Patent Application
20070101648
The present disclosure relates to methods and apparatus for reforming fuel.
Fuel reformers are used to reform fuel into a reformate gas such as hydrogen (H2) 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.
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 H2O (water). The catalyst is configured to catalyze an endothermic reaction between the H2O 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.
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
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 H2O. 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 H2O and the hydrocarbon (HC) are advanced to the catalyst 16 which catalyzes an endothermic reaction between the H2O and the HC so as to produce one or more components of the reformate gas such as H2 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 H2O 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 H2O for steam-reforming at the catalyst 16 but also acts to (2) partially oxidize a portion of the fuel into H2 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, H2O, H2, CO, CO2, HC, and N2. Exemplarily, the composition of the output may be about 9-10% H2O, about 7-9% H2, about 13-14% CO, and about 4-5% CO2, with the remainder including HC's, N2, and O2.
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 H2O and HC components of the output. In addition, to increase the yield of H2 and/or CO, the catalyst 14 may further be configured to catalyze a partial oxidation reaction between HC and O2 components of the output to produce more H2 and CO and/or catalyze a water-shifting reaction between H2O and CO components of the output to produce even more H2. As such, exemplarily, the output from the catalyst 16 and thus the final output of the apparatus 10 may comprise about 24% H2, about 20% CO, and about 4-5% CO2 (carbon dioxide), with much of the remainder being N2 (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'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's of the output of the combustion device 14 and the second zone 22 provides the H2O 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 H2O 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 H2O and the HC'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
The combustion device 14 may be embodied as any number of devices capable of oxidizing a portion of the fuel into H2O. 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
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 32a, 32b, 32c, as shown
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 32a 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 32b 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 32c 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's of the output for steam-reformation and possibly partial oxidation at the catalyst 16. The second zone 36 provides the H2 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 H2O 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 H2O. The less-than-stoichiometric fourth air-fuel ratio further facilitates oxidation of fuel into H2O to increase the H2O yield of the output. As such, stratification of the air-and-fuel mixture promotes generation of H2O, HC's, and CO for use at the catalyst 16 to increase the yield of the reformate gas (H2 and/or CO).
The air inputs 32a, 32b, 32c 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 32a, 32b, 32c 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.
