Abstract:
A closed loop type fuel cell system is provided including a recirculating unit that recirculates hydrogen and oxygen discharged from a main fuel cell into the main fuel cell and a reproducing unit that removes water produced in operation of the main fuel cell and impurities contained in the circulated hydrogen and oxygen. Further, a closed loop type fuel cell is provided that makes it possible to generate electricity by using a main fuel cell and purify water and impurities by allowing a side of a recirculating unit to selectively communicate with a side of a reproducing unit. Further, a closed loop type fuel cell is provided that is precluded by being damaged by precluding reduction of efficiency of electric generation of a mina fuel cell by selectively replacing a sacrifice fuel cell in a reproducing unit.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a closed loop type fuel cell system. 
         [0003]    2. Description of the Related Art 
         [0004]    Fuel cells are systems that generate electricity, using reaction between fuel (LNG, LGP, hydrogen, and methanol) and oxygen, and produces water and heat as byproducts, and which are electric generation devices having high electric generation efficiency without factors polluting the environment. 
         [0005]    The fuel cells are classified into a polymer electrolyte membrane fuel cell (PEMFC), a direct methanol fuel cell (DMFC), a phosphoric acid fuel cell (PAFC), a molten carbonate fuel cell (MCFC), a solid oxide fuel cell (SOFC), and the like, in accordance with the types of electrolytes. 
         [0006]    The PEMFC, PAFC, and DMFC in the fuel cells has low operation temperatures of 80 to 120° C., 190 to 200° C., and 25 to 90° C., respectively, and useful for the power sources of transport, such as vehicles, home, and portable devices. 
         [0007]    Therefore, researches of reducing the size, weight, and cost of the entire fuel cell systems have been conducted to advance and increase common use of the fuel cells. 
         [0008]    However, a large amount of byproducts are produced in an operation environment at a high-current region in the fuel cells and supply of gas to the catalytic layer and dispersion of protons to the polymer film are prevented by droplets of excessive water, such that the performance of the fuel cells is deteriorated. 
         [0009]    It is more serious that it is difficult to implement normal operation by reduction of performance of some cells due to non-uniform distribution of water in unit cells disposed in the fuel cells. 
         [0010]    As described above, the excessive water produced in the fuel cells, that is, flooding is an important factor that makes normal operation of the fuel cells difficult, in addition to reducing reaction efficiency, it is necessary to discharge the excessive water outside the fuel cells. 
         [0011]    Accordingly, “a method and device for performing internal purge infuel cell system” is disclosed in Korean Patent No. 0509818. 
         [0012]    The related art is briefly described. Voltages of a plurality of cells are sensed, water and gas mixture in a stack is purged outside the stack by using a pressure difference, by controlling a purge valve and a recirculation pump when flooding occurs, and the gas separated from the water can be re-supplied to the stack. 
         [0013]    However, the related art described above has the following problems. 
         [0014]    That is, since the degree of purity of the fuel supplied to the fuel cell cannot be 100%, impurities collect in the fuel cell even if the gas separated from the water is re-supplied to the fuel cell, such that electric generation efficiency is reduced. 
         [0015]    Further, when carbon of the separator and electrodes in the fuel cell and impurities, such as metal ions and particles of the peripheral components of the fuel cell collect, durability of the fuel cell is gradually influenced and current leaks in the cell, which reduces the life span or damages the fuel cell causes a large amount of repairing charges, and this is not preferable. 
         [0016]    Further, even if the water produced in the fuel cell is removed by recirculating the gas in the fuel cell by using the related art, the impurities flow back into the fuel cell by the gas supplied to the fuel cell, because it is a closed circuit, such that performance and durability of the fuel cell are reduced. 
       SUMMARY OF THE INVENTION 
       [0017]    The present invention has been made in an effort to provide a closed loop type fuel cell system including a recirculating unit that recirculates hydrogen and oxygen discharged from a main fuel cell into the main fuel cell and a reproducing unit that removes water produced in operation of the main fuel cell and impurities contained in the circulated hydrogen and oxygen. 
         [0018]    Further, the present invention provides a closed loop type fuel cell that makes it possible to generate electricity by using a main fuel cell and purify water and impurities by allowing a side of a recirculating unit to selectively communicate with a side of a reproducing unit. 
         [0019]    Further, the present invention provides a closed loop type fuel cell that is precluded by being damaged by precluding reduction of efficiency of electric generation of a mina fuel cell by selectively replacing a sacrifice fuel cell in a reproducing unit. 
         [0020]    A closed loop type fuel cell system according to an exemplary embodiment of the present invention includes: a main fuel cell that generates electricity by receiving fuel and oxygen; a supply unit that supplies gas containing fuel and oxygen to the main fuel cell; a recirculating unit that recirculates the gas containing hydrogen and oxygen discharged from the main fuel cell; a sensing unit that senses the voltages of a plurality of cells in the main fuel cell; a reproducing unit that selectively communicates with a side of the main fuel cell and removes water and impurities in the main fuel cell; and a control unit that controls the operations of the supply unit, the recirculating unit, the sensing unit, and the reproducing unit, in which the reproducing unit includes: a reproducing pipe that guides the flow direction of the gas containing hydrogen and oxygen passing through the recirculating unit; a reproducing valve that selectively blocks the reproducing pipe; a sacrifice fuel cell that produces water by reacting the gas containing hydrogen and oxygen supplied from the reproducing pipe with air; and a collecting unit that collects water produced in the sacrifice fuel cell. 
         [0021]    The recirculating unit includes: a gas-liquid separator that separates water and reacting gas produced in the main fuel cell into water and gas; a recirculating pipe that guides the gas separated from the water by the gas-liquid separator to the main fuel cell; and a recirculating pump that forces the flow of the gas in the recirculating pipe. 
         [0022]    The reproducing pipe and the recirculating pipe communicate with each other. 
         [0023]    The water collecting unit and the gas-liquid separator selectively communicate with a water tank storing water. 
         [0024]    The sacrifice fuel cell generates electricity by receiving hydrogen and hydrogen and a pair of electrodes that guide current flow are selectively grounded. 
         [0025]    The sacrifice fuel cell has capacity of electric generation smaller than the main fuel cell and is selective replaced. 
         [0026]    A switch that selectively connects/disconnects a pair of electrodes is disposed at a side of the sacrifice fuel cell and the switch is grounded when the reproducing valve is closed and then opened after a predetermined time passes. 
         [0027]    The supply unit includes a fuel tank that stores and selectively supplies hydrogen and an oxygen tank that stores and selectively supplies oxygen. 
         [0028]    A check valve that blocks the hydrogen discharged from the fuel tank in order not to flow into the recirculating pipe is disposed at a side of the recirculating pipe. 
         [0029]    The control unit opens the reproducing pipe, when one or more of the voltages of the plurality of cells are lower than a predetermined voltage. 
         [0030]    A drain that controls a water level by selectively discharge the water stored in the gas-liquid separator is disposed at a side of the gas-liquid separator. 
         [0031]    The main fuel cell, the supply unit, the recirculating unit, the sensing unit, the reproducing unit, and the control unit are positioned in a closed space. 
         [0032]    According to the present invention, the recirculating unit that recirculates the hydrogen and oxygen discharged from the main fuel cell to the main fuel cell and the reproducing unit that removes the water and impurities in the main fuel cell when the efficiency of electric generation of the main fuel cell are provided. 
         [0033]    Therefore, it is possible to maximize the fuel efficiency and maximize the efficiency of electric generation of the main fuel cell, using the operation of the reproducing unit, when the fuel cell system is disposed in a closed space, such as a submarine. 
         [0034]    Further, the sacrifice fuel cell in the reproducing unit can be selectively displaced in the present invention. 
         [0035]    Therefore, it is possible to selectively increase the efficiency of electric generation by selectively reproducing the main fuel cell when the efficiency of electric generation of the main fuel cell is reduced, such that it is possible to improve the durability of the main fuel cell. 
         [0036]    In addition, it is easy to maintain the main fuel cell by making the sacrifice fuel cell selectively replaceable. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0037]      FIG. 1  is a view showing the configuration of a closed loop type fuel cell system according to an exemplary embodiment of the present invention. 
           [0038]      FIG. 2  is a view showing the flow of fuel and hydrogen when a recirculating unit that is a component of the closed loop type fuel cell system according to an exemplary embodiment of the present invention operates. 
           [0039]      FIG. 3  is a view showing the flow of fuel and hydrogen when a reproducing unit that is a component of the closed loop type fuel cell system according to an exemplary embodiment of the present invention operates. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0040]    The configuration of a closed loop type fuel cell system according to an exemplary embodiment of the present invention is described with reference to the accompanying drawings. 
         [0041]      FIG. 1  is a view showing the configuration of a closed loop type fuel cell system according to an exemplary embodiment of the present invention. 
         [0042]    As shown in the figure, a closed loop type fuel cell system  100  generates electricity by receiving and reacting hydrogen H 2  that is fuel and oxygen O 2  and includes a main fuel cell  110 , a supply unit  120  that supplies gas containing fuel and oxygen to the main fuel cell  110 , a recirculating unit  130  that recirculates the gas containing hydrogen and oxygen discharged from the main fuel cell  110 , a sensing unit that senses the voltages of a plurality of cells in the main fuel cell  110 , a reproducing unit  150  that selectively communicates with a side of the main fuel cell  110  and removes water and impurities in the main fuel cell  110 , and a control unit  160  that controls the operations of the supply unit  120 , the recirculating unit  130 , the sensing unit  140 , and the reproducing unit  150 . 
         [0043]    The closed loop type fuel cell system  100  is a system  110  that can be used for an apparatus having a closed space, such as a minisub, a submarine, and a space ship, in which the main fuel cell  110 , the supply unit  120 , the recirculating unit  130 , the sensing unit  140 , the reproducing unit  150 , and the control unit  160  are disposed and operable in a closed space. 
         [0044]    In more detail, various fuel cells may be selectively used as the main fuel cell  110  as long as it is possible to receive fuel and air containing oxygen and generate electricity, and receives gas containing hydrogen and oxygen from the supply unit  120 . 
         [0045]    The supply unit  120  is provided to supply a gas containing hydrogen and oxygen to the main fuel cell  110  and includes a fuel tank  122  that stores and selectively supplies hydrogen and an oxygen tank  124  that stores oxygen and selectively supplies the oxygen in an exemplary embodiment of the present invention. 
         [0046]    The fuel tank  122  and the oxygen tank  124  communicate with a humidifier  170  and the humidifier  170  communicates with the main fuel cell  110 . Therefore, the hydrogen and oxygen in the fuel tank  122  and the oxygen tank  124  are supplied into the main fuel cell  110  after being humidified through the humidifier  170 . 
         [0047]    The humidifier  170  is provided such that the fuel and air supplied in the main fuel cell  110  can react well and the detail description is not provided. 
         [0048]    The sensing unit  140  is disposed above the main fuel cell  110 . The sensing unit  140  is disposed to sense voltages of a plurality of cells in the main fuel cell  110 . 
         [0049]    That is, the main fuel cell  110  generates high voltage by stacking a plurality of cells, and as the cells are used for a long period of time, different voltages are generated by differences in current flux and the amount of water generated in the cells, such that differences are generated among the cells. 
         [0050]    Therefore, the sensing unit  140  is provided too measure and diagnoses in advance differences in current flux and the amount of water even while the main fuel cell operates. 
         [0051]    The recirculating unit  130  is disposed at the right side of the sensing unit  140 . The recirculating unit  130  is provided to maximize coefficient of utilization of the fuel by recirculating the hydrogen and oxygen discharged without reacting in the main fuel cell  110  to the main fuel cell  110 . 
         [0052]    For this configuration, the recirculating unit  130  includes a gas-liquid separator  131  that separates water, which is produced in reaction of oxygen and hydrogen, and non-reacting gas in the main fuel cell  110 , a recirculating pipe  133  that guides the gas separated from the water in the gas-liquid separator  131  to the main fuel cell  110 , and a recirculating pump  137  that forces the flow of gas in the recirculating pipe  133 . 
         [0053]    Further, the recirculating unit  130  is provided for the humidifiers  170  that communicate with the fuel tank  122  and the oxygen tank  124 , respectively. 
         [0054]    That is, the recirculating units  130  are connected to the right upper portion and the right lower portion of the main fuel cell  110 , respectively, the recirculating unit  130  connected to the right upper portion of the main fuel cell  110  recirculates hydrogen to the front of the humidifier  170  and the recirculating unit  130  connected to the right lower portion of the main fuel cell  110  recirculates oxygen to the front of the humidifier  170 . 
         [0055]    Therefore, the gas (hydrogen or oxygen) separated from the water by the gas-liquid separator  131  can be recirculated through the recirculating pipe  133 . 
         [0056]    A check valve  153  is disposed at a side of the recirculating pipe  133 . The check valve  153  blocks the hydrogen supplied from the fuel tank  122  such that the hydrogen cannot flow into the recirculating pipe  133 , and forces the recirculating gas (hydrogen and oxygen) supplied to the front end of the main fuel cell  110  by the recirculating pump  137  to flow into the humidifier  170 . 
         [0057]    Further, a drain  190  is disposed at the lower portion of the gas-liquid separator  131 . The drain  190  guides water into a water tank  180 , when water discharged from the main fuel cell  110  increases above an appropriate level in the gas-liquid separator  131 . 
         [0058]    For this configuration, the drain  190  includes a drain pipe  192  making the gas-liquid separator  131  communicate with the water tank  180  and a drain valve  194  selectively closes the drain pipe  192 . 
         [0059]    Therefore, as the drain valve  194  is closed and opened, the water in the gas-liquid separator  131  flows into the water tank  180  through the drain pipe  192 , such that the water level in the gas-liquid separator  131  can be kept constant. 
         [0060]    The reproducing unit  150  that is a main component of the present invention is disposed at the right side of the recirculating unit  130 . The reproducing unit  150  allows the impurities in the main fuel cell  110  to be discharged to the outside by temporarily changing the flow of gas flowing in the recirculating pipe  133 , when the voltages of the cells in the main fuel cell  110  which are sensed by the sensing unit  140  are lower than a predetermined voltage. 
         [0061]    For this configuration, the reproducing unit  150  includes a reproducing pipe  152  that guides the flow direction of the gas containing hydrogen and oxygen passing through the recirculating unit  130 , a reproducing valve  154  that selectively blocks the reproducing pipe  152 , a sacrifice fuel cell  156  that produces water by reacting the gas containing hydrogen and oxygen supplied from the reproducing pipe  152  with air, and a collecting unit  158  that collects water produced in the sacrifice fuel cell  156 . 
         [0062]    The reproducing pipe  152  diverging from a side of the recirculating pipe  133  and communicates with the sacrifice fuel cell  156 , and guides the flow of gas by the operation of the reproducing valve  154 . 
         [0063]    Therefore, the sacrifice fuel cell  156  can receive hydrogen and oxygen when the reproducing valve  154  is open. 
         [0064]    The sacrifice fuel cell  156  selectively operate when the performance is deteriorated by the water in the main fuel cell  110  or in order to discharge impurities, as can be seen from the name, and has capacity of electric generation smaller than the main fuel cell  110  and can be selectively replaced. 
         [0065]    That is, the sacrifice fuel cell  156  generates electricity by receiving hydrogen and oxygen and has a switch  157  at a side of a pair of electrodes guiding the flow of current to be selective connected. Further, the gas discharged from the main fuel cell  110  is consumed in the sacrifice fuel cell  156  by the connection of the switch  157  into water while the other impurities collect in the sacrifice fuel cell  156 . 
         [0066]    Further, the supplied non-reacting gas is changed into water while the impurities are absorbed and accumulated, by electric connection in the sacrifice fuel cell  156 . Therefore, the sacrifice fuel cell  156  collects a small amount of impurities in the reacting gas supplied to increase durability of the main fuel cell  110  and the impurities in a close type fuel cell system. 
         [0067]    Accordingly, the sacrifice fuel cell  156  is exposed to a severe environment even though protecting the main fuel cell  110  and increasing the durability, such that it may be periodically replaced. 
         [0068]    Meanwhile, the operations of the sensing unit  140 , recirculating pump  137 , reproducing valve  154 , and switch  157  are controlled by the control unit  160 . 
         [0069]    That is, the control unit  160  operates the reproducing unit  150 , when one or more of the voltages of the cells are lower than a predetermined voltage, and operates the recirculating unit  130  when it is a normal voltage. 
         [0070]    In more detail, the control unit operates the recirculating unit  130 , with the recirculating pump  137  operating and the switch  157  turned off. 
         [0071]    On the contrary, the reproducing unit  150  is operated, with the recirculating pump  137  keeping stable, the reproducing valve  154  open after the reproducing pipe  152  is closed for a predetermined time, and the switch  157  turned on. 
         [0072]    Alternatively, the control unit  160  adjusts the water level by selectively opening the drain valve  194  in accordance with the water level in the gas-liquid separator  131 . 
         [0073]    As described above, the gas-liquid separator  131  selectively communicates with the water tank  180  by the drain pipe  192  while the main fuel cell  110  communicates with the water tank  180  by a drain channel  112  disposed at a side of the main fuel cell  110 . 
         [0074]    Further, the water collecting unit  158  also communicates with the water tank  180 . That is, a water level control pipe  182  and a control valve  184  that control the water level in the water collecting unit  158  are disposed at the left side of the water collecting unit  158 . 
         [0075]    The water level control pipe  182  communicates with the water collecting unit  158  and the water tank  180  at both ends and the control valve  184  selectively close the water level control pipe  182 . 
         [0076]    Therefore, the water in the water collecting unit  158  flows into the water tank  180  and is stored therein, in accordance with whether the control valve  184  is open. 
         [0077]    Accordingly, all the water in the main fuel cell  110 , the water in the gas-liquid separator  131 , and the water in the water collecting unit  158  flow into the water tank  180  and are stored therein. 
         [0078]    The process of generating electricity by operating the closed loop type fuel cell system  100  is described hereafter with reference to the arrows in  FIG. 2 . 
         [0079]      FIG. 2  is a view showing the flow of fuel and hydrogen when the recirculating unit  130  that is a component of the closed loop type fuel cell system according to an exemplary embodiment of the present invention operates. 
         [0080]    As shown in the figure, the supply unit  120  supplies hydrogen and oxygen into the humidifier  170  to allow the closed loop type fuel cell system  100  to generate electricity. The main fuel cell  110  receives the hydrogen and oxygen humidified through the humidifier  170  and generates electricity. 
         [0081]    Further, since the recirculating pipe  133  can guide the flow of gas when being open, the oxygen and hydrogen discharged without reacting in the main fuel cell  110  are separated from the water by the gas-liquid separator  131  and recirculated to the front of the humidifier  170 . 
         [0082]    In this operation, the reproducing valve  154  closes the reproducing pipe  152  to block gas and the sensing unit  140  continuously measures the voltages of the cells in the main fuel cell  110 . Further, the switch  157  is turned off. 
         [0083]    Therefore, the reuse ratio of the hydrogen and oxygen can be maximized by the operation of the recirculating unit  130 . 
         [0084]    The flow of gas when one or more of the voltages of the cells which are sensed by the sensing unit  140  are lower than a predetermined voltage and the reproducing unit  150  is operated is described hereafter with reference to  FIG. 3 . 
         [0085]      FIG. 3  is a view showing the flow of fuel and hydrogen when the reproducing unit  150  that is a component of the closed loop type fuel cell system according to an exemplary embodiment of the present invention operates. 
         [0086]    As shown in the figure, as the efficiency of electric generation of the main fuel cell  110  decreases, the reproducing unit  150  operates and the efficiency of electric generation and durability of the main fuel cell  110  can be increased. 
         [0087]    For this configuration, the control unit  160  closes the reproducing valve  154  and the switch  157  is turned on. Further, the recirculating pump  137  is controlled to stop the operation. 
         [0088]    Further, when hydrogen and oxygen are supplied from the fuel tank  122  and the oxygen tank  124 , high pressure is generated because the reproducing valve  154  keeps closed. 
         [0089]    Thereafter, as a predetermined time passes, the closed reproducing valve  154  is opened and the impurities in the main fuel cell  110  are instantaneously discharged with the hydrogen and oxygen. 
         [0090]    The impurities and gas discharged from the main fuel cell  110  are separated through the gas-liquid separator  131  and the gas rapidly moves to the reproducing pipe  152  and flows into the sacrifice fuel cell  156 . 
         [0091]    That is, since the recirculating pump  137  has stopped the operation and the internal pressure of the recirculating pipe  133  at the left side of the recirculating pipe  133  (recirculating pump  137 ) is higher than the internal pressure of the reproducing pipe  152 , gas cannot flow inside. 
         [0092]    Therefore, the sacrifice fuel cell  156  generates electricity the generated electricity flows to the ground because the switch  157  is turned on, such that the sacrifice fuel cell  156  produces water therein. 
         [0093]    The water produced in the sacrifice fuel cell  156  flows into the water collecting unit  158  and is stored therein, and can flow into the water tank  180  by the control valve  184  that is selectively opened. 
         [0094]    The water and impurities in the main fuel cell  110  are accumulated in the sacrifice fuel cell  156  by the operation described above, such that the impurities in the main fuel cell  110  are reduced, the durability can be correspondingly increased, and the main fuel cell  110  can be reproduced. 
         [0095]    The present invention is not limited to the embodiment described above and may be modified in various ways by those skilled in the art on the basis of the present invention without departing from the spirit of the present invention. 
         [0096]    For example, although the internal configuration of the main fuel cell is not disclosed in detail in the exemplary embodiment of the present invention, it is apparent to further provide a cooling water channel for increasing the efficiency of electric generation by reducing the amount of heat generated from the main fuel cell.