Patent Publication Number: US-8974765-B2

Title: Methods and apparatus for controlled production of hydrogen using aluminum-based water-split reactions

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/277,857 filed on Sep. 29, 2010. 
    
    
     BACKGROUND 
     a. Field of the Invention 
     The present invention relates generally to methods and apparatus for production of hydrogen, and, more particularly to methods and apparatus for producing hydrogen from an aluminum-based water-split reaction in a manner that is tailored to meet the requirements of particular equipment or applications, by differential distribution of one or more of the solid reactant materials in a matrix or other body such that areas of the differential distribution are contacted by the water in a sequential manner. 
     b. Related Art 
     As is well known, hydrogen gas has many different uses in a wide range of industries and activities. Perhaps the best known use is as a fuel, such as for combustion or use in a fuel cell, but there are many others, including lift gas for balloons or other lighter-than-air devices, use in certain types of welding, creation of artificial atmospheres for certain types of diving (diving air), and use in certain types of batteries, (e.g., pressurized nickel-hydrogen batteries), to give just a few examples. 
     Although it therefore has great utility, distribution of hydrogen has long been hampered by the difficulties inherent in storing and transporting it in gaseous form. When uncompressed (i.e., at atmospheric pressure) the gas simply occupies too much volume for practical use, and furthermore the gas generally needs to be under pressure for most uses. Storage in compressed form, however, requires use of pressure vessels of some form, which are typically heavy, bulky and dangerous to transport, as well as being relatively expensive. Typical are the ubiquitous high-pressure gas cylinders made of steel, commonly referred to as “K-cylinders.” These steel cylinders are notoriously heavy, cumbersome and difficult to transport, to the point where they are simply unsuitable for many applications that involve portability. The dangers that they present have also caused them to be prohibited from use in certain environments, for example, onboard certain naval vessels. Still further, conventional gas cylinders typically require valves and/or regulators to discharge the hydrogen at the required pressures/rates, which adds to complexity and cost. The cost of gas cylinders also makes it economically unviable to simply dispose of them after use, so that they must be transported back to a facility to be refilled at still additional cost. These sundry difficulties and expenses have the combined effect of rendering the use of hydrogen impractical in many circumstances where it would otherwise be beneficial. 
     An alternative to storing and shipping hydrogen as a pressurized gas is to generate it on location from chemical reactions using materials that can be stored/transported without needing pressure vessels. Water-hydride reactions (e.g., water+ lithium hydride) are perhaps the most well know, however the reactions are notoriously difficult to control, being rapid and highly exothermic, to the point of being potentially dangerous in some situations. Furthermore, disposal is a problem due to the potentially hazardous nature of the reaction products. 
     Hydrogen gas can also be produced using aluminum-based water-split reactions, which generally exhibit much more benign characteristics than hydride-based reactions. The reactions between aluminum and water (2Al+6H 2 O→2Al(OH) 3 +3H 2 ↑; 2Al+4H 2 O→2AlO(OH)+3H 2 ↑; 2AL+3H 2 O→Al 2 O 3 +3H 2 ↑) are well known, but until recently their use in practical applications has been problematic due to the phenomenon known as “passivation”: Bare metallic aluminum almost immediately forms a very inert aluminum oxide layer on its surface that shields the underlying bulk aluminum and thereby inhibits further reactions between the aluminum metal and surrounding gases or liquids. A number of different approaches were previously developed in an effort to overcome the passivation problem, such as mechanically modifying particles of aluminum by milling or fracturing, but these have generally proven too energy-intensive and/or expensive to be economically viable. More recently though, as exemplified by the process disclosed in PCT Patent Application No. WO 2008/027524, it has been found that the passivation problem can be overcome using a water-soluble inorganic salt such as sodium chloride or potassium chloride as a “catalyst” that causes progressive pitting of the aluminum; These salts remove the passivation layer, through corrosive attack of the surface. In addition by adding certain metal oxides, such as calcium oxide or magnesium oxide, the reaction can be accelerated as a result of the heat generated when the metal oxides are exposed to water. The particles of metallic aluminum, salt catalyst and metal oxide initiator are (in the prior art) blended together into a homogenous, powder-like mix, to which water is added (or vice versa) to produce hydrogen when desired. The dry materials are safe and easy to store and transport, and the reaction products are substantially inert and environmentally benign and therefore can be readily disposed of almost regardless of location. 
     Although generally successful in overcoming the problem of passivation per se, the system described in the preceding paragraph is subject to inherent limitations that make it less than completely satisfactory for many applications. A particular problem involves the difficulty of adjusting or tailoring the speed or other characteristics of the reaction to the divergent requirements of different applications: For example, certain applications, such as filling balloons for meteorological or military applications, require that large volumes of hydrogen be produced in a very rapid manner. Other applications such as supplying hydrogen for use by a fuel cell, welding apparatus or other device normally call for a slower rate of production over a much longer period of time. Also, certain applications may call for production of heat/steam together with the hydrogen, whereas in other cases these products may be undesirable. 
     As compared with hydride-based reactions, the basic aluminum-catalyst-initiator system does offer greater controllability, but nevertheless with significant limitations. For example, the reaction may be controlled to a certain extent by metering the rate at which water is introduced to the blended material, while measuring pressure or otherwise monitoring the rate at which the hydrogen is produced; however, the metering and monitoring devices, such as valves, sensors, microprocessors, and so on, represent significant complexity, weight and expense, and moreover the rate of control that can be achieved in this manner is subject to certain practical limitations. Changing the proportions of the constituents (metallic aluminum-salt-catalyst-metal oxide initiator and metal hydroxide) in the particulate blend can also provide some degree of adjustability, but the range of adjustment that can be achieved in this manner is comparatively limited and inadequate to meet the requirements of many differing applications such as those discussed above. 
     Accordingly, there exists a need for methods and apparatus that can effectively produce hydrogen gas on location by chemical reaction, so as to obviate the distribution problems associated with use of compressed hydrogen gas. Furthermore, there exists a need for such methods and apparatus that permit the rate, temperature and other characteristics of the reaction to be configured or adjusted to meet the divergent needs of different applications. Still further, there exists a need for such methods and apparatus that can be configured or adjusted to produce heat and/or steam as products where desired. Still further, there exists a need for such methods and apparatus that make effective use of aluminum-based water-split reactions, so as to avoid the drawbacks inherent in hydride-based reactions and the like. Still further, there exists a need for such methods and apparatus that are economical in nature, can be conveniently and safely implemented in a wide variety of locations and conditions, and that present minimal costs and environmental/safety concerns relating to disposal of the expended materials. 
     SUMMARY OF THE INVENTION 
     The present invention addresses the problems cited above, and provides methods and apparatus for producing hydrogen, plus heat and steam when desired using an aluminum-based water-split reaction, that offer the ability to control and tailor the characteristics of the reaction and thereby the output to meet the needs of differing applications. 
     In a broad aspect, the method comprises the steps of (a) providing a matrix having at least one inlet for introducing water at a predetermined location; (b) providing a plurality of solid reactant materials for reacting with water to produce hydrogen, the solid reactant materials comprising: metallic aluminum, at least one water-soluble inorganic salt catalyst that causes progressive pitting of the metallic aluminum to sustain reaction of the metallic aluminum with water, and at least one metal oxide initiator that upon exposure to water causes an increase in temperature to initiate reaction of the water with the metallic aluminum; (c) differentially distributing the plurality of solid reactant materials in the matrix relative to the at least one inlet so that at least one of the solid reactant materials is present at a selected area in the matrix relative to the inlet in an amount that is proportionately greater than at least one other of the solid reactant materials; and (d) introducing water into the matrix through the at least one inlet so that a flow of the water contacts the area of the matrix containing the proportionately greater amount of at least one solid reactant material and other areas in the matrix in a sequential manner so as to affect at least one characteristic of the reaction of the water with the solid reactant materials to produce hydrogen. 
     The step of differentially distributing the plurality of reactant materials relative to the at least one inlet may comprise differentially distributing the solid reactant materials so as to affect at least one characteristic of said reaction selected from the group consisting of rates of the reaction, temperatures of the reaction, pressures of the reaction, products of the reaction, and combinations thereof. The products of the reaction may comprise one or more of amounts of hydrogen produced by the reaction, amounts of heat produced by the reaction, and amounts of steam produced by the reaction. 
     The water-soluble inorganic salt catalyst may be selected from the group consisting of sodium chloride and potassium chloride and combinations thereof, and the metal oxide initiator may be selected from the group consisting of magnesium oxide and calcium oxide and combinations thereof. 
     The step of distributing the solid reactant materials may comprise concentrating the at least one solid reactant material in at least one predetermined area. The step of concentrating the at least one solid reactant material in at least one predetermined area may comprise positioning the solid reactant materials in a plurality of layers in the matrix. The plurality of layers may be arranged concentrically or spirally about a centrally located inlet for the water. The step of concentrating the at least one solid reactant material in at least one predetermined area may also comprise placing the at least one solid reactant material in defined packets at spaced-apart locations within the matrix. The at least one solid reactant material may also comprise only one of the solid reactant materials or a combination thereof. 
     The step of concentrating the at least one solid reactant material in at least one selected area of the matrix may comprise the step of concentrating the metal oxide initiator in an area proximate the at least one water inlet, so as to achieve a rapid increase in temperature immediately upon introduction of water via the inlet. The step may also comprise concentrating the inorganic salt catalyst proximate the at least one inlet so as to achieve a rapid increase in dissolved salt catalyst upon introduction of water via the inlet. Alternatively or additionally, the step of concentrating the at least one solid reactant material in at least one selected area in the matrix may comprise concentrating the at least one metal oxide initiator at a plurality of spaced locations through the matrix so as to achieve a moderated or comparatively constant level of temperature increase upon introduction and/or reintroduction of water via the at least one inlet; similarly, the at least one inorganic salt catalyst may be concentrated in a plurality of spaced locations in the matrix so as to achieve a moderated increase in dissolved salt catalyst as water is introduced. 
     The step of distributing the solid reactant materials in the matrix may comprise the steps of depositing the solid reactant materials on at least one water permeable substrate, and placing in the matrix the permeable substrate having the solid reactant materials deposited thereon. The water permeable substrate may be formed of a fibrous mass, such as a mass of metallic or nonmetallic fiber wool material. The step of placing the substrate in the matrix may comprise placing the substrate in a container so as to form an expendable cartridge. 
     In a broad aspect, the apparatus comprises: (a) a matrix having at least one inlet for introducing water at a predetermined location therein; (b) a plurality of solid reactant materials for reacting with water to produce hydrogen, the solid reactant materials comprising: metallic aluminum; at least one water-soluble inorganic salt catalyst that creates progressive pitting of the metallic aluminum to sustain reaction of the metallic aluminum with water, and at least metal oxide initiator that upon exposure to water cause an increase in temperature to initiate reaction of the water with the metallic aluminum; (c) the plurality of solid reactant materials being differentially distributed in the matrix relative to the at least one inlet so that at least one of the solid reactant materials is present at a selected area in a matrix relative to the inlet in an amount that is proportionately greater than at least one other of the solid reactant materials, so that when water is introduced into the matrix through the at least one inlet the flow of water will contact the area of the matrix containing the proportionately greater amount of at least one solid reactant material and other areas in the matrix in a sequential manner so as to affect at least one characteristic of the reaction of the water with the solid reactant materials to produce hydrogen. 
     The plurality of solid reactant materials may be differentially distributed in the matrix relative to the at least one inlet so as to affect at least one characteristic of the reaction selected from the group consisting of rates of the reaction, temperatures of the reaction, pressures of the reaction, products of the reaction, and combinations thereof. The products of the reaction comprises one or more of amounts of hydrogen produced by the reaction, amounts of heat produced by the reaction, and amounts of steam produced by the reaction. 
     The plurality of solid reactant materials may comprise solid reactant materials in particulate form. The water-soluble inorganic salt catalyst may be selected from the group consisting of sodium chloride and potassium chloride and combinations thereof, and the metal oxide initiator may be selected from the group consisting of magnesium oxide and calcium oxide and combinations thereof. 
     The at least one solid reactant material may be concentrated in at least one predetermined area in the matrix. The differentially distributed solid reactant materials may be positioned in a plurality of layers in the matrix. The plurality of layers may be arranged concentrically or spirally about a generally centrally located inlet for the water. The at least one solid reactant material may also be concentrated by placing the at least one solid reactant material in defined packets at spaced apart locations in a matrix. The at least one solid reactant material that is concentrated may comprise only one of the solid reactant materials or may comprise a combination of at least two of the solid reactant materials. 
     The at least one solid reactant material that is concentrated in at least one selected area of the matrix may comprise the at least one metal oxide initiator concentrated in an area proximate the at least one water inlet, so as to achieve a rapid increase in temperature immediately upon introduction of water via the inlet. The inorganic salt catalyst may also be concentrated proximate the at least one inlet so as so as to achieve a rapid increase in dissolved salt catalyst upon introduction of water via the inlet. Alternatively or additionally, the metal oxide initiator may be concentrated at a plurality of spaced locations through the matrix, so as to achieve a moderated, comparatively constant level of temperature increase upon introduction and/or reintroduction of water via the at least inlet. The at least one water-soluble inorganic salt catalyst may also be concentrated at a plurality of spaced locations within the matrix, so that the salt catalyst is dissolved in a moderated manner as water is introduced into the matrix. 
     The apparatus may further comprise at least one water permeable substrate on which the plurality of solid reactant materials are deposited to be placed in the matrix. The water permeable substrate may be formed of a fibrous mass, such as a mass of metallic or nonmetallic fiber wool material. 
     The water permeable substrate may comprise at least one layer that surrounds an inlet tube having a plurality of openings for distributing water into the matrix. The at least one layer of permeable material may comprise a plurality of layers of the permeable material, with differing combinations of the plurality of solid reactant materials deposited thereon. The layer of fibrous substrate material may also comprise a layer of the fibrous material having a first one or combination of the plurality of solid reactant materials distributed generally thereover, and at least one packet of one or a combination of a plurality of solid reactant materials placed at a discreet predetermined location or locations thereon. 
     The apparatus may further comprise a container that encloses the permeable substrate and plurality of solid reactant materials so as to form an expendable cartridge. The at least one layer of permeable substrate may be rolled spirally about the water distribution tube to form a cylindrical fuel body that is enclosed within the container. The container may have an inlet connection at at least one end thereof for admitting water to the distribution tube in the fuel body. The container may comprise a generally cylindrical container, suitably formed of thin aluminum metal to form a conveniently handled and economically disposable cartridge assembly. 
     These and other features and advantages of the present invention will be more fully understood from a reading of the following detailed description with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a simplified, somewhat schematic view of a hydrogen generation apparatus in accordance with the present invention, showing a cartridge that contains the dry reactant materials housed in the exemplary reaction chamber thereof and the manner in which a supply of water that is fed to the cartridge to produce the reaction; 
         FIG. 2  is a longitudinal cross-sectional view a reactant cartridge such as that used in a hydrogen generator of  FIG. 1 , showing the distribution of the components thereof about a central water inlet to tailor the characteristics of the reaction to the requirements of a particular application; 
         FIG. 3  is a transverse cross-sectional view of the fuel cartridge of  FIG. 2 , showing the distribution of the components thereof about the central water inlet in greater detail; 
         FIG. 4  is a transverse cross-sectional view of a reactant cartridge in accordance with another embodiment of the present invention, in which the chemical components are distribution in a generally concentric pattern about the central water inlet rather than being radially distributed locations as in the embodiment of  FIGS. 2-3 ; 
         FIG. 5  is a plan view of first and second flexible sheets of water permeable material on which the dry reactant materials are deposited for formation of a fuel cartridge in accordance with another embodiment of the present invention; 
         FIG. 6  is a transverse cross-sectional view of a fuel cartridge that is formed by rolling the sheets of  FIG. 5  together to form adjoining layers that overly one another in a spiral pattern about the central water inlet of the cartridge; 
         FIG. 7  is plan view of a flexible layer or sheet of water permeable material having the separate chemical components deposited in a predetermined pattern thereon, the layer being rolled up in the manner shown in  FIG. 6  to form a fuel cartridge in accordance with another embodiment of the present invention; 
         FIG. 8  is a diagrammatic view of a hydrogen generating apparatus in accordance with an embodiment of the present invention in which the reaction characteristics are tailored to provide lift gas for inflation of a balloon used, for example, for meteorological or military functions, as well as in other applications; 
         FIG. 9  is a perspective view of the apparatus of  FIG. 8 , showing the components thereof in greater detail; 
         FIG. 10  is a partial perspective view of the apparatus of  FIG. 9 , showing the manner in which a fuel cartridge such as that of  FIG. 2  is inserted in one of the reaction chambers of the apparatus for generation of hydrogen thereby; and 
         FIG. 11  is a longitudinal cross-sectional view of a reactant cartridge in accordance with another embodiment of the present invention, having co-axial compartments for the reactant materials that are divided by a metallic mesh, housed in an economical aluminum container that is disposable or can be recycled together with the expended reactant materials and products. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows in simplified form a basic reactor unit  10  for generating hydrogen in accordance with the present invention. As can be seen, the unit includes a reaction vessel or chamber  12  that receives disposable fuel cartridges  14 , the reaction chamber having an access lid  16  at its upper end and a water  18  at its lower end. An associated reservoir  19  holds a supply of water  20 , with flow thereof through the supply line  21  being controlled by an actuating valve  22 . 
     As will be described in greater detail below, the expendable cartridge  14  contains the dry reactant materials for the sustainable aluminum-based water-split reaction described above, namely, particulate metallic aluminum, a water-soluble inorganic salt catalyst and a metal oxide initiator, but with one or more of the components separated out or concentrated in areas/zones or “packages” that are configured to produce a reaction rate and/or other characteristics that are tailored to the requirements of a particular application. Characteristics that may be adjusted or otherwise affected by the differential distribution of the solid reactant materials include, but are not limited to, the rate, temperature, pressure and desired products of the reaction, the main desired products of the reaction including, depending on application, hydrogen, heat and/or steam. 
     Upon opening valve  22 , water passes through line  18  (e.g., by pressure or gravity) and enters the lower end of the cartridge  14  as shown in  FIG. 1 . As will be described in greater detail below, contact between the water and the dry materials in the cartridge initiates the aluminum-based water-split reaction, resulting in release of hydrogen gas from the cartridge, together with heat and steam depending on design. In the illustrated embodiment, the gas is collected in the head space  24  between the upper end of the cartridge  14  and the chamber lid  16 , from which it is bled off under pressure via H 2  supply line  26 . It will therefore be understood that the reaction chamber  12 , including chamber lid  16 , needs to be constructed so as to be able to contain the pressure of the accumulated gas, however, such pressure would normally be much lower than those involved in a K-cylinder or similar vessel, and the chamber is much smaller, so that the weight involved will be much smaller. 
     The hydrogen gas is supplied via line  26  to the user equipment or device, which may be for example of any of the types noted above. Depending on application, a pressure regulator valve  28  may optionally be included in the H 2  supply line; in certain applications the pressure regulator may be replaced by a back pressure, regulator to control the pressure of the reactant chamber. 
     As was noted above, a central aspect of the present invention, that allows tailoring of the reaction characteristics to the requirements of particular applications, is that the dry reactant materials forming the “fuel” of the reaction are differentially distributed in a designed manner rather than being homogenously blended as in prior approaches within an overall matrix. One or more of the materials may be substantially or completely segregated from the others in selected areas, or they may be located in areas of increased concentration or density relative to other areas, or be distributed in other arrangements designed heterogeneity. Moreover, the materials may be separated into packets, zones or the like having distinct boundaries, or there may be gradual or less distinct transitions between areas in some embodiments. Mesh, coarse-fiber “wool” or other permeable packaging and/or substrate materials including materials that dissolve or partially dissolve may be used to construct or define the areas containing the separated reactant materials, or the areas may be formed by zones or regions within the mass of the fuel itself. Moreover, it will be understood that particulate form is generally preferred for the components of the fuel, to provide rapid solubility and reaction rates, but this may not necessarily be so in all embodiments, and in some cases the salt catalyst or possibly another reactant or combination thereof may be in larger or even monolithic pieces. 
     As will be described in greater detail below, relative concentration or segregation of one or more of the reactant materials allows the materials to be positioned in a predetermined manner (e.g., spatial relationship, orientation, or other arrangement) with respect to one another and also to the direction of flow of water entering the matrix containing the dry fuel, thereby permitting both timing/sequence of exposure to the water and also the concentrations of material dissolved in the flow to be adjusted as desired. Adjustment of these aspects in turn provides a significant degree of control over the characteristics of a resulting reaction, allowing the designer to tailor those characteristics to the requirements of a particular application. For example, the components can be arranged to achieve a quick startup followed by the relative high rate of reaction and production of hydrogen, or to instead provide a less rapid startup and a slower and steadier production of hydrogen, as may be desired for a particular purpose. The arrangement of the fuel materials relative to the water flow and each other can be used to produce higher or lower reaction temperatures (including production of steam, if desired), optimize the reaction for higher or lower pressure outputs, construct cartridges for one-time or multiple use, and so on. 
       FIGS. 2-7  illustrate exemplary arrangements of the dry/solid components relative to the flow of water, with numerous additional configurations being possible. In the embodiment that is illustrated in  FIG. 2 , which is an enlarged, cross-sectional view of the exemplary reactant cartridge  14  shown in  FIG. 1 , the reactant is contained within a generally cylindrical shell  30  suitably formed of thin aluminum metal. In general shape and material the shells somewhat resembles a conventional aluminum beverage can, which has the benefit that it can be produced inexpensively using widely available equipment without significant modification. The lower end of the shell is closed by a bottom wall  32  while at the upper end there is an opening  34 , the latter being formed by removal of a pull away lid (not shown) prior to use. 
     As can be seen with further reference to  FIG. 2  and also  FIG. 3 , the reactant materials contained with the cartridge  14  are arranged in a generally concentric/radial pattern about an axial, centrally located water distribution tube  36 . In the embodiment that is illustrated, the water distribution tube  36  has a hollow core with a plurality of perforations  38 , through which water flows longitudinally into the cartridge and then outwardly into the surrounding materials, but it will be understood that in some embodiments a simple passage or bore formed in the materials without perforations may be used; it will similarly be understood that in some embodiments the water inlet may include or communicate with manifolds, distribution tubes, bores, channels and other features or structures for introducing water to the matrix along one or more relatively defined paths, with the differential distribution of the solid reactant materials being arranged relative to the flow path or paths accordingly. 
     Water enters tube  36  through a central opening  40  that communicates with water injection tube  18  where the latter enters the bottom of the reaction chamber  12 ; the opening may suitably be formed by a spike-shaped water nozzle (not shown) at the end of injection tube  18 , that pierces the bottom wall  32  of the container when it is set into and pressed downwardly within the reaction chamber. 
     As can most easily be seen in  FIG. 3 , packets  42 ,  44  of the metal oxide initiator (suitably, calcium oxide, magnesium oxide or a combination thereof) and water-soluble inorganic salt catalyst (suitably, sodium-chloride, potassium chloride or a combination thereof) are arranged in an alternating, radial pattern about the central water distribution tube  36 , and are embedded in a comparatively loosely packed mass of particulate aluminum  46  that extends concentrically around the distribution tube. Arranged outwardly and concentrically around the relatively loosely packed aluminum particulate is a somewhat more densely packed mass of particulate aluminum  48 , the latter being surrounded by the cylindrical shell  30 . In the illustrated embodiment, the “packets” of metal oxide initiator  42  and soluble inorganic salt catalyst are arranged in an alternating fashion, both around the water distribution tube and over the length of the cartridge (see  FIG. 2 ), to provide more even distribution, however it will understood that this is not essential and that in some embodiments single packets may extend the full length of the cartridge; furthermore, the cylindrical, generally rod-shaped configuration of the packets shown in  FIGS. 2-3  facilitates insertion during manufacture of the cartridge, but this again is somewhat arbitrary in nature and other shapes/configurations may be used. To assist in handling and manufacture, the packets may be formed by a layer or layers of water-soluble permeable material enclosing the reactant material, and the loosely packed aluminum particulate may be contained within a water soluble or permeable sleeve  50  that separates it from the concentrically outward mass of aluminum particulate  48 , such as a porous mat or screen, but again such features may not be present in all embodiments and the separate materials may simply be in direct contact with one another. Other forms of shells and containers may also be used in some embodiments, including containers formed of steel and other metals, as well as of non-metallic materials, including biodegradable materials to facilitate disposal materials to facilitate disposal in certain embodiments. 
     Referring again to  FIGS. 2-3  and also  FIG. 1 , when water is introduced through the opening  40  at the bottom of the fuel cartridge, it flows upwardly through the distribution tube  36  and from there outwardly through the loosely packed aluminum particulate into contact with the packets of metal oxide initiator and water-soluble inorganic salt catalyst. The comparatively loose packing of the aluminum particulate  46  allows the water to flow rapidly therethrough, so that the water contacts the metal oxide almost immediately to cause a rapid increase in temperature of the surrounding mass. Similarly, the salt catalyst in packets  44  is rapidly dissolved and distributed into the loosely packed particulate  46 . In combination, the resulting burst of heat and high concentration of salt catalyst cause the reaction to initiate almost instantaneously, so that significant volumes of hydrogen gas are produced without appreciable delay. Thereafter, the heat radiates outwardly from the core area into the more densely packed mass  48  of particulate aluminum, which provides the main body of “fuel” in the cartridge, while the dissolved salt simultaneously flows through the permeable sleeve  50  and likewise into the main mass  48  of particulate aluminum; as is discussed in the reference cited above, the chloride ion supplied by the salt, which creates the anti-passivation effect, is not consumed in the reaction, and therefore remains until all of the aluminum has been consumed. 
     The net effect of the design shown in  FIGS. 2-3  is a process that begins producing hydrogen almost immediately and continues to produce large volumes in a rapid manner until the supply of particulate aluminum is exhausted. These characteristics are well tailored to certain purposes, including for example supplying lift gas for inflation of balloons for meteorological/military purposes, will be described in greater detail below. After the cartridge has been expended it can be removed from the reaction chamber and discarded, the “waste” product being safe and environmentally benign as noted above. Another cartridge can then be inserted into the reaction chamber and used to generate additional hydrogen when desired. A supply of the cartridges may be kept on hand in a carton or case, being lightweight, safe and requiring no special storage or handling procedures. 
     Use of the fuel cartridges together with a dedicated hydrogen reactor apparatus, such that shown in  FIG. 1 , provides several advantages, including the ability to use lightweight, simple and inexpensive cartridges, and also the ability to use cartridges of different types and characteristics in a single reactor apparatus to meet differing needs. It will be understood, however, that in some embodiments one or all of the reactor functions may be incorporated into a single, possibly disposable device: For example, a fuel cartridge may be provided that incorporates an integrated reservoir holding a supply of water, and that may moreover incorporate features for collection and discharge of the hydrogen gas to a user device. 
       FIGS. 4-7  illustrate additional, exemplary forms of construction for fuel cartridges in accordance with the present invention. For example,  FIG. 4  shows a cartridge  54  in which the dry reactant materials are arranged in sequential, concentric layers about the water distribution tube  56 . In this embodiment, the particulate metal oxide initiator  58  is arranged in a generally coaxial mass about the water distribution tube  56 , so that upon introduction of water the initiator is the first material to be contacted so as to cause a rapid rise in temperature, and in particular causing heating of the water that is flowing therethrough. The heated water then enters a mass of the particulate, water-soluble inorganic salt  60  that is arranged concentrically about the metal oxide core, so that the elevated temperature of the water causes the salt to dissolve in a rapid and efficient manner. The flow of water then carries the dissolved salt (i.e., the chloride ions) outwardly and radially into the mass of particulate aluminum material  62  that is arranged concentrically around the inner two layers, inside the cylindrical shell  64  of the cartridge. The high temperature and concentration of the chloride ions again produces a rapid reaction with the particulate aluminum, generating large volumes of hydrogen in a rapid manner until the fuel is exhausted. By comparison with the embodiment shown in  FIGS. 2-3 , the cartridge having the construction shown in  FIG. 4  may not have the almost instantaneous “kickoff” and generation of hydrogen that is a feature of the former, but its construction is simpler and initiation is still relatively rapid, and it can be configured to generate hydrogen at a comparatively steady rate once commenced. 
       FIGS. 5-6  illustrate an embodiment in which the body of the cartridge is formed of multiple layers of flexible water permeable/porous material that are rolled together to form a spiral pattern through which the introduced water passes in a sequential manner. The example shown in  FIG. 5  includes a pair of layers  70 - 72 , each of which is formed of a cloth or fiber bat material constructed of inorganic or organic fibers or organic (e.g., metal fiber, glass fiber, cotton fiber) through which water is able to pass more-or-less freely; eminently suitable fiber materials include aluminum wools, stainless steel wools and silica wools (e.g., materials selling under the trade names Kaowool™ and Superwool™), which form relatively optimal substrates into which the particulate materials can be poured and retained. The first layer  70  includes a pattern of fuel  74  that is deposited on, imbedded within or adhered to the fibrous material, and in this embodiment is composed of a combination of particulate aluminum and the water-soluble inorganic salt catalyst. The second layer  72  has a similar construction, and includes a second pattern of fuel  76  that is composed of a combination of particulate aluminum and the metal oxide initiator. 
     As can be seen in  FIG. 6 , the two layers  70 ,  72  are placed atop one another and then rolled around a water distribution tube  78 , with the first layer  70  innermost, to form a spiral arrangement of alternating layers in a roll  80  that can be fitted within a cylindrical shell (not shown) to form the fuel cartridge. Water introduced through the distribution tube  78  therefore passes first through the area formed by layer  70  so as to dissolve the salt catalyst and pick up the chloride ion that prevents passivation, and immediately thereafter flows into the adjoining layer  72  containing the particulate aluminum and the metal oxide initiator that raises the temperature to initiate the reaction. As opposed to the arrangements of the embodiment shown in  FIGS. 2-3  and  4 , generation of hydrogen again begins quickly, but is more easily tailored to produce a steady yield at lower volumes; varying the amounts/concentrations of the reactant materials on the layers, as well as varying the permeability of the material used so as to control (in conjunction with pressure) the rate of flow of water therethrough provides the designer with opportunities to control the characteristics of the reaction comparatively precise manner. Moreover, the layered construction lends itself to construction of cartridges that can be used multiple times (e.g., by selectively stopping and restarting the flow of water) as opposed to the more single use, “one-shot” nature of the embodiments described above. 
       FIG. 7  illustrates an embodiment that is somewhat similar to that of  FIGS. 5-6  in that it utilizes a layer of fibrous/permeable material that is rolled up to form the body of the cartridge, but in this instance with a single layer  82  of substrate material having the dry reactant materials placed in packages or otherwise deposited at discrete locations in a predetermined pattern thereon. In this example, a mixture of particulate aluminum and water-soluble inorganic salt catalyst is deposited on/in the fibrous substrate in a substantially continuous layer over substantially the full length and width of the sheet. Packages or packets  86  formed of a mixture of particulate aluminum and metal oxide initiator are, in turn, deposited at a plurality of discreet, spaced-apart locations along the substrate. The fibrous substrate, which as noted above is suitably formed of a metallic or nonmetallic “wool” material, is then rolled up to form a cylindrical body having a spiral cross-section, for being placed in the shell of a cartridge in substantially the same manner as described above with reference to  FIG. 6 . 
     A particular advantage of the embodiment that is shown in  FIG. 7  is the comparative ease with which a fine degree of control can be exercised over the characteristics of the reaction, by selective sizing and positioning of the packets of initiator mix relative to the main layer of particulate aluminum fuel. For example, the packets can be comparatively small and distributed more or less evenly with respect to the main layer, as shown in  FIG. 7 , to produce a relatively steady reaction and moderated production of hydrogen and to also allow the reaction to be readily stopped and restarted by stopping and restarting the introduction of water. Alternatively, more closely spaced packets and/or large packets of initiator mix may be used to produce higher temperatures and faster reaction rates, or larger or more closely clustered packets may be grouped or placed at the end of the “blanket” of fibrous material that will be closest to the water injection tube then rolled up to provide a quick startup of the reaction immediately upon introduction of water through the tube. It will be understood that these are only a few examples of possible arrangements, and that many others may be used. 
       FIGS. 8-10  illustrate an embodiment of the invention with respect to an exemplary application, namely, providing hydrogen lift gas for inflating balloons for meteorological (weather) and military functions.  FIG. 8  shows the apparatus somewhat schematically, similar to  FIG. 1 , while  FIGS. 9-10  show the elements of the apparatus in greater detail. 
     As can be seen,  FIG. 8  shows a hydrogen generator  90  having a reaction chamber  92 , generally similar to that of  FIG. 1 , that receives a fuel cartridge  94 . In the illustrated embodiment, the cartridge suitably has the same configuration as the fuel cartridge  14  that is shown in  FIGS. 1-2 , but it will be understood that other configurations may also be used. 
     A supply of water  96  is contained in an onboard reservoir  98 , again in a manner similar to that described above. Water is drawn from the reservoir through a water supply line  100  by a manual pump  102  having a piston  104  that is actuated by a handle  106 . On the intake stroke, water is drawn through supply line  100  and through a first check valve  108 , and from there through a branch line  110  into the cylinder  112  of the pump. Then on the compression stroke, water is discharged from cylinder  112  through line  110 , and passes via a second check valve  114  and water injection line  116  into the interior of the fuel cartridge  14 , with backflow to the reservoir being prevented by the first check valve  108 . 
     Entry of water into the fuel cartridge initiates the reaction in the manner previously described, producing hydrogen gas that is captured within the interior spaces  118 ,  120  of the reaction chamber. The accumulated hydrogen gas as bled under pressure from the reaction chamber via a hydrogen supply line  122  and a check valve  124  enters the lower end of the reservoir arrow  198  as indicated by arrow  126 . The hydrogen gas bubbles through the volume of water  96 , cooling the gas and also preheating the water; preheating the water further increases efficiency of the system, and also pressurizes the reservoir to alleviate the need for subsequent pumping. The hydrogen gas then accumulates in the upper volume  128  of the reservoir, above the level of the water, from which is bled via a pressure regulator or back pressure regulator  130  to an inline desiccant tube  132 , as indicated by arrow  134 . The desiccant tube serves to dry the hydrogen, after which it passes through a discharge line  138  and into the interior volume  140  of a balloon  142 , as indicated by arrow  144 . The cartridge can be designed to produce a volume of hydrogen sufficient to fill a single balloon, i.e., each cartridge fills one balloon, after which it is discarded; alternately, the cartridge can be designed to produce a larger volume of hydrogen, and after the first balloon has been filled the flow of gas can be stopped by a valve (not shown) fitted in discharge line  138 , with subsequent balloons being filled as desired. 
       FIGS. 9-10  show the generator  90  in greater detail. As can be seen in  FIG. 9 , the apparatus preferably includes a pair of reaction chambers  94   a ,  94   b  connected to a single water reservoir  98  that also acts as a buffer, so as to be able to provide a continuous output of hydrogen gas by reacting cartridges in alternating chambers. Similar to  FIG. 1 , each reaction chamber includes a lid  150  that has a hinge  152  on one side and that is selectively clamped in a sealed position by a locking handle  154  on the other. Also shown is the pump  102  that is operated by handle  106 , the pressure regulator  130 , a pressure gauge  156 , and the inline desiccant tube  132 , which in this instance has a coiled configuration for enhanced space/packaging efficiency. 
     As can be seen in  FIG. 10 , a cartridge  14  is fed into the reactor  90  by opening the lid  150  of one of the reaction chambers  94   a ,  94   b , and then inserting the cartridge by hand  158  into the interior of the chamber with the open end  160  thereof (the end cap having been removed) disposed upwardly. In so doing, the bottom wall of the cartridge contacts and is punctured by the nozzle of the water injection tube, in the manner described above. The lid  150  is then pivoted downwardly about hinge  152  and locked down by handle  154  to seal the chamber. The water input line is lined up to select the reaction chamber that is loaded with the cartridge, and water is injected into the cartridge to commence the reaction in the manner described above. 
     After the cartridge has been expended to produce a volume of hydrogen, the locking handle  154  is released and the lid  150  is pivoted back to the open position as shown in  FIG. 10 . The cartridge can then be grasped and withdrawn with a stepped, increased diameter upper portion  162  of the chamber forming an angular gap around the cartridge into which the user&#39;s fingers can be inserted. Since the expended cartridge and reaction products are entirely safe, no protective clothing is required, and the cartridge can be disposed of in a convenient manner without danger to the environment. 
       FIG. 11  is a cross-section of a cartridge  170  in accordance with another embodiment of the present invention, demonstrating implementation using an economical, standardized aluminum container as the housing of the cartridge. In this example, the housing is formed by a standard 32-ounce disposable aluminum can  172  of a general type available from various suppliers, including the Ball Corporation (Broomfield, Colo.); as noted above, use of an off-the-shelf aluminum container that itself is designed to be disposable greater enhances economy of the system. 
     As can be seen with further reference to  FIG. 11 , the can  172  forming the housing is lined around the side and at the ends by layers of insulation  174 , suitably formed of a fibrous, non-metallic insulation material. Inside of the insulation are two coaxial compartments  176 ,  178 , divided by a metallic mesh  180 . The inner compartment  176  contains a mixture of aluminum, organic salt, and metal oxide which acts as a “starter pack”; this compartment contains a higher percentage of metal oxide in this compartment in order to provide rapid heating that jump starts the reaction. The outer compartment  178 , in turn, contains the same materials but with a higher percentage of aluminum, and therefore serves to produce the bulk of the hydrogen. The cartridge is suitable for use in the apparatus of  FIGS. 9-10 , in the manner described above. 
     It is to be recognized that various alterations, modifications, and/or additions may be introduced into the constructions and arrangements of parts described above without departing from the spirit or ambit of the present invention.