Abstract:
A combustion system is for generating energy by the combustion of a fuel, using a combustion device, such as, for example, a gasoline or diesel engine. An emission control system is provided for converting exhaust gas components using an automotive fluid, by the use of which energy, that is relatively environmentally protective and made available for varied applications. At least one hydrogen generating unit is provided for converting the automotive fluid at least partially into an hydrogen-containing fuel.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0001]    The present application claims priority to Application No. 102 19 799.7, filed in the Federal Republic of Germany on May 3, 2002, which is expressly incorporated herein in its entirety by reference thereto.  
         FIELD OF THE INVENTION  
         [0002]    The present invention relates to a combustion device for generating energy by burning a fuel, having a combustion device and an emission control system.  
         BACKGROUND INFORMATION  
         [0003]    In line with the advancing state of knowledge, legal requirements, for the protection of health and the environment, which regulate the emission from motor vehicles or other combustion machines, are constantly being intensified. To fulfill these requirements, various different measures may be taken up, for example, for vehicles.  
           [0004]    Up to now, for instance, even for exhaust-gas treatment, such as for lean exhaust gases of vehicles, the so-called “Selective Catalytic Reduction Method” (SCR method) may be used for the removal of nitrogen oxides (NO x ). In this connection, the reducing agent ammonia (NH 3 ), with nitrogen oxides of the exhaust gas, may be selectively converted to nitrogen and water. For instance, ammonia for performing the SCR method may be stored directly on board, using pressure liquefaction. There may be an attempt to generate NH 3  from a urea-water solution in a hydrolysis catalyzer upstream from the SCR catalyzer.  
           [0005]    Beyond that, requirements such as increasing safety and/or luxury may increase, so that additional assemblies may establish themselves more and more, such as in motor vehicles. However, in order to fulfill their function, these respective assemblies may need electrical energy, which therefore may need to be additionally supplied. According to conventional methods, supplying the correspondingly required energy may be connected with an increase in fuel usage and/or emissions relevant to the environment.  
         SUMMARY  
         [0006]    An example embodiment of the present invention may provide a combustion device for generating energy via the combustion of a fuel, having a combustion unit, such as, for example, a gasoline or diesel engine, and an emission control system for converting an exhaust gas component with an automotive fluid, using which, relatively environmentally protective energy may be supplied for various different applications.  
           [0007]    According to an example embodiment of the present invention, the combustion device may include at least one hydrogen generating unit for converting the automotive fluid at least partially to a hydrogen-containing fuel.  
           [0008]    With the aid of these exemplary measures, the first automotive fluid already present may be convertible into an hydrogen-containing fuel or rather, an additional, second automotive fluid and a residual material that may be as environmentally protective as possible. By using an appropriate storage unit, the generation of the hydrogen-containing fuel may be decoupled from its use, and stored in it temporarily.  
           [0009]    Alternatively or in combination with this, an energetic conversion of the hydrogen-containing fuel may be provided. In an example embodiment of the present invention, at least one hydrogen utilization unit for utilizing the hydrogen-containing fuel may be provided. Hydrogen may be used energetically in various different manners, such as, for example, in an environmentally protective manner. For example, hydrogen may be utilized further energetically by using a catalytically active burner, a separate combustion engine or a fuel cell for the combustion of the hydrogen-containing fuel.  
           [0010]    In the case of a combustion device according to an example embodiment of the present invention, a separate combustion engine may be provided for the combustion of the automotive fluid. By doing this, the automotive fluid may be utilized energetically in the alternative manner mentioned above.  
           [0011]    To generate electrical energy, an electric generator may be connected to one of the separate internal combustion engines or the like. The electrical energy may, for example, be used to supply subsidiary assemblies of the vehicle. The hydrogen utilization unit may be configured as a fuel cell system for generating electrical energy so that, for example, a so-called auxiliary power unit system (APU system) may be implemented for the electrical supply of subsidiary assemblies of a vehicle, etc.  
           [0012]    According to an example embodiment, at least one storage unit for storing electrical energy may be provided, so that a decoupling of the electrical energy generation from the energy use may be implemented. This may, for example, have the effect of a dimensioning of the process steps or systems components, just upstream, as, for instance, an automotive fluid supply, hydrogen generation, etc.  
           [0013]    In an example embodiment of the present invention, the automotive fluid at least partially includes ammonia. Using this measure may make it possible to use the already usual, so-called SCR method in accordance with the present invention. Accordingly, one may revert to a method that has proven itself, including corresponding components, whereby operating safety may be improved and a particularly economically favorable development of the present invention may be implemented.  
           [0014]    In an example embodiment of the present invention, at least one automotive fluid generating unit is provided for generating the automotive fluid from a starting substance. The separate automotive fluid generating unit may have a catalytically active configuration and/or a heating device for converting the starting substance into the automotive fluid. For example, the automotive fluid and/or the starting substance may be able to be at least partially converted to ammonia. The generation of the ammonia may be performed by the hydrolysis or thermolysis of the starting substance external to and/or internal to the exhaust branch.  
           [0015]    The starting substance may be at least partially developed as a urea-water solution, solid urea, ammonium carbamate, isocyanic acid, etc. The starting substance may be jacketed by or mixed with a carrier substance for better handling. At least one storage device may be provided for storing the starting substance.  
           [0016]    The mostly solid and/or liquid starting substances may be separated from the gaseous products, such as ammonia, carbon dioxide and/or water vapor, etc., using a separating device.  
           [0017]    As an example, when using a urea-water solution (HWL), the automotive liquid generating unit may be implemented as a comparatively simply configured, heatable reaction chamber.  
           [0018]    The hydrogen generating unit may include at least one heating device for heating the automotive liquid. With the aid of the heating device according to an example embodiment of the present invention, ammonia, for instance, may be converted by thermolysis into hydrogen and nitrogen. In this connection, the thermal conversion or decomposition of the ammonia may occur at temperatures of approximately 500° C., in the presence of suitable catalysts. For this, for example, iron-based and/or ruthenium-based catalysts may be used. In the case in which, for example, ammonia is generated from a starting substance, in which carbon dioxide and water may be created as by-products, the reaction equilibrium in the thermolysis of ammonia may not be significantly changed hereby. If required, the catalysts to be used for this may be appropriately adjusted.  
           [0019]    In addition, non-converted components of the starting substance or of ammonia may not have an undesired effect on a subsequent hydrogen conversion, that may be provided, in a fuel cell system or combustion device according to an example embodiment of the present invention.  
           [0020]    In an example embodiment of the present invention, at least one metering element may be provided for metering the automotive fluid to the emission control system and/or to the hydrogen generating unit. With the aid of such a metering element, a separate regulation and/or control of the individual automotive liquid(s) or hydrogen-containing fuel flows may be implemented in dependence upon the requirement of the respective user.  
           [0021]    Furthermore, using an appropriate metering element, the automotive liquid generation may be adjusted to the largely independent user, i.e., above all to the emission control system and the hydrogen generating unit For example, a partition of the starting substance stream into at least two partial streams occur with the aid of the appropriately regulated metering element or valve.  
           [0022]    The control of the metering element may occur using a control unit in which, for example, the size or quantity of the partial streams may be ascertained, among other things, with the aid of corresponding sensors or consumption rates.  
           [0023]    In addition, using the appropriate control unit, a summing formation of the partial streams of the starting substances may be performed, so as to ascertain the overall requirement. At this time, in vehicle applications, it may already be conventional to determine the partial stream for the SCR method according to an algorithm. The partial stream for generating electrical energy may be determined, for example, from the electrical energy requirement of the entire system, or rather, of the vehicle. The latter may have also already become conventional, by using a so-called vehicle electric system management system in current motor vehicles. Consequently, for ascertaining the partial streams or the overall requirement, one may refer to already usual components, whereby an economically favorable example embodiment of the present invention may be implemented.  
           [0024]    In a further example embodiment of the present invention, the fuel cell system may be arranged upstream of the emission control system, as seen in the flow direction of the automotive fluid or fuel. The hydrogen generating unit arranged in the flow direction of the automotive fluid, upstream of the fuel cell system, may, on account of this measure, convert, if required, only a certain proportion of the overall automotive fluid flow to a hydrogen-containing fuel flow. Hence, a substance mixture may flow out from the hydrogen generating unit which includes both the automotive fluid or ammonia and the hydrogen-containing fuel in proportions.  
           [0025]    A correspondingly operated hydrogen generating unit, in which only a proportional or partial conversion of the automotive fluid occurs, may, for example, be implemented, from a process engineering point of view, compared to an almost complete conversion. Because of this, the hydrogen generating unit may be developed and operated in a manner that may be economically more favorable.  
           [0026]    The hydrogen contained in the substances mixture may be converted into electrical energy in the fuel cell system. According to this example embodiment of the present invention, the automotive fluid and the ammonia may subsequently be used in the emission control system, arranged serially downstream from the fuel cell system, for the conversion of the exhaust gas components and for nitrogen oxide reduction.  
           [0027]    In an example embodiment of the present invention, the hydrogen utilization unit may be configured as the combustion device. With the aid of this measure, for example, the hydrogen generated may usable for a cold-starting phase and/or a full-load phase of the combustion device. Therefore, environmentally relevant exhaust gas emissions may be reduced in the starting phase and/or in full-load operation.  
           [0028]    According to an example embodiment of the present invention, both nitrogen oxide emissions and carbon dioxide emissions may be reduced, for example, by using a so-called APU.  
           [0029]    By conversion of the hydrogen-containing fuel from ammonia, a carbon monoxide-poor fuel may be generated. Currently used fuel cells, including low temperature fuel cells such as so-called PEM fuel cells, etc., may have an improved cold-starting behavior but may react to carbon monoxide by impairment of the operation, or rather, by a so-called “poisoning” of the diaphragm. According to an example embodiment of the present invention, costly reforming and/or cleaning methods may not be required for corresponding fuel cell systems. Because of this, the constructive and economic expenditure for putting into use the present invention may become comparatively low.  
           [0030]    An exemplary embodiment of the present invention is illustrated in the drawing and is described below with reference to the drawing. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0031]    [0031]FIG. 1 is schematically a block diagram of a combustion device according to an example embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0032]    According to FIG. 1, exhaust gases  2  of an internal combustion engine  1  are nitrogen oxide-controlled, using an SCR catalytic converter  62 . To do this, an ammonia stream  26  is metered into exhaust gas stream  2  using an ammonia metering device  30 , and may be mixed with it. Metering device  30  includes, in particular, a metering element  31  for setting the amount of ammonia supplied to exhaust gas stream  2 . Metering device  30  also includes a mixing unit, so that an almost uniform mixing or turbulence and/or diffusion of ammonia stream  26  with exhaust gas stream  2  may be achieved. The mixing device may, for example, be configured as a so-called static mixer.  
         [0033]    In addition to SCR catalytic converter  62 , if required, an oxidation catalytic converter may be provided upstream of metering device  30 , as seen in the flow direction, and an ammonia blocking catalytic converter is provided post-connected to this.  
         [0034]    With the aid of an ammonia generating unit  10 , by conversion of a starting substance  15  or first automotive fluid, such as HWL, ammonium carbamate, etc., stored in a reservoir  14 , ammonia  26 ,  28  is generated in a reactor  12 . When HWL is used, reactor  12  may be configured as a comparatively simple, heatable container  12 .  
         [0035]    Besides the chemical conversion of a starting substance  15  for generating the ammonia  26 ,  28 , desorption from ammonia storage media or synthesis as ammonia generating process  10  may also be used.  
         [0036]    The ammonia generated using reactor  12  as illustrated in FIG. 1 is divided into the two partial streams  26  and  28 , for example, by a regulatable valve  22 . Valve  22  may be controlled by using a control unit  24 . Control unit  24  is a component of control device  20  which is provided for dividing up the ammonia-containing product stream into partial streams  26  and  28 , and, if required, is a component of a vehicle electric system management system that may already be present in vehicles.  
         [0037]    Partial stream  28  is supplied to a hydrogen generator  40  and/or to an ammonia engine according to an example embodiment of the present invention. In hydrogen generator  40 , ammonia  28  is, above all, converted by thermolysis to hydrogen  44  and nitrogen. Components such as carbon dioxide and/or water, generated by reactor  12  and may also be contained in ammonia stream  28 , may not change the equilibrium of the reaction in hydrogen generator  40  significantly. The possibly provided catalytic configuration of hydrogen generator  40  is to be selected appropriately.  
         [0038]    In the flow direction after hydrogen generator  40 , according to FIG. 1, a fuel cell system  50  is provided for generating electric energy. This includes an electric storage unit  54 , for instance, and an accumulator and/or an element having relatively high electrical capacity. For example, in a layout of a system for an operating point at which there is a requirement of ca 0.5 kW in electrical terms, at a fuel cell efficiency of approximately 50%, approximately 2.4 g NH 3 /min may be made available.  
         [0039]    According to an example embodiment of the present invention, fuel cell system  50  may be positioned serially between hydrogen generator  40  and SCR catalytic converter  62 . To make this example embodiment of the present invention more clear, connection  5 , which is optionally to be provided, is illustrated schematically. In this case, there may be no division of the ammonia-containing substance stream into partial streams  26  and  28  using control device  20 , but a metering of the quantity of ammonia stream  28 . That is, partial stream  26  is omitted.  
         [0040]    The direct coupling of the chemical processes, above all in reactors  12 ,  40  among each other, and these, in turn, with the two different users  50 ,  62 , having changing dynamics, may require a comparatively high regulating expenditure and, in general, a larger dimensioning of the respective aggregates. For this reason it may be desired to provide appropriate storage elements between the different reactors  12 ,  40  and between reactors  12 ,  40  and users  50 ,  62 . To these storage units one may assign, if required, loading and/or unloading devices such as pumps, control or regulating elements, etc. For reasons of clarity, according to FIG. 1, a storage device  54  is illustrated only for current generation  50 .  
         [0041]    By the combination of several storage units and appropriate regulating strategies, one may uncouple subsystems  10 ,  20 ,  40  and  52  from the dynamics of users  50 ,  62 .  
         [0042]    By using a hydrogen storage between hydrogen generator  40  and fuel cell system  50 , the size and weight of electrical storage  54  may be reduced or it may possibly be completely avoided.  
         [0043]    The requirement for ammonia  26  for the SCR method in SCR catalytic converter  62  may be subject to strong temporal fluctuations, because the NO x  quantity in exhaust gas  2  changes, and with that the ammonia requirement within the range of seconds, on account of the dynamics of internal combustion engine  1 . In order to implement a system having corresponding ammonia dynamics, quantity metering  30  may be positioned as close as possible to the metering location.  
         [0044]    A pressure reservoir, such as, for example, one having a pump, etc., may be positioned upstream of metering device  30 , as seen in the flow direction of ammonia stream  26 . In corresponding systems having an almost constant pressure level, operation of a gas valve  31 , or rather the metering of ammonia stream  26  into exhaust gas  2  may be improved.  
         [0045]    To control valve  22  and ammonia generating system  10 , the pressure in the pressure reservoir mentioned before may be used as the controlled variable. To do this, one may, connect a pressure sensor of the storage system to control unit  24 .  
       LIST OF REFERENCE NUMERALS  
       [0046]    [0046] 1  combustion engine  
         [0047]    [0047] 2  exhaust gas  
         [0048]    [0048] 5  connection  
         [0049]    [0049] 10  NH 3  generator  
         [0050]    [0050] 12  reactor  
         [0051]    [0051] 14  reservoir  
         [0052]    [0052] 15  starting substance  
         [0053]    [0053] 20  control system  
         [0054]    [0054] 22  valve  
         [0055]    [0055] 24  control unit  
         [0056]    [0056] 26  ammonia stream  
         [0057]    [0057] 28  ammonia stream  
         [0058]    [0058] 30  metering device  
         [0059]    [0059] 31  metering element  
         [0060]    [0060] 40  H 2  generator  
         [0061]    [0061] 44  hydrogen  
         [0062]    [0062] 50  fuel cell system  
         [0063]    [0063] 52  fuel cell  
         [0064]    [0064] 54  reservoir  
         [0065]    [0065] 62  SCR catalytic converter