JP5115682B2 - Fuel cell fuel vaporization control method, fuel cell coated fuel, and fuel cell - Google Patents

Description

  The present invention relates to a method for controlling vaporization of fuel for a fuel cell, a coated fuel for a fuel cell, and a fuel cell.

  Since lower alcohols such as methanol and ethanol generally have a low boiling point and a high vapor pressure, they have a property of being easily vaporized at a temperature higher than room temperature. Among these volatile substances, there are those having a flash point and ignition point, and those having strong toxicity, and there are some that require sufficient care in handling. In order to stably hold such a highly dangerous substance, it is necessary to take measures such as lowering the temperature of the substance or sealing the substance, and storage and release conditions in a high temperature environment. We couldn't cope with the need for storage below.

  If the vaporization of such a volatile substance can be controlled, the volatile substance can be stored stably and safely even at room temperature. However, at present, it is effective for controlling the vaporization of such a volatile substance. No method has been proposed.

  On the other hand, in recent years, countermeasures against environmental problems and resource problems have become important, and one of the countermeasures is the development of a fuel cell that can directly generate electricity by supplying an organic solvent and water as a liquid fuel. It is active. In particular, a direct methanol fuel cell that uses methanol as a liquid fuel and can generate electricity by directly supplying methanol without reforming or gasifying it has a simple structure and is smaller and lighter. Since it is easy, it is promising as various distributed power sources and portable power sources including consumer power sources for portable small electronic devices and computers.

  Such a fuel cell that directly supplies liquid fuel to generate electricity is a membrane in which a positive electrode (air electrode) and a negative electrode (fuel electrode) are joined to both sides via an electrolyte composed of a solid polymer electrolyte membrane having proton conductivity. / It has a configuration in which a plurality of cells in which an electrode assembly (MEA) is supported by a positive electrode side (air electrode side) separator and a negative electrode side (fuel electrode side) separator are stacked. The positive electrode side (air electrode side) separator and the negative electrode side (fuel electrode side) separator supply oxidant gas to the positive electrode (air electrode) and supply liquid fuel to the negative electrode (fuel electrode), It also plays a role of discharging reaction products generated from an oxidant gas and liquid fuel by an electrochemical reaction performed via an electrolyte.

  That is, in a direct methanol fuel cell, when an aqueous methanol solution is supplied to the negative electrode (fuel electrode) side and air as an oxidant gas is supplied to the positive electrode (air electrode) side, methanol and Water reacts to generate carbon dioxide and releases hydrogen ions and electrons. At the positive electrode (air electrode), oxygen in the air takes in hydrogen ions and electrons that have passed through the electrolyte to produce water. Then, an electromotive force is generated in the external circuit. And the produced | generated water is discharged | emitted from the positive electrode (air electrode) side with the air which did not contribute to reaction, and a carbon dioxide is discharged | emitted from the negative electrode (fuel electrode) side with the methanol aqueous solution which did not contribute to reaction.

  In such a direct methanol fuel cell, it is preferable to increase the concentration of the methanol aqueous solution from the viewpoint of improving its output characteristics. However, since methanol is highly volatile and easily vaporizes under atmospheric pressure, and vaporized methanol easily ignites if there is an ignition source, its safety is regarded as a problem with respect to use and transportation. For this reason, legal restrictions are imposed on the amount and concentration of methanol brought into transportation facilities such as aircraft. Currently, restrictions on bringing methanol into aircraft are an obstacle to the practical application of direct methanol fuel cells, and there is a need to relax the regulations. However, there is a technical limit in reducing the risk of liquid leakage and the like, and a highly safe fuel is required to put the direct methanol fuel cell into practical use.

  The present invention provides a method for improving the safety of fuel for a fuel cell by controlling the vaporization of the fuel for the fuel cell, and a coated fuel for the fuel cell in which the vaporization of the fuel for the fuel cell is controlled, and the fuel cell An object of the present invention is to provide a fuel cell using the coated fuel for the fuel.

In order to solve the above-described problems, the fuel cell fuel vaporization control method of the present invention gels the fuel cell fuel by bringing the fuel cell fuel into contact with a polysaccharide and / or a polysaccharide derivative. ( Invention 1). In the said invention ( invention 1), it is preferable to make the said fuel for fuel cells contact with the said polysaccharide and / or a derivative of polysaccharide in presence of water ( invention 2).

According to the above inventions ( Inventions 1 and 2), the fuel cell fuel is gelled and stabilized even under temperature conditions that generally cause the fuel cell fuel to vaporize, and the fuel cell fuel is vaporized. Therefore, the safety of the fuel for the fuel cell can be improved.

  Here, in the present specification, “polysaccharide” is a polymer compound in which a plurality of monosaccharides are dehydrated and condensed by glycosidic bonds, and a simple polysaccharide that produces one kind of monosaccharide or a derivative thereof by hydrolysis, and Included are complex polysaccharides that yield two or more monosaccharides or their derivatives upon hydrolysis. In addition, the polysaccharide or the polysaccharide derivative may be naturally occurring or synthesized. Furthermore, the polysaccharide or the polysaccharide derivative may be in any state of a solid state, a liquid state, and a gel state.

In the said invention ( invention 1 and 2), it is preferable that the said fuel for fuel cells is alcohol ( invention 3), and it is preferable that the said alcohol is methanol ( invention 4).

In the said invention ( invention 1-4), it is preferable that the said polysaccharide is a cellulose ( invention 5). Since cellulose and cellulose derivatives have an excellent film forming action, a film made of cellulose and / or cellulose derivatives can be formed on the surface of the gel fuel by drying. According to this, even under the vaporization temperature condition of the fuel cell fuel, since the vaporization of the fuel cell fuel held in a gel state inside the coating is further suppressed, the fuel cell fuel with higher safety can be obtained. It can be.

In the said invention ( invention 1-5), it is preferable to dry the gel fuel which gelatinized the said fuel for fuels, and to form a film on the surface of the said gel fuel ( invention 6).

In addition, the coated fuel for a fuel cell of the present invention is characterized in that a coating is formed on the surface of the gel fuel obtained by gelling the fuel for the fuel cell ( Invention 7). In such a fuel cell-coated fuel, the gel fuel is held inside the coating, whereby vaporization of the fuel cell fuel is further suppressed and safety is increased. Since the shape can be maintained, it is excellent in handleability.

In the said invention ( invention 7), it is preferable that the said fuel for fuel cells is gelatinized with the polysaccharide and / or the derivative | guide_body of polysaccharide ( invention 8). According to the said invention ( invention 8), an effective film can be formed by the film forming action of the polysaccharide or the polysaccharide derivative.

Furthermore, the fuel cell of the present invention comprises means for extracting fuel cell fuel from the fuel cell coated fuel according to the above inventions ( Inventions 7 and 8) ( Invention 9).

  According to the present invention, it is possible to improve the safety of the fuel cell fuel by controlling the vaporization of the fuel cell fuel.

Hereinafter, a fuel cell fuel vaporization control method according to an embodiment of the present invention will be described.
In the fuel cell fuel vaporization control method according to this embodiment, the fuel cell fuel is brought into contact with a polysaccharide and / or a polysaccharide derivative.

  Examples of the fuel for the fuel cell include alcohols, ethers, hydrocarbons, acetals, formic acids and the like, but are not particularly limited thereto. Specifically, as a fuel for a fuel cell, lower fat having 1 to 4 carbon atoms such as methanol, ethanol, denatured alcohol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, tert-butanol, ethylene glycol and the like. Aromatic alcohols; ethers such as dimethyl ether, methyl ethyl ether and diethyl ether; hydrocarbons such as propane and butane; acetals such as dimethoxymethane and trimethoxymethane; formic acids such as formic acid and methyl formate; it can. These may be used individually by 1 type, and may mix and use 2 or more types. Among these, it is preferable to use methanol which is the fuel of the direct methanol fuel cell.

  The polysaccharide or the derivative of the polysaccharide can gel the fuel for a fuel cell by contacting with the fuel for the fuel cell, whereby a gel fuel can be obtained. The gel fuel is excellent in safety because the fuel cell fuel is suppressed from being vaporized even under temperature conditions where the fuel cell fuel is generally vaporized. In particular, when a gel fuel that has been gelled using polysaccharides or polysaccharide derivatives is dried, a film is formed on the surface of the fuel, which suppresses vaporization of fuel for fuel cells held inside the film. In addition, since the predetermined shape can be maintained by the presence of the coating film, the handleability is excellent. The polysaccharide or the derivative of the polysaccharide may be naturally occurring or synthesized. The polysaccharide or polysaccharide derivative may be used in any state of a solid state, a liquid state, and a gel state. One of these polysaccharides or polysaccharide derivatives may be used alone, or two or more thereof may be mixed and used.

  A polysaccharide is a polymer compound in which a plurality of monosaccharides are dehydrated and condensed by glycosidic bonds, and is a simple polysaccharide (homoglycan) that produces one kind of monosaccharide or a derivative thereof by hydrolysis. Examples include complex polysaccharides (heteroglycans) that produce monosaccharides or their derivatives.

  Examples of simple polysaccharides include glucans such as starch, amylose, amylopectin, glycogen, cellulose, dextran, nigeran, pullulan, lichenan, laminaran and curdlan; fructans such as inulin and levan; galactans such as galactogen and galactocacarose; Mannan such as plant mannan and microbial mannan; Pentozan such as xylan and arabinan; Polyuronic acid such as pectinic acid, alginic acid and protuberic acid; and polyaminosaccharide such as chitin, colominic acid and polygalactosamine.

  Examples of complex polysaccharides include hemicelluloses such as glucomannan, galactoglucomannan, and arabinogalactan; plant gums such as gum arabic, tracant gum, and karaya gum; neutral mucilages such as galactomannan, guagum (guaran), and konjac mannan; Examples include red algae viscous polysaccharides such as agar, porphyran, carrageenan; brown algal sulfated viscous polysaccharides such as fucoidan and ascofilan; and mucopolysaccharides such as hyaluronic acid, chondroitin, chondroitin sulfate, dermatan sulfate, keratan sulfate, and heparin. .

  Of these polysaccharides, cellulose belonging to simple polysaccharides is preferably used. Cellulose has an excellent film-forming action, and a film-like film is formed on the surface of the gel-like fuel by drying the gel-like fuel. Therefore, the fuel held inside the film-like film Vaporization of battery fuel is effectively suppressed. Therefore, the fuel for fuel cells can be handled easily and can be a highly safe coated fuel for fuel cells.

  Examples of polysaccharide derivatives include amylose derivatives and cellulose derivatives. Among these, cellulose derivatives are preferably used. Cellulose derivatives are suitable because they have a film-forming action like cellulose. In addition, most cellulose derivatives are used as binders for tablets and granules, matrix bases for sustained-release tablets, and jelly agents in the medical field, and thickening and gelling agents, health foods in the food field. It is suitable because it is used as a film coating agent and capsule, or as an anti-deformation agent contained in frying, bread and cake, etc., and safety to human bodies is recognized.

  Examples of the cellulose derivative include methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose, carboxymethyl cellulose and the like.

  The viscosity of the cellulose derivative varies depending on the degree of polymerization and the degree of ether substitution, but the viscosity is preferably 20 to 10,000 mPa · s (20 ° C., 2% aqueous solution). If the viscosity of the cellulose derivative exceeds 10,000 mPa · s, handling when forming a gelled gel fuel may be difficult, and if the viscosity of the cellulose derivative is less than 20 mPa · s, The holding power of the fuel cell fuel in the coated fuel becomes weak, and there is a possibility that the vaporization cannot be effectively suppressed.

  The addition amount of the polysaccharide and / or polysaccharide derivative is preferably 0.01 to 1 part by mass with respect to 1 part by mass of the fuel for the fuel cell. If the addition amount of the polysaccharide and / or polysaccharide derivative is within the above range, the fuel for the fuel cell can be effectively gelled.

  When the fuel for fuel cell is brought into contact with the polysaccharide and / or the polysaccharide derivative to gel the fuel for fuel cell, water may be further added. By adding water, vaporization of the fuel cell fuel from the gel fuel can be more effectively suppressed. A small amount of water may be added. Specifically, 0.01 to 0.5 parts by mass of water may be added to 1 part by mass of the fuel cell fuel.

  The method for bringing the fuel for the fuel cell into contact with the polysaccharide and / or the polysaccharide derivative is not particularly limited, and may be brought into contact with a conventional method. For example, the fuel for a fuel cell can be gelled by adding the fuel for a fuel cell to a polysaccharide and / or a derivative of the polysaccharide and stirring sufficiently.

  The temperature condition and pressure condition when the fuel cell fuel is brought into contact with the polysaccharide and / or polysaccharide derivative to gel the fuel cell fuel are not particularly limited, and the fuel is used at normal temperature and normal pressure. What is necessary is just to contact the fuel for batteries, and the polysaccharide and / or the derivative of polysaccharide. By mixing fuel cell fuel and polysaccharides and / or polysaccharide derivatives under normal temperature and normal pressure, and sufficiently stirring, a gel fuel obtained by gelling fuel cell fuel can be obtained. When a gaseous fuel is used as the fuel cell fuel, it is preferable to bring the fuel cell fuel into contact with the polysaccharide and / or polysaccharide derivative under pressure.

  The obtained gel fuel may be molded into a certain shape, and the shape of the gel fuel may be any shape suitable for a fuel cell using a fuel cell fuel. In forming the gel fuel into a certain shape, it is preferable to dry the gel fuel and form a film on the surface thereof. Thereby, the coating fuel for fuel cells which can maintain a predetermined shape can be obtained.

  The coating can be formed on the surface of the gel fuel by the film forming action of polysaccharides and / or polysaccharide derivatives. Since the fuel for fuel cells held in a gel state inside the coating is further suppressed from being vaporized, the coated fuel for fuel cells is highly safe. The fuel cell coated fuel is excellent in handleability because it can maintain a predetermined shape due to the presence of the coating. The shape of the fuel for the fuel cell may be, for example, a regular solid such as a sphere, a rectangle, or a cylinder, or may be a thin film or a fiber.

  The drying treatment of the gel fuel is not particularly limited, and can be performed by a conventional method. For example, the gel fuel may be left to dry at room temperature for a predetermined time, or may be dried using a normal dryer. The drying time of the gel fuel is not particularly limited, but is usually 10 to 180 minutes at room temperature.

  The method for extracting fuel cell fuel from the fuel cell coated fuel in which the vaporization of the fuel cell fuel is controlled according to the present invention can be performed by a conventional method. For example, by heating the fuel cell coated fuel and evaporating the fuel cell fuel from the fuel cell coated fuel, it can be taken out as a gaseous fuel cell fuel. Further, by bringing the fuel cell coated fuel into contact with water, the aqueous fuel cell fuel can be easily taken out from the fuel cell coated fuel.

  In consideration of using the fuel cell-coated fuel in a direct methanol fuel cell, it is preferable to bring the fuel cell-coated fuel into contact with water and take out the fuel cell fuel from the fuel cell-coated fuel. By doing in this way, since the fuel for fuel cells can be taken out as fuel aqueous solution, the said fuel aqueous solution can be directly supplied to the negative electrode (fuel electrode) of a fuel cell, and it is excellent in energy.

  The fuel cell using the coated fuel for the fuel cell is not particularly limited, and examples thereof include a direct methanol fuel cell, a solid polymer fuel cell, and a solid oxide fuel cell.

  This fuel cell includes means for extracting fuel cell fuel from the fuel cell coated fuel. The means is a means capable of taking out fuel cell fuel from the fuel cell coated fuel. For example, the fuel cell coated fuel is heated to evaporate the fuel cell fuel from the fuel cell coated fuel. It may have a structure in which water is added to the fuel cell coated fuel, the gel-like polysaccharide and / or polysaccharide derivative is filtered, and the aqueous fuel cell fuel is taken out. May be.

  The coated fuel for fuel cells obtained by the present invention does not diffuse like liquid fuel even when the fuel cell main body is damaged due to an unexpected situation, and the coated fuel for fuel cells is in contact with the limb. However, there is no skin irritation and there is a safety advantage.

  Further, according to the present invention, the flash point and ignition point of the fuel cell coated fuel can be made higher than the flash point and ignition point of the fuel cell fuel. Thereby, the vaporization of the fuel for the fuel cell can be controlled, the safety and stability at the time of storage of the fuel for the fuel cell can be improved, and the handling thereof can be facilitated. Thereby, it can be set as the fuel for fuel cells with high safety | security without risk of liquid leakage etc., without infringing on airplane carrying-in regulation.

  The embodiment described above is described for facilitating understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

  For example, the step of molding / drying a gel fuel obtained by gelling fuel cell fuel into a certain shape may be omitted.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to the following Example at all.

[Example 1]
4 g of methanol and 1 g of water were added to 1 g of methylcellulose solid powder, and the mixture was sufficiently stirred to gel. Gelled methanol was molded into a spherical shape with a particle size of 4 mm and dried at room temperature for 1 hour to obtain spherical gelled methanol. A film was formed on the surface of the obtained spherical gelled methanol, and it was solidified to a state where the shape could be sufficiently maintained.

  About the obtained spherical gelled methanol, the flash point was measured based on the “Seta closed-type flash point test method” which is a test method for determining dangerous materials as defined in the “Decree on Dangerous Goods Test and Properties”. Since the fuel for the fuel cell is vaporized at the flash point, it is possible to confirm whether or not the vaporization of the fuel for the fuel cell can be controlled by measuring the flash point.

  The flash point of the spherical gelled methanol obtained in Example 1 is 61.7 ° C., which is much higher than the flash point of 40 ° C., which is handled as a flammable solid of the second class of hazardous materials, and is obtained by the present invention. It was confirmed that the coated fuel is a non-hazardous material. Thereby, it was confirmed that the vaporization of methanol which is a fuel for fuel cells can be controlled by gelling methanol.

[Comparative Example 1]
For the stock solution methanol, the flash point was measured based on the “method of closed point flash point test method (JIS-K2265-1996, crude oil and petroleum product flash point test method)”, which is a method for measuring the flash point of liquid. . The flash point of the stock methanol was 11 ° C.

  From this, it was confirmed that by forming the stock solution methanol by the method of the present invention, the flash point can be raised by 50 ° C. or more, and the safety of the fuel for the fuel cell can be improved.

[Test Example 1] Fuel cell operation confirmation test When 1 g of the spherical gelled methanol obtained in Example 1 and 16 g of deionized water were brought into contact with each other, a 3 mass% aqueous methanol solution was obtained. When the obtained aqueous methanol solution was supplied to the negative electrode (fuel electrode) of a direct methanol fuel cell using a Nafion-based electrolyte, the operation of the fuel cell could be confirmed.

The fuel for fuel cells whose vaporization is controlled by the vaporization control method of the present invention is useful as a safe fuel cell fuel that can be brought into an aircraft.

Claims (6)

A fuel cell fuel vaporization control method comprising bringing a fuel cell fuel into contact with a polysaccharide and / or a polysaccharide derivative to gel the fuel cell fuel ,
The fuel for the fuel cell is methanol;
The polysaccharide is cellulose;
A fuel cell fuel vaporization control method, comprising: drying a gel fuel obtained by gelling the fuel cell fuel; and forming a coating on a surface of the gel fuel .   2. The fuel cell fuel vaporization control method according to claim 1, wherein the fuel cell fuel is brought into contact with the polysaccharide and / or polysaccharide derivative in the presence of water.   2. The polysaccharide derivative according to claim 1, wherein the polysaccharide derivative is one or more selected from the group consisting of methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, hydroxyethylmethylcellulose, and carboxymethylcellulose. Fuel cell fuel vaporization control method. A coated fuel for a fuel cell, characterized in that a coating is formed on the surface of a gel fuel formed by gelling the fuel for a fuel cell ,
The fuel for the fuel cell is gelled with polysaccharides and / or polysaccharide derivatives,
The fuel for the fuel cell is methanol;
The polysaccharide is cellulose;
A coated fuel for a fuel cell, wherein the coating is formed by drying the gel fuel . The derivative of the polysaccharide is one or more selected from the group consisting of methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, hydroxyethylmethylcellulose, and carboxymethylcellulose. Coated fuel for fuel cells . 6. A fuel cell comprising means for extracting fuel cell fuel from the fuel cell coated fuel according to claim 4 or 5 .