U.S. patent application number 09/803592 was filed with the patent office on 2002-11-14 for micro component hydrocarbon steam reformer system and cycle for producing hydrogen gas.
Invention is credited to Brooks, Christopher J., Seaba, James.
Application Number | 20020168307 09/803592 |
Document ID | / |
Family ID | 25186943 |
Filed Date | 2002-11-14 |
United States Patent
Application |
20020168307 |
Kind Code |
A1 |
Seaba, James ; et
al. |
November 14, 2002 |
Micro component hydrocarbon steam reformer system and cycle for
producing hydrogen gas
Abstract
A micro component steam reformer system for producing
hydrogen-enriched gas to power a fuel cell adapted for scalable
power requirements. The steam reformer system uses a cycle in
which, in laminar flow modules, a vaporized hydrocarbon is mixed
with fuel cell off gas having a hydrogen component and combusted to
heat vaporizers and a steam reformer. Vaporized hydrocarbons and
water vapor are introduced as a feed stock into the steam reformer
to produce a syn-gas which is cooled and purified. The resulting
principally hydrogen gas may be introduced into a hydrogen fuel
cell. Off gas from the fuel cell is recycled to provide hydrogen
and water for use in the system cycle.
Inventors: |
Seaba, James; (Albuquerque,
NM) ; Brooks, Christopher J.; (Dublin, OH) |
Correspondence
Address: |
PORTER WRIGHT MORRIS & ARTHUR, LLP
INTELLECTUAL PROPERTY GROUP
41 SOUTH HIGH STREET
28TH FLOOR
COLUMBUS
OH
43215
|
Family ID: |
25186943 |
Appl. No.: |
09/803592 |
Filed: |
March 9, 2001 |
Current U.S.
Class: |
422/198 ;
422/600 |
Current CPC
Class: |
C01B 3/323 20130101;
C01B 2203/142 20130101; H01M 8/04223 20130101; H01M 8/0612
20130101; C01B 2203/0866 20130101; C01B 2203/80 20130101; Y02P
20/10 20151101; C01B 2203/1604 20130101; C01B 2203/148 20130101;
C01B 2203/0805 20130101; C01B 2203/1229 20130101; B01B 1/005
20130101; H01M 8/0258 20130101; C01B 2203/047 20130101; C01B
2203/0816 20130101; C01B 3/0005 20130101; C01B 2203/0244 20130101;
C01B 2203/1247 20130101; C01B 2203/0822 20130101; C01B 2203/0877
20130101; C01B 2203/1223 20130101; H01M 8/04225 20160201; C01B
3/384 20130101; C01B 2203/066 20130101; B01J 2219/00873 20130101;
C01B 2203/0811 20130101; B01J 2219/00781 20130101; Y02E 60/32
20130101; C01B 2203/0233 20130101; Y02E 60/50 20130101; C01B
2203/1288 20130101; C01B 2203/82 20130101; H01M 8/0267 20130101;
H01M 8/04022 20130101; C01B 2203/0844 20130101; C01B 2203/044
20130101 |
Class at
Publication: |
422/198 ;
422/188 |
International
Class: |
B01L 007/00 |
Claims
1. A micro component system for producing a syn-gas enriched with
hydrogen from hydrocarbon compositions and water comprising: a
mixer for producing a feed stock of vaporized hydrocarbons and
water vapor, a steam reformer into which the feed stock is
directed, a combustor for generating heat energy from fuel cell off
gas and vaporized hydrocarbons to heat the steam reformer, and an
exit from the steam reformer for the syn-gas produced therein,
including means for providing in at least one of the stages in the
system a laminar flow of fluid to effect an energy exchange between
fluids.
2. A micro component power source in accordance with claim 1 in
which a gas enriched with hydrogen is produced from hydrocarbon
compositions and water comprising, interconnected in a cycle: a
fuel cell that consumes hydrogen and exhausts an off gas containing
hydrogen; a combustor for burning the fuel cell off gas to provide
a source of heat energy; a heat exchanger interconnected with the
source of heat energy for transferring heat to a steam reformer; a
means for introducing hydrocarbon compositions and water from a
source into the cycle; a steam reformer for receiving a mixture of
hydrocarbon compositions and water and catalytically reforming the
mixture into a gas enriched with hydrogen; and a flow path between
the steam reformer and the fuel cell for introducing the gas
enriched with hydrogen into the fuel cell.
3. The device of claim 1 or claim 2 in which a heat exchanger
directs fluids between which heat is exchanged into adjacent
laminar flows.
4. The device of claim 1 or claim 2 in which the means for
providing laminar flow includes a catalytically active surface in
contact with fluid flow.
5. The system of claim 2 including a second heat exchanger for
cooling the gas from the steam reformer, a water gas shift reactor
and a preferential oxidation reactor, whereby a gas predominantly
comprised of hydrogen is introduced into the fuel cell.
6. The system of claim 5 including one or more storage tanks for
separately storing at least one of fuel cell off gas, a liquid
hydrocarbon composition and water.
7. The system of claim 2 including an in-line Zeolite cracker.
8. The system of claim 1 or claim 2 or claim 5 or claim 6 or claim
7 in operative combination with a fuel cell.
9. The system of claim 2 including a start module comprising a heat
exchanger with adjacent sections for laminar flow in which hydrogen
from an external source is combusted to provide heat energy in one
section and hydrocarbon fluids are vaporized in an adjacent section
to initiate the vaporization of fluids and steam reforming in the
system.
10. A cycle useful in a micro component assembly for powering for a
fuel cell comprising: combusting a gas mixture including a hydrogen
component to heat at least one vaporizer and a steam reformer;
providing a vaporized hydrocarbon and water mixture and introducing
the mixture into the steam reformer to produce a feed gas; cooling
the feed gas and introducing the feed gas into a hydrogen fuel
cell; and combusting the off gas from the fuel cell to heat the
vaporizer and steam reformer.
11. An incrementally scalable power source in accordance with claim
1 in which scalable power increments of a predetermined magnitude
are determined by the capacity of a laminar flow unit.
12. The device of claim 11 in which the laminar flow unit is a
micro channel having a width to depth aspect ratio of from about
1:10 to about 1:100.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a micro component
hydrocarbon steam reformer system for producing hydrogen gas and a
reaction cycle useful in the system. Particularly, the system
relates to micro component apparatus and cycles useful in powering
fuel cells adapted for motor vehicle use and other discrete systems
having incremental and/or scalable energy requirements.
[0002] Hydrogen fuel cells are non-polluting, highly efficient
power sources.
<www.eren.doe.gov/RE/hydrogen_fuel_cells.html>. See, for
example, FUEL CELLS GREEN POWER, Los Alamos National Laboratory,
U.S. Department of Energy, 1999.
[0003] The use of fuel cells (despite their desirable
characteristics) in motor vehicles, transportation, mobile and
"small scale" applications (varying from powering a laptop computer
to providing power for an entire home), where a discrete source of
hydrogen is required, is hindered because a convenient, safe and/or
mobile source of hydrogen having a size appropriate for the
discrete use is not available.
[0004] It is an object of the invention to provide a hydrocarbon
steam reformer system that produces a hydrogen-enriched gas, such
as used to feed an electric power producing fuel cell. It is a
further object to provide such a system in a configuration and
using a cycle that is convenient, safe, and adaptable for small
scale use and is incrementally scalable to adjust to predetermined
power requirements.
[0005] Prior art convention in fuel cell technology, generally in
automotive applications, employs an auto-thermal reforming system
that, through a sequence of known chemical reactions, converts
hydrocarbons, water and air into hydrogen-enriched gas that feeds a
fuel cell. Steam reformer systems are known; but the art is
skeptical of the adaptability of steam reformer systems for motor
vehicle use. See "Fuel Cell Technology", Automotive Engineer,
September 2000, pages 78 et seq. In contrast, the system of the
invention enables the use of a steam reforming process for
automotive and other predetermined power requirement applications,
achieves improved operating efficiencies, and is adapted to
scalable operation and expansion in discrete modular assemblies.
The invention offers the advantages of small size and is
volumetrically scalable with respect to flow rates as determined by
power requirements for a specific situation.
SUMMARY OF THE INVENTION
[0006] In the preferred embodiment of the invention, an energy
balanced reaction cycle converts gasoline, a liquid mixture of
hydrocarbon compositions (C.sub.xH.sub.y) having properties
approximated by an iso-octane (C.sub.8H.sub.18) model, and water
(H.sub.2O), into a hydrogen (H.sub.2) enriched syn-gas fuel for
powering a fuel cell. An external heat source initiates the cycle
and the steam reformer cycle of the system is fed and partly fueled
by a source of hydrocarbons. The greater efficiency of the system
and the increased concentration of H.sub.2 in the syn-gas produced
by the invention contrasts with auto-thermal systems. Auto-thermal
systems convert gasoline, water and air into a hydrogen (H.sub.2)
enriched syn-gas. The addition of air lowers system efficiency and
generally produces an H.sub.2 concentration with a mole fraction in
the range of about 0.3 to about 0.4 with a high concentration of
nitrogen, a mole fraction of about 0.45, requiring a high flow
rate, less contact time in reaction chambers and larger reactor
size.
[0007] The steam reforming cycle and system of the invention
produces H.sub.2 concentrations in the mole fraction range of about
0.65 to about 0.75. Using a steam reformer, the cycle feeds a
stream of gasoline (or other suitable hydrocarbon) through a series
of catalytic reactors and heat exchangers to produce a hydrogen
(H.sub.2) enriched syn-gas to power a fuel cell in the system
cycle. External energy to drive the steam reforming process and to
effect the vaporization of liquids introduced into the system is
produced by fuel cell off gas and gasoline mixed with ambient air.
The external energy generates heat to drive the steam reforming and
vaporization processes in novel micro component reactor and heat
exchanger modules and devices.
[0008] Hydrogen is stored in a minor quantity by a suitable method,
and introduced from storage to a starter module that includes a
vaporizer which initiates the cycle. The cycle thereafter operates
from a combination of the fuel cell off gas and gasoline, producing
syn-gas useful for powering a fuel cell. The system does not
require a continuous injection of hydrogen from an external
source
[0009] The invention is described more fully in the following
description of the preferred embodiment considered in view of the
drawings in which:
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a schematic diagram of the system and cycle.
[0011] FIG. 1A, FIG. 1B, FIG. 1C, and FIG. 1D show characteristics
of the vaporizer, heat exchanger, steam reformer and water/gas
shift component devices used in a system.
[0012] FIG. 2 depicts representative process temperatures in the
cycle in the designated modules correlated with like modules
identified in FIG. 1.
[0013] FIG. 3A represents in an enlarged perspective detail, a view
of channels that direct laminar fluid flow in micro component
assembly devices used in the system.
[0014] FIG. 3B represents a section of wavyplate separator useful
in a laminar flow micro component module having different catalyst
compositions on opposite sides to promote the different reactions
occurring in the fluid flows on either side of the separator.
[0015] FIG. 3C is a detail of a perspective and cross sectional
view of a section of a laminar flow micro component module showing
channels on opposite sides of a separator plate for directing fluid
flow.
[0016] FIG. 4 is a representation of an embodiment of the invention
utilizing a start module, also showing fluid flow and principal
components in the system used with a hydrogen fuel cell.
DETAILED DESCRIPTION OF THE INVENTION AND THE PREFERRED
EMBODIMENT
[0017] Generally described, the system and cycle of the invention
is a steam reformer system for producing hydrogen enriched gas from
liquid or vaporized hydrocarbons. In an embodiment, gasoline is
steam reformed in a cycle to produce H.sub.2, preferably to power a
fuel cell. In the cycle, the off gas of the fuel cell is utilized
as a source of heat energy to power the cycle. A vaporized
hydrocarbon is mixed with fuel cell off gas having a hydrogen
component and combusted to heat the steam reformer. Vaporized
hydrocarbons and water vapor are introduced into the steam reformer
to produce a syn-gas primarily comprising H.sub.2, CO.sub.2, CO,
H.sub.2O, and CH.sub.4. The gas is cooled. CO is removed. The
resulting principally hydrogen gas is introduced into the hydrogen
fuel cell.
[0018] Water and gasoline are vaporized then mixed; the mixture is
processed and ultimately directed to a high temperature steam
reformer and then to a water gas shift reactor where hydrogen gas
is produced in known reactions approximated by the equations:
C.sub.8H.sub.18+12H.sub.2O- =4CO+4CO.sub.2+21 H.sub.2 and
CO+H.sub.2O.fwdarw.CO.sub.2+H.sub.2.
[0019] The resulting H.sub.2 rich syn-gas is then preferentially
oxidized in a reactor prior to introduction into the fuel cell. The
fuel cell will utilize about 60% to about 90% of the H.sub.2 in the
syn-gas mixture. The remaining unutilized H.sub.2 exits the fuel
cell and is mixed with hydrocarbons (gasoline) to supply energy to
drive the heat exchange, vaporization, steam reformer and water gas
shift processors and reactors in the system.
[0020] The cycle is started using hydrogen from the fuel cell off
gas that is stored in a suitable vessel interconnected with the
system. The cycle operates independently after start-up. A suitable
starting device is described in our application "Micro Component
Start Module for a Hydrogen Generation System" (to be filed). The
starting device is a module that includes a vaporizer and a
combustor initiated by the stored fuel cell off gas hydrogen. Once
initiated and operating, the heat energy source for the system
comprises vaporized hydrocarbons and fuel cell off gas that provide
the energy to drive the system. The off gas/hydrocarbon mixture is
catalytically combusted in the system in micro component vaporizer
and steam reformer devices that are serially interconnected in
conformance with the processing sequences described herein. After
the steam reformer processing, H.sub.2 is produced in a gas mixture
which is then treated in a water gas shift reactor and
preferentially oxidized before the gas is introduced into the fuel
cell to remove CO that may otherwise poison the fuel cell.
[0021] An example of the system and cycle illustrated in FIG. 1 is
described below:
EXAMPLE I
[0022] With reference to FIG. 1, a fuel processor for processing
hydrocarbon fuel to produce hydrogen includes first and second fuel
vaporizers 14 and 22, water vaporizer 18, mixer 26 for mixing
vaporized fuel and fuel cell off gas, first heat exchanger 30,
steam reformer 34, second heat exchanger 38, first water gas shift
reactor 42, third heat exchanger 46, second water gas shift reactor
50, fourth heat exchanger 54, preferential oxidation reactor 60,
storage tank 64 for storing fuel cell off gas, and fuel cell stack
68.
[0023] In the fuel processor, a hydrocarbon fuel, preferably a
liquid fuel such as gasoline, is vaporized by the first fuel
vaporizer 14. (In an embodiment, energy for vaporizer 14 may be
provided by the combustion of fuel cell off gas maintained in a
buffer or other storage.) The vaporized fuel is mixed with stored
fuel cell off gas, or hydrogen, from storage tank 64 in mixer 26
until the fuel processor is heated and running, at which point the
vaporized liquid hydrocarbon fuel is mixed in mixer 26 with fuel
cell off gas from the fuel cell stack 68. The mixture of fuel cell
off gas and vaporized fuel from the mixer 26 is introduced into and
primarily catalytically burned in the water vaporizer 18 to
vaporize water, raising the temperature of the water from ambient
temperature (approximately 25.degree. C.) to approximately
350.degree. C. The off gas/hydrocarbon mixture may also be
introduced for catalytic burning in the second fuel vaporizer 22
and steam reformer 34. Temperatures provided throughout relate to
specific experimental models and are variable dependent on
component design, system catalyst and heat characteristics, overall
tolerances, flow rates, and other design and reaction criteria.
[0024] In the second fuel vaporizer 22, hydrocarbon fuel for the
steam reformer 34 is vaporized, raising the temperature of the feed
stream from ambient (approximately 25.degree. C.) to approximately
350.degree. C. The vaporized fuel from the second fuel vaporizer 22
and the water vapor from the water vaporizer 18 are mixed and fed
to the first heat exchanger 30. The mixture of fuel and water vapor
is heated to approximately 700.degree. C. and fed to the steam
reformer 34. In the steam reformer 34, the fuel and water vapor
undergo a catalyst induced reaction to produce syn-gas comprising
H.sub.2, CO.sub.2, CO, H.sub.2O, and CH.sub.4. Heat generated in
the steam reformer 34 is directed back to heat exchanger 30 and
combustor 22. Where heat transfer is from a higher to lower
temperature, a recouperative heat exchanger module (i.e., without a
catalyst) may be utilized.
[0025] The syn-gas leaves the steam reformer and passes through a
second heat exchanger 38, where water is added to the syn-gas to
cool the syn-gas to approximately 450.degree. C. The syn-gas then
passes through a first water gas shift reactor 42 to reduce the
proportion of CO component gas from the syn-gas mixture. The
syn-gas then passes through third heat exchanger 46, where water is
added and the syn-gas cools to approximately 250.degree. C. The
syn-gas then passes through second water gas shift reactor 50 to
further reduce the CO component from the syn-gas. In the water gas
shift reactors, the catalyst induced reaction is
CO+H.sub.2OH.sub.2+CO.sub.2. After exiting the second water gas
shift reactor 50, the gas passes through a fourth heat exchanger
54, which reduces the syn-gas temperature to approximately
100.degree. C. Finally, the syn-gas is passed through the
preferential oxidation reactor 60 and to the fuel cell bank 68. The
off-gas from the fuel cell is then routed back to the mixer 26
and/or storage/buffer tank 64. Water produced in the fuel cell 68
may be cycled in the system, for example, to add water to the
syn-gas at the second and third heat exchangers 38 and 46, or
stored as a feed stock.
[0026] Zeolite crackers known in the art may be placed after the
first and/or second fuel vaporizers 14 and 22 to break down a
hydrocarbon fuel such as gasoline, into lighter hydrocarbons that
may catalytically burn easier in heating the water vaporizer 18 and
steam reformer 34.
[0027] FIG. 1A, FIG. 1B, FIG. 1C and FIG. 1D show in cross-section
characteristics of the system component vaporizers 14, 18 and 22,
heat exchangers 30, 38, 46 and 54, steam reformer 34, and water gas
shift reactors 42 and 50 used in the system. Using a vaporizer 200
as an example in FIG. 1A, separate laminar fluid flows are directed
through adjacent volumes 201 and 202 in a micro component structure
with a separator 203 forming adjacent channels for directing
laminar fluid flow. In the vaporizer, the liquid water or
hydrocarbon composition passes through one volume 201 of the
component assembly to be vaporized as the result of heat exchanged
by conduction with the fluid flow of heated gas in the adjacent
volume 202 of the component assembly. Heat exchangers for the
system are similarly structured micro component devices. Heat
exchanger 300 shown in FIG. 1B provides separate laminar fluid flow
channels directed through adjacent volumes 301 and 302 on opposite
sides of a separator 303 in the device in which heat energy between
the two adjacent channels may be exchanged primarily by conduction
or diffusion, depending on whether the respective fluids are in a
vaporized liquid or gas state. Likewise steam reformer 34 shown as
400 in FIG. 1C, provides separate laminar fluid flow channels
directed through adjacent volumes, optimally, a catalytic reaction
chamber 401, and a fluid flow heat source 402 on opposite sides of
a separator 403 in the device in which heat is exchanged primarily
by diffusion and conduction between gas flows on opposite sides of
the separator. The water/gas shift reactors 42 and 50 are similarly
structured devices with separated channels for directing fluid flow
in the channels defined by the separators on their opposite sides
as shown in the reactor 500 of FIG. 1D having separated channels
501 and 502 formed by channel separator 503.
[0028] In the modules in which a reaction occurs, the side of the
separator component on which a reaction occurs is optimally coated
with an appropriate catalyst to induce the appropriate process
reaction within the module on that side of the separator.
[0029] FIG. 3A illustrates in enlarged detail a section of a
wavyplate separator in a micro component assembly used in the
system, and the relationship of the separator to fluid flows on its
opposite sides. The separate fluid flows on the opposite sides of
the wavyplate may be in the same or in opposite directions. In FIG.
3A, a shaped or folded wavyplate 320 has two opposite sides 321 and
322 (322 is shown coated with a catalyst material 324),
respectively exposed to laminar fluid flows 331 and 332 in a heat
exchanger assembly. Such types of devices used in the system are
described in U.S. application for patent Ser. No. 09/627,267, filed
Jul. 28, 2000 for "Multi-purpose Micro Channel Micro Component"
owned by the assignees of the present application.
[0030] In one embodiment as a steam reformer chamber shown in FIG.
3B, the one side of the wavyplate 321 is formed with a coating of a
metal oxide catalyst material 321A to promote the steam reforming
reaction in fluid flow on that side of the separator plate.
Maintenance of the steam reforming reaction requires that heat be
input into the exchanger. The sustained 700.degree. C. heat for the
steam reforming reaction is provided by a further catalytically
induced exothermic reaction, in the fluid flow on the opposite side
of the separator, of a mixture of combustible materials, such as
fuel cell off gas containing hydrogen, and/or gasoline, and air on
the opposite side of the separator plate which is coated with a
catalyst 321B. In an example, center points of the sections (top to
top) of the wavyplate are approximately 3.0 millimeters apart. The
preferred steam reformer is a micro component assembly having a
high heat flux in which separate sections of a heat exchanger are
divided by a thin plate having an oxidation catalyst on one side
(exothermic, to provide heat) and a steam reforming catalyst
(endothermic) on the other, in which heat transfer occurs by
conduction. Fluid flow on opposite sides of the separator may be in
the same (co-flow) or opposite (counter-flow) directions.
[0031] In the various modules used in the system, the separator
should be as thin and rigid as possible, in the order of magnitude
of approximately 100 microns to approximately 1000 microns as a
maximum. Inconel.RTM. is a useful material. Design parameters
depend on accommodating thinness with separator rigidity and heat
transfer characteristics, i.e., .DELTA.T.degree./Thickness. In the
operation of the cycle, heat transfer between fluids is optimally
balanced depending on the flow rate of the fluid passing in the
steam reformer, the rate of steam reforming, the catalysts on both
sides, the capability of the oxidation catalyst and the flow rate
on the oxidation side. Heat utilization an/or catalyst
characteristics on the steam reforming side are design factors.
[0032] FIG. 3C shows a section of a micro component module 320 with
a wavyplate separator 321 forming laminar flow channels on both
sides of a separator in an enclosure having lower and upper sides
335A and 335B. For clarity, the right and left sides and inlet and
outlet orifices for flow in the channels of the module are not
shown. As noted above, micro component assemblies useful to be
adapted to vaporizer, heat exchanger, steam reformer and water/gas
shift devices for the system are described in co-pending
application Ser. No. 09/627,267 owned by the assignee of the
present application.
[0033] With reference to the various system modules shown in FIG.
1, the following Table I relates the modules to reference numerals
in the drawings, functions and reactions accomplished, and the
approximate preferred (design optimum) temperatures related to the
fluid processing accomplished therein:
1TABLE I Module Reference No. Function Reaction Temperature
.degree. C. 14 Vaporizer Hydrocarbon 25.degree. in/350.degree. out
(gasoline) fuel is vaporized. 18 Vaporizer Liquid water In:
25.degree. is vaporized. Out: 500.degree. +/- 200.degree. 22
Vaporizer Hydrocarbon In: 25.degree. (gasoline) fuel is Out:
500.degree. +/- 200.degree. vaporized. 30 Heat The temperature of
the In: 500.degree. +/- 200.degree. Exchanger hydrocarbon/water
Out: 800.degree. +/- 200.degree. vapor mixture is increased. 34
Steam Catalyst induced 800.degree. +/- 200.degree. Reformer
reaction to produce syn-gas: H.sub.2, CO.sub.2, CO, H.sub.2O, and
CH.sub.4. 38 Heat In: 800.degree. +/- 200.degree. Exchanger Out:
350 .degree. 42 Water/Gas CO is removed from 350.degree. Shift
Reactor the syn-gas. CO + H.sub.2O.rarw..fwdarw.H.sub.2 + CO.sub.2
46 Heat In: 350.degree. +/- Exchanger Out: 200.degree. +/- 50
Water/Gas CO in syn-gas is 200.degree. Shift Reactor optimally
reduced to 10 ppm. CO + H.sub.2O.rarw..fwdarw.H.sub.2 + CO.sub.2.
54 Heat 100.degree. +/- Exchanger 60 Preferential 100.degree. +/-
Oxidizer
[0034] Although current optimal temperatures and ranges determined
by testing and simulation are provided, optimal temperatures and
ranges depend on interrelationships among components, laminar flow
characteristics, and system design parameters. Modules 38 and 46
are principally water vaporizers where heat is provided on one side
of the module to vaporize water (vapor) flowing on the other side,
and depending on design factors otherwise, may not require an
exothermic catalyst on the side opposite the water/vapor flow.
[0035] In a similar manner, Table II (considered in conjunction
with FIG. 1 and FIG. 2) relates the micro component modules to the
properties of the opposite sides of the separators in the devices
with regard to the functions and/or reactions in the fluid flow
passing on opposite sides and the catalyst properties of the
respective separator sides. Useful catalysts identified with
respect to the example include platinum, palladium, cerium oxide,
aluminum hydroxide and cuprous oxide; other suitable catalysts may
be substituted for the functions specified. In steady state
simulations, catalyst composition for the steam reformer and water
gas shift reactors are not factors.
2TABLE II Module Reference No. Separator Properties and Function
Flow Side One Flow Side Two 14 (FIG. 1) Hydrocarbon (gasoline) fuel
25.degree. in/350.degree. out Vaporizer is vaporized. Catalyst:
None Catalyst: Pd, Pt Reference No. 14a Reference No. 14b 18 (FIG.
1) Liquid water 25.degree. in/350.degree. out 18a (FIG. 4) is
vaporized. Combustor for HC and H.sub.2 Vaporizer Catalyst: None
Catalyst: Pd, Pt Reference No. 18b Reference No. 18a 22 Hydrocarbon
(gasoline) fuel 25.degree. in/350.degree. out Vaporizer is
vaporized. Combustor for HC and H.sub.2 Catalyst: None Catalyst:
Pd, Pt Reference No. 22b Reference No. 22a 30 The temperature of
the 350.degree. in/700.degree. out Heat hydrocarbon/water vapor
Exchanger mixture is increased. Catalyst: None Catalyst: Pd, Pt
Reference No. 30a Reference No. 30b 34 Oxidation side: Steam
Reformer side: Steam Catalyst induced reaction 700.degree. Reformer
To produce syn-gas: H.sub.2, Combustor for HC and H.sub.2 CO.sub.2,
CO, H.sub.2O, and CH.sub.4. Catalyst: Pd, Pt Catalyst: Pd,
Pt/CeO/Al.sub.2O.sub.3 Reference No. 34a Reference No. 34b 38
700.degree. in/450.degree. out Heat Catalyst: Pt/Pd Catalyst: None
Exchanger Reference No. 38a Reference No. 38b (FIG. 1) Evaporator-
Cooler (FIG. 4) 42 CO is removed from the 450.degree. Water/Gas
syn-gas. Heat exchange. Shift CO + H.sub.2O.rarw..fwdarw.H.sub.2 +
CO.sub.2 Reactor Catalyst: Pt, CeO Catalyst: None Reference No. 42b
Reference No. 42a 46 350.degree. in/250.degree. out Heat Catalyst:
Pt, Pd Catalyst: None Exchanger Reference No. 46a Reference No. 46b
(FIG. 1) Evaporator- Cooler (FIG. 4) 50 CO in syn-gas is optimally
250.degree. Water/Gas reduced to 10 ppm. Heat Exchange. Shift
Reactor CO + H.sub.2O.rarw..fwdarw.H.sub- .2 + CO.sub.2. Catalyst:
CuO Catalyst: None Reference No. 50b Reference No. 50a 54
100.degree. Heat Catalyst: None Catalyst: None Exchanger Reference
No. 54a Reference No. 54b (FIG. 1) 60 100.degree. Preferential
Catalyst: Pt, Pd Catalyst: None Oxidizer Reference No. 60
EXAMPLE II
[0036] A second example is shown in FIG. 4. In operation, the
process is self-sustaining from fuel sources of hydrocarbons and
water. A balanced isothermal reactor is provided that converts
gasoline and water into hydrogen enriched gas that powers the fuel
cell bank. The gasoline vapor supplies all combustors used for
heating in the system; gasoline is both a fuel (as a source of heat
for the combustors) and the raw material used in the production of
hydrogen enriched gas. In the combustors, heat is generated from
gasoline by means of a catalytic combustion reaction induced by a
catalyst. Heat is transferred to the fluid on the opposite side of
the separator as explained above. Stored hydrogen is used only when
the system is started to initiate combustion in the first
vaporizer.
[0037] FIG. 4 shows the system in conjunction with a starting
device and a fuel tank and also illustrates the relationships of
the micro component modules and their sections as involved in fluid
flow in the system. In FIG. 4, an external fuel bank includes
separate storage tanks for the storage of predetermined quantities
of water (H.sub.2O), gasoline (or other hydrocarbon fuel) and fuel
cell off gas (or hydrogen (H.sub.2)) used in the system. A start
module includes sections respectively indicated as combustor,
vaporizer and combustor assembled in a common module. As noted, the
start-up device is described in our application to be filed. In
starting the processor, hydrogen mixed with air is introduced into
combustor and generates sufficient heat to vaporize gasoline and
produce hydrocarbon vapor that is mixed with hydrogen to supply
heat energy to combustor. Once fluid flow and reactions balance in
the system, the flow of stored hydrogen is terminated and vaporizer
and combustor in the system perform in the continuous reaction
cycle equivalently to vaporizer 14 shown in FIG. 1.
[0038] Table III describes properties of the combustor, vaporizer
and combustor sections of the starting device shown in FIG. 4. The
starting device may be configured as a "sandwich" of units having
the characteristics of the assembly shown in FIG. 3C.
3TABLE III Module Module Section Properties Function Combustor
Vaporizer Combustor Combustor/ Hydrogen is mixed Gasoline is
Vaporized Vaporizer/ with air and burned. vaporized. gasoline is
mixed Combustor Catalyst: Pd Catalyst: None with fuel cell off gas,
combusted and heat energy is directed to the vaporizer section.
Catalyst: Pt/Pd
[0039] Gasoline is the preferred fuel in the invention, because of
its widespread production and distribution network, its general
availability and its utility as a feed stock in the steam reforming
process. In virtual modeling of the system, iso-octane
(C.sub.8H.sub.18) was the preferred embodiment hydrocarbon for
providing heat energy (mixed with fuel cell off gas) and for
providing the feed stock component for the steam reforming in the
model base. Gasoline is a mixture comprising approximately 50 or
more hydrocarbons, C.sub.XH.sub.Y; iso-octane C.sub.8H.sub.Y is a
surrogate used as a model in virtual process simulations
[0040] The system is scalable to meet varying power requirements in
which incremental design units are determined by the number of
channels in the separate HEX (heat exchange, catalyst, reactor and
processor) units as well as the number of HEX units. Channels in
the units having a predetermined point to point separation are
optimally designed to have a maximum depth allowing fluid flow to
pass over a maximized surface area. For example, the length of a
channel determines the residence time of a fluid increment and is
in turn dependent on pressure change in the channel. In an example
of a channel unit with a nominal channel gap of 250 microns +/- 50
microns (allowing for the thickness of a catalyst coating) the
channel separation to depth aspect ratio may be in the range from
about 1:10 or 1:25 to 1:100, determined by design considerations,
to maximize surface area and reaction efficiency as design
parameters.
[0041] The system is an energy conversion unit with overall power
production ranges extending from a few watts to megawatts scalable
units of the systems are useful in robotics, laptop computers,
micro electronic devices, automobile engines, hydrogen re-fueling
stations and other mobile or fixed location applications where a
discrete, as opposed to distributed, source of hydrogen is required
by preference or necessity. The system is assembled from micro
component devices that are modular and scalable through the use of
small "units", based on laminar channel capacity, that may be
assembled incrementally to provide a predetermined source of
maximum power. For example, four 25 kw units may be incrementally
ganged to provide 100 kw and operated to provide a continuous 0-100
kw range and/or configured for optimum power needs such as a 50-75
kw range.
[0042] Fluid flows through the channels as a result of pressure
differential is in the order of a differential pressure drop of
less than 100 psi; laminar flow through the channels provides a low
pressure drop in the system. Water, in the form of condensate from
system exhaust, is introduced through a pump, as is the gasoline or
hydrocarbon component introduced under pressure. Reaction balance
in the system is achieved by variably adjusting pump and compressor
pressures to maintain fluid flow such that reactions are
balanced.
[0043] In addition to, or in combination with gasoline, methanol
and ethanol may be used in the system. Methane is a gas and would
not need to be vaporized. As noted, other hydrocarbon fuel sources
such as methanol, ethanol, methane, ethane, propane, butane and
other hydrocarbon fuels and mixtures thereof may be utilized as
combustion sources or hydrogen gas precursors in cycles of the
system adapted from the preferred embodiment in accordance with
suitable stoiciometric variations that result in a balanced
reaction cycle having the characteristics described herein. Certain
of these hydrocarbons are stored as liquids, but may be introduced
to the system as gases, in this instance, eliminating a need in the
system for vaporizer components at cycle beginning stages.
[0044] Having described the invention in detail, those skilled in
the art will appreciate that, given the present disclosure;
modifications may be made to the invention without departing from
the spirit of the inventive concept herein described. Rather, it is
intended that the scope of the invention be determined by the
appended claims.
* * * * *