U.S. patent application number 13/813500 was filed with the patent office on 2013-05-23 for chemical looping system.
The applicant listed for this patent is Horst Greiner, Alessandro Zampieri. Invention is credited to Horst Greiner, Alessandro Zampieri.
Application Number | 20130125462 13/813500 |
Document ID | / |
Family ID | 42931929 |
Filed Date | 2013-05-23 |
United States Patent
Application |
20130125462 |
Kind Code |
A1 |
Greiner; Horst ; et
al. |
May 23, 2013 |
CHEMICAL LOOPING SYSTEM
Abstract
A chemical looping system and a method of transferring oxygen
therein are provided. The system has an air reactor adapted to
receive air for oxidizing an oxygen carrier, a fuel reactor adapted
to receive a fuel and the oxidized oxygen carrier for at least
partially oxidizing the fuel by reducing the oxygen carrier to
produce a gas. The oxygen carrier has oxide-dispersion-strengthened
alloy particles.
Inventors: |
Greiner; Horst; (Forchheim,
DE) ; Zampieri; Alessandro; (Singapore, SG) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Greiner; Horst
Zampieri; Alessandro |
Forchheim
Singapore |
|
DE
SG |
|
|
Family ID: |
42931929 |
Appl. No.: |
13/813500 |
Filed: |
August 2, 2010 |
PCT Filed: |
August 2, 2010 |
PCT NO: |
PCT/EP2010/061200 |
371 Date: |
January 31, 2013 |
Current U.S.
Class: |
48/61 ;
48/197FM |
Current CPC
Class: |
Y02E 20/34 20130101;
F23C 10/005 20130101; Y02E 20/346 20130101; F23C 99/00 20130101;
C10L 3/10 20130101; F23C 2900/99008 20130101 |
Class at
Publication: |
48/61 ;
48/197.FM |
International
Class: |
C10L 3/10 20060101
C10L003/10 |
Claims
1.-15. (canceled)
16. A chemical looping system, comprising: an air reactor adapted
to receive air for oxidizing an oxygen carrier, and a fuel reactor
adapted to receive a fuel and the oxidized oxygen carrier for at
least partially oxidizing the fuel by reducing the oxygen carrier
to produce a gas, wherein the oxygen carrier comprises
oxide-dispersion-strengthened alloy particles.
17. The chemical looping system according to claim 16, wherein the
oxide-dispersion-strengthened alloy particles are composed of a
metal having a dispersion of a metal oxide or a carbide.
18. The chemical looping system according to claim 17, wherein the
metal is selected from the group consisting of: nickel, copper,
iron, cobalt, manganese, and cadmium.
19. The chemical looping system according to claim 17, wherein the
metal oxide is selected from the group consisting of: cerium oxide,
titanium oxide, and zirconium oxide.
20. The chemical looping system according to claim 17, wherein the
carbide is silicon carbide.
21. The chemical looping system according to claim 17, wherein the
metal oxide or the carbide is doped.
22. The chemical looping system according to claim 16, wherein the
fuel comprises a carbonaceous fuel.
23. The chemical looping system according to claim 16, wherein the
fuel reactor is adapted to combust the fuel to produce the gas.
24. The chemical looping system according to claim 16, wherein the
gas comprises CO.sub.2 and H.sub.2O.
25. The chemical looping system according to claim 16, wherein the
fuel reactor is adapted to partially oxidize the fuel to produce
the gas, and wherein the gas comprises a reformer gas.
26. The chemical looping system according to claim 25, wherein the
reformer gas comprises H.sub.2, CO, C.sub.2O and H.sub.2O.
27. The chemical looping system according to claim 16, wherein fuel
reactor is further adapted to receive a steam.
28. A method for transferring an oxygen in a chemical looping
system, comprising: providing an air reactor adapted to receive air
for oxidizing an oxygen carrier, and providing a fuel reactor
adapted to receive a fuel and the oxidized oxygen carrier for at
least partially oxidizing the fuel by reducing the oxygen carrier
to produce a gas, wherein the oxygen carrier comprises
oxide-dispersion-strengthened alloy particles.
29. The method according to claim 28, wherein the oxide-dispersion
strengthened alloy particles are composed of a metal having a
dispersion of a metal oxide or a carbide.
30. The method according to claim 29, wherein the metal is selected
from the group consisting of: nickel, copper, iron, cobalt,
manganese, and cadmium.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is the US National Stage of International
Application No. PCT/EP2010/061200 filed Aug. 2, 2010 and claims the
benefit thereof. The application is incorporated by reference
herein in its entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to a chemical looping system
and a method of transferring oxygen between therein.
BACKGROUND OF THE INVENTION
[0003] Chemical looping is a combustion technology with inherent
separation of greenhouse gas CO.sub.2. The technique involves the
use of a metal oxide as an oxygen carrier for transferring oxygen
from the air reactor to the fuel reactor. Thus, direct contact
between fuel and air is avoided. The output product of oxidation of
fuel, i.e., carbon dioxide, is kept separate from the rest of the
flue gases, such as nitrogen and any un-reacted oxygen. Two
reactors, i.e., the air reactor and the fuel reactor having
interconnected fluidized beds are used for this process. The metal
is oxidized to metal oxide with air in the air reactor and the
oxidized metal oxide is reduced to metal in the fuel reactor. The
reduced metal is transported back to the air reactor from the fuel
reactor. Alternatively, metal-oxides with different oxidation
states can be used as oxygen carriers between the air and the fuel
reactor. The outlet gas from the air reactor comprises N.sub.2 and
un-reacted O.sub.2 if any. The outlet gas from the fuel reactor
comprises CO.sub.2 and H.sub.2O which can be separate by
condensation. The CO.sub.2 being separate from the flue gas is
sequestration ready without the requirement of additional amount of
energy and additional expensive separation units.
[0004] Chemical looping system can be used for producing power by
combusting a gaseous fuel, and the technique is referred to as
chemical looping combustion (CLC). The system can also be used for
producing hydrogen and the technique is referred to as chemical
looping reforming (CLR). The CLC system is generally integrated
into a combined cycle power process.
SUMMARY OF THE INVENTION
[0005] It is an object of the embodiments of the invention to
reduce the rate of decrease of the active surface area of the
oxygen carrier particles for redox reactions in a chemical looping
system.
[0006] The above object is achieved by a chemical looping system
and a method of transferring oxygen in a chemical looping system
according to the independent claims.
[0007] The oxygen carrier comprising the
oxide-dispersion-strengthened alloy particles is oxidized in the
air reactor and transported to the fuel reactor. The fuel in the
fuel reactor reacts with the oxidized oxygen carrier and is
oxidized. The oxygen carrier is reduced and the reduced oxygen
carrier is transported back to the air reactor, where they are
oxidized again. Thus, the oxygen carriers are circulated between
the air reactor and the fuel reactor for transferring oxygen from
the air reactor to the fuel reactor. The oxygen carrier being
oxide-dispersion-strengthened alloy particles are less prone to
sintering, and thus, more resistance to agglomeration during the
high operating temperature of the chemical looping system. As the
oxygen carrier particles are more resistant to agglomeration, the
rate of decrease of the available active surface area for the
oxidation/reduction reactions is reduced and thus, improving the
redox activity over time. This enables the oxygen carriers to
achieve longer operation life and reduce the operation costs of the
chemical looping system.
[0008] According to an embodiment, the
oxide-dispersion-strengthened alloy particles are composed of a
metal having a dispersion of a metal oxide or a carbide. Dispersion
of the metal oxide or the carbide into the metal enables in
strengthening the metal and increase the redox activity. In
conventional systems, the oxygen carrier is prepared by using
binders such as alumina, silica, etc. In this case, the oxygen
carrier is generally composed of a metal which can be oxidized to
form a metal oxide to provide the oxygen for the combustion
process, and an inert element as a binder for increasing the
mechanical strength. Alternatively, the metal particles can be
impregnated with a substrate, such as, a porous alumina substrate.
In both cases, the target material performance with respect to
strength and redox activity is not achieved.
[0009] According to yet another embodiment, the metal is selected
from the group consisting of nickel, copper, iron, cobalt,
manganese. The metals have relatively good oxygen transfer
capabilities.
[0010] According to yet another embodiment, wherein the metal oxide
is selected from the group consisting of cerium oxide, titanium
oxide, and zirconium oxide.
[0011] According to yet another embodiment, wherein the carbide is
silicon carbide.
[0012] According to yet another embodiment, wherein the metal oxide
or the carbide is doped.
[0013] According to yet another embodiment, wherein the fuel
comprises a carbonaceous fuel. The carbonaceous fuel can be
combusted easily.
[0014] According to yet another embodiment, the fuel reactor is
adapted to combust the fuel to produce the gas. The fuel is
oxidized for combustion by reducing the oxygen carrier. The reduced
oxygen carrier can be transported to the air reactor for oxidation,
which is an exothermic reaction, thus producing energy.
[0015] According to yet another embodiment, the gas comprises
CO.sub.2 and H.sub.2O. The CO.sub.2 from the gas can easily be
separated by condensing H.sub.2O. Thus, the CO.sub.2 obtained is
sequestration ready as the same is separate from the flue gases.
The CO.sub.2 is separated from the flue gases without the
requirement of additional amount of energy and additional expensive
separation units.
[0016] According to yet another embodiment, wherein the fuel
reactor is adapted to partially oxidize the fuel to produce the
gas, wherein the gas comprises a reformer gas. The fuel is
partially oxidized by reducing the oxygen carrier. The reduced
oxygen carrier can be transported to the air reactor for
oxidation.
[0017] According to yet another embodiment, wherein the reformer
gas comprises H.sub.2, CO, C.sub.2O and H.sub.2O. The H.sub.2 of
the reformer gas can be used as a fuel. Additional H.sub.2 can be
obtained by reacting CO and H.sub.2O in a shift reactor. The
CO.sub.2 can easily be separated from H.sub.2, and the separated
CO.sub.2 is sequestration ready as the same is separate from the
flue gases. The CO.sub.2 is separated from the flue gases without
the requirement of additional amount of energy and additional
expensive separation units.
[0018] According to yet another embodiment, wherein fuel reactor is
further adapted to receive steam. The generation of H.sub.2 can be
enhanced by supplying steam into the fuel reactor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Embodiments of the present invention are further described
hereinafter with reference to illustrated embodiments shown in the
accompanying drawings, in which:
[0020] FIG. 1 illustrates a schematic block diagram of a chemical
looping system according to an embodiment herein,
[0021] FIG. 2 illustrates an enlarged view of an ODS alloy particle
according to an embodiment herein, and
[0022] FIG. 3 is a flow diagram illustrating a method of
transferring oxygen in a chemical looping system according to an
embodiment herein.
DETAILED DESCRIPTION OF THE INVENTION
[0023] Various embodiments are described with reference to the
drawings, wherein like reference numerals are used to refer to like
elements throughout. In the following description, for purpose of
explanation, numerous specific details are set forth in order to
provide a thorough understanding of one or more embodiments. It may
be evident that such embodiments may be practiced without these
specific details.
[0024] FIG. 1 illustrates a schematic block diagram of a chemical
looping system according to an embodiment herein. As illustrated in
the example of FIG. 1, the chemical lopping system 10 comprises an
air reactor 15 and a fuel reactor 20. Typically, the air reactor 15
and the fuel reactor 20 are fluidized bed reactors. In the present
example of FIG. 1, air is supplied as oxidant is into the air
reactor 15, as designated by the arrow 25. A fuel is supplied into
the fuel reactor 20, as designated by the arrow 30. The air reactor
15 and the fuel reactor are isolated and thus, there is no direct
contact between air and fuel. Oxygen from the air reactor 15 is
transferred to the fuel reactor 20 by circulating an oxygen carrier
between the air reactor 15 and the fuel reactor 20, as designated
by the arrows 35 and 40 respectively. The oxygen carrier is
oxidized in the air reactor 15 forming an oxide. The oxide is then
transported to the fuel reactor 20 where the fuel reduces the oxide
to its original state. The oxygen carrier in its original state is
transported back to the air reactor 15, where it is again oxidized
and is transported to the fuel reactor 20. This transportation of
the oxide to the fuel reactor 20 from the air reactor 15 and the
transportation of the oxygen carrier in its original state from the
fuel reactor 20 to the air reactor 15 is the circulation of the
oxygen carrier between the air reactor 15 and fuel reactor 20. The
air reactor 15 and the fuel reactor 20 are isolated and thus, there
is no direct contact between air and fuel. The oxygen carrier
transported from the air reactor 15 to the fuel reactor 20 provides
the necessary oxygen required for the oxidation of the fuel in the
fuel reactor 20.
[0025] According to an aspect, the oxygen carrier comprises
oxide-dispersion-strengthened (ODS) alloy particles. The ODS alloy
particles are composed of a metal having a dispersion of a metal
oxide or a carbide. The metal particles are strengthened by the
dispersion of the metal oxide or the carbide. The ODS alloy
particles transfer oxygen from the air reactor 15 to the fuel
reactor 20. The ODS alloy particles are in powder form, and thus,
the particles are not grouped together. The ungrouped ODS alloy
particles provide larger surface area for the redox reactions in
the air reactor 15 and the fuel reactor 20. The metal used for
preparing the ODS alloy particles include, but not limited to,
nickel, copper, iron, cobalt, manganese, cadmium, and the like. In
aspects, where a metal oxide is used for forming the ODS alloy
particles, the metal oxide may include, but not limited to, cerium
oxide, titanium oxide, zirconium oxide and the like. In an aspect,
the carbide, may include, but not limited to, silicon carbide and
tungsten carbide. The metal oxide and the carbide may be doped or
un-doped. In an aspect, the ODS alloy particles may be formed by
dispersing the metal oxide or the carbide into the metal by
mechanical alloying. In an aspect, advantageously the ODS alloy
particles may be supported on alumina, titanium oxide, YSR
particles or other ceramics. The ODS alloy particles could also be
recycled after the operation via thermal treatment to separate the
metal and the metal oxide dispersion.
[0026] Referring still to FIG. 1, as only oxygen present in air is
transported to the fuel reactor 20, the gas exiting the air reactor
15, as designated by the arrow 42, will comprise nitrogen and
un-reacted oxygen if any. The gas exited from the air reactor 15
can be discharged into the atmosphere causing minimal or no
CO.sub.2 pollution. The gas produced due to the oxidation of the
fuel by the oxygen carried in the fuel reactor 20 is exited from
the reactor 20, as shown by the arrow 44.
[0027] Referring still to FIG. 1, in an aspect, the chemical
looping system 10 can be operated as a chemical looping combustion
(CLC) to produce energy by combusting the fuel. A carbonaceous fuel
is supplied as the fuel into the fuel reactor 15. The term
"carbonaceous fuel" hereinafter is referred to any material made of
or containing carbon which is combustible or flammable. The
carbonaceous fuel comprises, but not limited to, fossil fuels and
fuels derived from fossil fuels. Advantageously, the carbonaceous
fuel supplied into the fuel reactor 20 may be a gaseous fuel, such
as, natural gas. Solid fuels can also used by gasifying the same to
gaseous fuels and thereafter introducing the same into the fuel
reactor 20. The gasification of the solid fuel may be performed in
the fuel reactor 20 or may be performed externally in a separate
reactor. In the present example, the carbonaceous fuel supplied
into the fuel reactor 20 is methane. Air is supplied as the oxidant
into the air reactor 15, as shown by the arrow 25. The metal
present in the ODS alloy particles is oxidized by air in the air
reactor 15 to form a metal oxide (M.sub.eO). The ODS alloy
particles containing the metal oxide are transported to the fuel
reactor 20, as shown by the arrow 35. The oxidation of the ODS
alloy particles is an exothermic reaction. As the chemical looping
system 10 is operated as a CLC system, the fuel in the fuel reactor
20 is completely oxidized by reducing the metal oxide of the ODS
alloy particles to metal. Thus, the fuel is combusted using the
oxygen carried by the oxygen carrier from the air reactor 15. The
reduction of the metal oxide of the ODS alloy particles to metal is
an endothermic reaction. The ODS alloy particles containing the
reduced metal are transported back to the air reactor 15, as shown
by the arrow 40. In the present aspect, the gas stream exiting the
fuel reactor 15, illustrated by the arrow 44 comprises CO.sub.2 and
H.sub.2O. CO.sub.2 can easily be separated from the exited gas
stream by condensing H.sub.2O. The separated CO.sub.2 is pure as
the same is separate from flue gases, and thus, ready for
sequestration. This assists in separating CO.sub.2 from N.sub.2 and
NO compounds without the consumption of additional energy and
implementation of additional separation units.
[0028] The redox reactions in the air reactor 15 and the fuel
reactor 20 can be summarized as follows:
Oxidation: exothermic
M.sub.e+1/2O.sub.2.fwdarw.M.sub.eO (1)
Reduction: endothermic
CH.sub.4+4M.sub.eO.fwdarw.CO.sub.2+2H.sub.2O+4M.sub.e (2)
Where M.sub.e is metal, M.sub.eO is metal oxide.
[0029] Referring still to FIG. 1, in another aspect, the chemical
looping system 10 can be operated as a chemical looping reforming
(CLR) to produce a reformer gas comprising H.sub.2 by partially
oxidizing the fuel. In accordance with this aspect, the fuel
supplied into the fuel reactor 20 comprises a carbonaceous fuel.
Advantageously, the carbonaceous fuel supplied into the fuel
reactor 20 may be a natural gas. In the present example, the
carbonaceous fuel supplied into the fuel reactor 20 is methane. In
an aspect, to increase the yield of H.sub.2, additional oxygen may
be supplied into the fuel reactor 20 in the form of steam
(H.sub.20). The steam may be supplied into the fuel reactor though
the same inlet with which the fuel is supplied or may be supplied
through a separate inlet. Air is supplied as the oxidant into the
air reactor 15, as shown by the arrow 25. The metal present in the
ODS alloy particles is oxidized by air in the air reactor 15 to
form a metal oxide (MW). The ODS alloy particles containing the
metal oxide are transported to the fuel reactor 20, as shown by the
arrow 35. The oxidation of the ODS alloy particles is an exothermic
reaction. The fuel in the fuel reactor 20 reacts with the metal
oxide of the ODS alloy particles and is partially oxidized and the
metal oxide is reduced to metal. The reduction of the metal oxide
of the ODS alloy particles to metal is an endothermic reaction. The
ODS alloy particles containing the reduced metal are transported
back to the air reactor 15, as shown by the arrow 44. The partial
oxidation of the fuel in the fuel reactor 20 produces a gas
comprising a reformer gas. In an aspect, the reformer gas can
comprise a syngas, CO.sub.2 and H.sub.2O. The syngas is a gas
comprising a mixture of CO and H.sub.2. In aspects where the
reformer gas comprises a syngas, additional H.sub.2 can be produced
by reacting CO and H.sub.2O in a subsequent shift reactor. CO.sub.2
can easily be separated from the reformer gas. The separated
CO.sub.2 is pure as the same is separate from flue gases, and thus,
ready for sequestration. This assists in separating CO.sub.2 from
N.sub.2 and NO compounds without the consumption of additional
energy and implementation of additional separation units.
[0030] The reactions in the air reactor 15, fuel reactor 20 and the
shift reactor can be summarized as follows:
Oxidation: exothermic
M.sub.e+1/2O.sub.2.fwdarw.M.sub.eO (3)
Reduction: endothermic
2CH.sub.4+4M.sub.eO.fwdarw.CO.sub.2+CO+H.sub.2O+3M.sub.2+4M.sub.3
(4)
Shift reactor:
CO+H.sub.2O.fwdarw.CO.sub.2+H.sub.2 (5)
Where M.sub.e is metal, M.sub.eO is metal oxide.
[0031] FIG. 2 illustrates an enlarged view of an ODS alloy particle
according to an embodiment herein. In the example of FIG. 2, it is
shown that the ODS alloy particle 45 is formed of a metal 50 and
particles of a metal oxide 55 dispersed into the metal 26.
[0032] The ODS alloy particles 45 have increased strength relative
to particles of simple metal. Using the ODS alloy particles 45 as
oxygen carriers prevent sintering of the particles at the high
operation temperature, and thus, prevent the decrease in the
surface area per filling volume of the particles 45. Sintering of
the metal-fuel particles leads to agglomeration of the particles
during high temperature treatment, and thus, degradation in the
performance of a chemical looping system with time, as the surface
area per filling volume of the particles decreases. Thus, the
degradation rate of the performance of the chemical looping system
10 of FIG. 1 with time is reduced and the life-time of the chemical
looping system 10 is increased by using ODS alloy particles 45 as
oxygen carriers as the same are less prone to sintering, and thus,
more resistant to agglomeration. The ODS alloy particles being more
resistant to agglomeration enable in reducing the rate of decrease
of the active surface area for redox reactions at the fuel reactor
20 of FIG. 1 and the oxidation reactor 15 of FIG. 1 and also
improve the redox activity over time of the oxygen carrier.
Additionally, the ODS alloy particles can posses relatively higher
ionic conductivity during redox processes if the dispersed oxide on
the metal is an O.sub.2 conductor. The higher ionic conductivity
enables in enhancing the redox reaction rate.
[0033] FIG. 3, with reference to FIG. 1 through FIG. 2, is a flow
diagram illustrating a method of transferring oxygen in a chemical
looping system according to an embodiment herein. At block 60, an
air reactor 15 adapted to receive an oxidant for oxidizing an
oxygen carrier is provided. Next, at block 65, a fuel reactor 20
adapted to receive a fuel and the oxidized oxygen carrier for at
least partially oxidizing the fuel by reducing the oxygen carrier
to produce a gas, and wherein, the oxygen carrier comprises
oxide-dispersion-strengthened alloy particles.
[0034] The embodiments described herein enable in increasing the
efficiency of the chemical looping system. Moreover, the duration
for which the oxygen carriers can be re-circulated within the
chemical looping system is increased. Additionally, this enables in
reducing the operating cost of the system.
[0035] While this invention has been described in detail with
reference to certain preferred embodiments, it should be
appreciated that the present invention is not limited to those
precise embodiments. Rather, in view of the present disclosure
which describes the current best mode for practicing the invention,
many modifications and variations would present themselves, to
those of skill in the art without departing from the scope and
spirit of this invention. The scope of the invention is, therefore,
indicated by the following claims rather than by the foregoing
description. All changes, modifications, and variations coming
within the meaning and range of equivalency of the claims are to be
considered within their scope.
* * * * *