Abstract:
A chemical reactor comprises a flow channel, a source, and a destination. The flow channel is configured to house at least one catalytic reaction converting at least a portion of a first nanofluid entering the channel into a second nanofluid exiting the channel. The flow channel includes at least one turbulating flow channel element disposed axially along at least a portion of the flow channel. A plurality of catalytic nanoparticles is dispersed in the first nanofluid and configured to catalytically react the at least one first chemical reactant into the at least one second chemical reaction product in the flow channel.

Description:
STATEMENT OF GOVERNMENT INTEREST 
     This invention was made with government support under Contract No. DE-FC36-09GO19006 awarded the Department of Energy. The government has certain rights in the invention. 
    
    
     BACKGROUND 
     This specification relates generally to fluids in flow channels, and more specifically to catalytic reactions of fluids in flow channels. 
     Chemical reactions can take place in any number of reactors suited to control the rate and parameters. Reactions can take place in vessels, fluidized beds, etc. In some instances, there is little available operational space to include a separate reactor vessel. Further, due to time, space, and/or safety considerations, it may be undesirable to store certain reaction products for any length of time. This is the case, for example, in motorized vehicles. 
     SUMMARY 
     A chemical reactor comprises a flow channel, a source, and a destination. The flow channel is configured to house at least one catalytic reaction converting at least a portion of a first nanofluid entering the channel into a second nanofluid exiting the channel. The flow channel includes at least one turbulating flow channel element disposed axially along at least a portion of the flow channel. The source is in fluid communication with an entrance of the flow channel and configured to contain at least one first chemical reactant serving as a first base fluid for the first nanofluid. The destination is in fluid communication with an exit of the flow channel receiving at least one second chemical reaction product serving as a base fluid for the second nanofluid. A plurality of catalytic nanoparticles is dispersed in the first nanofluid and configured to catalytically react the at least one first chemical reactant into the at least one second chemical reaction product in the flow channel. 
     Optionally, the turbulating flow channel element is compressible and resiliently secured in the flow channel. 
     The turbulating flow channel element optionally includes a plurality of individual thermally conductive turbulator elements secured to one another and nonuniformly distributed generally around a central axis of the flow channel. 
     The turbulating flow channel element is optionally a flexible screw auger. 
     At least some of the plurality of catalytic nanoparticles optionally comprise a substantially pure metal or a metal alloy containing at least one metal selected from the group: nickel, platinum, iridium, and palladium. 
     At least some of the plurality of catalytic nanoparticles optionally comprise a substantially pure metal or metal alloy containing nickel. 
     At least one outer surface of the turbulating flow channel element optionally includes a porous, chemically inert, and thermally conductive coating. 
     The optional porous, chemically inert, and thermally conductive coating optionally comprises aluminum oxide (Al 2 O 3 ) 
     The optional porous, chemically inert, and thermally conductive coating optionally comprises polytetrafluoroethylene (PTFE) 
     A fuel system can optionally comprise an embodiment of the chemical reactor, wherein optionally the source is a fuel tank, the at least one first chemical reactant includes a vehicle fuel existing in a first chemical form, the at least one second reaction product is a vehicle fuel existing in a second chemical form, and the destination is a motive engine configured to derive motive power from the second chemical form of the vehicle fuel. 
     The first reactant form of the fuel for the fuel system can optionally comprise at least one type of hydrocarbon. 
     The first reactant form of the fuel for the fuel system can optionally comprise an endothermic fuel suitable for hypersonic or near-earth aerospace vehicles. 
     In the fuel system, the catalytic reaction is optionally a thermal cracking reaction. 
     In the fuel system, the first reactant form of the fuel optionally comprises a hydride. 
     In the fuel system, the hydride optionally comprises ammonia borane (NH 3 BH 3 ). 
     In the fuel system, the hydride optionally comprises alane (AlH 3 ). 
     In the fuel system, the hydride optionally includes at least one hydrogen-charged carbon boron-nitrogen heterocycle material. 
     In the fuel system, the second chemical form of the fuel optionally includes hydrogen (H 2 ). 
     In the fuel system, at least some of the plurality of catalytic nanoparticles optionally comprise a substantially pure metal or a metal alloy containing at least one metal selected from the group: nickel, platinum, iridium, and palladium. 
     A method of providing vehicle fuel to a motive engine comprises adding a plurality of catalytic nanoparticles to a fuel existing in a first chemical form to form a first fuel nanofluid. The first fuel nanofluid is flowed through a flow channel having a turbulating element secured therein. The flow channel forms at least part of a system providing fluid communication between a fuel tank and a motive engine. The flow channel also houses a first chemical reaction converting the first nanofluid into a second nanofluid facilitated by the plurality of catalytic nanoparticles. The second nanofluid includes at least one reaction product includes a fuel existing in a second chemical form that is suitable for use in a second chemical reaction powering the motive engine. 
     The method optionally further comprises adding or removing heat from the flow channel for controlling the reaction rate in the flow channel. 
     The method optionally includes adding heat to the flow channel that is derived from the second chemical reaction in the motive engine. 
     In the method, the first chemical form of the fuel optionally comprises at least one type of hydrocarbon. 
     In the method, the first chemical form of the fuel optionally comprises a hydride. 
     In the method the fuel existing in a second chemical form optionally comprises hydrogen (H 2 ). 
     When the fuel existing in a second chemical form comprises hydrogen (H 2 ), the method optionally further comprises the step of separating at least a portion of the converted hydrogen (H 2 ) from a remainder of the second nanofluid prior to using the hydrogen in the second chemical reaction. 
     When the fuel existing in a second chemical form comprises hydrogen (H 2 ), and the method further comprises the step of separating at least a portion of the converted hydrogen (H 2 ) from a remainder of the second nanofluid prior to using the hydrogen in the second chemical reaction, the motive engine is optionally an internal combustion engine. 
     When the fuel existing in a second chemical form comprises hydrogen (H 2 ), and the method further comprises the step of separating at least a portion of the converted hydrogen (H 2 ) from a remainder of the second nanofluid prior to using the hydrogen in the second chemical reaction, the motive engine is optionally at least one electric motor driven at least in part by electrical power provided via the second chemical reaction of the hydrogen taking place in a hydrogen fuel cell. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a flow diagram of a chemical reaction. 
         FIG. 2A  depicts a fluid, a flow channel, and flow channel element. 
         FIG. 2B  is a magnified view of a portion of  FIG. 2A . 
         FIG. 2C  shows a radial cross-section of the flow channel with the flow channel element and the nanofluid. 
         FIG. 3  shows a reaction flow diagram for a fuel system. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  includes chemical reactor system  10 , first reactant source  12 , nanofluid transport channel  14 , transport channel element  16 , second reaction product destination  18 , first inlet nanofluid  20 A, and second outlet nanofluid  20 B.  FIG. 1  is a simplified, generic flow chart of chemical reactor system  10 . Transport channel  14  provides fluid communication between first reactant source  12  and second reaction product destination  18 . Transport channel element  16  is disposed in transport channel  14 . 
     As will be explained in more detail below, first inlet and second outlet nanofluids  20 A,  20 B include a plurality of catalytic nanoparticles dispersed in a fluid base. During transport from source  12  to destination  18 , one or more reactants (from source  12 ) contained in nanofluid  20 A simultaneously undergo at least one desired chemical reaction to form at least one reaction product forming at least a part of nanofluid  20 B. In conjunction with the catalytic nanoparticles (not shown in  FIG. 1 ), transport channel element  16  helps facilitate one or more catalytic reactions of inlet nanofluid  20 A into outlet nanofluid  20 B. The catalytic reaction(s) can be endothermic or exothermic, and configured to proceed at an easily controllable rate during transport through channel  14 . In the event that the catalytic reaction is endothermic or exothermic, temperatures inside channel  14  can be managed by respectively adding or removing thermal energy Q from nanofluid  20 . This can be done either by controlling the initial fluid temperature proximate source  12 , and/or by thermally conducting thermal energy Q into or out of nanofluids  20 A/ 20 B via channel  14  and element  16 . 
     Element  16  evenly disperses and controls the flow and thermal profile of nanofluids  20 A/ 20 B across channel  14 , including adjacent the channel walls. This arrangement also saves the space and time of having separate reactor vessels and transport channels. Transport channel  14  with element(s)  16  can be adapted to any number of applications. As  FIG. 1  shows a very generic representation of channel  14  and reactor  16 , source  12  and destination  18  will depend on the particular application of reactor system  10 . In certain example embodiments, system  10  is part of a fixed in place plant. In certain of these examples, source  12  can be a feedstock or storage tank, while destination  18  can represent the final plant outlet. It will also be recognized that source  12  and/or destination  18  can alternatively be the respective beginning or end of one or more intermediate plant subsystems. It will also be recognized that certain elements specific to individual systems have been omitted for clarity. Examples of such equipment can include but are not limited to separators, filters, valves, return/recycle lines, etc. 
     In certain other embodiments, system  10  can be all or part of a fuel system installed onto a motorized vehicle. The stored fuel or feedstock existing in a first chemical form at source  12  can be converted into a usable fuel or fuel precursor having a second chemical form during transport to destination  18 . Here, the second chemical form of the fuel is directly usable by a motive engine at destination  18  to produce motive power. An example of this type of embodiment is shown and explained with respect to  FIG. 3 . 
       FIG. 2A  depicts flow channel  14 , transport channel element  16 , reactant nanofluid  20 A, reaction product nanofluid  20 B, outer turbulator elements  22 , and central wire element  24 . Channel  14  can be the interior of any path such as a standalone pipe or tube, including one or more fuel lines. Standalone channel  14  can be disposed through a larger hollow article, such as a strut, casing, frame, or other structure, or alternatively can be bored through a solid component. 
     As shown in  FIG. 1 , element  16  is disposed within at least a portion of flow channel  14 . Element  16  includes a plurality of outer turbulator elements  22 , the combination of which facilitate mixing and heat transfer in channel  14 . In certain embodiments, element  16  is compressible and can be retained resiliently to the interior of at least a longitudinal portion of flow channel  14 . In this way, resilient compressible element  16  can be radially compressed to facilitate insertion and retention. Resilient element  16  radially expands to contact the walls of channel  14 , holding itself in place without the need for separate fastening means. In this example, channel  14  is a cylindrical channel, as is the general shape of element  16 . However, it will be appreciated that elements  16  can be adapted to non-cylindrical flow channels. In addition, element  16  can also include a central wire  24  extending longitudinally generally down its axial center to which at least some of outer turbulator elements  22  are secured. This can provide additional axial stability and rigidity to facilitate insertion and removal of element  16 . 
     By providing element  16  to facilitate mixing and heat transfer, it helps maintain a catalytic reaction in channel  14  converting first reactants in nanofluid  20 A into second reaction products in nanofluid  20 B. In this example element  16  is fabricated from a plurality of individual irregular cylindrical turbulator elements  24  wrapped and/or secured around one another. The plurality of individual turbulator elements can be made flexible and nonuniformly distributed around a central axis forming a compressible structure (element  16 ) for placement in channel  14 . The exact configuration of turbulators  24  can be customized to control the reaction rate (and thus the rate of heat transfer, generation, and/or absorption in nanofluids  20 A,  20 B) and the temperature window of the catalytic reaction. Example catalytic reactions are described below. 
       FIG. 2B  includes flow channel  14 , channel element  16 , nanofluids  20 A,  20 B, element outer surfaces  22 , turbulator elements  24 , catalytic nanoparticles  26 , base fluid  28 , and flow boundary  30 .  FIG. 2B  is a magnified view of a portion of  FIG. 2A .  FIG. 2C  is a radial cross-section of channel  14  and element  16  with nanofluids  20 A,  20 B. 
     Nanofluids  20 A,  20 B includes a dispersion of nanoparticles  26  in respective base fluids  28 A,  28 B. Nanoparticles  26  can have a diameter of less than about 100 nm. A nanofluid suspension such as nanofluids  20 A,  20 B differ from conventional fluid suspensions (such as fluidized beds) as nanoparticles  26  do not accumulate to block flow, or settle under gravity during flow transients. As described in more detail below with respect to specific example embodiments, a plurality of catalytic nanoparticles  26  are selected and configured to facilitate a reaction converting first reactants in base fluid  28 A (provided from source  12 ) into second reaction products in base fluid  28 B proximate destination  18 . In one example, nanoparticles  26  are configured to catalyze an endothermic reaction. In other examples, nanoparticles  26  are configured to facilitate an exothermic reaction requiring heat removal. 
     As noted above, element(s)  16  can be customized to be compressible and resiliently securable in conjunction with the cross-section and length of individual flow passage(s)  14 . In addition to eliminating the need for fasteners, this also allows optimization of the combination of element  16  relative to passage  14  for improved control of both heat transfer and reaction rate while maintaining the system in a compact package. A suitable structural basis for a static embodiment of element  16  is a heat exchanger thermal transfer element. Examples of such elements are available from Cal Gavin Limited of Alcester, Warwickshire, United Kingdom and sold under the trade designation HITRAN®. Such elements are typically used in heat exchanger tubes to increase their thermal efficiency. Alternatively, element  16  can be rotating element such as a flexible screw auger. The auger and/or the flow channel  14  can include polytetrafluoroethylene (PTFE) either as a coating or as a structural element to facilitate strength and resiliency when element  16  contacts flow boundary  30 . A flexible element  16  can help reduce foaming in certain fluid suspensions such as ammonia borane. These and similar arrangements can increase available heat transfer surface area relative to a bare channel  14   
     In this example, proximate fluid source  12  (shown in  FIG. 1 ) a plurality of catalytic nanoparticles  26  can be added to inlet fluid base  28 A to form nanofluid  20 A/ 20 B. Nanoparticles  26  can comprise a substantially pure metal or an alloy having one or more transition or noble metals. Examples of these metals include but are not limited to nickel, platinum, iridium, or palladium. Selection and size of nanoparticles  26  depend on optimization of the particular chemical reaction being performed, as well as the thermal requirements to facilitate the catalytic reaction of nanofluid  20 A/ 20 B. As described above, nanoparticles  26  remain suspended in fluid base  28 A as it is converted catalytically into outlet fluid base  28 B during transport toward outlet  18  (shown in  FIG. 1 ). The arrangement of turbulator elements  22  and optional central wire element can help to keep nanoparticles  26  well mixed in the base fluid as it is converted from reactants  28 A to reaction products  28 B. The motion and suspension of nanoparticles  26  in base fluid  28 A/ 28 B in combination with element  16  also contributes favorably to improve overall thermal conductivity of nanofluid  20 A/ 20 B, further enhancing heat transfer and reaction control. 
     Because flow channel element  16  extends out to and contacts the edges of flow channel  14 , nanofluid  20 A/ 20 B is continuously mixed as it flows around the various outer turbulator elements  22  and optional central wire  24  (shown in  FIG. 2A ). Thus laminar flow is substantially reduced or eliminated at and around flow boundary  30 , preventing uneven accumulation of base fluid  28 A proximate destination  18  caused by a lack of catalytic contact. Nanofluids also can be modeled as single-phase fluids, while traditional fluid suspensions have more complex dynamics and less predictable multi-phase models. This and similar arrangements also minimize cross-sectional temperature gradients consistent with laminar flow at boundary  30 . This not only improves uniform fluid heat transfer, but also allows steady and predictable reaction rate through flow channel  14  by allowing for more precise temperature control. 
     In an ordinary flow channel, the fluid cannot uniformly react due to boundary effects. Any reactants contained adjacent the flow boundary would be less likely to have the reaction induced because it would be difficult to achieve the proper balance of reactant, catalyst surface area, and temperature. To complete the reaction, reactive and heat transfer surface areas would have to be added to the flow transport channel in other ways. Surface area can be increased by enlarging the inner diameter of the fluid channel, however this exponentially increases the pressure drop through the channel and would require a corresponding exponential increase in mechanical energy to push the fluid through. A separate reactor for the chemical reaction could be provided but would increase complexity, add weight and reduce available space for other uses. This could be problematic in transportation applications, such as automotive and aerospace vehicles requiring chemical reaction or reformation of fuel prior to being converted to mechanical energy. 
     In some embodiments, outer surfaces of turbulators  22  will also have a thermally conductive coating so as to minimize thermal resistance. This can further facilitate heat transfer Q into or out of channel  14  by providing direct thermal conductivity between the walls of channel  14 , channel element  16 , and nanofluids  20 A,  20 B. In certain embodiments, coating  26  can be a thermally conductive, minimally reactive substance such as a metal oxide, so as to provide adequate thermally conductive surface area to maintain the heat transfer coefficient. Here, coating  26  is applied using a wash coat comprising a liquid suspension of the coating, such as aluminum oxide (Al 2 O 3 ). 
       FIG. 3  includes fuel system  10 ′, first fuel source  12 ′, fuel transport channel  14 ′, transport channel element  16 ′, second fuel destination  18 ′, first fuel nanofluid  20 A′, and second fuel nanofluid  20 B′.  FIG. 3  is a more specific example of system  10  more directly applicable to a fuel system for a motor vehicle. In the example of  FIG. 3 , first fuel nanofluid  20 A′ includes a transportation fuel existing in a first chemical form serving as the base fluid for a dispersion of catalytic nanoparticles. The first chemical form of the fuel is stored in tank  12 ′ and nanoparticles (e.g. nanoparticles  26  described above) are added to the base fluid proximate the exit of tank  12 ′ and/or the entrance to channel  14 ′. Catalytic nanoparticles facilitate chemical reaction of the base fluid from tank  12 ′ into a transportation fuel having a second chemical form during transport through channel  14 ′ to the motive engine  18 ′. Element  16 ′ provides continuous mixing and heat transfer throughout channel  14 ′. Nanoparticles remain in second nanofluid  20 B′ which now includes fuel existing in the second chemical form. This second fuel form serves as base fluid for nanofluid  20 B′. In the motive engine  18 ′, at least one of the reaction products in the second form of the fuel undergoes a subsequent reaction or other processing in order to convert the reaction products into motive power for a vehicle as explained below. 
     It will be of course recognized that other elements typically disposed in a fuel system (e.g., separators, filters, sensors, etc.) can be included in system  10 ′ but are omitted from  FIG. 3  for clarity. For example, in embodiments relating to conversion of hydrocarbon based fuels it will be recognized that the first chemical forms of the fuel are typically processed or scrubbed of catalyst fouling constituents such as sulfur and lead before nanoparticles are added to form first fuel nanofluid  20 A′. 
     System  10 ′ can be all or part of a small mobile scale fuel system such as in a motorized land, sea, or aerial traveling vehicle. For example, system  10 ′ can be installed on a vehicle powered by hydrogen fuel cells using a concept generally known as hydrogen storage. Here, fuel  20 A′ is stored in a first stable and compact hydrogen dense form. Examples include hydrides such as ammonia borane (NH 3 BH 3 ), which can be catalytically thermolysed in an exothermic reaction. Ammonia borane itself exists in a solid form but can be dissolved or suspended in an appropriate fluid. For example, ammonia borane can be dissolved in certain ionic liquid solvents. It can also be suspended in temperature stable oil-based liquids like silicone oils. Alternatively, alane (AlH 3 ) can be used as a hydride, which undergoes an endothermic reaction to release hydrogen for a fuel cell. Other classes of hydrogen storage fuels can include carbon-boron-nitrogen heterocycle materials that are currently under development. Used materials can be captured from the stream, recycled and regenerated for repeated use as hydrogen storage fuels. 
     Nickel or other suitable catalytic nanoparticles are added to the first base fluid fuel from tank  12 ′ with both being flowed through channel  14 ′. Fuel in first nanofluid  20 A′ undergoes a reaction from its first chemical form to release hydrogen (H 2 ) as fuel in a second chemical form suitable providing power to motive engine  18 ′. Hydrogen as the second fuel form, other reaction byproducts, and unreacted quantities of the first chemical form of the fuel can form part of second nanofluid  20 B′. The H 2  can be isolated from one or more other components of nanofluid  20 B using equipment appropriate for the particular reaction, then subsequently combined with atmospheric or other available oxygen in a hydrogen fuel cell to generate electric power for driving one or more electric motors (engine  18 ′). Details on fuel cells are relatively well known and will not be repeated here. Catalyst and/or other reaction byproducts such as the can be captured from the stream of fuel  20 B, stored, and regenerated at a later time into their first hydride or other hydrogen storage form. 
     In another example, fuel from tank  12 ′ may be a more complex “endothermic” fuel for hypersonic turbine or ramjet engines. Endothermic fuels can provide a heat sink function due to immense cooling demands of hypersonic aircraft. In one example, the first or second chemical form of the fuel can be used as a heat sink for temperature management purposes (e.g. lubricant oil cooling) prior to being harnessed for motive power. Thus a portion of the waste energy from the second reaction can be captured and utilized to maintain the first reaction, providing heat Q to maintain channel  14 ′ at a suitable temperature to facilitate the catalytic reaction. Conversion of the first chemical form of the fuel in to the second form may include a form of “fuel cracking”. As one specific example of this approach, the fuel is a liquid hydrocarbon specially designed for use in hypersonic or near-earth aerospace applications. 
     Since nanoparticles  26 ′ are dispersed in nanofluids  20 A′/ 20 B′, filtering and/or separating means as described above (not shown) can optionally be provided to remove the particles from the stream and return them back to the beginning of flow channel  14 ′ proximate first tank  12 ′. The nanoparticles can alternatively be consumed during the use of the fuel in its converted second chemical form if the fuel is to be combusted with air. 
     In addition to on-vehicle uses, system  10 ′ can be part of land or sea based fueling infrastructure for powering fuel cell vehicles. In certain embodiments of this alternative example, system  10 ′ can be installed at a terminus or lateral extension of a hydrocarbon transport pipeline (substituted for fuel tank  12 ′). System  10 ′ could then include additional piping  14 ′ containing flow channel element  16 ′. Nanoparticles  30  (shown in  FIGS. 2A-2C  and  FIG. 4 ) can catalyze the appropriate reaction to convert the arriving or locally stored first fuel  20 A′ into second form  20 B′ (hydrogen) prior to being provided to one or more motorized vehicles (substituted for motive engine  18 ′). By way of example, system  10 ′ can be used to provide converted hydrogen fuel to motorized vehicles directly at a fueling station connected to the pipeline, or indirectly via tankers or other transport means at a terminal whereby the reaction product(s) are sent to one or more remote fueling stations. 
     In this example, first fuel  20 A′ may be a specialized or a commercially produced hydrocarbon mixture, such as compressed natural gas (CNG), liquefied petroleum gas (LPG), gasoline, diesel fuel, or the like. Steam may be added to fuel  20 A′ causing it to undergo an endothermic reforming reaction catalyzed by catalytic nanoparticles in channel  14 . In such a reaction, primarily H 2  and CO 2  gases are produced. The CO 2  and other byproducts and contaminants are substantially removed prior to fueling and/or operating the vehicle. 
     While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.