Patent Publication Number: US-2019186040-A1

Title: Vertical electrolytic device

Description:
TECHNICAL FIELD 
     The present disclosure relates to a vertical electrolytic device used for a surface reforming process of a separator of a fuel cell or the like. 
     BACKGROUND ART 
     In general, fuel cells are environmentally-friendly power generation systems that generate electricity and thermal energy through an electrochemical reaction between hydrogen and oxygen, and are often provided in a stack structure in which several tens to several hundreds of layers of fuel cell units, each of which generates about 1 V, are stacked. 
     Such fuel cells may be used in various fields, and recently, they have been developed and used as a source of automotive fuel. 
     A fuel cell unit is an assembly of electrodes and an electrolyte, including an anode supplying hydrogen ions, a cathode supplying oxygen, and an electrolyte exchanging hydrogen ions between the anode and the cathode. 
     To stack such fuel cell units, separators are placed between the fuel cell units, and such separators may be used to isolate hydrogen and oxygen, to electrically connect the fuel cell units, and to maintain hardness of the stack. 
     Such separators need to have high electrical conductivity and high corrosion resistance. Therefore, stainless steel-based metal separators are typically used, and in particular, STS316-based steel plates, gold-plated for conductivity, are often used. 
     However, conventional separators have become costly due to such a gold plating process. To address this problem, a surface reforming technique using passive film removal, which does not require a gold plating process and is cost-effective, has been developed for securing high conductivity. 
     Particularly, the surface reforming technique using passive film removal refers to a process of passing a stainless steel surface, after removing an oxide layer formed thereon through electrolysis using sulfuric acid, through a solution containing nitric acid and hydrofluoric acid (mixed acids) to regenerate a conductive film. This technique may be used to secure a degree of conductivity comparable to the gold plating process. 
       FIG. 1  is a block diagram illustrating a surface reforming process for a general separator of a fuel cell. To produce a separator of a fuel cell that requires conductivity, a surface reforming apparatus  1  needs to continuously supply a strip S that forms the body of the separator, and to this end, includes winders  2  and  5  (POR: pay off roll, TR: tension reel) for unwinding and winding the strip S. 
     Also, the surface reforming apparatus  1  passes the continuously supplied strip S through an electrolytic device  10 , a washing device  30 , a mixed acid immersion device  50 , and a final washing device  70 , to impart conductivity to the strip S through each process. 
     Meanwhile,  FIG. 2  is a block diagram illustrating an electrolytic device according to the related art. Referring to  FIG. 2 , a surface reforming electrolytic device  10  includes an electrolysis bath  12  storing an electrolyte, such as sulfuric acid or the like, and an electrode part  14 , including cathodes and anodes alternately disposed, immersed in the electrolyte. The electrode part  14  is disposed vertically with respect to the strip S. Further, an immersion roll  18  is provided in the electrolytic bath  12  for travel of the strip S. 
     In the electrolytic device  10 , while the strip S is passing through the electrode parts  14 , hydrogen gas is generated from cathode electrodes  15  and  17 , and oxygen gas is generated from the portion of the strip Sunder the influence of the cathode electrodes  15  and  17 . In addition, oxygen gas is generated from the surface of the anode electrode  16 , and hydrogen gas is generated from the portion of the strip S under the influence of the anode electrode  16 . 
     As described above, gases G generated from the electrode parts  14  and the portions of the strip S under the influences thereof tend to attach to the electrode parts  14  and the portions of the strip S as bubbles, and such bubbles G may hinder the electrolysis process. 
     Particularly, although the bubbles G generated in upper portions of the strip S may easily rise and escape therefrom, the bubbles G generated in lower portions of the strip S tend to remain attached to the surface of the lower portions of the strip S and cannot easily escape therefrom. 
     To solve this problem, the electrolytic device  10  in the related art has had a nozzle part  20  installed in the electrolysis bath to remove the bubbles G attached to the surface of lower portions of the strip S, and uses this nozzle part  20  to remove the bubbles G by spraying the electrolyte under high pressure. However, since the strip S may be moving horizontally, the bubbles G attached to the lower portions of the strip S may only be removed to a limited extent. 
     DISCLOSURE 
     Technical Problem 
     An aspect of the present disclosure is to provide a vertical electrolytic device which easily discharges bubbles generated from an electrolysis process by allowing a strip, used as a separator of a fuel cell or the like, to move vertically during the electrolysis process. 
     Technical Solution 
     According to an aspect of the present disclosure, a vertical electrolytic device includes: an electrolytic bath in which an electrolyte is stored, including a top opening and a bottom opening to allow vertical movement of a strip, the bottom opening being formed to correspond to the strip to prevent discharge of the electrolyte stored therein; and at least one pair of electrode parts, disposed to face each other with the strip disposed therebetween inside the electrolytic bath. 
     In detail, the electrode parts may be disposed in multiple pairs in a vertical direction and may include cathode and anode electrodes alternately disposed in a travel direction of the strip. 
     In detail, the electrolytic bath may further include at least one pair of nozzle parts configured to spray the electrolyte onto the electrode parts or to the surface of the strip. 
     Preferably, the nozzle parts may be provided below the electrode parts. 
     In addition, amain tank provided below the electrolytic bath and configured to store the electrolyte being discharged from the electrolytic bath, and a circulation means for supplying the electrolyte stored in the main tank to the electrolytic bath or to the nozzle parts may be further comprised. 
     Alternatively, the electrolytic bath may include one or more independent chambers, each of which independently accommodates one pair of electrode parts and one pair of nozzle parts, wherein the independent chamber disposed above may be disposed to allow the electrolyte discharged from a bottom opening thereof to connect to the electrolyte stored in the independent chamber disposed below. 
     In detail, a lower surface of the independent chamber may be downwardly inclined toward the bottom opening. 
     In detail, a passage through which bubbles are discharged may be formed between the independent chamber disposed above and the independent chamber disposed below. 
     In detail, each of the independent chambers may further include an auxiliary tank configured to store an electrolyte overflowing or falling from above, and an auxiliary circulation means for supplying the electrolyte stored inside the auxiliary tank to each of the independent chambers or to the nozzle parts. 
     Advantageous Effects 
     As set forth above, according to an exemplary embodiment in the present disclosure, as an electrolysis process takes place while the strip is moving vertically, it may be possible to minimize the attachment of bubbles generated during the electrolysis process to the strip; and to prevent the bubbles from causing defects on the surface of the strip, thus contributing to quality improvement. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram illustrating a general surface reforming process of a separator of a fuel cell. 
         FIG. 2  is a block diagram of an electrolytic device according to the related art. 
         FIG. 3  is a block diagram of a vertical electrolytic device according to an exemplary embodiment of the present disclosure. 
         FIG. 4  is a block diagram of a vertical electrolytic device according to another exemplary embodiment of the present disclosure. 
         FIG. 5  is a block diagram of a vertical electrolytic device according to another exemplary embodiment of the present disclosure. 
         FIG. 6  is a block diagram of a vertical electrolytic device according to another exemplary embodiment of the present disclosure. 
     
    
    
     BEST MODE FOR INVENTION 
     An exemplary embodiment of the present disclosure will be described in greater detail in conjunction with the attached drawings. The exemplary embodiments of the present disclosure may be modified in various forms, and the scope of the present disclosure is not limited to the exemplary embodiments described herein. In the drawings, the shapes and sizes of elements maybe exaggerated for increased clarity, and like reference numerals may designate like elements throughout the specification and drawings. 
       FIG. 3  is a block diagram illustrating a vertical electrolytic device according to an exemplary embodiment of the present disclosure. 
     Referring to  FIG. 3 , a vertical electrolytic device  110  according to the present exemplary embodiment may be used for a surface reforming process in the manufacturing of a separator of a fuel cell or the like, and in particular, maybe configured to perform electrolysis while a strip used for surface reforming is vertically passing therethrough. 
     The vertical electrolytic device  110  may include an electrolyte bath  112  to which a strip S can be supplied vertically, and configured to keep the strip S immersed in an electrolyte while moving. In addition, the electrolyte bath  112  may have openings formed in top and bottom portions to allow vertical movement of the strip. 
     In the present exemplary embodiment, the strip S may be supplied from the top portion to the bottom portion; however, the direction in which the strip S can be supplied is not limited thereto. Alternatively, the strip S may be supplied from the bottom portion to the top portion. 
     In present exemplary embodiment, the strip S is disclosed as being supplied from the top portion to the bottom portion. Such a structure, even when bubbles are generated from the surface of the strip S during the electrolysis process, serves to keep the bubbles, rising in a direction opposite to a travel direction of the strip S, from easily attaching to the strip S. 
     In the present exemplary embodiment, as the strip S is supplied from the top portion to the bottom portion, a top opening and a bottom opening of the electrolyte bath  112  may serve as an inlet and an outlet, respectively. 
     Preferably, the top portion of the electrolyte bath  112  may include a cover (not illustrated) to keep foreign materials from entering, wherein the cover can be opened, and includes a gas discharge hole for discharge of gas and an inlet through which the strip S can be introduced. 
     The vertically supplied strip S may be discharged from the bottom portion of the electrolyte bath  112 , and to this end, an outlet  116  through which the strip S can be discharged may be formed on a lower surface  113  of the electrolyte bath  112 . Preferably, the outlet  116  formed on the lower surface  113  of the electrolyte bath  112  may have a minimal size allowing discharge of the strip S, to control the electrolyte level, and for example, may be formed in the shape of a slot elongated in a width direction of the strip S. 
     The electrolyte bath  112  may contain at least one pair of electrode parts  114  disposed to face each other with the vertically moving strip S disposed therebetween. 
     For example, the electrode parts  114  may be disposed in multiple pairs along a vertical direction, and for example, cathode and anode electrodes may be alternately disposed in a travel direction of the strip S. 
     Preferably, in the present exemplary embodiment, the electrode parts  114  may be a cathode electrode  115 , an anode electrode  116 , and a cathode electrode  117 , sequentially disposed in a travel direction of the strip S. 
     In the vertical electrolytic device  110 , while the strip S is passing through each of the electrode parts  114 , hydrogen gas may be generated from the cathode electrodes  115  and  117 , and oxygen gas may be generated from a portion of the strip S under the influence of the cathode electrodes  115  and  117 . Also, oxygen gas may be generated from the surfaces of the anode electrodes  116 , and hydrogen gas may be generated from a portion of the strip S under the influence of the anode electrodes  116 . 
     In the present exemplary embodiment, due to vertical movement of the strip S, each of bubbles G generated by the electrode parts  114  may rise to the top portion due to buoyancy or the like, and may be discharged. 
     Preferably, in the electrolyte bath  112 , at least one pair of nozzle parts  120  configured to spray the electrolyte onto the electrode parts  114  or to the surface of the strip S may be further installed to allow the bubbles G generated from the hydrolysis process to easily detach from the electrode parts  114  or the strip S, and to allow the electrode parts  114  or the strip S to come into contact with the electrolyte more easily. 
     The electrolyte may be supplied to the electrolyte bath  112  through a separate electrolyte supplying means. Alternatively, the electrolyte may be supplied through a nozzle. 
     According to the present exemplary embodiment, the electrolyte chamber  112  may be formed by a single chamber, and a plurality of electrode parts  114  and nozzle parts  120  may be installed therein, however, the electrolyte chamber  112  may be modified to have various forms to improve performance thereof. 
     For example, the electrolyte bath  112  may include at least one or more independent chambers  112   a , each of which independently accommodates one pair of electrode parts  114  and one pair of nozzle parts  120 . 
     Such electrolyte baths  112  may be provided such that the electrolyte discharged from the outlet  116  formed on the bottom portion of the independent chamber  112   a  disposed above can connect with the electrolyte stored in another independent chamber  112   a  disposed below. 
     In particular, one pair of electrode parts  114  and one pair of nozzle parts  120  may be independently provided in each of the independent chambers  112   a , and the electrolyte discharged from the outlet  116  of one independent chamber  112   a  disposed above, by being continuously discharged, may be electrically connected to the electrolyte stored in another independent chamber  112   a  disposed below. 
     Preferably, in the present exemplary embodiment, three such independent chambers  112   a  may be provided, and one pairs of electrode parts  114  provided to the three independent chambers  112   a  maybe cathode electrodes  115 , anode electrodes  116 , and cathode electrodes  117 , sequentially disposed in a travel direction of the strip S. 
     In particular, the lower surface  113  of each independent chamber  112   a  may be inclined downwardly toward the outlet  116 . 
     The lower surface  113  of one independent chamber  112   a  disposed above may prevent from entering, the bubbles G generated from an electrolysis process in another independent chamber  112   a  disposed below. 
     Also, the bubbles G generated from the electrolysis process in the independent chamber  112   a  disposed below may be externally discharged along the lower surface  113  of the independent chamber  112   a  disposed above, and the bubbles G may be discharged through a passage formed between the independent chamber  112   a  disposed above and the independent chamber  112   a  disposed below. 
     Preferably, the lower surface  113  of the independent chamber  112   a  disposed above maybe positioned below the level of electrolyte stored in the independent chamber  112   a  disposed below. Accordingly, the electrolyte being discharged from the independent chamber  112   a  disposed above may remain connected to the electrolyte in the independent chamber  112   a  disposed below. 
     Also, each of the independent chambers  112   a,  when vertically disposed, may have a gap formed by the inclined lower surface thereof that serves as a passage, and through this gap, the bubbles G generated and rising from the independent chamber  112   a  disposed below may be discharged. 
       FIG. 4  is a block diagram of a vertical electrolytic device according to another exemplary embodiment of the present disclosure. 
     Referring to  FIG. 4 , a vertical electrolytic device  110  in the present exemplary embodiment may be configured to recirculate and thereby continuously supply an electrolyte discharged from electrolysis baths  112 . 
     To this end, below the electrolysis baths  112 , a main tank  130  in which the electrolyte discharged from the electrolysis baths  112  is stored may be installed, and a circulation means for supplying the electrolyte stored in the main tank  130  back to the electrolysis baths  112  or nozzle parts may be further provided. 
     In particular, the circulation means may include a pipe connecting the main tank  130  with the electrolysis bath  112  or the nozzle parts, and a pump and a valve for supplying the electrolyte to the pipe. 
     In addition, the main tank  130  may include a plurality of immersion rolls  132  immersed in the electrolyte and configured to switch a supply direction of a strip S. 
     In addition, each independent chamber  112   a  may have the electrolyte overflowing through an open top portion of, and the electrolyte overflowing from another independent chamber  112   a  disposed above may fall thereto. 
     As described above, the electrolyte overflowing from each independent chamber  112   a,  after being collected into the main tank  130 , may be supplied back to each independent chamber  112   a  or to the nozzle parts through the circulation means, and may be sprayed through the nozzle parts and recirculated. 
     The circulation means may include a pipe P connecting the independent chambers  112   a  or the nozzle parts  120 , and a pump and a valve (not illustrated) for supplying the electrolyte to this pipe P. 
     Preferably, each independent chamber  112   a  may be provided with an auxiliary tank  134  for storing the electrolyte overflowing or falling from above. Such an auxiliary tank  134  may be formed at an upper edge of the independent chamber  112   a , and may supply the electrolyte stored in the auxiliary tank  134  to another independent chamber  112   a  or nozzle parts  120  disposed below. 
     To this end, the auxiliary tank  134  may be provided with an auxiliary circulation means for supplying the electrolyte stored therein to each independent chamber  112   a  or to the nozzle parts  120 . The auxiliary circulation means may be provided in the same structure as the circulation means, and may include, for example, a pipe P connecting the auxiliary tank  134  to the electrolysis bath  112  or the nozzle parts  120 , and a pump and a valve for supplying the electrolyte to this pipe P. 
     Preferably, the circulation means provided in the main tank  130  may be configured to supply the electrolyte to the independent chamber  112   a  disposed uppermost and nozzle parts  120  installed therein, and the circulation means provided in the auxiliary tank  134  may be configured to supply the electrolyte to another independent chamber  112   a  disposed below the independent chamber  112   a  disposed uppermost, and nozzle parts  120  installed therein. 
       FIG. 5  is a block diagram illustrating a vertical electrolytic device  210  according to another exemplary embodiment of the present disclosure. In this exemplary embodiment, the electrolysis baths  212 , which are individual independent chambers  212   a , are illustrated as being vertically arranged and having lower surfaces that are downwardly inclined; however, the shape and the arrangement of such independent chambers  212   a  are not limited thereto. 
     For example, in this exemplary embodiment, the independent chamber  212  may have lower surfaces  213  that are flat. 
     In addition, the independent chamber  212   a  may have an outlet  213   a  formed on the lower surface  213  thereof. In particular, the outlet  213   a  may extend downwardly from the lower surface  213  to a predetermined height. Such an outlet  213   a  may prevent the bubbles G discharged from another independent chamber  212   a  disposed below from entering the independent chamber  212   a  disposed above. 
     In addition, the independent chamber  212   a  disposed below may be formed to have a width larger than a lower width of the independent chamber  212   a  disposed above. For example, an upper perimeter of the independent chamber  212   a  disposed below may be wider than a lower perimeter of the independent chamber  212   a  disposed above. Accordingly, the electrolyte overflowing from the independent chamber  212   a  disposed above may be collected into the independent chamber  212   a  disposed below. 
     Further, each independent chamber  212   a  of the electrolytic device  210  may include one pair of electrode parts  214 , and nozzle parts  220  configured to spray the electrolyte onto the electrode parts  214  or the surface of the strip S. 
     In the electrolytic device  210  having above configuration, the strip S can be electrolyzed in each independent chamber  212   a , and the strip S, travelling vertically during this process, may prevent the bubbles G from attaching to the electrode parts  214  and the surface of the strip S. Even when some bubbles G are attached to the electrode parts  214  and the surface of the strip S, the electrolyte sprayed from the nozzle parts  220  may effectively cause the some bubbles G to detach therefrom. 
     Further, the bubbles G discharged and rising from the independent chamber  212   a  disposed below may be prevented from entering the independent chamber  212   a  disposed above by the lower surface  213  of the independent chamber  212   a  disposed above and a stepped portion  214   a  raised around the outlet  116  of the lower surface  213  of the independent chamber  212   a  disposed above. Such bubbles G may be discharged externally through an open passage created as the perimeter of the independent chamber  212   a  disposed above is formed to be larger than the perimeter of the independent chamber  212   a  disposed above. 
       FIG. 6  is a block diagram illustrating a vertical electrolytic device  310  according to another exemplary embodiment of the present disclosure. In this exemplary embodiment, a lower surface  313  of each independent chamber  312   a , the electrolysis bath  312 , may be downwardly inclined toward an outlet  313   a,  and the independent chamber  312   a  disposed below may be formed wider than a lower width of the independent chamber  312   a  disposed above. 
     In this structure, even without having an auxiliary tank  334  installed at the edge of the independent chamber  312   a , the electrolyte overflowing from the independent chamber  312   a  disposed above may be collected into the independent chamber  312   a  disposed below. 
     Further, each independent chamber  312   a  of the electrolytic device  310  may include one pair of electrode parts  314 , and nozzle parts  320  configured to spray the electrolyte onto the electrode parts  314  or to the surface of the strip S. 
     In the electrolytic device  310  having the above configuration, the strip S can be electrolyzed in each independent chamber  312   a , and the strip S, travelling vertically during this process, may prevent the bubbles G from attaching to the electrode parts  314  and the surface of the strip S. Even when some bubbles G are attached to the electrode parts  314  and the surface of the strip S, the electrolyte sprayed from the nozzle parts  320  may effectively cause the some bubbles G to detach therefrom. 
     Furthermore, the bubbles G discharged and rising from the independent chamber  312   a  disposed below may rise and move outwardly along the inclined lower surface  313  of the independent chamber  312   a  disposed above, thus not entering the independent chamber  312   a  disposed above. In addition, such bubbles G may be discharged externally through an open passage created as the perimeter of the independent chamber  312   a  is formed to be larger than the perimeter of the independent chamber disposed above. 
     The exemplary embodiments and the attached drawings should not be construed as limiting the scope of the present disclosure, and it will be apparent to those skilled in the art that alternatives, modifications, and variation can be made without departing from the scope of the present disclosure as defined by the appended claims.