HYDROGEN-GENERATING DEVICE CONTAINING AQUEOUS

SOLUTION OF CHEMICAL HYDRIDE AS RAW MATERIAL Technical Field [1] The present invention relates to a hydrogen-generating device containing an aqueous solution of a chemical hydride as a raw material. Background Art [2] Fuel cells convert chemical energy generated by an oxidation of a fuel to electrical energy. Fuel cells are virtually similar to conventional chemical cells in that they use oxidation and reduction reactions. On the other hand, fuel cells are different from chemical cells in which cell reactions are performed in a closed system, in that reactants are continuously supplied into a reaction system from the outside and reaction products are continuously discharged to the outside of the reaction system. One of the most typical fuel cells is a fuel cell using hydrogen and oxygen as reactants. [3] Apparatuses for the supply of hydrogen to fuel cells using hydrogen as a fuel or a unit requiring hydrogen include an apparatus which stores hydrogen in a gas state in a high pressure tank and discharges a desired amount of hydrogen at a predetermined pressure through a valve, an apparatus which liquefies hydrogen, stores it in a liquid state, and vaporizes a desired amount of the hydrogen in a liquid, and an apparatus which adsorbs hydrogen into a hydrogen storage alloy. [4] The first apparatus requires a hydrogen storage pressure container which is resistant at 120-150 atm and various surrounding units for controlling pressures. Thus, this apparatus has a generally complicated constitution and a large size. As it cannot be compacted, it cannot, for example, be loaded on a vehicle. When hydrogen is exhausted, this apparatus should be refilled with hydrogen at 120-150 atm and separately requires a filling unit, which is inconvenient, and has high costs. [5] The second apparatus comprises a liquefying unit for liquefying hydrogen by cooling hydrogen gas to -250 ° C or less and a specific container having high heat insulation for maintaining the liquefied hydrogen in a liquid state. Further, this apparatus comprises a vaporizing unit for vaporizing the liquefied hydrogen at an ap¬ propriate pressure and temperature, etc. Thus, this apparatus is complicated, cannot be easily transported, and has high maintenance costs and has a risk of exploding. [6] In case of the third apparatus, when the adsorption of hydrogen to the hydrogen storage alloy and release of the hydrogen from the hydrogen storage alloy are repeated, a local stress can occur in the alloy, and thus, a physical strain or cracks can be generated in the alloy. As a result, there is a risk of an abnormal hydrogen leakage. [7] In the conventional hydrogen supplying apparatuses described above, storage tanks for storing hydrogen must have resistance to pressure and heat insulation. The con¬ ventional apparatuses include various surrounding units for injecting hydrogen or for supplying hydrogen to units requiring hydrogen. Thus, the conventional apparatuses have a large size, a complicated structure, a risk of exploding and high costs. Disclosure of Invention Technical Solution [8] The present invention provides a hydrogen-generating device containing an aqueous solution of a chemical hydride as a raw material, which generates hydrogen gas from an aqueous solution of the chemical hydride contained in a low pressure container via a chemical reaction. Thus, the device does not require a separate source of power for generating hydrogen and has about an atmospheric pressure in the container and thus, has low risk. Further, the device has a simple structure and can be portable and suf¬ ficiently mounted on a hydrogen vehicle, and also, can be used for supplying hydrogen to a fuel cell installed in small electronic items, such as a camcorder, a notebook computer, or a mobile phone. Especially, the device automatically controls a rate of generating hydrogen and operates regardless of installation directions, and thus, can be conveniently used and have a stable supply of hydrogen. [9] According to an aspect of the present invention, there is provided a hydrogen- generating device containing an aqueous solution of a chemical hydride as a raw material, comprising: a container for containing the aqueous solution of the chemical hydride and venting hydrogen gas generated from the aqueous solution to its outside; a hydrogen-generating catalyst which is placed in the container and generates hydrogen gas from the aqueous solution of the chemical hydride via a chemical reaction when contacting the aqueous solution of the chemical hydride; a reaction control unit which contains the hydrogen-generating catalyst therein and is open or closed according to a decrease or an increase in a pressure in the container to control a rate of generation of hydrogen. [10] The container may comprise: a porous container which has a predetermined volume and many pores for venting the hydrogen gas; and a gas-liquid separation membrane which adheres closely to the porous container to block the pores of the porous container and through which the hydrogen gas separated from the aqueous solution passes. [11] The hydrogen-generating device may comprise a housing containing the container sealed from the outside and collecting the hydrogen gas vented from the container to supply the hydrogen gas to an external unit in which the hydrogen gas to be used. [12] The reaction control unit may comprise: a holding casing which is fixed to the housing and has its portion extending into an inside space of the container; and a moving casing which contains the hydrogen-generating catalyst, is installed capable of moving in the holding casing, and is open or closed by moving relative to the holding casing according to a decrease or an increase in a pressure in the container. [13] The holding casing may have external through holes for inducing the aqueous solution of the chemical hydride to flow into the moving casing, and the moving casing may have internal through holes to allow the aqueous solution of the chemical hydride which has passed through the external through holes to flow toward the hydrogen- generating catalyst in the moving casing, wherein the internal through holes are closed when the moving casing moves in the holding casing due to the increase in an internal pressure of the container. [14] The holding casing may further comprise an elastic support unit therein, the elastic support unit restoring the position of the moving casing to open the internal through holes of the moving casing when the internal pressure of the container is decreased. [15] An internal space of the holding casing may be open to the outside of the housing through an air hole and the elastic support unit may comprise bellows having one end fixed to the moving casing so as to be sealed in the holding casing and being open to the outside of the housing through the air hole so as to apply an atmospheric pressure to the moving casing. [16] The elastic support unit may further comprise a spring which supports the moving casing in the same direction as the bellows supports the moving casing. [17] The gas-liquid separation membrane may be composed of Teflon-based GoreTex, polytetrafluoroethylene (PTFE), polyvinylidenefluoride (PVDF), or tetrafluo- roethylene-perfluoro alkylvinyl ether copolymer (PFA), or a polysulfone-based polymer, or a mixture thereof. Description of Drawings [18] FIGS. 1 and 2 are cross-sectional views illustrating a complete constitution and operation of a hydrogen-generating device containing an aqueous solution of the chemical hydride as a raw material, according to an embodiment of the present invention; and [19] FIG. 3 is a cross-sectional view of a reaction control unit of the hydrogen- generating device illustrated in FIG. 1. Best Mode [20] Hereinafter, embodiments according to the present invention will be described in more detail with reference to the attached drawings. [21] A hydrogen-generating device containing an aqueous solution of a chemical hydride as a raw material, according to an embodiment of the present invention, contains a hydrogen-generating catalyst and the aqueous solution of the chemical hydride in a container and generates hydrogen gas by reacting the hydrogen-generating catalyst with the aqueous solution of the chemical hydride at predetermined conditions. [22] FIGS. 1 and 2 are cross-sectional views illustrating a complete constitution and operation of a hydrogen-generating device 11 containing an aqueous solution of the chemical hydride 27 as a raw material, according to an embodiment of the present invention. [23] Referring to FIGS. 1 and 2, the hydrogen-generating device 11 containing the aqueous solution of the chemical hydride as a raw material comprises a housing 21 having a predetermined volume and having one side sealed by a cap 23, a container 55 installed in the housing 21, having one side sealed by the cap 23, and containing the aqueous solution of the chemical hydride 27, and a reaction control unit 25 fixed to the center portion of the cap 23, connecting an inside space of the container 55 to the outside of the housing 21, and containing a hydrogen-generating catalyst 37 therein. [24] The aqueous solution of the chemical hydride 27 contains, for example, a metal hydroxide selected from LiBH , LiH, NaBH , LiAlH , MgH , NaAlH , CaH , KH, 4 4 4 2 4 2 KBH 4 , Ca(BH 4 ) 2 , Mg(BH 4 ) 2 , and KAlH 4 , as a solute and generates hydrogen gas via a chemical reaction with the hydrogen-generating catalyst 37. [25] The housing 21 is an external case for the hydrogen-generating device 11 and has a gate 29 on one side. The gate 29 is a path for discharging the hydrogen gas generated from the container 55 to a unit requiring hydrogen. The gate 29 has a valve 61 to control the supply of the hydrogen gas. [26] The cap 23 is screwed onto the housing 21. If necessary, the cap 23 may be welded to the housing 21. [27] The container 55 comprises a first porous container 13, a second porous container 17, and a gas-liquid separation membrane 15 adhering closely to an inner wall of the second porous container 17. The second porous container 17 is screwed onto an inner surface of the cap 23. The first porous container 13 is disposed on an inner surface of the gas-liquid separation membrane 15 and combined to the second porous container 17. Although one side of the container 55 is open, the open portion is combined to the cap 23, and thus, the inner space of the container 55 is sealed from the outside. [28] The cap 23 may be screwed onto the container 55. If necessary, the cap 23 may be welded to the container 55 to make an air-tight seal between the cap 23 and the housing 21. In order to supplement the aqueous solution of the chemical hydride 27, a separable screw-combination of the cap 23 to the container 55 is more advantageous. This is applied to the combination of the cap 23 to the housing 21. [29] The first porous container 13 has a plurality of pores 13a. The pores 13a are paths for venting the hydrogen gas generated from the aqueous solution of the chemical hydride 27 to the outside the first porous container 13. The first porous container 13 may be formed of synthetic resin or metals, or other materials which can provide a pre¬ determined volume. [30] The gas-liquid separation membrane 15 is a membrane through which gas is able to pass and liquid is not able to pass. The gas-liquid separation membrane 15 maintains the aqueous solution of the chemical hydride 27 in the first porous container 13 and discharges only the hydrogen gas generated from the aqueous solution of the chemical hydride 27 to the outside of the container 55 such that the hydrogen gas is collected in a hydrogen transport path 31. [31] The gas-liquid separation membrane may be composed of Teflon-based GoreTex, polytetrafluoroethylene (PTFE), polyvinylidenefluoride (PVDF), or tetrafluo- roethylene-perfluoro alkylvinyl ether copolymer (PFA), or a polysulfone-based polymer, or a mixture thereof. [32] The second porous container 17 covering an outer surface of the gas-liquid separation membrane 15 supports the gas-liquid separation membrane 15 to adhere the gas-liquid separation membrane 15 closely to the first porous container 13. Like the first porous container 13, the second porous container 17 has a plurality of pores 17a. The pores 17a are pores to pass the hydrogen gas which has passed through the gas- liquid separation membrane 15. The second porous container 17 is separated from an inner sidewall of the housing 21, thereby providing the hydrogen transport path 31 between the second porous container 17 and the housing 21. [33] The hydrogen gas generated from the container 55 is collected in the hydrogen transport path 31, through which the hydrogen gas travels toward the gate 29. [34] The reaction control unit 25 comprises a holding casing 33 passing through the center portion of the cap 23 to communicate the inner space of the container 55 with the outside of the housing 21, a moving casing 35 installed in the holding casing 33, containing the hydrogen-generating catalyst 37, and being able to move in an 'a' direction or in its opposite direction, and a support unit supporting the moving casing 35 in a 'b' direction. [35] Referring to FIG. 3, a specific construction of a reaction control unit 25 will be explained. [36] The holding casing 33 is a cylindrical element with a predetermined volume of an inner space 39 and has an extension portion 33e on its end portion (hereinafter, referred to as 'front end') extending toward the inner space of the container 55, the extension portion 33e having a diameter extending in a radius direction. The extension portion 33e has external through holes 33a, a front end hole 33c, and a support surface 33b. [37] The support surface 33b is a plane surface having a ring shape and being per- pendicular to a longitudinal direction of the holding casing 33. The support surface 33b has a groove 49 having a predetermined width and depth. A packing 49a is disposed in the groove 49. [38] The aqueous solution of the chemical hydride 27 flows into the holding casing 33 through the external-through holes 33a of the extension portion 33e. The front end hole 33c is a hole for the control of pressure, which is formed such that the moving casing 35 is pressured by the aqueous solution of the chemical hydride 27 in a 'P' direction. [39] The moving casing 35 is disposed inside the holding casing 33 and as an inner pressure of the container 55 increases, the moving casing 35 is forced in the 'P' direction, or the moving casing 35 is forced in the 'b' direction due to an elastic force applied by a spring 43 and a bellows 41 such that the position of the moving casing 35 is restored. [40] An outer circumferential surface of the moving casing 35 contacts an inner circum¬ ferential surface of the holding casing 33 and a line movement of the moving casing 35 is guided by the inner circumferential surface of the holding casing 33. Although the aqueous solution 27 may leak into a gap between the inner circumferential surface of the holding casing 33 and the outer circumferential surface of the moving casing 35, the penetrated aqueous solution 27 cannot flow outside the cap 23 (see FIG. 1) due to the bellows 41 and a gasket 51. [41] The hydrogen-generating catalyst 37 is contained in the moving casing 35. When the hydrogen-generating catalyst 37 comes into contact with the aqueous solution of the chemical hydride 27, hydrogen gas is generated from the aqueous solution of the chemical hydride 27. [42] The moving casing 35 has internal through holes 35 a. The internal through holes 35a induce the aqueous solution of the chemical hydride 27 to flow into the moving casing 35 such that the aqueous solution 27 can contact the hydrogen-generating catalyst 37. The internal through holes 35a are paths connecting the inside of the moving casing 35 to the outside of the moving casing 35. After the moving casing 35 moves in the 'b' direction, the internal through holes 35a communicate with the outside of the holding casing 33 through the external through holes 33a. [43] The moving casing 35 has an attachment surface 35c. The attachment surface 35c faces the support surface 33b and has a projection 35b, which is integrated on the attachment surface 35c. When the moving casing 35 moves in the 'a' direction, the projection 35b is inserted into the groove 49 and then, completely adhered to the packing 49a in the groove 49. [44] When the projection 35b is inserted into the groove 49, the inner space of the moving casing 35 is sealed from the outside of the holding casing 33 and the hydrogen gas generated from the aqueous solution of the chemical hydride 27 in the moving casing 35 cannot leak out from the moving casing 35 and thus, cannot escape from the reaction control unit 25. [45] The gasket 51 is fixed to a rear end portion of the holding casing 33. The gasket 51 is securely adhered to the holding casing 33 such that not gap is formed between them. The gasket 51 may be composed of stainless steel. [46] The bellows 41 is known and has one end fixed to the moving casing 35 so as to be sealed to the moving casing 35 and the other end combined to the gasket 51. Connective portions of both ends of the bellows 41 with the moving casing 35 and the gasket 51 are completely sealed, and thus, although the aqueous solution 27 leaks into the gap between the holding casing 33 and the moving casing 35, the aqueous solution 27 cannot freely flow inside the bellows 41. [47] The bellows 41 may be composed of a rubber-based material, a Teflon-based material, a plastic material, a metal-based material, or a mixture thereof. [48] The rubber-based material may include chloroprene rubber, silicone rubber, acryl rubber, butyl rubber, fluor rubber, chlorosulfonated polyethylene rubber, natural rubber, styrene-butyrene rubber, butadiene rubber, ethylene-propylene rubber, etc. The Teflon-based material may include polytetrafluoroethylene (PTFE), polyvinyli- denefluoride (PVDF), tetrafluoroethylene-perfluoro alkylvinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylenetetrafluoroethylene (ETFE), chlorotrifluoroethylene (CTFE), or polyvinyl fluoride (PVF). [49] The bellows 41 has a restoring force and supports the moving casing 35 in the 'b' direction such that the moving casing 35 is in a state illustrated in FIG. 3. For example, when a pressure P is removed after the moving casing 35 was pushed in the 'a' direction by the pressure P, the bellows 41 pushes the moving casing 35 in the 'b' direction to restore the moving casing 35 at the original position. [50] A cap 45 is combined to the rear end portion of the holding casing 33. The cap 45 has an air hole 47 at its center and is screwed onto the holding casing 33. If necessary, the cap 45 may be welded to the holding casing 33. [51] The air hole 47 in the cap 45 allows the inner space of the bellows 41 to communicate with the outside. That is, the air hole 47 is a hole through which air may enter or exit the bellows 41 when the moving casing 35 reciprocates. Due to the air hole 47, the internal pressure of the bellows 41 is always equal to atmospheric pressure. [52] Reference number 53 denotes packings. [53] A spring 43 is interposed between the cap 45 and the moving casing 35. The spring 43 elastically supports the moving casing 35 in the 'b' direction. [54] Referring back to FIGS. 1 and 2, an operation of the hydrogen-generating device 11 will be explained. [55] Referring to FIG. 1, the moving casing 35 is in a maximally distant state in the 'b' direction in the holding casing 33. In this state, an supporting force applied by the spring 43 and the bellows 41 equilibrates with a static pressure in the aqueous solution of the chemical hydride 27. [56] At this time, the inner space of the moving casing 35 in the force equilibrium state can communicate through the internal through holes 35a and the external through holes 33a with the outside of the holding casing 33. [57] While the inner space of the moving casing 35 is open, the aqueous solution 27 passes through the external through holes 33a and the internal through holes 35a and comes in contact with the hydrogen-generating catalyst 37 and chemically reacts with the hydrogen-generating catalyst 37, thereby generating hydrogen gas. [58] The hydrogen gas generated in the moving casing 35 passes through the gas-liquid separation membrane 15 of the container 55 and is collected in the hydrogen transport path 31. At this time, the gate 29 is closed by the valve 61 until the internal pressure of the hydrogen transport path 31 reaches a predetermined pressure. [59] As the hydrogen gas generated from the aqueous solution of the chemical hydride 27 fills the hydrogen transport path 31, the internal pressure of the hydrogen transport path 31 gradually increases. In this case, the internal pressure of the container 55 is increased since the increased pressure of the transport path 31 flows in through walls of the container 55. [60] As the internal pressure of the container 55 increases, the static pressure of the aqueous solution 27 which is applied to the moving casing 35 increases. Thus, the moving casing 35 moves slowly, as illustrated in FIG. 2. [61] Referring to FIG. 2, due to the pressure applied to the outer surface of the moving casing 35 in the 'P' direction, the moving casing 35 maximally moves toward the cap 45 while compressing the spring 43. A distance and a speed of movement of the moving casing 35 are proportional to the internal pressure of the hydrogen transport path 31. The internal pressure of the hydrogen transport path 31 increases slowly, and thus, the moving casing 35 moves slowly. [62] When the moving casing 35 has moved as close as possible to the cap 45, the projection 35b is inserted into the groove 49 and the inner space of the moving casing 35 is closed. When the internal through holes 35a are closed, the hydrogen gas generated in the moving casing 35 cannot exit in order to come into contact with the aqueous solution 27, as described above. [63] While the moving casing 35 is closed, the gate 29 is open to supply the hydrogen gas to an external unit requiring the hydrogen gas. After the hydrogen gas exits through the gate 29, the internal pressure of the hydrogen transport path 31 decreases and accordingly, the internal pressure of the container 55 decreases. Then, the pressure applied to the moving casing 35 in the 'P' direction gradually decreases and the moving casing 35 moves in the opposite direction (i.e., the 'b' direction in FIG. 1) due to an at¬ mospheric pressure and the elastic restoring force by the bellows 41 and the spring 43. During this, an external air flows in the bellows 41 and the projection 35b exits from the groove 49, and the inner space of the moving casing 35 is open. [64] As the inner space of the moving casing 35 is open, the chemical reaction of the hydrogen-generating catalyst 37 with the aqueous solution 27 is continued and hydrogen gas is again generated. The generated hydrogen gas fills the hydrogen transport path 31 and increases the internal pressure of the container 55, repeating the above operation. [65] As a result, the hydrogen-generating device 11 containing an aqueous solution of the chemical hydride as a raw material, according to the present invention, generates hydrogen gas without a separate source of power or apparatus and is stable since the internal pressure of the container 55 is not high. Especially, since the aqueous solution of the chemical hydride 27 is closed in the gas-liquid separation membrane 15 of the container 55, the hydrogen-generating device 11 can be operated in a normal way although it is installed inclined. [66] While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. Industrial Applicability [67] A hydrogen-generating device according to an embodiment of the present invention generates hydrogen gas from an aqueous solution of the chemical hydride contained in a low pressure container via a chemical reaction, and thus, does not require a separate source of power for generating hydrogen, and has about an atmospheric pressure in the container and thus, has low risk. Further, the device has a simple structure and can be portable and sufficiently mounted on a hydrogen vehicle, and can be used for supplying hydrogen to a fuel cell installed in small electronic items, such as a camcorder, a notebook computer, or a mobile phone. Further, the device automatically controls a rate of generating hydrogen and operates regardless of installation directions, and thus, can be conveniently used and have a stable supply of hydrogen.