U.S. patent application number 17/697561 was filed with the patent office on 2022-06-30 for systems and methods for carbon capture.
The applicant listed for this patent is 8 RIVERS CAPITAL, LLC. Invention is credited to Jeremy Eron Fetvedt, Brock Alan Forrest, Xijia Lu, Navid Rafati.
Application Number | 20220203297 17/697561 |
Document ID | / |
Family ID | 1000006200325 |
Filed Date | 2022-06-30 |
United States Patent
Application |
20220203297 |
Kind Code |
A1 |
Lu; Xijia ; et al. |
June 30, 2022 |
SYSTEMS AND METHODS FOR CARBON CAPTURE
Abstract
The present disclosure provides systems for carbon capture in
combination with production of one or more industrially useful
materials. The disclosure also provides methods for carrying out
carbon capture in combination with an industrial process. In
particular, carbon capture can include carrying out calcination in
a reactor, separation of carbon dioxide rich flue gases from
industrially useful products, and capture of at least a portion of
the carbon dioxide for sequestration of other use, such as enhanced
oil recovery.
Inventors: |
Lu; Xijia; (Durham, NC)
; Forrest; Brock Alan; (Durham, NC) ; Fetvedt;
Jeremy Eron; (Raleigh, NC) ; Rafati; Navid;
(Durham, NC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
8 RIVERS CAPITAL, LLC |
Durham |
NC |
US |
|
|
Family ID: |
1000006200325 |
Appl. No.: |
17/697561 |
Filed: |
March 17, 2022 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16864944 |
May 1, 2020 |
11285437 |
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17697561 |
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62843012 |
May 3, 2019 |
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62936723 |
Nov 18, 2019 |
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62965405 |
Jan 24, 2020 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B01D 53/62 20130101;
B01D 5/0075 20130101; B01D 2258/0283 20130101; B01D 2257/504
20130101; B01D 2251/606 20130101; B01D 5/0072 20130101; B01D 53/96
20130101; C01B 32/55 20170801 |
International
Class: |
B01D 53/62 20060101
B01D053/62; C01B 32/55 20060101 C01B032/55; B01D 5/00 20060101
B01D005/00; B01D 53/96 20060101 B01D053/96 |
Claims
1. A system for calcination with carbon capture, the system
comprising: a reactor configured to heat a carbonate-containing raw
material in the presence of an oxidant to form a decomposition
stream containing at least solids and carbon dioxide gas; a
separator configured to separate the decomposition stream into a
gas stream including the carbon dioxide gas and a solids stream; a
heat exchange unit configured to receive one or both the gas stream
including the carbon dioxide gas and the solid stream and withdraw
heat therefrom to provide a cooled gas stream including the carbon
dioxide and a cooled solids stream; and a CO.sub.2 separation unit
configured to separate the cooled gas stream including the carbon
dioxide into a CO.sub.2 lean stream and a CO.sub.2 rich stream.
2. The system of claim 1, wherein the reactor and the separator are
combined as a single unit.
3. The system of claim 1, further comprising an oxygen-forming unit
configured to provide oxygen to the reactor.
4. The system of claim 1, further comprising a water separator
downstream from the heat exchanger.
5. The system of claim 1, wherein the CO.sub.2 separation unit
comprises at least one membrane separation stage configured to
separate the cooled gas stream including the carbon dioxide into
the CO.sub.2 lean stream and the CO.sub.2 rich stream.
6. The system of claim 5, further comprising a low temperature
CO.sub.2 purification unit configured to receive at least the
CO.sub.2 rich stream from the at least one membrane separation
stage.
7. The system of claim 6, further comprising a compression unit
configured to compress the cooled gas stream including the carbon
dioxide, the compression unit being positioned upstream from the at
least one membrane separation stage.
8. The system of claim 7, further comprising an expander positioned
downstream from the at least one membrane separation stage.
9. The system of claim 1, further comprising a power generation
cycle integrated with the heat exchanger.
10. The system of claim 9, wherein the power generation cycle
comprises a compression unit configured to provide a compressed
working fluid to an inlet of the heat exchanger, a turbine
configured to receive the compressed working fluid from an outlet
of the heat exchanger, and a cooler positioned between, and in
fluid connection, with an outlet of the turbine and an inlet of the
compression unit.
11. The system of claim 1, further comprising a carbonator
configured to receive a portion of the solids stream from the
separator.
12. The system of claim 11, wherein the carbonator includes a solid
product outlet in communication with an inlet of the reactor and
configured for delivery of regenerated raw material to the
reactor.
13. The system of claim 1, further comprising a clinker unit
configured to receive a portion of the solids stream from the
separator.
14. The system of claim 13, wherein the clinker unit includes one
or more inlets configured for entry of one or more raw
materials.
15. The system of claim 13, further comprising a clinker cooler
unit configured to receive a stream of cement clinker from the
clinker unit and cool the stream of cement clinker with a portion
of the cooled gas stream.
16. The system of claim 1, wherein the system is integrated with a
steel-making plant.
17. The system of claim 1, wherein the system is integrated with a
power production plant.
18. The system of claim 17, wherein the system further comprises an
ash burning unit.
19. A method for calcination with carbon capture, the method
comprising: processing a carbonate-containing raw material in a
heated reactor to provide a decomposition stream comprising at
least solids and carbon dioxide gas; separating the decomposition
stream in a separation unit into a gas stream including the carbon
dioxide and a solids stream; cooling one or both of the gas stream
including the carbon dioxide and the solids stream in a heat
exchanger; one or both of providing at least a portion of the
solids stream as a product for export and delivering at least a
portion of the solids stream to a further reactor for forming a
secondary product; purifying the gas stream including the carbon
dioxide to provide a substantially pure stream of carbon dioxide
for export; and carrying out a power production cycle that is
integrated with the heat exchanger.
20-50. (canceled)
51. A method for calcination with carbon capture, the method
comprising: processing a carbonate-containing raw material in a
heated reactor to provide a decomposition stream comprising at
least solids and carbon dioxide gas; separating the decomposition
stream in a separation unit into a gas stream including the carbon
dioxide and a solids stream; cooling one or both of the gas stream
including the carbon dioxide and the solids stream in a heat
exchanger; one or both of providing at least a portion of the
solids stream as a product for export and delivering at least a
portion of the solids stream to a further reactor for forming a
secondary product; purifying the gas stream including the carbon
dioxide to provide a substantially pure stream of carbon dioxide
for export; and processing a portion of the solids stream exiting
the separator in a clinker unit.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority to U.S. Provisional
Patent Application No. 62/843,012, filed May 3, 2019, U.S.
Provisional Patent Application No. 62/936,723, filed Nov. 18, 2019,
and U.S. Provisional Patent Application No. 62/965,405, filed Jan.
24, 2020, the disclosures of which are incorporated herein by
reference.
FIELD OF THE DISCLOSURE
[0002] The present disclosure relates to systems and methods for
capture and optional purification of one or more moieties from a
provided stream, particularly with capture of at least carbon
dioxide.
BACKGROUND
[0003] Many technologies enabling carbon capture from
calcination/cement plants have been invented by different groups,
including oxy-combustion cement processes, calcium looping
processes, post-combustion capture via membrane separation, and
other solvent based separation processes. No known technologies
include complete process integration between the carbon capture
technologies (such as a calcination/cement operation) and the power
required to enable it (including CO.sub.2 capture from calcination,
fuel combustion, and electricity consumption) as well the
purification of the CO.sub.2 stream that has been captured.
Furthermore, the capture of carbon emissions not originating from
kiln based calcination activities typically requires an external
reactor known as a carbonator in order to enable calcium looping as
a parallel function. In addition, processes for NOx/SOx removal
from calcination/cement plants flue gas and adjacent external
emissions are not included in the existing technologies.
[0004] Calcination related industrial processes, such as lime and
cement production, are some of the world's most energy and CO.sub.2
intensive industrial production processes. In a 2013 report,
emissions from cement production process were estimated to account
for nearly 5% of the world's total anthropogenic CO.sub.2
emissions. Different from power generation, CO.sub.2 is produced
not only from the combustion of fossil fuels, but also from the
calcination of raw meal (which contains 70-80 wt. % CaCO.sub.3).
This calcination produces the largest share of CO.sub.2 emissions
of the process, around 60%. CO.sub.2 from fossil fuels combustion,
electricity, and transportation represents 40% of the total
CO.sub.2 emissions in the cement process. In total, the production
of one kg of cement releases about 0.6-0.7 kg of CO.sub.2.
Currently, the International Energy Agency (IEA) has a goal set
wherein 50% of all cement plants in Europe, Northern America,
Australia and East Asia will apply carbon capture and storage (CCS)
by 2050.
SUMMARY OF THE DISCLOSURE
[0005] The present disclosure provides systems useful for capturing
carbon dioxide while also providing one or more industrially useful
products, such as cement, steel, quicklime, and electrical power.
The present disclosure further provides methods utilizing such
systems. As such, it is possible according to the present
disclosure to provide quicklime and other industrial products that
are substantially or completely "carbon dioxide-free" in that the
quicklime and other industrial products can be formed in a manner
wherein substantially no carbon dioxide or completely no carbon
dioxide is released to the atmosphere. The quicklime and other
industrial products that are available for use in a variety of
industries (e.g., cement, steel, electrical power generation, etc.)
without adding carbon output to the environment.
[0006] In one or more embodiments, the present disclosure can
provide systems that are useful for calcination of one or more
materials while also providing for carbon capture, particularly
capture of at least a portion of any carbon dioxide that is
produced from the system. In example embodiments, such systems can
be specifically useful for calcination of a carbonate-containing
raw material, such as a calcium carbonate (CaCO.sub.3) containing
material, and more particularly limestone. The systems may include:
a reactor configured to heat a carbonate-containing raw material in
the presence of an oxidant to form a decomposition stream
containing at least solids and carbon dioxide gas; a separator
configured to separate the decomposition stream into a gas stream
including the carbon dioxide gas and a solids stream; a heat
exchange unit configured to receive one or both the gas stream
including the carbon dioxide gas and the solid stream and withdraw
heat therefrom to provide a cooled gas stream including the carbon
dioxide and a cooled solids stream; and a CO.sub.2 separation unit
configured to separate the cooled gas stream into a CO.sub.2 lean
stream and a CO.sub.2 rich stream. The systems may be further
defined in relation to one or more of the following statements,
which may be combined in any order or number.
[0007] The reactor and the separator may be combined as a single
unit. Alternatively, the reactor and the separator may be
individual units that are interconnected through one or more lines.
For example, one or more outlets of one or more reactors may be in
communication with one or more inlets of one or more separators.
Likewise, a plurality of reactors may be utilized as a reactor unit
and/or a plurality of separators may be used as a separation
unit.
[0008] The systems further can comprise one or more oxygen-forming
unit(s) configured to provide oxygen to the reactor. Alternatively,
or additionally, oxygen may be provided to the reactor as part of a
mixed gas stream. For example, a flue gas from a power production
plant may be directed to the reactor to provide all or part of the
necessary oxidant in the reactor. As such, the present systems may
be integrated with a power plant or other system that is configured
to provide an oxygen-containing gas, and the system may include one
or more lines interconnecting the power plant or other
gas-producing plant with the reactor of the present systems.
[0009] The present systems further may comprise a water separator
downstream from the heat exchanger. Further, a plurality of water
removing components may be used and may be provided separately or
as a single unit. As such, a plurality of water removing components
may be provided in sequence.
[0010] The CO.sub.2 separation unit can comprise at least one
membrane separation stage configured to separate the cooled gas
stream including the carbon dioxide into the CO.sub.2 lean stream
and the CO.sub.2 rich stream. Further, the system may include a low
temperature CO.sub.2 purification unit configured to receive at
least the CO.sub.2 rich stream from the at least one membrane
separation stage. Additionally, the system may include one or more
compression units. For example, a compression unit may be
configured to compress the cooled gas stream including the carbon
dioxide. In particular, the compression unit can be positioned
upstream from the at least one membrane separation stage. If
desired, the system likewise can include an expander positioned
downstream from the at least one membrane separation stage.
[0011] The systems further may comprise a carbon dioxide membrane
separator positioned downstream of the compression unit and
upstream from the CO.sub.2 separation unit. The carbon dioxide
membrane separator may be configured to exhibit a defined
performance level. For example, the carbon dioxide membrane
separator may be configured to provide at least 50% bulk recovery
of CO.sub.2 from the incoming gas stream and output a permeate
product including the carbon dioxide.
[0012] An expander may be positioned downstream from the carbon
dioxide membrane separator. The expander can be useful to cool the
permeate product and may be utilized as part of a cryogenic
CO.sub.2 separation unit.
[0013] The system can further comprise a power generation cycle
integrated with the heat exchanger. For example, the power
generation cycle can comprise a compression unit configured to
provide a compressed working fluid to an inlet of the heat
exchanger, a turbine configured to receive the compressed working
fluid from an outlet of the heat exchanger, and a cooler positioned
between, and in fluid connection, with an outlet of the turbine and
an inlet of the compression unit. A generator or other suitable
power-producing component can be included in the power generation
cycle to, for example, produce electricity.
[0014] The system can further comprise a carbonator configured to
receive a portion of the solids stream from the separator.
Alternatively, or additionally, the carbonator may be configured to
receive at least a portion of the gas stream including the carbon
dioxide from the separator.
[0015] The carbonator can include a solid product outlet in
communication with an inlet of the reactor and can be configured
for delivery of regenerated raw material to the reactor. For
example, when limestone (CaCO.sub.3) is utilized as the raw
material in the reactor, the solids that are produced can include
quicklime (CaO). In the carbonator, the quicklime can be reacted
with a carbon dioxide-containing stream to produce CaCO.sub.3,
which can be recycled back to the reactor. The carbon
dioxide-containing stream can be, for example, an industrial flue
gas that can be taken from an existing power plant, lime production
plant, cement plant, steel plant, and/or other industrial process.
In this manner, the present system may be physically integrated
with a further system for processing of the carbon
dioxide-containing stream taken from the further system.
[0016] The system further can comprise a clinker unit configured to
receive a portion of the solids stream from the separator. The
clinker unit may be configured for formation of cement clinker, for
example. Accordingly, the clinker unit can include one or more
inlets configured for entry of one or more raw materials. The raw
materials particularly may be materials suitable for formation of
cement clinker when combined with quicklime.
[0017] The system likewise may further comprise a clinker cooler
unit configured to receive a stream of cement clinker from the
clinker unit and cool the stream of cement clinker with a portion
of the cooled gas stream from the compression unit. A cement
clinker product suitable for forming cement may thus be exported
from the system.
[0018] The system, in one or more embodiments, may be specifically
configured to be integrated with a steel-making plant. In
particular, the reactor may be configured to receive one or more
streams from the steelmaking plant, such as a fuel gas stream
(e.g., a coke oven gas stream, a blast furnace gas stream, and/or a
basic oxygen furnace gas stream). Likewise, the system may be
configured such that solids from the reactor (or the separator) may
be delivered to one or more components of the steelmaking system
(e.g., a blast furnace and/or a basic oxygen furnace). Further, an
oxygen source may be shared between one or more components of the
steelmaking system and the reactor in the present system.
[0019] The system similarly may be integrated with a power
production plant. For example, a line may be utilized to direct
flue gas from the power production plan to the reactor of the
present system. Alternatively, or additionally, coal ash from a
power production plant may be processed through the present
system.
[0020] The system particularly can further include an ash burning
unit. The ash burning unit can be a reburner to provide thermally
treated ash that has a low loss on ignition. Such treated ash may
then be delivered for formation of other products, such as cement,
concrete, fly ash bricks, aggregates, and the like. Similarly, the
system can be configured to deliver a portion of the produced
solids (e.g., quicklime) for mixing with high moisture ash to
reduce the moisture level thereof and provide ash that is suitable
for downstream uses, such as noted above. Likewise, a portion of
the solids can be exported and optionally mixed with ash.
[0021] In one or more embodiments, the present disclosure can
provide methods or processes that are likewise useful for
calcination of one or more materials while also providing for
carbon capture, particularly capture of at least a portion of any
carbon dioxide that is produced from the processes. In example
embodiments, such methods or processes can be specifically useful
for calcination of a carbonate-containing raw material, such as a
calcium carbonate (CaCO.sub.3) containing material, and more
particularly limestone. Particularly, such methods can comprise:
processing a carbonate-containing raw material in a heated reactor
to provide a decomposition stream comprising at least solids and
carbon dioxide gas; separating the decomposition stream in a
separation unit into a gas stream including the carbon dioxide and
a solids stream; cooling one or both of the gas stream including
the carbon dioxide and the solids stream in a heat exchanger; one
or both of providing at least a portion of the solids stream as a
product for export and delivering at least a portion of the solids
stream to a further reactor for forming a secondary product; and
purifying the gas stream including the carbon dioxide to provide a
substantially pure stream of carbon dioxide for export. The methods
may be further defined in relation to one or more of the following
statements, which may be combined in any order or number.
[0022] A decomposition stream produced according to the present
methods particularly indicates that the stream contains one or more
compounds or materials that arise from calcination of the raw
material where the raw material is broken down into constituent
parts. For example, calcination of CaCO3 produces carbon dioxide
gas and calcium oxide solids, and calcination of types of raw
materials, particularly other carbonate-containing materials, may
likewise produce a solids component and a carbon dioxide-containing
gas.
[0023] The reactor in the present methods may be operated at an
increased pressure (i.e., greater than ambient pressure), and such
pressure particularly may be in the range of about 1.5 bar to about
8 bar.
[0024] The reactor likewise may be operated at an increased
temperature, such as about 850.degree. C. to about 1100.degree.
C.
[0025] The reactor may be heated through combustion in the reactor
of a fuel with oxygen.
[0026] The oxidant can comprise substantially pure oxygen provided
by one or more oxygen production units. Alternatively, or
additionally, the oxidant can comprise oxygen that is present in a
mixed gas stream such as a flue gas. For example, a flue gas from a
power production plant can be a mixed gas stream that includes
oxygen, and carbon dioxide in the flue gas can be captured as a
result of being introduced into the present methods.
[0027] The heated reactor and the separation unit can be an
integral unit. Alternatively, the heated reactor and the separation
unit can be independent units. Likewise, a plurality of reactors
may be used in a reactor unit, and/or a plurality of separators may
be utilized in a separation unit.
[0028] The heat exchanger can be one or more of a heat recovery
steam generator (HRSG), a gas heated reformer (GHR), or a
recuperative heat exchanger. Likewise, a plurality of individual
heat exchangers may be combined.
[0029] The gas stream including the carbon dioxide can be cooled in
the heat exchanger(s) to a temperature of about 20.degree. C. to
about 150.degree. C.
[0030] The method further can comprise passing the gas stream
including the carbon dioxide that is exiting the heat exchanger
through one or more water removal units to provide a dried gas
stream including the carbon dioxide.
[0031] The method can be configured such that purifying the gas
stream including the carbon dioxide can comprise passing the gas
stream including the carbon dioxide through at least one membrane
separation stage configured to separate the gas stream including
the carbon dioxide into a CO.sub.2 lean stream and a CO.sub.2 rich
stream. In such embodiments, it can be preferable to pass at least
the CO.sub.2 rich stream through a low temperature CO.sub.2
purification unit. Optionally, the CO.sub.2 lean stream may also be
passed through the low temperature CO.sub.2 purification unit.
[0032] The method further can comprise compressing the gas stream
including the carbon dioxide upstream from the at least one
membrane separation stage. This can include, in some embodiments,
pressurizing the gas stream including the carbon dioxide to a
pressure of about 3 bar to about 15 bar to provide a pressurized
gas stream including the carbon dioxide. Pressurization can utilize
one or more compression stages. When multiple compression stages
are used, it can be preferred to utilize intercooling to remove the
heat of compression after one or more of the pressurization
stages.
[0033] When pressurization is utilized, the method further can
comprise expanding at least the CO.sub.2 rich stream downstream
from the at least membrane separation stage. If desired, the
CO.sub.2 lean stream likewise can be expanded.
[0034] In some embodiments, the at least one membrane separation
unit can be configured to provide at least 50% bulk recovery of
CO.sub.2 from the gas stream including the carbon dioxide in the
CO.sub.2 rich stream. Preferably, the CO.sub.2 rich stream can have
a CO.sub.2 concentration no lower than 50%.
[0035] The method further can comprise carrying out a power
production cycle that it integrated with the heat exchanger. For
example, the power production cycle can comprise compressing a
working fluid in a compression unit to provide a compressed working
fluid, heating the compressed working in the heat exchanger,
passing the compressed working fluid exiting the heat exchanger
through a turbine to generate power and form an expanded working
fluid, and passing the expanded working fluid back to the
compression unit. A generator or other suitable power-producing
component can be included in the power generation cycle to, for
example, produce electricity.
[0036] The method further can comprise processing a portion of the
solids stream exiting the separator in a carbonator. For example,
the carbonator can be configured to provide a regenerated raw
material, and at least a portion of the regenerated raw material
can be recycled back to the reactor. In example embodiments, the
raw material can be limestone (CaCO.sub.3), and the solids steam
exiting the reactor can comprise quicklime (CaO). The method
likewise can comprise processing a flue gas including carbon
dioxide through the carbonator such that at least a portion of the
carbon dioxide from the flue gas is reacted with the quicklime to
form CaCO.sub.3. The limestone then can be the regenerated raw
material that is sent back to the reactor.
[0037] The quicklime that is produced in a method utilizing
limestone as a raw material for calcination thus can be cycled in
the method as a carbon capture substrate. Such looping processes
are known, but utilization of such looping has been problematic in
the art since the quicklime rapidly loses its activity for carbon
capture. In the present methods, this problem is overcome by
separating the produced quicklime into an export fraction and a
carbonation fraction (i.e., a portion that is sent to the
carbonator to capture carbon dioxide as noted above). The methods
preferably can be configured such that an export to carbonation
ratio range is utilized. By implementing such ratio, quicklime is
constantly being removed from the system, and the possibility of
the "same" CaO particles repeatedly being recycled through the
carbonator and the calcination reactor enough times to deactivate
the CaO below a desired activity level is statistically limited. In
some embodiments, this is achieved by configuring the methods so
that the ratio of the export CaO to the CaO entering the carbonator
is preferably in the range of about 5:1 to about 0.5:1. The ratio
may be narrowed based upon the further parameters of the method,
and further useful ratio ranges can be about 4:1 to about 1:1 or
about 4:1 to about 2:1 or about 3:1 to about 1:1.
[0038] The method further can comprise processing a portion of the
solids stream exiting the separator in a clinker unit. For example,
the method can comprise adding one or more raw materials effective
for cement production into the clinker unit such that solids from
the solids stream react with the one or more raw materials
effective for cement production to form cement clinker. This can be
particularly useful when the solids stream includes quicklime, and
the added raw materials in the clinker unit can include sand, coal
ash, or other materials suitable for cement production. As such,
the clinker unit can be a clinker unit from a conventional cement
production plant, and the clinker unit may be operated under
substantially similar conditions as would be used in a conventional
cement production process.
[0039] The method further can comprise passing the cement clinker
through a clinker cooler unit so as to cool the cement clinker.
Such cooling can be carried out using a cooled portion of the gas
stream including the carbon dioxide. This stream can be taken, for
example, from a compressor unit or another point that is preferably
downstream from any water separation.
[0040] The method further can comprise integrating the method for
calcination with carbon capture into a steel-making process. In
particular, the reactor may be configured to receive one or more
streams from the steelmaking plant, such as a fuel gas stream
(e.g., a coke oven gas stream, a blast furnace gas stream, and/or a
basic oxygen furnace gas stream). Likewise, the method may be
configured such that solids from the reactor (or the separator) may
be delivered to one or more components in the steelmaking process
(e.g., a blast furnace and/or a basic oxygen furnace). Further, an
oxygen source may be shared between one or more components of the
steelmaking process and the reactor in the present methods.
[0041] The method further can comprise injecting coal ash into the
reactor and/or a separate reburner. Likewise, the method can
comprise recovering thermally treated coal ash from the reactor
and/or reburner. At least a portion of the thermally treated can be
mixed with quicklime. Such treated ash may then be delivered for
formation of other products, such as cement, concrete, fly ash
bricks, aggregates, and the like. Similarly, the method can be
configured to deliver a portion of the produced solids (e.g.,
quicklime) for mixing with high moisture ash to reduce the moisture
level thereof and provide ash that is suitable for downstream uses,
such as noted above. Likewise, a portion of the solids can be
exported and optionally mixed with ash.
[0042] The heated reactor can be heated in particular with a fuel
that comprises sour gas (i.e., natural gas or another gas stream
that includes a sulfur species, such as H.sub.2S, and optionally
also carbon dioxide). The sour gas can mix with limestone in the
reactor to form gypsum, which can be removed with the solids
stream. As such, the sulfur species in the sour gas can be
effectively removed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0043] FIG. 1A and FIG. 1B provide an illustration of components of
systems according to example embodiments of the present disclosure
useful in the capture of carbon dioxide with simultaneous
production of one or more industrially useful products;
[0044] FIG. 2 is a flowchart illustrating a process according to an
example embodiment of the present disclosure whereby limestone can
be processed to make quicklime with power production and carbon
dioxide capture;
[0045] FIG. 3 is a flowchart illustrating a process according to an
example embodiment of the present disclosure whereby limestone can
be processed to make quicklime with power production and carbon
dioxide capture while simultaneously processing an industrial flue
gas for carbonation of a portion of the quicklime;
[0046] FIG. 4 is a flowchart illustrating a process according to an
example embodiment of the present disclosure whereby limestone can
be processed to make quicklime with power production and carbon
dioxide capture while simultaneously forming cement;
[0047] FIG. 5 is a flowchart illustrating a process according to an
example embodiment of the present disclosure whereby limestone can
be processed to make quicklime with power production, carbon
dioxide capture, and mineral sequestration of at least a portion of
the carbon dioxide; and
[0048] FIG. 6 is a flowchart illustrating a process according to an
example embodiment of the present disclosure whereby limestone can
be processed to make quicklime with power production and carbon
dioxide capture while simultaneously forming steel.
[0049] FIG. 7 is a flowchart illustrating a process according to an
example embodiment of the present disclosure whereby carbon capture
and coal combustion residuals (CCR) recycling may be carried
out.
DETAILED DESCRIPTION OF THE DISCLOSURE
[0050] The present subject matter will now be described more fully
hereinafter with reference to exemplary embodiments thereof. These
exemplary embodiments are described so that this disclosure will be
thorough and complete, and will fully convey the scope of the
subject matter to those skilled in the art. Indeed, the subject
matter can be embodied in many different forms and should not be
construed as limited to the embodiments set forth herein; rather,
these embodiments are provided so that this disclosure will satisfy
applicable legal requirements. As used in the specification, and in
the appended claims, the singular forms "a", "an", "the", include
plural referents unless the context clearly dictates otherwise.
[0051] The present disclosure relates to systems and methods for
direct capture of at least one moiety (e.g., CO.sub.2) from a
provided stream. In particular, the systems and methods can be
related to one or more industrial processes.
[0052] Limestone calcination is responsible for a portion
(presently in excess of 7%) of the world's total greenhouse gas
(GHG) emissions. The fuel consumed in converting calcium carbonate
(limestone) into calcium oxide (quicklime) accounts for
approximately 30%, and the off gas (i.e., carbon dioxide) that is
liberated during calcination accounts for approximately 70% of this
allocation. Nonetheless, calcination is a vital activity for
industrialization seeing that it is a core process in cement
manufacturing and generates a critical feedstock for a wide variety
of industries. For example, lime is a critical commodity in the
following markets: iron and steel (e.g., removing impurities and
enhancing productivity); construction (e.g., making lightweight and
highly insulating construction materials as well as aggregates,
fillers, and bonding agents); civil engineering (e.g., improving
stability and load bearing capacity of soil and improving asphalt
durability); environmental protection (e.g., drinking water
treatment to remove heavy metals, wastewater treatment to remove
impurities, and flue gas purification); agriculture (e.g.,
nutrients for fertilizer, animal nutrition, and animal hygiene for
preventing diseases); chemical industry (e.g., feedstock for
forming calcium carbide and filler for paint, pharmaceuticals, and
polyvinylchloride products); other industrial uses (e.g., removing
impurities from sugar as well as glass and paper production); and
export.
[0053] In one or more embodiments, the present disclosure relates
to systems and methods whereby carbon dioxide (or other moieties)
may be directly captured from an industrial process or from any
process including calcination of a carbonate containing material,
such as calcium carbonate (e.g., limestone). Systems suitable for
carrying out the integration of carbon dioxide capture with one or
more further processes may incorporate a variety of components that
may be combined in any number to achieve the desired system
configuration. Individual components or units useful for forming
example embodiments of the systems are described in detail below,
and it is understood that a person of skill reading the present
disclosure will be able to recognize the useful and varied
combinations that are encompassed herein in addition to any express
embodiments that are further described below.
Reactor
[0054] In one or more embodiments, the present systems and method
may incorporate the use of at least one reactor wherein a raw
material may be heated in the presence of oxygen, and carbon
dioxide (or another moiety) may be formed. Depending upon the
specific mode of operation and the raw material that is utilized,
the reactor may be more particularly referred to as a kiln or a
calciner. In example embodiments, a reactor may be configured as a
calciner for receiving a mineral component (e.g., limestone) and
driving off carbon dioxide. Any of a number of configurations may
be utilized in relation to the reactor. For example, the reactor
may be configured as a vertical kiln, a horizontal kiln, an
indirectly heated kiln, or in any other suitable configuration. The
reactor may be a stand-alone component or may be a segment or
section of a reactor unit. In some embodiments, a reactor may be
operated at a relatively low pressure but above ambient. For
example, the operational pressure may be up to about 10 bar, up to
about 8 bar, up to about 5 bar, or up to about 4 bar, such as in
the range of about 1.5 bar to about 8 bar, about 2 bar to about 5
bar, or about 2 bar to about 3 bar. In particular, the operational
pressure of a reactor may be any desired value that can reasonably
be achieved with a conventional air blower design. The reactor
preferably is oxygen enriched in that an oxygen source is provided
to the reactor to ensure that desired chemical reactions proceed in
the reactor environment. In some embodiments, the reactor can be
operated as a pressure that is around 1 bar (e.g., +/-10%).
[0055] Pressurization of the reactor can be achieved by an
incoming, blown oxidant and/or a gaseous, or vaporized, fuel source
to be combusted or oxidized for heat production. The combusted or
oxidized fuel source can provide beneficial heating to other
components of the system, such as a calcination reactor. The fuel
source may be any suitable material. In some embodiments, as noted
above, a gaseous fuel may be utilized, and non-limiting examples
include natural gas, synthesis gas, sour gas, BOS gas, digester
gas, fuel oil, or the like. In some embodiments, a solid fuel may
be used (e.g., particularized coal, biomass, lignite, or the like)
and, in such embodiments, the oxidant may be the sole source of
pressurization for the reactor. In such embodiments, it may be
useful to operate the blower with increased discharge head to
compensate for the lack of fuel contribution and create the desired
internal reactor pressure. If desired, a liquid fuel may also be
utilized. Fuel composition may vary as desired, and a mixture of
fuel types may be used. In some embodiments as further described
herein, it can be useful for the fuel to include at least a minimum
carbon content. For example, the fuel entering the reactor may be
at least 2%, at least 5%, at least 10%, or at least 15% molar
carbon based on the total fuel content passing into the reactor
(with a maximum carbon content being understood to be inherently
limited by the chemical composition of the fuel).
[0056] Like the fuel, a variable chemistry may also be utilized in
relation to the oxidant source. In some embodiments, substantially
pure oxygen may be used (e.g., greater than 95%, greater than 98%,
or greater than 99% molar oxygen); however, such purity levels are
not required. In some embodiments, the oxidant may comprise a flue
gas from an industrial process that may be operated in combination
with or separately from the present system. Preferably, the oxidant
stream entering the reactor is adapted to or configured to have a
sufficient oxygen content to provide for substantially complete
combustion of the input fuel (e.g., combustion of at least 95%, at
least 98%, or at least 99% molar). Otherwise, air or oxygen from an
air separation unit (ASU) or vacuum pressure swing absorption
(VPSA) unit can be mixed with the flue gas to supplement this
requirement or used as an unaltered input. The table below provides
example embodiments of performance permutations for various oxidant
sources. The cases include configurations where air, flue gas from
a supercritical coal power plant, flue gas from a combined cycle
power plant, and direct gas turbine exhaust gas serve as the
oxidant sources. It should be noted that the oxidant source does
not need to be free of acid gas compounds or particulates. As
described herein, the acid gases and particulates can effectively
be scrubbed out by the mineral product, solids separation, and/or
water separation. This can be a large financial benefit for
co-locating with a facility, such as a coal fired power plant.
TABLE-US-00001 OXIDANT SOURCE GT FLUE CCGT FLUE SCPC FLUE VARIABLE
GAS GAS GAS AIR fuel input 177 107 115 82 (MW LHV) CO.sub.2 capture
load 10.52 16.78 18.75 8.25 (MW) CO.sub.2 export load 6.33 5.33
6.45 3.96 (MW) net power produced -31.5 -0.45 -0.23 0.2 (MW) lime
produced 684,265 491,186 491,186 491,186 (tonne/yr) CO.sub.2
produced 675,850 569,205 687,618 421,699 (tonne/yr)
[0057] The reactor may be fired at a temperature that preferably is
suitable for carbonate mineral decomposition. For example, firing
temperature may be about 850.degree. C. or greater, about
900.degree. C. or greater, about 950.degree. C. or greater, or
about 1000.degree. C. or greater (e.g., up to the practical limits
of the equipment utilized), such as in a range of about 850.degree.
C. to about 1100.degree. C., about 900.degree. C. to about
1100.degree. C., or about 950.degree. C. to about 1100.degree.
C.
[0058] The reactor may be operated sequentially with a solids
separation component which may be integral with the reactor (e.g.,
positioned at an outlet of the reactor) or may be a component of a
reactor unit, or may be a stand-alone component of the overall
system. Any suitable separation equipment may be utilized, such as
a cyclone separator, a candle filter, and/or any other combination
of these technologies and others. The performance of the solids
separator should be sufficient that the exiting gas is appropriate
for use with a heat recovery device. In some embodiments, exiting
gas may undergo further cleansing such that it can be directly fed
to the inlet of a high speed turbomachinery.
[0059] In some embodiments, the reactor and any optional,
associated components may be adapted to or configured to provide a
gas exit stream (i.e., a flue gas) that is substantially free of
any solid particles (e.g., no more than 0.01% by weight of
particulates based on the overall mass of the exiting gaseous
stream) or that is completely free of any solid particles.
Moreover, such exiting gas stream may be configured to be at a
specified temperature, such as no greater than about 700.degree. C.
Such temperature limitation for the exiting gas stream may be
advantageous to allow for downstream heat recuperation via
commercially available equipment that preferably can utilize
non-nickel based alloys. In order to achieve the limitation of
about 700.degree. C. in coordination with a reactor temperature in
a higher range as noted above, it can be useful to exchange a
portion of the heat with one or more further streams, which may
include one or more of the reactor input streams. For example, in a
vertical kiln, a carbonate mineral feedstock can be provided
counter currently to the combustion flue gas stream exiting the
kiln. The rate of mineral introduction into the kiln can be
controlled in such a manner that the temperature of the
carbonate-containing stream entering the kiln can be heated from
ambient to a defined value that can substantially correspond to a
temperature approaching the temperature of the gaseous stream
exiting the kiln, such as in the range of approximately 650.degree.
C. to near 700.degree. C. A comparable mode of operation may also
be implemented in a bottom portion of the kiln in relation to an
incoming oxidant and/or fuel stream. In particular, incoming
oxidant and/or fuel may be heated up against the exiting
decarbonized product. This will have the added effect of improving
fuel efficiency.
[0060] The scale of the reactor can be sized in some embodiments
such that it is compatible for use primarily as part of a power
generation system. For example, a gas turbine can directly
introduce its exhaust into the reactor to provide heat. The burner
in the reactor may operate at a level that is just sufficient to
create enough mineral product for scrubbing of the gas turbine
exhaust gas impurities. Otherwise, burning more fuel may
effectively function as "duct" firing for downstream power
generation at a steam turbine. Scaling the reactor accordingly can
be of substantially no effect on downstream system components, such
as those described below in relation to dewatering through CO.sub.2
export. This effectively may be a combined cycle with integrated
carbon capture, particulate removal in the form of cyclone
filtration and venturi scrubbing instead of electrostatic
precipitation or bag filters, and NOx removal in the form of dry
scrubbing instead of SCR. Should the gas turbine be removed and
coal used as the fuel source, the present system may effectively
function as a coal power station with all of the above advantages
but also flue gas desulfurization (FGD) via the reactor.
[0061] In some embodiments, a carbonator can be attached to the
reactor to increase the flue gas CO.sub.2 capture rate. Calcium
oxide ("quicklime" or CaO) produced from the reactor can be at a
temperature of about 900.degree. C. to about 1,000.degree. C. A
portion of the CaO exiting the reactor may be cooled to reduce the
temperature to a lower range, such as about 600.degree. C., then it
can be fed to a carbonator to remove CO.sub.2 from industrial flue
gas via a carbonation reaction (CaO+CO.sub.2=CaCO.sub.3). The
operating temperature of the carbonator thus can be in a range of
about 600.degree. C. to about 650.degree. C. The CaCO.sub.3 exiting
the carbonator can be recycled back to the reactor for calcination.
The CaO that is not cooled and fed to the carbonator can be
exported. The ratio of the export CaO to the CaO entering the
carbonator is preferably in the range of about 5:1 to about 0.5:1,
such as about 4:1 to about 1:1 or about 4:1 to about 2:1 or about
3:1 to about 1:1. Utilizing such ratio can be critical to ensure
that the calcium looking does not result in deactivation of the
calcium oxide for carbon dioxide capture. The industrial flue gas
can be preheated to a temperature in the range of about 400.degree.
C. to about 500.degree. C. against a hot stream in the system
before entering the carbonator, and this can be useful to maintain
a preferred operating temperature of the carbonator. The CO.sub.2
lean flue gas from the carbonator can be cooled to close to the
ambient temperature before being vented. The recuperated heat can
be used to steam power generation.
[0062] In some embodiment, equipment for existing plants may be
utilized instead of requiring the provision of a new reactor. For
example, the kiln in a cement plant or a quicklime plant can be
retrofitted for operation according to the present disclosure in
order to capture CO.sub.2 from the cement and/or quicklime
plant.
[0063] In some embodiment, high carbon/moisture content coal ash
can be co-injected into the reactor to reduce the carbon/moisture
content. Carbon in the coal ash can provide heating value to the
fuel consumption for the reactor operation. The thermal treated
coal ash blended with CaO can be used for making cement, concrete,
and other building materials. In some embodiment, the coal ash
re-burner can be a standalone unit placed at the exit of the
reactor. The reactor flue gas, fuel, and oxidant can be injected
into the coal ash re-burner to burn off the carbon in the coal ash.
The thermal treated coal ash can be exported without being blended
with CaO.
Heat Recuperator
[0064] In one or more embodiments, systems as described herein can
incorporate one or more heat recuperator components and/or heat
recuperator units. For example, a single heat recuperator (e.g., a
recuperative heat exchanger, a heat recovery steam generator
(HRSG), a gas heated reformer (GHR), or the like) may be utilized
independently. Alternatively, or additionally, a plurality of heat
recuperators (e.g., a plurality of any of the aforementioned
example embodiments and the like and/or a combination of different
types of the aforementioned heat recuperators) may be utilized.
Accordingly, the substantially or completely solids-free gas stream
(or flue gas) exiting the reactor or reactor unit can be subjected
to at least one heat recuperation step. As such, the heat
recuperator(s) may be adapted to or configured to transfer as much
of the remaining heat as possible to a heat transfer working fluid
and/or provide the thermal input for an additional chemical
process. In some example embodiments, a HRSG may be used in
conjunction with the flue gas to power a three pressure reheat
steam turbine arrangement for power generation. Alternatively, or
additionally, the flue gas may be used to heat a GHR for H.sub.2
generation from natural gas. In this last scenario, it may be
necessary to integrate a duct burner into the flue gas stream to
facilitate the production of temperatures in excess of 700.degree.
C. Ideally, heat for a GHR may be in the range of approximately
1,000.degree. C. The heat recuperator(s) preferably can be adapted
to or configured to transfer a sufficient quantity of heat to meet
the noted uses (or other uses) while providing the gas stream at a
significantly reduced temperature. In some embodiments, it can be
useful for the gas stream exiting the heat recuperator(s) to be at
a temperature that is substantially close to ambient. For example,
the temperature of the stream exiting the heat recuperator(s) or
heat recuperator unit may be in a range of about 20.degree. C. to
about 150.degree. C., about 20.degree. C. to about 100.degree. C.,
or about 30.degree. C. to about 80.degree. C.
Drier/Water Separator
[0065] In one or more embodiments, systems as described herein can
incorporate one or more driers or drying unit which may incorporate
components adapted to or configured to remove water or moisture in
general from the gas stream. In some embodiments, drying/water
separation can be carried out utilizing a single unit adapted to or
configured to perform a plurality of drying steps or may be carried
out utilizing a plurality of individual drying components adapted
to or configured to perform different types of drying actions. A
first drying component can be any element adapted to or configured
to remove any remaining heat in the stream in excess of about
ambient temperature. This can include providing for sensible heat
rejection to bring the flue gas to about ambient temperature (e.g.,
+/-10.degree. C. or +/-5.degree. C.). In an example embodiment, a
wet venturi scrubber may be used as the first drying component. In
addition to providing cooling, a venturi scrubber can be useful to
assist in dissolving acid gas chemistry into a liquid phase and
removing any fine solids still entrained in the flue gas. A
suitable cooling medium for such scrubber can include condensed
process water that may be temperature controlled via a dry cooling
tower arrangement.
[0066] A second drying component can include one or more
desiccation components. Such may provide for a desiccation phase
where water vapor can be removed such that the dew point of any
remaining water near or below the liquefaction temperature for
carbon dioxide, such as in the range of about -40.degree. C. or
below, about -50.degree. C. or below, or about -55.degree. C. or
below. In an example embodiment, a suitable desiccation component
may include a bed of activated alumina or similar desiccant. A
desiccant unit may particularly be used in the CO.sub.2
purification unit as further described below. As such, water
separation may take place in multiple steps that can be separated
by other components/steps of the system and method.
Pressurization
[0067] In one or more embodiments, systems as described herein can
incorporate one or more pressurization components or a
pressurization unit. These may include any type of compression
device or compression unit (e.g., a single stage compressor or a
multi-stage compressor that may or may not be intercooled between
one or more of the compression stages, including, if desired, after
the final compression stage) and/or a pump. Any pressurization
component may be preferably adapted to or configured to provide a
discharge pressure that can be in the range of about 3 bar to about
15 bar, about 4 bar to about 12 bar, or about 5 bar to about 10
bar. The pressurization component(s) or pressurization unit may
include a post-compression heat exchanger that can be adapted to or
configured to remove at least a portion of any remaining heat of
compression such that the flue gas may be cooled once again to near
ambient temperature. Pressurization may be optional; however,
pressurization can be particularly useful for facilitating CO.sub.2
removal as pressurization can be beneficial upstream of any
membrane separation stage and can also allow for refrigeration
through downstream expansion of the compressed stream.
Acid Gas Separator
[0068] In one or more embodiments, systems as described herein can
incorporate one or more acid gas separation components. For
example, in some embodiments, a CO.sub.2 separation membrane
component or unit may be utilized. In further embodiments, a water
scrubber can be provided upstream from the membrane separation
component or unit. Since the flue gas leaving the pressurization
component(s) or unit preferably can be in a pressure range as noted
above, any residual SOx and NOx in the flue gas will be oxidized to
terminal acid species via the oxygen in the flue gas. The acid gas
separator, such as a separation membrane, can be adapted to or
configured to provide at least 50% bulk recovery of the input
CO.sub.2 as part of the permeate product with a CO.sub.2
concentration no lower than 50%.
[0069] As mentioned above, the fuel input to the reactor can either
be gaseous, solid, or liquid. The chemistry of the fuel can be vary
as desired since a bulk of the CO.sub.2 generated in the system can
be derived from the carbonate mineral that is input into the
reactor along with the fuel and oxidant. In order for any CO.sub.2
membrane used herein to be of reasonable scale, performance, and
cost, it can be desirable in some embodiments for the system to be
adapted or configured to provide for a flue gas CO.sub.2
concentration (i.e., immediately downstream from the reactor) to be
such that the flue gas has a CO.sub.2 concentration or about 30% or
greater by weight, about 35% or greater by weight, or about 40% or
greater by weight. In some embodiments, CO.sub.2 concentration in
the flue gas exiting the kiln can be about 30% to about 90%, about
35% to about 75%, or about 40% to about 60% by weight based on the
total weight of the flue gas stream. As this value goes down, the
inlet pressure to the membrane separator used in the acid gas
removal component or unit must increase, and the permeate purity
begins to degrade. Therefore, while the fuel chemistry can vary, in
some embodiments, it can be beneficial for the fuel to include at
least a minimum carbon content as already noted above. If the
carbon content is below the desired range, nitrogen and sulfur
contaminants can be of minimal to moderate economic concern but not
technical concern. NOx and SOx species that are formed will bond to
the partially oxidized mineral product. For example, in embodiments
where quicklime (CaO) is formed from limestone in the reactor, NOx
and SOx will combine with the CaO to create calcium sulfate
(gypsum) and calcium nitrate (Norwegian saltpeter). In fact, the
formation of these compounds may be encouraged by the addition of
steam to the kiln in some embodiments. Furthermore, any NOx or SOx
that does make its way to the high pressure water scrubbing step
will be dissolved as liquid phase acid. The economic impact thus
may only arise in embodiments wherein it is desirable to form and
sale these compounds. In such embodiments, the present systems
therefore can include any components necessary to effect separation
of such materials from the primary product. The ability to provide
for removal of NOx and SOx utilizing such scrubbing technology can
be beneficial to allow for the use of relatively lower quality
fuels such as heating fuel oil (HFO) (e.g., diesel #9, "bunker"
fuel) and high sulfur petcoke.
Carbon Dioxide Purifier
[0070] In one or more embodiments, systems as described herein can
incorporate one or more carbon dioxide purification component or
unit. In example embodiments, the purifier can include a low
temperature purifier, which optionally may include a cryogenic
purifier. The purifier(s) can be beneficial such that the CO.sub.2
product is further refined to a higher concentration via the
off-gassing of N.sub.2 and O.sub.2 content. The final refrigeration
requirement of this step will be determined by the desired CO.sub.2
purity for end use. Nonetheless, the retentate from the membrane
separation can be expanded from a pressure as defined above to near
ambient pressure, such as by utilizing a turbo-expander. The shaft
power generated then may be used to help offset the energy used in
upstream compression. In some embodiments, the carbon dioxide
purifier and the pressurization component(s) may be linked. For
example, the turbo-expander and compressor may be configured as a
"compander" type system, such as is commonly used for industrial
gas production in air separation units. The low-pressure retentate
exiting the turbo-expander can be at a temperature of preferably
about -40.degree. C. or below, about -50.degree. C. or below, or
about -55 .degree. C. or below. This gas may be used, for example,
as supplemental refrigeration for the cryogenic purification.
[0071] The carbon dioxide purifier can be adapted to or configured
to provide a CO.sub.2 product in a condition such that the stream
is about 90% or greater, about 95% or greater, about 98% or
greater, or about 99% or greater CO.sub.2 based on the total weight
of the stream. At this value, it may not be necessary for the
cryogenic purifier to use a distillation column. Condensation of
CO.sub.2 into the liquid phase can be sufficient. If a higher
purity is desired (e.g., above a concentration of about 95%) it may
be beneficial to include a column as previously noted. As well, a
distillation column with off gas recycle may also assist in higher
CO.sub.2 recovery rates. As a final matter, regardless of the
CO.sub.2 concentration that is desired, the present systems can
include any suitable equipment such that the liquid carbon dioxide
product may be pumped to a desired pressure and sent to export.
[0072] In one or more embodiments, a low temperature CO.sub.2
purification unit can specifically comprise one or more compressors
(e.g., a compression unit as otherwise described above), one or
more heat exchangers, and one or more separators. In particular,
the CO.sub.2 purification unit can include at least one membrane
separation stage that is effective to provide at least 50% bulk
recovery of the input CO.sub.2 in a CO.sub.2 rich stream with a
CO.sub.2 concentration no lower than 50%. In some embodiments, a
desiccant drier bed can be provided downstream of the compression
steps to provide further drying of the gas stream. The methods of
operation can include passing at least one cold product stream
through at least one heat exchanger to recover its cold energy for
cooling the compressed and dried gas stream. For example, the
supplementary cold energy for cooling the compressed and dried
CO.sub.2 stream can be provided by evaporating a portion of a
liquid CO.sub.2 product stream. In other embodiments, supplementary
cooling can be provided by an external refrigeration loop.
Example Systems and Methods of Operation
[0073] Example embodiments of a system useful according to the
present disclosure, including for carrying out any of the example
embodiments of methods of operation further described herein may be
as substantially shown in FIG. 1A and FIG. 1B. As seen therein,
line 1 can be adapted to or configured to provide a mineral or
other raw material into the reactor 10 (which may particularly be
referenced as a calciner or calcination reactor in the example
embodiment). In example embodiments, the mineral can be limestone,
and line 1 can be adapted to or configured to deliver a feed stream
and/or makeup stream of the limestone (or other mineral depending
upon the particular process employed) to the reactor 10 for
formation of quicklime (CaO). The CaO may exit the reactor 10
through line 11. As least a portion of the CaO in line 11 may exit
the system for export through line 5. In some embodiments, at least
a portion of the CaO in line 11 may be passed through line 12 to
the carbonator 20 for carbonation to re-form calcium carbonate to
be sent back to the calciner in line 1'. During normal operation,
limestone can be brought in as makeup from an external mine/source.
In embodiments wherein the system may be operating with an optional
carbonator 20 in parallel to the reactor 10, calcium carbonate
product from the carbonator may also be feed to the calcination
reactor through line 1'. It should be noted that in both scenarios,
the input of new makeup brought in from an external mine/source may
remain substantially unchanged since the export flow rate of
quicklime leaving the plant/system preferably also is substantially
unchanged. As illustrated in FIG. 1A, the reactor 10 is configured
as a unit including a reactor section 10a and a cyclone solids
separator section 10b.
[0074] As noted above, the carbonator 20 may be optionally present
and thus may be excluded. Accordingly, any lines described as
entering or exiting the carbonator 20 may likewise be optional and
may be excluded. In some embodiments, a carbonator unit 20 may be
expressly utilized in the present systems. As seen in FIG. 1A, line
2 can be adapted to or configured to provide a stream of a sorbent
that can optionally be used to bond to CO.sub.2 content in a mixed
CO.sub.2 gas stream (e.g., a flue gas) that can be provided to the
carbonator through line 4. For example, the sorbent in line 2 may
be a mineral, such as olivine that, in the presence of heat and/or
steam, can bond to the CO.sub.2 and generate a solid exportable
product. In such embodiments, quicklime generated in the reactor 10
may proceed substantially completely through line 5 as a product
for export and will not be partially diverted to the carbonator 20
through line 12. Likewise, product from the carbonator 20 in such
embodiments would not be fed to the reactor 10 through line 1'.
Vent gas from the carbonator 20 may be passed therefrom through
line 3, and the vent gas stream preferably can be substantially
free of CO2. In some embodiments, the carbonator 20 can be operated
at a temperature of about 600.degree. C. to about 650.degree. C.,
and the vent gas in line 3 can undergo heat recovery prior to being
released into the atmosphere by passing the vent gas in line 3
through an optional heat exchanger 25, which may provide heat to
one or more further streams as described herein.
[0075] As otherwise noted herein, a flue gas stream may be utilized
in one or more embodiments of the present disclosure, and such flue
gas may be provided as the mixed CO.sub.2 stream through line 4.
The flue gas may comprise predominately or at least in part carbon
dioxide and may originate from a power plant or some other
emissions source that can be used in a variety of different ways.
In some embodiments, the flue gas in line 4 may be utilized as at
least a portion of the oxidant source for achieving combustion of
the fuel in the calcination kiln 10. This is seen in line 4', which
may supplement or replace the oxidant in line 6. If the flue gas
does not include a sufficient oxygen content, it may be
supplemented with additional O.sub.2 in line 6. The oxidant
provided in line 6 may be any suitable oxygen source as otherwise
described herein, such as substantially pure oxygen and/or air. In
embodiments wherein the carbonator 20 is utilized, the flue gas in
line 4 can still be used as an oxygen source for the calcination
reactor 10 or not at all. If the flue gas is not used in such
manner, then all of the oxygen must come from the oxidant line 6.
Otherwise, all or a portion of the flue gas may be fed to the
carbonator 20 to be scrubbed of CO.sub.2 and then vented. All or a
portion of the flue gas in line 4 may be heated in the heat
exchanger 25 against the vent gas in line 3. A blower 4a and/or a
blower 6a may be utilized for pressurizing the flue gas in line 4
and/or the oxidant in line 6, respectively. One of the blowers may
be optionally present; however, it is understood that at least one
of the blowers is present in the noted line to provide for the
necessary pressurization. Fuel can be passed to the reactor via
line 7 and may include any material as already described
herein.
[0076] Water and steam may be passed through line 9 and line 8,
respectively, in embodiments wherein an HRSG is utilized as the
heat recuperator 30. As illustrated in the embodiment of FIG. 1A,
the feedwater in line 9 can pass through a pump 9a to be circulated
through the heat recuperator 30 where it is heated to form steam,
which may be withdrawn for use in other processes, for power
production, and the like. Optionally, a portion of the steam in
line 8 may be directed through line 8' to the carbonator 20.
[0077] Exhaust gas that has been cooled in the heat recuperator 30
can pass through line 13 for further processing, as shown in FIG.
1B. As illustrated, the exhaust gas in line 13 passes sequentially
through a water separator 40 and a desiccant drier 50 to provide a
substantially dry (e.g., less than 0.5% water) exhaust gas in line
14. The dry exhaust then proceeds to pressurization unit 60 where
it passes through a series of compression states (62, 64, 66) and
associated after-coolers (63, 65, 67) to provide the pressurized
exhaust in line 15. The pressurized gas is processed through a
membrane separator 70 to provide a lean CO.sub.2 stream in line 16
and a rich CO.sub.2 stream in line 17. The rich CO.sub.2 stream can
be processed through a turbo-expander 80 which, as illustrated, can
be linked to the compressor unit 60 through a compander 100, and
the expanded, rich CO.sub.2 stream can then be passed through a low
temperature CO.sub.2 separator 90 along with the lean CO.sub.2
stream in line 16. The low temperature CO.sub.2 separator 90 thus
can provide substantially carbon free air (e.g., less than 0.1%
carbon by weight), carbon lean air, and a carbon dioxide stream,
which can be subjected to carbon capture utilization and
sequestration (CCUS), such as providing for EOR or other uses.
Although the compander 100, membrane 70, and turbo-expander 80 are
shown, it is understood that one or more of these components may be
excluded in some embodiments.
[0078] In FIG. 1B, one or more of the components illustrated
therein may be re-arranged as desired to effect the CO.sub.2
purification that is desired. For example, the desiccant drier 50
may be alternatively positioned downstream of the compression
stages (62, 64, 66). Likewise, one or more of the compression
stages (62, 64, 66), the compander 100, the expander 80, the
membrane separator 70, and the low temperature CO.sub.2 separator
90 may be combined to form a CO.sub.2 purification unit. In other
words, a CO.sub.2 purification unit as utilized herein may include
at least a low temperature CO.sub.2 separator 90 and at least one
membrane separation stage 70. In other embodiments, a CO.sub.2
purification unit as utilized herein may include at least a low
temperature CO.sub.2 separator 90, at least one membrane separation
stage 70, and at least one or more compressors (e.g., 62, 64, 66).
In some embodiments, the CO.sub.2 purification unit include a
desiccant drier (e.g., unit 50), which may be positioned between
one or more compressors and at least one membrane separation stage
70.
Operational Embodiments of the System
[0079] System components as described herein may be combined in a
variety of manners for implementation various operational
embodiments of the present disclosure. Provided below are multiple
example embodiments of methods whereby the system components may be
utilized for carbon capture in combination with production of
other, industrially useful products, and/or power production. In
various embodiments described herein, the systems may be utilized
at least in part for lime production, cement production, steel
making, and similar industrial processes.
[0080] In one or more embodiments, the system may be operated
predominately, substantially, or completely in an oxy-fired
process. In such embodiments, waste heat from the reactor 10 may be
used for power generation to reduce the power consumption of carbon
capture and purification from the calcination process. The
described process can be integrated with post-combustion CO.sub.2
capture from the flue gas from existing power plants and
lime/cement/steel making plants, or integrated with a caustic
liquid scrubbing system for direct air capture by adding a
carbonation reactor in the process. Oxygen rich calcination process
can be either partial oxy-fuel combustion or full oxy-fuel
combustion. Oxygen generation in various embodiments may be from an
air separation unit, a membrane based generation process, pressure
swing absorber (PSA), vacuum pressure swing absorber (VPSA),
bio-reactor, and/or other processes.
[0081] An example embodiment of such operation of the presently
disclosed systems is illustrated in FIG. 2, wherein reactor 200 can
be configured for operation with carbon capture. As seen in FIG. 2,
limestone can be injected in line 201 into a reactor 200 together
with oxygen in line 241 from a VPSA unit 240, fuel in line 242, and
recycled CO.sub.2 gas in line 236 for calcination reaction. All the
input gas and solid streams can be preheated by the flue gas and
hot solids (CaO) from the reactor 200 in the heat exchanger network
210 before being injected into the reactor to improve the heat
utilization. Solid product, which can be, for example, quicklime
(CaO), can be separated from flue gas in a solid gas separator 205
(e.g., a cyclone separator). The CaO in line 207 and the flue gas
in line 206 pass through the heat exchanger 210 such that cooled
flue gas exits in line 211 and CaO for export exits in line 212.
The reactor 200 in such embodiments preferably may be operated at a
temperature of about 900.degree. C. to about 1000.degree. C. and a
pressure that is above ambient pressure. The heat exchanger network
can be, for example, at least one gas-to-gas heat exchanger and
gas-to-solid exchanger. Reactor 200 inlet streams can be preheated
in the heat exchanger network 210. Additional waste heat from
reactor exhaust streams can be used to drive a closed loop power
cycle to produce CO.sub.2 free electricity to reduce or fully cover
the calciner plant power consumption. Steam, supercritical
CO.sub.2, and/or other working fluid can be used for the power
cycle. The waste heat being used for preheating calciner inlets and
the waste heat used for driving the closed loop power cycle can be
adjusted to obtain a lowest operational cost (fuel cost vs.
electricity cost). Another option is using most of the waste heat
for power generation to produce excess power as by-product. As
illustrated in FIG. 2, a compressed working stream in line 256 is
passed through the heat exchanger 210 and exits as heated stream
213, which is expanded in turbine 245. The expanded stream in line
246 is cooled in cooler 250 and exits in line 251 to be compressed
again in a compressor and/or pump unit 255 to regenerate the
working fluid for re-heating in the heat exchanger.
[0082] Low temperature quicklime in line 212 exiting the heat
exchanger network can be exported directly for sale, or mixed with
water to produce hydrated lime, or sent for clinker formation at a
cement plant. Flue gas in line 211 exiting the heat exchanger
network typically can be near ambient temperature with liquid water
removed from the gas in separator 215 (water exiting in line 217)
before compression. The dry gas in line 216 can be compressed in
the compressor unit 220 to a relatively high pressure (e.g., about
10 bar or greater) and sent in line 221 to a water scrubber 225. In
the water scrubber 225, NO and residual SO.sub.2 generated from the
calciner can be quickly oxidized by the excess oxygen in the flue
gas into NO.sub.2 and SO.sub.3 under high pressure environment,
then react with water to form H.sub.2SO.sub.4 and HNO.sub.3 being
dissolved in the liquid water and removed in line 227 from the
CO.sub.2 stream, which exits in line 226. Water can be input to the
separator 225 through line 224. Some strong oxidants, such as
H.sub.2O.sub.2 and O.sub.3, can be optionally injected into the
water scrubber to facilitate SO.sub.2/NO oxidation. Cleaned
CO.sub.2 stream in line 226 from the water scrubber can be sent to
a cryogenic type CO.sub.2 purification unit 230 to generate over
99% purity CO.sub.2 in line 232 for use in, for example, EOR and
other industrial chemical processes. A portion of clean CO.sub.2
can be recycled back to the reactor through line 233 for combustion
temperature control. The clean CO.sub.2 in line 233 can be
compressed in blower 235 before passing in line 236 to the reactor
200. Gas that is substantially free of CO.sub.2 may be vented from
the CO.sub.2 purification unit 230 in line 231.
[0083] In another example embodiment, as illustrated in FIG. 3,
oxy-calcination can be integrated with post-combustion carbon
capture. In such embodiments, the reactor system 200 can be
operated with an adjacent carbonation reactor 260. Heat from the
outlet of the reactor 200 may be used to operate a carbonation
reactor 260 that, for example, scrubs CO.sub.2 from a flue gas.
Given that carbonation is typically an exothermic reaction, the
heat of the reactor may be recovered and reintegrated into the core
reactor operation. This method of moving heat back and forth can
beneficially provide for exploitation of the heat of formation but
at an elevated temperature.
[0084] As seen in the example embodiment of FIG. 3, oxy-fired
calcination process can be integrated with a post combustion
industrial carbon capture process (CaO+CO.sub.2=CaCO.sub.3). At the
exit of the separator 205, CaO at about 900.degree. C. in line 207
can be split into two streams. One CaO stream in line 207a can be
sent to the heat exchanger network for waste heat recuperation
before export. The other CaO stream in line 207b can be sent to a
carbonator to capture CO.sub.2 from industrial flue gas provided
through line 203 in a carbonator operated at about 650.degree. C.
The industrial flue gas can be taken from an existing power plant,
lime production plant, cement plant, steel plant and/or other
industrial process. At the exit of the carbonator 260, CaCO.sub.3
can be separated (in line 261) from flue gas (in line 262) and
directly sent back to the calciner reactor 200 for CaO
regeneration. CO.sub.2 lean flue gas from the carbonator 260 in
line 262 at around 650.degree. C. can be cooled in a heat exchanger
265 down to near ambient temperature before venting in line 266.
The high grade heat (see element 267 in FIG. 3) can be used for
preheating the inlet streams of the calciner reactor 200 or
carbonator 260 or for power generation. The remaining components in
FIG. 3 may be configured for operation substantially as described
in relation to FIG. 2.
[0085] Although calcium looping technology for carbon capture has
been previously described, it is well known for suffering from an
inherent failure in relation to quicklime sorbent deactivation. In
particular, the active fraction of the quicklime sorbent is known
to reduce significantly based on the number of cycles through the
calcium looping process. Whereas sorbent activity may begin in the
range of about 0.7 to about 0.8, this quickly decreases to under
0.4 in as few as five cycles, to under 0.2 in between 10 and 15
cycles, and begins approaching only 0.1 in approximately 25 to 30
cycles. This issue is resolved according to the presently disclosed
systems and methods by integrating calcium looping carbon capture
with the proposed lime production process. This solution is
achieved because the CaO makeup rate for calcium looping is
increased significantly. In addition, a significant portion of the
combustion heat used for endothermic calcination reaction is
released in the carbonator (i.e., via the exothermic carbonation
reaction) at about 650.degree. C. and recuperated in the heat
exchanger for inlet stream preheating or power generation. Thusly,
the overall cycle efficiency is improved significantly.
[0086] In a further example embodiment, as illustrated in FIG. 4,
calcination for cement production can be provided with carbon
capture through reactor operation with clinker integration. As seen
in FIG. 4, calcination for cement production can be carried out
wherein CaO in line 207 is sent to a clinker unit 270 together with
fuel in line 243, oxidant in line 241b (with oxidant passing to the
reactor 200 through line 241a), and clinker additives in line 271
(e.g., sand, coal ash, etc.). The operating temperature of the
clinker unit 270 can be in the range of about 1200.degree. C. to
about 1500.degree. C. or about 1300.degree. C. to about
1400.degree. C. A solids stream comprising cement clinker can exit
the clinker unit 270 through line 272 and can be cooled in the
clinker cooler unit 275 before exiting as cooled cement clinker in
line 276. A flue gas exiting the clinker unit 270 in line 273 can
be sent back to the reactor 200 for use as the oxidant stream. As
such, oxygen from the VPSA 240 (or a different oxygen source) can
be blended with the flue gas in line 273. Accordingly, line 273 and
line 241 may combine prior to entry into the reactor 200. The
clinker unit 270 can be cooled by partially compressed, recycled
CO.sub.2 in line 222 from the compressor 220 in a clinker cooler
unit 275. The warm CO.sub.2 gas in line 277 from the clinker cooler
unit 275 can be sent back to the primary heat exchanger network 210
for heat recuperation, then it may be mixed with the calciner flue
gas and enter the water separator 215 through line 211.
Alternatively, the clinker 270 can be operated in air-combustion
mode, and the CO.sub.2 from the clinker flue gas can be captured in
a carbonator as otherwise described in previous example
embodiments. The remaining components in FIG. 4 may be configured
for operation substantially as described in relation to FIG. 2
and/or FIG. 3.
[0087] In a further example embodiment, as illustrated in FIG. 5,
kiln operation can be carried out with carbon capture and mineral
sequestration. In this example embodiment, an oxygen-enriched
calcination process is integrated with a CO.sub.2 mineral
sequestration
(Mg.sub.3Si.sub.2O.sub.5(OH).sub.4+3CO.sub.2=3MgCO.sub.3+2SiO.sub.2+2H.su-
b.2O). Limestone is passed to the reactor 200 in line 201 along
with oxygen in line 241 from an ASU 340, air in line 341, and fuel
in line 242. The reaction exhaust in line 202 is passed through the
separator 205. Separated CaO in line 207 can be sent to a heat
exchanger 210 for heat recuperation before being exported in line
212. The flue gas in line 206 from the separator 205 at a
temperature of about 900.degree. C. can be sent to a carbonator 260
along with an industrial flue gas in line 203 reacting with
magnesium silicate from line 264 for CO.sub.2 mineral
sequestration. CO.sub.2 lean flue gas in line 263 from the
carbonator at around 650.degree. C. can be cooled in the heat
exchanger 210 down to near ambient temperature before passing
through the water separator 215. Water can exit in line 217 with
the dry flue gas venting in line 216. The high grade heat can be
used for preheating the inlet streams of the calciner reactor 200
and/or the carbonator 260, or for power generation and eventual
CO.sub.2 cleanup of residual content that still may exist in the
flue gas.
[0088] In another example embodiment, as seen in FIG. 6, the
present systems and methods may be integrated with one or more
steelmaking operations. Accordingly, a system as described herein
may be integrated into a steelmaking plant and/or a method as
described herein may be integrated into a steelmaking process. As
shown, steel making processes can generate a plurality of different
flue gas streams which can often be rich in carbon dioxide content.
Like with power plant flue gas streams, various steel making flue
gases may have an oxygen content and thus may be provided to the
reactor of the present disclosure for use as an oxidant.
Additionally, some steel making flue gases may contain fuel content
and thus may be added to the present reactor as an optional fuel
source. Off gas streams, such as those coming from a basic oxygen
furnace, may be used to supplement the fuel injection of the
reactor.
[0089] As shown in FIG. 6, calcium carbonate (limestone) may be
milled through a raw mill and optionally filtered to a
substantially uniform particle size before being injected to a
calciner reactor as described herein. Further inputs to the
calciner reactor may include a fuel in a fuel line, oxidant (e.g.,
oxygen from an oxygen plant or other oxygen source), and one or
more gas streams. For example, coke oven gas may be passed through
a line from a coke oven that is configured to burn coal to form
coke to be input to a blast furnace and, likewise, blast furnace
gas may be passed through a line from a blast furnace to the
calciner reactor. Similarly, basic oxygen furnace gas from a basic
oxygen furnace may be passed through a line to the calciner
reactor. Exiting the calciner reactor can be one or more of a
CO.sub.2 rich flue gas in a gas line and solids (e.g., calcium
oxide) that can be provided through one or more solids line(s). For
example, quicklime may be provided for export. Alternatively, or
additionally, quicklime may be provided to one or both of the blast
furnace and the basic oxygen furnace. The gas line may proceed to a
steam cycle or another power cycle that can be utilized for power
production (e.g., electricity). Gas exiting the power cycle can be
processed through one or more further units as described herein
(e.g., a separation membrane or a cryogenic separation unit) to
provide substantially pure carbon dioxide for CCUS and optionally
to provide one or more further gases, such as nitrogen, oxygen, and
argon. The present systems and methods particularly are integrated
directly with the steelmaking system/method in relation the mutual
use of various streams as noted above. In the steelmaking process,
iron ore can be input to a sintering plant to provide iron pellets
that can be processed through a blast furnace to form pig iron. The
pig iron can be processed through a basic oxygen furnace to provide
molten steel, which can then be processed through a caster &
roller unit to provide the steel product(s). In such integrated
systems/processes, one or more units from the steelmaking system
can provide one or more streams that can be input to the present
reactor. Likewise, the present reactor can output one or more
streams that can be used as one or more inputs into one or more
units of the steelmaking system. In this manner, carbon dioxide can
be captured without penalty.
[0090] It is understood that any of the components illustrated in
relation to FIGS. 1A through 5 may be included in the systems and
methods illustrated in relation to FIG. 6. For example, although a
calciner is shown in FIG. 6, it is understood that the calciner
indicates that a reactor as described herein may be utilized, and
this may include a plurality of reactors. Further, since both a
flue gas and solids streams are illustrated exiting the calciner,
it is understood that the illustrated calciner indicates that at
least one separation component is integrated therewith for
separation of the gases from the solids. Likewise, it is understood
that the reactor(s) and the separator(s) may be an integrated unit
or may be separate units. Additionally, it is understood that the
"steam cycle" illustrated in FIG. 6 is indicative of a plurality of
components that are utilized for producing electricity. Referring
to FIG. 1A and FIG. 1B, the steam cycle of FIG. 6 may include an
HRSG 30 that can be used to heat a water stream 9 and produce a
steam stream 8 that can be cycled through suitable turbines for
production of electricity utilizing suitable generators. Referring
to FIG. 2, the steam cycle of FIG. 6 may include a heat exchanger
210, a turbine 245 (and any necessary generators), a cooler 250, a
compressor/pump unit 255, and lines 256 and 213 for circulation of
a working fluid. It is likewise understood that, in such
embodiments, the working fluid need not necessarily be water/steam,
and the phrase "steam cycle" can simply indicate power generation
through circulation of a working fluid.
[0091] In a further example embodiment, reactor operation may be
carried out with integration of an alkali solvent-based direct air
capture system. Such systems and methods can use, for example, KOH,
NaOH, or other alkali liquid based solvents to capture CO.sub.2 (or
other moieties) from gaseous mixtures, such as air and/or the flue
gas from an air combustion process. In one or more embodiments,
such capture can arise through the following reaction:
2 .times. KOH + CO 2 = H 2 .times. O + K 2 .times. CO 3 . ( 1 )
##EQU00001##
KOH can be regenerated through a calcium looping process or cycle
as shown below.
K 2 .times. CO 3 + C .times. a .function. ( O .times. H ) 2 = 2
.times. KOH + CaCO 3 ( 2 ) CaCO 3 = CaO + CO 2 ( 3 ) CaO + H 2
.times. O = C .times. a .function. ( O .times. H ) 2 ( 4 )
##EQU00002##
[0092] Direct air capture systems can require electricity to run an
air capture reactor, CO.sub.2 compressors, and other equipment.
Such systems also require low grade heat for steam generation for a
CaO/H.sub.2O reaction and high grade heat (e.g., around at least
900.degree. C.) for a CaCO.sub.3 dissociation reaction. The
electricity and heat for the air capture system may be produced by
the proposed carbon capture kiln system. Such integration can be
useful to improve the CO.sub.2 capture efficiency and reduce the
system cost. Examples of power production systems and methods which
may be utilized in the present disclosure are provided in U.S. Pat.
Nos. 8,596,075, 8,776,5328, 869,889, 8,959,887, 8,986,002,
9,062,608, 9,068,743, 9,410,481, 9,416,728, 9,546,815, 10,018,115,
and U.S. Pub. No. 2012/0067054, the disclosures of which are
incorporated herein by reference. Such systems particularly can
utilize CO.sub.2 as the working fluid to produce power and heat
with full carbon capture.
[0093] CaCO.sub.3 from within the calcium looping cycle can be
added to fresh CaCO.sub.3 feedstock and decomposed into CaO and
CO.sub.2 in a reactor operated at a temperature of about
900.degree. C. to about 1100.degree. C.
[0094] Flue gas from the calciner reactor (e.g., comprising
CO.sub.2, H.sub.2O, and other minor contaminants) can be cooled
down to about ambient temperature for water and CO.sub.2
separation. The heat in the calciner flue gas can be used to
pre-heat CaCO.sub.3 to about 600.degree. C. to about 700.degree. C.
before CaCO.sub.3 is injected into the calciner, and the heat can
also be used for heating the closed loop power cycle working fluid
to the turbine inlet temperature. Here, the working fluid can be
steam, CO.sub.2, supercritical CO.sub.2, or other materials. After
water separation, CO.sub.2 can be compressed to high pressure and
purified to a high purity by a CO.sub.2 membrane and a cryogenic
based CO.sub.2 purification unit.
[0095] Flue gas from the calciner can be partially cooled to a
range of about 300.degree. C. to about 500.degree. C. for
CaCO.sub.3 pre-heating, then sent to a single stage or double stage
oxy-fired gas re-heater with steam/CO.sub.2 tubing inside to raise
the temperature up to about 650.degree. C. to about 700.degree. C.
for a closed loop power generation cycle. The export CO.sub.2 can
be used for EOR, chemical production, sequestration, and/or other
uses.
[0096] CaO at about 900.degree. C. in the calciner can be separated
from a gas product via a separation unit and cooled downed to about
600.degree. C. to about 700.degree. C. against one or a combination
of low temperature steam, oxidant, or CO.sub.2, and hot CaO can
also be cooled by mixing with low temperature, recycled CaO. The
CaO at a temperature of about 600.degree. C. to about 700.degree.
C. can be sent to a steam slaker to generate a stream of
Ca(OH).sub.2. A portion of the CaO can be exported from the system
as a byproduct. For example, the portion of the CaO can be sold as
quicklime or hydrated lime by water slaking. The remaining portion
of the CaO can be recycled within the chemical looping cycle.
[0097] CaO can be sent to a steam slaker to form Ca(OH).sub.2 by
reacting with steam. The heat released by the reaction in the steam
slaker can be used to directly pre-heat CaCO.sub.3 slurry and/or
indirectly heat the closed loop power cycle working fluid, such as
steam or CO.sub.2. The steam slaker can be operated, for example,
at a temperature of about 150.degree. C. to about 500.degree.
C.
[0098] High temperature CaO exiting the steam slaker can be cooled
down to the ambient temperature and form a CaO water slurry. The
heat withdrawn from the high temperature CaO can be used to
pre-heat the closed looping power cycle working fluid.
[0099] A CaO water slurry can be sent to a reactor for CO.sub.2
solvent regeneration, such as by reacting with K.sub.2CO.sub.3 or
Na.sub.2CO.sub.3, to form CaCO.sub.3 and KOH or NaOH. The reaction
with K.sub.2CO.sub.3 is shown below.
K 2 .times. CO 3 + C .times. a .function. ( O .times. H ) 2 = 2
.times. KOH + CaCO 3 ( 5 ) ##EQU00003##
[0100] Liquid KOH or NaOH can be used for capturing CO.sub.2 from a
gaseous sample (e.g., air or flue gas) by spraying the liquid
solvent to make contact with the air in, for example, an air
contactor. The subsequent reaction with KOH is shown below.
2 .times. KOH + CO 2 = H 2 .times. O + K 2 .times. CO 3 ( 6 )
##EQU00004##
[0101] Air can be preheated for partial CO.sub.2 removal by using a
solid state CO.sub.2 absorbent running at a temperature of about
130.degree. C. to about 150.degree. C. In some embodiments, the low
grade heat for the process can be taken from the turbine exhaust
stream or ASU heat from the oxy-fired power cycle.
[0102] K.sub.2CO.sub.3 and/or Na.sub.2CO.sub.3 from the air
contactor can be sent to the CaO slurry reactor for KOH/NaOH
regeneration. CaCO.sub.3 from the CaO slurry reactor can be sent to
steam slaker for preheating and then sent to the oxy-fired calciner
for CaO regeneration.
[0103] A closed loop power cycle can be used for the power
generation to self-supply the power for part of the system or
substantially the entire system. The heat for the closed loop power
cycle can be, for example, from the calciner and/or the steam
slaker. The working fluid can be steam, CO.sub.2, or other
materials.
[0104] Steam, air, or calciner flue gas CO.sub.2 can be recycled
back to the calciner reactor as a temperature moderator and
fluidization medium.
[0105] The calciner reactor and/or steam slaker can be a
circulating fluidized bed reactor, a transport reactor, or a
bubbling bed reactor, horizontal or vertical kiln, or indirect
heated kiln.
[0106] The CaO slurry pellet reactor can be any reactor, such as a
fluidized bed reactor (used in other direct air capture cycles) or
a constant stirred reactor.
[0107] A system for direct atmospheric capture of a moiety, such as
CO.sub.2, can comprise a number of components, units, or other
elements. The integrated power production system can include, for
example, at least one heat source (e.g., a combustor, a solar
heater, heat transfer from a steam stream), at least one power
producing turbine, at least one generator, at least one heat
exchanger, at least one separator, at least one compressor and/or
pump, and any number of lines useful for passage of various streams
between said components, units, or elements.
[0108] The direct atmospheric capture system can include, for
example, at least one air contactor unit, at least one
pump/compressor, at least one reactor, at least one lime slaking
unit (e.g., a steam slaker), at least one calciner, one or more
mixing tanks, one or more heat exchangers, one or more coolers, and
any number of lines useful for passage of various streams between
said components, units, or elements. An air separation unit may
also be included in the combined system.
[0109] It is understood that the alkali liquid solvent based direct
atmospheric capture system can be combined with the CaO
cogeneration and/or the integrated power production system in that
one or more streams passing through one or more lines may be
integrated into at least two of the noted systems. In this manner,
for example, heat produced in one system may be transferred for use
in the other system. Likewise, electricity generated in the power
production system may be directly utilized by the direct
atmospheric capture system. The present systems and methods thus
benefit from the one or more outputs (e.g., CaO, Ca(OH).sub.2, and
the like) being useful as commodities to offset the cost associated
with direct air capture. Moreover, the present systems and methods
may be combined with existing CaO production systems to create an
overall carbon neutral facility. Even further, the ability to
utilize heat generated in the calcium looping process to provide at
least part of the heating for the closed loop power production
cycle can provide for high efficiency, particularly in light of the
ability to substantially or completely eliminate the need for
CO.sub.2 capture from the power production system and/or the CaO
generation process.
[0110] The present systems and methods are beneficial at least in
part because of the ability to utilize substantially carbon free
power in carrying out direct air capture of one or more moieties
therefrom. By eliminating emissions associated with power
production it is possible to increase the effective amount of air
capture achieved relative the actual capital expense investment
since there is no additional cost for handling power plant
emissions. Furthermore, the heat integration that is enabled
between the air capture system and the power plant results in a net
improvement in energy use per unit of carbon captured since more
electricity can be produced. This synergy is based on the
integration of heat recovery given the regeneration of CaO and not
the use of the caustic capture agent.
[0111] In one or more embodiments, the present disclosure can
relate to a system configured for alkali liquid solvent based
direct air capture of one or more moieties (e.g., CO.sub.2) with
one or both of simultaneous power production and CaO generation.
Such systems can comprise, for example: an air capture plant; a
calciner; at least one heat recovery unit; and a closed loop power
generation unit. The air capture plant can be configured for
utilizing a caustic agent for reacting with the one or more
moieties in an air stream, such as according to reaction 1 shown
above. The calciner can be configured for regeneration of the
caustic agent, such as according to a calcium looping cycle as
described above. The at least one heat recovery unit can include
one or more components configured for cooling of recovered solids
and gases from the calciner and may include, for example, a steam
slaker. The closed loop power generation unit can include
components as otherwise described herein and may include minimally
at least one or more heat recovery turbines and optionally one or
more heat exchangers, compressors, and/or additional heat
sources.
[0112] In some embodiments, the present disclosure can relate to a
method for alkali liquid solvent based direct air capture of one or
more moieties (e.g., CO.sub.2) with one or both of simultaneous
power production and CaO generation. Direct air capture with
simultaneous CaO production can be advantages because of the
ability to utilize the heat generated in the processes for further
purposes, such as to raise steam and produce the needed power. Heat
sources in the process can include the flue gas from the calciner,
heat generated in the steam slaker, heat from an ASU, and/or heat
from a turbine exhaust in the closed loop power cycle. The method
can comprise, for example, contacting air (or another gaseous
stream) with a caustic agent that is effective to react with at
least one moiety (e.g., CO.sub.2) in the air or other gaseous
stream and thereby remove at least a portion of the at least one
moiety from the air or other gaseous stream. The method thereafter
can comprise regenerating the caustic agent to form at least one
stream comprising at least CaO and the at least one moiety, whereby
said regenerating includes heat production. The method also can
comprise recovering at least a portion of the heat produced in the
regenerating and applying the recovered heat to a closed loop power
production cycle. The method thus can result in the capture of the
at least one moiety that is removed from the air or other gaseous
stream as well as the production of at least on commodity, such as
the CaO.
[0113] In one or more embodiments, the present disclosure can
provide for carbon capture along with coal combustion residuals
(CCR) recycling. More particularly, the disclosure can provide
systems and methods providing integration between a calcium oxide
generation process, carbon dioxide capture and purification, and
CCR treatment, as well as beneficial uses of end products. A
flowchart illustrating various embodiments of such systems and
methods is shown in FIG. 7.
[0114] Referring to FIG. 7, a commercially available reactor for
calcium oxide (CaO) production can be utilized as the calciner
reactor. An oxidant stream can be pre-heated against export, hot
CaO particles inside of the reactor before being injected into a
combustion zone to combust fuel (e.g., coal, natural gas or other
fuel as described herein). The oxidant stream can be through a line
in the form of power plant flue gas that can be supplemented with
pure oxygen that can be provided through the same or a different
line in order to achieve stable combustion (increase O.sub.2 mole
fraction) at the burner of the reactor. The oxygen can be sourced
from an ASU, VPSA, or other oxygen source. The reactor can be
operated at a temperature of about 900.degree. C. (or other
suitable temperature, such as described herein). At the outlet of
the reactor, a cyclone can be used for gas and solids
separation.
[0115] A portion of CaO produced from the reactor can be used for
stabilizing and drying wet ponded CCR. As illustrated, the CaO is
combined with wet coal ash in a coal ash pond to effect drying of
the coal ash. Dried ponded CCR can be sent to a screening system
(e.g. froth floatation) to separate CCR with high loss on ignition
("LOI") from CCR with low LOI. CCR with low LOI (e.g., having an
LOI of less than 3-4%) combined with CaO produced from the reactor
can be used for cement/concrete/fly ash production. CCR with high
LOI can be sent to a CCR reburner (or ash reburner) for thermal
treatment to reduce the carbon content in the CCR. The oxidant
stream in the CCR reburner can be the high temperature reactor
exhaust gas supplemented with pure oxygen in order to achieve
stable combustion in the reburner. Fuel can be optionally injected
into the reburner in case the carbon in the CCR is not sufficient
for stable combustion. The CCR reburner can be designed, for
example, as a fluidized bed combustor for treating CRR with a large
particle size, or a cyclone furnace type burner for treating CCR
with a small particle size, such as fly ash. Ammonia in CCR can be
removed from the reburner.
[0116] CCR reburner flue gas exiting the cyclone can enter a heat
recuperation step to preferably transfer as much of the remaining
heat as possible to generate steam for power generation. The steam
generated in the heat recuperator can be sent to power plant steam
cycle to either increase the power output or reduce the fuel input
of the power plant. This can have the net effect of allowing for
flue gas carbon capture and CCR treatment without a reduction in
power output from a co-located power plant. This type of treatment
may likewise be employed in the integrated system/method
illustrated in FIG. 6 in relation to the steelmaking process.
[0117] Once the CCR flue gas has been cooled to close to ambient
for maximum heat recovery, it can enter a water separator to remove
liquid water. One example configuration can include a wet venturi
scrubber which can provide additional cooling and also assist in
dissolving acid gas chemistry into a liquid phase and removing any
fine solids still entrained in the flue gas. The cooling medium for
the scrubber can be condensed process water that can be temperature
controlled via a dry cooling tower arrangement. Following water
separation, the cooled gas can enter a compressor. Discharge
pressure for the machine can be in the range of about 5 bar to
about 15 bar.
[0118] Upon exiting the compressor, the flue gas can be cooled once
again to near ambient temperature. Depending on the amount of SOx
and NOx in the kiln flue gas, the flue gas can be optionally
scrubbed by a water stream to remove residual SOx and NOx species
in the forms of H.sub.2SO.sub.4 and HNO.sub.3. This can be done
under a pressurized oxidation environment via a catalytic oxidation
process, commonly referred to as the "lead chamber" acid process,
which has been further developed and demonstrated to be effective
for the removal of these species from a pressurized oxidation
working fluid.
[0119] The clean flue gas then can be sent to commercially
available membrane assisted cryogenic type CO.sub.2 Purification
Unit (CPU) to provide clean captured CO.sub.2 with over 99% purity.
The membrane design can provide at least 90% bulk recovery of the
input CO.sub.2 as part of the permeate product with a CO.sub.2
concentration no lower than 50%. Next, the permeate flow can enter
a carbon dioxide purification unit (CPU) in which the contaminated
CO.sub.2 stream (permeate stream) can be purified to desired level
of downstream application via a cryogenic separation process. The
CPU unit, as an example, can comprise a feed compressor to raise
the pressure of the processing CO.sub.2 stream to enhance the
liquefaction of carbon dioxide. The membrane unit and/or the CPU
illustrated in relation to FIG. 6 and/or FIG. 7 can be as otherwise
described herein in relation to acid gas separation, and
particularly carbon dioxide separation.
[0120] The present systems and methods can be adapted to or
configured to provide about 90% CO.sub.2 capture, and the CO.sub.2
can be, for example, from a power plant, a limestone calcination
process, a fuel, and/or CCR combustion. Purified CO.sub.2 can be
exported for sequestration, EOR, and/or chemical production to
increase revenue and claim CO.sub.2 tax credits, such as 45 Q.
Thermally treated CCR can be combined with CaO produced from the
calciner to make cement, concrete, fly ash brick, and other
materials by adjusting the mixing ratio between thermal treated CCR
and CaO. In addition, captured CO.sub.2 from the present systems
and methods can be used to cure concrete and fly ash brick
co-produced in the same system, reduce curing time, and realize on
site CO.sub.2 mineral sequestration.
[0121] The above-described systems and methods can provide a
plurality of advantages and beneficial uses. In some embodiments,
the systems and methods can provide an integrated solution of
managing various wastes from coal power plants. For example, CaO
produced from the present systems can be used for wet pond drying
and stabilization and also can be combined with thermal treated CCR
to produce salable by-products, including cement, concreate, fly
ash bricks, and others. CO.sub.2 produced from power plants and the
present systems can be internally captured and can be on-site
mineral sequestered via CO.sub.2 curing concrete and fly ash
bricks. Thermal treatment of the CCR in some embodiments can take
place in the same reactor where the CaO is produced. In such a
scenario, loss of ignition carbon content in the CCR may serve to
offset fuel input into the reaction vessel. As well, the CCR can be
fed to the reactor in a ratio with the CaO that is formed such that
the dried solid discharged mixture may embody a product comparable
to cement.
[0122] In some embodiments, the systems and methods can provide
in-situ SOx, NOx, particulates and soluble acid removal and coal
ash treatment. For example, fuel and CCR derived impurities from
natural gas or coal fired power plants, such as SOx, NOx, NH.sub.3,
and fine particulates and soluble acid can be removed
simultaneously in the present systems. Compounds such as calcium
sulfate and calcium nitrate can be formed from the SOx and NOx as
it comes in contact from cooling export CaO. The trace amount of
fine particles, SOx, NOx and soluble acid, such as chlorine and
ammonia in the kiln and CCR reburner flue gas leftover, can be
removed in the downstream water separator. In addition, another use
of the produced quicklime can be to combine with coal ash from
existing coal plants to produce cement on-site by adding a cement
clinker at the back end of the process.
[0123] In some embodiments, the systems and methods can provide
flexible integration with existing flue gas streams. For example,
as discussed above, other contaminants can be removed in the
present systems, and CO.sub.2 sorbent can be insensitive to the
flue gas chemistry. The systems can be integrated with flue gas
streams flexibly with little or no modification. For instance, coal
flue gas entering into the present systems and methods can be
either prior to or after Selected Catalytic Removal (SCR) unit or
FGD units, which makes the system integration become relatively
simple and low risk.
[0124] In some embodiments, the systems and methods can provide
CO.sub.2 capture with minimal parasitic load. For example, the kiln
and CCR reburner exhaust heat can be used to generate steam, which
can drive a steam turbine to generate power that offsets any
parasitic loads associated with the present systems. As evidenced
by detailed Aspen modeling of the present systems, minimal net
electric demand is associated with such systems. Electricity
generated from the kiln and CCR reburner heat can cover much of the
parasitic load of post-combustion capture, CaO byproduct
generation, and CO.sub.2 cleanup and purification, and exact
amounts can be affected by targeted capture rate. In addition,
carbon in CCR can be used as fuel in the system to generate
electricity and increase captured CO.sub.2 output.
[0125] In some embodiments, the systems and methods can provide
improved economics through production of by-product quicklime
(CaO), thermal treated high quality CCR, cement, concrete, fly ash
bricks, and CO.sub.2. For example, the present system particularly
can arise from an integration between low carbon quicklime
generation processes, thermal treatment of CCR with high LOI, and
power plant post-combustion carbon capture processes. The synergy
between three different processes can be fully utilized to improve
the economics of the carbon capture system and reduce net capture
costs significantly. The revenue from various by-products generated
from the present systems can CCR clean up from a cost center to a
profit center.
[0126] In some embodiments, a CCR re-burner and a kiln can be one
reactor. High LOI CCR and limestone thus can be co-injected into
the combined reactor for combustion and calcination. The mass ratio
of CCR and limestone can be utilized as a tuning parameter to
define the CaO content in the treated CCR for different end
uses.
[0127] It is understood that any of the components illustrated in
relation to FIGS. 1A through 5 may be included in the systems and
methods illustrated in relation to FIG. 7. For example, although a
calciner is shown in FIG. 7, it is understood that the calciner
indicates that a reactor as described herein may be utilized, and
this may include a plurality of reactors. Further, since both a
flue gas and solids streams are illustrated exiting the calciner,
it is understood that the illustrated calciner indicates that at
least one separation component is integrated therewith for
separation of the gases from the solids. Likewise, it is understood
that the reactor(s) and the separator(s) may be an integrated unit
or may be separate units. Additionally, it is understood that the
"steam cycle" illustrated in FIG. 7 is indicative of a plurality of
components that are utilized for producing electricity. Referring
to FIG. 1A and FIG. 1B, the steam cycle of FIG. 7 may include an
HRSG 30 that can be used to heat a water stream 9 and produce a
steam stream 8 that can be cycled through suitable turbines for
production of electricity utilizing suitable generators. Referring
to FIG. 2, the steam cycle of FIG. 7 may include a heat exchanger
210, a turbine 245 (and any necessary generators), a cooler 250, a
compressor/pump unit 255, and lines 256 and 213 for circulation of
a working fluid. It is likewise understood that, in such
embodiments, the working fluid need not necessarily be water/steam,
and the phrase "steam cycle" can simply indicate power generation
through circulation of a working fluid.
[0128] In some embodiments, the systems and methods can provide
carbon capture from flue gas, CCR, and the quicklime/cement
industry in one system. For example, the present systems and
methods can capture CO.sub.2 from existing flue gas streams and
decarbonize quicklime, fly ash bricks, cement, and CCR cleanup in a
combined system. Total emissions from the cement industry
contributes approximately 8% of global CO.sub.2 emissions. The
majority of CO.sub.2 emissions from cement are process emissions
(CaCO.sub.3=CaO+CO.sub.2) and fossil fuel combustion for
calcination. The present systems and methods thus can be effective
to substantially decarbonize the cement industry by capturing
CO.sub.2 from quicklime generation and from cement flue gas in an
integrated system.
[0129] In some embodiments, sour gas (e.g., natural gas containing
H.sub.2S and CO.sub.2) can be the fuel fed into the reactor, and
limestone can be injected into the reactor to capture sulfur
species in the reactor and form gypsum (via the reaction of
CaCO.sub.3+SO.sub.2=CaSO.sub.4+CO.sub.2). The sulfur lean reactor
flue gas can enter a downstream heat recuperator, water separator,
and membrane assisted CO.sub.2 separation and purification unit to
produce carbon captured power using sour gas as the feedstock. The
gypsum can be separated out in the solids stream, and gypsum can be
recovered for export and/or for combination with quicklime in a
cement production process.
[0130] Systems as described herein can utilize commercially
available equipment, including a direct-fired rotary kiln system
for quicklime generation, fluidized bed combustor or cyclone
furnace for CCR reburn, waste heat recuperator for steam
generation, a downstream CO.sub.2 membrane separator, as well as
cryogenic type CO.sub.2 purification unit (CPU). Example
units/components that may be utilized include one or more of the
following (in the singular or in multiples): kiln(s)/reactor(s);
air blower(s); fluidized bed combustor(s); heat recovery steam
generator(s) (HRSG); steam turbine(s); BFW pump(s); coalescing
filter(s)/dryer(s); compander(s); integrally geared compressor(s);
CO.sub.2 separation membrane(s); CO.sub.2 purification unit(s);
vacuum condenser(s); and/or evaporative cooling tower(s).
[0131] In further embodiments, a direct capture system according to
the present disclosure may partially or completely exclude the use
of alkali liquid solvents based on KOH/NaOH. For example, at least
a portion of any lime present in the system may serve as the agent
directly capturing carbon dioxide from a gaseous stream. By adding
CaO to an aqueous solution, the pH of said solution can be
increased due to the increasing alkalinity. This in effect can
create a buffering capacity against acidity. Should a gaseous
stream containing carbon dioxide be contacted with the alkaline
water mixture, it will promote the dissolution of carbon dioxide
into the liquid phase. The carbon dioxide will dominantly appear in
the solution as stable bi-carbonate and carbonate species. The
solution thereafter may be disposed of as appropriate.
[0132] As a non-limiting example, in the enhanced oil recovery
(EOR) industry, carbon dioxide that is captured during the
production of CaO can be injected into an EOR well. Oil and
produced water come to the surface while the carbon dioxide remains
in the well and is substantially sequestered. The oil and water can
be separated and, thereafter, the water can be mixed with the
produced CaO. The mixture then can be contacted with either air
and/or some other carbon dioxide containing flue gas until it is
saturated with bi-carbonate/carbonate. The mixture then can be
pumped into a disposal well. In another example, the CaO may simply
be dumped in a body of water such as the ocean.
[0133] An advantage to this type of carbon capture is that it can
function as a carbon negative arrangement. For every mole of CaO
produced, less than two moles of CO.sub.2 will be generated;
however, the CaO in aqueous solution can capture 2 moles of
CO.sub.2, thus resulting in a net CO.sub.2 capture.
[0134] Use of the words "about" and "substantially" herein can
indicate that while the exact values disclosed are encompassed, the
present disclosure likewise encompasses slight variations
therefrom. Thus, a value indicated as being "about" the stated
amount or "substantially" the stated amount includes the stated
amount as well as variations therefrom that may be expected to
occur in relation to other processing conditions, equipment
limitations, and/or inability in the field to exact measure the
noted value. "About" and/or "substantially" thus can encompass
variations of +/-5%, +/-2%, or +/-1% of the exact, stated
value.
[0135] Many modifications and other embodiments of the presently
disclosed subject matter will come to mind to one skilled in the
art to which this subject matter pertains having the benefit of the
teachings presented in the foregoing descriptions and the
associated drawings. Therefore, it is to be understood that the
present disclosure is not to be limited to the specific embodiments
described herein and that modifications and other embodiments are
intended to be included within the scope of the appended claims.
Although specific terms are employed herein, they are used in a
generic and descriptive sense only and not for purposes of
limitation.
* * * * *