Patent Publication Number: US-2012045388-A1

Title: Hydrogen generation device and hydrogen generation method

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of China application serial no. 201010258192.8, filed on Aug. 18, 2010. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a hydrogen generation device and a hydrogen generation method, and more particularly, to a hydrogen generation device using a solid reactant and a hydrogen generation method using a solid reactant. 
     2. Description of Related Art 
     A fuel cell (FC) is a power generation device capable of directly converting chemical energy into electricity. With advantages of low pollution, low noise, high energy density, and high energy conversion efficiency over the traditional electricity generation methods, the fuel cell is a prospective clean energy source. 
     Taking a proton exchange membrane FC as an example, the operation principle thereof is as follows. Hydrogen is oxidized in an anode catalyst layer to generate hydrogen ions (H + ) and electrons (e − ). The hydrogen ions can be transmitted to a cathode through a proton exchange membrane, and the electrodes are transmitted to a load through an external circuit for working, and then are transmitted to the cathode. Oxygen supplied to the cathode, the hydrogen ions, and the electrodes may have a reduction reaction in a cathode catalyst layer to generate water. The fuel hydrogen gas for the anode hydrogen oxidation reaction may be obtained through a hydrogen storage technology by using the solid sodium borohydride (NaBH 4 ) which relies on the reaction of water and the solid NaBH 4  to produce the hydrogen gas. 
     To reduce a size of the reactant, the solid NaBH 4  is pressed as a tablet. Water would slowly enter the tablet-form solid NaBH 4  by way of infiltration. When the water supply is insufficient, the water is only reacted on the surface of the tablet-form solid NaBH 4  without infiltrating inside the solid NaBH 4 , which may reduce a hydrogen generation efficiency. Moreover, the generated hydrogen may bubble the surface of the solid NaBH 4 , which hinders the water to enter the interior of the solid NaBH 4 . Furthermore, when water reacts with the NaBH 4 , the tablet-form NaBH 4  tends to expand and deform due to the generated gas. 
     Taiwan Patent Publication Nos. TW200738890 and TW200640072 and U.S. Pat. No. 7,674,540 disclose technologies relating to the fuel cell. 
     SUMMARY OF THE INVENTION 
     Accordingly, the invention is directed to a hydrogen generation device which may enhance the generation efficiency of hydrogen formed by a reaction of the solid reactant and reaction solution. 
     The invention is also directed to a hydrogen generation method which may enhance the generation efficiency of hydrogen formed by a reaction of the solid reactant and the reaction solution. 
     To achieve one of or all aforementioned and other advantages, an embodiment of the invention provides a hydrogen generation device including a tank, a porous structure, and a guide structure. The tank is used to contain a reaction solution. A solid reactant is distributed in the porous structure. The guide structure is connected with the tank and used to guide the reaction solution in the tank to the porous structure, such that the reaction solution reacts with the solid reactant to generate hydrogen. 
     To achieve one of or all aforementioned and other advantages, an embodiment of the invention provides a hydrogen generation method. The method includes providing a porous structure with a solid reactant distributed in the porous structure; and guiding the reaction solution to the porous structure such that the solid reactant reacts with the reaction solution to generate hydrogen. 
     In view of the foregoing, in embodiments of the invention, the reaction solution is guided to the porous structure through the guide structure such that the reaction solution can directly react with the solid reactant distributed in the porous structure thus enhancing the hydrogen generation efficiency. Besides, the generated hydrogen could escape directly through the pores of the porous structure for a fuel cell to generate electricity. 
     Other objectives, features and advantages of the invention will be further understood from the further technological features disclosed by the embodiments of the invention wherein there are shown and described preferred embodiments of this invention, simply by way of illustration of modes best suited to carry out the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a hydrogen generation device according to one embodiment of the invention. 
         FIG. 2  illustrates a hydrogen generation device according to another embodiment of the invention. 
         FIG. 3A  is a flow chart of a hydrogen generation method. 
         FIGS. 3B to 3C  illustrate a process of generating hydrogen by the hydrogen generation device of  FIG. 1 . 
         FIGS. 3D to 3E  illustrate a process of distributing the solid reactant in the porous structure. 
         FIGS. 4A and 4B  illustrates another process of generating hydrogen by the hydrogen generation device of  FIG. 1 . 
         FIGS. 4C and 4D  illustrate a process of distributing a solid catalyst in the porous structure. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings which form a part hereof, and in which are shown by way of illustration specific embodiments in which the invention may be practiced. In this regard, directional terminology, such as “top,” “bottom,” “front,” “back,” etc., is used with reference to the orientation of the Figure(s) being described. The components of the invention can be positioned in a number of different orientations. As such, the directional terminology is used for purposes of illustration and is in no way limiting. On the other hand, the drawings are only schematic and the sizes of components may be exaggerated for clarity. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the invention. Also, it is to be understood that the phraseology and terminology used herein are for the purposes of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless limited otherwise, the terms “connected,” “coupled,” and “mounted” and variations thereof herein are used broadly and encompass direct and indirect connections, couplings, and mountings. Similarly, the terms “facing,” “faces” and variations thereof herein are used broadly and encompass direct and indirect facing, and “adjacent to” and variations thereof herein are used broadly and encompass directly and indirectly “adjacent to”. Therefore, the description of “A” component facing “B” component herein may contain the situations that “A” component directly faces “B” component or one or more additional components are between “A” component and “B” component. Also, the description of “A” component “adjacent to” “B” component herein may contain the situations that “A” component is directly “adjacent to” “B” component or one or more additional components are between “A” component and “B” component. Accordingly, the drawings and descriptions will be regarded as illustrative in nature and not as restrictive. 
       FIG. 1  illustrates a hydrogen generation device according to one embodiment of the invention. Referring to  FIG. 1 , the hydrogen generation device  100  of the embodiment includes a tank  110 , a porous structure  120 , and a guide structure  130 . The tank  110  is used to contain a reaction solution  50   a . A solid reactant  60   a , such as sodium borohydride (NaBH 4 ), solid magnesium hydride (MgH 2 ), calcium hydride (CaH 2 ), or aluminium (Al), in the form of powder, particle, crystal or other forms is distributed in the porous structure  120  (e.g. in pores of the porous structure  120 , where the diameter of the pores ranges from 5 um to 200 um). An example of the porous structure  120  is expanded polymer, such as expanded polyurethane. The guide structure  130  is connected with the tank  110  and disposed between the tank  110  and the porous structure  120 , for guiding the reaction solution  50   a  in the tank  110  to the porous structure  120 . As such, when the reaction solution  50   a  is guided to the porous structure  120 , the reaction solution  50   a  could directly react with the solid reactant  60   a  distributed in the porous structure  120 , thus enhancing the hydrogen generation efficiency. 
     Specifically, the solid reactant  60   a  is uniformly distributed in the pores of the porous structure  120 , and the reaction solution  50   a  could be guided to the porous structure  120  through the guide structure  130 . Due to permeation effect, the reaction solution  50   a  is delivered from the surface of the porous structure  120  into pores of the porous structure  120  to react with the solid reactant  60   a  in the pores. The hydrogen generation efficiency is thus enhanced because of the increased contact surface between the reaction solution  50   a  and the solid reactant  60   a . The pores of the porous structure  120  may act as gas passages. Therefore, the generated hydrogen could escape directly through the pores of the porous structure  120  for a fuel cell to generate electricity. Furthermore, because the hydrogen is delivered through the pores, the expansion and deformation of the porous structure  120  storing the solid reactant due to the generated gas could be avoided. 
     In practice, the hydrogen generation device  100  of one embodiment further includes a pump  140 . The pump  140  is connected with the guide structure  130  to guide the reaction solution  50   a  to the porous structure  120 . It is noted that, however, this specific arrangement should not be regarded as limiting. Rather, the reaction solution could be guided in another manner, for example, as illustrated in the embodiment below with reference to  FIG. 2 . 
       FIG. 2  illustrates a hydrogen generation device according to another embodiment of the invention. Referring to  FIG. 2 , the hydrogen generation device  200  of the embodiment includes a tank  210 , a porous structure  220 , and a guide structure  230 . The construction and function of the tank  210 , porous structure  220  and guide structure  230  are similar to those of the tank  110 , porous structure  120 , and guide structure  130  in the above embodiment explanatorily shown in  FIG. 1 . Therefore, explanations thereof are not repeated herein. 
     In the embodiment explanatorily shown in  FIG. 2 , the hydrogen generation device  200  further includes a pressurization device  240 . The pressurization device  240  is connected with the tank  210  to pressurize the tank  210  such that the reaction solution  50   b  is delivered from the tank  210  to the porous structure  220  through the guide structure  230 . 
     In addition, the hydrogen generation device  200  further includes a spray device  250 . The spray device  250  is disposed at an end of the guide structure  230 . The reaction solution  50   b  is sprayed to the porous structure  220  through the spray device  250 , such that the reaction solution  50   b  could more uniformly permeate into the porous structure  220  to react with the solid reactant  60   b.    
     The following description and relevant Figures explain a hydrogen generation method according to one embodiment of the invention.  FIG. 3A  is a flow chart of a hydrogen generation method.  FIGS. 3B to 3C  illustrate a process of generating hydrogen by the hydrogen generation device of  FIG. 1 . Similar process may also be applied in the embodiment of  FIG. 2 .  FIGS. 3D to 3E  illustrate a process of distributing the solid reactant into the porous structure. As shown in  FIG. 3A , the hydrogen generation method of the embodiment includes the following steps: 
     Step S 602 : providing a porous structure  120 , with a solid reactant distributed in the porous structure  120 ; and 
     Step S 604 : guiding a reaction solution  50   c  to the porous structure  120  such that the solid reactant  60   d  reacts with the reaction solution  50   c  to generate hydrogen. 
     At step S 602 , in order to distribute the solid reactant  60   d  into the porous structure  120 , the following method may be included (referring to  FIGS. 3D to 3E ): guiding a reaction solution  60   c  (which will be described hereafter) into the porous structure  120 ; and heating the porous structure  120  such that the solid reactant  60   d  precipitates from the reaction solution  60   c . This solid reactant  60   d  is the same as the solid reactant  60   a  in  FIG. 1 . Using this method with a system similar to  FIG. 1 , the solid reactant  60   d  could be distributed in the porous structure  120 . Specifically, when guiding the solution  60   c  to the porous structure  120 , the solution  60   c  may first be contained in the tank  110 ′ and then be guided to the porous structure  120  through the guide structure  130 ′ connected with the tank  110 ′. A pump  140 ′ may also be used in this system to deliver the solution  60   c . In the process of heating the porous structure  120 , an anti-splashing layer (not shown) may cover the porous structure  120  to prevent the precipitated solid reactant  60   d  from splashing out of the porous structure  120 . Other method may also be used to provide the reaction solution  60   c  to the porous structure  120 , such as immersing the porous structure  120  directly into the reaction solution  60   c.    
     Particularly, the solution  60   c  used to precipitate the solid reactant  60   d  may be a solution obtained by dissolving sodium borohydride (NaBH 4 ) in liquid ammonia (NH 3 ) or dissolving NaBH 4  in water. When the porous structure  120  is heated to make the solid reactant  60   d  be precipitated from the solution  60   c , the liquid NH 3  or water used for the solution  60   c  is evaporated by heat and leaves the solid NaBH 4  distributed in the porous structure  120  (e.g. distributed in the pores) in the form of powder, particle, crystal or other forms. Solid magnesium hydride (MgH 2 ), calcium hydride (CaH 2 ), or aluminium (Al) powder may also be distributed in the porous structure  120  in a similar manner. 
     When the reaction solution  50   c  is guided to the porous structure  120  at step S 604 , the reaction solution  50   c  may be contained in the tank  110  and then guided to the porous structure  120  through the guide structure  130  connected with the tank  110 . In the embodiment, the reaction solution  50   c  is used to react with the solid reactant  60   d  to generate hydrogen. The reaction solution  50   c  may be, for example, cobalt chloride (CoCl 2 ) solution, iron chloride (FeCl 2 ) solution, cobalt sulfate (CoSO 4 ) solution, nickel chloride (NiCl 2 ) solution, or other solutions that contain catalyst and could react with the solid reactant  60   d  to generate hydrogen. However, these specific examples should not be regarded as limiting. Rather, in other embodiments, the reaction solution  50   c  may, for example, be liquid water, malic acid, citric acid, sulfuric acid (H 2 SO 4 ), sodium bicarbonate (NaHCO 3 ) solution, or calcium carbonate (CaCO 3 ) solution. 
       FIGS. 4A and 4B  illustrates another process of generating hydrogen using the hydrogen generation device of  FIG. 1 . Referring to  FIGS. 4A and 4B , in the embodiment, in generating the hydrogen, the same steps as steps S 602  and S 604  in  FIG. 3A  are performed, i.e. providing a porous structure  120 , with a solid reactant distributed in the porous structure  120 ; and guiding a reaction solution  50   c  to the porous structure  120  such that the solid reactant  60   d  reacts with the reaction solution  50   c  to generate hydrogen. The present embodiment is different from the previous embodiment in that: in addition to the solid reactant  60   d  distributed in the porous structure  120 , there is also solid catalyst  70   c  distributed in the porous structure  120 . 
     Since both the solid reactant  60   d  and the solid catalyst  70   c  are distributed in the porous structure  120 , step S 602  (providing the porous structure  120 ) further includes distributing the solid catalyst  70   c  in the porous structure  120 .  FIGS. 4C and 4D  illustrate a process of distributing a solid catalyst in the porous structure using a system similar to  FIG. 1 . Referring to  FIGS. 4C and 4D , the process includes guiding a catalyst solution  70   a  to the porous structure  120 ; and heating the porous structure  120  such that the solid catalyst  70   c  is precipitated from the catalyst solution  70   a.    
     The catalyst solution  70   a  may be, for example, CoCl 2  solution, FeCl 2  solution, CoSO 4  solution, or NiCl 2  solution, which may generate solid catalyst  70   c  such as CoCl 2 , FeCl 2 , CoSO 4  or NiCl 2  by heating the catalyst solution  70   a . When the catalyst solution  70   a  is guided to the porous structure  120 , the catalyst solution  70   a  may be contained in the tank  110 ″ and then guided to the porous structure  120  through the guide structure  130 ″ connected with the tank  110 ″. A pump  140 ″ may also be used in this system to deliver the catalyst solution  70   a . In the process of the heating the catalyst solution  70   a , an anti-splashing layer (not shown) may cover the porous structure  120  to prevent the precipitated solid catalyst  70   c  from splashing out of the porous structure  120 . 
     It should be understood that the sequence of distributing the solid reactant  60   d  and distributing the solid catalyst  70   c  in the porous structure  120  may be determined based on actual needs in practice. If distributing the solid catalyst  70   c  in the porous structure  120  is prior to distributing the solid reactant  60   d  in the porous structure  120  using the solution  60   c , the solid reactant  60   d  are dissolved in a solvent that does not react with the solid reactant  60   d  to generate hydrogen, e.g. NaBH 4  is dissolved in low-concentration sodium hydroxide (NaOH) instead of water, for preventing hydrogen generation under catalysis while guiding the solution  60   c  to the porous structure  120  that contains the solid catalyst  70   c.    
     Additionally, in the embodiment, since the solid catalyst  70   c  and solid reactant  60   d  are already distributed in the porous structure  120 , the reaction solution  50   c  may be a solution that does not contain catalyst but could react with the solid reactant  60   d  to generate hydrogen, for example, liquid water, malic acid, citric acid, H 2 SO 4 , NaHCO 3  solution or CaCO 3  solution. Hydrogen generated through the reaction between the reaction solution  50   c  and the solid reactant  60   d  could likewise escape through the pores of the porous structure  120  for a fuel cell to generate electricity. 
     In summary, in embodiments of the invention, the solution containing solid reactant is guided to the porous structure and the porous structure is heated such that the solid reactant precipitates and is distributed in the porous structure in the form of powder or crystal. Therefore, when the reaction solution is guided to the porous structure, the reaction solution could directly react with the solid reactant distributed in the porous structure thus enhancing the hydrogen generation efficiency. Besides, the generated hydrogen could escape directly through the pores of the porous structure for the fuel cells to generate electricity. 
     The foregoing description of the preferred embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form or to exemplary embodiments disclosed. Accordingly, the foregoing description should be regarded as illustrative rather than restrictive. Obviously, many modifications and variations will be apparent to practitioners skilled in this art. The embodiments are chosen and described in order to best explain the principles of the invention and its best mode practical application, thereby to enable persons skilled in the art to understand the invention for various embodiments and with various modifications as are suited to the particular use or implementation contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents in which all terms are meant in their broadest reasonable sense unless otherwise indicated. Therefore, the term “the invention”, “the present invention” or the like does not necessarily limit the claim scope to a specific embodiment, and the reference to particularly preferred exemplary embodiments of the invention does not imply a limitation on the invention, and no such limitation is to be inferred. The invention is limited only by the spirit and scope of the appended claims. Moreover, these claims may refer to use “first”, “second”, etc. following with noun or element. Such terms should be understood as a nomenclature and should not be construed as giving the limitation on the number of the elements modified by such nomenclature unless specific number has been given. The abstract of the disclosure is provided to comply with the rules requiring an abstract, which will allow a searcher to quickly ascertain the subject matter of the technical disclosure of any patent issued from this disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Any advantages and benefits described may not apply to all embodiments of the invention. It should be appreciated that variations may be made in the embodiments described by persons skilled in the art without departing from the scope of the invention as defined by the following claims. Moreover, no element and component in the present disclosure is intended to be dedicated to the public regardless of whether the element or component is explicitly recited in the following claims.