchanger, subjected to gas-liquid separation, through line 17b PEFC15 To the fuel electrode 15a.

  Also in the PEFC system 50 according to the present embodiment, the same effects as the PEFC system 10 according to the first embodiment can be obtained.

  Further, in the PEFC system 50 according to the present embodiment, the mixed liquid 21 is subcooled boiled using the circulation means 51 to remove the heat and cool the PEFC 15, so that the PEFC according to the first embodiment. Compared with the system 10, the cooling capacity of the PEFC 15 (heat transfer efficiency between the PEFC 15 and the mixed liquid 21) is higher. As a result, in the PEFC system 50 according to the present embodiment, a decrease in the progress rate of the chemical reaction at the air electrode 15b of the PEFC 15 is almost minimized as compared with the PEFC system 10 according to the first embodiment. Can be suppressed.

(Third embodiment)
A schematic diagram of a fuel reformer according to another preferred embodiment of the present invention is shown in FIG. In addition, the same code | symbol is attached | subjected to the member similar to FIG. 1, and description is abbreviate | omitted about these members.

  The fuel reformer according to the first and second embodiments merely raises and floats the microbubbles 26 generated in the mixed liquid 21.

As shown in FIG. 6, the fuel reformer according to the present embodiment
A reaction vessel 14 in which a liquid mixture 21 is stored;
A circulating means 51 for circulating the mixed liquid 21 inside the reaction tank 14;
PEFC (heating means) 15 for heating the circulating means 51 and heating and boiling the mixed liquid 21 circulating inside the circulating means 51;
With
The circulation means 51 has, at its end on the last flow side, a head portion 61 that discharges and drops the mixed liquid 21 to the mixed liquid pool inside the reaction tank 14,
The head unit 61 is provided with an ultrasonic oscillation device (microbubble generating means) 23 that generates microbubbles in the mixed liquid 21 flowing in the head unit 61.
It is a thing.

  The fuel reformer according to the present embodiment is connected to a supply means (methanol tank 12, supply device 11, and supply line 16), a hydrogen line 17, and a recovery heat exchanger 13, which is the present embodiment. This PEFC system 60 is used.

  Next, a fuel reforming method using the PEFC system 60 according to the present embodiment will be described with reference to the accompanying drawings.

  Similar to the fuel reforming method according to the second embodiment, the liquid mixture 21 is extracted from the methanol tank 12 and circulated, and the liquid mixture 21 is heated by heat transfer from the PEFC 15.

  The mixed liquid 21 that has undergone “subcool boiling” and has undergone heat exchange at the heat transfer surface inner wall 54 a is introduced into the head portion 61 provided at the end on the last flow side of the circulation means 51. In the head unit 61, the mixed solution 21 is ultrasonically excited by the ultrasonic oscillator 23. At this time, the boiling bubbles that have disappeared during the subcooling boiling are actually present in the liquid mixture 21 as extremely small bubbles. Therefore, by this ultrasonic vibration, cavitation is generated with a very small bubble as a nucleus. When the liquid mixture 21 including this cavitation is discharged from the liquid mixture discharge port (return port) 62 of the head portion 61, the pressure is reduced (the pressure is released) to generate methanol microbubbles 26 (microbubble formation). Step). At this time, water vapor and methanol vapor are enclosed in the microbubbles 26, and the fine powdery reforming catalyst 31 is adsorbed and adhered around the microbubbles 26.

  Thereafter, the liquid mixture 21 including a large number of microbubbles 26 is dropped from the liquid mixture discharge port (return port) 62 of the head portion 61 into the liquid mixture reservoir inside the reaction tank 14. Here, the microbubbles 26 have a property of getting on the fluid flow. Therefore, the microbubbles 26 discharged and dropped together with the mixed liquid 21 from the mixed liquid discharge port 62 ride on the flow of the mixed liquid 21 without being repelled by the liquid surface of the mixed liquid pool, and once reach the bottom of the reaction tank 14. It sinks and then rises and rises.

Thereafter, similarly to the fuel reforming method according to the first embodiment, a steam reforming reaction occurs inside the microbubbles 26 to generate hydrogen gas _GH (hydrogen gas generation step). Mixture G _M hydrogen gas G _H and methanol mist in the reaction vessel 14 (methanol vapor + water vapor) is withdrawn via a line 17a, the heat exchanger, subjected to gas-liquid separation, through line 17b PEFC15 To the fuel electrode 15a.

  Also in the PEFC system 60 according to the present embodiment, the same effects as the PEFC system 50 according to the second embodiment can be obtained.

Further, in the PEFC system 60 according to the present embodiment, since the microbubbles 26 are discharged and dropped from the mixed liquid discharge port 62 together with the mixed liquid 21, the microbubbles 26 once sink to the bottom of the reaction tank 14. After that, it rises and rises. For this reason, compared with the PEFC systems 10 and 50 according to the first and second embodiments, the residence time of the microbubbles 26 in the reaction vessel 14 can be lengthened. As a result, since the reaction time available for the steam reforming reaction becomes longer, it becomes possible to perform more reliable fuel reforming, and by extension the purity of the hydrogen gas G _H occupied in the air-fuel mixture G _M It gets even higher.

(Fourth embodiment)
FIG. 7 is a schematic view of a fuel reforming apparatus according to still another preferred embodiment of the present invention, and FIGS. 8 (a) and 8 (b) are enlarged views of main parts of FIG. In addition, the same code | symbol is attached | subjected to the member similar to FIG. 1, and description is abbreviate | omitted about these members.

  In the fuel reformers according to the first to third embodiments, the microbubbles 26 are generated in the liquid mixture 21 using the ultrasonic oscillator 23.

As shown in FIG. 7, the fuel reformer according to the present embodiment is
A reaction vessel 14 in which a liquid mixture 21 is stored;
A circulating means 51 for circulating the mixed liquid 21 inside the reaction tank 14;
PEFC (heating means) 15 for heating the circulating means 51 and heating and boiling the mixed liquid 21 circulating inside the circulating means 51;
With
The circulation means 51 has, at its end on the last flow side, a head portion 61 that discharges and drops the mixed liquid 21 to the mixed liquid pool inside the reaction tank 14,
A foam forming mesh member (microbubble generating means; FIG. 8 (FIG. 8 ()) that generates microbubbles in the liquid mixture 21 flowing in the head section 61 at the liquid mixture discharge port 62 (see FIG. 8A) of the head section 61. b) see) 81 is provided,
It is a thing.

  The fuel reformer according to the present embodiment is connected to a supply means (methanol tank 12, supply device 11, and supply line 16), a hydrogen line 17, and a recovery heat exchanger 13, which is the present embodiment. This PEFC system 70 is used.

  The foam forming mesh member 81 is not a simple mesh member, but has a shape in which a large number of short orifices are bundled and arranged in a planar shape. The size and shape of the orifice are appropriately selected according to the target bubble diameter of the microbubble 26 and are not particularly limited.

  Next, a fuel reforming method using the PEFC system 70 according to the present embodiment will be described with reference to the accompanying drawings.

  Similar to the fuel reforming method according to the third embodiment, the liquid mixture 21 is extracted from the methanol tank 12 and circulated, and the liquid mixture 21 is heated by heat transfer from the PEFC 15.

  The mixed liquid 21 that has undergone “subcool boiling” and has undergone heat exchange at the inner wall 54 a of the heat transfer surface is introduced into the head portion 61 provided at the end on the last flow side of the circulation means 51. Thereafter, the mixed liquid 21 is discharged and dropped into the mixed liquid reservoir inside the reaction tank 14 through the foam forming mesh member 81 provided in the mixed liquid discharge port 62.

  At this time, the boiling bubbles that have disappeared during the subcooling boiling are actually present in the liquid mixture 21 as very small bubbles. Therefore, by discharging the mixed liquid 21 through the foam forming mesh member 81, the mixed liquid 21 is depressurized, and microbubbles appear again (microbubble forming step). As a result, methanol microbubbles 26 are generated. At this time, water vapor and methanol vapor are enclosed in the microbubbles 26, and the fine powdery reforming catalyst 31 is adsorbed and adhered around the microbubbles 26.

  Thereafter, the liquid mixture 21 containing a large number of microbubbles 26 is discharged and dropped into the liquid mixture reservoir inside the reaction tank 14. The microbubbles 26 discharged and dropped together with the mixed liquid 21 from the mixed liquid discharge port 62 ride on the flow of the mixed liquid 21 without being repelled by the liquid surface of the mixed liquid pool, and once sink to the bottom of the reaction tank 14. Then it rises and emerges.

Thereafter, similarly to the fuel reforming method according to the first embodiment, a steam reforming reaction occurs inside the microbubbles 26 to generate hydrogen gas _GH (hydrogen gas generation step). Mixture G _M hydrogen gas G _H and methanol mist in the reaction vessel 14 (methanol vapor + water vapor) is withdrawn via a line 17a, the heat exchanger, subjected to gas-liquid separation, through line 17b PEFC15 To the fuel electrode 15a.

  Also in the PEFC system 70 according to the present embodiment, the same effects as the PEFC system 60 according to the third embodiment can be obtained.

  In the PEFC system 70 according to the present embodiment, the microbubbles 26 are formed simply by discharging the mixed liquid 21 through the foam forming mesh member 81 provided in the mixed liquid discharge port 62. No power is required to form the bubbles 26. In addition, since a special driving device for forming the microbubbles 26 is not required, a failure or the like hardly occurs, and the reliability of the system is increased. For this reason, compared with the PEFC systems 10, 50, 60 according to the first to third embodiments, power saving, improvement in reliability, and cost reduction can be achieved.

  As described above, the present invention is not limited to the above-described embodiment, and it goes without saying that various other things are assumed.

  Next, although this invention is demonstrated based on an Example, this invention is not limited to this Example.

  FIG. 9 shows a schematic diagram of the fuel reformer used in the fuel reforming test. In addition, the same code | symbol is attached | subjected to the member similar to FIG. 1, and description is abbreviate | omitted about these members.

  As shown in FIG. 9, a flask 92 is placed in the container 91 of the ultrasonic cleaner 90. In the flask 92, a mixed liquid 21 composed of an aqueous methanol solution and a fine powder Cu-Zn reforming catalyst is placed, and a pellet-shaped Cu-Zn reforming catalyst 22 is disposed at the bottom. Is done. The flask 92 is sealed with a rubber stopper 95, and the space in the flask 92 and the syringe 97 communicate with each other through the connecting pipe 95. In the container 91, water 93 is introduced to the vicinity of the liquid level of the mixed liquid 21, and the temperature of the water 93 can be adjusted by a heater 94. In addition, an ultrasonic oscillation device 23 is provided on the bottom surface of the container 91.

  A fuel reforming test was performed using the fuel reforming apparatus having the above configuration. Here, the methanol concentration of the aqueous methanol solution was about 37.5%. The water temperature of the water 93 was adjusted to 73 ° C. Furthermore, the frequency of the ultrasonic wave to be excited was 32.5 kHz.

The gas generated in the flask 92 and collected in the syringe 97 was subjected to gas analysis using gas chromatography. As a result, the molar ratio of the gas is
H ₂ : 90.0, N ₂ : 56.6, CO ₂ : 29.9, O ₂ : 12.6, CO: 0,
Met. As can be seen from the gas analysis results, the gas produced by the fuel reforming did not contain CO. From this, it was confirmed that when the fuel reforming was performed using the fuel reformer shown in FIG. 9, the steam reforming reaction proceeded completely, so that CO ₂ was generated instead of CO.

  In addition, when fuel reforming was performed with ultrasonic vibration, the amount of gas produced was 10 ml / h. In contrast, when fuel reforming was performed without ultrasonic vibration, the amount of gas produced was 1 ml / h. Therefore, when fuel reforming is performed using the fuel reforming apparatus shown in FIG. 9, the fuel reforming efficiency, that is, the hydrogen gas generation efficiency is remarkably improved by forming the microbubbles 26 by ultrasonic vibration. It was confirmed that it could be improved.

1 is a schematic view of a fuel reformer according to a preferred embodiment of the present invention. It is a figure which shows the relationship between the bubble diameter of a microbubble, and the differential pressure | voltage of a bubble inside and atmospheric pressure. It is a model figure of a microbubble. It is a modification of FIG. It is the schematic of the fuel reformer which concerns on other preferable one Embodiment of this invention. It is the schematic of the fuel reformer which concerns on another suitable one Embodiment of this invention. It is the schematic of the fuel reforming apparatus which concerns on another preferable one Embodiment of this invention. FIG. 8B is an enlarged view of the main part of FIG. 7, and FIG. 8B is a view taken along the line 8b-8b in FIG. It is the schematic of the fuel reformer used in the fuel reforming test of [Example].

Explanation of symbols

14 Reaction tank 15 PEFC (heating means)
20 Methanol aqueous solution 21 Mixed solution 23 Ultrasonic oscillator (microbubble generation means)
26 Microbubbles 31 Powdered reforming catalyst

Claims (20)

A fuel reformer that performs steam reforming of methanol,
A reaction tank in which a mixed liquid composed of a methanol aqueous solution and a finely powdered reforming catalyst is stored;
Microbubble generating means for generating microbubbles in the mixed liquid inside the reaction vessel,
Heating means for heating the reaction vessel;
A fuel reformer characterized by comprising:   2. The fuel reformer according to claim 1, wherein the microbubble generating means is an ultrasonic oscillator.   3. The fuel reformer according to claim 1, wherein the heating means is a fuel cell using hydrogen gas as fuel.   The fuel reformer according to any one of claims 1 to 3, wherein porous particles are arranged at the bottom of the reaction tank.   The fuel reformer according to claim 4, wherein the porous particles are tablet-shaped reforming catalysts.   The fuel reformer according to any one of claims 1 to 5, wherein the heating and heat transfer surface inner wall of the reaction tank is formed on an uneven surface. A fuel reformer that performs steam reforming of methanol,
A reaction tank in which a mixed liquid composed of a methanol aqueous solution and a finely powdered reforming catalyst is stored;
A circulating means for circulating the mixed liquid in the reaction tank;
Heating means for heating at least a part of the circulating means and heating the mixed liquid circulating inside the circulating means;
Microbubble generating means for generating microbubbles in the heated mixed liquid;
A fuel reformer characterized by comprising:   The said circulation means has a head part which discharges and drops a liquid mixture to the liquid mixture reservoir inside the said reaction tank in the end of the last flow side, The microbubble generation means was provided in the head part. Fuel reformer.   The fuel reformer according to claim 7 or 8, wherein the microbubble generating means is an ultrasonic oscillator.   9. The fuel reformer according to claim 8, wherein the microbubble generating means is a foam forming mesh member provided at a liquid mixture discharge port of the head portion.   11. The fuel reformer according to claim 7, wherein the heating means is a fuel cell using hydrogen gas as fuel.   The fuel reformer according to any one of claims 7 to 11, wherein the circulation means includes a heating heat exchanger.   The fuel reformer according to any one of claims 7 to 12, wherein the heating and heat transfer surface inner wall of the circulation means is formed in an uneven surface. A fuel reformer according to any one of claims 1 to 13,
Supply means for supplying an aqueous methanol solution into the reaction tank of the fuel reformer;
A hydrogen line that extracts hydrogen gas and methanol mist generated inside the reaction tank, heat-exchanges the gas mixture, gas-liquid separation, and a hydrogen line that supplies only hydrogen gas to the fuel cell;
A solid polymer fuel cell system comprising: A fuel reforming method for performing steam reforming of methanol,
Using an ultrasonic oscillator to ultrasonically vibrate a mixed solution composed of an aqueous methanol solution and a fine powdery reforming catalyst stored in the reaction vessel, and generating cavitation in the mixed solution; ,
Heating the liquid mixture inside the reaction vessel by boiling heat transfer to form microbubbles with cavitation as a nucleus in the liquid mixture;
A step of reforming methanol inside the microbubbles formed by adhering a reforming catalyst around it to generate hydrogen gas; and
A fuel reforming method comprising:   The fuel reforming method according to claim 15, wherein the reaction vessel is heated so that a liquid temperature of the mixed solution becomes 60 to 85 ° C. A fuel reforming method for performing steam reforming of methanol,
Extracting a part of the mixed solution composed of the aqueous methanol solution stored in the reaction tank and the finely powdered reforming catalyst using a circulation means;
Heating the liquid mixture flowing inside the circulation means to subcool the liquid mixture;
Re-feeding the mixed liquid after subcooled boiling into the reaction vessel;
Forming microbubbles in the mixture using the microbubble generating means;
A step of reforming methanol inside the microbubbles formed by adhering a reforming catalyst around it to generate hydrogen gas; and
A fuel reforming method comprising:   18. The fuel reforming method according to claim 17, wherein the circulating means is heated so that the temperature of the liquid mixture flowing inside the circulating means is 60 to 85 ° C.   When returning the mixed liquid after subcooled boiling to the inside of the reaction vessel, the mixed liquid is subjected to ultrasonic vibration using an ultrasonic oscillating device, and cavitation is generated in the mixed liquid, and the mixed liquid is stored in the mixed liquid. The fuel reforming method according to claim 17 or 18, wherein the fuel is discharged and dropped. When returning the mixed liquid after subcooled boiling to the inside of the reaction vessel, the mixed liquid is discharged and dropped into a mixed liquid reservoir through a foam forming mesh member provided at the return port, and cavitation is performed in the mixed liquid. The fuel reforming method according to claim 17 or 18, wherein the fuel is produced.

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