Abstract:
The present invention is a hydrogen refueling station incorporating a fuel cell system serving simultaneously as the power generator and an electrochemical extractor of the pure hydrogen from the hydrogen-rich gas (reformate) produced in steam hydrocarbon reforming process. The hydrogen is stored in a high pressure receiver to be dispensed to vehicles as a fuel. The hydrogen refueling station of the present invention does not require the refilling with DI water.

Description:
RELATED APPLICATIONS 
       [0001]    This non-provisional patent application claims priority to a provisional application Ser. No. 60/893,723 filed on Mar. 8, 2007 and incorporated herewith by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The subject invention relates to a hydrogen refueling station for hydrogen extraction from the hydrogen-rich gas. 
       BACKGROUND OF THE INVENTION 
       [0003]    Hydrogen is known as fuel of choice for both the electric power and transportation industries. While it is likely that renewable energy sources will ultimately be used to generate hydrogen, fossil-based technologies will be utilized to generate hydrogen in the near future. Modern hydrogen production is significant and important to number of industries requiring hydrogen produce effluents containing significant amounts of unused hydrogen. The hydrogen requires clean-up before the hydrogen is re-used in other applications. The hydrogen must be separated from other combustion gases, such as carbon dioxide, before it is re-used. 
         [0004]    Fuel cells are one of the sources of renewable energy that generate electrical power that can be used in a variety of automotive and non-automotive applications. These fuel cells generate electrical power that can be used in a variety of applications. The fuel cells constructed with proton exchange membranes (PEM fuel cells) may eventually replace the internal combustion engine in motor vehicles. The PEM fuel cells have an ion exchange membrane, which acts as a solid electrolyte, affixed between an anode and a cathode. To produce electricity through electrochemical reactions, hydrogen rich fuel is supplied to the anode and air is supplied to the cathode. An electrochemical reaction between hydrogen and the oxygen contained in the air produces an electrical current, water and heat as reaction products. This water is removed from the cathode. 
         [0005]    The ideal fuel for current power generating system based on PEM fuel cells is pure hydrogen. The fuel cell consuming the hydrogen possesses the highest efficiency regarding to other fuel types supplied. By the way the balance of the plant is simplest and smallest in the case if the hydrogen is fed as a fuel which is critical for automotive application of the fuel cell. The major challenge to hydrogen application for the transportation is the refueling infrastructure development. The hydrogen does not exist naturally in the elemental form and, in many applications of PEM fuel cells, is generated by the electrolysis or in hydrocarbon reforming from natural gas, methane, methanol, gasoline and other as the primary fuels through. The electrolysis application consumes significant amount of power, ultimately, requesting the connection to the power grid and the DI water supply. 
         [0006]    The hydrocarbon reforming systems typically generate carbon monoxide (CO) as part of the product hydrogen rich gas (typically called the reformate), which poisons the platinum catalyst used on the anode side of the PEM fuel cell and causes considerable drop in the performance. There could be other gaseous by-products such as H 2 O, CO 2 , N 2 , NH 4 , H 2 S which dilute the hydrogen in the fuel supplied to PEM fuel cells. Considerable effort has been directed toward the method development to selectively filter hydrogen out of reformate. 
         [0007]    Prior art is replete with various methods and devices for purifying hydrogen. The U.S. Pat. No. 6,824,593 to Edlund et al. U.S. Pat. No. 6,723,156 to Edlund et al. teach a hydrogen purification membranes, hydrogen purification devices, and fuel processing and fuel cell systems that include hydrogen purification devices. The hydrogen purification membranes include a metal membrane, which is at least substantially comprised of palladium or a palladium alloy. In some embodiments, the membrane contains trace amounts of carbon, silicon, and/or oxygen. In some embodiments, the membranes form part of a hydrogen purification device that includes an enclosure containing a separation assembly, which is adapted to receive a mixed gas stream containing hydrogen gas and to produce a stream that contains pure or at least substantially pure hydrogen gas therefrom. The hydrogen purification devices taught by the aforementioned patents are use a palladium or a palladium alloy membrane, which is highly permeable for hydrogen. In particular, as described in another U.S. Pat. No. 6,569,226 to Dorris et al., a membrane for separating hydrogen from fluids is provided comprising a sintered homogenous mixture of a ceramic composition and a metal. The metal may be palladium, niobium, tantalum, vanadium, or zirconium or a binary mixture of palladium with another metal such as niobium, silver, tantalum, vanadium, or zirconium, which is highly permeable for hydrogen. 
         [0008]    The U.S. Pat. No. 6,066,592 to Kawae, et al. discloses a ceramic support coated with palladium or a palladium alloy such as Pd—Ag to serve as a hydrogen separator. The U.S. Pat. No. 5,980,989 to Takahashi, et al. discloses a gas separator membrane in which a metal for separating a gas such as palladium or a palladium alloy is filled into pores opened on the surface of a porous substrate to close them. 
         [0009]    Alluding to the above, the United States Patent Application Publication No. 20040142215 to Barbir et al. teaches that hydrogen can be pumped electrochemically across a proton exchange membrane from the reformate stream. The United States Patent Application Publication No. 20040142215 to Barbir et al. fails to suggest expressly or impliedly a method to prevent hydrogen filter anode catalyst from being infiltrated or polluted with carbon monoxide. 
         [0010]    There is a constant need for an improved design of a hydrogen purification and reformation systems thereby eliminating problems associated with current prior art methods and systems. Thus, the inventive concept as set forth further below is directed to eliminate one or more problems associated with the prior art methods and systems eliminating problems associated with current designs of prior art designs and methods. 
       SUMMARY OF THE INVENTION 
       [0011]    The inventive concept relates to a fuel cell system providing internal hydrogen extraction from the hydrogen-rich gas derived from a fuel processing device and the balance of plant which is independent on a power grid. A hydrogen refueling station is based on a fuel cell system fed with the hydrogen-rich fuel received from a steam reformer. The invention also relates to alkaline electrolyte and phosphoric acid fuel cell systems having a proton exchange membrane (PEM) fuel system without limiting the scope of the present invention. The PEM fuel cell system (the fuel cell) includes at least two identical fuel cell sections. Each fuel cell section includes at least one cell comprising a membrane-electrode-assembly including a proton-exchange membrane, primary and hydrogen electrodes disposed on opposite sides of the proton-exchange membrane. 
         [0012]    At least one primary electrode faces to a primary flow field with an inlet adjacent to a primary manifold of the fuel cell section. An outlet is adjacent to an exhaust manifold of the fuel cell section. At least one hydrogen electrode faces a hydrogen flow field with an inlet adjacent to a hydrogen manifold of the fuel cell and with an outlet adjacent to a hydrogen exhaust manifold of the fuel cell. The fuel cell operated between several modes. One of the modes as will be described in details below. The hydrogen-rich fuel is produced in the reformer as a product of a water-gas shift reaction between a hydrocarbon and water. It is supplied to the primary manifold of the fuel cell section which operates in the hydrogen filtering mode. Due to the current applied the fuel cell section operating under the hydrogen pump effect wherein the hydrogen contained in the reformate dissociates into electrons and hydrogen ions at the primary electrode or as the anode, the hydrogen ions pass through the electrolyte to the hydrogen electrode, and the electrons flow to the hydrogen electrode to produce H 2  which is collected in a hydrogen manifold which is common for the fuel cell system. 
         [0013]    Alluding to the above, the hydrogen from the hydrogen manifold is pumped by a hydrogen compressor at a high pressure into a receiver to be further distributed into fuel tanks of vehicles. A gas flow rejected from the exhaust manifold the fuel cell section may contain high concentration of CO. There are some reasons to supply the primary exhaust back to a reformer: hydrogen remains and CO can be oxidized to produce heat for fuel processing; CO is converted to CO 2  and is eliminated as the hazardous gas to humans. 
         [0014]    In a power generation mode of the hydrogen refueling station, the oxygen-rich gas, mainly air, as oxidant, is supplied by the compressor to the fuel cell power generating section through its primary manifold and pure hydrogen, as a fuel, is consumed on the hydrogen electrodes from the common hydrogen manifold. Polluting a catalyst with carbon monoxide contained in the hydrogen-rich fuel causes the performance deterioration of the fuel cell section operating in the hydrogen filtering mode. At a pre-defined level of the performance deterioration, such as the critical increase in the voltage, the critical ratio between the power provided to the fuel cell section and the power generated by the fuel cell system, the fuel cell section is switched to the power generating mode. 
         [0015]    Simultaneously another fuel cell section is switched from the power generating mode to the hydrogen filtering mode. Carbon monoxide absorbed on the primary electrode catalyst of the fuel cell section switched to the power generating mode is oxidized to carbon dioxide due to the introduction of air to the primary electrodes, now acting as cathodes. 
         [0016]    An cathode exhaust rejected from the exhaust manifold of the fuel cell section being in the power generating mode. Initially, the cathode exhaust is supplied to a humidifier wherein some moisture from the cathode exhaust is transferred to the oxygen-rich gas intended for feeding the section. Then, the cathode exhaust pre-cooled in a heat exchanger is directed to a water trap wherein water condensate is discharged to a water tank to be used as a reactant for the water-gas shift reaction in the reformer. The combustion exhaust is also processed consequently in a heat exchanger and a water trap to donate the water into the water tank. Total water amount collected is supposed to be equal to water used for the reformate production and makes the hydrogen refueling station independent on any external DI water supply. 
         [0017]    A system exhaust combining the cathode exhaust exiting the water tank and a hot combustion exhaust from the reformer burner is introduced to a turbo generator at elevated temperature wherein there is the conversion of the flow energy into the electrical power. The system exhaust contains the nitrogen, moisture and carbon dioxide and is environmental friendly. The power derived from the fuel cell section being in the power generating mode and the turbo generator covers the total power consumption of the hydrogen refueling station. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    Other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: 
           [0019]      FIG. 1  illustrates a schematic view of a hydrogen refueling station of the present invention; and 
           [0020]      FIG. 2  is a schematic view illustrating the effect of the hydrogen pump upon the application of the hydrogen refueling station of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0021]    Referring to the Figures, wherein like numerals indicate like or corresponding parts, a first embodiment of a hydrogen refueling station is shown in  FIG. 1  and is generally designated by the reference numeral  100 . The hydrogen refueling station  100  includes a fuel cell stack  110 , a primary fuel reformer  130  comprising an internal burner  132  and a converter  134 , a fuel cell air compressor  140 , a reformer air compressor  142 , a high pressure hydrogen compressor  144 . The hydrogen refueling station  100  includes a turbo generator  146 , a primary fuel pump  150 , a water pump  152 , a primary fuel tank  160 , a water tank  162 , a high pressure receiver  164 , a humidifier  170  separated with a moisture permeable membrane  172  into an air feed compartment  174  and an air exhaust compartment  176 . The hydrogen refueling station  100  also includes an reformat heat exchanger  180 , an air exhaust heat exchanger  181  having a blower  182  as cooling means, a reformate exhaust heat exchanger  183 . The hydrogen refueling station  100  includes a system exhaust heat exchanger  184  having a blower  185  as cooling means; a reformate liquid trap  186 ; a air exhaust liquid trap  187 ; a system exhaust liquid trap  188 ; solenoid valves  190   a - 193   a  and  190   b - 193   b.    
         [0022]    The fuel cell stack  110  includes fuel cell sections  112   a  and  112   b . Each fuel cell section  112   a  and  112   b  includes at least one cell  120 . Each cell  120  includes a membrane-electrode-assembly  121  combining a proton-exchange membrane  122 , two electrodes disposed on opposite sides of the membrane  122 . A primary electrode  123  of each cell  120  faces a primary flow field  125  with an inlet adjacent to a primary manifold  113  of the fuel cell section  112   a  or  112   b  and with an outlet adjacent to an exhaust manifold  114  of the fuel cell section  112   a  or  112   b . Each cell  120  also includes a hydrogen electrode  124  faces a hydrogen flow field  126  adjacent to a hydrogen manifold  115  of the fuel cell stack  110 . The primary manifold  113  of the fuel cell sections  112   a  and  112   b  is secured, consequently, solenoid valves  190   a ,  190   b  and  191   a ,  191   b . The exhaust manifold  114  of the fuel cell sections  112   a  and  112   b  is secured, consequently, solenoid valves  192   a ,  192   b  and  193   a ,  193   b . The primary manifold  113  of the fuel cell section  112   a  ( 112   b ) is in fluid communication either with an outlet of the converter  134  of the primary fuel reformer  130  through a gas side of the reformate liquid trap and the reformate heat exchanger by means of the solenoid valve  190   a  ( 190   b ) open or with the fuel cell air compressor  140  through the air feed compartment  174  of the humidifier  170  by means of the solenoid valve  191   a  ( 191   b ) open. 
         [0023]    The exhaust manifold  114  of fuel cell section  112   a  ( 112   b ) is in fluid communication either with an inlet of the internal burner  132  of the primary fuel reformer  130  through the reformate exhaust heat exchanger  183  by means of the solenoid valve  192   a  ( 192   b ) open or with an inlet of the turbo generator  146 , consequently, through the air exhaust compartment  176  of the humidifier  170 , the air exhaust heat exchanger  181 , a gas side of the air exhaust liquid trap  187  and the reformate heat exchanger  180  by means of solenoid valve  193   a  ( 193   b ) open. The hydrogen manifold  115  of the fuel cell stack  110  is in fluid communication with the high pressure receiver  164  by means of the high pressure hydrogen compressor  144 . 
         [0024]    Also the primary fuel reformer  130  has other fluid communications: an inlet of the converter  134  is in fluid communication with the primary fuel tank  160  by means of the primary fuel pump  150  and with the water tank  162  by means of the water pump  152 , an inlet of the internal burner  132  of the primary fuel reformer is in fluid communication with the reformer air compressor  142 , an outlet of the internal burner  132  of the primary fuel reformer is in fluid communication with the inlet of the turbo generator  146 . 
         [0025]    An outlet of the turbo generator  146  is in fluid communication with a gas side of the system exhaust liquid trap  188  through the reformate exhaust heat exchanger  183  and the system exhaust heat exchanger  184 . A liquid side of reformate liquid trap  186  is adjusted to the fluid communication of the inlet of the internal burner  132  of the primary fuel reformer  130  with the exhaust manifold  114  of fuel cell section  112   a  ( 112   b ) in a section between the reformate exhaust heat exchanger  183  and the solenoid valve  192   a  ( 192   b ). Liquid sides of the air exhaust liquid trap  187  and the system exhaust liquid trap  188  are in fluid communication with the water tank. 
         [0026]    As shown in  FIG. 1 , a hydrogen filtering mode operates in hydrogen filtering mode whereby the reformate is introduced from the outlet of the converter  134  of the primary fuel reformer  130  to the primary manifold  113  of fuel cell section  112   a  and, then, through the primary flow fields  125  to the primary electrodes  123  as the solenoid valve  191   a  is moved between an opened position and a closed position. The reformate exhaust is then rejected from the exhaust manifold  114  of the fuel cell section  112   a  as the solenoid valve  191   a  is moved between the opened position and the closed position. The current is applied to the fuel cell section  112   a  forcing a major portion of the hydrogen contained in the reformate to electrochemically pass from the primary electrodes  123  to the hydrogen electrodes  124 , as shown in  FIG. 2 , and, then, through the hydrogen flow fields  126  to the hydrogen manifold  115  of the fuel cell stack  110 . 
         [0027]    When the fuel cell stack  110  is in a power generating mode, the air as oxygen containing gas is introduced by the fuel cell air compressor  140  to the primary manifold  113  of the fuel cell section  112   b  and, then through the primary flow fields  125  to the primary electrodes  123  by as the solenoid valve  191   a  is moved between the opened position and the closed position. The minor portion of hydrogen delivered to the hydrogen manifold  115  of the fuel cell stack  110  by means of the fuel cell section  112   a  being in the hydrogen filtering mode is fed to the hydrogen electrodes  124  of the fuel cell section  112   b  through the hydrogen flow fields  126  as a fuel. The air exhaust is rejected from the exhaust manifold  114  of the fuel cell section  112   b  by as the solenoid valve  191   a  is moved between the opened position and the closed position. The current generated by the fuel cell section  112   b  covers the main power demand of the hydrogen refueling station  100 . 
         [0028]    Alluding to the above, the major portion of hydrogen delivered to the hydrogen manifold  115  of the fuel cell stack  110  is pumped by the high pressure hydrogen compressor  144  into high pressure receiver  164  wherefrom the hydrogen is dispensed to vehicles. The converter  134  of the primary fuel reformer  130  is fed with a primary fuel and water as reagents for the hydrogen-rich fuel generation proportionally delivered to the inlet of the converter  134 , consequently, by the primary fuel pump  150  from the primary fuel tank  160  and by means of the water pump  152  from the water tank  162 . The reformate delivered from the outlet of the converter  134  of the primary fuel reformer  130  to the fuel cell section  112   a  being in the hydrogen filtering mode as a source of the hydrogen, first, is pre-cooled in the reformate heat exchanger  180  to make its thermal condition acceptable for the fuel cell operation, then, passes through the gas side of the reformate liquid trap  186  wherefrom a reformate condensate is withdrawn from the reformate to the liquid side of the reformate liquid trap  186  in order to prevent the flooding of fuel cell section  112   a.    
         [0029]    The reformate condensate is discharged from the liquid side of the reformate liquid trap  186  into the reformate exhaust stream. The internal burner  132  of the primary fuel reformer  130  is fed with a fuel which is, first, the hydrogen containing in the reformate exhaust, second, some carbon monoxide containing in the reformate exhaust, third, the primary fuel containing in the reformate condensate diverted from the reformate in the reformate liquid trap  186  with a oxidant as the oxygen containing in the air delivered by the reformer air compressor  142 , first, to generate a heat to maintain the reformate generation in the converter  134  of the primary fuel reformer  130 . 
         [0030]    The air exhaust is delivered from the exhaust manifold  114  of the fuel cell section  112   b  being in the power generating mode, first, to the air exhaust compartment  176  of the humidifier  170  wherefrom some moisture and some heat of the air exhaust is transferred through the moisture permeable membrane  172  to the air flowing across the air feed compartment  174  in order to humidify the air in according with the proper operation requirement for the fuel cell section  112   b  and to pre-cool the air exhaust, second, to the air exhaust heat exchanger  181  wherein some moisture from the air exhaust is condensed by means of a cooling flow provided by the blower  182 , third, through the gas side of the air exhaust liquid trap  186  wherefrom a water condensate is withdrawn from the air exhaust to the liquid side of the reformate liquid trap  186 , fourth, through the reformate heat exchanger  180  to be pre-heated before the introduction into the turbo generator  146 , fifth, to the inlet of the turbo generator  146 . 
         [0031]    A combustion exhaust from the outlet of internal burner  132  of the primary fuel reformer  130  is supplied to the inlet of the turbo generator  146 . Under the hydrogen refueling station operation a system exhaust created at the inlet of the turbo generator  146  by mixture of the combustion exhaust and the air exhaust is delivered at elevated temperature to the turbo generator  146  wherein the flow energy is converted into the electrical power to partly cover the power demand of the hydrogen refueling station  100 . 
         [0032]    The system exhaust from the outlet of the turbo generator  146  is delivered, to reformate exhaust heat exchanger  183  be pre-cooled and then to the system exhaust heat exchanger  184  wherein some moisture from the system exhaust is condensed by a cooling flow provided by the blower  185 . The gas side of the air exhaust liquid trap  188  wherefrom a water condensate is withdrawn from the system exhaust to the liquid side of the system exhaust liquid trap  188 . The water from the liquid sides of the air exhaust liquid trap  186  and the air exhaust liquid trap  188  is delivered into the water tank  162 . 
         [0033]    Water balance in the water tank  162  is controlled by the blower  182  and  185  maintaining the proper cooling flows through the air exhaust heat exchanger  181  and the system exhaust heat exchanger  184  in order to recover a proper water amount. In event of performance degradation of the fuel cell section  112   a  being in the hydrogen filtering mode due to a primary catalyst poisoning is switched to the power generating mode by changing a) the position of the solenoid valves ( 190   a ,  193   a  are open;  191   a ,  192   a  are closed) b) the electrical connection for the power generation; simultaneously the fuel cell section  112   b  being in the power generating mode is switched to the hydrogen filtering mode by changing a) the position of the solenoid valves ( 191   b ,  192   b  are open;  190   b ,  193   b  are closed) b) the electrical connection for the power consumption. Based on the usage of the methanol as a primary fuel the major parameters of the hydrogen refueling station producing pure hydrogen as much 6,000,000 L per a week are how they are shown in  FIG. 1 . 
         [0034]    While the invention has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.