Abstract:
A reformer system for generating a hydrogen-containing gas for a fuel cell system, especially in a motor vehicle, includes an evaporator arrangement ( 12 ) to be fed with hydrocarbon and mixed material for generating a hydrocarbon vapor/mixed material mixture, and a reformer arrangement ( 14 ) with reformer catalytic converter material ( 40, 42 ) for converting the hydrocarbon vapor/mixed material mixture to hydrogen-containing gas. The reformer arrangement ( 14 ) is surrounded by a mixed material flow space ( 22 ), through which at least a part of the mixed material to be introduced into the evaporator arrangement ( 12 ) can flow for the transmission of heat between the reformer arrangement ( 14 ) and the mixed material. An ignition arrangement ( 52 ) is assigned to the mixed material flow space ( 22 ) for igniting and burning the mixed material flowing through same in the mixed material flow space.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of priority under 35 U.S.C. § 119 of German Patent Application DE 10 2006 028 699.5 filed Jun. 22, 2006, the entire contents of which are incorporated herein by reference. 
       FIELD OF THE INVENTION 
       [0002]    The present invention pertains to a reformer system for generating a hydrogen-containing gas for a fuel cell system, especially in a motor vehicle, comprising an evaporator arrangement to be fed with hydrocarbon and mixed material for generating a hydrocarbon vapor/mixed material mixture, a reformer arrangement with reformer catalytic converter material for converting the hydrocarbon vapor/mixed material mixture to hydrogen-containing gas, whereby the reformer arrangement is surrounded by a mixed material flow space, through which at least a part of the mixed material to be introduced into the evaporator arrangement can flow for the transmission of heat between the reformer arrangement and the mixed material. Furthermore, the present invention pertains to a process for operating such a reformer system. 
       BACKGROUND OF THE INVENTION 
       [0003]    A reformer system of this type has become known from DE 10 2004 020 507 A1. In this reformer system, the mixed material, which is essentially composed of air and fuel cell exhaust gas, i.e., anode exhaust gas, flows through the mixed material flow space and thus along the outside of the reformer arrangement, in which this mixed material, which is thoroughly mixed with hydrocarbon vapor, is then also converted into a hydrogen-containing gas, which is generally also designated as reformate. Some of the heat forming during this conversion process can be transmitted to the mixed material flowing in the mixed material flow space, so that this mixed material can be introduced, preheated, into the reformer arrangement, and thus, a stable reforming process can be guaranteed at suitable temperatures. 
         [0004]    One problem with this arrangement is that, in the start phase of the reformer system, i.e., at the beginning of the conversion process, the mixed material already flows through the mixed material flow space and also in this phase, heat is already drawn from the area of the reformer arrangement. In this phase, however, the reformer arrangement has not yet reached the operating temperature needed for a stable conversion process, such that the reaching of the process temperature is delayed by the flowing about of the reformer arrangement with the comparatively cold mixed material. 
         [0005]    Introducing a fuel stream, i.e., a hydrocarbon stream, and a mixed material stream into a reformer arrangement has become known from DE 103 59 231 A1. The mixed material stream, which is essentially composed of air and anode exhaust gas, is ignited and burned in a reaction chamber lying in front of a reaction space of the reformer arrangement, in which the reformate is produced. In this way, in this state of the art, the water content contained in the mixed material, i.e., in the mixture of anode exhaust gas and air, shall be increased, and thus, the reforming efficiency in the reaction space shall be increased. 
       SUMMARY OF THE INVENTION 
       [0006]    The object of the present invention is to perfect a reformer system of this type, such that the start phase of the reforming process can be shortened with a simple design. 
         [0007]    According to the present invention, this object is accomplished by a reformer system for generating a hydrogen-containing gas for a fuel cell system, especially in a motor vehicle, comprising an evaporator arrangement to be fed with hydrocarbon and mixed material for generating a hydrocarbon vapor/mixed material mixture, a reformer arrangement with reformer catalytic converter material for converting the hydrocarbon vapor/mixed material mixture into hydrogen-containing gas, whereby the reformer arrangement is surrounded by a mixed material flow space, through which at least a part of the mixed material to be introduced into the evaporator arrangement can flow for the transmission of heat between the reformer arrangement and the mixed material. 
         [0008]    This system is further characterized in that an ignition arrangement is assigned to the mixed material flow space for igniting and burning the mixed material flowing through same in the mixed material flow space. 
         [0009]    In the design of a reformer system according to the present invention, due to the combustion of the mixed material occurring in thermal interaction with the reformer arrangement, it is ensured that no heat is withdrawn, above all, in the start phase of the reforming of the reformer arrangement proper, but rather the reformer arrangement and the reformer catalytic converter material arranged therein are additionally heated by the heat forming during the combustion of the mixed material. This leads to a distinctly faster rise in the temperature of the reformer catalytic converter material to the needed process temperature, in order to then be able to carry out a stable reforming process for generating a hydrogen-containing gas. Furthermore, the heat forming during this combustion is also used for the mixed material and the combustion gases forming during the combustion of the mixed material to be able to be introduced into the reformer arrangement with a higher temperature, which contributes to the stabilization of the mixture formation (“cold flame”). Furthermore, water is produced during this combustion, which is introduced together with the other combustion gases and components into the reformer arrangement and is converted into hydrogen during the catalytic reaction and also contributes to the reduction of soot formation. After reaching this process temperature, the combustion can then be completed in the area of the mixed material flow space, so that subsequently heat can be taken up by the reformer arrangement due to this mixed material coming through, i.e., can cool same, in order to prevent an excessive rise in temperature beyond the suitable process temperature. 
         [0010]    For example, a feed device may be provided for feeding air and anode exhaust gas from a fuel cell system as mixed material or mixed material component through the mixed material flow space. Furthermore, the present invention pertains to a process for operating a reformer system according to the present invention, in which process air and anode exhaust gas of a fuel cell system as mixed material or mixed material component is burned in the mixed material flow space and is forwarded to the evaporator arrangement, whereby the air is supplied with such excess regarding the anode exhaust gas that during the subsequent thorough mixing of the air introduced into the evaporator arrangement with hydrocarbon vapor, a hypostoichiometric air/hydrocarbon vapor mixture ratio is produced. 
         [0011]    Thus, it is important here that even if mixed material is burned in the mixed material flow space, the combustion products forming during this combustion still contain sufficient air or oxygen that the conversion process can run in a suitable manner with subsequent introduction into the reformer arrangement together with the hydrocarbon vapor. It is advantageous here, for example, to produce a hypostoichiometric mixture ratio with a lambda value of about 0.4, whereby this mixture ratio refers to the ratio of air/hydrocarbon vapor in the mixing chamber and accordingly a corresponding ratio of air and anode exhaust gas must already be prepared beforehand for flowing through and combustion in the mixed material flow space. 
         [0012]    Advantageously, provisions are furthermore made for the mixed material flowing through the mixed material flow space to be ignited and burned at least in a start phase of the reformer system. Thus, a cooling off of the reformer arrangement in the start phase of the reformer system can be avoided and same can be additionally heated, while, after the start phase, i.e., when the process temperature is essentially reached, heat can be removed from the area of the reformer arrangement. 
         [0013]    The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    In the drawings: 
           [0015]      FIG. 1  is a schematic sectional view of a reformer system according to the present invention; and 
           [0016]      FIG. 2  is a schematic sectional view of a fuel cell system including reformer system and fuel cell according to the present invention; 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0017]    Referring to the drawings in particular, the present invention is explained in detail below with reference to the attached  FIG. 1 . A reformer system according to the present invention is generally designated by  10  in  FIG. 1 . This reformer system  10  may basically be organized into an evaporator area or an evaporator arrangement  12  and a reformer area or a reformer arrangement  14 . The evaporator arrangement  12  and the reformer arrangement  14  may be arranged with their essential components in a common, tubular housing  16 , which can be radially expanded for providing an annular introduction space  18  in the passage between the evaporator arrangement  12  and the reformer arrangement  14 . This housing  16  is surrounded by an outer housing  20 , so that a mixed material flow space  22  is formed in the area surrounding the reformer arrangement  14 . Mixed material enters this flow space  22  via inlet openings  24 , then flows along the reformer arrangement  14  and the outside of the evaporator arrangement  12  in order to reach a mixing chamber  26  after axial diversion into and then out of the annular introduction space  18 . 
         [0018]    This mixing chamber  26  is axially limited by a bottom component  28 , which has a porous evaporator medium  30  on its side facing away from the mixing chamber  26 . A fuel supply line feeds liquid fuel or hydrocarbon into this porous evaporator medium  30 . An electrically energizable heating means  34  provided on the back side of the porous evaporator medium, which is carried at a carrier  36  with insulation, heats the porous evaporator medium  30  and thus contributes to the increased evaporation of the hydrocarbon in the direction of the mixing chamber  26 . The hydrocarbon vapor thus generated is mixed in the mixing chamber  26  with the mixed material introduced into same and then reaches the area of the reformer arrangement  14 . It should be pointed out here that this mixed material flow and also the flow of the mixture formed in the mixing chamber  26  can be generated by a mixed material blower  60  or another feeding arrangement. 
         [0019]    In the reformer arrangement  14 , the mixed material first flows through a flame retention baffle  38  and then reaches a first catalytic converter arrangement  40 . In the direction of flow to the first catalytic converter arrangement  40  follows a second catalytic converter arrangement  42 . As an alternative, a catalytic converter may be provided with two catalytic converter zones. A temperature sensor  44  is arranged downstream of the second catalytic converter arrangement  42 . Furthermore, an ignition member  46  is assigned to the mixing chamber  26 , which ignition member  46  protrudes into this mixing chamber  26  and, as will still be explained below, can ignite the mixture formed in the mixing chamber by means of energizing and can result in combustion. 
         [0020]    The flame retention baffle  38 , the first catalytic converter arrangement  40  and the second catalytic converter arrangement  42  are carried at the housing  16  via elastic material  48  in order to thus not transmit vibrations occurring during operation to these three components. 
         [0021]    Furthermore, it is recognized that the reformer arrangement  14  or the housing  16  in that longitudinal area, in which the second catalytic converter arrangement  42  is arranged, is surrounded radially on the outside by a tubular or housing-like insulation element  50 , so that the mixed material entering through the openings  24  in that area, in which the housing  16  is surrounded by the insulation element  50 , essentially cannot enter into thermal interaction with the reformer arrangement  14 , but rather only in the subsequent longitudinal section, in which essentially the first catalytic converter arrangement  40  is also arranged. 
         [0022]    Furthermore, a second ignition member  52  is provided in the area of the mixed material flow space  22 , which second ignition member  52  extends into this mixed material flow space  22  and, as explained below, can ignite and bring to combustion the mixed material flowing therein. 
         [0023]    By incorporating a reformer system of this type into a fuel cell system with a fuel cell  70 , a hydrogen-gas-containing reformate is thus generated by this reformer system  10 , which can be used in a fuel cell together with air or atmospheric oxygen in order to generate electrical energy. The residual reformate leaving the fuel cell may, as so-called anode exhaust gas, be fed back to the reformer for better mixture formation by means of a feed unit (blower)  60  and then be thoroughly mixed with air or be introduced into the mixed material flow space  22  together with air via the openings  24 , so that this mixture of air and anode exhaust gas essentially provides the previously already mentioned mixed material. 
         [0024]    In a start phase of the fuel cell system, i.e., even in a start phase of the reformer system  10 , it must, at first, be ensured that various system areas be brought to the suitable operating temperature. This concerns, above all, the two catalytic converter arrangements  40 ,  42 , of which the first catalytic converter arrangement  40  is designed, such that essentially an exothermic catalytic reaction takes place there, while essentially an endothermic catalytic reaction takes place in the second catalytic converter arrangement. It is generally necessary to raise the temperature in the area of the catalytic converter arrangement  14  to an activation temperature of about 330° C. This may take place in the start phase by the mixture of hydrocarbon vapor and mixed material formed in the mixing chamber  26 , essentially consisting of air in this case, being ignited and burned. The combustion exhaust gases leave the mixing chamber  26  and flow through the two catalytic converter arrangements  40 ,  42 , whereby these quickly take up heat from the combustion exhaust gases and are brought to the operating temperature. In order to then start the reforming process, the combustion in the mixing chamber  26  is ended, for example, by means of a brief interruption of the fuel stream or of the hydrocarbon stream, so that a mixture of hydrocarbon vapor and air or mixed material is then forwarded into the two catalytic converter arrangements  40 ,  42  and starts the reforming process there. A reformate with increasingly rising hydrogen gas content then leaves the reformer system  10  and reaches the fuel cell. Above all, when the fuel cell proper is likewise not yet at operating temperature in this phase of operation and provided that the process for generating electrical energy was not yet started, the anode exhaust gas will have essentially the same composition as the reformate that leaves the fuel cell system  10 . This residual reformate or anode exhaust gas is fed back or introduced into the mixed material flow space  22  together with air through the openings  24 . Since the temperature of the two catalytic converter arrangements  40 ,  42  is comparatively low in this start phase and still lies distinctly below the optimal process temperature, the second ignition member  52  is electrically energized according to the present invention, so that in the area of the mixed material flow space, conditions are created, under which the mixed material is ignited and burned. The heat forming during this combustion heats the reformer arrangement  14  from outside and prevents the heat forming in the starting reforming process from being increasingly transmitted outwardly to the mixed material flowing in the mixed material flow space  22 . 
         [0025]    This leads to a distinctly faster increase in the temperature in the area of the reformer arrangement  14  and thus to a distinctly faster reaching of the suitable optimal process temperature. 
         [0026]    Moreover, the mixture forming reaction in the mixing chamber experiences the corresponding educt preheating. 
         [0027]    Not only to cool off less intensively or to heat even faster by heating the reformer arrangement  14  from the outside, but also to be able to prepare the conditions in the reformer arrangement  14  proper for carrying out a reforming process, it must be ensured that even after burning the mixed material in the mixed material flow space  22 , a sufficient amount of air or atmospheric oxygen is still present in order to prepare a mixture suitable for the reforming process in the mixing chamber  26  with the hydrocarbon vapor. This mixture is preferably hypostoichiometric and should have a lambda value of about 0.4. I.e., the combustion in the mixed material flow space  22  is carried out with such an excess of air that a corresponding residual air or residual oxygen quantity can be guaranteed for the introduction into the mixing chamber  26 . 
         [0028]    After suitable thermal conditions for carrying out a stable reforming process are then created in the reformer arrangement  14  without the risk of generating hazardous components, such as, e.g., soot, the combustion in the mixed material flow space  22  is ended. This may take place, for example, by the air stream being briefly interrupted. Also, the ending of the energizing of the ignition member  52  may lead to the extinguishing of the combustion depending on the external conditions and also depending on the mixing ratio of the components of the mixed material. Subsequently, the comparatively cold or colder mixed material then flows through the mixed material flow space  22  and may in the next operation then remove heat from the area of the reformer arrangement  14 , especially from the area of the first catalytic converter arrangement  40  and thus be forwarded into the mixing chamber  26  already preheated. Since in this normal operating phase, the mixed material then reaches the mixing chamber  26  with unchanged mixing ratio from the mixed material flow space  22 , the air content or the atmospheric oxygen content can be reduced compared to the combustion phase, so that the hypostoichiometric mixture in the mixing chamber  26  is then again generated in conjunction with the evaporated hydrocarbon quantity. 
         [0029]    With the present invention, it is possible in a simple manner to distinctly shorten the start phase of the reforming process in a reformer system. Since a heating of the mixed material is ensured both in the start phase and in the normal operating phase, namely either by combustion of same or by heat uptake by the reformer arrangement  14 , the provision of additional heating means for the mixed material to be introduced into the mixing chamber can be eliminated. 
         [0030]    It is a matter of course that the ignition or combustion of the mixed material can take place not only in that area of the mixed material flow space  22 , in which this surrounds the reformer arrangement  14 . Rather, with corresponding structural embodiment, the mixed material could also be ignited and burned already before the introduction to the reformer arrangement in another area, lying upstream, of the mixed material flow space and possibly also still before introduction through the openings  24 , so that the heat forming during the combustion can be transmitted to the reformer arrangement  14  in case of further flow through that area of the mixed material flow space  22 , which can also be seen in  FIG. 1 . 
         [0031]    While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.