U.S. patent application number 11/907930 was filed with the patent office on 2009-04-23 for methods and devices for hydrogen generation.
Invention is credited to Richard M. Mohring, Qinglin Zhang.
Application Number | 20090101520 11/907930 |
Document ID | / |
Family ID | 40562364 |
Filed Date | 2009-04-23 |
United States Patent
Application |
20090101520 |
Kind Code |
A1 |
Zhang; Qinglin ; et
al. |
April 23, 2009 |
Methods and devices for hydrogen generation
Abstract
Systems and methods for hydrogen generation based on the
hydrolysis of a solid fuel are disclosed. The hydrogen generator
comprises a fuel chamber for storing a solid chemical hydride and a
chamber for storing a liquid reagent, and a liquid outlet disposed
within the fuel chamber. The contact between the solid chemical
hydride and the liquid reagent produces a substantially fluid
nongaseous product and hydrogen gas. The fuel chamber is configured
for movement relative to the outlet within the fuel chamber,
thereby causing relative movement between the liquid outlet and
unreacted solid fuel.
Inventors: |
Zhang; Qinglin; (Manalpan,
NJ) ; Mohring; Richard M.; (East Brunswick,
NJ) |
Correspondence
Address: |
DICKSTEIN SHAPIRO LLP
1825 EYE STREET NW
Washington
DC
20006-5403
US
|
Family ID: |
40562364 |
Appl. No.: |
11/907930 |
Filed: |
October 18, 2007 |
Current U.S.
Class: |
205/637 ;
204/232 |
Current CPC
Class: |
C01B 3/065 20130101;
Y02E 60/36 20130101; Y02E 60/362 20130101 |
Class at
Publication: |
205/637 ;
204/232 |
International
Class: |
C25B 1/04 20060101
C25B001/04 |
Goverment Interests
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0001] The invention was made with Government support under
Contract N00164-06-C-6058 awarded by the United States Navy. The
United States Government has certain rights in this invention.
Claims
1. A hydrogen gas generating system comprising: a reaction chamber
configured to contain a solid chemical hydride; at least one liquid
reagent storage chamber for containing an aqueous reagent; a liquid
reagent conduit line for conveying the aqueous reagent from the at
least one liquid reagent storage chamber to the reaction chamber,
wherein said liquid reagent conduit line includes at least one
liquid outlet within said reaction chamber; an actuator configured
to move the reaction chamber relative to said at least one liquid
outlet within said reaction chamber; a liquid reagent regulator;
and a hydrogen gas outlet, wherein reaction of said chemical
hydride and said aqueous reagent generates hydrogen and a
nongaseous product.
2. The hydrogen gas generating system of claim 1, wherein the
reaction chamber and the liquid reagent storage chamber are
arranged in a volume exchanging configuration.
3. The hydrogen gas generating system of claim 1, wherein said
liquid reagent storage chamber comprises an inner container.
4. The hydrogen gas generating system of claim 1, wherein said
reaction chamber comprises an inner container.
5. The hydrogen gas generating system of claim 1, further
comprising a moveable wall or a flexible wall separating said fuel
chamber and said liquid reagent storage chamber.
6. The hydrogen gas generating system of claim 1, further
comprising an acid adsorbent separating said fuel chamber and said
liquid reagent storage chamber
7. The hydrogen gas generating system of claim 6, wherein said acid
adsorbent is selected from the group consisting of polyacrylic acid
polymers, silicates, carbons, and metal hydroxide salts.
8. The hydrogen gas generating system of claim 1, further
comprising at least one gas permeable membrane in contact with the
reaction chamber, wherein the membrane is configured to allow
hydrogen to pass through the membrane while preventing solid and
liquid materials from passing through the membrane.
9. The hydrogen gas generating system of claim 1, wherein said
actuator configured to move the reaction chamber comprises a
spring.
10. The hydrogen gas generating system of claim 9, wherein said
spring is configured to pull or push the reaction chamber.
11. The hydrogen gas generating system of claim 1, wherein said
chemical hydride is a boron hydride.
12. The hydrogen gas generating system of claim 1, wherein said
aqueous reagent comprises water or an acidic solution.
13. The hydrogen gas generating system of claim 12, wherein said
acidic solution is selected from the group consisting of solutions
of hydrochloric acid, sulfuric acid, and phosphoric acid.
14. The hydrogen gas generating system of claim 12, wherein said
acidic solution is selected from the group consisting of solutions
of formic acid, acetic acid, citric acid, malic acid, and maleic
acid.
15. The hydrogen gas generating system of claim 1, further
comprising a battery to power a liquid reagent regulator.
16. A hydrogen fuel cartridge comprising: a reaction chamber and a
liquid fuel storage chamber contained within a housing, wherein
said reaction chamber and said liquid fuel storage chamber are
arranged in volume exchanging configuration; a liquid reagent
conduit line for conveying the aqueous reagent from the liquid
reagent storage chamber, wherein said liquid reagent conduit line
terminates in at least one fixed liquid outlet within said reaction
chamber; an actuator configured to move the reaction chamber
relative to said at least one fixed liquid outlet within said
reaction chamber; at least one hydrogen separator; and a hydrogen
outlet.
17. The hydrogen fuel cartridge of claim 16 further comprising a
liquid reagent regulator.
18. The hydrogen fuel cartridge of claim 17, wherein said liquid
reagent regulator is selected from the group consisting of a
peristaltic pump, a piezoelectric pump, a piston pump, a diaphragm
pump, a centrifugal pump, and an axial flow pump.
19. The hydrogen fuel cartridge of claim 17, wherein said liquid
reagent regulator is selected from the group consisting of a
solenoid valve, a ball valve, a pinch valve, and a diaphragm
valve.
20. The hydrogen fuel cartridge of claim 16, further comprising a
mixing element in fluid communication with the liquid reagent
conduit line.
21. A method of generating hydrogen comprising: providing a solid
chemical hydride in a reaction chamber; providing an aqueous
reagent; conveying the aqueous reagent through a distribution point
to contact the chemical hydride in the reaction chamber and to
produce hydrogen gas and a nongaseous product; and moving the
reaction chamber relative to the aqueous reagent distribution point
within said reaction chamber.
22. The method of generating hydrogen of claim 21, further
comprising transporting said hydrogen to a hydrogen device selected
from the group consisting of a fuel cell, a hydrogen-burning
engine, and a hydrogen storage device.
23. The method of generating hydrogen of claim 22, wherein the
hydrogen device is a fuel cell that generates electricity by
oxidizing hydrogen.
24. The method of generating hydrogen of claim 21, wherein the
aqueous reagent is water and wherein the method further comprises
transporting water from the fuel cell to the reaction chamber.
25. The method of generating hydrogen of claim 21, wherein the
aqueous reagent is water and wherein the method further comprises
transporting water from the fuel cell to a chamber for storing the
aqueous reagent or to a mixing element.
Description
FIELD OF THE INVENTION
[0002] The present invention relates to the generation of hydrogen
from a fuel that is stored in solid form and from which hydrogen is
generated using a liquid reagent.
BACKGROUND OF THE INVENTION
[0003] Hydrogen is the fuel of choice for fuel cells. However, its
widespread use can be complicated by the difficulties in storing
the gas. Many hydrogen carriers, including hydrocarbons, metal
hydrides, and chemical hydrides are being considered as hydrogen
storage and supply systems. In each case, systems need to be
developed to release the hydrogen from its carrier, either by
reformation as in the case of hydrocarbons, desorption from metal
hydrides, or hydrolysis of chemical hydrides.
[0004] Complex chemical hydrides, such as sodium borohydride and
lithium borohydride, have been investigated as hydrogen storage
media. The gravimetric hydrogen storage density of sodium
borohydride is 10.8% and lithium borohydride is 18%. Sodium
borohydride has garnered particular interest, because it can be
dissolved in alkaline water solutions with virtually no
reaction--hydrogen is not generated until the solution contacts a
catalyst to promote hydrolysis. In a typical heterogeneous
catalyzed system, the stoichiometric reaction of borohydrides with
water to produce hydrogen gas and a borate is illustrated by the
following chemical reaction for alkali metal borohydride
compounds:
MBH.sub.4+4H.sub.2O.fwdarw.MBO.sub.2.2H.sub.2O+4H.sub.2+heat
(1)
[0005] To maintain the borohydride and borate solids in solution,
water in excess of that required for the stoichiometric hydrolysis
reaction is typically stored, since water generally reacts with the
borate products to form hydrated borate compounds. Extra water may
be added to the system to compensate for this loss, such as by
using a dilute borohydride fuel solution, which limits the
effective hydrogen storage density of such hydrogen generation
systems.
[0006] It is desirable to have a hydrogen generator that maximizes
the hydrogen stored within a given volume. Such generators offer
the potential of compact and safe hydrogen storage that, when
coupled with a fuel cell, can provide systems to meet the growing
demand for portable power.
BRIEF SUMMARY OF THE INVENTION
[0007] The present invention provides apparatus and methods for
hydrogen generation by the hydrolysis of a solid fuel, and methods
of operating a power module. The apparatus include a reaction
chamber bounded by at least one moveable wall and adapted to
contain at least one solid fuel capable of generating hydrogen upon
contact with the solid fuel, and at least one liquid outlet for
contacting the solid fuel with a liquid reagent in the reaction
chamber to produce hydrogen gas and a product. The apparatus
further includes a hydrogen outlet line in communication with the
reaction chamber, and a hydrogen separator adapted to prevent
solids and liquids in the reaction chamber from entering the
hydrogen outlet line.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] A complete understanding of the present invention may be
obtained by reference to the accompanying drawings when considered
in conjunction with the following detailed description, in
which:
[0009] FIG. 1 is an illustration of a hydrogen generation system in
accordance with an embodiment of the present invention.
[0010] FIG. 2 is a schematic illustration of an exemplary fuel
cartridge comprising a hydrogen generation system in accordance
with an embodiment of the present invention.
[0011] FIG. 3 is a schematic illustration of an exemplary fuel
cartridge comprising a hydrogen generation system in accordance
with another embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0012] The present invention provides methods and apparatus for
contacting a chemical hydride fuel with a liquid reagent to
generate hydrogen gas and other nongaseous products.
[0013] The present invention provides apparatus for hydrogen
generation by the hydrolysis of a solid fuel. In a preferred
embodiment, the apparatus include a liquid reagent storage region,
a reaction chamber bounded by at least one moveable wall and
adapted to contain at least one solid fuel capable of generating
hydrogen upon contact with the solid fuel, and at least one liquid
outlet (distribution point) for contacting the solid fuel with the
liquid reagent in the reaction chamber to produce hydrogen gas and
a product. The apparatus further includes a hydrogen outlet line in
communication with the reaction chamber, and a hydrogen separator
adapted to prevent solids and liquids in the reaction chamber from
entering the hydrogen outlet line.
[0014] The present invention further provides methods of generating
hydrogen gas by a hydrolysis reaction utilizing a solid fuel
capable of generating hydrogen and a product when contacted with an
liquid reagent. A liquid reagent is provided, and the liquid
reagent and the solid fuel are contacted in a reaction chamber
bounded by at least one moveable wall, wherein such contact
generates hydrogen gas and a product.
[0015] The present invention further provides methods of generating
hydrogen gas by a hydrolysis reaction utilizing a solid fuel
capable of generating hydrogen and a product when contacted with a
liquid reagent. A liquid reagent is provided, and the liquid
reagent and the solid fuel are contacted in a reaction chamber
bounded by at least one moveable wall and in which at least one
liquid outlet is disposed, wherein such contact generates hydrogen
gas and a product and movement of the movable wall exposes
unreacted solid fuel to the at least one liquid outlet in the
reaction chamber.
[0016] In another embodiment, the present invention provides
methods of operating a power module, by providing a power module
having a hydrogen gas inlet in communication with a hydrogen gas
outlet of an associated hydrogen generator. A solid fuel capable of
generating hydrogen and a product when contacted with a liquid
reagent is provided. A liquid reagent is provided, and the liquid
reagent and the solid fuel are contacted in a reaction chamber
bounded by at least one moveable wall, wherein such contact
generates hydrogen gas and a product.
[0017] As used herein, the term "nongaseous" comprises solid and
liquid forms; the nongaseous products may be a mixture of solid and
liquid materials, and comprise a metal salt product.
[0018] The preferred chemical hydride fuel components of the
present invention are chemical hydrides in solid form. These
chemical hydrides may be utilized in mixtures, but are preferably
utilized individually. The term chemical hydrides as used herein
includes the alkali and alkaline earth metal hydrides and boron
hydrides; these compounds react with water to produce hydrogen gas
and a metal salt, the nature and composition of which depends on
the nature of chemical hydride.
[0019] The term "solid form" encompasses any dry or substantially
dry form, including powder, granules or pellets.
[0020] The alkali and alkaline earth metal hydrides have the
general formula MH.sub.n wherein M is a cation selected from the
group consisting of alkali metal cations such as sodium, potassium
or lithium and alkaline earth metal cations such as calcium, and n
is equal to the charge of the cation. Examples of suitable metal
hydrides, without intended limitation, include NaH, LiH, MgH.sub.2,
and the like. The alkali and alkaline earth metal hydrides
typically produce metal hydroxide salts and hydrogen gas when
hydrolyzed, for example, the reaction of sodium hydride with water
produces hydrogen gas and sodium hydroxide, though the products are
not limited to metal hydroxide salts.
[0021] The terms "boron hydride" or "boron hydrides" as used herein
include boranes, polyhedral boranes, and anions of borohydrides or
polyhedral boranes, such as those provided in co-pending U.S.
patent application Ser. No. 10/741,199, entitled "Fuel Blends for
Hydrogen Generators," filed Dec. 19, 2003 (U.S. Pat. Appl. Publ.
No. 2005/0132640), the entire disclosure of which is hereby
incorporated herein. Suitable boron hydrides include, without
intended limitation, the group of borohydride salts
M(BH.sub.4).sub.n, triborohydride salts M(B.sub.3H.sub.8).sub.n,
decahydrodecaborate salts M.sub.2(B.sub.10H.sub.10).sub.n,
tridecahydrodecaborate salts M(B.sub.10H.sub.18).sub.n,
dodecahydrododecaborate salts M.sub.2(B.sub.12H.sub.12).sub.n, and
octadecahydroicosaborate salts M.sub.2(B.sub.20H.sub.18).sub.n,
among others, where M is a cation selected from the group
consisting of alkali metal cations, alkaline earth metal cations,
aluminum cation, zinc cation, and ammonium cation, and n is equal
to the charge of the cation; and neutral borane compounds, such as
decaborane (14) (B.sub.10H.sub.14); ammonia borane compounds of
formula NH.sub.xBH.sub.y, wherein x and y independently=1 to 4 and
do not have to be the same, of formula NH.sub.xRBH.sub.y, wherein x
and y independently=1 to 4 and do not have to be the same, and R is
a methyl or ethyl group, and of formula NH.sub.3B.sub.3H.sub.7, and
dimethylamine borane (NH(CH.sub.3).sub.2BH.sub.3). For the
above-mentioned boron hydrides, M is preferably sodium, potassium,
lithium, or calcium. These metal hydrides may be utilized in
mixtures, but are preferably utilized individually. The boron
hydrides typically produce a boron-oxygen salt and hydrogen gas
when hydrolyzed. For example, the reaction of an alkali metal
borohydride with water as shown in Equation (1) produces a hydrated
alkali metal metaborate which may be represented by formula
MBO.sub.2.n H.sub.2O, though other products may be produced. For
sodium borohydride (NaBH.sub.4), n preferably is 2; however, n is
variable and is determined by the temperature and the borohydride
salt, among other factors.
[0022] The chemical hydride may be anhydrous or hydrated and
preferably contains less than about 50 wt % water. The hydrated
forms of certain borohydride salts, notably sodium borohydride,
exist at low to moderate temperatures. For example, sodium
borohydride dihydrate (NaBH.sub.4.2H.sub.2O, 51.2 wt % NaBH.sub.4
and 48.8 wt % water) is formed at temperatures below 36.4.degree.
C., potassium borohydride trihydrate exists at temperatures below
7.5.degree. C., and potassium borohydride monohydrate exists at
temperatures below 37.5.degree. C.
[0023] A metal borohydride fuel component may be combined with a
solid stabilizer agent, preferably one selected from the group
consisting of metal hydroxides, anhydrous metal metaborates,
hydrated metal metaborates, and mixtures thereof. Solid stabilized
fuel compositions comprising 20 to 99.7 wt-% borohydride and 0.3 to
80 wt-% hydroxide salts are disclosed in co-pending U.S. patent
application Ser. No. 11/068,838 entitled "Borohydride Fuel
Composition and Methods" filed on Mar. 2, 2005, the entire
disclosure of which is incorporated by reference herein in its
entirety.
[0024] The liquid reagent may be water or may comprise a soluble
catalyst in an aqueous solution. The liquid reagent may be an
aqueous acidic solution, i.e., a reagent having a pH less than
about 7. Suitable acidic reagents include, but are not limited to,
both inorganic acids such as hydrochloric acid (HCl), sulfuric acid
(H.sub.2SO.sub.4), and phosphoric acid (H.sub.3PO.sub.4), and
organic acids such as acetic acid (CH.sub.3COOH), formic acid
(HCOOH), maleic acid, malic acid, citric acid, and tartaric acid,
among others. The acidic reagents may also comprise a combination
of organic and/or inorganic acids. Different acids have different
characteristics such as solution density and viscosity so the
choice of acid may be different for various applications.
Preferably, the acidic reagent is a solution containing the acidic
reagent in a range from about 0.1 to about 40 wt %. In some
embodiments, the acidic reagent is an aqueous solution with a water
concentration in the range of about 44 to about 52 molar (M) water,
preferably about 46 to about 50 M water and most preferably about
48 M water (in comparison, pure water can be considered to have a
water concentration of 55 M water) and has a pH less than 7.
[0025] The liquid reagent may be a transition metal solution, i.e.,
a solution containing a water soluble transition metal salt, for
example, the chloride salts of cobalt (CoCl.sub.2), nickel
(NiCl.sub.2), or copper (CuCl.sub.2). In such cases, as the reagent
solution contacts the borohydride, the metal ion is typically
reduced by the borohydride and deposited as metal particles or
metal boride compounds in the solid borohydride contained within
the reaction chamber, and accumulate in the reaction chamber as the
borohydride is consumed. Since these materials can also catalyze
hydrolysis of borohydride, the increased concentration of metal
catalyst with increased time of operation ensures that the
borohydride fuel is completely converted to hydrogen.
[0026] A plurality of liquid reagents may be used in embodiments of
the present invention. The plurality of liquid reagents may be fed
concurrently; for example, a first liquid reagent comprising a
metal salt solution can be fed in combination with a second liquid
reagent comprising an acidic reagent; or a first liquid reagent
comprising water may be fed in combination with a concentrated
acidic reagent. Alternatively, the hydrogen generator may operate
by initially feeding a first liquid reagent comprising a transition
metal solution to the boron hydride fuel to accumulate metal
particles or metal boride compounds in the solid fuel, and then
feeding a second liquid reagent comprising water or an acidic
reagent to the boron hydride fuel to react with the remaining
fuel.
[0027] In hydrogen generation systems in accordance with
embodiments of the present invention, hydrogen is produced by
contacting a solid chemical hydride fuel with a liquid reagent to
transform the chemical hydride fuel into hydrogen gas and an
oxidized product which is typically a metal salt or oxide compound
("product" or "discharged fuel"). The rate of hydrogen generation
can be regulated by controlling the contact between the acidic
reagent and the solid chemical hydride. The hydrogen generation
reaction can be stopped by preventing contact between the acidic
reagent and the solid chemical hydride.
[0028] Preferred embodiments of the present invention provide
hydrogen generation systems in which relative movement between a
liquid reagent outlet and a solid fuel is provided. For the methods
of the present invention, it is preferred that the discharged fuel
move away from and unreacted fuel move to stationary liquid reagent
distribution points. Preferably, the hydrogen generation systems
allow volume exchange such that the products can occupy the space
originally occupied by the solid chemical hydride and/or liquid
reagent.
[0029] Referring now to FIG. 1, an exemplary generator 100 to
produce hydrogen from the hydrolysis of solid hydride fuel in
accordance with the teachings herein comprises a reaction chamber
110 and a liquid reagent storage chamber 120 preferably separated
by an optional wall 130 wherein the reaction chamber and the liquid
reagent chamber are in communication via a liquid reagent conduit
140; the liquid reagent conduit 140 may be split into a plurality
of conduits 140a. The liquid reagent conduit or conduits terminate
in at least one liquid outlet 150 disposed within the reaction
chamber 110. The at least one liquid outlet 150 may take the form
of a distribution tube or other mechanical sprayer, as well as
other means for delivering drops of a liquid such as atomizers,
spargers, and spray nozzles. Thus, as defined in this application,
the term "liquid outlet" encompasses any liquid distribution
mechanism, or liquid delivery mechanism, or liquid distribution
region, point or structure (such as a tube or sprayer, for example)
that includes at least one element (at least one distribution
point) located at a fixed position relative to the hydrogen
generator.
[0030] Wall 130 can be configured to prevent contact of the solid
hydride fuel with the liquid reagent, and is preferably a plunger
or disk separator that will move along during the hydrogen
generation process. Wall 130 can be replaced with or supplemented
with acid adsorbents; suitable acid adsorbents include, but are not
limited to, polymeric adsorbents such polyacrylic acid polymers,
resins, silicates, carbons, and metal hydroxide salts such as
sodium hydroxide and potassium hydroxide.
[0031] The hydrogen generator further comprises an actuator 170
configured to apply a bias to the reaction chamber 110. FIG. 1
illustrates one preferred nonlimiting location of an actuator;
alternatively, the actuator could be placed between the reaction
chamber 110 and the liquid reagent storage chamber 120, preferably
in contact with the optional wall 130 to either pull the reaction
chamber 110 towards the liquid reagent storage chamber 120 or to
push the two chambers apart.
[0032] Either or both of the chambers 110 and 120 may further
comprise an inner container; wall 130 need not be used in such a
design. Suitable liquid-tight materials for the inner container
include, but are not limited to, nylon; polyurethane;
polyvinylchloride (PVC); polyethylene polymers, such as low density
polyethylene (LDPE), linear low density polyethylene (LLDPE), high
density polyethylene (HDPE), and ethylene-vinyl acetate copolymers
(EVA); natural rubber; synthetic rubber; and metal foil. The inner
container for reaction chamber 110 may further comprise at least
one gas permeable membrane or filter that is preferably
substantially impermeable to liquids and solids. The term
"substantially" in this context means preferentially allowing
passage of gases relative to the passage of solids and/or liquids
or, in preferred cases, allowing passage only of gases. Examples of
suitable gas permeable membranes include materials that are more
permeable to hydrogen than to a liquid such as water, for example,
silicon rubber, polyethylene, polypropylene, polyurethane,
fluoropolymers or any hydrogen-permeable metal membranes such as
palladium-gold alloys. The gas permeable membrane is preferably
microporous and hydrophobic. Ballast hydrogen may be stored within
the hydrogen generator, for instance, in void space within reaction
chamber 110, either internal or external to any optional inner
container.
[0033] Reaction chamber 110 is bounded on one side by a porous wall
175 and preferably by a wall 130 on the opposite side. The porous
wall 175 is configured to permit the passage of hydrogen gas from
the reaction chamber 110 to a hydrogen outlet 160, and may be a
screen plate.
[0034] Preferably, at least one liquid outlet 150 is initially at a
position that is about 1/3 to 1/4 of the total depth of reaction
chamber 110 from wall 130. That is, in an exemplary example, for a
4 inch long reaction chamber measured from wall 175 to wall 130, at
least one liquid outlet is initially positioned from about 31/3
inches to about 21/2 inches from the wall 130. As the reaction
chamber 110 changes during operation, for example, moves and/or
expands, at least one liquid outlet preferably remains fixed within
the hydrogen generator (i.e., its absolute position is unchanged)
while its relative position with respect to unreacted fuel within
the reaction chamber 110 changes.
[0035] The hydrogen generator may further comprise a liquid reagent
regulator to deliver the liquid reagent to the reaction chamber.
Liquid reagent regulators include, for example, pumps such as, but
not limited to, peristaltic pumps, piezoelectric pumps, piston
pumps, diaphragm pumps, centrifugal pumps, and axial flow pumps, or
valves such as, but not limited to, solenoid valves, ball valves,
pinch valves, and diaphragm valves.
[0036] Hydrogen outlet 160 preferably connects to a power module
comprising a fuel cell or hydrogen-burning engine to deliver
hydrogen for conversion to energy, or to a hydrogen storage device,
including balloons, gas cylinders or metal hydrides. Preferably, a
gas permeable membrane is in communication with hydrogen outlet
line 160, preferably at the inlet. The hydrogen generated in the
reaction chamber 110 passes through the membrane to separate the
hydrogen gas and maintain solids and liquids within the reaction
chamber. Examples of suitable gas permeable membranes include
materials that are more permeable to hydrogen than to a liquid such
as water, for example, silicon rubber, polyethylene, polypropylene,
polyurethane, fluoropolymers or any hydrogen-permeable metal
membranes such as palladium-gold alloys.
[0037] Actuator 170 is in communication with wall 175 and provides
mechanical energy to move the chemical hydride fuel in the reaction
chamber 110 by either being expanded or compressed beyond its
relaxed, neutral state. Nonlimiting examples of useful actuators
include tension/extension springs, compression springs, helical
springs, and coil springs. In some configurations, the actuator
will be extended during operation, and will "push" the wall 175
such that the solid fuel contained within the reaction chamber 110
moves in relation to at least one liquid distribution point as
provided in FIG. 1. In other configurations, the actuator will be
compressed during operation, and the actuator will "pull" the fuel
bed in the reaction chamber 110 to facilitate the relative movement
of at least one distribution point.
[0038] An optional inlet may be included to allow water generated
by the hydrogen fuel cell or collected from a condenser or source
elsewhere within the power system to be fed to the liquid reagent
reservoir 120, or to an optional water storage compartment. By
feeding recovered water to the liquid reagent reservoir 120, a
liquid reagent stored in a concentrated form can be diluted prior
to contact with the solid chemical hydride. Alternatively, the
recovered water could be fed concurrently with a liquid reagent as
described herein.
[0039] The components of a hydrogen generation system in accordance
with the teachings herein may be contained with an outer housing to
form a fuel cartridge 200 suitable to use with a fuel cell power
system, for example. In reference to FIG. 2, wherein features that
are similar to those shown in previous figures have like numbering,
an exemplary fuel cartridge 200 comprises a reaction chamber 110
with an inner container 210, a liquid reagent storage chamber 120
with an inner container 220, a wall 130, a liquid reagent conduit
140, at least one liquid outlet 150, hydrogen outlet 160, and an
actuator 170 configured to apply a bias to the reaction chamber
110. Preferably, the fuel cartridge further comprises a gas
permeable membrane 260 in communication with hydrogen outlet line
160 and a liquid reagent regulator 240 to deliver the liquid
reagent to the reaction chamber. Fuel cartridges may comprise
additional optional components such as at least one pressure relief
valve 280, user interface components to determine the amounts of
solid and/or liquid reagent remaining in the cartridge, components
for acid feed control and hydrogen delivery, and power conditioning
components.
[0040] Referring now to FIG. 3, wherein features that are similar
to those shown in previous figures have like numbering, a hydrogen
generation system 300 in accordance with embodiments of the present
invention incorporated with a fuel cell system 270 comprises a
reaction chamber 110 with an inner container 210, a liquid reagent
storage chamber 120 with an inner container 220, a wall 130, a
liquid reagent conduit 140, hydrogen outlet 160, and an actuator
170 configured to apply a bias to the reaction chamber 110.
Preferably, the fuel cartridge further comprises a gas permeable
membrane 260 in communication with hydrogen outlet line 160 and a
liquid reagent regulator 240 to deliver the liquid reagent to the
reaction chamber. A fuel cartridge can also comprise an auxiliary
power system preferably selected from the group comprising of a
rechargeable battery, a capacitor, and a supercapacitor, to provide
electrical power during startup and hydrogen flow transients.
[0041] Water accumulated in a hydrogen fuel cell system 270 can be
recycled to the hydrogen generation system 300 via conduit line
250. The conduit line 250 may connect directly to the liquid
reagent storage chamber 120, or may transport the water to a mixing
element 230. The mixing element 230 allows the water to be combined
with the liquid reagent to provide the active concentration needed
for hydrogen generation.
[0042] The mixing element 230 may comprise a chamber or junction in
the conduits where the liquid reagent and the fuel cell water can
be delivered using separate pumps and mixed to the desired active
concentration. The mixing element 230 may alternately comprise a
three-way valve, such as a solenoid, in which the desired
water/liquid reagent ratio is controlled by the 3-way valve
switching frequency.
[0043] In these and other embodiments of the fuel cartridge
according the present invention, the liquid reagent regulator 240
comprises a separable pump wherein a pump head resides in one of
the fuel cartridge or fuel cell power system and a controller
resides in the other of the fuel cartridge or fuel cell power
system. The controller comprises a motor or an electrical contact.
In general, peristaltic and piston pumps operate through the use of
a pump head comprised of a series of fingers in a linear or
circular configuration or at least one piston which can compress
the fuel line; the fingers may be in a variety of configurations
and alternatively referred to as rollers, shoes, or wipers. The
compression of the fuel line by the fingers forces the liquid
through the line; when the line is not compressed and open, fluid
flows into the fuel line. A diaphragm pump configuration comprises
a diaphragm in the wall of fuel line, check valves on the upstream
and downstream sides of the diaphragm, and a pump head. In general,
diaphragm pumps operate through the use of a pump head comprised of
a series of cams in a linear or circular configuration or at least
one piston which can compress the diaphragm; the compression of the
membrane by the fingers forces the liquid through the line; when
the membrane expands and is not compressed, fluid is drawn into the
fuel line. The cams may be in a variety of configurations and
alternatively referred to as rollers, shoes, or wipers. The check
valves constrain and control the directional flow through the
diaphragm and fuel line.
[0044] In reference to the previous figures, a preferred method for
generating hydrogen using a generator as described herein comprises
conveying a liquid reagent from a storage chamber 120 through
conduit 140 using a liquid reagent regulator 240 to a reaction
chamber 110 containing a solid chemical hydride fuel whereupon it
reacts with the fuel to create hydrogen gas and a nongaseous
product. Preferably, the solid chemical hydride fuel comprises a
mixture of sodium borohydride and sodium hydroxide (preferably
containing from about 87 to about 95 wt % sodium borohydride, and
from about 5 to about 13 wt % sodium hydroxide). Preferably the
liquid reagent is an acidic reagent comprised of hydrochloric acid,
phosphoric acid, or sulfuric acid.
[0045] As the liquid reagent is removed from the chamber 120 and
hydrogen is generated in the reaction chamber 110, the actuator 170
forces the reaction chamber to move into the volume created by
removal of the liquid reagent while the absolute position of the at
least one liquid reagent outlet 150 remains unchanged. Thus,
unreacted solid fuel is moved to the liquid reagent outlet 150. As
hydrogen is produced, it preferably passes through the bed of
unconverted solid fuel (i.e., "fresh fuel") before passing through
the gas permeable membrane 260 and the hydrogen outlet 160. The
unconverted solid fuel bed can thus act as a "scrubber" to remove
any liquid reagent entrained in the gas stream via reaction with
the unconverted solid fuel. The hydrogen generation system is
configured in a volume exchanging configuration in which the
reaction products can occupy the space originally occupied by the
liquid reagent.
[0046] In a preferred embodiment of a method for hydrogen
generation, the system further comprises a battery to control a
liquid reagent regulator. For example, the liquid reagent is
delivered using a liquid reagent regulator such as a peristaltic
pump controlled by a PLC circuit. In operation, when the charge
level of the battery drops to a defined level, for example, about
50% of its fully charged capacity and the system pressure drops
below a set point, for example, less than about 1 psig, the liquid
reagent regulator will be operated to provide the liquid reagent at
a specified feed rate, for example, about 16 mL/h. When the system
pressure exceeds a second set point, for example, above about 5
psig, the controller will signal the liquid reagent regulator to
shut off.
[0047] While the present invention has been described with respect
to particular disclosed embodiments, it should be understood that
numerous other embodiments are within the scope of the present
invention. Accordingly, it is not intended that the present
invention be limited to the illustrated embodiments, but only by
the appended claims.
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