U.S. patent application number 12/160803 was filed with the patent office on 2009-01-01 for systems and methods of converting fuel.
Invention is credited to Liang-Shih Fan, Puneet Gupta, Fanxing Li, Luis Gilberto Velazquez Vargas.
Application Number | 20090000194 12/160803 |
Document ID | / |
Family ID | 38257054 |
Filed Date | 2009-01-01 |
United States Patent
Application |
20090000194 |
Kind Code |
A1 |
Fan; Liang-Shih ; et
al. |
January 1, 2009 |
Systems and Methods of Converting Fuel
Abstract
Systems and methods for converting fuel are provided wherein the
system comprises at least reactors configured to conduct
oxidation-reduction reactions. The first reactor comprises a
plurality of ceramic composite particles, wherein the ceramic
composite particles comprises at least one metal oxide disposed on
a support. The first reactor is configured to reduce the least one
metal oxide with a fuel to produce a reduced metal or a reduced
metal oxide. The second reactor is configured to oxidize the
reduced metal or reduced metal oxide to produce a metal oxide
intermediate. The system may also comprise a third reactor
configured to oxidize the metal oxide intermediate to regenerate
the metal oxide of the ceramic composite particles.
Inventors: |
Fan; Liang-Shih; (Columbus,
OH) ; Gupta; Puneet; (Houston, TX) ; Velazquez
Vargas; Luis Gilberto; (Columbus, OH) ; Li;
Fanxing; (Columbus, OH) |
Correspondence
Address: |
DINSMORE & SHOHL LLP
ONE DAYTON CENTRE, ONE SOUTH MAIN STREET, SUITE 1300
DAYTON
OH
45402-2023
US
|
Family ID: |
38257054 |
Appl. No.: |
12/160803 |
Filed: |
January 12, 2007 |
PCT Filed: |
January 12, 2007 |
PCT NO: |
PCT/US07/00956 |
371 Date: |
July 14, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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60758424 |
Jan 12, 2006 |
|
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60758507 |
Jan 12, 2006 |
|
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60808928 |
May 26, 2006 |
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Current U.S.
Class: |
48/199R ; 501/94;
502/102 |
Current CPC
Class: |
C10J 2300/0983 20130101;
C10J 2300/0969 20130101; C10J 2300/093 20130101; Y02E 20/34
20130101; C01B 2203/0485 20130101; C10J 3/482 20130101; C10J
2200/09 20130101; C01B 3/56 20130101; C01B 2203/043 20130101; C01B
2203/042 20130101; C10J 3/82 20130101; C10J 2300/165 20130101; Y02P
30/30 20151101; C10J 2300/0973 20130101; C01B 2203/86 20130101;
C01B 3/50 20130101; Y02P 30/00 20151101; Y02E 20/346 20130101; C01B
3/16 20130101; C01B 2203/0465 20130101; C10J 3/54 20130101; C10J
3/725 20130101 |
Class at
Publication: |
48/199.R ;
502/102; 501/94 |
International
Class: |
C10J 1/20 20060101
C10J001/20 |
Claims
1. A system for converting fuel comprising: a first reactor
comprising a plurality of ceramic composite particles, the ceramic
composite particles comprising at least one metal oxide dispersed
on a support, wherein the first reactor is configured to reduce the
at least one metal oxide with a fuel to produce a reduced metal or
a reduced metal oxide, and is further configured to produce carbon
dioxide, steam, or combinations thereof; a second reactor
configured to oxidize at least a portion of the reduced metal or
reduced metal oxide from the first reactor to produce a metal oxide
intermediate, and is further configured to produce hydrogen, carbon
monoxide, syngas, heat or combinations thereof wherein the oxidant
utilized in the oxidizing steps comprises steam, carbon dioxide,
air, oxygen, or combinations thereof, wherein the oxidants being
configured to produce the syngas in the second reactor; and a third
reactor in communication with the first reactor, the second reactor
or both that is configured to regenerate the at least one metal
oxide by oxidizing the metal oxide intermediate of the second
reactor, and is further configured to produce heat in the third
reactor.
2. A system according to claim 1 wherein the second reactor is also
configured to produce H.sub.2, CO, heat, or combinations
thereof.
3. A system according to claim 1 wherein the H.sub.2/CO ratio of
the syngas is controlled by recycling part of the second reactor
product, or controlling the amount of CO.sub.2 and steam oxidants
inputted into the second reactor.
4. A system according to claim 1 wherein the ceramic composite
particles comprise a promoter.
5. A system according to claim 1 wherein the fuel comprises a solid
fuel, a liquid fuel, a gaseous fuel, or combinations thereof.
6. A system according to claim 1 further comprising a separation
unit configured to remove ash, char, or unwanted materials from a
product stream of the second reactor, the third reactor, or
both.
7. A system according to claim 8 wherein the ash separator
comprises a cyclone, a sieve, a particle classifier, or
combinations thereof.
8. A system according to claim 1 wherein the first and second
reactors are configured to operate at a pressure of between about 1
atm to about 150 atm.
9. A system according to claim 1 wherein the first and second
reactors are configured to operate at a temperature of between
about 400 to about 1200 C.
10. A system according to claim 1 wherein the metal oxide comprises
a metal selected from the group consisting of Fe, Cu, Ni, Sn, Co,
Mn, and combinations thereof, and the support material comprises at
least one component selected from the group consisting of SiC,
oxides of Al, Zr, Ti, Y, Si, La, Sr, Ba, and combination
thereof.
11. A system according to claim 1 further comprising a power
generation section configured to produce electricity from a product
of the second reactor.
12. A system according to claim 1 further comprising at least one
heat exchanger configured to heat a feed comprising water, steam
and combinations thereof.
13. A system according to claim 1 wherein the first reactor and the
second reactor comprise at least one moving bed reactor, a series
of fluidized bed reactors, a rotatory kiln, a fixed bed reactor, or
combinations thereof.
14. A system according to claim 13 wherein the first reactor and
the second reactor defines a countercurrent contacting pattern
between gas and solids.
15. A system according to claim 1 wherein the first reactor is a
moving bed reactor comprising a mixing device inserted in the
moving bed to radially distribute the ceramic composite particles
and mix unconverted fuel with the ceramic composite particles.
16. A system according to claim 1 wherein the first reactor is a
moving bed reactor defines an annular region created around the
moving bed, the annular region being location where a fuel is
introduced.
17. A system according to claim 1 further comprising a conveyor or
pneumatic feeding device configured to deliver the solid fuel to
the first reactor.
18. A system according to claim 1 further comprising a solid fuel
gasifier, a candle filter, a mercury removal unit, a gas cleanup
component, a pressure swing absorption unit, a water gas shift
reactor, or combinations thereof.
19. A system according to claim 1 wherein the first reactor
comprises metal carbonates, metal oxides, or metal hydroxides
configured to capture pollutants, heavy metals, or combinations
thereof.
20. A system according to claim 1 wherein the first reactor is
operable to receive a recycled H.sub.2 stream at a bottom portion
of the reactor.
21. A system according to claim 1 wherein the first reactor is
operable to receive the fuel at a first reactor region below a feed
region of the ceramic composite particles.
22. A system according to claim 1 wherein the first reactor is
operable to receive feeds including oxygen, CO.sub.2, air, steam,
and combinations thereof at a location adjacent the middle region
in which the fuel is fed.
23. A system according to claim 1 wherein the system is coupled to
a solid oxide fuel cell.
24. A system according to claim 1 wherein the system is in fluid
communication with a Fischer-Tropsch reactor.
25. A system according to claim 24 further comprising a refining
section.
26. A system according to claim 1 wherein the first and second
reactors comprise packed beds in the form of portable cassettes,
wherein the portable cassettes are configured to generate and store
hydrogen in a vehicle.
27. A system comprising: a Fischer-Tropsch reactor configured to
produce hydrocarbon fuel from a feed mixture comprising fuel; a
first reactor comprising a plurality of ceramic composite
particles, the ceramic composite particles comprising at least one
metal oxide disposed on a support, wherein the first reactor is
configured to reduce the at least one metal oxide with fuel to a
reduced metal or a reduced metal oxide, the fuel being comprised at
least partially of the hydrocarbon product of the Fischer-Tropsch
reactor; and a second reactor configured to oxidize the reduced
metal or reduced metal oxide with steam to produce metal oxide
intermediates, wherein the second reactor is also configured to
produce syngas.
28. A system according to claim 27 further comprising: a gaseous
fuel feed source; a refining system to treat the hydrocarbon
products generated in the system.
29. A system according to claim 27, wherein the oxidant is steam,
CO, air, O.sub.2, or combinations thereof.
30. A system according to claim 27, wherein the steam utilized in
the second reactor comprises at least partially steam generated in
a Fischer-Tropsch reactor or a gasifier.
31. A system according to claim 27 further comprising a third
reactor in communication with the first reactor and configured to
regenerate the at least one metal oxide by oxidizing the metal
oxide intermediates.
32. A system according to claim 27 wherein the second reactor is
also configured to produce hydrogen.
33. A system according to claim 27 wherein the fuel fed to the
first reactor comprises at least partially syngas produced by
gasification of a hydrocarbon fuel.
34. A system according to claim 27 wherein byproducts of the
Fischer-Tropsch reactor are recycled to the first reactor.
35. A system according to claim 27 further comprising a steam
turbine configured to produce electricity from steam generated in
the system.
36. A system according to claim 27 further a gaseous fuel mixing
location, wherein a gaseous fuel feed and a hydrogen containing
product from the second reactor are operable to mix to produce a
gaseous fuel having a molar ratio of hydrogen to carbon monoxide
equal to about 2 to 1, the gaseous fuel being used in the feed
mixture of the Fischer-Tropsch reactor.
37. A method of preparing ceramic composite particles comprising
the steps of reacting a metal oxide with a support material; heat
treating the mixture of metal oxide and support material at
temperatures of between about 200 to about 1500.degree. C. to
produce ceramic composite powders; converting the ceramic composite
powders into ceramic composite particles; reducing and oxidizing
the ceramic composite particles prior to use in a reactor.
38. A method according to claim 37 further comprising adding a
promoter material to the mixture of metal oxide and support
material.
39. A method according to claim 37 wherein heat treating occurs in
the presence of inert gas, steam, oxygen, air, H.sub.2, and
combinations thereof at a pressure of between vacuum pressure and
about 10 atm.
40. A method according to claim 37 further comprising chemically
treating the mixture of metal oxide and promoter to activate a
ceramic composite powder.
41. A method according to claim 37 wherein the reacting step occurs
via spray drying, direct mixing, co-impregnation, or combinations
thereof.
42. A method according to claim 37 wherein the conversion of
ceramic composite powders occurs via extrusion, granulation,
pelletization, and combinations thereof.
43. A particle produced by the method of claim 37.
44. A particle according to claim 43 wherein the metal oxide
comprises a metal selected from the group consisting of Fe, Cu, Ni,
Sn, Co, Mn, and combinations thereof.
45. A particle according to claim 43 wherein the ceramic composite
comprises at least 40% by weight of the metal oxide.
46. A particle according to claim 43 wherein the support material
comprises at least one component selected from the group consisting
of SiC, oxides of Al, Zr, Ti, Y, Si, La, Sr, Ba, and combination
thereof.
47. A particle according to claim 43 wherein the ceramic composite
comprises at least 5% by weight of the support material.
48. A particle according to claim 43 wherein the particle comprises
a promoter comprising a pure metal, a metal oxide, a metal sulfide,
or combinations thereof, wherein the metal comprises one or more
from the group consisting of Fe, Ni, Sn, Li, Na, K, Rb, Cs, Be, Mg,
Ca, Sr, Ba, B, P, V, Cr, Mn, Co, Cu, Zn, Ga, Mo, Rh, Pt, Pd, Ag,
and Ru.
49. A particle according to claim 48 wherein the ceramic composite
comprises up to 40% by weight of the promoter material.
50. A method according to claim 37 wherein the ceramic composite
particles are in the form of pellets, monoliths, blocks, or
combinations thereof.
51. A method according to claim 37 wherein the particle is operable
to maintain activity after 10 or more regeneration cycles.
Description
[0001] The present invention is generally directed to systems and
methods of converting fuel, and is generally directed to
oxidation-reduction reactor systems used in fuel conversion.
[0002] There is a constant need for clean and efficient energy
generation systems. Most of the commercial processes that generate
energy carriers such as steam, hydrogen, synthesis gas (syngas),
liquid fuels and/or electricity are based on fossil fuels.
Furthermore, the dependence on fossil fuels is expected to continue
in the foreseeable future due to the much lower costs compared to
renewable sources. Currently, the conversion of carbonaceous fuels
such as coal, natural gas, petroleum coke is usually conducted
through a combustion or reforming process. However, combustion of
carbonaceous fuels, especially coal, is a carbon intensive process
that emits large quantities of carbon dioxide to the environment.
Sulfur and nitrogen compounds are also generated in this process
due to the complex content in coal.
[0003] Chemical reactions between metal oxides and carbonaceous
fuels, on the other hand, may provide a better way to recover the
energy stored in the fuels. Several processes are based on the
reaction of metal oxide particles with carbonaceous fuels to
produce useful energy carriers. For example, Ishida et al. U.S.
Pat. No. 5,447,024 describes processes wherein nickel oxide
particles are used to convert natural gas through a chemical
looping process into heat, which may be used in a turbine. However,
recyclability of pure metal oxides is poor and constitutes an
impediment for its use in commercial and industrial processes.
Moreover, this technology has limited applicability, because it can
only convert natural gas, which is more costly than other fossil
fuels. Another well known process is a steam-iron process, wherein
coal derived producer gas is reacted with iron oxide particles in a
fluidized bed reactor to be later regenerated with steam to produce
hydrogen gas. This process however suffers from poor gas conversion
rates due to improper contact between reacting solids and gases,
and is incapable of producing a hydrogen rich stream.
[0004] As demands increase for cleaner and more efficient systems
of converting fuel, the need arises for improved systems, and
system components therein, which will convert fuel effectively,
while reducing pollutants.
[0005] In one embodiment of the present invention, a system for
converting fuel is provided. The system comprises a first reactor
comprising a plurality of ceramic composite particles, wherein the
ceramic composite particles comprise at least one metal oxide
disposed on a support. The first reactor is configured to reduce at
least one metal oxide with a fuel to produce a reduced metal or a
reduced metal oxide. The system also comprises a second reactor
configured to oxidize the reduced metal or reduced metal oxide to
produce a metal oxide intermediate, and a third reactor configured
to regenerate at least one metal oxide by oxidizing the metal oxide
intermediate.
[0006] In another embodiment of the present invention, a method of
converting fuel to hydrogen, CO, or syngas is provided. The method
comprises the steps of: reducing a metal oxide in a reduction
reaction between a fuel and a metal oxide to a reduced metal or a
reduced metal oxide; oxidizing the reduced metal or reduced metal
oxide with an oxidant to a metal oxide intermediate, while also
producing hydrogen, CO, or syngas; and regenerating the at least
one metal oxide by oxidizing the metal oxide intermediate.
[0007] In yet another embodiment, a system comprising a
Fischer-Tropsch reactor is provided. The Fischer-Tropsch reactor is
configured to produce hydrocarbon fuel from a feed mixture
comprising gaseous fuel. The system also comprises a first reactor
comprising a plurality of ceramic composite particles, wherein the
ceramic composite particles comprise at least one metal oxide
disposed on a support. The first reactor is configured to reduce
the metal oxides with a gaseous fuel to a reduced metal or a
reduced metal oxide, wherein the gaseous fuel comprises at least
partially the hydrocarbon fuel produced by the Fischer-Tropsch
reactor. The system also comprises a second reactor configured to
oxidize the reduced metal or reduced metal oxide with steam to
produce metal oxide intermediates.
[0008] In another embodiment, a method of preparing ceramic
composite particles is provided. The method comprises reacting a
metal oxide with a support material; heat treating the mixture of
metal oxide and support material at temperatures of between about
200 to about 1500.degree. C. to produce ceramic composite powders;
converting the ceramic composite powders into ceramic composite
particles; and reducing and oxidizing the ceramic composite
particles prior to use in a reactor.
[0009] Additional features and advantages provided by embodiments
of the present invention will be more fully understood in view of
the following detailed description.
[0010] The following detailed description of the illustrative
embodiments of the present invention can be best understood when
read in conjunction with the following drawings, where like
structure is indicated with like reference numerals and in
which:
[0011] FIG. 1 is a schematic illustration of a system for producing
hydrogen from coal according to one or more embodiments of the
present invention.
[0012] FIG. 2 is a schematic illustration of another system for
producing hydrogen from coal according to one or more embodiments
of the present invention;
[0013] FIG. 3 is a schematic illustration of another system for
producing hydrogen from coal using direct chemical looping and
sieves for ash separation according to one or more embodiments of
the present invention;
[0014] FIG. 4 is a schematic illustration of another system for
producing hydrogen from coal using direct chemical looping and
cyclones for ash separation according to one or more embodiments of
the present invention;
[0015] FIG. 5 is a schematic illustration of another system for
producing hydrogen from coal, wherein the system utilizes a third
reactor for heat recovery according to one or more embodiments of
the present invention;
[0016] FIG. 6 is a schematic illustration of another system for
producing hydrogen from coal, wherein the system utilizes a sorbent
in the first reactor for sulfur removal according to one or more
embodiments of the present invention;
[0017] FIG. 7 is a schematic illustration of system for producing
hydrogen from syngas according to one or more embodiments of the
present invention;
[0018] FIG. 8 is a schematic illustration of another system for
producing hydrogen from coal, wherein carbon dioxide produced in
the first reactor is recycled back to the second reactor according
to one or more embodiments of the present invention;
[0019] FIG. 9 is a schematic illustration of another system for
producing steam from coal according to one or more embodiments of
the present invention;
[0020] FIG. 10 is a schematic illustration of yet another system
for producing hydrogen from syngas according to one or more
embodiments of the present invention;
[0021] Fig. 11 is a schematic illustration of another system for
producing hydrogen from syngas, wherein the system comprises
pollutant control components according to one or more embodiments
of the present invention;
[0022] FIG. 12 is a schematic illustration of a system of chemical
looping in conjunction with Fischer-Tropsch (F-T) synthesis
according to one or more embodiments of the present invention;
[0023] FIG. 13 is a schematic illustration of another system of
chemical looping in conjunction with Fischer-Tropsch synthesis
according to one or more embodiments of the present invention;
[0024] FIG. 14 is a schematic illustration of another system of
chemical looping in conjunction with Fischer-Tropsch synthesis
according to one or more embodiments of the present invention;
[0025] FIG. 15 is a schematic illustration of yet another system of
chemical looping in conjunction with Fischer-Tropsch synthesis,
wherein the system comprises pollutant control components according
to one or more embodiments of the present invention;
[0026] FIG. 16 is a schematic illustration of another system of
chemical looping in conjunction with Fischer-Tropsch synthesis,
wherein the system operates without the use of a gasifier according
to one or more embodiments of the present invention;
[0027] FIG. 17 is a schematic illustration of a system of chemical
looping for onboard H.sub.2 storage on a vehicle according to one
or more embodiments of the present invention;
[0028] FIG. 18(a) is a schematic illustration of a reactor cassette
used in the onboard H.sub.2 storage system of FIG. 17, wherein the
reactor cassette comprises Fe containing media and a packed bed of
small pellets according to one or more embodiments of the present
invention;
[0029] FIG. 18(b) is a schematic illustration of another reactor
cassette used in the onboard H.sub.2 storage system of FIG. 17,
wherein the reactor cassette comprises Fe containing media and a
monolithic bed with straight channels for steam flow according to
one or more embodiments of the present invention;
[0030] FIG. 18(c) is a schematic illustration of yet another
reactor module used in the onboard H.sub.2 storage system of FIG.
17, wherein the reactor cassette comprises Fe containing media and
a monolithic bed with channels for steam and air flow according to
one or more embodiments of the present invention;
[0031] FIG. 19 is a schematic illustration of a reactor cassette
used in the onboard H.sub.2 storage system of FIG. 17, wherein the
reactor cassette utilizes a series of monolithic bed reactors with
air injection to provide heat for steam formation according to one
or more embodiments of the present invention;
[0032] FIG. 20 is a schematic illustration of a system of chemical
looping in conjunction with a solid oxide fuel cell according to
one or more embodiments of the present invention;
[0033] FIG. 21 is a schematic illustration of a reactor utilized in
the system of the present invention, wherein the reactor is a
moving bed reactor comprising an annular region disposed near a
fuel feed location according to one or more embodiments of the
present invention;
[0034] FIG. 22 is a schematic illustration of a reactor utilized in
the system of the present invention, wherein the reactor is a
moving bed comprising a annular region as well as a cone inserted
into the moving bed according to one or more embodiments of the
present invention; and
[0035] FIG. 23 is a schematic illustration of another reactor
utilized in the system of the present invention, wherein the
reactor is a moving bed reactor comprising an annular region
according to one or more embodiments of the present invention.
[0036] Referring generally to FIG. 1, the present invention is
directed to systems and methods for converting fuel by redox
reactions of ceramic composite particles. As shown in FIG. 1, the
system comprises two primary reactors, as well as additional
reactors and components, which will be described in detail below.
The first reactor 1, which is configured to conduct a reduction
reaction, comprises a plurality of ceramic composite particles
having at least one metal oxide disposed on a support. As would be
familiar to one of ordinary skill in the art, the ceramic composite
particles may be fed to the reactor via any suitable solids
delivery device/mechanism. These solids delivery devices may
include, but are not limited to, pneumatic devices, conveyors, lock
hoppers, or the like. Ceramic composite particles are described in
Thomas et al. U.S. Published App. No. 2005/0175533 A1, which is
incorporated herein in its entirety by reference. In addition to
the particles and particle synthesis methods disclosed in Thomas,
the Applicants, in a further embodiment, have developed alternative
methods of making the ceramic composite, which may improve the
efficacy and activity of the ceramic composite particles in the
present system. Two of these alternative methods are
co-precipitation and spray drying.
[0037] The third alternative method includes the step of physically
mixing a metal oxide with a ceramic support material. Optionally, a
promoter material may be added to the mixture of metal oxides and
support material. After mixing, the mixture is heat treated at
temperatures of between about 200 to about 1500.degree. C. to
produce ceramic composite powders. Heat treating may occur in the
presence of inert gas, steam, oxygen, air, H.sub.2, and
combinations thereof at a pressure of between vacuum pressure and
about 10 atm. The method may also include a chemical treatment
step, wherein the mixture of metal oxides and support material are
treated with an acid, base, or both to activate the ceramic
composite powder. After powder production, the ceramic composite
powders may be converted into ceramic composite particles by
methods known to one of ordinary skill in the art. These methods
may include, but are not limited to, extrusion, granulation, and,
pressurization methods such as pelletization. The particle may
comprise various shapes and forms, for example, pellets, monoliths,
or blocks.
[0038] The method then includes the step of reducing and oxidizing
the ceramic composite particles prior to use in a reactor. This
cycle is important for the ceramic composite particles because this
mixing process may produce a particle with increased activity,
strength and stability. This cycle is important for the ceramic
composite particles to increase their activity, strength and
stability. This treatment also leads to a reduced porosity (0.1-50
m.sup.2/g) as well as crystal structure changes that make the
particle readily reducible and oxidizable without loosing its
activity for multiple such reaction cycles. The porosity in Thomas
patent is not reported but it is stated that the particle was
porous and had mesopores. Although the description of particle
synthesis in this application is limited to spray dry,
co-precipitation, and direct mixing approach, ceramic composite
particles produced by other techniques such as sol-gel, wet
impregnation, and other methods known to one of ordinary skill in
the art are also operable in the reactors of the present
system.
[0039] The metal oxide of the ceramic composite comprises a metal
selected from the group consisting of Fe, Cu, Ni, Sn, Co, Mn, and
combinations thereof. Although various compositions are
contemplated herein, the ceramic composite typically comprises at
least 40% by weight of the metal oxide. The support material
comprises at least one component selected from the group consisting
of SiC, oxides of Al, Zr, Ti, Y, Si, La, Sr, Ba, and combinations
thereof. The ceramic composite comprises at least 5% by weight of
the support material. In further embodiments, the particle
comprises a promoter material. The promoter comprises a pure metal,
a metal oxide, a metal sulfide, or combinations thereof. These
metal based compounds comprise one or more elements from the group
consisting of Fe, Ni, Sn, Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba, ,
B, P, V, Cr, Mn, Co, Cu, Zn, Ga, Mo, Rh, Pt, Pd, Ag, and Ru. The
ceramic composite comprises up to 40% by weight of the promoter
material. In an exemplary embodiment of the ceramic composite, the
metal oxide comprises Fe.sub.2O.sub.3 supported on a TiO.sub.2
support, and specifically a support comprising a mixture of
TiO.sub.2 and Al.sub.2O.sub.3. In another exemplary embodiment, the
ceramic composite may also comprise Fe.sub.2O.sub.3 supported on an
YSZ (Yittria stabilized Zirconia) support.
[0040] Referring back to the reduction reaction of the first
reactor 1, the first reactor 1 receives a fuel, which is utilized
to reduce the at least one metal oxide of the ceramic composite to
produce a reduced metal or a reduced metal oxide. As defined
herein, "fuel" may include: a solid carbonaceous composition such
as coal, tars, oil shales, oil sands, tar sand, biomass, wax, coke
etc; a liquid carbonaceous composition such as gasoline, oil,
petroleum, diesel, jet fuel, ethanol etc; and a gaseous composition
such as syngas, carbon monoxide, hydrogen, methane, gaseous
hydrocarbon gases (C1-C6), hydrocarbon vapors, etc. For example,
and not by way of limitation, the following equation illustrates
possible reduction reactions:
Fe.sub.2O.sub.3+2CO.fwdarw.2Fe+2CO.sub.2
16Fe.sub.2O.sub.3+3C.sub.5H.sub.12.fwdarw.32Fe+15CO.sub.2+18H.sub.2O
[0041] In this example, the metal oxide of the ceramic composite,
Fe.sub.2O.sub.3, is reduced by a fuel, for example, CO, to produce
a reduced metal oxide, Fe. Although Fe is the predominant reduced
composition produced in the reduction reaction of the first reactor
1, FeO or other reduced metal oxides with a higher oxidation state
are also contemplated herein.
[0042] The first reactor 1 and second reactor 2 may include various
suitable reactors to allow an overall countercurrent contacting
between gas and solids. Such may be achieved using a moving bed
reactor, a series of fluidized bed reactors, a rotatory kiln, a
fixed bed reactor, combinations thereof, or others known to one of
ordinary skill in the art.
[0043] As shown in FIGS. 21-23, the first reactor 1 may comprise a
moving bed reactor with an annular region 8 created around the
moving bed. Although various orientations for the annulus 8 are
possible, the annulus 8 is typically located at a region where a
reducing fuel is being introduced. As shown in FIG. 22, the moving
bed reactor may also include a mixing device, e.g. a cone 9,
inserted in the moving bed to radially distribute the ceramic
composite particles and mix unconverted fuel with the ceramic
composite particles. Although FIG. 22 illustrates the cone 9 in
conjunction with the annulus 8, it is contemplated that the moving
bed reactor may incorporate a cone 8, but not an annulus in some
embodiments. The annular region 8 allows the first reactor 1 to
introduce solid and liquid fuels into the middle of a moving bed of
solids ceramic composites. In one embodiment, the fuel may be
introduced pneumatically and then partially combusted in the
annulus 8. The unburnt fuel drops down onto the heap of ceramic
composites in the annulus 8 and is mixed with them for further
reactions. FIGS. 21, 22 and 23 show some of the different methods
to form the annular region 8. FIG. 21 uses an internal hopper to
create the annular region. FIG. 23 uses an internal hopper along
with a rotary valve to create an even larger annular region with
better control over the flow of ceramic composite particles. FIG.
22 creates an external annular region for the flow of the moving
bed and uses a mixing device, e.g. a cone 9 to disperse the solids
axially so that unconverted fuel may be distributed uniformly over
the entire cross section of the moving bed.
[0044] The first reactor 1 may be constructed with various durable
materials suitable to withstand temperatures of up at least
1200.degree. C. The reactor may comprises carbon steel with a layer
of refractory on the inside to minimize heat loss. This
construction also allows the surface temperature of the reactor to
be fairly low, thereby improving the creep resistance of the carbon
steel. Other alloys suitable for the environments existing in
various reactors may also be employed, especially if they are used
as internal components configured to aid in solids flow or to
enhance heat transfer within a moving bed embodiment. The
interconnects for the various reactors can be of lock hopper design
or rotary/star valve design to provide for a good seal. Other
interconnects as can be determined easily by a person skilled in
the art may also be used.
[0045] After reduction in the first reactor 1, the reduced metal or
reduced metal oxide particles are then delivered to the second
reactor 2 to undergo an oxidation reaction. The second reactor 2,
which may comprise the same reactor type or a different reactor
type than the first reactor 1, is configured to oxidize the reduced
metal or reduced metal oxide to produce a metal oxide intermediate.
As used herein, "metal oxide intermediate" refers to a metal oxide
having a higher oxidation state than the reduced metal or metal
oxide, and a lower oxidation state than the metal oxide of the
ceramic composite. For example, and not by way of limitation, the
following equation illustrates possible oxidation reactions:
3Fe+4H.sub.2O.fwdarw.Fe.sub.3O.sub.4 +4H.sub.2
3Fe+4CO2.fwdarw.Fe.sub.3O.sub.4+4CO
[0046] In this example which centers on ceramic composites that
utilize Fe.sub.2O.sub.3 as the metal oxide, oxidation in the second
reactor using steam will produce a resultant mixture that includes
metal oxide intermediates comprising predominantly Fe.sub.3O.sub.4.
Fe.sub.2O.sub.3 and FeO may also present. Furthermore, although
H.sub.2O, specifically steam, is the oxidant in this example,
numerous other oxidants are contemplated, for example, CO, O.sub.2,
air, and other compositions familiar to one of ordinary skill in
the art.
[0047] Referring to the solid fuel conversion embodiment of FIG. 1,
the system comprises two moving bed reactors 1 and 2. The first
reactor 1, which defines a moving bed, operates by having the
solids (Fe.sub.2O.sub.3 and coal) moving downwards in a densely
packed mode, while the gases, for example, H.sub.2, steam, CO,
CO.sub.2, or combinations thereof move upwards. This movement of
solids and gases is defined as a countercurrent contacting pattern.
The Fe.sub.2O.sub.3 containing ceramic composite particles are
introduced from the top via a gravitational feeder while solid
fuel, e.g. coal is introduced at a region of the first reactor 1
lower than the feed location of the ceramic composite particles.
Typically, the reactors operate at a temperature in the range of
about 400 to about 1200.degree. C. and a pressure in the range of
about 1 to about 150 atm; however, one of ordinary skill in the art
would realize that temperatures and pressures outside these ranges
may be desirable depending on the reaction mechanism and the
components of the reaction mechanism. In the embodiment of FIG. 1,
coal is introduced in pulverized form by pneumatically conveying
with oxygen or carbon dioxide or steam. After the coal is delivered
to the first reactor 1, coal will devolatilize and form char. The
volatiles may also react with Fe.sub.2O.sub.3 to form CO.sub.2 and
water. The outlet gas composition of the first reactor 1 may
contain predominantly CO.sub.2 and steam. Subsequently, the
CO.sub.2 and steam may be fed to a condenser 4 to separate the
steam and the CO.sub.2. The CO.sub.2 obtained after condensation of
water will be relatively pure and may be sequestered under the
ocean or in geological formations or enhanced oil recovery without
emitting to the atmosphere and contributing to green house warming
of the earth.
[0048] The char formed on devolatilization of coal will then react
with partially reduced iron oxide as it flows downwardly in the
first reactor 1. To enhance the char reaction with iron oxide, a
small amount of hydrogen is introduced at the bottom of the moving
bed to result in the formation of H.sub.2O on its reaction with
partially reduced iron oxide. The H.sub.2O produced will react with
downwardly flowing char leading to its gasification into H.sub.2
and CO. The hydrogen formed will then react with the partially
reduced iron oxide in order to further reduce the reduced iron
oxide, thereby enhancing the char-iron oxide reaction rates. The
hydrogen introduced at the bottom of the reactor will also ensure
that the iron oxide particles are greatly reduced to Fe as they
exit the first reactor 1. In some cases, some carbon is
intentionally left unconverted in the particle to generate CO using
steam in the second reactor. In yet some other cases, an excess of
ceramic composite particles comprising Fe.sub.2O.sub.3 may be
inserted into the first reactor 1 in order to enhance reaction
rates.
[0049] The exiting reduced Fe containing particles may then be
introduced into the second reactor 1. Like in the first reactor 1,
the second reactor 2 may also comprise a moving bed with a
countercurrent contacting pattern of gas and solids. Steam is
introduced at the bottom of the reactor and it oxidizes the reduced
Fe containing particles as the particles move downwardly inside the
second reactor 2. In this embodiment, the product formed is
hydrogen, which is subsequently discharged from the top of the
second reactor 2. It will be shown in further embodiments that
products such as CO and syngas are possible in addition to
hydrogen. Though Fe.sub.2O.sub.3 formation is possible in the
second reactor 2, the solid product from this reactor is expected
to be mainly metal oxide intermediate, Fe.sub.3O.sub.4. The amount
of Fe.sub.2O.sub.3 produced in the second reactor 2 depends on the
oxidant used, as well as the amount of oxidant fed to the second
reactor 2. The steam present in the hydrogen product of reactor 2
may then be condensed in order to provide for a hydrogen rich
stream. At least part of this hydrogen rich stream may be recycled
back to the first reactor 1 as described above. In addition to
utilizing the same reactor type as the first reactor 1, the second
reactor 2 may similarly operate at a temperature between about 400
to about 1200.degree. C. and pressure of about 1 to about 150
atm.
[0050] To regenerate the metal oxide of the ceramic composite, the
system utilizes a third reactor 3, which is configured to oxidize
the metal oxide intermediate to the metal oxide of the composite.
Referring to the embodiment FIG. 1, the third reactor 3 may
comprise an air filled line or tube used to oxidize the metal oxide
intermediate. Referring to the FIG. 5 embodiment, the oxidation of
the metal oxide intermediate may be conducted a heat recovery unit
3. The following equation lists one possible mechanism for the
oxidation in the third reactor 3:
2Fe.sub.3O.sub.4+0.5O.sub.2.fwdarw.3Fe.sub.2O.sub.3
[0051] Referring to the embodiment of FIG. 1, the Fe.sub.3O.sub.4
product may be oxidized to Fe.sub.2O.sub.3 in solid conveying
system 6. Different mechanisms can be used for solid
transportation. FIG. 1 shows it as a transport system using
pneumatic conveyor driven by air. Belt conveyors, bucket elevators,
screw conveyors, moving beds and fluidized bed reactors may also be
used to transport the solids. The resultant depleted air stream is
separated from the particles and its high-grade-heat content
recovered for steam production. After regeneration, the ceramic
composite particle is not degraded and maintains full particle
functionality and activity. In further embodiment, the particle may
undergo numerous regeneration cycles, for example, 10 or more
regeneration cycles, and even greater than 100 regeneration cycles,
without losing its functionality. This system can be used with
existing systems involving minimal design change, thus making it
economical.
[0052] The iron particles exiting the first reactor 1 may also
contain ash and other unwanted byproducts. If the ash is not
removed after the first 1 or second reactor 2 stages, the ash may
keep building up in the system. Numerous devices and mechanisms for
ash removal would be familiar to one of ordinary skill in the art.
For example, ash may be removed based on the size of ash with
respect to the iron oxide particles from any of the solid streams
in the system. If pulverized coal is used as the fuel source, it
will yield fine ash particles, typically lower than 100 .mu.m in
size. The size of the ceramic composite particles may vary based on
the metal components used and the oxidation-reduction reaction in
which the ceramic composite is utilized. In one embodiment, the
particle comprises a size between about 0.5 to about 50 mm. As a
result, simple sieving, for example, simple sieving at high
temperatures, may result in removal of ash. Simple sieving uses the
size and density differences between the wanted and unwanted solid
particles in the separation process. Other methods, for example,
mechanical methods, and methods based on weight, or magnetic
properties, may be used to separate ash and unwanted materials.
Separation devices, such as cyclones, will be further discussed in
later embodiments.
[0053] Heat integration and heat recovery within the system and all
system components is highly desirable. Heat integration in the
system is specifically focused on generating the steam for the
steam requirements of the second reactor 2. This steam can easily
be generated using the high grade heat available in the hydrogen,
CO.sub.2 and depleted air streams exiting reactors 1, 2, 3,
respectively. In the process described above, there is also a
desire to generate pure oxygen. To generate this pure oxygen, at
least part of the hydrogen may be utilized.
[0054] The residence time in each reactor is dependent upon the
size and composition of individual ceramic composite particles, as
would be familiar to one or ordinary skill in the art. For example,
the residence time for a reactor comprising Fe based metal oxides
may range from about 0.1 to about 20 hours.
[0055] As stated above, additional unwanted elements may be present
in addition to ash. Trace elements like Hg, As, Se are not expected
to react with Fe.sub.2O.sub.3 at the high temperatures of the
process. As a result they are expected to be present in the
CO.sub.2 stream produced. If CO.sub.2 is to be used as a marketable
product, these trace elements must be removed from the stream.
Various cleanup units, such as mercury removal units are
contemplated herein. Similar options will need to be exercised in
case the CO.sub.2 stream is let out into the atmosphere, depending
upon the rules and regulations existing at that time. If it is
decided to sequester the CO.sub.2 for long term benign storage,
e.g. in a deep geological formation, there may not be a need to
remove these unwanted elements. Moreover, CO.sub.2 may be
sequestered via mineral sequestration, which may be more desirable
than geological storage, because it is safer and more manageable.
Additionally sequestering CO.sub.2 has an economic advantage for
global CO.sub.2 credit trading, which may be highly lucrative.
[0056] Furthermore, sulfur may constitute another unwanted element,
which must be accounted for in the system. In a solid fuel
conversion embodiment, sulfur, which is present in coal, is
expected to react with Fe.sub.2O.sub.3 and form FeS. This will be
liberated on reaction with steam in reactor 2 as H.sub.2S and will
contaminate the hydrogen stream. During the condensation of water
from this steam, most of this H.sub.2S will condense out. The
remaining H.sub.2S can be removed using conventional techniques
like amine scrubbing or high temperature removal using a Zn, Fe or
a Cu based sorbent. Another method for removing sulfur would
include the introduction of sorbents, for example, CaO, MgO, etc.
Additionally, as shown in the embodiment of FIG. 6, sorbents may be
introduced into the first reactor 1 in order to remove the sulfur
and to prevent its association with Fe. The sorbents may be removed
from the system using ash separation device.
[0057] Although the embodiments of the present system are directed
to producing hydrogen, it may be desirable for further treatment to
produce ultra-high purity hydrogen. As would be familiar to one of
ordinary skill in the art, some carbon or its derivatives may carry
over from reactor 1 to 2 and contaminate the hydrogen stream.
Depending upon the purity of the hydrogen required, it may be
necessary to use a pressure swing adsorption (PSA) unit for
hydrogen to achieve ultra high purities. The off gas from the PSA
unit may comprise value as a fuel and may be recycled into the
first reactor 1 along with coal, in solid fuel conversion
embodiments, in order to improve the efficiency of hydrogen
production in the system.
[0058] Referring to FIG. 2, the hydrogen produced in the second
reactor 2 may provide additional benefits to the system. For
instance, the hydrogen may be fed a power generation section 10
configured to produce electricity from a hydrogen product of the
second reactor 2. As would be familiar to one of ordinary skill in
the art, the power generation section 10 may comprise air
compressors 12, gas turbines 14, steam turbines, electric
generators 16, fuel cells, etc. In another embodiment, unconverted
H.sub.2 from fuel cell can be recycled to the middle region of
reactor 2, this helps to increase fuel cell efficiencies while
reducing the fuel cell size. Thus improve the overall system
efficiency.
[0059] Referring to FIG. 3, another coal conversion system similar
to FIG. 1 is provided. Part of the CO.sub.2 is recycled back as
carrier gas for the injection of coal. Both of the reactors operate
under 400-1200.degree. C. and the reduced metal particles would be
transported to the second reactor 2 by an inert gas such as N.sub.2
from the air separation unit. The hydrogen produced in second
reactor 2 may also be used for transportation of reduced metal
oxide particles. The reduced metal will be separated out from the
nitrogen gas and fed into the second reactor 2 to react with steam
to generate H.sub.2. The H.sub.2 generated would contain H.sub.2S
due to the sulfur inside the coal, and would attach to the particle
to form MeS. As shown, a traditional sulfur scrubbing unit 22 may
be used to remove H.sub.2S and generate pure H.sub.2. The oxidized
particles from the outlet of the second reactor 2 would go through
an ash separation system using a sieve. In this embodiment, most of
the ash and metal oxide particles, as a result of attrition, would
be separated out for regeneration, while the rest of the metal
oxide particles would be introduced back into the inlet of the
first reactor 1 using a feed device, for example, a pneumatic
conveyor by air, where the makeup ceramic composite would also be
fed. As used herein, makeup ceramic composite particles refer to
fresh particle used to replace the fines or ceramic composite
particles rendered too small or ineffective due to attrition and
deactivation. The typical makeup ceramic composite rate would be
less than 2% of the particle flow rate in the system.
[0060] Referring to FIG. 4, a different solid conveying system, as
well as a different ash separation unit, may be used for coal
direct reactor system. Here, the reduced metal particles are
transferred to the second reactor 2 using a bucket elevator in an
N.sub.2 environment. After being oxidized in the second reactor 2
to metal oxide intermediates, the metal oxide intermediates are
sent to a cyclone 3 using a pneumatic conveyor with air so that the
particle is already oxidized by the time it reaches the cyclone.
The fines due to attrition and the coal ash may be removed along
with air while the particles will be separated out with the cyclone
and fed into the first reactor along with the makeup metal oxide
particles. The makeup rate is again less than 2% of the particle
flow rate in the system. Other devices like a particle classifier
or other devices commonly known to one of ordinary skill in the art
may also be used for ash separation.
[0061] Referring to the FIG. 5 embodiment, a third reactor 3 in
form of a fluidized bed is utilized to recover the heat for further
oxidation of the particles exiting the second reactor i.e. the
metal oxide intermediates, such as Fe.sub.3O.sub.4. In other
embodiments and figures this reactor was shown as the transport
line from the second reactor 2 to first reactor 1 where air or
oxygen is introduced. It will be a transport reactor, a fast
fluidized bed, a fluidized bed, a riser or pneumatic conveying
system. Here, the metal oxide intermediates, e.g. Fe.sub.3O.sub.4,
from the outlet of the second reactor 2 are injected into a heat
recovery unit 3 where oxygen or air is introduced to oxidize the
particles back into their highest oxidation state i.e. the metal
oxide of the ceramic composite, e.g. Fe.sub.2O.sub.3. In addition
to the oxidation conversion, heat is generated in this process, and
the particles' temperature may also increase drastically. The
particles with significantly higher temperature may be introduced
back into the first reactor 2 and the heat stored in the particle
would provide, at least in part, the heat required for reduction
reactions. For particles with high heat capacity, it may desirable,
in one exemplary embodiment, to utilize a support such as SiC,
which has high thermal conductivity.
[0062] As shown in the embodiment of FIG. 6, sorbent materials,
such as modified calcium carbonate or calcium oxide or calcium
hydroxide, may be injected into the first reactor 1 to remove the
sulfur from the coal. The CaCO.sub.3 injection rate will range from
about 1% to about 15% of the metal oxide flow rate in the system;
however, the injection rate varies depending on the composition of
the coal used. Magnesium oxide may also be used as a sorbent.
Generally, the size of the sorbent particle is smaller than the
ceramic composite particles, and may in some exemplary embodiment,
comprises a particle size ranging from about 100 .mu.m to about 1
mm depending on the size of the ceramic composite particle in the
system. The spent sorbent, after sulfur capture, would be separated
out with ash and regenerated afterwards for further use in the
first reactor 1. In this embodiment, pure H.sub.2 may be produced
without the need of a scrubber.
[0063] Referring generally to FIGS. 7-9, system embodiments for
converting gaseous fuels are provided. As shown in FIG. 9, part of
the CO.sub.2 produced in the first reactor 1 may be split and
introduced into second reactor 2 along with steam. By controlling
the feed rates of steam and CO.sub.2, syngas having a different
H.sub.2 and CO ratio can be obtained. The syngas can be introduced
to a gas turbine to generate electricity or it can be used for
chemical/liquid fuel synthesis. In order to generate syngas with an
H.sub.2/CO ratio of about 2:1 for Fischer-Tropsch synthesis to
produce liquid fuel, a typical steam and CO.sub.2 feed rate ratio
should be around 2:1. The present system in conjunction with
Fischer-Tropsch synthesis will be discussed in greater detail
below. The output ratio of H.sub.2/CO may also be varied by
recycling part of the output after condensation of water to a
middle section of the second reactor 2. This will allow more water
gas shift reaction to convert unconverted CO.sub.2 into CO.
[0064] As shown in the FIG. 9 embodiment of syngas conversion,
reduced metal particles are burnt with air in the second reactor 2.
The heat generated may be extracted using water to generate high
temperature steam. The steam can then be either used for
electricity generation or it can be used to extract heavy oil from
oil shale. In the embodiment of FIG. 10, the system must account
for the fact that H.sub.2S in raw syngas would react with metal to
form metal sulfide. Reduced metal and metal sulfide would be
introduced to the second reactor 2 to react with steam. The product
stream in this system would contain H.sub.2 and H.sub.2S. H.sub.2S
may be taken out using traditional scrubber technology and a
H.sub.2 rich stream would be achieved. By using gaseous fuel, e.g.
syngas, instead of solid fuel, the ash separation process may be
avoided.
[0065] Referring to the FIG. 11 embodiment, a hot gas sulfur
removal unit using sorbents such as CaO is utilized to remove bulk
quantities of H.sub.2S in raw syngas to below 100 ppm. The
pretreated syngas is then mixed with steam and CO.sub.2 of
appropriate quantity, typically <15% and introduced to the
bottom of the first reactor 1. Due to the equilibrium between
H.sub.2S and steam/CO.sub.2, H.sub.2S as well as Hg will not react
with the particles inside the first reactor 1. As a result, the
pollutant will come out of the first reactor 1 along with CO.sub.2
and can be sequestrated together. Only pure metal particles will
enter the second reactor 2 and therefore, H.sub.2 rich streams may
be generated without using low temperature sulfur and mercury
removal units. Additionally, ceramic composite particles with
degraded activity or size, which are no longer effective in the
processes of the first and second reactor, may be used instead of
CaO to remove the H.sub.2S, for example, to a level below 30
ppm.
[0066] Referring generally to FIG. 13, the chemical looping system,
as a hydrogen generator, may be coupled with Fischer-Tropsch (F-T)
synthesis system, directed to producing chemicals or liquid fuels.
Syngas from modern gasifiers usually fail to provide enough H.sub.2
concentration to meet the requirements of F-T synthesis
(H.sub.2/CO=2:1). The feedstock for the first reactor 1 is part of
the byproduct from the F-T reactor 100 and unconverted syngas. In a
further embodiment, the feedstock may include part of the product
from the refining system. The rest of the byproduct and unconverted
syngas is recycled to the F-T reactor 100 to enhance the
conversion, or, it can also be recycled to the gasifier to make
more syngas. Moreover, steam for the second reactor can be obtained
from both the gasifier and the F-T reactor 100, as F-T reactions
are usually highly exothermic. The H.sub.2 product of the second
reactor 1, which may contain some CO and which is generated from
chemical looping reactors is recycled back to adjust the H.sub.2/CO
ratio of the F-T feed to about 2:1. This adjustment may occur, in
some embodiments, after the clean syngas exits the gasifier 30 and
is delivered to gas cleanup units 22. In this case, a
stoichiometric amount of byproducts and unconverted syngas are used
to generate H.sub.2 for gas tune up i.e., adjustment of the ratio
to about 2:1, while the rest of the gas stream is recycled back
into the F-T reactor 100. By converting the C1-C4 byproducts and
unconverted syngas into H.sub.2, which is the feedstock of F-T
reactor 100, system efficiency and product selectivity can be
greatly improved. The operating pressure for the chemical looping
system would be similar to the F-T process, for example, around 20
atm for medium pressure synthesis.
[0067] The embodiments of FIG. 12 and 14 are similar to the one
described in FIG. 13; with one major difference being that all the
byproducts are used to generate H.sub.2. The excessive amount of
H.sub.2 can be used for hydrocracking of the wax product from the
F-T reactor 100. If an excessive amount of H.sub.2 remains after
hydrocracking, a combustion turbine or a fuel cell can be utilized
to generate electricity for plant use or for the energy market in
general.
[0068] In the F-T embodiment of FIG. 15, hot gas cleanup is used
before the first reactor 1 and the rest of the pollutants would
come out from the first reactor 1 without attachment to the
particles. Here, part of the CO.sub.2 generated from the first
reactor 1 is introduced to a product cleanup unit or a CO.sub.2
separation unit to extract substantially pure CO.sub.2 from the
exhaust gas stream of the first reactor 1. The substantially pure
CO.sub.2 is then introduced into second reactor 2 along with steam
to form clean syngas with a H.sub.2/CO ratio of about 2:1. The
syngas is then used in F-T reactor 100 to produce liquid fuels or
chemicals. The byproduct stream from the F-T reactor 100 would also
be recycled back to first reactor to further increase the syngas
production rate of the chemical looping system. Referring to FIG.
16, the F-T system may be combined with a coal converting system
instead of syngas. In this embodiment, sorbents may be fed into the
system to take out sulfur. Byproducts of F-T synthesis may also be
fed into the first reactor 1 to make more syngas. In this solid
fuel conversion embodiment, a gasifier is not needed; consequently,
the system may comprise less equipment, thereby lowering costs and
capital investment while improving system efficiency.
[0069] In all the F-T embodiments, part of the steam generated in
the F-T reactor may be superheated by high temperature streams from
the chemical looping system of the present invention or gasifiers.
The superheated steam may comprise various uses, for example,
driving a steam turbine for parasitic energy or as a feed stock in
reactor 2.
[0070] In the embodiment of FIG. 17, an additional use for the
present system is provided. In this example, metal oxide particles
such as Fe.sub.2O.sub.3 are processed into a packed bed or monolith
in a module or cartridge for onboard H.sub.2 storage in a vehicle
230. Here, the modules are processed in a central facility 210 to
get reduced to its metal form using carbonaceous fuel such as
syngas. The reduced modules are then distributed to fuel stations
200 and installed into a car 230 to replace the spent modules.
Steam would be obtained from the PEM fuel cell or Hydrogen Internal
Combustion Engine and would be introduced into the model to react
with the reduced particles to generate H.sub.2 to drive the car.
The typical temperature for the reaction would be around
250-700.degree. C., as the reaction is exothermic. The temperature
in the module can either be maintained by well designed insulations
or the heat recovery in other areas of the system. The modules
would consist of different individual enclosures and each enclosure
can either be a packed bed of pellets or it can be monolith. In one
exemplary embodiment, the monolith may comprises small channels
with diameter of 0.5-10 mm while the thickness of the wall that is
made of particles are kept below 10 mm. FIGS. 18(a)-(c), and FIGS.
18 illustrates some examples of the modules, i.e. reactors with Fe
containing media having: (a) a packed bed of small pellets; (b) a
monolithic bed with straight channels for steam; and (c) a
monolithic bed with channels for steam and air.
[0071] FIGS. 18c and FIG. 18b show that air will flow through some
of the channels while steam flows through the rest of the channels.
By this kind of flow arrangement, the channels with air going
through would generate heat for the adjacent channels keeping them
at desirable temperature (250-700.degree. C.) for hydrogen
production. FIG. 19 shows one possible arrangement using the
enclosure design shown in FIG. 18(c). Here, different enclosures
are packed into a module and connected with one another to
consistently generate H.sub.2 for a fuel cell or an internal
combustion engine in the car 230. The air and steam channels may be
strictly separated from one another using the special monolith
design and connection scheme.
[0072] Referring to FIG. 20, the present system may also be
utilized in fuel cell technologies. In this exemplary embodiment of
FIG. 20, reduced metal particles are directly fed into a solid
oxide fuel cell that can process solid fuels directly. In effect,
the solid oxide fuel cell acts the second reactor 2 in the
oxidation reduction system. Particles are reduced in the fuel
reactor and then introduced to the fuel cell to react with oxygen
or air under 500-1000.degree. C. to produce electricity. The
oxidized particle is recycled back to the fuel reactor to be
reduced again. Because of the applicability of the present system,
it is contemplated that the present invention may be incorporated
in numerous other industrial processes.
[0073] It is noted that terms like "preferably, " "generally",
"commonly," and "typically" are not utilized herein to limit the
scope of the claimed invention or to imply that certain features
are critical, essential, or even important to the structure or
function of the claimed invention. Rather, these terms are merely
intended to highlight alternative or additional features that may
or may not be utilized in a particular embodiment of the present
invention.
[0074] For the purposes of describing and defining the present
invention it is noted that the term "substantially" is utilized
herein to represent the inherent degree of uncertainty that may be
attributed to any quantitative comparison, value, measurement, or
other representation. The term "substantially" is also utilized
herein to represent the degree by which a quantitative
representation may vary from a stated reference without resulting
in a change in the basic function of the subject matter at
issue.
[0075] Having described the invention in detail and by reference to
specific embodiments thereof, it will be apparent that
modifications and variations are possible without departing from
the scope of the invention defined in the appended claims. More
specifically, although some aspects of the present invention are
identified herein as preferred or particularly advantageous, it is
contemplated that the present invention is not necessarily limited
to these preferred aspects of the invention.
* * * * *