Patent Publication Number: US-2007101648-A1

Title: Method and apparatus for endothermic fuel reformation

Description:
FIELD OF THE DISCLOSURE  
      The present disclosure relates to methods and apparatus for reforming fuel.  
     BACKGROUND OF THE DISCLOSURE  
      Fuel reformers are used to reform fuel into a reformate gas such as hydrogen (H 2 ) or carbon monoxide (CO). Such reformate gas may be used for a variety of purposes such as hydrogen-enhancement of engine combustion, emission abatement, and fuel cell operation.  
     SUMMARY OF THE DISCLOSURE  
      According to an aspect of the present disclosure, there is provided a fuel reforming apparatus for reforming a fuel. The apparatus comprises a combustion device and a catalyst. The combustion device is configured to oxidize a portion of the fuel into H 2 O (water). The catalyst is configured to catalyze an endothermic reaction between the H 2 O and another portion of the fuel so as to produce a reformate gas. An associated method is disclosed.  
      The above and other features of the present disclosure will become apparent from the following description and the attached drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a diagrammatic view showing a fuel reforming apparatus for reforming a fuel into a reformate gas for use by one or more components;  
       FIG. 2A  is a diagrammatic view showing a combustion device of the fuel reforming apparatus embodied as a plasma fuel reformer; and  
       FIG. 2B  is a sectional view taken along lines  2 B- 2 B of  FIG. 2A .  
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS  
      While the concepts of the present disclosure are susceptible to various modifications and alternative forms, specific exemplary embodiments thereof have been shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit the disclosure to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives following within the spirit and scope of the invention as defined by the appended claims.  
      Referring to  FIG. 1 , there is shown a fuel-reforming apparatus  10  for reforming a fuel such as a hydrocarbon fuel (e.g., diesel, natural gas) into a reformate gas containing hydrogen (H 2 ) and/or carbon monoxide (CO). The reformate gas may be used with a component  12  that may be embodied in a variety of ways including, but not limited to, an internal combustion engine (e.g., diesel engine, gasoline engine) for hydrogen-enhanced combustion, an emission abatement device (e.g., NOx trap, particulate trap, and/or selective catalytic reduction catalyst) for abatement of emissions present in exhaust gas of the engine, and/or a fuel cell. As such, the apparatus  10  may be mounted onboard a vehicle (or in connection with a stationary power generator) to supply the reformate gas as needed.  
      The fuel-reforming apparatus  10  comprises a combustion device  14  and catalyst  16  downstream from the combustion device  14 . The combustion device  14  oxidizes a portion of the fuel into H 2 O. The output of the combustion device  14  further includes another portion of the fuel in the form of, for example, a hydrocarbon (e.g., methane) cracked or uncracked by the combustion device  14 . The H 2 O and the hydrocarbon (HC) are advanced to the catalyst  16  which catalyzes an endothermic reaction between the H 2 O and the HC so as to produce one or more components of the reformate gas such as H 2  and CO. As such, steam-reforming of the HC occurs at the catalyst  16  resulting in reduced temperatures (e.g., about a 200° C. drop in temperature to about 600° C.) at the catalyst  16 , thereby promoting the longevity of the useful life of the catalyst  16 .  
      Further, by generating the H 2 O with the combustion device  14 , the combustion device  14  is able to perform “double duty” in the sense that it (1) not only provides the H 2 O for steam-reforming at the catalyst  16  but also acts to (2) partially oxidize a portion of the fuel into H 2  and CO (or at least initiate such partial oxidation). Moreover, the combustion device  14  may be considered to perform “triple duty” in cases where the combustion device  14  is used to crack a portion of the fuel into a simpler HC.  
      The output of the combustion device  14  may thus comprise a number of components including, for example, H 2 O, H 2 , CO, CO 2 , HC, and N 2 . Exemplarily, the composition of the output may be about 9-10% H 2 O, about 7-9% H 2 , about 13-14% CO, and about 4-5% CO 2 , with the remainder including HC&#39;s, N 2 , and O 2 .  
      The output of the combustion device  14  is advanced to the catalyst  16  which, as alluded to above, catalyzes an endothermic steam-reforming reaction between H 2 O and HC components of the output. In addition, to increase the yield of H 2  and/or CO, the catalyst  14  may further be configured to catalyze a partial oxidation reaction between HC and O 2  components of the output to produce more H 2  and CO and/or catalyze a water-shifting reaction between H 2 O and CO components of the output to produce even more H 2 . As such, exemplarily, the output from the catalyst  16  and thus the final output of the apparatus  10  may comprise about 24% H 2 , about 20% CO, and about 4-5% CO 2  (carbon dioxide), with much of the remainder being N 2  (nitrogen). Thus, the catalyst  16  includes not only a steam-reforming portion but may also include a partial oxidation portion and/or a water-shifting portion in order for it also to perform double or triple duty. The following documents relating to catalysts are hereby incorporated by reference herein: (1) U.S. Pat. Nos. 6,261,991; 6,284,217; 5,599,517; 6,946,114; 6,458,334; 4,897,253; 6,627,572; 4,598,062; 6,821,494; and 5,139,992; (2) R. P. O&#39;Connor, E. J. Klein, and L. D. Schmidt, “High Yields of Synthesis Gas By Millisecond Partial Oxidation of Higher Hydrocarbons,”  Catalysis Letters,  70, 99-107 (2000); (3) Jameel Shihadeh, Di-Jia Liu, “Low Cost Autothermal Diesel Reforming Catalyst Development,”  U.S. Department of Energy Journal of Undergraduate Research,  4, 120-125 (2004); and (4) J. M. Zalc, V. Sokolovskii, and D. G. Löffler, “Are Noble Metal-Based Water-Gas Shift Catalysts for Automotive Fuel Processing?”,  Journal of Catalysis,  206, 169-171 (2002). Suppliers of catalysts include Süd-Chemie AG of Munich, Germany; Engelhard Corporation of Iselin, N.J.; and Johnson Matthey Plc of London, England.  
      To facilitate production of the output of the combustion device  14 , an air-and-fuel mixture may be introduced into a combustion region  18  of the device  14  in a stratified manner. In particular, the combustion device may have a fuel input  30  and an air input  32  that cooperate to stratify the air-and-fuel mixture into a number of zones having different air-fuel ratios. For example, the air-and-fuel mixture may be stratified into a first zone  20  and a second zone  22 . In such a case, the first zone  20  provides the HC&#39;s of the output of the combustion device  14  and the second zone  22  provides the H 2 O of the output of the combustion device  14 . To do so, the first zone  20  may have a first air-fuel ratio that is substantially fuel-richer than the stoichiometric ratio of the fuel and the second zone  22  may have a second air-fuel ratio that is fuel-leaner than the first air-fuel ratio so as to be at about or fuel-leaner than the stoichiometric ratio.  
      Energy supplied by the combustion device  14  may be applied primarily to the second zone  22  to facilitate complete oxidation of the fuel into at least H 2 O while allowing the fuel of the first zone  20  to pass through the combustion region  18  either cracked or uncracked but otherwise not oxidized. In this way, the H 2 O and the HC&#39;s can be provided for steam-reforming at the catalyst  16 .  
      It is to be understood that the device  14  may have any number of fuel inputs and air inputs to achieve a desired stratification of the air-and-fuel mixture to, in turn, provide a desired composition of the output of the device  14 . As in the above example, there may be one fuel input and one air input. In other examples, there may be only one fuel input and a plurality of air inputs, only one air input and a plurality of fuel inputs, or a plurality of fuel inputs and a plurality of air inputs. In the exemplary embodiment of  FIGS. 2A and 2B  discussed below, there are one fuel input and three air inputs.  
      The combustion device  14  may be embodied as any number of devices capable of oxidizing a portion of the fuel into H 2 O. For example, the combustion device  14  may be embodied as any one or more of a catalyst, a fuel-fired burner, and/or a plasma fuel reformer, to name just a few.  
      Referring to  FIGS. 2A and 2B , illustratively, the combustion device  14  is configured, for example, as a plasma fuel reformer. In such a case, the device  14  is configured to generate an electrical arc  24  between an upper electrode  25  and a lower electrode  26  spaced apart from the upper electrode to define an electrode gap  28  therebetween. The arc  24  is generated in the combustion region  18  located in the vicinity of the electrodes  25 ,  26  and is responsible for initiating conversion of fuel of the air-and-fuel mixture into the components of the output from the device  14 .  
      In the exemplary plasma fuel reformer embodiment of the combustion device  14 , the combustion device  14  has one fuel input  30  and three air inputs  32   a,    32   b,    32   c,  as shown  FIG. 2A , that cooperate to provide the exemplary stratification pattern shown in  FIG. 2B . In particular, referring to  FIG. 2B , the fuel input  30  and the air inputs  32   a,    32   b,    32   c  cooperate to stratify the air-and-fuel mixture into a first zone  34 , a second zone  36 , a third zone  38 , and fourth zone  40 .  
      The first zone  34  is located centrally on an axis  42  of the combustion device  14  and has a first air-fuel ratio substantially fuel-richer than the stoichiometric ratio of the fuel. The fuel input  30  is configured, for example, as a fuel injector mounted on the axis  42  in axial alignment with the first zone  34  so that the first zone  34  is the most fuel-rich of the four zones  34 ,  36 ,  38 ,  40 .  
      The second, third, and fourth zones  36 ,  38 ,  40  are arranged in successive, generally concentric rings about the first zone  34 . As such, the second zone  36  surrounds the first zone  34 , the third zone  38  surrounds the second zone  36 , and the fourth zone  40  surrounds the third zone  38 .  
      The second zone  36  has a second air-fuel ratio that is fuel-leaner than the first air-fuel ratio. Exemplarily, the oxygen-to-carbon ratio of the second zone  36  is about 1.0. The first air input  32   a  is primarily responsible for supplying the air of the second zone  36 .  
      The third zone  38  has a third air-fuel ratio fuel-leaner than the second air-fuel ratio so as to be at about the stoichiometric ratio. The second air input  32   b  is primarily responsible for supplying the air of the third zone  38 .  
      The fourth zone  40  has a fourth air-fuel ratio fuel-leaner than the third air-fuel ratio and the stoichiometric ratio. The third air input  32   c  is primarily responsible for supplying the air of the fourth zone  40 .  
      The generally stoichiometric third air-fuel ratio is conducive to generation of the arc  24  therein. As such, the arc  24  is present primarily in the third zone  38 .  
      The four zones  34 ,  36 ,  38 ,  40  are advanced through the combustion region  18  so as to provide the components of the output of the device  14 . In particular, the first zone  34  provides the cracked or uncracked HC&#39;s of the output for steam-reformation and possibly partial oxidation at the catalyst  16 . The second zone  36  provides the H 2  and CO of the output, the CO being useful for, among other reasons, possible water-shifting at the catalyst  16 . Each of the third and fourth zones  38 ,  40  provides the H 2 O of the output for steam reformation and possible water-shifting at the catalyst  16 . More particularly, as alluded to above, the stoichiometric third air-fuel ratio facilitates generation of the arc  24  therein while also facilitating oxidation of fuel into H 2 O. The less-than-stoichiometric fourth air-fuel ratio further facilitates oxidation of fuel into H 2 O to increase the H 2 O yield of the output. As such, stratification of the air-and-fuel mixture promotes generation of H 2 O, HC&#39;s, and CO for use at the catalyst  16  to increase the yield of the reformate gas (H 2  and/or CO).  
      The air inputs  32   a,    32   b,    32   c  may be arranged in a variety of ways to produce the thus-described stratification in conjunction with the fuel input  30 . For example, each of the air input  32   a,    32   b,    32   c  may be secured to and/or formed in the device  14  to provide the device  14  with three concentric annular passageways to direct air to the respective zones.  
      Exemplarily, the combustion device  14  may be configured in a manner similar to any of the plasma fuel reformers disclosed in U.S. patent application Ser. Nos. 10/452,623 and 10/843,776 and U.S. Provisional Patent Application No. 60/660,362, the disclosure of each of which is hereby incorporated by reference herein. It is be further understood that the device  14 , when configured as a plasma fuel reformer, may include a housing containing not only components of the plasma-generating head but also the catalyst  16 . In other words, the housing of the plasma-generating head may be secured directly to a reactor tube containing the catalyst  16  and extending for a length to increase the residence time of the reactants in the reactor tube to promote production of the reformate gas.  
      While the concepts of the present disclosure have been illustrated and described in detail in the drawings and foregoing description, such illustration and description is to be considered as exemplary and not restrictive in character, it being understood that only illustrative embodiments have been shown and described and that all changes and modifications that come within the spirit of the disclosure are desired to be protected.  
      There are a plurality of advantages of the concepts of the present disclosure arising from the various features of the systems described herein. It will be noted that alternative embodiments of each of the systems of the present disclosure may not include all of the features described yet still benefit from at least some of the advantages of such features. Those of ordinary skill in the art may readily devise their own implementations of a system that incorporate one or more of the features of the present disclosure and fall within the spirit and scope of the invention as defined by the appended claims.