Abstract:
Disclosed is a fuel supplying apparatus, for a direct carbon fuel cell, which has improved output density by ensuring the flow properties of an anode medium. The fuel supplying apparatus for a direct carbon fuel cell comprises: a flow pipe which forms a flow path around a tube-shaped cell contained in an anode medium in which a carbon fuel is mixed; and a bubbling means which provides a gas from below the flow pipe to the inside of the anode medium and thus enables the anode medium to flow by the upward movement of the gas. Consequently, the carbon fuel is forcibly provided to the anode of the tube-shaped cell by the flow of the anode medium which is linked with the upward movement of the gas.

Description:
TECHNICAL FIELD 
     The present invention relates to a direct carbon fuel cell, and more specifically, to a fuel supplying apparatus and system for a direct carbon fuel cell, which have improved output density by ensuring the flow properties of an anode medium. 
     DISCUSSION OF RELATED ART 
     While rich countries struggle to reduce CO 2  emissions, China, India, and other rising economies are consuming more and more fossil fuels with a high demand for energy. Coal is taking up its position as an important energy resource with its vast worldwide reserves. 
     However, this fuel source is challenged by steadily increasing CO 2  emissions. To address the issue, various approaches are being attempted, which include efficient carbon conversion, extracting pure coal, and direct use of coal as a fuel. However, they are difficult to generally adopt. under different situations and in terms of efficiency and costs. 
     An attention-receiving alternative is the direct carbon fuel cell (DCFC) technique that may produce gigawatt power by employing coal as an energy source while recycling waste heat. 
     This novel technology would play is critical role in the distributed power generation industry. 
     DCFC power generation systems exhibit a high energy conversion efficiency reaching about 80%, which is higher than the thermal power generation systems and the highest among all the existing types of fuel cell systems, Unlike other hid cells, the DCFC directly uses coal or other carbon-containing material as its fuel, which leads to many environmental or economic benefits, such as reduced emissions of SOS, NON, PM, CO 2 , or other pollutants and noise-free power generation. 
     A DCFC includes a cathode, an anode, and an electrolyte. Oxygen ions generated by a reduction reaction at the cathode travel to the anode via the electrolyte. The oxygen ions react with carbon at the anode, thus producing CO 2 . CO 2  reacts with the oxygen ions to generate carbonate ions. The carbonate ions oxidize the carbon to generate CO 2  and electrons, generating, electricity. 
       FIG. 1  schematically illustrates an example of power generation by a DCFC. 
     In order to reduce concentration polarization of the anode to increase output density, the cathode-supported solid oxide electrolyte direct carbon fuel cells using molten carbonate as its anode medium requires the carbon fuel to be mixed well with the anode medium together with forcedly. supplying the anode medium to the fuel cell. 
     Accordingly, a need exists for a method for forcing the anode medium, i.e., molten carbonate, to flow. 
     A proposed conventional method is to use a liquid pump. 
     However, this method is challenged. by the high-corrosive molten carbonate whose temperatures reaches 700° C. to 1000° C. 
     SUMMARY 
     An object of the present invention is to provide a fuel supplying apparatus and system for a direct carbon fuel cell, which may increase output density by forcing the molten carbonate, an anode medium, to flow to thereby reduce the concentration polarization of the anode. 
     Another object of the present invention is to provide a fuel supplying apparatus and system for a direct carbon fuel cell, which may forcedly mix the anode medium formed of a molten carbonate with a carbon fuel and supply the mix to the anode of the direct carbon fuel cell. 
     Still another object of the present invention is to provide a fuel supplying apparatus and system for a direct carbon fuel cell, in which a flow pipe is formed around one or more tubular cells each including an cathode supporter and a solid oxide electrolyte, and the anode medium may be forced to flow in the flow pipe by supplying carbon dioxide. 
     According to the present invention, a fuel supplying appall us for a direct carbon fuel cell comprises: a flow pipe forming a flow path around to tubular cell soaked in a fuel electrode medium mixed with a carbon fuel; and a bubbling means supplying a gas from under the flow pipe to an inside of the fuel electrode medium so that the fuel electrode medium flows as the gas moves up, wherein the flow of the fuel electrode medium forces the carbon fuel to be supplied to a fuel electrode of the tubular cell. 
     Here, the flow pipe includes a collecting part at a lower portion thereof, the collecting part widening downwards, and the collecting part may guide the gas supplied from under the flow pipe to the flow path in the flow pipe. 
     An end of a supplying pipe included in the bubbling means may be configured to supply the gas to the flow path between the tubular cell and the flow pipe. 
     The supplying pipe included in the bubbling means extends from top to bottom along an outer wall of the flow pipe, and the end of the supplying pipe may be formed inside a lower portion of the flow pipe. 
     The supplying pipe may be spirally formed along the outer wall of the flow pipe. 
     The fuel supplying apparatus may further comprise a distributing member on the flow path in the flow pipe, the distributing member distributing the gas supplied from the bubbling means and supplying upward the distributed gas. 
     The distributing member may be formed of a disc with multiple through-holes. 
     The distributing member may include a porous layer. 
     The bubbling means may independently generate and provide the gas. 
     The bubbling means may re-circulate and supply the gas that is generated by an electrochemical reaction of the carbon fuel and is then discharged to an outside of the fuel electrode medium. 
     The flow pipe may form the flow path around a plurality of tubular cells. 
     Meanwhile, according to the present invention, a fuel supplying system for a direct carbon fuel cell comprises: one or more tubular cells each including an cathode formed at an inside thereof, a anode formed at an outside thereof, and a solid oxide electrolyte formed between the cathode and the anode; and the fuel supplying apparatus supplying a forcedly flowing anode medium to the tubular cells. 
     Accordingly, the present invention may allow the anode medium to flow so that the carbon fuel may be forced to be supplied to the anode of the direct carbon fuel cell, with the carbon fuel mixed with the anode medium. 
     Therefore, the concentration polarization Of the anode of the tubular cell in the direct carbon fuel cell may be reduced to increase output density. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a view schematically illustrating an example of generating power in a typical direct carbon fuel cell. 
         FIG. 2  is a view illustrating a configuration of a fuel supplying apparatus for a direct carbon fuel cell according to a preferred embodiment of the present invention. 
         FIGS. 3 and 4  are views illustrating variations of the configuration shown in  FIG. 2 , adopting different methods for supplying carbon dioxide, according to other embodiments of the present invention. 
         FIGS. 5 to 7  are views illustrating respective corresponding variations of the configurations shown in  FIGS. 2 to 4 , with as plurality of tubular cells, according to other embodiments of the present invention. 
         FIG. 8  is a view illustrating a variation of the configuration shown in  FIG. 2 , with a distributing member, according to another embodiment of the present invention. 
         FIG. 9  is a view illustrating a variation of the configuration shown in  FIG. 5 , with a distributing member, according to another embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Hereinafter, embodiments of the present invention are described in detail with reference to the accompanying drawings. The terms used herein should be interpreted not in typical or dictionary definitions but to comply in concept with the technical matters of the present invention. 
     The configurations disclosed in the specification and the drawings are mere examples and do not overall represent the technical spirit of the present invention. Therefore, various changes may be made thereto, and equivalents thereof also belong to the scope of the present invention. 
     Disclosed is a fuel supplying apparatus for a direct carbon fuel cell having a structure in which power generation is conducted with a tubular cell soaked in a mixture of a liquid anode medium and a carbon fuel. 
     Here, the tubular cell has a structure in which a cathode and an anode are respectively formed at an inside and outside of the tubular cell, with a solid oxide electrolyte formed between the cathode and the anode. 
     The cathode may include lanthanum strontium manganite (LSM), and the electrolyte may include ittria-stabilized zirconia (YSZ). The anode may include carbon fuel particles mixed with a circulatable molten salt. 
     The anode medium may include a molten carbonate, and the carbon fuel may include a carbon powder, a coal powder, coke, a biomass fuel, and an organic waste. 
     Referring to  FIG. 2 , according to the present invention, one more tubular cells  12  are soaked in a molten carbonate, an anode medium  14  contained in a bath  10 . 
     According to an embodiment of the present invention, a flow pipe  16  is provided to form a vertical-directional cylindrical flow path around the periphery of the tubular cell  12  soaked in the anode medium  14  contained in the bath  10 . 
     The flow pipe  16  has a cylindrical upper portion. A collecting part  18  is integrally formed with the flow pipe  16  at a lower portion of the flow pipe  16 . The collecting part  18  is shaped as a trumpet that widens downwards. 
     By the above configuration, the flow pipe  16  forms a flow path therein while encompassing the tubular cell  12 . The flow pipe  16  is disposed to be completely soaked in the anode medium  14  so that flows may be created at an upper side and lower side of the flow pipe  16 . 
     According to an embodiment of the present invention, a bubbling means may be further provided to supply a gas to a lower portion of a cylindrical flow path formed inside the flow pipe  16 . The bubbling means is configured so that as a gas supplied from the bubbling means travels upwards, the anode medium  14  flows over the flow path. 
     A gas supplied from the bubbling means is preferably carbon dioxide (CO 2 ) that is generated as a result of the electrochemical reaction shown in  FIG. 1 . For the purpose of description, the gas is hereinafter carbon dioxide. 
     The bubbling means may include a supplying pipe  20  that extends to a lower portion of the flow pipe  16  to supply carbon dioxide, as shown in  FIG. 2 . 
     Unlike this, the bubbling means may include a supplying pipe  22  that extends along an outer wall of the flow pipe  16  from top to bottom, as shown in  FIGS. 3 and 4 . 
     In case the bubbling means includes the supplying pipe  20  extending to the lower portion of the flow pipe  16  as shown in  FIG. 2 , an end of the supplying pipe  20  may be positioned to supply carbon dioxide to as lower portion of a flow path formed by the flow pipe  16 . 
     By the configuration shown in  FIG. 2 , carbon dioxide may be directly supplied to the flow path of the flow pipe  16 , or the carbon dioxide may be supplied to be guided to an inner wall of the collecting part  18 , and the carbon dioxide may be moved upwards in the flow path. 
     In case the bubbling means includes the supplying pipe  22  extending from an upper portion to a lower portion thereof along the flow pipe  16  as shown in  FIGS. 3 and 4 , an end of the supplying pipe  22  is preferably formed at an inside of a lower portion of the flow pipe  16 . More preferably, the end of the supplying pipe  22  may be configured to pass through the collecting part  18  to supply carbon dioxide to the inside of the flow pipe  16 . 
     By the configurations shown in  FIGS. 3 and 4 , carbon dioxide may be supplied to be guided to an inner wall of the collecting part  18 , and the carbon dioxide may be moved upwards. 
     The bubbling means including the supplying pipes  20  and  22  as shown in  FIGS. 2 and 3  may include a pumping device  24  that may independently generate and provide carbon dioxide. 
     Alternatively, the bubbling means may re-circulate and supply carbon dioxide generated by an electrochemical reaction inside the bath  10 , as shown in  FIG. 4 . To this end, the bubbling means may include a circulating device  26  that externally collects carbon dioxide generated by an electrochemical reaction in the bath  10  while re-circulating and supplying a portion of the generated carbon dioxide through the supplying pipe  22 . 
     Referring to  FIG. 4 , the circulating device  26  may be configured to discharge the carbon dioxide collected to an upper portion of the bath  10  to the outside through an exhaust pipe  28  while circulating and supplying a portion of the carbon dioxide to the supplying pipe  22 . 
     Further, according to embodiments of the present invention, the supplying pipes  20  and  22  shown in  FIGS. 2 to 4  may have various configurations depending on the manufacturer&#39;s intention. As an example, the supplying pipe  20  or  22  may be configured to spirally wind up along an outer side of the flow pipe  16 . 
     By the configurations shown in  FIGS. 2 to 4 , according to an embodiment of the present invention, carbon dioxide may be supplied to a lower portion of a flow path created inside the flow pipe  16 . 
     The carbon dioxide supplied to the lower portion of the flow pipe  16  is moved up through the flow path created in the flow pipe  16 . 
     As the carbon dioxide moves up along the flow path in the flow pipe  16 , the anode medium  14  over the flow path may be pushed to flow by the carbon dioxide. 
     If carbon dioxide is steadily supplied through the supplying pipe  20  or  22 , the anode medium  14  in the flow pipe  16  is forced to flow as the carbon dioxide travels upwards. 
     More specifically, the anode medium  14  outside the flow pipe  16  flows into a lower portion of the flow pipe  16  in order to fill the space that is formed as the carbon dioxide moves upwards, and the anode medium  14  at an upper portion of the flow pipe  16  is forced to overflow the flow pipe  16  by the moving-up carbon dioxide. 
     Accordingly, the anode medium  14  may be circulated to pass through the flow path of the flow pipe  16  in the bath  10 . 
     As the anode medium  14  flows and circulates as above, the mixture of the carbon fuel and the anode medium  14  may be accelerated. 
     Further, as the mixed carbon fuel and anode medium  14  is circulated through the flow path formed by the flow pipe  16  as above, the carbon fuel and the anode medium  14  abutting the tubular cell  12  are circulated. Therefore, the circulating carbon cell and anode medium  14  may accelerate reactions of the anode of the tubular cell  12 . 
     Meanwhile, according to an embodiment of the present invention, a plurality of tubular cells  12  may be configured inside the flow pipe  16 , as shown in  FIGS. 5 to 7 . According to an embodiment of the present invention, two tubular cells  12  are, for the purpose of description, configured as shown in  FIGS. 5 to 7 . 
       FIG. 5  illustrates an example in which two tubular cells  12  are configured inside the flow pipe  16 , corresponding to  FIG. 2 ,  FIG. 6  illustrates an example in which two tubular cells  12  are configured inside the flow pipe  16 , corresponding to  FIG. 3 , and  FIG. 7  illustrates an example in which two tubular cells  12  are configured inside the flow pipe  16 , corresponding to  FIG. 4 . 
     The configurations shown in  FIGS. 5 to 7  are substantially the same as those shown in  FIGS. 2 to 4  except for a plurality of tubular cells  12  (two tubular cells  12 ) configured inside the flow pipe  16 , and description of the same components or their operations is not repeated. 
     The number of tubular cells  12  arranged in the flow pipe  16  may be varied depending on the manufacturer&#39;s intention considering the flow efficiency of the anode medium. 
     Also in the embodiments described M connection with  FIGS. 5 to 7 , as carbon dioxide supplied from an end of the supplying pipe  20  or  22  included in the bubbling means to the inside of the flow pipe  16  moves upwards, the anode medium  14  is caused to flow as described above in connection with  FIGS. 2 to 4 . 
     As described above, as the anode medium  14  flows and circulates along the flow path in the flow pipe  16 , the mixture of the carbon fuel and the anode medium  14  may be accelerated. 
     Further, the mixture-accelerated carbon fuel and anode medium  14  circulate, while abutting the plurality of tubular cells  12 . Therefore, the circulating carbon cell and anode medium  14  may accelerate reactions of the plurality of anode of the tubular cell  12 . 
     Meanwhile, according to an embodiment of the present invention, a distributing means  50  may be further provided on the flow path m the flow pipe  16  to distribute gas bubbles supplied from the supplying pipe  20  of the bubbling means and to supply upward the distributed gas bubbles. 
     The distributing member  50  may be formed of a disc with multiple through-holes  52  as shown in  FIG. 8  According to the manufacturer&#39;s intention, the distributing member  50  may have various shapes. In an exemplary variation thereof, the distributing member  50  may be formed of a ring-shaped plate with multiple through-holes  52 , the ring-shaped plate structured to allow a tubular cell  12  to pass through the center thereof. Further, the distributing member  50  may be structured to have a porous layer. 
     As shown in  FIG. 9 , the distributing member  50  provided under a plurality of tubular cells  12  in the flow pipe  16  may distribute gas bubbles supplied from the supplying pipe  20  of the bubbling means and supply upward the distributed gas bubbles. 
     In the embodiment described in connection with  FIG. 9 , gas bubbles supplied by the bubbling means may be evenly distributed to the plurality of tubular cells  12 , so that the anode medium  14  may uniformly flow in the flow pipe  16  in which the plurality of tubular cells  12  are arranged. 
     According to an embodiment of the present invention, a fuel supplying apparatus for a direct carbon fuel cell, as configured above, together with one or more tubular cells each having an cathode and a anode respectively formed at an inside and outside thereof, with a solid oxide electrolyte formed between the cathode and the anode, may configure a direct carbon fuel cell system. Accordingly, the fuel supplying apparatus according to the present invention may be configured to supply a forcedly-flowing anode medium to the tubular cells. 
     As such, according to the present invention, a flow of the anode medium in the flow pipe may be secured, forcing the anode medium to be supplied to the direct carbon fuel cell, with the anode medium mixed with a carbon, fuel. 
     Therefore, the concentration polarization at the anodes of the tubular cells may be reduced, leading to an increased output density.