Abstract:
A housing containing two or more individual operating components called modules is disclosed. The modules themselves are independently contained in one or more vessels with attendant connectivity structures such as pipes, tubes, wires and the like. Each such vessel or device is configured to conduct at least one unit reaction or operation necessary or desired for generating or purifying a hydrogen enriched product gas formed from a hydrocarbon feed stock. Any vessel or zone in which such a unit operation is conducted, and is separately housed with respect at least one other vessel or zone for conducting a unit operation, is considered a module. Unit reactions or operations include: chemical reaction; combusting fuel for heat (burner); partial oxidation of the hydrocarbon feed stock; desulfurization of, or adsorbing impurities in, the hydrocarbon feed stock or product stream (“reformate”); steam reforming or autothermal reforming of the hydrocarbon feed stock or pre-processed (“reformate”) product stream; water-gas shifting of a pre-processed (reformate) stream; selective or preferential oxidation of pre-processed (reformate) stream; heat exchange for preheating fuel, air, or water; reactant mixing; steam generation; water separation from steam, preheating of reactants such as air, hydrocarbon fuel, and water, and the like.

Description:
RELATED APPLICATION  
       [0001]    The present application claims benefit of the priority of U.S. Provisional Application Ser. No. 60/345,170 filed Dec. 21, 2001. 
     
    
     
       TECHNICAL FIELD  
         [0002]    The present invention relates generally to fuel processors for converting hydrocarbon fuels to a hydrogen-enriched gas or reformate, and in particular, to designs directed to optimizing integration of one or more unit processes desired in reforming including integration of several chemical reactors or modules into a single housing.  
         BACKGROUND OF THE INVENTION  
         [0003]    Electrochemical devices have long been recognized as having advantages over more conventional forms of power generation. Due to the nature of the electrochemical conversion of hydrogen and an oxidant into electricity, the fuel cell is not subject to certain Carnot engine limitations, unlike typical prime movers that generate mechanical work from heat. Though fuel cells can operate on stored hydrogen, fuel cell systems utilizing fuel processors have demonstrated similar advantages utilizing hydrocarbon fuels such as gasoline and methanol, and have certain advantages in terms of storage capacity, weight, and availability of infrastructure. In addition, fuel cell systems operating on hydrocarbon fuels also have a distinct thermal efficiency advantage over traditional devices. Also, emissions such as carbon dioxide, carbon monoxide, hydrocarbons, and oxides of nitrogen are relatively low.  
           [0004]    Despite its potential, however, fuel processor technology has remained largely untapped as a source for hydrogen for fuel cell systems for a variety of reasons. One significant reason is the size and complexity of the overall fuel processor and fuel processor/fuel cell system. In large part, this complexity arises from the need for many chemical conversion steps in going from the chemical energy contained in hydrocarbon fuels to the provision of a hydrogen-enriched gas. For this reason, it has remained very challenging to package entire fuel cell systems into small spaces; for example, in vehicle and portable applications  
           [0005]    One obstacle to making fuel processor systems more compact is the thermal and spatial requirements of the sub-components and the connectivity between various complementary reaction vessels. Furthermore, as these complex systems are made to be more compact, it becomes even more challenging to organize reactors or modules and thermally integrate each piece of the system while maintaining an ability to assemble and service it.  
           [0006]    Classical forms of fuel processors are typically large chemical plants, not subject to severe constraints on weight, footprint, or thermal efficiency. Therefore there is little guidance from such conventional technology and there remains a need for fuel processors that are compact, thermally efficient, and easy to service.  
           [0007]    EP 1 057 780 A2 A assigned to Toyota, discloses an attempt to provide integration of multiple unit operations in a single device (see e.g. FIGS. 39 and 40). The disclosed design provides for sequential process or reaction modules in a reforming process and fuel conditioning process. Reactor or module sections  30  and  62  are connected via a clamped connection. A pipe  66  joins modules  62  to  64  and redirects reformate flow 180 degrees. Reactor module sections  64  and  80  are also connected by a clamp connection. The assembled fuel processor of this Toyota design is difficult to mount under the floor of a vehicle without allowing mechanical strain to be applied to at least some of these joints, including the clamped connections. Housing  61  provides an insulating function but does not appear to stabilize any of the above-discussed connections in any significant way, in particular the connections between modules  30 - 62 ,  62 - 64 , and  64 - 80 , respectively.  
           [0008]    It is also noted that housing  61  is double walled and insulating is carried out by a space defined between the walls of the housing  61 . Accordingly, there is a significant space utilization inefficiency in that unused interstitial space remains between the modules  62 ,  64  and the housing  61 .  
           [0009]    Other approaches having significant degrees of success at providing a fuel processor with optimized thermal and mechanical integration of unit processes are those concentrically arranged, e.g. nested cylinders as disclosed in U.S. Pat. Nos. 6,254,839 and 6,245,303; and WO 00/66487, all assigned to the assignee of this application. However, in certain applications, such as in on-board transportation applications, physical shape and orientation of an integrated reactor can be restricted by the particular design considerations for a particular vehicle. Accordingly, for any given reactor output desired, a concentric design may provide a reactor diameter to reactor length ratio which is not as favorable as a non-concentric design. This consideration may become more pronounced as the degree of integration within a single reactor housing increases towards providing all of the unit operations desired or necessary to provide acceptable quantity and quality of hydrogen for the application.  
           [0010]    The present invention meets the above deficiencies in the art, as well as providing a variety of other benefits and advantages associated with the construction and use of integrated fuel processors.  
         SUMMARY OF THE INVENTION  
         [0011]    According to one aspect of the present invention, a housing contains two or more individual devices. The devices themselves are independently contained in one or more vessels with attendant connectivity structures such as pipes, tubes, wires and the like. Each such vessel or device is configured to conduct at least one unit reaction or operation necessary or desired for generating or purifying a hydrogen enriched product gas formed from a hydrocarbon feed stock.  
           [0012]    For the purposes of the invention, any vessel or zone in which such a unit operation is conducted, and is separately housed with respect at least one other vessel or zone for conducting a unit operation, shall be referred to as a module.  
           [0013]    Unit reactions or operations include: chemical reaction; combusting fuel for heat (burner); partial oxidation of the hydrocarbon feed stock; desulfurization of, or adsorbing impurities in, the hydrocarbon feed stock or product stream (“reformate”); steam reforming or autothermal reforming of the hydrocarbon feed stock or pre-processed (“reformate”) product stream; water-gas shifting of a pre-processed (reformate) stream; selective or preferential oxidation of pre-processed (reformate) stream; heat exchange for preheating fuel, air, or water; reactant mixing; steam generation; water separation from steam, preheating of reactants such as air, hydrocarbon fuel, and water, and the like.  
           [0014]    According to another aspect of the invention, such modules and their attendant connectivity structures present somewhat irregular perimeter geometries and/or present somewhat asymmetric assemblies, while the housing presents a more regular and/or symmetrical cross section and/or perimeter.  
           [0015]    According to another aspect of the invention, the interstitial space among the modules, their attendant connectivity, and the inner surface of the housing, is configured to serve a useful function. Among these useful functions are: (a) providing either a fluid or a solid substance in the interstitial space to insulate the reactors or modules components and/or their connectivity, or to assist in thermal equilibrium among same; (b) flowing fluid through the interstitial space for heat exchange to accomplish heating or cooling of the module or both; (c) providing a flow of fluid through the interstitial space for heat exchange to accomplish heating of the fluid for further use in the system, such as preheating a reactant feed stream; and, (d) providing a granular or monolithic catalyst in the interstitial space and providing a flow of fluid through the interstitial space for reaction on the catalyst.  
           [0016]    According to another aspect of the invention, the housing provides improved mechanical support for the modules.  
           [0017]    According to another aspect of the invention, the housing itself, in particular its end closures provide interconnection of fluid flows among the reactors or modules.  
           [0018]    According to another aspect of the invention, either the housing, or the internal modules and their connectivity, or both, are arranged so that at least one portion of the interstitial space can be fitted with one or more unitary bodies providing for any one of insulation, catalysis, heat exchange or any combination of the above. Preferably these bodies can be made with regular geometries. The bodies may be porous, elongate or cooperatively stacked segments, or combinations of these.  
           [0019]    According to another aspect of the invention, the housing is sized and shaped to provide a least bounding generally regular geometry to bound the modules and their connectivity.  
           [0020]    Prior art designs for fuel processors typically stop at the level of integration of unit functions into a module. The modules are then placed wherever convenient and interconnected as required. We have found instead that when the system is best constructed as comprising more than one module, it is efficient to assemble the modules in a common housing so as to provide a physically integrated unit. The initial motivation for this assembly in a housing was to maintain the units in a fixed relationship to each other, and in some cases to minimize system heat losses. However, we have found that the process of integrating modules in a housing provides many additional unexpected benefits, particularly in the areas of manufacture, ease of repair, and service. The systematic use of design and assembly principles produces an integrated fuel processor that is both highly efficient and easy to assemble and maintain.  
           [0021]    The following are examples of benefits provided by the integrated fuel processor of the invention: more flexibility in selecting the physical shapes of units; e.g., monolithic catalyst supports; better serviceability while retaining a very compact fuel processor. Reactors or modules can be changed out very quickly and replaced as opposed to having to dismantle an entire fuel processor assembly; utilization of the interstitial space as a conduit for flowing a heat exchange medium, including a process gas, for thermal integration of the modules. Alternatively, the interstitial space can be void of any process fluid and may contain insulating materials such as a ceramic fiber blanket. In the first instance, the housing could be a pressurized vessel; in the second instance, the housing would not need to withstand internal pressure and may be vented to the atmosphere. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]    The present invention can be more readily understood with reference to the accompanying drawings, in which like numerals are employed to designate like components throughout the disclosure, and where:  
         [0023]    [0023]FIG. 1 is a first perspective, partially exploded view of a fuel processor in accordance with the present invention having two main modules;  
         [0024]    [0024]FIG. 2 is a cross sectional assembled view taken along line  2 - 2  of the embodiment of the fuel processor shown in FIG. 1;  
         [0025]    [0025]FIG. 3 is a schematic cross sectional side view taken along line  3 - 3  of the embodiment of the fuel processor shown in FIG. 1;  
         [0026]    [0026]FIG. 4 is a second perspective view of the embodiment of the fuel processor shown in FIG. 1 without the common housing and illustrating one embodiment of module attachment to end closures;  
         [0027]    [0027]FIG. 5 is a schematic of another embodiment of a fuel processor in accordance with the present invention having three main modules;  
         [0028]    [0028]FIG. 5A is a cross sectional view taken along line  5 A- 5 A of the embodiment of the fuel processor shown in FIG. 5;  
         [0029]    [0029]FIG. 6 is a drawing (FIG. 39) from EP 1 057 780 A2 disclosing a fuel processor; and  
         [0030]    [0030]FIG. 7 is a drawing (FIG. 40) from EP 1 057 780 A2 disclosing a fuel processor. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0031]    While this invention is susceptible of embodiment in many different forms, preferred embodiments of the invention will be described below in detail with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspect of the invention to the embodiments disclosed. It should also be understood that not every disclosed or contemplated embodiment of the invention needs to utilize all of the various principles disclosed herein to achieve benefits according to the invention.  
         [0032]    FIGS.  1 - 4  disclose a fuel processor  10  for converting hydrocarbon fuel into a hydrogen-enriched gas or reformate. The fuel processor  10  includes two modules  12   a  and  12   b,  each of which is self-contained and configured to conduct a unit operation required for reforming hydrocarbons in the hydrocarbon fuel feed stock. As necessary or desired the fuel processor  10  sufficiently purifies the resulting syn-gas or reformate for its ultimate use, such as integration with a fuel cell (not shown).  
         [0033]    Unit Operation And Orientation Of Modules  
         [0034]    A housing  14  houses two modules, first module  12   a  and second module  12   b.  Each module  12   a,    12   b  is configured to conduct at least one unit reaction/operation required toward a desired yield of hydrogen. The unit reactions contemplated for the example of fuel processor  10  may be carried out by, in a preferred operational order, a burner, a reformer (selected from a partial oxidation (POx) reactor, a steam reformer, or a combination autothermal reformer), a shift reactor (both high temperature and low temperature shift), and a preferential oxidation (PrOx) reactor. All of these unit reactions need not be present or identically arranged with their respective reactor components for all uses. For example, the module  12   a  may include a partial oxidation reaction in section  20  thermally coupled with a steam reforming reaction of the hydrocarbon feed stock (the combination thereof providing autothermal reforming or “ATR”) in section  22 , to generate a reformate. Both a high temperature water-gas shift (HTS) and a low temperature water-gas shift (LTS) reaction may be carried out in two succeeding sections  16  and  18  of module  12   b.    
         [0035]    Modules  12   a,    12   b,  are aligned in parallel and together present a somewhat irregular and interrupted perimeter geometry. The obround housing  14  on the other hand, presents a more regular and/or symmetrical cross section and/or perimeter. The housing  14  is sized and shaped to provide a least bounding generally regular geometry (obround in this case) to bound the side-by-side cylindrical modules  12   a  and  12   b,  according to one aspect of the invention.  
         [0036]    In other embodiments, as with housing  14 , the housing shape is also selected based on its ease of manufacture and the ability to fit the space allocated to the particular fuel processor. Another consideration is whether the housing is to be pressurized. Generally, the housing is sized to provide efficient packaging and serviceability of the modules and associated connections.  
         [0037]    For example, FIG. 5 discloses a fuel processor  11  having three (3) main cylindrical modules  34 ,  36 , and  38  each for conducting distinct unit operations. A least bounding geometry, or right circular cylindrical housing  40 , houses the reactors or modules  34 ,  36 ,  38 . It should be understood that other geometries, for example a triangular cylinder could provide a least bounding regular geometry for housing the three modules  34 - 38 .  
         [0038]    The unit processes contemplated by way of example in fuel processor  11  are; ATR in module  38 ; HTS and LTS successively in module  36 ; and preferential oxidation in one or more stages or thermal gradients in module  34 .  
         [0039]    Interstitial Space  
         [0040]    FIGS.  1 - 3  disclose an interstitial space  24  defined among the modules  12   a  and  12   b  and an inner surface  26  of the housing in fuel processor  10 . FIG. 4 discloses an interstitial space  42  defined among the modules  34 - 36  and an inner surface  44  of a housing  40 .  
         [0041]    [0041]FIG. 1 discloses that a significant portion of the interstitial space  24  of fuel processor  10  is advantageously occupied by insert modules  28 . The inserts  28  conduct a unit operation but advantageously are designed to fit the interstitial space left by housing two cylinders by an obround housing. In other words, the interstitial space  24  defines the vessel in which this unit operation occurs. In one embodiment the inserts  28  are preferably a foam structure which can also provide insulation of the modules  12   a  and  12   b  and heat exchange with the modules  12   a  and  12   b.  In another embodiment, a heat exchanger such as that disclosed in U.S. Ser. No. 60/304,987 may be configured to fit into irregularly shaped interstitial spaces.  
         [0042]    [0042]FIG. 2 discloses a preferred use of the inserts  28  and the interstitial space  24 . In the disclosed embodiment, the foam inserts support one or more catalysts suitable for promoting preferential oxidation of CO in the reformate stream generated by modules  12   a  and  12   b.    
         [0043]    It is contemplated that in other embodiments fuel processors such as  10  or  11  having corresponding interstitial spaces such as  24  or  42  could: (a) permit routing of individual conduits configured to exchange heat with a fluid in the interstitial space and/or the modules, or both, such as for preheating a feed stock in the conduit; (b) be configured as in fuel processor  10  to itself substantially define a conduit for a fluid flow fluid for heat exchange with the modules including heat exchange modules; (c) house one or more solid substances to insulate all or part of the modules and/or their connectivity; or (d) house a granular catalyst or absorbents or adsorbents pretreatment of feed stock or a post-treatment of reformate. Of course, interstitial space  42  of fuel processor  11  could be configured to contain foam inserts, such as inserts  28  and function in a similar manner, albeit the inserts having a slightly different shape.  
         [0044]    Mechanical Connection  
         [0045]    FIGS.  1 - 4  disclose the unique structural integrity, modularity, and fluid connectivity provided by utilization of the principles of the invention. FIG. 4 in particular, discloses the fuel processor  10  without its housing  14 . In this view is can be seen that the modules  12   a,    12   b  are fixed by end closures  30 , 32  in secure alignment with each other, and with respect to the perimeter where housing  14  will reside. Because the modules  12   a,    12   b  are secured, the inserts  28  are easily stabilized by having a shape that inter fits within an interstitial space between the modules  12   a,    12   b  and the housing inner surface  26 .  
         [0046]    Fuel processor  11  (FIG. 5) is constructed in a similar manner, whereby the modules  34 - 38  are secured in proper alignment by connection to end closures  46  and  48 .  
         [0047]    In other embodiments, it is contemplated that added support for the modules could be provided by spacers placed between the modules or the inner surfaces of the housings  14  and  40  of the fuel processors  10  and  11 . Such spacers may be in the form of discrete mechanical shims, brackets or the like, or could be comprised of sheets of metal foam, mesh, expanded metal, dimpled metal or screen so as not to displace fluid or restrict fluid flow.  
         [0048]    In other embodiments it is contemplated that mechanical stability will be increased if the modules are cross-braced or otherwise supported against each other. It may also be convenient to shape the housing so that when it is fitted down over the modules, contacts or attachments between the modules and the inside of the housing increase the mechanical stability of the modules with respect to each other and to the cover.  
         [0049]    In general, according to the invention, when modules are secured to end caps/closures and are provided with internal spacing support when required, then the integrated fuel processor does not place any strain on the seals connecting the modules.  
         [0050]    Fluid Communication Between Modules  
         [0051]    [0051]FIGS. 1, 3,  4  and  5 , disclose the advantageous interconnection of fluid flows among the modules  12   a ,   12   b,  and the interstitial space  24  as disclosed in FIGS.  1 - 3  and provided by the invention.  
         [0052]    In fuel processor  10 , a raised cross-over manifold  50  integral with end closure  30  interconnects one end of each of modules  12   a  and  12   b  for flow of reformate as shown in FIG. 2. Likewise, an embedded channel-type cross over manifold  52  is integral with end closure  32  for providing fluid communication between module  12   a  and the interstitial space  24 , in the manner disclosed in FIG. 2. While these fluid manifolds are disclosed as relatively integral with end closures  30 ,  32  it is contemplated that any suitable pipe, conduit or the like may be suitably attached to, or otherwise integrated into an end closure to receive benefits according to the invention.  
         [0053]    An outlet pipe  54  is provided on end closure  30  for exiting hydrogen enriched product gas and for connection with appropriate external routing to an end use, such as a fuel cell. Inlet port  56  is provided on end closure  32  for supplying fuel, fuel and steam, fuel and water, and oxygen, or any combination thereof as desired for carrying out the reforming process desired in module  12   b.    
         [0054]    [0054]FIG. 4 discloses that the modules  12   a,    12   b  are connected to end closure  32  by bellows connectors  58  and  60 . These connectors advantageously provide stable alignment of the modules while permitting relative longitudinal expansion and contraction of the modules versus the housing  14  during thermal excursions of the fuel processor  10 .  
         [0055]    [0055]FIG. 5 discloses fluid connectivity into, out of, and within the fuel processor  11  in a like manner to that of fuel processor  10 . This is accomplished through manifolds  62  and  66  on end closures  46 , 48  respectively and inlet  68  and outlet  64  on end closures  48 ,  46  respectively.  
         [0056]    In general a further advantage of the combination of the housing and the mani-foldbearing end closures is that assembly is markedly simplified. A significant fraction of the required “plumbing” (interconnections among fluid flows) can be built into the manifolds (and into the modules), so that many fewer individual connections will be required to assemble a fuel processor.  
         [0057]    To that end, passages may be provided in the end units, or other portions of the processor, in any known way. These includes machining, forming, stamping, drilling, or welding or brazing of other structures onto the end caps, and combinations of these. The passages will be provided with fittings into or onto which the modules may be affixed. Means of fixation of modules on the end fittings or the manifolds attached to them can also be any known in the art, with due regard for the nature, pressure and temperature of the fluids to be passed through the manifold.  
         [0058]    Modularity  
         [0059]    As can clearly be seen in view of the above disclosures, the modules  12   a,   12   b  of fuel processor  10  and  34 - 38  of fuel processor  11 , can be easily assembled and replaced by removal of either one or both of the end closures ( 30 ,  32  or  46 ,  48 ) of the respective housings  14  and  40 . This is due in one respect to the convenient arrangement of the physical vessels comprising the modules. It is also due in another respect by the convenient grouping of unit functions into a particular module. For example, certain catalysts may be poisoned more readily by certain contaminants than others, certain catalysts may have a shorter operational life than others, etc. Thus, in the present designs, catalysts for HTS can be removed without removal of the ATR module or its catalyst section and vice versa. Likewise, the choice of which catalysts to put together in a module can be optimized according to expected needs for changing during operation.  
         [0060]    This also highlights the linear concentric modularity of module sections, such as sections  16  and  18  (HTS and LTS, respectively) and  20 , 22  (partial oxidation and steam reforming). The modules  12   a,   12   b  can in a desired embodiment separate into sections and hence even a section of a module may be easily assembled or removed and replaced by simple removal of the end closures.  
         [0061]    In general, according to the invention, for efficiency, several functional units may be integrated into a single module, but it is not always practical, or even desirable, to integrate the entire system into a single module. Considerations affecting the degree of modularity include ease of assembly and repair, replacement of consumables, thermal compatibility, and system efficiency.  
         [0062]    All modules can contain one or more of catalysts, catalytic reaction zones, adsorbents, heat exchangers, mixers, or other units. These are fully contained within a given module or sections thereof. However, according to the invention, the interstitial space not taken up by a self-contained module, may contain these individual items or assist in these functions as desired for a particular design. Leak-tight modules such as heat exchangers that can assume odd shapes to fill voids can be also used.  
         [0063]    Heat Exchange Configurations  
         [0064]    As disclosed with respect to fuel processors  10  and  11 , in modular configurations, individual modules may contain more than one unit function integrated into the module. For example, it is usually expedient (although not required in the invention) to integrate the heat-absorbing steam reforming reaction into a module so as to provide direct contact with available heat emitting reactions, particularly partial oxidation units, auxiliary heat burners, exothermic reactions, autothermal reactions, burners and/or high temperature water gas shift units; and to combine these with integrated heat exchange means. On the other hand, lower temperature reactions may expediently be placed in separate modules, or in a common second module.  
         [0065]    Heat exchanger modules typically transfer heat from hot components, such as the exhaust of a catalytic burner and the reformate, to components requiring preheating, such as water requiring conversion to steam, or fuel requiring vaporization.  
         [0066]    Additionally, modularization increases the efficiency of heating elements that are disposed between the inner surface of a thermally insulated module wall and an element requiring heating, such as a steam reformer. A heater such as a burner, when employed as an ignition source, will operate much more efficiently, particularly if its exhaust can be used as a needed auxiliary heat source or thermal insulator. After running the fuel processor for a short while, the burner&#39;s ignition source can often be extinguished when the burner material attains a sufficiently high temperature to ignite incoming reactants. Accordingly, in other embodiments of the invention a fuel processor comprising a partial oxidation module or and ATR module, can include a burner the exhaust of which can be flowed in the interstitial space to heat a thermal conductor which is disposed about the module, and, optionally, contacts by direct convection the module.  
         [0067]    In other embodiments, anode waste gas from a fuel cell can be fed to a module to assist reforming, or it can be fed to a burner incorporated into a module, or it can be directed through an interstitial space between modules for heat exchange, or a combination of these.  
         [0068]    Method  
         [0069]    As best disclosed in FIG. 2, a method of reforming hydrocarbon fuels in fuel processor  10  according to the invention includes conducting a first unit operation on a reaction stream flowing in a first direction in module  12   b,  and generating a reformate from a first unit operation, ATR. At the same time, reformate is flowed in a second direction through module  12   a  while conducting a second unit operation water-gas-shift. The flow direction through these modules  12   a,   12   b  is in opposite directions.  
         [0070]    Residence time of reactants in a reactor section (module or sub-component of a module) e.g. in the flow through a catalyst bed, (such as is the case with catalytic partial oxidation, steam reforming, autothermal reforming, water-gas-shift, and preferential oxidation), is a significant factor in efficacy and efficiency of a fuel processor. The length of a such reaction zone or reactor is a significant factor in determining residence time. (Other factors influencing residence time, or its inverse, space velocity, include pressure, bed cross sectional area, and pore volume of the catalyst bed. Advantageously according to the invention, the total residence time of reactants flowing through all of the unit operations of fuel processor  10  can be twice as long as a fuel processor of equivalent overall length, i.e. from end closure to end closure. Put another way, if modules  12   a  and  12   b  were not packaged side by side but in a linear succession, the fuel processor  10  would have to be approximately twice as long. For some applications, such a configuration would be unsuitable. The structural integrity too, of such a linearly aligned processor would be likely compromised by comparison.  
         [0071]    The above advantage is multiplied in fuel processor  10  by use of the interstitial space  24  as a vessel for conducting the unit operation of preferential oxidation. This use of common housing  14  for non-concentric reaction zones reduces overall length of fuel processor  10  by approximately a factor of three (3) with respect to the modules contemplated in fuel processor  10 .  
         [0072]    It is also contemplated that further method or process advantages will be achieved by providing a common housing for at least two non-concentrically aligned modules wherein the interstitial space is used as a vessel for simultaneously exchanging heat among, a heat exchange fluid flowing in either one of the first or second directions in connection with both the first and second unit operations. In particular a process advantage is achieved where the heat exchange fluid is reformate generated in the second unit operation, and more particularly when catalyzing a reaction in the heat exchange fluid by flowing the fluid through a catalyst while simultaneously exchanging heat. In particular, such a process is disclosed in fuel processor  10  as conducting preferential oxidation on porous monolithic supports  28  aligned in the direction of flow of the heat exchange fluid.  
         [0073]    Method Of Constructing A Fuel Processor  
         [0074]    As disclosed in FIGS.  1 - 5 , the present invention provides advantages in the manufacture and maintenance of a fuel processor. Specifically processes for making a fuel processor include providing at least two modules configured to conduct at least one distinct unit operation each and aligning the modules non-concentrically. The process also includes housing the modules in a common housing and securing each module proximate its opposite ends to, or proximate to, an end closure of the housing.  
         [0075]    As also disclosed in FIGS.  1 - 5 , another aspect of a process according to the invention is configuring the fuel processor so that an interstitial space among the modules and the housing can be used as a vessel or conduit for useful work, such as for performing a unit operation therein without the need for further modularization or the provision of further vessels.  
         [0076]    Although this specification discloses, illustrates, and describes specific embodiments, numerous modifications come to mind without significantly departing from the spirit of the invention. The scope of the protection is limited only by the scope of the accompanying claims.